Power supply circuit of an electrical energy storage unit

Abstract

Electrical power supply circuit (1) for an electrical energy storage unit (2), this electrical power supply circuit comprising: - a control unit (3), - a primary circuit (4) comprising a primary inductive cell receiving an input voltage Vin, - a secondary circuit (6), capable of being connected to an electrical energy storage unit (2), comprising a secondary inductive cell connected on the one hand to a sub-circuit (8) consisting of N branches in parallel each comprising a capacitor of capacity Ci and an inductance Li in series, with 1 ≤ i ≤ N, and on the other hand to an impedance matching device (14), in which the primary circuit (4) and the secondary circuit (6) are configured so as to exchange without contact by inductive coupling of electrical energy with a coupling rate k, at the fundamental frequency F1 of the alternating voltage at the input of the primary circuit (4),the alternating voltage Vin at the input of the primary inductive cell is modulated by the control unit (3) in order to present N harmonics with N ≥ 2, and the pairs Ci, Li of the sub-circuit (8) are configured to resonate at the frequency F2i-1 with F2i-1 = (2i-1)*F1. Abstract figure: Fig.1,

Description

Title of the invention: Power supply circuit for an electrical energy storage unit

[0001] The present invention relates to a contactless electrical power supply circuit for a vehicle electrical energy storage unit.

[0002] The electrical energy storage unit has, for example, a nominal voltage of 12V, 48V, 60V or more, for example greater than 300V, for example 400V, 800V or 1000V.

[0003] It is known to electrically power a vehicle electrical energy storage unit by contactless transmission using inductive coupling at a power of between 3 and 50 kW, when the vehicle is stationary or when it is moving. This power supply by contactless transmission is then carried out by means of magnetically coupled remote electrical sub-circuits tuned to the same resonant frequency. The magnetically coupled sub-circuits each implement an LC type resonant cell.

[0004] The solution according to the application filed in France under No. 22 09978 on 09 / 30 / 2022, which is not part of the state of the art, consists of applying an alternating voltage to the terminals of a primary inductive cell coupled by inductive coupling to a secondary inductive cell which, by impedance adaptation, makes it possible to transmit low-frequency electrical energy into an electrical energy storage unit, for example an electric vehicle battery.

[0005] The regulations for charging by inductive coupling impose a maximum magnetic and electric field level.

[0006] The maximum limit of magnetic and electric field level imposes a maximum power that can be transmitted by inductive coupling. In particular, knowing the waveform of the magnetic field (generally sinusoidal) which is an image of the current that passes from the primary inductive cell to the secondary inductive cell, it is possible to calculate the theoretical maximum power that can be transferred by inductive coupling.

[0007] There is a need to increase the maximum power that can be transmitted by inductive coupling without increasing the value of the magnetic and electric fields.

[0008] The invention aims to meet this need and achieves this by means of an electrical power supply circuit for an electrical energy storage unit, the circuit comprising:

[0009] - a control unit,

[0010] - a primary circuit comprising a primary inductive cell receiving a voltage alternative entry Wine,

[0011] - a secondary circuit, capable of being connected to an energy storage unit electrical, comprising a secondary inductive cell connected on the one hand to a sub-circuit consisting of N branches in parallel each comprising a capacitor of capacitance Q and an inductance L; in series, with 1 < i < N, and on the other hand to an impedance matching device,

[0012] in which the primary circuit and the secondary circuit are configured so as to exchange without contact by inductive coupling of electrical energy at the fundamental frequency Fi of the alternating voltage Vin at the input of the primary inductive cell,

[0013] the alternating voltage Vin at the input of the primary inductive cell is modulated by the control unit in order to present N harmonics with N > 2, and

[0014] the pairs C;, L; of the subcircuit are configured to resonate at the frequency F2U with F2U = (2i-l)*FL

[0015] Contactless exchange by inductive coupling of electrical energy is done for example with a coupling rate k.

[0016] The power supply circuit according to the invention makes it possible to obtain a current waveform passing from the primary inductive cell to the secondary inductive cell which approaches a square shape instead of a sinusoidal shape.

[0017] The alternating voltage Vin at the input of the primary inductive cell designates the voltage at the terminals of this primary inductive cell.

[0018] Advantageously, for the same amplitude and on the same load impedance value, switching from a sinusoidal current shape to a square current shape makes it possible to double the transmitted power.

[0019] To arrive at a current shape approaching a square shape, the signal is decomposed into all or part of its harmonics.

[0020] Typically, a square waveform can be decomposed into N odd harmonics, i.e. signals of frequencies F, 3*F, 5*F, 7*F, [...], 2i-l*F, with F the fundamental frequency of the signal.

[0021] To achieve a result which tends towards a square shape, the invention proposes to use a finite number of harmonics, adapted in phase and amplitude, in order to approach this square shape of the current.

[0022] The number N of harmonics is for example less than or equal to 5, corresponding to the first 3 odd harmonics, namely the fundamental frequency, the harmonic of rank 3, and the harmonic of rank 5.

[0023] The N branches of the sub-circuit are tuned to each resonate at one of the N odd-order harmonics of frequency F, 3*F, 5*F, 7*F, [...], 2i-l*F.

[0024] Advantageously, the use of a square-shaped signal for the transfer of energy by inductive coupling makes it possible to increase the maximum power that can be transmitted by inductive coupling without increasing the value of the magnetic and electric fields. Indeed, the maximum power that can be transmitted for a given current amplitude is proportional to the effective value of the current signal. However, for a signal of given amplitude, the effective value of a square-shaped signal is greater than the effective value of a sinusoidal signal.

[0025] The secondary circuit may comprise:

[0026] - a first switching arm, comprising two electronic switches com- serially controllable, the switches of this first arm being controlled according to a first cyclic ratio by the control unit, and

[0027] - a second switching arm, comprising two electronic switches controllable in series, the switches of this second arm being controlled according to a second cyclic ratio by the control unit,

[0028] the first and second arms being mounted in parallel, the control unit being configured to control the assembly of the first and second switching arms so that the two switching arms emulate the N branches in parallel and the impedance matching device.

[0029] To achieve impedance matching, one of the first and second switching arms may switch at the fundamental frequency of the contactless exchanged energy, and the other of the first and second arms may switch at a higher frequency, for example equal to or greater than 5 times the fundamental frequency of the contactless exchanged energy. One of the switching arms switches, for example, at the fundamental frequency of the contactless exchanged energy with a duty cycle of 50%, and the other switching arm switches at a frequency equal to or greater than 5 times the fundamental frequency of the energy transmitted from the primary circuit and with a duty cycle modulated according to the measured alternating current and the voltage on the alternating input of the two switching arms.

[0030] The switching arms can be controlled by the control unit so that the values of the capacitances C;, of the inductances L; and the behavior of the impedance matching device are emulated as a function of the value of the coupling ratio k between the primary inductive cell and the secondary inductive cell. This emulation can be done using an impedance function in digital form obtained by analytical calculation of the complex impedance equivalent to the presence of parallel branches each comprising the components Li and Ci in series. Alternatively, the impedance function in digital form can be an artificial transfer function. This artificial transfer function, which does not aim to take into account the presence of parallel branches each comprising the components Li and Ci in series, can correspond to a finite impulse response filter or to an infinite impulse response filter.

[0031] In a variant, the N parallel branches of the secondary circuit are produced by physical components, and not by emulation.

[0032] Preferably, for a given odd-order harmonic, the modulation of the voltage Vin by the control unit is such that the difference between the amplitude of this harmonic in the voltage Vin is between + and - 10% of the value an for this amplitude given by the following formula:

[0033] an = x sin ( — )

[0034] where A denotes the amplitude of the voltage Vin at the input of the primary inductive cell and n denotes the rank of the harmonic considered.

[0035] Preferably, the modulation of the voltage Vin by the control unit is such that the phase shift between all the harmonics of this voltage, considered two by two, is less than or equal to ±20°, or even zero.

[0036] Typically, the electrical energy storage unit may be a lithium-ion type battery. This battery has, for example, a nominal voltage of 12V, 48V, 60V or more, for example greater than 300V, for example 400V, 800V or 1000V.

[0037] Typically, the contactless exchange by inductive coupling of electrical energy takes place at a fundamental frequency lower than 5 kHz, for example lower than 3 kHz, or even lower than 2 kHz or 1 kHz, in particular still substantially equal to 400 Hz or 50 Hz.

[0038] The primary inductive cell can receive the input voltage Vin, from an inverter connected to a voltage rectifier, the voltage rectifier being able to be connected to a voltage network. This voltage inverter is then controlled by the control unit to carry out the above modulation.

[0039] The electrical network provides, for example, a nominal effective voltage of 230V or 110V with a frequency of 50 Hz or 60 Hz. The electrical network is, for example, single-phase.

[0040] The electrical network is, for example, a regional or national electrical network. It may be an independent local network, comprising, for example, one or more batteries powered by energy sources such as wind turbines, solar panels, fuel cells or hydroelectric generators.

[0041] In all of the above, the control unit can be configured to control the different switching arms of the primary circuit and the secondary circuit so as to selectively carry out:

[0042] - a charge of the electrical energy storage unit from the voltage network, Or

[0043] - a load of the voltage network from the electrical energy storage unit.

[0044] Thus, depending on the need, the exchange of electrical energy can be carried out in a one way or the other.

[0045] In all of the above, each controllable electronic switch is for example a transistor, for example bipolar, MOS or IGBT, or a thyristor. Each controllable electronic switch is for example bidirectional.

[0046] In all of the above, the control unit may be a digital processing circuit, for example an ASIC (Application-specific integrated circuit) type integrated circuit or a microcontroller.

[0047] A single control unit, for example a digital processing circuit, may be provided, this control unit controlling the switching arms of the primary circuit and the secondary circuit.

[0048] The control unit may comprise a primary circuit control module and a secondary circuit control module.

[0049] The secondary circuit may comprise a current sensor connected in series with the secondary inductive cell. When the secondary circuit comprises two switching arms in parallel, the current sensor and the secondary inductive cell are for example connected in series between the two midpoints of the switching arms.

[0050] In order to allow a contactless exchange of electrical energy between the primary circuit and the secondary circuit, the primary inductive cell and the secondary inductive cell are configured so as to exchange electrical energy without contact by inductive coupling.

[0051] The primary inductive cell may comprise a coil for generating magnetic energy and the secondary inductive cell may comprise a coil for recovering magnetic energy from the primary inductive cell.

[0052] The invention also relates, according to another of its aspects, to a component for the electrical power supply of an electrical energy storage unit, comprising the electrical circuit as defined above, the component defining in particular a structure supporting the primary circuit and the secondary circuit rigidly coupled together. Such a component is commonly called an “on-board charger”. This component is capable of being embedded in a hybrid or electric vehicle.

[0053] The invention also relates, according to another of its aspects, to a device for supplying electricity to an electrical energy storage unit, comprising:

[0054] - a charging terminal for a hybrid or electric vehicle, in which is arranged the primary circuit of the electrical circuit as defined above, and

[0055] - a component capable of being embedded in a hybrid or electric vehicle, in in which the secondary circuit of the electrical circuit as defined above is arranged.

[0056] This terminal then receives electrical energy from an electrical network via a cable which can be a single-phase cable or a three-phase cable. In this case, the primary circuit and the secondary circuit are not integrated into the same physical component.

[0057] The invention may be better understood by reading the following description of a non-limiting example of its implementation and by examining the attached drawing in which:

[0058] [Fig-1] schematically represents an electrical circuit according to an example of implementation of the invention.

[0059] [Fig.l] shows an electrical power supply circuit for an electrical energy storage unit 2. This electrical energy storage unit 2 is, for example, a vehicle battery, which may have a nominal voltage of 48V, 60V, 300V, 400V, 800V or more. This battery is used to power an electric or hybrid vehicle propulsion system.

[0060] This electrical power supply circuit 1 comprises:

[0061] - a control unit 3,

[0062] - a primary circuit 4, and

[0063] - a secondary circuit 6.

[0064] The primary circuit 4 comprises a primary inductive cell consisting of an inductor 10 and a capacitor 12 connected in series, this primary inductive cell receiving an input voltage Vin. In the example considered, this input voltage Vin is received from an inverter 7 connected to a voltage rectifier 11, the voltage rectifier being connected to a voltage network 5.

[0065] The secondary circuit 6 is connected to an electrical energy storage unit 2, and it comprises a secondary inductive cell consisting of an inductor 20 and a capacitor 22 connected in series. The secondary inductive cell is in [Fig.l] mounted upstream of a sub-circuit 8 and an impedance matching device 14.

[0066] Subcircuit 8 comprises N branches in parallel, each comprising a capacitor of capacitance C; and an inductance L; in series, with 1 < i < N.

[0067] The primary circuit 4 and the secondary circuit 6 are configured so as to exchange without contact by inductive coupling of electrical energy with a coupling rate k, at the fundamental frequency Fi of the alternating voltage at the input of the primary inductive cell of the primary circuit 4, and also at higher odd-order harmonics, as will be seen later.

[0068] The alternating voltage at the input of the primary inductive cell is for example the output voltage of the inverter 7 of the primary circuit 4, modulated by the control unit 3 with the duty cycle for example in order to produce N harmonics of odd rank with N > 2, and the pairs Ci, L; of the sub-circuit 8 of the secondary circuit 6 are configured to resonate at the frequency F2i_i with F2i_i = (2i-l)*Fi In the example considered, the number of harmonics N is equal to 3.

[0069] The input voltage of the primary inductive cell is therefore a signal comprising three frequencies F, 3*F and 5*F, or a signal that can be seen as the sum of three frequencies F + 3*F + 5*F, in which F is the fundamental frequency of the input voltage Vin.

[0070] As shown in [Fig.l], the N branches of the sub-circuit 8 are connected in parallel with each other and the sub-circuit 8 is connected in series with the secondary inductive cell 20 on the one hand and with the impedance matching device 14 on the other hand.

[0071] The power supply circuit implements a contactless exchange of electrical energy by inductive coupling between the primary circuit 4 and the secondary circuit 6, for charging the electrical energy storage unit 2.

[0072] Typically, the contactless exchange by inductive coupling of electrical energy takes place at a fundamental frequency lower than 5 kHz, for example lower than 3 kHz, or even lower than 2 kHz or 1 kHz, in particular still substantially equal to 400 Hz or 50 Hz.

[0073] Within the secondary circuit 6, the subcircuit 8 contains N branches in parallel, with N the number of odd harmonics of the signal. Each branch comprises a capacitor Ci and an inductance L; in series with i = 1 to N. Typically, the number N is less than or equal to 5. In the example considered, the subcircuit 8 comprises three pairs Li / Ci, L2 / C2 and L3 / C3 connected in parallel.

[0074] Advantageously, the N pairs Li / Ci, Li / Ci, L2 / C2 and L3 / C3 in the example considered are tuned to resonate at the frequencies F, 3*5 and 5*F in order to recover the maximum power carried by each harmonic of the signal transmitted by inductive coupling from the primary circuit 4 to the secondary circuit 6.

[0075] Advantageously, a greater number of harmonics N makes it possible to obtain a signal with a shape closer to a square signal for the current flowing in the primary inductive cell and increases the effective value of the signal. The power gain as a function of the number of harmonics used is as follows: - 22% for a signal consisting of 2 odd-order harmonics, i.e. a signal including the harmonics F+3*F, - 27% for a signal consisting of 3 odd-order harmonics, i.e. a signal including the harmonics F+3*F+5*F, and - 29% for a signal consisting of 4 odd-order harmonics, i.e. a signal including the harmonics F+3*F+5*F+7*F,

[0076] with F the fundamental frequency of the signal.

[0077] The sub-circuit 8 and the impedance matching device 14 of the secondary circuit 6 can be produced using two physical assemblies mounted in cascade. The impedance matching device then comprises, as shown in [Fig.l]:

[0078] - a first switching arm, comprising two electronic switches com- 15 controllable in series, the switches of this first arm being controlled according to a first cyclic ratio by the control unit 3, and

[0079] - a second switching arm, comprising two controllable electronic switches 15 in series, the switches of this second arm are controlled according to a second duty cycle by the control unit 3.

[0080] The first and second arms are mounted in parallel. The control unit 3 is configured to control the first and second switching arms so as to perform impedance matching. One of the switching arms switches, for example, at the fundamental frequency of the energy exchanged without contact with a first duty cycle of 50%, and the other switching arm switches at a frequency equal to or greater than 5 times the fundamental frequency of the energy exchanged without contact and with a second duty cycle modulated according to the measured alternating current and the voltage on the alternating input of the two switching arms, between their respective midpoints.

[0081] In a variant, the assembly with the two switching arms according to 14 produces by emulation the subcircuit 8, none of the capacitors C,cl of the inductances L; being then physically present. This emulation of the components of the subcircuit 8 makes it possible to do without the numerous components necessary for the filtering of the different harmonics of the signal transmitted from the primary circuit 4 to the secondary circuit 6 by inductive coupling. Each switching arm of the secondary circuit 6 is then controlled so as to emulate the presence of as many branches in parallel in the secondary circuit 6 as there are odd-order harmonics in the voltage Vin at the input of the primary inductive cell of the primary circuit 4.This control is carried out for example by measuring the current flowing in the secondary inductive cell and by determining the duty cycle applied to the switching arms of the secondary circuit 6 so that the voltage on the continuous output of these switching arms is equal to the product between this current and an impedance function in digital form.

[0082] The impedance function in digital form can be obtained by analytical calculation of the complex impedance equivalent to the presence of parallel branches each comprising the components L; and C; in series, this complex impedance then being converted into the complex domain discretized in z then converted into the time domain. Alternatively, the impedance function in digital form can be an artificial transfer function. This artificial transfer function can correspond to a finite impulse response filter or an infinite impulse response filter. The use of an artificial transfer function to emulate the subcircuit 8 can allow the latter to have a resistive part whose value differs from one frequency F, 3F, 5F... to the other present in the signal transmitted by inductive coupling of primary circuit 4 to secondary circuit 6.

[0083] In this variant, the assembly with the two switching arms according to 14 thus produces by emulation the sub-circuit 8 while producing the impedance matching device.

[0084] Similar to what was described in the application filed in France on June 2, 2023 by the Applicant under number FR2305573, the capacitor 22 of the secondary circuit 6 is not necessarily a physical component, which can be emulated by controlling the switching arms of the secondary circuit 6.

[0085] The secondary circuit 6 may comprise a secondary current sensor mounted in series with the secondary inductive cell 20. This secondary current sensor may advantageously send information on the measured current to the control unit 3.

[0086] Advantageously, the switching arms of the secondary circuit 6 are controlled by the control unit 3 so that the values of the capacitances Ci, the inductances Li and the behavior of the impedance matching device 14 are emulated as a function of the value of the coupling rate k. Advantageously, the measurement of the current passing through the secondary inductive cell 20 makes it possible to calculate the coupling coefficient k.

[0087] The control carried out by the control unit 3 can allow, whether the branches in parallel according to the sub-circuit 8 are obtained physically or by emulation, to satisfy the following two conditions, to maximize the power transmitted by inductive coupling:

[0088] - for each odd-rank harmonic present in the voltage Vin, the modulation of the voltage Vin by the control unit 3 is such that the difference between the amplitude of this harmonic in the voltage Vin is between + and - 10% of the value an for this amplitude given by the following formula:

[0089] [Math.2] — 3.^4. y cin [ .'LA ] — hXjt 1,111 \ 2 /

[0090] where A denotes the amplitude of the voltage Vin at the input of the primary inductive cell and n denotes the rank of the harmonic considered.

[0091] - the modulation of the voltage Vin by the control unit 3 is such that the phase shift between all the harmonics of this voltage, considered two by two, is less than or equal to ±20°, or even zero.

[0092] Compliance with these two conditions can allow the shape of the current flowing in the primary inductive cell to approximate a square shape.

[0093] The invention has been described above with the help of embodiments shown in the figure, without limitation of the general inventive concept.

[0094] Many other modifications and variations suggest themselves to those skilled in the art, after reflection on the different embodiments illustrated in this application.

[0095] These embodiments are given by way of example and are not intended to limit the scope of the invention, which is determined exclusively by the claims below.

[0096] In the claims, the word "comprising" does not exclude other elements or steps, and the use of the indefinite article "a" or "an" does not exclude a plurality.

[0097] The mere fact that different features are recited in mutually dependent claims does not indicate that a combination of these features cannot be advantageously used. Finally, any reference used in the claims should not be interpreted as a limitation of the scope of the invention.

Claims

Claims

1. Electrical power supply circuit (1) for an electrical energy storage unit (2), this electrical power supply circuit comprising: - a control unit (3), - a primary circuit (4) comprising a primary inductive cell receiving an input voltage Vin, - a secondary circuit (6), capable of being connected to an electrical energy storage unit (2), comprising a secondary inductive cell connected on the one hand to a sub-circuit (8) consisting of N branches in parallel each comprising a capacitor of capacitance Q and an inductance Li in series, with 1 < i < N, and on the other hand to an impedance matching device (14), in which the primary circuit (4) and the secondary circuit (6) are configured so as to exchange without contact by inductive coupling electrical energy at the fundamental frequency Fi of the alternating voltage Vin at the input of the primary inductive cell,the alternating voltage at the input of the primary inductive cell is modulated by the control unit (3) in order to present N harmonics with N > 2, and the pairs Q, L; of the sub-circuit (8) are configured to resonate at the frequency F2i_i with F^ = (2i-l)*FL,

2. A power supply circuit according to claim 1, wherein the number N of branches in parallel is less than or equal to 5.

3. Power supply circuit (1) according to claim 1 or 2, wherein the secondary circuit (6) comprises: - a first switching arm, comprising two controllable electronic switches (15) in series, the switches of this first arm being controlled according to a first duty cycle by the control unit, and - a second switching arm, comprising two controllable electronic switches (15) in series, the switches of this second arm being controlled according to a second duty cycle by the control unit, the first and second arms being mounted in parallel, the control unit (3) being configured to control the assembly of the first and second switching arms so that the two switching arms switching emulates the N branches in parallel and the impedance matching device.

4. 4. Circuit according to claim 3, wherein the switching arms are controlled by the control unit (3) such that the values of the capacitances C;, the inductances L; and the behavior of the impedance matching device (14) are emulated as a function of the value of the coupling rate k of the inductive coupling.

5. 5. Circuit according to any one of the preceding claims, in which for a given odd-order harmonic, the modulation of the voltage Vin by the control unit (3) is such that the difference between the amplitude of this harmonic in the voltage Vin is between + and - 10% of the value an for this amplitude given by the following formula: „ — 2xA vcin 1 3 “n “ nxjr * \ 2 / where A designates the amplitude of the voltage Vin at the input of the primary inductive cell and n designates the order of the harmonic considered.

6. 6. Circuit according to any one of the preceding claims, in which the modulation of the voltage Vin by the control unit (3) is such that the phase shift between all the harmonics of this voltage (Vin) is less than or equal to ±20°, or even zero.

7. 7. A circuit according to any one of the preceding claims, wherein the electrical energy storage unit (2) has a voltage greater than or equal to 60 volts.

8. 8. A circuit according to any preceding claim, wherein the contactless exchange by inductive coupling of electrical energy takes place at a fundamental frequency of less than 5 kHz.

9. 9. Circuit according to any one of the preceding claims, in which the primary inductive cell (10) receives an input voltage Vin, from an inverter (7) connected to a voltage rectifier (11), the voltage rectifier being capable of being connected to a voltage network (5).

10. Circuit according to any one of the preceding claims, in which the number (N) of harmonics of the alternating voltage at the input of the primary inductive cell (10) is equal to the number (N) of branches in parallel of the sub-circuit (8) of the secondary circuit (6).

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