Power quality improvement using Zig-Zag transformer and DSTATCOM in three phase power distribution system

This paper proposes a topology consisting of Zig-Zag transformer for neutral current compensation and reduced rating three-leg single capacitor DSTATCOM for load balancing and unity power factor operation in the presence of unbalanced and distorted load voltages. The detailed analysis of different voltages induced and currents flowing inside Zig-Zag transformer shows that Zig-Zag transformer provides low impedance path to zero sequence currents. In addition to that, the potential of the floating neutral of the Zig-Zag transformer connected to a three-phase source measured with respect to the neutral of that three-phase source equals the zero sequence voltage component of that source. This property can be used to get neutral current compensation in three-phase four-wire power distribution system even in presence of unbalanced and distorted voltages. As the neutral current (total zero sequence current) is being taken care by Zig-Zag transformer, a reduced rating DSTATCOM can be used for load balancing and unity power factor operation using instantaneous symmetrical components theory. A detailed simulation study for the proposed scheme is carried out using PSCAD software.