Energy distribution system

Abstract

The present invention relates to an energy distribution system (20) for an aircraft comprising at least two electric power train units, each unit comprising a propulsion unit (1) powered by a plurality of energy storage units (13) and configured to supply a first direct current (DC) voltage. The energy distribution system (20) comprises at least one converter unit (25) configured to energize a DC bus (16) having a DC voltage lower than the first DC voltage provided by each energy storage unit (13), each converter unit (25; 35) comprising a DC / DC converter configuration (21) configured to convert the first DC voltage from the at least one energy storage unit (13) to a second DC voltage at the DC bus (16), and a DC bus battery (22) having a normal operating DC voltage of the second DC voltage. When the DC bus (16) is energized from the energy storage unit (13), the DC bus (16) supplies energy for charging the DC bus battery (22), and when the energy storage unit cannot energize the DC bus (16), the DC bus battery (22) supplies energy to the DC bus (16).

Description

Technical Field

[0001] The present invention relates to an energy distribution system configured to create a common DC bus for aircraft with improved stability. The present invention further relates to an aircraft equipped with the energy distribution system.

Background Art

[0002] An indispensable system in an electric aircraft functions properly by continuously supplying power and energy. This can be achieved by providing multiple redundant energy sources for each system or by distributing energy to critical systems through one or more common direct current (DC) buses. FIG. 1 shows a conventional system in which a common high-voltage DC bus is used to supply power to a propulsion unit and a DC / DC converter is provided to create a common low-voltage DC bus for supplying power to critical and non-critical loads.

[0003] In a conventional system, if the common high-voltage DC bus cannot energize the common low-voltage DC bus, there is a risk of voltage spikes or DC voltage interruption in the DC voltage of the common low-voltage DC bus.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In view of such a situation, a more stable and safe energy supply is required to energize the low-voltage DC bus.

[0005] It is an object of the present invention to provide an energy distribution system that aims to reduce, mitigate, or eliminate one or more of the above technical defects and drawbacks, either alone or in any combination.

Means for Solving the Problems

[0006] This objective is achieved by an energy distribution system for an aircraft comprising at least two electric power train units. Each power train unit comprises a propulsion unit supplied with power by a plurality of energy storage units, and each energy storage unit is configured to supply a first direct current (DC) voltage via a DC connection to the propulsion unit. The first DC voltage supplied by the energy storage units of each power train unit varies according to the state of charge and the power demand from the connected propulsion unit. The energy distribution system comprises at least one converter unit configured to energize a DC bus having a DC voltage lower than the first DC voltage provided by each energy storage unit, and each converter unit of the at least one converter unit comprises a DC / DC converter configuration configured to convert the first DC voltage from at least one energy storage unit to a second DC voltage at the DC bus, and a DC bus battery having a normal operating DC voltage of the second DC voltage. When the DC bus is energized from at least one energy storage unit, the DC bus supplies energy for charging the DC bus battery, and when at least one energy storage unit cannot energize the DC bus, the DC bus battery supplies energy to the DC bus.

[0007] An advantage of the present invention is that a more stable low-voltage DC bus is obtained compared to prior art solutions because the DC bus battery serves in transient phenomena.

[0008] Another advantage of the present invention is that emergency power can be obtained by the DC bus battery when the energy storage unit cannot energize the DC bus.

[0009] Further aspects and advantages are obtained from the detailed description.

Brief Description of the Drawings

[0010] The above content will become clear from the following detailed description of exemplary embodiments, as shown in the accompanying drawings in which like reference numerals refer to like elements across different drawings. The drawings are not necessarily to scale and emphasis has instead been placed on illustrating exemplary embodiments.

Figure 1

DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, aspects of the present disclosure will be described in more detail with reference to the accompanying drawings. However, the systems disclosed herein can be implemented in many different forms and should not be construed as limited to the aspects of the present disclosure. Throughout, like numbers in the drawings indicate like elements.

[0012] The terms used herein are for the purpose of describing particular aspects of the present disclosure only and are not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” include the plural forms as well, unless the context clearly dictates otherwise.

[0013] Some of the exemplary embodiments disclosed herein are directed to energy distribution systems intended for use in aircraft such as airplanes, helicopters, or other flyable machines.

[0014] FIG. 1 shows an energy distribution system 10 for providing a low-voltage DC bus within an aircraft according to the prior art. In this context, the expression “low-voltage DC bus” is exemplified by a 270V DC bus used to supply power to critical and non-critical loads within an aircraft. Other voltages may be used depending on the actual implementation of the system components.

[0015] In FIG. 1, the energy distribution system 10 includes four propulsion units 1 powered by four energy storage units 13 via a common high-voltage DC bus 14. Each propulsion unit 1 includes a drive unit 11 (comprising an alternating current (AC) electric motor that receives power from the common high-voltage DC bus 14 via a DC / AC inverter) and a propeller 12. The energy storage unit 13 may comprise a rechargeable battery or a battery pack. The voltage of the common high-voltage DC bus 14 varies, for example, between 480 and 800V (DC), depending on the state of charge and the power demand from the connected propulsion units 1.

[0016] A DC / DC converter 15 is provided to energize a 270V common DC bus 16 that supplies power to critical loads 17a and non-critical loads 17b operating at 270V DC. Further, a DC / DC converter 18 is provided to energize a 28V common DC bus 19 that supplies power to critical loads 17a and non-critical loads 17b operating at 28V DC. The loads are typically labeled 17 as shown in FIG. 3 and include both critical and non-critical loads.

[0017] Figure 2 shows an energy distribution system 20 for providing a low-voltage DC bus (e.g., 270V (DC)) in an aircraft according to an exemplary first embodiment of the present invention. The energy distribution system includes a plurality of power train units (four power train units A, B, C, and D in this embodiment). Each power train unit includes a propulsion unit 1 and a plurality of energy storage units 13. The propulsion unit 1 includes a drive unit 11 and a propeller 12. The drive unit 11 includes an alternating current (AC) electric motor and a DC / AC inverter. The DC / AC inverter receives DC power from the energy storage unit 13 and supplies AC power to the electric motor. In some examples, the electric motor is an induction motor and the DC / AC inverter is a variable frequency inverter. The plurality of energy storage units 13 are configured to supply a first direct current (DC) voltage via a DC connection to the drive unit 11 in the propulsion unit. The first DC voltage supplied by the energy storage unit 13 in each power train unit varies according to the state of charge and the power demand from the connected propulsion unit. For example, the first DC voltage can vary between 480 and 800V (DC).

[0018] The energy distribution system 20 further includes at least one converter unit 25 configured to energize a DC bus 16 having a DC voltage lower (e.g., 270V (DC)) than the first DC voltage (e.g., 480 - 800V (DC)) provided from each energy storage unit 13. The converter unit 25 includes a DC / DC converter configuration 21 configured to convert the first DC voltage from each energy storage unit 13 to a second DC voltage at the DC bus 16, and a DC bus battery 22 having a normal operating DC voltage of the second DC voltage.

[0019] The energy distribution system may include an external input 26 configured to supply energy to the DC bus 16 using an external connection when the aircraft is on the ground, provided that the switch 24 is closed. The switch 24 may be controlled by a controller (not shown) or may be a manually switchable switch.

[0020] The DC / DC converter configuration 21 includes four separate DC / DC converters a - d, one for each energy storage unit 13. For example, the energy storage unit of power train "A" is connected to DC / DC converter "a", and the energy storage unit of power train "B" is connected to DC / DC converter "b". The outputs from the separate DC / DC converters a - d are collectively connected to the DC bus 16.

[0021] The DC bus battery 22 is controlled by a battery management unit (BMU) 23 that is powered by the DC bus battery 22 via an internal DC / DC converter within the DC bus battery 22. Additionally, the DC bus battery 22 may be configured to supply power to the DC bus 16 at aircraft startup.

[0022] When the DC bus 16 is energized from the energy storage unit 13, it supplies energy to charge the DC bus battery 22, and also supplies energy to the critical load 17a and the non-critical load 17b that operate at 270V DC. Further, the DC bus battery 22 is configured to supply energy to the DC bus 16 when the energy storage unit 13 cannot be energized to the DC bus 16 via the DC / DC converter configuration 21. This may occur due to depletion of the charge in the energy storage unit 13. Also, the DC bus battery helps to provide a stable DC voltage level when a voltage spike or sudden surge occurs from the connected load 17. In the present embodiment, a DC / DC converter 18 is provided to energize the common DC bus 19 at 28V that supplies power to the critical load 17a and the non-critical load 17b that operate at 28V DC.

[0023] FIG. 3 shows an energy distribution system 30 for providing a plurality of low-voltage DC buses, for example at 270V (DC), within an aircraft according to an exemplary second embodiment. The energy distribution system 30 is mainly different from the system described with reference to FIG. 2 in one aspect. The energy distribution system 30 includes two converter units, a first converter unit 35-1 and a second converter unit 35-2, instead of using a single converter unit 25. Each converter unit is configured to energize separate DC buses 16-1, 16-2. In some embodiments, the first converter unit 35-1 is identical to the second converter unit 35-2.

[0024] Each of the converter units 35-1, 35-2 includes a DC / DC configuration 21 and is energized to a separate DC bus 16 and a DC bus battery 22 with a BMU 23. Each of the converter units 35-1, 35-2 further includes switches 33-1, 33-2 that are used to connect the separate DC buses to each other via an interconnection 34.

[0025] The energy distribution system 30 may include an external input 26 configured to supply energy to the DC buses 16-1 and 16-2 using an external connection when the aircraft is on the ground, provided that the switches 24 and 33 are closed. The switches 24 and 33 may be switches controlled by a controller (not shown) and / or manually switchable switches.

[0026] In this embodiment, each DC / DC converter configuration 21 includes separate DC / DC converters a to d, one for each energy storage unit 13. Each energy storage unit 13 is connected to two independent DC / DC converter configurations 21.

[0027] When each of the DC buses 16-1 and 16-2 is energized from the energy storage unit 13 via the DC / DC converters a to d, it supplies energy for charging each DC bus battery 22, and also supplies energy to a load 17 (critical load and / or non-critical load) operating at 270V DC. Also, the DC bus battery 22 is configured to supply energy to each DC bus 16 when the energy storage unit 13 cannot energize the DC buses 16-1 and 16-2 via the DC / DC converter configuration 21. Also, the DC bus battery helps to provide a stable DC voltage level when a voltage spike or sudden surge occurs from the connected load 17. In this embodiment, a separate DC / DC converter 18 is connected to each 270V DC bus 16 and energizes separate 28V DC buses 19-1 and 19-2 that supply power to a load 17 (critical load and / or non-critical load) operating at 28V DC. A switch 35 is provided between the 28V DC buses, and when closed, creates a common 28V DC bus. The switch 34 may be a switch controlled by a controller (not shown) and / or a manually switchable switch.

[0028] FIG. 4 shows an energy distribution system 40 for providing a plurality of low voltage DC buses, such as 270V (DC) and / or 28V (DC), in an aircraft according to an exemplary third embodiment.

[0029] The energy distribution system 40 differs mainly in one aspect from the system described with reference to FIG. 3. Instead of using individual DC / DC converters 18 to energize the 28V DC buses 19-1, 19-2 from the 270V DC buses 16-1, 16-2, the energy distribution system 40 further includes two converter units, a first converter unit 45-1 and a second converter unit 45-2, configured to energize the respective DC buses 19-1, 19-2.

[0030] Each converter unit 45-1, 45-2 includes a DC / DC converter configuration 41-1, 41-2 and is configured to energize the respective 28V DC buses 19-1, 19-2 and a low voltage DC bus battery 42 including a BMU 43. Each converter unit 45-1, 45-2 further includes switches 48-1, 48-2 that are used together to connect separate 28V DC buses to each other via an interconnection 47.

[0031] The energy distribution system 40 may further include an external input 46 configured to supply energy to the DC buses 19-1, 19-2 using an external connection when the aircraft is on the ground, provided that switches 44 and 48-1, 48-2 are closed. The switches 44 and 48 may be switches controlled by a controller (not shown) and / or manually switchable switches.

[0032] In this embodiment, the first DC / DC converter configuration 41-1 includes separate DC / DC converters a' and b' connected to two energy storage units 13 in power train units A and B, and the second DC / DC converter configuration 41-2 includes separate DC / DC converters c' and d' connected to two energy storage units 13 in power train units C and D.

[0033] When each DC bus 19 is energized from the energy storage unit 13, it supplies energy not only to charge each low-voltage DC bus battery 42, but also to supply energy to a load 17 (critical load and / or non-critical load) operating at 28 V DC. The low-voltage DC bus battery 42 is configured to supply energy to each 28 V DC bus 19-1, 19-2 when the energy storage unit 13 cannot energize the 28 V DC buses 19-1, 19-2. Also, the low-voltage DC bus battery helps to provide a stable 28 V DC voltage level when a voltage spike or sudden surge occurs from the connected load 17.

[0034] FIG. 5 shows an energy distribution system 50 for providing, for example, a 270 V (DC) low-voltage DC bus in an aircraft according to an exemplary fourth embodiment. The energy distribution system 50 is mainly different from the system described with reference to FIG. 4 in one aspect. The propulsion units 11, 12 are connected to a common high-voltage DC bus 51, and the energy storage unit 13 is connected to be energized from the common high-voltage DC bus 51, and the voltage can vary between 480 and 800 V (DC). The common high-voltage DC bus may be included in any of the above-described embodiments without departing from the concept of the present invention. The 28 V DC bus is omitted in FIG. 5.

[0035] Also, FIG. 5 shows a control unit 52 configured to control switches 33-1, 33-2, and optionally switch 24. The control unit 52 may be configured to control switches 44, 48-1, and 48-2 additionally arranged with respect to the 28V DC bus of FIG. 4. The control unit 52 monitors the state of the DC / DC converter 21 and senses the voltage levels of each 270V DC bus 16-1, 16-2 via a voltage sensor (not shown). If any voltage sensor indicates a decrease in voltage level, or if the state of the monitored DC / DC converter affects the voltage level of the DC bus, when a fault such as a voltage spike or surge occurs, the DC bus battery 22 may be used to energize the DC bus and stabilize the voltage level. Also, if the voltage level drops in any of the low-voltage DC buses, the control unit 52 may interconnect the low-voltage DC buses by closing switches 33-1, 33-2. The control unit may be controlled, if necessary, by an external signal from, for example, a pilot or a flight control computer.

[0036] FIG. 6 is a flowchart 60 showing an exemplary embodiment of an operation that may be performed by the control unit 52 of FIG. 5. The flow starts at step 61, and at step 62 the control unit monitors the state of each low-voltage DC bus to determine whether all low-voltage DC buses are energized.

[0037] In some embodiments, the state of the DC / DC converter is monitored.

[0038] In some embodiments, determining whether each low-voltage DC bus is energized includes sensing the voltage level of each low-voltage DC bus. In some embodiments, a combination of monitoring the state of the DC / DC converter and sensing the DC bus voltage is performed. If all DC / DC converters are operable and all low-voltage DC buses are energized (step 63), the flow returns to step 62 via step 63, indicating that each low-voltage DC bus is energized while each DC bus battery is being charged. However, if the control unit detects that a certain low-voltage DC bus is not energized, the flow proceeds to step 65. If one of the low-voltage DC buses is energized (step 65), the control unit closes the interconnect switches 33-1, 33-2 to energize the other low-voltage DC bus (step 66). If the DC bus is not energized, the flow proceeds to step 69, where each low-voltage DC bus is energized from its corresponding DC bus battery. Thereafter, the flow returns to step 62.

[0039] The flowchart optionally includes step 67 between step 65 and step 69. If the system includes an external charger connected to a normal voltage adapted to the voltage level of the low-voltage bus (step 67), the flow proceeds to step 68, where the charging switch 24 and one or both of the interconnect switches 33-1 and 33-2 are closed, and one or both of the DC buses are energized. Thereafter, the flow is returned to step 62 via step 64.

[0040] The present invention relates to an energy distribution system for an aircraft comprising at least two electric power train units. Each power train unit comprises a propulsion unit (1) supplied with power by a plurality of energy storage units (13), each energy storage unit being configured to supply a first direct current (DC) voltage via a DC connection to the propulsion unit (1). The first DC voltage supplied by the energy storage units of each power train unit varies according to the state of charge and the power demand from the connected propulsion unit. The energy distribution system is configured to energize a DC bus having a DC voltage lower than the first DC voltage provided by each energy storage unit, and at least one converter unit comprises a DC / DC converter configuration configured to convert the first DC voltage from at least one energy storage unit into a second DC voltage at the DC bus, and a DC bus battery having a normal operating DC voltage of the second DC voltage. When energized from at least one energy storage unit, the DC bus supplies energy for charging the DC bus battery, and when at least one energy storage unit cannot energize the DC bus, the DC bus battery supplies energy to the DC bus.

[0041] According to some embodiments, the energy distribution system further comprises an external input configured to supply energy to the DC bus of each converter unit via one or more switches.

[0042] According to some embodiments, at least one converter unit comprises a first converter unit and a second converter unit. Each converter unit is configured to energize a separate DC bus.

[0043] According to some embodiments, the separate DC buses are configured to be connected to each other via one or more switches.

[0044] According to some embodiments, each DC / DC converter arrangement comprises a separate DC / DC converter for each energy storage unit.

[0045] According to some embodiments, when the energy distribution system comprises a first converter unit and a second converter unit, each energy storage unit is connected to two independent DC / DC converter configurations.

[0046] According to some embodiments, the DC bus battery is controlled by a BMU powered by the DC bus battery, which may be accomplished via an internal DC / DC converter within the bus battery.

[0047] According to some embodiments, the DC bus battery is configured to power the DC bus during start-up of the aircraft.

[0048] According to some embodiments, each propulsion unit comprises a DC / AC inverter, an electric motor, and a propeller.

[0049] According to some embodiments, a DC / DC converter arrangement is configured to convert a first DC voltage from each energy storage unit to a second DC voltage at the DC bus.

[0050] According to some embodiments, each electric propulsion unit is powered by one energy storage unit.

[0051] According to some embodiments, each electric propulsion unit is powered by an energy storage unit via a common DC bus.

[0052] The present invention also relates to an electric aircraft equipped with an energy distribution system according to any of the above items.

[0053] The present invention also relates to a method for controlling the above-described energy distribution system. The method includes monitoring the state of a DC / DC converter that converts the first DC voltage to the second DC voltage when power is supplied to the DC bus, charging each DC bus battery via the DC bus when the DC / DC converter is operable, and connecting the DC bus battery to energize the DC bus when one of the DC buses is not energized.

[0054] According to some embodiments, at least one converter unit of the energy distribution system includes a first converter unit and a second converter unit, and each converter unit is configured to energize a separate DC bus. Further, when a malfunction of at least one DC / DC converter is detected, it further includes connecting the energized DC bus to the non-energized DC bus by closing one or more switches.

[0055] In the drawings and the specification, exemplary aspects of the present disclosure are disclosed. However, many variations and modifications can be made to these aspects without substantially departing from the principles of the present disclosure. Therefore, the present disclosure should be considered exemplary rather than limiting, and should not be considered limited to the specific aspects described above. Thus, even when specific terms are used, they are used only in a general and explanatory context and not for the purpose of limitation.

[0056] The description of the exemplary embodiments in this specification is presented for purposes of illustration. This description is not intended to cover all exemplary embodiments or to limit the disclosure to the exact form disclosed, and modifications and variations are possible in light of the teachings above. Alternatively, modifications and variations are possible by implementing various alternatives to the presented embodiments.

[0057] The examples in this specification are selected and described to enable those skilled in the art to utilize the exemplary embodiments in various ways and with various modifications to suit a particular application by explaining the principles, nature, and applications of the various exemplary embodiments. It should be understood that the exemplary embodiments in this specification may be implemented in any combination.

Claims

1. An energy distribution system (20; 30; 40; 50) for an aircraft, comprising at least two electric power train units (A - D), each of said power train units comprising a propulsion unit (1) supplied with power by a plurality of energy storage units (13), each of said energy storage units being configured to supply a first direct current (DC) voltage via a DC connection to said propulsion unit, and the first DC voltage supplied by the energy storage units (13) of each of said power train units varying according to the state of charge and the power demand from the connected propulsion unit (1), said energy distribution system (20; 30; 40; 50) comprising at least one converter unit (25; 35 - 1, 35 - 2; 45 - 1, 45 - 2) configured to energize a DC bus (16 - 1, 16 - 2; 19 - 1, 19 - 2) having a DC voltage lower than the first DC voltage provided by each of said energy storage units (13), each converter unit of said at least one converter unit (25; 35 - 1, 35 - 2; 45 - 1, 45 - 2) comprising a DC / DC converter configuration (21; 41 - 1, 41 - 2) configured to convert the first DC voltage from said at least one energy storage unit (13) to a second DC voltage at the DC bus (16 - 1, 16 - 2; 19 - 1, 19 - 2), a DC bus battery (22; 42) having a normal operating DC voltage of said second DC voltage, and wherein when the DC bus (l6 - 1, 16 - 2; 19 - 1, 19 - 2) is energized from said at least one energy storage unit (13), the DC bus (16 - 1, 16 - 2; 19 - 1, 19 - 2) supplies energy for charging the DC bus battery (22; 42), and when said at least one energy storage unit cannot energize the DC bus (16 - 1, 16 - 2; 19 - 1, 19 - 2), the DC bus battery (22; 42) supplies energy to the DC bus (16 - 1, 16 - 2; 19 - 1, 19 - 2). An energy distribution system characterized thereby.

2. An external input (26; 46) configured to supply energy to the DC buses (16-1, 16-2; 19-1, 19-2) of each converter unit (25, 35-1, 35-2; 45-1, 45-2) via one or more switches (24, 33-1, 33-2; 44, 48-1, 48-2). The energy distribution system according to claim 1, characterized by further comprising.

3. The at least one converter unit includes a first converter unit (35-1; 45-1) and a second converter unit (35-2; 45-2), and each converter unit is configured to be energized to a separate DC bus (16-1, 16-2; 19-1, 19-2). The energy distribution system according to claim 1 or 2, characterized by being.

4. The separate DC buses (16-1, 16-2; 19-1, 19-2) are configured to be connected via one or more switches (33-1, 33-2; 48-1, 48-2). The energy distribution system according to claim 3, characterized by being.

5. Each DC / DC converter configuration (21; 41-1, 41-2) includes a separate DC / DC converter (a-d; a'-d') for each of the at least one energy storage unit (13). The energy distribution system according to any one of claims 1 to 4, characterized by comprising.

6. Each of the at least one energy storage unit (13) is connected to two independent DC / DC converter configurations (21). The energy distribution system according to claim 5, which depends on claim 3 or 4, characterized by being.

7. The DC bus battery (22; 42) is controlled by a battery management unit (23; 43) powered by the DC bus battery (22; 42). The energy distribution system according to any one of claims 1 to 6, characterized by being.

8. The DC bus battery (22; 42) is configured to supply power to the DC buses (16-1, 16-2; 19-1, 19-2) at startup of the aircraft. The energy distribution system according to claim 7, characterized by being.

9. Each propulsion unit includes a DC / AC inverter, an electric motor, and a propeller (12). The energy distribution system according to any one of claims 1 to 6, characterized by comprising.

10. The DC / DC converter configuration (21) is configured to convert the first DC voltage from each energy storage unit (13) to the second DC voltage at the DC bus (16-1, 16-2), characterized in that the energy distribution system according to any one of the above claims.

11. Each electric propulsion unit (1) is characterized in that power is supplied by one energy storage unit (13), and the energy distribution system according to any one of Claims 1 to 10.

12. Each electric propulsion unit (1) is characterized in that power is supplied by the energy storage unit (13) via a common DC bus (51), and the energy distribution system according to any one of Claims 1 to 10.

13. An electric aircraft equipped with the energy distribution system according to any one of Claims 1 to 12.

14. A method for controlling the energy distribution system according to any one of Claims 1 to 11, comprising: Monitoring the state of the DC / DC converter that converts the first DC voltage to the second DC voltage when energizing the DC bus (step 62); When the DC / DC converter is operable (63), charging each DC bus battery via the DC bus (step 64); When one DC bus is not energized (65), connecting the DC bus battery and energizing the DC bus (step 69), characterized in that the method for controlling the energy distribution system.

15. The at least one converter unit of the energy distribution system comprises a first converter unit and a second converter unit, each converter unit is configured to energize a separate DC bus, and when a malfunction of at least one DC / DC converter is detected (65), closing one or more switches (66) to connect the energized DC bus to the non-energized DC bus, further comprising the step of, characterized in that the method according to Claim 14.

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