A research on direct torque control method in view of space voltage vector

This text aims to solve such problems as the large pulsation of battery electric locomotive traction motor torque at low speed, the unpredictable frequency spectrum of the torque, and the large frequency and wastage of high-speed inverter switching. Starting from space voltage vector, this text adopts the method of multiple vector synthesis and mutual switch control of motor air-gap flux according to speed variation, to analyze and design an AC variable speed system of direct torque control. This text analyzes the control mode of hexagon flux linkage and polygon flux linkage in detail, and states the implementation process of rotor flux observation and choosing switch state based on flux tolerance. Results of simulation experiment indicate that the method of flux mutual switch control can restrain the pulsation issues of magnetic torque and stator flux linkage at electrical machine´s low speed more effectively than hexagon flux linkage direct torque control, and at the same time it posses good dynamic and static performance.