Active Common Mode Current Reduction in Multiinverter Systems

The paper deals with the common mode current issue in a multidrive system. Common mode currents are caused by steep variations of the common mode voltage, strictly related to the sequence of the inverter states during the voltage pulsewidth modulation. An inexpensive technique that allows compensation of the common mode voltage variation in rnultidrive systems composed of two or more inverters is proposed in order to eliminate the common mode currents. The common mode current paths and generation mechanisms are reviewed and the influence of the inverter state sequence on the common mode voltage and currents is pointed out. Based on such considerations, a new digital PWM modulation strategy is introduced to compensate the common mode voltage variations generated in a two PWM inverter system.