Direct thrust control of linear induction motor in full operation range for traction application

In this paper, mathematic model of linear induction motor (LIM) is developed considering the influences of end effects. A full speed range direct thrust control (DTC) scheme for LIM is proposed considering the parameters dynamic variation and characteristic of railway traction application. In low speed range, an improved indirect stator-quantities control (ISC) with circular flux track is applied to replace the hysteresis controller and switching table in traditional DTC, which can improve the low speed performance effectively as well as maintain the robustness. In medium and high speed range, direct thrust control with hexagonal flux track is utilized to reduce the switching frequency and power loss of the inverter. Experiment results show that the transitions between different schemes are smooth. Moreover, the system has great dynamic and steady state performance. The proposed method has good application prospect in the traction control of LIM driven systems.