Research On The Optimization Method Of Energy Logistics For Improving The Ability To Consume Renewables

The high share of intermittent new energy and the large-scale random load of the electric vehicle brings great challenges to the planning,operation and maintenance of the power system.In this context,energy storage system and long-distance ultra-high-voltage transmission will be urgently needed.However,the operation mode of the two is not flexible and the transmission efficiency for new energy is low.Therefore,new ideas are imminently needed to solve the consumption problem of the high share of new energy in an economic way.Given the above problems,this paper proposes a new way for mobile energy storage system to promote large-scale consumption of new energy power.Through the battery transportation and logistics(BTL)between the new energy power station and the load centre,the flexible flow of energy in the system is strengthened,and the spatial and temporal distribution of green power is optimized.On this basis,the techno-economics of the mobile and the stationary energy storage system are compared.The main contributions include:(1)A simulation method of electric vehicle(EV)charging load based on the demographic portrait is proposed,and on this basis,typical load profiles of future cities with large-scale electric vehicles are constructed.Firstly,to improve the simulation accuracy of travel pattern for different demographic attributes and social characteristics,the probabilistic distribution models of spatial-temporal travel variables are established for different groups,locations and day types.Then,by refining the modelling of users’charging preference and vehicles’power consumption rate,a simulation method of the daily EV charging load curve is proposed based on the probabilistic models of travel pattern and the Monte Carlo algorithm.Finally,it is verified based on the data from the US National Household Travel Survey.The results show that,the shape of the charging load curve is significantly affected by the demographic characteristic and charging preference of EV user,and the power consumption rate of the vehicle.By considering additional refined conditions,the accuracy of the probabilistic distribution models of spatial-temporal variables is improved.(2)A new concept that promoting large-scale consumption of new energy through "energy logistics" is put forward.A joint optimal scheduling model of mobile energy storage system and transportation logistics system is established.Aiming at the lowest transportation cost and the load shifting of the urban load curve,the railway transportation routes and the amount of trains for empty batteries and full batteries are optimized.With these as the boundary conditions,the departure time and the freight volume of trains,and the battery charging and discharging are further optimized.Finally,the branch-and-bound algorithm is used to solve the problem.Take Northeast China and North China as examples to verify.The results show that,with the energy density of battery increases from 170Wh/kg to 250Wh/kg,the transportation cost for the two regions decreases respectively from 0.40 and 0.38 yuan/kWh to 0.25 yuan/kWh,indicating that the economy of BTL is acceptable and continues to improve.Besides,without the expansion of transmission lines,BTL increases the utilization ratio of new energy and significantly reduces the difference between the peak and the valley of the load curve.(3)Technical and economic characteristics of the mobile energy storage system and the stationary energy storage system are compared from the perspective of the ability to consume new energy and the overall levelized cost of energy(OLCOE)for energy storage.Firstly,through the planning and production operation simulation of stationary energy storage in the power system,the expanded capacity of stationary energy storage and transmission line in the regional power grid,as well as the operation mode of power system in different spatial-temporal scenarios are obtained.Then,an OLCOE model for energy storage is established to quantify the economy of stationary and mobile energy storage,which considers investment cost,operation cost,transmission cost(stationary energy storage),transportation cost(mobile energy storage),as well as scrap and recycling cost.Taking the actual power grid and railway model of Northeast China and North China as examples,an analysis of the techno-economic performance is carried out.The results show that,the OLCOE of mobile energy storage is lower than that of stationary energy storage under the scenario with large-scale integration of new energy.However,due to different resources and power supply conditions,the consumed new energy electricity of unit storage capacity varies significantly in different regions.