Online rotor resistance estimation using the transient state under the speed sensorless control of induction motor

In the speed sensorless control of the induction motor, the machine parameters (especially rotor resistance R(2)) have a strong influence on the speed estimation. It is known that the simultaneous estimation of the rotor speed and R(2) is impossible in the slip frequency type vector control, because the rotor flux is constant. But the rotor flux is not always constant in the speed transient state. In this paper, the R(2) estimation in the transient state without signal injection to the stator current is proposed, This algorithm uses the least mean square algorithm and the adaptive algorithm, and it is possible to estimate R(2) exactly. This algorithm is verified by the digital simulations and experiments.