Control Strategy of LCL-type Grid-connected Inverter

In the context of increasingly complex power grids, it is necessary to study more efficient control methods for grid connected inverters. The LCL type filter performs better than single inductor filtering in the case of smaller inductance and low switching frequency, and has a significant advantage in attenuating high-order harmonics. However, LCL type filters are undamped third-order systems that are prone to resonance. This article adopts capacitor current inner loop feedback control to suppress the resonance peak of LCL type filter grid connected inverter. The theoretical basis and implementation method of current outer loop feedback control strategy based on QPR regulator in the αβ coordinate system and PI regulator in the dq coordinate system are given. Finally, the superiority of QPR regulator is obtained and verified through simulation.