Control device for a wound rotor and motor vehicle

Abstract

The invention relates to a control device for a wound rotor (5) of an electric machine (3) of a vehicle (1), comprising: - two input terminals (14, 15) - two output terminals (16, 17) configured to be connected to the wound rotor, - a capacitive module (7) connected between the two input terminals, - a discharge circuit (21) configured to be powered by the capacitive module and configured to be either in an active state in which it controls the discharge of the capacitive module through a winding of the wound rotor, or in an inactive state in which the discharge of the capacitive module is inhibited. The device includes a computer processing unit adapted to transmit an inhibition signal to the discharge circuit, said discharge circuit being in an inactive state when it receives the inhibition signal and in an active state otherwise. A motor vehicle comprising such a device is also proposed. Figure for the abstract: Fig. 1

Description

Title of the invention: Control device for a wound rotor and motor vehicle Technical field of the invention

[0001] The present invention relates generally to the field of electrical machines, and in particular to wound-rotor electric machines powered by a traction battery.

[0002] It relates more particularly to a control device for a wound rotor and a motor vehicle comprising such a device. State of the art

[0003] A powertrain of an electric or hybrid motor vehicle typically includes a battery, known as a "traction battery," which powers a three-phase motor via an inverter. The inverter typically includes a capacitive module (usually referred to by the English term "DC link") mounted in parallel with the connection terminals to the traction battery.

[0004] After the traction battery has been disconnected from the inverter, the capacitive module retains a significant residual charge. For example, the voltage across its terminals at the time of disconnection is equal to the output voltage of the traction battery. Depending on the type of vehicle in which the traction battery is installed, this voltage can be as high as 250 volts, 450 volts, or even 800 volts.

[0005] In the event that the battery disconnection results from an accident, this voltage may be dangerous for the occupants of the vehicle or for the rescue or maintenance personnel who intervene on the vehicle.

[0006] Therefore, in order to ensure safe operation of the motor vehicle, it is necessary that the voltage across the terminals of the capacitive module be quickly reduced to a safe value, preferably less than or equal to 60 volts. Several solutions exist for this purpose.

[0007] A first solution, known as the passive solution, consists of placing a resistive circuit in parallel with the capacitive module. In this way, the discharge of the capacitive module occurs via this resistive circuit. However, this solution has two drawbacks. Firstly, it results in continuous losses in the resistive circuit, even during normal vehicle operation. Secondly, at very high voltages, for example 800V, discharging the capacitive module in a sufficiently short time, for example 5 seconds, requires a high resistance value for the resistive circuit, which further increases the losses.

[0008] A second solution, called active, can be used for wound-rotor electric machines. It consists of controlling the arms of the motor vehicle's inverter in order to discharge the capacitive module into the rotor or stator windings. For example, this solution is implemented when an accident is detected.

[0009] However, in certain situations, the information relating to the detection of the accident is not correctly reported to the circuit which controls the discharge of the capacitive module, which is therefore not triggered. Presentation of the invention

[0010] In order to remedy the aforementioned disadvantages of the prior art, the present invention proposes a reliable and economical means for unloading the capacitive module of a vehicle traction chain.

[0011] More particularly, the invention proposes a control device for a wound rotor of an electric machine of a motor vehicle, comprising: - two input terminals configured to be respectively connected to two terminals of a traction battery of the motor vehicle, - two output terminals configured to be connected to the wound rotor, - a capacitive module connected between the two input terminals, - a discharge circuit configured to be powered by the capacitive module and configured to be either in an active state in which it controls the discharge of the capacitive module through a wound rotor winding, or in an inactive state in which the discharge of the capacitive module is inhibited, in which a computer processing unit is provided which is adapted to transmit an inhibition signal to the discharge circuit, said discharge circuit being in the inactive state when it receives the inhibition signal and in the active state otherwise.

[0012] Thus, thanks to the inhibition signal, the presence of the microcontroller is essential to maintaining the discharge circuit in its inactive state. In the event of a microcontroller failure, for example in the event of an accident, it no longer matters whether or not the microcontroller had time to receive an accident detection signal or transmit a discharge control signal. The mere absence of the microcontroller triggers the discharge of the capacitive module through the wound rotor. The reliability of the process is therefore improved.

[0013] Other advantageous and non-limiting features of the device according to the invention, taken individually or in all technically possible combinations, are as follows: - The computer processing unit includes an interface module configured to communicate with the outside of the device, and the computer processing unit is configured to detect a fault in the communication of the interface module with outside the device and to stop the transmission of the inhibition signal in case of fault detection. - The computer processing unit is configured to check the integrity of the data received by the interface module; detection of a communication failure with the outside of the vehicle occurs if any of the received data is corrupted. - The computer processing unit is configured to verify the integrity of the received data by implementing a cyclic redundancy check algorithm. - The computer processing unit is configured to verify the integrity of the received data by implementing a clock synchronization algorithm. - The failure to communicate with the outside world is detected if the interface module is out of service. - the device includes a chopper having a first controlled switch connected between a first of the two input terminals and a first of the two output terminals, a second controlled switch connected between a second of the two input terminals and a second of the two output terminals, a first diode connected in one direction between the second input terminal and the first output terminal and a second diode connected in the opposite direction between the first input terminal and the second output terminal, the discharge circuit being configured to control the discharge of the capacitive module through the chopper by a pulse width modulation type control of the first controlled switch or the second controlled switch. - the discharge circuit is configured to, when it commands the discharge of the capacitive module, control the first controlled switch by a pulse width modulation type command by keeping the second controlled switch in the conducting state as long as the value of the current in the wound rotor is less than a predetermined threshold, and to control the second controlled switch by a pulse width modulation type command if the current in the wound rotor is greater than the predetermined threshold. - the discharge circuit is powered by the capacitive module via a voltage reducer configured to provide a supply voltage to the discharge circuit as long as the voltage across the terminals of the capacitive module is greater than or equal to 60 volts, preferably greater than or equal to 40 volts.

[0014] Also proposed is an electric or hybrid motor vehicle equipped with a wound-rotor electric machine, a traction battery and a device according to the invention, the traction battery being connected between the two input terminals and the wound rotor being connected between the two output terminals.

[0015] Of course, the various features, variants, and embodiments of the invention can be combined with one another in various ways, provided they are not incompatible or mutually exclusive. Detailed description of the invention

[0016] The following description with regard to the attached drawing, given by way of non-limiting example, will make it clear what the invention consists of and how it can be carried out.

[0017] On the attached drawing:

[0018] [Fig-1] is a schematic view of a motor vehicle equipped with a device according to the invention.

[0019] Figure 1 shows an arbitrary motor vehicle (car, truck, motorcycle, airplane, boat) with hybrid or electric propulsion. Preferably, it is an electric land vehicle.

[0020] In the embodiment of the invention shown schematically in [Fig.1], this motor vehicle 1 comprises a battery of accumulators 2 (or traction battery), an electric machine 3 and a power electronics module 4.

[0021] Here, the electrical machine 3 is a wound-rotor synchronous motor, which therefore comprises a stator and a wound rotor. In [Fig. 1], the wound rotor 5 is represented by an electrical resistor.

[0022] The storage battery 2 is here a lithium-ion (or Li-ion) type battery having two supply terminals. In this example, the storage battery 2 is configured to supply an electrical voltage of a maximum value of 800 volts between its terminals.

[0023] The power electronics module 4 is configured to convert the direct current supplied by the battery 2 into a form suitable for the operation of the electric machine 3.

[0024] It includes a first input terminal 14 and a second input terminal 15, each connected here to a separate power supply terminal of the accumulator battery 2.

[0025] The power electronics module 4 includes a capacitive module 7 (commonly called "DC Link") which is connected between the first input terminal 14 and the second input terminal 15 and which is configured to stabilize the input voltage of the power electronics module 4 by limiting fluctuations in the DC current supplied by the battery 2.

[0026] It includes an inverter not shown, which is connected to the terminals of this capacitive module 7 and which allows, by appropriate control, to supply a three-phase alternating current to the stator of the electric machine.

[0027] It further comprises a first output terminal 16 and a second output terminal 17, each connected here to a separate terminal of the wound rotor 5.

[0028] Here, the chopper 6 is a two-quadrant chopper. It comprises, firstly, a first controlled switch 10 which is connected between the first input terminal 14 and the first output terminal 16, and a second controlled switch 11 which is connected between the second input terminal 15 and the second output terminal 17. Here, the first controlled switch 10 and the second controlled switch 11 are transistors, and in particular in this example, insulated gate bipolar transistors (IGBTs). A first diode 12 is connected between the second input terminal 15 and the first output terminal 16, its cathode being connected to the first output terminal 16. A second diode 13 is connected between the first input terminal 14 and the second output terminal 17, its cathode being connected to the first input terminal 14.

[0029] The motor vehicle 1 further comprises a low voltage module 9, in particular configured to transmit control signals to the power electronics module 4, in particular to control the chopper 6. For example, the control signals emitted by the low voltage module 9 are transmitted to the power electronics module 9 via a control module 19 which acts as an interface between the low voltage module 9 and the power electronics module 4.

[0030] The low voltage module 9 preferably includes a computer processing unit, here a microcontroller 18 (but which could be, in other embodiments, a microprocessor or a set of logic gates), which is notably configured to control the chopper 6. In particular, it is configured to control the first controlled switch 10 and the second controlled switch 11 so as to supply the wound rotor 5 from the battery of accumulators 2.

[0031] The microcontroller 18 further includes an interface module 20 enabling communication (receiving and transmitting signals) with the outside of the low voltage module 9, for example with other modules or sensors of the motor vehicle 1. Here, the interface module 20 is a CAN module (“Controller Area Network”, according to the usual Anglo-Saxon acronym).

[0032] The microcontroller 18 is configured to ensure the proper functioning of the interface module 20, that is, to detect a communication fault with the outside of the low-voltage module 9. For example, a communication fault is detected if the interface module 20 is defective (for example, out of service) or if received data is corrupted (that is, if it is not intact). In the sense of According to the invention, data is considered corrupted, or non-integral, if an error detection algorithm has detected an error in the data. To this end, the microcontroller 18 is configured to verify the integrity of the received data (i.e., to check if at least part of the received data is corrupted) by implementing one or more error detection algorithms, for example, a cyclic redundancy algorithm or a clock synchronization algorithm.

[0033] When the motor vehicle 1 is running, i.e., as soon as the ignition is switched on (when the driver starts the vehicle and powers up its control units), the voltage across the capacitive module 7 equalizes with the voltage across the battery 2 (less any fluctuations that the capacitive module 7 is configured to absorb). When the battery 2 and the power electronics module 4 are disconnected (for example, immediately after a power switch 8 is opened), the capacitive module 7 maintains a residual voltage substantially equal to the voltage across the battery 6.

[0034] In order to prevent any risk related to the high voltage value across the terminals of the capacitive module 7, a control device is provided, configured to control, when necessary, a discharge of the capacitive module 7 through the wound rotor 5. The control device here comprises the microcontroller 18, the chopper 6 and a discharge circuit 21 which, in the example illustrated in [Fig.1], is located in the low voltage module 9.

[0035] The discharge circuit 21 is configured to be either in an active state in which it controls the discharge of the capacitive module 7 through the wound rotor 5, or in an inactive state in which the discharge of the capacitive module 7 is inhibited. In other words, in the inactive state, the discharge circuit 21 does not control the discharge of the capacitive module 7.

[0036] In its active state, the discharge circuit 21 is configured to control the chopper 6 (via the control module 19) in order to discharge the capacitive module 7 to the wound rotor 5. Specifically, in its active state, the discharge circuit 21 is configured to control the first controlled switch 10 by pulse-width modulation (PWM) and to maintain the second controlled switch 11 in the conducting state. The current flowing through the wound rotor 5 is thus regulated by the control of the first controlled switch 10.

[0037] In its active state, the discharge circuit 21 is further configured to cease the control of the first controlled switch 10 and to control the second controlled switch 11 by pulse-width modulation if the value of the current in the wound rotor 5 exceeds a predetermined value, for example 5 amperes. Indeed, an increase in the current value in the wound rotor 5 beyond a certain threshold, despite PWM control of the first controlled switch 10, is probably due to a fault in the latter, which is stuck in the conducting state. In this case, it is advisable to perform pulse-width modulation control on the second controlled switch 11, rather than on the first controlled switch 10.

[0038] In its inactive state, the discharge circuit 21 is configured here not to transmit a command to the chopper 6, which is then conventionally controlled by the microcontroller 18 (via the control module 19) in order to rotate the wound rotor 5 relative to the stator.

[0039] The discharge circuit 21 is maintained in its inactive state if the microcontroller 18 emits an inhibition signal SI. This signal is emitted by the microcontroller 18 solely for the purpose of maintaining the discharge circuit 21 in its inactive state. When the contact is made, the microcontroller 18 is configured to continuously transmit the inhibition signal SI, unless it detects a communication fault with the external low-voltage module 9. In this case, it ceases to emit the inhibition signal SL.

[0040] In the case where the microcontroller 18 emits a control signal for the wound rotor 5 and, simultaneously, the inhibition signal SI, the discharge control has priority over the control of the wound rotor 5. In this case, the discharge circuit 21 controls the discharge of the capacitive module 7.

[0041] The discharge circuit 21 is here powered by the capacitive module 7 via a step-down voltage regulator 22 configured to provide a low supply voltage, for example, less than or equal to 12 volts, here 5 volts. Here, the step-down voltage regulator 22 is configured to supply the 5-volt voltage as long as the voltage across the capacitive module 7 is greater than or equal to 40 volts. In other words, when the voltage across the capacitive module 7 is less than 40 volts, the capacitive module 7 is no longer powered and the discharge of the capacitive module 7 is stopped.

[0042] In normal operation, for example while driving, or when the ignition of the motor vehicle 1 is switched on and no problem (for example, an accident) occurs, the microcontroller 18 transmits the inhibition signal SI to the discharge circuit 21, which is therefore in its inactive state. Furthermore, the microcontroller 18 transmits control signals to the chopper 6 in order to control the first controlled transistor 10 and the second controlled transistor 11 so that the rotor is powered according to the torque required by the motor 3.

[0043] If the battery 2 is disconnected from the power electronics module 4, for example when the ignition of the motor vehicle 1 is switched off, the microcontroller is no longer powered and is therefore no longer able to transmit the inhibition signal SI to the discharge circuit 21 (nor any other signal). The discharge circuit, powered by the capacitive module 7, therefore goes into its active state and triggers the discharge of the capacitive module 7 by controlling the chopper 6, until the discharge circuit 21 is no longer powered (here, until the voltage reducer 22 is no longer able to power it, i.e. until the voltage across the capacitive module 7 is less than or equal to 40 volts).

[0044] In the event of an accident during operation, the microcontroller 18 receives, via the interface module 20, a signal indicating the occurrence of an accident. Upon receiving this signal, the microcontroller 18 ceases the transmission of the inhibition signal SI (as well as any control of the wound rotor). The discharge circuit then enters its active state and controls the discharge of the capacitive module 7.

[0045] In the event of a communication fault detected at the interface module, for example when the latter is defective or if the microcontroller 18 detects an error in one of the data received by the interface module 20, then the microcontroller 18 ceases the emission of the inhibition signal SI and the discharge circuit 21 goes into its active state.

[0046] Thus, the risks associated with the residual high voltage across the terminals of the capacitive module 7 are eliminated, or at least greatly reduced.

[0047] The invention is not limited to the embodiment described above.

[0048] The implementation of clock synchronization or cyclic redundancy algorithms for detecting errors in the data received by the interface module has been described previously. The invention is also compatible with any other error detection algorithm suitable for the communication protocol used, for example, the CAN protocol.

[0049] A CAN type interface module has been described. Alternatively, the interface module can be of any type allowing communication with the rest of the motor vehicle, for example a LIN type interface module (“Local Interconnect Network”).

[0050] A microcontroller configured to cease transmitting the inhibit signal upon detection of a communication fault in the interface module has been described. The invention is not limited to this feature and covers embodiments in which the microcontroller does not detect a communication fault. In this case, only a fault in the microcontroller prevents the transmission of the inhibit signal.

Claims

Demands

1. A control device for a wound rotor (5) of an electric machine (3) of a motor vehicle (1), comprising: - two input terminals (14, 15) configured to be connected respectively to two terminals of a traction battery (2) of the motor vehicle (1), - two output terminals (16, 17) configured to be connected to the wound rotor (5), - a capacitive module (7) connected between the two input terminals (14, 15), - a discharge circuit (21) configured to be powered by the capacitive module (7) and configured to be either in an active state in which it controls the discharge of the capacitive module (7) through a winding of the wound rotor (5), or in an inactive state in which the discharge of the capacitive module (7) is inhibited, characterized in that it comprises a computer processing unit (18) adapted to transmit a signal to the discharge circuit (21). inhibition (SI),said discharge circuit (21) being in the inactive state when it receives the inhibition signal (SI) and in the active state otherwise.

2. Device according to claim 1, wherein the computer processing unit (18) includes an interface module (20) configured to communicate with the outside of the device, and wherein the computer processing unit (18) is configured to detect a fault in the communication of the interface module (20) with the outside of the device and to cease the transmission of the inhibition signal (SI) in the event of detection of the fault.

3. Device according to claim 2, wherein the computer processing unit (18) is configured to check the integrity of the data received by the interface module (20), the detection of the failure of communication with the outside of the vehicle (1) taking place if one of the received data is corrupted.

4. Device according to claim 3, wherein the computer processing unit (18) is configured to verify the integrity of the received data by implementing a cyclic redundancy check algorithm.

5. Device according to claim 3 or 4, wherein the computer processing unit (18) is configured to verify the integrity of the data received by implementing a clock synchronization algorithm.

6. Device according to any one of claims 2 to 5, wherein the failure to communicate with the outside is detected if the interface module (20) is out of service.

7. A device according to any one of the preceding claims, comprising a chopper (6) having a first controlled switch (10) connected between a first (10) of the two input terminals (14, 15) and a first (16) of the two output terminals (16, 17), a second controlled switch (11) connected between a second (15) of the two input terminals (14, 15) and a second (17) of the two output terminals (16, 17), a first diode (12) connected in one direction between the second input terminal (15) and the first output terminal (16), and a second diode (13) connected in the opposite direction between the first input terminal (14) and the second output terminal (17), the discharge circuit (21) being configured to control the discharge of the capacitive module (7) through the chopper (6) by pulse-width modulation control of the first controlled switch (10) or of the second switch controlled (11).

8. Device according to claim 7, wherein the discharge circuit (21) is configured to, when controlling the discharge of the capacitive module (7), control the first controlled switch (10) by a pulse-width modulation type control by keeping the second controlled switch (11) in the conducting state as long as the value of the current in the wound rotor (5) is less than a predetermined threshold, and to control the second controlled switch (11) by a pulse-width modulation type control if the current in the wound rotor (5) is greater than the predetermined threshold.

9. A device according to any one of the preceding claims, wherein the discharge circuit (21) is powered by the capacitive module (7) via a step-down voltage regulator (22) configured to provide a supply voltage to the circuit

10. discharge (21) as long as the voltage across the terminals of the capacitive module (7) is greater than or equal to 60 volts. Electric or hybrid motor vehicle equipped with a wound-rotor electric machine (3) (5), a traction battery (2) and a device according to any one of claims 1 to 9, the traction battery (2) being connected between the two input terminals (14, 15) and the wound rotor (5) being connected between the two output terminals.

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