A novel technique of rotor resistance estimation considering variation of mutual inductance

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Abstract
The study proposes a method to estimate AC induction-machine mutual inductance and rotor resistance based on terminal voltage, current, and shaft speed as input signals. For certain operating regions of the machine, it is verified that the mutual inductance can be accurately estimated regardless of wide stator resistance variation. The equations to estimate mutual inductance and rotor resistance are derived from the machine's nonlinear differential equations. The nonlinear equations are solved using integration. The initial condition for each integration is found by an averaging of measured input signals. The validity of the suggested method is confirmed by computer simulation and experimental tests. The simulation results considered the dynamics of the induction machine, current controller, and field-oriented controller and show that the mutual inductance and rotor resistance can be estimated with reasonable accuracy even in the transient state. Mutual inductance and rotor resistance estimations for the experimental test results support the simulation results with negligible error.