A Novel Direct Torque Control for Electrically Excited Synchronous Motor Drives with High Power Factor and Low Ripples in Flux and Torque

摘要

A direct torque control (DTC) method for electrically excited synchronous motor (ESM) drives has been investigated in this paper. It is based on the compensation of the stator flux linkage vector error using the space vector modulation to decrease the ripples in torque and flux linkage. In order to increase the power factor and load ability of ESMs, an optimum rotor field current control scheme has been presented, which is suited well in the whole speed range. In the closed loop of the rotor current control, the reference rotor current is directly calculated with the torque and stator flux linkage modulus references. Compared to the traditional DTC method, the results of experiments show that the presented DTC has low ripples in torque and flux linkage, and almost achieves unity power factor.