Design of a Hybrid Two-Stage Inverter and Hybrid Modulation Strategy for High-Speed Permanent Magnet Synchronous Motor Drive

This paper designs a hybrid two-stage inverter and a hybrid modulation strategy for high-speed permanent magnet synchronous motor(HSPMSM) drive system. The first-stage of the proposed inverter consists of a SiC-Mosfet and a SiC-shottky-barrier diode(SBD), and the second-stage is a conventional two-level voltage-source-inverter(VSI) based on Si-IGBTs. In order to achieve high carrier-frequency-ratio at high speed range, based on the designed hybrid inverter, a hybrid modulation strategy is proposed. In the proposed hybrid modulation strategy, zero-voltage-vector is generated by the SiC-Mosfet and the SBD, and the second-stage VSI is only used to generate the effective-voltage-vector. Since the second-stage VSI does not need to generate zero-voltage-vector, the switching number of Si-IGBTs is three times lower than the conventional scheme. Although the switching frequency of the SiC Mosfet is much higher than the Si-IGBTs, the total loss of the proposed inverter is still significantly lower than the traditional scheme owing to the low switching loss of the SiC based power switches. Device level simulation is executed in Ansys/Simplorer and Matlab/Simulink. Device-level-simulated results verify that the proposed scheme can significantly improve the efficiency and reduce the loss at a little sacrifice of the cost.