Sensorless speed observer based on third-order spatial field harmonic for multiphase induction motor drives

This paper presents an electric drive consisting of a multiphase induction motor fed by a multiphase inverter. The control system is similar to that of a traditional field-oriented control for three-phase motors, but the machine speed is estimated by a novel sensorless observer. Since multiphase motors with M phases (M is supposed odd) have the capability of controlling the odd spatial harmonics of the magnetic field up to the (M-2)th order, the developed observer excites the third-order spatial harmonic of the magnetic field to estimate the rotor speed. Simulation results are provided to assess the performance of the observer.