Method and apparatus for regulating potential state of dc conductor
By adjusting the potential state of the DC conductor and utilizing semiconductor switching and clock control technology, the problem of reduced insulation resistance in the electrolyzer was solved, thus achieving safe and reliable operation and extended lifespan of the electrolyzer.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SMA SOLAR TECH AG
- Filing Date
- 2024-12-12
- Publication Date
- 2026-07-14
AI Technical Summary
During the operation of the electrolyzer, as the operating time increases, the insulation resistance between the DC conductors gradually decreases, leading to an increase in current and posing a safety hazard. Existing technologies are unable to effectively suppress or restore the insulation resistance to avoid electrolyzer failure.
By adjusting the potential state of the DC conductor to make it have the same polarity relative to the ground potential, and by using semiconductor switching and clock control technology, the PID effect caused by ion migration is reduced or reversed, ensuring insulation performance. An auxiliary power supply is used to provide electrical power when necessary to maintain the normal operation of the electrolyzer.
It effectively reduces or reverses the PID effect, extends the service life of the electrolyzer, avoids electrolyzer failure caused by reduced insulation resistance, and achieves safe and reliable operation of the electrolyzer.
Smart Images
Figure CN122397183A_ABST
Abstract
Description
Technical Field
[0001] This application relates to methods and apparatus for regulating the potential state of a DC conductor, and to a DC power grid having such apparatus and an electrolyzer.
[0002] background The electrolyzer can be supplied with DC power via a DC port to perform electrolysis. This DC power can be obtained from the AC power grid and supplied to the electrolyzer via a rectifier and DC conductors. Here, the potential difference between the DC conductors corresponds to the DC voltage applied to the electrolyzer. The potential state of each DC conductor relative to ground depends on the type of AC power grid and its grounding, as well as the type of rectifier, particularly whether the rectifier has electrical isolation.
[0003] During electrolyzer operation, it was observed that the current flowing from the electrolyzer to ground gradually increases with operating time, resulting in a decrease in the electrolyzer's insulation resistance. For safety reasons, electrolyzer operation must be interrupted when the insulation resistance drops below a predetermined limit or the grounding current exceeds the corresponding limit. Therefore, it is desirable to suppress this slow decrease in insulation resistance during continuous electrolyzer operation, or to raise the insulation resistance back above the limit without maintenance intervention (e.g., replacing electrolyzer components).
[0004] Overview The first and second DC conductors are configured to supply electrical power to the electrolyzer. The electrical power can be transferred from the AC grid (AC: alternating current / alternating voltage) to the DC conductors via a rectifier.
[0005] In a method for adjusting the potential state of a first DC conductor and a second DC conductor, in a first operating mode, the potential state of the first DC conductor and the second DC conductor is adjusted such that the two DC conductors have the same polarity relative to ground potential.
[0006] The device for adjusting the potential state of the first DC conductor and the second DC conductor is designed to adjust the potential state of the first DC conductor and the second DC conductor in a first operating mode such that the two DC conductors have the same polarity relative to ground potential.
[0007] The described adjustment enables the targeted influence of the potential state of the DC conductor. Specifically, the described adjustment can reduce so-called potential-induced degradation (PID) in electrolyzers, particularly those with multiple electrolytic stacks. In the PID effect, the insulating properties of the electrolyzer can be impaired due to ion migration within the electrolyzer, caused by the potential state of the DC conductor. By targeting the potential state of the DC conductor, this ion migration can be reduced or reversed, thereby reducing or reversing the PID effect.
[0008] The potential state of the DC conductors can be adjusted, for example, by the power electronics of the device, so that the potentials of the two DC conductors have the same polarity relative to ground. This can, for example, reduce or avoid the PID effect.
[0009] In one embodiment of the method, in a first operating mode, the potential state is adjusted to achieve regeneration of the electrolyzer. Depending on the electrolyzer's structure, it may be required that the two DC conductors have positive or negative potentials relative to ground to achieve regeneration. In one embodiment, the device adjusts the potential state with the corresponding polarity.
[0010] When the electrolyzer is regenerated, the PID effect, particularly the undesirable ion migration or the resulting chemical reactions, is at least partially reversed. To achieve this, the potential states of the DC conductors are selectively chosen to achieve the reversal effect. Specifically, the potentials of the DC conductors can be adjusted to be as close as possible to each other and to maintain a minimum distance from ground.
[0011] In one embodiment of the method and / or apparatus, the first operating mode has a first sub-operating mode in which the potential difference between the first DC conductor and the second DC conductor is adjusted such that the voltage applied to the electrolyzer is lower than a threshold voltage. In this embodiment, the voltage applied to the electrolyzer is lower than the threshold voltage, which can be selected, for example, with reference to the characteristic curve of the electrolyzer, so that the electrolyzer is within a predetermined operating range.
[0012] Here, the threshold voltage can depend on the electrolyzer's starting voltage (Einsatzspannung), and specifically corresponds to the starting voltage. The starting voltage of the electrolyzer refers to the voltage at which the electrolysis process begins in the electrolyzer. The starting voltage can also be called the decomposition voltage. The threshold voltage can particularly be located in the range between 10% and 50% of the starting voltage. In this embodiment, the potential state of the DC conductor is selected such that the voltage applied to the electrolyzer is so small that the electrolyzer does not perform electrolysis. The potential state can be adjusted so that other desired processes, such as regeneration processes, can be performed in the electrolyzer without significant electrolysis during this period, and without providing the power required for this.
[0013] In embodiments of the method and / or apparatus, in the first sub-operational mode, the DC conductor is isolated from the AC power grid. This is particularly advantageous when the AC power grid has a fixed ground reference, such as a TN grid. It can then be specified that the electrical power required to regulate the potential state is obtained from a source other than the AC power grid, for example from an auxiliary power source that provides electrical power for a potential state with a supply voltage independent of the AC power grid's potential and specifically electrically isolated from the AC power grid. The auxiliary power source can, for example, obtain electrical power from a battery and / or generator. However, the auxiliary power source can also have an electrically isolated connection from the AC power grid, for example via a transformer, thus not excluding the auxiliary power source from drawing power from the AC power grid.
[0014] In one embodiment of the method and / or apparatus, the first operating mode has a second sub-operating mode. Here, the first and second operating modes can be used alternately. In the second sub-operating mode of the first operating mode, electrical power is supplied to the electrolyzer via a rectifier from the AC grid to perform the electrolysis process, wherein in the second sub-operating mode, the potential difference between the first and second DC conductors is adjusted according to the electrolysis process. Specifically, this second sub-operating mode can be specifically configured to supply electrical power to the electrolyzer from the AC grid to perform electrolysis. Simultaneously, the potential adjustment enables the reduction of PID effects and / or the regeneration of the electrolyzer.
[0015] In one embodiment, in the second sub-operation mode, the potential difference between the first DC conductor and the second DC conductor can depend on the operating voltage of the electrolyzer. Specifically, the potential difference can be adjusted such that the voltage applied to the electrolyzer corresponds to the operating voltage of the electrolyzer. In this embodiment, the potential state of the DC conductor is selected such that the voltage applied to the electrolyzer is high enough to enable the electrolyzer to perform electrolysis. The operating voltage of the electrolyzer is higher than the starting voltage and depends particularly on the type of electrolyzer.
[0016] In one embodiment of the method and / or apparatus, a second operating mode is provided, wherein either the first or second DC conductor is grounded, and electrical power is supplied to the electrolyzer via a rectifier to perform the electrolysis process. In the second operating mode, the potential difference between the first and second DC conductors is adjusted according to the electrolysis process. This second operating mode can be specifically configured to supply electrical power from the AC grid to the electrolyzer to perform electrolysis. Unlike the first operating mode, in which the potentials of the two DC conductors are adjusted such that they have the same polarity relative to ground (i.e., both are on the same side of ground), in the second operating mode, the potentials of the two DC conductors can sometimes have different polarities (i.e., they are on different sides of ground).
[0017] In some implementations, in the second operating mode, the potential difference between the first DC conductor and the second DC conductor corresponds to the operating voltage of the electrolyzer. In this implementation, the potential state of the DC conductor is selected such that the voltage applied to the electrolyzer is large enough to enable the electrolyzer to perform electrolysis.
[0018] In one embodiment of this method, the potential state is adjusted by clocking a semiconductor switch disposed between a first DC conductor and ground potential or a second DC conductor and ground potential. Here, clocking can be performed, for example, by the described apparatus. By connecting one of the DC conductors to ground using a clock-controllable semiconductor switch, a so-called soft, current-carrying connection between the DC conductor and ground can be achieved. The current can be controlled via clocking, thereby adjusting the potential state. This semiconductor switch enables a so-called "soft grounding."
[0019] In one embodiment of this method, the ground current flowing through the semiconductor switch is monitored. The ground current is the current flowing between the DC conductor connected to the semiconductor switch and ground. Monitoring is performed, for example, using the described apparatus. Specifically, monitoring can be performed by using ammeter A to detect the ground current, which can be arranged within the apparatus. The magnitude of the ground current can then be determined in the apparatus's computing device, and a response can be triggered when the ground current is excessive. Thus, a ground fault protection scheme can be implemented that responds to ground currents exceeding critical values, thereby responding to ground faults.
[0020] Each of the two DC conductors can have a predetermined minimum gap between its respective potential and the ground potential. It can be specified that this minimum gap is maintained in each of the described operating modes. This minimum gap is specifically adjusted by regulating the potential. By maintaining the minimum gap, regeneration progress is ensured for a predetermined duration, or degradation is sufficiently suppressed.
[0021] The DC power grid includes an electrolyzer, the described device, and a first DC conductor and a second DC conductor. Optionally, the DC power grid has an auxiliary power source for supplying electrical power to the device as needed. For example, when the DC power grid is disconnected from the AC power grid and electrical power cannot be obtained from the AC power grid, there may be a need to supply electrical power to the device. The need for electrical power to regulate the potential state can then be met, for example, through the auxiliary power source.
[0022] List of Attachments The embodiments of this application will be further explained and described below with reference to the accompanying drawings. In the drawings: Figure 1 A DC power grid with a device for regulating the potential state is schematically shown. Figure 2A first embodiment of the potential state of a DC conductor is schematically illustrated, including an exemplary ground current profile. Figure 3 A second embodiment of the potential state of a DC conductor is schematically shown. Figure 4 A third embodiment of the potential state of a DC conductor is schematically illustrated. Figure 5 A fourth embodiment of the potential state of a DC conductor is schematically illustrated. Figure 6 A fifth embodiment of the potential state of a DC conductor is schematically shown.
[0023] In the accompanying drawings, the same reference numerals are used for the same or similar elements. The illustrations in the figures may not be drawn to scale.
[0024] Attached Figure Description Figure 1 A device 10 for adjusting the potential states of the first DC conductor DC+ and the second DC conductor DC- is schematically shown. AC power from the AC power grid 12 can be converted into DC power via rectifier 20 and transmitted to the DC conductors DC+ and DC-.
[0025] DC grid 30 includes a device 10, DC conductors DC+ and DC-, a DC switch 18, a fuse 24, and an electrolyzer 14. The electrolyzer 14 has multiple so-called electrolysis stacks 16 connected in series. Each electrolysis stack 16 has at least one electrolytic cell in which the desired electrolysis process takes place. For example, the electrolysis can be water electrolysis to produce hydrogen and oxygen. The electrolyzer 14 is supplied with DC power via the DC conductors DC+ and DC-, which is obtained from an AC grid 12 via a rectifier 20. For example, the AC grid 12 can be a public power grid. The AC grid 12 can be single-phase or multi-phase. The AC grid 12 can be grounded or ungrounded.
[0026] In the first operating mode, device 10 adjusts the potential states of the two DC conductors DC+ and DC- so that they have the same polarity relative to ground potential GND. Therefore, the device is designed to perform a method in the first operating mode that adjusts the potential states of the two DC conductors DC+ and DC- so that they have the same polarity relative to ground potential GND. For this purpose, device 10 has a semiconductor switch 22, which is clock-controlled by the device. The semiconductor switch establishes a connection between the first DC conductor DC+ or the second DC conductor DC- and ground potential GND. This connection is clock-controlled, i.e., the semiconductor switch 22 is turned on and off according to a duty cycle 26, so that the flowing current can be adjusted by the clock-controlled duty cycle 26. The clock control of semiconductor switch 22 can be performed in such a way that the potential states of the two DC conductors DC+ and DC- can be selectively adjusted relative to each other and relative to ground potential GND.
[0027] Optionally, the flowing current can be detected by ammeter A. This device can detect the current flowing through the semiconductor switch via ammeter A and, if necessary, disconnect the DC switch to isolate the electrolyzer 14 from the rectifier 20. Furthermore, the DC power grid 30 is protected by fuse 24 to prevent excessive ground current.
[0028] As an alternative to the first operating mode, a second operating mode is executed. The operation of the DC power grid 30 can be switched between the first and second operating modes. In the second operating mode, the potentials of the first DC conductor DC+ and the second DC conductor DC- are adjusted so that an electrolysis process can be performed in the electrolyzer 14. Electrical power is transferred from the AC power grid 12 to the electrolyzer 14 via the DC conductors DC+ and DC- to perform electrolysis. The voltage applied to the electrolyzer 14 and corresponding to the potential difference between the first DC conductor DC+ and the second DC conductor DC- is greater than the starting voltage of the electrolyzer 14 and corresponds to, for example, the operating voltage of the electrolyzer 14.
[0029] If the DC power grid 30 with electrolyzer 14 operates on the AC power grid 12 (which is designed as a TN grid), then when the DC power grid 30 is connected to the AC power grid 12 (which is designed as a TN grid, such as a star-grounded AC power grid 12) via rectifier 20, in the second operating mode, the voltages of the first DC conductor DC+ and the second DC conductor DC- are symmetrical with respect to the ground potential GND. Consequently, the second DC conductor DC- has a negative voltage relative to ground GND. This negative voltage can cause negatively charged ions to flow to ground, thereby degrading the electrolyzer 14 due to the PID effect and potentially significantly shortening its lifespan. Figure 1 As shown, if multiple electrolytic reactors 16 are connected in series, this effect may be significantly amplified.
[0030] Even when the electrolyzer 14 is connected to an electrically isolated AC power grid 12 (e.g., an IT power grid) via a rectifier, a PID effect can still be observed. Here, in the second operating mode, a voltage is generated between the two DC conductors DC+ and DC- when the potentials of the two DC conductors DC+ and DC- are symmetrical or approximately symmetrical with respect to the ground potential GND. Therefore, the PID effect can occur in different types of AC power grids 12, TN power grids, or IT power grids.
[0031] The advantage provided by the described device 10 and the described method is that, in the first operating mode, this PID effect can be mitigated, reduced, or even reversed.
[0032] Figure 2 Another embodiment of the potential states of the first DC conductor DC+ and the second DC conductor DC- in a second operating mode is illustrated by way of example. The second operating mode can be used alternately with the first operating mode. The following describes how the method and apparatus 10 can function as ground current monitoring in the second operating mode.
[0033] In this embodiment, the DC power grid 30 is powered by an electrically isolated AC power grid 12 (e.g., an IT grid) via a rectifier 20. One of the DC conductors (in the illustrated example, the second DC conductor DC-) is grounded. The first DC conductor is regulated to a potential state such that the voltage between the conductors is large enough to allow electrolysis to occur in the electrolyzer 14.
[0034] The PID effect can be mitigated or avoided by grounding one of the DC conductors (here, the second DC conductor DC-). Which of the two DC conductors, DC+ and DC-, is grounded can depend on, for example, the type of rectifier 20 used.
[0035] Figure 2 The intermediate graph shows a possible curve for the duty cycle 26 of the clock control of semiconductor switch 22. (As shown...) Figure 2 The figure below shows a possible curve for the grounding current 28.
[0036] The potential state is adjusted by clock control of the semiconductor switch 22 using a method and apparatus for adjusting the potential state, such as... Figure 2 As shown in the diagram above. To maintain the potential state, for example due to a fault, the clock control must be adjusted over time, and the ground current 28 rises, for example due to the fault. If the ground current 28 reaches a first threshold 32, the clock control stops, and the electrolyzer 14 is disconnected from the rectifier 20, for example by disconnecting the DC switch 18. If the ground current 28 continues to rise, for example due to the fault worsening, the fuse 24 is triggered, for example, when it reaches a threshold 34.
[0037] Figure 3 A first embodiment of a first sub-operating mode of a first operating mode is shown. The potential of ground GND and the potential corresponding to the maximum DC voltage 36 of the DC power grid 30 are shown.
[0038] The potentials of the first DC conductor DC+ and the second DC conductor DC- are adjusted by device 10 so that both are positive relative to the ground potential GND. Therefore, both have positive polarity relative to the ground potential GND.
[0039] The potential difference between the first DC conductor DC+ and the second DC conductor DC- is adjusted so that the voltage applied to the electrolyzer 14 is lower than a threshold voltage. The threshold voltage is lower than the starting voltage of the electrolyzer 14, so that no electrolysis occurs in the electrolyzer 14 in the first sub-operation mode. The threshold voltage can, for example, be located in the range between 10% and 50% of the starting voltage.
[0040] Since electrolysis does not occur in electrolyzer 14 in the first sub-operation mode, the DC conductors DC+ and DC- of the DC grid 30 can be isolated from the AC grid 12. Furthermore, this allows the first sub-operation mode to be executed independently of the type of AC grid 12. Therefore, the first sub-operation mode can be used for different types of AC grid 12, such as TN grids or IT grids.
[0041] If the DC grid 30 is disconnected from the AC grid in the first sub-operation mode, electrical power for regulating the potential state can be obtained from the auxiliary power supply 21 of the DC grid 30.
[0042] Figure 4 A second embodiment of the first sub-running mode of the first running mode is shown.
[0043] The potentials of the first DC conductor DC+ and the second DC conductor DC- are adjusted by device 10 so that both are negative relative to ground potential GND. Therefore, both have negative polarity relative to ground GND.
[0044] The potential difference between the first DC conductor DC+ and the second DC conductor DC- is adjusted so that the voltage applied to the electrolyzer 14 is lower than a threshold voltage. The threshold voltage is lower than the starting voltage of the electrolyzer 14, so that no electrolysis occurs in the electrolyzer 14 in the first sub-operation mode. The threshold voltage can, for example, be located in the range between 10% and 50% of the starting voltage.
[0045] Since electrolysis does not occur in electrolyzer 14 in the first sub-operation mode, the DC conductors DC+ and DC- of the DC grid 30 can also be separated from the AC grid 12 in this mode. Furthermore, this allows the first sub-operation mode to be executed independently of the type of AC grid 12. Therefore, the first sub-operation mode can be used for different types of AC grids 12, such as TN grids or IT grids.
[0046] If the DC grid 30 is disconnected from the AC grid in the first sub-operation mode, electrical power for regulating the potential state can be obtained from the auxiliary power supply 21 of the DC grid 30.
[0047] Figure 5 A first embodiment of a second sub-operation mode of the first operating mode is shown. In the second sub-operation mode, electrical power is supplied from the AC grid 12 to the electrolyzer 14 via the rectifier 20 to perform the electrolysis process in the electrolyzer 14.
[0048] The potentials of the first DC conductor DC+ and the second DC conductor DC- are adjusted by device 10 so that both are positive relative to the ground potential GND. Therefore, both have positive polarity relative to the ground potential GND.
[0049] In the second sub-operation mode, the potential difference between the first DC conductor DC+ and the second DC conductor DC- is adjusted such that, in the second sub-operation mode, the potential difference between the first DC conductor DC+ and the second DC conductor DC- corresponds to the operating voltage of the electrolyzer 14. The potential difference between the first DC conductor DC+ and the second DC conductor DC- corresponds at least approximately and in such a way as to the operating voltage of the electrolyzer 14, so that the electrolysis process can be performed in the electrolyzer 14.
[0050] Figure 6 A second embodiment of a second sub-operational mode of the first operating mode is shown. In the second sub-operational mode, electrical power is supplied from the AC grid 12 to the electrolyzer 14 via the rectifier 20 to perform the electrolysis process in the electrolyzer 14.
[0051] The potentials of the first DC conductor DC+ and the second DC conductor DC- are adjusted by device 10 so that both are negative relative to the ground potential GND. Therefore, both have negative polarity relative to the ground potential GND.
[0052] In the second sub-operation mode, the potential difference between the first DC conductor DC+ and the second DC conductor DC- is adjusted such that, in the second sub-operation mode, the potential difference between the first DC conductor DC+ and the second DC conductor DC- corresponds to the operating voltage of the electrolyzer 14. The potential difference between the first DC conductor DC+ and the second DC conductor DC- corresponds at least approximately and in such a way as to the operating voltage of the electrolyzer 14, so that the electrolysis process can be performed in the electrolyzer 14.
[0053] Reference tag list 10 devices 12AC power grid 14 Electrolyzers 16 Electrolytic Reactor 18DC switches 20 rectifiers 21 Auxiliary Power Supply 22-Clock Controlled Semiconductor Switch 24 fuses 26. Duty cycle of semiconductor switches 28 Grounding Current 30DC power grid 32 First threshold 34 Second Threshold 36 Maximum DC Voltage A ammeter DC+, DC- DC conductors GND (Ground Potential)
Claims
1. A method for adjusting the potential states of a first DC conductor and a second DC conductor (DC+, DC-), wherein, The DC conductors (DC+, DC-) are configured to supply electrical power to the electrolyzer (14), and the electrical power can be transmitted from the AC grid (12) to the DC conductors (DC+, DC-) via the rectifier (20), wherein, in the first operating mode, the potential states of the first DC conductor and the second DC conductor (DC+, DC-) are adjusted such that the two DC conductors (DC+, DC-) have the same polarity relative to the ground potential (GND).
2. The method according to claim 1, wherein, In the first operating mode, the potential state is adjusted so that the two DC conductors (DC+, DC-) have positive polarity relative to the ground potential (GND).
3. The method according to claim 1, wherein, In the first operating mode, the potential state is adjusted so that the two DC conductors (DC+, DC-) have negative polarity relative to the ground potential (GND).
4. The method according to claim 1, 2 or 3, wherein, The first operating mode includes a first sub-operating mode in which the potential difference between the first DC conductor and the second DC conductor (DC+, DC-) is adjusted so that the voltage applied to the electrolyzer (14) is lower than the threshold voltage.
5. The method according to claim 4, wherein, The threshold voltage depends on the starting voltage of the electrolyzer (14), wherein the threshold voltage is specifically located in the range between 10% and 50% of the starting voltage.
6. The method according to claim 4 or 5, wherein, In the first sub-operation mode, the DC conductors (DC+, DC-) are separated from the AC power grid (12).
7. The method according to any one of claims 4 to 6, wherein, Electrical power for adjusting the potential state is obtained from the auxiliary power supply (21).
8. The method according to any one of the preceding claims, wherein, The first operating mode includes a second sub-operating mode in which electrical power is supplied from the AC grid (12) to the electrolyzer (14) via the rectifier (20) to perform an electrolysis process, wherein the potential difference between the first DC conductor and the second DC conductor (DC+, DC-) is adjusted according to the electrolysis process in the second sub-operating mode.
9. The method according to claim 6, wherein, In the second sub-operation mode, the potential difference between the first DC conductor and the second DC conductor (DC+, DC-) depends on the operating voltage of the electrolyzer.
10. The method according to any one of the preceding claims, wherein, A second operating mode is provided, in which the first DC conductor or the second DC conductor (DC+, DC-) is grounded, wherein electrical power is supplied from the AC grid (30) to the electrolyzer (14) via the rectifier (20) to perform the electrolysis process, and wherein, in the second operating mode, the potential difference between the first DC conductor and the second DC conductor (DC+, DC-) is adjusted according to the electrolysis process.
11. The method according to any one of the preceding claims, wherein, The potential state is adjusted by clocking a semiconductor switch (22) disposed between the first DC conductor (DC+) and the ground potential (GND), or disposed between the second DC conductor (DC-) and the ground potential (GND).
12. The method according to claim 9, wherein, The ground current (28) flowing through the semiconductor switch (22) is monitored.
13. The method according to any one of the preceding claims, wherein, Each of the two DC conductors (DC+, DC-) has a minimum spacing between its potentials relative to ground potential (GND).
14. A device (10) for adjusting the potential state of a first DC conductor and a second DC conductor (DC+, DC-), wherein, The DC conductors (DC+, DC-) are configured to supply electrical power to the electrolyzer (14), and the electrical power can be transmitted from the AC grid (12) to the DC conductors (DC+, DC-) via the rectifier (20), wherein the device (10) is designed to adjust the potential state of the first DC conductor and the second DC conductor (DC+, DC-) in a first operating mode such that the two DC conductors (DC+, DC-) have the same polarity relative to ground potential (GND).
15. The apparatus according to claim 14, wherein, The device (10) is configured to adjust the potential state in the first operating mode such that the two DC conductors (DC+, DC-) have positive polarity relative to the ground potential (GND).
16. The apparatus according to claim 14, wherein, The device (10) is configured to adjust the potential state in the first operating mode such that the two DC conductors (DC+, DC-) have negative polarity relative to the ground potential (GND).
17. The apparatus according to claim 14, 15 or 16, wherein the apparatus (10) is configured to clock-control a semiconductor switch (22) for adjusting the potential state, the semiconductor switch being disposed between the first DC conductor (DC+) and the ground potential (GND), or disposed between the second DC conductor (DC-) and the ground potential (GND).
18. The apparatus according to any one of claims 14 to 17, wherein, The device (10) is designed to monitor the ground current (28) flowing through the semiconductor switch (22).
19. A DC power grid (30) having an electrolyzer (14), a device (10) according to any one of claims 14 to 18, and a first DC conductor and a second DC conductor (DC+, DC-).
20. The DC power grid (30) according to claim 19 further includes an auxiliary power supply (21) for supplying electrical power to the device (10) as needed.