Multiple fixed hydraulic geometry turbine control system

A plurality of selected fixed hydraulic geometry turbine generators are programmed for operation at rated efficiencies by interrupting flow to the turbines under control of a programmable power controller receiving water level, flow and power monitoring inputs. The turbines selected are of discreet sizes simultaneously operative only under maximum flow conditions of the hydropower source, and otherwise operated in accordance with an optimum duty schedule to match varying flow conditions.

BACKGROUND OF THE INVENTION 
This invention relates to multiple turbine-generator control systems for 
hydroelectric power installations. 
Power control systems for hydroelectric turbine driven generators generally 
involve the internal regulation of turbine operation. Operation of two or 
more hydraulic turbines are, for example, regulated through inflow valves 
or gates for speed and power control purposes to match load demand 
according to U.S. Pat. No. 4,245,163 to Philippe. According to U.S. Pat. 
No. 3,848,171 to Speth, turbine blades are adjusted automatically under 
variable flow conditions to obtain maximum efficiency. A speed controlling 
valve of gate is utilized for turbine control in a feedback mode of 
operation in a hydroelectric power environment according to U.S. Pat. No. 
3,556,668 to Murbukh. 
Load sharing, multiple turbine driven generators are disclosed in U.S. Pat. 
Nos. 4,164,661, 4,195,231, 3,651,331 and 3,703,663. None of the turbines 
disclosed in the foregoing patents are associated with the variable flow, 
hydropower sources since the control systems are usually designed to meet 
load demand. The use of a control system to match turbine performance with 
load for maximum efficiency is taught in U.S. Pat. No. 3,300,647 to Gogia. 
Despite the availability of various prior art multiple turbine-generator 
power generating systems as referred to herein, there are certain 
drawbacks in such systems for which there is a renewed interest for small 
scale hydroelectric power generating plants, below 5 megawatts, for 
example. The turbine-generator adjustments necessary to meet varying water 
flow rates are costly and less than satisfactory for such small scale 
hydropower plants because of reduced turbine efficiency. The usual 
hydraulic turbine, for example, having provisions for adjusting flow to 
handle flow decreased to a lower limit of 30% of rated flow, will have a 
reduced efficiency of 80% to 85% of its design efficiency. The ability to 
handle varying flow is necessary because a 100% continuous flow condition 
is rarely found in hydropower sites. As to fixed hydraulic geometry 
turbines that are less costly and capable of being mass produced, use 
thereof is not now deemed to be a viable alternative because of a drop in 
rated efficiency to 80% of rated value at 80% of rated flow and toward 
zero efficiency at 40% of rated flow. 
It is therefore an important object of the present invention to provide a 
more cost effective and efficient hydroelectric power plant, especially 
useful for small hydropower sites, utilizing a plurality of less costly 
fixed geometry hydraulic turbines operating with maximum efficiency 
despite varying flow conditions. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a plurality of fixed hydraulic 
geometry turbines of different discreet sizes with associated generators 
of the induction type are selected for a given hydropower site to provide 
maximum energy recovery under variable flow conditions. The turbines have 
no adjustments or variable inflow controls, but are instead enabled or 
disabled in accordance with an optimum on-off duty schedule programmed 
into a power controller to match varying water flow conditions. Each 
turbine when in operation therefore operates at its rated efficiency to 
provide maximum operating efficiency for the power plant with output power 
that varies depending on the water flow available from the hydropower 
source. The power controller operates through control gates to interrupt 
flow to selected turbines and open circuit breakers for associated 
generators in accordance with input data from water level, flow and power 
monitoring sensors and a duty scheduling program. Data logging and remote 
data communicating functions may also be performed for data display and 
program updating purposes. Thus, operation of each turbine is so limited 
that it operates only at its rated efficiency in a programmed schedule 
providing an optimum selection necessary to match varying water flow 
conditions. 
These together with other objects and advantages which will become 
subsequently apparent reside in the details of construction and operation 
as more fully hereinafter described and claimed, reference being had to 
the accompanying drawings forming a part thereof, wherein like numerals 
refer to like parts throughout.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to the drawings in detail, FIG. 1 illustrates a hydroelectric 
power generating installation generally referred to by reference numeral 
10 from which generated electrical energy is supplied through a power 
output bus 12 to a utility power grid. The installation 10 includes a 
plurality of fixed hydraulic geometry turbines 14 respectively driving 
induction generators 16 supplying the electrical energy to the common 
output bus 12 without any load or voltage controls. Each of the turbines 
14 and associated generators 16 are of a mass produced type of proven 
design and cost-effectiveness, with fixed hydraulic orifices and no means 
to control the amount of water flow therethrough. Such turbines operate at 
a rated efficiency when an optimum flow of water is conducted therethrough 
dependent on the size of the turbine. Thus, such turbines cannot 
individually handle variable flow conditions since the efficiency thereof 
will drop for example from 100% rated value under 100% optimum flow toward 
zero efficiency below 40% optimum flow. 
Energy is derived from a hydropower source 18, such as a body of water at 
an elevation above the turbines from which a variable flow is available. 
Flow valves or gates 20 control water flow at optimum flow rates from 
source 18 parallel to the respective turbines 14 during operation as 
shown. Operation of one or more of the turbines 14 may be interrupted by 
cut-off of flow thereto from source 18 through the flow controls 20 under 
command of turbine selection logic 22. The available flow from source 18 
is sensed by flow sensors 24 from which input data is fed to the logic 22 
which also receives input data from turbine efficiency detector component 
26. Thus, whenever the flow from source 18 is decreased significantly 
below a maximum available value adapted to operate all of the turbines 14 
in parallel at the rated efficiences thereof, an output signal from the 
logic 22 is applied to the flow controls 24 to interrupt flow to selected 
ones of the turbines. Turbine selection is determined by the input data 
from the turbine efficiency detection component 26 and the programming of 
the logic 22. Outputs of the logic disable, through generator controls 28, 
those generators 16 drivingly connected to the inoperative turbines, and 
provide information to a data log 30. The output power is also monitored 
by power monitor 32 for providing protective shut-down control under 
conditions such as overload and power loss that would cause equipment 
damage. 
By way of example, the table of FIG. 2 shows three turbines simultaneously 
operating at their rated efficiencies under 100% maximum flow conditions 
of the hydropower source. Each of the three turbines is of a different 
size, respectively, operating at rated efficiency when conducting 20%, 30% 
and 50% of the maximum water flow. At 70% flow, turbine Nos. 1 and 3 are 
programmed to operate, while turbines Nos. 2 and 3 are programmed to 
operate at 80% flow and all units at 100% flow. 
FIG. 3 illustrates the control system in association with one of the 
turbine-generator sets, generally referred to by reference numeral 34. 
Water is conducted to the turbine-generator set 34 through a conduit 36 at 
an optimum flow rate for turbine operation at rated efficiency. The water 
is derived from the hydropower source 18 in the form of a body of water 38 
contained by a dam 40. Flow through conduit 36 is interrupted by closing 
of a flow control in the form of gate 42 and is monitored by a flow meter 
type of sensor 44. Opening and closing of the gate is effected through a 
gate control 46 by an output from power controller 48 forming part of the 
turbine selection logic hereinbefore described with respect to FIG. 1. 
Signal inputs to the power controller are supplied from water level 
sensors 50 and 52, gate control sensors 53, monitors 54 connected to the 
generator controls 28 and output bus 12, generator speed sensor 56 and 
vibration-temperature sensor 58. Programming of the power controller is 
effected by a central processing unit (CPU) 60 to which a mathematical 
model memory section 62 is connected. Input data to the CPU 60 is received 
from monitors 54 and from a remote source through modems 64 and 66 
interconnected by telephone lines 68. The remote source includes a 
terminal 70 to which an input keyboard 72 is connected. Readout of data 
logged by the control system may be effected through a local display 74 
connected to an output port of the power controller 48 and remote readout 
components 76 connected to remote terminal 70. 
FIG. 4 illustrates the control system in greater detail showing the common 
output bus 12 coupled to a utility tie-in line through switch 78. The 
outputs of the generators 16 are connected through separate circuit 
breakers 80 to the output bus 12 under control of circuit breaker controls 
82 forming part of the generator controls aforementioned. The power 
monitors include a separate overload relay 84 inductively coupled to the 
power output lines 86 of each of the generators, a watt-hr meter 88 
connected to each of the generators, a voltage sensor 92 inductively 
coupled to the output bus and a frequency sensor 94 connected to the 
output bus. Power for operation of the programmable controller 48 is 
supplied from the output bus through switch 96, transformer 98 and control 
panel 100. 
Digital inputs to the controller 48 are obtained from the power monitors 
including frequency sensor 94, voltage sensor 92, watt-hour meter 88, 
speed sensors 56 and flow meter 44. Switch contact closing inputs for the 
controller are obtained from the vibration-temperature and circuit breaker 
sensors associated with each of the generators. Switch controlling outputs 
to the flow controls 46 and circuit breakers are obtained from the output 
ports of controller 48 as shown, while communication outputs are also 
provided for the displays 74 and 76 and modem 64. 
FIG. 5 illustrates some of the data flow associated with the system 
hereinbefore described. In response to a start command at 102, water flow 
conditions are sensed at 104 to determine the available flow from the 
hydropower source. Depending on such flow conditions, none or any 
combination of one or more logic functions 106, 108 and 110 receive flow 
gate opening commands to initiate operation of the fixed geometry 
turbines. In response to a turbine reaching a base speed, a command is 
generated at 112 to provide a circuit breaker closing input to 114 in 
order to initiate the supply of electrical energy from a turbine-generator 
set operating at rated efficiency. In the event there is a significant 
deviation in flow to the turbine or drop in its efficiency, such 
conditions are sensed to produce commands at 116, 118 or 120 thereby 
providing a stop sequence command at 122 for one of the turbine-generator 
sets. 
From the foregoing description it will be apparent that the present 
invention involves the selection of a plurality of fixed hydraulic 
geometry turbines of discreet sizes for any given hydroelectric 
installation. Such selection is based on analysis of the flow duration 
curves generated for all available fixed geometry turbines to provide the 
optimum energy recovery, unit size combination and programmed on-off duty 
cycle schedule. Based on such data stored and updated in the memory 62, 
the power controller 48 is programmed to optimize the number and size of 
turbines placed on duty for any given flow condition. 
The foregoing is considered as illustrative only of the principles of the 
invention. Further, since numerous modifications and changes will readily 
occur to those skilled in the art, it is not desired to limit the 
invention to the exact construction and operation shown and described, and 
accordingly, all suitable modifications and equivalents may be resorted 
to, falling within the scope of the invention.