METHOD FOR THE THERMAL PROTECTION OF AN ON-BOARD CHARGING DEVICE FOR AN ELECTRIFIED VEHICLE

Abstract

The present invention relates to a method for thermal protection of an electric charging device for a traction battery of an electrified vehicle in which said charging device is capable of electric charging on a terminal from an electrical supply network and of on-board electric charging by regenerative braking, the method comprising, in the event of detection (21) of the exceeding of a first temperature threshold (T1), the triggering (22) of a charging mode during which the charging power is reduced, and in the event of detection (23) of the exceeding of a second temperature threshold (T2) higher than the first threshold (T1), the triggering (24) of a charging mode during which electric charging on a terminal and electric charging by regenerative braking are inhibited for a predetermined duration following the instant of exceeding of the second threshold (T2). Figure 2

Description

Title of the invention: METHOD FOR THE THERMAL PROTECTION OF AN ON-BOARD CHARGING DEVICE FOR AN ELECTRIFIED VEHICLE

[0001] The field of the invention relates to a method for thermal protection of a charging device of an electrified vehicle, in particular a rechargeable motor vehicle.

[0002] Electrified vehicles, in the case of electric and plug-in hybrid motor vehicles, comprise a traction battery, generally of high power, cooperating with electrical recharging means on an electrical supply network external to the vehicle. Such vehicles are equipped with a recharging device whose function is to control the charging current delivered by a terminal connected to the supply network. In addition, it is also responsible for the on-board conversion function of an electrical voltage. In terminal recharging situations, it performs the conversion of an alternating voltage to a direct voltage (AC / DC), in particular during recharging in mode 2 or mode 3 in which it is necessary to convert an alternating voltage of 220V to a direct voltage compatible with the battery system, up to 450V for example.When driving, the charging device also performs DC / DC conversion between the battery and the vehicle's on-board systems, for example the on-board network (14V) and the electric traction machine of the powertrain.

[0003] The electrical power flows that pass through the charging device generate a temperature rise that must be controlled and evacuated in order to avoid damage to the electrical circuits and the battery. Conventionally, known protection measures provide for limitations on the charging current and an increase in the cooling level in the event that critical temperatures are exceeded. In particular, document FR2999812A3 is known, describing a cooling system optimized for so-called fast charging, comprising two heat transfer fluid circulation circuits. Document CN109378536A is also known, describing the management of charging and discharging of an electrified vehicle battery.

[0004] It is necessary to improve existing thermal protection solutions. One objective of the invention is to guarantee the integrity of the charging device for all vehicle usage situations, when charging at a terminal and when driving. Another objective is to improve the thermal monitoring of the charging device of an electrified vehicle and to control protection measures for each situation likely to cause a critical temperature rise.

[0005] More specifically, the invention relates to a method for thermal protection of an electric charging device for a traction battery of an electrified vehicle in which said charging device is capable of electric charging on a terminal from an electrical supply network and of on-board electric charging by regenerative braking, the method comprising the following steps of triggering a first battery charging mode, continuously measuring the temperature of said charging device, and in the event of detection of exceeding a first temperature threshold, triggering a second charging mode during which the charging power is reduced compared to the power of the first mode.

[0006] According to the invention, the method further comprises, in the event of detection of the exceeding of a second temperature threshold greater than the first threshold, the triggering of a third recharging mode during which the electrical recharging at the terminal and the electrical recharging by regenerative braking are inhibited for a predetermined duration following the instant of exceeding of the second threshold.

[0007] According to a variant, the second recharging mode consists of reducing the recharging power progressively as a function of the increase in temperature up to a temperature limit.

[0008] According to a variant, in the event of detection of a temperature of the charging device which is higher than a third temperature threshold after the expiration of the predetermined duration, the inhibition of the electrical charging on the terminal permanently and the recording of a thermal failure diagnosis.

[0009] According to a variant, it further comprises the inhibition of electric recharging by regenerative braking as long as the temperature is above the third threshold.

[0010] Preferably, the third threshold is lower than the first threshold.

[0011] According to the method, in the event of detection of a temperature of the charging device which is lower than a fourth temperature threshold before the elapse of the predetermined duration, the method comprises the reactivation of the electric charging at the terminal and the electric charging by regenerative braking.

[0012] According to a variant, the third recharging mode further comprises the control of a setpoint of an on-board thermal regulation system so as to increase the cooling level of said system.

[0013] According to a variant, the instruction controls the speed of a ventilation device and / or the speed of a hydraulic pump and / or the opening of a valve in a hydraulic circuit.

[0014] The invention provides an electrified vehicle powertrain comprising a traction battery, a device for electrically recharging said traction battery in which said recharging device is capable of electrical recharging at a terminal from an electrical supply network and of on-board electrical recharging by regenerative braking, wherein a control unit is configured to implement the thermal protection method according to any of the preceding embodiments.

[0015] The invention provides an electrified vehicle comprising such a powertrain.

[0016] The method guarantees the integrity of the charging device and aims to avoid thermal operating conditions where electrical charging takes place in degraded mode. In particular, it allows a return to normal operating conditions in situations of charging at a terminal and regenerative braking.

[0017] Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows, comprising embodiments of the invention given as non-limiting examples and illustrated by the appended drawings, in which:

[0018] [fig. 1] schematically represents an electrified vehicle comprising a unit of control capable of implementing the method according to the invention;

[0019] [fig.2] represents a flowchart illustrating an algorithm of the protection method thermal according to the invention.

[0020] The invention applies to electrified vehicles, in particular rechargeable, hybrid and electric motor vehicles.

[0021] In [fig.l], an example of an electrified vehicle 1 capable of implementing the invention is shown. The vehicle 1 comprises a powertrain equipped with a control unit 2, an electric traction machine (not shown) powered by a traction battery system 3 and a battery recharging device 4.

[0022] The battery system 3 comprises a high-voltage electric battery, generally of several hundred volts, for example 450V, ensuring the supply of electrical energy to the electric machine. The electric battery comprises electric cells, for example of the Lithium-ion type. The battery system 3 comprises a battery system management computer.

[0023] The charging device 4 comprises charging means cooperating with a power outlet 6 so as to be able to electrically connect to an external charging terminal 7 connected to an electrical supply network 8. It is responsible for managing the communication between the different charging terminals and for monitoring and controlling the electrical charging at the terminal. The charging device 4 also comprises an electrical converter of the alternating / direct AC / DC and direct / direct DC / DC type. A first function is to convert an alternating voltage delivered by the charging terminal 7 into a direct voltage compatible with the battery. Depending on the charging mode, the charging device controls a charging setpoint defining a charging voltage and a charging current compatible with the battery. The charging power can be controlled by the charging device 4 according to various parameters and instructions. In the context of the method according to the invention, the temperature of the charging device 4 is a parameter for controlling the charging power. According to a second function, the charging device 4 is also provided for converting electrical voltages between the on-board systems of the vehicle, in particular between the high-voltage battery 3 and the on-board network, of approximately 14V, and between the high-voltage battery 3 and the electric traction machine, in a driving situation and during regenerative braking.

[0024] To ensure thermal protection of the battery 3 and the charging device 4, the powertrain also comprises a thermal regulation system 5 for the on-board electrical systems, the cooling level of which is adjustable by the thermal protection method according to the invention. In this non-limiting example, the thermal regulation system 5 is a thermodynamic cycle loop type circuit consisting of a main cooling circuit with heat transfer fluid and heat exchange elements. It may comprise secondary water cooling circuits and mechanical ventilation means depending on the cooling architecture. In this example, the thermal regulation system 5 comprises means for controlling the flow rate of the heat transfer fluid, in particular a pump and hydraulic valves, and means for controlling the operating speed of the fans.These control means, controlled by a computer, make it possible to adjust the desired cooling level at the level of the battery 3, the charging device 4 and the other electronic components to be thermally controlled in accordance with the method according to the invention.

[0025] The control unit 2 is provided with an integrated circuit computer and electronic memories and is configured to control the thermal protection method of the charging device according to the invention, but also other functions of the powertrain, such as electric traction, regenerative braking charging, the thermal regulation system and the charging device. The computer could be external to the control unit 2, while being coupled to the latter. In the latter case, it can itself be arranged in the form of a dedicated computer comprising a possible dedicated program, for example. Consequently, the control unit, according to the invention, can be produced in the form of software modules (or computer modules (or even "software")), or electronic circuits (or "hardware"), or a combination of electronic circuits and software modules.

[0026] In [fig.2], an embodiment of the thermal protection method according to the invention is shown. The thermal protection method aims to protect the electrical components during the generation of electrical flows between the charging device and other on-board components of the vehicle. The method provides for the continuous measurement of the temperature T of the charging device at all times in order to control the different charging modes and thermal protection measures.

[0027] At a step 20, there is a vehicle life situation where an electric recharge is triggered. This is either a recharge at a terminal or a recharge while driving of the regenerative braking type. An electric flow is generated at the level of the recharging device. The recharge is carried out according to a first mode at an electric recharge power dependent on the type of recharge. For example, in recharge at a terminal, the charging power can be 7kW, 1kW or more in so-called ultra-fast recharge. In regenerative braking, the recharge power depends on the braking torque and the power of the electric traction machine. The thermal regulation system is controlled at a default cooling level, dependent on the cooling strategy of the recharging modes.For example, the speed of the hydraulic pump is controlled at a value of 20% to 30% of the maximum set level, the speed of the fans is controlled at a value of 20% to 30% of the maximum level and the opening of the valves of the hydraulic circuit at an opening of 70% of the maximum opening. These values are cited as a non-limiting example and depend on the architecture of the vehicle's on-board thermal regulation system.

[0028] In a step 21, the method comprises monitoring the instantaneous temperature T of the charging device relative to a first threshold T1, for example configured at 120 degrees Celsius. In the event that the temperature threshold T1 is exceeded, the method comprises in a step 22 the triggering of a second charging mode with degraded power, during which the charging power is reduced relative to the power of the first mode controlled in step 20. This protective measure is known and generally aims to avoid damage to the battery. This degraded charging mode is controlled by the charging device by sending a charging instruction to the charging terminal consisting of limiting the charging current.

[0029] According to a variant of the method, the recharging power is reduced progressively as a function of the increase in temperature up to a limit Tmax, for example of a value of 130 degrees Celsius. For example, the power reduction is linear and is controlled according to the following relationship: Pd = Pn x (Tmax-Tx) / (Tmax-Tl), where Pd is the recharging power in degraded mode after the instant of exceeding the threshold Tl, Pn is the recharging power in nominal mode before the instant of exceeding Tl, Tmax is the temperature limit in reduced power control, Tl is the value of the temperature of the trigger threshold of the degraded recharging mode.

[0030] In another variant, the recharging power is limited to a fixed power, lower than the recharging power controlled before the instant of exceeding the threshold TL

[0031] A thermal evaluation is carried out continuously during a step 23 after the instant of exceeding the first threshold TL In the situation where the continuous temperature rise, and in the event of detection of the exceeding of a second temperature threshold T2, of a value greater than the first threshold T1, the charging device controls in a step 24 the triggering of a third charging mode configured to ensure the execution of several protection measures. In a charging situation at a terminal, the electric charging is inhibited for a predetermined inhibition duration Din following the instant of exceeding the second threshold T2. In a driving situation, the electric charging by regenerative braking is inhibited for the predetermined inhibition duration Din following the instant of exceeding the second threshold T2. The predetermined inhibition duration is equal for example to 10 seconds. T2 is for example between T1 and Tmax, or may be equal to or greater than Tmax.

[0032] Furthermore, preferably in step 24, the third recharging mode is configured to increase the cooling level applied by the thermal regulation system at the recharging device simultaneously with the recharging inhibition. Preferably, the cooling level is increased to the maximum level. For this purpose, the recharging device controls a setpoint for increasing the speed of the hydraulic pump of the heat transfer fluid circuit, preferably to the maximum speed, a setpoint for increasing the opening of the cooling valves of the hydraulic circuit, preferably to the maximum opening section, and a setpoint for increasing the fan speed, preferably to the maximum speed. These measures are cited as a non-limiting example and depend on the architecture of the on-board thermal regulation system of the vehicle. Other setpoints can be envisaged by the method according to the invention.

[0033] When the inhibition time Din has elapsed, a new thermal evaluation 25 is carried out by the protection method.

[0034] In the situation where the temperature of the charging device is lower than T1 but still higher than a third threshold T3 at the end time of the inhibition duration Din, for example 115 degrees Celsius, the method further comprises, in a step 26, the inhibition of the electrical charging at the terminal permanently and the recording of a thermal failure diagnosis in a failure log. This inhibition is maintained for the current charging phase at the terminal. In a driving situation, in step 26, the regenerative braking function is inhibited as long as the temperature of the charging device has not fallen below the third threshold T3. Preferably, in order to re-establish acceptable thermal conditions, whether for the charging situation at the terminal or for a driving situation, the instructions for increasing the cooling level controlled during step 24 remain active.Preferably, at the maximum cooling level. Furthermore, it is envisaged in a variant of step 26 that a warning signal is generated to warn the driver. This signal indicates that a thermal failure has been. detected and that a garage check is necessary. The alert may be displayed as a warning light on the dashboard. The alert is generated simultaneously with the recording of the diagnosis in the fault log.

[0035] Alternatively, in the situation where the temperature of the charging device has decreased more sharply, the temperature becoming equal to or lower than a fourth threshold T4 at the end time of the inhibition duration Din, the method, at a step 27, authorizes a reactivation of the charging. Preferably, the threshold T4 is equal to the threshold T3, or may be lower than T3. In these thermal conditions, during step 27, in the case of charging at the terminal, the charging device again authorizes electric charging at the terminal at a normal charging power, identically to step 20. In a driving situation, electric charging by regenerative braking is authorized. Furthermore, the thermal regulation system returns to normal operating parameters.The hydraulic pump speed, valve opening and fan speed setpoints are controlled at default cooling level values, identical to the values controlled in step 20.

Claims

Claims

1. Method for thermal protection of an electric charging device for a traction battery of an electrified vehicle in which said charging device is capable of electric charging on a terminal from an electrical supply network and of on-board electric charging by regenerative braking, the method comprising the following steps: - triggering (20) a first battery charging mode, - continuously measuring the temperature of said charging device, - in the event of detection (21) of exceeding a first temperature threshold (T1), triggering (22) a second charging mode during which the charging power is reduced compared to the power of the first mode, - characterized in that it further comprises, in the event of detection (23) of exceeding a second temperature threshold (T2) greater than the first threshold (T1),the triggering (24) of a third charging mode during which electric charging at the terminal and electric charging by regenerative braking are inhibited for a predetermined duration (Din) following the instant of exceeding the second threshold (T2).,

2. Thermal protection method according to claim 1, characterized in that the second recharging mode consists of reducing the recharging power progressively as a function of the increase in temperature up to a temperature limit (Tmax).

3. Thermal protection method according to claim 1 or 2, characterized in that it further comprises, in the event of detection of a temperature (T) of the charging device (4) which is higher than a third temperature threshold (T3) after the elapse of the predetermined duration (Din), the inhibition (26) of the electrical charging on the terminal permanently and the recording of a thermal failure diagnosis.

4. Thermal protection method according to claim 3, characterized in that it further comprises the inhibition (26) of electrical recharging by regenerative braking as long as the temperature (T) is above the third threshold (T3).

5. Thermal protection method according to claim 3 or 4, characterized in that the third threshold (T3) is lower than the first threshold (T1).

6. Thermal protection method according to any one of claims 1 to 5, characterized in that in the event of detection of a temperature of the charging device which is lower than a fourth temperature threshold (T4) before the elapse of the predetermined duration (Din), the method comprises the reactivation (27) of the electrical charging at the terminal and the electrical charging by regenerative braking.

7. Thermal protection method according to any one of claims 1 to 6, characterized in that the third recharging mode further comprises the control of a setpoint of an on-board thermal regulation system (5) so as to increase the cooling level of said system (5).

8. Thermal protection method according to claim 7, characterized in that the setpoint controls the speed of a ventilation device and / or the speed of a hydraulic pump and / or the opening of a valve in a hydraulic circuit.

9. Powertrain of an electrified vehicle comprising a traction battery, a device for electrically recharging said traction battery in which said recharging device is capable of electrically recharging at a terminal from an electrical supply network and of on-board electrical recharging by regenerative braking, characterized in that it comprises a control unit configured to implement the thermal protection method according to any one of claims 1 to 8.

10. A plug-in electrified vehicle comprising a powertrain according to claim 9.

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