Research On Multi Level Coordinated Planning Of Distribution Network In Muping District

Distribution network planning and design is an important link in the development and construction of power system.Distribution network planning and design level is directly related to the structure of power grid,power supply reliability,power quality and other aspects of power system characteristics,directly affects the economic and social benefits of power supply enterprises.There are several voltage levels in actual distribution network.It is one of the most important tasks for power supply enterprises to make unified and coordinated planning for distribution network with multiple voltage levels based on multiple objectives.In the planning process,we should not only solve the traditional optimization problems in distribution network planning,but also consider the impact of distributed generation on load forecasting,planning and operation.Due to the local access of distributed generation,the net load of the whole power grid has changed greatly,and it is difficult to predict accurately the development trend of regional load in the future.At the same time,the traditional power grid planning model is no exception from top to bottom,one-size-fits-all planning,that is,the upper power grid planning is completed and then to the lower power grid,which obviously can not meet the requirements of smart grid development.In this paper,Mouping District Distribution Network Expansion Planning is studied.Analysis of the present situation of distribution network in Mouping District,and points out the existing problems of distribution network at all levels.In addition to the specific problems such as line overload,low transformer capacity,poor power supply capacity,unreasonable grid structure and low power supply reliability,the distribution network at all levels is also faced with the problems of coordinated planning of multi-level distribution network and grid-connected access of distributed generation.In addition,it points out the additional problems faced by distribution network planning in Mouping District:Coordination Planning of multi-level distribution network and grid-connected access of distributed generations,coordination between upper and lower power grids must be taken into account in planning of multi-voltage distribution network,and distribution network reliability,voltage stability and network loss are all affected by the access of distributed generations.This has an impact,leading to the distribution network planning must take into account the impact of distributed power access when considering these issues.By establishing the power model of distributed generation based on Weibull probability function and calculating the output of distributed generation,combined with the load forecasting value of distribution network in Muping District,the load forecasting results after taking into account the output of distributed power supply are obtained,which is the basis of planning.On the basis of defining the characteristics of distributed generation nodes,the gradient descent method combined with Newton method is used to calculate the power flow in Mouping District distribution network with distributed generation.A multi-objective programming model of distribution network in Mouping District is proposed.The planning objectives are the lowest cost of substation construction and maintenance,the lowest cost of distribution line construction and operation,and the highest reliability of power supply.The constraints of the planning model are defined.The improved genetic algorithm is used to solve the planning model,and the genetic operations such as selection,crossover and mutation of the genetic algorithm are improved so that it can be adapted to the coordinated planning of multi-level distribution network.Through analysis and verification,the improved genetic algorithm has better convergence ability and can effectively solve the problem of falling into local optimal solution.In this paper,the genetic algorithm coding is in the form of matrix.The capacity of distributed generation is coded on the diagonal line.The element values in the upper triangle of matrix are used to code the distribution network topology.The different integer values of non-zero elements represent different voltage levels.The topology of multi-layer distribution network with voltage levels is implemented.Effective coding.A repairing scheme of infeasible solution based on matrix encoding is proposed.By simple operation of matrix elements,ring networks and islands can be repaired quickly.On the basis of load forecasting,the installed capacity of newly built substations is included in the planning content,and the optimal capacity combination of newly built substations is obtained by calculation.