Robust Sliding Mode Controller Design for DC-DC Converters with Adaptive Gains

Abstract

Conventional DC-DC converters are an industry standard in several fields such as in solar PV applications for maximum energy extraction. However, the inherent non-linearity in these conventional types (e.g., boost, buck and buck-boost) makes it necessary to develop robust control techniques that can maintain the desired system operation in the presence of system disturbances. Variable Space Structure (VSS) controllers are convenient for such systems as their switching nature matches the DC-DC converters operational principle, and the Sliding Mode Control (SMC) mechanism may be employed in this context. This paper proposes an adaptive SMC method for the fourth order SEPIC converter, based on altering the sliding surface dynamics to continuously adjust the gains and drive the system to slide along an adaptive sliding surface to achieve stable converter operation. The mathematical model of the fourth order SEPIC is derived and the proposed adaptive SMC approach is simulated in MATLAB/Simulink. It is shown that one can achieve enhanced performance compared to the conventional SMC methods in the presence of system disturbances. The same methodology employed to SEPIC can also be expanded to other converters.