Zero Voltage Soft-Switching Phase-Shift PWM Controlled Three-Level DC-DC Converter for Railway Auxiliary Electric Power Unit

This paper presents a new type of soft switching dc-dc converter with high frequency(HF)-link for auxiliary power unit (APU) of railway applications. The proposed topology features a single-stage power conversion process with dc voltage regulation by a diode-clamped three-level dc-dc converter. A time-domain analysis on the high-frequency transformer current is presented in terms of zero voltage soft switching (ZVS) in all the active switches. Performances of the proposed APU is demonstrated by a 2 - kW miniature prototype under the control principle of zero voltage soft-switching (ZVS) phase shift pulse-width-modulation (PS-PWM), after which the feasibility is discussed from a practical point of view.