EP3048305B1 - Reduction of the energy consumption of a variable speed water pump taking into account the current system load - Google Patents

Description

The invention relates to a method for reducing the energy consumption of a feed pump according to the preamble of claim 1 and a system for conveying water from at least one well into a pipe network according to the preamble of claim 10.

Processes and plants of the type mentioned are mainly used in water works to promote drinking water wells in a water supply network, but can also be used in industrial plants that require large amounts of fresh water.

The feed pumps are usually electric centrifugal pumps, which are used as submersible pumps within the well. The feed pumps are located either directly on the mains or are equipped with a frequency converter with which the drive speed of the feed pump is regulated according to a set flow rate.

While energy consumption can not be influenced at all on feed pumps located directly at the mains, in feed pumps with frequency converters it is usually only a secondary factor in the control or regulation of the pumps.

However, since feed pumps for conveying water from wells have a large energy requirement, a reduction in energy consumption through consumption-optimized operation of the feed pumps offers a considerable energy saving potential.

The EP 2 610 693 A1 discloses a method of optimizing the energy efficiency of a pumping system having at least one pump controlling the liquid level of a reservoir. The method includes two stages, an identification stage and an energy optimization stage. In the first stage, the pump is operated with a series of flow conditions to determine data points, on the basis of which energy efficiency optimization properties are determined. In the following second Stage, an actual geodetic altitude is determined and on the basis of it and the optimization properties, an energy minimization value for the pump control is selected.

The EP 2 944 821 A1 discloses a method for energy-optimized speed control of a pump set. Depending on a given system characteristic curve is calculated by evaluating a mathematical function that assigns a target flow rate required for volume flow energy consumption of the pump unit, the one speed at which this volume flow specific energy consumption is minimal, and then operated the pump unit at this speed.

From the JP S54 122401 A is a highly efficient control for dewatering pumps is known in which the current head is calculated and these corresponding analog signals are placed in a functional operator in which a maximum efficiency curve is stored. The operator then calculates the pump speed based on the current delivery head for maximum efficiency operation.

The EP 0 150 068 A2 discloses a method and apparatus for controlling various operating parameters of pumps. The control is based on characteristic curves, for the description of which the speed and the power requirement are used as electrical measured variables.

Proceeding from this, the present invention seeks to improve a method and a system of the type mentioned in that the feed pump works as close to or at its lowest energy operating point.

This object is achieved in the method according to the invention by the method steps of claim 1 and in the inventive system by the features of claim 10.

The solution according to the invention makes it possible, even in complex wells, to determine the operating point of each feed pump individually and independently of the other feed pumps at a given time energetically most favorable operating point and then this operating point by changing the input speed of the respective Adjust pump to minimize the energy consumption of each pump separately.

For this it is only necessary to determine for each pump, the lowering of the water level in the well and the pressure and the delivery or flow rate at the output of the pump, the latter being needed to control the feed pump and to verify the calculation.

The feed pump is preferably an electric feed pump equipped with a frequency converter whose drive speed is controlled or regulated by the frequency converter by changing or adjusting the frequency of the alternating current applied to the drive motor of the feed pump and thus the drive speed of the feed pump. In this case, the target flow rate of the lowest energy operating point is transmitted to the control or regulating unit, which compares the target flow rate with a measured actual flow rate and generates a control value for the frequency from the difference of the two flow rates. The frequency converter then changes the frequency of the alternating current until the actual flow rate corresponds to the set flow rate.

1. 1) Die Durchflussmenge Q1 im Betriebspunkt der Förderpumpe mit dem geringsten spezifischen Leistungs- oder Energiebedarf ist identisch mit der Durchflussmenge Q2 im berechneten Schnittpunkt der Pumpenwirkungsgradkennlinie mit hohem Wirkungsgrad und der dynamischen Anlagenkennlinie. In diesem Fall stellt diese identische Durchflussmenge die Soll-Durchflussmenge dar, an welche die Ist-Durchflussmenge der Förderpumpe durch Veränderung von deren Antriebsdrehzahl herangeführt wird.
2. 2) Die Durchflussmenge Q1 im Betriebspunkt der Förderpumpe mit dem geringsten spezifischen Leistungs- oder Energiebedarf ist größer als die Durchflussmenge Q2 im berechneten Schnittpunkt der Pumpenwirkungsgradkennlinie mit hohem Wirkungsgrad und der dynamischen Anlagenkennlinie. In diesem Fall wird die Durchflussmenge im Betriebspunkt der Förderpumpe mit dem geringsten spezifischen Leistungs- oder Energiebedarf als Soll-Durchflussmenge gewählt, an welche die Ist-Durchflussmenge der Förderpumpe herangeführt wird, weil dann der spezifische Leistungs- oder Energiebedarf trotz der größeren Durchflussmenge Q1 geringer ist.
3. 3) Die Durchflussmenge Q1 im Betriebspunkt der Förderpumpe mit dem geringsten spezifischen Leistungs- oder Energiebedarf ist kleiner als die Durchflussmenge Q2 im berechneten Schnittpunkt einer Pumpenwirkungsgradkennlinie mit hohem Wirkungsgrad und der dynamischen Anlagenkennlinie. In diesem Fall wird wie folgt vorgegangen: Solange die Durchflussmenge Q1 erreicht wird, wird die Ist-Durchflussmenge der Förderpumpe an diese Durchflussmenge Q1 als Soll-Durchflussmenge herangeführt. Wenn hingegen die Durchflussmenge Q1 von der Förderpumpe nicht mehr erreicht wird, dann wird die Ist-Durchflussmenge der Förderpumpe an die Durchflussmenge Q2 als Soll-Durchflussmenge herangeführt.

In principle, the energy consumption of the feed pump can already be considerably reduced with each of the two flow rates Q1 or Q2. In order to achieve a maximum reduction in energy consumption, however, according to the invention, both flow rates Q1 and Q2 are determined and compared with one another in order to obtain the respective optimum set flow rate. In this comparison basically three results are possible:

1. 1) The flow rate Q1 at the operating point of the feed pump with the lowest specific power or energy requirement is identical to the flow rate Q2 in the calculated intersection of the high efficiency pump efficiency curve and the dynamic system characteristic curve. In this case, this identical flow rate represents the target flow rate to which the actual flow rate of the feed pump is brought by changing the drive speed.
2. 2) The flow rate Q1 at the operating point of the feed pump with the lowest specific power or energy requirement is greater than the flow rate Q2 in the calculated intersection of the high efficiency pump efficiency curve and the dynamic system characteristic curve. In this case, the flow rate at the operating point of the feed pump with the lowest specific power or energy demand is selected as the target flow to which the actual flow rate of the feed pump is introduced, because then the specific power or energy demand is lower despite the larger flow Q1 ,
3. 3) The flow rate Q1 at the operating point of the feed pump with the lowest specific power or energy requirement is smaller than the flow rate Q2 at the calculated intersection of a high efficiency pump efficiency curve and the dynamic system characteristic. In this case, the procedure is as follows: As long as the flow rate Q1 is reached, the actual flow rate of the feed pump is introduced to this flow rate Q1 as a target flow rate. If, however, the flow rate Q1 is no longer reached by the feed pump, then the actual flow rate of the feed pump is brought to the flow rate Q2 as a target flow rate.

The operating point with the lowest specific power or energy requirement is that operating point of the feed pump in which a characteristic of the specific power or energy demand of the feed pump, preferably including the drive motor, a serving for controlling the feed pump and a power supply to Drive motor serving power line has a minimum. The flow rate that is delivered from the feed pump to the pipe or pipe network at the minimum of the specific power or energy demand is the flow Q1.

To determine the operating point with the lowest specific power or energy consumption of the feed pump, a characteristic curve is calculated which indicates the respective specific power or energy requirements of the feed pump as a function of the dynamic system characteristic curve, which in turn results from the geodetic height, the lowering of the water level in the well and line losses in the line or in the mains network is calculated. The minimum of this calculated characteristic represents the operating point with the lowest specific power or energy requirement.

Suitably, the characteristic curve of the specific power or energy demand of the feed pump, the pump efficiency curve and the dynamic system characteristic in a usual for marking feed pumps in wells diagram or coordinate system are shown in which the abscissa, the delivery or flow rate of the feed pump and on the ordinate Conveying height of the feed pump are applied, the former expediently in m ³ / h and the latter expediently in mWS (meter water column) is given.

In this diagram or coordinate system, the specific power or energy demand curve indicates the quantity or volume of power or energy required to extract one m ^{3 of} water from the well into the pipeline or pipeline, which is expediently expressed in kWh per m ³ . This curve is a curve that drops to the minimum with increasing flow in the manner of a relatively steep parabola and then rises again in the form of a relatively flat parabola.

The hereinafter also simplified referred to as efficiency curve pump efficiency curve is a "static" characteristic that indicates a certain efficiency of the feed pump as a function of the flow rate at the output of the feed pump and the delivery head. The pump efficiency curve is an increasing with increasing flow or flow rate and increasing head, the slope of which increases with increasing flow or flow rate and increasing head. The pump efficiency characteristic is preferably the efficiency curve for the maximum efficiency of the feed pump, which is usually in the range of about 70 to 80 percent in feed pumps for wells, such as centrifugal pumps, so that the most energetically favorable operating point can be set can. On both sides of the preferred efficiency curve are each pairs of efficiency characteristics, in which the pump operates with the same but lower efficiency. When an efficiency curve is used that is within a tolerance range of less than about 5 percent of the maximum efficiency efficiency curve, energy savings are usually still possible, but energy savings are then no longer optimal.

The dynamic system characteristic represents the resistance of the line or the pipeline network at a certain delivery or flow rate at the output of the feed pump. The dynamic system curve is also a curved, rising with increasing delivery or flow rate and increasing head, but is flatter than the pump efficiency curve and cut them.

The method according to the invention is preferably implemented by suitable software which is accessed by the control unit. As delivery pump performance characteristics are mostly provided by the suppliers of drawn pumps, which can not be directly processed by the software, the desired pump efficiency curve is converted from the corresponding drawn pump efficiency curve of the manufacturer to an electronic form obtained by software evaluate or process. For this purpose, according to a preferred embodiment of the invention from the pump efficiency curve of the manufacturer, preferably from the pump efficiency curve for the maximum efficiency, value pairs extracted and converted by means of a polynomial regression (polynomial regression) in a usable for the calculation and display electronic form. In a corresponding manner, other characteristics described below are brought into an electronic form that can be evaluated or processed by the software.

According to an advantageous embodiment of the invention, an overall efficiency curve is calculated to calculate the characteristic of the specific power or energy demand, indicating or reproducing the overall efficiency of the feed pump including the drive motor, the frequency converter and the power line as a function of the current system characteristic.

From this overall efficiency characteristic, the respective total power is calculated for each flow rate or for a plurality of incremental flow rate support points. In order to calculate the characteristic curve of the specific power or energy requirement, the respective total power only needs to be divided by the respectively associated flow rate in order to obtain the characteristic curve or a plurality of incremental interpolation points of the characteristic curve.

The calculation of the overall efficiency characteristic curve is preferably carried out in several steps, wherein in a first step pump characteristics for a number of other frequencies or speeds are derived from a pump characteristic curve usually provided by the manufacturer of the feed pump for the maximum frequency or speed. Preferably pump characteristics of the feed pump are determined for about five to ten different frequencies. These frequencies suitably include the maximum frequency applied by the frequency converter to the drive motor and a number of other frequencies at predetermined frequency intervals between the maximum frequency and the lowest frequency adjustable by the frequency at which the delivery pump is still allowed to operate. For a feed pump designed for a maximum frequency of 100 Hz, the maximum frequency is 100 Hz, while the lowest frequency is about 65 Hz.

In a second step, the intersection points of the current system characteristic curve are then calculated with the pump characteristic curves calculated in the first step, and the associated flow rate is determined for each of these intersection points.

In a third step, pump efficiency curves for a number of other frequencies or speeds are derived from a maximum efficiency or speed pump efficiency curve typically provided by the pump manufacturer, as previously described for the pump characteristic.

In a fourth step, the pump efficiency η at each frequency is determined from each of the flow rates determined in the second step and from the associated pump efficiency curve determined in the third step.

In a fifth step, from the obtained value pairs of flow rate and pump efficiency η, a pump efficiency curve becomes the current one Plant characteristic calculated. This calculation is preferably carried out by polynomial regression (polynomial regression).

From the pump efficiency curve, a current overall efficiency curve, which is also dependent on the system characteristic curve, is then calculated in a sixth step, into which efficiency characteristics of the electric drive motor, the frequency converter and, if appropriate, the power line are preferably included in addition to the pump efficiency characteristic. The calculation of the overall efficiency characteristic is carried out by multiplying the pump efficiency characteristic with the other efficiency characteristics to be considered.

The efficiency characteristics of the electric drive motor of the feed pump, the frequency converter and the power line for supplying power to the drive motor are usually available from the manufacturers of these components, so they need not be calculated.

The derived from the plant characteristic curve or dependent on the plant characteristic curves, such as the overall efficiency curve and the characteristic of the specific power or energy demand are constantly recalculated as the plant characteristic, preferably at short intervals and / or whenever the system characteristic changes ,
This is the case, for example, when the lowering of the water level in the well or line losses in the pipeline or pipeline network change.

The determination of the dynamic system characteristic from the geodetic height, the lowering of the water level in the well and the pipe losses in the pipe network is preferably carried out by the characteristics of these variables are electronically added in the above diagram or coordinate system by the software used.

The system characteristic curve is a "dynamic" characteristic, which includes the calculation of the constant geodetic height as well as a "dynamic" characteristic of the lowering of the water level in the well and a "dynamic" characteristic of the line losses in the line network. From the plant characteristic curve it can be deduced, which resistance the pipeline network of the pump at a certain delivery or Flow rate, which in turn can be calculated, which pressure is necessary to promote the specific flow or flow through the pipe network. From the current system characteristic curve it can be seen which resistance the pump's line network opposes with the current delivery or flow rate.

The geodetic height is the height difference between the highest point of the pipeline network, in which promotes the feed pump, and the water level in the well from which promotes the feed pump. The calm water level is the water level that sets in the well when no water is pumped out of the well. The geodetic height is a constant value that is independent of the flow or flow rate. In the above-mentioned diagram or coordinate system, the characteristic curve of the geodesic height, which is also referred to simply as the geodetic characteristic curve, is therefore a straight line running parallel to the abscissa.

The characteristic curve of the lowering of the water level in the well, also referred to below as a simplified lowering characteristic curve, is a "dynamic" characteristic which is determined for each well during normal or controlled operation of the feed pump by stepwise or preferably continuous measurements. The actual water level in the well is determined, for example, by means of a pressure gauge at the bottom of the well or at the level of the submersible pump and subtracted from the calm water level. The "dynamic" characteristic shows the course of the lowering of the water level as a function of the delivery or flow rate and the delivery height of the feed pump. In the above diagram or coordinate system, the lowering of the water level in the well is dependent on the flow or flow rate characteristic curve, which usually increases linearly with the flow or flow rate.

The line losses of the line network are derived for each pump from the prevailing at the output of the pump pressure, which is determined stepwise or preferably continuously during the normal or regular operation of the pump. In the following also simplified referred to as a line characteristic curve of the line losses is a "dynamic" curve, which is a curved curve in the above diagram or coordinate system, which increases with increasing delivery or flow rate and with increasing head, the slope increases.

In well systems with a single pump, the line losses of the network usually increase in square of the flow or flow rate. In order to facilitate the determination of the line losses from the pressure at the outlet of the feed pump, the pressure in the line is preferably measured before the first branching of the line network behind the feed pump. The height level, in which the pressure in the pipeline network is measured, flows into the calculation, if the pressure is not measured directly at the outlet of the feed pump, but for example at the wellhead, which is located at submersible pumps at a higher level than the output of the pump , The measurement of the pressure at the well head is preferred because the line has not yet branched there and because the measurement of the pressure there is easier than inside the well at the output of the feed pump.

While in previous methods for operating well systems with feed pumps of the lowering of the water level in the well "static" is determined by pumping tests and the line losses are taken from tables or diagrams, the characteristics of the lowering of the water level and the line losses of the pipe network in the inventive method " dynamically "determined by measuring quantities from which the instantaneous lowering of the water level and the instantaneous line losses of the pipeline network can be derived separately for each delivery pump.

In contrast to the known static determination of the lowering of the water level in the well by pumping tests, the dynamic determination of the subsidence according to the invention also makes it possible to detect a blockage of the well. Such a blockage, in which not enough water can flow into the wells, is usually noticeable in that during operation of the feed pump does not set after some time a constant flow water level at which the delivery or flow rate of the feed pump and the Inflow into the well keep the balance, but that the water level drops further and further.

As already stated, in addition to the lowering of the water level in the associated well, the pressure and the delivery or flow rate at the outlet of the pump are determined for each delivery pump. However, like the pressure, the delivery or flow rate need not be measured directly at the outlet of the delivery pump. Instead, the measurement can be anywhere before the first one Branching of the line done and preferably takes place at the wellhead. The measurement of the delivery or flow rate is preferably carried out by means of an inductive measuring device and takes place according to a further advantageous embodiment of the invention as the measurement of the lowering of the water level and the pressure stepwise or preferably continuously.

A further preferred embodiment of the invention provides that displayed on a screen, the characteristic of the specific power or energy demand of the feed pump, the pump efficiency curve, the current system characteristic and a pump curve for the current input speed of the feed pump and.

The pump characteristic curve is a "dynamic" characteristic which, for a specific drive speed or frequency of the feed pump in the above-mentioned diagram or coordinate system, shows its operating points in the form of a delivery or flow rate of the feed pump as a function of the delivery height. The pump curves are in the above-mentioned diagram or coordinate system curved, decreasing with increasing flow or flow rate and increasing head, curves, the slope of which increases usually with increasing flow or flow rate and increasing head. Like the pump efficiency curve, the pump characteristics are converted into electronic form by extracting pairs of values and polynomial regression from drawn diagrams of the manufacturers so that they can be displayed on the screen by means of the software. The representation is made for the respective drive speed of the feed pump, so that the associated frequency is needed.

Together with the characteristic curves mentioned above, the screen also expediently displays the minimum of the characteristic of the specific power or energy requirement as well as the point of intersection of the pump characteristic with the instantaneous system characteristic and the intersection of the pump efficiency characteristic with the instantaneous system characteristic.

Thus, the operator at the minimum of the characteristic of the specific power or energy demand, the flow Q1 can be read, in which the specific power or energy consumption of the feed pump is the lowest. At the intersection of the pump efficiency curve with the system characteristic can continue the Flow Q2 be read. By displaying the intersection of the pump curve with the system characteristic curve, which represents the calculated instantaneous actual operating point of the feed pump, it can also be seen whether this actual operating point coincides with the desired operating point determined according to the invention or approaches it in the event of a deviation, which facilitates an inspection.

In addition, the on-screen operator can immediately compare whether the flow rate at the minimum of the specific power or energy demand curve or that at the intersection of the pump efficiency curve with the system characteristic is greater or less, thereafter one of the alternatives mentioned above under 2) and 3) to choose.

The actual operating point calculated from the intersection of the pump characteristic curve with the system characteristic curve, the desired operating point point calculated from the intersection of the pump efficiency curve with the system curve and the operating point with the lowest specific power or energy requirement of the feed pump are each output in the form of a delivery or flow rate , wherein the former represent the actual flow or flow rate and the latter energetically favorable target flow or flow rates. One of these desired delivery or flow rates is fed to the control unit, as previously described, which generates a control value for the frequency converter.

In the operation of a well with one or more wells from each of which promotes a feed pump, the system characteristic of each pump usually changes, for example, when the water level in the associated wells drops or the line losses in the network change or wells with multiple wells one or more feed pumps are switched on or off. The change in the system characteristic causes a shift in the system characteristic in the above-mentioned diagram or coordinate system. This also results in a different characteristic of the specific power or energy requirement as well as new intersections of the system characteristic with the pump efficiency characteristic. According to the invention, the control or regulation unit then determines the new minimum of the characteristic curve of the specific power or energy requirement and the new points of intersection and displays them on the screen. At the same time, it determines the associated desired delivery or flow rate and compares it with the measured actual value. Flow or flow rate to the setpoint for to generate the frequency converter. This then changes the frequency and the drive speed of the feed pump, whereby the pump curve and thus the current operating point of the feed pump in the above diagram or coordinate system shifts until the actual flow or flow rate of the desired flow or flow rate corresponds. This is the case when either the actual flow rate or the flow rate equals the minimum of the characteristic of the specific power or energy demand or if the intersection of the pump characteristic and the system characteristic coincides with the intersection of the pump efficiency characteristic and the system characteristic.

Thus, either the minimum of the characteristic of the specific power or energy demand or the intersection of the high-efficiency pump efficiency curve and the system characteristic acts as a reference in the control of the feed pump, the energy saving potential being that the instantaneous actual flow rate expressed as the actual flow rate Operating point of the feed pump this minimum or intersection is tracked.

• Fig. 1 zeigt eine schematische Darstellung einer erfindungsgemäßen Brunnenanlage mit einem Brunnen und einer Förderpumpe;
• Fig. 2 zeigt eine schematische Darstellung einer erfindungsgemäßen Brunnenanlage mit mehreren Brunnen und mehreren Förderpumpen;
• Fig. 3 zeigt ein Diagramm der aus einer geodätischen Kennlinie, einer Absenkungskennlinie und einer Leitungskennlinie zusammengesetzten Anlagenkennlinie der Brunnenanlage aus Fig. 1 in Abhängigkeit von der Förder- oder Durchflussmenge und der Förderhöhe der Förderpumpe;
• Fig. 4 zeigt ein entsprechendes Diagramm der Anlagenkennlinie aus Fig. 3 sowie einer Pumpenwirkungsgradkennlinie und zwei Pumpenkennlinien der Förderpumpe der Brunnenanlage aus Fig. 1;
• Fig. 5 zeigt ein entsprechendes Diagramm der Anlagenkennlinie, der Pumpenwirkungsgradkennlinie und zwei Pumpenkennlinien der Förderpumpe, von denen eine mittels des erfindungsgemäßen Verfahrens so verschoben worden ist, dass sie durch den Schnittpunkt der Pumpenwirkungsgradkennlinie und der Anlagenkennlinie verläuft;
• Fig. 6 zeigt ein Diagramm entsprechend Fig. 4, das auf einem Bildschirm eines Rechners einer Leitwarte der Brunnenanlage dargestellt wird;
• Fig. 7 zeigt ein Diagramm entsprechend Fig. 4 und Fig. 6, das jedoch zusätzlich eine Kennlinie des spezifischen Leistungs- oder Energiebedarfs der Förderpumpe sowie die Förder- oder Durchflussmenge im Minimum dieser Kennlinie und die Förder- oder Durchflussmenge am Schnittpunkt der Pumpenwirkungsgradkennlinie und der Anlagenkennlinie anzeigt;
• Fig. 8 zeigt ein Diagramm mit Pumpenkennlinien bei verschiedenen Frequenzen sowie der Anlagenkennlinie zur Berechnung von Wirkungsgradkennlinien der Förderpumpe;
• Fig. 9 zeigt ein Diagramm mit den berechneten Wirkungsgradkennlinien der Förderpumpe bei verschiedenen Frequenzen, den Wirkungsgradkennlinien eines Antriebsmotors und eines Frequenzumrichters der Förderpumpe, der Wirkungsgradkennlinie einer Stromleitung zum Antriebsmotor, sowie einer Gesamtwirkungsgradkennlinie, die zur Berechnung der Kennlinie des spezifischen Leistungs- oder Energiebedarfs dient und auf dem Bildschirm dargestellt werden kann.

In the following the invention will be explained in more detail with reference to two embodiments shown in the drawing.

• Fig. 1 shows a schematic representation of a well system according to the invention with a well and a feed pump;
• Fig. 2 shows a schematic representation of a well system according to the invention with several wells and several feed pumps;
• Fig. 3 shows a diagram of the composite of a geodetic characteristic, a lowering curve and a line characteristic curve of the well system Fig. 1 depending on the delivery or flow rate and the delivery head of the feed pump;
• Fig. 4 shows a corresponding diagram of the system characteristic Fig. 3 and a pump efficiency curve and two pump characteristics of the feed pump of the well Fig. 1 ;
• Fig. 5 shows a corresponding diagram of the plant characteristic, the pump efficiency curve and two pump characteristics of the feed pump, one of which has been moved by means of the method according to the invention so that it passes through the intersection of the pump efficiency curve and the system characteristic;
• Fig. 6 shows a diagram accordingly Fig. 4 , which is displayed on a screen of a computer of a control room of the well system;
• Fig. 7 shows a diagram accordingly Fig. 4 and Fig. 6 but additionally indicating a characteristic curve of the specific power or energy requirement of the feed pump and the delivery or flow rate in the minimum of this characteristic curve and the delivery or flow rate at the intersection of the pump efficiency curve and the system characteristic curve;
• Fig. 8 shows a diagram with pump characteristics at different frequencies and the system characteristic curve for calculating efficiency characteristics of the feed pump;
• Fig. 9 shows a diagram with the calculated efficiency characteristics of the feed pump at different frequencies, the efficiency characteristics of a drive motor and a frequency converter of the feed pump, the efficiency curve of a power line to the drive motor, and an overall efficiency curve, which is used to calculate the characteristic of the specific power or energy demand and on the screen can be represented.

In the Fig. 1 Well system 10 shown essentially consists of a single drinking water well 12 and a well pump 12 installed in the pump 14, which pumps drinking water from the well 12 through a line 18 into a reservoir 16.

The pump 14 is a submersible pump, which is submerged within the well 12 in the water and designed, for example, as a centrifugal pump with an electric drive motor 15. The reservoir 16 may be, for example, a high reservoir or a Verdüsung.

The well system 10 further comprises means 20 for continuously determining the lowering of the water level in the well 12, a fountain head 22 arranged Pressure gauge 24 for continuously measuring the water pressure in the line 18 behind the pump 14 and also arranged on the wellhead 22 flow rate meter 26 for continuously measuring the delivery or flow rate of the pump 14th

The means 20 comprise a pressure gauge 28, which is arranged approximately at the level of the pump 14 in the well 12 and continuously detects the hydrostatic pressure of the water column above the pressure gauge 28. As in Fig. 1 represented by a hatched area, the height of the water column in the well between a water level H ₀ , which occurs when the pump 14 for a long time does not deliver water from the well 12, and an operating water level H ₁ , which is in operation of the feed pump 14th when the amount of water delivered by the pump 14 and the flow of water from the environment into the wells 12 are balanced. From the hydrostatic pressure of the water column in the well, the respective lowering of the water level H _Abs ( Fig. 1 ), which corresponds to the height difference ΔH between the still water level H ₀ and the instantaneous actual water level H _Ist and is generally between the two values H ₀ and H ₁ .

In addition, the well system 10 includes a control and regulation unit 30 for controlling and regulating the drive speed of the feed pump 14. The control unit 30 is connected by signal lines 32 with the measuring devices 24, 26 and the means 20. In addition, the control unit 30 communicates on the one hand with a computer 34 of a control room 36 of the well system 10 and on the other hand with a frequency converter 38 which is connected by a power line 40 to the drive motor 15 of the feed pump 14. The computer 34 includes a screen 42, on the characteristics of the well system 10 and the feed pump 14 and the result of the control and regulation of the drive speed for visual inspection can be displayed. By means of the frequency converter 38, the frequency of the drive motor 15 of the pump 14 applied alternating voltage can be changed and thus the drive speed of the pump 14 can be changed continuously from the minimum speed specified by the manufacturer to the rated speed without the drive torque drops.

The arranged at the well head 22 pressure gauge 24 measures the water pressure in the line 18 at the level of the well head 22. The measured water pressure in the line 18 is transmitted via the control unit 30 to the computer 34, where the measured Pressure and the hydrostatic pressure of the water column between the output of the feed pump 14 and the measuring point at the wellhead 22 are added to calculate the pressure at the outlet of the feed pump 14. The line losses in the line 18 are in a defined relationship to the pressure at the outlet of the feed pump 14 and can be calculated by the computer 34 from the pressure measured by the pressure gauge 24.

The flow rate measuring device 26 is an inductive measuring device, from which the measured delivery or flow rate in the line to the control and regulation unit 30 and to the computer 34 is transmitted. Since the line 18 does not branch in front of the well head 22, the measured delivery or flow rate corresponds to the delivery or flow rate at the outlet of the pump 14.

The pressure of the water column measured by the pressure gauge 28 is transmitted to the control unit and from there to the computer, which calculates the lowering of the water level H _Abs from the measured pressure.

For the control or regulation of the feed pump 14, the geodetic height H _{geod is still} required, ie the height difference between the still water level H ₀ and the highest point of the riser, as in Fig. 1 shown.

The computer 34 generates from the geodetic height H _geod , the instantaneous reduction of the water level H _Abs and the current pressure at the output of the feed pump 14 each have a characteristic of these variables. For a better understanding these characteristics are in Fig. 3 represented in a diagram or coordinate system in which the abscissa indicates the delivery or flow rate of the feed pump in m ³ / h and the ordinate the delivery height of the feed pump 14 in mWS.

Since the geodesic height H _geod is a constant, the characteristic is a straight line parallel to the abscissa, which in Fig. 3 is shown by a dotted line A. The characteristic of the lowering of the water level is also a straight line, but increases in proportion to the delivery or flow rate of the feed pump 14, as in Fig. 3 represented by a broken line B. The characteristic of the line losses is a curved curve which increases due to the increasing line resistance in accordance with the square of the delivery or flow rate, as in FIG Fig. 3 represented by a dash-dotted line C.

From these three characteristics A, B and C is calculated by the computer 34 as a sum of the three characteristics A, B and C, a system characteristic curve, which in Fig. 3 is shown by a solid line D. The system characteristic D is a dynamic characteristic which shifts with each change in the pressure at the outlet of the pump 14 and any change in the lowering of the water level in the diagram.

In the computer 34, a maximum efficiency pump efficiency curve and a pump characteristic are stored for the same diagram or coordinate system, of which the former is a parabolic rising curve, as in FIG Fig. 4 represented by a broken line E, and the latter is a sloping curved curve, as in Fig. 4 represented by a dotted line F. Next to these two curves E and F shows Fig. 4 also the plant characteristic D.

The pump efficiency curve E is a static characteristic which indicates the maximum efficiency of the pump 14 as a function of the delivery or flow rate and of the delivery head. For example, in a feed pump 14 designed as a centrifugal pump, the maximum efficiency is about 72 to 78%. The pump characteristic curve F is a dynamic characteristic curve which, for a specific frequency or drive speed of the feed pump 14, shows its operating points in the form of a delivery or flow rate as a function of the delivery head.

Since both pump efficiency characteristics and pump characteristics are usually not in a form permitting processing of the characteristics by software, but supplied by the respective pump manufacturer in the form of drawn diagrams, it is necessary to convert these characteristics into a form suitable for electronic processing. As in Fig. 4 is shown schematically for a manufacturer-pump characteristic G for the maximum frequency or drive speed, this is done by extracting a set of value pairs X from the drawn characteristic and then a curve is generated by polynomial regression, which is processed by the software implemented in the computer 34 and can be displayed on screen 42 and in Fig. 4 is shown as a dotted line G. The polynomial regression mentioned is a known method, which therefore need not be described in detail here.

In order to operate the feed pump 14 always in an energetically most favorable operating point, the computer continuously calculates the intersections S1 and S2 of the instantaneous system characteristic D with the pump characteristic F for the instantaneous drive speed or frequency and with the pump efficiency curve E for the maximum efficiency. The intersection S1 in Fig. 4 and 5 represents the instantaneous operating point of the pump 14, while the point of intersection S2 in Fig. 4 and 5 represents an energetically favorable operating point.

In addition, the computer 34 continuously calculates a characteristic curve, the respective specific power or energy requirements of the feed pump 14 including its drive motor 15, its frequency converter 38 and its power line 40 depending on the delivery or flow rate at the output of the feed pump 14 and of the delivery indicates. The minimum of this characteristic represents the operating point with the lowest specific power or energy requirement. This characteristic is in Fig. 7 represented by the curve J.

The characteristic J is calculated by the computer 34 in several steps:
In the first step, a set of value pairs X is extracted from a drawn manufacturer pump characteristic curve for a maximum pump frequency of 100 Hz, and then a polynomial regression generates a curve G100 which can be processed by the software implemented in computer 34 and displayed on screen 42. From this curve G100 in Fig. 8 Then further pump characteristics G95, G90, G85, G80, G75, G70 and G65 are derived for lower frequencies of 95 Hz, 90 Hz, 85 Hz, 80 Hz, 75 Hz, 70 Hz and 65 Hz, as in Fig. 8 shown. The frequencies mentioned are only examples. Other frequencies may be used.

In the second step, the intersections S100, S95, S90, S85, S80, S75, S70 and S65 of the current system characteristic D are calculated with the pump characteristics G100, G95, G90, G85, G80, G75, G70 and G65 and for each of these intersections S100, S95, S90, S85, S80, S75, S70 and S65 determines the associated flow rate Q100, Q95, Q90, Q85, Q80, Q75, Q70 and Q65 which are on the abscissa below the respective intersection S100, S95, S90, S85 , S80, S75, S70 and S65 can be read.

In the third step, a set of value pairs X is extracted from a drawn manufacturer pump efficiency curve for the maximum pump frequency of 100 Hz, and then a polynomial regression generates a curve K100, which is processed by the software implemented in the computer 34 and displayed on the screen 42 in a diagram can be, where the abscissa indicates the flow rate and the ordinate the efficiency in%. As in Fig. 9 from this curve K100 then further pump efficiency curves K95, K90, K85, K80, K75, K70 and K65 for the frequencies of 95 Hz, 90 Hz, 85 Hz, 80 Hz, 75 Hz, 70 Hz and 65 Hz are derived.

In the fourth step, from each of the flow rates Q100, Q95, Q90, Q85, Q80, Q75, Q70 and Q65 and the associated pump efficiency characteristics K100, K95, K90, K85, K80, K75, K70 and K65, the pump efficiency becomes η100, η95, η90 , η85, η80, η75, η70 and η65 (not shown) at the respective frequency of 100 Hz, 95 Hz, 90 Hz, 85 Hz, 80 Hz, 75 Hz, 70 Hz and 65 Hz.

In the fifth step, the value pairs Q100, n100; Q95, η95; Q90, η90; Q85, η85; Q80, η80; Q75, η75 and Q65, η65 of flow rate Q and pump efficiency η by polynomial regression an associated pump efficiency curve (not shown) is calculated, which is also dependent on the current system characteristic D.

In the sixth step of this pump efficiency curve and an efficiency curve KM of the electric drive motor 15, an efficiency curve KU of the frequency converter 38 and an efficiency curve KL of the power line multiplication by an overall efficiency curve M is calculated, the overall efficiency of the feed pump 14 including its drive motor 15, its frequency 38 and its power line 40 as a function of current system characteristic D represents. The curves KM, KU and KL are either supplied by the manufacturer of the respective component 15, 38 or 40 or transferred from drawn manufacturer's characteristics by extraction of value pairs and subsequent polynomial regression in a form that can be processed by the software and displayed on the screen 42 ,

In the seventh step, from the overall efficiency characteristic curve M for a plurality of flow rate support points, for example 60 m ³ / h, 65 m ³ / h, 70 m ³ / h, ... 130 m ³ / h, 135 m ³ / h , 140 m ³ / h the corresponding total power calculated.

In the eighth step, the characteristic curve J of the specific power or energy requirement is calculated from this by dividing the associated total power for each flow rate support point by the associated flow rate and interpolating the resulting values into the characteristic curve J.

To determine the energetically most favorable operating point of the feed pump 14, the computer 34 then calculates the delivery or flow rate at the minimum of the characteristic J of the specific power or energy requirement and displays this on the screen 42 by a vertical line Q1. At the same time, the computer 34 also calculates the delivery or flow rate at the intersection S2 of the pump efficiency characteristic E with the system characteristic D and displays it on the screen by a vertical line Q2 as well, as in FIG Fig. 7 shown.

Subsequently, the computer 34 compares the two flow rates Q1 and Q2 calculated in this way. If the comparison shows that the delivery or flow rates Q1 and Q2 are identical, then the computer 34 transmits one of these delivery or flow rates Q1, Q2 as the target flow rate to the control unit 30. If the comparison shows that the Flow or flow rate Q1 is greater than the delivery or flow rate Q2, the computer 34 transmits the delivery or flow rate Q1 as a target flow rate to the control unit 30. If the comparison shows that the flow or flow Q1 smaller is as the flow or flow Q2, as in Fig. 7 illustrated, then the computer 34 transmits the delivery or flow rate Q1 as a target flow rate to the control unit 30 as long as this delivery or flow rate Q1 is achieved by the feed pump 14. If the feed pump 14 no longer reaches this delivery or flow rate Q1 because the specific total pressure conditions in the line 18 or the line network 52 of the well system 10 no longer make this possible, then the computer 34 transmits the delivery or flow rate Q2 as the target flow rate the control unit 30th

In the control and regulation unit 30, the setpoint flow rate transmitted by the computer 34 is compared with the instantaneous actual flow rate measured by the flow rate measurement device 26 and transmitted to the control and regulation unit 30. The control unit 30 then generates from a possible difference between the two values a control value for the frequency converter 38, which then changed by a corresponding change in frequency, the drive speed of the feed pump 14 until the actual flow rate coincides with the target flow rate. Depending on whether the computer 34 has transmitted the delivery or flow rate Q1 or Q2 as the target flow rate to the control and regulation unit 30, shifts the change in frequency, the pump characteristic F, until their intersection S1 with the system curve D either exactly is above the minimum of the characteristic J or coincides with the intersection S2. The latter is in Fig. 5 for the pump characteristic H calculated at the new frequency.

To monitor the well system 10 and the energy-optimal control or regulation of the feed pump 14 is also the in Fig. 7 displayed diagram displayed on the screen 42 of the computer 34. In this way, the operator can on the one hand visually compare which of the delivery or flow rates Q1 or Q2 is greater. On the other hand, the operator can see whether the point of intersection S1 of the pump curve F with the system curve D is as desired exactly above the minimum of the curve J or coincides with the intersection S2 or if the intersection S1 is tracked as desired the minimum or the intersection S2 when the measured pressure at the outlet of the pump 14 and / or the lowering of the water level in the well 12 change and thereby the system curve D shifts.

In addition to the in Fig. 4 and 5 shown characteristics D, E, F and H are displayed on the screen 42 of the computer 36, the measured actual flow rate and the target flow rate at the output of the pump 14 as numerical values side by side. In this way, the operator can compare the two values at a glance.

In addition, the current specific power or energy demand of the feed pump 14, the measured pressure at the outlet of the feed pump 14, the instantaneous water level in the well 12, the actual frequency of the feed pump 14 supplied AC and the delivery or flow rate at the output of Feed pump 14 displayed as numerical values.

The fountain 50 in Fig. 2 differs from the well system 10 described above in that it comprises a plurality of wells 12 and a plurality of feed pumps 14, which convey through a common line network 52 into the reservoir 16, but controlled by a single control unit 30 and a single computer 34 be managed. The feed pumps 14 can be switched on or off individually if required, if the amount of water to be pumped is to be increased or decreased. By connecting or disconnecting individual feed pumps 14 results for the other currently in operation feed pumps 14 constantly new system characteristics D, which are continuously calculated by the computer 34 using the software.

The calculation is done separately for each operating pump 14 and independently of the other operating pumps 14 in operation in the manner previously described by continuously calculating an associated system characteristic D for each of the operating pumps 14 in operation by thereafter the characteristic curve J of the specific power or energy requirement and its minimum and, if appropriate, also the intersections S1 and S2 of the calculated system characteristic D with the associated pump characteristic F and with the associated pump efficiency characteristic E for the maximum efficiency, and finally Flow rate at the intersection S1 of the calculated system characteristic D with the associated pump characteristic F by changing the frequency and the drive speed of the pump 14 by means of the control unit and the associated frequency converter 38 to the target flow rate Q1 and Q respectively 2 in the Minimum of the characteristic J or at the intersection S2 of the calculated system characteristic D with the associated pump efficiency characteristic E is introduced.

Since the determination of the pressure at the outlet of each feed pump 14 and the instantaneous lowering of the water level in each well 12 and the calculation for each feed pump 14 is made independently of the other wells 12 and feed pumps 14, the method described above can also be used for control or regulation Complex wells 50 are used by continuously in all the pump 14 of the well system 50 in the manner described above, the calculated energetically most favorable operating point is set.

Claims (12)

1. Method for reducing the energy consumption of a delivery pump (14) which delivers water from a well (12) into a line (18) or a line network (52), wherein the actual throughflow rate of the delivery pump (14) is brought to a target throughflow rate by changing of the drive rotational speed of an electric drive motor (15) of the delivery pump (14), wherein the target throughflow rate corresponds either to the throughflow rate (Q1), indicated hereinafter as "first throughflow rate", at the operating point of the delivery pump (14) with the lowest specific power or energy requirement, a characteristic curve (J) of the respective specific power or energy requirement of the delivery pump (14) being calculated in dependence on a dynamic system characteristic curve (D) for the purpose of determining said operating point, or to the throughflow rate (Q2), indicated hereinafter as "second throughflow rate", at the calculated point of intersection (S2) of a pump efficiency characteristic curve (E) with high efficiency and the dynamic system characteristic curve (D), wherein the dynamic system characteristic curve (D) is calculated from the geodetic height (H_geod), the drop in the water level (H_drop) in the well (12) and line losses in the line (18) or in the line network (52), and wherein the pump efficiency characteristic curve (E) with high efficiency lies within a tolerance range of 5% of an efficiency characteristic curve for the maximum efficiency,
   wherein the first throughflow rate (Q1) is compared with the second throughflow rate (Q2),
   wherein, if the first throughflow rate (Q1) is greater than the second throughflow rate (Q2), the first throughflow rate (Q1) is selected as the target throughflow rate,
   and wherein, if the first throughflow rate (Q1) is less than the second throughflow rate (Q2), the actual throughflow rate of the delivery pump (14) is brought to the first throughflow rate (Q1) as long as the first throughflow rate (Q1) is reached, and the actual throughflow rate of the delivery pump (14) is brought to the second throughflow rate (Q2) if the first throughflow rate (Q1) is no longer reached.
2. Method according to Claim 1, characterized in that a minimum of the characteristic curve (J) of the specific power or energy requirement of the delivery pump (14) is calculated in dependence on the dynamic system characteristic curve (D).
3. Method according to Claim 2, characterized in that, for the purpose of calculating the characteristic curve (J) of the specific power or energy requirement of the delivery pump (14), an overall efficiency characteristic curve (M), which depends on the system characteristic curve (D), is calculated.
4. Method according to Claim 2 or 3, characterized in that the characteristic curve (J) of the specific power or energy requirement of the delivery pump (14) is recalculated continuously, at short time intervals or whenever the system characteristic curve (D) is changed.
5. Method according to one of the preceding claims, characterized in that the line losses in the line (18) or in the line network (52) during the operation of the delivery pump (14) are derived from the pressure at the outlet of the delivery pump (14), which pressure is determined continuously or in steps.
6. Method according to one of the preceding claims, characterized in that the drop (H_drop) in the water level during the operation of the delivery pump (14) is derived continuously or in steps from a still water level (H₀) and an actual water level in the well (12).
7. Method according to one of the preceding claims, characterized in that the pump efficiency characteristic curve (E) is a dynamic pump efficiency characteristic curve which is derived from a displayed pump efficiency characteristic curve in that value pairs are extracted from the displayed pump efficiency characteristic curve and subjected to transformation by means of polynomial regression.
8. Method according to one of the preceding claims, characterized in that the actual throughflow rate at the outlet of the delivery pump (14) is determined and is compared with the target throughflow rate at the operating point of the delivery pump (14) with the lowest specific power or energy requirement or with the target throughflow rate at the calculated point of intersection (S2) of the pump efficiency characteristic curve (E) and the dynamic system characteristic curve (D), and in that the drive rotational speed of the delivery pump (14) is regulated by means of a frequency converter (38), which is supplied with an adjustment value calculated from the difference between the target throughflow rate and the actual throughflow rate.
9. Method according to one of the preceding claims, characterized in that the pump efficiency characteristic curve (E), the instantaneous system characteristic curve (D) and a pump characteristic curve (F) for the instantaneous drive rotational speed of the delivery pump (14), the point of intersection (S1) of the pump characteristic curve (F) and the instantaneous system characteristic curve (D) and the point of intersection (S2) of the pump efficiency characteristic curve (E) and the instantaneous system characteristic curve (D), and the characteristic curve (J) of the specific power or energy requirement of the delivery pump (14), together with the throughflow rate (Q1) at the minimum of the characteristic curve (J), are displayed on a screen (42).
10. Well system (10, 50) having at least one delivery pump (14) for delivering water from a well (12) into a line (18) or a line network (52), having a control or regulating unit (30) which brings an actual throughflow rate of the delivery pump (14) to a target throughflow rate by changing of the drive rotational speed of an electric drive motor (15) of the delivery pump (14), wherein the target throughflow rate corresponds either to the throughflow rate (Q1), indicated hereinafter as "first throughflow rate", at the operating point of the delivery pump (14) with the lowest specific power or energy requirement, a characteristic curve (J) of the respective specific power or energy requirement of the delivery pump (14) being calculated in dependence on a dynamic system characteristic curve (D) for the purpose of determining said operating point, or to the throughflow rate (Q2), indicated hereinafter as "second throughflow rate", at the calculated point of intersection (S2) of a pump efficiency characteristic curve (E) with high efficiency and the dynamic system characteristic curve (D), wherein the dynamic system characteristic curve (D) is calculated from the geodetic height (H_geod), the drop in the water level (H_drop) in the well (12) and line losses in the line (18) or in the line network (52), and wherein the pump efficiency characteristic curve (E) with high efficiency lies within a tolerance range of 5% of an efficiency characteristic curve for the maximum efficiency,
    wherein a processor (34) which communicates with the control and regulating unit (30) compares the first throughflow rate (Q1) with the second throughflow rate (Q2),
    wherein, if the first throughflow rate (Q1) is greater than the second throughflow rate (Q2), the processor (34) selects the first throughflow rate (Q1) as the target throughflow rate,
    and wherein, if the first throughflow rate (Q1) is less than the second throughflow rate (Q2), the processor (34) selects the first throughflow rate (Q1) as the target throughflow rate as long as the delivery pump (14) reaches the first throughflow rate (Q1), and selects the second throughflow rate (Q2) if the delivery pump (14) no longer reaches the first throughflow rate (Q1).
11. Well system according to Claim 10, characterized by multiple delivery pumps (14), wherein the control or regulating unit (30) brings the.actual throughflow rate of each of the delivery pumps (14) to a target throughflow rate by changing of the drive rotational speed of the electric drive motor (15) thereof, wherein the target throughflow rate corresponds to the throughflow rate (Q1) at the operating point of the respective delivery pump (14) with the lowest specific power or energy requirement or to the throughflow rate (Q2) at the calculated point of intersection (S2) of a pump efficiency characteristic curve (E) with high efficiency and a dynamic system characteristic curve (D) .
12. Well system according to Claim 10 or 11, characterized by means (24, 34) for determining continuously or in steps the pressure at the outlet of the delivery pump (14) or delivery pumps (14).

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