Sensorless Starting of a Wound-Field Synchronous Starter/Generator for Aerospace Applications

The present paper describes an angle and speed estimation algorithm suitable for the control of a wound-field synchronous starter/generator without position sensors for aircraft engine starting applications. The proposed control strategy is based on the injection of a high-frequency voltage signal and the subsequent demodulation of the resulting high-frequency stator current components. The coupling due to high- speed operation that degrades the estimation accuracy of similar algorithms based on signal injection is taken into account. Modelling of the machine response to a high-frequency voltage signal injected into the estimated d-axis is presented, also considering the influence of damping circuits both on the d- and q-axis. Local asymptotic stability of the proposed observer is also demonstrated. Through extensive experimental results the proposed control technique is shown capable of guaranteeing full-torque sensorless operation at zero speed and sustained operation up to engine ignition speed.