Abstract:
Ring gate control system and control method are disclosed herein. An example ring gate control system includes a first servomotor group, a second servomotor group, and a third servomotor group. Each servomotor group is associated with a respective control point located around an annular face of a ring gate. The servomotors within the groups coupled to the annular face of the ring gate at respective linkage points, a transmitter coupled to the annular face of the ring gate and a control valve coupled between a hydraulic source and the at least two actuators and a controller coupled to each of the control valves and to each of the transmitters. The controller is separately operating a closed control loop for each servomotor group to control positions of the control points to control a horizontal orientation of the ring gate.

Description:
RELATED APPLICATIONS 
       [0001]    This patent claims priority to Russian Patent Application No. 2013120514, filed May 6, 2013, which is hereby incorporated by reference herein in its entirety. 
       FIELD OF THE DISCLOSURE 
       [0002]    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. 
       BACKGROUND 
       [0003]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  illustrates a cross sectional view of a hydro-electric power plant turbine system using a ring gate to shut off the flow of water to a Francis turbine. 
           [0005]      FIG. 2A  illustrates a perspective view of an example ring gate and servomotor system having three servomotor groups, each having two servomotors, that can be used to control movement of the ring gate of  FIG. 1 . 
           [0006]      FIG. 2B  illustrates a top view of an example ring gate and servomotor system having three servomotor groups, each having two servomotors, that can be used to control movement of the ring gate of  FIG. 1 . 
           [0007]      FIG. 3A  illustrates a perspective view of an example ring gate and servomotor system having three servomotor groups, each having three servomotors, that can be used to control movement of the ring gate of  FIG. 1 . 
           [0008]      FIG. 3B  illustrates a top view of an example ring gate and servomotor system having three servomotor groups, each having three servomotors, that can be used to control movement of the ring gate of  FIG. 1 . 
           [0009]      FIG. 4  illustrates an example combined schematic diagram of a control system that can be used to control the example ring gate of  FIGS. 2 and 3 . 
           [0010]      FIG. 5  illustrates a structural diagram of an example control system that can be used to control the example ring gate of  FIGS. 2 and 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    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. 
         [0012]    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. 
         [0013]    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. 
         [0014]    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. 
         [0015]    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. 
         [0016]    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. 
         [0017]    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. 
         [0018]      FIG. 1  illustrates a cross sectional view of an example turbine system  10  that is used in a hydro-electric power generation plant. The turbine system  10  is used to generate electricity from water flowing from an upstream reservoir, such as a river or a lake, through a penstock pipe and the turbine system  10  to a downstream depository, such as a river (not shown). A spiral casing  16  is connected to an upstream penstock pipe that provides water for driving the turbine  21 . As illustrated in  FIG. 1 , guide vanes  18  of a wicket gate  20  are disposed between the spiral casing  16  and a turbine housing  17  to direct water flow to a turbine runner from all sides of the housing  17  during operation of the turbine  21 . A gate ring  24  is a relatively thin, short solid cylinder that surrounds a turbine. In the closed position, the gate ring  24  blocks the water flow. In the open position, the gate ring  24  is retracted from the water flow passage. 
         [0019]    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  FIG. 1 , the ring gate system can include six or more servomotors. Each servomotor  22  is a hydraulic cylinder that drives movement of the piston rod  23  connected to the gate ring  24 . The gate ring  24  is illustrated in  FIG. 1  in a fully retracted (fully open) position so that the gate ring  24  is completely out of the fluid flow path from the spiral casing  16  to the turbine housing  17 . The servomotors  22  operate together to force the gate ring  24  down into the flow path to shut off and/or control the flow of water between the spiral casing  16  and the turbine hosing  17  when the gate ring  24  is in the fully closed (un-retracted) position. More particularly, when the gate ring  24  is in the closed position, the gate ring  24  is completely disposed in the path between the staving of the spiral casing  16  and the guide vanes  18  of the wicket gate  20 . The ring gate control system moves the gate ring  24  in a vertical direction to open or to fully shut off water flow to the turbine guide vanes  18 . 
         [0020]    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  22 A,  22 B,  22 C 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. 
         [0021]      FIGS. 2A ,  2 B,  3 A and  3 B illustrate two examples in which servomotor groups, feedback position/velocity transmitters, control points and linkage points are configured to control the gate ring  24  of  FIG. 1 .  FIGS. 2A and 2B  illustrates an example in which the number of servomotors in the groups is even.  FIGS. 3A and 3B  illustrate an example in which the number of servomotor in the groups is odd. Three control points  30 A,  30 B,  30 C are defined and spaced apart equally at the circumference on the gate ring  24 . Linkage points  28 A,  28 B and  28 C of servomotor groups are symmetrically disposed about one of the three planes crossing the respective control points  30 A,  30 B and  30 C of the servomotor group and coinciding with an axis of the gate ring  24  Servomotors  22 A,  22 B and  22 C are coupled to gate ring at the respective linkage points  28 A,  28 B,  28 C via the piston rods  23 . Three feedback position/velocity transmitters  34 A,  34 B,  34 C are coupled to the gate ring  24  at the respective control points  30 A,  30 B,  30 C. 
         [0022]    In the example of  FIG. 2B , the lines associated with the control points  30 A,  30 B, and  30 C are separated by 120° so that the control points  30 A,  30 B, and  30 C are equally separated from each other along the annular face of the ring gate  24 .  FIG. 2B  shows the servomotors in each servomotor group positioned along the annular face of the ring gate  24  based on an angle α. For example, the linkage points  28 A associated with the servomotors  22 A are separated by angle α and positioned so each linkage point  28 A is equidistant from the control point  30 A. The even distribution of the servomotors  22 A around the control point  30 A balances forces used to drive the ring gate  24 . In this example, the angle α is about 60°. In other examples, the angle α is to be equal to or less than 60°. Further, in examples where additional servomotors are implemented, the servomotors are positioned to evenly distribute force on the ring gate  24  in relation to the control points  30 A,  30 B, and  30 C. 
         [0023]    In the case of an even number of servomotors in the servomotor groups, the position/velocity transmitters  34 A,  34 B and  34 C are coupled to control points via brackets, as shown at  FIG. 2A . 
         [0024]    As shown at  FIG. 3A , in the case of an odd number of servomotors in servomotor groups, the position/velocity transmitters  34 A,  34 B and  34 C are incorporated in the servomotors, which are coupled to respective control points  30 A,  30 B and  30 C via the piston rods  23 .  FIG. 3B  shows a plan view of the ring gate  24  of  FIG. 3A . The illustrated example also shows the positioning between the respective linkage points  28 A,  28 B, and  28 C of the servomotors  22 A,  22 B, and  22 C. In this example, each of the linkage points within an servomotor group is separated by an angle β. In some examples, the angle β is about 30° or less than 30°. In this example, the angle β is based on a line that crosses the respective control points  30 A,  30 B, and  30 C and intersects at a central or longitudinal axis of the ring gate  24 . 
         [0025]    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. 
         [0026]      FIG. 4  illustrates a combined schematic diagram of the control system described herein for the example of  FIG. 3 . The servomotors in each group are connected hydraulically to each other in parallel and together to respective proportional valves. Three proportional valves  46 A,  46 B,  46 C are separately coupled to a programmable controller  50 . Position/velocity transmitters  34 A,  34 B,  34 C also are separately coupled to the programmable controller  50 . The position/velocity transmitters  34 A,  34 B,  34 C are built into the servomotor and are separably coupled to the control points. All proportional valves are supplied with pressurized oil through oil line  44 A and return line  44 B via oil pressure system  42 . 
         [0027]      FIG. 5  illustrates a structural diagram of the control system that controls the ring gate of  FIGS. 2 and 3 .  FIG. 5  discloses the links between the functional parts of the ring gate system. 
         [0028]    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)  46 A,  46 B,  46 C to supply the appropriate oil flow to groups of respective servomotors  22 A,  22 B and  22 C that provoke servomotor groups movement with velocity &lt;&lt;smv&gt;&gt; and changing positions (vertical coordinates) &lt;&lt;pp&gt;&gt; of the respective control points  30 A,  30 B and  30 C. Feedback position/velocity transmitters  34 A,  34 B,  34 C generate current position (vertical coordinates) outputs &lt;&lt;pp&gt;&gt; and velocity outputs &lt;&lt;pv&gt;&gt; of the respective control points  30 A,  30 B and  30 C. 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. 
         [0029]    As the three control points  30 A,  30 B,  30 C 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  30 A,  30 B,  30 C, 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  30 A,  30 B,  30 C 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 .