IJIRST International Journal for Innovative Research in Science & Technology Volume 2 Issue 06 November 2015 ISSN (online): 2349-6010 A Time Domain Reference-Algorithm for Shunt Active Power Filters Prof. Sumita D Chakrabortty Assistant Professor (Head of Department) Department of Electrical Engineering Mahavir Swami College of Engineering & Technology, Surat Prof. Naimesh Zaveri Professor(Head of Department) Department of Electrical Engineering C K Pithawala College of Engineering & Technology, Surat Abstract The aim of this paper is to identify an optimum control strategy of three-phase shunt active filters to minimize the total harmonic distortion factor of the supply current Power Quality (PQ) is an important measure of an electrical power system. The term PQ means to maintain purely sinusoidal current wave form in phase with a purely sinusoidal voltage wave form. The power generated at the generating station is purely sinusoidal in nature. The deteriorating quality of electric power is mainly because of current and voltage harmonics due to wide spread application of static power electronics converters, zero and negative sequence components originated by the use of single phase and unbalanced loads, reactive power, voltage sag, voltage swell, flicker, voltage interruption etc. The simulation and the experimental results of the shunt active filter, along with the estimated value of reduction in rating, show that the shunt filtering system is quite effective in compensating for the harmonics and reactive power, in addition to being cost-effective. Keywords: Shunt voltage inverter APF, Time domain, instantaneous active power, carrier based PWM, Control strategy etc. I. INTRODUCTION The wide use of power devices (based on semi-conductor switches) in power electronic appliances (diode and thyristor rectifiers, electronic starters, UPS and HVDC systems, arc furnaces, etc ) induces the appearance of the dangerous phenomenon of harmonic currents flow in the electrical feeder networks, producing distortions in the current/voltage waveforms. As a result, harmful consequences occur: equipment overheating, malfunction of solid-state material, interferences with telecommunication systems, etc... Damping harmonics devices must be investigated when the distortion rate exceeds the thresholds fixed by the ICE 61000 and IEEE 519 standards. For a long time, tuned LC and high pass shunt passive filters were adopted as a viable harmonics cancellation solution. II. SHUNT ACTIVE FILTERING ALGORITHMS The control algorithm used to generate the reference compensation signals for the active power filter determines its effectiveness. The control scheme derives the compensation signals using voltage and/or current signals sensed from the system. The control algorithm may be based on frequency domain techniques or time domain techniques. In frequency domain, the compensation signals are computed using Fourier analysis of the input voltage/current signals. In time domain, the instantaneous values of the compensation voltages/currents are derived from the sensed values of input signals. There are a large number of control algorithms in time domain such as the instantaneous PQ algorithm, synchronous detection algorithm, synchronous reference frame algorithm and DC bus voltage algorithm. The instantaneous PQ algorithm by Akagi is based on Park s transformation of input voltage and current signals from which instantaneous active and reactive powers are calculated to arrive at the compensation signals. This scheme is most widely used because of its fast dynamic response but gives inaccurate results under distorted and asymmetrical source conditions. All rights reserved by www.ijirst.org 111
III. TYPES OF THE ACTIVE FILTERS BASED ON TOPOLOGIES A. Shunt Active Filter Fig. 1: Shunt Active Filter B. Series Active Filter Fig. 2: Series Active Filter C. Hybrid Active Filter Fig. 3: Hybrid Active Filter All rights reserved by www.ijirst.org 112
D. Unified Power Quality Conditioner Fig. 4: Unified Power Quality Conditioner IV. TIME DOMAIN METHODS A. Instantaneous Reactive Power Theory Fig. 5: Instantaneous Reactive Power Theory All rights reserved by www.ijirst.org 113
Fig. 6: Flow chart for the calculation of compensating current using instantaneous reactive power theory B. Synchronous Reference Frame Fig. 7: Synchronous Reference Frame C. Sinusoidal Subtraction Method Fig. 8: Sinusoidal Subtraction Method All rights reserved by www.ijirst.org 114
V. SIMULATION RESULTS A. Simulation of Shunt Active Filter Based On P-Q Theory for Transient Load Condition Fig. 9: Simulation Diagram of Shunt Active Filter Based on P-Q Theory for Transient Load Condition Fig. 10: waveforms of phase-a (a) distorted load current (b) compensating current by filter (c) source current after compensation All rights reserved by www.ijirst.org 115
Fig. 11: harmonics spectrum of phase-a (a) distorted load current (b) compensating current by filter (c) source current after compensation Fig. 12: Wave Forms of (a) Distorted Load Current in Phase-A and (b) THD of Load Current (27.45%) Fig. 13: Wave Forms of (a) Compensated Source Current in Phase-A, and (b) THD of Source Current (2.74%) All rights reserved by www.ijirst.org 116
Fig. 14: Dynamic Response of P-Q Theory VI. CONCLUSION In this paper, based on generalized active and reactive powers theory, in a-b-c reference frame-based a compensation algorithm for transient load conditions is proposed. This method has been verified by PSIM simulation. The proposed method can be applied to balanced and unbalanced source voltages in magnitude and phase angle. REFERENCES [1] H. Akagi, Y. Kanazawa & A. Nabae, "Instantaneous reactive power compensators comprising switching devices without energy storage components," IEEE Trans. Industry Applications, vol. 20(3), pp. 625-630, 1984. [2] C.L. Chen, C.E. Lin & C.L. Huang, "Reactive and harmonic current compensation for unbalanced three-phase systems using the synchronous detection method," Electric Power systems Research, vol 26, pp163-170, 1993. [3] S. Bhattacharya & D. Divan, "Synchronous frame based controller implementation for a hybrid series active filter system," in Proc. 13th IAS Annual meeting, pp. 2531-2540, 1995. [4] H. L. Jou, "Performance comparison of the three-phase-active-power-filter algorithms," in Proc. IEE Conf. On Generation, Transmission, Distribution, pp. 646-652, 1995. [5] M. Rastogi, N. Mohan & A.A.Edris, "Filtering of harmonics currents and damping of resonances in power systems with a hybrid active filter," IEEE Applied Power Electronics Conf., Dallas,Texas,USA, pp. 607-612, 1995. [6] Bhavaraju. V.B & Enjeti. P.N, "Analysis and design of an active power filter for balancing unbalanced loads," IEEE Trans. Power Electronics, vol. 8(4), pp. 640-647, 1993. [7] Satya Prakash Dubey, Pukhraj Singh, and H. V. Manjunath, "DSP Based Neural Network Controlled Parallel Hybrid Active Power Filter", International Journal of Emerging Electric Power Systems: Vol. 4: No. 2, Article 2., 2005. [8] B.N.Singh et.al., Design and Digital Implementation of Active Filter with Power Balance Theory, IEEE Proc on EPA, Vol 2, No.5, Sept 2005 pp.1149-1160. [9] M. Machmoum, N. Bruyant, Control Methods for Three-phase Active Power Filters under Non-ideal Mains Voltages, in proceedings Power System Technology, Powercon 2000, International Conference on, Vol. 3, 2000, pp. 1613-1618. [10] G.D. Marques, A Comparison of Active Power Filter Control Methods in Unbalanced and Non- Sinusoidal Conditions, IECON 98, August 31- September 4, pp. 444-449. [11] V. Soares, P. Verdelho, G.Marques, A Control Method for Active Power Filters under Unbalanced Non-Sinusoidal Conditions, in Proc. PEVD 96, 23-25 Sep. 1996, pp.120-124. [12] Shyh-Jier Huang, Jing-Chang wu, Hurng-Liang Jou, A Study of Three-Phase Active Power Filters under Non-ideal Main Voltage, Electric Power Systems Research 49 (1999), pp. 129-137. [13] F.Z. Peng, J.S.Lai, Generalizard Instantaneous Reactive Power Theory for Three Phase Power Systems, IEEE Transaction on Instrumentation and Measurement Vol. 45, no.1, 1996. [14] Cheng-Che Chen, Yuan Yih Hsu, A Novel Approach to Design of a Shunt Active Filter for an Unbalanced Three-Phase Four Wire System Under Non-Sinusoidal Conditions, IEEE Transactions on Power Delivery, Vol. 15, no. 4, October 2000, pp. 1258-1264 [15] G. Bhuvaneswari and M.G.Nair, "A novel current compensation technique for shunt active power filters," in Proc. IASTED Conf. On Power and Energy systems, pp.109-113, 2003. [16] Kim. S and Enjeti. P.N, "A New hybrid active power filter (APF) topology," IEEE Trans. Power Electronics, vol. 17(1), pp. 48-54, 2002. [17] Bor-Ren Lin et.al., Analysis and operation of hybrid active filter for harmonic elimination, Electric Power Systems Research, Vol.62, pp.191-200, 2002. All rights reserved by www.ijirst.org 117