US-12627251-B2 - Method for estimating the magnet temperature in an electrical machine, method for controlling said electrical machine, electronic device for estimating the magnet temperature in an electrical machine and system for controlling said electrical machine

US12627251B2US 12627251 B2US12627251 B2US 12627251B2US-12627251-B2

Abstract

A method for estimating the magnet temperature in an electrical machine carried out by means of an electronic computer involves estimating a value of a total magnetic flux of the electrical machine and estimating a value of a first partial flux, representing a magnetic flux due to a reluctance of the electrical machine. The method also involves the steps of calculating a value of a second partial flux as a function of a difference between said value of the total magnetic flux and said value of the first partial flux and determining a value of a magnet temperature as a function of said value of the second partial flux.

Inventors

Ruggero SECCIA
Luca ZAI
Pasquale Forte

Assignees

ELDOR CORPORATION S.P.A.

Dates

Publication Date: 20260512
Application Date: 20220513
Priority Date: 20210517

Claims (15)

1 . An electronic device for estimating the magnet temperature in an electrical machine including a rotor rotatable in a stator, comprising: a processing unit configured to: a) estimate a value of a total magnetic flux of the electrical machine; b) estimate a value of a first partial flux, representing a share of said total magnetic flux determined solely by a stator contribution; c) calculate a value of a second partial flux as a function of a difference between said value of the total magnetic flux and said value of the first partial flux; and d) determine a value of a magnet temperature as a function of said value of the second partial flux.
2 . The electronic device according to claim 1 , wherein said processing unit is further configured to: determine in advance a value of a reference magnet temperature; estimate the value of the total magnetic flux and the value of the first partial flux with reference to said value of the reference magnet temperature.
3 . The electronic device according to claim 2 , wherein said processing unit further comprises: a number of first maps relating the value of the total magnetic flux to a specific magnet temperature or range of magnet temperatures; a number of second maps relating the value of the first partial flux to a specific magnet temperature or range of magnet temperatures.
4 . The electronic device according to claim 3 , wherein the processing unit further comprises a first estimation module configured to: determine at least two known values of the total magnetic flux within at least two of said first maps as a function of operating conditions of the electrical machine; determine, according to a predetermined interpolation logic, a total flux value Fe at the reference magnet temperature.
5 . The electronic device according to claim 3 , wherein the processing unit comprises at least a second estimation module configured to: determine at least two known values of the first partial flux within said at least two of said first maps as a function of the operating conditions of the electrical machine; determine, according to a predetermined interpolation logic, the value of the first partial flux at the reference magnet temperature.
6 . The electronic device according to claim 2 , wherein said processing unit is further configured to: e) update the reference magnet temperature by replacing the value of said reference magnet temperature with the value of the magnet temperature determined in step d).
7 . The electronic device according to claim 6 , wherein the processing unit is further configured to recursively perform the steps from point a) to point e).
8 . The electronic device according to claim 1 , and further comprising: a detection element of a first quantity representing a control voltage of the electrical machine; a detection element of a second quantity representing a current circulating in windings of the stator of said electrical machine, wherein the processing unit is configured to: estimate the value of a total magnetic flux of the electrical machine at least partially as a function of said first quantity and estimate the value of the first partial flux as a function of said second quantity, or vice versa.
9 . A control system for an electrical machine, comprising: the electronic device for estimating the magnet temperature according to claim 2 ; a control device of the electrical machine, configured to send a control signal to the electrical machine according to a first quantity representing a control voltage and a value of a current temperature of said electrical machine; wherein said electronic device is configured to: update the value of said current temperature by replacing the value of said current temperature with the value of said magnet temperature determined in step d); change the control signal according to the updated value of the current temperature.
10 . A method for estimating the magnet temperature in an electrical machine including a rotor rotatable in a stator, said method being carried out by an electronic computer and comprising the steps of: A) estimating a value of a total magnetic flux of the electrical machine; B) estimating a value of a first partial flux, representing a share of said total magnetic flux determined solely by a stator contribution; C) calculating a value of a second partial flux as a function of a difference between said value of the total magnetic flux and said value of the first partial flux; and D) determining a value of a magnet temperature as a function of said value of the second partial flux.
11 . The method according to claim 10 , and further comprising a preliminary step of determining a value of a reference magnet temperature, wherein steps A) and B) are performed by estimating said value of the total magnetic flux and said value of the first partial flux with reference to said value of the reference magnet temperature.
12 . The method according to claim 11 , and further comprising a step for updating the reference magnet temperature carried out by replacing the value of the reference magnet temperature with the value of the magnet temperature determined in step D).
13 . The method according to claim 10 , wherein steps A) to D) are performed recursively.
14 . The method according to claim 10 , and further comprising the steps of: determining or detecting a first quantity representing a control voltage of the electrical machine; determining or detecting a second quantity representing a current circulating in windings of the stator of said electrical machine, wherein the estimation of the value of the total magnetic flux is at least partly carried out as a function of said first quantity and the estimation of the value of the first partial flux is carried out as a function of said second quantity, or vice versa.
15 . A control method for the electrical machine comprising the steps of: determining a value of a current magnet temperature of an electrical machine; determining a value of a control voltage of an electrical machine; generating a control signal of said electrical machine according to said value of the control voltage and said value of the current temperature; estimating a value of a magnet temperature of said electrical machine by implementing the method according to claim 10 ; updating the value of the current temperature by replacing the value of the current temperature with the value of said magnet temperature determined in step D); and changing the control signal according to the updated value of the current, updated temperature.

Description

This application is the National Phase of International Application PCT/IB2022/054462 filed May 13, 2022 which designated the U.S. This application claims priority to Italian Patent Application No. 102021000012575 filed May 17, 2021, which applications are incorporated by reference herein. This invention relates to a method for estimating the magnet temperature in an electrical machine and to a method for controlling said electrical machine. In addition, this invention also relates to an electronic device for estimating the magnet temperature in an electrical machine and to a system for controlling said electrical machine. This invention has its main application in the area of electric or hybrid traction, in particular in the automotive sector, in the design and construction of hybrid or electric drive systems. Of the main parameters that are the subject of analysis in the control of an electrical machine, the magnet temperature is one of those that, while having a significant impact in the efficiency of the machine, are more complex to use, since difficult to measure directly. The absence of correct information relating to this parameter, in fact, may lead both to a reduction in performance and to energy consumption or safety problems. In terms of safety, in particular, a control based on an incorrect magnet temperature may entail: the exceeding of limit electric values;a loss of control, in the event of operation at the limits of the battery voltage;problems of demagnetisation of the magnet itself, due to exceeding its limit operating temperature. For this reason, in the prior art, numerous methods or systems for detecting or estimating the magnet temperature have been developed; these are briefly illustrated below. A first known solution consists in estimating methods based on equivalent thermal models that, in any case, are rather onerous in terms of computation and difficult to calibrate, since they require a thorough knowledge both of the thermal parameters and of the electric ones of the machine. This substantially limits the use thereof on a large scale. Alternatively, it is possible to estimate the magnet temperature by measuring the open-circuit voltage, as illustrated in the U.S. Pat. No. 7,979,171, which, in any case, needs de-energising of the machine during its normal operation, so that it is mainly suitable for bank applications. Solutions using temperature sensors inserted directly in the magnet, with transmission of data through the collector or in wireless mode, are also known, as described in the patent US20040007997. Disadvantageously, in any case, the presence of sensors negatively impacts the machine both in terms of cost and structure, since the machine parameters and shape are altered. Among the solutions known today, there are also methods that involve correlating the estimate of the temperature to the magnetic flux of the machine (US20200036311), which, in any case, entails an estimate that is not very accurate since it does not consider the different contributions determining the machine's total flux. The purpose of this invention is, thus, to provide an electronic device for estimating the magnet temperature in an electrical machine, a system for controlling said electrical machine, a method for estimating the magnet temperature in an electrical machine, and a method for controlling said electrical machine that can overcome the drawbacks of the prior art noted above. In particular, the purpose of this invention is to provide a method for estimating the magnet temperature in an electrical machine that is reliable and, at the same time, computationally simple. An additional purpose of this invention is to provide a method for controlling an electrical machine that is efficient and, at the same time, safe. Again, the purposes of this invention include providing an electronic device for estimating the magnet temperature in an electrical machine and a control system for said electrical machine that are reliable and, at the same time, economical. Said purposes are achieved with an electronic device for estimating the magnet temperature in an electrical machine, a system for controlling said electrical machine, a method for estimating the magnet temperature in an electrical machine, and a method for controlling said electrical machine having the features of one or more of the claims below. In particular, said purposes are achieved with an electronic device for estimating the magnet temperature in an electrical machine, comprising a processing unit configured to: a) estimate a value of a total magnetic flux of the electrical machine;b) estimate a value of a first partial flux, representing a magnetic flux due to a reluctance of the electrical machine;c) calculate a value of a second partial flux as a function of a difference between said value of the total magnetic flux and said value of the first partial flux;d) determine a value of a magnet temperature as a function of said value of th