Zuo Wang

Continuous Output Feedback TSM Control for Uncertain Systems With a DC–AC Inverter Example

This brief proposes a continuous output feedback terminal sliding mode (TSM) control method for the output tracking problem of nonlinear systems with mismatched uncertainties. This method is developed by two consecutive steps: 1) design a sliding mode observer to estimate the derivative and high-order derivatives of system output and 2) construct a continuous TSM controller based on system output and the estimations of its high-order derivatives. The proposed controller not only guarantees system output converges to its reference in finite time but also keeps the continuity of control action. Experiments on single-phase dc–ac inverter circuits are also carried out to show the effectiveness of the proposed controller.

Generalized proportional integral observer based backstepping control for DC-DC buck converters with mismatched disturbances

Considering load uncertainties in the DC-DC buck converter, the mismatched disturbances are imposed on the system, which would cause degradation of the control performance. Conventional backstepping control (BSC) scheme fails to achieve a high precision performance especially in the presence of strong disturbances. In addition, the disturbances caused by load uncertainties are complex in reality, which often turn out to be time series polynomial forms. Generalized proportional integral observer (GPIO) based backstepping control scheme is advocated in this paper to solve this problem. The GPIO based backstepping algorithm performs not only a promising disturbance rejection ability but also a nice property of tracking performance. A rigorous stability analysis for the closed-loop system is presented. The feasibility and efficiency of the proposed method is validated by both simulation and experimental results.

A Simple Control Approach for Buck Converters With Current-Constrained Technique

The output voltage tracking problem with overcurrent protection for a pulse width modulation-based dc–dc buck converter is investigated in this brief. On the one hand, large transient current during the start-up phase is required for fast dynamics. On the other hand, overlarge transient current may lead to a risk of hardware damage. Conventionally, this problem is solved by choosing conservative control parameters, while the dynamic performance is sacrificed to a certain extent. Besides, the load uncertainty is inevitable in practical applications. Hence, a control design that keeps a good balance between dynamic performance, overcurrent protection, and robustness is desired. To this end, a novel and simple current-constrained controller is constructed. Both dynamic performance and current constraint are taken into account. The low complexity of the proposed current-constrained controller yields a higher reliability of dc–dc buck converter control system, and reduces cost of hardware. Moreover, it shows a nice property of robustness against load uncertainty. Control action is penalized by adjusting controller gains automatically when inductor current tends to the barrier bound. Rigorous stability analysis is given under the presented controller. Comparative simulation and experimental results between the proposed control scheme and the classic proportion–integration–differentiation control scheme on the buck converter system are illustrated to verify the feasibility and effectiveness of the proposed control scheme.

Finite-time control for DC-AC inverter system with mismatched disturbances using continuous nonsingular terminal sliding modes

An output voltage regulation problem for single-phase DC-AC inverter system under external input voltage variations and load resistance uncertainties is investigated in this paper via a continuous nonsingular terminal sliding mode control (NTSMC) approach. Aiming to reject the effects of mismatched disturbances, the finite-time disturbance observer (FTDO) is introduced for disturbance estimations within the DC-AC circuit. By integrating the disturbance estimation information into the design of the nonlinear dynamic sliding mode surface, a finite-time NTSMC method is developed to achieve finite time tracking performance in the presence of mismatched disturbances and uncertainties. It is shown that the proposed method can guarantee the stability of closed-loop system. The robustness of the proposed controller against input voltage variations and load uncertainties is demonstrated by simulation results.

A GPI based sliding mode control method for boost DC-DC converter

For different DC-DC converter applications in engineering systems, there exists different kinds of disturbances. For example, in wind energy systems, besides step disturbances, there may also have polynomial form disturbances. In order to ensure disturbance rejection ability, one of the effective methods is disturbance compensation based control method. However, many of the previous disturbance observers designed are for step disturbances or slow time varying disturbances. To this end, a novel sliding mode control (SMC) approach is developed for PWM-based DC-DC boost converter systems. First generalized proportional-integral observers (GPI) are employed to estimate the disturbances. Due to the existence of mismatched disturbances in the DC-DC converter, disturbance estimation is introduced into the sliding surface. Thus a composite sliding mode is obtained. Numerical simulations and experimental results show the effectiveness of the proposed method.

Incremental passivity based control for DC-DC boost converter with circuit parameter perturbations using nonlinear disturbance observer

In this paper, the output voltage trajectory tracking for the conventional DC-DC boost power converter in the presence of circuit parameter perturbations is investigated. Based on the property of incremental passivity, a simple feedback controller is designed. Meanwhile, to obtain a better disturbance rejection property, we employ two nonlinear disturbance observers (NDOBs) to attenuate the uncertainties in the output voltage and inductor current channels, respectively. Moreover, global trajectory tracking performance of the system under disturbances is ensured. Finally, simulation and experiment studies are offered to confirm the feasibility and efficiency of the presented approach. The related results reveal the proposed controller delivers a nice antidisturbance performance as well as a superior nominal tracking ability.