A method and control system for controlling a multi-phase rotating electric machine

Abstract

The invention relates to a method for controlling a multiphase electric machine, the stator of which is controlled by a control bridge comprising a plurality of switching arms, supplied by the on-board electrical network of a vehicle and connected to one phase of the stator of the electric machine via a central point. When the electric machine is operated as a generator and the voltage (V*) of the electrical network exceeds a predetermined first value (VS1), for example in the case of a load dump, the method comprises a step (E400) of short-circuiting at least one phase winding of the stator, a measuring step (E500) for determining whether the current intensity is positive and, if so, injecting a current from the electrical network into the previously short-circuited winding in order to reduce the voltage in the electrical network.

Description

Technical Field

[0001] The invention relates to a method for controlling a multiphase rotating electrical machine connected to an electrical network, in particular an on-board electrical network of a motor vehicle, in the event of a load dump, and to a control system suitable for implementing the method.

[0002] The invention also relates to an electrical system comprising the control system and a multi-phase rotating electrical machine controlled by the control system. Background Art

[0003] In a motor vehicle, the on-board network is used to supply power to various electrical devices installed on the vehicle. The electricity is supplied by at least one battery. This is recharged by a rotating electrical machine, based on the energy supplied by the rotation of the vehicle's thermal engine. A rotating electrical machine is generally understood to be any multiphase rotating electrical machine used to generate a direct output current for supplying the on-board network. In particular, it can include an alternator or even a starter-alternator.

[0004] If the charge is suddenly disconnected from the onboard power supply, the battery or both, a "load dump" phenomenon occurs, which leads to an overvoltage in the onboard power supply. In fact, since the electric motor does not react immediately to the load dump, it continues to provide the same output current, while the current consumption of the onboard power supply has dropped. As a result, all capacitors connected to the onboard power supply are charged and the DC voltage on the onboard power supply increases significantly.

[0005] This overvoltage can damage or reduce the reliability of not only the rotating electrical machine itself, but also any electrical appliances connected to the vehicle network.

[0006] It is therefore worthwhile to detect overvoltages of such high magnitude and, if applicable, also protect the rotating electrical machine.

[0007] To this end, a method for controlling a multi-phase rotating electrical machine is known from the prior art, said control method being of the type involving short-circuiting at least one phase winding of the stator in the event of a load dump, said method comprising the step of short-circuiting said at least one phase winding of the stator when the voltage of the network exceeds a first predetermined value.

[0008] This simple method of the prior art allows reducing the voltage on the on-board network by keeping at least one phase of the stator short-circuited, while this voltage does not return to an acceptable level.

[0009] However, it may take a considerable amount of time before the voltage on the on-board network returns to an acceptable level. Summary of the invention

[0010] The object of the present invention is to at least partially overcome this disadvantage.

[0011] To this end, according to a first aspect, the invention relates to a method for controlling a multiphase rotating electrical machine, the stator of which is controlled by a control bridge comprising a plurality of switching arms mounted in parallel, each arm comprising a high-side switch and a low-side switch connected together at a center tap, the center tap being connected to a phase of said rotating electrical machine, said rotating electrical machine operating as a generator and connected to an electrical network, in particular an on-board network of a motor vehicle, said method comprising the step of short-circuiting at least one phase winding of the stator when a voltage measurement of said network exceeds a first predetermined value,

[0012] The method is further characterized in that it comprises, after the short-circuiting step, a step of activating a switching arm whose center tap is connected to the at least one short-circuited phase winding, during which step:

[0013] 1. Measure the strength in the short-circuited winding;

[0014] 2. If the measured intensity is positive, the high side switch of the activated switch arm moves to the closed position;

[0015] 3. Otherwise, the high side switch of the activated switching arm moves to the OFF position.

[0016] It should be noted that within the meaning of the present invention, the intensity is positive when the current flows into or returns to the at least one short-circuited winding from the center tap connected to the at least one short-circuited winding.

[0017] The control method according to the invention is therefore of the type which involves short-circuiting at least one phase winding of the stator in the event of a load dump.

[0018] The control method according to the invention may also have one or more of the following features, considered individually or in all technically possible combinations.

[0019] The method is noteworthy in that when at least one phase winding of the stator is short-circuited, the control bridge of the stator is controlled to introduce a current from the on-board power supply system into the previously short-circuited phase winding of the stator, thereby reducing the voltage on the on-board power supply system.

[0020] In a particular embodiment of the invention, if the measured intensity is positive, the low side switch of the activated switching arm moves to the open position.

[0021] In a particular embodiment of the invention, if the measured intensity is not positive, the low side switch of the activated switching arm moves to a closed position.

[0022] In a particular embodiment of the invention, during the step of short-circuiting at least one phase winding of the stator, the high-side switch of said activated switching arm is moved into the open position.

[0023] In a particular embodiment of the invention, during the step of short-circuiting at least one phase winding of the stator, the high side switch of said activated switching arm moves to the open position before the low side switch of said activated switching arm moves to the closed position.

[0024] In a particular embodiment of the invention, during the step of short-circuiting at least one phase winding of the stator, all phase windings of said stator are short-circuited and all high-side switches of all switching arms are moved to the open position.

[0025] In a particular embodiment of the invention, the voltage measurement of said network is obtained by filtering the voltage of said network with a predetermined time constant.

[0026] In a particular embodiment of the invention, the activation step is repeated at least until the voltage measured by the voltage measuring means is less than a second predetermined value.

[0027] In a specific embodiment of the invention, said activating step is repeated for a predetermined period of time.

[0028] In a particular embodiment of the invention, all phase windings of the stator are short-circuited during the short-circuiting step and, after the short-circuiting step, an activation step is performed for all switching arms.

[0029] Accordingly, according to a second aspect, the object of the invention is a control system for a multiphase rotating electrical machine operated as a generator and connected to an electrical network, in particular an on-board electrical network of a motor vehicle, via a first and a second power supply terminal, the control system comprising:

[0030] - a control bridge comprising a plurality of switching arms mounted in parallel, each arm comprising a high-side switch and a low-side switch connected together at a center tap connected to a phase winding of said rotating electrical machine, said control bridge being able to supply voltage to said electrical network;

[0031] - a control circuit capable of opening or closing the switches of the control bridge;

[0032] - means for measuring the voltage between the first and second power supply terminals;

[0033] The control system is characterized in that, for at least one predetermined phase winding also connected to the predetermined switching arm, the control system further comprises means for measuring the current through the predetermined phase winding, and when the voltage measured by the voltage measuring means exceeds a first value:

[0034] - the control circuit closes the low-side switch of a predetermined switching arm;

[0035] - a current measuring device measures the current through a predetermined phase;

[0036] - if the measured current intensity is positive, the control circuit closes the high-side switch of a predetermined switching arm;

[0037] - Otherwise, the control circuit opens the high-side switch of the predetermined switching arm.

[0038] In a particular embodiment of the invention, the control circuit opens the low side switch of said predetermined switching arm if the measured current intensity is positive.

[0039] In a particular embodiment of the invention, the control circuit closes the low-side switch of said predetermined switching arm if the measured current intensity is not positive.

[0040] In a specific embodiment of the present invention, the control circuit closes the low-side switch of the predetermined switching arm and opens the high-side switch of the predetermined switching arm.

[0041] In a particular embodiment of the invention, the control circuit closes the low side switch of a predetermined switching arm and short-circuits the at least one predetermined phase winding of the stator.

[0042] In a specific embodiment of the present invention, the control circuit closes the low side switch of the predetermined switching arm, short-circuiting the at least one predetermined phase winding of the stator, and before the low side switch of the predetermined switching arm moves to the closed position, the high side switch of the predetermined switching arm moves to the open position.

[0043] In a specific embodiment of the present invention, the control circuit closes the low-side switch of a predetermined switching arm, short-circuiting all phase windings of the stator, and controls all high-side switches of all switching arms of the bridge to move to the open position before all low-side switches of all switching arms move to the closed position.

[0044] In a particular embodiment of the invention, after detecting an indication that the voltage measured by the voltage measuring device exceeds the first predetermined value and doing so in an iterative manner for a predetermined period of time or as long as the voltage measured by the voltage measuring device exceeds the second predetermined value:

[0045] - the control circuit closes the low-side switch of a predetermined switching arm;

[0046] - a current measuring device measures the current through a predetermined phase;

[0047] - if the measured current intensity is positive, the control circuit closes the high-side switch of a predetermined switching arm;

[0048] - Otherwise, the control circuit opens the high-side switch of the predetermined switching arm.

[0049] In a particular embodiment of the invention, after detecting an indication that the voltage measured by the voltage measuring means exceeds a first predetermined value and after a predetermined phase winding short circuit, the control system iteratively controls for a predetermined period of time or as long as the voltage measured by the voltage measuring means exceeds a second predetermined value:

[0050] - a current measuring device measures the current through a predetermined phase;

[0051] - if the measured current intensity is positive, the control circuit opens the low-side switch of the predetermined switching arm and closes the high-side switch of the predetermined switching arm;

[0052] - Otherwise, the control circuit opens the high-side switch of the predetermined switching arm and closes the low-side switch of the predetermined switching arm.

[0053] In a particular embodiment of the invention, after detecting an indication that the voltage measured by the voltage measuring means exceeds a first predetermined value and repeatedly does so within a predetermined time period or as long as the voltage measured by the voltage measuring means exceeds a second predetermined value:

[0054] - a current measuring device measures the current through a predetermined phase;

[0055] - if the intensity of the measured current is positive, the control circuit opens the low-side switch of the predetermined switching arm and closes the high-side switch of the predetermined switching arm;

[0056] - Otherwise, the control circuit opens the high-side switch of the predetermined switching arm and closes the low-side switch of the predetermined switching arm.

[0057] In a particular embodiment of the invention, the control system is characterized in that, for each phase, it also comprises means for measuring the current through this phase, and in that, for each phase:

[0058] - the control circuit closes the low-side switch of the switching arm connected to the phase via its center tap;

[0059] - a current measuring device measures the current through the phase;

[0060] - if the current intensity measured in the phase is positive, the control circuit closes the high-side switch of the switching arm connected to the phase via its center tap;

[0061] - Otherwise, the control circuit opens the high-side switch of the switching arm connected to the phase via its center tap.

[0062] The control system benefits from the same aforementioned advantages as the control method.

[0063] According to a third aspect, another object of the invention is an electrical system comprising a control system according to the second aspect of the invention and a multi-phase disc-wound rotor rotating electrical machine controlled by said control system.

[0064] The electrical system benefits from the same aforementioned advantages as the control method and the control system.

[0065] According to a fourth aspect, another object of the invention is a control system for a multiphase rotating electrical machine, which is operated as a generator and is connected to an electrical network, in particular an on-board network on a motor vehicle, via a first and a second power supply terminal, the control system comprising:

[0066] - a control bridge comprising a plurality of switching arms mounted in parallel, each arm comprising a high-side switch and a low-side switch connected together at a center tap connected to a phase winding of said rotating electrical machine, said control bridge being able to supply voltage to said electrical network;

[0067] - a control circuit capable of opening or closing the switches of the control bridge;

[0068] - means for measuring the voltage between the first and second power supply terminals;

[0069] The control system is characterized in that, for at least one predetermined phase winding also connected to the predetermined switching arm, the control system further comprises means for measuring the current through the predetermined phase winding, and when the voltage measured by the voltage measuring means exceeds a first value:

[0070] - the control circuit opens the high-side switch of the predetermined switching arm and short-circuits the at least one predetermined phase winding; then

[0071] - a current measuring device measures the current through a predetermined phase;

[0072] - if the intensity of the measured current is positive, the control circuit opens the low-side switch of the predetermined switching arm and closes the high-side switch of the predetermined switching arm;

[0073] - Otherwise, the control circuit opens the high-side switch of the predetermined switching arm and closes the low-side switch of the predetermined switching arm.

[0074] In a particular embodiment of the invention, after a short circuit of said at least one predetermined phase winding and after detecting an indication that the voltage measured by the voltage measuring means exceeds a first predetermined value and does so in an iterative manner for a predetermined period of time or as long as the voltage measured by the voltage measuring means exceeds a second predetermined value:

[0075] - a current measuring device measures the current through a predetermined phase;

[0076] - if the intensity of the measured current is positive, the control circuit closes the high-side switch of a predetermined switching arm;

[0077] - Otherwise, the control circuit opens the high-side switch of the predetermined switching arm.

[0078] In a particular embodiment of the invention, after a short circuit of said at least one predetermined phase winding and after detecting an indication that the voltage measured by the voltage measuring means exceeds a first predetermined value and does so in an iterative manner for a predetermined period of time or as long as the voltage measured by the voltage measuring means exceeds a second predetermined value:

[0079] - a current measuring device measures the current through a predetermined phase;

[0080] - if the intensity of the measured current is positive, the control circuit opens the low-side switch of the predetermined switching arm and closes the high-side switch of the predetermined switching arm;

[0081] - Otherwise, the control circuit opens the high-side switch of the predetermined switching arm and closes the low-side switch of the predetermined switching arm.

[0082] According to a fifth aspect, another object of the invention is an electrical system comprising a control system according to the second aspect of the invention and a multi-phase disc-wound rotor rotating electrical machine controlled by said control system.

[0083] In other embodiments, it is also conceivable that the control method, the control system and the electrical system according to the present invention are combined to have all or some of the above-mentioned features. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Certain features and advantages of the present invention will become apparent from the detailed description provided with reference to the accompanying drawings, in which:

[0085] Figure 1 A first embodiment of an electrical system according to the invention is shown;

[0086] Figure 2 A control method according to a specific embodiment of the present invention is shown as a flow chart;

[0087] Figure 3 The relationship between the current measured in the short-circuited phase and the state of the high-side switch of the switching arm associated with this phase is shown in the form of a graph. DETAILED DESCRIPTION

[0088] Figure 1 A first embodiment of an electrical system 100 according to the invention is shown. The electrical system is intended for use in a motor vehicle, for example.

[0089] The electrical system 100 is connected to the on-board network 1 of the motor vehicle and comprises at least one DC voltage source 102. The DC voltage source 102 comprises a positive terminal and a negative terminal, the negative terminal being usually connected to an electrical ground GND, such as the chassis of the motor vehicle. The DC voltage source 102 is designed to provide a DC input voltage E between these terminals.

[0090] The electrical system 100 firstly comprises a multiphase rotating electric machine 106. In the example described herein, the multiphase rotating electric machine 106 comprises stator phases U, V, W, which in the example described comprise first respective terminals connected to a neutral point N. In the example described, the electric machine 106 is a three-phase electric machine. The electric machine 106 is, for example, a synchronous electric machine coupled to a starter-alternator belt so as to drive the belt when operating as a motor and to be driven by the belt when operating as a generator.

[0091] The electrical system 100 further comprises a control system 101 according to the present invention, the system comprising:

[0092] a) A control bridge 108 connected to the terminals of the DC voltage source 102 on the one hand and to the motor 106 on the other hand in order to supply the stator phases U, V, W of the motor 106 from the DC voltage source 102. The control bridge 108 thus comprises a high terminal BH OS and low terminal BB OS , which are connected to the positive terminal and negative terminal of the DC voltage source 102 respectively. The control bridge 108 is used to receive or supply the high-end BH OS The stator current i E ;

[0093] b) electronic control circuit 120;

[0094] c) Used to measure high-side BH OS and low terminal BB OS means 130 for a voltage between;

[0095] d) Measuring device 140 U , used to measure the current I flowing in the stator phase U u Strength;

[0096] e) Measuring device 140 V , used to measure the current I flowing in the stator phase V v the strength of

[0097] f) Measuring device 140 w , used to measure the current I flowing in the stator phase W w Strength

[0098] The control bridge 108 also includes arms respectively associated with stator phases U, V, W. Each arm includes a high terminal BH connected to OS The high side switch and connected to the low terminal BB OS The high-side switch and the low-side switch are also connected to the center tap (P U ,P V ,P W) are connected together at . Each arm is intended to be controlled to switch between two configurations. In a first configuration, referred to as the high-side configuration, the high-side switch is closed and the low-side switch is opened, so that the input voltage E is applied to the second end of the relevant stator phase U, V, W. In a second configuration, referred to as the low-side configuration, the high-side switch is opened and the low-side switch is closed, so that zero voltage is applied to the second end of the relevant stator phase U, V, W. The control bridge 108 is controlled by an electronic control circuit 120 to switch each arm between the two configurations, thereby regulating the current through the stator phase U, V, W.

[0099] In the embodiments described herein, the high-side and low-side switches of the control bridge 108 are isolated gate field effect transistors, more commonly referred to as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

[0100] Device 140 for measuring the current flowing in stator phase U of electric machine 106 U Measure from the center tap P U The current flowing from the center tap P U When entering stator phase U, this current is positive, otherwise it is negative.

[0101] Similarly, the device 140 for measuring the current flowing in the stator phase V of the electric machine 106 V Measure from the center tap P V The current flowing from the center tap P V This current is positive when entering stator phase V, otherwise it is negative.

[0102] Similarly, the device 140 for measuring the current flowing in the stator phase W of the motor 106 W Measure from the center tap P W The current flowing from the center tap P W When entering stator phase W, this current is positive, otherwise it is negative.

[0103] The electrical system 100 further includes a terminal BH connected to the control bridge 108. OS ,BB OS The capacitor 104 is provided between the capacitor 104 and the capacitor 104. The capacitor 104 includes, for example, one or more capacitors, such as chemical capacitors.

[0104] refer to Figure 2 , the main steps of the control method according to the invention implemented by the control system 101 when the rotating electrical machine 106 is in its generator operating mode will now be described.

[0105] Initially (step D), the rotary electric machine 106 is in generator mode.

[0106] During a step E100 , the electronic control circuit 120 alternately controls the opening and closing of the low-side and high-side switches of the control bridge 108 in an operating mode known as synchronous rectifier mode.

[0107] At the same time, during step E200 , the voltage measuring device 130 measures the high terminal BH OS and low terminal BH OS and sends the measured voltage to the control circuit 120. For example, by OS and low terminal BH OS The voltage V* is obtained by filtering the voltage between 1 and 2 to avoid any current ripple caused by rectification and to avoid false detection of load losses.

[0108] During a step E300 , the measured voltage V* is compared by the control circuit 120 with a first predetermined value VS1 , for example 58 V.

[0109] If the measured voltage is lower than the first predetermined value VS1 , no load loss is detected and the control system repeats parallel steps E100 and E200 .

[0110] If measured voltage V* is above first predetermined value VS1 , an overvoltage on onboard network 1 is detected, for example due to disconnection of DC voltage source 102 , and electronic control circuit 120 short-circuits stator phases U, V and W of rotating electrical machine 106 during step E400 .

[0111] The short circuit is achieved by commanding all low-side switches of the switching arms of the control bridge 108 to close. In other words, all switching arms of the control bridge 108 are in their low configuration.

[0112] Then, during a step E500 , the measuring device 140 U Measure the current I flowing in stator phase U u .

[0113] During step E600 , the control circuit 120 measures the current I u Compares with zero value.

[0114] If the current I u is positive, during step E800 the electronic control circuit commands the closing of the high-side switch and the opening of the low-side switch of the switching arm associated with stator phase U

[0115] Otherwise, (I u is negative or zero), during a step E700, the electronic control circuit commands the opening of the high-side switch and the closing of the low-side switch of the switching arm associated with stator phase U.

[0116] Simultaneously with steps E500 , E600 , E700 , E800 , in the embodiment described herein, the method performs steps E510 , E610 , E710 , E810 , E910 .

[0117] During step E510 , the measuring device 140 V Measure the current I flowing in stator phase V V .

[0118] During step E610 , the control circuit 120 measures the current I V Compares with zero value.

[0119] If the current I V is positive, during a step E810 , the electronic control circuit commands the closing of the high-side switch and the opening of the low-side switch of the switching arm associated with stator phase V.

[0120] Otherwise, (I V is negative or zero), during a step E710, the electronic control circuit commands the opening of the high-side switch and the closing of the low-side switch of the switching arm associated with stator phase V.

[0121] Simultaneously with steps E500, E600, E700, E800 and E510, E610, E710, E810, in the embodiment described herein, the method performs steps E520, E620, E720, E820, E920.

[0122] During step E520 , the measuring device 140 W Measure the current I flowing in the stator phase W W .

[0123] During step E620 , the control circuit 120 measures the current I W Compares with zero value.

[0124] If the current I W is positive, during a step E820 , the electronic control circuit commands the closing of the high-side switch and the opening of the low-side switch of the switching arm associated with stator phase W.

[0125] Otherwise, (I W is negative or zero), during a step E720, the electronic control circuit commands the opening of the high-side switch and the closing of the low-side switch of the switching arm associated with stator phase W.

[0126] After steps E700 , E710 , E720 or steps E800 , E810 , E820 , the voltage measuring device 130 measures the high terminal BH during a step E900 . OS and low terminal BH OSand sends the measured voltage to the control circuit 120.

[0127] During a step E1000 , the measured voltage V* is compared by the control circuit 120 with a second predetermined value VS2 , for example 54 V.

[0128] If the measured voltage V* is higher than the second predetermined value VS2, the control system repeats parallel steps E500-E800, E510-E810, E520-E820 and E900.

[0129] If the measured voltage is lower than the second predetermined value VS2, the control method stops (step F).

[0130] Figure 3 shows the current I measured in the winding of phase U u and specifies the time period during which the high-side switch of the switching arm associated with stator phase U is closed.

[0131] In the aforementioned embodiment of the control method according to the invention, steps E500-E800, E510-E810, E520-E820 and E900 are periodically performed as long as the measured voltage V* is above the second predetermined value VS2. In an alternative embodiment, steps E500-E800, E510-E810, E520-E820 and E900 are periodically performed during a predetermined time interval DT (e.g. 40ms).

[0132] In the above-described embodiment of the control method according to the invention, steps E500-E800, E510-E810, E520-E820 are performed simultaneously for all phases of the stator. As an alternative embodiment, only steps E500-E800 are performed. In other words, in this alternative embodiment, the control method only takes into account the current I measured in the winding of phase U. u strength.

[0133] Of course, the invention is not limited to the embodiments described with reference to the drawings and alternative embodiments may be envisaged without departing from the scope of the invention.

[0134] For example, in the embodiments described above, the transistors are all MOSFET transistors. As an alternative embodiment, the transistors may be insulated gate bipolar transistors (IGBTs).

Claims

1. A method for controlling a multiphase rotating electrical machine (106), the stator of which is controlled by a control bridge (108), the control bridge comprising a plurality of switching arms mounted in parallel, each arm comprising a high-side switch and a low-side switch connected together at a center tap, the center tap being connected to a phase (U, V, W) of the rotating electrical machine, the rotating electrical machine operating as a generator and connected to an electrical network (1), the method comprising a short-circuiting step (E400) of short-circuiting at least one phase winding of the stator when a voltage measurement value (V*) of the electrical network (1) exceeds a first predetermined value (VS1), the method further being characterized in that it comprises, after the short-circuiting step (E400), an activation step (E500, E600, E700, E800) of activating a switching arm, the center tap of which is connected to at least one short-circuited phase winding, during which step: - measuring the strength in short-circuited windings; - if the measured intensity corresponds to a current flowing into or returning to said at least one short-circuited phase winding from said center tap connected to said at least one short-circuited phase winding, the high-side switch of said activated switching arm moves to a closed position and the low-side switch of said activated switching arm moves to an open position; - Otherwise, the high-side switch of the activated switching arm moves to the open position and the low-side switch of the activated switching arm moves to the closed position.

2. A method as claimed in the preceding claim, wherein: The measurement of the voltage of the grid is obtained by filtering the voltage of the grid with a predetermined time constant.

3. A method as claimed in any one of the preceding claims, wherein: The activation step is repeated at least until the voltage measured by the voltage measuring device is less than a second predetermined value (VS2).

4. The method according to any one of claims 1 to 2, wherein: The activating step is repeated for a predetermined period of time.

5. The method according to any one of claims 1 to 2, wherein: All phase windings of the stator are short-circuited during the short-circuiting step, and wherein, after the short-circuiting step, an activation step is performed for all switching arms.

6. A control system (101) for a multiphase rotating electrical machine (106) operating as a generator and connected to a power grid (1) via first and second power supply terminals, the control system (101) comprising: - a control bridge (108) comprising a plurality of switch arms mounted in parallel, each arm comprising a high-side switch and a low-side switch connected together at a center tap connected to a phase winding of the rotating electrical machine, the control bridge (108) being capable of supplying a voltage to the grid; - a control circuit (120) capable of opening or closing the switches of the control bridge (108); - means (130) for measuring the voltage between the first and second power supply terminals; The control system (101) is characterized in that, for at least one predetermined phase winding (U) connected to a predetermined switching arm, the control system (101) further comprises means (140) for measuring the current through the predetermined phase winding U ), and when the voltage (V*) measured by the voltage measuring device exceeds a first predetermined value (VS1): - the control circuit (120) closes the low-side switch of a predetermined switching arm; - Current measuring device (140 U ) measuring the current through a predetermined phase; - If the current (I U ) corresponds to the intensity of the current flowing into or returning to the predetermined phase from the center tap connected to the predetermined phase, the control circuit (120) closes the high-side switch of the predetermined switching arm and opens the low-side switch of the predetermined switching arm; - Otherwise, the control circuit (120) opens the high-side switch of the predetermined switching arm and closes the low-side switch of the predetermined switching arm.

7. A control system as claimed in the preceding claim, wherein: After detecting an indication that the voltage measured by the voltage measuring device exceeds the first predetermined value and doing so in an iterative manner for a predetermined period of time or as long as the voltage measured by the voltage measuring device exceeds the second predetermined value: - the control circuit (120) closes the low-side switch of a predetermined switching arm; - Current measuring device (140 U ) measuring the current through a predetermined phase; - If the current (I U ) corresponds to the intensity of the current flowing into or returning to the predetermined phase from the center tap connected to the predetermined phase, the control circuit (120) closes the high-side switch of the predetermined switching arm and opens the low-side switch of the predetermined switching arm; - Otherwise, the control circuit (120) opens the high-side switch of the predetermined switching arm and closes the low-side switch of the predetermined switching arm.

8. The control system according to claim 6 or 7, characterized in that: For each phase (U, V, W), it also includes means for measuring the current through this phase (140 U , 140 V , 140 W ), and for each phase: - the control circuit (120) closes the low-side switch of the switching arm connected to the phase via its center tap; - Current measuring device (140 U , 140 V , 140 W ) measures the current through the phase (U, V, W); - If the current measured in this phase (I U , I V , I W ) corresponds to the intensity of the current flowing into or returning to the phase from the center tap connected to the phase, the control circuit (120) closes the high-side switch of the switching arm connected to the phase through its center tap, and opens the low-side switch of the switching arm connected to the phase through its center tap; - Otherwise, the control circuit (120) opens the high-side switch of the switching arm connected to the phase via its center tap and closes the low-side switch of the switching arm connected to the phase via its center tap.

9. An electrical system (100) comprising a control system (101) according to any one of claims 6 to 8 and a multi-phase disc-wound rotor rotating electrical machine (106) controlled by the control system (101).

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