This specification is based upon and claims the benefit of priority from United Kingdom Patent Application GB 2311374.9, filed Jul. 25, 2023, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a multilane power distribution system, in particular, for aerospace direct current (DC) power systems.
In aircraft DC power distribution systems, it is known to implement multiple energy sources such as multiple batteries or fuel cells and multiple loads such as electric propulsion units (EPUs). The multiple loads and sources may be connected through a DC distribution system using a multilane architecture, meaning that the DC distribution system includes a plurality of power buses.
The multilane architecture provides for the possibility that different lanes are connected to allow sharing of power from the batteries and/or to provide for redundancy. However, when batteries are connected, this may result in unwanted inrush current and/or a current flowing among batteries. In particular, an initial current transient of a different voltage bus may trigger a battery pack main protection, cause battery thermal runaway, and/or melt battery cell connections.
There is a need to provide a method for controlling a multilane power distribution system that allows to connect batteries or other DC power sources of such power distribution system in an efficient manner that addresses the aforementioned problems or at least provides a useful alternative to known multilane power distribution systems.
The present disclosure provides a multilane power distribution system as set out in the appended claims.
In a first aspect, a multilane power distribution system is provided. The multilane power distribution system includes a plurality of DC power sources and a plurality of load devices, wherein each DC power source powers at least two of the load devices, and wherein each load device is powered by at least two of the DC power sources. The multilane power distribution system further includes a DC connection network that includes power buses for connecting the DC power sources and the load devices, wherein the power buses have a high side voltage rail for the positive voltage and a low side voltage rail for the negative voltage. At least two of the power buses are connectable by switchable elements, namely, a first switchable element for the positive voltage rails and a second switchable element for the negative voltage rails, the switchable elements when switched on electrically connecting the terminals of two of the DC power sources connected by the respective power buses.
There is further provided a bypass path that bypasses one of the switchable elements, wherein the bypass path includes a bypass resistor and a further switchable element.
Aspects of the disclosure are thus based on the idea to provide for a bypass path that includes a bypass resistor and a switchable element, wherein the bypass resistor limits any inrush current when the two DC power sources are connected. The bypass path thus provides for a high resistance path with a switchable element that allows to dampen the initial current and keep the initial current within safe limits of a DC power source protection such as a battery pack protection. The switchable element allows to switch the bypass path on and off.
A further advantage associated with the present system lies in that the bypass path allows the voltage levels of the two DC power sources and/or of capacitive loads connected to the DC power sources to slowly align with each other, wherein, after such alignment, the other switchable element may be switched on.
The bypass resistor may be or include an inductor having an inductive resistance. Alternatively, or in addition, the bypass resistor may be or include an ohmic resistor.
In case of an inductor having an inductive resistance, the present system is based on the realization that, due to self-induction, a voltage is induced in each inductor. The induced voltage, according to Lenz's law, counteracts the cause of its generation, i.e., the current flow through the coil. This results in a reduction of the current intensity. Thus, in addition to the ohmic resistance of its windings, every coil has an additional inductive resistance that is caused by its inductance. The inductive resistance of a coil is greater the higher the counter voltage induced in it is. This allows to avoid even very high inrush currents.
In case of an inductor having an ohmic resistance only, the present system may rely on a fixed resistance independent of current and voltage that behaves in accordance with Ohm's law. A high ohmic resistance may be chosen to limit and dampen an initial inrush current.
In some embodiments, the bypass path bypasses the first switchable element, namely, the switchable element of the high side voltage rail. The switchable element for the low side voltage rail, on the other hand, is not affected by the bypass path.
In some embodiments, the system further includes a control unit that controls the state of the first, second, and further switchable elements. In particular, the control unit may be configured to close one of the first and second switchable elements and the further switchable element, and, after a defined time period, close the other of the first and second switchable elements. Accordingly, initially, either the first or the second switchable element (such as the switchable element for the low side voltage rail) and the further switchable element for the bypass path are switched on, (i.e., closed). Any inrush current is limited and damped by the bypass resistor as discussed. Subsequently, when the different voltages have aligned, the other of the switchable elements (such as the switchable element for the high side voltage rail) is switched on/closed. At this point, the further switchable element may be opened again, as it is not of use anymore.
In some embodiments, the control unit is configured to: close one of the first and second switchable elements; subsequently, after a first defined time period, close the further switchable element; and subsequently, after a second defined time period, close the other of the first and second switchable elements.
Accordingly, in such embodiments, there is a sequence of three acts. In a first act, one of the first and second switchable elements is closed. Subsequently, in a second act, the switchable element of the bypass path is closed. Further, in a third act, the other of the first and second switchable elements is closed. Again, at this point, the further switchable element of the bypass path may be opened again.
In certain examples, the control unit is configured to centrally control all DC power sources, all switchable elements, and all load devices. Such a central control unit oversees controlling and commanding of each of DC power sources and the load devices, thereby being able to connect particular DC power sources in case need arises (such as when one of the load devices fails). Such a central control unit may also consider other parameters such as a mission profile and load demands.
In certain examples, each DC power source may power at least two of the load devices through a respective power converter such as an inverter, wherein each power converter drives one of the load devices.
In some embodiments, the switchable elements are contactors. This is associated with the advantage that a full galvanic isolation of the respective positive and negative lanes may be achieved. However, in other embodiments, the switchable element may be a relay. A contactor within the meaning of the present disclosure is any electromechanical control device that is used to make or break an electrical connection. A contactor is controlled by a circuit that has a much lower power level than the switched circuit. A contactor knows two switching positions and may be monostable, wherein bi-stable contactors may be provided as well in embodiments of the present system.
A contactor may be activated by electromagnets. For example, when a control current flows through a solenoid coil of an electromechanical contactor, the magnetic field pulls the mechanical contacts into the active state. Without current, a spring restores the idle state, and all contacts return to their initial position. The connections for control current for the solenoid coil as well as the contacts for auxiliary circuits (if any) and currents to be switched are isolated from each other in the contactor. There is no conductive connection between control and switching contacts. Such contactors are well known to the skilled person.
In some embodiments, the DC connection network is configured such that one considered DC power source is connectable to one other DC power source only, such that there is at least one pair of associated DC power sources, wherein two DC power sources that are connectable are connectable through the switchable elements.
According to such embodiments, there are provided pairs of associated DC power sources that may be connected through a switchable element. It is thus provided that a particular DC power source may be electrically connected to a particular associated DC power source only, and not to any of the other DC power sources of the system. Such bidirectional association is associated with the advantage that a central control is simplified as two DC power sources have to be considered only when readjusting DC power source connections.
In some embodiments, the DC power source includes an electric battery. However, the present system is not limited to such embodiments. For example, there may be provided fuel cells as DC power sources, a mixture of batteries and fuel cells, or a turbo generator/active rectifier.
In some embodiments, the load device includes an electric motor. However, the present system is not limited to such embodiments. For example, other load devices such as pumps may be provided for.
One application of the present system lies in electric Vertical Take Off and Landing aircrafts (e-VTOLs). During take-off and landing, the propulsion system of e-VTOLs is at its limit. E-VTOLs use several independent engines that provide for redundancy. A DC Electric Power Distribution Unit (which is a control unit) distributes and connects the energy sources to the loads. One of the functions of the distribution unit is to connect multiple energy sources, e.g., in case of an engine failure.
The skilled person will appreciate that except where mutually exclusive, a feature or parameter described in relation to any one of the above aspects may be applied to any other aspect. Furthermore, except where mutually exclusive, any feature or parameter described herein may be applied to any aspect and/or combined with any other feature or parameter described herein.
The disclosure is explained in more detail on the basis of embodiments with reference to the accompanying drawings in which:
With increased penetration of electrical systems and the progression towards full electric and hybrid propulsion systems, the use of DC multilane power distribution systems has gained increased use.
The power sources G1, G2, Y1, Y2, B1, B2, R1, R2 may be or include batteries and are, in the following, referred to as batteries, without limiting the power sources to batteries. For example, in aerospace applications, the power sources may alternatively be fuel cells or a rectifier extracting power from a turbo generator. The load devices EPU 1 to EPU 8 may be electronic propulsion units (EPUs) and are, in the following, referred to as EPUs, without limiting the load devices two EPUs.
The architecture of the multilane power distribution system of
First, each battery G1, G2, Y1, Y2, B1, B2, R1, R2 powers two EPUs. For example, battery G1 powers EPU 1 and EPU 6. In another example, battery G2 powers EPU 4 and EPU 7.
Second, each of the EPUs EPU 1 to EPU 8 is powered by two of the batteries G1, G2, Y1, Y2, B1, B2, R1, R2. For example, EPU 1 is powered by battery G1 and by battery Y1. EPU 2 is powered by battery R1 and battery B1. EPU 3 is powered by battery R2 and by battery B2, etc.
Third, two of the batteries are assigned to each other in the sense that a particular of the batteries may be electrically connected to another one of the batteries, wherein each battery may be connected to one associated other battery only. For example, batteries G1, G2 are assigned to each other. They may be connected through a contactor 14 that connects the respective power buses (also referred to as lanes) PB-G1, PB-G2.
In a similar manner, batteries Y1, Y2 are assigned to each other. They may be connected through a contactor 13 that connects the respective power busses PB-Y1, PB-Y2. Further, batteries R1, R2 are assigned to each other. They may be connected through a contactor 12 that connects the respective power buses PB-R1, PB-R2. Also, batteries B1, B2 are assigned to each other. They may be connected through a contactor 11 that connects the respective power buses PB-B1, PB-B2.
The power busses PB-G1/2, PB-Y1/2, PB-B1/2, PB-R1/2 form a DC distribution network, wherein two associated batteries and their corresponding lanes/power buses (such as batteries G1, G2 and power buses PB-G1, PB-G2) form a sub-distribution system within the overall DC distribution system.
Each power bus includes a high side voltage rail connected to a positive battery voltage and a low side voltage rail connected to a negative battery voltage, as is seen, e.g., in
The network of
Each of the EPUs EPU 1 to EPU 8 includes two electrical motors. For example, EPU 1 includes electric motor F1-G1 driven by battery G1 through a power converter/inverter (not shown). EPU 1 further includes electric motor F1-Y1 that is driven by battery Y1 through another power converter/inverter (not shown). For example, the power converters each provide for a three phase alternating current that drives the respective electric motors F1-G1 and F1-Y1. In this respect, the electric motors such as electric motors F1-G1 and F1-Y1 may be two physically different machines connected to the same shaft, or two sets of windings wound in the same machine, each fed by a different power converter.
In a similar manner, each of the other EPUs EPU 2-8 include two electrical motors F2-R1, F2-B1, F3-R2, F3-B2, F4-G2, F4-Y2, A1-R1, A1-B1, A2-G1, A1-Y1, A3-G2, A3-Y2, A4-R2, A4-B2, and corresponding power converters as well.
In the depicted embodiment, the EPUs may include propellers, wherein some of the propellers turn in one direction and the same number of propellers turn in the other direction, such as is used in e-VTOLs. However, this represents an embodiment only.
During certain mission profiles, the lanes are kept independent, whereas under certain conditions, the lanes may be connected to allow sharing of power from the batteries. For example, in
Accordingly, it is beneficial under certain conditions, for example, during a failure condition, to electrically connect batteries that are associated and together form a sub-distribution system, such as electrically connecting batteries G1, G2 through contactor 14 or batteries Y1, Y2 through contactor 13. However, sharing energy stored in batteries is not straightforward, and different batteries will be discharged differently and will, therefore, have different voltages at the time they are connected. When batteries are connected that have different voltages, this would result in unwanted inrush current and/or current flowing among the batteries.
Further, as discussed with respect to
The batteries G1, G2 contact through the voltage rails also the EPUs EPU 1 and EPU 4, respectively.
A specific sequence in closing the different contactors 14-L, 14-H, 14-BP is implemented under the control of a control unit, as is discussed with respect to
More particularly, in
Control unit 20 provides for a specific sequence of closing the contactors in case two batteries such as batteries G1, G2 are to be electrically connected. Such sequence is depicted in
After some time t2, when the voltage difference is zero or below a defined threshold, the first contactor 14-H is closed and the contactor 14-BP in the bypass path 15 is opened in the layout of
Further, in
In an alternative embodiment, in the layout of
It should be understood that the above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Also, those skilled in the art will appreciate that other aspects of the disclosure may be obtained from a study of the drawings, the disclosure, and the appended claims. All methods described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. Various features of the various embodiments disclosed herein may be combined in different combinations to create new embodiments within the scope of the present disclosure. In particular, the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein. Any ranges given herein include any and all specific values within the range and any and all sub-ranges within the given range.
Number | Date | Country | Kind |
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2311374.9 | Jul 2023 | GB | national |