FR2978879A1 - METHOD FOR DIAGNOSING A SHORT CIRCUIT IN AN ELECTRICAL ASSEMBLY OF A MOTOR VEHICLE COMPRISING A CAPACITIVE COMPONENT AND DIAGNOSTIC DEVICE - Google Patents

Abstract

A method of diagnosing a short circuit in an electrical assembly comprising a capacitive component, the method comprising: - when a first power supply circuit comprising a protection resistor and allowing power to the electrical assembly is closed, a step of determining the value of the intensity of the electric current flowing in the first supply circuit, - a step of testing the value of the intensity of the electric current, and - a step of deducing the existence or not of a short circuit in the electrical assembly.

Description

The invention relates to a method for diagnosing a short circuit in an electrical assembly, particularly in an electrical assembly of a motor vehicle, in particular in a high-voltage electrical assembly of a motor vehicle. The invention also relates to a method of supplying such an electrical assembly. The invention also relates to a device for implementing the diagnostic method and a device for implementing the feed method. Finally, the invention relates to a motor vehicle comprising such a device for implementing the diagnostic method or a device for implementing the feed method.

An electrical power network on board an electric or hybrid motor vehicle generally comprises a storage battery provided with a protective fuse, an electrical assembly constituting a load and including in particular an electric drive motor, a main contactor making it possible to establish an electrical connection between the accumulator battery and the assembly constituting the charge, and a control system such as a supervision calculator.

Generally, the need to preload the electrical assembly exists when this set includes capacitive elements, which are therefore intended to be connected to the terminals of the battery. This case is verified in an electric or hybrid motor vehicle since the various power devices, inverters, chargers, etc., have input capacitors totaling a few milli farads. Consequently, when the main contactor closes, the line resistances and inductances introduce significant inrush currents into the network, these inrush currents can damage the electronic device capacities, the contacts of the contactor or the fuse. of the storage battery.

The principle of precharging is based on the switching on of the power supply lines of the electrical assembly, of a passive electronic device, in parallel with the main contactor, in order to slow down the appearance of the voltage of the storage battery on the electrical assembly.

If a preload contactor is available in series with a simple precharging resistor, the electrical assembly can be preloaded according to a time constant proportional to the value of the resistor and to the capacitive load of the electrical assembly. But in case of a short circuit in the electrical assembly at the time of the preload, there is a risk of destroying the precharging resistor. In such a case, the battery must then be removed from the vehicle and disassembled in order to change the precharging resistance which causes delays and significant costs.

Document FR2771863A1 discloses a short-circuit detection device. In this, the voltage of the electrical assembly is regularly determined at predetermined intervals. If the variation of voltage in the interval is less than a threshold value, a supervision system opens a relay upstream of the precharging resistor. However, such a solution is problematic. In particular, it does not distinguish a short-circuit case from a faulty relay case (always open or always controlled in the open state).

Document FR2831272A1 also discloses a short-circuit detection device operating by checking the sum of the currents passing through each of the branches of the electrical network (42V in the example). It requires to have a current sensor on all the branches of the high voltage electrical network and that the mass of all the branches is common.

Document WO201089338A2 discloses a short-circuit detection device operating by measuring the total current consumed by high-voltage devices. If a threshold is exceeded, a computer drives a relay that makes it possible to pass the current through a resistor whose purpose is to limit the intensity of the short-circuit current. Another relay mounted upstream can be used as a circuit breaker. The resistance must be dimensioned to dissipate the energy of the short circuit, which can be high.

Thus, currently, a short circuit of one of the high-voltage consumers causes the destruction of the precharging resistor. In addition, there is no diagnosis of this defect. His repair becomes an arduous task. The only solution is to replace the parts destroyed after the short circuit. This is possible only after a few tests that allow to deduce that the destruction is located at the level of the precharging resistor. The object of the invention is to provide a short-circuit diagnostic method that obviates the disadvantages mentioned above and improves the methods known from the prior art. In particular, the invention provides a simple and effective method for preventing deterioration of the precharging resistor in the event of a short circuit in an electrical assembly comprising a capacitive component.

According to the invention, the method of diagnosing a short-circuit in an electrical assembly comprising a capacitive component comprises: when a first supply circuit comprising a protection resistor and allowing the supply of the whole electrical circuit is closed, a step of determining the value of the intensity of the electric current flowing in the first supply circuit, - a step of testing the value of the intensity of the electric current, and - a step of deduction of the existence or not of a short circuit in the electrical assembly.

It can be concluded that there is an electrical short circuit if the intensity of the electric current flowing in the first supply circuit is greater than a first threshold for a duration greater than a predetermined duration.

According to the invention, the method for powering an electrical assembly comprising a capacitive component comprises: a step of implementing the diagnostic method defined above; a step of opening the first power supply circuit; it is concluded that there is a short circuit in the electrical assembly, or - a step of maintaining the closure of the first power supply circuit if it is concluded that there is no short circuit in the electrical assembly.

The supply method may comprise: a step of closing the first power supply circuit; a step of opening of the first power supply circuit when the electric voltage across the electrical assembly has reached a value greater than a second threshold or when the difference in absolute value between the electrical voltage across the electrical assembly and the voltage across the battery has reached a value lower than a third threshold.

The power supply method may comprise: a step of closing a second power supply circuit for powering the electrical assembly, before the opening of the first power supply circuit when the electric voltage at the terminals of the power supply electrical assembly has reached a value greater than a second threshold or when the difference in absolute value between the electrical voltage across the electrical assembly and the voltage across the battery has reached a value below a third threshold.

The invention also relates to a data storage medium readable by a computer on which is recorded a computer program comprising computer program code means for implementing the steps of the diagnosis or feeding method defined above.

According to the invention, the device for diagnosing a short circuit in an electrical assembly comprising a capacitive component comprises hardware and / or software means capable of implementing the diagnostic method defined above.

The hardware and / or software means may comprise a means for determining the intensity of the electric current flowing in the first power supply circuit when the first power supply circuit is closed, a means for testing the value of the intensity of the power supply. electric current and a means of deducing the existence or not of a short circuit in the electrical assembly.

According to the invention, the device for controlling the power supply of an electrical assembly comprising a capacitive component comprises hardware and / or software means capable of implementing the power supply method defined above. The hardware and / or software means may comprise a diagnostic device defined above.

The hardware and / or software means may comprise means for controlling a switching means capable of opening the first supply circuit if the intensity of the electric current flowing in the first supply circuit is greater than a first threshold. and able to keep closed the first power supply circuit if the intensity of the electric current flowing in the first supply circuit is less than or equal to this first threshold.

The hardware and / or software means may comprise means for controlling a switching means adapted to close the first power supply circuit and able to open the first circuit, when the electrical voltage across the terminals of the electrical assembly has reached a value greater than a second threshold or when the difference in absolute value between the electrical voltage across the electrical assembly and the voltage across the battery has reached a value lower than a third threshold. The hardware and / or software means may comprise means for controlling a switching means capable of closing a second power supply circuit for powering the electrical assembly, during or following the opening of the first circuit. when the voltage at the terminals of the electrical assembly has reached a value greater than a second threshold or when the difference in absolute value between the electrical voltage across the terminals of the electrical assembly5 and the voltage at the terminals of the battery has reached a value lower than a third threshold.

According to the invention, an electric or hybrid motor vehicle comprises a previously defined diagnostic device or a previously defined power control device.

The appended drawing represents, by way of example, an embodiment of a diagnostic device according to the invention. FIG. 1 is a diagram of a high-voltage architecture of an electric or hybrid motor vehicle presenting an embodiment of a diagnostic device according to the invention.

Figure 2 is a timing diagram showing the evolution of electrical parameters in the architecture.

Figures 3 and 4 are time diagrams showing the change in the intensity of the electric current flowing through the precharge resistor in different situations.

Figure 5 is a flow chart of an embodiment of a power control method according to the invention.

Fig. 6 is a flow chart of an embodiment of a diagnostic method according to the invention.

An embodiment of a high-voltage architecture 1 of an electric or hybrid motor vehicle is described below with reference to FIG. 1. This architecture mainly comprises a high-voltage battery 2, an electrical assembly 3 comprising in particular an inverter 10 and an electric drive motor of the motor vehicle, and a power control device 21. The electrical assembly comprises a capacitive component represented by a capacitor symbol in dashed lines. The capacitive component is for example greater than 1 mF, preferably greater than 5 mF.

The power control device comprises an electrical disconnector device 4 between the battery and the electrical assembly. It allows in particular to cut the electrical connection between the battery and the electrical assembly. Nevertheless, the power control device allows the precharging of the electrical assembly which is initially discharged, via a current limiting device 8, as a preloading resistor 8 or protection. Such an isolator device must withstand very large currents. Indeed, the electrical power transferred through this device is very important in hybrid or electric vehicles.

For safety reasons, it is necessary to be able to isolate the battery in the event of a crash or during maintenance operations (after discharge of the electrical assembly).

In addition, it is necessary to ensure the preload of the electrical assembly after a certain time has elapsed since the last use of the vehicle. For example, the disconnector device 4 is produced by means of mechanical contactors 5, 6, 7 that are controlled, making it possible both to perform isolation maneuvers and to perform preloading maneuvers. The closing of the contactors 5 and 7 allows the electrical assembly to be charged through a current limiting device 8 in a first supply circuit of the electrical assembly comprising branches 10, 12. The closing of the contactors 6 and 7 allows the connection of the battery to the electrical assembly through a second power supply circuit comprising branches 11, 12. The opening of all the contactors makes it possible to achieve good galvanic isolation of the battery. A fuse is provided in series with the battery to protect the electrical elements against significant short-circuit overcurrent. The disconnector device can be realized thanks to any controlled switch technology, in particular thanks to transistors or relays.

These controlled switches 5, 6, 7 are controlled by a computer 23 also forming part of the power control device. In addition, the computer receives information on the intensity of the current supplied by the battery, electrical voltage information at the terminals of the battery and electrical voltage information at the terminals of the electrical assembly. For example, the computer is for this purpose connected to a means 9 for determining the intensity of the current supplied by the battery and / or to a means 26 for determining the voltage across the battery and / or a means 27 determining the voltage across the electrical assembly.

In addition, the control device, in particular the computer, comprises a means 24 for testing the value of the electrical intensity coming from the battery and a means 25 for deducing the existence or not of a short circuit in the battery. the electrical assembly. These test and deduction means constitute a diagnostic device 22. The diagnostic device may comprise the means 9 for determining the intensity of the current supplied by the battery.

Thus, the diagnostic device comprises all the hardware and / or software means making it possible to implement the diagnostic method that is the subject of the invention, in particular to implement the steps of the diagnostic method that is the subject of the invention. In addition, the control device comprises all the hardware and / or software means making it possible to implement the power control method that is the subject of the invention, in particular to implement steps of the object power control method. of the invention.

One embodiment of the power control method is described below with reference to FIG. 5. It is assumed that initially the electrical assembly is discharged.

In a first step 110, the computer 23 controls the closing of the controlled switch 5 and the controlled switch 7. This closes the first supply circuit through the conductors 10 and 12. This initiates a precharge phase. . The precharging resistor is found in series in the first supply circuit of the electrical assembly and avoids a peak current that could destroy power connectors. In the precharging phase, as shown in FIG. 2, the voltage across the electrical assembly and the intensity of the current supplied by the battery change substantially as in a capacitor charge. It is the same during a discharge phase also shown in Figure 2.

In a second step 120, the diagnostic method that is the subject of the invention is implemented. An embodiment of the diagnostic method is described below with reference to FIG. 6. At the end of the diagnostic process, it is concluded that there is or no short circuit in the electrical assembly. This second step is performed simultaneously or just after the first step. In a third step 130, it is tested whether the diagnostic procedure led to conclude that there is or no short circuit. If it is concluded that there is a short circuit, then a fourth step 140 is started in which the controlled switch 5 is opened and, preferably, in which the controlled switch 7 is opened.

If it has been concluded that there is no short circuit, we proceed to a fifth step 150 in which the difference in voltage existing between the battery voltage and the voltage of the electrical assembly is tested. If the absolute value of this difference is greater than a Threshold threshold 2, step 120 is looped. For example, Threshold threshold 2 is about 15 V.

On the other hand, if this difference is less than or equal to the Threshold threshold 2 during a confirmation delay of, for example, 0.3 s, a sixth step 160 is set in which the controlled switch 6 is closed, then the controlled switch 5 is opened. This opens the first supply circuit and closes the second supply circuit through the conductors 11 and 12. The precharging resistor is no longer solicited.

Alternatively to what has been described previously, it is possible to compare, in the fifth step 150, the voltage of the electrical assembly with a Threshold threshold 3. In this case, if the voltage of the electrical assembly is greater than the threshold, then goes to step 160 and if the voltage of the electrical assembly is below the threshold, it is looped on step 120. For example, Threshold Threshold 3 is about 400 V.

One embodiment of the procedure or method of diagnosis is described below with reference to FIG. 6.3. In a first step 210, the intensity of the current supplied by the battery is determined, for example by measurement.

In a second step 220, the value of this intensity is tested. For example, it is compared to a threshold I_seuil_court_court. If the intensity is greater than the threshold for a duration T_tempo_confirmation, it is concluded in a step 230 to the existence of a short circuit. If the intensity is not greater than the threshold during this time, it is concluded in a step 240 to the absence of short circuit. The duration T_tempo_confirmation makes it possible to wait until the value of the current supplied by the battery in the event of a short circuit is sufficiently different from the current value supplied by the battery in the absence of a short circuit. Indeed, at the moment of the closing of the controlled switches 5 and 7, the intensity of the current supplied by the battery is substantially the same whether or not there is a short circuit in the electrical assembly.

The diagnostic procedure is then completed and then returns to step 130 of the control method.

FIG. 3 shows the evolution of the current in the precharging phase in the event of a short circuit in the electrical assembly. The IR current (also referenced IBatt thereafter) which passes through the precharging resistor is maximum and is worth (VBatt / Rp with VBatt the battery voltage and Rp the precharge resistance). If nothing is done, the resistance gradually warms up and its resistance value increases gradually. The current flowing through it decreases progressively. The precharging resistor is dimensioned only to dissipate a low energy, so it resists a short time at a high power and ended up being destroyed (fusion of the component). The intensity of the IR current then collapses sharply.

The same figure shows the changes in the current through the resistor in the case of a short circuit for a high battery voltage (VBatt = 400V) and a low battery voltage (VBatt = 240V). These voltages are given by way of example of minimum and maximum battery voltages encountered in nominal operation. In this example, consider a preload resistance value Rp = 30 Ohms.

Thanks to the diagnostic method according to the invention, it is possible to detect a short circuit at the electrical assembly by monitoring the value of the battery current IBatt during the precharging phase.

As seen above, if IBatt> I_seuil_court_circuit for at least a time "T_tempo_confirmation", the computer 23 controls the instantaneous opening 15 of the switches 5 and 7 so as to protect the precharging resistor.

A range of calibration of the parameters I_circuit_heat_heat and T_stem_confirmation is shown in FIG. 4. It depends on: - the minimum and maximum voltages across the resistor Rp (240V and 400V in the previous example), - the accuracy of the average 9 for determining the current (current sensor), - the profile of the nominal current, 25 - the value of the precharging resistor, - the energy supported by the resistor (before the breakage, that is to say the destruction of the precharging resistor).

In order to avoid false detections, the value of the threshold I_circuit_circuit threshold 30 must be greater than the nominal value of the intensity of the current to which the precision of the current determination means is added.

However, its value must be low enough to detect a short circuit regardless of the voltage across the battery.

In order to avoid a false detection, the value of the duration T_tempo_confirmation must be sufficiently high. Peaks of stealth currents should not be taken into account. Its value must be low enough to require at least the resistance and avoid its destruction. In addition, the determination of the current is often filtered which causes a delay in the main information used by the computer for the diagnosis.

Typically, in the case of the example described, a threshold value I_circuit_circuit threshold between 3 A and 6 A, for example 5 A, is chosen.

Typically, in the case of the example described, a value of duration T_tempo_confirmation is chosen between 100 ms and 400 ms, for example 200 ms.

In this document, the term "determination of the intensity of electric current" should be interpreted broadly. In particular, it must be interpreted as including a determination of the power or energy consumed in the precharge resistor, or in another resistor. Indeed, these quantities are directly related to each other.

The methods according to the invention improve the methods known from the prior art. In particular, they make it possible to avoid the destruction of the precharging resistor. They make it possible to detect a short-circuit in an electrical network having a precharging device and to protect the healthy electrical organs against this short-circuit, thus avoiding a propagation of the fault which causes an additional cost of repair.

Claims (14)

1. A method of diagnosing a short circuit in an electrical assembly (3) comprising a capacitive component, the method comprising: - when a first supply circuit comprising a protection resistor (8) and allowing the supply of the electrical assembly is closed, a step of determining the value of the intensity of the electric current flowing in the first supply circuit, - a step of testing the value of the intensity of the electric current, and - a step of deducing the existence or not of a short circuit in the electrical assembly. 2. Diagnostic method according to the preceding claim, characterized in that it concludes the existence of a short circuit of electrical assembly if the intensity of the electric current flowing in the first supply circuit is greater than one. first threshold (I_seuil_court_court) for a duration greater than a predetermined duration (T_tempo_confirmation). 3. A method of power supplying an electrical assembly (3) comprising a capacitive component, the method comprising: - a step of implementing the diagnostic method according to one of the preceding claims, - a step of opening the first power supply circuit if it is concluded that there is a short circuit in the electrical assembly, ora step of maintaining the closure of the first power supply circuit if it is concluded that there is no short circuit in the electric assembly. 4. Power supply method according to the preceding claim, characterized in that it comprises: - a step of closing the first power supply circuit, - a step of opening the first power supply circuit, when the voltage at the terminals of the electrical assembly has reached a value greater than a second threshold (Threshold 3) or when the difference in absolute value between the electrical voltage across the electrical assembly and the voltage across the battery has reached a lower value at a third threshold (Threshold 2). 5. Power supply method according to the preceding claim, characterized in that the method comprises: - a closing step of a second power supply circuit for the power supply of the electrical assembly, before the opening of the first circuit d supply when the electrical voltage across the electrical assembly has reached a value greater than a second threshold (Threshold 3) or when the difference in absolute value between the electrical voltage across the electrical assembly and the voltage across the terminals the battery has reached a value lower than a third threshold (Threshold 2). 6. Data storage medium readable by a computer on which is recorded a computer program comprising means of computer program codes for implementing steps of the diagnostic or power supply method according to one of the preceding claims. 7. Device (22) for diagnosing a short circuit in an electrical assembly (3) comprising a capacitive component, characterized in that it comprises hardware means (24, 25) and / or software capable of implementing the diagnostic method according to claim 1 or 2. 8. Diagnostic device according to the preceding claim, characterized in that the hardware and / or software means comprise means (9) for determining the intensity of the electric current flowing in the first supply circuit when the first circuit of power supply is closed, means (24) for testing the value of the intensity of the electric current and means (25) for deducing the existence or not of a short circuit in the electrical assembly. 9. Device (21) for controlling the power supply of an electrical assembly comprising a capacitive component, characterized in that it comprises hardware means (22, 4, 26, 27) and / or software capable of implementing the feeding method according to one of claims 3 to 5. 10. Power supply control device according to the preceding claim, characterized in that the hardware and / or software means comprise a diagnostic device (22) according to claim 7 or 8. 11. Power control device according to claim 9 or 10, characterized in that the hardware and / or software means comprise means (23) for controlling a means (5) decommutation suitable for opening the first circuit d supply if the intensity of the electric current flowing in the first supply circuit is greater than a first threshold and able to keep the first supply circuit closed if the intensity of the electric current flowing in the first supply circuit is less than or equal to this first threshold. 12. A power control device according to claim 10 or 11, characterized in that the hardware and / or software means comprise means (23) for controlling a switching means (5) adapted to close the first circuit. and able to open the first circuit, when the electrical voltage across the electrical assembly has reached a value greater than a second threshold (Threshold 3) or when the difference in absolute value between the voltage across the terminals of the electrical assembly and the voltage at the terminals of the battery has reached a value lower than a third threshold (Threshold 2). 13. Power supply control device according to one of claims 10 to 12, characterized in that the hardware and / or software means comprise means (23) for controlling a means (6) switching capable of closing a second supply circuit for supplying the electrical assembly, during or following the opening of the first supply circuit when the electrical voltage across the electrical assembly has reached a value greater than a second threshold (Threshold 3) or when the difference in absolute value between the electrical voltage across the electrical assembly and the voltage across the battery reaches a value lower than a third threshold (Threshold 2). Electric or hybrid motor vehicle comprising a diagnostic device (22) according to one of claims 7 to 9 or a power control device (21) according to one of claims 10 to 13.5.