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 volt age, strictly related to the sequence of the inverter slates during the vol tage pulsewidth modulation. An inexpensive technique that allows compensati on of the common mode voltage variation zn multidrive systems composed of t wo or more inverters is proposed in order to eliminate the common, mode cur rents. The common mode current paths and generation mechanisms are reviewed and th e influence of the inverter state sequence on the common mode voltage and c urrents is pointed out. Based on such considerations, a new digital PWM mod ulation strategy is introduced to compensate the common, mode voltage varia tions generated in a two PWM inverter system.