Mitigation of load harmonics from grid connected wind turbine using shunt active power filter

Abstract

The increasing utilization of power electronics controlled devices in power system has increased distortion level in current and voltage waveforms in the form of harmonics. The increase in harmonic level also affects the performance of generator, thereby reducing its efficiency and lifespan. In this research, load harmonic mitigation method has been proposed for grid connected variable speed wind turbine generator using Shunt Active Power Filter (APF). The main advantage of this method is eliminating the effect of load harmonics from terminals of wind turbine generator and from the Point of Common Coupling (PCC). To evaluate the performance of shunt APF, two strategies have been utilized separately for extracting harmonic reference signal: the instantaneous reactive power method (pq method) and Synchronous Reference Frame (SRF) technique. To prove the effectiveness of the proposed system, MATLAB simulations have been carried out on 120 kV grid connected Permanent Magnet Synchronous Generator (PMSG) based wind turbine. Furthermore, nonlinear load is also attached to PCC under fixed and variable wind speed between 8 to 12 m/s separately. For proper operation of APF, switching pulses have been produced by hysteresis band current control. This technique decreases the magnitude of Total Harmonic Distortion (THD) to an acceptable limit set by IEEE-519 standard for harmonic control. Results have also shown that the shunt APF with SRF technique yields better performance under fixed and fluctuating wind speed compared to pq method.