Electrolysis system

Abstract

The invention relates to an electrolysis system (100) comprising at least two electrolysis devices (1A, 1B), a current supply source (3) having a DC voltage output (7), and a central supply line (5), the central supply line (5) being connected to the DC voltage output (7) of the current supply source (3) such that a DC current can be fed to the central supply line (5) at a first DC voltage (31). The electrolysis devices (1A, 1B) are electrically connected in parallel to the central supply line (5), and wherein a central voltage source converter (13), in particular a modular multilevel converter (13), is connected at a network connection point (35) for supplying a direct current from the utility network (25), which converts an alternating current at the input into a first direct voltage (31) at the output at the direct voltage output (7). In this case, each electrolysis device (1A, 1B) is connected in parallel to the DC voltage output (7) of the voltage source converter (13) via a DC / DC converter (11A, 11B) which converts the first DC voltage (31) into a second DC voltage (33, 33A, 33B), such that the second DC voltage (33A, 33B) drops across the electrolysis device (1A, 1B), each DC / DC converter (11A, 11B) can be controlled and / or adjusted to adaptively adjust the magnitude of the second DC voltage (101, 102) thereof.

Description

Technical Field

[0001] The invention relates to an electrolysis system, which comprises at least two electrolysis devices and a current supply source. Background Art

[0002] Electrolysis, i.e. the process of inducing a chemical reaction by means of an electric current, has applications in many technical fields and is used, for example, to obtain various substances. For example, hydrogen and oxygen can be obtained by electrolysis of water. For the operation of electrolysis plants (also called electrolysis stacks or electrolyzers or electrolysis plants), it is desirable that these electrolysis plants be operated as energy-efficiently and as safely as possible, especially on an industrial scale.

[0003] Nowadays, hydrogen is produced from water, for example, by means of proton exchange membrane (PEM) electrolysis, anion exchange membrane or alkaline electrolysis. Electrolysis equipment produces hydrogen and oxygen from supplied water by means of electrical energy. The process takes place in a so-called electrolysis stack consisting of a plurality of electrolysis cells. The electrolysis stack can in turn consist of a plurality of electrolysis modules, which in turn consist of a plurality of electrolysis cells. Water is introduced as a reactant into an electrolysis stack to which a direct current voltage (DC voltage) is applied, wherein, after passing through the electrolysis cells, two fluid flows consisting of water and gas bubbles (O2 and H2) emerge.

[0004] It is known to this end that a plurality of electrolyzers or electrolysis systems can be electrically connected in parallel, for example, wherein the electrolyzers are each supplied via their own, electrically separate circuits by a transformer with step switches for coarse adjustment of the electrolyzers and a rectifier with a thyristor circuit for fine adjustment of the electrolysis system, which is a very complex solution. As an alternative to this, it is also known to connect the electrolyzers in parallel and operate them via a rectifier in order to reduce the circuit complexity, but this can lead to a current distribution depending on the ratio of the resistances of the electrolyzers and thus to a significant derating and the risk of operating one or more electrolyzers outside their safe operating range.

[0005] High direct currents are required to operate a water electrolysis system. Since the electrical energy grid is usually operated as an alternating current grid, power electronic rectifiers are required to connect the electrolysis to the grid. For future large-scale systems, this situation and existing solutions necessitate the use of many rectifier systems operated in parallel.

[0006] Document EP 3 752 665 A1 discloses a network connection of an electrolysis device having a plurality of electrolyzers connected in parallel. Here, the rectifier has a thyristor group, which has a plurality of thyristors. By controlling the rectifier, the level of the DC voltage at the output can be adaptively adjusted. The adjustability of the rectifier is achieved by selecting the ignition moment of the thyristors in the thyristor group. In order to stabilize the DC voltage generated by the rectifier, a capacitor connected in parallel with the output of the rectifier is also provided in document EP 3 753 665 A1. In addition, an adjustable filter device with inductance and capacitance is provided, by means of which the resonance generated by the rectifier can be attenuated, and the resonance is generated by the switching of the thyristor group of the rectifier during operation.

[0007] Therefore, for future large-scale plants with a large number of electrolysis devices in the electrolysis system, a corresponding number of power electronic rectifiers must be provided for the network connection, which are used in complex rectifier systems and connected in parallel in order to be able to provide the high direct current requirements of the electrolysis devices. Due to the network reaction caused by the resonance of the thyristors (so-called harmonics), this can only be achieved with a correspondingly high filtering expenditure and is particularly associated with relatively high additional costs for the arrangement and operation of the filtering device. Therefore, due to the widely used thyristor-based rectification, the technical limitations and expenditure are very disadvantageous for large-scale plants. However, this is an acceptable price to pay for the solutions known to date, because thyristor technology is a proven technology. Summary of the invention

[0008] The object of the present invention is therefore to provide an electrolysis system with a direct current supply for a plurality of electrolysis plants connected in parallel, which is designed for large plants and has cost advantages over known solutions while having improved operating properties with regard to energy-saving operation.

[0009] According to the invention, this object is achieved by an electrolysis system comprising at least two electrolysis devices, a current supply source with a DC voltage output and a central power supply line, wherein the central power supply line is connected to the DC voltage output of the current supply source so that a DC current can be fed into the central power supply line at a first DC voltage, and wherein the electrolysis devices are electrically connected in parallel to the central power supply line, wherein, for supplying the DC current from the public grid, a voltage source converter (VSC), in particular a modular multilevel converter (MMC), is connected at the network connection point, which converts the AC voltage at the input into a DC voltage at the output at the DC voltage output. A first DC voltage, wherein each electrolysis device is connected in parallel to a DC voltage output of a voltage source converter (VSC), in particular a modular multilevel converter (MMC), via a DC / DC converter that converts the first DC voltage into a corresponding second DC voltage, so that the second DC voltage drops across the electrolysis device, wherein each DC / DC converter can be controlled and / or adjusted to adaptively adjust the level of its second DC voltage, wherein a controllable bridge switch is provided so that when the bridge switch is closed, the corresponding DC / DC converter can be bridged so that the first DC voltage can be directly applied to the connected electrolysis device.

[0010] With the invention, individual power regulation of the electrolysis equipment is achieved for the first time in an electrolysis system by an advantageous cooperation of a voltage source converter (VSC), in particular an IGBT-based converter, such as a modular multilevel converter (MMC converter), at the network connection point with the corresponding DC / DC converter of the electrolysis equipment. The conversion of the alternating current into a direct current is performed only once in the case of a network connection to the network connection point by a central voltage source converter (VSC), for example designed as a modular multilevel converter (MMC). For this purpose, an IGBT-based rectifier is used at the connection, which is provided, for example, by a modular multilevel converter. Thus, the centralized connection of the voltage source converter (VSC), in particular designed as a modular multilevel converter (MMC), on the AC network enables the provision of direct current power for electrolysis at a first direct voltage at the direct voltage output on the central power supply line. Thus, the central power supply line functions as a direct current bus line in terms of its function, which provides electrical power at a first direct voltage.

[0011] Therefore, the present invention is based on the following recognition: that is, due to the high requirements of electrolysis for direct current, rectifiers based on thyristor technology are currently preferred. The rectifier and AC connection technology based on thyristors that have been preferred so far is proven, reliable, and has relatively few losses in operation. However, the use of thyristors can lead to severe network reactions caused by resonance, so-called harmonics, and thus also lead to high reactive power requirements. In particular, for future large-scale electrolysis systems with multiple electrolysis equipment or electrolyzers, this creates significant additional filtering requirements and compensation requirements, which correspondingly raises costs and space requirements. Since both reactive power requirements and harmonics are related to the operating point, the filter system must be designed for all operating points of the connected large-scale electrolysis equipment in order to achieve the required operational flexibility and network stability of large-scale equipment on an industrial scale.

[0012] Furthermore, due to the ever-decreasing rotating masses, for example due to the shutdown of nuclear and coal-fired power plants, it is expected that the network short-circuit power and thus the network stability of future networks will decrease significantly. It is therefore increasingly important that large installations can provide network services for the public grid in addition to their own functions. This can only be achieved to a limited extent with current thyristor technology (active power regulation). Furthermore, further additional measures are required in order to be able to apply thyristor technology in the case of very weak networks.

[0013] When combining renewable energy plants (EE plants), such as photovoltaic plants, which may already provide a DC voltage, with electrolysis plants, the use of thyristor technology also requires multiple conversions of the voltage form (DC-AC-DC), which leads to increased costs and losses.

[0014] If different thyristor rectifiers are operated in parallel, for example in a large system, they can be supplied with a phase-shifted alternating voltage in order to reduce the filtering requirements. However, in this approach, all rectifiers must be kept at a relatively uniform operating point, i.e., draw similar power. If, for example, operation at different operating points is to be considered due to different aging of the individual electrolysis modules, the filtering requirements are increased again. This significantly limits the operating flexibility or can only be improved with high system and cost expenditures.

[0015] The present invention uses a voltage source converter (VSC), in particular a modular multilevel converter (MMC), for the first time to transmit power between the AC network and the DC network in the electrolysis system, which has many advantages compared to the thyristor-based power supply topology. It is particularly advantageous that bidirectional power transmission can be achieved for the electrolysis system between the public power grid and the central power supply line, which can provide network services, such as voltage support or assume network-related functions.

[0016] The use of bipolar transistors with insulated gate electrodes (IGBTs) in modular multilevel converters for supplying direct current to electrolysis has proven to be particularly advantageous for the operating characteristics of electrolysis systems. IGBTs are semiconductor devices used in power electronics because they combine the advantages of bipolar transistors (such as good conduction characteristics, high cut-off voltage and robustness) with the advantages of field effect transistors that they require almost no power for control. Therefore, IGBTs are widely used, for example, in so-called three-phase B6 bridge circuits with IGBT-based rectifiers, whereby very precise control of the electrolysis current is achieved with good rectification. The significant advantages of IGBTs are high voltage and current limits: voltages of up to 6500 V and currents of up to 3600 A with powers of up to several megawatts, which predestines IGBTs for use in electrolysis equipment. Therefore, the use of IGBTs in voltage source converters (VSCs), which are designed in particular as modular multilevel converters (MMCs) based on IGBTs, is very advantageous in the context of the electrolysis system proposed by the invention.

[0017] In electrolysis, the first DC voltage for the electrolysis equipment is reduced to the corresponding second DC voltage by the corresponding DC / DC converter, and there is no conversion loss worth mentioning for each desired value. Therefore, in the electrolysis system, the electrolysis equipment is adjustable and can also be switched on and off in terms of electrolysis power. Partial load capacity or partial load control is achieved by regulating the electrolysis current. In addition to or instead of the network connection with the public power grid, the ability of independent network operation can also be ensured as required by coordinating power regulators, which, for example, has significant cost advantages for remote onshore equipment or offshore equipment. In order to provide higher electrolysis current, multiple DC / DC converters can be connected in parallel as required and applied in corresponding connecting lines.

[0018] In order to further improve the energy efficiency in the electrolysis system, it is further provided that the electrolysis system includes a plurality of controllable bridge switches, so that in the connection line, the corresponding DC / DC converter, such as a buck converter based on IGBT, can be bridged by the controllable bridge switches respectively assigned as needed. In the case of bridging the DC / DC converter, the first DC voltage is completely dropped across the electrolysis equipment connected to the bridged DC / DC converter. Therefore, in the case of the DC / DC converter bridging, the second DC voltage is consistent with the first DC voltage. The bridging of the DC / DC converter can replace the operation of the DC / DC converter that makes the second DC voltage (i.e., the output voltage of the DC / DC converter) and the first DC voltage (i.e., the input voltage of the DC / DC converter) as large as possible. Thus, the electrical loss that may be generated during the conventional operation when the DC / DC converter is powered on can be avoided. Advantageously, in order to operate particularly energy-saving, for example, only the electrolysis equipment with the minimum resistance can be powered via the DC / DC converter, while other electrolysis equipment is powered directly via the first DC voltage. The control of the individual bridge switches can be performed, for example, by a central computer of the electrolysis system, wherein the computer is used in particular for controlling and / or regulating the DC / DC converter. Thus, a bridge device with a plurality of controllable bridge switches is provided in the electrolysis system, and a particularly advantageous and energy-saving full-load control of an electrolysis device connected to a central DC power supply line is achieved.

[0019] In a particularly preferred embodiment of the electrolysis system, the DC / DC converter is an IGBT-based step-down converter for individual power regulation of the electrolysis device.

[0020] Preferably, the voltage source converter (VSC), in particular designed as a modular multilevel converter (MMC), is designed for bidirectional operation and is connected to a central network connection point, so that voltage support of the public grid can be performed by providing reactive power.

[0021] Further network services can also advantageously be provided in this context, for example taking over network-related functions.

[0022] It is also preferred that the voltage source converter (VSC) is a modular multilevel converter based on IGBTs, so that the electric power from the central power supply line can be fed into the public power grid at the network connection point as required. This is a specific and advantageous form of bidirectional operation of the electrolysis system. This is possible if, for example, DC power is additionally fed into the central power supply line from a renewable energy device (EE device) or when some electrolysis devices or modules of the electrolyzer are in partial load operation or maintenance so that there is excess power on the central power supply line that the electrolysis device cannot draw. Therefore, in normal operation, the MMC optionally transfers power from the DC side to the AC side or vice versa, which contributes to a particularly flexible operation and management of the electrolysis system.

[0023] In a preferred embodiment, the electrolysis devices are connected in parallel with one another relative to a central power supply line, so that the electrolysis devices are connected to the central power supply line via corresponding connecting lines.

[0024] The advantages of the DC bus principle with a central DC current supply line come into play, which allows and provides corresponding independent connection lines for the electrolysis equipment. In the electrolysis system described, the central DC supply network can be flexibly dismantled and expanded with further electrolysis equipment if necessary, and the feed-in power of the power supply source into the DC network can be adapted to the required absorption power of the electrolysis equipment or electrolyzer, if necessary.

[0025] In the case of power being drawn via a network connection point on the public grid, this can be flexibly performed and set by means of a central modular multilevel converter.

[0026] In this case, a corresponding IGBT-based buck converter is preferably connected in the connecting line, the input voltage of which corresponds to the first DC voltage and the second DC voltage of which can be adapted to the corresponding operating voltage of the electrolysis system.

[0027] Therefore, the required operating voltage at the output of the IGBT-based buck converter in the corresponding connecting line can be individually adapted and set to the level of the individual electrolysis devices. In this connecting line, precise regulation and control of the second DC voltage and thus of the operation of the electrolysis device is achieved.

[0028] In this case, it is also particularly advantageous to use a plurality of modular high-current DC / DC converters connected in parallel in a connecting line, if necessary, so that industrial applications can be realized in conjunction with an electrolysis system having a plurality of electrolysis devices.

[0029] A step-down converter (also known as a step-down converter) converts a first DC voltage on a central DC power supply line into a second DC voltage of a lower output voltage as an output voltage.

[0030] The connecting lines advantageously form DC cables or DC branches of a central power supply line for one or more electrolysis devices or electrolyzers in the relevant connecting line that can be operated with direct current. Thus, any number of electrolysis devices of any size can be advantageously connected to one or more such central DC branch cables by means of adjustable IGBT-based DC / DC converters, in particular so-called step-down converters or buck converters, which accordingly expand the electrolysis system.

[0031] In a particularly preferred embodiment, the buck converter is modular in the connection, wherein the buck converter has at least two DC / DC buck converters connected in parallel, whose input voltage corresponds to the first DC voltage.

[0032] In this case, at least two DC / DC buck converters of a preferably modular buck converter connected in parallel are electrically connected to one another at the output and are each designed to regulate a second DC voltage.

[0033] Thus, the electrolysis power can be accurately adjusted to the corresponding operating voltage of the electrolysis equipment being powered in the connection line according to the operating conditions. The IGBT-based and modular power supply topology allows power regulation and tolerance of operational faults or failures, so that the individual modules of the electrolysis equipment can continue to operate in the event of a fault. This improves safety, reliability and cost-effectiveness. In addition, another advantage is that the DC / DC converters connected in parallel can be operated in an "interleaved" operating mode, thereby improving the quality of the DC current on the one hand, which improves the efficiency of the electrolytic cell and simplifies the design of passive components (such as inductors).

[0034] The use of IGBT-based DC / DC converters in the connecting lines thus allows individual power regulation of the individual electrolysis cables in the connecting lines without significant effects on the network reaction. Cost reduction can also be achieved by modular construction of the DC / DC converters. In addition, the modular concept allows the electrolysis plant to continue to operate with reduced efficiency if necessary in the event of a single semiconductor failure. In the currently preferred solution with thyristors, a semiconductor failure leads to a complete failure of the rectifier cable or the associated module series of the electrolysis plant, which can only be eliminated by complex repairs, so that downtimes must be taken into account.

[0035] In order to improve the energy efficiency in the electrolysis system, it can be provided that the electrolysis system includes a plurality of bridge switches, wherein in the connecting line, the IGBT-based buck converter can be bridged by switches respectively as needed. In the case of the bridged buck converter, the first DC voltage completely drops across the electrolysis equipment connected to the bridged buck converter. In the case of the bridged buck converter, the second DC voltage is thus consistent with the first DC voltage. The operation of the buck converter that makes the second DC voltage, i.e. the output voltage of the buck converter, as much as possible the same as the first DC voltage, i.e. the input voltage of the buck converter can be replaced by the bridged buck converter, so that the loss that may be generated in such operation of the buck converter can be avoided. Therefore, in order to operate particularly energy-saving, for example, it is advantageous to only power those electrolysis equipments with the lowest resistance via the buck converter, while other electrolysis equipments are directly powered via the first DC voltage. The control of the switch can be performed, for example, by a computing device of a circuit component, wherein the computing device is particularly also used to control and / or regulate the buck converter.

[0036] The proposed power supply topology in the electrolysis system offers a net gain in flexibility in many respects compared to known solutions. The use of IGBT-based modular multilevel converters (MMC) at the central network connection point enables the provision of additional network services for the public grid. In addition, renewable energy plants such as wind power plants or photovoltaic plants can feed their generated electrical energy directly into the central supply line designed as a DC bus, and the electrolysis plants in the individual connection lines can be regulated independently of each other.

[0037] The modular buck converter is therefore preferably connected to an electrolysis system having a plurality of electrolysis modules which are electrically connected in series.

[0038] As a result, an adjustable supply of direct current is achieved in the connecting line for the electrolysis device with the electrolysis modules. Therefore, the total electrolysis power in the connecting line can be accurately and adaptively adjusted according to the needs by the regulated direct current power. In particular, for example, in the case of a reduction in the power supply on the central direct current supply line or in the case of a temporary reduction in the hydrogen production, a partial load operation can be implemented in the electrolysis device. It is also possible and particularly advantageous that the electrolysis modules of the electrolysis device can be bridged individually by means of a bridge circuit with switchable bridge lines and with controllable electrical switches, and the electrolysis modules of the electrolysis device can be taken out of operation as required, for example for maintenance purposes or partial load operation of the electrolysis device.

[0039] Therefore, in a preferred embodiment, the buck converter can be an adjustable buck converter, so that the electrolysis current supply of the electrolysis device can be adaptively adjusted to a possibly fluctuating feed-in power of the current supply source in the central power supply line.

[0040] The adjustability of the buck converter allows the electrolysis device to be supplied with a direct current electrolysis current in a flexible and adaptive manner in the connection line to the electrolysis power. Whether the buck converter is operated continuously or intermittently depends on the inductance, the switching frequency, the input voltage, the output voltage and the flowing output current. Since these parameters can sometimes change rapidly, the transition between the two operating modes is usually taken into account (for example, prevented) when designing circuits, especially regulators. The two operating modes differ in the control characteristic curve, that is, the dependence of the output voltage on the duty cycle, and in terms of interference emissions.

[0041] Preferably, the step-down converter is an adjustable step-down converter, which adjusts the output voltage during uninterrupted operation by means of pulse width modulation. In this way, continuous operation of the step-down converter is achieved and the electrolysis current of the electrolysis device, which is fed into the corresponding connecting line, can be adjusted.

[0042] In a further preferred embodiment of the electrolysis system, the power supply source has a wind power installation as a power generator, to which a rectifier having a DC voltage output is connected, wherein the DC voltage output is designed for a first DC voltage.

[0043] In this way, a connection, more precisely a direct current connection, is achieved in the electrolysis system via a central direct current supply line, and the electrolysis system is powered by a wind energy device or a wind farm, wherein independent network operation is advantageously possible. If the electrolysis system is operated in an independent network, it is not connected to the public grid or the connection is not activated, so the network connection at the network connection point can be cut off as required, that is, the central modular multilevel converter can be shut down or even omitted. However, bidirectional operation is possible at any time, so that it can also be fed into the public grid. It is also possible that the renewable energy device already provides direct current at an appropriate voltage level (Spannungsniveau), so that in this case no additional rectifier is required to feed in renewable electricity.

[0044] In a further preferred embodiment, the power supply source has a photovoltaic system as a power generator, whose DC voltage output is designed for a first DC voltage, wherein the DC voltage output is connected to a central power supply line.

[0045] The DC voltage level at the DC voltage output can thus be flexibly adapted to a predetermined first DC voltage on the central DC power supply line. If necessary, a step-up converter (so-called boost converter) is connected downstream of the photovoltaic generator to set a predetermined DC voltage level at the DC voltage output. This is necessary if the DC output of the photovoltaic system itself cannot provide a sufficiently high DC voltage level to feed into the central power supply line.

[0046] With this design, an electrolysis device is advantageously connected or coupled to a central power supply line via a central DC network in an electrolysis system and supplied with power obtained by a photovoltaic device. Photovoltaic-based independent network operation can also be performed as required. In a manner similar to the scheme for connecting an electrolysis device to a wind power plant described above and with corresponding advantages, operation independent of the public power grid is performed in an independent network, which enables particularly high design flexibility as required or as a supplement to a network connection and self-sufficient use without a public power grid, and is also feasible for bidirectional operation in an electrolysis system via a modular multilevel converter. When photovoltaic power is fed into a central power supply line, a step-up converter (DC / DC converter) is usually provided in the photovoltaic aspect to increase the voltage of the photovoltaic generator as required so that a DC current can be accurately fed into the central power supply line at a predetermined first DC voltage.

[0047] Preferably, in the electrolysis system, the central power supply line is designed to operate at a first DC voltage in the medium voltage range of 20 kV, in particular between 1.5 kV and 30 kV. Therefore, the design should be adaptively adjusted to the operating voltage of the electrolysis equipment in the electrolysis system. It can be flexibly designed for higher operating voltages of 10 kV to 30 kV as required.

[0048] However, the DC voltage level at the DC voltage output of the voltage source converter (VSC), in particular the modular multilevel converter, can be flexibly adapted to the corresponding requirements of the electrolysis system and the transmission path, wherein a high output voltage is preferably selected as the predetermined first DC voltage, which is preferably at least greater than 1.5 kV. Here, when planning and designing the DC voltage level on the central power supply line, for example, reference can also be made to the nominal voltage of the network level commonly used in the field of energy transmission, or this value can be used as a reference point for the DC voltage level of the first DC voltage. Here, on high-voltage lines at different network levels of medium voltage and high voltage, electrical energy is transmitted with the following common nominal voltages: medium voltage: 3 kV, 6 kV, 10 kV, 15 kV, 20 kV, 30 kV, high voltage: 60 kV, 110 kV. The central power supply line here very advantageously serves as a central DC bus line, through which a DC current supply based on high voltage can be directly realized for the electrolysis system in the electrolysis system.

[0049] Further advantages, features and details of the invention are apparent from the following description of preferred exemplary embodiments and from the drawings. The features and feature combinations mentioned in the above description and the features and feature combinations mentioned below in the description of the drawings and / or shown only in the individual drawings can be used not only in the respectively given combination but also in other combinations or alone without departing from the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] An embodiment of the present invention is explained in more detail with reference to the accompanying drawings. Here, it is shown schematically and greatly simplified:

[0051] Figure 1 An electrolysis system having an electrolysis device and a wind energy device is shown;

[0052] Figure 2 An electrolysis system having an electrolysis device and a photovoltaic device is shown;

[0053] Figure 3 A DC bus supply topology is shown with a central supply line for DC current and an electrolysis device connected thereto;

[0054] Figure 4 Shows the corresponding Figure 1 A power supply topology having a modularly constructed buck converter including a plurality of DC / DC converters;

[0055] Figure 5 A schematic block diagram shows a power supply topology of an electrolysis system with a central modular multilevel converter (MMC) at the network connection point;

[0056] Figure 6 Shown with Figure 5 A corresponding power supply topology for an electrolysis system with a bridging device.

[0057] The same reference numerals in the figures have the same meaning. DETAILED DESCRIPTION

[0058] Figure 1 The electrolysis system 100 according to the invention is shown. The electrolysis system 100 comprises an electrolysis cell 1 having two electrolysis devices 1A, 1B and a current supply source 3 connected to the electrolysis cell 1. The current supply source 3 has a wind energy device 19 as a current generator, which serves as a source of renewable energy devices (EE devices) and green current. The electrolysis system 100 is supplied with electrolysis current by a central power supply line 5 to which a DC voltage is applied, so that a central DC bus line is formed by the central power supply line 5, by means of which the electrolysis cell 1 can be directly supplied with DC current for the electrolysis process.

[0059] Here, each electrolysis device 1A, 1B of the electrolysis system 100 is connected to the power supply connection 23A, 23B on the central power supply line 5 via a corresponding connecting line 9A, 9B, so that the parallel connection of the electrolysis devices 1A, 1B is realized. Here, the electrolysis device 1A has at least one electrolyzer 15A, and the electrolysis device 1B has at least one electrolyzer 15B. The electrolyzers 15A, 15B can be selectively designed as PEM electrolyzers, AEM electrolyzers (AEM: anion exchange membrane) or alkaline electrolyzers, but can also be a combination. Here, a plurality of electrolyzers 15A, 15B can be connected continuously in the cables of the corresponding electrolysis devices 1A, 1B, which are powered via corresponding connecting lines 9A, 9B.

[0060] With regard to the power supply source 3, a rectifier 13A with a DC voltage output 7 is connected downstream of the wind power installation 19 at the output of the generator of the wind power installation 19. The alternating current generated by the generator of the wind power installation 19 can thus be converted into a DC current and fed into the central power supply line 5 at the DC voltage output 7 with a predetermined first DC voltage 31. This enables a central DC network designed for a predetermined first DC voltage 31, for example for a DC medium voltage. When connecting the wind power installation 19 to the central power supply line 5 in order to couple in the electrical power generated by the wind power installation 19 and fed into the central power supply line 5, no further active components, such as a transformer, are required, so that a particularly simple power supply topology can be achieved.

[0061] The DC voltage level at the DC voltage output 7 of the rectifier 13A can be flexibly adapted to the corresponding requirements in the electrolysis system 100, wherein preferably a high output voltage of the medium voltage level is selected as the predetermined first DC voltage 31, which is at least greater than 1.5 kV. Typically, a medium voltage level of 20 kV is set for the first DC voltage 31. For the first DC voltage 31 on the central power supply line 5, when planning and designing the central DC network through the central power supply line 5, for example, the nominal voltage of the network level commonly used in the field of energy transmission can also be referred to, or the value can be used as a reference point for the DC voltage level. Here, on the high-voltage line at different network levels of medium voltage and high voltage, electrical energy is transmitted with the following common nominal voltages: medium voltage: 3 kV, 6 kV, 10 kV, 15 kV, 20 kV, 30 kV, high voltage: 60 kV, 110 kV. The central power supply line 5 here very advantageously serves as a central DC bus line, through which the electrolysis equipment 1A and 1B connected in the electrolysis system 100 can be directly supplied with DC current based on high voltage.

[0062] In order to coordinate the connection and direct current supply of the electrolysis apparatus 1A, 1B with the respective second direct voltage 33A, 33B as operating voltage, a step-down converter 11A is connected in the connecting line 9A and a step-down converter 11B is connected in the connecting line 9B accordingly. The step-down converters 11A, 11B, also called step-down converters, are based on IGBT technology, i.e. transistor technology, which, in contrast to the thyristor technology commonly used hitherto, enables individual power regulation of the individual electrolysis cables in the connecting lines 9A, 9B. In this case, the input of the step-down converter 11A is connected to the power supply connection 23A, and similarly the input of the step-down converter 11B is connected to the central power supply line 5 via the power supply connection 23B. The step-down converters 11A, 11B are connected at the output to the electrolyzers 15A, 15B in the connecting lines 9A, 9B, respectively, so that the electrolysis in the electrolyzers 15A, 15B is provided with a respective direct current at a voltage level that can be set in each case for the second direct voltage 33A, 33B of the operating voltage. During operation of the electrolysis system 100, a medium voltage direct current network is provided on the central power supply line 5 as a central direct current network at a first direct voltage 31 and is used to supply the electrolysis devices 1A, 1B connected in parallel on the central power supply line 5. By using high voltage, direct current can be provided and direct current power can be fed into the central power supply line 5. In this case, the electrolysis system 100 can be designed or expanded particularly flexibly, for example by connecting further electrolysis devices 1A, 1B including further electrolyzers 15A, 15B via connecting lines 9A, 9B. If no power is drawn from the public power grid 25, the electrolysis system 100 can optionally be operated off-grid, independent of the grid. However, it is preferred to draw power at the central grid connection point 35 and to connect to the public power grid 25.

[0063] The step-down converters 11A, 11B connected to the connecting lines 9A, 9B are implemented as DC / DC converters (step-down converters) and are each designed such that their input voltage corresponds to a predetermined first DC voltage 31 in the central DC network on the central power supply line 5 and their respective output voltage is adjusted or set to a second DC voltage 33A, 33B as the respective operating voltage of the connected electrolysis device 1A, 1B. The step-down converters 11A, 11B are adjustable step-down converters, so that the electrolysis current supply to the electrolysis device 1A, 1B can be adapted and adjusted accordingly according to the fluctuating feed-in power of the current supply source 3 to the central power supply line 5. The step-down converters 11A, 11B can be adjustable step-down converters, for example, in which the output voltage is adjusted by means of pulse width modulation in uninterrupted operation, which enables continuous operation with a certain performance. The step-down converters 11A, 11B are based on IGBTs, so that individual power regulation is achieved in the electrolysis device 1A, 1B. Since the step-down converters 11A, 11B are based on IGBTs, the influence of network reaction from the public grid 25 is limited and maximum decoupling is achieved, thereby enabling stable operation.

[0064] exist Figure 1 In the electrolysis system 100 shown, the electrolysis devices 1A, 1B can also be arranged, for example, at the bottom of the tower of the corresponding wind power device 19 and directly connected there to the central power supply line 5. This is advantageous, for example, for onshore applications of the wind power device 19 and for installation in remote areas and for independent network operation. The wind power device 19 in this application also refers to an onshore or offshore wind farm with a plurality of wind power devices 19.

[0065] according to Figure 1 In the embodiment of the present invention, in the electrolysis system 100, a connection to the public grid 25 is additionally established in terms of the current supply source 3. For this purpose, a separate power supply connection 23C is provided in the central power supply line 5, such as Figure 1 . The connection to the public grid 25 is accomplished via the connection transformer 27 at the network connection point 35 and the central modular multilevel converter 13 with a DC voltage output 7 connected downstream. The central modular multilevel converter 13 is based on IGBT technology and has a corresponding number of IGBTs as power devices. The modular multilevel converter (13) is a feasible and preferred specific design of a voltage source converter (VSC). Therefore, in principle, other VSC-based converters can also be used at the network connection point 35 to feed power from the public grid 25 into the central power supply line 5.

[0066] The modular multilevel converter 13 is designed and can be flexibly adjusted in the following manner so that a first DC voltage 31 is provided at its DC voltage output 7 and fed into the central power supply line 5. The corresponding voltage level of the first DC voltage is optionally given by a medium voltage level of 3kV, 6kV, 10kV, 15kV, 20kV, 30kV or a high voltage level of 60kV or 110kV, for example. The voltage level can be flexibly adjusted and changed here. In addition, when the power supply connection 23C is used as the network connection, bidirectional operation can be achieved by the modular multilevel converter 13, so that if necessary, a DC current can be fed into the central power supply line 5 from the public power grid 25 and a DC current can be fed out from the DC network of the central power supply line 5 at the first DC voltage 31.

[0067] Thus, if necessary, current from the public grid 25 can also be fed into the central power supply line 5 at the power supply connection 23C after voltage adjustment and used for electrolysis purposes in the electrolysis system 1. This has the advantage that, for example, when the wind energy device 19 needs maintenance and does not generate current or only generates limited current during dark and windy periods, a replacement requirement is met by providing a connection to the public grid 25, thereby temporarily providing a backup solution to ensure as continuous power supply as possible and smooth operation of the hydrogen-producing electrolysis device 1A, 1B. If necessary, one or more electrolysis systems 15A, 15B can also be operated at partial load or removed from the DC network when the DC power supply on the central power supply line 5 is insufficient. If necessary, appropriate partial load operation is achieved in the corresponding connecting lines 9A, 9B by means of adjustable buck converters 11A, 11B, by means of which the DC power can be set accordingly via the corresponding second DC voltage 33A, 33B at the output of the buck converter 11A, 11B. In the case of completely independent grid operation of the combined installation, the replacement requirements cannot usually be met due to the lack of an available connection to the public grid 29. However, in this case, the replacement requirements of the wind power installation 19 or the photovoltaic installation 21 (see Figure 2 ) feed, by specially setting up and providing "redundancy" or providing system reserves in an independent network, for example, by modularly constructing these renewable energy feed-in systems and installing some reserve modules in the electrolysis equipment 15A, 15B, it is possible to achieve a maintenance-independent power supply and uninterrupted operation in a substantially self-sufficient manner. In this case, it is also possible to merge and provide common reserve modules to multiple central power supply lines 5, and these reserve modules are either switchable or supply power to multiple power supply lines through coupling of the central power supply line 5.

[0068] Due to the use of modular multilevel converters 13, IGBT-based rectifiers at the network connection point 35, harmonics are only slightly emitted. No additional filtering is required at all, or at most only to a much lesser extent than in comparable thyristor-based systems. The reactive power requirements of this connection and supply topology can be set flexibly. Therefore, only little or even no reactive power compensation is required.

[0069] Since the reactive power requirements of the IGBT-based modular multilevel converters 13 as central rectifier systems can be set individually, they can not only regulate power but also provide assistance for voltage support of the public grid 25. In independent networks, such as local renewable energy networks, these IGBT-based modular multilevel converters 13 can also have a network-forming role.

[0070] In this scheme, the renewable energy device that provides DC voltage itself can be directly fed into the DC bus. The converter required when using a thyristor-based rectifier is omitted. Additional conversion losses are thus eliminated. If the power fed into the central power supply line 5 acting as a DC bus is higher than the power consumed by the electrolysis in the electrolysis unit 1, the IGBT-based converter 13 at the network connection point 35 can also feed the excess current into the public power grid 25. By connecting or electrically interconnecting the various electrolysis devices 1A and 1B via the central power supply line 5, a decoupling of the system is generated. The electrolysis cables of the electrolysis devices 1A and 1B or the various electrolyzers 15A and 15B can be operated at the corresponding respective working points. The adjustability of the entire electrolysis system 100 is also improved.

[0071] In another embodiment of the electrolysis system 100 according to the present invention, Figure 2 , an alternative current supply source 3 for supplying a direct current to the electrolysis cell 1 is shown. The current supply source 3 has a photovoltaic system 21 with a plurality of photovoltaic modules, not shown in detail. The photovoltaic system 21 can be, for example, a large-scale, high-performance open-air system, preferably in a sunny area, so that photovoltaic power of 10 MW or more of electrical power can be used for electrolysis. With respect to the electrolysis cell 1, a photovoltaic system with a DC current of 10 MW or more is used. Figure 1 The device concept shown is a substantially similar device concept, and the electrical connection and power supply of the corresponding device components, namely the electrolysis devices 1A, 1B, are completed via a central power supply line 5, which is also designed as a central DC bus line or DC connecting cable. To achieve this, the electrolysis device 1A is connected to the corresponding power supply connection 23A and the electrolysis device 1B is connected to the power supply connection 23B via the corresponding connecting lines 9A, 9B in which the corresponding IGBT-based buck converters 11A, 11B are connected.

[0072] In the electrolysis system 100 thus configured, the current supply source 3 has a photovoltaic device 21 as a current generator, a so-called photovoltaic generator, which already provides a DC voltage designed for a predetermined first DC voltage 31 at the generator output, wherein the DC voltage output 7 is formed by the photovoltaic generator output and is directly connected to the central power supply line 5.

[0073] However, in order to set the photovoltaic system 21 as power supply source 3 to a desired and advantageous DC voltage level of the first DC voltage 31 for feeding DC power into the central power supply line 5, it is also possible to Figure 2 In the embodiment shown in FIG. 1 , a boost converter 17 is connected to the DC output of the photovoltaic generator of the photovoltaic system 21 .

[0074] In power electronics, a boost converter 17, also called a step-up converter or a step-up regulator (English: Boost-Converter or Step-Up-Converter), is a special form of a DC voltage converter. The amplitude of the output voltage is always greater than the amplitude of the input voltage, so the boost converter 17 is used to provide a first DC voltage 31 predetermined for feeding at the desired DC voltage level at the DC voltage output 7. The higher voltage reduces the material requirement and thus reduces the cost of the line after the feeding through the current supply source 3.

[0075] The step-up converter 17 is designed for the voltage level and provides a first DC voltage 31 at the output. In this case, the step-up converter 17 is adjustable so that the output voltage provided can be flexibly and adaptively adjusted. The power of the photovoltaic device 21 is directly coupled into and fed into the central power supply line 5 at the DC voltage output 7 of the step-up converter 17. In order to transmit electrical power and absorb electrical power by the electrolysis unit 1, the electrolysis devices 1A, 1B are connected to the central power supply line 5 via corresponding connecting lines 9A, 9B, as described in more detail above. In addition, the decoupling of the regulation of the electrolysis current demand in the connecting lines 9A, 9B is achieved by the corresponding step-down converters 11A, 11B, and thus a separate operating mode of these DC connecting cables is achieved, which is particularly significant when partial load is required. In the case of photovoltaic applications, network current can also be fed into the central power supply line 5 from the public grid 23 and in accordance with Figure 1 Like the described embodiment, a central modular multilevel converter 13 is provided at the network connection point.

[0076] Figure 3The basic scheme for supplying and coupling a plurality of electrolysis devices 1, 1A, 1B by means of a central DC bus power supply line 5 is schematically and simplified. In this scheme, a three-phase alternating current connection is provided at a network connection point 35. At the network connection point 25, a central modular multilevel converter 13 based on IGBT is connected to the alternating current input, and a central power supply line 5 as a DC bus is connected to and leads out of the DC current output 7 of the converter. The modular multilevel converter 13 provides a first DC voltage 31, for example a medium voltage of 20 kV as an output voltage. The electrolysis unit 1 has a plurality of electrolysis devices 1A, 1B, 1C, which in turn have a plurality of electrolysis modules 29A, 29B, 29C, 29D, 29E electrically connected one after another. Each electrolysis device 1A, 1B, 1C is connected to the central power supply line 5 via corresponding connecting lines 9A, 9B, 9C. Here, in order to provide the corresponding second DC voltages 33A, 33B, 33C, step-down converters 11A, 11B, 11C based on IGBT technology are respectively connected in the connecting lines 9A, 9B, 9C. Therefore, the level of the second DC voltages 33A, 33B, 33C can be controlled or adjusted respectively. Bidirectional operation is achieved by the IGBT-based modular multilevel converter 13, so that the excess power on the central power supply line 5 can be fed into the public power grid 25 via the network connection point 35.

[0077] Figure 3 The possibility of feeding direct current from renewable energy systems (EE systems) into the central power supply line 5 is not shown in detail. Figure 1 and Figure 2 Embodiment of the invention.

[0078] By means of a scheme for powering and coupling a plurality of electrolysis devices 1A, 1B, 1C, a regulated direct current supply to the powered electrolysis devices 1A, 1B, 1C having electrolysis modules 29A-29E is achieved in the corresponding connecting lines 9A, 9B, 9C, wherein two direct voltage levels are taken into account. As a result, the total electrolysis power in the connecting lines 9A, 9B, 9C can be adaptively adjusted by means of the regulated direct current power, respectively, according to the requirements, by means of correspondingly adjusting the second direct voltages 33A, 33B, 33C. In particular, for example, if the power supply on the central direct current power supply line 5 decreases or if it is necessary to temporarily reduce the hydrogen production, partial load operation can be implemented in the electrolysis devices 1A, 1B, 1C respectively. It is also possible and particularly advantageous here to utilize a switchable bridge circuit and a controllable electrical switch in the Figure 3A bridge circuit, not shown in detail, makes it possible to bridge the electrolysis modules 29A-29E of the electrolysis devices 1A, 1B, 1C individually and modularly and thereby to take one or more electrolysis modules 29A-29E of the electrolysis devices 1A, 1B, 1C out of operation as required or optionally, for example for maintenance purposes or to perform a partial load operation required by the respective electrolysis device 1A, 1B, 1C or selected electrolysis modules 29A-29E, for example depending on the degree of aging or an upcoming maintenance interval.

[0079] Reference Figure 4 The modular DC / DC conversion scheme in the buck converter 11 is explained as an example. Figure 3 The invention is part of a power supply topology with a modular buck converter 11, which is formed by a plurality of parallel-connected DC / DC converters 11A, 11B, 11C and supplies power to the electrolysis device 11A. Two DC voltage lines with corresponding positive and negative polarity are provided for the central power supply line 5, to which the DC / DC converters 11A, 11B, 11C are connected with their DC voltage inputs with the correct polarity as modules of the buck converter 11, respectively. By means of this parallel connection, a connecting line 9A is formed for supplying power to the electrolysis device 1A. The electrolysis device 1A comprises an electrolyser 15A, which comprises a plurality of electrolysis modules 29A-29E.

[0080] By using IGBT-based DC / DC converters 11A, 11B, 11C, it is possible to individually regulate the power of the electrolysis device 1A connected via the connecting line 9A without significantly affecting the network reaction. By modularly constructing the buck converter 11 including a plurality of DC / DC converters 11A, 11B, 11C, greater device flexibility and redundancy for reliable operation can be achieved while appropriately reducing costs. Therefore, the modular construction of the buck converter 11 enables the electrolysis device 1A to continue to operate at least with reduced power in the event of individual semiconductor failures in the device, which is advantageous compared to known solutions, in which semiconductor failures can lead to failures of the rectifier cable or the associated electrolyzer 15A, which can only be eliminated by repairs under the condition of equipment shutdown.

[0081] The DC / DC converters 11A, 11B, 11C include a transistor 37 designed as an IGBT, a memory choke 39, and a diode 41, respectively. Figure 4. The transistor 37 and the storage choke 39 are arranged in series with the electrolyzer 15A which is to be supplied with power via the buck converter 11. The diode 41 is connected in parallel with the corresponding electrolyzer 15A. The level of the second DC voltage 33 dropped across the electrolyzer 11A, which is provided by the buck converter 11, can be adjusted via the transistor 37. For this purpose, the transistor 37 can be connected to the Figure 4 The computing device 43 not shown in detail is connected to the Figure 5 and the related description, wherein the control and / or regulation of the buck converter 11 is performed accordingly via the computing device 43. The individual electrolysis modules 29A-29E of the electrolysis device 1A or the electrolyzer 15A can be controlled by Figure 4 The bridge circuit can be equipped with a switchable bridge circuit and a controllable electrical switch so that it can be bridged individually and modularly. Thus, if necessary or optionally, one or more electrolysis modules 29A-29E of the electrolysis device 1A can be taken out of operation. This is very advantageous, for example, for maintenance purposes or to perform a partial load operation required by the corresponding electrolysis device 1A or selected electrolysis modules 29A-29E, for example depending on the degree of aging or an upcoming maintenance interval.

[0082] according to Figures 1 to 3 The exemplary embodiment shown, in combination with an IGBT-based modular multilevel converter 13 at the network connection point 35, can provide additional network services for the public grid 25. Renewable energy devices (EE devices) can hereby be fed additionally or as required directly into the central supply line 5 as a DC bus (this is in the case of Figure 3 and Figure 4 1A, 1B, 1C can be regulated independently of one another. In this case, the alternating current from the public grid 25 is rectified only once, specifically centrally at the network connection point 35. For this purpose, when the device is connected to the medium voltage network, a central component of an IGBT-based modular multilevel converter 13 is used to supply a first DC voltage to the central power supply line 5.

[0083] Figure 5A schematic and greatly simplified illustration of a portion of an electrolysis system 100 is shown. The figure only illustrates particularly advantageous circuit connection schemes and bridging schemes in the electrolysis system 100. A circuit for supplying a plurality of electrolyzers 15A, 15B electrically connected in parallel with each other with direct current is provided, wherein the electrolyzers 15A, 15B are connected in parallel to the output of a central modular multilevel converter 13 serving as a rectifier via buck converters 11A, 11B based on IGBTs, respectively. The modular multilevel converter 13 converts the alternating voltage applied on the input side from the public power grid 25 into a first direct voltage 31 and is based on IGBTs. This first direct voltage 31 drops across parallel connection branches 45A, 45B determined by connection lines 9A, 9B, which respectively include one of the electrolyzers 15A, 15B and one of the buck converters 11A, 11B. The first direct voltage 31 is converted by the buck converter 11A into a second direct voltage 33A dropped across the electrolyzer 15A. Correspondingly, the first DC voltage 31 is also converted by the second step-down converter 11B into a second DC voltage 33B dropped across the electrolyzer 11B. In addition to the two shown electrolyzers 11A, 11B, the power supply topology shown in the electrolysis system 100 can of course also be used to supply a DC voltage to further electrolyzers, which are correspondingly also connected in parallel to the output of the central modular multilevel converter 13 as further branches via step-down converters. Figure 3 corresponding.

[0084] In order to enable the electrolyzers 15A, 15B to operate at a desired operating point, for example, within a safe operating range, the buck converters 11A, 11B can be controlled and / or regulated to adaptively adjust the level of the second DC voltage 33A or 33B. In addition, the modular multilevel converter 13 can also be controlled and / or regulated to adaptively adjust the level of the first DC voltage 31. It is thus possible to feed DC power into the central power supply line 5 at a predetermined first DC voltage 31. In particular, it can be provided that the modular multilevel converter 13 and the buck converters 11A, 11B and, if necessary, the additional buck converters of the additional connecting branches can be controlled and / or regulated. In order to control or regulate the rectifier 13 and / or the buck converters 11A, 11B, the power supply topology of the electrolysis system 100 can, for example, include a computing device 43, by which the modular multilevel converter 13 and / or the buck converters 11A, 11B can be controlled or regulated. For this purpose, the computing device 43 can be connected to one or more measuring devices (not shown here), by which, for example, the amount of substance produced by one of the electrolyzers 15A, 15B, the corresponding resistance of one or more of the electrolyzers 15A, 15B and / or the corresponding current flow through one or more of the electrolyzers 15A, 15B can be determined. Here, for example, the modular multilevel converter 13 can be controlled and / or regulated to adaptively adjust the level of the first DC voltage 31 or the buck converters 11A, 11B can be controlled or regulated to adaptively adjust the level of the second DC voltage 33A, 33B according to the determined amount of substance and / or according to the corresponding resistance of the electrolyzers 11A, 11B or, if necessary, other influencing variables and / or the corresponding current flow through the electrolyzers 11A, 11B. External factors include, for example, the current electricity price and whether the current can be generated by renewable energy. This applies accordingly to other electrolyzers and other buck converters that are present in addition to the connecting branches 45A, 45B. The buck converters 11A, 11B and any further buck converters present are components of a power supply topology of the electrolysis system 100 , to which the electrolyzers 11A, 11B and any further electrolyzers present can be connected.

[0085] Figure 6 shows a bridge device according to Figure 5 The power supply topology of the electrolysis system 100 is as follows. Figure 6The illustrated embodiment additionally provides that controllable bridging switches 47A, 47B with corresponding activatable switching elements are provided, which can also be controlled via the computing device 43, so that the buck converters 11A, 11B can be bridged when the switches are closed accordingly. In the case of bridging the buck converters 11A, 11B via the bridging switches 47A, 47B, i.e. in the case of corresponding activation of the switching elements for the corresponding bridging paths for bridging, the first DC voltage 31 generated by the modular multilevel converter 13 is dropped directly across the electrolyzer 11A or 11B, to be precise, the corresponding buck converter 11A, 11B is bridged. In the case of bridging, the corresponding electrolyzer 15A, 11A is thus supplied with the first DC voltage 31 as required and optionally directly from the intermediate circuit via the corresponding connecting lines 9A, 9B. Thus, in the case of Figure 6 In the example of bridging switch 47A, the corresponding switch for bridging the path is closed and the buck converter 11A is bridged. The bridge switch 47B is not activated. In this case, the switching element of the bridge switch 47B is switched to a switching state in which the buck converter 11B is energized. Thus, a bridging device with a plurality of controllable bridge switches 47A, 47B is provided in the electrolysis system 100 and enables a particularly advantageous and energy-saving full-load control of the electrolysis devices 1A, 1B connected to the central DC power supply line.

[0086] In the electrolysis system 100, the electrolysis unit 1 includes, in addition to the described power supply topology, all electrolyzers connected thereto. These electrolyzers can, for example, each include at least one proton exchange membrane, wherein the proton exchange membrane is particularly used to produce hydrogen by electrolysis of deionized water and / or distilled water. However, electrolyzers based on alkaline electrolysis or on anion exchange membrane electrolysis can also be used.

[0087] The use of modular multilevel converters 13 (MMC converters) enables centralized supply of direct current and transmission of direct current in the electrolysis system 100, in particular bidirectionally. Network services beyond the actual transmission task can be provided by means of modular multilevel converters 13. It is particularly advantageous to use it in combination with electrolysis equipment in an electrolysis system 100 having a central power supply line 5 according to the invention designed as a DC bus. The use of modular high-current DC / DC converters for parallel connection of the second DC voltage 22 in the electrolysis system 100 in combination with the electrolysis equipment 11A, 11B is very advantageous for industrial applications. As a result, the electrolysis equipment 11A, 11B can be coupled via the DC bus in a large hydrogen production plant.

[0088] Although the present invention has been shown and described in detail by means of preferred embodiments, the present invention is not limited to the disclosed examples and further variations may be devised therefrom by those skilled in the art without departing from the scope of protection of the present invention.

Claims

1. An electrolysis system (100), comprising at least two electrolysis devices (1A, 1B), a current supply source (3) having a DC voltage output (7) and a central power supply line (5), wherein: The central power supply line (5) is connected to a DC voltage output (7) of the current supply source (3) so that a DC current can be fed into the central power supply line (5) at a first DC voltage (31), and the electrolysis devices (1A, 1B) are electrically connected in parallel to the central power supply line (5), wherein a voltage source converter (13) is connected at a network connection point (35) for supplying DC current from a public power grid (25), the voltage source converter converting an AC voltage at the input end into a first DC voltage (31) at the output end at the DC voltage output (7), wherein each electrolysis device (1A, 1B) is connected via a first DC voltage (31) converted into a second DC voltage (33A) , 33B) are connected in parallel to the DC voltage output part (7) of the voltage source converter (13), so that the second DC voltage (33A, 33B) drops across the electrolysis equipment (1A, 1B), wherein each of the DC / DC converters (11A, 11B) can be controlled and / or adjusted to adaptively adjust the level of its second DC voltage (33A, 33B), wherein a controllable bridge switch is provided so that when the bridge switch is closed, the corresponding DC / DC converters (11A, 11B) can be bridged, so that the first DC voltage (31) can be directly applied to the connected electrolysis equipment (1A, 1B).

2. The electrolysis system (100) according to claim 1, wherein: The DC / DC converter (11A, 11B) is an IGBT-based step-down converter (11A, 11B) used for individual power regulation of the electrolysis device (11A, 11B).

3. The electrolysis system (100) according to claim 1 or 2, wherein: The voltage source converter (13) is designed for bidirectional operation and is connected to the central network connection point (35) so that the public grid (25) can be voltage-supported by providing reactive power.

4. The electrolysis system (100) according to claim 3, wherein: The voltage source converter (13) is an IGBT-based modular multilevel converter (13), so that electrical power from the central power supply line (5) can be fed into the public grid (25) at the network connection point (35) as required.

5. The electrolysis system (100) according to any one of the preceding claims, wherein: The electrolysis devices (1A, 1B) are connected in parallel with each other relative to the central power supply line (5), so that the electrolysis devices (1A, 1B) are connected to the central power supply line (5) via corresponding connecting lines (9A, 9B).

6. The electrolysis system (100) according to claim 5, wherein: A corresponding IGBT-based buck converter (11A, 11B) is connected to the connecting lines (9A, 9B), whose input voltage is consistent with the first DC voltage (31), and whose second DC voltage (33B, 33C) can be adaptively adjusted according to the corresponding operating voltage of the electrolysis equipment (1A, 1B).

7. The electrolysis system (100) according to claim 6, wherein: The buck converter (11A, 11B) is modular in the connecting line (9A, 9B), wherein the buck converter (11A, 11B) has at least two DC / DC buck converters (21A, 21B, 21C) connected in parallel, whose input voltage corresponds to the first DC voltage (31).

8. The electrolysis system (100) according to claim 7, wherein: The at least two parallel-connected DC / DC buck converters (21A, 21B) of the modular buck converter (11A, 11B) are electrically connected to each other at the output end and are respectively used to adjust the second DC voltage (33A, 33B).

9. The electrolysis system (100) according to claim 8, wherein: A modular step-down converter (11A, 11B) is connected to an electrolysis device (1A, 1B) having a plurality of electrolysis modules (29A, 29B, 29C, 29D, 29E) connected electrically in series.

10. The electrolysis system (100) according to any one of the preceding claims, wherein: The power supply source (3) has a wind power installation (19) as a current generator, to which a rectifier (13A) having a DC voltage output (7) is connected, wherein the DC voltage output (7) is designed for the first DC voltage (31).

11. The electrolysis system (100) according to any one of the preceding claims, wherein: The power supply source (3) has a photovoltaic system (21) as a current generator, whose DC voltage output (7) is designed for the first DC voltage (31), wherein the DC voltage output (7) is connected to the central power supply line (5).

12. The electrolysis system (100) according to any one of the preceding claims, wherein: The central power supply line (5) is designed for operation at a first DC voltage (31) of 20 kV, in particular in the medium voltage range between 1.5 kV and 30 kV.

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