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Title:
METHOD OF GENERATING A THERMAL MODEL OF AN ELECTRICAL MACHINE
Document Type and Number:
WIPO Patent Application WO/2022/167069
Kind Code:
A1
Abstract:
A method of generating an initial thermal model of an electrical machine as manufactured for monitoring the thermal behaviour of the electrical machine as manufactured, the method comprising: a) providing a basic thermal model which is a thermal model of the electrical machine as designed, and b) adjusting at least some of the parameters of the basic thermal model based on temperature measurements and measurements of other operating parameters of the electrical machine as manufactured obtained in a quality control test, to obtain the initial thermal model.

Inventors:
KAKOSIMOS PANAGIOTIS (SE)
CHEN WENLIANG (SE)
KOLONDJOVSKI ZLATKO (FI)
RÖNNBERG KRISTIAN (SE)
Application Number:
PCT/EP2021/052551
Publication Date:
August 11, 2022
Filing Date:
February 03, 2021
Export Citation:
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Assignee:
ABB SCHWEIZ AG (CH)
International Classes:
G01K7/42; G01M15/00; H02P29/60
Foreign References:
EP1959532A12008-08-20
US20200341062A12020-10-29
EP36699566A
Attorney, Agent or Firm:
KRANSELL & WENNBORG KB (SE)
Download PDF:
Claims:
CLAIMS

1. A method of generating an initial thermal model of an electrical machine (n) as manufactured for monitoring the thermal behaviour of the electrical machine (n) as manufactured, the method comprising: a) providing a basic thermal model which is a thermal model of the electrical machine as designed, and b) adjusting at least some of the parameters of the basic thermal model based on temperature measurements and measurements of other operating parameters of the electrical machine (n) as manufactured obtained in a quality control test, to obtain the initial thermal model.

2. The method as claimed in claim 1, wherein the adjusting involves comparing temperature measurements with corresponding temperature estimations obtained from the basic thermal model and adjusting parameters which contribute to a discrepancy between the temperature measurements and the temperature estimations larger than a threshold value.

3. The method as claimed in claim 1 or 2, wherein the adjusting involves adjusting parameters related to heat losses of the basic thermal model based on the measurements of the other operating parameters.

4. The method as claimed in any of the preceding claims, wherein at least some of the other operating parameters that are measured result by supplying the electrical machine (11) with a voltage waveform of predefined characteristics.

5. The method as claimed in claim 4, wherein the predefined characteristics include at least one of amplitude, frequency, and harmonic content.

6. The method as claimed in claim 4 or 5, wherein the voltage waveform is a sinusoidal waveform.

7. The method as claimed in any of the preceding claims, comprising comparing the parameters of the initial thermal model with corresponding parameters of initial thermal models of other electrical machines of the same type as said electrical machine (11) as manufactured, obtained from quality control testing to determine whether the parameters are within an acceptable range.

8. The method as claimed in claim 7, comprising generating an alarm in case at least one of the parameters deviate with more than a predetermined threshold value from the acceptable range.

9. The method as claimed in claim 7 or 8, comprising storing all the parameters of the initial thermal model in a database (19).

10. The method as claimed in any of the preceding claims, comprising prior to step b) modifying the basic thermal model to a modified basic thermal model by adjusting parameters of the basic thermal model based on corresponding parameters of initial thermal models of other electrical machines of the same type as said electrical machine as manufactured, obtained from quality control testing and stored in a database (19), wherein in step b) the parameters of the modified basic thermal model are instead adjusted.

11. The method as claimed in any of the preceding claims, wherein the basic thermal model is a lumped-parameter thermal network, a finite element model or a finite volume model.

12. The method as claimed in any of the preceding claims, wherein the other operating parameters include at least some of machine currents, machine voltages and machine speed.

13. The method as claimed in any of the preceding claims, comprising monitoring the electrical machine (11) as manufactured by means of the initial thermal model. 15

14. A computer program comprising computer code which when executed by processing circuitry (5) of a thermal model generator (1) causes the thermal model generator (1) to perform the method of any of the preceding claims. 15. A thermal model generator (1) for generating an initial thermal model of an electrical machine (11) as manufactured for monitoring the thermal behaviour of the electrical machine (11) as manufactured, the thermal model generator comprising: processing circuitry (5), and a storage medium (7) comprising computer code which when executed by the processing circuitry (5) causes the thermal model generator (1) to perform the method as claimed in any of claims 1-13.

Description:
METHOD OF GENERATING A THERMAL MODEL OF AN ELECTRICAL MACHINE

TECHNICAL FIELD

The present disclosure generally relates to electrical machines.

BACKGROUND

Thermal models are used to predict the temperature and heat distribution in electrical machines. By knowing the temperature and heat distribution, monitoring and control of electrical machines may be improved.

To obtain a more accurate thermal model, the thermal model can be specifically adapted to a particular electrical machine during machine operation. EP36699566 Al discloses online measurement of the temperature at a predetermined location in an electrical machine and calculation of the temperature at a predetermined position in the electrical machine very close to or at the position of the temperature sensor, using the temperature measurement and other parameter measurements. Model parameters can be adapted in this way.

SUMMARY

The model disclosed in EP36699566 is adapted during online operation, i.e. post-commissioning of the electrical machine. The present inventors have found that by performing model adaptation during final product qualitytesting, before machine commissioning and online operation, the accuracy of the thermal model during online operation may be improved.

In view of the above, a general object of the present disclosure is to provide a method of generating a thermal model for an electrical machine which solves or at least mitigates the problems of the prior art.

There is hence according to a first aspect of the present disclosure provided a method of generating an initial thermal model of an electrical machine as manufactured for monitoring the thermal behaviour of the electrical machine as manufactured, the method comprising: a) providing a basic thermal model which is a thermal model of the electrical machine as designed, and b) adjusting at least some of the parameters of the basic thermal model based on temperature measurements and measurements of other operating parameters of the electrical machine as manufactured obtained in a quality control test, to obtain the initial thermal model.

The basic thermal model is a general thermal model of the thermal behaviour of an electrical machine as designed according to certain design specifications. The basic thermal model typically differs from the thermal behaviour of the electrical machine as manufactured, for example due to manufacturing tolerances.

The basic thermal model is a theoretical model of the thermal behaviour of the electrical machine derived from the design specifications of the electrical machine. The basic thermal model may be derived from the geometry, dimensions, and material properties of the electrical machine.

The basic thermal model may also be referred to as a “design stage thermal model”.

The basic thermal model is by means of the present method updated to an initial thermal model to better approximate the thermal characteristics of a specific electrical machine as manufactured according to a certain design. Temperature estimation may thereby be made more precise during operation of the electrical machine as manufactured.

The temperature measurements may be temperature measurements measured at positions in the electrical machine which correspond to thermal distribution positions of the basic thermal model or they may be transformed temperature measurements measured at different positions than the thermal distribution positions of the basic thermal model mapped to the corresponding thermal distribution positions of the basic thermal model. Each temperature measurement may in this case be subjected to a unique mapping, i.e. a mathematical function, which transforms the measured temperature from the measured position to a unique thermal distribution position of the basic thermal model.

Examples of other operating parameters are machine currents, machine voltages and machine speed.

The basic thermal model may for example be represented by a matrix equation. The parameters being adjusted may for example be weights in the form of matrices in the matrix equation, or the parameters maybe the elements of the weight matrices. The weights may in the matrix equation be multiplied with thermal parameters describing the thermal behaviour of the electrical machine as designed.

In the basic thermal model, the weights may for example be identity matrices, the elements of which maybe adjusted during step b) to obtain a closer approximation of the thermal behaviour of the electrical machine as manufactured.

Alternatively, or additionally, the parameters being adjusted in step b) may for example be material-related, such as thermal conductivity, material dimensions, and/or material geometry.

According to one embodiment the adjusting involves comparing temperature measurements with corresponding temperature estimations obtained from the basic thermal model and adjusting parameters which contribute to a discrepancy between the temperature measurements and the temperature estimations larger than a threshold value.

Thus, temperature measurements from specific locations of the electrical machine as manufactured are compared with corresponding temperature estimations, i.e. temperature estimations of the same locations as obtained from the basic thermal model. If the temperature measurements are transformed, the new location is compared with a temperature estimation of the new location. In case the thermal model is a lumped-parameter thermal network (LPTN), the distribution of the heat flow and temperature in the electrical machine is estimated by using an equivalent circuit which comprises thermal resistances, thermal capacitances, heat sources and temperature sources. The thermal resistances and thermal capacitances, and/or weights, are parameters of the basic thermal model that can be adjusted in step b) in case the discrepancy between the temperature measurements and the temperature estimations is larger than a threshold value.

According to one embodiment the adjusting involves adjusting parameters related to heat losses of the basic thermal model based on the measurements of the other operating parameters.

Heat losses may also be referred to as heat sources or power losses.

According to one embodiment at least some of the other operating parameters that are measured result by supplying the electrical machine with a voltage waveform of predefined characteristics.

The quality control test setting makes it possible to control the characteristics of the voltage waveform in a predefined way. This is not possible online during operation of the machine after commissioning, because the voltage waveform is generated based on machine control requirements for a certain application and is limited to the possibilities of the equipment on-site.

By controlling the characteristics of the voltage waveform in a predefined way, the other operating parameters such as machine currents can be made free from upper harmonics, or at least relatively free from upper harmonics. Alternatively, or additionally, the harmonics content of e.g. the machine currents may be compensated for because the voltage waveform has predefined characteristics, i.e. known characteristics, making the harmonic content of the operating parameters known. Using measurements of these operating parameters makes the estimation of the heat losses more accurate, resulting in a better thermal model than what can be achieved during online operation. According to one embodiment the predefined characteristics include at least one of amplitude, frequency, and harmonic content.

According to one embodiment the voltage waveform is a sinusoidal waveform.

One embodiment comprises comparing the parameters of the initial thermal model with corresponding parameters of initial thermal models of other electrical machines of the same type as said electrical machine as manufactured, obtained from quality control testing to determine whether the parameters are within an acceptable range.

With “same type” is meant electrical machines made according to the same design, i.e. having the same basic thermal model.

One embodiment comprises generating an alarm in case at least one of the parameters deviate with more than a predetermined threshold value from the acceptable range.

The alarm may be an alarm about a deviation in manufacturing of the electrical machine as manufactured.

One embodiment comprises storing all the parameters of the initial thermal model in a database.

The method may comprise updating an acceptable range of values for each parameter based on the adjusted parameters and the corresponding parameter of other electrical machines of the same type stored in the database. The statistical variation of the parameters may thereby be determined.

In case a parameter deviates with more than a predetermined amount from the corresponding range of values previously determined in quality control testing of electrical machines of the same type, the parameter may according to one example not be used for updating the acceptable range. Prior to step b) one embodiment comprises modifying the basic thermal model to a modified basic thermal model by adjusting parameters of the basic thermal model based on corresponding parameters of initial thermal models of other electrical machines of the same type as said electrical machine as manufactured, obtained from quality control testing and stored in a database, wherein in step b) the parameters of the modified basic thermal model are instead adjusted. Thus, the modified basic thermal model provides a better starting point to obtain the initial thermal model for a specific electrical machine as manufactured.

According to one embodiment the basic thermal model is a lumped- parameter thermal network, a finite element model or a finite volume model.

According to one embodiment the other operating parameters include at least some of machine currents, machine voltages and machine speed.

One embodiment comprises monitoring the electrical machine as manufactured by means of the initial thermal model.

There is according to a second aspect of the present disclosure provided a computer program comprising computer code which when executed by processing circuitry of a thermal model generator causes the thermal model generator to perform the method of the first aspect.

There is according to a third aspect of the present disclosure provided a thermal model generator for generating an initial thermal model of an electrical machine as manufactured for monitoring the thermal behaviour of the electrical machine as manufactured, the thermal model generator comprising: processing circuitry, and a storage medium comprising computer code which when executed by the processing circuitry causes the thermal model generator to perform the method of the first aspect.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, etc., unless explicitly stated otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

The specific embodiments of the inventive concept will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. i schematically shows an example of a thermal model generator for generating an initial thermal model of an electrical machine as manufactured;

Fig. 2 shows an example of a test system including the thermal model generator in Fig. 1; and

Fig. 3 is a flowchart of a method of generating an initial thermal model of an electrical machine as manufactured by means of the thermal model generator in Fig. 1.

DETAILED DESCRIPTION

The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplifying embodiments are shown. The inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description.

Fig. i depicts a block diagram of an example of a thermal model generator i. The thermal model generator 1 is configured to generate an initial thermal model of an electrical machine as manufactured from a basic thermal model of an electrical machine as designed. The thermal model generator i is thus configured to generate an initial thermal model of a manufactured electrical machine based on a basic thermal model, which is a theoretical model of the electrical machine as derived from its design specifications.

The electrical machine maybe a motor or a generator.

The electrical machine as manufactured, in the following simply “electrical machine”, is provided with a plurality of temperature sensors, each temperature sensor being configured to measure the temperature in a respective one of a plurality of different locations of the electrical machine during a quality control test.

The temperature sensors may for example be configured to detect the temperature of the stator windings, the rotor windings, the rotor surface, the stator chassis, and/or the bearings.

The thermal model generator 1 comprises an input unit 2 configured to receive temperature measurement from the temperature sensors.

The input unit 2 is further configured to receive measurements of other operating parameters of the electrical machine from other types of sensors configured to detect other operating parameters of the electrical machine.

The thermal model generator i maybe configured to receive the temperature measurement and measurements of the other operating parameters by wireless, wired, or a combination of wireless and wired communication.

The thermal model generator 1 comprises processing circuitry 5 configured to receive the temperature measurements and the measurements of other operating parameters from the input unit 2 and to process these measurements.

The thermal model generator 1 may comprise a storage medium 7.

The storage medium 7 may comprise a computer program including computer code which when executed by the processing circuitry 5 causes the thermal model generator 1 to perform the method as disclosed herein. The processing circuitry 5 may for example use any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate arrays (FPGA) etc., capable of executing any herein disclosed operations concerning determining the initial thermal model of an electrical machine as manufactured.

The storage medium 7 may for example be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory.

Fig. 2 shows a test system 9 comprising the thermal model generator 1 and an electrical machine 11. The electrical machine 11 has a rotor having a rotor shaft 11a, a stator configured to electromagnetically interact with the rotor, and a stator chassis 11b.

The electrical machine 11 is set up for a quality control test. This is typically done in the factory. The quality control test may be a type test. The quality control test is typically performed before the electrical machine 11 is delivered to site.

The electrical machine 11 is provided with a plurality of temperature sensors 13, 15. A first temperature sensor 13 may for example be configured to detect the temperature at the stator chassis 11b, and a second temperature sensor 15 may be configured to detect the temperature at the bearings at one end of the rotor.

The electrical machine 11 may further be provided with other types of sensors for detecting other operating parameters of the electrical machine 1. The electrical machine n may for example be provided with voltage sensors configured to detect machine voltages such as stator and/or rotor voltages, and current sensors configured to detect machine currents such as stator and/ or rotor currents.

The electrical machine n maybe provided with means for detecting and/or estimating the rotor speed, i.e. machine speed.

The machine voltages, machine currents, and machine speed are examples of other operating parameters of the machine.

The temperature sensors 13, 15, and the other types of sensors, such as voltage sensors and current sensors, are connected to the thermal model generator 1. The thermal model generator 1 thereby receives temperature measurements and measurements of the other operating parameters of the electrical machine 11.

The thermal model generator 1 is configured to be connected to a database 19, which for example may be located in a cloud 17, or in the thermal model generator 1.

The database 19 may store parameters of initial thermal models of a plurality of electrical machines of the same type as the electrical machine 11 that is to be subjected to a quality control test, from previous quality control tests. The parameters stored from other electrical machines may form acceptable ranges of values for these parameters.

A method of generating an initial thermal model of the electrical machine 11 by means of the thermal model generator 1 will now be described with reference to Fig. 3.

In a step a) a basic thermal model of the electrical machine as designed is provided. The basic thermal model may for example be determined using geometries, dimensions, and material properties of the design specification of the electrical machine. The parameters of the basic thermal model may according to one example be adjusted by comparing them with corresponding parameters of other electrical machines of the same type in the database 19. The basic thermal model is thereby modified and becomes a modified basic thermal model.

In a step b) at least some of the parameters of the basic thermal model, or the modified basic thermal model, are adjusted based on the temperature measurements and on measurements of the other operating parameters measured or obtained during the quality control test. An initial thermal model is thereby obtained.

The initial thermal model is obtained when the adjusting in step b) has been completed. Thus, the initial thermal model is obtained when all parameters that needed to be adjusted have been adjusted to better approximate the electrical machine 11.

In step b) the temperature measurements are compared with corresponding temperature estimations obtained from the basic thermal model or modified basic thermal model. In case a comparison between a temperature estimation and a temperature measurement reveals a discrepancy that is larger than a threshold value, a parameter of the basic thermal model which is involved in the calculation of the estimated temperature is adjusted.

Step b) also involves adjusting parameters of the basic thermal model related to heat losses based on the measurements of the other operating parameters. Hereto, parameters related to heat losses may be adjusted by comparing the measurements of the other parameters with heat losses estimated by means of the basic thermal model. In case an estimated heat loss deviates with more than a threshold value from that obtained from the basic thermal model, one or more parameters involved in the estimation of the heat loss in question are adjusted.

In the quality control test, the electrical machine 11 is fed with a voltage waveform of predefined characteristics from for example a power converter, a transformer or from the grid. The predefined characteristics include at least one of amplitude, frequency, and harmonic content. The voltage waveform may for example be a sinusoidal waveform to obtain as little harmonics as possible in the machine currents and voltages.

The parameters of the initial thermal model may be compared with corresponding parameters of initial thermal models of other electrical machines of the same type obtained from quality control testing to determine whether the parameters are within an acceptable range.

In case a parameter deviates with more than a predetermined threshold value from the acceptable range the thermal model generator i may generate an alarm.

The parameters of the initial thermal model maybe stored in the database 19. In this way, the initial thermal model of a fleet of electrical machines may eventually be stored in the database 19 and statistical data about the parameters such as acceptable ranges can be generated and stored in the database 19.

The initial thermal model may be used for monitoring the electrical machine 11 when the electrical machine has been commissioned and is operated onsite.

The inventive concept has mainly been described above with reference to a few examples. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.