Power supply system

Abstract

The present invention relates to a power supply system for an electrical device comprising: - a DC power bus; - a first battery (BATT1) and a second battery (BATT2) connected in parallel and each capable of providing a first DC voltage on the DC power bus; - an auxiliary battery (B_AUX) configured to provide a second DC voltage (U_AUX); - a control unit (UC) configured to: select at least one battery from the first battery and the second battery in order to set the voltage on the DC power bus by connecting the at least one battery to the DC power bus; command the connection of the non-selected battery to the DC power bus and to charge the auxiliary battery (B_AUX) by setting the auxiliary battery in series with the non-selected battery and by switching the battery cells of the non-selected battery in order to control the charging current (I_aux) for the auxiliary battery.

Description

TECHNICAL FIELD

[0001] The present invention relates to an improved power supply system, particularly usable in electric or hybrid vehicles. BACKGROUND

[0002] The traction of electric or hybrid vehicles is achieved by using a battery pack of several electric energy storage batteries combined together.

[0003] The battery pack delivers a DC voltage in a known manner, and the task of the DC / AC converter is to convert this DC voltage in order to deliver a control voltage on its two or three phases (depending on the configuration of the motor) to the electric motor of the vehicle. The battery pack can comprise several batteries, each battery itself comprising several modules and each module usually comprising several electrochemical cells. The system can be reversible and the mechanical braking of the motor can also make it possible to charge the batteries of the battery pack in energy regeneration mode.

[0004] Furthermore, it is known that, in order to power the on-board network of the vehicle (i.e. for example, headlamps, windows, ABS, power steering) and more basic functions (such as remote central opening / closing), a standard 12V (or 24V) lead-acid battery is usually used. The presence of this additional lead-acid battery is due to the need to have a voltage of 12V even when the vehicle is not started and to have an independent 12V power supply that does not discharge the traction batteries. In the case of electric or hybrid vehicles, this auxiliary battery is charged by the battery pack of the vehicle through a DC / DC converter, or by an alternator in the case of combustion vehicles.

[0005] In applications other than motor vehicles, it can also be necessary to have an additional battery to start the system.

[0006] For reasons of weight, bulk and cost savings, it is desirable not to use such a DC / DC converter (or an alternator in the case of internal combustion vehicles). In this case, a simple solution is needed to charge the auxiliary battery, regardless of the system architecture and its operating mode, i.e. whether it is in normal power supply mode, in (regenerative) braking mode or in charging or discharging on the AC network.

[0007] In particular, the installation of the auxiliary battery must be able to adapt to an architecture that permanently delivers a constant DC voltage (for example 48V DC or 400V DC in electric vehicles) through a DC power bus.

[0008] The patent application EP20798148A2 has already described an architecture for electric or hybrid vehicles that is able to deliver different voltage levels without using a DC / DC converter.

[0009] The patent application US2018 / 043789A1 also describes a power supply system without DC / DC converter.

[0010] However, these previous solutions generally do not simultaneously satisfy both of the following conditions:

[0011] - maintain a constant voltage on the bus, and

[0012] - also charge the auxiliary battery.

[0013] It is therefore the object of the present invention to propose a power supply system that:

[0014] - is able to permanently deliver a DC voltage at a substantially constant level (within 5V) while the vehicle is running;

[0015] - integrates an auxiliary battery into its architecture and charges it without using a converter;

[0016] - is able to charge on an external AC network while maintaining the delivery of a DC voltage (low or high voltage);

[0017] - is able to deliver an AC voltage while maintaining the delivery of a DC voltage;

[0018] - avoids the use of electrical converters as much as possible.

[0019] This system will be particularly suitable for use in an electric or hybrid vehicle to participate in the traction of the vehicle and also to power the various devices of the vehicle. SUMMARY

[0020] This object is achieved by a power supply system for electrical devices, comprising:

[0021] - a DC power bus,

[0022] - a first battery able to deliver a first DC voltage on said DC power bus, said first battery comprising first battery cells, each first battery cell being switchable between an active state and an inactive state,

[0023] - an auxiliary battery configured to deliver a second DC voltage different from the first DC voltage,

[0024] - a control unit,

[0025] - a second battery able to deliver said first DC voltage on said DC power bus, said second battery being connected in parallel to said first battery, said second battery comprising second battery cells, each second battery cell being switchable between an active state and an inactive state,

[0026] - a first switching device arranged for connecting or disconnecting the first battery to / from the DC power bus,

[0027] - a second switching device arranged for connecting or disconnecting the second battery to / from the DC power bus,

[0028] - a third switching device configured to connect or disconnect the auxiliary battery in series with the first battery and / or in series with the second battery,

[0029] said control unit is configured to:

[0030] o select at least one battery among the first battery and the second battery in order to set said voltage on the DC power bus by connecting said at least one battery to the DC power bus,

[0031] o command to charge the auxiliary battery by connecting the unselected battery to the DC power bus and by setting the auxiliary battery in series with the unselected battery and by switching the battery cells of said unselected battery in order to control the charging current for said auxiliary battery.

[0032] The architecture of the invention has the advantage of being fully symmetrical since it can select one or the other of said two main batteries to deliver the voltage on the bus and can use the unselected battery to charge the auxiliary battery.

[0033] According to one particular feature, the first switching device is arranged to connect or disconnect the first battery to / from a charge / discharge unit intended to be connected to an AC network.

[0034] According to another particular feature, the second switching device is arranged to connect or disconnect the second battery to / from said charge / discharge unit.

[0035] According to another particular feature, the control unit is configured to command to charge the unselected battery by connecting it to said charge / discharge unit.

[0036] According to another particular feature, the control unit is configured to command to deliver a variable voltage to said charge / discharge unit by connecting the first battery or the second battery to said charge / discharge unit.

[0037] According to another particular feature, the control unit is configured to command to connect the auxiliary battery in series with both the first battery and the second battery in order to charge the auxiliary battery using the current present on the DC power bus.

[0038] According to another particular feature, the control unit comprises means for monitoring the following quantities:

[0039] o the voltage between the terminals of the first battery,

[0040] o the voltage between the terminals of the second battery,

[0041] o the voltage between the terminals of the auxiliary battery,

[0042] o the current flowing through the first branch having the first battery,

[0043] o the current flowing through the second branch having the second battery,

[0044] o the charging current for the auxiliary battery,

[0045] o the voltage of the DC power bus.

[0046] According to another particular feature, the control unit comprises means for determining and monitoring the state of charge of the first battery, the state of charge of the second battery and the state of charge of the auxiliary battery, on the basis of the values of the monitored quantities.

[0047] According to another particular feature, the control unit comprises means for controlling the charging current of the auxiliary battery by applying a connection phase and a connection disconnection phase between the auxiliary battery and said non-selected battery.

[0048] According to another particular feature, the first battery and the second battery each comprise a number of battery cells connected in series and in parallel, each battery cell comprising at least one capacitive component and some switching means.

[0049] The application also relates to a control method implemented in a control unit of a power supply system as described above, said method comprising the following steps:

[0050] - selecting at least one battery from among the first battery and the second battery, in order to transmit said voltage on the DC power bus by connecting said at least one battery to the DC power bus,

[0051] - commanding the connection of the non-selected battery to the DC power bus and the charging of the auxiliary battery by placing the auxiliary battery in series with the non-selected battery and by switching the battery cells of said non-selected battery in order to control the charging current for said auxiliary battery.

[0052] According to one particular feature, the control unit is configured to command the charging of the non-selected battery by connecting the non-selected battery to said charging / discharging unit.

[0053] According to another particular feature, the control unit is configured to command the connection of the auxiliary battery in series with both the first battery and the second battery, in order to charge the auxiliary battery using the current (I_R) present on the DC power bus.

[0054] According to another specific feature, the control unit is configured to command the delivery of a variable voltage to said charging / discharging unit by connecting the first battery or the second battery to said charging / discharging unit.

[0055] Finally, the application relates to the use of a system as defined above in an electric or hybrid vehicle in order to power one or more electrical devices of said vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0056] Other features and advantages will become apparent from the following detailed description, given with reference to the drawings listed below:

[0057] - Figure 1 The electrical architecture of the system is schematically illustrated;

[0058] - Figure 2 The control architecture of the system is schematically illustrated;

[0059] - Figure 3A 、 Figure 3B and Figure 3C The electrical architecture of the system is schematically illustrated; Figure 1 controlled to apply the three operating modes of the system;

[0060] - Figure 4 The principle of charging the auxiliary battery while charging on the network is illustrated;

[0061] - Figure 5 The principle of switching between the two batteries of the system so that a DC voltage can be continuously delivered is illustrated;

[0062] - Figure 6 An example of an embodiment of a transformer that can be used in the system of the application is illustrated;

[0063] - Figure 7 An example of an embodiment of a battery whose cells are switched is illustrated. DETAILED DESCRIPTION

[0064] In the remainder of the description, the term "DC" means "direct current" and the term "AC" means "alternating current". Reference will also be made to "AC voltage" to designate a variable voltage and to "DC voltage" to designate a continuous voltage.

[0065] The application relates to a power supply system for electrical devices. This system is particularly suitable for being installed in an electric or hybrid vehicle. The system is then located on the vehicle and can participate in the traction of the vehicle or in the powering of various devices of the vehicle.

[0066] The system comprises a DC power bus comprising two power lines L1, L2 between which a first DC voltage U DC can be applied. This voltage can be generated directly by a battery pack of suitable capacity. For battery packs used in electric or hybrid vehicles, this first voltage can be for example 48 V DC or 400 V DC. Furthermore, a charging current can occur on the bus in the case of electric vehicle braking or when charging through the combustion engine of a hybrid vehicle.

[0067] The power supply system thus comprises at least one battery pack.

[0068] In the context of the invention, the battery pack comprises at least a first battery BATT1 and a second battery BATT2.

[0069] Each battery can comprise several modules, each module comprising several electrical energy storage cells.

[0070] By "electrical energy storage cell" is meant a basic cell or a group of basic cells arranged in series and / or in parallel. By "basic cell" can be meant a storage element (cell, capacitor assembly, microbattery, etc.), a generator (fuel cell, zinc-air stack, photovoltaic cell), or a combination of the two (generator associated with a buffer storage element). If the switchable cell consists of a group of basic cells arranged in series and / or in parallel, the switchable cell can be switched as a whole between an active state and an inactive state (the switch applies to the terminals of the group of basic cells).

[0071] The battery pack is intended to deliver as output the first DC voltage U DC available on the DC power bus (for example 48 V DC or 400 V DC).

[0072] According to Figure 7 According to the particular features of the invention illustrated, each battery of the battery pack is Figure 7The batteries (BATT) in the system are produced according to an architecture known as switched battery cell architecture. This solution can replace the (DC / DC or DC / AC) converter at the output of the battery pack. In this architecture, each battery cell Cell_x can be controlled individually. Several battery cells connected in series and / or in parallel can form a module M_y. In particular, each battery cell of the battery pack can be switched between an active state and an inactive state by means of a suitable switching device S_x1, S_x2 connected in series-parallel with its capacitive component C_x (battery, capacitor or supercapacitor type). The task of the control system is then to control the switching devices so as to make the voltage delivered by each battery vary globally. This type of architecture is well known and is described in particular in patent application numbers WO2013 / 007810A1, WO2012 / 117111A1, WO2012 / 117110A2, WO2012 / 117 / 109A1 and US9493090B2.

[0073] Reference is made to Figure 1 , the two batteries BATT1, BATT2 of the system are connected in parallel between the two power lines L1, L2 of the DC power bus and form two distinct branches, a first branch with the first battery BATT1 and a second branch with the second battery BATT2. These two batteries can thus operate redundantly to deliver a DC voltage on the DC power bus. When one of these two batteries is delivering the voltage U DC of the DC power bus, the other battery can be charging on the AC network or delivering an AC voltage to components external to the system.

[0074] In this way, the system is able to permanently maintain the voltage U DC on the bus by selectively connecting one or the other of the two branches.

[0075] The first and second branches each comprise two connection terminals, a first terminal (B1 for the first branch, B3 for the second branch) intended to be connected to the first power line L1 of the bus and a second terminal (B2 for the first branch, B4 for the second branch) intended to be connected (directly or indirectly) to the second power line L2 of the bus. As will be seen below, the switching devices are arranged to manage the selective connection of each branch to the DC power bus.

[0076] In addition, the system comprises a third battery, called auxiliary battery B_AUX. This third battery can be, for example, a lead-acid battery, or indeed a battery of the iron-phosphate type, capable of delivering a voltage of 12 V or 24 V. It can, for example, power the on-board network of the vehicle, i.e. for example the headlamps, the windows, the ABS, the power steering, but also more basic functions such as remote-controlled central opening / closing. The auxiliary battery B_AUX comprises two terminals B5, B6 in order to be integrated into the system.

[0077] In addition, the system can have a transformer TR which forms a charging / discharging unit and comprises two terminals called input terminals B7, B8 and two terminals called output terminals B9, B10. The two output terminals of the transformer TR can be connected to an AC network in order to charge the system. In addition, it is also possible to provide an AC voltage at the output of the transformer (between the two output terminals B9, B10 of the transformer) based on a rectified voltage U_AC_r (for example a 48 V AC rectified voltage) provided by one or the other of the two batteries between the two input terminals B7, B8 of the transformer. In order to charge on the network, the cells of the battery of the charging battery (BATT1 or BATT2) are switched in a manner adapted to be in phase with the AC network. To this end, the switched architecture battery which must be charged on the AC network is controlled by the control system so that the AC current of the battery is perfectly in phase with the voltage of the network. An algorithm with as input data the voltage of the AC network or its rectified image and the exchange current between the network and the battery regulates the exchange current which is relative to a setpoint current which itself is substantially in phase with the voltage of the network. In one particular embodiment, via the operation of the transformer TR, the potential difference at the input (between the terminals B7 to B8) is an attenuation and rectified reproduction of the potential difference present between the output terminals (B9-B10). The current setpoint is then an image of the rectified network voltage, or indeed a rectified sinusoidal signal substantially in phase with the rectified network voltage.

[0078] The transformer can be of any type and is composed of several components which make it possible to charge the batteries on the AC network and to deliver an AC voltage. One example of an embodiment is presented in Figure 7 and will be described below.

[0079] According to one particular aspect of the application, the entire system can be operated according to various modes as follows:

[0080] - a first operating mode (MOD1), called normal operating mode: in the absence of a network, a constant DC voltage (for example 48 V DC or 400 V DC) is delivered on the DC power bus. Only one battery or two batteries can be connected to the bus in order to set the DC voltage. One of the two batteries can also be configured to control the charging current for the auxiliary battery.

[0081] - a second operating mode (MOD2), charging on the bus (in regenerative mode or by charging mode of the internal combustion engine): the system uses the current generated on the DC power bus to charge. One or both of the two batteries BATT1, BATT2 can be charged simultaneously by virtue of the current present on the bus. It is also possible to control one of the two batteries in order to control the charging current for the auxiliary battery B_AUX, the other battery then absorbing the current difference between the current flowing on the bus and the current absorbed by the battery managing the charging of the auxiliary battery B_AUX. As a variant, the two batteries can also charge the auxiliary battery B_AUX in parallel, while maintaining a constant DC voltage on the bus.

[0082] - a third operating mode (MOD3), charging on the AC network: the system synchronizes one of the two batteries (BATT1 or BATT2) with the AC voltage of the network in order to charge via the transformer TR. Thus, only one of the two batteries is charged on the network, the second battery having to maintain the DC voltage of the bus (for example 48 V DC or 400 V DC). When the batteries are charged on the network, the system itself can also connect the auxiliary battery B_AUX in series and control the charging current for the auxiliary battery B_AUX. The same principle applies in the case of delivery of a voltage U_AC outside the system (this is in order to deliver power to the grid or to power an external load). In the latter case, one of the two batteries is dedicated to the delivery of the voltage U_AC, while the other battery continues to deliver a constant DC voltage on the bus. Advantageously, the control of the battery delivering the voltage U_AC can be adapted to the type of equipment connected at the output (network or load). It is worth noting that if what is connected at the output is the grid ("vehicle-to-grid" use), the control of the battery advantageously makes it possible to control the phase and the amplitude of the output current relative to the network voltage.

[0083] In order to select the various operating modes and possibly to charge the auxiliary battery, the system comprises various switching means. Generally, these switching means must be able to:

[0084] - connect each battery BATT1, BATT2 in different ways to the two lines of the bus or to the two terminals of the transformer;

[0085] - connect the auxiliary battery B_AUX in series with the first battery and / or in series with the second battery;

[0086] - bypassing the auxiliary battery B_AUX.

[0087] In other words, it is possible to connect, as desired, between the two lines of the DC power bus or between the two terminals of the transformer:

[0088] - only the first battery or only the second battery, or

[0089] - both batteries in parallel, or

[0090] - the assembly of the first battery + the auxiliary battery in series, or

[0091] - the assembly of the second battery + the auxiliary battery in series, or

[0092] - the assembly of the first battery + the second battery + the auxiliary battery.

[0093] To achieve these objectives, the system can comprise various switching devices. With reference to the appended drawings, the system can thus comprise, without limitation:

[0094] - a first switching device C1 arranged in series with the first battery BATT1 and intended to connect the first battery to the first power line of the bus or to the first terminal of the transformer;

[0095] - a second switching device C2 arranged in series with the second battery BATT2 and intended to connect the second battery to the first power line of the bus or to the first terminal of the transformer;

[0096] - a third switching device C3 arranged to connect a first branch between the two power lines of the bus, directly or through the auxiliary battery B_AUX; the auxiliary battery is then placed in series with the first battery;

[0097] - a fourth switching device C4 arranged to connect a second branch between the two power lines of the bus, directly or through the auxiliary battery B_AUX; the auxiliary battery is then placed in series with the second battery.

[0098] For example, the first switching device C1 can comprise a first switch S1 arranged between the first terminal of the first branch and the first power line and a second switch S2 arranged between the first terminal of the first branch and the first terminal of the transformer.

[0099] For example, the second switching device C2 can comprise a first switch S3 arranged between the first terminal of the second branch and the first power line and a second switch S4 arranged between the first terminal of the second branch and the first terminal of the transformer.

[0100] For example, the third switching device C3 can comprise a first switch S5 arranged between the second terminal of the first branch and the second power line and a second switch S6 arranged between the second terminal of the first branch and the first terminal of the auxiliary battery, the second terminal of the auxiliary battery being directly connected to the second power line.

[0101] For example, the fourth switching device C4 can comprise a first switch S8 arranged between the second terminal of the second branch and the second power line and a second switch S7 arranged between the second terminal of the second branch and the first terminal of the auxiliary battery, the second terminal of the auxiliary battery being directly connected to the second power line.

[0102] Furthermore, with reference to Figure 2 , in order to manage the operating modes MOD1, MOD2, MOD3, the system comprises:

[0103] - means for measuring the voltage U_batt1 between the terminals of the first battery;

[0104] - means for measuring the current I_batt1 flowing through the first branch;

[0105] - means for measuring the voltage U_batt2 between the terminals of the second battery;

[0106] - means for measuring the current I_batt2 flowing through the second branch;

[0107] - means for measuring the voltage U_AC_r between the input terminals of the transformer;

[0108] - means for measuring the voltage U_AC between the output terminals of the transformer;

[0109] - means for transmitting control commands to the various switching devices;

[0110] - means for measuring the cell temperature of each battery of the system.

[0111] The system comprises a control and processing unit UC, the task of which is to manage the various operating modes and to control the switching devices and the cells of each battery in order to implement the selected operating mode. The control unit therefore comprises:

[0112] - means 10 for monitoring the following quantities:

[0113] o the voltage U_batt1 between the terminals of the first battery,

[0114] o the voltage U_batt2 between the terminals of the second battery,

[0115] o the voltage U_aux between the terminals of the auxiliary battery,

[0116] o the current I_batt1 flowing through the first branch,

[0117] o the current I_batt2 flowing through the second branch,

[0118] o the charging current I_aux of the auxiliary battery B_AUX,

[0119] o the voltage U_DC of the DC power bus,

[0120] o the voltage U_AC present between the output terminals of the transformer,

[0121] o the voltage U_AC_r present between the input terminals of the transformer;

[0122] - means 20 for determining and monitoring the state of charge SOC_batt1 of the first battery, the state of charge SOC_batt2 of the second battery and the state of charge SOC_aux of the auxiliary battery, based on the values of the monitored quantities;

[0123] - means 30 for determining the operating mode (MOD1, MOD2 or MOD3) to be applied, taking into account the various constraints:

[0124] o maintaining the voltage U_DC on the bus at a substantially constant level;

[0125] o maintaining the state of charge of the first battery and the state of charge of the second battery at a level higher than a defined threshold or at a substantially identical level (for example, balancing the voltage, or the balancing state of charge possibly weighted by temperature, ageing, power availability, etc.);

[0126] o maintaining the state of charge of the auxiliary battery above a defined threshold;

[0127] - a device 40 for determining the charging current I aux c to be applied to the auxiliary battery B AUX; depending on the state of charge of the auxiliary battery, there can be modulation of the magnitude of the charging current I aux c in order to optimize the quality of the charge. In a low state of charge SOC aux of the auxiliary battery, a large charging current can be delivered, and at the end of the charge, a reduction in the amplitude of the charging current will make it possible to achieve a deeper charge. In any case, the maximum charging current must not be exceeded. This maximum charging current can be determined in advance by the manufacturer (for example depending on the temperature and the condition of not deviating from the allowed voltage range). Optimally, this maximum charging current can depend on the state of charge of the auxiliary battery B AUX, its state of health and its internal impedance, in order to extend its service life without excessively compromising its charging time. Then, in application, one of the objectives is to keep this auxiliary battery B AUX as much charged as possible so that it remains fully available. If the current on the DC bus is negative and / or if there is no AC charging power from the network, the auxiliary battery B AUX will be kept in a charged state with the full phase. It should be noted that the worst operating case can be the mode referred to as "normal" mode MOD 1 summarized above, in which the auxiliary battery B AUX is not necessarily charged. In this case, the auxiliary battery will not be charged as long as its state of charge SOC aux is not critical and below a threshold. If the current needed on the DC bus is not too high, one of the two batteries BATT 1 or BATT 2 can switch to a current regulation mode in order to charge the auxiliary battery B AUX. The relative size of the capacities (in Ah) between the auxiliary battery and the two batteries BATT 1, BATT 2 makes it so that in most cases, the two batteries BATT 1, BATT 2 need to be charged before the auxiliary battery is over-discharged; therefore, this charging mode is rather rare. It can meet extreme cases, for example the vehicle being in a stationary or low speed (low power draw from BATT 1 and BATT 2) state, while accessories such as power steering draw a large current from the auxiliary battery;

[0128] - a device 50 for generating commands for the switching device in order to place the system in the selected operating mode, and for the switching of one or the other of the two battery cells Cell Batt 1, Cell Batt 2 in order to regulate the charging current of the auxiliary battery B AUX.

[0129] It should be noted that, considering the data collected, the control and processing unit UC is able to control the transition from one operating mode to another, in particular from the switching of the first battery BATT1 to the second battery BATT2, or vice versa, in order to deliver a voltage on the DC bus and perform the same operation in order to charge the auxiliary battery B_AUX. It is thus possible to permanently reconfigure the system, in particular in order to guarantee a good balance of the system (in terms of energy, heat, etc.); this advantage is obtained by the symmetrical structure proposed herein (the two main batteries can be statistically used in the same way, in particular ensuring a uniform aging and state of charge).

[0130] In each of the three operating modes summarized above, it can be provided to connect to the auxiliary battery B_AUX in order to charge it, as detailed below.

[0131] First operating mode Figure 3A : one of the two batteries (for example the second battery BATT2) is connected to the DC power bus in order to deliver a voltage U DC on the bus, and the auxiliary battery B_AUX can be connected in series with the other battery (here the first battery BATT1). The second battery BATT2 can generate a current I batt2. Thus, the first battery BATT1 is connected to the bus in order to draw a charging current I batt1 and is controlled by the control unit in order to deliver a charging current I aux suitable for charging the auxiliary battery B_AUX. Of course, the operation between the first and second batteries can be reversed.

[0132] Figure 3A The system architecture for implementing this first operating mode is illustrated. In Figure 3A , it can be seen that:

[0133] - by closing the switch S3 and the switch S8, the second branch is connected to the DC power bus.

[0134] - by closing the switch S1 and the switch S6, the first branch is connected to the DC power bus through the auxiliary battery.

[0135] A variant of this operating mode consists in connecting the two batteries BATT1 and BATT2 to the DC power bus in order to deliver a voltage U DC on the bus, and in disconnecting the battery B_AUX from the batteries BATT1 and BATT2 by opening the switches S6 and S7. This operating mode can be advantageous if a high power is required on the bus.

[0136] Second operating mode Figure 3BA current I_R is generated on the DC power bus (in regenerative braking mode or by means of the vehicle's internal combustion engine). This current I_R can be used to charge the auxiliary battery. The auxiliary battery B_AUX is thus connected in series with at least one of the two batteries, for example the first battery BATT1, and the at least one of the two batteries is connected to the bus and controlled by the control unit UC in order to generate a charging current I_aux suitable for charging the auxiliary battery B_AUX. The second battery BATT2 can also be connected to the bus in order to be charged with the current I_R available on the bus.

[0137] Figure 3B The system architecture for implementing the second operating mode is illustrated. In this figure, it can be seen that: Figure 3B

[0138] - by closing the switch S3 and the switch S8, the second branch is connected to the DC power bus.

[0139] - by closing the switch S1 and the switch S6, the first branch is connected to the DC power bus through the auxiliary battery.

[0140] According to the desired charging current of the auxiliary battery B_AUX, the second battery BATT2 can also be connected in series with the auxiliary battery B_AUX by closing the switches S3 and S7 and opening the switch S8. The auxiliary battery B_AUX then receives all the charging current I_R.

[0141] It should be noted that when the auxiliary battery B_AUX is connected in series with both batteries BATT1, BATT2, the charging current I_aux of the auxiliary battery can not be regulated and then directly corresponds to the charging current I_R.

[0142] Third operating mode Figure 3C : One or the other of the two batteries (BATT1) is charged on the AC network through the transformer TR. If necessary, the other battery, which is not charged, can continue to deliver the DC voltage. The auxiliary battery B_AUX can be charged through the branch that is being charged and connected to the AC network. The charging of the auxiliary battery B_AUX is controlled according to the voltage level of the network, the current flowing through the cells of the battery BATT1 and according to the state of charge of the auxiliary battery B_AUX. The auxiliary battery B_AUX can be connected as soon as the network voltage is greater than 12 V. The connection time of the auxiliary battery B_AUX depends on its state of charge.

[0143] Figure 3C The system architecture for implementing the third operating mode is illustrated. In this figure, it can be seen that:

[0144] - by closing the switch S3 and the switch S8, the second branch is connected to the DC power bus. ​

[0145] - by closing switch S2 and switch S6, the first branch is connected to the transformer through the auxiliary battery. In this configuration, it should be noted that when the potential difference between the input terminals B7 and B8 of the transformer falls below the voltage U_aux present between the terminals of the auxiliary battery, it can be necessary to open switch S6 and close switch S5.

[0146] Figure 4 The operating principle of the third operating mode is illustrated. This diagram shows a timing diagram which schematically illustrates the principle of connection and disconnection of the auxiliary battery B_AUX while it is charging. In this diagram, it can be seen that when the voltage U_AC exceeds 12V, the auxiliary battery B_AUX is connected, this connection having a duration period T1. In this configuration, since the auxiliary battery B_AUX sees all the charging current of the battery to which it is connected, in order to regulate the power delivered to the auxiliary battery, the auxiliary battery B_AUX is disconnected, this disconnection having a duration period T2. This disconnection period T2 can have any width between 0 and the time interval separating the beginning of the period T1 and the end of the period T3. Likewise, the period T2 can have any temporal position, starting from the moment when the period T2 falls between the beginning of the period T1 and the end of the period T3. As a variant, between the beginning of the period T1 and the end of the period T3, the period T2 can be distributed in the form of several discontinuous zones.

[0147] Figure 5 The diagram shown illustrates how to switch the two batteries BATT1, BATT2 without modifying the principle of charging of the auxiliary battery while charging on the AC network.

[0148] In order to perform the functions carried out by each branch of the battery pack and thus to maintain the voltage U_DC, the control unit UC must follow the following steps:

[0149] - initially, one of the two batteries (BATT1) delivers the voltage U_DC, the other battery (BATT2) is connected to the transformer in order to deliver an AC voltage useful outside the system or to charge on the AC network.

[0150] - at tl: the battery cells of the second battery BATT2 are commanded to be switched in order to stop charging (for example at zero voltage).

[0151] - at t2: the second switching device C2 is controlled in order to disconnect the battery BATT2 from the network.

[0152] - at t3: the battery cells of the second battery BATT2 are commanded to be switched in order to generate a voltage V_DC (for example 48V DC or 400V DC).

[0153] - at t4: the first and second switching devices C1 and C2 are controlled so as to connect the first and second batteries BATT1 and BATT2 to the DC power bus. The two batteries are then in parallel to deliver the voltage U DC.

[0154] - at t5: the battery cells of the first battery are commanded to be switched so as to make the first battery stop delivering the voltage U DC.

[0155] - at t6: the first switching device C1 is controlled so as to disconnect the first battery BATT1 from the DC power bus.

[0156] - at t7: the battery cells of the first battery BATT1 are commanded to be switched so as to follow the network voltage U AC.

[0157] - at t8: the first switching device is controlled so as to connect the first battery BATT1 to the network (or so as to deliver a voltage useful outside the system).

[0158] When switching between the two main batteries, the principle of connecting the auxiliary battery as explained above in connection with Figure 4 remains valid.

[0159] With reference to Figure 6 , even if it does not constitute the core of the invention, it should be noted that the transformer TR can be a simple 50 / 60 Hz transformer associated with an active rectifier bridge. This 50 / 60 Hz transformer makes it possible to reduce the voltage of the AC network before rectification to generate a voltage compatible with the voltages that the first and second batteries BATT1 and BATT2 can manage.

[0160] • when charging on the network, its rectifier bridge can therefore be in passive mode, equivalent to a diode or active bridge, to reduce the losses in the switches.

[0161] • when generating an AC voltage (for example 110 V or 230 V AC), it is necessary to control its rectifier bridge so that it generates positive and negative half-waves, the two batteries BATT1 and BATT2 being able to generate only positive arcs. The transformer then indeed sees an AC voltage, which is essential for the operation of the transformer.

[0162] As a variant, it is also possible to use a transformer called HF ("high frequency") transformer, which is smaller in volume. The input voltage is then made to change polarity at high frequency (typically > 10 kHz) and then made to flow into the high frequency transformer. At the output of this transformer, the high frequency voltage is rectified, it can be necessary to invert one of the two "low frequency" half-waves if one wants to restore the negative polarity.

[0163] In Figure 6Below the diagram, it is possible to see the effect of each stage on the signal. From the moment the appropriate command is sent to the switch, the power of the operation is bidirectional. Therefore, it is possible to both charge from the network and deliver an AC voltage similar to the network voltage from the battery.

[0164] From the preceding text, it can be understood that the solution has many advantages, among which:

[0165] - By making the two batteries redundant, it is possible to permanently deliver a constant voltage on the DC power bus;

[0166] - It is possible to charge the auxiliary battery in all operating modes;

[0167] - It is possible to deliver the various voltages required to implement the operating modes without specific DC / DC or DC / AC converters;

[0168] - It is possible to deliver an AC voltage to components external to the system.

Claims

1. A power supply system for electrical equipment, comprising: -DC power bus, - A first battery (BATT1) capable of delivering a first DC voltage on the DC power bus, the first battery comprising first battery cells, each of the first battery cells being capable of switching between an active and a passive state. - An auxiliary battery (B_AUX) is configured to deliver a second DC voltage (U_AUX) different from the first DC voltage. -Control unit (UC), The power supply system is characterized by comprising: - A second battery (BATT2) capable of delivering the first DC voltage on the DC power bus, the second battery being connected in parallel with the first battery, the second battery comprising second battery cells, each of the second battery cells being capable of switching between an active and a passive state. - A first switching device (C1) is arranged to connect or disconnect the first battery from the DC power bus. - A second switching device (C2) arranged to connect or disconnect the second battery from the DC power bus. - A third switching device (C3, C4) is configured to connect or disconnect the auxiliary battery in series with the first battery and / or connect or disconnect it in series with the second battery. The control unit (UC) is configured to: o Select at least one battery from the first battery and the second battery, so as to set the voltage on the DC power bus by connecting the at least one battery to the DC power bus. The o command connects the unselected battery to the DC power bus and commands the auxiliary battery (B_AUX) to charge by setting the auxiliary battery (B_AUX) in series with the unselected battery and by switching the battery cells of the unselected battery to control the charging current (I_aux) for the auxiliary battery.

2. The system according to claim 1, characterized in that, The first switching device (C1) is arranged to connect or disconnect the first battery from a charging / discharging unit intended for connection to an AC network.

3. The system according to claim 2, characterized in that, The second switching device (C2) is arranged to connect or disconnect the second battery from the charging / discharging unit.

4. The system according to claim 3, characterized in that, The control unit (UC) is configured to command the charging of the unselected battery by connecting the unselected battery to the charging / discharging unit.

5. The system according to any one of claims 2 to 4, characterized in that, The control unit (UC) is configured to command a variable voltage to be delivered to the charging / discharging unit by connecting the first battery or the second battery to the charging / discharging unit.

6. The system according to any one of claims 1 to 5, characterized in that, The control unit (UC) is configured to command the auxiliary battery (B_AUX) to be connected in series with both the first battery (BATT1) and the second battery (BATT2) so as to charge the auxiliary battery using the current (I_R) present on the DC power bus.

7. The system according to any one of claims 1 to 6, characterized in that, The control unit includes a device (10) for monitoring the following parameters: o The voltage between the terminals of the first battery (U_batt1), o The voltage between the terminals of the second battery (U_batt2), o The voltage (U_aux) between the terminals of the auxiliary battery, The current (I_batt1) flowing through the first branch containing the first battery. The current (I_batt2) flowing through the second branch containing the second battery. o is the charging current (I_aux) used for the auxiliary battery (B_AUX). o The voltage of the DC power bus (U_DC).

8. The system according to claim 7, characterized in that, The control unit (UC) includes means (20) for determining and monitoring the state of charge (SOC_batt1) of the first battery, the state of charge (SOC_batt2) of the second battery, and the state of charge (SOC_aux) of the auxiliary battery based on the values ​​of the monitored parameters.

9. The system according to any one of claims 1 to 8, characterized in that, The control unit includes means for controlling the charging current (I_aux) of the auxiliary battery (B_AUX) by applying a connection phase and a connection disconnect phase between the auxiliary battery and the unselected battery.

10. The system according to any one of claims 1 to 9, characterized in that, Both the first battery and the second battery include several battery cells connected in series and parallel, and each battery cell includes at least one capacitor component and some switching devices.

11. A control method implemented in a control unit (UC) of a power supply system as defined in any one of the preceding claims, characterized in that, Includes the following steps: - Select at least one battery from the first battery and the second battery so as to deliver the voltage on the DC power bus by connecting the at least one battery to the DC power bus. The command connects the unselected battery to the DC power bus and commands the auxiliary battery (B_AUX) to be charged by setting the auxiliary battery (B_AUX) in series with the unselected battery and by switching the battery cells of the unselected battery to control the charging current (I_aux) for the auxiliary battery.

12. The method according to claim 11, characterized in that, The control unit is configured to command the charging of the unselected battery by connecting the unselected battery to the charging / discharging unit.

13. The method according to claim 11 or 12, characterized in that, The control unit is configured to command the auxiliary battery to be connected in series with both the first battery (BATT1) and the second battery (BATT2) so as to charge the auxiliary battery (B_AUX) using the current (I_R) present on the DC power bus.

14. The method according to claim 12, characterized in that, The control unit (UC) is configured to command a variable voltage to be delivered to the charging / discharging unit by connecting the first battery or the second battery to the charging / discharging unit.

15. Use of the system as defined in any one of claims 1 to 10 in an electric or hybrid vehicle for supplying power to one or more electrical devices of the vehicle.

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