JPH0656151B2 - Feedforward operation control method for multiple pumps - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a buffer (eg, pond, tank, heat storage tank,
Etc.), the operation switching frequency of a plurality of devices (eg, pumps, blowers, refrigerators, etc.) in a system having
The present invention relates to an online correction type feedforward device operation control method for energy saving and the like. Here, for simplification of description, a drainage system having a pond on the suction side of the pump will be described as an example.

Conventionally, in a drainage system, a method of determining the operating schedule of pumps by controlling the number of operating pumps so that the internal water level that changes with time in accordance with the inflow amount falls within a certain range. No. 78102) has been proposed. In addition, a method of determining by operating pump speed control or the like, for example, (Japanese Patent Application Laid-Open No. 53-143002)
Is also proposed.

Figure 1 shows the model of the target water system. The purpose of operation control of the pump in this model is to prevent the reservoir 50, which stores the water supplied from the inflow port 500, from overflowing in this water system, and not to empty the reservoir, and also to the constraint condition (details will be described later). The pump 51 is operated so as to drain the water to the outside water side 52 so as to satisfy (1).

This will be described below with reference to FIG.

In FIG. 2, the horizontal axis represents time (t) and the vertical axis represents cumulative flow rate (ΣQ).

First, the case where the actual head is constant will be described. A curve 21 is a predicted inflow amount cumulative curve obtained by predicting the inflow amount to the reservoir from past results, and a curve 22 is the predicted inflow amount cumulative value added with the initial reservoir water amount (upper limit prediction curve). . A curve 23 is a value obtained by subtracting the reserve water amount in the reservoir from the predicted inflow amount cumulative value (lower limit prediction curve), and a curve 24 is the cumulative discharge amount of the pump (pong operation route). In order not to empty the reservoir, curve 24 should not run above curve 22, and in order not to flood the reservoir, curve 24 should not run below curve 23. That is, the curve 24 is
It must be between curves 22 and 23.

Since it is assumed that the actual head is constant, the discharge amount per pump is constant. Therefore, the cumulative discharge amount when operating with a certain pump combination A, B, C can be shown by straight lines A, B, C having a certain slope as shown in FIG.
Further, the curved points of the curve 24 mean changes in the number of operating pumps, speed, and blade angle. Obviously, it is better that the change frequency is low in terms of maintenance of the pump equipment. For this purpose, the best possible curve 24 should be found.

As a method of finding a curve, in the conventional method, the cumulative discharge amount curve is drawn from the starting point for all combinations of installed pumps,
The point that intersects the curve 22 or the curve 23 is obtained, the same operation is repeated with the intersection as a new start point, and the length from the intersection to the intersecting point is the longest, or the number of intersecting points is the smallest, or , The one with the smallest accumulation of evaluation values (for example, energy consumption) attached to each line segment was searched for as the curve 24.

The curve 24 obtained by this control method has the longest length to the intersecting point, the one having the smallest number of intersecting points, the one having the smallest accumulated evaluation value of individual line segments, etc. However, since the conditions such as the number of pumps are not changed until they intersect with each other, it is not a curve having perfect optimality. In this sense, it is called a suboptimal curve.

The control method described above (a) is capable of preliminarily limiting the number of candidates by adopting a calculation (comparison of evaluation function values) for selecting a specific driving route, and a method using a dynamic programming method, for example, , (Japanese Patent Laid-Open No. 52-20402), the memory in the arithmetic unit and the arithmetic time can be shortened.

(b) In the calculation for selecting the candidate driving route, the bending curve driving route is obtained as a candidate only at the boundary defined by the upper limit curve and the lower limit curve.Therefore, the number of bends must be selected for the driving route selected as a candidate. The smaller one will be selected. Therefore, the number of operations for switching the number of pumps and the like is small, and control with less damage to the device is possible.

(c) The above can be performed when the speed of the pump is controlled.

(d) It is possible to consider changes in the pump discharge rate due to changes in the actual head.

While having advantages such as the following, it also has the following disadvantages.

(a) Since the predicted value of the inflow load is used in determining the operating schedule of the pump, if there is an error in the predicted value, it may not be possible to operate properly with the calculated operating schedule.

(b) Since the operating schedule is re-determined from the beginning each time the predicted value of the inflow load is revised momentarily, it takes a long time to calculate, and the operating schedule thus obtained has a high frequency of switching the number of units when viewed as a whole. Probability is high.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a simple and economical pump operation control method.

Hereinafter, the principle of the present invention will be described in detail with reference to the drawings. In the present invention, as shown in FIG. 4, it is assumed that the predicted value of the inflow load is updated every moment based on the latest information up to the time when the prediction calculation is performed. In FIG. 4, the dotted line shows the case of considering based on the predicted value at time t ₀ , and the solid line shows the time t ₁ (t ₁ > t
_This is the case based on the predicted value in ( ₀ ).

In Fig. 4 (a), the horizontal axis represents time t, and the vertical axis represents the cumulative flow rate. FIG. 4 (b) is an explanatory view when Q is taken, and FIG.
It is explanatory drawing when the flow rate Q is plotted on the vertical axis.

In FIG. 4, 41 is a measured value of the cumulative load flow rate, 42 is an amount obtained by adding an initial storage margin amount (= storage capacity−initial storage amount 40) to the cumulative pump discharge flow rate, 44 is a target storage amount, and 45 is a cumulative load. The predicted flow rate, 46 is the switching number of operating units, 47 is the pump discharge flow rate, 48 is the predicted load flow rate, and 49 is the operating unit switching time.

The basic idea of the present invention is that the pump operation schedule (dotted lines 47, 42, and 46) based on the predicted value of inflow load (dotted lines 48, 45) is first used in the same manner as the conventional method. ●)). Next, unlike the conventional method, among the operation schedules determined in this way, the information about the switching time (the one corresponding to the ● in 49) is ignored, and only the information about what kind of pump combination is changed and in what order is used. To use.

On the contrary, the combination of pumps determined in this way and the order of their use are given as known information, and the reservoir is spilled or emptied based on the new predicted value of flow rate load (solid line 48, 45). The switching time is decided every moment so as not to turn it off (the solid line of 47 and 42 and the circle of 46).

Here, if the new predicted value and the first predicted value are significantly different and the schedule cannot be obtained successfully by using the initially determined pump combination and the order of use thereof, the conventional method is used again. Redetermine the driving schedule.

Further, when the pump is operated according to the operation schedule thus determined and the measured value of the water level exceeds the preset dangerous water level, the conventional feedback control is performed and the safe water level is restored.

By using the above method, the following is possible.

(1) Even if the predicted value of flow rate has an error and the predicted value is corrected every moment, the operation schedule can be corresponded every moment.

(2) In the case of the above (1), the operation schedule can be performed while keeping the number of switchings small.

(3) In the case of the above (1), since it is only necessary to re-determine the switching time instead of re-determining all the operation schedules, the calculation time is short and it is suitable for online control.

Hereinafter, the present invention will be described in detail with reference to examples.

As shown in FIG. 5, a feedforward operation control device for a plurality of devices according to the present invention has a load prediction unit 1, a driving schedule determination unit 2, a switching time correction determination unit 3, a device controller 4, and a re-prediction unit. It comprises a discriminator 5 and a detector 6. The switching time correction determination unit 3 includes an internal convex point search unit 31, a switching time correction unit 32, and a driving schedule addition calculation determination unit 33. The detector 6 detects the flow rate and the water level state 210 from the process 7, and the device controller 4 transmits a start / stop signal 211 to the device 8 such as a pump.

In FIG. 5, solid arrows indicate the flow of operation of the device according to the present invention, and broken arrows indicate the flow of information. The operation of the device according to the invention will be described below.

In the load predicting unit 1, for example, JP-A-55-5841 is used.
According to the method disclosed in Japanese Patent Publication No. 2, the inflow is predicted and its value 20
1, 207 are sent to the driving schedule determining unit 2 and the re-prediction determining unit 5, respectively. The operation schedule determining unit 2 determines the schedule including the number of operating vehicles switching time and the number of operating vehicles, for example, according to the method disclosed in Japanese Patent Laid-Open No. 52-78102, and the switching time correction determining unit 3 as the information 202.
In addition to sending to the internal convex point searching unit 31 in, the predicted value of the water level when driving on the determined schedule road is obtained and sent to the re-prediction determining unit 5 as information 208. In the re-prediction determination unit 5, the information 209 of the measured value regarding the inflow amount of the process and the state of the water level sent from the detector 6, the predicted value 207 of the inflow amount sent from the load prediction unit 1 and the operation schedule determination unit 2 From the sent water level predicted value 208,
The difference between the measured value and the predicted value is obtained, and it is discriminated from time to time whether the difference is larger than a predetermined value. If the difference becomes large, control is transferred to the load prediction unit 1 to re-predict the load. Let In the case of re-prediction, the load prediction unit 1 sends the re-prediction value 206 of the inflow amount directly to the internal convex point search unit 31 of the switching time correction determination unit 3.

When the re-prediction value 206 is input, the switching time correction determination unit 3 does not empty or overflow the pond even with respect to the re-prediction value.
Of 02, the operating unit switching time is corrected.

Specifically, first, in the internal convex point search unit 31, a convex curve is formed inside the region between the temporal cumulative curve of the re-prediction value 206 of the load and the parallel translation curve of the pond storage capacity. A point is searched and information 203 indicating the point is sent to the switching time correction unit 32. The search method is to find the point where the increasing rate of the gradient becomes negative for the temporal cumulative curve and the point where the increasing rate of the gradient becomes positive for the curve obtained by translating the temporal cumulative curve by the pond storage capacity. by.

Next, the control shifts to the switching time correction unit 32, in which the intersection point of the temporal cumulative curve of the inflow amount re-estimated value 206 and the pump discharge amount cumulative curve determined corresponding to the first inflow amount predicted value 201 is first intersected. Is different from the intersection point (that is, the operation number switching time) determined corresponding to the first predicted inflow amount 201, and the discharge after the pump operation number switching time, which is the first different time, is checked. The quantity accumulation curve (that is, the number of operating vehicles schedule-switching time) is corrected as follows.

As a discharge amount cumulative curve after the switching time, (1) has a slope corresponding to the discharge amount of the next number of pumps among the number of pumps determined corresponding to the first inflow amount predicted value, (2) (a) A straight line passing through the area internal convex point searched by the internal convex point search unit 31, or (b) a cumulative curve of the discharge amount cumulative curve and the load re-prediction value before switching, or a parallel movement of the cumulative curve for the pond storage capacity. Of the straight line that passes through the intersection with the cumulative accumulation curve, or (c) the line that passes through the points on the cumulative discharge amount curve at the current time, (3) the intersection with the cumulative discharge amount curve that corresponds to the first predicted value. Search for a straight line after the current time, and (4) a straight line that does not intersect with the upper and lower limit cumulative curves created from the re-estimation values for the longest time that is longer than the given time.

Here, if the slope adopted in (5) and (1) intersects with the upper and lower limit cumulative curves within the given time of (4), the number of pumps that should come next in (1) The gradient corresponding to the discharge amount of is adopted.

(6) The intersection of the straight line searched in this way and the discharge amount cumulative curve corresponding to the first predicted value is the new unit switching time, but at that switching time the pumps that were operating up to that point were switched. If the operating time of is less than the given time of (4), select a straight line that does not intersect the second longest upper and lower limit cumulative curve in (4).

However, even if (7) the switching time is earlier than the operation start time of the pump that has been operating up to that time, the condition (3) (being after the current time) may be satisfied.

(8) Repeat the above operation until the target time is reached.

The switching time correction unit 32 outputs the driving schedule 204 determined above and sends it to the next driving schedule additional calculation determination unit 33.

The operation schedule addition calculation determination unit 33 checks whether or not the operation schedule 204 obtained by the switching time correction unit 32 has also exhausted the gradient of the discharge amount cumulative curve with respect to the first predicted value before reaching the target time, If it has been used up, the control is transferred to the driving schedule determining unit 2 so that the driving schedule determination is newly calculated from that point. If the schedule is still not determined, the control is transferred to the drive schedule determination unit 2 again so as to redetermine the drive schedule from the current time.

When all the driving schedules are determined, the information 205 is passed to the device controller 4.

The device controller 4 receives the driving schedule 205,
Signal 211 for supplying (starting) or stopping energy to the device 8
To send.

Although the description so far has been given by taking the drainage system having the pond on the suction side of the pump as an example, the present invention aims to reduce the operation switching frequency of a plurality of devices in the system having the buffer, save energy, and the like. It can be used for operation control of the online correction type feedforward device. For example, it can be used for controlling the number of blowers having an air tank, controlling a compressor of a refrigerator, and the like.

As described above, according to the present invention, the following effects can be obtained.

(1) Even if there is an error in the predicted value of the inflow load, if the error exceeds the specified value, it is possible to change the pump operation schedule by re-estimating, and it is possible to perform optimal pump operation. it can.

(2) Rather than re-determining all the operation schedules with load re-estimation, the combination of the number of pumps and the order in which they are used among the schedules determined based on the first predicted value are used as they are, and the switching time Since it adopts the method of modifying and changing only, the calculation time is short and it can be used for online control.

[Brief description of drawings]

FIG. 1 is a model diagram of a drainage system, FIG. 2 is an explanatory diagram of a method for determining a pump operation schedule, FIG. 3 is an explanatory diagram of a relationship between a combination of operating pumps and a cumulative discharge amount, and FIG. 4 is an explanation of the principle of the present invention. FIG. 5 and FIG. 5 are block configuration diagrams of an embodiment of the present invention. 3 ... Switching time correction determining unit.

Front page continuation (72) Inventor Fumito Shinomiya 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Omika Plant (56) Reference JP-A-52-78102 (JP, A) JP-A-SHO 53-143002 (JP, A) JP-A 52-20402 (JP, A) JP-A 55-58412 (JP, A) JP-A 54-98040 (JP, A) JP-A 55-143614 (JP, A) JP-A-57-25197 (JP, A) JP-A-52-88801 (JP, A)

Claims (1)

[Claims] 1. A pump operation control method for preventing a reservoir from overflowing due to an inflow of a certain amount of water, which predicts an inflow flow rate of a load, and based on the predicted load value, the operating unit switching time and the operating unit number. A sub-optimal operating schedule consisting of the following, and when the difference between the predicted flow rate and water level and the actual measured flow rate and water level when the pump is operated according to the determined operating schedule becomes large, Forecasting is performed, and a lower limit load cumulative curve that is a temporal cumulative value of the load re-predicted value and an upper limit load cumulative curve obtained by moving it upward in parallel by the storage capacity of the pond are created, and based on the above-mentioned predicted load value. The structure of the sub-optimal operation schedule is set so that the pump discharge amount accumulation curve according to the determined sub-optimal operation schedule passes through without exceeding the upper and lower limit load accumulation curves. The correction of the operating unit switching time, which is an element, is performed by the following processing, that is, (a) searching for a point that is convex inside the upper and lower limit load cumulative curve, and (b) another component of the sub-optimal operating schedule having a slope. Which is equal to the discharge amount corresponding to the number of operating units, and the convex point, or the intersection of the discharge amount cumulative curve before switching and the upper and lower limit load cumulative curve, or the point on the discharge amount cumulative curve at the current time. Of the straight lines passing through the longest time, the intersection of the straight line that does not intersect with the upper and lower load accumulation curves and the pump discharge amount accumulation curve after the load re-estimation time is set as the new operating unit switching time, and the process (a ) And (b), if the discharge amount cumulative curve does not reach the target time through the upper and lower limit load cumulative curves without intersecting with the upper and lower limit load cumulative curves, it does not reach the target time. The feed-forward operation of a plurality of pumps, characterized in that the operation schedule for the entire time is determined by newly determining the operation schedule from the point Control method.