Power supply device for an electrolyzer

Abstract

The invention relates to a power supply device (1) for an electrolyzer (2), wherein a first winding (111) of a first transformer (11) is provided for connection to a power supply grid (20), wherein a line-commutated power converter (13) is connected on the AC voltage side to a second winding (112) of the first transformer (11), wherein the DC voltage-side connection (131) of the line-commutated power converter (13) is configured as a connection for the electrolyzer (2). To improve the power supply device (1), it is proposed that a self-commutated power converter (14) is connected on the AC voltage side to a second winding (122) of a second transformer (12), wherein the self-commutated power converter (14) is connected on the DC voltage side to a power source, wherein a first winding (121) of the second transformer (12) is connected electrically in series with one of the windings (111, 112) of the first transformer (11). The invention further relates to an electrolyzer device (10) having such a power supply device (1) and having at least one electrolyzer (2). The invention further relates to a method for operating such a power supply device (1) or such an electrolyzer device (10). The invention further relates to a control device configured to carry out such a method.

Description

[0001] Description

[0002] Power supply device for an electrolyzer

[0003] The invention relates to a power supply device for an electrolyzer with a first transformer and a grid-commutated power converter, wherein a first winding of the first transformer is provided for connection to a power supply network, wherein the grid-commutated power converter is connected on the AC side to a second winding of the first transformer, wherein the DC side connection of the grid-commutated power converter is designed as a connection for the electrolyzer. Furthermore, the invention relates to an electrolysis device with such a power supply device and at least one electrolyzer. The invention further relates to a method for operating such a power supply device or such an electrolysis device. Furthermore, the invention relates to a control device.

[0004] Electrolysis rectifiers for supplying electrical energy to an electrolyzer must be capable of regulating fluctuations in the mains voltage of a power grid and providing a higher DC voltage as the electrolyzer ages. Various circuit topologies are currently used for this purpose in systems with a capacity of more than 5 MW.

[0005] A first circuit topology is the controlled rectifier with thyristors, which is designed in a six-, twelve- or higher pulse version (B6C, B12C, B18C, B24C). This represents a cost-effective solution for high power levels. The DC voltage, the output voltage of the thyristor rectifier, is set via the control angle α, or a tap changer with electromechanical or electronic switching is used. An alternative design uses an uncontrolled rectifier with a buck converter. The buck converter is designed for the full current and requires chokes for its operation. Often several buck converters are used in order to be able to meet harmonic requirements.

[0006] Another alternative circuit topology involves the use of a grid-side voltage-link converter, such as those used in photovoltaic and wind turbine applications. When using these converters, the secondary voltage of the transformer is selected to be sufficiently low to generate the required DC voltage. However, this is currently rarely or never used in electrolysis.

[0007] The following refers to the term "winding" of a transformer. This term includes both a single-phase winding, which has a single partial winding for the particular phase, and a multi-phase, particularly a three-phase, winding, in which the winding has a corresponding number of partial windings. A partial winding is provided for each phase, so that, for example, a three-phase winding has three partial windings. These partial windings can be designed, for example, as a star winding or a delta winding.

[0008] The term "arranged in series" or "electrically in series" indicates that the voltages of the components arranged in series add up. They do not necessarily have to carry the same current.

[0009] The invention is based on the object of improving the energy supply for an electrolyzer.

[0010] This object is achieved by a power supply device for an electrolyzer, wherein the power supply device has a first transformer and a second transformer, a grid-commutated power converter and a self-commutated power converter, wherein a first winding of the first transformer is provided for connection to a power supply network, wherein the grid-commutated power converter is connected on the AC side to a second winding of the first transformer, wherein the DC side connection of the grid-commutated power converter is designed as a connection for the electrolyzer, wherein the self-commutated power converter is connected on the AC side to a second winding of the second transformer, wherein the self-commutated power converter is connected on the DC side to an energy source,wherein a first winding of the second transformer is arranged electrically in series with one of the windings of the first transformer. This object is further achieved by an electrolysis device with such a power supply device, wherein the power supply device has at least one electrolyzer, wherein the electrolyzer is electrically connected to the DC voltage side connection of the grid-commutated power converter. This object is further achieved by a method for operating such a power supply device or such an electrolysis device, wherein the voltage at the DC voltage side connection of the grid-commutated power converter is controlled or regulated by means of the AC voltage side voltage of the self-commutated power converter. This object is further achieved by a control device with the features of claim 12.

[0011] Further advantageous embodiments of the invention are specified in the dependent claims.

[0012] The invention is based, among other things, on the knowledge that a fluctuation in the mains voltage can be compensated for by a self-commutated power converter. In this case, the only limited adjustment range required for the direct voltage is utilized. + / - 10% is typical for fluctuations in the mains voltage of the power supply network. To compensate for the mains voltage fluctuation, the voltage of the self-commutated power converter is added to or subtracted from the mains voltage by means of the second transformer, so that the desired voltage is obtained for the supply of the mains-commutated power converter. After pre-charging has been completed, the mains-commutated power converter no longer needs to regulate the direct voltage it generates. If the line-commutated power converter is designed as a thyristor rectifier, it can be operated with a control angle of zero.In other words, the line-commutated converter can be designed as a thyristor rectifier. Alternatively, it can also be designed as a diode rectifier by operating with a zero control angle.

[0013] The line-commutated converter can be designed, for example, as a six-pulse, twelve-pulse or higher-pulse converter.

[0014] The fluctuating mains voltage is compensated for by the self-commutated converter. If the voltage intermediate circuit converter is designed for a power output of, for example, 15% of the power output of the line-commutated converter, a voltage fluctuation of the mains voltage of the power grid of + / - 10% and an additional 10% increase in voltage due to ageing can be compensated.

[0015] An age-related increase in voltage is particularly necessary when producing hydrogen by electrolysis. During this process, the electrodes age, which is counteracted by increasing the electrolysis voltage. Compared to the voltage used in the electrolysis of hydrogen, the increase is relatively high. This makes the proposed energy supply device particularly suitable for an electrolyzer for producing hydrogen. Since the self-commutated converter transmits active power, it must be connected on the DC side to an energy source or an energy storage device that can absorb and / or release electrical energy depending on the mains voltage conditions. In the following, the term energy source also includes an energy storage device that can absorb and release electrical energy.In a simple embodiment, the grid-commutated power converter can be used as such an energy source storage device via the DC voltage side connection of the grid-commutated power converter.

[0016] The rated power and / or maximum power of the self-commutated converter is lower than that of the grid-commutated converter. It has proven advantageous to supply the majority of the power to be provided to the electrolyzer via the grid-commutated converter. This converter has low losses and can be implemented with a high power density. This allows the energy supply device to be particularly compact and with high performance.

[0017] Furthermore, it has proven particularly advantageous to dimension the self-commutated converter such that the self-commutated converter has a rated power and / or maximum power in the range of 10% to 20% of the rated power or maximum power of the line-commutated converter. This not only makes it possible to meet an age-related increase in voltage requirements, but also ensures low-loss and thus effective operation of the line-commutated converter over a defined tolerance range of the line voltage.

[0018] The rated power is the power that can be transmitted permanently by the power converter. The maximum power represents the power that can be transmitted briefly, i.e. not permanently, without the power converter being damaged. In an advantageous embodiment of the invention, the structural output of the first transformer is greater than the structural output of the second transformer. Due to the copper it requires, the transformer is not only heavy but also expensive to manufacture. It has therefore proven advantageous to make the second transformer smaller by transmitting the majority of the power via the first transformer and the line-commutated power converter. This allows the power path via the first transformer to be optimized in terms of power and cooling, while the second transformer can be dimensioned to be significantly smaller in terms of its power capacity.With this arrangement, the overall system can be significantly optimized towards high economic efficiency.

[0019] In a further advantageous embodiment of the invention, the first winding of the second transformer is arranged electrically in series with the first winding of the first transformer. In this embodiment, the first winding of the second transformer is arranged electrically in series with the first winding, also referred to as the primary winding, of the first transformer. The self-commutated converter then generates a voltage which, taking into account the transformation ratio of the second transformer, is subtracted from or added to the mains voltage of the power supply network depending on the phase position. Since the second winding of the first transformer is not part of a series circuit, it can be designed as a star or delta winding in a multi-phase embodiment of the winding. This makes it easy to implement a twelve-pulse circuit for the line-commutated converter.

[0020] In a further advantageous embodiment of the invention, the first winding of the second transformer is arranged electrically in series with the second winding of the first transformer. This arrangement has the advantage that only the first transformer needs to be designed with insulation at the voltage level of the power supply network. This makes the second transformer simpler in construction and more cost-effective to manufacture.

[0021] In a further advantageous embodiment of the invention, the self-commutated power converter is connected on the DC side to the DC side connection of the line-commutated power converter. This means that the line-commutated power converter serves as an energy source for the self-commutated power converter to absorb electrical energy. If the self-commutated power converter transfers electrical energy to the DC side, this energy can be made available to the load, the electrolyzer, and reduces the energy required to be transferred from the line-commutated power converter to the load. In this case, the existing components of the electrolysis device can be advantageously used for the tasks of transferring electrical energy within the system.

[0022] In a further advantageous embodiment of the invention, the self-commutated power converter is connected on the DC side to a DC side connection of a further power converter, wherein the further power converter is connected on the AC side to a third winding of the first transformer. The further self-commutated power converter provides the self-commutated power converter with an energy source in order to be able to exchange the active power required for its operation. This further power converter, for example designed as a self-commutated power converter, makes it possible to dimension the line-commutated power converter with a smaller power output since it no longer has to provide the said active power requirement to the self-commutated power converter via the DC connection. Instead, this proportion of power can be made available to the load. This increases the performance of the electrolysis device.In a further advantageous embodiment of the invention, the second winding of the first transformer has at least two taps. To compensate for aging, the first or second winding of the first transformer is designed with multiple taps, i.e. at least two taps. Reconnecting is only necessary as aging progresses to the extent that it takes a few years. Therefore, reconnecting can be done manually, also referred to as manual reconnection. This reduces the costs compared to an electromechanical switch solution. In particular, the taps can be arranged on the low-voltage side, i.e. on the second winding. For mechanical switches, such an arrangement would be disadvantageous due to the higher currents that have to be switched compared to the first winding. Manual reconnection eliminates this disadvantage.In addition, the arrangement of the taps in the second winding makes the transformer design significantly more cost-effective.

[0023] In a further advantageous embodiment of the invention, the AC side voltage of the self-commutated power converter is controlled or regulated in such a way that the voltages of the windings arranged electrically in series are in phase or phase-shifted by 180°. The power supply device therefore acts like a line-commutated power converter in relation to the power supply network. If the line voltage is greater than the input voltage of the line-commutated power converter required to regulate the DC voltage, the self-commutated power converter generates a voltage at the corresponding winding of the windings arranged electrically in series that is in phase with the other winding of the windings arranged electrically in series. This has the effect that the input voltage for the line-commutated power converter is lower than the line voltage.If the mains voltage is lower than the input voltage of the line-commutated converter required to regulate the DC voltage, the self-commutated converter generates a voltage at the corresponding winding of the windings arranged electrically in series that is 180° out of phase with respect to the other winding of the windings arranged electrically in series. This means that the input voltage for the line-commutated converter is higher than the mains voltage. In-phase and 180° out of phase can also be assumed if the ideal value (0° or 180°) is deviated from the ideal value by + / - 5°. This means that the DC voltage at the DC side connection of the line-commutated converter can be regulated by the self-commutated converter, whereby at the same time the line-commutated converter behaves like a thyristor rectifier with a control angle of zero.This ensures optimal utilization of the active power transmission capacity of the line-commutated converter. In other words, an advantageous embodiment results in particularly high utilization of the line-commutated converter, particularly when the line-commutated converter is designed as a thyristor rectifier and operated with a zero control angle.

[0024] The invention is described and explained in more detail below with reference to the exemplary embodiments shown in the figures. They show:

[0025] FIG 1 to FIG 3 show exemplary embodiments of a power supply device,

[0026] FIG 4 shows an embodiment of an electrolysis device,

[0027] FIG 5 a vector diagram for different voltage configurations and

[0028] FIG 6 a table with the effect of

[0029] Use of different taps of the first transformer on the voltage at the DC side connection of the line-commutated converter.

[0030] FIG. 1 shows an exemplary embodiment of a power supply device 1. This device has a first transformer 11 with a first winding 111 and a second winding 112. In addition, the second winding 112 has two taps 5 with which the transformation ratio of the first transformer 11 can be changed. The second winding 112 is connected via one of the taps 5 to a line-commutated power converter 13. This line-commutated power converter

[0031] 13 converts electrical energy transmitted via the first transformer 11 into a direct voltage, which can be made available to an electrolyzer 2 (not shown here) at a direct voltage terminal 131. The line-commutated power converter 13 can, as symbolically indicated, be designed, for example, as a thyristor rectifier.

[0032] The taps 5 can alternatively or additionally also be arranged on the first winding 111.

[0033] In addition, the power supply device 1 has a second transformer 12 with a first winding 121 and a second winding 122. The second winding 122 of the second transformer 12 is connected to a self-commutated power converter 14. This self-commutated power converter

[0034] 14 can, for example, as symbolically indicated, use IGBTs as semiconductors. Since these semiconductors can be switched off, they can be used to construct a self-commutated power converter 14. The task of the self-commutated power converter 14 is, among other things, to compensate for fluctuations in the mains voltage. For this purpose, the self-commutated power converter 14 generates a voltage which is coupled in via the second transformer 12. For this purpose, the first winding 121 of the second transformer 12 is arranged electrically in series with the first winding 111 of the first transformer 11. This adds up the voltage Ui, which is applied to the first winding 111 of the first transformer 11, and the voltage U2, which is applied to the first winding 121 of the second transformer 12. The sum of these voltages Ui and U2 corresponds to the mains voltage U N. By generating a corresponding voltage U2 at the first winding 121 of the second transformer 12, a voltage Ul can be set at the first winding 111 of the first transformer 11.

[0035] Electrical energy is required to generate voltage U2 by the self-commutated converter 14. This energy must be provided to the self-commutated converter 14 by an energy source or an energy storage device.

[0036] For this purpose, the self-commutated converter 14 in this embodiment is connected on the DC side to the DC side terminal 131 of the line-commutated converter 13. Thus, the line-commutated converter 13 serves as an energy source for the self-commutated converter 14.

[0037] In this exemplary embodiment, the AC side is designed as a three-phase system. Alternatively, a single-phase system is also possible.

[0038] FIG. 2 shows a further exemplary embodiment of the energy supply device 1. To avoid repetition, reference is made to the description of FIG. 1 and to the reference numerals introduced there. The taps 5 of the second winding 111 are not shown in this figure, but can be arranged on the first winding 111 and / or second winding 112 of the first transformer 11 in the present exemplary embodiment, just as in the exemplary embodiment of FIG. 1. In this exemplary embodiment, the first winding 121 of the second transformer 12 is connected to the second winding 112 of the first transformer 11.

[0039] 3 shows a further exemplary embodiment of the energy supply device 1. To avoid repetition, reference is made to the description of FIGS. 1 and 2 and to the reference symbols introduced there. As in the exemplary embodiment in FIG. 1, the first winding 121 of the second transformer 12 is connected to the first winding 111 of the first transformer 11. A further power converter 15 serves as the energy source for supplying the self-commutated power converter 14 with electrical energy on the DC voltage side. For this purpose, the self-commutated power converter 14 is connected on the DC voltage side to a DC voltage terminal 151 of the further power converter 15. The further power converter can be designed either as a line-commutated converter or, as shown, as a self-commutated power converter, for example with IGBT semiconductors.

[0040] FIG. 4 shows an electrolysis device 10 in which an electrolyzer 2 is connected to the DC voltage-side connection 131 of the energy supply device 1. It is also possible to connect a plurality of electrolyzers 2, in particular at least two electrolyzers 2, to an energy supply device 1 to form an electrolysis device 10. The energy supply device 1 of the electrolysis device 10 draws electrical energy from an energy supply network 20 to which the energy supply device 1 is electrically connected. This electrical connection can advantageously be three-phase, as shown.

[0041] FIG 5 shows a vector diagram of the different voltages using the example of the embodiment in FIG 1 . If the mains voltage U N the input voltage Ui , which is required to generate the desired DC voltage U DCis required, the self-commutated converter 14 does not need to generate voltage U2. However, if the mains voltage U N higher than the required voltage Ui , the self-commutated converter 14 generates a voltage U2 which is in phase, as indicated by the same arrow direction, with the voltage Ui at the first winding 111 of the first transformer 11 . If the mains voltage U Nsmaller than the desired voltage Ui, the self-commutated converter 14 generates a voltage at the first winding 121 of the second transformer 12 which is in antiphase, i.e. 180° out of phase with the voltage Ui at the first winding 111 of the first transformer 11. Thus, the grid-commutated converter 13 can always be operated at the optimum operating point. FIG. 6 shows the effect of the taps 5 of the first transformer 11. Since the functioning of the taps 5 is independent of a specific voltage, relative voltages (marked with lower case letters) are mentioned in the table, where the relative grid voltage u N , the relative transformer voltages Ui and U2 are related to the nominal voltages of the mains. The relative output voltage u DC refers to the maximum DC voltage U that can be generated DC required at the end of the electrolyzer's lifetime.

[0042] The designations of the relative voltages Ui , U2 , u N and u DC refer to the voltages Ui , U2 , U shown in FIG 1 N and U DC . The design on which the table is based assumes that the mains voltage U N by a maximum of 10% around its nominal value and the self-commutated converter 14 is capable of providing + / - 15% of the nominal voltage of the grid. At Ui=105%, the grid-commutated converter 13, for example designed as a thyristor rectifier, which can be operated with a control angle a of 0 ° after completion of the pre-charging, supplies a relative DC voltage u via the tap C. DC of 100%, across the tap B a relative DC voltage u DC of 90% and across the tap ff A a relative DC voltage u DCof 80%. With these three taps A, B, C, which only rarely need to be reconnected due to the progressive aging of the electrolyzer and can therefore be designed to be manually reconnected, an age-related, relative DC voltage can be DC in the range of 70% to 100%.

[0043] Thus, the table in FIG. 6 shows a control strategy how the output-side DC voltage U can be controlled with the three taps 5, also called winding taps, and a control range of the self-commutated converter 14 of + / - 15% of the nominal voltage of the network. DC can be controlled. By combining the taps and the self-commutated converter 14, the full required voltage control range can be achieved.

[0044] With the help of the voltage Ui on the first capacitor 11, the required DC voltage U DC, which results in particular from the aging condition of the electrolyzer, can be set at all operating points within the range of the specified mains voltage tolerances within a bandwidth of 10%. If a further deviation occurs, the tap is changed accordingly. Thus, for example, with three taps 5, a total DC voltage range of 30% can be covered over the service life, as shown.

[0045] The mains voltage fluctuations in the range of + / - 10% are compensated by the self-commutated converter 14 in such a way that the DC voltage U required to achieve the output side is DC desired voltage Ui is applied to the first transformer 11.

[0046] A corresponding control can be transferred to the arrangements of FIG 2 and FIG 3.

[0047] Thus, the proposed design of the energy supply device 1 when dimensioning the self-commutated power converter 14 with a voltage control range of + / - 15% of the nominal voltage of the grid allows a cost-effective energy supply for one or more electrolyzers to be specified, which is low-loss, grid-friendly and meets the requirements with regard to the aging of the electrolyzer.

Claims

Patent claims 1. Energy supply device (1) for an electrolyzer (2), comprising - a first transformer (11) and a second transformer (12), - a line-commutated converter (13) and - a self-commutated power converter (14), wherein a first winding (111) of the first transformer (II) is provided for connection to a power supply network (20), wherein the grid-commutated power converter (13) is connected on the AC side to a second winding (112) of the first transformer (11), wherein the DC side connection (131) of the grid-commutated power converter (13) is designed as a connection for the electrolyzer (2), wherein the self-commutated power converter (14) is connected on the AC side to a second winding (122) of the second transformer (12), wherein the self-commutated power converter (14) is connected on the DC side to an energy source, wherein a first winding (121) of the second transformer (12) is arranged electrically in series with one of the windings (111, 112) of the first transformer (11), wherein the rated power and / or the maximum power of the self-commutated power converter (14) is less than that of the grid-commutated power converter (13).

2. Power supply device (1) according to claim 1, wherein the construction power of the first transformer (11) is greater than the construction power of the second transformer (12).

3. Power supply device (1) according to one of claims 1 or 2, wherein the first winding (121) of the second transformer (12) is electrically connected in series with the first winding (III) of the first transformer (11).

4. Energy supply device (1) according to one of claims 1 to 3, wherein the first winding (121) of the second Transformer (12) is arranged electrically in series with the second winding (112) of the first transformer (11).

5. Energy supply device (1) according to one of claims 1 to 4, wherein the self-commutated power converter (14) is connected on the DC voltage side to the DC voltage side terminal (131) of the mains-commutated power converter (13).

6. Energy supply device (1) according to one of claims 1 to 5, wherein the self-commutated power converter (14) is connected on the DC voltage side to a DC voltage side terminal (151) of a further power converter (15), wherein the further power converter (15) is connected on the AC voltage side to a third winding (113) of the first transformer (11).

7. Power supply device (1) according to one of claims 1 to 6, wherein the second winding (112) of the first transformer (11) has at least two taps (5).

8. Electrolysis device (10) with a power supply device (1) according to one of claims 1 to 7 and at least one electrolyzer (2), wherein the electrolyzer (2) is electrically connected to the DC voltage side connection (131) of the grid-commutated power converter (13).

9. A method for operating a power supply device (1) according to one of claims 1 to 7 or an electrolysis device (10) according to claim 8, wherein the voltage at the DC-side terminal (131) of the grid-commutated power converter (13) is controlled or regulated by means of the AC-side voltage of the self-commutated power converter (14).

10. The method according to claim 9, wherein the AC side voltage of the self-commutated converter (14) is controlled or regulated such that the voltages of the windings (111,121 or 112,121) arranged electrically in series are in phase or phase-shifted by 180°.

11. Method according to one of claims 9 or 10, wherein the line-commutated power converter (13) is designed as a thyristor rectifier and is operated with a control angle (α) of zero.

12. Control device, in particular for an energy supply device (1) according to one of claims 1 to 6 or for an electrolysis device (10) according to claim 7, configured to carry out a method according to one of claims 8 to 11.

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