Research On Energy Flow Control Of Doubly-fed Linear Motor

In recent years,with the development of economy and the changing of urban structure,rail transit has became an indispensable infrastructure of transportation.The train with linear motor has became an important part of the rail transportation system because of its advantages of high climbing ability and small turning radius.In this paper,the DFLM(doubly-fed linear motor)is the research object,the method of theoretical analysis and simulation verification is used to analyze the energy flow between the stator side and rotor side in various operation conditions,and the bilateral modulation method of DFLM is introduced.The operation data between two stations of Chengdu Metro Line 5 is adopted to simulate and verify the feasibility and validity of the contactless power base on bilateral modulation method.At first,the special structure of the DFLM is introduced,and its operation principle is analyzed,on this basis,the mathematical model of DFLM in the three-phase stationary coordinate system is derived,and based on principle of power invariance,the mathematical model of DFLM in the two-phase rotating coordinate system is derived.Secondly,combined with the end effect of the DFLM,the one-dimensional electromagnetic field analysis method is used to derive the analytical formulas of the motor airgap magnetic destiny,in addition,combined with the full-filled slots structure of the DFLM,the airgap analytic expression under the influence of slot effect is derived.Matlab Simulink software is adopted to simulate the results of the deduction above,and the simulation results is compared with Ansoft finite element simulation results.The simulation results show that,there is no obvious distortion of airgap magnetic flux density at the entry-end and exit-end,but there are many sawtooth spikes in the waveforms,which shows that influence of the longitudinal dynamic end effect on DFLM is very small,and influence of the slot effect is more obvious.Base on the analysis results of the above effects,DFLM equivalent circuit is obtained,which is the basis of the analysis and control of DFLM energy flow.Finally the stator current oriented vector control strategy of DFLM is it introduced,on this basis,according to the equivalent circuit,the energy flow situation of motoring and braking condition is analyzed,and the simulation verification is carried out.At the same time,applying DFLM to realize contactless power of urban rail train is considered.The bilateral control strategy is used to adjust the operating condition of the motor by controlling the stator frequency to make the energy storage of the rotor side meet the electricity requirement of the vehicle equipment.Then the control strategy is simulated with the operation data between two stations of Chengdu Metro Line 5.The simulation results show that the energy flow direction of the motor can be adjusted flexibly by bilateral control of stator and rotor,it not only can make the energy storage of the rotor side meet the electricity requirement of the vehicle equipment,but also can avoid the situation of energy saturation.