Method and device for monitoring a contactor in a high-voltage electrical circuit

Abstract

A method relating in particular to the monitoring of a contactor configured to establish electrical contact between a terminal of a power supply and a terminal of an electrical circuit that can be pre-charged to a voltage theoretically equal to that of said power supply. After obtaining (305) a first voltage of said electrical circuit at said terminal of said contactor in response to a command to establish said electrical contact between said terminal of said power supply and said terminal of said electrical circuit, and after obtaining (315) a second voltage of said electrical circuit at said terminal of said contactor following the establishment of said electrical contact between said terminal of said power supply and said terminal of said electrical circuit, damage to said contactor is estimated (320) based on a difference between said first and second voltages. Figure for the abbreviation: Figure 3

Description

Title of the invention: Method and device for monitoring a contactor in a high-voltage electrical circuit. Technical field

[0001] The invention relates to a method and device for monitoring a contactor placed between a power supply and an electrical circuit that is to be precharged, the contactor being susceptible to damage from an electric arc resulting from imperfect precharging of the electrical circuit. The power supply and the electrical circuit may be high-voltage, such as a high-voltage traction power supply and electrical circuit of an electric vehicle. The invention also relates to monitoring the precharge quality of an electrical circuit. Previous techniques

[0002] The use of high-voltage (HV) circuits in electric or hybrid vehicles (in its various versions, including mild, plug-in, and full hybrid versions) requires specific precautions during certain phases to avoid damaging certain components of these circuits or to prevent their premature wear. In particular, in the traction electrical circuit of an electric or hybrid vehicle, it is generally necessary to be able to isolate the traction electrical power source (for example, a battery pack) from components capable of producing or consuming energy, for example, when the vehicle is not in use, for maintenance operations, or in the event of a crash.

[0003] Thus, in order to power the vehicle's traction electrical circuit, it is necessary to control the connection of the traction power supply to this electrical circuit. Due to the presence of capacitors with significant electrical capacitance in the circuit's electrical components and the high voltage, a pre-charge of the circuit components' capacitances must be performed to connect the traction power supply to the traction electrical circuit. By limiting the voltage difference between the traction power supply and the capacitances of the circuit components, it is possible to reduce the electrical arc formed at the moment of connection (it being noted that this significant current spike can lead to damage to the network connection / disconnection device).

[0004] There are several technical solutions for closing this type of electrical traction circuits.

[0005] By way of illustration, there are devices comprising two relay-type contactors, one on the positive terminal and one on the negative terminal of the battery, and a reversible DC-DC converter capable of supplying power from a traction power supply to a vehicle service network and of supplying power from a vehicle service source to the traction electrical circuit, thus enabling precharging. The control sequence of the contactors in such devices includes a precharging phase of the traction circuit by the DC-DC converter to bring the network voltage to the level of the traction power supply voltage and a closing phase of the traction network relays during which both relays are closed.

[0006] Patent application WO 2021 / 139782 is an example of prior art.

[0007] It is observed that the accuracy of the voltage sensors used to obtain the voltage from the traction power supply and the vehicle's traction electrical network is limited. Similarly, the DC-DC converter has limited regulation accuracy. Therefore, a residual potential difference remains when the contactor closes the traction electrical network. This potential difference causes an electric arc, the amplitude of which is a strong inducer of damage to the traction electrical network contactors. This electric arc has a very short duration, and the on-board current sensors are often not capable of measuring such a short phenomenon. It is therefore difficult to estimate the damage to the contactors. Description of the invention

[0008] The object of the invention is to propose a simple and effective solution for estimating the quality of a precharge of a high voltage circuit, estimating the damage of a contactor placed between a power source and the precharged circuit and more generally monitoring this contactor.

[0009] According to one aspect, the invention relates to a method for monitoring a contactor configured to establish electrical contact between a terminal of a power supply and a terminal of an electrical circuit that can be pre-charged to a voltage theoretically equal to that of said power supply, the method comprising

[0010] - obtaining a first voltage of said electrical circuit, at said terminal of said contactor, in response to a command to establish said electrical contact between said terminal of said power supply and said terminal of said electrical circuit;

[0011] - obtaining a second voltage of said electrical circuit, at said terminal of said contactor, following the establishment of said electrical contact between said terminal of said power supply and said terminal of said electrical circuit; and

[0012] - estimation of damage to said contactor based on a difference between the aforementioned first and second tensions.

[0013] The method according to the invention thus makes it possible to better understand the damage to contactors and therefore to refine their specifications. It also allows the implementation of predictive maintenance to anticipate failures and provides diagnostic assistance.

[0014] According to one feature, the method further comprises

[0015] - comparison of said difference between said first and second tensions and at minus a threshold and

[0016] - incrementing at least one counter according to a result of said comparison.

[0017] According to one feature, the method further comprises a transmission of a value of said at least one counter to a remote server.

[0018] According to one feature, said contactor is a first contactor, an electrical connection between said power supply and said electrical circuit being made using the first contactor and a second contactor, said first and second contactors being connected to different terminals of said power supply and to different terminals of said electrical circuit, the establishment of an electrical connection between said power supply and said electrical circuit, at said terminals of said first contactor, being made after the establishment of an electrical connection between said power supply and said electrical circuit, at said terminals of said second contactor.

[0019] According to one feature, said power supply is a first power supply, said electrical circuit being pre-charged from a second power supply using a DC-DC converter, said second voltage being obtained in response to a pre-charge stop command by said DC-DC converter.

[0020] According to one feature, said power supply is a high traction voltage power supply of a vehicle and said electrical circuit is a high traction voltage electrical circuit of said vehicle.

[0021] According to one feature, the method further comprises an estimation of the intensity of an electric arc in said contactor, said intensity being estimated as a function of said difference between said first and second voltages and of a value of an internal resistance of said power supply.

[0022] According to another aspect, the invention relates to a monitoring device for a contactor connected to a terminal of an electrical power supply and to a terminal of an electrical circuit that can be pre-charged to a voltage theoretically equal to that of said electrical power supply, the device comprising

[0023] - means for measuring a voltage of said electrical circuit, at said terminal of said contactor, said measuring means being configured to obtain a first voltage in response to a command to establish said electrical contact between said terminal of said power supply and said terminal of said electrical circuit, and to obtain a second voltage following the establishment of said electrical contact between said terminal of said power supply and said terminal of said electrical circuit; and

[0024] - a calculation unit configured to estimate damage to said contactor in function of a difference between the said first and second tensions.

[0025] The device according to the invention thus makes it possible to better understand the damage to contactors and therefore to refine their specifications. It also allows the implementation of predictive maintenance to anticipate failures.

[0026] According to one feature, said calculation unit is further configured to compare said difference between said first and second voltages and at least one threshold and increment at least one counter according to a result of said comparison.

[0027] According to another feature, said computing unit is further configured to identify said command to establish said electrical contact and to identify a pre-charge stop command by a DC-DC converter, used to pre-charge said electrical circuit from a second power supply source, different from said power supply source, called first power supply, said second voltage being obtained in response to said pre-charge stop command and according to which said computing unit is configured to control said measuring means. Brief description of the drawings

[0028] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0029] [Fig.1] schematically represents an architecture of an assembly comprising a high-voltage power supply and a high-voltage circuit, in which the invention can be implemented;

[0030] [Fig.2] schematically illustrates an example of a preload timing diagram for a DC-DC converter and control for contactors, for the purpose of establishing a connection between an electrical power source and an electrical circuit;

[0031] [Fig.3] schematically illustrates an example of steps in a monitoring process of a contactor placed between an electrical power source and an electrical circuit that can be pre-charged, according to embodiments of the invention;

[0032] [Fig.4] schematically illustrates an example of a chronogram illustrating a voltage surge measured in a pre-charged high-voltage electrical circuit, when a power supply is connected to that circuit, characterizing damage to a contactor placed between the power supply and the circuit, used to establish contact; and

[0033] [Fig. 5] illustrates an example of a computer capable of implementing a process according to particular embodiments of the invention. Detailed description of at least one embodiment

[0034] A detailed description of particular embodiments of the invention will be given below, with reference to the drawings in which the same references identify the same structural elements in each of the figures.

[0035] According to some embodiments, the damage to a contactor that establishes electrical contact between a power supply and an electrical circuit pre-charged to a voltage theoretically equal to that of the power supply is estimated based on the intensity of an electric arc produced during connection. The power supply and the electrical circuit are, for example, a high-voltage power supply and a high-voltage electrical circuit, respectively. When the power supply and the electrical circuit are a power supply and a traction electrical circuit of a vehicle, high voltage is, for example, a voltage between 250V and 1200V.The intensity of the electric arc produced during connection can itself be estimated based on the internal resistance of the power supply and a voltage variation in the electrical circuit at the moment the contactor is activated to establish the connection between the power supply and the pre-charged electrical circuit. This voltage variation thus allows for monitoring the contactor. In some embodiments, this voltage variation is determined by measuring the voltage of the electrical network at the moment the circuit is closed.

[0036] By way of illustration, the voltage variation can be determined between the time the contactor is activated (e.g., the time when the closing of a second contactor is commanded, when the connection between the power supply and the electrical circuit is made using two contactors, for example two relays) and the time the pre-charge is stopped, for example the time when a DC-DC converter leaves a pre-charge mode.

[0037] Depending on the absolute value of the voltage variation, it is possible to qualify and / or quantify the quality of the preload and to estimate damage to the contactor establishing the contact between the high-voltage power supply and a high-voltage circuit. The voltage variation thus allows the contactor to be monitored.

[0038] Fig. 1 schematically represents an architecture of an assembly comprising a high-voltage power supply and a high-voltage circuit, in which the invention can be implemented.

[0039] According to the illustrated example, the assembly 100 includes a high-voltage power supply 105, here a battery pack, a high-voltage electrical circuit 110, a set of contactors, here a contactor 115-1 connected to the + terminal of the source 105 and a contactor 115-2 connected to the - terminal of the source 105, a controller 120 and a low-voltage battery 125.

[0040] Still according to the illustrated example, the high voltage electrical circuit 110 includes a direct current - direct current converter 130 (DC-DC converter), a measuring element 135 and other referenced high voltage components 140.

[0041] In a pre-charge mode, the DC-DC converter pre-charges the high-voltage electrical circuit 110, using the low-voltage accumulator 125, so that the voltage of the high-voltage electrical circuit 110 is as close as possible to the voltage of the high-voltage power supply source 105. The pre-charge mode and the normal operating mode of the DC-DC converter are controlled here by the controller 120.

[0042] The controller 120 also monitors the open and closed state of contactors 115-1 and 115-2. According to the illustrated example, contactor 115-1 is closed before contactor 115-2. In other embodiments, contactor 115-1 is closed after contactor 115-2. In still other embodiments, contactor 115-1 is closed alternately before and after contactor 115-2. Also according to specific embodiments, the closing order of contactors 115-1 and 115-2 is determined based on an estimated deterioration of the contactors.

[0043] It is observed that other elements can be used for the pre-charging of the high-voltage electrical circuit 110.

[0044] Fig. 2 schematically illustrates an example of a preload timing diagram for a DC-DC converter and a control diagram for contactors, for the purpose of establishing a connection between an electrical power supply and an electrical circuit.

[0045] As illustrated, the control signal of the DC-DC converter, referenced 200, controls the mode of the DC-DC converter, for example the DC-DC converter 130 of [Fig.1], in a normal operating mode between times t0 and tb, in a preload mode between times ti and t4, and in a normal operating mode after time t4.

[0046] The control signal of a first contactor, referenced 205, controls the first contactor, for example contactor 115-1 of [Fig. 1], in an open mode until time t2 and in a closed mode after time t2. In the open mode, no No electrical connection is established between the contactor terminals, whereas in a closed mode, an electrical connection is established between the contactor terminals. Similarly, the control signal of a second contactor, referenced 210, controls the second contactor, for example contactor 115-2 of [Fig. 1], in an open mode until time t3 and in a closed mode after time t3.

[0047] As illustrated, the voltage 215 across the terminals of the power supply, for example, the battery pack 105 of [Fig. 1], is constant or nearly constant during the connection sequence to the electrical circuit. For example, it is equal to 380V. In contrast, the voltage 220 of the high-voltage electrical circuit, for example, the high-voltage electrical circuit 110 of [Fig. 1], increases as soon as the pre-charge mode of the DC-DC converter is activated at time t1 to reach a voltage close to that of the power supply, for example, between 360V and 400V, before time t2, such that the voltage of the high-voltage electrical circuit is close to the voltage of the power supply when contact is established between the high-voltage electrical circuit and the power supply.

[0048] [Fig.3] schematically illustrates an example of steps in a method for monitoring a contactor placed between an electrical power source and an electrical circuit that can be pre-charged, for example the contactor 115-2 in [Fig.1], according to embodiments of the invention.

[0049] As illustrated, a first step aims to determine whether a first voltage measurement of the electrical circuit that can be pre-charged, at the contactor terminal, should be taken (step 300). As soon as a first measurement is required, it is taken (step 305). According to particular embodiments, a first measurement should be taken as soon as the power supply is connected to the electrical circuit, that is, according to the example in [Fig. 2], as soon as the signal 210 commands the contactor to close (time t3 in [Fig. 2]). When two contactors are used, the power supply is connected to the electrical circuit as soon as the second contactor is closed. The first measurement is obtained, for example, from a voltage sensor belonging, for example, to the other components 140 in [Fig. 1].

[0050] A subsequent step aims to determine whether a second voltage measurement of the electrical circuit that can be pre-charged, again at the contactor terminal, should be taken (step 310). As soon as a second measurement is required, it is taken (step 315). According to particular embodiments, a second measurement should be taken as soon as the pre-charge mode is terminated, that is, according to the example in [Fig. 2], as soon as the signal 200 commands the DC-DC converter to switch to mode normal use (time t4 on [Fig.2]). Again, this measurement can be obtained from a voltage sensor belonging to the other components 140 of [Fig.1].

[0051] In a subsequent step, the damage to the contactor is estimated based on the difference between the first and second measurements obtained, for example, based on the absolute value of this difference (step 320). In some embodiments, the estimation of the contactor damage includes comparing the difference between the first and second measurements obtained with one or more thresholds defining intervals, in order to estimate a damage level. Each interval can correspond to a damage level. Furthermore, a counter can be associated with each interval to estimate the aging of the contactor. These counters can be initialized to zero when the contactor is new and incremented as soon as the contactor is used to establish a connection between the power supply and the electrical circuit that can be pre-charged.

[0052] According to other embodiments, a damage level is calculated directly from the difference between the first and second measurements obtained, for example, using a function defined from the behavior of the contactor. Such damage levels can also be used to increment counters at intervals.

[0053] The difference between the first and second measurements obtained, the result of comparing this difference with one or more thresholds, the calculated damage level, and / or the counter values ​​can be transmitted to a remote server (step 325), for example, as soon as the first and second measurements are obtained, periodically, or on demand. The data stored on a remote server can be accessed by an external system, which can use it for maintenance operations, statistical purposes (for example, to improve the manufacturing specifications of a contactor), etc.

[0054] As an further illustration, the value of these counters can be added to frames exchanged locally, for example in high-voltage relay failure context frames in a vehicle, in particular to help in the search for the root causes of a failure.

[0055] Fig. 4 schematically illustrates an example of a timing diagram showing a voltage jump measured in a pre-charged high-voltage electrical circuit when a power supply is connected to that circuit, characterizing damage to a contactor placed between the power supply and the circuit, used to make the contact.

[0056] The signals shown in [Fig. 4] correspond to the signals shown in [Fig. 2], between times t3 and t4 which here define a monitoring window of 400 the evolution of the voltage, that is to say between the moment when the contactor is requested to connect the power supply to the pre-charged electrical circuit and the moment when the mode switches from a pre-charge mode to a normal operating mode.

[0057] As illustrated, the voltage of the pre-charged circuit at the contactor terminal jumps 405 within the monitoring window 400, corresponding to the formation of an electric arc in the contactor. The height of the voltage jump is related to the intensity of the electric arc formed. Thus, by measuring the evolution of the electrical circuit voltage at the contactor terminal when the power supply is connected to it, it is possible to estimate the intensity of the electric arc formed and the resulting damage to the contactor. The history of this damage is advantageously stored, for example, in the form of meter readings, to enable, in particular, preventive maintenance and to improve the design of contactors.

[0058] [Fig.5] illustrates an example of a computer that can implement a process according to particular embodiments of the invention, in particular the process illustrated in [Fig.3].

[0059] As illustrated, the 500 computer includes one or more communication buses, shared or not, to which the following are connected:

[0060] - a central processing unit or microprocessor 505 (CPU, abbreviation for central Processing unit (in Anglo-Saxon terminology);

[0061] - a random access memory or cache memory 510 (RAM, acronym for random access memory (in Anglo-Saxon terminology) comprising registers adapted to store variables and parameters created and modified during the execution of programs implementing the steps described above;

[0062] - a read-only memory 515 (ROM) Anglo-Saxon) which may include an operating system and programs implementing the steps described above;

[0063] - a 520 input interface for receiving data, for example signals from control; and

[0064] - a 525 output interface for controlling one or more elements, for example to control a voltage sensor in order to measure a voltage. The input and output interfaces may or may not be separate.

[0065] The computer 500 may also include a communication interface 530 connected to a communication network, for example a wireless communication network and / or a local communication network, the interface being capable of transmitting and receiving data.

[0066] The communication bus enables communication and interoperability between the various elements included in or connected to the computer 500. The bus representation is not limiting and, in particular, the central processing unit is capable of communicate instructions to any element of the 500 computer directly or via another element of the 500 computer.

[0067] The executable code of the programs enabling the computer 500 to implement, in whole or in part, the method according to the invention, can be stored, for example, in the read-only memory 515. According to an alternative, the executable code of the programs can be received via the communication network, through interface 530, to be stored in the same manner as described above. More generally, the program(s) can be loaded into one of the storage means of the computer 500 before being executed.

[0068] The central processing unit 505 will command and direct the execution of the instructions or portions of software code of the program(s) according to the invention, instructions which are stored, for example, in the read-only memory 515 or in the other aforementioned storage elements. Upon power-up, the program(s) stored in non-volatile memory, for example the read-only memory 515, are transferred to the random access memory 510, which then contains the executable code of the program(s), as well as registers for storing the variables and parameters necessary for implementing the method according to the invention.

[0069] Of course, the present invention is not limited to the embodiments described above by way of example. It extends to other variants.

[0070] Depending on the embodiment chosen, certain acts, actions, events, or functions of each of the methods described in this document may be performed or occur in a different order than described, or may be added, merged, or not performed or occur, as the case may be. Furthermore, in some embodiments, certain acts, actions, or events are performed or occur concurrently rather than sequentially.

[0071] Although described through a number of detailed embodiments, the proposed device, system, and method include various variants, modifications, and improvements that will be obvious to those skilled in the art, it being understood that these various variants, modifications, and improvements form part of the scope of the invention, as defined by the following claims. Furthermore, different aspects and features described above may be implemented together, separately, or substituted for one another, and all the different combinations and subcombinations of aspects and features form part of the scope of the invention. In addition, some of the systems and equipment described above may not incorporate all of the modules and functions described for the preferred embodiments.

Claims

Demands

1. A method for monitoring a contactor configured to establish electrical contact between a terminal of an electrical power supply and a terminal of an electrical circuit that can be pre-charged to a voltage theoretically equal to that of said electrical power supply, the method comprising: - obtaining (305) a first voltage of said electrical circuit, at said terminal of said contactor, in response to a command to establish said electrical contact between said terminal of said electrical power supply and said terminal of said electrical circuit; - obtaining (315) a second voltage of said electrical circuit, at said terminal of said contactor, following the establishment of said electrical contact between said terminal of said electrical power supply and said terminal of said electrical circuit; and - estimating (320) damage to said contactor based on a difference between said first and second voltages.

2. Method according to claim 1, further comprising - comparison of said difference between said first and second voltages and at least one threshold and - incrementing of at least one counter according to a result of said comparison.

3. Method according to claim 2, further comprising a transmission (325) of a value of said at least one counter to a remote server.

4. A method according to any one of claims 1 to 3, wherein said contactor is a first contactor, an electrical connection between said power supply and said electrical circuit being made using the first contactor and a second contactor, said first and second contactors being connected to different terminals of said power supply and to different terminals of said electrical circuit, the establishment of an electrical connection between said power supply and said electrical circuit, at said terminals of said first contactor, being made after the establishment of an electrical connection between said power supply and said electrical circuit, at said terminals of said second contactor.

5. A method according to any one of claims 1 to 4, wherein said power supply is a first power supply, said electrical circuit being pre-charged from a second power supply using a DC-DC converter, said second voltage being obtained in response to a pre-charge stop command by said DC-DC converter.

6. A method according to any one of claims 1 to 5, wherein said power supply is a high-voltage traction power supply of a vehicle and said electrical circuit is a high-voltage traction electrical circuit of said vehicle.

7. A method according to any one of claims 1 to 6, further comprising an estimation of the intensity of an electric arc in said contactor, said intensity being estimated as a function of said difference between said first and second voltages and of a value of an internal resistance of said power supply.

8. A monitoring device for a contactor connected to a terminal of an electrical power supply and to a terminal of an electrical circuit that can be pre-charged to a voltage theoretically equal to that of said electrical power supply, the device comprising - means for measuring (135) a voltage of said electrical circuit, at said terminal of said contactor, said means for measuring being configured to obtain a first voltage in response to a command to establish said electrical contact between said terminal of said electrical power supply and said terminal of said electrical circuit and to obtain a second voltage following the establishment of said electrical contact between said terminal of said electrical power supply and said terminal of said electrical circuit; and - a calculation unit (120) configured to estimate damage to said contactor based on a difference between said first and second voltages.

9. Device according to claim 8, wherein said calculation unit is further configured to compare said difference between said first and second voltages and at least one threshold and increment at least one counter according to a result of said comparison.

10. Device according to claim 8 or claim 9, wherein said computing unit is further configured to identify said command to establish said electrical contact and to identify a pre-charge stop command by a DC-DC converter, used to pre-charge said electrical circuit from a second power supply source, different from said power supply source, referred to as the first power supply, said second voltage being obtained in response to said pre-charge stop command and wherein said computing unit is configured to control said measuring means.

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