Method for controlling a hybrid engine that dampens vibrations based on stator phase currents, engine for implementing this method, and aircraft equipped with it

Abstract

Method for controlling a motor (M) comprising a turbomachine (TM) coupled to an electric machine (MEL), and an electronic motor control unit (20) connected to a power converter (12) to selectively drive the electric machine in motor mode and generator mode from a reference torque filtered in a self-adaptive manner to exclude a range of excitation frequencies for at least one torque mode of the motor as a function of the stator phase currents of the electric machine. Corresponding motor and aircraft incorporating such a motor. FIGURE IN ABRIDGED: Fig. 2

Description

Title of the invention: Method for controlling a hybrid motor that dampens vibrations based on phase-segment static currents, motor for implementing this method, and aircraft equipped with it

[0001] The present invention relates to the field of electrical machines and in particular those used in hybrid motorization systems combining an electric machine and a thermal machine.

[0002] BACKGROUND OF THE INVENTION

[0003] 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 to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0004] 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 consequences, with the aim of improving the energy efficiency of aircraft.

[0005] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions and more generally reduce the environmental footprint of its activity.

[0006] This sustained research and development work focuses on both new generations of aircraft engines, the lightening of aircraft, in particular through the materials used and lighter on-board equipment, and the development of the use of electrical technologies to provide propulsion.

[0007] In the context of this work on aircraft propulsion, a hybrid thermal / electric propulsion system was proposed.

[0008] This hybrid engine comprises: - a turbomachine having a shaft line running through a high-pressure stage and a low-pressure stage, - an electric machine having a shaft connected to the turbomachine's shaft line to operate either as a motor by supplying mechanical torque to the turbomachine's shaft line, or as a generator by being driven by the turbomachine's shaft line, - an inverter for controlling the electrical machine in the two aforementioned operating modes, the inverter being controlled by an electronic motor control unit, - a continuous power supply circuit, for example with batteries, connected to the inverter and arranged to be reversible so as to selectively supply the electric machine when the electric machine is operating as a motor or to receive the electrical energy supplied by the electric machine when the electric machine is operating as a generator.

[0009] The electrical system comprising the electric machine, the inverter and the power supply circuit must be sized to provide the electrical power necessary to inject power into the turbomachine in particular to assist the start-up of the turbomachine and limit its fuel consumption during certain phases of flight, and to ensure sufficient power supply to the aircraft's electrical equipment when the electric machine is operating as a generator.

[0010] The electrical system must also be reliable, robust and arranged so as not to disrupt the operation of the turbomachine.

[0011] The Applicant has observed that the electric machine, and in particular the electromagnetic torque it generates, can include a dynamic component (oscillation around the continuous torque) capable of generating excitation of certain torsional modes of the drivetrain. This excitation results in a torque oscillation which, depending on its frequency, can excite the torsional vibrational modes of the driveshafts. The excitation of these torsional modes causes a significant increase in vibration levels (this increase is commonly referred to as overvoltage), phase shifts, and damping phenomena at both low and high frequencies on the driveshafts. This can lead to vibrational fatigue of the drivetrain, which, in the worst-case scenario, can result in a failure of the drivetrain. Such a failure can be catastrophic if it affects the turbomachine.

[0012] SUBJECT OF THE INVENTION

[0013] The invention aims in particular to improve these electrical systems, especially with regard to the control of the vibrational phenomena that they can generate. Summary of the invention

[0014] To this end, the invention provides a method for controlling a motor comprising a turbomachine, an electric machine coupled to a first shaft of the turbomachine, an electronic motor control unit, a power converter for selectively driving the electric machine in motor mode and in generator mode based on a reference torque provided by the electronic control unit, and a reversible power supply circuit connected to the power converter to selectively supply the electric machine in motor mode or be supplied by the electric machine in generator mode. The method comprises the steps of: - identify excitation frequency ranges of at least one turbomachine torsion mode by the electric machine as a function of stator phase currents of the electric machine; - and, in operation of the motorization, determine stator phase currents of the electric machine, and filter the reference torque at the level of the electronic control unit, by applying a filter whose cutoff frequency range is adjusted to exclude at least a range of excitation frequencies corresponding to the determined stator phase currents.

[0015] Thus, filtering the reference torque (such as a setpoint or torque command) makes it possible to avoid the excitation frequencies of all or part of the mechanical torsion modes. Since it appears that the range of excitation frequencies of the torsion modes is not constant and depends in particular on the load imposed on the motor by the equipment to which it is connected (see [Fig. 4]), the cutoff frequency of the filter used in the invention is adapted according to the stator phase currents of the electric machine. This ensures that the reference torque does not cause excitation of the torsion modes regardless of the operating conditions of the motor.

[0016] An additional advantage of analyzing stator phase currents for adapting the filter cutoff frequency is to allow the identification of the mechanical torsion mode or modes independently of whether the electrical machine is operating in motor mode or generator mode.

[0017] Preferably, the determination of phase stator currents includes a spectral analysis of measured stator currents.

[0018] The invention also relates to a motorization system comprising a heat engine, an electric machine coupled to the heat engine, and an electronic motorization control unit connected to a power converter controlling The electric machine is selectively switched between motor and generator modes from a reference torque, and a reversible power supply circuit is connected to the power converter to selectively supply the electric machine in motor mode or be supplied by the electric machine in generator mode. The electronic control unit includes a device for determining the stator phase currents of the electric machine and a self-adaptive filtering device for the reference torque. The self-adaptive filtering device has a predetermined cutoff frequency range, based on the determined stator phase currents, to correspond to a range of excitation frequencies for at least one torsion mode of the first shaft.

[0019] According to optional features, used individually or in whole or in combination: - the electronic control unit includes a table relating cutoff frequency ranges of the self-adaptive filtering element and phase stator currents, each cutoff frequency range of the self-adaptive filtering element being substantially equal to the excitation frequency range of at least one torsion mode of the turbomachine for the corresponding phase stator currents. - the electronic control unit is connected to a device for acquiring the speed of the first shaft of the turbomachine and to a device for measuring the stator phase currents of the electric machine. - The electronic control unit is arranged to implement a hybridization strategy by which it determines at each instant: • whether the electrical machine is to operate as a generator or as a motor; • a first mechanical power that the electric machine must take from the turbomachine when it operates as a generator, and a second mechanical power that the electric machine must supply to the turbomachine when it operates as a motor; • the reference torque which corresponds to the mechanical power thus determined and which is transmitted to the filtering element. - the filtered reference torque is transmitted to a current loop driving the power converter and, preferably, the current loop includes a space vector pulse width modulation device. - The turbomachine comprises two first shafts, one belonging to a high-pressure stage and the other to a low-pressure stage, and the propulsion system comprises two electric machines, namely one whose second shaft is coupled to the first shaft of the high-pressure stage and a second whose second shaft is coupled to the first shaft of the low-pressure stage pressure.

[0020] The invention finally relates to a vehicle and more particularly to an aircraft equipped with such a motorization.

[0021] Other features and advantages of the invention will become apparent from the following description of particular, non-limiting embodiments of the invention. Brief description of the drawings

[0022] Reference will be made to the attached drawings, among which:

[0023] [Fig-1] [Fig.1] is a schematic view of an aircraft according to the invention;

[0024] [Fig.2] [Fig.2] is a schematic view of a motorization of this aircraft, according to a a particular embodiment of the invention;

[0025] [Fig. 3 Figure 3 is a more detailed schematic view of this motorization;

[0026] [Fig.4] [Fig.4] is a schematic view of the motorization according to a variant of this particular embodiment;

[0027] [Fig.5] [Fig.5] is a graph showing the evolution of the excitation frequency of the first torsion mode depending on the power supplied by the electric machine

[0028] [Fig.6] [Fig.6] is a Bode plot representing a frequency analysis of the mechanical transmission chain of the thermal machine. DETAILED DESCRIPTION OF THE INVENTION

[0029] With reference to figures 1 and 2, the invention is described in application to a hybrid propulsion system M of an aircraft A. The hybrid propulsion system M here comprises a tur-bomachine TM and an electric machine MEL.

[0030] The turbomachine TM – here more particularly a turbojet, turboprop, or turboshaft engine – is known in itself and will only be roughly described here. The turbomachine TM comprises a high-pressure stage (HP) and a low-pressure stage (BP). The high-pressure stage (HP) includes a shaft coupled via a gear set (not shown) to a shaft of the low-pressure stage (BP), forming a kinematic chain comprising a line of shafts L.

[0031] The MEL electric machine comprises an electric motor 10 having an output shaft 11 coupled via a set of gears G to one and / or the other of the shafts of the TM turbomachine. The electric motor 10 is here a permanent magnet motor.

[0032] The electric motor 10 has electromagnetic windings connected to power electronics comprising a DC / AC power converter, such as here an inverter 12 arranged to operate the electric motor 10 either in motor mode or in generator mode. The inverter 12 is itself connected to a power supply circuit 13 which is connected to the electrical circuit E of the aircraft A, which includes batteries, and is arranged to be reversible so as to selectively supply the electric motor 10 from the batteries to drive the output shaft 11 in rotation when the electric motor 10 of the electric machine MEL is in motor mode or to be powered by the electric machine MEL when the electric motor 10 of the electric machine MEL is in generator mode in particular to recharge the batteries and / or to directly power electrical equipment connected to the electrical circuit E of the aircraft A. The electric machine MEL, and in particular the electric motor 10, the inverter 12 and the power supply circuit 13 are known in themselves.

[0033] The drive unit M comprises a control unit 20 arranged to control the turbomachine TM and the electric machine MEL. The control unit 20 is an electronic unit (of the integrated circuit, FPGA, ASIC, microcontroller type, etc.) comprising, for example, one or more processors and one or more memories containing one or more computer programs for controlling the drive unit M. The control unit 20 here comprises a control module 21 for the turbomachine TM and a control module 22 for the electric machine MEL and implements a hybridization logic symbolized by 23. The control module 21 for the turbomachine TM is of the FADEC or EEC type, known per se. The control module 22 for the electric machine MEL comprises a current loop driving the inverter 12 according to: - a current setpoint Iq* provided by the hybridization logic 23, - current values ​​(ia, ib, ic) of the phases of the electric motor 10 provided by a current acquisition device 24, here a Hall effect device, connected to the control unit 20, - of an angular position Omeca and an angular velocity Qmeca of the output shaft 11 of the electric motor 10 provided by a resolver 25 connected to the control unit 20. The angular data Qmeca and Omeca are classically derived from the signal processing of the resolver 25.

[0034] The control of the MEL electric machine is carried out in the control module 22 using: - the currents ia and i[3 which are the axis currents a and [3 resulting from the Clarke transform receiving at input the phase currents ia, ib, ic; - the currents id and iq which are the currents of axis d and q resulting from the Park transform receiving at input the currents ia and i[3; - the current setpoints Id* and Iq* which are the current setpoints of axes d and q.

[0035] Typically, the current loop of the control module 22 also involves: - the voltages Vd** and Vq** which are the d and q axis reference voltages from the PI controllers receiving the Id*-id signals as input respectively and Iq*-iq; - the voltages Vd* and Vq* which are the reference voltages of axes d and q resulting from the decoupling of the voltages Vd** and Vq** as a function of the currents iq and id and the angular velocity Qméca; - the voltages Va* and V|3* which are the reference voltages of axes a and [3 resulting from the inverse Park transform receiving as input the voltages Vd* and Vq*.

[0036] The Park transforms are also carried out using Oélec which is the electrical angular position of the electric motor 10 and which is equal to the angular position Oméca multiplied by the number of pole pairs of the electric motor 10 (block noted Ocorrection on the [Fig.2]).

[0037] The voltages Va* and V|3* power a spatial vector pulse width modulation (SVM) device providing duty ratios Duty 1, Duty 2, Duty 3 for driving inverter 12.

[0038] A reference voltage Vdc supplied by the power supply circuit 13 powers the PI controllers, the spatial vector pulse width modulation device SVM and the inverter 12.

[0039] The hybridization logic 23 is arranged to implement a hybridization strategy (block 231) by which it determines at each instant, according to the orders of the aircraft pilot, the phase of flight and the signals coming from the aircraft sensors: - whether the MEL electrical machine is to operate as a generator or as a motor; - the mechanical power that the MEL electric machine must draw from the turbomachine PM when operating as a generator and the mechanical power that the electrical machine MEL must supply to the turbomachine PM when operating as a motor; - a torque setpoint or reference torque C*_avant corresponding to the mechanical power determined in the previous step.

[0040] The hybridization logic 23 receives as input an angular velocity Q of the output shaft 11 from the resolver 25 and phase stator currents from the current acquisition device 24. The hybridization logic 23 is arranged to perform a frequency analysis of the phase stator currents (block 232) and to determine, as a function of the amplitude and frequencies of the phase stator currents and the rotational speed of the electric motor 10, a range of cutoff frequencies fc corresponding to excitation frequencies of torsional modes of the shaft line L (block 233).

[0041] The determination of the cutoff frequency range as a function of the phase stator currents is obtained, for example, by using a two-dimensional table (look-up table type) which relates the cutoff frequencies to values phase stator currents as a function of the rotational speed of the heat engine TM (more precisely, the rotational speed of the shaft, HP or BP, to which the output shaft 11 of the electric motor 10 is coupled). Such a table is obtained, for example, by determining the excitation frequencies of the torsional modes of the drive train as a function of the phase stator currents, either through simulation or experimentally, using tests of an electric machine MEL coupled to a speed-controlled load machine to simulate the turbomachine TM across the entire range of speeds and torques. These tests aim to identify the frequencies that amplify the torque oscillations in the drive train M.

[0042] We are particularly interested in the harmonics produced by the MEL electric machine, whose frequencies are close to the torsional modes of the TM turbomachine. Some harmonics, especially those of lower order, have more energy than others and, if their frequencies are close to the torsional modes, can generate overvoltages (indeed, the higher the order of the harmonic, the lower its energy levels). Furthermore, low-frequency modes generate high vibrational displacements. Harmonics likely to generate high overvoltages include: - the first harmonic produced by a mechanical imbalance; - the 2nd harmonic produced by a coaxiality defect between the rotor and the stator; - the harmonic whose rank corresponds to the product of the number of poles and the number of phases of the electric motor 11 and produced by a torque oscillation; - the harmonic whose rank corresponds to the product of the number of teeth and the number of notches and produced by stator tooth forces.

[0043] For example, a Campbell diagram of the TM turbomachine is used to determine the natural frequencies of the TM turbomachine components as a function of the rotational speed. On such a diagram, oblique lines are drawn representing the natural frequencies of the various engine components, horizontal lines corresponding to the frequencies of the torsional modes, and vertical lines corresponding to the minimum and maximum speeds of the TM turbomachine. The risk zones correspond to the intersection of the natural frequency lines with the lines representing the frequencies of the torsional modes obtained by a frequency analysis using a Bode plot to identify the frequency or frequencies most at risk. In [Fig. 6], a maximum value of the torsional mode is observed at a frequency of approximately 29 Hz with an amplification of approximately 50 dB.This clearly constitutes the risk zone where the most energetic harmonics (such as torque oscillation) must be controlled to minimize their impact on the resulting overvoltage. The aim is therefore to control the harmonics. the most energetic ones that can cross the frequency or frequencies at risk.

[0044] Three excitation components are preferably taken into account here: - a natural torque oscillation component which is due to the salience of the poles of the electric motor 10 and which appears independently of the operation of the power electronics; - a component related to the control of the electric motor 11 which generates a torque oscillation via the 6th harmonic; - a component related to the dead times of the inverter which also generates a torque oscillation via the 6th harmonic.

[0045] The hybridization logic 23 also includes a self-adaptive band-stop filter 234, which receives the torque setpoint C*_before as input and provides a filtered torque setpoint C*_after as output. The self-adaptive filter 234 has a cutoff frequency, or rather a range of cutoff frequencies fc, which is set according to the phase stator currents to filter the torque setpoint C*_before so as to exclude the excitation frequency ranges fc from the torsion modes.

[0046] The filtered torque setpoint C*_after is then transformed into a current setpoint (block 235) to form the current setpoint Iq* used as input to the current loop of the control module 22.

[0047] Torque and speed measurements are preferably taken on the output shaft 11 upstream of the gear set coupling the output shaft 11 and the shaft line of the TM turbomachine. For the speed measurement, it is possible to use the derivative of the Oméca mechanical position angle given by the resolver 25. Alternatively, it is possible to use the measurement at the output of the gear set because it is difficult to perform a measurement at the coupling point: the measurement at the output of the gear set makes it possible to determine the torque and speed of the output shaft 11 by knowing the gear ratio of the gear set (calculated from the number of teeth or the diameter of each pinion).

[0048] In the context of the invention, these measurements are used to calculate, in real time and during the operation of the motor M, stator phase currents. The frequency and amplitude of the stator phase currents serve as inputs to the table of block 233, and the output of block 233 is the cutoff frequency of filter 234, which is therefore also provided in real time.

[0049] Filter 234 has more precisely the following FT form:

[0050] / \ çiJ? 7 ff with the following parameters: =--; —— : • / 0 is the cutoff frequency, i.e. the rejected center frequency; • K is the width of the rejected band; • s is the Laplace variable.

[0051] The filter thus defines a range of frequencies which must be attenuated between two limits (two cutoff frequencies given by the width of the band K around the central cutoff frequency).

[0052] It is understood that the parameters of the filter 234 (cutoff frequency and bandwidth) are updated in real time according to the stator phase currents determined at each instant according to a given periodicity.

[0053] The method of the invention thus includes a preliminary step of identifying the excitation frequency ranges of at least one torsion mode of the shaft line of the motorization M and steps carried out by the control unit 20 during the operation of the motorization M, namely: determining phase stator currents and filtering the torque setpoint to exclude the excitation frequency range corresponding to the determined phase stator currents.

[0054] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0055] In particular, the motorization may have a different structure from that described.

[0056] The motorization may include: - a single MEL BP electric machine, coupled to the BP shaft of the low-pressure BP stage of the turbomachine, or - a single MEL HP electric machine, coupled to the HP shaft of the high-pressure HP stage of the turbomachine, or - a MEL BP electric machine coupled to the BP shaft of the low-pressure BP stage of the turbomachine and a MEL HP electric machine coupled to the HP shaft of the high-pressure HP stage of the turbomachine as in the second embodiment of [Fig.3]. In this case, the filtering can be carried out for only one of the electric machines or for both electric machines.

[0057] The table can be defined to have input values ​​of constant intervals (e.g., 5, 10, 15, 20) or not (e.g., 3, 5, 7, 10, 15, 20, 25... if the excitation frequency varies significantly between 3 and 10). The table can be replaced by a law matching stator currents of phase with frequencies to be avoided.

[0058] The cutoff frequency range of the filtering element as a function of the phase stator currents can be determined to avoid excitation of one or more torsion modes of the shaft line as a function of the impact of these torsion modes on the reliability of the motorization M.

[0059] The electric motor 11 can be of any type and in particular a wound rotor motor, a permanent magnet motor or an asynchronous motor.

[0060] The invention is usable with any turbomachine and is not limited to the use of this engine on aircraft.

Claims

Claims

1. Method for controlling a motorization (M) comprising a turbomachine (TM), an electric machine (MEL) coupled to a first shaft of the turbomachine, an electronic control unit (20) for the motorization, a power converter (12) for controlling the electric machine selectively in motor mode and in generator mode from a reference torque supplied by the electronic control unit, and a reversible power supply circuit (13) connected to the power converter to selectively power the electric machine in motor mode or be powered by the electric machine in generator mode, characterized in that the method comprises the steps of: identifying excitation frequency ranges of at least one torsion mode of the turbomachine by the electric machine as a function of phase stator currents of the electric machine;and, in operation of the motorization, determining phase stator currents of the electric machine, and filtering the reference torque at the level of the electronic control unit, by applying a filter whose cut-off frequency range is adjusted to exclude at least one excitation frequency range corresponding to the determined phase stator currents.;

2. The method of claim 1, wherein determining the phase stator currents comprises spectral analysis of measured stator currents.

3. Motorization (M) comprising a turbomachine (TM), an electric machine (MEL) coupled to a first shaft of the turbomachine, an electronic control unit (20) for controlling the motorization, a power converter (12) for controlling the electric machine selectively in motor mode and in generator mode from a reference torque supplied by the electronic control unit, and a reversible power supply circuit (13) connected to the power converter to selectively power the electric machine in motor mode or be powered by the electric machine in generator mode, characterized in that the electronic control unit (20) comprises a member for determining phase stator currents of the electric machine and a self-adaptive filtering member (234) for the reference torque, the self-adaptive filtering member having a frequency range of determined cut-off, as a function of the determined phase stator currents, to correspond to a range of excitation frequencies of at least one torsional mode of the turbomachine.

4. Motorization (M) according to claim 3, in which the electronic control unit (20) comprises a table relating cut-off frequency ranges of the self-adaptive filtering member (234) and phase stator currents, each cut-off frequency range of the self-adaptive filtering member (234) being substantially equal to the excitation frequency range of at least one torsion mode of the turbomachine for the corresponding phase stator currents.

5. Motorization (M) according to claim 3 or 4, in which the electronic control unit (20) is connected to a device for acquiring a speed of the first shaft of the turbomachine and to a device for measuring the stator phase currents of the electric machine (MEL).

6. Motorization (M) according to any one of claims 3 to 5, in which the electronic control unit (20) is arranged to implement a hybridization strategy (231) by which it determines at each instant: - whether the electric machine (MEL) must operate as a generator or as a motor; - a first mechanical power that the electric machine must take from the turbomachine (TM) when it operates as a generator, and a second mechanical power that the electric machine must supply to the turbomachine when it operates as a motor; - the reference torque (C*_avant) which corresponds to the mechanical power thus determined and which is transmitted to the filtering member (234).

7. Motorization (M) according to any one of claims 3 to 6, in which the filtered reference torque is transmitted to a current loop controlling the power converter (12).

8. Motorization (M) according to claim 7, in which the current loop comprises a space vector pulse width modulation device.

9. Motorization (M) according to any one of claims 3 to 8, in which the turbomachine (TM) comprises two first shafts, one belonging to a high pressure stage (HP) and the other to a low pressure stage (LP) and the motorization comprises two electrical machines (MEL), namely a first (MEL HP) whose second shaft is coupled to the first shaft of the high pressure stage (HP) and a second (MEL BP) whose second shaft is coupled to the first shaft of the low pressure stage (LP).

10. Aircraft comprising a motorization (M) according to any one of claims 3 to 9.

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