Deadbeat Repetitive Control for a grid-connected inverter with LCL Filter

In order to improve the quality of the power injected into the grid, a deadbeat (DB) control strategy based on weighted average current with plug-in repetitive control (RC) scheme is proposed for a grid-connected inverter with LCL filter. Firstly, we calculate weighted average current of input and output current of the LCL filter, and use this variable to simplify the control strategy. Therefore, the equivalent model of the LCL filter is reduced from the third-order to the first-order. Secondly, DB controller is designed in discrete-time based on this simplified model. In order to suppress the harmonics of fed-in grid current, the RC is proposed to plug-in with the DB controller in parallel by providing the required harmonic elimination of the periodic signals. In the proposed combined control, the deadbeat control can track a given signal with fast dynamic response, and the RC can make the steady state error converge to zero gradually. The simulation and experimental results have demonstrated the effectiveness and advantages of the proposed method.