Adaptive Energy Management And Capacity Configuration Of Stationary Hybrid Energy Storage System In Urban Rail Transit

With the continuous expansion of urban rail transit,in order to improve energy and environmental issues,further improving the energy efficiency of urban rail transit has become the focus of the government,industry and the whole society.The energy storage system installed in the traction substation can effectively recycle the regenerative braking energy of the train,reduce the energy consumption of the traction substation,and achieve the purpose of improving energy efficiency.The stationary hybrid energy storage system combining supercapacitor and lithium titanium oxide(LTO)battery can enable the energy recovery device to have both high power density and high energy density,which can solve the shortcomings of a single energy storage element and further improve the energy-saving effect.At present,the research on energy management strategies and capacity configuration of stationary energy storage systems is mainly based on a single energy storage system,and there is a lack of related research on stationary hybrid energy storage system.In order to give full play to the performance advantages of stationary hybrid energy storage system,this paper focuses on energy management strategy and capacity configuration,and provides theoretical support for the application of stationary hybrid energy storage systems.An adaptive adjustment strategy of the charge and discharge voltage thresholds of stationary hybrid energy storage systems based on fuzzy logic control is proposed to solve the problem of reducing the energy recovery rate of regenerative braking caused by the fluctuation of the no-load voltage of the substation and the change of the headway.The energy flow law of the traction power supply system under different no-load voltages and headways is analyzed,and the corresponding relationship between the energy flow and the voltage threshold adjustment is established for the purpose of improving the energy saving rate and ensuring the energy interaction between trains.Through this correspondence,a fuzzy logic control strategy for adaptive adjustment of the charge and discharge voltage thresholds of the energy storage system is constructed.This strategy does not need to obtain the information of other substations and trains,and relies on the energy state changes of the substation and the energy storage system to realize the judgment of the change trend of no-load voltage and headway,and automatically complete the corresponding voltage threshold adjustment.Taking the Beijing Metro Batong Line as the analysis object,the effectiveness of the proposed strategy is verified by simulation under the conditions of no-load voltage fluctuation and headway change.In order to give full play to the advantages of the two energy storage elements,battery and supercapacitor,effectively improve the energy recovery rate of regenerative braking and prolong the battery life,this paper proposes a hybrid energy storage system based on the state of charge of the energy storage system and the operation condition of the train.the power distribution strategy.Firstly,an offline optimization model of the power distribution of the hybrid energy storage system is constructed,and the optimal power distribution results under typical operating conditions are obtained by using the genetic algorithm.Then,according to the results,the power distribution characteristics under the corresponding operating conditions are extracted,and the optimal distribution rules of the charge power of the hybrid energy storage system are further explored through mathematical modeling.Based on this,an adaptive power distribution strategy is proposed.The strategy considers the state of charge of the energy storage system and the demand for charge and discharge power.On the basis of rule-based distribution,the neural network model is used to optimize distribution ratio according to the residual charge capacity and residual regenerative braking energy of the supercapacitor.In this paper,a simulation example is used to compare the proposed strategy with other strategies to verify the performance of the strategy proposed in this paper.Affected by many factors such as train operating conditions,power supply network parameters and headways,the capacity distribution of stationary hybrid energy storage systems is an optimization problem of complex systems with multiple objectives and multiple constraints.Directly using the intelligent optimization algorithm to realize the optimal configuration of the capacity of the multi-energy storage system has the problems of slow solution speed,low accuracy and easy to fall into the local optimum.To this end,this paper proposes a dual-layer two-stage capacity optimization configuration model for hybrid energy storage systems.The equivalent energy storage system is defined in the upper-layer model,considering the influence of different no-load voltage of each substation on the capacity configuration and voltage threshold setting of the energy storage system,and combines the multi-objective particle swarm optimization algorithm and the traction power supply system simulation platform to realize the two-stage optimization of the equivalent energy storage system capacity and voltage threshold.In the lower layer model,the optimization result of the upper layer is used as the input condition,and the second-order cone programming model of the hybrid energy storage system is established.For the Beijing Metro Batong Line,the energy storage system capacity configuration results of 11 substations on the whole line are given,and the advantages of the proposed capacity optimization configuration model in reducing the output energy consumption and investment cost of substations are verified.In order to verify the effectiveness and feasibility of the strategy proposed in this paper,a power hardware-in-the-loop(PHIL)experimental platform is built.Using the power amplifier as the medium,through the digital simulation platform to interact with the hardware test platform containing the hybrid energy storage system and DC/DC converter to simulate the traction power supply system environment under complex multi-train operation conditions.Experiments are carried out on the voltage threshold adjustment strategy and power distribution strategy proposed in this paper through the DSP controller to verify the effectiveness and feasibility of the proposed strategy.In addition,based on the MW-level stationary hybrid energy storage device at Liyuan substation on the Batong Line of Beijing Metro,an all-day grid-connected operation test based on the energy management strategy proposed in this paper is carried out to further verify the energy-saving effect and engineering practicability of the proposed strategy.The thesis has 126 figures,38 tables,and 128 references.