The influence of grid-connected three-phase inverters on voltage unbalance

The increasing presence of single-phase distributed generators and unbalanced loads in the electric power system may lead to unbalance of the three phase voltages, resulting in increased losses and heating. To decrease this voltage unbalance problem three-phase four-wire inverter-connected distributed generation units may be used. In this paper, the influence of the control strategy of three-phase inverter-connected distributed generation (DG) units on voltage unbalance is studied. One of the control strategies is a damping control method for a three-phase four-wire inverter for DG units which behaves resistively towards voltage disturbances independently of the input power. The other control methods are the classical sinusoidal control strategy and the resistive control strategy. The simulation results show the positive effect of the damping control strategy on voltage unbalance.