Zero-sequence Current Control in a Back to Back Inverter with Pump Back Test Configuration

The pump back test is popular in the industry for high power characterization since it does not have the requirement for high-power DC power supply and AC load. The configuration of the pump back test includes two converters, with the dc side connecting to the common dc power supply and ac side connecting each other through an ac filter. One problem of the pump back test is that the circulating loop provides a flow path for the zero-sequence current. Therefore zero sequence current (ZSC) is obvious, especially when the zero sequence component is injected. To solve this problem, a novel zero-sequence current control method is proposed in this paper, which not only can be used for sine pulse width modulation (SPWM) but also suitable for zero-sequence injection pulse width modulation. With the help of this control method, total harmonic distortion (THD) can be largely mitigated in ac current. Simulation results and experimental validation are shown to demonstrate the performance of the proposed control method.