JPH04358768A - Operation control device for variable speed hydraulic machinery - Google Patents

Abstract

PURPOSE:To provide an input adjustment control operation method, capable of being practically stable operation, without following excessive vibration especially from an excessive vibration region due to a secondary flow to a region having less input, in the pumping operation control for variable speed hydraulic machinery. CONSTITUTION:A guide vane opening A is made to be quickly reduced with input kept nearly constant after rotation speed N and the guide vane opening A or either of them, satisfying operation command input P under a water-level difference Hi between upper and lower ponds, reaches the set values Nil and Ail of a rotation speed and a guide vane opening or either of them, needed for evading an excessive vibration generation region due to the secondary flow of a runner previously set by the reduction command of the input P. The rotation speed N is switched to acceleration control, in a range unfollowing the increase of the input P, from deceleration control so far.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for controlling the operation of variable speed hydraulic machinery, and in particular, stable operation control of the input adjustment range during pumping operation to an input range smaller than the region where excessive vibration occurs due to the secondary flow of the runner. This invention relates to a method for controlling the operation of variable speed hydraulic machines that enables

0002

[Prior Art] As a control method during pumping operation of a variable speed hydraulic machine, a method in which backflow is avoided by controlling the guide vane opening degree and rotation speed (Japanese Patent Laid-Open No. 1491-1981)
8), Example of considering control priority (Japanese Patent Application Laid-Open No. 59-203
883, JP-A-60-128886, JP-A-62-25
5581, Japanese Unexamined Patent Publication No. 1-244171), examples that enabled high-efficiency operation (Unexamined Japanese Patent Applications No. 48-21045, No. 57-1)
13971, Japanese Patent Publication No. 58-18595, Japanese Patent Publication No. 1-26
8499) etc. By the way, it is known that during pumping operation of a variable speed pump turbine, if the amount of pumped water decreases, a secondary flow will occur in the runner and vibration will increase.In order to avoid this, it is necessary to The design is such that the pump input adjustment control operation is performed only within this range, and the pump is not operated in a smaller flow rate range, that is, in a region where the pump input is small.

[0003] As described above, since the input adjustment range of the pump is to operate up to just before the secondary flow generation point, the input adjustment range is necessarily limited and within a relatively narrow range. A control method has been proposed in which when the head increases and the flow rate decreases until the secondary flow region is reached, the rotational speed N is increased by the ratio of the 1/2 power of the head H to avoid the secondary flow region. (Japanese Unexamined Patent Publication No. 14918/1986). However, in this operating method, the rotational speed is increased using only the head as a parameter, and the input P also increases due to this increase in the rotational speed. For example, when performing input reduction control during variable speed operation, the rotational speed increases immediately after entering the vicinity of this region, so the input P increases again. For this reason, if the input is controlled to decrease again, it will re-enter the secondary flow region. In this proposed method,
It is actually impossible to control operation past the secondary flow region to a region with even smaller inputs. in this way,
During pumping operation of a variable speed hydraulic machine, no operation method has been proposed that allows stable input adjustment control operation even in an input region smaller than the secondary flow region.

0004

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to achieve practical use in pumping operation control of variable speed hydraulic machines without causing excessive vibration, particularly in areas where the input is smaller than the excessive vibration area due to secondary flow. An object of the present invention is to provide an input adjustment control operation method that enables stable operation.

[0005]

[Means for Solving the Problems] A pumping operation control method for a variable speed hydraulic machine according to the present invention detects a water level difference H between an upper reservoir and a lower reservoir using a water level detection device, and sets an arbitrary head difference H inputted in advance.
Rotational speed N and guide vane opening degree A for input P at time i
On the operating function, the rotation speed N and the guide vane opening A before entering the excessive vibration region due to the secondary flow, or the value of either one of them, is input as Ni1 and Ai1. In input reduction control operation, this Ni1 and A
After reaching i1 or one of these set values, the guide vane opening degree A is rapidly decreased, and
By increasing the rotational speed N within a range that does not involve an increase in input, the excessive vibration region due to the secondary flow is passed through while input reduction control is maintained. In order to quickly pass only this excessive vibration region with a very small input change, it is also possible to change the rotational speed acceleration rate only in this region. In addition, after passing through the above excessive vibration region due to the secondary flow, the rotation speed N
It is also possible to perform input reduction control by decelerating the input speed. Further, when controlling the rotational speed deceleration after passing through this excessive vibration region, the guide vane opening degree may be switched from decreasing control to increasing control.

[0006]

[Function] According to the present invention, the excessive vibration region due to the secondary flow can be passed through with only a slight input change, and on the other hand, even if the operating region enters the excessive vibration region due to the secondary flow, it is possible to pass through the excessive vibration region due to the secondary flow. However, since there is a time lag before excessive vibration occurs (about 3 to 10 seconds according to actual measurements on actual equipment), excessive vibration can be avoided if the excessive vibration area is passed within a lag of at least 3 seconds. . In order to pass this time in 3 seconds, if we assume that the guide vane opening/closing speed is 100% for 60 seconds, it will be 5% during the guide vane operation for 3 seconds, and on the other hand, the input change rate during automatic frequency adjustment operation must be Assuming 100% input for 100 seconds, the input change width will be 3% in 3 seconds. In other words, by passing through the excessive vibration region within 5% of the maximum opening in terms of guide vane opening, or within 3% of the maximum input in terms of input change width, it is possible to further reach the region with smaller input without excessive vibration. This enables stable pumping operation over a wide range of areas, including

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a Francis type pump-turbine to which the present invention is applied and a generator-motor directly connected thereto. A plurality of guide vanes 2 for adjusting the flow rate are arranged in a circular row in the outer peripheral flow path of the runner 1.
Opening/closing is controlled by a guide vane control device 4 via a guide vane operating mechanism 3. The runner 1 is directly connected to a generator motor 6 via a main shaft 5, and this generator motor 6 is controlled by a water level difference detection device 7 between the upper and lower dams and a variable speed control device 8 to adjust the rotational speed N and speed corresponding to the specified input at the head. The guide vane opening degree is controlled to be A.

FIG. 2 shows an example of the characteristics of head (head) H and flow rate (pumped water amount) Q using guide vane opening degree A as parameters when such a pump-turbine is operated at a constant speed. Conventionally, the guide vane opening A is changed along the operating envelope B formed by the guide vane opening curve group A1 to A7 as the operating head becomes higher.
→A4...Control is being performed to narrow down the appropriate opening operation. On the other hand, as the amount of pumped water is decreased, regardless of the guide vane opening degree A, there is a flow rate Q0 at which a secondary flow that causes a reverse flow occurs on the inlet side of the runner during pump operation, and in this secondary flow generation region, This will result in excessive vibration of the equipment. Therefore, the intersection point C with this Q0 time envelope is usually
The plan is to operate only at a head lower than the head H0 corresponding to .

FIG. 3 shows the characteristics when the characteristics on the envelope at the rotational speed N0 in FIG. 2 are changed in rotation in terms of the relationship between the head H and the input P. When the rotation of the runner increases, N0 changes to N1 and N2 curves and C
The points are C1 and C2, and when the rotation is lowered, N0 becomes N
The curve changes to -1 and N-2, and point C moves to C-1 and C-2. Normal variable speed control operation is this C-
1, C-2, C0, C1, C2 The operation is only on the side where the head is lower than the so-called reverse flow start line on the lines. Therefore, the control range for variable speed operation is as shown in Figure 3.
This reverse flow start line, the operational maximum head Hmax, the minimum head Hmin, the maximum input Pmax of the plant, the maximum rotation speed Nmax and the minimum rotation speed N on the variable speed control device
min or, although not shown in the figure, is within a hatched area surrounded by a cavitation generation limit line or the like. For example, at a certain head Hi, the maximum input Pima
When adjusting the input from x to the minimum input Pimin, the rotation speed is Nimax as shown in Figs.
While decelerating from Aimax to Nimin, the operating state shifts to the direction of higher head on the envelope curve in Figure 2, so the guide vane opening A changes from Aimax to Aim.
It will be reduced to in.

FIG. 6 shows the region where excessive vibration occurs due to secondary flow, and the excessive vibration determined by experiment is plotted on the diagram showing the relationship between input P and guide vane opening A when the head is Hi. The occurrence area is indicated by hatching. In order to further reduce the input from Pimin shown in FIG. 5 when the head is Hi, if the guide vane is controlled to close along the dotted line in FIG. 6, which is the guide vane opening degree curve on the envelope shown in FIG. In the input range marked with * in the figure, excessive vibration is caused by the secondary flow.

[0011] In order to prevent this excessive vibration, the present invention inputs in advance the rotational speed Ni and the guide vane opening Ai1, or any one of them, before entering the excessive vibration region at the head Hi. put. According to one embodiment of the present invention, when the rotational speed and/or guide vane opening reaches the set value, as shown by the solid line in FIG.
The guide vane is rapidly narrowed down while the input P is held substantially constant, and the guide vane opening is reduced to a value Ai4 after passing through a preset excessive vibration region. During this time, the rotational speed is temporarily switched from the previous deceleration control to speed increase control. As a result, as shown in Fig. 8, the relationship between the input P and the guide vane opening A that passes through the excessive vibration region is changed to the normal one by passing the relationship between the input P and the guide vane opening A as narrow as possible and with only an extremely small input decrease. Even during AFC operation, when entering the excessive vibration generation area, the excessive vibration is passed within a time lag (minimum of about 3 seconds) until the excessive vibration occurs, so the generation of excessive vibration can be avoided in practical operation. After passing through the excessive vibration area, the guide vane opening degree Ai4
When reaching , the rotational speed is decreased again and input reduction control is performed.

FIG. 9 shows the rotational speed N when the head Hi is changed.
FIG. 4 is a diagram showing the relationship between the guide vane opening degree A and the guide vane opening degree A, which is determined according to the present invention. Further, FIG. 10 is a diagram showing the relationship between the input P and the guide vane opening degree A when the head Hi is changed according to the present invention. Further, FIG. 11 shows the input functions for these operation controls in terms of the relationship between the head H and the input P. In the figure, the hatched area represents the conventional input adjustable range, and the dotted area represents the operational input adjustable range increased by the operational control method of the present invention. As is clear from this figure, the lower limit value at which input adjustment is possible when the head is high has been significantly reduced from Pimin to Pi'min.

FIG. 12 shows the operating characteristics in FIG. 7 when the head is Hi at the rotation speed N and the guide vane opening degree A. After the rotation speed deceleration control is restarted after reaching the guide vane opening degree Ai4, the rotation speed is changed to the preset Ni5. When reaching this point, the guide vane opening is switched from the previous decreasing control to increasing control, and after passing through the excessive vibration region, the operation is controlled with the guide vane opening as large as possible to minimize the occurrence of cavitation. This is an example in which this is done. Although the above-mentioned embodiment described the control when the pump input is decreased, the present invention is not limited to this, but the present invention is not limited to this, but also applies a completely opposite control method to the control when the pump input is increased. In actual operation, it is possible to pass through without excessive vibration and perform input increase control stably.

[0014]

[Effects of the Invention] As is clear from the above description, according to the present invention, it is possible to quickly pass over the minimum width cross section of the guide vane opening in the region where excessive vibration occurs due to secondary flow with a small input change width. As a result, stable pumping operation can be performed even beyond the range where input is small without causing excessive vibration in practical operation, and pumping operation can be performed in a range including the secondary flow region. .

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a Francis-type pump-turbine and a generator-motor to which the present invention is applied.

FIG. 2 is a characteristic diagram of pump operation showing the relationship between head and flow rate at constant speed.

FIG. 3 is a diagram showing the operating range based on the characteristics of head, pump input, and rotation speed in a conventional variable speed machine.

4 is a diagram showing the relationship between the rotational speed and the guide vane opening degree when the head is Hi during variable speed characteristic operation in FIG. 3; FIG.

FIG. 5 is a diagram showing the relationship between input and guide vane opening during the same operation.

FIG. 6 is a diagram in which the region where excessive vibration occurs due to secondary flow is experimentally determined and plotted.

FIG. 7 is a diagram showing the relationship between rotational speed and guide vane opening degree according to another embodiment of the present invention when the head is Hi.

FIG. 8 is a diagram illustrating excessive vibration generation areas on a diagram showing the relationship between input and guide vanes.

FIG. 9 is a diagram showing the relationship between rotational speed and guide vane opening degree using head as a parameter.

FIG. 10 is a diagram showing the relationship between input and guide vane opening using head as a parameter.

FIG. 11 is a diagram showing the relationship between head and input to which the operation control method according to the present invention can be applied.

FIG. 12 is a diagram showing the relationship between rotational speed and guide vane opening degree according to another embodiment of the present invention.

[Explanation of symbols]

1 Runner 2 Guide vane 3 Guide vane operation mechanism 4 Guide vane control device 5 Main shaft 6 Generator motor 7 Water level difference detection device 8 Variable speed control device

Claims (3)

[Claims] Claim 1: An operation control method during pumping operation of a hydraulic machine such as a pump or a pump-turbine equipped with an electric motor or a generator-motor whose rotational speed can be variably controlled; The rotational speed N and/or the guide vane opening A that satisfy the operation command input P are necessary in order to avoid an excessive vibration generation area due to the secondary flow of the runner, which is preset by the input P reduction command. After the rotational speed and guide vane opening, or one of them, reaches the set values Ni1 and Ai1, the guide vane opening A is rapidly decreased while the input is kept almost constant, and the rotational speed N is decreased. A method for controlling the operation of a variable speed hydraulic machine, characterized by switching from conventional deceleration control to speed increase control within a range that does not involve an increase in input P. [Claim 2] The rotational speed and the guide vane opening, or either one of them, is a predetermined set value Ni1, Ai1.
The operation is controlled by setting the amount of increase in the rotational speed N with respect to the amount of decrease in the guide vane opening A to a rate of change of two or more steps or a rate of change increased by a smooth curvature. The method for controlling the operation of a variable speed hydraulic machine according to claim 1. [Claim 3] Further Ai from the predetermined set value Ai1.
Guide vane opening Ai3, which predetermines the speed increase ratio of the rotational speed N on the condition that the guide vane opening has decreased to 2.
3. The method for controlling the operation of a variable speed hydraulic machine according to claim 2, wherein the speed increase control is performed so that the amount of input decrease during the period is within 3% of the rated maximum input.