Method for recharging a battery using a voltage source lower than that of the battery and corresponding vehicle

Abstract

Method for recharging a battery using a voltage source lower than that of the battery and corresponding vehicle. The present invention relates to a method for recharging a vehicle battery further comprising an electric motor and an inverter connected to the battery and to stator windings of the electric motor, a neutral point of the electric motor being connected to a positive terminal of a voltage source delivering a voltage lower than the battery voltage, the inverter having three switching arms each comprising a low switch and a high switch, the recharging method comprising a battery recharging step carried out by alternately switching the high and low switches of at least one of the switching arms, the recharging method being characterized in that during the recharging step,One of the switching arms is inactive while the lower switches of a second and third switching arm switch in opposite phase. (Figure 6)

Description

Title of the invention: Method for recharging a battery using a voltage source lower than that of the battery and corresponding vehicle

[0001] The present invention relates to the fields of automotive and electrotechnics, and more specifically concerns a method of recharging a high-voltage battery of an electric or hybrid vehicle, and an electric or hybrid vehicle having means to implement such a method.

[0002] An electric or hybrid vehicle has a high-voltage battery, with a maximum open-circuit voltage generally between 400 and 800 V (volts), which discharges to power an electric motor that propels the vehicle. The high-voltage battery must therefore be recharged from a charging station external to the vehicle. When this station is capable of supplying a DC voltage higher than the high-voltage battery's maximum open-circuit voltage, simply connecting the outputs of the charging station to the vehicle's high-voltage battery terminals is sufficient to recharge it.

[0003] However, some charging stations only provide a DC voltage lower than the maximum open-circuit voltage of the high-voltage battery. In particular, some charging stations can only supply a maximum of 400V. To charge a high-voltage battery with a voltage greater than 400V using such a charging station, the outputs of the charging station must be connected to the input of a voltage booster, the output of which, providing a voltage higher than that of the high-voltage battery to be charged, is connected to the terminals of the latter.

[0004] Such a voltage booster comprises at least one inductor, an output capacitor, and two switches. Given the power these components must withstand, they represent a significant cost. To reduce the cost of an electric or hybrid vehicle equipped with such a voltage booster, it is often implemented by reusing power components already present in the vehicle. These components include, for example, the stator windings of the vehicle's electric motor, the switches of a vehicle inverter used to power the electric motor from the energy supplied by the high-voltage battery, and a smoothing capacitor connected to the terminals of the high-voltage battery in the vehicle.

[0005] By using the vehicle's inverter, charging can utilize six switches instead of two (in the case of a three-phase inverter), thereby reducing the current ripple that could otherwise occur at the charging station output and the high-voltage battery input. However, such use can create a magnetic field. drawing power from the electric motor, which generates significant iron losses during charging and reduces the efficiency of this charging.

[0006] These iron losses also risk damaging the rotor by causing significant heating. Finally, due to the couplings between the stator windings and the rotor, current ripples vary according to the rotor's position and can also reduce charging efficiency.

[0007] By choosing simultaneous operation of the switches, the resulting stator magnetic field created in the electric motor is almost zero and these disadvantages are very limited, but at the cost of a very strong current ripple at the input and output of the voltage booster, which can eventually damage the high-voltage battery and disrupt the operation of the charging device.

[0008] It should also be noted that when the vehicle's stator windings are used as inductors for the vehicle's voltage booster, the electric motor's rotor is not energized. When the rotor is a wound rotor, energizing the stator windings during high-voltage battery charging can generate a very high induced voltage in the rotor, which can damage it. However, such an induced voltage does not exist when the rotor is a permanent magnet rotor.

[0009] There is therefore a need to improve the implementation of the voltage boosting function in an electric or hybrid vehicle, to enable the high-voltage battery to be recharged as efficiently and cheaply as possible, without damaging the vehicle's electric motor.

[0010] The present invention aims to remedy at least in part the aforementioned drawbacks by providing an electric or hybrid vehicle and a method for recharging a high-voltage battery of such a vehicle, reusing the inverter and the electric motor of the vehicle, and in which, in particular, the switching of the inverter switches minimizes the current ripple.

[0011] To this end, the invention proposes a method for recharging a battery of an electric or hybrid vehicle, the vehicle further comprising an electric motor and an inverter, the inputs of the inverter being connected to the battery terminals, the outputs of the inverter being connected to stator windings of the electric motor, and a neutral point of the electric motor being connected to a positive terminal of a voltage source delivering a voltage lower than the voltage at the battery terminals, the inverter having three switching arms each comprising a midpoint, a lower switch connected to the midpoint and to a negative terminal of the battery, an upper switch connected to the midpoint and to a positive terminal of the battery, the recharging method comprising a battery recharging step carried out by alternately switching the upper and lower switches of at least one of the switching arms, the charging process being characterized in that during the charging stage, a first of the switching arms is inactive while the lower switches of a second and a third of the switching arms switch in opposite phase.

[0012] In this application, the vehicle battery is understood to be a high-voltage battery capable of powering the inverter and the electric motor while the vehicle is in motion. Similarly, the electric motor and the inverter in this patent application refer to a traction or propulsion electric motor and a traction or propulsion inverter for the vehicle.

[0013] Moreover, in this application, components are "connected" to each other when only a few conductors or components of zero or near-zero resistance electrically connect them, such as switches.

[0014] Furthermore, in this patent application, unless otherwise stated, an input or output connection of a functional assembly such as an inverter or a voltage booster is understood as a connection to the terminals of that input or output, respectively, with respect to the function mentioned. Thus, since the inverter's function is to invert the current only when the vehicle is moving, its outputs are connected to the stator windings of the electric motor. The inverter outputs are, of course, connected to the midpoints of the inverter's switching arms. The inverter may have more than three switching arms, for example, six switching arms.

[0015] In load mode in the invention (the terms "load" or "recharge" are considered equivalent in this application), the inactive switching arm of the inverter corresponds to a switching arm whose upper and lower switches are constantly left in the open state during the ongoing load. The upper and lower switches of each of the other switching arms of the inverter switch alternately, that is, the lower switch closes when the upper switch opens and vice versa, of course with a dead time delay. The lower switches of these two other switching arms switch in opposite phase, that is, for the entire duration that one of these lower switches is closed, the other of these lower switches is open.Depending on the duty cycle chosen, these two bottom switches can be open simultaneously for a longer period than a dead time; for example, if the duty cycle is 40% for each bottom switch, there will be twenty percent of the duration of a switching cycle during which these two bottom switches will be open.

[0016] Furthermore, in the charging method according to the invention, with the battery charged, when one of the upper switches is closed, the current in the upper switch flows from the midpoint of the switching arm incorporating this upper switch to a positive terminal of the battery. Similarly, in the charging method according to the invention, When one of the lower switches is closed, the current in the lower switch flows from the midpoint of the switching arm containing that lower switch to a negative terminal of the battery.

[0017] Thanks to this switching method, the current ripple is reduced at the terminal and the battery, and the mutual inductances between the stator windings also reduce the current ripple in the stator windings, without creating a magnetic field drawing power from the electric motor, which would cause the rotor to rotate. Thus, iron losses are reduced and battery charging efficiency is optimized. Furthermore, the invention does not require costly means for locking the rotor or changing its position. Since the invention is implemented in inverter control means, it is inexpensive and easy to implement.

[0018] When the rotor is a permanent magnet rotor, the use of the charging method according to the invention does not induce a voltage in the rotor that could damage it. When the rotor has a rotor winding, the charging step is, for example, preceded by a step of short-circuiting the rotor winding. This cancels out the induced voltage.

[0019] According to an optional and advantageous feature of the invention, the charging step is preceded by a step of measuring the angular position of a magnetic axis of an electric motor rotor, and a step of selecting the second and third commutating arms as those suitable for charging the stator windings with axes forming angles of less than sixty degrees with the rotor's magnetic axis. The rotor's magnetic axis, when wound, corresponds to the axis of its winding. The axis of a winding is taken here, when the winding consists of a set of turns stacked one on top of the other, as the axis orthogonal to these turns and passing through their midpoint. When a winding comprises several sets of turns, the winding axis similarly corresponds to the principal direction of the magnetic flux formed by the sets of turns.

[0020] During the charging stage, the rotor will align itself with the stator field resulting from the switching of the inverter switches. Choosing switching arms that form the smallest angles with the rotor's magnetic axis minimizes rotor displacement when it aligns with the resulting stator magnetic field, and therefore minimizes the risk of vehicle movement. Indeed, once the rotor is aligned with the resulting stator field, it no longer moves, as the resulting stator field is fixed.

[0021] The invention also relates to an electric or hybrid vehicle comprising a battery, an electric motor and an inverter, the inverter inputs being suitable for to be connected to the battery terminals, the inverter outputs being connected to stator windings of the electric motor, and a neutral point of the electric motor being capable of being connected to a positive terminal of a voltage source delivering a voltage lower than the voltage at the battery terminals, the inverter having three switching arms each comprising a midpoint, a lower switch connected to the midpoint and to a negative terminal of the battery, an upper switch connected to the midpoint and to a positive terminal of the battery, the electric or hybrid vehicle comprising means for charging the battery by alternately switching the upper and lower switches of at least one of the switching arms,The electric or hybrid vehicle is characterized in that the charging means are configured to leave the upper and lower switches of a first switching arm open and to switch the lower switches of a second and third switching arm in opposite phase.

[0022] When the rotor includes a rotor winding, the vehicle charging means are preferably capable of activating means for short-circuiting the rotor winding.

[0023] In one embodiment of the invention, the vehicle includes means for measuring the angular position of a magnetic axis of a rotor of the electric motor, and means for selecting the second and third switching arms as those switching arms suitable for charging with current the stator windings of axes forming angles of less than sixty degrees with the magnetic axis of the rotor.

[0024] The vehicle according to the invention preferably comprises a capacitor suitable for connection on one side to the positive terminal of the voltage source and on the other side to a negative input terminal of the inverter. This capacitor, connected to the input of the vehicle's charging system, which consists of at least the stator windings and the inverter, is pre-charged before the high-voltage battery is recharged in order to prevent excessive current surges from damaging the components of the charging system when it is connected to the voltage source.

[0025] In this case, the vehicle according to the invention preferably also includes a first switch having a first terminal connected to the neutral point and a second terminal suitable for being connected to the positive terminal of the voltage source. This first switch allows the neutral point of the capacitor to be disconnected while the vehicle is in motion.

[0026] Furthermore, the vehicle according to the invention optionally includes a second switch having a first terminal suitable for connection to the positive terminal of the voltage source, and a second terminal suitable for connection to a positive terminal of the battery. This second switch allows the charging terminal to be connected directly. to the battery to recharge it when the charging station delivers a voltage higher than the battery voltage.

[0027] Finally, the vehicle according to the invention preferably includes a smoothing capacitor suitable for connection to the battery terminals and the inverter inputs. This smoothing capacitor limits current ripples at the battery level and can optionally be replaced by other internal battery components having the same function.

[0028] The vehicle according to the invention has advantages similar to those of the charging method according to the invention.

[0029] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given by reference to the accompanying schematic drawings on the other hand, in which:

[0030] [Fig. 1] represents a vehicle charging system according to the invention implementing a charging method according to the invention, the vehicle being connected to an external charging station, in one embodiment of the invention,

[0031] [Fig.2] represents a first switching scheme usable in the charging system of [Fig.1], as well as stator currents in an electric motor of the vehicle, and an input current in the charging system corresponding to this first switching scheme not being proposed by the invention,

[0032] [Fig.3] represents a second switching scheme usable in the charging system of [Fig.1], as well as the corresponding stator currents in an electric motor of the vehicle and an input current in the charging system, this second switching scheme not being proposed by the invention,

[0033] [Fig.4] represents a third switching scheme usable in the charging system of [Fig.1], as well as the corresponding stator currents in an electric motor of the vehicle and an input current in the charging system, this third switching scheme not being proposed by the invention,

[0034] [Fig.5] represents a fourth switching scheme usable in the charging system of [Fig.1], as well as the corresponding stator currents in an electric motor of the vehicle and an input current in the charging system, this fourth switching scheme not being proposed by the invention,

[0035] [Fig.6] represents a fifth switching scheme usable in the charging system of [Fig.1], as well as the corresponding stator currents in an electric motor of the vehicle and an input current in the charging system, this fifth switching scheme being proposed by the invention,

[0036] [Fig.7] represents steps of a recharging process according to the invention, in the embodiment of [Fig.1],

[0037] [Fig.8] represents the electric motor of the vehicle of [Fig.1], in a use case of the embodiment of [Fig.1], in a variant of the invention, and

[0038] [Fig.9] represents the electric motor of the vehicle of [Fig.1], in a use case of the embodiment of [Fig.1], in a main variant of the invention.

[0039] According to one embodiment of the invention, a vehicle according to the invention comprises a charging system represented in [Fig.1], incorporating elements of the vehicle's traction chain.

[0040] In this embodiment of the invention, the vehicle includes a battery 28 with a nominal open-circuit voltage of 800V. It is therefore a high-voltage battery. In this application of the invention, the battery 28 is sufficiently discharged to require recharging and therefore has a voltage Vbatt at its terminals of, for example, between 500 and 600V. The vehicle is connected to an external charging station 40, capable of supplying a maximum of 400V.

[0041] The charging station 40 has internal contacts that close before the start of charging the battery 28. During this charging, it behaves as a voltage source, with a DC voltage at its terminals equal to 400V.

[0042] The vehicle charging system, connected to the charging station 40, includes a relay 38, one terminal of which is connected to the negative terminal of the charging station 40, and the other terminal of which is connected to the negative terminal of a capacitor 22. The capacitor 22 has a positive terminal connected to the positive terminal of the charging station 40 and is therefore connected in parallel to the charging station 40 via the relay 38. The capacitor 22 and the relay 38 form a pre-charge system at the input of the charging system, the relay 38 being closed only after the capacitor 22 has been pre-charged by the battery 28, before the battery is recharged. The capacitor 22 also filters voltage variations and stabilizes the voltage at the charging station.

[0043] The charging system further comprises a first switch 36 connected on one side to the positive terminal of the capacitor 22 and on the other side to a neutral point N, forming a positive input terminal of a voltage booster of the charging system. A negative input terminal of the voltage booster is connected to the negative terminal of the capacitor 22. The voltage booster is therefore connected at the input to the capacitor 22 via the first switch 36, and is connected at the output to the battery 28 via relays 32 and 34, referred to as battery relays. The negative input terminal of the voltage booster is a common negative terminal for the inverter 24 and the capacitor 22. It is connected to the negative terminal of the battery 28 via the battery relay 34 and therefore also corresponds to a negative output terminal of the voltage booster. A positive output terminal of the voltage booster is, for its part, it is connected to the positive terminal of battery 28 via battery relay 32.

[0044] A second switch 30 is connected on one side to the positive terminal of the charging terminal 40, and on the other side to a positive terminal of the battery 28 via the battery relay 32. This second switch allows the battery 28 to be connected directly to the charging terminal 40, without an intermediate voltage booster, when the charging terminal delivers a voltage higher than the voltage of the battery 28.

[0045] The voltage booster consists of stator windings L1, L2, L3 of a three-phase electric motor 20 (referenced [Fig.8]) of the vehicle, an inverter 24 and a smoothing capacitor 26 at the output of the voltage booster, the smoothing capacitor 26 being connected to the terminals of the battery 28 via the battery relays 32 and 34.

[0046] The relays or switches in this application are mechanical or semiconductor-based relays.

[0047] The stator windings L1, L2, L3 are mounted in star and therefore connected together at the neutral point N.

[0048] The inverter 24 comprises three switching arms, each comprising: - a midpoint respectively M1, M2, M3, - a lower switch respectively 1_L, 2_L, 3_L connected on one side to the respective midpoint M1, M2, M3 and on the other side to the negative terminal of battery 28 via the battery relay 34, and - a high switch respectively 1_H, 2_H, 3_H connected on one side to the respective midpoint M1, M2, M3 and on the other side to the positive terminal of the battery 28 via the battery relay 32.

[0049] The midpoints M1, M2, M3 are connected to the free ends of the stator windings respectively L1, L2, L3, opposite the neutral point N.

[0050] The upper switches 1_H, 2_H, 3_H and lower switches 1_L, 2_L, 3_L are controlled switches, for example, transistors. The charging system therefore includes a control circuit (not shown) capable of controlling these switches so as to make them switch according to a duty cycle α. This control circuit is part of the vehicle charging means.

[0051] In order to fully understand the advantages of the charging method according to the invention, switching schemes not proposed by the invention but which could be considered for charging the battery 28, and the associated disadvantages, are now described in relation to figures 2 to 5.

[0052] In these figures, as well as in [Fig. 7] described later, the duty cycle a corresponds to the ratio between the closing time of the lower switches 1_L, 2_L and 3_L and the switching period Tpwm, which is the inverse of the frequency f of this switching. In other words, over a switching period Tpwm, the lower switches are closed at * Tpwm microseconds and open at (1- a) * Tpwm microseconds, these opening and closing times being able to be distributed over the switching period. For a switching frequency of 20 kHz (kilohertz), the switching period Tpwm is 50qs (microseconds).

[0053] Furthermore, in these figures, the curves V1_L, V2_L, and V3_L represent the control voltages of the lower switches 1_L, 2_L, and 3_L, respectively, in volts, although the units are not shown. In the case of [Fig. 2], these control voltages are non-zero over a closing time interval of duration a * Tpwm. This time interval is identical for the three lower switches 1_L, 2_L, and 3_L; that is, they are closed simultaneously for one switching period, while the upper switches 1_H, 2_H, and 3_H are open for this time interval. This is therefore a so-called pulsed control.

[0054] The stator currents II, 12,13 circulating respectively in the stator windings L1, L2, L3 increase during the charging of the inductances constituted by these windings, i.e. during the closing of the lower switches 1_L, 2_L and 3_L, and decrease during the charging of the smoothing capacitance 26, i.e. during the opening of the lower switches 1_L, 2_L and 3_L corresponding to a period of closure of the upper switches 1_H, 2_H and 3_H.

[0055] It should be noted that the upper switches 1_H, 2_H and 3_H are always controlled alternately with their respective lower switches 1_L, 2_L and 3_L, that is to say that when the upper switch 1_H, 2_H or 3_H is closed, then the lower switch 1_L, 2_L or 3_L of the same switching arm is open, and vice versa, within dead time delays.

[0056] The input current lin of the voltage booster is equal to the sum of the stator currents II, 12,13 and therefore exhibits a strong variation over a switching period.

[0057] Consequently, this pulsed control causes a strong current ripple in the load terminal 40 because the sum of the stator currents II, 12, and 13 reach their maxima at the same instant. However, this pulsed control is simple to implement and does not require introducing a phase shift between the switch commands. It should be noted that the voltage induced at the rotor of the electric motor 20 is not a concern in this embodiment, since this rotor is, in this embodiment of the invention, a wound rotor that is short-circuited during battery 28 charging.

[0058] In the case of [Fig. 3], the bottom switches 1_L, 2_L, and 3_L close for the same duration but with staggered timing relative to each other. Indeed, since the switching period is divided into sixths, the bottom switch 1_L is closed for the first three-sixths of the switching period and open for the last three-sixths, while the bottom switch 2_L is closed from the The switch is closed during the third to fifth sixths inclusive of the switching period, and the low switch 3_L is closed during the first sixth of the switching period and the last two sixths of the switching period. This control of the switches is called interleaved.

[0059] The stator currents II, 12, 13, flowing respectively in the stator windings L1, L2, L3, increase and decrease with a phase shift relative to each other, which is similar to a phase shift. Assuming the switching period is 180°, the stator currents II, 12, 13 are therefore 120° out of phase with each other. The input current lin of the voltage booster, being the sum of these stator currents II, 12, 13, thus exhibits a small, but nonetheless non-zero, current ripple. Furthermore, this interleaved control generates a powerful stator field capable of moving the vehicle if the rotor is not mechanically blocked. Such a blockage, however, is restrictive.

[0060] Furthermore, the inventor has observed that the effect of mutual inductances between stator windings cannot be neglected. Indeed, a distinction is made between: - the self-inductance of a stator winding, which can be measured on the stator winding alone, isolated from any influence of the rotor and other stator windings, and - the apparent inductance of this stator winding, taking into account the mutual inductances, on the one hand, between the stator winding and other stator windings, and on the other hand, between the stator winding and the rotor.

[0061] Fig. 4 shows that when only one low switch 1_L is controlled, the other low switches remaining open during a charge of the battery 28, then there is no effect related to mutual inductances, the current linear at the input of the voltage booster exhibiting a current ripple identical to that observed with a voltage booster with a single inductance and only two switches.

[0062] On the other hand, as shown in [Fig. 5], when two lower switches 1_L and 2_L are controlled in the same way, i.e. closed and open at the same time, the mutual inductances between the stator windings L1 and L2 reduce the apparent inductance of each of these stator windings L1 and L2. As a result, the current lin at the input of the voltage booster exhibits a current ripple that is greater than twice the current ripple shown in [Fig. 4].

[0063] The invention uses the effect of these mutual inductances to increase the apparent inductance of the stator windings and decrease the current ripple in each of the stator windings. Figure 6 shows a switching scheme that can be used by a charging method according to the invention, shown in Figure 7, implemented by the charging system in Figure 1.

[0064] In this switching scheme, the lower switches 1_L and 2_L are switched in opposite phase. The lower switch 3_L is not used and remains always open, like its corresponding high switch 3_H. In this case, the effect of the mutual inductances between windings L1 and L2 increases their respective apparent inductances, which generates a current ripple in each of these stator windings L1, L2, smaller than if only one of these windings were loaded with current as in [Fig. 4]. This switching scheme allows for a near-zero current ripple seen from the terminal, while reducing Joule losses in the stator windings, and thus improving the efficiency of the battery 28 charging.

[0065] Returning to [Fig. 7], the charging method 100 includes a short-circuiting step 102 of the rotor of the electric motor 20. This step does not exist in the variants of the invention in which the rotor has permanent magnets. The short-circuiting 102 uses short-circuiting means belonging to the vehicle. This may be a controlled switch connected to the two supply terminals of the rotor winding R (referenced in Figures 8 and 9) of the rotor.

[0066] This short-circuiting step 102 can be preceded or followed by a step 103 of closing the first switch 36, the second switch 30 and the relay 38 being open, of pre-charging the capacitor 22 and then of closing the relay 38.

[0067] The charging method 100 further includes a measurement step 104 of the angular position of a magnetic axis d of the rotor winding R of the electric motor 20, shown [Fig. 8], relative to a reference axis, for example the axis a of the stator winding L1. This measurement 104 makes it possible to determine the acute angle θ1 that the axis d of the rotor makes with the axis a of the stator winding L1, the acute angle θ2 that the magnetic axis d of the rotor makes with the axis b of the stator winding L2, and the acute angle θ3 that the axis d of the rotor makes with the axis c of the stator winding L3. This measurement 104 is performed by a rotor position sensor, which is part of the charging means of the charging system and, more generally, of the vehicle.

[0068] In the configuration of [Fig. 8], when using the commutation scheme of [Fig. 6], the stator winding L1 produces an elementary stator field ¢1, the stator winding L2 produces an elementary stator field ¢2, resulting in a total stator field ¢8. The rotor, immersed in these stator fields ¢1, ¢2, will therefore tend to align with the total stator field ¢8. Indeed, although short-circuited, the rotor carries a small induced current and behaves like a magnet. The rotor is therefore likely to rotate through an angle θ3 corresponding to the acute angle between the magnetic axis d of the rotor and the direction of the total stator field ¢8, this angle being greater than 30° and thus potentially leading to a significant displacement of the vehicle.

[0069] In order to minimize rotor displacement and the associated risk of vehicle displacement, measurement step 104 is followed by a selection step 106 of the switching arms whose switches will be controlled during the next battery charging stage 108, using a switching scheme similar to that of [Fig. 6]. In this selection stage 106, switching arms connected to stator windings whose axes form an angle of less than 60 degrees with the magnetic axis d of the rotor are selected. This selection stage 106 is implemented by a vehicle control unit, which is part of the vehicle charging system. The control unit is connected to the inverter control circuit 24.

[0070] During the next charging step 108, the electric motor 20 being in the configuration of [Fig.9], instead of driving the lower switches 1_L and 2_L, the lower switches 2_L and 3_L are driven because the stator windings L2 and L3 form angles y2 and y3 less than 60 degrees with the magnetic axis d of the rotor.

[0071] The stator winding L3 then produces an elementary stator field ¢3, the stator winding L2 produces an elementary stator field ¢2, the resulting stator field ¢8 forming an angle ∅ with the magnetic axis d of the rotor, less than 30 degrees. Even if the rotor aligns with the resulting stator field ¢8, this should not lead to any significant displacement of the vehicle. The charging step 108 effectively brings the rotor into a stable equilibrium state.

[0072] During this charging step 108, the lower switches 2_L and 3_L are controlled in opposite phase, forming a switching pattern with two interlaced switching arms at 180 degrees, the third switching arm not being used (the upper and lower switches 1_H and 1_L remaining open). In this switching scheme, corresponding to that of [Fig. 6] but with different switching arms, the duty cycle is 50%. In an alternative embodiment, during this step 108, the duty cycle is less than 50%, for example, 40%. In this case, the lower switches 2_L and 3_L are still controlled in opposite phase, i.e., when one is closed the other is open, but they are both open simultaneously 20% of the time. Conversely, when one of the upper switches 2_H or 3_H is open, the other is closed, but they are closed at the same time 20% of the time.In other words, when one of the stator windings in use charges with current, the other discharges with current into the battery 28, but during certain periods, here 20% of the time, both stator windings can discharge at the same time into the battery 28.

[0073] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. In particular, the characteristics of the different embodiments of the invention envisaged in this application can be combined to carry out the invention, provided that these embodiments are not incompatible with each other.

Claims

Demands

1. A method for recharging (100) a battery (28) of an electric or hybrid vehicle, the vehicle further comprising an electric motor and an inverter (24), the inputs of the inverter (24) being connected to the terminals of the battery (28), the outputs of the inverter (24) being connected to stator windings (L1, L2, L3) of the electric motor (20), and a neutral point (N) of the electric motor (20) being connected to a positive terminal of a voltage source (40) delivering a voltage (VDC) lower than the voltage (Vbatt) at the terminals of the battery (28), the inverter (24) having three switching arms each comprising a midpoint (M1, M2, M3), a low switch (L1, L2, L3) connected to the midpoint (M1, M2, M3) and to a negative terminal of the battery (28), an high switch (H1, 2_H, 3_H) connected to the midpoint (M1, M2, M3) and to a positive terminal of the battery (28),the charging method (100) comprising a charging step (108) of the battery (28) being carried out by alternately switching the high and low switches of at least one of the switching arms (1_L, 2_L, 3_L, 1_H, 2_H, 3_H), the charging method (100) being characterized in that during the charging step (108), a first of the switching arms is inactive while the low switches (2_L, 3_L) of a second and a third of the switching arms switch in opposite phase.

2. A charging method (100) according to claim 1, characterized in that the charging step (108) is preceded by a measurement step (104) of the angular position of a magnetic axis (d) of a rotor (R) of the electric motor (20), and a selection step (106) of the second and third switching arms as being those switching arms suitable for charging with current the stator windings (L2, L3) of axes forming angles of less than sixty degrees with the magnetic axis (d) of the rotor (R).

3. A charging method (100) according to claim 1 or 2, wherein the rotor (R) comprises a rotor winding, and wherein the charging step (108) is preceded by a short-circuiting step (102) of the rotor winding.

4. Electric or hybrid vehicle comprising a battery (28), an electric motor (20) and an inverter (24), the inputs of the inverter (24) being suitable for connection to the terminals of the battery (28), the outputs of the inverter (24) being connected to stator windings (L1, L2, L3) of the electric motor (20), and a neutral point (N) of the electric motor (20) being suitable for connection to a positive terminal of a voltage source (40) delivering a voltage (VDC) lower than the voltage (Vbatt) at the terminals of the battery (28), the inverter (24) having three switching arms each comprising a midpoint (M1, M2, M3), a low switch (1_L, 2_L, 3_L) connected to the midpoint (M1, M2, M3) and to a negative terminal of the battery (28), and an high switch (1_H, 2_H, 3_H). connected to the midpoint (M1, M2, M3) and to a positive terminal of the battery (28),the electric or hybrid vehicle comprising means for charging the battery (28) by alternately switching the upper and lower switches of at least one of the switching arms, the electric or hybrid vehicle being characterized in that the charging means are configured to leave open the upper and lower switches (1_H, 1_L) of a first of the switching arms and to switch in opposite phase the lower switches (2_L, 3_L) of a second and a third of the switching arms.

5. Electric or hybrid vehicle according to claim 4, further comprising means for measuring the angular position of a magnetic axis (d) of a rotor (R) of the electric motor (20), and means for selecting the second and third switching arms as those switching arms suitable for charging the stator windings (L2, L3) of axes forming angles of less than sixty degrees with the magnetic axis (d) of the rotor (R).

6. Electric or hybrid vehicle according to claim 4 or 5, wherein the rotor (R) comprises a rotor winding and wherein the charging means are capable of activating means for short-circuiting the rotor winding.

7. Electric or hybrid vehicle according to any one of claims 4 to 6, further comprising a capacitor (22) capable of being connected on the one hand to the positive terminal of the voltage source (40) and on the other hand to a negative input terminal of the inverter (24).

8. Electric or hybrid vehicle according to claim 7, further comprising a first switch (36) having a first terminal connected to the neutral point (N) and a second terminal suitable for being connected to the positive terminal of the voltage source (40).

9. Electric or hybrid vehicle according to claim 7 or 8, further comprising a second switch (30) having a first terminal suitable for being connected to the positive terminal of the voltage source (40), and a second terminal suitable for being connected to a positive terminal of the battery.

10. Electric or hybrid vehicle according to any one of claims 4 to 9, further comprising a smoothing capacity (26) suitable for connection to the terminals of the battery (28) and to the inputs of the inverter (24).

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