Conveyor device with two conveyor elements connected in parallel
By connecting two conveying elements in parallel in the conveying device, and dynamically switching drive control with a unified flow regulator and switching device, the energy efficiency and wear problems with large flow ratio in the prior art are solved, and stable and efficient Media conveying.
Patent Information
- Application Number
- CN201980100749.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2019-07-25
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2039-07-25
AI Technical Summary
In the prior art, when the medium is transported, especially when the flow rate ratio is large, the energy efficiency is low and difficult to effectively adjust, resulting in turbulence and air pockets, causing wear.
设计一种输送装置，其中两个并联连接的输送元件由统一的流量调节器调节，通过切换装置在流量目标值变化时动态切换驱控，确保仅在必要的流量范围内运行，避免不必要的能量消耗。
It realizes stable operation and efficient adjustment of the conveyor device in the case of a large proportion between large flow and small flow, avoids the occurrence of turbulence and air pockets, and improves the energy efficiency and the service life of the equipment.
Smart Images
Figure CN114503048B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a conveying device for a medium.
[0002] wherein the conveying device has a conveying line, via which the medium is conveyed from a source location to a destination location,
[0003] wherein the transport line has a transport section between a source location and a destination location,
[0004] - wherein the conveying element is arranged in a conveying section,
[0005] - wherein the conveying element is regulated by a flow regulator,
[0006] - wherein the flow regulator is fed with a flow target value and an actual flow value,
[0007] In this case, the flow controller calculates a corresponding manipulated variable for the pump using a control algorithm as a function of the flow target value and the flow actual value. Background Art
[0008] In many cases, media, especially liquids, must be transported from a source to a destination with the aid of a conveying element. For example, oil or water must be transferred from a first tank to be filled in a second tank. In the case of liquid media, the conveying element is a pump. In the case of large volume flows, the pump is usually designed as a centrifugal pump. In the case of gaseous media, the conveying element is usually a compressor, a gas compressor or a blower.
[0009] In some cases, the medium can be conveyed without regulation. However, very specific medium flows must usually be set, for example 100 liters per second (the values mentioned are to be understood as purely exemplary).
[0010] In the simplest design, for regulated delivery, the delivery element is operated at a constant speed and a continuously adjustable resistance is accordingly arranged, which is arranged in the delivery line before or after the delivery element. In the case of a pump that delivers a liquid medium, this can be an adjustable valve, for example. Although this solution is simple, it is very inefficient in terms of energy. In particular, the delivery element is always operated at full power so that it can deliver the required maximum flow rate. In addition, this approach has limitations for smaller flows, because in the case of excessive throttling, turbulence can occur in the flow and, in addition, cavitation can even occur in the valve air gap when valves are used. Cavitation leads to considerable wear.
[0011] An improved solution is to operate the conveying element at a variable speed. In this case, as described above, the conveying element is regulated by a flow regulator, wherein a flow target value and an actual flow value are fed to the flow regulator and the flow regulator calculates a manipulated variable for the conveying element using a control algorithm based on the flow target value and the actual flow value. In this case, the conveying element (more precisely: the drive of the conveying element) is driven by the flow regulator based on the manipulated variable. The manipulated variable is the speed of the conveying element or its drive.
[0012] The latter mentioned approach is very effective if the flow rate must be adjusted only within relatively narrow limits. Because in this case, the conveying element and its drive must be optimized to the desired flow rate, wherein the desired flow rate, according to the premise, must be adjusted only within relatively narrow limits. In this case, the ratio between the maximum and minimum occurring flow rate, for example in the case of liquids as the medium, should have a ratio of at most 5:1, better even only 4:1 or less, for example 2:1.
[0013] If the mentioned ratio is changed to a larger value, for example to 5:1 or more, then (at least in some cases) a corresponding operation of the conveyor element is still possible in principle. However, such operation is energy inefficient at relatively small flow rates, since both the conveyor element itself and the drive of the conveyor element are designed for a certain rotational speed and the efficiency decreases significantly at significantly lower rotational speeds. Furthermore, the conveyor element cannot usually be operated below a minimum flow rate. Summary of the invention
[0014] The object of the present invention is to provide a possibility according to which even in the case of a large ratio between a maximum required flow rate and a minimum required flow rate, a correspondingly designed conveying device can in principle be operated and can also be operated efficiently.
[0015] This object is achieved by a conveying device having the features of the invention. Advantageous embodiments of the conveying device according to the invention are the subject of the individual exemplary embodiments.
[0016] In the conveying device for a medium according to the present invention, it is proposed that:
[0017] the conveying device has a conveying line, via which the medium is conveyed from a source location to a destination location,
[0018] - the transport pipeline has a transport section between a source location and a destination location,
[0019] - two conveying elements are arranged in the conveying section,
[0020] - the conveying elements are connected in parallel with each other,
[0021] - the conveying elements are regulated by corresponding flow regulators,
[0022] - supplying a flow target value that is unified for both flow regulators and a flow actual value that is unified for both flow regulators to the two flow regulators,
[0023] - the flow regulator calculates the corresponding manipulated variable for the corresponding conveying element based on the flow target value and the flow actual value using the corresponding control algorithm,
[0024] - the conveying device has a switching device, and the flow target value is conveyed to the switching device,
[0025] the switching device is designed so that, when the flow target value drops below the lower switching threshold, the switching device prohibits the actuation of one conveying element by one flow regulator and permits the actuation of the other conveying element by the other flow regulator, so that the medium flows only via the other conveying element as long as the flow target value remains above the minimum value and below the upper switching threshold, and
[0026] -The switching device is constructed so that when the flow target value rises above the upper switching threshold, the switching device prohibits the control of another conveying element by another flow regulator and allows the control of one conveying element by one flow regulator, so that as long as the flow target value remains below the maximum value and above the lower switching threshold, the medium flows only through one conveying element.
[0027] Therefore, according to the present invention, two conveying elements are connected in parallel with each other. In the case of a pump, the conveying element is usually configured as a centrifugal pump. However, in any case, the size of the conveying element is designed differently. Since the size of the two conveying elements is designed differently, one of the two conveying elements can be called a large conveying element without loss of generality, and the other conveying element is called a small conveying element. A variable speed drive is associated with the conveying element as a drive. The drive can especially be an electric drive controlled by a converter. Each conveying element is regulated by its own flow regulator, wherein the corresponding flow regulator can be parameterized for the control and operation optimization of the corresponding conveying element. However, the same flow target value and the same flow actual value are delivered to the two flow regulators. However, at any time point, only one of the two conveying elements is controlled according to the adjustment variable of the assigned flow regulator. The corresponding other conveying element is not driven.
[0028] Assume that the large conveying element is driven at a specific point in time. This state is maintained until the flow target value drops below the lower switching threshold. The switching device monitors whether it falls below the lower switching threshold. If the flow target value falls below the lower switching threshold, then from this point in time, the large conveying element is no longer driven according to the regulation variable of the flow regulator associated with it, but is switched to the small conveying element, so that the small conveying element is driven by the flow regulator associated with it. From now on, this state is maintained until the flow target value rises above the upper switching threshold. The switching device also monitors whether it exceeds the upper switching threshold. If the flow target value exceeds the upper switching threshold, then from this point in time, the small conveying element is no longer driven according to the regulation variable of the flow regulator associated with it, but is switched to the large conveying element again, so that the large conveying element is driven according to the regulation variable of the flow regulator associated with it.
[0029] Of course, the lower switching threshold should not be greater than the upper switching threshold. However, the two switching thresholds can have the same value. However, the upper switching threshold is preferably even greater than the lower switching threshold. Thus, a hysteresis behavior is achieved, so that a stable operation of the conveying device is ensured. However, in any case, the maximum value is greater than each of the two switching thresholds and the minimum value is less than each of the two switching thresholds.
[0030] When switching from one conveying element to another, unstable situations may occur temporarily. In order to achieve the most stable and smooth switching, the flow regulators whose conveying elements are not driven are respectively permanently tracked. Therefore, the tracking value is delivered to the flow regulator of the conveying element to which the control is prohibited. The tracking value is obtained by multiplying the adjustment variable of the following flow regulator with the corresponding predetermined factor, wherein the conveying element of the flow regulator is driven by the flow regulator. Preferably, the predetermined factor of a conveying element corresponds to the quotient of the rated flow of another conveying element divided by the rated flow of this conveying element. In a similar manner, the predetermined factor of another conveying element preferably corresponds to the quotient of the rated flow of one conveying element divided by the rated flow of the other conveying element. However, in any case, the two factors are reciprocals of each other. Therefore, if one factor is represented by f1 and the other factor is represented by f2, then f1*f2=1 applies.
[0031] In order to avoid overloading of the conveying element when starting, a corresponding ramp generator is preferably associated with the flow regulator. From the time when the corresponding conveying element is allowed to be driven by the corresponding flow controller, the rotation speed of the corresponding conveying element is accelerated according to a predetermined corresponding ramp by means of the corresponding ramp generator. In this way, the operating behavior of the conveying device is stabilized.
[0032] The two flow regulators are preferably coupled to one another so that the flow regulators not only always achieve the same flow target value and the same flow actual value, but also always operate in the same operating mode. Possible operating modes are in particular manual operation and automatic operation. In manual operation, the operator predetermines the speed for one of the conveying elements. In automatic operation, the flow regulation is carried out as a function of the flow target value and the flow actual value. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The following description of the embodiments in combination with the accompanying drawings will more clearly explain the above-described characteristics, features and advantages of the present invention and the methods and means for achieving them. Herein, it is shown in a schematic diagram:
[0034] Figure 1 Showing part of the engineering facility,
[0035] Figure 2 A conveying device is shown,
[0036] Figures 3 to 5 shows a time graph, and
[0037] Figure 6 Another delivery device is shown. DETAILED DESCRIPTION
[0038] according to Figure 1 , a medium 1 is to be transported from a source location 2 to a destination location 3. The medium 1 is usually a liquid medium, such as water or oil. However, in individual cases, it can also be a gaseous medium. For example, the source location 2 can be a tank from which the medium 1 is taken. The destination location 3 can be, for example, a reactor in which the medium 1 is mixed with at least one other medium or processed in another way. However, other designs are also possible.
[0039] The conveying device has a conveying line 4 for conveying the medium 1 from the source location 2 to the destination location 3. The conveying line 4 has a conveying section 5 between the source location 2 and the destination location 3. The conveying section 5 is Figure 1 is bounded by a vertical dashed line and is Figure 2 Shown in detail in.
[0040] according to Figure 1 and 2 , two conveying elements 6, 7 are arranged in the conveying section 5. If the medium 1 is a liquid, the conveying elements 6, 7 are configured as pumps. In this case, the pump is usually configured as a centrifugal pump. If the medium 1 is a gas, the conveying elements 6, 7 can be configured as a compressor, a gas compressor or a blower, for example. However, in any case, the dimensions of the conveying elements 6, 7 are designed differently.
[0041] The conveying elements 6, 7 are connected in parallel with each other. The conveying section 5 thus has a front node 8 at which the conveying line 4 branches off into two branches 9, 10. One of each of the conveying elements 6, 7 is arranged in each of the two branches 9, 10. Usually, there is also a rear node 11 at which the two branches 9, 10 rejoin.
[0042] The conveying elements 6 and 7 are Figure 2 The flow rate is controlled by the corresponding flow rate controller 12, 13. The two flow rate controllers 12, 13 are usually designed as PI controllers or PID controllers. The letters P, I and D in this context represent, as is generally known, the following: P=proportional, I=integral and D=differential.
[0043] The flow target value F* is supplied to the flow regulators 12, 13. In addition, the flow actual value F is also supplied to the flow regulators 12, 13. The flow actual value F can be detected, for example, by means of a flow sensor 14, which is arranged in the conveying line 4, more precisely before the front node 8 or after the rear node 11 (if present).
[0044] It can be seen that the same flow target value F* and the same flow actual value F are supplied to the flow regulators 12, 13. Therefore, for the two flow regulators 12, 13, the flow target value F* and the flow actual value F are unified. In addition, the flow regulators 12, 13 can be arranged before the summing point 15, and the control difference δF, that is, the difference between the flow target value F* and the flow actual value F, is formed in the summing point. In this case, the control difference δF is supplied to the flow regulators 12, 13. Alternatively, the control difference δF can also be formed in the flow regulators 12, 13.
[0045] The two flow regulators 12 and 13 work according to corresponding control algorithms C1 and C2. The two control algorithms C1 and C2 determine, for example: whether the corresponding flow regulator 12 and 13 works as a P regulator, a PI regulator, a PID regulator, etc., the size of the proportional gain, the reset time of the integral component, etc. The two control algorithms C1 and C2 are individually and independently coordinated to the optimal control of the corresponding conveying elements 6 and 7. Each of the two flow regulators 12 and 13 uses its control algorithm C1 and C2 to determine the corresponding control variables S1 and S2 for the conveying elements 6 and 7 regulated by it according to the flow target value F* and the actual flow value F (or the control difference δF). The corresponding control variables S1 and S2 can be, in particular, the corresponding target rotational speeds. The flow regulators 12 and 13 control the corresponding conveying elements 6 and 1, or more precisely, the drivers 16 and 17 of the corresponding conveying elements 6 and 7 (see Figure 1). The conveying elements 6, 7 or their drives 16, 17 can thus be speed-regulated. The drives 16, 17 can in particular be designed as electric drives. In this case, the drives 16, 17 can be fed, for example, via corresponding inverters (not shown in the figure).
[0046] Only one of the two conveyor elements 6, 7 is activated. In order to activate and deactivate the conveyor elements 6, 7, the conveyor device has a switching device 18. In particular, the flow target value F* is supplied to the switching device 18. The switching device 18 is designed so that (depending on the value of the flow target value F*) it allows one of the conveyor elements 6, 7 to be driven by the corresponding flow regulator 12, 13 and prohibits the other of the two conveyor elements 6, 7 to be driven by the corresponding flow regulator 13, 12. This is referred to in the following. Figure 3 and 4 Explain in more detail. The enabling and disabling of the control of the conveying elements 6, 7 (or their drivers 16, 17) can be caused, for example, by outputting corresponding activation signals A1, A2 to the two conveying elements 6, 7 via the switching device 18. Here, at any point in time, the corresponding activation signals A1, A2 are output to only one of the two conveying elements 6, 7. When the corresponding activation signals A1, A2 are turned off, the corresponding conveying elements 6, 7 are completely turned off.
[0047] according to Figure 3 , the flow target value F* has a minimum value MIN at time point t1. After time point t1, the flow target value F* gradually increases to a maximum value MAX as a function of time t. Specifically, the flow target value F* reaches the upper switching threshold SO at time point t2, and reaches the maximum value MAX at time point t3. From time point t4, the flow target value F* drops to the minimum value MIN again. Specifically, the flow target value F* reaches the lower switching threshold SU at time point t5 and reaches the minimum value MIN at time point t6.
[0048] At time t1, according to Figure 4 , the activation signal A2 is output, so that the conveying element 7 is driven according to the actuation signal S2 determined by the flow regulator 13. Correspondingly, the activation signal A1 is not output.
[0049] This state is maintained until the flow target value F* reaches the upper switching threshold SO at time t2. When the upper switching threshold SO is exceeded, the activation signal A2 is switched to the activation signal A1. This achieves that the conveying element 6 is now driven by the flow regulator 12 according to the actuation signal S1 determined thereby, and the conveying element 7 is no longer driven by the flow regulator 13.
[0050] This state is maintained until the flow rate target value F* reaches the lower switching threshold value SU at time t5. When the flow rate target value F* falls below the lower switching threshold value SU, the activation signal A1 is switched back to the activation signal A2.
[0051] As a result, it is achieved that the medium 1 flows only via the delivery elements 6, 7 to which the corresponding activation signals A1, A2 are delivered. In particular, the medium 1 thus flows only via the delivery element 6 as long as the flow target value F* remains above the upper switching threshold SO and below the maximum value MAX. Likewise, the medium 1 flows only via the delivery element 7 as long as the flow target value F* remains below the lower switching threshold SU and above the minimum value MIN.
[0052] In order to completely prevent any flow of the medium 1 via the unactivated conveying elements 6, 7, a blocking element 19, 20, for example a corresponding valve, can be arranged in each of the two branches 9, 10. In this case, as long as the activation signal A1, A2 of the conveying element is supplied to the conveying element 6, 7 arranged in the same branch 9, 10, the corresponding blocking element 19, 20 is kept permanently fully open by the switching device 18. If the corresponding activation signal A1, A2 of the conveying element is not supplied to the corresponding conveying element 6, 7, the corresponding blocking element 19, 20 is closed.
[0053] In order to achieve the smoothest possible switching from one conveyor element 6 to another conveyor element 7 and vice versa, the tracking value N1 is then always supplied to the flow regulator 12 when the conveyor element 6 regulated by the flow regulator 12 is not actuated. In a similar manner, the tracking value N2 is always supplied to the flow regulator 13 when the conveyor element 7 regulated by the flow regulator 13 is not actuated. The tracking values N1, N2 determine with which value the integral component of the respective flow regulator 12, 13 is initialized at the time when the respective flow regulator is activated (i.e. the manipulated variables S1, S2 determined thereby are output to the respective conveyor element 6, 7). In accordance with Figure 3 and 4 In the example of , this is the time point t2 for the flow regulator 12. This is the time point t5 for the flow regulator 13. In particular, the integral component of the respective flow regulator 12, 13 is determined so that the manipulated variable S1, S2 of the respective flow regulator 12, 13 is equal to the respective tracking value N1, N2 at the switching time point t2 or t5.
[0054] according to Figure 2The tracking values N1 and N2 are obtained by the switching device 18. However, the tracking values can also be obtained by another device. The following method is used to obtain the corresponding tracking value N1 or N2 by multiplying the corresponding control variable S2 or S1 of the other flow regulator 13 and 12 with the corresponding predetermined factor f1 and f2. That is, N1=f1*S2 and N2=f2*S1. When calculating the tracking value N1 or N2, the control variable limitation of the flow regulator 12 and 13 is also taken into account. The two factors f1 and f2 are reciprocals of each other. Therefore, it is applicable that f1*f2=1 or f2=1 / f1.
[0055] The two factors f1, f2 can be determined as required. Preferably, however, this determination is made as a function of the rated flow of the respective delivery element 6, 7. If the rated flow of the delivery element 6 is denoted by FN1 and the rated flow of the delivery element 7 is denoted by FN2, then preferably f1=FN2 / FN1 applies and vice versa f2=FN1 / FN2 applies.
[0056] After switching the conveyor element 6, 7, the newly activated conveyor element 6, 7 requires a certain time until it reaches the desired rotational speed (as given by the corresponding manipulated variables S1, S2 or the corresponding tracking values N1, N2). Since the newly activated conveyor element 6, 7 accelerates against the resistance, if it reaches the actually desired rotational speed too quickly, the conveyor element is overloaded. For this reason, the corresponding ramp generator 21, 22 is set according to Figure 2 The illustration is associated with the conveying elements 6, 7. For example, when the conveying elements 6, 7 are driven by means of a drive fed by an inverter, the ramp generators 21, 22 can be arranged in the inverter. With the help of the corresponding ramp generators 21, 22, the rotational speed of the corresponding conveying elements 6, 7 is accelerated according to the predetermined corresponding ramps, starting from the activation of the corresponding conveying elements 6, 7. The acceleration is carried out until the limit rotational speed. For example, the limit rotational speed can be determined by tracking values N1, N2 at the time of activating the corresponding conveying elements 6, 7. After running through the corresponding ramp, the corresponding ramp generator 21 is switched to inactive again. Then, from this point in time, the corresponding conveying elements 6, 7 are normally driven by the corresponding flow regulators 12, 13. This is described below in conjunction with Figure 5 The conveying element 6 and its flow regulator 12 are explained in more detail.
[0057] Figure 5 A possible time profile of the flow target value F* is shown by way of example. Figure 5, the flow target value F* rises in the course of time above the upper threshold value SO at the time t11. At the time t11, the flow rate target value F* rises above the upper threshold value SO. At the time t11, the flow rate target value F* rises above the upper threshold value SO. At the time t11, the flow rate target value F* rises in the course of time above the upper threshold value SO. At the time t11, the flow rate target value F* rises above the upper threshold value SO at the time t1 ... Figure 5 , the rotational speed target value n1 increases linearly from the time t11 until it reaches the end of the ramp at the time t12. Only at this time can the "normal" manipulated variable S1 be output to the conveying element 6.
[0058] A similar embodiment applies to the delivery element 7 and its flow regulator 13 , ie to the reverse switching. However, the specific speed nS2 of the speed target value n2 according to the ramp of the ramp generator 22 and the duration of the acceleration operation may deviate from the corresponding values of the ramp generator 21 .
[0059] It is very easy to implement the conveying device, i.e. the two flow regulators 12, 13, in a more comprehensive process control by means of control technology. In particular, it is possible that in the context of a process control system, the two regulator instances are internally connected so that the same flow target value F* and the same flow actual value F or the same regulation difference δF are always delivered to the flow regulators 12, 13, wherein the flow regulators 12, 13 are implemented by means of two regulator instances. In addition, the two flow regulators 12, 13 can also be easily coupled to each other in the process control system, so that the flow regulators not only always obtain the same flow target value F* and the same flow actual value F, but also always operate in the same operating mode (i.e. automatic operation or manual operation). It is also possible in the context of an operating and monitoring system to describe only a single flow regulator for the conveying section 5, which (obviously) only regulates a single conveying element. Usually, this is a flow regulator 12, 13 for conveying elements 6, 7 with a larger rated flow. However, it is also possible to describe the conveying section 5 as it is, i.e. with the two branches 9, 10 and the conveying elements 6, 7 arranged therein. In this case, however, usually only a single flow regulator is described for the two conveying elements 6, 7. The latter-mentioned description can alternatively be permanent or, for example, in the event of a malfunction of one of the two conveying elements 6, 7, can be output instead of the first-mentioned description.
[0060] It is also possible to easily expand the conveying device to three, four, etc. conveying elements connected in parallel. The expansion to three conveying elements is briefly outlined below.
[0061] Therefore, assuming that Figure 6As shown, the following configuration of the conveying device is obtained, in which the conveying section 5 has, in addition to the branches 9, 10 with the conveying elements 6, 7, a further branch 23, in which a further conveying element 24 is arranged. Without limiting the generality, it can be assumed that the conveying element 7 is the conveying element with the smaller rated flow and that the rated flow of the further conveying element 24 is smaller than the rated flow of the smaller conveying element 7. In this case, as described above in Figures 3 to 5 As explained in , the switching between the conveying elements 6, 7 can remain unchanged. Further switching between the smaller conveying element 7 and the further conveying element 24 can be completely similar to Figures 3 to 5 However, as long as the interaction between the conveying element 7 and another conveying element 24 is involved, the following supplementary solution must be implemented:
[0062] The maximum value of the interaction of the conveyor element 7 with the further conveyor element 24 is equal to the upper switching threshold SO, SU or the lower switching threshold SO, SU of the interaction of the conveyor elements 6 and 7 .
[0063] The upper switching threshold or the lower switching threshold for the interaction of the conveyor element 7 and the further conveyor element 24 is equal to the minimum value MIN.
[0064] The minimum value of the further conveying element 24 should be chosen to be (sufficiently) small.
[0065] In a completely analogous manner, further expansion with further conveyor elements is also possible.
[0066] Therefore, in summary, the present invention relates to the following facts:
[0067] The medium 1 is transported from a source location 2 to a destination location 3 via a transport line 4. The transport line 4 has a transport section 5 between the source location 2 and the destination location 3, in which two transport elements 6 and 7 are arranged. The transport elements 6 and 7 are connected in parallel to each other and are regulated by corresponding flow regulators 12 and 13. The same flow target value F* and the same flow actual value F are supplied to the two flow regulators 12 and 13. The flow regulators determine the corresponding manipulated variables S1 and S2 for the corresponding transport elements 6 and 7 therefrom. The switching device 18 of the transport device is constructed so that when the flow target value F* drops below the lower switching threshold value SU, it prohibits the control of the one transport element 6 by the one flow regulator 12 and allows the control of the other transport element 7 by the other flow regulator 13, so that as long as the flow target value F* remains above the minimum value MIN and below the upper switching threshold value SO, the medium 1 flows only through the other transport element 7. In a similar manner, when the flow target value F* rises above the upper switching threshold SO, it is prohibited to drive another conveying element 7 through another flow regulator 13, and it is allowed to drive the conveying element 6 through the flow regulator 12, so that as long as the flow target value F* remains below the maximum value MAX and above the lower switching threshold SU, the medium 1 only flows through the conveying element 6.
[0068] The invention has the following advantages: The actual flow F of the medium 1 can be precisely regulated in an energy-saving manner. Due to the use of a dedicated flow regulator 12, 13, a high regulation quality is achieved. By tracking the corresponding inactive flow regulator 12, 13, an integrator saturation of the flow regulator 12, 13 can be avoided and an at least almost smooth transition can be achieved when switching the conveying elements 6, 7. On the other hand, there is hardly any change for the operator of the system.
[0069] Although the present invention has been illustrated and described in detail by preferred embodiments, the present invention is not limited to the disclosed examples, and those skilled in the art can derive other variants therefrom without departing from the scope of protection of the present invention.
Claims
1. A conveying device for a medium (1), wherein the conveying device comprises a conveying line (4), via which the medium (1) is conveyed from a source location (2) to a destination location (3), -in, The conveying line (4) has a conveying section (5) between the source location (2) and the destination location (3). - wherein two conveying elements (6, 7) are arranged in the conveying section (5), - wherein the conveying elements (6, 7) are connected in parallel with one another, - wherein the conveying elements (6, 7) are regulated by corresponding flow regulators (12, 13), - wherein a uniform flow target value (F*) for the two flow regulators (12, 13) and a uniform flow actual value (F) for the two flow regulators (12, 13) are supplied to the two flow regulators (12, 13), wherein the flow regulator (12, 13) calculates corresponding manipulated variables (S1, S2) for corresponding conveying elements (6, 7) based on the flow target value (F*) and the flow actual value (F) using corresponding control algorithms (C1, C2), - wherein the delivery device comprises a switching device (18), to which the flow target value (F*) is delivered, wherein the switching device (18) is designed such that, when the flow target value (F*) drops below a lower switching threshold value (SU), the switching device prohibits the actuation of one conveying element by one flow regulator and permits the actuation of another conveying element by another flow regulator, so that the medium (1) flows only via the other conveying element as long as the flow target value (F*) remains above a minimum value (MIN) and below an upper switching threshold value (SO), and wherein the switching device (18) is configured such that, when the flow target value (F*) rises above the upper switching threshold value (SO), the switching device prohibits the actuation of another conveying element by another flow regulator and permits the actuation of one conveying element by one flow regulator, so that as long as the flow target value (F*) remains below a maximum value (MAX) and above a lower switching threshold value (SU), the medium (1) flows only via one conveying element, - supplying the tracking value (N1, N2) to a flow regulator (12, 13) which prohibits the actuation of the associated conveying element (6, 7), - the tracking value (N1, N2) is obtained by multiplying the manipulated variable of the flow controller, which controls the conveying element of the flow controller, by a corresponding predetermined factor, and - The two factors (f1, f2) are reciprocals of each other.
2. The conveying device according to claim 1, It is characterized in that A corresponding ramp generator (21, 22) is associated with the flow regulator (12, 13), by means of which the rotational speed of the corresponding conveying element (6, 7) is increased according to a predetermined corresponding ramp, starting from the time when the corresponding conveying element (6, 7) is allowed to be driven by the corresponding flow regulator (12, 13).
3. The conveying device according to claim 1 or 2, It is characterized in that The two flow regulators (12, 13) are coupled to one another so that the flow regulators not only always obtain the same flow target value (F*) and the same flow actual value (F), but also always operate in the same operating mode.