This brief is concerned with the finite-time tracking control problem for switched nonlinear systems with arbitrary switching and hysteresis input. The neural networks are utilized to cope with the unknown nonlinear functions. To present the finite-time adaptive neural control strategy, a new criterion of practical finite-time stability is first developed. Compared with the traditional command filter technique, the main advantage is that the improved error compensation signals are designed to remove the filtered error and the Levant differentiators are introduced to approximate the derivative of the virtual control signal. The finite-time adaptive neural controller is proposed via the new command filter backstepping technique, and the tracking error converges to a small neighborhood of the origin in finite time. Finally, the simulation results are provided to testify the validity of the proposed method.

For three-phase ac–dc converters, load disturbances, and parameter uncertainties cause large fluctuations of the dc-link voltage, even resulting in system instability. In order to cope with this problem, the disturbance observer-based finite-time control (DOFTC) is put forward in this article, where the finite-time disturbance observer is designed to fast and accurately estimate disturbances. Subsequently, the stability of the ac–dc converter closed-loop system is analyzed and theoretically proved. Finally, experimental results verify the effectiveness of the DOFTC strategy, where good dynamic and steady-state performance is achieved under load disturbance and parameter uncertainties. Compared with the enhanced state observer-based sliding mode control and adaptive control method, the proposed DOFTC method not only reduced the fluctuations of the dc-link voltage by at least 55% but also improved the transient response.

For the three-phase ac/dc converter, unbalanced grid voltages cause grid current distortions and dc-link voltage fluctuations, threatening the safe operation of the power grid or loads. To address this issue, the control targets of the ac/dc converter under unbalanced grids are transformed into a unified power tracking problem by introducing modified power references. Then, the finite-time command filtered control (FTCFC) of the ac/dc converter is proposed, and the dual-loop control structure of inner power and outer dc-link voltage is studied, where the active and reactive powers are independently regulated without the current control loop and the phase-locked loop. In this method, the proposed command filter estimates the power references' derivatives, and the fixed-time disturbance observer is designed to suppress the unknown load disturbances on the dc-link voltage control loop. Theoretical analysis and experimental results validate the effectiveness of the proposed FTCFC method, and the fast and accurate power tracking performance is achieved for all three control modes. Compared with the PI+backstepping control, the FTCFC method improves the tracking performance of the dc-link voltage and powers and reduces the current THD by 35.2%.

Vienna-type rectifier is widely used in many applications due to the merits of controllable dc-link voltage, realizable three-level operation, and compact size. However, the input currents near the zero-crossing point are distorted inevitably due to it’s special topology. Based on the analysis of the causes of current distortion, a lagging reactive power compensation method is proposed. The d-q axis current models are developed and two finite-time current controllers are designed to enhance the interference suppression performance. The asymptotic convergence of the d-q axis current systems are proved, respectively. In addition, neutral point potential balancing is achieved by employing proportional controller without increasing the cost of the system. The validity of the proposed hybrid control strategy has been verified by simulation and experimental results. Compared to the conventional strategy, this new hybrid control strategy can help to achieve excellent performance and stronger disturbance rejection.

High-frequency link matrix rectifier (HFLMR) is getting much interest in EV charger applications due to its high efficiency and compact volume. However, the inputs and outputs of HFLMR are highly coupled resulting in reduced system dynamic performance and robustness. This paper proposes a dual closed-loop backstepping control (DCL-BSC) strategy to solve these problems, which consists of a dc output current outer-loop controller and a grid current inner-loop controller. Firstly, the nonlinear mathematical model of HFLMR is established, and the six-segment SVPWM scheme is used as the modulation method. Then, the DCL-BSC scheme is designed in detail based on the Lyapunov stability theory. And a compensation method based on the phase shift angle is developed to realize the unity power factor. Compared with the conventional dual closed-loop PI control (DCL-PIC) method, the proposed method has better steady-state and dynamic performance, and robustness against system disturbances. Simulation and experimental results are used to verify the effectiveness of the proposed control scheme.