A unified model-free super twisting sliding mode control strategy for single-/three-phase compatible onboard EV chargers

Single/three-phase compatible onboard charger (OBC) are gaining popularity due its high flexibility and efficiency. These compatible charger consists of a reconfigurable AC–DC front end—operable as either a three-phase two-level inverter or a single-phase interleaved totem-pole rectifier and a back-end CLLC resonant DC–DC converter regulating the battery-side voltage. Proportional integral (PI) and proportional resonant (PR) based controllers are used to control the DC-link and output voltage of OBC’s using the inner and outer loops structure, but they provides less robustness and efficiency under larger perturbation and load variations. This paper proposes a unified model-free sliding mode control (MFSTSMC) based DC-link control strategy for outer loop onboard electric vehicle (EV) chargers compatible with both single and three-phase grid operations. The MFSTSMC is also proposed for the back-end CLLC resonant output voltage control. Unlike conventional methods, the proposed a model accomplishes the intended voltage tracking, while maintaining stability and feasibility for both the DC-link and battery-side voltages, ensuring finite-time convergence, chattering-free operation, and high robustness to nonlinearities and parameter variations, without requiring explicit system modeling. Inner-loop PR and PI current controllers maintain sinusoidal input currents and ensure grid-code compliance. Simulation and experimental validations indicate that the proposed MFSTSMC-based technique provides enhanced transient performance, accelerated dynamic response, and improved disturbance rejection relative to traditional PI–PR–PI and fixed-gain sliding-mode controllers. The integrated and flexible control framework offers a dependable, rapid, and model-agnostic energy management solution for advanced onboard electric vehicle chargers, enabling smooth single and three-phase operation.