| As an important part of the development of urban public transportation,urban rail transit has the characteristics of energy saving,land saving,large transportation volume,less pollution,and safety.It is an effective means to solve urban traffic congestion.However,the traction power supply system has large fluctuations in load power,which reduces the utilization rate of traction substation equipment.At the same time,because the traction substation uses a 12-pulse or 24-pulse diode uncontrolled rectification power supply,energy cannot be fed back to the AC grid through the traction substation As a result,a large amount of regenerative braking energy is wasted.Therefore,in order to reduce the energy consumption and operating costs of urban rail transit,the introduction of energy storage systems in the field of rail transit has become a research hotspot in recent years.The energy storage system has the advantages of small loss and high efficiency,and can suppress intermittent energy fluctuations to realize the recycling and utilization of renewable energy.Based on the above background,the text focuses on the capacity allocation and optimization of ground-based energy storage systems in urban rail lines.Firstly,this paper combines the electricity price characteristics of large industrial users,and based on the urban rail transit energy management,establishes an optimal energy storage configuration model that takes into account the load characteristics of the traction power supply system.Taking the minimum overall cost of the energy storage life cycle of the traction power supply system of urban rail transit as the outer objective function,taking into account factors such as the power,capacity and annual load peaking rate of the energy storage system;The maximum return during the daily dispatch period is the inner objective function.The optimization of the charge and discharge power in each period of energy storage is studied.Combined with Changsha Metro Line 1 to simulate the model,the results show that the comprehensive cost and the total revenue show opposite changes with the change of the rated energy storage energy;meanwhile,the energy storage determined when the cost is the lowest and the benefit is the greatest The rated power determines the operating cost of the traction substation.Compared with the case where the energy storage system is not used,it has a better effect in alleviating the "peak-cutting and valley-filling" of the power grid and the energy saving and reduction of traction substations.Secondly,on the basis of the optimal allocation model of urban rail transit energy storage capacity under the two-unit electricity price,the economic impact of photovoltaic access on the traction power supply system of urban rail transit is studied.In this paper,by establishing an energy storage optimization model for a traction system with photovoltaic power generation,the objective is to take the lowest total cost in the traction power supply system’s dispatching operation cycle as an objective function;and at the planning stage,a comprehensive benefit evaluation indicator(considering the energy storage recovery cycle and annual investment return And penalty parameters)to measure the economic impact of photovoltaic access on the traction power supply system of urban rail transit.Based on the historical load data of a single traction transformer substation,the model was simulated with particle swarm optimization(PSO)to optimize the model.The optimal values of photovoltaic installation capacity and lithium battery installation capacity were determined.The simulation results showed that a reasonable ratio of photovoltaic and storage capacity was established.The capacity can be connected to the traction power supply system,combined with the "low storage and high discharge" strategy of the lithium battery,it can achieve "peak cutting and valley filling" of the system load,reduce the overall operating cost of the system,and improve the economics of system operation. |
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