Electrolyzer device, electrolyzer and method for operating the electrolyzer device

Abstract

The invention relates to an electrolyzer device (32a-f) with at least one first electrolysis cell (10a-f), with at least one second electrolysis cell (12a-f), and with at least one main power supply (14a-f) which is at least intended to supply the first electrolysis cell (10a-f) and the second electrolysis cell (12a-f) together with electrical energy, in particular electrolysis energy. It is proposed that the electrolyzer device (32a-f) comprises at least one first auxiliary power supply (16a-f) assigned to the first electrolysis cell (10a-f) and at least one second auxiliary power supply (18a-f) assigned to the second electrolysis cell (12a-f), wherein the auxiliary power supplies (16a-f, 18a-f) are designed to balance the electrolysis cells (10a-f, 12a-f) relative to each other by electrically unloading and / or electrically supplying the respective electrolysis cell (10a-f, 12a-f).

Description

State of the art

[0001] The invention relates to an electrolyzer device according to the preamble of claim 1, an electrolyzer according to claim 15 and a method according to the preamble of claim 16.

[0002] An electrolyzer device has already been proposed, comprising at least one first electrolysis cell, at least one second electrolysis cell, and at least one main power supply, which is designed to supply both the first and second electrolysis cells with electrical energy. Since electrolysis cells in stacks are never absolutely identical, for example due to manufacturing tolerances, they can exhibit different cell voltages during operation at the same current level.This can result in negative effects regarding the overall aging of all electrolysis cells in the combined operation of the electrolysis cell stack, especially since a "worse" electrolysis cell, which has a higher voltage at the same current level compared to a "better" electrolysis cell, consumes more power than the "better" electrolysis cell and thus, at the same current level, the "worse" electrolysis cell ages faster than the "better" electrolysis cell.On the other hand, negative effects can also result with regard to the overall performance of all electrolysis cells in the combined operation of the electrolysis cell stack, especially since the operation of the "better" electrolysis cells must be restricted if the "worse" cell would reach too high a voltage due to the equally high current, and thus a maximum possible power in a series connection of electrolysis cells would be limited by the weakest link, i.e. the "worst" electrolysis cell of the electrolysis cell stack.

[0003] The object of the invention is, in particular, to provide a generic device with advantageous properties for the operation of electrolyzers, especially by eliminating the disadvantages of the prior art. This object is achieved according to the invention by the features of claims 1, 15 and 16, while advantageous embodiments and further developments of the invention can be found in the dependent claims. Advantages of the invention

[0004] The invention relates to an electrolyzer device, for example a proton exchange membrane electrolyzer device, an electrolyzer device with cells for alkaline electrolysis or another electrolyzer device comprising other electrochemical cells, with at least one first electrolysis cell, for example a proton exchange membrane electrolysis cell, an electrolysis cell for alkaline electrolysis or an electrolysis cell based on another operating principle, with at least one second electrolysis cell, for example a proton exchange membrane electrolysis cell, an electrolysis cell for alkaline electrolysis or an electrolysis cell based on another operating principle, and with at least one main power supply unit, which is at least intended to supply the first electrolysis cell and the second electrolysis cell together with electrical energy, in particular electrolysis energy.

[0005] It is proposed that the electrolyzer device comprise at least one first auxiliary power supply, assigned to at least the first electrolysis cell, and at least one second auxiliary power supply, assigned to at least the second electrolysis cell. The auxiliary power supplies are designed to balance the electrolysis cells by, in particular, independently discharging and / or supplying the respective electrolysis cells. This advantageously improves the service life of electrolyzers. It also advantageously evens out the aging of different electrolysis cells within the electrolyzer or at least within a cell cluster (stack) of the electrolyzer. Furthermore, it advantageously improves the overall efficiency of all electrolysis cells in an electrolysis cell stack or in an electrolyzer.It is advantageous to enable the operation of the electrolyzer in which at least one electrolysis cell can reach the end of its life at a desired time, e.g. together with at least one neighboring electrolysis cell of a cell cluster (stack) of an electrolyzer or together with all other electrolysis cells of an electrolyzer or at least of a cell cluster (stack) in the electrolyzer.

[0006] Furthermore, the auxiliary power supplies can advantageously enable highly precise minimum production (in the watt range). They can also advantageously allow for targeted control over the aging of specific electrolysis cells or cell stacks (keyword: timely stack replacement). Additionally, a system can be kept running despite a malfunction, such as a partially defective electrolysis cell. Moreover, the auxiliary power supplies could be used to power peripheral components of an electrolyzer system, allowing the electrolyzer system to be operated solely via the DC power supply of the cell stacks or the electrolyzer itself (keyword: power-to-home).

[0007] The term "electrolyzer device" shall be understood to mean, in particular, at least a part of a device and / or machine, especially an electrolyzer, designed to carry out at least one electrolysis step, particularly of water. In particular, the electrolyzer device may also comprise the entire device and / or machine, especially the entire electrolyzer. The term "electrolysis cell" shall be understood to mean, in particular, a functional unit by means of which at least one electrochemical electrolysis reaction can be carried out. In particular, the electrolysis cell may form a cell-stack compatible electrolysis cell, in particular of an electrolysis cell stack. Advantageously, the electrolysis cell comprises at least one anode at which oxygen is preferably formed under normal operating conditions.Preferably, the electrolysis cell comprises at least one cathode, at which hydrogen is preferably formed during normal operation. Advantageously, the electrolysis cell comprises at least one membrane, in particular an advantageously selective proton-conducting membrane, preferably a polymer electrolyte membrane. Particularly preferably, the anode and the cathode are separated from each other at least by the membrane. In particular, the anode and / or the cathode is planar and / or layered and / or a layer and / or coating. Preferably, the membrane is at least partially, and particularly preferably at least predominantly, made of Nafion. Preferably, the electrolysis cell comprises at least one functional element, in particular a bipolar element, preferably a bipolar plate.In particular, a first side of the bipolar element forms an anode side of the electrolysis cell, and in particular, a second side of the bipolar element forms a cathode side of an immediately adjacent electrolysis cell. In particular, the first electrolysis cell and / or the second electrolysis cell can be configured as described in this context. In particular, at least some, advantageously at least a large proportion, and especially advantageously all electrolysis cells of the electrolyzer device are configured at least substantially identically and / or of the same and / or an analogous design.In this context, "at least essentially identical" objects are to be understood in particular as objects that are constructed in such a way that they can each fulfill a common function and that, apart from manufacturing tolerances, differ in their construction at most by individual elements that are inessential for the common function, and advantageously as objects that are identically designed apart from manufacturing tolerances and / or within the scope of manufacturing possibilities, whereby identical objects are to be understood in particular as objects that are symmetrical to each other.

[0008] Preferably, the electrolyzer device comprises a plurality, preferably a multiplicity, of electrochemical cells, in particular those that are at least substantially identical. In particular, the first electrolysis cell and / or the second electrolysis cell can each be any electrochemical cell of an electrolysis cell stack, especially one located at the edge or centrally, where the terms "first" and "second" are not necessarily to be understood as describing a sequence and / or arrangement, but only as a possible option. In particular, it is conceivable that the first electrolysis cell and / or the second electrolysis cell are arranged, in particular, directly adjacent to, or not adjacent to, the cells.Furthermore, it is conceivable that features described with respect to the first and second electrolysis cells apply to at least a large proportion and / or to all electrolysis cells of the electrolysis cell stack or the electrolyzer. Advantageously, the electrolysis device comprises at least one electrolysis cell stack, in particular an electrolysis stack comprising a plurality, preferably a multiplicity, of stacked electrolysis cells. Preferably, the electrolysis cell stack comprises at least the first electrolysis cell and / or the second electrolysis cell.Preferably, the electrolysis cell stack comprises repeating units that include several different functional elements, advantageously different functional electrolysis cell stack elements, for example, particularly in the specified order, at least one bipolar plate and / or at least one perforated sheet and / or perforated sheet or the like, and / or at least one gas diffusion layer, in particular an oxygen diffusion layer, advantageously a titanium felt and / or a membrane, advantageously a polymer electrolyte membrane, and / or another gas diffusion layer, in particular a hydrogen diffusion layer, advantageously a carbon felt, and / or a compression buffer, in particular a compression pad, advantageously an expanded metal, comprising in particular another perforated sheet and / or perforated sheet. In particular, each electrolysis cell extends from one bipolar plate to the next bipolar plate.The electrolysis cell stack can comprise any number of electrochemical cells, for example, ten, 20, 30, 50, 100, 150, 200, or more, fewer, or any number in between. Advantageously, the electrolysis device has exactly one electrolysis cell stack. However, it is also conceivable that the electrolysis device comprises several electrolysis cell stacks, in particular those that are at least substantially identical or differently configured, at least some of which can be electrically and / or hydraulically connected in series. Advantageously, the first electrolysis cell and the second electrolysis cell are arranged in a common electrolysis cell stack. However, it is also conceivable that the first electrolysis cell and the second electrolysis cell are arranged in different cell stacks.

[0009] In particular, the main power supply is designed to supply at least the electrolysis cells of the electrolysis cell stack, preferably electrolysis cells of several electrolysis cell stacks, simultaneously and / or jointly with current and / or voltage. The electrolysis energy is intended for use in the electrolysis process, especially in the splitting of water. "Intended" is understood to mean specifically programmed, designed, and / or equipped. The phrase "intended for a specific function" is understood to mean that the object fulfills and / or performs this specific function in at least one application and / or operating state.

[0010] The electrolysis cell stack, in particular a PEM cell stack, consists especially of many individual electrolysis cells, which are preferably connected electrically in series. Several electrolysis cell stacks, especially PEM cell stacks, can be connected electrically in series in the electrolyzer to form series of electrolysis cell stacks. Several series of electrolysis cell stacks can also be connected electrically in parallel in the electrolyzer. Preferably, a measuring system is used for each electrolysis cell stack, which, for example, monitors the voltage of the individual electrolysis cells. A defect in a single electrolysis cell leads to the failure of the entire electrolysis cell stack. Consequently, an electrolysis cell stack is only as good as its weakest individual electrolysis cell (PEM cell).Electrolysis cell stack failures can occur due to various factors, including mechanical damage, leaks, excessively high electrolysis cell voltages, excessively low or high electrolysis cell operating temperatures, or excessively rapid load changes. However, the most significant contributing factor is that manufacturing tolerances and aging of the electrolysis cells can lead to voltage differences even at the same current. To achieve a suitably long service life and / or to enable continued use in an electrolysis cell stack cascade even after replacing an older stack with a new one, the voltage levels of all electrolysis cells must be kept as uniform as possible. Maintaining consistent voltage levels across all electrolysis cells within a stack can be effectively achieved through precise balancing of the electrolysis cells.The balancing process advantageously reduces the load on "poor" cells and increases the load on "good" cells. This improves the overall efficiency and brings the end-of-life of all electrolysis cells in the electrolysis cell stack closer together. Consequently, the described measuring system not only ensures the safety of the electrolysis cell stack but can also equalize the cell voltages of the electrolysis cells within the stack.

[0011] It is conceivable that a simulation could be created to test algorithms for balancing the electrolysis cells, capturing every possible state. This would advantageously provide a basis for the automated operation of the electrolysis cell stack with the measurement system. This simulation could also consider all other sensors of the electrolysis cell stack for safety functions. The electrolysis cells in the simulation should be freely configurable, allowing the resulting software functionality to be used for various types of electrolysis cells, in any number per electrolysis cell stack and in any arrangement of electrolysis cell stacks, as well as for defining and detecting various fault conditions.Should a fault occur in or originate from one of the auxiliary power supplies, an effective safety measure can be implemented, particularly if the auxiliary power supplies are bidirectional chargers, e.g., for electric vehicles, which are preferably connected together on the AC side. The bidirectional chargers can advantageously be switched off as soon as their input sides are disconnected from a supply voltage. Thus, the bidirectional chargers could be equipped with contactors on the input side, which are switched by the electrolyzer's control system. This allows for the advantageous implementation of a safety shutdown, e.g., in the event of an emergency stop.

[0012] The auxiliary power supplies are designed to be different from and / or separate from the main power supply. In particular, the electrolyzer device can have more than two auxiliary power supplies. Naturally, the electrolyzer device can comprise more than two electrolysis cells, each with its own associated auxiliary power supply. Preferably, the number of auxiliary power supplies per electrolysis cell stack corresponds to at least an even fraction of all electrolysis cells in the cell stack, or even to the total number of electrolysis cells in the cell stack. It is conceivable that individual auxiliary power supplies are assigned to a substack of electrolysis cells within the electrolysis cell stack containing more than one electrolysis cell, and / or that they balance the substack in relation to other substacks of electrolysis cells within the electrolysis cell stack, also containing more than one electrolysis cell and preferably having the same number of electrolysis cells as the substack."Electrical discharge" refers specifically to the removal of electrical power, particularly from the respective electrolysis cell. "Electrical feed" refers specifically to the addition of electrical power, particularly to the respective electrolysis cell.

[0013] The electrolyzer device, in particular the electrolyzer and / or at least one electrolysis cell stack of the electrolyzer, includes a control unit, e.g., an IC / microcontroller, which controls the balancing of the electrolysis cells, preferably automatically, e.g., the current direction and current levels of the electrical supply and / or discharge. A "control unit" is understood to mean, in particular, a unit with at least one control electronics module. "Control electronics" is understood to mean, in particular, a unit with a processor and a data memory module. In particular, each electrolysis cell stack can have its own control unit, or a common control unit can be provided for a plurality of electrolysis cell stacks of the electrolyzer, preferably for all electrolysis cell stacks of the electrolyzer.In particular, the electrolysis cells each have voltage measurement points at which the cell voltage is measured and monitored. These voltage measurement points can be designed as individual voltage contact elements, as described in German patent application DE 10 2017 108 439 A1, the disclosure of which is hereby incorporated in its entirety into this patent application. In particular, the control and / or regulating units can form at least part of a stack management system for electrolyzers, which is similar in structure to a battery management system for accumulators. Alternatively, however, it is also conceivable that the control and / or regulating units (which are at least similar to battery management systems) are intended for a control system that is independent and / or autonomous, in particular from the control system of the electrolyzer.

[0014] In particular, the auxiliary power supplies each form balancer modules. The balancer modules are designed, preferably automatically, to balance the electrolysis cells relative to each other by supplying and / or discharging them electrically, especially by applying current. Preferably, all balancer modules of an electrolysis cell stack, more preferably of an electrolysis cell stack series, are designed to jointly balance all electrolysis cells of the electrolysis cell stack, preferably of the electrolysis cell stack series, relative to each other, especially by including the associated control and / or regulation units, so that they preferably have at least substantially identical cell voltages during operation.The term "balancing electrolysis cells with respect to each other" refers specifically to ensuring that the balanced electrolysis cells have at least substantially identical cell voltages. To make the electrical discharge and / or electrical supply by the various auxiliary power supplies independent of each other, and / or to prevent a short circuit on one side of the bus, the auxiliary power supplies are preferably designed to be at least electrically isolated from one another.

[0015] If the first and second electrolysis cells are electrically connected in series, and / or if the auxiliary power supplies are designed to adjust the cell voltages of the individual electrolysis cells to each other, particularly to align them, by electrically discharging and / or electrically supplying the respective electrolysis cells, the service life and / or the overall efficiency of electrolyzers can be advantageously improved, especially through the effects already described above. Alternatively, the first and second electrolysis cells could also be electrically connected in parallel. In particular, the cell voltages of the individual electrolysis cells are adjusted to each other such that their time factors, preferably their remaining service lives, are aligned.In addition, the cell voltages could be deliberately kept at different values ​​in order to match the remaining lifespans of "good" and "bad" cells.

[0016] Furthermore, it is proposed that the auxiliary power supplies be designed to extract power from an electrolysis cell with a cell voltage that is higher than a predetermined value by electrically relieving the load. This advantageously allows the cell voltage of a "less efficient" electrolysis cell to be reduced, so that, in particular, the "less efficient" electrolysis cell can be operated below its maximum voltage, thus achieving the highest possible overall power output from all electrolysis cells, e.g., those connected in series or parallel. In particular, this electrical relieving of the primary energy direction corresponds to the balancing function of the electrolyzer device according to the invention. The predetermined value can, for example, be an average value of all cell voltages of the electrolysis cells connected in series, e.g., of the electrolysis cell stack, or an optimal value for the cell voltage of the electrolysis cell (e.g., specific to the electrolysis cell type).For example, a typical value for maximum cell voltages of PEM electrolysis cells could be around 2.5 V. An optimal value for maximum cell voltages of PEM electrolysis cells could be between 1.75 V and 2.2 V, preferably around 2 V. However, other cell voltage values ​​are also conceivable and may depend, in particular, on individual cell characteristics. Preferably, the operation of the auxiliary power supplies / balancer modules should be as independent as possible from the current load of the electrolyzer, the electrolysis cell stack, and / or the main power supply. However, the degree of influence can also increase or decrease with the current electrolysis power, so that a high power output from the main power supply could minimize the benefit of the balancer modules. Preferably, the operation of the auxiliary power supplies / balancer modules should be independent of the primary energy source or sink (the main power supply).The system can operate at full power even though the electrolyzer / electrolysis cell stack is only running at minimum power. However, the electrolyzer / electrolysis cell stack must be at least partially operational (with active peripherals) to balance the electrolysis cells. Therefore, hydrogen is always produced when the voltage applied to an electrolysis cell reaches a certain level – regardless of whether this voltage is supplied by the main power supply or by auxiliary power supplies.

[0017] Additionally, it is proposed that the auxiliary power supplies be designed to supply power to an electrolysis cell with a cell voltage that is relatively low compared to a predetermined value. Advantageously, this can achieve a more uniform service life for the electrolysis cells. In particular, the electrical supply corresponds to the secondary energy direction of the balancing function of the electrolyzer device according to the invention.

[0018] Furthermore, it is proposed that the auxiliary power supplies be designed for active balancing of the electrolysis cells. This allows for the advantageous achievement of high efficiency. Losses and / or waste heat can be kept to a minimum. In particular, with active balancing of the electrolysis cells, the energy extracted from one or more electrolysis cells of the electrolyzer is fed back to other electrolysis cells of the electrolyzer, or even to another electrolyzer or the power grid. In contrast to active balancing of electrolysis cells, an alternative is passive balancing. With passive balancing, for example, a load, e.g., a resistive load, could be operated in parallel as a sink on the electrolysis cell(s) whose cell voltage is too high.This could reduce the current flow through the electrolysis cell(s) and thus lower the cell voltage. For example, in the simplest case of passive balancing, a resistor is connected in parallel to each electrolysis cell using a switch. The switches would then be controlled by digital outputs from a programmable logic controller (PLC), such as the control unit. The amount of power drawn could then be regulated by gradually adding further resistors in parallel to each electrolysis cell. The extracted energy would then be converted into (waste) heat.

[0019] Furthermore, it is proposed that the auxiliary power supplies be designed as bidirectional voltage converters. This enables particularly advantageous balancing of electrolysis cells. The overall efficiency can be advantageously increased and / or the lifetimes of individual electrolysis cells can be influenced as desired, e.g., homogenized if required. If the cell voltage of one or more electrolysis cells is to be reduced, the auxiliary power supplies, designed as bidirectional voltage converters, draw power from these electrolysis cells by operating them in parallel as a load. The absorbed power is preferably fed into an AC supply network.Conversely, auxiliary power supplies deliver a controlled increase in power to the electrolysis cells, which operate at a relatively low voltage. This is achieved by operating them in parallel with the electrolysis cells as a power source, which then draws the necessary power from the AC mains or other auxiliary power supplies currently handling the electrical load. When each electrolysis cell, or multiple electrolysis cells, are connected in series to an auxiliary power supply, they can be operated according to a desired characteristic curve and / or their voltage can be matched to that of another electrolysis cell or a series of other electrolysis cells. In particular, the input and output of each balancer module / auxiliary power supply are galvanically isolated. With active balancing using bidirectional voltage converters to and from a common grid, power can be supplied to and drawn from a single auxiliary power supply.As an alternative to the bidirectional voltage converter to a common network, active balancing can also be implemented using individual isolated voltage converters, unidirectionally to a common network, or using isolated voltage converters, twice unidirectionally (quasi-bidirectionally) to and from a common network.

[0020] In the case of isolated voltage converters connected unidirectionally to a common network, a contactor or relay would be connected to each electrolysis cell, and one (or several in parallel) voltage converter would be connected to each cell, so that it is powered by the respective electrolysis cell. The voltage converter would need to have an input voltage range corresponding to that of the electrolysis cell. The output of the voltage converter could be used as a power source in any configuration, powered by the electrolysis cells / cell arrays. It would need to be designed so that the power supplied by the cells can be absorbed by a load. Alternatively, the load could be adapted accordingly. Depending on the application, this could involve a stable voltage potential or a dynamically changing voltage potential.For example, this could be achieved by using a buffer of capacitors with a nominal voltage of 48 V. DCand downstream (feed-in) inverters, through which the power is fed into the grid. Overloading the voltage converters could be prevented, for example, by regulating the load's power consumption. Switches and current limiting could potentially be omitted if the isolated voltage converter can be actively controlled. Uncontrolled devices are generally inherently power-limiting due to technical limitations. In the case of isolated voltage converters that are connected unidirectionally (quasi-bidirectionally) to and from the common grid in two directions, a similar configuration to the one described above is used, except that in addition to the isolated voltage converters of this type, isolated voltage converters with opposite current flow would also be employed. Thus, these voltage converters would be connected together on the input side.The output of the voltage converter of the previously described design would then simultaneously be the input of the opposite voltage converter. The voltage range of the output of the "incoming" voltage converter would then have to lie within the range of the input of the "outgoing" voltage converter, which would also be the voltage range of the electrolysis cell. In the case of bidirectional voltage converters to and from a common network, one bidirectional voltage converter replaces the two isolated unidirectional voltage converters of the previously described design, which are used in opposite directions. Another alternative to all three cases described above would be active balancing directly from one electrolysis cell to another. However, this would require n. 2 (once unidirectional) or 2n 2(quasi-bidirectional or bidirectional) switches are needed to interconnect all outputs and / or inputs of the voltage converters, where n describes the number of electrolysis cells of the electrolyzer or electrolysis cell stack.

[0021] If the bidirectional voltage converter is designed as a conventional bidirectional charger for electric vehicles with galvanically isolated input and output, e.g., as a bidirectional DC charger for electric vehicles with an AC mains connection for AC mains feed-in and AC mains supply, a simple design and / or cost-effective implementation can be advantageously achieved. It is also beneficial to utilize systems already developed for other applications, thereby increasing overall efficiency. In particular, conventional isolated chargers for electric vehicles, whose DC voltage range is suitable for the application, can be used for PEM cell series with minimal effort if they are controllable (specifying voltage and current setpoints).Preferably, conventional bidirectional DC chargers for electrolysis cell stacks can be used without significant modification if the voltage and / or current of the electrolysis cell stack is comparable to that used in electromobility. For application at the electrolysis cell level, additional devices are necessary, such as the addition of further, also bidirectional, voltage converters that operate in the lower voltage range of electrolysis cells, particularly PEM cells (2 V vs. 120 V at currents of 100 A). Such voltage converters are commercially available and are used, for example, in data centers for CPU power supply.

[0022] Furthermore, it is proposed that the bidirectional voltage converter, in particular the bidirectional charger for electric cars, be electrically connected in series with at least one other bidirectional voltage converter. Advantageously, this enables the balancing of the electrolysis cells. It also advantageously allows for simple adaptation of the electrolyzer device to voltage and / or current ranges in electrolyzers. In particular, the electrolyzer device comprises a series connection of auxiliary power supplies, which are designed in particular as bidirectional voltage converters and thus form sources and sinks for electrical power, wherein each node in the series connection of the auxiliary power supplies is connected to a point, in particular a node, within a series connection of electrolysis cells of the electrolysis cell stack / the electrolyzer.

[0023] Furthermore, it is proposed that the auxiliary power supplies be interconnected in such a way that they can supply at least some of the power drawn from one electrolysis cell to another. This advantageously allows for high efficiency. In particular, it can advantageously amplify the resulting relative difference in the load acting on the respective cells. A particularly cost-effective balancing can be achieved. Specifically for the implementation of this proposal, the electrolyzer device includes an intermediate storage device, such as a DC link. The DC link can be implemented as a DC network or, preferably, an AC network. This implementation always involves two steps: e.g., from electrolysis cell stack A to the DC link network and from the DC link network to electrolysis cell stack B. If this is not desired, e.g.,Because the conversion is only to occur once, each output of every auxiliary power supply for each electrolysis cell stack would have to be electrically connected to every other electrolysis cell stack. While this would be theoretically feasible using switches, the number of switches would increase exponentially with the number of electrolysis cell stacks in the electrolyzer. In particular, an AC power supply connected by the utility company is preferable as the intermediate circuit, since it is inherently stabilized. This ensures that no power is ever fed back into the grid. If a separate local intermediate circuit is to be built, it would have to be protected against overload, for example, with a crowbar circuit.

[0024] Alternatively or additionally, power supplies, especially auxiliary power supplies, are provided for the passive balancing of the electrolysis cells. This allows for a cost-effective alternative that requires little or even no electronics.

[0025] In this context, it is also proposed that the power supplies, particularly the auxiliary power supplies, each include a switchable load resistor or a plurality of parallel-connected, separately switchable load resistors. This advantageously enables passive balancing. In particular, the term "auxiliary power supply" seems at first glance unsuitable for describing a switchable load resistor, since no power is either fed into or drawn from the grid for balancing purposes. Nevertheless, for the purposes of these documents, a switchable load resistor that serves to extract power through heating should preferably be understood as an auxiliary power supply.

[0026] It is further proposed that at least one of the auxiliary power supplies be assigned to at least one other electrolysis cell, e.g., a third one, which is electrically connected in series with the other electrolysis cell assigned to that auxiliary power supply. This advantageously provides a cost-effective balancing option, particularly for large systems. Specifically, the auxiliary power supply, preferably all auxiliary power supplies, is assigned to a sub-stack of electrolysis cells. While this no longer allows for individual cell balancing, subgroups (sub-stacks) of electrolysis cells can still be advantageously balanced relative to each other. For example, one auxiliary power supply can be used per electrolysis cell stack of the electrolyzer. In particular, a package of electrolysis cells can be selected such that common DC voltages, such as approximately 12 V, 48 V, 96 V, 144 V, etc., are available across the auxiliary power supplies.In particular, the electrolysis device requires a minimum number of auxiliary power supplies per total series connection of electrolysis cells of two.

[0027] Furthermore, it is proposed that the first electrolysis cell is part of a first electrolysis cell stack and that the second electrolysis cell is part of a second electrolysis cell stack, with the auxiliary power supplies being designed to balance the electrolysis cell stacks relative to each other by, in particular, independently, electrically discharging and / or electrically supplying the respective electrolysis cell stacks. This advantageously improves the service life of electrolyzers. Advantageously, the aging of different electrolysis cell stacks within the electrolyzer can be balanced. Advantageously, the overall efficiency of all electrolysis cell stacks in an electrolyzer can be improved. Advantageously, it enables operation of the electrolyzer in which all electrolysis cell stacks of the electrolyzer reach the end of their service life simultaneously.

[0028] Furthermore, an electrolyzer, in particular an electrolysis plant, comprising the electrolyzer device and a method for operating the electrolyzer device, is proposed, wherein the electrolysis cells are balanced relative to each other by means of an electrical discharge and / or electrical supply to the respective electrolysis cell, in particular independently of each other, by means of at least one first auxiliary power supply, which is assigned to at least the first electrolysis cell, and by means of at least one second auxiliary power supply, which is assigned to at least the second electrolysis cell. This advantageously improves the service life and / or the overall efficiency of electrolyzers.

[0029] The electrolyzer device, the electrolyzer, and the method according to the invention are not limited to the application and embodiment described above. In particular, the electrolyzer device, the electrolyzer, and the method according to the invention may, to achieve a functionality described herein, comprise a different number of individual process steps, elements, components, and units than the number specified herein. Drawings

[0030] Further advantages become apparent from the following description of the drawings. The drawings illustrate six exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0031] They show: Fig. 1 schematically an electrolyzer with an electrolyzer device, Fig. 2 a schematic representation of one of the electrolysis cell stacks of the electrolyzer, Fig. 3 a schematic circuit diagram of part of the electrolyzer with the electrolyzer device, Fig. 4 a schematic flowchart of a procedure for operating the electrolyzer device, Fig. 5 a schematic circuit diagram of part of the electrolyzer with an alternative electrolyzer device, Fig. 6 a schematic circuit diagram of part of the electrolyzer with another alternative electrolyzer device, Fig. 7 a schematic circuit diagram of part of the electrolyzer with a second further alternative electrolyzer device, Fig. 8 a schematic circuit diagram of part of the electrolyzer with a third further alternative electrolyzer device and Fig. 9 a schematic circuit diagram of part of the electrolyzer with a fourth alternative electrolyzer device. Description of the exemplary implementations

[0032] The Fig. Figure 1 schematically shows an electrolyzer 30a. The electrolyzer 30a forms an electrolysis system. The electrolyzer 30a is designed as an example proton exchange membrane electrolyzer. However, the invention described here is also applicable to other types of electrolyzers. The electrolyzer 30a comprises electrolysis cell stacks 26a, 28a (see also Figure 1). Fig. 2) The electrolysis cell stacks 26a, 28a are electrically interconnected in electrolysis cell stack series 34a, 36a. The electrolysis cell stack series 34a, 36a are also referred to as cascades. For example, each of the electrolysis cell stack series 34a, 36a of the electrolyzer 30a comprises five electrolysis cell stacks 26a, 28a. For example, the electrolyzer 30a, and in particular the electrolysis plant, comprises eighteen electrolysis cell stack series 34a, 36a. For example, the proposed number of electrolysis cell stacks 26a, 28a represents a 10-megawatt electrolysis plant. Of course, the number of electrolysis cell stacks 26a, 28a or electrolysis cell stack series 34a, 36a that deviate from the exemplary numbers, either higher or lower, are also conceivable. The electrolysis cell stacks 26a, 28a of an electrolysis cell stack series 34a are electrically connected in series with each other.The electrolysis cell stacks 34a and 36a are electrically connected in parallel. The individual electrolysis cell stacks 26a and 28a of the electrolysis system can be interchangeable or replaceable.

[0033] The electrolyzer 30a includes an electrolyzer device 32a. Fig. Figure 2 shows a schematic side view of one of the electrolysis cell stacks 26a of the electrolyzer 30a with the electrolyzer device 32a. Components such as a fluid supply, a housing, and the like of the electrolyzer 30a are shown in the Fig. 2 not shown. However, this can of course include such. The electrolyzer device 32a has a first electrolysis cell 10a. The electrolyzer device 32a has a second electrolysis cell 12a. In the present case, the electrolysis cell stack 26a has a plurality of electrolysis cells 10a, 12a, of which, for the sake of clarity, only twelve are shown schematically and not all of which are labeled with reference numerals. In addition, the electrolysis cells 10a, 12a of the electrolysis cell stack 26a are in the Fig. Figure 2 is not shown to scale. In particular, the electrolysis cells 10a, 12a of the electrolysis cell stack 26a may be significantly flatter than shown in the schematic representation of the Fig. 2. For example, the electrolysis cell stack 26a can comprise 20, 30, 50, 100, 150, or 200 electrolysis cells 10a, 12a. The first electrolysis cell 10a and the second electrolysis cell 12a are electrically connected in series. All electrolysis cells 10a, 12a of the electrolysis cell stack 26a are electrically connected in series. All electrolysis cells 10a, 12a belonging to a common electrolysis cell stack series 34a, 36a are electrically connected in series.

[0034] The electrolysis cell stack 26a has a first end plate 38a and a second end plate 40a. The first end plate 38a and the second end plate 40a define the electrolysis cells 10a, 12a of the electrolysis cell stack 26a on opposite sides of the electrolysis cell stack 26a. The end plates 38a, 40a are connected to each other, for example, by means of connecting struts (not shown), and exert a pressure on the electrolysis cells 10a, 12a of the electrolysis cell stack 26a. This pressure counteracts, in particular, any pressure resulting from the formation of hydrogen gas and / or oxygen gas, and / or ensures or at least contributes to a tight seal between the pressed-together electrolysis cells 10a, 12a and / or between the individual electrolysis cells 10a, 12a. The electrolysis cell stack 26a has connection elements 42a, 44a for connection to a power supply.The energy supply is provided by a main power supply unit 14a of the electrolyzer device 32a (see . Fig. 3) In a normal operating state, the electrolysis cell stack 26a is supplied with electrical power via the connection elements 42a, 44a. A total voltage is present between the foremost electrolysis cell 10a, which is connected in particular to the first end plate 38a, and the rearmost electrolysis cell, which is connected in particular to the second end plate 40a. In the normal operating state, each individual electrolysis cell 10a, 12a of the electrolysis cell stack 26a has a voltage between approximately 1 V and approximately 2.5 V.

[0035] The electrolyzer device 32a has contact elements 46a, 48a (see Fig. 2) which differ from a connection element 42a, 44a for the main power supply 14a and of which, in particular, one is located at an anode potential and one at a cathode potential of a respective corresponding electrolysis cell 10a, 12a. Two contact elements 46a, 48a are each assigned to a single electrolysis cell 10a, 12a. In particular, the contact elements 46a, 48a assigned to a specific electrolysis cell 10a, 12a are each a contact element 46a of the corresponding electrolysis cell 10a and a contact element 48a of an immediately adjacent electrolysis cell 12a. In particular, a specific contact element 46a, 48a is assigned to two immediately adjacent electrolysis cells 10a, 12a in this way, wherein the corresponding contact element 46a, 48a is at an anode potential of one electrolysis cell 10a, which corresponds to a cathode potential of the other electrolysis cell 12a.For example, in the present case, the first electrolysis cell 10a is assigned the contact element 46a and the further contact element 48a. Furthermore, in the present case, the further contact element 48a is also assigned to the second electrolysis cell 12a. The contact elements 46a and 48a are accessible from the outside of the electrolysis cell stack 26a. The contact elements 46a and 48a are located outside an active interior of the electrolysis cells 10a and 12a and / or outside an active interior of the electrolysis cell stack 26a. The contact elements 46a and 48a allow electrical contact between the electrolysis cells 10a and 12a, in particular their anode and cathode.

[0036] The Fig. Figure 3 schematically shows a circuit diagram of part of the electrolyzer 30a with the electrolyzer device 32a. The electrolyzer device 32a includes the main power supply 14a. The main power supply 14a is designed to supply the first electrolysis cell 10a and the second electrolysis cell 12a with electrical energy. The main power supply 14a is designed to supply all electrolysis cells 10a and 12a of the electrolysis cell stack 26a with electrolysis energy. The main power supply 14a is designed to supply all electrolysis cells 10a and 12a of the electrolyzer 30a with electrolysis energy. The main power supply 14a is connected to a supply network 54a.

[0037] The electrolyzer device 32a has a first auxiliary power supply 16a. The first auxiliary power supply 16a is assigned to the first electrolysis cell 10a. The electrolyzer device 32a has a second auxiliary power supply 18a. The second auxiliary power supply 18a is assigned to the second electrolysis cell 12a. The respective electrolysis cells 10a and 12a are each from the same electrolysis cell stack 26a. In the exemplary embodiment, each further electrolysis cell is assigned a second auxiliary power supply 18a. Fig. Each of the three electrolysis cells 10a and 12a is assigned its own auxiliary power supply. Auxiliary power supplies 16a and 18a are designed to balance the electrolysis cells 10a and 12a by independently discharging the respective electrical load on each cell. Auxiliary power supplies 16a and 18a are designed to balance the electrolysis cells 10a and 12a by independently supplying the respective electrical load on each cell. Auxiliary power supplies 16a and 18a are designed to equalize the cell voltages of the individual electrolysis cells 10a and 12a by discharging and / or supplying the respective electrical loads on each cell. The auxiliary power supplies 16a, 18a are each designed to extract power from the respective associated electrolysis cell 10a, 12a by electrically relieving the load when the latter has a cell voltage that is higher than a given value.The auxiliary power supplies 16a, 18a are each designed to supply power to the respective assigned electrolysis cell 10a, 12a by means of electrical power supply when the cell voltage is lower than the specified value. The specified cell voltage value can be adjustable, for example via a control and / or regulation unit 50a of the electrolyzer device 32a. The auxiliary power supplies 16a, 18a can also be configured as, for example, modularly expandable, multi-channel balancers with galvanically isolated channels for each electrolysis cell 10a, 12a connected to the multi-channel balancer (see ). Fig. 2).

[0038] The auxiliary power supplies 16a and 18a are designed for actively balancing the electrolysis cells 10a and 12a. Each auxiliary power supply 16a and 18a is configured as a bidirectional voltage converter 20a. The bidirectional voltage converter 20a is electrically connected in series with other bidirectional voltage converters 22a of the electrolyzer device 32a. The auxiliary power supplies 16a and 18a, and in particular the bidirectional voltage converters 20a, are interconnected in such a way that they can supply at least some of the power drawn from one of the electrolysis cells 10a to another of the electrolysis cells 12a. The respective currents can be transferred between the electrolysis cells 10a and 12a by means of active and passive components, such as semiconductor components. Alternatively, a setup using a multiplexer, which connects each electrolysis cell 10a, 12a to a common DC-DC converter, is also conceivable.The auxiliary power supplies 16a and 18a are connected to a common network 52a. The common network 52a can be formed by an intermediate circuit, e.g., an AC supply network, in particular the supply network 54a, to which the main power supply 14a is also connected.

[0039] The Fig. Figure 4 shows a schematic flowchart of a method for operating the electrolyzer device 32a. In a process step 56a, the electrolysis cells 10a, 12a are supplied with electrolysis energy by the main power supply 14a. In at least one further process step 58a, the electrolysis cells 10a, 12a, which are in electrolysis operation, are balanced against each other by means of independent electrical discharges using their respective auxiliary power supplies 16a, 18a, in particular such that the cell voltages of the electrolysis cells 10a, 12a are equalized by the electrical discharge.In at least one further or alternative process step 60a, the electrolysis cells 10a, 12a, which are in electrolysis operation, are balanced with respect to each other by means of independent electrical power supplies via their respective auxiliary power supplies 16a, 18a, in particular such that the cell voltages of the electrolysis cells 10a, 12a are equalized by the electrical power supply. The power for the electrical power supply is taken either directly from the supply network 54a or from all other auxiliary power supplies of the electrolyzer device 32a (the power source is then, for example, a common bus), which is temporarily relieving another electrolysis cell of the electrolyzer device 32a of its electrical load (possibly via an intermediate circuit). In at least one further process step 62a, the electrolysis cells 10a, 12a of the electrolyzer device 32a are operated with the respective desired cell voltages, e.g., essentially identical cell voltages.For example, a so-called "overshoot" of the cell voltage of a "good" electrolysis cell may be necessary to achieve a common EOL (end-of-life), or vice versa in the case of a "bad" electrolysis cell.

[0040] In the Fig. Figures 5 to 9 show five further embodiments of the invention. The following descriptions and drawings are essentially limited to the differences between the embodiments, whereby, with regard to identically designated components, in particular components with the same reference numerals, reference is also generally made to the drawings and / or the description of the other embodiments, in particular the Fig. 1 to 4, reference can be made. To distinguish the embodiments, the letter a is the reference numeral of the embodiment in the Fig. 1 to 4 are appended. In the exemplary embodiments of the Fig. In numbers 5 to 9, the letter a is replaced by the letters b to f.

[0041] The Fig. Figure 5 shows an alternative electrolyzer device 32b with an electrolysis cell stack 26b comprising at least one electrolysis cell 10b, 12b. The alternative electrolyzer device 32b has a first auxiliary power supply 16b. The first auxiliary power supply 16b is assigned to the first electrolysis cell 10b. The alternative electrolyzer device 32b has a second auxiliary power supply 18b. The second auxiliary power supply 18b is assigned to the second electrolysis cell 12b. The alternative electrolyzer device 32b has a further electrolysis cell 76b. The first auxiliary power supply 16b is assigned to the further electrolysis cell 76b. The respective electrolysis cells 10b, 12b, 76b are each from the same electrolysis cell stack 26b. The first auxiliary power supply 16b, which is assigned to the further electrolysis cell 76b, is electrically connected in series with the second auxiliary power supply 18b, which is assigned to the second electrolysis cell 12b.Additional electrolysis cells can be used in the exemplary embodiment of the . Fig. 5 each be assigned to one of the auxiliary power supplies 16b, 18b. Preferably, an equal number of electrolysis cells 10b, 12b, 76b are assigned to each auxiliary power supply 16b, 18b. The electrolysis cells 10b, 12b, 76b assigned to each of the auxiliary power supplies 16b, 18b each form an electrolysis cell balance pack 64b, 66b. The auxiliary power supplies 16b, 18b are designed to balance the electrolysis cells 10b, 12b, 76b of the respective electrolysis cell balance packs 64b, 66b by independently relieving the electrical load on the respective electrolysis cell balance packs 64b, 66b. The auxiliary power supplies 16b, 18b are intended to balance the electrolysis cells 10b, 12b, 76b of the respective electrolysis cell balance packages 64b, 66b by independently supplying electrical power to the respective electrolysis cell balance packages 64b, 66b.

[0042] The Fig. Figure 6 shows a further alternative electrolyzer device 32c with several electrolysis cell stacks 26c, 28c, each comprising several electrolysis cells 10c, 12c. The first electrolysis cell 10c is part of the first electrolysis cell stack 26c. The second electrolysis cell 12c is part of the second electrolysis cell stack 28c. The further alternative electrolyzer device 32c has a first auxiliary power supply 16c. The first auxiliary power supply 16c is assigned to the first electrolysis cell stack 26c. The further alternative electrolyzer device 32c has a second auxiliary power supply 18c. The second auxiliary power supply 18c is assigned to the second electrolysis cell stack 28c. Further electrolysis cell stacks 68c can be added in the exemplary embodiment of the Fig. Six additional auxiliary power supplies 70c are assigned to each electrolysis cell stack 26c, 28c, 68c. Preferably, exactly one electrolysis cell stack 26c, 28c, 68c is assigned to exactly one auxiliary power supply 16c, 18c, 70c. However, it is also conceivable that several electrolysis cell stacks 26c, 28c, 68c are assigned to a common auxiliary power supply 16c, 18c, 70c. In this case, however, the number of electrolysis cell stacks 26c, 28c, 68c assigned to one auxiliary power supply 16c, 18c, 70c in the further alternative electrolyzer device 32c should always be the same. The auxiliary power supplies 16c, 18c, and 70c are designed to balance the electrolysis cell stacks 26c, 28c, and 68c by independently discharging the respective electrolysis cell stacks 26c, 28c, and 68c. The auxiliary power supplies 16c, 18c, and 70c are also designed to balance the electrolysis cell stacks 26c, 28c, and 68c by independently supplying the respective electrolysis cell stacks 26c, 28c, and 68c.

[0043] The Fig. Figure 7 shows a second alternative electrolyzer device 32d with several electrolysis cell stacks 26d, each containing several electrolysis cells 10d, 12d. The second alternative electrolyzer device 32d has a first auxiliary power supply 16d. The first auxiliary power supply 16d is assigned to the first electrolysis cell 10d. The second alternative electrolyzer device 32d has a second auxiliary power supply 18d. The second auxiliary power supply 18d is assigned to the second electrolysis cell 12d. The Fig. The embodiment shown in section 7 essentially corresponds to the embodiment of the Fig. 1 to 4 with the exception of the design of the auxiliary power supplies 16d, 18d. The auxiliary power supplies 16d, 18d are designed as a combination of two unidirectional voltage converters 72d arranged in opposite directions and galvanically isolated from each other, which are connected to a common network 52d. This advantageously allows a quasi-bidirectionality of the voltage converter to be obtained.

[0044] The Fig. Figure 8 shows a third alternative electrolyzer device 32e with several electrolysis cell stacks 26e, each containing several electrolysis cells 10e, 12e. The third alternative electrolyzer device 32e has a first auxiliary power supply 16e. The first auxiliary power supply 16e is assigned to the first electrolysis cell 10e. The third alternative electrolyzer device 32e has a second auxiliary power supply 18e. The second auxiliary power supply 18e is assigned to the second electrolysis cell 12e. The Fig. The embodiment shown in section 8 essentially corresponds to the embodiment of the Fig. 1 to 4 with the exception of the design of the auxiliary power supplies 16e, 18e. The auxiliary power supplies 16e, 18e are each designed as a unidirectional voltage converter 74e connected to a common network 52e. This allows only balancing of the cell voltages of the electrolysis cells 10e, 12e by means of electrical discharge (or only by means of electrical supply when the unidirectional voltage converters 74e are reversed). The reverse direction is not available in this embodiment.

[0045] The Fig.Figure 9 shows a fourth alternative electrolyzer device 32f with several electrolysis cell stacks 26f, each comprising several electrolysis cells 10f, 12f. The fourth alternative electrolyzer device 32f has a first auxiliary power supply 16f. The first auxiliary power supply 16f is assigned to the first electrolysis cell 10f. The fourth alternative electrolyzer device 32f has a second auxiliary power supply 18f. The second auxiliary power supply 18f is assigned to the second electrolysis cell 12f. The auxiliary power supplies 16f, 18f are each provided for passive balancing of the electrolysis cells 10f, 12f. The auxiliary power supplies 16f, 18f are not provided for discharge by supplying power to a grid. The auxiliary power supplies 16f, 18f are not provided for supplying power by supplying power from a grid. The auxiliary power supplies 16f, 18f are formed solely by electrical resistors.The auxiliary power supplies 16f, 18f each comprise a switchable load resistor 24f or a plurality of parallel-connected, separately switchable load resistors 24f, 24'f, 24''f. Reference sign 10 First electrolysis cell 12 Second electrolysis cell 14 Main power supply 16 First auxiliary power supply 18 Second auxiliary power supply 20 Bidirectional voltage converter 22 Another bidirectional voltage converter 24 load resistor 26 First electrolysis cell stack 28 Second electrolysis cell stack 30 Electrolyzer 32 Electrolyzer device 34 electrolysis cell stack row 36 electrolysis cell stack row 38 End plate 40 End plate 42 Connection element 44 Connection element 46 Contact element 48 contact elements 50 Control and / or regulating unit 52 Common Network 54 Supply network 56th process step 58th process step 60th process step 62nd process step 64 Electrolysis cell balance package 66 Electrolysis cell balance package 68 More electrolysis cell stacks 70 Additional auxiliary power supply 72 Combination of two unidirectional voltage converters 74 Unidirectional voltage converter 76 Additional electrolysis cells QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2017 108 439 A1

[0013]

Claims

[1] Electrolyzer device (32a-f) with at least one first electrolysis cell (10a-f), with at least one second electrolysis cell (12a-f), and with at least one main power supply (14a-f), which is at least intended to supply the first electrolysis cell (10a-f) and the second electrolysis cell (12a-f) together with electrical energy, in particular electrolysis energy, characterized by at least one first auxiliary power supply unit (16a-f) assigned to the first electrolysis cell (10a-f), and at least one second auxiliary power supply unit (18a-f) assigned to the second electrolysis cell (12a-f), wherein the auxiliary power supplies (16a-f, 18a-f) are provided to balance the electrolysis cells (10a-f, 12a-f) with one another by electrically relieving and / or electrically feeding the respective electrolysis cell (10a-f, 12a-f). [2] Electrolyzer device (32a-f) according to claim 1, characterized bythat the first electrolysis cell (10a-f) and the second electrolysis cell (12a-f) are electrically connected in series. [3] Electrolyzer device (32a-f) according to claim 1 or 2, characterized by that the auxiliary power supplies (16a-f, 18a-f) are provided to adapt the cell voltages of the individual electrolysis cells (10a-f, 12a-f) to one another, in particular to match them to one another, by electrically relieving and / or electrically feeding the respective electrolysis cells (10a-f, 12a-f). [4] Electrolyzer device (32a-f) according to one of the preceding claims, characterized by that the auxiliary power supplies (16a-f, 18a-f) are provided to draw power from an electrolysis cell (10a-f, 12a-f) with a cell voltage increased relative to a predetermined value by electrically relieving the load. [5] Electrolyzer device (32a-d) according to one of the preceding claims, characterized bythat the auxiliary power supplies (16a-d, 18a-d) are provided to supply power to an electrolysis cell (10a-d, 12a-d) having a cell voltage that is low relative to a predetermined value by means of electrical feeding. [6] Electrolyzer device (32a-f) according to one of the preceding claims, characterized by that the auxiliary power supplies (16a-f, 18a-f) are provided for actively balancing the electrolysis cells (10a-f, 12a-f). [7] Electrolyzer device (32a-c) according to one of the preceding claims, in particular according to claim 6, characterized by that the auxiliary power supplies (16a-c, 18a-c) are each designed as bidirectional voltage converters (20a-c). [8] Electrolyzer device (32a-c) according to claim 7, characterized by that the bidirectional voltage converter (20a-c) is designed as a conventional bidirectional charger for electric cars, the input and output of which are galvanically isolated. [9] Electrolyzer device (32a-c) according to claim 7 or 8, characterized by that the bidirectional voltage converter (20a-c) is electrically connected in series with at least one further bidirectional voltage converter (22a-c). [10] Electrolyzer device (32a-d) according to one of the preceding claims, in particular according to one of claims 6 to 9, characterized by that the auxiliary power supplies (16a-d, 18a-d) are interconnected in such a way that they can at least partially supply a power which is taken from one of the electrolysis cells (10a-d) to another of the electrolysis cells (12a-d). [11] Electrolyzer device (32f) according to one of claims 1 to 4, characterized by that the auxiliary power supplies (16f, 18f) are provided for passive balancing of the electrolysis cells (10f, 12f). [12] Electrolyzer device (32f) according to claim 11, characterized bythat the auxiliary power supplies (16f, 18f) each comprise a switchable load resistor (24f) or a plurality of parallel-connected, separately switchable load resistors (24f, 24'f, 24''f). [13] Electrolyzer device (32b; 32c) according to one of the preceding claims, characterized by that at least one of the auxiliary power supplies (16b, 18b; 16c, 18c) is assigned to at least one further electrolysis cell (76b; 76c), which is electrically connected in series with the other electrolysis cell (10b, 12b; 10c, 12c) assigned to this auxiliary power supply (16b, 18b; 16c, 18c). [14] Electrolyzer device (32c) according to one of the preceding claims, characterized bythat the first electrolysis cell (10c) is part of a first electrolysis cell stack (stack, 26c) and that the second electrolysis cell (12c) is part of a second electrolysis cell stack (stack, 28c), wherein the auxiliary power supplies (16c, 18c) are provided to balance the electrolysis cell stacks (26c, 28c) with one another by, in particular independent of one another, electrically relieving and / or electrically feeding the respective electrolysis cell stacks (26c, 28c). [15] Electrolyzer (30a-f), in particular electrolysis plant, with an electrolyzer device (32a-f) according to one of the preceding claims. [16] Method for operating an electrolyzer device (32a-f), in particular according to one of the preceding claims, with at least one first electrolysis cell (10a-f), with at least one second electrolysis cell (12a-f), and with at least one main power supply (14a-f) which supplies the first electrolysis cell (10a-f) and the second electrolysis cell (12a-f) together with electrical energy, in particular electrolysis energy, characterized by that the electrolysis cells (10a-f, 12a-f) are balanced with each other by electrically relieving and / or electrically feeding the respective electrolysis cell (10a-f, 12a-f) by means of at least one first auxiliary power supply unit (16a-f) which is assigned to the first electrolysis cell (10a-f) and by means of at least one second auxiliary power supply unit (18a-f) which is assigned to the second electrolysis cell (12a-f).

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