Research On Comprehensive State Evaluation Method Of Distribution Network Based On Cloud Model

With the increasing scale of China's power grids,the distribution network plays a vital role in the whole power system as the link between power generation,transmission system and the user.The urban distribution network is an important part of the distribution network,and it is also one of the infrastructure of the whole city.Once a failure occurs,it will not only cause huge economic losses,but also have great influence on the society.The accurate state assessment of urban distribution network,the timely discovery of its state changes and the existing security risks can not only provide an important basis for the distribution network planning and construction,but also ensure the stable operation of the power system.Therefore,the establishment of a scientific and reasonable comprehensive evaluation system for urban distribution network is of great practical significance to the main problems and weak links of the city distribution network and to guide the development and construction of the urban power grid in the future.Based on the factors affecting the operation state of urban distribution network and the interrelated characteristics of various factors,the method of combining qualitative and quantitative analysis is proposed to construct the urban distribution network index system.First of all,according to the guidance and experience of urban distribution network and the experience of experts and combining the guidance on the construction and transformation of the distribution network,from five aspects of safety,quality,economy,intelligence,environmental protection and sustainability,preliminary construction of index system through qualitative analysis of fishbone diagram and Delphi.Then,a quantitative screening based on the correlation-principal component analysis method was introduced to completed the simplification of the independence and significance of the indicator system;Finally,use a reasonable verification method based on the amount of information to verify the rationality of the reduced indicator system and complete the construction of a key indicator system for the status assessment of urban distribution networks.In the evaluation process,in order to take into account the subjective and objective weights and avoid the defect that the weight does not change with the state,a weight calculation method based on cooperation game and variable weight theory is proposed.Firstly,the subjective weight is calculated by the compatible matrix analysis method,and then the objective weight is calculated by entropy weight method and anti-entropy weight method respectively.Secondly,the weight of the three methods is fitted by cooperative game to obtain the combined weights.Finally,the combined weight is modified by variable weight.For the traditional assessment method can not take into account the randomness and fuzziness of the data,and the membership function of the urban distribution network index is not standard,the fuzzy comprehensive evaluation model based on the cloud model is designed.Firstly,the cloud model is used for single item evaluation to obtain the cloud similarity vector.Then,the fuzzy operation of the cloud similarity vector of the single item evaluation results is evaluated by fuzzy comprehensive evaluation on the framework of fuzzy comprehensive evaluation.Finally,the evaluation state is obtained by using the maximum similarity principle.The proposed method is applied to evaluate the state of urban distribution network.The evaluation model designed can provide accurate assessment results.