Importance

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Abstract

Steam turbine control systems often incorporate electromechanical pilot-valve actuator assemblies to regulate hydraulically-driven actuator pistons that modulate steam valves, thereby controlling turbine speed. The general operation and quick-response requirements of these pilot-valve actuator assemblies can suffer from shortcomings (such as, excessive friction, contaminated oil, and defective electromagnetic components) that degrade the control system's overall performance. For these reasons, this disclosure relates to a method for overcoming insufficient, pilot-valve actuator response by using an integrated control system dedicated to these electromechanical assemblies. Pilot-valve actuators can be equipped with a single coil or multiple coils (usually a primary and a secondary). In a dual-coil configuration, the primary is energized according to an output of a PID controller, whereas the secondary coil is regulated by a separate control element. When the speed at which the steam-valve actuator reacts is adequate, the energizing signals to the individual coils may be equal, or the secondary coil may not be energized at all. But whenever the steam-valve actuator's speed is not adequate, the secondary coil is quickly energized to a higher level; consequently assuring prompt and reliable response of the integrated, turbomachinery speed-control system.

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First Claim