Common-mode voltages of space-vector modulated matrix converters compared to three-level voltage source inverter

In adjustable speed PWM AC drives common-mode stator voltage produces bearing currents, which have been a severe problem in industrial drives. Thus, to develop methods for the minimization of these bearing currents it is essential to have knowledge about the common-mode voltages (CMVs) of different types of frequency converters. This paper compares the CMVs of three space-vector modulated frequency converters: 1) three-to-three-phase direct matrix converter (DMC), 2) three-to-three-phase indirect matrix converter (IMC), 3) three-level voltage source inverter (3LVSI) with a supply side diode bridge. Experimental and simulated results show that the maximum CMVs of the converters can be minimized with a suitable modulation method. With a suitable method MC produces a smaller CMV maximum but the CMV steps of the 3LVSI are always smaller regardless of the modulation method used in MCs. No noticeable differences were found between the DMC and the IMC when CMVs were compared.