Isolated and reconfigurable power converter

Abstract

The present invention relates to a power conversion system for an aircraft onboard electrical power system, the power conversion system being capable of converting high voltage DC to low voltage DC and vice versa, the power conversion system comprising switching means configured such that the system operates in accordance with a plurality of configurations each forming an isolated DC / DC converter.

Description

Technical Field

[0001] This invention relates to onboard electrical systems in aircraft, and more particularly to the structure of power converters integrated into such electrical systems. Background Technology

[0002] To power the onboard equipment on the aircraft, numerous power converters are used, allowing power to be supplied to the individual devices from the aircraft's high DC voltage network at a low DC voltage.

[0003] With current technology, many types of power converters are available, and the selection of a power converter depends on the DC voltage level of the aircraft's network, the voltage level required for proper operation of the device, and the control of the converter. Specifically, the most decisive control parameters are the switching frequency, duty cycle, and phase shift between the power bridges. However, other parameters, such as dwell time (the switching delay between the two power arms), can also affect control quality.

[0004] Typically, an aircraft's onboard high-voltage DC network delivers a nominal DC voltage of approximately 270V. However, the voltage delivered by this network can vary significantly, potentially being 10% or even 20% higher or lower than the nominal voltage. This high variation, possibly related to grid load or generation instability, affects the converter's operating point. Even when a converter has been selected and sized to convert a high DC voltage of 270V to a low DC voltage varying between 16V and 30V, its operation is no longer optimal when the voltage delivered by the onboard high-voltage DC network varies.

[0005] Two examples of existing technology level converters in Figure 1 and 2 It is displayed in the middle.

[0006] Figure 1 This demonstrates an example of an isolated DC / DC converter architecture, also known as a Dual Active Bridge (DAB).

[0007] The structure includes a power converter, specifically an insulating transformer 4, which converts a high DC voltage V1 applied across the first H-bridge to a low DC voltage V2 applied across the second H-bridge. The two H-bridges 6 and 8 each include four transistors 10a, 10b, 12a, 12b and 14a, 14b, 16a, 16b, respectively.

[0008] The primary terminals 18a and 18b of transformer 4 are connected to the first 10 and second 12 branches of the first H-bridge 6. Specifically, inductor 22 is arranged between one of the primary terminals 18a of transformer 4 and the second branch 12 of the first H-bridge 6.

[0009] Inductor 22 (also known as leakage inductance) can generate overvoltage when the current in the transformer is cut off.

[0010] The secondary terminals 20a and 20b of transformer 4 are connected to the first 14 and second 16 branches of the second H-bridge 8.

[0011] Capacitors 24 and 26 can be arranged across each of the first 6 and second 8H bridges. These are filter capacitors, whose function is to reduce ripple in the input and output voltages of the converter. Resistors are modeled for the device powered by the voltage V2 delivered at the output of the conversion structure 2.

[0012] This conversion structure 2 can be used to convert a high voltage V1 between 220V and 330V to a low voltage V2 between 16V and 32V at a fixed frequency in the range of 10kHz to 1MHz (note that by replacing resistor 28 with a voltage source, the structure becomes reversible, with V2 becoming the input voltage and V1 becoming the output voltage).

[0013] exist Figure 2 In the second example of the conversion structure 30 shown, transformer 4 converts a high DC voltage V1 to a low DC voltage V2, which is applied to the terminals of the first bridge at H6 and the second bridge at H8, respectively. The two bridges are composed of four transistors 10a, 10b, 12a, 12b and 14a, 14b, 16a, 16b.

[0014] In addition to leakage inductance 22, inductance 32 (also known as magnetizing inductance) is also arranged between the primary terminals 18a and 18b of transformer 4. Furthermore, capacitor 34 is arranged between one of the primary terminals 18b of transformer 4 and the first branch 10 of the first H-bridge 6.

[0015] This conversion structure 30 therefore includes a resonant structure consisting of inductors 22 and 32 and capacitor 34, and is also referred to as a series-parallel resonant conversion structure LLC. The resonant structure provides a sinusoidal current output and switches at a variable frequency between 100kHz and 3000kHz depending on the load variations of the onboard network. The input and output ranges are the same for the DAB structure, i.e., between 220V and 330V and between 16V and 32V, respectively.

[0016] therefore, Figure 1 Structure 2 shown is optimal for applying a high voltage at the nominal level of 270V at the input (using simple control), and Figure 2The structure 30 shown is optimal for high voltages between 220V and 330V applied at the input. Outside these ranges, when there are variations in the voltage delivered by the aircraft's onboard high-voltage DC network, the two conversion structures 2 and 30 do not perform optimally, and therefore each conversion structure is limited.

[0017] The present invention aims to remedy these shortcomings in a simple, reliable and inexpensive manner. Summary of the Invention

[0018] This document relates to a power conversion system for an aircraft onboard electrical system, capable of converting high DC voltage to low DC voltage and vice versa, the system comprising:

[0019] - Provides high DC voltage V bus1 At least a first high-voltage DC bus and providing a low DC voltage V bus2 At least a second low-voltage DC bus;

[0020] - A first H-bridge, which is arranged between the terminals of a first bus and includes first and second branches;

[0021] - A second H-bridge, which is arranged between the terminals of the second bus and includes first and second branches;

[0022] - A power converter that can convert high DC voltage V bus1 Transformed into low DC voltage V bus2 And / or vice versa, it includes first and second primary terminals connected to the first branch and the second branch of the second H-bridge, respectively, and at least first and second secondary terminals;

[0023] - At least a first inductor, which is arranged in series between the second branch of the first H-bridge and the first primary terminal of the power converter; characterized in that the system further includes:

[0024] - At least one first capacitor, the first terminal of which is connected to the first branch of the first H-bridge;

[0025] - At least one second capacitor, the first terminal of which is connected to the first primary terminal of the power converter;

[0026] - Switching components that control the opening or closing of current, these switching components are configured such that the system operates according to the following configuration:

[0027] - A first isolated DC / DC converter configuration, wherein the second primary terminal of the power converter is connected to the first branch of the first H-bridge;

[0028] - A second isolated DC / DC converter configuration includes a resonant circuit formed by the following:

[0029] - First inductor, and

[0030] - A first capacitor, the second terminal of which is connected to the second primary terminal of the power converter;

[0031] - A third configuration, which forms an isolated DC / DC converter including a resonant circuit, said resonant circuit being formed by:

[0032] - The second terminal of the first capacitor is connected to the second primary terminal of the power converter.

[0033] - A second capacitor, the second terminal of which is connected to the second primary terminal of the power converter, and

[0034] - First inductor.

[0035] Therefore, this system enables optimized operation of the power converter, providing at least three operating configurations. Thus, depending on the input operating range, the system operates in one of the three configurations via a switching element, thereby enabling a wider operating range than systems with fixed configurations.

[0036] Therefore, the system can operate in a first configuration similar to a DAB isolation switching structure, a second configuration similar to an isolation switching structure including an LC resonant circuit, and a third configuration similar to an isolation switching structure including an LCC resonant circuit. Thus, the switching element means that the resonant circuit can be activated or deactivated depending on the configuration of the system to be switched.

[0037] With relatively simple controls, it is possible to reconfigure the conversion system to maintain a good level of efficiency in the power conversion system.

[0038] Therefore, current reconfigurable converter systems are electromagnetically compatible (EMC). The reduction in EMC stress is primarily attributed to the expansion of the switching frequency range. In fact, by increasing the values ​​of these frequencies, it becomes possible to reduce the size of the passive components that make up the EMC filter.

[0039] The switching component may include a first switching element, a second switching element, and a third switching element.

[0040] According to another characteristic of the conversion system:

[0041] -The first switching element may be arranged between the first capacitor and the second primary terminal of the power converter;

[0042] -The second switching element may be arranged between the first H-bridge branch and the second primary terminal of the power converter;

[0043] - A third switching element may be arranged between the second capacitor and the second primary terminal of the power converter.

[0044] Therefore, by opening and / or closing the switch, it is possible to reconfigure the conversion system to operate as follows:

[0045] -DAB structure, in which leakage inductance is part of the structure. In response to relatively simple controls such as phase-shift modulation, the optimal operating range is limited to the nominal point of an input voltage equal to 270V ± 5% and an output voltage equal to 28V ± 5%.

[0046] - An isolated switching structure comprising an LLC resonant circuit formed by an inductor and capacitor. Responding to relatively simple control, this structure is suitable for varying loads and voltages, where the switching frequency varies over a small range. This converter can operate at an input voltage of 270V ± 20% and an output voltage between 16V and 32V.

[0047] - An isolated switching structure comprising an LCC resonant circuit formed by an inductor and capacitor. Responding to relatively simple control, this structure is suitable for load and voltage variations, where the switching frequency varies over a wide range. This converter can operate at an input voltage of 270V ± 20% and an output voltage between 16V and 32V.

[0048] The switching components may include a reconfiguration module that is capable of individually controlling the first, second, and third switching elements to keep them in an open and / or closed state.

[0049] Control via this reconfiguration module allows for center switching between the three configurations.

[0050] Specifically, the reconfiguration module controls the first, second, and third switching elements such that:

[0051] - In the first configuration, the first switching element remains closed, while the second and third switching elements remain open;

[0052] - In the second configuration, the second switching element remains closed, while the first and third switching elements remain open;

[0053] - In the third configuration, the first switching element remains open, while the second and third switching elements remain closed.

[0054] The system may include a second inductor disposed between the primary terminals of the power converter, such that in a second configuration, the resonant circuit is formed by a first inductor, a second inductor, and a first capacitor, the second terminal of the first capacitor being connected to the second primary terminal of the power converter.

[0055] Therefore, the second configuration can operate as an isolated converter structure including an LLC resonant circuit formed by inductors and capacitors with a variable switching frequency within a reduced range of input voltage values ​​between 220V and 330V.

[0056] The first switching element, the second switching element, and the third switching element may include electrical or mechanical switches and transistors.

[0057] Therefore, the use of controllable switches, such as switches and transistors, makes it possible to switch between three configurations of a switching system by means of simple control of these switches. The switches used can be electrical and / or mechanical. And the transistors used can be, for example, bipolar transistors, insulated-gate bipolar transistors, metal-oxide-semiconductor field-effect transistors, or gallium nitride transistors.

[0058] Capacitor Cbus1 can be placed between the terminals of the second branch of the first H-bridge. Similarly, capacitor Cbus2 can be placed between the terminals of the second branch of the second H-bridge. These capacitors filter the voltage ripple of the DC voltage bus.

[0059] The first and / or second H-bridge may each include at least four power components. The four power components of the first bridge may be transistors or transistors with anti-parallel diodes. Preferably, diodes are used only in the second H-bridge because the first H-bridge requires a controllable switch to provide AC voltage at the transformer input.

[0060] The system may include a third low-voltage DC bus, and wherein the power converter includes third and fourth secondary terminals respectively connected to a first branch and a second branch of a third H-bridge arranged across the third high-voltage DC bus.

[0061] The system may have an operating range between 220V and 330V at the terminals of the first bus. Attached Figure Description

[0062] The above-described [ Figure 1 This demonstrates an existing dual active bridge (DAB) type isolated DC / DC converter structure;

[0063] The above-described [ Figure 2 [] indicates the existing second isolated DC / DC conversion structure;

[0064] [ Figure 3 This invention demonstrates a conversion system according to this application. Detailed Implementation

[0065] The following text is for reference only. Figure 3 , Figure 3This indicates that, according to the present invention, a high DC voltage V will be delivered by the aircraft's onboard electrical network. bus1 Convert to at least one low DC voltage V bus2 The power conversion system 32, wherein the low DC voltage level is suitable for powering various equipment of the aircraft, such as emergency wind turbines (known as RAT, which stands for ram air turbine), batteries, etc.

[0066] Figure 3 The conversion system 32 shown in the image is capable of converting high DC voltage V bus1 Converted to two low DC voltages V that can power various aircraft equipment bus2 and V bus3 (Not necessarily the same)

[0067] The power conversion system 32 can also perform the conversion in reverse. In this case, some components of the system are selected accordingly, as will be detailed later.

[0068] Figure 3 The circuit diagram shown is a simplified representation of the conversion system 32 according to the present invention. For simplicity, the aircraft's onboard network is provided with a high DC voltage V. bus1 The first high-voltage DC bus indicates that the two low-voltage DC buses are supplied with low DC voltage V, which is suitable for powering the equipment of the aircraft. bus2 The second low-voltage DC bus and provides low DC voltage V bus3 The third low-voltage DC bus is indicated.

[0069] These three voltage buses cross capacitor C respectively bus1 C bus2 and C bus3 These three capacitors are filter capacitors that reduce voltage variations at the input and output of the converter (i.e., smooth out the converted voltage).

[0070] The conversion system 32 also includes first H-bridges 34, second H-bridges 36, and third H-bridges 38. Each of these bridges 34, 36, and 38 includes first branches 40, 44, and 48, and second branches 42, 46, and 50. The first H-bridge 34 spans capacitor C. bus1 Arrangement, second H-bridge 36-span capacitor C bus2 Arrangement, and the third H-bridge spans 38 capacitors C bus3 Therefore, the voltage across the first H-bridge 34 is equal to the voltage V of the first high-voltage DC bus. bus1 Similarly, the voltages at the terminals of the second 36 and third 38H bridges are equal to the voltage V of the second low-voltage DC bus, which is designated to power the onboard equipment. bus2 and the voltage V of the third low-voltage DC bus bus3 .

[0071] Because the structure of the H-bridge is known to those skilled in the art, a brief description is given below. Each of these H-bridges includes first branches 40, 44, 48 and second branches 42, 46, 50, the ends of which are electrically connected to each other in pairs. Two switching components 40a, 40b, 44a, 44b, 48a, 48b and 42a, 42b, 46a, 46b, 50a, 50b are arranged on each of the first branches 40, 44, 48 and the second branches 42, 46, 50, and are identical on all branches 40, 44, 48 and 42, 46, 50. These switching components 40a, 40b, 44a, 44b, 48a, 48b and 42a, 42b, 46a, 46b, 50a, 50b can be unidirectional or bidirectional controlled or uncontrolled electrical components. Preferably, the first H-bridge 34 includes unidirectional or bidirectional controlled electrical components, i.e., transistors or circuit breakers. The second 36 and third 38 H-bridges may include controlled or uncontrolled electrical components, i.e., transistors, diodes, and switches. Where the switching system is capable of switching in both directions, only bidirectional transistors or switches may be used in the second 36 and third 38 H-bridges.

[0072] Therefore, as Figure 3 As can be seen from the diagram, the ends of the second branches of the first 34, second 36, and third 38H bridges are electrically connected to capacitor C, respectively. bus1 C bus2 and C bus3 The terminals.

[0073] System 32 further includes a power converter 52, which is more precisely a transformer herein. Transformer 52 is claimed to be a high-frequency single-phase transformer, as known in the art, capable of converting a high AC voltage from the first bridge 34 to a low AC voltage from the second bridge 36 and to a low AC voltage from the third bridge 38, and / or vice versa. Transformer 52 includes primary terminals 54a and 54b, and secondary terminals 56a, 56b, 56c, and 56d.

[0074] Bridges 34, 36, and 38H are electrically connected to the primary terminals 54a and 54b and the secondary terminals 56a, 56b, 56c, and 56d of the power converter 32.

[0075] like Figure 3 As can be seen, the first stage terminal 56a is electrically connected to the first branch 44 of the second H-bridge 36, specifically to the two power components 44a and 44b. Similarly, the second stage terminal 56b is electrically connected to the second branch 46 of the second H-bridge 36, specifically to the two power components 46a and 46b.

[0076] The third secondary terminal 56c is electrically connected to the first branch 48 of the third H-bridge 38, specifically to the two power components 48a and 48b. Similarly, the fourth secondary terminal 56d is electrically connected to the second branch 50 of the third H-bridge 38, specifically to the two power components 50a and 50b.

[0077] Finally, the first primary terminal 54a is indirectly and electrically connected to the second branch 42 of the first H-bridge 34, and specifically indirectly and electrically connected to the two power components 42a and 42b. Similarly, the second primary terminal 54b is indirectly and electrically connected to the first branch 40 of the first H-bridge 34, and specifically indirectly and electrically connected to the two power components 40a and 40b.

[0078] The component is arranged between the second branch 42 and the first primary terminal 54a, and between the first branch 40 and the second primary terminal 54b.

[0079] The first inductor L1 is connected in series between the second branch 42 of the first H-bridge 34 and the first primary terminal 54a of the power converter 52. This first inductor L1 can be replaced by the transformer leakage inductance, which is a transformer fault that limits the converted power of the transformer, with the high-frequency transformer being appropriately sized and optimized.

[0080] The second inductor L2 is arranged between the primary terminals 54a and 54b of the power converter 52. This second inductor L2 can be replaced by the magnetizing inductance of the transformer, which is the self-inductance of the primary winding of the transformer, provided that the size of the high-frequency transformer 52 is set and optimized accordingly.

[0081] The first terminal of the first capacitor C1 is connected to the first branch 40 of the first H-bridge 34, and its second terminal is connected to the second primary terminal 54b of the power converter 52 via the first switching element K1. Therefore, the first switching element K1 is arranged between the first capacitor C1 and the second primary terminal 54b of the power converter 52.

[0082] The first terminal of the second capacitor C2 is connected to the first primary terminal 54a of the power converter 52, and its second terminal can be connected to the second primary terminal 54b of the power converter 52 via the third switching element K3. Therefore, the third switching element K3 is arranged between the second capacitor C2 and the second primary terminal 54b of the power converter 52.

[0083] The second switching element is arranged between the first branch 40 of the first H-bridge 34 and the second primary terminal 54b of the power converter 52.

[0084] The three switching elements K1, K2, and K3 are electrical or mechanical switching elements and / or controllable transistors, and parts thereof form a switching member capable of controlling the opening or closing of an electric current. Specifically, the switching member includes a reconfiguration module capable of individually controlling the switching elements K1, K2, and K3 to hold them in an open and / or closed state.

[0085] Therefore, the switching elements K1, K2, and K3 are arranged to allow the system to operate in three configurations.

[0086] The conversion system 32 is configured in a first configuration, in which the reconfiguration module controls the first switching element K1 to remain closed and controls the second K2 and third K3 switching elements to remain open. In the first configuration, the converter system 32 forms an isolated dual active bridge DC / DC converter. In this configuration, the second primary terminal 54b of the power converter 52 is directly connected to the first branch 40 of the first H-bridge 34. With simple control, this configuration is particularly suitable for a voltage V close to a nominal voltage of 270V bus1 , with a variation of approximately 5% around this value.

[0087] The conversion system 32 is configured in a second configuration, in which the reconfiguration module controls the second switching element K2 to remain closed and the first K1 and third K3 switching elements to remain open. In this second configuration, the converter system 32 forms an isolated DC / DC converter with a resonant circuit formed by:

[0088] - a first inductor L1,

[0089] - a second inductor L2, and

[0090] - a first capacitor C1, whose second terminal is connected to the second primary terminal of the power converter.

[0091] The LLC resonant circuit formed by L1, L2, and C1 makes the converter system 32 particularly suitable for a voltage V in the range [220V; 330V] bus1 , where the required small switching frequency range is between fmin and three times fmin (50 kHz < fmin < 500 kHz), and has operation in continuous or discontinuous conduction mode.

[0092] The conversion system 32 is configured in a third configuration, in which the reconfiguration module controls the first switching element K1 to remain open and the second K2 and third K3 switching elements to remain closed. In this third configuration, the converter system 32 forms an isolated DC / DC converter with a resonant circuit formed by:

[0093] - a first capacitor C1, whose second terminal is connected to the second primary terminal of the power converter,

[0094] - The second capacitor C2, whose second terminal is connected to the second primary terminal of the power converter, and

[0095] - First inductor L1.

[0096] The LLC resonant circuit formed by L1, C1, and C2 makes the converter system particularly suitable for voltage ranges of [220V; 330V]. bus1 It has the required wide switching frequency range and operation only in discontinuous conduction mode, i.e., switching frequency between 50 kHz and 3 MHz.

[0097] Table 1 summarizes the states of switching elements K1, K2, and K3 in each of the three configurations: [Table 1]

[0098]

[0099] Therefore, it depends on the voltage V delivered by the aircraft's onboard network. bus1 The module control switching elements are reconfigured according to changes in voltage V to adapt to the voltage V. bus1 The configuration ensures the operation of the conversion system 32.

[0100] Using a simple control structure that persists even when the configuration changes (e.g., phase shift control), the optimal operating conditions for the switching elements are as follows:

[0101] - Nominal operating point (input voltage equals 270V and output voltage equals 28V): Configuration 1 in DAB.

[0102] -Discontinuous conduction with a wide frequency range, unlike the nominal operating point: Configuration 3 in LCC.

[0103] - Unlike the nominal operating point, continuous conduction with a reduced frequency range: Configuration 2 in LLC.

Claims

1. A power conversion system for an aircraft onboard electrical power system, capable of converting a high DC voltage into a low DC voltage and vice versa, the system comprising: - providing at least a first high-voltage DC bus providing a high DC voltage V bus1 and at least a second low-voltage DC bus providing a low DC voltage V bus2 ​ - a first H-bridge (34) arranged between the terminals of the first high voltage DC bus and comprising a first branch (40) and a second branch (42); - a second H-bridge (36) arranged between the terminals of the second low voltage DC bus and comprising a first branch (44) and a second branch (46); - a power converter (52) able to convert a high DC voltage V bus1 into a low DC voltage V bus2 and / or vice versa, comprising a first primary terminal (54a) and a second primary terminal (54b) and at least a first secondary terminal (56a) and a second secondary terminal (56b), said at least a first secondary terminal (56a) and a second secondary terminal (56b) being connected to a series connection point of the upper and lower bridge arms of the first branch (44) and to a series connection point of the upper and lower bridge arms of the second branch (46) of the second H-bridge (36), respectively; - at least a first inductance (LI) arranged in series between the series connection point of the upper and lower arms of the second branch (42) of the first H-bridge (34) and the first primary terminal (54a) of the power converter (52); characterized in that the system further comprises: - at least a first capacitor (CI) whose first terminal is connected to the series connection point of the upper and lower arms of the first branch (40) of the first H-bridge (34); - at least a second capacitor (C2) whose first terminal is connected to the first primary terminal (54a) of the power converter (52); - switching means capable of controlling the opening or closing of the current, these switching means being configured so that the system operates according to the following configurations: - a first configuration, isolated DC / DC converter, in which the second primary terminal (54b) of the power converter (52) is connected to the series connection point of the upper and lower arms of the first branch (40) of the first H-bridge (34); - a second configuration, isolated DC / DC converter, comprising a resonant circuit formed by: - the first inductance (LI), and - the first capacitor (CI) whose second terminal is connected to the second primary terminal (54b) of the power converter (52); - a third configuration, forming an isolated DC / DC converter comprising a resonant circuit formed by: - the first capacitor (CI) whose second terminal is connected to the second primary terminal (54b) of the power converter (52), - the second capacitor (C2) whose second terminal is connected to the second primary terminal (54b) of the power converter (52), and - the first inductance (LI).

2. The system of claim 1, wherein, The switching means comprise a first switching element (Kl), a second switching element (K2) and a third switching element (K3).

3. The system according to claim 2, characterized in that: - the second switching element (K2) is arranged between the first capacitor (CI) and the second primary terminal (54b) of the power converter (52); - the first switching element (Kl) is arranged between the series connection point of the upper and lower arms of the first branch (40) of the first H-bridge (34) and the second primary terminal (54b) of the power converter (52); - the third switching element (K3) is arranged between the second capacitor (C2) and the second primary terminal (54b) of the power converter (52).

4. The system of claim 2, wherein, The switching means comprises a reconfiguration module capable of individually controlling the first, second and third switching elements so as to maintain them in open and / or closed state.

5. The system of claim 4, wherein, The reconfiguration module controls the first, second and third switching elements so that: - in the first configuration, the first switching element (K1) remains closed and the second switching element (K2) and the third switching element (K3) remain open; - in the second configuration, the second switching element (K2) remains closed and the first switching element (K1) and the third switching element (K3) remain open; - in the third configuration, the first switching element (K1) remains open and the second switching element (K2) and the third switching element (K3) remain closed.

6. The system of claim 2, comprising a second inductance (L2) arranged between the primary terminals (54a, 54b) of the power converter (52), so that in the second configuration, the resonant circuit is formed by the first inductance (LI), the second inductance (L2) and the first capacitor (CI), the second terminal of the first capacitor being connected to the second primary terminal (54b) of the power converter (52).

7. The system according to any of the preceding claims 2 to 6, characterized in that, The first switching element (K1), second switching element (K2) and third switching element (K3) comprise switches.

8. System according to the preceding claim 7, characterized in that The first switching element (K1), second switching element (K2) and third switching element (K3) comprise transistors.

9. The system of claim 1, wherein, A capacitor Cbusl is arranged between the two terminals of the second branch (42) of the first H-bridge (34).

10. The system of claim 1, wherein, A capacitor Cbus2 is arranged between the two terminals of the second branch (46) of the second H-bridge (36).

11. The system of claim 1, having an operating range between 220 V and 330 V at the terminals of the first high-voltage DC bus.

12. The system of claim 1, wherein, The power converter is an isolated single-phase transformer.

13. The system of claim 1, comprising a third high voltage DC bus, and wherein, The power converter comprises third and fourth secondary terminals connected to series connection points of upper and lower bridge arms of a first branch and to series connection points of upper and lower bridge arms of a second branch of a third H-bridge arranged across the third high-voltage DC bus, respectively.

14. The system of claim 1, wherein, The first and / or second H-bridge each comprises four power components.

15. The system of claim 14, wherein, The four power components of the first H-bridge are diodes or transistors.

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