| When evaluating the power quality of distribution network,the national standard is generally regarded as an important basis to measure whether the power quality reaches the standard,but the evaluation opinion of power user for power quality is ignored.The power quality of distribution network is directly related to the normal and safe operation of user’s equipment and the efficient development of industrial production,as the main part of using the electric energy,it is necessary for power user to evaluate whether the power quality meets the expectation from the perspective of user’s power demand,therefore,when evaluating the power quality of distribution network,the evaluation opinion of power user is indispensable.The evaluation opinion of power user is mainly reflected in the user satisfaction,as a result,bringing the user satisfaction into power quality evaluation index system can make evaluation result fully oriented to the demand of power user,so as to reflect the power quality of distribution network more comprehensively and provide theoretical guidance for the government of power quality.The theoretical research on the evaluation method includes the establishment of evaluation index system,the determination of evaluation index weight and the proposal of the evaluation method.Firstly,the national standard evaluation index system of harmonic,three-phase unbalance,voltage deviation and other three common power quality problems is established,and the user satisfaction evaluation system for the power demand of the user side is established,the two systems together constitute the power quality comprehensive evaluation index system.At the same time,the value range of each evaluation index is graded,which is taken as an important standard of subsequent evaluation.Then,the two evaluation index systems are respectively weighted,the power quality national standard evaluation index adopts combination weighting method,the subjective weighting methods select Gl method and superiority chart method,the objective weighting methods select principal component analysis method and cross entropy weighting method,the principle of combination is to maximize deviation.The evaluation index of user satisfaction adopts G1 method.Finally,two evaluation methods of power quality are proposed to realize the horizontal and vertical comprehensive evaluation of node power quality.namely horizontal evaluation method based on improved radar chart method and vertical evaluation method based on optimal increment and inferior increment,and the method for identifying weak spots of power quality is put forward.The validation of the correctness of the evaluation method is realized through evaluation and analysis of the case.Based on an actual case,Monte Carlo method is used to establish random models of power quality disturbances,and the index data of nodes to be evaluated are obtained by simulation in MATLAB/Simulink.The evaluation and analysis are carried out by the proposed evaluation method,and weak spots of power quality are acquired.By comparing with the actual situation of the case,the correctness of the proposed evaluation method is verified.Compared with the evaluation results when user satisfaction is not taken into account,it is found that the proposed evaluation method can amplify the impact of user’s sensitive power quality problems on the overall evaluation results,and provide user with evaluation results that are more in line with their actual power quality demand,which verifies the rationality of the proposed evaluation method.Compared with the results obtained by the grey comprehensive assessment method and TOPSIS evaluation,it is found that the power quality ranking of the proposed method is basically the same as that obtained by the two commonly used assessment methods,and the degree of differentiation is greater,therefore,the proposed method can clearly compare the power quality status of each node horizontally,which verifies the feasibility of the proposed method. |
PDF Full Text Request