Isolated DC/DC converter with three-level high-frequency link and bidirectional power flow ability for electric vehicles

A high-frequency isolated bidirectional DC/DC converter based on the combination of an H-bridge, a three-level half-bridge and a three-phase full bridge topology is proposed for electric vehicle applications. The 24 V low-voltage battery pack is the power supply of the converter and it is raised to about 144 V, which is then converted to three-phase AC voltage to drive the induction motor. A multilevel high-frequency link is proposed to implement the conversion from the low voltage side (LVS) to the high voltage side (HVS). The switching patterns and single-phase three-level pulse width modulation is proposed to maintain the voltage on HVS and to control the power flowing out of the battery. The zero voltage switching characteristics of the low rating-voltage metal-oxide-semiconductor field-effect transistors on LVS and HVS are analyzed. The algorithms to suppress DC bias of magnetising current and to equalise the capacitor voltages are also introduced. The effectiveness and the control strategy of the proposed converter are verified by simulation and experimental results.