Battery system comprising means for synchronizing voltage and regulating current with a power supply network

Abstract

The present invention relates to a battery system comprising a distributed multilevel inverter in elementary modules of cells of the battery, allowing the generation of an alternating voltage waveform on a current line of the battery and bidirectional operation on a power supply network. According to the invention, the battery control unit comprises a means (20) for determining electrical characteristics of an alternating voltage waveform of the supply network (RES), a means (21) for synchronising the electrical characteristics of an alternating voltage waveform of the current line (LT1, LT2, LT3) of the battery system (BAT) with the power supply network waveform (RES), an electrical connection means (Kres) for connecting the current line (LT1, LT2, LT3) to the supply network (RES), controlled based on the synchronisation state (STE) of the voltage waveforms of the battery system (BAT) and the network (RES), and a means for regulating the current (22) of the battery system (BAT) by controlling a voltage setpoint (Vref) of the current line of the battery system (BAT).

Description

DESCRIPTION TITLE: BATTERY SYSTEM COMPRISING MEANS FOR SYNCHRONIZING VOLTAGE AND CURRENT REGULATION WITH AN ELECTRICAL POWER SUPPLY NETWORK

[0001] The present invention claims priority from French application No. 2300095 filed on 05.01.2023, the content of which (text, drawings and claims) is incorporated herein by reference.

[0002] The field of the invention relates to an electrochemical cell battery system comprising elementary cell modules forming a multilevel inverter distributed in the battery.

[0003] In stationary applications, electrochemical batteries are used in high-voltage power grids for grid regulation and to store energy generated by photovoltaic and wind power installations, among others. In the automotive sector, plug-in hybrid electric vehicles (PHEVs) include a battery and power electronics equipped with a voltage converter to adapt the current and voltage delivered by the battery to the various onboard electronic components of the vehicle. For these vehicles, the power electronics typically include a charger that converts alternating current (AC) to direct current (DC) for recharging the battery from a wide-area AC power grid.

[0004] Bidirectional chargers allow the battery to be charged from the mains power supply and discharged to an external electrical system in the case of so-called V2X (Vehicle-to-Everything) applications. For example, documents W0-A1-2022 / 200144 and W0-A1-2021004639A1 describe a vehicle power supply system comprising a bidirectional charger capable of charging the battery from mains power and supplying power to an external load connected to a separate, dedicated vehicle outlet.

[0005] These battery discharge solutions are designed solely for powering a load connected to a vehicle's electrical outlet and do not provide discharge to a mains power supply. Furthermore, these bidirectional chargers require AC / DC and DC / AC converter stages that typically experience energy losses of 10 to 20% of the delivered power during conversion.

[0006] The aim is to improve the energy efficiency of battery power systems. The applicant has developed a disruptive architecture known as a distributed multilevel inverter, which eliminates the need for the voltage converters typically integrated between an electrochemical cell battery and the AC power grid. This architecture has been the subject of several patent applications by the applicant. Examples include documents W0-A1-2017 / 153366, W0-A1-2021 / 048477, and FR-A1-3121797. These documents describe a cell architecture comprising current lines formed by elementary modules, each containing an electrochemical cell, or a cluster of cells, and a switching module forming an H-bridge.These documents also describe innovative control methods for this architecture, enabling the balancing of cell loads and the generation of polyphase or direct current.

[0007] More specifically, it is possible to generate an alternating voltage and current from the battery output that can be directly fed into an electric motor or the power grid. This architecture is particularly efficient because electrical efficiencies during charging and discharging have been measured to exceed 96%, and, most importantly, it eliminates the need for voltage conversion stages in electromobility applications. In stationary applications, particularly for renewable energy installations, where the battery system stores energy or regulates the grid through controlled discharge, it is possible to connect the battery system directly to the power grid without integrating a power conversion system (PCS). This results in significant cost savings.

[0008] The aim is to propose an electrical energy storage system that addresses the aforementioned problems and improves the connection of such a system to the electrical grid. One objective of the invention is to provide a battery system for electromobility and stationary applications based on an integrated multilevel inverter structure, enabling bidirectional operation of the battery system with the single-phase and polyphase AC power grid. Another objective of the invention is to provide a solution that optimizes current regulation during charging and discharging on the power grid.

[0009] More specifically, the invention relates to an electrochemical cell battery system designed to be recharged / discharged on an extended power supply network operating at alternating voltage. The system comprises at least one current line having a plurality of elementary modules, each equipped with a cell or a cluster of cells, forming a distributed multilevel inverter, and a control unit for the elementary modules capable of generating a selected alternating voltage waveform at the terminals of the current line according to a reference voltage setpoint. According to the invention, the system further comprises:

[0010] - a means of determining the electrical characteristics of an alternating voltage waveform from the power supply network,

[0011] - a means of synchronizing the electrical characteristics of an alternating voltage waveform from the battery system's current line with the alternating voltage waveform from the power grid,

[0012] - a means of electrically connecting the power line to the power grid, controlled according to a synchronization state of the voltage waves of the battery system and the grid,

[0013] - a means of regulating the current of the battery system by controlling the reference voltage setpoint of the current line of the battery system.

[0014] The system according to the invention may include the following additional features, alone or in combination:

[0015] - it comprises three current lines in which the synchronization means includes a means of transforming the measured voltages of the battery system and network lines into first vector commands, a means of determining a first voltage setpoint in vector command by a first regulator taking the first vector commands as inputs, and a first means of modulating the first voltage setpoint into a reference voltage setpoint of the battery system;

[0016] - it comprises three current lines in which the current regulation means includes a means of transforming measured currents from the battery system lines and a reference current setpoint into second vector current commands, a means of determining a second voltage setpoint in vector control by a second regulator taking the second vector commands as inputs and a second means of modulating the second voltage setpoint into a reference voltage setpoint of the battery system;

[0017] - it also includes an estimator of the phases of the power supply network, and in which the means of transformation of the first and / or second vector commands also depend on said phase estimates.

[0018] - it also includes an estimator of the voltage amplitude difference between the voltage waveform of the power grid and the battery system and in which the synchronization state is dependent on the deviation from a predetermined error threshold.

[0019] The invention further relates to an electrified motor vehicle comprising a rechargeable battery system and an electrical interface for connecting the battery system to an extended power supply network for charging and discharging from the power supply network, in which the battery system is according to any one of the preceding embodiments.

[0020] The invention further relates to a stationary battery system comprising a rechargeable battery system and an electrical interface for connecting the battery system to a power supply network. extended electrical system in which the battery system is according to any of the preceding embodiments.

[0021] A method for controlling an electrochemical cell battery system for discharge / recharge on an extended power supply network is also envisaged, comprising the following successive steps:

[0022] - the determination of electrical characteristics of an alternating voltage waveform from the power supply network,

[0023] - the synchronization of the electrical characteristics of an alternating voltage waveform from at least one current line of the battery system with the alternating voltage waveform of the power grid,

[0024] - the electrical connection of the power line to the power grid in case it is detected that the synchronization state of the voltage waves of the battery system and the grid is below a predetermined error threshold,

[0025] - then the regulation of the current of the battery system line by controlling a reference voltage setpoint adapted to the control of the current line of the battery system.

[0026] According to one variant, the synchronization process involves the following steps:

[0027] - the transformation of measured voltages from battery system and grid lines into initial vector commands,

[0028] - the determination of a first voltage setpoint in vector control by a first regulator taking as inputs the first vector commands,

[0029] - the modulation of the first voltage setpoint in vector control to generate the reference voltage setpoint adapted to the control of the battery system to generate the voltage wave to be synchronized.

[0030] According to one variant, the current regulation of the battery system involves the following steps:

[0031] - the transformation of measured currents from the battery system lines and a reference current setpoint into second vector current commands,

[0032] - the determination of a second voltage setpoint in vector control by a second regulator taking the second vector commands as inputs,

[0033] - the modulation of the second voltage setpoint in vector control to generate the reference voltage setpoint adapted to the control of the battery system to regulate the charge / discharge current of the battery system.

[0034] The invention further provides for the battery system control unit according to the invention, comprising integrated circuit means specifically configured to implement the control method for charging and discharging into the electrical power supply network. The invention further provides for a computer program comprising instructions which, when executed by a battery system control unit, cause the unit to implement any one of the embodiments of the control method for charging and discharging into an electrical power supply network.

[0035] The invention offers the following advantages:

[0036] The synchronization and current regulation process by the control unit improves the safety of charging or discharging by preventing overcurrent at the time of closing the high-voltage contactors.

[0037] The energy efficiency during charging is significantly higher than known state-of-the-art solutions, reaching approximately 98.5% experimentally. In electromobility applications, the cost of charging, and therefore of using a vehicle, is greatly reduced.

[0038] Furthermore, this charging principle uses the same components whether charging at 11 kW, 22 kW, or even higher in three-phase, and these same components are used to provide traction for the vehicle. In a conventional architecture, it is generally necessary to differentiate the components of Conversion for high-power charging, above 300 kW, and those for traction. This reduces the cost of power electronics.

[0039] Other features and advantages of the present invention will become more apparent upon reading the following detailed description, which includes embodiments of the invention given by way of non-limiting examples and illustrated by the accompanying drawings, in which:

[0040] [Fig.1] schematically represents one embodiment of the electrical architecture of the battery system according to the invention;

[0041] [Fig.2] represents the synchronization and current regulation functions of the battery system according to the invention;

[0042] [Fig.3] are graphs illustrating the voltage and phase synchronization phase of the current lines of the battery system according to the control method according to the invention;

[0043] [Fig. 4] are graphs illustrating the current regulation phase of the current lines of the battery system according to the control method according to the invention;

[0044] [Fig.5] represents a method of controlling the battery system according to the invention allowing the charging and discharging of the battery system on an electrical power supply network and the regulation of the current;

[0045] [Fig.6] schematically represents one embodiment of the battery system for an electrified vehicle.

[0046] The invention relates to an energy storage system for electrified motor vehicles and stationary storage systems in electrical installations, for example, for renewable energy or grid regulation installations. The system comprises an electrochemical battery with interconnected elementary cell modules forming a distributed multilevel inverter structure within the battery, allowing the battery to be connected to an electrical system operating at both direct and alternating voltage without the need for an inverter. The battery system can be directly connected to a wide-area power grid and to an electric drive machine. More specifically, the invention relates to means and method for synchronizing the battery system and for regulating the charge and discharge current on a power supply network.

[0047] In this description, the term distributed multilevel inverter means that the current line, or each current line of the battery, in the case of a polyphase architecture, particularly three-phase, is formed by a plurality of elementary modules. Each elementary module comprises a cell or a cluster of cells, as well as a switching module forming an H-bridge. The control unit includes a means of controlling the elementary modules of the current line according to a reference setpoint and is capable of generating a chosen AC voltage waveform on each current line. This architecture is described in more detail in Figure 1.

[0048] Referring to Figure 1, the BAT battery system comprises MCLk elementary modules forming the distributed multilevel inverter structure within the battery and includes three current lines LT1, LT2, and LT3 in which the MCLk elementary modules are arranged. Alternatively, the BAT battery system may have a single current line LT1, only two current lines, or four or more current lines. In summary, the battery system can be single-phase or polyphase. The BAT battery system includes high-voltage switches Kres, also called high-voltage contactors, for electrically connecting the BAT battery to the power grid RES. Each current line LT1, LT2, and LT3 is connected on one side to a grid connection switch, KR1, KR2, and KR3 respectively, and on the other side to a neutral terminal N of the battery.The extended RES power supply network operates on alternating current voltages of 50Hz or 60Hz, for example. The BAT battery system can produce three three-phase voltages offset by 2TT / 3. The control of each current line is similar, differing only by a 2TT / 3 offset between them.

[0049] In the case of an electromobility application, the BAT battery system also includes Kmel high-voltage switches for electrically connecting the BAT battery to the MEL electric drive machine. Each current line LT1, LT2, and LT3 is connected on one side to a connection switch on the electric drive machine, KM1, KM2, and KM3 respectively, and on the other connected to a neutral terminal (N) of the battery. The electric motor can be an asynchronous or synchronous machine, possibly a DC machine since the battery system is capable of generating any form of voltage waveform, alternating or direct.

[0050] Furthermore, switches (not shown in Figure 1) can be provided to electrically connect the three lines LT1, LT2, and LT3 in series, thus allowing the BAT battery to be connected to a single-phase network. Alternatively, the BAT battery system may optionally include a single current line LT1.

[0051] The BAT battery system has a voltage of several hundred volts at its terminals, for example, 350 volts or 1000 volts. In a 350-volt system, each LT1, LT2, LT3 line is equipped, for example, with 24 elementary cell modules or cell clusters connected in series. However, depending on the electrical requirements, the BAT battery system has a nominal voltage of only several tens of volts (24V, 36V, 48V, for example), particularly for automotive applications, or a maximum voltage of 1500 volts DC or even higher, especially for stationary storage systems.

[0052] The battery system (BAT) also includes a BMS control unit, one of whose functions is to control the voltage waveform of line LT1, or each line LT1, LT2, and LT3, based on a reference setpoint Vref, using the MCLk elementary modules. Each MCLk elementary module can contain a single CLk cell, or a cluster of CLk cells of two, three, four, five, six, or more, forming the elementary voltage Vclk. The MCLk elementary module also includes a COMk switching module capable of configuring the MCLk elementary module into three different states to deliver the Vmclk voltage, which is respectively the said elementary voltage Vclk, a zero voltage, and the inverted Vclk voltage at the connection terminals of the MCLk module.

[0053] The COMk switching module, for example, consists of two switching parts forming an H-bridge that can be controlled in three different states by a control signal from the battery's BMS control unit (BAT), specifically addressing the MCLk module. The states are represented by a The control variable uik can take, for example, the values ​​1, 0, -1, representing the three different states respectively controlling the elementary voltage Vclk, a zero voltage, and the inverted voltage -Vclk at the connection terminals of the elementary module k addressed by the control signal uik. Each switching module COMk comprises electronic components, such as power transistors, possibly of the MOSFET or HEMT (High Electron Mobility Transistor) type, driven by the control signals of the BMS control unit. Thus, the voltage Vmclk across each elementary module MCLk within a set of n modules can be controlled according to a control signal uik based on the following relationship:

[0054] [Math 1]

[0056] The BMS control unit can control, on each voltage line LT1, LT2, and LT3, any voltage waveform consisting of steps of amplitude equal to the elementary voltage Vclk, according to a reference voltage setpoint Vref. The reference voltage setpoint Vref can be a sinusoidal waveform with a frequency of 50 Hz, any alternating waveform, for example a square wave, or it can be a constant voltage, for example.

[0057] Within the framework of the invention, the control unit includes means for synchronizing the reference voltage setpoint Vref with a network voltage and for regulating a charge and discharge current by regulating the reference setpoint Vref. The BMS control unit is capable of determining at any given time the number q of elementary modules required from the plurality n to produce the voltage waveform for each phase voltage required by the setpoint Vref, where all elementary cells have the same elementary voltage Vclk.

[0058] An electrochemical cell is a battery that stores electrical energy and has two terminals, a positive electrode and a negative electrode, with a voltage of a few volts, most often between 2.3V and 4.2V. Cells can be of the Lithium-ion, Nickel-Cadmium, or Nickel-metal hydride (NMH) cells. More precisely, a lithium-ion cell is primarily composed of a porous positive electrode, a porous negative electrode, a separator, and an electrolyte. The operating principle of a lithium-ion cell is based on the reversible exchange of lithium ions between the two porous electrodes. Cells can be, for example, of the lithium iron phosphate (LIPH) type, lithium polymer (LIPH) type, or with a solid electrolyte.

[0059] With reference to Figure 2, the means of the BMS control unit are described that implement the function of synchronizing the voltage waves generated by the battery system and regulating the charge and discharge current once the battery system is electrically connected to the power grid. This embodiment relates to the case of three-phase voltage synchronization. The synchronization function occurs before the battery system is electrically connected to the power grid, i.e., before the switches KR1, KR2, and KR3 are closed, in order to prevent an overcurrent situation at the time of connection. This embodiment described in Figure 2 is not limiting; in particular, variants of voltage synchronization and current regulation for the battery system can be considered for single-phase or polyphase systems, i.e., two-phase, three-phase, or more.

[0060] The BMS control unit is equipped with an integrated circuit computer and electronic memories, the computer and memories being configured for the functions involved in current synchronization and regulation. The control unit can be implemented in the form of software modules (or computer modules), or electronic circuits (or hardware), or a combination of electronic circuits and software modules such as ASIC (Application Specific Integrated Circuit) or DSP (Digital Signal Processor) type circuits.

[0061] The BMS control unit includes means to estimate or measure the instantaneous electrical characteristics of a voltage waveform Vres of each current line in the power grid. This measurement is possible when the battery system is not yet electrically connected to the grid, i.e., when switches KR1, KR2, and KR3 are open. Furthermore, the control unit includes means to estimate or measure the characteristics Instantaneous electrical values ​​of the voltage Vbat and current Ibat of each current line in the battery system. Referring to Figure 2, these values ​​are represented by the inputs Vres, Vbat, and Ibat, respectively, of the BMS control unit. These values ​​allow for the estimation of the Vres voltage of the power supply network.

[0062] Furthermore, a means is provided 20 for estimating the phase of each current line in the power supply network. It allows for the simultaneous estimation of the frequency (around 50 Hz or 60 Hz) and the phase shift 201 of the network voltages.

[0063] The BMS control unit includes a voltage regulation module 21 whose function is to synchronize the power supply network and the battery system in voltage and phase, and a current regulation module 22 which intervenes to control the charging and discharging current once the battery system is synchronized with the network.

[0064] The function of the regulation module 21 is to regulate the voltage, amplitude, and phase of the battery system voltages, taking the mains voltages as a reference. From this regulator 21, the control unit determines a reference voltage (Vref) which drives the battery cell cluster control module to generate the voltage waves on each line during the synchronization phase.

[0065] The control module 21 can act either directly on sinusoidal quantities, or via the control of estimated direct and quadrature components, or through control techniques involving mathematical transforms, for example. In single-phase or polyphase (two-phase, three-phase, or more), the control module 21 includes a control loop implementing a controller based on the estimated electrical characteristics of the battery system and the power grid to drive the reference voltage Vref of the line or each current line of the battery system.

[0066] In the case of a three-phase application, as shown in Figure 2, means are provided 210 and 211 to transform the voltage signals from the power grid Vres and the battery system Vbat into a digital model of vector controls in the Park plane Vresl and Vbat1 respectively, with a rotating field at 50 Hz. The resulting vector controls Vresl and Vbat1 are used in a control loop by a controller 212 to determine a voltage setpoint for the battery system in the form of a vector control setpoint Vsync. In addition, the controller 212 determines an instantaneous error estimate Verr of the voltage signals.

[0067] The transformation means 210 and 211 are mathematical and signal processing functions that execute a Park transform, a concept familiar to those skilled in the art in the field of electrical engineering for controlling a three-phase electrical machine. The Park transform has the advantage of simplifying and improving the performance of current and voltage controllers. The possibility of implementing other control principles is not excluded. The controller 212 is a known control function that those skilled in the art can adapt for controlling the voltage setpoint. The controller 212 is, for example, of the proportional-integral type. Other types of controllers are conceivable. Alternatively, the transformation means 210 and 211 can be estimators of the sinusoidal electrical characteristics of the measured signals or estimators of the direct and quadrature components.

[0068] A control switching module 23 selects either voltage regulation during the synchronization phase or current regulation once synchronization is achieved. Module 23 uses a control switching block 231 that activates one or the other control mode based on the estimated error Verr between the network and battery system voltages.

[0069] More specifically, a block 230 compares the Verr error signal to a predetermined threshold. As long as the Verr signal is above the threshold, the voltage regulation remains operational. The resulting Vsync voltage setpoint from the regulation block 21 is used to drive the battery and generate the waveform on each of the current lines.

[0070] When the Verr signal falls below the threshold, block 230 detects that the voltage synchronization is correct in amplitude and phase shift, and that the battery system can be electrically connected to the grid. This activates the battery system's current regulation. Since the voltages are synchronized, an overcurrent effect in the battery system is avoided. The block 230 is capable of controlling the Kres high voltage switches referenced in Figure 1. When synchronization is detected and maintained stable for a confirmation time, the switches are closed.

[0071] In addition, the BMS control unit includes a modulation function 24 allowing it to deliver a voltage setpoint suitable for controlling the battery system from a voltage setpoint coming from either the voltage regulation module 21 or the current regulation module 22. For voltage synchronization, block 240 operates the modulation of the Vsync setpoint at the output of the voltage regulation control loop.

[0072] Similar to transformation blocks 210 and 211, block 240 takes as input the phase shift estimate 201 of the network voltage signals so that the inverse transformation adapts to any variability in the network phases.

[0073] Figure 3 shows a graph simulating the battery system voltage synchronization operation. The x-axis represents the time axis. The upper frame of this graph represents the battery system voltage on a current line and the mains voltage, configured in this example as 400 Volts RMS, on the corresponding line. The middle frame represents the synchronization error Verr between the mains and battery system voltages, expressed in Volts. The lower frame represents the number Qcl of cell clusters activated during synchronization. In this example, the current line has 24 cell clusters connected in series to the battery current line.

[0074] This graph shows that the first battery cell clusters are activated starting at 0.2 seconds, and that the error decreases and then stabilizes at 0.6 seconds. The upper frame shows the gradual increase in battery voltage (Vbat) as cells activate, with 22 of the 24 clusters being used. Simultaneously, the synchronization error decreases, and after a confirmation period, the control unit closes the current line contactor, activating current regulation.

[0075] With reference to Figure 2, the function of the regulation module 22 is to regulate the current of the battery system by taking the following input parameters A reference current setpoint Iref and the estimated instantaneous current Ibat on the battery system in Irms value. From this regulator 22, the control unit determines a setpoint Vref which drives the battery cell cluster control module to generate the voltage waves on each line during the synchronization phase.

[0076] Current regulation is achieved by controlling the battery system's reference voltage (Vref). This regulation is achieved through a feedback loop that controls the measured battery current and a current setpoint. The resulting current flowing through the battery system depends on the voltage difference relative to the grid voltage. Regulating the voltage to a value higher than the grid voltage commands a discharge current, and regulating the voltage to a value lower than the grid voltage commands a recharge current.

[0077] The current regulation module 22 can act either directly on sinusoidal quantities, or via the control of the estimated direct and quadrature components, or through control techniques involving mathematical transforms, for example. In single-phase or polyphase (two-phase, three-phase, or more), the regulation module 22 includes a control loop implementing a controller based on the measured electrical characteristics of the battery system and a current setpoint to drive the voltage setpoint Vref of the line or each current line of the battery system.

[0078] In the case of a three-phase application, as shown in Figure 2, means 220 and 221 are provided for transforming a current setpoint Iref in RMS amperes and the measured current of the battery system Ibat into vector commands in the Park plane Irefl and Ibatl respectively, with a rotating field at 50 Hz. The resulting vector commands Irefl and Ibatl are used in a control loop by a controller 222 to determine a voltage setpoint for the battery system in the form of a vector control setpoint Vregc.

[0079] The transformation means 220 and 221 are mathematical and signal processing functions executing a Park transform, known to those skilled in the art in the field of electrical engineering for the Control of a three-phase electrical machine. The Park transform has the advantage of simplifying and improving the performance of current and voltage controllers. The possibility of implementing other control principles is not ruled out. The controller 222 is a known feedback control function that a person skilled in the art can adapt for controlling the voltage setpoint. The controller 222 is, for example, of the proportional-integral type. Other types of controllers are conceivable. Alternatively, the transformation means 220 and 221 can be estimators of the electrical characteristics of the measured signals or estimators of the direct and quadrature components.

[0080] Each of the voltage regulation transformation blocks 210 and 211, and the current regulation blocks 220 and 221, takes as input the phase shift estimate 201 of the grid voltage signals so that the vector commands used in the regulation loop adapt to any variability in the grid phases. Indeed, the phases are likely to vary in the event of a load surge or an increase in grid power generation. This improves the accuracy of the synchronization and current regulation.

[0081] The Vregc setpoint in vector control, derived from the current regulation 22, ensures current control by regulating the voltage setpoint Vref of the battery system for the current line(s). The Vregc setpoint is transmitted to the modulation block 240 once synchronization is confirmed to provide a reference voltage setpoint suitable for driving the battery system. The same modulation block 240 used for synchronization 21 is used, or a different modulation block specifically designed for current regulation.

[0082] Figure 4 shows a graph simulating the current regulation operation of the battery system. The x-axis represents the time axis. The upper frame of this graph represents the reference current Iref and the resulting RMS current of a current line. The middle frame represents the current of the network line 1res and the corresponding current of the battery system line. The lower frame represents the number Qcl of cell clusters activated during current regulation. In this example, The current line consists of 24 clusters of cells connected in series in the battery current line.

[0083] This graph shows that starting at 1.15 seconds, a current setpoint Iref is set to 16A RMS. Very quickly, the battery current increases until it reaches the setpoint Iref at 1.4 seconds. The current regulation dynamics during this transient phase are very rapid because the electrical circuit impedance is very low. Current convergence occurs in less than 200 milliseconds. The current waveform is stabilized, with the current flowing through the clusters (I) always being positive. The alternating current (1res) corresponds to the current in the grid.

[0084] Figure 5 shows a flowchart describing the battery system control method according to the invention for synchronizing and regulating the charge and discharge current. The method is implemented by the integrated circuit computing means of the battery system control unit. A computer program can be provided by the battery system control unit, comprising instructions which, when executed, cause the unit to implement the control method for synchronizing and regulating the battery system current. The method is applicable to charging and discharging on both single-phase and polyphase power supplies.Current synchronization and regulation can be performed on one battery current line or several current lines, for example two battery current lines in a two-phase configuration connected to a two-phase network, three battery current lines in a three-phase configuration connected to a three-phase network, or four or more current lines.

[0085] In a first step E1, the process involves determining the electrical characteristics of a voltage wave from the power supply network, in particular the voltage and phase of each current line in the network.

[0086] The process then involves controlling the E2 synchronization of the electrical characteristics of the voltage waveform of the line or each current line of the battery system with the corresponding power grid waveform. During synchronization, the Kres contactors are opened, in (See Figure 1.) Synchronization consists of regulating the voltage value and phase of the battery system by taking the network voltage as a reference.

[0087] The process includes, at one stage during synchronization, a check (E3) of a synchronization state to determine the closing time of the high-voltage contactors. The synchronization state is the voltage error between the grid waveform and the battery voltage waveform relative to a predetermined error threshold.

[0088] As long as the error is greater than the threshold, the voltage regulation remains active and the resulting voltage setpoint controls the battery system. The contactors remain open.

[0089] As soon as the error becomes less than the error threshold, the process commands a step E4 to connect the electrical line or each current line of the battery system to the power supply network.

[0090] Then, in step E5, the process regulates the current of the battery system line(s) by taking into account a current setpoint I in RMS value and an estimate of the battery's RMS current. The process also determines a voltage setpoint for controlling the voltage waveform of the battery system line. By generating a voltage amplitude difference between the synchronized voltage waveforms, either a charging current or a discharging current is generated on the battery line(s).

[0091] The voltage and current control loops for E2 synchronization and E5 current regulation in the process consist of a feedback loop with a correction mechanism. In a non-limiting example, the feedback loop is of type PL correction.

[0092] In cases where the battery system and the grid are three-phase, the voltage and current control loops for E2 synchronization and E5 current regulation involve transforming or estimating the setpoints and measured values ​​of the battery system into vector commands in the Park plane with a rotating field at 50 Hz. The Park transform has the advantage of simplifying and improving the performance of the controllers. of current and voltage. The possibility of implementing other control principles is not ruled out.

[0093] Furthermore, the control method according to the invention is applicable to a single-phase or polyphase battery system. In single-phase or polyphase configuration, the voltage synchronization step E2 and the current regulation step E5 can act either directly on the sinusoidal quantities, or via the control of the direct and quadrature components which are estimated, or by control techniques involving mathematical transforms, for example.

[0094] Figure 6 describes an application of the battery system 60 according to the invention for an electrified vehicle with a fully electric or hybrid powertrain. The vehicle includes an electric drive machine 64 capable of transmitting torque to the drive wheels 62 of the vehicle via a transmission 61. The electric drive machine 64 may be three-phase. The vehicle includes a battery system 60 with a multilevel inverter architecture distributed throughout the battery as described in Figure 1. The battery has three current lines capable of generating three-phase voltage waves. The vehicle further includes a battery charging interface 68 for charging from an AC power supply. The charging interface 68 is a charging unit that electrically connects the terminals of the battery 60 to the charging station for AC charging according to the method of the invention.The charging interface 68 is also suitable for fast charging with DC voltage. The battery system 60 is advantageous because its control unit 65 adapts the voltage waveform to either AC or DC without the need for a voltage converter.

[0095] The vehicle also includes a supervisory system 66 cooperating with the control unit 65 of the battery system 60. The battery system 60 can be directly electrically connected to the electric drive machine 64, thus improving its energy efficiency in traction. The battery can also be connected to a high-voltage DC on-board electrical network 63 of the vehicle, for example, operating at a nominal voltage of 350 volts, and to a low-voltage on-board network 67 operating at a nominal voltage of the 12 Volt type, including a battery. The on-board DC voltage networks 63 and 67 can be powered by the battery 60 via an AC / DC converter, optionally.

[0096] Similarly, thanks to the invention, the battery 60 can be securely connected to an external extended power supply network via a charging station operating at alternating voltage after the synchronization phase has been completed. The charge and discharge current is regulated by the battery control unit 65 by regulating the voltage of the battery system lines 60.

Claims

CLAIMS 1. Battery system (BAT) with electrochemical cells, intended to be recharged / discharged on an extended electrical power supply network (RES) operating at alternating voltage, the system (BAT) comprising at least one current line (LT1) comprising a plurality of elementary modules (MCLk), each provided with a cell or a cluster of cells, forming a distributed multilevel inverter and a control unit (BMS) of the elementary modules (MCLk) capable of generating an alternating voltage waveform chosen at the terminals of the current line (LT1) as a function of a voltage reference setpoint (Vref), the system (BAT) being characterized in that it further comprises: - a means for determining (20) electrical characteristics of an alternating voltage wave of the supply network (RES), - a means (21) for synchronizing the electrical characteristics of an alternating voltage wave of the current line (LT 1 ) of the battery system (BAT) with the alternating voltage wave of the supply network (RES), - an electrical connection means (Kres) of the current line (LT1) to the power supply network (RES) controlled according to a synchronization state (STE) of the voltage waves of the battery system (BAT) and the network (RES), - a means for regulating the current (22) of the battery system (BAT) by controlling the voltage reference setpoint (Vref) of the current line of the battery system (BAT).

2. System according to claim 1, comprising three current lines (LT1, LT2, LT3) in which the synchronization means (21) comprises a means of transforming (210, 211) the measured voltages (Vbat, Vres) of the lines (LT1, LT2, LT3) of the battery system (BAT) and of the network (RES) into first vector commands (Vresl, Vbatl), a means of determining (212) a first voltage setpoint in vector control (Vsync) by a first regulator taking as inputs the first vector commands (Vresl, Vbatl), and a first means of modulating (240) the first voltage setpoint (Vsync) into a reference setpoint (Vref) in battery system voltage (BAT).

3. System according to claim 1 or 2, comprising three current lines (LT1, LT2, LT3) in which the current regulation means (22) comprises a means for transforming (220, 221) measured currents (Ibat) of the lines (LT1, LT2, LT3) of the battery system (BAT) and a reference current setpoint (Iref) into second current vector commands (Irefl, Ibatl), a means for determining (222) a second voltage setpoint in vector control (Vregc) by a second regulator taking as inputs the second vector commands (Irefl, Ibatl) and a second means for modulating (240) the second voltage setpoint (Vregc) into a voltage reference setpoint (Vref) of the battery system.

4. System according to claim 2 or 3, further comprising an estimator (202) of the phases (201) of the power supply network (RES), and in which the transformation means (210, 211, 220, 221) of the first (Vresl, Vbatl) and / or second vector commands (Irefl, Ibatl) also depend on said phase estimations (201).

5. System according to any one of claims 1 to 4, further comprising an estimator (212) of the voltage amplitude deviation (Verr) between the voltage wave of the supply network (RES) and the battery system (BAT) and in which the synchronization state (STE) is dependent on the deviation (Verr) from a predetermined error threshold.

6. An electrified motor vehicle comprising a rechargeable battery system (60) and an electrical interface (68) for connecting the battery system (60) to an extended electrical supply network for recharging and discharging on the supply network, wherein the battery system (60) is according to any one of claims 1 to 5.

7. A stationary battery system comprising a rechargeable battery system and an electrical interface for connecting the battery system to a wide area electrical supply network wherein the battery system is according to any one of claims 1 to 5.

8. Method for controlling a battery system (BAT) with electrochemical cells for discharging / recharging on a wide area power supply network (RES) comprising the following successive steps: - The determination (E1) of electrical characteristics of an alternating voltage wave of the supply network (RES), - Synchronization (E2) of the electrical characteristics of an alternating voltage wave of at least one current line (LT 1 ) of the battery system (BAT) with the alternating voltage wave of the supply network (RES), - The electrical connection (E4) of the current line to the power supply network in case of detection (E3) that the synchronization state of the voltage waves of the battery system (BAT) and the network (RES) is lower than a predetermined error threshold, - Then the regulation (E5) of the current of the line (LT1) of the battery system (BAT) by controlling a voltage reference setpoint (Vref) adapted to the control of the current line (LT1) of the battery system (BAT).

9. Control method according to claim 8 in which the synchronization (E2) comprises the following steps: - the transformation of the measured voltages (Vbat, Vres) of lines (LT 1 , LT2, LT3) of the battery system (BAT) and of the network (RES) into first vector commands (Vresl , Vbatl ), - determining a first voltage setpoint in vector control (Vsync) by a first regulator (212) taking as inputs the first vector commands (Vresl, Vbatl), - modulation of the first voltage setpoint in vector control (Vsync) to generate the reference voltage setpoint (Vref) to generate the voltage wave to be synchronized.

10. Control method according to claim 8 or 9 in which the current regulation (E5) of the battery system (BAT) comprises the following steps: - the transformation of the measured currents (Ibat) of the lines (LT1, LT2, LT3) of the battery system (BAT) and of a reference current setpoint (Iref) into second current vector commands (Irefl, Ibatl), - the determination of a second voltage setpoint in vector control (Vregc) by a second regulator (222) taking as inputs the second vector commands (Irefl, Ibatl), - modulation of the second voltage setpoint in vector control (Vregc) to generate the reference voltage setpoint (Vref) to regulate the charge / discharge current of the battery system (BAT).

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