T-Type Converter with Zero Common-Mode Voltage Modulation for Potential Transformer-less EV Charger Application

This paper introduces a modified space vector modulation technique aimed at eliminating common-mode voltage (CMV) in a three-phase three-level T-Type converter for potential transformer-less Electric Vehicle (EV) charger application. The proposed approach exclusively employs the Zero and Medium (ZM) vectors to achieve ideally zero CMV during normal operation, thereby enhancing system safety and reliability. In such an application, due to safety reasons, a residual current detection device should be added to guarantee human safety. Simulation results demonstrate the effectiveness of the approach through a comparative analysis of CMV generation in three distinct scenarios. The first scenario involves standard space vector modulation (SVM), where there is significant generation of CMV. The second scenario illustrates the implemented modulation technique with minimized dead-time that achieves close to zero CMV generation. The third scenario shows the effect of dead-time on implemented modulation technique which reintroduces some CMV but is still significantly lower compared to the conventional SVM. The implemented ZM vector modulation is verified with a 5 kW SiC based T-type converter prototype switching at approximately 20 kHz where an 89.42% reduction in CMV is achieved.