Method for determining the state of a switch in a hybrid powertrain, and corresponding control method, device and vehicle
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- AMPERE SAS
- Filing Date
- 2024-07-26
- Publication Date
- 2026-07-08
Smart Images
Figure EP2024071300_06032025_PF_FP_ABST
Abstract
Description
[0001] Method for determining the state of a switch in a hybrid powertrain, corresponding control method, device and vehicle
[0002] The present invention relates to the fields of the automotive industry and electrical engineering, and more specifically concerns the control of a hybrid powertrain, used in a specific series hybrid mode.
[0003] Some hybrid vehicle powertrains are of the type comprising at least one electric machine, capable of supplying torque to the vehicle concerned, and a thermal engine coupled to the wheels and associated with an alternator-starter itself possibly capable of supplying additional torque to the torque supplied by the electric machine or by the thermal engine.
[0004] When such a powertrain operates in parallel hybrid mode, the electric machine and the thermal engine are each able to supply torque to the vehicle's wheels, independently.
[0005] When operating in series hybrid mode, the thermal engine powers the electric machine via the alternator-starter which functions as an electrical energy generator from the torque provided by the thermal engine. In this series hybrid mode, the electric machine receives an alternating voltage formed by an inverter connected to a voltage rectifier itself connected to the alternator-starter. The electric machine then provides the traction or propulsion of the car on its own. However, the inverter is connected at the input to a high-voltage network of the vehicle, powered by a traction battery, which makes it possible in particular to power low-voltage consumers of the vehicle via a direct current-direct current converter, and to power the electric machine when the powertrain operates in parallel hybrid mode.
[0006] However, the voltage at the traction battery terminals may be lower than that which the alternator-starter can supply via the voltage rectifier, which may limit the performance of the electric machine in series hybrid mode.
[0007] In order to overcome this limitation, it is possible to disconnect the traction battery from the vehicle's high-voltage network when operating in series hybrid mode. Such a series hybrid operating mode, in which the traction battery is disconnected from the high-voltage network, is hereinafter referred to as battery-free series hybrid mode, and is described in particular in French patent FR3120339.
[0008] In such an operating mode, the voltage at the inverter terminals is regulated by the voltage rectifier powered directly by the alternator-starter, which allows the electric machine to provide a torque to the vehicle's wheels greater than that which the electric machine would provide if the battery were still connected to the high-voltage network.
[0009] Such a battery-free series hybrid operating mode is particularly useful when the traction battery is faulty and prevents any recharging of the battery, which would risk the start of combustion due to overheating. This operating mode therefore protects the traction battery and also prevents it from discharging quickly, which can prevent the vehicle from restarting when the combustion engine is switched off, depending on the gearbox architecture chosen for the hybrid powertrain.
[0010] However, switching from a series hybrid mode to a series hybrid mode without a battery requires a diagnosis of the switches connecting the traction battery to the high-voltage network. Such a diagnosis aims to verify that these switches, which are mechanical relays or transistors, are not stuck and open correctly after a switch opening command.
[0011] Usually, after a command to open the switches, to carry out this diagnosis, it is sufficient to cut off all the power consumers from the high-voltage network, then to measure the voltage at the terminals of a capacitor connected in parallel with the battery, downstream of the switches, this capacitor making it possible to stabilize the voltage at the terminals of the high-voltage network. Without energy input from the high-voltage battery, the capacitor discharges slowly. It is therefore sufficient to observe a decrease in the voltage at the terminals of the capacitor to diagnose the opening of at least one of the switches.
[0012] However, when the switches are opened to switch to series hybrid mode without a battery, the voltage across the capacitor is maintained by the voltage regulation operated by the voltage rectifier, with the high-voltage network being supplied by the alternator-starter. The diagnostic method described above can no longer work. The battery current must then be measured, but the battery current sensor designed for such a measurement is not always reliable, especially in the event of a failure of the traction battery, as this current sensor is integrated into the battery casing housing the energy storage cells of the traction battery.
[0013] There is therefore a need, when a hybrid powertrain of a vehicle switches to series hybrid mode without a battery, for a reliable diagnosis of the opening of at least one of the switches connecting a traction battery of the vehicle to a high voltage network of the vehicle.
[0014] The present invention aims to remedy at least in part the aforementioned drawbacks by providing a method for determining the open or closed state of at least one switch connecting a traction battery of the vehicle to a high voltage network of the vehicle when a hybrid powertrain of the vehicle switches to series hybrid mode without a battery, a vehicle, a control method and an associated control device, which do not use the battery sensors to make such a determination.
[0015] To this end, the invention proposes a method for determining the open or closed state of at least one switch in a hybrid powertrain of a vehicle, the hybrid powertrain comprising a first electric machine and a heat engine capable of supplying, in parallel hybrid mode or in series hybrid mode, torque to a transmission chain of the vehicle, a first inverter capable of powering the first electric machine, the hybrid powertrain further comprising:
[0016] - a second electrical machine mechanically connected to the thermal engine,
[0017] - a second inverter capable of powering the second electrical machine,
[0018] - a traction battery,
[0019] - a capacity connected in parallel on the one hand to the first inverter, on the other hand to the second inverter, and also connected in parallel to a branch formed at least by the traction battery and the switch mounted in series with each other, the determination method being implemented during a transition of the hybrid powertrain to operation in series hybrid mode without battery, in a method for controlling the hybrid powertrain, this transition taking place during a step of supplying torque by the first electric machine during which the first inverter is connected to the traction battery, the step of supplying torque comprising a measurement or estimation of the voltage across the capacity, the transition to operation in series hybrid mode without battery comprising:
[0020] - a step of applying a set voltage to the input of the second inverter operating as a rectifier, capable of supplying current to the first inverter, the set voltage having an initial value taken equal to the voltage measured at the terminals of the capacitor, and
[0021] - a step of controlling the opening of the switch following the application step, the determination method being characterized in that it comprises:
[0022] - at least one step of modification of the set voltage, and
[0023] - a step of determining the closed or open state of the switch, using at least a first measurement or estimation of current at the input of the second inverter before the step of modifying the setpoint voltage, and at least a second measurement or estimation of current at the input of the second inverter when the modified setpoint voltage is reached.
[0024] It should be noted that in this application, the traction battery is understood as a battery powering the first inverter and the first electrical machine when the vehicle is running, unlike a possible vehicle service battery powering a low-voltage electrical network of the vehicle (for example 14V) to which various consumers are connected, including a main computer of the vehicle. The traction battery can therefore also be understood as a propulsion battery depending on the architecture of the transmission chain used. Unless otherwise stated, the battery referred to in this application is the traction battery of the vehicle.
[0025] The determination method according to the invention is, for example, implemented partly in software in a vehicle computer, for example the main computer of the vehicle, and partly in hardware by a control circuit of the second inverter. It has the advantage of not requiring any hardware modification of the vehicle since the control circuit of the second inverter exists independently of the determination method according to the invention.
[0026] It is applied to a hybrid powertrain comprising at least a first electric machine and a thermal engine mechanically connected to a second electric machine, for example an alternator-starter. If the hybrid powertrain comprises several first electric machines, the second inverter powers one or more of these during the step of supplying torque by the first electric machine. In addition, the hybrid powertrain is possibly capable of operating only in series hybrid mode, the invention applying to such a mode but in which the traction battery is disconnected from a high-voltage network of the vehicle.
[0027] The determination method according to the invention makes it possible to determine the open or closed state of at least one switch connecting the traction battery to the high-voltage network of the vehicle, that is to say in particular to the capacitor. The switch is a controlled relay or a transistor. When it is diagnosed as closed, after the opening control step, it means that it is faulty, and the transition to series hybrid mode without battery cannot be carried out. When a single switch is controlled to open during the opening control step, it is indeed the state of this switch which is determined by the determination method according to the invention. However, when the opening control is applied to two switches each connecting one of the terminals of the battery to the high-voltage network, the determination carried out by the determination method according to the invention makes it possible to determine the open state of at least one of the two switches, or the closed state of the two switches.In fact, in this case, it is sufficient to open just one of the two switches to isolate the traction battery from the high-voltage network. The method for determining the open or closed state of at least one switch is therefore to be understood as a method for diagnosing the correct disconnection of the traction battery from the vehicle's high-voltage network.
[0028] The setpoint voltage applied to the input of the second inverter operating as a rectifier, i.e. to the terminals of the capacitor, is determined so as to allow a nominal power supply to the first electrical machine in the context of vehicle running, and a nominal power supply to the low-voltage electrical consumers when they are connected to the capacitor via a direct current - direct current converter. The setpoint voltage is taken equal to the voltage at the terminals of the capacitor before the switch opening command, i.e. at the terminals of the traction battery before this opening, so as not to discharge the traction battery.
[0029] The determination method uses a first measurement or estimation of current at the input of the inverter before the modification of the set voltage, and a second measurement or estimation of current after reaching the set voltage, that is to say after a response time of the regulation operated by the second inverter. These two measurements or estimations of current use current sensors linked to the inverter and not to the battery, which makes the determination method reliable compared to the prior art. The estimations can use measurements carried out on the second electrical machine, allowing by calculation an estimation of the current on the DC bus supplying the two inverters.
[0030] It should be noted that a measure at the capacity level is used, but it can also be an estimate from a set of measurements, the term "measurement" being understood in the broad sense.
[0031] Furthermore, the choice of the setpoint voltage makes it possible to open the switch at a time when the current flowing across the battery terminals is almost zero, which reduces wear and the risk of the switch sticking. When the traction battery remains connected to the high-voltage network, the two measurements are different since we move from a situation where the current across the battery terminals is almost zero to a situation where the traction battery behaves as an additional energy source or as an additional consumer on the high-voltage network. Thanks to the invention, it is therefore possible to determine the state of at least one switch connecting the battery to the high-voltage network, in a reliable manner.
[0032] According to a preferred characteristic of the invention, the step of modifying the setpoint voltage is followed by a step of restoring the setpoint voltage to its initial value. This restoration step takes place after the second measurement and makes it possible in particular not to charge or discharge the battery if it turns out not to be disconnected from the high voltage network.
[0033] In a preferred embodiment of the invention, the determination method according to the invention comprises a step of reducing the setpoint voltage to its initial value reduced by a predetermined quantity, then a step of increasing the setpoint voltage to its initial value increased by the predetermined quantity, the first current measurement or estimation taking place when the reduced voltage setpoint is reached and the second current measurement or estimation taking place when the increased voltage setpoint is reached.
[0034] This implementation of the invention makes it possible not to recharge the traction battery if the switch has not opened, knowing that if the traction battery is faulty, excessive recharging leads to a risk of combustion of the cells. Thus, in the case where the switch has remained closed, this implementation begins by discharging the battery then by recharging it which also makes it possible not to excessively discharge the battery, which will be necessary to restart the vehicle.
[0035] Preferably, the determination method according to the invention comprises several steps of reducing the setpoint voltage, each being followed by a step of increasing the setpoint voltage, a first measurement or estimation of current at the input of the second inverter taking place after each time a reduced setpoint voltage is reached and a second measurement or estimation of current at the input of the second inverter taking place after each time an increased setpoint voltage is reached.
[0036] This procedure takes into account a possible variation in current consumption by the electrical consumers of the high-voltage network, during the implementation of the determination method according to the invention. Having several measurements after several stages of modification of the setpoint voltage makes it possible to average these current variations due to consumers other than the traction battery, and to make the switch opening diagnosis robust to these variations.
[0037] For example, the determining step determines an open state of the switch when the average of the absolute value differences between the first measurements or estimates and the second measurements or estimates is less than a predetermined current threshold, otherwise the determining step determines a closed state of the switch.
[0038] In an alternative embodiment, the determination step determines an open state of the switch if the difference in absolute value between the first measurement or estimate and the second measurement or estimate is less than a predetermined current difference, otherwise the determination step determines a closed state of the switch.
[0039] In yet another alternative embodiment, the determination method comprises several steps of modifying the setpoint voltage, each followed by a step of restoring the setpoint voltage to its initial value, a first measurement or estimation of current at the input of the second inverter taking place after each time the initial value of the setpoint voltage is reached, and a second measurement or estimation of current at the input of the second inverter taking place after each time a modified setpoint voltage is reached, and in which the determination step determines an open state of the switch when the average of the differences in absolute value between the first measurements or estimations and the second measurements or estimations is less than a predetermined current difference, otherwise the determination step determines a closed state of the switch.In this other variant, the steps of modification of the setpoint voltage alternate, for example, between a decrease and an increase in the setpoint voltage.
[0040] The invention also relates to a method for controlling a hybrid powertrain of a vehicle, the hybrid powertrain comprising a first electric machine and a heat engine capable of supplying, in parallel hybrid mode or in series hybrid mode, torque to a transmission chain of the vehicle, a first inverter capable of powering the first electric machine, the hybrid powertrain further comprising:
[0041] - a second electrical machine mechanically connected to the thermal engine,
[0042] - a second inverter capable of powering the second electrical machine,
[0043] - a traction battery,
[0044] - a capacity connected in parallel on the one hand to the first inverter, on the other hand to the second inverter, and also connected in parallel to a branch formed at least of the traction battery and a switch mounted in series with each other, the control method comprising:
[0045] - a step of supplying torque by the first electric machine during which the first inverter is connected to the traction battery, the step of supplying torque comprising a measurement or estimation of the voltage at the terminals of the capacitor, and a transition of the hybrid powertrain to operation in series hybrid mode without battery, the transition comprising:
[0046] - a step of applying a set voltage to the input of the second inverter operating as a rectifier, capable of supplying current to the first inverter, the set voltage having an initial value equal to the voltage measured across the terminals of the capacitor, and
[0047] - a step of controlling the opening of the switch following the application step, the control method being characterized in that the control step is followed by a method of determining the open or closed state of the switch according to the invention. The invention also relates to a device for determining the open or closed state of at least one switch in a hybrid powertrain of a vehicle, the hybrid powertrain comprising a first electric machine and a heat engine capable of supplying, in parallel hybrid mode or in series hybrid mode, torque to a transmission chain of the vehicle, a first inverter capable of powering the first electric machine, the hybrid powertrain further comprising:
[0048] - a second electrical machine mechanically connected to the thermal engine,
[0049] - a second inverter capable of powering the second electrical machine,
[0050] - a traction battery,
[0051] - a capacity connected in parallel on the one hand to the first inverter, on the other hand to the second inverter, and also connected in parallel to a branch formed at least by the traction battery and the switch mounted in series with each other, the hybrid powertrain comprising control means comprising means for switching to operation in series hybrid mode without battery, the control means comprising means for supplying torque by the first electrical machine when the first inverter is connected to the traction battery and means for measuring or estimating the voltage across the capacity, the switching means being activated during such a connection and comprising:
[0052] - means for applying a set voltage to the input of the second inverter operating as a rectifier, capable of supplying current to the first inverter, the set voltage having an initial value equal to a voltage measured at the terminals of the capacitor by the measuring or estimating means, and
[0053] - means for controlling the opening of the switch after application of the set voltage by the application means, the determination device being characterized in that it comprises:
[0054] - means for modifying the set voltage, activated by the opening control means, and
[0055] - means for determining the closed or open state of the switch using current measurement or estimation means delivering at least a first measurement or estimation of current at the input of the second inverter before a modification of the setpoint voltage by the modification means, and a second measurement or estimation of current at the input of the second inverter when the modified setpoint voltage is reached. Finally, the invention relates to a vehicle comprising a hybrid powertrain comprising a first electric machine and a heat engine capable of supplying torque in parallel hybrid mode or in series hybrid mode to a transmission chain of the vehicle, a first inverter capable of powering the first electric machine, the hybrid powertrain further comprising:
[0056] - a second electrical machine mechanically connected to the thermal engine,
[0057] - a second inverter capable of powering the second electrical machine,
[0058] - a traction battery,
[0059] - a capacity connected in parallel on the one hand to the first inverter, on the other hand to the second inverter, and also connected in parallel to a branch formed at least of the traction battery and a switch mounted in series, the vehicle being characterized in that it further comprises a device for determining the open or closed state of the switch according to the invention.
[0060] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:
[0061] [fig 1] represents a hybrid powertrain of a vehicle implementing a control method according to the invention, in one embodiment of the invention,
[0062] [fig 2] represents a high voltage network of the vehicle of figure 1, to which elements of the powertrain of figure 1 are connected,
[0063] [fig 3] represents steps of the control method according to the invention of the hybrid powertrain of figure 1, comprising steps of a method according to the invention for determining the state of a switch of the high voltage network of figure 2, in this embodiment of the invention,
[0064] [fig 4] represents curves of voltage variations and current variations associated with steps of the determination method of figure 3,
[0065] [fig 5] represents variations in the current at the terminals of a traction battery of the vehicle when the latter is not disconnected from the high voltage network of figure 2 during the implementation of steps of the determination method of figure 3, and
[0066] [fig 6] represents voltage and current measurements taking place during steps of the determination method of figure 3. According to an embodiment of the invention, a vehicle according to the invention comprises a hybrid powertrain 2 shown in figure 1. This specific hybrid powertrain 2 comprises a clutch gearbox, the different engagements of which make it possible to achieve different gearbox ratios. This gearbox is robotized, that is to say that the changes from one gear ratio to another are automated. Of course, other types of hybrid powertrains can be used as a variant, for example not using clutches for gear changes.
[0067] The hybrid powertrain 2 comprises a thermal engine 24, capable of rotating a solid primary shaft 21 on which a clutch makes it possible to impose a 2T or 4T speed ratio depending on its engagement via idle gears with a secondary shaft 23 connected to a differential system of the vehicle, mechanically connected to the wheels of the vehicle.
[0068] The hybrid powertrain 2 also comprises a first electric machine 20 mounted on a hollow primary shaft having a speed ratio 1E or 2E depending on the engagement of a clutch on the secondary shaft 23 with idler gears cooperating with the hollow primary shaft.
[0069] The hollow and solid primary shafts are not directly mechanically connected to each other, which allows the heat engine 24 and the first electric machine 20 to operate independently, except by using a first idler gear of a transfer shaft 25 on which a clutch is mounted and which can cooperate with the hollow primary shaft, the transfer shaft 25 being mechanically connected to the output of the heat engine 24.
[0070] Finally, the hybrid powertrain 2 comprises a second electric machine 22 capable of rotating the transfer shaft 25. This second electric machine 22 is a high-voltage alternator-starter operating, for example, at 48V (volts). A second idler gear on the transfer shaft 25 makes it possible to impose a 3T speed ratio when the clutch on the transfer shaft 25 is engaged in this second idler gear and the latter cooperates with an idler gear actuating the solid primary shaft 21, this 3T speed ratio then being associated with the second electric machine and heat engine assembly.
[0071] The hybrid powertrain 2 requires the use of a series hybrid operating mode, particularly when the vehicle speed is less than 20 km / h, and during certain gear changes. In this series hybrid mode, the first electric machine 20 alone provides propulsion or traction of the vehicle, being powered at least in part by the second electric machine 22 coupled to the heat engine 24.
[0072] Figure 2 shows the vehicle's high voltage network and its connections to the electrical machines 22, 20 to better understand the operation of the series hybrid mode.
[0073] When the vehicle is stationary, the vehicle's high-voltage network is powered solely by a traction battery 3. A switch 32 connects the positive terminal of the traction battery 3 to one of the terminals of a capacitor 36, the other of the terminals of the capacitor 36 being connected to a negative terminal of the traction battery 3. The capacitor 36 makes it possible to smooth out voltage variations on the high-voltage network, which comprises at least the capacitor 36 as well as the various connections to the vehicle's high-voltage consumers. These include in particular a direct current - direct current converter 42, connected at the input in parallel with the capacitor 36 and at the output to the vehicle's low-voltage consumers, such as computers.
[0074] A first inverter 40 is also connected in parallel to the input of the capacitor 36 and to the output of the first electrical machine 20. It therefore makes it possible to power the electrical machine 20 from electrical energy coming from the high voltage network, or to supply electrical energy to the high voltage network from energy recovered for example during braking by the first electrical machine 20.
[0075] Finally, a second inverter 38 is connected in parallel to the input of the capacitor 36 and to the output of the second electrical machine 22. The latter being coupled to the output of the thermal engine 24, the second inverter 38 makes it possible to supply electrical energy to the high voltage network when the thermal engine 24 is operating, or on the contrary to supply additional torque to the powertrain 2 when it receives energy from the high voltage network.
[0076] In series hybrid mode, the thermal engine 24 is not coupled to the wheels, it operates only to supply the high voltage network via the second electrical machine 22 and the second inverter 40, the energy produced making it possible to supply the first inverter 40 and therefore the first electrical machine 20 ensuring the running of the vehicle, without the traction battery 3, possibly supplying part of the energy necessary for running or for other high voltage consumers, discharging quickly.
[0077] In order not to limit the performance of the first electric machine 20, which could produce more torque by not limiting the voltage Vcapa across the terminals of the capacitor 36 to the value of the voltage Vbatt across the terminals of the traction battery 3, or in the case where the traction battery 3 presents a risk of failure, a control method 100 of the hybrid powertrain 2, shown in FIG. 3, comprises a switch from the series hybrid mode to a series hybrid mode without battery, that is to say in which the traction battery 3 is disconnected from the high voltage network.
[0078] The control method 100 is mainly implemented in software in a computer 50 of the vehicle. This communicates via a CAN bus (from the English “Controller Area Network”) with the actuators of the vehicle and in particular its gearbox, as well as with the control circuits of the first and second inverters 40, 38.
[0079] A first step 110 of the control method 100 is a supply of torque by the first electric machine 20 in series hybrid mode during which the traction battery 3 is connected to the high voltage network and therefore to the capacity 36.
[0080] To switch to a series hybrid mode without battery, it is necessary to regulate the voltage across the capacitor 36 before disconnecting the traction battery 3, so that the capacitor 36 does not discharge very quickly (in a few tens of milliseconds) during this disconnection, in particular due to the electrical consumption of the low-voltage electrical consumers connected to the direct current - direct current converter. In order to avoid a reduction in the torque at the wheel, it is therefore necessary to maintain the voltage Vcapa of the capacitor 36 after disconnecting the traction battery 3, within limits allowing the operation of the first inverter 40, with a voltage Vcapa of, for example, between 200V and 400V.
[0081] For this, a step 112 during the step 110 of providing torque, is a step of measuring or estimating 112 the voltage Vcapa at the terminals of the capacitor 36.
[0082] This step 112 is followed by a step 120, still during the torque supply step 110, of applying a setpoint voltage Vcons to the input of the second inverter 3 operating as a rectifier. In order to make the disconnection of the traction battery 3 transparent for the electrical consumers and on the torque supplied to the wheels of the vehicle, and to open the switch 32 without a significant current flowing through this switch 32, which would increase the risks of this switch 32 sticking (i.e. it would no longer respond to opening commands), a setpoint voltage Vcons is chosen equal in value to the voltage Vcapa previously measured at the terminals of the capacitor 36. For this, the computer 50 communicates to the control circuit 380 of the second inverter 38, this value of the setpoint voltage Vcons to be applied at the input of the second inverter 38, i.e. at the terminals of the capacitor 36.The control circuit 380 then operates a regulation allowing the voltage Vcapa to be maintained across the terminals of the capacitor 36, at this value of the setpoint voltage Vcons, even after disconnection of the traction battery 3, this value being called in the following the initial value of the setpoint voltage Vcons. The initial setpoint voltage Vcons is therefore the voltage Vcapa measured before opening the switch 32.
[0083] The next step 130 is the opening command of the switch 32, allowing the transition from series hybrid mode to series hybrid mode without battery, if this opening takes place.
[0084] To verify that this opening has indeed taken place after this opening command step 130, the control method 100 comprises a method 200 for determining the state of the switch 32. This determination method is implemented by the computer 50 in cooperation with the control circuit 380 of the second inverter 38. The control circuit 380 also comprises means for measuring or estimating the long current at the input of the second inverter 38, and means for measuring or estimating the voltage at the input of the second inverter 38, i.e., across the terminals of the capacitor 36. In the following, we refer to measuring the voltage across the terminals of the capacitor 36 and measuring the long current, knowing that this may be a direct or indirect measurement, i.e., an estimation.
[0085] The determination method 200 comprises a step 210 of decreasing the initial setpoint voltage Vcons, for example by 5 volts. Once the new setpoint voltage Vcons has been reached, i.e. after 50 milliseconds for example, a first measurement 212 of the long current at the input of the second inverter 38 is carried out by the measuring means of the control circuit 380 and sent back to the computer 50.
[0086] The next step of the determination method 200 is a step 220 of increasing the setpoint voltage Vcons to its initial value increased for example by 5 volts. This increase is equal in absolute value to twice the reduction made in the previous step so as not to modify on average the charge level of the traction battery 3. Once the new setpoint voltage Vcons is reached, a second measurement 222 of the background current at the input of the second inverter 38 is carried out by the measuring means of the control circuit 380 and fed back to the computer 50.
[0087] Figure 4 shows, on the upper window:
[0088] - in dotted lines a simulation curve of the voltage Vcapa at the terminals of the capacitor 36 during steps 210 and 220 in the case where the switch 32 remained blocked in the on state,
[0089] - in a thin line a simulation curve of the voltage Vcapa at the terminals of the capacitor 36 during steps 210 and 220 in the case where the switch 32 is open, and
[0090] - in bold the setpoint voltage Vcons during steps 210 and 220.
[0091] The ordinate is expressed in volts and the abscissa in seconds.
[0092] We observe a response time of the second inverter 38 to observe the modifications of the setpoint voltage Vcons, of several tens of milliseconds.
[0093] The corresponding behavior of the bottom current is shown in the lower window of Figure 4, where:
[0094] - the dotted curve is a simulation curve of the background current at the input of the second inverter 38 in the case where the switch 32 remains stuck in the on state, and
[0095] - the thin line curve is a simulation curve of the background current at the input of the second inverter 38 in the case where the switch 32 is open.
[0096] The ordinate is expressed in amperes and the abscissa in seconds.
[0097] It can be seen that when the switch 32 has opened correctly, the current flowing at the input of the second inverter 38 has the same value of approximately 10.3A (amperes) after reaching the setpoint voltage Vcons reduced by 5V, and after reaching the setpoint voltage Vcons increased by 10V, i.e. after reaching the initial setpoint voltage Vcons increased by 5V. This current value is the same as before these modifications of the setpoint voltage Vcons.
[0098] Conversely, when the switch 32 remains blocked in the closed position, the current flowing at the input of the second inverter 38 has a value of approximately 9.8A after reaching the voltage setpoint Vcons reduced by 5V, and a value of approximately 10.8A after reaching the voltage setpoint Vcons increased by 10V.
[0099] It is therefore theoretically possible to determine whether the switch 32 has remained closed by measuring a difference in absolute value between the first measurement and the second current measurement which is greater than a predetermined threshold, for example 0.8A to take into account measurement noise.
[0100] Figure 5 shows a simulation curve of the current Ibatt flowing in traction battery 3 in the case where the switch remained stuck in the closed position, the ordinate being expressed in amperes and the abscissa in seconds.
[0101] It is noted that the battery recharges with a current of 5A when the set voltage Vcons is reduced, which explains the concomitant decrease in the lond current at the terminals of the second inverter 38, and that the battery discharges with a current of 5A when the set voltage Vcons is increased, which explains the concomitant increase in the background current at the terminals of the second inverter 38.
[0102] In this embodiment of the invention, the reduced setpoint voltage Vcons is applied for 100 milliseconds, and the increased setpoint voltage Vcons is applied over the same duration, the setpoint voltage Vcons then being restored to its initial value on the curves of Figures 4 and 5. This makes it possible to diagnose the good or bad disconnection of the traction battery 3 without modifying on average the state of charge of the battery. Given that the first step 210 is a step of reducing the setpoint voltage Vcons, if the determination method is interrupted before its end, the traction battery 3 can only have discharged and therefore will not present any risk of overheating.
[0103] However, the curves of Figures 4 and 5 assume that the electrical consumers of the high-voltage network other than the traction battery 3 draw a constant current of approximately 10.3 A throughout the determination method 100, whereas in reality their consumption is not as constant. In order to overcome this variation in the current consumption of these other consumers, steps 210, 212, 220 and 222 are repeated so as to be able to average this current consumption and ultimately to partially cancel it out.
[0104] For this, a counter i is incremented in step 220 of increasing the setpoint voltage Vcons. During a step 230 following the second measurement 222 of the current lond at the input of the second inverter 38, the counter i is compared to a predetermined number M of executions of steps 210 and 220. If the counter i has a value strictly lower than this number M (branch N in FIG. 3) then the determination method 100 iterates steps 210, 212, 220 and 222.
[0105] After a number M of executions of steps 210, 212, 220 and 222, the counter i being equal in value to the number M (branch Y in figure 3), the determination method 200 comprises a step 240 of reestablishing the initial setpoint voltage Vcons, of value equal to the voltage measured at the terminals of the capacitor 36 before the step 130 of opening control of the switch 32.
[0106] Finally, the next step is the determination 250 of the open or closed state of the switch 32 as a function of the first and second measurements taking place during the previous steps of decreasing 210 and respectively increasing 220 the setpoint voltage Vcons.
[0107] Figure 6 shows voltage and current measurement curves corresponding to a number M equal to 4 of execution of steps 210 and 220:
[0108] More specifically, the top window of Figure 6 shows:
[0109] - in dotted lines a measurement curve of the voltage Vcapa at the terminals of the capacitor 36 during steps 210 and 220 in the case where the switch 32 remained blocked in the on state,
[0110] - in a thin line a measurement curve of the voltage Vcapa at the terminals of the capacitor 36 during steps 210 and 220 in the case where the switch 32 is open, and
[0111] - in bold the setpoint voltage Vcons during steps 210 and 220.
[0112] The ordinate is expressed in volts and the abscissa in seconds.
[0113] Similarly the lower window of Figure 6 shows:
[0114] - in dotted lines a measurement curve of the long current at the input of the second inverter 38 in the case where the switch 32 remained stuck in the on state, and
[0115] - in a thin line a measurement curve of the long current at the input of the second inverter 38 in the case where the switch 32 is open.
[0116] The ordinate is expressed in amperes and the abscissa in seconds. These curves are much less smooth than the curves in Figure 4. However, by taking an average of the first measurements and an average of the second measurements, the "noise" due to variations in electrical energy consumption by low-voltage consumers in particular, is almost cancelled out. Indeed, in the example in Figure 6, the average of the differences between the second current measurements and the first current measurements is approximately 1.2A in the case where switch 32 is blocked in the on state, while this average is approximately 0.3A in the case where switch 32 has been opened. The predetermined threshold of 0.8A mentioned above in relation to Figure 4 can therefore be retained.
[0117] In summary, in step 250 of determining the state of the switch 32, for each first measurement and second measurement of long current at the input of the inverter corresponding to the same value of counter i, the difference in absolute value between this first measurement and this second measurement is calculated. Then the average of the N differences thus calculated is calculated. If this average is less than the predetermined threshold of 0.8A then an open state of the switch 32 is determined, otherwise a closed state of the switch 32 is determined.
[0118] Alternatively, only one execution of the decrease step 210 and the increase step 220 is carried out, with a greater variation in the setpoint voltage Vcons. Indeed, by increasing the amplitude of the voltage pulses, the level of current variation that can be observed is increased, making the diagnosis all the more reliable but causing the battery (in the case of a relay stuck closed) to be crossed by even greater currents. It is therefore rather interesting to be able to eliminate a maximum of noise without this lever as in the main embodiment of the invention, allowing a compromise between diagnosis time and current level.
[0119] The predetermined current threshold is set in particular as a function of the variations in the setpoint voltage Vcons imposed during the decrease step 210 and during the increase step 220. It is preferably between 0.5 and 1A when the setpoint voltage Vcons varies by approximately 5 volts compared to its initial value.
[0120] It should also be noted that the variation of 5 volts is chosen in this embodiment of the invention as a function in particular of the voltage Vbatt at the terminals of the traction battery before the opening command 130 of the switch 32. Of course, numerous variant embodiments are conceivable, for example in which the voltage variations differ as a function of the value of the counter i, or in which each modification of the setpoint voltage is followed by a return of the setpoint voltage to its initial value, or in which several first measurements are carried out during the same step of reducing the setpoint voltage, and several second measurements are carried out during the same step of increasing the setpoint voltage.In the latter case, the determination step performs, for example, a first average of the first measurements for each distinct step of reduction of the set voltage, and a second average of the second measurements for each distinct step of increase of the set voltage, then an average of the differences in absolute value between each first average and each second average.
[0121] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention.
Claims
CLAIMS 1- Method for determining (200) the open or closed state of at least one switch (32) in a hybrid powertrain (2) of a vehicle, the hybrid powertrain (2) comprising a first electric machine (20) and a heat engine (24) capable of supplying, in parallel hybrid mode or in series hybrid mode, torque to a transmission chain of the vehicle, a first inverter (40) capable of supplying the first electric machine (20), the hybrid powertrain (2) further comprising: - a second electric machine (22) mechanically connected to the heat engine (24), - a second inverter (38) capable of powering the second electrical machine (22), - a traction battery (3), - a capacitor (36) connected in parallel on the one hand to the first inverter (40), on the other hand to the second inverter (38), and also connected in parallel to a branch formed at least of the traction battery (3) and the switch (32) mounted in series with each other, the determination method (200) being implemented during a transition of the hybrid powertrain (2) to operation in series hybrid mode without battery, in a control method (100) of the hybrid powertrain (2), this transition taking place during a step of supplying torque (110) by the first electric machine (20) during which the first inverter (40) is connected to the traction battery (3), the step of supplying torque (110) comprising a measurement or estimation (112) of the voltage (Vcap) across the capacitor (36), the transition to operation in series hybrid mode without battery comprising: - a step of applying (120) a setpoint voltage (Vcons) to the input of the second inverter (38) operating as a rectifier, capable of supplying current to the first inverter (40), the setpoint voltage (V cons) having an initial value equal to the measured voltage (V cap) across the terminals of the capacitor (36), and - a control step (130) for opening the switch (32) following the application step (120), the determination method (200) being characterized in that it comprises: - at least one modification step (210, 220) of the setpoint voltage (Vcons), and - a step of determining (250) the closed or open state of the switch (32), using at least a first measurement or estimation of current at the input of the second inverter (38) before the step of modifying the setpoint voltage (Vcons), and at least a second measurement or estimation of current at the input of the second inverter (38) when the modified setpoint voltage (V cons) is reached. 2- Method for determining (200) the open or closed state of at least one switch (32) according to claim 1, in which the step of modifying (210, 220) the setpoint voltage (Vcons) is followed by a step of restoring (240) the setpoint voltage (V cons) to its initial value. 3- Method for determining (200) the open or closed state of at least one switch (32) according to claim 1 or 2, comprising a step of decreasing (210) the setpoint voltage (Vcons) to its initial value decreased by a predetermined quantity, then a step of increasing (220) the setpoint voltage (V cons) to its initial value increased by the predetermined quantity, the first current measurement or estimation taking place when the decreased voltage setpoint (V cons) is reached and the second current measurement or estimation taking place when the increased voltage setpoint (V cons) is reached. 4- Method for determining (200) the open or closed state of at least one switch according to claim 3, comprising several steps of decreasing (210) the setpoint voltage (Vcons), each being followed by a step of increasing (220) the setpoint voltage (Vcons), a first measurement or estimation of current at the input of the second inverter (38) taking place after each reaching of a reduced setpoint voltage (V cons) and a second measurement or estimation of current at the input of the second inverter (38) taking place after each reaching of an increased setpoint voltage (V cons). 5- Method for determining (200) the open or closed state of at least one switch according to claim 3 or 4, in which the determining step (250) determines an open state of the switch (32) when the average of the differences in absolute value between the first measurements or estimations and the second measurements or estimations is less than a predetermined current threshold, otherwise the determining step (250) determines a closed state of the switch (32). 6- Method for determining (200) the open or closed state of at least one switch according to claim 1 or 2, in which the determining step (250) determines an open state of the switch (32) if the difference in absolute value between the first measurement or estimate and the second measurement or estimate is less than a predetermined current difference, otherwise the determining step (250) determines a closed state of the switch (32). 7- Method for determining (200) the open or closed state of at least one switch according to claim 1 or 2, comprising several steps of modifying the setpoint voltage (V cons) each followed by a step of restoring the setpoint voltage (V cons) to its initial value, a first measurement or estimation of current at the input of the second inverter (38) taking place after each reaching of the initial value of the setpoint voltage (V cons), and a second measurement or estimation of current at the input of the second inverter (38) taking place after each reaching of a modified setpoint voltage (V cons), and in which the determining step (250) determines an open state of the switch (32) when the average of the differences in absolute value between the first measurements or estimations and the second measurements or estimations is less than a predetermined current difference,otherwise the determining step (250) determines a closed state of the switch (32)., 8- Method for controlling (100) a hybrid powertrain (2) of a vehicle, the hybrid powertrain (2) comprising a first electric machine (20) and a heat engine (24) capable of supplying, in parallel hybrid mode or in series hybrid mode, torque to a transmission chain of the vehicle, a first inverter (40) capable of powering the first electric machine (20), the hybrid powertrain (2) further comprising: - a second electric machine (22) mechanically connected to the heat engine (24), - a second inverter (38) capable of powering the second electrical machine (22), - a traction battery (3), - a capacitor (36) connected in parallel on the one hand to the first inverter (40), on the other hand to the second inverter (38), and also connected in parallel to a branch formed at least of the traction battery (3) and a switch (32) mounted in series with each other, the control method (100) comprising: - a step of supplying torque (110) by the first electric machine (20) during which the first inverter (40) is connected to the traction battery (3), the step of torque supply (110) comprising a measurement or estimation (112) of the voltage (Vcap) across the capacitor (36), and a switch of the hybrid powertrain (2) to operation in series hybrid mode without battery, the switch comprising: - a step of applying (120) a setpoint voltage (Vcons) to the input of the second inverter (38) operating as a rectifier, capable of supplying current to the first inverter (40), the setpoint voltage (V cons) having an initial value equal to the measured voltage (V cap) across the terminals of the capacitor (36), and - a step (130) of controlling the opening of the switch (32) following the application step (120), the control method (100) being characterized in that the control step (130) is followed by a method (200) of determining the open or closed state of the switch (32) according to any one of claims 1 to 7. 9- Device for determining the open or closed state of at least one switch in a hybrid powertrain (2) of a vehicle, the hybrid powertrain (2) comprising a first electric machine (20) and a heat engine (24) capable of supplying, in parallel hybrid mode or in series hybrid mode, torque to a transmission chain of the vehicle, a first inverter (40) capable of supplying the first electric machine (20), the hybrid powertrain (2) further comprising: - a second electric machine (22) mechanically connected to the heat engine (24), - a second inverter (38) capable of powering the second electrical machine (22), - a traction battery (3), - a capacitor (36) connected in parallel on the one hand to the first inverter (40), on the other hand to the second inverter (38), and also connected in parallel to a branch formed at least by the traction battery (3) and the switch (32) mounted in series with each other, the hybrid powertrain (2) comprising control means comprising means for switching to operation in series hybrid mode without battery, the control means comprising means for supplying torque by the first electric machine (20) when the first inverter (40) is connected to the traction battery (3) and means for measuring or estimating the voltage (V cap) at the terminals of the capacitor (36), the switching means being activated during such connection and including: - means for applying a setpoint voltage (V cons) to the input of the second inverter (38) operating as a rectifier, capable of supplying current to the first inverter (40), the setpoint voltage (V cons) having an initial value equal to a voltage measured at the terminals of the capacitor (36) by the measuring or estimating means, and - means for controlling the opening of the switch (32) after application of the set voltage (V cons) by the application means, the determination device being characterized in that it comprises: - means for modifying the set voltage (V cons), activated by the opening control means, and - means for determining the closed or open state of the switch (32) using current measurement or estimation means delivering at least a first current measurement or estimation at the input of the second inverter (38) before a modification of the setpoint voltage (V cons) by the modification means, and at least a second current measurement or estimation at the input of the second inverter (38) when the modified setpoint voltage (V cons) is reached. 10- Vehicle comprising a hybrid powertrain (2) comprising a first electric machine (20) and a thermal engine (24) capable of supplying torque in parallel hybrid mode or in series hybrid mode to a transmission chain of the vehicle, a first inverter (40) capable of supplying the first electric machine (20), the hybrid powertrain (2) further comprising: - a second electric machine (22) mechanically connected to the heat engine (24), - a second inverter (38) capable of powering the second electrical machine (22), - a traction battery (3), - a capacitor (36) connected in parallel on the one hand to the first inverter (40), on the other hand to the second inverter (38), and also connected in parallel to a branch formed at least by the traction battery (3) and a switch (32) mounted in series, the vehicle being characterized in that it further comprises a device for determining the open or closed state of the switch (32) according to claim 9.