Design and Development of a Mixed Si-GaN Open-End Winding Inverter for Electric Vehicles

This article presents the design and development of a hybrid multilevel inverter for electric vehicle (EV) applications employing an open-end winding motor (OEWM) configuration. This architecture allows for the use of commercially available 650-V GaN devices in EVs with high-voltage (800–1000 V) batteries. It combines a three-level T-type converter with silicon IGBTs (Si-IGBTs), which processes the full battery voltage at a low switching frequency, with an auxiliary two-level GaN inverter operating at a lower voltage (below 350 V) and at 50 kHz to play the role of an active filter. This results in a six-level output voltage waveform, leading to approximately 50% lower voltage total harmonic distortion than conventional solutions. Experimental validation confirms that the proposed topology achieves high efficiency and improved voltage and current waveforms. It also reduces common-mode voltage while decreasing the number of power devices and the overall system volume and cost relative to conventional fully GaN-based multilevel converters. Additionally, since operating GaN devices at high switching frequencies (above 50–100 kHz) in vehicular applications is counterproductive, as it increases switching losses without significantly improving the quality of voltage and current waveforms, a relatively low switching frequency is adopted for GaN devices to exploit their full potential in improving efficiency.