Method for detecting an open circuit between a traction battery and an electric machine of a powertrain of a hybrid motor vehicle

Abstract

The invention relates to a method for detecting an open circuit between a traction battery and an electric machine of a powertrain of a hybrid motor vehicle during driving, the method comprising a step (E1) in which the first voltage U1 at the output of the traction battery is measured by the battery management system; a step (E2) in which the second voltage U2 at the terminals of the electric machine is measured by the computer; a calculation step (E3) according to the following mathematical formula: E = |U2 - U1|; a step (E4) in which the open circuit is detected by the supervisor when the difference E calculated during the calculation step is greater than or equal to a predetermined threshold value for a period of time that is greater than a predetermined period of time, and a reconfiguration step (E5) when the open circuit has been detected.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: METHOD FOR DETECTING AN OPEN CIRCUIT BETWEEN A TRACTION BATTERY AND AN ELECTRIC MOTOR OF A POWERTRAIN UNIT IN A HYBRID MOTOR VEHICLE. The present invention claims priority from French application No. FR2500747 filed on January 24, 2025, the content of which (text, drawings, and claims) is incorporated herein by reference.

[0003]

[0001] The invention relates to means for detecting open circuits in hybrid powertrains of motor vehicles.

[0004]

[0002] Prior art patent application EP3774434 is known, describing a motor vehicle comprising an electrical system including a high-voltage network and a low-voltage network. The high-voltage network includes a traction battery, an electric machine, an inverter, and a high-voltage consumer component. The low-voltage network includes an on-board network battery and a low-voltage consumer component. The high-voltage and low-voltage networks are connected to each other via a DC / DC converter. A method for detecting a short circuit is described. A boost current is applied to the high-voltage network from the low-voltage network via the DC / DC converter. The boost current voltage is measured in the high-voltage network and compared to an expected boost voltage.A short circuit is detected when the difference between the measured boost voltage and the expected boost voltage exceeds a predefined limit. The short-circuit detection process is implemented before the traction battery connects to the high-voltage network. The traction battery is electrically isolated when a short circuit is detected. However, there are drawbacks. Applying a boost current can lead to premature wear, or even damage, to high-voltage network components, such as the inverter or other high-voltage loads. Furthermore, this process is only implemented when the traction battery connects to the high-voltage network. Consequently, it cannot detect a short circuit occurring while the vehicle is in motion.

[0005]

[0003] The objective of the present invention is to remedy these drawbacks and to detect an open circuit between an electric machine and a traction battery of a motor vehicle while driving, while preserving the other electronic components of the vehicle.

[0006]

[0004] To achieve this objective, the invention proposes a method for detecting an open circuit between a traction battery and an electric machine of a powertrain of a hybrid motor vehicle during driving, said vehicle comprising a display device capable of displaying a visual signal and a 12V battery configured to power said display device, the traction battery comprising a battery management system configured to measure a first voltage l / l at the output of the traction battery and main contactors capable of opening to electrically isolate said traction battery or closing to power the electric machine, said electric machine comprising terminals and a computer configured to measure a second voltage U2 at the terminals, said vehicle comprising an internal combustion engine,the powertrain comprising a DC / DC converter capable of lowering the traction battery voltage to a lower voltage to supply a low-voltage network, an alternator-starter and a supervisor capable of controlling the activation or deactivation of the internal combustion engine, capable of controlling the opening or closing of the main contactors, capable of controlling the activation or deactivation of the electric machine, the alternator-starter and the DC / DC converter, and capable of controlling the activation or deactivation of the visual signal, notable in that said method comprises the following steps:,

[0007] - a measurement step of the first voltage l / l at the output of the traction battery by the battery management system, the first voltage U1 being transmitted to the supervisor;

[0008] - a measurement step of the second voltage U2 across the terminals of the electrical machine by the computer, the second voltage U2 being transmitted to the supervisor;

[0009] - a step of calculating the difference E between the second voltage U2 and the first voltage U1 according to the following mathematical formula: E = | Z72 - Z71| ;

[0010] - a step of detection of the open circuit by the supervisor when the deviation E calculated during said calculation step is equal to or greater than a predetermined threshold value for a period of time greater than a predetermined period of time;

[0011] - a reconfiguration step during which the supervisor commands the activation of the internal combustion engine, commands the opening of the main contactors, commands the deactivation of the electric machine, the alternator-starter and the DC / DC converter, and commands the activation of the visual signal on said display device to warn the driver that the open circuit has been detected.

[0012]

[0005] Thanks to the invention, the risks of formation of electric arcs likely to cause electrocution of the occupants of the vehicle or a fire in the vehicle are greatly reduced.

[0013]

[0006] Advantageously, the vehicle includes an automatic stop and restart device, the supervisor commands the deactivation of the automatic stop and restart device during said reconfiguration step.

[0014]

[0007] This prevents the automatic restart of the electric machine, which is no longer powered by the traction battery, when the latter has been deactivated during said reconfiguration step.

[0015]

[0008] Advantageously, the method includes a recovery step during which the supervisor commands the deactivation of the visual signal, commands the activation of the electric machine, the alternator-starter and the DC / DC converter, and commands the closing of the main contactors, said recovery step being implemented when restarting the vehicle when the deviation E calculated during said calculation step is less than said predetermined threshold value.

[0016]

[0009] This makes it possible to cut off the high voltage network in order to reduce electrical risks or fire risks to the vehicle.

[0017]

[0010] Advantageously, the supervisor commands the reactivation of the automatic stop and restart device during said recovery step.

[0011] Thus, it is possible to reduce the vehicle's energy consumption thanks to the automatic stop and restart device when the open circuit is no longer detected.

[0018]

[0012] Preferably, the method comprising a step of emitting an additional visual signal on said display device when the 12V battery has a voltage below a predetermined threshold voltage.

[0019]

[0013] Following the reconfiguration step, the vehicle is powered solely by the 12V battery. It is therefore important to warn the driver when the amount of energy stored in said 12V battery becomes critical, so that he can bring his vehicle to a stop.

[0020]

[0014] Advantageously, the predetermined threshold voltage is between 6V and 10V, preferably 8V.

[0021]

[0015] Advantageously, the predetermined threshold value is between 20V and 40V, preferably 30V.

[0022]

[0016] Advantageously, the predetermined time period is between 1 second and 15 seconds, preferably 5 seconds.

[0023]

[0017] The invention also relates to a vehicle comprising a controller configured to implement the steps of the method for detecting an open circuit between a traction battery and an electric machine of a powertrain of a hybrid motor vehicle during driving described above.

[0024]

[0018] Furthermore, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, lead the latter to implement the steps of the method of detecting an open circuit between a traction battery and an electric machine of a powertrain of a hybrid motor vehicle during driving described above.

[0025]

[0019] The invention will be further detailed by describing a non-limiting embodiment, and based on the accompanying figure illustrating the invention, in which [Fig. 1] schematically illustrates, in the form of a flowchart, a method for detecting an open circuit between a traction battery and an electric motor of a powertrain of a hybrid motor vehicle during driving according to an embodiment of the invention.

[0020] Figure 1 schematically illustrates, in the form of a flowchart, a method for detecting an open circuit between a traction battery and an electric motor of a powertrain of a hybrid motor vehicle during driving according to an embodiment of the invention. The vehicle is said to be "hybrid" because said vehicle comprises the electric motor and an internal combustion engine.Thus, the vehicle's traction can be provided alternately by purely electrical means or purely by thermal means. The vehicle includes a 12V battery powered by a low-voltage network, or 12V network. Conversely, the traction battery is powered by a high-voltage network, or 48V network. Furthermore, the vehicle includes a display device capable of showing a visual signal. The display device is powered by the 12V battery, commonly referred to as the auxiliary battery. For example, the display device could be a dashboard, and the visual signal a warning light that can turn on or off on the dashboard. Alternatively, the display device could be a human-machine interface comprising, for example, a screen, and the visual signal an image or message displayed on the screen.The traction battery includes a battery management system, more commonly known as a BMS (Battery Management System). The battery management system is an electronic system that monitors parameters related to the traction battery, such as the voltage, current, and / or temperature of the electrochemical cells that make up the traction battery. The battery management system balances the charging and discharging of the electrochemical cells to prevent overcharging, over-discharging, or overheating of one or more cells. The battery management system is configured to measure an initial voltage U1 at the output of the traction battery. In addition, the traction battery includes main contacts capable of opening or closing.When the main contactors are closed, the traction battery supplies power to the electric machine. Conversely, when the main contactors are closed, the traction battery is electrically isolated because electric current can no longer flow between the traction battery and the electric machine. The electric machine has terminals. Furthermore, the electric machine includes a computer configured to measure a second voltage U2 across its terminals. The powertrain includes a DC / DC converter, commonly called a DC / DC converter (acronym for Direct Current / Direct Current). The DC / DC converter is an electronic device that converts a direct current voltage into a different, lower or higher, direct current voltage.The DC / DC converter is responsible for reducing the traction battery voltage to a lower level to supply the low-voltage network, such as a 12V low-voltage network. The powertrain also includes a starter-generator. The starter-generator is a hybrid electromechanical device combining the functions of a starter and an alternator. When operating as an alternator, the starter-generator generates electricity to recharge the traction battery. When operating as a starter, it ensures the rapid starting of the internal combustion engine.In addition, said powertrain includes a supervisor capable of performing several actions, including controlling the activation or deactivation of the internal combustion engine, controlling the opening or closing of the main traction battery contactors, controlling the activation or deactivation of the electric machine, controlling the activation or deactivation of the alternator-starter, controlling the activation or deactivation of the DC / DC converter, and controlling the activation or deactivation of the visual signal on the display device.

[0026]

[0021] The method comprises a plurality of steps. In a step measuring the first voltage E1, the first voltage U1 is measured at the battery output by the battery management system. The first voltage U1 is then transmitted from the battery management system to the powertrain supervisor. In a step measuring the second voltage E2, the second voltage U2 is measured at the terminals of the electric machine by the computer of said electric machine. The second voltage U2 is then transmitted from said computer to the powertrain supervisor, in the same way that said first voltage U1 is also transmitted to the supervisor in said step measuring the first voltage E1. In a calculation step E3, a difference E is calculated in absolute value between said second voltage U2 and said first voltage U1 by the following mathematical formula: E = \U2 -L71| .During an open circuit detection step E4, the open circuit is detected when the deviation E calculated during said calculation step E3 is equal to or greater than a predetermined threshold value for a period of time exceeding a predetermined time period. Optionally, said predetermined threshold value is between 20V and 40V, preferably 30V. Optionally, the predetermined time period is between 1 second and 15 seconds. The predetermined time period is preferably equal to 5 seconds.

[0027] A reconfiguration step E5 is implemented when an open circuit is detected during the open circuit detection step E4. During the E5 configuration step, the powertrain supervisor commands the electric motor to be deactivated and the internal combustion engine to be activated so that it takes over. This allows the driver to continue driving using only the internal combustion engine. In addition, the supervisor commands the main traction battery contactors to be opened to electrically isolate the traction battery. The supervisor also commands the deactivation of the starter-alternator. Since the internal combustion engine is running, the starter-alternator's function is no longer required. As for its alternator function, the starter-alternator generates a 48V current.However, the traction battery is electrically isolated, so the 48V current produced by the starter-generator cannot be used or stored. Therefore, it is necessary to deactivate the starter-generator to prevent the 48V current generation from causing overheating or even a fire in the vehicle. Finally, the supervisor controls the deactivation of the DC / DC converter. The vehicle has a 12V battery, which powers the various vehicle controllers, as well as the headlights and the cabin heating and ventilation system, for example. The 12V battery does not directly contribute to the vehicle's traction. Electric traction is provided by the traction battery.The DC / DC converter is deactivated during the E5 reconfiguration step because, with the traction battery electrically isolated and the starter-generator deactivated, the 12V battery is no longer supplied with electricity via the DC / DC converter. Therefore, it is preferable to deactivate the DC / DC converter to preserve the 12V system. Furthermore, the supervisor commands the activation of a visual signal on the display device to warn the driver that an open circuit has been detected, that the vehicle will undergo reconfiguration, and that the driver should therefore stop the vehicle when possible. Preferably, the procedure includes a step for emitting an additional visual signal when the 12V battery voltage falls below a predetermined threshold voltage.As mentioned previously, the 12V battery is no longer supplied with power during the E5 reconfiguration step. The stored electricity is therefore depleted, which triggers an additional visual signal on the display to alert the driver that the 12V battery needs charging. This prompts the driver to stop before the components powered by the 12V battery also cease to function. Preferably, the predetermined threshold voltage is between 6V and 10V. Even more preferably, the predetermined threshold voltage is 8V.

[0028]

[0022] Preferably, the vehicle is equipped with an automatic stop-start system, also known as Start and Stop. This system allows the vehicle to automatically stop when it is stationary for an extended period, for example, when waiting at a red traffic light or in a traffic jam. The system also ensures that the vehicle restarts automatically when the driver releases the brake pedal or presses the clutch pedal. The system thus reduces the vehicle's energy consumption. In the context of this invention, the supervisor controls the deactivation of the automatic stop-start system when the reconfiguration step E5 is implemented following the detection of an open circuit.This prevents the electrical machine from automatically restarting after being deactivated by the supervisor.

[0029]

[0023] Optionally, the method includes a recovery step E6. The recovery step E6 is implemented when the vehicle is restarted, that is, when the vehicle has been switched off and the driver switches the ignition back on to start the vehicle, and when the deviation E calculated during the calculation step E3 is less than the predetermined threshold value. The recovery step E6 is characterized by a return to a standard configuration, which was the initial configuration in which the vehicle was before the reconfiguration step E5. Thus, during the recovery step E6, the supervisor commands the deactivation of the visual signal and the activation of the electric motor to return to electric traction mode. The supervisor also commands the activation of the starter-alternator and the DC / DC converter.Furthermore, the supervisor commands the closing of the main contactors of the traction battery to restore electrical current between the electric machine and the traction battery. The 12V battery is then re-supplied with electricity via the DC / DC converter. The restoration step E6 is represented by dashed lines in Figure 1 because it is optional, unlike the other steps in the process, which are shown with solid lines.

[0030]

[0024] When the vehicle includes the automatic stop and restart device as previously described, and when said process includes the recovery step E6, then the supervisor commands the activation of the stop and restart device during said recovery step E6.

[0031]

[0025] Furthermore, the invention relates to a computer program configured to implement said method for detecting an open circuit between a traction battery and an electric motor of a powertrain of a hybrid motor vehicle during driving. The invention also relates to a motor vehicle comprising a controller configured to implement said method described above.

Claims

DEMANDS 1. A method for detecting an open circuit between a traction battery and an electric machine of a powertrain of a hybrid motor vehicle during driving, said vehicle comprising a display device capable of displaying a visual signal and a 12V battery configured to power said display device, the traction battery comprising a battery management system configured to measure a first voltage U1 at the output of the traction battery and main contactors capable of opening to electrically isolate said traction battery or closing to power the electric machine, said electric machine comprising terminals and a computer configured to measure a second voltage U2 at the terminals, said vehicle comprising an internal combustion engine,the powertrain comprising a DC / DC converter capable of lowering the traction battery voltage to a lower voltage to supply a low-voltage network, an alternator-starter and a supervisor capable of controlling the activation or deactivation of the internal combustion engine, capable of controlling the opening or closing of the main contactors, capable of controlling the activation or deactivation of the electric machine, the alternator-starter and the DC / DC converter, and capable of controlling the activation or deactivation of the visual signal, characterized in that said method comprises the following steps:, - a measurement step of the first voltage U1 (E1) at the output of the traction battery by the battery management system, the first voltage U1 being transmitted to the supervisor; - a measurement step of the second voltage U2 (E2) at the terminals of the electrical machine by the computer, the second voltage U2 being transmitted to the supervisor; - a calculation step (E3) of the difference E between the second voltage U2 and the first voltage U1 according to the following mathematical formula: E = | Z72 - Z71| ; - an open circuit detection step (E4) by the supervisor when the difference E calculated during said calculation step is equal to or greater than a predetermined threshold value for a period of time greater than a predetermined period of time; - a reconfiguration step (E5) during which the supervisor commands the activation of the internal combustion engine, commands the opening of the main contactors, commands the deactivation of the electric machine, the alternator-starter and the DC / DC converter, and commands the activation of the visual signal on said display device to warn the driver that the open circuit has been detected.

2. Method according to claim 1, characterized in that the vehicle includes an automatic stop and restart device, the supervisor commands the deactivation of the automatic stop and restart device during said reconfiguration step (E5).

3. Method according to claim 1 or 2, characterized in that the method comprises a recovery step (E6) during which the supervisor commands the deactivation of the visual signal, commands the activation of the electric machine, the alternator-starter and the DC / DC converter, and commands the closing of the main contactors, said recovery step being implemented during the restart of the vehicle when the deviation E calculated during said calculation step (E3) is less than said predetermined threshold value.

4. Method according to claim 2 and 3, characterized in that the supervisor commands the reactivation of the automatic stop and restart device during said recovery step (E6).

5. A method according to any one of claims 1 to 4, characterized in that the method comprises a step of emitting an additional visual signal on said display device when the 12V battery has a voltage below a predetermined threshold voltage.

6. Method according to claim 5, characterized in that the predetermined threshold voltage is between 6V and 10V, preferably 8V.

7. A method according to any one of claims 1 to 6, characterized in that the predetermined threshold value is between 20V and 40V, preferably 30V.

8. A method according to any one of claims 1 to 7, characterized in that the predetermined time period is between 1 second and 15 seconds, preferably 5 seconds.

9. A vehicle comprising a controller configured to implement the steps of the method for detecting an open circuit between a traction battery and an electric machine of a powertrain of a hybrid motor vehicle during driving according to any one of claims 1 to 8.

10. Computer program comprising instructions which, when the program is executed by a computer, cause the computer to implement the steps of the method for detecting an open circuit between a traction battery and an electric machine of a powertrain of a hybrid motor vehicle while driving according to any one of claims 1 to 8.

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