Method for monitoring and protecting an electrical hybridisation system against the risk of fire

Abstract

The invention relates to a method for monitoring and protecting an electrical hybridisation system against the risk of fire, the electrical hybridisation system comprising two rotary machines, each having at least one stator winding, each stator winding being associated with an AC-to-DC converter and a distribution box for delivering, on the basis of the DC voltages delivered by the AC-to-DC converters, a high DC voltage, on the one hand, for local loads and, on the other hand, for the electrical network of an aircraft, in which method current and voltage measurements are carried out in the distribution box, the converters and the stator windings of the rotary machines and if, once these measurements are consolidated together in a control card, the risk of fire is determined, the contactors of the distribution box and / or of the converters are selectively opened and the rotary machines are mechanically disconnected.

Description

[0001] Description

[0002] Title of the invention: METHOD FOR MONITORING AND PROTECTING AN ELECTRIC HYBRIDIZATION SYSTEM AGAINST THE RISK OF FIRE

[0003] Technical Field

[0004] The present invention relates to the field of protection systems for electrical distribution networks in aircraft with electric or hybrid propulsion and it relates more particularly to a method for monitoring and protecting an electrical hybridization system ensuring full coverage of faults likely to present a risk of fire.

[0005] Prior art

[0006] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various carbon emission restrictions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new aircraft types and those currently in operation, requiring the implementation of technological solutions to comply with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0007] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of aircraft.

[0008] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity. This sustained research and development work focuses on new generations of engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electric technologies to provide propulsion, and, as essential complements to technological progress, aeronautical biofuels.

[0009] Thus, the traditional protection principles for electrical networks and systems are based on simple and mostly passive devices. The protections mainly provide protection for the electrical installation (not the equipment) according to the thermal behavior of the cables and very locally according to a differential mode to detect cable disconnections. In addition to distribution, there are also generator protections based on the thermal behavior of the generator windings and the dynamic behavior of the voltage to remain within the acceptable envelope for consumers (common failure mode which can lead to catastrophic events).

[0010] However, in existing distribution systems, each line is connected by a breaking element, contactor or static switch (SSPC), to the high voltage direct current (HVDC) distribution bar, and faults will be detected by a set of current sensors, protection being achieved by opening the line.

[0011] The monitoring and protection of an electrical system are therefore well known and widespread in aircraft electrical distribution systems, but until now these have been with moderate voltages (< 230 VAC) and with only one source connected at a time (apart from certain 28 VDC systems).

[0012] However, in electric hybridization systems for aircraft turbomachines, the voltage of the electrical network is continuous and of the order of 800 VDC, typically between 540 and 1000 VDC, and the system is subject to the consequences of altitude. Indeed, with a high direct voltage, electrical faults can lead to arcs much more energetic than with low voltage or alternating voltage, very quickly causing serious damage which can go as far as a fire, or an uncontrolled fire, which cannot be accepted to meet the certification requirements for aircraft turbomachines to which such an electric hybridization system is subject.

[0013] An electrical monitoring and protection system must therefore not leave any fault uncovered and must act quickly to avoid dangerous damage, but at the same time, it must not cause unscheduled shutdowns that are too frequent. In the event of a fault, it is therefore necessary to keep as much equipment as possible available, and therefore connected, so as not to excessively degrade the availability of the aircraft's turbomachine (engine).

[0014] For high voltage applications, the energies involved, the potential damage and the negative effect of altitude on the dielectric characteristic of air mean that traditional protections adapted to the thermal properties of cables are no longer acceptable because they are too slow. Furthermore, new protection requirements are necessary to cover phenomena (for example electric arcs) which were ineffective at low voltage but which become critical at high voltage.

[0015] Statement of the invention

[0016] The present invention is therefore the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributing to reducing their environmental impact. Its main purpose is to ensure coverage of all possible faults and verification of their consistency to provide robustness in the detection of these faults. Another purpose is to guarantee rapid action in the event of faults to avoid major or dangerous degradation and propagation to other parts of the turbomachine or its connection with the aircraft.

[0017] These aims are achieved by a method for monitoring and protecting an electrical hybridization system against the risk of fire, the electrical hybridization system comprising two rotating machines each having at least one stator winding, each stator winding being associated with an AC / DC converter, and a distribution box for delivering, from the DC voltages delivered by the AC / DC converters, a high DC voltage on the one hand for local loads and on the other hand for the electrical network of an aircraft, method characterized in that current and voltage measurements are carried out in the distribution box, the converters and the stator windings of the rotating machines and if, once these measurements have been consolidated together in a control card, the risk of fire is proven,selective opening of contactors of the distribution box and / or converters and mechanical disconnection of rotating machines is carried out.

[0018] Thanks to this principle of consolidating available measurements from sensors existing in the various system equipment, all areas are covered without adding additional sensors. The high-voltage DC electrical installation is thus protected with a good level of expected performance, particularly in terms of its reaction time and robustness, all of which is carried out in a coherent manner.

[0019] Preferably, the measurement of an overcurrent or an overvoltage in the distribution box and / or the converters or the detection of an excessive temperature or a low oil pressure in the rotating machines causes the opening of the converter switches, the opening of the distribution box contactor and then the mechanical disconnection of the rotating machine.

[0020] Advantageously, the measurement of an overcurrent at the output of the distribution box causes the opening of the contactor or static switch associated with the faulty local load and, in the event of an opening fault, the opening of all the contactors or static switches associated with the other local loads.

[0021] Preferably, measuring an overcurrent at an input on the converter side of the distribution box causes the switches of this converter to open, followed by the opening of the contactor of the distribution box, then if necessary the mechanical disconnection of the rotating machine.

[0022] Advantageously, the detection of an electric arc in one of the rotating machines causes the switches of the associated converter to be short-circuited and then the rotating machine to be mechanically disconnected.

[0023] Preferably, the detection of an electrical arc on the aircraft's electrical network causes the distribution box contactor to open.

[0024] Advantageously, the switches of the converters and the distribution box are opened each time a rotating machine is stopped, started up or during maintenance.

[0025] Preferably, the opening of the contactors and switches is defined by threshold and trigger duration parameters determined for each according to the configuration of the electrical network and the characteristics of the equipment of the electric hybridization system.

[0026] Advantageously, a disconnection test of rotating machines is carried out periodically or each time they are stopped.

[0027] Preferably, the current and voltage, oil pressure and temperature measurements are consolidated together in a management and processing module preferably arranged in the distribution box. Brief description of the drawings

[0028] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting character and in which:

[0029] [Fig. 1] Figure 1 illustrates a first example of an electric hybridization system according to the invention,

[0030] [Fig. 2] Figure 2 illustrates a second example of an electric hybridization system according to the invention,

[0031] [Fig. 3] Figure 3 shows a diagram of the integration of measurements in the electric hybridization system of Figure 1,

[0032] [Fig. 4] Figure 4 shows a diagram of the integration of protections in the electric hybridization system of Figure 1, and

[0033] [Fig. 5] Figure 5 illustrates the different protection zones monitored with the invention.

[0034] Description of the embodiments

[0035] The principle of the invention is based on in-depth knowledge and monitoring of the various equipment in the electrical hybridization system to improve system protection. While the components remain conventional compared to what is done in electrical protection, such as static contactors and switches, or even mechanical disconnection systems for rotating machines, their triggering is determined on the one hand with greater precision and selectivity and on the other hand with more global transverse consolidation and / or cross-checking algorithms.

[0036] The measurements made in the various devices are consolidated with each other and the cross-referencing of current and voltage measurements allows for the refinement of fault detection. Knowledge of the measurements and the state of the system, particularly the open or closed state of the switches, allows for the addition of global validations, such as current summations.

[0037] Figure 1 illustrates a first example of an electrical hybridization system according to the invention composed of two rotating machines 10, 12, possibly of the PMG (Permanent Magnet Generator - PMG) type, of two AC / DC electronic converters (Power Electronics - PE) 14, 16 respectively associated with these rotating machines, of a distribution box 18 of the PDMU (Power Distribution Management Unit) type whose bipolar high voltage direct current (HVDC) distribution bar is connected on the one hand to the converters and on the other hand to the electrical network of the aircraft 20 and to local loads 22, 24, 26 for example.

[0038] The electric hybridization system is equipped with sensors, some necessary for the operation of the system (voltage regulation and power control in the converters), others added specifically to ensure the detection of faults in the system. The sensors installed at different locations in the system provide current measurements, voltage measurements, insulation measurements, arc detection, temperature measurements, oil pressure measurements, and measurements of the position and speed of the rotors of the rotating machines. They will be detailed further with regard to Figure 3.

[0039] The electric hybrid system is also equipped with electrical protections that open the faulty line(s), for example to stop the flow of a faulty current and / or to isolate a dangerous voltage. Additional protection may consist of mechanically disconnecting the rotor of the rotating machine from its drive (by declutching or clutching) in order to stop its rotation. The protections are integrated either in the distribution box, or in the converters, or in the rotating machines and will be detailed further with regard to Figure 4.

[0040] The definition of the electrical protections, by threshold and duration parameters, makes it possible to ensure the selectivity of the protections between them, and is determined according to the configuration of the electrical network and the characteristics of the equipment of the electrical hybridization system. The control of these electrical protections can be distributed throughout the system, or even external to the turbomachine, but it is preferably arranged in the distribution box 18 which comprises a control card 28 for monitoring and protecting the system according to the invention.

[0041] Figure 2 shows another example of an electrical hybridization system also composed of two rotating machines 30, 32 of the PMG (Permanent Magnet Generator) type, each with two stator winding channels 300, 302, 320, 322, four AC / DC electronic converters (Power Electronics) 34, 36, 38, 40 respectively associated with four stator windings of the two rotating machines, two PDMU (Power Distribution Management Unit) distribution boxes 42, 44, local loads 46, 48, 50 and two output links 52, 54 to the aircraft electrical network. A control card 56 for monitoring and protecting the system may be arranged in one of the two distribution boxes, or in both, or, as illustrated, outside of them.

[0042] Figure 3 illustrates all of the measurement sensors arranged in the various equipment of the electric hybridization system of Figure 1. References 100, 102 correspond to a first sensor ensuring a measurement of the position or speed of the rotor in each of the two rotating machines 10, 12. References 104, 106 correspond to a second sensor ensuring either a measurement of the current in the neutral to ground connection through an impedance in each of the two rotating machines 10, 12, or a measurement of the voltage across this neutral to ground connection impedance. References 108, 110 correspond to a third sensor ensuring, if necessary, a measurement of the unbalance current between the two stars in parallel in each of the two rotating machines 10, 12. References 112, 114 correspond to a fourth sensor ensuring a measurement of the temperature of the stator windings of each of the two rotating machines 10, 12.References 116, 118 correspond to a fifth sensor ensuring a measurement of the currents in the phases of the stator windings in each of the two rotating machines 10, 12. References 120, 122 correspond to a sixth sensor ensuring a measurement of the phase currents and the voltages between the phases on the AC side, at the input of the electronic converters 14, 16. References 124, 126 correspond to a seventh sensor ensuring a measurement of the currents and the voltage on the DC side, at the output of the electronic converters 14, 16. References 128, 130 correspond to an eighth sensor ensuring a measurement of the currents and voltage at the input of the distribution box 18. References 132, 134, 136 correspond to a ninth sensor ensuring a measurement of the currents at each of the inputs of the local loads 22, 24, 26.Reference 138 corresponds to a tenth sensor ensuring a voltage measurement on the high voltage direct current (HVDC) distribution bar of the distribution box 18. Reference 140 corresponds to an eleventh sensor ensuring a measurement of the insulation (denoted “IMD”), connected to the high voltage direct current distribution bar. This measurement can also possibly be made only during maintenance by an external body. Reference 142 corresponds to a twelfth sensor ensuring a temperature measurement on the high voltage direct current distribution bar and reference 144 corresponds to a thirteenth sensor ensuring a measurement of the currents and voltage, and an arc detection at the output of the distribution box 18 towards the electrical network of the aircraft 20. Figure 4 illustrates all of the protections arranged in the different equipment of the electrical hybridization system of Figure 1.References 200, 202 correspond to a mechanical disconnection device in each of the two rotating machines 10, 12. References 204, 206 correspond to an opening of the AC phase lines in each of the two rotating machines (alternatively this opening could be made at the input of the two electronic converters 14, 16). References 208, 210 correspond to the electronic switches, used for protection, of the electronic converters 14, 16. References 212, 214 correspond to a contactor for each of the inputs of the distribution box 18. Reference 216 corresponds to a contactor for the local load 22. References 218, 220 correspond to electronic switches, of the SSPC type, for each of the local loads 24, 26 and reference 222 corresponds to a contactor on the connection with the electrical network of the aircraft 20.

[0043] To define a protection strategy without having to add sensors or protections in the electrical hybridization system, it is proposed to combine the information available by a measurement and processing operating unit in order to carry out the monitoring and protection functions necessary to correctly protect the system with good levels of detection, location and isolation of the fault, quickly and robustly, before it has time to create significant damage. For this, and as shown in Figure 5, the electrical hybridization system is separated into four distinct protection zones corresponding to four different types of consolidation. The first is made on the perimeter of the contactor 212, 214, forming the protection component of the distribution box 18 and corresponds to a so-called type A consolidation.The second is made on the perimeter formed by the distribution box 18 in its entirety and corresponds to a so-called type B consolidation. The third is made on the perimeter of the electronic converter 14, 16 and the associated protection component (contactor 212, 214) in the distribution box 18 and corresponds to a so-called type C consolidation. The fourth is made on a wide perimeter grouping the rotating machine 10, 12 and its associated electronic converter 14, 16, as well as the associated protection component 212, 214 in the distribution box 18 and corresponds to a so-called type D consolidation.

[0044] Type A: Electrical signal characteristics:

[0045] The electrical hybridization system equipment in the turbomachine is all known, so the only lack of visibility is on the connection to the aircraft's electrical network. The electrical characteristics of the currents and voltages associated with the equipment are used to adjust the thresholds and trigger times of the protections, and to add frequency or harmonic analyses when relevant. The current-time curves of the protections on the input lines in the distribution box are adjusted in relation to the output characteristics of the converters when they are in generator mode or in motor mode, depending on the network configuration, and to their power limitations, and not only on the heating characteristics of the cables.

[0046] Type B: Internal consolidation of the distribution box:

[0047] The distribution box is a node in the network, with few internal losses (Joule losses and power taken by the internal power supply), and without a large capacitor on the DC high voltage distribution bar. Also, the algebraic sum of the currents entering and leaving the distribution box must be almost zero at all times. A significant deviation from this sum of currents would indicate a serious internal fault or a current sensor fault. An example of a protection condition can be given by the following formula:

[0048] If ABS (Converter_currentA + Converter_currentB + AC_current + Load_currentA + Load_currentB ...) > threshold

[0049] So Default

[0050] Type C: Consolidation by consistency between the converter and the distribution box and between the converter and the rotating machine:

[0051] The measurements in the distribution box and those at the converter output are compared. The currents of the positive and negative poles and the differential voltage must be identical respectively (for the voltage, except for the cable drop, but this is very small). If a difference appears, this indicates a problem on the line between the two devices or a sensor fault. In both cases, the line is planned to be opened. An example of a protection condition can be given by the formula:

[0052] If ABS (I_pole+_distribution box - I_pole+_converter) > threshold

[0053] Or ABS (I_pole-_distribution box - I_pole-_converter) > threshold

[0054] Or ABS (V_distribution box - V_converter) > threshold

[0055] So Default

[0056] Type D: Consolidation with measurements implemented in the rotating machine: The winding of the rotating machine incorporates current transformers whose measurements are made in the associated converter, with the advantage that these transformers provide an isolated measurement of the power circuit. The current transformers are placed on each phase and on the neutral connections connected by a resistance to the

[0057] 5 mass.

[0058] Measuring the current in the neutral allows a quasi-direct measurement of the current flowing in an insulation fault, and as the current transformer is dedicated, its characteristics are defined so that it makes a measurement with good precision. Detecting faults by the current flowing in the neutral connection also takes into account

[0059] 10 counts the frequency of the ripples in it to recognize where the fault is located, in the first rotating machine and the AC wiring connected to it, or in the second rotating machine and its AC wiring, or in a DC connection.

[0060] The following tables are given to illustrate the detailed application of the protection system to an electric hybrid system. Each table lists for each protection device 15, the faults it protects, from which measurements it detects them, and by which mode of action it acts. In addition, the possible consolidation to confirm or invalidate a measurement is given, and the possible test of the protection device, according to the four types of consolidation defined previously.

[0061] The analysis is similar on both LP and HP systems, each consisting of the PMG machine and the associated PE converter. The following tables indicate generically "PMG" and "PE".

[0062] 5 The control of the protection system is better understood with the following table which lists the faults likely to cause a risk of fire, the measurements and consolidations carried out to check the availability of the protection which will then be activated to avoid this risk.

[0063]

[0064] In general, it will be noted that the invention can be applied to a system in motor (propulsion) or generator mode, in single channel or multi-channel, and for both three-phase and multi-phase machines (with a number of phases > 3), for

[0065] 5 magnet machines (PMG) or wound rotor machines, with the electronic converter separated from the machine and connected by intermediate wiring, or on the contrary integrated or glued to it with very short electrical connections.

[0066] The invention can be applied to any electric hybridization system mounted in a carrier other than an airplane, helicopter, VTOL, etc., as well as to an electric propulsion system.

[0067] 10 combining several pieces of equipment.

Claims

Claims

1. Method for monitoring and protecting an electrical hybridization system against the risk of fire, the electrical hybridization system comprising two rotating machines each having at least one stator winding, each stator winding being associated with an AC / DC converter, and a distribution box for delivering, from the DC voltages delivered by the AC / DC converters and via an HVDC distribution bar, a high DC voltage on the one hand for local loads and on the other hand for the electrical network of an aircraft, method characterized in that current and voltage measurements are carried out in the distribution box, the converters and the stator windings of the rotating machines and if, once these measurements have been consolidated together in a control card, the risk of fire is proven,selective opening of contactors of the distribution box and / or converters and mechanical disconnection of rotating machines is carried out.

2. Monitoring and protection method according to claim 1, in which the measurement of an overcurrent or an overvoltage in the distribution box and / or the converters or the detection of an excessive temperature or a low oil pressure in the rotating machines causes the opening of the converter switches, the opening of the contactor of the distribution box and then the mechanical disconnection of the rotating machine.

3. Monitoring and protection method according to claim 1, in which the measurement of an overcurrent at the output of the distribution box causes the opening of the contactor or static switch associated with the faulty local load and in the event of an opening fault, the opening of all the contactors or static switches associated with the other local loads.

4. Monitoring and protection method according to claim 1, in which the measurement of an overcurrent at an input on the converter side of the distribution box causes the switches of this converter to open, followed by the opening of the contactor of the distribution box, then if necessary the mechanical disconnection of the rotating machine.

5. A monitoring and protection method according to claim 1, wherein the detection of an electric arc in one of the rotating machines causes the short-circuiting the switches of the associated converter then mechanical disconnection of the rotating machine.

6. Monitoring and protection method according to claim 1, in which the detection of an electric arc on the electrical network of the aircraft causes the opening of the contactor of the distribution box.

7. Monitoring and protection method according to any one of claims 1 to 6, in which the switches of the converters and of the distribution box are open each time a rotating machine is stopped, when it is started up or during its maintenance.

8. Monitoring and protection method according to any one of claims 1 to 7, in which the opening of the contactors and switches is defined by threshold and trigger duration parameters determined for each according to the configuration of the electrical network and characteristics of equipment of the electrical hybridization system.

9. Monitoring and protection method according to any one of claims 1 to 8, in which a disconnection test of the rotating machines is carried out periodically or at each of their stops.

10. A monitoring and protection method according to any one of claims 1 to 9, wherein the current and voltage, oil pressure and temperature measurements are consolidated together in a management and processing module.

11. Monitoring and protection method according to claim 10, wherein the management and processing module is arranged in the distribution box.

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