Cross-coupling and decoupling techniques in the current control of grid-connected voltage source converter

Cross-coupling issue of current control in dq frame will deteriorate the system performance especially for low PWM pulse-ratio applications. The decoupling techniques based on inductor current feed-forward (ICFF) and complex vector PI controllers (VPI) are usually employed to decouple the closedloop system. In this paper, the cross-coupling issue was analyzed and described with complex (coefficient) transfer function. And an intuitive criterion was established to describe how much the closed-loop system was decoupled. The current control structure with reference current feed-forward (RCFF) instead of ICFF was proposed to achieve as fast current performance as that of a decoupled system. The three current control decoupling techniques with ICFF, VPI and RCFF were compared with each other. And their advantages and disadvantages were shown in details. Finally, simulation and experiments results were shown.