Low-speed control improvements for a two-level five-phase inverter-fed induction machine using classic direct torque control

A novel technique that improves the low-speed performance of a five-phase induction machine (IM) driven by a two-level inverter using the classic direct torque control (DTC) technique is presented. Demagnetization of the stator flux is investigated when the IM runs at lower speeds, and a solution is provided to overcome this phenomenon. The proposed technique reduces the demagnetization phenomenon by using the +/- 36 degrees displaced voltage vector during low-speed operation but employs the +/- 72 degrees displaced voltage vectors otherwise. The demagnetization of the stator flux is shown by simulation and experiment to be eliminated using the proposed technique. It can be observed that the proposed technique can significantly improve the rate of change of stator flux, the torque response, and the speed response compared with traditional method.