JPS6038560B2 - Hydroelectric power plant output control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an output control device for a power plant whose effective head fluctuates, such as a pumped storage power plant or a power plant with a small amount of water storage.

Most modern hydroelectric power plants are pumped storage type, which uses surplus electricity to pump water from the lower dam to the upper dam, and then uses the water from the upper dam to generate electricity during peak loads.

Such pumped storage power plants tend to have large capacity and high head for economic reasons, and their functional systems are shown in FIGS. 1 and 2. Figure 1 shows the functions of the generator, and Figure 2 shows the functions when pumping water. However, in terms of efficiency, it is desirable to operate the main engine of a hydroelectric power plant at the rated output based on the standard head, but in pumped storage power plants, the water level in the upper dam falls and the water level in the lower dam rises during power generation operation. , the effective head will constantly change during operation.

Furthermore, when it comes to large-capacity aircraft, AFC operation is required from the system operation perspective.
Any output is required, such as ALR operation. Therefore, the rated output operation is not necessarily based on the standard head. Therefore, it is inevitable that the operation will be performed with low efficiency. However, in low-efficiency operation, the shape of the forced vortex in the draft tube becomes unstable, especially due to the swirling component of the water coming out of the water turbine runner, causing intense noise and vibrations not only in the turbine itself but also in the entire power plant. or These will be explained in detail below.

In FIG. 3 showing the cross section of the draft tube, now,
The water turbine has an output Pkw (=9.
It is assumed that spots x, Q, H) are appearing. At this time, taking the airfoil shape of the design cross section shown in the figure as an example, the state of the flow at the runner vane exit section will be considered with respect to the velocity triangle shown in FIG. 4. Fourth
In the figure, U is the circumferential speed of the runner and the diameter D2 of that part
The size is determined from the rotational speed N.

Note that the direction indicates the direction of circumferential speed. W represents the relative velocity of the water stream to the rotating runner outlet section, its direction is along the vane outlet section, and its magnitude is determined from the meridian velocity Vm. When considered in FIG. 3, the meridian velocity Vm indicates the flow velocity assuming that the water flow exiting the guide vane does not have a swirling component around the main axis. That is, the meridian velocity Vm is the flow rate Q
is divided by the area A of that part. V then represents the actual velocity of the water at the runner outlet. Since the speed of the moving runner is U and the relative speed of the water to this runner is W, the absolute speed of the water (velocity relative to the stationary part) V is U,
It is represented as the diagonal of a parallelogram formed by W.
Therefore, the flow rate Q can be calculated without changing the rotational speed N, head date, etc.
If Q' and Q'' are increased, the corresponding relative velocities and absolute velocities of the water flow exiting the runner are W', V' and W
″, V″.

Here, the circumferential component of the absolute velocity changes to VU, Vu', VU''. This is the swirling component of the flow (component of the circumferential velocity). When , it has a swirling component in the opposite direction to the runner.In other words, as long as a fixed-blade water turbine operates with a constant rotational speed N and constant head, the swirling component of the flow exiting the runner disappears only at a certain flow rate Qw. , a general flow rate (load) always has a swirling component of either forward or reverse.Next, we will consider the mechanism of swirling flow generation due to fluctuations in head.In this case, the operating state of the water turbine is the rotational speed N,
Assume that there is no swirling flow at the runner outlet on the head day, when the flow rate is Q, and the guide vane function at that time is a. Now, the head date has changed to H', but assuming that the rotational speed N and the guide vane opening have not changed, the water turbine flow rate Q has changed from Q:C Matsuyu to Q':c false H'. change.

Then, since the flow rate flowing into the runner vane changes, the speed W of the water flow at the runner outlet also changes. In other words, the fourth
As is clear from the figure, there is no swirling component when the flow rate is Q, so naturally there is a swirling component when the flow rate is Q' (sheep Q). In this case, if the guide vane function 8 is changed so that the flow rate becomes Q, a flow without a swirling portion can be obtained at that flow rate Q. Naturally, if H >H', then minus 8', and H minus H'
Then, 0>hi'. Here, the existence of swirling flow significantly reduces the efficiency of the turbine, and the swirling flow at the outlet of the stretch runner disappears at a specific flow rate for each arbitrary head.
On the inlet side of the runner, the runner vane and the water always collide with each other, and collision-free inflow is possible only at a certain head. This state is the most efficient operation of the water turbine.
Next, the swirling flow in the draft tube and the vibration of the water turbine will be explained.

The swirling flow that leaves the runner eventually becomes a free vortex. Here, the free vortex is one that moves at a constant rate (R.V.ri), where R is the distance from the center of the draft tube and VU is the circumferential velocity component. When the circumferential velocity component in the radial direction increases beyond the gradient limit, the portion within a distance R is no longer a free vortex, and the whole rotates as one (forced vortex). In general, the angular velocity of this forced vortex is higher in the upper part (the part closer to the runner), so it is not uncommon for the pressure to be lower and a reverse flow to occur from the bottom to the top. If the suction height is large and the pressure level in this part is low, water vapor will be generated and voids will easily occur. The behavior (shape) of these forced vortices is not stable as shown in Figure 3, and they are constantly moving around, repeatedly creating and disappearing voids, which can cause intense noise, and can cause damage not only to the water turbine but also to the entire power plant. vibrate or cause power fluctuations. Therefore, the magnitude of vibrational energy is generally proportional to the magnitude of swirling energy.

Therefore, as can be seen from FIG. 4, as the load becomes overloaded or light, the swirling component VU of the flow becomes larger, and the vibration noise becomes more intense. However, when the flow rate is below a certain level, even if the swirling component increases, the degree of the swirling component gradually softens due to the decrease in energy due to the decrease in flow rate. All of the above can shorten the lifespan of the mechanical parts, cause problems with the main engine's shaft shaking, and cause structural problems and power fluctuations for the entire Yomo house.

Therefore, especially in low-head, low-load operation, care must be taken in operation and maintenance to operate within a range with as little vibration as possible depending on the head at that time. Conventionally, in order to eliminate the above-mentioned disadvantages, an acceleration-detecting vibration sensor was attached to the blades of a water turbine, and the detection signal was guided to the stationary side via a slip ring, and an alarm was issued when the vibration detection output exceeded a predetermined value. It has also been proposed to adjust the guide vane function according to the vibration detection output.

However, with this method, vibrations are directly detected by a vibration sensor attached to the moving part, which makes handling and maintenance of the vibration sensor, as well as the handling and maintenance of the parts for transmitting signals from the moving part to the stationary part, difficult. Moreover, there is a problem in terms of reliability. As mentioned above, it is necessary to avoid continuing the operation of the generator in an output band with large vibrations as much as possible.

Therefore, an object of the present invention is to provide an output control device for a hydroelectric power plant, which allows the generator to quickly exit the operation in the output band when the generator is operated in the output band with large vibrations. There is a particular thing.

In order to achieve this objective, the present invention calculates a no-operation zone corresponding to the vibration zone based on the effective head, and when the generator is operated in this no-operation zone, the no-operation zone is entered. Escape from the prohibited driving zone based on the previous output increase/decrease command.

In other words, when the output increase/decrease command before entering the no-operation zone is an output increase command, the guide vane opening is controlled in the opening direction so that the generator output exceeds the upper limit of the no-operation zone, and vice versa. When the previous output increase/decrease command is an output decrease command, the guide vane is controlled in the closing direction so that the generator output becomes less than the lower limit of the prohibited operation zone. An embodiment of the present invention will be described below.

Figure 5 shows the relationship between the guide vane function and the generator output P in a water turbine, using the head day that can vary between the minimum head HHmin and the maximum head Hmax as a parameter, and within the operating range. This indicates that there is a vibration zone B and non-vibration zones A and C. Vibration zone B is an area where vibrations are particularly intense, and this is determined by the characteristics of the water turbine, and this area is a no-operation zone, while non-vibration zones A and C are operation-permissible zones. As can be seen from the figure, the vibration zone (output width or guide vane width) changes depending on the head date. For example, if the head is H
The vibration zone when the head is max is indicated by the guide vane relation width (opening 8, opening 2), and the vibration zone when the head is Hmin is indicated by the guide vane relation width (03<minus a4). It will be done. FIG. 6 is a diagram showing the control sequence of the guide vane control means of the output control device of the present invention, K, is an IJ ray for increasing output, K3 is an IJ ray for decreasing output, K3
is an IJ relay for storing output reduction commands, K4 is an IJ relay for storing output reduction commands, K5 is a relay for operating the output increase in the driving permissible zone, K6 is the relay for operating the output increasing in the driving prohibited zone, and K7 is the relay for controlling the output increase in the driving prohibited zone. IJ Ray, K for output reduction operation in permissible operation band
8 is an IJ relay for output reduction operation in the prohibited driving zone.

In addition, the output increase command and output decrease command can be performed manually or by A.
It is applied to contacts PB and PB2 from FC, ALR, etc., and P
X is a driving prohibition zone detection means having contacts KP, ~KP4;
M is a motor for the water turbine output setting device. In such a configuration, when an output increase command is input to the generator, contact P
B, is turned on and relay K, is energized.

Then, contacts K and A of this IJ relay K are turned on, so that relay K3 operates and is self-held via contact K3A. If the generator output P is now in the area C of FIG. By turning on B, relay K5
is energized. Thus, when relay contact &A is turned on, motor M is driven and the guide vane is controlled in the opening direction. Then, when the generator output P increases as the guide vane opening degree 8 increases and enters from the region C to the region B, the contact KP2 of the prohibited operation zone detection means PX turns on.

Then, since relay K3 is self-held, contact K3C is on, and relay K is energized. In other words, in this case, even if the contact PBI is turned off, that is, the output increase command is no longer issued, the motor M
is controlled in an increasing direction. In addition, if the output increase command stops after leaving the operation prohibition zone B and then enters the operation prohibition zone again due to a change in head, the relay K6 is activated and the motor M is controlled to increase so that the operation always avoids the operation prohibition zone. . On the other hand, when an output reduction command is input to the generator, the zero point P
& is turned on, relay K2 is energized, and contact K2A of this relay K2 is turned on, so that relay K4 is operated.
Self-retained via contact KA.

When the generator output P is in the area A of FIG. 5, the prohibited operation zone detection means PX is inactive, so the relay heating point K2
By turning on B, relay K7 is energized. Thus, relay contact K7 is energized. Thus, relay contact K? When A is turned on, motor M is controlled to decrease. When the generator output P enters the region B from the region A, the contact KP4 of the prohibited operation zone detection means PX is turned on.

On the other hand, since relay K is energized and contact K4C is on, relay K8 is energized. That is, in this case, even if the contact PB is turned off, that is, the output reduction command is no longer issued, the motor M is controlled to decrease until the generator output P reaches the region C, that is, until it becomes less than the lower limit of the prohibited operation zone.
Further, when the output reduction command is stopped and the operation prohibition zone is entered again due to a change in the head, the relay equalization is operated and the motor M is controlled to decrease so that the operation always avoids the operation prohibition zone.
In the case of IJ relay K3 for storing the output increase command, the reset of K3 and & is operated via relay K2 by the output decrease command, and the reset of K3 and & is the contact K4 of relay K.
In the case of the relay K4 for storing the output decrease command, the contact K3B of the relay K3 operated via the relay K by the output increase command is opened.

Although not shown in the diagram, if the make contact of the main engine (water turbine, generator) operating relay is inserted in series into the excitation circuit of each relay KC, K, relay K3 will move when the main engine is stopped.
, K4 can be reset. Next, FIG. 7 shows a control system of the RI-RY which controls the contacts KP, -KP4 of the prohibited driving zone detecting means PX and will be described.

PT is a potentiometer that outputs a negative voltage proportional to the upper dam water level in conjunction with a float (not shown) for detecting the upper adjustment dam water level, and PL is linked to a float (not shown) for detecting the lower adjustment dam water level. This is a potentiometer that outputs a positive voltage proportional to the lower dam water level. This type of water level detection device can also be used as one originally provided for various display devices, control devices, etc. of power plants. Further, 1 is a summing amplifier consisting of input resistors R and R2, an operational amplifier OP, and a feedback resistor R3, and its output VI is proportional to the effective head corresponding to the difference between the water level of the upper dam and the water level of the lower dam. Indicates voltage. Furthermore, 2 and 3 are function generators, respectively, which have input/output characteristics corresponding to the lower and upper limits of the no-operation zone corresponding to the vibration zone shown in FIG. That is, assume that the head is now Ho. When the function generator 2 receives a voltage V proportional to the head, the output voltage V2 becomes a voltage proportional to the lower limit of the operation prohibition band, the guide vane function 85, with respect to the head ratio.
The output voltage V3 is a voltage proportional to the guide vane at the upper limit 86 of the no-operation zone with respect to the head ratio. Potentiometer PT3 moves to the guide vane and operates.
It outputs a signal V4 proportional to the scale of the scale.

This signal V4 is input to the negative input terminals of comparators 4 and 5, respectively, and compared with signals V2 and V3. Therefore, when V2-V4<0, that is, the guide vane is open above the lower limit of the prohibited operation zone 05, the comparator 4 outputs a logic signal "
1", and the comparator 5 outputs a logic signal "rl" when V3-V4>0, that is, when the guide vane is not opened to the upper limit 86 of the no-operation zone. NAND circuit 6 is comparator 4
When the outputs of both 1 and 5 become 1, a logic 0 is output, thereby energizing relay RY. Thus,
The circuit portion from the function generators 2 and 3 to the relay RY constitutes a no-operation zone calculation circuit that calculates a no-operation zone determined according to the effective head.

As described above, according to the present invention, by providing a no-operation zone detection means for calculating the no-operation zone that varies depending on the effective head in a pumped storage power plant, the output zone where large vibrations occur in the low efficiency region is automatically detected. Since avoidance operation is possible, there is no need for an operator to constantly monitor head and output, and a safe and reliable output control device can be provided, especially in an unmanned power plant. In particular, the device of the present invention has the practical advantage of being easy to transmit signals and maintenance, and improving reliability, unlike a device in which a vibration sensor is attached to a movable part of a water turbine.

Note that it is applicable not only to pumped storage power plants but also to power plants where the head fluctuates. Also, since there is a correlation between the water turbine guide vane opening, the water turbine output, the generator output, and even the generator output current, the generator output that has a correlation therewith instead of the guide vane opening in the above embodiment Other physical quantities such as

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams showing the general functions of a pumped storage power plant, Figures 3 and 4 are explanatory diagrams illustrating examples of its operation, and Figure 5 is a guide vane relationship and power generation. Characteristic diagrams showing the relationship between machine outputs, and FIGS. 6 and 7 are circuit diagrams showing examples of circuits to which the present invention is applied. K, ~K8... Relay, PX... Driving prohibited zone detection means, M, . ．． Motor, PT, ~PT3... Potentiometer, 1... Summing amplifier, 2, 3... Function generator, 4
, 5... Comparator, 6... NAND circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. An output control device for a hydroelectric power plant that increases or decreases the output of the generator by controlling the opening and closing of a guide vane based on the effective head at that time when a command to increase or decrease the output of the generator is issued. An operation prohibition zone detection means for determining an operation prohibition zone of the generator output, and when the generator output enters the operation prohibition zone, an output increase/decrease command before entering the operation prohibition zone is an output increase command; so that the generator output exceeds the upper limit of the operation prohibition zone, and when the output increase/decrease command before entering the operation prohibition zone is an output decrease command, the generator output becomes less than the lower limit of the operation prohibition zone. and guide vane control means for controlling opening and closing of the guide vanes, respectively.