Dynamic control of torque in overmodulation and in the field weakening region

Abstract

At high angular velocity, the induction motor is operated in the field weakening range due to the voltage limit of the inverter. Field oriented vector control (FOC) is unsuitable for this operation duetocoupling, non-linearities,andsaturationof linear current controllers. A proposed direct torque control space vector modulation (DTC–SVM) scheme using SVM does not use coordinate transforms or current controllers to achieve DTC. Control of the stator flux vector allows for dynamic change in the torque in all regions,including field weakening with the six-step operation. This paper describes the torque control dynamic in the field weakening range, using a step change in stator flux vector magnitude and it’s angular velocity. The method is demonstrated experimentally.