Abstract

In recent times, scholarly attention on Wide-bandgap (WBG) devices, like silicon carbide (SiC) and gallium nitride (GaN) transistors, focuses on power conversion for heightened efficiency in electric vehicles. GaN HEMTs, with superior characteristics like low on-resistance and high-speed switching, enable compact power converters with increased integration and power density, crucial for EV advancement.
GaN-powered converters require accurate models for device behavior. Manufacturers use internal data and physics-based models, but these are unavailable to the public and time-consuming to develop. Accurate analytical models, mimicking transistor dynamics and predicting energy loss, offer a solution without extensive computational demands.This thesis validates superior GaN device switching model, proven via experiments and reduced parasitics confirmed with double pulse tests, affirming enhanced accuracy.
Due to the fast switching of GaN device, high voltage slew rate or dv/dt at the inverter output gives rise to switching harmonics, higher voltage stress at the motor winding, and EMI issues in the motor drive system. This thesis conducts a comprehensive review of filter design for GaN-based inverters to attenuate the harmonics and hence mitigate the high dv/dt and EMI issues. A case study is also provided for a three-phase inverter developed. Another limitation of GaN-based converter technology has resulted from the limited voltage and current capability of GaN transistors available in the market. To apply GaN transistors in high-power applications, multi-phase multi-level converter design is also investigated in this thesis. A comparative study on a new neutral pointless multi-level inverter against the traditional topologies is carried out.