Adjustable gain controller for valve position control loop and method

Abstract

An adjustable gain controller for a steam turbine valve position control loop includes an electronic operator, a proportional controller, a derivative controller and an integral controller. A steam flow condition error signal is amplified by the reciprocal of the valve's regulation value. The amplified error signal is supplied to the electronic operator and to the integral controller. The electronic operator includes means for initially selecting a value of A and n and generating a gain factor from a nonlinear gain characteristic function utilizing those values in combination with the valve's regulation value and the normalized error signal. The electronic operator multiplies the amplified error signal by the gain factor and applies the resultant signal to the proportional controller and the derivative controller. The output signals from the proportional, derivative and integral controllers are summed together and that sum is input into an electrohydraulic valve actuator system. The electrohydraulic valve actuator directly positions the steam valve. Hydraulic and mechanical jitter is reduced by adjusting the values of A and n to reduce the jitter in the electrohydraulic valve actuator system.