This patent claims priority to Russian Patent Application No. 2013120514, filed May 6, 2013, which is hereby incorporated by reference herein in its entirety.
The present patent relates to hydropower machinery and, more particularly, to ring gate control systems of a hydroelectric turbine installation that allows or shuts off water flow through an electrical power generation turbine.
Hydroelectric turbine installations used in electrical power generating plants utilize ring gates to effect shut off of a water flow path from an upstream reservoir, such as a river or a lake, through an electrical power generation turbine to a downstream depository. Ring gates (which are also referred to as cylindrical gates) are used in hydroelectric turbines as penstock shut off devices instead of conventional butterfly valves or spherical valves. A ring gate includes a gate ring which is a thin, short solid cylinder that surrounds a turbine runner which, when placed in the closed position, blocks the water flow passage between a distributor and a stay ring of a hydroelectric generator. The gate ring, which serves as an isolating valve, is typically disposed in the distributor of the turbine between the stay vanes and the wicket gates. When the ring gate is in the open position, the gate ring is typically housed in a compartment formed between a stay ring and a head cover, where the gate ring remains completely retracted from the water flow passage. During normal operation, the ring gate is closed after the wicket gates are closed and, at unit start-up, the ring gate is opened before the wicket gates start to open. For emergency conditions and/or situations, the gate ring may be used to close against full flow.
To assure proper functioning of a gate ring during operation, a control system that controls movement of the gate ring keeps the gate ring in a horizontal state with specific accuracy when the gate ring is traveling between the open and closed positions. The horizontal orientation prevents wedging of the gate ring during movement. Also, to assure proper functioning of a gate ring during operation, the control system that controls movement of the gate ring limits deformation of the gate ring, which also avoids wedging, while imparting a significant amount of force on the gate ring to move the gate ring. As a result of these constraints and to assure proper two dimensional gate ring orientation of the gate ring during movement, ring gate drive systems use more than three servomotors to move the gate ring.
Examples of known ring gate control systems that use mechanical links are described in U.S. Pat. No. 4,434,964 and PCT Patent Publication WO 99/43954. As described, a ring gate is operated by a set of servomotors positioned at spaced apart locations around the circumference of a gate ring. These servomotors are synchronized by mechanically coupling pairs of adjacent servomotors using chain loops such that each set of two adjacent servomotors are connected by a continuous chain loop. In one configuration, a total of six chain loops is required for a six servomotor arrangement. Moreover, each chain loop must include its own chain tensioner to maintain proper tension in each of the individual chains. To keep the gate ring in a horizontal orientation, accurate and rigid screw pairs and drives are required.
Each of these ring gate control systems includes many mechanical parts that are subject to wear and tear (e.g., the chain loops and sprockets for the chains), are relatively complicated and expensive to build and maintain and require laborious adjustment, tuning (e.g., using chain loop tensioners) and maintenance. In addition, when mechanical links are applied to more than three servomotors, the control system becomes statically indeterminate, and the effective hauling ability decreases because the servomotors load each other mutually due to parameters spread in their control channels. As a result, the ability to take external loading by the gate ring is decreased.
PCT Patent Publication WO 99/43954 describes a control system that uses both hydro-mechanical and electro-hydraulic links to keep a gate ring in a horizontal orientation. The system includes a considerable number of hydraulic valves as well as volume batchers. The system also includes a number of motors and/or pumps equal to the number of servomotors. The configuration of hydraulic valves, motors, pumps, etc., makes the system complicated and more expensive because of the amount of hydraulic equipment and the labor associated with tuning the system. In addition, for more than three servomotors, the control system becomes statically indeterminate, which decreases the effective hauling ability of the system. When the control system is statically indeterminate, the controller tuning algorithm is also indeterminate, which increases the amount of labor associated with tuning the control system.
An example ring gate control system disclosed herein uses three identical and separate position control closed loops that control vertical coordinates of three control points with high precision. These control points are spaced apart equally about the circumference of the gate ring. The vertical coordinates of the control points define a horizontal orientation of the gate ring uniquely. Position control closed loops receive the same input signals and operate together to move the ring gate between an open position and a closed position. Because of the high precision of the position control closed loops, displacements of the control points during movement differ from each other insignificantly and the gate ring maintains horizontal orientation within predetermined limits.
In some examples, each position control closed loop includes a separate group of servomotors (e.g., hydraulic cylinders). Each servomotor group includes two or more individual servomotors coupled to drive the gate ring. Each group of servomotors is associated with moving one of the three control points. Each position control closed loop also includes a separate feedback position/velocity transmitter coupled to its respective control points. A control valve controls the operation of the servomotors within the servomotor group. In some examples, the servomotors within the servomotor group are hydraulically connected to each to other in parallel. In some examples, an electric controller controls the operation of the control valve and closes the position control loop via feedback from the position/velocity transmitter.
The disclosed example ring gate control system is simpler in design than prior art ring gate control systems, because the ring gate control system does not require mechanical linkages disposed between each of the servomotors and does not require a separate control valve for each servomotor. As such, the example control system has less components, is easier to assemble and has increased reliability. Also, the example control system, which uses three independent position closed control loops, is statically determinate, because the control loops control the positions of the three control points on the gate ring. Being statically determinate enables easy and clear closed control loop tuning procedures, which enables a higher degree of reliability. The ring gate control system described herein has fewer components, becomes statically determinate, which enables easy and clear tuning of the closed control loops and uses only three independent control channels, which may be easily tuned. The foregoing features provide for more reliability during the operation of the ring gate control system.
The example turbine system 10 includes a ring gate system having multiple servomotors 22 mechanically coupled to the gate ring 24 via piston rods 23. While only two servomotors 22 are illustrated in
To maintain the state of the gate ring 24 in a horizontal orientation within a certain or predetermined level of accuracy during movement of the gate ring 24 between the open and the closed positions, in some examples, the example ring gate control system described herein controls the operation or movement of the gate ring 24 by separately controlling three identical groups of servomotors connected to the gate ring 24. Each servomotor group may include two or more individual servomotors coupled to linkage points at the circumference on the gate ring 24. Because each group of servomotors 22A, 22B, 22C includes more than one servomotor, the ring gate control system 40 can use an adequate number of servomotors to provide the power or force necessary to move the gate ring 24 oriented in a horizontal orientation to a desired degree of accuracy. The number of servomotors within servomotor group may be any desired number such as two, three, four, etc. However, in the examples described herein, the number of servomotors within each of the different groups is the same. It is preferable that within a servomotor group the servomotors are the same type and/or size. The sizes of the servomotors may be different, but within each of the different groups there are to be pairs of the same size servomotors. Also, the servomotors of the pair are to be disposed symmetrically about a plane crossing the respective control point and being coincident with a gate ring axis. In an example using an odd number of servomotors within a servomotor group, a single servomotor have no pair. In some examples, the servomotor groups are identical.
In the example of
In the case of an even number of servomotors in the servomotor groups, the position/velocity transmitters 34A, 34B and 34C are coupled to control points via brackets, as shown at
As shown at
Position/velocity transmitters used in the control system described herein are of contactless type. The position/velocity transmitters measure the position and/or velocity of the gate ring 24 based on measurement displacement via effect of interaction between permanent magnet and waveguide. Such transmitters generate position and velocity outputs.
The ring gate control system described herein is made up of three independent position closed control loops CCLA, CCLB, CCLC. These position closed control loops are identical. Output signals from controller 50 control the servovalves (proportional valves) 46A, 46B, 46C to supply the appropriate oil flow to groups of respective servomotors 22A, 22B and 22C that provoke servomotor groups movement with velocity <<smv>> and changing positions (vertical coordinates) <<pp>> of the respective control points 30A, 30B and 30C. Feedback position/velocity transmitters 34A, 34B, 34C generate current position (vertical coordinates) outputs <<pp>> and velocity outputs <<pv>> of the respective control points 30A, 30B and 30C. Electrical regulators A, B, C, via position outputs of position/velocity transmitters, implement three position based closed control loops CCLA, CCLB, CCLC. Velocity outputs of the transmitters may be used for reducing position errors of the position closed control loops by implementing inner feedbacks of the closed control loops.
As the three control points 30A, 30B, 30C are spaced equally around the gate ring 24, the closed control loops define and control the vertical coordinates of the three control points and, thus, define the position and the horizontal state of the gate ring 24. When controlling the coordinates of the three control points 30A, 30B, 30C, as described above, the closed control loops are independent of one another because the ring gate control system 40 is statically defined and any minor vertical displacements of one control point does not cause vertical displacements of other control points. Thus, the ring gate control system 40 is made up of three independent position based closed control loops, each of which is easy to operate and tune with high accuracy. The closed control loops receive equal input signals so that deviation of the gate ring horizontal orientation is defined by differences of the control points vertical displacement. Additionally or alternatively, deviation of the gate ring horizontal orientation is defined by differences of position errors of the position based closed control loops CCLA, CCLB, CCLC. Consequently, synchronization of travel of the three control points 30A, 30B, 30C defining the horizontal state of the gate ring 24 is provided by the high accuracy of the three independent position control loops, which are also able to correct the relative or absolute vertical coordinates of the control points during operation of the ring gate 24.
Number | Date | Country | Kind |
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2013120514 | May 2013 | RU | national |