Flux-weakening control strategy of separately excited DC machine utilizing voltage regulation for modifying field current

This paper proposes a new approach flux-weakening control strategy of the separately excited DC machine. The proposed method is based on the closed-loop speed control in which the field current is independently controlled to adjust the flux-linkage in the flux-weakening operation. In order to achieve the maximum torque in the constant-torque region, the maximum field current is employed, while it is gradually modified in the constant-power region, following the increased speed, by the voltage regulation part. The modification current is determined based on the utilization of the difference voltages between command and voltage limit of DC-DC converter. The proposed method exhibits advantages such as high torque at low speed, wider operating speed range, robustness against machine parameters, and high efficiency in the constant-power region rather than without flux-weakening control. The effectiveness of the proposed method is verified by simulation results.