PUMP CONTROL SYSTEM AND METHOD FOR CONTROLLING A PUMP WITH AUTOMATIC PUMP MODEL CALIBRATION

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a United States National Phase Application of International Application PCT/EP2023/073929, filed Aug. 31, 2023, and claims the benefit of priority under 35 U.S.C. § 119 of Danish Application PA 2022 70441, filed Sep. 13, 2022, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure is directed to a pump control system and a method for controlling a pump with automatic pump model calibration. Furthermore, the present disclosure is directed to a pump assembly with such a pump control system or being controlled by such a method.

BACKGROUND

Pumps may be used as circulator pumps for circulating water or another liquid through a pipe system, e.g. a heating or cooling system. Typically, circulator pumps may be operated in different operating modes. For example, a circulator pump may be operated to provide a constant output pressure, i.e. in constant pressure mode. Another operating mode is typically “proportional pressure mode”, wherein the operating points of the circulator pump follow a linear line in a pressure-flow-diagram, a so-called pq-diagram. It is a general goal of pump controlling to control the pump in such a way that the pump runs precisely at a desired operating point, e.g. in the pq-diagram. Usually, the output pressure P and the flow q are measured and the measured values are fed back in a closed-loop control, so that the pump runs at the desired operating point.

However, flow sensors are expensive and often not available for pump control. If no measured flow value is available for pump control, it is known that pump control systems and methods use the affinity laws to estimate the current operating point based on other operating values, e.g. the actual power consumption P, the motor current I and/or motor speed of the pump ω. Using such operating values for an indirect estimation of the operating point, however, requires a precise model of the pump characteristic, e.g. a model function in the Pq-diagram.

Pump manufacturers typically determine the pump characteristics in a laboratory and/or field tests for certain pump types and provide data sets with a plurality of model parameter sets indicative of operating value model functions that describe the pump characteristics of a certain model type.

Typically, a certain pump type comes in a plurality of variants and a large amount of combinations of customised options. The true pump characteristics may differ slightly among the plurality of variants, whereas the same model function is used by the pump control system to describe the pump characteristic. So, the true pump characteristic may differ from the assumed modelled pump characteristic. Manufacturing tolerances add further differences between the actual pump characteristic and the assumed model pump characteristic. The true pump characteristic may even depend on the pipe system that the pump is connected to, so that there is an inherent uncertainty about the modelled pump characteristic that a pump manufacturer is able to provide with a pump control system. Last but not least, the pump characteristic may change dynamically over time due to wear and tear of mechanical and/or electrical components, so that an older pump behaves differently than a brand new pump.

U.S. Pat. No. 7,945,411 B1, DE 10 2009 050 083 B4, U.S. Pat. Nos. 9,897,084 B1 and 9,470,217 B1 describe control systems, wherein either the pump is forced to run at a known fix operation point for calibration, or wherein an actual flow is measured or estimated to determine the actual operating point.

SUMMARY

Therefore, it is an object of the present invention to provide an improved pump control system and an improved method for controlling a pump, wherein a pump model is used to control the pump without a measured flow or estimated flow and without forcing the pump into known operational points.

According to a first aspect of the present disclosure, a pump control system is provided comprising:

• • a storage element having stored a plurality of model parameter sets for a plurality of pump speeds, wherein each model parameter set is indicative of an operating value model function corresponding to a pump speed;
  • control electronics configured to command the pump to run at a set pump speed based on the operating the value model function corresponding to the set pump speed, wherein a corresponding model parameter set of the stored model parameter sets is retrieved from the storage element; and
  • model updating electronics, wherein the model updating electronics are configured to:
  • determine an actual operating value at the set speed;
  • compare the actual operating value with a maximum of the operating value model function and/or a minimum of the operating value model function; and
  • automatically determine an updated model parameter set if the actual operating value is higher than the maximum of the operating value model function or if the operating value is lower than the minimum of the operating value model function, wherein the updated model parameter set is indicative of a higher new operating value model function if the actual operating value is higher than the maximum of the operating value model function, and wherein the updated model parameter set is indicative of a lower new operating value model function if the actual operating value is lower than the minimum of the operating value model function, wherein the storage element is further configured to store the updated model parameter set.

The operating value may be the power consumption of the pump, a motor current, or another electrical performance value that is readily available to be determined. It should be noted that the updating or calibrating of the model parameter set does not require a measured flow value or an estimated flow value. Furthermore, the pump is not forced to run at a fixed known operating point. The updating or calibrating of the model parameter sets may be performed dynamically and automatically during normal pump operation. The updating or calibrating can be performed continuously, regularly and/or sporadically over the lifetime of the pump.

The inventive idea uses the fact that normal operation of a circulator pump is often at or around a minimum or maximum operating value. If the determined actual operating value is between a minimum and a maximum of the operating value model function, it may be impossible to evaluate the model function without having a measured or estimated flow to determine the exact operation point. Outside of the operating value range, i.e. above a maximum of the operating value model function and below a minimum of the operating value model function, a deviation between the actual operating value and the operating value model function cannot be explained by the uncertainty in flow. In this case, it can be assumed that the operating value model function does not reflect the true pump characteristic. Therefore, the operating value model function is updated or calibrated if the actual operating value is higher than the maximum of the operating value model function and if the actual operating value is lower than the minimum of the operating value model function.

Optionally, the model updating electronics may be configured to shift or scale the operating value model function upward to the higher new operating value model function and/or to shift or scale the operating value model function downward to a lower new operating value model function. In this case, the shape of the operating value model function may remain unamended. Alternatively, or in addition, the model updating electronics may be configured to apply a correction function to tweak shape of the operating value model function. For example, in case of an upward updating, the model function may be lifted only in a predefined range about the maximum of the model function. Analogously, in case of a downward updating, the model function may be lowered in a predefined range about the minimum of the model function.

Optionally, a shift amount and/or a scale factor may be applied, wherein the shift amount and/or the scale factor is a predetermined constant or depends in a predetermined way on set pump speed. In case of a constant shift amount and/or scale factor, the updating logic is very simple and all pump speeds are given the same weight. If, however, the accuracy of the model function is known to be better for certain pump speeds, it may be advantageous to apply a shift amount and/or a scale factor that depends in a predetermined way on the set pump speed.

Optionally, the shift amount and/or the scale factor may depend on a difference and/or ratio between the actual operating value and the maximum or the minimum, respectively, of the model function. Thereby, the model function is fitted to the determined actual operating value.

Optionally, the operating value model function may be a model curve of the operating value in dependence of a pump flow within a predetermined flow range. Preferably, the model curve comprises a single well-defined minimum and maximum within the predetermined flow range.

Optionally, the higher new operating value model function is at least in a subrange of the predetermined flow range higher than the previous operating value model function, and the lower new operating value model function may be at least in a subrange of the predetermined range lower than the previous operating model function.

As explained above, in case that the actual operating value is between the minimum and the maximum of the operating value model function, the model function may not be automatically updated or calibrated. However, it may be advantageous to run the pump in a set of calibration batch runs in this case. For example, such calibration batch runs may be started when a new pump is installed and initially operated for the first time. Alternatively, or in addition, such a calibration batch runs may be part of a regular maintenance action. It is preferred that the calibration batch runs are not automatically started, but started manually by skilled personnel or user.

Optionally, the model updating electronics may be further configured to:

• • determine a maximum actual operating value and/or a minimum actual operating value among the calibration batch runs,
  • compare the maximum actual operating value with the maximum of the operating value model function and/or the minimum actual operating value with the minimum of the operating value model function; and
  • automatically update the operating value model function to a higher new operating value model function if the maximum actual operating value is higher than the maximum of the operating value model function, and/or automatically update the operating value model function to a lower new operating value model function if the minimum actual operating value is lower than the minimum of the operating value model function.

In other words, the calibration batch runs at different speeds are used to check if a maximum actual operating value is above a maximum of the model function and whether a minimum actual operating value is below a minimum of the model function. Thereby, a broader range or area of operating points can be scanned to update or calibrate the model parameter sets that are indicative of the model functions corresponding to the respective pump speeds.

Optionally, the model updating electronics may be integrated into the control electronics that command the pump to run at a set pump speed based on the current operating value model function. Alternatively, or in addition, the model updating electronics may be arranged separately and the model updating electronics is merely in signal connection with the storage element to store the updated model parameter set received from the model updating electronics.

According to a second aspect of the present disclosure, a pump assembly is provided comprising a pump, an electric motor for driving the pump, and an electronics housing for housing motor control electronics, wherein the above-mentioned pump control system is arranged within the electronics housing. This has the advantage that the pump assembly is able to perform an automatic pump model calibration without having any access or connection to a remote pump control system or a remote model updating electronics.

According to a third aspect of the present disclosure, a method for controlling a pump is provided, wherein the method comprises the following steps:

• • running a pump at a set pump speed based on an operating value model function corresponding to the set pump speed;
  • determining an actual operating value at the set pump speed;
  • comparing the actual operating value with a maximum of the operating value model function and/or a minimum of the operating value model function; and
  • automatically updating the operating value model function to a higher new operating value model function if the actual operating value is higher than the maximum of the operating value model function, and/or automatically updating the operating value model function to a lower new operating value model function if the actual operating value is lower than the minimum of the operating value model function.

Optionally, updating the operating value model function to a higher new operating value model function may include shifting or scaling the operating value model function upward and/or updating the operating value model function to a lower new operating value model function may include shifting or scaling the operating value model function downward.

Optionally, a shift amount and/or a scale factor may be applied, wherein the shift amount and/or the scale factor may be a predetermined constant or may depend in a predetermined way on the set pump speed.

Optionally, a shift amount and/or a scale factor may be applied, wherein the shift amount and/or the scale factor depends on a difference and/or ratio between an axial operating value and the maximum of the operating value model function or the minimum of the operating value model function.

Optionally, the method may further comprise running the pump in a set of calibration batch runs at different pump speeds if the actual operation value is at or higher than the minimum of the operating value model function and if the actual operating value is at or lower than the maximum of the operating value model function.

Optionally, the method may further comprise the following steps:

• • determining a maximum actual operating value and/or a minimum actual operating value among the calibration batch runs;
  • comparing the maximum actual operating value with the maximum of the operating value model function and/or the minimum actual operating value with the minimum of the operating value model function; and
  • automatically updating the operating model function to a higher new operating value model function if the maximum actual operating value is higher than the maximum of the operating value model function, and/or automatically updating the operating value model function to a lower new operating value model function if the minimum actual operating value is lower than the minimum of the operating value model function.

The method disclosed herein may be implemented in form of compiled or uncompiled software code that is stored on a computer readable medium with instructions for executing the method. Alternatively, or in addition, the method may be executed by software installed in electronics residing within an electronics housing of a pump assembly, or software running in a cloud-based system and/or a building management system (BMS), e.g. in the pump control system disclosed herein.

The pump control system and method described herein may be implemented and integrated in electronics residing within an electronics housing of a pump assembly, or in at least one central controller controlling a plurality of pumps, e.g. as part of a building management system (BMS). It is also possible to implement the control system and method described herein at least partially in a remote cloud computing environment. A cloud computing environment may be particularly useful in case of geographically widely spread fluid distribution systems, such as a municipal water supply system or a district heating or cooling system.

Embodiments of the present disclosure will now be described by way of example with reference to the drawings. The various features of novelty which characterize the invention are pointed out with particularity in forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of a pump assembly according to the present disclosure;

FIG. 2 is a Pq-diagram showing an example of pump characteristics of a pump assembly running at twelve different speeds;

FIG. 3 is the pump characteristic diagrams as shown in FIG. 2 for four different pumps of the same pump type;

FIG. 4 is a pump characteristic in a Pq-diagram for a single pump speed;

FIG. 5 is a schematic diagram of a method for controlling a pump according to the present disclosure; and

FIG. 6 is schematic diagram of further preferred steps of a method for controlling a pump according to the present disclosure.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings, FIG. 1 shows a pump assembly 1 according to the present disclosure. The hardware of the pump assembly 1 is here essentially identical to the known pump type “Grundfos Magna3 50-60”. The hardware comprises a pump housing 3 having an inlet flange 5 and an outlet flange 7. The inlet flange 5 and the outlet flange 7 may be connected to a pipe system (not shown) for pumping water or another liquid through the pipe system. The inlet flange 5 and the outlet flange 7 are arranged coaxially on an axis L that defines the predominant pump direction. The pump assembly 1 further comprises an electric motor drive 9 for driving an impeller (not visible) residing within the pump housing 3. The motor rotor and the impeller rotate about a rotor axis R extending perpendicular to the axis L. The pump assembly 1 further comprises an electronics housing 11 for housing motor control electronics. The motor control electronics are configured to command the pump motor to run at a set pump speed. A front face of the electronics housing 11 comprises a human machine interface 13 comprising a display 15 and buttons 17 for outputting and inputting information, commands, settings, parameters and/or programs. The pump assembly 1 may comprise automatic pump control algorithms to run automatically and/or may be set manually to run at a certain operating point by using the human machine interface 13.

The pump control electronics within the electronics housing 11 is programmed in such a way that the pump assembly 1 comprises a new pump control system according to the present disclosure. The pump control system of the pump assembly 1 comprises a storage element having stored a plurality of model parameter sets for a plurality of pump speeds, wherein each model parameter set is indicative of an operating value model function corresponding to a pump speed. If the operating value model function is very precise, the pump assembly 1 is able to run at a desired operating point without having a measured or estimated flow value. For example, the operating value could be the actual power consumption of the pump assembly or a current drawn by the motor drive of the pump assembly 1. Another example of an operating value may be an output pressure measured by a pressure sensor. The advantage of considering an actual power consumption or a motor current as the modelled operating value is that these are readily available without a need for a pressure sensor.

The pump control system of the pump assembly 1 further comprises control electronics configured to command the pump to run at a set pump speed based on the operating value model function corresponding to the set pump speed, wherein a corresponding model parameter set of the stored model parameter sets is retrieved from the storage element. The initial model parameter sets stored in the storage element when a new pump assembly 1 is commissioned may be determined for a pump type in laboratory tests or field tests using certain fitting and modelling procedures.

FIG. 2 shows a result of such a fitting or modelling procedure to determine model parameter sets being indicative of operating value model functions. In the example shown in FIG. 2, the operating value is the power consumption P of the pump assembly 1, so that FIG. 2 shows a Pq-diagram, wherein the power consumption P of the pump assembly 1 is shown in dependence of the pumped flow q. FIG. 2 shows so-called “power curves” for twelve different pump speeds ω1 to ω12. There are numerous ways to fit the “power curve” to the data points as shown in FIG. 2. FIG. 2 actually shows two different model functions, wherein model function #2 is a fine-tuning of the model function #1. The model function may, for example, be a polynomial function. The model function may be described by a model parameter set that is initially determined by a simulation or a fitting procedure under laboratory or field test conditions.

FIG. 3 shows how the power consumption model function P_ω(q) of FIG. 2 fits to four different pumps of the same pump type. As can be seen, manufacturing tolerances may lead to significant deviations between the data points and the model function P_ω(q). Such deviations may also be due to pump variants of the same pump type or wear and tear after a certain amount of operating hours.

FIG. 4 illustrates how a model function P_ω(q) is automatically updated or calibrated for each individual pump assembly 1 during normal operation of the pump assembly 1 in order to reduce the deviations between the true current pump characteristic and the assumed modelled pump characteristic. FIG. 4 shows a power curve for a single pump speed over a predetermined range of flows between a minimum flow q_min and a maximum flow q_max. The power curve in FIG. 4 has a well-defined minimum P_min and a well-defined maximum P_max. FIG. 4 shows three different operating areas A, B and C. Operating area A includes all operating points with a power consumption below the minimum P_min of the power consumption model function P_ω(q).

The operating area B includes all operating points with a power consumption between P_min and P_max. Operating area C includes all operating points with a power consumption above the maximum Pmax of the power consumption model function P_ω(q). The idea to improve the model function is now to lower the model function if the actual currently determined power consumption P is in the operating area A, i.e. below the minimum P_min of the model function for the currently set pump speed ω. The rationale is here that the deviation between the actual determined power consumption P and the model function P_ω(q) cannot be due to the uncertainty in flow. Analogously, the model function is raised if the actual currently determined power consumption P is in the operating area C, i.e. above the maximum P_max of the model function P_ω(q). The same rationale applies here that such a deviation cannot be explained by an uncertainty in flow. In case the actual currently determined power consumption is in the operating area B, i.e. between the minimum P_min and maximum P_max of the model function, the model function P_ω(q) may be kept unamended for the time being. The reason for this is that a deviation could be due to an uncertainty in the current unknown flow q.

FIG. 5 shows the applied method for controlling the pump assembly 1 in a flow diagram. In a first step 501, the pump is run at a set pump speed ω based on an operating value model function P_ω(q) corresponding to the currently stored model parameter sets. In a second step 503, an actual power consumption P of the pump assembly 1 is determined. The actual power consumption P is then compared in following steps 505a, b with the minimum P_min of the power consumption model function P_ω(q) and/or with the maximum P_max of the power consumption model function P_ω(q). It should be noted that the comparisons 505a, b could be performed in parallel or subsequently, wherein one comparison is obsolete if the other one is affirmative. However, both comparisons 505a, b are performed if the first one of the comparisons is negative. If comparison 505a is affirmative, i.e. P<P_min, the model function P_ω(q) is lowered (step 507a) and new model parameter sets for the new lowered power consumption model function P_ω,down(q) is stored at the storage element in order to subsequently run the pump based on the new lower power consumption model function P_ω,down(q). Analogously, if comparison 505b is affirmative, i.e. P>P_max, the power consumption model function P_ω(q) is raised (step 507b) to a new higher power consumption model function P_ω,up(q). A new parameter set model parameter set indicative for the new higher power consumption model function P_ω,down(q) is stored in the storage element in order to subsequently run the pump based on the new higher power consumption model function P_ω,up(q). Only in case that both comparisons 505a and 505b are negative, i.e. the currently determined actual power consumption P is in the operating area B, i.e. between P_min and P_max, the power consumption model function P_ω(q) may remain unamended (step 509) for the time being.

FIG. 6 shows further steps that could be manually triggered in case the pump assembly 1 is running in the operating area B of FIG. 4, i.e. that the currently determined power consumption P is at or higher than the minimum P_min of the power consumption model function P_ω(q) and if the actual power consumption P is at or lower than the maximum P_max of the power consumption model function P_ω(q). For example, in step 601, the pump assembly 1 could be run in a set of calibration batch runs at different speeds. Thereby, a larger part of the operating range can be scanned for deviations between the actual power consumption P and the power consumption model function P_ω(q). In step 603, a minimum actual power consumption P_batch,min and/or a maximum actual power consumption P_batch,max among the calibration batch runs is determined. Similar to FIG. 5, two comparison steps 605a and 605b follow, wherein the minimum actual power consumption P_batch,min is compared with the minimum P_min of the power consumption model function P_ω(q) and the maximum actual power consumption P_batch,max is compared with the maximum P_max of the power consumption model function P_ω(q). The power consumption model function P_ω(q) only remains unamended if both comparisons are negative. If the minimum actual operating value among the calibration batch runs is lower than the minimum P_min of the power consumption model function P_ω(q), the power consumption model function P_ω(q) is lowered (step 607a) to a lower new power consumption model function P_ω,down(q). Analogously, if the maximum actual operating value P_batch,max among the calibration batch runs is higher than the maximum P_max of the power consumption model function P_ω(q), the power consumption model function P_ω(q) is updated or calibrated (step 607b) to a new higher power consumption model function P_ω,up(q). Only in case that both comparisons 605a and 605b are negative the power consumption model function P_ω(q) may remain unamended for the time being (step 609).

Where, in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as optional, preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

The above embodiments are to be understood as illustrative examples of the disclosure. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. While at least one exemplary embodiment has been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art and may be changed without departing from the scope of the subject matter described herein, and this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

In addition, “comprising” does not exclude other elements or steps, and “a” or “one” does not exclude a plural number. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above. Method steps may be applied in any order or in parallel or may constitute a part or a more detailed version of another method step. It should be understood that there should be embodied within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of the contribution to the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the disclosure, which should be determined from the appended claims and their legal equivalents.

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.

LIST OF REFERENCE NUMERALS

• • 1 pump assembly
  • 3 pump housing
  • 5 inlet flange
  • 7 outlet flange
  • 9 motor drive
  • 11 electronics housing
  • 13 human machine interface (HMI)
  • 15 display
  • 17 buttons
  • L axis of predominant flow direction
  • R rotor axis
  • 3 pump speed
  • P power consumption
  • q flow
  • P_ω(q) operating value model function
  • P_min minimum of model function
  • P_max maximum of model function
  • P_batch,min minimum actual operating value
  • P_batch,max maximum actual operating value