METHOD FOR OPERATING A PUMP SYSTEM

Abstract

Method for operating a pump system preferably comprising more than one pump, comprising the steps of: Obtaining at least one target parameter to be optimized based on target values of each pump; Obtaining an operation target, wherein the operation target is provided by one or more of the pumps operating each with an individual operation parameter; Acquiring a relationship for more than one and preferably all of the pumps between the operation parameter and the target value and determine a target function; Determining a maximum/minimum of the target function and obtaining operation parameter of at least one pump; and Controlling of at least one pump to operate with the obtained operation parameter to optimize the target parameter.

Claims

1. A method for operating a vacuum pump system preferably comprising more than one pump, comprising the steps of: obtaining at least one target parameter to be optimized based on target values of each pump; obtaining an operation target, wherein the operation target is provided by one or more of the pumps operating each with an individual operation parameter; acquiring a relationship for more than one and preferably all of the pumps between the operation parameter and the target value and determine a target function; determining a maximum/minimum of the target function and obtaining operation parameter of at least on pump; and controlling of at least one pump to operate with the obtained operation parameter to optimize the target parameter.

2. The method according to claim 1, characterized in that the operation target is flow or pressure provided by the pump system.

3. The method according to claim 1, characterized in that the operation target is within margin-offsets.

4. The method according to claim 1, characterized in that the target parameter is one or more of energy consumption, water/oil consumption, maintenance reduction of the pump system.

5. The method according to claim 1, characterized in that determining a maximum/minimum of the target function is performed in a first run with the FS considered as VSD, providing continuous operation parameter.

6. The method according to claim 5, characterized in that, if in the first run not all FS having an operation parameter being zero or full speed, using the determined operation parameter as starting point for a second run for determining a maximum/minimum of the target function, wherein a step size for determining the maximum/minimum of the target function is increased.

7. The method according to claim 1, characterized in that if the operation target is the flow provided by the pump system and the optimization parameter is the energy consumption or water/oil consumption, then the target function is given by
f(x)=Σ.sub.i=1.sup.ng.sub.i(x.sub.i*Q.sub.imax)+Σ.sub.j=1.sup.mx.sub.j*Power.sub.j, with n being the number of VSD and m being the number of FS, g.sub.i the acquired relationship between operation parameter x.sub.i and the target value for VSD pumps and Power.sub.j the energy consumption or water/oil consumption of the FS pump j.

8. The method according to claim 6, wherein the stepsize for the first run is below 0.2 and preferably below 0.1.

9. The method according to claim 6, characterized in that the stepsize for the second run is above 0.5 and preferably 1.

10. The method according to claim 1, characterized in that, if the target parameter includes maintenance reduction, then the method further includes the steps of: sorting the pumps by their running hours; selecting those pumps with minimum running hours which together can provide the operation target.

11. The method according to claim 10, characterized in that, if the target parameter includes energy consumption or water/oil consumption, then include at least the selected pumps into the target function.

12. A pump system comprising more than one pump, wherein each pump is preferably built as variable speed pump, VSD, or fixed speed pump, FS, and a controller connected to each pump in order to control operation of the pump, wherein the controller is configured to perform the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In the following the present invention is described in more detail with reference to the accompanied drawings.

[0037] The figures show:

[0038] FIG. 1 an exemplified relationship of a certain pump between the flow and power consumption per unit flow,

[0039] FIG. 2 an embodiment of the method according to the present invention,

[0040] FIG. 3a detailed embodiment of the method according to the present invention,

[0041] FIG. 4A a detailed embodiment of the method according to the present invention,

[0042] FIG. 4B an example of the embodiment given in FIG. 4a and

[0043] FIG. 5 an embodiment of the pump system according to the present invention.

DETAILED DESCRIPTION

[0044] The method according to the present invention relates to operating a pump system. Therein, preferably the pump system comprises more than one pump, wherein each pump might be built as Variable Speed pump (VSD) or Fixed-Speed pump (FS). Each of the pumps might be a compressor or a vacuum pump. Preferably, more than one VSD and/or more than one FS are employed. Therein, the pumps in the pump system work together in order to provide a flow or pressure to the pressurized system connected to the pump system in order to perform a certain task.

[0045] The steps of the method according to the present invention are depicted in FIG. 2:

[0046] In step S01, at least one target parameter to be optimized is obtained either by presetting the target parameter by the manufacturer or by an input operation of the customer. Therein, the target parameter is based on the target value of at least one and preferably the target value of each pump in the pump system. Thus, the target parameter in fact represents the parameter which shall be optimized by the present operating method. Preferably, the target parameter might be the energy consumption of the pump system or the water/oil consumption of the pump system (in particular if a waterring pump is employed) or the maintenance reduction of the pump system, i.e. increase of the maintenance intervals for the pump system. Therein, each of the pumps within the pump system contributes to the target parameter by its individual target value, for example each pump has a certain energy consumption combining with the energy consumption of the other pumps in the pump system resulting in the complete energy consumption of the complete pump system to be optimized as target parameter.

[0047] In step S02, at least an operation target is obtained either by presetting the operation target by the manufacturer or by an input operation of the customer. Therein, the operation target might be a flow or a pressure delivered by the pump system. Therein, the operation target is provided by one or more of the pumps of the pump system operating each with an individual operation parameter. Therein, the operation parameter denotes the contribution of the respective pump to the combined operation target of all pumps in the pump system or at least of the considered pumps in the pumps system. Therein, the operation parameter might be related to the running speed of the pump.

[0048] In step S03, a relationship is acquired for each pump between the operation parameter and the target value. In particular, if in the pump system different types of pumps and/or different pumps, such as different sizes, ages or pumps of different manufacturers are applied, there is a specific relationship for each individual pump between the operation parameter, such as the running speed of the pump or the provided flow at a certain pressure and the specific target value, e.g. the energy consumption. Therein, the relationship is usually non-linear. An example for of such a relationship between the flow and the energy consumption for a certain vacuum pump is depicted exemplarily in FIG. 1 showing the non-linear behavior. Therein, the relationship between the operation parameter and the target value for each pump might be provided by a look-up table. From the acquired relationship for each pump a combined target function for each of the considered pumps in the pump system and preferably for all pumps in the pump system is determined. Therein, the target function provides a relationship between the operation parameters of each of the considered pumps and the target parameter.

[0049] In step S04, a maximum or minimum of the target function is determined. Therein, the maximum or minimum is selected depending on the target parameter to be optimized, whether this target parameter need to be maximized or minimized. For example, energy consumption is of course to be minimized, resulting in determining a minimum of the target function. Therein, from the maximum/minimum of the target function an operation parameter of at least one pump and preferably operation parameters for each of the pumps in the pump system are obtained.

[0050] In step S05, the at least one pump and preferably all pumps in the pump system are controlled to operate with the obtained operation parameter to optimize the target parameter. Thus, by determining the maximum/minimum of the target function, the target parameter can be optimized and respective operation parameters for the considered pumps can be obtained. Therein, the operation parameter is selected such that the operation target is still met, i.e. the pump system provides a required flow or pressure in order to perform a certain task by the pump system.

[0051] In a specific example Q denotes a flow that to be distributed among all available pumps as operation target. Further, Q.sub.i denotes a flow that the pump i delivers and x.sub.i denote the flow ratio that is compared to the maximum flow of the pump i at the setpoint pressure according to

[00003]$x_i=\frac{Q_i}{Q_{\mathrm{imax}}}.$

[0052] Further, g.sub.i denotes a look-up table for the power of pump i at a setpoint pressure being a VSD. Similarly, let Power.sub.j denote the fixed power that pump j consumes at the setpoint pressure being a FS. Further, let n denotes the number of all available VSDs and let m denote the number of all available FS. Then the target parameter is a vector X={x.sub.1,x.sub.2, . . . x.sub.n, . . . x.sub.n+m} to be optimized and the target function can be provided by

f(x)=Σ.sub.i=1.sup.ng.sub.i(x.sub.i*Q.sub.imax)+Σ.sub.j=1.sup.mx.sub.j*Power.sub.j.

[0053] The target function underlays some constrains since the VSD can either deliver no flow or a flow between the VSDs minimum flow and its maximum flow, i.e.

[00004]$x_i\in \left\{0\right\}\&\left[\frac{Q_{\mathrm{imin}}}{Q_{\mathrm{imax}}},1\right].$

[0054] The FS pumps can provide only 0 flow or its maximum flow, i.e. x.sub.j∈{0,1}.

[0055] Further, the operation target must be within certain margins delimited by offset.sub.low and offset.sub.high which can be written as

Q−offset.sub.low≤Σ.sub.i=1.sup.nQ.sub.i=Σ.sub.j=1.sup.mQ.sub.j≤Q+offset.sub.high.

[0056] Due to the numerous pumps and their individual dependencies it is not possible to directly determine the gradient for each of the pumps individually. Further, numeric gradients cannot be determined for step functions. Instead each descent step is split into n sub steps, wherein N=n+m refers to the total number of pumps. In each sub step i it is calculated

x.sub.1′=x.sub.1−lr*grad.sub.x.sub.1

x.sub.2′=x.sub.2=lr*grad.sub.x.sub.2

x.sub.n′=x.sub.n−lr*grad.sub.x.sub.n

x.sub.i′=g.sup.−1(flow.sub.demand−g(x.sub.1′,x.sub.2′, . . . ,x.sub.N′))

with g.sup.−1 being the function which converts the flow Q.sub.i into the ratio x.sub.i. Therein, the step size lr is not always fixed. Instead the step size lr might be adapted in each sub step. The result of the sub step whose total power consumption is minimum is received as the output of the step. Thus, by the above calculation the target parameter approaches its optimum in small steps lr considering continues flow that can be provided by the VSD.

[0057] However, if the same approach is adapted to the FS having only the flow corresponding to 0 or the maximum flow of the FS, resulting in undesired and unrealistic results which cannot be realized by the FS.

[0058] A solution is provided and depicted in FIG. 3. In step S41, determining of a maximum/minimum of the target function is performed in a first run with the FS considered as VSD, i.e using small steps towards the optimum of the target parameter. Therein, the step size lr is preferably below 0.2 and even more preferably below 0.1.

[0059] In step S42, it is checked whether in the first run all FS having an operation parameter being 0 or full speed which can be delivered by the FS.

[0060] In step S43, if not all FS having an operation parameter being 0 or full speed, the operation parameter determined in step S41 are used as starting point for a second run for determining the maximum/minimum of the target function, wherein the step size lr for determining the maximum/minimum of the target function is increased for the FS. Preferably, the step size lr is selected to be above 0.5 and preferably 1. Thus, due to the first run the operation parameters are already close to the optimum with respect to the target parameter. In the second run due to the increased step size of lr it is ensured that for each of the FS an operation parameter being 0 or 1 is obtained.

[0061] Thus, by the two runs of the determination of the maximum/minimum of the target function on the one hand, the operation parameters for an optimized target parameter can be found, wherein for the FS the constrains are considered providing either 0 flow or its maximum flow. As a consequence, a pump system with a plurality of different pumps including VSD and FS pumps can be reliably operated in an optimized state.

[0062] Alternatively, the target parameter can also be reduction of the maintenance or increase of maintenance intervals as depicted in FIGS. 4A and 4B. In step S50 the considered pumps and preferably all pumps of the pump system are sorted by the running hours. In step S51 those pumps with minimum running hours are selected which together can provide the operation target. The situation is also exemplarily depicted in FIG. 4B for a vacuum pump system having five vacuum pumps 10. These vacuum pumps are in accordance to step S50 sorted by the running hours to form the sorted vacuum pumps 12. Those vacuum pumps 15 are selected which are able to provide the operation target. In the example of FIG. 4B the selected vacuum pumps 15 being vacuum pumps 2 and 1 which are sufficient in order to provide the operation target. Thus, only vacuum pumps 2 and 1 are controlled to be operated as operating vacuum pumps 20 in order to provide the operation target, thereby reducing the maintenance requirements, i.e. increasing the maintenance intervals.

[0063] Further, it is possible to prioritize either the reduction of energy consumption or the increase of maintenance intervals. If the reduction of the energy consumption has priority, then in step S53 all pumps are selected regardless of their running hours. In the example of FIG. 4B all five vacuum pumps 19 are selected for determining the maximum/minimum of the target function in order to optimize the energy consumption of the five vacuum pumps. Thus, all five vacuum pumps are operated as operating vacuum pumps 24 in order to deliver the operation target with minimized energy consumption.

[0064] In between for a more balanced priority of increase of maintenance intervals and a reduction of energy consumption, dependent on the priority in step S52 more than those pumps required in order to provide the operation target are selected from the available pumps. In the example of FIG. 4B three of the five vacuum pumps 17 are selected and considered in the target function in order to optimize the target parameter of energy consumption. In this example the two remaining vacuum pumps 3 and 5 may have high running hours. In order to avoid maintenance and increase maintenance intervals, these two vacuum pumps 3, 5 are speared out and only the three vacuum pumps 2, 1, 4 are operated as operating vacuum pumps 22. Therein, the number of selected vacuum pumps is in dependence on the given priority. Thus, with shifting priority from reduction of maintenance requirements as of example 15 in FIG. 4B towards the priority on reduction of energy consumption as of example 19 numerous steps are available corresponding to an increased number of vacuum pumps considered in the target function in order to determine the optimized operation parameters to achieve an optimization of the target parameter. The vacuum pumps system can be operated in an optimal state.

[0065] Referring to FIG. 5 showing an example for a pump system having five pumps 32, . . . ,40 arranged in parallel and connected with a common inlet 42 and preferably connected with a common outlet 44 in order to provide a sufficient flow to the pressurized system connected to the pump system to perform a certain task. Therein, the pumps 32, . . . ,40 are each either a compressor or a vacuum pump. Further, each of the pumps 32, . . . ,40 are built as a VSD or a FS. Therein, all pumps 32, . . . ,40 are connected to a common control 31, wherein the control 31 is configured to perform the above mentioned method of operation.

[0066] Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

[0067] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.