Asynchronous Discontinuous SVPWM Strategy for High-power Three-level ANPC Traction Inverter at Low Modulation Ratio Region

For the three-level active neutral point clamped (3L-ANPC) traction inverter, in the low modulation ratio region, narrow pulses of phase voltage should be avoided. In addition, the current is larger at low speed. To reduce the switching loss, it is necessary to reduce the switching frequency. In this paper, asynchronous discontinuous SVPWM (DSVM) strategies for the low modulation ratio region are proposed, including thirteen sector division methods. The switching frequency, harmonic content, common mode voltage (CMV), pulse width, and other characteristics of these sequences are analyzed. Based on this, the DSVM strategies with comprehensive performance optimization are obtained. The simulation results show that the proposed strategy has the advantages of reducing switching frequency, avoiding narrow pulses, and optimizing harmonics.