Hybrid Pulse Frequency and Width Modulation scheme for Three-port Resonant DC/DC Converters

Power router has been proposed in recent years to serve for the smart grid to ensure the high power quality, power optimization, etc. It is mainly consisted by DC converters and multi-port resonant high frequency transformer to ensure the high power density and control flexibility. Practically, it is hard for the multi-port resonant DC/DC converter to operate at the resonant point while guaranteeing wide voltage gain. Therefore, a hybrid pulse frequency and width modulation scheme is proposed in this paper for three-port resonant DC/DC converters. Firstly, a topology of CLLC resonant three-port isolated bidirectional DC/DC converter is analyzed. Secondly, in order to stabilize voltage output and maximize power transmission simultaneously, the switch frequency is adjusted according to the change of power to ensure it work near the maximum gain point. Subsequently, the duty-ratio of the pulse is adjusted to acquire the desired voltage gain. Meanwhile, the voltage ripple of two ports has been decreased. The simulation results show that the proposed hybrid control scheme is superior to the conventional approach in the aspects of transmission efficiency and quality of the output DC voltage.¹