Single-Phase Grid Forming Control Strategy with Offset elimination for V2X implementation in Smart EV Battery Chargers

Abstract

A single-phase grid forming (SPGFM) control strategy is proposed in this article. The proposed SPGFM strategy is intended for Smart Battery Chargers (SBCs). The advantage of SPGFM control strategy is that enables the SBCs to operate in two modes: stand-alone and grid-connected, which is necessary for "Vehicle-to-everything" (V2X) applications. Moreover, it allows to eliminate the offset in the injected grid current, due to the low power quality in distribution grids. Since the proposed SPGFM strategy is intended for SBCs, it is implemented in a two stage DC- AC power converter which is composed of a Dual Active Bridge Series-Resonant (DABSR) DC-DC converter, cascaded to a Voltage Source Inverter (VSI). Hence, the DABSR converter regulates the DC bus voltage, while the SPGFM control strategy is implemented in the VSI. The criteria design for the DC bus voltage control, active and reactive power control, droop control for frequency and voltage and the AC current control are explained. The control strategy is validated in stand-alone and grid-connected modes using a 2.2KW power converter. Whereas the robustness of the proposed control strategy is validated with an AC power source with a little offset.