System for controlling a voltage converter - Patents.com

Abstract

To provide a control system and an electric machine that reduce the load exerted on switches.SOLUTION: In a control unit (1) comprising a control system (2), a control module (22) comprises: a first module (20) for measuring a voltage (V) of a DC voltage source connected between two terminals (B+, B-); a module (21) for comparing the measured voltage (V) with a first safety threshold (OV1); a second measurement module (23) for measuring a speed of rotation (Ω) of a rotary electric machine (M); and a control module (22) which generates an open-circuit command made up of a command to open a first group of switches and a command to open a second group of switches if a variation over time (dV*) of the measured voltage (V) of the DC voltage source is less than a first safety variation and if the speed of rotation (Ω) measured by the second measurement module (23) is less than a first safety speed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an electrical system comprising a rotating electric machine for a motor vehicle, the machine being controlled by a voltage converter, and more particularly to a system for controlling a voltage converter and to an electric machine comprising a rotating electric machine and such a control system. [Background technology]

[0002] In the case of electrical equipment such as voltage converters, it is known to connect a voltage source, for example a DC voltage source, to an electric machine, for example a rotating electric machine, by means of a power module, whose role is to safely control the nature and amount of electrical energy transferred from the energy source to the electric machine.

[0003] Among power modules, controllable switches are known, such as transistor switches, such as metal oxide semiconductor field effect transistors (also referred to by the acronym MOSFET), silicon metal oxide semiconductor field effect transistors (also referred to by the acronym Si MOSFET), silicon carbide metal oxide semiconductor field effect transistors (also referred to by the acronym Sic MOSFET), insulated gate bipolar transistors (also referred to by the acronym IGBT), or gallium nitride field effect transistors (also referred to by the acronym GaN FET).

[0004] The switches can power the stator phases in motor mode from the battery, which electrically feeds the vehicle's on-board network, or in alternator mode, which feeds the on-board network to recharge the vehicle's battery. In the case of an electronic machine with three phases in the stator, the voltage converter comprises three low-side switches, each connecting one of the three phases to ground, and three high-side switches, each connecting one of the three phases to a positive terminal corresponding to the vehicle's on-board network.

[0005] If an item of electronic equipment of the automobile connected to the on-board network fails, an overvoltage may occur in the on-board network, i.e. a voltage much higher than the nominal voltage of this network may appear in the on-board network. For example, such an overvoltage may occur if a switch of a voltage converter fails, i.e. the switch remains open or closed when the control system commands it to switch closed or open, respectively.

[0006] Such overvoltages can damage or reduce the reliability of not only rotating electrical machines, voltage converters, and their control systems, but also any electrical equipment connected to the in-vehicle network, such as DC-DC converters, car radios, etc.

[0007] It is known that the control system of an electric machine comprises a voltage detector and controls the closing and opening of other switches as a function of the identified fault to limit or stop overvoltages. For example, in the case of a high-side switch that remains closed, the detector will detect the fault that this switch remains closed and will transmit information about the detection of this fault to a control module of the control system. The control system will then command the closing of the other two high-side switches, thereby setting all phases of the stator to the same potential, i.e. shorting the phases, thus ensuring the safety of the rotating electrical system.

[0008] In this way, the control system protects the voltage converter and the rotating electrical machine by systematically closing all switches on the same side when an overvoltage is detected. This makes such a system unnecessary to install fault detection and identification means on each switch. It is therefore less bulky and less expensive than other control systems.

[0009] However, such systems subject switches such as MOSFET transistors to high loads due to the intensity of the currents flowing through them during a short circuit, which inevitably increases their temperature. These currents and the resulting temperatures have a negative effect on the lifespan of the transistors and therefore of the voltage converter. They also reduce the efficiency of the voltage converter.

[0010] SUMMARY OF THE PRESENT EMBODIMENT The object of the present invention is therefore to overcome the drawbacks of the prior art, in particular by proposing an operation which reduces the load acting on the switch. Summary of the Invention

[0011] According to a first aspect of the invention, there is provided a system for controlling a voltage converter, comprising: a voltage converter adapted to connect a rotating electric machine to a DC voltage source, in particular to an on-board network, said voltage converter comprising a plurality of switching arms connected in parallel, each arm comprising at least one high-side switch and at least one low-side switch connected together at a midpoint adapted to connect to said rotating electric machine, said high-side switches forming a high group and said low-side switches forming a low group, The control system includes: a first module for measuring the voltage of said DC voltage source; a module for comparing said measured voltage with a first safety threshold, a second measurement module configured to measure the rotational speed of said rotating electrical machine; a control module which generates a first short circuit command if the comparison module indicates that the measured voltage is greater than a first safety threshold, the first short circuit command consisting of a command to close a first group of switches selected between the high group and the low group and a command to open a second group of switches comprising the switches of the high group or the switches of the low group that do not form the first group.

[0012] The control system is notable for the following: The control module includes: - if the change in the measured voltage of the DC voltage source over time is less than a first safe change, and - if the rotational speed measured by the second measurement module is less than a first safe speed, An open circuit command is generated, the open circuit command consisting of a command to open the first group of switches and a command to open the second group of switches.

[0013] A high-side switch or a low-side switch is understood to mean an electronic power supply switch, for example of the IGBT (Insulated Gate Bipolar Transistor) type or of the Metal Oxide Field Effect Transistor type, also known by the acronym MOSFET.

[0014] With this combination of features, such an open circuit switch control module can cut off the current flow in the voltage converter when the measured voltage is stable, thereby reducing the load duration on the high group switches and the low group switches and avoiding short circuits. Heat generation from the switches due to Joule effect is thus reduced throughout the voltage converter.

[0015] As soon as the criteria regarding voltage over time and rotation speed are verified, the first short circuit command is interrupted and an open circuit command is selected. As soon as one of the criteria is no longer met, the open circuit command is interrupted.

[0016] Advantageously, the control module generates an open circuit command if the measured voltage is below a first limit value, in particular greater than 110% of a first safety threshold.

[0017] Advantageously, the comparison module compares the measured voltage with a second safety threshold greater than the first safety threshold, and the control module generates a second short circuit command if the measured voltage is greater than or equal to the second safety threshold, the second short circuit command consisting of a command to close the switches of the second group and a command to open the switches of the first group.

[0018] Such a control system allows the voltage converter to be quickly made safe if one of its switches becomes shorted or open circuited.

[0019] Advantageously, said control module comprises: - if the measured rotational speed is less than a second safe speed, and if the change over time of the measured voltage of the DC voltage source is less than a second safe change; Generate the open circuit command.

[0020] Advantageously, the control module generates an open circuit command when the measured voltage is below a second limit value, in particular equal to a second safety threshold value.

[0021] As soon as the criteria regarding the voltage change over time and the rotation speed are verified, the second short circuit command is interrupted and an open circuit command is selected. As soon as one of the criteria is no longer met, the open circuit command is interrupted.

[0022] If the measured voltage is below the second safety threshold, the second short circuit command is not interrupted and the first short circuit command is selected.

[0023] Advantageously, the open circuit command follows the first short circuit command. Advantageously, the open circuit command follows the second short circuit command.

[0024] Advantageously, the control module generates a normal operation command, for example in a motor mode of the rotating electric machine, for example in a generator mode of the rotating electric machine, when the measured voltage is below the third limit value, in particular equal to the first safety threshold value, after which the control system is re-enabled.

[0025] Advantageously, the first safety threshold is in the range 110% to 125% of the nominal voltage V of the DC voltage source supplying the converter, for example 120% of the nominal voltage of the DC voltage source. For example, the nominal power supply voltage is equal to 48V and the first safety threshold is in the range 53V to 56V.

[0026] Advantageously, the second safety threshold is in the range of 120% to 145% of the nominal voltage V of the DC voltage source of the voltage converter, for example 133% of the nominal voltage of the DC voltage source. For example, the nominal power supply voltage is equal to 48V and the first safety threshold is in the range of 58V to 67V.

[0027] Advantageously, the first safe speed and / or the second safe speed is a speed at which the electromotive force of the rotating electric machine is below a predetermined voltage, for example 48 V. Advantageously, the first safe speed is equal to the second safe speed. In such an arrangement, it is ensured that the control module commands the opening of the high and low groups only when the rotational speed of the rotating machine is low, for example following a decision by the driver of the vehicle to slow down the vehicle or due to the presence of a system for slowing down the speed by disconnecting the electric machine from the control system.

[0028] Advantageously, the first safe change is negative, in particular less than -0.2 V / μs. Advantageously, the second safe change is negative, in particular less than -0.2 V / μs. Advantageously, the first safe change is equal to the second safe change. A change larger than this safe change reflects a possible overvoltage in the voltage converter, for example due to a load drop.

[0029] Advantageously, the first limit value is greater than a first safety threshold value, which is in the range of 110% to 125% of the nominal voltage of the DC voltage source of the voltage converter, and may for example be 133% of the nominal voltage of the DC voltage source.

[0030] Advantageously, the second limit value is less than the second safety threshold value. The second limit value is greater than the second safety threshold value. The second limit value is in the range of 120% to 150% of the nominal voltage of the DC voltage source of the voltage converter, and may be, for example, 133% of the nominal voltage of the DC voltage source.

[0031] Advantageously, the third limit value is less than the first safety threshold value. The third limit value is in the range of 100% to 125% of the nominal voltage of the DC voltage source of the voltage converter, and may be, for example, 115% of the nominal voltage of the DC voltage source.

[0032] Advantageously, said first group of switches is said row group.

[0033] Advantageously, the first group of switches is a group of high-side switches.

[0034] Advantageously, the voltage measured by the first measurement module is the voltage between two terminals of the voltage converter adapted to be connected to the DC voltage source.

[0035] According to another aspect of the present invention, the present invention comprises: - first and second power supply terminals adapted for connection to a DC voltage source, in particular a vehicle battery; a rotating electric machine comprising a stator having at least three phases; a voltage converter for feeding the rotating electric machine from the DC voltage source, the voltage converter comprising a number of switching arms connected in parallel, each arm comprising a high-side switch and a low-side switch connected to each other at a midpoint, each switching arm being connected to at least one phase of the rotating electric machine, and a control unit for the high-side switches and the low-side switches, the control unit comprising a control system as described above, The present invention relates to an electrical system comprising:

[0036] Advantageously, said control unit comprises: a controller configured to control said high-side switch and said low-side switch; a machine control module configured to receive from an electronic control unit of the vehicle a command to either switch the rotating electric machine into a motor mode or to switch the rotating electric machine into an alternator mode, the machine control module being arranged to convert this command into a command for controlling the high-side switch and the low-side switch of the voltage converter; a logic module for prioritizing the commands issued by the control system over the commands issued by the machine control module, the logic module transmitting to the controller the commands for the switches received by either the machine control module or the control system; It further comprises:

[0037] Advantageously, the control unit further comprises at least one fault detection module, for example a phase current direction fault module. When the fault module detects a fault, the control unit generates a first short circuit command or a second short circuit command, or the first short circuit command followed by a second short circuit command.

[0038] According to another aspect of the invention, the invention relates to a mobile object comprising the electrical system described above.

[0039] According to another aspect of the invention, the invention relates to a method for controlling a system for controlling a voltage converter as described above, said voltage converter being connected to a rotating electric machine and to a DC voltage source, in particular to an on-board network, said method comprising the steps of: a first measurement module for measuring the voltage of said DC voltage source; a second measurement module for measuring the rotational speed of said electric machine; a measurement module for comparing said measured voltage with a first safety threshold and for comparing the variation of said measured voltage over time with a safety variation; - comparing said measured rotation speed with a safe speed; said control module generating a command to open a first group of switches selected from a group of high-side switches and a group of low-side switches if said comparison module indicates that said measured voltage is greater than a first safety threshold, if the change in the measured voltage of said DC voltage source over time is less than a safe change, and if the rotation speed measured by said second measurement module is less than a safe speed; Equipped with.

[0040] The invention will be better understood on reading the following description, given purely by way of example, and with reference to the accompanying drawings, given as non-limiting examples, in which the same reference symbols are provided for similar objects, in which: [Brief description of the drawings]

[0041] [Figure 1] FIG. 1 is a schematic diagram of an electrical system comprising a control unit for a voltage converter according to a first aspect of the invention. [Diagram 2] FIG. 2 is a schematic diagram of the control unit of FIG. 1 comprising a system for controlling a voltage converter according to another embodiment of the invention. [Diagram 3] FIG. 3 is a histogram representing the voltage measured across the terminals of a DC voltage source according to a first example of use of the control system of FIG. [Figure 4]FIG. 4 is a histogram representing the voltage measured across the terminals of a DC voltage source in accordance with another example of use of the control system of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] It should be noted that the drawings disclose the invention in detail in order to enable the invention to be carried out, but without limiting it, and said drawings are used in particular to more clearly define the invention where appropriate.

[0043] 1 shows an electrical system SE with a first power supply terminal B+ and a second power supply terminal B-, which are connected to a DC power source B, for example a car battery, so that other items of electrical equipment (not shown) of the vehicle can be powered by the on-board network. The voltage between terminals B+, B- of the DC voltage source B is for example 48 V. This corresponds to a "low voltage" application. In this case, the second terminal B- is the ground of the electrical system SE.

[0044] The electrical system SE comprises a rotating electrical machine M comprising a stator having at least three phases U, V, W and three coils u, v, w wound on the stator, in this example the coils u, v, w are connected in a star configuration and each has a corresponding phase U, V, W, respectively, at its output.

[0045] The electrical system SE further comprises a voltage converter O for powering a rotating electrical machine M from said DC voltage source B. In such an arrangement, phases U, V, W of the electrical machine M are powered with three-phase AC by the voltage converter.

[0046] The voltage converter O comprises a number of switching arms connected in parallel between terminals B+ and B-. The voltage converter O comprises as many arms as there are phases of the rotating electric machine M. In this case, in the example described here, the voltage converter O comprises three arms. The voltage converter O therefore comprises a first arm X, a second arm Y and a third arm Z.

[0047] Each arm X, Y, Z includes a high-side switch HS_X, HS_Y, HS_Z and a low-side switch LS_X, LS_Y, LS_Z. The high-side and low-side switches of the arms X, Y, Z are connected to each other at intermediate points PX, PY, PZ. The high-side switches form a switch group called a high group HS. Similarly, the low-side switches form a switch group called a low group LS. The switches of the low group LS and the switches of the high group HS are, in this case, metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0048] In the examples described herein, each high-side or low-side switch is a metal oxide field effect transistor with a respective flyback diode.

[0049] In this case, in this example, therefore, there is a first high-side switch HS_X in the first arm X connected to the first low-side switch LS_X by a first intermediate point PX, there is a second high-side switch HS_Y in the second arm Y connected to the second low-side switch LS_Y by a second intermediate point PY, and there is a third high-side switch HS_Z connected to the third low-side switch LS_Z by a third intermediate point PZ.

[0050] Each intermediate point PX, PY, PZ is connected to at least one phase U, V, W of said rotating electrical machine M. Thus, in this example, the first intermediate point PX is connected to phase U, the second intermediate point PY is connected to phase V and the third intermediate point Z is connected to phase W.

[0051] The voltage converter O further comprises a unit 1 for controlling the high-side HS_X, HS_Y, HS_Z switches and the low-side LS_X, LS_Y, LS_Z switches. Said control unit 1 thus comprises for each switch an output connected to the command of the corresponding switch. In order not to overload Fig. 1, only a connection between an output of the control unit 1 and a command of the third low-side switch LS_Z and another output of the control unit 1 and a command of the second high-side switch HS_Y is shown.

[0052] A control unit 1 controls the switches of each arm X, Y, Z via pulse width modulation (PWM).

[0053] FIG. 2 shows the control unit of FIG. 1 with a control system 2 for a voltage converter 2 according to another embodiment of the invention.

[0054] The control unit 1 comprises a control system 2 comprising a first module 20 for measuring the voltage of a DC voltage source B. In the example described herein, the measurement module 20 measures the voltage V between terminals B+ and B-. In other words, in the example described herein, the first measurement module 20 measures the voltage of a DC voltage source B, which in this case has a nominal voltage of 48V.

[0055] The control system 2 comprises a comparison module 21 arranged to receive information on the voltage V measured by the measurement module 20. The comparison module 21 compares the measured voltage V with a first safety threshold OV1, which is for example stored in a non-volatile memory of the comparison module 21. A third limit value, to which the voltage V is compared, is also stored in the non-volatile memory of the comparison module 21. The value of the third limit value is in this case equal to the value of the first safety threshold.

[0056] The control system 2 comprises a second measurement module 23 arranged to measure the rotational speed Ω of the electric machine M. The second measurement module 23 updates the completed measurements according to a configurable duration, for example every 100 ms.

[0057] The first safety threshold OV1 is in particular in the range of 110% to 125% of the nominal voltage V of the DC voltage source B supplying the converter O, for example 120% of the nominal voltage of the DC voltage source. In this case, the first safety threshold OV1 is equal to 56V.

[0058] The comparison module 21 is also configured to compare the measured voltage V with a second safety threshold OV2, which is higher than the first safety threshold OV1. The second safety threshold OV2 is for example stored in a non-volatile memory of the comparison module 21. The comparison module 21 is also configured to calculate a change over time dV* of the voltage V from two successive measurements of the voltage V. A second limit value to which the voltage V is compared is also stored in the non-volatile memory of the comparison module 21. In this case, the value of the second limit value is equal to the value of the second safety threshold.

[0059] The second safety threshold OV2 is in particular in the range of 120% to 140% of the nominal voltage V of the DC voltage source B of the voltage converter O, for example 133% of the nominal voltage of the DC voltage source. In this case, the second safety threshold OV2 is equal to 64V.

[0060] The control system 2 further comprises a control module 22. In the example described here, the control module 22 is made on the basis of logic gates. As an alternative embodiment, the control module 22 can be a microcomputer.

[0061] The comparison module 21 transmits information regarding the first safety threshold OV1 to the control module 22, for example in the form of a high logic level if the measured voltage V is greater than the first safety threshold OV1 and a low logic level otherwise.

[0062] The comparison module 21 transmits information regarding the second safety threshold OV2 to the control module 22, for example in the form of a high logic level if the measured voltage V is greater than the second safety threshold OV2 and a low logic level otherwise.

[0063] Upon receiving the information corresponding to the first safety threshold OV1, the control module 22 issues a first short-circuit command consisting of a command to close a first group of switches LS, HS selected from a group of high-side switches, i.e. high group HS, or a group of low-side switches, i.e. low group LS, and a command to open a second group of switches comprising switches of the high group or switches of the low group that do not form the first group. In the illustrated example, the first group of switches is the low group LS and the second group of switches is the high group HS. The first short-circuit command ASC_LS is a command to close all switches of the low group LS and a command to close all switches of the low group LS.

[0064] The control module 22 also receives information on the voltage change dV* from the comparison module 21 and information on the speed Ω from the second measurement module 23 .

[0065] Starting with all switches in the low group LS closed and all switches in the high group HS open, if the voltage change dV* is less than a first safe change and the rotation speed Ω is less than a first safe speed, the control module 22 generates an open circuit command consisting of a command to open all switches in the low group LS and all switches in the high group HS.

[0066] By configuring the switches in this way, when the measured voltage is deemed stable, the voltage converter O can be put into an open circuit state, momentarily interrupting the flow of current in the voltage converter O. This reduces the load duration of the switches and avoids short circuits. Heating from the switches due to the Joule effect is thus reduced throughout the voltage converter.

[0067] The first safe change is preferably less than -0.2V / μs. The first safe speed is the speed at which the electromotive force of the electric machine M is less than 48V.

[0068] Upon receiving information corresponding to exceeding the second safety threshold OV2, the control module 22 emits a second short-circuit command ASC_HS, which in this case is composed of a command to close the switches of the second group, in this case the high group HS, and a command to close the switches of the first group, in this case the low group LS.

[0069] The control module 22 receives information on the voltage change dV* from the comparison module 21 and again information on the speed Ω from the second measurement module 23 .

[0070] Starting with all switches in the low group LS open and all switches in the high group HS closed, if the measured voltage V is below the second safety threshold OV2, the voltage change dV* is below the second safe change, and the rotation speed Ω is below the second safe speed, the control module 22 generates an open circuit command.

[0071] In the illustrated example, the value of the second change is equal to the value of the first change, in this case -0.2V / μs. In the illustrated example, the second safe speed is equal to the first safe speed.

[0072] Optionally, the control module 12 may also comprise one or more inputs AE arranged to receive error information, for example error information relating to an excessively low voltage (undervoltage (UV)) in the on-board network. Upon receiving the error information of one or more inputs AE, the control module 12 likewise issues commands to close the first group of switches and, optionally, to open the second group of switches.

[0073] In the embodiment described herein, the control unit 1 further comprises a machine control module 3, a logic module 4 and a controller 5, also called a "driver".

[0074] The machine control module 3 comprises an input (not shown) for receiving an instruction from the vehicle's electronic control unit to either switch the rotating electric machine M into motor mode depending on the supplied torque value or into alternator mode depending on the resistive torque so as to recharge the vehicle's DC voltage source. The machine control module 3 converts this instruction into commands for the high-side HS switch and the low-side LS switch, said commands being transmitted via the logic module 4 and the controller 5. In other words, by means of the machine control module 3, the logic module 4 and the controller 5, the high-side switch HS and the low-side switch LS receive commands, for example via pulse width modulations PWM_HS, PWM_LS, respectively, to open or close.

[0075] In particular, the logic module 3 is configured to prioritize commands issued by the control system 2 over commands issued by the machine control module 2. In other words, the control system 2 has priority over the machine control module 3. If the machine control module 3 is a microprocessor and if the control module 22 and the logic module 4 are made using logic gates, the reaction time of the machine control module 3 (typically around 10 microseconds) is longer than the reaction time of the control module 21 (typically around 1 microsecond). The prioritization performed by the logic module thus ensures the safety of the voltage converter O and the rotating electric machine M more quickly.

[0076] 3 and 4 show histograms of the evolution of the voltage V measured between terminals B+ and B− in two use cases of a voltage converter O and a control system for a voltage converter O.

[0077] In the histogram of FIG. 3, over a first period of time, in this case between the instants T0 and T2, the voltage converter O normally controls the high-side and low-side switches according to commands from the electronic control unit of the vehicle. During this period, the measured voltage V is lower than the first safety threshold OV1 and, in particular, for a first duration, is equal to the nominal voltage of the DC voltage source B, in this case 48 volts. At the instant T1, while the rotating electric machine is in generator mode, the first DC power source B disconnects from the on-board network. This disconnection creates a load dump effect that causes an overvoltage in the on-board network. Following this disconnection, at the instant T2, the measured voltage V exceeds the first safety threshold OV, in this case 56 volts. The comparison module 21 of the control system 2 sends information to the control module 22 indicating that the measured voltage V is greater than the first safety threshold OV1. Upon receiving this command, the control module 22 generates a first short-circuit command ASC_LS, commanding the closing of the first group of switches and the opening of the second group of switches. In this case, in this example, the control module 22 sends commands to the logic module 4 to close the low side switches to ground the phases, and to open the high side switches, which the logic module 4 resends to the controller 5 to command the switches of the low group LS to be closed and the switches of the high group HS to be opened, independent of commands that the machine control module 3 also sent.

[0078] The comparison module 21 calculates the change dV* and compares it with the first safe change. In FIG. 3, the change dV* corresponds to the slope of the voltage signal V. The change dV* appears positive until the voltage V stabilizes between the first safe threshold OV1 and the second safe threshold OV2. The change dV* then becomes negative at a time T3, which is the time when the change dV* is less than the first safe change. At the same time, or successively, the control module 22 compares the rotation speed Ω of the rotating electric machine M with the first safe speed. In FIG. 3, after the time T3, the rotation speed Ω is less than the first safe speed of the electric machine. Thus, at the time T3, the control module 22 generates an open circuit command, commanding the opening of the first group of switches and the opening of the second group of switches. In this case, in this example, the control module 22 sends to the logic module 4 a command to open the low-side switch and, if necessary, a command to open the high-side switch. The logic module 4 resends these commands to the controller 5 to command the opening of the switches in the low group LS and the high group HS, independent of the commands similarly sent by the machine control module 3.

[0079] In the histogram of Fig. 4, unlike the histogram of Fig. 3, the voltage V is not stable between the first safety threshold OV1 reached at the time T2 and the second safety threshold OV2 reached at the time T2'. In this case, the control module 22 generates successively a first short-circuit command ASC_LS and then a second short-circuit command ASC_HS consisting of commands to open the switches of the first group and to close the switches of the second group. In this case, in this example, the control module 22 sends to the logic module 4 a command to open the low-side switches and a command to close the high-side switches. The logic module 4 resends these commands to the controller 5 in order to command the opening of the switches of the low group LS and the closing of the switches of the high group HS, independently of the commands similarly sent by the machine control module 3.

[0080] The voltage V then stabilizes at a value above the second safety threshold OV2. The driver of the vehicle receives a signal encouraging him to slow down the vehicle, which results in a reduction in the speed of the vehicle and therefore of the rotating electric machine M. Alternatively, the vehicle is equipped with a device for disconnecting the transmission system which could slow down the speed of the rotating electric machine M. This stabilization indicates that the correct strategy for short-circuiting the switching arms of the voltage converter O has been applied for the type of fault that created the overvoltage.

[0081] Thus, when the rotational speed of the rotating electric machine M is below the safe speed, the control system 2 generates an open circuit command, commanding the opening of the high and low groups, so as to return to an open circuit when the voltage measured across the terminals of the DC voltage source B falls below the second safety threshold OV2. This is shown in Figure 4.

[0082] In FIG. 4, the change dV* is positive until the voltage V exceeds the second safety threshold OV2 and stabilizes. Then, the change dV* becomes negative at time T3, which is the time when the change dV* is less than the first safe change. The control module 22 also compares the rotation speed Ω of the rotating electric machine M with the first safe speed. In FIG. 4, after time T3, the rotation speed Ω is less than the first safe speed of the electric machine. At time T4, the voltage V falls below the second safety threshold OV2. At time T4, the three conditions are met and the control module 22 generates an open circuit command, commanding the first group of switches to open and the second group of switches to open.

[0083] 3 and 4, the voltage V falls below the first safety threshold OV1 again at time T5 and the control module 22 generates again a command for normal operation, for example in a motor mode of the rotating electric machine, for example in a generator mode of the rotating electric machine, after which the control system is re-enabled.

[0084] It should also be noted that the present invention is not limited to the above-described embodiments, and indeed, various modifications to the above-described embodiments will be apparent to those skilled in the art in light of the teachings disclosed herein.

[0085] Thus, while in the above embodiment the first group of switches are low-side switches and the second group of switches are high-side switches, in alternative embodiments the first group of switches may be high-side switches and the second group of switches may be low-side switches.

[0086] Likewise, the rotating machines described above are three-phase machines. Alternatively, the rotating electric machine may have more generally n phases, for example a six-phase machine, where n=6. In this case, the voltage converter O also comprises n switching arms.

[0087] Similarly, in the above embodiment, the coils u, v, w are connected in a star configuration. As an alternative embodiment, the coils u, v, w may be connected in a delta configuration.

[0088] Similarly, in the above-described embodiment, the logic module 4, the control module 21 and the machine control module 3 are made as separate entities. In an alternative embodiment, the logic module 4, the control module 21 and the machine control module 3 can be made as a single entity, for example a microcontroller with programmable logic circuits of the FPGA (Field Programmable Gate Array) type.

[0089] The terms used in the above detailed description of the invention should not be construed as limiting the invention to the embodiments disclosed herein, but should be construed as including all equivalents that can be conceived by one skilled in the art by applying his or her general knowledge in the practice of the disclosed teachings.

Claims

1. A control system (2) for controlling a voltage converter (O), comprising: said voltage converter (O) is adapted to connect a rotating electric machine (M) to a DC voltage source (B), said voltage converter (O) comprising a plurality of switching arms (X, Y, Z) connected in parallel, each arm comprising a high-side switch (HS_X, HS_Y, HS_Z) and at least one low-side switch (LS_X, LS_Y, LS_Z) connected together at a midpoint (PX, PY, PZ) adapted to connect to said rotating electric machine (M), said high-side switches forming a high group (HS) and said low-side switches forming a low group (LS), The control system (2) a first measurement module (20) for measuring the voltage (V) of said DC voltage source (B); a comparison module (21) for comparing said measured voltage (V) with a first safety threshold (OV1); a second measurement module (23) configured to measure the rotational speed (Ω) of said rotating electrical machine (M); a control module (22) for generating a first short circuit command (ASC_LS) if the comparison module (21) indicates that the measured voltage (V) is greater than a first safety threshold (OV1), said first short circuit command being composed of a command to close a first group of switches selected between the high group and the low group and a command to open a second group of switches comprising the switches of the high group or the switches of the low group that do not form the first group; Equipped with The control module (22) - if the change over time (dV*) of the measured voltage (V) of the DC voltage source (B) is less than a first safe change, and - if the rotational speed (Ω) measured by the second measurement module (23) is less than a first safe speed, A control system (2) for generating an open circuit command, said open circuit command being composed of a command to open the switches of said first group and a command to open the switches of said second group.

2. The comparison module (21) compares the measured voltage (V) with a second safety threshold (OV2) that is greater than the first safety threshold (OV1); 2. The control system (2) of claim 1, wherein the control module (22) generates a second short circuit command (ASC_HS) when the measured voltage (V) is greater than or equal to the second safety threshold (OV2), the second short circuit command consisting of a command to close the second group of switches and a command to open the first group of switches.

3. The control module includes: - if the measured rotation speed (Ω) is less than a second safe speed, and if the change over time (dV*) of the measured voltage (V) of the DC voltage source (B) is less than a second safe change; A control system (2) as claimed in claim 2, characterized in that it generates the open circuit command.

4. 2. The control system (2) of claim 1, wherein the first safe speed is a speed at which the electromotive force of the rotating electrical machine is below a predetermined voltage.

5. 2. The control system (2) according to claim 1, characterized in that the first safe change is negative.

6. 2. The control system (2) of claim 1, wherein said first group of switches is said row group.

7. 2. The control system (2) of claim 1, wherein the voltage (V) measured by the first measurement module is the voltage between two terminals (B+, B-) of the voltage converter (O) configured for connection to the DC voltage source (B).

8. a first power supply terminal (B+) and a second power supply terminal (B-) adapted for connection to a DC voltage source (B); a rotating electric machine (M) comprising a stator having at least three phases (U, V, W), a voltage converter (O) for supplying the rotating electric machine (M) from the DC voltage source (B), comprising a number of switching arms (X, Y, Z) connected in parallel, each arm (X, Y, Z) comprising a high-side switch (HS_X, HS_Y, HS_Z) and a low-side switch (LS_X, LS_Y, LS_Z) connected to each other at an intermediate point (PX, PY, PZ), each intermediate point (PX, PY, PZ) connecting the switching arms (X, Y, Z) to at least one phase (U, V, W) of the rotating electric machine (M), and a control unit (1) for the high-side and low-side switches, the control unit (1) comprising a control system (2) according to any one of claims 1 to 7, An electrical system (SE) comprising:

9. The control unit (1) a controller (5) configured to control said high-side switch and said low-side switch; a machine control module (3) configured to receive, from a vehicle's electronic control unit, a command to either switch the rotating electric machine (M) into a motor mode or to switch the rotating electric machine (M) into an alternator mode, the machine control module (3) being arranged to convert this command into a command for controlling the high-side switch and the low-side switch of the voltage converter (O); a logic module (4) for prioritizing the commands issued by the control system (2) over the commands issued by the machine control module (3), said logic module (4) transmitting to the controller (5) the commands for the switches received by either the machine control module (3) or the control system (2); The electrical system (SE) of claim 8, further comprising:

10. A mobile object, characterized in that it comprises an electrical system (SE) according to claim 8.

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