Reduction of Common Mode Voltage and Conducted EMI Through Three-Phase Inverter Topology

This letter presents a three-phase voltage source inverter (VSI) topology to reduce the common mode (CM) voltage and electromagnetic interference (EMI) of electric motor drives. Instead of using filters, active or passive, or specific pulse width modulated (PWM) techniques to reduce the CM voltage, the proposed topology has inherently less CM voltage generation. With the addition of two switches placed in series on the dc lines, this topology effectively reduces the CM voltage during zero switching states by "floating" the inverter from the dc source. This topology can be implemented with any PWM method and does not add any additional complexity to the standard control techniques. The operation and CM reduction capability of the topology is first demonstrated in simulation and then verified with experimental results. A comparison of both common mode voltage and EMI is made to a conventional three-phase VSI to demonstrate the effectiveness of the proposed topology.