Modeling And Simulation Of Digital Electro-hydraulic Control System For Steam Turbine

The digital electro-hydraulic(DEH) control system of steam turbine is thesignificant guarantee for the safe, stable and economic operation of the power plant,and it also plays an important role in the reliable and efficient operation of the powergrid. It is difficult and risky to make some relative research, technical renovation andtest work on the practical generator unit directly for the reason that the DEH hasmany complicated structure and equipment. The only way for solving the aboveproblem is proceeding experimental study adopting the simulation technology whichtakes the advantages of simulation technology.Firstly, the universal characteristic curves calculation method of the governingstage in the steam turbine is studied in this thesis. The universal characteristic curvesof the governing stage in the steam is the precondition for building the accuratemathematic model of the DEH system. An improved algorithm is provided in thisthesis in allusion to the deficiencies exist in the previous calculation methods forcalculating the universal characteristic curves of the governing stage. Then taking a600MW unit as an example, we analyze the static characteristics of DEH system’scomponents from the angle of mechanism modeling, finally we get the four quadrantdiagram of DEH system. The study shows that the curve in the first quadrant is linearwhich is stacked by two nonlinear curves the curves of transmission amplificationmechanism and steam distribution mechanism. The different position of softwareconvex cam and mechanical CAM device in the control system is the main reason forthe difference between four quadrant diagrams of two control systems above. Therelationship between the quantities of the turbine’s inlet steam and the oil motivepiston stroke showed in the fourth quadrant of the four quadrant diagram hasnonlinear characteristics in itself, which results that we could not choose keeping itliner as the principle of overlop degree, so the primary and the secondary principles of the valves’ overlap in the DEH system proposed in this thesis. Finally，themathematic dynamic characteristic model of the DEH system is built on the basis ofstatic characteristic of the DEH system. The dynamic characteristic of the powercorrector in the DEH system and load adjustment characteristic of the intermediatereheat unit with DEH system is given by simulation programming. Using a300MWsteam turbine as an example, the optimization of control measures of the DEH systemis obtained by means of analyzing the characteristics of regulation system under FCBcondition by simulation.