Patent ID: 6719523
Filing Date: 2004-04-13
Classification: F01D

Abstract:
A method for controlling steam flow-rate through a steam turbine using a control system comprising a controller for steam-turbine speed to generate a steam-valve actuator set point, a pilot valve directing hydraulic fluid flow to-and-from a steam-valve actuator, a transmitter sending a signal proportional to a steam-valve actuator position, and an additional controller for a pilot-valve position, the method comprising:(a) calculating a first value proportional to a difference between the steam-valve actuator set point and the steam-valve actuator position; (b) calculating a second value equal to a first time-derivative of the steam-valve actuator position as a control variable for the pilot-valve controller; (c) calculating a position signal within the pilot-valve controller based upon the first and second values; and (d) positioning a pilot-valve actuator based upon the position signal of the pilot-valve controller.