A Fault-Tolerant Induction Generator System Based on Instantaneous Torque Control (ITC)

A fault-tolerant scheme of an induction generator using instantaneous torque control (ITC) is proposed in this paper. In the case that a power switch of the converter goes wrong, the system can be reconfigured to a four-switch three-phase (FSTP) generator system and continue supplying some power. In the reconfigured system, the ITC strategy can also be applied; the only differences lie in the available voltage space vectors and optimal switching-table. There are only two bridges working in the post-failure operation, which results in halved output power compared with that of prefailure six-switch three-phase system. This paper also investigates the special issues of the voltage ripples and drifts of the midpoint voltage of the dc bus capacitor of the FSTP system. The optimization of capacitor and the improvement of ITC strategy can effectively solve the two issues. In order to further improve the quality of the output dc voltage, the space vector modulation -ITC strategy is examined by modeling and experimental tests, which can greatly reduce the fluctuations of output voltage. Its voltage ripple is only 0.5 V on the output voltage of 270 V dc.