Pll based shunt active harmonic filter to compensate multiple non linear loads
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Pll based shunt active harmonic filter to compensate multiple non linear loads

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  • 1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 198 PLL BASED SHUNT ACTIVE HARMONIC FILTER TO COMPENSATE MULTIPLE NON-LINEAR LOADS Smt. Smita Singhai Govt. Engineering College Sejbahar, Raipur(C.G.) INDIA-492015 Prof. Bharti Dewani Asst. Prof. DIMAT Raipur(C.G., India) ABSTRACT In this paper, three phase shunt active power filter is given for compensating multiple non- linear loads. The circuit models a standard shunt AHF with IGBT inverter and series inductor on the AC side and DC capacitor energization. The AHF uses a PLL to generate a reference sinusoidal source current which is in-phase and has the same RMS gain as the load current. Current control is implemented through feedback modulation of a dynamic hysteresis band PWM controller. The shunt line current tracks the reference current within a hysteresis band. By comparing the reference currents calculated by the controller with the measured values of compensation currents, the command signals for the inverter semiconductor switches can be produced. Keywords: Shunt AHF, IGBT inverter, Series Inductor, PLL(phase locked loop), Hysteresis Switching, Non-linear Load, Harmonics. 1. INTRODUCTION Nonlinear loads cause voltage and current waveforms distortion in the ac power network. It results in harmonic related problems including substantially higher transformer and line losses, reactive power and resonance problems, over-voltages, over-heating, Electro Magnetic Interference (EMI) problems, and other undesirable effects. The result is reducing system stability [1]-[3]. Passive filters alone have been traditionally used to eliminate the harmonics in utilities due to their low cost and high efficiency. Shunt-connected passive filters, tuned to show low impedances at different dominant harmonic frequencies, are widely used. Conventionally passive L-C filters were used to reduce harmonics and capacitors were used to improve the power factor of the ac loads. However, passive filters have the demerits of fixed compensation, large size, and resonance. Including all these INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET) ISSN 0976 – 6464(Print) ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August, 2013, pp. 198-205 © IAEME: www.iaeme.com/ijecet.asp Journal Impact Factor (2013): 5.8896 (Calculated by GISI) www.jifactor.com IJECET © I A E M E
  • 2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 199 drawbacks, these filters also generate fixed quantity of reactive power at fundamental frequency affecting sometimes the voltage regulation at the PCC. Active filters were developed to mitigate problems of passive filters. Shunt Active Filters are used for compensating current harmonics. Series Active Filters are used for compensating voltage harmonics. They are more effective in harmonic compensation and improved system performance. But using only active filters is a very expensive solution because it requires comparatively high power converter ratings. Hybrid Active Filter (HAF) topologies which combine the advantages of both active and passive filters [4]-[6] is more appealing in terms of cost and performance. They are cost-effective by reducing the KVA rating of the active filter as much as possible while offering harmonic isolation and voltage regulation [5]. Two kinds of hybrid active filters have been developed: a hybrid series active filter and a shunt hybrid active filter. To compensate for both current and voltage system harmonics, a shunt and series active filter configuration must be used respectively. Integrating this filter serves to eliminate load harmonics whilst ensuring the supply remains fundamental. For harmonic elimination, active filter can be classified on the basis of various control technique- open loop system & closed loop system. Open- loop systems sense the load current and the harmonics it contains. They inject a fixed amount of power in the form of current (mainly reactive) into the system, which may compensate for most of the harmonics and/or reactive power available. No reference current is required for this type Closed loop control systems incorporate a feedback loop providing greater accuracy of current injection for harmonic compensation as well as reactive power reduction well over open loop system [7]-[10]. There is reference variable to check the performance and accuracy of the filter.[11-18] 2. ACTIVE HARMONIC FILTER Proposed methodology uses a combination of a grid current forcing shunt APF with a series reactor installed at the Point of Common Coupling (PCC) to handle the harmonic and unbalance problems from mixed loads. [20] The three-phase shunt active power filter is a three-phase current controlled “voltage-source inverter” (CC-VSI) with a mid-point earthed, split capacitor in the dc bus and inductors in the ac output (It is essentially three independent single phase inverters with a common dc bus). Figure 1. Proposed Active Power Filter Configuration
  • 3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 200 The circuit models a shunt AHF with IGBT inverter and series inductor on the AC side and DC capacitor energization. The load consists of two diode rectifiers which are phase-shifted by 30 degrees. The Delta-Y connected rectifier is connected after 10 cycles to change the load from 6-pulse to 12-pulse. The AHF uses a PLL to generate a reference sinusoidal source current which is in-phase and has the same RMS gain as the load current. The current error between the load current and the reference current is generated by the IGBT Bridge through hysteresis switching. The AHF aims to inject this current error at the point of common coupling in order to match the source current as closely as possible with the reference current. 3. PLL (PHASE LOCKED LOOP) Three different types of harmonic detection strategies used to determine the current reference for the active filter. These are- 1. Measuring the load harmonic current to be compensated and using this as a reference command; 2. Measuring source harmonic current and controlling the filter to minimize it; and 3. Measuring harmonic voltage at the active filter point of common coupling (PCC) and controlling the filter to minimize the voltage distortion. Proposed methodology involves measurement of the load current and subsequent extraction of its harmonic content. The harmonic components, so extracted, are adjusted for polarity and used as reference commands for the current controller. For estimation of reference current various techniques are used- High pass filter method, Low pass filter method, Time domain approaches- Instantaneous reactive power algorithm, Synchronous detection algorithm, Constant active power algorithm, Constant power factor algorithm, Fictitious power compensation algorithm, Synchronous frame based algorithm, Synchronous flux detection algorithm, Frequency domain approaches- Conventional Fourier and FFT algorithms Sine multiplication technique, Modified Fourier series techniques. Proposed methodology uses PLL (phase Locked loop) and hysteresis switching for estimation of reference current.[12] Let the load current, input frequency and terminal voltage be the input to the PLL. Three phase distorted supply voltages are sensed and given to the PLL which generates sine terms. The sensed supply voltage is multiplied with a suitable value of gain before being given as an input to the PLL. Here K=1…N, be the gain value assigned for controlling. Figure 2: Proposed reference signal generation (PLL)
  • 4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 201 Here IL is the load current VT is the load voltage, ω is the output signal of the adaptive detecting circuit; and f is the fundamental reference frequency which is in phase with ac source voltage. As the input sinusoidal reference signal, i.e. the fundamental component of the system voltage has the same frequency and in phase with the desired fundamental components of load current and load voltage, the dc component of the output of integrator will tune accordingly until they are equal in magnitude. The corresponding fundamental real components of the current and voltage are then extracted from the sampled load current and load voltage. The output signal of the adaptive detecting current and voltage are just the reactive power and harmonic components of the nonlinear load voltage and current. 4. HYSTERESIS SWITCHING Current control is implemented through feedback modulation of a dynamic hysteresis band PWM controller. The shunt line current tracks the reference current within a hysteresis band. By comparing the reference currents calculated by the controller with the measured values of compensation currents, the command signals for the inverter semiconductor switches can be produced. Figure 3: Proposed hysteresis controller In proposed methodology, the load current, and the current of active filter be the input to the shunt firing unit. The gate signal obtained from this unit is the input to the IGBT. Thus obtaining gate signal by means of hysteresis current controlling technique is performed. The gate signal is obtained by means of using hysteresis current controlling technique. To detect the current to be compensated, reference current should be obtained. PLL value is improved by means of RMS value of load current. 4. SIMULATION RESULTS Simulation is carried out on a Matlab /Simulink software.[19] Figure 4 represents the simulation model. Harmonics generated by non-linear loads is removed by PLL based Shunt Active Power Filter. Proposed model not only considers the harmonics due to non-linear load but it also considers the disturbance occurs in supply. In this simulation the input current wave shape is non- sinusoidal which represents unbalanced supply. Simulation time is 0.25 seconds. Figure 5 (figure 5.1 to 5.6) shows the Simulation Results. Table 1 shows experimental & simulation parameters.
  • 5. International Journal of Electronics and Communication 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July Table 1: SAPF Experimental and Simulation Parameters Figure 4. Simulation Model of Shunt Power Figure 5.1 3 phase source current waveform S.No. Source Voltage Frequency Load Two Diode Rectifiers International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 202 SAPF Experimental and Simulation Parameters Simulation Model of Shunt Power Active Filter phase source current waveform Figure 5.2 V-DC BUS voltage waveform Parameters Value Voltage Vabc 4160*sqrt(2)/sqrt(3) Frequency F 50Hz Two Diode Rectifiers Resistance 1*10-3 ohms Snubber Resistance 1x103 ohms Snubber Capacitance 1x10-6 ohms Engineering & Technology (IJECET), ISSN August (2013), © IAEME voltage waveform
  • 6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 203 Figure 5.3 V-DC BUS LOAD2 voltage Figure 5.4 3 phase injected current Waveform Waveform Figure 5.5 3 phase Reference current waveform Figure 5.6 3 phase load current of of AHF Waveform Figure 5. Simulation Results 5. DISCUSSION In this Project Shunt active power filter is used to compensate current harmonics by providing same-but-reverse harmonic compensating current. Hence the shunt active power filter now operates as a current source providing the harmonic components generated by the load but the phase
  • 7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 204 is shifted now by 180o . This phenomenon is for all type of loads considered in a harmonic source. Moreover, with an efficient control scheme, the active power filter can also compensate the load power factor. By this, the power distribution system can see the non linear load and the active power filter as an ideal resistor. To order to present the compensation for harmonic voltage sources, a simulation model can be presented via facilitating the circuit constants based on a three phase ac system. For obtaining harmonic free supply at load end, PLL (phase locked loop) & harmonic switching is used. A PLL is feedback system that fixes relation between output clock phase and input clock phase. Actually phase of both input signal and output signal are synchronized or locked, hence name called “Phase Locked Loop”. The hysteresis band current control technique has been proven to be the most suitable technique for all the applications of current controlled voltage source inverters in the active power filters. The hysteresis band current control is characterized by its unconditioned stability, high speed response, and valid accuracy. Simulation results, this system provides unity power factor operation of non-linear loads with harmonic current sources, harmonic voltage sources, reactive, and unbalanced components. 5. CONCLUSION This project proposes the implementation of a three-phase active power filter together with a decoupling reactor in series with the load operated to directly control the ac grid current to be sinusoidal and in phase with the grid voltage. From the simulation results, this system provides unity power factor operation of non-linear loads with harmonic current sources, harmonic voltage sources, reactive, and unbalanced components. 6. ACKNOWLEDGEMENT The authors owe a great deal of sincere thanks to all of those involved, directly or indirectly, in the preparation of this research paper. 7. REFERENCES 1. M. El-Habrouk, M.K. Darwish and P. Mehta, “Active Power Filter: A Review,” IEEE Proc. Electr.Power.Appl, pp. 403-413, Sept 2000 2. B. Singh, K. Al-Haddad and A. Chandra, “A Review of Active Filter for Power Quality Improvements,” IEEE Trans. on Industrial Electronics, pp. 960-971, Feb 1999 3. Fang Zheng Peng, “Harmonic Sources and Filtering Approaches,” IEEE Industry Applications Magazine, pp. 18-25, July 2001 4. Fang Zheng Peng, “Application issues of Active Power Filters,” IEEE Industry Applications Magazine, pp. 21-30, Sept 1998 5. H.L. Jou, “Performance Comparison of the Three-phase Active-power-filter Algorithms,” IEE Proc. Gener. Trans. Distrib., pp. 646-652, Nov 1995 6. Adil M. Al-Zamil and D.A Torrey, “A Passive Series, Active Shunt Filter for High Power Applications,” IEEE Trans. on Power Electronics, pp. 101-109, January 2001 7. L. Borle, “Method and control circuit for a switching regulator”, U.S. Patent US5801517, granted 1-September-1998 8. L. Borle and C. V. Nayar, “Ramptime Current Control”, IEEE Applied Power Electronics Conference (APEC’96), March 1996, pp 828-834. 9. L. Borle and C. V. Nayar, “Ramptime Current Control”, IEEE Applied Power Electronics Conference (APEC’96), March, 1996, pp 828-834.
  • 8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 205 10. S. Rahmani, Ab. Hamadi, Student Member IEEE, and K. Al-Haddad, Fellow IEEE “A New Combination of Shunt Hybrid Power Filter and Thyristor Controlled Reactor for Harmonics and Reactive Power Compensation” 2009 IEEE Electrical Power & Energy Conference. 11. Hirofumi Akagi, Fellow, IEEE, and Ryota Kondo, “ A Transformerless Hybrid Active Filter Using a Three-Level Pulsewidth Modulation (PWM) Converter for a Medium-Voltage Motor Drive” IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 25, NO. 6, JUNE 2010 12. ZHENG Jiakun, MENG Chao, LI Po, HONG Yongqiang, “The Study of Transformerless Shunt Hybrid Active Power Filter Compensation for Unbalanced Load” 2012 IEEE 7th International Power Electronics and Motion Control Conference - ECCE Asia June 2-5, 2012, Harbin, China. 13. Ab. Hamadi, S. Rahmani, Member IEEE, and K. Al-Haddad, Fellow member IEEE “A Novel Hybrid Series Active Filter for Power”, pp 1100-1104 , 2005 14. R. D. Patidarl, Student Member, IEEE and S. P. Singh, “A Fast Acting 1/z Controller for Shunt Active Filter Operation for Harmonics and Reactive Power Compensation” 2008 IEEE Region 10 Colloquium and the Third International Conference on Industrial and Information Systems, Kharagpur, INDIA December 8 -10, 2008. 15. M.asadi, A.Jalilian, H.F.Farahani, “Compensation of unbalanced non linear load and neutral current using stationary reference frame in shunt active filters” , 2010 IEEE. 16. Jeeva S. Pridaaa1, P Tamizharasi2 and J. Baskaran3, “Implementation of Synchronous Reference Frame Strategy based Shunt Active Filter” IEEE 2011 17. Prof.Lathika, B.S Ms.Sreedevi.G. Dr.S.Rama Iyer, “HYBRID POWER FILTER” 2008 Australasian Universities Power Engineering Conference (AUPEC'08) 18. D.Mohan , P.Ganesan, “HARMONIC COMPENSATION USING ELEVEN LEVEL SHUNT ACTIVE FILTER”, 2010 Second International conference on Computing, Communication and Networking Technologies 19. Om Nayak, Surya Santoso, and Paul Buchanan. Power electronics spark new simulation challenges. IEEE Computer Applications in Power, 15(4):37-44, October 2002 20. JenoPaul P, Ruban Deva Prakash T, JacobRaglend Electrical & Electronics Engineering Nooral Islam University, Tamilnadu, “Adaptive PLL controller based shunt Active Filter for power quality improvement in Matrix converter” International Journal of Applied Engineering Research, DINDIGUL Vol 1,No 4, 2011. 21. Anuradha Tomar and Dr. Yog Raj Sood , “All About Harmonics in Non-Linear PWM AC Drives”, International Journal of Electrical Engineering & Technology (IJEET), Volume 3, Issue 1, 2012, pp. 138 - 144, ISSN Print : 0976-6545, ISSN Online: 0976-6553. 22. Abhijit D. Ghorapade and Snehal S. Mule, “Simulation of IGBT Based Speed Control System for Induction Motor using Fuzzy Logic”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 3, 2013, pp. 282 - 291, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. 23. Dr. Leena G, Bharti Thakur, Vinod Kumar and Aasha Chauhan, “Fuzzy Controller Based Current Harmonics Suppression using Shunt Active Filter with PWM Technique”, International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 1, 2013, pp. 162 - 170, ISSN Print : 0976-6545, ISSN Online: 0976-6553.