Research On Regenerating Energy Utilization Technique In Urban Rail System

With the rapid development of city rail vehicle system, braking energy recycling of city rail vehicle has gradually become great focus. City track traffic vehicle during braking process will produce a considerable amount of braking energy. In order to recycle the braking energy, the paper presents three schemes: energy storage type, grid-connected type and combination of two types. In addition, tests and simulation are researched in this paper. Brake energy recovery technology to realize recycling of regenerated energy and also maintain the stability of DC traction network voltage, effectively preventing the fluctuation of power load in the city track traffic and the failure of regeneration, which have good economic and social benefits.Firstly, this paper establishes a simulation platform with750V electrified railway equivalent model, which can simulate the effect which startup, cruise and braking develop on DC traction network voltage by vector control motor. That provides a good tool for energy utilization technology of regenerative braking.Secondly, this paper designs a grid-connected type of regenerative braking energy system to recycle electric energy. In study of the grid-connected control scheme, the control strategy of DC-AC converter is gained. Moreover, software locked loop of three-phase voltage is designed and the realization method of SVPWM is analyzed. At the same time, the result of simulation verifies the correctness and validity of SPLL and DC-AC converter control strategy.Thirdly, the hardware and software of regenerative braking energy utilization system are designed and a DC-AC converter is developed. The control strategy is verified based on designed test platform. The experimental results verify the correct of proposed strategy.Fourthly, this paper designed super capacitor energy storage system to provide traction for train or absorb the regenerative braking energy and develop the mathematical model based on analysis of the composition and design method of system. In addition, the paper develops charge and discharge control strategy of super capacitor energy storage system and gets simulation results. A dual DC-DC converter is designed and complete buck and boost experiment.Fifthly, this paper presents a type of regenerative braking energy grid-connected system based on the advantages and disadvantage of full power feedback and full storage of regenerative braking energy. This system reduces the capacity, volume and cost of energy storage and buffers impulse, brought braking energy feedback, for AC grid. The paper designs two algorithms of the priority of energy feedback and energy storage and compares these two algorithms by simulation. The results show energy storage priority control strategy is more suitable for regenerated energy recycling.Finally, In order to make use of the regenerative braking energy stored in the super-capacitor and improve the efficiency of the energy storage device, the auxiliary inverter power unit is designed, and the VF and PQ control scheme are used. The simulation and experimental results verify rationality of the auxiliary inverter power unit.