###### Abstract  
With the continuous development of the active distribution network (ADN), the problem of security and stability has become increasingly prominent. From the perspective of improving the defense capability of ADN, a new a multi-angle dynamic risk assessment index system based on the comprehensive vulnerability rate model is proposed in this paper. Risk threshold is used to monitor the status of the distribution network, which determine whether ADN needs to enter the active defense period. The minimum amount of load shedding outside the fault isolation region is regarded as the objective function, considering other constraints such as limited resources, the coordinated active defense strategy (CADS) is formed in this paper. Finally, the accuracy of the comprehensive vulnerability rate and the risk assessment value are verified by example analysis, and the superiority of the CADS is verified by comparing different defense strategies. active distribution network; comprehensive vulnerability rate; multisource situational awareness; risk assessment; active defense; load transfer; data fusion; islands +
Footnote †: journal: Applied  
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reasonable evaluation models, and there is not formed a perfect risk assessment evaluation index system of the ADN in the ice weather yet. In [13], a model based on ice faults in clusters was proposed which introduced some vulnerability indexes to analyze the risk of future ice storms. Furthermore, related research on distribution network fault recovery strategies is also common. However, to date, most of them focus on the method of repair and the post-disaster recovery process after the accident [14; 15; 16], there is a lack of active defense strategy based on fault prediction. Some relevant ideas and technical analysis of security defense were proposed in [17; 18; 19; 20]. One method is the strategy based on DC ice-melting technology in icing weather, which is difficult to guarantee efficiency because it is only applicable to transmission lines or fault areas with ice melting devices but no effective defense and protection for loads outside the fault region. The other method is use matching plans as a method based on historical data and typical situations, this model cannot meet the requirements of real-time online decision-making, the information utilization is very low, and there is a lack of coordinated ability for the local and global distribution network by using the defense strategy, which cannot guarantee efficient use of resources and the maximum power supply. Therefore, in order to improve the adaptability of active distribution network in ice weather, the main contributions are introduced from three aspects in this paper:  
1. The multisource situational awareness method is used to analyze the internal operation situation of the distribution network in this paper, define the network topology situation, the power supply situation, the defense resource, the power flow situation, and cascading fault factor, thus the comprehensive vulnerability rate model is established. 2. An ice hazard dynamic risk assessment index system concluding the ice-covered dynamic intrusion index, ice disaster-resistance capability index and demand response potential index is proposed in this paper so that it can monitor the current operating status of the distribution network in real time. In order to evaluate the risk status of different distribution lines at a certain moment and determine whether a certain line needs to take active defense plan at the current moment, the concept of risk threshold is proposed in this paper. 3.