FR3009869A1 - METHOD FOR DETECTING A POWER BATTERY DISCONNECTION IN A MOTOR VEHICLE - Google Patents

Abstract

The invention proposes a method for detecting an electric battery disconnection (10) in a system equipped with two electrical networks interconnected by a DC voltage DC converter (4). The battery (10) belongs to one of the two networks (2), and the converter (4) is configured to recharge the battery (2). A predefined voltage signal (Uvar) is added to a DC voltage component (Us) delivered by the converter (4) to the network (2) comprising the battery (10), and the current (I) passing through the battery ( 10) by searching for a current signal (Ialternative) corresponding to the added voltage signal (Uvar), to verify that the battery (10) is connected to the network (2).

Description

The invention relates to the securing of the power supply of motor vehicle edge systems. It can also be applied more generally to electrical systems, in particular to embedded electrical systems, combining two electrical networks, interconnected by a DC / DC voltage converter (DC direct current converter), one of the following: networks comprising an electric storage battery recharged by the DC / DC converter. The invention relates more particularly to securing the low-voltage power supply of an automotive electrical system comprising two electrical networks interconnected by a DC / DC converter. These two networks can operate at identical nominal voltages or at different nominal voltages. Typically, in vehicles where at least some electrical machines serve either to recover braking energy, or to assist in the propulsion of the vehicle, or both, the vehicle may comprise a high voltage network including electrical machinery, so to limit the losses by Joule effect in the conductors and in order to be able to use conductive cables of smaller diameter.

For other standard functions the vehicle may include a second power grid powered at a lower voltage. For example, it is possible to have a first electrical network operating at a voltage of between 24 and 58 volts, for example at a voltage of 48 volts, and a second electrical network, low voltage operating at nominal voltages of between 10.5 and 15 volts. .

The second electrical network "low voltage" may include a dedicated electric storage battery, which is for example recharged by means of a DC / DC converter from the high voltage network during the vehicle running phases.

For reasons of management of the electrical energy of the "low voltage" network and management of the charging of the "low voltage" accumulator battery, the DC / DC converter can be controlled by an electronic control unit which is it - even powered by the battery of the low voltage network. For certain safety functions of the vehicle, it may be necessary to secure the power supply of the "low voltage" network. One way to secure this power supply may be to use the power supply redundancy by the "low voltage" storage battery on the one hand, and by the supply of electricity to the low voltage network by the second network via the DC / DC converter. In this case, it is important, before switching off the low-voltage network supply via the DC / DC converter, to check that the low-voltage battery is actually connected to the low-voltage grid, so that it can then supply power to the low-voltage grid. This may be the case, for example, for vehicles designed to save energy, thanks to "stop and start" systems in which a heat engine used to propel the vehicle is switched off when a stop at a red light and is restarted quickly when the driver re-presses the accelerator pedal. If the supply of electrical power to the "low voltage" network can only be secured to the "low voltage" storage battery, it is essential to ensure that this "low voltage" storage battery is not disconnected before engaging the automatic engine stop. The patent application EP 195 8851 proposes the use of a second battery for securing the low-voltage onboard network. The addition of a second battery weighs down the vehicle and increases the cost of the vehicle.

The aim of the invention is to propose a system for monitoring the good connection of a battery of a low-voltage network in a motor vehicle powered by two electrical networks interconnected by a DC / DC converter, in particular when one of the networks includes a battery recharged through the converter from the other network. The network fed through the DC / DC converter sometimes comprises a starter, but generally does not include a generator of energy (alternator or alternator starter for example), the latter being carried on the first power grid. The proposed monitoring device must be reliable, not disturb the electrical components and electrical consumers of the two networks and must be able to be set up for a low cost and without burdening the vehicle.

To this end, the invention proposes a method of detecting an electric battery disconnection in a system equipped with two electrical networks interconnected by a DC voltage converter (DC / DC) in DC voltage, the battery belonging to one two networks, and the converter for recharging the battery, that is to say connected so as to recharge the battery. More generally, the control of the converter is configured to ensure, when the converter is running, the power supply of the network comprising the battery, and to recharge the battery so that it can take power in turn the network when the converter is inactive. A predefined voltage signal is added to a DC voltage component supplied by the converter to the network comprising the battery, and the current flowing through the battery is measured by searching for a current intensity signal corresponding to the voltage signal added, to verify that the battery is connected to the network. The system can be for example an electric motor vehicle or a hybrid propulsion vehicle. The converter can be configured to recharge the battery at intervals of time, the battery supplying the network of which it is part during the other time intervals if necessary. The nominal operating voltage of the network associated with the battery is preferably lower than the nominal voltage of the other network. Preferably, this other network comprises a second battery of higher nominal voltage. In the present text, unless otherwise stated, the term "battery" designates by default the battery belonging to the network supplied with voltage by the converter, that is to say the network of lowest nominal voltage. The highest rated voltage network may include a battery, but this is preferably referred to as a "second battery". According to an advantageous embodiment, the added voltage signal and the desired intensity signal are periodic signals. These signals may be for example reciprocal periodic signals, or periodic signals of constant sign. The amplitude of the voltage signals is preferably reduced in comparison with the nominal voltage of the network fed by converter and by the battery, for example the amplitude is less than 2V for a nominal voltage network close to 14V. The amplitude of the voltage signal may for example be between 0.2V and 1.5V, and preferably between 0.2V and 0.5V. The frequency of the periodic signals may for example be between 20 Hz and 100 Hz. The frequency of the periodic signals can be constant. According to another variant embodiment, it is possible to send a particular pattern of periodic signals, for example a pattern making it possible to obtain a noise induced in current close to that induced by a conventional thermal vehicle alternator. Intensity signal detection strategies already developed for such alternator vehicles can then be used. According to a particularly advantageous embodiment, the added voltage signal is a modification, of predefined sign, of the voltage level, and the intensity signal is a variation, of predefined sign, of the intensity level. It is a sudden change, of predefined sign, of the level of tension, and the signal of intensity is a variation, of predefined sign, of the level of intensity. The amplitude of the variation of the voltage level is preferably reduced in comparison with the nominal voltage of the converter-fed network and the battery. For example, an amplitude voltage step of between 0.2 V and 2 V can be applied, and preferably between 0.2 V and 1 V. According to one embodiment, the voltage signal is not added and the signal is not sought. when the absolute value of the intensity passing through the battery is below an intensity threshold. The intensity threshold is preferably constant. For example, it is possible to trigger the addition of the AC voltage component if the absolute value of the intensity crossing the battery remains below the intensity threshold for a duration greater than a time threshold, and to continue this addition as long as the intensity remains below the intensity threshold.

According to another variant embodiment, the supply voltage of the circuit comprising the battery can be reduced if the absolute value of the intensity crossing the battery is below the intensity threshold, so as to oblige the battery, if it is connected. to its network, to charge a current in the network. The simple reading of the current passing through this battery then makes it possible to detect its possible disconnection. According to one embodiment, after adding the voltage signal without detecting the corresponding intensity signal, the amplitude of the voltage signal is increased and a measurement is made. new detection attempt. It is possible to make a single increase in the amplitude of the voltage signal, or to provide several amplitude levels to be tested one after the other. The voltage signal can be added to a setpoint controlling the output voltage of the converter. Here is called the output voltage of the converter, the voltage that the converter delivers to the network comprising the battery. According to another embodiment, the voltage signal can be produced by a dedicated oscillating circuit and be added to the output voltage of the converter.

The invention also proposes a motor vehicle equipped with two electrical networks having two different voltage levels and interconnected by a DC voltage converter (DC / DC). The converter is configured to recharge the battery, and the vehicle includes an estimator of the current through the battery. Preferably, the estimator is a current sensor connected directly between the negative terminal of the battery and the ground-i.e. without any other electrical consumer or connection point of an electrical consumer interposed between the battery terminal and the ground of the circuit, or connected directly between the positive terminal of the battery and the ground. The vehicle comprises means for adding a predefined voltage signal to a DC voltage delivered by the converter to the battery, and comprises filtering means able to detect in the intensity signal measured by the intensity estimator, a signal current corresponding to the added voltage signal. By corresponding intensity signal is meant a current intensity signal normally obtained during the transmission of the voltage signal, when the battery is correctly connected to the network. Typically, if the voltage signal is periodic, the intensity signal can be of a substantially identical frequency. If the voltage signal is a sudden change in voltage level, the intensity signal may be an offset of the previous intensity curve, a predefined sign depending on the sign of the voltage level change. The vehicle may include an electronic control unit configured to trigger the addition of the voltage signal when the absolute value of the current through the battery becomes below an intensity threshold. Preferably, the addition of the voltage signal is triggered if the absolute value of the intensity crossing the battery remains below an intensity threshold the intensity threshold may for example be between 0.5A and 2A according to the accuracy of the current measuring device - for a predefined period, for example for more than one second, or for a period of between 1 and 5s. Advantageously, the electronic control unit is configured to emit an alert message if for a duration greater than a duration threshold, the intensity signal is not detected while the voltage signal is added to the signal. DC output voltage of the converter. An alert message may for example be displayed at the driver's address, or be sent by voice synthesis. The alert message of the electronic control unit can lead to the implementation of safeguarding measures allowing the vehicle to arrive safely despite disconnection of the battery, for example a prohibition of the power off of the electrical network feeding the battery network through the converter. Safeguarding measures may include raising the idle speed of a combustion engine. The safeguarding measures may for example include the prohibition of a "stop and start" procedure with automatic shutdown of a heat engine during temporary stops of the vehicle if the engine uses a starter powered by the battery.

Other objects, features and advantages of the invention will appear on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings, in which: FIG. 1 is a diagrammatic representation of a vehicle equipped with a detection device according to the invention, - Figure 2 is a schematic representation of the electrical system of a vehicle equipped with a detection device according to the invention 1, and - Figure 3 is a simplified example of operating algorithm of a detection system according to the invention. As illustrated in FIG. 1, a vehicle according to the invention comprises a first electrical network 3 and a second electrical network 2, the first electrical network 3 or high voltage network operating at a substantially higher voltage, for example a voltage at less than 1.5 times higher and preferably substantially twice as high as the second network 2 or "low voltage" network 2. In the example illustrated, the vehicle 1 is a "light hybrid" type vehicle, it is that is to say that it comprises a heat engine 5 adapted to advance the vehicle and comprises at least one electric machine 6 which is connected to certain wheels of the vehicle so as to be able to contribute as an electric motor to supply the driving torque of the vehicle. progress of the vehicle. The electric machine 6 also functions as an electric generator, for example to recover electrical energy during so-called regenerative braking phases or to act as an alternator to supply the electrical network 2 for energy management purposes or charging the BT battery.

The heat engine may typically be associated with a starter 8 capable of mechanically starting the rotation of the heat engine when it is stopped, particularly for initial starts if the electrical network 3 (Batt HT 11 and electric machine 6) does not have the power necessary to ensure the start of the cold engine 5. The starter 8 is powered for example by the low voltage network 2. According to other embodiments, the heat engine 5 may not be associated with a starter 8 and be launched directly by the electrical machine 6 connected to the high voltage network 3 and providing other functions mentioned above. The second electrical network 2 is connected to a low voltage mass 21 and powered by a first low voltage battery 10. The low voltage battery 10 may for example have a nominal operating voltage of between 12 and 13 volts. The first high voltage electrical network 3 comprises a high voltage battery 11 and is connected to a high voltage mass 22 which may possibly be the same mass as the low voltage mass 21. In the absence of other current sources, for example the absence of production of electric current by the electrical machine 6, the high voltage network 3 is powered by the battery 11. A DC DC converter 4 ("DC / DC converter") is interposed between the low voltage network 2 and the high voltage network 3, so as to be able to send a direct current from the high voltage network 3 to the low voltage network 2. The converter 4 is controlled by an electronic control unit 12 which itself is supplied with low voltage current by the second network 2. The converter 4 may comprise an alternating voltage generator 13 made by a hardware solution or by a strategy integrated into the control software. which enables the DC voltage sent to the second low voltage network 2 to be superimposed on an AC component whose amplitude is smaller than the average DC voltage sent to the network 2. During the phases in which the converter 4 does not send current to the second network 2, it is powered only by the low voltage battery 10. The second low voltage network 2 typically includes low voltage consumers such as human-machine interfaces 23 allowing the driver to drive the vehicle and access the various controls of the vehicle, includes other consumers contributing to the comfort of the driver and passengers, these consumers 14 may for example include, a heating system, a sound system, and may include vehicle safety systems such as systems braking or trajectory control, steering assistance or visibility.

The low voltage battery 10 is connected to an intensity estimator 7, for example to a current sensor 7, screwed on the negative terminal of the battery 10. The intensity value I measured by the current sensor 7 is transmitted to the electronic control unit 12.

In the embodiment illustrated in FIG. 1, the voltage converter 4 comprises a signal generator 13 able to modify the output voltage of the converter 4, in other words the voltage that the converter 4 applies between the terminals through which it is connected. to the second low voltage network 2. The signal generator 13 may for example be configured to be able to add to the output voltage of the converter, a periodic signal, for example an alternating signal, or another type of signal such as an offset of the output voltage applied quickly and for a predefined time.

FIG. 2 diagrammatically illustrates the operation of a detection system according to the invention, making it possible to detect whether the low-voltage battery 10 is no longer connected to the low-voltage network 2. FIG. 2 shows elements that are common to FIG. 1, the same elements being designated by the same references. In FIG. 2, only a part of the low voltage network is represented, as well as the output of the converter 4. In the example illustrated in FIG. 2, the converter 4 is driven by the electronic control unit 12 by the sending a setpoint Ucons for delivering a DC output voltage Us to the low voltage network 2. This DC voltage Us is sent to a first input of an adder 18, the second input of an adder 18 receiving a voltage Uvar delivered by a AC voltage generator 16 external to the converter 4. The AC voltage generator 16 is for example powered by the converter 4, or is powered directly by the battery 11. The low voltage network 2 is thus powered, at the output of the adder 18, by a voltage UBT which has a DC component, and an oscillation component of reduced amplitude with respect to the average value of the DC component. The amplitude chosen is however such that it makes it possible to cause a variation of substantially the same frequency of the current I flowing through the low voltage battery 10, the amplitude of this current intensity oscillation being detectable by the current sensor 7 according to FIG. precision it has, for example an amplitude of the order of 1A or an amplitude of a few Amperes, for example between 1 to 3 A. The electronic control unit 12 is configured to be able to detect this AC component of the current I when the battery 10 is correctly connected to the low voltage network 2, in particular when the positive terminal 9 of the battery is connected to the output of the DC / DC converter and the negative terminal of the battery 10 is correctly connected to the low voltage mass 21 When the battery 10 is disconnected from the network 2 by any of its terminals, it is no longer traversed by the corrective current component. corresponding to the alternating voltage signal delivered by the alternating voltage generator 16. The current sensor 7 may for example be interposed between the negative terminal of the battery 10 and the low-voltage mass 21. The current sensor could, according to others variants, be placed directly on the + terminal of the battery 10. In order not to disturb too much the operation of low voltage consumers, it is possible to supply the low voltage network with a DC voltage from the converter 4, as long as the current detected by the current sensor 7 is greater in absolute value than a threshold intensity. Above this threshold intensity, depending on the sign of the intensity, it can be considered that either the battery delivers a current to the consumers 14, or it receives a charging current of the converter 4, and therefore it is a priori connected to the network 2.

Below this threshold intensity, it can be considered that either the DC / DC converter delivers the power supply to all the consumers of the network 2 without recharging the battery 10 or the battery is not properly connected to the network 2. In below this threshold intensity, the electronic control unit 12 can therefore trigger the generation of the alternating signal Uvar and at the same time perform a filtering of the intensity signal I arriving from the current sensor 7 in order to look for an AC current component corresponding to the Alternating voltage signal Uvar. According to some embodiments, a first amplitude of the alternating voltage signal Uvar can be added in a first step, and if this amplitude does not make it possible to obtain a detection of a corresponding signal of intensity, increase to one or more the amplitude of the signal Uvar while continuing to search for the signal corresponding to the level of the measured intensity - by the ammeter 7. When the amplitude of the signal 1. "), '' reaches a certain value and the a variable intensity signal is still not detected, the electronic control unit 12 may, for example, trigger an alert sent to the driver's attention to warn him of a bad connection of the battery, and may It also triggers an emergency operating mode in which the active converter 4 is kept until the vehicle controls are switched off in order to prevent the vehicle from being immobilized before reaching its destination. In some embodiments, the voltage signal may be driven by the same electronic control unit as that connected to the current sensor 7, so as to: control the amplitude of the voltage signals with feedback to from the oscillations of intensity of current possibly proven, and to avoid a divergence of these oscillations of intensity of current. FIG. 3 is a simplified representation, in the form of an algorithm 20, of a mode of activation of the electronic control unit 12 enabling it to estimate whether the battery 10 is indeed connected to the network 2. illustrated on the algorithm 20 of FIG. 3, the electronic control unit 12 regularly carries out a test 26 to check whether the absolute value of the intensity crossing the battery is greater than an Innie threshold value As long as this absolute value remains above the current threshold, the electronic continuous control unit monitors the absolute value of the current, and does not trigger the generation of the DC voltage output signal of the DC converter: / DC '4. When the absolute value of the intensity becomes lower or study intensity threshold 1 ,,, 'ie: when the test 26 is negative, we go to a step 27. The electronic control unit then analyzes the signal of .eaptenrH current: 7 to search for intensity signal corresponding to nredefinf generated either. directly by the converter either by one. device whose voltage is added to the DC / DC set voltage. If the current intensity signal is detected, here an electronic reciprocating signal returns to step 26 and continues. to monitor the absolute value of the intensity of current flowing through the battery. If the current intensity signal is not detected, the electronic control unit may proceed to a step 25 where it alerts the driver that the battery is disconnected, and where it triggers backup measures if necessary, to enable the vehicle to drive until the driver explicitly asks for the stop of the vehicle, considering himself as arrived at destination. According to other embodiments. if the electronic control unit, during the test 27, does not detect the desired current intensity signal, it can go to a step 28 where it controls an amplitude increase of the voltage signal at the output of the DC / DC . The control unit can then check, for example in a step 24, if the amplitude of the voltage -igrial has reached a threshold beyond which one no longer wishes to go. If the maximum allowable signal amplitude is reached and the intensity signal has still not been detected, it goes to alert 23 warning the driver that the battery is disconnected. Otherwise, once the amplitude of the voltage signal is increased, it returns to step 27 of intensity signal search to test whether this time a current signal has become detachable. The invention is not limited to the embodiments described and can be declined in many variants. The two networks: interconnected by the DCIDC converter can operate at nominal voltages close to or substantially equal nominal. It is conceivable to emit the predefined voltage signal continuously, superimposed on the DC voltage of the DC / DC converter. It is conceivable to emit the predefined voltage signal only in intervals of time, when the value ab, solue of the intensity crossing the battery passes below a certain threshold. According to another variant embodiment, a low AC component can be continuously emitted, and then the amplitude of this component can be increased if a corresponding intensity signal is not detectable. It is conceivable to continuously search for an alternating current component or to search for a specific current intensity signal only when the average absolute value of the intensity falls below a certain threshold. The voltage signal added to the DC output voltage of the converter may be a periodic signal, a constant frequency signal or a complex signal chosen to reproduce certain characteristics of the current noise usually generated by an alternator. The voltage signal Uvar may be a non-reciprocal periodic signal, or even a voltage increment applied in the form of a slot, that is to say comprising a rising edge, in an attempt to detect a corresponding sign current intensity increment. . The desired current intensity signal will then be non-reciprocating, and then, for example, a change in the absolute value of the intensity of the current will be sought. In other words, the voltage delivered by the converter 4 is increased or reduced, preferably as quickly as possible (while limiting the impact of this voltage change on the consumers of the network 2) by applying a rising voltage front or a falling edge, to set this voltage value to a new constant value. This rapid change of voltage delivered by the converter will preferably be controlled by the control electronics 12 by a modification of the target voltage. An acceptable alternative solution may be to integrate this converter output voltage change internally of the DC / DC converter. The advantage of this last type of signal is that it can allow the implementation of a simplified disconnection detection strategy in that it consists only in detecting that a non-zero current, the battery 10 before by reaction to this output voltage evolution of the converter 10 is discharged in order to ensure the supply continuity of the network 2, or load, according to the selected voltage evolution. It can also minimize the disturbances caused to the electrical consumers of the low voltage network 2 if the amplitude of the output voltage change of the converter can remain low while being sufficient to detect the reaction of the battery.

The system for detecting a bad battery connection according to the invention makes it possible to warn the driver if the battery is incorrectly connected and also makes it possible to set up procedures for safeguarding the operation of the vehicle so that it can arrive at good port without using low voltage battery.

Claims (10)

REVENDICATIONS1. Method for detecting an electric battery disconnection (10) in a system equipped with two electrical networks (2, 3) interconnected by a dc voltage converter (DC / DC) (4), the battery (10) belonging to one of the two networks (2), and the converter (4) being configured to recharge the battery (10), characterized in that a predefined voltage signal (Uvar) is added to a DC voltage component (Us) delivered by the converter (4) to the network (2) comprising the battery (10), and in that a current (I) passing through the battery (10) is measured by searching for a signal intensity of current (Ialternative) corresponding to the added voltage signal (Uvar), to verify that the battery (10) is connected to the network (2). 2. The detection method according to claim 1, wherein the added voltage signal (Uvar) and the desired intensity signal (Ialternative) comprise periodic signals. The detection method according to claim 1, wherein the added voltage signal is a predefined sign change in the voltage level, and the intensity signal is a predefined sign variation of the intensity level. 4. Detection method according to one of claims 1 to 3, wherein the voltage signal (Uvar) is not added and the current signal (Ialternative) is sought only when the absolute value of the intensity ( I) passing through the battery (10) is below an intensity threshold (Imin). 5. Detection method according to any one of the preceding claims, wherein, after adding the voltage signal (Uvar) without detecting the corresponding intensity signal (Ialternatif), the amplitude of the voltage signal is increased and makes a new attempt to detect the current intensity signal. 6. Detection method according to any one of the preceding claims, wherein the voltage signal is obtained by adding a signal to a set value controlling the output voltage of the converter (4). The detection method according to any one of claims 1 to 5, wherein the voltage signal (Uvar) is produced by a dedicated oscillating circuit (16) and is added to the output voltage (Us) of the converter (4). ). 8. Motor vehicle (1) equipped with two electrical networks (2, 3) interconnected by a DC voltage DC converter (4), the converter (4) being configured to recharge the battery (10) , the vehicle comprising an estimator (7) of the current intensity (I) passing through the battery (10), characterized in that the vehicle comprises means for adding a predefined voltage signal to a DC voltage delivered by the converter ( 4) to the battery (10), and filter means adapted to detect in the intensity signal (I) measured by the intensity estimator (7), a current intensity signal (lalternative) corresponding to the added voltage signal (Uvar). Vehicle according to claim 8, comprising an electronic control unit (12) configured to trigger the addition of the voltage signal (Uvar) when the absolute value of the intensity (I) of current flowing through the battery (10) becomes less than an intensity threshold (Imin). Vehicle according to one of Claims 8 or 9, in which the electronic control unit (12) is configured to emit an alert message if, for a duration greater than a duration threshold, the intensity signal ( Alternative) is not detected while the voltage signal (Uvar) is added to the DC output voltage (Us) of the converter.