Impact of parameter variations on speed estimation in sensorless rotor flux oriented induction machines

The aim of this paper is to investigate speed estimation error and other detuning effects that will take place due to parameter variations in an indirect rotor flux oriented (RFO) induction machine. Speed estimation is performed using rotor flux based MRAC scheme and only steady-state behaviour, under ideal conditions, is dealt with. Variation of all the parameters that influence operation of the drive is considered, in order to enable a comparative insight into the relative importance of various parameter variation effects. The approach used in the study closely parallels the one developed by Levi and Wang (see IEEE Ind. Elec. Soc. Annu. Meet., IECON, p.977-82, 1997) for the same drive. However, while the previous paper investigated only steady-state detuning caused by omission of iron loss representation in the control system and in the estimator, this paper studies all the possible sources of detuning (stator and rotor resistance variation, main flux saturation, leakage inductance variation). All the results are valid for modified rotor flux and back EMF methods as well.