Research On State Evaluation And Preventive Reconfiguration Of Self-healing Distribution System

Smart distribution system is an important part of smart grid, the basic characteristic ofwhich is self-healing. Self-healing of distribution system is an intelligent control methodwhich is implemented based on the perception of operating states. Therefore, the definitionand classification of operation states, states evaluation analysis and designing controlstrategy under each state are the requirements of achieving self-healing function.First of all, based on the existing researches of self-healing distribution system,various aspects of achieving self-healing function are analyzed, including statesclassification, states evaluation and self-healing control. The relationship of all aspects isput forward: states classification is the basis of states evaluation and self-healing control,states evaluation provides indexes for state judgment and self-healing control, andself-healing control achieves the state transition and optimization of the distribution system.Second, the operating states characteristics of the self-healing distribution system arestudied. It is summed up that reliability is the core operating performance requirement,taking into account the integrity and economy. According to the different importance ofperformance, this paper adopts the decision tree method to classify the operation states ofdistribution system hierarchically. State classification criterion is the indexes of assessingthe performance requirements. The implementation of self-healing control is to achievestate transition, which takes the corresponding performance index as objective.Then, according to the static safety and power supply security of distribution system,states evaluation method is raised. Static safety reflects the ability of withstanding the loadfluctuation, and power supply security is to check the safety under the N-1condition. Basedon security region, the indexes of static safety and power supply security are proposed,which could be expressed as the load rate of all network feeders. The safety critical pointsare obtained through the continuous power flow method. According to the characteristics ofsecurity region, the safety margin index of the system can be get, which provides thecontrol target and decision basis for the self-healing power distribution networks.Finally, according to the characteristics and state index of the early warning operationstate, preventive reconfiguration model under security constraint is put forward. Accordingto the characteristics of the multi-feeders system, the strategy of preventive reconfigurationis also proposed, which can be divided into the power supply mode optimization and theload transfer optimization under fixed mode. Through the operation switch concept proposed in this paper, the two reconfiguration strategies are combined with the GSOalgorithm to modify the algorithm so as to improve the efficiency of global optimization.In conclusion, the methods of state classification, state evaluation and preventivereconfiguration for the self-healing power distribution networks are proposed in this paper,which will improve the system safety, reliability and economy and are of great significancefor power distribution system to achieve self-healing function.