Fuzzy FDI System for Flyback Converters

In this article, the design of a fault detection and isolation (FDI) system for a flyback converter, based on a fuzzy unknown input observer, is presented. The proposed FDI system aims to detect the saturation in the inductor core as a fault, considering the current increment can cause an avalanche effect provoking a failure in the system. A Takagi–Sugeno model of the flyback converter is used. The observer's convergence and the stability of the fault diagnosis system are guaranteed by Lyapunov's theory and the estimation error used to determine the necessary LMIs. A comparison of different FDI methods applied in fuzzy systems is performed in order to select the most robust system, capable of estimating the current in the system even in the presence of external disturbances. The system validation is performed in both, simulation and online implementation, using experimental data.