Fault-Tolerant PMSG Drive With Reduced DC-Link Ratings for Wind Turbine Applications

Fault-tolerant permanent magnet synchronous generator drives might play an important role in improving the reliability and availability levels of the modern wind turbines. However, the acceptance by the wind turbine industry will be low if its implementation cannot be accomplished in a cost-effective way. In this paper, a low-cost fully integrated fault-tolerant converter with the ability to handle power switch open-circuit faults is proposed. The two topologies proposed for post-fault operation of the grid- and PMSG-side converters are a five-leg converter with a shared leg connected to a phase of the generator and to the transformer neutral point and a three-switch three-phase rectifier, respectively. Both do not require the oversizing of any component of the conventional system in order to operate within a limited range. Moreover, the fault diagnostic technique does not require additional measurements, and the integration into the drive controller of all diagnostic and control algorithms can be performed without great increase of the computational effort. Control strategies are proposed for the considered converter topologies, and their performance is analyzed by means of experimental results.