Pump control method

Abstract

The invention relates to a pump control method for the control of the operation of a pump system with at least two pump assemblies (2) which are arranged parallel or in series to one another. The method includes determining a specific total power E.sub.S of the complete pump system which defines a total power in relation to a hydraulic total load of the complete pump system, determining a specific individual power E.sub.P,n of each pump assembly (2) which defines an individual power in relation to the individual hydraulic load of the respective pump assembly (2), computing an individual load factor E.sub.gain,n for each pump assembly (2) according to the equation $E_{\mathrm{gain},n}=\frac{E_S}{E_{P,n}}$
and adapting the individual hydraulic load (Q.sub.n; H.sub.n) of the pump assemblies (2) in dependence on a desired hydraulic load (Q.sub.D; H.sub.D) as well as on the individual load factor E.sub.gain,n of the respective pump assembly (2).

Claims

1. A pump control method for the control of the operation of a complete pump system with at least two pump assemblies, which pump assemblies are arranged in parallel or in series to one another, the method comprising the steps of: determining a specific total power E.sub.S of the complete pump system which defines a total power in relation to a hydraulic total load of the complete pump system; determining a specific individual power E.sub.P,n of each of the pump assemblies which defines an individual power in relation to an individual hydraulic load of the respective pump assembly; and computing an individual load factor for each pump assembly according to the equation $E_{\mathrm{gain},n}=\frac{E_S}{E_{P,n}};$ and adapting the individual hydraulic load of the pump assemblies in dependence on a desired hydraulic load as well as on the computed individual load factor E.sub.gain,n of the respective pump assembly, wherein: the step of adapting the individual hydraulic load of the pump assemblies is effected in dependence of a desired individual load of the respective pump assembly; the desired individual hydraulic load is determined by division of a desired hydraulic total load by the number of active pump assemblies; the pump assemblies comprise at least a first pump assembly and a second pump assembly; the individual hydraulic load of the first pump assembly is different from at least the individual hydraulic load of the second pump assembly; the specific individual power of the first pump assembly is different from at least the specific individual power of the second pump assembly; the individual load factor for each pump assembly corresponds to an efficiency of a respective pump assembly compared to a total efficiency of the complete pump system; the first pump assembly has an efficiency that is different from at least an efficiency of said second pump assembly; the first pump assembly generates a greater part of the total hydraulic load than at least the second pump assembly; the first pump assembly operates at a greater efficiency than the second pump assembly.

2. A pump control method according to claim 1, wherein the step of adapting the individual hydraulic load of each pump assembly is effected by way of a multiplication of the desired hydraulic load by the respective load factor E.sub.gain,n or a variable derived from the respective load factor E.sub.gain,n.

3. A pump control method according to claim 1, wherein the at least two pump assemblies are connected in series and the step of adapting the individual hydraulic load of each of the pump assemblies is further effected by way of multiplication of the desired hydraulic total load by the square of the respective load factor E.sub.gain,n.

4. A pump control method according to claim 1, wherein one of the pump assemblies of the at least two pump assemblies is switched off when the respective individual load factor E.sub.gain,n which belongs to said one of the pump assemblies, lies below a predefined minimum.

5. A pump control method according to claim 1, wherein one of the pump assemblies of the at least two pump assemblies is switched on when an associated, estimated individual load factor E.sub.gain,n, which belongs to said one of the pump assemblies, lies above a predefined maximum.

6. A pump control method according to claim 1, wherein the that at least two pump assemblies are arranged parallel to one another, wherein the hydraulic total load of the complete pump system is the flow of the complete pump system, and the individual hydraulic load of each pump assembly is the individual flow of the respective pump assembly.

7. A pump control method according to claim 6, wherein the desired hydraulic total load is a desired total flow.

8. A pump control method according to claim 1, wherein the at least two pump assemblies are connected in series, wherein the hydraulic total load of the complete pump system is the differential pressure across the complete pump system, and the individual hydraulic load of each pump assembly is the individual differential pressure across the respective pump assembly.

9. A pump control method according to claim 8, wherein the desired hydraulic total load is a desired total differential pressure.

10. A pump control method according to claim 1, wherein for a pump assembly which has been switched off, a power of the pump assembly which has been switched off, before the switching-off, is taken into account.

11. A pump control method according to claim 1, further comprising at least one of individually regulating the individual hydraulic load for each pump assembly and regulating the hydraulic total load.

12. A pump control method according to claim 1, further comprising effecting a measurement value detection of the individual hydraulic load as well as of the power of the pump assembly in one or in each pump assembly.

13. A pump control method according to claim 1, wherein a determining of the specific individual power E.sub.P,n of each pump assembly and the computation of the individual load factor E.sub.gain,n for each pump assembly is carried out by an individual control unit for the respective pump assembly or by a central control unit for several pump assemblies.

14. A pump control method according to claim 1, wherein said steps of determining the specific total power E.sub.S of the complete pump system, determining the specific individual power E.sub.P,n of each of the pump assemblies, computing the individual load factor for each pump assembly and adapting the individual hydraulic load of the pump assemblies is continuously carried out during operation of the pump system.

15. A pump control method according to claim 1, wherein the desired individual hydraulic load of each pump assembly is set in a manner such that the individual hydraulic loads of the at least two pump assemblies are in a predefined relation to one another.

16. A pump system comprising: at least two pump assemblies which are arranged in parallel or in series; a system control configured to: set a desired hydraulic total load for the complete pump system; determine a specific total power E.sub.S for the complete pump system; determine a specific individual power E.sub.P,n of individual pump assemblies, which defines an individual power relative to an individual hydraulic load of the respective pump assemblies; compute an individual load factor E.sub.gain,n for the respective pump assemblies according to the following equation $E_{\mathrm{gain},n}=\frac{E_S}{E_{P,n}};$ and adapt a desired individual hydraulic load of the respective pump assemblies in dependence on the desired hydraulic load and on the load factor E.sub.gain,n, wherein the pump assemblies are settable as to speed and comprise drive motors controlled with a closed control loop, the individual hydraulic load of one of the at least two pump assemblies being different from at least the individual hydraulic load of another one of the at least two pump assemblies, the specific individual power of one of the at least two pump assemblies being different from at least the specific individual power of another one of the at least two pump assemblies, the individual load factor for each of the at least two pump assemblies corresponding to an efficiency of a respective pump assembly compared to a total efficiency of the complete pump system, one of the at least two pump assemblies having an operating efficiency that is greater than at least an operating efficiency of another one of the at least two pump assemblies, wherein the one of the at least two pump assemblies with the greater operating efficiency generates a greater part of the total hydraulic load than at least another one of the at least two pump assemblies.

17. A pump system according to claim 16, wherein the system control comprises individual control units respectively assigned to a pump assembly and integrated into the respective pump assembly for determining the individual load factor E.sub.gain,n and for setting the individual hydraulic load.

18. A pump system according to claim 16, wherein the pump system forms a field of wells.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic view showing a pump system with several pump assemblies connected in parallel;

(3) FIG. 2 is a schematic view showing a pump system with several pump assemblies connected in parallel, as is applied in a field of wells;

(4) FIG. 3 is a schematic view showing the arrangement of several pump assemblies connected in series;

(5) FIG. 4 is a schematic view showing the control or regulation method for adapting the load distribution onto several pump assemblies; and

(6) FIG. 5 is a schematic view showing an additional regulation, in order to maintain the distribution of the hydraulic loads in a predefined relation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) Referring to the drawings, the pump control method according to the invention or the pump system according to the invention can be applied in different designs, in particular with a parallel connection and/or series connection of several pump assemblies. FIG. 1 shows an application, in which three pump assemblies 2 are arranged parallel to one another in a circuit. This is a booster application, in which the three delivery flows Q.sub.1, Q.sub.2 and Q.sub.3 of the three pump assemblies 2 add into a total delivery flow Q.sub.S. The differential pressure or the delivery head H.sub.S is the same with all three pump assemblies 2. The pump assemblies 2 thereby can be differentially dimensioned as indicated in FIG. 1 by the size.

(8) FIG. 2 shows an arrangement of three pump assemblies 2 which are connected in parallel, but are not arranged in a circuit. Such an application is applied for example in a field of wells, wherein the three pump assemblies 2 can be assigned to different wells. Here too, the pump assemblies 2 are differently dimensioned, as is indicated by the different sizes in FIG. 2. With this design, the three pump assemblies 2 have different delivery flows Q.sub.1, Q.sub.2 and Q.sub.3 as well as different delivery heads H.sub.1, H.sub.2, H.sub.3 which sum into a total delivery flow Q.sub.S or a total delivery head H.sub.S.

(9) FIG. 3 shows an application, with which two pump assemblies 2 are connected in series, for example in order to permit a greater pressure increase. The delivery flow Q.sub.S through both pump assemblies 2 is the same, but the delivery heads H.sub.1 and H.sub.2 of the two pump assemblies sum or add into a total delivery head H.sub.S. Here too, the two pump assemblies 2 can be differently dimensioned.

(10) Since the pump assemblies 2 operate differently efficiently due to the different dimensioning of these pump assemblies 2 and the different hydraulic connection conditions, according to the invention, due to a special pump control method, one envisages distributing the complete hydraulic load, which means either the complete delivery flow Q.sub.S or the complete delivery head H.sub.S onto the different pump assemblies 2 such that an as large as possible energy efficiency is achieved. The pump assemblies 2 thereby are electrically driven and each has a local individual control unit 4. Each pump system moreover yet has a central control unit 6 which is signal-connected to the individual control units 4. This can either be effected via electrical or optical signal leads or also via wireless signal connections, as for example radio connections or a powerline communication.

(11) The control method is hereinafter described in more detail by way of FIG. 2. Thereby, parts of the control or regulation, as is shown in FIG. 4 are assigned to the individual control units 4 or are carried out by these, whereas other parts are carried out by the central control unit 6. In FIG. 2 are exemplary shown three pumps with three delivery flows Q.sub.1, Q.sub.2 and Q.sub.3 as well as three delivery heads H.sub.1, H.sub.2 and H.sub.3. In FIG. 2, only two pump with the delivery flows Q.sub.1 and Q.sub.2 as well as the two delivery heads H.sub.1 and H.sub.2 are regarded. However, it is to recognize that essentially an optional number of pumps can find use. Therefore, following an index n is used to distinguish an individual parameter of an optional pump. The individual pump assemblies absorb an electrical power P.sub.n and produce a delivery flow Q.sub.n (in FIG. 4: Q.sub.1, Q.sub.2) as well as a differential pressure or a delivery head H.sub.n (in FIG. 4: H.sub.1, H.sub.2). The electrical powers P.sub.n (here P.sub.1 and P.sub.2) or the electrical power consumption of all pump assemblies 2 are summed in the summing module 8 which can be assigned to the central control unit 6. Accordingly, the delivery flow Q.sub.n (here Q.sub.1 and Q.sub.2), i.e. the hydraulic load of the pump assemblies 2 is summed in the summing module 10. Accordingly the delivery heads H.sub.n (here H.sub.1 and H.sub.2) as a hydraulic load are summed in the summing module 12. Thereby, it is to be understood that the summing module 10 is applied for summing the delivery flows Q.sub.n, in particular with a parallel connection of the pump assemblies 2, whereas the summing module 12 is applied for summing the delivery heads H.sub.n with a series connection of the pump assemblies 2. If the system is envisaged only for one of these applications, then accordingly one of the summing modules 10, 12 can be completely done away with. The necessary variables are preferably detected by the pump assemblies 2 or the individual control units 4 assigned to them, and are transferred to the summing modules 8, 10 and 12 which can be an integral part of the central control unit 6.

(12) The output data, i.e. the sum P.sub.s of the absorbed powers P.sub.n is led from the summing module 8 to the computation module 14, in which a specific total power E.sub.S of the complete system is computed by way of the electrical power being related to the hydraulic load or the total power being divided by the total hydraulic load. In the case of a parallel connection of pumps, the hydraulic load is the total delivery flow Q.sub.S which is issued or outputted from the summing module 10. In the case of a series connection of the pump assemblies 2, the total hydraulic load is the total delivery head H.sub.S which is issued from the summing module 12. One selects between the sums of the summoning modules 10 and 12 via a selection module 16, depending on whether the system is applied to a series connection or a parallel connection. If the system is configured exclusively for one of these applications, then accordingly if one makes do without one of the summing modules 10 or 12, accordingly one can also make do without the selection module 16. The computation module 14 conduce the cost optimization, while the specific total power E.sub.S for the regulation of the total system will be considered.

(13) Either the total delivery flow Q.sub.S or the total delivery head H.sub.S is led to a further computation module 18, likewise at the exit or output side of the selection module. Moreover, at the input side, a reference-delivery flow Q.sub.ref or reference-delivery head Href is led as a to reached hydraulic load or hydraulic reference load is led to the computation module 18. The computation module 18 forms a controller for the total delivery flow Q.sub.S or the total delivery head H.sub.S to reach the required hydraulic desired value and releases a desired delivery flow Q.sub.D or a desired delivery head H.sub.D as a desired hydraulic overall load. The desired hydraulic load, i.e. the desired delivery flow Q.sub.D and/or the desired delivery head H.sub.D are led from the computation module 18 to a distribution module 20. Accordingly, the specific total power E.sub.S is led from the computation module 14 to the distribution module 20 which further distributes this data to the individual control units 4 of the individual pump assemblies.

(14) The individual control units 4 in each case comprise a load factor evaluation module 22, in which an individual load factor E.sub.gain,n (here E.sub.gain,1 and E.sub.gain,2) is formed by way of the division of a specific total power E.sub.S by the specific individual power E.sub.P,n. The specific individual power E.sub.P,n is thereby detected by the respective pump assembly 2, just as the individual hydraulic load in the form of the flow Q.sub.n or the delivery head H.sub.n. The individual power P.sub.n is divided by the individual hydraulic load, by which means the specific individual power E.sub.P,n is determined. The specific load factor E.sub.gain,n is formed in the load factor evaluation module 22 from these input variables on the basis of the formula:

(15) $E_{\mathrm{gain},n}=\frac{E_S}{E_{P,n}}$

(16) The load factor E.sub.gain,n is led to a load adaptation module 24, in which on basis of the load factor E.sub.gain,n and the desired hydraulic load, i.e. on the basis of the desired delivery flow Q.sub.D or the desired delivery head H.sub.D the desired individual delivery flow Q.sub.n,D (here Q.sub.1,D and Q.sub.2,D) or the desired individual delivery head Q.sub.n,D (here H.sub.1,D and H.sub.2,D) for the respective pump assembly 2 are adjusted. For this, with pumps connected in parallel and which are closed-loop controlled with regard to the flow Q.sub.n, preferably the load factor E.sup.2.sub.gain,n, is multiplied by the desired hydraulic load, i.e. the desired flow Q.sub.D. With a series connection, accordingly the desired individual delivery head H.sub.D is multiplied by the square E.sup.2.sub.gain of the load factor E.sub.gain. The hydraulic load is accordingly regulated in the subsequent controller 26 according to the desired individual delivery head Q.sub.n,D or the desired individual delivery flow Q.sub.n,D on the basis of the flow Q.sub.n (here Q.sub.1 and Q.sub.2) or on the basis of the delivery head H.sub.n (here H.sub.1 and H.sub.2) which are actually detected in the pump assembly 2 as feedback. A speed controller 28 which accordingly sets the speed nn of the pump assembly 2 is arranged at the output side of the regulator 26.

(17) On account of the use of the load factor E.sub.gain,n which is individually formed for each pump assembly 2, it is ensured that that pump assembly which has the best energy sufficiency, has a greater share of the hydraulic load to be mustered, than a pump assembly 2 which has a lower energy efficiency. The individual control units 4 can moreover be designed such that they completely switch off the pump assembly under certain conditions. This is preferably effected when the formed load factor E.sub.gain,n for the respective pump assembly 2 falls short of a predefined minimum. A switching-on again occurs when the individual load factor E.sub.gain,n exceeds a predefined maximum or a predefined reference or setpoint again. In the switched-off condition, it is the specific individual power E.sub.P,n which prevailed or was measured before the switching-off instead of the actual specific individual power E.sub.P,n which forms the basis of the evaluation of the load factor E.sub.gain,n.

(18) An additional regulation which is represented in FIG. 5 can be put on a higher level, in order to be able to ensure that the hydraulic load distribution is effected in defined limits, given several pump assemblies 2, in particular in a well field as is shown in FIG. 2, with pump assemblies 2 connected in parallel. Three pump assemblies 2 which are indicated with the numerals 1-3 are provided in the examples represented in FIG. 5. The portioned load distribution is to be set by the closed-loop control, for example on the basis of the following inequation b.sub.1>a.sub.i1q.sub.1+a.sub.i2q.sub.2+a.sub.i3q.sub.3. In this formula, b.sub.i is preferably a constant, which is typically 0. a.sub.i1, a.sub.i2 and a.sub.i3 are constants which indicate or define the limits for the mixing ratio.

(19) The flows which are actually produced by the pump assemblies are indicated at Q.sub.1, Q.sub.2 and Q.sub.3 in FIG. 5. These are added in the summing module 10 into the flow Q.sub.S, as has been described by way of FIG. 4.

(20) The flow regulation as described by way of FIG. 4 is effected in the controller or computation module 18, wherein the output signal for each of the pump assemblies 2 is added to a feedforward signal

(21) $\frac{Q_{\mathrm{ref}}}{k},$
wherein k is the number of pumps which are in operation and Q.sub.ref the set-total flow. Simultaneously, each individual flow Q.sub.1, Q.sub.2,Q.sub.3 is multiplied by a factor a.sub.i1, a.sub.i2 and a.sub.i3 respectively. The thus multiplied signals are added to the constant b.sub.i according to the previously mentioned formula. An adaptation factor g is subsequently determined in a regulation module 32. Thereby, the adaptation factor g is formed depending on the extent to which the inequation in the adder 30 is fulfilled or not. The adaptation factor is multiplied by the constants a.sub.i1, a.sub.i2 and a.sub.i3 and the result is subsequently added in an adder 34 to the feedforward factor

(22) $\frac{Q_{\mathrm{ref}}}{k}$
and to the output of the controller 18, individually for each pump assembly 2. Thus, values for the desired individual delivery flow Q.sub.1,D, Q.sub.2,D and Q.sub.3,D are issued as a result and these correspond to the desired individual hydraulic load Q.sub.n,D, i.e. the desired individual flow Q.sub.n,D in FIG. 4. Then according to FIG. 4, the multiplication by the individual load factor E.sub.gain,n is effected subsequently in the load adaptation module 34. Thus, simultaneously with the energy optimization, it is ensured that the individual pumps in each case muster a certain share of the hydraulic load or of the flow, or that this share moves within certain limits.

(23) The previously described controller module adders of the control can all be designed as software modules in a computation system.

(24) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

APPENDIX

List of Reference Numerals

(25) 2—pump assemblies 4—individual control units 6—central control unit 8, 10, 12—summing modules 14—computation module 16—selection module 18—computation module 20—distribution module 22—load factor evaluation module 24—load adaptation module 26—controller 28—speed controller 30—adder 32—regulating module 34—adder E.sub.P,n—specific individual power of an individual pump E.sub.S—specific total power of the total system P.sub.n—power of an individual pump Q.sub.n—flow of an individual pump H.sub.n—delivery head of an individual pump Q.sub.ref—reference flow of the total system H.sub.ref—reference delivery head of the total system H.sub.D—desired delivery head of the total system Q.sub.D—desired delivery flow of the total system H.sub.n,D—desired individual delivery head Q.sub.n,D—desired individual delivery flow E.sub.gain—load factor n,.sub.n—speed of an individual pump a, b—constants g—adaptation factor Q.sub.S—delivery flow feedback of the total system H.sub.S—delivery head feedback of the total system P.sub.S—delivery power feedback of the total system K—number of pumps in operation