Composite Controller Design for Buck Converters Based on Terminal Sliding Mode and Disturbance Observer

It can be seen from the literature that the existing control methods for the control of DC-DC Buck converters are mostly based on the pure state feedback. When the disturbances are large, the gains of the controllers are usually required to be tuned large enough so as to suppress the adverse effects of disturbances, while the large gains usually affect the dynamic and steady-state performance of the closed-loop systems. To tackle this problem, a composite control scheme was proposed by combining the terminal sliding mode and disturbance observer techniques to further improve the dynamic and steady-state performance of Buck converter's control system. First of all, taking the external disturbance, system uncertainties and parameter perturbations into account, the average state model of DC-DC Buck converters should be firstly built. On this basis, a sliding mode controller by virtue of the non-singular terminal sliding mode control technique was designed for the Buck converter such that the fundamental voltage regulation can be implemented. Finally, by applying the disturbance observer technique, a nonlinear disturbance observer was constructed to estimate the unknown disturbance, and the estimated value as the feedforward term plus the state feedback constitute the composite controller, which can further improve the performance of the closed-loop system. Simulation and experimentation results verified the effectiveness of the proposed method. © 2018, Chinese Society of Agricultural Machinery. All right reserved.