Fast diagnosis strategy for open-circuit fault of switch devices in open-winding PMSM system based on voltage error estimation

In the dual inverter topology of open-winding permanent magnet synchronous motor system, due to the symmetry of the topology, switch devices have high similarity in working characteristics, which undoubtedly increases the difficulty in locating faulty devices. In this paper, by analysing the difference of inverter output characteristics before and after switch devices open-circuit fault, the relationship between the inverter output voltage error and fault location is found, and a fault diagnosis strategy is proposed. In this strategy, a construction method of fault phase characteristic current and the estimation equation of inverter output-voltage error are designed. Then, the real-time diagnosis of single device fault and two devices with the same characteristics fault at the same time is realized. Since the strategy proposed in this paper does not need additional voltage sensors, it has the same applicability as the traditional current method. In addition, the diagnosis method based on voltage information reduces the diagnosis time. Besides, this method is independent of the PWM strategy and is not sensitive to the phenomena of dead time and delayed insulated gate bipolar transistors switching. Finally, experimental results demonstrate the effectiveness of the proposed fault diagnosis strategy.