Open-Switch Fault-Diagnostic Method for Back-to-Back Converters of a Doubly Fed Wind Power Generation System

In order to improve the reliability and availability of the converters of wind turbines, condition monitoring and fault diagnosis are considered crucial means to achieve these goals. In this text, according to the current variation characteristics of the converter, this paper presents a novel approach for real-time diagnostics of open-switch faults in back-to-back converters of a doubly fed wind turbine. The average value of the normalized converter phase currents and the absolute normalized currents are used as principal quantities to formulate the diagnostic variables. The proposed fault-diagnostic variables prove to be carrying information about multiple open-switch faults. In addition to, by the combination of these variables with the average absolute values of the normalized converter phase currents, an adaptive fault-diagnostic threshold is proposed, which ensures the robustness of the diagnosis of single and double open-switch faults. Finally, through the diagnostic variables and the adaptive threshold, the dynamic fault-diagnostic method for open-switch faults in the back-to-back converter of a doubly fed wind turbine is formed. The simulation and experimental results also indicate that the fault-diagnostic method can not only diagnose the multiple open-circuit faults of a back-to-back converter, but also have a better robustness.