Modeling and optimized control of fault-tolerant H-bridge fed multiphase drives

In this paper, a model and an enhanced control strategy for fault-tolerant drive topologies based on multiphase, H-bridge-fed electric machines is presented. The model incorporates non-linear effects of structural saliencies, higher order harmonics and saturation. Unsymmetric operation states can be simulated and the torque is estimated including torque ripple due to higher order harmonics. Based upon the derived torque equation, a new approach for the determination of the optimal current waveforms in normal and fault operation is presented. The control strategy allows for a significant reduction of copper losses in normal operation and constant torque production in fault mode with open phase or short circuit-phase condition. The effectiveness of the developed control strategy is demonstrated by simulations and test bench measurements with a five-phase, H-bridge fed wheel hub drive.