Valve management function is the key link of speed control system. However

the current model of turbine speed control system does not consider the influence of valve management function. Thus

through analyzing the flow characteristics of valve

this paper establishes the Simulink simulation model of speed control system with valve management function

and introduces the linear factor β to measure the linear degree of valve management function. Through simulation and calculation analysis

the damping characteristics of the speed control system under the open-loop control and closed-loop control are obtained

and the influences of the linear factor β

PI control parameters KP

KI

time constant Tydj of the hydraulic servo motor and volume time constant TCH of the high cylinder front steam chamber on the damping characteristics of the system are further analyzed. Through the transfer function calculation

the system stability judgment condition and the function relationship between β and KP

KI

Tydj and TCH are obtained

and the calculation method of β's negative damping critical value and over damping critical value are given

which can be used as the analysis basis for some units when the speed governing system swings.