Study on shunt active power filter with high quality grid current waveform

Shunt active power filter (APF) is suitable to compensate current-type harmonics generated by nonlinear load, but high compensation precision is difficult to be obtained due to very high slew rate of harmonic current e.g. inductive rectifier and phase lag of close-loop control system. In this paper, LCL-filter is used as output filter to get high slew rate of compensation current and sufficient attenuation ratio for switching frequency with small LC parameters. What´s more, repetitive control algorithm with differential compensator is adopted to eliminate steady-state error of control loop. Based on these two approaches, very high quality grid current waveform both at low and high frequency can be obtained. Simulation results validate the feasibility of the schemes proposed by this paper.