Research On User-side Multi-agent Interaction And Energy Trading Mechanism For Power System Flexibility Enhancement

With the introduction of the goal of “peak carbon dioxide emissions and carbon neutrality”,the energy structure of the power system is developing towards a clean and low-carbon one.In the future,the penetration rate of renewable energy resources in the power system will be further increased.In addition to reliability and economy,flexibility has become an important index to characterize the operation characteristics of the power system.At present,the flexible requirements of the power system in China are mainly provided by conventional generators such as thermal units.As the penetration rate of renewable energy resources in the power system continues to increase,the existing flexible regulation resource is difficult to meet the flexibility requirements of the future power system.The user-side distributed energy resource is numerous and its operation mode is flexible,which is an effective supplement to the flexibility of conventional generators.Therefore,it is necessary to exploit the potential regulating ability of user-side resources to further promote the consumption of renewable energy resources.With the transformation of the energy supply mode,the development of smart grids,as well as the deepening of the electricity market reform,the operation mode of the distribution system will undergo a major change.Microgrid(MG)and load aggregator(LA)are effective forms to aggregate and manage a variety of flexible resources on the user-side for future smart grids.And it will be common that multiple entities coexist in the same distribution system.Therefore,the coordinated optimization of the multiple entities is important for the efficient and rational use of energy and the flexibility improvement of the system.On the other hand,in the electricity market environment,the economic dispatch and auxiliary services of the power system,such as flexible ramping product(FRP)need to be realized through market means.The establishment of a reasonable energy trading mechanism,which can obtain equal-interest energy trading and dispatch strategy is important for the realization of the flexible and economic operation of the system as well.This paper studies the user-side multi-agent interaction and energy trading mechanism to provide theoretical support for the safe,economic and flexible operation of the system with high penetration of renewable energy resources.The main contents and contributions of this paper are as follows.The user-side multiple distributed energy resources are modeled in the form of MG,and the coordinated optimization for the distribution system operator(DSO)with multiple MGs are studied.A data-driven modeling method is adopted to fully consider the uncertainty of renewable energy in the distribution system and MG.The DSO and each MG are modeled as an independent entity,and a robust economic dispatch model is built for each entity.Considering the coupling variables of the point of common coupling,a distributed solution method based on the alternating direction method of multipliers combined with the column and constraint generation algorithm is proposed to realize the decoupling of the power exchange between the DSO and MG and the coordinated optimization.Base on numerical examples,the flexible adjustment ability of MG with different FRP prices is analyzed,and the effect of MG on improving the internal flexibility of the distribution system is verified.The user-side multiple distributed energy resources are modeled in the form of LA.A bilevel optimization model is constructed with DSO at the upper level and multiple LAs at the lower level.DSO participates in the wholesale electricity market on behalf of the internal loads and LAs,determining the optimal operation strategy including the strategy of power purchasing and selling in the electricity wholesale market,the scheduling results of DSO’s internal controllable equipment,as well as the transaction power and prices with each LA.The coordinated optimization of the distribution system with multiple LAs is realized based on the proposed bi-level optimization model.The flexible adjustment ability of the whole distribution system with different FRP prices is analyzed,and the effect of the proposed bi-level optimization model on the flexible operation of the upstream grid is verified.As a new type of ancillary service,the FRP is introduced to the distribution system electricity market,and the market-clearing mechanism for the joint optimization of electricity and FRP considering uncertainties is studied.Aiming at the optimal dispatch for the distribution system with multiple LAs,a robust optimization model is established.A market-clearing mechanism based on the distribution locational marginal price and the uncertainty distribution locational marginal price is proposed,in which the energy is priced by the distribution locational marginal price and the FRP is priced by the uncertainty distribution locational marginal price.The private information of the DSO and each LA is protected through the iterative clearing of the upper and lower level.Considering the risk tolerance of the lower LAs,both risk-neutral and risk-averse models are constructed for each LA.The FRP is priced reasonably the proposed market mechanism.The enthusiasm of flexible resources to provide FRP is improved,and all LAs are encouraged to actively respond to the uncertainty of internal renewable energy.The concept of LA is extended to a consumer,and the distributed energy trading problem of the distribution system composed of multiple consumers is studied.A P2 P transactive energy trading model is established based on Nash bargaining,and a fair distribution of benefit is realized.The P2 P transactive energy trading problem is further decomposed into two subproblems: optimal power flow problem and payment bargaining problem.The distributed solution of each prosumer is realized based on the alternating direction method of multipliers.Each consumer only needs to exchange relevant information with neighboring consumers,thus its privacy information is preserved.The flexibility of the distribution system is further enhanced through the cooperation between different consumers,which is beneficial for dealing with the fluctuations of renewable energy.The economy of the whole distribution system is improved while the safe and stable operation of the distribution system is ensured.