Extended observer-based simultaneous online parameter estimation of inverter-fed squirrel-cage induction machines considering the influence of current and speed measurement errors

This paper deals with the online parameter estimation of squirrel-cage induction machines using the Gradient Descent Method and coupled stator and rotor flux observers. Stator resistance, rotor resistance and mutual inductance can be estimated simultaneously in real time. For a non-ambiguous parameter tracking, an additional voltage is superimposed. The influence of inverter nonlinearity, current and speed measurement errors is investigated. The presented approach is applicable to a standard industrial drive, including current measurement and motor speed feedback. The concept is verified by experimental tests for open loop V/f control as well as for field-oriented control.