This paper presents an improved generalized super-twisting control (IGSTC) scheme for neutral-point-clamped (NPC) converters subject to the line-inductance parameter uncertainties. By optimizing the algorithm structure, the proposed method accelerates transient response. An online fixed-time inductance estimation algorithm is integrated into the current-tracking loop, significantly enhancing the system’s robustness against inductance variations. Through Lyapunov-based analysis, the practical finite-time stability of the IGSTC and the practical fixed-time convergence of the identification algorithm are rigorously established. Finally, comprehensive simulations under both nominal and varying inductance scenarios validate that the superior performance of the proposed strategy.

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.

This article explores a novel variable-gain super-twisting observer (VGSTO)-based fixed-time sliding mode control (FTSMC) method for the dc-link voltage control of three-level neutral-point-clamped (NPC) active front-end (AFE) converters. Among the literature review, the super-twisting observer is an attractive solution for disturbance estimation. However, its convergence velocity is limited when the trajectories are far away from the origin. To overcome this drawback, a novel VGSTO is proposed in this work, whose innovation lies in adopting dynamically adapted exponent coefficients in the conventional super-twisting observer; thus, it turns into a linear observer outside a ball around the origin, which increases the convergence rate of conventional super-twisting observer, and the disturbance rejection ability is enhanced significantly. In addition, an FTSMC is designed for the NPC converter and its settling time is independent of the initial states, which breaks through the limitation of the traditional finite-time sliding mode controllers and assures the dynamic performance of the NPC converter. The proposed control scheme is assessed and compared with other representative observer-based sliding mode control methods based on a three-level NPC AFE converter test bench, and the experimental results verify its feasibility and effectiveness.

This paper introduces a fixed-time sliding mode control (FTSMC) scheme that utilizes a fixed-time disturbance observer (FTDOB) for three-level neutral-point-clamped (3L-NPC) converters. Therein, a FTSMC with adaptive exponential coefficient is developed to regulate the dc-link voltage. Compared with existing methods, the proposed approach features a settling time upper bound that is independent of the initial error, which ensures the dynamic performance of the 3L-NPC converters. Furthermore, a FTDOB is employed to estimate external disturbances and act as feedforward compensation of the 3L-NPC converters to enhance its disturbances rejection ability. Finally, a series of simulation results illustrate the advantages of the proposed scheme by compared with several representative methods used in 3L-NPC converters.

In this paper, a fixed-time active disturbance rejection-based sliding mode control scheme is proposed for the three-phase three-level neutral-point-clamped (NPC) active front-end (AFE) converter to regulate the dc-link voltage. In order to further improve the disturbance rejection ability of the active disturbance rejection control (ADRC) when applied in NPC converter, a fixed-time disturbance observer is used to estimate the disturbances instead of the traditional extended state observer in ADRC. In addition, a sliding mode controller with constant plus proportional rate reaching law (CPPRL) is designed to regulate the dc-link voltage, and the dynamic performance and control accuracy of NPC converter is improved without increasing the chattering. Finally, the performance of the proposed control scheme is evaluated by a class of comparative simulations, and the results confirm the effectiveness and feasibility of the proposed approach.