| With the large-scale popularization and rapid development of urban rail transit,the huge energy consumption in the driving process has gradually become a problem that can not be ignored.Furthermore,the operation of metro vehicles in the interval has the characteristics of short time,frequent start and stop,and a large amount of recoverable braking energy.Therefore,to improve the utilization rate of regenerative braking energy and reduce the consumption of electric energy have become an urgent problem for modern metro operation system.Flywheel energy storage system(FESS),as a kind of energy storage mode with no pollution and high power density,has a broad application prospect in improving the utilization ratio of regenerative braking energy and restraining the fluctuation of traction network voltage.The flywheel energy storage motor(FESM)described in this paper adopts high-speed permanent magnet synchronous motor(PMSM),and takes the motor as the control research object.Based on the analysis of the working mechanism of FESM and the derivation of its mathematical model of charge and discharge,this paper,with the support of Natural Science Foundation of China project(51707082,51877071),studies the nonlinear and strong coupling problems in FESM.The main work and research results are as follows:Firstly,the basic structure and working principle of FESS are introduced.The mathematical model of FESM is given.The main parameters that affect the capacity and power of FESM are analyzed,which lays a foundation for the design of its charge and discharge control system.Secondly,based on the engineering application background of Alstom a type car produced in France in Nanjing Metro Line 1,the locomotive dynamics model is established.The relationship between the resistance of the locomotive and the output traction and braking force is analyzed,and the energy and power of the single start and stop process are calculated quantitatively.Combined with the simulation results of traction power supply system,the necessity of setting energy recovery system to suppress the fluctuation of traction network voltage is illustrated.The basic performance parameters,such as FESS setting scheme and corresponding matching capacity,are determined to recover the regenerative braking energy of urban rail transit.Thirdly,the load characteristics of traction motor in FESM are introduced and simplified as equivalent DC model.This leads to the power balance model of FESM converter,based on which the current and torque characteristics of FESM under charge and discharge conditions are analyzed intuitively.According to the performance requirements of FESM under charging condition,the motor control strategy with speed as the primary control index is determined.The limitations of traditional speed control methods are summarized.In view of the speed requirements under the specific background of urban rail operation,a second-order sliding mode speed control based on super spiral algorithm is proposed,and its construction principle and stability are described in detail.Finally,according to the performance requirements of FESM under discharge condition,the principle of motor control with bus capacitance voltage as the primary control index is introduced.By analyzing the defects of the voltage closed-loop function under the traditional PI control,the necessity of improving the double closed-loop sliding mode voltage control is illustrated.The advantages of the proposed method are verified by simulation software.Through the analysis of cooperative operation of traction motor and FESM,the effectiveness of setting FESS for regenerative braking energy is verified through the improvement of network voltage fluctuation. |
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