JPS6132684B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used in pump equipment for water supply, sewerage, irrigation, drainage, etc. This invention relates to a method for controlling the number of operating pumps.

In order to simplify the explanation below, an example of an irrigation pump facility will be explained.

Conventionally, when sending irrigation water to a water use end such as a field, the water is first sent to a reservoir using a pump, and then the water is sent to the use end. At this time, the problem is the control of the pump. In particular, when there are multiple pumps, it is an important problem to control these pumps economically and with a simple device to adjust the amount of water pumped.

As conventional methods for solving this problem, there are the following two methods.

One method is based on the reservoir water level, which controls the flow rate by increasing or decreasing the number of pumps in operation according to the water level. For example, as shown in FIG. 1, when switching the number of pumps, the pumps are started and stopped at the upper and lower water level set values set for the number of pumps. In other words, in this example where there are 3 pumps P (n=3), 2
00201 and 202 are pump stop water levels of No. 1, No. 2, and No. 3 pumps, 200', 201', and 202' are pump start water levels of No. 1, No. 2, and No. 3 pumps, and so on. Note that 205 is a water level gauge, 206 is a pump, and 207 is a pump well.

Other methods minimize the number of switching times,
This is a program control method in which the number of pumps is increased or decreased according to a pre-predicted load flow curve, as shown in FIG. 2, with the aim of improving operational efficiency. With this method, the discrepancy between the amount of water pumped under program control and the actual load flow rate can be absorbed by the capacity of the reservoir.

From a minor point of view, these two systems are devised to reduce the number of switching operations while making effective use of the capacity of the reservoir, but when viewed from the perspective of the water system as a whole, they have the disadvantage that they cannot necessarily be called optimal operation. .

In order to eliminate this drawback, the applicant previously proposed a method for determining the optimal pump operation method based on the cumulative predicted flow rate of the load. There is a "control method" (Japanese Patent Application No. 1983-95867).

This control method has the following characteristics.

(a) Dynamic programming (hereinafter referred to as "pump operation curve") to determine the optimal pumping station water volume cumulative value curve (hereinafter referred to as pump operation curve) that passes between the predicted load volume cumulative value curve and the curve obtained by adding the reservoir capacity to the predicted load volume cumulative value curve.
(abbreviated as DP)).

(b) The stages of DP are time steps.

(c) Regarding the type of change in the number of operating units when moving operation from one time step to the next time step,
Benartei is given according to the purpose and is used as the evaluation standard for DP.

By using this method, it is possible to reliably obtain the optimum pump operating method according to the purpose. but,
Since time steps are used as stages, if the time increments are made small, a large storage capacity is required, resulting in a large or expensive computing device.

The storage capacity X required for this dynamic programming method with ^penalty (PDP method) is: When calculating 24 hours in minutes, it becomes X≧28.8×10 ³ [pieces].

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a pump control device that is simple and allows economical operation of a plurality of pumps.

In order to achieve the above object, the present invention allows the pump operation curve to pass between the predicted load amount cumulative value curve and the curve obtained by adding the reservoir capacity to this curve, and before the operation curve collides with both of the above curves, the slope The rule is to change the number of pumps (switch the number of pumps), that is, to provide a switching point midway, and moreover, multiple pumps are operated so as to optimize the pump operation evaluation function.

Hereinafter, the principle of the present invention will be explained in detail with reference to the drawings.

First, a model of the target water system is shown in Figure 3.
This is a typical pattern that accounts for more than 80% of water system models. In order to meet the water demand (load) after the reservoir, water is pumped to the reservoir once, and can be applied to water supply, sewerage, agricultural irrigation, etc.

The purpose here is to operate the pump in this water system so as to optimize the evaluation function within a range that does not overflow the reservoir and does not result in insufficient supply for the load.

If you consider this diagrammatically, it will look like Figure 4. Curve 1 is a cumulative value curve of predicted loads after the reservoir, and curve 2 is a curve obtained by adding reservoir capacity to curve 1. The pump pumping amount cumulative value curve (pump operation curve) 3 must be operated optimally within a range that does not fall outside the range between curves 1 and 2.
This is because if curve 3 falls below curve 1, the load cannot be met, and if it falls above curve 2, the pond will overflow.

Here, "optimal" refers to minimizing power consumption (operating cost), etc.

At this time, the slope of the pump operation curve 3 is determined by the amount of pumped water per unit time when each number of pumps is operated (FIG. 5). That is, since the number of vehicles in operation is switched every time the slope changes, when operating with the minimum number of switching, the change point of the slope of curve 3 must be minimized.

Organizing the above, for example, the problem can be set as follows.

"By minimizing the number of slope changes,
The optimum pump operation curve 3 is passed through without going beyond the curves 1 and 2. ” An approximate answer to the above problem is shown below.

First, a predicted load cumulative value curve 1 and a curve 2 obtained by adding the reservoir capacity to the curve 1 are curved or linearly approximated in an arbitrary section. (Curves 21 and 2 in Figure 6
2) At this time, if there are any of the following limiting conditions, 21 and 22 should be raised or lowered by that amount.

Keep the pond water level above a certain level (→ Raise curve 21)
Consider the error in the predicted load (→Curves 21 and 22)
The route of the pump operation curve is searched between the curves 21 and 22 thus determined according to the following rules.

Figure 7 shows the flowchart. The symbols in parentheses in the figure correspond to the symbols below.

(A) First, start from the starting point (value of initial water storage amount) 5 and find the route when each number of pumps is operated until it intersects curves 21 and 22. In this figure, when 0 units are in operation, 5→6, and when 1 unit is in operation, 5→
7. When operating two machines, the number becomes 5 → 8.

(B) Next, the number of operating vehicles is switched using points on straight lines 5-6 and 5-7 as intermediate switching points so that operation can be performed without switching the number of operating vehicles for a long time. 33,3 in the figure
4, etc., but to find this intermediate switching point, for example, the following (i) or (ii) can be used.

(i) Find a route between curves 21 and 22 that can be operated for a long time with each number of vehicles, find the intersections of this route with straight lines 5-6 and 5-7, and use these as intermediate switching points. In this case, curves 21 and 22
Straight lines 30, 32 that are tangent to
and the straight line 31 between them is a route that can be driven for a long time.

(ii) Divide the first pump operation line 5-6 or 5-7 in certain time steps, extend the route for each number of pumps from each increment point, and choose one that can be operated for a long time. .

(C) If the pump operation curve thus obtained reaches the final time, the pump operation curve is now complete. If it is not reached, the second pump operation straight line can be regarded as the first pump operation straight line, a switching point can be created midway as before, the number of pumps can be changed, and the driving route can be further searched.

(D) For the last time, you may consider searching the route backwards from the last time. At this time, if there is a target water storage amount, the route for each vehicle operation can be found in the opposite direction based on that value. In the diagram,
11 is the target water storage amount value, and when 0 units are operating, 11→
12, when driving one car, 11 → 13, etc. is the route explored this time. In this way, the intersections of straight lines 11-12, 12-13 and the route searched from the starting point (for example, 35, 36
etc), it is possible to complete the pump operation curve to finally reach the target water storage volume.

(E) The route of the completed driving curve is, for example, 5→33→39, 5→33→36 in Figure 6.
→11, 5 → 34 → 37 → 11 etc. All the routes explored in this way are memorized, and eventually from among these routes,
Determine the optimal operating curve using the evaluation function.

For example, if the evaluation function is to minimize power consumption, the power consumption of each memorized route is calculated from the operation duration and the number of vehicles in operation, and the minimum one is selected from among them. be.

With this determination method, since the operation time can be set to any length, when the maximum number of switching times is small, the DP
The storage capacity required for calculations can be significantly reduced.

The ^storage capacity X' required for this calculation is:
~about 6 When N = 10 units and f = 3 times, X'< 5 to 6 x 10 ³ [pieces].

Therefore, in this example, it can be seen that the storage capacity according to the present invention is about 1/6 compared to the storage capacity X28.8×10 ³ when DP is used.

Hereinafter, the present invention will be explained in detail with reference to Examples (FIG. 8). The time period for planning operations (for example, 24
The predicted load amount after the reservoir (time) is externally input to the predicted load input device 101. The predicted load curve approximation device 102 divides this into arbitrary sections and approximates the curve. Next, the amount of pumped water for each number of pumps is given to the pump characteristic input device 103. Further, the initial water storage amount/restriction conditions (target water storage amount, constant minimum water storage amount, maximum number of switching times, etc.) are input into the initial condition input device 104 and the restriction condition input device 105, respectively.

Based on this information, first, curve 2 in Figure 6
1 and 22, and then follow the rules described so far to find a midway switching point that requires fewer switchings of the number of pumps in operation. Search for all routes. This is done by the driving route search device 106. Thereafter, the optimal operating number determining device 107 selects the route that optimizes the evaluation function from among the selectable routes, and determines the number of pumps operating at each time. It will be done.

The results are output to the display device 109, and the pump start command device 110 issues an operation command to each pump 111.

In the above embodiment, the optimal route is searched from the starting point, but it goes without saying that the search may be performed from the final point.

As explained above, the present invention is a method of determining the quasi-optimal number of pumps to be operated and controlling the pumps, and is characterized in that the storage capacity required for the calculation is reduced, so that the device can be made smaller. Furthermore, the principle of this algorithm for determining the number of devices is simple and easy to understand, and even if the device stops working during the calculation, it can be replaced by a human.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of pump number control based on reservoir water level, Figure 2 is an explanatory diagram of pump number control using a program, Figure 3 is a water system model diagram, and Figure 4 is a pump operation curve and predicted cumulative load flow rate. Figure 5, a diagram showing the relationship between the value curves, shows the number of pumps in operation and
FIG. 6 is an explanatory diagram of how to search for the route of the operating curve; FIG. 7 is a flowchart of searching for the route of the operating curve; and FIG. 8 is a diagram of the pump number control device.

Claims (1)

[Claims] 1. In a predictive control method for controlling the amount of fluid stored in a fluid storage means by the amount of inflow flowing into the storage means by switching the number of operating pumps of a plurality of pumps, (a) the capacity of the storage means and the initial storage amount; (b) a lower limit prediction curve signal obtained from the load amount cumulative prediction signal; and (b) a lower limit prediction curve signal obtained from the load amount cumulative prediction signal. (c) Based on the initial storage amount signal, pass between the upper and lower current prediction curves and start from a point representing the initial storage amount. An intermediate switching point is the intersection of the individual operation route when each number of pumps is operated until it intersects with the upper and lower limit predicted curves, and the individual operation route and the operation route that does not require switching the number of pumps for a predetermined period of time or more. (d) select one driving route from among the driving routes based on a predetermined evaluation function; (e) A predictive control method, characterized in that the fluid storage amount is controlled based on a signal corresponding to the selected driving route.