PWM-based sensorless control of electrically excited synchronous machine using mutual inductance

This paper proposes a sensorless control of an electrically excited synchronous machine (EESM) using mutual inductance. EESM is a synchronous machine that has a field winding to generate field flux. The field winding and the stator winding are mutually coupled together with mutual inductance. The mutual inductance is derived as a function of the rotor position by the principle of a rotary transformer. With the derived mutual inductance, the proposed method estimates the rotor position from the mutually induced field current by fundamental pulse-width modulation (PWM) switching voltage of stator winding. High-frequency current sampling synchronized with PWM switching is used to process the field current. The simulation results of sensorless speed control and position estimation under saturation condition validate the proposed method and its robustness to parameter variation.