Matrix converters are arrays of controllable semiconductor bidirectional switches which connect input phases to arbitrary output phases. These converters received much attention because of their diverse advantages and became very promising candidates to replace the conventional two stage ac/dc/ac converter. These advantages include resolving the need for bulky dc link capacitors which cause longer lifetime and operating in high temperature environment, high quality input power factor, bidirectional current flow. These attractive features of Matrix Converter (MC) made it useful in many applications including aerospace, military and etc. Although its modulation techniques and commutation issues have been thoroughly investigated, system reliability remains an open issue and was investigated individually. The most common reliability problem is that a bidirectional switch has an open switch or short switch fault during the operation. In his thesis, the detection of open circuit and short circuit faults in these switches were investigated. In this thesis, a matrix converter, driving an adjustable speed permanent magnet synchronous motor, is examined. A new method for detecting open circuit and short circuit faults in IGBTs of MC was suggested. In the proposed algorithm, fault detection was designed based on the trans-conductance value of the IGBT. By monitoring the output current, input and output voltages of the matrix converter the IGBT trans-conductance in the “ON” state is estimated. Then, a proper fault signal is defined to indicate the deviation of the trans-conductance from nominal value. The fault signal is then compared to a threshold which has been calculated to guarantee a predefined rate of false detections. When an IGBT is “Open” or “Short” erroneously, then the trans-conductance deviates from the nominal value and the fault signal exceeds the threshold which indicates an error in the system. Key words: Matric Converter,IGBT Transistor, Trans-conductance, detection of open circuit and short circuit fault.
