Connector device and dc load power flow control method using the same

Abstract

A connector device (1) is provided, configured to connect an AC power grid (2) to a DC load (3). The connector device includes: a multi-winding transformer (4) configured to be connected to the AC power grid (2); a series voltage injection transformer (8) connected to the multi-winding transformer (4); an AC / AC converter (13) connected to the series voltage injection transformer (8); and a rectifier (17) connected to the series voltage injection transformer (8), configured to be connected to the DC load (3). Furthermore, a method for controlling power flow is provided.

Description

Technical Field

[0001] This disclosure relates to a connector device and a method for controlling the power flow to a DC load using the connector device. Background Technology

[0002] A typical hydrogen electrolyzer is typically powered by a low-voltage and / or high-current DC load fed by a power electronic converter that transforms AC grid voltage into DC voltage. The typical power electronic converter topology for large-scale green hydrogen production is based on a multi-pulse thyristor rectifier circuit. However, because thyristor rectifiers generate harmonics and consume reactive power, they can cause power quality problems, necessitating additional equipment to address these issues and meet grid specifications for large-scale electrolyzer plants. This leads to increased system costs and a larger footprint. Summary of the Invention

[0003] Embodiments of this disclosure relate to a connector device. Another embodiment relates to a method of using such a connector device.

[0004] This is achieved through the subject matter of the independent claims. Further embodiments will be apparent from the dependent claims and the following description.

[0005] A connector device is described. The connector device is configured to connect an AC power grid to a DC load. Specifically, the AC power grid is configured to transmit power from at least one power station to at least one load. For example, the DC load is configured to be powered by the AC power grid. Specifically, the connector device is configured to convert AC power from the AC power grid to DC power for the DC load.

[0006] According to an embodiment, the connector device includes a multi-winding transformer configured to be connected to an AC power grid. The multi-winding transformer is configured for voltage transformation, impedance matching, phase shifting, and / or electrical isolation.

[0007] A multi-winding transformer typically includes at least two windings. Specifically, these at least two windings are connected to each other. "Connected to each other" here means that the at least two windings are magnetically coupled. For example, each winding in a multi-winding transformer may have a different number of turns, different wire sizes, and / or different insulation levels. For example, one winding of the multi-winding transformer (a single winding) is connected to an AC power grid. This single winding is configured to receive AC power from the AC power grid.

[0008] According to this embodiment, the connector device includes a series voltage injection transformer connected to a multi-winding transformer. The series voltage injection transformer is connected to one of the windings of the multi-winding transformer that is located away from the AC power grid, specifically a single winding.

[0009] Exemplarily, the series voltage injection transformer is configured to receive at least a portion of the AC power from the multi-winding transformer. Exemplarily, the series voltage injection transformer is configured to inject compensating voltage into parallel connecting lines, which are specifically configured to receive at least another portion of the AC power from the multi-winding transformer.

[0010] Advantageously, using a series voltage injection transformer helps stabilize voltage distribution, reduce voltage fluctuations, and improve the power quality delivered to DC loads. Furthermore, the design of the fractional power converter adds an additional degree of freedom.

[0011] According to this embodiment, the connector device includes an AC / AC converter connected to a series voltage injection transformer. Exemplarily, the connector device includes several AC / AC converters, for example, at least two AC / AC converters. These AC / AC converters are specifically connected in parallel. Advantageously, this can meet the future needs of DC loads with very high rated current (e.g., hydrogen electrolyzers).

[0012] For example, the AC / AC converter is connected to a series voltage injection transformer. Specifically, the AC / AC converter is connected to parallel connection lines that are specifically configured to receive at least another portion of AC power from a multi-winding transformer.

[0013] An AC / AC converter typically includes at least two converters, specifically at least two power semiconductor converters. Exemplarily, one of the two converters is a parallel converter, and the other of the two converters is a series converter. The two converters are exemplarily connected to each other via a DC link, specifically in series.

[0014] According to this embodiment, the connector device includes a rectifier connected to a series voltage injection transformer, the rectifier being configured to connect to a DC load. The rectifier is configured to convert AC power into DC power usable by the DC load. The rectifier is configured to allow current to flow only in one direction (specifically towards the DC load).

[0015] For example, the rectifier is a diode bridge rectifier. A diode bridge rectifier includes, for example, a plurality of diodes arranged in a bridge configuration, such as at least six diodes arranged in a bridge configuration (specifically for a three-phase configuration).

[0016] Advantageously, the connector device disclosed herein provides a unique and versatile solution for feeding and regulating power to DC loads without affecting the power quality of the AC grid, while providing grid services such as reactive power support and active harmonic filtering, without any additional power conditioning devices.

[0017] Furthermore, the connector assembly advantageously includes an AC / AC converter with a relatively low rating. Specifically, it is advantageous to regulate the power flowing through the DC load using only a fraction of the rated load power, thereby achieving efficient operation and a compact footprint solution. Moreover, the series voltage injection transformer between the AC / AC converter and the DC load provides additional design freedom for the AC / AC converter, allowing the power semiconductor converter of the AC / AC converter to be effectively utilized without significant derating.

[0018] According to another embodiment, a multi-winding transformer includes at least two windings, namely, a primary winding and a secondary winding. Exemplarily, a multi-winding transformer includes only two windings, namely, a primary winding and a secondary winding.

[0019] According to another embodiment, the primary winding is configured to be connected to an AC power grid.

[0020] According to another embodiment, the secondary winding is connected to a series voltage injection transformer. Specifically, the secondary winding supplies AC power from the AC grid of the primary winding to the series voltage injection transformer.

[0021] According to another embodiment, the series voltage injection transformer includes at least one transformer unit. The series voltage injection transformer may include only one transformer unit, specifically a three-phase transformer unit. The series voltage injection transformer may also include at least three transformer units, specifically only three transformer units.

[0022] Specifically, when the series voltage injection transformer comprises at least three transformer units, each transformer unit has a primary coil (e.g., an input coil) and a secondary coil (e.g., an output coil). Specifically, the primary and secondary coils are connected via electromagnetic induction. Exemplarily, the primary coil is directly connected to a multi-winding transformer. Exemplarily, the secondary coil is directly connected to a switching element.

[0023] According to another embodiment, the series voltage injection transformer includes a switching element connected in parallel with at least one transformer assembly. The switching element is, for example, a mechanical switch (such as a contactor) or a power electronic switch (exemplarily including at least one power semiconductor switch) or a combination thereof.

[0024] According to another embodiment, the AC / AC converter includes an AC / DC converter and a DC / AC converter connected in series. For example, each AC / DC converter and DC / AC converter includes at least one semiconductor switching device. Specifically, the semiconductor switching device is an insulated-gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0025] According to another embodiment, the DC / AC converter is connected to a series voltage injection transformer on one side of the switching element.

[0026] According to another embodiment, the AC / DC converter is connected to the DC / AC converter via a DC link. For example, the DC link includes a capacitor. For example, the capacitor is configured to store electrical energy.

[0027] Advantageously, the capacitors are configured to smooth voltage ripple and fluctuations, thereby ensuring a stable DC voltage supply.

[0028] According to another embodiment, the energy storage device is connected to a DC link. Exemplarily, the energy storage device is directly connected to the DC link. Alternatively, the energy storage device is connected to the DC link via another DC / DC converter.

[0029] According to another embodiment, the AC / DC converter is connected to at least three connection lines between the multi-winding transformer and the series voltage injection transformer. In this embodiment, the AC / DC converter is configured as a parallel converter, while the DC / AC converter is configured as a series converter.

[0030] According to another embodiment, the AC / AC converter is connected to at least three additional connection lines between the series voltage injection transformer and the rectifier. In this embodiment, the AC / DC converter is configured as a series converter, while the DC / AC converter is configured as a parallel converter.

[0031] According to another embodiment, a multi-winding transformer includes at least three windings, namely, a primary winding, a secondary winding, and a tertiary winding. Exemplarily, a multi-winding transformer includes only three windings, namely, a primary winding, a secondary winding, and a tertiary winding.

[0032] According to another embodiment, the tertiary winding is connected to an AC / AC converter. In this embodiment, the secondary winding is directly connected to a series voltage injection transformer, specifically the primary coil. Specifically, the tertiary winding is directly connected to the AC / AC converter, specifically an AC / DC converter. Exemplarily, the tertiary winding supplies AC power from the AC grid of the primary winding to the AC / AC converter.

[0033] According to another embodiment, the tertiary winding is connected to another series voltage injection transformer and to another AC / AC converter, which in turn is connected to the other series voltage injection transformer. Specifically, the other series voltage injection transformer and the other AC / AC converter are each implemented as the series voltage injection transformer and the AC / AC converter, such that all characteristics associated with the series voltage injection transformer and the AC / AC converter also apply to the other series voltage injection transformer and the other AC / AC converter.

[0034] According to another embodiment, another rectifier is connected to the other series voltage injection transformer. Specifically, the other rectifier is implemented such that all characteristics associated with the other rectifier also apply to the other rectifier.

[0035] According to another embodiment, the other rectifier is configured to be connected to another DC load. Specifically, the other DC load is implemented such that all characteristics associated with the other DC load also apply to it. Exemplarily, the DC load and the other DC load are electrically and spatially separated from each other.

[0036] According to another embodiment, a rectifier and another rectifier are connected to each other and configured to be connected to a DC load. Exemplarily, the DC load and another DC load are electrically connected to each other and spatially separated from each other.

[0037] For example, a rectifier is connected in parallel with another rectifier, or a rectifier is connected in series with another rectifier.

[0038] According to another embodiment, the load is a hydrogen electrolyzer. Exemplarily, for hydrogen electrolyzer applications, the voltage regulation range UD on the load side is quite narrow, while the current regulation range ID is very wide (e.g., at the end-of-life (EoL), the voltage V and current I range from 483 V ≤ UD ≤ 600 V, and from 3840 A ≤ ID ≤ 9640 A).

[0039] Advantageously, the connector device is modular, adaptable to electrolyzers from different manufacturers, and easily expandable, making it attractive for use in large-scale hydrogen electrolyzer plants.

[0040] According to another embodiment, the load is an energy storage device. For example, the energy storage device is configured to be charged via a rectifier. Exemplarily, the energy storage device comprises an electric vehicle.

[0041] Another embodiment relates to a method for controlling the power flow to a DC load using a connector device (specifically, the connector device described above). Therefore, the features described in conjunction with the connector device also apply to this method, and vice versa.

[0042] According to an embodiment, the DC voltage output of the rectifier is controlled based on the AC voltage input to the rectifier, thereby controlling the power flow to the DC load.

[0043] According to another embodiment of the method, an operating curve for the DC load is provided.

[0044] According to another embodiment of the method, the operating curve is divided into three operating regions based on the load conditions of the DC load.

[0045] According to another embodiment of the method, for two regions corresponding to light load conditions and heavy load conditions respectively, the power flow is regulated by controlling the voltage amplitude of the injection voltage of the series voltage injection transformer.

[0046] According to another embodiment of the method, for regions corresponding to medium load conditions, the power flow is regulated by controlling the injection voltage phase angle of the series voltage injection transformer.

[0047] Another embodiment relates to a computer program including instructions that, when executed by a computing device, cause the computer program to perform the methods described above. Specifically, the computer program may be implemented as hardware control, software control, and / or firmware control, or a combination thereof.

[0048] Another embodiment relates to a computer-readable storage medium having the computer program product described above stored thereon. Attached Figure Description

[0049] The accompanying drawings are included to provide further understanding. In the drawings, elements with the same structure and / or function may be designated by the same reference numerals. It should be understood that the embodiments shown in the drawings are illustrative and not necessarily drawn to scale.

[0050] Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 Each schematically illustrates a connector device according to an exemplary embodiment.

[0051] Figure 6A connector device controlled by a method according to an exemplary embodiment is shown schematically.

[0052] Figure 7 A diagram illustrating different regions used by the method according to an exemplary embodiment is shown schematically. Detailed Implementation

[0053] according to Figure 1 The connector device 1 of the exemplary embodiment includes a multi-winding transformer 4, which is configured to be connected to an AC power grid 2 and connected to a series voltage injection transformer 8 via a connecting line.

[0054] The multi-winding transformer 4 includes a primary winding 5 facing the AC power grid 2 and a secondary winding 6 facing the connecting line. The series voltage injection transformer 8 includes three transformer units 9. Each of the three transformer units 9 includes a primary coil 10 and a secondary coil 11. Each primary coil 10 is connected to the secondary winding 6 via a connecting line. Further, the series voltage injection transformer 8 includes three switching elements 12. Each switching element 12 is connected in parallel with one of the three transformer units 9. Specifically, each switching element 12 is connected in parallel with one of the secondary coils 11.

[0055] The connector assembly 1 also includes an AC / AC converter 13 connected to the series voltage injection transformer 8 at a parallel connection line 20, specifically connected in parallel with the series voltage injection transformer 8. The AC / AC converter 13 includes an AC / DC converter 14 and a DC / AC converter 15, specifically a parallel converter and a series converter. The AC / DC converter 14 is connected to the DC / AC converter 15 via a DC link 16. Specifically, the DC sides of the AC / DC converter 14 and the DC sides of the DC / AC converter 15 are opposite to each other and connected via the DC link 16.

[0056] AC / DC converter 14 is connected to connection line 18 between multi-winding transformer 4 and series voltage injection transformer 8. Specifically, the AC side of AC / DC converter 14 is connected to connection line 18. DC / AC converter 15 is connected to series voltage injection transformer 8 on the side facing rectifier 17, specifically to each secondary coil 11. Specifically, the AC side of DC / AC converter 15 is connected to series voltage injection transformer 8.

[0057] The connector assembly 1 also includes a rectifier 17 connected to a series voltage injection transformer 8, which is configured to be connected to a DC load 3. Specifically, the primary coil 10 is connected to the rectifier 17, specifically via an additional connecting line 19.

[0058] Specifically, AC / DC converter 14 (i.e., the parallel converter) is connected to secondary winding 6. The advantage of this configuration is that it allows the use of a standard two-winding transformer, thus saving costs. Regarding the capacity design of the parallel converter, since the fundamental AC load current will always be at least approximately in phase with the voltage synthesized by the series voltage injection into transformer 8, the injected voltage will also be in phase with the load current, and the series converter will primarily deliver active power. Therefore, the capacity of the parallel converter can be advantageously designed to be at least equal to the active power of the series converter, plus the reactive power required to satisfy unity power factor on both sides of the AC grid. The parallel converter is also advantageously configured to cancel low-order current harmonics, thereby performing active harmonic filtering. This function requires the parallel converter to have a higher rated capacity.

[0059] and Figure 1 Compared to connector device 1, according to Figure 2 The connector device 1 of the exemplary embodiment includes a multi-winding transformer 4 having a primary winding 5, a secondary winding 6, and a tertiary winding 7. The primary winding 5 is configured to be connected to an AC power grid 2. The secondary winding 6 is connected to connecting lines 18, which are connected to a series voltage injection transformer 8. Specifically, each connecting line is connected to one of the primary coils 10 facing the secondary winding 6. The tertiary winding 7 is connected to the AC / DC converter 14 of the AC / AC converter 13, specifically via parallel connecting lines 20.

[0060] For example, AC / DC converter 14 (i.e., parallel converter) is connected to the tertiary winding 7 and is controlled to maintain a constant DC link voltage, regulate reactive power exchange with AC grid 2, maintain unity power factor at the point of common coupling (PCC), and cancel harmonic currents introduced by rectifier 17.

[0061] Therefore, through appropriate control, such as combination Figure 6As described, the parallel converter can provide favorable grid service. Adding an additional winding (e.g., tertiary winding 7) to the main transformer provides additional design variables for optimizing the capacity design of the AC / AC converter 13. The series converter is connected to the rectifier 17 and the AC grid 2 via a series voltage injection transformer 8, thereby controlling the AC voltage fed to the rectifier 17 and regulating the DC power flow on the load side. Specifically, the series converter is controlled to regulate the voltage injected into the AC line and reduces DC ripple on the load side by superimposing voltage harmonics, thereby flattening the top of the injected AC voltage and reducing the DC filter requirements on the load side.

[0062] Advantageously, due to the presence of the series voltage injection transformer 8, the current stress on the series converter can be reduced by utilizing the turns ratio of the multi-winding transformer 4, and the AC / AC converter 13 can be appropriately designed to achieve better semiconductor utilization.

[0063] Since the voltage amplitude injected by the series converter is proportional to the DC voltage regulation range of the load, which is quite narrow for a hydrogen electrolyzer, the series converter only needs to handle a small fraction of the load's rated power. Utilizing this portion of power advantageously reduces the losses of the AC / AC converter 13 during power conversion and reduces overall power loss, resulting in a compact footprint.

[0064] For example, the energy storage device (e.g., a battery energy storage device (BESS)) is directly connected to the DC link. This advantageously enables rapid frequency control for AC grid 2 and supports the load (specifically, the hydrogen electrolyzer) during startup and in the event of a fault on the AC grid 2 side. For example, in this case, grid control of the AC / DC converter (e.g., virtual synchronous machine control) may be included to support the AC grid voltage and frequency.

[0065] and Figure 1 In comparison, based on Figure 3 In the connector device 1 of the exemplary embodiment, the parallel converter and the series converter are interchanged. The series voltage injection transformer 8 includes, as shown in the example... Figure 1 and Figure 2 The three switching elements 12 shown are, for better illustration, in... Figure 3 Not shown in the image.

[0066] AC / DC converter 14 is connected to series voltage injection transformer 8, specifically, to secondary coil 11. Specifically, the AC side of AC / DC converter 14 is connected to series voltage injection transformer 8.

[0067] The DC / AC converter 15 is connected to another connection line 19, through which the series voltage injection transformer 8 is specifically connected to the rectifier 17.

[0068] Specifically, with Figure 1 In contrast, the order of the series converter and the parallel converter is reversed, so that the current harmonics generated by the rectifier 17 are suppressed at the harmonic source due to the active harmonic filtering capability of the parallel converter, and the harmonic current will not flow through the series voltage injection transformer 8.

[0069] and Figure 1 Compared to connector device 1, according to Figure 4 The connector device 1 of the exemplary embodiment includes a multi-winding transformer 4 having a primary winding 5, a secondary winding 6, and a tertiary winding 7. The tertiary winding 7 is connected to another series voltage injection transformer 21 and another AC / AC converter 13, and the other series voltage injection transformer 21 and the other AC / AC converter 13 are connected to the tertiary winding 7 in the same manner as... Figure 1 The series voltage injection transformer 8 and AC / AC converter 13 described herein are connected to the secondary winding 6 in the same manner. Furthermore, this other series voltage injection transformer 21 is connected to another rectifier 23.

[0070] Rectifier 17 and the other rectifier 23 are connected to each other. Furthermore, rectifier 17 and the other rectifier 23 are connected to a load. Specifically, rectifier 17 and the other rectifier 23 are connected in series on the DC load 3 side. This configuration can advantageously reduce DC ripple on the DC load 3 side and will also be applicable to next-generation high-pressure hydrogen electrolyzers in the future.

[0071] and Figure 4 In comparison, according to Figure 5 The connector device 1 in the exemplary embodiment also includes another load. The rectifier 17 and the other rectifier 23 are not connected to each other. The other rectifier 23 is connected to the other DC load 24.

[0072] This means that, according to Figure 5 The connector device 1 of the exemplary embodiment is based on a 12-pulse configuration. This configuration includes adding an additional module with another AC / AC converter and another rectifier 23 to the tertiary winding 7 of the multi-winding transformer. This configuration can advantageously help reduce AC harmonic filtering requirements, simplify control, and reduce the rating of the parallel converter.

[0073] In order to use connector device 1 (exemplarily according to...) Figure 1 The connector device 1) controls the power flow to the DC load 3, and controls the DC voltage output of the rectifier 17 according to the AC voltage input to the rectifier 17, so as to control the power flow to the DC load 3.

[0074] Therefore, controller 25 is connected to connector device 1. Controller 25 is configured, for example, to control the voltage V injected by series voltage injection transformer 8. Series The amplitude is used to regulate the voltage V of DC load 3. DC And the power flowing to DC load 3.

[0075] The parallel converter is controlled to maintain the DC link voltage 16V. DC-Ling The current is kept constant, suppressing current harmonics generated by rectifier 17 and maintaining unity power factor. Furthermore, controller 25 is configured, for example, to control the active power on the DC side as a function of the AC side frequency f. Grid The changes are used to regulate frequency and dampen power oscillations on both sides of the AC power grid.

[0076] For example, both the parallel converter and the series converter can be individually controlled by the controller 25 via pulse width modulation, as indicated by the black arrow pointing to the respective converter.

[0077] For example, in the symmetrical voltage injection method, in order to control the power flow to the DC load 3, the series converter is configured to inject a symmetrical bipolar voltage (ΔU = ± xV) into the AC voltage (U1) on the side facing the secondary winding 6, such that the accumulated AC voltage (U1) fed to the rectifier 17 is... AC The amplitude of ) can be increased relative to the AC voltage (U1) on the side facing the secondary winding 6 (U AC = U1 + xV) or decrease (U AC = U1- xV).

[0078] Through connector device 1 and / or this method, the DC voltage is advantageously regulated on the DC load 3 side while active harmonic filtering and reactive power support are performed on the AC grid 2 side, specifically without any additional power quality improvement devices. Advantageously, series voltage injection transformer 8 is configured to inject voltage on the AC side of rectifier 17. Series voltage injection transformer 8 advantageously provides additional degrees of freedom in the design of AC / AC converter 13 and helps to optimize the use of power semiconductors without significantly derating the AC / AC converter.

[0079] Specifically, the connector device 1 is advantageously modular and easily expandable, making it an attractive option for large-scale hydrogen electrolyzers. Due to the advantage that the connector device 1 requires only a partially rated power converter, it is less expensive compared to conventional solutions that require a fully rated power converter.

[0080] Advantageously, with proper control, voltage ripple on the load side and current harmonics on the grid side can be reduced. This can reduce the filtering requirements on both the load side and the grid side.

[0081] Combination Figure 7 The diagram in the image uses a combination of... Figure 6 The described method allows the operation of DC load 3 to be divided into three distinct operating regions based on load conditions (e.g., the operating curve of DC load 3), i.e., as follows: Figure 7 The indicated areas are A, B, and C.

[0082] The load voltage is indicated on the y-axis, and the load current is indicated on the x-axis. This corresponds to the operating curve of DC load 3, specifically for two different curves.

[0083] For regions A and C, which correspond to light and heavy load conditions respectively, the power flow is regulated by controlling the voltage amplitude of the injected voltage of the series converter (e.g., by using anti-phase operation and in-phase operation respectively). For region B, which corresponds to medium load conditions, the power flow is regulated by controlling the phase angle of the injected voltage of the series converter (e.g., by using out-of-phase operation). In region B, the series converter also exchanges reactive power with AC grid 2.

[0084] Anti-phase operation is described exemplarily. In region A, the voltage injected by the series converter is out of phase with the AC-side voltage, i.e., 180° phase shift (e.g., out of phase), and the power flow to the DC load 3 is controlled only by changing the voltage amplitude. In this operating region, there is no reactive power exchange between the series converter and the DC load 3 and / or the AC grid 2.

[0085] Out-of-phase operation is described exemplarily. For region B, the phase angle of the voltage injected into the series converter is changed while the magnitude of the injected voltage is maintained at a predetermined level corresponding to the minimum achievable modulation index. This is done to prevent the series converter from operating at extremely low modulation indices and near the zero-voltage range of the series converter (which is practically impossible). In this operating mode, because the phase angle of the injected voltage changes while the voltage magnitude remains constant, the series converter also exchanges active and reactive power with the AC grid.

[0086] In-phase operation is described exemplarily. In region C, the voltage injected by the series converter is in phase with the AC-side voltage, and the power flow to DC load 3 is controlled only by changing the voltage amplitude. In this operating region, there is no reactive power exchange between the series converter and DC load 3 and / or AC grid 2.

[0087] For example, with the asymmetric voltage injection method, the series converter is configured to be in-phase or out-of-phase under all load conditions of rectifier 17. For the case where the series converter operates only in-phase, the voltage U1 is selected to be lower than the minimum AC voltage requirement U of rectifier 17. AC,minThis allows the series converter to effectively increase U1 by ΔU, where ΔU varies from +xV to +yV, as shown below. Figure 8 As shown.

[0088] For the series converter operating only in anti-phase mode, voltage U1 is selected to be higher than the maximum AC voltage requirement U of rectifier 17. AC,max This allows the series converter to effectively reduce U1 by ΔU, where ΔU varies from -xV to -yV, as shown below. Figure 9 As shown.

[0089] Since the ratings of the series converter and the series voltage injection transformer 8 are proportional to the amplitude of the injection voltage, this control method allows the series converter to have a higher rated power compared to the symmetrical voltage injection method.

[0090] The embodiments and exemplary models described above can be combined accordingly.

[0091] Figure Labels 1 Connector assembly 2. Power Grid 3 DC loads 4. Multi-winding transformer 5. Primary winding 6 Secondary winding 7. Tertiary winding 8 Series voltage injection transformer 9. Transformer Unit 10 Primary coil 11 Secondary coil 12 Switching elements 13 AC / AC converter 14 AC / DC converters 15 DC / AC converters 16 DC Links 17 Rectifier 18 Connecting wires 19. Additional connecting wires 20 parallel connecting lines 21 Another series voltage injection transformer 22 Another AC / AC converter 23 Another rectifier 24 Another DC load 25. Controller.

Claims

1. A connector device (1) configured to connect an AC power grid (2) to a DC load (3), the connector device comprising: - A multi-winding transformer (4), which is configured to be connected to the AC power grid (2). - A series voltage injection transformer (8) is connected to the multi-winding transformer (4). - AC / AC converter (13), the AC / AC converter being connected to the series voltage injection transformer (8), and - A rectifier (17) connected to the series voltage injection transformer (8) and configured to be connected to the DC load (3).

2. The connector device (1) according to claim 1, wherein, - The multi-winding transformer (4) includes at least two windings, namely, a primary winding (5) and a secondary winding (6). - The primary winding (5) is configured to be connected to the AC power grid (2), and - The secondary winding (6) is connected to the series voltage injection transformer (8).

3. The connector device (1) according to claim 1 or 2, wherein, - The series voltage injection transformer (8) includes at least one transformer assembly (9), and - The series voltage injection transformer (8) includes a switching element (12) connected in parallel with the at least one transformer device (9).

4. The connector device (1) according to any one of claims 1 to 3, wherein, - The AC / AC converter (13) includes an AC / DC converter (14) and a DC / AC converter (15) connected in series.

5. The connector device (1) according to claims 3 and 4, wherein, - The DC / AC converter (15) is connected to the series voltage injection transformer (8) on one side of the switching element (12).

6. The connector device (1) according to any one of claims 4 or 5, wherein, - The AC / DC converter (14) is connected to the DC / AC converter (15) via a DC link (16).

7. The connector device (1) according to claim 6, wherein, - The energy storage device is connected to the DC link (16).

8. The connector device (1) according to any one of claims 5 to 7, wherein, - The AC / DC converter (14) is connected to at least three connection lines (18) between the multi-winding transformer (4) and the series voltage injection transformer (8), or - The AC / AC converter (13) is connected to at least three additional connection lines (19) between the series voltage injection transformer (8) and the rectifier (17).

9. The connector device (1) according to any one of claims 2 to 7, wherein, - The multi-winding transformer (4) includes at least three windings, namely, the primary winding (5), the secondary winding (6), and the tertiary winding (7), and - The tertiary winding (7) is connected to the AC / AC converter (13).

10. The connector device (1) according to any one of claims 2 to 7, wherein, - The multi-winding transformer (4) includes at least three windings, namely, the primary winding (5), the secondary winding (6), and the tertiary winding (7), and - The tertiary winding (7) is connected to another series voltage injection transformer (8) and to another AC / AC converter (22), which is connected to the other series voltage injection transformer (21), and - Another rectifier (23) is connected to the other series voltage injection transformer (21).

11. The connector device (1) according to claim 10, wherein, - The other rectifier (23) is configured to be connected to another DC load (24).

12. The connector device according to claim 10, wherein, - The rectifier (17) and the other rectifier (23) are connected to each other and configured to be connected to the DC load (3).

13. The connector device (1) according to any one of claims 1 to 12, wherein, - The load is a hydrogen electrolyzer, or - The load is an energy storage device.

14. A method for controlling power flow to a DC load (3) using a connector device (1) according to any one of claims 1 to 13, the method comprising: - Based on the AC voltage input to the rectifier (17), control the DC voltage output of the rectifier (17) to make it so that - Control the power flow to the DC load (3).

15. The method of claim 14, comprising: - Provide the operating curve of the DC load (3), - Based on the load conditions of the DC load (3), the operating curve is divided into three operating regions. - For the two regions corresponding to light load conditions and heavy load conditions respectively, the power flow is regulated by controlling the voltage amplitude of the injection voltage of the series voltage injection transformer (8), and - For the region corresponding to medium load conditions, the power flow is regulated by controlling the injection voltage phase angle of the series voltage injection transformer (8).

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