Improved direct power control of a grid-connected voltage source converter during network unbalance

This paper deals with an improved direct power control (DPC) strategy for the pulse width modulation (PWM) voltage source converter (VSC) under unbalanced grid voltage conditions. In order to provide enhanced control performance for the VSC, the resonant controllers tuned at the double grid frequency are applied in the DPC design to eliminate the power pulsations and dc link voltage ripples produced by the transient unbalanced grid faults. In this way, the output power and dc link voltage of the VSC can be directly regulated without positive and negative sequential decomposition. As a result, and as has been verified by experiment, the proposed method can provide fast dynamic response with easy implementation.