Signle Phase To Three Phase Unified Power Quality Conditioner

Published in: Electrical | Electronics | Electronics And Communication

52 Views

signle phase to three phase unified power quality conditioner

Vanaparthi S / Hyderabad

1 year of teaching experience

Qualification: Intermediate

Teaches: Mathematics, Science

Contact this Tutor

Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids ABSTRACT CHAPTER-I 1.1 INTRODUCTION IN rural or remote regions in Brazil, as well as in some areas of countries such as Australia and New Zealand, for instance, electrical power distribution systems (EPDS) with single-wire earth return (SWER) have been commonly adopted as a solution for electrical power supplying. This is due to the fact that the reduction of costs in the distribution of energy to serve large territorial extensions with low demographic densities is an important requirement, since lower installation and maintenance costs are achieved .0ther alternatives are the use of energy distribution by means of two conductors (phase-to-neutral) without earth return, or even using two-phase systems (phase-to-phase). Considering these alternatives, capital investments for the realization of SWER distribution grid facilities installations are still lower.The demand for electrical energy in single-phase rural distribution grids has considerably increased in the last decades, both in agriculture and in livestock, mainly due to the increasing evolution and modernization of the technologies used, as well as the increase in the mechanization of production processes. It is possible to mention, for example, the automation of irrigation, as well as the post-harvest agricultural processing involving seed selection and milling, ventilation and refrigeration, washing and packaging lines, among others. Within this context, there is an imminent trend Of increasing energy demand in rural properties, as well as the need to improve power quality enhancement due to the change in the characteristics of the loads. The voltage regulation is characterized as one of the main problems of power quality (PQ) found in the rural single-phase grids, because when subjected to large loads, these grids have significant voltage drops, whereas at times of low consumption the voltage tends to rise. Nevertheless, a solution not so efficient due to constant load variations can be adopted by adjusting the taps of the transformer of the SWER network. Another solution, more efficient in this case, is the use of single-phase voltage regulators. Some ways to bypass large capital investments to meet the growing demand of rural properties have been adopted. In the impacts caused between distributed generation systems implemented through photovoltaic systems and the SWER distribution systems are presented. On the other hand, in, the use of energy storage systems by means of batteries and their use at peak demand is discussed.lt is possible to notice an increasing need to use three-phase distribution grids to meet the demand for electrical energy in rural areas due to changes in the characteristics of the loads. Currently, most of them could be driven by three-phase induction motors instead of single-phase motors, for they have a higher starting torque . Furthermore, the use of medium and high power three-phase voltage inverters involved in modern automated systems also Justifies the need for three-phase grids in rural areas. Therefore, the Page 1
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids presence of a local three-phase energy distribution system in areas that make use of the SWER distribution system becomes more and more indispensable. For this purpose, several solutions and/or configurations of single-phase-to-three-phase (IPh- to-3Ph) converters have been addressed in the literature . These include Iph-to-3Ph four-wire converters, which are able of supplying three-phase and single-phase loads , or IPh-to-3Ph three-wire converters intended to supply only three-phase loads -Dedicated to feed three- phase three-wire loads and integrating the functioning Of the unified power quality conditioner (UPQC), the IPh-to-3Ph converter presented in performs universal filtering, i.e., it operates as series-parallel active power filter, in which the series converter is composed Of a single-phase full-bridge inverter (two inverter legs), while the parallel converter is composed of a three-phase three-leg inverter, totaling five inverter legs. In, also integrating the functionality of a UPQC, a IPh-to-3Ph converter was dedicated for creating a local three-phasefour-wire (3P4W) EPDS from a single-phase distribution system. The series converter is composed of a half-bridge inverter (one inverter leg), while the parallel converter is composed of a three-leg split-capacitor inverter, totaling four inverter legs. Thus, it was allowed feed single-and three-phase loads. On the other hand, limited results have only been presented by means of simulations. In addition, no detail regarding to the dimensioning and control of the converters were suitably treated.ln this paper, the IPh- to-3Ph converter presented in is experimentally validated. It is called UPQC-1Ph-to 3Ph and its power circuit configuration is shown in Fig. 1. This system is indicated for applications in rural or remote areas where, for economic reasons, only single-phase EPDS, such as SWER system, is accessible to the consumer. Once the proposed system deployed in this paper was conceived based on the UPQC functionalities, some discussions related to the UPQC should be performed. Since they simultaneously perform the functions Of series active power filter (SAPF) and parallel active power filter (PAPF), the UPQCs have been commonly employed to mitigate PQ problems, both in single-phase distribution systems and in 3P4W distribution systems. Since they simultaneously perform the functions of series active power filter (SAPF) and parallel active power filter (PAPF), the UPQCs have been commonly employed to mitigate PQ problems, both in single-phase distribution systems and in 3P4W distribution systems.Usually, the UPQCs are controlled to perform series and parallel compensation, synthesizing non-sinusoidal quantities of voltage and current, i.e., the series converter Page 2
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids synthesizes non-sinusoidal voltage quantities to compensate for grid voltage disturbances, while the parallel converter synthesizes non-sinusoidal current quantities with the purpose of suppressing harmonic currents and compensating the reactive power of the loads. For this compensation strategy, some calculation method capable of generating the voltage and current compensation references should be used.On the other hand, some studies presented in the literature have used the dual compensation strategy to control the series and parallel converters of the UPQC. In this strategy, sinusoidal voltage and current references are employed to control both the converters. In this case, the series converter synthesizes sinusoidal current quantities and, consequently, operates as a sinusoidal current source, providing a high impedance path for the current harmonics of the load. The parallel converter synthesizes sinusoidal voltage quantities and, in this case, operates as a sinusoidal voltage source, providing a low impedance path for the current harmonics of the load. It is also observed that the performances of the controllers are notably better when they operate with sinusoidal references, when compared to those that use non-sinusoidal references. In addition, since the control references are sinusoidal, the controllers implemented in the synchronous reference frame will have continuous reference Of voltage and current, facilitating even more the control. Another advantage of dual compensation is in the form Of generation Of control references, which is performed only with the use of a Phase-Locked Loop (PLL) system. The main contribution presented in this paper is to validate experimentally the UPQC- IPh-to- 3Ph destined to feed single-and three-phase loads from the SWER power distribution systems, commonly found in rural and/or remote areas and suffer with PQ problems. By adopting the dual compensation strategy, the proposed UPQC-lPh-to-3Ph makes possible to drain from the single-phase electrical grid a sinusoidal current in phase with the grid voltage. Furthermore, the system can also suppress harmonics from the grid voltage, as well as compensate for voltage disturbances, such as voltage sags/swell. In other words, the UPQC- IPh-to-3Ph can conceive a local 3P4W system with regulated, balanced and sinusoidal load voltages with low harmonic contents improving the PQ indicators. Therefore, the proposed system can achieve two important functions simultaneously, as described:(i) convert the single-phase grid into a three-phase grid, generating a 3P4W distribution system with earthed neutral wire to the final consumer, allowing to connect single-and there-phmse perform the series and parallel active power filtering improving PQ indicators, such as power factor, harmonic distortion. Furthermore, in order to Page 3
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids assist in the proper dimensioning of the UPQC-lPh-to-3Ph power converters, an analysis involving the power flow through the serial and parallel converters is also presented. CHAPTER- 2 2.POWER SYSTEM 2.1 Introduction These days power frameworks are muddled systems. They have many creating stations and burden focuses that are interconnected through force transmission lines. Power is produced and supplied to shoppers by means of transmission and dissemination arranges and contributes a noteworthy partake in the shopper markets of the world. Power frameworks of the present day time are more solid and serve client load with no intrusion in utility voltage. Era offices ought to have the ability to create obliged energy to take care of the client demand. Mass force created must be transported through transmission frameworks more than a long separation without over warming or imperiling framework strength. It is obligation of the conveyance framework to convey power to every client's administration passage. In the setting of dependability era, transmission, and conveyance frameworks are comprised of a few subsystems as recorded in Table 2.1. A disentangled portrayal of a general force framework alongside it sub frameworks is demonstrated in Fig 2. I Table 2.1 Electric power systems and their subsystems Sl.No. Systems neration Subsystems Generation plants / Generation substations Page 4
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids 2 3 Small ransmisslon stribution Transmission lines / Transmission substations/ switching stations Distribution substations Primary distribution systems Dispersed distribution transformers Generator Transformer b»se voltage b 275000 volts or 400.030 volts hr tansm—ion Cia I Grid Trans former disrbuton redwces to v Ottaqe to 400 volts or 230 volts redozæ voltage to 33.000kv Tra red] ces vottaqe Tra r vottaqe to 403 «•ltsor voas Distrib Ge ation La rge Industrial reducæ v r • omrnercial Dome stic Page 5
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig.2.1 Schematic diagram of overall power system network Electrical Power Generation is commanded by huge generators that are remote from clients and in like manner, supply energy to end clients through a system of transmission and conveyance lines. Be that as it may, new advancements and approach choices are gradually switching the decrease in neighborhood era. Eva near to the client (disseminated era or DG, likewise alluded to as inserted era) offers the extension for provincially delivered energy to substitute for power conveyed from the network (request substitution) and supply any surplus force into the lattice. DG in this manner offers the possibility to diminish system speculation generally expected to administration crest interest. DG can likewise, contingent upon circumstances, expand or lessen the requirement for system growth to guarantee the dependability of power supply. This is critical on the grounds that speculations to meet rising crest to normal interest and to guarantee dependable supply have been real wellsprings of expense increments in the system. Society is turning out to be progressively reliant on a practical dependable electric power supply. Untrustworthy electric force supplies can be greatly immoderate to electric utilities and their clients. Prescient dependability appraisal consolidates authentic blackout information and scientific models to gauge the execution Of particular system and framework arrangements. 2.2 Need for Distributed Generation 2.2.1 A Brief History of DG Generally, focal plants have been a vital piece Of the electric lattice, in which substantial creating offices are particularly found either near to assets or generally situated a long way Page 6
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids from populated burden focuses. These, thusly, supply the customary transmission and circulation (T&D) matrix that conveys mass energy to load focuses and from that point to buyers. These were produced when the expenses of transporting fuel and incorporating producing advancements into populated regions far surpassed the expense of creating T&D offices and duties. Focal plants are normally intended to exploit accessible economies of scale in a site-particular way, and are manufactured as "erratic," custom tasks. These economies Of scale started to fall flat in the late 1960s and, by the begin of the 21st century, Central Plants could seemingly no more convey aggressively shabby and solid power to more remote clients through the framework, on the grounds that the plants had come to cost not exactly the matrix and had turn out to be reliable to the point that about all force disappointments began in the network. In this manner, the matrix had turn into the principle driver Of remote clients' energy expenses and force quality issues, which turned out to be more intense as advanced hardware obliged greatly solid power. Effectiveness picks up no more originate from expanding creating limit, however from littler units found closer to locales of interest. For instance, coal force plants are constructed far from urban areas to keep their overwhelming air contamination from influencing the masses. Also, such plants are frequently manufactured close collieries to minimize the expense of transporting coal. Hydroelectric plants are by their inclination restricted to working at destinations with adequate water stream. Low contamination is an essential point of interest of consolidated Page 7
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids cycle plants that smolder normal gas. The low contamination allows the plants to be sufficiently close to a city to give region warming and cooling. Circulated vitality assets are mass-created, little, and less site-particular. Their improvement emerged out of: l. Concerns over saw externalized expenses of focal plant era, especially ecological concerns, 2. The expanding age, weakening, and limit limitations upon T&D for mass force; 3. The expanding relative economy Of large scale manufacturing of littler machines overwhelming assembling of bigger units and on location development; 4. Along with higher relative costs for vitality, higher general many-sided quality and aggregate expenses for administrative oversight, tax organization, and metering and charging. Capital markets now understand that privilege estimated assets, for individual clients, circulation substations, or miniaturized scale lattices, have the capacity to offer critical yet minimal known financial points of interest over focal plants. Littler units offered more prominent economies from large scale manufacturing than enormous ones could increase through unit size. These expanded values because Of changes in monetary danger, designing adaptability, security, and natural nature of these assets can regularly more than counterbalance their evident expense disservices. DG, versus focal plants, must be defended on an existence cycle premise. Sadly, a large portion of the direct, and basically the majority of the roundabout, advantages Of DG are not caught inside conventional utility income bookkeeping. Page 8
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids While the levelized aera expense of appropriated era (DG) is more extravagant than traditional sources on a kWh premise, this does not consider negative parts Of ordinary fills. The extra premium for DG is quickly declining as interest increments and innovation advances, and adequate and solid interest may bring economies of scale, advancement, rivalry, and more adaptable financing, that could make DG clean vitality a piece Of a more expanded future. Circulated era lessens the measure Of vitality lost in transmitting power on the grounds that the power is produced close where it is utilized, maybe even in the same building. This additionally decreases the size and number of electrical cables that must be developed. Regular DER frameworks in a food in tax (FIT) plan have low support, low contamination and high efficiencies. Previously, these attributes obliged devoted working specialists and huge complex plants to lessen contamination. On the other hand, advanced installed frameworks can give these qualities mechanized operation and renewable, for example, daylight, wind and geothermal. This diminishes the measure of force plant that can demonstrate a benefit. 2.22 Distribution System with Distributed Generation (DG) Conveyed vitality, likewise area or decentralized vitality is produced or put away by a mixture of little, network joined gadgets alluded to as appropriated vitality assets (DER) or Page 9
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids dispersed vitality asset frameworks. Customary force stations, for example, coal- terminated, gas and atomic controlled plants, and additionally hydroelectric dams and extensive scale sunlight based force stations, are concentrated and frequently oblige power to be transmitted over long separations. By difference, DER frameworks are decentralized, measured and more adaptable advances that are found near to the heap they serve. CENTRAL vs. DISTRIBUTED GENERATION Central Generation Central Plant Central Plant Distributed Generation Solar Building Wind Fuel Cell Central Plant Micro -Turbine Generator Fig.2.2 Central Vs Distributed Generation Dispersed era (or DG) for the most part alludes to little scale (normally I kW — 50 MW) electric force generators that deliver power at a site near to clients or that are fixed to an electric circulation framework. Appropriated generators incorporate, however are not constrained to synchronous generators, incitement generators, responding motors, small scale turbines (burning turbines that keep running on high-vitality fossil powers, for example, Oil, propane, normal gas, gas or diesel), ignition gas turbines, energy units, sun Page 10
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids powered photovoltaic's, and wind turbines. 2.3Microgrid Small scale framework Concept CERTS Micro matrix has two discriminating parts, the static switch and the smaller scale source. The static switch can independently island the small scale matrix from aggravations, for example, shortcomings, IEEE 1547 occasions or force quality occasions. Subsequent to islanding, the reconnection of the smaller scale network is accomplished self-sufficiently after the stumbling occasion is no more present. This synchronization is accomplished by utilizing the recurrence contrast between the islanded microgrid and the utility network safeguarding a transient free operation without needing to match recurrence and stage points at the association point. Each miniaturized scale source can flawlessly adjust the force on the islanded Micro matrix utilizing a force versus recurrence hang controller. This recurrence hang likewise protects that the Micro matrix recurrence is not quite the same as the framework to encourage reconnection to the utility. Fundamental microgrid structural planning is indicated in Fig 2.3. Page 11
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig. 2.3 Micro grid Architecture Diagram This comprises of a gathering Of outspread feeders, which could be a piece Of an appropriation framework or a building's electrical framework. There is a solitary purpose of association with the utility called purpose Of normal coupling. A few feeders, (Feeders A-C) have delicate burdens, which oblige neighborhood era. The non-basic burden feeders don't have any neighborhood era. Feeders A-C can island from the matrix utilizing the static switch that can isolate in under a cycle. In this sample there are four micro sources at hubs 8, 1 1, 16 and 22, which control the operation utilizing just neighborhood voltages and streams estimations. 2.4 Power System Stability At present the interest for power is rising wonderfully particularly in creating nation like India. This determined interest is prompting operation of the force framework at its farthest point. On top of this the requirement for dependable, steady and quality force is additionally on the ascent because of electric force touchy commercial ventures like data innovation, Page 12
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids correspondence, gadgets and so on. In this situation, taking care of the electric force demand is not by any means the only criteria additionally it is the obligation of the force framework specialists to give a steady and quality energy to the shoppers. These issues highlight the need Of comprehension the force framework solidness. In this course we will attempt to see how to assess the soundness Of a force framework, how to enhance the security lastly how to counteract framework getting to be unsteady. Power framework steadiness is the capacity of an electric force framework, for a given introductory working condition, to recover a condition of working balance subsequent to being subjected to a physical aggravation, with the greater part of the framework variables limited so that for all intents and purposes the whole framework stays in place. The unsettling influences said in the definition could be blames, burden changes, generator blackouts, line blackouts, voltage breakdown or some mix of these. Power framework strength can be extensively ordered into rotor point, voltage and recurrence dependability. Each of these three dependable qualities can be further arranged into extensive unsettling influence or little aggravation, transient or long haul. Page 13
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Power System Stability Frequency stability Rotor Angle Stabi it} Small-Disturbance Angle Stabillty Short Term Stabilty Transient Stability Large. Disturbance Voltage Stabi lty Short Term Snail. Disturbance Vo tage Stability Long Term Short Term Long Term Fig.2.4 of power system stability CHAPTER - 3 3.FLEXIBLE AC TRANSMISSION SYSTEMS 3.1 INTRODUCTION Page 14
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Flexible ac transmission systems, called facts, got in the recent years a well known term for higher controllability in power systems by means of power electronic devices. Several facts- devices have been introduced for various applications worldwide. A number of new types of devices are in the Stage Of being introduced in practice. In most of the applications the controllability is used to avoid cost intensive or landscape requiring extensions of power systems, for instance like upgrades or additions of substations and power lines. Facts-devices provide a better adaptation to varying operational conditions and improve the usage Of existing installations. The basic applications of facts-devices are: • Power flow control, • Increase of transmission capability, • Voltage control, • Reactive power compensation, • Stability improvement, • Power quality improvement, • Power conditioning, • Flicker mitigation, • Interconnection Of renewable and distributed generation and storages. Figure (3.1) shows the basic idea of facts for operation limits of transmission lines for different voltage. The usage of lines for active power transmission should be ideally up to the thermal limits. Voltage and stability limits shall be shifted with the means of the several different facts devices. It can be seen that with growing line length, the opportunity for facts devices gets more and more important. The influence of facts-devices is achieved through switched or controlled shunt compensation, series compensation or phase shift control. The devices work electrically as fast current, voltage or impedance controllers. The power electronic allows very short reaction times down to far below one second. Page 15
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Thermal Limit 76SkV Limit Stability Limit too 600 j rniEs Figure 3.1 Operational limits of transimission lines for different voltage The development of facts-devices has started with the growing capabilities Of power electronic components. Devices for high power levels have been made available in converters for high and even highest voltage levels. The overall starting points are network elements influencing the reactive power or the impedance of a part of the power system. Figure (3.2)showsover view of major FACTS device a number Of basic devices separated into the conventional ones and the facts-devices. For the facts side the taxonomy in terms of 'dynamic' and 'static' needs some explanation. The term 'dynamic' is used to express the fast controllability of facts-devices provided by the power electronics. This is one of the main differentiation factors from the conventional devices. The term 'static' means that the devices have no moving parts like mechanical switches to perform the dynamic controllability. Therefore most of the facts-devices can equally be static and dynamic.The left column in figure 3.2 contains the conventional devices build out of fixed or mechanically switch able components like resistance, inductance or capacitance together with transformers. The facts-devices contain these elements as well but use additional power electronic valves or converters to switch the elements in smaller steps or with switching patterns within a cycle of the alternating current. The left column of facts- devices uses thyristor valves or converters. Page 16
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids These valves or converters are well known since several years. They have low losses because of their low switching frequency of once a cycle in the converters or the usage of the thyristors to simply bridge impedances in the valves. (switctwd) (Switches) Phase FACTS.Chviees stXÉ) Static Va' (Svc) 'Tcsc) Dynamic HVDC Back to Back (HVDC B2B' Convertor NSC) Static nchtonws Co (STATcOM) Stab; S' n ssc) UPFC HVDC vSC to Back VSC 32B) Figure 3.2 over view of major FACTS device The right column of facts-devices contains more advanced technology of voltage source converters based today mainly on insulated gate bipolar transistors (IGBT) or insulated gate commutated thyristors (IGCT). Voltage source converters provide a free controllable voltage in magnitude and phase due to a pulse width modulation of the IGBTS or IGCTS. High modulation frequencies allow to get low harmonics in the output signal and even to compensate disturbances coming from the network. The disadvantage is that with an increasing switching frequency, the losses are increasing as well. Therefore special designs of the converters are required to compensate this. 3.3 BASIC TYPES OF FACTS CONTROLLERS In general, FACTS Controllers can be divided into four categories: • Series Controllers • Shunt Controllers • Combined series-series Controllers • Combined series-shunt Controllers Page 17
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Series Controllers:[Figure 3.3(a)] The series Controller could be a variableimpedance, such as capacitor, reactor, etc., or a power electronics based variable sourceof main frequency, subsynchronous and harmonic frequencies (or a combination) toserve the desired need. In principle, all series Controllers inject voltage in series withthe line. Even variable impedance multiplied by the current flow through it, representsan injected series voltage in the line. As long as the voltage is in phase quadraturewith the line current, the series Controller only supplies or consumes variable reactivepower. Any other phase relationship will involve handling of real power as well. 1--t>H Fig.3.3(a) series controller Shunt Controllers:[Figure 3.3(b)] As in the case of series Controllers, the shuntControllers may be variable impedance, variable source, or a combination of these.ln principle, all shunt Controllers Inject current into the system at the point of connection.Even variable shunt impedance connected to the line voltage causes a variablecurrent flow and hence represents injection of current into the line. As long as theinjected current is in phase quadrature with the line voltage, the shunt Controller onlysupplies or consumes variable reactive power. Any Other phase relationship will involvehandling of real power as well. Fig.3.3(b) shunt controller Combined series-series Controllers:[Figure.3.3(c)] This could be a combinationof separate series controllers, which are controlled in a coordinated manner, in amultiline transmission system. Or it could be a unified Controller, inwhich series Controllers provide independent series reactive compensation for each line but also transfer real power among the lines via the Page 18
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids power link. The real power transfer capability of the unified series-series Controller, referred to as Interline PowerFlow Controller, makes it possible to balance both the real and reactive power flowin the lines and thereby maximize the utilization of the transmission system. Note thatthe term "unified" here means that the de terminals Of all Controller converters areall connected together for real power transfer. dc Fig.3.3(c) .Combined series-series Controllers Combined series-shunt 3.3(d)] This could be acombination of separate shunt and series Controllers, which are controlled in a coordinated manner, or a Unified Power Flow Controller with series and shunt elements. In principle, combined shunt and series Controllersinject current into the system with the shunt part of the Controller and voltage inseries in the line with the series part of the Controller. However, when the shunt andseries Controllers are unified, there can be a real power exchange between the seriesand shunt Controllers via the power link. Fig 3.3(d) Combined series-shunt Controllers 3.4 CONFIGURATIONS OF FACTS-DEVICES: 3.4.1 Shunt devices Page 19
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids The most used facts-device is the svc or the version with voltage source converter called STATCOM. These shunt devices are operating as reactive power compensators. The main applications in transmission, distribution and industrial networks are: • Reduction of unwanted reactive power flows and therefore reduced network losses. • Keeping of contractual power exchanges with balanced reactive power. • Compensation Of consumers and improvement of power quality especially with huge demand fluctuations like industrial machines, metal melting plants, railway or underground train systems. • Compensation Of thyristor converters e.g. in conventional HVDC lines. • Improvement Of static or transient stability. 3.4.2 svc Electrical loads both generate and absorb reactive power. Since the transmitted load varies considerably from one hour to another, the reactive power balance in a grid varies as well. The result can be unacceptable voltage amplitude variations or even a voltage depression, at the extreme a voltage collapse.A rapidly operating static Var compensator (SVC) can continuously provide the reactive power required to control dynamic voltage oscillations under various system conditions and thereby improve the power system transmission and distribution stability. Applications Of the SVC systems in transmission systems: A. To increase active power transfer capacity and transient stability margin B. To damp power oscillations C. To achieve effective voltage control In addition, SVC's are also used Page 20
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids 1.1n transmission systems A. To reduce temporary over voltages B. To damp sub synchronous resonances C. To damp power oscillations in interconnected power systems 2. In traction systems A. To balance loads B. To improve power factor C. To improve voltage regulation 3.5 STATCOM The STATCOM is a solid-state-based power converter version of the SVC. Operating as a shunt-connected SVC, its capacitive or inductive output currents can be controlled independently from its terminal AC bus voltage. Because of the fast-switching characteristic of power converters, STATCOM provides much faster response as compared to the SVC. In addition, in the event of a rapid change in system voltage, the capacitor voltage does not change instantaneously; therefore, STATCOM effectively reacts for the desired responses. For example, if the system voltage drops for any reason, there is a tendency for STATCOM to inject capacitive power to support the dipped voltages. STATCOM is capable of high dynamic performance and its compensation does not depend on the common coupling voltage. Therefore, STATCOM is very effective during the power system disturbances-Moreover, much research confirms several advantages of STATCOM. These advantages compared to other shunt compensators include: • Size, weight, and cost reduction Page 21
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids • Equality Of lagging and leading output • Precise and continuous reactive power control with fast response • Possible active harmonic filter capability This chapter describes the structure, basic operating principle and characteristics of STATCOM. In addition, the concept of voltage source converters and the corresponding control techniques are illustrated. 3.5.1 Structure of STATCOM Basically, STATCOM is comprised of three main parts (as seen from Figure below 3.5. l) a voltage source converter (VSC), a step-up coupling transformer, and a controller. In a very- high-voltage system, the leakage inductances of the step-up power transformers can function as coupling reactors. The main purpose of the coupling inductors is to filter out the current harmonic components that are generated mainly by the pulsating output voltage of the power converters. Fig 3.5.1.Reactivepower generation by a STATCOM 3.5.2 Control of STATCOM Page 22
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids The controller of a STATCOM operates the converter in a particular way that the phase angle between the converter voltage and the transmission line voltage is dynamically adjusted and synchronized so that the STATCOM generates or absorbs desired VAR at the point of coupling connection. Figure(3.5.3) shows a simplified diagram of the STATCOM operating in inductive or capacitive load with a converter voltage source _ IE and a tie reactance, connected to a system with a voltage source, and a The venin reactance, XTIEX_THVTH. 3.53Two Modes Of Operation There are two modes Of operation for a STATCOM, inductive mode and the capacitive mode. The STATCOM regards an inductive reactance connected at its terminal when the converter voltage is higher than the transmission line voltage. Hence, from the system's point Of view, it regards the STATCOM as a capacitive reactance and the STATCOM is considered to be operating in a capacitive mode. Similarly, when the system voltage is higher than the converter voltage, the system regards an inductive reactance connected at its terminal. Hence, the STATCOM regards the system as a capacitive reactance and the STATCOM is considered to be operating in an inductive mode 7TH -E, STATCOM Figure 3.53 STATCOM operating in inductive or capacitive modes In other words, looking at the pharos diagrams on the right of Figure, whenl/, the reactive current component of the STATCOM, leads (THVE—I) by 900, it is in inductive mode and when it lags by 900, it is in capacitive mode.. Page 23
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids 3.5.4 Current Controlled STATCOM Figure (3.5.4) above shows the reactive current control block diagram of the STATCOM. An instantaneous three-phase set of line voltages, VI, at BUS I is used to calculate the reference angle, O, which is phase-locked to the phase a of the line voltage, Via. Inner Low llq Frame Trnfcrmer 8 Phase-Locked Gate : P&rn Imeerter LOSE Figure 3.5.4 Current controlled block diagram of STATCOM An instantaneous three-phase set of measured converter currents, il, is decomposed into its real or direct component, lid, and reactive or quadrature component, liq, respectively. The quadrature component is compared with the desired reference value, liq* and the error is passed through an error amplifier which produces a relative angle, a, Of the converter voltage with respect to the transmission line voltage. The phase angle, 01, of the converter voltage is calculated by adding the relative angle, a, Of the converter voltage and the phase — lock-loop angle, O. The reference quadrature component, liq*, Of the converter current is defined to be either positive if the STATCOM is emulating an inductive reactance or negative if it is emulating a capacitive reactance. The DC capacitor voltage, voc, is dynamically adjusted in relation with the converter voltage. The control scheme described above shows the implementation of the inner current control loop which regulates the reactive current flow through the STATCOM regardless of the line voltage. Page 24
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids 3.5.5 Voltage Controlled STATCOM In regulating the line voltage, an outer voltage control loop must be implemented. The outer voltage control loop would automatically determine the reference reactive current for the inner current control loop which, in turn, will regulate the line voltage. Outer Loop "q Calc u l.tor VI d Vlq Tran sforTNr Figure 3.5.SVoltage controlled block diagram of STATCOM Figure (3.5.5) shows a voltage control block diagram of the STATCOM. An instantaneous three-phase set of measured line voltages, VI, at BUS 1 is decomposed into its real or direct component, Vid, and reactive or quadrature component, Vlq, is compared with the desired reference value, VI', (adjusted by the droop factor, Kdroop) and the error is passed through an error amplifier which produces the reference current, liq*, for the inner current control loop. The droop factor, Kdroop, is defined as the allowable voltage error at the rated reactive current flow through the STATCOM. 3.5.6 Basic operating principles Of ST ATCOM The STATCOM is connected to the power system at a PCC (point of common coupling), through a step-up coupling transformer, where the voltage-quality problem is a concern. The PCC is also known as the terminal for which the terminal voltage is UT. Page 25
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids All required voltages and currents are measured and are fed into the controller to be compared with the commands. The controller then performs feedback control and outputs a set Of switching signals (firing angle) to drive the main semiconductor switches of the power converter accordingly to either increase the voltage or to decrease it accordingly. A STATCOM is a controlled reactive-power source. It provides voltage support by generating or absorbing reactive power at the point of common coupling without the need of large external reactors or capacitor banks. Using the controller, the VSC and the coupling transformer, the STATCOM operation is illustrated in Figure(3.5.6) below. Coupling X T 3 *ase AC V'üage C DC Figure 3.5.6 STATCOM operations in a power system The charged capacitor Cdcprovides a DC voltage, Udcto the converter, which produces a set of controllable three-phase output voltages, U in synchronism with the AC system. The synchronism of the three-phase output voltage with the transmission line voltage has to be performed by an external controller. The amount of desired voltage across STATCOM, which is the voltage reference, Uref, is set manually to the controller. The voltage control is Page 26
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids thereby to match UT with Uref which has been elaborated. This matching of voltages is done by varying the amplitude of the output voltage U, which is done by the firing angle set by the controller. The controller thus sets UT equivalent to the Uref. The reactive power exchange between the converter and the AC system can also be controlled in eq (l). This reactive power exchange is the reactive current injected by the STATCOM, which is the current from the capacitor produced by absorbing real power from the AC system. (1) Where Iqis the reactive current injected by the STATCOM UT is the STATCOM terminal voltage Ueqis the equivalent the venin voltage seen by the STATCOM Xeqis the equivalent the venin reactance of the power system seen by the STATCOM If the amplitude of the output voltage U is increased above that of the AC system voltage, UT, a leading current is produced, i.e. the STATCOM is seen as a conductor by the AC system and reactive power is generated. Decreasing the amplitude of the output voltage below that of the AC system, a lagging current results and the STATCOM is seen as an inductor. In this case reactive power is absorbed. If the amplitudes are equal no power exchange takes place. 3.5.7 Characteristics Of Statcom The derivation of the formula for the transmitted active power employs considerable calculations. Using the variables defined in Figure (3.5.7) below and applying Kirchhoff's laws the following equations can be written; UT—Uz (UI —2 -2 JX2 (2) JX2 —q Page 27
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids x,ex. Figure 3.5.7 Two machine system with STATCOM By equaling right-hand terms of the above formulaseq 2,3, a formula as shown in eq (4,5) for the current 11, UT is obtained as ur=ul -LUI = UI - L -Jl_q (Xl+X2) -g• (Xl+X2) (4) (5) Where UR is the STATCOM terminal voltage if the STATCOM is out of operation, i.e. when O. The fact that Iqis shifted by 900 with regard to UR can be used to express IqasEq (6) is given bellow XlX2 ur=L+lJquR u R (Xl+X2 Applying the sine law to the diagram below the following two equations result sinß sinö sing sin rx IL-u21cxl+x2) (6) (7) (8) Page 28
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids from which the formula is eq (10) for sin is derived. IJ2 sin 6 X 1 Sina = The formula is eq(l l) for the transmitted active power can be given as IJIU2Sin5 UT sma — (Xl+X2) (10) (11) TO dispose of the term UR the cosine law is applied to the diagram in Figure above Therefore, (Xl+X2) (Xl+X2) (12) U2Sin5 (Xl+X2) (13) With these concepts of STATCOM, it is thus important to utilize these principles in accommodating shunt compensation to any system. Transmitted power versus transmission angle characteristic of a STATCOM as shown in fig (3.5.8) below.Since this thesis only reflects on the voltage control and power increase, the requirements of the STATCOM would be further elaborated. P(p.u.) 1.0 —1.0 Figure 3.5.8 Transmitted power versus angle characteristic of a STATCOM. Page 29
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids 3.6 SINGLE-PHASE VOLTAGE SOURCE INVERTERS Single-phase voltage source inverters (VSIs) can be found ashalf-bridge and full-bridge topologies. Although the powerrange they cover is the low one, they are widely used in powersupplies, single-phmse UPSs, and currently to form elaboratehigh-power static power topologies, such as for instance, themulticell configurations that are reviewed. Themain features of both approaches are reviewed and presentedin the following. 3.6.1 Half-bridge VSI Figure (3.6. l) shows the power topology of a half-bridge VSI,where two large capacitors are required to provide a neutralpoint N, such that each capacitor maintains a constant voltagevi=2. Because the current harmonics injected by the operationof the inverter are low-order harmonics, a set of largecapacitors (C. and CY) is required. It is clear that bothswitches S. and Sy cannot be on simultaneously because ashort circuit across the dc link voltage source vi would beproduced. There are two defined (states 1 and 2) and oneundefined (state 3) switch state . Inorder to avoid the short circuit across the dc bus and theundefined ac output voltage condition, the modulating techniqueshould always ensure that at any instant either the top orthe bottom switch of the inverter leg is on. i' Vi/2 s. c, c. s. 1), D. Page 30
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Figure 3.6.1 Single-phase half-bridge VSI. Figure shows the ideal waveforms associated with the half-bridge inverter shown in Fig.(3.6. l). The States for theswitches S. and Sy are defined by the modulating technique, which in this case is a carrier-based PW M. 3.6.2 The Carrier-Based Pulse width Modulation (PWM) Technique As mentioned earlier, it is desired that the ac output voltage. VaN follow a given waveform (e.g., sinusoidal) on a continuous basis by properly switching the power valves. The carrier- based PWM technique fulfils such a requirement as it defines the on and off states of the switches of one leg of aVSI by comparing a modulating signal Vc (desired ac output voltage) and a triangular waveformVd (carrier signal). In practice, when Vc>VD the switch S. is on and the switch is off; similarly, when Vc<VD the switch S. is off and the switch Sy is on. A special case is when the modulatingsignalVc is a sinusoidal at frequency fc and amplitude AVC , and the triangular signal VDis at frequency fD and amplitude AVD. This is the sinusoidal P WM (SPWM) scheme. In this case, the modulation index ma (also known as the amplitude- modulation ratio) is defined aseq(14) (14) And the normalized carrier frequency mf (also known as the frequency-modulation ratio) iseq(15) Figure clearly shows that the ac output voltage (15) v = is basically a sinusoidal waveform plus harmonics,which features: (a) the amplitude of the fundamental component of the ac output voltage satisfying the following expressioneq(16) (16) The PWM technique allows an ac output voltage to begenerated that tracks a given modulating signal. A special caseis the SPWM technique (the modulating signal is a sinusoidal)that provides in the linear region an ac output voltage thatvaries linearly as a Page 31
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids function Of the modulation index and theharmonics are at well-defined frequencies andamplitudes.These features simplify the design of filtering components.Unfortunately, the maximum amplitude of the fundamental acvoltage is Vi=2 in this operating mode. Higher voltages areobtained by using the overmodulation region (Ma l);however, low- order harmonics appear in the ac output voltage. Very large values of the modulation index (Ma 3:24) lead toa totally square ac output voltage that is considered as thesquare-wave modulating technique that is discussed in thenext section. Pulse Width Modulation techniques are used to reduce the harmonics in the system. These reduce the lower order harmonics. The disadvantages of P WM Techniques are switch life is reducing due to the very low ON and OFF times. Analysis of PW M techniques are done by using Fourier Transforms. 3.6.3 Full-bridge VSI Figure (3.6.3) shows the power topology of a full-bridge VSI. This inverter is similar to the half-bridge inverter; however, a second leg provides the neutral point to the load. As expected, both switches and Sl- (or and s2-) cannot be on simultaneously because a short circuit across the dc link voltage source vi would be produced. There are four defined(states 1, 2, 3, and 4) and one undefined (state 5) switch states. Figure 3.6.3 Single-phase full-bridge VSI. Page 32
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids The undefined condition should be avoided so as to bealways capable Of defining the ac output voltage. In order toavoid the short circuit across the dc bus and the undefined acoutput voltage condition, the modulating technique shouldensure that either the top or the bottom switch of each leg ison at any instant. It can be observed that the ac output voltagecan take values up to the dc link value vi , which is twice thatobtained with half-bridge VSI topologies.Several modulating techniques have been developed that areapplicable to full- bridge VSIs. Among them are the PWM(bipolar and unipolar) techniques. 3.6.4 BIPOLAR PWM TECHNIQUE States I and 2 are used to generate the ac outputvoltage in this approach. Thus, the ac output voltage waveformfeatures only two values, which are viand -vi. Togenerate the states, a carrier-based technique can be used asin half-bridge configurations (Fig. 3.5), where only onesinusoidal modulating signal has been used. It should benoted that the on state in switch in the half-bridgecorresponds to both switches Sl+and S2- being in the onstate in the full- bridge configuration. Similarly, S _ in the onstate in the half-bridge corresponds to both switches S 1 _ andS2* being in the on state in the full-bridge configuration. Thisis called bipolar carrier-based SPWM. The ac output voltagewaveform in a full-bridge VSI is basically a sinusoidal waveformthat features a fundamental component of amplitude volthatsatisfies the expression 601 — = vana In the linear region of the modulating technique (ma (17) l),which is twice that obtained in the half-bridge VSI. Identicalconclusions can be drawn for the frequencies and amplitudesof the harmonics in the ac output voltage and dc link current,and for operations at smaller and larger values Of odd mf(including the over modulation region (ma l)), than in halfbridge VSIs, but considering that the maximum ac outputvoltage is the dc link voltage vi . Thus, in the overmodulationregion the fundamental component of amplitude VOI satisfiesthe expression VI <i301 = Vabl < —Vi (18) Page 33
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids In contrast to the bipolar approach, the unipolar P WM technique uses the states 1, 2, 3, and to generate the ac output voltage. Thus, the ac output voltage waveform can instantaneouslytake one Of three values, namelyVi,-Vi the signal vc is used to generate van, and-vc;is used to generateVbNiVbNi—vaN1 .On the other is called unipolar carrier-basedPWM. Identical conclusions can be drawn for the amplitude of the fundamental component and harmonics in the ac outputvoltage and dc link current, and for operations at smaller and larger values of mf, (including the over modulation region (ma 1)), than in full-bridge VSIs modulated by the bipolar SPWM. (vas, and t'bN) However, because the phase voltages are identical but 18()_ out of phase, the output voltage will not contain even harmonics. Thus, if mf is taken even, the harmonics in the ac output voltage appear at normalized odd frequencies fh centered around twice the normalized carrier frequency mf and its multiples. Specifically (19) where k 3; 5; .. . and the harmonics in the dc link current appear at normalized frequencies fp centered around twice the normalized carrier frequency mf and its multiples. Specifically, Imf±k ± 1 (20) Where k = l; 3; 5;. This feature is considered to be an advantage because it allows the use of smaller filteringcomponents to obtain high-quality voltage and current waveforms while using the same switching frequency as in VSIs modulated by the bipolar approach. Page 34
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids CHAPTER - 4 POWER QUALITY 4.1 INTRODUCTION The contemporary container crane industry, like many other industry segments, is often enamored by the bells and whistles, colorful diagnostic displays, high speed performance, and levels of automation that can be achieved. Although these features and their indirectly related computer based enhancements are key issues to an efficient terminal operation, we must not forget the foundation upon which we are building. Power quality is the mortar which bonds thefoundation blocks. Power quality also affects terminal operating economics, crane reliability, our environment, and initial investment in power distribution systems to support new crane installations. To quote the utility company newsletter which accompanied the last monthly issue of my home utility billing: 'Using electricity wisely is a good environmental and business practice which saves you money, reduces emissions from generating plants, and conserves ournatural resources.' As we are all aware, container crane performance requirements continue to increase at an astounding rate. Next generation container cranes, already in the bidding process, will require average power demands of 1500 to kW — almost double the total averagedemand three years ago. The rapid increase in power demand levels, an increase in container crane population, SCR converter crane drive retrofits and the large AC and DC drives needed to power and control these cranes will increase awareness of the power quality issue in the very near future. 4.2 POWER QUALITY PROBLEMS For the purpose of this article, we shall define power quality problems as: Any power problem that results in failure or misoperation of customer equipment,manifests itself as an economic burden to the user, or produces negative impacts on the environment. When applied to the container crane industry, the power issues which degrade power quality include: • Power Factor Page 35
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids • Harmonic Distortion • Voltage Transients • Voltage Sags or Dips • Voltage Swells The AC and DC variable speed drives utilized on board container cranes are significant contributors to total harmonic current and voltage distortion. Whereas SCR phase control creates the desirable average power factor, DC SCR drives operate at less than this. In addition, line notching occurs when SCR's commutate, creating transient peak recovery voltages that can be 3 to 4 times the nominal line voltage depending upon the system impedance and the size of the drives. The frequency and severity of these power system disturbances varies with the speed Of the drive. Harmonic current injection by AC and DC drives will be highest when the drives are operating at slow speeds. Power factor will be lowest when DC drives are operating at slow speeds or during initial acceleration and deceleration periods, increasing to its maximum value when the SCR's are phased on to produce rated or base speed. Above base speed, the power factor essentially remains constant. Unfortunately, container cranes can spend considerable time at low speeds as the operator attempts to spot and land containers. Poor power factor places a greater kVA demand burden on the utility or engine- alternator power source. Low power factor loads can also affect the voltage stability which can ultimately result in detrimental effects on thelife of sensitive electronic equipment or even intermittent malfunction. Voltage transients created by DC drive SCR line notching, AC drive voltage chopping, and high frequency harmonic voltages and currents are all significant sources of noise and disturbance to sensitive electronic equipment It has been our experience that end users often do not associate power quality problems withContainer cranes, either because they are totally unaware of such issues or there was no economicConsequence if power quality was not addressed. Before the advent of solid-state power supplies,Power factor was reasonable, and harmonic current injection was minimal. Not until the cranePopulation multiplied, power demands per crane increased, and static power conversion became the way of life, did power quality issues begin to emerge. Even as harmonic distortion and powerFactor issues surfaced, no one was really prepared. Even today, crane builders and electrical driveSystem vendors avoid the issue during competitive bidding for new cranes. Rather than focus onAwareness and understanding of the Page 36
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids potential issues, the power quality issue is intentionally orunintentionally ignored. Power quality problem solutions are available. Although the solutions are not free, in most cases, they do represent a good return on investment. However, if power quality is not specified, it most likely will not be delivered. Power quality can be improved through: • Power factor correction, • Harmonic filtering, • Special line notch filtering, • Transient voltage surge suppression, • Proper earthing systems. In most cases, the person specifying and/or buying a container crane may not be fully aware of the potential power quality issues. If this article accomplishes nothing else, we would hope toprovide that awareness.ln many cases, those involved with specification and procurement of container cranes may not be cognizant of such issues, do not pay the utility billings, or consider it someone else's concern. As a result, container crane specifications may not include definitive power quality criteria such as power factor correction and/or harmonic filtering. Also, many of those specifications which dorequire power quality equipment do not properly define the criteria. Early in the process of preparing the crane specification: • Consult with the utility company to determine regulatory or contract requirements that must besatisfied, if any. • Consult with the electrical drive suppliers and determine the power quality profiles that can beexpected based on the drive sizes and technologies proposed for the specific project. Evaluate the economics Of power quality correction not only on the present situation, but consider the impact of future utility deregulation and the future development plans for the terminal. 4.3 THE BENEFITS OF POWER QUALITY Page 37
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Power quality in the container terminal environment impacts the economics of the terminal operation, affects reliability of the terminal equipment, and affects other consumers served by the same utility service. Each of these concerns is explored in the following paragraphs 4.3.1. ECONOMIC IMPACT The economic impact of power quality is the foremost incentive to container terminal operators. Economic impact can be significant and manifest itself in several ways: Many utility companies invoke penalties for low power factor on monthly billings. There is no industry standard followed by utility companies. Methods of metering and calculating power factor penalties vary from one utility company to the next. Some utility companies actually meter kVAR usage and establish a fixed rate times the number of k VAR-hours consumed. Other utility companies monitor kVAR demands and calculate power factor. If the power factor falls below a fixed limit value over a demand period, a penalty is billed in the form of an adjustment to the peak demand charges. A number of utility companies servicing container terminal equipment do not yet invoke power factor penalties. However, their service contract with the Port may still require that a minimum power factor over a defined demand period be met. The utility company may not continuously monitor power factor or kVAR usage and reflect them in the monthly utility billings; however, they do reserve the right to monitor the Port service at any time. If the power factor criteria set forth in the service contract are not met, the user may be penalized, or required to take corrective actions at the user's expense. One utility company, which supplies power service to several east coast container terminals in the USA, does not reflect powerfactor penalties in their monthly billings, however, their service contract with the terminal reads as follows: 'The average power factor under operating conditions Of customer's load at the point where service is metered shall be not less than 85%. If below 85%, the customer may be required to furnish, install and maintain at its expense corrective apparatus which will increase thePower factor of the entire installation to not less than 85%. The customer shall ensure that no excessive harmonics or transients are introduced on to the [utility] system. This may require special power conditioning equipment or filters.' The Port or terminal operations personnel, who are responsible for maintaining container cranes, or specifying new container crane equipment, should be aware of these requirements. Terminal operators who do not deal with Page 38
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids penalty issues today may be faced with some rather severe penalties in the future. A sound, future terminal growth plan should include contingencies for addressing the possible economic impact of utility deregulation.Harmonic currents and low power factor created by nonlinear loads, not only result in possible power factor penalties, but also increase the power losses in the distribution system. These losses are not visible as a separate item on your monthly utility billing, but you pay for them each month. Container cranes are significant contributors to harmonic currents and low power factor. Based on the typical demands Of today's high speed container cranes, correction Of power factoralone on a typical state of the art quay crane can result in a reduction of system losses that converts to a 6 to 10% reduction in the monthly utility billing. For most of the larger terminals, this is a significant annual saving in the cost Of operation. The power distribution system design and installation for new terminals, as well as modification of systems for terminal capacity upgrades, involves high cost, specialized, high and medium voltage equipment. Transformers, switchgear, feeder cables, cable reel trailing cables, collector bars, etc. must be sized based on the kVA demand. Thus cost of the equipment is directly related to the total kVA demand. As the relationship above indicates, kVA demand is inversely proportional to the overall power factor, i.e. a lower power factor demands higher kVA for the same kW load. In the absence of power quality corrective equipment, transformers are larger, switchgear current ratings must be higher, feeder cable copper sizes are larger, collector system and cable reel cables must be larger, etc. Consequently, the cost Of the initial power distribution system equipment for a system which does not address power quality will most likely be higher than the same system which includes power quality equipment. 4.3.2 EQUIPMENT RELIABILITY Poor power quality can affect machine or equipment reliability and reduce the life of components. Harmonics, voltage transients, and voltage system sags and swells are all power quality problems and are all interdependent. Harmonics affect power factor, voltage transients can induce harmonics, the same phenomena which create harmonic current injection in DC SCRvariable speed drives are responsible for poor power factor, and dynamically varying power factor of the same drives can create voltage sags and swells. The effects of harmonic distortion, harmonic currents, and line notch ringing can be mitigated using specially designed filters. 4.3.3 POWER SYSTEM ADEQUACY Page 39
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids When considering the installation Of additional cranes to an existing power distribution system, a power system analysis should be completed to determine the adequacy of the system to support additional crane loads. Power quality corrective actions may be dictated due to inadequacy of existing power distribution systems to which new or relocated cranes are to be connected. In other words, addition of power quality equipment may render a workable scenario on an existing power distribution system, which would othenvise be inadequate to support additional cranes without high risk of problems. 4.3.4 ENVIRONMENT No issue might be as important as the effect of power quality on our environment. Reduction in system losses and lower demands equate to a reduction in the consumption of our natural nm resources and reduction in power plant emissions. Page 40
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids CHAPTER-5 MATLAB& SIMULINK 5.1 INTRODUCTION Mat lab is a high-performance language for technical computing. It integrates computation, visualization, and programming in an easy-to-use environment where problems and solutions are expressed in familiar mathematical notation. Typical uses include Math and computation Algorithm development Data acquisition Modeling, simulation, and prototyping Data analysis, exploration, and visualization Scientific and engineering graphics Application development, including graphical user interface building. Matlab is an interactive system whose basic data element is an array that does not require dimensioning. This allows you to solve many technical computing problems, especially those with matrix and vector formulations, in a fraction of the time it would take to write a program in a scalar no interactive language such as C or FORTRAN. The name Matlab stands for matrix laboratory. Matlab was originally written to provide easy access to matrix software developed by the linpack and eispack projects. Today, Matlab engines incorporate the linpack and bias libraries, embedding the state of the art in software for matrix computation. Matlab has evolved over a period of years with input from many users. In university environments, it is the standard instructional tool for introductory and advanced courses in mathematics, en ineerin , and science. In indust , Matlab is the tool of Page 41
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids choice for high-productivity research, development, and analysis. Matlab features a family of add-on application-specific solutions called toolboxes. Very important to most users of Matlab, toolboxes allow you to learn and apply specialized technology. Toolboxes are comprehensive collections Of Matlab functions (M-files) that extend the Matlab environment to solve particular classes of problems. Areas in which toolboxes are available include signal processing, control systems, neural networks, fuzzy logic, wavelets, simulation, and many others. 5.2 The Matlab system consists Of five main parts: Development Environment: This is the set of tools and facilities that help you use Matlab functions and files. Many of these tools are graphical user interfaces. It includes the Matlab desktop and Command Window, a command history, an editor and debugger, and browsers for viewing help, the workspace, files, and the search path. The Matlab Mathematical Function Library: This is a vast collection of computational algorithms ranging from elementary functions, like sum, sine, cosine, and complex arithmetic, to more sophisticated functions like matrix inverse, matrix Eigenvalues, Bessel functions, and fast Fourier transforms. The Matlab Language: This is a high-level matrix/array language with control flow statements, functions, data structures, input/output, and object-oriented programming features. It allows both "programming in the small" to rapidly create quick and dirty throw- away programs, and "programming in the large" to create large and complex application programs. Matlab has extensive facilities for displaying vectors and matrices as graphs, as well as annotating and printing these graphs. It includes high-level functions for two-dimensional and three-dimensional data visualization, image processing, animation, and presentation graphics. It also includes low-level functions that allow you to fully customize the appearance of graphics as well as to build complete graphical user interfaces on your Matlab applications. Page 42
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids The Matlab Application Program Interface (API). This is a library that allows you to write C and FORTRAN programs that interact with Matlab. It includes facilities for calling routines from Matlab (dynamic linking), calling Matlab as a computational engine, and for reading and writing MAT-files. 5.3SIMULINK 5.3 Introduction Simulink is a software add-on to Matlab which is a mathematical tool developed by The Math works,(http://www.mathworks.com) a company based in Natick. Matlab is powered by extensive numerical analysis capability. Simulink is a tool used to visually program a dynamic system (those governed by Differential equations) and look at results. Any logic circuit, or control system for a dynamic system can be built by using standard building blocks available in Simulink Libraries. Various toolboxes for different techniques, such as Fuzzy Logic, Neural Networks, dsp, Statistics etc. are available with Simulink, which enhance the processing power of the tool. The main advantage is the availability of templates / building blocks, which avoid the necessity of typing code for small mathematical processes. 5.4Concept of signal and logic flow In Simulink, data/information from various blocks are sent to another block by lines connecting the relevant blocks. Signals can be generated and fed into blocks dynamic / static).Data can be fed into functions. Data can then be dumped into sinks, which could be scopes, displays or could be saved to a file. Data can be connected from one block to another, can be branched, multiplexed etc.ln simulation, data is processed and transferred only at Discrete times, since all computers are discrete systems. Thus, a simulation time Step Page 43
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids (otherwise called an integration time step) is essential, determined by the fastest dynamics in the simulated and the selection of that step is Fig. 5.4.(a) Simulink library browse a) Connecting blocks c lock Click oft O use button h and hold down. Step Input Unconnected line without large black r r OWhead. Another atternpt r-nuSt be made to c the blocks cursor to her O. and release. A line the one below sh torrn. co I vvith large black arr OWhead, C)utput Of the •Tran ster Fen • block •will go to the as t he Fig.S.4 (a)Connecting blocks Page 44
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids b) Sources and sinks The sources library contains the sources of data/signals that one would use in a dynamic system simulation. One may want to use a constant input, a sinusoidal wave, a step, a repeating sequence such as a pulse train, a ramp etc. One may want to test disturbance effects, and can use the random signal generator to simulate noise. The clock may be used to create a time index for plotting purposes. The ground could be used to connect to any unused port, to avoid warning messages indicating unconnected ports.The sinks are blocks where signals are terminated or ultimately used. In most cases, we would want to store the resulting data in a file, or a matrix of variables. The data could be displayed or even stored to a file. the Stop block could be used to stop the simulation if the input to that block (the signal being sunk) is non-zero. Figure 3 shows the available blocks in the sources and sinks libraries. Unused signals must be terminated, to prevent warnings about unconnected signals. Fig.S.4(b) Sources and sinks c) Continuous and discrete systems Page 45
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids All dynamic systems can be analyzed as continuous or discrete time systems. Simulink allows you to represent these systems using transfer functions, integration blocks, delay blocks etc. Fig. S.4(c) continous and descrete systems d) Non-linear operators: A main advantage of using tools such as Simulink is the ability to simulate non-linear systems and arrive at results without having to solve analytically. It is very difficult to arrive at an analytical solution for a system having non-linearity's such as saturation, signup function, limited slew rates etc. In Simulation, since systems are analyzed using iterations, non-linearity's are not a hindrance. One such could be a saturation block, to indicate a physical limitation on a parameter, such as a voltage signal to a motor etc. Manual switches are useful when trying simulations with different cases. Switches are the logical equivalent of if-then statements in programming. Page 46
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig.S.4(d) simulink blocks e) Mathematical operations Mathematical operators such as products, sum, logical operations such as and, or, etc. can be programmed along with the signal flow. Matrix multiplication becomes easy with the matrix gain block. Trigonometric functions such as sin or tan inverse (at an) are also available. Relational operators such as 'equal to', 'greater than' etc. can also be used in logic circuits 4.2 Fig. 5.4(e) Simulink math blocks f) SIGNALS & DATA TRANSFER In complicated block diagrams, there may arise the need to transfer data from one portion to another portion of the block. They may be in different subsystems. That signal could be dumped into a go to block, which is used to send signals from one subsystem to another.Multiplexing helps us remove clutter due to excessive connectors, and makes matrix (column/row) visualization easier. Page 47
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids 11 l_Üary: Routt' g SWit& and systems Found: •angle' 00 g) Making subsystems Drag a subsystem from the Simulink Library Browser and place it in the parent block where you would like to hide the code. The type of subsystem depends on the purpose of the block. In general one will use the standard subsystem but other subsystems can be chosen. For instance, the subsystem can be a triggered block, which is enabled only when a trigger signal is received.Open (double click) the subsystem and create input / output PORTS, which transfer signals into and out of the subsystem. The input and output ports are created by dragging them from the Sources and Sinks directories respectively. When ports are created in the subsystem, they automatically create ports on the external (parent) block. This allows for connecting the appropriate signals from the parent block to the subsystem. h) Setting simulation parameters: Running a simulation in the computer always requires a numerical technique to solve a differential equation. The system can be simulated as a continuous system or a discrete Page 48
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids system based on the blocks inside. The simulation start and stop time can be specified. In case of variable step size, the smallest and largest step size can be specified. A Fixed step sizeis recommended and it allows for indexing time to a precise number of points, thus controlling the size of the data vector. Simulation step size must be decided based on the dynamics of the system.A thermal process may warrant a step size of a few seconds, but a DC motor in the system may be quite fast and may require a step size of a few milliseconds. r_ja fig S.4(h) simulation parameters Page 49
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids CHAPTER - 7 PROJECT DESCRIPTION& RESULTS 7.1 DESCRIPTION OF THE UPQC-1PH-TO-3PH TOPOLOGY The topology of the UPQC-lPh-to-3Ph is shown in Fig. 7.1. This one is formed by two P WM converters, being a half-bridge inverter and a split-capacitor 3-Leg inverter sharing the same dc-bus. As can be noted, a half-bridge inverter is used to compose the series converter, while it was composed of a full-bridge inverter. Thus, besides using one leg less compared to the topology presented in the dc-bus is formed by the split-capacitor configuration, allowing access to the earthed return conductor of the load, as well to be used in SWER distribution systems. As can be noted in Fig.7.l, the four-wire of the load is connected to the dc-bus central point. The series converter, also called SAPF, is current controlled so that the input drained current is sinusoidal and in phase with the grid voltage, resulting in a power factor (PF) very close to one. A filter inductor is placed in series with the primary winding of the single-phase series coupling transformer. (19 s vs Lfs VCs vac Sin#- VLC 'L e d' Lfp Page 50
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig.7. 1. Topology of the UPQc-1Ph-to-3Ph. The parallel converter, called PAPF, is voltage controlled and it imposes three-phase sinusoidal, regulated and balanced voltages to the loads. The load voltage Of phase "a" is controlled to be in phase with the grid voltage . Second-order LC filters are used to attenuate the high-frequency voltage components. Since the inverter leg connected to phase "a" is controlled to operate as a sinusoidal voltage source, the harmonic and fundamental components of the grid voltage are indirectly compensated by the system, and there is no need to use any specific algorithm to calculate/extract such components. The compensation voltage components, which are composed of harmonic and fundamental components, will appear across the terminals of the series coupling transformer. La v s v The power flow through the UPQC-lPh-to-3Ph will depend on both the load characteristics, such as fundamental power factor and total harmonic distortion (THD) of current, as well as the characteristics of the grid, such as the differences between the amplitudes of the grid and load voltage (phase "a"), as well as the grid voltage T HD. 7.2 GENERATION OF THE CONTROL REFERENCES AND DIAGRAMS OF THE CONVERTERS In this section, the strategies of generation Of control references of the series and parallel converters as well as their modeling are presented. A. Current Reference Of the Series Converter The single-phase current reference used to control the SAPF is obtained in the synchronous reference frame dq, as shown in Fig.7.2. Thus, the load currents ( , , ) are measured and transformed from the three-phase stationary reference frame (abc-axes) to the two-phase stationary reference frame () using the Clarke transformation. Then, by means of the Park transformation, the stationary current quantities of the reference frameare transformed to the synchronous reference frame (dq-axes). In the rotating frame, the coordinates of the unit vector and are obtained using the PLL system presented in , in which is the estimated phase- angle of the grid voltage. The quantity , shown in Fig, represents the active components of the La i Lb i Lc i O axes aa CIO CJD sin(O) cos(O) C] d i load currents, i.e., it is composed of an average component and oscillating components in the reference frame d (d-axis). Page 51
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids ido id,i. sine sine Fig. 7.2. Generation scheme of the series converter current reference the synchronous reference frame dq. Once a IPh-to-3Ph system is being treated, the amplitude of the single-phase input/grid reference current must be properly adjusted to ensure that the average single-phase input power is equivalent to the average three-phase output power . cs i * s P L P In the synchronous reference frame, L P and s P are,respectively, given by: PL = vddciddc (1) (2) where and represent, respectively, the dc components of voltage and current in the d-axis, while and represent the respective peak voltage and peak current of the single-phase grid. dc vddc idsp Vsp I Assuming that, the amplitudes of the three-phase output voltages () are equal in amplitude to the grid voltage , can be written by: LP Vsp Vdc vd (3) Considering an ideal system, in a way that and through (l), (2) and (3), the relationship between the current and the current is given as follows: s L P P D dc id sp I —Fid dc = G cid dc (4) The presence of the gain is observed in (4), which must necessarily be inserted in the algorithm of Fig. to adapt the input and output powers of the UPQC-lPh-to-3Ph. c G 6 D The current dc i shown in Fig. represents the output signalof the dc-bus voltage proportional- integral controller (PI). It isadded to the direct synchronous axis current G id and it isresponsible for controlling the balance/power flow of thesystem. In other words, dc i is used to perform the followingfunctions: i. regulating the voltage of the dc-bus tocompensate for the losses involving the filtering passiveelements and the switching devices; ii adjust the Page 52
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids amplitude ofthe sinusoidal reference current cs i * (series converter), whenthere are variations Of amplitude (sags/swells) between theinput voltage and the output voltage (phase "a"). The current is added to and then filtered by means of a low-pass filter (LPF) generating . G id 6id C] dc idc id Fig. 7.2 also shows the control loop used to cancel the voltage unbalances of the dc-bus capacitors, where the equivalent model adopted to represent the unbalance control is presented in [17]. The output signal of the mentioned controller ( ) acts adjusting the dc level of the grid current. Thus, the reference current Of the series converter is given by: unb i Pcs = iddcsin(9) — iunb (5) To improve the dynamic filtering response, a moving average filter (MAE) [21] was used, acting as LPF. The MAF is characterized by being an easy-to-implement filter capable of rejecting the multiple frequency components of the cutoff frequency, which is defined as the inverse of the integration period (T) or by the fundamental component period. Fig. 7.3 shows the structure of the MAF, which is composed of an integrator block, a transport delay block, a subtractor and a divisor. Input Signal Divisor Delay Integrator Fig. 73. Moving average filter (MAF). Since the single-phase system is connected to the grid, it should be considered the presence of voltage ripples at 120Hz on the dc-bus of the UPQC-lPh-to-3Ph. This ripple may result in the appearance of the 12()Hz harmonic in the series converter current reference, since this current contains information Of . cs i *dc Therefore, one way of attenuating the signal amplitude atthis unwanted frequency would be used an LPF in the dc-busvoltage control loop. Nevertheless, its use could interfere withthe dynamics of the control making it slower. For this reason,it was opted to use only one LPF (MAF) after the sum of thedc-bus controller current ( dc i ) with the direct axis current( G id ), as shown in Fig.7.3. fundamental negative sequence component will also appear in the synchronous reference frame at the 120Hz frequency, i.e., T/2 of the fundamental component Page 53
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids period. Consequently, it becomes necessary that the cutoff frequency of the moving average filter be 120Hz, i.e., the integer n shown in Fig. 7.3 must be equal to 2. B. Current Controller Of the Series Converter Fig. shows, by means of a block diagram, the PI current controller as well as the average model of the series converter. Thus, the transfer function of the system can be written by: i•cs (S ) LeqS2 + (KpsK 2 (6) Req + 2 where and are the proportional-integral (PI) current controller gains; is the PWM gain; is the equivalent inductance, such that is the series filter inductance, is the leakage inductance reflected to the primary of the transformer (grid side), N is the transformation ratio of the transformer, is the equivalent resistance, such that is the resistance of the series transformer. Fig. 7.4. Block diagram of the current controller and the average model of the series converter. C. Reference Voltage of the Parallel Converter The output voltage Of phase "a" is controlled to be in phase with the grid voltage. Thus, given the estimated phase-angle of the grid voltage, as well as the desired voltage amplitude of the load , the output voltage references are given by: Cl LP V via VLpsinC09 PGs-in 00-1200) D. Voltage Controller Of the Parallel Converter (7) (9) Page 54
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig. presents, by means of a block diagram, the voltage control loops as well as the average model Of the parallel converter considering only phase "a". The multi-loop control is implemented by an internal current control loop, where only a proportional controller is used, and an external voltage control loop, in which a PI controller is used. Thus, from the diagram of Fig. the transfer function of the system can be written by: — -K pwm ( 2 VI-a (S) Via (S ) X2—KpvKp, (10) + Y2S2 Y. VdC/2 9+1] Fig. 7.5. Block diagram of the voltage control loops and of the average model of the parallel converter. Based on , and represent the respective proportional and integral controller gains Of the external voltage loop, is the proportional gain of the internal current loop, is the P WM gain, is the filter capacitor, is the estimated filter capacitor, is the filtering inductance, is the internal resistance of the filter inductor and is the total dc-bus voltage. v Kpv Kii Kppwm Kfp Cfp C Sfp LLfp Rfp Ldc V As shown in Fig. 7.5, a feed-forward control loop is used in the output voltage control. The current Of the filter capacitor is estimated, since it is not measured. fp Ci- fp CA E. DC-Bus Voltage Controller By adopting a procedure similar to that presented, it is possible to obtain the voltage control of the dc-bus diagram as shown in Fig. Thus, the small signal closed-loop transfer function of the dc-bus control system is given by: Page 55
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids + VdKIdc (S ) CdcVdcs2 + V d K Pdcs + v d K MC (11) where and are the respective proportional and integral gains of the dc-bus PI controller; is the equivalent dc-bus capacitance; is the total dc-bus voltage and is the direct voltage in the synchronous Pdc K Idc K dc Cdc Vd sp v3 2 V [A reference frame. 7.3 RESULTS UPQC Single phase to 3-phase: Page 56
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Figl: Source Voltage and current Source Voltage to take on Y-axis lunit=50volts and source current taken Y-axis lunit=50amp X-axis taken on time period lunit=0.05sec Fig2: Load voltages Load voltage taken X-axis time period lunit=O.05sec&Y-axis take on voltage lunit=50volts Load wave can be observe it not be sinesoidel wave because fluxuation & harmonic can be apered in output wave form Page 57
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig3:Load currents Load current can be taken X-axis in three phase load R,Y&B. lunit=5amp Y-axis can be taken time period lunit=O.05sec Fig4: load current, source current& parallel current Page 58
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Load current, source current & parallel current can be taken X-axis Figl: Source Voltage and current Source Voltage to take on Y-axis lunit=50volts and source current taken Y-axis lunit=50amp X-axis taken on time period lunit=O.05sec Page 59
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig2: Load voltages Load voltage taken X-axis time period lunit=O.05sec&Y-axis take on voltage lunit=50volts Load wave form can be observe ,using fuzzy logic fluxuation & harmonic can be reduced by using fuzzy logic. Fig3:Load currents Load current can be taken X-axis in three phase load R,Y,B &N . Load current output waveform of harmonic &fulxuation can be reduced using fuzzy logic. lunit=5amp Page 60
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Y-axis can be taken time period lunit=O.05sec wwwwwwwuwo Fig4: load current, source current& parallel current Load current, source current & parallel current can be taken X-axis, Y-axis can be taken time period lunit=O.05sec Load 1: Currents and voltages of the UPQC-1Ph-to-3Ph feeding the three-phase load 1: Proposed simulation diagram loadl Page 61
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Figl: Source Voltage and current Source Voltage to take on Y-axis lunit=20volts and source current taken Y-axis lunit= X-axis taken on time period lunit=0.05sec Fig2: Load voltages Load voltage taken X-axis time period lunit=O.05sec&Y-axis take on voltage lunit=50volts Load wave can be observe it not be sinesoidel wave because fluxuation & harmonic can be apered in output wave form Page 62
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids IIUUIUIMIIIUUMIIIUMI Fig3:Load currents Load current can be taken X-axis in three phase load R,Y&B. lunit=5amp Y-axis can be taken time period lunit=O.05sec Fig4: load current, source current& parallel current Load current, source current & parallel current can be taken X-axis, Y-axis can be taken time period lunit=O.05sec Load 1 : Currents and voltages of the Fuzzy logic-IPh-to-3Ph feeding the three-phase load 1: Page 63
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Proposed simulation diagram loadl Figl: Source Voltage and current Source Voltage to take on Y-axis lunit=20volts and source current taken Y-axis lunit= X-axis taken on time period lunit=0.05sec Page 64
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig2: Load voltages Load voltage taken X-axis time period lunit=O.05sec&Y-axis take on voltage lunit=50volts Load wave form can be observe ,using fuzzy logic fluxuation & harmonic can be reduced by using fuzzy logic. Fig3:Load currents Load current can be taken X-axis in three phase load R,Y&B. lunit=5amp Y-axis can be taken time period lunit=O.05sec Page 65
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig4: load current, source current& parallel current Load current, source current & parallel current can be taken X-axis, Y-axis can be taken time period lunit=O.05sec Load 2: Currents and voltages of the UPQC -IPh-to-3Ph feeding the three-phase load 2: Page 66
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Figl: Source Voltage and current Source Voltage to take on Y-axis lunit=20volts and source current taken Y-axis lunit= X-axis taken on time period lunit=0.05sec Fig2: Load voltages Load voltage taken X-axis time period lunit=O.05sec&Y-axis take on voltage lunit=50volts Page 67
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Load wave can be observe it not be sinesoidel wave because fluxuation & harmonic can be apered in output wave form IMMIiAllMåNåul IMååålUllUMIUlMlMl Fig3:Load currents Load current can be taken X-axis in three phase load R,Y&B. lunit=5amp Y-axis can be taken time period lunit=O.05sec Fig4: load current, source current& parallel current Load current, source current & parallel current can be taken X-axis, Page 68
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Y-axis can be taken time period lunit=O.05sec Load 2: Currents and voltages of the Fuzzy logic-IPh-to-3Ph feeding the three-phase load 2: Figl: Source Voltage and current Source Voltage to take on Y-axis lunit=20volts and source current taken Y-axis lunit= X-axis taken on time period lunit=0.05sec Page 69
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Fig2: Load voltages Load voltage taken X-axis time period lunit=O.05sec&Y-axis take on voltage lunit=50volts Load wave form can be observe ,using fuzzy logic fluxuation & harmonic can be reduced by using fuzzy logic. Fig3:Load currents Page 70
Single-Phase to Three-Phase Unified Power Quality Conditioner Applied in Single Wire Earth Return Electric Power Distribution Grids Load current can be taken X-axis in three phase load R,Y&B. lunit=5amp Y-axis can be taken time period lunit=O.05sec —wznuwnu Fig4: load current, source current& parallel current Load current, source current & parallel current can be taken X-axis, Y-axis can be taken time period lunit=O.05sec CONCLUSION This paper presented the study and the experimental validation of a local three-phase four-wire power distribution system. The system, indicated for applications in rural or remote areas where three-phase distribution grids are not accessible, was conceived based on unified power quality conditioner functionalities. With serial and parallel filtering capability, two inverter topologies were used to compose the UPQC-lPh-to-3Ph. Thereby, the single-phase series converter was deployed using a half-bridge inverter, while the three-phase parallel converter was implemented using a 3-Leg split capacitor inverter. Using the dual compensation strategy, the proposed system was able of feeding linear and non-linear three- phase loads acting with universal active filtering capability, i.e., acting as SAPF and PAPF. Page 71

Need a Tutor or Coaching Class?

Post an enquiry and get instant responses from qualified and experienced tutors.

Post Requirement

Related Study Notes

Power Plant Engineering

Electronics

833 Views
Notes On Performance Parameters Of Rectifier

Electrical

893 Views
BJT Biasing

Electrical, Electronics

12,766 Views
Bayesian Estimators

Electronics

260 Views
8051 MicroController Interrupts

Electronics, Embedded Systems

179 Views
Electrostatics

Electrical, Electronics

4,502 Views
Notes On Combinational Circuits

Electronics

786 Views
Notes On Grade 7 Science

Electrical, Physics, Science

1,396 Views
Core Python

Computer Science, Electronics, Embedded Systems

6,437 Views
Embedded Systems Notes

Electronics, Embedded Systems

177 Views

Upload Study Notes

If you have your own Study Notes which you think can benefit others, please upload on LearnPick. For each approved Study Note you will get 100 Credit Points and 100 Activity Score which will increase your profile visibility.

Upload Now

We use cookies

Choose Country Code

Direction

Ask a Question

Signle Phase To Three Phase Unified Power Quality Conditioner

Vanaparthi S / Hyderabad

Need a Tutor or Coaching Class?

Related Study Notes

Upload Study Notes