Electric or hybrid propulsion system and method for compensating oscillatory current oscillations

Abstract

This disclosure relates to an electric or hybrid propulsion system (10) of an aircraft comprising: a DC voltage bus (19), at least two power electronic components (3) connected in parallel to the DC voltage bus (19), a motor control including a sensor (8) configured to measure electrical parameters representative of at least one of the power electronic components (3), the measured electrical parameters including, in particular, a current intensity flowing through the DC voltage bus (19) and / or a voltage across the terminals of the DC voltage bus (19), each power electronic component (3) being electrically connected to a separate stator winding, each stator winding being contained in an electrical machine (5),the electric machine (5) being configured to convert electrical energy transmitted by the DC voltage bus (19) to the electric machine (5) via the power electronic components (3) into mechanical torque to provide thrust to an aircraft, the propulsion system comprising an active compensation system (18) of at least one power electronic component (3) configured to attenuate oscillatory currents flowing between at least one power electronic component (3) and the other power electronic components (3) via the DC voltage bus (19) according to the measured electrical parameters. Figure for the abstract: Fig. 1,

Description

Title of the invention: Electric or hybrid propulsion system and method for compensating oscillatory current oscillations. FIELD OF THE INVENTION

[0001] The invention relates generally to the field of electric or hybrid motors. It finds advantageous application in aeronautical propulsion systems. STATE OF THE ART

[0002] The field of electric or hybrid-powered aviation is booming, with increasing demand for intra-urban and inter-urban transport of goods and people. Aircraft suitable for such propulsion include vertical take-off and landing (VTOL) aircraft; short take-off and landing (STOL) aircraft; and also some conventional take-off and landing (CTOL) aircraft.

[0003] Electric or hybrid aeronautical propulsion systems typically comprise one or more electric machines powered by direct current (DC) voltage sources. The DC voltage source is an HVDC (High Voltage Direct Current) network. For example, the DC voltage source may include batteries, distribution networks, or fuel cells.

[0004] A major problem with electric propulsion systems is the mass of the various components, and particularly the onboard battery. Indeed, unlike a thermal propulsion system, whose mass decreases during flight due to fuel consumption, the battery of an electric propulsion system remains essentially constant during flight, regardless of its state of charge. Furthermore, some electric or hybrid aircraft—VTOL and CTOL in particular—are designed to carry only a few passengers at most, and the mass of the onboard propulsion system can therefore represent a significant percentage of the vehicle's overall mass.

[0005] One solution considered by the prior art to minimize the battery mass is to use a single DC voltage source, with a plurality of power electronic components connected in parallel to this voltage source by a power harness that brings together the electrical conductors carrying the energy to each of the power electronic components. A DC voltage source as defined here may include, in particular, batteries, fuel cells, or an HVDC power distribution network—for example, in the form of busbars. HVDC – to which the power electronic components are connected. Each power electronic component ensures the transmission of electrical power from the DC voltage source to a stator winding of an electrical machine. The power electronic component can also convert the electrical power supplied by the voltage source, transmitting it to the electrical machine as a waveform adapted to its architecture – this is known as a power converter. In particular, inverters can be used when the electrical machine must be powered by an AC voltage.

[0006] Each power converter provides at output a polyphase power, for example three-phase, applied to a stator winding of an electrical machine.

[0007] However, such an architecture has the disadvantage that a difference in load at the input of the different power converters may exist, due to dispersions on the power components, on the measuring sensors enabling the control and regulation of each electrical machine and / or on the stator windings of each machine, or even on the lengths of the power harness ensuring the transmission of current between the DC voltage source and the power components.

[0008] This load difference gives rise to so-called "recirculation" currents, distinct from the main current flowing between the voltage source and the power components. These recirculation currents correspond to oscillatory exchanges of electrical power that occur between the power electronic components due to the aforementioned load imbalance, via the DC power harness. These currents exhibit high-frequency harmonics that induce fatigue in the power electronics due to the charge / discharge cycles that occur in the capacitive components of the power electronics, and more generally through thermal heating of the power electronics, thus compromising their reliability.When the propulsion system includes a network or HVDC bus monitoring system, these currents can be interpreted by the monitoring system as a bus malfunction. Therefore, if a mechanism exists to cut off or reduce the power supply when a bus malfunction is detected, this mechanism may be mistakenly activated when recirculating currents are detected, causing a partial or total loss of mechanical torque at the output of the electric machines. The unpredictable nature of these currents also means they impose wear on power components that is difficult to predict, thus compromising the reliability of the propulsion system.

[0009] A solution provided by the state of the art for mitigating the consequences of currents of Recirculation involves adding a passive damping device to the power harness at the input of each power converter. However, such dampers include capacitors and inductors, thus increasing the mass of the propulsion system, particularly when it includes several power components connected to the DC voltage source. This can compromise the aircraft's flight range or payload capacity. Furthermore, these dampers must be specifically sized for each electrical machine to account for variations within the machine. Description of the invention

[0010] One object of the invention is to reduce the wear of the components of an electric or hybrid propulsion system and to increase their reliability.

[0011] Another object of the invention is to propose an electric or hybrid propulsion system comprising a DC voltage source, the system being able to minimize recirculation currents between different power electronics components connected in parallel to the DC voltage source.

[0012] Another object of the invention is to propose an electric or hybrid propulsion system as mentioned in the preceding paragraph, and which also has a limited total mass.

[0013] Another object of the invention is to enable optimal compensation of recirculation currents for a wide variety of propulsion system topologies.

[0014] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft and to those currently in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0015] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft.

[0016] Consequently, the Applicant is constantly working to reduce its climate impact through the use of methods and the operation of development processes virtuous development and manufacturing practices that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0017] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0018] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft.

[0019] To this end, according to a first aspect of the invention, an electric or hybrid propulsion system for an aircraft is proposed, comprising: - a DC voltage bus, - at least two power electronic components connected in parallel to the DC voltage bus, - a motor control system including a sensor configured to measure electrical parameters representative of at least one of the power electronic components, the measured electrical parameters including in particular a current intensity flowing through the DC voltage bus and / or a voltage across the terminals of the DC voltage bus,

[0020] each power electronic component being electrically connected to a separate stator winding, each stator winding being contained within an electrical machine,

[0021] the electric machine being configured to convert electrical energy transmitted by the DC voltage bus to the electric machine via the power electronic components into mechanical torque to provide thrust to an aircraft,

[0022] the propulsion system comprising an active compensation system for at least one power electronic component configured to attenuate oscillatory currents flowing between at least one power electronic component and other power electronic components via the DC voltage bus according to measured electrical parameters.

[0023] Thus, attenuating the oscillatory currents between the power electronic components based on measurements taken by sensors included in the motor control system makes it possible to minimize these currents without complicating the propulsion system: it is not necessary to add additional components specifically dedicated to this attenuation to the propulsion system, with the resulting increase in mass. This reduces fatigue on the power electronic components and their reliability, as well as that of the system itself, is increased without increasing the mass or cost of the system.

[0024] This active compensation also takes into account the topology of the propulsion system (i.e., the arrangement of the harnesses, power electronic components, and electrical machines) and therefore allows for optimal compensation based on this topology, unlike other compensation systems—such as, for example, dampers placed at the input of power converters—which are only optimal for a specific propulsion system topology.

[0025] According to one embodiment, the mechanical torque produced by the electric machine is configured to drive a propeller, either directly or by means of a reduction system.

[0026] According to one embodiment, a heat engine is connected to the propeller directly or by means of the reduction system and is configured to produce additional mechanical torque for driving the propeller in addition to the mechanical torque produced by the electric machine.

[0027] According to one embodiment, the electrical machine is of the permanent magnet synchronous type.

[0028] According to one embodiment, the compensation system for at least one power electronic component comprises: - A bandpass filter configured to generate an intermediate oscillatory signal by resetting the average value of a first parameter chosen from a voltage across the bus and a current flowing through the bus, and - A PID or RST regulator, the regulator being configured to admit the oscillatory intermediate signal and to output an oscillatory forward current setpoint of frequency substantially equal to that of the oscillatory intermediate signal, the oscillatory forward current setpoint including a phase shift relative to the oscillatory intermediate signal configured to dampen the oscillatory intermediate signal.

[0029] According to one embodiment, the propulsion system comprises: - a first DC voltage bus - a second DC voltage bus, - four power electronic components, two of the power electronic components being connected in parallel to the first DC voltage bus and two of the power electronic components being connected in parallel to the second DC voltage bus,

[0030] the electrical machine comprising four stator windings, each stator winding being supplied with electrical energy by one of the four electrical components Ironic in their power,

[0031] the two DC voltage buses not being electrically connected.

[0032] According to one embodiment, the propulsion system comprises: - a first DC voltage bus - a second DC voltage bus, - four power electronic components, two of the power electronic components being connected in parallel to the first DC voltage bus and two of the power electronic components being connected in parallel to the second DC voltage bus, - two electrical machines, each comprising two stator windings, the first stator winding of each electrical machine being supplied with electrical energy by one of the power electronic components connected to the first DC voltage bus, the second stator winding of each electrical machine being supplied with electrical energy by one of the power electronic components connected to the second DC voltage bus,

[0033] the two DC voltage buses not being electrically connected.

[0034] Another aspect of this disclosure relates to a method for compensating oscillatory currents flowing in a propulsion system as described above, the oscillatory currents flowing between the power electronic components via the DC voltage bus, the compensation method comprising: - obtaining current or voltage measurements from the sensor, and - the attenuation of oscillatory currents as a function of the measurements obtained.

[0035] According to one embodiment of the method, the measured electrical parameters include a first parameter chosen from a current intensity flowing through the bus and a voltage across the bus terminals; obtaining measurements includes measuring the intensities of oscillatory currents; and the attenuation includes successive steps of: a. obtaining an intermediate oscillatory signal by resetting an average value of the first parameter, b. emission of an oscillating direct current setpoint by applying a counter-oscillation of frequency substantially equal to that of the oscillating intermediate signal, the oscillating direct current setpoint comprising a phase shift with respect to the oscillating intermediate signal configured to dampen the oscillating intermediate signal.

[0036] Another aspect of this disclosure relates to an aircraft comprising a propulsion system as described above. DESCRIPTION OF FIGURES

[0037] Other features, purposes and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0038] Fig. 1 schematically illustrates an electric or hybrid propulsion system, according to a first aspect of disclosure;

[0039] Figure 2A schematically illustrates an electric or hybrid propulsion system including power supply redundancy, according to one aspect of the disclosure.

[0040] Figure [Fig. 2B] schematically illustrates another electric or hybrid propulsion system, according to one aspect of the disclosure.

[0041] Fig. 3 schematically illustrates a method for compensating oscillatory currents circulating in an electric or hybrid propulsion system, according to a second aspect of the invention;

[0042] The [Fig.4] is a functional diagram illustrating a vector control method for an electrical machine, known from the state of the art;

[0043] The [Fig.5] is a functional diagram illustrating a vector control method for an electric or hybrid propulsion system according to the first aspect of the invention;

[0044] The [Fig.6] is a Bode diagram representing the frequency response of a propulsion system according to the first aspect of the invention, for different lengths of an input power harness of the propulsion system;

[0045] Fig. 7A illustrates a time evolution of a current and a voltage at the level of a DC electrical bus of a propulsion system after application of the method according to the second aspect of the invention;

[0046] Fig. 7B illustrates a time evolution of a mechanical torque produced by an electric or hybrid propulsion system after application of the process according to the second aspect of the invention;

[0047] Fig. 7C illustrates a harmonic analysis of the alternating current on a DC electrical bus of a propulsion system after application of the method according to the second aspect of the invention;

[0048] Figure 8 schematically illustrates an aircraft, comprising an electric or hybrid propulsion system according to the first aspect of the invention.

[0049] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0050] With reference to [Fig. 1], a first aspect of the invention relates to a propulsion system powered by a DC voltage source 1. The DC voltage source 1 is part of an HVDC electrical network or HVDC bus 19, the voltage source 1 being able to include, in particular, batteries or fuel cells. The source of Voltage source 1 can also be another type of voltage source suitable for supplying high-voltage direct current. The DC voltage source 1 is connected to a plurality of power electronics components 3 (hereinafter referred to as "power electronics") arranged in parallel, such that each power electronics component 3 receives a given electrical power from the voltage source 1. In addition to the DC voltage source 1, the HVDC bus 19 includes a power harness, hereinafter referred to as the input power harness 2 due to its position upstream of the power electronics components 3 in the direction of electrical power flow, which provides an electrical connection between the DC voltage source 1 on the one hand and each power electronics component 3 on the other.

[0051] Each power electronics 3 is in turn connected to a star (a stator winding) of an electrical machine 5, via an output power harness 4. Preferably, all the power electronics 3 supply the same electrical machine 5, but it is possible to provide several electrical machines 5, each supplied by one or more power electronics 3.

[0052] The electric machine allows the conversion of the electrical power transmitted to it into a mechanical torque. This torque can, in particular, power a propeller 6, for example, a propulsion propeller of an aircraft, either directly mechanically connected to the electric machine 5, or connected to the electric machine 5 via a reduction gear which allows the angular speed of the electric machine 5 to be decoupled from the angular speed of the propeller 6.

[0053] According to one embodiment, the propulsion system 10 is entirely electric, that is to say, the electric machine alone provides the power to the propeller 6. Alternatively, it may be a hybrid propulsion system 10, further comprising a thermal engine 7 which provides part of the power required to rotate the propeller 6.

[0054] The propulsion system conventionally comprises a motor control unit capable of controlling the angular velocity of the electric machine 5 and the mechanical torque it can produce. The motor control unit includes sensors 8 configured to perform measurements relating to electrical parameters of the propulsion system 10, which are used to control and regulate the angular velocity of the electric machine 5 and / or the mechanical torque it produces.

[0055] The motor control preferably includes at least one sensor 8 for each power electronic 3 included in the propulsion system 10.

[0056] Due to the architecture of the propulsion system 10, with the power electronics 3 connected in parallel to the voltage source 1, oscillatory currents can develop between the power electronics 3 on the input power harness 2 as soon as a difference exists between the electrical charge at the input of the different power electronics 3. When this load difference is significant, the frequency of these oscillatory currents can approach a resonant frequency of the system and prematurely damage the components of the power electronics 3 or the power harnesses 2, 4.

[0057] The propulsion system 10 includes, for at least one of the power electronic components 3, a compensation system 18 which accepts, as input, measurements taken by the sensors 8 of the motor control, indicative of the oscillatory currents flowing between this power electronic component 3 and the other power electronic components 3 on the input harness 2. Advantageously, the propulsion system 10 includes such a compensation system 18 for each of the power electronic components 3. The measurements are, for example, current and / or voltage measurements taken at the input of the power electronics 3 comprising the compensation system 18, or voltage measurements across the HVDC bus 19 and / or current intensity flowing through the HVDC bus 19. The compensation system 18 sends to the electric machine 5, based on these measurements, a command to compensate for the oscillatory currents.Since the sensors 8 are necessary for motor control, independently of the oscillatory current compensation system 18, it is therefore not necessary to include, in the propulsion system 10, heavy electronic components such as coils or capacitors to allow for the compensation of oscillatory currents.

[0058] According to a first embodiment, illustrated in [Fig. 1], the sensors 8 are arranged at the input of the power electronics 3, and are configured to measure an electrical input power of the power electronics 3 from the DC voltage source 1. These may include sensors used by the motor control independently of the compensation system 18 to know the current intensity through the HVDC bus 19 (which are used, in particular, in a conventional way, by the motor control to perform so-called "system functions" such as limiting or regulating the DC power, or estimating the torque produced by the electric machine) or sensors used by the motor control to acquire the voltage across the terminals of the HVDC bus 19 (which are used in particular for regulating the electric machine).Thus, it is not necessary to provide sensors specific to the compensation system 18, and the mass or size of the propulsion system is not increased. This embodiment also has the advantage that the structure of the power electronics 3 allows the sensors 8 to be integrated at the power electronics input, and that no offset is required between the input harness 2 and the sensors 8. Such an offset would necessitate adding an additional housing and harnesses, which would increase the mass and size of the compensation system. 18. In addition, this embodiment has the advantage of preventing the sensors from measuring parasitic oscillations, which could resemble recirculation currents but be due to other factors - which can be the case when the sensors 8 are located downstream of the power electronics 3.

[0059] Other embodiments of the sensors 8 are however conceivable: sensors 8 can be arranged at the level of the bus 19, or in the electric machine 5 so as to measure an angular position and / or an angular velocity of the electric machine 5. They can also be arranged at the output of the power electronics 3 so as to measure an electrical power downstream of them, at the level of the output power harness 4.

[0060] According to one embodiment, the electric machine 5 is of the synchronous type, in particular of the permanent magnet synchronous machine (PMSM) type, and the output power harness 4 supplies the electric machine 5 with a three-phase power supply, that is to say, a winding wound on the stator of the electric machine 5 – called the stator winding – comprises three distinct windings in a star connection, which can be supplied by alternating currents whose phases are offset from each other by 120°. In this case, the sensors 8 may include, but are not limited to, sensors arranged at the output of the power electronics 3, at the level of the output power harness 4, so as to measure the power transmitted to each of the three stator windings of the electric machine 5.

[0061] According to one embodiment, a stator of an electrical machine 5 comprises two stator windings.

[0062] A stator winding of an electrical machine 5 can be connected to the corresponding output power harness 4 by a star connection 24, so as to allow the transmission of three-phase electrical power from the output power harness 4 to the stator windings of the permanent magnet synchronous electrical machine 5. Each power electronics unit 3 is then connected to a stator winding or star connection 24 of one of the electrical machines 5. Optionally, a single machine 5 can be multi-star, that is to say, it comprises several distinct stator windings, each star-connected 24 and connected to a distinct power electronics unit 3 by a respective harness 4. In one embodiment, the stator windings have strictly more than three windings. The stator windings may, in particular, comprise five or six windings.

[0063] According to one embodiment, the electric machine 5 is a multi-star, synchronous or asynchronous, wound-rotor, polyphase electric machine.

[0064] The oscillatory current compensation system 18 comprises, according to one embodiment, a bandpass filter 11 and a PID controller 12. The PID controller 12 can possibly be replaced by an RST regulator.

[0065] The bandpass filter 11 is configured to zero out an average value of a first parameter, which is either a current intensity corresponding to the oscillatory currents between the power electronics 3, or an associated voltage, so as to obtain at the filter output an intermediate oscillatory current signal 22 with a zero average value but a non-zero amplitude, equal to the amplitude of the oscillations of the first parameter. The frequency passband of the bandpass filter 11 is determined by electrical parameters measured by the motor control sensors 8. These may be electrical parameters of the power electronics 3, such as a differential resistance or inductance, or electrical parameters of the input power harness 2, for example, a line resistance or inductance. It may also be an electrical capacitance of the HVDC bus 19.

[0066] The PID regulator 12 accepts as input the intermediate oscillatory signal 22 produced by the bandpass filter 11, and is configured to output a forward oscillating current setpoint 14, of frequency equal to that of the intermediate oscillatory signal 22, with a phase shift configured to dampen the intermediate oscillatory signal 22.

[0067] The propulsion system 10 may, according to certain embodiments, include power supply redundancy. In other words, the propulsion system includes more than one DC voltage source 1, and correspondingly, more than one HVDC bus 19, which are electrically independent. Thus, in the event of a failure or malfunction of one HVDC bus 19, it is ensured that electrical power is always supplied to the electrical machines 5. When the propulsion system includes several electrically independent HVDC buses 19, oscillatory currents can only appear between power electronic components 3 connected to the same HVDC bus 19, via the input harness 2 that enables this connection – no oscillatory current can appear between two power electronic components 3 connected to two separate HVDC buses 19.

[0068] According to an embodiment including power supply redundancy, illustrated in [Fig. 2A], the propulsion system 10 comprises an electric machine 5 powered by four separate stars 24. The electric machine 5 thus comprises four separate stator windings, each stator winding being connected upstream to a separate power electronic component 3. Two of the four power electronic components 3 are powered by a first HVDC bus 19, the other two power electronic components 3 being powered by a second HVDC bus 19 electrically independent of the first HVDC bus. Each HVDC bus 19 comprises a DC voltage source 1 and an input power harness 2 which allows the transmission of electrical power generated by the DC voltage source 1 to the two power electronic components 3 connected to it. During a In the event of a malfunction of the first HVDC bus 19, two of the four stator windings of the electric machine 5 will not be supplied with electrical power, while the other two stator windings will indeed be supplied via the second HVDC bus 19, and will allow the propulsion system 10 to function - and vice versa in the event of a malfunction of the second HVDC bus 19. The compensation system 18 as defined previously then makes it possible to attenuate oscillatory currents flowing on an input harness 2, either between the power electronic components 3 connected to the first HVDC bus 19, or between the power electronic components 3 connected to the second HVDC bus 19.

[0069] According to another redundant power supply embodiment, illustrated in [Fig. 2B], the propulsion system 10 comprises two separate electric machines 5. Each electric machine is powered by two separate star connections 24, the first star 24 being connected upstream by an output harness 4 to a power electronic component 3, which is itself connected upstream to a first HVDC bus 19, and the second star 24 being connected upstream by an output harness 4 to a power electronic component 3, which is itself connected upstream to a second HVDC bus 19. Thus, each of the two electric machines 5 is powered partly by electrical power from the first HVDC bus 19 and partly by electrical power from the second HVDC bus 19.In the event of a malfunction of the first HVDC bus 19, each electric machine 5 will be powered by one of its two stator windings, the electrical power of which comes from the second HVDC bus 19 - and vice versa in the event of a malfunction of the second HVDC bus 19. The compensation system 18 as defined previously then makes it possible to attenuate oscillatory currents flowing on an input harness 2, either between the power electronic components 3 connected to the first HVDC bus 19, or between the power electronic components 3 connected to the second HVDC bus 19.

[0070] According to a second aspect, and with reference to [Fig.3], the invention relates to a method for compensating oscillatory currents circulating in a propulsion system 10 as defined above, these currents circulating between the power electronics 3 and being due to a difference in load at the input of the different power electronics 3 connected in parallel to the DC voltage source 1. The compensation method includes obtaining 101 measurements of electrical parameters representative of the power components 3 by the sensors 8 of the motor control, and attenuating the oscillatory currents according to these measurements.

[0071] According to one embodiment, obtaining measurements 101 includes obtaining measurements of the intensity of the oscillatory currents flowing between the power electronics 3, and attenuating the oscillatory currents includes obtaining 102 a oscillatory intermediate signal 22 by resetting, for example by the bandpass filter 11, an average value of the intensity of the oscillatory currents, and the emission 103 of a direct oscillating current setpoint 14 by applying, for example by the PID controller 12, a counter-oscillation of frequency substantially equal to that of the oscillatory intermediate signal 22, with a phase shift configured to dampen the oscillatory intermediate signal 22. As described previously, these steps can be implemented on voltage values ​​rather than current intensity values.

[0072] Figure 4 illustrates a vector control system according to the prior art, used to control a three-phase synchronous electric machine 5' (i.e., one whose stator winding comprises three windings). The vector control consists of transmitting a current setpoint to the machine 5' along a two-axis coordinate system, referred to as the quadrature axis q and the direct axis d, centered on, and fixed relative to, a rotor of the machine 5'. A setpoint 13' along the direct axis d affects only the magnetic flux in the machine 5' and not the mechanical torque produced by it, while a setpoint 16' along the quadrature axis q affects only the mechanical torque and not the magnetic flux of the machine 5'. The values ​​of the current setpoints 13' and 16' can be obtained by Park transforming the current setpoint values ​​transmitted to each stator winding.The instructions pass through a regulator 9' which determines the phase currents to be supplied to each of the stator windings of the machine 5'. Then, the phase currents thus obtained pass through a power converter 3' which provides at output an electrical power with a current intensity and a voltage adapted to the machine 5'.

[0073] According to an implementation of the compensation method, shown in [Fig. 5], the motor control implements vector control of the electric machine 5, and the compensation system 18 uses this vector control to issue an oscillating forward current setpoint 14 produced by the compensation system 18, which applies only along the forward axis id. This ensures that the oscillating currents between the power electronics 3 are attenuated without affecting the mechanical torque generated by the electric machine 5, as no current setpoint is transmitted along the quadrature axis iq. The oscillating forward current setpoint 14 is added to a forward current setpoint 13, provided by the motor control independently of the compensation method, to produce a combined current setpoint 15. The quadrature axis iq current setpoint 16, however, remains unchanged by the application of the compensation method.

[0074] It should be noted that the oscillating direct current setpoint 14 having an average value of zero, it does not affect the magnetic or thermal state of the electrical machine.

[0075] More specifically, the compensation system 18 can then include the bandpass filter 11 and the PID controller 12 as described above. The bandpass filter 11 receives as input electrical parameters measured by the sensors 8 of the motor control – for example, a current and / or a voltage at the input of the power electronics 3 or at the bus 19 – and generates the intermediate oscillatory signal 22.

[0076] Figures 6 to 7C present simulation results of an electric propulsion system 10 as defined above.

[0077] Figure 6 is a Bode plot. The simulations shown therein were obtained for a propulsion system 10 comprising two power electronics 3 connected to an electric machine 5, each by a star connection 24, with a compensation method comprising the emission 103 of a setpoint only along the direct axis id. Several lengths of input power harness 2 (2.5 m; 5.0 m; 7.5 m and 10.0 m) were tested. The peak gain and associated frequency values ​​are listed in Table 1 below, with reference to the four configurations shown in Figure 5.

[0078] [Tables] Configuration Input power harness length (m) Peak gain (dB) Peak frequency (kHz) I 2.5 m 8.44 4.49 II 5.0 m 10.1 3.61 III 7.5 m 11.2 3.1 IV 10 m 12 2.76

[0079] Figures 7A to 7C show simulation results for a propulsion system 10 comprising a permanent magnet synchronous machine 5 and four power electronics 3, each connected to the machine 5 by a separate star connection 24. The system includes two DC voltage sources 1, each source being connected to two of the power electronics 3 placed in parallel. The compensation method implemented includes the emission 103 of a setpoint only along the direct axis id

[0080] Figure 7A shows the time evolution of the oscillatory currents and an electrical voltage at bus 19 of the power harness 2. The initiation of the oscillatory current compensation process occurs at 0.5 seconds. It can be seen that the oscillatory currents before compensation reach an amplitude of over 200 amperes, reduced to a few amperes a few hundredths of a ampere. seconds after this initiation. The oscillatory amplitude of the voltage at bus 19 is also greatly reduced, from about 60 Volts to about 20 Volts.

[0081] Fig. 7B shows that the mechanical torque produced by the propulsion system 10 is not substantially affected by the implementation of the oscillatory current compensation method.

[0082] Figure 7C represents a harmonic analysis of the alternating current on bus 19, with and without implementation of the compensation method. With the compensation method implemented, the maximum current intensity decreases from 106 Amperes to approximately 4 Amperes at the system resonance frequency of approximately 2.5 kHz.

[0083] According to a third aspect, shown in [Fig. 8], the invention relates to an aircraft 25 comprising an electric or hybrid propulsion system 10 as defined above. This may, in particular, be a light aircraft, such as a VTOL or STOL for the transport of goods and / or people over short intra-urban or inter-urban distances.

Claims

Claims

1. Electric or hybrid propulsion system (10) of an aircraft comprising: - a direct voltage bus (19), - at least two electronic power components (3) connected in parallel to the direct voltage bus (19), - a motor control comprising a sensor (8) configured to measure electrical parameters representative of at least one of the electronic power components (3), the measured electrical parameters including in particular an intensity of current flowing through the direct voltage bus (19) and / or a voltage at the terminals of the direct voltage bus (19), each electronic power component (3) being electrically connected to a separate stator winding, each stator winding being included in an electrical machine (5),the electrical machine (5) being configured to convert electrical energy transmitted by the DC voltage bus (19) to the electrical machine (5) via the power electronic components (3) into mechanical torque to provide thrust to an aircraft, characterized in that it comprises an active compensation system (18) of the at least one power electronic component (3) configured to attenuate oscillatory currents flowing between the at least one power electronic component (3) and the other power electronic components (3) via the DC voltage bus (19) as a function of the measured electrical parameters.,

2. Propulsion system according to claim 1, the mechanical torque produced by the electric machine (5) being configured to drive a propeller (6), directly or by means of a reduction system.

3. Propulsion system according to claim 2, a heat engine (7) being connected to the propeller directly or by means of the reduction system and being configured to produce additional mechanical torque for driving the propeller (6) in addition to the mechanical torque produced by the electric machine (5).

4. Propulsion system according to any one of claims 1 to 3, the electric machine (5) being of the permanent magnet synchronous type.

5. Propulsion system according to any one of claims 1 to 4, the compensation system (18) of the at least one power electronic component (3) comprising: - A bandpass filter (11) configured to generate an oscillatory intermediate signal (22) by resetting to zero an average value of a first parameter chosen from a voltage at the terminals of the bus (19) and an intensity flowing through the bus (19), and - A PID regulator (12) or an RST regulator, the regulator being configured to admit the oscillatory intermediate signal (22) and emit an oscillatory direct current setpoint (14) of frequency substantially equal to that of the oscillatory intermediate signal (22), the oscillatory direct current setpoint (14) comprising a phase shift relative to the oscillatory intermediate signal (22) configured to dampen the oscillatory intermediate signal (22).

6. Propulsion system according to any one of claims 1 to 5, comprising: - a first DC voltage bus (19) - a second DC voltage bus (19), - four power electronic components (3), two of the power electronic components (3) being connected in parallel to the first DC voltage bus (19) and two of the power electronic components (3) being connected in parallel to the second DC voltage bus (19), the electrical machine (5) comprising four stator windings, each stator winding being supplied with electrical energy by one of the four power electronic components (3), the two DC voltage buses (19) not being electrically connected.

7. Propulsion system according to any one of claims 1 to 5, comprising: - a first DC voltage bus (19) - a second DC voltage bus (19), - four power electronic components (3), two of the power electronic components (3) being connected in parallel to the first DC voltage bus (19) and two of the power electronic components (3) being connected in parallel to the second DC voltage bus (19), - two electrical machines (5) each comprising two stator windings, a first stator winding of each electrical machine (5) being supplied with electrical energy by one of the power electronic components (3) connected to the first DC voltage bus (19), a second stator winding of each electrical machine (5) being supplied with electrical energy by one of the power electronic components (3) connected to the second DC voltage bus (19), the two DC voltage buses (19) not being electrically connected.

8. Method for compensating oscillatory currents circulating in a propulsion system according to any one of claims 1 to 7, the oscillatory currents circulating between the electronic power components (3) via the direct voltage bus (19), the compensation method comprising: - obtaining (101) current or voltage measurements by the sensor (8), and - attenuating the oscillatory currents as a function of the measurements obtained.

9. A method of compensating oscillatory currents according to claim 8, the measured electrical parameters comprising a first parameter chosen from an intensity of current flowing through the bus (19) and a voltage across the terminals of the bus (19), obtaining (101) measurements comprising measuring intensities of the oscillatory currents, the attenuation comprising successive steps of: a. obtaining (102) an intermediate oscillatory signal (22) by resetting to zero an average value of the first parameter, b. transmitting (103) an oscillating direct current setpoint (14) by applying a counter-oscillation of frequency sens- possibly equal to that of the oscillatory intermediate signal (22), the oscillatory direct current setpoint (14) comprising a phase shift relative to the oscillatory intermediate signal (22) configured to dampen the oscillatory intermediate signal (22).

10. An aircraft (25) comprising a propulsion system (10) according to any one of claims 1 to 7.

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