Research on double transistor open circuit fault diagnosis of T-type three level rectifier based on mixed logical dynamical model

The T-type three-level rectifier has garnered significant attention due to its ability to enhance the voltage waveform quality in power systems and reduce electromagnetic interference with other equipment. To ensure high reliability in high-power wind and photovoltaic power generation systems, conducting fault diagnosis for T-type three-level rectifiers is crucial. This paper first analyzes the input current characteristics of both in-phase and out-of-phase dual transistor open-circuit faults. A current-extended observer is developed using a hybrid logic dynamic model to estimate the current value during normal operation. The residual state equation is derived by comparing this estimated current with the actual fault current. A residual information table for fault currents is created through differential solutions of the residual state equation, enabling fault localisation by comparing the residual information against predefined threshold values. Finally, the feasibility and accuracy of the proposed fault diagnosis method are validated through simulations and experiments.