Establishment Of Evaluation Model For Distribution Network Economic Operation And Analysis

In the new electric power institution, the distribution network economic operation isan important research topic. To evaluate the distribution network economic operation cannot only access the existing situation of distribution network, but also find out its weaklink. It has an important practical significance for distribution network economicoperation, planning and energy conservation. At present, there are many studies on theevaluation of distribution network, but most of them are about the economics of networkplanning or network transformation benefit analysis. Therefore, this paper delves into theexisting problems in the evaluation of distribution network economic operation, andprovides the corresponding methods, at the same time, testifies the effectiveness of theproposed methods by simulation examples. The major contents of this paper arepresented as follows:Firstly, in order to establish the reasonable evaluation index system of distributionnetwork economic operation, a closed-loop method based on group gray fuzzy clusteringis proposed. Based on the initial subjective index system given by expert, the fuzzyclustering is improved to objectively classify the uncertainty index. Then by using thegroup grey relational analysis method, the indexes to be selected are determined, and theexpert reliability of the index to be selected is fused by D-S evidences theory. Finally,according to the fusion results, the closed-loop adjustment of indexes to be selected isperformed to eliminate the redundant indexes. The effectiveness and practicability of theproposed index system are verified by calculation example.Secondly, a closed-loop weighting determination method based on D-S evidencestheory is proposed. First of all, the subjective index weights from experts are collectedand the conflict expert opinions are rejected, and by using the improved D-S evidencestheory, the subjective weight is determined. Then if the subjective weight is insufficient,the objective weight needs to be worked out further. And the Spearman method is used totestify and ensure the consistent of the subjective and objective weight, which achievedthe closed-loop adjustment of the algorithm. The eventual weight that can meet the requirement of objective and subjective is calculated based on the above results.Thirdly, based on the above determined evaluation index system and weight ofdistribution network economic operation, its fuzzy comprehensive evaluation model isestablished. And combining the expert opinions and actual operation of distributionnetwork, the membership function and the model parameters for each index are given.Then, by using the fuzzy comprehensive evaluation method, the membership of the index,the index weight and index scores are acquired. Meanwhile, the economy of distributionnetwork operation is evaluated systematically and scientifically.Fourthly, in view of the multi-dimensional and multi-level evaluation factorsincluding uncertainties in the evaluation of distribution network economic operation, afuzzy comprehensive evaluation model based on interval number is proposed. To lowerthe subjectivity of weight as well as avoid the divergence of overall score, an improvedInterval AHP is used to calculate the index weight. Then taking the different characters ofdistribution network in the different regions into account, interval trapezoidalmembership function is used and the concept of the center of the interval number isdefined to build the evaluation model. Finally, the rating level of overall score intervals isdetermined by the concept of interval conformity degree. And the conclusive result ofcase analysis demonstrates the feasibility of the proposed method.Finally, a model based on discrete BCC for optimal allocation of distributiontransformer is established. Firstly, the replacement principle of distribution transformer isformulated, and an interval objective function is given which concludes fuzzy intervalloss costs, power loss costs and installation debugging costs. Taking the uncertainties ofload condition into consideration, the loss variation of the entire distribution network iscalculated by using the forward-backward power flow algorithm based on fuzzy intervalmethod. Then, the replacement of distribution transformers is optimized by using discreteBCC, which provides the optimal configuration of distribution transformer.