Sensorless Control of Electrically Excited Synchronous Machines Considering Magnetic Saturation and Flux Linkage Dynamics for Automotive Applications

For electrically excited synchronous machines (EESMs) used in automotive applications, the flux linkages are nonlinear and the magnetic saturation plays an important role. The coupling between $d$ -axis and exciter axis in EESMs introduces a significant fluctuation of the flux linkages due to current changes. To cope with these problems, a novel observer incorporating flux linkage saturation and dynamics caused by the coupling is proposed. The flux is not regarded as linear, but the absolute and differential inductances are used in the observer. Moreover, the current dynamics induced flux variations are compensated for. As the system is nonlinear and time-varying, Lyapunov's method is used to prove the stability of the system and to derive a speed-adaptive algorithm. The experimental results on an EESM test bench confirm the effectiveness of the proposed method.