Photovoltaic-powered electrolysis equipment

Abstract

The invention relates to an apparatus (10) for electrolysis using photovoltaically generated DC power, comprising an electrolysis device (E) and a DC voltage converter (12, 14). The DC voltage converter is configured to supply DC power to the electrolysis device (E) via a DC bus (16), wherein the DC power can be generated by photovoltaic sub-generators (TG1, TG2, TG3) connected to the DC voltage converter (12, 14), wherein the sub-generators (TG1, TG2, TG3) are connected to the DC voltage converter (12, 14) via a first disconnector (TS2, TS6), wherein the first disconnector (TS2, TS6) is coupled to an insulation monitoring device (ISO1, ISO2) such that closing the first disconnector (TS2, TS6) verifies that the sub-generator (T The invention also relates to a method for operating a device (10) for electrolysis using photovoltaically generated DC power.

Description

Technical Field

[0001] The invention relates to a device for electrolysis using photovoltaically generated DC power and a method for operating the device. Background Art

[0002] Electrolyzers are devices in which a chemical reaction, i.e., a transformation of substances, is induced by an electric current. This occurs during electrolysis. In water electrolysis, water is split into hydrogen and oxygen. It is recommended to connect a photovoltaic generator (PV generator) to the electrolyzer via a DC voltage converter.

[0003] A DC voltage converter is a circuit that converts a DC voltage supplied at the input into a DC voltage with a higher, lower, or opposite voltage level. This conversion is performed using cyclically operated electronic switches and one or more energy stores. DC voltage converters are self-commutated converters, also known as DC regulators.

[0004] A photovoltaic system (PV system) can include multiple electrical components, particularly PV modules, distributed over a large surface area. A group of PV modules, arranged in series, is also called a PV string. Multiple PV strings connected in parallel are called a PV main string. Multiple PV main strings connected in parallel are called PV sub-generators. A PV generator in a PV system can have one or more PV sub-generators connected in parallel.

[0005] PV generators are typically grounded via ground fault detection interruption (GFDI) in large installations exceeding 500 kW, or they are operated ungrounded. This places restrictions on system design, particularly regarding compliance with UL 62109.

[0006] The electrical power supplied to the electrolysis device must be selected to match the power consumption of the electrolysis device. For example, an electrolysis device typically has a power consumption of 1 to 20 MW. The electrical power supplied must be designed accordingly based on this power consumption. Summary of the Invention

[0007] The object of the present invention is to enable the highest possible power from photovoltaics (PV) to be supplied to an electrolysis device, which can be scaled as required.

[0008] This object is achieved by an apparatus according to the invention for electrolysis using photovoltaically generated DC power and by a method according to the invention for operating an apparatus for electrolysis using photovoltaically generated DC power. Preferred embodiments are given below.

[0009] An apparatus for electrolysis using photovoltaically generated DC power includes an electrolysis device, a DC voltage converter, and at least one PV sub-generator. The electrolysis device is, for example, a water electrolysis device for splitting water into hydrogen and oxygen. The DC voltage converter is configured to supply DC power to the electrolysis device via a DC bus, wherein the DC power can be generated by a photovoltaic sub-generator connected to the DC voltage converter. The sub-generator is connected to the DC voltage converter via a first disconnector, wherein the first disconnector is coupled to an insulation monitoring device such that closing the first disconnector presupposes successful verification of sufficient insulation of the sub-generator. The sub-generator includes a main string, wherein a second disconnector is arranged between the main string and the first disconnector. The second disconnector is coupled to a fault current monitor of the main string such that the second disconnector opens if a predeterminable fault current limit value is exceeded.

[0010] The device enables, for example, an electrolysis device to be grounded via a soft grounding of the electrolyte and to supply the electrolysis device with the highest possible, scalable PV power. The electrolysis device can be grounded, for example, via its electrolyte at the negative pole or at the zero point. Grounding can be achieved via an ohmic resistor in the range of 1 to 100 ohms. The coupling of the respective at least one PV sub-generator is performed via a DC voltage converter.

[0011] The device enables the supply of electrical power to an electrolysis device via a PV sub-generator, wherein a ground fault in a PV sub-generator can be reliably detected by a fault current monitor of the main string of the PV sub-generator, leading to the shutdown of the associated PV sub-generator. This shutdown is achieved via a second disconnector. If another PV sub-generator is connected to a DC voltage converter, the other PV sub-generator has another second disconnector with an associated fault current monitor. The additional fault current monitor monitors the fault current of the main string or strings assigned to the other PV sub-generator. The fault current monitor is, for example, an RCD (Residual Current Device). In the event of a ground fault at or in a sub-generator, a fault current detected by the fault current monitor, such as an RCD, flows. The associated sub-generator can then be shut down via the second disconnector, which is, for example, a double-pole switch.

[0012] This allows for a flexible, scalable combination of PV sub-generators and DC voltage converters, which power the electrolysis device in parallel. It is also possible to connect multiple PV sub-generators to a DC voltage converter. The PV sub-generators connected to the DC voltage converters then collectively form a PV generator. The device includes multiple DC voltage converters, each of which is connected to a corresponding DC voltage converter. The DC voltage converters are configured to supply DC power to the electrolysis device via a DC bus. Each PV generator can have one or more PV sub-generators. This improves the scalability and flexibility of the device.

[0013] In addition to the DC voltage converter, the device may include further DC voltage converters, each of which may be connected to one or more sub-generators. Each sub-generator may include one or more main strings, with the second disconnector being arranged between the respective main string and the first disconnector. It is also possible for the second disconnector to be arranged between the respective sub-generator and the first disconnector.

[0014] Each of the sub-generators within the DC converter arrangement is dimensioned such that the leakage current under standard conditions is so low that it cannot cause the sub-generator to burn.

[0015] In particular, it is possible to implement DC coupling, in which the load side is grounded. It is also possible to ground the load, i.e., the electrolysis system. Grounding is also possible at any intermediate potential. Direct low-ohmic grounding or grounding via impedance is possible. Grounding can be shifted during operation in the electrolysis system by asymmetry. The electrolysis system consists of multiple electrolysis cells connected in series. Grounding can also optionally be done indirectly via parasitic resistances of the electrolyte.

[0016] In one embodiment, the DC voltage converter is a buck converter that converts a DC voltage supplied at an input terminal into a DC voltage with a lower voltage value.

[0017] The PV generators are operated in an isolated manner. This means that they do not have an independent ground connection. This is verified by an insulation monitoring device, and the first disconnector is closed only when the insulation of the PV generator is ensured. Before each connection via the first disconnector, the insulation monitoring device, for example, an insulation meter, determines the insulation resistance of each PV generator. The first disconnector is only connected, i.e., closed, when the insulation resistance is greater than a minimum resistance.

[0018] Furthermore, a grounding device is implemented in the device, which can be closed via a ground connection when the fault current is exceeded. This increases the safety of the device.

[0019] In one embodiment, the poles of the sub-generators can be electrically connected to the poles of the DC bus, wherein, in particular, during operation of the sub-generators, the poles of the sub-generators are electrically connected to the poles of the DC bus. Preferably, the DC voltage converter includes a changeover switch for selecting the electrically connected poles of the sub-generators. Furthermore, in one embodiment, the DC voltage converter is configured to select the poles to be connected while taking into account a fault current monitor.

[0020] In one embodiment, the fault current detector has a coaxial conductor for the conductor to be monitored. This has the advantage that even if the rated current becomes higher and exceeds, for example, 250 A, leakage magnetic fields in the magnetic core, for example, a toroidal core, of the detector, for example, an RCD, are only generated to a small extent. In an alternative embodiment, the fault current detector has an alternating layer stack of layers for the conductor to be monitored.

[0021] In one embodiment, a main string comprises multiple strings connected in parallel, wherein fault current monitoring is performed for the main string and / or for the respective strings. Optionally, an RCD can be located at each string, at each main string, or at multiple main strings of a sub-generator. Each sub-generator comprises multiple main strings, each of which is additionally provided with a so-called main string protection device at each pole.

[0022] In one embodiment, the system includes a PV generator having one or more sub-generators, wherein the PV generator is connected to a DC voltage converter via a first disconnect switch, wherein the first disconnect switch is coupled to the insulation monitoring device such that closing the first disconnect switch presupposes a successful test of sufficient insulation of the PV generator. In this embodiment, the scalability of the system is further improved.

[0023] In a preferred embodiment, the main string has a rated power of more than 500 kW and / or the DC converter has a rated power of more than 2 MW. It is possible to implement a PV generator with a high, flexible total power, in particular also with a peak power exceeding 8 MW. This is achieved, in particular, by scaling, insulation detection using a first disconnector, and protection by isolating the PV sub-generators via a second disconnector.

[0024] Each of the parallel-connected PV generators is connected to a DC voltage converter and is designed so that, even in a worst-case scenario, such as when exposed to moisture and / or high voltage, the parasitic leakage current does not exceed a specific limit value, such as 1.66 A. In some embodiments, in the event of a short circuit in one of the parallel-connected PV generators, the current from the other generator can be detected and blocked by controlling the semiconductor switches of the other DC voltage converter. In some embodiments, the sub-generators can be protected by means of a protective device such that, in the event of a short circuit in the relevant sub-generator, the other DC voltage converter applies a current to protect the portion of the PV generator that is affected by the short circuit.

[0025] In addition to the second disconnector, the sub-generator and the first disconnector can also be provided with a further DC switch in the PV generator. This further increases safety.

[0026] In a method for operating an apparatus for electrolysis using photovoltaically generated DC power, the apparatus includes an electrolysis device and a DC voltage converter. The DC voltage converter supplies DC power to the electrolysis device via a DC bus. The DC power is generated by a photovoltaic sub-generator connected to the DC voltage converter, and the sub-generator is switchably connected to the DC voltage converter. The sub-generator includes a main string, wherein the main string includes a fault current monitor and is switchably connected to the DC voltage converter. The method includes the following steps:

[0027] Before the sub-generators are connected to the connected DC voltage converter: the insulation of the sub-generators is checked by means of an insulation monitoring device, wherein the sub-generators are only connected if a minimum insulation value is exceeded,

[0028] After switching on the sub-generators: the main string is monitored by a fault current monitor, wherein the main string is isolated from the DC voltage converter if the monitored fault current exceeds a predefinable limit value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is described below with the aid of the accompanying drawings, in which:

[0030] Figure 1 shows an apparatus for electrolysis using direct current power generated by photovoltaics,

[0031] Figure 2 shows an exemplary apparatus for performing electrolysis using photovoltaically generated DC power,

[0032] Figure 3 A method for operating a system for electrolysis using photovoltaically generated DC power is schematically illustrated. DETAILED DESCRIPTION

[0033] Figure 1 A device 10 for electrolysis using photovoltaically generated DC power is shown. An electrolysis device E is connected to DC voltage converters 12 and 14 via a DC bus. DC voltage converters 12 and 14 can be disconnected from a DC bus 16 via disconnect switches TS3 and TS7, respectively. DC bus 16 is designed to supply DC power to electrolysis device E, which uses this DC power to perform electrolysis in electrolysis device E, for example, to decompose water into hydrogen and oxygen. The electrolysis device is grounded via an ohmic resistor 18.

[0034] exist Figure 1 Two DC voltage converters 12, 14 are shown. Installation 10 can be scaled and may include only one DC voltage converter 12, 14 or more than two DC voltage converters 12, 14. A PV generator PV-G1, PV-G2 is connected to each DC voltage converter 12, 14. The electrical power generated by the PV generators PV-G1, PV-G2 is converted by the DC voltage converters 12, 14 and supplied to the electrolysis device E via a DC bus 16. Each of the PV generators PV-G1, PV-G2 can be disconnected from its associated DC voltage converter 12, 14 via a first disconnector TS2, TS6.

[0035] PV generator PV-G1 is connected to a first side of a DC voltage converter 12. On a second side of DC voltage converter 12, DC bus 16 is connected to DC voltage converter 12 via disconnector TS3 and a converter protection device. DC voltage converter 12 can be disconnected from DC bus 16 via disconnector TS3. PV generator PV-G1 can be disconnected from DC voltage converter 12 via first disconnector TS2. First disconnector TS2 is connected to insulation monitoring device ISO1. When system 10 starts operating, insulation monitoring device ISO1 is used to check whether PV generator PV-G1 is electrically isolated. Only if this is the case is first disconnector TS2 closed and PV generator PV-G1 electrically connected to DC voltage converter 12.

[0036] The PV generator PV-G1 has two sub-generators TG1 and TG2. The PV generator PV-G1 may also have only one sub-generator TG1, TG2 or more than two sub-generators TG1, TG2. Each of the sub-generators TG1 and TG2 has a residual current detector RCD1, RCD2, for example, in the form of a residual current device (RCD). The residual current detector RCD1 monitors the residual current in the sub-generator TG1, and if the detected residual current exceeds a certain predefined limit value, the sub-generator is disconnected from the DC voltage converter 12 via a second disconnect switch TS1. The residual current detector RCD2 monitors the residual current in the sub-generator TG2, and if the detected residual current exceeds a certain predefined limit value, the sub-generator is disconnected from the DC voltage converter 12 via a second disconnect switch TS4.

[0037] In the example shown, the sub-generator TG1 has a main string HS1, which itself has two strings STR1 and STR2. The sub-generator TG1 can also have multiple main strings HS1. The main string HS1 can also have only one string STR1 and STR2, or more than two strings STR1 and STR2.

[0038] In the example shown, the sub-generator TG2 has a main string HS2, which itself has two strings STR3 and STR4. The sub-generator TG2 may also have multiple main strings HS2. The main string HS2 may also have only one string STR3 and STR4, or more than two strings STR3 and STR4.

[0039] PV generator PV-G2 is connected to a first side of a DC voltage converter 14. On the second side of DC voltage converter 14, DC bus 16 is connected to DC voltage converter 14 via disconnector TS7 and an ohmic resistor. DC voltage converter 14 can be disconnected from DC bus 16 via disconnector TS7. PV generator PV-G2 can be disconnected from DC voltage converter 14 via first disconnector TS6. First disconnector TS6 is connected to insulation monitoring device ISO2. When system 10 starts operating, insulation monitoring device ISO2 is used to check whether PV generator PV-G2 is electrically isolated. Only if this is the case is first disconnector TS6 closed and PV generator PV-G2 electrically connected to DC voltage converter 14.

[0040] PV generator PV-G2 has a sub-generator TG3. PV generator PV-G2 may also have multiple sub-generators TG3. Sub-generator TG3 has a residual current detector RCD3, for example, in the form of a residual current detection device. Residual current detector RCD3 monitors the residual current in sub-generator TG3 and, if the detected residual current exceeds a predeterminable limit value, disconnects the sub-generator from DC voltage converter 14 via second disconnector TS5.

[0041] In the example shown, the sub-generator TG3 has a main string HS3, which itself has two strings STR5 and STR6. The sub-generator TG3 may also have multiple main strings HS3. The main string HS3 may also have only one string STR5 and STR6, or more than two strings STR5 and STR6.

[0042] exist Figure 2 In one embodiment of the device 10 shown in FIG, the device 10 has an electrolysis device E, which is grounded via an ohmic resistor 18. DC power is supplied to the electrolysis device E via a DC bus 16. The DC power is generated by two PV generators PV-G1, PV-G2, converted by DC voltage converters 12, 14, and fed into the DC bus 16.

[0043] DC voltage converter 12 is connected to DC bus 16 via isolating switch TS3 and an ohmic resistor and can be disconnected from the DC bus via isolating switch TS3. DC voltage converter 14 is connected to DC bus 16 via isolating switch TS7 and an ohmic resistor and can be disconnected from the DC bus via isolating switch TS7.

[0044] The PV generator PV-G1 has an insulation monitoring device ISO1 which is connected to a first disconnector TS2. Only when sufficient insulation of the PV generator PV-G1 is detected by the insulation monitoring device ISO1 is the first disconnector TS2 closed and the PV generator PV-G1 connected to the DC voltage converter 12.

[0045] PV generator PV-G1 has a sub-generator TG1, which is protected by a residual current detector RCD1 and an associated second disconnector TS1. If an excessively high residual current is detected by detector RCD1, sub-generator TG1 is disconnected from DC converter 12 via second disconnector TS1. Sub-generator TG1 has a main string HS1 with a string STR1.

[0046] The PV generator PV-G2 has an insulation monitoring device ISO2 which is connected to a first disconnector TS6. Only when sufficient insulation of the PV generator PV-G2 is detected by the insulation monitoring device ISO2 is the first disconnector TS6 closed and the PV generator PV-G2 connected to the DC voltage converter 14.

[0047] PV generator PV-G2 has a sub-generator TG3, which is protected by a residual current detector RCD3 and an associated second disconnector TS5. If the detector RCD3 detects an excessively high residual current, sub-generator TG3 is disconnected from DC converter 14 via second disconnector TS5. Sub-generator TG3 has a main string HS3 with a string STR5.

[0048] Figure 3 A flow chart of a method for operating the device 10 is schematically shown.

[0049] Step S1 is carried out when the installation 10 is started. If in step S1 the insulation monitoring devices ISO1, ISO2, ISO3 detect that the assigned PV generators PV-G1, PV-G2 are sufficiently insulated (see Figure 1 + Figure 2 ), then in step S2, the configured first isolating switches TS2, TS6 (see Figure 1 + Figure 2 ) is closed and the PV generators PV-G1, PV-G2 are connected to the associated DC voltage converters 12, 14 (see Figure 1 + Figure 2 ) electrical connection.

[0050] Step S3 is performed during operation of the device 10. In step S3, the respectively assigned sub-generators TG1, TG2, TG3 (see Figure 1 + Figure 2 ) exceeds a predeterminable threshold value. If it does, in step S4, the sub-generators TG1, TG2, TG3 whose fault current exceeds the threshold value are disconnected by means of the configured second disconnectors TS1, TS4, TS5 (see Figure 1 + Figure 2 ) and the configured DC voltage converters 12, 14 (see Figure 1 + Figure 2 )disconnect.

[0051] Reference Signs List

[0052] 10 Equipment for electrolysis

[0053] 12, 14 DC voltage converter

[0054] 16 DC bus

[0055] 18 ohm resistor

[0056] E Electrolysis device

[0057] PV-G1, PV-G2 PV generators

[0058] TG1, TG2, TG3 sub-generators

[0059] HS1, HS2, HS3 main strings

[0060] STR1, STR2, STR3, STR4, STR5, STR6 strings

[0061] TS1, TS4, TS5 second disconnector

[0062] TS2, TS6 first disconnector

[0063] TS3, TS7 third disconnector

[0064] RCD1, RCD2, RCD3 monitors

[0065] ISO1, ISO2 insulation monitoring devices

[0066] S1, S2, S3, S4 method steps.

Claims

1. An apparatus (10) for electrolysis using photovoltaically generated DC power, comprising: - an electrolysis device (E), a DC voltage converter (12, 14) configured to supply DC power to the electrolysis device (E) via a DC bus (16), wherein the DC power can be generated by a photovoltaic sub-generator (TG1, TG2, TG3) connected to the DC voltage converter (12, 14), The sub-generators (TG1, TG2, TG3) are connected to the DC voltage converters (12, 14) via first disconnectors (TS2, TS6), wherein the first disconnectors (TS2, TS6) are coupled to insulation monitoring devices (ISO1, ISO2) such that closing of the first disconnectors (TS2, TS6) presupposes a successful verification of sufficient insulation of the sub-generators (TG1, TG2, TG3). The sub-generators (TG1, TG2, TG3) have a main string (HS1, HS2, HS3), a second disconnector (TS1, TS4, TS5) being arranged between the main string (HS1, HS2, HS3) and the first disconnector (TS2, TS6), the second disconnector being coupled to a detector (RCD1, RCD2, RCD3) for a fault current of the main string (HS1, HS2, HS3) such that the second disconnector (TS1, TS4, TS5) is opened if a predeterminable limit value of the fault current is exceeded.

2. The device according to claim 1, wherein The DC voltage converter (12, 14) is a step-down converter.

3. The device according to claim 1 or 2, wherein: The poles of the sub-generators (TG1, TG2, TG3) can be electrically connected to the poles of a DC bus (16).

4. The device according to claim 3, wherein During operation of the sub-generators (TG1, TG2, TG3), poles of the sub-generators (TG1, TG2, TG3) are electrically connected to poles of the DC bus (16).

5. The apparatus according to claim 3, wherein The DC voltage converter (12, 14) has a changeover switch for selecting the electrically connected poles of the sub-generators (TG1, TG2, TG3).

6. The device according to claim 5, wherein The DC voltage converter (12, 14) is provided for selecting the pole to be connected taking into account the fault current monitor (RCD1, RCD2, RCD3).

7. The apparatus according to claim 1 or 2, wherein: The fault current detectors (RCD1, RCD2, RCD3) have coaxial conductors for the conductors to be monitored.

8. The apparatus according to claim 1 or 2, wherein: The fault current monitors (RCD1, RCD2, RCD3) have an alternating layer stack of layers for the conductors to be monitored.

9. The apparatus according to claim 1 or 2, wherein: The main string (HS1, HS2, HS3) has a plurality of strings (STR1, STR2, STR3, STR4, STR5, STR6) connected in parallel, wherein the fault current monitoring (RCD1, RCD2, RCD3) is performed for the main string (HS1, HS2, HS3) and / or for the corresponding strings (STR1, STR2, STR3, STR4, STR5, STR6).

10. The apparatus according to claim 1 or 2, wherein: The sub-generators (TG1, TG2, TG3) have a plurality of main strings (HS1, HS2, HS3) connected in parallel, wherein a second disconnector (TS1, TS4, TS5) is respectively arranged between the corresponding main strings (HS1, HS2, HS3) and the first disconnector (TS2, TS6).

11. The apparatus according to claim 1 or 2, wherein: The device comprises a PV generator (PV-G1, PV-G2) having one sub-generator (TG1, TG2, TG3) or a plurality of sub-generators (TG1, TG2, TG3), wherein the PV generator (PV-G1, PV-G2) is connected to the DC voltage converter (12, 14) via a first disconnector (TS2, TS6), wherein the first disconnector (TS2, TS6) is coupled to the insulation monitoring device (ISO1, ISO2) such that closing of the first disconnector (TS2, TS6) presupposes a successful verification of sufficient insulation of the PV generator (PV-G1, PV-G2).

12. The apparatus according to claim 11, wherein The device comprises a plurality of PV generators (PV-G1, PV-G2), wherein the PV generators (PV-G1, PV-G2) are each connected to a DC voltage converter (12, 14), and the DC voltage converters (12, 14) are configured to supply DC power to the electrolysis device (E) via the DC bus (16).

13. The apparatus according to claim 1 or 2, wherein: The main strings (HS1, HS2, HS3) have a rated power greater than 500 kW.

14. The apparatus according to claim 1 or 2, wherein: The DC voltage converter (12, 14) has a rated power of more than 2 MW.

15. A method for operating an apparatus (10) for electrolysis using photovoltaically generated DC power, the apparatus comprising an electrolysis device (E) and a DC voltage converter (12, 14), the DC voltage converter supplying DC power to the electrolysis device via a DC bus, the DC power being generated by photovoltaic sub-generators (TG1, TG2, TG3) connected to the DC voltage converter (12, 14), wherein: The sub-generators (TG1, TG2, TG3) are switchably connected to the DC voltage converter (12, 14), wherein the sub-generators (TG1, TG2, TG3) have main strings (HS1, HS2, HS3), wherein the main strings (HS1, HS2, HS3) have fault current monitors (RCD1, RCD2, RCD3), and the main strings (HS1, HS2, HS3) are switchably connected to the DC voltage converter (12, 14), wherein the method comprises the following steps: Before the sub-generators (TG1, TG2, TG3) are connected to the connected DC voltage converters (12, 14), the insulation of the sub-generators is checked by means of insulation monitoring devices (ISO1, ISO2), wherein the sub-generators are only connected if a minimum insulation value is exceeded. After the sub-generators (TG1, TG2, TG3) are switched on: the main strings (HS1, HS2, HS3) are monitored by the fault current monitors (RCD1, RCD2, RCD3), wherein the main strings (HS1, HS2, HS3) are isolated from the DC voltage converters (12, 14) when the monitored fault current exceeds a predeterminable limit value.

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