Characterizations of Resonant Converters Based DC Transformers for Microgrid Application

Conventional line frequency transformers have the disadvantages of large volume and low efficiency. The medium or high frequency transformers based on power converters can achieve high power conversion with small footprint have drawn popularity in numerous industrial applications. Unregulated resonant converters, LLC and CLLC resonant converters, with fixed voltage conversion ratio operating at resonant frequency, which are also known as DC transformers (DCTs), are attractive owning to their high efficiency characteristic. Nevertheless, there are issues associated with DCTs in real applications. Regulation capability and automatic resonant frequency tracking capability are the two most important issues for DCTs. The main work of this paper is to characterize the resonant converters based DCTs, and overview the issues and solutions associated with DCTs. Guidelines can be provided for researchers and engineers when designing the resonant converters based DCTs.