EP2260559A2

EP2260559A2 - Electrical network

Info

Publication number: EP2260559A2
Application number: EP09729547A
Authority: EP
Inventors: Alain Tardy
Original assignee: Thales SA
Current assignee: Thales SA
Priority date: 2008-04-09
Filing date: 2009-04-09
Publication date: 2010-12-15
Also published as: FR2930085B1; FR2930085A1; WO2009125012A2; WO2009125012A3; CN102037625A; JP2011521606A; CN102037625B; JP5597876B2

Abstract

The invention relates to an electrical network. The invention is particularly useful in aeronautics for commercial jumbo jets that increasingly comprise onboard electrical devices. The electrical network includes: two devices (21, 26, 27, 35, 36) capable of either providing or consuming electric power, and a transferring means, connected between the two devices (21, 26, 27, 35, 36) and enabling power exchange between the two devices (21, 26, 27, 35, 36). According to the invention, the transferring means includes a reversible continuous-alternative converter (22, 23, 24, 25), the converter (22, 23, 24, 25) capable of being controlled in continuous-continuous step-down or step-up mode. In a particular embodiment of the invention, the first device is a high tension continuous bus, and the network includes several second devices, whereon the charges (26, 27) and a low tension continuous bus upon which a battery (35) may be connected. The network includes a plurality of non-dedicated converters that may be connected between the first device and any of the second devices.

Description

Electrical network

The invention relates to an electrical network. The invention finds particular utility in aeronautics for large commercial aircraft which comprise more and more onboard electrical equipment. This equipment is very varied in nature and its energy consumption is very variable over time. For example, the internal air conditioning and lighting systems are in almost continuous operation, so redundant safety systems such as steering controls are used only exceptionally.

Generally, the aircraft has three-phase electrical generators to supply all the electrical equipment on board called loads thereafter. These generators deliver for example a voltage of 115 V at a frequency of 400 Hz to an AC bus of the aircraft. On board an aircraft, there is for example one or more main generators, well known in the Anglo-Saxon literature under the name "Main Generator". These are rotating electrical machines driven by the engine (s) of the aircraft. Other generators can feed the AC bus such as for example an auxiliary generator well known in the English literature as the "Auxillary Power Unit" and driven by a turbine dedicated to this generator or a generator park put airplane layout when on the ground, by many airports. This fleet generator makes it possible to avoid using the auxiliary generator when the aircraft is on the ground.

Recently, following the appearance of high power loads (electric motors or AC sub-networks) requiring to be powered by three-phase voltage inverters, high voltage DC buses powered from the AC bus have been installed on board aircraft. through rectifiers. These high voltage DC buses are well known in the English literature as HVDC for "High Voltage Direct Current". Subsequently, the high voltage DC bus will be called the HVDC bus.

The aircraft also has batteries to power certain loads when alternative sources (generators or park group) are not available. In particular, the batteries must rescue some computers or critical electrical systems such as flight controls, braking, thrust reversing engines or starting turbines through a low-voltage DC bus. Batteries historically have a low voltage for example

Continuous 24V (or possibly 48V continuous in the future) to supply as directly as possible power supplies of critical computers whose current standard is 28V continuous and to limit the number of batteries in series. For higher electrical power loads such as the braking system, thrust reversal or engine starting, continuous DC-DC converters are used to be able to use low-voltage batteries whose voltage is much lower than that of HVDC high-voltage continuous bus. One could also consider using higher voltage specific batteries for these loads so as to limit or cancel the necessary voltage rise between the battery and the HVDC bus.

Continuous low voltage buses, for example continuous 28V, are generally created from the AC bus by means of a transformation and rectification unit, produced by many aeronautical equipment manufacturers. This unit is well known in the Anglo-Saxon literature under the name "Transformer Rectifier Unit" and will be called thereafter: TRU. The TRU is powered by the AC bus and provides a DC voltage of 28V. The TRU generally comprises a transformer operating at the AC mains frequency of the aircraft, for example between 300 Hz and 1200 Hz.

The low voltage batteries are then charged either directly by the low voltage DC buses or through a battery charger using a continuous DC converter. Another solution for realizing the energy transfer link between a low-voltage DC bus and an HVDC bus is to implement either a bidirectional pulse-width modulated continuous-DC dedicated converter using a high-frequency transformer, or two continuous continuous-to-peak converters using each a high frequency transformer. High frequency means a frequency greater than 1 kHz.

This solution, using high frequency pulse width modulated converters with a high power level, is generally much less reliable, more expensive and heavier than the conversion solution implementing a TRU powered by an AC network.

Since the TRU is not bidirectional, the AC bus is then supplied from the low-voltage DC bus by a generator or by a dedicated three-phase inverter. The purpose of the invention is to simplify the realization of the following conversion functions by limiting the use of resources dedicated to these functions: 1. supply of a DC voltage controlled continuous bus from a DC voltage bus Y; 2. Charge a X-voltage battery from a DC voltage bus

Y;

3. supply of a regulated voltage DC bus Y from a DC voltage bus X or a voltage battery X;

4. charging a Y voltage battery from a voltage bus X; In the conversion functions described above, X is smaller than Y. Other conversion functions can of course be extrapolated from the means of the invention.

For this purpose, the subject of the invention is an electrical network comprising:

• two equipment likely to supply or consume electricity,

Transfer means connected between the two devices and allowing the two devices to exchange energy, characterized in that the transfer means comprise a reversible DC-to-AC converter, the converter being able to be controlled continuously-DC in step-down mode or as a voltage booster.

A first of the two devices forms for example a power supply bus such as for example a first continuous bus. One of the second equipment forms for example a second continuous bus which can connect an accumulator battery that can either be charged by the second bus or provide it with energy if needed.

In a particular embodiment where the two devices are formed of two continuous buses whose voltages are different X and Y, the transfer means allow the exchange of electrical energy between the buses in one direction and the other. Each bus can be connected to a battery. The invention makes it possible to control the exchange of energy from or towards the battery or batteries. The transfer means make it possible to regulate the voltage of one of the buses when it is powered by the other or to regulate the current flowing between the continuous buses.

For this purpose, the transfer means comprise between the two buses:

1. one or more reversible DC / DC multi-phase inverters, whose DC input is connected to the voltage bus Y and can be controlled:

• three-phase voltage inverter;

• Continuous-to-DC down-converter, single-phase in parallel; • or continuous-current step-up DC voltage converter in parallel;

2. optionally connected to the AC output of the inverter, a voltage-reducing TRU whose transformation ratio makes it possible to deliver the voltage X from the voltage Y; 3. possibly a reversible DC-AC inverter, the DC input of which is connected to the voltage bus X, which can be controlled in three-phase inverter down-voltage mode and whose AC output is connected to a voltage-boosting TRU whose ratio transformation allows to deliver the voltage Y from the voltage X present at the input of the inverter.

In a particular embodiment where the first equipment forms a power supply bus such as for example an HVCD bus, the network comprises a plurality of second devices, a plurality of reversible converters for exchanging energy between the bus and the different second devices, and switching means for varying an association between the converters and the second equipment. Advantageously, the converters can all exchange energy with each second equipment. Any second device does not have a dedicated converter.

In other words, a reversible DC-to-AC converter can be used to power different aircraft loads from the aircraft power bus. It is possible to pool several converters through switching means for varying the association between converters and loads, batteries or a second DC bus being considered as a particular load or source. Thus, in the event of the unavailability of a converter, it is possible to assign another converter to the connection between batteries and buses by using the switching means. These switching means can operate in real time thus improving the availability of batteries and more generally the reliability of the electrical network of the aircraft.

The invention is described in relation to an electrical network on board an aircraft. It is understood that it can be implemented in any other field such as for example the automotive field where the electric motor develops and therefore the use of batteries. The batteries can be replaced by any other energy storage element such as for example a capacitor or a super capacitor. For convenience, in the following description, we will use the term battery for any energy storage element.

The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, a description illustrated by the attached drawing in which:

FIG. 1 represents a circuit diagram of a network installed on board an aircraft;

Figure 2 schematically shows a TRU used in the network of Figure 1;

FIG. 3 diagrammatically represents an exemplary embodiment of a converter used in the network of FIG. 1; For the sake of clarity, the same elements will bear the same references in the different figures.

FIG. 1 schematically represents various electrical equipment on board an aircraft, in particular a wide-body commercial aircraft. A main generator 10 denoted MG is driven by one of the engines of the aircraft. The generator 10 operates when the engines of the aircraft operate and delivers for example a voltage of 115 V at a frequency of 400 Hz to an AC network 11 of the aircraft. Disconnection means 12 for opening the link connecting the generator 10 to the network 11. An auxiliary generator 13, APU noted, is driven by a turbine dedicated to the generator 13 to supply the AC network 1 1 the voltage of 115 V. Similarly, disconnection means 14 open the link connecting the auxiliary generator 13 to the network 11. The turbine operates using the fuel of the aircraft and is implemented when the aircraft is on the ground.

On board the aircraft, is also installed a rectifier 20 connected to the AC network 1 1 and for delivering a DC voltage to a high voltage DC power supply bus 21 denoted HVDC according to an English abbreviation for: "High Voltage Direct Curent. A voltage commonly used for the high voltage DC bus 21 is 540V.

The DC bus 21 supplies several energy converters 22 to 25 each intended to feed a load, for example 26 and 27 by means of switching means 30. The representation of FIG. 1 is schematic. In practice, a load can be fed by several converters or a converter can supply several loads. Some charges can be supplied with DC voltage and the associated converter then converts the voltage of the DC bus 21 into a voltage that can be used by the load in question. In a jumbo jet, there are many charges using an AC voltage of 1 15 V at a frequency of 400 Hz. To power these loads, the converters 24 and 25 are inverters. Known inverters have the particularity of being reversible. Each converter 22 to 25 can be assigned in real time to the various loads 26 and 27 as a function of the instantaneous need of each load and according to the availability of each of the converters 22 to 25. The switching means 30 make it possible to vary in real time the association between converters 22 to 25 and loads 26 and 27. The combination of converters 22 to 25 and loads 26 and 27 is based on the instantaneous power requirement and the instantaneous control mode of the load that it is associated. The mode of control of the load depends essentially on the type of load. By way of example commonly used in an aircraft, mention may be made of speed, torque or position regulation, anti-icing or de-icing, constant power operation and various engine control strategies (defluxing, control with or without sensor).

The switching means 30 comprise, for example electrically controlled switches for associating each converter to all the loads that are compatible. Compatible means that several loads can operate using the same converter, especially when they require the same power supply, for example a voltage of 115 V at a frequency of 400 Hz. Converters for delivering the same power supply form a group whose members are interchangeable. The different members of a group are advantageously identical. This reduces the costs of converting the converters by standardizing their production and simplifies the maintenance of the aircraft by keeping in stock only one type of converter. As will be seen later, certain types of converters can deliver several different power supplies depending on the driving mode of the converter. Thus, to the same group of converters, one can for example associate charges operating in AC voltage, for example 1 15V 400Hz, and charges operating in DC voltage such as batteries.

The group is reconfigurable according to the instantaneous need for loads that can be powered by this group. It is not necessary to have a converter dedicated to each load. Indeed, the charges do not all work simultaneously. The number of converters in the same group is defined according to the maximum instantaneous power that all the loads associated with a group can consume. This power is lower than the addition of the maximum powers of each load. The switching means 30 therefore reduce the number of on-board converters and therefore the mass of these converters. In addition, reconfiguration improves the availability of loads. Indeed, in case of failure of a converter, another converter of the same group can immediately take over to feed a given load. Certain critical loads, such as for example control surfaces, can thus operate with a secure power supply without requiring the redundancy of a converter only dedicated to these commands. The set of converters of the same group then forms a common resource capable of supplying a group of loads. Within the same common resource, the different converters that compose it are undifferentiated.

A particular load of the network is constituted by a battery 35 connected to one of the converters via the switching means 30. In conventional manner on aircraft, it known to use a battery 28V nominal continuous voltage. Other battery voltages are of course possible for the implementation of the invention. From a bus 21, 540V continuous, one can drive the converter 22 so that it directly delivers the DC voltage of 28V to a second DC bus 33 can supply the battery 35. It is possible to interpose between the second bus 33 and the battery 35 a battery charger for regulating the current charging the battery. It is also advantageous to insert, for charging the battery 35, between the converter 22 and the battery 35, a transformation and rectification unit 36 called TRU thereafter. The TRU 36 is supplied with AC voltage 1 15V 400Hz and provides a DC voltage of 28V. The use of a TRU facilitates the operation of the converter 22 used in the inverter which receives a DC voltage of 540V. The assembly formed by the TRU 36 and the battery 35 can be considered as a load that can be associated with one of the converters by the switching means 30. FIG. 2 diagrammatically represents an example of a TRU 36 comprising a transformer or autotransformer 37 receiving the alternating voltage 1 15V 400Hz three-phase delivered by the converter 22 operating as an inverter. In the embodiment where the TRU 36 is located between the converter 22 or 23 and the DC bus 33, the transformer 37 allows to lower the voltage it receives. The transformer 37 delivers a three-phase voltage of the order of 20V which once rectified by a rectifier

38 allows to obtain the DC voltage of 28V to supply the battery 35.

The rectifier 38 is for example made by means of a bridge of full-wave diodes delivering a voltage smoothed by capacitors.

FIG. 3 is a schematic and simplified representation of an exemplary embodiment of one of the converters 22 to 25. The converter comprises two terminals 40 and 41, the terminal 40 being connected to the positive pole of the DC bus 21 and the terminal 41 being connected to the positive negative pole of the DC bus 21. Between the terminals 40 and 41, the converter comprises three branches 42, 43 and 44 each comprising two electronic switches, T421 and T422 for the branch 42, T431 and T432 for the branch 43 and, T441 and T442 for the branch 44. In each branch 42, 43 and 44 the two switches are connected in series and a diode is connected in parallel with each switch. The reference of the diode is D followed by the numerical part of the reference of the associated switch, for example the diode D 421 is connected across the switch T 421. Each diode is connected antiparallel to the direction of the current flowing. in each switch of the positive terminal 40 to the negative terminal 41 of the DC bus 21. The switches T421 to T442 are for example all identical and bipolar transistor type insulated gate well known in the English literature by the acronym IGBT for : "Insulated Gatte Bipolar Transistor". In each branch 42, 43 and 44, at the common point of the two switches, a self, respectively L42, L43 and L44 is connected by its first terminal. A second terminal, 46, 47 and 48 of each inductor, respectively L42, L43 and L44, allows the converter to supply a three-phase load. Capacitors C421 to C442 are connected between one of the terminals 46, 47 and 48 and one of the terminals 40 and 41. When the electrical energy is supplied to the converter by the continuous network 21, the converter can operate in voltage inverter. On the other hand, when the electrical energy is supplied alternately between the terminals 46, 47 and 48, for example by a regenerative charge or a battery, the converter can operate as a current rectifier. It is possible to use a TRU 36 comprising internal means for regulating the DC voltage that it delivers to the battery 35. But advantageously, the regulation of the voltage delivered to the battery 35 is done by means of driving the converter 22 associated with the battery 35, for example by varying a duty cycle of the converter 22. The means for providing this regulation comprise a link 39 connecting the TRU 36 to the converter in question. The switching means 30 may comprise for this purpose switches 50 and 51 for selecting the converter connected to the input of the TRU 36. When the converter 22 operates inverter to supply the battery 35, the voltage measured at the output of the TRU 36 on the bus 33 makes it possible to adapt a cyclic opening and closing ratio of the switches T421 to T 442 to maintain the DC voltage delivered by the TRU within a predetermined range. An electronic device, belonging to the converter 22, makes it possible to control the opening and the closing of the switches T421 to T 442. In a known manner, such a device is mandatory in each converter, or associated with it, so that the switches it comprises function consistently. It is therefore advantageous to deport the regulation function of the voltage supplied to the battery 35 of the TRU 36 to the associated converter by using its electronic control device. This arrangement also improves the overall reliability of the power grid. Indeed, by simplifying the TRU, which no longer includes internal control means, its reliability increases. Moreover, the possible failures of an electronic control device of a converter are mitigated in real time by a possible reconfiguration of the converters within a group to which the battery 35 is associated.

When the battery 35 is to be used to power the DC bus 21, a reconfiguration of the switching means 30 is operated to bypass the TRU 36. In other words, the battery 35 is directly connected to the terminals 46, 47 and 48 without crossing the TRU 36 which is unidirectional. This connection is made, via a link 52, by the switching means 30. The converter, as shown in Figure 3, then operates as a single-phase elevator. More precisely, each branch and its associated inductor makes it possible to raise the voltage supplied by the battery 35. For example, for the branch 42, alternatively the switch T422 is used to store energy in the inductor L42 in the form of a current flowing through it and the diode D421 to release the energy stored to the terminal 40 connected to the DC bus 21. The three branches and the associated inductors operate with a phase shift of ττ / 3. The converter can be driven to operate as a multi-phase inverter to supply the battery 35 through the TRU 36 or N single-phase voltage boosters to supply the DC bus 21 from the battery, where N represents the number of phases of the inverter, the N elevators being out of phase by π / N.

The operation in N single-phase voltage boosters has a disadvantage when the DC bus voltage 33 is much lower than the DC bus voltage 21. The efficiency of the converter is then rather poor. To overcome this drawback, it is possible to interpose between the first DC bus 21 and the selected converter a TRU making it possible to supply the first bus 21 from the second bus 33. This TRU then comprises a transformer enabling the voltage to be raised receives. This embodiment requires completely disconnecting the converter to connect the terminals 40 and 41 of the converter, either to the HVDC 21 continuous bus, but to the DC low voltage bus 33. The TRU is then connected between the terminals 46, 47 and 48 of the converter. on the one hand and the HVDC continuous bus 21.

More generally, an inverter as shown in FIG. 3 can be driven in a first direction, when it receives energy from the bus 21, either in multiphase inverter or in N DC-DC converters. The inverter can also be driven in a second direction, opposite to the first one, either as a current rectifier, when it receives an alternating voltage of a regenerative load, or as N DC-DC up-converter converters. The control of the converter can be modified in real time simultaneously with the switches of the switching means 30.

This type of reversible DC-AC converter can be controlled continuously-DC in lift or step down is much simpler to make and much more reliable than a bidirectional continuous-DC converter comprising a high frequency transformer.

Claims

1. Electrical network comprising:

Two equipment (21, 26, 27, 35, 36) capable of either supplying or consuming electrical energy,

Transfer means connected between the two devices (21, 26, 27, 35, 36) and allowing the two devices (21, 26, 27, 35, 36) to exchange energy, characterized in that the transfer means comprise a converter (22, 23, 24, 25) DC-reversible reversible, the converter (22, 23, 24, 25) can be controlled continuously-DC by step-down or voltage booster.

2. Electrical network according to claim 1, characterized in that a first of the two devices (21, 26, 27, 35, 36) forms a power supply bus (21), in that the network comprises a plurality of second devices (26, 27, 35, 36), a plurality of reversible converters (22, 23, 24, 25) for exchanging energy between the bus (21) and the different second devices (26, 27, 35, 36), and switching means (30) for varying an association between the converters (22, 23, 24, 25) and the second devices (26, 27, 35, 36).

3. The electrical network of claim 2, characterized in that the converters (22, 23, 24, 25) can all exchange energy with each second equipment (26, 27, 35, 36).

4. Electrical network according to claim 3, characterized in that the converters (22, 23, 24, 25) are identical.

Electrical network according to one of the preceding claims, characterized in that the first device is a first continuous bus (21) and in that the second device (26, 27, 35, 36) is a second bus (33). to which a storage battery (35) can be connected.

6. The electrical network according to claim 5, characterized in that between the converter (22, 23, 24, 25) and the second DC bus (33), the network comprises a processing and rectifying unit (36).

Electrical network according to claim 6, characterized in that the transformation and rectification unit (36) located between the converter (22, 23, 24, 25) and the second DC bus comprises a transformer for lowering the voltage. he receives.

8. Electrical network according to any one of claims 6 or 7, characterized in that the voltage of the second DC bus is regulated using control means of the converter (22, 23, 24, 25).

Electrical network according to one of the preceding claims, characterized in that between the first continuous bus (21) and the converter (22,

23, 24, 25) the network comprises a transformation and rectification unit for supplying the first bus (21) from the second bus (33).

Electrical network according to claim 9, characterized in that the transformation and rectification unit located between the first DC bus (21) and the converter (22, 23, 24, 25) comprises a transformer for raising the voltage. he receives.

1 1. Electrical network according to one of the preceding claims, characterized in that the converter (22, 23, 24, 25) can operate as a multi-phase inverter or in N single-phase voltage boosters, N representing the number of phases of the inverter, the N elevators being out of phase by π / N.