METHOD FOR CONTROLLING AN ELECTRIC TURBOMACHINE

Abstract

A method for controlling an electric machine (31, 32) comprising a shaft coupled to a rotating, movable turbomachine body, the method comprising the steps of: - obtaining an angular acceleration ( ) of the shaft from a rotational speed ( ) of the shaft, the rotational speed being previously determined using a sensor or estimated; - determining a corrective torque ( ) from the angular acceleration ( ), the corrective torque depending on an acceleration torque ( ) of the shaft of the electric machine (31, 32) calculated by multiplying the angular acceleration ( ) of the shaft and an inertia ( ) of the electric machine (31, 32); - correcting a torque setpoint ( ) intended for the electric machine (31, 32) using the corrective torque ( ), so as to produce a corrected torque setpoint; - controlling the electric machine (31, 32) using the corrected torque setpoint. Figure for the abstract: Fig. 7

Description

Title of the invention: METHOD FOR CONTROLLING THE ELECTRIC MACHINE OF A TURBOMACHINE technical field

[0001] This disclosure relates to the general field of electrical systems, and in particular the correction of control setpoints for hybrid turbomachine electrical systems, including torque or power controls of electrical machines. STATE OF THE ART

[0002] 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 currently in operation, 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.

[0003] 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.

[0004] Consequently, the Applicant is constantly working to reduce its climate impact by employing sustainable development methods and minimizing greenhouse gas emissions. This sustained research and development work focuses in particular on new generations of aircraft engines and the development of the use of electric technologies for propulsion.

[0005] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this respect, contributes to reducing the environmental impact of aircraft. Thus, it is possible to hybridize the aircraft's propulsion system, and in particular the turbomachine. This involves adding a hybrid electrical system that forms an interface between the rotating mechanical shafts and the aircraft's electrical network.

[0006] More specifically, electrical machines or generators apply or draw power from the mechanical shafts of the turbomachine (for example, from high-pressure and low-pressure shafts), based on commands issued by a control system (or FADEC, acronym for "Full Authority Digital Engine Control").

[0007] Previously, one solution for ensuring the aircraft's electrical power supply, or even for assisting the turbomachine's start-up, consisted of using an integrated drive generator (IDG) decoupled from the mechanical shafts, or using a variable frequency generator (VFG) with low mechanical damping, thus placing significant stress on the mechanical chain. These two generators are not controlled by a command issued by the FADEC control system but by generator control units (GCUs) under the aircraft manufacturer's responsibility.

[0008] In the context of turbomachine hybridization, the control system's setpoint does not take into account the dynamics of the electric machine shaft coupled to a rotating, moving turbomachine body (high-pressure or low-pressure mechanical shaft), and therefore the acceleration torque of the electric machine shaft driven in rotation beyond the turbomachine's ignition phase. In particular, there is a risk that the target transient operating conditions will not be achieved, for example during acceleration, or that the fuel injection control law will compensate for a lack of power / torque supplied by the electric machine. The turbomachine's transient operation is therefore not optimal and can lead to excessive fuel consumption. Description of the invention

[0009] One purpose of this disclosure is to improve the accuracy of the torque applied or extracted by the electric machine on the associated rotating body, particularly during the acceleration and deceleration phases of the turbomachine.

[0010] This objective is achieved by a method for controlling an electrical machine comprising a shaft coupled to a rotating, movable turbomachine body, the method comprising the steps of:

[0011] - obtaining an angular acceleration of the shaft from a rotational speed of the tree previously determined using a sensor or estimated;

[0012] - determination of a corrective torque from the angular acceleration, the torque corrective dependent on an acceleration torque of the shaft of the electrical machine calculated by multiplying the angular acceleration of the shaft and an inertia of the electrical machine;

[0013] - correction of a torque setpoint intended for the electric machine using the corrective torque so as to produce a corrected torque setpoint;

[0014] - control of the electric machine using the corrected torque setpoint.

[0015] The proposed method makes it possible to improve the accuracy of the instruction provided to the The electric machine takes into account the angular acceleration of its shaft in the calculation of the torque setpoint. This makes it possible to achieve a target torque or power on the turbomachine body from which the electric machine draws or to which the electric machine supplies mechanical power, during accelerations or decelerations of the turbomachine where the angular acceleration of the electric machine shaft is non-zero.

[0016] The system advantageously does not require the addition of sensors and integrates into the existing equipment of the turbomachine. In particular, it uses the rotational speed of the electric machine shaft, which is generally already used by the control unit to perform feedback control of the electric machine.

[0017] The invention is advantageously complemented by the following features, taken individually or in any of their technically possible combinations:

[0018] - the method includes determining the rotational speed of the shaft by frequency filtering of a raw shaft rotation speed;

[0019] - the angular acceleration of the shaft is obtained by a servo loop phase lock;

[0020] - Obtaining the angular acceleration of the shaft from the rotational speed comprises the following steps:

[0021] - calculation of an integral of an angular acceleration of the previous tree having been previously obtained, and

[0022] - obtaining the angular acceleration of the shaft from a difference between the determined shaft rotation speed and integral;

[0023] - estimating the angular acceleration of the shaft from the rotational speed includes the following steps:

[0024] - obtaining a gross angular acceleration of the shaft from the velocity of rotation,

[0025] - frequency filtering of the raw angular acceleration;

[0026] - the correction torque is determined by saturation (i.e., thresholding) of the torque acceleration.

[0027] According to a second aspect, a computer program product is proposed comprising program code instructions for the execution of the steps of the described process, when this program is executed by a processor.

[0028] According to a third aspect, a control system for an electric machine is proposed, the electric machine comprising a shaft suitable for coupling to a rotating, movable turbomachine body, the system comprising: - a rotational acceleration calculation module configured to estimate an angular acceleration of the shaft from a rotational speed of the shaft previously determined by an acquisition module including a sensor and / or an estimator; - a torque correction module configured to determine a corrective torque from the angular acceleration of the shaft, and to correct a torque setpoint using the corrective torque, so as to produce a corrected torque setpoint, - a control unit configured to control the electric machine using the corrected torque setpoint.

[0029] The system may include the acquisition module, and the sensor included in the acquisition module may be a shaft rotation sensor, for example an angular velocity sensor or an angular position sensor.

[0030] According to a fourth aspect, a hybrid turbomachine electrical system is proposed, comprising an electric machine, the electrical system including an electric machine control system as described above. DESCRIPTION OF FIGURES

[0031] Other features, objectives 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:

[0032] Fig. 1 is a cross-sectional view of a turbomachine.

[0033] Fig. 2 is a schematic representation of a hybrid electrical system.

[0034] Figure 3 is a schematic representation of the interface between machines electrical and turbomachine bodies.

[0035] Fig. 4 schematically illustrates the difference between the torque setpoint supplied to the electric machine and the torque measured in transient regime.

[0036] Fig. 5 is a schematic representation of a system in one embodiment of the invention, in the example of an electric machine coupled to the low-pressure shaft.

[0037] The [Fig.6] is a schematic representation of a system in another embodiment of the invention.

[0038] The [Fig.7] is a flowchart of steps of a control process according to an embodiment of the invention.

[0039] The [Fig.8] is a flowchart of steps of a control process according to another embodiment of the invention.

[0040] Fig. 9 represents the evolution over time of the rotational speed measured during the test and of torque values ​​before and after correction by taking into account the acceleration.

[0041] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0042] Description of the turbomachine

[0043] By way of illustration, [Fig. 1] schematically represents a section of a propulsion unit 1 in a plane containing a longitudinal axis X corresponding to the axis of rotation of the rotor parts of the turbomachine 10. The propulsion unit 1 is intended to be mounted on an aircraft 100, by means of a pylon (not shown). The propulsion unit 1 comprises the turbomachine 10 and a nacelle 20 surrounding the turbomachine 10.

[0044] This disclosure is not limited to a twin-spool, twin-flow turbojet with direct fan drive 11 as illustrated. It extends more generally to different turbojet architectures, including unfaired turbojets, and other types of turbomachinery, which may have a different number of bodies and / or flows.

[0045] The turbomachine 10 comprises, from upstream to downstream in the direction of the gas flow, a blower 11, a compression section 16 comprising a low pressure compressor 161 and a high pressure compressor 162, a combustion chamber 14, an expansion section 15 comprising a high pressure turbine 152 and a low pressure turbine 151, and an exhaust casing.

[0046] Each of the low-pressure compressor 161, high-pressure compressor 162, high-pressure turbine 152, and low-pressure turbine 151 comprises a rotor part and a stator part, the rotor part being capable of being driven in rotation relative to the stator part around the longitudinal axis X. The blower 11, the rotor part of the low-pressure compressor 161, and the rotor part of the low-pressure turbine 151 are connected to each other by a low-pressure shaft 181 extending along the longitudinal axis X, thus forming a low-pressure body (LP body) which is a first body mounted to rotate freely around the longitudinal axis X.

[0047] The rotor part of the high-pressure compressor 162 and the rotor part of the high-pressure turbine 152 are connected to each other by a high-pressure shaft 182 extending also along the longitudinal axis X, around the low-pressure shaft 181, thus forming a high-pressure body (HP body) which is a second body mounted movable in rotation around the longitudinal axis X.

[0048] As can be seen in [Fig. 1], the compression section 16, the combustion chamber 14 and the expansion section 15 are surrounded by a motor housing 21, to which are connected the stator parts of the low-pressure compressor 161, the high-pressure compressor 162, the high-pressure turbine 152 and the low-pressure turbine 151. The motor housing 21 delimits a primary channel 13 allowing the flow of a primary gas stream A. A secondary channel 12 allows the flow of a secondary gas stream B.

[0049] Aircraft electrical system

[0050] This disclosure relates to the internal hybridization of the turbomachine 10, i.e., an electrical system interfacing with the low-pressure and high-pressure shafts 181, 182 of the turbomachine 10. The electrical system is a hybrid system comprising an electric machine 31, 32, and an electric machine control system, which will be described in detail later. In generator operation, it extracts mechanical power from the rotating HP and LP turbine shafts of the turbomachine and converts it into electrical power to supply the aircraft 10's electrical network. In engine operation, it provides mechanical power to the HP and LP turbine shafts, notably to assist in starting the turbomachine 10.

[0051] Typically, each of the two rotating bodies or shafts 181, 182 is respectively associated with the electric machine 31, 32 (or generator motor). More precisely, the electric machine 31, 32 comprises a shaft 311, 312 suitable for being coupled to the rotating BP body of the movable turbomachine.

[0052] The electrical machines 31, 32 can supply power to the various electrical systems or electrical loads of the aircraft 100 via the electrical network. Thus, the electrical system 3 provides the interface between the LP, HP bodies of the turbomachine 10 and the electrical network of the aircraft 100, in order to meet the electrical power requirements of external and / or internal loads of the propulsion system 1 by mechanically drawing power from the turbomachine 10 via the electrical machines 31, 32. "External loads" refers to electrical loads specific to the aircraft 100, for example, an electric motor, a heating and / or air conditioning system, or a compressor.External loads are electrical systems that provide a number of functionalities when the aircraft 100 is in flight or in ground operation, such as pressurizing and / or illuminating the cabin of the aircraft 100, or operating the cockpit. Internal loads refer to loads specific to the turbomachine 10 (known as the "More Electric Engine" or MEE in Anglo-Saxon terminology), for example, a starter, variable geometry mechanisms, de-icing systems, or other types of actuators.

[0053] With reference to [Fig.2], the low-pressure body BP is coupled to the shaft of the electric machine 31, and the high-pressure body HP is coupled to the shaft of the electric machine 32. More generally, the present disclosure extends to any turbomachine architecture 10 comprising an electric machine coupled to a rotating movably mounted turbomachine body, in particular to the low-pressure shaft 181 and / or the high-pressure shaft 182. One could, for example, consider a turbomachine 10 comprising an HP body, an BP body and a rotating intermediate body, each body being associated with a respective electric machine.

[0054] The electrical system 3 is controlled by a FADEC control system comprising a control computer 4 (or EEC, "electric engine controller"). The control computer 4 is configured to provide electromagnetic torque control of the electrical machines 31, 32. Methods for controlling the electrical machine 31, 32 using a torque setpoint will be detailed later. Power control is also possible; a conversion of the power setpoint to a torque setpoint can be obtained by multiplying the power setpoint by a gain corresponding to the inverse of the rotational speed of the electrical machine shaft, as will be seen later. The use of a power setpoint has the advantage of being better suited to mechanical considerations relating to rotating bodies.

[0055] In the illustrated embodiment, the electrical system 3 includes a fuel metering unit 40 configured to inject a determined quantity of fuel according to a fuel law Ccarb calculated by the control computer 4. Indeed, the electrical system 3 of the turbomachine 10 is then further regulated from the fuel law.

[0056] The HP,BP turbomachine body preferably includes variable geometries (not shown). Thus, the electrical system 3 includes an electromechanical or hydraulic actuator 41 configured to adjust the position of the variable geometries based on an orientation command Cpos calculated by the control computer 4. These optional elements improve the performance of the turbomachine 10.

[0057] In the context of hybridization, the control computer 4 transmits a setpoint to a control unit 310,320 of the electric machine 31,32.

[0058] With reference to Figure 2, the electric machine 31 is controlled by the control unit 310, and the electric machine 32 is controlled by the control unit 320. For example, the control unit 310, 320 is designed to regulate the electric current supplied to the electric machine 31, 32 by a control signal Z31, Z32. The current signal Z31, Z32 can correspond to the phase currents enabling the associated electric machine 31, 32 to reach a target rotational speed, particularly at start-up, or to supply or draw power from the mechanical shaft 181, 182. target mechanics. In the case of a three-phase electric machine, the supply is made according to three phases calculated by the control unit 310,320 from the setpoint provided.

[0059] As explained previously, the control unit 310,320 is configured to calculate phase currents of the associated electric machine 31,32 from the received torque setpoint.

[0060] Mechanical chain of the shafts

[0061] Fig. 3 schematically illustrates the mechanical chain achieving the coupling between the low pressure body BP and the electric machine 31, and the coupling between the high pressure body HP and the electric machine 32. In alternative examples, the electric machine could be coupled to any other turbomachine body such as an intermediate body in a triple-body architecture.

[0062] Typically, the mechanical chain can include a RED reducer, that is to say a gear system whose transmission ratio is less than 1. The RED reducer is configured to increase the motor torque at the output of the electric machine 31,32 and reduce the rotational speed ft;32 of the shaft 311,312 of the electric machine 31,32.

[0063] Preferably, the mechanical chain may optionally include a sensor 5 configured to measure the torque exerted by the shaft of the electric machine 31 on the low-pressure shaft 181. The sensor 5 is, for example, a torque meter located on the shaft 311 of the electric machine 31. The torque Cmes measured by the sensor 5 also corresponds to the opposite of the torque CBP exerted by the low-pressure shaft 181 on the shaft of the electric machine 31.

[0064] The mechanical chain may also include at least one accessory gearbox (or AGB), typically housed in a cavity within the nacelle 20. The accessory gearbox AGB includes a set of gears for driving a plurality of shafts in rotation around their own axis, and accessories mounted on the plurality of shafts to derive useful mechanical power from their rotation.

[0065] As explained previously, the description will henceforth be limited to the case of a torque setpoint. The invention extends more broadly to a power setpoint, the same principles applying.

[0066] Determination of the acceleration torque of the electric machine

[0067] Applying the fundamental principle of dynamics to the electrical machine 31 allows us to obtain the acceleration torque Cacc^ \ of the shaft of the electrical machine 31 as the difference between the sum of the torque setpoint C31 provided by the control computer 4 and the torque CBP exerted by the low-pressure shaft 181 on the shaft of the electrical machine 31, and the resistive torque Cres experienced by the electrical machine 31:

[0068] [Math.l] C«cc,31 — J3]~dt~ = ^31 ^BP " ^res •>

[0069] with J the inertia of the rotor of the electric machine 31 in kg.m2, dt the acceleration of the shaft of the electric machine 31 in rad.s2, the torques Cacci [1], C3], CBP, Cres being in Nm or kg.m2s2. We have

[0070] [Math.2] ^3! “ 31 dt ~ ^res BP v res^v mes

[0071] An uncorrected setpoint provided by the control computer 4 to the control unit 310 is equivalent to the torque term C31, within the limits of the accuracy of the hybrid electrical system, and does not take into account the acceleration of the shaft of the electric machine 31.

[0072] Advantageously, the setpoint supplied to the electric machine 31, 32 takes into account the dynamics of the turbomachine 10 and in particular the acceleration torque Cacc^\, Cm:c32 of the shaft of the electric machine 31, 32 driven in rotation respectively by the rotating body HP, BP during the transient regime of the turbomachine 10. Indeed, in transient regime, where the rotational speed w3i' ^32 of the shaft is not constant, the acceleration of the shaft of the electric machine dt, dt 31,32 is non-zero, so the acceleration torque Cacc^2 is non-negligible.

[0073] This difference is illustrated in Figure 4. The evolution of the torque command provided by the control unit 4 is shown, along with the measured torque Cmes. The difference in steady-state operation, in which the acceleration of the shaft of the electric machine 31 is zero, corresponds to the resistive torque. The resistive torque Cres is generally evaluated on a test bench, so that the FADEC control system can store in memory a lookup table determining the resistive torque Cres as a function of the engine speed, to be taken into account in the calculation of the torque setpoint.

[0074] The corrected torque setpoint can be obtained by the control method as detailed below.

[0075] A method for controlling the electric machine 31,32 is subsequently described, comprising the correction of the torque setpoint C3] provided by the control computer 4.

[0076] Figures 5 and 6 show a control system for the electric machine 31 coupled to the BP body.

[0077] The system includes an acquisition module Mco configured to determine the rotational speed W31 of the shaft prior to the implementation of the control method. Generally, the electrical system 3 can use such an acquisition module Mco to implement the regulation.

[0078] For example, the acquisition module Mco may include a sensor configured to measure the rotational speed a?3i and / or the angular position of the shaft 311 of the electric machine 31.

[0079] Alternatively or complementarily, the Mco acquisition module may include an angular position sensor configured to measure the angular position 31, 6*32 of the shaft and a differentiator, for example including a phase-locked loop, to calculate the rotational speed 31, ü'32 of the shaft from the measured angular position 31, 32. Such an Mco acquisition module is called a resolver. Such Mco acquisition modules are known from the prior art.

[0080] Alternatively or complementarily, the acquisition module Mco may include an observer configured to estimate the rotational speed ^31, a'32 and / or the angular position #3 [, 832 of the shaft. The observer is, for example, configured to estimate the rotational speed ^31, t;;32 from the stator currents of the electric machine 31,32.

[0081] The operation of the observer will be described later.

[0082] With reference to Figure 6, the acquisition module Mco includes a sensor 51 configured to measure the rotational speed 'Ui of the shaft of the electric machine 31.

[0083] The acquisition module Mco includes a frequency filter Fq. The frequency filter Fn is configured to filter the raw rotational speed of the shaft so as to obtain a filtered rotational speed w31 of the shaft of the electric machine 31.

[0084] The frequency filter Fn can be a low-pass filter, for example a first-order low-pass filter, with a cutoff frequency below 1 kHz, typically on the order of 100 Hz. The cutoff frequency of the frequency filter Fn is preferably chosen so as not to affect the dynamics of the measured or estimated raw rotational speed w3i. The frequency filter Fn can also be, without limitation, a higher-order low-pass filter or a band-pass filter. Such a frequency filter Fq is optional.

[0085] The system also includes a rotational acceleration calculation module Ma configured to determine the angular acceleration of the machine shaft dt dt electrical 31,32 from the rotation speed ^32 of the shaft previously determined using the acquisition module M œ.

[0086] For example, the acceleration calculation module Ma includes a phase-locked loop (PLL) such that the angular acceleration of the shaft and the velocity of dt ' dt rotation w32 of the shaft are in the same phase.

[0087] The phase-locked servo loop includes an integrator configured to calculate an integral of the angular acceleration of the shaft, and dt a PI controller configured to estimate the angular acceleration of the shaft at dt at a time t based on the difference between the rotational speed b w32 of the shaft determined at time t and the integral of the angular acceleration of the shaft dt dt calculated by the integrator at the previous time step. The system may include a memory to store the integral of the previously obtained angular acceleration.

[0088] The PI controller is of the proportional-integral type. Such a PI controller network is, in a manner known per se, characterized by a proportional gain Kp and an integral gain Ki. The integrator eliminates the steady-state error, and the proportional gain controls the system dynamics.

[0089] Other implementations are possible, and the angular acceleration can be obtained by other calculation methods implemented by the acceleration calculation module Ma, for example by a derivator.

[0090] The rotational acceleration calculation module Ma includes a frequency filter Facc configured to filter the angular acceleration ^32 of the shaft, obtained by dt ' dt Example at the output of a PI controller. This advantageously reduces abrupt variations in angular acceleration due to measurement noise.

[0091] Typically, the Facc frequency filter is of the low-pass type. For example, the Facc frequency filter can be a first-order low-pass filter, a low-pass filter of order higher than 1, or, without limitation, a band-pass filter. Such a Facc frequency filter is optional.

[0092] The system also includes a torque correction module Mc.

[0093] In the embodiment illustrated in Figure 6, the torque correction module Mc is configured to multiply the angular acceleration ^31 of the shaft by the gain dt J equals the value of the inertia of the electrical machine 31. This allows us to Convert the angular acceleration quantity in rad / s² to a quantity in Nm / dt corresponding to the acceleration torque of the shaft of the electric machine 31. Alternatively, the gain can take into account a sum of inertias of elements enabling the coupling of the shaft 311 of the electric machine 31 to the low pressure shaft 181, or respectively of mechanical elements between the electric machine 32 and the HP body.

[0094] The inertia of the electric machine 31 is typically obtained by measurements carried out on a test bench of the electric machine 31, and stored in a memory of the system 3. For example, the inertia ( of the electric machine 31 is less than 0.5 kg.m2, in particular between 0.01 kg.m2 and 0.1 kg.m2.

[0095] The torque correction module Mc includes a maximum torque saturation unit SAT intended to apply saturation to the acceleration torque C.^ 31, C(Uc ^ supplied as input.

[0096] For example, the SAT saturation unit is configured to increase the acceleration torque Cacc32 obtained by an upper limit. The corrective torque C^cor is then equal to the acceleration torque Cacci,^ Cacc32 of the shaft if the acceleration torque Cacc32 of the shaft is less than the maximum torque, and equal to the maximum torque otherwise. The upper limit, that is, the chosen maximum torque, is typically less than or equal to twice the product of the inertia of the electric machine and the maximum acceleration considered. The maximum acceleration considered is, for example, between 2000 RPM / s and 2500 RPM / s.

[0097] For example, the saturation unit SAT is configured to limit the acceleration torque Cucc2, obtained by a lower bound. Equivalently, during deceleration, the acceleration torque has a negative value, the absolute value of which is bounded above. The corrective torque ^32£»r cst is then equal to the acceleration torque Cacc^2 of the shaft if the acceleration torque Caccn, Cacc^2 of the shaft is greater than the minimum torque, and equal to the minimum torque otherwise. The lower bound, i.e., the negative minimum torque, is typically greater than or equal to twice the product of the inertia of the electric machine f and the maximum (negative) deceleration envisaged. The presence of the saturation unit SAT is optional.

[0098] In the illustrated embodiments, the system is configured to add the corrective torque to the torque setpoint C3i from the control computer 4 so as to provide the control unit 310 with an electromagnetic torque setpoint corrected by the corrective torque Cjicor taking into account the acceleration torque Cacc_3i of the shaft of the electric machine 31. The present invention integrates into the complex environment of the turbomachine 10, and in particular into the hybrid electrical system 3, without requiring any additional installation. Advantageously, the torque or power control correction is integrated into the hybrid electrical system 3, and is not externalized to the control unit 4 (FADEC). This allows for more responsive control correction, i.e., at a higher frequency, and avoids the transmission of signals over long distances (several hundred meters) which can cause noise or delays.

[0099] In the embodiment of Figure 6, where the turbomachine control computer 4 is configured to generate a power setpoint P31, the system includes a setpoint conversion module G configured to calculate the torque setpoint C3i from the power setpoint and the rotational speed w3ide of the shaft. The setpoint conversion module G takes as input the power setpoint calculated by the control computer 4 and provides as output the torque setpoint C3].

[0100] The Mco Mtt' Mc modules can be distinct physical components, specialized for their task. Alternatively, the system comprises a processor and memory in which the embedded algorithm specific to the processor is implemented, and the Med Ma' Mc modules are software modules, i.e., different parts of this program. When the program is executed by the processor, the processor implements a control process, the steps of which will be described later. The processor is arbitrary; in particular, it can have one or more cores (to implement parallel processing).The processor can in particular be a programmable logic circuit, for example a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a digital signal processor (DSP), or another type of electronic circuit.

[0101] The electrical system 3 may include a memory accessible by the processor, and allowing in particular the storage of calculated or estimated values, program code instructions, and parameters relating to the different modules.

[0102] The system further comprises the control unit 310, 320. The control unit 310, 320 includes a processor which may be separate or preferably integrated into the processor of the electrical system 3. The processor is configured to calculate the current setpoints for driving the associated electrical machine 31, 32. To do this, the processor communicates with the control computer 4, which sends it a torque (or power) setpoint. The processor determines the currents at apply in real time from the digitization of measurements (analog-to-digital conversion) and the received setpoint.

[0103] These operations can be carried out at a frequency of several kilohertz.

[0104] The control unit 310,320 also includes a memory for storing data, for example calculated measurements or setpoints or thresholds (for example acceleration torque saturation).

[0105] This same control unit can ensure digital filtering on the speed measurement (Mco), the realization of the phase-locked loop (Mfl) as well as the correction of the acceleration torque (M^) on the setpoint torque.

[0106] Control method

[0107] A method for controlling the electric machine 31,32 will now be described in relation to Figures 7 and 8.

[0108] By way of illustration, we assume nominal operation of the turbomachine 10 in which the high-pressure shaft 182 is rotating at its nominal speed. For example, we wish to increase the rotational speed of the turbomachine's high-pressure shaft by 500 RPM, that is, to reach a rotational speed equal to the nominal speed plus 500 RPM. The acceleration can be limited to a threshold acceleration in RPM / s.

[0109] During a preliminary step S0, the acquisition module Mco measures or estimates the rotational speed w3i, w32. The implementation of the proposed control method advantageously does not require the addition of additional sensors to the acquisition module already present in the system.

[0110] Preferably, the acquisition of the measurement of rotational speed w3i, a,32 and / or of the angular position #31, / / 32 of the shaft by the acquisition module Mco is done in a sufficiently fast manner so as to be representative of an acceleration or deceleration of the turbomachine 10. By "sufficiently fast" it is understood that the acquisition module Mco is configured to perform a measurement at a frequency greater than 100 Hz, preferably greater than 1 kHz, and even more preferably greater than 10 kHz.

[0111] In one embodiment, the rotational speed a,32 is determined by the observer taking into account, for example, a model of the dynamics of the electric machine 31,32 and the current setpoint / 31 supplied to the input of the electric machine 31 by the control unit 310, or a measurement of the current supplied to the electric machine 31. The acquisition module Mco can implement the observer digitally or analogically. The sensor can be, without limitation, a rotational speed sensor as described above, or a current sensor, depending on the quantities from which the rotational speed w3i, °32 is determined. The observer is, for example, a Kalman filter or a Luenberger type observer.

[0112] Preferably, the observer is configured to calculate a new estimate of the rotational speed a'3i, o;32 and / or the position 631, 832 of the shaft at a frequency greater than 1 kHz, preferably greater than 10 kHz. As explained previously, this ensures that the quantity obtained is an adequate representation of the changes in rotational speed of the shaft 311 (or rotor) of the electric machine 31,32 and therefore, a fortiori, of the acceleration or deceleration of the turbomachine 10.

[0113] Preferably, the frequency filter Fn introduced previously performs a frequency filtering of a raw rotation speed of the shaft to determine the rotation speed W31' a'32 of the shaft.

[0114] Frequency filtering advantageously limits abrupt variations due to measurement noise. The Ff2 filter is preferably the choice of a compromise between the tolerable noise level, the response time and the ability to integrate it (in the case of an analog filter, i.e. an electronic solution) or to implement it (in the case of a digital filter, i.e. a software solution).

[0115] For example, the Mco acquisition module performs a noisy rotational speed measurement, which is dependent on the speed of the turbomachine 10, i.e., on the rotational speed. The frequency filter FQ is, for example, a first-order low-pass filter with a cutoff frequency of 100 Hz. Adding this filtering can increase the system's response time by 63%. The challenge lies in finding the right compromise between measurement noise and the expected response dynamics.

[0116] The frequency filter Fn can also perform a filtering of the rotation speed previously determined by an observer.

[0117] Since the measurement or estimation of rotational speed is then used to calculate an acceleration, as will be detailed later, it is appropriate that the frequency filter Fq be configured so that the measurement (respectively the estimation) is sufficiently filtered so as not to derive from measurement noise (respectively observation noise) which would lead to sudden over-torques in the corrected torque command supplied to the control unit 310.

[0118] During an SI step, the acceleration calculation module Ma estimates the angular acceleration of the shaft from the rotational speed w3b ü,32 of the shaft dt ' dt predetermined.

[0119] The acceleration calculation module Ma performs a derivation operation from the rotational speed ^31 of the shaft or determines the angular acceleration ^21 of dt the shaft from the filtered rotational speed measurement m3].

[0120] Preferably, the acceleration calculation module Ma estimates the angular acceleration of the shaft by means of a phase-locked servo loop. dt ' dt

[0121] Here, the acceleration calculation module Ma controls the phase of the output signal, i.e., the angular acceleration d,'hi. of the shaft of the electric machine 31,32 dt dt on the phase of the input signal, that is to say the rotational speed or of filtered rotation speed preference w3|.

[0122] Preferably, the acceleration calculation module Ma estimates the angular acceleration d"'v. at a frequency greater than 1 kHz, preferably greater than 10 kHz. dt

[0123] Since the electrical system 3 operates at a sampling frequency higher than that of the control computer 4, which is typically on the order of several tens of hertz, the proposed method makes it easy to correct internally the uncorrected torque setpoint C31, C32 of the electrical system 3 without introducing a significant delay at the compensation level.

[0124] In the illustrated embodiment, the integrator of the acceleration calculation module Ma calculates the corrected angular velocity from the integral of the angular acceleration <^31 dœ32 of the shaft obtained at a previous time step Qu b. The integral dt ' dt The angular acceleration at the previous time step Qq is then subtracted from the rotational speed w3i' w32 of the shaft provided by the acquisition module Mco. The resulting difference Aw3) is fed into the PI controller, which then provides the angular acceleration 4¾ of the shaft. dt ' dt

[0125] In other words, the SI step of obtaining the angular acceleration el 11)32 dt ' dt of the shaft includes a step of calculating a differential Aw31 of rotational speed corresponding to the difference between the measured or estimated rotational speed, provided by the acquisition module Mco at the next time step t + 5t, and the rotational speed Qu b obtained by integrating the acceleration at time t. dt

[0126] The difference Aco3J is preferably calculated from the filtered rotation speed at time t + 5t. The time step 5t corresponds to the inverse of the sampling frequency of system 3, and is typically less than 10 ms.

[0127] The PI controller can be a proportional control loop. This allows for regulation by taking an integral gain Ki of zero, and a proportional gain Kp corresponding to the sampling frequency of system 3, for example a proportional gain equal to 1000. The value of the proportional gain Kp is chosen so as to have a 63% response time on the order of milliseconds.

[0128] Alternatively, the integral gain Ki of the PI controller network can be non-zero. This makes it possible to reduce or even eliminate a static error, and thus to have a control loop with zero static error.

[0129] Preferably, the acceleration calculation module Ma first estimates a raw angular acceleration of the shaft from the rotational speed w31' ü-32, which is then frequency-filtered. The frequency filter Facc described above performs frequency filtering of the raw angular acceleration of the shaft to obtain the filtered angular acceleration ^2. The frequency filter Facc can be a dt' dt filter low-pass filter characterized by a cutoff frequency below 1 kHz, preferably on the order of 100 Hz. The cutoff frequency of the Facc frequency filter is chosen so as not to impact the dynamics of the angular acceleration of the shaft while ensuring the filtering of measurement noise.

[0130] System 3 corrects a torque setpoint C31, C32 so that the electric machine 31, 32 is controlled by a corrected setpoint. More precisely, the torque setpoint C31, C32 is typically calculated from or equal to a setpoint provided by the control computer 4.

[0131] During a step S2, the torque correction module Mc determines the correction torque C^cor from the angular acceleration ^21 £22=. • " dt ' dt

[0132] The torque correction module Mc calculates the acceleration torque Cacc32 of the shaft of the electrical machine 31,32 by multiplying the angular acceleration (raw or filtered) of the shaft and an inertia J., dt ' dt of the electric machine 31,32. The correction torque C^]cor, C^mr determined can be equal to the acceleration torque C^.31, Cacc32- Taking into account the acceleration torque in the correction torque makes it possible to compensate for deviations of several Newton-meters (for a torque setpoint) or kiloWatts (for a power setpoint) of deviation, which could cause overconsumption of fuel, in order to compensate for the deviation and reach the target transient regime.

[0133] Preferably, the saturation unit S AT saturates the accelerating torque Caccy2 to a maximum value (or a minimum value for negative values ​​during deceleration of the turbomachine 10). The correction torque C3, C32 depends on the accelerating torque Cacc[], Caecy2, but can be different and equal to the maximum value if the accelerating torque Cacc3, Cacc2 exceeds the maximum value. Thus, the correction torque C3, C32.CW is between bounds such that the corrected setpoint is maintained between a maximum decelerating torque and a maximum accelerating torque tolerable by the electric machine. 31,32. This advantageously avoids over-torque when calculating the corrected torque setpoint.

[0134] During a step S3, the torque setpoint C31, C32 intended for the electric machine 31,32 is corrected using the corrective torque C^i£ <fr, de sorte à produire une consigne de couple corrigée. Typiquement, la consigne de couple corrigée est calculée par addition de la consigne de couple C31, C32 non corrigée et du couple correctif \fon C^or- La correction de la consigne de couple ou de puissance calculée par le calculateur de régulation 4 est ici réalisée par le système de manière logicielle par la mise en œuvre d’un calcul simple.

[0135] During a step S4, the control unit 310, 320 controls the electric machine 31, 32 using the corrected torque setpoint. Thus, the acceleration (or deceleration) of the shaft of the electric machine 31 is taken into account by the control unit 310 for the calculation of the control of the electric machine 31.

[0136] Optionally, during a step S21, the setpoint conversion module G of the system calculates the torque setpoint C31, C32 from the power setpoint P31, P32 and the rotational speed ^31' a,32 of the shaft.

[0137] The rotational speed (,'32) previously determined by the acquisition module M is transmitted to the setpoint conversion module G. Typically, the setpoint conversion module G multiplies the power setpoint by a gain corresponding to the inverse of the rotational speed ^31' ^32 of the electric machine shaft (in rad / s). Thus, the setpoint conversion module G converts the power setpoint into an electromagnetic torque setpoint C31, C32 representative of the dynamics of the electric machine 31, 32. The system sampling frequency is typically greater than 1 kHz, preferably greater than 10 kHz. Such a sampling frequency is representative of the operating frequency of a turbomachine test bench.

[0138] It will be understood that the setpoint conversion module G is optional, and in an embodiment where the control computer 4 provides a torque setpoint as output, the system would not include the setpoint conversion module G.

[0139] In general, the control method and system described can be applied indifferently to the electric machine 32 coupled to the HP body or to the two electric machines 31, 32 of the turbomachine 10, or to any number of electric machines coupled to rotating bodies, so as to extract or supply mechanical power on the associated rotating shaft.

[0140] The results of the torque correction process according to an example of the invention are presented in [Fig.9].

[0141] The upper curves represent the evolution of the measured speed as a function of time. Initially, the turbomachine is in steady state, and the electric machine has a rotational speed tü. We wish to reach a set rotational speed by passing through a transient regime, during which the acceleration is non-zero.

[0142] The lower curves represent the evolution of the torque setpoint issued by the control unit 4 (black line), the mechanical torque measured during the test (dark gray line), and the mechanical torque corrected by the described method and taking acceleration into account (light gray). As expected, during the transient regime, a difference is observed between the measured torque and the corrected torque.

[0143] The chosen settings allow the acceleration torque compensation to be achieved in a few milliseconds, which makes it possible to satisfy the regulation needs of the turbomachine.

[0144] As observed in [Fig. 9], the corrected torque is closer to the setpoint than the measured torque. The torque compensation is on the order of several Newton-meters and therefore several kilowatts. Even when the acceleration torque is corrected, a deviation from the setpoint is always present. This difference from the setpoint is due to the inaccuracy of the current measurements from which the electromagnetic torque is calculated.

[0145] The compensation of the acceleration torque of the electric machines by the proposed system therefore allows the improvement of the accuracy of torque or power applied by the hybrid electric system 3 during the accelerations or decelerations of the turbomachine 10.

Claims

Demands

1. A method for controlling an electric machine (31,32) comprising a shaft coupled to a rotating movable turbomachine body, the method comprising steps of: - obtaining an angular acceleration (^31 4¾ ) of the shaft at dt ' dt from a rotational speed (^hb of the shaft, the rotational speed being previously determined using a sensor or estimated; - determining a corrective torque C^or) from the angular acceleration ^22), the corrective torque depending dt ' dt of an acceleration torque Cacc^ of the shaft of the electric machine (31,32) calculated by multiplying the angular acceleration (rfw3! ^3.2) of the shaft and an inertia (J3r J^) of the dt ' dt " ' electric machine (31,32); - correction of a torque setpoint (C31, C32) intended for the electric machine (31,32) using the corrective torque (C3 Leon QsZœr)' so as to produce a corrected torque setpoint; - control of the electric machine (31,32) using the corrected torque setpoint.

2. Method according to claim 1, further comprising a determination of the rotational speed (°hb w32) of the shaft by frequency filtering of a raw rotational speed of the shaft.

3. A method according to any one of claims 1 and 2, wherein the angular acceleration (^21 ^22) of the shaft is obtained by dt ' dt a phase-locked servo loop.

4. A method according to any one of claims 1 to 3, wherein obtaining the angular acceleration (^j, 4¾ ) of the shaft from dt ' dt of the rotational speed (w3b ^32) comprises the following steps: - calculating an integral of an angular acceleration (^“31 ) of dt ' dt the previous shaft having been previously obtained; and - obtaining the angular acceleration ^32 ) of the shaft from dt ' dt of a difference between the rotational speed (a'3b w32) of the shaft determined and the integral.

5. A method according to any one of claims 1 to 4, wherein obtaining the angular acceleration (<^3] ) of the shaft from the rotational speed (w31' w32) comprises the following steps: - obtaining a raw angular acceleration of the shaft from the rotational speed (w3b w32); - frequency filtering of the raw angular acceleration.

6. A method according to claim 5, wherein the corrective torque (Cc] is determined by saturation of the acceleration torque (*--3 Leon ^32,cor JFF v ^'acc^b ^acc,32^-

7. Product computer program comprising program code instructions for carrying out the steps of the process according to any one of claims 1 to 6, when such program is executed by a processor.

8. Control system for an electric machine (31,32), the electric machine (31,32) comprising a shaft suitable for coupling to a rotating movable turbomachine body, the system comprising: - a rotational acceleration calculation module (M a) configured to obtain an angular acceleration ) of the shaft at dt ' dt from a rotational speed (W31' w32) of the shaft previously determined by an acquisition module (M w) comprising a sensor and / or an estimator; - a torque correction module (M c) configured to determine a corrective torque C^or) from the angular acceleration (^n ^32 ) of the shaft, and to correct a torque setpoint (C31, C32) using the corrective torque C^or)' so as to produce a corrected torque setpoint; and - a control unit (310,320) configured to control the electric machine (31,32) using the corrected torque setpoint.

9. System according to the preceding claim, wherein the system comprises the acquisition module (Mœ), and the sensor is a shaft rotation sensor, for example an angular velocity sensor or an angular position sensor.

10. Hybrid turbomachine electrical system comprising an electric machine (31, 32), the electrical system comprising an electric machine control system according to any one of claims 8 or 9.

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