A novel control approach for LCL-based shunt active power filter with high dynamic and steady-state performance

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, output impendence of voltage source converter (VSC) and control loop phase lag. LCL-filter reserving sufficient attenuation ration for switching ripple with small LC parameters is suitable to be used as output filter to get high slew rate of compensation current. However, LCL-filter, as a three order one, is difficult to be stable. This paper proposes a simple control method with one beat delay introduced to feedback current; meanwhile, repetitive control algorithm, as outer control loop, is adopted to eliminate steady-state error of the whole control system. Based on this double-loop control scheme, very high quality steady-state grid current waveform and fast dynamic response can be obtained. Simulation results validate the feasibility of the method proposed by this paper.