Design and Research on Two-Loop Control Strategy of PV Grid-Connected Inverter with LCL Filter

摘要

LCL filter offers a better choice of attenuating switching frequency harmonics, since compared with L or LC filters the value of required inductance is smaller. But LCL filter may cause resonance which is a disaster for the system's stability. In order to solve the problem, a twocurrent-loop control strategy which includes grid-current outer loop and filter-capacitor-current inner loop is used here. The filter-capacitor-current 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 specific method to give out the accurate value of the controller parameters relating to certain performance. The practicability of the method is tested and the anti-distortion ability of the system is analyzed. Finally experimental results verify the availability and correctness of the proposed method.