New IM torque control with implicit rotor field tracking

The paper proposes an IM torque control based on the stator current vector reference frame. The introduced control concept rejects the paradigm of decoupled control with constant rotor flux vector. Instead of this widespread assumption the proposed control is derived from the augmented dynamic equilibrium conditions assuring the existence and uniqueness of the inverse mapping between the required torque end stator current vector. By manipulating simultaneously the magnitude and the rotation speed of the stator current vector in an appropriate way the rotor flux trajectories are forced to change only inside the globally stable sector under all operating conditions. Additional features as maximal torque per ampere steady state ratio, almost perfect command tracking at non-zero rotor flux and insensitivity to the bounded perturbation of the rotor time constant, characterize introduced control. Implementation of this control requires estimation of the machine torque and cascaded current controllers. Experimental results confirm the key expectations and show the potential and benefits of the proposed control.