Reactive power generation for single-phase transformerless Vehicle-to-Grid inverters: A review and new solutions

Vehicle to Grid (V2G) technology enables Battery Powered Vehicles including Electric and Plugin Hybrid Electric Vehicles as distributed Energy Storage for the smart grid. V2G inverters are advanced power converters that provide active and reactive bidirectional power flow between the grid and the onboard energy storage. A V2G power conditioner includes a high frequency isolated dc-dc converter and a two-quadrant voltage source inverter. This paper proposes application of the transformer-less inverters for V2G power conversion. Transformer-less inverters such as H5, HERIC, and FB-DCB are popular for Photovoltaic (PV) generation systems, offering high efficiency unidirectional power conversion at unity power-factor. The high efficiency and superior performance of these topologies in reducing common mode and circulating currents are beneficial for V2G application; however, the reactive power generation of these topologies has not been investigated. In this paper, the reactive power generation capability of these topologies is investigated. Traditional modulation methods are evaluated for reactive power generation. Additionally, novel modulation methods are proposed for improved operation at non-unity power factors. The advantages and disadvantages of the modulation methods for each topology are explored through MATLAB simulations.