Method for controlling a hybrid propulsion system for damping vibration according to stator phase current, drive system for implementing such a method

Abstract

The invention relates to a method for controlling a drive system (M) comprising a turbine engine (TM) coupled to an electric machine (MET), an electronic control unit (20) for controlling the drive system, the electronic control unit being connected to a power converter (12), and a driver for selectively driving the electric machine in an engine mode and a generator mode in accordance with a reference torque filtered in an adaptive manner in order to exclude an excitation frequency range of at least one torsional mode of the drive system in accordance with a stator phase current of the electric machine. The invention also relates to a corresponding drive system and to an aircraft comprising such a drive system.

Description

[0001] This invention relates to the field of electric motors, and more particularly to electric motors used in hybrid propulsion systems that combine an electric motor with a heat engine. Background Technology

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Specifically, countries have taken, are taking, or will take various measures to limit carbon emissions. In particular, an ambitious standard, applicable to both new and existing aircraft, requires the implementation of technical solutions to comply with current regulations. The civil aviation industry has been committed to contributing to addressing climate change for many years.

[0003] Technological research efforts have yielded significant improvements in the environmental performance of aircraft. The applicant has considered factors affecting all stages of design and development to obtain lower energy consumption and more environmentally friendly aviation components and products, whose integration and use in civil aviation have a moderate environmental impact, aiming to improve the energy efficiency of aircraft.

[0004] Therefore, the applicant is committed to reducing its negative climate impacts by adopting various methods and utilizing responsible development and manufacturing processes that minimize greenhouse gas emissions and more broadly reduce the environmental footprint of its activities.

[0005] This ongoing research and development involves next-generation aircraft engines, lightweight equipment (particularly through the materials used and lightweight airborne equipment), and the application of electrical technologies for propulsion.

[0006] As part of the research on aircraft propulsion systems, a thermal / electric hybrid propulsion system was proposed.

[0007] This hybrid propulsion system includes: - A turbine with a shaft line running through the high-pressure stage and the low-pressure stage. - An electric motor having a shaft connected to the turbine shaft system to operate as an electric motor by providing mechanical torque to the turbine shaft system, or to operate as a generator by being driven by the turbine shaft system; - An inverter, used to enable the motor to operate in the aforementioned two operating modes, is controlled by the electronic control unit of the propulsion system; - A DC power supply circuit (e.g., battery-based) is connected to the inverter and arranged to be reversible so as to selectively supply power to the motor when the motor is operating as a motor, or to receive electrical energy supplied by the motor when the motor is operating as a generator.

[0008] The electrical system, which includes the motor, the inverter, and the power supply circuit, must be designed to provide the necessary electrical power to power the turbine, particularly to assist in starting the turbine and limiting its fuel consumption during certain phases of flight, and to ensure that the motor provides sufficient power to the aircraft's electrical equipment when it is operating as a generator.

[0009] The electrical system must also be reliable, robust, and arranged so as not to interfere with the operation of the turbine.

[0010] The applicant discovered that the motor, and particularly the electromagnetic torque it generates, may contain a dynamic component (oscillations about a continuous torque) that can generate excitations for certain torsional modes of the propulsion system's powertrain. This excitation causes torque oscillations, which, depending on their frequency, may excite torsional vibration modes of the propulsion system's shaft. The excitation of these torsional modes leads to a significant increase in vibration levels (often referred to as overshoot), phase shift, and low- and high-frequency damping phenomena on the propulsion system's shaft. This can lead to vibrational fatigue of the powertrain, and in the worst case, to powertrain failure. If a turbine is involved, such a failure could be catastrophic.

[0011] Purpose of the invention

[0012] The specific object of this invention is to improve these electrical systems, particularly with regard to controlling the vibration phenomena that they may produce. Summary of the Invention

[0013] Therefore, according to the present invention, a method for controlling a propulsion system is provided, the propulsion system comprising a turbine, a motor coupled to a first shaft of the turbine, an electronic control unit for the propulsion system, a power converter for selectively operating the motor in motor mode and 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 power to the motor in motor mode or to the motor in generator mode. The method includes the following steps: - Identify the excitation frequency range of at least one torsional mode of the turbine excited by the motor, based on the stator phase current of the motor; - And, during the operation of the propulsion system, the stator phase current of the motor is determined, and the reference torque is filtered at the electronic control unit by applying a filter, the cutoff frequency range of which is adjusted to exclude at least one excitation frequency range corresponding to the determined stator phase current.

[0014] Therefore, filtering of the reference torque (e.g., setpoint or torque command) allows for the avoidance of all or part of the excitation frequency of the mechanical torsional mode. Since the range of excitation frequencies for the torsional mode is not constant and depends particularly on the load exerted on it by the equipment connected to the propulsion system (see...). Figure 4 Therefore, the cutoff frequency of the filter used in this invention is adapted to the stator phase current of the motor. This ensures that the reference torque will not induce torsional mode excitation regardless of the operating conditions of the propulsion system.

[0015] Another advantage of analyzing stator phase currents to match the filter cutoff frequency is that it allows for the identification of one or more mechanical torsion modes independently of whether the motor is operating in motor mode or generator mode.

[0016] Preferably, the determination of the stator phase current includes spectral analysis of the measured stator current.

[0017] The present invention also relates to a propulsion system comprising a heat engine, a motor coupled to the heat engine, an electronic control unit for the propulsion system and connected to a power converter, the power converter selectively operating the motor in motor mode and generator mode based on a reference torque, and a reversible power supply circuit connected to the power converter to selectively supply power to or be supplied by the motor in motor mode or generator mode. The electronic control unit includes: components for determining the stator phase current of the motor; and components for adaptively filtering the reference torque, the adaptive filtering components having a cutoff frequency range determined according to the determined stator phase current, the cutoff frequency range corresponding to the excitation frequency range of at least one torsional mode of the first shaft.

[0018] Based on the optional features that can be used individually, in whole or in part: - The electronic control unit includes a table relating the cutoff frequency range of the adaptive filter to the stator phase current, wherein for the corresponding stator phase current, each cutoff frequency range of the adaptive filter is substantially equal to the excitation frequency range of at least one torsional mode of the turbine.

[0019] - The electronic control unit is connected to components for acquiring the speed of the first shaft of the turbine and components for measuring the stator phase current of the motor.

[0020] - The electronic control unit is configured to implement a hybrid strategy, which determines its state at each moment: Should the motor operate in generator mode or electric motor mode? The first mechanical power that needs to be drawn from the turbine when the electric machine operates in generator mode, and the second mechanical power that needs to be provided to the turbine when the electric machine operates in motor mode; A reference torque corresponding to the determined mechanical power and transmitted to the filtering component.

[0021] - The filtered reference torque is transmitted to the current loop driving the power converter, and preferably, the current loop includes a space vector pulse width modulation component.

[0022] - The turbine includes two first shafts, one first shaft belonging to the high-pressure stage and the other first shaft belonging to the low-pressure stage, and the propulsion system includes two electric machines, namely a first electric machine and a second electric machine. The second shaft of the first electric machine is coupled to the first shaft of the high-pressure stage, and the second shaft of the second electric machine is coupled to the first shaft of the low-pressure stage.

[0023] Finally, the present invention relates to a vehicle, and more specifically to an aircraft equipped with such a propulsion system.

[0024] Other features and advantages of the present invention will become apparent upon reading the following description of specific and non-limiting embodiments of the present invention.

[0025] Brief description of the attached figures

[0026] Reference will be made to the accompanying drawings, in which: Figure 1 Figure 1 is a schematic diagram of an aircraft according to the present invention; Figure 2 Figure 2 is a schematic diagram of the propulsion system of the aircraft according to a specific embodiment of the present invention; Figure 3 Figure 3 is a more detailed schematic diagram of the propulsion system; Figure 4 Figure 4 is a schematic diagram of the propulsion system according to a variant of the specific embodiment; Figure 5 Figure 5 is a graph showing the variation of the excitation frequency of the first torsional mode with the power provided by the electric machine; Figure 6 Figure 6 is a Bode diagram representing the frequency analysis of the mechanical transmission chain of the heat engine.

[0027] Detailed Description of the Invention

[0028] Reference Figure 1 and​​​​​​ Figure 2 The invention is described in conjunction with the hybrid propulsion system M of aircraft A. Here, the hybrid propulsion system M comprises a turbine TM and an electric motor MEL.

[0029] The turbine TM—more specifically, a turbojet engine, turboprop engine, or turboshaft engine—is known in itself and will only be described briefly here. The turbine TM comprises a high-pressure stage HP and a low-pressure stage LP. The high-pressure stage HP comprises a shaft coupled to the shaft of the low-pressure stage LP via a gear assembly (not shown), forming a power transmission system comprising a shaft system L.

[0030] The motor MEL includes a motor 10, whose output shaft 11 is coupled to one and / or the other shaft of the turbine TM via a gear assembly G. The motor 10 here is a permanent magnet motor.

[0031] The electromagnetic windings of motor 10 are connected to power electronic devices, including a DC / AC power converter, such as inverter 12 in this example, which is arranged to operate motor 10 in either motor mode or generator mode. Inverter 12 itself is connected to power supply circuit 13, which is connected to circuit E of aircraft A containing a battery, and is arranged reversibly to selectively supply power from the battery to motor 10 to rotate drive output shaft 11 when motor 10 is in motor mode, or to be powered by motor MEL when motor 10 is in generator mode, particularly for charging the battery and / or directly supplying power to electrical equipment connected to circuit E of aircraft A. Motor MEL, particularly motor 10, inverter 12, and power supply circuit 13 themselves, are known.

[0032] The propulsion system M includes a control unit 20 arranged to control the turbine TM and the motor MEL. The control unit 20 is an electronic unit (integrated circuit, FPGA, ASIC, microcontroller, etc.), for example, containing one or more processors and one or more memories containing one or more computer programs for controlling the propulsion system M. The control unit 20 here includes a control module 21 for the turbine TM and a control module 22 for the motor MEL, and implements hybrid logic represented by the symbol 23. The control module 21 for the turbine TM is of the known FADEC or EEC type. The control module 22 for the motor MEL includes a current loop that drives the inverter 12 according to the following parameters: - Current setpoint Iq provided by mixed logic 23 ; - Current values ​​(ia, ib, ic) of each phase of the motor 10 provided by the current acquisition device 24 (here, a Hall effect device) connected to the control unit 20. - The angular position θmeca and angular velocity Ωmeca of the output shaft 11 of the motor 10 are provided by the resolver 25 connected to the control unit 20. The angular data Ωmeca and θmeca typically come from the processing of signals from the resolver 25.

[0033] In control module 22, the following parameters are used to control motor MEL: - Currents iα and iβ are the α-axis currents and β-axis currents generated by the Clarke transform when the phase currents ia, ib, ic are received as inputs; - Currents id and iq are the d-axis and q-axis currents generated by the Parker transformer when it receives currents iα and iβ as input; - Current setpoint Id andIq These are the set points for the d and q current axes.

[0034] Typically, the current loop of control module 22 also involves: - Voltage Vd and Vq They are the signals Id received respectively. -id and Iq -iq is the d-axis and q-axis reference voltage generated by the PI corrector as input; - Voltage Vd and Vq They are voltages Vd and Vq Based on the d-axis and q-axis reference voltages generated after decoupling from the currents iq and id and the angular velocity Ωmeca; - Voltage Vα and Vβ They are the received voltage Vd and Vq The α and β axis reference voltages are generated as inputs from the inverse Parker transformation.

[0035] The Parker transformation is also performed using θelec, which is the electrical angular position of motor 10, equal to the angular position θmeca multiplied by the number of pole pairs of motor 10. Figure 3 (The module represented by θcorrection in the text).

[0036] Voltage Vα and Vβ Power is supplied to the space vector pulse width modulation device (SVM), which provides duty cycles Duty 1, Duty 2, and Duty 3 to drive inverter 12.

[0037] The reference voltage Vdc provided by the power supply circuit 13 supplies power to the PI corrector, the space vector pulse width modulation device SVM, and the inverter 12.

[0038] Hybrid logic 23 is configured to implement a hybrid strategy (module 231) that determines at each moment based on commands from the aircraft pilot, the flight phase, and signals from sensors on the aircraft: - Should the motor MEL operate as a generator or a motor? - The mechanical power that the motor MEL needs to draw from the turbine TM when operating as a generator, and the mechanical power that the motor MEL needs to supply to the turbine TM when operating as a motor; - The torque setpoint or reference torque C corresponding to the mechanical power determined in the previous step. _before.

[0039] The hybrid logic 23 receives the angular velocity Ω of the output shaft 11 from the resolver 25 and the stator phase current from the current acquisition device 24 as inputs. The hybrid logic 23 is arranged to perform frequency analysis on the stator phase current (module 232) and determine the cutoff frequency range fc corresponding to the excitation frequency of the torsional mode of the shaft system L (module 233) based on the amplitude and frequency of the stator phase current and the rotational speed of the motor 10.

[0040] The cutoff frequency range due to the stator phase current is determined, for example, using a two-dimensional table (lookup table) that correlates the cutoff frequency with the stator phase current value based on the rotational speed of the heat engine TM (more specifically, the rotational speed of the shaft HP or LP coupled to the output shaft 11 of the motor 10). Such a table is obtained, for example, by determining the excitation frequency of the torsional mode of the propulsion system's powertrain based on the stator phase current (by simulating the turbine TM by testing the motor MEL coupled to a speed-controlled load machine across the entire speed and torque range, either through simulation or experimentally). These tests aim to determine the frequencies at which the torque oscillations on the powertrain of the propulsion system M are amplified.

[0041] Special attention needs to be paid to harmonics generated by the motor MEL whose frequencies are close to the torsional mode of the turbine TM. In fact, some harmonics, especially lower-order harmonics, have more energy than others, and if their frequencies are close to the torsional mode, they can cause overshoot (the higher the harmonic order, the lower its energy level). Furthermore, low-frequency modes can produce high vibrational displacements. Harmonics that may cause significant overshoot include: - First harmonic generated by mechanical imbalance; - Second harmonics generated by coaxiality defects between the rotor and stator; - Harmonics of the order corresponding to the product of the number of poles and phases of the motor are generated by torque oscillations; The harmonics of the order corresponding to the product of the number of teeth and the number of slots are generated by the stator tooth force.

[0042] For example, Campbell's plot of the turbine TM is used to determine the functional relationship between the natural frequencies and rotational speed of the turbine TM's components. In such plots, diagonal lines represent the natural frequencies of the propulsion system components; horizontal lines correspond to the frequencies of the torsional mode; and vertical lines correspond to the turbine TM's minimum and maximum speeds. Risk areas correspond to the intersections of the natural frequency lines and the torsional mode frequency lines obtained through Bode plot frequency analysis, identifying one or more of the most dangerous frequencies. Figure 6 The maximum value of the torsional mode was observed at approximately 29 Hz, with an amplification of about 50 dB. This clearly constitutes a risk region, and the harmonics carrying the most energy (e.g., torque oscillations) must be controlled to minimize their impact on the resulting overshoot. Therefore, the aim is to control the high-energy harmonics most likely to cross one or more dangerous frequencies.

[0043] In this case, it is preferable to consider three excitation components: - The inherent component of torque oscillation is caused by the salient pole effect of the electric motor 10, and its occurrence is unrelated to the operation of the power electronic equipment; - The component related to the drive of the motor 11 generates torque oscillation through the 6th harmonic; - The component related to the inverter's dead time also generates torque oscillations through the 6th harmonic.

[0044] The hybrid logic 23 also includes an adaptive filter 234 (band-stop type) that receives torque setpoint C. _before is used as input and provides the filtered torque setpoint C. The output is _after. The adaptive filter 234 has a cutoff frequency, or more precisely, a cutoff frequency range fc, which is adjusted according to the stator phase current to the torque setpoint C. The _before filter is used to exclude the excitation frequency range fc of the torsional mode.

[0045] Filtered torque setpoint C _after is then converted into a current setpoint (module 235) to form a current setpoint Iq that serves as the input to the current loop of control module 22. .

[0046] Torque and speed measurements are preferably performed on the output shaft 11, upstream of the gear assembly that couples the output shaft 11 and the turbine TM shaft system. For speed measurement, the derivative of the mechanical position angle θmeca given by the rotary transformer 25 can be used. As a variation, measurements can be performed at the output end of the gear assembly, since measurements at the coupling point are difficult: by knowing the gear ratio of the gear assembly (calculated based on the number of teeth or diameter of each gear), the torque and speed of the output shaft 11 can be deduced from the measurements at the output end of the gear assembly.

[0047] In the context of this invention, these measurements are used to calculate the stator phase current in real time during operation of the propulsion system M. The frequency and amplitude of the stator phase current are used as inputs to the table of module 233, and the output of module 233 is the cutoff frequency of filter 234, which is also provided in real time.

[0048] Filter 234 more specifically has the following form of FT: The parameters are as follows: f 0 is the cutoff frequency, which is the suppressed center frequency; K It is the width of the suppressed frequency band; s is a Laplace variable.

[0049] Therefore, the filter defines the frequency range that will definitely be attenuated, which lies between two extreme values ​​(two cutoff frequencies given by the bandwidth K around the central cutoff frequency).

[0050] It is understandable that the parameters of filter 234 (cutoff frequency and bandwidth) are updated in real time based on the stator phase current determined at each moment according to a given period.

[0051] Therefore, the method of the present invention includes an a priori step of identifying the excitation frequency range of at least one torsional mode of the shaft system of the propulsion system M, and a step performed by the control unit 20 during operation of the propulsion system M, namely: determining the stator phase current and filtering the torque setpoint to exclude the excitation frequency range corresponding to the determined stator phase current.

[0052] Of course, the present invention is not limited to the described embodiments, but covers any variations that fall within the scope of the invention as defined by the claims.

[0053] In particular, the propulsion system may have a structure different from the structure described.

[0054] The propulsion system may include: - A single motor MEL LP, coupled to the LP shaft of the low-pressure stage LP of the turbine, or - A single motor MEL HP, coupled to the HP shaft of the high-pressure stage HP of the turbine, or - like Figure 3 As in the second embodiment, motor MEL LP is coupled to the LP shaft of the low-pressure stage LP of the turbine, and motor MEL HP is coupled to the HP shaft of the high-pressure stage HP of the turbine. In that case, filtering can be performed on only one or both motors.

[0055] This table can be defined with constant interval input values ​​(e.g., 5, 10, 15, 20) or non-constant interval input values ​​(e.g., 3, 5, 7, 10, 15, 20, 25, etc., if the excitation frequency varies significantly between 3 and 10). This table can be replaced by a law that matches the stator phase current to the frequency to be avoided.

[0056] Based on the impact of these torsional modes on the reliability of the propulsion system M, the cutoff frequency range of the filter component as a function of the stator phase current can be determined to avoid excitation of one or more torsional modes of the shaft system.

[0057] The electric motor 11 can be of any type, particularly a wound rotor motor, a permanent magnet motor, or an asynchronous motor.

[0058] This invention can be used in any turbine, and is not limited to the use of the propulsion system in aircraft.

Claims

1. A method for controlling a propulsion system (M), the propulsion system (M) comprising a turbine (TM), a motor (MEL) coupled to a first shaft of the turbine, an electronic control unit (20) for the propulsion system, a power converter (12) for selectively operating the motor in motor mode or generator mode based on a reference torque provided by the electronic control unit, and a reversible power supply circuit (13) connected to the power converter to selectively supply power to the motor in motor mode or to the motor in generator mode, characterized in that, The method includes the following steps: Based on the stator phase current of the motor, identify the excitation frequency range of at least one torsional mode of the turbine excited by the motor; Furthermore, during operation of the propulsion system, the stator phase current of the motor is determined, and the reference torque is filtered at the electronic control unit by applying a filter, the cutoff frequency range of which is adjusted to exclude at least one excitation frequency range corresponding to the determined stator phase current.

2. The method as described in claim 1, characterized in that, The determination of the stator phase current includes spectral analysis of the measured stator current.

3. A propulsion system (M) comprising a turbine (TM), a motor (MEL) coupled to a first shaft of the turbine, an electronic control unit (20) for the propulsion system, a power converter (12) for selectively operating the motor in motor mode or generator mode based on a reference torque provided by the electronic control unit, and a reversible power supply circuit (13) connected to the power converter to selectively supply power to the motor in motor mode or by the motor in generator mode, characterized in that, The electronic control unit (20) includes: a component for determining the stator phase current of the motor; and a component (234) for adaptively filtering the reference torque, the adaptive filtering component having a cutoff frequency range determined based on the determined stator phase current, the cutoff frequency range corresponding to the excitation frequency range of at least one torsional mode of the turbine.

4. The propulsion system (M) as described in claim 3, characterized in that, The electronic control unit (20) includes a table that associates the cutoff frequency range of the adaptive filter (234) with the stator phase current, wherein each cutoff frequency range of the adaptive filter (234) is substantially equal to the excitation frequency range of at least one torsional mode of the turbine for the corresponding stator phase current.

5. The propulsion system (M) as claimed in claim 3 or claim 4, characterized in that, The electronic control unit (20) is connected to a device for acquiring the speed of the first shaft of the turbine and a device for measuring the stator phase current of the motor (MEL).

6. The propulsion system (M) as claimed in any one of claims 3 to 5, characterized in that, The electronic control unit (20) is arranged to implement a hybrid strategy (231), which determines at each time step: - Should the motor (MEL) operate in generator mode or electric motor mode? - The first mechanical power that the motor needs to draw from the turbine (TM) when operating in generator mode, and the second mechanical power that the motor needs to supply to the turbine when operating in electric motor mode; - The reference torque (C) corresponding to the determined mechanical power and transmitted to the filter component (234) _before).

7. The propulsion system (M) as claimed in any one of claims 3 to 6, characterized in that, The filtered reference torque is transmitted to the current loop that drives the power converter (12).

8. The propulsion system (M) as claimed in claim 7, characterized in that, The current loop includes a space vector pulse width modulation device.

9. The propulsion system (M) as claimed in any one of claims 3 to 8, characterized in that, The turbine (TM) includes two first shafts, one of which belongs to the high-pressure stage (HP) of the turbine and the other of which belongs to the low-pressure stage (LP) of the turbine. The propulsion system includes two motors (MELs), namely a first motor (MEL HP) and a second motor (MEL LP). The second shaft of the first motor is coupled to the first shaft of the high-pressure stage (HP), and the second shaft of the second motor is coupled to the first shaft of the low-pressure stage (LP).

10. An aircraft comprising a propulsion system (M) as claimed in any one of claims 3 to 9.

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