Operation-control method for hydraulic machine

A method for controlling operations of hydraulic machines, in which two or more hydraulic machines are positioned in water conduits separated or branched upstream thereof with the branch water conduits downstream therefrom being joined together or maintained separate. Thus, these hydraulic machines are communicated with each other through the branch water conduits. In this method, the lower limit of a closing operational speed of guide vanes in one hydraulic machine is preferentially or overridingly controlled in the transient phase of operation, by detecting the closing operational speed of guide vanes of the other hydraulic machines. As a result, an abnormal condition in hydraulic pressure in upstream or downstream water conduits may be prevented, which condition would be caused in the event that the operational conditions of respective hydraulic machines are abruptly changed one after another.

BACKGROUND OF THE INVENTION 
This invention relates to two or more hydraulic machines which are 
connected with each other through branch water manifold which are branched 
upstream and/or downstream of the machines, and more particulary to an 
operation-control method for hydraulic machines which method controls or 
limits operational interaction of respective hydraulic machines and 
prevents an abnormal hydraulic-pressure condition in water conduits. 
Recently, there have been constructed many manifold type hydraulic power 
plants from viewpoint of economy of civil engineering works, in which a 
water conduit is branched into branch water conduits with each hydraulic 
machine being located in each branch conduit. In a power plant of the type 
described, respective hydraulic machines are mutually affected in terms of 
hydraulic pressure through branch conduits. According to the conventional 
method for controlling the operations of hydraulic machines, machines are 
independently controlled. Accordingly, the operation control for one 
hydraulic machine is independent of a change in an operational condition 
of the other machines, so that an optimum control is not conducted for 
prevention of influence of the pressure of one water conduit on the other 
or for prevention of a resulting transient change in the operational 
condition of the machine. To overcome this shortcoming, it may be one of 
solutions to feed a change in the operation condition of one hydraulic 
machine to the other to control the operational condition thereof. The 
Japanese Laid-open Patent Publication No. TOKUKAISHO 47-16831 teaches a 
method for controlling guide vane openings to prevent an instable 
operation of one hydraulic machine, which is caused due to a change in 
operational condition of the other. However, there has not been proposed a 
method for controlling the operational speed of guide vanes, which most 
affects a transient hydraulic-pressure change in water conduits. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an operation - control 
method for preferential or overriding control of operational speeds of 
guide vanes in hydraulic machines by exchanging informations of 
operational conditions between hydraulic machines which are communicated 
with each other through branch conduits, thereby preventing an abnormal 
hydraulic pressure condition in water conduits upstream and downstream 
thereof. 
According to the present invention, there is provided an operation control 
method for hydraulic machines, in which a change in operational condition 
of one hydraulic machine (for instance, a change in the form of a signal 
representing the fact that the displacement of a main distributing valve 
exceeds a given value) is fed to the other hydraulic machines for 
preferential or overriding control of the operational speed of guide vanes 
in the other hydraulic machines in its transient phase of operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, pump turbines 1, 2 are connected to branch water 
conduits 3, 4 upstream thereof, and the branch water conduits 3, 4 are 
joined together at a branch point 5 and then connected via water conduit 
6, a surge tank 7 and a water inlet conduit 8 to an upper reservoir 9. 
Furthermore, the pump turbines 1, 2 are connected downstream thereof to 
tailraces 10, 11, which are joined at a branch point 12 and connected to a 
lower reservoir 13. Alternatively, the tailraces 10, 11 may be connected 
to the lower reservoir 13, without being joined together. 
With the pump turbines of the aforesaid arrangement, the flow rate control 
of water for the turbine is conducted by means of guide vanes positioned 
in the outer peripheral portion of a pump turbine runner. 
Referring to FIG. 2, there is shown a control system for two pump turbines 
in a water conduit system shown in FIG. 1. The respective elements in a 
control device for the pump turbine 2, which are similar to those in a 
control device for the pump turbine 1 are designated like reference 
numerals with primes. Accordingly, description will be given only of a 
control device for the pump turbine 1 shown to the left in FIG. 2. 
The control device for the pump turbine 1 includes a first portion for 
controlling guide-vane openings in the pump turbine 1, i.e., one hydraulic 
machine, a second portion for detecting guide vane openings of the 
aforesaid one hydraulic machine to produce a signal for use in 
preferential or overriding control of the guide vane openings in the other 
hydraulic machine, and a third portion for receiving a signal of detected 
guide vane openings in the other hydraulic machine for preferential or 
overriding control of the guide vane openings in the aforesaid one 
hydraulic machine. 
The first portion of the control device includes: a first pilot valve 
bushing 18, a valve servo-motor 30, and a guide-vane servo-motor 56. The 
first pilot valve bushing 18 includes a cylinder 19, a plunger 16 provided 
within the cylinder 19, and a rod 14 integral with the plunger 16. 
Integrally secured to the rod 14 is an abutting plate 84, and the rod 14 
is preferentially or overridingly controlled through the medium of the 
abutting plate 84 by the third portion of the control device. A speed 
control operating portion (not shown) produces a speed control signal to 
achieve a desired power generating condition, and feeds the signal to the 
other end of the rod 14 for controlling a position of the plunger 16 in 
the cylinder 19. The cylinder 19 is provided with an oil outlet port 20, 
pressure oil inlet port 22, and a port 24 positioned between the ports 20, 
22. The port 24 is communicated through a pipe 26 with the valve 
servo-motor to be described hereinafter. 
The valve servo-motor 30 includes a cylinder 31 whose interior is divided 
into an upper chamber and a lower chamber, a main pressure distributing 
plunger 34 disposed within the lower chamber in the cylinder 31, and a 
valve servo-motor piston 32 which is integrally connected to the main 
pressure distributing plunger 34. The cylinder 31 is provided with a 
pressure oil inlet port 46 and a port 38, which are communicated with the 
upper chamber, respectively, with the pipe 26 being connected to the port 
38. The cylinder 31 is provided with ports 40, 50 communicated with its 
lower chamber, pressure oil inlet port 44, and oil outlet port 48. A rod 
36 is integrally coupled through a link 54 to the cylinder 19 in the first 
pilot valve bushing 18, and adapted to maintain a positional relationship 
between the cylinder 19 in the bushing 18 and the plunger 16 constant, 
after a transient change in operation. In other words, the link 54 serves 
as a feedback mechanism for feeding a power from the valve servo-motor 
piston 32 back to the first pilot valve bushing 18. 
The guide-vane servo-motor 56 is provided with a cylinder 57, and a 
servo-motor piston 58 fitted in the cylinder 57 and integral with a 
servo-motor piston rod 60. The servo-motor piston rod 60 pierces through 
an end wall of the cylinder 57 to be mechanically coupled to guide vanes 
(not shown) in pump turbine 1, thereby opening and closing the guide 
vanes. The opposite ends of the cylinder 57 are communicated via pipes 42, 
52 with ports 40, 50 in the valve servo-motor 30, respectively. 
The second portion in the control device includes a second pilot valve 
bushing 62 and a link mechanisms 74, 92, 90. The second pilot valve 
bushing 62 is provided with a cylinder 63, and a plunger 64 disposed in 
the cylinder 63, while the plunger 64 has a rod 36 for common use with the 
valve servo-motor piston 32 in the valve servo-motor 30. The cylinder 63 
is provided with a pressure oil inlet port 68, an oil outlet port 70 and a 
port 66, while the oil outlet port 70 is communicated with a variable 
throttle 76, and the port 66 is communicated through a pipe 72 with the 
third portion of the control device for the pump turbine 2. The cylinder 
63 is mechanically coupled through the link mechanisms 74, 92, 90 to the 
third portion of the control device for the pump turbine 2, thereby 
maintaining the consistent positional relationship of the third portion of 
the control device for the pump turbine 2. In other words, the link 
mechanisms 74, 92, 90 constitute feedback mechanisms for feeding a power 
from a stopper piston 82' for the pump turbine 2 back to the second pilot 
valve bushing 62 for the pump turbine 1. 
The third portion of the control device includes a stopper cylinder 80, and 
a stopper piston 82 disposed within the stopper cylinder. The stopper 
cylinder 80 is provided with a pressure oil inlet port 86 and a port 87, 
while the port 87 is communicated through a pipe 72' with the second 
portion in the control device for the pump turbine 2. As shown in FIG. 3, 
the stopper piston 82 has a rod 88 which extends through a hole provided 
in an abutting plate 84 so as to be coupled through a link mechanism to 
the second portion in the control device for the pump turbine 2. 
While description has been had for the control device for the pump turbine 
1, it should be understood that the control device for the pump turbine 2 
is of the same construction as that for the pump turbine 1. It should be 
further noted that the respective pressure oil inlet ports are connected 
to a common hydraulic pressure source. 
Description will now be given of the operations of the control devices for 
the pump turbines 1 and 2 as shown in FIGS. 2 and 3. Assume that a load on 
a pump turbine is shut off. Then, a speed control signal is delivered from 
a speed control operating portion for the pump turbine 1, so that the rod 
14 in the first pilot valve bushing 18, and hence plunger 16 is moved 
downwards. As a result, operating oil which is present in the upper 
chamber in the valve servo-motor 30 but below the valve servo-motor piston 
32 is discharged through the port 38, pipe 26, and port 24 and oil outlet 
port 20 in the first pilot valve bushing 18. Accordingly, the valve 
servo-motor piston 32 is displaced downwards due to the pressure of oil 
fed through the pressure oil inlet port 46, whereby the plunger for the 
main pressure distributing valve is lowered. A port 50 in the valve 
servo-motor 30 is communicated with a pressure oil inlet port 44, while a 
port 40 is communicated with an oil outlet port 48. Thus, pressure oil is 
delivered through a pipe 52 to the left side of the servo-motor piston 58 
in the guide vane servo-motor 56, while operating oil on the right side of 
the servo-motor piston 58 is discharged through a pipe 42 outside. 
Accordingly, the servo-motor piston 58 is displaced to the right, thereby 
closing the guide vanes in the pump turbine 1. Meanswhile, the plunger 64 
coupled through the rod 36 to the valve servo-motor piston 32 is moved 
downwards, along with the valve servo-motor piston, thereby bringing the 
pressure oil inlet port 68 and port 66 into mutual communication, thereby 
delivering pressure oil through the pipe 72 to the stopper cylinder 80' 
for the pump turbine 2. As a result, the stopper piston 82' for the pump 
turbine 2 is moved upwards. 
At this time, the displacement of the stopper piston 82' has been fed back 
to the link mechanisms 74, 92, 90, so that the positional relationship may 
be maintained constant. Meanwhile, the aforesaid displacement of the 
stopper piston 82' should be suitably determined by conditions such as 
water conduit condition, performance of pump turbine and the like. 
In this respect, a speed control signal from a speed control operating 
portion for the pump turbine 2, as well, is transmitted to the rod 14' in 
a like manner. As shown in FIG. 3, the movement of the rod 14', i.e., the 
movement of the abutting plate 84' is limited by a vertical position of 
the stopper piston 82'. More particularly, in case a load on the pump 
turbine 1 is shut off, if an upward displacement of the stopper piston 82' 
is small, then a closing signal for the guide vanes of the pump turbine 2 
is limited. On the other hand, if an upward displacement of the stopper 
piston 82' is larger than a given value, then a closing signal for the 
guide vanes in the pump turbine 2 is shut off, so that the rod 14' 
receives an opening signal so as to move upwards only. In this case, the 
plunger 16' brings the port 24' and pressure oil inlet port 22' in a 
shut-off condition, a partial communicating or complete communicating 
condition with each other in response to the displacement of the rod 14', 
so that the displacement of the rod 14' may be proportional to the 
operational speed to open and close the guide vanes in the pump turbine 2. 
In other words, the operational speed of guide vanes in the pump turbine 2 
is preferentially or overridingly controlled due to the displacement of 
the stopper piston 82 in a transient phase of the operation. 
The preferential or overriding control of the operational speed of guide 
vanes signifies as follows: for instance, when a load-shut-off signal is 
fed to the pump turbine 1 and the guide vanes in the pump turbine 1 are 
rapidly closed at a speed of 10% sec., then the guide vanes in the pump 
turbine 2 are so controlled as to be closed at an operational speed no 
higher than 2%/sec. On the other hand, when the guide vanes in the pump 
turbine 1 are closed at an operational speed lower than 2%/sec., then the 
guide vanes in the pump turbine 2 are controlled so as to be closed at an 
operational speed no higher than 10%/sec. Stated differently, the 
respective control devices impose limitations on the closing operational 
speeds of guide vanes in pump turbines, in a manner that when a closing 
operational speed of guide vanes in one pump turbine is unusually high, 
(for instance, the stopper piston 82' is suddenly moved upwards, and thus 
the abutting plate 84' is lifted), the guide vanes in another pump turbine 
are opened. However, the respective control devices will not control so as 
to positively close the guide vanes in a counterpart pump turbine. 
Possible measures for directly or indirectly detecting a change in an 
operational condition of a counterpart hydraulic machine would be such as 
rotational speed N, a change in rotational speed relative to time, dN/dt, 
guide vane opening Y, a change in the guide vane opening relative to time, 
dY/dt, and a combination thereof. The feature of the present invention 
lies in the fact that the aforesaid signal from the counterpart or other 
hydraulic machine is detected, and then an extent of the operational speed 
of guide vanes in one hydraulic machine to be preferentially or 
overridingly controlled is determined in the light of water conduit 
condition and characteristics of hydraulic machines, so that the 
operational speed of the guide vanes being opened in the aforesaid one 
hydraulic machine may be preferentially or overridingly controlled. Many 
modifications and alterations may be inferred by those skilled in the art 
according to the aforesaid feature of the present invention. 
For instance, the amount of liquid in a piping, which is dependent on the 
operational speed of a guide vane servo-motor in other hydraulic machine 
is detected, followed by a suitable computation, whereby the amount of 
liquid within a piping which is dependent on the operational speed of the 
guide vane servo-motor in one hydraulic machine is controlled in a 
transient phase of the operation. 
According to the present invention, a mutually cooperative operation 
control in a branched water conduit type power plant may be effected. As a 
result, an abnormal hydraulic pressure condition in water conduits 
upstream or downstream of the hydraulic machines, which would be caused or 
affected by the operational condition of a counterpart hydraulic machine, 
may be prevented.