Analysis And Optimization Of Valve Control Performance For Steam Turbine DEH System Under Different Conditions

Valve control performances in steam turbine DEH system under different conditions are studied in this thesis. Firstly, the strategy for single valve control in isolated power network is discussed. Then the coordinated control for multiple valves is analyzed theoretically. Simulation and experimental results are put forward in the paper. Lastly, quick closing technique of the valve for over-speed protection under load rejection is also discussed in detail. The main contents are as follow:(1)A simulation model of single-valve control is built based on rotation speed feedback under the condition of isolated power network, and then the problem that the single-valve control under isolated power network adopts the large power network control mode is analyzed. It makes conclusion that the delay time of DEH rotate speed feedback ceases to be effective in isolated power network condition. Based on the above conclusion, a design of single-valve control under isolated network condition is proposed in this paper, which a new speed control card is adopted of which the delay time is much shorter than DEH system rotation speed feedback. It is showed in simulation results that the design of small grid single-valve control is feasible.(2)An optimization plan is proposed in this paper to lessen valve sloshing in sequent-valve operation. The valve sloshing will be lessened by decreasing the slop of flow characteristics curve with the good linearity of flow command and actual flow.(3)Quick closing technique of the valve for over-speed protection under load rejection is studied in this paper. A simulation model of the valve quick closing is built. Then the performance of valve quick closing under load rejecting test is analyzed on MATLAB platform. Finally, the valve quick closing is proved effective in the load rejection test.