Next-Generation SiC/GaN Three-Phase Variable-Speed Drive Inverter Concepts

Variable-speed drive (VSD) systems should feature high power density and low installation costs, offer wide input and/or output voltage/motor speed ranges and ensure low EMI without requiring shielded motor cables. Accordingly, next-generation high-switching-frequency SiC/GaN PWM inverters should integrate LC output filters and generate continuous output voltages to prevent conducted or radiated EMI, reflections on long motor cables, high-frequency motor losses, dv/dt-related motor insulation stresses and bearing currents, such that conventional low-cost motor technology can be utilized. This short paper complements a keynote presentation and briefly describes new three-phase buck-boost PWM inverter topologies with sinusoidal output voltages currently under research at the Power Electronic Systems Laboratory of ETH Zürich. First, a new phase-modular buck-boost inverter concept (Y-inverter) is introduced and subsequently condensed into a three-phase current DC-link DC/AC converter that employs an input-side single-bridgeleg voltage-to-current DC/DC conversion. Next, the four-quadrant switches of the converter’s DC/AC stage, formed by common-source connection of conventional unipolar power MOSFETs, are replaced with novel dual-gate monolithic bidirectional GaN switches with bipolar voltage blocking capability and small chip area. The implementation of the resulting buck-boost DC/AC converter requires only a single low-volume magnetic component and allows a seamless extension to three-phase AC/AC operation. Thus, the converter concept has to be seen as potential competitor to state-of-the-art voltage DC-link converter systems for future industry applications and even as preferred choice over AC/AC matrix converters which show a higher output voltage filtering effort.