| In recent years,with the rapid development of urban rail transit in China,the energy consumption of urban rail transit increases sharply.In order to make full use of the regenerative braking energy of the train,reduce the output energy of the traction substation and suppress the voltage fluctuation of the dc traction network,an energy storage device can be introduced into the dc traction power supply system.With the increase of departure density,the peak power of traction substation gradually increases,and the energy demand to reduce this peak power is large.Moreover,due to the frequent start-stop of the trainand large braking and traction power,the hybrid energy storage device of Li Ti O battery with high energy density and supercapacitor with high power density is adopted.With the addition of battery,the energy storage device can also be used as an emergency standby power source for emergency self-traction of the train in case of wide-area power failure.Based on the control strategy of single battery or supercapacitor energy storage system,the energy,power and cost differences between lithium titanate batteries and ultracapacitor and the energy flow characteristics of dc traction power supply system are considered in this paper.An energy management strategy based on dynamic adjustment of charging and discharging threshold and battery/supercapacitor power distribution ratio to reasonably control the SOC range of lithium batteries and supercapacitors is proposed.The proposed energy management strategy not only ensures the full absorption of the regenerative energy of the train and reduces the failure rate of the train regeneration,but also reduces the peak output power of the traction substation and improves the overall economic benefits of the energy storage device.In this paper,firstly,the traction substation,train and hybrid energy storage system in dc traction power supply system are modeled,and the characteristics of each part are analyzed,so as to provide theoretical basis for the establishment of traction power supply system simulation platform and the control strategy research of hybrid energy storage system.Secondly,according to the simulation platform of traction power supply system,when the train departure interval is relatively small,the residual regenerative energy of the train is small,and the peak output power of traction substation is high.When the departure interval is large,the residual regenerative energy of the train is large and the output peak power of the traction substation is small.At the same time,the influence of charging and discharging threshold on energy absorption and release of energy storage device is analyzed.Combined with the characteristics of batteries and supercapacitor energy storage components,this paper proposes a SOC dynamic adjustment energy management strategy for hybrid energy storage devices based on train departure intervals.The strategy according to the departure interval dynamic allocation power between battery and ultracapacitor,and by adjusting the charge and discharge threshold to realize the SOC control ofbattery and supercapacitor.While ensuring the full absorption of the remaining regeneration energy of the train to reduce the train regeneration failure,the peak output power of traction substation is reduced according to the demand,and the overall economic benefit of the energy storage device is improved.The feasibility and effectiveness of the proposed control strategy are verified and compared by the multi-station multi-vehicle simulation platform.Finally,a 1MW ground Li Ti O battery-supercapacitor hybrid energy storage device is built,and different experimental conditions are designed to verify the high-power performance and functional logic of the energy storage device.It lays a foundation for the experimental verification of SOC dynamic adjustment energy management strategy of hybrid energy storage device based on train departure interval. |
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