Finite-Time Sliding Mode Control for DC-DC Buck Converters Subject to Time-Varying Disturbances

A composite integral sliding mode controller (CISMC) is investigated for buck converter systems under various disturbances. The disturbances, such as unknown input voltage fluctuations and resistance uncertainties, enter converter system from both matched and mismatched channels, which severely degrade the system performance. The proposed CISMC consists of a disturbance observer with finite-time convergence performance (FTDO) and an sliding mode controller in integral form (ISMC). Constructing a new modified integral sliding mode surface that contains disturbance estimations, the effects of mismatched disturbances can be eliminated. Using this composite method, the output error of converters can accurately converge to zero in finite time. Therefore, this algorithm can adapt the converters to the applications requiring higher steady-state and dynamic performance. A rigorous stability analysis and simulation results under the condition of multiple time-varying disturbances is given to prove the effectiveness of CISMC.