Sensorless Estimation of Rotor Current and Rotor Position for Inductive Electrically Excited Synchronous Machines

Adopting electrically excited synchronous machines (EESM) as traction machines in electric vehicles has multiple advantages such as no usage of rare earth magnets, high power density and unity power factor over a wide operating range. Combining the EESM with a contactless, inductive power transfer system (WPT) eliminates drawbacks of slip rings and brushes such as dust generation and wear and tear. Utilizing a WPT system for rotor power transfer requires the usage of a rotor current observer for closed-loop control as direct measurement is unfeasible. In this publication, a stator flux observers known from position sensorless control is adopted for rotor current estimation. The performance of the observer over a wide speed range with a closed-loop rotor current control is verified both simulatively and experimentally.