JPH01208572A - Method for operating variable speed hydraulic machine - Google Patents

Abstract

PURPOSE:To improve the following property with respect to an output changing command and carry out a stable operation by detecting the rate of change, etc., of an output target value at the time of receiving an output changing command and correctingly controlling the rotating speed of a generator, etc., with a value in which the detected value is multiplied by a negative gain. CONSTITUTION:The shaft output Pt of a water turbine 12 rotated by water introduced from a hydraulic steel pipe 11 is converted into an electric output PG by means of a variable speed generator 13. On the other hand, an output target value P* is compared with an actual generator output PG by an output control device 15 to calculate the target opening value a* of a guide vane 17. A guide-vane opening (a) is set by means of a guide vane control device 16. Also, a rotating speed target value N* in line with the output target value P* is outputted from an optimum rotating speed setting device 19 to a rotating speed controller 18. In this case, the rate of change or differential value of the output target value P* is calculated by a rotating speed correction control device 20. The calculated speed correction value Nc is added to the rotating speed target value N*.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for controlling the operation of a variable speed hydraulic machine such as a water turbine having guide vanes or a pump water turbine during power generation.

(Prior art) In hydraulic machines such as water turbines or pump water turbines installed in hydroelectric power plants, the shaft output during operation of the water turbine is determined by the opening degree of the guide vane when the head is constant. When changing the output in hydroelectric power generation equipment equipped with a generator or generator-motor, it is customary to control the opening and closing of the guide vanes so that the guide vane opening degree corresponds to the output target value of the generator or generator-motor. be.

FIG. 4 shows a schematic configuration of a hydroelectric power generation facility to which the present invention is applied, in which the energy of water led from an upper reservoir 10 through a penstock 11 is converted into mechanical energy by a water wheel or a pump water wheel 12, and then A linear induction generator or a wound induction generator motor 13 is driven, and the generated energy is supplied as electric power to a power system (not shown). After energy has been absorbed by the water wheel or pump water wheel 12, the water is drained to the lower pond 14 as waste water.

The water wheel or pump water wheel 12 is provided with a guide vane (not shown), and by changing the opening degree of the guide vane, the flow rate Q of water supplied to the water wheel or pump water wheel 12 via the penstock 11 is adjusted.

FIG. 5 shows an example of a conventionally used control device, in which the output target value P rate and the generator output PC are input to the output control device 15, which outputs the guide vane opening target value a*. . The guide vane control device W16 sets the guide vane opening degree a in accordance with the guide vane opening degree target value a*.

The opening degree of the guide vane 17 is controlled by this guide vane opening degree a, which adjusts the flow rate flowing into the water turbine or pump turbine 12, adjusts its shaft output pt, and changes the output PG of the generator or generator motor 13. .

On the other hand, the generator or generator motor 13 is connected to a rotation speed control device 18 such as a cycloconverter that controls the rotation speed, and the rotation speed of the generator or generator motor 13 is set by an optimum rotation speed setting device 19 to output the rotation speed. The rotational speed is controlled to a rotational speed target value N* according to the target value P*. Therefore, the generator output PG is the shaft output pt of the water turbine or pump water turbine 12,
Release of inertial energy of the rotating part due to a change in the rotational speed N,
The value is determined by the sum of absorption components.

FIG. 6 shows an example of output control when the output is changed in this way. This figure shows time T on the horizontal axis, and changes in generator output PG, guide vane opening a1, effective head He of the water turbine, and turbine flow rate Q1 rotational speed N1 rotational speed target value N* on the vertical axis. In the diagram of the generator output PC, the solid line PG indicates the actual generator output, and the broken line indicates the output target value P*.

As can be seen from Figure 6, immediately after point A, where the generator output begins to change, the actual output PG deviates significantly from the output target value P*, even though the goal is to lower the output. There is a phenomenon in which the temperature rises for -10 seconds and then falls. This phenomenon occurs when the penstock 11 connected to a water turbine or pump turbine
This is caused by internal water hammer.

That is, in the hydroelectric power generation facility having the above-mentioned configuration, when the flow rate of water is changed by changing the opening degree of the guide vane, the water hammer or pump installed at the end of the penstock 11 is affected by the water hammer action of the penstock 11. The water pressure at the inlet of the water turbine 12 fluctuates. Assuming that the inlet pressure of the water wheel or pump water wheel 12 at this time is H, this inlet pressure H can be expressed as follows from the basic equation of water hammer.

H−CΦdQ/d t+Ho ”−(1) Here, Q is the flow rate of water flowing through the penstock 11, and Ho is the flow rate Q
C is a negative constant determined by the length of the penstock 11, the cross-sectional area, the density of water, etc.

That is, the water pressure H is determined according to the rate of change dQ/dt of the water flow IIQ, and when the flow rate Q decreases, the water pressure H becomes higher than the water pressure Ho before the change.

Therefore, considering the characteristics shown in Fig. 6, when the guide vane opening degree a starts to be closed in an attempt to decrease the generator output PG, the flow rate Q decreases, and as a result, the water hammer phenomenon described above occurs in the penstock. As the population pressure of the water turbine increases, the effective head He of the water turbine also increases.

Since the shaft output pt of a water turbine is approximately proportional to the product of the water flow rate Q and the effective head He of the water turbine, if the increase in the effective head He of the water turbine due to the above water hammer effect is large, the shaft output of the water turbine will temporarily increase. However, the generator output P also increases. That is, if the absolute value 1dQ/di of the time rate of change of the water flow ff1Q is large, the above-mentioned problem will occur.

Here, dQ/dt will be considered. This water flowff
The time change rate of 1Q can be expressed as follows.

dQ/dt - dQ/dP - dP/dt - (2) As is clear from this equation, the value of dQ/dt changes depending on dQ/dP, which is the characteristic of the water turbine and pump turbine, and dP
/dt also changes. That is, when the time rate of change of the output is large, the value of dQ/dt becomes large, causing the above-mentioned problem.

On the other hand, the optimum rotational speed setter 19 outputs a rotational speed target value N* in order to achieve the highest efficiency operation of the water turbine based on the output target value P*. There is a relationship as shown in FIG. 7 between the output target value P* and the rotational speed target value N*. That is, where the output target value P* is large, the rotational speed target value N* is also large, and where the output target value P* is small, the rotational speed target value N* is also small.

As shown in FIG. 6, when a command is issued to lower the output target value P*, the rotational speed target value N* also decreases. Since the rotational speed N is controlled by the rotational speed control device 18 so as to approach the rotational speed target value N*, the rotational speed N also gradually decelerates.

As mentioned above, when the output target value P* decreases, the shaft output pt of the water turbine temporarily increases due to the water hammer of the penstock 11,
Moreover, since the rotational speed N is controlled in a decreasing direction, the inertial energy of the rotating part is released. Therefore, even though the output target value P* is in the decreasing direction, the generator output P
This means that G will rise once.

(Problems to be Solved by the Invention) In this way, in the conventional output control method, the output of the generator or generator motor responds in the opposite direction to a request from the power grid. This was a problem in terms of operation.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for operating a hydraulic machine that can follow output requests from a system with good followability and can stably control output.

[Structure of the invention]

(Means for Solving the Problems) The method of operating a variable speed hydraulic machine of the present invention includes a hydraulic machine such as a water turbine or a pump water turbine having a guide vane for adjusting the amount of water, and a variable speed hydraulic machine directly connected to the hydraulic machine. In the operating method of a variable speed control hydraulic machine that is equipped with a generator or a generator motor and has a rotation speed control device that controls the rotation speed of the variable speed generator motor, etc., when changing the power generation output, a change in the output target value P * The present invention is characterized in that the rate of change or differential value is detected, and the rotational speed of the variable speed generator/motor etc. is controlled using a value obtained by multiplying the rate of change or differential value by a negative gain.

(Function) According to the method of the present invention configured as described above, since the rotational speed is corrected by the value obtained by multiplying the rate of change or differential value of the output target value P* by a negative gain, the output target value P* Fluctuations in output caused by water hammer in the penstock caused by changes in flow rate due to changes in flow rate can be absorbed or released as rotational energy of the rotating parts, so that the generator output is in the opposite direction to the output target. It is possible to suppress transient phenomena such as temporary swinging.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a configuration example of an output control system to which the control method according to the present invention is applied. Water guided by a penstock 11 passes through a guide vane 17 and rotates a water wheel or a pump water wheel 12. The shaft output pt of the water turbine or pump water turbine thus generated is converted into an electrical output PG by the variable speed generator 13.

When the output target value P* is given, it is compared with the actual generator output PG by the output control device 15, and the guide vane opening target value a* is calculated. This value is input to the guide vane control device 16 to set the guide vane opening degree a.

On the other hand, the optimum rotational speed setter 19 outputs a rotational speed target value N* corresponding to the output target value P* to the rotational speed control device 18.

Further, the rotational speed correction control device 20 calculates the rate of change or differential value of the output target value P*.

The output of this rotational speed correction control device 20 is the speed correction value Nc
is added to the rotation speed target value N* of the optimum rotation speed setter 19, so the rotation speed control device 18 is controlled by the corrected optimum rotation speed.

Next, the operation of the embodiment of the present invention described above will be explained with reference to FIGS. 1 and 2. Note that the definitions of lines and symbols in FIG. 2 are the same as in FIG. 5.

Here, if a command is given to lower the output target value P*, then the rate of change or differential value of the output target value P* takes a negative value. Therefore, the rotation speed correction control device 2
When the value is 0, this rate of change or differential value is multiplied by a negative gain to obtain the speed correction value Nc. In this case, the speed correction value Nc becomes a positive value, and a value obtained by adding this to the rotational speed target value N* is sent to the rotational speed control device 18.

The rotational speed control device 18 controls the actual rotational speed to be higher than the rotational speed target value N* by the speed correction value Nc. When the rotational speed is increased, a part of the water wheel shaft output pt is absorbed as inertial energy of the rotating part.

In this way, Fig. 6 1″: Surplus energy (
If the rotational speed is increased so that the water wheel shaft output) is absorbed as inertia energy of the rotating part, the generator output PG will not increase once in response to the command to lower the output target value P*, and the second As shown in the figure, the followability of the generator output PG to the output target value P* becomes better, and stable output control becomes possible.

In the above-described embodiments, the case where the output target value P* is decreased has been described, but the output control can be performed in the same manner even when a command to increase the output target value P* is received.

That is, when the output target value P* increases, the output control device 15 commands the target value a* in the direction of opening the guide vane. When this opening command a* is input, the guide vane 17 is opened by the guide vane control device 16.

At this time, the flow rate increases in the penstock, causing a water hammer phenomenon and reducing the effective head. Due to this reduction in effective head, the shaft output of the water turbine or pump turbine decreases even though an output increase command has been issued.

On the other hand, the rotational speed correction control device 20 converts the value Nc (in this case, negative) that has produced a negative gain in the rate of change or differential value (in this case, positive) of the output target value P* to the rotational speed target value. In addition to N*, by performing control to reduce the rotational speed N, a decrease in the shaft output of the water turbine or pump water turbine is compensated for in the form of releasing inertial energy of the rotating part. This improves the followability of the generator output PG to the output target value P*, and enables stable output control.

In addition, as shown in FIG.
, llb are branched, and seven water turbines or pump water turbines 12a, 12b are installed in each of them.If there are many operating units that are simultaneously controlled to the output target value P*, the flow rate change dQ/ Since dt is large, the change in the effective head due to the water hammer phenomenon of the penstock is large, and when the number of operating units that are simultaneously controlled to the target output P* is small, the flow rate change dQ/dt is small, so the effective head due to the water hammer phenomenon described above is large. Considering that the change in the head is relatively small, the absolute value of the negative gain multiplied by the rate of change or differential value of the output target value P* in the rotational speed correction control device 20 is set to be large when the number of operating machines is large. , when the number of operating units is small, the output can be controlled so that the followability of the generator output PG to the output target value P* is optimal even if the number of operating units changes.

〔Effect of the invention〕

As explained above, according to the present invention, output control during power generation operation is extremely stable, and hydroelectric power generation equipment can be controlled with good followability.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a control device for carrying out the method of operating a variable speed hydraulic machine of the present invention, Fig. 2 is a graph showing its operation, and Fig. 3 is a branch waterway showing another embodiment of the present invention. Figure 4 is a schematic diagram of a conventional hydroelectric power plant, Figure 5 is a block diagram of a conventional hydroelectric power plant control device, Figure 6 is a graph showing its operation, and Figure 7 is a schematic diagram of a conventional hydroelectric power plant. The figure is a graph showing the relationship between the output target value P* and the rotational speed target value N*. 10-...Kamiike, 11...Hydraulic iron pipe, lla, ll
b... Branch pipe line, 12, 12a, 12b... Water turbine or pump water turbine, 13.13a, 13b... Variable speed generator motor, 14... Lower pond, 15... Output control device,
16... Guide vane control device, 17... Guide vane, 18... Rotation speed control device, 19... Optimal rotation speed setter, 2o... Rotation speed correction control device.

Claims (1)

[Claims] In a power generation operation method of a hydroelectric power generation facility that has a hydraulic machine such as a water turbine or a pump water turbine that has guide vanes to adjust the amount of water, and a variable speed generator or generator motor directly connected to this hydraulic machine, an output change command is received. In this case, the rate of change or differential value of the output target value P* is detected, and the rotational speed of the generator or generator motor is corrected and controlled using a value obtained by multiplying the rate of change or differential value by a negative gain. How to operate hydraulic machinery.