A Modular Multifunction Power Converter Based on a Multiwinding Flyback Transformer for EV Application

In this article, a revolutionary and novel single-stage, multiport power conversion block is proposed. The power conversion concept is based on a bidirectional flyback converter with four-quadrant switches that permit us to seamlessly control the direction of the energy flow and to select which ports are active. This approach, denominated as multicell multiport bidirectional flyback (M2BF), can be used as a modular and a multifunction building block interfacing ac and dc sources and loads in complex conversion systems like the one we can encounter in electric vehicle (EV) applications. The multiport property is obtained due to the multiwinding flyback transformer that interfaces different sources and loads in a simple and effective way. We present and analyze this concept in detail, focusing on different operation modes it can provide (multiport dc-dc conversion, ac-dc conversion, vehicle-to-grid, grid-to-vehicle, and so on) and their possible implementation in the energy distribution network of an EV, where this unique multifunction multiport converter could bring an important breakthrough. The operating principles of the M2BF for different operating modes are described and analyzed, placing emphasis on the modularity of the proposed concept. The overall concept is evaluated and quantified using a gallium nitride (GaN)-based prototype achieving efficiencies higher than 91% that additionally validates the proposed idea experimentally. The presented analysis and experimental results clearly identify the advantages and limitations of the presented concept leaving no doubt about its usefulness to the future EV distribution network.