Bi-Directional EV Charging With Robust Power Controlled Adaptive Phase-Shift Algorithm

The charging current variation at various level of battery operating conditions and state of charge (SOC), often requires precise and accurate control in EV charging to achieve desired power transmission. This article proposes a gain adaptive sliding mode control (ASMC) with a modified phase-shift algorithm to facilitate EV fast charging at various levels of non-linear battery dynamics. The ASMC improves the front-end AC-DC charging performance with additional robustness by eliminating the conventional fixed gain control architecture and incorporating dynamic parameter updation at various levels of active or reactive power transmission. In order to support EV fast charging, a modified phase estimation technique is also proposed with an objective to minimize power-mismatch and phase-shift error during bi-directional charging phenomenon. In most of the existing phase-estimation techniques, voltage based PI-controller is used to determine the power transfer limit in bi-directional EV chargers without considering different charging modes and battery SOC. However, the presented control technique is entirely gain adaptive and includes the battery dynamics based upon constant current (CC) or constant voltage (CV) charging phenomenon. The control algorithm is simulated in both grid-to-vehicle (G2V) and vehicle-to-grid (V2G) modes of operation to comprehensively analyze the active power exchange without affecting the utility power quality. A laboratory prototype is also developed with a 3.3 kW bi-directional charging topology to validate the controller performances.