Single stage AC-DC bidirectional converter with high frequency galvanic isolation suitable for V2G applications

Abstract

This work introduces a novel single-stage, bidirectional, isolated AC-DC converter obtained by the utilization of the high frequency components of the AC voltage on a three-phase VSI. These components are usually filtered as the VSI is intended to transfer power only at the grid frequency. The proposed converter exploits the possibility of power transfer at both the grid and switching frequency. As usual, power is transferred to grid at the fundamental grid frequency by suitable inductive filters. On the other hand, power is transferred to the DC side at switching frequency, thus achieving high frequency galvanic isolation; this is made by means of three resonant tanks (connected to each VSI phase) and a single, phase-shifted, active bridge at the DC side. This configuration allows the bidirectional power transfer with the simplicity of the VSI for the grid side, and the features of the Dual Active Bridge Series Resonant Converter at the DC side (ZVS, power control by means of shift angle). The operation of the converter is detailed, and the steady state power transfer is analyzed, simulation results for a 2.4 kW prototype are presented as validation.