A Performance Improvement of V/f Control Using a Disturbance Observer

This paper proposes a dead-time compensation method with a disturbance observer and a current controller for V/f control. Dead-time compensation is very important to improve motor drive performances in the low speed region. The proposed compensation method is composed in the d-q rotational frame. The ripple of the d-axis current caused by the dead-time is suppressed by an auto current regulator, the ripple of the q-axis current according to the dead-time is suppressed by the disturbance observer. The control of the d-axis current is added the auto current regulator to the V/f control. As a result, the magnitude of the motor current can keep more than the rated exciting current in spite of the low speed region with the V/f control. The control of the q-axis current only uses the disturbance observer to suppress the voltage error of the dead-time. In this paper, the performance of the proposed controller in the low speed region is discussed based on the experimental results. The proposed method can improve the current distortion to less than quarter against the conventional method. Although the disturbance observer requires motor parameters, it is not so sensitive