Design and performance evaluation of a digitally controlled 1 kW three-phase interleaved ZVS converter for plug-in EV and HEV battery charger

This paper describes the development of a three-phase interleaved soft-switched dc-dc converter suitable for plug-in battery chargers in electric or hybrid car applications. Its architecture consists of three half-bridge converters (“phases”) sharing the same input and the same output port. All phases operate with fixed 50% duty cycle, at the same frequency and with 120° phase-shift with respect to one another, so that current ripple at both the input and the output is minimized. Power control is performed by changing the operating frequency. With an appropriate design all phases will work with soft-switching (Zero-voltage switching, ZVS) and, by using “phase shedding”, the converter´s efficiency can be kept extremely high over very wide load range. The paper, after providing its design guidelines, illustrates the operation of a 1 kW three-phase interleaved soft-switched dc-dc converter prototype built as a proof of concept to demonstrate the capabilities of this architecture and shows the results of its bench evaluation. Special emphasis has been given to some aspects related to its control, realized using a digital controller specific for power conversion applications.