A novel parameter design method of dual-loop control strategy for grid-connected inverters with LCL filter

LCL filter is applied to reduce the high harmonic originated from grid-connected inverters, which could reduce value of inductance and improvement system dynamic performance. Account of the resonance problem of LCL filter, a current dual-loop control strategy is introduced. The current-mode dual-loop control strategy based on capacitor current loop which is chosen as the inner loop to damp the resonance. The implementation of this strategy is easy and the system performance is good. However, the tuning procedure is complex since the outer and inner controller can not cooperate well if the parameters of the controllers are not suitable and there is no one paper which provides a method to calculate the exact value of the two-current-loop controller's parameters. This paper proposed a pole assignment method based on deficient degreed of freedom (DOF). The design method is feasible and superior to traditional trial-and-error method. Finally experimental results verify the availability and correctness of the proposed method.