Comparison and Mitigation of Common Mode Voltage in Power Converter Topologies

All switching converter topologies, operating from a grounded utility system and feeding a floating output system, create common mode voltages that are present on the load equipment. This paper develops a systematic analysis on the common mode voltage in various converter topologies typically used in ac drives, including two-level VSI (voltage source inverter), CSI (current source inverter) and multilevel inverters. The active front end rectifier used with each topology is also included in the analysis. The sources of common mode voltage are analyzed and the magnitudes of common mode voltages generated by different converter topologies are compared. The practical consequences of the common mode voltage and mitigation techniques are discussed. Simulation and experimental results are provided for verification.