Novel control method for LCL active power filter

A novel control approach was presented for a LCL-filter-based active power filter (APF), since the stability and steady-state error of the APF were influenced by grid parameter varying. The control approach consists of a novel generalized integrator and a novel active damping. The gain of traditional generalized integrator was attenuated at harmonic frequency by the grid frequency excursion, which made the steady-state error increase. This problem is solved by the novel generalized integrator based on parameter adjusted online. Otherwise a passive or active damping was needed to restrain the resonance of LCL filter, but the possible wide range of grid impedance values weakened the effectiveness of the damping, even challenged the stability of the LCL-filter-based APF system. Therefore the novel active damping based on sliding mode control was designed. The simulation and experiment results demonstrate that the control approach makes the APF system have a good robustness.