An on-line fault diagnosis method for power rectifier device based on fault current characteristic

This paper analyzes the current characteristics of short circuit and open circuit of single thyristor as well as the current characteristics of open circuit of AC line, and comes up with a new on-line fault diagnosis method for the rectifier device. For the single thyristor short circuit, the theoretical DC value calculated using the measured AC current will be greater than the real-time DC value measured, and the DC components of the fault phase and non-fault phase are opposite in sign, which can be used to locate the fault thyristor. In the open circuit situation, if the DC component value of current calculated by slide window is continually larger than the threshold value, it is single thyristor open circuit, and the fault thyristor can be identified by the sign of fault phase DC component; if the DC component value of current firstly increases above a certain value and then reduces to 0, the fault can he identified as AC line open circuit, and the fault phase can be located with the help of minimum amplitude of the fundamental wave. This method takes both open circuit and short circuit faults into consideration, and it can also be applied to the fault diagnosis of multiple parallel rectifiers. Simulation results show that the fault identification speeds are 1ms, 10ms, and 2ms in thyristor short circuit, thyristor open circuit, and AC line open circuit cases respectively, and that the fault location speeds are 20ms, 30ms, and 22ms correspondingly. The method can diagnose the faults of single element in a rectifier quickly and accurately, which can effectively prevent the expanding of fault and improve the repair efficiency. So it has theoretical and practical value.