Efficiency evaluation of fault-tolerant operating strategies applied to three-phase permanent magnet synchronous motor drives

This paper presents a comparative analysis of fault-tolerant operating strategies intended to compensate inverter faults, applied to variable speed three-phase permanent magnet synchronous motor drives, with focus on the machine efficiency. Three commonly used control techniques applied to these energy conversion systems are considered, namely the vector control with space vector modulation, vector control with hysteresis current controllers and direct torque control. All these control methods are evaluated for two distinct fault-tolerant converter topologies. The first one is based on the connection of the motor phase to the dc bus midpoint while the second one consists of the connection of the machine neutral to the dc bus mid-point. A detailed experimental analysis is performed for all these cases, including the drive normal operation, through the presentation of motor efficiency maps, allowing its full characterization in all possible operating points.