Identification of the induction motor parameters at standstill including the magnetic saturation characteristics

Abstract

Identification of the induction motor parameters at standstill is studied in this thesis. The main goal of this work is to search for the feasible and applicable speed sensorless self-commissioning schemes. The magnetic saturation of the magnetizing inductance is taken into account. The magnetizing inductance is modeled as a function of the stator flux. Two different identification schemes are chosen based on the literature review. First method uses the single-axis sinusoidal excitation as the test signal. Second method uses the DC-decay test for the magnetizing inductance estimation and DC-biased sinusoidal excitation for the leakage inductance and rotor resistance identification. The DC-decay test is found to be a suitable method for identification of the magnetizing inductance. The single-axis sinusoidal excitation is found to be problematic in the saturation region. The source of the inaccuracy in the single-axis sinusoidal excitation is studied and the reasons are explained. The sensitivity of the schemes to the stator resistance and stator voltage errors is evaluated. Both methods show a very high sensitivity to the stator voltage errors in the case of the magnetizing inductance estimation. However, the DC-decay test shows a lower estimation error in the presence of the stator resistance errors. The estimation of the leakage inductance is robust against the stator voltage errors when the method based on the single-axis sinusoidal excitation is used. The estimation of the rotor resistance using the DC-biased excitation depends on the DC offset current in the presence of both the stator resistance and stator voltage errors.