JP2647116B2 - How to operate a variable speed hydraulic machine - Google Patents

Description

Description: Object of the Invention (Industrial application field) The present invention relates to a power generation operation control method for a variable speed hydraulic machine such as a water turbine or a pump water turbine having a guide vane.

(Prior art) In a hydraulic machine such as a turbine or a pump turbine installed in a hydroelectric power plant, the shaft output during the operation of the turbine is determined by the opening of the guide vanes under a constant head. When the output is changed in a hydroelectric power plant equipped with a generator or a generator motor, it is customary to control the opening and closing of the guide vanes so that the guide vane opens in accordance with the output target value of the generator or the generator motor. is there.

FIG. 4 shows a schematic configuration of a hydroelectric power plant to which the present invention is applied. The energy of water guided from an upper pond 10 by a penstock 11 is converted into mechanical energy by a water turbine or a pump water turbine 12 and is wound. The induction generator or the wound induction motor 13 is driven, and the generated energy is supplied as electric power to a power system (not shown). The water after the energy is absorbed by the turbine or the pump turbine 12 is drained to the lower pond 14 as waste water.

A guide vane (not shown) is provided on the water turbine or the pump turbine 12, and the flow rate Q of water supplied to the water turbine or the pump turbine 12 via the penstock 12 is adjusted by changing the opening degree.

FIG. 5 shows an example of a conventionally used control device, in which a target output value P * and a generator output PG are input to an output control device 15 to output a guide vane opening target value a *. . The guide vane controller 16 sets the guide vane opening a in accordance with the guide vane opening target value a *. The opening degree of the guide vane 17 is controlled by the guide vane opening degree a, the flow rate flowing into the water turbine or the pump turbine 12 is adjusted, the shaft output Pt thereof is adjusted, and the generator or the generator motor 13 is adjusted.
Output PG is changed.

On the other hand, a rotation speed control device 18 such as a cycloconverter for controlling the rotation speed is connected to the generator or the generator 13, and the rotation speed of the generator or the generator motor 13 is adjusted by an optimum rotation speed setter 19. The rotation speed is controlled to a target rotation speed N * according to the output target value P *. Therefore, the generator output P
G is the shaft output Pt of the turbine or pump turbine 12 and the rotation speed N
Is determined by the sum of the release and absorption of the inertial energy of the rotating part due to the change in

FIG. 6 shows an example of output control when the output is changed in this way. In this figure, the horizontal axis represents time T, and the vertical axis represents generator output PG, guide vane opening a, and effective head H of the turbine.
e, the state of changes in the turbine flow rate Q, the rotation speed N, and the rotation speed target value N *. In the figure of the generator output PG, the solid line PG indicates the actual generator output, and the broken line indicates the output target value. P * is shown.

As can be seen from FIG. 6, at the point of the point A where the generator output starts to change, the actual output PG is far from the output target value P *, and the target is to reduce the output. Regardless, there is a phenomenon of rising once and then falling. This phenomenon is caused by the penstock connected to the turbine or pump turbine.
It is caused by a water hammer inside.

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

H = C · dG / dt + Ho (1) Here, Q represents the flow rate of the water flowing through the penstock 11, Ho represents the inlet water pressure of the water turbine or the pump turbine 12 before the flow rate Q changes, and the C penstock 11 Is a negative constant determined by the length, cross-sectional area, water density, etc.

That is, the water pressure H depends on the rate of change dQ / dt of the flow rate Q of water.
Is determined, and when the flow rate Q decreases, the hydraulic pressure H becomes higher than the hydraulic pressure Ho before the change.

Accordingly, in consideration of the characteristics shown in FIG. 6, when the guide vane opening a is started to be reduced in order to reduce the generator output PG,
The flow rate Q decreases, and as a result, a water hammer phenomenon occurs in the penstock mentioned above, and the inlet pressure of the turbine increases, so that the effective head He of the turbine also increases.

Since the shaft output Pt of the turbine is almost proportional to the product of the flow rate Q of water and the effective head He of the turbine, if the increase of the effective head He of the turbine due to the above-mentioned water hammer is large, the shaft output of the turbine once increases. Then, the generator output P also increases. That is, the flow rate Q of water
If the absolute value | dQ / dt |

Here, dQ / dt is considered. The time rate of change of the flow rate Q of water can be expressed as the following equation.

dQ / dt = dQ / dP · dP / dt (2) As is apparent from this equation, the value of dQ / dt varies depending on dQ / dP which is a characteristic of the water turbine and the pump turbine, and dP / dt.
It also changes with dt. That is, when the time change rate of the output is large, the value of dQ / dt becomes large, and the above-described problem occurs.

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

As shown in FIG. 6, when a lowering direction command is issued as the output target value P *, the rotation speed target value N * also becomes the lowering direction. Since the rotation speed N is controlled by the rotation speed controller 18 so as to approach the rotation speed target value N *, the rotation speed N also gradually decreases.

As described above, when the output target value P * decreases, the shaft output Pt of the water turbine once increases due to the water hammer of the penstock 11, and the rotation speed N is controlled in the decreasing direction. The inertial energy will be released. Therefore, the generator output PG is notwithstanding the output target value P * in the decreasing direction.
Will rise once.

(Problems to be Solved by the Invention) As described above, in the conventional output control method, the output of the generator or the generator motor once responds in reverse to the request from the power system, so that Operationally, it was a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of operating a hydraulic machine which has a good ability to follow an output request from a system and can stably control the output.

[Configuration of the invention]

(Means for Solving the Problems) The method of operating a variable speed hydraulic machine according to the present invention comprises a hydraulic machine such as a water turbine or a pump turbine having a guide vane for adjusting the water flow, and a variable speed hydraulic machine directly connected to the hydraulic machine. In a method of operating a variable speed control hydraulic machine having a generator or a generator motor and a rotation speed control device for controlling the rotation speed of the variable generator motor or the like, when a change in power generation output is commanded, a change in an output target value P * Detect the rate or derivative,
The rotation speed of the variable speed generator motor or the like is controlled by a value obtained by multiplying the change rate or the differential value by a negative gain.

(Operation) According to the method of the present invention configured as described above, the rotation speed is corrected by the value obtained by multiplying the negative rate by the rate of change or the differential value of the output target value P *. The output fluctuation caused by the water hammer of the penstock caused by the change in the flow rate caused by the change in the flow rate can be absorbed or released as the rotational energy of the rotating part. Transient phenomena such as swinging once.

(Example) Hereinafter, an example of the present invention is described with reference to drawings.

FIG. 1 shows an example of the configuration of an output control system to which the control method according to the present invention is applied, in which water guided by a penstock 11 passes through a guide vane 17 and passes through a turbine or a pump turbine 12.
To rotate. The shaft output Pt of the turbine or the pump turbine generated by this is converted into the electric output Pt by the variable speed generator 13.
Converted to G.

When the output target value P * is given, the output control device 15 compares the output target value P * with the actual generator output PG to calculate the guide vane opening target value a *. This value is input to the guide vane control device 16 to set the guide vane opening a.

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

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

Since the output of the rotation speed correction control device 20 is added as a speed correction value Nc to the rotation speed target value N * of the optimum rotation speed setting device 19, the rotation speed control device 18 is controlled by the corrected final rotation speed. Will be.

Next, the operation of the above-described embodiment of the present invention will be described with reference to FIGS. The definitions of the lines and symbols in FIG. 2 are the same as those in FIG.

Here, assuming that a lowering command is given as the output target value P *, in this case, the rate of change or differential value of the output target value P * takes a negative value. Therefore, the rotation speed correction control device
At 20, the speed correction value Nc is obtained by multiplying the rate of change or the differential value by a negative gain. In this case, the speed correction value Nc becomes a positive value, and a value obtained by adding this to the rotation speed target value N * is sent to the rotation speed control device 18.

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

In this way, the rotational speed is adjusted so that the generator output PG shown in FIG. 6 absorbs the surplus energy (water turbine output) that rises inversely with respect to the output target value P * as the inertia energy of the rotating part. If the output is increased, the generator output PG does not temporarily increase in response to the command to lower the output target value P *, and as shown in FIG. , And stable output control becomes possible.

In each of the above-described embodiments, the case where the output target value P * decreases is described. However, the output control can be performed in the same manner even when a command to increase the output target value P * is issued.

That is, when the output target value P * increases, the output control device 15 commands the target value a * in the direction in which the guide vanes are opened. When the opening command a * is input, the guide vane 17 is opened by the guide vane control device 16. At this time, since the flow rate in the penstock increases, a water hammer phenomenon occurs, and the effective head decreases. Due to the reduction of the effective head, the shaft output of the water turbine or the pump turbine is reduced despite the output increase command being issued.

On the other hand, the rotation speed correction control device 20 calculates a value Nc (in this case, negative) in which a change rate or a differential value (in this case, positive) of the output target value P * gives a negative gain to the rotation speed target value. N
In addition to *, by reducing the rotational speed N, the decrease in the shaft output of the turbine or the pump turbine is compensated in the form of the release of inertial energy of the rotating part. This improves the followability of the generator output PG to the output target value P *,
Stable output control can be performed.

As shown in FIG. 3, the above-described control method is performed by using a single penstock (single pipe section) 11 and a plurality of branch pipes 11a, 11a.
b branches off and they are respectively turbine or pump turbine 12a, 12b
Output target value P when applied to a power plant with
* If the number of operating units controlled simultaneously is large, the flow rate changes
Since the dQ / 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 controlled simultaneously to the target output P * is small, the flow rate change dQ / dt is small, and the water hammer phenomenon is small. In consideration of the fact that the change in the effective head due to is relatively small, the rotation speed correction control device 20 determines the insulation value of the negative gain multiplied by the rate of change or the differential value of the output target value P * when the number of operating units is large. The output is controlled so that the followability of the generator output PG to the output target value P * becomes optimum even when the number of operating vehicles changes, by reducing the number when the number of operating vehicles is small.

〔The invention's effect〕

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

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device for carrying out a method of operating a variable speed hydraulic machine according to 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. 4 is a schematic diagram of a conventional hydroelectric power plant, FIG. 5 is a block diagram of a control device of a conventional hydroelectric power plant, FIG. 6 is a graph showing the operation thereof, FIG. The figure is a graph showing the relationship between the output target value P * and the rotation speed target value N *. 10 ... Kamiike, 11 ... Penstock, 11a, 11b ... Branch pipe, 1
2,12a, 12b …… Water or pump turbine, 13, 13a, 13b ……
Variable speed generator motor, 14 ... Shimoike, 15 ... Output control device,
16 Guide vane control device, 17 Guide vane, 18
…… Rotation speed control device, 19 …… Optimal rotation speed setting device, 20
...... Rotation speed correction control device.

Claims (1)

(57) [Claims] 1. A power generation operation method for a hydroelectric power plant having a hydraulic machine such as a turbine or a pump turbine having a guide vane for adjusting a water flow and a variable speed generator or a generator motor directly connected to the hydraulic machine. When an output change command is received, a change rate or a differential value of the output target value P * is detected, and the rotational speed of the generator or the generator motor is corrected by a value obtained by multiplying the change rate or the differential value by a negative gain. A method for operating a hydraulic machine, characterized by controlling.