Adaptability of weighted average current control to the weak grid considering the effect of grid-voltage feedforward

The weighted average current control (WACC) strategy has been widely used in LCL-filter-based grid connected inverters, because it can reduce the order of grid connected inverter system to the first order. However, when the LCL-filter-based inverter is connected to a weak grid with grid-voltage feedforward, the phase and gain margins of WACC will be significantly reduced, which leads to limited gain of current control loop and finally affects the controller's performance. In this paper, a new WACC weighted factor calculation method is proposed to improve the adaptability of WACC to weak grid, by analyzing the effect of grid-voltage feedforward on the grid connected inverter's control loop. The method is based on the optimization of the proportional feedforward, and the weighted factor calculation will not be affected by grid impedance. In this case, the stability of the controller is immune to the grid impedance and the current control loop gain is improved. Both theoretical analysis and experimental results are presented to validate proposed control method.