Analysis and Design of an Integrated Bidirectional Three-Phase AC–DC Resonant Converter

Abstract

This paper proposes a novel isolated bidirectional AC-DC converter where the front end and primary side of DC-DC isolated converter are merged giving rise to 25&#x0025; fewer devices. Owing to the integrated topology the devices of the proposed converter are naturally soft switched and the size of the filtering components in the AC-DC stage is reduced compared to a low frequency hard switched AC-DC stage. A Space Vector Modulation (SVM) and control technique is proposed for generating switching pulses for DC link voltage control and bidirectional power transfer. A design optimization technique is proposed to mathematically determine the switching frequency of the converter and subsequently, the resonant tank parameters based on the operating conditions, topology, modulation, and the Wide Band Gap (WBG) Silicon Carbide (SiC) device characteristics. The proposed converter and its design approach are validated through prototyping for a scaled-down bidirectional charger for warehouse Electric Vehicles (EVs), and experimental results from two test cases, one with the actual grid with an input ac line (<i>i.e.,</i> 208&#x00A0;V) voltage and second with an AC power supply of input line (<i>i.e.,</i> 400&#x00A0;V) voltage. The former is tested for a peak power rating of 2.5&#x00A0;kW and the later is tested for a 5&#x00A0;kW output power. The switching frequency from the proposed optimization method is determined to be around 130&#x00A0;kHz for both cases. Peak efficiency of 95.3&#x0025; is achieved. The battery voltage varies from 350-600&#x00A0;V.