Speed Sensorless Direct Torque Control of Asymmetric Six-Phase Induction Motor

This paper presents Direct Torque Control (DTC) of asymmetric six-phase induction motor without using speed sensor. Speed adaptive flux observer is used for the purpose of speed and stator resistance estimation. Observer stability is ensured by selecting gain matrix based on Lyapunov’s stability theorem. DTC technique in multi-phase drive tends to introduce harmonics in phase currents, if effect of voltage vectors in auxiliary (xy) subspace is not reduced. One of the recently developed technique having capability to reduce magnitude of flux vector in auxiliary (xy) subspace results in substantial current harmonics reduction, is implemented. Application of speed adaptive flux observer is tested with and without xy subspace component reduction technique. The comparative performance of speed adaptive flux observer is examined under steady state and dynamic condition with and without xy subspace components reduction. Validity of speed sensorless control scheme is demonstrated by experimental results in both steady state and dynamic conditions.