###### Abstract  
Floating nuclear power plants contain sensitive loads of nuclear reactors. After equipment faults, fast and efficient power supply recovery should be realized. To realize the unified analysis of system topology and power flow distribution, a power supply recovery strategy based on Petri nets is proposed. Considering that systems of different voltage levels cannot be connected instantaneously, a two-stage power supply recovery mode is adopted. Emergency power supply is put in first, and then the whole network is reconstructed. In the network reconstruction process, load transfer is realized through switching the transformation to redistribute the load of each switchboard and adjust the power output of each power source. Corresponding to the Petri net model, the above process is similar to the dynamic transmission process of a token in each library by firing the transition. Therefore, the topological model of system is constructed based on the Petri net, and a power flow analysis is proposed through its dynamic updating mechanism. The objective function of the network reconstruction is established by integrating load recovery amount, switch operation cost and generator operation efficiency, and the optimal switching state combination scheme that satisfies the system constraints is obtained by the multi-population genetic algorithm (MFGA). Simulation results show that the proposed method can provide complete power supply recovery. floating nuclear power plants; power supply recovery; Petri net; network reconstruction; power flow analysis +
Footnote †: journal: Applied Sciences  
1 State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, China 1  
[PERSON]  
2 Department of Electrical Engineering and Electronics, The University of Liverpool, Liverpool L69 3 BX, UK 2  
[PERSON]  
1 State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, China 1
different voltage levels in the system, pre-magnetization is required [13]. The process is complex and takes a certain amount of time. Therefore, the operation cost of different switches should be distinguished when changing the topological structure. In addition, the actual capacity of the generator in the system is designed to be close to the load demand. The generator should operate at the rated power state as far as possible to ensure the operation efficiency. In the floating nuclear power plant, generators and loads are directly connected to the power distribution board. The power supply lines are short, so the power loss and voltage sag caused by line impedance can be neglected. However, all components in the system should have unified topological structure analysis and power flow analysis. Topological analysis for the shipboard power system is an important basis for power flow analysis. At present, the commonly used topology analysis methods for the shipboard power system include the adjacency matrix method [14; 15] and the tree search method [16]. The adjacency matrix is based on the node/branch model. The connection relationship between any two nodes in the network is determined by analyzing the adjacency matrix of the network. The tree search method is used to search the adjacent nodes of a node for topology analysis. The different search methods are into depth-first or breadth-first. The above two topology analysis methods have simple data organization ability and strong adaptability. However, topology analysis and power flow analysis are required to interact efficiently when the power supply of the system is restored, and whether the topology meets the safe operation requirements should be verified by line power flow and generator output constraints. For the power flow analysis, traditional methods such as the Newton-Raphson method and PQ decomposition cannot be applied effectively in the plant system [17].