Control Methods to Mitigate Common Mode EMI and Reduce Switching Losses In Grid-Connected Inverters

Three-phase four-leg voltage source inverters that use pulse density modulation achieve simultaneous commutation of the switching devices on each inverter leg. This switching scheme should result in the elimination of common mode voltage within the circuit; however, the presence of dead-time during the commutation of the switches results in the generation of some common mode voltage events. In this thesis, a software-based approach to compensate for the common mode voltage generated during dead-time has been simulated and experimentally validated. The novel compensation strategy reduces the amplitude of the common mode spikes and ensures robust compliance with the conducted electromagnetic interference requirements in MIL-STD-461G for naval ship applications. Benefits arising from this research are considerable as this software compensation method reduces electromagnetic interference and common mode voltage typically generated by three-phase power converters and drastically reduces the size of the common mode filter required to meet the limits in the military standard. By eliminating the common mode choke and reducing the need for filters, the power converter will have decreased weight and volume, which are critical for shipboard applications.