Reducing the Common-Mode Voltage through Carrier Peak Position Modulation in an SPWM Three-Phase Inverter

High common-mode voltage (CMV) of an output will be produced in the conventional sinusoidal pulse width modulation three-phase inverter. Although the carrier phase-shift method can be used to reduce the peaks of CMV, it has the best suppression effect only when the SPWM modulation index is no more than 2/3. This letter presents a new scheme of carrier peak position modulation to break the limitation of modulation index. In this scheme, the peak positions of the triangular carriers are delayed or advanced to avoid the zero state. Thus, the peaks of CMV will be reduced under any modulation index. The feasibility and validity of this scheme are verified through the experiments.