Soft-switching Analysis of Current-fed HFAC Resonant Converter for Aircraft Auxiliary Power Supply System

For the aircraft auxiliary power supply system, High frequency alternating current (HFAC) power distribution systems (PDS) have less transmission loss and higher practicality than DC power supply, which has been a more attractive option. As the core of energy conversion and control, the current-fed (CF) resonant inverter applied in the current source HFAC power supply needs to own the advantages of soft-switching of the switches and stable sinusoidal output voltage. However, the existing CF push-pull inverter with a fourth-order CLCL resonant tank has a hard-switching problem due to the diodes in parallel. This paper proposes a method with auxiliary capacitors, which helps achieve soft-switching. Besides, a detailed analysis of the hard-switching problem, the implementation process of soft-switching, and the selection methods of auxiliary capacitors are given. Finally, a resonant inverter prototype with a wide input range from 42V to 60V and output voltage of 50kHz,100V peak is designed to verify the proposed solution.