Over-Modulation with Improved Stability for Synchronous Reluctance Motor Drives Incorporating Field-Weakening Operation

This paper presents a simple and stable overmodulation scheme for direct torque controlled synchronous reluctance motor (SRM) drives incorporating field-weakening (FW) operation. It contributes to produce fast torque response and extended constant power speed range for SRM drives. Moreover, an adaptive activation mechanism is proposed to ensure the stability of drives under all operating conditions. Besides, the problems of high torque ripples and variable switching frequency experienced by conventional direct torque control are solved by employing a constant switching frequency based torque regulator and combining it with the proposed over-modulation scheme. Simulation and experimental results are provided to verify the effectiveness of the proposed approach.