POWER FACTOR CORRECTION USING SVC TECHNIQUE

Transcription

1 POWER FACTOR CORRECTION USING SVC TECHNIQUE A PROJECT REPORT Submitted in partial fulfillment of the requirement for the award of the Degree of BACHELOR OF TECHNOLOGY IN (ELECTRICAL AND ELECTRONIC ENGINEERING) by HarshitaSethi (10BEE0024) Dhruvi Chopra (10BEE0083) Under the Guidance of Prof. S. Meikandasivam GUIDE SCHOOL OF ELECTRICAL ENGINEERING VIT University VELLORE , Tamil Nadu, India MAY 2014

2 POWER FACTOR CORRECTION USING SVC TECHNIQUE A PROJECT REPORT Submitted in partial fulfillment of the requirement for the award of the Degree of BACHELOR OF TECHNOLOGY IN (ELECTRICAL AND ELECTRONIC ENGINEERING) by Harshita Sethi (10BEE0024) Dhruvi Chopra (10BEE0083) Under the Guidance of Prof. S. Meikandasivam GUIDE SCHOOL OF ELECTRICAL ENGINEERING VIT University VELLORE , Tamil Nadu, India MAY 2014

3 CERTIFICATE This is to certify that the project work titled POWER FACTOR CORRECTION USING SVC TECHNIQUE submitted by Harshita Sethi (10BEE0024) and Dhruvi Chopra (10BEE0083) is in partial fulfillment of the requirements for the award of BACHELOR OF TECHNOLOGY DEGREE, is a record of bona fide work done under my guidance. The contents of this project work, in full or in parts, have neither been taken from any other source nor have been submitted to any other Institute or University for award of any degree or diploma and the same is certified. Prof. S. Meikandasivam Guide The thesis is satisfactory / unsatisfactory I n t e r n a l E x a m i n e r E x t e r n a l E x a m i n e r Approved by Dean School Of Electrical Engineering

4 ACKNOWLEDGEMENTS It is our privilege to express our sincerest regards to our project coordinator, Prof. S. Meikandasivam, for their valuable inputs, able guidance, encouragement, whole-hearted cooperation and constructive criticism throughout the duration of our project. We deeply express our sincere thanks to Dean of SELECT, VIT University for encouraging and allowing us to present the project on the topic Power Factor Correction using SVC Technique at our department premises for the partial fulfillment of the requirements leading to the award of B-Tech degree. We take this opportunity to thank all our lecturers and staff of the Electrical Laboratory who have directly or indirectly helped our project and provided encouragement throughout our career. Last but not the least we express our thanks to our friends for their cooperation and support. DHRUVI CHOPRA (10BEE0083) HARSHITA SETHI (10BEE0024)

5 ABSTRACT Power factor correction is of utmost importance in electrical power system. Low power factor is undesirable from economic point of view. This project shows Static var compensator as an effective solution to improve the power factor and regulate system voltage. Three different types of SVCs viz. fixed capacitor, Thyristor switched capacitor (TSC) and combination of thyristor switched capacitor (TSC) and thyristor controlled reactor (TCR) are used to improve the power factor. Readings are taken through a small laboratory setup with 1 phase supply and the power factor of the system is improved. Both software and hardware results are obtained to analyze the role of these compensators in power system.

6 List of figures Page no. Figure 1. Power Triangle 6 Figure 2. Transmission system without compensation 8 Figure 3. Transmission system with Series compensation with a voltage source. 8 Figure 4. Transmission system with compensation 9 Figure 5. Transmission system with Series compensation with a voltage source 9 Figure 6. Thyristor-controlled series capacitor (TCSC) 11 Figure 7. Impedance Vs Firing angle Characteristic 12 Figure 8. Static VAR compensator(svc) 13 Figure 9. Static synchronous compensator (STATCOM) 14 Figure 10. Static synchronous series compensator (SSSC) 15 Figure 11. Unified power Flow Controller (UPFC) 16 Figure 12. Star connected Fixed capacitors 17 Figure 13. Delta connected Fixed capacitors 17 Figure 14. SVC system 18 Figure 15. V-I characteristics of SVC 18 Figure 16. Thyristor switched capacitor 19 Figure 17. Conditions for firing of thyristors to avoid transients during switching 19 Figure 18. Thyristor Controlled Reactor (TCR) 19 Figure 19. Voltage & Current Waveforms in a TCR for different thyristor phase 20 shift angles. Figure 20. TCR Voltage Current Characteristics 21 Figure 21. TSC TCR Circuit with control loop 21 Figure 22. SVC V-I Characteristics 22 Figure 23. RTI1104 Board Library 24

7 Figure 24. RTI1104 Board Library Master PPC 25 Figure 25. Single line diagram of Uncompensated System 26 Figure 26. Simulink model of Uncompensated System 27 Figure 27. Single line diagram of compensated system with fixed capacitor banks 28 Figure 28. Simulink model of Fixed capacitor compensated System 28 Figure 29. Single line diagram of compensated 29 Figure 30. Simulink model of TSC compensated System 30 Figure 31. Single line diagram of compensated system using TSC-TCR method 31 Figure 32. Simulink model of TSC-TCR compensated System 32 Figure 33. Simulink results of Uncompensated System 33 Figure 34. Simulink results of fixed capacitor compensated System 34 Figure 35. Simulink results of TSC compensated System 34 Figure 36. Simulink results of TSC-TCR compensated System 35 Figure 37. Energy meter reading for uncompensated system 37 Figure38. Laboratory setup with compensation using fixed capacitors 37 Figure 39. Energy meter reading for fixed capacitor compensated system 38 Figure 40. Laboratory setup 39 Figure 41. Permanent setup of SVC 40 Figure 42. Output from Sensors. (Voltage Blue, Current Pink) 41 Figure 43. Simulink Model to generate firing pulses for thyristor valves 41 Figure 44. Firing Pulse 42

8 List of tables Page No. Table 1: Load ratings 28 Table 2. Fixed Compensation result system with fixed capacitor banks 30 Table 3. TSC Compensation results system using TSC method 31 Table 4. TSC-TCR Compensation results 33 Table 5. Comparison between different SVC techniques 38 Table 6. Load data of an uncompensated system 38 Table 7. Load data of system compensated using fixed capacitors 40 Table 8. Load data of system compensated using TSC 45

9 List of Abbreviations SVC TSC TCR TCSC STATCOM SSSC UPFC PF Static Var Compensation Thyristor Switched capacitor Thyristor controlled reactor Thyristor-controlled series capacitor Static Synchronous compensator Static Synchronous series compensator Unified power flow control Power factor

10 TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES LIST OF ABBREVIATIONS CHAPTER 1 Introduction CHAPTER 2 CHAPTER Objective 1.2 Literature survey 2.1 Power and Power Factor 2.2 Need for Power Factor Correction 2.3 Power Factor Improvement Technique Series Compensation Shunt Compensation Synchronous Condensers FACTS Controllers Thyristor controlled Series Capacitor (TCSC) Static Var Compensator (SVC) Static Synchronous Compensator (STATCOM) Static Synchronous Series Compensator (SSSC) Unified Power Flow Controller (UPFC) 3.1 Shunt Compensation using Fixed Capacitors 3.2 Static Var Compensation (SVC) Thyristor Switched Capacitor (TSC) Thyristor Controlled Reactor (TCR) Combination of TSC TCR 3.3 dspace CHAPTER Simulation Design Uncompensated System Compensation using Fixed Capacitor Banks Compensation using Thyristor Switched Capacitor (TSC) Compensation using combination of TSC and TCR

11 4.2 Analysis of simulation results 4.3 Comparison between different SVC devices 4.4 Hardware Design Compensation Using Fixed Capacitors Compensation Using SVC CHAPTER 5 Conclusion REFERENCES

12 CHAPTER 1 INTRODUCTION The importance of a voltage stable and almost lossless power distribution system with a high rate of availability and reliability is the most important objective of an electrical network. The interaction between supplier and customer is the interface where the definition of power quality does not only affect the determination of the electrical equipment but also the economical billing scheme due to the load demand. The occurrence of additional reactive load demand leads to a power factor below unity. In power systems with a constant supply voltage addition of load leads to an increase in the load current and consequently to higher voltage drops and losses along the distribution network. These conditions lower the efficiency of the network. To accommodate these changes, an equivalent design of higher power rating for all current carrying components in the system is necessary in case of high reactive load demand. Additionally energy suppliers fine their customers when his power factor falls below a certain value since the billing scheme is defined for the consumption of active as well as reactive power. Due to all these effects fast load compensation methods are needed. Load compensation can be carried out in different ways depending on the considered aim of improvement. The methods which are used are: reactive power compensation, unbalanced load compensation and minimization of harmonic distortion. The following study shows the power factor improvement and the stabilization of the supply voltage of a supply network with an increased number of loads over the time by different static VAR compensation (SVC) methods.. Firstly the behavior of a fixed mechanically switched capacitor bank is observed, secondly thyristor switched capacitors (TSC) and thirdly the combination of thyristor switched capacitor(tsc) with thyristor controlled reactor (TCR) is modeled. 1.1 OBJECTIVE To model compensated systems employing different SVC techniques i.e. fixed capacitors, TSC and combination of TSC and TCR for obtaining reactive power compensation, power factor correction and voltage control in Matlab Simulink. And also to develop hardware setup for fixed capacitors and TSC. The purpose of this document is to discuss static VAR Compensation (SVC) as effective solutions for power factor correction of an electrical system. A comparison between reactive power control and improvement of power factor obtained by different methods is presented and the results are analysed for the system with and without compensation. 1.2 LITERATURE SURVEY

13 1) A SMALL SCALE STATIC VAR COMPENSATOR FOR LABORATORY EXPERIMENT, Taufik and Bryan Paet, PECon 08 In this paper, a small scale SVC lab experiment effectively demonstrates SVC s function in correcting power factor through the use of power thyristors in a phase-controlled circuit. The small-scale SVC circuit serves as an effective way to see how power electronics helps utilities deliver efficient power by flexible and fast adjustment of the normally lagging power systems. 2) REACTIVE POWER MANAGEMENT AND VOLTAGE CONTROL OF LARGE TRANSMISSION SYSTEM USING SVC, PravinChopade, Dr. Marwan Bikdash,Dr.IbraheemKateeb,Dr.Ajit D. Ketkar, IEEE 2011 The superiority of SVC over fixed capacitor compensation is proved. Also SVC has much superior voltage control capabilities both, in steady and transient state than the conventional switched shunt capacitor and reactor compensation. 3) LOCATION OF FACTS DEVICES ON POWER SYSTEM FOR VOLTAGE CONTROL, U. EMINOGL U, T. ALCINOZ,S.HERDEM,2003 This paper presents the effect of different static load models on the location of Static VAr Compensator (SVC). The static load types, in which active and reactive powers vary with voltage as an exponential form, are used. PI controllers are used to control SVC firing angles. 4) OPTIMUM SWITCHING OF TSC-TCR USING GA TRAINED ANN FOR MINIMUM HARMONIC INJECTION, D. B. Kulkarniand G. R. Udupi, IEEE 2009 This paper proposes a new method of controlling the injected harmonics of TSC-TCR system by using genetic algorithm based ANN training. The scheme can be effectively used at the existing TSC-TCR installations to reduce harmonic injections while catering to fluctuating loads. 5) IMPROVEMENT OF AN SVC USING AN ACTIVE POWER FILTER CONNECTED IN PARALLEL WITH SYNCHRONOUS SWITCHED CAPACITORS, Ming Zhang and Hui Sun, IEEE 2007 This paper presents the solution for reactive power compensation and harmonic filtering by combining a shunt passive filter in series with a small rated active filter and a synchronous vacuum circuit breaker with permanent magnetic actuator. Passive filters reduce the harmonic currents flowing into the source, and the active filter improves the filtering characteristics of the passive filter. 6) MITIGATION OF CAPACITOR BANK SWITCHING TRANSIENTS BY USING SVCS IN LARGE PLANTS INSTEAD OF CAPACITOR BANK AND CIRCUIT BREAKER,M. Taherzadeh, R. Rostaminia, M. Joorabian, M. Saniei, PEDSTC2013

14 In this paper, the model simulation is done using Matlab/Simulink software, and voltages and transient currents generated when correcting power factor are studies once by using capacitor bank and circuit breaker and once by using SVc. Inrush currents, over-voltages and FFT analysis has been obtained in each two cases. 7) DESIGN OF AN ON-LINE MICROPROCESSOR BASED INDIVIDUALPHASE CONTROL OF A STATIC VAR COMPENSATOR, Daniel Kuay-Chyan Chen, Yuang- Shung Lee, Chi-Jui Wu, IEEE 1991 The compensation value of each phase of the SVC is calculated by three analog adders and sent to the micro-controller which is synthesized by a M68HCllEVM microprocessor board. Then the micro-controller determines the on/off connection of the capacitors and the firing angle of the thyristors in each phase. 8) DESIGN OF A MICROPROCESSOR-CONTROLLED PERSONAL STATIC VAR COMPENSATOR (PSVC),Scott Zemerick, PowsiriKlinkhachorn, and Ali Feliachi, IEEE 2002 A prototype personal static var compensator (PSVC) has been designed for load power factor correction. The PSVC prototype consists of two main branches a TSC (Thyristor Switched Capacitor) branch and a TCR (Thyristor Controlled Reactor) branch. A microprocessor is responsible for calculating the displacement power factor and for executing the fuzzy logic control scheme for the two branches. 9) EVALUATION OF GENERATOR-SETS WITH POWER FACTOR CORRECTION CIRCUITS, DimitriosKalpaktsoglou, Ahmed Al-Busaidi, Volker Pickert, 2009 In this paper, four conventional and three CSC rectifiers have been assessed based on their overall performance. From all CSC s investigated the SVC rectifier, demonstrates highest efficiency, highest PF and highest output voltage. 10) ABB MANUAL In this manual, the benefits of SVC to power distribution and transmission are discussed. TSC switching takes place when the voltage across the thyristor valve is zero, making it virtually transient free. TSCs are characterized by stepped control, no transients, no harmonics and low losses. 11) POWER ELECTRONICS IN ELECTRIC UTILITIES: STATIC VAR COMPENSATOR, LASZLO GYUGYI

15 In this paper, basic thyristor controlled reactor, basic thyristor switched capacitor banks, functional control scheme for the FC-TCR type svc and basic TSC-TCR type svc with their associated waveforms illustrating their operating principles are discussed. 12) REACTIVE POWER COMPENSATION TECHNOLOGIES, STATE OF-THE-ART REVIEW, Juan Dixon, Luis Morán, José Rodríguez, RicardoDomke This paper presents an overview of the state of the art in reactive power compensation technologies. The principles of operation, design characteristics and application examples of VAR compensators implemented with thyristors and self-commutated converters are presented. 13) FACTS CONTROLLERS IN POWER TRANSMISSION AND DISTRIBUTION, K.R. Padiyar In this book, the Static Var Compensator (SVC), a first generation FACTS controller is taken up for study. It is a variable impedance device where the current through a reactor is controlled using back to back connected thyristor valves. The application of thyristor valve technology to SVC is an overshoot of the developments in HVDC technology. 14) IGBT/POWER MOSFET GATE DRIVE PHOTO-IC COUPLERS TLP250(INV)/TLP250F(INV) The 8 pin opto-coupler is designed exclusively for use in IGBT drive application. These opto-couplers are capable to drive IGBT and Power MOSFET directly, makes system design easier allows simpler circuit configuration and improve systems reliability. 15) DSPACE DSP DS-1104 BASED STATE OBSERVER DESIGN FOR POSITION CONTROL OF DC SERVO MOTOR, JaswandiSawant, DivyeshGinoya Controller board like dspace DS1104 is appropriate for motion controls and is fully programmable from the MATLAB/Simulink environment. The dspace uses its own realtime interface implementation software to generate and then down load the real-time code to specific dspace boards. It enables the user to design digital controller simply by drawing its block diagram using graphical interface of Simulink.

16 CHAPTER POWER AND POWER FACTOR Reactive loads such as inductors and capacitors dissipate zero power, yet the fact that they drop voltage and draw current gives the deceptive impression that they actually do dissipate power. This phantom power is called reactive power, and it is measured in a unit called Volt-Amps- Reactive (VAR), rather than watts. The mathematical symbol for reactive power is (unfortunately) the capital letter Q. The actual amount of power being used, or dissipated, in a circuit is called true power, and it is measured in watts (symbolized by the capital letter P, as always). The combination of reactive power and true power is called apparent power, and it is the product of a circuit's voltage and current, without reference to phase angle. Apparent power is measured in the unit of Volt-Amps (VA) and is symbolized by the capital letter S. Fig 1: Power Triangle The ratio of the real power used by the load to the apparent power drawn by it from the supply is defined as the power factor of the electrical system. The power factor is called lagging for inductive loads and leading for capacitive loads. Most of the loads used in a power system are inductive in nature like induction motor, transformer etc. When such lagging power factor loads are introduced in a circuit, the voltage at the receiving end tends to decrease due to an increase in the load current. This results in an increase in the reactive power demand and losses in the circuit. A reduced power factor is undesirable because it results in poor reliability, safety problems, reduced system capacity and higher energy costs...(1)

17 2.2 NEED FOR PF CORRECTION An electrical or electronic device power factor is the ratio of the power that it draws from the mains supply and the power that it actually consumes. An ideal device has a power factor of 1.0 and consumes all the power that it draws. It would present a load that is linear and entirely resistive, that is, one that remains constant irrespective of input voltage, and has no significant inductance or capacitance. Today s commercial, industrial, retail and even domestic premises are increasingly populated by electronic devices such as PCs, monitors, servers and photocopiers which are usually powered by switched mode power supplies (SMPS). If not properly designed, these can present non-linear loads which impose harmonic currents and possibly voltages onto the mains power network.harmonics can damage cabling and equipment within this network, as well as other equipment connected to it. Problems include overheating and fire risk, high voltages and circulating currents, equipment malfunctions and component failures, and other possible consequences.a non-linear load is liable to generate these harmonics if it has a poor power factor. In practice, some devices do have unity power factors, but many others do not. A device has a poor power factor for one of two reasons; either it draws current out of phase with the supply voltage, or it draws current in a non-sinusoidal waveform. The out of phase case, known as displacement power factor, is typically associated with electric motors inside industrial equipment, while the non-sinusoidal case, known as distortion power factor, is typically seen with electronic devices such as PCs, copiers and battery chargers driven by switched-mode power supplies (SMPSs). 2.3 POWER FACTOR IMPROVEMENT TECHINQUES The power factor in an electrical system varies with load and sometimes becomes lower than that desired. In such cases, the need to take steps to correct power factor arises. There are various techniques by which power factor of a system can be improved to a desired value. They are: i. Series Compensation ii. Shunt Compensation iii. Synchronous Condenser The above mentioned methods are conventional. Nowadays FACTS devices are used to improve transmission line capability and improve power factor of the system. FACTS stand for flexible AC transmission system. This paper discusses Shunt Compensation of transmission line using Static Var Compensation (SVC) TSC, TSC-TCR and fixed capacitors, techniques for power factor correction.

18 2.3.1 Series Compensation Series compensation is commonly used in high-voltage AC transmission systems. Series compensation increases power transmission capability, both steady state andtransient, of a transmission line. Since there is increasing opposition from the public to construction of EHV transmission lines, series capacitors are attractive for increasing the capabilities of transmission lines. Typical series compensation systems use capacitors to decrease the equivalent reactance of a power line at rated frequency. The connection of a series capacitor generates reactive power that, in a self-regulated manner, balances a fraction of the line's transfer reactance. The result is improved functionality of the power transmission system through: i) increased angular stability of the power corridor, ii) improved voltage stability of the corridor, iii) Optimized power sharing between parallel circuits. In the series compensation, either voltage source or current source can be connected in series with the power system to inject voltage or current respectively. This will help to compensate the reactive power present in the system. Figure 2 shows the single line diagram and the phasor diagram of an uncompensated transmission line. Here V 2 is taken as the reference voltage. Figure 3 shows the single line diagram and phasor diagram of the transmission line after a voltage source is connected in series with the line. With the appropriate value of V comp unity power factor can be obtained. Figure 2.Transmission system without compensation Figure 3. Transmission system with Series compensation with a voltage source. As mentioned earlier, the most common approach of using series compensation is to connect capacitor banks along with some protection device in series with the transmission line. But this method has many disadvantages. Connecting capacitors in series with the transmission line give

19 rise to subsynchronous resonance which may damage the generator shaft. Also some protection device must always be connected with the capacitors to protect the capacitors from high currents during the faults Shunt compensation Shunt compensation has been widely used in transmission system to regulate the voltage magnitude, improve the voltage quality, and enhance the system stability. Shunt-connected reactors are used to reduce the line over-voltages by consuming the reactive power, while shuntconnected capacitors are used to maintain the voltage levels by compensating the reactive power to transmission line. Other than connecting inductor or capacitors, voltage source and current source var generators can also be connected in parallel to the line. The main advantages of using voltage or current source VAR generators (instead of inductors or capacitors) is that the reactive power generated is independent of the voltage at the point of connection. Figure 4.Transmission system with compensation Figure 5. Transmission system with Series compensation with a voltage source Figure 4 shows the single line diagram and the phasor diagram of an uncompensated transmission line. Figure 5 shows the single line diagram and phasor diagram of the transmission line after a current source is connected in parallel with the line. The reactive current injected in the line is reducing the reactive power and helping in bringing power factor towards --unity Synchronous Condensers A synchronous condenser is a synchronous machine, the reactive-power output of which can be continuously controlled by varying its excitation current. When the synchronous machine is

20 connected to the ac system and is underexcited, it behaves like an inductor, absorbing reactive power from the ac system. However, when it is overexcited, it functions like a capacitor, injecting reactive power into the ac system. The machine is normally excited at the base current when its generated voltage equals the system voltage; it thus floats without exchanging reactive power with the system. A synchronous condenser is usually connected to the EHV ac system through a coupling transformer. After the unit is synchronized, the field current is adjusted to either generate or absorb reactive power as required by the ac system. The machine can provide continuous reactive power control when used with the proper automatic exciter circuit. Synchronous condensers have been used at both distribution and transmission voltage levels to improve stability and to maintain voltages within desired limits under varying load conditions and contingency situations. However synchronous condensers are rarely used today because of the drawbacks associated with it. As they are rotating devices, they require regular maintenance and become more expensive than equivalent-rating static compensators. In addition to it, they require substantial foundations and a significant amount of starting and protective equipment. They also contribute to the short circuit current and they cannot be controlled fast enough to compensate for rapid load changes. Moreover, their losses are much higher than those associated with static compensators, and the cost is much higher compared with static compensators FACTS Controllers FACTS can be defined as AC transmission systems incorporating power electronics-based and other static controllers to enhance controllability and increase power transfer capability. Similarly, a FACTS controller is defined as a power electronics-based system or other static equipment that provides control of one or more ac transmission parameters.they can be classified as the following. i. Series controllers. ii. Shunt controllers. iii. Combined series-shunt controllers Depending on the power electronics device used, FACTS controllers can also be divided into two categories viz. variable impedance type and voltage source convertor based. The series FACTS controllers are as follows i. Thyristor controlled series capacitor or compensator(tcsc) ii. Static synchronous series compensator(sssc) The shunt FACTS controllers are as follows i. Static var compensator(svc)

21 ii. Static synchronous compensator(statcom) The combined series- shunt FACTS controller is unified power flow controller (UPFC) which is a combination of SSSC and STATCOM. Out of these above mentioned controllers TCSC and SVC are variable impedance based controllers. Whereas SSSC, STATCOM and UPFC are the voltage source convertor based controllers Thyristor controlled series capacitor or compensator(tcsc) Series compensation is much more effective than shunt compensation. In shunt compensation, the point of injection of reactive power (mostly midpoint) plays a major role in the efficiency of the compensation. Proper care is needed to select the appropriate point of injection. Series compensation faces no such problem. The controller can be connected anywhere in the transmission line. In addition to this, series compensation increases power transmission capability, improves system stability, reduces system losses, improves voltage profile of the lines and optimize power flow between parallel lines. Using series capacitor alone gives rise to sub synchronous resonance. In order to avoid SSR and improve stability TCSC is used. TCSC is a capacitor with a thyristor controlled reactor connected in parallel to it, as shown in figure 6. This combination provides smoothly variable series capacitive reactance. Figure 6 Thyristor-controlled series capacitor (TCSC) The TCSC concept is that it uses an extremely simple main circuit. The capacitor is inserted directly in series with the transmission line and the thyristor-controlled inductor is mounted directly in parallel with the capacitor. Thus no interfacing equipment like e.g. high voltage

22 transformers is required. This makes TCSC much more economic than some other competing FACTS technologies. Thus it makes TCSC simple and easy to understand the operation. The thyristor controlled reactor (TCR) is a variable inductive reactor X L controlled by firing angle α. For the range of 0 to 90 of α, X L (α) start vary from actual reactance X L to infinity. This controlled reactor is connected across the series capacitor, so that the variable capacitive reactance (figure) is possible across the TCSC to modify the transmission line impedance. Figure 7 Figure shows the impedance characteristics curve of a TCSC device. It is drawn between effective reactance of TCSC and firing angle α. Net reactance of TCR, X L (α) is varied from its minimum value X L to maximum value infinity. Likewise effective reactance of TCSC starts increasing from TCR X L value to till occurrence of parallel resonance condition X L (α) = X C, theoretically X TCSC is infinity. This region is inductive region. Further increasing of X L (α) gives capacitive region, Starts decreasing from infinity point to minimum value of capacitive reactance X C. Thus, impedance characteristics of TCSC shows, both capacitive and inductive region are possible though varying firing angle (α). Figure 7.Impedance Vs Firing angle Characteristic Thyristor-controlled series capacitors (TCSC) can provide many benefits for a power system including controlling power flow in the line, damping power oscillations, and mitigating subsynchronous resonance Static var compensator(svc)

23 Static Var Compensator is a shunt connected static Var generator or absorber whose output is adjusted to exchange capacitive or inductive current so as to maintain or control specific parameters of the electrical power system (typically bus voltage). The var requirements in transmission lines swing from lagging to leading, depending on the load. Shunt compensation by capacitors and reactors is one way. However, it is slow, and power circuit breakers have to be de-rated for frequent switching duties. SVC obviate these limitations. SVC can be classified into following categories, also shown in figure 8. i. Thyristor-controlled reactor (TCR) ii. iii. iv. Thyristor-switched capacitor (TSC) Fixed capacitor and thyristor-controlled reactor (FC-TCR) Thyristor-switched capacitor (TSC) and thyristor-controlled reactor (TCR) Figure 8. Static VAR compensator(svc) TCR and TSR are both composed of a shunt-connected reactor controlled by two parallel, reverse-connected thyristors. TCR is controlled with proper firing angle input to operate in a continuous manner, while TSR is controlled without firing angle control which results in a step change in reactance. TSC shares similar composition and same operational mode as TSR, but the reactor is replaced by a capacitor. The reactance can only be either fully connected or fully disconnected zero due to the characteristic of capacitor.

24 With different combinations of TCR/TSR, TSC and fixed capacitors, a SVC can meet various requirements to absorb/supply reactive power from/to the transmission line. In this project three different SVC techniques are discussed. Those are i. Fixed capacitors ii. TSC iii. Combination of TSC and TCR Static synchronous compensator(statcom) It is a device connected in derivation, basically composed of a coupling transformer that serves of link between the electrical power systems (EPS) and the voltage synchronous controller (VSC) that generates the voltage wave comparing it to the one of the electric system to realize the exchange of reactive power. The control system of the STATCOM adjusts at each moment the inverse voltage so that the current injected in the network is in quadrature to the network voltage, in these conditions P=0 and Q=0. In its most general way, the STATCOMcan be modeled as a regulated voltage source V i connected to a voltage bar Vs through a transformer. Figure 9 shows a typical circuit of a STATCOM. Figure 9. Static synchronous compensator(statcom) Static synchronous series compensator (SSSC) Static Synchronous Series Compensator (SSSC), which is a solid-state voltage source inverter, injects an almost sinusoidal voltage, of variable magnitude, in series with a transmission line. Most of the injected voltage which is in quadrature with the line current emulates an inductive or

25 a capacitive reactance in series with the transmission line. This emulated variable reactance, inserted by the injected voltage source, influences the electric power flow in the transmission line. The reactance compensation controller is used to operate the inverter in such a way that the injected alternating voltage in series with the transmission line is proportional to the line current with the emulated reactance being the constant of proportionality. When an SSSC injects an alternating voltage leading the line current, it emulates an inductive reactance in series with the transmission line causing the power flow as well as the line current to decrease as the level of compensation increases and the SSSC is considered to be operating in an inductive mode. When an SSSC injects an alternating voltage lagging the line current, it emulates a capacitive reactance in series with the transmission line causing the power flow as well as the line current to increase as the level of compensation increases and the SSSC is considered to be operating in a capacitive mode. Figure 10. Static synchronous series compensator (SSSC) Unified Power Flow controller(upfc) UPFC is a combination of SSSC and STATCOM connected together by a common dc link provided by a dc storage capacitor. This arrangement functions as an ideal ac to ac power converter in which the real power can freely flow in either direction between the ac terminals of the two inverters and each inverter can independently generate (or absorb) reactive power at its own ac output terminal. The series converter of the UPFC injects via series transformer, an ac voltage with controllable magnitude and phase angle in series with the transmission line. The shunt converter supplies or absorbs the real power demanded by the series converter through the common dc link. Figure 11 shows the structure of UPFC, with SSSC in series with the line and STATCOM in parallel.

26 Figure 11. Unified power Flow Controller (UPFC) The basic function of the inverter connected in parallel (inverter 1) is to supply or absorb the real power demanded by the inverter connected in series to the ac system (inverter 2), at the common dc link. Inverter 1 can also generate or absorb controllable reactive power, if it is desired, and thereby it can provide independent shunt reactive compensation for the line. Hence it can control simultaneously or selectively, all the parameters affecting power flow in the transmission line. Also it can independently control both the real and reactive power flow in the line. CHAPTER SHUNT COMPENSATION USING FIXED CAPACITORS Shunt capacitors are employed in lagging power factor circuits to supply required amount of reactive power for maintaining the voltage. Fixed capacitors are connected in parallel (star or delta) with the load. It raises the power factor of the load by completely neutralizing the lagging reactive component of the load current. This results in significant reduction in losses and an improvement of power quality and stability. Figure 12 and 13 show a system with shunt compensation in star and delta connections respectively. This method is used in factories and industries because it is very economical, has low losses, requires little maintenance and can be easily installed.

27 Figure 12 Star connected Fixed capacitors Figure 13 Delta connected Fixed capacitors In a single phase or a three phase system, the capacitance required for compensation is calculated using the following formulas: The required capacitive kvar is given by- The Capacitance to be inserted in each phase for compensation is given by-..(2)..(3) Where, cos 1 is the existing power factor. cos 2 is the desired power factor. P is in kilowatts. V is the phase to ground voltage., f is supply frequency 3.2 STATIC VAR COMPENSATION In a power system, it is desirable to use a compensator which responds spontaneously to achieve effective improvement of voltage regulation and reactive power control, thus enhancing system stability. SVC has emerged as a reliable method for VAR generation and absorption to obtain high speed reactive power compensation. The various types of reactive power control elements that constitute a static Var system are: 1- Thyristor Controlled Reactor (TCR) 2- Thyristor Switched Capacitor(TSC) 3- TCR and Fixed Capacitor

28 4- TCR and TSC Figure 14 represents the SVC system with TSC, TCR and fixed capacitor connected in parallel. SVC can be understood as an inductor and a capacitor connected in parallel, both of which can absorb or generate variable reactive power respectively according to the demands of the system. The SVC regulation characteristics which are combined characteristics of both inductor and capacitor are shown in Figure 15. Figure 14 SVC system Fig 15 V-I characteristics of SVC Thyristor Switched Capacitor (TSC) The arrangement consists of a capacitor in series with a bidirectional thyristor pair for each phase as shown in figure 16. The TSCs can be switched on or off by controlling the firing angle of the thyristor pair. In three phase, TSC can be connected between line to neutral (Y) or line to line (Δ), while in single phase, TSC can be connected between the two line conductors. The advantage of TSC over TCR is that it does not generate harmonics and therefore does not require any filtering. The value of TSCs is chosen such that it generates leading vars to compensate the effect of the inductive load and to attain unity power factor.

29 Fig 16 Thyristor switched capacitor avoid transients during switching Fig 17 Conditions for firing of thyristors to To avoid heavy oscillatory currents during turning on of TSC, the firing angle of the thyristors should be carefully chosen. Therefore, TSC should be switched on/off when the applied voltage is at its peak. Also it is required that the capacitor should be pre-charged to the peak value of the applied voltage before switching. Failure to maintain these conditions results in generation of very large amplitude switching currents leading to overheating of thyristor and capacitor bank and harmonic distortion of the system. Figure 17 explains these conditions. At peak, dv/dt=0 which implies that current through capacitor i c /C is also zero thus causing heavy-current free switching Thyristor Controlled Reactor (TCR)

30 Figure 18 Thyristor Controlled Reactor (TCR) A Thyristor Controlled Reactor (TCR) is a reactance connected in series with a bidirectional thyristor valve of high Power and high Voltage thyristors which themselves are connected in series to obtain the necessary total voltage and current rating for the valve as shown in figure 18. when phase-angle control is used, a continuous range of reactive power consumption is obtained. It results, however, in the generation of odd harmonic current components during the control process. Full conduction is achieved with a gating angle of 90. Partial conduction is obtained with gating angles between 90 and 180, as shown in Fig. 19. By increasing the thyristor gating angle, the fundamental component of the current reactor is reduced. This is equivalent to increase the inductance, reducing the reactive power absorbed by the reactor. However, it should be pointed out that the change in the reactor current may only take place at discrete points of time, which means that adjustments cannot be made more frequently than once per half-cycle. Static compensators of the TCR type are characterized by the ability to perform continuous control, maximum delay of one half cycle and practically no transients. The principal disadvantages of this configuration are the generation of low frequency harmonic current components, and higher losses when working in the inductive region (i.e. absorbing reactive power). The relation between the fundamental component of reactor current and the phase shift angle or the firing angle α is given by: I = (2π 2α + sin 2α) (4) The voltage and current waveforms in a TCR for different thyristor phase-shift angles, α is shown in figure 19.

31 Figure 19 Voltage& Current Waveforms in a TCR for different thyristor phase shift angles. The Voltage current Characteristic of TCR is shown in figure 20. Figure 20 TCR Voltage Current Characteristics

32 3.2.3 Thyristor Switched Capacitor and Thyristor Controlled Reactor (TSC TCR) Figure 21 TSC TCR Circuit with control loop The Figure 21 shows the circuit diagram of Thyristor Switched Capacitor and Thyristor Controlled Reactor (TSC TCR) with the closed controlled loop. In the figure we can see the TSC and TCR are connected in parallel to each other the whole system shown above is connected in parallel to load and used to govern the power factor using the control of firing angles of the thyristor valve. The combination of TSC and TCR is together called as SVC system. The Figure 22 shows the operating characteristics of SVC. Consider the nominal bus voltage is Vn. If the system voltage is increased to V1 then the operating point of the SVC would be at A. Therefore, SVC absorbs reactive power equal to current I3 and the voltage decreased to V3 that is in standard restrict. If voltage of the system decreased to V2, operating point of the SVC would be point B and therefore, SVC generates reactive power equal to current I4. As you see, SVC enables us to control the voltage of the bus by generating or absorbing the reactive power that is reactive power management.

33 Figure 22 SVC V-I Characteristics The TSC is switched in using two thyristor switches (connected back to back) at the instant in a cycle when the voltage across valve is minimum and positive. This results in minimum switching transients. In steady state, TSC does not generate any harmonics. To switch off a TSC, the gate pulses are blocked and the thyristors turns off when the current through them fall below the holding currents. While in TCR, The thyristor valve is phase-controlled, this allows the value of delivered reactive power to be adjusted to meet varying system conditions. Thyristor-controlled reactors can be used for limiting voltage rises on lightly loaded transmission lines. The variation of current is obtained by the control of gate firing instant of the thyristors and can be continuously varied from zero (corresponding to zero conduction angle) to maximum (corresponding to conduction angle of 180) by phase control in which the firing angle α (w.r.t to zero crossing of voltage) is varied from 180 to 90. The fundamental current equation is shown in equation4 and the waveform is shown in figure 22.

34 3.3 DSPACE DSpace is the most widely-used digital repository software in the world. DSpace is the software of choice for academic, non-profit, and commercial organizations building open digital repositories. DSpace preserves and enables easy and open access to all types of digital content including text, images, moving images, mpegs and data sets. And with an ever-growing community of developers, committed to continuously expanding and improving the software, each DSpace installation benefits from the next. In our project we are using DSpace software and DS1104 board for interfacing hardware and software system. The DS1104 board is considered a platform on which a simulation is run, just as Matlab is also a platform to run non-real-time simulations on. They are both platforms that ControlDesk can interface to. ControlDesk is a userinterface. To create the software interface between the controller and the plant (i.e., the interface that generates control inputs and reads sensors values), the digital to analog conversion (DAC) blocks are provided in Simulink when the DSpace software is available. Hence we use a DAC block to generate the control input to the plant or the hardware system and an ADC block to read the voltage and current from the sensors. There are two ways to access the DSpace blocks that can be used in Simulink. First, they are listed by typing simulink in the Matlab command window which, via ControlDesk you access by right-clicking on the Simulink icon on the upper left corner when the Platform tab is selected. Another way to see the DSpace blocks, and the one that we will use in our project since it offers a few more features, is to type rti from the Matlab command window. The window shown in figure 23 is seen. Figure 23 RTI1104 Board Library

35 If we double-click on each of these blocks, we are going to find the blocks necessary to build the simulation that we need. The RTI1104 Board Library shown in figure 23 is divided into some main sections. The I/O resources of the DS1104 are split between the two processors on the board, the Master PPC (Power PC) and the Slave DSP F240. By clicking on either one we can have access to blocks we can place in the model that provide I/O functionality associated with the respective processor. In our project work we are using on Master PPC processor. When we double-click on the Master PPC then the window shown in figure 24 appears. Figure 24 RTI1104 Board Library Master PPC The window in figure 24 has some of the most commonly used elements for the controller board, such as ADCs, DACs, Encoders, etc. From these blocks we use the blocks which are suitable in the software model of our project. Load Voltage or supply voltage is given as input to the Matlab using DSpace. In the software part, the control loop to govern the thyristor valve of TSC is developed. The input voltage waveform is taken through ADC and it is then differentiated. When the slope of the input waveform is equal to zero and the load current is increased, a firing pulse is generated and given to the thyristors valve. The firing pulse is the output of the DSpace which is taken from digital input output port of the DSpace controller.

36 CHAPTER SIMULATION DESIGN The main of this project is to compensate the reactive power and bring the power factor towards unity. In order to achieve this, data is collected from a laboratory in VIT University. A one phase RL load system, present in the lab, is taken under study. Readings are taken after varying the load and the behavior of the power factor and reactive power is studied. Out of those readings, two load readings are taken to create the similar system in Matlab simulink. The compensation is done by three different SVC techniques and then the result is analyzed Uncompensated System A one phase 230 V 50 Hz supply is given to two different readings of loads. The ratings of the loads are shown in table1. At a time only one load is switched ON. For the first three second, load 1 is turned ON. After three seconds, load 1 is OFF and load 2 is turned ON. As can be seen in table 1, the power factor obtained by these loads is 0.62 and This value is very less for practical cases and increases losses in the system. Hence there is a need to improve the power factor. The waveforms of active power, reactive power, power factor and current for the uncompensated system are shown in figure. Figure 25 show the single line diagram of system under study and figure 26 shows the simulink model of the uncompensated system with RL load connected with 1 phase supply. The loads are connected to the supply through circuit breaker, which helps in properly connecting and disconnecting the loads whenever required. Specifications Load1 Load2 Voltage(rms) Frequency Active Power Reactive Power Power factor Figure 25. Single line diagram of Uncompensated System Table 1: Load ratings

37 Figure 26. Simulink model of Uncompensated System Compensation using Fixed Capacitor bank It can be seen from the study of uncompensated system that the power factor of the present system is very low which in turn make the system inefficient with huge losses. So to make the system more efficient, as one of the many techniques, capacitor bank are connected in parallel with the same system studied earlier. The turning ON of loads is th same as seen in uncompensated system. The capacitor banks are supplying the reactive power demanded by the loads and as a result overall reactive power of the system will decrease. This in turn increases the power factor and also makes the voltage more stable. The capacitor banks are connected to the system through circuit breakers whose opening and closing depends on the feedback loop provided in the system. So according to the amount of load present in the system the suitable no. of capacitor banks can be connected to the system to provide right amount of compensation. As the load increases, the load current also rises up. This load current is continuously monitored and used as the feedback condition to open or close the circuit breaker which connects the capacitor banks to the system. The current in the feedback loop is monitored using PID controller. The controller helps in reducing any error present, improves the system response and also helps in attaining steady state faster.

38 Figure 27 show the single line diagram of system under study and figure 4 shows the simulink model of the system with RL load connected with 1 phase supply with fixed capacitor banks in parallel. The waveforms of active power, reactive power, power factor and current for this system are shown in figure 28. Table 2 shows the readings as observed by the simulation results of the fixed compensated system. It can be seen clearly that the power factor of the loads is 0.79 and Also the reactive power of the system for load 1 came down from 215 var to 131var and that for load 2, it came down from 226 var to var. This clearly shows the improvement in the power factor and the compensation of reactive power achieved with the help of fixed capacitors. Figure 27. Single line diagram of compensated Specifications Load1 Load2 Voltage(rms) Current(rms) Active Power Reactive Power Power factor Table 2. Fixed Compensation results system with fixed capacitor banks Figure 28. Simulink model of Fixed capacitor compensated System

39 4.1.3 Compensation using thyristor switched capacitors(tsc) For the demonstration of the reactive power control using TSC a 1 phase system with RL load is taken under study. The specifications of the load present are given in table1. The connection of TSC in the system is represented by a single line diagram in figure 29. Here a setup of capacitor, whose switching is decided by anti-parallel connection of thyristors, is connected parallel to the loads. The capacitor is connected to the system through either of the thyristor based on the pattern of the input supply. The firing of the thyristors is controlled through a feedback circuit. The feedback circuit along with the full simulation model of TSC compensated system is shown in figure 30. As seen in the figure, in the feedback circuit the loads current and voltage are continuously monitored. At the time of switching of thyristors, the load current can be enormously high which can damage the entire setup. So it is important to fire the thyristors properly so that transient free switching can be obtained. In order to do so, the thyristors are fired at the peak of the load voltage because at this time current through inductor is minimum. Hence a proper switching is obtained. The feedback loop generates a firing pulse at the peak of the voltage that is to be given to the anti-parallel connection of thyristors. Also it monitors current level to decide the no. of TSCs to be switched ON at a time so that right amount of compensation can be obtained. The monitoring is done by PID controller which controls the error and improves system response. The results obtained during compensation using TSC are shown in table 3. It is clear from the table that the output obtained using fixed capacitor compensation are almost the same as that by using TSC. But using TSC gives transient free switching of capacitors as well as low harmonics. Specifications Load1 Load2 Voltage(rms) Current(rms) Active Power Reactive Power Power factor Figure 29. Single line diagram of compensated Table 3. TSC Compensation results system using TSC method

40 Figure 30. Simulink model of TSC compensated System Compensation using thyristor switched capacitors(tsc) and thyristor controlled reactor(tcr) Table 1 shows the specifications of the system under study for the demonstration of power factor improvement using the combination of thyristor switched capacitor (TSC) and thyristor switched reactor (TCR). Using TSC for compensation may give transient free and low harmonic results, but as the load increases this method becomes infeasible. As for increasing loads, to achieve reactive power control more and more capacitor banks has to be added to the system, which is impractical. TCR gives a controlled range of inductance for different firing angles. So a complete range on inductive reactive can be achieved using TCR based on the value of firing angle. On introducing TCR in parallel with the TSC, a range of both capacitive and inductive reactance is achieved. So without adding extra capacitor banks to the system, but adding TCR full compensation can be attained.

41 The firing of the TSC is same as in case of compensation using TSC alone. The load voltage and current is monitored using PID controller in the feedback loop and the firing pulse is obtained at the peak of the load voltage. TCR has varying firing angle which depends on the load current, load voltage and the value of reactor connected with the TCR leg. The relation between all these is discussed earlier. The connection of TSC and TCR in the system is represented by a single line diagram in figure 31. The simulink model of this system is shown in figure 32. As shown in figure, from the given relation of the firing angle with load current and voltage, the different firing angles are obtained and at those angles firing pulse is generated to trigger the thyristors of TCR leg. The results obtained are shown in table 4. It is clear that just by adding TCR to the present TSC the power factor raised from 0.79 with TSC to 0.90 with TSC and TCR for the first load and 0.90 with TSC to 0.94 in TSC and TCR. Figure 31. Single line diagram of compensated system using TSC-TCR method Specifications Load1 Load2 Voltage(rms) Current(rms) Active Power Reactive Power Power factor Table 4. TSC-TCR Compensation results

42 Figure 32. Simulink model of TSC-TCR compensated System 4.2 ANALYSIS OF SIMULATION RESULTS It is observed that all the compensation techniques are successfully improving the power factor and decreasing the reactive power. Each of their reach is different from one another. Compensation with fixed capacitor bank and with TSC has almost the same results while the improvement of power factor through combination of TCS-TCR, used as compensation technique, is best among the three techniques used. The graph depicting their performance is as shown. Figure 33 shows the graph of uncompensated system. As it can be observed that power factor in this case is 0.62 for the first load and 0.79 for the second load. The change of load value is taking place at 3 seconds in the simulation. The reactive power for first and second load is 215 var and 226 var respectively. The power factor at this stage is clearly very low and needs to be improved.

43 Figure 33. Simulink results of Uncompensated System To make the present uncompensated more efficient with less losses, different SVC techniques are used. Figure 34 shows the simulink graphs of the system compensated by fixed capacitor banks. The figure shows the load current, load voltage, active and reactive power flow in the system and the power factor. It can be observed that now the power factor of the system is increased to 0.79 for the first load and 0.9 for the second load. Also the reactive power is reduced 215 var to 131 var in case of first load and 226 var to 142 var in case of second load. Hence the compensation is successfully achieved to some extent. Here the reach of improvement depends upon the value of capacitor bank used. More the capacitance more will be the compensation. But on further increment in capacitor can lead to leading power factor and the value of the power factor will decrease again. The System will become capacitive in nature. So the capacitance of the capacitor banks connected should only be up to an optimum value.

44 Figure 34. Simulink results of fixed capacitor compensated System Figure 35 shows the simulink graphs of the system compensated by thyristor switched capacitors(tsc). The figure shows the load current, load voltage, active and reactive power flow in the system and the power factor after the compensation is being done. Figure 35. Simulink results of TSC compensated System It can be observed that now the power factor of the system is increased to 0.79 for the first load and 0.9 for the second load. Also the reactive power is reduced 215 var to 131 var in case of first load and 226 var to 142 var in case of second load. Hence the compensation is successfully achieved to some extent.

45 Next SVC technique used is combination of TSC and TCR in the system. The graphs showing the results of this compensation technique is shown in figure 36. The figure shows the load current, load voltage, active and reactive power flow and the power factor of the system after connecting TSC and TCR in parallel to the system. Fig. 36 Simulink results of TSC-TCR compensated System It is clear from the figure that the results obtained from the combination of TSC and TCR for compensation is the best. 4.3 COMPARISON BETWEEN DIFFERENT SVC DEVICES Further comparison of results and analysis of the different techniques used can be made easily through table 5 shown below. For the same amount of load as mentioned in table 1, the power factor obtained through all the three techniques are shown in the table 5. Also for different value of capacitance results are compared. It can be seen that compensation through fixed capacitors and through TSC yields almost the same results. But in TSC, harmonics are reduced and transient free switching is obtained. Whereas the results obtained through the combination of TSC and TCR give the best results. This technique has all the advantages of TSC in addition to the fact that with same amount of capacitance; the compensation obtained is even more than that given by TSC with more capacitance.

46 TABLE 5 Comparison between different SVC techniques Capacitor Value Uncompensated load power factor Power Factor achieved through different SVC devices Without capacitor FC TSC TSC-TCR Load 1 Load 2 Load 1 Load 2 Load 1 Load 2 Load 1 Load 2 2.5µF µF µF HARDWARE DESIGN A small laboratory setup is considered to conduct the project in a laboratory in VIT University. A 1 phase 230 V 50 Hz supply was given to a 1 phase variable RL load. And readings are obtained for both uncompensated system and compensated system by varying the load. Figure 38 shows the laboratory setup with 1phase supply and RL load present. Table 6 represents the data of an uncompensated system obtained by variation of inductive load. The table also shows the required amount of capacitance to be added to the corresponding load in order to bring the power factor to unity. Vs (in V) I (in A) Phi (in ⁰) Power factor P (in kw) Q (in kvar) C (in µf) Table 6. Load data of an uncompensated system The results are viewed in an energy meter. For one condition of load for uncompensated system, the readings in the energy meter along with the voltage and current phasors are shown in figure A. In the reading shown in figure 37, the RL load is maximum and the power factor obtained is All the other readings are obtained in similar manner and the result is verified through software.

47 Figure 37. Energy meter reading for uncompensated system Compensation using Fixed Capacitors Figure38. Laboratory setup with compensation using fixed capacitors

48 Figure 38 shows the laboratory setup of a system compensated by using fixed capacitors. Here, 2 capacitors of 2.5µ each are taken as fixed capacitors to compensate the reactive power demanded by the load. The capacitors are connected in parallel with the RL load and 1 phase 230V 50Hz supply is given to the system. Different readings are then obtained by varying the RL load. One set of reading for a particular value of load, as observed in the energy meter in shown in figure 39. In this case, the RL load is maximum same as in case of figure 37. Here the power factor obtained after connecting 5µF capacitors is Thus the power factor is improved from 0.60 in case of uncompensated system to 0.77 with the help of fixed capacitors. Figure 39. Energy meter reading for fixed capacitor compensated system Table 7 shows the results obtained by varying RL load in case of compensation through fixed capacitors. The results are also verified in Simulink. Vs (in V) I (in A) Phi (In ⁰) Power factor P (in kw) Q (in kvar) µF µF µF µF Table 7. Load data of system compensated using fixed capacitors C

49 4.4.2 Compensation using SVC Figure 40 Laboratory setup Hardware setup consists of TSC only. The hardware setup done in laboratory and is shown in figure 40. The setup of TSC is made permanent in a Dot Board. As we can observe in the figure 41, the whole hardware setup is made permanent on a wooden board. The setup consists of 2 1X1 wooden board. Figure 41. Permanent setup of SVC

50 The first wooden board consists of 3 capacitors of 2.5 µf each; voltage and current transducer with rectifier circuit (i.e. circuit in the Printed Circuit Board) and anti-parallel connected thyristor (combined together in a dot Board) are all together clamped in a wooden board (as seen in figure 41). To make the necessary connections between the above mentioned elements banana connectors are used. Another board consists of a transformer, 4 set of opto-coupler and banana connectors to connect the input of the opto-coupler from dspace and output of the otpo-coupler to thyristor gates. The pulse to trigger the thyristors in Thyristor Switched Capacitor is generated in MATLAB Simulink and interfaced to the hardware model through dspace. The input given to the dspace through ADC or the output of the Voltage and current transducer is shown in figure 42. Figure 42 Output from Sensors. (Voltage Blue, Current Pink)

51 Figure 43 Simulink Model to generate firing pulses for thyristor valves Figure 44 Firing Pulse