Current and flux regulation in field-weakening operation [of induction motors]

Induction motor field-weakening techniques have been developed which provide maximum torque capability above rated speed. Unfortunately most of these techniques are valid only for steady-state operation and show significant sensitivity to DC bus voltage and machine parameters. This paper analyzes the requirements of dynamically providing maximum torque under field-weakening operation. Three major issues are addressed: current regulator design; saturation techniques for current regulators in order to ensure best performance under voltage constraints; and flux regulator design to minimize transient errors when varying flux. Maximum DC bus utilization through the proper use of saturation techniques, dynamic response and reduced sensitivity are the advantages of the proposed solution.