Robust Control Of LNG Tank Pressure System Based On Mirror Mapping

In recent years,the problem of global environmental pollution has attracted increasing attention.To find new energy to replace the traditional energy with high carbon content such as coal is a major way to solve the problem of environmental protection.Among them,natural gas,as an emerging green energy,is favored by all countries in the world because of its advantages of high efficiency,no pollution and large output.According to relevant statistics,in recent years,natural gas accounts for a higher and higher proportion in the energy consumption system of all countries in the world.A large part of China’s natural gas imports are carried out by LNG carriers.Therefore,on the basis of the liquid cargo loading and unloading simulator of LNG tanker,this paper studies the control of the liquid cargo tank pressure maintenance system in the process of cargo loading and unloading.The main research contents of this paper are as follows:(1)by controlling the cargo tank insulation space filling exhaust rate of nitrogen gas,through mirror-injection and CGSA principle construct a stable optimization of controller,use image mapping technology to unstable process is transformed into stable minimum phase system,based on four order CGSA algorithm robust controller was designed,and the robust performance index analysis,The proposed control scheme is compared with the Smith control law.The purpose of differential pressure control of the insulating layer of LNG tanker is to keep the pressure difference between inside and outside the insulating layer within a reasonable range,so as to ensure the structural integrity of the cargo tank of LNG tanker.(2)The compressor is used to control the LNG steam flow in the tank,and a robust control model of the pressure system in the tank is constructed based on the mirror mapping and H∞optimization.The parameters of the controller are configured by using the graphic stability theory,and the stability region of the stability parameter λ is deduced.The controller can be adjusted only by adjusting a single stability parameter.The purpose of differential pressure control on the insulating layer of LNG tanker is to control and simulate the pressure in the cargo tank more effectively in the process of loading and unloading,so as to improve the safety of LNG tanker in the process of loading and unloading.The method proposed in this paper can better suppress the external disturbance,and the robustness of the closed-loop system is greatly improved,and the controller structure is simple and practical.