Method for controlling charging of an electrical energy storage device

Abstract

The invention relates to a method for controlling charging of an electrical energy storage device (2) of a motor vehicle provided with an electric motor system (4) powered by the storage device (2), the method comprising a step (40) of controlling the motor system (4) in a so-called regenerative braking mode, allowing electric current to be generated from a torque provided by wheels of the vehicle in order to recharge the storage device (2), the control step (40) comprising a step (36) of degrading the energy efficiency of the motor system (4) taking into account a temperature of the storage device (2), so as to limit a charging current of the storage device (2) and to increase heat losses dissipated by the motor system (4), the vehicle being configured to transfer the heat losses to the storage device (2).

Description

[0001] DESCRIPTION

[0002] TITLE: Method for controlling a charge of an electrical energy storage device

[0003] The invention relates to a method for controlling the charge of an electrical energy storage device, in particular an accumulator battery. It is intended for motor vehicles equipped with an electric motor system supplied with electric current by said storage device.

[0004] In this field, it is known to control the charge of an electric vehicle battery using a map indicating the maximum power it is capable of delivering, when the electric machine to which it is connected operates in motor mode, or of absorbing, when the electric machine to which it is connected operates as a generator. This is particularly the case for batteries based on Li-ion technology.

[0005] This mapping is highly dependent on the battery's state of charge and its temperature. For example, a battery charged to 50%, at a temperature of -20°C, will accept a maximum power equal to half of what it could accept at 0°C.

[0006] Furthermore, it is known to charge the battery of an electric vehicle by recovering the mechanical braking energy transformed into electrical energy by the electric machine used to power the vehicle and then operating as a generator, according to a method known as regenerative braking.

[0007] In cold weather conditions, as mentioned above, the battery temperature can limit the battery's recharging capabilities. Since the current is limited, the electrical power, and therefore also the torque of the electric machine in regenerative braking mode, is reduced and additional braking must, if necessary, be provided using a conventional braking system. Part of the energy transformed into heat by the mechanical braking system is thus lost and the energy potential available for recharging the battery is reduced, resulting in a loss of vehicle range. In such conditions, self-heating of the battery by the Joule effect is observed during recharging, but this phenomenon is not sufficient to quickly reach the optimal operating temperature of the battery.

[0008] Another solution for increasing battery temperature is to precondition the vehicle before leaving. For this, it is known to use thermal resistors placed in a hydraulic circuit to heat the battery via the hydraulic circuit. However, this involves an additional cost due to the electrical energy required to power the electrical resistors.

[0009] Another known solution is the recovery of heat released by the engine system to heat the fluid in the hydraulic circuit and, consequently, the battery. A disadvantage of this solution remains the temperature rise time, which is long given the quantity of heat that can be recovered and the thermal inertia of the circuit.

[0010] Document JP°05252606 describes a system in which, when a battery cannot absorb all or part of the energy from regenerative braking because it is already too charged, the efficiency of the electric motor is degraded so as to dissipate part of the energy in thermal form in the electric motor and in an inverter, thus requiring additional means of cooling the electric motor and the inverter. The system is complex and expensive and, above all, does not allow for the case where the battery cannot absorb the energy because it is too cold to be dealt with.

[0011] The invention aims to at least partially overcome the above drawbacks and to this end proposes a method for controlling the charge of an electrical energy storage device of a motor vehicle equipped with an electric motor system powered by said storage device, said method comprising a step of controlling said motor system in a mode, called regenerative braking, allowing generation of an electric current from a torque supplied by wheels of the vehicle to recharge said storage device, said control step comprising a step of degrading the energy efficiency of said motor system taking into account a temperature of said storage device, so as to limit a charging current of said storage device and to increase thermal losses dissipated by said motor system,said vehicle being configured to transfer said thermal losses to said storage device.,

[0012] According to the invention, the heat released by the motorization system is used to increase the temperature of the electrical energy storage device by deliberately reducing the efficiency of the motorization system, which, on the one hand, limits the current produced by said system so that it does not exceed what the electrical energy storage device is in any case capable of accepting in cold conditions, and on the other hand, with identical braking, increases the heat released by the motorization system. In this way, the recharging of the battery is optimized by reducing its temperature rise time, this by optimizing the heat produced by the motorization system itself.

[0013] According to various additional characteristics of the invention, which may be taken together or separately and which form as many embodiments of the invention:

[0014] - said motorization system comprises an electric machine, or even a device for controlling an electric current supplying and / or generated by said machine,

[0015] - said method comprises a step of estimating the temperature and / or a state of charge of said storage device,

[0016] - said method comprises a step of evaluating a maximum power admissible by said electrical storage device as a function of said temperature and / or said state of charge,

[0017] - said evaluation step uses a map, called a battery, providing information relating to said maximum admissible power from information relating to said temperature and / or said state of charge,

[0018] - said degradation step is carried out when, in regenerative braking mode, an electrical power that can be supplied by said motorization system is greater than the power determined according to said step of evaluating the maximum power admissible by said storage device,

[0019] - said step of controlling the motorization system comprises a step of using a mapping, called standard, - said step of degrading the efficiency of said motorization comprises a step of using an alternative mapping to said standard mapping,

[0020] - said standard mapping includes, for a given available voltage as well as a given torque setpoint and a recorded speed of said motorization system, values ​​of the current of said motorization system, chosen to limit losses,

[0021] - said alternative mapping includes, for a given torque setpoint, values ​​of the current of said motorization system identical to a point, called the retained point, of the standard mapping corresponding to a torque value, identical or close, and a speed greater than a speed recorded by said motorization system, for a voltage less than or equal to the available voltage,

[0022] - said voltage lower than the available voltage is the lowest operating voltage permitted for said storage device,

[0023] - the said point retained is a point generating the greatest possible losses for a difference between a torque provided by the said motorization system and the said torque setpoint of less than 5 Nm,

[0024] - the speed higher than the recorded speed of said engine system is the highest speed permitted for said vehicle,

[0025] - said method comprises a complementary mechanical braking step when a torque setpoint cannot be reached by the degradation step,

[0026] - said vehicle is equipped with a cooling circuit for said engine system making it possible to transfer the heat dissipated by the engine to a heat transfer fluid circulating in said circuit,

[0027] - said circuit is configured to heat said storage device using said heat transfer fluid.

[0028] The invention also relates to a control device provided with hardware and software means for implementing the method described above.

[0029] The invention also relates to an electric vehicle comprising said control device. The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly during the detailed explanatory description which follows, of at least one embodiment of the invention given by way of purely illustrative and non-limiting example, with reference to the appended schematic drawings among which:

[0030] [Fig 1] schematically illustrates an example of a control method in accordance with the invention;

[0031] [Fig 2] illustrates, using a flowchart, an example of implementation of a step of the method in accordance with the invention;

[0032] [Fig 3] schematically illustrates an example of a map used according to an implementation mode of the method in accordance with the invention;

[0033] [Fig 4] schematically illustrates an example of a hydraulic circuit used according to an embodiment of the method in accordance with the invention;

[0034] [Fig 5] illustrates the losses generated during the implementation of a method in accordance with the invention, according to a first mode of operation;

[0035] [Fig 6] illustrates the losses generated when implementing the same process as that in question in Figure 5, this time in another operating mode.

[0036] As illustrated in Figure 1, the invention relates to a method for controlling a charge of an electrical energy storage device 2 of a motor vehicle equipped with an electric motorization system 4 powered by said storage device 2.

[0037] Said motorization system 4 comprises an electric machine capable of operating as a motor and as a generator. It further comprises, for example, a device for controlling an electric current supplying and / or generated by said electric machine. Said device for controlling the electric current supplying and / or generated by said electric machine comprises, for example, an inverter and / or a rectifier. These latter make it possible, in particular, to transform the direct current supplied by said storage device 2 into alternating currents supplying said electric machine, or vice versa, for example using vector control. Said storage device 2 comprises, for example, one or more electric batteries. Said vehicle further comprises an electrical circuit 6 connecting said storage device 2 and said motorization system 4.Said method is implemented, in particular, using a management system 8 on board the vehicle, such as a digital information processing management system comprising microprocessors.

[0038] Said method comprises a step of controlling an operation of said motorization system 4 making it possible to alternately use said motorization system 4 in an operating mode in which the electric machine operates in motor mode to drive the vehicle while being supplied with electric current by said storage system 2 and an operating mode in which said electric machine operates as a generator. In such a mode, said motorization system 4 allows generation of an electric current from a torque supplied by wheels of the vehicle to recharge said storage device 2. Such a mode is also called regenerative braking mode.

[0039] Said step of controlling the operation of the motorization system advantageously comprises a step of using a map, called standard. Said map is, for example, a three-dimensional map. For example, at each speed of the measured electric machine, each torque setpoint to be supplied by the electric machine or supplied to the electric machine, and each voltage of said measured storage device corresponds to a set of stator current setpoints, or even rotor current setpoints, to be applied to said electric machine.

[0040] In a context where only one setpoint is to be respected, namely the torque, and where two or three degrees of freedom are available with the currents, this, in particular, according to a vector control, there are then in theory an infinite number of current solutions to reach the same torque setpoint. Each of these solutions will correspond to a different efficiency. For the said standard mapping, the choice of a solution will be guided by the maximization of efficiency. In other words, the standard mapping includes the current values ​​which respect the torque setpoint and minimize losses. Indeed, motorization system by motorization system, the loss currents and therefore the thermal losses may be different for the same stator and / or rotor current values, this due to different configurations, in particular, of their electrical machine and / or their control device.In the illustrated embodiment, said vehicle comprises a braking system 10. Said braking system 10 is configured to generate a braking instruction 12 from an actuation of a brake pedal of said braking system 10.

[0041] Said braking instruction 12 is processed by said management system 8. Said step of controlling the operation of the motorization system 4 then makes it possible to switch from the operating mode in which the electric machine operates in motor mode to the operating mode in generator mode. For this purpose, here, said braking instruction is transformed into a torque instruction 14 to be applied to the motorization system 4. Thanks to the torque then supplied to the electric machine, the latter produces an electric current which is used to recharge said storage device 2 via the electric circuit 6 and the device for controlling the electric current supplying and / or generated by said electric machine.

[0042] In the illustrated embodiment, said management system 8 is further intended to receive information 16 relating to the rotation speed of said electrical machine. It is also intended to receive information 18 relating to a maximum power admissible by said storage device 2 during its recharging and / or information 20 relating to an operating voltage of said storage device.

[0043] In this context and as already mentioned above, said standard mapping comprises, for a given available voltage, corresponding to the information 20 relating to the operating voltage of said storage device 2, as well as for a given said torque setpoint 14, and for a recorded speed of said motorization system 4, corresponding to the information 16 relating to the rotation speed of said electrical machine, values ​​of the current of said motorization system 4, chosen to limit losses in an optimized manner.

[0044] As illustrated in Figure 2, the maximum power admissible by said storage device 2 during its recharging depends on its state of charge and its temperature. By state of charge, we mean a ratio between the quantity of electric current still capable of being supplied by the battery to the maximum quantity of current capable of being supplied by the battery when it is fully charged.

[0045] In this figure, the state of charge (SOC) is indicated on the abscissa, in %. The maximum power admissible by said storage device 2 during its recharge is indicated on the ordinate, in kW. Different curves are present, each corresponding to a given temperature of said storage device 2.

[0046] It is observed that the maximum power admissible by said storage device 2 during its recharging decreases with the state of charge. It also decreases with the temperature.

[0047] This has the consequence that, if the torque applied to the electric machine were to lead to too high a current, this could be incompatible with the temperature being too low and / or the state of charge being too low of said storage device 2. It is then necessary to reduce this torque and, not only will the storage device then recharge less quickly because the current supplied by the electric machine will be lower but also, if the braking instruction requires it, a braking torque will have to be supplied directly to the wheels and will produce heat which will be lost.

[0048] To avoid this, according to the invention, said step of controlling the operation of the motorization system 4 comprises a step of degrading the energy efficiency of said motorization system 4. Said step of degrading the efficiency takes into account a temperature of said storage device 2 so as to limit a charging current of said storage device 2 and to increase thermal losses dissipated by said motorization system 4. Furthermore, said vehicle is configured to transfer said thermal losses to said storage device 2.

[0049] In this way, the recharging of said storage device 2 is optimized, in cold conditions, by using the heat produced by the motorization system 4, this to heat the storage device 2 while the entire current capable of being produced by the motorization system 4, according to a standard efficiency, cannot in any case be used for recharging as long as the temperature of the battery is not higher. The rise in temperature of said storage device 2 is thus accelerated by using the excess heat released by the motorization system 4 which operates for this purpose in a deliberately degraded mode. In addition, the use of a mechanical braking system and the emission of possible particles by wear of parts of said mechanical braking system are limited.

[0050] As illustrated in Figure 3, according to the illustrated embodiment, said method comprises a step 32 of estimating the temperature and / or the state of charge of said storage device 2. Said method also comprises a step 34 of evaluating said maximum power admissible by said storage device as a function of said temperature and / or said state of charge.

[0051] Said evaluation step 34 advantageously uses a map, called battery, delivering information relating to said maximum admissible power from information relating to said temperature and / or said state of charge. This is, for example, a map 100 such as that illustrated in FIG. 2 already mentioned.

[0052] Said degradation step, illustrated 36, is then carried out when, in regenerative braking mode, an electrical power that can be supplied by said motorization system 4 is greater than the power determined according to said evaluation step 34 of the maximum power admissible by said storage device 2, in particular according to said battery mapping. This is illustrated by a test step 38 of the method according to the invention occurring, according to the illustrated embodiment, after said evaluation step 34.

[0053] At the end of this test step 38, if said electrical power that can be supplied by said motorization system is less than the maximum power admissible by said storage device 2, then the degradation step 36 does not occur and the step of controlling the operation of the braking system 4, illustrated 40, allows operation in regenerative braking mode according to its standard efficiency. Said step 40 of controlling the motorization system 4 comprises for this purpose, for example, a step 42 of exploitation of the standard mapping mentioned above, referenced 44 in FIG. 3.

[0054] Conversely, if said electrical power that can be supplied by said motorization system is greater than the maximum power admissible by said storage device 2, then the degradation step 36 occurs. Said step 36 of degradation of an efficiency of said motorization comprises, for example, a step of exploitation of a mapping 46 alternative to said standard mapping 44.

[0055] Said alternative mapping 46 preferably comprises, for a given torque setpoint 14, values ​​of the current of said motorization system identical to a point, called the retained point, of the standard mapping 44 corresponding to a torque value, identical or close. An advantage of using current values ​​from the standard mapping is that the points in question have already been tested for the establishment of said standard mapping and therefore do not require new validation. Furthermore, in the context of the alternative mapping 46, to degrade the efficiency and allow losses to be increased, said retained point corresponds to a speed higher than the recorded speed of said vehicle, this for a voltage lower than or equal to the available voltage.

[0056] Said voltage lower than the available voltage is, for example, the lowest operating voltage permitted for said storage device 2, in particular 240V.

[0057] The said point retained is, for example, a point generating the greatest possible losses for a difference between a torque provided by the said motorization system and the said torque setpoint of less than 5 Nm.

[0058] The speed higher than the recorded speed of said vehicle is, for example, the highest speed permitted for said vehicle.

[0059] Alternatively, said method comprises a complementary mechanical braking step when a torque setpoint cannot be reached, in particular by the degradation step 36.

[0060] As illustrated in Figure 4, to enable said transfer of heat released by said motorization system 4 to said storage system 2, said vehicle is provided with a circuit 50 for cooling said motorization system 4 making it possible to transfer the heat dissipated by said motorization system 4 to a heat transfer fluid circulating in said circuit 50. Said circuit 50 is further configured to heat said storage device 2 using said heat transfer fluid.

[0061] For this, here, said circuit 50 comprises a loop, called main, successively comprising according to the direction of circulation of the fluid in said main loop, said storage device 2, an electric heating device 52, a first valve 54, a second valve 56, a first pump 58, a cooler 59, and a third valve 60.

[0062] Said circuit 50 further comprises a first bypass branch 62 extending between the first valve 54 and the third valve 60. Said first bypass branch 62 successively comprises, according to the direction of circulation of the fluid in said first bypass branch 62, said third valve 60, a fourth valve 64, a second pump 66, the electric current control device, referenced 68, the electric machine, referenced 70, a direct / direct current converter 72, a charger 74, a fifth valve 76 and said first valve 54.

[0063] Said fourth and fifth valves 64, 76 are further connected here by a second bypass branch 78 of said circuit 50. Said second bypass branch 78 comprises a cooling radiator 80, configured to be crossed by an air flow illustrated by the arrow marked A.

[0064] According to an operating mode of said circuit 50, the fluid circulates in parallel in said main loop and said first bypass branch 62. In this way, the calories taken by the fluid at said current control device 68 and / or the electrical machine 70 from the losses generated by the method according to the invention are transferred to the storage device 2 via the intermediary called circuit 50.

[0065] The electric heating device 52 is intended, for example, to provide an additional or alternative heating source when the motorization system 4 does not generate sufficient losses, in particular when it is not in regenerative braking mode. The illustrated circuit is given only as an example and many other configurations are possible while remaining within the scope of the invention.

[0066] Figures 5 and 6 illustrate the losses generated by a motorization system using a so-called standard mapping, in the case of Figure 5, and a so-called alternative mapping, in the case of Figure 6. The losses are indicated by their gray level according to the scale appearing on the right, the values ​​being in Watt. The abscissa axis indicates a torque setpoint value, in Nm, and the ordinate axis indicates a speed value measured on an output shaft of said electric machine, in rpm.

[0067] It can be seen that the value of the losses generated with the alternative mapping, figure 6, is higher than that generated with the standard mapping, up to 4 kW difference in some cases. The quantity of heat recoverable is therefore significant, while maintaining, according to the advantageous embodiment mentioned above, identical current values ​​in both cases, but used for different points of said mappings.

Claims

CLAIMS 1. Method for controlling the charge of an electrical energy storage device (2) of a motor vehicle equipped with an electric motorization system (4) powered by said storage device (2), said method comprising a step (40) of controlling said motorization system (4) in a mode, called regenerative braking, allowing generation of an electric current from a torque supplied by wheels of the vehicle to recharge said storage device (2), said control step (40) comprising a step (36) of degrading the energy efficiency of said motorization system (4) taking into account a temperature of said storage device (2), so as to limit a charging current of said storage device (2) and to increase thermal losses dissipated by said motorization system (4), said vehicle being configured to transfer said thermal losses to said storage device (2).

2. Method according to claim 1 wherein said method comprises a step (32) of estimating the temperature and / or a state of charge of said storage device (2) and a step of evaluating (34) a maximum power admissible by said storage device (2) as a function of said temperature and / or said state of charge.

3. Method according to the preceding claim in which said evaluation step (34) uses a map, called battery, delivering information relating to said maximum admissible power from information relating to said temperature and / or said state of charge.

4. Method according to any one of the preceding claims in which said degradation step (36) is carried out when, in regenerative braking mode, an electrical power which can be supplied by said motorization system (4) is greater than the power determined according to said step of evaluating the maximum power admissible by said storage device (2).

5. Method according to the preceding claim in which said step (40) of controlling the motorization system (4) comprises a step (42) of using a mapping (44), called standard, and said step (36) of degrading the efficiency of said motorization system (4) comprises a step of using a mapping (46) alternative to said standard mapping (44).

6. Method according to the preceding claim in which said standard mapping (44) comprises, for a given available voltage as well as a given torque setpoint and a recorded speed of said motorization system (4), values ​​of the current of said motorization system (4), chosen to limit losses.

7. Method according to any one of claims 5 or 6 in which said alternative mapping (46) comprises, for a given torque setpoint, values ​​of the current of said motorization system (4) identical to a point, called retained point, of the standard mapping (44) corresponding to the same torque value and a speed greater than a recorded speed of said motorization system, for a voltage less than or equal to the available voltage.

8. Method according to the preceding claim in which: - said voltage lower than the available voltage is the lowest operating voltage permitted for said storage device (2), - said point retained is a point generating the greatest possible losses for a difference between a torque of said motorization system (4) and said torque setpoint of less than 5 Nm, and / or - the speed higher than a recorded speed of said engine system is the highest speed permitted for said vehicle.

9. Method according to any one of the preceding claims, in which said vehicle is provided with a circuit (50) for cooling said motorization system (4) making it possible to transfer the heat dissipated by said motorization system (4) to a heat transfer fluid circulating in said circuit (50), said circuit (50) being configured to heat said storage device (2) using said heat transfer fluid.

10. Control device provided with hardware and software means for implementing the method according to any one of the preceding claims.

11. Electric vehicle comprising the control device of the preceding claim.

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