Design and Implementation of a Fuzzy Time-Varying Sliding Regime Controlled UPS Systems

Abstract

In this paper, a robust tracking fuzzy controller using time-varying sliding regime is proposed for UPS systems. The controller combines the merits of sliding regime control, fuzzy logic control. Time-varying sliding surface is used to ensure the existence of sliding regime from an initial state, while the conventional sliding surface can not achieve the robust performance against disturbances before the sliding regime occurs. Fuzzy technique is applied to select a dominated sliding surface when errors lie in the second and the fourth quadrants and shift a predetermined sliding surface when errors lie in the first and the third quadrants in order to achieve the propose of fast and robust tracking. Using the proposed method, the magnitude of the control input signals and undesirable chattering phenomenon are remarkable lessened and simultaneously improves the robustness of the UPS system. Simulation results are presented, showing a good dynamic performance of the proposed method.