Freewheeling current-based sensorless field-oriented control of Five-Phase PMSMs under IGBT failures of a single phase

Model-based sensorless field-oriented control (FOC) suffers from over-parameterization and can be laborious to use for a five-phase Permanent Magnet Synchronous Motor (5Φ-PMSM). On the other hand, Insulated Gate Bipolar Transistor (IGBT) frequently fails in an electric drive. Under IGBT failure, a freewheeling current is observed, and, above all, it carries the failed phase back-Electromotive Force (back-EMF) information. Based on this observation, this paper presents the design of a brand new sensorless FOC by exploiting the freewheeling current to accommodate both IGBT and position sensor failures, which is expected to further enhance the drive's fault-tolerant capability. The mathematical model of this current is firstly established to provide a theoretical basis and a comprehensive understanding of the presented sensorless FOC. By virtue of this model, a second-order generalized integrator with a frequency locked loop (SOGI-FLL) can be used as a simple and elegant way to extract position/speed estimates. Experimental results are provided to validate the proposed sensorless FOC philosophy.