Energy distribution system
By designing energy distribution systems of multiple electrical powertrain units and converter units in the aircraft, the low-voltage DC bus voltage instability caused by insufficient power supply of the common high-voltage DC bus is solved, and a more stable low-voltage DC bus power supply and emergency power supply are achieved.
Patent Information
- Application Number
- CN202380067801.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-07-29
- Filing Date
- 2023-07-28
- Publication Date
- 2025-04-29
AI Technical Summary
In the prior art, when the common high voltage DC bus cannot power the common low voltage DC bus, it may cause the DC voltage on the low voltage DC bus to experience voltage spikes or power down, and lack a stable and safe energy supply.
An energy distribution system is designed, including at least two electrical powertrain units, each powertrain unit powered by an energy storage unit, and a first DC voltage is supplied to the propulsion unit through a DC connection. The system also includes a converter unit, including a DC/DC converter arrangement and a DC bus battery for converting the first DC voltage to a second DC voltage on the low voltage DC bus and powered by the DC bus battery when the energy storage unit is unable to be powered.
With this energy distribution system, a more stable low-voltage DC bus can be obtained, which helps in transient situations and provides emergency power in emergencies.
Smart Images
Figure CN119907769A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to an energy distribution system configured to create a common DC bus on an aircraft with enhanced stability. The present disclosure further relates to an aircraft including the energy distribution system. Background Art
[0002] Essential systems in electric aircraft rely on a continuous supply of power and energy to function properly. This can be achieved using multiple redundant energy sources for each system, or by distributing energy to critical systems via one or more common direct current (DC) buses. FIG1 shows a prior art system in which a common high voltage DC bus is used to power the propulsion units, and a DC / DC converter is provided to create a common low voltage DC bus from which critical and non-critical loads are powered.
[0003] A disadvantage of prior art systems is that the DC voltage on the common low voltage DC bus may experience voltage spikes, or even brown out, if the common high voltage DC bus fails to power the common low voltage DC bus.
[0004] Therefore, a more stable and safe energy supply is needed to power the low voltage DC bus. Summary of the invention
[0005] An object of the present disclosure is to provide an energy distribution system that seeks to mitigate, alleviate or eliminate one or more of the above-mentioned deficiencies and disadvantages in the art, either alone or in any combination.
[0006] The object is achieved by an energy distribution system for an aircraft having at least two electrical powertrain units, each powertrain unit comprising a propulsion unit powered by an energy storage unit, the energy storage unit being configured to supply a first direct current (DC) voltage to the propulsion unit via a DC connection. The first DC voltage supplied by the energy storage unit in each powertrain 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 power a DC bus having a DC voltage lower than the first DC voltage provided from each respective energy storage unit. Each converter unit of the at least one converter unit comprises: a DC / DC converter arrangement configured to convert the first DC voltage from each energy storage unit to a second DC voltage on the DC bus; and a DC bus battery having a nominal operating DC voltage of the second DC voltage. The DC bus provides energy for charging the DC bus battery when powered from the energy storage unit, and the DC bus battery supplies energy to the DC bus when the energy storage unit is unable to power the DC bus.
[0007] An advantage of the present invention is that a more stable low voltage DC bus can be obtained compared to prior art solutions, since the DC bus battery also helps with transients.
[0008] Another advantage of the present invention is that in the event that the energy storage unit cannot supply power to the DC bus, emergency power can be obtained from the DC bus battery.
[0009] Further aspects and advantages may be obtained from the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The foregoing will become apparent from the following more particular description of example embodiments, as illustrated in the accompanying drawings in which like reference numerals refer to the same parts throughout the different views. The drawings are not necessarily drawn to scale, emphasis instead being placed upon illustrating the example embodiments.
[0011] FIG1 shows an energy distribution system for providing a low voltage DC bus in an aircraft according to the prior art;
[0012] Figure 2 An energy distribution system for providing a low voltage DC bus in an aircraft is shown according to a first example embodiment;
[0013] Figure 3 An energy distribution system for providing a plurality of low voltage DC buses in an aircraft is shown according to a second example embodiment;
[0014] Figure 4 An energy distribution system for providing multiple low voltage DC buses in an aircraft is shown according to a third example embodiment;
[0015] Figure 5 An energy distribution system with a control unit for providing a low voltage DC bus according to a fourth embodiment is shown; and
[0016] Figure 6 is a flow chart illustrating a method of powering a low voltage DC bus. DETAILED DESCRIPTION
[0017] The following will be more fully described with reference to the accompanying drawings. However, the system disclosed herein can be implemented in many different forms and should not be construed as limited to the aspects set forth herein. The same reference numerals in the accompanying drawings always refer to the same elements.
[0018] The terms used herein are only used for the purpose of describing specific aspects of the present disclosure and are not intended to limit the present invention. Unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" used herein are intended to include plural forms as well.
[0019] Some of the example embodiments presented herein are directed to energy distribution systems intended for use with aircraft, such as airplanes, helicopters, or other machines capable of flight.
[0020] FIG1 shows an energy distribution system 10 for providing a low voltage DC bus in an aircraft according to the prior art. In this regard, the term "low voltage DC bus" is exemplified as a 270V DC bus that can be used to power critical and non-critical loads in an aircraft. Other voltages may also be used depending on the actual implementation of the system components.
[0021] In Figure 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 (with an alternating current AC electric motor receiving power from the common high-voltage DC bus 14 via a DC / AC inverter) and a propeller 12. The energy storage unit 13 may include a rechargeable battery or battery pack. The voltage on the common high-voltage DC bus 14 varies between 480V-800V DC (as an example) depending on the state of charge and the power demand from the connected propulsion unit 1.
[0022] A DC / DC converter 15 is provided to power a common 270V DC bus 16, which supplies power to critical loads 17a and non-critical loads 17b operating at 270V DC. Another DC / DC converter 18 is provided to power a common 28V DC bus 19, which supplies power to critical loads 17a and non-critical loads 17b operating at 28V DC. Figure 3 As shown in , the loads are collectively denoted as 17 and include critical loads and non-critical loads.
[0023] Figure 2An energy distribution system 20 for providing a low voltage DC bus (e.g., 270V DC) in an aircraft according to a first example embodiment of the present invention is shown. The energy distribution system includes a plurality of powertrain units, in this example four powertrain units A, B, C, and D. Each powertrain unit includes a propulsion unit 1 and an energy storage unit 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 provides 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 energy storage unit 13 is configured to supply a first direct current DC voltage to the drive unit 11 in the propulsion unit via a DC connection. The first DC voltage supplied by the energy storage unit 13 in each powertrain unit varies according to the state of charge and the power demand from the connected propulsion unit, and as an example, the first DC voltage can vary between 480V-800V DC.
[0024] The energy distribution system 20 further includes a converter unit 25 configured to power a DC bus 16 having a DC voltage (e.g., 270V DC) lower than a first DC voltage (e.g., 480V-800V DC) provided from each corresponding energy storage unit 13. The converter unit 25 includes: a DC / DC converter arrangement 21 configured to convert the first DC voltage from each energy storage unit 13 into a second DC voltage on the DC bus 16; and a DC bus battery 22 having a nominal operating DC voltage of the second DC voltage.
[0025] The energy distribution system may include an external input 26 configured to provide energy to the DC bus 16 using an external connection when the aircraft is on the ground (if the switch 24 is closed). The switch 24 may be controlled by a controller (not shown) or be a manually activated switch.
[0026] The DC / DC converter arrangement 21 includes four individual DC / DC converters a-DC / DC converter d, one DC / DC converter for each energy storage unit 13. The energy storage unit of powertrain "A" is connected to DC / DC converter "a", the energy storage unit of powertrain "B" is connected to DC-DC converter "b", and so on. The outputs from the individual DC / DC converters a-DC / DC converter d are commonly connected to the DC bus 16.
[0027] The DC bus battery 22 is controlled by a battery management unit (BMU) 23, which is powered by the DC bus battery 22 through an internal DC / DC converter within the DC bus battery 22. In addition, the DC bus battery 22 may be configured to power the DC bus 16 when starting the aircraft.
[0028] The DC bus 16 provides energy for critical loads 17a and non-critical loads 17b operating at 270V DC, as well as energy for charging the DC bus battery 22 when powered from the energy storage unit 13. The DC bus battery 22 is also configured to supply energy to the DC bus 16 when the energy storage unit 13 is unable to power the DC bus 16 through the DC / DC converter arrangement 21. This may occur due to the depletion of charge in the energy storage unit 13. In addition, the DC bus battery also helps to provide a stable DC voltage level if a voltage spike or sudden surge is generated from the connected load 17. In this embodiment, another DC / DC converter 18 is provided to power a common 28V DC bus 19, which supplies power to the critical loads 17a and non-critical loads 17b operating at 28V DC.
[0029] Figure 3 An energy distribution system 30 for providing multiple low voltage DC buses (eg, 270V DC) in an aircraft is shown according to a second exemplary embodiment. The energy distribution system 30 differs in one major respect from the combination of Figure 2 Instead of using one converter unit 25, the energy distribution system 30 includes two converter units, namely a first converter unit 35-1 and a second converter unit 35-2, and each converter unit is configured to power a separate DC bus 16-1, DC bus 16-2. In some embodiments, the first converter unit 35-1 is identical to the second converter unit 35-2.
[0030] Each converter unit 35-1 and 35-2 comprises a DC / DC arrangement 21 for powering a separate DC bus 16 and a DC bus battery 22 with a BMU 23. Furthermore, each converter unit 35-1 and 35-2 further comprises a switch 33-1 and a switch 33-2, respectively, which together serve to connect the separate DC buses to each other via an interconnection 34.
[0031] Energy distribution system 30 may include external input 26 configured to provide energy to DC buses 16-1 and 16-2 using an external connection when the aircraft is on the ground (if switches 24 and 33 are closed). Switches 24 and 33 may be controlled by a controller (not shown) and / or may be manually activated switches.
[0032] In this embodiment, each DC / DC converter arrangement 21 comprises a separate DC / DC converter a-DC / DC converter d for each energy storage cell 13 , and each energy storage cell 13 is connected to two separate DC / DC converter arrangements 21 .
[0033] Each DC bus 16-1 and 16-2 provides energy for a load 17 (which may be a critical load and / or a non-critical load) operating at 270V DC, and provides energy for charging each DC bus battery 22 when powered from the energy storage unit 13 via the DC / DC converter a-DC / DC converter d. The DC bus battery 22 is also configured to supply energy to each DC bus 16 when the energy storage unit 13 is unable to power the DC buses 16-1 and 16-2 through the DC / DC converter arrangement 21. In addition, the DC bus battery also helps to provide a stable DC voltage level if a voltage spike or sudden surge is generated from the connected load 17. In this embodiment, a separate DC / DC converter 18 is connected to each 270V DC bus 16 to power a separate 28V DC bus 19-1 and 19-2, which supplies power to the load 17 (which may be a critical load and / or a non-critical load) operating at 28V DC. A switch 35 is provided between the 28V DC busses to create a common 28V DC bus when closed. The switch 34 may be controlled by a controller (not shown) and / or be a manually activated switch.
[0034] Figure 4 An energy distribution system 40 for providing multiple low voltage DC buses (eg, 270V DC and / or 28V DC) in an aircraft is shown according to a third exemplary embodiment. The energy distribution system 40 differs from the combination of Figure 3 Instead of using a separate DC / DC converter 18 to power the 28V DC bus 19-1 and the 28V DC bus 19-2 from each 270V DC bus 16-1 and the 270V DC bus 16-2, the energy distribution system 40 includes two additional converter units, namely a first converter unit 45-1 and a second converter unit 45-2, which are configured to power each DC bus 19-1 and the DC bus 19-2.
[0035] Each additional converter unit 45-1 and 45-2 includes a DC / DC arrangement 41-1 and 41-2 for powering each 28V DC bus 19-1 and 28V DC bus 19-2 and a low voltage DC bus battery 42 with a BMU 43. In addition, each converter unit 45-1 and 45-2 also includes a switch 48-1 and 48-2, respectively, which together are used to connect the individual 28V DC buses to each other via an interconnect 47.
[0036] The energy distribution system 40 may further include an external input 46 configured to provide energy to the DC bus 19-1 and the DC bus 19-2 using an external connection when the aircraft is on the ground (if the switch 44, the switch 48-1 and the switch 48-2 are closed). The switch 44 and the switch 48 may be controlled by a controller (not shown) and / or may be a manually activated switch.
[0037] In this embodiment, the first DC / DC converter arrangement 41-1 includes a separate DC / DC converter a' and a DC / DC converter b' connected to the two energy storage units 13 in powertrain unit A and powertrain unit B, and the second DC / DC converter arrangement 41-2 includes a separate DC-DC converter c' and a DC-DC converter d' connected to the two energy storage units 13 in powertrain unit C and powertrain unit D.
[0038] Each DC bus 19 provides energy for loads 17 (which may be critical loads and / or non-critical loads) operating at 28V DC, and when powered from the energy storage unit 13, provides energy for charging each low-voltage DC bus battery 42. The low-voltage DC bus battery 42 is also configured to supply energy to each 28V DC bus 19-1 and 19-2 when the energy storage unit 13 is unable to power the 28V DC buses 19-1 and 19-2. In addition, the low-voltage DC bus battery also helps provide a stable 28V DC voltage level if a voltage spike or sudden surge is generated from the connected load 17.
[0039] Figure 5 An energy distribution system 50 for providing a low voltage DC bus (eg, 270 VDC) in an aircraft is shown according to a fourth exemplary embodiment. The energy distribution system 50 differs in one major respect from a combination of Figure 4The propulsion unit 11 and the propulsion unit 12 are connected to a common high-voltage DC bus 51, and the energy storage unit 13 is connected to power the common high-voltage DC bus 51, which has a voltage that can be varied between 480V-800V DC. The common high-voltage DC bus can be included in any of the foregoing embodiments without departing from the inventive concept. In addition, Figure 5 The 28V DC bus is omitted.
[0040] also, Figure 5 The figure shows a control unit 52, which is configured to control switch 33-1, switch 33-2 and optionally switch 24. The control unit 52 may also be configured to control Figure 4 The control unit 52 monitors the state of the DC / DC converter 21 and senses the voltage level of each 270V DC bus 16-1 and 16-2 via a voltage sensor (not shown). If any of the voltage sensors indicates a drop in the voltage level, or the monitored state of the DC / DC converter will affect the voltage level of the DC bus, the DC bus battery 22 can be used to power the DC bus and stabilize the voltage level in the presence of disturbances (e.g., voltage spikes, surges). In addition, if one of the low-voltage DC buses experiences a drop in voltage level, the control unit 52 can interconnect the low-voltage DC buses by closing switches 33-1 and 33-2. If necessary, the control unit can also be controlled by an external signal (e.g., from a pilot or flight control computer).
[0041] Figure 6 The figure shows that Figure 560 is a flowchart of an example embodiment of the operations performed by the control unit 52 in FIG. The process starts at step 61, and in step 62, the control unit monitors the state of each low voltage DC bus to determine whether all low voltage DC buses are powered. In some embodiments, this is accomplished by monitoring the state of the DC / DC converters. In some embodiments, determining whether each low voltage DC bus is powered includes sensing the voltage level of each low voltage DC bus. In some embodiments, a combination of monitoring the state of the DC / DC converters and sensing the DC bus voltage is performed. If all DC / DC converters are operational and all low voltage DC buses are powered, step 63, the process returns to step 62 via step 63, indicating that each DC bus battery is charged while each low voltage DC bus is powered. However, if the control unit detects that one of the low voltage DC buses is not powered, the process continues to step 65. If one of the low voltage DC buses is powered step 65, the control unit closes the interconnected switches 33-1, 33-2 to power the other low voltage DC buses (step 66). If no DC bus is powered, the process continues to step 69 where each low voltage DC bus is powered by its associated DC bus battery. Thereafter, the process is fed back to step 62.
[0042] The flowchart also includes an optional step 67 between step 65 and step 69, if the system includes an external charger connected to a nominal voltage adapted to the voltage level of the low voltage bus (step 67), the process continues to step 68, wherein the charging switch 24 and one or both of the interconnecting switches 33-1 and 33-2 are closed to power one or both of the DC buses. Thereafter, the process is fed back to step 62 via step 64.
[0043] The invention relates to an energy distribution system for an aircraft, the energy distribution system having at least two electrical powertrain units, each powertrain unit comprising a propulsion unit powered by an energy storage unit, each energy storage unit being configured to supply a first direct current DC voltage to the propulsion unit via a DC connection. The first DC voltage supplied by the energy storage unit in each powertrain unit varies depending on the state of charge and the power demand from the connected propulsion unit. The energy distribution system comprises at least one converter unit, the at least one converter unit being configured to supply a DC bus having a DC voltage lower than the first DC voltage supplied from each respective energy storage unit. Each converter unit of the at least one converter unit comprises:
[0044] - a DC / DC converter arrangement configured to convert a first DC voltage from at least one of the energy storage units into a second DC voltage on the DC bus; and
[0045] - A DC bus battery having a nominal operating DC voltage of a second DC voltage.
[0046] The DC bus provides energy for charging a DC bus battery when powered from the at least one energy storage unit, and the DC bus battery supplies energy to the DC bus when the at least one energy storage unit is unable to power the DC bus.
[0047] According to some embodiments, the energy distribution system further comprises an external input configured to provide energy to the DC bus of each converter unit via one or more switches.
[0048] According to some embodiments, the at least one converter unit comprises a first converter unit and a second converter unit, each converter unit being configured to power a separate DC bus.
[0049] According to some embodiments, the separate DC buses are configured to be connected via one or more switches.
[0050] According to some embodiments, each DC / DC converter arrangement comprises a separate DC / DC converter for each of the at least one energy storage unit.
[0051] According to some embodiments, when the energy distribution system comprises a first converter unit and a second converter unit, each of the at least one energy storage unit is connected to two independent DC / DC converter arrangements.
[0052] According to some embodiments, the DC bus battery is controlled by a BMU powered by the DC bus battery. This can be achieved by an internal DC / DC converter within the bus battery.
[0053] According to some embodiments, the DC bus battery is configured to power the DC bus when starting the aircraft.
[0054] According to some embodiments, each propulsion unit comprises a DC / AC inverter, an electric motor and a propeller.
[0055] According to some embodiments, the DC / DC converter arrangement is configured to convert a first DC voltage from each of the energy storage units to a second DC voltage on the DC bus.
[0056] According to some embodiments, each electric propulsion unit is powered by an energy storage unit.
[0057] According to some embodiments, each electric propulsion unit is powered by an energy storage unit via a common DC bus.
[0058] The invention also relates to an electric aircraft comprising an energy distribution system according to any of the above items.
[0059] The present invention also relates to a method for controlling the above-mentioned energy distribution system, wherein the method comprises the following steps:
[0060] - when powering the DC bus, monitoring a state of a DC / DC converter for converting a first DC voltage into a second DC voltage;
[0061] - if the DC / DC converter is operational, charging each DC bus battery via the DC bus; and
[0062] - If one DC bus is not powered, connect the DC bus battery to power that DC bus.
[0063] According to some embodiments, at least one converter unit of the energy distribution system includes a first converter unit and a second converter unit, each converter unit is configured to power a separate DC bus, and at least one DC / DC converter is detected to have failed. The method further includes the step of connecting the powered DC bus to the unpowered DC bus by closing one or more switches.
[0064] In the drawings and specification, exemplary aspects of the present disclosure have been disclosed. However, many changes and modifications may be made to these aspects without substantially departing from the principles of the present disclosure. Therefore, the present disclosure should be regarded as illustrative rather than restrictive, and is not limited to the specific aspects discussed above. Accordingly, although specific terms are employed, they are used only in a general and descriptive sense and not for the purpose of limitation.
[0065] The description of the example embodiments provided herein is presented for illustrative purposes. The description is not intended to be exhaustive or to limit the example embodiments to the precise form disclosed, and in view of the above teachings, modifications and changes are possible or can be obtained from the practice of various alternatives to the provided embodiments. The examples discussed herein are selected and described in order to explain the principles and properties of the various example embodiments and their practical applications, so that those skilled in the art can use the example embodiments in various ways and various modifications suitable for the intended specific use. It should be appreciated that the example embodiments presented herein can be practiced in any combination with each other.
Claims
1. An energy distribution system for an aircraft (20; 30; 40； 50), having at least two electrical powertrain units (AD), each powertrain unit comprising: a propulsion unit (1), powered by an energy storage unit (13), each energy storage unit being configured to supply a first direct current (DC) voltage to the propulsion unit via a DC connection, the first DC voltage supplied by the energy storage unit (13) in each powertrain unit varying according to a state of charge and a power demand from the connected propulsion unit (1), wherein the energy distribution system (20; 30; 40; 50) comprises at least one converter unit (25; 35-1, 35-2; 45-1, 45-2) configured to supply power to a DC bus (16-1, 16-2; 19-1, 19-2), the DC bus (16-1, 16-2; 19-1, 19-) having a DC voltage lower than the first DC voltage provided from each corresponding energy storage unit (13), each of the at least one converter unit (25; 35-1, 35-2; 45-1, 45-2) comprising: a DC / DC converter arrangement (21; 41-1, 41-2) configured to convert the first DC voltage from at least one of the energy storage units (13) into a second DC voltage on the DC bus (16-1, 16-2; 19-1, 19-2); and a DC bus battery (22; 42) having a nominal operating DC voltage of said second DC voltage; wherein the DC bus (16-1, 16-2; 19-1, 19-2) provides energy for charging the DC bus battery (22; 42) when powered by the at least one energy storage unit (13), and when the at least one energy storage unit is unable to power 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).
2. The energy distribution system according to claim 1, further comprising: An external input terminal (26; 46) is configured to provide energy to the DC bus (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).
3. The energy distribution system according to any one of claims 1 to 2, wherein: The at least one converter unit comprises a first converter unit (35-1; 45-1) and a second converter unit (35-2; 45-2), each converter unit being configured to power a separate DC bus (16-1, 16-2; 19-1, 19-2).
4. The energy distribution system according to claim 3, wherein: 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).
5. The energy distribution system according to any one of claims 1 to 4, wherein: Each DC / DC converter arrangement (21; 41-1, 41-2) comprises a separate DC / DC converter (ad; a'-d') for each of the at least one energy storage unit (13).
6. An energy distribution system according to claim 5 when dependent on claim 3 or 4, wherein: Each of the at least one energy storage unit (13) is connected to two independent DC / DC converter arrangements (21).
7. The energy distribution system according to any one of claims 1 to 6, wherein: The DC bus battery (22; 42) is powered by a battery management unit (23; 43) to control.
8. The energy distribution system according to claim 7, wherein: The DC bus battery (22; 42) is configured to provide a power supply to the DC bus (16-1, 16-2; 19-1, 19-2) power supply.
9. The energy distribution system according to any one of claims 1 to 6, wherein: Each propulsion unit comprises a DC / AC inverter, an electric motor and a propeller (12).
10. An energy distribution system according to any one of the preceding claims, wherein: The DC / DC converter arrangement (21) is configured to convert the first DC voltage from each of the energy storage units (13) to the second DC voltage on the DC bus (16-1, 16-2).
11. The energy distribution system according to any one of claims 1 to 10, wherein: Each electric propulsion unit (1) is powered by an energy storage unit (13).
12. The energy distribution system according to any one of claims 1 to 10, wherein: Each electric propulsion unit (1) is powered by an energy storage unit (13) via a common DC bus (51).
13. An electric aircraft, comprising: An energy distribution system according to any one of claims 1 to 12.
14. A method for controlling an energy distribution system according to any one of claims 1 to 11, wherein: The method comprises the following steps: monitoring (62) a state of the DC / DC converter for converting the first DC voltage to the second DC voltage while powering the DC bus; If the DC / DC converter is operational (63), charging each DC bus battery via the DC bus (64); and If one DC bus is not powered (65), the DC bus battery is connected (69) to power the DC bus.
15. The method according to claim 14, wherein: The at least one converter unit of the energy distribution system comprises a first converter unit and a second converter unit, each converter unit being configured to power a separate DC bus, and wherein at least one DC / DC converter is detected to have failed (65), and the method further comprises the step of connecting the powered DC bus to a non-powered DC bus by closing (66) one or more switches.