Dynamic torque control performance of the Direct Flux Control scheme in field weakening range

At high angular velocity, the induction motor is operated in the field weakening range due to voltage limit of the inverter. Field oriented vector control is unsuitable for this operation due to coupling, non-linearities and saturation of linear current controllers. Proposed Direct Flux Control scheme does not use current controllers to achieve dynamic torque control. Vector control of the stator flux vector allows for dynamic change in torque in all regions, including field weakening with six-step operation. This paper describes the dynamic torque control by using stator flux vector magnitude change and it´s angular velocity. Such control is carried out by using fixed switching frequency dead-beat control of stator flux. The method is demonstrated experimentally.