Control And Co-simulation Of Doubly-fed Linear Motor

With the development of urban rail transit in China,the driving modes of rail transit are gradually diversified.Among them,the linear motor driven train has become an important part of the rail transit drive system because of its strong climbing ability,small turning radius,low noise,environmental friendly and safety.Doubly-fed linear motor(DFLM)is a new type of linear motor.Its unique double-sided winding structure makes it have a variety of different operation and control modes,and has potential application in the field of rail transit.This paper studies several existing difficulties in the practical application of DFLM.Firstly,the paper introduces the basic structure of DFLM,analyzes the working principle of DFLM,and builds the mathematical model of motor in three-phase static coordinate system.The mathematical model of DFLM in two-phase rotating coordinate system is deduced to simplify the analysis and provide a theoretical basis.Secondly,the thrust fluctuation of DFLM is studied.The bilateral slotted structure of the motor is the main cause for the thrust fluctuation of the motor.The two-dimensional model of the motor is established,and the air gap distribution function of the motor is deduced.The current layer method is used to deduce the air gap magnetic field distribution,and then the analytical formula of motor thrust is obtained to analyze the cogging effect on motor thrust.Based on the Fractional Slot theory,the structure of unequal pole distance between rotor and stator is adopted to suppress the thrust fluctuation of motor.Specifically,the mover adopts a short polar distance structure,and a wide teeth are used at the end of the polar distance to compensate the polar distance.The results show that the motor thrust fluctuation is less in the compensation structure after the pole distance period of a pair of rotor,which is conducive to the application of the DFLM.Thirdly,based on the principle of vector control,the motor stator and rotor current are selected as the directional vectors,and the vector control system is built in MATLAB.At the same time,the improved stator flux observation model is selected to simulate the dynamic output performance of the motor during acceleration,constant speed and deceleration.The simulation results show that the DFLM control system based on mover current vector orientation has fast dynamic response and good speed following effect.Finally,the Co-simulation control system of DFLM combined with Maxwell,Simplorer and MATLAB is built.The finite element model of motor is built in Maxwell,the power supply circuit of control system is built in Simplorer,the vector control algorithm is built in MATLAB.The Co-simulation of motor is completed to verify the dynamic effect of motor structure and rotor current vector control system.The results show that the motor joint simulation are more comprehensive and the output is closer to the real operation of motor.The unequal pole distance structure of DFLM has better thrust performance,and the control system based on mover current vector orientation has good dynamic effect.