Sensorless very low and zero speed estimations with on-line secondary resistance estimation of induction motor without adding any signal

In the speed sensorless control of the induction motor, the machine parameters (especially the secondary resistance R₂) have a strong influence to the speed estimation. It is known that the simultaneous estimation of the speed and the R₂ is impossible in the slip frequency type vector control, because the secondary flux is constant. In addition, the output voltage error due to the dead time and the voltage drop of the inverter influences the secondary flux estimation, but the simultaneous compensation of the output voltage and the primary resistance R₁ is very difficult. In this paper the R₂ estimation without adding any additional signal to the stator current is proposed. In the high frequency range, the R₂ is estimated in the transient state, and in the very low frequency range, the R₂ is estimated in proportion to the estimated R₁ when the ideal voltage source by the power op-amp is used instead of the voltage source inverter to avoid the output voltage error. In use of these algorithms, the low speed estimation was possible and the zero speed control was achieved under the 10-40% load condition. This paper clarified that the zero speed estimation is possible with the primary and secondary resistance estimations when the output voltage is ideal