Patent ID: 8476871

Claim:
A method comprising: receiving signals indicative of stator currents and rotor currents of a doubly-fed induction machine, the stator currents and the rotor currents being represented as a 2-phase vector in a α-β coordinate frame; processing the rotor current vector with a rotor position estimate vector; determining a scalar error quantity in dependence upon the stator current vector and the processed rotor current vector; integrating the scalar error quantity; determining an estimate of the rotor angular frequency in dependence upon the integrated scalar error quantity; determining a rotor position estimate by integrating the estimate of the rotor angular frequency; determining a rotor position estimate vector in dependence upon the rotor position estimate; providing the rotor position estimate vector for processing the rotor current vector; and, providing a signal indicative of the rotor position estimate vector and a signal indicative of the estimate of the rotor angular frequency for controlling the doubly-fed induction machine.