Research On Steam Turbine Digital Electro-Hydraulic Control System

The steam turbine is a large-scale original motor that operates at a highspeed and usually works under high temperature and high pressure. It is one ofthe main equipment in the thermal power plant. The DEH system is importantand essential for the safe, steady and economical operation of steam turbine. Thequality of its performance influences directly the economy, security and powersupply quality of steam turbine and electric network. Through identifying theDEH system, we can monitor the operational state and the changes of Unit andpredict the performance of DEH system, thus providing important reference forthe mid-and long-term steady analysis of the electric network and thecontrolling of the frequency. Therefore the establishment of the model of DEHsystem and the identification of its parameters are significant for the steadyanalysis of the electric network. Meanwhile, with the development of industrialautomation, the more technical requirements are put forward for the relatedactuator in the automatic control system, so the choice of the actuator and analysis of performance are significant for the steady of the control system ofthe steam turbine.Firstly, this paper analyses deeply the operation principle of each module ofthe DEH system which is used widely in the steam turbine at present. Themathematics model for the DEH system has been built up according to theoperation principle. A classical parameter identification method, named the leastsquare method, is researched in this paper. It is concise and It has been usedwidely. We analyze the precision of the identification procedure in differentsampling frequencies and in different input signals through simulation. Then wetake the identification method into the practical test after ascertaining theappropriate input signal and sampling frequency. By pretreatment of the realdata, satisfactory results about the identification are achieved.Secondly, through an analysis of movement principle of actuator, this paperhas gained the movement equation of the Direct Drive servo Valve(DDV valve),combining the mathematics model of other parts and making use of the tool ofSIMULINK in the software of MATLAB, simulate models for the DEH systemhave been built up; Making use of the simulate models, has simulated everystate of the DEH system of the steam turbine, and analyses the adjustingperformance of the system according to the response curve, has studied theeffect about the adjusting performance of dynamic quality of the actuator; It isthe conclusion that regarding DDV valve as the interface of servo system satisfythe request of the control system on control precision and stability of steam turbine; In order to satisfy the more difficult technical requirements, put forwardto need develop and study the intelligent electro-hydraulic actuator.Finally, aiming at the questions of 3# steam turbine control system ofShen-tou power plant, dispose a redundancy operator station for the controlsystem, on the operator station disposed newly, making use of Siemens Winccconfiguration software, configure picture which has intact function and accordswith operating personnel's instructions; Optimize the program of the systematicmaster controller, set up the essential protection point. Adjusting speed controlwith SIMADYND can improve systematic dependability, stability effectively;Have increased the functions, such as writing down the information, giving analarm and trend picture and so on, can reduce the handling time effectively,reduce the economic losses that the accident causes.