| The clean and low-carbon transformation of the power system is the key to achieving the goal of carbon neutrality.Therefore,distributed generation(DG)is being connected to the distribution network on a large scale.The output of renewable energy,represented by wind power and photovoltaic,is random and fluctuating due to the influence of natural factors,which increases the demand for operational flexibility of active distribution network.Soft open point integrated with energy storage system(ESOP)is a flexible interconnection device using fully controlled power electronic devices.Compared with the traditional tie switch.ESOP can realize flexible control of active and reactive power,so it has important application value in active distribution network.Considering the operation flexibility demands of active distribution network,this paper studies the optimal planning of ESOP in active distribution network.The main research contents are as follows:(1)The flexibility requirements of the distribution network under different renewable energy penetration rates are analyzed.Based on the equipment connected in the active distribution network,the flexibility resources are divided,and the mathematical model of each flexibility resource and ESOP is established.At the same time,based on the typical scene of wind and solar output and the probability distribution function of prediction error,Monte Carlo sampling is used to generate the operation scene,and the K-means scene clustering algorithm is used to cluster the scene,so as to obtain the flexibility demand scene of active distribution network,which provides the scene basis for the formulation of the planning scheme in the following chapters.(2)Aiming at the role of flexibility of ESOP connected to active distribution network and the problem of planning and construction,two distribution network flexibility evaluation indexes including net load regulation and branch load margin are proposed from the perspective of node and grid flexibility resources respectively.The operation cost of distribution network and ESOP planning and construction cost are proposed as the economic indicators of distribution network.After that,an optimal planning model with flexible and economic operation of distribution network containing ESOP planning as objective function is established.The model is transformed into a second-order cone programming model for solution.Through the simulation of the modified IEEE 33-node system,the results show that the proposed flexibility evaluation indicators can accurately quantify the operation flexibility of distribution network,and the proposed optimization planning model can realize the operation flexibility and economy distribution network.(3)In order to increase the access capacity of DG in the distribution network in the planning stage and consider the influence of the uncertainty of wind power and photovoltaic outputs on the flexibility of the active distribution network in the operation stage,a coordinated planning method of DG,ESOP and flexible resources is proposed.Firstly,flexibility margin and shortage indicators are proposed for typical flexibility resource regulation capacity.Then,taking the construction cost,annual operation cost and annual income of the distribution network as the objective function,considering the investment constraints and flexible resource operation constraints,a two-stage distributionally robust coordinated planning model considering the coordinated planning scheme of DG,flexible resources and ESOP and the comprehensive norm uncertainty of wind power and photovoltaic outputs multi-operation scenarios is established.Finally,the column constraint generation algorithm is used for solving and the effectiveness of the proposed model is verified by an modified IEEE33 node system. |
