Grid voltage modulated control of grid-connected voltage source inverters under unbalanced grid conditions

In this paper, an improved grid voltage modulated control (GVM) with power compensation is proposed for grid-connected voltage inverters when the grid voltage is unbalanced. The objective of the proposed control is to remove the power ripple and to improve current quality. Three power compensation objectives are selected to eliminate the negative sequence components of currents. The modified GVM method is designed to obtain two separate second-order systems for not only the fast convergence rate of the instantaneous active and reactive powers but also the robust performance. In addition, this method converts the system into a linear invariant system though designing a new voltage input. Simulation results are presented to verify the correctness and validity of the proposed control strategy and power compensation method.