A current control strategy of three-phase grid-connected inverter with LCL filter based on one-cycle control

Abstract

A digital one-cycle control strategy combined with the Quasi Proportional Resonant (QPR) controller is applied to the three-phase grid-connected inverter with LCL filter in this paper. The control system contains dual loops with inner loop of capacitive current and outer loop of net current. Instead of conventional SPWM modulation method, one-cycle control for the inner loop has functions of control and modulation, and then the bipolar control algorithm of one-cycle controller with capacitor current is derived to improve anti-interference performance of the system and to shorten the tuning process, the QPR controller in stationary reference frame is adopted to the outer-loop, which elides complicated coordinates transformation. Considering the high-order feature of the system, the parameters of controllers are designed by using the high-order poles assignment. Finally, a 3kW three-phase grid-connected inverter simulation is performed and the results verify feasibility of the scheme.