低转矩磁链脉动型电励磁同步电机直接转矩驱动系统的研究

电励磁同步电动机定子电感通常较小,转子阻尼绕组的存在使得电机暂态电感更小。若采用转矩及磁链滞环型直接转矩控制(基本DTC)策略电机电磁转矩及定子磁链脉动较大。针对电励磁同步电动机引入一种空间矢量调制型直接转矩控制(SVM-DTC)策略。它基于电励磁同步电动机中转矩角控制电磁转矩原理,利用空间电压矢量合成出最佳电压矢量实时补偿定子磁链矢量误差,以达到减小电动机在运行中电磁转矩及定子磁链脉动量之目的,同时又能基本维持开关频率恒定。仿真和实验结果证明,与基本DTC相比较,SVM-DTC电磁转矩和定子磁链脉动大幅度降低;电机起动电流峰值大大减小,稳态电流畸变较小;同时系统能够平稳地由恒转矩区过渡到弱磁区运行。

Research on a Direct Torque Control for Electrically Excited Synchronous Motor Drive with Low Ripple in Flux and Torque

The electrically excited synchronous motor (ESM) has typically small synchronous inductance values and quite low transient values because of the damper windings mounted in the rotor. Therefore the torque and stator flux linkage ripples are high in the direct torque control(DTC) drive of ESM with torque and flux linkage hysteresis controller(basic DTC). A DTC scheme with space vector modulation(SVM) for ESM was investigated in this paper. It is based on the compensation of the stator flux linkage vector error using the space vector modulation in order to decrease the torque and flux linkage ripples and produce fixed switching frequency under the principle that the torque is controlled by the torque angle in ESM. Compared with the basic DTC, the results of simulation and experiment show that the torque and flux linkage ripples are reduced, the maximum current value is decreased during the startup and the current distortion is much small in the steady state under the SVM-DTC. The field-weakening control was incorporated with the SVM-DTC successfully.