# Multi-Domain Modeling and Analysis of Marine Steam Power System Based on Digital Twin
###### Abstract  
The marine steam power system includes a large amount of thermal equipment; meanwhile, the marine environment is harsh and the working conditions change frequently. Operation management involves many disciplines, such as heat, machinery, control, electricity, etc. It is a complex multi-discipline physical system with typical nonlinear, multi-parameter, strong coupling characteristics. In order to realize the health management of a marine steam power system, based on digital twin technology combined with the Modelica language, modular modeling, etc., this paper conducts in-depth research on the multi-domain modeling of the marine steam power system, characteristic analysis of variable working conditions, fault simulation, etc. The analysis results show that the dynamic response trend of the model is consistent with the actual operation, the error of the main steam flow at 1800 s is the largest and is \(-4.9\%\), and the error of the main steam flow, steam turbine output power, cooling water outlet temperature and other key parameters is within \(\pm 5\%\). Virtual reality mapping between the digital model and the physical equipment is realized, which lays a foundation for mastering the dynamic characteristics of the marine steam power system. steam power system; multi-domain modeling; Modelica; dynamic characteristics; digital twin +
Footnote †: journal: Marine Science and Engineering  
local controller, etc. of a ship's power propulsion system according to the complex and coupled characteristics of the ship's power system, and analyzed the stability and dynamic characteristics of the system [3]. [PERSON] et al. studied the steam turbine generator and feed water pump turbine of an LNG ship, analyzed their efficiency by measuring the actual operating parameters, and concluded that the energy conversion efficiency of the steam turbine generator could be improved by 1-3% by replacing the steam turbine with a motor to provide power for the feed water pump [4]. [PERSON] et al. used Matlab/Simulink to simulate high, medium and low pressure steam turbines, analyzed the influence of the reheater, valve opening change and position height change on the system, and proposed that the key to control is to establish a steady-state response when the turbine is connected to the generator and other controllers in a closed loop [5]. In summary, many scholars have carried out systematic research on marine power systems, including modeling methods, mathematical models, engineering applications, etc., but most scholars still carry out single-domain simulation and dynamic characteristic analysis for the subsystems and key equipment in the power system, while there is relatively little research on the coordination, multi-domain coupling, dynamic response and fault simulation of each piece of thermal equipment in the marine power system. Due to the fact that traditional modeling methods focus on static analysis, it is difficult to analyze dynamic characteristics under variable conditions and fault conditions. Therefore, the establishment of a high-precision digital model of the system is the key to further promoting the digital and intelligent development of marine systems. As a new technology, digital twin is a key technology for realizing the mapping of physical system to a digital model [6]. It makes full use of the physical model, equipment status, operating environment and other data, integrates multi-disciplinary and multi-timescale simulation processes, and completes virtual reality mapping in the information space, thus reflecting the full life cycle of the corresponding physical equipment [7]. Therefore, the combination of multi-domain modeling, modular modeling and other methods to establish a high-precision digital model under the digital twin technology and carry out a dynamic characteristics simulation analysis can not only overcome the shortcomings of traditional modeling methods, but also lay a solid foundation for the successful application of digital twin technology in the marine steam power system.