Multi-stage power supply of electrolysis system
By switching between the main AC-DC and DC-DC converters in a multi-stage power supply system, combined with DC link capacitors and STATCOM devices, the problems of low current regulation efficiency and high cost in electrolysis systems are solved, achieving full-range current regulation and reactive power compensation, thereby improving system efficiency and reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SIEMENS ENERGY GLOBAL GMBH & CO KG
- Filing Date
- 2024-09-03
- Publication Date
- 2026-04-10
AI Technical Summary
Existing electrolysis systems suffer from low efficiency and high cost in providing current regulation and power compensation, especially when the grid strength is weak, requiring additional filtering and reactive power compensation, and the current regulation range is limited.
A multi-stage power supply system is adopted, including a main AC-DC converter and a DC-DC converter. The controller unit switches the conversion unit in different voltage ranges, and the DC link capacitor stores charge to realize full-range current regulation of the electrolytic cell. Reactive power compensation is provided through the STATCOM device.
It improves the efficiency and reliability of the power supply system, reduces costs, enables complete current rise and fall, reduces the need for filtering and reactive power compensation, and enhances adaptability to the power grid.
Smart Images
Figure CN121844477A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to power supplies for electrical loads, in particular to power supplies connected to an AC grid, i.e. a private or public grid, and providing direct current power to electrical loads using an alternating current (AC) to direct current (DC) conversion. More particularly, the present disclosure relates to a multi-stage power supply for an electrolysis system and an electrolysis system. Furthermore, the present disclosure relates to a method of operating a multi-stage power supply for an electrolysis system, a computer program product and a computer readable storage medium. BACKGROUND
[0002] Electrolysis is a process of splitting water into hydrogen and oxygen using electricity. The reaction takes place in a cell, e.g. a polymer electrolyte membrane (PEM) cell, and requires a supply of direct current (DC). An electrolysis system can comprise one or more electrolysis cells which constitute a high power load and can have a high current demand of DC current, e.g. 7-10 kA.
[0003] A power supply is a critical component of an electrolysis system, as the power supply needs to provide the required current and voltage quality to the electrolysis cells to make the electrolysis system operate in a controlled and safe manner. In particular, proper loading and unloading of the electrolysis cells can be of utmost importance, e.g. during ramp-up and ramp-down operation. Furthermore, the power supply must reliably work under any conditions of the AC grid. Hydrogen is highly flammable, therefore, hydrogen generation during loading and unloading, i.e. de-loading, must also be kept within suitable safety limits and any power fluctuations and quality deviations of the DC current and DC voltage supplied to the electrolysis cells must comply with the operating range of the electrolysis cells.
[0004] This can be achieved by a single-stage power supply utilizing an AC to DC (AC-DC) line commutated converter having a thyristor-based rectifier coupled to receive an alternating current from a transformer connected to an AC grid, wherein the line commutated converter controls the voltage and current required by the electrolysis cells in a so-called “de-boost mode” which allows to regulate the current flowing into the electrolysis cells between 0% and 100% and thus allows a controlled ramp-up and ramp-down of the electrolysis system. However, such a configuration can require additional external filtering and reactive power compensation to ensure compliance with grid specifications of the connected AC grid, in particular if the grid strength is weak, and can thus result in additional costs and effort.
[0005] By utilizing a self-commutated power supply topology based on an AC-DC converter, which is a voltage source converter and regulates the DC voltage in so-called "boost mode", the need for additional filtering and reactive power compensation can be reduced or avoided. However, in a boost mode configuration, the output current of the power supply can only be regulated within a certain range and above a minimum current threshold, i.e. the electrolyzer input current cannot be raised and lowered from 0 A.
[0006] To enable such full raising and lowering, but also to avoid additional filtering and reactive power compensation, a two-stage conversion system can be used, in which the power is processed by a rectifier (IGBT, thyristor or diode), but additionally further by an additional direct current to direct current (DC-DC) converter in a buck mode. In this configuration, it is possible to provide power to the electrolyzer in a controlled manner: the use of IGBTs in the first stage AC-DC converter allows to take advantage of voltage source converters, while the second stage DC-DC converter allows to regulate the current provided to the electrolyzer over the entire operating range. However, this approach requires two converters, which are designed for the full rated power of the connected electrolyzer, resulting in high costs. Furthermore, due to the losses in both the first and second stage converters, the efficiency of this solution can be low. SUMMARY
[0007] It is an object of the present invention to propose an alternative possibility for providing DC power from an AC grid to a high power load such as an electrolyzer, which allows for a full raising and lowering of the input current and at the same time avoids or reduces the need for additional filtering and reactive power compensation, but is less costly and can be more efficient in operation.
[0008] This object is achieved by the multi-stage power supply for an electrolysis system of claim 1 and the electrolysis system of claim 5. Respective methods of operating such a multi-stage power supply for an electrolysis system, computer program products and computer readable storage media are disclosed in claims 6, 9 and 10, respectively. Advantageous additional embodiments of the invention are disclosed in the respective dependent claims.
[0009] According to a first aspect of the present application, a multi-stage power supply for an electrolysis system is provided, wherein an electrolysis cell of the electrolysis system has an input voltage operating range, and the multi-stage power supply comprises a controller unit, at least a first power conversion unit and a second power conversion unit which are connectable to an input of the electrolysis cell, and one or more direct current (DC) link capacitors. The first power conversion unit has a first output voltage operating range which comprises a first subset of the input voltage operating range of the electrolysis cell, the first subset being above and equal to a threshold output voltage of the first power conversion unit, and the second power conversion unit has a second output voltage operating range which comprises a second subset of the input voltage operating range of the electrolysis cell, the second subset being below the threshold output voltage of the first power conversion unit, wherein the first output voltage operating range and the second output voltage operating range together only fully cover the input voltage operating range of the electrolysis cell. The first power conversion unit is a main alternating current to direct current (AC-DC) converter unit having a first converter output connected to the one or more DC link capacitors, and the converter unit is configured to provide the electrical power required by the electrolysis cell via the first converter output for the first subset of the input voltage operating range when the output voltage at the first converter output is above or equal to the threshold output voltage, i.e. during said time, and the second power conversion unit has a second converter output, and the second power conversion unit is configured to provide the electrical power required by the electrolysis cell via the second converter output for the second subset of the input voltage operating range when the output voltage at the first converter output is below the threshold output voltage, i.e. during said time. The threshold output voltage is a minimum output voltage threshold of the first power conversion unit, and the controller unit is configured to select the second power conversion unit instead of the first power conversion unit to provide the electrical power to the input of the electrolysis cell when the output voltage at the first converter output is below the threshold output voltage.
[0010] The controller unit can be or be part of a controller, in particular a programmable controller, i.e. a programmable device comprising at least a processor and a memory unit, which is connected, e.g. to receive the sensed voltage level and to select the operating mode of the power supply, e.g. by setting switches for allowing and inhibiting the connection of the power conversion units.
[0011] The power conversion units are or comprise DC-DC converter units or AC-DC converter units, and can additionally comprise additional circuitry, e.g. input filters, e.g. high frequency filters.
[0012] Depending on the embodiment of the multi-stage power supply, the main alternating current to direct current (AC-DC) converter unit can be the only AC-DC converter unit of the multi-stage power supply, or can be the first of a plurality of AC-DC converters.
[0013] The DC link capacitor connected to the output of the power conversion unit has a sufficiently large capacitance to store enough charge so that even if the power conversion unit itself cannot provide the required power during a specific period of time, it allows power to be supplied uninterruptedly at the required level during that period of time.
[0014] The first output voltage operating range of the first power conversion unit includes a first subset of the input voltage operating range of the electrolytic cell that is higher than or equal to the threshold output voltage of the first power conversion unit. This means that the first output voltage operating range is a range that starts from the threshold output voltage of the first power conversion unit and partially covers the input voltage range of the electrolytic cell, but does not include voltage levels below the threshold output voltage.
[0015] The characteristic that the first and second output voltage operating ranges together completely cover the input voltage operating range of the electrolyzer excludes any topology in which a power conversion unit not only partially covers but completely covers the entire input voltage operating range of the electrolyzer.
[0016] The minimum output voltage threshold of the first power conversion unit, which defines the threshold output voltage, depends on the type of AC-DC converter selected for the first power conversion unit. For example, if the AC-DC converter is based on IGBTs to implement the rectifier circuit used, the first power conversion unit will begin to provide the required DC output current when the output voltage at the output of the first converter reaches the minimum output voltage of that particular circuit. The minimum output voltage can be selected as the minimum output voltage threshold. In another embodiment, the minimum output voltage threshold can be defined relative to the minimum output voltage, for example, 10% higher than the minimum output voltage. This threshold is used by the controller unit to determine whether to select either the first or second power conversion unit to provide electrical power to the input of the electrolyzer. In other words, below this threshold, the second power conversion unit is used to provide power, but once the threshold output voltage is reached, the first power conversion unit is selected to provide the required DC power to the electrolyzer.
[0017] Neither of the first and second power conversion units has to be configured to provide the required DC power over the entire input operating range of the electrolyzer, and the first power conversion unit only needs to provide power for a part of the operating range starting from a threshold output voltage, while for the part of the operating range below the threshold, i.e. for example during current ramp-up or ramp-down phases of the electrolysis system, only the second power conversion unit provides the required power to the electrolyzer, i.e. the second power conversion unit only has to be designed for lower power as it only operates during ramp-up and ramp-down phases. The multi-stage power supply can be operated efficiently and each power conversion unit has to meet lower requirements compared to a power conversion unit designed to cover the complete ramp-up and ramp-down over the entire input voltage operating range of the connected electrolyzer, allowing to increase efficiency, reliability and availability at lower cost by using standard components suitable for standard voltage levels.
[0018] For example, within a low voltage range (0-1000V) there are standard voltage levels, e.g. 400V or 690V, where the required equipment is readily available. As there is already a supply chain, components with these ratings are optimized, reliable and cost-effective. Equipment in other industrial fields, e.g. using wind turbines for power generation, also often makes use of 690V components. Therefore, power supply components such as protection circuits, transformers, converters are available at low cost and there is a supply chain for such components on the market.
[0019] In a preferred embodiment, the size of the second subset of the input voltage operating range of the electrolyzer, i.e. the range below the threshold output voltage at the output of the first converter, is less than 20%, e.g. 10%, of the input voltage operating range of the electrolyzer, which leads to a reduction of the cost, an improvement of the size and a reduction of the cooling requirements of the second power conversion unit used only during the ramp-up phase of the electrolyzer.
[0020] In an embodiment of the multi-stage power supply, it further comprises a switchable pre-charge circuit element configured to pre-charge the one or more DC link capacitors when the first converter output voltage is below the threshold output voltage. This allows to pre-charge the one or more DC link capacitors before they can be charged by the first power conversion unit.
[0021] In an exemplary embodiment, the switchable pre-charge circuit element comprises an additional alternating current to direct current (AC-DC) converter unit. This allows to pre-charge the one or more DC link capacitors from the AC grid if the additional AC-DC converter unit is configured to operate within the operating range below the output voltage threshold of the first power conversion unit having the main AC-DC converter. However, in an alternative embodiment, the switchable pre-charge circuit element can comprise or be connected to a DC power source, e.g. a battery.
[0022] Furthermore, according to the first aspect of the application, the second power conversion unit of the multi-stage power supply is a direct current to direct current (DC-DC) converter unit having a second converter input connected to the first converter output of the first power conversion unit, and the multi-stage power supply further comprises a switchable bypass circuit having a bypass switch, e.g. a contactor switch, which is connected to bypass the second power conversion unit when the bypass switch is in an on state. The DC-DC converter unit can be an isolated or non-isolated DC-DC converter.
[0023] In the on state, the bypass circuit is enabled and connects the second converter input to the second converter output. In the off state, the bypass circuit is disabled and the second power conversion unit converts the current received from the first converter output. Since the controller unit is configured to select the second power conversion unit instead of the first power conversion unit to provide power to the input of the electrolytic cell when the output voltage at the first converter output is below the threshold output voltage, the controller unit switches the bypass switch to the off state when the output voltage at the first converter output is below the threshold output voltage. Since the one or more DC link capacitors are also connected to the first converter output, the second power conversion unit will receive DC current at least from the pre-charged DC link capacitors. Once the first power conversion unit is ready to provide DC current, i.e. once the output voltage at the first converter output rises to the minimum output voltage threshold, the controller unit can switch the bypass switch to the off state and the DC current provided by the first power conversion unit is then directed to the input of the electrolytic cell, bypassing the second power conversion unit, i.e. the DC-DC converter.
[0024] With this improved two-stage converter topology, which uses only a partial scale DC-DC converter as the second power conversion unit and which can be bypassed once the electrolytic cell reaches a certain load, the multi-stage power supply operates as a single-stage power supply with an optional stage. The advantage of the proposed topology is an increase in efficiency and a reduction in cost of the overall power supply. Since the operation of the DC-DC converter is limited, the reliability of the overall converter system is increased.
[0025] The described operation depends on the state of the bypass switch, which is set to the open state when the power supply starts operation. Thus, power flows through both converters and a controlled boost of the electrolyzer can be achieved. Once the minimum output voltage threshold of the first stage converter, i.e. the first power conversion unit, is reached, the bypass switch is turned on, i.e. switched to the on state, and the second power conversion unit with the DC-DC converter is bypassed, which means that power is only directed through the first power conversion unit. With this topology, the DC-DC converter of the second power conversion unit only needs to be designed for lower power, as it only works during boost and buck of the electrolysis system.
[0026] In an additional embodiment of the multi-stage power supply, the controller unit is further configured to switch the bypass switch to the open state and also disable the second power conversion unit when the electrolyzer is not present or does not consume electrical power. In this case, the electrolyzer is not present or not working and does not produce hydrogen. With the bypass switch in the open state and the second power conversion unit disabled, the first power conversion unit with the main AC-DC converter unit together with the DC link capacitor constitutes a static synchronous compensator (STATCOM) device for the AC grid the multi-stage power supply of the electrolysis system is connected to. The STATCOM function is to provide flexible reactive power to the power system, i.e. the AC grid and its connected entities, such as power plants and consumers. This can be seen as an additional business case for the owner of the electrolysis system.
[0027] Furthermore, the STATCOM device, i.e. the multi-stage power supply in STATCOM mode, provides active filtering capabilities. The STATCOM device can individually and selectively filter out harmonics present in the power system, which are generated by the surrounding power consumers, e.g. a thyristor-based power supply adjacent to the electrolysis system (as thyristor-based rectifiers activated by a firing angle signal tend to generate harmonics on the input AC current). The reactive power supply and active filtering are suitable to combine the described multi-stage power supply in a hybrid system, which in embodiments can include an IGBT-based converter connected to the electrolyzer, and an adjacent power supply for an additional electrolysis system, wherein the power supply comprises a thyristor-based converter.
[0028] In an alternative example embodiment of the multi-stage power supply, the second power conversion unit is not a DC-DC converter unit. Instead, an additional alternating current to direct current (AC-DC) current converter unit, which switchable pre-charge circuit element is configured to pre-charge one or more DC link capacitors when the first converter output voltage is below the threshold output voltage, is the second power conversion unit. In other words, instead of using a DC-DC converter for the second power conversion unit, the pre-charge circuit of the one or more DC link capacitors is suitably configured or designed to be able to boost or step down the electrolyzer during the time the output voltage at the first power converter output is below the threshold output voltage. In particular, the output voltage operating range of the switchable pre-charge circuit element is configured such that it includes a second subset of the input voltage operating range of the electrolyzer below the threshold output voltage of the first power conversion unit, i.e. the minimum output voltage threshold.
[0029] In this example of the multi-stage power supply, the first converter output and the second converter output are connected to the input of the electrolyzer via an output switch. This allows connecting and disconnecting the power supply from the electrolyzer.
[0030] In one example, the controller unit is further configured to switch the output switch to the open state when the electrolyzer is not present or does not consume electrical power. Disconnected from the electrolyzer, the remaining power supply can be used as a STATCOM device for the AC grid.
[0031] According to a second aspect of the present invention, an electrolysis system comprises at least one electrolyzer and a multi-stage power supply according to the first aspect of the present invention, thus achieving the advantages and features of the claimed multi-stage power supply.
[0032] According to a third aspect of the present invention, a method of operating a multi-stage power supply for an electrolysis system according to the first aspect of the present invention is provided. The method comprises connecting an input of the multi-stage power supply to an AC grid, determining a minimum output voltage threshold of a first power conversion unit of the multi-stage power supply as a threshold output voltage, sensing an output voltage at a first converter output of the first power conversion unit, determining whether the output voltage at the first converter output is below the threshold output voltage, and when the output voltage at the first converter output is not below the threshold output voltage, selecting the first power conversion unit to provide electrical power to an input of the electrolyzer, and when the output voltage at the first converter output is below the threshold output voltage, selecting a second power conversion unit of the multi-stage power supply instead of the first power conversion unit to provide electrical power to the input of the electrolyzer.
[0033] In one embodiment, the method further comprises, when the first converter output voltage is below the threshold output voltage, pre-charging one or more DC link capacitors connected to the first converter output with a switchable pre-charge circuit element of the multi-stage power supply.
[0034] And in a preferred embodiment of the method, the step of determining whether the output voltage at the first converter output is below a threshold output voltage comprises determining that the second power conversion unit is a direct current to direct current (DC-DC) converter unit having a second converter input connected to the first converter output of the first power conversion unit, and the multi-stage power supply further comprises a switchable bypass circuit having a bypass switch, which bypass circuit is connected to bypass the second power conversion unit when the bypass switch is in an on state, the step of selecting the first power conversion unit to provide electrical power to the input of the electrolysis cell when the output voltage at the first converter output is not below the threshold output voltage comprises switching the bypass switch to the on state, and the step of selecting the second power conversion unit of the multi-stage power supply instead of the first power conversion unit to provide electrical power to the input of the electrolysis cell when the output voltage at the first converter output is below the threshold output voltage comprises switching the bypass switch to the off state.
[0035] Furthermore, according to a fourth aspect of the present application, a computer program product comprises code portions which, when executed on a programmable device, enable a multi-stage power supply to perform the steps of the method according to the third aspect of the present application. In other words, the computer program product comprises code portions which, when executed on a programmable device, enable a multi-stage power supply to perform the method according to an embodiment of the present application.
[0036] The programmable device can be a programmable device of the multi-stage power supply, in particular a controller unit of the multi-stage power supply, which is adapted to send, process and receive signals from different units of the multi-stage power supply, e.g. an output voltage signal at the first converter output and a switching signal for changing the state of the bypass switch. In another embodiment, the programmable device can be connected or connectable to the multi-stage power supply. According to a fifth aspect of the present application, a computer readable storage medium comprises a computer program product according to the fourth aspect of the present application.
[0037] The computer program product corresponds to a computer program comprising at least software code portions for performing the steps of the method according to the present application when run on a programmable device, e.g. a controller unit or other computer, to enable a multi-stage power supply to perform the functions according to the present application.
[0038] The computer program can be provided on a computer readable storage medium, i.e. a data carrier such as a CD, a DVD, a memory stick or other storage medium, which stores the data which are loadable into the memory of the programmable device, wherein the data represent the computer program. As another example, the data carrier can also be a data connection, e.g. a telephone cable or data cable or a wireless connection.
[0039] Although not explicitly described, the presented embodiments can be implemented in any combination or sub-combination.BRIEF DESCRIPTION OF DRAWINGS BRIEF DESCRIPTION OF DRAWINGS
[0040] The nature, features and advantages of the application and the manner of realizing them will become more apparent and the application will be better understood from the following description of exemplary embodiments with reference to the drawings on which: Figure 1 schematically illustrates a first example of an electrolysis system comprising a multi-stage power supply according to an embodiment of the application; Figure 2 schematically illustrates a second example of an electrolysis system comprising a multi-stage power supply; Figure 3 schematically illustrates an example of a method of operating a multi-stage power supply for an electrolysis system according to an embodiment of the application; and Figure 4 schematically illustrates an example graph of input voltage versus input current at an input of an electrolysis cell connected to a multi-stage power supply. DETAILED DESCRIPTION
[0041] In Figure 1 the first example of an electrolysis system 100 comprising a multi-stage power supply 120 according to an embodiment of the application is schematically illustrated. The electrolysis system further comprises an electrolysis cell 110 having an input voltage operating range, an electrolysis cell input 111 being connected to a power supply output 121 of the multi-stage power supply 120, which power supply output 121 is connectable to an AC power supply, in particular to an (public) AC grid 101, by means of a switching device 122. An AC voltage received from the AC grid 101 is provided via the switching device 122 in an on-state to a transformer unit 123, which transformer unit 123 converts the grid voltage to a lower voltage, for example below 1000 V. In the illustrated embodiment, it is converted to three phase-shifted AC voltage signals. In the illustrated embodiment, the controller unit 124 is a programmable controller unit and comprises a processor 125 and a memory 126.
[0042] The multi-stage power supply 120 has a controller unit 124 configured to send and receive all required signals to and from different units, elements and switches (not shown connected) of the multi-stage power supply 120. In the illustrated embodiment, the controller unit 124 is a programmable device having at least a processor 125 and a memory 126, wherein the memory 126 comprises code portions of a computer program product which, when executed by the processor of the programmable device, enable the multi-stage power supply 120 to perform the steps of the method of operation described in connection with Figure 3 the description.
[0043] The multi-stage power supply 120 comprises a first power conversion unit 127 and a second power conversion unit 128 connectable to an input 111 of the electrolysis cell 110. In the illustrated embodiment, the first power conversion unit 127 comprises a main AC-DC converter unit 129, e.g. with an IGBT-based rectifier, the input of which is connected to a high frequency filter unit 130, the input of which is connected to receive a converted low voltage AC signal from the transformer arrangement 123 through a circuit breaker switch 131, e.g. an air circuit breaker (ACB), for damage protection, e.g. due to overcurrent.
[0044] The first power conversion unit 127 has a first output voltage operating range comprising a first subset of the input voltage operating range of the electrolysis cell 110, the first subset being above and equal to a threshold output voltage of the first power conversion unit 127, and the second power conversion unit 128 has a second output voltage operating range comprising a second subset of the input voltage operating range of the electrolysis cell 110, the second subset being below the threshold output voltage of the first power conversion unit 127. The first output voltage operating range and the second output voltage operating range together fully cover the input voltage operating range of the electrolysis cell 110.
[0045] The first power conversion unit 127 is or comprises a main AC-DC converter unit 127 and has a first converter output 132 connected to a set of two DC link capacitors 133, 134.
[0046] The first power conversion unit 127 provides the electrical power required by the electrolysis cell 110 via the first converter output 132 for the first subset of the input voltage operating range during an output voltage at the first converter output 132 being above or equal to the threshold output voltage, and the second power conversion unit 128 provides the electrical power required by the electrolysis cell 110 via the second converter output 135 for the second subset of the input voltage operating range during an output voltage at the first converter output 132 being below the threshold output voltage. The threshold output voltage is a minimum output voltage threshold of the first power conversion unit 127. The controller unit 124 is configured to select the second power conversion unit 128 instead of the first power conversion unit 127 to provide the electrical power to the input 111 of the electrolysis cell 110 when the output voltage at the first converter output 132 is below the threshold output voltage.
[0047] In the shown embodiment, the multi-stage power supply 120 further comprises a switchable pre-charge circuit element 136 configured to pre-charge the DC link capacitors 133, 134 when the first converter output voltage is below a threshold output voltage, in order to pre-charge them before they can be charged by the first power conversion unit 127. The shown switchable pre-charge circuit element 136 comprises at least a pre-charge switch 137 for enabling and disabling pre-charging. The switchable pre-charge circuit element 136 has an additional AC-DC converter unit 138 for pre-charging the DC link capacitors 133, 134 from the AC grid 101 if the additional AC-DC converter unit 138 is configured to operate in an operating range below the output voltage threshold of the first power conversion unit 127 having the main AC-DC converter unit 129.
[0048] In the shown embodiment, the second power conversion unit 128 is or comprises a DC-DC converter unit having a second converter input 141 connected to the first converter output 132 of the first power conversion unit 127. Further, the multi-stage power supply 120 comprises a switchable bypass circuit 139 having a bypass switch 140, e.g. a contactor switch. When the bypass switch 140 is in an on-state, i.e. closed or enabled, the switchable bypass circuit is connected to bypass the second power conversion unit 128.
[0049] In Figure 2 the second example of the electrolysis system 100 comprising the multi-stage power supply 120 is schematically shown. The same or similar elements as shown in Figure 1 the first example are shown with the same reference signs. Only the elements that differ from Figure 1 the first example will be described in detail.
[0050] In Figure 2 the shown exemplary embodiment of the multi-stage power supply 120, the second power conversion unit is not a DC-DC converter unit. Instead, the additional AC-DC converter unit 138 of the switchable pre-charge circuit element 136 for pre-charging the DC link capacitors 133, 134 is considered to be the second power conversion unit when the first converter output voltage is below the threshold output voltage. In other words, the additional AC-DC converter unit 138 of the switchable pre-charge circuit element 136 is suitably configured to be able to step up or step down the electrolyzer 110 during the output voltage at the first power converter output is below the threshold output voltage. To this end, the output voltage operating range of the switchable pre-charge circuit element 136 is configured such that it comprises a second subset of the input voltage operating range of the electrolyzer 110 below the minimum output voltage threshold of the first power conversion unit 127.
[0051] When the output voltage at the first converter output 132 is lower than the threshold output voltage (i.e. the minimum output voltage threshold), the selection of the second power conversion unit (i.e. in the shown embodiment the switchable pre-charge circuit element 136 with the additional AC-DC converter unit 138) by the controller unit 124 instead of the first power conversion unit 127 to provide electrical power to the input 111 of the electrolysis cell 110 is performed by the controller unit 124 by setting the pre-charge switch 137 to the on state to connect the pre-charge circuit element 136 with the output of the transformer unit 123. The additional AC-DC converter unit 138 can for example comprise a thyristor based rectifier.
[0052] The first converter output 132 corresponding to the second converter output in this embodiment can be connected to the input 111 of the electrolysis cell 110 via the output switch 240. This allows connecting and disconnecting the power supply from the electrolysis cell 110.
[0053] In Figure 3 , an example of a method 300 of operating a multi-stage power supply for an electrolysis system according to an embodiment of the present application is schematically shown. After the method of operating a multi-stage power supply for an electrolysis system has started 301, for example as shown in Figure 1 , the input of the multi-stage power supply is connected 302 to an AC grid, the minimum output voltage threshold of the first power conversion unit of the multi-stage power supply is determined 303 to be the threshold output voltage, and the output voltage is sensed 304 at the first converter output of the first power conversion unit.
[0054] In a next step, it is determined 305 whether the output voltage at the first converter output is lower than the threshold output voltage. In case the determination (i.e. the comparison result) indicates that the output voltage at the first converter output is not lower than the threshold output voltage (indicated as “-” in Figure 3 ), the first power conversion unit is selected 306 to provide electrical power to the input of the electrolysis cell when the output voltage at the first converter output is not lower than the threshold output voltage (i.e. during the time period in which the output voltage at the first converter output is not lower than the threshold output voltage). In case the determination (i.e. the comparison result) indicates that the output voltage at the first converter output is lower than the threshold output voltage (indicated as “+” in Figure 3 ), the second power conversion unit of the multi-stage power supply is selected 307 to provide electrical power to the input of the electrolysis cell instead of the first power conversion unit when the output voltage at the first converter output is lower than the threshold output voltage, i.e. during the time period in which the output voltage at the first converter output is lower than the threshold output voltage.
[0055] The method then continues with the step of sensing 304 the output voltage at the first converter output of the first power conversion unit.
[0056] In Figure 3 In an embodiment of the method as shown, prior to the step of selecting 307 the second power conversion unit, the step of pre-charging 308 one or more DC link capacitors connected to the first converter output with the switchable pre-charge circuit element of the multi-stage power supply when the first converter output voltage is below the threshold output voltage, i.e. during a time period in which the first converter output voltage is below the threshold output voltage.
[0057] The method ends, for example, when the multi-stage power supply is deactivated.
[0058] In an embodiment of the method 300, the step of determining 305 whether the output voltage at the first converter output is below the threshold output voltage comprises determining that the second power conversion unit is a DC-DC converter unit having a second converter input connected to the first converter output of the first power conversion unit, and that the multi-stage power supply further comprises a switchable bypass circuit having a bypass switch connected to bypass the second power conversion unit when the bypass switch is in an on state, the step of selecting 306 the first power conversion unit to provide power to the input of the electrolysis cell when the output voltage at the first converter output is not below the threshold output voltage comprises switching the bypass switch to the on state, and the step of selecting 307 the second power conversion unit of the multi-stage power supply to provide electrical power to the input of the electrolysis cell instead of the first power conversion unit when the output voltage at the first converter output is below the threshold output voltage comprises switching the bypass switch to the off state.
[0059] In Figure 4 In an embodiment of the method as shown, the step of selecting 307 the second power conversion unit is performed when the first converter output voltage is below the threshold output voltage. Figure 1 In an embodiment of the electrolysis system with a multi-stage power supply as shown in
[0060] Those skilled in the art will realize that the boundaries between the modules are only illustrative and that alternative embodiments can merge modules or employ alternative combinations of the various modules. It will also be appreciated that, where embodiments are described to have a certain order of steps, the steps can be performed in a different order or simultaneously, at least in part. Other steps can be added and some described steps can be omitted.
[0061] In this text, the terms "input" and "output" refer to input and output interfaces, pins or any other input and output connections. However, the terms "input" and "output" relate to complete input or output interfaces, i.e. both the connections in the DC circuit and the connections to all three shown phases of a three-phase AC connection. For the sake of clarity, in the drawings, usually only one set of connections of these groups of connections is numbered by a drawing reference number, although it identifies the set of connections.
[0062] Unless otherwise stated, terms such as "first" and "second" are arbitrarily assigned and are merely intended to differentiate between two or more components. Thus, these terms are not intended to signify chronological order, or priority of use or application, or importance of an associated component. For example, a "second" component is not necessarily the second component applied or utilized, nor does a "first" component hold any priority or significance of use over a "second" component.
[0063] The mere fact that certain features are recited in mutually different claims does not indicate that combinations of these features cannot be employed to advantage.
[0064] While the application has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, and that other variations and modifications of the application can be made by those skilled in the art without departing from the scope of the application.
[0065] In summary, the invention relates to a multi-stage power supply 120 for an electrolysis system 100, wherein the electrolysis cell 110 has an input voltage operating range, and the multi-stage power supply 120 comprises a controller unit 124, at least a first power conversion unit 127 and a second power conversion unit 128 connectable to an input 111 of the electrolysis cell 110, and a DC link capacitor 133, 134, wherein the first power conversion unit 127 has a first output voltage operating range, the first output voltage operating range comprising a first subset of the input voltage operating range of the electrolysis cell 110, the first subset being above and equal to a threshold output voltage of the first power conversion unit 127, the second power conversion unit 128 has a second output voltage operating range, the second output voltage operating range comprising a second subset of the input voltage operating range below the threshold output voltage, the first output voltage operating range and the second output voltage operating range together only fully covering the input voltage operating range of the electrolysis cell 110, the first power conversion unit 127 comprises a main AC-DC converter unit having a first converter output 132 connected to the DC link capacitor 133, 134, and the main AC-DC converter unit is configured to provide the required electrical power for the electrolysis cell 110 for the first subset of the input voltage operating range via the first converter output 132 when the output voltage at the first converter output is above or equal to the threshold output voltage, and the second power conversion unit 128 has a second converter output 135, and to provide electrical power for the second subset of the input voltage operating range when the voltage at the first converter output 132 is below the threshold output voltage, which is the minimum output voltage threshold of the first power conversion unit 127, wherein the controller unit 124 selects the second power conversion unit 128 instead of the first power conversion unit to provide power to the electrolysis cell input 111 when the voltage at the first converter output 132 is below the threshold, wherein the second power conversion unit 128 is or comprises a DC-DC converter unit having a second converter input 141 connected to the first converter output 132 of the first power conversion unit 127, and wherein the multi-stage power supply 120 further comprises a switchable bypass circuit 139 having a bypass switch 140, which is connected to bypass the second power conversion unit 128 when the bypass switch 140 is in an on state.
[0066] Furthermore, an electrolysis system 100, a method 300 of operating a multi-stage power supply for an electrolysis system, a computer program product and a computer readable storage medium are provided.
Claims
1. A multi-stage power supply (120) for an electrolysis system (100), wherein, The electrolytic cell (110) of the electrolysis system (100) has an input voltage operating range, and the multi-stage power supply (120) includes: Controller unit (124); At least a first power conversion unit (127) and a second power conversion unit (128) capable of being connected to the input terminal (111) of the electrolytic cell (110); and One or more DC link capacitors (133, 134), wherein, The first power conversion unit (127) has a first output voltage operating range, which includes a first subset of the input voltage operating range of the electrolytic cell (110), the first subset being higher than or equal to the threshold output voltage of the first power conversion unit (127). The second power conversion unit (128) has a second output voltage operating range, which includes a second subset of the input voltage operating range of the electrolytic cell (110), the second subset being lower than the threshold output voltage of the first power conversion unit (127). The first output voltage operating range and the second output voltage operating range together completely cover the input voltage operating range of the electrolytic cell (110). The first power conversion unit (127) is or includes a main AC-to-DC converter unit having a first converter output (132) connected to the one or more DC link capacitors (133, 134), and the main AC-to-DC converter unit is configured to provide the electrical power required by the electrolytic cell (110) via the first converter output (132) for a first subset of the input voltage operating range when the output voltage at the first converter output is higher than or equal to the threshold output voltage. The second power conversion unit (128) has a second converter output (135) and is configured to provide the required electrical power to the electrolytic cell (110) via the second converter output for a second subset of the input voltage operating range when the output voltage at the first converter output (132) is lower than the threshold output voltage, wherein, The threshold output voltage is the minimum output voltage threshold of the first power conversion unit (127), wherein, The controller unit (124) is configured to select the second power conversion unit (128) instead of the first power conversion unit (127) to provide electrical power to the input terminal (111) of the electrolytic cell (110) when the output voltage at the output terminal (132) of the first converter is lower than the threshold output voltage, wherein, The second power conversion unit (128) is or includes a DC-DC converter unit having a second converter input (141) connected to the first converter output (132) of the first power conversion unit (127), and wherein, The multi-stage power supply (120) also includes a switchable bypass circuit (139) with a bypass switch (140), which is connected to bypass the second power conversion unit (128) when the bypass switch (140) is in the on state.
2. The multi-stage power supply according to claim 1 further includes: A switchable precharge circuit element (136) is configured to precharge the one or more DC link capacitors (133, 134) when the output voltage of the first converter is lower than the threshold output voltage.
3. The multi-stage power supply according to claim 2, wherein, The switchable precharge circuit element (136) includes an additional AC-to-DC converter unit (138).
4. The multi-stage power supply according to any one of the preceding claims, wherein, The controller unit (124) is also configured to switch the bypass switch (140) to the off state when the electrolytic cell (110) is absent or does not consume electrical power, and to disable the second power conversion unit (128).
5. An electrolysis system (100) comprising at least one electrolytic cell (110) and a multi-stage power supply (120) according to any one of claims 1 to 4.
6. A method (300) for operating a multi-stage power supply for an electrolysis system according to any one of claims 1 to 4, comprising: Connect the input terminal of the multi-stage power supply (302) to the AC power grid; The minimum output voltage threshold of the first power conversion unit of the multi-stage power supply is determined (303) as the threshold output voltage; The sensor (304) senses the output voltage at the first converter output terminal of the first power conversion unit; Determine (305) whether the output voltage at the output terminal of the first converter is lower than the threshold output voltage; When the output voltage at the output terminal of the first converter is not lower than the threshold output voltage, the first power conversion unit is selected (306) to provide electrical power to the input terminal of the electrolytic cell; as well as When the output voltage at the output terminal of the first converter is lower than the threshold output voltage, the second power conversion unit of the multi-stage power supply (307) is selected instead of the first power conversion unit to provide electrical power to the input terminal of the electrolytic cell.
7. The method according to claim 6, further comprising: When the output voltage of the first converter is lower than the threshold output voltage, the switchable pre-charge circuit element of the multi-stage power supply is used to pre-charge one or more DC link capacitors connected to the output of the first converter (308).
8. The method according to claim 6 or 7, wherein, The step of determining (305) whether the output voltage at the output terminal of the first converter is lower than the threshold output voltage includes determining that the second power conversion unit is a DC-DC converter unit having a second converter input terminal connected to the output terminal of the first converter of the first power conversion unit, and determining that the multi-stage power supply further includes a switchable bypass circuit with a bypass switch, wherein when the bypass switch is in the on state, the switchable bypass circuit is connected to bypass the second power conversion unit; When the output voltage at the output terminal of the first converter is not lower than the threshold output voltage, the step of selecting (306) the first power conversion unit to provide electrical power to the input terminal of the electrolytic cell includes switching the bypass switch to the on state; and When the output voltage at the output terminal of the first converter is lower than the threshold output voltage, the step of selecting (307) the second power conversion unit of the multi-stage power supply instead of the first power conversion unit to provide electrical power to the input terminal of the electrolytic cell includes switching the bypass switch to the off state.
9. A computer program product comprising a code portion that, when executed on a programmable device, enables the programmable device to perform the steps of the method (300) according to any one of claims 6 to 8.
10. A computer-readable storage medium comprising the computer program product according to claim 9.