Optimized Design of Multi-Channel Resonant Converter for Fuel Cell Application

Abstract

This research presents a multi-channel phase shift inductor-inductor-capacitor (LLC) resonant converter with a wide input and output voltage range that has been specially optimized for fuel cell applications. The worst-case minimum stack voltage and the battery voltage range were used to determine the optimal parameters of the LLC converter. The voltage gain of the converter operating at a constant power was considered, and an algorithm for such a calculation is proposed. Current balancing is implemented using channel temperature measurements, circumventing the need for expensive current sensors. A natural selfbalancing mechanism is investigated for converters operating at high frequencies exceeding the series resonance frequency of a resonant converter. Efficiency optimization recommendations for the transformer turn ratio of the converter are illustrated. Multi-object optimization is implemented to achieve an optimized design so that both the minimum and maximum voltage gains can be realized; simultaneously, the transformer turn ratio is kept at a minimum to maintain high efficiency. An experimental prototype of a four-channel converter is implemented and verified at a 5-kW power level. Active content and the C language code files for converter calculations are also provided in this paper.INDEX TERMS Current sharing, fuel-cell converter, multi-objective optimization, resonant converter.