Power supply device for an electrolytic cell

Abstract

The invention relates to a power supply device (1) for an electrolysis cell (2), wherein a first winding (111) of a first transformer (11) is provided to be connected to a power supply network (20), wherein an on-grid rectifier (13) is connected on the AC voltage side to a second winding (112) of the first transformer (11), wherein a DC voltage side interface (131) of the on-grid rectifier (13) is designed as an interface of the electrolysis cell (2). In order to improve the power supply device (1), the invention proposes that an off-grid rectifier (14) is connected on the AC voltage side to a second winding (122) of a second transformer (12), wherein the off-grid rectifier (14) is connected on the DC voltage side to an electrical power 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). The invention also relates to an electrolysis device (10) having such a power supply device (1) and at least one electrolysis cell (2). The invention also relates to a method for operating such a power supply device (1) or such an electrolysis device (10). The invention also relates to a control device which is configured to carry out such a method.

Description

Technical Field

[0001] This invention relates to a power supply device for an electrolytic cell, the power supply device comprising a first transformer and a grid-controlled rectifier, wherein a first winding of the first transformer is configured to be connected to a power grid, wherein the AC voltage side of the grid-controlled rectifier is connected to a second winding of the first transformer, and wherein the DC voltage side interface of the grid-controlled rectifier is designed as an interface for the electrolytic cell. Furthermore, this invention relates to an electrolytic apparatus having such a power supply device and at least one electrolytic cell. The invention also relates to a method of operating such a power supply device or such an electrolytic apparatus. Additionally, the invention relates to a control device. Background Technology

[0002] Electrolytic rectifiers used to supply power to electrolyzers must be able to regulate fluctuations in the grid voltage and provide higher DC voltages as electrolyzers age. For this purpose, various circuit topologies are currently utilized for facilities with power exceeding 5 MW.

[0003] The first circuit topology is a controlled rectifier with thyristors, designed in six-pulse, twelve-pulse, or higher pulse configurations (B6C, B12C, B18C, B24C). This is a low-cost solution for high power applications. In this process, the DC voltage, i.e., the output voltage of the thyristor rectifier, is set via a control angle α, or using a tap changer with electromechanical or electronic switching.

[0004] An alternative architecture uses an uncontrolled rectifier with a buck converter. The buck converter is designed for full current operation and requires a reactor for operation. In this case, multiple buck converters are typically used to meet harmonic requirements.

[0005] Another alternative circuit topology is the use of grid-side voltage intermediate loop converters, which are also used in photovoltaic and wind power generation facilities. To use these converters, the secondary voltage of the transformer is correspondingly reduced to generate the required DC voltage. However, this circuit topology is currently not used, or rarely used, in electrolysis.

[0006] The term "transformer winding" is used below. This term includes both single-phase windings, which have only a single partial winding for each phase, and multi-phase windings, particularly three-phase windings, where the winding has a corresponding number of partial windings. One partial winding is provided for each phase, such that a three-phase winding has three partial windings. These partial windings can be designed, for example, as star windings or delta windings.

[0007] The term "series" or "electrically connected in series" refers to the fact that the voltages of components arranged in series are added together. Therefore, it is not necessary for the same current to flow through these components. Summary of the Invention

[0008] The purpose of this invention is to improve the power supply for electrolytic cells.

[0009] This objective is achieved by a power supply device for an electrolytic cell, wherein the power supply device includes a first transformer and a second transformer, a grid-controlled rectifier and a self-controlled rectifier, wherein a first winding of the first transformer is configured to be connected to a power grid, wherein the grid-controlled rectifier is connected to a second winding of the first transformer on the AC voltage side, wherein the DC voltage side interface of the grid-controlled rectifier is designed as an interface for the electrolytic cell, wherein the self-controlled rectifier is connected to a second winding of the second transformer on the AC voltage side, wherein the self-controlled rectifier is connected to a power source on the DC voltage side, and wherein the first winding of the second transformer is electrically connected in series with one of the windings of the first transformer. This objective is also achieved by an electrolytic apparatus having such a power supply device, wherein the electrolytic apparatus has at least one electrolytic cell, wherein the electrolytic cell is electrically connected to the DC voltage side interface of the grid-controlled rectifier. Furthermore, this objective is achieved by a method of operating such a power supply device or such an electrolytic apparatus, wherein the voltage at the DC voltage side interface of the grid-controlled rectifier is controlled or regulated by means of the AC voltage side voltage of the self-controlled rectifier. Furthermore, this objective is achieved by a control device having the features of claim 12.

[0010] Other advantageous designs of the invention are given in the dependent claims.

[0011] This invention is particularly based on the understanding that fluctuations in grid voltage can be compensated for using a self-controlled rectifier. In this process, only the limited necessary adjustment range of the DC voltage is utilized. Grid voltage fluctuations in power supply networks are typically + / - 10%.

[0012] To compensate for grid voltage fluctuations, a second transformer is used to add to or subtract from the grid voltage from the self-controlled rectifier, thereby generating the desired voltage for the grid-controlled rectifier's supply. In this case, the grid-controlled rectifier no longer needs to regulate the DC voltage it generates after pre-charging. If the grid-controlled rectifier is designed as a thyristor rectifier, it can operate at zero control angle. In other words, the grid-controlled rectifier can be designed as a thyristor rectifier. Alternatively, it can also be designed as a diode rectifier by operating at zero control angle.

[0013] For example, grid-controlled rectifiers can be configured as six-pulse, twelve-pulse, or higher-pulse rectifiers.

[0014] Compensation for fluctuating grid voltage is implemented using a self-controlled rectifier. If the intermediate voltage circuit inverter is designed to have, for example, 15% of the power of the grid-controlled rectifier, then ±10% of the grid voltage fluctuations and an additional 10% of the additional voltage demand due to aging can be regulated.

[0015] The additional voltage requirements due to aging are particularly evident in hydrogen production via electrolysis. During this process, electrode aging occurs, which is offset by increasing the electrolysis voltage. This increase is relatively large relative to the voltage required for hydrogen electrolysis. Therefore, the proposed power supply device is particularly suitable for electrolyzers used in hydrogen production.

[0016] Because self-controlled rectifiers transmit active power, they must be connected to a power source or energy storage device on the DC voltage side, which can receive and / or output electrical energy according to grid voltage conditions. In the following text, the term "power source" also includes energy storage devices capable of receiving and outputting electrical energy. In a simple design, a grid-controlled rectifier can be used as such a power source and energy storage device, connected to the DC voltage side.

[0017] The rated and / or maximum power of the self-controlled rectifier is less than that of the grid-controlled rectifier. It has proven advantageous to conduct most of the power required to supply the electrolyzer via the grid-controlled rectifier. Its losses are low, and it can achieve high power density. Therefore, the power supply unit can be particularly compact and provide high performance.

[0018] It has also been proven that it is particularly advantageous for self-controlled rectifiers to be sized such that they have a rated power and / or maximum power within 10% to 20% of the rated or maximum power of grid-controlled rectifiers. This not only provides for the additional voltage requirements due to aging but also ensures that grid-controlled rectifiers operate with low losses and thus high efficiency within the defined tolerances of the grid voltage.

[0019] Rated power refers to the power that the rectifier can continuously transmit. Maximum power indicates the power that the rectifier can transmit for a short period of time, rather than continuously, without being damaged.

[0020] In an advantageous design of the invention, the design power of the first transformer is greater than that of the second transformer. Transformers are not only heavy but also costly to manufacture due to the copper they require. Therefore, it has proven advantageous to keep the size of the second transformer smaller by transmitting most of the power via the first transformer and the grid-controlled rectifier. Thus, the power path through the first transformer can be optimized in terms of power and cooling, while the second transformer can be made significantly smaller in terms of performance. With this configuration, the entire system can be significantly optimized towards higher economic efficiency.

[0021] In another advantageous embodiment of the invention, the first winding of the second transformer is electrically connected in series with the first winding of the first transformer. In this design, the first winding of the second transformer is electrically connected in series with the first winding (also called the primary winding) of the first transformer. A voltage is then generated by a self-controlled rectifier, and this voltage is subtracted from or added to the grid voltage according to the phase relationship, taking into account the turns ratio of the second transformer. 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 multiphase winding design. Therefore, a twelve-pulse circuit for a grid-controlled rectifier can be implemented in a simple manner.

[0022] In another advantageous embodiment of the invention, the first winding of the second transformer is electrically connected in series with the second winding of the first transformer. This configuration has the advantage that only the first transformer must be designed in terms of insulation according to the voltage level of the power grid. This makes the structure of the second transformer simpler and the manufacturing cost lower.

[0023] In another advantageous embodiment of the invention, the self-controlled rectifier is connected to the DC voltage side interface of the grid-controlled rectifier on the DC voltage side. Thus, on one hand, the grid-controlled rectifier serves as the power source for the self-controlled rectifier to receive electrical energy. If the self-controlled rectifier transfers electrical energy to the DC voltage side, this energy can be supplied to the load (i.e., the electrolyzer), reducing the energy requirement from the grid-controlled rectifier to the load. In this process, existing components of the electrolysis unit can be advantageously used for the task of transferring electrical energy within the system.

[0024] In another advantageous embodiment of the invention, the self-controlled rectifier is connected on the DC voltage side to the DC voltage side interface of another rectifier, which is connected on the AC voltage side to the third winding of the first transformer. The self-controlled rectifier is powered by the other self-controlled rectifier, enabling it to exchange the active power required for its operation. For example, this other rectifier, designed as a self-controlled rectifier, allows for a reduction in the power required by the grid-controlled rectifier, as it no longer needs to provide the aforementioned active power demand to the self-controlled rectifier via the DC voltage interface. Instead, this portion of the power can be supplied to the load. This improves the performance of the electrolysis unit.

[0025] In another advantageous design 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. Rewiring is only required after several years when aging gradually intensifies. Therefore, rewiring can be performed manually, also known as manual rewiring. This reduces costs compared to electromechanical switching solutions. In particular, the taps can be arranged on the low-voltage side, i.e., on the second winding. This arrangement is disadvantageous for mechanical switches because a larger current is required for switching compared to the first winding. This disadvantage is eliminated by manual rewiring. Furthermore, by arranging the taps in the second winding, the transformer design is significantly more advantageous.

[0026] In another advantageous embodiment of the invention, the AC voltage side voltage of the self-controlled rectifier is controlled or regulated such that the voltages of the electrically series-connected windings are in phase or phase-shifted by 180°. Therefore, the power supply unit functions like a grid-controlled rectifier relative to the power grid. If the grid voltage is greater than the input voltage required for the grid-controlled rectifier to regulate the DC voltage, the self-controlled rectifier generates a voltage in phase with the other winding of the electrically series-connected winding on the corresponding winding. This makes the input voltage of the grid-controlled rectifier less than the grid voltage. If the grid voltage is less than the input voltage required for the grid-controlled rectifier to regulate the DC voltage, the self-controlled rectifier generates a voltage 180° phase-shifted relative to the other winding of the electrically series-connected winding on the corresponding winding. This makes the input voltage of the grid-controlled rectifier greater than the grid voltage. A deviation of + / - 5° from the ideal value (0° or 180°) can also be considered as in phase and phase-shifted by 180°. Therefore, the DC voltage at the DC voltage side interface of the grid-controlled rectifier can be regulated by a self-controlled rectifier, where the grid-controlled rectifier simultaneously behaves as a thyristor rectifier with a zero control angle. This allows the grid-controlled rectifier to be optimally utilized in terms of its active power transmission. In other words, in an advantageous design, especially when the grid-controlled rectifier is designed as a thyristor rectifier and operates with a zero control angle, the utilization rate of the grid-controlled rectifier is particularly high. Attached Figure Description

[0027] The present invention will now be described and illustrated in more detail with reference to the embodiments shown in the figures. The figures show: Detailed Implementation

[0028] Figure 1 An embodiment of the power supply device 1 is shown. This power supply device includes a first transformer 11 having a first winding 111 and a second winding 112. Furthermore, the second winding 112 has two taps 5, which can be used to change the turns ratio of the first transformer 11. The second winding 112 is connected to a grid-controlled rectifier 13 via one of the taps 5. The grid-controlled rectifier 13 converts the electrical energy transmitted through the first transformer 11 into a DC voltage, which can be supplied at a DC voltage side interface 131 to an electrolytic cell 2 (not shown). As schematically illustrated, the grid-controlled rectifier 13 can be designed, for example, as a thyristor rectifier.

[0029] Alternatively or supplementally, tap 5 may also be arranged on the first winding 111.

[0030] Furthermore, the power supply unit 1 has a second transformer 12, which has a first winding 121 and a second winding 122. The second winding 122 of the second transformer 12 is connected to a self-controlled rectifier 14. As schematically shown, the self-controlled rectifier 14 can, for example, use IGBTs as semiconductors. Since these semiconductors are turn-off, the self-controlled rectifier 14 can be constructed using them. The task of the self-controlled rectifier 14 includes, in particular, compensating for fluctuations in the mains voltage. For this purpose, the self-controlled rectifier 14 generates a voltage that is coupled into the input through the second transformer 12. For this purpose, the first winding 121 of the second transformer 12 is electrically connected in series with the first winding 111 of the first transformer 11. Therefore, the voltage U1 applied to the first winding 111 of the first transformer 11 is added to the voltage U2 applied to the first winding 121 of the second transformer 12. The sum of these voltages U1 and U2 corresponds to the mains voltage U. N By generating a corresponding voltage U2 on the first winding 121 of the second transformer 12, the voltage U1 on the first winding 111 of the first transformer 11 can be set.

[0031] The self-controlled rectifier 14 requires electrical energy to generate voltage U2. This electrical energy must be supplied to the self-controlled rectifier 14 through a power source or energy storage device. Therefore, in this embodiment, the self-controlled rectifier 14 is connected on the DC voltage side to the DC voltage side interface 131 of the grid-controlled rectifier 13. The grid-controlled rectifier 13 thus acts as the power source for the self-controlled rectifier 14.

[0032] In this embodiment, the AC voltage side is designed as three-phase. Alternatively, a single-phase design can also be used.

[0033] Figure 2 Another embodiment of the power supply device 1 is shown. To avoid repetition, see reference... Figure 1 The description and the reference numerals in the figures are shown. Tap 5 of the first winding 111 is not shown in this figure, but as in... Figure 1 In this embodiment, the windings can also be arranged on the first winding 111 and / or the second winding 112 of the first transformer 11. In this embodiment, the first winding 121 of the second transformer 12 is connected to the second winding 112 of the first transformer 11.

[0034] Figure 3 Another embodiment of the power supply device 1 is shown. To avoid repetition, see reference... Figure 1 and Figure 2 The description and the reference numerals in the accompanying drawings. (and) Figure 1As in the previous embodiment, the first winding 121 of the second transformer 12 is connected to the first winding 111 of the first transformer 11. Another rectifier 15 acts as the power source for the self-controlled rectifier 14 on the DC voltage side. For this purpose, the self-controlled rectifier 14 is connected on the DC voltage side to the DC voltage side interface 151 of the other rectifier 15. This other rectifier can be designed as a grid-controlled or self-controlled rectifier as shown, for example, having IGBT semiconductors.

[0035] Figure 4 An electrolysis apparatus 10 is shown, wherein the electrolytic cells 2 are connected to the DC voltage side interface 131 of the power supply unit 1. Furthermore, multiple electrolytic cells 2, particularly at least two, can be connected to the power supply unit 1 to form the electrolysis apparatus 10. The power supply unit 1 of the electrolysis apparatus 10 obtains electrical energy from a power grid 20 electrically connected to it. As shown, this electrical connection can advantageously be designed as three-phase.

[0036] Figure 5 Showing Figure 1 The example is a vector diagram of different voltages. If the grid voltage U... N This is equivalent to generating the required DC voltage U. DC If the required input voltage U1 is met, then the self-controlled rectifier 14 does not need to generate voltage U2. However, if the grid voltage U N If the voltage is higher than the required voltage U1, a voltage U2 is generated by the self-controlled rectifier 14 that is in phase with the voltage U1 on the first winding 111 of the first transformer 11 (as can be seen from the same arrow direction). If the grid voltage U N If the voltage is less than the desired voltage U1, the self-controlled rectifier 14 generates a voltage on the first winding 121 of the second transformer 12 that is out of phase with the voltage U1 on the first winding 111 of the first transformer 11, i.e., a phase shift of 180°. Therefore, the grid-controlled rectifier 13 can always operate at the optimal operating point.

[0037] Figure 6 The effect of tap 5 on the first transformer 11 is shown. Since the operation of tap 5 is independent of a specific voltage, the table lists the relative voltages (in lowercase letters), where the relative voltage is u. N The relative transformer voltages u1 and u2 relate to the rated voltage of the power grid. The relative output voltage u... DC Involves the maximum achievable DC voltage U required at the end of the electrolyzer's service life. DC .

[0038] Relative voltages u1, u2, u N and u DC The name corresponds to Figure 1 The voltages U1, U2, and U shown are N and UDC In the design upon which this table is based, it is assumed that the grid voltage U N The voltage fluctuates by a maximum of 10% around its rated value, and the self-controlled rectifier 14 is capable of providing + / - 15% of the grid rated voltage. When u1 = 105%, for example, the grid-controlled rectifier 13, designed as a thyristor rectifier that can operate at a control angle α of 0° after pre-charging, provides 100% of the relative DC voltage u through the lead-in point C. DC Provide 90% of the relative DC voltage u through lead-out point B. DC Provide 80% of the relative DC voltage u through lead-out point A. DC By using the three leads A, B, and C, which require rewiring only in rare cases due to the gradual aging of the electrolytic cell and can therefore be manually rewired, a relative DC voltage u ranging from 70% to 100% due to aging can be achieved. DC .

[0039] Figure 6 This illustrates a control strategy, namely, how to use the three taps 5 (also known as winding taps) and the adjustment range of + / -15% of the grid rated voltage of the self-controlled rectifier 14 to control the output DC voltage U. DC The control strategy is as follows: The required full voltage regulation range can be achieved through the combination of taps and self-controlled rectifier 14.

[0040] With the help of the voltage U1 on the first transformer 11, the required DC voltage U can be applied at all operating points. DC (Especially due to the aging of the electrolytic cell) The bandwidth is set at 10 percentage points within the aforementioned grid voltage tolerance range. If further deviations exist, the taps are replaced accordingly. Therefore, as shown in the figure, for example, three taps 5 can cover a total of 30 percentage points of the DC voltage range over their service life.

[0041] Voltage fluctuations within the + / -10% range are compensated by the self-controlled rectifier 14, resulting in a DC voltage U on the first transformer 11 that reaches the output side. DC The required voltage U1.

[0042] The corresponding control can be applied to Figure 2 and Figure 3 Configuration.

[0043] Therefore, by using the proposed power supply device 1 structure, when setting the size of the self-controlled rectifier 14 with a voltage regulation range of + / -15% of the grid rated voltage, it is possible to provide a low-loss, grid-friendly, and low-cost power supply that meets the aging requirements of one or more electrolytic cells.

Claims

1. A power supply device (1) for an electrolytic cell (2), comprising: - First transformer (11) and second transformer (12) - Grid-controlled rectifier (13), and - Self-controlled rectifier (14). The first winding (111) of the first transformer (11) is configured to be connected to the power grid (20), wherein the grid-controlled rectifier (13) is connected to the second winding (112) of the first transformer (11) on the AC voltage side, wherein the DC voltage side interface (131) of the grid-controlled rectifier (13) is designed as the interface of the electrolytic cell (2), wherein the self-controlled rectifier (14) is connected to the second winding (122) of the second transformer (12) on the AC voltage side, wherein the self-controlled rectifier (14) is connected to the power supply on the DC voltage side, wherein the first winding (121) of the second transformer (12) is electrically connected in series with one of the windings (111, 112) of the first transformer (11), wherein the rated power and / or maximum power of the self-controlled rectifier (14) is less than the rated power and / or maximum power of the grid-controlled rectifier (13).

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

3. The power supply device (1) according to any 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 (111) of the first transformer (11).

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

5. The power supply device (1) according to any one of claims 1 to 4, wherein, The self-controlled rectifier (14) is connected to the DC voltage side interface (131) of the grid-controlled rectifier (13) on the DC voltage side.

6. The power supply device (1) according to any one of claims 1 to 5, wherein, The self-controlled rectifier (14) is connected on the DC voltage side to the DC voltage side interface (151) of another rectifier (15), wherein the other rectifier (15) is connected on the AC voltage side to the third winding (113) of the first transformer (11).

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

8. An electrolysis apparatus (10) comprising a power supply device (1) according to any one of claims 1 to 7 and at least one electrolytic cell (2), wherein, The electrolytic cell (2) is electrically connected to the DC voltage side interface (131) of the grid-controlled rectifier (13).

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

10. The method according to claim 9, wherein, Control or adjust the AC voltage side voltage of the self-controlled rectifier (14) such that the voltage of the electrically connected windings (111, 121 or 112, 121) is in phase or phase-shifted by 180°.

11. The method according to any one of claims 9 or 10, wherein the grid-controlled rectifier (13) is configured as a thyristor rectifier and operates at a zero control angle (α).

12. A control device, particularly for a power supply device (1) according to any one of claims 1 to 6 or for an electrolysis device (10) according to claim 7, said control device being configured to implement the method according to any one of claims 8 to 11.

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