Elimination of Common-Mode Voltage in Three-Phase Sinusoidal Power Converters

This paper presents an active solution to a commonmode voltage created by typical three-phase inverters. It is shown that the addition of a fourth leg to the bridge of a threephase inverter eliminates the common-mode voltage to ground created by the modulation of the inverter. An appropriate fourphase LC filter is inserted between the inverter and the load in order to create sinusoidal output line-to-line voltage. A simple modification of the modulation strategy is implemented for the four-phase inverter to achieve a three-phase wye-output neutralto-ground voltage which is equal to zero at all times for an ideal inverter. The modulation strategy thereby completely eliminates the common-mode potential produced by traditional modulation techniques with traditional three-phase inverter topologies.