Method for determining the temperature of a component of a power inverter

Abstract

The invention relates to a computer-implemented method for determining the temperature of a first component of a power inverter (6), the inverter (6) being connected to a rotating electrical machine (2), the machine (2) comprising a second component (3), separate from the first component, through which an alternating current flows. The method comprises a step of measuring the temperature of the second component by a temperature sensor (4). The method is characterized in that it comprises a step (140) of determining the temperature of the first component of the inverter (6) based on the temperature of the second component (3) measured by the temperature sensor (4). Figure for the abstract: Figure 1

Description

Title of the invention: Method for determining the temperature of a component of a power inverter

[0001] The invention relates to the temperature of power inverters.

[0002] In particular, it relates to a method for determining the initialization temperature of a component of a power converter in a vehicle when the vehicle is restarted after a period of parking.

[0003] To avoid malfunctions and potential damage, the temperatures of the components of an inverter must be known. Since it is difficult and expensive to place a temperature sensor in each inverter, especially in a motor vehicle, the temperatures are estimated from component-specific thermal models and based on the electrical power supplied to the components.

[0004] However, when the vehicle has been parked for some time and is restarted, the initial temperature of these components is difficult to determine. Some of them, which have a low thermal time constant, cool down rapidly to the temperature of the inverter's cooling water. However, components with a high thermal time constant, such as a DC capacitor, may still exhibit a high temperature at the time of restart.

[0005] A classic method for determining the initialization temperature of a component of an inverter having a high thermal time constant consists of obtaining the thermal time constant of the component, the parking time of the vehicle, the last known or estimated temperature of the component before parking, and calculating the initialization temperature of the component from these values.

[0006] The drawback of this method is that the parking time stored by the system inside the vehicle is generally inaccurate because it is recorded discretely, resulting in an incorrect initialization temperature when the actual parking time does not correspond to one of the possible discrete values. Another drawback is that the last known or estimated temperature before parking may be lost if the storage of this value is faulty, making it impossible to determine the initialization temperature.

[0007] The purpose of this document is to improve the determination of the temperature of a component of an inverter.

[0008] In order to achieve this objective, a computer-implemented method is proposed to determine the temperature of a first component of a power inverter, the inverter being connected to a rotating electrical machine, the machine comprising a second component, distinct from the first component, in which an alternating current flows in the second component, the process comprising the following steps:

[0009] - measure the temperature of the second component using a sensor temperature,

[0010] - determine the temperature of the first component of the inverter based on the temperature of the second component measured by the temperature sensor.

[0011] Indeed, the component's temperature is influenced by its losses. It appears that for some components of a power inverter, the losses are primarily due to the alternating current supplied by the inverter. Consequently, the temperature of the first inverter component and the temperature of the second component operating on alternating current are related, even if the inverter and the second component are not thermally connected. The temperature of the first component can be calculated without a sensor located inside the inverter and relies on precise data. In particular, this method does not require estimating a standstill time and determining the component's thermal time constant. It is therefore simpler and more accurate. It also does not require storing a last known or estimated temperature before standstill.

[0012] Other optional features, taken individually or in combination, are presented below.

[0013] Preferably, the first component is a DC coupling capacitor or a DC busbar inverter or an AC interface of the inverter.

[0014] Thus, the temperature of the inverter's DC-link capacitor is determined as a function of the machine's temperature. Indeed, the losses in the DC capacitor are primarily due to the AC current, the same AC current flowing in the machine.

[0015] Advantageously, the second component is a stator of an electric motor of the rotating electric machine, the measured temperature being a temperature of the stator of the electric motor.

[0016] Indeed, the stator circulates an alternating current. Its temperature, mainly due to the losses associated with this alternating current, makes it possible to determine the temperature of the first component of the inverter.

[0017] Preferably, the temperature of the second component being a first measured temperature, the method further comprises the following steps:

[0018] - measure, by another temperature sensor, a second measured temperature inverter cooling water, and

[0019] - determine the temperature of the first inverter component based on the first and second temperatures measured.

[0020] Thus, in this example, the temperature of the inverter component also depends on the temperature of the inverter cooling water.

[0021] Advantageously, the temperature of the first component of the inverter is determined according to the following formula: r - t . -T 1 ' mverter-component — ' water^ v aistmct-companent 2 water)

[0022] where Tinverter componentestiatempérature determined of the first component of the inverter, idistinct componemest the first measured temperature of the second component, Twater is the second measured temperature of the cooling water, and k is a predetermined value.

[0023] The predetermined value k depends on the specific arrangement and can be calculated or deduced experimentally.

[0024] The invention also relates to a method for determining the initialization temperature of a component of a power inverter, comprising, when the inverter is initialized after sleep, a step of determining the initialization temperature of the component according to the method described above.

[0025] Thus, the method described above makes it possible to determine the initialization temperature of a component of a power inverter, particularly after a standstill, without storing the standstill duration and the temperature before standstill. The initialization temperature of the inverter component is simpler and more accurate because it is based on the temperature of a component of the machine.

[0026] Preferably, with the initialization temperature being a first initialization temperature, the method comprises the following steps:

[0027] - determine the thermal time constant of the inverter component;

[0028] - determine the last known temperature of the component;

[0029] - determine the sleep time of the inverter;

[0030] - when the inverter is initialized after sleeping, determine a second Inverter component initialization temperature as a function of the thermal time constant, the last known temperature of the component, and the inverter sleep time;

[0031] -perform a plausibility check of the first, respectively of the second, initialization temperature, on the basis of the second, respectively of the first, initialization temperature.

[0032] Thus, in this example, the temperature of the inverter component is determined by the first method described above, but also by a second conventional method. The result of the first or second method is therefore verified using the second or first method respectively, and it can be corrected.

[0033] The invention also relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to implement the steps of the method described above for determining a temperature or of the method described above for determining the initialization temperature.

[0034] The invention also relates to a computer-readable storage medium comprising instructions which, when executed by a computer, cause the latter to implement the steps of the method described above for determining a temperature or of the method described above for determining the initialization temperature.

[0035] The invention also relates to a system comprising:

[0036] - a power inverter, the power inverter comprising a first component,

[0037] - a rotating electrical machine connected to the inverter and comprising a second a component distinct from the first component, in which the second component is capable of carrying an alternating current;

[0038] - a temperature sensor for measuring the temperature of the second component,

[0039] characterized in that the system further comprises computer means configured to control the steps of:

[0040] - by the sensor, measurement of a first temperature of the second component (3);

[0041] - determine the temperature of the first inverter component as a function of the first temperature. Brief description of the figures

[0042] The invention will be better understood upon reading the following description, which is given by way of example only and is made with reference to the accompanying drawings in which:

[0043] Fig. 1 is a schematic view of a vehicle comprising a system according to the invention;

[0044] Figure 2 is a schematic view of the system comprising an inverter according to the invention; and

[0045] The [Fig.3] is a diagram of a method according to the invention. Detailed description

[0046] [Fig. 1] illustrates a motor vehicle 1 comprising a rotating electric machine 2. The rotating electric machine 2 is, in this example, an electric motor that powers the vehicle 1. Alternatively, any type of rotating electric machine could be considered in the invention, for example an electric motor to power a braking system of the vehicle 1.

[0047] The rotating electrical machine 2 comprises a stator 3 and a rotor, which are not shown in detail. The stator 3 includes a temperature sensor 4, for measuring the temperature of the stator 3.

[0048] The vehicle 1 also includes a battery 5 to power the rotating electric machine 2.

[0049] The vehicle 1 also includes an inverter 6, connected between the battery 5 and the rotating electric machine 2, in order to transform the direct current from the battery 5 into alternating current to power the machine 2 and to transform the alternating current from the machine 2 into direct current to charge the battery 5.

[0050] The inverter 6 also includes a computer unit 7 connected to the temperature sensor 3 and to the rotating electrical machine 2. The unit 7 includes computer means for controlling the machine 2 and for executing a method 100 described later.

[0051] In unit 7, the conventional computing means include a processing unit 8 and a computer-readable storage medium 9 comprising instructions which, when executed by the processing unit 8, cause the unit to carry out the steps of the process 100. Indeed, this medium 9 includes a computer program 10 comprising instructions which, when the program 10 is executed by a computer or computing means such as the processing unit 8, cause the computer to carry out the steps of the method 100.

[0052] The inverter 6 also includes a cooling water circuit 11. This circuit cools the inverter 6 by passing through or around the components of the inverter 6 in a manner known to those skilled in the art. No details will be described regarding the arrangement of the circuit 11.

[0053] The inverter 6 also includes a second temperature sensor 12 arranged to measure the temperature of the cooling water circulating in the circuit 11.

[0054] Figure 2 illustrates the components of the inverter 6. The inverter 6 includes a DC connector 13 connected to the battery 5 in a manner not shown. The direct current flowing through the DC connector is called I.DC.

[0055] The inverter 6 includes a DC current bar 14 connected to the DC current connector 13 and circulating the DC current IDC.

[0056] The inverter 6 also includes a DC coupling capacitor 15 connected to the DC busbar 14. An alternating current flows through the DC coupling capacitor 15. The value of the root mean square (rms) current, called Icap>rmset, flowing through the DC coupling capacitor 15, is given by the following formula:

[0057] where M represents the modulation index and Phi represents the angle between the alternating voltage and the alternating current. IAC rms is the root mean square current of the alternating current IAC flowing in the stator 3 of the rotating electrical machine 2.

[0058] The inverter 6 also includes a DC-Busbar inverter 16, connected to the DC-link capacitor 15 and in which flows a current Iinv whose quadratic current, called Iinv rms, is given by the following formula:

[0059] The inverter 6 also includes power switches 17 connected to the inverter 16 of the DC bus, including insulated-gate bipolar transistors (IGBTs) or MOSFETs, circulating an alternating current IAC whose mean squared current is IAC rms. This current is the alternating current to be supplied to the machine 2.

[0060] The inverter 6 also includes an AC interface 18 connected to the power switches 17 and circulating the alternating current IAC to be supplied to the rotating electrical machine 2. The AC interface can be a power bar or an AC cable.

[0061] An example of a method 100 for determining the initialization temperature of a DC coupling capacitor 15 of the power inverter 6 is now described with reference to [Fig. 3]. Determining this initialization temperature is necessary to properly control the electric current supplied to the rotating electrical machine 2. Indeed, the thermal models of the inverter components are calculated to ensure the thermal protection of the inverter. Thus, the power switches 17 are controlled by the unit 7 according to a temperature criterion, which has consequences for the electrical machine 2. An incorrect initialization temperature could, for example, generate an inadequate torque (too high or too low) in the machine 2.

[0062] Method 100 is implemented by the computer unit 7 after a parking time of the vehicle 1. During the parking time, the rotating electric machine 2 was switched off, the inverter 6 was in standby mode.

[0063] At step 110, vehicle 1 is restarted. The rotating electric machine 2 is running, the inverter 5 is running. The initialization temperature must be determined.

[0064] At step 120, unit 7 measures the temperature Tdistinct component of the stator 3 of machine 2, using the first temperature sensor 4 placed on the stator 3.

[0065] At step 130, unit 7 measures, by means of the second temperature sensor 12, the temperature Twater of the cooling water 11 of the inverter 6.

[0066] In step 140, unit 7 determines the Tinverter component of the capacitor 15 of the DC link using the following formula:

[0067] t. -T ■ -T ]• ■* mverter-compment ~ ■* water ' n aistuwt-component * water f

[0068] k is a coefficient determined by a person skilled in the art using experimental or design data, since k is specific to the arrangement.

[0069] This formula is derived from the fact that, according to the formulas mentioned above concerning the electric current flowing through the components of the inverter 5, the losses of the stator 3 and the losses of the DC coupling capacitor 15 are primarily due to the alternating current IAc. These losses are responsible for the temperature of these components. Therefore, although the DC coupling capacitor 15 and the stator 3 are not thermally connected, their respective temperatures are related.

[0070] Unit 7 has now determined the initialization temperature of the capacitor 15 in the intermediate circuit and can now control the inverter 6 based on this temperature. Furthermore, the temperature evolution, using any thermal model, can then be determined by Unit 7 based on this initialization temperature, in order to ensure thermal protection of the capacitor 15 in the intermediate circuit without any abnormal consequences on the torque generated by machine 2.

[0071] The following steps are additional and optional steps to verify and possibly modify the initialization temperature that has been found.

[0072] In step 150, the unit nit 7 determines the thermal time constant Tconstant of the capacitor 15 of the DC link of the inverter 6. This value is notably stored in a memory of the unit 7, because this constant value is determined or known during the design of the inverter 6.

[0073] In step 160, unit 7 determines the last known temperature Tbeforesieep of the CC coupling capacitor 15. In particular, the last known temperature is the temperature determined by unit 7 using a thermal model, before the inverter goes into standby mode when the vehicle parks.

[0074] In step 170, unit 7 determines the temperature Twater beforesieep of the cooling water 11 at the moment when the vehicle 1 parks, just before the inverter goes into standby mode.

[0075] In step 180, unit 7 determines a sleep time Tpark of the inverter 6, that is to say a period between the moment when the inverter 6 goes into sleep mode, when the vehicle parks, and the moment when the inverter 6 must be initialized again after sleeping, when the vehicle 1 restarts.

[0076] In step 190, unit 7 determines a second initialization temperature Tinverter-component nt 2 of the DC coupling capacitor 15 based on the following formula:

[0077] T. ~T 4- f Tl / • » -T. r, 1 1 mverter-component-2 x water ' \ 1 bej oresleep lwaterjoejoresieep ) v jcmstma

[0078] To improve safety, in step 200, unit 6 performs, in this example, a plausibility check of the first Tinvertercomponent initialization temperature, based on the second Tinverter component initialization temperature 2-

[0079] A plausibility check is a method known to those skilled in the art that allows one to verify whether a result value is legitimate based on another reference value. Such a check may lead to modifying the first value found, based on the second value. For example, if a certain threshold of the plausibility check is exceeded, the initialization is considered unreliable. Consequently, the initialization may take place with, for example, a worst-case temperature to ensure thermal protection.

[0080] Steps 160 to 100 can be performed before steps 120 to 150. In this case, plausibility checks are then performed on the second initialization temperature of the Tinverter component 2^n as a function of the first initialization temperature. Tinverter component*

[0081] The invention is not limited to the illustrated realizations and other realizations will appear to persons competent in this field.

[0082] First, the invention is not limited to a method for determining an initialization temperature. Indeed, the relationship between the temperature of the capacitor 15 of the inverter 6 and the temperature of the stator 3 of the rotating electrical machine 2 is not limited to initialization after standby mode; it is therefore possible to determine the temperature of the capacitor at any time.

[0083] Furthermore, instead of the temperature of the DC coupling capacitor 15, it is possible to determine, using the same formula and an adapted value of the coefficient k, the temperature of the DC busbar inverter 16 and the AC interface 18. Indeed, based on the formulas described above with reference to these components, the main losses of these components are also due to the alternating current IAc. Therefore, the invention is not limited to calculating the temperature of the DC coupling capacitor 15; it can be implemented to determine the temperature of other components of the inverter 6.

[0084] Furthermore, if the CA interface 18 were considered as part of the rotating electrical machine 2 and if the temperature sensor 4 were placed on the CA interface 18 instead of the stator 3, the same method would allow the temperature of the DC-linked capacitor 15 or the DC bus inverter 16 to be determined based on the temperature measured on the CA interface 18, with an appropriate k value. By Therefore, the invention is not limited to measuring the temperature of a stator; it can be implemented to measure the temperature of another component of the rotating electrical machine 2 in order to determine the temperature of a component of the inverter 6.

[0085] Thus, more generally, the invention proposes a computer-implemented method 100 for determining the temperature of a first component 15 of a power inverter 6, the inverter being connected to a rotating electrical machine 2, the machine comprising a second component 3, distinct from the first component 15, in which an alternating current flows in the second component 3, the method 100 comprising a step 120 of measuring the temperature of the second component 3 by a temperature sensor 4, the method 100 comprising a step 140 of determining the temperature of the first component 15 of the inverter 6 on the basis of the temperature of the second component 3 measured by the temperature sensor 4.

[0086] The invention also proposes a system comprising

[0087] - a power inverter 6, the power inverter comprising a first component 15, 16 or 18;

[0088] - a rotating electrical machine 2 connected to the inverter 6 and comprising a second component 3 distinct from the first component 15, 16 or 18, in which the second component 3 is capable of carrying an alternating current;

[0089] - a temperature sensor 4 for measuring the temperature of the second component 3,

[0090] - computer means 7, 8 and 9 configured to control the steps of:

[0091] - by sensor 4, measurement of a first temperature of the second component 3;

[0092] - determine the temperature of the first component 15, 16 or 18 of the inverter in function of the first temperature. Nomenclature

[0093] 1: vehicle

[0094] 2: rotating electric machine

[0095] 3: stator of machine 2

[0096] 4 temperature sensor

[0097] 5: battery

[0098] 6 inverter

[0099] 7: computer unit

[0100] 8: processing unit

[0101] 9: computer storage medium

[0102] 10: computer program

[0103] 11: Cooling water circuit

[0104] 12: temperature sensor

[0105] 13: DC Connector

[0106]

[0107]

[0108]

[0109]

[0110] 14: DC busbar 15: DC capacitor 16: DC busbar inverter 17: Power switches 18: AC interface

Claims

Claims

1. A computer-implemented method (100) for determining the temperature of a first component (15, 16, 18) of a power inverter (6), the inverter (6) being connected to a rotating electrical machine (2), the machine (2) comprising a second component (3), distinct from the first component (15, 16, 18), in which an alternating current flows in the second component (3), the method (100) comprising a step (120) of measuring the temperature of the second component by a temperature sensor (4), the method (100) being characterized in that it comprises a step of determining (140) the temperature of the first component (15, 16, 18) of the inverter (6) on the basis of the temperature of the second component (3) measured with the temperature sensor (4).

2. Method (100) according to the preceding claim, wherein the first component is a DC link capacitor (15) or a DC bus inverter (16) or an AC interface (18) of the inverter (6).

3. A method (100) according to any preceding claim, wherein the second component (3) is a stator of an electric motor of the rotating electric machine (2), the measured temperature being a temperature of the stator (3) of the machine.

4. Method (100) according to any one of the preceding claims, wherein the temperature of the second component (3) being a first measured temperature, the method further comprises the following steps: - measuring (130), by a further temperature sensor (12), a second measured temperature of the cooling water of the inverter (6), and - determining (140) the temperature of the first component of the inverter (6) on the basis of the first and second measured temperatures.

5. Method (100) according to the preceding claim, wherein the temperature of the first component of the inverter (6) is determined according to the following formula: T inverter-component — ^water + distinct-component ~ ^water} where T inverter component is the determined temperature of the first component (15, 16, 18) of the inverter (6), T distinct-cOmPOnent is the first measured temperature of the second component (3), Twater is the second measured temperature of the cooling water, and k is a predetermined value.

6. Method (100) for determining the initialization temperature of a component (15, 16, 18) of a power inverter (6), comprising, when the inverter (6) is initialized after sleep, a step (140) of determining the initialization temperature of the component (15, 16, 18) according to any one of the preceding claims.

7. Method (100) according to claim 6, wherein, the initialization temperature determined according to claim 6 being a first initialization temperature, the method comprises the following steps of: - determining (150) the thermal time constant of the inverter component; - determining (160) the last known temperature of the component; - determining (180) a sleep duration of the inverter; - when the inverter is initialized after sleeping, determining (190) a second initialization temperature of the inverter component as a function of the thermal time constant, the last known temperature of the component and the sleep duration of the inverter; - performing (200) a plausibility check of the first, respectively second, initialization temperature, on the basis of the second, respectively first, initialization temperature.

8. A computer program (10) comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method (100) of any preceding claim.

9. A computer-readable storage medium (9) comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method (100) according to one of claims 1 to 7.

10. System comprising: - a power inverter (6), the power inverter comprising a first component (15, 16, 18), - a rotating electrical machine (2) connected to the inverter (6) and comprising a second component (3) distinct from the first component (15, 16, 18), wherein the second component (3) is capable of circulating an alternating current; - a temperature sensor (4) for measuring the temperature of the second component (3), characterized in that the inverter further comprises computer means (7, 8, 9) configured to control the steps of: - by the sensor (4), measurement of a first temperature of the second component (3); - determining the temperature of the first component (15, 16, 18) of the inverter as a function of the first temperature.

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