Abstract: Steam turbine speed-control systems often incorporate pilot valves for controlling the position of hydraulic actuators for steam valves. Operational efficiency of these pilot valves can suffer from imperfections due to manufacturing defects, wear, contaminated oil, and the like, thereby impairing the control system's overall performance. This disclosure relates to a method for improving performance accuracy by incorporating a control system (including additional controllers) dedicated to overcoming the deficiencies of pilot valves or other control system components. With such a system, the lack of adequate control response can be detected by calculating the first time-derivative of a variety of main controlled-parameters. Such parameters can be directly related to steam flow control, such as steam valve position, steam flow rate, and pressure within the steam turbine; or they may be related to the driven equipment: generator power output, flow rate through a compressor, and compressor discharge pressure.

Abstract: Steam turbine speed-control systems often incorporate pilot valves for controlling the position of hydraulic actuators for steam valves. Operational efficiency of these pilot valves can suffer from imperfections due to manufacturing defects, wear, contaminated oil, and the like, thereby impairing the control system's overall performance. This disclosure relates to a method for improving performance accuracy by incorporating a control system (including additional controllers) dedicated to overcoming the deficiencies of pilot valves or other control system components. With such a system, the lack of adequate control response can be detected by calculating the first time-derivative of a variety of main controlled-parameters. Such parameters can be directly related to steam flow control, such as steam valve position, steam flow rate, and pressure within the steam turbine; or they may be related to the driven equipment: generator power output, flow rate through a compressor, and compressor discharge pressure.

Abstract: Steam turbine speed-control systems often incorporate pilot valves for the purpose of controlling the position of hydraulic actuators for steam valves. However, the operational efficiency of these pilot valves can suffer from imperfections due to manufacturing defects, wear, and the like, thereby impairing the control system's overall performance. For these reasons, this disclosure relates to a method for overcoming a faulty pilot valve by incorporating a control system (including additional controllers) dedicated to the pilot valve. In this type setup, not only can the position of the pilot valve be a control variable, but the velocity of actuation of this valve can also be used as another control variable. Therefore, the results of separate controllers, using these two control variables, can be combined to improve the dynamic response of the steam turbine speed-control system.

Abstract: Steam turbine speed-control systems often incorporate pilot valves for the purpose of controlling the position of hydraulic actuators for steam valves. However, the operational efficiency of these pilot valves can suffer from imperfections due to manufacturing defects, wear, and the like, thereby impairing the control system's overall performance. For these reasons, this disclosure relates to a method for overcoming a faulty pilot valve by incorporating a control system (including additional controllers) dedicated to the pilot valve. In this type setup, not only can the position of the pilot valve be a control variable, but the velocity of actuation of this valve can also be used as another control variable. Therefore, the results of separate controllers, using these two control variables, can be combined to improve the dynamic response of the steam turbine speed-control system.

Abstract: Pilot valves used in electrohydraulic control systems are driven by either an electromagnetic electromechanical actuator or an electromotor electromechanical actuator. A drawback of electromagnetic actuation is that on brief interruptions of electrical power the actuator causes a trip response to the pilot valve, whereas a drawback of electromotor actuation is that on complete interruptions of electrical power the actuator cannot independently cause a trip response of the pilot valve on demand. The proposed modification, involving the pilot valve, provides a means to effect a trip response regardless of the electromechanical actuator type used, together with overcoming the drawback of electromotor actuation. To realize the trip response, an additional piston (connected to the electromotor actuator's stem) is positioned between the actuator stem and the pilot valve.