| With the wide use of nonlinear loads in distribution network,problem of harmonic pollution has become more and more serious,thereby having bad effects on the normal and stable operation of power system and bringing certain economic loss to power grid and related customers.Therefore,it is very necessary to quantitatively determine the harmonic responsibility of the relevant customers causing harmonic pollution of the power system.The ultimate goal is to force related customers to reduce the harmonic content injects into the grid through the means of reward and punishment,keeping electrical environment of power system in compliance with relevant standards and maintaining a healthy state.Firstly,the customers connecting to the distribution network is similar to the black boxes.Therefore,it is necessary to accurately identify non-harmonic sources and harmonic source,thus clarifying the division object of harmonic responsibility.Based on it,the harmonic source should be modeled.Among them,the modelling methods of traditional nonlinear loads are theoretically analyzed from the many perspectives,the result shows that the Norton approach method is cost-effective and more easily applied.After choosing the Norton equivalent model,the parameters of Norton equivalent model should be calculated.The parameter calculation methods of Norton equivalent model are introduced,and these methods are also compared from many perspectives.The result shows that the reference impedance method is more easily applied in engineering.Finally,the feasibility and rationality of the Norton equivalent model calculated by the reference impedance method are verified by a specific example.Secondly,the traditional methods based on the superposition projection principle of quantitative calculation of harmonic responsibility are not applicable in certain cases,and under the same working condition,the calculation results of harmonic responsibility based on different indexes are of great difference,which is not conducive to realize rewarding and punishing electricity charge.Aim at this situation,a method of comprehensive calculation of harmonic responsibility,considering index weight,is proposed.According to detailed decomposition of apparent power under harmonic condition by IEEE Std.1459-2010,the index set of harmonic responsibility is established,then,the analytic hierarchy process method(AHP)and entropy weight method are used to calculate subjective weight and objective weight of each index respectively,thus obtaining comprehensive weight.Combining the calculation results of harmonic responsibility based on different indexes and comprehensive weights,the comprehensive and quantitative calculation of harmonic responsibility is carried out,and it can effectively avoid inconsistent calculation results of harmonic responsibility.Thirdly,traditional adjustment scheme of rewarding-penalizing electricity charge is analyzed.It is realized that the traditional scheme mainly considers reactive power,ignoring harmonic responsibility.Through theoretical analysis and simulation,results show that the values of power factor which is the basis of traditional adjustment scheme of different customers are easily affected by each other.These bring into awareness that power factor cannot reveal the characteristics of customers.So,the adjustment scheme of rewarding-penalizing electricity charge based on power factor is easily controversial.Based on it,considering evaluating methods of electricity charge of reactive power in various countries,the method adopted by New Zealand Northern Group which does not take power factor as the basis is selected to evaluate electricity charge of reactive power.As a result,a new adjustment scheme of rewarding-penalizing electricity charge,which combines the quantitative calculation results of harmonic responsibility and reactive power,is proposed,thus taking the two steady-state interferences of reactive power and harmonics into consideration,it is of great significance to improve and perfect the charging system of power system of China.Fourthly,the general program flow chart and the flow chart of each subroutine are designed,and through specific example,the identification of harmonic source customer,modeling and parameter calculation,the calculation of harmonic responsibility of harmonic source and the electricity charge according to new adjustment scheme are completed in order.It proves that the work done in this thesis has good continuity and logic,and also has a certain application prospect in engineering.Finally,for IEEE Std.1459-2010,the expansion research is carried out.According to detailed definition of power quantity of three-phase system and single-phase system in IEEE Std.1459-2010,new index of nonfundamental apparent power distortion rate of three-phase system and single-phase system is defined from the perspective of apparent power,which is also applied in location of harmonic control source.Through the specific examples,the practical value of the proposed index is proved,which indicates that IEEE Std.1459-2010 has great application potential on enriching the evaluation index system of distribution network. |
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