Research On Power Quality Comprehensive Assessment Of Distribution Network With Distributed Generation

With the increase of power load year by year,the utilization of clean energy and distributed generation technology have developed rapidly under the background of China's sustainable development strategy.More distributed generation and non-linear loads are connected to the distribution network,which has an impact on power quality.The comprehensive assessment of power quality is of great theoretical and practical significance to the classification of power quality and the establishment of a scientific and fair power market competition system.This thesis firstly analyzes the existing power quality indicators based on national standards and establishes the comprehensive power quality evaluation index system.Based on the analysis of the influence of distributed power supply access on power quality of distribution network,the PSCAD model of distributed photovoltaic and wind power access to low-voltage distribution network is established.And the evaluation index of power quality of distribution network with distributed power supply is studied from the perspective of theory and simulation.Then the current comprehensive evaluation methods of power quality are studied and compared.In this thesis,a comprehensive quantitative evaluation model of power quality based on improved TOPSIS with combined weighting is established.This method combines subjective weight values based on AHP and CRITIC method with entropy weight method.The objective weight values are optimally combined,and combined weights are assigned to the power quality indicators.The comprehensive closeness of the fusion of the ideal solution distance weighting and the gray correlation degree are used to improve the TOPSIS method.An example of a wind farm is used to verify that the method can evaluate the power quality reasonably and effectively.At last,the comprehensive grade evaluation method of power quality is analyzed.In this thesis,a comprehensive grade evaluation model based on particle swarm optimization random forest is established.Based on the power quality standards and industry requirements,the power quality levels are classified at different voltage levels,and then the power quality comprehensive grade evaluation model is established based on the decision tree's random forest algorithm and particle swarm optimization algorithm.The monitoring data of power quality of 10 k V and 110 k V buses of substations with distributed power connected to the distribution network in a certain area in 2018 is collected and evaluated according to the comprehensive grade evaluation model.The results of the calculation examples verify the feasibility of the comprehensive grade evaluation method,offering a certain reference value for the power quality the evaluation of power quality in the process of power market reform.