Medium voltage drive based on the H bridge inverter and its common-mode voltage

Because of the shortage of the IGCTpsilas series connection to obtain 6 kV output, the medium voltage drive (MVD) based on the H bridge neutral point clamped three-level inverter is introduced. Consequently, the arising of the common mode voltage (CMV) is discussed, the equivalent CMV circuit is deduced, and the common-mode circle currents are proposed in this paper. With the analysis of the relationship between the modulation strategy and the output CMV of the MVD, the symmetric pulse width modulation (S-PWM) modulation strategy based on the H bridge three-level inverter is developed to eliminate the output CMV of the inverter. With the leakage capacitors of the MVD taken into accounts, the neutral point of the three-level inverter connection to the ground through a resistor is discussed to suppress the CMV of the rectifier. Furthermore, the high power high voltage experimental results show the efficiencies of the conclusions in this paper.