CN105556320A - Method for detecting a disconnection of a power supply battery of a motor vehicle - Google Patents

Abstract

The invention proposes a method for detecting a disconnection of an electric battery (10) in a system provided with two electrical networks interconnected by a DC/DC voltage converter (4). The battery (10) belongs to one of the two networks (2), and the converter (4) is configured to recharge the battery (2). The method involves adding a predefined voltage signal (Uvar) to a continuous voltage component (Us) delivered by the converter (4) to the network (2) comprising the battery (10), and measuring the current (I) passing through the battery (10), searching for a current signal (Ialternatif) therein that corresponds to the added voltage signal (Uvar), in order to check that the battery (10) is correctly connected to the network (2).

Description

Method for detecting disconnection of a power supply battery of a motor vehicle

technical field

The invention relates to the protection of the power supply of an on-board network of a motor vehicle. The invention can also be applied more generally to power systems, in particular vehicular power systems, combining two power networks interconnected by DC/DC voltage converters (DC-to-DC converters), one of these networks consisting of the DC /DC converter recharges the power storage battery.

The invention relates more particularly to the protection of an automotive electrical system supplying low voltage electricity to a vehicle comprising two electrical networks interconnected by a DC/DC converter. The two networks can be operated with the same nominal voltage or with different nominal voltages. In vehicles where at least some electric machines are used to recover braking energy, or to help propel the vehicle, or both, the vehicle may typically include a high voltage network comprising a plurality of electric machines so as to be confined in conductors Joule effect losses and to enable the use of reduced diameter conductive cables.

Background technique

For other standard functions, the vehicle may include a second electrical network powered at a lower voltage. For example, a first power network operating at a voltage between 24 and 58 Volts, eg a voltage of 48 Volts, and a second low voltage power network operating at a nominal voltage between 10.5 and 15 Volts may be provided.

The second "low voltage" electricity network may comprise dedicated batteries recharged from the high voltage network by means of a DC/DC converter, for example during phases in which the vehicle is driven.

For reasons related to the management of the electrical energy of the "low voltage" network and to the management of the recharging of the "low voltage" accumulator, the DC/DC converter may be controlled by an electronic control unit which in turn is controlled by the The battery supplies power. For some safety functions of the vehicle it may be necessary to protect the power supply of the "low voltage" network. One way of protecting this power supply could be to use this redundant power supply on the one hand a "low voltage" battery and by supplying the low voltage network with power from the second network via a DC/DC converter. In this case it is important to check that the low-voltage battery is effectively connected to the low-voltage network before deactivating the power supply to the low-voltage network by the DC/DC converter, in order to later be able to secure power to the "low-voltage" network supply.

This may be the case, for example, for vehicles where energy savings are expected to benefit from a "stop and start" type of system in which the heat engine used to propel the vehicle is stopped during a stop at a red light and when the driver again presses on Quickly restarts when the accelerator pedal is on. If protection of the electricity supply to the "low voltage network" can be provided only by a "low voltage" battery, it is absolutely necessary to ensure that this "low voltage" battery is not disconnected prior to the automatic shutdown of the engine.

Patent application EP1958851 proposes the use of a second battery for protection of the low-voltage vehicle network. Adding a second battery increases the weight of the vehicle and increases the cost price of the vehicle.

Contents of the invention

The object of the present invention is to propose, in a motor vehicle supplied by two electrical networks interconnected by means of a DC/DC converter, especially when one of these networks comprises a battery recharged by means of the converter from the other network, to use A system for monitoring the proper connection of batteries in a low-voltage network. The network powered by means of the DC/DC converter sometimes includes starters, but generally does not include energy generators such as alternators or starter generators, which are carried on the first electrical network.

The proposed monitoring device must be reliable, must not interfere with the electrical components and consumers of the two networks, and must be able to be installed at low cost and without adding weight to the vehicle.

To this end, the invention proposes a method for detecting a disconnection of a power battery in a system equipped with two power networks interconnected by a direct current to direct current (DC/DC) converter, the battery Belongs to one of these two networks and the converter allows battery recharging, ie is connected so as to be able to recharge the battery.

More generally, the control of the converter is configured to ensure the supply of energy to the network comprising the battery when the converter is operating, and to recharge the battery so that the battery can in turn be power the network.

A predetermined voltage signal is added to the DC voltage component delivered by the converter to the network comprising the battery, and the current through the battery is measured by searching therein for an amperage signal corresponding to the added voltage signal , to confirm that the battery is properly connected to the network.

The system may eg be an electric motor vehicle or a hybrid motor vehicle. The converter may be configured such that at certain time intervals the battery is recharged, during necessary further time intervals the battery powers the network of which the battery forms part. The rated operating voltage of the network associated with the battery is preferably lower than the rated voltage of the other network. This further network preferably includes a second battery with an increased rated voltage. In this document, unless stated otherwise, the term "battery" automatically refers to a battery belonging to a network supplied with voltage by a converter, ie a network with a lower rated voltage. The network with a higher rated voltage may comprise a battery, but this battery is preferably referred to by the term "second battery".

According to an advantageous embodiment, the added voltage signal and the searched intensity signal are periodic signals.

These signals may eg be alternating periodic signals or periodic signals with a constant sign. The amplitude of these voltage signals is preferably reduced below the rated voltage of the network powered by the converter and the battery, for example less than 2V for a network rated close to 14V. The magnitude of the voltage signal may for example be comprised between 0.2V and 1.5V, preferably between 0.2V and 0.5V. The frequency of these periodic signals may for example be comprised between 20 Hz and 100 Hz. The frequency of these periodic signals may be constant. According to another variant, the periodic signal can be sent in a particular pattern, for example in such a pattern that the induced current noise obtained can approach that induced by a conventional alternator of a combustion-powered vehicle. Already developed signal strength detection strategies can then be used for such vehicles with alternators.

According to a particularly advantageous embodiment, the added voltage signal is a modification of a predetermined sign, a voltage level, and the intensity signal is a variation of a predetermined sign, an intensity level. This is a sudden change in voltage level of a predetermined sign, and the intensity signal is a change in intensity level of a predetermined sign. The magnitude of the variation of the voltage level is preferably reduced below the rated voltage of the network powered by the converter and by the battery. For example, a voltage step between 0.2V and 2V and preferably comprising between 0.2V and 1V may be applied.

According to one embodiment, the voltage signal is added and the current signal is searched for only if the absolute value of the intensity across the cell is below an intensity threshold. This intensity threshold is preferably constant. For example, if the absolute value of the intensity across the battery remains below the intensity threshold for a duration greater than the time threshold, the addition of the alternating voltage component may be activated and may be activated as long as the intensity remains below the intensity threshold Continue this addition.

According to another variant, if the absolute value of the intensity passing through the battery is below the intensity threshold, the supply voltage of the circuit comprising the battery may be reduced in order to cause the battery to output current in the network when connected to it. A simple reading of the current through this battery then makes it possible to detect its potential connectivity.

According to one embodiment, after the voltage signal has been added without a corresponding intensity signal being detected, the magnitude of the voltage signal is increased and a new detection attempt is made. A single increase in the magnitude of the voltage signal may be produced, or several magnitude levels tested in succession may be provided.

The voltage signal may be added to a setpoint value controlling the output voltage converter. The output voltage of the converter here means the voltage delivered by the converter to the network comprising the battery.

According to another embodiment, the voltage signal may be generated by a dedicated resonant circuit and may 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 means of a direct current to direct current (DC/DC) converter. The converter is configured to recharge the battery, and the vehicle includes an estimator for the magnitude of current passing through the battery. The estimator is preferably connected directly between the negative terminal of the battery and ground (i.e., without any other consumer or connection point of consumers between the ground of the circuit and the terminal of the battery), or by A current sensor connected directly between the positive terminal of the battery and ground.

The vehicle includes means for adding a predetermined voltage signal to the DC voltage delivered by the converter to the battery, and includes means capable of detecting, in the intensity signal measured by the intensity estimator, a signal corresponding to the added voltage signal. Filtering devices for current signals. The term corresponding to "strength signal" means the current strength signal normally obtained with the emission of the voltage signal when the battery is properly connected to the network. Typically, if the voltage signal is periodic, the intensity signal may be periodic with substantially the same frequency. If the voltage signal is a sudden change in voltage level, the intensity signal may be an offset to a previous intensity curve, an offset to a predetermined signal depending on the sign of the voltage level change.

The vehicle may comprise an electronic control unit configured to activate such an added voltage signal when the absolute value of the intensity of the current through the battery falls below an intensity threshold. If the absolute value of the intensity across the cell remains below an intensity threshold for a predetermined duration (for example more than 1 second), or for a duration between 1 and 5 s, the intensity threshold depends on the accuracy of the current measuring device. Such an added voltage signal is preferably activated if the degree can, for example, be comprised between 0.5 A and 2 A.

The electronic control unit is advantageously configured to issue a warning message if the intensity signal is not detected for a duration greater than a duration threshold even though the voltage signal has been added to the DC output voltage of the converter. Warning messages can be displayed, for example, to the driver or can be sounded. The warning message of the electronic control unit can lead to the implementation of protective measures allowing the driver to reach his destination safely despite the disconnection of the battery, such as prohibiting switching off the electricity network that supplies the battery's network by means of the converter . These protective measures may include increasing the idle speed of the heat engine. These safeguards may include, for example, prohibiting the "stop and start" procedure of automatic shutdown by the heat engine during temporary parking of the vehicle if the heat engine uses the starter powered by the battery.

Description of drawings

Further objects, features and advantages of the present invention will become more apparent by reading the following description, given solely by way of non-limiting example, and by reference to the accompanying drawings, in which:

- Figure 1 is a schematic view of a vehicle equipped with a detection device according to the invention,

- Figure 2 is a schematic diagram of the electrical system of a vehicle 1 equipped with a detection device according to the invention, and

- Figure 3 is a simplified example of the operating algorithm of the detection system according to the invention.

detailed description

As illustrated in FIG. 1 , the vehicle according to the invention comprises a first electrical network 3 and a second electrical network 2 , the first electrical network 3 or the high-voltage network operating at a significantly higher voltage, for example at least 2 or "low voltage" network 2 is 1.5 times larger and preferably substantially twice as large in voltage.

In the illustrated example, the vehicle 1 is of the "mild hybrid" type, that is to say it comprises a heat engine 5 capable of moving the vehicle forward and comprises at least one electric machine 6 connected to the vehicle some of the wheels so that they can act as electric motors to contribute to providing engine torque to propel the vehicle. The electric machine 6 also acts as a generator, e.g. to recover electrical energy during 'regenerative' braking phases or as an alternator to provide power to the electricity network for needs related to energy management or battery BT recharging. 2 power supply.

This heat engine may typically be associated with a starter 8 capable of mechanically starting the heat engine to spin when this heat engine is stopped, especially for the electricity network 3 (BattHT11 and electric machines 6) not available to ensure The situation of the necessary power for cold start of the heat engine 5 . The starter 8 is supplied, for example, by the low-voltage network 2 .

According to a further variant, the heat engine 5 may not be associated with the starter 8 and may be started directly by the electric machine 6 connected to the high-voltage network 3 and ensuring the additional functions cited above.

The second electricity network 2 is connected to low voltage ground 21 and is powered by the first low voltage battery 10 . The low-voltage battery 10 may, for example, have a nominal operating voltage comprised 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 ground 22 which may be the same ground as the low voltage ground 21 .

The high voltage network 3 is powered by the battery 11 when there are no other sources of current, for example when no current is generated by the electric machine 6 . A direct current to direct current converter 4 (“DC/DC converter”) is arranged between the low voltage network 2 and the high voltage network 3 in order to be able to send 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 in turn is supplied with low voltage current by the second network 2 . The converter 4 may comprise an AC voltage generator 13 provided by a hardware solution or by a strategy integrated in the control software, which makes it possible to make the ratio of the DC voltage to the second low voltage network 2 sent to the network 2 The AC component of the low voltage in the DC is superimposed.

During the phases when the converter 4 is not sending current to the second network 2 , this network is powered solely by the low-voltage battery 10 . The second low-voltage network 2 typically includes a number of low-voltage consumers (such as a human-machine interface 23 that allows the driver to control the vehicle and access various commands of the vehicle), and includes additional components that contribute to driver and passenger comfort. Electrical consumers, which may include, for example, a heating system, an audio system, and possibly vehicle safety systems (such as braking systems or route control systems, and directional or visibility assistance systems), for example.

The low voltage battery 10 is connected to a strength estimator 7 (for example to a current sensor 7 ), which is screwed to the negative terminal of the battery 10 . The value of the intensity I measured by the current sensor 7 is passed to the electronic control unit 12 .

In the embodiment shown in FIG. 1 , the voltage converter 4 comprises a signal generator 13 capable of modifying the output voltage of this converter 4 , in other words the converter 4 applies the voltage used for its connection to the second low-voltage network 2 . the voltage between these terminals. The signal generator 13 may, for example, be configured to be able to add a periodic signal, such as an AC signal or another type of signal, to the output voltage of the converter, such as applying a bias to the output voltage rapidly and for a predetermined duration. place.

FIG. 2 schematically illustrates the operation of the detection system according to the invention, making it possible to detect whether the low-voltage battery 10 is still connected to the low-voltage network 2 . A number of elements shown in Fig. 1 can be seen in Fig. 2, like elements being designated by like reference numerals. Only a part of this low-voltage network is shown in FIG. 2 , as well as the output of the converter 4 .

In the example shown in FIG. 2 , the converter 4 is controlled by the electronic control unit 12 by sending a setpoint Ucons in order to deliver a direct output voltage U _s to the low voltage network 2 . This DC voltage U _s is sent to a first input of an adder 18 whose second input receives a voltage U _var delivered by an AC voltage generator 16 arranged at the converter 4 external. The alternating voltage generator 16 is supplied, for example, by the converter 4 or directly by the battery 11 .

The low-voltage network 2 is therefore supplied at the output of the adder 18 with a voltage U _BT which has a DC component and an amplitude oscillation component which is reduced compared to the average value of the DC component. However, the amplitude is chosen such that it produces fluctuations of substantially the same frequency as the current I passing through the low-voltage battery 10, the amplitude of this current intensity oscillation can be detected by the current sensor 7 depending on its accuracy, for example about 1 A Amplitude or magnitude of a few amperes (for example between 1 and 3A).

The electronic control unit 12 is configured such that 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 network 2 When ground 21, this AC component of the current I can be detected. When the battery 10 is disconnected from the network 2 at any of its terminals, the alternating current component corresponding to the alternating signal of the voltage delivered by the alternating voltage generator 16 may no longer pass through said battery.

The current sensor 7 can be arranged, for example, between the negative terminal of the battery 10 and the low-voltage ground 21 . According to other variants, this current sensor can be arranged directly at the + terminal of the battery 10 .

In order not to interfere too much with the operation of the low-voltage consumer, the low-voltage network can be supplied with a DC voltage originating from the converter 4 when the absolute value of the current detected by the current sensor 7 is greater than a magnitude threshold. Above this intensity threshold, depending on the sign of the intensity, it can be expected that the battery outputs current to the consumers 14 , or receives charging current from the converter 4 , and thus connects the priori to the network 2 .

Below this threshold strength, it can be expected that the DC/DC converter delivers power supply to all electrical consumers of the network 2 without recharging the battery 10 or that the battery is not properly connected to the network 2 . Below this threshold intensity, the electronic control unit 12 can thus activate the generation of the alternating signal U _var and at the same time perform a filtering of the intensity signal I from the current sensor 7 in order to search therein for an alternating current component corresponding to the alternating voltage signal U _var .

According to some variants, in a first step an alternating voltage signal U _var of a first magnitude can be added and if this magnitude does not make it possible to obtain a detection result for a corresponding intensity signal, this can be increased one or more times The amplitude of the signal U _var while continuing to search for a signal corresponding to the level of intensity measured by the galvanometer 7 . When the amplitude of the signal U _var reaches a certain value and still no intensity variation signal is detected, the electronic control unit 12 may for example activate the sending of an alarm to the driver to warn of a bad connection of the battery and may also activate the emergency operating mode, In the emergency operating mode, the converter 4 remains active until the commanded total stop of the vehicle to prevent the vehicle from becoming immobile before reaching its destination.

In some embodiments, the voltage signals may be controlled by the same electronic control unit connected to the current sensor 7, so that the amplitude of these voltage signals can be controlled with feedback based on any amperage oscillations and thus avoid these amperage oscillations deviation.

FIG. 3 is a simplified illustration of the mode of operation of the electronic control unit 12 in the form of an algorithm 20 that allows said unit to estimate whether the battery 10 is efficiently and properly connected to the network 2 . As shown in the algorithm 20 of FIG. 3 , the electronic control unit 12 periodically performs a test 21 in order to check whether the absolute value of the intensity across the cell is greater than a threshold I _min .

If this absolute value remains above the intensity threshold I _min , the electronic control unit continues to monitor the absolute value of the intensity and does not activate the generation of an alternating voltage signal at the output of the DC/DC converter 4 .

When the absolute value of this intensity becomes lower than or equal to the intensity threshold I _min , ie when test 21 is negative, step 22 is performed. The electronic control unit then analyzes the signal of the current sensor 7 in order to search among them for an intensity signal corresponding to a predetermined signal generated directly by the DC/DC converter or by adding a voltage to the output voltage of the DC/DC output generated by one of the devices. If the amperage signal (here signal "Iac") is detected, the electronic control unit returns to step 21 and continues to monitor the absolute value of the amperage through the battery. If the amperage signal is not detected, the electronic control unit may go to step 25, wherein the electronic control unit warns the driver that the battery is disconnected, and wherein the electronic control unit activates the necessary protective measures in order to allow the vehicle Go until the driver explicitly asks the vehicle to stop considering that he has reached his destination.

According to other variants, if the electronic control unit does not detect the sought amperage signal during the test 22, the unit can go to step 23, in which the electronic control unit controls the increase in DC/ The magnitude of the voltage signal at the output of DC.

The control unit can then detect, for example in step 24 , whether the amplitude of the voltage signal has reached a threshold value which is not expected to be exceeded. If the maximum allowed signal amplitude is reached and no signal of this strength is still detected, an alarm 25 is provided to warn the driver that the battery is disconnected. Otherwise, once the amplitude of the voltage signal has been increased, it returns to step 22 in which the intensity signal is searched in order to test whether the current intensity signal becomes detectable this time.

The invention is not limited to the exemplary embodiments described and can be provided in many variants. The two networks interconnected by the DC/DC converter can be operated with similar rated voltages or even with substantially equal rated voltages.

The predetermined voltage signal superimposed with the DC voltage of the DC/DC converter may be issued permanently. The predetermined voltage signal may only be sent at time intervals when the absolute value of the intensity across the battery falls below a certain threshold.

According to another variant, a weak AC component can be emitted continuously and the amplitude of this component can be increased if a corresponding strength signal cannot be detected. The AC intensity component may be searched continuously, or a particular current intensity signal may be searched only when the average absolute value of the intensity drops below a certain threshold. This voltage signal that is added to the DC output voltage of the converter may be a periodic signal, a constant frequency signal, or a complex signal selected to replicate certain characteristics of the current noise typically generated by an alternator. The voltage signal U _var may be a periodic non-alternating signal or a voltage increment (ie comprising a rising leading edge) applied in the form of time slots in order to try to detect current intensity increments with corresponding signs. For example, the current intensity signal being searched for will thus be non-alternating, and a change in the absolute value of the intensity of this current will then be searched for. In other words, the voltage delivered by the converter 4 is increased or decreased by applying a voltage rising or falling leading edge (while limiting the effect of this voltage change on the consumers of the network 2 ), preferably as quickly as possible, so as to be consistent with the new A constant value of , establishes this voltage value. This rapid voltage change provided by the converter is preferably controlled by the electronic controller 12 through modification of the set point voltage. An acceptable alternative solution could be to integrate this modification of the converter output voltage within the DC/DC converter.

The advantage of this latter signal type is that it may allow the implementation of a simplified disconnection detection strategy, in that it consists only of detecting a non-zero current, in response to this progression of the output voltage of the converter 10, the battery 10 must make itself Discharge in order to ensure continuous power supply to the network 2, or recharge itself depending on the chosen voltage course. This type of signal also makes it possible to minimize interruptions generated at consumers of the low-voltage network 2 , if the magnitude of changing the output voltage of the converter can be kept small while at the same time being sufficient to detect the response 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 improperly connected and also makes it possible to put in place procedures to protect the operation of the vehicle, allowing the driver not to use low voltage batteries and reach its destination safely.

Claims (10)

1. A method for detecting disconnection of a power battery (10) in a system equipped with two power networks interconnected by a direct current to direct current (DC/DC) converter (4) ( 2, 3), the battery (10) belongs to one of the two networks (2), and the converter (4) is configured to recharge the battery (10), characterized in that a predetermined voltage signal (U _var ) is added to a DC voltage component (U _s ) delivered by the converter (4) to the network (2) including the battery (10), and in that the current through the battery (10) ( I) is measured in such a way that a current intensity signal ( _Iac ) corresponding to the added voltage signal (U _var ) is searched for in order to confirm that the battery (10) is properly connected to the network (2 ). 2. The detection method as claimed in claim 1, wherein the added voltage signal ( _Uvar ) and the searched intensity signal ( _Iac ) comprise a plurality of periodic signals. 3. The detection method of claim 1, wherein the added voltage signal is a modification of a predetermined sign, a voltage level, and the intensity signal is a variation of a predetermined sign, an intensity level. 4. The detection method as claimed in any one of claims 1 to 3, wherein only when the absolute value of the intensity (I) passing through the cell (10) is lower than an intensity threshold (I _min ), adding The voltage signal (U _var ) and the current signal ( _Iac ) are searched. 5. Detection method as claimed in any one of the preceding claims, wherein, after having added the voltage signal (U _var ) without detecting a corresponding intensity signal (I _AC ), the amplitude of the voltage signal is increased value, and a new attempt is made to detect this amperage signal. 6. The detection method as claimed in any one of the preceding claims, wherein the voltage signal is obtained by adding a signal to a setpoint value controlling the output voltage of the converter (4). 7. The detection method as claimed in any one of claims 1 to 5, wherein the voltage signal (U _var ) is generated by a dedicated resonant circuit (16) and added to the output of the converter (4) Voltage (U _s ). 8. A motor vehicle (1) equipped with two electrical networks (2, 3) interconnected by a direct current to direct current (DC/DC) converter (4), the converter (4) Configured to recharge the battery (10), the vehicle comprises an estimator (7) for the strength of the current (I) passing through the battery (10), characterized in that the vehicle comprises a predetermined The voltage signal is added to a DC voltage delivered by the converter (4) to the battery (10) and can be detected in the intensity signal (I) measured by the intensity estimator (7) in relation to the added Filter device for a current intensity signal ( _Iac ) corresponding to a voltage signal (U _var ). 9. The vehicle as claimed in claim 8, comprising an electronic control unit (12), which is configured to: when the absolute value of the current intensity (I) passing through the battery (10) drops below a The addition of this voltage signal (U _var ) is activated at an intensity threshold (I _min ). 10. The vehicle as claimed in one of claims 8 or 9, wherein the electronic control unit (12) is configured to: even if the voltage signal (U _var ) has been added to If the intensity signal ( _Iac ) is also not detected in the DC output voltage (U _s ) of the converter, a warning message is issued.