The control for grid connected inverter of distributed generation under unbalanced grid voltage

This paper describes a new control scheme of grid connected inverter of DG (distributed generation) under unbalanced grid voltage. In this paper, the proposed scheme of synchronous reference frame (SRF) controller can reduce the influence of unbalanced grid voltage, which is mainly caused by unbalanced distribution of single-phase and non-linear loads, etc. In order to realize the control goal, a positive SRF which rotates counterclockwise and a negative SRF which rotates clockwise are used to control the positive sequence current and negative sequence current, separately. According to PF =1 of grid side and average output active power is constant, the positive sequence reference current and negative sequence reference current are obtained. The positive sequence ac link feedback current is derived through a notch filter to eliminate the 100Hz negative sequence in the positive SRF. The same as the negative sequence ac link feedback current. The effectiveness of the proposed scheme has been demonstrated through computer simulation.