Operation of an electrolysis system in fault states

Abstract

The present invention relates to a method for operating an electrolysis system, in particular in the event of fault states in the power supply, for example in the event of grid-side fault states. Accordingly, a method for operating an electrolysis system is proposed, wherein the electrolysis system provides a product gas flow by means of a primary power supply and a primary fluid supply. According to the invention, the primary power supply is monitored (S100) and input of the primary fluid supply (S120) and / or output of the product flow (S130) are adapted if a fault state in the primary power supply (S110) is detected.

Description

[0001] Description

[0002] Operation of an electrolysis plant under fault conditions

[0003] Technical area

[0004] The present invention relates to a method for operating an electrolysis plant, in particular when fault conditions occur in the power supply, for example in the case of network-side fault conditions.

[0005] State of the art

[0006] In order to connect industrial-sized electrolysis plants to the public grid, they must comply with the grid connection requirements. Electrolysis plants must have a so-called "fault ride-through" capability to prevent the electrolysis plant from being disconnected from the grid, for example, in the event of a brief voltage dip or voltage surge. In other words, grid conditions require that the electrolysis plant remain fully connected to the grid even in the event of such a grid-side fault condition. This ensures that the grid operator can ensure that the load or consumer remains connected to the grid even after the fault has been rectified.

[0007] If such an electrolysis plant were to be immediately disconnected from the grid due to even minor fluctuations in the grid, for example, in the event of a brief short circuit, the grid operator would have considerable difficulty adjusting the supplied power to the required or consumed power after the fault has been rectified. This is because electricity generation in the corresponding power plants, as well as distribution or load in the grid, typically cannot be adjusted or scaled down in a timely manner. Accordingly, large electricity consumers such as electrolysis plants should remain connected to the power supply even in the event of a fault condition, such as a voltage dip.

[0008] Furthermore, the (continuous) continuation of chemical processing of the product flow downstream of the electrolysis plant has proven to be somewhat problematic. Should the plants that are required to accommodate the product flow be unable to continue operations due, for example, to a grid-related power supply failure, it should be ensured that the electrolysis plant continues to operate in order to provide as much load as possible to the grid.

[0009] To demonstrate compatibility with grid connection requirements, current electrolysis plants may implement a specific rectifier system, which must operate and be connected even in the event of a fault condition. Furthermore, specific control units and pumps are required, among other things, which must be operated by an uninterruptible power supply system, such as a separate battery system, or must be able to restart sufficiently quickly. However, such additional systems are costly and require significant modifications to existing electrolysis plants, especially since the systems receiving the product flow must also be appropriately equipped.

[0010] Accordingly, there is a need to ensure a cost-effective connection of an electrolysis plant to a power supply even in the event of fault conditions and to have a fallback option in case the plants receiving the product flow fail due to an external fault. Description of the invention

[0011] Based on the known prior art, it is an object of the present invention to provide an improved method for operating an electrolysis plant.

[0012] The problem is solved by a method having the features of claim 1. Advantageous further developments emerge from the subclaims.

[0013] Accordingly, a method for operating an electrolysis plant is proposed, wherein the electrolysis plant provides a product gas flow by means of a primary power supply and a primary fluid supply. According to the invention, the primary power supply is monitored, and the feed of the primary fluid supply and / or the output of the product flow are adjusted upon detection of a fault condition in the primary power supply.

[0014] By adjusting the feed of the primary fluid supply and / or the output of the product flow, at least the electrolysis can be adapted to the prevailing conditions and can continue to operate at least partially in the event of a fault condition. This applies in particular if the provision of the primary fluid supply is dependent on the primary power supply. For example, by actuating a valve arrangement, the primary fluid supply can be at least partially replaced by a secondary fluid supply that is not dependent on the primary power supply.

[0015] It can also be provided that the output of the product flow is adjusted accordingly. For example, the production rate can be temporarily scaled down and / or a portion of the product flow, in particular a by-product flow, can be drained or blown out. The latter can be particularly advantageous if further processing of the product flow (e.g. of a chemical nature or by compression in the downstream process) cannot be continued in the current error state, for example if this is particularly prone to errors in the event of pressure fluctuations. Another reason may be that processing cannot be continued due to unexpected network disruptions in the event of an external error. In this way, specified system pressures can still be maintained.

[0016] In other words, the invention ensures that electrolysis-based production does not have to be stopped, or at least not completely. In this way, a fault-ride-through (FRT) capability is provided and guaranteed, even if the downstream processes can no longer be operated. Advantageously, the existing electrolysis systems can be used to provide the grid with a corresponding load, and the use of costly additional components that would otherwise have to take on the load can be dispensed with. In this way, a longer start-up time for the downstream processes can also be accepted, which avoids costly and technically complex replacement there, so that at least some of the time separate control units, pump systems and / or uninterruptible power supply systems are not required.

[0017] Preferably, the primary power supply is a grid. As explained above, maintaining a connected state of the electrolysis system or at least the electrolyzer is necessary for grid stability in order to prevent an uneven load or overload of the grid after the fault has been rectified. The grid can be connected to the electrolysis system, in particular, by means of a conventional rectifier.

[0018] As explained above, the adjustment for the primary fluid supply and / or the generated product gas flow can advantageously be carried out using a corresponding valve circuit. Preferably, the adjustment of the feed of the primary fluid supply at least partially comprises the use of a compressed gas storage buffer, or the fluid supply is provided exclusively by a compressed gas storage buffer through the adjustment.

[0019] Adjusting the feed has the advantage that an inflow for the electrolyzer can be provided due to the corresponding pressure in the storage buffer. This even applies if there is a short-term power outage and the primary fluid supply is dependent, for example, on the primary power supply. The inflow, particularly of water and cooling liquids, can be the same or reduced compared to the primary fluid supply, for example if production is temporarily and possibly only slightly scaled down. Depending on the starting gas and the product flow to be provided, several compressed gas storage buffers can be provided, which can optionally contain different gases or gas mixtures.

[0020] In order to support the continued operation of the electrolysis plant or at least of the electrolyzer, it can further be provided that the electrolysis plant switches on an auxiliary generator when a fault condition in the primary power supply is detected, wherein the auxiliary generator is operated by means of a gas flow from a compressed gas storage buffer and / or at least a partial flow from the product gas flow.

[0021] Alternatively or in addition to the inlet-side compressed gas storage buffer for the fluid supply, a gas flow can also be provided, which is operated to generate electricity. The auxiliary generator can thus provide a secondary power supply, which at least partially replaces the primary power supply. For example, the secondary power supply can completely replace the primary power supply if the primary power supply is temporarily interrupted, whereby the secondary power supply can optionally be reduced relative to the primary power supply. The auxiliary generator can in particular be coupled to a turbine in order to provide rotation resulting in electricity generation based on the gas flow.

[0022] Thanks to the auxiliary generator, a secondary power supply can thus be provided, for example for the electrolyzer and / or the fluid supply, whereby a separate, uninterruptible power supply system by means of a battery system can be at least partially or completely dispensed with. However, one or more batteries or capacitor banks can optionally be provided in addition. Such batteries or battery systems or capacitors can, for example, also serve as a secondary power supply or be provided as a tertiary power supply, whereby they can, for example, supply (different) parts of the electrolysis system with power or additionally support the power supply. However, even in such a case, the provided auxiliary generator considerably reduces the required battery capacity.

[0023] The auxiliary generator can also be operated at least partially using a partial flow from the product gas flow. The partial flow can, in particular, comprise or consist of a by-product of the electrolysis. In this way, a power supply can be provided based on the product flow itself, which can support continued operation of the electrolysis plant or at least the electrolyzer, particularly in the event of short-term failures in the primary power supply.

[0024] The auxiliary generator can also provide a secondary power supply for a heating system of the electrolysis plant. Such heating can be particularly advantageous if the electrolysis plant, for example the electrolyzer and / or the fluid supply, needs to be temperature-controlled to provide the product flow. Furthermore, a power supply for a heating system can be particularly advantageous for offshore and / or decentralized electrolysis plants if the electrolysis plant is electrically coupled to a wind turbine and / or photovoltaic system, for example. Heating can thus be particularly advantageous if, for example, a wind turbine is not operational for a certain period of time due to insufficient wind or a photovoltaic system due to insufficient sunlight.In this way, heating can be particularly advantageous for bridging such downtimes, especially during a cold period.

[0025] The electrical energy provided by the auxiliary generator can also be used, at least in part, to charge a battery configured as a secondary or tertiary power supply for the electrolysis plant. For example, if the electrolyzer's output is reduced and the electrical energy provided by the auxiliary generator generates a surplus, this surplus can be efficiently used to charge one or more batteries, which can, for example, serve as a secondary or tertiary power supply at a later time.

[0026] Although the auxiliary generator can preferably be switched on when a fault condition exists in the primary power supply, it can optionally also be provided that the auxiliary generator is switched on during normal operation of the electrolysis plant. In particular, a partial flow of the product flow can be diverted and used to operate the auxiliary generator. In other words, it can also be provided that a flow of a by-product of the electrolysis is used to operate the auxiliary generator so that one or more batteries can be charged during normal operation of the electrolysis plant without a fault condition existing in the primary power supply. This can be particularly advantageous in decentralized or offshore electrolysis plants in order to provide a sufficient secondary or tertiary power supply for a coupled, non-operational wind turbine and / or photovoltaic system.Adjusting the output of the product flow upon detection of a fault condition in the primary power supply may also include draining at least a portion of the product flow and / or storing it in a compressed gas storage buffer. The portion may, in particular, comprise a by-product of the electrolysis. Preferably, the electrolysis plant is configured to provide hydrogen or other products serving as potential fuels. Thus, it may, in particular, be provided that the portion comprises generated oxygen or consists of generated oxygen.

[0027] A potential advantage of the vented partial flow is that at least the electrolysis can be continued even if, for example, downstream chemical processing or another process, such as compression, is interrupted. The vented partial flow can then continue to be used to operate an auxiliary generator to provide a secondary power supply, as explained above. Alternatively or additionally, the partial flow or another partial flow can also be stored in a compressed gas storage buffer, wherein the contents of the compressed gas storage buffer can preferably also be used to operate an auxiliary generator.

[0028] This can be particularly advantageous if, in addition to the primary power supply, no (further) central power supply is provided, as is the case, for example, with offshore wind turbines. Thus, in the event of an interrupted power generation of an electrically coupled wind turbine as the primary power supplier, the partial flow stored in the compressed gas storage buffer can, as explained above, at least partially provide a secondary or tertiary power supply for the electrolysis plant. In this way, any power required from costly battery-based auxiliary systems can be considerably reduced. The partial flows provided for the auxiliary generator and that for the compressed gas storage buffer can be formed from different by-products.They can also be formed from the same by-product, whereby the respective partial flow can be provided, for example, by actuating a valve arrangement downstream of the electrolyzer. Particularly advantageously, oxygen can be used as a by-product in the production of hydrogen or other fluids serving as potential fuels for the partial flow. This is because oxygen is typically provided as the main by-product, so that a sufficient quantity and thus a sufficiently stable partial flow can be provided for the auxiliary generator.

[0029] The use of this partial flow can be optional and / or additionally provided during normal operation in order to enable a further increase in efficiency compared to the typically high loss in conventional electrolysis plants.

[0030] Even if the electrolysis plant cannot be supplied from the primary power supply for a time, it is preferably provided that the electrolysis plant remains at least partially connected to the primary power supply when a fault condition is detected. Preferably, at least the electrolyzer is connected to the primary power supply if, for example, downstream chemical processing or compression fails or is interrupted. In other words, the electrolysis plant can preferably remain connected to a grid, even if, for example, the electrolyzer is operated using a secondary power supply. In this way, the consumer remains connected to the grid, so that if a fault is rectified on the grid, a contribution can be made to stabilizing the grid or the power balance.The switching state of the electrolysis plant with the primary power supply can be selected based on a property of the fault condition determined from the detected fault condition and / or on the type of primary power supply. For example, the electrolysis plant or electrolyzer can be switched off or interrupted if the fault condition was detected within predefined limit values. For example, the primary power supply can be a grid, with predefined grid conditions, which are contained in the grid connection conditions, specifying for which time interval of a fault condition and / or up to which voltage dip or voltage increase the electrolysis plant should remain connected to the grid and in operation. However, if this time interval is exceeded, the electrolysis plant can be decoupled or switched off.Preferably, however, the electrolysis plant according to the invention continues to be operated, if necessary, independently of downstream processes, for example by means of a secondary and / or tertiary power supply, wherein the operation is supported by an adjustment of the feed and / or the product flow.

[0031] However, if the primary power supply is provided by, for example, a wind turbine, alternative boundary conditions can be specified and, for example, a faster disconnection and a switch to an auxiliary system can be initiated.

[0032] In order to support the continued operation of the electrolysis plant, it can further be provided that the operation of the electrolysis plant is changed from normal operation to control operation when a fault condition is detected, or that a pre-control operation is superimposed on the normal operation. Based on the detected fault condition, a duration of the fault condition can be determined and operation can be adjusted based on the duration of the fault condition. This has the advantage, among other things, that the feed-in and / or the product flow can be adjusted quickly. Likewise, certain control loops can be interrupted or stopped based on the forecast duration of the fault condition, which can be determined, for example, based on the voltage dip and / or the type of fault condition.This can be particularly true if the time required for the respective control loop is not significantly shorter than the predicted duration of the fault condition. This can prevent overcompensation during successive normal operation.

[0033] Short description of the characters

[0034] Preferred further embodiments of the invention are explained in more detail by the following description of the figures. In the figures:

[0035] Figure 1 is a schematic representation of network conditions and specified switching states; and

[0036] Figure 2 is a schematic representation of a process sequence according to the invention with preferred process steps.

[0037] Detailed description of preferred embodiments

[0038] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the various figures are provided with identical reference symbols, and a repeated description of these elements is partially omitted to avoid redundancies.

[0039] Figure 1 shows a schematic diagram of the grid conditions for a connected or to-be-connected electrolysis plant. The lines represent boundary conditions that the electrolysis plant must comply with, with a corresponding, predefined switching state being maintained within or above the lines.

[0040] In this exemplary example of an undervoltage event, a voltage (U) is plotted against time (t) in seconds. It is shown that in the event of a voltage drop, as shown in area A1, the electrolysis plant should generally be kept in the switched-on state. If the voltage drop is severe, for example towards 0 V, as shown by the bottom dashed line, this switched-on and operational state only needs to be maintained for a short time. In this example, the time limit for such a fault state is around 0.2 seconds. In the event of a smaller voltage drop, the time for which the switched state should be maintained increases linearly.Above a predetermined threshold value, as shown by the uppermost dashed line for area A2, the switched state should generally be maintained regardless of the duration of the existing fault condition or the voltage deviation from the setpoint.

[0041] However, if the duration of the fault condition exceeds range Al, as shown in range B, it is generally permissible for the electrolysis plant to be disconnected from the grid, at least for a short time, or for its operation to be modified or stopped. If the electrolysis plant meets these limit conditions, it is grid compatible and, in this respect, is accordingly capable of fault ride-through.

[0042] Figure 2 shows a schematic representation of how the presence of a fault condition in the primary power supply can be monitored and which steps can be taken to ensure continued operation of the electrolysis plant in the event of a fault condition.

[0043] Accordingly, in a first step S 100, a primary power supply of the electrolysis plant is monitored, wherein in step S 110 it is determined whether a fault condition exists in the primary power supply. If there is no fault condition ("NO"), the electrolysis plant can continue to operate in normal mode, S 112. However, if it is determined that a fault condition exists ("YES"), the electrolysis plant can optionally switch from regular operation to control operation, S 114. Furthermore, according to the invention, an adjustment of the feed of the primary fluid supply, S 120, and / or an adjustment of the output of the product flow, S 130, can be carried out. In particular, the primary fluid supply can be reduced, S 122, wherein, for example, an inlet-side water supply of an electrolyzer can be reduced.In this way, the fluid supply can be advantageously adapted to a reduction in the production rate of the electrolyzer.

[0044] Alternatively or additionally, it can be provided that the fluid supply at least partially comprises the use of a compressed gas storage buffer, S 124, wherein each compressed gas storage buffer can supply a respective gas or gas mixture to the electrolyzer. Both the reduction of the primary fluid supply, S 122, and the use of the compressed gas storage buffer, S 124, can be enabled by appropriate actuation of a valve arrangement.

[0045] Furthermore, the output of the product flow can be adjusted, S130, by discharging or blowing out part or all of the product flow, S132. In this way, even if further chemical processing or compression of the product flow downstream of the electrolyzer is interrupted, it can be ensured, for example, that predetermined pressure conditions can be maintained in the system and the electrolyzer can continue to operate. Part or all of the flow can be stored in a compressed gas storage buffer, S134.

[0046] In order to support the operation of the electrolysis plant or at least of the electrolyzer in the event of a loss of the primary power supply, it can further be provided that a secondary power supply is provided, S 140 . For this purpose, an auxiliary generator can advantageously be connected, S 142 , which can be operated using a coupled turbine and a gas flow. In this respect, the discharged (partial) flow, S 132 , is also particularly advantageous, especially since the (partial) flow S 132 can be used directly to operate the auxiliary generator S 142 in order to provide the secondary power supply for the electrolysis plant, S 140 .

[0047] The (partial) flow S 132 provided for the connected auxiliary generator in step 142 can be the same (partial) flow used to fill the compressed gas storage buffer S 134 or an alternative (partial) flow if, for example, different and (clearly) separable by-products are provided in the product flow. Likewise, a compressed gas storage buffer filled in step S 134 can provide a gas flow for operating the auxiliary generator in step S 142, whereby a tertiary power supply can also be provided if, for example, an insufficient partial flow or even no product flow is provided.

[0048] This can also be advantageous if the auxiliary generator connected and operated in step S 142 is not used, or not only, for the secondary power supply of the electrolysis plant, but is used for a heating system and / or for charging a battery system of the electrolysis plant. The connection of the auxiliary generator based on the partial flow or the compressed gas storage buffer can optionally also be advantageous regardless of the presence of a fault condition in the primary power supply, in order to enable more efficient use of the available product flow, in particular for decentralized electrolysis plants or electrolysis plants that are decoupled from the grid, such as electrolysis plants electrically coupled to offshore wind turbines.

[0049] Where applicable, all individual features shown in the embodiments can be combined and / or exchanged without departing from the scope of the invention.

Claims

Patent claims 1. A method for operating an electrolysis plant, wherein the electrolysis plant provides a product gas flow by means of a primary power supply and a primary fluid supply, characterized in that the primary power supply is monitored (S100) and a feed of the primary fluid supply (S120) and / or the output of the product flow (S130) are adjusted upon detection of a fault condition in the primary power supply (S110).

2. The method of claim 1, wherein the primary power supply is a grid.

3. The method according to claim 1 or 2, wherein the adjustment of the feed of the primary fluid supply (S120) comprises at least partially the use of a compressed gas storage buffer (S124) or wherein the fluid supply is provided by the adjustment exclusively from a compressed gas storage buffer.

4. Method according to one of the preceding claims, wherein the electrolysis plant switches on an auxiliary generator upon detection of a fault condition in the primary power supply (S142), wherein the auxiliary generator is operated by means of a gas flow from a compressed gas storage buffer (S134) and / or at least a partial flow from the product gas flow (S132).

5. The method according to claim 4, wherein the auxiliary generator provides a secondary power supply (S140) which at least partially replaces the primary power supply.

6. The method according to claim 4 or 5, wherein the auxiliary generator provides a secondary power supply for a heating system of the electrolysis plant.

7. The method according to any one of claims 4 to 6, wherein the electrical energy provided by the auxiliary generator is used at least in part to charge a battery configured as a secondary or tertiary power supply of the electrolysis plant.

8. Method according to one of the preceding claims, wherein upon detection of an error condition (S110), at least a partial flow of the product flow or the entire product flow is drained (S132) and / or stored in a compressed gas storage buffer (S134).

9. A method according to any one of claims 4 to 8, wherein the partial flow comprises or consists of generated oxygen.

10. The method according to any one of the preceding claims, wherein the electrolysis plant remains at least partially connected to the primary power supply upon detection of a fault condition (S110).

11. The method according to claim 10, wherein the switching state of the electrolysis plant with the primary power supply is selected based on a property of the fault condition determined from the detected fault condition and / or on the type of the primary power supply.

12. Method according to one of the preceding claims, wherein the operation of the electrolysis plant is changed from a regular operation to a control operation (S114) upon detection of an error condition (S110) or wherein a pre-control operation is superimposed on the regular operation.

13. The method according to claim 12, wherein a duration of the error condition is determined based on the detected error condition (S110), and wherein the operation is adjusted based on the duration of the error condition.

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