Patent ID: 11874336
Assignee: WUHAN UNIVERSITY
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A method for diagnosing an open-circuit fault of a power switching device of a three-phase three-level rectifier, executed by a processor when executing a computer program, the method comprising:
Step (1) of selecting an expected value of a phase-to-phase voltage between an X-phase and a Y-phase of the rectifier at a current time and an actual value of the phase-to-phase voltage, and using a deviation between the two as a diagnosis variable;
Step (2) of obtaining voltage current information required for diagnosis from a control system of the rectifier, and calculating the diagnosis variable by adopting a screening technique;
Step (3) of classifying fault sections according to fault characteristics of faulty switches at different times, and updating a diagnosis threshold at the current time for a current fault section;
Step (4) of judging whether the diagnosis variable exceeds a threshold range and a polarity thereof according to the diagnosis variable and the diagnosis threshold;
Step (5) of identifying and locating a fault of an internal switching transistor according to the judgment result; and
Step (6) of checking a diagnosis result of the fault to verify whether the diagnosis result is correct, and correcting the diagnosis result of a fault of an external switching transistor that is misdiagnosed as the fault of the internal switching transistor to implement identification and location of an external switching fault, wherein the fault of the internal switching transistor is determined based on the diagnosis result is correct, and the fault of the external switching transistor is determined based on the diagnosis result is wrong,
wherein alternating current side three-phase voltages, three-phase currents and a direct current side voltage obtained by the three-phase three-level rectifier through sampling are sent to the control system, and, according to the alternating current side three-phase voltages, the three-phase currents, the direct current side voltage, an alternating current side inductance and an alternating current side equivalent resistance, the control system obtains three-phase switching control signals of each power switching device of the three-phase three-level rectifier through calculation and sends the three-phase switching control signals to the three-phase three-level rectifier.