Power Flow Analysis of Three-Port Resonant DC Transformer And Discussion on Phase Shift Control

In small-scale hybrid AC/DC microgrid for residential applications, the CLLC-type resonant DC Transformer (DCT) is widely used because of its advantages of bidirectional power flow, electrical isolation, high efficiency, low cost and soft switching. However, single CLLC resonant converter has only one fixed output voltage, which makes it difficult to be compatible with most household appliances. In this paper, three-port resonant DCT has been proposed for residential applications. Resonant DCT operating modes has been analyzed in all scenarios. In order to make the converter work at its best efficiency, a method of frequency shift and phase shift control is used. Matlab / Simulink is used to verify the control of the output voltage in this way. The limitation and problem of the phase shift control in this topology has also been identified and discussed in the paper by experiment.