Power converter for converting multi-phase AC grid input power to DC output power and hydrogen production facility

Abstract

The invention relates to a power converter for converting multi-phase AC grid input power to DC output power. In order to allow power supply to DC power consuming devices with high power requirements, a power converter comprises at least one phase block, each phase block having at least two separate converter single-phase string devices, each converter single-phase string device comprising a separate active rectifier portion comprising an H-bridge with semiconductor switches, the rectifier is used for rectifying single-phase AC input power into intermediate DC power, and a separate DC / DC converter. The latter comprises: an inverter section having an H-bridge with semiconductor switches for inverting the intermediate DC power into a first intermediate AC power having a boosted frequency; a transformer for converting the first intermediate AC power into a second intermediate AC power; and a passive diode rectifier including a diode bridge for rectifying the second intermediate AC power. The invention also relates to a hydrogen production plant having an electrolyser stack and such a power converter.

Description

Technical Field

[0001] The present invention relates to a power converter for converting a multiphase AC grid input power having a grid frequency and at least two phases from a grid into a DC output power of the power converter. The invention also relates to a hydrogen production facility having an electrolyser stack and such a power converter. Background Art

[0002] The demand for hydrogen is expected to increase significantly in the coming years. Hydrogen can be produced by hydrogen production facilities equipped with electrolyzer stacks. Such production facilities require a high-power DC power supply. The voltage of the multiphase AC grid input power can also be referred to as the grid input voltage. Due to the high power demand, hydrogen production facilities are typically supplied by a "medium voltage" grid with a grid input voltage ranging from 7.5 kV to 15 kV.

[0003] Conventional power converters for such hydrogen production facilities typically include an active rectifier with semiconductor switches to generate the final DC output power, i.e., directly before the DC power output of the converter. This is generally believed to improve efficiency and allow for better control compared to using passive diode rectifiers to generate the DC output power.

[0004] Conventional semiconductor switches are not suitable for switching the high grid input voltages mentioned. In conventional power converters, a common conventional transformer is connected to the AC grid input power. The common conventional transformer initially converts the AC grid input power at the grid frequency into internally supplied AC power at a reduced voltage. The active rectifier with semiconductor switches, used to generate the DC output power, is driven by the internally supplied AC power at a reduced voltage.

[0005] These common, conventional transformers must handle the necessary high total current at relatively low grid frequencies (e.g., 50 Hz or 60 Hz). These common, conventional transformers are very large and heavy. Consequently, conventional power converters are also very bulky. This makes transporting these converters to the installation site difficult and expensive. Furthermore, they cannot be fully prefabricated, such as in a factory. Instead, they must be assembled directly at the installation site. Therefore, implementation at the hydrogen production facility requires considerable effort. A large number of specially trained operators are required directly at the installation site. Furthermore, even if the complete power converter is preassembled at the factory for testing, the necessary partial disassembly required for transportation and final assembly at the installation site can introduce defects or issues that may not have surfaced during testing.

[0006] Furthermore, there is the problem that if very high DC output powers are required, for example exceeding 10 MW, the semiconductor switches used in the active rectifier for generating the DC output power are very expensive or not available at all. Summary of the Invention

[0007] The problem to be solved by the present invention is to provide an efficient, cost-effective, easy to install and reliable power supply to DC power consuming devices with high power requirements.

[0008] This problem is solved by a power converter having the features of claim 1 .

[0009] The power converter is for converting a multi-phase AC grid input power having a grid frequency and at least two phases from a (power) grid into a DC output power of the power converter.

[0010] The power converter comprises at least one dual phase block, wherein each of said phase blocks comprises at least two separate single phase string devices of converters.

[0011] Each converter single-phase string device includes:

[0012] a separate active rectifier section for rectifying the single-phase AC input power into an intermediate DC power, the active rectifier section comprising an active bridge (e.g., an H-bridge) having semiconductor switches; and

[0013] a separate DC / DC converter for converting the intermediate DC power into output DC power of the converter single-phase string device, wherein the DC / DC converter comprises:

[0014] - an inverter part for inverting the intermediate DC power into a first intermediate AC power having a stepped-up frequency, wherein the inverter part comprises an active bridge (e.g. an H-bridge) having semiconductor switches;

[0015] - a transformer for transforming the first intermediate AC power into a second intermediate AC power; and

[0016] - a passive diode rectifier for rectifying the second intermediate AC power into the output DC power of the converter single-phase string arrangement, wherein the passive diode rectifier comprises a diode bridge.

[0017] The power converter according to the present invention is suitable for supplying high-current DC power consumers, such as electrolyzer stacks and ultra-high-power DC chargers (e.g., for large trucks and / or mining vehicles). The power converter includes several individual single-phase converter strings, such that the power flow during conversion is distributed across the strings.

[0018] In particular, the power converter may provide direct high power conversion from "medium voltage" multiphase AC grid input power to regulated "low voltage" DC output power.

[0019] The output DC power of a respective converter single-phase string device may be referred to as a respective "string output DC power."

[0020] Passive diode rectifiers with diode bridges allow for very high string output DC power. Diodes are reliable and sufficiently efficient. They can be of a type with a low voltage drop. Diodes are less expensive than semiconductor switches. For example, active semiconductor switches for switching voltages above 1 kV and currents greater than 1 kA are prohibitively expensive. Inverters including active bridges with semiconductor switches allow for sufficiently precise control of the string output DC power (and therefore the total DC output power of the power converter) to eliminate the need for semiconductor switches in the converter's single-phase string arrangement "downstream" of the transformer.

[0021] Since the passive diode bridge tends to withstand higher loads more easily, the power converter requires fewer total single-phase strings of converters to provide a given maximum DC output power.

[0022] This invention eliminates the need for bulky and heavy traditional transformers at the power input to the grid. Compared to traditional solutions, it reduces floor space by two to three times. For example, a complete 10 MW solution can be provided in a 20-foot container. This simplifies logistics and reduces installation and commissioning efforts at the installation site. It also allows for higher power density and requires less raw materials.

[0023] Each single-phase string of converters provides multi-stage conversion of the corresponding single-phase AC input power. The first stage of conversion is rectification via the active rectifier section. The second stage of conversion is generation of a first intermediate AC power via the inverter section. Conventional power converters used for applications relevant herein typically provide only one stage of conversion after an initial conventional transformer operating at the grid frequency. Multi-stage conversion allows for more flexible control of the string output DC power.

[0024] The inverter portion and the active rectifier portion each include an active bridge, such as an H-bridge, having semiconductor switches. Together, the active rectifier portion can form the "active front end" of the power converter. The active front end can be controlled particularly flexibly to adapt to variations / disturbances in the multi-phase AC grid input power. Furthermore, since both the inverter portion and the active rectifier portion each include an active bridge having semiconductor switches, it facilitates startup, shutdown, and regulation of the DC output power without interference. For example, while the active rectifier portion remains operational, it can take less than a few milliseconds to start the DC output power from zero to maximum DC output power and / or reduce the DC output power from maximum DC output power to zero.

[0025] Ultimately, power converters help improve grid quality and stability.

[0026] In particular, the multi-phase AC grid input power may have n phases, where n is a (predetermined integer and) at least 2. Each phase block may include at least n separate single-phase strings of converters. In other words, for each phase block, the number of separate single-phase strings of converters may at least correspond to the number of phases of the multi-phase AC grid input power.

[0027] According to one aspect, the multi-phase AC grid input power may have at least three phases (n≥3).

[0028] The boosted frequency can be higher than the grid frequency. This allows a more compact transformer to be used in a corresponding converter single-phase string arrangement.

[0029] In particular, the boosted frequency may correspond to at least 10 times the grid frequency, and may be at least 15 times. This ensures that the converter single-phase string arrangement may comprise a particularly small and lightweight transformer.

[0030] The boost frequency may be in the range of 500 Hz to 10 kHz, for example 1 kHz.

[0031] The transformer may be a "medium frequency" transformer configured to operate at at least one frequency in the range of 500 Hz to 10 kHz (e.g., 1 kHz). This allows for substantial reductions in size, weight, and cost compared to conventional transformers for grid frequencies (e.g., 50 Hz or 60 Hz).

[0032] According to one aspect, the semiconductor switches of the active rectifier portion include insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), and / or silicon carbide semiconductor switches (SiC switches). Additionally or alternatively, the semiconductor switches of the inverter portion include IGBTs, MOSFETs, and / or SiC switches. These semiconductor switches can be used in high-power applications. They are reliable and have good efficiency.

[0033] In particular, the semiconductor switches of the active rectifier part may be IGBTs, and / or the semiconductor switches of the inverter part may be IGBTs.

[0034] In one embodiment, each active rectifier section has a phase leg topology with at least three levels. Additionally or alternatively, each inverter section can have a phase leg topology with at least three levels. This reduces the switching voltage required for individual semiconductor switches. Consequently, there is greater freedom in selecting cost-effective and energy-efficient semiconductor switches. The at least three levels in the active rectifier section can be used to cascade active rectifier sections of different phase blocks.

[0035] According to another aspect, each active rectifier section can be in a neutral point clamped topology (NPC topology). Additionally or alternatively, each inverter section can be in a neutral point clamped topology. The NPC topology can achieve particularly low switching losses and low current ripple.

[0036] In particular, in each converter single-phase string device, both the active rectifier part and the inverter part can be in a neutral point clamped topology and can share a corresponding neutral point, which simplifies the circuit of the converter single-phase string device.

[0037] The active rectifier section and the inverter section of the same converter single-phase string arrangement may use the same capacitor arranged between these sections (eg, connected to a DC bus for intermediate DC power supplied to the inverter section).

[0038] Because each converter single-phase string device includes its own transformer, the voltage of its second intermediate AC power is different from the voltage of its first intermediate AC power (at least during operation when the first intermediate AC power is non-zero). Because its string output DC power comes from rectifying its second intermediate AC power, the ratio between the voltage of its string output DC power and the voltage of its first intermediate AC power can be adapted to the requirements of the DC power consuming devices supplied by the power converter (and therefore at least partially by the converter single-phase string device).

[0039] In one embodiment, in each converter single-phase string arrangement, the transformer provides electrical isolation between the active rectifier portion and the passive diode rectifier. This protects the DC power consuming devices from disturbances in the grid.

[0040] In each converter single-phase string device, the transformer may be configured to reduce the voltage of the second intermediate AC power compared to the voltage of the first intermediate AC power. The ratio of the voltage of the second intermediate AC power (the second intermediate DC power voltage) divided by the voltage of the first intermediate AC power (the first intermediate AC power voltage) may be less than 1. Typically, grid voltage is too high to be directly rectified to supply high-current DC power consumers, such as electrolyzer stacks and ultra-high power DC chargers (e.g., for large trucks and / or mining vehicles). The term "ultra-high power DC charger" may refer to a DC charger with a maximum power requirement of at least 8 MW. Even if the voltage of the individual single-phase input AC power (of the individual converter single-phase string devices) is reduced compared to the grid voltage by an active bridge of active rectifiers cascaded from different phase blocks, the first intermediate AC voltage itself may still be too high to be directly rectified to supply DC power to the intended DC power consumers.

[0041] Because the string output DC power is derived from rectifying the second intermediate AC power, the string output DC power voltage is also reduced. In this way, the string output DC power voltage can be adapted to the requirements of DC power consuming devices. Because the voltage of the first intermediate AC power and the intermediate DC power are higher than the voltage of the second intermediate AC power, and vice versa, the current flowing through the inverter section is lower than the current flowing through the passive diode rectifier.

[0042] In one embodiment, in each converter single-phase device, the transformer is configured to transform the first intermediate AC power into the second intermediate AC power so that the voltage of the second intermediate AC power is less than one-third of the voltage of the first intermediate AC power. For example, even if the voltage of the intermediate DC power and / or the voltage of the first intermediate AC power is higher than 2 kV, the voltage of the string output DC power is sufficiently reduced for use in relevant applications.

[0043] According to one aspect, in each converter single-phase string arrangement, the DC / DC converter may have no series capacitor.

[0044] According to another aspect, the power converter includes at least two phase blocks. This allows for increasing the total DC output power of the power converter without overloading the individual single-phase strings of converters. For example, several (at least two) of the phase blocks can be arranged in parallel to reduce the current in the individual single-phase strings of converters. Additionally or alternatively, several (at least two) of the phase blocks can be arranged in a cascade topology to reduce the individual single-phase AC input power of the associated single-phase strings of converters.

[0045] In particular, the active rectifier parts of the converter single-phase string devices of several (at least two) phase blocks together form a cascaded active bridge for each phase, which ensures an efficient implementation for reducing the individual single-phase AC input power of the associated converter single-phase string device.

[0046] In one embodiment, the DC output terminals (for supplying output DC power) of the single-phase string of converter devices in the same phase block are electrically connected in parallel. In particular, the output DC power of all single-phase string of converter devices can be electrically connected in parallel. Thus, the different single-phase string of converter devices contribute to a common total output DC power of the power converter.

[0047] According to one aspect, the DC / DC converters (of different converter single-phase string devices) are independent of each other. As described above, each converter single-phase string device has its own separate DC / DC converter with its own separate inverter part, transformer and passive rectifier. The semiconductor switches of the inverter part of one of the DC / DC converters can be controlled / switched independently of the semiconductor switches of the other DC / DC converters. For example, this can be used for interleaving. Each DC / DC converter can be supplied by a separate intermediate DC power bus of the corresponding converter single-phase string device. In particular, no converter single-phase string device can share an intermediate DC power bus, transformer or rectifier. This allows precise individual control of the output DC power of the individual converter single-phase string devices.

[0048] The power converter may include an LCL filter located between a power input terminal for the multiphase AC grid input power and the converter single-phase string device most directly connected to the power input terminal. The LCL filter provides harmonic suppression, offering good performance while being cost-effective.

[0049] In one embodiment, the power converter includes a control system. The control system may be configured to control the operation of (at least) semiconductor switches of an inverter portion of a single-phase string arrangement of the converter. Additionally or alternatively, the control system may be configured to control the operation of semiconductor switches of (at least) an active rectifier portion of the single-phase string arrangement of the converter.

[0050] The power converter may include an input power analyzer. The input power analyzer may be configured to determine one, several, or all of the following:

[0051] - Grid voltage;

[0052] - individual voltages between phases of several phases of AC grid input power;

[0053] - Phase offset between phases of the multiphase AC grid input power;

[0054] - Current of several phases of AC grid input power;

[0055] - individual phase currents of several phases of AC grid input power; and

[0056] - Individual voltages of the multi-phase AC grid input power (eg with respect to a neutral point and / or a reference potential, such as ground).

[0057] The control system may be connected to the input power analyser.The input power analyser may form part of the control system.

[0058] The control system can be configured to adapt the control of the semiconductor switches (of the active rectifier section and / or the inverter section) based on the measurements received from the input power analyzer. This allows, on the one hand, the control of the power converter to adapt to variations and disturbances in the power grid. On the other hand, the measurements can help adapt the control of the power converter to reduce grid disturbances caused by the power converter.

[0059] In particular, the input power analyzer may be configured to at least determine the grid frequency.

[0060] In one embodiment, the control system is configured to control the semiconductor switches of the inverter portion of the converter single-phase string device so that the boosted frequency of the first intermediate AC power corresponds to a respective integer multiple of the grid frequency, wherein each integer multiple is at least 10, and may be at least 15. Additionally or alternatively, each integer multiple may be at most 200.

[0061] In particular, all integer multiples may be the same. In other words, in this case, the control system is configured to control the semiconductor switches of the inverter portion of the converter single-phase string arrangement so that the first intermediate AC power has the same boosted frequency corresponding to an integer multiple of the grid frequency, wherein the integer multiple is at least 10, possibly at least 15. Additionally or alternatively, the integer multiple may be at most 200.

[0062] According to one aspect, the control system is configured to control the active rectifier portion separately from the inverter portion. In particular, the control system can be configured such that it can operate the active rectifier portion to generate intermediate DC power while keeping the inverter portion (and therefore the DC / DC converter) inactive. The control system can be configured to start, stop, and / or adjust the operation of the inverter portion (and therefore the DC output power) while keeping the active rectifier portion fully operational. This reduces the risk of the power converter causing disturbances in the power grid. Furthermore, it allows for faster adaptation of the inverter portion's operation (and therefore the DC output power).

[0063] According to another aspect, for a corresponding one of the converter single-phase string devices, the output DC current of the output DC power is adjustable for any output voltage level of the output DC power between zero and a maximum value. For example, for each voltage level of the output DC power, the output DC current can be adjusted to a configurable value (e.g., a configurable value arbitrarily adjustable between zero and the maximum current for a given voltage level). For each voltage level in the range from zero to the maximum value, the output DC current can be continuously adjusted. However, the maximum value can depend on the voltage level of the output DC power. This allows for fast but controllable polarization of the electrolyzer stack without the need for additional hardware. In addition, there is a very fast output short circuit limit, for example, less than 1ms.

[0064] Additionally or alternatively, the output DC voltage may be adjustable. This may apply to each converter single-phase string device. In one embodiment, the output DC voltage is adjustable from at least 2% to 100% of the nominal voltage, and may be adjustable from 0V to a maximum voltage. The output DC voltage is continuously adjustable / fully controllable within this range.

[0065] In one embodiment, the transformer includes at least two separate output winding units. The separate output winding units can be connected to the passive diode rectifier in parallel or in series. This also includes the case where the connection between the separate output winding units and the diode rectifier can be switched between parallel and series connection, for example, by a switch.

[0066] According to one aspect, the passive diode rectifier may include at least two branches, each having a separate passive diode bridge. Each passive diode bridge may be connected to a separate output winding unit (of the same single-phase string of converters). The diode bridges may be connected in parallel or in series to the DC output terminals of the corresponding single-phase string. This also includes the case where the connection between the branches and the DC output terminals can be switched between parallel and series, for example, via a switch.

[0067] In one embodiment, the semiconductor switches of the individual active rectifier sections each have a blocking voltage of at least 4 kV. Additionally or alternatively, the semiconductor switches of the individual inverter sections may each have a blocking voltage of at least 4 kV. This allows for multi-phase AC grid input power with high voltage.

[0068] In one embodiment, the power converter is adapted for multi-phase AC grid input power, having a grid frequency in the range of 15 Hz to 65 Hz (e.g., 50 Hz), which may be 40 Hz to 65 Hz, and / or a grid input voltage in the range of 7 kV to 15 kV. The power converter can be supplied with power from a typical medium voltage grid. This facilitates implementation of the power converter.

[0069] Additionally or alternatively, the power converter can be configured to provide a maximum voltage of the DC output power in the range of 700 V to 1500 V and / or a maximum output current of the DC output power of at least 3700 A. Thus, the power converter is suitable for use in DC power consuming devices with very high power requirements, such as electrolyzer stacks in hydrogen production facilities and for ultra-high power DC chargers (e.g., for large trucks and / or mining vehicles).

[0070] According to one aspect, the power converter is configured for providing a maximum DC output power of at least 8 MW.Such a high DC output power may be required to supply the electrolyser stack.

[0071] The power converter can have a modular structure. All single-phase strings of converters can have the same structure / topology. Thus, a power converter, particularly a phase block, can be formed by combining several single-phase strings of converters with the same structure / topology. This ensures cost-effective manufacturing and scalability to individual needs.

[0072] The power converter may have a common power input for the multi-phase AC grid input power. Additionally or alternatively, the power converter may have a common power output for the DC output power of the power converter. This facilitates fast and easy integration of the power inverter.

[0073] According to one aspect, the power converter is fully assembled before transport to the (final) installation site and remains fully assembled during transport to the (final) installation site.

[0074] The power converter may include a common outer housing. The outer housing may house all phase blocks of the power converter and may house all other components of the power converter (i.e., all components distinct from the outer housing). For example, the outer housing may have dimensions similar to a standard 20-foot container. In particular, the outer housing may be compatible with a standard 20-foot container.

[0075] In one embodiment, the power converter is configured as a DC / DC converter interleaved with a single-phase string device for use with the same phase of the multi-phase AC grid input power. This reduces the RMS ripple of the DC output power of the power converter. The ripple voltage and / or ripple current of the electrolyzer stack can be reduced by using a small capacitor for the DC output voltage.

[0076] The above mentioned issues are further addressed by a hydrogen production facility which includes:

[0077] - electrolyzer stacks for hydrogen production; and

[0078] - A power converter according to any embodiment of the invention, for supplying DC output power (of the power converter) to the electrolyser stack.

[0079] The embodiments, variations and advantages described with respect to the power converter apply correspondingly to the hydrogen production facility, and vice versa.

[0080] The above-mentioned problems are solved by the disclosed converter single-phase device. The disclosed embodiments, modifications and advantages apply accordingly.

[0081] Additional features, advantages and possible applications of the invention are derived from the following description of exemplary embodiments and the accompanying drawings. All features described and / or illustrated in the drawings form the subject matter of the invention individually or in any desired combination, regardless of how they are combined in the claims or in their reference to previous claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0083] Figure 1 Schematically illustrates an embodiment of a power converter according to the invention having two phase blocks, wherein each phase block comprises three converter single-phase string devices;

[0084] Figure 2More detailed schematically shows the Figure 1 one of the converter single-phase string devices in the power converter;

[0085] Figure 3 Schematically shows the Figure 1 The power converter control system shown together Figure 2 Converter single-phase string device;

[0086] Figure 4 Schematically illustrates Figure 1 The functional sections of the power converter are shown;

[0087] Figure 5 Schematically shows the Figure 1 and Figure 4 a hydrogen production facility comprising a power converter and an electrolyzer stack, wherein the power converter is connected to a medium voltage three-phase AC grid and supplies DC output power to the electrolyzer stack;

[0088] Figure 6 Schematically shows the Figure 2 and Figure 3 A transformer and passive diode rectifier of a variant of a single-phase string device of a converter, wherein the transformer has two separate output winding units connected in series to the passive diode rectifier;

[0089] Figure 7 A similar variation is schematically shown in which the transformer has two separate output winding units connected in parallel to a passive diode rectifier;

[0090] Figure 8 A similar variant is schematically shown, in which the connection of the output winding unit to the passive diode rectifier can be switched between series and parallel by means of a switch;

[0091] Figure 9 Schematically shows the Figure 2 and Figure 3 A transformer and a passive diode rectifier of yet another variation of a converter single-phase string device, wherein the transformer has two separate output winding units, and the passive diode rectifier has two branches, each branch having a separate passive diode bridge connected to a corresponding one of the separate output winding units for power supply only, and wherein the branches are connected in parallel to the output terminals of the converter single-phase string device;

[0092] Figure 10 Schematically shows the Figure 9 A similar variation wherein the branches are connected in series to the output terminals of the converter single-phase string arrangement; and

[0093] Figure 11 The interleaving between the first intermediate AC powers of different converter single-phase string devices is schematically shown. DETAILED DESCRIPTION

[0094] exist Figure 1 1 shows an embodiment of a power converter 100 according to the present invention. A power input 102 of power converter 100 is connected to an electric power grid 90. Grid 90 supplies multiphase AC grid input power having a grid frequency fG to power converter 100. The grid input voltage is referred to as GIV, and the (total) grid input current is referred to as GIC. Power converter 100 converts the multiphase AC grid input power into DC output power TOV, TOC. The voltage of the DC output power is referred to as TOV, and the (total) current of the DC output power is referred to as TOC.

[0095] In this example, the grid 90 is a medium voltage grid with three phases. The grid input voltage GIV can be, for example, 10 kV. The grid frequency fG is, for example, 50 Hz or 60 Hz.

[0096] Power converter 100 supplies its DC output power TOV, TOC to a DC power consumer, such as an electrolyzer stack 201. Electrolyzer stack 201 requires high DC power during operation, for example, up to 11 MW. Accordingly, in this exemplary embodiment, power converter 100 is configured to supply a maximum DC output power TOV, TOC of at least 11 MW.

[0097] Power converter 100 includes a housing 107. Housing 107 has, for example, the dimensions and external shape of a standard 20-foot container. This allows for easy and safe transportation to the final installation site. Power converter 100 is fully assembled and tested at the manufacturing site and then transported in its entirety to the final installation site. Implementation at the final installation site is particularly easy because power converter 100 arrives fully assembled and tested.

[0098] The power converter 100 includes two phase blocks 106A, 106B, namely a first phase block 106A and a second phase block 106B, arranged in a housing 107. Each of the phase blocks 106A, 106B includes, for example, a separate converter single-phase string arrangement 1 for each phase of the AC grid input power G IV , G IC . Since the number of phases n is three in this example, each of the phase blocks 106A, 106B includes three separate converter single-phase string arrangements 1, and a total of six separate converter single-phase string arrangements are shown.

[0099] The power converter 100 has a modular structure. The phase blocks 106A, 106B themselves have a modular structure. All converter single-phase string devices 1 have the same structure. They can be completely identical. This facilitates production and allows the structure of the power converter 100 to be easily adapted to the DC output power requirements and / or the power grid. If an even higher DC power output is required, other phase blocks similar to the phase blocks 106A, 106B can be added in parallel. Additionally or alternatively, each phase block 106A, 106B can include, for example, two converter single-phase string devices 1 for each phase of the AC grid input power GIV, GIC.

[0100] For example, if the grid 90 has only two phases, one converter single-phase string device 1 can be omitted in each phase block 106A, 106B. If the grid has, for example, four phases, each phase block 106A, 106B can include an additional fourth converter single-phase string device 1 for the fourth phase, and so on.

[0101] Figure 2 The structure of an individual converter single-phase string device 1 is shown in more detail. The converter single-phase string device 1 comprises an active rectifier portion 10 and a DC / DC converter 20.

[0102] The active rectifier portion 10 has a phase leg topology with three levels and has a neutral-point-clamped topology (NPC topology).

[0103] In more detail, the active rectifier section 10 includes an H-bridge with semiconductor switches 12. It comprises two phase legs 11. Each phase leg 11 includes four semiconductor switches 12 arranged in series and two clamping diodes 14 (e.g., in the form of semiconductor diodes). Each semiconductor switch 12 may have a body diode or a dedicated diode 13. The ends of the phase legs 11 are connected in parallel to intermediate DC power buses 15 and 16. The clamping diodes 14 are each connected in parallel to a common neutral point NP with their upstream ends relative to the forward direction.

[0104] In each phase leg 11, the first of the diodes 14 (e.g. Figure 2 The downstream end (with respect to the forward direction) of the upper diode 14 in the semiconductor switches 12 is connected to the first semiconductor switch (eg, Figure 2 The uppermost semiconductor switch 12 in the semiconductor switch 12 is electrically contacted with the electrical connection portion between the second semiconductor switch; the second diode in the diode 14 (eg, Figure 2 The downstream end of the lower diode 14 in the semiconductor switch 12 is connected to the third semiconductor switch in the semiconductor switch 12 and the fourth semiconductor switch in the semiconductor switch 12 (for example, Figure 2 The electrical connection portion between the bottom semiconductor switch 12) is electrically contacted.

[0105] The string input 2 for single-phase AC input power SInV, SInC includes two input lines. One of the input lines is connected to the middle of the first phase leg 11 of the rectifier section 10 (i.e., between the second and third semiconductor switches 12), and the other of the input lines is connected to the middle of the second phase leg 11. The voltage of the single-phase AC input power for the individual converter single-phase string devices 1 is referred to as SInV. The current of the single-phase AC input power for the individual converter single-phase string devices 1 is referred to as SInC.

[0106] from Figure 2 and Figure 1 and Figure 4Comparison between the active rectifier sections 10 of different phase blocks 106A, 106B clearly shows that the active rectifier sections 10 are cascaded. For example, the active rectifier sections 10 of phase blocks 106A, 106B for the first phase together form a cascaded H-bridge for the first phase (H-bridge cascade), the active rectifier sections 10 of phase blocks 106A, 106B for the second phase together form a cascaded H-bridge for the second phase (H-bridge cascade), and the active rectifier sections 10 of phase blocks 106A, 106B for the third phase together form a cascaded H-bridge for the third phase (H-bridge cascade). In this example, two different single-phase converter string devices 1 are used for each phase of the multi-phase AC grid input power G IV , G IC , but more than two single-phase converter string devices 1 may also be used.

[0107] Due to the cascade connection and the three-level topology, the individual semiconductor switches 12 of the active rectifier section 10 actually need to switch only half of the grid input voltage GIV (in this example: 5 kV instead of 10 kV). The voltage SInV of the single-phase AC input power for the individual converter single-phase string devices 1 corresponds to half the grid input voltage for the corresponding phase.

[0108] In this example, all semiconductor switches 12 of the active rectifier portion 10 are insulated gate bipolar transistors (IGBTs) each provided with a corresponding diode 13. More generally, the semiconductor switches 12 may include, for example, metal oxide semiconductor field effect transistors (MOSFETs) and / or silicon carbide semiconductor switches (SiC switches).

[0109] Furthermore, in this exemplary embodiment, the semiconductor switch 12 has a blocking voltage of at least 4 kV.

[0110] The active rectifier portion 10 rectifies the single-phase AC input power SInV, SInC into an intermediate DC power, which is then supplied to the DC / DC converter 20 via the intermediate DC power buses 15 , 16 .

[0111] like Figure 2 As can be seen, each individual DC / DC converter 20 includes an inverter portion 30 , a transformer 40 and a passive diode rectifier 50 .

[0112] The inverter portion 30 is connected to the intermediate DC power bus 15 , 16 . In other words, the inverter portion 30 is powered by the corresponding active rectifier portion 10 .

[0113] Like the active rectifier section 10 , the inverter section 30 has a three-level phase leg topology and a neutral point clamped topology (NPC topology). The inverter section 30 includes an H-bridge with semiconductor switches 32 and two phase legs 31 . Each phase leg 31 includes four semiconductor switches 32 arranged in series and two clamping diodes 34 (e.g., in the form of semiconductor diodes). Each semiconductor switch 32 may have a body diode or a dedicated diode 33 . The ends of the phase legs 31 are connected in parallel to the intermediate DC power buses 15 , 16 . The clamping diodes 34 are each connected in parallel to a common neutral point NP via their upstream ends relative to the forward direction. The active rectifier section 10 and the inverter section 30 of the same single-phase string converter device share the same common neutral point NP. The clamping diodes 34 are arranged in the same manner as the clamping diodes 14 in the active rectifier section 10 .

[0114] Between the phase leg 11 of the active rectifier section 10 and the phase leg 31 of the inverter section 30, a capacitor leg 37 is connected between the intermediate DC power buses 15, 16. The capacitor leg 37 comprises two capacitors 35, 36 connected in series between the intermediate DC power buses 15, 16. The neutral point NP is located between the two capacitors 15, 16. In this disclosure, it is assumed that the capacitor leg 37 forms part of the inverter section 30. Since the neutral point NP is shared by the active rectifier section 10 and the inverter section 30, it can also be assumed that the capacitor leg 37 forms part of the active rectifier section 30, either alternatively or additionally, but this is more of a matter of nomenclature.

[0115] In this example, all semiconductor switches 32 of the active inverter portion 30 are insulated gate bipolar transistors (IGBTs) each provided with a corresponding diode 33. More generally, the semiconductor switches 32 may include, for example, metal oxide semiconductor field effect transistors (MOSFETs) and / or silicon carbide semiconductor switches (SiC switches).

[0116] Furthermore, in this exemplary embodiment, the semiconductor switch 32 has a blocking voltage of at least 4 kV.

[0117] As described above, the inverter section 30 is connected to the intermediate DC power buses 15, 16. When the active rectifier section 10 is operated, the active rectifier section 10 supplies the intermediate DC power to the inverter section 30. The inverter section 30 inverts the intermediate DC power into the first intermediate AC power PAC1, which is supplied to the input coil 41 of the transformer 40.

[0118] The boosted frequency f1 of the first intermediate AC power PAC1 is significantly higher than the grid frequency fG, for example, 20 times higher than the grid frequency fG. For example, the grid frequency fG is 50 Hz, while the boosted frequency f1 is 1 kHz. Compared to a common conventional transformer for the grid frequency fG, which may be arranged directly on the power input 102 side, the transformer 40 can be particularly small and lightweight.

[0119] The transformer 40 includes at least one input coil 41 (primary winding unit) and at least one output coil 42 (secondary winding unit) and transforms the first intermediate AC power PAC1 into the second intermediate AC power PAC2.

[0120] In this embodiment, the voltage of the second intermediate AC power PAC2 is reduced compared to the voltage of the first intermediate AC power PAC1 (at least as long as the voltage of the first intermediate AC power PAC1 is not zero, which would cause the voltage of the second intermediate AC power PAC2 to also be zero). For example, the voltage of the second intermediate AC power PAC2 may correspond to the voltage of the first intermediate AC power PAC1 multiplied by a voltage factor. For example, the voltage factor may be in the range of 0.2 to 0.4. This may be applicable at least when the power converter 100 provides maximum DC output power.

[0121] The frequency of the second intermediate AC power PAC2 may be the same as the frequency f1 of the first intermediate AC power PAC 1. Typically, the transformer 40 does not affect the frequency, at least substantially.

[0122] The second intermediate AC power PAC2 is supplied from the transformer 40 (eg, from at least one output coil 41 of the transformer 40 ) to the passive diode rectifier 50 .

[0123] The passive diode rectifier 50 comprises a diode bridge 51 composed of diodes 52 (eg in the form of semiconductor diodes). Figure 3 and Figure 4 Four diodes 52 are shown. However, Figure 3 Each diode 52 in may actually comprise several diodes connected in parallel.

[0124] In this embodiment, the passive diode rectifier 50 does not have any active semiconductor switches. In fact, the passive diode rectifier 50 of this embodiment includes only passive components. This makes the passive diode rectifier 50 robust and cost-effective, but it can also supply the very high maximum output DC power SOV, SOC of the single-phase converter device 1.

[0125] The voltage of the output DC power of an individual converter single-phase device 1 is referred to as SOV; the current of the output DC power of an individual converter single-phase device 1 is referred to as SOC. For example, the maximum output DC voltage SOV may be in the range of 600 V to 1.5 kV, and / or the maximum output DC current SOC may be at least 1000 A. The maximum output DC power SOV and SOC may be, for example, at least 1.4 MW.

[0126] The passive diode rectifier 50 may include a smoothing capacitor 53 connected between output DC power buses 55, 56 of the converter single-phase string device 1 after the diode bridge 51. The output DC power buses 55, 56 are connected to the DC output terminal 3 of the converter single-phase string device 1.

[0127] Therefore, the DC / DC converter 20 comprises only a single active bridge, namely an H-bridge of the inverter part 30 with semiconductor switches 32 .

[0128] like Figure 1 and Figure 4 As shown, in this embodiment, the power converter 100 includes a common DC power output terminal 103. The DC power output terminals of the two phase blocks 106A and 106B are connected in parallel to the common DC power output terminal 103. In more detail, the DC output terminals 3 (see Figure 2 and Figure 3 ) are electrically connected in parallel to a common DC power output terminal 103. In a variation, for example, the DC output terminals 3 of the converter single-phase string devices 1 of the first phase block 106B are connected in parallel and connected to a first DC power consumer (e.g., a first electrolyzer stack), and the DC output terminals 3 of the converter single-phase string devices 1 of the second phase block 106B are connected to a second DC power consumer (e.g., a second electrolyzer stack).

[0129] Go to Figure 4 All active rectifier sections 10 are collectively referred to as an active front end 110 (AFE 110 ) of the power converter 100 . Similarly, all DC / DC converters 20 of the plurality of converter single-phase string devices 1 are collectively referred to as a DC / DC stage 120 of the power converter 100 .

[0130] However, the individual converter single-phase string devices 1 (at least the DC / DC converters 20) are essentially independent of each other. In particular, each DC / DC converter 20 can be controlled individually. Figure 1In FIG. 1 , each DC / DC converter 20 has its own separate corresponding active rectifier part 10 . In principle, each DC / DC converter 20 can operate autonomously with respect to the other DC / DC converters 20 .

[0131] Power converter 100 includes a control system 60 . Figure 3 The control system 60 is shown operatively connected to the semiconductor switches 12 of the active rectifier portion 10 and the semiconductor switches 32 of the inverter portion 30 .

[0132] Since the inverter portion 30 includes the semiconductor switches 32 , the inverter portion 30 can regulate the first intermediate AC power PAC1 , for example, by adjusting the length of current pulses supplied to the transformer 40 .

[0133] refer to Figure 3 , the control system 60 is able to operate the semiconductor switches 12 of the active rectifier portion 10 independently of the semiconductor switches 32 of the inverter portion 30 of the same converter single-phase string device 1. In other words, the control system 60 can operate the active rectifier portion 10 (and therefore the active front end 110 of the entire power converter 100) independently of the DC / DC converter 20 (and therefore independently of the DC / DC stage of the entire power converter 100).

[0134] For example, when the inverter section 30 is inactive (such that no first intermediate AC voltage PAC1 is supplied to the transformer 40), the control system 60 can maintain operation of the active rectifier section 10. This facilitates rapid power-up of the output DC power SOV, SOC: only the operation of the inverter section 30 needs to be activated. Consequently, this allows the DC power consuming devices (e.g., the electrolyzer stack 201) to be started very quickly. Similarly, the supply of the output DC power SOV, SOC can be quickly reduced or stopped simply by adjusting or stopping the operation of the inverter section 30.

[0135] Furthermore, selective control of the active rectifier section 10 and the inverter section 30 (and therefore of the active front end 110 and DC / DC stage 120 of the overall power converter 100) is used to reduce the negative effects of disturbances in the grid 90 on the output DC power SOV, SOC (and therefore on the DC output power TOV, TOC of the overall power converter 100). This provides greater flexibility during grid faults (fault ride-through).

[0136] Vice versa, selective control is used to reduce the risk of power converter 100 causing disturbances in grid 90 , such as when starting, changing, or stopping the supply of power to electrolyser stack 201 .

[0137] In particular, the power converter 100 (and in particular the control system 60 ) may be configured to operate the active front end 100 as a static synchronous compensator (STATCOM) even when no DC output power TOV, TOC is supplied to the DC power consumer (eg, the electrolyzer stack 201 ).

[0138] The maximum output DC voltage SOV may be given by a maximum result of multiplying the first intermediate AC power PAC1 by the voltage factor.

[0139] The output DC power SOV and SOC (specifically, the voltage SOV) of the individual converter single-phase string devices 1 can be adjusted between 1V and a maximum SOV. The control system 60 is configured to adjust the pulses used to generate the intermediate AC power PAC1. For example, the control system 60 is configured to adjust the pulse length used to generate the intermediate AC power PAC1. The control system 60 controls the semiconductor switches 32 of the inverter section 30 accordingly. In this way, the control system 60 can influence and adjust the output DC power SOV and SOC.

[0140] Additionally or alternatively, the output DC power SOV, SOC, and output DC current SOC can be adjusted within a range of output DC voltages. This range can be from at least 1V to a maximum value (i.e., the maximum output DC voltage SOV), and can be from 0V to the maximum output DC voltage SOV. The output DC current SOC can be precisely controlled, enabling rapid shutdown, particularly in the event of a fault.

[0141] The control system 60 performs regulation, for example by adapting the on-time and off-time of the semiconductor switch 32 via control signals to the semiconductor switch 32. This affects the pulse width of the first intermediate AC power PAC1.

[0142] like Figure 1 and Figure 4 As shown, the power converter 100 optionally includes an LCL filter 105 disposed between the power input 102 and the phase blocks 106A, 106B.

[0143] In addition, power converter 100 optionally includes an input power analyzer 104 for analyzing the multiphase AC grid input power GIV, GIC from grid 90. Input power analyzer 104 analyzes at least the frequency fG of grid 90. Control system 60 is connected to input power analyzer 104. Based on signals received from input power analyzer 104, control system 60 controls semiconductor switches 32 of inverter section 30 so that the frequency f1 of first intermediate AC power PAC1 is consistent across all converter single-phase string devices 1, where frequency f1 corresponds to an integer multiple of grid frequency fG. For example, this integer multiple is 20. This helps avoid low-frequency, subharmonic, and interharmonic distortion.

[0144] Additionally or alternatively, the power converter 100 is configured for interleaving of the DC / DC converters 20 of the converter single-phase string arrangement 1. The control system 60 controls the inverter portion 30 accordingly.

[0145] In particular, the power converter 100 can be configured to interleave between DC / DC converters 20 powered by the same phase of the grid 90. For example, the control system 60 can control the semiconductor switches 32 of the inverter portion 30 of the converter single-phase string devices 1 powered by the same phase of the grid 90 according to a phase-shifted carrier. For example, the control system 60 can perform interleaving between a complete first phase block 106A and a complete second phase block 106B. In this example with two phase blocks 106A and 106B, the second phase block 106B can operate with a 90° interleaving / phase shift.

[0146] refer to Figure 1 and Figure 11 Explain the principle of interleaving. Figure 11 1 , a first intermediate AC power PAC1 provided by the inverter portion 30 of the first DC / DC converter 20 and a first intermediate AC power PAC1′ provided by the inverter portion 30 of the second DC / DC converter 20 are shown. The first intermediate AC power PAC1 and the first intermediate AC power PAC1′ have the same periodicity, with a period duration T. The first intermediate AC power PAC1′ is time-shifted relative to the first intermediate AC power PAC1 by a time difference Δt.

[0147] In particular, the time difference Δt may be calculated by Δt=T / (2*K), where K is the number of interleaving groups.

[0148] The number K may correspond to the number of phase blocks 106A, 106B. Figure 1 and Figure 4 For the converter 100 shown, K=2, and thus Figure 11 The indicated Δt=T / 4 may apply.

[0149] According to one aspect, the inverter parts 30 of the converter single-phase string devices 1 (and thus the first intermediate AC powers PAC1 , PAC1 ′) powered by the same phase of the grid input power are interleaved with respect to each other. Figure 1 and Figure 4 The first intermediate AC power of all DC / DC converters 20 in the phase block 106A corresponds to Figure 11 PAC1 in, and Figure 1 and Figure 4 The first intermediate AC power of all DC / DC converters 20 in phase block 106B corresponds to Figure 11 PAC2 in.

[0150] In the case of adding an additional third phase block (not shown), the value of K may be 3, and Δt may correspond to T / 6. The first intermediate AC power of all DC / DC converters in the second phase block is time-shifted by T / 6 relative to the first intermediate AC power of all DC / DC converters in the first phase block, and the first intermediate AC power of all DC / DC converters in the third phase block is time-shifted by T / 6 relative to the first intermediate AC power of all DC / DC converters in the second first phase block (i.e., time-shifted by T / 3 relative to the first intermediate AC power of all DC / DC converters in the first phase block). In other words, in this case, the relative interleaving / phase offset between subsequent phase blocks is 360° / (2*N) = 60°.

[0151] In general, the "groups" used for interleaving may be composed differently.In other embodiments, the DC / DC converters 20 of the same phase block 106A, 106B may be controlled by interleaving relative to each other.

[0152] Due to the interleaving, when the output DC powers SOV, SOC of the individual converter single-phase string devices 1 are combined into the DC output powers TOV, TOC, fluctuations in the output DC powers SOV, SOC of the individual converter single-phase string devices 1 (due to the alternating single-phase AC input powers SInV, SInC) are at least partially compensated.

[0153] According to one aspect, power oscillations generated by single-phase rectification within an individual converter single-phase string arrangement 1, having a frequency corresponding to a multiple of the grid frequency fG, can be forwarded to the DC output terminals 3 of the individual converter single-phase string arrangement 1. On the one hand, this results in greater stress on the DC / DC converter 20. On the other hand, this allows the use of particularly small capacitors 35, 36. Since the DC output terminals 3 are connected in parallel to the common DC power output 103 of the power converter 100, the power oscillations caused by the different phases ultimately cancel each other out. Although the capacitors 35, 36 can be kept small, this aspect allows the intermediate DC power to have low voltage ripple.

[0154] Furthermore, in the exemplary embodiment, there is no series capacitor in the connection between the inverter portion 30 and the transformer 40. In other words, there is no additional capacitor between the inverter portion 30 and the transformer 40. The disclosed measures help to achieve a relatively smooth DC output power TOV, TOC without the need for such a series capacitor.

[0155] By using a phase topology with more than three levels and by cascading active rectifier sections 10 with more cascaded levels, the voltage that must be switched by the individual semiconductor switches 12, 32 can be further reduced. This allows handling of higher grid input voltages GIV and / or the use of semiconductor switches 12, 32 with lower blocking voltages.

[0156] Figure 5 A hydrogen production facility 200 is schematically shown, comprising a Figure 1 and Figure 4 The power converter 100 and the electrolyzer stack 201 are shown. The power input 102 of the power converter 100 is connected to the grid 90. The DC power output 103 of the power converter 100 is connected to the electrolyzer stack 201. Therefore, if the grid 90 supplies electricity obtained from renewable energy sources, the present invention can be used to produce hydrogen, such as "green" hydrogen.

[0157] Naturally, the power converter 100 may also be used with other DC power consuming devices having high power demands, such as with multi-MW DC chargers and data centers.

[0158] refer to Figure 6 right Figure 2 and Figure 3 A variation of the converter single-phase string device 1 is explained in more detail. Figure 6 Only the transformer 240 and the passive diode rectifier 50 of the modified single-phase string device 1 are shown. The other parts of the converter single-phase string device 1 are the same as those of FIG. Figure 2 and Figure 3The same elements have the same reference numerals and are not explained again. Only the differences are explained.

[0159] exist Figure 6 In FIG. 2 , the transformer 240 has two separate output winding units 242A, 242B. The different separate output winding units 242A, 242B are connected in series to the passive diode rectifier 50 .

[0160] refer to Figure 7 right Figure 2 and Figure 3 Another variation of the converter single-phase string device 1 is explained below. In more detail, Figure 7 Only the transformer 240 and the passive diode rectifier 50 of the modified single-phase string device 1 are shown. The other parts of the converter single-phase string device 1 are the same as those of FIG. Figure 2 and Figure 3 The same elements have the same reference numerals and are not explained again. Only the differences are explained.

[0161] exist Figure 7 In FIG. 2 , the transformer 240 has two separate output winding units 242A, 242B (secondary winding units 242A, 242B). The different separate output winding units 242A, 242B are connected in parallel to the passive diode rectifier 50 .

[0162] pass Figure 6 and Figure 7 The configuration shown can be made using the same type of transformer 240 Figure 2 and Figure 3 Different variants of the converter single-phase device 1 are shown, which are suitable for different DC output power requirements. Figure 6 As in FIG, different individual output winding units 242A, 242B are connected in series to the passive diode rectifier 50, the output DC voltage SOV is higher than that in FIG. Figure 7 The case where the individual output winding units 242A, 242B are connected in parallel to the passive semiconductor rectifier 50. For example, if the number of windings is the same for the individual winding units 242A, 242B, then Figure 6 The output DC voltage SOV (at DC output terminal 3) is Figure 7 twice the output DC voltage SOV in (for the same first intermediate AC power PAC1). Vice versa, Figure 6 The output DC current SOC is Figure 6 twice the output DC current SOC in (for the same first intermediate AC power PAC1).

[0163] By using the same type of transformer 240 to manufacture suitable variations for different DC output power requirements, production is simplified and costs are reduced.

[0164] Figure 8 A further variant shown comprises a device for Figure 6 and Figure 7 Switch 243 is provided for switching between the two configurations. Switch 243 can be a manual switch configured for high power. This allows for easier on-site adaptation to different DC output power requirements. However, it should be emphasized that the advantages of transformer 240 with two separate output winding units 242A and 242B in terms of scalability and manufacturing costs also apply without optional switch 243.

[0165] refer to Figure 9 right Figure 2 and Figure 3 A further variant of the converter single-phase string device 1 is explained below. Figure 9 Only the transformer 240 and the passive diode rectifier 50 of the modified single-phase string device 1 are shown. The other parts of the converter single-phase string device 1 are the same as those of FIG. Figure 2 and Figure 3 The same elements have the same reference numerals and are not explained again. Only the differences are explained.

[0166] Again, a transformer 240 is used having (at least) two separate output winding units 242A, 242B. The separate output winding units 242A, 242B are connected in parallel to the passive diode rectifier 150.

[0167] In more detail, the passive diode rectifier 150 includes several branches 157A, 157B. Each branch 157A, 157B is connected to only one of the individual output winding units 242A, 242B. Therefore, the second intermediate AC power PAC is supplied to each branch 157A, 157B only from the corresponding individual output winding unit 242A, 242B. 2A 、PAC 2B .

[0168] Each branch 157A, 157B has its own individual passive diode bridge 51 for providing rectification. This allows reducing the electrical power that must be handled by the individual passive diode bridges 51.

[0169] exist Figure 9 In the embodiment, branches 157A and 157B are connected in parallel to the DC output terminal 3. The currents rectified by the branches 157A and 157B are added together to form the output DC current SOC.

[0170] In addition, Figure 9In the embodiment, each branch 157A, 157B has an optional individual smoothing capacitor 53 connected in parallel to the corresponding passive diode bridge 51 between the output DC power buses 55, 56. Additionally or alternatively, there may be a common capacitor 53 (not shown) for the branches 157A, 157B.

[0171] Figure 10 The variant shown is Figure 9 The variant shown is similar. The only difference is that the branches 157A, 157B of the passive diode rectifier 250 are connected in series to the DC output terminal 3.

[0172] and Figure 8 Similarly, a manual switch (not shown) may be added between the DC output terminal 3 and the branches 157A, 157B to allow Figure 9 and Figure 10 to switch between the configurations shown.

[0173] If Figure 10 As in FIG. 1 , different branches 157A, 157B are connected in series to the DC output terminal 3, the output DC voltage SOV is higher than Figure 9 157A, 157B are connected in parallel to the DC input terminal 3 as in FIG. For example, if the number of windings is the same for the individual winding units 242A, 242B, then Figure 10 The output DC voltage SOV (at DC output terminal 3) is Figure 9 twice the output DC voltage SOV in (for the same first intermediate AC power PAC1). Vice versa, Figure 10 The output DC current SOC is Figure 10 twice the output DC current SOC in (for the same first intermediate AC power PAC1).

[0174] In each of the illustrated variations, the number of windings may be the same for the individual output winding units 242A, 242B. Alternatively or additionally, the transformer 240 may have the same transformation characteristics for the individual output winding units 242A, 242B.

[0175] The power converter 100 may comprise a converter single-phase string device 1 according to any variant. The same power converter 100 may comprise a converter single-phase string device 1 according to different variants.

Claims

1. A power converter (100) for converting a multiphase AC grid input power (GIV, GIC) having a grid frequency (fG) and at least two phases from a grid (90) into a DC output power (TOV, TOC) of the power converter (100), wherein: The power converter (100) comprises at least one phase block (106A, 106B), wherein each of the phase blocks (106A, 106B) comprises at least two separate converter single-phase string devices (1), Each converter single-phase string device (1) comprises: a separate active rectifier section (10) for rectifying a single-phase AC input power (SInV, SInC) into an intermediate DC power, the active rectifier section (10) comprising an H-bridge having semiconductor switches (12); and A separate DC / DC converter (20) for converting the intermediate DC power into output DC power (SOV, SOC) of the converter single-phase string device (1), wherein the DC / DC converter (20) comprises: - an inverter part (30) for inverting the intermediate DC power into a first intermediate AC power (PAC1) having a stepped-up frequency (f1), wherein the inverter part (30) comprises an H-bridge having semiconductor switches (32); - A transformer (40, 240) configured to convert the first intermediate AC power (PAC1) into a second intermediate AC power (PAC2, PAC 2A 、PAC 2B );as well as - a passive diode rectifier (50, 150, 250) for converting the second intermediate AC power (PAC2, PAC 2A 、PAC 2B ) is rectified into the output DC power (SOV, SOC) of the converter single-phase string device (1), wherein the passive diode rectifier (50, 150, 250) includes a diode bridge (51).

2. The power converter (100) according to claim 1, wherein: The semiconductor switches (12) of the active rectifier part (10) are insulated gate bipolar transistors, and / or wherein the semiconductor switches (32) of the inverter part (30) are insulated gate bipolar transistors.

3. The power converter (100) according to any one of the preceding claims, wherein Each active rectifier section (10) has a phase leg topology with at least three levels; and / or wherein each inverter section (30) has a phase leg topology with at least three levels.

4. The power converter (100) according to any one of the preceding claims, wherein Each active rectifier section (10) is in a neutral point clamped topology; and / or, each inverter section (30) is in a neutral point clamped topology.

5. The power converter (100) according to claim 4, wherein: In each converter single-phase string device (1), the active rectifier part (10) and the inverter part (30) both have a neutral point clamped topology and share a corresponding neutral point (NP).

6. The power converter (100) according to any one of the preceding claims, wherein In each converter single-phase string device (1), The transformer (40, 240) provides electrical isolation between the active rectifier portion (10) and the passive diode rectifier (50, 150, 250); and / or The transformer (40, 240) is configured to transform the intermediate AC power (PAC1) into the second intermediate AC power (PAC2, PAC 2A 、PAC 2B ), so that the second voltage intermediate AC power (PAC2, PAC 2A 、PAC 2B ) is less than one third of the voltage of the first intermediate AC power (PAC1).

7. The power converter (100) according to any one of the preceding claims, wherein The power converter (100) includes at least two phase blocks (106A, 106B).

8. The power converter (100) according to claim 7, wherein: The active rectifier parts (10) of the converter single-phase string arrangement (1) of the at least two phase blocks (106A, 106B) together form a cascaded H-bridge for each phase.

9. The power converter (100) according to any one of the preceding claims, wherein The DC output terminals (3) of the converter single-phase string device (1) are electrically connected in parallel.

10. The power converter (100) according to any one of the preceding claims, wherein The DC / DC converters (20) are independent of each other.

11. The power converter (100) according to any one of the preceding claims, wherein The power converter (100) comprises an LCL filter (105) located between a power input terminal (102) for the multi-phase AC grid input power (GIV, GIC) and the converter single-phase string device (1) most directly connected to the power input terminal (102).

12. The power converter (100) according to any of the preceding claims, comprising a control system (60) and an input power analyzer (104) for determining at least the grid frequency (fG), wherein The control system (60) is configured to control at least the operation of the semiconductor switches (32) of the inverter portion (30) of the converter single-phase string device (1), and wherein the input power analyzer (104) is connected to the control system (60), The control system (60) is configured to control the semiconductor switches (32) of the inverter part (30) of the converter single-phase string device (1) so that the first intermediate AC power (PAC1) has the same boosted frequency (f1) corresponding to an integer multiple of the grid frequency (fG), wherein the integer multiple is at least 10.

13. The power converter (100) according to any one of the preceding claims, wherein For a corresponding one of the converter single-phase string devices (1), an output DC current (SOC) of the output DC power (SOV, SOC) is adjustable for any output DC voltage (SOV) level of the output DC power (SOV, SOC) between zero and a maximum value.

14. The power converter (100) according to any one of the preceding claims, wherein The transformer (240) includes at least two separate output winding units (242A, 242B), wherein the separate output winding units (242A, 242B) are connected to the passive diode rectifier (50, 150, 250) in parallel or in series.

15. A hydrogen production facility (200), comprising: - an electrolyser stack (201) for producing hydrogen, and - A power converter (100) according to any one of the preceding claims, for supplying the DC output power (TOV, TOC) to the electrolyser stack (201).

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