Multiple criteria for high performance real-time diagnostic of single and multiple open-switch faults in ac-motor drives: Application to IGBT-based voltage source inverter

In this paper, the diagnosis of the open-switch damage in pulse-width modulated voltage source inverter (PWM-VSI) is addressed. The proposed strategy uses multiple normalized diagnostic variables and requires only the measurement of two output inverter currents that were used for a closed-loop control of the electric drive. It consists in analyzing and combining the information provided from the line currents shapes in α-β frame and their normalized mean values, under both healthy and faulty operating conditions. In a first step, twenty-seven patterns built with output inverter currents in α-β axis are used to detect the faulty legs. Six of them are dedicated to the IGBTs single-fault modes and the others to the multiple open-switch modes. A second step is achieved by normalizing the average line currents which allows not only the identification of the single-fault but also makes it possible to distinguish several multiple-fault cases having the same signatures in α-β frame. The proposed technique has the features of simple algorithm, independence of the transient states, single and multiple faults diagnosis, fast fault diagnosis, and being easily included to the existing software without any additional sensors. Experimental results, using a dSpace system with DS1104 controller board based on the digital signal processor (DSP) TMS320F240 and a 3-kW squirrel-cage induction motor drive, are displayed to validate the effectiveness of the proposal.