Abstract:
A hydroelectric turbine generator and control system is provided that optimizes the maximum possible power output at all times by strictly monitoring power output from the generator unit and modulating the wicket gate angle and the runner blade pitch independently of one another. The hydroelectric turbine generator includes a means for separately controlling wicket gate angle and runner blade pitch. The wicket gate angle control mechanism controls the flow into the system, pre conditions flow for maximum power and maintains reservoir level. The runner blade pitch control mechanism continuously monitors the system power output based on actual power produced, and adjusts system parameters in order to achieve maximum power output.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 60/958,368 filed Jul. 5, 2007. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a system and apparatus for generating electrical power. More specifically, this invention is directed to a hydroelectric turbine generator and computer based control system. The hydroelectric turbine generator can be installed and operated in low head, high volume “run of the river” hydroelectric sites throughout the world. 
     The hydroelectric turbine is specifically designed for small hydro applications and is not a “scaled down” larger turbine. The hydroelectric turbine takes advantage of the current state of the art technology, and applies it in the most appropriate manner for currently underutilized small hydro power sites. In Connecticut, Massachusetts and New York alone, there are 4,100 registered dams. Of these registered dams, approximately 350 are used for hydro power generation. There are approximately 3,750 undeveloped potential hydro power sites in this small region. In many cases, these are former mill sites with a prior history of hydro power production. There are an endless number of potential clean renewable power generating sites throughout the world, which can be developed using the present invention. Some of these sites are not former mill sites, are not registered dams and are currently considered to be not cost justifiable. 
     The present invention and technology will allow a vast, untapped, clean renewable power generating potential to be developed and utilized in a cost justified manner. Moreover, a hydroelectric turbine according to the present invention will open significant power production opportunities for other portions of the world including, “third world country” applications where the cost and complexities of current hydro equipment have made it difficult or impossible to consider. 
     2. Brief Description of the Related Art 
     Hydroelectric power generation is well known in the prior art. U.S. Pat. No. 4,674,279 to Ali, et al. (hereinafter, “the &#39;279 Patent”) discloses a control system for a hydroelectric power plant of the run-of-river type wherein the load on the turbine generator unit(s) are matched to the flow of the river. The unit(s) operate at the maximum head available for existing flow conditions to produce the maximum energy available from the river flow for the installed capacity of the plant and within the allowable, safe operating capability range of the turbine-generator unit(s). The control system can be employed with a plurality of turbine-generator units in a hydroelectric power plant. 
     As disclosed in the &#39;279 Patent, the turbine has a main housing and runner. Supply of water to the runner is controlled by wicket gates. The flow control means includes flow controls or modulating devices (wicket gates, runner blades or nozzles). The flow control means, or wicket gate position sensing, provides a signal indicative of the actual position of the flow control or wicket gates. The control system operates to cause either: (i) the opening of the flow control means or wicket gates to increase operation of turbine; or (ii) the closing of the flow control means or wicket gates to decrease operation of turbine. The control system automatically operates in response to variations in flow or in response to river conditions. 
     Other prior art discloses additional types of “Kaplan” style hydraulic turbines and control systems related to controlling the pitch of the runners and/or wicket gates. For example, U.S. Pat. No: 5,441,384 to Gokhman specifically describes a plurality of angles and a plurality of arrangements for wicket gates and blade runners. U.S. Pat. No: 4,610,599 to Long describes a control system for a hydraulic “Kaplan” turbine. More specifically this patent provides a method of control for adjustable wicket gates and adjustable blade runners in a hydraulic turbine. 
     U.S. Pat. No. 5,322,412 to Erlach (hereinafter, “the &#39;412 Patent”) and U.S. Pat. No. 5,754,446 to Fisher, Jr. (hereinafter, “the &#39;446 Patent”) describe a method for optimizing the controls of hydraulic “Kaplan” turbines. The &#39;412 Patent describes the use of adjustable wicket gates and runners to optimize performance. The control system senses fluctuations in bearing pressure and/or generator AC output to change wicket gate and runner angles. Similarly, the &#39;446 Patent describes the use of various sensors to control the adjustment of wicket gate and runner angles thereby optimizing the performance of the turbine. 
     None of these prior art disclosures provide a specifically designed hydroelectric turbine for use in small, micro or mini-hydro applications. Also, in the prior art, the relationship between the wicket gates and runner blades is dependent; the runner blade position is directly controlled by the wicket gate position rather than truly optimizing runner blade angle for maximum power output. Moreover, such prior art devices do not provide for a preconditioned flow by the wicket gate for optimal performance of the runner blade. 
     It is therefore an object of the present invention-to overcome these limitations in the prior art and to provide a hydroelectric turbine specifically designed for small hydro applications. It is also an object of the present invention to provide a means for independently controlling wicket gates and runner blades to achieve optimal power generation. Similarly, it is an object of the present invention to provide a means for preconditioning the flow to the runner blades by the wicket gates to achieve optimal power generation. 
     DESCRIPTION OF THE INVENTION 
     The present invention is designed for low head, high flow volume sites. The hydroelectric turbine comprises a double regulated propeller and utilizes the Kaplan turbine and gate system to produce electrical power efficiently through a wide range of flows common in “run of the river systems”. The hydroelectric turbine is designed to operate at efficiency levels greater than 90%, and can handle flows as low as 20 cfs. The total unit output flexibility is typically between 100 kw and 700 kw. 
     A hydroelectric turbine in accordance with the present invention can run on or off of a power grid; is modular in design, therefore multiple units can be operated in series; has the ability to alternate between the primary turbine and a series of turbines; and comprises a means for automatic recognition and synchronization when using multiple units. 
     The present invention comprises an integrated self-contained computer based control system. The closed looped control software modulates both wicket gate and blade positions based on actual generator power output. The software program implements continuous searching capabilities for optimized power output starting with an initial wicket gate-to-blade position relationship. The program then utilizes a search-and-fine-tune algorithm to optimize peak operational efficiency based on runner blade angle and actual power output independent of wicket blade angle. 
     In a typical embodiment of the present invention, no hydraulic systems are required. Instead, all actuations, including runner blade angle and wicket gate angle, are achieved through servo motors and mechanical devices. The variable wicket gate blade angles and the rotating running blade angles are independent of one another allowing the wicket gate blades to pre-condition flow to the runner blades for maximum power production. 
     Rotational speed reduction is accomplished through the use of timing belts instead of an oil filled gear box. This eliminates the need for hydraulic or lubrication oil reservoirs located in close proximity to the water source and allows for simplified maintenance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 . illustrates top, isometric, side, and water exit views of a hydroelectric turbine unit in accordance with the present invention. 
         FIG. 2 . illustrates a cross-sectional side view of the hydroelectric tubine unit of  FIG. 1  with greater detail on individual components and systems. 
         FIG. 3  provides sectional views taken along Section A and Section B of  FIG. 2 . Section A depicts the water exit end of the hydroelectric turbine and Section B depicts a cross-sectional cut into the runner angle mechanism. 
         FIG. 4  provides sectional views taken along Section C and Section D of  FIG. 2 . Section C depicts a cross-sectional cut between the wicket gate and the runner of the hydroelectric turbine and Section D depicts the water entrance end of the hydroelectric turbine and the drive shaft-to-generator speed reduction system. 
         FIG. 5  provides an overview flow diagram of a power generation control means according to the present invention. 
         FIG. 6  provides a flow diagram of a wicket gate control means according to the present invention. 
         FIG. 7  provides a flow diagram of a runner blade control means according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Typically, the present invention comprises one or more hydroelectric Kaplan turbine generators. Each Kaplan turbine generator utilizes a plurality of fixed wicket gate blades and a plurality of rotating runner blades rotating along an axis. Wicket gates are a key component in hydroelectric turbines that control the flow of water from the input pipes to the turbine propellers or runner blades. Typically, wicket gates do not pre-condition the flow of water prior to contacting the runner blades because of their dependent relationship to the runner blades, physical location with the turbine, and because they are used to maintain reservoir level. 
     Top, isometric, side, and water exit views of a hydroelectric turbine unit  10  in accordance with the present invention are depicted in  FIG. 1 . A cross-sectional side view of hydroelectric turbine unit  10  is provided in  FIG. 2 . As shown in  FIG. 2 , the unit features comprise a runner angle servo  12 ( a ), a runner angle mechanism  12 ( b ), and a runner  12 ( c ). The unit features further comprise a wicket servo/gearbox  12 ( d ), a wicket angle mechanism  12 ( e ), and a wicket gate  12 ( f ). As further shown in  FIG. 2 , the unit comprises a generator drive shaft  12 ( g ) and a drive shaft-to-generator speed reduction means  12 ( h ). 
     As shown in  FIG. 3 , Section A depicts the water exit end  12 ( i ) of the hydroelectric turbine and Section B depicts a cross-sectional cut into the runner angle mechanism. Rotationally mounted runners  12 ( c ) and fixedly mounted wicket gate  12 ( f ) are shown in both sectional views. 
     As shown in  FIG. 4 , Section C depicts a cross-sectional cut between the wicket gate  12 ( f ) and the runner  12 ( c ) of the hydroelectric turbine  10 . Section D depicts the water entrance end  12 ( c ) of the hydroelectric turbine  10  and the drive shaft-to-generator speed reduction system  12 ( h ). 
     A preferred embodiment of the present invention comprises a stationary wicket gate arrangement with independent relationship to the rotating runner blades. The independence of the wicket gate to the runner blades allows for preconditioning of the flow of water prior to contact with the runner blades. The wicket gate can be set for various runner blade angles as determined by a control means. Formerly, each wicket gate angle cooperated with a preset runner blade angle such that a change in the wicket gate automatically changed the runner angle to the same preset condition. The present invention provides for the independent control of the wicket gate such that its angle adjusts to maintain reservoir level and to pre-condition the flow of water thus allowing the runner blades to independently, as determined by a control means, achieve optimal power output. 
     A preferred embodiment of the present invention further comprises a torque converter to precisely control a variable speed propeller and a fixed speed generator. Accordingly, the propeller of the present invention can be managed to run at the most efficient speed for any given operating conditions thereby generating optimum torque while permitting the power generated to be fed back into the power grid (typically, 50-60 Hz). The hydroelectric turbine generator control system employs a series of controllers and sensors to measure operating conditions and automatically fine-tune the overall system through a number of feedback loops. Some operating parameters controlled by the control system include: inlet volume and direction; variable wicket gate angles; variable runner blade propeller pitch; target elevation of the source of flow; the system flow rates; and other standard hydroelectric generator controls. 
     A power output control means according to the present invention is described via a flowchart in  FIG. 5 . A water level sensor  14  obtains a reading of water height in the reservoir. The water height is resultant of: (i) the amount of volumetric flow in the river; and (ii) the amount of volumetric flow that is allowed through the hydroelectric turbine  10 . The amount of volumetric flow that is allowed through the hydroelectric turbine  10  is the effect of wicket gate angle  16  and runner blade angle  18  on total volumetric water flow through the system. The water height reading from the water level sensor  14  and the target water height  20  are then passed to the wicket gate controller  22 . The wicket gate controller  22  then determines the appropriate adjustment in wicket gate angle  24  to obtain the target water height  20 . 
     Theoretical power output of a “run of the river” hydroelectric turbine can be calculated by the equation:
 
 P=g*Q*H*e  
 
Where P is power in kilowatts, g equals the gravitational constant which is approximately 9.81 meters per second squared, Q is the volumetric flow through the system in cubic meters per second, H is the pressure head in meters, and e is the efficiency rating of the hydroelectric turbine unit. Therefore, it is evident that as the position of the wicket gates and the runner blades change and have an effect on the flow through the hydroelectric turbine; and they also have a substantial effect on the power output of the generator.
 
     These effects are illustrated in  FIG. 5  by the effect of wicket gate angle on power output  26  and the effect of runner blade angle on power output  28 . A reading of the actual (not theoretical) power output from the generator  30  is then passed to the runner blade controller  32  which makes a decision for the appropriate change in runner blade angle to increase power output. The runner blade controller  32  then sets the runner blade angle  34  restarting the runner blade control loop. 
       FIG. 6  embodies the wicket gate controller  22  in greater detail. The wicket gate control loop represents a standard parallel Proportional-Integral-Derivative (“PID”) control loop. The loop begins by taking a set point, which in this case is the target water height  20  and subtracting the actual water height (recorded from the water level sensor  14 ) in the summation block  36  to find the system error  38 . The error  38  is then passed to each of the three elements of the PID control. The first element, the proportional term  40  is described by the equation:
 
 P   out   =K   p   e ( t )
 
Where P out  is the determined proportional change needed to correct the error  38  in the system, K p  is the proportional gain coefficient which is a scaling factor to regulate the effect of the proportional term on the system, and e(t) is the measured error as a function of time. The proportional term of the PID loop primarily accounts for the magnitude of the error in the system.
 
     The second element of the PID control loop is the integral element  42  which is described by the equation: 
               I   out     =       K   i     ⁢       ∫   0   l     ⁢       e   ⁡     (   τ   )       ⁢           ⁢     ⅆ   τ                 
Where I out  is the determined change necessary to correct the error with respect to the integral of the error in the system, K i  is the integral coefficient which is a scaling factor to regulate the effect of the integral term on the system, the integral term consists of the integration of the error from time zero to a prescribed time limit. The integral element of the PID control loop accounts for the amount of time that an error exists and therefore makes an appropriate adjustment.
 
     The final element of the PID portion of the wicket gate control is the derivative term  44  which is best described by the equation: 
               D   out     =       K   d     ⁢       ⅆ   e       ⅆ   t               
Where D out  is the determined correction for the error in the system based on the derivative of the error, K d  is the derivative coefficient which is a scaling factor to regulate the effect of derivative term on the system, and de/dt is the derivative of the error with respect to time. The derivative term of the PID control loop accounts for the rate at which the water height approaches the target water height to avoid overshooting or undershooting the target.
 
     The prescribed corrections from each of the three elements of the PID control portion of the wicket gate control are then summed up  46  to produce the total necessary correction to the system to obtain the target water height  20 . The determined correction in water height is then conditioned to apply to the wicket gate by multiplying by a scaling factor  48  and adding an offset factor  50  to bring the correction into an appropriate range for the wicket gate angles  52 . The adjustment in wicket gate angle is then made  52 . As a safety precaution, the wicket gate controller  22  then sends a signal to the runner blade controller  32  indicating the current wicket gate position  52 . In the case that the wicket gates are closed, the runner blade controller  32  will take no action. The wicket gate controller  22  then allows for a prescribed time increment  54  to pass before taking another water height reading, therefore beginning the process again. 
       FIG. 7  illustrates a detailed view of the runner blade control  32 . The runner blade control  32  first takes consideration to the wicket gate angle  52 ; this consideration only bears on the actions of the runner blade in the singular condition that the wicket gates are closed. This consideration is to prevent excessive runner blade searching. If the wicket gate angle  52  is greater than zero (not fully closed)  56  then the runner blade control loop  32  continues the control process. The controller then recognizes the settling timer  58  to prevent a condition of system-chasing where the control system does not allow the physical hydroelectric turbine system to stabilize, causing unwanted and incorrect changes. If the condition of timer completion is met  60  then the control loop is allowed to proceed. 
     The system then obtains the current power output reading from the generator  62  and compares it with the power output of the generator obtained on the previous iteration  64 . If the current power generated is less than the power generated on the previous iteration the loop proceeds  66 , otherwise, if the power generated has increased from the previous iteration, no change is made in the system and the loop is reinitialized. If the loop proceeds, the system then pays consideration to the action taken on the previous iteration. If the runner blades were opened a fixed increment on the previous iteration  68  then the runner blades are closed a fixed increment on the current iteration  70 . If the runner blades were closed a fixed increment on the previous iteration  72  then the runner blades are opened a fixed increment on the current iteration  74 . The settling timer is then reset  76  to allow for the physical system to stabilize due to the change in water height with respect to the change in runner blade angle  18 . The runner blade control loop  32  then begins again. 
     Although the invention has been described in considerable detail with respect to particular embodiments of Applicant&#39;s device, it will be apparent that the invention is capable of numerous modifications and variations, apparent to those skilled in the art, without departing from the spirit and scope of the invention.