Real-time estimation of induction machine parameters using sinusoidal PWM voltage signals

A method for estimating in real-time operating parameters for a multi-phase induction machine with a stator and a rotor for use in a torque delivery driveline having a torque input member, a torque output member and a torque controller having a processor unit with a memory and parameter estimation algorithms stored in memory, the driveline responding to torque commands that are related functionally to operating variables including stator voltage, stator voltage frequency and stator current in a synchronously rotating frame relative to electrical excitation speed, the processor unit operating on the variables in accordance with instructions imposed on it by the stored algorithms, the method including the steps of:

• expressing stator voltage as a function of stator current, stator resistance, stator flux and stator excitation frequency;
• establishing a functional relationship between rotor current, rotor flux, rotor resistance, electrical speed of applied stator voltage and rotor electrical speed;
• transforming the functional relationship to eliminate derivatives and flux variables when the induction machine is in a steady state;
• computing rotor current as a function of measured stator current;
• computing stator voltage as a function of induction machine parameters, stator current, electrical speed and slip frequency;
• projecting stator voltage on axes related to the stator current in a synchronously rotating frame;
• transforming projected stator voltage orthogonal components and determining characteristic parameters using the orthogonal voltage components and stator current amplitude;
• and
• computing stator resistance and stator inductance as a function of the characteristic parameters when load on the torque output member is minimal.