A Unified Control of Grid-Interactive Off-Board EV Battery Charger With Improved Power Quality

Abstract

This article presents a self-tuning filter (STF) and sliding mode control (SMC)-based control algorithm for a grid-interactive off-board electric vehicle (EV) battery charger to power the EV batteries and simultaneously improve the grid power quality. In grid-connected operation (GCO), the charger uses the STF-based control strategy to estimate the fundamental load current and synchronize voltage templates to generate a pure sinusoidal reference current. Compared to the phase-locked loop (PLL) and the second-order generalized integrator (SOGI), the STF-based technique precisely estimates the synchronizing voltage templates during nonideal grid voltage conditions. Therefore, in GCO, the charger reference current ensures the unit power factor in the grid-to-vehicle/vehicle-to-grid (G2V/V2G) operation mode and the harmonic free grid current in the charger-for-grid (C4G) operation mode. Furthermore, the charger operates in the vehicle-to-load (V2L) operation mode during grid outages to maintain an uninterrupted supply to the residential load. The control algorithm also includes a grid synchronization technique to achieve a smooth transition between GCO and V2L. Furthermore, an SMC-based dc-link voltage controller (SMC-DLVC) is proposed to reduce dc-link voltage overshoot with finite-time convergence during external disturbances in all operation modes. The performance of the proposed control algorithm is validated in a 12.6-kVA off-board charger laboratory prototype under ideal/nonideal grid voltage conditions.