Modeling of Liquefied Natural Gas Cold Power Generation for Access to the Distribution Grid

Yu Qi, Pengliang Zuo, Rongzhao Lu, Dongxu Wang and Yingjun Guo ()
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Yu Qi: School of Electric Engineering, Hebei University of Science and Technology, Shijiazhuang 050027, China
Pengliang Zuo: Caofeidian Xintian LNG Co., Ltd., Tangshan 063200, China
Rongzhao Lu: Caofeidian Xintian LNG Co., Ltd., Tangshan 063200, China
Dongxu Wang: Caofeidian Xintian LNG Co., Ltd., Tangshan 063200, China
Yingjun Guo: School of Electric Engineering, Hebei University of Science and Technology, Shijiazhuang 050027, China

Energies, 2024, vol. 17, issue 21, 1-19

Abstract: Cold energy generation is an important part of liquefied natural gas (LNG) cold energy cascade utilization, and existing studies lack a specific descriptive model for LNG cold energy transmission to the AC subgrid. Therefore, this paper proposes a descriptive model for the grid-connected process of cold energy generation at LNG stations. First, the expansion kinetic energy transfer of the intermediate work mass is derived and analyzed in the LNG unipolar Rankine cycle structure, the mathematical relationship between the turbine output mechanical power and the variation in the work mass flow rate and pressure is established, and the variations in the LNG heat exchanger temperature difference, seawater flow rate, and the turbine temperature difference in the cycle system are investigated. Secondly, based on the fifth-order equation of state of the synchronous generator, the expressions of its electromagnetic power, output AC frequency, and voltage were analyzed. Finally, the average equivalent models of the machine-side and grid-side converters are established using a direct-fed grid-connected structure, thus forming a descriptive model of the overall drive process. The ORC model is built in Aspen HYSIS to obtain the time series expression of the torque output of the turbine; based on the ORC output torque, the permanent magnet synchronous generator (PMGSG) as well as the direct-fed grid-connected structure are built in MATLAB/Simulink, and the active power and current outputs of the grid-following-type voltage vector control method and the grid-forming-type power-angle synchronous control method are also verified.

Keywords: liquefied natural gas; cold energy generation; organic Rankine cycle; energy drive modeling; grid-connected converter (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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