JPH01163475A - Control method for variable speed pumped storage power plant - Google Patents

Abstract

PURPOSE:To avoid a water-hammer interference in a common pipe line by temporarily correctingly controlling the rotating speed of a variable speed pumped storage power plant at the time of rapidly changing the operating condition of the other hydraulic machine which commonly use an upper-course or a lower-course pipe line. CONSTITUTION:At the time of starting the other machine which commonly use an upper-course or a lower-course pipe line in a pumping mode or carrying out the input rapid increasing operation thereof, a correction signal for increasingly correcting the rotating speed N of the corresponding variable speed pumped storage power plant 4 by a defined value DELTANa is previously applied to an adder 18. This defined value DELTANa can be varied in accordance with the operating quantity of the guide vane of the other machine. Also, the correcting control by the correction value DELTANa may be simultaneously performed at the time of carrying out the rapid change operation of the operating condition of the other machine, when the rapid changing operation of the other machine is finished and as the water hammer in the common pipe line subsides, the correction signal of this defined value DELTANa is returned to zero.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable speed pumping (power generation) plant, in particular, in which an upstream or downstream pipe is shared with other hydraulic machines, and the pump operation area has hump characteristics. Pumps with reverse flow characteristics (reverse flow characteristics) provide a suitable control method for variable speed pumping (power generation) plants equipped with pump turbines.

[Conventional technology]

It is generally considered that in a pump-turbine, it is unavoidable that a hump characteristic (partially dH/dQ>O) as shown by the dotted line in FIG. 5 occurs on the high-head side. Operation in this area is not only unstable and accompanied by vibration and noise, but also because the flow rate Q appears as a trivalent function under the same head, the flow rate Q suddenly changes and the phenomenon of flying occurs, which is accompanied by an abnormal water hammer phenomenon. There is. The degree of depression in this hump characteristic varies depending on the opening degree of the guide vane, as shown in Figure 6, but even if a clear depression characteristic does not occur, the same problem occurs to a greater or lesser extent due to unstable flow within the runner. . The reason for this is said to be that when the flow rate is low, the water flow is biased in the radial direction as shown in FIGS. 3 and 4, causing a backflow. Further, in such a state, the flow separates from the blade surface, resulting in a so-called stall state.

By the way, in Japanese Patent Application No. 61-26694, when increasing the load on the variable speed pumping device, first the output of the drive device is increased and the rotation speed is increased so that the operating point of the pump turbine does not fall into the above-mentioned hump characteristic transiently. After that, the guide vane should be raised.

When reducing the load, the patent discloses a plan in which closing of the guide vanes and lowering of the rotational speed are performed simultaneously, but the closing of the guide vanes is completed sooner than the lowering of the rotational speed. However, if the upper or downstream pipeline of the pump-turbine is shared with other hydraulic machines (i.e., if multiple hydraulic machines are installed branching from the same pipeline), one of the other If a hydraulic machine changes its operating state and changes its flow rate, water hammer will occur in this hydraulic machine, and this will be transmitted to the pump-turbine we are currently considering via the shared pipe, so it will definitely have an effect.

In particular, when the lift height H is shifted upward, there is a possibility that the hump characteristics may deteriorate, no matter how perfectly the variable speed pumping device alone can control the pump.

Furthermore, in Japanese Patent Application Laid-Open No. 61-149583, when starting the pump, that is, when moving the pump water turbine (pump) from the shut-off state to full-scale variable speed pumping operation at a desired load, a staircase is opened in accordance with the opening of the guide vanes, which are gradually opened. A pump starting method is disclosed in which the rotational speed command is gradually increased to finally achieve an appropriate rotational speed and an appropriate guide vane opening at the desired load.

However, this known example does not mention at all the control method after starting full-scale variable speed pumping operation.

Furthermore, Japanese Patent Application No. 60-14918 discloses a method in which when the water level difference between the upper and lower pond water levels exceeds a predetermined value, the rotational speed is increased and corrected in accordance with this overshoot. However, it is completely immune to a drop in hump characteristics (backflow characteristics) due to a temporary increase in the total head of the pump-turbine due to water hammer in the shared pipeline, which is the object of the present invention.

As mentioned above, the conventional hump characteristic avoidance control method only partially discloses the control rules that should exist within a single variable speed pumping system.

That is, there is no disclosure of countermeasures against the drop in hump characteristics due to water hammer in a shared pipeline, which is the object of the present invention.

[Problem that the invention seeks to solve]

The present invention eliminates the disadvantages of the prior art described above and provides a simple and reliable solution to prevent the operating point from approaching the hump characteristic abnormally even when subjected to water hammer effects from other hydraulic machines sharing the pipeline. An object of the present invention is to provide a control method for a variable speed pumped storage power plant.

[Means for solving problems]

Changes in the operating status of other hydraulic machines that share a pipe, especially when starting up in pump mode or during sudden input operations, can cause water hammer in the shared pipe to cause a change in the total head (pump outlet water pressure) of the variable speed pumping plant. Note that the difference in inlet water pressure) increases with - hours,
Prior to or at the same time as starting up the hydraulic machine or input sudden increase operation, the rotational speed N of the pump turbine of the variable speed pumped storage power generation plant is temporarily increased and corrected.

Then, after the danger of water hammer interference in the shared pipeline by the hydraulic machine has passed, the N correction control is removed and N is returned to its original proper value control.

[Effect] Even if the total head increases due to water hammer from the shared pipeline and the operating point approaches the hump characteristic, the N is increased and corrected before or at the same time to move the hump characteristic itself away. It is possible to reliably avoid the operating point from falling into the hump characteristic.

A more detailed explanation is as follows.

FIG. 6 is a graph showing the relationship between Q and H at each guide vane opening measured under a certain rotational speed, and under this rotational speed, the optimal adjustment is the dotted envelope.

The two lines in FIG. 7 indicate optimal setting curves under the rotational speeds N1 and Nz, which were obtained in the same way as the envelope curve in FIG. 6. Nao N
1>Nz.

That is, it can be considered that this optimum setting curve moves upward and to the right as the rotation speed increases.

When the water level difference between the upper and lower ponds is the same, the total head H increases as the flow rate Q increases, and this is called the load curve at this water level difference (see Figure 7).

As is clear from Figure 7, when the rotation speed is increased, the hump characteristic starting point HX increases even under the same guide vane opening, so even if the total head H increases temporarily due to the influence of water hammer in the shared pipeline, the hump Characteristic deterioration can be avoided.

〔Example〕

An explanation will be given below with reference to FIG. 1, which is an embodiment of the present invention.

FIG. 1 is a control circuit diagram according to the present invention (the details of the AC excitation circuit for power control are not shown as they are not directly related to the present invention). Simple water level difference between upper and lower water tanks, that is, total head H
an adder 18 that compares the output signal Na from the rotation speed function generator 12 which uses G as input to calculate the appropriate rotation speed Na at that time and the actual rotation speed N; 16 a power control correction signal generator; 7 a power controller; 3 power converters, 2 electric motors.

A control loop consisting of the moment of inertia GD2 is configured as a negative feedback circuit. Note that GD2 is a block for showing the effect of the moment of inertia of the electric motor and pump, and does not include any special device. Further, in order to make the deviation between Na and N zero, the power control correction signal generator 16 includes an integral element. The correction signal ε, which is the output of the power control correction signal generator 16, is added to the power command Po, and this composite signal PO+E is compared with the actual motor output PM.

Power controller7. The power control loop consisting of the power converter 32, the generator motor 2, and the restoration circuit for the actual motor output PM is configured as a negative feedback circuit, and the power controller 7 has (Po+t) and P.
An integral element is included to make the deviation of M zero. A guide vane opening function generator 13 receives the load commands Po and Ha and calculates the appropriate guide vane opening YOPT at that time, and a comparator 21 compares the output signal Ya with the actual guide vane opening Y. A control loop consisting of the 9 guide vane controller and the restoration of the actual guide vane opening Y is configured as a negative feedback circuit, and the integral element included in the guide vane controller 9 guides the guide vane so that the deviation between Ya and Y becomes zero. The vanes are controlled.

Thus, N=Na by the rotational speed control circuit.

PM:PO+ε can be set by the power control circuit, and Y '' Y a can be set by the guide vane control circuit.

Here, the deviation between the input pp required by the pump and the actual input PM to the motor is the moment of inertia (G
By the way, the moment of inertia can be considered as a kind of integral element.

Also, the above (7) letter! J16, 7, 3, 2. The rotational speed control circuit, which consists of restoring GD" and actual N, is configured as a negative feedback circuit, so it is controlled so that the deviation between PM and pp becomes zero. That is, PM = Pp, and the function generator's If we ignore the error, Y a = P o, so P
Originally, p should be controlled to be equivalent to Pa, that is, pp=PO. If you remove the above, Po = Pp = PM = Po +
i, and the power correction signal E is finally set to zero.

From the above, the actual input P according to the external power command Po
M can be controlled.

FIG. 9 is a graph showing the above explanation for the embodiment of FIG. 1.

Time t. shows the response when the drive output command PO is raised in a stepwise manner.

First, the motor output PM rises as shown in graph g with a slight delay.

In addition, the output Ya of the guide vane opening function generator and the output Na of the rotation speed function generator are determined by graphs b and c, respectively, depending on the time constant that the function generator has and a specially given additional time constant.
Respond as follows.

The response of the actual guide vane opening Y to Ya in graph b is as shown in d. Note that the linear portion in the response of Y indicates that the guide vane is limited by the opening speed limit of the guide vane servo motor (this is given by the stroke limit of the guide vane pressure distribution valve, etc.).

The rotational speed N of the pump is accelerated by the difference between the motor output PM shown in graph g and the pump input Pp shown in graph e, increases as shown in graph f, and finally stops increasing when it reaches N''Na.

Incidentally, the pump human power Pp increases as shown in graph e by adding the increment due to both the increase in the guide vane opening degree Y and the increase in the rotational speed N.

In graph f, the movement of the rotational speed N is slow but stable, and this is because a sufficient damping effect is given to the 16 power correction signal generators.

This can be achieved, for example, by configuring the 16 power correction signal generator with a parallel circuit of a proportional element and an integral element, and appropriately selecting their gains.

The above explanation is for a normal case in which sudden water hammer is not transmitted from other units sharing the pipeline, but the operating point correction function in such a case, which is the key point of the present invention, is provided as follows.

When another unit that shares the upstream or downstream pipeline starts up in pumped storage mode or undergoes sudden input operation, a correction signal is added in advance to increase the rotation speed of the variable speed pumped storage power plant by a predetermined value ΔNa. 18.

Of course, this ΔNa can also be changed depending on the guide vane operation amount of the other machine. Further, the ΔNa correction control may be utilized at the same time when the operating state of the other machine is suddenly changed.

Then, when the sudden operation of the other machine is finished and the water hammer in the shared pipeline has subsided, the ΔNa correction signal is returned to zero.

FIG. 10 summarizes the response of the variable speed pumped storage power plant when the above-mentioned ΔNa correction control is performed.

In this case, unlike in FIG. 8, the motor output command Pa is not moving, so both Yopt + Y remain unchanged.

FIG. 2 shows an example of a device configuration in which the wound induction machine 2 is used as a variable speed motor using the control circuit shown in FIG. 1. The same numbers in the figures indicate the same products. The primary side of the wound induction machine 2 is connected to the power system 1, and the secondary side is connected to the power converter 3.
The input of the induction machine 2 is controlled by the phase and voltage control of the AC excitation current by the power converter 3. The actual input PM is detected by the power detector 6 and input to the comparator 20, and the actual rotation speed N is detected by the rotation speed detector 5 and input to the comparator 18, respectively.

FIG. 9 is a device configuration diagram showing another embodiment using the control circuit shown in FIG. 1, in which a synchronous machine 10 is used as the variable speed motor and a power converter 17 is used between the system 1 and the synchronous machine 10. It is. A phase detector 11 is provided to match the phase command to the power converter.

〔Effect of the invention〕

As is clear from the foregoing, the effect of the present invention is to reliably avoid a drop in hump characteristics even when receiving water hammer from other units sharing the pipeline, and to ensure stable and reliable operation of the variable speed pumped storage power generation system.

In pump-turbine plants, a design in which multiple pump-turbines share the upstream or downstream pipeline is rather common in pursuit of economic efficiency, and the effect of providing a variable speed pumped storage power generation system that can be safely applied to this type of plant is small. do not have.

[Brief explanation of the drawing]

Fig. 1 is a control circuit diagram showing one embodiment of the variable speed pumping system of the present invention, Fig. 2 is an example of the case where the present invention is applied to a variable speed pumping system using a wound induction motor, Figs. 4
The figure is an explanatory diagram of the hump characteristic, and Figure 5 shows the hump characteristic.
-Q graph, FIG. 6 is a graph showing the relationship between guide vane opening and hump characteristics, FIG. 7 is a graph showing the relationship between rotational speed and hump characteristics, and FIG. 8 is for detailed explanation of the present invention shown in FIG. FIG. 9 is a graph of another type of variable speed pumping system using the present invention, and FIG. 10 is a graph for explaining in detail the present invention of FIG. 1, similar to FIG. 8. 5th r

Claims (1)

[Claims] 1. A pump-turbine that shares an upstream or downstream pipeline with another hydraulic machine and has hump characteristics (reverse flow characteristics) in the pump operation area, and a supply of AC power of the same frequency from the power system. Regarding the pumped storage mode operation of a variable speed pumped storage power generation plant having a pumped storage drive device with a frequency converter configured to drive the pump turbine at a rotational speed suitable for the operating conditions at that time, When the operating conditions of other hydraulic machines that share the pipeline suddenly change, the rotation speed of the variable speed pumped storage power generation plant is temporarily corrected and the water in the shared pipeline due to the sudden change in the operating status of the other hydraulic machines is adjusted. A control method for a variable speed pumped storage power generation plant, in which the temporary correction control is canceled after the shock has subsided. 2. When other hydraulic machines that share the upstream or downstream pipeline start up in pumping mode or input increases suddenly, correction control is performed to increase the rotational speed of the variable speed pumped storage power generation plant prior to this. Control method for variable speed pumped storage power plant. 3. When another hydraulic machine that shares the upstream or downstream pipeline starts up in pumping mode or increases its input rapidly, correction control is simultaneously performed to increase the rotation speed of the variable speed pumped storage power plant. Control method for variable speed pumped storage power plant.