Research And Design Of Modular Regenerative Braking Energy Storage System For Urban Rail Transit Train

With the continuing development of urbanization,urban rail transit depends on the advantages of high speed,heavy load,punctuality,security and stability became one of the most important ways to solve the traffic jams in big cities.Due to site interval close,the subway trains start and stop frequently and it will waste a lot of energy if we don't recycle them.So in this paper,the existing regenerative braking energy utilization programs will be analyzed and compared,combined with the characteristic which ultra capacitor charge and discharge speedy,regenerative braking energy storage system has been studied and designed.When the subway train brakes,the energy storage system absorbs excess regenerative braking energy and release to the contact line when the train starts,realized the reuse of braking energy from subway trains and stabilized the voltage of contact line.Through the collection of domestic and foreign literature,introduced the subway train traction power supply and braking methods.Stress analysis was carried out during the train braking process,combined with kinetic energy changes,the amount of regenerative braking energy available for a single brake is calculated.Using a modular energy storage system design,the energy storage system is divided into four independent energy storage modules in a cascade way to share the contact line voltage.Lithium-ion ultra capacitors are used as energy storage monomer and designed the internal capacitor array of the energy storage module to make sure it has high reliability in high voltage and current working environment.The bidirectional DC/DC converter acts as a bridge connects the contact line and the energy storage part.By using multiplexing topology design reduced the current fluctuation rate effectively.Designed a current cut-off negative feedback control method to guarantee the regenerative braking energy flow can be controlled.Through simulation analysis of the topology and control strategy by using Simulink,combining with experimental platform tests,verified the feasibility of the design.To solve the problem which voltage imbalance among the four energy storage modules,designed voltage equalizers,proposed a constant-frequency control strategy with variable hysteresis width,combining with the energy estimation algorithm to reduce the energy loss caused by energy flowing which balance voltage frequently among the modules,achieving a rapid and efficient voltage balance process between the four energy storage modules.Through simulation and small system tests,proving the correctness of the design.