| With the development of new energy generation technology and the emergence of a large number of DC loads,the proportion of DC sources and loads on the distribution network side has been increasing.Compared with AC distribution network,DC distribution network is more convenient for new energy access and can provide better power service for a large number of new loads.The distribution of tidal currents in DC distribution network not only depends on the load and power source,but also is influenced by the grid structure.In the planning stage,we should implement differentiated construction standards according to the distribution and characteristics of load,distributed power and energy storage,and not simply plan the distribution grid.It is necessary to build a high level,overall design,and collaborate to optimize the configuration of distributed power and energy storage while planning the grid structure.DC distribution grid planning and design and optimal operation have a strong coupling relationship,the two interact with each other,mutual constraints.In addition,a large number of new energy units with high penetration rate are often connected to the DC distribution network.In order to make the power system operate safely and economically,it is necessary to adopt a reasonable method to coordinate and optimize the DC distribution network.Therefore,this paper focuses on the DC distribution grid grid and the method of cooperative optimal configuration of source and storage and the method of multi-time scale optimal dispatching respectively,and the main contents are as follows:Firstly,the factors to be considered in determining the voltage sequence of DC distribution network are clarified,the principles and methods for determining the voltage sequence of DC distribution network are introduced,and the recommended values of voltage sequence are given;the current common topologies of DC distribution network are summarized,elaborated and analyzed;The typical power supply modes currently used in different scenarios in engineering applications are introduced.Secondly,based on the typical topology of DC distribution network,a two-layer planning model is established with the typical power supply mode of existing demonstration projects for the optimal configuration of DC distribution network grid structure and distributed power and energy storage.The upper model optimizes the site selection and capacity allocation of distributed power and energy storage,while the lower model optimizes the DC distribution network grid structure;the upper model is linearized into a mixed integer linear programming model and solved by CPLEX solver,while the lower model is solved by particle swarm optimization algorithm.A 13-node DC distribution grid test system is used to analyze the proposed model and verify the validity and applicability of the model.Finally,considering the multi-timescale characteristics of wind power and photovoltaic forecast data,the capacity characteristics of pumped storage and electrochemical storage,and the multi-timescale characteristics of load-side demand response resources,the "source-storage-load" rolling optimization dispatch model with three timescales:day-ahead,intra-day 15 min,and realtime is established.The model is modeled by the scenario-based stochastic planning method in day-ahead and intra-day scheduling,and by the chanceconstrained stochastic planning method in real-time scheduling;then the model is programmed in the YALMIP toolkit on the MATLAB platform and solved by calling the CPLEX solver;The model is analyzed in the modified IEEE 39-node test system by comparing and analyzing the wind abandonment rate,light abandonment rate,and the system performance of the three different scheduling models. |
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