Design and Integration of the Bi-directional Electric Vehicle Charger into the Microgrid as Emergency Power Supply

Abstract

Vehicle to grid (V2G) is currently not cost effective to justify the bi-directional EV charger as it reduces the battery cycle life. Replacing the dedicated emergency power supply of the load area with the bi-directional EV charger is a more viable option. This paper introduces the seamless integration of the bi-directional EV charger into the distribution load areas. The proposed system design improves the efficiency, guarantees the galvanic isolation and supports the 3-phase-5-wire microgrid. With virtual synchronous machine (VSM) control, instantaneous mode switching during the islanding is achieved when EV(s) are connected to the charger; otherwise, a black start strategy are proposed to handle the scenario. A 50kW lab prototype was successfully constructed, integrated and tested within an industrial load area and the actual EV. Moreover, the lab data show that the VSM with the proper controller tuning can condition the low order harmonics in the microgrid load current.