Electrical insulation barrier

Abstract

This document relates to an electrical isolation barrier (35) for an aircraft DC-DC converter structure comprising: a power transformer (36) having: a primary winding (36a) electrically connected to the inverter (32) of the high-voltage power grid (31); a secondary winding (36b) electrically connected to the rectifier (38) of the low-voltage power grid (37); and a closed magnetic circuit (36c), said primary winding (36a) and said secondary winding (36b) being wound around the closed magnetic circuit (36c); and at least two primary capacitors (Cp), each arranged in series with the primary winding (36a) of the transformer, and / or at least two secondary capacitors (Cs), each arranged in series with the secondary winding (36b) of the power transformer (36). Abstract figure: Figure 3

Description

Title of the invention: Electrical insulation barrier technical field

[0001] This document falls within the field of electrical isolation barriers for aircraft DC-DC current conversion structures. Previous technique

[0002] The aeronautical field continually seeks to improve the management and distribution of electrical energy within aircraft systems. With the anticipated increase in electrical power requirements of new aircraft models, it is becoming necessary to develop onboard electrical networks.

[0003] In certain aircraft network architectures, the propulsion high voltage (HV) networks (voltage for example between 540V and 800V direct current, or 540VDC and 800VDC) and non-propulsion networks and the low voltage (LV) networks (corresponding for example to a direct voltage of 28V as defined by the Air Transport Association 24 - or ATA 24 standards) are interconnected by means of isolated direct-direct current converters, called DC-DC converters, which serve as interfaces between the two networks.

[0004] The isolation provided by these DC-DC converters is essential, as it constitutes the main barrier preventing the propagation or injection of HV voltage from the HV network to the LV network. Due to the possibility of events classified as catastrophic, aircraft manufacturers require reinforced, or even doubled, isolation to guarantee immunity against the propagation of such faults.

[0005] Therefore, the safety standards for aeronautical systems require at least a double isolation barrier between the HV and LV networks.

[0006] An existing solution for achieving a double isolation barrier involves, for example, two consecutive galvanic isolation barriers using transformers.

[0007] Fig. 1 illustrates such a conversion structure 2 which includes a high voltage HVDC source electrically connected to an inverter 4, a low voltage LVDC source electrically connected to a rectifier 6, and two transformers 8a, 8b each forming a galvanic isolation barrier and separating the inverter 4 from the rectifier 6.

[0008] Galvanic isolation for such applications is generally ensured by a high frequency (HF) technology, which consists of interlacing a first 8a-1, 8b-1 and second 8a-2, 8b-2 windings, called HV and LV windings, thus compromising the robustness of the solution.

[0009] Another existing solution is the combination of a galvanic isolation barrier and an active circuit which separates the HV and LV networks in the event of fault detection.

[0010] Figure 2 illustrates such a conversion structure 20, which comprises a single transformer 22 and an active circuit 24 forming a switching device. The active circuit 24 is controlled and is capable of isolating the high-voltage and low-voltage networks in the event of a fault detection.

[0011] In this example, the active circuit 24 is arranged in series between the HVDC source and the inverter 4.

[0012] However, the active circuit 24 requires control devices and introduces losses, because it has to manage the current from the HVDC source.

[0013] These conventional solutions do not fully meet the requirements in terms of efficiency (for example due to the presence of two transformers), mass (for example due to the use of two transformers or an active circuit) and reliability (for example due to the active circuit).

[0014] Planar windings can be used by separating the primary and secondary windings, but this approach tends to reduce magnetic coupling and increase losses in the windings.

[0015] Furthermore, this approach presents only a single galvanic barrier formed by the transformer alone.

[0016] There is therefore a need to find an alternative solution that reinforces existing insulation methods. Summary

[0017] To this end, the present document proposes an electrical isolation barrier for an aircraft DC-DC conversion structure comprising: - a power transformer which includes: • a primary winding electrically connected to the inverter of the high-voltage electrical network; • a secondary winding electrically connected to the rectifier of the low-voltage electrical network; and • a closed magnetic circuit, said primary winding and said secondary winding being wound around the closed magnetic circuit; and - at least two primary capacitors, each arranged in series with the primary winding of the transformer and / or at least two secondary capacitors, each arranged in series with the secondary winding of the power transformer.

[0018] In this way, the galvanic isolation provided by said at least one power transformer, forming a galvanic barrier, is reinforced with said at minus two primary and secondary capacitors, each of which forms a capacitive barrier.

[0019] In other words, said at least two primary and secondary capacitors forming the capacitive barriers provide additional so-called capacitive insulation.

[0020] The electrical insulation barrier offers an alternative that reduces losses and improves efficiency compared to conventional solutions of the prior art.

[0021] By reinforcing galvanic isolation with capacitive barriers, an asymmetric isolation barrier is formed (galvanic barrier and capacitive barrier), which barrier improves the safety and reliability of aircraft electrical systems.

[0022] In operation, the primary and secondary capacitors also make it possible to eliminate the direct current component of the alternating current passing through them.

[0023] The electrical isolation barrier may comprise only two primary capacitors and / or only two secondary capacitors.

[0024] According to this aspect, a double capacitive isolation barrier is achieved between the HV and LV networks: a primary capacitive isolation barrier formed by the two primary capacitors and a secondary capacitive isolation barrier formed by the two secondary capacitors.

[0025] The electrical isolation barrier comprises a triple isolation barrier with a galvanic barrier (power transformer), a primary capacitive isolation barrier (primary capacitors) and a secondary capacitive isolation barrier (secondary capacitors).

[0026] In this embodiment, the capacitors also serve to eliminate the DC component of the current on both the primary winding side and the secondary winding side, which further improves performance.

[0027] The electrical isolation barrier may comprise only three primary capacitors and / or only three secondary capacitors.

[0028] In addition to enabling enhanced capacitive isolation, the three primary capacitors and the three secondary capacitors are suitable for electrical connection to three-phase elements.

[0029] Additionally, the use of three primary capacitors and three secondary capacitors provides redundancy and fault tolerance, since the failure of one capacitor does not compromise the entire electrical insulation barrier on the primary and secondary winding side.

[0030] Finally, increasing the number of capacitors improves filtering and noise suppression.

[0031] This document may also relate to a DC-DC converter structure for aircraft comprising: - A high-voltage electrical network that includes: • A high-voltage electrical source capable of delivering a direct current voltage, known as high-voltage direct current; and • An inverter electrically connected to the high-voltage power source; and - A low-voltage electrical network that includes: • A low-voltage electrical source capable of delivering a direct current voltage, known as low-voltage direct current; and • A rectifier electrically connected to the low voltage power source, the high voltage power network and the low voltage power network being electrically isolated by an electrical insulation barrier according to the aforementioned type.

[0032] In this way, the efficient and reliable conversion of electrical energy from the high voltage electrical network to the low voltage electrical network is guaranteed.

[0033] In operation, the high voltage power source provides a continuous high voltage output, which is then converted by the inverter into a form suitable for the aircraft's electrical system.

[0034] Similarly, the low voltage power source delivers a DC low voltage output, which is rectified by the rectifier for use in the aircraft's electrical system.

[0035] The electrical insulation provided by the insulation barrier ensures the safe and reliable operation of the high voltage and low voltage networks, preventing any undesirable electrical interaction or propagation of a fault from the high voltage network to the low voltage network (or vice versa).

[0036] For example, in the case of the presence of at least two primary capacitors, a potential overvoltage fault occurring on the high-voltage network side can either be absorbed by said at least two primary capacitors or cause them to fail (capacitors equivalent to an open circuit). Thus, the propagation of the overvoltage fault to the rest of the conversion structure is prevented.

[0037] The high DC voltage (to be understood as nominal) can be between 500 VDC and 1000 VDC.

[0038] The low DC voltage (to be understood as nominal) can be between 12 VDC and 35 VDC, preferably equal to 28 VDC.

[0039] By adapting to these operating voltage ranges, the conversion structure can be applied to various aeronautical systems with different energy requirements, these voltage ranges being specific to aircraft.

[0040] The power transformer may include an insulator between the primary winding and the secondary winding, said insulator having a dielectric strength greater than twice, preferably three times, the high DC voltage.

[0041] In other words, the insulator can have sufficient electrical rigidity to withstand twice, preferably three times, the high direct voltage.

[0042] Said at least two primary capacitors and / or said at least two secondary capacitors may have an equivalent impedance so that said at least two primary capacitors and / or said at least two secondary capacitors are capable of carrying the electric current through the primary winding and / or the secondary winding respectively.

[0043] According to this aspect, the equivalent impedance of said at least two primary capacitors (arranged in parallel) is therefore formulated as follows 7--1___ with Nd the number of primary capacitors, and co the angular frequency. ^eq__p - jNpwCp p

[0044] Similarly, the equivalent impedance of said at least two secondary capacitors (arranged in parallel) is therefore formulated as follows 7__1__ with Ns the number of secondary capacitors. ^eq_s - jNsWCs

[0045] In this way, the primary winding and the secondary winding ensure the segregation of the high voltage and low voltage networks.

[0046] The fact that the capacitors are capable of carrying the current flowing in the respective adjacent windings (i.e. to which they are electrically connected) also guarantees the robustness and reliability of the structure in the face of high voltage levels.

[0047] In other words, by incorporating these design features, the structure can effectively handle the voltage requirements of the electrical system.

[0048] The conversion structure ensures a high level of electrical insulation and minimizes the risk of electrical failure or malfunction, thus contributing to the overall safety and performance of the aircraft's electrical systems.

[0049] Said at least two primary capacitors and / or said at least two secondary capacitors may each comprise an impedance such that said at least two primary capacitors and / or said at least two secondary capacitors have a voltage across their terminals less than 2%, preferably 1%, of the voltage through the primary winding and / or the secondary winding respectively.

[0050] In this way, it is ensured that the capacitors operate within a safe voltage range, minimizing the risk of failure or electrical malfunction.

[0051] By maintaining the voltage across the capacitors at a low level compared to the voltage across the windings, the capacitors provide insulation and effective protection. This prevents overvoltages or voltage fluctuations from affecting the performance and reliability of the conversion structure.

[0052] In addition, this helps to minimize voltage drops in the capacitors, thereby reducing the power losses associated with the capacitors.

[0053] More specifically, said at least two primary capacitors and / or said at least two secondary capacitors may each comprise an impedance Zc such that Zc = AV / IRMS with AV the voltage across the capacitor considered, and IrmsIê the effective current through the capacitor considered (i.e. the root mean square value of the alternating current).

[0054] The inverter and / or rectifier may include a high voltage switching cell and / or a low voltage switching cell, which high voltage switching cell and / or low voltage switching cell comprises a number of pairs of transistors in parallel with each other equal to the number of primary capacitors and / or secondary capacitors, each primary capacitor and / or secondary capacitor being electrically connected to an electrical potential arranged between a corresponding pair of transistors.

[0055] The use of a switching cell with parallel pairs of transistors allows for efficient and controlled switching of the high-voltage and / or low-voltage electrical signals of the corresponding networks. The parallel arrangement of the transistors increases current handling capacity and reduces power losses, thereby improving the overall efficiency and performance of the inverter and / or rectifier.

[0056] Connecting each primary and / or secondary capacitor to an electrical potential between a pair of transistors ensures that the capacitors are properly charged and discharged during the switching operation.

[0057] For example, the transistor pairs of the switching cell can be MOSFET transistor pairs.

[0058] The inverter can be a three-phase inverter and the rectifier can be a three-phase rectifier.

[0059] The three-phase inverter and three-phase rectifier provide a balanced and regular output, minimizing harmonic distortion and ensuring stable and reliable operation of the conversion structure.

[0060] The use of a three-phase inverter and rectifier in the structure also reduces power losses and distributes power over several phases, resulting in a more balanced and efficient use of power.

[0061] In addition, the three-phase configuration offers advantages in terms of scalability and flexibility: it allows the integration of additional power sources or loads.

[0062] This document may also relate to an aircraft electrical distribution or propulsion network comprising at least one DC-DC conversion structure of the type described above.

[0063] By integrating the proposed structure, the aircraft can efficiently manage and distribute electrical power, meeting the specific requirements of high-voltage and low-voltage networks. This allows the aircraft to operate efficiently and reliably, supporting various onboard electrical applications and systems.

[0064] This document may also relate to an aircraft comprising the electrical distribution or propulsion network according to the aforementioned type. Brief description of the figures

[0065] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0066] [Fig. 1] schematically illustrates a double galvanically isolated DC-DC current conversion structure according to the prior art,

[0067] [Fig.2] schematically illustrates a DC-DC conversion structure with an active circuit according to the prior art,

[0068] [Fig.3] schematically illustrates a DC-DC current conversion structure according to a first embodiment of the present document,

[0069] [Fig.4] schematically illustrates a DC-DC current conversion structure according to a second embodiment of the present document,

[0070] [Fig. 5] schematically illustrates a DC-DC conversion structure according to a third embodiment of the present document, and

[0071] [Fig.6] schematically illustrates a DC-DC current conversion structure according to a fourth embodiment of the present document. Description of the implementation methods

[0072] Reference is now made to [Fig.3] which illustrates a DC-DC current conversion structure 30 according to a first embodiment of the present document.

[0073] The DC-DC current conversion structure 30 comprises, on the one hand, a high voltage network 31 comprising a high voltage HVDC source electrically connected to an inverter 32.

[0074] The inverter 32 includes a high voltage switching cell 34 which high voltage switching cell 34 comprises a first pair of transistors T1-T2 and a second pair of transistors T3-T4.

[0075] The inverter 32 is electrically connected at the output to an electrical isolation barrier 35.

[0076] The DC-DC current conversion structure 30 includes, on the other hand, a low voltage network 37 comprising a low voltage LVDC source electrically connected to a rectifier 38.

[0077] Similar to the inverter 32, the rectifier 38 includes a low voltage switching cell 34' which low voltage switching cell 34' comprises a third pair of transistors T5-T6 and a fourth pair of transistors T7-T8.

[0078] It is to be understood that the transistors of the inverter 32 and / or the rectifier 38 can be MOSFET transistors.

[0079] The rectifier 38 is electrically connected at the input to the electrical isolation barrier 35.

[0080] The electrical insulation barrier 35 includes a power transformer 36.

[0081] On the one hand, the power transformer 36 has a primary winding 36a, called the HV winding, electrically connected to the inverter 32 (and therefore to the high voltage network 31) via primary capacitors Cp arranged in series with the HV winding 36a.

[0082] More particularly, a first terminal of the HV winding 36a is electrically connected to a first electrical potential arranged between the transistors of the first pair of transistors T1-T2 of the high voltage switching cell 34, and a second terminal of the HV winding 36a is electrically connected to a second electrical potential arranged between the transistors of the second pair of transistors T3-T4 of the high voltage switching cell 34.

[0083] On the other hand, the power transformer 36 has a secondary winding 36b, called the LV winding, electrically connected to the rectifier 38 (and therefore to the low voltage network 37).

[0084] More particularly, a second terminal of the LV winding 36b is electrically connected to a third electrical potential arranged between the transistors of the fourth pair of transistors T5-T6 of the low voltage switching cell 34', and a second terminal of the LV winding 36b is electrically connected to a fourth electrical potential arranged between the transistors of the fourth pair of transistors T7-T8 of the low voltage switching cell 34'.

[0085] The HV 36a and LV 36b windings are each wound around a column of a closed magnetic circuit 36c of the power transformer 36.

[0086] The power transformer 36 further includes an insulator 36d arranged between the HV winding 36a and the LV winding 36b.

[0087] In operation, the DC-DC current conversion structure 30 has a double isolation barrier: a first capacitive isolation barrier is formed by the primary capacitors Cp and a second galvanic isolation barrier is formed by the power transformer 36.

[0088] Thus, a possible fault such as an overvoltage or a short circuit appearing on the side of the HV 31 network can either be supported by the first capacitive isolation barrier (i.e. the primary capacitors Cp), or lead to a failure mode of the first capacitive isolation barrier which creates an open circuit.

[0089] Reference is now made to [Fig.4] which illustrates a DC-DC current conversion structure 40 according to a second embodiment of the present document.

[0090] In this second embodiment, the electrical isolation barrier 35 does not include primary capacitors Cp, but secondary capacitors Cs.

[0091] Compared to the first embodiment, the secondary capacitors Cs form the second capacitive isolation barrier, which capacitors Cs are arranged in series with the LV winding 36b, and between the LV winding 36b and the rectifier 38 (and therefore the low voltage network 37).

[0092] Thus, any fault appearing on the transformer 36 side can be absorbed by the second capacitive isolation barrier (i.e., the secondary capacitors Cs). In other words, the second capacitive barrier prevents the propagation of high voltage in the event of a loss of insulation provided by the transformer 36.

[0093] In addition, the secondary capacitors are sized to support the permissible current in the LV 36b winding, which is greater than that of the HV winding (by a factor equal to the turns ratio).

[0094] Reference is now made to [Fig.5] which illustrates a DC-DC current conversion structure 50 according to a third embodiment of the present document.

[0095] The third embodiment is a superposition of the first embodiment and the second embodiment.

[0096] In the third embodiment, the electrical isolation barrier 35 comprises both primary capacitors Cp in series with the HV winding 36a, and secondary capacitors Cs in series with the LV winding 36b.

[0097] The primary capacitors Cp are arranged between the inverter 32 and the power transformer 36, and the secondary capacitors Cs are arranged between the rectifier 38 and the power transformer 36.

[0098] In this way, the conversion structure 50 is robust to faults that may occur either on the side of the HV network 31 or on the side of the transformer 36.

[0099] Reference is now made to [Fig.6] which illustrates a DC-DC current conversion structure 60 according to a fourth embodiment of the present document.

[0100] In this fourth embodiment, the inverter 32 is a three-phase inverter, and the corresponding high-voltage switching cell 34 comprises three pairs of transistors T9-T10, T11-T12, T13-T14.

[0101] The rectifier 38 is a three-phase rectifier, and the corresponding low-voltage switching cell 34' comprises three pairs of transistors T9-T10, T11-T12, T13-T14.

[0102] The electrical isolation barrier 35 comprises three primary capacitors Cp. Each primary capacitor Cp is electrically connected to the HV winding 36a, on the one hand, and to a corresponding pair of transistors of the high voltage switching cell 34 of the three-phase inverter 32, on the other hand.

[0103] In other words, each primary capacitor Cp is electrically connected to the HV winding 36a, on the one hand, and to an electrical potential between the transistors of a pair of MOSFET transistors of the high voltage switching cell 34 among the pairs T9-T10, T11-T12, T13-T14, on the other hand.

[0104] The rectifier 38 is a three-phase rectifier, and the corresponding low-voltage switching cell 34' comprises three pairs of transistors T15-T16, T17-T18, T19-T20.

[0105] The electrical isolation barrier 35 further comprises three secondary capacitors Cs. Each secondary capacitor Cs is electrically connected to the LV winding 36b, on the one hand, and to a corresponding pair of transistors of the low voltage switching cell 34' of the three-phase rectifier 38, on the other hand.

[0106] In other words, each secondary capacitor Cs is electrically connected to the LV winding 36b, on the one hand, and to an electrical potential between the transistors of a pair of transistors of the low voltage switching cell 34' among the pairs T15-T16, T17-T18, T19-T20, on the other hand.

[0107] The use of multiple phases (the different bridges formed between the electrical potentials and the capacitors Cp, Cs) ensures redundancy and fault tolerance, since the failure of one phase does not compromise the entire system. In operation, this guarantees the continuous operation of the electrical distribution of the conversion structure, even in the event of a component failure.

Claims

Demands

1. Electrical isolation barrier (35) for an aircraft DC-DC conversion structure comprising: - a power transformer (36) which includes: • a primary winding (36a) intended to be electrically connected to an inverter (32) of a high-voltage electrical network (31); • a secondary winding (36b) intended to be electrically connected to a rectifier (38) of a low-voltage electrical network (37); and • a closed magnetic circuit (36c), said primary winding (36a) and said secondary winding (36b) being wound around the closed magnetic circuit (36c); and - at least two primary capacitors (Cp) each arranged in series with the primary winding (36a) of the transformer and / or at least two secondary capacitors (Cs) each arranged in series with the secondary winding (36b) of the power transformer (36).

2. Electrical isolation barrier (35) according to claim 1 comprising only two primary capacitors (Cp) and / or only two secondary capacitors (Cs).

3. Electrical isolation barrier (35) according to claim 1 comprising only three primary capacitors (Cp) and / or only three secondary capacitors (Cs).

4. Aircraft DC-DC conversion structure (30, 40, 50, 60) comprising: - A high-voltage electrical network (31) which includes: • A high-voltage (HVDC) power source capable of delivering a direct current voltage, referred to as high-voltage direct current; and • An inverter (32) electrically connected to the high-voltage (HVDC) power source; and A low-voltage electrical network (37) which includes: • A low voltage (LVDC) power source capable of delivering a direct current voltage, referred to as low voltage direct current; and • A rectifier (38) electrically connected to the low voltage (LVDC) power source, the high voltage power network (31) and the low voltage power network (37) being electrically isolated by an electrical insulation barrier (35) according to any one of the preceding claims.

5. Structure (30, 40, 50, 60) according to claim 4, wherein the power transformer (36) comprises an insulator (36d) between the primary winding (36a) and the secondary winding (36b), said insulator (36d) having a dielectric strength greater than twice, preferably three times, the high DC voltage, said at least two primary capacitors (Cp) and / or said at least two secondary capacitors (Cs) have an equivalent impedance such that said at least two primary capacitors (Cp) and / or said at least two secondary capacitors (Cs) are capable of carrying the electric current through the primary winding (36a) and / or the secondary winding (36b) respectively.

6. Structure (30, 40, 50, 60) according to claim 4 or 5, wherein said at least two primary capacitors (Cp) and / or said at least two secondary capacitors (Cs) each comprise an impedance such that said at least two primary capacitors (Cp) and / or said at least two secondary capacitors (Cs) have a voltage across their terminals less than 2%, preferably 1%, of the voltage through the primary winding (36a) and / or the secondary winding (36b) respectively.

7. Structure (30, 40, 50, 60) according to any one of claims 4 to 6, wherein the inverter (32) and / or the rectifier (38) comprises a high-voltage switching cell (34) and / or a low-voltage switching cell (34'), which high-voltage switching cell (34) and / or low-voltage switching cell (34') comprises a number of transistor pairs (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T12, T13, T14, T15, T16, T17, T18, T19, T20) in parallel with each other equal to the number of primary capacitors (Cp) and / or secondary capacitors (Cs), each primary capacitor (Cp) and / or secondary capacitor (Cs) being electrically connected to an electrical potential arranged between a corresponding pair of transistors (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TU, T12, T13, T14, T15, T16, T17, T18, T19, T20).

8. Structure (60) according to any one of claims 4 to 7, wherein the electrical insulation barrier (35) is according to claim 3, the inverter (32) is a three-phase inverter and the rectifier (38) is a three-phase rectifier.

9. Aircraft electrical power distribution or propulsion network comprising at least one DC-DC conversion structure (30, 40, 50, 60) according to any one of claims 4 to R

10. of O. Aircraft comprising the electrical distribution or propulsion network according to the preceding claim.

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