FR2836604A1 - Electrical power supply by generator for charging battery, e.g. in vehicle, increases charging current when load is activated - Google Patents

Abstract

The supply comprises a generator (36) configured to generate a charge current and associated batteries (31,41) to generate an auxiliary current to supply power consuming devices (32,34), the system further includes a management unit designed to respond to a signal (C1,C2) for activating the power consuming device to modify a control (CTRL) of the operating mode of the power generator to increase the charging current in anticipation of an actual activation of the power consuming device.

Description

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TWO-VOLTAGE POWER SUPPLY SYSTEM
The present invention relates to a dual-voltage power supply system, and finds applications in particular in on-board networks for motor vehicles.

 The concept of a dual-voltage on-board network for the power supply of energy-consuming equipment on board motor vehicles has recently appeared as a response to the increase in the number and the operating power of these equipment.

 There is thus known a power supply system for a motor vehicle, comprising a high voltage network having a first battery delivering a first continuous supply voltage (hereinafter high voltage), and a low voltage network having a second battery delivering a second DC supply voltage (hereinafter low voltage), lower than said first DC supply voltage. The first battery is used to power high-power electrical loads, such as an air conditioning system, discharge lamp headlights, the vehicle starter, a controlled clutch device, window lift motors, etc. The second battery is used to power low-power electrical loads such as the dashboard or passenger compartment lighting means, the radio, the centralized locking / unlocking device for the doors, the signaling lights, etc.

 By battery is meant within the meaning of the present invention and hereinafter, any device forming a rechargeable electric energy reservoir, at the terminals of which a non-zero continuous electric voltage is available, at least in a non-zero state of charge of the device. Such a device thus consists, for example, of a conventional storage battery.

 A consensus currently seems to be emerging around the following voltage values, for the standardization of the dual-voltage on-board networks of motor vehicles of the future: 42 volts for high voltage, and 14 volts for low voltage.

 In a conventional on-board network (having a single-voltage electrical supply system), illustrated by the diagram in FIG. 1, one or more

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 devices consuming electrical energy such as 1 (electrical charges) are connected to the two terminals of a battery 2 to receive the DC supply voltage delivered by the latter. In other words, the device 1 is supplied by the supply voltage supplied by the battery 2. In addition, an electrical energy generator 3 (such as an alternator) is also connected to the terminals of the battery 2, and delivers a current of charge Ic. The device 1 can be either activated (it then consumes an electric current), or deactivated (it then consumes no electric current).

 In general, the charging current Ic is adapted to correspond to the current consumed by the device 1 when it is activated and / or to recharge the battery 2 when it is at least partially discharged. Admittedly, the alternator 3 operates continuously, since it is driven by the rotational movement of the engine of the vehicle when, of course, it is launched. However, the alternator includes regulation means to adapt the amount of electrical energy it generates per unit of time to what is necessary to respond to the current calls from the device 1 when it is activated and / or from the battery 2 when it is discharged.

 However, the alternator bandwidth, that is to say its response to a step of the current consumed in the on-board network, is low. It follows that the current calls by the high power electrical charges of the on-board network are not always taken into account by the alternator.

 This is illustrated by the graph in Figure 2. In this figure, curve 4 shows the shape of the current consumed in the on-board network, from a situation where the battery is fully charged and where no current consuming device of the on-board network is not activated (and where consequently the consumed current and the charging current Ic are zero) curve 5 shows the shape of the alternator's response, i.e. the current of charge Ic issued by the latter. On this graph, the original instant is taken as the instant when an electric charge of power is activated. In the following, the terms "anticipation" or "anticipate" are used with reference to this convention.

 The difference between the electrical energy supplied by the alternator 3 and the electrical energy consumed by the electrical load of power 1 is

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 graphically represented by area 6 between curves 4 and 5.

This zone 6 is the hatched zone in FIG. 2. This difference in electrical energy is supplied by the battery 2. This results in various drawbacks, in particular the need for oversizing the battery, the alternator and the section of cables connecting this one to that one, a reduced battery life, and variations in the supply voltage of the on-board network which affect the operation of on-board equipment.

 In a dual-voltage on-board network, the electrical supply system comprises two on-board networks, one (the high-voltage network) comprising the high-voltage battery and the equipment supplied by the high supply voltage which it delivers. , and the other (the low voltage network) comprising the low voltage battery and the equipment supplied by the low supply voltage which it delivers. A single electric current generator is included in the high voltage network, in particular in order to recharge the high voltage battery and to respond to current calls from the equipment of the high voltage network, which are hypothetically the most important. In addition, the high-voltage battery and the low-voltage battery are coupled together by means of an energy converter such as a switching voltage converter operating in step-down voltage (called "Buck" converter in jargon). skilled in the art). The purpose of this converter is to recharge the low voltage battery from the high supply voltage supplied by the high voltage battery.

 For such a system the aforementioned drawbacks, which are linked to the low bandwidth of the alternator, are incurred by the high voltage on-board network.

 The object of the present invention is to mitigate these drawbacks in the case of a two-voltage electrical supply system, comprising a high-voltage on-board network and a low-voltage on-board network, by taking advantage of the structural characteristics. of such a system.

 The invention thus provides a power supply system, in particular for a motor vehicle, comprising a first battery forming a reservoir of electrical energy (high voltage battery) and delivering a

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 first continuous supply voltage (high supply voltage), a second battery forming a reservoir of electrical energy (low voltage battery) and delivering a second continuous supply voltage (low supply voltage), lower than said first voltage supply, as well as at least one device consuming electrical energy (electrical power load), supplied by the first supply voltage, and controlled to be selectively activated or deactivated.

 According to the invention, the system comprises a reversible electrical energy converter arranged to, in a first operating mode, recharge the second battery from the first supply voltage, and to, in a second operating mode, recharge the first battery from the second supply voltage. The system further comprises a management unit arranged to place the voltage converter in the second operating mode in response to the activation or to an activation signal of at least one of said devices consuming electrical energy.

 Thus, the difference between the electric energy supplied by an electric current generator of the high voltage network and the electric energy consumed by the electric power load is partially supplied by the high voltage battery and partially by the low voltage battery. It follows that, for a given current draw, the drawbacks mentioned in the introduction which result from the low bandwidth of the generator, being borne by the two batteries at the same time and not by the high voltage battery alone, are reduced for each batteries compared to the case of a system according to the prior art.

 This advantage is obtained at the cost of implementing on the one hand a reversible converter, such as a reversible switching voltage converter called a "synchronous 8uck-8oost" converter in the jargon of a person skilled in the art, and on the other hand, an appropriate management unit.

 Another aspect of the invention relates to a method for managing a power supply system comprising a high voltage network having a first battery forming a reservoir of electrical energy (high voltage battery) and delivering a first continuous supply voltage ( high

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 supply voltage), a low voltage network having a second battery forming an electrical energy reservoir (low voltage battery) and delivering a second continuous supply voltage (low supply voltage), lower than said first supply voltage continuous, as well as at least one device consuming electrical energy (power load), supplied by the first continuous supply voltage, and controlled to be selectively activated or deactivated.

 According to the invention, the method comprises the method comprising the steps according to which: - a reversible electrical energy converter is arranged in order, in a first operating mode, to supply electrical energy to the low voltage network from the electrical energy stored in said first battery, and for, in a second mode of operation, supplying electrical energy to the high voltage network from the electrical energy stored in said second battery; and, - the voltage converter is placed in said second operating mode in response to the activation or to an activation signal of at least one device consuming electrical energy supplied by said first supply voltage, and controlled to be selectively enabled or disabled.

 When the system further comprises an electrical energy generator arranged to generate a charging current supplied to the high-voltage electrical network, an operating command of the electrical energy generator can be modified to increase the amount of electrical energy than the latter. this generates per unit of time, in response to an activation signal from the device consuming electrical energy but before the activation thereof.

 Other particularities and advantages of the present invention will appear in the description below of nonlimiting exemplary embodiments, with reference to the appended drawings, in which: - Figure 1, already analyzed is a diagram of a system of food according to the prior art;

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 - Figure 2, also already analyzed, is a graph illustrating the difference between the electrical energy consumed by an electrical load of power and the electrical energy produced by the alternator of the system of Figure 1; - Figure 3 is a diagram illustrating a first embodiment of a system according to the invention; - Figure 4 is a graph illustrating an example of exchange of electrical energy in a system according to Figure 3; - Figure 5 is a diagram illustrating a second embodiment of a system according to the invention; FIG. 6 is a graph illustrating the difference between the electrical energy consumed by a power load and the electrical energy produced by the alternator of the high voltage network in a system according to FIG. 5.

 In Figure 3, there is shown schematically a first embodiment of a system according to the invention. It is a dual-voltage electrical supply system, in particular for a motor vehicle, comprising a high voltage network 30 and a low voltage network 40.

 The high voltage network 30 includes a battery 31 forming a reservoir of electrical energy. The battery 31 delivers a continuous supply voltage, or high supply voltage VH.

 The high voltage network 30 also includes one or more devices consuming electrical energy, supplied by the high supply voltage VH. These are respective high-power equipment, such as that mentioned in the introduction. The devices 32, 34 are connected in parallel to the high-voltage battery 31. In the example of FIG. 3, each device such as 32 or 34 is connected to the terminals of the battery 31 in series with a respective on / off switch 33 or 35, so as to be controlled to be selectively activated or deactivated.

 Current flows through a device when activated. In other words, an activated device consumes an electric current. Conversely, no current flows in a deactivated device.

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 The switches 33, 35 are either control buttons actuated manually by a user, or electrically controlled switches, such as relays, power MOS transistors or the like.

 The high voltage network 30 finally comprises an electrical energy generator 36, suitable for generating a charging current Ic which is supplied to the high voltage network 30. It is for example a synchronous alternator (comprising an inductor circuit and a induced circuit) or a variable reluctance alternator-starter. It is connected in parallel with the high voltage battery 31, and therefore with the devices 32,34. The current Ic is suitable for recharging the high voltage battery 31, and for the current supply of the devices 32,34.

 The low voltage network 40 includes a battery 41 forming a reservoir of electrical energy. The battery 41 delivers a continuous supply voltage, or low supply voltage Vg.

 The low supply voltage VB is lower than the high supply voltage VH. In one example, the high voltage VH is equal to 42 volts and the low voltage VB is equal to 14 volts. The terms "high" and "low" used with reference to the supply voltages VH and VS respectively, should be interpreted relatively to each other only.

 The low voltage network 40 also includes one or more devices consuming electrical energy 42, 44 supplied by the low supply voltage VB. These are respective low power equipment, such as that mentioned in the introduction. The devices 42, 44 are connected in parallel on the low voltage battery 41. In the example of FIG. 3, each device such as 42 or 44 is connected to the terminals of the battery 41 in series with a respective on / off switch 43 or 45 having the same function as the aforementioned switches 33 and 35. In general, these will be control buttons that can be operated manually by a user.

 According to the invention, the system also comprises a reversible electrical energy converter 50. This is for example a current converter

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 limited in voltage. In one example, it is a switching DC / DC voltage converter, of the synchronous Buck-Boost type.

 The converter 50 is connected, via a first negative terminal 53 and a first positive terminal 52, to the negative and positive terminals of the high-voltage battery 31, respectively. Likewise, it is connected via a second negative terminal 53 and a second positive terminal 54, respectively at the negative and positive terminals of the low-voltage battery 41.

partir de la basse tension d'alimentation VL. Plus généralement, le convertisseur 50 est agencé pour fournir de l'énergie électrique au réseau basse tension 40 à partir de l'énergie électrique stockée dans la batterie haute tension 31 dans le mode abaisseur, et, inversement, pour fournir de l'énergie électrique au réseau haute tension 30 à partir de l'énergie électrique stockée dans la batterie basse-tension 41 dans le mode élévateur. The converter 50 is arranged for, in a first operating mode or step-down mode, recharging the low voltage battery 41 from the high supply voltage VH, and for, in a second operating mode or booster mode, recharging the battery high voltage 31 to

from the low supply voltage VL. More generally, the converter 50 is arranged to supply electrical energy to the low-voltage network 40 from the electrical energy stored in the high-voltage battery 31 in the step-down mode, and, conversely, to supply electrical energy to the high-voltage network 30 from the electrical energy stored in the low-voltage battery 41 in the boost mode.

 Thus, for example, in the booster mode, the generator 50 generates a charging current Ip which is delivered to the high voltage network 30 by the terminal 52 of the converter 50. The current Ip is said to be charging current by considering the point of view of the high voltage network 30, because, of course, it is generated by discharging the low voltage battery 41 from the low voltage network 40.

 The load current Ip which is generated by the converter 50 in the step-down mode in response to the activation of one of the high power devices such as 32 or 34, is a current of transient nature. Indeed, it aims to compensate for or at least attenuate the transient difference between the current draw in the high voltage network 30 and the load current Ic delivered by the current generator 36, which results from the low bandwidth of this last.

 Finally, the system comprises a management unit 60, such as a microcontroller or a microprocessor and its peripherals. The unit 60 is arranged to place the voltage converter 50 in said second mode of

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 operation (boost mode) in response to the activation of one or more of the devices consuming electrical energy from the high-voltage network, such as 32 or 34.

 To this end, the unit 60 comprises inputs 61 and 62 for receiving a detection signal DET1 and DET2 respectively, in the event of detection of the activation of the device respectively 31 and 32. The signal DET1 is for example the voltage at the terminals of the device 32, referenced with respect to the negative terminal of the low voltage battery 31. Similarly, the signal DET2 is the voltage across the terminals of the device 34, referenced with respect to the negative terminal of the low voltage battery 31. Thus, account given the internal impedance of the device 32 and / or 34, the signal DET1 and / or DET2 varies when the device respectively 32 and / or 34 is activated. This voltage variation is detected by the unit 60. It is possible to add a resistance in the device 32 and / or 34, if its internal resistance is not high enough for said variation to be detected by the unit 60 .

 In response to the detection of the activation of the device 32 and / or 34, the management unit 60 delivers, on an output 63, a control signal which is applied to a control input 55 of the converter 50. In an example , the link between the management unit 60 and the converter 50 comprises at least two wires, in order to be able to control the passage of the converter in more than two different determined states, in particular a state corresponding to a stop of operation, a state corresponding to the step-down mode and a state corresponding to step-up mode.

 It is advantageous that the control signal transmitted by the management unit 60 to the converter 50 is specific to, or contains an indication of the device or devices consuming electrical energy which has just been activated. In this way, the amount of electrical energy transferred from the low voltage network to the high voltage network can depend on and / or be specific to the electrical energy consuming device 32, 34 which is activated.

 On the graph of FIG. 4, in which the same elements as in FIG. 2 bear the same references, curve 7 gives an example of the shape of the transient load current Ip generated by the converter 50 in the booster mode in response to the activation of a power load in the

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 high voltage network 30 which generates a current draw symbolized by the curve 4 (from a given situation where the high voltage battery 31 is fully charged, and where no equipment of the high voltage network 30 is activated).

 As can be seen in the figure, which represents an ideal example, the load current Ip exactly compensates for the difference between the current call 4 in the network 30 which starts at time t = 0, and the current load Ic (curve 5) generated by the current generator 36. In particular, the current Ip has a value which corresponds to that of the current call 4 when the current Ic is still zero. Then, the current Ip decreases in proportion to the increase in the current Ic, to cancel out when the current Ic reaches the level of the current draw 4. This result can be obtained by appropriately controlling a duty cycle in the converter 50, as a function of the control signal which is transmitted by the management unit 60.

 However, this is not essential, and the object of the invention is achieved as soon as the difference between the current draw 4 and the load current Ic generated by the energy generator 36 (curve 5) is attenuated by the appearance of the charging current Ip supplied by the converter 50 from the energy stored in the low voltage battery 41.

The evolution of the current Ip can be fixed in advance, for example from a table of values of the duty cycle of the converter 50, which can be stored in the management unit 60 or in the converter 50. As indicated above, this development can also be determined selectively from knowledge of that of high power electrical energy consuming devices 32,34 which is activated at time t = 0. This can easily be done by the management unit 60 from the detection signals
DET1, DET2. As a variant or in addition, this change can be controlled dynamically, as a function of the intensity of the current draw 4 and / or of the change in the load current Ic generated by the current generator 36. To this end, one can take into account the level of the high supply voltage VH, and / or the voltage level of the detection signals
DET1, DET2.

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 In one example, the high voltage battery 31, and / or the low voltage battery 41 are storage batteries. Alternatively, one or the other of these batteries, or both, can also be batteries called "capacitive buffers", which include high value electrochemical capacitors (called "supercap" in the jargon of the 'skilled person) to store electrical energy in electrochemical form.

 The invention also provides a second embodiment, illustrated by the diagram in Figure 5 in which the same elements as in Figure 3 have the same references.

 In this second embodiment, the management unit 60 is, in addition, arranged to, in response to an activation signal from the device consuming electrical energy but before activation thereof, modify a command of operation of the electrical energy generator 36 in order to increase the amount of electrical energy that it generates per unit of time.

 For this purpose, the management unit can comprise two inputs 64 and 65 connected to the positive terminal of the low voltage battery 41 as shown (or of the high voltage battery 31, or of any other source of voltage in the system) by l 'Intermediate respective switches 71 and 72. These switches are for example control buttons operated by a user to activate the equipment devices 32 and 34 respectively.

Thus arranged, the switches 71 and 72 generate activation signals respectively C1 and C2 which are received by the inputs respectively 64 and 65 of the unit 60.

 In this second embodiment, the switches 23 and 35 which are mounted in series with the equipment respectively 32 and 34, are controlled switches.

 In response to the activation signals C1 and / or C2, the management unit 60 generates control signals respectively CTRL1 and / or CTRL2, which control the closing of the switches respectively 33 and / or 35 to activate the equipment respectively 32 and / or 34.

 The management unit 60 comprises timing means for delaying the generation of the control signals CTRL1, CTRL2 with respect to the reception of the corresponding activation signals C1, C2. However, from the

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 reception of an activation signal such as C1 or C2, the management unit generates a command CTRL3, which is delivered on an output 66 of the unit 60. The output 66 is connected to a command input 67 of the generator current 36, to transmit a control signal CTRL3 to it. The command CTRL3 is a command for modifying an operating instruction of the electrical energy generator 36, which determines the quantity of electrical energy that the latter generates per unit of time.

 Thus, the electric current generator 36 anticipates the current draw in the high voltage network 30 by preparing the production of electric energy before this energy is actually consumed by equipment of the network. By this anticipation, the drawbacks linked to the low bandwidth of the generator 36 are mitigated.

 When the electric power generator 36 is a synchronous alternator having an inductor circuit and an induced circuit, the above operating command is for example an excitation command of the inductor circuit with respect to a setpoint for regulating the voltage generated across the armature. By increasing this command, the increase in the amount of energy produced per unit of time by the generator 36 is prepared.

 When the electric power generator 36 is a variable reluctance alternator-starter, said operating command is for example a current regulation setpoint.

 The graph in FIG. 6, in which the same elements as in FIGS. 2 and 4 have the same references, curve 5 represents the shape of the charging current Ic generated by the generator 36. As can be seen in the figure , the curve 5 is shifted towards the negative values of the time axis (ie to the left), compared to the same curve in Figures 2 and 4. The time delay applied by the management unit between the activation signals C1, C2 on the one hand and the corresponding control signals CTRL1, CTRL2 on the other hand, is denoted To in the figure. It corresponds to the time difference between the instant when the curve 5 begins to grow from the zero value, and the instant t = 0.

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Ainsi qu'on peut le voir sur la figure 6, la zone 6'correspondant à la différence entre l'énergie électrique consommée dans le réseau haute tension 30 et l'énergie électrique produite par le générateur 36 (c'est-à-dire la zone hachurée comprise entre les courbes 4 et 5), est plus petite que la zone correspondante 6 de la figure 2 ou de la figure 4. Ceci se traduit par une atténuation des inconvénients mentionnés en application.

As can be seen in FIG. 6, the area 6 ′ corresponding to the difference between the electrical energy consumed in the high voltage network 30 and the electrical energy produced by the generator 36 (i.e. the hatched area between curves 4 and 5) is smaller than the corresponding area 6 in FIG. 2 or in FIG. 4. This results in an attenuation of the drawbacks mentioned in application.

 The second embodiment above is more advantageous than the first embodiment described above with reference to the diagram in FIG. 4, because it makes it possible to reduce the amount of electrical energy taken via the converter 50 from the low voltage network 40 , and more particularly to the low voltage battery 41.

 The invention has been described above in general, and in nonlimiting exemplary embodiments. Any variation in the concrete implementation is possible, without departing from the scope of the invention, according to the contingencies specific to a given application and / or to obtain other advantages.

 Thus, for example, the management unit 60 can advantageously be integrated into the energy converter 50, so that the latter can be produced in the form of a single circuit, acting as a body for managing electrical energy in the dual-voltage on-board network of the motor vehicle.

Claims (11)

 CLAIMS 1. Power supply system, in particular for a motor vehicle, comprising: - a high voltage electrical network (30) having a first battery (31) forming a reservoir of electrical energy and delivering a first continuous supply voltage (VH) ; - a low voltage electrical network (40) having a second battery (41) forming a reservoir of electrical energy and delivering a second continuous supply voltage (Vg), lower than said first supply voltage; - at least one device consuming electrical energy (32, 34), supplied by said first supply voltage, and controlled to be selectively activated or deactivated; - a reversible electrical energy converter (50) arranged to, in a first operating mode, supply electrical energy to the low-voltage network from the electrical energy stored in said first battery, and for, in a second operating mode, supplying electrical energy to the high voltage network from the electrical energy stored in said second battery; - a management unit (60) arranged to place the voltage converter in said second operating mode in response to the activation or to an activation signal of said device consuming electrical energy. 2. The system as claimed in claim 1, further comprising an electrical energy generator (36) arranged to generate a charging current () c) supplied to the high-voltage electrical network, and in which the management unit is, in addition , arranged for, in response to a signal (C1, C2) for activating the device consuming electrical energy but before activating it, modify a command (CTRL3) for operating the energy generator <Desc / CRUD Page number 15>  electrical to increase the amount of electrical energy it generates per unit of time. 3. The system as claimed in claim 2, in which the electric power generator being a synchronous alternator having an inductor circuit and an induced circuit, said operation command is an excitation command for the inductor circuit with respect to a regulation setpoint. of the voltage generated across the armature. 4. The system of claim 2, wherein the electric power generator being a variable reluctance alternator-starter, said operating command is a current regulation setpoint. 5. System according to any one of claims 1 to 4, in which the energy converter is a generator of voltage-limited current. 6. System according to any one of claims 1 to 5, in which the energy converter is a switching voltage converter of the synchronous Buck-Boost type. 7. System according to any one of claims 1 to 6, in which the management unit is integrated into the energy converter. 8. System according to any one of claims 1 to 7, wherein the first battery, and / or the second battery are accumulator batteries. 9. System according to any one of claims 1 to 8, in which the first battery, and / or the second battery are capacitive buffers.  10. A method of managing a power supply system comprising a high voltage electrical network (30) having a first battery (31) forming a reservoir of electrical energy and delivering a first continuous supply voltage (VH), a network low-voltage electric (40) <Desc / Clms Page number 16>  \ - the voltage converter is placed in said second operating mode in response to the activation or to an activation signal from at least one of said devices consuming electrical energy.

 having a second battery (41) forming a reservoir of electrical energy and delivering a second continuous supply voltage (Vg), lower than said first supply voltage, and at least one device for consuming electrical energy (32,34) supplied by said first supply voltage, and controlled to be selectively activated or deactivated, the method comprising the steps according to which: - a reversible electrical energy converter (50) is arranged to, in a first operating mode, supply electrical energy to the low voltage network from the electrical energy stored in said first battery, and for, in a second operating mode, supplying electrical energy to the high voltage network from the electrical energy stored in said second battery; 11. The method of claim 10, according to which, the system further comprising an electrical energy generator (36) arranged to generate a load current supplied to the high-voltage electrical network, an operation control of the energy generator is modified. electrical to increase the amount of electrical energy that it generates per unit of time, in response to an activation signal of the device consuming electrical energy but before the activation thereof.