Comparison of Unidirectional Three- and Four-Wire-Based Boost PFC-Rectifier Topologies for Non-Isolated Three-Phase EV On-Board Chargers Under Common-Mode Aspects

In order to design a high-density, high-power transformerless on-board charger, e.g. the Vienna Rectifier (VR) would be a suitable topology as three-phase PFC-front end. However, limits regarding residual currents in conjunction with the given parasitic capacitances of the traction battery and with the explicit y-capacitors connecting within specific loads the high-voltage DC-system (HV-system) to ground complicate the use of a conventional Vienna Rectifier (VR). Therefore, a modified configuration is proposed which changes however the operation mode significantly leading to a low common-mode (CM) noise. The paper explains those changes analytically and validates them by simulations and measurements on a hardware prototype of 11 kW. Moreover, this prototype is used to compare a conventional VR with the proposed four-wire topology, denoted here also as ZeroCM-topology. Especially under low-load conditions, the proposed ZeroCM-variant offers significant benefits.