Method for operating a supply unit for an electrolyser, supply unit for carrying out the method, and extension unit
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SMA SOLAR TECH AG
- Filing Date
- 2025-12-17
- Publication Date
- 2026-07-30
Smart Images
Figure EP2025087566_30072026_PF_FP_ABST
Abstract
Description
[0001] 24-434- P- WO - 1 - submitted version
[0002] METHOD FOR OPERATING A SUPPLY UNIT FOR AN ELECTROLYSER, SUPPLY UNIT FOR EXECUTING THE METHOD AND EXTENSION UNIT
[0003] Technical field of the invention
[0004] The invention relates to a method for operating a power supply unit for supplying an electrolyzer from an alternating current network (AC network). In particular, the method aims to reliably supply the electrolyzer via the power supply unit even in the event of a fault in the AC network and / or a fault within a thyristor-based rectifier of the power supply unit, and to avoid, as far as possible, an otherwise necessary emergency shutdown of the electrolyzer.
[0005] State of the art
[0006] To meet the increasing demand for hydrogen, electrolysis plants are being installed more and more frequently. This includes not only a growing number of electrolysis plants, but also an increase in their nominal power output. Electrolysis plants with nominal outputs ranging from a few megawatts to several hundred megawatts are already commonplace. An electrolysis plant with such high output represents a large consumer in an energy supply network (ESN), and its operation can significantly impact the stability of the ESN—or individual sections thereof. Therefore, ESN operators impose specific requirements on such electrolysis plants to ensure the stability of the AC grid.For example, strong and dynamic fluctuations in the power output of such an electrolysis plant are regulated, as such large fluctuations in power consumption are difficult to compensate for by correspondingly fluctuating energy generation from the power generation units supplying the AC grid. This is particularly true when the primary energy used for electrolysis includes a high proportion of renewable energy. This renewable energy also exhibits natural fluctuations, which oppose those of the consumers connected to the grid. In particular, emergency shutdowns of large electrolysis plants are undesirable from the grid operator's perspective and should be avoided whenever possible. 24-434-P-WO-2-submitted version.
[0007] An emergency shutdown of an electrolyzer may be necessary for safety reasons, particularly if the hydrogen produced during electrolysis mixes with oxygen also produced during electrolysis or with oxygen from the ambient air, creating a highly reactive or even explosive mixture. This can be triggered, for example, by a leak within the electrolyzer from which hydrogen can escape into the environment. An explosive mixture of hydrogen and oxygen can also occur within a specific operating range of the electrolyzer. This can happen when electrolysis is carried out with a low current density, and therefore with a relatively low hydrogen and oxygen production rate, i.e., with a relatively low power consumption of the electrolyzer compared to its nominal power output.In this case, the constant diffusion of hydrogen gas through separators and into oxygen-rich areas within the electrolysis cells can lead to the formation of an explosive gas mixture. This is particularly true when electrolysis takes place over a certain period of time at relatively low voltage and / or relatively low current.
[0008] Electrolyzers in these power classes are typically supplied from the AC mains via thyristor-based rectifiers – not least for cost reasons. With such a rectifier, a voltage dip in the AC mains usually also results in a voltage dip in a DC section of the rectifier, which is difficult to counteract and then leads to an emergency shutdown of the electrolyzer connected to the rectifier. The devices and the method described here address this issue and provide a more robust and fault-resistant electrical supply for the electrolyzer.
[0009] German patent application DE 10 2020 124 964 A1 discloses a method for operating a hybrid rectifier with a thyristor rectifier and a transistor rectifier to supply a DC load from an AC network with a variable DC voltage. The method includes the following steps:
[0010] If the DC voltage at the DC output of the hybrid rectifier is below a voltage threshold: operate the hybrid rectifier in a first operating state in which the transistor rectifier is powered by the DC output. 24-434-P-WO-3- submitted version
[0011] is separated and connected to the AC input, and the total active power of the hybrid rectifier is transported via the thyristor rectifier and not via the transistor rectifier, and
[0012] If the DC voltage at the DC output of the hybrid rectifier is equal to or above the voltage threshold: the hybrid rectifier is operated in a second operating state in which the thyristor rectifier and the transistor rectifier are each connected to the AC input and the DC output, and the total active power of the hybrid rectifier is transported via both the thyristor rectifier and the transistor rectifier.
[0013] The publication DE 10 2020 112880 A1 discloses a method for operating an electrolyzer that is supplied via an actively controlled rectifier from an AC power grid, comprising the following steps:
[0014] - Operating the electrolyzer in a normal operating mode with an input voltage above the electrolyzer's open-circuit voltage, exhibiting predominantly ohmic behavior,
[0015] - Operating the electrolyzer in a standby mode at an input voltage below the open-circuit voltage with predominantly capacitive behavior, and
[0016] - Transition from standby operating mode to normal operating mode during an initial transition period, which is reduced by keeping the electrolyzer input voltage above a first voltage threshold other than 0V during standby operating mode.
[0017] Object of the invention
[0018] The invention is based on the objective of providing a method for operating a power supply unit that ensures an improved electrical supply to an electrolyzer from an AC network. In particular, it aims to prevent emergency shutdown of the electrolyzer in the event of a voltage dip in the AC network and its impact on the stability of the AC network. Furthermore, the invention aims to provide a suitable power supply unit for carrying out the method, as well as an expansion unit for a 24-434-P-WO-4-filed version.
[0019] to reveal thyristor-based rectifiers, with which the thyristor-based rectifier can be supplemented to form a corresponding power supply unit.
[0020] Solution
[0021] The object of providing a method of the type mentioned above is achieved according to the invention by the features of independent claim 1. The object of providing a power supply unit for carrying out the method is achieved according to the invention by the features of independent claim 9. The object of providing an expansion unit for a thyristor-based rectifier is achieved according to the invention by the features of independent claim 16. Advantageous embodiments of the method are set out in dependent claims 2 to 8, and advantageous embodiments of the power supply unit are set out in dependent claims 10 to 15. Dependent claim 17 relates to an advantageous embodiment of the expansion unit.
[0022] Description of the invention
[0023] The method according to the invention aims to operate a power supply unit for supplying an electrolyzer from an AC network, wherein the power supply unit is arranged between the electrolyzer and the AC network. The power supply unit is designed for rectification and for this purpose comprises a thyristor-based rectifier and a transistor-based converter. The method includes the following steps:
[0024] Normal operation of the power supply unit with a properly functioning AC network, wherein active power for the electrolyzer is provided to a certain extent, in particular to a predominant extent, by the thyristor-based rectifier, and
[0025] Emergency operation of the power supply unit in the event of a fault in the AC network or the thyristor-based rectifier, in particular a voltage dip in the AC network or faulty firing behavior of thyristors of the thyristor-based rectifier, wherein operation of the transistor-based converter prevents a DC voltage UEI applied to the electrolyzer from falling below a first voltage threshold UTH,I. 24-434-P-WO-5-submitted version
[0026] The power supply unit described above can, in particular, correspond to a power supply unit that is described in more detail below as the power supply unit according to the invention. The active power provided by the thyristor-based rectifier during normal operation of the power supply unit can correspond to the total active power supplied to the electrolyzer by the power supply unit, or comprise a predominant proportion of the total active power supplied to the electrolyzer by the power supply unit. In this case, the nominal power of the transistor-based converter can be less than the nominal power of the thyristor-based rectifier. Specifically, it is possible that the transistor-based converter provides virtually no active power during normal operation, or at least only a small proportion of the active power supplied to the electrolyzer.Alternatively, it is also possible that the transistor-based converter provides a significant portion of the total active power supplied to the electrolyzer by the power supply unit, even during normal operation. Depending on the nominal power rating of the transistor-based converter, this portion can be greater than the active power provided by the thyristor-based rectifier during normal operation. In any case, during normal operation of the power supply unit, the transistor-based converter is typically actively involved in power supply simultaneously with the thyristor-based rectifier. Specifically, the transistor-based converter can supply power to the electrolyzer in the form of active power and / or exchange power with the AC grid in the form of reactive power, e.g., compensation reactive power.
[0027] The invention prevents, or at least significantly reduces, a drop in the DC voltage applied to the electrolyzer via the transistor-based converter in the event of a voltage dip in the AC network or a fault in the thyristor-based rectifier. The invention utilizes the effect that the transistor-based converter, due to its topology and by means of a corresponding clocking of its semiconductor switches, is designed to operate in a boosting manner towards the electrolyzer. It is therefore able to generate a DC voltage that is higher than the amplitude of an AC voltage present in the AC network. In contrast to the transistor-based converter, the thyristor-based rectifier exhibits a dipping behavior towards the electrolyzer. It is therefore only able to... 24-434-P-WO-6-filed version
[0028] The goal is to generate a DC voltage that is less than or equal to the amplitude of an AC voltage applied to its AC input. Therefore, the thyristor-based rectifier can only counteract a voltage dip in the AC network with great difficulty, if at all, at its DC output. This is especially true when its thyristors are already operating almost fully conducting due to a high power flow. However, by including a transistor-based converter alongside the thyristor-based rectifier in the power supply unit, the transistor's boosting operation allows it to counteract the voltage dip in the AC network and thus prevent the DC voltage at the electrolyzer from also dropping.
[0029] By appropriately selecting the first voltage threshold UTHJ, a safety-related shutdown of the electrolyzer—that is, an emergency shutdown—can be prevented. The first voltage threshold UTHJ can be higher than the electrolyzer's open-circuit voltage ULL, ensuring that at least a small amount of electrolysis occurs or is maintained. Furthermore, the first voltage threshold UTHJ can be chosen to be high enough to guarantee a sufficient oxygen production rate during the electrolysis reaction. This prevents the continuous diffusion of hydrogen molecules into the oxygen-rich region of the electrolyzer from exceeding a concentration that would lead to the formation of an explosive gas mixture.Otherwise, this would lead to an undesirable emergency shutdown of the electrolyzer for safety reasons, which would then cause an immense power fluctuation in the AC network supplying it, further destabilizing the already faulty AC network. In summary, the method according to the invention enables the cost-effective conversion of a large power flow by means of the thyristor-based rectifier. Additionally, the transistor-based converter eliminates, or at least reduces, the undesirable side effects of the thyristor-based rectifier that could jeopardize a stable supply to the electrolyzer in the event of a fault in the AC network or the thyristor-based rectifier. The nominal power of the transistor-based converter can certainly be lower than the nominal power of the thyristor-based rectifier.The electrical supply of the electrolyzer via the described method and the disclosed supply unit is designed in the version 24-434-P-WO-7-submitted.
[0030] Overall, it is more robust and grid-friendly. Specifically, it can counteract a voltage drop in the AC grid. An emergency shutdown of the electrolyzer and the associated destabilizing effect on the AC grid can be largely prevented. The behavior explained here using the example of a voltage drop in the AC grid can be applied in the same way to a fault in the thyristor-based rectifier.
[0031] A power supply unit according to the invention for supplying an electrolyzer from an AC network comprises a thyristor-based rectifier and a transistor-based converter. The power supply unit further includes:
[0032] an AC connection for connecting the power supply unit to the AC mains, and
[0033] The power supply unit has a DC connection for connecting it to the electrolyzer. The thyristor-based rectifier is located within the power supply unit in a first path leading from the AC connection to the DC connection. An AC input of the thyristor-based rectifier is connected to the AC connection of the power supply unit, and a DC output of the thyristor-based rectifier is connected to the DC connection of the power supply unit. The transistor-based converter is located in a second path parallel to the first path or between the thyristor-based rectifier and the DC connection of the power supply unit. A key characteristic of the power supply unit is the inclusion of a control unit for its operation, particularly for controlling the thyristor-based rectifier and the transistor-based converter.The control unit is designed and configured to operate the supply unit in a state connected to the AC network and the electrolyzer according to the method according to the invention.
[0034] The transistor-based converter can include a unidirectional converter that allows power flow only towards the DC terminal of the power supply, but not towards the AC terminal of the power supply or towards the thyristor-based rectifier. Alternatively, the transistor-based converter can also include a bidirectional converter, allowing power flow both towards the DC terminal of the power supply and towards the AC terminal. (24-434-P-WO-8 - submitted version)
[0035] is designed for the connection of the power supply unit or in the direction of the thyristor-based rectifier.
[0036] The transistor-based converter of the power supply unit is designed, due to its topology, to operate in a voltage-boosting manner towards the electrolyzer connected to the DC input. In contrast, the thyristor-based rectifier, due to its thyristors, is designed to operate in a voltage-decreasing, but not a voltage-boosting, manner towards the DC input. In the event of a voltage dip in the AC network, the transistor-based converter can therefore counteract a drop in the DC voltage applied to the DC input and the connected electrolyzer, thus preventing or at least reducing the drop. The same applies in the event of a fault, where the drop in DC voltage at the DC output of the thyristor-based rectifier is caused by faulty thyristors or faulty firing behavior of thyristors in the thyristor-based rectifier.Overall, the supply to the electrolyzer can be stabilized by the transistor-based converter providing the electrolyzer with active power PTra in emergency operation of the supply unit and operating in a boosting direction towards the electrolyzer.
[0037] To detect a voltage dip in the AC network, the power supply unit can have a measuring device that directly detects AC voltages present in the AC network. Alternatively or additionally, the measuring device can also monitor the DC voltage at the DC output of the thyristor-based rectifier for a voltage dip. This also makes it possible to monitor the thyristor-based rectifier for faults simultaneously with the AC network. If the measuring device detects a voltage dip in the AC network or a voltage dip at the output of the thyristor-based rectifier, it can signal this to the control unit, which then initiates emergency operation of the power supply unit. The operating principle already described in the procedure also applies to the power supply unit, resulting in the same advantages.Advantageous embodiments of the invention are specified in the following description and the dependent claims, the version of which is 24-434-P-WO-9- filed.
[0038] Features can be applied individually and in any combination.
[0039] In an advantageous embodiment of the power supply unit—as well as of the method—the thyristor-based rectifier can be arranged in a first path between the AC and DC terminals of the power supply unit. The transistor-based converter can be arranged in a second path, parallel to the first path, between the AC and DC terminals of the power supply unit. In this embodiment, the transistor-based converter can, in particular, comprise a transistor-based AC / DC converter. Different AC voltages can be present at the thyristor-based rectifier arranged in the first path and at the AC / DC converter of the transistor-based converter arranged in the second path.Specifically, the amplitude of an AC voltage applied to the first (AC-side) terminal of the transistor-based converter can be smaller than the amplitude of an AC voltage applied to the AC input of the thyristor-based rectifier. This results in overlapping voltage bands at the second (DC-side) terminal of the transistor-based converter and the DC output of the thyristor-based rectifier. This is advantageous for simultaneously powering the electrolyzer during normal operation using both the thyristor-based rectifier and the transistor-based converter. Different amplitudes at the DC input of the thyristor-based rectifier in the first path and at the first terminal of the transistor-based converter in the second path can be set using a transformer located in only one of the two paths.Alternatively, the power supply unit can also have two transformers with different turns ratios, with one transformer arranged in each of the two paths. In another variant, a transformer with a common primary winding but different secondary windings for the two paths can also be used. The transistor-based converter can be designed as a single-stage converter and include an AC / DC converter but not a DC / DC converter. Alternatively, however, it is also possible for the transistor-based converter to be designed as a two-stage converter, which includes a transistor-based DC / DC converter in series with the transistor-based AC / DC converter. In particular, the DC / DC converter can have a step-down capability towards the DC terminal.24-434-P-WO-10- submitted version.
[0040] The invention comprises a transistor-based DC / DC converter. The DC / DC converter can be configured as a pure buck converter or as a combined buck-boost converter. The transistor-based DC / DC converter is thus designed to precharge the electrolyzer connected to the DC input. Otherwise, this precharging would have to be done via the thyristor-based rectifier. However, due to the small firing angles of the thyristors associated with precharging, this would result in significant reactive power exchanged with the AC grid, which is generally undesirable. Within the scope of the invention, the precharging of the electrolyzer can be carried out via the DC / DC converter, which acts as a buck converter in the direction of the DC input. This completely eliminates, or at least significantly reduces, the reactive power exchanged with the AC grid during precharging.
[0041] In normal operation of the power supply unit, the electrolyzer receives all—or a large portion—of its active power via the thyristor-based rectifier. In this case, the transistor-based converter can be deactivated or supply only a small amount of active power to the electrolyzer. In emergency operation of the power supply unit, the transistor-based converter, regardless of whether it is a single-stage or two-stage converter, can operate by boosting the voltage towards the DC input. In this mode, it can supply the electrolyzer with all, or at least a substantial, if not the majority, of its active power, thereby counteracting a drop in the electrolyzer's DC voltage.
[0042] Not only during the electrolyzer's pre-charging phase, but also during normal operation of the power supply unit, i.e., during the normal electrolysis reaction, the thyristor-based rectifier generates reactive power Q-my flowing into the AC grid. This, too, can be undesirable. In an advantageous variant of the method, the transistor-based converter, configured as an AC / DC converter, can also provide compensating reactive power Chra during normal operation of the power supply unit. This can be superimposed on the reactive power Q-my generated by the thyristor-based rectifier and at least partially compensate for it. Thus, even during normal operation, it is possible to minimize the reactive power exchanged with the AC grid—and therefore the undesirable feedback effect on the AC grid. 24-434-P-WO-11-submitted version
[0043] In an alternative version of the method—and the device—the transistor-based converter can include a step-up transistor-based DC / DC converter. In this case, the thyristor-based rectifier can be arranged between the AC and DC terminals, with its AC input connected to the AC terminal of the power supply. A reverse current protection device can be arranged between the DC output of the thyristor-based rectifier and the DC terminal of the power supply or the electrolyzer connected thereto. The transistor-based converter, configured as a transistor-based DC / DC converter, can be arranged in a third path parallel to the reverse current protection device.In this way, the reverse current protection device and the transistor-based DC / DC converter can be connected in parallel and in series between the thyristor-based rectifier and the DC terminal of the power supply unit – and thus also in series between the thyristor-based rectifier and the electrolyzer connected to the DC terminal. The transistor-based DC / DC converter can be configured to operate in a step-up mode towards the DC terminal.
[0044] This power supply unit operates as follows: During normal operation, the transistor-based DC / DC converter can be deactivated, so no power flows through it. The entire power flow for the electrolyzer can then be provided by the thyristor-based rectifier. The reverse current protection device is conductive in this configuration. In the event of a voltage dip in the AC network or a fault in one or more thyristors of the thyristor-based rectifier, the DC voltage at the DC output of the thyristor-based rectifier drops. This drop in DC voltage at the DC output can be detected by a suitable measuring unit and signaled to the control unit. Alternatively, instead of detecting a fault at the DC output of the thyristor-based rectifier, the measuring unit can, of course, also detect a fault in the AC network directly within the AC network itself.After the control unit has signaled a fault, it can initiate emergency operation of the power supply unit. In emergency operation, the transistor-based DC / DC converter can then be activated, which subsequently begins its boosting operation towards the DC connection – and thus towards the electrolyzer. Although the voltage at the DC output of the thyristor-based rectifier is now low due to the fault in the AC network or in the version submitted under 24-434-P-WO-12.
[0045] If the voltage of the thyristor-based rectifier drops, a boost-operating transistor-based DC / DC converter can prevent the DC voltage at the power supply unit's DC input from falling below the first voltage threshold UTHJ. Since the electrolyzer is connected to the DC input, the same applies to the DC voltage at the electrolyzer. This effectively prevents an emergency shutdown of the electrolyzer, which would otherwise occur if the voltage falls below the first threshold UTH.
[0046] The reverse current protection device can be a diode or a parallel connection of several diodes. Alternatively, it can also be designed as a so-called active diode or a parallel connection of several active diodes. An active diode is a parallel connection of an actively controlled switch, for example, a semiconductor switch, and a diode, or an actively controlled semiconductor switch that incorporates an inherent body diode. In this configuration, the actively controlled switch of the reverse current protection device can be operated in the closed position during normal operation of the power supply unit, thereby reducing the voltage drop across the reverse current protection device and thus its power loss.In emergency operation of the power supply unit, the actively controllable switch can be open, so that, due to the blocking effect of the diode, a power flow through the reverse current protection device is prevented.
[0047] One cause that leads to a safety-related emergency shutdown of the electrolyzer is the formation of an explosive gas mixture during electrolysis. To prevent such an emergency shutdown, it is therefore advantageous to minimize the formation of an explosive gas mixture of hydrogen and oxygen. Specifically, a mixture of hydrogen and oxygen forms an explosive gas mixture within a certain hydrogen concentration range, which, under atmospheric conditions, can range from 4 vol% to 77 vol% hydrogen by volume. To detect the formation of an explosive gas mixture, it can therefore be beneficial to continuously monitor the hydrogen content in the oxygen section of the electrolyzer during electrolysis. Experience has shown that the hydrogen content in the oxygen section increases at low electrolysis rates – i.e., at 24-434- P- WO - 13- submitted version
[0048] DC voltages slightly above the open-circuit voltage (ULL) of the electrolyzer are observed – with decreasing DC voltage and / or decreasing power consumption of the electrolyzer. This can be due to the constant diffusion of hydrogen through the separator into the oxygen section of the electrolyzer, which becomes increasingly significant at low electrolysis rates. To prevent such low electrolysis rates from occurring in the first place, it is advantageous to define a voltage range for the electrolyzer's DC voltage within which electrolysis may only be carried out for a specific duration. Thus, electrolysis within this defined DC voltage range is time-limited.In one embodiment of the method, if a drop below the first voltage threshold UTH is anticipated during emergency operation, the DC voltage UEI at the electrolyzer can be reduced to a second voltage threshold UTH,2. This reduction of the DC voltage can be implemented such that the time At, during which the DC voltage lies between the voltage thresholds UTHJ and UTH,2, does not exceed a predetermined maximum value Atmax. The second voltage threshold UTH,2 can correspond to the open-circuit voltage of the electrolyzer or be lower than it, so that no electrolysis occurs at the DC voltage level of the second voltage threshold UTH,2. In this way, the duration of an electrolysis rate that could potentially lead to the formation of an explosive gas mixture is limited, and the risk of such a mixture forming is further reduced.
[0049] Advantageously, the power supply unit can have, in addition to its DC connection, a further DC connection for supplying electrical power to at least one peripheral unit of the electrolyzer. This further DC connection can be connected via another DC / DC converter to the transistor-based converter or to a DC output of the thyristor-based rectifier. Depending on the design of the transistor-based converter, the further DC / DC converter can be connected to its first terminal, its second terminal, or to its DC link. The further DC / DC converter can also be a transistor-based DC / DC converter and can be configured as a boost converter, buck converter, or a combined boost / buck converter. The task of the further DC / DC converter is to function, either alone or in combination with the 24-434-P-WO-14- submitted version.
[0050] The transistor-based converter maintains a DC voltage at the secondary DC input within a tolerance range, ensuring the proper operation of the connected peripheral unit. This is particularly important in the event of a fault in the AC network or the thyristor-based rectifier, i.e., during emergency operation of the power supply. Specifically, the secondary DC / DC converter can be designed to prevent the DC voltage at the secondary DC input from falling below a third voltage threshold, UTH,3, during emergency operation of the power supply. This can be achieved through appropriate operation, particularly by adjusting the clocking of its semiconductor switches and, if necessary, in combination with the transistor-based converter.
[0051] In an advantageous embodiment, the power supply unit can additionally include an energy storage device, in particular a battery or a supercapacitor, which is connected to the transistor-based converter. Depending on the design of the transistor-based converter, the energy storage device can be connected to one of its two terminals or to the DC link of the transistor-based converter. Alternatively, in a two-stage transistor-based converter with an AC / DC converter and a downstream DC / DC converter, the energy storage device can also be connected to a DC link of the two-stage transistor-based converter. The connection of the energy storage device to the transistor-based converter can be direct or via a charging / discharging converter.The energy storage system enables the power supply unit to compensate for even deep and / or prolonged voltage dips in the AC grid without the first voltage threshold UTHJ being undershot, which would otherwise trigger an emergency shutdown of the electrolyzer. This is difficult or even impossible for a power supply unit without energy storage. Furthermore, should an emergency shutdown of the electrolyzer become unavoidable, any power gradient affecting the AC grid can be further mitigated.
[0052] An expansion unit according to the invention for a thyristor-based rectifier for the electrical supply of an electrolyzer comprises:
[0053] a first connection for connection to an AC network or a DC output of the thyristor-based rectifier, 24-434- P- WO - 15- submitted version
[0054] a second connection for connection to the electrolyzer
[0055] a transistor-based converter with a first terminal and a second terminal, the first terminal of which is connected to the first terminal of the expansion unit and the second terminal of which is connected to the second terminal of the expansion unit, and
[0056] A control unit for controlling the expansion unit, in particular the transistor-based converter. The expansion unit is characterized in that, in combination with the thyristor-based rectifier, it forms a power supply unit according to the invention. The power supply unit can be operated in a state connected to the AC network and the electrolyzer according to the method according to the invention.
[0057] If the first connection of the expansion unit is designed for connection to an AC network, the expansion unit can additionally include a transformer. This ensures that the AC voltage at the AC input of the thyristor-based rectifier and the AC voltage applied to the transistor-based converter of the expansion unit each have different amplitudes. The expansion unit can also be used to convert an existing power supply unit that includes a thyristor-based rectifier but no transistor-based converter, and therefore exhibits the disadvantages described above, into a power supply unit according to the invention. The expansion unit also offers the advantages already mentioned in connection with the method and the power supply unit according to the invention.
[0058] In one embodiment, the expansion unit can have, in addition to its DC connection, a further DC connection for supplying electrical power to at least one peripheral unit of the electrolyzer. This further DC connection can be connected via a further DC / DC converter, in particular a transistor-based further DC / DC converter, to the first connection of the expansion unit, to the second connection of the expansion unit, or to the transistor-based converter itself. The further DC / DC converter is designed, in emergency operation of the power supply unit, to prevent a DC voltage present at the further DC connection from inducing a third-party DC voltage, by means of appropriate operation—possibly in combination with the transistor-based converter.
[0059] The voltage threshold UTH,3 is undershot. The additional DC / DC converter – like the additional DC / DC converter of the power supply unit – can be a boost converter, a buck converter, or a combined boost / buck converter.
[0060] Brief description of the characters
[0061] The invention is illustrated below with the aid of figures. Of these, Fig. 1 shows a first embodiment of a supply unit according to the invention;
[0062] Fig. 2 shows a second embodiment of a supply unit according to the invention;
[0063] Fig. 3 shows a third embodiment of a supply unit according to the invention;
[0064] Fig. 4 shows a flowchart of the method according to the invention in one embodiment;
[0065] Fig. 5 shows an extension unit according to the invention in a first embodiment;
[0066] Fig. 6 shows an extension unit according to the invention in a second embodiment;
[0067] Figure description
[0068] Figure 1 shows a first embodiment of a power supply unit 1 according to the invention for supplying electrical power to an electrolyzer 30 from an AC network 40. The power supply unit 1 is connected to the AC network 40 via an AC connection 21 and to the electrolyzer 30 via a DC connection 22 and is designed to rectify AC power into DC power. Between the AC connection 21 and the DC connection 22, the power supply unit 1 has a first path 23 for a power flow P-my, in which a first transformer 11 and a thyristor-based rectifier 2 are arranged. A primary side 11P of the first transformer 11 is connected to the AC connection 21 and a secondary side 11S of the first transformer 11 is connected to an AC input 2.1 of the thyristor-based rectifier 2. A DC output 2.2 of the thyristor-based rectifier 2 is connected to the DC connection 22 of the supply unit via a measuring unit 15.Parallel to the first path 2324-434- P- WO - 17- submitted version.
[0069] The power supply unit has a second path 24 between the AC terminal 21 and the DC terminal 22, in which a power flow Pira flows. In this second path, starting from the AC terminal 21 of the power supply unit 1, a second transformer 12 with a primary side 12P connected to the AC terminal 21 and a secondary side 12S, as well as a transistor-based converter 3, are arranged. The secondary side 12S of the second transformer 12 is connected to a first terminal 3.1 of the transistor-based converter 3. The transistor-based converter 3 in Fig. 1 is designed for rectification and is configured as a single-stage converter with a transistor-based AC / DC converter 4. A second terminal 3.2 of the transistor-based converter 3 is connected to the DC terminal 22 of the power supply unit 1 via a DC isolator 9. The DC isolator 9 is optional. Alternatively, the second terminal 3.2 of the transistor-based converter 3 is connected to the DC terminal 22 of the power supply unit 1 via a DC isolator 9.The power supply unit 1 is connected directly to the DC terminal 22 without the intermediate DC isolating unit 9. The power supply unit 1 also includes an energy storage device 16, which is connected via a charge / discharge converter (not shown in Fig. 1) to the DC-side second terminal 3.2 of the transistor-based converter 3. The power supply unit 1 further includes another DC terminal 28 for supplying a peripheral unit of the electrolyzer 30 (e.g., a pump, a heater, etc.; not shown in Fig. 1). This additional DC terminal 28 is connected via another transistor-based DC / DC converter 7 to the DC-side second terminal 3.2 of the transistor-based converter 3. Additionally, the supply unit 1 includes a control unit 10. This is connected to the thyristor-based converter 2, the transistor-based converter 3, the further DC / DC converter 7, the measuring unit 15 and the energy storage unit 16 for control purposes and data exchange (in Fig.1. The control and communication technology connections are symbolized by dashed lines.
[0070] The power supply unit 1 provides the electrolyzer 30 with rectified power P from the AC mains 40. To ensure simultaneous power supply via both the first path 23 and the second path 24, identical voltages are required at the DC output 2.2 of the thyristor-based rectifier 2 and the second (DC-side) terminal 3.2 of the transistor-based converter 3 during operation. The voltage ranges that can be covered at the DC output 2.2 and at the second terminal 24-434- P- WO - 18- submitted version
[0071] 3.2 of the transistor-based converter 3 should therefore overlap. Therefore, an amplitude Ü is T h y the AC voltage applied to AC input 2.1 of the thyristor-based rectifier 2 is greater than an amplitude ÜTra an AC voltage applied to the first (i.e., AC-side) terminal 3.1 of the transistor-based converter 3. The following applies to the amplitudes of the AC voltages in the parallel paths 23, 24: Ü T h y > Ü Tra , which is achieved via corresponding translation ratios of the first transformer 11 and the second transformer 12.
[0072] In normal operation of the power supply unit 1, a large portion of the total active power P is supplied to the electrolyzer 30 by the thyristor-based rectifier 2. The electrolysis rate is controlled via the active power P, essentially by the active power P-my in the first path 23. For this purpose, the firing angles of the thyristors of the thyristor-based rectifier 2 can be set or varied accordingly by the control unit 10. This results in reactive power Q-my in the first path 23, which—if no further precautions are taken—would flow into the AC network 40 via the AC connection 21. However, excessive exchange of reactive power Q with the AC network 40 is usually undesirable. Therefore, in normal operation, the reactive power is reduced by generating a compensating reactive power Qm in the second path 24 via the transistor-based AC / DC converter 4 of the transistor-based converter 3.This is superimposed on the reactive power Q-my 23 generated in the first path by the thyristor-based rectifier 2, thereby reducing the total reactive power Q flowing into the AC network 40.
[0073] In the event of a voltage dip in the AC network 40 or the failure of one or more thyristors of the thyristor-based rectifier 2, a DC voltage drops at the DC output 2.2 of the thyristor-based rectifier 2. The voltage dip is detected by the measuring unit 15 and signaled to the control unit 10. The control unit 10 then initiates the emergency operation of the power supply unit 1.
[0074] In emergency operation of the power supply unit 1, the transistor-based converter 3, shown in Fig.
[0075] 1. The AC / DC converter 4 is controlled to provide additional active power Pira. The transistor-based AC / DC converter 4 is designed for boost operation towards the DC terminal 22. Im24-434-P-WO-19- submitted version
[0076] In contrast to the thyristor-based rectifier 2, the transistor-based converter 3 can thus counteract, reduce, or even prevent the voltage drop at the DC output 2.2 of the thyristor-based rectifier 2. Specifically, by appropriately timing its transistors, it ensures that the DC voltage at the DC terminal 22 of the power supply unit—and thus the DC voltage UEL at the electrolyzer 30—does not fall below a first voltage threshold UTH,I. In this way, the transistor-based converter 3 prevents an emergency shutdown of the electrolyzer 30, which could otherwise occur due to the voltage drop and the potentially associated formation of an explosive gas mixture in the electrolyzer 30.
[0077] To ensure that the electrolyzer's peripheral device 30, which is connected to the additional DC port 28 of the power supply unit 1, is properly supplied – i.e., with the correct voltage level – during emergency operation, the control unit 10 also controls the additional DC / DC converter 7 so that the DC voltage at the additional DC port 28 remains within predefined limits specified by the connected peripheral device. Generally, the DC voltage at the additional DC port 28 differs from the DC voltage UEL required at the DC port 22.
[0078] In the event that the voltage drop at the DC output 2.2 of the thyristor-based rectifier 2 is more severe and / or lasts longer, such that the transistor-based converter 3 cannot draw sufficient power from the AC network 40, a supplementary power supply can be provided from the energy storage device 16. In this way, even in the case of a more severe and / or longer-lasting fault, a sufficient supply to the electrolyzer 30 and its peripheral devices is ensured, and an emergency shutdown of the electrolyzer 30 during emergency operation of the power supply unit 1 can be effectively prevented.
[0079] The first embodiment of the supply unit according to Fig. 1 includes a transformer 11, 12 in each of the two paths 23, 24. However, this is merely exemplary and not limiting, as it only represents one variant for supplying AC voltages with different amplitudes Ü. T h y , ÜTra with Ü T h y > Ü Tra to be implemented in the two paths 23 and 24. Alternatively, the different amplitudes Ü can be used. T h y , Ü Tra this can also be achieved by the version submitted in 24-434-P-WO-20.
[0080] Only one of the two paths 23, 24 has a transformer. In this case, the AC voltage in the path without a transformer corresponds to the AC voltage present at AC terminal 21 and thus in the AC network 40. Furthermore, instead of two transformers 11, 12, a single transformer with one common primary winding per phase but two galvanically isolated secondary windings for the two paths 23, 24 can be used.
[0081] Fig. 2 shows a second embodiment of the supply unit 1 according to the invention in a state connected to the AC network 40 and an electrolyzer 30. The supply unit corresponds in many features to the first embodiment shown in Fig. 1. For the similar features, reference is therefore made to the description of Fig. 1. In the following, only the differences from the embodiment of Fig. 1 are explained.
[0082] In contrast to the first embodiment, in the second embodiment of the power supply unit 1, the transistor-based converter 3 arranged in the second path 24 is designed as a two-stage converter and comprises a transistor-based AC / DC converter 4 and a transistor-based DC / DC converter 5 connected downstream of the DC terminal 22. As in Fig. 1, the AC / DC converter 4 is designed as a bidirectional AC / DC converter and is configured to operate in a boost mode towards the DC terminal 22. The DC / DC converter 5 is also a bidirectional converter and is configured to operate in a buck mode towards the DC terminal 22. The DC / DC converter 5 can be a pure buck converter or a combined buck-boost converter. The energy storage device 16, again shown as a battery in Fig. 2, is connected to a DC link of the two-stage transistor-based converter 3.It can be connected to the DC link either directly or via a charge / discharge converter (not shown in Fig. 2). In the embodiment according to Fig. 2, a further DC connection 28 for connecting a peripheral device of the electrolyzer 30 (e.g., a pump, a heater, etc.) is not shown. In an alternative variant, however, it is also possible that this is present and connected via a further DC / DC converter 7 to the second connection 3.2 of the version 24-434-P-WO-21.
[0083] transistor-based converter 3 or is connected to its DC intermediate circuit.
[0084] Normal operation of the second embodiment of the power supply unit 1 largely corresponds to the normal operation of the first embodiment as shown in Fig. 1. A large portion of the active power P required by the electrolyzer is provided by the thyristor-based rectifier 2 in the form of active power P-my. The transistor-based converter 3 can also provide an active power component Pira, but this is not strictly necessary. As in Fig. 2, the transistor-based AC / DC converter 4 is also driven to generate a compensating reactive power Qna, which is superimposed on the reactive power Q-my of the thyristor-based rectifier 2 in order to minimize the total reactive power Q exchanged with the AC network 40.
[0085] In the event of a fault in the AC network 40 or the thyristor-based rectifier 2, which is detected as shown in Fig. 1, the control unit 10 initiates emergency operation of the power supply unit 1. In emergency operation, the transistor-based converter 3 – in Fig. 2, the combination of AC / DC converter 4 and DC / DC converter 5 – is operated in boost mode towards the DC input 22. The DC / DC converter 5 can also be operated in step-down mode towards the DC input 22, as long as the combination of the boosting AC / DC converter 4 and the step-down DC / DC converter 5 ensures overall boost mode operation towards the DC input 22. In the second embodiment of Fig. 2, the transistor-based converter 3 also supports the DC voltage applied to the electrolyzer 30 in emergency operation and counteracts the drop in DC voltage by increasing it in the direction of the DC connection 22.By providing a corresponding active power Pira, it prevents the DC voltage UEI applied to the electrolyzer 30 from falling below the first voltage threshold UTH,I.
[0086] By designing the DC / DC converter 5 as a step-down converter towards the DC terminal 22, the electrolyzer 30 can also be precharged via the transistor-based converter 3. This would otherwise have to be done via the thyristor-based rectifier 2, which would result in significant reactive power Q-my. 24-434-P-WO-22-submitted version
[0087] Figure 3 shows a third embodiment of the power supply unit 1 according to the invention in a state connected to an AC network 40 and an electrolyzer 30. An AC connection 21 is connected to the AC network 40 and a DC connection 22 to the electrolyzer 30. The AC connection 21 is connected to the DC connection 22 via a first path 23. A transformer 11 is connected with its primary side 11P to the AC connection 21 and with its secondary side 11S to an AC input 2.1 of a thyristor-based rectifier 2. A DC output 2.2 of the thyristor-based rectifier 2 is connected via a measuring unit 15 and a reverse current protection device 8 – shown by way of example as a diode in Figure 3 – to the DC connection 22 of the power supply unit 1.Parallel to the reverse current protection device 8, the transistor-based converter 3 is arranged in a third path 25, such that the reverse current protection device 8 and the transistor-based converter 3 are connected in parallel and in series between the thyristor-based rectifier 2 and the DC terminal 22. In Fig. 3, the transistor-based converter 3 is configured as a transistor-based DC / DC converter 6, which is designed for boost operation in the direction of the DC terminal 22. It can be a pure boost converter or a combined boost / buck converter. The power supply unit 1 has a control unit 10 for its control. The control unit 10 is connected, for control purposes and data exchange, to the thyristor-based rectifier 2, the transistor-based converter 3, and the measuring unit 15, as symbolized by dashed lines.
[0088] In normal operation of the third embodiment of the power supply unit 1, the entire active power or nearly the entire active power P for the electrolyzer 30 is provided by the thyristor-based rectifier 2, i.e., P ≤ P-my. To adjust / change the active power P-my, the firing angles of the thyristors of the thyristor-based rectifier 2 are set / varied by the control unit 10. This is accompanied by a reactive power Q-my, which is exchanged with the AC network 40 via the AC connection 21. The transistor-based converter 3 can be deactivated in normal operation, meaning its semiconductor switches are not clocked. In the event of a voltage drop in the AC network 40 or a faulty thyristor or faulty firing behavior of a thyristor, the DC voltage at the DC output 2.2 of the thyristor-based rectifier 2 drops.The sinking is detected by the measuring unit 15 and signaled to the control unit 10,24-434- P- WO - 23 - submitted version.
[0089] which interprets the drop as an error and subsequently initiates emergency operation of supply unit 1.
[0090] In emergency operation, the semiconductor switches of the transistor-based converter 3 are clocked by the control unit 10 such that it converts active power PTra and operates in boost mode towards the DC terminal 22. The active power PTra of the DC / DC converter 6 is transferred to the DC terminal 22 and the electrolyzer 30 connected to it. In emergency operation, the transistor-based converter 3, configured as a DC / DC converter 6, builds up a voltage difference between its first terminal 3.1 and its second terminal 3.2. Due to this voltage difference, the reverse current protection device 8 is in its blocking state, and all the power PThy flowing through the thyristor-based rectifier 2 also flows through the transistor-based converter 3 in emergency operation. Due to the boost mode operation towards the DC terminal 22, the DC / DC converter 6 counteracts the drop in DC voltage at the DC output 2.2 of the thyristor-based rectifier 2 and can prevent the voltage UEL applied to the electrolyzer from falling below the first voltage threshold UTHJ.
[0091] In Fig. 3, the reverse current protection device 8 is implemented as an exemplary diode. Alternatively, however, it is also possible for the reverse current protection device 8 to have one or more actively controllable semiconductor switches and to operate functionally like an active diode. In a variant of the power supply unit 1 shown in Fig. 3, the reverse current protection device 8 can have two actively controllable semiconductor switches arranged in anti-series, and the transistor-based converter 3 can be designed as a combined buck-boost converter. In this way, the reverse current protection device 8 can be switched off regardless of the direction of an existing voltage difference. By then operating the DC / DC converter 6 in a buck-boosting state in the direction of the DC terminal 22, this can be used to precharge the electrolyzer 30.Compared to precharging the electrolyzer 30 by the thyristor-based rectifier 2, this would result in a significantly lower reactive power Q.
[0092] Figure 4 shows an embodiment of the method according to the invention. This can be carried out with a supply unit 1 according to one of Figures 1-3. The method starts in a first step S1. For example, see 24-434-P-WO-24 - submitted version
[0093] Assuming that the power supply unit 1 is operating normally, the first step checks whether there is an AC voltage dip in the AC network 40 or a fault in the thyristor-based rectifier 2. This can be detected by a drop in the DC voltage at the DC output 2.2 of the thyristor-based rectifier 2. If a fault is present (“+” at S1), the procedure jumps to the third step S3, in which the power supply unit 1 is operated in emergency mode. In this mode, the transistor-based converter 3 is operated with a boost voltage such that the DC voltage UEI applied to the electrolyzer 30 does not fall below a first voltage threshold UTHJ. If no fault is detected in the first step S1, the procedure proceeds to the third step S3.
[0094]
[0095] (at S1), the procedure jumps to a second step S2, and the supply unit operates in normal mode. In both the second step S2 and the third step S3, the procedure jumps back to the first step S1, where it checks for errors. Depending on whether an error is detected or not, the procedure either jumps to the third step S3, where the supply unit operates in emergency mode, or to the second step S2, where the supply unit operates in normal mode.
[0096] Figure 5 shows a first embodiment of an expansion unit 50 according to the invention. With the expansion unit 50, an existing purely thyristor-based power supply unit for an electrolyzer 30 can be converted into an embodiment of a power supply unit 1 according to the invention, as shown in Figure 2.
[0097] The expansion unit 50 in Fig. 5 is largely similar in its construction and components to the second path 24 of the power supply unit 1 in Fig. 2. The expansion unit 50 has a first terminal 51 for connection to an AC network 40 and / or an AC input of the thyristor-based rectifier of the existing power supply unit (not shown in Fig. 5). The expansion unit 50 also includes a second terminal 52 for connection to the electrolyzer 30. The first terminal 51 is connected to the second terminal 52 via a transformer 12 and a transistor-based converter 3. A primary side 12P of the transformer 12 is connected to the first terminal 51, and a secondary side 12S is connected to the first terminal 3.1 of the transistor-based converter 3. The turns ratio of the transformer 12 is selected such that 24-434- P- WO - 25 - submitted version
[0098] an amplitude Ü Traan AC voltage applied to the transistor-based converter 3 is smaller than an amplitude Ü T h y"which is present at the AC input of the thyristor-based rectifier of the existing power supply unit. The transistor-based converter 3 is implemented as an example bidirectional two-stage converter and includes a transistor-based bidirectional AC / DC converter 4 and a transistor-based bidirectional DC / DC converter 5. The transistor-based DC / DC converter 5 is designed to operate in a buck-shifting manner towards the second terminal 52 and can therefore include a buck converter or a combined buck / boost converter. In this way, it can be used to precharge the electrolyzer 30. The transistor-based converter 3—that is, the combination of the AC / DC converter 4 and the DC / DC converter 5—is also designed to operate in a boost-shifting manner towards the second terminal 52."The expansion unit 50 further includes an energy storage device 16, which is connected to a DC link between the AC / DC converter 4 and the DC / DC converter 5. The energy storage device can be connected to the DC link directly or via a separate charge / discharge converter. In the first case, the charging function can be implemented by either the AC / DC converter 4 or the DC / DC converter 5, while the discharging function for the energy storage device 16 can be implemented by the DC / DC converter 5. A measuring unit 56 for detecting voltage and / or current is arranged between the transistor-based converter 3 and the second terminal 52.
[0099] A control unit 53 is provided for controlling the expansion unit 50. The control unit 53 is designed to cooperate with another control unit outside the expansion unit 50 for the purpose of joint control. For this purpose, the control unit 53 has a control connection that leads out of the expansion unit 50 (symbolized by a dashed line in Fig. 5).
[0100] By connecting the expansion unit 50 of Fig. 5 to the existing purely thyristor-based supply unit, an embodiment of the supply unit 1 according to the invention is obtained, which is shown in Fig. 2. The first connection 51 of the expansion unit 50 then represents 24-434- P- WO - 26 - submitted version
[0101] The AC connection 21 of the power supply unit 1 from Fig. 2. The second connection 52 of the expansion unit 50 represents the DC connection 22 of the power supply unit 1 from Fig. 2. The operating mode of the existing power supply unit supplemented by the expansion unit 50 is analogous to the operation as described in connection with the embodiment of Fig. 2. Specifically, a voltage dip in the AC network 40 and / or a fault in the thyristor-based rectifier leads to a drop in the DC voltage UEL applied to the electrolyzer 30. This is detected by a measuring unit 56 and signaled to the control unit 53, which then initiates emergency operation and controls the transistor-based converter 3 in such a way that the DC voltage applied to the second connection – which corresponds to the DC voltage UEL applied to the electrolyzer – does not fall below the first voltage threshold UTH.
[0102] Optionally, the expansion unit can have a further DC output 58, which is connected via a further DC / DC converter 7 to the second terminal 3.2 of the transistor-based converter 3 or to its DC link. A peripheral device for the electrolyzer 30 can be connected via the further DC output 58, so that the peripheral device is also reliably supplied in the event of a fault in the AC network 40 or in the thyristor-based rectifier 2. Figure 6 shows a second embodiment of an expansion unit 50 according to the invention. With the expansion unit 50 shown here, an existing purely thyristor-based power supply unit for an electrolyzer 30 can be converted into an embodiment of a power supply unit 1 according to the invention, as shown in Figure 3.
[0103] The expansion unit 50 in Fig. 6 largely corresponds in its construction and components to the part of the power supply unit 1 in Fig. 3 that is arranged between the thyristor-based rectifier 2 and the DC connection 22. The expansion unit in Fig. 6 comprises a first connection 51, which is designed for connection to the thyristor-based rectifier 2 – specifically to the DC output 2.2 of the thyristor-based rectifier 2. The expansion unit 50 comprises a second connection 52, which is designed for connection to the electrolyzer 30. A measuring unit 56 for detecting a voltage and / or a current is arranged at the first connection 51. A reverse current protection device (824-434-P-WO-27 - submitted version) is located between the measuring unit 56 and the second connection 52.
[0104] The expansion unit 50 further comprises a transistor-based converter 3, which in this embodiment of the expansion unit 50 is arranged in a path 25 parallel to the reverse current protection device 8. The transistor-based converter 3 is designed as a DC / DC converter 6 and configured to operate in a boosting manner towards the second terminal 52. For this purpose, it can comprise a boost converter or a combined boost / buck converter. The expansion unit 50 includes a control unit 53 for its control. The control unit 53 is designed to cooperate with another control unit (not shown in Fig. 6) outside the expansion unit 50 for the purpose of joint control. For this purpose, the control unit 53 has a control connection that leads out of the expansion unit 50 (symbolized by a dashed line in Fig. 5).
[0105] By combining the expansion unit 50 of Fig. 6 with the existing purely thyristor-based power supply unit, an embodiment of the power supply unit 1 according to the invention is obtained, as shown in Fig. 3. To combine the expansion unit 50 of Fig. 6 with the existing thyristor-based power supply unit, an existing continuous electrical connection between the thyristor-based rectifier and the electrolyzer 30 can be removed and replaced by the expansion unit 50. In this way, the first terminal 51 of the expansion unit 50 then corresponds to the DC output 2.2 of the thyristor-based rectifier 2 of the power supply unit 1 in Fig. 2. The second terminal 52 of the expansion unit 50 then represents the DC terminal 22 of the power supply unit 1 from Fig. 3.The operation of the existing power supply unit combined with the expansion unit 50 is analogous to the operation described in connection with the embodiment of Fig. 3, to which reference is made here. Specifically, a voltage dip in the AC network 40 and / or a fault in the thyristor-based rectifier of the existing power supply unit leads to a drop in the DC voltage at the DC output of the thyristor-based rectifier. This is detected by the measuring unit 56 and signaled to the control unit 53, which then initiates emergency operation and controls the transistor-based converter 3 in such a way that it enters boost mode and converts a DC voltage present at its first terminal 3.1 into a higher DC voltage.
[0106] The voltage is converted and then applied to its second terminal 3.2. The voltage difference causes the reverse current protection device 8 to operate in its blocking state. The control unit 53 now controls the transistor-based converter 3 such that the DC voltage applied to its second terminal 3.2 – which also corresponds to the DC voltage UEL applied to the electrolyzer 30 – does not fall below the first voltage threshold UTH,I.
[0107] The expansion unit has an additional DC output 58, which is connected via another DC / DC converter 7 to the first terminal 3.2 or to the second terminal 3.2 of the transistor-based converter 3. A peripheral device of the electrolyzer 30 can be connected to this additional DC output 58, ensuring that the peripheral device is also reliably supplied in the event of a fault in the AC network 40 or in the thyristor-based rectifier 2. The additional DC output 58 is optional and not mandatory. -434- P- WO submitted version
[0108] Reference sign: Supply unit
[0109] thyristor-based rectifier
[0110] AC input
[0111] DC output
[0112] transistor-based converter
[0113] Connection
[0114] Connection
[0115] transistor-based AC / DC converter transistor-based DC / DC converter (TSS) transistor-based DC / DC converter (HSS) DC / DC converter reverse current protection device
[0116] control unit
[0117] transformer
[0118] P Primary page
[0119] S Secondary page
[0120] transformer
[0121] P Primary page
[0122] S Secondary page
[0123] capacity
[0124] Unit of measurement
[0125] AC connection
[0126] DC connector
[0127] First path
[0128] Second path
[0129] Third Path
[0130] Additional DC connection
[0131] Electrolyzer
[0132] AC network
[0133] Expansion unit
[0134] First connection
[0135] second connection
[0136] Control unit-434- P- WO - 30 - submitted version
[0137] Measuring unit Additional DC connection -S3 Process step
Claims
1. 24-434- P- WO - 31 - submitted version Patent claims 1. Method for operating a supply unit (1) for the electrical supply of an electrolyzer (30) from an AC network (40), wherein the supply unit (1) is arranged between the electrolyzer (30) and the AC network (40), is designed for rectification operation and for this purpose comprises a thyristor-based rectifier (2) and a transistor-based converter (3), comprising the steps: - Normal operation of the supply unit (1) with a properly operating AC network (40), wherein an active power for the electrolyzer (30) is provided to a certain extent, in particular to a predominant extent, by the thyristor-based rectifier (2), and - Emergency operation of the supply unit (1) in the event of a fault in the AC network (40) or the thyristor-based rectifier (2), in particular a voltage dip in the AC network (40) or a faulty ignition behavior of thyristors of the thyristor-based rectifier (2), wherein operation of the transistor-based converter (3) prevents a DC voltage UEI applied to the electrolyzer (30) from falling below a first voltage threshold UTH,I.
2. Method according to claim 1, wherein within the supply unit (1) the thyristor-based rectifier (2) is arranged in a first path (23) and the transistor-based converter (3) is arranged in a second path (24) parallel to the first path (23), and wherein the transistor-based converter (3) comprises a transistor-based AC / DC converter (4).
3. Method according to claim 1 or 2, wherein the transistor-based converter (3) is configured as a two-stage converter comprising a deep-setting transistor-based DC / DC converter (5) connected in series with the transistor-based AC / DC converter (4).
4. The method of claim 1, wherein the transistor-based converter (3) comprises a boost-capable transistor-based DC / DC converter (6), wherein a reverse current protection device (8) is arranged between the thyristor-based rectifier (2) and the electrolyzer (30), and wherein the transistor-based DC / DC converter (6) is arranged in a third path (25) parallel to the reverse current protection device (8). 24-434-P-WO-32-filed version 5. Method according to one of the preceding claims, wherein the transistor-based converter (3) provides an active power PTra to the electrolyzer (30) in emergency operation of the supply unit (1) and is operated in a boosting direction towards the electrolyzer (30).
6. Method according to one of claims 1 to 3, wherein a compensation reactive power Chra is provided to the AC network (40) during normal operation of the supply unit (1) by the transistor-based converter (3).
7. Method according to one of the preceding claims, wherein the first voltage threshold UTHJ is above an open-circuit voltage of the electrolyzer (30).
8. Method according to one of the preceding claims, wherein, when a drop below the first voltage threshold UTHJ is foreseeable in emergency operation, the DC voltage UEI at the electrolyzer (30) is reduced to a second voltage threshold UTH,2, wherein the reduction of the voltage is carried out in such a way that a time period At, during which the DC voltage lies between the thresholds UTHJ and UTH,2, does not exceed a predetermined maximum value Atmax.
9. Supply unit (1) for supplying an electrolyzer (30) from an AC network (40) with a thyristor-based rectifier (2) and a transistor-based converter (3), comprising: - an AC connection (21) for connecting the power supply unit (1) to the AC network (40), and - a DC connection (22) for connecting the power supply unit (1) to the electrolyzer (30), - wherein the thyristor-based rectifier (2) is arranged in a first path (23), wherein an AC input (2.1) of the thyristor-based rectifier (2) is connected to the AC terminal (21) and a DC output (2.2) of the thyristor-based rectifier (2) is connected to the DC terminal (22), - wherein the transistor-based converter (3) is arranged in a second path (24) parallel to the first path (23) or between the thyristor-based rectifier (2) and the DC terminal (22), characterized in that the supply unit (1) further comprises a control unit (10) which is designed to control the supply unit (1) in a 24-434- P- WO - 33 - submitted version to operate in the state connected to the AC network (40) and the electrolyzer (30) according to the method of one of the preceding claims.
10. Power supply unit (1) according to claim 9, characterized in that the transistor-based converter (3) comprises a DC / DC converter (6) arranged in a third path (25) parallel to a reverse current protection device (8), wherein the arrangement of the DC / DC converter (6) and the reverse current protection device (8) is arranged in series between the thyristor-based rectifier (2) and the DC terminal (22), and wherein the DC / DC converter (6) is designed to operate in a boosting manner in the direction of the DC terminal (22).
11. Power supply unit (1) according to claim 9, characterized in that the thyristor-based rectifier (2) is arranged in the first path (23) between the AC terminal (21) and the DC terminal (22) and the transistor-based converter (3) is arranged in the second path (24) parallel to the first path (22) and comprises a transistor-based AC / DC converter (4).
12. Power supply unit (1) according to one of claims 9 and 11, characterized in that the transistor-based converter (3) is designed as a two-stage converter which, in addition to the transistor-based AC / DC converter (4), comprises a transistor-based DC / DC converter (5), wherein the DC / DC converter (5) is designed to operate in a deep-setting manner in the direction of the DC connection (22).
13. Supply unit (1) according to one of claims 9, 11 and 12, characterized in that an amplitude Ü Traan AC voltage applied to the transistor-based converter (3) is smaller than an amplitude Ü T h y an AC voltage applied to the thyristor-based rectifier (2).
14. Power supply unit (1) according to one of claims 9 to 13, characterized in that the power supply unit (1) has a further DC connection (28) for the electrical supply of at least one peripheral unit of the electrolyzer (30), wherein the further DC connection (28) is connected via a further DC / DC converter (7) to the transistor-based converter (3) or the DC output (2.2) of the thyristor-based rectifier (2), and wherein the further DC / DC converter (7) is designed to operate in emergency mode. 24-434-P-WO-34-filed version The power supply unit (1) is operated accordingly - possibly in combination with the transistor-based converter (3) - to prevent the DC voltage applied to the further DC connection (28) from falling below a third voltage threshold UTH,3.
15. Power supply unit (1) according to any one of claims 9 to 14, further comprising an energy storage device (16), in particular a battery or a supercapacitor, which is connected to the transistor-based converter (3).
16. Expansion unit (50) for a thyristor-based rectifier (2) for the electrical supply of an electrolyzer (30) comprising: - a first connection (51) for connection to an AC network (40) or a DC output (2.2) of the thyristor-based rectifier (2) - a second terminal (52) for connection to the electrolyzer (30) - a transistor-based converter (3) with a first terminal (3.1) and a second terminal (3.2), which is connected with its first terminal (3.1) to the first terminal (51) of the expansion unit (50) and with its second terminal (3.2) to the second terminal (52) of the expansion unit (50), and - a control unit (53) for controlling the expansion unit (50), in particular the transistor-based converter (3), characterized in that the extension unit (50) in combination with the thyristor-based rectifier (2) forms a supply unit (1) according to one of claims 9 to 15.
17. Expansion unit (50) according to claim 16, further comprising a further DC connection (58) for the electrical supply of at least one peripheral unit of the electrolyzer (30), wherein the further DC connection (58) is connected via a further DC / DC converter (7) to the transistor-based converter (3) or a DC connection (2.2) of the thyristor-based rectifier (2), wherein the further DC / DC converter (7) is designed, in emergency operation of the supply unit (1), to prevent, by appropriate operation - optionally in combination with the transistor-based converter (3) - a DC voltage applied to the further DC connection (58) from falling below a third voltage threshold UTH,3.