Current sensor fault detection and isolation combining model-based and signal-based algorithms in PMSG drives

This paper presents a new on-line open-phase and current-sensor fault detection and isolation method for permanent-magnet synchronous generator (PMSG) drives with neutral point voltage control. Simple signal processing implementations for sensor outage and open-phase faults detection are combined with a cumulative-sum (CUSUM) algorithm capable of detecting smaller sensor output errors (offset or gain variation). The algorithm uses output signals from eight current sensors (two on each phase and two on the neutral wire). Experimental tests have been done on a 2kW-PMSG at different speeds and braking torques where different sensor-fault combinations have been tested with and without open-phase fault. Finally a test has been done while the shaft speed and the torque were varying in order to test the ability of the algorithm to work in transient conditions. Results show that the algorithm allows 3-out-of-6 redundancy in case of sensor outage and 5-out-of-6 redundancy in case of sensor offset or gain change with globally limited computational cost. Combinations of two outages and one offset or gain error can be isolated. In case of open-phase fault the algorithm can continue to detect sensor faults if at least one sensor is working on each remaining phase and on the neutral. A short fault detection time is obtained in case of sensor outage with a transitional detection by the CUSUM algorithm followed by the final detection by the signal processing algorithm.