Internal model decoupling control of direct-drive permanent magnet synchronous motor based on disturbance observer

By using the vector control for direct-drive permanent magnet synchronous motor (DD-PMSM), the current static decoupling between d-axis and q-axis is realized, however, there still exists the dynamic coupling relationship. The d-q currents cannot be decoupled by the tradition PI method, and although the decoupling is accomplished to some extent by the internal model decoupling control method, the dynamic decoupling results are not quite satisfying when load torque or reference speed changes. Focused on the problem, a kind of internal model decoupling control method based on disturbance observer is proposed in the paper. The method regards voltage error caused by current coupling and changes of load torque, reference speed and motor parameters as system disturbances and a disturbance observer is used to observe the disturbance values. Then the observed values are regarded as compensation signal to compensate for the output of current internal model decoupling controller. The simulation results demonstrate that the d-q currents can not only be completely decoupled, but also the system has a strong robustness to parameters change and a good dynamic performance by using the proposed method.