Health State Recognition And Evaluation Of Distribution Network And Its Application In Distribution Network Planning

How to study the health index of complex and changeable distribution network is a new problem in the development of modern power grid.But the most of existing researches were confined to high-voltage transformers.The health diagnosis of medium-voltage equipment and network has not been systematically studied,lacking a deep theoretical research and information law mining on research methods.The calculation model and evaluation index were relatively simple,and the health index has not yet been organically combined with distribution network planning.The power grid has gradually transited from the incremental era to the stock era in China.The equipment reinforcement and replacement strategy mainly based on the life cycle of equipment and operation and maintenance experience at present needs to be improved urgently,avoiding replacement of equipment in advance or only when it broke down.Therefore,In order to solve the problems mentioned above and achieve efficient planning,design,operation and maintenance of increasing huge assets and equipment,the theory of distribution network health index and its application in distribution network planning were systematically discussed in this paper.The main research results are as follows:Firstly,the intension and concept of distribution network health index were put forward and the evaluation index system of distribution network health status was established.The intension of distribution network health index and classification standard of distribution network health grade were established.The "three high diseases" of distribution network were put forward.Then the main internal and external factors affecting the health status of distribution network were determined.The construction method and calculation formulas of evaluation index system for distribution network health status were put forward.And the evaluation index system was verified by feature extraction methods,such as extreme learning machine and traditional principal components analysis.Secondly,the intelligent diagnosis and evaluation methods of distribution network health status were proposed from two different perspectives.From the whole system,taking the whole distribution network as a system,the HI calculation method based on deep LSTM was put forward by using HI evaluation index system of distribution network,according to the time sequence characteristics of health status diagnosis for distribution network.From the individual equipment,the HI calculation model of distribution network based on improved PageRank algorithm was established by using the HI of equipment,the topological relationship between equipment and the important role of equipment in the network.The validity of the two methods was verified by simulation examples.Thirdly,a distribution network planning method based on health index was proposed,and an optimization planning model of distribution network based on health index was established.In order to formulate the optimal equipment replacement strategy and deal with the risks brought by uncertain factors such as distributed generation,a new multi-objective expansion planning method for distribution network based on health index was proposed.The planning idea and process of this method were described and the difference and relationship between this method and existing distribution network planning methods were analyzed.A multi-objective optimal planning model of distribution network was established,which takes into account the health status of equipment and network and active control means.And a hybrid optimization algorithm combining improved niche genetic algorithm and spanning tree algorithm was proposed for for real sized networks with a manageable computational cost.The effectiveness of HI-based distribution network planning model and solution algorithm was verified by the simulation results.Finally,the HI evaluation system of distribution network was developed and verified by practical cases.The overall structure,software architecture and function modules of HI evaluation system for distribution network are designed and developed.The health index of distribution network in Nanjing and Beijing was calculated and analyzed by using the health evaluation method of distribution network based on deep LSTM and improved PageRank algorithm.At the same time,the distribution network planning method based on health index was used to optimize the actual distribution network planning in Nanjing.