On-board power system for an aircraft and method for operating an on-board power system for an aircraft

Abstract

The invention relates to an on-board power supply arrangement (10) for an aircraft with at least one connectable consumer, wherein the on-board power supply arrangement (10) - a high-voltage energy source (1) for providing a first high-voltage potential (HV+) and a second high-voltage potential (HV-), - further comprising a first insulation resistance (R1) between the first high-voltage potential (HV+) and an electrical ground (2) and a second insulation resistance (R2) between the second high-voltage potential (HV-) and the electrical ground (2), wherein the at least one consumer and the high-voltage energy source (1) form a ground-free system, - an insulation monitoring device (8) for monitoring the insulation resistances (R1, R2), wherein the insulation monitoring device (8) has a compensation circuit which is designed and configured to reduce a difference between the insulation resistances (R1, R2) by actively symmetrizing voltages (U1, U2), characterized in that the insulation monitoring device (8) is coupled to a control device (4) to form a combined symmetry insulation monitoring device (3), wherein a current variable, in particular a symmetry current (Is), can be controlled with the control device (4) as a function of the voltages (U1, U2) to be symmetrized with respect to ground (2).

Description

[0001] The present disclosure relates to an on-board power supply arrangement having the features of claim 1 and a method for operating an on-board power supply arrangement having the features of claim 10.

[0002] Electric propulsion is increasingly being used in aircraft, such as airplanes or drones. In this context, a high-voltage electrical system can be used, which has a high-voltage energy source that can be coupled to at least one consumer.

[0003] This high-voltage electrical system and at least one consumer are usually designed as a so-called IT system (Isolé Terre System), in which there is no electrical connection between active electrical conductors and earthed components.

[0004] However, parasitic resistances, such as those found in cables, loads, or batteries, typically result in high-impedance connections between the positive or negative high-voltage potential and a ground. These connections are also referred to as insulation resistances.

[0005] For example, it is known from DE 10 2019 202 892 A2 to monitor insulation resistance for safety reasons using an insulation monitoring device. If a predefined threshold is undershot, a signal (e.g., as a warning signal) can be generated and—depending on the operating state of the high-voltage electrical system—disconnected from the batteries via the battery contactors, thus establishing a safe state. Other devices in this area are known, for example, from DE 10 2021 003843 A1 or DE 10 2018 211625 A1.

[0006] The magnitude of the insulation resistance is usually unknown and varies over time. The insulation resistances usually also have parasitic capacitances connected in parallel.

[0007] In particular, it must be assumed that the two insulation resistances can differ greatly from each other, which would mean that the high voltage would no longer be distributed symmetrically to ground if no countermeasures are taken.

[0008] Therefore, efficient devices and methods for insulation monitoring, manufacturing and / or maintaining symmetry are needed.

[0009] According to a first aspect, an on-board power supply arrangement having the features of claim 1 is provided.

[0010] At least one consumer can be connected to such an on-board power supply. Key electrical consumers include electric drive motors for propellers or rotors (e.g., in vertical takeoff aircraft). Of course, secondary consumers (e.g., auxiliary actuators (landing gear, rotor swivel mechanism for propeller operation, landing flaps), wing heaters to prevent icing, and cabin heaters) can also be operated with a specific embodiment of the on-board power supply.

[0011] The on-board electrical system arrangement has a high-voltage energy source for providing a first high-voltage potential HV+ and a second high-voltage potential HV-.

[0012] The vehicle electrical system arrangement further includes a first insulation resistor R1 between the first high-voltage potential HV+ and an electrical ground, and a second insulation resistor R2 between the second high-voltage potential HV- and the electrical ground. The at least one consumer and the high-voltage energy source form a ground-free system.

[0013] The on-board electrical system also includes an insulation monitoring device for monitoring the insulation resistances R1, R2, which can be used, in particular, to monitor for undershoots of limit values. The insulation monitoring device has a compensating circuit designed and configured to reduce a difference between the insulation resistances R1, R2 through active balancing of voltages.

[0014] The insulation monitoring device is coupled to a control device to form a combined symmetry insulation monitoring device. The control device can control a current value, in particular a symmetry current, depending on the voltages to be balanced with respect to ground. This combined insulation monitoring and control device prevents or at least limits the negative consequences of asymmetry.

[0015] Since current and voltage are essentially dual, it is essentially equivalent to create a balance using a controllable voltage source and then measure the resulting current for insulation monitoring. The voltage source design also requires a control loop to maintain the voltage at the setpoint. Ultimately, the technical solution is no different; only the description is based on the dual perspective.

[0016] This allows the control variable "current," in particular the balancing current, to be measured and then used to calculate the insulation resistances R1, R2. The control device can also have a control loop with a setpoint for a common-mode voltage. This allows for efficient balancing.

[0017] The insulation monitoring device can also specify a setpoint, in particular a common-mode voltage value, and have a current value, in particular the symmetry current, as an input value. This enables coupling with the control device.

[0018] The control device can, for example, be constructed as an analog circuit comprising an operational amplifier and a symmetrical transistor circuit. This makes it easy to perform a comparative measurement and corresponding control of the symmetry.

[0019] Alternatively, the control device can be designed as a digital circuit in which, for example, a microcontroller is programmed according to the intended symmetrization.

[0020] In a further embodiment, the high-voltage energy source comprises a battery, a generator, in particular a generator driven by a gas turbine, and / or a fuel cell.

[0021] The on-board power system arrangement can also be integrated into an aircraft, in particular a UAM aircraft or an airplane.

[0022] In one embodiment of the on-board power supply arrangement, it can also be coupled to a consumer which is designed in particular as an electric drive motor for a propeller or a rotor, as an auxiliary actuator and / or as a wing heater against icing and cabin heating.

[0023] The aspect addressed here is also solved by a method having the features of claim 10.

[0024] It will be understood by those skilled in the art that a feature or parameter described in relation to one of the above aspects may be applied to any other aspect, provided they are not mutually exclusive. Furthermore, any feature or parameter described herein may be applied to any aspect and / or combined with any other feature or parameter described herein, provided they are not mutually exclusive.

[0025] Embodiments will now be described by way of example with reference to the figures, in which: Fig. 1 an embodiment of an on-board power supply arrangement; Fig. 2 Details of an on-board power system arrangement with a combined symmetry insulation monitoring device.

[0026] In the Fig. Figure 1 shows an embodiment of an on-board power system 10 with a high-voltage power source 1, which is used in an aircraft. The aircraft can be, for example, a UAM aircraft, a drone, or an airplane in which corresponding electrical loads are present. At least one load can be connected to the on-board power system 10, although the loads are not shown here for reasons of clarity.

[0027] In the illustrated embodiment, the high-voltage energy source 1 is a battery. In other embodiments, the high-voltage energy source 1 can also be a generator driven by a gas turbine or a fuel cell.

[0028] A chassis of the aircraft forms an electrical ground 2.

[0029] High-voltage energy source 1 now supplies two high-voltage terminals HV+ and HV-, via which the loads can be connected. High-voltage energy source 1 and the loads are floating; they form an IT system in a generally known manner.

[0030] The cables, consumers and other electrical components used here have parasitic resistances as real components, which in the Fig. 1 are shown summarily as insulation resistances R1, R2. These insulation resistances R1, R 2 parasitäre , parallel-connected capacitors (not shown here).

[0031] The values ​​of the insulation resistances R1, R2 are not known a priori and are also subject to changes over time.

[0032] In the following, a combined control and monitoring device 3 is described, which comprises a control device 4 for controlling a current quantity, here a symmetry current I Sand an insulation monitoring device 8. This combined device is also referred to as a symmetric insulation monitoring device 3, which is used in particular in Fig. 2 is shown.

[0033] The insulation monitoring device 8 serves to monitor the insulation resistances R1, R2. If, for example, one of the insulation resistances R1, R2 falls below a predetermined threshold value, appropriate measures are initiated. For example, a signal S (see Fig. 2) will be submitted.

[0034] However, during operation, it's not just the absolute values ​​of the insulation resistances R1 and R2 that are important, but also the symmetry between the circuit branches of the respective insulation resistances.

[0035] In an asymmetrically operated vehicle electrical system 10, different insulation resistances R1, R2 may occur, resulting in different voltages measured from the positive HV potential HV+ to ground 2 and measured from the negative HV potential HV- to ground 2. In this case, the vehicle electrical system would be operated asymmetrically if no appropriate countermeasures are taken.

[0036] The control device 4 acts on two variable resistors R3, R4 such that the voltages U1, U2 between the high-voltage potentials HV+, HV- and ground 2 become equal. The insulation monitoring device 8 specifies a setpoint for the control device 4, namely the common-mode voltage U cm , which is described below.

[0037] An output value of the control device 4 is a current, the balancing current I st, which is used as input value for the insulation resistance determination by the insulation monitoring device 8.

[0038] Thus, the insulation monitoring device 8 is connected to the control device 4 via the specification of the common mode voltage U cm and via the balancing current I S coupled.

[0039] The combined insulation monitoring and balancing device 3 has two specific tasks. First, it monitors the insulation of the high-voltage potentials HV+, HV- to the predetermined electrical ground 2, and second, it balances the high-voltage potentials HV+, HV- with respect to ground 2. Balancing reduces the rate of insulation aging because the voltage to be isolated is kept as low as possible.

[0040] The balancing function is realized by a control loop, which in the illustrated embodiments has a balancing current IS which controls the voltages U1 and U2 to be balanced. This is Fig. 1 is represented by dashed lines. The control device 4 can be integrated with the insulation monitoring device 8 in a single component or integrated into another component.

[0041] In alternative embodiments, a different current value can also be determined, depending on which the voltages U1, U2 to be symmetrized are then controlled.

[0042] In any case, the resulting current, here the symmetry current I S , and used in the calculation of the insulation resistances R1, R2.

[0043] It can also happen that R1 and R2 are almost the same size and therefore only a small symmetry current I S occurs with perfect symmetrization. Thus, the balancing current I Salone is not suitable for determining the insulation resistances R1, R2. Instead, it is useful to apply small asymmetries to the system in order to be able to determine the insulation resistances R1, R2. If you want to determine two quantities (here R1 and R2), two independent measurements are required. The asymmetry is achieved by not making the system perfectly symmetrical, but rather deliberately creating a deviation from the ideal state. This results in a current measurement in each case (i.e. for perfect symmetry and for imperfect symmetry with a small voltage deviation of the common-mode voltage from zero). This allows two measured values ​​to be determined, which can then be used to calculate the desired quantities.

[0044] The insulation resistances R1, R2 can be calculated as follows: The total voltage U G of the high voltage system is given by UG=U1+U2, which corresponds to the sum of the voltages U1, U2, i.e. the positive measured voltages relative to ground 2.

[0045] The so-called common mode voltage is defined by UCM=(U1−U2) / 2.

[0046] The node point theorem (Kirchhoff’s 1st law) for the symmetry current Is (ground current) then results in: IS+U1 / R1−U2 / R2=0.

[0047] This determines the common mode voltage as UCM=UG / 2*(R1−R2) / (R1+R2)−IS*R1*R2 / (R1+R2).

[0048] From the two pairs of values ​​(U CM,A , I S,A ) and (U CM,B , I S,B ), which represent the corresponding common-mode voltages U CM and symmetry currents Is, the two insulation resistances R1, R2 can be calculated.

[0049] In particular, the total insulation resistance of most interest results from: R1*R2 / (R1+R2)=(UCM,B−UCM,A) / (IS,A−IS,B)

[0050] The calculation itself and also the sequential specification of the two states A and B (i.e. the specification of U CM,A and U CM,B ) is conveniently carried out by a small control computer (microcontroller or FPGA or similar).

[0051] In the Fig. Figure 2 shows an embodiment of a control device 4 together with the insulation monitoring device 8, which is integrated into the circuit of the vehicle electrical system 10. As described above, the insulation monitoring device 8 monitors the insulation resistances R1, R2 (see Fig. 1) and may emit a signal S if the resistance falls below a certain value

[0052] An operational amplifier 5 provides a setpoint for the common-mode voltage U CMAt the output of the operational amplifier 5, a symmetrical transistor circuit 6 with bipolar transistors is arranged, which controls the balancing current Is (ground current) so that the setpoint of the common-mode voltage U CM is maintained. The collector terminals of transistors 6 are each connected to the high-voltage potential lines HV+ and HV-. The emitter terminals of the transistors are connected to ground 2 via emitter resistors 7. Other transistor designs can also be used in other embodiments.

[0053] By means of the device 4, which is designed analogously here, the necessary symmetry current Is can be set by the control device 4 for a predetermined common-mode voltage.

[0054] This enables the simultaneous symmetrization of the system to the specified common-mode voltage U CM and the determination of the necessary balancing current I S .

[0055] An advantage of active balancing control using a control loop compared to passive balancing using resistors is that the common-mode voltage U CM of the system can be kept very small. In addition, it is easily possible (e.g. in the embodiment according to Fig. 2 by the choice of emitter resistors 7 with limited base voltage or by adding collector resistors), to limit the maximum symmetry current Is, so that in the event of an insulation fault, the fault current is only insignificantly increased by the counteracting symmetrization.

[0056] Separating insulation monitoring and active balancing is not practical, since active balancing compensates for the asymmetry necessarily caused by insulation monitoring and thus prevents insulation measurement. The illustrated embodiments, which combine both mechanisms, circumvent this.

[0057] It should be understood that the invention is not limited to the embodiments described above, and various modifications and improvements may be made without departing from the concepts described herein. Any of the features may be used separately or in combination with any other features, provided they are not mutually exclusive, and the disclosure extends to and encompasses all combinations and subcombinations of one or more of the features described herein. List of reference symbols 1 high-voltage energy source 2 Mass 3 Symmetry insulation monitoring device 4 Control device 5 operational amplifiers 6 transistors 7 Emitter resistance 8 Insulation monitoring device 10 On-board power system arrangement I S Symmetry current HV+ first high voltage potential HV- second high voltage potential R1 first insulation resistance R2 second insulation resistance S Signal of the insulation monitoring device U1 first voltage to ground U2 second voltage relative to ground U CM Common mode voltage QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 202 892 A2

[0005] DE 10 2021 003843 A1

[0005] DE 10 2018 211625 A1

[0005]

Claims

[1] On-board power supply arrangement (10) for an aircraft with at least one connectable consumer, wherein the on-board power supply arrangement (10) - a high-voltage energy source (1) for providing a first high-voltage potential (HV+) and a second high-voltage potential (HV-), - further comprising a first insulation resistance (R1) between the first high-voltage potential (HV+) and an electrical ground (2) and a second insulation resistance (R2) between the second high-voltage potential (HV-) and the electrical ground (2), wherein the at least one consumer and the high-voltage energy source (1) form a ground-free system, - an insulation monitoring device (8) for monitoring the insulation resistances (R1, R2), wherein the insulation monitoring device (8) has a compensation circuit which is designed and arranged to reduce a difference between the insulation resistances (R1, R2) by actively balancing voltages (U1, U2), characterized by that the insulation monitoring device (8) is coupled to a control device (4) to form a combined symmetry insulation monitoring device (3), wherein a current variable, in particular a symmetry current (I S ), which can be controlled depending on the voltages (U1, U2) to be symmetrized with respect to ground (2). [2] On-board power system arrangement according to claim 1, characterized by that the current magnitude, especially the symmetry current (I S ), and this can be used in the calculation of the insulation resistances (R1, R2). [3] On-board power system arrangement according to claim 1 or 2, characterized by that the control device (4) has a control circuit in which a setpoint for a common-mode voltage (U CM ) is present. [4] On-board power system arrangement according to at least one of the preceding claims, characterized by that the insulation monitoring device (8) has a setpoint, in particular a value for a common-mode voltage (U CM ) and a current value, in particular the symmetry current (Is) as input value. [5] On-board power system arrangement according to at least one of the preceding claims, characterized by that the control device (4) is constructed as an analog circuit and has an operational amplifier (5) and a symmetrical transistor circuit (6). [6] On-board power system arrangement according to at least one of claims 1 to 4, characterized by that the control device (4) is designed as a digital circuit. [7] On-board power system arrangement according to at least one of the preceding claims, characterized by that the high-voltage energy source (1) comprises a battery, a generator, in particular a generator driven by a gas turbine, and / or a fuel cell. [8] On-board power system arrangement according to at least one of the preceding claims, characterized by that it is integrated into an aircraft, in particular a UAM aircraft or an airplane. [9] On-board power system arrangement according to at least one of the preceding claims, characterized by that it is coupled to a consumer which is designed in particular as an electric drive motor for a propeller or a rotor, as an auxiliary actuator and / or as a wing heater against icing and cabin heating. [10] Method for operating an on-board power supply arrangement (10) for an aircraft with at least one connectable consumer, wherein the on-board power supply arrangement (10) - a high-voltage energy source (1) for providing a first high-voltage potential (HV+) and a second high-voltage potential (HV-), - further comprising a first insulation resistance (R1) between the first high-voltage potential (HV+) and an electrical ground (2) and a second insulation resistance (R2) between the second high-voltage potential (HV-) and the electrical ground (2), wherein the at least one consumer and the high-voltage energy source (1) form a ground-free system, - an insulation monitoring device (8) for monitoring the insulation resistances (R1, R2), wherein the insulation monitoring device (8) has a compensation circuit which is designed and arranged to reduce a difference between the insulation resistances (R1, R2) by actively balancing voltages (U1, U2), characterized bythat the insulation monitoring device (8) is coupled to a control device (4) to form a combined symmetry insulation monitoring device (3), wherein a current variable, in particular a symmetry current (I S ), depending on the voltages (U1, U2) to be symmetrized with respect to ground (2).

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