EP2469094B1 - Method for operating a double pump or multi pump assembly - Google Patents

Description

The present invention relates to a method for operating a pump unit with at least one base load-operated first pump and at least one second peak-load pump, which is switched on as needed and operated in parallel to the at least one first pump, wherein the pump unit regulated in such a predetermined control characteristic will be that the recorded power is minimal. Furthermore, the invention relates to a computer program with instructions for carrying out this method and a pump unit of the type mentioned with an electronic control system, which is set up for carrying out the method according to the invention.

Pump units consisting of two parallel pumps are called double pumps. In contrast, pumps with more than two parallel pumping pumps are called multipumps or pressure stations. The pumps are usually driven by an electric motor. The fields of application of such pumps are, for example, in heating systems as circulating pumps or in the supply of fresh water for pressure generation. A double pump and a corresponding control thereof is for example from the European patent specification EP 0 864 755 B1 known. Further shows also the EP 2 161 455 A1 a double pump.

Two different control concepts can be used for the control of double or multi-pumps. According to a first control concept The pumps of the unit over the entire control range to cover the required flow rate synchronously, ie operated at the same speed. In contrast, in a second control concept, initially only one of the pumps of the pump unit is used to cover a required delivery flow. This pump is called base load pump and is responsible for covering the flow rate in the so-called base load range. However, if a flow is required that is outside the base load range, ie has an operating point beyond the maximum delivery speed of the base load pump, the second or a second pump is connected, then to deliver the required flow together with the base load pump. This second or further pump can be referred to as peak load pump, which allows with its additional hydraulic power that the double pump or multi-pump unit operating points beyond the maximum characteristic of the base load pump, ie achieved in the so-called peak load range. It should be noted that in a multi-pump unit two or more pumps can be jointly responsible for covering the base load and therefore together form a base load pump to which a peak load pump is hinzuschaltbar. Subsequently, therefore, "base load pump" is used in the singular, knowing that for the purposes of this application, two or more pumps can be understood by it.

In the aforementioned second control concept, the base-load pump is operated at maximum speed, whereas the peak-load pump delivers only that hydraulic power contribution that is required to achieve the additionally required delivery flow. If the operating point can not be reached in a multi-pump unit with the second or further, connected pump at maximum speed, then another pump is connected. This is done until the required flow rate is reached.

The peak load range in a double pump and multi-pump unit includes all those operating points in the characteristic field that are not reachable by the base-load pump alone. In contrast, the base load range includes all those operating points that can basically be achieved by the base-load pump alone. There are operating points in the base load range in which a synchronous Operation of base load and peak load pump is more energy efficient than operating the base load pump alone. Based on the characteristic field of the base-load pump, these operating points are approximately in the range of medium to high flow at low to medium discharge pressure. This area is called efficiency-optimized area. A performance-optimized operation in double pumps and multipumps is therefore achieved in that in the said characteristic range a peak load pump is connected and both or all pumps run synchronously. Such operation at a reduced speed is then energetically cheaper than a sole operation of the base load pump with a correspondingly high speed.

To determine the efficiency-optimized range, a high metrological effort is required, which is performed at the manufacturer of the generic pump units on the test bench before the pump unit comes on the market. The entire characteristic field of the pump set is measured operating point for operating point, the corresponding measured data is stored and subsequently evaluated. At least those operating points that lie below the maximum characteristic of the base-load pump are approached exclusively with the base-load pump and in synchronous operation of the base-load pump and the peak-load pump, wherein in each of the two cases the respective absorbed power of the pump unit is determined and the two services compared with each other. From the comparison of the services can then be determined whether the pump unit is operated energetically cheaper, if only the base load pump is running or if the synchronous operation of base load and peak load pump leads to a lower power consumption. The measurement of the characteristic field and the performance of the comparative experiments to determine the efficiency-optimized range within the characteristic field require considerable human and temporal resources and thus make the double or multi-pump aggregate more expensive.

A boundary line, which characterizes the theoretical transition between the operation of the pump unit in the base load range with only the base load pump to the efficiency-optimized range with base load and peak load pump is according to the prior art in the control electronics of the pump unit deposited. During operation of the pump unit can then be determined by measuring the differential pressure between the suction side and pressure side and estimating or measuring the flow, if an operating point of the unit is below the limit and thus only the base load pump should be operated, or if the operating point is above the limit line and The pump set should be operated with base load and peak load pump. The limit line therefore indicates for each delivery pressure at which volume flow the peak load pump should be connected for energy reasons.

The object of the present invention is to operate a double pump or multi-pump aggregate efficiency-optimized, without a prior metrological recording and evaluation of characteristics of the pump set is required to determine the limit for switching from base load operation in the peak load operation.

This object is solved by the features of claim 1. Advantageous developments of the method according to the invention are specified in the subclaims.

According to the invention, a method is proposed for operating a pump unit having at least one base load-operated first pump and at least one second-pump operating at peak load, which is activated as needed and operated in parallel to the at least one first pump, with the pump unit being regulated on a predetermined control characteristic in that the power consumed is minimal, wherein the pump unit is operated in dependence on an upper and a lower limit either with at least two pumps or with at least one pump switched off, starting from a synchronous operation of the pumps at an operating point in which the pumps with operated in the same speed and / or power, in a first step, the value of at least one operating variable of the pump unit is stored as a reference value, in a second step, the funded by the second pump flow is reduced in one third step depending on the reactions of the regulated first pump a Assignment of the operating point to a load range is done and replaced in a fourth step, the upper or lower limit by the reference value.

The inventive method makes it possible to make do without the measurement of the characteristic area of the pump unit before its commissioning. Rather, the boundary line or the switching point for a set during operation of the pump set control characteristic during operation is determined as a kind of "limit band". This is done by determining at each current operating point whether this operating point lies in the peak load range, in the efficiency-optimized range or in the base load range of the pump set, the limit band being limited in its width by the lower and upper limit values. A measurement of the volume flow, the delivery head or the differential pressure for the determination of the switching point is no longer necessary by the proposed method.

A particular advantage of the method according to the invention is that the position and width of the boundary strip are adapted and reduced during operation of the pump unit. This causes wear and wear on the pump set to require no change in the operating setting. Also, software and / or firmware updates remain unaffected. The pump set is always operated energy-optimized.

Preferably, the synchronous speed of the pump unit is used as the operating variable for determining the upper and lower limit values, and these are stored as a reference speed. The synchronous speed is that speed at which the base-load pump and the peak load pump are operated synchronously, ie at the same speed. The rotational speed can be determined in a simple manner, for example by calculation on the basis of current and voltage, which are determined metrologically or present numerically in a model (observer). Alternatively, the speed may be determined by means of a speed sensor well known in the art.

As an alternative to the synchronous speed, the electrical power consumed by the pump unit can also be used as the operating variable.

The volume flow delivered by the second pump can be reduced by reducing the speed of the second pump. This can be done in a simple manner by appropriate control of the pump. Alternatively, the volume flow of the second pump can also be reduced in that an arranged between the second pump and the confluence point of the flow rate of the second pump to the total volume flow of the pump unit valve is increasingly closed. However, this requires additional structural and control measures on the pump unit.

In addition to the synchronous speed, the power absorbed by the pump unit in synchronous operation can be determined and stored as a reference power. This makes it possible to carry out a performance comparison of the absorbed power of the pump unit for the assignment of the current operating point to a load range, in particular to the efficiency-optimized range. The comparison of the power is then carried out before the reduction of the volume flow of the second pump and after the reduction of this volume flow.

Preferably, the reference value, in particular the reference speed as an upper limit, in particular a speed limit can be stored if after the volume flow reduction at least a first condition is met, which is assigned to one of the load areas peak load range or efficiency-optimized range. Thus, if the first condition is satisfied, it can be determined that the current operating point is in the peak load range or the efficiency optimized range.

Furthermore, the reference value, in particular the reference speed can be stored as a lower limit, in particular speed limit, when at least one second condition is assigned, which is assigned to the base load range. If this second condition is satisfied, it can thus be determined that the current operating point of the pump set lies in the base load range.

After evaluating the first and second conditions, it can usually be ascertained in which load range the current operating point of the pump set falls, that is, whether the current operating point lies in the peak load range, in the base load range or in the efficiency-optimized range. If it is in the base load range, the reference value is set as the lower limit value. On the other hand, if it is in the peak load range or efficiency-optimized range, the reference value is set as the upper limit value.

This procedure can be performed according to the invention for all operating points on a respectively set control characteristic of the pump unit on which the pump unit is operated according to a higher-level control, the upper and lower limit is dynamically adjusted during operation, if a new operating point is present closer to the theoretical limit line.

At the upper limit or above this upper limit, the pump unit according to the invention is provided with at least two pumps, i. in the case of a double pump operated with both pumps. Further, the pump set will be at the lower limit or below the lower limit with at least one pump off, i. operated in the case of a double pump with only one pump. If the synchronous rotational speed of the pump assembly used by the process according to the invention always starts when a new operating point sets, it can be easily determined on the basis of a comparison of the current synchronous rotational speed with the stored upper rotational speed limit value and the stored lower rotational speed limit value whether the current operating point is equal to or above the upper limit value or equal to or below the lower limit value. In these cases no adjustment of the limit values takes place.

If the pump set is operated at an operating point with a synchronous speed between the upper limit and the lower limit, the above four steps are repeated starting from the synchronous operation of the running pumps. This causes both the upper limit and the lower limit values are dynamically adjusted during operation, whereby they are increasingly brought closer to the limit line separating the base load range from the efficiency-optimized range.

Preferably, the method according to the invention is carried out separately for each predetermined control characteristic. Thus, an upper and a lower limit of the operating variable, in particular the synchronous speed is set on each control characteristic on which a higher pressure regulator regulates the pump unit, between which the transition from the base load range to the efficiency-optimized range and depending on which the unit with at least one shut down pump or at least two pumps is operated.

The control characteristic may be such a characteristic in which the pressure generated by the pump unit is kept constant over the volume flow. Such a control characteristic is known as Δp-constant characteristic. Alternatively, control characteristics are known in which the pressure of the pump unit is adjusted proportionally to the volume flow. Such characteristics are known as Δp-variable. Since the transition from the base load range to the efficiency-optimized range for each control characteristic lies at a different operating point, it makes sense, when the current control characteristic changes, to determine the determined limit values in a characteristic-specific manner, ie. store assigned to this last characteristic. Thus, in the case that is changed back to a previous control characteristic, the limit values previously determined for this control characteristic can be reused.

Preferably, new limit values are used when changing the control characteristic. Like the limit values for the previous control characteristic, these new limits are set to initial values and then determined numerically based on the setting of operating points. In this case, the synchronous speed can be used again as a reference variable.

It is particularly advantageous in the method according to the invention that it is in the usual running operation of the pump unit after his Commissioning can be performed without the knowledge of characteristic characteristics, so that it is possible to dispense with a factory analysis of the characteristic field of the pump unit before its commissioning.

As explained above, the reference value of the operating variable can be stored as an upper limit value if, after the volume flow reduction, in particular the speed reduction of the second pump, at least one first condition is met. This condition may be, for example, reaching or exceeding the maximum speed of the first pump. If this condition is met, it follows from the conclusion that the current operating point is in the peak load range, in which a flow is required, which can not be supplied by the at least one base load pump alone. Because by reducing the volume flow, in particular the speed of the second pump, the base load pump must apply the missing flow rate of the second pump, i. be operated at a higher flow rate. If the speed of the base-load pump rises to or above the maximum speed with this volume flow transfer, the first condition would be met and the current operating point is in the peak load range.

Alternatively, a comparison with the stored reference power may be used as the first condition, wherein the current power consumption of the first pump, i. the base-load pump is compared with this reference power and is checked as the first condition exceeding this reference power. With this condition, it can be determined whether the current operating point of the pump set is in the efficiency-optimized range.

This finding is based on the finding that, in the case of a current operating point of the pump set, the first pump can achieve an assumption of the volume flow of the second pump below the maximum speed characteristic of the first pump. However, if the power consumption of the base-load pump is higher than the previously recorded in synchronous operation of the pump unit with base load pump and peak load pump power, it is energetically favorable to operate for this operating point, the base load pump and the peak load pump simultaneously, in particular synchronously. Increases The power consumption of the first pump after the volume flow reduction of the second pump via the stored reference power, it is thus determined that the current operating point is in the effective wheel-optimized range of the characteristic field of the pump unit.

Of the two alternative conditions mentioned above, the comparison of the power consumption to the stored reference power represents the stricter criterion, because even in the case of an operating point in the peak load range, the power of the base-load pump will rise above the reference value.

However, the two aforementioned first conditions can also be applied in a commuative manner, whereby they are examined in a ranking order. Thus, first, the exceeding of the maximum speed of the first pump can be checked and, if this maximum speed is not reached or exceeded, the current power consumption of the first pump determined and compared with the stored reference power. The speed can be easily determined because the higher-level pressure regulator, which regulates the pump set to a predetermined control characteristic, outputs a speed setpoint, the amount of which can be easily determined. If this reaches a maximum value, the resource-intensive and more complex metrological and mathematical determination of the power consumption of the first pump or a numerical comparison of this value with the stored reference power can be saved.

As described above, the reference value of the operation quantity may be stored as a lower limit value when at least a second condition associated with the base load range is satisfied. As a second condition, the case may be used that the power consumption of the first pump in response to a volume flow reduction of the second pump, at least on average substantially no longer changed, ie in particular no longer increased. This condition is reached at an unchanged operating point in the base load range at some point. For this purpose, however, the volume flow reduction should be carried out continuously or successively stepwise such that the time period from the last to the next reduction is less than the time constant of the system response to the volume flow reduction. The following is true Consider: starting from a synchronous operation of the first and the second pump, these contribute 50% to the volume flow of the pump set. Since the pressure side of each pump of the pump unit, a check valve or a check valve is arranged, as for example in the European patent application EP 2 161 455 A1 If this is the case, a slight reduction in the second pump's flow rate of just a few percent already results in the pressure-side outlet of the second pump being largely closed. As a result, the first pump dominates the volume flow significantly. This means that a further reduction in the flow rate of the second pump will not affect the performance of the first pump. Against this background, a power consumption of the first pump that does not change significantly on average during the volume flow reduction of the second pump is the proof that the current operating point of the pump set lies in the base load range.

Alternatively to this criterion can be used as a second condition of the case that the volume flow or the speed of the second pump due to the reduction reaches or falls below a minimum value. This criterion can be used if the former criterion is not met, i. the power consumption of the first pump, in particular fluctuates on average, so that on the basis of this determination can not be made a clear statement about the operating point, unless in any case the power consumption does not rise above the stored reference power.

However, in this non-meaningful case, the volumetric flow of the second pump, in particular the rotational speed of the second pump, is gradually reduced to such an extent that the volumetric flow and / or the rotational speed reaches or falls below a minimum value and the power consumption of the first pump is still not exceeded the stored reference power has risen, this is a proof that the current operating point of the pump unit is in the base load range, the required flow can be provided by the base load pump alone and the operation of the base load pump alone causes a lower power consumption of the pump unit, as if base load - And peak load pump are operated synchronously.

It therefore makes sense if the second condition is only checked if the first condition is not met.

Preferably, at or immediately after the storage of the lower limit value, the value of an operating variable of the first pump is additionally stored as the base load reference value. This base load reference value represents a comparison value with which the current value of the considered operating variable of the first pump in the base load operation can be compared in order to detect a change in state of the first pump. The base load operation here is that operation in which only the at least one base load pump operates, i. in which at least one pump of the pump set is switched off.

From the base load operation, it is then possible to switch back to synchronous operation when the current value of the operating variable of the first pump rises above the stated base load reference value or becomes equal to or greater than a maximum value of this operating variable.

Preferably, its speed can be used as the operating variable of the first pump, since it can be determined in a simple manner on the basis of the speed information of the superordinate pressure regulator of the pump unit.

It is furthermore particularly advantageous if an offset is added to the base load reference value. As a result, a hysteresis is achieved when switching back to synchronous operation and a multiple, briefly in succession following switching between base load operation and synchronous operation prevented.

As already mentioned, the volume flow reduction of the second pump can take place stepwise or continuously. This has the advantage over an abrupt shutdown of the second pump that the higher-level pressure regulator is not affected in its control task and a sudden pressure drop in the hydraulic system is avoided. In addition, responding to a sudden volume flow request quickly by re-starting the second pump.

For example, a stepwise reduction can be made with values between 200 rpm and 50 rpm, in particular about 75 rpm to 150 rpm, preferably about 100 rpm. In the case of a continuous reduction of the speed, this can be done, for example, with a negative slope of 50-150 U / min per second, in particular 100 U / min per second.

In addition to the aforementioned measures, it is possible after the volumetric flow reduction to return to the synchronous operation of the pump unit when the power consumption of the first pump decreases. This can be used as a third condition that is applicable in addition to the other two conditions. It is fulfilled when, during the implementation of the method steps according to the invention, in particular after the volume flow reduction, the required delivery rate decreases, i. the operating point of the pump set changes in the direction of low volume flows. In this case, checking the first and second conditions would be negative. For this reason, it is advantageous, in the case of a sinking power consumption of the first pump after the volume flow reduction of the second pump to return to the synchronous operation and continue from this operation, the method, i. repeat the assignment of the new operating point to one of the load ranges. The third condition is thus a fallback condition.

Preferably, it is checked only after a waiting period, if at least one of the conditions is met. This procedure takes into account the case that immediately after a volume flow reduction is still no statement about the assignment of the current operating point to a load range feasible because the system reaction has not yet done or ended, in particular a higher-level pressure control has not yet corrected.

Furthermore, it can be provided that the volume flow of the second pump is further reduced if none of the conditions is met. In any case, this can be done as long as no minimum value for the volume flow, in particular the minimum speed of the second pump, has yet been reached.

Preferably, in each state of the method according to the invention can be converted into a synchronous operation, when the first pump reaches an inadmissible operating state, in particular when the speed of the first pump reaches or exceeds a maximum value. This procedure takes into account the fact that in the short term, an increased volume flow demand can be made of the pump unit, which can not be operated with the operation of one or more base-load pump alone. Accordingly, in this case, all pumps of the pump set are switched on again and operated synchronously, so that the method for the changed operating point can start anew.

Furthermore, it is advantageous if the first condition is immediately returned to the synchronous mode and the reference value is stored as the upper limit value only when the operating state before the volume flow reduction is restored after the return. This procedure represents a plausibility check and takes into account the case that changes during the review of the first condition of the operating point of the pump set. Because only in the case of no change in the operating point, the pump unit will return to the original operating state in the reversal of the volume flow reduction, in which the synchronous speed and / or power consumption of the pump unit again corresponds to / before the volume flow reduction. Only in this case is it possible to conclude that the operating state is in the peak load range or in the efficiency-optimized range, so that the reference value can be correctly stored as the upper limit value.

It is further advantageous if the lower limit is reset to a minimum value and is returned to the synchronous operation, when the first pump reaches an inadmissible operating state in the base load operation, in particular reaches or exceeds a maximum speed. With this procedure, a safety device is implemented, which applies in the event that the stored lower limit is incorrect. In order to avoid a malfunction of the pump unit, then a reset of the lower limit value and went into synchronous operation, when the first pump reaches an inadmissible operating state.

According to the invention, the above-described method can be implemented in a computer program, i. be formed by a computer program product containing instructions for carrying out the method according to the invention, and which is carried out when it is executed on a microcomputer of a control electronics. The method can be implemented both in a control electronics of the pump unit and in an external control device, in particular in a control computer.

Finally, the invention relates to a pump unit with at least one base load-operated first pump and at least one second peak-load pump, which is switched on and operated parallel to the at least one first pump, wherein the pump unit is controllable on a predetermined control characteristic that the recorded power is minimal, and wherein it has a control electronics, which is adapted to carry out the method described above. In this case, the aforementioned computer program with the instructions for carrying out the method can be loaded onto a microcomputer of the control electronics.

Figur 1:

schematische Darstellung eines Doppelpumpenaggregats

Figur 2:

schematische Darstellung eines Multipumpenaggregates

Figur 3:

übergeordnete Schrittfolge des erfindungsgemäßen Verfahrensablaufs

Figur 4:

Beispielhafte Implementierung des erfindungsgemäßen Verfahrens zur Leistungsregelung des Pumpenaggregats mit dynamischer Grenzwertanpassung als Programmablaufplan

Figur 5:

Kennlinienfeld eines Doppelpumpenaggregats

Figur 6:

Beginn des Verfahrens mit einem beispielhaften Betriebspunkt im Grundlastbereich

Figur 7:

Darstellung des Kennlinienfeldes mit neu gesetzter unterer Grenze und neuem Betriebspunkt im Spitzenlastbereich

Figur 8:

Darstellung des Kennlinienfeldes mit gesetzter unterer und neuer obererGrenze und neuem Betriebspunkt im wirkungsgradoptimiertem Bereich

Figur 9:

Veranschaulichung der Anpassung der oberen Grenze am Kennlinienfeld

Figur 10:

Veranschaulichung der Anpassung der unteren Grenze am Kennlinienfeld

Figur 11:

Veranschaulichung des Verfahrens nach der Wahl einer neuen Regelkennlinie Δp-c im Kennlinienfeld mit neuem Betriebspunkt im Grundlastbereich

Figur 12:

Veranschaulichung einer neuen Regelkennlinie Δp-v im Kennlinienfeld

Figur 13:

Darstellung des zeitlichen Verlaufs der Leistungen und der Drehzahl der Pumpen und des Pumpenaggregats bei schrittweiser Drehzahlreduzierung der zweiten Pumpe über die Zeit

The invention will be explained in more detail below with reference to an exemplary embodiment with reference to the accompanying figures. Show it:

FIG. 1:

schematic representation of a double pump unit

FIG. 2:

schematic representation of a multi-pump unit

FIG. 3:

Superordinate step sequence of the process sequence according to the invention

FIG. 4:

Exemplary implementation of the inventive method for power control of the pump set with dynamic limit value adjustment as a program flowchart

FIG. 5:

Characteristic field of a double pump unit

FIG. 6:

Start of the procedure with an exemplary operating point in the base load range

FIG. 7:

Representation of the characteristic field with newly set lower limit and new operating point in the peak load range

FIG. 8:

Representation of the characteristic field with set upper and lower upper limit and new operating point in the efficiency-optimized range

FIG. 9:

Illustration of the adaptation of the upper limit of the characteristic field

FIG. 10:

Illustration of the adjustment of the lower limit on the characteristic field

FIG. 11:

Illustration of the method after the selection of a new control characteristic Δp-c in the characteristic field with a new operating point in the base load range

FIG. 12:

Illustration of a new control characteristic Δp-v in the characteristic field

FIG. 13:

Representation of the time course of the power and the speed of the pumps and the pump set with gradual speed reduction of the second pump over time

FIG. 1 shows a schematic representation of a double pump, ie a pump unit 1 with two identical pumps 2a, 2b, which are hydraulically connected in parallel. They have a common suction line 4, to which the two pumps 2a, 2b are connected with their suction side. On the pressure side, the pumps 2 a, 2 b open into a common pressure line 5, wherein a check valve 3 a is arranged in the transition region to the pressure line 5. This non-return valve prevents pumped fluid from entering one pump into the pressure side of the other pump, thus creating unnecessary hydraulic resistance. Rather, the non-return valve 3a directs the flow of the two pumps 2a, 2b in the pressure line. 5

Each pump 2a, 2b is associated with a pump electronics 6, which controls the electric motor drive unit of the pump 2a, 2b. The pump electronics 6 is connected to an operating voltage and energized the respective electric motor by means of a frequency converter. The frequency converter is controlled by a pulse width modulated (PWM) signal from a microprocessor of the pump electronics in response to a speed reference is produced. This speed setpoint is output by a controller, which is also part of the pump electronics, in particular implemented in the microprocessor of the electronics.

This controller is superior to the method according to the invention and regulates a pump 2a, 2b according to a control characteristic which can be specified at the respective pump electronics 6. In each case, the pressure generated by a pump 2a, 2b is regulated, wherein the pumps 2a, 2b are set up for measuring the differential pressure between the suction side and the pressure side. Alternatively, the pump unit 1 may also be pressure-controlled, wherein only the control of one of the two pumps 2a, 2b is needed.

In the exemplary embodiment according to FIG. 1 the two pump electronics 6 of the pumps 2a, 2b are connected in parallel via a control line 8. The pump electronics 6 of the second pump 2b can receive the same control signal for their frequency converter via this control line 8, which is output by the pump electronics 6 of the first pump 2a. The first pump 2a thus functions, together with its regulating / control electronics 6, as a type of master, whereas the second pump 2b is controlled with its regulating / control electronics 6 as a type of slave. According to this control arrangement, a synchronous operation of the two electromotive drive units of the first pump 2a and the second pump 2b is achieved. However, the pump electronics 6 of the second pump 2b is completely identical in design to the pump electronics 6 of the first pump 2a and can if necessary control the second pump 2b completely independently of the pump electronics 6 of the first pump 2a.

FIG. 2 shows an exemplary second embodiment of the pump unit 1 according to the invention with a plurality of parallel operating pumps 2a, 2b. Of this variety, however, only three pumps in the FIG. 2 shown. In this case, two pumps 2a act as synchronously running base load pumps and a pump 2b as a peak load pump. All pumps are connected to a common suction line 4 and open into a common pressure line 5. Between each pump 2a, 2b and the pressure line 5, a check valve 3 is arranged, which like the non-return valve 3a in FIG. 1 each prevents that under pressure standing pumped medium enters the pressure-side region of a less pumping or pump switched off.

Also in this embodiment according to FIG. 2 each pump 2a, 2b is equipped with a pump electronics 6, which can control the corresponding pump 2a, 2b completely self-sufficient, that can energize the electric motor drive unit such that the pump 2a, 2b is controlled on a predetermined control characteristic. The pump electronics 6 according to FIG. 2 are therefore identical to the pump electronics 6 in FIG. 1 , Basically, the pump electronics 6 can be connected to each other via control lines, not shown, and implement control technology, a master / slave arrangement in this second embodiment. Alternatively to this variant is in FIG. 2 a higher-level central control unit 7 is shown, with which the individual pump electronics 6 are connected via a respective control line 9. About this central control unit 7, the rotational speeds of the individual pumps 2a, 2b of the pump unit 1 in FIG. 2 specified.

The in the Figures 1 and 2 Pump units 1 shown are preferably used as circulation pumps in heating systems or as printing stations for fresh water delivery.

The method according to the invention will be described below with reference to a double pump unit 1 according to FIG FIG. 1 illustrated. In this case, the first pump 2a is used to operate the base load and the second pump 2b to operate the peak load. According to this understanding, the first pump 2a is referred to in the context of the invention as a base load pump, whereas the second pump 2b is referred to as a peak load pump. The peak load pump 2 b is required on the one hand to cover a flow requirement that can not be met by the base load pump alone. However, it is also operated synchronously to the base load pump in an area of the characteristic field in which the synchronous operation of both pumps is energetically more favorable than the exclusive operation of the base-load pump.

The inventive method can easily on a multi-pump unit according to FIG. 2 can be extended by the base load pump 2a and a connected peak load pump 2a control technology together as a base load pump 2a are considered, to which a further pump 2b, namely the new peak load pump 2b is connected.

FIG. 3 shows the superordinate sequence of the method according to the invention. The method is performed immediately when commissioning the pump unit 1 and learns to himself, when it is energetically cheaper to operate only the base load pump or when a synchronous operation of base load and peak load pump 2a, 2b is energetically cheaper.

Start of the procedure is according to FIG. 3 at the step 10 marked with "start". First of all, an upper limit value n_o and a lower limit value n_u are defined, and values are given to these limit values in a step 12 labeled "reset". In this case, the upper limit n_o is set equal to the maximum speed n_max of the base load pump 2a and the lower limit n_u is set equal to the minimum speed n_min of the base load pump 2a. Since the two pumps 2a, 2b are designed to be identical, these limits also correspond to those of the peak load pump 2b and the double pump unit 1 in synchronous operation.

When setting or resetting the limit values n_u, n_o, a further limit value n_u_GLP is additionally set, which defines a base load reference value of the rotational speed. This reference value is occupied in the course of the process with that speed n_GLP of the base load pump 2a which is applied to the base load pump 2a when the base load operation, i. is transferred to the operation with only the base load pump 2a. This speed value then serves as a reference to the current speed n_GLP of the base-load pump 2 a, by means of which an abnormal speed increase of the base-load pump 2 a can be ascertained. This will be explained in more detail below.

The essential steps of the process according to the invention are in FIG. 3 summarized by the APL (Adaptive Peak Load) designated block 20, its implementation FIG. 4 shows and explained below. APL 20 implements a power control of the pump set 1 with dynamic threshold adjustment.

During the execution of the method steps of the APL block 20, a new setpoint presetting 14, i. If the control characteristic changes, the process is restarted and new limit values n_u, n_o, n_u_GLP are set for this control characteristic. In this case, the previously determined limit values relative to the original control characteristic, i. the original setpoint default are stored so that they can be reused when returning to the previous setpoint setpoint. A new setpoint specification 14 does not mean that the previously determined limit values are deleted. Rather, new limit values n_u, n_o, n_u_GLP are only set when a control characteristic is set in the pump unit 1, which has never been set before. If you change to a previously set characteristic, the limit values already determined for this characteristic will continue to be used. If, on the other hand, there is no change in the control characteristic during the execution of the steps of the APL block 20, these APL steps are repeated cyclically.

FIG. 4 graphically illustrates the individual steps of the APL block 20 in FIG FIG. 3 of the method according to the invention in a logical flowchart. The method begins with a synchronous operation 21 of the pump unit 1, in which the pump electronics 6 of the base load pump 2a and the peak load pump 2b regulate them such that the speed of the base load pump n_GLP and the speed of the peak load pump n_SLP are identical and correspond to a predetermined synchronous speed n_sync. The synchronous operation is in FIG. 4 characterized by the block 21. The synchronous speed n_sync is specified by the higher-level controller, which adjusts the pump unit 1 in such a way that the differential pressure Δp or the delivery height H of the pump unit 1 in accordance with the predetermined volume flow Q given by the hydraulic system in which the pump unit 1 is integrated Control characteristic holds.

Starting from this synchronous operation, it is first checked in a step 22 whether the synchronous rotational speed n_sync is smaller than the lower limit value n_u.

At the beginning of the procedure, this condition can not be fulfilled anyway because the lower limit n_u has been set equal to the minimum speed n_min of the base load pump 2a in step 12. In the course of the method, however, the lower limit n_u is dynamically raised and then indicates that each synchronous speed n_sync belongs to an operating point lying in the base load range 17 below this lower limit value n_u. Occurs such a case, the peak load pump is turned off in step 36, since in the base load range 17, the exclusive operation of the base load pump 2a to provide the required flow Q and sufficient energy is more favorable than the synchronous operation of base load and peak load pump 2a, 2b.

If the lower limit value n_u has been correct, the speed n_GLP of the base-load pump 2a should increase only slightly in order to compensate for the reduced volume flow due to the elimination of the peak load pump 2b. However, should the speed n_GLP of the base-load pump 2a increase to the maximum speed n_max, which is subsequently checked in step 37, the lower limit value n_u has been set incorrectly. It is therefore reset to the initial value in the subsequent step 38, i. reset to the minimum speed n_min. In this case, the peak load pump 2 b is immediately connected again and the pump unit 1 is operated in synchronous operation 21.

The further method steps are described below with reference to FIGS FIGS. 5 to 13 explained.

FIG. 5 shows a schematic representation of the family of characteristics of a double pump 1 according to FIG. 1 , The characteristic field is formed by a plurality of characteristic curves 44 of constant speed and pipe network parabolas 43 whose pitch is predetermined by the pipe network resistance of the hydraulic system in which the pump unit 1 is integrated. The characteristic field is limited to the top by a maximum characteristic 41 of the pump unit 1. This characteristic 41 corresponds to the operating points of the pump unit 1, which can be reached at maximum synchronous speed of the two individual pumps 2a, 2b. In contrast, the characteristic indicated by the reference numeral 18 is the maximum characteristic of one of the pump 2a, 2b, in particular the base load pump 2a.

This characteristic curve 18 identifies all operating points that can be reached during exclusive operation of the base-load pump 2 a at the maximum rotational speed n_max. Between the maximum characteristic 41 of the pump unit 1 and the maximum characteristic curve 18 of the basic load pump 2a is the peak load region 15. Thus, the pump unit 1 can reach an operating point within this peak load range 15, the operation of base load pump 2a and peak load pump 2b is required.

Towards the bottom, the characteristic field is limited by a minimum characteristic 42 of the base-load pump 2 a. Between the minimum characteristic 42 and the maximum characteristic 18, each operating point of the pump unit 1 can be achieved exclusively by the base-load pump 2 a. This intermediate region is divided into the base load region 17, in which it is energetically more favorable to operate only the base load pump 2a, and an efficiency-optimized region 16, in which the pump unit 1 receives less power when base-load pump 2a and peak load pump 2b are operated simultaneously, in particular synchronously , against an exclusive operation of the base load pump 2a. This efficiency-optimized region 16 is substantially in the range of low to medium volume flows Q at low to medium head H.

The transition between the base load region 17 and the efficiency-optimized region 16 is characterized by a boundary line 40, whose position has been found by measuring the characteristic field on the test bench according to the prior art. According to the invention, however, the position of this boundary line 14 is found out with increasing accuracy during operation of the pump unit 1.

To illustrate the method steps according to FIG. 4 will be on first FIG. 6 Referenced. The pump unit 1 is first controlled according to a first control characteristic 19, on which the pressure Δp of the pump unit 1 or the delivery height H is kept constant over the volume flow Q. In FIG. 6 the lower limit value n_u and the upper limit value n_o are plotted. It is first assumed that after the commissioning of the pump unit 1 and the set synchronous operation 21, a first Operating point 11 sets, which is in the base load range 17. This is determined by the method as follows.

With reference to FIG. 4 was first determined in step 22 that the currently applied synchronous speed in the operating point 11 is not less than the lower limit n_u. It is then checked in step 23 whether the current synchronous speed n_sync is smaller than the upper limit value n_o. This is the case at the operating point 11 because the upper limit n_o has been set equal to the maximum speed n_max of the base load pump 2a. In step 23 it is also checked whether the synchronous speed n_sync is less than the maximum speed n_max. Since the method according to the invention has not yet set a new upper limit value n_o at this point, the aforementioned second condition is identical to the first one. It therefore only becomes significant if, in the course of the method, the upper limit n_o is set to a value below the maximum speed n_max.

For the operating point 11 in FIG. 6 the conditions tested in step 23 are met. This is followed by a storage of the current synchronous speed n_sync as reference speed n_ref, step 24a. Subsequently, the total electrical power P_Σ is determined and stored in step 24b as a reference power P_ref. Thereafter, in step 25, the speed n_SLP of the peak load pump 2b is reduced, for example, by 100 rpm. As a result, the flow rate of the peak load pump 2b is reduced. The two pumps 2a, 2b are no longer operated synchronously. The reaction of the pump unit 1 to this speed reduction will now be analyzed.

The higher-level speed controller now controls the resulting from the speed reduction of the peak load pump pressure drop of the pump unit 1, characterized in that the speed of the base-load pump is increased. At the same time any existing valves in the hydraulic system, for example, thermostatic valves readjust. In order to wait for this system reaction, a wait time t_wait is waited for in step 35. This is between one and 20 s, preferably between 5 and 15 s, in particular about 10 s, and it can be chosen in particular as a product of the settling time of the pressure regulator and a factor which is preferably between two and five. Wait a counter for the waiting time can be set to zero immediately after a speed reduction in step 25 and then counted up numerically. Only after expiry of the waiting time t_wait is it checked how the pump unit 1 reacts to the speed reduction of the peak load pump 2b in step 25.

In this case, it is first checked in step 26 whether the rotational speed n_GLP of the base-load pump 2a reaches or exceeds its maximum value n_max due to the speed reduction of the peak load pump 2b. If this were the case, then the current operating point 11 would be in the peak load range 15. However, this is not the case here.

Furthermore, it is checked in step 26 as an alternative condition whether the now adjusting electrical power consumption P_GLP of the base load pump 2 a rises above the stored power reference value P_ref. If this were the case at the operating point 11, it would either be in the efficiency-optimized range 16 or in the peak load range 15. If the speed condition n_GLP ≥ n_max is checked before the power condition P_GLP> P_ref and the speed condition is not satisfied, then the power condition would have been checked in that the operating point lies in the efficiency-optimized region 16.

However, a hierarchical examination of the two conditions in step 26 is not absolutely necessary, since both in the case of performance of the performance condition and in the case of meeting the speed condition in each synchronous operation is transferred, step 29. The procedural response to the occurrence of one of these conditions is therefore the same.

For the operating point 11 in FIG. 6 the verification of the stated conditions in step 26 results in a negative result. It is therefore already established at this point that the operating point 11 is in the base load range 17.

It is then checked in step 27, whether the base-load pump 2a has reached a steady, ie stable state, that is, the recorded electric power P_GLP is substantially constant. This is checked by whether the derivative of the absorbed electric power of the base load pump P_GLP is substantially zero. Instead of the derivative can be used for the numerical calculation of sizes a microprocessor also the difference quotient ΔP_GLP / .DELTA.t are used, with which the power consumption change ΔP_GLP per waiting time .DELTA.t = t_warten is determined. Furthermore, a moving averaging can be applied to the measured or calculated values to filter out disturbances from the measured current and voltage values for calculating the power.

If the power P_GLP of the base-load pump 2 a still changes after the speed reduction, no concrete statement can yet be made as to whether or not the operating point 11 lies in the base load range 17. It then proceeds from step 27 to the next step 28. A special case exists when, contrary to the expectation of a speed increase of the base load pump 2 a to compensate for the lack of volume flow rate of the peak load pump 2 b, the power consumption of the base load pump 2 a decreases. This can then be the case if in the meantime a lower flow rate Q than before the speed reduction of the peak load pump 2 b is required and the higher pressure regulator of the pump unit 1 this downshifts in the power. Since the peak load pump 2b is given a specific speed by the method according to the invention, only the base load pump 2a remains under the controlled influence of the superordinate pressure regulator so that it downshifts the power of the base-load pump 2a. Whether this is the case is checked in step 28. If this case occurs, then the operating point 11 has changed and a statement about its original position can not be made at this point. From step 28, therefore, the method according to the invention returns to synchronous operation 21, from where it begins anew with the changed operating point.

However, if the condition in step 28 is not met, the power of the base-load pump 2a either increases or fluctuates as a result of the volume flow transfer, so that no concrete statement can be made about the operating point.

A further speed reduction of the peak load pump 2b is then performed in step 25 and the system response is again awaited. Subsequently, the conditions 26, 27 and 28 are checked again.

In the case of the operating point 11 in FIG. 6 a time t_waiting of about 10 seconds is required until the power consumption of the base-load pump 2a is set to a steady state, see in FIG. 13 the curve P1_MA.

In this case, from step 27 in FIG. 4 Transitioned to step 32a and the previously stored reference speed r_ref, which is associated with the operating point 11, is stored as the lower limit n_u, since it is now clear that the operating point 11 is in the base load range 17. The peak load pump 2b is then turned off, step 32b. Since in this way the rotational speed n_GLP of the base-load pump 2 a can change again, it makes sense to provide here a further waiting time, which in FIG. 4 but not taken into account. After switching off the peak load pump 2 b, the current speed n_GLP of the base load pump 2 a including an added offset is stored as a base load reference value n_u_GLP, step 32 c.

The pump unit 1 is now operated in the base load mode 33, in which the peak load pump 2b is turned off, ie their speed n_SLP is zero, whereas the base load pump 2a continues to be operated at a non-zero speed n_GLP. This is in block 33 in FIG. 4 shown.

During the base load operation 33, the rotational speed n_GLP of the base-load pump 2a is constantly checked. If it rises above the stored base load reference value n_u_GLP, it returns directly to synchronous mode 21. For safety reasons, it is also checked in condition 34 for the case of an incorrectly set base load reference value n_u_GLP whether the speed of the base-load pump n_GLP rises above its maximum speed n_max. If this is the case, is also transferred to the synchronous mode 21.

Fig. 7 shows that the lower limit n_u is now set to the speed value that existed at the first operating point 11 before the volume flow reduction of the second pump 2b. This means that every other operating point has one speed is also in the base load range 17 below the new lower limit n_u. The area below the lower limit n_u is in FIG. 7 therefore marked hatched.

Furthermore, in FIG. 7 assumed that sets an operating point in the peak load range 15 as the second operating point 13. Starting from the previous base load operation 33 in FIG. 4 As a result, the speed n_GLP of the base-load pump will increase considerably compared to the base-load reference value n_u_GLP, in particular increase above the maximum speed n_max. The in step 34 in FIG. 4 mentioned and constantly checked conditions are therefore met and it is transferred to the synchronous mode 21.

The then adjusting synchronous speed n_sync must necessarily be above the previously stored in the operating point 11 synchronous speed, so that the condition 22 in FIG. 4 is not fulfilled. Since the upper limit value n_o still corresponds to the maximum synchronous speed value n_max, the condition tested in step 23 or the two conditions mentioned there are fulfilled. The current synchronous speed n_sync is therefore stored again as a speed reference value n_ref, step 24a, and the electrical power P_Σ recorded by the pump unit is determined and stored as reference power P_ref, step 24b. Subsequently, the speed n_SLP of the peak load pump 2b is reduced, step 25, and the reaction of the pump set 1 to this speed reduction is awaited, step 35, and analyzed.

The reduction of the rotational speed n_SLP will cause the rotational speed n_GLP of the base-load pump 2a to reach its maximum value n_max because the operating point 13 conditions a volumetric flow Q which lies beyond the maximum characteristic curve 18 of the basic-load pump 2a. For this reason, the condition in step 26 will be satisfied after a certain time, so that the synchronous operation is returned, step 29 in FIG FIG. 4 ,

It is thus stated that the new operating point 13 is in the peak load range 15, so that the synchronous speed stored as reference speed n_ref n_sync can be set as the upper limit n_o, step 31. However, before it is checked whether after returning to synchronous operation in step 29, the speed of the base load pump n_GLP returns to its original value, namely to the original synchronous speed n_sync. This condition is in step 30 in FIG. 4 checked. Only if this is the case, the reference value n_ref is set as upper limit n_o. Otherwise, the current operating point has changed again, so that a clear statement about its location is not possible. The procedure is then continued in synchronous mode 21. However, for the case illustrated purely by way of example, the operating point 13 remains unchanged, so that the reference value n_ref is set as upper limit n_o. This is in FIG. 8 shown.

In FIG. 8 FIG. 11 further illustrates that synchronous speeds above the upper limit n_o belong to operating points in which both the base load pump 2 a and the peak load pump 2 b should be operated. Furthermore, in FIG. 8 a third operating point 45 assumed by way of example, which is now in the efficiency-optimized region 16.

Starting from the synchronous operation 21, in which the method is still due to the previous operating point 13, a synchronous rotational speed n_sync will again set above the lower limit n_u with the new operating point 45, so that the condition in step 22 in FIG FIG. 4 is not fulfilled. In contrast, both are met in step 23 to be tested conditions so that the current synchronous speed n_sync can be stored again as a reference value n_ref, step 24. Furthermore, the currently recorded electrical power P_Σ the pump unit 1 is again stored as a reference power P_ref, step 24b. After these storage steps, the speed n_SLP of the peak load pump 2b is again reduced, step 25, and waited until the higher-level pressure regulator has corrected.

The reduction of the speed n_SLP of the peak load pump 2b will on the one hand lead to the speed n_GLP of the base load pump 2a not running to its speed limit n_max, since the operating point 45 is below the maximum characteristic 18. However, it will be the case that the power P_GLP picked up by the base-load pump 2a due to the volume flow transfer by the Base load pump 2a rises above the stored reference power P_ref. This will be in step 26 in FIG. 4 detected. It is then again set for the pump unit 1 energetically better synchronous operation 29. Subsequently, it is again checked whether the rotational speed n_GLP of the base-load pump 2a returns to the reference rotational speed n_ref. If this is the case, the reference speed is stored as a new upper limit n_o, step 31. The adjustment of the upper limit is in FIG. 9 illustrated.

According to FIG. 10 It is now assumed that a fourth operating point 47 sets, which is again in the base load range 17 and on the adjusted control characteristic curve 19 requires a volume flow Q, which causes a synchronous speed n_sync above the lower limit value n_u. Therefore, the condition in step 22 in FIG FIG. 4 again not fulfilled. On the other hand, both conditions to be tested in step 23 are fulfilled, so that the current synchronous speed n_sync is again stored as reference speed n_ref, step 24a, the current power P_Σ is stored as reference power P_ref, step 24b, and subsequently the speed of the peak load pump n_SLP is reduced , Step 25.

Since the new operating point 47 is in the base load range 17, none of the conditions tested in step 26 will be met. This means that the base-load pump 2a neither reaches its maximum speed n_max nor achieves a power consumption which is above the reference power P_ref due to the speed reduction of the peak load pump 2b. The speed reduction of the peak load pump 2b will cause the power P_GLP picked up by the base load pump 2a to initially increase but then reach a saturation value when the base load pump 2a has almost completely taken over the flow rate of the peak load pump 2b. Since the power P_GLP of the base-load pump no longer changes significantly in this case, the condition in step 27 is fulfilled. The reference speed n_ref is then set as the new lower limit n_u, step 32a, the peak load pump 2b turned off, step 32b, and the then present actual speed n_GLP of the base load pump 2a plus an offset set as the new base load reference value n_u_GLP, step 32c.

The pump unit 1 is then operated in the base load mode 33, in which the peak load pump 2 a is turned off and the pump unit 1 is controlled exclusively with the base load pump 2 a on the set control characteristic 19.

The increase of the lower limit n_u to the new operating point 47 is in FIG. 10 illustrated. It becomes clear that the distance between the upper limit n_o and the lower limit n_u becomes lower in the current process, in particular when there is a new operating point which is closer to the theoretical limit line 40.

In FIG. 11 now the change to a new constant control characteristic 40 is illustrated. A new lower limit n_u and a new upper limit n_o are set, which are assigned a minimum value or maximum value for the rotational speeds. In FIG. 11 is again a new, fifth operating point 48 located, which is in the base load range 17. The method will now be described in accordance with the above-described steps in FIG. 4 as before on the basis of Figures 6-10 explained. Based on FIG. 11 It is still clear that the limit values n_u, n_o determined for the previous control characteristic 19 remain, so that in the case of a return to the original control characteristic 19 these limit values n_u, n_o can be reused.

FIG. 12 illustrates the application of the method according to the invention with a further control characteristic 39, according to which the delivery pressure Δp of the pump unit 1 is controlled linearly via the volume flow Q. In FIG. 12 are already shown adjusted values for the lower limit n_u and the upper limit n_o, which have been determined during operation. Between the two limits, the boundary line 40 runs.

FIG. 13 illustrates the graph of the measured values for the speed n_setpoint specified for the peak load pump 2b, for the total output P1_Sum of the pump set, for the power P1_MA of the base load pump and for the power P1_SL of the peak load pump, for a head H of 15 m and a flow Q of 55 m ³ / H.

Starting from the stationary state of the pump unit 1, the speed n_soll of the peak load pump 2b is reduced by 100 rpm. In this case, the power consumption P1_SL of the peak load pump 2b decreases significantly, whereas the power P1_MA of the base load pump 2a increases by a higher amount. After about 10 seconds, the power P1_MA the base load pump 2a has reached a value of about 4000 watts. Although a subsequent further speed reduction of 100 rpm has a reduction in the power P1_SL received by the peak load pump 2b, it does not change the power consumption P1_MA of the base load pump 2a. This is because the non-return valve 3a in the pump unit 1 leads to the fact that even a small shift in the delivery rate contributions towards the base-load pump 2a clearly dominates it. Thus, even a speed reduction of about 5% of the rated operating speed of the peak load pump 2 b causes the volume flow Q is almost exclusively supplied by the base load pump 2 a. The peak load pump 2b can therefore be switched off already after the first speed reduction, since it provides no appreciable contribution.

The consideration of the total power P1_Sum absorbed by the pump unit 1 FIG. 13 shows that this total power is always above the curve of the power P1_MA the base load pump 2a. This means that the operating point from which in FIG. 13 is assumed before the speed reduction is in the base load range 17, in which the power consumption of the base load pump 2a does not increase above the previously recorded in synchronous operation 21 before the speed reduction power P1_Sum the total unit. FIG. 13 therefore illustrates the physical quantities on the pump set 1, when an operating case according to FIG. 6 is present.

LIST OF REFERENCE NUMBERS LIST OF REFERENCE NUMBERS

1

pump unit

2a

first pump, base load pump

2 B

second pump, spike load pump

3

check valve

3a

check valve

4

suction

5

pressure line

6

pump electronics

7

central control unit

8th

control line

9

control lines

10

commencement of proceedings

11

first operating point

12

Resetting the limits / Reset

13

second operating point

14

new setpoint specification

15

Peak load

16

efficiency-optimized range

17

Base load

18

Maximum characteristic of the base load pump

19

Control characteristic Δp-c

20

Power control of the pump set with dynamic limit value adjustment

21

synchronous operation

22

Query operating point in the base load range

23

Query operating point in peak load range

24a

Storage reference speed

24b

Storage reference performance

25

Speed reduction

26

Checking a first condition

27

Check a second condition

28

Review of a third condition

29

synchronous operation

30

Operating point change check

31

Adjust the upper limit

32a

Adjust the lower limit

32b

Transition to base load operation

32c

Storage of a base load reference value

33

Base load operation

34

Checking the operating state of the base load pump

35

Checking a waiting time

36

Transition to base load operation

37

Checking the operating state of the base load pump

38

Reset the lower limit

39

Control characteristic Δp-v

40

boundary line

41

Maximum characteristic of the pump set

42

Minimum characteristic of the basic load pump

43

Pipe network parables

44

Characteristic curves of constant speed

45

third operating point

46

new control characteristic Δp-c

47

fourth operating point

48

fifth operating point

Claims (22)

1. Method for operating a pump assembly (1) having at least one first pump (2a) serving a base load and at least one second pump (2b) serving a peak load, which is connected up as required and is operated in parallel with the at least one first pump (2a), the pump assembly (1) being controlled to a predefined control characteristic curve (19, 39) in such a way that the power consumed is minimal, characterized in that the pump assembly (1) is operated on the basis of an upper and a lower limiting value (n_o, n_u) of an operating variable (n_sync) either with at least two pumps (2a, 2b) or with at least one pump (2b) switched off, wherein, starting from synchronous operation (21) of the pumps (2a, 2b) at an operating point (11, 13) at which the pumps (2a, 2b) are operated with the same rotational speed (n_sync) and/or power,

   a. in a first step (24a), the value of at least one operating variable (n_sync) of the pump assembly (1) is stored as a reference value (n_ref),

   b. in a second step (25), the volume flow delivered by the second pump (2b) is reduced,

   c. in a third step (26, 27), depending on the reaction of the controlled first pump (2a), the operating point (11, 13) is allocated to a load range (15, 16, 17), and

   d. in a fourth step (31, 32a), the upper or lower limiting value (n_o, n_u) is replaced by the reference value (n_ref).
2. Method according to Claim 1, characterized in that the operating variable is the synchronous rotational speed (n_sync) of the pump assembly (1), which is stored as reference rotational speed (n_ref).
3. Method according to Claim 1 or 2, characterized in that the power (P_Σ) consumed by the pump assembly (1) in synchronous operation (21) is determined and is stored (24) as reference power (P_ref).
4. Method according to one of the preceding claims, characterized in that the reference value (n_ref), in particular the reference rotational speed (n_ref), is stored (31) as an upper limiting value (n_o), in particular a rotational speed limiting value (n_o), if, following the volume flow reduction (25), at least one first condition (26), which is associated with one of the load ranges (15, 16) comprising peak-load range (15) or optimized-efficiency range (16), is satisfied.
5. Method according to one of the preceding claims, characterized in that the reference value (n_ref), in particular the reference rotational speed (n_ref), is stored (32a) as a lower limiting value (n_u), in particular a rotational speed limiting value (n_u), if at least one second condition (27), which is associated with the base load range (17), is satisfied.
6. Method according to Claims 4 and 5, characterized in that the pump assembly (1) is operated at an operating point (11) with a synchronous rotational speed (n_sync) equal to or above the upper limiting value (n_o) with at least two pumps (2a, 2b) and equal to or below the lower limiting value (n_u) with at least one pump (2b) switched off.
7. Method according to Claims 4 and 5 or Claim 6, characterized in that the pump assembly (1) at an operating point (13) with a synchronous rotational speed (n_sync) between the upper limiting value (n_o) and the lower limiting value (n_u), the steps a. to d. are repeated, starting from synchronous operation (21) of the pumps (2a, 2b).
8. Method according to one of the preceding Claims 4 to 7, characterized in that in the event of a change to the control characteristic curve (19, 39, 46), the limiting values (n_o, n_u) associated with this old characteristic curve (19, 39, 46) are stored, and a new upper and lower limiting value (n_o, n_u) are used for the new control characteristic curve (19, 39, 46).
9. Method according to one Claims 4 to 8, characterized in that the first condition (26) is satisfied when the rotational speed (n_GLP) of the first pump (2a) reaches or exceeds a maximum rotational speed (n_max) or when the power consumption (P_GLP) of the first pump (2a) exceeds the reference power (P_ref).
10. Method according to one of Claims 5 to 9, characterized in that the second condition (26) is satisfied when the power consumption (P_GLP) of the first pump (2a) remains substantially the same on average, or when the rotational speed (n_SLP) of the second pump (2b) reaches or falls below a minimum value.
11. Method according to Claim 4 and one of Claims 5 to 10, characterized in that the second condition (27) is checked only when the first condition (26) is not satisfied.
12. Method according to one of Claims 5 to 11, characterized in that when the lower limiting value (n_u) is stored (32a), the value of an operating variable (n_GLP) of the first pump (2a) is stored (32c) as base load reference value (n_u_GLP) .
13. Method according to Claim 12, characterized in that a change is made (34) from operation (33) with at least one pump (2b) switched off to synchronous operation (21) with at least two pumps (2a, 2b) when the current value of the operating variable (n_GLP) of the first pump (2a) rises above the base load reference value (n_u_GLP) or is equal to or greater than a maximum value (n_max) of this operating variable (n_GLP).
14. Method according to Claim 12 or 13, characterized in that the operating variable of the first pump (2a) that is used is its rotational speed (n_GLP).
15. Method according to Claim 12, 13 or 14, characterized in that an offset is added (32c) to the base load reference value (n_u).
16. Method according to one of the preceding claims, characterized in that following the volume flow reduction (25), a change to synchronous operation (21) is made again if, as a third condition (28), the power consumption (P_GLP) of the first pump (2a) decreases.
17. Method according to one of the preceding Claims 4 to 16, characterized in that only after a waiting time (t_wait) is a check made to see whether at least one of the conditions (26, 27, 28) is satisfied.
18. Method according to one of the preceding Claims 4 to 17, characterized in that the volume flow from the second pump (2b) is reduced further (25) if none of the conditions (26, 27, 28) is satisfied.
19. Method according to one of the preceding claims, characterized in that a change is made to synchronous operation (21) if the rotational speed (n_GLP) of the first pump (2a) reaches or exceeds a maximum value (n_max), or in that when the first condition (26) is satisfied, a return is made immediately to synchronous operation (29), and the reference value (n_ref) is stored (31) as an upper limiting value (n_o) only when, following the return, the operating state before the volume flow reduction is established again (30).
20. Method according to one of the preceding claims, characterized in that the lower limiting value (n_u) is reset (38) to a minimum value and a return is made to synchronous operation (21) if the first pump (2a) reaches an inadmissible operating state, in particular reaches or exceeds a maximum rotational speed (n_max).
21. Computer program with instructions for carrying out the method according to one of the preceding claims when it is executed on a microcomputer of control electronics (6, 6a, 6b).
22. Pump assembly (1) having at least one first pump (2a) serving a base load and at least one second pump (2b) serving a peak load, which can be connected up as required and operated in parallel with the at least one first pump (2a), the pump assembly (1) being controllable to a predefined control characteristic curve (19, 39) in such a way that the power consumed is minimal, characterized in that it has control electronics (6, 6a, 6b) which are configured to carry out the method according to one of Claims 1 to 20.

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