A hybrid DTC drive for high performance induction motor control

This paper presents a simple overmodulation strategy to achieve high torque capability for a wide speed range using a hybrid DTC scheme. The hybrid DTC drive incorporates both DTC-hysteresis and Direct Self Control (DSC) operations. In the proposed method, the control of circular flux locus is changed to the hexagonal when the motor operates under acceleration condition. By controlling the locus flux into the hexagonal, it is possible to extent the limit of stator voltage to the six-step mode, as the speed approaching to its base speed. As a consequence, an extended constant torque region as well as higher capability of torque in a flux weakening region can be achieved. In the proposed method, the hexagonal flux operation can be established by modifying the flux error status, before it is being fed to the look-up table. The feasibility of the hybrid DTC in providing high performance control is verified with some simulation and experimental results.