Abstract
As the coupling and integration of multi-energy flow in the integrated energy system (IES) deepen increasingly, the cascading failure will develop across different energy systems more easily and widely through the energy hub (EH). And it brings great challenges to the security and reliability of IES. The defects of the present cascading failure model of IES have been summarized, and a novel search strategy of fault chains in IES combined heating and power network was proposed in this paper. First, the initial risk assessment index of each energy branch is proposed to form the initial fault sets. Then, combined heat and power control (CHPC) strategies are introduced to deal with the branch overload conditions during the cascading failure. What is more, in order to reduce the workload and overcome the limitation of present methods, we analyzed the relevance of the branches to be predicted by using the kernel fuzzy C-means (KFCM) clustering algorithm and select the branches with the highest value of relevance as the subsequent failure. Based on the predicted fault chain, vulnerability analysis is presented to locate critical component and find out the correlation between cascading outages. The comprehensive evaluation index is also established to effectively evaluate the impact severity of cascading failure. Finally, the case studies are carried out on the combined heating and power systems to demonstrate the effectiveness of the proposed method.
Highlights
As the main carrier of the energy internet, the integrated energy system (IES) plays an important role in promoting the energy comprehensive utilization efficiency and meeting the integrated energy demand [1], [2]
When the thermal demand is Qt0, the combined heat and power (CHP) with a variable thermoelectric ratio can supply the power in the range of the line segment ‘‘ON’’, and there exists additional adjustable margin ( Qm3 plus Qm4) of heat generation in the energy hub (EH), where the Qm3 can be regarded as the extra heat supply generated from the electric boilers (EB), gas boilers (GB) and HS, the Qm4 can be regarded as the heat supplied for heat storage
While in case I, without taking the combined heat and power control (CHPC) strategies into account, only one fault chain ‘‘d10 → d1 → d2’’ will be formed for the initial outage of d10, as well as the fault chain ‘‘l12 → d1 → d2’’ corresponding to the initial outage of l12, which indicates that the CHPC strategies play an important role in the development of the cascading failure, and the simulation model considering CHPC strategies in this paper is of effectiveness and rationality
Summary
As the main carrier of the energy internet, the integrated energy system (IES) plays an important role in promoting the energy comprehensive utilization efficiency and meeting the integrated energy demand [1], [2]. Focusing on the interaction effects of coupled heating and power network, the cascading outage events for different initial outages will be simulated to form the complete fault chain. The cascading failure model can be divided into four main steps: 1) selection of the initial fault sets; 2) application of the combined heat and power control strategies; 3) prediction of the subsequent random failure; 4) comprehensive assessment of the fault chain. The power and heat slack nodes are both selected from the different EHs, which means that the operation sate of the whole IES should be balanced only by EHs, which results in the stronger coupling between two energy networks, and increases the probability and complexity of the IES cascading failures. It is meaningful to focus on the islanded mode of IES in this paper
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