Improved torque capability through overmodulation for Direct Torque Control hysteresis-based induction machines

This paper presents a simple overmodulation method employed in direct torque control (DTC) hysteresis-based structure. The overmodulation method is utilized to obtain higher torque capability for a wider range of speed operation. The proposed overmodulation strategy is based on the control of stator flux vector. It is shown that the switching pattern of the voltage vector in the overmodulation mode can be established by changing the stator flux locus from circular to the hexagonal shape. The main benefit in the proposed strategy is its simplicity and it can be well-implemented in many electric drive applications to obtain maximum torque capability for a wider speed range operation.