Short-circuit current control system for an electrical network

Abstract

The present invention relates to a system (0) for controlling the short-circuit current of an electrical network (3) comprising a power converter (2) controlled by a control system (4) and configured to rectify and regulate the voltage of the electrical machine (1), the control system (4) comprising: a synchronization unit (41); a control unit (42): - in active short-circuit mode, - in "freewheel" mode, - by asynchronous pulse width modulation, a regulation unit (43); so that in the event of a short circuit, the control system (4) controls the power converter (2) in order to deliver to the electrical network (3) a direct current equal to the predetermined value. Figure for abstract: Fig. 1

Description

Title of the invention: System for controlling the short-circuit current of an electrical network Technical field

[0001] The present invention relates generally to the field of alternating current electrical machines, such as Permanent Magnet Synchronous Machines (PMSM) supplying high voltage direct current networks (called HVDC for "High Voltage Direct Current" in English terminology). And the invention relates in particular to the control of the short-circuit current of such a network. STATE OF THE ART

[0002] Conventionally, an electrical network such as the HVDC electrical networks of electric or hybrid propulsion aircraft is powered by electrical machines, typically Permanent Magnet Synchronous Electrical Machines (PMSM, or PMSP in English terminology). These electrical machines deliver an alternating current, they must be associated at their output with a control system comprising a power converter whose function is to supply the HVDC electrical network with a direct current and to control the power converter. Such a power converter is conventionally an active power converter controlled by its own control system and which makes it possible to rectify and regulate the voltage to supply the HVDC electrical network.

[0003] A problem is that in the event of a fault on the electrical network, in particular during a short circuit, the voltage of the electrical network collapses and the MSAP directly supplies the short-circuited electrical network through freewheeling diodes (control mode called "Free Wheeling" in English terminology) of the power converter. The short-circuit current is then defined by the electromotive force of the electrical machine divided by the impedance (essentially the inductance of the electrical machine).

[0004] This short-circuit current of the electrical network must be limited to approximately twice the nominal current, in order to limit the constraints on the sizing of the cables and protections of the electrical network.

[0005] For certain applications, in particular aeronautical applications, in which additional mechanical integration constraints apply and where a generating PMSM is required to operate over a wide speed range, it is not possible to design a permanent magnet machine and a control system capable of limiting the value of the short-circuit current to the expected value. Statement of the invention

[0006] An aim of the present application is to remedy the aforementioned drawbacks, by proposing a system which is capable of regulating the short-circuit current while being capable of operating with a quasi-zero DC voltage in the event of a short circuit on the electrical network.

[0007] To this end, according to a first aspect of the invention, a system for controlling the short-circuit current of an electrical network is proposed, the electrical network being configured to be powered by a permanent magnet synchronous electrical machine, the electrical control system comprising a power converter configured to rectify and regulate the voltage of the electrical machine, the power converter being controlled by a control system, configured to generate, from a measurement of the output currents of the electrical machine and the power converter, control signals for the power converter, the control system comprising: - a synchronization unit, comprising sensors configured to measure the currents of the electrical machine so as to obtain signals in phase with the currents of the electrical machine, the synchronization unit being configured to multiply the signals in phase by a gain, thus obtaining setpoint signals; - a control unit, configured to compare the setpoint signals received from the synchronization unit with a reference triangular signal, the triangular signal having a frequency corresponding to the desired switching frequency for the power converter, the control unit being configured to emit the control signals by pulse width modulation, the control signals being configured:

[0008] - to control the power converter in active short-circuit mode and short- circuit the electrical machine when the setpoint signals are damaged,

[0009] - to control the power converter in “freewheel” mode and supply power the electrical network with a short-circuit current of the electrical machine, when the amplitude of the setpoint signals is greater by a predetermined factor f compared to the reference triangular signal,

[0010] - to control the power converter by width modulation asynchronous pulse, and control the short-circuit current of the electrical network so that the short-circuit current conforms to a predetermined value, when the amplitude of the set signals is between 0 and f times the amplitude of the reference triangular signal; - a regulation unit calculating the difference between a measurement of the output current of the power converter and the predetermined value of the short-circuit current, the regulation unit multiplying the difference by a corrector to obtain the gain, the corrector comprising a limiter;

[0011] so that in the event of a short circuit, the control system controls the power converter via the control signals in order to deliver to the electrical network a direct current equal to the predetermined value.

[0012] The control system according to the invention is advantageously supplemented by the following characteristics, taken alone or in any of their technically possible combinations:

[0013] - the power converter comprises semiconductors connected respectively to the positive or negative potentials of the electrical network, the semiconductors being controlled by the control system, the control signals of the control unit being configured:

[0014] - either to put all the semiconductors connected to a potential into a passing state and put all the semiconductors connected to the other potential into a blocked state when the setpoint signals are damaged, so as to short-circuit the electrical machine, the semiconductors passing from the blocked state to the on state and vice versa at the switching frequency,

[0015] - either to put in a passing state, synchronously with the direction of the currents machine phases, all semiconductors when the amplitude of the setpoint signals are higher by a predetermined factor f compared to the triangular signal, so as to supply the electrical network with the short-circuit current of the electrical machine,

[0016] - either to control the short-circuit current of the electrical network by switching from asynchronously the semiconductors when the amplitude of the set signals is between 0 and f times the amplitude of the triangular signal, so that the short-circuit current conforms to a predetermined value;

[0017] - the sensors of the synchronization unit are measuring shunts, sensors Hall effect or Néel effect current transformers, or current transformers;

[0018] - the corrector of the regulation unit is of the Proportional Integral type;

[0019] - the power converter is an active rectifier of the two-level inverter type, Vienna rectifier or multilevel rectifier;

[0020] - semiconductors are insulated gate field effect transistors, optionally silicon carbide, or insulated gate bipolar transistors with antiparallel diodes;

[0021] The invention also relates to a method for controlling the short-circuit current of an electrical network by a control system according to the invention, comprising the following steps:

[0022] , the method comprising the following steps:

[0023] - acquisition of in-phase signals from a measurement of the machine currents electric;

[0024] - multiplication by a gain of the in-phase signals in order to obtain the signals;

[0025] - switching between active short-circuit, “freewheel” and control modes asynchronous pulse width modulation of the power converter according to a comparison between the amplitude of the reference signals and the amplitude of the reference triangular signal: the control mode switches to active short-circuit mode when the reference signals are impaired, to "freewheel" mode when the amplitude of the reference signals is greater by a predetermined factor f compared to the reference triangular signal and to asynchronous pulse width modulation mode when the amplitude of the reference signals is between 0 and f times the amplitude of the reference triangular signal;

[0026] - calculation of a corrected gain, as being the image of a correction function taking as input the difference between an output current measurement of the power converter with the predetermined value of the short-circuit current and the predetermined value of the short-circuit current;

[0027] - implementation of the switching acquisition steps using the corrected gain.

[0028] Finally, the invention relates to a turbomachine comprising a system for controlling the short-circuit current of an electrical network according to the preceding characteristics, as well as a turbomachine comprising an electrical network whose short-circuit current is controlled by a control method comprising the above steps. DESCRIPTION OF THE FIGURES

[0029] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0030] [Fig.l] is a schematic view of a control system in one embodiment of the invention;

[0031] [Fig.2] is an overall schematic view of an embodiment of a control system according to the invention;

[0032] [Fig. 3] is a detailed schematic view of an embodiment of a control system according to the invention;

[0033] [Fig.4a] is a graph of an output current in Amperes versus time of a power converter in an embodiment according to the invention;

[0034] [Fig.4b] is a graph of an output current, in Amperes as a function of time, of a filter of a power converter in an embodiment according to the invention;

[0035] [Fig.4c] is a graph of the amplitude in Volts as a function of time of three control signals emitted by a control unit of a power converter of a control system according to the invention;

[0036] [Fig.5a] is a graph of the output current in Amperes versus time of a power converter of the control system in an embodiment according to the invention;

[0037] [Fig.5b] is a graph of the voltage in Volts as a function of time of a capacitor of a power converter of the control system of an electric machine in an embodiment according to the invention;

[0038] [Fig.5c] is a graph of the gain of a short-circuit current control system, as a function of time, in an embodiment according to the invention;

[0039] [Fig.5d] is a graph of the amplitude of three control signals emitted by a control unit of the control system as a function of time in an embodiment according to the invention;

[0040] [Fig.6a] is a graph of the output current in Amperes of a power converter in an embodiment according to the invention and the output current in Amperes of a power converter of the state of the art, both as a function of time;

[0041] [Fig.6b] is a graph of the amplitude of three control signals emitted by a control unit of a power converter, as a function of time, in an embodiment according to the invention;

[0042] [Fig.6c] is a graph of the amplitude of three control signals emitted by a control unit of a state-of-the-art power converter, as a function of time;

[0043] [Fig.7] is a flowchart of a control method implemented by a control system according to the invention.

[0044] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0045] In relation to [Fig. 1], an electrical network 3 is supplied by an electrical machine 1. A control system 0 for a short-circuit current of the electrical network 3 is placed between the electrical network 3 and the electrical machine 1. Such a control system makes it possible to regulate the short-circuit current.

[0046] Still in relation to [Fig.l], the control system 0 comprises an active power converter 2, which rectifies and regulates the output voltage of the electric machine 1. The power converter 2 is controlled by a control system 4.

[0047] More precisely, in the illustrated case [Fig.l], where an electrical machine 1 with permanent magnets supplies a three-phase DC electrical network 3, the power converter 2 comprises a controlled active rectifier, DC or AC filters depending on the needs and current sensors as well as optionally voltage, temperature and position sensors. The power converter 2 can use any type of active rectifier topology, for example a two-level inverter, a Vienna rectifier or a multi-level rectifier. The power converter 2 comprises semiconductors 21, 22 connected at the input to the different phases of the electrical machine 1, while at the output the semiconductors 21 are connected to the positive potential of the electrical circuit 3 and the semiconductors 22 to the negative potential, to supply the loads of the electrical network 3.The power converter 2 is controlled by the control system 4 which controls the on or off state of the semiconductors 21, 22.

[0048] Semiconductors 21, 22 are understood to mean any type of semiconductor such as transistors, for example insulated gate field effect transistors (MOSFETs). To withstand high voltages, MOSFETs based on silicon carbide (called SiC MOSFETs) will advantageously be used. Alternatively to MOSFETs, the power converter 2 may comprise insulated gate bipolar transistors (IGBTs) provided with antiparallel diodes. The semiconductors 21, 22 are used in switching and therefore adopt an on or off state, in which the passage of current between the drain and the source of a semiconductor 21, 22 is possible and a blocking state or, in which a semiconductor 21, 22 behaves like an open switch.

[0049] The principle implemented by the control system 4 in the event of a short circuit is based on three modes of control of the power converter 2.

[0050] The first mode, called "active short circuit" ("active short circuit" abbreviated ASC in English terminology) consists of closing all the semiconductors 21, 22 of the power converter 2 connected to the positive potential of the electrical network 3 while opening all the semiconductors 21, 22 connected to the negative potential (or the reverse) in order to short-circuit the electrical machine 1, the current of the electrical network 3 then being zero. This mode has the advantage of limiting the risks of overvoltages on the electrical network 3 but does not allow the loads of the electrical network 3 to be supplied in short-circuit, and can generate heating of the semiconductors 21, 22 of the power converter 2 which must withstand the short-circuit current.

[0051] The second mode, called “free wheeling” (abbreviated FW), consists of opening all the controlled semiconductors 21, 22 of the power converter 2. The EMF of the electrical machine 1 then imposes its short-circuit current through the freewheeling diodes of the power converter 2, which makes it possible to supply the short-circuit of the electrical network 3 with the short-circuit current of the electrical machine 1, but without control of the short-circuit current applied to the electrical network 3, that is to say that the current is equal to the short-circuit current of the electrical machine 1. This second mode can be optimized by synchronous rectification control in the case where insulated gate field effect transistors (MOSFETs) are used as semiconductors 21, 22. To withstand high voltages, silicon carbide-based MOSFETs (SiC MOSFETs) will advantageously be used. Alternatively to MOSFETs, the power converter 2 can use insulated gate bipolar transistors (IGBTs) equipped with antiparallel diodes.

[0052] A third mode called “asynchronous pulse width modulation” consists of controlling the power converter 2 by alternating the ASC and FW modes successively. The output current of the controlled active rectifier of the power converter 2 is then alternately equal to 0 or to the short-circuit current of the electrical machine 1. This current is then preferentially filtered by a DC filter, to provide an output current from the power converter 2 to the electrical network 3 between 0 and the short-circuit current of the electrical machine 1.

[0053] In the event of a short circuit on the electrical network 3, the third mode is implemented by the control system 4. Outside of this case, the power converter 2 is controlled in a mode called “nominal operating mode” which is not the subject of the invention.

[0054] To implement this third control mode in the event of a short circuit, the control system 4, illustrated [Fig.2] and 3, comprises a synchronization unit 41, a control unit 42 and a regulation unit 43. The operation of each unit is detailed below.

[0055] Synchronization unit

[0056] The synchronization unit 41 has the function of synchronizing the control signals S sent to the power converter 3 with the phase currents. Knowledge of the phase and frequency of the current of the electrical machine 1 makes it possible, using a chopping principle, to define operating sequences in ASC during which no power is transmitted to the electrical network 3, and operating sequences in FW during which the electrical machine 1 supplies the electrical network 3 in short-circuit.

[0057] For this purpose, the synchronization unit 41 measures the currents of the electrical machine 1 using sensors, for example measuring shunts, Hall or Néel effect sensors, current transformers or any other suitable device. The measurement of the sensors provides three signals in phase Sp with the currents of the machine electric 1, having a virtually constant amplitude, independently of the rotation speed of the electric machine 1.

[0058] Indeed, for a three-phase short circuit, the no-load EMF of the electrical machine 1 between phase and neutral is written:

[0059] E + + *Jcc

[0060] With:

[0061] Eph_N: No-load EMF of electrical machine 1 between phase and neutral

[0062] L: Inductance of the electric machine 1

[0063] 1: Cable inductance

[0064] w: pulsation (2 xnxf)

[0065] f: Electrical frequency of the electrical machine 1

[0066] R: Resistance of the winding of the electric machine 1

[0067] r: Cable resistance

[0068] Icc: Short-circuit current of the electrical machine 1

[0069] In the embodiment described here in which the electrical machine 1 is in generator mode and of high power, the resistances of the windings and cables can be considered as negligible compared to the inductive impedances. The preceding equation is then simplified:

[0070] EphN= (L +

[0071] The no-load EMF being proportional to the frequency, the short-circuit current Icc is constant for the operating frequencies of the electrical machine 1 as a generator at nominal operating speeds.

[0072] In the case of a short circuit on the electrical network 3, the resistances of the semiconductors 21, 22 of the power converter 2 and the resistances of the cables of the electrical network 3 remain negligible compared to the impedance of the electrical machine 1, and the inductive impedance of the cables of the electrical network 3 in static operation is zero (direct current network, therefore zero frequency).

[0073] The phase signals Sp are then multiplied by a gain from the regulation unit 43, to obtain setpoint signals Spg transmitted to the control unit 42. The use of phase signals Sp allows the control system 4 to operate over the entire speed range of the electrical machine 1.

[0074] Control unit

[0075] The control unit 42 receives the setpoint signals Spg from the synchronization unit 41 and compares them with a reference triangular signal St. The reference triangular signal St has a constant amplitude and a frequency corresponding to the desired switching frequency for the power converter 2. Depending on the result of the comparison, the control unit 42 generates control signals S by Pulse Width Modulation (PWM), according to the following function: - if the Spg setpoint signals are impaired, the power converter 2 is controlled in ASC mode: the electrical machine 1 is short-circuited, for example by controlling the semiconductors 21, 22 of the power converter 2 to close those connected to the positive potential of the electrical network 3 while opening all the semiconductors 21, 22 connected to the negative potential of the electrical network 3 or conversely, by opening the semiconductors connected 21, 22 to the positive potential of the electrical network 3 while closing all the semiconductors 21, 22 connected to the negative potential of the electrical network 3 as a function of the switching frequency; - if the amplitude of the setpoint signals Spg is greater by a predetermined factor f than the reference triangular signal St, the power converter 2 is controlled in FW mode: the electrical network 3 is then supplied with the short-circuit current of the electrical machine 1 by controlling all the semiconductors 21, 22 of the power converter 2 in active rectifier mode; - if the amplitude of the reference signals Spg is between 0 and f times the amplitude of the reference triangular signal St, the power converter 2 is controlled by modulating the pulse widths between these two modes, i.e. by asynchronously switching the semiconductors 21, 22.

[0076] An example of short-circuit current control by asynchronous pulse width modulation of the power converter 2 is illustrated in Figures 4a, 4b and 4c in relation to the example of control system 0 illustrated [Fig.3]. Figures 4a, 4b and 4c are on the same time scale. In [Fig.4a] is shown the output current I(Ci) + I(Li) of the power converter 2. In [Fig.4b] is shown the output current ILi of a DC filter of the power converter 2, regulated to a predetermined and stable current target value. [Fig.4c] shows the amplitude of three control signals S, V4, Vi5 and Vi6, emitted by the control unit 42, each control signal V4, Vi5 and Vi6 corresponding respectively to a phase of the electrical machine 1 and to the signals denoted A, B and C of [Fig.3].The simultaneous, or synchronous, non-zero state of the three control signals S V4, Vi5 and V16 corresponds to an order to put the semiconductors 21 into the on-state, i.e. to an ASC operation of the power converter 2 during which no current is transferred to the electrical network 3: 1(Ci) + I(Li) is zero. Conversely, the simultaneous zero state of the three control signals S V4, Vi5 and Vi6 corresponds to . an order to put the semiconductors 21 in a blocked state and to close the semiconductors 22, that is to say to an ASC operation of the power converter 2 during which no current is transferred to the electrical network 3. Outside of these states, the PWM makes it possible to transfer current to the output of the power converter 2, filtered current in order to deliver to the electrical network 3 a direct current equal to the target value.

[0077] Regulation unit

[0078] The regulation unit 43 compares the direct output current of the power converter 2 with the predetermined target current value. The difference between these two values ​​is applied to a corrector or to any other type of compatible control, for example a Proportional Integral (PI) corrector equipped with an output limiter. The corrector then calculates a gain, transmitted to the synchronization unit 41.

[0079] In normal operation, the control called "nominal operating mode" regulates the generator. This is a conventional control which can be in current or in voltage. In the absence of a short circuit, the direct current supplied to the electrical network 3 is much lower than the target value of the short-circuit current (conventionally in a ratio greater than or equal to 2). Also, with reference to the embodiment of figures 3, 4a, 4b, 4c, the integral function of the PI corrector increases the target value up to the upper limitation.

[0080] At the time of the short circuit in the electrical network 3, the discharge current of the capacitor at the terminals of the converter 2 is very high (approximately 6 kA in the example of [Fig.5a]). The “nominal operating mode” control mode is then inhibited to activate the short-circuit current regulation mode previously described. This change of mode can be activated either by exceeding a current threshold, or by a DC voltage measurement below a low threshold, or by a combination of the two pieces of information. The difference between the measured current and the target value then allows the regulation unit 43 to quickly force the gain to 0. Such a zero gain, transmitted to the synchronization unit 41, causes the emission of Spg nuis setpoint signals to the control unit 42 and therefore to control the power converter 2 in ASC mode so as not to supply an additional current in the short-circuited network.

[0081] The power converter 2 then remains in ASC mode until the current drops back to the target value and naturally starts regulating the short-circuit current, which is confirmed by the desynchronization of the control orders of the semiconductors 21, 22 of the three phases.

[0082] The control system 4 is therefore configured to ensure an optimal transient state with the nominal control mode of the power converter 2 used, when there is no short circuit on the electrical circuit 3. Depending on Depending on the application, this control mode can be a vector control, an intersecting PWM type control with or without third harmonic, a torque control based on current control or a control based on generator power regulation or DC voltage control.

[0083] An example of transition between the nominal control mode and the short-circuit control mode, described previously, is illustrated by Figures 5a, 5b, 5c and 5d in relation to the example of control system 0 illustrated [Fig. 3]. Figures 5a, 5b, 5c and 5d are on the same time scale. In [Fig.5a] is shown the output current I(Li) of the power converter 2, in [Fig.5b] the voltage VPi of the capacitor of the filter of the power converter 2. In [Fig.5c] is shown the gain V_PI emitted by the regulation unit 43, [Fig.5d] illustrates the amplitude of three control signals S V4, Vi5 and V16, emitted by the control unit 42. In this example, a short circuit whose establishment corresponds to the initial point of increase of the output current I(Li) of [Fig.5a] causes the discharge of the capacitor, i.e. the decrease of the voltage VPi [Fig.5b], and the switch from nominal mode to short-circuit current control mode, caused by the drop of the V_PI gain to 0 in [Fig.5c]. The control signals S V4, Vi5 and V16 are then synchronous. The power converter 2 then remains in ASC mode until the short-circuit current I(Li) decreases and reaches the target value, which causes the V_PI gain to increase and therefore the desynchronization of the control signals S V4, V15 and V16.

[0084] Figures 6a, 6b and 6c show an example which allows the effectiveness of the invention to be seen compared to a conventional “freewheel” synchronous rectification system. [Fig.6a] shows the short-circuit current I(L3) of the conventional system, still in relation to the example of control system 0 illustrated [Fig.3], and the short-circuit current I(Li) of the power converter 2 controlled according to the invention. [Fig.6b] shows the control signals S V4, Vi5 and Vi6 emitted by the control unit 42 according to the invention with a target value of 500A, while [Fig.6c] shows the control signals S Vio, Vn and Vi8 of a conventional system operating in FW mode. It can be seen that the short-circuit current I(L3) is much higher, around 1250A in this example, than the short-circuit current I(Li) regulated to 500A by the control system 4 of the invention.

[0085] Of course, the values ​​given above are given as examples and should not limit the invention described to these orders of magnitude alone. The control system 4 allows effective regulation of the short-circuit current for any electrical machine and its power converter, whether the electrical machine is operating in generator or motor mode. At the time of clarification of the short- circuit, the increase in the load impedance will no longer allow the short-circuit current to be supplied to the electrical network 3. The output gain of the control loop 53 will increase until saturation, leading to operation in “freewheel” mode, which will allow the voltage of the electrical network 3 to be increased in a controlled manner and will allow a return to the nominal control mode as soon as the DC voltage across the capacitor terminals has become higher than a threshold.

[0086] Thus, the transitions between the nominal control mode and the short-circuit control mode take place without sudden variations or resetting of the control parameters.

[0087] Control method

[0088] On the other hand, the control system 4 implements, iteratively and continuously, a method for controlling the short-circuit current of the electrical network 3, illustrated [Fig.7]. During a step E0, the measurement of a current greater than a predefined threshold and / or a voltage less than a predefined threshold triggers the transition between the nominal control mode and the short-circuit control mode of the control system 0. A step El then consists of the acquisition of the measurements of the currents of the electrical machine 1 by the sensors of the synchronization unit 41 to obtain the phase signals Sp. These signals are multiplied by the gain G in order to obtain the setpoint signals Spg transmitted to the unit of the control unit 42 in step E2.During a step E3, the control unit 42 controls the power converter 2 according to a comparison between the amplitude of the setpoint signals Spg and the amplitude of the reference triangular signal St: the power converter 2 is controlled in active short-circuit mode when the setpoint signals Spg are null, in “freewheel” mode when the amplitude of the setpoint signals Spg is greater by a predetermined factor f compared to the reference triangular signal St and in asynchronous pulse width modulation mode when the amplitude of the setpoint signals Spg is between 0 and f times the amplitude of the reference triangular signal St. A step E4 implemented by the regulation unit 43 allows the calculation of a corrected gain Gc from the difference between an output current measurement of the power converter 2 and the predetermined value of the short-circuit current.This difference is an error measurement injected into a corrector with the predetermined value of the short-circuit current (which is a setpoint value) in order to calculate the corrected gain Gc. A step E5 then consists of repeating steps El to E3 using the corrected gain Gc. When a measurement of the DC voltage of the electrical network 3 is greater than a predefined threshold, the transition from the short-circuit control mode to the nominal control mode is carried out during a step E6.

Claims

1. Claims Control system (0) for the short-circuit current of an electrical network (3), the electrical network (3) being configured to be powered by a permanent magnet synchronous electrical machine (1), the electrical control system (0) comprising a power converter (2) configured to rectify and regulate the voltage of the electrical machine (1), the power converter (2) being controlled by a control system (4), configured to generate, from a measurement of the output currents of the electrical machine (1) and of the power converter (2), control signals S of the power converter (2), the control system (4) being characterized in that it comprises: - a synchronization unit (41), comprising sensors configured to measure the currents of the electrical machine (1) so as to obtain signals in phase Sp with the currents of the electrical machine (1), the synchronization unit (41) being configured to multiply the signals in phase Sp by a gain G, thus obtaining setpoint signals Spg; - a control unit (42), configured to compare the setpoint signals Spg received from the synchronization unit (41) with a reference triangular signal St, the triangular signal St having a frequency corresponding to the desired switching frequency for the power converter (2), the control unit (42) being configured to emit the control signals S by pulse width modulation, the control signals S being configured: - to control the power converter (2) in active short-circuit mode and short-circuit the electrical machine (1) when the Spg setpoint signals are impaired, - to control the power converter (2) in “freewheel” mode and supply the electrical network (3) with a short-circuit current from the electrical machine (1), when the amplitude of the reference signals Spg is greater by a predetermined factor f than the reference triangular signal St,

2. - to control the power converter (2) by asynchronous pulse width modulation, and to control the short-circuit current of the electrical network (3) so that the short-circuit current complies with a predetermined value, when the amplitude of the setpoint signals Spg is between 0 and f times the amplitude of the reference triangular signal St; - a regulation unit (43) calculating the difference between a measurement of output current of the power converter (2), measurement carried out by a current sensor, with the predetermined value of the short-circuit current, the regulation unit (43) multiplying the difference by a corrector to obtain the gain G, the corrector comprising a limiter; so that in the event of a short circuit, the control system (4) controls the power converter (2) via the control signals S in order to deliver to the electrical network (3) a direct current equal to the predetermined value. Control system (0) for the short-circuit current of an electrical network according to claim 1, in which the power converter (2) comprises semiconductors (21) connected to the positive potentials and semiconductors (22) connected to the negative potentials of the electrical network (3), the semiconductors (21, 22) being controlled by the control system (4), the control signals S of the control unit (42) being configured: - either to put all the semiconductors (21, 22) connected to one potential into an on state and to put all the semiconductors (21, 22) connected to the other potential into a blocked state when the setpoint signals Spg are impaired, so as to short-circuit the electrical machine (1), the semiconductors (21, 22) passing from the blocked state to the on state and vice versa at the switching frequency, - or to put in an on state, synchronously with the direction of the machine phase currents, all semiconductors (21,22) when the amplitude of the setpoint signals Spg are greater by a predetermined factor f than the triangular signal St, so as to supply the electrical network (3) with the short-circuit current of the electrical machine (1), - either to control the short-circuit current of the electrical network (3) by asynchronously switching the semiconductors (21, 22) when the amplitude of the setpoint signals Spg is between 0 and f times the amplitude of the triangular signal St, so that the short-circuit current conforms to a predetermined value.

3. Control system (0) for the short-circuit current of an electrical network according to one of claims 1 or 2, in which the sensors of the synchronization unit (41) are measuring shunts, Hall effect or Néel effect current sensors, or current transformers.

4. Control system (0) for the short-circuit current of an electrical network according to one of claims 1 to 3, in which the corrector of the regulation unit (43) is of the Proportional Integral type.

5. Control system (0) for the short-circuit current of an electrical network according to one of claims 1 to 4, in which the power converter (2) is an active rectifier of the two-level inverter type, Vienna rectifier or multi-level rectifier.

6. Control system (0) for the short-circuit current of an electrical network according to one of claims 2 to 5, in which the semiconductors (21, 22) are insulated gate field effect transistors (MOSFET), optionally made of silicon carbide, or insulated gate bipolar transistors (IGBT) provided with antiparallel diodes.

7. Method for controlling the short-circuit current of an electrical network (3) by a control system (0) according to one of claims 1 to 6, the method comprising the following steps: - E1 acquisition of the phase signals Sp from a measurement of the currents of the electrical machine (1); - E2 multiplication by a gain G of the phase signals Sp in order to obtain the signals Spg; - E3 switching between the active short-circuit, "freewheel" and asynchronous pulse width modulation control modes of the power converter (2) according to a comparison between the amplitude of the setpoint signals Spg and the amplitude of the reference triangular signal St: the control mode switches to active short-circuit mode when the setpoint signals Spg are nuis, in "freewheel" mode when the amplitude of the setpoint signals Spg is greater by a predetermined factor f compared to the reference triangular signal St and in asynchronous pulse width modulation mode when the amplitude of the setpoint signals Spg is between 0 and f times the amplitude of the reference triangular signal St; - E4 calculation of a corrected gain Gc, as being the image of a correction function taking as input the difference between an output current measurement of the power converter (2) with the predetermined value of the short-circuit current and the predetermined value of the short-circuit current; - E5 implementation of steps El to E3 using the corrected gain Gc.

8. Turbomachine comprising a control system (0) for the short-circuit current of an electrical network (3) according to one of claims 1 to 6.

9. Turbomachine comprising an electrical network (3) whose short-circuit current is controlled by a control method according to claim 7.

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