Comprehensive Optimization Of Onshore Wind Farm Collection System Based On Spanning Tree Algorithm

In order to meet the energy demand of social development and respond to the call of green development,wind power generation technology has developed rapidly in recent years.Due to China’s abundant onshore wind resources,relatively low investment in onshore wind farms,easy project installation and low maintenance costs,onshore wind farms have attracted continuous attention in recent years.In order to design a more reasonable collecting system,it is necessary to study the onshore wind farm.Cable connection structure,substation location and cable type selection are closely related to the optimal design of wind farm collector system.Considering the characteristics of onshore wind farms,topography and restricted areas should be included in the optimization process.Improper treatment of these factors will reduce the economy of the wind farm,and the safe operation of the whole onshore wind farm collection system will also be affected.The electricity generated by each wind turbine should be collected as expected to the substation,the cables in the onshore wind farm should meet the requirements of current carrying capacity.In addition,the influence of failure of each component group on system reliability should be considered.Based on the above description,with the support of the national natural science foundation of China(51707029),this paper proposes three factors that can be optimized in the construction of onshore wind farm collection system.The following specific methods are given to optimize the collection system:(1)Optimization of collection system considering topography.In this optimization process,the influence of topography on structure of collection system is considered and the minimum initial investment of cable is taken as the optimization objective.The minimum spanning tree algorithm is used to find the optimal cable connection under the topography condition.At the same time,the importance of substation location is explained by comparing case study and the optimal substation location can be found.(2)Optimization of collection system considering restricted area.There may be restricted areas where cables are not allowed to pass in onshore wind farms.This optimization process makes a detailed analysis of the restricted areas’ influence on the topological structure in the project.This method takes the minimum initial investment of cables as the optimization goal.The minimum external rectangle is used to deal with the irregular restricted area.The Dijkstra algorithm is given to deal with the connection problem of cable bypassing the restricted area.The final topology is generated by the dynamic minimum spanning tree algorithm which considers the optimal cable investment under current carrying capacity.(3)Optimization of collection system considering reliability.In this optimization process,the failure possibility of the wind turbine and cables in collecting system is considered.The lowest cost per unit of electricity produced by the wind farm in the operation cycle is taken as the optimization target.Firstly,the dynamic minimum spanning tree algorithm is used to obtain the initial cable topology and analyze the failure probability of each component group.Then the PSO optimization algorithm is used to find additional cables to add to the initial topology.The reliability and economy of the system are improved finally.In order to verify the effectiveness of the optimization methods proposed in this paper for each consideration factor,and these methods’ applicability to the construction of onshore wind farm collection system.The simulations are carried out in a regular wind farm which has totally 36 wind turbines of 2 MW.Through the analysis and comparison of data results,the necessity of considering these factors in detail is illustrated and the optimization methods proposed in this paper can actually improve the economy of collection system.