Electric power generation network for an airplane

Description

Technical field of the invention

[0001] The present invention relates to the field of electrical power supply for an aircraft. It relates to an electrical power supply network for an aircraft equipped with a plurality of electrical loads to be powered.

[0002] The present invention falls in particular within the framework of electrical architectures integrating power sources comprising a gas turbine associated with a generator forming a turbogenerator, and loads or consumers of electrical energy such as electric thrusters.

[0003] The present invention does not target any particular aircraft and can be applied to both fixed-wing aircraft and rotary-wing aircraft of the helicopter or multicopter type. Technical background

[0004] The state of the art includes in particular documents WO-A1-2017 / 140706, US-A1-2015 / 102663, WO-A1-2009 / 052843, EP-A1-2 192 681. As is known, aircraft propulsion is achieved by means of gas turbines mechanically coupled to propulsion elements, in particular a fan for a modern double-flow turbojet, a propeller for a turboprop or a rotor for turboshaft engines, particularly for helicopter turboshaft engines.

[0005] It is known to provide for coupling a turbomachine with an electric current generator and an electric motor to drive a propeller, thus forming a propulsion system.

[0006] Thus, a direct current propulsion system has been proposed having a rectifier at the output of an alternating current generator followed by an inverter at the input of an electric motor, in order to deliver an alternating current at the output of the inverter for the electrical power supply of the electric motor.

[0007] For such an electrical architecture, the number of energy power sources and electrical loads to be supplied is known, so the main function of such an electrical power supply network is to guarantee the adequate voltage level on the electrical power supply network, for example High Voltage Direct Current (HVDC for High Voltage Direct Current in English) and to provide the necessary power whatever the demand of the electrical loads to be supplied.

[0008] It is known in prior art architectures that power sources are connected to a distribution bus so as to isolate failures of an energy power source and thus prevent the loss of an energy power source from the electrical power supply network from causing a total loss of the network, which would be very damaging.

[0009] A major disadvantage of these networks in which all the power sources are connected to a single distribution bus is that, on the other hand, the occurrence of a failure leading to the loss of the distribution bus itself has the consequence of making the electrical loads it supplies with energy unavailable, in particular the electric propulsion motors, which can be detrimental to the flight safety of the aircraft.

[0010] It has therefore been proposed to segment the electrical power supply network and to distribute the power sources and the electrical loads to be supplied over a plurality of distribution buses. For example, the distribution network proposed by document WO-A1-2017 / 140706 comprises a plurality of generators adapted to provide a source of electrical energy, each comprising a stator associated with a rectifier, the stators of the generators being connected to at least two distribution buses arranged to supply the plurality of electrical loads, the power supply network comprising contactors adapted to electrically connect or disconnect the distribution buses from each other by sectors.

[0011] For example, alternatively, for VTOL type aircraft electrical architectures (acronym for Vertical Take Off and Landingin English) it has been proposed to connect each stator and each rectifier of an electrical machine to a separate distribution bus, in other words, the electrical supply network has as many independent distribution buses as there are rectifiers.

[0012] Such an architecture allows for load segregation, i.e. a given actuator is powered by two separate distribution buses, with the power on a given distribution bus thus being supplied by a rectifier and a battery.

[0013] However, although this electrical architecture allows for the segregation of power sources in order to compensate for the loss of a distribution bus, it requires the use of a high number of batteries (in particular it requires as many batteries as there are distribution buses present on the network) which increases its mass and its cost, and the interest of hybridization is reduced.

[0014] The present invention is a simple and effective solution to overcome these drawbacks. Summary of the invention

[0015] To this end, the invention relates to an electrical power supply network for an aircraft provided with a plurality of electrical loads to be supplied, said power supply network comprising at least two generators configured to form part of a turbogenerator of the aircraft and adapted to provide a source of electrical power each comprising two stators, each stator being associated with a rectifier, the stators of the generators being connected to at least two distribution buses arranged to supply the plurality of electrical loads, the power supply network comprising contactors adapted to electrically connect or disconnect the distribution buses from each other, the rectifiers of the generators being mounted alternately on the distribution buses.

[0016] The electrical network according to the invention has the advantage of being able to segment and distribute the electrical loads to be supplied and the sources of electrical energy in order to protect the electrical network from the risk of failure in the event of a fault on a distribution bus.

[0017] According to a first example of implementation, by default, the contactors are configured to electrically connect the distribution buses.

[0018] This makes it possible to multiply the number of electrical energy sources that can supply the electrical loads to be supplied, the electrical network then being more tolerant to the loss of one or more electrical energy sources.

[0019] According to a second exemplary embodiment, by default, the contactors are configured to electrically disconnect the distribution buses.

[0020] Thus, in the event of a fault on a distribution bus, the latter is isolated from the rest of the electrical supply network, the latter being partially preserved and capable of supplying part of the electrical loads not affected by the failure of the distribution bus. Indeed, for a VTOL type application, the propulsion units consist of double star electrical machines mechanically driving a propeller. Each star associated with its inverter is connected to a separate HVDC bus. Thus, the faulting of an HVDC bus does not result in the loss of a propulsion unit.

[0021] Advantageously, energy storage means are also connected to the distribution buses.

[0022] These energy storage means participate in the generation and stabilization of the electricity supply network by providing surplus energy obtained by hybridizing the electricity supply of the electrical loads to be supplied, particularly electric motors.

[0023] Preferably and advantageously, the energy storage means are batteries associated with direct current to direct current converters (known by the acronym DC / DC, from the English “Direct Current / Direct Current”).

[0024] Thus, such a DC / DC converter placed between the battery and the direct current electrical network makes it possible to stabilize the electrical network. The addition of such a converter also has the advantage of perfectly controlling, and therefore protecting, the current supplied or absorbed by the battery. Advantageously, the rectifiers of each generator include contactors at their input and output.

[0025] This makes it possible to electrically disconnect a faulty rectifier from the distribution bus on which it is mounted and isolate it from the rest of the network.

[0026] Advantageously, the power supply network also includes contactors at each electrical load to be supplied and at each energy store.

[0027] This makes it possible to electrically disconnect a faulty electrical load or energy store from the distribution bus on which they are mounted and isolate them from the rest of the network.

[0028] Advantageously, the electrical network includes a centralized control unit per generator associated with its energy storage unit.

[0029] Thus, in the case where the contactors are naturally open, the dynamics of centralized control of the electrical network allows good management of the power requirement and voltage stabilization of the distribution buses while increasing the energy efficiency of all sources. Centralized control also has an advantage when closing the contactors, since it is possible to impose a similar voltage on the two HVDC buses, in order to limit the current peak due to balancing the electrostatic energies of the two buses.

[0030] On the contrary, decentralized control does not allow for high control dynamics and high efficiency optimization. On the other hand, its main advantage lies in the situation where the contactors are naturally closed. The separation of the two HVDC buses does not prevent the bus voltage from continuing to be regulated, since all the rectifiers operate individually.

[0031] The invention also relates to an aircraft turbogenerator characterized in that it is equipped with a power supply network having any one of the aforementioned characteristics.

[0032] Thus, a turbogenerator equipped with such an electrical network makes it possible to guarantee the supply of electrical energy to the electrical loads of the network while providing the possibility of isolating a part of the network which would be affected by a failure. Brief description of the figures

[0033] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: [ Fig. 1 ] There figure 1illustrates an example of an illustrative electrical power supply network not covered by the claims but included to facilitate the understanding of the invention, comprising two generators each having three stators mounted in parallel on two distribution buses; [ Fig. 2 ] There figure 2 illustrates another example of an illustrative electrical power supply network not covered by the claims, comprising two generators each having two stators mounted in parallel on two distribution buses; [ Fig. 3 ] There figure 3 illustrates a power supply network similar to that of the figure 2 , in which, according to the invention, the rectifiers of the generators are crossed on the distribution buses; and [ Fig. 4 ] There figure 4 illustrates an exemplary embodiment of the electrical supply network according to the invention comprising inductors and resistors between two distribution buses. Detailed description of the invention

[0034] In reference to the figures 1 to 3 , the present invention relates to an electrical power supply network 1 for an aircraft comprising a plurality of electrical loads C1, C2, C3, C4 to be supplied. These electrical loads are, for example, electric motors associated with inverters and each driving a propeller.

[0035] This electrical network 1 comprises an aircraft gas turbine (not shown) mechanically connected to two generators 2, 3 thus forming a turbogenerator assembly. However, the electrical network 1 could comprise more than two generators.

[0036] In the illustrative example of the figure 1, generator 2 is a so-called "triple star" or nine-phase generator, in other words it comprises three electrical chains 2a, 2b, 2c connected to electrical loads C1, C2 to be supplied. Each electrical chain 2a, 2b, 2c comprises a stator (not shown) integrating a set of coils forming a polyphase element at the output, and a rectifier 20a, 20b, 20c.

[0037] Similarly, generator 3 is a generator and comprises three electrical chains 3a, 3b, 3c connected to electrical loads C1, C2 to be supplied. Each electrical chain 3a, 3b, 3c comprises a stator (not shown) and a rectifier 30a, 30b, 30c.

[0038] Each generator 2, 3, could however, as an illustrative example not covered by the claims, comprise only one stator, and consequently only one electrical chain, the generator then being called a “simple star”, or two stators as illustrated in figures 2and, according to the invention, 3, known as the “double star” generator.

[0039] The electrical loads C1, C2, C3, C4 are connected to the generators 2, 3 via two direct current distribution buses 4, 5, which is not limiting. The electrical loads C1, C2, C3, C4 can be passive or active loads, such as converters with regulation, for example an inverter and a three-phase motor. For safety reasons, the number of distribution buses is at least equal to two. Indeed, an aim of the present invention is to be able to isolate a fault that would occur on a distribution bus in order to prevent this fault from propagating to the entire electrical supply network 1.

[0040] However, the number of distribution buses can be higher, and at most equal to the number of rectifiers. For weight and cost reasons, it is preferable to minimize the number of HVDC buses, ideally as many as generators.

[0041] The electrical chains 2a, 2b, 2c and 3a, 3b, 3c, and consequently their respective stators and rectifiers 20a, 20b, 20c, 30a, 30b, 30c, are mounted in parallel on the distribution buses 4, 5.

[0042] As can be seen on the figure 3, according to the invention the rectifiers 20a, 20b and 30a, 30b of the generators 2, 3 respectively, are mounted alternately on the distribution buses 4, 5. In other words, the rectifiers 20a, 20b and 30a, 30b of the generators 2, 3 are crossed on the buses 4, 5. In the case where the HVDC buses are isolated, this configuration has the advantage of not losing all the generation from the turbine on one bus. This makes it possible to minimize the power that the battery must provide.

[0043] More particularly and advantageously, the number of distribution buses of the electrical power supply network according to the invention is equal to the desired number of electrical load segregations. Thus, in the illustrated examples, which are in no way limiting, the loads C1, C2, C3, C4 are segregated into two sets distributed over the two distribution buses 4, 5.

[0044] In reference to the figures 2 And 3, the electrical supply network also comprises energy storage means mounted on the distribution buses 4, 5. These energy storage means are, for example, electric batteries 6, 7. The energy storage means may, however, be implemented other than in the form of batteries and may be, for example, thermal batteries or supercapacitors. Such energy storage means make it possible in particular to temporarily supplement a power requirement, in particular when starting the turbogenerator assembly or during a sudden flight maneuver requiring power with a very short response time.

[0045] In order to improve the power supply network 1 by guaranteeing stability of the electrical power supply network 1 and by ensuring the permanent availability of the possibility of hybridization of the electrical power supply network 1, it is advantageously provided to associate with each battery 6, 7, a DC / DC converter 60, 70, arranged between each battery 6, 7 and the direct current electrical network.

[0046] The electrical power supply network 1 also comprises a plurality of contactors 10 associated with the various elements mounted on the electrical power supply network 1 and making it possible to connect or disconnect these elements from the distribution buses 4, 5 to which they are connected and to isolate them when they are faulty in order to prevent such a fault, such as a short circuit, from spreading to the entire electrical power supply network 1.

[0047] Thus, each rectifier 20a, 20b, 20c, 30a, 30b, 30c can be disconnected from the distribution buses 4, 5 by means of contactors 10, at their AC input or their DC output.

[0048] Likewise, each electrical load C1, C2, C3, C4 to be supplied and each battery 6, 7, via their respective inverter 60, 70 if applicable, can be disconnected from the distribution buses 4, 5 by means of contactors 10.

[0049] The electrical supply network 1 according to the invention is particularly remarkable in that it comprises contactors 100 adapted to electrically connect or disconnect the distribution buses 4, 5 from one another, in other words either the distribution buses 4, 5 are connected to one another, or they are isolated from one another.

[0050] According to a first embodiment, the contactors 100 are configured to, by default, electrically connect the distribution buses 4, 5 to each other.

[0051] This first embodiment has the interesting advantage of being able to multiply the energy sources that can supply the electrical loads of the electrical supply network 1. Indeed, the different generators 2, 3 and the different batteries 6, 7 of the network 1 being thus shared, the entire network 1 can compensate for a loss of one or more energy sources and continue to supply, in part, the loads C1, C2, C3, C4.

[0052] When the distribution buses 4, 5 are thus linked, it is possible, via the contactors 100, to disconnect them in the event of a fault such as a short circuit on one of the buses 4, 5 so as to prevent such a fault from spreading to the entire network.

[0053] Starting from this initial state in which the distribution buses 4, 5 are connected, in other words one in which the contactors 100 are in a closed state, if a fault occurs on one of the buses 4, 5 requiring disconnection, for example if a short circuit is detected on one of the buses, the contactors 100 are configured so as to be able to switch to an open state, under a short-circuit current. The contactors 100 are then assimilated to disconnection elements.

[0054] The use of all these contactors 10, 100, although interesting in order to protect the entire electrical supply network 1, can weigh down the network 1, which is not desired.

[0055] Thus, an interesting but in no way limiting example of an embodiment is that the contactors 100 comprise “pyrofuse” elements, namely conductive sections configured to melt when too high a temperature is reached in the cable, corresponding to too high a current passing through the cable.

[0056] According to a second embodiment, the contactors 100 are configured to, by default, electrically disconnect the distribution buses 4, 5 from each other.

[0057] This second embodiment has the interesting advantage of being able, by default, to promote the protection of the entire network 1. The distribution buses 4, 5 thus separated, in other words isolated from each other, it is possible, in the event of a fault on one of the buses 4, 5, such as a short circuit, not to lose the entire electrical supply network 1. Consequently, in the event that a short circuit occurs on one of the buses 4, 5, part of the electrical loads C1, C2, C3, C4 would continue to be supplied.

[0058] When the distribution buses 4, 5 are thus isolated from each other, it is possible and easy, via the contactors 100, to connect them in the event of a one-off need for additional electrical energy on part of the network 1

[0059] Starting from this initial state in which the distribution buses 4, 5 are disconnected, in other words one in which the contactors 100 are in an open state, if for example one of the batteries 6, 7 does not provide the electrical energy necessary to supply part of the electrical loads C1, C2, C3, C4 of the network 1, the contactors 100 are configured so as to be able to switch to a closed state, in order to allow the part of the network having this occasional need for electrical energy to benefit from another source of electrical energy supply.

[0060] The present invention thus provides numerous advantages. It makes it possible to segregate the electrical supply network 1, thus making it possible to prevent a distribution bus 4, 5 from being a cause of failure of the entire network. In addition, the possibility of being able to connect or disconnect the buses 4, 5 in the initial state or when a fault or a need occurs allows simplicity in the regulation of the entire electrical supply network 1.

[0061] Advantageously, the electrical supply network 1 comprises a control unit (not shown) for the generators 2, 3 and the batteries 6, 7, which can be either decentralized or centralized.

[0062] In the case where the control unit is decentralized, the electrical energy sources, namely the generators 2, 3 and the batteries 6, 7, participate independently in the supply of the electrical supply network 1.

[0063] Starting from an initial state in which the contactors 100 are closed so as to connect the distribution buses 4, 5, a disconnection of the buses 4, 5 (in other words, the opening of the contactors 100) is transparent to the control unit, so that no reconfiguration of the control is necessary.

[0064] However, the electrical loads C1, C2, C3, C4 such as electric motors driving the thrusters of an aircraft not affected by this disconnection must compensate for the energy power requirement. Indeed, the detection of a failure such as a short circuit therefore leads to a change in the operating setpoint of the electrical loads C1, C2, C3, C4, namely the electric motors powering the thrusters, in order to maintain the flight dynamics of the aircraft. In parallel, it is necessary to adapt a setpoint of the energy power supplied by the gas turbine to the generators 2, 3 must be adapted. The batteries 6, 7 are necessary to intervene during the power transient because the dynamics of the turbine do not allow the electrical dynamics of the motors to be followed.

[0065] In the case where the distribution buses 4, 5 are initially disconnected, the loss of one or more sources of electrical energy requires the closing of the contactors 100 to obtain a connection of the distribution buses 4, 5 in order to pool the different energy sources (generators 2, 3 and batteries 6, 7) across the entire network 1 and to guarantee the power requirement of the electrical loads C1, C2, C3, C4 to be supplied.

[0066] However, when the distribution buses 4, 5 are initially disconnected and it is desired to connect them, it is appropriate that a voltage level between the distribution buses 4, 5 is substantially equivalent. Indeed, when connecting the buses 4, 5, if a voltage difference is present between the buses 4, 5, this can create a current peak during a rebalancing of these voltages. This current peak, if it is small, for example of the order of a few tens of amperes, can be absorbed by the network 1, on the other hand, if it is too high, for example of the order of several hundred amperes, the current peak cannot then be absorbed which can be harmful for the entire electrical network 1.

[0067] However, with such a decentralized control unit, since the voltage levels of the distribution buses 4, 5 of network 1 are not known, the risk of a current peak occurring when connecting buses 4, 5 is high. This current peak is due to the rebalancing of the voltages of the two capacitors, this current is limited only by the impedances of the conductive sections.

[0068] Similarly, such a current peak can be partly absorbed by the batteries 6, 7. In the same way, the use of super-capacitors 8, 9 on the network allows to better absorb the current peak, but this does not change the harmful nature of the current peaks and their capacity to deteriorate the components. The addition of inductors Lc and resistors Rc between the two HVDC buses 4, 5, as illustrated in the figure 4 , makes it possible to limit transient variations in current and to dissipate part of this current in the form of heat.

[0069] However, it is necessary to be able to equalize the first and second voltages of the distribution buses 4, 5, or at least have similar voltages, before connecting them.

[0070] Thus, according to a second embodiment of the invention, the control unit is centralized, in other words it is possible to intervene on the electrical energy sources of the network 1 in order to regulate their energy power requirements.

[0071] Such a centralized control unit comprises means for measuring, on the one hand, a first voltage in a first of the distribution buses 4, 5 and, on the other hand, a second voltage in a second of the distribution buses 4, 5. The centralized control unit also comprises means for controlling the converters 60, 70 configured to vary the first voltage and the second voltage.

[0072] The centralized control unit has the interesting advantage of being able to act directly on the converters 60, 70 so as to vary the voltages of the distribution buses 4, 5 so that the first voltage and the second voltage are substantially equal. Thus, the risk of having a current peak at the connection of the distribution buses 4, 5 is then eliminated.

Claims

1. An electrical energy supply network (1) of an aircraft provided with a plurality of electrical loads (C1, C2, C3, C4) to be supplied, said supply network (1) comprising at least two generators (2, 3) configured to be part of a turbogenerator of the aircraft and adapted to provide an electrical energy source comprising, each, at least one stator associated with a rectifier (20a, 20b, 20c; 30a, 30b, 30c), the stators of the generators (2, 3) being connected to at least two distribution buses (4, 5) arranged to supply the plurality of electrical loads (C1, C2, C3, C4), the electrical energy supply network comprising contactors (100) adapted to electrically connect or disconnect the distribution buses (4, 5) from each other, the rectifiers (20a, 20b, 20c; 30a, 30b, 30c) of the generators (2, 3) being mounted alternately on the distribution buses (4, 5).

2. The supply network (1) according to claim 1, characterized in that, by default, the contactors (100) are configured to electrically connect the distribution buses (4, 5).

3. The supply network (1) according to claim 1, characterized in that, by default, the contactors (100) are configured to electrically disconnect the distribution buses (4, 5).

4. The supply network (1) according to one of the preceding claims, characterized in that energy storage means are also mounted on the distribution buses (4, 5).

5. The supply network (1) according to the preceding claim, wherein the energy storage means are batteries (6, 7) associated with converters (60, 70).

6. The supply network (1) according to one of the preceding claims, characterized in that the rectifiers (20a, 20b, 20c; 30a, 30b, 30c) of each generator (2, 3) comprise contactors (10) at the level of their input and their output.

7. The supply network (1) according to one of the preceding claims, characterized in that it also comprises contactors (10) at the level of each electrical load (C1, C2, C3, C4) to be supplied and of each energy storage device (6, 7).

8. The supply network (1) according to one of the preceding claims, characterized in that it comprises a centralized control unit for the generators (2, 3) and the energy storage devices (6, 7).

9. An aircraft turbogenerator, characterized in that it is equipped with a supply network (1) according to any one of claims 1 to 8.