System combination comprising at least two electrolysis systems and a power supply source

Abstract

The invention relates to a system combination (100), comprising: at least two electrolysis systems (1A, 1B); a power supply source (3) having a direct voltage output (7); and a central supply line (5); wherein the central supply line (5) is connected to the direct voltage output (7) of the power supply source (3), so that a direct current can be fed into the central supply line (5) and a central DC network designed for a high voltage is provided, to which DC network the electrolysis systems (1A, 1B) are connected by means of the central supply line (5). The power supply source (3) has, as a power generator, a wind turbine (19), to which a rectifier (13A) having a direct voltage output (7) is connected, the direct voltage output (7) being designed for the high voltage. At least one of the electrolysis systems (1A, 1B) is disposed at the base of the tower of the wind turbine (19) and is connected there directly to the central supply line (5). The invention also relates to a of a DC network in a system combination of this type, wherein a number of electrolysis systems (1A, 1B) is connected to a central supply line (5) for direct current, and wherein a direct current is fed, at a specified high voltage, into the central supply line (5) by means of a direct voltage output (7).

Description

[0001] Description

[0002] Plant network comprising at least two electrolysis plants and one power supply source

[0003] The invention relates to a system network comprising at least two electrolysis systems and a power supply. The invention further relates to a use.

[0004] An electrolysis plant is a device that uses electrical current to transform substances (electrolysis). Due to the variety of different electrochemical electrolysis processes, there are also a variety of electrolysis plants, such as an electrolysis plant for water electrolysis.

[0005] Hydrogen is currently produced from water using processes such as proton exchange membrane (PEM) electrolysis, anion exchange membrane (AEM), or alkaline electrolysis. These electrolysis systems use electrical energy to produce hydrogen and oxygen from the supplied water. This process takes place in an electrolysis stack composed of several electrolysis cells. Water is introduced as the reactant into the electrolysis stack, which is subjected to a direct current (DC) voltage. After passing through the electrolysis cells, two fluid streams emerge, consisting of water and gas bubbles (O2 and H2, respectively).

[0006] Current considerations are to use surplus energy from renewable energy sources during periods of abundant sun and wind, i.e., when solar or wind power generation is above average, to produce valuable materials. One valuable material in particular could be hydrogen, which is produced by water electrolysis plants. Hydrogen can, for example, be used to produce so-called renewable energy gas – also known as RE gas. RE gas is a combustible gas obtained from renewable sources using electrical energy. Hydrogen represents a particularly environmentally friendly and sustainable energy source. It has the unique potential to realize energy systems, transport, and large parts of the chemical industry without CO2 emissions. For this to succeed, however, the hydrogen must not come from fossil sources, but must be produced using renewable energy.At least a growing share of the electricity generated from renewable sources is now being fed into the public power grid. This means that, depending on the electricity mix, a corresponding share of green hydrogen can be produced when an electrolysis plant is powered by electricity from the public grid.

[0007] In industrial-scale electrolysis, the direct current is predominantly provided via line-commutated rectifiers. Due to the nature of the rectifiers, this rectification of a line-side alternating voltage can result in oscillations that can place a strain on the AC and / or DC grids.

[0008] Laid-open document EP 3 723 254 A1 discloses such an electrolysis plant which is connected to the public power grid and is accordingly supplied with mains current. For this purpose, the electrolysis plant has a circuit arrangement comprising four coil arrangements and four rectifiers. The first coils of the coil arrangements are each connected to the DC voltage side of one of the rectifiers. The circuit arrangement further comprises two transformers, each having a primary winding and two secondary windings. The primary windings of the transformers are connected to the power grid, e.g. a medium-voltage grid or a high-voltage grid. In this way, despite the reduced iron content within the first coil, a desired smoothing of the direct current, or damping of the harmonics, can be achieved. One source of renewable energy arises from the increasing use of wind power.Large electrical outputs can be achieved, particularly with offshore wind turbines. However, the challenge is that they have to be located far away from the consumers. The energy must therefore be transported to the consumers with as little loss as possible. Hydrogen is a highly suitable transport medium and energy carrier. It can be transported in gaseous form, for example, through pipelines. A positive side effect is that a hydrogen-carrying pipeline can also serve as an energy storage device, since the internal pressure can be varied within certain limits.

[0009] Based on these considerations, it is of particular economic interest to produce hydrogen directly at the energy generation site, i.e., autonomously and independently of the public grid. To this end, it is proposed to install the electrolysis plants on offshore platforms in the maritime sector directly at or in the immediate vicinity of offshore wind turbines and to supply them with electricity using the generated electricity.

[0010] Similar concepts have also been proposed for the mainland, where electricity from onshore wind turbines or photovoltaic systems could be used, at least in part, for hydrogen production by directly connecting and feeding it into an electrolysis plant. In all of these applications, the electrolysis plant is part of a so-called island grid. The electrolysis power is therefore not drawn from the public grid, but rather supplied directly by a wind turbine or PV system and fed into an electrolyzer in the electrolysis plant. It may also be possible to temporarily store the electrical energy generated by a wind turbine or PV system, for example, in a battery.In contrast to the grid-controlled operation described above, this brings with it particular challenges and problems with regard to the electrical connection and interconnection of the electrolysis plant with the respective renewable energy generation plant, be it a wind turbine or a photovoltaic plant, in particular to ensure safe and, above all, trouble-free operation of the electrolysis plant in a direct plant network with the renewable energy generation plant.

[0011] In both grid-connected and island operations, there is a great need for technical solutions to enable a reliable and cost-effective electrical connection of one or more electrolysis plants to the respective power generator. This is all the more important as very large and complex electrolysis plants or electrolysis systems with a large number of electrolyzers must be supplied simultaneously and connected to an external power source.

[0012] In particular, questions arise regarding cost-effective power transmission from the respective power supply source to the electrolysis plants, which in these combined plants are sometimes connected together in a complex system network.

[0013] The invention is therefore based on the object of specifying a system network in which the most reliable and cost-effective electrical connection and supply of electrolysis systems with a power supply source is achieved, whereby a high level of operational flexibility is achieved, in particular with regard to the partial load capability of the electrolysis systems.

[0014] This object is achieved according to the invention by a system network comprising at least two electrolysis systems, a power supply source with a direct voltage output and a central supply line, wherein the central supply line is connected to the direct voltage output of the power supply source, so that a direct current can be fed into the central supply line and a central DC network designed for high voltage is provided, to which the electrolysis systems are connected via the central supply line, wherein the power supply source has a wind turbine as the power generator, to which a rectifier with a direct voltage output is connected, wherein the direct voltage output is designed for the high voltage, and wherein an electrolysis system is arranged at the base of the tower of the wind turbine and is connected there directly to the central supply line.

[0015] The invention is based on the recognition of the problem that when sometimes different external power supply sources are combined with electrolysis plants to form a plant network, connection questions and questions of efficient power transmission arise. This applies both to island operation and to grid-controlled operation when the electrolysis plants are connected to the public power grid. Depending on the distance of the electrolyzers of an electrolysis plant, which are to be supplied with direct current, from the respective power supply source, power transmission at a low voltage leads to a very high material expenditure, e.g. the electrical conductors used, in order to limit transmission losses as much as possible.This is particularly true when the distance is great, for example when the generator in a wind turbine is located high up in the nacelle and the electrolysis plant is located on the ground near the tower or even a great distance away. This simple example alone can easily require several hundred meters of cable to supply an electrolysis plant and connect it to a power source. The cable routes and the associated material usage alone add up to a significant cost for connecting and supplying the electrolysis plant. Added to this are the costs for electrical equipment for the connection and power transmission.

[0016] For example, well-known solutions proposed on an industrial scale include reducing line losses by reducing the current and increasing the voltage. Transformers are often used to increase the transmission voltage. These require an alternating current system, i.e., an AC network designed for network operation at a frequency of currently 50 Hz to 60 Hz. In fact, the higher transmission voltage selected reduces the transmission losses via the connecting and supply lines. However, this design also has disadvantages, as the transformers are correspondingly large, heavy, and expensive.

[0017] The combination of renewable energy generation (RE) plants with electrolyzers, which usually already provide direct current, also leads to multiple voltage conversions (DC-AC-DC), resulting in increased losses and costs. Therefore, the conversion of electricity on the way from the power source to the electrolysis plants should be reduced to the minimum necessary.

[0018] Especially for onshore wind and solar power plants, a parallel connection of the wind / solar farm to the public power grid, which operates with alternating current, is often required. This gives rise to the challenge of finding an optimal supply topology that takes into account the number of conversions, the costs of power distribution (such as material costs for copper and aluminum), grid perturbations, and the partial load capacity of the electrolysis systems.

[0019] Previous approaches have not offered satisfactory concepts in this area, lacking integrated solutions. Existing systems are used that are simply coupled together. This results in unnecessarily high conversion losses in a plant network that are economically unacceptable on an industrial scale.

[0020] To solve the connection and transmission problem in a plant network with several electrolysis plants as cost-effectively and efficiently as possible, the invention proposes connecting the electrolysis plants via a specially configured central DC grid. This DC grid provides the specified high voltage and electrical power on the central supply line and acts as a transmission and distribution network for the direct current. The required transmission power is brought from the power source to the electrolysis plant via the central DC grid, thus making the electrolysis current available. The high voltage of the higher-frequency DC grid can be flexibly selected and adjusted to the required DC voltage connection value.

[0021] This makes it possible for the DC output of a generator or solar system to be delivered at a suitably high voltage at the specified high voltage, and for the DC power to be fed into the central supply line of the DC grid directly or via a DC-DC converter. The specified high voltage, which is significantly higher than the usual public grid voltage, reduces the material requirements and thus the costs of the cables downstream of the power source. Thus, depending on the required connected load for the connected electrolysis systems, DC voltages of several kilovolts up to 100 kV and corresponding transmission capacities are possible, for which the DC grid is designed and provided at the supply line connection.

[0022] A particular advantage is that the invention makes it possible to overcome even greater line distances between the power supply source and the electrolysis plants at particularly low cost, without having to carry out repeated AC conversions for step-up and step-down transformation. This would require several transformers, which is costly. This makes island grid operation and the corresponding direct DC connection of the electrolysis plants economically feasible, particularly in remote areas, such as with remote onshore wind turbines. Transmission distances of several kilometers up to several hundred kilometers are flexibly possible. The high-voltage grid on the central supply line can be flexibly designed, adapted, and controlled to suit the respective application with regard to power supply source, DC voltage level, transmission and distribution path, and consumption power of the connected electrolysis plants.This allows for direct supply and DC connection to each electrolysis plant, as well as partial load operation, while avoiding conversion losses compared to an AC intermediate circuit. Transformers are eliminated. A direct current can be fed into the central supply line via the power supply source at the DC voltage output. The electrolysis plants in the plant network are each connected to the central supply line and draw the electrical DC power for the electrolysis process from the central DC grid.

[0023] This allows for a very advantageous connection of any number of electrolysis plants to the power supply source via the central supply line, with the central DC supply line acting as a DC bus line in the plant network. The particularly low-loss transferability of the DC power, even over longer distances, is advantageous. Compared to conventional connections and design based on an available AC grid frequency, this not only saves material costs for cables and numerous connecting transformers, but also saves installation space for the plant components. To ensure an appropriate connected load, it is also possible to have one or more DC strings, particularly those electrically connected in parallel, which form the central supply line within the meaning of the present invention.

[0024] The concept with the central DC supply line is easily scalable and highly flexible with regard to the number of electrolysis plants supplied via the DC grid and the type of power source. The DC grid on the central supply line also creates decoupling or independence with regard to the possible generation methods of the electrical power fed into the central supply line. This means that the plant network can be designed for island grid operation, or a connection to a public grid is possible. Advantageous combinations are also possible, including the purchase of power from various power sources, such as wind energy, photovoltaics, or hydropower.

[0025] In the system network of the invention, it is provided that the power supply source has at least one wind turbine as a power generator, to which a rectifier with a DC voltage output is connected, wherein the DC voltage output is designed for the high voltage.

[0026] In this way, a connection or direct current connection and supply of the electrolysis plant from a wind turbine is achieved in the plant network via the central DC supply line, whereby island grid operation is advantageously possible. If the plant network is operated in an island grid, there is no connection to the public power grid. This means that the grid frequency of the public power grid of 50 Hz to 60 Hz is irrelevant for the design and operation of the electrical components in the frequency-independent DC grid. In particular, costs for components and conversion losses, for example transformers, or for the necessary conversion, transmission or re-rectification are eliminated. This results in a more favorable cost position, while at the same time allowing flexibility in the design and selection of the connection components in the DC grid. Grid frequency-independent operation is achieved with the central supply line designed as a DC bus.

[0027] This makes it possible to overcome large distances and cable routes between the power generators and the electrolysis plants at low cost without having to carry out a new AC conversion for step-up and step-down transformation, which can only be achieved using several transformers.

[0028] Furthermore, the individual control or switching on and off of the preferably used DC / DC converters allows for very precise adjustment of the electrolysis units to the (fluctuating) power output of the power generator. If an individual electrolysis unit falls below a critical power consumption threshold, the hydrogen gas concentration on the oxygen side rises to an unacceptably high level, creating a risk of explosion. This avoids critical conditions and enables safe partial load operation.

[0029] Furthermore, the invention proposes arranging an electrolysis system at the base of the wind turbine tower within the system network and connecting it directly to the central direct current supply line. Especially in remote onshore wind turbines, it is particularly advantageous to connect an electrolysis system near the wind turbine to the DC bus line within the system network. If DC / DC converters are then preferably used, the intermediate line is designed with a high direct voltage, thus reducing the use of materials, particularly copper and aluminum, and correspondingly lowering manufacturing costs.

[0030] In a particularly preferred embodiment of the system network, the electrolysis systems are connected in parallel to one another with respect to the central supply line, wherein an electrolysis system is connected to the central supply line via a respective connecting line.

[0031] This leverages the advantages of the DC bus principle with its central direct current supply line, which allows for and also provides for an independent connection line for each electrolysis plant. Within the plant network, the central DC supply network can be flexibly expanded as needed and can be expanded to include additional electrolysis plants, possibly by adjusting the feed-in power of the power sources feeding into the DC grid to the required power consumption of the electrolyzers.

[0032] In a preferred embodiment, a step-down converter is connected in a connecting line, the input voltage of which corresponds to the high voltage in the central DC network and the output voltage of which is designed for a respective operating voltage of the electrolysis plant.

[0033] The use of multiple modular high-current DC / DC converters connected in parallel in a single connecting cable is particularly advantageous. This enables industrial application in combination with an electrolysis plant.

[0034] The buck converter (also known as a step-down converter) converts an input voltage into a lower output voltage.

[0035] A connecting line advantageously forms a central DC line or a DC branch from the central supply line for one or more electrolysis systems or electrolyzers operating with direct current. Thus, any number of electrolysis systems of any size can be advantageously connected to one or more such central DC branch lines using adjustable DC / DC converters, particularly so-called step-down converters or buck converters.

[0036] The DC / DC converters individually reduce the DC voltage to the desired values ​​without significant conversion losses. This allows the electrolysis plants in the system network to be controlled in terms of electrolysis output and switched on and off. Partial load capability or partial load control is achieved by regulating the electrolysis current.

[0037] Coordinating the power controllers ensures islanding capability, which offers significant cost advantages for remote onshore or offshore plants. To provide higher electrolysis currents, multiple DC / DC converters can be connected in parallel and used in a single connecting line.

[0038] In a preferred embodiment, the step-down converter is therefore designed as a controllable step-down converter, so that the supply of electrolysis current to the electrolysis plant can be adapted to a fluctuating feed-in power of the power supply source into the central supply line.

[0039] The controllability of the buck converter enables a flexible supply of electrolysis direct current to the electrolysis system in a connecting cable that can be adjusted to the electrolysis output. Whether the buck converter operates continuously or intermittently depends on the inductance, switching frequency, input voltage, output voltage and the flowing output current. Since these parameters can sometimes change rapidly, the transition between the two operating modes must generally be taken into account (e.g. prevented) when designing the circuit, particularly a regulator. The two operating modes differ in terms of the control characteristic, i.e. the dependence of the output voltage on the duty cycle (see below), and in terms of interference emission.

[0040] Preferably, the step-down converter is designed as a controllable buck converter with output voltage control via pulse-width modulation in continuous operation. This allows for continuous operation of the buck converter and controllability of the electrolysis current supplied to the electrolysis system.

[0041] In a particularly preferred embodiment, the wind turbine in the system network is designed without a mechanical gearbox - i.e. gearless - and is configured for operation with variable rotor frequency, wherein the wind turbine has a generator whose alternating current output is connected to the input of the rectifier.

[0042] In a particularly preferred embodiment, the power supply source comprises a photovoltaic system with a DC voltage output as a power generator, wherein the DC voltage output is designed for the high voltage, and wherein the DC voltage output is connected to the central supply line.

[0043] This allows the DC voltage level at the DC output to be flexibly adjusted to the specified high voltage on the central DC supply line. If necessary, boost converters, known as boost converters, are connected downstream of the PV generator to adjust the specified DC voltage level at the DC output. This is necessary if the DC output of the photovoltaic system itself does not provide a sufficiently high DC voltage level to feed into the central supply line.

[0044] With this design, an advantageous connection and supply of the electrolysis plant with electricity generated from a photovoltaic system is achieved via the central DC grid on the supply line. This enables island grid operation based on photovoltaics. In an analogous approach and with the same advantages as the connection of the electrolysis plant to a wind turbine described above, operation in an island grid is independent of the public grid frequency, which enables particularly great design flexibility and self-sufficient application options away from the public power grid. The grid frequency of the public power grid of 50 Hz to 60 Hz is therefore irrelevant for the design and operation of the electrical components within the DC grid.In this case, a boost converter (DC / DC converter) may be required to increase the voltage of the PV generator as needed, in order to ensure that direct current with the specified high voltage is fed into the central supply line at the right level.

[0045] In a preferred embodiment, the power supply source comprises a hydroelectric power plant with a generator as the power generator, wherein a rectifier with a DC voltage output is connected to the generator.

[0046] It is possible and advantageous for a hydropower plant to use a generator that outputs a higher frequency than the grid frequency directly at the generator output. This means that the hydropower plant's generator can be advantageously designed to match the frequency of the rectifier's AC voltage input. Conversely, the rectifier can also be flexibly adapted and selected to the respective output frequency of the hydropower plant's generator. This reduced complexity and number of components can result in additional cost advantages when connected to a hydropower plant, whereby island-grid operation of the plant network is also possible here. The output speed and thus the AC frequency of the generator is determined by the number of poles and the rotation speed.Generators for hydropower plants, in particular, are therefore available for a higher-frequency AC output, so that a corresponding rectifier with an input designed for a higher frequency is used in the system network. This advantageously enables off-grid operation, i.e., without the need to consider the grid frequency of the public power grid. Frequency-adapted coupling, for example, using expensive and large transformers, is therefore unnecessary or even unnecessary in the central DC grid.

[0047] In a further preferred embodiment, the power supply source is formed by the public power grid, wherein a rectifier is provided whose DC voltage output is designed for the high voltage of the central supply line. As a result, a grid connection is advantageously provided in the system network, if required, via which grid current rectified by the rectifier at the predetermined high voltage can be fed into the central supply power. The grid connection is advantageously set up for bidirectional operation, so that it is also possible for electrical power from the central supply line to be fed into the public grid. This grid feed into the public power grid may be necessary in order to compensate for a reduced consumption of the electrolysis plants or a possible temporary overproduction of renewable electricity on the part of the power generation plants, iea wind turbine, a photovoltaic system or a hydroelectric power plant, to dissipate the power usefully.

[0048] It is also possible and advantageous that in the system network the power generation source is formed or fed from combinations of different power generators, such as wind turbines, photovoltaic systems or hydropower plants, which are connected to the central supply line via respective DC voltage outputs.

[0049] The system network is therefore advantageously designed and set up for connection to the public power grid as needed. This allows both grid operation and island operation. If a connection to the public power grid is to be made, it is possible and preferable for the rectifier to be designed as a central rectifier, e.g. as a central rectifier station, with appropriate performance in order to save components and provide a central connection point for the collection and rectification of grid power. This type of central connection to the public power grid via a central rectifier can be implemented particularly easily, for example, at the grid connection point of a wind turbine or wind farm, with bidirectional use being provided.When fed into the central supply line, the mains current is rectified, and when fed into the public power grid, the direct current taken from the DC grid is reversed from the central supply line.

[0050] If, for example, a wind or solar farm is to be additionally connected to the public power grid, a grid connection to the central DC grid formed by the central supply line can be established using the additional rectifier or inverter provided for this purpose. The voltage level of the DC strings can be flexibly selected so that no additional transformer is required for connection to the power grid. The rectifier or inverter can independently regulate the voltage at the output of the DC string by either absorbing additional power from the grid or feeding excess power into the grid.

[0051] This rectifier or inverter is preferably designed with an IGBT (insulated gate bipolar transistor) as the system's grid perturbations are minimal, allowing for savings on filters and reactive power compensation systems. Additional grid services can be provided. This is particularly advantageous when connecting to weak grids, for example, via a long spur line.

[0052] An IGBT is a popular component in power electronics because it combines the advantages of a bipolar transistor, such as good conduction behavior, high blocking voltage, robustness, and the advantages of a field-effect transistor, with virtually power-free control. The striking advantages of IGBTs are their high voltage and current limits, with operating voltages of up to 6500 V and currents of up to 3600 A at an output of up to 100 MW. This makes the IGBT ideal for use in the rectifier 15 for the operating range of the electrolyzer 3. Depending on the application, the use of an IGCT, i.e. an integrated gate-commutated thyristor, is also conceivable. This offers advantages such as reduced circuitry complexity, an increase in the maximum pulse frequencies for control, and better switching times when connected in series. IGCTs are used in high-power power converters.A single module typically switches several kiloamperes at a typical blocking voltage of 4500 V.

[0053] In a particularly preferred embodiment, the power supply source has a boost converter with a DC voltage output, by means of which a predetermined high voltage can be provided for the central supply line.

[0054] A boost converter, also known as a step-up regulator or boost converter, is a type of DC-DC converter in electronics. The output voltage is always greater than the input voltage. This allows the DC voltage level at the DC output to be flexibly adjusted to the specified high voltage on the central DC supply line. The use of a boost converter is particularly advantageous when connected to a PV generator as the power source, where the PV DC voltage is increased so that the specified high voltage for feeding into the central supply line is provided at the DC output.

[0055] A further, particularly preferred aspect of the invention relates to the use of a DC network in the described system network, wherein a number of electrolysis systems are connected to a central supply line for direct current, wherein a direct current at a predetermined connection value for the high voltage is fed into the central supply line via a direct voltage output.

[0056] During use, a high-voltage direct current with a specified high voltage significantly above the grid voltage is provided at the terminals of the central supply line. This allows the electrolyzers of the electrolysis plants connected to the central DC bus line to be individually supplied centrally via a direct current network.

[0057] In use, the predetermined high voltage on the central supply line is preferably provided by a step-up converter with a DC voltage output with an output voltage above 1.5 kV, in particular above 10 kV.

[0058] It is particularly preferred that the central supply line be operated with a direct voltage at a high voltage of 10 kV to 110 kV, preferably 30 kV to 60 kV.

[0059] The central DC line largely eliminates the need for transformers, unlike an AC-based power supply. The material and installation space required for an AC grid connection due to the weight and size of the transformers can be significantly reduced by designing and specifying a central high-voltage direct current supply network. This reduces the use of materials, especially iron and copper, which in turn requires less installation space.

[0060] The invention is particularly advantageous for the connection or electrical connection of preferably on-shore wind turbines to electrolysis plants in a plant network. In conventional applications, the generator current is brought to a constant 50 Hz output frequency when connected to the AC grid using an inverter (AC-DC-AC) so that the wind turbine can be connected without a mechanical gearbox - as a so-called "gearless" wind turbine - and with a variable rotor frequency. If an electrolysis plant is to be connected, it can now be connected, for example, simply at the base of the tower directly to the central DC supply line (DC bus line). Since DC / DC converters are used, the intermediate line can be designed with a high voltage in order to save material, particularly copper and aluminum, and to reduce costs.

[0061] By connecting several electrolysis plants in parallel, each comprising a series connection of electrolyzers, a good partial load capacity of the entire electrolysis system can be achieved on the central DC supply line. If necessary, the power of the wind turbine can be transferred to the AC grid. This can be the case if the electrolysis plant malfunctions, if the electrolyzers in the electrolysis plant are undergoing maintenance, or if the electrolysis system is not designed for the peak power of the wind turbine.

[0062] In a particularly advantageous application in an isolated grid, a grid-side converter can be dispensed with, and a connection to the central supply line is established between the generator and a respective electrolysis plant with the electrolyzers, using the same principle. In this case, the need for transformers is significantly reduced. A comparatively small, high-frequency transformer is required for galvanic isolation—even if only as needed—to ensure a cost-effective connection of the electrolysis plant to the generator at a high voltage.

[0063] Advantages and advantageous embodiments of the system combination of the invention are to be regarded as advantages and advantageous embodiments of the corresponding use and vice versa.

[0064] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the single figures, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0065] Embodiments of the invention are explained in more detail with reference to the accompanying drawings. These show schematically and in a highly simplified manner:

[0066] FIG 1 shows a plant combination with an electrolysis plant and a wind turbine;

[0067] FIG 2 shows a system network with an electrolysis plant and a photovoltaic system.

[0068] The same reference symbols have the same meaning in the figures.

[0069] FIG. 1 shows a system network 100 according to the invention. The system network 100 comprises an electrolysis system 1 with two electrolysis systems 1A, 1B and a power supply source 3 connected to the electrolysis system 1. The power supply source 3 has a wind turbine 19 as the power generator, which serves as a renewable energy system (RE system) and a source of green electricity. The electrolysis system 1 is supplied with electrolysis current via a central supply line 5, which is supplied with direct voltage. Thus, the central supply line 5 forms a central DC bus line, by means of which the electrolysis system 1 can be directly supplied with direct current for the electrolysis process.

[0070] Each of the electrolysis systems 1A, 1B of the electrolysis system 1 is connected to a supply connection 23A, 23B on the central supply line 5 via a respective connecting line 9A, 9B, so that a parallel connection of the electrolysis systems 1A, 1B is realized. The electrolysis system 1A has at least one electrolyzer 15A, and the electrolysis system 1B has at least one electrolyzer 15B. The electrolyzers 15A, 15B can be designed either as a PEM electrolyzer, as an AEM electrolyzer (AEM: anion exchange membrane), or as an alkaline electrolyzer, although combinations are also possible. It is possible that a plurality of electrolyzers 15A, 15B are connected in series in a line of the respective electrolysis plant 1A, 1B, which is to be supplied via the corresponding connecting line 9A, 9B.

[0071] On the power supply source 3 side, a rectifier 13A having a DC voltage output 7 is connected downstream of the wind turbine 19 on the output side of a generator of the wind turbine 19. This means that an alternating current generated by the generator of the wind turbine 19 can be converted into a direct current at a predetermined high voltage at the DC voltage output 7 and fed into the central supply line 5. This creates a central DC network designed for high voltage. In order to couple the power generated by the wind turbine 19 and fed into the DC power center, no further active components such as transformers are required when connecting the wind turbine 19 to the central supply line 5, so that a particularly simple supply topology is achieved.

[0072] The DC voltage level at the DC voltage output 7 of the rectifier 13A can be flexibly adapted to the respective requirements in the system network 100, with a high output voltage being selected as the predetermined high voltage, which is preferably greater than 1.5 kV. Here, when designing and constructing the central DC network through the central supply line 5, the nominal voltages of the network levels commonly used in energy transmission can be used, for example, or these values ​​can serve as a guide for the DC voltage level. Electrical energy is transmitted on high-voltage lines in various medium-voltage and high-voltage network levels with the following common nominal voltages: medium voltage of 3 kV, 6 kV, 10 kV, 15 kV, 20 kV, 30 kV, high voltage of 60 kV, 110 kV.The central supply line 5 acts very advantageously as a central DC bus line, which directly enables a high-voltage direct current supply to an electrolysis system 1.

[0073] For a connection and DC power supply of the electrolysis systems 1A, 1B that is matched to the operating voltage, a step-down converter 11A is connected to the connecting line 9A and a step-down converter 11B is connected to the connecting line 9B. The input of the step-down converter 11A is connected to the supply connection 23A and, similarly, the input of the step-down converter 11B is connected via the supply connection 23B to the central supply line 5. On the output side, the step-down converters 11A, 11B are each connected to the electrolyzer 15A, 15B in the connecting line 9a, 9B, so that a respective DC current at an adjustable voltage level for the operating voltage is provided for the electrolysis in the electrolyzers 15A, 15B.During operation of the system network 100, a high-voltage direct current network is provided as a central DC network on the central supply line 5 and used to supply electrolysis current to the electrolysis systems 1A, 1B connected in parallel to the central supply line 5. By using a high voltage, a direct current can be provided or higher-frequency alternating current can be provided and fed into the central supply line 5. The system network 100 can be designed and expanded particularly flexibly, for example by connecting additional electrolysis systems 1A, 1B comprising additional electrolyzers 15A, 15B via a connecting line 9A, 9B. Advantageously, the system network 100 enables grid-independent island grid operation.

[0074] The step-down converters 11A, 11B connected to the connecting lines 9A, 9B function as DC / DC converters (step-down converters) and are each designed such that their input voltage corresponds to the specified high voltage in the central DC network on the central supply line 5, and their respective output voltage is adapted or adjusted to a respective operating voltage of the electrolysis system 1A, 1B. The step-down converters 11A, 11B are designed as adjustable step-down converters, so that the supply of the electrolysis system 1A, 1B with electrolysis current can be adapted and tracked to a fluctuating feed-in power of the power supply source 3 into the central supply line 5.The step-down converters 11A, 11B can be designed, for example, as adjustable step-down converters with a control of the output voltage via the method of pulse width modulation in continuous operation, which enables continuous operation with particularly high performance.

[0075] In the system network 100 shown in FIG. 1, it is also possible for an electrolysis system 1A, 1B to be arranged, for example, at the base of the tower of a respective wind turbine 19, and there directly connected to the central supply line 5. This is advantageous, for example, for onshore applications and the installation of wind turbines 19 in remote areas and for island grid operation. A wind turbine 19 here also refers to a wind farm or wind park—onshore or offshore, with a plurality of wind turbines 19.

[0076] According to the embodiment of FIG 1, on the side of the power supply source 3 in the system network 100, a connection to the public power grid 25 is possible, alternatively or additionally. For this purpose, as illustrated in FIG 1 in dashed line, a separate supply connection 23C is provided in the central supply line 5. The connection to the public power grid 25 is made via a connecting transformer 27 and a downstream rectifier 13B with a DC voltage output 7. The rectifier 13B is designed such that its DC voltage output 7 is designed for the high voltage of the central supply line 5 and outputs the specified high voltage at a corresponding voltage level, ie optionally, for example, medium voltage levels of 3 kV, 6 kV, 10 kV, 15 kV, 20 kV, 30 kV, or high voltage of 60 kV or 110 kV. The voltage level can be flexibly adapted and changed.Furthermore, bidirectional operation is possible when using the supply connection 23C as a grid connection, so that direct current can be fed in from the public power grid 25 into the central supply line 5 as well as direct current can be fed out from the DC grid of the central supply line 5 as needed.

[0077] Thus, if required, electricity from the public power grid 25 can also be fed into the central supply line 5 at the supply connection 23C with an adjusted voltage and made available for use for electrolysis purposes in the electrolysis system 1. The advantage here is that by providing a connection to the public power grid 29, for example, backup demand e can be covered, for example when the wind turbine 19 is not producing electricity or is producing only a very limited amount of electricity due to maintenance, or during phases of a lull in the light, so that a backup solution is maintained to ensure the most continuous supply and uniform operation of the electrolysis systems 1A, 1B for hydrogen production. If necessary, even in the event of an undersupply of electrical DC power on the central supply line 5, one or more electrolysis systems 15A, 15B can be operated at partial load or taken off the DC grid.Adapted partial load operation is achieved, if required, in the respective connecting line 9a, 9B by means of the adjustable step-down converters 11A, 11B, by means of which the DC power can be adjusted via the output voltage at the output of the step-down converter 11A, 11B. In a pure island grid operation of the system network, a backup supply is generally not required due to the lack of an available connection to a public grid 29.

[0078] In a further embodiment of an inventive

[0079] 1B. The power supply source 3 comprises a photovoltaic system 21 with a large number of PV modules (not shown in detail). The photovoltaic system 21 can, for example, be designed as a large-area and powerful open-field system - preferably in sunny regions - so that PV outputs of 10 MW and more are available for the electrolysis. On the electrolysis system 1 side, a substantially analogous system concept to that in FIG. 1 is used, and corresponding system components, i.e. the electrical connection and supply of the electrolysis systems 1A, 1B, are provided via the central supply line 5, which in turn is designed as a central DC bus line or DC connection strand.To achieve this, the electrolysis system 1A is electrically connected to the supply connection 23A and, accordingly, the electrolysis system 1B is electrically connected to the supply connection 23B via a respective connecting line 9A, 9B.

[0080] Thus, in the system network 100 configured in this way, the power supply source 3 comprises a photovoltaic system 21, a so-called PV generator, as the power generator. This already supplies a direct voltage at the generator output, which can already be designed for the specified high voltage, with the direct voltage output 7 then being formed by the PV generator output and being directly connected to the central supply line 5.

[0081] In order to achieve a desired and advantageous DC voltage level for feeding direct current into the central supply line 5 with the photovoltaic system 21 as the power supply source 3, it is also possible, as shown in the exemplary embodiment in FIG. 2, to connect a step-up converter 17 to the DC output of the generator of the photovoltaic system 21. The step-up converter 17, also called a boost converter or step-up regulator, is a special form of DC-DC converter in power electronics. The output voltage is always greater than the input voltage, so that the step-up converter 17 provides the high voltage of the desired DC voltage level specified for feeding in the power supply source 3 at the DC voltage output 7. The higher voltage reduces the material requirements and thus the costs of the lines after feeding in by the power supply source 3.

[0082] The boost converter 17 is designed for the operating frequency voltage level and delivers the specified high voltage at the output. The boost converter 17 is designed to be adjustable, allowing flexible adjustment of the supplied output voltage. The power of the photovoltaic system 21 is coupled and fed into the central supply line 5 directly at the DC voltage output 7 of the boost converter 17. For the transmission and collection of electrical power by the electrolysis system 1, the electrolysis storage units 1A, 1B are connected to the central supply line 5 via a respective connecting line 9A, 9B, as described in more detail above. The respective step-down converters 11A, 11B also decouple the regulation of the electrolysis current demand e in the connecting lines 9A, 9B, thus enabling individual operation of these DC connecting lines, which is particularly important for partial load requirements.Feeding grid power from the public power grid 23 into the central supply line 5 is also possible in the PV application and is implemented in an analogous manner to that described in FIG 1.

[0083] The invention provides a system network 100 with which electrical power, in particular from a renewable power supply source 3, can be fed into an electrolysis system 1 having a number of electrolysis storage units 1A, 1B, so that 100% green hydrogen can be generated in the electrolyzers 15A, 15B. This is achieved very advantageously in the described system network 100 comprising at least two electrolysis systems 1A, 1B, a power supply source 3, and the central supply line 5, which is designed as a central AC bus line and provides an alternating current at an operating frequency above the grid frequency of the public grid. Thus, a higher frequency AC network is provided and used in the system network 100, wherein a number of electrolysis systems 1A, 1B are connected to and operated by a central supply line 5, wherein a higher frequency alternating current is fed into the central supply line 5.

[0084] To operate the system network 100, a number of electrolysis systems 1A, 1B are connected to the central supply line 5 for direct current, with a direct current at a predetermined high voltage being fed into the central supply line 5 via the direct voltage output 7. A DC network is formed by the central supply line 5, and a central DC network is used as the supply topology for the electrolysis systems 1A, 1B. The predetermined high voltage on the central supply line can be provided in a photovoltaic system 21 as the power supply source 3 by a boost converter 17 with a direct voltage output 7 with an output voltage above 1.5 kV, in particular above 10 kV. The central supply line 5 can also be operated with a direct current at a high voltage of 10 kV to 110 kV, preferably 30 kV to 60 kV. Specified high voltages can be optionally used, e.g.Medium voltage levels of 3 kV, 6 kV, 10 kV, 15 kV, 20 kV, 30 kV, or high voltage levels of 60 kV or 110 kV correspond to or be based on these. The voltage level can be flexibly adapted and changed, in particular through the use of controllable DC-DC converters as step-up converters 17 and / or step-down converters 11A, 11B. The same applies in the system network 100 for an optional additional connection to the public power grid 25 with regard to the rectifier 13B, which is advantageously designed as a controllable rectifier 13B and for bidirectional operation.

Claims

Patent claims 1. Plant network (100) comprising at least two electrolysis plants (1A, 1B), a power supply source (3) with a direct voltage output (7) and a central supply line (5), wherein the central supply line (5) is connected to the direct voltage output (7) of the power supply source (3) so that a direct current can be fed into the central supply line (5) and a central DC network designed for a high voltage is provided, to which the electrolysis plants (1A, 1B) are connected via the central supply line (5), wherein the power supply source (3) has a wind turbine (19) as a power generator, to which a rectifier (13A) with a direct voltage output (7) is connected, wherein the direct voltage output (7) is designed for the high voltage, and wherein an electrolysis plant (1A, 1B) is arranged at the base of the tower of the wind turbine (19) and is connected there directly to the central supply line (5).

2. Plant network (100) according to claim 1, in which the electrolysis plants (1A, 1B) are connected in parallel with one another with respect to the central supply line (5), wherein an electrolysis plant (1A, 1B) is connected to the central supply line (5) via a respective connecting line (9A, 9B).

3. System network (100) according to claim 2, in which a step-down converter (11A, 11B) is connected into a connecting line (9A, 9B), the input voltage of which corresponds to the high voltage in the central DC network and the output voltage of which is designed for a respective operating voltage of the electrolysis system (1A, 1B).

4. Plant network (100) according to claim 3, wherein the step-down converter (11A, 11B) is designed as a controllable step-down converter, so that the supply of the electrolysis plant (1A, 1B) with electrolysis current is connected to a fluctuating feed-in power of the power supply source (3) into the central supply line (5) is adjustable.

5. System combination (100) according to claim 4, wherein the step-down converter (11A, 11B) is designed as a controllable step-down converter with control of the output voltage via the method of pulse width modulation in continuous operation.

6. Plant combination (100) according to one of the preceding claims, in which the wind turbine (19) is designed without a mechanical transmission and is configured for operation with a variable rotor frequency, and in which the wind turbine (19) has a generator whose alternating current output is connected to the input of the rectifier (13A).

7. System network (100) according to one of the preceding claims, in which the power supply source (3) has a photovoltaic system (21) as a power generator, the DC voltage output (7) of which is designed for the high voltage, wherein the DC voltage output (7) is connected to the central supply line (5).

8. Plant combination (100) according to one of the preceding claims, in which the power supply source (3) comprises a hydroelectric power plant with a generator as a power generator, wherein a rectifier (13B) with a DC voltage output (7) is connected to the generator.

9. System network (100) according to one of the preceding claims, in which the power supply source (3) is formed by the public power grid (25), wherein a rectifier (13B) is provided, the DC voltage output (7) of which is designed for the high voltage of the central supply line (5).

10. System network (100) according to one of the preceding claims, in which the power supply source (3) comprises a step-up converter (17) with a DC voltage output (7). by means of which a predetermined high voltage can be provided for the central supply line (5).

11. Use of a DC network in a system network (100) according to one of the preceding claims, wherein a number of electrolysis systems (1A, 1B) are connected to a central supply line (5) for direct current, wherein a direct current at a predetermined high voltage is fed into the central supply line (5) via a direct voltage output (7).

12. Use according to claim 11, wherein the predetermined high voltage on the central supply line (5) is provided by a boost converter (17) with a DC voltage output (7) with an output voltage above 1.5 kV, in particular above 10 kV.

13. Use according to claim 12, wherein the central supply line is operated with a direct voltage at a high voltage of 10 kV to 110 kV, preferably 30 kV to 60 kV.

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