Weak Fault Detection of Rotor Winding Inter-Turn Short Circuit in Excitation System Based on Residual Interval Observer

Aiming at the fact that the rotor winding inter-turn weak faults can hardly be detected due to the strong electromagnetic coupling effect in the excitation system, an interval observer based on current residual is designed. Firstly, the mechanism of the inter-turn short circuit of the rotor winding in the excitation system is modeled under the premise of stable working conditions, and electromagnetic decoupling and system simplification are carried out through Park Transform. An interval observer is designed based on the current residual in the two-phase coordinate system, and the sensitive and stable conditions of the observer is preset. The fault diagnosis process based on the interval observer is formulated, and the observer gain matrix is convexly optimized by linear matrix inequality. The numerical simulation and experimental results show that the inter-turn short circuit weak fault is hardly detected directly through the current signal, but the fault is quickly and accurately diagnosed through the residual internal observer. Compared with the traditional fault diagnosis method based on excitation current, the diagnosis speed and accuracy are greatly improved, and the probability of misdiagnosis also decreases. This method provides a theoretical basis for weak fault identification of excitation systems, and is of great significance for the operation and maintenance of excitation systems.