Parallel-connected current source rectifiers as the input stage of the off-board EV battery charger

Abstract

This paper presents a study on two parallel threephase current-source rectifiers applied as an input stage of the EV off-board battery charger. This part of the system is expected to operate at grid frequency to avoid switching losses and cooperate with two series-input parallel-output isolated DC-DC converters according to three-level unfolding principles. At first, a reference approach based on three-level voltage-source converter is explained and, then, two control methods of parallel-connected currents rectifiers are presented and illustrated with circuit simulations. Operating conditions of semiconductors are analyzed and compared, including a case study of power losses in a 3x400V/20 kVA EV charger. Finally, thyristor switches are proposed to be applied in both rectifiers in order to reduce on-state losses. This concept is also verified by circuit simulations and, similarly to rectifiers based on RB-IGBTs, enables losses below 1% of nominal power.