Research On Planning Method For Low-Voltage Problem Of Distribution Network

The National Energy Administration issued the “Distribution Network Construction and Transformation Action Plan(2015-2020)” that clearly stated that “the distribution network planning for low-density load areas should be scientific and detailed” and build“urban and rural planning,safety,reliability,economic efficiency,and technology.”Advanced,environmentally friendly modern distribution network,therefore,adhere to the“consideration of both construction and conservation”,improve the efficiency of resource utilization is an important part of power demand protection.At present,the low-voltage problem of China’s distribution network is serious,and most of them are concentrated in the agricultural and pastoral areas with low load density.However,with reference to the Technical Guidelines for Planning and Design of Power Grids,we know that China’s low-density load regions refer to the division standards for power supply areas of the State Grid.In the D-type(rural)and E-type(pastoral)areas where the load density is less than 1MW/km2,the grid structure in these areas is weak,and the medium-voltage lines have a light load or overload operation time.The existing rural network construction or reconstruction faces long-term problems of single planning and design and equipment selection,which leads to high investment costs for rural network construction,and the improvement of rural residents’ power supply quality is not obvious.Studying medium voltage route planning method for low load density area has very important engineering value and practical significance.In this paper,starting from the two aspects of the power supply radius of the medium-voltage feeder,its wire diameter optimization and distribution network path planning,the power distribution network differentiation planning method considering the uncertainty of the load forecasting error and the multi-target based on the SEC and Pareto games are studied.Planning method.1)Analyze and summarize the causes of “low-voltage problems” in distribution networks with low load density and their treatment measures.According to the“low-voltage” problems that occur at different levels of the distribution network,summarize general control measures,and then Based on the current status of low-voltage problems in low-load density areas in Sichuan Province,based on the 10 k V medium voltage line specification of the “Technical Guidelines for Planning and Design of Distribution Networks”,DIGSILENT software was used to model and simulate different wire diameters and different loads for 10 k V overhead lines.The voltage at the end of the measurement is used to derive the reasonable power supply radius for different wire diameter models under different load configurations.The related research results can provide effective technical guidance for medium-voltage feeders in distribution networks with low load density,and provide certain data support for the study of distribution network planning methods in this paper.2)Dividing the regional differentiation of thought into distribution network planning,taking full consideration into the load forecasting error of uncertainty,this paper proposes a differentiated uncertainty planning method to medium voltage lines selection of distribution network in low density load area.On the basis of load forecasting error probability characteristics model,a mathematic model using chance constrained programming theory is built,to solve the problem of the confidence level values,Firstly,the anti-risk ability of the regional distribution network is divided and evaluated by the comprehensive weighting method based on the analytic hierarchy process and the deviation maximization method.Then,the corresponding confidence level is selected for different regions.Compared to traditional planning method,the planning method put forward in this paper can not only coordinate the risk and cost,but also give full consideration to the differentiation characteristics of the regional development,thus effectively raising the level of refinement in distribution network planning.3)In this paper,the safety,efficiency and cost(SEC)concept of asset life management are introduced into the distribution network planning,and a multi-objective programming model considering safety,efficiency and cost is established.The improved strength Pareto evolutionary algorithm is used to solve the Pareto optimal frontier,the original grid and the corridor information of the distribution network are considered in the process of solving at the same time.Finally,the Planning program set of SEC of the grid structure is obtained,then the comprehensive benefit index is used to sort the Pareto non-inferior solution set in the second-level optimization decision-making,so as to select the optimal decision-making scheme.