JPH058441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a water supply system that transports water from a reservoir to a plurality of reservoirs using pumps, and particularly relates to a flow rate distribution control method for the reservoirs.

[Background of the invention]

A conventional water distribution reservoir flow distribution control method, for example, as described in Japanese Patent Application Laid-Open No. 56-22112, when water is sent from a reservoir to a plurality of reservoirs, the inflow valves of each reservoir are cyclically controlled, and A method is known in which concentrated water supply is repeated repeatedly using a fixed speed water pump. Each reservoir serves as a buffer when supplying water to the load. For example, in the case of two reservoirs with load fluctuations as shown in Figure 2 a, the water level fluctuations in reservoirs 1 and 2 will be as shown in Figure 2 b and c. The inflow amounts to the water distribution reservoirs 1 and 2 are as shown in d and e in the figure, and the opening degrees of the inflow valves of the water distribution reservoirs 1 and 2 are as shown in the figure f and g.

The logic of this method is simple, as the inflow valve is controlled on and off for each reservoir to keep the water level within the allowable range. However, in order to control each water distribution reservoir, the valve opening degree must be turned on and off frequently, and depending on load fluctuations, rapid fluctuations in the amount of inflow to the water distribution reservoir occur. Therefore, unstable phenomena such as hunting in water level, flow rate, pressure, etc., and water hammer against the water pump are likely to occur. moreover,
There was no consideration given to the efficient operation of the full capacity of the reservoir, leading to problems such as increased pump operating costs.

[Purpose of the invention]

An object of the present invention is to overcome the problems of the prior art as described above, to perform stable inflow control by avoiding sudden fluctuations in the amount of inflow to each distribution reservoir by efficiently operating multiple distribution reservoirs, and to achieve stable operation. An object of the present invention is to provide a flow distribution control method for a water supply system that reduces costs.

[Summary of the invention]

The flow rate distribution control method for a water supply system according to the present invention controls water storage rates of a plurality of water distribution reservoirs having different capacities to be equal.

In other words, in a flow rate distribution control method for a water distribution system that distributes water from a reservoir to multiple reservoirs using water pumps and water pipes, the water level in each reservoir varies depending on the load and is detected at predetermined intervals. Calculate the amount of water stored between variable water levels for each distribution reservoir, calculate the average water storage rate from the storage amount and the known variable capacity of each distribution reservoir, and set the water storage rate of each distribution reservoir to the above average storage rate. It is characterized by controlling the inflow amount of each water distribution reservoir.

This enables accurate inflow control by making full use of the available capacity of each reservoir, and achieves stable flow distribution control.

Additionally, water pumps are operated when the average water storage rate falls outside a predetermined range, or when the amount of water delivered from the reservoir falls within the variable capacity of the entire reservoir for a known predicted load. It is characterized by controlling the number of units.

As a result, the number of pumps is controlled to the minimum necessary under conditions that cannot be controlled only by controlling the opening and closing of the inflow valve, so frequent switching of the number of pumps is eliminated, and operating costs can be reduced.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail.

In Fig. 1, 1 is a reservoir, for example a water purification plant, 2 is a group of water pumps, and the water sent from 2 is connected to three water pipes 10, 20...n0 arranged in parallel. sent to the water pond. The water distribution flow rate from each water distribution reservoir is sent to the demand end which is four load groups. 13, 23...n3 is an inflow control valve that adjusts the inflow into each water reservoir, and generally an electric valve is used.

Taking the water distribution reservoir 10 as an example, 11, 21, n
1 is a water level transmitter, and water distribution reservoirs 10, 20, n0
water level is measured and water level signals l ₁ , l ₂ , _lo are input to the arithmetic and control device 100 . In addition, the water flowing through the water pipe 3 branches at points 16, 26, and n6,
It flows into the water distribution reservoirs 10, 20, n0. 12,2
2, n2 is a flow rate transmitter, and water distribution reservoir 10, 2
By measuring the inflow flow rate of 0, n0, flow rate signals q ₁ , q ₂ ,
q _o is input to the arithmetic and control unit 100. Also 13,
23, n3 is a flow rate control valve, and water distribution reservoir 10, 2
0, n0)). The pressure transmitters 14, 24, n4 measure the primary side pressure and inlet pressure of the flow control valve, and the pressure transmitter 1
5, 5, n5 (secondary side pressure, outlet pressure) are measured, and pressure signals P ₁₁ , p ₁₂ , P ₂₁ , P ₂₂ , P _o1 ,
P _o2 is input to the control calculation device 100 . 20,
..., the same applies to the water distribution reservoir n0.

As mentioned above, the control calculation device 100 has 10 to
The water level measurement value of the water distribution reservoir of n0, the inflow flow rate measurement value, the primary side pressure of the flow rate control valve, and the secondary side pressure are input. Reference numeral 200 denotes a condition setting device, which has a function of setting and storing various setting values and constants, and is similar to a setting console in a computer system. The operating conditions of each water distribution reservoir are input here. Taking the water distribution reservoir 10 as an example, the upper limit value l _1H , l _2H , l _oH ), the lower limit value l _1L ,
l _2L , l _oL ), the bottom area of the distribution reservoir S ₁ , S ₂ , S _o ) and the predicted hourly runoff volume d ₁ ¹ , d ₁ ² ...d ₁ ²⁴ , ...d _o ¹ , d _o ²
...d _o ²⁴ ) is set. Water distribution reservoir 20~n0
The same applies to The control calculation device 100 is
From here, the operating conditions for each reservoir are input.

Based on this input information, the control arithmetic unit 100 sets targets for the flow rate control valves 13, 23, . Calculates and outputs the valve loss coefficient O _p1 *, O _p2 *...O _po corresponding to the opening degree. A valve controller 17 has a function of converting P _p1 * into a target valve opening and then controlling the position of the inflow control valve so that it becomes equal to the target opening.

300 is a pump number control calculation device which calculates a planned value of the number of pumps that will transport water commensurate with the predicted hourly inflow of each water distribution reservoir, outputs it to a pump number switching device 5, and switches the number of pumps in group 2. Control.

Next, the functions of the control calculation device 100 and the operation of the present invention will be described with reference to FIG.

Using the input information collectively shown at the left end of FIG. 3, the calculation units 111, 121...1n1,
10, 20... Find the variable capacity and water storage amount of the water distribution reservoir of n0. An example of the calculation unit 111 is as follows.

V ₁ = (l _1H − l _1L ) * S ₁ … (1) V ₁ ′ = (l ₁ − l _1L ) * S ₁ … (2) Here l _1H … upper limit of variable water level l _1L ...Lower limit value of variable water level S ₁ ...Base area of the water distribution reservoir l ₁ ...Water level of the water distribution reservoir v ₁ ...Variable capacity (capacity between variable water levels) v ₁ ′... Between variable water levels Similar calculations are performed in the calculation units 121, 131, . . . 1n1.

The calculation unit 101 performs the following calculations.

Calculate the average water storage rate r* of the n distribution reservoirs.

＊＝ _o 〓 ⁱ⁼¹ v _i ′／ _o 〓 ⁱ⁼¹ V _i …… (3) The water storage rate in the variable capacity of all water distribution reservoirs is r*
Correct the inflow amounts q ₁ , q ₂ ...q _o so that they are equal to .

The water storage rates r ₁ , r ₂ , and r _o of each reservoir are calculated using the following formula.

r ₁ = v ₁ ′/v ₁ r ₂ = v ₂ ′/v ₂ 〓 r _o = v _o ′/v _o …… (4) From equations (3) and (4), the corrected inflow amount q ₁ * ,q ₂ *……q _o
* is calculated using the following formula.

q ₁ *=q ₁ +(r*-r ₁ )・v ₁ /t q ₂ *=q ₂ +(r*-r ₂ )・v ₂ /t 〓 q _o *=q _o + (r*- r _o )·vo _/ t... (5) Here, t is the cycle for controlling the flow rate. In other words, the current flow rate is increased or decreased so that the water storage rates of each distribution reservoir become equal during time t.

The corrected inflow amount q ₁ *, q ₂ obtained by the calculation unit 101
*...q _o * is the primary side pressure of the flow control valve P ₁₁ , P ₂₁ ...
...P _o1 , secondary side pressure P ₁₂ , P ₂₂ ... together with P _o2, the target opening calculation section 112, 122...1n2 of the flow rate control valve
is input.

The operation will be explained using the calculation unit 112 as an example.

Flow rate adjustment is often performed using an electric valve, and the relationship between flow rate/pressure and valve loss coefficient is expressed by the following equation.

(P ₁₁ - P ₁₂ ) = 1/2g (4/πD ² ) ²・O _p1・q ₁ ² ...(6) where P ₁₁ : Valve primary pressure P ₁₂ : Valve secondary pressure g : Power acceleration π : Circumference D : Valve inner diameter O _p1 : Valve loss coefficient q ₁ : Water flow rate (inflow amount of water distribution reservoir 10) 1/2g (4/πD ² ) The term ² is a constant that differs for each valve. Therefore, if this is K ₁ , equation (6) is transformed as O _p1 = P ₁₁ − P ₁₂ /K ₁ ·q ₁ ² …… (7). O _p1 is called a loss coefficient and is a variable that represents the amount of valve operation and corresponds to the valve opening degree (hereinafter referred to as ``opening degree''). From equation (7), the target opening degree O _p1 * of the valve is determined as shown in equation (8).
Note that (P ₁₁ −P ₁₂ ) can be considered to be approximately constant in a range where the flow rate fluctuation is small.

O _p1 *=P ₁ −P ₁₂ /K ₁・q ₂ * ² ... (8) Similar calculations are performed in the calculation sections 122, 132...1n2, and the flow rate control valves 13, 23...n
3 target opening degrees O _p1 *, O _p2 *...O _po * are output. The calculated target opening degrees are sent to the valve controllers 17, 27, . In addition, in the above, the water storage rate average value r
* is based on equation (3), but each water storage rate r ₁ and r ₂ in equation (4)
...It may be based on the average value of r _o .

Next, referring to FIG. 4, the operation of the pump number calculating device 300 combined with the above-described flow rate control will be explained.

The input information collectively shown at the left end of FIG. 4 is input from the condition setting device 200. Furthermore, d _i
¹ , d _i ² . . . d _i ²⁴ (i=1 to n) is the predicted outflow amount for each hour for 24 hours from the i-th distribution reservoir. Arithmetic unit 3
In step 01, a predicted outflow cumulative value curve for 24 hours a day is calculated (corresponding to curve A in the diagram of block 302).
The predicted runoff integrated value curve A of block 302 is input to the calculation unit 303 together with the operating conditions of each water distribution reservoir, and the following calculations are performed.

Similarly to equation (1), the variable capacity of each water reservoir v ₁ ,
v ₂ ...V _o is calculated, and these are further added to calculate the total variable capacity V of all water distribution reservoirs.

V= _o 〓 ⁱ⁼¹ v ₁ ... (9) Next, a curve is calculated by adding the total possible fluctuation amount V to the predicted outflow accumulation curve A (corresponding to curve B in the diagram of block 304). Curves A and B are input to the calculation unit 305, and the number of pumps is planned so that the integrated water flow amount from pump group 3 (corresponding to curve C in block 306) falls within curves A and B, and the planned number of pumps P is calculated. _st
Output as *. Planned value of the number of pumps in operation P _st
* is sent to the pump number switching device 5 shown in FIG. 1, and controls the pump group 2.

Figures 5a to 5c show simulation results in which flow rate control was performed for two water distribution reservoirs according to this embodiment. Figure a shows the amount of load fluctuation representing the amount of outflow from the distribution reservoir, the amount of water sent from the pump, and the amount of water sent from the reservoirs 1 and 2.
shows the change in inflow amount. b shows the change in valve opening when the inflow of the water distribution reservoirs 1 and 2 is controlled by the inflow control valve. c indicates a change in the water storage rate of the water distribution reservoirs 1 and 2.

By controlling the inflow using valves, it is possible to maintain the same water storage rate in both reservoirs even when the load fluctuates, and to control the total amount of flow flowing into both reservoirs to be constant. It can also be seen that the valve operation is gentle and stable control can be achieved.

The above is an embodiment of the present invention, and as a result of controlling both inlet control valves using simple logic so that the water storage rate of multiple distribution reservoirs is constant, the fluctuation of each distribution reservoir is possible. It is now possible to use capacity in bulk. For this reason, as if 1
It can be treated like a single water distribution reservoir, resulting in the following effects:

(1) Stable reservoir operation is possible even in the face of disturbances such as demand fluctuations.

(2) There will be no imbalance in water storage rates between distribution reservoirs, allowing for fair and safe operation.

(3) When planning pump operations, the variable capacity of all distribution reservoirs can be fully utilized. In addition, since the predicted runoff volume cumulative curve is planned by summing the predicted runoff volumes of all water distribution reservoirs, the curve becomes a gentle curve that absorbs the fluctuations of each water distribution reservoir. Therefore, a stable operation plan can be established over a long period of time with a small number of changes in the number of vehicles.

In the above example, the number of pumps to be operated was planned based on the predicted outflow of the distribution reservoir, but in another example, the water storage rate (r* in Figure 3) of multiple distribution reservoirs was monitored and this was determined. Predetermined specified values r _nax , r _MIN
In comparison, if r* exceeds r _MAX , reduce the number of pumps, and conversely, if it falls below r _MIN ,
There is an operation method that increases the number of pumps.

According to this embodiment, simulation results are shown when load fluctuations similar to those shown in FIG. 2 occur. 6a to 6c show conventional water level constant control, and FIGS. 7a to 7c show water storage rate equalization control according to the present invention.

Figure 6 shows an example of three reservoirs, and it can be seen that in order to maintain each reservoir at a constant water level (constant water level control), the reservoir valve opening varies significantly. On the other hand, Figure 7 shows the case where the water storage rate is controlled to be equal in each pond.
Although the fluctuations in the valve opening degree (c in the figure) and the amount of inflow into the reservoir (lower part in the figure a) are small, the fluctuations in the water level in the reservoir are large, as shown in b in the figure. However, even in this case, the water storage rate of each pond changes in the same way (almost the same change as in Figure 5 c), and the load reaches its peak at time t _k , so operation continues without changing the number of pumps. You can. The range between the upper and lower limits of the water level is a range in which water level fluctuations are originally allowed, and this is effectively utilized to significantly reduce the number of valve changes and the number of pump changes.

According to the present invention, constant relative water storage rate control of a water distribution reservoir at available capacity can be realized using simple logic. This has made it possible to operate multiple water distribution reservoirs as if they were one reservoir. Since the buffer capacity of multiple water distribution reservoirs can be utilized to the maximum, (1) costs can be reduced through continuous stable operation of water pumps;

(2) The distribution reservoir can be operated efficiently and stably.

That is, although the capacity of water distribution reservoirs varies, the inlet valves and piping of small reservoirs are usually small-scale. According to the method of the present invention, since the flow rate distribution to the distribution reservoir is in accordance with the capacity of the distribution reservoir, the flow rate control width is small, and therefore the amount of operation of each control valve can be reduced, resulting in stable flow rate without hunting etc. It has the great advantage of being controllable.

〔Effect of the invention〕

According to the present invention, it is possible to effectively utilize the capacity of a plurality of water distribution reservoirs and reduce the number of valve opening operations and the number of times the number of pumps is changed, thereby enabling stable and economical distribution flow control.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the device of the present invention, Fig. 2 is an explanatory diagram of a conventional example, Fig. 3 is an arithmetic logic block diagram of the control calculation device that forms the core of the device of the present invention, and Fig. 4 is a calculation for the number of pumps. An example of the calculation logic of the device, Figure 5 shows simulation results when the device of the present invention is applied to two distribution reservoirs, and Figures 6 a to c show the conventional constant water level control when applied to three distribution reservoirs. Simulation Results: Figures 7a to 7c show simulation results of the water storage rate control of the present invention in the same pattern as in Figure 6. 1...Reservoir, 2...Pump(s), 3...
Water transmission pipe, 4... Demand end, 5... Pump number switching device, 10, 20... n0... Water distribution reservoir, 11, 2
1, n1... Water level transmitter, 12, 22, n2...
Flow rate transmitter, 14, 24, n4...Primary side pressure transmitter, 13, 23, n3...Flow rate control valve, 15,
25, n5...Secondary side pressure thickness depth transmitter, 16,2
6, n6... Pipe branch point, 17, 27, n7...
Valve controller, 100... Control calculation device, 200...
Condition setting device, 300... Pump number calculation device.

Claims (1)

[Claims] 1. In a flow rate distribution control method for a water distribution system that distributes water from a reservoir to a plurality of distribution reservoirs using a water transmission pump and water pipes, each distribution reservoir varies depending on the load and is detected at predetermined intervals. The amount of water stored between the variable water levels for each distribution reservoir is calculated from the water level, and the average water storage rate is calculated from the amount of stored water and the known variable capacity of each distribution reservoir, and the storage rate of each distribution reservoir is calculated from the average water storage rate. 1. A flow distribution control method for a water transmission system, characterized by controlling the inflow amount of each water distribution reservoir so that 2. Claims characterized in that the average water storage rate is the average value of the water storage rates of each distribution reservoir, which is determined by the ratio of the storage amount between the variable water levels of each distribution reservoir and the variable capacity. 2. The method for controlling flow rate distribution of a water supply system according to item 1. 3. The water transmission system according to claim 1, wherein the predetermined water storage rate is determined by the ratio of the total amount of water stored between the variable water levels of each water distribution reservoir to the total sum of the variable capacity. System flow distribution control method. 4. In a flow distribution control method for a water distribution system that distributes water from a reservoir to multiple distribution reservoirs using water transmission pipes and multiple water pumps, distribution is based on the water level of each distribution reservoir that fluctuates depending on the load and is detected at predetermined intervals. The amount of water stored between the variable water levels for each water reservoir is calculated, and the average water storage rate is calculated from the amount of stored water and the known variable capacity of each distribution reservoir. A flow distribution control method for a water distribution system, characterized in that the inflow of a water distribution reservoir is controlled, and when the average water storage rate falls outside a predetermined range, the number of operating water pumps is controlled to switch. .