Research On Power Quality Evaluation Technology Of Distribution Network

At present,under the background of China’s dual carbon goal,the high-quality and efficient utilization of electric energy is the key to ensure people’s livelihood,promote national economic development,promote national scientific and technological progress and achieve high-quality development.This thesis discusses a comprehensive evaluation method that can fully consider the randomness and uncertainty of power quality events.At the same time,in view of the current research on power quality related software mostly focuses on power quality analysis and monitoring,which is mostly oriented to the analysis made after power quality events,this thesis designs a power quality simulation platform based on guide.The specific contents include:Firstly,this thesis introduces the power quality evaluation system,including power quality index system,power quality index weight and power quality comprehensive evaluation model.Secondly,this thesis proposed a combined weight determination method based on moment estimation and weight risk degree.And improved the shortcomings of the traditional relative intensity entropy weight method and critical method.After the subjective and objective weights are determined respectively,the optimal combination weight model is established with the objective of minimizing the deviation relative to the subjective and objective weights.On this basis,the weight adjustment operator based on weight risk is introduced to reward the indicators with the same view of subjective and objective weights,and punish the indicators with huge subjective and objective differences,so as to further make the weighting result reasonable.Then,aiming at the deficiency of constant weight,the optimality operator is introduced.A variable weight construction method based on penalty optimality operator is proposed.Finally,the variable weight of each index is obtained,which lays the foundation for the later power quality evaluation.Thirdly,this thesis introduced the grey theory and cloud theory respectively.On this basis,proposed a power quality evaluation method based on grey cloud model.Combining the traditional whitening weight function with cloud theory,constructed the evaluation index grade grey cloud model.Using the quantitative value method based on ideal value and limit value to replace the traditional data standardization method.Proposed a construction method of index cloud model.The calculation methods of hierarchical cloud correlation degree based on index cloud model and index quantitative value are adopted respectively.Finally,use the weighted average principle to replace the traditional maximum membership principle to determine the evaluation grade.Comparing with the results of the literature,and the application scenarios of the two methods are analyzed.Finally,the basic model of distribution network and power quality interference source model are built in Matlab / Simulink environment,and a human-computer interface is designed by using guide toolbox.The ieee33 node system diagram is built through this platform,and the load flow tool in powergui module is used for power flow calculation.The results are compared with the results calculated by Matpower to verify the effectiveness of this platform.Finally,taking IEEE14 node system diagram as an example,the simulation scheme is determined by PEM.This platform can customize the line structure parameters and fault type parameters according to the actual needs,realize the simulation of the impact of power quality events on the whole system before they occur,and provide power supply quality data as a reference for power personnel in the process of power system planning,which is very practical.