| Since the proposal of "3060" carbon emission reduction target,the dominant position of new energy in the future power system has been clear.China will further promote the implementation of renewable energy replacing fossil energy and construct a clean,low-carbon,safe and efficient energy system,so as to form a new power system with new energy as the main body.However,the uncertainty of the output of large-scale renewable energy will bring challenges to the grid operation.At present,energy storage is considered to be the most important tool to solve the uncertainty of new energy,and it is the guarantee for the safe and stable operation of new power system.However,energy storage has the characteristics such as high investment cost,long payback period and poor profitability.These adverse factors seriously restrict the development of energy storage industry in China.After the configuration of energy storage in the new power system,it can improve the operation efficiency of conventional generator units,reduce the line loss of power grid,reduce emissions and bring other external values,so as to promote the transformation of the new power system from the extension expansion type to the connotation efficiency increasing type.But this external value is not reflected in the income of energy storage operators,which is an important reason for the poor economy of energy storage.In order to promote the healthy and sustainable development of China's energy storage industry and improve the utilization efficiency of energy storage resources,it is urgent to study the optimization of energy storage selection,location and capacity in the new power system environment from the perspective of energy storage operators,so as to maximize the benefits of energy storage;on this basis,from the perspective of social welfare,the comprehensive value of energy storage in the new power system is measured scientifically,and the compensation method of the comprehensive value of energy storage is studied.In view of this,the main contents of this paper are as follows:(1)Characteristics of new power system and application analysis of energy storage.Firstly,the characteristics of the new power system are analyzed.Secondly,the application of energy storage in the fields of power generation,power transmission and distribution,and user side is analyzed.Finally,the type and technical characteristics of the energy storage system are analyzed and compared.(2)The selection optimization research of energy storage under multi application scenario in the new power system.Firstly,based on the Fuzzy Delphi method,an evaluation index system reflecting the characteristics of energy storage from multiple dimensions is established from the perspectives of technology,economy,efficiency and environment,which is suitable for different application scenarios of energy storage in new power system.Secondly,Bayesian Best-Worst Method and fuzzy cumulative prospect theory are used to build a comprehensive evaluation model.The model can comprehensively rank the energy storage alternatives in each application scenario,and output the optimal solution in the specific scenario,via maximizing the use of data information and considering the different risk preferences of decision-makers and investors at the same time.(3)Study on location and capacity determination of energy storage considering multiple random disturbances in new power system.Firstly,a two-layer model of energy storage location and capacity optimization is constructed.By dealing with the uncertainty of multiple random disturbances in the new power system,the robust transformation method is adopted to establish the uncertainty sets of wind power,photovoltaic and load to describe the uncertainty characteristics.Secondly,the solution method of two-layer model is given,in which the upper model adopts the improved genetic algorithm of optimal preservation strategy as well as multi-point uniform crossover,and the lower model uses the column and constraint generation(C&CG)algorithm to transform it into the optimization model including the main problem and sub problem.(4)Research on comprehensive value measurement of energy storage in new power system.Firstly,based on the externality theory,this paper analyzes the positive externality of energy storage in the new power system.Secondly,based on the optimal allocation scenario of energy storage in the new power system,combined with the analysis of positive externality,the comprehensive value measurement model of energy storage is constructed to measure the comprehensive value of energy storage in the new power system.According to the comparison of each sub cost item in the total cost of the objective function,it can show the composition and specific flow direction of the comprehensive value of energy storage,and further clarify the formation mechanism of the comprehensive value of energy storage in the new power system.(5)Research on energy storage compensation mechanism in new power system.Firstly,by using the relevant analysis Indicators of discounted cash flow of technical economy,this paper makes an economic comparative analysis of energy storage from the perspective of considering and neglecting the comprehensive value,and analyzes the profit and loss balance of energy storage by discussing different scenarios of cost and realization degree of comprehensive value.Secondly,based on the results of comprehensive value measurement of energy storage,taking environmental protection and risk into consideration,the improved Shapley method is used to construct the comprehensive value compensation model of energy storage combined with the principles of "who benefits,who compensates" and "according to the value contribution".The model searches for the best coefficient of compensation for the comprehensive value of energy storage,and determines the amount of compensation that needs to be returned to the energy storage operator from the income of the relevant stakeholders.Based on the above research,the main conclusions are as follows:(1)Pumped storage is the best choice under the scenario of renewable energy consumption and equivalent saving of grid investment.Lithium-ion battery is the best choice for ancillary services and demand response management scenarios.Pumped storage,lithium-ion battery and compressed air energy storage are in the top three in the four scenarios,which are better than the other three energy storage types.The importance ranking of indicators in four scenarios shows that experts pay different attention to energy storage performance in different application scenarios.Sensitivity analysis shows that the degree of risk aversion of decision makers has a great influence on the evaluation results of compressed air energy storage,flywheel energy storage and vanadium redox battery.The results show that the ranking of the three is lower in the high-risk situation,and it will rise when the comprehensive performance value is improved in the low-risk situation.(2)From the results of energy storage location,energy storage will be deployed in the important transmission nodes and near the renewable energy access nodes in the new power system.The access of renewable energy will increase the optimal allocation capacity of energy storage,and the charging and discharging operation strategy of energy storage system will be affected by the output characteristics of renewable energy.The two-layer model of energy storage location and capacity optimization constructed in this paper can effectively resist the multiple random uncertainties in the new power system,and reduce the impact of the deviation of renewable energy output and load forecasting on the system operation cost.(3)The comprehensive value of energy storage is greater in the new power system with renewable energy,which is 57800 yuan in the example system daily.In the scenario without renewable energy,reducing unit start-up cost and unit fuel value account for the main part of the comprehensive value of energy storage,which is 74.47%and 20.07%,respectively.In the scenario without renewable energy,reducing line loss,unit fuel and unit start-up cost value account for the main part of the comprehensive value of energy storage,which is 41.18%,21.80%and 33.22%,respectively.Combined with the output curve of traditional coal-fired units,the change of coal consumption per unit power generation and the charging and discharging operation of energy storage,it can be seen that energy storage can significantly reduce the peak load of traditional coal-fired units.By reducing the peak valley difference,energy storage can make the traditional coal-fired units in a more economical and efficient operation state,so as to reduce the unit coal consumption of the units.From the results of the scenario with renewable energy,if the energy storage system can be reasonably configured,the situation of long-distance power transmission will be reduced,resulting that the line loss cost will be reduced.(4)The results of energy storage economic analysis show that from the perspective of ignoring the comprehensive value of energy storage,the net present value of energy storage investment is negative,and the internal rate of return is 2.47%,which is far lower than the reference value of 6%.Considering the comprehensive value of energy storage,the net present value of income from energy storage is positive.After 9.68 years,all the initial investment can be recovered,and the internal rate of return of energy storage investment is 6.70%.Therefore,it is beneficial to invest in energy storage for new power system.The results of break even analysis show that when the cost remains at the current level,the comprehensive value of energy storage needs to achieve 98.82%to make up for the cost;When the realization degree of comprehensive value of energy storage is 0,energy storage needs to reduce the current cost by 20.07%to achieve profit and loss balance.Through policy analysis,it is found that the current guiding focus of energy storage commercialization in China is to encourage energy storage to participate in ancillary services.Under the guidance of the policies,relevant institutions establish ancillary services market,and constantly improve regional and local ancillary services market transaction rules and settlement mechanism.At present,there is still a lack of compensation mechanism for the comprehensive value of energy storage.The results of comprehensive value compensation based on improved Shapley value method show that the compensation of energy storage accounts for 38.58%of the comprehensive value of energy storage in new power system.Power generation enterprises need to pay 56.64%of the total amount of compensation,while power grid companies need to pay 43.36%of the total amount of compensation,and the payment amount is 63.00%of the value from distribution of power generation enterprises and power grid companies,respectively.In order to ensure the effective implementation of the comprehensive value compensation mechanism of energy storage in the new power system,this paper puts forward the guarantee measures from the following three aspects:1)Establish the compensation supervision mechanism to ensure the smooth channel of energy storage compensation;2)Improve the compensation supporting policies and measures,design energy storage compensation development plan;3)Increase the sources of compensation funds and support the implementation of energy storage compensation mechanism.The compensation of the comprehensive value of energy storage is a gradual,sustainable,overall and strategic practice process,which needs a long time,phased and step-by-step promotion.Relevant departments must work out scientific compensation development plan to ensure the continuous and orderly development of compensation work,so as to promote the sustainable development of energy storage industry in the new power system.This paper studies the optimization plan and comprehensive value measurement of energy storage in the new power system.In the future research,it is necessary to further study the formation mechanism and measurement method of sub value in the comprehensive value of energy storage,so as to provide more accurate economic value reference for the construction of energy storage compensation mechanism,and provide reference suggestions for the sustainable development of China's energy storage industry. |
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