Research On The Drive System Of Linear Induction Motor For Linear Metro

The linear induction motor (LIM) rail transit system is developed quickly in china, it is necessary to research the drive system of the LIM rail transit system. This dissertation probes into the LIM drive system. Productive research leads to findings in the following scopes: reciprocal power-fed test rig for LIM drive system, high performance control strategy for LIM, optimal efficiency control of LIM, and optimize braking model of LIM rail transit system.The end effects and vertical force characteristics of linear induction motor are researched with finite element analysis method, and the curves of the electromagnetic force are got. Because the air gap of LIM is easily change when the vehicles are move, so that the control performance of LIM is affected. A vector control method based on a combined sliding-mode variable structure current controller is proposed for the above question. Simulation and test results show that the proposed control strategy has good steady-state performance, good features of speed and load force adjustment when the air gap of LIM is changed.After analyzing the development of the test rig for LIM rail transit system, a new reciprocal power-fed test system for LIM is proposed. The work principle and energy conserving principle of the system are expatiated. The dissertation designs and builds the mechanism component and transit component of the system, and develops a converter control system including DSP control board, 1GBT driver board, etc. The author comes out the associated control strategy of twin motors based on vector control, when the balance relations of the thrust force of the twin motors were analyzed. Simulation and test results show that the reciprocal power-fed test system for LIM using the above control strategy has good steady-state performance, good features of speed and load force adjustment, and the availability of emulating traction and braking condition tests of linear metro vehicles.This dissertation analyzes the power flow, loss component and efficiency characteristic of LIM, and also the loss model of inverter. An optimal efficiency control strategy combined with vector control is proposed based on loss mode of LIM. In order to reduce the effect for the dynamic performance, a switch control method is proposed. The stability of the control strategy is analyzed. Simulation results show the validity of the proposed control strategy compared with the traditional vector control method, especially in low load condition. Test results show that the efficiency of LIM is improved a little because of the inexactitude parameter of LIM. Steady and dynamic tests show that the proposed control strategy has good steady-state and dynamic performance.By analyzing the braking scheme of linear metro and power loss in braking process, a combined braking control strategy based on feedback braking and energy-consuming braking is put forward. Both theoretical analysis and simulation results show that the feasibility and validity of the proposed method. Considered about the characteristic of the linear metro line in Beijing and the above method, this dissertation gives the optimized braking mode suggestion of linear metro line in Beijing.