Research On Multi-objective Optimal Planning For Transmission Network Based On Improved Group Search Algorithms

Considering that the major function of transmission networks in power system is power transmission,it is of great practical significance to study how to obtain rational transmission planning and expansion scheme based on requirements of current network structure.In order to better satisfy the uncertain growth in loads and demand for economic power flow operation in the whole system,it is urgent to carry out investigation on the multi-objective transmission network planning issue.The planning of transmission networks is categorized into two parts: study of solution to transmission network planning issue and study of transmission network planning model.In the study field of solution to transmission network planning issue,firstly,it is discussed in this thesis that whether the group search algorithm is applicable to solution to related problems in transmission network planning.Then,analysis of the applicability of group search algorithm is carried out in different cases to verify the effectiveness of this algorithm in transmission network planning field.In the meanwhile,the deficiencies of this algorithm are analyzed and corresponding improvement is made on this algorithm.Considering overly complex search mechanism,strong randomness,insufficient ergodicity and reduction in later-stage search capability,which are demonstrated by the group search algorithm in dealing with large-scaled planning problem.Then,an improved group search algorithm is designed by improving the search strategies for the found,the following and the wandering.As a result,the search efficiency of the improved algorithm is enhanced and the case calculation verifies the effectiveness and feasibility of this improved algorithm.In the study field of transmission network planning model,a multi-objective function model considering the branch load rate and investment & operation cost is established in this paper to carry out transmission network planning.Specifically,the calculations of economy and variance in system branch load rates are covered in this model separately.In the meanwhile,this model considers the line economy and guarantees the load rates as well as distributes branch power flow more rationally,thus improving power grid operation environment.Finally,the reliability of this model is verified in multiple cases.