Mitigation of Deane and Hamill phenomenon in gallium nitride high-voltage power supply for electric propulsion system application

The step-up resonant converters are widely adopted to provide high voltage in kV-level for electric propulsion system due to their high efficiency, low mass, modularisation, and high-power density. The bipolar Cockcroft-Walton voltage multiplier (BiCWVM) is a major circuit that steps up the voltage in the resonant converter. However, the diode non-linearity in BiCWVM can introduce self-sustained quasi-periodic oscillations in the voltage and current waveforms, which is commonly known as the Deane and Hamill (DH) phenomenon. The oscillation can lead to higher magnetic loss and control failure, and it is more likely to present in the gallium nitride-based converter due to the high-frequency operation. The authors aim to investigate and mitigate the DH phenomenon systematically so that proper mitigation can be implemented. To facilitate the investigation, the circuit before the BiCWVM in the converter is derived and modelled as a voltage source v_m and a series inductor L_sy. Also, the reverse recovery process of the diode in the BiCWVM can be represented by a piecewise-linear (PWL) model, with the simplified circuit and PWL model, the relationship between voltage and current under different operating conditions can be determined with ease. The relationship allows to understand the mechanism of diode reverse recovery in BiCWVM that leads to DH phenomenon. Finally, a hybrid-/full-silicon carbide (SiC) design is proposed to mitigate the DH phenomenon, which is verified experimentally for a 300-kHz, 5-W, 20-V/1.5-kV GaN-based step-up resonant converter.