Electrolysis plant and plant network comprising an electrolysis plant and a renewable energy plant

Abstract

The invention relates to an electrolysis plant (1) comprising an electrolyser (3) and a circuit assembly (5), which has an input (7) for connecting to a power source and an output (9) connected to the electrolyser (3), wherein the circuit assembly (5) has an electrical filter unit (11) which is designed in such a way that high-frequency signal components, in particular from the external power source, can be very effectively damped. The invention also relates to a plant network (100) comprising an electrolysis plant (1) and comprising a renewable energy plant (50). A power source with an output (52) is formed by the renewable energy plant (50) and the electrolysis plant (1) is directly connected to the output (52) of the renewable energy plant (1).

Description

[0001] Description

[0002] Electrolysis plant and plant network comprising an electrolysis plant and a renewable energy plant

[0003] The invention relates to an electrolysis system comprising an electrolyzer and a circuit arrangement. The invention further relates to a system combination comprising an electrolysis system and a renewable energy system connected to the electrolysis system.

[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] Nowadays, hydrogen is produced from water, for example, using proton exchange membrane (PEM) electrolysis or alkaline electrolysis. The electrolysis plants use electrical energy to produce hydrogen and oxygen from the supplied water. This process takes place in an electrolysis stack made up 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 consisting of water and gas bubbles (O2 and H2 respectively) emerge.

[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 exceeds average levels, to generate valuable resources. One such resource 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 EE gas. EE gas is a combustible gas that is obtained from renewable sources using electrical energy.

[0007] 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 cannot come from fossil sources, but must be produced using renewable energies. At least a growing share of the electricity generated from renewable sources is now fed into the public power grid. Thus, a corresponding share of green hydrogen can be produced, depending on the electricity mix, if an electrolysis plant is operated with electricity from the public grid.

[0008] In industrial-scale electrolysis, the direct current is predominantly provided by line-commutated rectifiers. This rectification of a line-side alternating voltage can result in harmonics due to the way the rectifiers operate, which can place a strain on the AC and / or DC grids.

[0009] 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 which comprises 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 also comprises two transformers, which each have 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 in the transformer can take place. 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 are located far away from the consumers. The energy should therefore be transported to the consumer 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.

[0010] 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 adjacent to or in the immediate vicinity of offshore wind turbines, and to supply them with electricity using the generated power.

[0011] Similar concepts have also been proposed for the mainland, using electricity from onshore wind turbines or photovoltaic systems, 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 an island grid. The electrolysis power is therefore not drawn from the public grid, but rather supplied directly by a wind turbine or a PV system and fed into an electrolyzer in the electrolysis plant.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.

[0012] The invention is therefore based on the object of specifying an electrolysis plant by means of which electricity from a renewable source can be fed directly and smoothly into the electrolysis plant.

[0013] This object is achieved according to the invention by an electrolysis system comprising an electrolyzer and a circuit arrangement which has an input for connection to a power source and an output which is connected to the electrolyzer, wherein the circuit arrangement has an electrical filter device which is designed in such a way that high-frequency signal components can be attenuated.

[0014] The invention is based on the knowledge that electrolysis systems, in particular the PEM water electrolysis cells of the electrolyzer, are very sensitive to high-frequency stray electrical currents. These stray currents can couple into the electrolysis system via earth connections or earth faults. Due to necessary system components of an electrolysis system such as process technology, gas separators, auxiliary systems, water-carrying supply lines, etc., the connection to earth on the electrolysis side is inadequate (earth fault or ground loop). It is therefore important, on the one hand, to prevent current paths from closing via the earth, i.e., forming an earth fault or earth loop. On the other hand, the coupling of electromagnetic interference fields per se should be avoided as far as possible, or at least the interference should be reduced.This problem is particularly pronounced when an electrolysis plant is directly connected to a DC power source, such as a photovoltaic system or a wind turbine. In this complex system combination consisting of a renewable energy generation plant and an electrolysis plant with a direct feed-in of the electrolysis current from renewable energy to operate the electrolysis, the adverse effects of a ground loop and the coupling of alternating electromagnetic fields into the power electronics components used scale accordingly. For example, the widespread and preferred use of insulated-gate bipolar transistors (IGBTs for short) in the rectifier that supplies the electrolysis plant with high current. An IGBT can generate relatively strong interference signals, especially on the ground side.The IGBT is a semiconductor component used in power electronics because it combines the advantages of a bipolar transistor, such as good forward behavior, high reverse voltage, robustness, and the advantages of a field-effect transistor through almost power-free control. In a so-called three-phase B6 bridge circuit with an IGBT-based rectifier, for example, this results in very precise control of the electrolysis current with good rectification. The striking advantages of IGBTs are their high voltage and current limits: voltages of up to 6500 V and currents of up to 3600 A with an output of up to several megawatts, which makes IGBTs ideal for use in electrolysis plants.

[0015] With the invention, a filter device is provided on the DC side in an electrolysis plant with the circuit arrangement, so that effective filtering of interference signals resulting from high-frequency stray electrical currents between the external power supply source and the DC-operated electrolyzer is achieved. The fact that the filter-based circuit arrangement is an integral component of the electrolysis plant itself proves to be advantageous for flexible coupling and direct connection to different power sources. This inherently provides a wide range of connection options and grid-independent operation, in particular island operation, is particularly advantageously possible. The original power source or power supply source can be either a DC source or an AC source and this is advantageously provided directly from renewable energies.The filter device ensures that the electrolyzer is supplied with a stable direct current in both environments and applications. The filter device provides a particularly simple solution that is flexibly adaptable. It is advantageous to also connect systems and components for the electrolysis plant's own power supply, i.e. the auxiliary systems, the control system, etc., downstream of the filter and to use them to operate these systems and components, since high-quality direct current is already provided there. The invention can be used to attenuate, in particular, high-frequency signal components from an external power source to which the electrolysis plant can be connected in order to supply it with an electrolysis current.But also a filtering of high-frequency signal components from other interfering power sources of the electrolysis plant itself or in its surroundings, which can lead to interfering coupling.

[0016] In the circuit arrangement, the filter device functions in a similar way to a mains filter and can be specifically designed for use in an electrolysis plant. In this case, the filter device can, for example, be designed as an electrical circuit which both limits electrical interference emanating from electrical devices and components of the electrolysis plant with the electrolyzer into the power source (radio interference suppression), and also significantly improves the electromagnetic compatibility and protection of the electrolysis plant against interference from the feeding power source. The latter leads to an increase in the interference immunity of the electrolysis plant. This is of particular interest and advantage in applications in which the electricity from a renewable source is to be fed directly and interference-free into the electrolysis plant as direct current, i.e.with direct feed-in or DC feed-in from a renewable energy plant.

[0017] In the circuit arrangement, the filter device can optionally be designed as a low-pass filter and comprise inductors and capacitors. The area of ​​application in an electrolysis system for a direct connection and supply of an electrolyzer with electrolysis current is preferably the medium-voltage and low-voltage range, depending on the power source. The filter device is advantageously integrated as a component of the circuit arrangement directly into the electrolysis system, which is particularly sensitive to disruptive stray currents, or possibly into current-carrying system components that cause interference. It is possible and advantageous for the circuit arrangement with the filter device to be designed as a separate module that can be connected and integrated into the electrolysis system. This ensures a filtered and interference-free direct voltage at a desired and predetermined voltage or current level for the electrolysis.

[0018] The circuit arrangement is therefore particularly advantageously designed as a filter device and conceived for the provision of direct current by an external power source, in particular an external direct current source, for supplying the electrolyzer with electrolysis current. This is achieved by directly coupling or directly connecting the input to an external power source, in particular directly to an external direct current source. A wind turbine or a photovoltaic system can advantageously be connected to the electrolysis system as an external direct current source, each of which can advantageously be designed to be grid-independent in so-called island operation for both offshore and onshore applications.

[0019] In advantageous applications with an available external DC source as the power source, this can be connected directly and immediately via the input of the circuit arrangement, thus achieving an interference-free DC supply to the electrolyzer. By filtering and decoupling via the filter device provided in the circuit arrangement, damaging interference from high-frequency stray currents is reliably avoided, and thus earth fault currents and unwanted voltage losses in the sensitive electrolyzer, in particular coupling into the electrolysis cells. Safe operation of the electrolysis system with a high level of reliability and an improved service life is achieved because losses due to voltage-reducing current paths are reduced. At the same time, a simple and reliable direct connection of the electrolysis system to an energy generation system based on renewable energies is achievable, and the desired grid-independent operation is possible.

[0020] In a particularly preferred embodiment, the filter device has a low-pass filter.

[0021] A low-pass filter or low-pass filter is a particularly easy-to-integrate solution for suppressing or filtering out high-frequency interference from the power source and allowing only the required direct current to pass through for electrolysis. The low-pass filter can be designed as a passive analog low-pass filter, comprising, for example, a resistor, a coil, and a capacitor, or several of these electrical components. With additional active components such as operational amplifiers or transistors, it is also possible to include an active analog low-pass filter in the filter device. If digital signal processing is required on demand, discrete-time low-pass filters are implemented in filter structures such as FIR or IR filters. This is done using digital circuits such as FPGAs or sequential computer programs.

[0022] Low-pass filters for high power applications in high frequency and electrical power engineering—as preferred in this case for the electrolysis plant—are constructed from capacitors and coils. They are generally found at the load outputs of frequency converters, Class-D amplifiers, switching power supplies, and in line filters.

[0023] In a preferred embodiment of the electrolysis system, the filter device is designed as a first-order low-pass filter having an RC element.

[0024] In the simplest case, the low-pass filter advantageously consists of a resistor-capacitor combination, a so-called RC element, and represents a first-order Butterworth filter. The functional model assumes that the source impedance of the filter's input voltage is zero and the load impedance is infinitely high at the filter's output voltage.

[0025] In an RC element, a sudden change in the input voltage is followed by the output voltage by the same step size, but delayed in the course of an exponential function with a time constant i = RC, the so-called transfer function of the RC element.

[0026] In a particularly simple embodiment, a simple coil or coil arrangement for damping, especially the high-frequency signal components, is also conceivable. This coil is connected, for example, directly between a rectifier and the electrolyzer and carries the full load current during operation, i.e., it is not connected to ground, but rather to the rectifier and the electrolyzer.

[0027] Preferably, the filter device has an inductance that dampens the high frequency components.

[0028] In a further preferred embodiment of the electrolysis system, the filter device is designed as a second-order or higher-order low-pass filter, which has at least one LRC low-pass filter. This allows for particularly effective filtering and interference suppression for a direct DC connection of the power source to the electrolysis system.

[0029] A second order low pass filter is advantageously obtained for the circuit arrangement by connecting an inductance L in series with a resistor R, since its reactance X L also one - namely to the capacitor reactance X c opposite - frequency dependence . R is chosen to be large enough that no or only a slight voltage increase in the frequency response occurs .

[0030] By connecting several low-pass filters in series in the circuit arrangement, it is also possible to advantageously increase the order of the filter. For example, two second-order low-pass filters connected in series form a fourth-order low-pass filter. The attenuation changes above the cut-off frequency by 4 x 20 dB / decade = 80 dB / decade, which corresponds to a slope of 24 dB / octave. However, two low-pass filters connected together with the same cut-off frequency do not result in a higher-order low-pass filter with the same cut-off frequency. Relevant formulas and tables are available for dimensioning a low-pass filter with the desired cut-off frequency. These can be used depending on how the electrolysis system is connected to the external power source. Another problem can arise that a low-pass filter in a chain is influenced by the output resistance of the upstream low-pass filter and the input resistance of the downstream low-pass filter.This effect can be counteracted with impedance converters, which can be additionally integrated into the circuit arrangement if required. In general, for an n-order low-pass filter, n storage elements, i.e. capacitors or coils, are required in the circuit arrangement. The attenuation of an n-order low-pass filter increases above the cut-off frequency by n - 20 dB / decade. Furthermore, it is preferably possible to use several parallel filters, in particular low-pass filters, and advantageously to connect them in combination to form a filter arrangement in the electrolysis plant. The respective filters are set to different frequencies or frequency bands, which they are intended to suppress.

[0031] In a preferred embodiment of the electrolysis system, the filter device is designed as an active filter, wherein the filter device has an operational amplifier.

[0032] Operational amplifiers can be used to advantageously implement active low-pass filters in the filter device. These have the advantage that the frequency response is maintained even when a load is connected to the output. They can also be dimensioned so that they place minimal load on the current source, allowing it to have an impedance greater than zero.

[0033] In a particularly preferred embodiment of the electrolysis system, it comprises a rectifier whose output is connected to the input of the circuit arrangement and whose input can be connected to an external alternating current source, so that a direct current freed of high-frequency signal components can be fed to the electrolyzer via the filter device. From a technical perspective, a direct current freed of high-frequency signal components also includes and comprises a direct current largely or mostly freed of high-frequency signal components.

[0034] The electrolysis system is therefore particularly advantageously equipped and set up for direct connection to an alternating current source, such as for connection to a wind turbine whose generator supplies alternating current. On the DC side, i.e. at the output of the inverter, the inverter is connected to the circuit arrangement. On the AC side, i.e. at the input of the inverter, the inverter can be connected to an external alternating current source. By interconnecting the inverter with the circuit arrangement, an interference-suppressed connection of the electrolysis system to an alternating current source is provided for the operation of the electrolysis system. It is also possible for the inverter to already be an integral component of the circuit arrangement in this application.The circuit arrangement then includes the inverter and the filter device for an AC connection to the electrolysis system, and these components interact advantageously. This makes the electrolysis system suitable for direct connection on the AC side to an AC power source, such as a wind turbine in stand-alone operation. The electrolysis system is located in close proximity to the wind turbine or integrated into the wind farm with numerous wind turbines.

[0035] Preferably, the rectifier is adjustable and / or designed as a three-phase rectifier, in particular the rectifier is designed as a B6 bridge rectifier.

[0036] The controllability of the rectifier(s), which are advantageously designed as three-phase rectifiers or as B6 bridge rectifiers, makes it possible to adjust the total current generated by the rectifier(s) and thus, for example, to precisely control the operation of an electrolyzer connected to the circuit arrangement.

[0037] In a preferred embodiment of the electrolysis system, a filter device is connected in series between the rectifier and the electrolyzer. The series connection of the rectifier and the electrolyzer represents a possible and advantageous arrangement for the filter device. The electrolyzer is thus protected from disruptive coupling of high-frequency stray currents, for example, via ground loops. In this arrangement, the load current is completely carried by the filter device.

[0038] In an alternative or additional preferred embodiment of the electrolysis system, a filter device is connected to the rectifier, wherein the filter device is connected to a reference potential, in particular to earth potential or ground. As a result, the load current does not have to be carried by the filter device. This alternative embodiment leads to a solution that has a particularly favorable effect on costs.

[0039] In this embodiment, the filter device's input side is connected directly to the direct current side, i.e., the rectifier output, and a second connection is connected to ground potential. The rectifier output is also connected to the electrolyzer, so that the rectifier output, the filter device's input, and the direct current supply line to the electrolyzer are at the same potential.

[0040] In principle, it is also possible, and in certain applications advantageous, to combine the above-described serial connection of the filter device with the alternative connection via ground potential in the circuit arrangement. However, a respective design and selection of one of the two circuit variants is generally preferable, as this is less complex and costly to implement.

[0041] A further aspect of the invention arises from the design of the electrolysis system for a preferred electrical connection of the electrolysis system to an external power source, in particular to an external direct current source, wherein a renewable energy system is directly electrically connected to the electrolysis system. This creates an integrated system network.

[0042] In a particularly preferred embodiment, the system network comprises an electrolysis system and a renewable energy system, wherein the renewable energy system forms a power source with an output, and wherein the electrolysis system is connected to the output of the renewable energy system. This enables island grid operation in the system network independent of the public grid and direct use of electricity exclusively from renewable sources for electrolysis, so that green hydrogen is formed.

[0043] Preferably, the renewable energy plant in the plant network includes a wind turbine.

[0044] It is also possible for the renewable energy plant in the plant network to be a wind turbine or a wind farm with a large number of wind turbines. In this case, an electrolysis plant can also be supplied with alternating current from several wind turbines interconnected on the AC side. The wind-based generation of 100% renewable green electricity is particularly attractive in combination with electrolysis. The rectifier in the electrolysis plant, which is connected on the output side to the input of the circuit arrangement or is electrically connected to its input, ensures filtering and interference suppression. The rectifier converts the alternating current from the wind turbine into direct current and at the same time advantageously provides the desired direct voltage level at the input for operating the electrolyzer. At the same time, a direct connection to the wind turbine and an integrated plant network is achieved.

[0045] This also advantageously opens up the possibility of filtering several electrolyzers in an electrolysis plant that are connected in parallel. Filtering can be carried out either centrally behind the rectifier in the electrolysis plant, or with several smaller, appropriately designed filter units directly on the several electrolyzers connected in parallel, which can then be switched on and off to vary a partial load. Especially when the electrolysis process of an electrolyzer is at a standstill, this electrolyzer is particularly susceptible to high-frequency stray currents caused by the operation of the electrolyzers or sub-systems of the electrolysis plant connected in parallel.

[0046] In an alternative or additional embodiment of the system network, it is preferred that an electrolysis system is connected to a renewable energy system, wherein the renewable energy system has a photovoltaic system, so that a direct current source with an output is formed, and wherein the electrolysis system is connected to the output of the photovoltaic system.

[0047] In an alternative embodiment, it is also preferably possible and preferred for the renewable energy system in the system network to be a photovoltaic system. A PV system already provides direct current during operation, which is easily usable for electrolysis.

[0048] On the renewable energy system side, combination systems are also possible in the system network, which include both a wind turbine and a photovoltaic system. With a PV system, rectification is not required - in contrast, a wind turbine generally first generates and then makes alternating current available. For electrolysis purposes in the system network with a wind turbine, a rectifier is therefore required. This rectifier is preferably already a component of the electrolysis system set up accordingly for operation with a wind turbine. However, a rectifier can also already be provided in the wind turbine itself in order to provide direct current at the connection or transfer point to the electrolysis system.

[0049] For a combined system configuration, it may also be preferable to connect a battery or other energy storage device in parallel with a wind turbine and / or a photovoltaic system and integrate it into the system network. The battery or energy storage device is then preferably also connected to a DC / DC converter, similar to the electrical integration of a photovoltaic system.

[0050] This allows for a direct connection to a battery or energy storage device, with the battery or energy storage device preferably being supplied and charged by a power source. As a supplement to the renewable energy system (RE system), the battery or energy storage device is useful and highly advantageous, also for load control and consistent power supply to the electrolysis system with power from the battery, and especially as a buffer in low-wind and / or low-sun weather conditions.

[0051] In the case of a photovoltaic system, it is preferably provided that the photovoltaic system in the system network has a DC / DC chopper or DC / DC converter which forms the output.

[0052] In this case, the output of the DC / DC converter forms a DC power source for the photovoltaic system at a predefined DC voltage level. The electrolysis system is directly connected to the output of the photovoltaic system. It is also conceivable and possible that the DC / DC converter is a component of the electrolysis system's power electronics and is adapted accordingly to the PV voltage level.

[0053] A DC-DC converter, also called a DC-DC converter, is an electrical circuit that converts a DC voltage supplied at the input into a DC voltage with a higher, lower, or inverted voltage level. The conversion takes place with the help of a periodically operating electronic switch and one or more energy storage devices. DC-DC converters are self-commutated power converters. In the field of electrical power engineering, they are also called DC / DC chopper devices. The inductance used to temporarily store the energy (inductive converter) consists of a coil or a converter-transformer.

[0054] Advantages and advantageous embodiments of the electrolysis plant of the invention are to be regarded as advantages and advantageous embodiments of the plant network and vice versa.

[0055] Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. 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 combination specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0056] Examples of the invention are explained in more detail with reference to the accompanying drawings. These show schematically and in a highly simplified manner:

[0057] FIG 1 shows a system network with an electrolysis plant and a wind turbine in direct DC coupling;

[0058] FIG 2 shows a system network according to FIG 1 with alternative filter circuit;

[0059] FIG 3 shows a system network with an electrolysis system and a photovoltaic system in direct DC coupling;

[0060] FIG 4 shows a system network according to FIG 3 with alternative filter circuit;

[0061] : The same reference numerals have the same meaning in the figures. FIG 1 shows a system combination 100 according to the invention. The system combination 100 comprises an electrolysis system 1 and a wind turbine 50A connected to the electrolysis system 1 as a renewable energy system (RE system) and source of green electricity. The electrolysis system 1 has an electrolyzer 3 and a circuit arrangement 5 which is electrically connected to the electrolyzer 3. The circuit arrangement 5 is connected to the electrolyzer 3 via the output 9. Furthermore, the circuit arrangement has an input 7 via which a direct current can be supplied to the electrolysis system. The input 7 is designed for connection to an external power source, in particular an external direct current source. The direct current, so-called electrolysis direct current, is supplied from a direct current source via the circuit arrangement 5.For the interference-free and noise-suppressed supply of a direct current of high quality, the circuit arrangement 5 has an electrical filter device 11. The filter device 11 is designed such that high-frequency signal components from the current source can be very effectively attenuated and suppressed. For this purpose, the filter device 11 is designed as a low-pass filter which has an RC element, in other words as a passive component. Other possible designs for the filter device 11 are as a 2nd order low-pass filter or a higher order which has an LRC low-pass filter, in other words an inductance, an ohmic resistance and a capacitance. The circuit arrangement 5 can also advantageously be equipped with a filter device 11 designed as an active filter. The filter device 11 then has, for example, an operational amplifier as the active component.The filter device 11 greatly reduces problems with earth faults and the corresponding adverse coupling of high-frequency interference signals into the electrolysis system 1. This protects the particularly sensitive components of the electrolyzer 3, in particular the large number of electrolysis cells, and guarantees a setpoint voltage of high consistency and quality. The electrolysis system 1 further comprises a rectifier 15, the output of which is connected to the input 7 of the circuit arrangement 5. On the input side, the rectifier 15 is connected to an alternating current source, in the exemplary embodiment to a 50A wind turbine supplying an alternating current. The direct alternating current connection (AG connection) is made via the output 52 of the 50A wind turbine.Due to the electrical filter device 11 in the circuit arrangement 5, a direct current largely freed from high-frequency signal components can be fed to the electrolyzer 3 via the filter device 11 in the case of the direct connection.

[0062] The rectifier 15 supplies the circuit arrangement 5 with direct current, which in turn enables highly effective filtering for the direct DC connection by means of the filter device. Thus, the electrolyzer 3 is supplied with a direct current, the electrolysis current. The electrolyzer 3 can be designed as a PEM electrolyzer or as an alkaline electrolyzer.

[0063] 1 in a series circuit to the circuit arrangement 5 with the filter device 11, which in turn supplies the electrolyzer 3 with electrolysis direct current via the output 9. The wind turbine 50A first generates an alternating current in the generator. In order to be able to transfer a direct current to the electrolyzer 3, a rectifier 15 is provided in the electrolysis plant 1, so that the direct connection at the output 52 on the AC side is made via this rectifier 15, the rectifier here advantageously being an electrical power component of the electrolysis plant 1. However, it is also possible for rectification to take place before the transfer in the wind turbine 50A itself. In order to vary the voltage orthe current intensity for the electrolysis, the rectifier 15 is adjustable and is designed as a three-phase rectifier in the form of a B6 bridge rectifier. This has an IGBT (not shown in more detail) as a semiconductor component, an insulated gate bipolar transistor. This is a component often used in power electronics because it combines the advantages of the bipolar transistor such as good conduction behavior, high blocking voltage, robustness and the advantages of a field effect transistor with almost power-free control. The striking advantages of IGBTs are their high voltage and current limits: voltages of up to 6500 V and currents of up to 3600 A at an output of up to several megawatts make IGBTs ideal for use in electrolysis plants. This makes the IGBT in the rectifier 15 ideal for the operating range of the electrolyzer 3.

[0064] Depending on the application, the use of a so-called IGCT in the rectifier 15, i.e., an integrated gate-commutated thyristor, is also conceivable. This offers advantages such as reduced wiring complexity, increased maximum pulse frequencies for control, and improved 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.

[0065] The circuit arrangement 5 ensures very effective interference suppression via the filter device 11. This greatly reduces high-frequency electrical stray currents during operation, which can couple in via earth loops and impair the electrolyzer 3 with its very sensitive electrolysis cells, since the ohmic losses due to earth loops can lead to a very detrimental voltage drop across the electrolysis cells. The lower the electrical resistance of the ground connection between the components involved, the smaller the potential difference. This is conventionally achieved using cables and plug connections with low resistance, a large cross-section of the shields, low contact resistance and, depending on the design, possibly also optionally provided additional galvanic decoupling. The filter device 11 can also simply contain a transformer, i.e.an iron core with coils, which represents a further measure of interference suppression and filtering in order to generally reduce, in particular, stray currents against earth.

[0066] It is therefore possible to achieve the desired filter effect in the filter device 11 even using an inductance and to design and adapt the filter device 11 accordingly. For example, the filter device 11 of the electrolysis system 1 can also contain several passive filters for different frequencies or mixed passive and active filter arrangements for the filter device 11. This can be achieved, among other things, by using a coil / line with high inductance in series, an RC element (low-pass filter), a 2nd order LRC low-pass filter, the use of a higher order low-pass filter, or active filtering.

[0067] During operation of the system network 100, green electricity is generated in the wind turbine 50A. The alternating current generated in the generator is converted into direct current in the rectifier 15. As a result, the renewable energy system 50—using the example of the wind turbine 50A—ultimately provides a direct current source, so that a direct current is fed directly into the input 7 of the electrolysis system 1 via the output of the rectifier 15 and initially passed on to the circuit arrangement 5. In the circuit arrangement 5, filtering is carried out by the filter device 11, so that stray currents are suppressed or avoided.

[0068] The circuit arrangement 5 provides an interference-free or hum-free electrolysis DC voltage at output 9, which stably operates the electrolyzer 3, splitting water into hydrogen and oxygen. Ground loops are avoided. The advantageous direct DC connection of the electrolysis system 1 to the wind turbine 52A enables off-grid island operation and decentralized generation of green electricity, onshore or offshore depending on the application. The proportion of green hydrogen is 100%.

[0069] In a further exemplary embodiment of a system combination 100 according to the invention with a wind turbine 50A, an alternative filter circuit is shown in FIG. 2. In this case, no serial connection of the circuit arrangement 5 with the filter device 11 is provided, but rather the filter function is integrated in that the circuit arrangement 5 is connected directly to the rectifier 15 on the output side and is connected to a reference potential 17, in particular earth potential, zero potential or ground. The electrolyzer 3 is thus then supplied with filtered and interference-suppressed direct voltage of high quality via the output 9. The mode of operation of the filtered direct connection of the electrolysis system 1 to the wind turbine 50A provided via the circuit arrangement 5 is analogous to the system combination 100 described in FIG. 1.

[0070] 3 shows a system network 100 with an electrolysis system 1 and a photovoltaic system 50B in direct DC coupling, a system concept with a very advantageous direct current source for supplying the electrolysis system 1 with direct current. The renewable energy system 50 has a photovoltaic system 50B with a large number of PV modules (not shown in more detail). The photovoltaic system 50B can, for example, be designed as a large-area and powerful free-field system - preferably in sunny regions - so that PV outputs of at least 5 MW of electrical power are available for the electrolysis. On the electrolysis system 1 side, a system concept analogous to that in FIG. 1 is used and corresponding system components, i.e. with a circuit arrangement 5 and with an electrolyzer 3, wherein the circuit arrangement 5 is arranged in series between the photovoltaic system 50B and the electrolyzer 3.The filter device 11 is accordingly integrated in a series circuit and connected upstream of the electrolyzer 3.

[0071] In order to achieve a desired and advantageous voltage level for connection to the electrolysis system 1, in the example in FIG 3 a DC-DC chopper 19 is connected to the photovoltaic system 50B. A DC-DC chopper 19 is also referred to as a DC-DC converter, so that the DC voltage supplied to its input from the photovoltaic system 50B is converted into a DC voltage with a higher, lower or inverted voltage level. The conversion takes place with the aid of a periodically operating electronic switch and one or more energy storage devices. DC-DC chopper 19, also referred to as DC-DC converters, are among the self-commutated power converters that play a major role in the field of electrical power engineering. The inductance used to temporarily store the energy (inductive converter) consists of a coil or a converter-transformer.

[0072] The DC / DC converter 19 connected to the photovoltaic system 50B is connected on the output side at output 52 to the input 7 of the circuit arrangement 5, so that a direct connection to the electrolysis system 1 and supply with PV direct current is achieved, wherein the stray currents are effectively suppressed by the filter device 11, in particular the low-pass filter. In this case, a DC current source of the photovoltaic system 52B at a predeterminable DC voltage level is formed by the output 52 of the DC / DC converter. The electrolysis system 1 is directly and immediately connected to the output 52 of the photovoltaic system. It is also conceivable and possible for the DC / DC converter 19 to be a component of the power electronics of the electrolysis system 1 itself and to be adapted and preconfigured accordingly to the PV voltage level.In a further exemplary embodiment of a system combination 100 according to the invention with a photovoltaic system 52B, an alternative filter circuit is shown in FIG. 4. In this case, no serial connection of the circuit arrangement 5 with the filter device 11 is provided, but rather the integration and safeguarding of the filter function takes place in that the circuit arrangement 5 is connected directly to the DC / DC chopper 19 on the output side and is connected to a reference potential 17, in particular earth potential, zero potential or ground. The electrolyzer 3 is thus then supplied with filtered and interference-suppressed high-quality DC voltage via the output 9. The mode of operation of the direct connection of the electrolysis system 1 to the photovoltaic system 50B, which is provided via the circuit arrangement 5 and is interference-free via the filter device 11, is analogous to the system combination 100 described in FIG. 3.

[0073] The invention provides an electrolysis plant 1 by means of which a direct current or an alternating current from a renewable source can be fed directly and smoothly into the electrolysis plant 1, so that 100% green hydrogen can be generated in the electrolysis. This is particularly advantageous in the described plant network 100 comprising an electrolysis plant 1 and a renewable energy plant 50, which are directly electrically connected to one another and located in close proximity to one another and advantageously integrated into a plant network 100.

[0074] The circuit arrangement 5 with the filter device 11 enables a particularly simple and effective direct DC connection. This appears to be cost-effective compared to alternative solutions using transformers, which utilize the principle of galvanic isolation or decoupling. Even if a complex and expensive transformer system is not available or cannot be used due to local system-related conditions and restrictions, filtering with the electrical filter device 11 on the DC side according to the invention is preferable, with high-frequency signal components being attenuated. This can be achieved, among other things, by using a coil / line with high inductance in series, an RC element (low-pass filter), a 2nd order LRC low-pass filter, the use of a higher-order low-pass filter or active filtering.Filtering in the circuit arrangement 5 comprising the filter device 11 takes place either directly at the rectifier 15 or between the rectifier 15 and the electrolyzer 3. Filtering at an earth line, for example, in a star point earthing in the generator system or at or in the rectifier 15, is also possible. Filtering at a defined earth connection in the electrolysis system, e.g., in the center of a module row, where the potential is already close to the reference potential 17 or earth potential, is also possible.

[0075] The application of the electrolysis system 1 of the invention for both PEM hydrogen electrolysis systems and alkaline electrolysis systems in a system network 100 with a renewable energy system 50 is particularly advantageous. Here, the problem of suppressing high-frequency ground currents in a direct connection, particularly a direct DC connection, was recognized and solved very advantageously.

Claims

Patent claims 1. Electrolysis system (1) comprising an electrolyzer (3) and a circuit arrangement (5) which has an input (7) for connection to a power source and an output (9) which is connected to the electrolyzer (3), wherein the circuit arrangement (5) has an electrical filter device (11) which is designed such that high-frequency signal components, in particular from the power source, can be attenuated.

2. Electrolysis system (1) according to claim 1, wherein the filter device (11) has a low-pass filter.

3. Electrolysis system (1) according to claim 1 or 2, wherein the filter device (11) is designed as a first-order low-pass filter comprising an RC element.

4. Electrolysis system (1) according to one of the preceding claims, wherein the filter device (11) has an inductance that dampens the high frequency components.

5. Electrolysis system (1) according to one of the preceding claims, wherein the filter device (11) is designed as a second-order or higher-order low-pass filter comprising at least one LRC low-pass filter.

6. Electrolysis system (1) according to one of the preceding claims with a filter device (11) designed as an active filter, which includes an operational amplifier.

7. Electrolysis system (1) according to one of the preceding claims, comprising a rectifier (15) which is connected on the output side to the input (7) of the circuit arrangement (5) and which can be connected on the input side to an external AC power source, so that a direct current free of high-frequency signal components can be supplied to the electrolyzer (3) via the filter device (11).

8. Electrolysis system (1) according to claim 7, wherein the rectifier (15) is adjustable and / or designed as a three-phase rectifier, in particular as a B6 bridge rectifier.

9. Electrolysis system (1) according to claim 7 or 8, wherein a filter device (11) is connected in series between rectifier (15) and electrolyzer (3).

10. Electrolysis system (1) according to one of claims 7, 8 or 9, wherein a filter device (11) is connected to the rectifier (15) and is connected to a reference potential (17), in particular to earth.

11. System (100) comprising an electrolysis system (1) according to one of the preceding claims and a renewable energy system (50), wherein the renewable energy system (50) forms a power source with an output (52), and wherein the electrolysis system (1) is connected to the output (52) of the renewable energy system (50).

12. System (100) according to claim 11, wherein the renewable energy system (50) comprises a wind turbine (50A).

13. System (100) comprising an electrolysis system (1) according to one of claims 1 to 6 and a renewable energy system (50), wherein the renewable energy system (50) comprises a photovoltaic system (50B) such that a direct current source with an output is formed, and wherein the electrolysis system (1) is connected to the output (52) of the photovoltaic system (50B).

14. System (100) according to claim 13, wherein the photovoltaic system (50B) has a DC converter (19) which forms the output (52).

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