A Common-Mode Voltage Reduction for Two-Stage Three-Phase Transformerless PV Inverters

This paper presents a common-mode voltage cancellation method for two-stage transformerless string PV inverters. The exact common-mode equivalent circuit is firstly modeled to exhibit simultaneously the instantaneous common-mode voltages of boost DC-DC converter and three-phase two-level inverter. The selection of zero voltage for PWM inverter is then proposed in order to pave the way for common-mode voltage cancellation. The simulation results show the accuracy of exact common-mode model. In addition, the common-mode voltages can moderately cancel each other out, and the leakage current of the overall system is significantly attenuated.