Fast rotor flux control of direct-field-oriented induction motor operating at maximum efficiency using adaptive rotor flux observer

A method of using an adaptive rotor flux observer to rapidly control the rotor flux of direct-field-oriented induction motors driven by a deadbeat rotor flux controller has been developed. The method ensures maximum efficiency in the steady state without degradation of the dynamic response. Furthermore, to solve the problem of flux current variations that arise from small errors in the measurement of the stator voltage and current, a flux current reference is calculated from the appropriate rotor flux in the steady state. Simulation and experimental results for an induction motor have demonstrated that this method yields the maximum efficiency and good speed response to changes in both torque and motor speed without any degradation in the transient characteristics