Method for operating a hydrogen production system

Abstract

The invention relates to a method for operating a hydrogen production system (150, 450, 550, 650) having at least one wind turbine (110, 410, 510, 610) for supplying at least one electrolyzer (114, 414, 514, 614) of the hydrogen production system (150, 450, 550, 650) with electrical power, comprising determining a reference angular speed of the wind turbine (110, 410, 510, 610) based on at least one wind speed parameter predicted for the wind turbine (110, 410, 510, 610) for a future time window, regulating the wind turbine by setting a pitch angle during the future time window, wherein the pitch angle is determined based on the determined reference angular speed and the current angular speed of the wind turbine (110, 410, 510, 610), predicting power generatable by the wind turbine (110, 410, 510, 610) during the future time window based on the determined reference angular speed, controlling the at least one electrolyzer (114, 414, 514, 614) of the hydrogen production system (150, 450, 550, 650) by setting an at least almost constant rate of change of current during at least a portion of the future time window, wherein the rate of change of current is based on the predicted power.

Description

[0001] Method for operating a hydrogen production system

[0002] The invention relates to a method for operating a hydrogen production system. In addition, the invention relates to a controller and a hydrogen production system.

[0003] In the present time, electrical power generation systems are increasingly used for the provision of electrical energy, in which the generating of electrical energy is based on so-called renewable energy sources. Electric power generation systems generally have at least one power generation device, preferably a plurality of power generation devices.

[0004] More particularly, wind energy systems and wind farms, respectively, comprising at least one wind turbine as an energy generation device are used more and more as electrical energy generation systems. In particular, a wind turbine is configured to convert the kinetic wind energy into electrical energy. Such wind farms are not only located at onshore sites, but increasingly also at offshore sites. There are many reasons for choosing an offshore site instead of an onshore site: for example, the available space onshore may be limited. In addition, it has been shown that the energy yield can be increased at offshore wind farms, for example. Offshore locations are usually characterized by relatively continuous wind conditions and high average wind speeds (compared to onshore sites), so that offshore wind farms are increasingly being built.

[0005] In prior art, an offshore wind farm may comprise a plurality of (stationary) offshore structures (i.e., no ships or the like), such as a plurality of offshore wind turbines and at least one offshore substation (also called converter station) by which an offshore wind farm can be electrically connected, for example, to an onshore substation or a further offshore substation. In particular, an offshore wind farm has an internal grid (e.g., comprising power cables respectively energy cables in the form of submarine power cables) configured to electrically connect at least two offshore structures of a wind farm. An onshore substation, in turn, may be connected to an external grid, such as public power grid respectively an electrical distribution network.

[0006] Furthermore, hydrogen production systems having at least one wind turbine respectively a wind farm with at least one wind turbine for supplying a hydrogen production plant of the hydrogen production system with electrical power are also known from prior art. A hydrogen production plant comprises at least one electrolyzer. An electrolyzer is configured to produce respectively generate hydrogen.

[0007] Hydrogen production systems and hydrogen producing wind farms, respectively, may utilize at least one wind turbine that is either grid-connected or decoupled from an external (public) electric grid. In the case of a grid-connected hydrogen wind turbine respectively farm, power is not drawn from the grid by the at least one electrolyzer. The at least one electrolyzer acts, in particular, as an electrical load for the at least one wind turbine.

[0008] In both cases however, the electric power generated by the at least one wind turbine is fed to the at least one electrolyzer for the purpose of hydrogen production in a decentral, semi-central or central system.

[0009] A decentral system means that in particular an electrolyzer or an electrolyzer stack is electrically coupled to each wind turbine, and their operations alongside that of the wind turbine they are coupled to are independent of the other wind turbines in the wind farm. Semi-central or central system means, in particular, that all the output electrical energy respectively power produced by a plurality of wind turbines of a wind farm of the hydrogen production system is synchronized and paralleled to an electrical bus via a single string or multiple strings respectively, using an array network of medium or high voltage cables to an offshore platform or onshore platform. The at least one wind turbine operated in such a hydrogen production system needs to efficiently and effectively produce hydrogen, in particular, without human supervision (in particular, at an offshore site). They may deploy doubly-fed induction generator with partial converter, or alternatively, electrically-excited or permanent magnet synchronous generator with full power converter. The at least one electrolyzer may be a PEM (proton exchange membrane) electrolyzer.

[0010] One concern in the prior art is to extend the service life of the at least one electrolyzer of a hydrogen production system with at least one wind turbine. A particular problem of the prior art is the abnormal and accelerated degradation in the membrane electrodes of the at least one electrolyzer of such a hydrogen production system.

[0011] Document US 7 667 343 B2 discloses a hydrogen production system having an off-grid permanent magnet wind turbine generator wherein the coupling full power converter is controlled to stay in operable range for a longer time so that the hydrogen production of hydrogen production plant, in particular, the at least one electrolyzer, is similarly sustained for a longer time. This is achieved by extending the industrystandard pitch control system to cover a wider operational angular speed range and capture more energy. Further, according to US 7 667 343 B2 energy storage is also integrated in the system to assist in the startup of the system. Document US 7 667 343 B2 is focused on increasing the availability of electrical energy production and in turn, more hydrogen production.

[0012] In addition, in US 7 667 343 B2, a controller is described for the interfacing power converter of the electrolyzer to regulate voltage and current to keep to the operating limits of the electrolyzer for optimal hydrogen production. However, document US 7 667 343 B2 did not address the topic of degradations in the electrodes of interfacing electrolyzers. In addition, the controller of US 7 667 343 B2 for the current control scheme is integrated to the full power converter and its implementation for the electrolyzer is a reactive response to the rotational speed of the generator of the wind turbine. Therefore, it is an object of the present invention to provide a possibility to reduce the drawbacks of the prior art and, in particular, to increase the service life of the at least one electrolyzer of a hydrogen production system having at least one wind turbine.

[0013] The object is solved according to a first aspect of the invention by a (computer implemented) method according to claim 1 for operating a hydrogen production system having at least one wind turbine for supplying at least one electrolyzer of the hydrogen production system with electrical power. The method comprises: determining a reference angular speed of the wind turbine based on at least one wind speed parameter predicted for the wind turbine for a future time window, regulating the wind turbine by setting a pitch angle during the future time window, wherein the pitch angle is determined based on the determined reference angular speed and the current angular speed of the wind turbine, predicting power generatable by the wind turbine during the future time window based on the determined reference angular speed, controlling the at least one electrolyzer of the hydrogen production system by setting an at least almost constant rate of change of current during at least a portion of the future time window, wherein the rate of change of current is based on the predicted power.

[0014] A further aspect of the invention is a controller according to claim 14 for a hydrogen production system having at least one wind turbine for supplying at least one electrolyzer of the hydrogen production system with electrical power. The controller comprises at least one determining module (e.g., in form of computer code executable by a processor of the controller). The determining module is configured to determine a reference angular speed of the wind turbine based on at least one predicted wind speed parameter for the wind turbine for a future time window. The controller comprises at least one regulating module (e.g., in form of computer code executable by a processor of the controller). The regulating module is configured to regulate the wind turbine by setting a pitch angle during the future time window. The pitch angle is determined based on the reference angular speed and the current angular speed of the wind turbine. The controller comprises at least one power predicting module (e.g., in form of computer code executable by a processor of the controller). The power predicting module is configured to predict power generatable by the wind turbine during the future time window based on the reference angular speed. The controller comprises at least one controlling module (e.g., in form of computer code executable by a processor of the controller). The controlling module is configured to control the at least one electrolyzer of the hydrogen production system by setting an at least almost constant rate of change of current during at least a portion of the future time window. The rate of change of current is based on the predicted power.

[0015] In contrast to the prior art, according to the present invention, by providing a method (and a controller) for regulating the at least one wind turbine based on a predicted wind speed parameter and for controlling the power demand of the at least one electrolyzer of the hydrogen production system such that the rate of change of current respectively power is kept at least almost constant respectively steady, the drawbacks of the prior art are reduced. In particular, the service life of the at least one electrolyzer of the hydrogen production system having at least one wind turbine is increased. More particularly, in contrast to prior art the controller according to the present invention provides a proactive response to be aided by forewarning wind speeds.

[0016] In particular (as will be described hereinafter in more details), the method according to the invention may comprise an interplay of (a) proactive (i) active pitch regulation, (ii) turbine power control and (hi) electrolyzer power demand control, in particular, to ensure (b) a steady ramp rate of power to the at least one electrolyzer so that a constant rate of change of the current density of the electrolyzer cells is maintained regardless the intermittency of wind resources, wherein (c) the control responses of the three (a) (i), (ii) and (hi) are, in particular, coordinated in a feedforward system respectively controller according to the measured forewarning respectively predictive wind speed parameter.

[0017] In particular, according to the invention, a system is provided which “absorbs the transient power of wind resources” so that abrupt power variation is avoided and a steady, controlled change in current density of the at least one electrolyzer is achieved, in particular, for low wind speed region of the operation of the at least one wind turbine.

[0018] More particularly, it has been recognized that a main reason for the reduced service time of an electrolyzer of a hydrogen production system with at least one wind turbine is an abnormal and accelerated degradation in the membrane electrodes of the at least one electrolyzer caused by the fluctuating power transfer between the at least one wind turbine and the at least one electrolyzer respectively the fluctuating power generated by the at least one wind turbine.

[0019] Degradations in an electrolyzer are determined by voltage degradation rate (pV / h), i.e., the proportion at which the short circuit cell voltage of the membrane electrodes of an electrolyzer depreciates respectively reduces over the course of service lifetime. In particular, it has been recognized that there are five power operating conditions which cause cell degradations in an electrolyzer. These five power operating conditions are: maintaining operation, low power fluctuation operation, constant turning operation, high power fluctuation operation, and constant rated power operation.

[0020] Of the five power fluctuating operations, both low power fluctuations and high power fluctuations account for over 35 % of the degradations encountered. The total voltage degradation rate under power fluctuations is given by equation (a), wherein nelis the cells number of the electrolyzer, Vfand tfis the voltage degradation rate and operating times under fluctuations respectively. Based on equation (a), a reduction in the length of tfor its complete elimination will effectively mitigate or eliminate degradations due to power fluctuations. The technique to achieve this is proposed in this invention.

[0021] AVd= nel. (tfVf) [a]

[0022] According to the invention a method for mitigating the degradations in the membrane electrode assemblies of at least one electrolyzer is provided. In particular, the method can be executed by a controller according to the invention. The controller may be implemented in a data processing device comprising one or more processors and memory means. In particular, the at least one processor of the controller may be configured to execute the computer implemented method according to the invention.

[0023] The method according to the invention serves to operate, in particular, control respectively regulate at least one wind turbine respectively at least one electrolyzer.

[0024] In particular, a hydrogen production system may be provided. A hydrogen production system may comprise at least one hydrogen production plant. A hydrogen production plant comprises at least one electrolyzer. The at least one electrolyzer may be configured to produce respectively generate a fluid medium, in particular, in form of hydrogen and / or ammonia.

[0025] The hydrogen production plant may comprise at least one hydrogen power supply for the at least one electrolyzer. Furthermore, the hydrogen production plant may comprise at least one (hydrogen) processing module respectively (hydrogen) finishing module. The at least one processing module may be configured to process (wet) hydrogen produced by the at least one electrolyzer. In the present case, wet hydrogen refers in particular to hydrogen saturated with water respectively a two-phase mixture of gaseous hydrogen and liquid water. In the present case, dry hydrogen refers in particular to hydrogen that is not saturated with water, i.e., whose dew temperature is (significantly) below the actual temperature at the pressure present. In other words, in particular, wet hydrogen gas can be produced by the at least one electrolyzer which, when cooled, becomes a gas-liquid mixture in the form of a water-hydrogen mixture. The gas respectively gaseous phase carries the liquid phase with it.

[0026] The at least one hydrogen processing module can comprise at least one hydrogen drying module. The hydrogen drying module can be configured to dry the produced wet hydrogen. Preferably, the hydrogen drying module (e.g., after separation of the liquid phase) can be an adsorption drying module (in particular, a TSA (temperature swing adsorption) module) and / or a refrigeration drying module. The adsorption drying module may be in particular configured to dry the wet hydrogen by adsorption using a (suitable) adsorber, in particular silica beads. The at least one hydrogen drying module can be configured to cool the wet hydrogen to a temperature of at least less than 5°C. It shall be understood that in variants of the invention, other hydrogen drying modules can be used alternatively or additionally.

[0027] Furthermore, the at least one hydrogen processing module can comprise a catalytic deoxo stage, in particular, for treating the wet hydrogen before drying as described above. Such a stage serves to remove oxygen (<0.5%). In variants of the invention, such treatment can also take place at a later stage, for example, at a hydrogen destination structure to which the treated hydrogen can be transported, for example, via a hydrogen pipeline network.

[0028] Preferably additionally, according to a further embodiment of the method according to the invention, the at least one (hydrogen) processing module may comprise at least one (hydrogen) compression module. The compression module may be configured to compress the processed fluid medium, in particular the dried hydrogen. The compression module may comprise at least one (hydrogen) compressor (in particular a (vertical) piston compressor). The compression module can be configured to compress the produced fluid medium, such as the dried hydrogen, to at least 50 barg (and for example at most 250 barg), preferably to essentially 70 barg.

[0029] Alternatively or additionally, the at least one (hydrogen) processing module may comprise at least one transforming module configured to transform the produced hydrogen to ammonia (e.g., via the Haber-Bosch-method or the like).

[0030] Furthermore, the at least one hydrogen production system may comprise at least one water treatment module. The at least one water treatment module can be configured to treat the water such that it can be used by the at least one electrolyzer of the hydrogen production plant to produce the fluid medium, such as hydrogen. In particular, the water treatment module can treat seawater for the electrolysis process to be performed.

[0031] Preferably, the at least one water treatment module can be a seawater desalination module with membrane-based pressure filtration. Such a seawater desalination module can carry out reverse osmosis, ultrafiltration and / or electrodialysis (also known as electrodeionization (EDI)) to treat the water respectively to treat the seawater accordingly. Such treatment can be used to treat seawater, in particular in an energy-efficient manner, which can be used for water electrolysis. The treated water can also be referred to as ultrapure water or "demin water".

[0032] Alternatively or additionally, the at least one hydrogen production plant may comprise at least one inert gas generation module configured to generate an inert gas. For example, the inert gas generation module may comprise an inert gas storage tank, in particular in the form of a pressurized inert gas storage tank configured to (temporarily) store the generated inert gas and in particular for conveying the inert gas through an inert gas pipeline network. Preferably, a nitrogen generation module can be provided as the inert gas generation module, wherein the nitrogen generation module can be configured to generate nitrogen from air, preferably by pressure swing adsorption. It shall be understood that other inert gas generation modules can also be provided alternatively or additionally in variants of the invention.

[0033] Further, it shall be understood that the at least one electrolyzer plant may comprise less modules, further modules, or other modules. For instance, the electrolyzer plant may additionally comprise an intake and filtration module.

[0034] As already described, the at least one wind turbine serves to supply at least the at least one electrolyzer, preferably the whole hydrogen production plant comprising the at least one electrolyzer, with electrical energy and power, respectively. In particular, at least the at least one electrolyzer of the hydrogen production plant is supplied with electrical energy by the at least one wind turbine.

[0035] The at least one wind turbine is configured to convert the kinetic wind energy in electrical energy. The wind turbine may be an onshore wind turbine or an offshore wind turbine. The hydrogen production system may comprise at least one (previously described offshore) wind farm with one or more wind turbines and at least one hydrogen production plant comprising the at least one electrolyzer.

[0036] According to the invention, in order to regulate and / or control the power transfer from the at least one wind turbine to the at least one electrolyzer, a reference angular speed of the wind turbine (supplying the at least one electrolyzer with electrical power) is determined based on at least one predicted wind speed parameter for the wind turbine for a future time window. In other words, based on a wind speed parameter, in particular, the wind speed and / or wind direction (at the at least one wind turbine) predicted for the future time window for said wind turbine the future angular speed, namely, the reference angular speed of the wind turbine for said future time window, can be determined, in particular, predicted. In the present case, a future time window means, in particular, a time period in the near future (e.g., within the next x minutes (e.g., between 0 and 10 minutes). Preferably, at least the said angular speed respectively velocity can be determined during a (respective) current time window for the future time window immediately following the current time window. In other words, a future time window refers in particular to the (respective) time window that follows a current time window.

[0037] Furthermore, in the present case, determining a reference angular speed means, in particular, that a parameter value is determined from which the angular speed can be at least (directly) deduced for said future time period. The reference angular speed is, in particular, a speed value that can be achieved with said predicted wind parameter by respectively at said wind turbine. The reference angular speed is, in particular, determined on said predicted wind parameter such that in case of low wind speeds (e.g., smaller than 30 m / s) the reference angular speed, and thus, in particular, the generatable power, is maximized. A respective criterion can be predefined. The determining of the reference angular speed can be additionally based on said criterion respectively the rules of said criterion.

[0038] According to the invention, the wind turbine is regulated by setting a pitch angle during respectively for the future time window based on the determined reference angular speed and the current angular speed of said wind turbine. In particular, the pitch angle to be set by the controller is determined based on the (determined) reference angular speed and the current angular speed of the wind turbine. In particular, the current angular speed of the wind turbine can be fed-back to the controller, in particular, for performing an error adjustment. In the present case, error adjustment means, in particular, that the pitch angle will be tuned by the determined reference angular speed if the current angular speed ends up being not of the same value as the determined reference angular speed (value).

[0039] As has already been described, the power generatable by the at least one wind turbine during a specific time period depends on the (possible) angular speed of the wind turbine during said time period. According to the invention, the power generatable by the wind turbine during said future time window is determined respectively predicted based on the determined reference angular speed.

[0040] As has been already described, in order to reduce cell degradations of an electrolyzer, power fluctuations at the electrolyzer should be reduced. In order to reduce the power fluctuation, according to the invention, it is proposed to control the at least one electrolyzer (in particular, the power demand of said electrolyzer) of the hydrogen production system by setting an at least almost constant rate of change of current during the future time window. By setting a constant rate of change of current respectively power, a constant rate of change of the current density of the at least one electrolyzer cell can be maintained regardless the intermittency of wind resources The rate of change of current is based on the predicted power.

[0041] Controlling the at least one electrolyzer of the hydrogen production plant by an at least almost constant rate of change of current at least during a part of the future time window means, in particular, that the power transfer from the at least one wind turbine to the at least one electrolyzer is controlled such that at least an almost steady ramp rate of power to the at least one electrolyzer is provided.

[0042] Further, an at least almost constant rate of change of current during the future time window, in particular, during at least a portion of the future time window means, in particular, that the rate of change of during said portion is kept at least almost constant respectively steady.

[0043] In particular, a response of the controller to the interfacing electrolyzer power supply of the at least one electrolyzer is proactively coordinated with the forewarning power control of the wind turbine to deliver the needed voltage and smoothen the current's rate of change as given equation (b), wherein V and P are the voltage and power respectively across the at least one electrolyzer.

[0044] According to an embodiment of the method according to the invention, the at least one electrolyzer may be a PEM (proton exchange membrane) electrolyzer. A PEM electrolyzer is particular suitable to be used in a hydrogen production system having one of more wind turbines according to the invention. As described, the degradations of a membrane of a PEM electrolyzer can be reduced by the method according to the invention. It shall be understood that in variants of the invention, the at least one electrolyzer may alternatively or additionally be an electrolyzer of a different type, such as a high temperature electrolyzer or the like.

[0045] According to a further embodiment of the method according to the invention, the at least one predicted wind speed parameter is a predicted wind speed and / or wind direction at the wind turbine. The predicted wind speed parameter is based on a wind measurement, in particular, conducted by a LIDAR equipment (of the hydrogen production system), at the wind turbine. It shall be understood that in variants of the invention, alternatively or additionally, another wind measurement equipment can be used.

[0046] Preferably, the at least one wind measurement device may be configured to measure at least one wind parameter and to predict the at least one wind speed parameter for the future time window based on the at least one measured wind parameter.

[0047] In particular, the at least one predicted wind speed parameter may be obtained from forecasting measurement or data acquisition system such a LIDAR equipment. In the . . . , , , , upwind . control scheme respectively the method according to the invention, W5may be at least one predicted wind speed parameter, in particular, the measured forewarning

[0048] > > upwind . . . .. , upstream wind speed. W5may be an input to the controller according to the

[0049] _ . upwind . .. .. . . . . . . , , r invention. Based on W5the controller (in particular, the determining module of the controller) may determine the reference angular speed cor refobtained from the window {W}5, wherein 8 is the window length of the forecast respectively prediction.

[0050] According to a preferred embodiment of the method according to the invention, the future time window has a time length between 1 s and 120 s, preferably between 2 s and 50 s (e.g., 20 s). A time window of a minimum of 20 s for the predicting of the at least one predicted wind speed parameter, e.g., from Lidar or a similar system, is preferably proposed according to this embodiment. This allows, in particular, for providing sufficient time for the ramp down or ramp up to of the rated (in particular, desired) current density. This may give the latitude to look into the wind to proactively determine the possible wind energy production rates, adjust the power respectively current delivered by the at least one wind turbine and power respectively current drawn by the at least one electrolyzer, in particular, to ensure steadiness at each operating point irrespective of the prevailing wind speeds.

[0051] According to a further preferred embodiment of the method according to the invention, the rate of change of current is a stepped rate of change of current with a predefined step size (of the change step). In other words, the rate of change of current may be performed in a stepwise manner with always the same step size. This reduces the computing effort while at the same time an at least almost (in particular, sufficient) constant rate of power respectively current to the at least one electrolyzer is provided.

[0052] In an ideal scenario, the power ramp scheme respectively the current ramp scheme according to the invention to eliminate the described fluctuations would utilize a very small step change or rate of change in current (for instance, at least almost continuously) as per equation (b). However, it has been recognized that the overall efficiency of hydrogen production by the at least one electrolyzer may become poor since wind energy utilization would be low. Thus, to achieve a better efficiency for production of hydrogen while reducing fluctuations in power supply to the at least one electrolyzer (and consequently mitigate degradations in electrode membrane due to these fluctuations), a stepped change in current and consequently, current density, is proposed according to a preferred embodiment.

[0053] According to said particularly preferred embodiment of the method according to the invention, the predefined change size (of the applicable change step) may be between 2% / s and 10 % / s, preferably between 4% / s and 6% / s (e.g., 5% / s). In particular, it has been shown that with a step size between 4% / s and 6% / s a sufficiently constant rate of power respectively current to the at least one electrolyzer can be provided (while the computing effort can be reduced). In this way, the probability of unutilized wind energy can be minimized while ensuring minimal fluctuation since the electrolyzer load can be effectively controlled to respond to forecasted respectively predicted wind speeds.

[0054] According to a further embodiment of the method according to the invention, the method may further comprise: providing a predefined power speed characteristic curve, and wherein the predicting power generatable by the wind turbine during the future time window is based on the reference angular speed and the predefined power speed characteristic curve.

[0055] The power speed characteristic curve may define the relation between (reference) angular speed and generatable power of the (specific) wind turbine. For instance, the power speed characteristic curve is provided as an assignment table. Based on the determined reference angular speed (value), the power (value) assigned to said determined reference angular speed (value) can be determined.

[0056] For instance, the power speed characteristic curve can be stored in a data memory of the controller, or a computing equipment connected with the controller. According to a further embodiment of the method according to the invention, the method may further comprise: determining whether the predicted power satisfies a predefined power criterion, and controlling the at least one electrolyzer of the hydrogen production plant by the at least almost constant rate of change of current during the future time window only if the predicted power criterion is not satisfied.

[0057] In other words, the current density of the at least one electrolyzer may be only changed if the predefined power criterion is not satisfied. In particular, it has been recognized that a reduction of the current density is only necessary in case the predicted power does not satisfy a predefined power criterion. The predefined power criterion can be stored in a data memory of the controller, or a computing equipment connected with the controller.

[0058] According to a preferred embodiment of the method according to the invention, the method may further comprise: controlling the at least one electrolyzer such that the current density is kept at least almost constant if the predicted power criterion is satisfied.

[0059] In the present case, keeping the current density at least almost constant means, in particular, that there is no rate of change of current (during the future time window).

[0060] According to a further preferred embodiment of the method according to the invention, controlling the at least one electrolyzer such that the current density is kept constant may comprise adapting respectively changing the cell voltage of the electrolyzer such that the current density is kept constant. By keeping the current density (as long as possible) constant, the service life of the at least one electrolyzer can be further increased. According to a further preferred embodiment of the method according to the invention, the power criterion may comprise at least one predefined power range. The at least one predefined power range is, in particular, between 75 % of the rated power of the wind turbine and 100 % of the rated power of the wind turbine. It has been recognized that in a predefined power range between 75 % of the rated power of the wind turbine and 100 % the current density can be kept constant, in particular, by reducing and / or increasing the cell voltage.

[0061] An electrolyzer (normally) has a predefined optimal current density, in particular, at a predefined optimal voltage range. In the present case, optimal current density means, in particular, a current density optimal for operation of the electrolyzer. In the present case, an optimal voltage range means, in particular, a voltage range optimal for operation of the electrolyzer.

[0062] Typical optimal current density for the cell membrane of an (PEM) electrolyzer may be in the range of e.g., 2 A / cm2at e.g., cell voltage between 1.5 V and 2 V. Under intermittent power supply, current drawn and the equivalent current density would become erratic. This is more visible and problematic with decreasing wind speeds because of insufficient power to keep the at least one electrolyzer running at rated or at least near rated capacity. To keep the current density at the predefined optimal current density (value), e.g., 2 A / cm2, in particular, under declining wind speeds, it is proposed that if the predefined power criterion is met, the controller may control the at least one electrolyzer such that the current density is kept constant (typically at rated maximum) while ramping down (or ramping up) the voltage within the predefined optimal voltage range, e.g., between 1.5 V and 2 V. In particular, this is possible up until the predefined minimum rated cell voltage of e.g., 1.5 V is reached. The predefined minimum rated cell voltage may be reached at 75% of rated power.

[0063] It has been recognized that below 75 % of rated power, this means, in particular, in low wind speed region (where wind turbines may operate most of the time), current density must subsequently be reduced according to the decrease in wind resources in order to keep the at least one electrolyzer functional for hydrogen production. As described herein before, this decrease in current density can be done in a planned and regulated manner to avoid degradations of the membrane(s) of the at least one electrolyzer.

[0064] If the power criterion is not satisfied, in particular, if the predicted power is in the region below 75% of rated power, since changes in wind power may be inconsistent, it follows that changes in current drawn by the at least one electrolyzer and consequently, current density would be inconsistent and abrupt, thus, leading the cell membranes to degradations due to the fluctuations. Hence, according to a preferred embodiment of the method according to the invention, it is proposed controlling the at least one electrolyzer of the hydrogen production plant by the at least almost constant rate of change of current during the future time window only if the predicted power criterion is not satisfied.

[0065] According to a further embodiment of the method according to the invention, the hydrogen production system may comprise a plurality of wind turbines for supplying the at least one electrolyzer of the hydrogen production system with electrical power. In particular, the hydrogen production system may comprise a wind farm with two or more wind turbines. The controlling of the at least one electrolyzer of the hydrogen production plant may comprise centrally coordinating the power transfer from the plurality of wind turbines to the hydrogen production plant such that the rate of change of current is kept at least almost constant.

[0066] According to a further embodiment of the method according to the invention, the hydrogen production plant of the hydrogen production system may comprise a plurality of electrolyzers (e.g., of a respective plurality of hydrogen production plants and electrolyzer units, respectively). The controlling of the plurality of electrolyzers of the hydrogen production system may comprise centrally coordinating the power transfer from the at least one wind turbine to the plurality of electrolyzers such that the rate of change of current is kept at least almost constant for each of the plurality of electrolyzers.

[0067] If there is a plurality of wind turbines, said wind turbines may be connected to an (common) electrical bus on a substation of the wind farm via strings, e.g., of medium voltage power cables or high voltage power cables. A plurality of wind turbines may be connected to form a string. Each individual wind turbine in the cable array network may preferably retain its independence in energy production by the means of the aforementioned controller, in particular, the described forewarning speed prediction.

[0068] However, power transfer between the one or more electrolyzers, arranged on e.g., a central platform, and the wind turbines via the interfacing electrical bus (e.g., a MV bus) may be centrally coordinated via (explicit) communication among the wind farm controller, the electrolyzer controllers and the wind turbine controllers such that the rate of change of current (and thus the current densities in the one or more electrolyzer(s) (e.g., electrolyzer stacks)), driven by di / dtref, is maintained. The previously described controller may at least partially be implemented in the wind farm controller and / or the respective wind turbine controllers (or as a standalone controller).

[0069] In an initial step, in order to ensure optimal energy utilization at all times, the number of electrolyzers and wind turbines in operation can be determined, e.g., by a central controller of the hydrogen production system, such as the wind farm controller. Preferably, at all times, the wind farm controller can determine all operable elements in the system, i.e., active, not faulty wind turbines and electrolyzer stacks.

[0070] In a (subsequent) step, the power transfer can be initiated using an equal allocation of system input power made available on the MV bus collector of the substation by the wind turbines according to equation (c), wherein k is the number of operational electrolyzers and n is the active power available for the window length {w5and j is the number of active wind turbines in the array network and the hydrogen production system, respectively. all i = 1, 2, . . . , k (c)

[0071] The central controller and the previously described controller may send power allocation signals di / dtrefto the one or more electrolyzer controller(s), in particular, in real-time, which can be harmonized with available Uj on the AC power bus of each electrolyzer over the window length 8. In this way of explicit, coordinated communication, the need to abruptly modify the electrolyzer load can be avoided since di / dtrefcan be allocated according to the power projected to be available on the AC power bus and the number of operable electrolyzers.

[0072] A further aspect of the invention is a (previously described) hydrogen production system. The hydrogen production system comprises at least one hydrogen production plant having at least one electrolyzer. The hydrogen production system comprises at least one wind turbine configured to supply the hydrogen production plant with electrical power. The hydrogen production system comprises at least one previously described controller (according to claim 14).

[0073] As described hereinbefore, according to an embodiment of the hydrogen production system, the hydrogen production system may comprise a wind farm with a plurality of wind turbines and preferably at least one substation and at least one hydrogen production plant.

[0074] According to a preferred embodiment of the hydrogen production system according to the invention, the hydrogen production system may comprise at least one wind measurement device. The at least one wind measurement device may be configured to measure at least the wind speed and / or wind direction. The wind measurement device may, in particular, comprise at least one LIDAR equipment. The wind measurement device may be configured to predict the at least one wind speed parameter based on the at least one measured wind parameter, e.g., the wind speed and / or wind direction.

[0075] A further aspect of the invention is a computer program comprising instructions which, when the computer program is executed by at least one processor of a controller, cause the processor to execute and / or control the previously described method, in particular, according to claim 1.

[0076] It is noted that expressions such as "first", "second", etc. do not specify a series order, but only serve to distinguish between two elements.

[0077] The features of the hydrogen production systems, controllers, methods and computer programs can be freely combined with one another. In particular, features of the description and / or the dependent claims, even when the features of the dependent claims are completely or partially avoided, may be independently inventive in isolation or freely combinable with one another.

[0078] These and other aspects of the present patent invention become apparent from and will be elucidated with reference to the following figures. The features of the present application and of its exemplary embodiments, as presented above, are understood to be disclosed also in all possible combinations with each other.

[0079] In the figures show:

[0080] Fig. 1 a schematic view an embodiment of the hydrogen production system according to the present invention with an embodiment of the controller according to the present invention,

[0081] Fig. 2 a diagram of an embodiment of the method according to the present invention, Fig. 3 a diagram of an exemplified course of the cell voltage at an electrolyzer and an exemplified course of a current density at said electrolyzer,

[0082] Fig. 4 a schematic view of a further embodiment of the hydrogen production system according to the present invention,

[0083] Fig. 5 a schematic view of a further embodiment of the hydrogen production system according to the present invention,

[0084] Fig. 6 a schematic view of a further embodiment of the hydrogen production system according to the present invention, and

[0085] Fig. 7 a diagram of a further embodiment of the method according to the present invention.

[0086] Similar reference signs in different Figures indicate similar elements.

[0087] Figure 1 shows a schematic view of an embodiment of the hydrogen production system 150 according to the present invention with an embodiment of the controller 100 according to the present invention. The hydrogen production system 150 may be an onshore hydrogen production system and / or an offshore hydrogen production system.

[0088] The hydrogen production system 150 comprises at least one hydrogen production plant having at least one electrolyzer 114. Preferably, the at least one electrolyzer 114 is a PEM electrolyzer.

[0089] Further, the hydrogen production system 150 comprises at least one wind turbine 110. The at least one wind turbine 110 is configured to convert the kinetic wind energy into electrical energy respectively electrical power. The at least one wind turbine 110 is configured to supply at least the at least one electrolyzer 114 with electrical power, which is generated by the at least one wind turbine 110.

[0090] Optionally, the hydrogen production system 150 may comprise at least one wind measurement device 112 configured to measure at least one wind speed parameter, such as the wind speed and / or wind direction, in particular, at the at least one wind turbine 110. The wind measurement device 112 may comprise at least one LIDAR equipment. Based on the at least one measured wind speed parameter, the measurement device 112 (or another prediction equipment, e.g., of the controller 100) can be configured to predict a wind speed parameter for the wind turbine 110 for a future time window, such as the predicted wind speed and / or the predicted wind direction, in particular, at the at least one wind turbine 110 during a future time window.

[0091] In particular, the at least one predicted wind speed parameter may be obtained from the measurement device 112 in form of a forecasting measurement or data acquisition system. In the control scheme respectively the method according to the invention, upwind , , , , . , , . . , ,

[0092] W5may be the at least one predicted wind speed parameter, in particular, the

[0093] > r ■ , , rt-r upwind . . . measured forewarning upstream wind speed. W5may be an input to the

[0094] .. > . . . upwind . .. , . , r , controller. Based on W5the controller may determine the reference angular speed cor refobtained from the window {w}5 wherein 8 is the window length of the forecast.

[0095] The future time window may have a time length respectively window length 8 between 1 s and 120 s, preferably between 20 s and 50 s (e.g., 20 s). A time window of a minimum of 20 s for the predicting of the at least one predicted wind speed parameter is preferred.

[0096] As has been already described, the hydrogen production system 150 may comprise at least one controller 100. The controller 100 may comprise at least one processor 116 and memory means 118. The processor 116 and the memory means 118 are configured to execute software modules 102, 104, 106, 110 respectively software code.

[0097] The controller 100 comprises at least one determining module 102 configured to determine a reference angular speed of the wind turbine 100 based on the predicted wind speed parameter.

[0098] Further, the controller 100 comprises at least one regulating module 104 configured to regulate the wind turbine 110 by setting a pitch angle p during the future time window, wherein the pitch angle is determined based on the determined reference angular speed and the current angular speed of the wind turbine 110. For instance, the regulating module 104 or a further (not shown) determining module is configured to determine the pitch angle p.

[0099] The controller 100 comprises at least one power predicting module 106 configured to predict the power generatable by the wind turbine 110 during the future time window based on the determined reference angular speed.

[0100] Furthermore, the controller 100 comprises at least one controlling module 108 configured to control the at least one electrolyzer 114 of the hydrogen production system 150 by setting an at least almost constant rate of change of current during the future time window, wherein the rate of change of current is based on the predicted power.

[0101] Further, Tgis torque for control and pitch angle p of the rotor blades and regulates angular speed cor, wherein mechanical power = cor x Tg(equation (d) ) . Torque may implicitly be controlled by the controller 100. Normally, only speed of a wind turbine may be controlled via pitch p respectively pitch angle p to deliver the needed power. Torque can be calculated by the aforementioned equation (d). In particular, the controller 100 is used both for controlling the at least one wind turbine 110 with respect to the generated power and for controlling the power demand of the at least one electrolyzer 114. Hereby, a constant rate of change of the current density of the electrolyzer cells can be achieved. In particular, said rate of change is smoothened.

[0102] The functioning, in particular, of the controller will be described in more details with the aid of Figure 2. Figure 2 shows a diagram of an embodiment of the (computer- implemented) method according to the present invention. The method serves for operating a hydrogen production system 150 having at least one wind turbine 110 for supplying the at least one electrolyzer 114 of the hydrogen production system 15 with electrical power.

[0103] In step 201, a determining of a reference angular speed of the wind turbine is performed based on a wind speed parameter predicted for the wind turbine for a future time window.

[0104] In step 203, a regulating of the wind turbine 110 is performed by setting the pitch angle p during respectively for the future time window. In particular, the controller can send the pitch angle to the wind turbine controller which will set the pitch angle of the wind turbine 110 accordingly.

[0105] The pitch angle p is determined based on the determined reference angular speed and the current angular speed of the wind turbine. In particular, the current angular speed of the wind turbine 110 can be fed-back to the controller 100, in particular, for performing an error adjustment. Error adjustment means, in particular, that the pitch angle p will be tuned by the determined reference angular speed if the current angular speed ends up being not of the same value as the determined reference angular speed.

[0106] Furthermore, in step 205, a predicting of power generatable by the wind turbine 110 during the future time window is performed based on the determined reference angular speed. The predicting of the power generatable by the wind turbine 110 may be based on the reference angular speed and a predefined power speed characteristic curve. For instance, the power speed characteristic curve can be stored in a (not shown) data memory of the controller 100 or a computing equipment connected with the controller).

[0107] The power speed characteristic curve may define the relation between the reference angular speed and generatable power of the specific wind turbine 110 operating with said reference angular speed. For instance, the power speed characteristic curve is provided as an assignment table. A power (value) can be assigned to each reference angular speed (value). Based on the determined reference angular speed (value), the power (value) assigned to said determined reference angular speed (value) can be determined by the controller 100. As has been described above, the wind turbine 110 is operated with said reference angular speed during said future time window by regulating said wind turbine 110 by setting a respective pitch angle p (see step 203).

[0108] In step 207, a controlling of the at least one electrolyzer 114 of the hydrogen production system 150 is performed by setting an at least almost constant rate of change of current (see also equation (b)) during at least a portion of the future time window. The rate of change of current is based on the predicted power. In particular, the power transfer from the at least one wind turbine 110 to the at least one electrolyzer 114 is controlled such that at least an almost steady ramp rate of power to the at least one electrolyzer 114 is provided. The rate of change of current preferably during the full first time window is kept at least almost constant respectively steady.

[0109] Preferably, the rate of change of current may be (only) changeable for the future time window by a predefined change step. In other words, the rate of change of current is a stepped rate of change of current wherein the step change has a predefined (and fixed) step size. The predefined step size may be between 2% / s and 10 % / s, preferably between 4% / s and 6% / s (e.g., 5% / s). With a step size between 4% / s and 6% / s a sufficiently constant rate of power respectively current to the at least one electrolyzer can be provided (while the computing effort can be reduced). In this way, the probability of unutilized wind energy can be minimized while ensuring minimal fluctuation since the electrolyzer load can be effectively controlled to respond to forecasted respectively predicted wind speeds.

[0110] It is noted that the described steps can be at least partly performed in parallel to each other.

[0111] In a preferred embodiment, prior to step 207, it can be checked in an optional (not shown) step whether the predicted power satisfies a predefined power criterion. The predefined power criterion can be stored in the (not shown) data memory.

[0112] Step 207 may only be performed if the predicted power criterion is not satisfied, e.g., the predicted power does not lie within the predefined power range. In a further (not shown) optional step of the method, a controlling of the at least one electrolyzer 114 can be performed such that the current density is kept at least almost constant if the predicted power criterion is satisfied. Controlling of the at least one electrolyzer 114 such that the current density is kept at least almost constant may depend on the predicted power. Keeping the current density at least almost constant means, in particular, that there is no rate of change of current during the future time window or from a current time window to a subsequent time window. Controlling the at least one electrolyzer 114 such that the current density is kept constant may preferably comprise adapting the cell voltage of the electrolyzer 114 such that the current density is kept constant, in particular, depending on the predicted power.

[0113] For instance, an optimal current density for the cell membrane of an electrolyzer 114 may be in the range of e.g., 2 A / cm2at e.g., cell voltage between 1.5 V and 2 V. To keep the current density at the predefined optimal current density (value), e.g., 2 A / cm2, in particular, under declining wind speeds, it is proposed that if the predefined power criterion is met (e.g., if the predicted power is in the range of 75 % of rated power to 100% rated power), the controller 100 may control the at least electrolyzer 114 such that the current density is kept constant (typically at rated maximum), in particular, by varying the cell voltage within the predefined optimal voltage range, e.g., between 1.5 V and 2 V, such that the current density (value) remains constant. In particular, this is possible up until the predefined minimum rated cell voltage of e.g., 1.5 V is reached. The predefined minimum rated cell voltage may be reached at 75% of rated power.

[0114] If the power criterion is not satisfied, in particular, if the predicted power is in the region below 75% of rated power since changes in wind power may be inconsistent, it follows that changes in current drawn by the at least one electrolyzer 114 and consequently, current density would be inconsistent and abrupt, thus, leading the cell membranes to degradations due to the fluctuations. If the predicted power criterion is not satisfied, a controlling of the at least one electrolyzer 114 of the hydrogen production system 150 can be performed according to step 207.

[0115] Figure 3 shows a diagram of an exemplified course of the cell voltage V at an electrolyzer (e.g., electrolyzer 114) and an exemplified course of a current density la at said electrolyzer. P (%) means the rated power.

[0116] As can be seen from Figure 3, if the power criterion is satisfied (in the present example, if the predicted power is in the power range of 75 % of rated power to 100% of rated power), the current density la can be kept constant at the predefined optimal current density of e.g., 2 A / cm2by varying the voltage V (in particular, by ramping down respectively ramping up the voltage V).

[0117] As can be further seen from Figure 3, if the power criterion is not satisfied (in the present example, if the predicted power is outside the power range of 75 % of rated power to 100% of rated power), the current density la must be reduced. According to the invention, this is performed in an at least almost constant manner, as described hereinbefore. In particular, this means that the gradient of Id is constant, as can be directly seen from Figure 3.

[0118] Figure 4 shows a schematic view of a further embodiment of the hydrogen production system 450 according to the present invention. In order to avoid repetitions, in the following only the differences between the embodiment of Figure 1 and the embodiment of Figure 4 are essentially described. With regard to the other elements of the hydrogen production system 450 it is essentially referred to the previous embodiment. In particular, only in favour of a better overview, the details of the controller 400 are not shown in Figure 4. The controller 400 can, in particular, be formed as described in Figure 1.

[0119] The hydrogen production system 450 comprises at least one wind turbine 410, at least one controller 400 and preferably at least one wind measurement device 412.

[0120] The wind turbine 410 comprises a power generating unit 422. The power generating unit 422, e.g., arranged in a nacelle of the wind turbine 422, may comprise a generator, switches, power converters, a wind turbine controller 420 and the like. The wind turbine controller 420 may be communicatively connected at least to the controller 400 via a (wired and / or wireless) data network 442. In particular, the pitch angle can be send by the controller 400 to the wind turbine controller 420 via the data network 442.

[0121] The depicted hydrogen production system 450 comprises at least one hydrogen production plant 444 (also denoted as electrolyzer unit) having at least one electrolyzer 414. The electrolyzer 414 or a stack of electrolyzers 414 may be configured to produce hydrogen at e.g., 30 bar. The at least one electrolyzer 414 may be arranged outside the wind turbine 410, for instance, in a housing on a (not shown) main access platform. The hydrogen production plant 444 may further comprise at least one electrolyzer power supply 424. The electrolyzer power supply 424 may comprise power converters, switches, an electrolyzer power supply converter 426 and the like. The electrolyzer power supply 424 may be configured to supply the at least one electrolyzer 414 and further hydrogen processing modules 430, water treatment modules 432 of the hydrogen production plant 444 via power lines respectively power cables 440. The electrolyzer power supply controller 426 may be communicatively connected at least to the controller 400 via a (wired and / or wireless) data network 442. The at least one electrolyzer power supply 424 may be arranged outside the wind turbine 410, for instance, in a housing on the main access platform.

[0122] The electrolyzer plant 444 may comprise at least one (hydrogen) processing module 430 respectively (hydrogen) finishing module, e.g., arranged on a main access platform. The processing module may be configured to process the produced (wet) hydrogen.

[0123] The at least one hydrogen processing module can comprise at least one (not shown) hydrogen drying module. The hydrogen drying module can be configured to dry the generated wet hydrogen. Preferably, the hydrogen drying module (after separation of the liquid phase) can be an adsorption drying module (in particular a TSA (temperature swing adsorption) module) and / or a refrigeration drying module. The adsorption drying module may be in particular configured to dry the wet hydrogen by adsorption using a (suitable) adsorber, in particular silica beads. The at least one hydrogen drying module can be configured to cool the wet hydrogen to a temperature of at least less than 5°C. Furthermore, the at least one hydrogen processing module can comprise a (not shown) catalytic deoxo stage, in particular, for treating the wet hydrogen before drying as described above. Such a stage serves to remove oxygen (<0.5%). In variants of the invention, such treatment can also take place at a later stage, for example, at a hydrogen destination structure to which the treated hydrogen can be transported, for example, via a hydrogen pipeline network. Preferably additionally, the at least one hydrogen processing module 430 may comprise at least one hydrogen compression module 430. The hydrogen compression module 430 may be configured to compress the (processed) hydrogen, in particular, the dried hydrogen. The hydrogen compression module 430 may comprise at least one hydrogen compressor (in particular a (vertical) piston compressor). The hydrogen compression module 430 can be configured to compress the dried hydrogen to at least 50 barg (and for example at most 250 barg), preferably to essentially 70 barg.

[0124] As can be seen from Figure 4, the hydrogen compression module 430 may comprise at least one hydrogen compression controller 434. The hydrogen compression controller 434 may be communicatively connected at least to the hydrogen controller 428 via the data network 442. The at least one hydrogen compression module 430 may be arranged outside the wind turbine 410, for instance, in a housing on the main access platform.

[0125] In further variants of the invention, the at least one hydrogen processing module may comprise at least one (not shown) transforming module configured to transform the produced hydrogen to ammonia (e.g., via the Haber-Bosch-method or the like).

[0126] The at least one electrolyzer plant 444 may comprise at least one water treatment module 432, e.g., arranged in a housing on the main access platform. The at least one water treatment module 432 can be configured to treat the water such that it can be used by the at least one electrolyzer 414 to produce hydrogen. In particular, the water treatment module 432 can treat seawater for the electrolysis process. Preferably, the at least one water treatment module 432 can be a seawater desalination module with membrane-based pressure filtration. Such a seawater desalination module can carry out reverse osmosis, ultrafiltration and / or electrodialysis (also known as electrodeionization (EDI)) to treat the water respectively to treat the seawater accordingly. Such treatment can be used to treat seawater, in particular in an energy- efficient manner, which can be used for water electrolysis. The treated water can also be referred to as ultrapure water or "demin water". The treated water can be fed to the electrolyzer module 414 via at least one fluid pipe of a (not shown) internal fluid network.

[0127] Alternatively or additionally, the at least one electrolyzer plant 444 may comprise at least one (not shown) inert gas generation module configured to generate an inert gas.

[0128] As can be further seen from Figure 4, the hydrogen production system 450 comprises at least one auxiliary device 438, in particular, a plurality of auxiliary devices 438. Exemplified and non-exhaustive examples of auxiliary devices 438 are hydraulics, pumps, heaters etc. for lubrication, cooling, climate conditioning and so on.

[0129] Figure 5 shows a schematic view of a further embodiment of the hydrogen production system 550 according to the present invention. As can be seen, the embodiment of Figure 5 is similar to the embodiment of Figure 4. The main difference between Figure 4 and Figure 5 can be found in the design of the power generation unit 522 and the electrolyzer power supply 524.

[0130] In particular, only in favour of a better overview, the details of the controller 500 are not shown. The controller 500 can, in particular, be formed as in Figure 1 or 4.

[0131] The hydrogen production system 550 comprises at least one wind turbine 510, at least one controller 500 and preferably at least one wind measurement device 512.

[0132] The wind turbine 510 comprises a power generating unit 522. The power generating unit 522, e.g., arranged in a nacelle of the wind turbine 510, may comprise a generator, a switch, a power converter, and a wind turbine controller 520. The wind turbine controller 520 may be communicatively connected at least to the controller 500 via a (wired and / or wireless) data network 542, at least for receiving the pitch angle from the controller 500. The depicted hydrogen production system 550 comprises at least one hydrogen production plant 544 having at least one electrolyzer 514. The electrolyzer 514 or a stack of electrolyzers 514 may be configured to produce hydrogen at e.g., 30 bar. The at least one electrolyzer 514 may be arranged outside the wind turbine 510, for instance, in a housing on a (not shown) main access platform.

[0133] The hydrogen production plant 544 may further comprise at least one electrolyzer power supply 524. The electrolyzer power supply 524 may comprise a power converter, switches, and an electrolyzer power supply converter 526. The electrolyzer power supply 524 is configured to supply the at least one electrolyzer 514 and further hydrogen processing modules 530, a water treatment module 532 as well as at least one auxiliary device 538 via power lines respectively power cables 540.

[0134] The electrolyzer power supply controller 526 may be communicatively connected at least to the controller 400 via the data network 542. The at least one electrolyzer power supply 524 may be arranged outside the wind turbine 510, for instance, in a housing on the main access platform.

[0135] The electrolyzer plant 544 may comprise at least one (hydrogen) processing module 530 respectively (hydrogen) finishing module, e.g., arranged on a main access platform. The processing module may be configured to process the produced (wet) hydrogen. The at least one hydrogen processing module can comprise at least one (not shown) hydrogen drying module, as described hereinbefore.

[0136] Preferably additionally, the at least one hydrogen processing module may comprise at least one hydrogen compression module 530. The hydrogen compression module 530 may be configured to compress the processed hydrogen, in particular the dried hydrogen, as descried hereinbefore. The hydrogen compression module 530 may comprise at least one hydrogen compression controller 534. The hydrogen compression controller 534 may be communicatively connected at least to the hydrogen controller 528 via the data network 542. The at least one hydrogen compression module 530 may be arranged outside the wind turbine 510, for instance, in a housing on the main access platform.

[0137] In further variants of the invention, the at least one hydrogen processing module may comprise at least one (not shown) transforming module configured to transform the produced hydrogen to ammonia (e.g., via the Haber-Bosch-method or the like).

[0138] The at least one electrolyzer plant 544 may comprise at least one water treatment module 532, e.g., arranged in a housing on the main access platform, in particular, as described hereinbefore. The water treatment module 532 comprises at least one water treatment controller 536. The water treatment controller 536 may be communicatively connected at least to the hydrogen controller 528 via the data network 542.

[0139] Alternatively or additionally, the at least one electrolyzer plant 544 may comprise at least one (not shown) inert gas generation module configured to generate an inert gas.

[0140] The hydrogen production system 550 comprises at least one auxiliary device 538, in particular, a plurality of auxiliary devices 538, as in particular previously described.

[0141] Figure 6 shows a schematic view of a further embodiment of the hydrogen production 650 system according to the present invention. As can be seen, the embodiment of Figure 6 is similar to the embodiments of Figure 4 and 5. The main difference between Figure 6 and Figure 4 respectively 5 is that there are a plurality of wind turbines 61O.n and a plurality of electrolyzers 614, in particular, of a plurality of hydrogen production plants 644.1, 644.n.

[0142] In particular, only in favour of a better overview, the details of the controller 600 are not shown. The controller 600 can, in particular, be formed as in Figure 1, 4 or 5. The hydrogen production system 650 comprises a plurality of wind turbines 61O.n. In particular, the hydrogen production system 650 may comprise at least one string with a plurality of wind turbines 61O.n, preferably a plurality of strings, wherein each string may comprise a plurality of wind turbines 610. n.

[0143] The plurality of wind turbines 61O.n, in particular, the one or more strings, may be electrically connected to a substation 654 of the hydrogen production system 650 via at least one power cable.

[0144] The depicted substation 654 comprises a (middle voltage) collector bus system 656 configured to electrically connect the one or more strings (e.g., between two and twelve) of (offshore) wind turbines 61O.n. Each string may comprise a plurality of offshore wind turbines 61O.n (e.g., between four and twelve).

[0145] Furthermore, the depicted substation 654 may have one or more electrical outputs. An exemplified first output may be configured to supply the at least one electrolyzer plant 644.1, 644.n with electrical energy. An exemplified second output may be configured to connect the substation 654 respectively the offshore wind farm of the hydrogen production system 650 with an external grid 662 via an electrical connection. It shall be understood that a (not shown) onshore substation may be provided. A third output may connect the substation 654 via a connection 658 to at least one (not shown) auxiliary device of the hydrogen production system 650.

[0146] The hydrogen production system 650 comprises at least one controller 600, preferably a plurality of controllers 600.n, and preferably at least one (not shown) wind measurement device. Each wind turbine 610. n comprises a (not shown) power generating unit, as in particular described hereinbefore.

[0147] Further, the hydrogen production system 650 may comprise at least one central controller 652, in particular, in the form of a wind farm controller of the wind farm of the hydrogen production system 650. By means of a data network 642, the at least one controller 600.n may be communicatively connected to the central controller 652.

[0148] The depicted hydrogen production system 650 may comprise two or more hydrogen production plants 644.1, 644.n each having at least one electrolyzer 614. The respective electrolyzer 614 or the respective stack of electrolyzers 614 may be configured to produce hydrogen at e.g., 30 bar. The respective electrolyzer 614 may be arranged outside the wind turbines 61O.n, for instance, in a housing on a central or semi-central platform.

[0149] Each hydrogen production plant 644.1, 644.n (in favor of a better overview, only one hydrogen production plant 644.1 is depicted in more details) may further comprise at least one electrolyzer power supply 624. Each electrolyzer power supply 624 may comprise a power converter, switches, and an electrolyzer power supply converter 626.

[0150] A respective electrolyzer power supply 624 is configured to supply the at least one respective electrolyzer 614 and further hydrogen processing modules 630, water treatment modules 632 as well as at least one auxiliary device 638 of the respective electrolyzer power supply 624 via power lines respectively power cables 640. It shall be understood that there may also be at least one central further hydrogen processing module for a plurality of electrolyzers and / or electrolyzer power plant, such as a central water treatment module.

[0151] Each electrolyzer power supply controller 626 may be communicatively connected at least to the central controller 652 via the data network 642. The respective electrolyzer power supply 624 may be arranged outside the wind turbines 610. n, for instance, in a housing on the central or semi-central platform.

[0152] Each electrolyzer plant 644., 644.n may comprise at least one (hydrogen) processing module respectively (hydrogen) finishing module, e.g., arranged on the central or semi-central platform. The processing module may be configured to process the produced (wet) hydrogen. The respective hydrogen processing module can comprise at least one (not shown) hydrogen drying module, as described hereinbefore.

[0153] Preferably additionally, a hydrogen processing module may comprise at least one hydrogen compression module 630. A hydrogen compression module 630 may be configured to compress the processed hydrogen, in particular the dried hydrogen, as descried hereinbefore. A hydrogen compression module 630 may comprise at least one hydrogen compression controller 634. The hydrogen compression controller 634 may be communicatively connected at least to the hydrogen controller 628 and the central controller 652 via the data network 642.

[0154] In further variants of the invention, the hydrogen processing modules may comprise at least one (not shown) transforming module configured to transform the produced hydrogen to ammonia (e.g., via the Haber-Bosch-method or the like).

[0155] Each electrolyzer plant 644.1, 644.n may comprise at least one water treatment module 632, e.g., arranged on the central or semi-central platform, in particular, as described hereinbefore. Each water treatment module 632 comprises at least one water treatment controller 636. The water treatment controller 636 may be communicatively connected at least to the hydrogen controller 628 and to the central controller 652 via the data network 642.

[0156] Alternatively or additionally, each electrolyzer plant 644.1, 644.n may comprise at least one (not shown) inert gas generation module configured to generate an inert gas.

[0157] The hydrogen production system 650 comprises at least one auxiliary device 638, in particular, a plurality of auxiliary devices 638, as in particular previously described.

[0158] The operation of the hydrogen production system 650 (or a similar system) will be described hereinafter with the aid of Figure 7. Figure 7 shows a diagram, in particular, a flowchart, of an embodiment of the method according to the present invention. The method of Figure 7 can, in particular, be combined with the method of Figure 2.

[0159] In these systems 650, as shown in figure 6, where the wind turbines 61O.n are connected to an electrical bus on the substation 654 via one or more strings of medium or high voltage power cables 642, each individual wind turbine 610. n in the cable array network retains its independence in energy production by the means of the aforementioned forewarning speed prediction of the decentral system, in particular, based on the respective controllers 600. n. However, power transfer between the hydrogen power plants 644.1, 644.n on the central or semi-central platform and the wind turbines 610. n via e.g., a MV (middle voltage) bus may be centrally coordinated via explicit communication among the controllers 600.n, the central controller 652, the electrolyzer controllers 628 and / or the (not shown) wind turbine controllers such that the rate of change of current densities in the electrolyzers, driven by di / dtref, is maintained.

[0160] After starting the method, in step 701, the central controller 652 initializes the index i as per equation (c) to determine k. In particular, in order to ensure optimal energy utilisation at all times, the number of electrolyzers 614.n and wind turbines 61O.n in operation may be determined by means of the central controller 652. Preferably, at all times, the central controller can determine all operable elements in the system, i.e., active, not faulty wind turbines and electrolyzer units / stacks.

[0161] In particular, in step 703 an obtaining may be performed, by means of an (explicit) communication of the central controller 652 with those of the wind turbines 61O.n in the array network: i.) the value of n for the window length 8 for each j to determine Uj and ii.) the corresponding di / dtreffor each k.

[0162] In step 705, an initiating is performed of a check to ensure equal power allocation: is k and j still the same as at start? If no, it is returned to step 701. If yes, the method can be continued with step 707. In particular, the power transfer may be initiated using an equal allocation of system input power made available on the bus collector 656 of the substation 654 by the wind turbines 61O.n according to equation (c). As already described, k is the number of operational electrolyzers 614 (respectively hydrogen production plants 644., 644.n] and n is the active power available for the window length {W, }5^ ^and j is the number of active wind turbines 61O.n in the array network and the hydrogen production system 650, respectively.

[0163] In step 707, the central controller 652 may relay Uj and di / dtrefto each controller of k, and in step 709, for each of k, load control is implemented by the respective electrolyzer power supply units 624 according to di / dtref. The central controller 652 may send power allocation signals di / dtrefto the electrolyzer controllers 628 in realtime, which is harmonized with available n; on the AC power bus 640 of each hydrogen production plant 644.1, 644.n over the window length 8. In this way of explicit, coordinated communication, the need to abruptly modify the electrolyzer load may be avoided since di / dtrefis allocated according to the power projected to be available on the AC power bus 640 and the number of operable electrolyzer 614.

Claims

C l a i m s1. A method for operating a hydrogen production system (150, 450, 550, 650) having at least one wind turbine (110, 410, 510, 610) for supplying at least one electrolyzer (114, 414, 514, 614) of the hydrogen production system (150, 450, 550, 650) with electrical power, comprising: determining a reference angular speed of the wind turbine (110, 410, 510, 610) based on at least one wind speed parameter predicted for the wind turbine (110, 410, 510, 610) for a future time window, regulating the wind turbine by setting a pitch angle during the future time window, wherein the pitch angle is determined based on the determined reference angular speed and the current angular speed of the wind turbine (110, 410, 510, 610), predicting power generatable by the wind turbine (110, 410, 510, 610) during the future time window based on the determined reference angular speed, controlling the at least one electrolyzer (114, 414, 514, 614) of the hydrogen production system (150, 450, 550, 650) by setting an at least almost constant rate of change of current during at least a portion of the future time window, wherein the rate of change of current is based on the predicted power.

2. The method according to claim 1, wherein the at least one electrolyzer (114, 414, 514, 614) is a PEM electrolyzer.

3. The method according to claim 1 or 2, wherein the at least one predicted wind speed parameter is a predicted wind speed and / or wind direction at the wind turbine (110, 410, 510, 610), and wherein the at least one predicted wind speed parameter is based on a wind measuring, in particular, conducted by a LIDAR equipment.

4. The method according to any of the preceding claims, wherein the future time window has a time length between 1 s and 120 s, preferably between 20 s and 50 s.

5. The method according to any of the preceding claims, wherein the rate of change of current is a stepped rate of change of current with a predefined step size.

6. The method according to claim 5, wherein the predefined step size is between 2% / s and 10 % / s, preferably between 4% / s and 6% / s (e.g., 5% / s).

7. The method according to any of the preceding claims, further comprising: providing a predefined power speed characteristic curve, and wherein the predicting of power generatable by the wind turbine (110, 410, 510, 610) during the future time window is based on the reference angular speed and the predefined power speed characteristic curve.

8. The method according to any of the preceding claims, further comprising: determining whether the predicted power satisfies a predefined power criterion, and controlling the at least one electrolyzer (114, 414, 514, 614) of the hydrogen production system (150, 450, 550, 650) by the at least almost constant rate of change of current during the future time window only if the predicted power criterion is not satisfied.

9. The method according to claim 8, further comprising: controlling the at least one electrolyzer (114, 414, 514, 614) such that the current density is kept at least almost constant if the predicted power criterion is satisfied.

10. The method according to claim 9, wherein controlling the at least one electrolyzer (114, 414, 514, 614) such that the current density is kept constant comprises adapting the cell voltage of the electrolyzer (114, 414, 514, 614) such that the current density is kept constant.

11. The method according to any of the preceding claims 8 to 10, wherein the power criterion comprises at least one predefined power range.

12. The method according to claim 11, wherein wherein the at least one predefined power range is between 75 % of the rated power of the wind turbine (110, 410, 510, 610) and 100 % of the rated power of the wind turbine (110, 410, 510, 610).

13. The method according to any of the preceding claims, wherein the hydrogen production system (150, 450, 550, 650) comprises a plurality of wind turbines (110, 410, 510, 610) for supplying the at least one electrolyzer (114, 414, 514, 614) with electrical power, wherein the controlling of the at least one electrolyzer (114, 414, 514, 614) of the hydrogen production system (150, 450, 550, 650) comprises centrally coordinating the power transfer from the plurality of wind turbines (110, 410, 510, 610) to the electrolyzer (114, 414, 514, 614) such that the rate of change of current is kept at least almost constant.

14. The method according to any of the preceding claims, wherein the hydrogen production system (150, 450, 550, 650) comprises a plurality of electrolyzers (114, 414, 514, 614), wherein the controlling of the plurality of electrolyzers (114, 414, 514, 614) of the hydrogen production system (150, 450, 550, 650) comprises centrally coordinating the power transfer from the at least one wind turbine (110, 410, 510, 610) to the plurality of electrolyzers (114, 414, 514, 614) such that the rateof change of current is kept at least almost constant for each of the plurality of electrolyzers (114, 414, 514, 614).

15. A controller (100, 400, 500, 600) for a hydrogen production system (150, 450, 550, 650) having at least one wind turbine (110, 410, 510, 610) for supplying at least one electrolyzer (114, 414, 514, 614) of the hydrogen production system (150, 450, 550, 650) with electrical power, comprising: at least one determining module (102) configured to determine a reference angular speed of the wind turbine (110, 410, 510, 610) based on at least one predicted wind speed parameter for the wind turbine (110, 410, 510, 610) for a future time window, at least one regulating module (104) configured to regulate the wind turbine (110, 410, 510, 610) by setting a pitch angle during the future time window, wherein the pitch angle is determined based on the determined reference angular speed and the current angular speed of the wind turbine (110, 410, 510, 610), at least one power predicting module (106) configured to predict power generatable by the wind turbine (110, 410, 510, 610) during the future time window based on the reference angular speed, and at least one controlling module (108) configured to control the at least one electrolyzer (114, 414, 514, 614) of the hydrogen production system (150, 450, 550, 650) by setting an at least almost constant rate of change of current during at least a portion of the future time window, wherein the rate of change of current is based on the predicted power.

16. A hydrogen production system (150, 450, 550, 650), comprising: at least one hydrogen production plant (444, 544, 644) having the at least one electrolyzer (114, 414, 514, 614), at least one wind turbine (110, 410, 510, 610) configured to supply at least the at least one electrolyzer (114, 414, 514, 614) with electrical power, and at least one controller (100, 400, 500, 600) according to claim 15.

17. The hydrogen production system (150, 450, 550, 650) according to claim 16, further comprising at least one wind measurement device (112, 412, 512) configured to measure at least the wind speed and / or wind direction at the wind turbine (110, 410, 510,610),18. The hydrogen production system (150, 450, 550, 650) according to claim 17, wherein - the wind measurement device (112, 412, 512) comprises at least one LIDAR equipment.

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