System and method for operating a steam turbine and an electric power generating plant
First Claim
1. A system for operating a steam turbine comprising nonlinear operating steam valve means for determining the flow of steam through at least one section of the turbine, means for determining a representation of the actual value of at least one variable turbine condition selected from the turbine speed condition and the turbine load condition, programmed digital computer means having a reference representation of said one turbine condition, said computer system further having means for generating at least one predetermined linearizing characterization to offset the nonlinear relationship of valve position to steam flow, said digital computer means having means for generating position control signals for said valve means in accordance with the reference representation and the linearizing characterization and the actual condition representation, and means for controlling said valve means in accordance with the determined position control signals.
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Abstract
A programmed digital computer control system determines the turbine steam flow changes required to satisfy the speed and load demand made on the operation of a large electric power stream turbine for which substantially constant throttle pressure steam is generated. Load control is directed to plant electric power generation and it is based on feedforward valve positioning operation with feedback multiplication calibration for plant load and/or turbine speed error. Changes in the turbine operating level are limited by dynamic constraints applied by the computer.
53 Citations
68 Claims
- 1. A system for operating a steam turbine comprising nonlinear operating steam valve means for determining the flow of steam through at least one section of the turbine, means for determining a representation of the actual value of at least one variable turbine condition selected from the turbine speed condition and the turbine load condition, programmed digital computer means having a reference representation of said one turbine condition, said computer system further having means for generating at least one predetermined linearizing characterization to offset the nonlinear relationship of valve position to steam flow, said digital computer means having means for generating position control signals for said valve means in accordance with the reference representation and the linearizing characterization and the actual condition representation, and means for controlling said valve means in accordance with the determined position control signals.
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5. A method for operating a steam turbine having steam valve means for determining the flow of steam through at least one section of the turbine, the steps of said method comprising sensing the turbine speed and the turbine load, storing in a digital computer means at least one linearizing characterization of valve position demand as a function of a variable based on turbine operating demand to linearize the relationship of steam flow to the variable, operating the digital computer means to determine control actions in accordance with the linearizing characterization and the sensed speed and load and at least a load reference from which the turbine operating demand is derived, and controlling the valve means in accordance with the determined control actions.
- 6. A control system for operating an electric power steam turbine having steam valve means for determining the flow of steam through at least one section of the turbine, said control system comprising means for determining a representation of an input load demand, means for determining a representation of the actual value of the load, means for determining in accordance with another predetermined characterization a correctively modified load demand representation dependent upon error between the actual and the input demand values of the load, means for determining in accordance with a predetermined feedforward characterization a representation of steam valve position demand required to satisfy the correctively modified load demand representation, and means for controlling the valve means in accordance with the steam valve position demand representation.
- 18. A method for operating a steam turbine having steam valve means for determining the flow of steam through at least one section of the turbine, the steps of said method comprising determining a representation of an input load demand, determining a representation of the actual value of the load, determining in accordance with another predetermined characterization a correctively modified load demand representation dependent upon error between the actual and the input demand values of the load, determining in accordance with a predetermined feedforward characterization a representation of a steam valve position demand required to satisfy the correctively modified load, and operating said steam valve means in accordance with the steam valve position demand representation.
- 21. A steam turbine control system for a large electric power steam turbine which is provided with a plurality of turbine sections and a predetermined throttle valve arrangement and a predetermined governor valve arrangement, said system comprising means for determining representations of an input load demand and the actual value of turbine load, means for determining a representation dependent upon error between the actual and the input demand values of load, means for determining a representation of turbine speed error and for determining a correctively modified load demand representation in accordance with the speed error representation, means for determining a correctively modified load demand representation in accordance with the load error representation, means for determining in accordance with a predetermined feedforward static and dynamic characterization a representation of steam valve position demand at least for each of the governor valves as required to satisfy the load and speed correctively modified load demand during a load control operating mode, and means for controlling at least the governor steam valves in accordance with the steam valve position demand representations.
- 30. A system for operating an electric power generating plant comprising a steam turbine, means including a steam generating system for supplying steam to said turbine, a generator driven by said turbine and adapted to generate a predetermined electrical load for network operation with other generators, said turbine including a plurality of turbine sections, a predetermined throttle valve arrangement, a predetermined governor valve arrangement, said throttle and governor valves disposed to control the flow of steam between said steam generating system and said turbine, means for determining a representation of turbine speed error and for determining a correctively modified electrical load demand representation in accordance with the speed error representation, means for determining a representation of the actual value of turbine load, means for determining a representation dependent upon error between the actual and the input demand values of load, means for determining a correctively modified electrical load demand representation in accordance with the load error representation, means for determining in accordance with a predetermined feedforward static and dynamic characterization a representation of steam valve position demand at least for each of the governor valves as required to satisfy the load and speed correctively modified electrical load demand, and means for controlling said throttle and governor steam valves in accordance with the steam valve position demands.
- 34. A steam turbine control system for a large electric power steam turbine which is provided with a plurality of turbine sections and a predetermined throttle valve arrangement and a predetermined governor valve arrangement, said system comprising means for correctively controlling in accordance with a predetermined characterization the position of at least each of the governor valves in response to a representation of total load demand input during a load control operating mode, means for determining a representation of turbine speed error and for correctively modifying the operation of said valve position controlling means in accordance with the speed error representation, and means for controlling in accordance with another differing predetermined characterization the position of at least each of the throttle valves as required to satisfy turbine speed demand during a speed control operating mode.
- 38. A steam turbine control system for a large electric power steam turbine which drives a generator to produce electric power through breaker means and which is provided with a plurality of turbine sections and a predetermined throttle valve arrangement and a predetermined governor valve arrangement, said system comprising a digital computer having a representation of a speed reference for use during a speed control mode and a load control mode and a representation of a load reference for use during the load control mode, means for generating signals corresponding to the actual speed and load values and for coupling the signals to said computer, said computer including means for generating a representation of steam valve position demand as a function of representations of the actual and reference speed values during speed control and as a function of representations of the actual and reference speed and load values during load control, and a closed loop electrohydraulic positioning control for controlling the valve means in accordance with the steam valve position demand signal.
- 40. A steam turbine control system for a large electric power steam turbine which drives a generator to produce electric power through breaker means and which is provided with a plurality of turbine sections and a predetermined throttle valve arrangement and a predetermined governor valve arrangement, said system comprising digital computer means having a representation of a speed reference for use during a speed control mode and a load control mode and a representation of a load reference for use during the load control mode, means for generating signals corresponding to the actual speed and load values and for coupling the signals to said computer means, said computer means including means for generating a representation of steam valve position demand as a function of representations of the actual and reference speed values during speed control and as a function of representations of the actual and reference speed and load values during load control, said computer means further including means for transferring between load and speed control modes according to whether the breaker means is closed or open, and means for controlling the individual throttle and governor valves in accordance with the position demand representation.
- 50. A steam turbine control system for a large electric power steam turbine which is provided with a plurality of turbine sections and a predetermined throttle and governor valve arrangement, said system comprising means for generating a signal representative of actual turbine speed, means for generating a signal representative of actual turbine load, means for generating a representation of steam valve position demand as a function of representations of the actual turbine speed and load and reference speed and load values, means for periodically coupling said signals to said position demand generating means and for periodically operating said position demand generating means to generate the position demand representation continuously, and means for positioning the throttle and governor valves in accordance with the position demand representation.
- 54. A steam turbine control system for a large steam turbine having a predetermined throttle and governor valve arrangement, said system comprising means for generating a signal representative of actual turbine speed, means for generating a signal representative of generated megawatt electrical load, means for generating a representation of steam valve position demand as a function of representations of the actual turbine speed and megawatt load and reference speed and megawatt load values, means for coupling said signals to said position demand generating means, said position demand generating means having means for comparing representations of the actual speed and a reference speed and representations of the actual megawatt load and a reference load to provide speed and megawatt error representations, said position demand generating means having means for generating a corrective load demand representation in a load control path in accordance with the speed and megawatt error representations, said megawatt error representation being multiplied against the load control path in the generation of the corrective load demand representation and the valve position demand representation being generated in accordance with the corrective load demand representation, and means for positioning the throttle and governor valves in accordance with the position demand representation.
- 60. A steam turbine control system for a large electric power steam turbine which is provided with a plurality of turbine sections and a predetermined throttle and governor valve arrangement, said system comprising means for generating a signal representative of actual turbine speed, means for generating a signal representative of actual turbine load, digital computer means, means for coupling said signals to said computer means, said digital computer means including means for comparing representations of the actual speed and a reference speed and representations of the actual load and a reference load to provide speed and load error representations, said digital means further including means for generating a corrective load demand representation in a load control path in accordance with the load and speed error representations and for generating a corrective speed demand representation in a speed control path in accordance with the speed error representation, said digital computer means including means for generating representations of at least throttle valve position demands in accordance with the corrective speed demand representation on speed control and at least governor valve position demands in accordance with the corrective load demand representation on load control, said digital computer means further including means for generating changes in the throttle and governor valve position demand representations during valve mode changes in the speed and load control modes of operation, and means for positioning the throttle and governor valves in accordance with the position demand representations.
Specification