Finite-Time Sliding Mode Control for NPC Converters With Enhanced Disturbance Compensation

In this paper, a generalized proportional integral observer (GPIO)-based finite-time sliding mode control scheme is proposed to enhance the convergence rate and disturbance rejection capacity of the grid-connected three-level neutral-point-clamped (NPC) converter. Firstly, a generalized super-twisting algorithm (GSTA) is designed in the voltage regulation loop and the instantaneous power loop of the NPC converter. Compared with the conventional super-twisting algorithm (STA), this method provides a faster convergence speed while the system trajectories are far from the origin, which is applied to the NPC converter to improve its dynamic performance and robustness. Additionally, by introducing a generalized proportional integral observer (GPIO) combined with the GSTA in the voltage regulation loop, the unknown time-varying disturbances can be rejected effectively. The stability of the proposed control scheme is proved. Finally, a set of comparative experiments between the proposed controller and the classic STA-based method have been carried out based on a three-level NPC converter prototype, and the results confirmed the efficacy of the proposed control strategy.