η-ρ Pareto optimization of bidirectional half-cycle discontinuous-conduction-mode series-resonant DC/DC converter with fixed voltage transfer ratio

In solid-state-transformer technology, the isolation and power transfer between low voltage and medium voltage side is performed by a high power DC/DC converter. This DC/DC converter provides a defined ratio between input and output voltages, whereby, in order to reduce switching losses, zero-current-switching modulation schemes are often mandatory. The series-resonant-converter operated in half-cycle discontinuous-conduction-mode possesses all the aforementioned features, thus making it highly attractive for solid-state-transformer applications. For this reason, a comprehensive analytical model of the converter's static and dynamic behavior is provided in this paper. In addition, a method to model the switching losses under ZCS conditions, which is based on the behavior of the stored charge in the semiconductors, is presented. This enables an efficiency/power density (η-ρ) Pareto optimization of the aforementioned converter system.