Active flux based motion-sensorless vector control of DC-excited synchronous machines

This paper introduces a novel, active flux based, motion-sensorless vector control system for dc-excited synchronous motor, suitable for wide speed range applications. The active flux vector, defined as the torque producing flux, is aligned always along the rotor d axis and renders the machine model as with non-salinent poles magnetic saturation. This vector is obtained from the estimated stator-flux vector minus L_qi_s vector, via a combined current-voltage model stator-flux observer, and through L_q(i_m) depending on the total magnetization current. This way, the rotor position and speed estimation is simplified and wide speed range control is feasible. The paper introduces all components of the proposed system including a novel commissioning procedure for magnetization curves identification and a novel method for initial rotor position estimation. Details of control system implementation on DSP controller test platform and plenty of experimental test results for a traction system using dc-excited synchronous motor with 80 Vdc battery are presented. The test results fully validated the proposed solutions and show high performance starting from 15 rpm with heavy load disturbance rejection and rather quick torque response.