Nonsingular Fast Terminal Sliding Mode Control of LLC Resonant Converter for EV Charger

LLC resonant converter is widely used in electric vehicle (EV) charger for the advantages of low switching loss and high power density. However, its dynamic performance and robustness are easily influenced by multiple disturbance factors. This paper proposes a nonsingular fast terminal sliding mode (NFTSM) control strategy for the LLC resonant converter to improve the dynamic performance and robustness. First, the second-order small-signal model is obtained by the linearized and simplified large-signal mathematical model which is established based on the extended description function method. Then, the NFTSM controller is designed based on the small-signal model. And the system stability is proved by Lyapunov's stability theorem. Finally, Simulation results verify the feasibility and effectiveness of the proposed control scheme.