Research On Regenerative Braking Energy Utilization Technique Based On Stationary Electrochemical Double Layer Capacitors In Metro Systems

Along with the centralization of the population in the world, urban rail transit (URT) grows flourish. As an important part of the URT, the metro vehicle gets the favour of all countries for several reasons such as large capacity, high speed and efficiency, safty and reliability as well as running on the dedicated lines. Because the non-controlled rectifier diode is used by the DC traction substation, the regenerative braking energy can only be consumed by braking resistor. The control mode is widely used for its easiness, reliability and low cost, but the regenerative energy can not be utilized resulting in the rising of ambient temperature. In this paper, the utilization technique for recovery regenerative energy based on stationary electrochemical double layer capacitors (EDLCs) energy storage systems (ESSs) is investigated.The regenerative energy is absorbed by trackside ESSs based on EDLCs when the metro brakes, while released as the metro starts to achieve recycling utilization for the re-generative energy. Furthermore, the DC bus voltage is controlled within the allowable range. All the operation is completed by detecting the DC voltage and other parameters. Compared with the traditional resistance braking technology, the regenerative energy can be utilized effectively by ESSs. On the other hand, the rated power of DC traction substation is reduced.Firstly, regenerative braking energy utilization techniques including resistance bra-king technology, inverter technologies, battery ESSs, flywheel ESSs and EDLCs ESSs are discussed. Based on the research of working principle and technical advantage, t-hese regenerative braking energy utilization techniques are compared in the production cost, service life, energy saving effect and so on. Trackside ESSs based on EDLCs studied in this paper has advantages in low maintenance cost, long service life, high efficiency, energy savings and stabilizing the line voltage.Sencondly, the load torque of metro vehicle is deduced and confirmed. Traction motor control model is built according to rotor flux oriented vector control method. Taking Shenzhen Metro Line 5 as the application background, the metro simulation model based on MATLAB/Simulink is built and simulation interface is optimized. In the light of operating schedules and circuit parameters, the running state of metro in the typical power supply sections is simulated. Based on the simulation results, the basis of choosing the desired power and capacity of ESSs is proposed.Thirdly, the capacity configuration of EDLCs ESSs is researched. According to the power conservation, an indirect voltage control strategy is elaborated in detail and optimized. Through simulation, the energy storage device and control strategy are verified. The feasibility of ESSs is demonstrated from the relationship between cost and benefit. For the convenience of operation, the human-computer interaction interface is designed building on the MATLAB/Simulink GUI module. Simulation results show that the regenerative energy can be utilized effectively by ESSs, the DC bus voltage is controlled, and the rated power of DC traction substation is reduced.Lastly, a bi-directional DC/DC converter (BDC) is designed and a low-power e-xperiment prototype is built. The experiment test of BDC (Buck mode and Boost m-ode) is completed to verify the correctness of energy storage and control strategy.