Advancing V2G Technology: Design of an Adaptive Bi-directional Three Phase AFE Converter for High-Power Applications

Abstract

The grid-connected active front end (AFE) converter is an essential component of the Vehicle-to-Grid (V2G) system. In the current scenario, only a battery charger with unidirectional power capability for various power levels is being developed, which improves the grid’s power quality in compliance with the standard. A bi-directional battery charger with a high-power rating for V2G applications is a challenging task that is the focus of the current research. This paper presents a three-phase bi-directional grid-connected AFE converter for a 15 kW charging system. The novelty of this paper is to design and implement an adaptive synchronous reference frame (SRF) model-based controller for bi-directional power flow between the electric vehicle (EV) and grid. It uses an adaptive constant current/constant voltage (CC/CV) mode while integrating a bi-directional DC/DC converter to the proposed AFE system. The significant advantages of the proposed AFE system are high power quality at the grid side, along with suitable total harmonics distortion (THD) and ripple-free DC output voltage. Moreover, the bi-directional offboard charger responds to inductive and capacitive reactive power requests in less than three grid cycles, demonstrating a rapid reaction to grid commands. This paper achieves a fast transient response with a less peak overshoot to improve the steady-state performance. The performance of AFE is further analyzed using simulations, and it has finally been verified using a 15 kVA AFE converter on the laboratory set-up.