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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING & 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME TECHNOLOGY (IJEET) ISSN 0976 – 6545(Print) ISSN 0976 – 6553(Online) IJEET Volume 4, Issue 4, July-August (2013), pp. 245-254 © IAEME: www.iaeme.com/ijeet.asp Journal Impact Factor (2013): 5.5028 (Calculated by GISI) ©IAEME www.jifactor.com THREE PHASE SHUNT ACTIVE FILTER WITH CONSTANT INSTANTANEOUS POWER CONTROL STRATEGY * Mr.R.J.Motiyani1, *Mr.A.P.Desai2 1 Department of Electrical Engineering, S.N.Patel Intitute of Technology & Research Centre, Umrakh, Surat, India 2 Department of Electrical Engineering, S.N.Patel Intitute of Technology & Research, Centre, Umrakh, Surat, India ABSTRACT This paper discusses development of the matlab simulation of three-phase shunt active filter for non-linear rectifier load with constant instantaneous power control strategy. The shunt active filter with constant instantaneous power control strategy compensates the oscillating real and reactive power of the nonlinear load; it guarantees that only a constant real power p (average real power of load) is drawn from the power system. Therefore, the constant instantaneous power control strategy provides optimal compensation from a power flow point of view even under non-sinusoidal or unbalanced system voltages. Keywords: Pulse Width Modulation (PWM) converter, Generalized Fryze current control strategy. 1. INTRODUCTION The Shunt Active Filters generally consist of two distinct main Block; The PWM converter The active controller The PWM converter is responsible for power processing in synthesizing the compensating current that should be drawn from the power system. The active filter controller is responsible for signal processing [2]. It determines the instantaneous compensating current reference in real time which is continuously passed to the PWM converter. Fig.1 shows the basic configuration of a shunt active filter for harmonic current compensation of a specific load. 245 International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME i s i L i C L V i L * i C Fig.1 Basic configuration of a shunt active filter 2. ACTIVE FILTER CONTROLLERS The control algorithm implemented in the controller of the shunt filter determines the compensation characteristics of the shunt active filter. There are many ways to design a control algorithm for active filtering. Certainly; the p-q theory forms a very efficient basis for active filter controllers [2]. Following are the different control strategies: • Constant instantaneous power control • Sinusoidal current control • Generalized Fryze current control 3. ACTIVE FILTERS FOR CONSTANT POWER COMPENSATION The constant power compensation control strategy for a shunt active filter was the first development based on the p-q theory and was introduced by Akagi et al.in 1983[1].The principle of this compensation method are described in fig.1.In terms of real and reactive power, in order to draw a constant instantaneous power from the source, the shunt filter should be installed as close as % possible to the nonlinear load. It should compensate the oscillating real power p of this load [3]. Hence, the shunt active filter should supply the oscillating portion of the instantaneous active current of the load, that is, Oscillating portion of instantaneous active current on the α axis i α p ; % = vα (− p ) % iα % p 2 2 vα + v β 1 246 International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME Oscillating portion of instantaneous active current on the β axis i β p ; % = v β (− p ) iβ % p 2 % 2 vα +vβ 2 The reason for adding a negative sign to the real power in the above equations is to match them with the current directions adopted in fig.2. If the shunt active filter draws a current that produces exactly oscillating power ( − p ) of load. The power system would supply only constant % portion of real power ( p ) of load. In order to compensate oscillating power ( − p ), which implies an % oscillating flow of energy, the dc capacitor of the PWM converter must be made large enough to behave as energy storage element, to avoid large voltage variations. Following the instantaneous reactive current i aq and i β q on α and β axis. Instantaneous reactive current on the α axis i aq = v α (−q ) iα q 2 2 vα + v β 3 Instantaneous reactive current on the β axis iβ q = −v α (−q ) iβ q 2 2 vα + v β 4 Note that the total reactive power being compensated is − q = − q − q . The reason for the % negative sign is the same as explain for the real oscillating power compensation. Contrarily for compensation of oscillating power ( − p ), compensation of the total reactive power ( −q ) does not % require any energy storage element. If the shunt active filter compensates the oscillating real and reactive power of the load, it guarantees that only a constant real power p (average real power of load) is drawn from the power system. Therefore, the constant instantaneous power control strategy provides optimal compensation from a power flow point of view, even under non-sinusoidal or unbalanced system voltages [2]. 4. CONTROL BLOCK DIAGRAM Fig.2 shows control block of constant instantaneous power strategy of three phase shunt active filter. Three phase instantaneous voltages and currents phases of balanced or unbalanced source in the abc-reference frame is converted into instantaneous voltages and currents on the αβ 0 - axis [7].The Clarke Transformation and its inverse transformation of three-generic voltages are given by, 247 International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME 1 1 v 1 − − v a v v α 2 α a 2 2 v = v v b v β 3 3 3 b β p = vαiα + v β i β v c 0 2 − 2 v c i a 1 1 i α q = v β i α − vα i β i 1 − − i a b i α 2 2 2 i β i c = i i β 3 3 3 b 0 2 − 2 i c p q + + + p V ref − p loss V DC −1 p+ p % loss −q * i * i ca vα * − p + p i cα = 2 1 2 v α v β % cα * 1 0 * i * 2 1 i * loss i * v 3 i cα ca cb * v + v v β −v α − q cβ − i cβ α β β i cb = * * * 3 2 2 i cβ i cc i cc − 1 − 3 2 2 Fig.2 Control block for the constant instantaneous power control strategy 1 1 1 2 2 2 v v 0 2 1 1 a v α = 1 − − v b 5 3 2 2 v β 3 3 v c 0 − 2 2 248 International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME 1 1 0 2 v a v 2 1 1 3 0 v b = − 2 v α 6 3 2 2 v vβ c 1 1 3 − − 2 2 2 Similarly,three-phase generic instaneous line currents, i i a b and i c can be transformed on the αβ 0 axes by 1 1 1 2 2 2 i i 0 2 1 1 a i α = 1 − − i b 7 3 2 2 i β 3 3 i c 0 − 2 2 and its inverse transformation is 1 1 0 2 i a i 2 1 1 3 0 i b = 3 2 − 2 2 i α i iβ c 1 1 3 − − 2 2 2 8 One advantage of applying the αβ 0 thransformation is to separate zero-sequence components from the abc-phase componets.As per p-q Theory,it is defined in three-phase systems with or without a neutral conductor.Three instantaneous powers-the instantaneous zero-sequence power p ,the instantanous real power p ,and the instantanous phase voltages and line currents on the 0 αβ 0 axies as p 0 i 0 0 v 0 0 p =0 vα v β i α 9 q 0 vβ − v α i β These two powers have constant values and a superposition of oscillating compoents.Therefore,it is insteresting to separate p and q into two parts: 249 International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME Real power: p= p+ p % Imaginary power: q = q + q % Averege Oscillating powers powers A dc voltage regulator should be added to control strategying a real implementation as shown in fig.2.In fact, a small amount of average real power( p loss ) must be drawn contiously from the power system to supply switching and ohmic losses in the PWM converter.Otherwise,this energy would be supplied by dc capacitor which would dicharge contiously.The power converter of the shunt active filter is a boot-type converter.It means that the dc voltage must be kept higher than the peak value of the ac-bus voltage in order to guarantee the controllability of the PWM current control.Fig.2 suggests that the real power of the nonlinear load should contiously measured and % separated into its average real power ( p ) and oscillating ( P ) parts.This would be the fuction of the block named “selection of the powers to be compensated” .In a real implementation,the sepation of % p and P from p is realized through a low-pass filter. Reference currrents i *C a , i * b and i* for C Cc switching of IGBTs’PWM invetor is found from inverse Clarke Transformation.The switching pattens of IGBT’s are found by comparing of reference currents and contionously sensed currents from lines. 5. SIMULATION V Id Discrete, Ts = 5e-005 s. pulses Goto1 Vabc Scope2 powergui Rectifier measurements Control A Scope + A A i B B B + - C C - C Current Measurement Three-Phase Parallel RLC Branch rectifier A Vabc h A neutral B Iabc I C Goto B a SOURCE b C c Three-Phase Ground2 V-I Measurement Conn1 + v Conn3 - Scope3 Voltage Measurement1 Conn5 Scope5 A a Subsystem1 In1 B b B C c A Subsystem2 Three-Phase Breaker GROUND C SHUNT ACTIVE FILTER Subsystem i + - Current Measurement1 Scope1 Ground1 Fig.3 Matlab simulation of shunt active filter supplying non-linear load of rectifier with constant instantaneous power control strategy 250 International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME 1 i ref g 1 2 im eas Fig.4 Subsystem of hysterisis block -K- Gain -K- 2 -K- Gain8 Ialpha Gain1 -K- Gain2 3 1 -K- Ibeta Gain3 Gain9 -.5 Gain4 1 Vabc -.5 Gain5 1 -K- I0 -K- Gain6 Gain10 -K- Gain7 Fig.5 Subsystem of Clarke Transformation block 6. TESTS AND RESULTS Results of Matlab simulation shown in fig.3 of three shunt active filter supplying non-linear load of rectifier with constant instantaneous power control strategy are shown as following figures. Input source of this simulation is used as three phase programmable voltage source which parameters (voltage=220 V (line to line), frequency=50Hz) with internal resistance as RCL series branch with resistance r=0.1ohm and inductance of 0.000010H.Line between source and load as non liner load as three phase rectifier with RL circuit is of inductance of L=0.4mH.Matab simulation has non-linear load as three phase rectifier with RL circuit which parameters are r=20 ohm and L= 0.4mH.Fig.6 shows voltage with value of aprroximate180 volt applied to three phase rectifier from lines from source voltages. Fig.7 shows the load current per phase of nonlinear three rectifier with RL load. Balanced or unbalance source can supplied with three phase active filter with constant instantaneous power control strategy to non linear load as shown Fig. 8 the constant average active power(P) and reactive power (Q) of non linear rectifier with RL load. Fig.9 shows the load current per phase of nonlinear three rectifiers’ circuit.Fig.10 and 11 show output voltage and current of three phase rectifier circuit supplied to RL Load. 251 International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME Fig.6 Load 3-phase voltages or input voltages of three rectifier supplied RL Circuit Fig. 7 Load current per phase of Non linear three rectifier with RL load Fig. 8 Constant Active Power (P) and reactive power (Q) of Non linear three rectifier with RL load Fig. 9 Load currents or input currents of Non linear three rectifier with RL load 252 International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 4, July-August (2013), © IAEME Fig. 10 Output voltage of three phase rectifier circuit supplied to RL Load Fig.11 Output current of three phase rectifier circuit supplied to RL Load 7. CONCLUSION Here in, Simulation of three phase shunt active filter supplying to non linear load with constant instantaneous power control is successfully simulated using Matlab.It has been realized that the three phase shunt active filter with Constant instantaneous power strategy compensates the oscillating real and reactive power of the load; it guarantees that only a constant real power p (average real power of load) is drawn from the power system. Hence, the constant instantaneous power control strategy provides optimal compensation from a power flow point of view even under non-sinusoidal or unbalanced system voltages. 8. REFERENCES 1. H.Akagi,Y.Kanazawa,and A.Nabae, “Instantanous Reactive Power Compensator comprising Switching Devices Without Energy Storage Components”, IEEE Transactions on Industrial Applications,vol.IA-20,no-3,1984,pp.625-630. 2. 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M.Routimo,M,Salo,and H.Tuusa,”comparision of voltage and current source shunt active power filters,”in conference records IEEE-PESC 2005,pp-2571-2577. 7. H.Akagi,”Trends in Active Power Filters,” in EPE’95-European Conference Power Electronics Appl.,vol.0,Sevilla,Spain,sep.1995,pp.0.017-0.026. 8. N.G.Hingorani,”Power Electronics in Electric Utilities: Role of Power Electronics in Future Power Systems,”Proceddings of IEEE,vol.76,no.4,April,1988 9. N.G.Hingorani,”High Power Electronics and Flexible AC Transmission System,” IEEE Power Engineering Reviews,July 1988. 10. 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. 11. o. ucak, i. kocabas, a. terciyanli, design and implementation of a shunt active power filter with reduced dc link voltage. 12. Mohd Abdul Lateef, Syed Maqdoom Ali and Dr.Sardar Ali, “Reactive Power Aspects in Reliability Assessment of Power Systems”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 3, 2013, pp. 124 - 131, ISSN Print: 0976-6480, ISSN Online: 0976-6499. 13. Mahavir Singh Naruka, D S Chauhan and S N Singh, “Power Factor Improvement in Switched Reluctance Motor Drive using PWM Converter”, International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 4, 2013, pp. 48 - 55, ISSN Print : 0976- 6545, ISSN Online: 0976-6553. BIOGRAPHIES R. J. Motiyani has received the M.E degree in Electrical Power Engineering from M. S. University, Baroda, and Gujarat in 2005. Currently he is working with S.N.Patel Institute of Technology & Research Centre as Associate Professor in Electrical Engineering Department. A.P. Desai has received the B.E degree in Electrical Engineering from VNSGU, Surat; Gujarat in 2008.He has received M.E.degree in M.E. (electrical engineering) from Shantilal shah Engineering college, Bhavnagar in 2013. Currently he is working with S.N.Patel Institute of Technology & Research Centre as Assistant Professor in Electrical Engineering Department. 254