Research On Calculation And Comprehensive Evaluation Method Of Distribution Network Additional Loss Considering Power Quality Disturbance

In recent years,with the continuous increasing in the penetration rate of distrbuted power supply and the massive increasing of non-linear load,the problem of power quality disturbances in distribution networks has become increasingly serious and complex,which caused additional loss also have been attracted more attention by power supply enterprises.Therefore,it is necessary to study these losses separately,which can achieve more refined analysis of distribution network loss and provide reference for solving the blind problem in power quality governance and energy conservation and loss reduction work.Firstly,in this paper,the author briefly analyzes the influence mechanism of harmonics,three-phase unbalance and voltage deviation on distribution network loss,pointing out the shortage of distribution transformer calculation model under harmonic disturbance.Introducing the AC winding coefficient to characterize the influence of skin effect and proximity effect on the winding resistance of transformers under harmonic conditions,a calculation model for harmonic additional loss in distribution transformers is constructed.Using three-dimensional finite element modeling of the ANSYS Electronics Suite to analyzes different operating conditions,it is shown that the calculation model has good applicability,providing a model foundation for the next step on the additional loss of distribution networks under composite power quality disturbances.Secondly,this paper proposes the additional loss calculation model of distribution network under power quality disturbance.A simulation model of low-voltage distribution network is built in Matlab/Simulink to analyze the influence of each power quality disturbance on the additional loss of distribution network.Meanwhile,the correctness of the proposed additional loss calculation model is verified.The results show that the additional loss under the composite power quality disturbance are not equal to the direct sum of the additional loss of each single power quality disturbance,and the main reason for not satisfying the superposition is that the threephase unbalance and harmonic additional loss are coupled with each other,and the superposition is difficult to be satisfied with the increase of the three-phase unbalance.Finally,based on the additional loss calculation model mentioned above,relevant evaluation indicators are established for the additional loss values of distribution lines and transformers.Based on the combination weighting method,a comprehensive evaluation method for additional loss is proposed.The basic weights obtained by the subjective and objective weighting method are combined to establish an optimization model.The objective function is to minimize the deviation between the evaluation value of the combination weight vector and the original subjective and objective basic weight vector evaluation value.The combination weight value is obtained through the Pathfinder Grey Wolf optimization algorithm.The comprehensive evaluation of additional loss caused by power quality disturbances using combined weight values not only can effectively reflect the actual operating characteristics and expert experience of the distribution network,but also avoid unreasonable weighting caused by subjective factors and fluctuations in raw data.The obtained results can clarify the main equipment causing additional loss and the main power quality disturbances in the distribution network.The rationality and effectiveness of the proposed evaluation model were verified through simulation examples testing and analysis.