Quasi-single-stage direct current transformer

Abstract

According to the quasi-single-stage direct-current transformer, the first rectification branch is directly connected with the output module, the second rectification branch is connected with the output module through the voltage regulation module, efficiency and performance can be considered, and the quasi-single-stage direct-current transformer has the advantages of being high in response speed and low in loss of a single-stage structure; the voltage regulation flexibility of the two-stage structure is kept; the output end of the regulating circuit adopts an independent output mode or an at least partial parallel output mode, so that the requirements of different electrolytic bath capacities and voltage grades are met, the power conversion of various electrolytic baths from medium-voltage direct current to low-voltage can be supported, the capacity of the direct-current hydrogen production power supply is greatly improved, and the energy consumption is reduced. And the application requirements of renewable energy source volatility and intermittency are met.

Description

Technical Field

[0001] This application belongs to the field of power system topology technology, and in particular relates to a quasi-single-stage DC transformer. Background Technology

[0002] Hydrogen energy is the optimal way to store renewable energy on a large scale and over long periods. Hydrogen storage containers are 10 times cheaper than stationary energy storage batteries, offering flexible midstream transportation and a wide range of downstream applications. The proportion of renewable energy in future power systems will further increase, presenting a supply and demand pattern of "wind and solar as the mainstay, with diversified support." However, the volatility of renewable energy poses a significant challenge to grid stability, necessitating stable and periodic energy storage and regulation to achieve cross-seasonal, long-term power regulation. Off-grid hydrogen production is an effective means to achieve this. Compared to AC hydrogen production schemes, DC hydrogen production systems offer higher power quality, better stability, faster and more reliable power regulation, and lower transmission losses, making them a more promising topology.

[0003] In related technologies, DC transformers used as hydrogen production power sources typically require two voltage conversions: AC-DC and DC-DC, to output the DC voltage required by the electrolyzer. Each conversion results in energy loss, especially in high-power scenarios such as large-scale off-grid hydrogen production from renewable energy sources, where the cumulative losses are particularly significant. Summary of the Invention

[0004] This application provides a quasi-single-stage DC transformer that balances efficiency and performance. It combines the advantages of a single-stage structure, such as fast response and low loss, with the voltage regulation flexibility of a multi-stage structure. It also meets the requirements of different electrolyzer capacities and voltage levels, and can support power conversion from medium-voltage DC to low-voltage various types of electrolyzers. This significantly increases the capacity of DC hydrogen production power supplies and adapts to the application requirements of renewable energy with its volatility and intermittency.

[0005] In a first aspect, embodiments of this application provide a quasi-single-stage DC transformer, comprising: An inverter circuit, multiple isolation transformers, multiple rectifier circuits, and multiple regulating circuits are connected in sequence. The input terminals of the multiple isolation transformers are connected in parallel. The multiple isolation transformers correspond one-to-one with the multiple rectifier circuits. The multiple rectifier circuits correspond one-to-one with the multiple regulating circuits. The output terminals of the regulating circuits adopt an independent output mode or at least a partially parallel output mode. The output terminals of the regulating circuits are connected to the electrolytic cell. Each rectifier circuit includes a first rectifier branch and a second rectifier branch, and each regulating circuit includes a voltage regulating module and an output module, with the output terminal of the voltage regulating module connected to the input terminal of the output module. The output terminal of the first rectifier branch is connected to the output module of the corresponding regulating circuit. The output of the second rectifier branch is connected to the input of the voltage regulation module, and the output of the voltage regulation module is connected to the output module.

[0006] In some embodiments, the first rectifier branch includes a first conducting module and a first returning module, the output terminal of the isolation transformer is connected to the first conducting module and the first returning module respectively, and the output module is connected between the first conducting module and the first returning module; The second rectifier branch includes a second conduction module, a second return module, and a charging energy storage module. The output terminal of the isolation transformer is connected to the second conduction module and the second return module respectively. The charging energy storage module is connected between the second conduction module and the second return module. The output terminal of the charging energy storage module is connected to the input terminal of the voltage regulation module.

[0007] In some embodiments, the first conduction module includes a first diode, the second return module includes a second diode, the second conduction module includes a third diode, the second return module includes a fourth diode, and the charging energy storage module includes a first capacitor.

[0008] In some embodiments, the isolation transformer includes a primary winding; The first diode is connected between the first end of the first primary winding and the output module, and the second diode is connected between the second end of the first primary winding and the output module. The third diode is connected between the first end of the first winding and the first capacitor, and the fourth diode is connected between the second end of the first winding and the first capacitor. The conduction direction of the first diode is opposite to that of the third diode, and the conduction direction of the second diode is opposite to that of the fourth diode.

[0009] In some embodiments, the isolation transformer includes a secondary winding and a tertiary winding, the secondary winding and the tertiary winding sharing a common terminal; The first diode is connected between the first end of the second stage winding and the output module, and the second diode is connected between the common terminal and the output module. The third diode is connected between the first end of the third winding and the first capacitor, and the fourth diode is connected between the common terminal and the first capacitor. The conduction direction of the first diode is opposite to that of the third diode, and the conduction direction of the second diode is opposite to that of the fourth diode.

[0010] In some embodiments, the voltage regulation module includes a two-level multi-phase interleaved regulation module or a three-level multi-phase interleaved regulation module; And / or, the output module includes an output capacitor.

[0011] In some embodiments, the system further includes: a plurality of resonant circuits, each of which corresponds to a plurality of isolation transformers; Each resonant circuit includes a resonant inductor and a resonant capacitor. The resonant inductor is located in the circuit between the output of the inverter circuit and the isolation transformer. The resonant capacitor is located in the circuit between the output terminal of the inverter circuit and the isolation transformer, or in the circuit between the isolation transformer and the voltage regulation module.

[0012] In some embodiments, the inverter circuit includes a full-bridge inverter circuit, which includes four bridge arms connected in an H-shape. Each bridge arm includes at least one switching module. When the number of switching modules is greater than or equal to two, the switching modules are connected in series.

[0013] In some embodiments, each switching module includes a switching transistor, a fifth diode, a first voltage equalization unit, and a second voltage equalization unit; The fifth diode, the first voltage equalization unit, and the second voltage equalization unit are all connected in parallel across the two ends of the switching transistor. The conduction direction of the fifth diode is opposite to that of the switching transistor.

[0014] In some embodiments, a clamping circuit is also included, the output of which is connected to the input of the inverter circuit. The clamping circuit includes an anode reactor, a clamping diode, a clamping resistor, and a clamping capacitor. The clamping diode is connected between the anode reactor and the clamping capacitor. The series connection of the clamping diode and the anode reactor is in parallel with the clamping resistor.

[0015] This application provides a quasi-single-stage DC transformer. The first rectifier branch of the quasi-single-stage DC transformer is directly connected to the output module, and the second rectifier branch is connected to the output module through a voltage regulation module. This design balances efficiency and performance, possessing the advantages of a single-stage structure (fast response and low loss) while retaining the voltage regulation flexibility of a two-stage structure. Furthermore, the output of the regulation circuit adopts an independent output mode or at least a partially parallel output mode, meeting the requirements of different electrolyzer capacities and voltage levels. It can support power conversion for various types of electrolyzers, from medium-voltage DC to low-voltage, significantly increasing the capacity of DC hydrogen production power supplies and adapting to the application requirements of renewable energy with fluctuating and intermittent characteristics. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a DC transformer provided in an embodiment of this application; Figure 2 This is a schematic diagram of another DC transformer provided in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of another DC transformer provided in the embodiments of this application; Figure 4 This is a schematic diagram of the structure of another DC transformer provided in the embodiments of this application; Figure 5 This is a schematic diagram of the structure of another DC transformer provided in the embodiments of this application; Figure 6 This is a schematic diagram of the structure of another DC transformer provided in the embodiments of this application; Figure 7 This is a schematic diagram of another DC transformer provided in the embodiments of this application. Detailed Implementation

[0018] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0019] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0020] In the field of off-grid hydrogen production from renewable energy sources, renewable energy (such as solar and wind power) is typically converted into electricity, which is then used to produce and store clean hydrogen energy. In related technologies, photovoltaic solar panels output direct current (DC), and the electrolyzer also requires DC power. Therefore, large-scale DC aggregation of new energy sources reduces conversion stages, improves transmission efficiency, and lowers costs compared to AC aggregation. Furthermore, compared to AC hydrogen production schemes, DC hydrogen production systems offer higher power quality and better stability; faster and more reliable power regulation; and lower transmission losses, making them a more promising topology.

[0021] The increasing capacity of new energy power generation necessitates the continuous expansion of converter capacity, requiring the use of larger power units or parallel topologies of multiple low-voltage converters to meet high-power conversion requirements. While parallel structures of multiple low-voltage converters offer flexible redundancy control and effectively improve system reliability, their efficiency is significantly lower than under rated conditions at low loads, necessitating control strategies to optimize and improve the overall efficiency of the parallel system. Currently, the power output of parallel structures of multiple low-voltage converters is generally below 10MW. As power increases to above 10MW, the low DC bus voltage will lead to increased line losses and shorter transmission distances, posing challenges to improving the operating efficiency of hydrogen production systems. Therefore, the applicability of low-voltage parallel solutions requires further investigation.

[0022] Conventional hydrogen production power supplies are mostly designed and considered based on grid-connected systems, with AC power input. Hydrogen production power supplies used in off-grid DC hydrogen production for new energy applications have low input voltage levels and low capacity, making it impossible to achieve mixed access of multiple electrolyzers and failing to meet the application requirements of medium-voltage DC for large-scale off-grid hydrogen production of renewable energy in the future.

[0023] To address the aforementioned technical problems, this application provides a quasi-single-stage DC transformer, comprising: an inverter circuit, multiple isolation transformers, multiple rectifier circuits, and multiple regulating circuits connected in sequence. The input terminals of the multiple isolation transformers are connected in parallel, and each isolation transformer corresponds one-to-one with a rectifier circuit. Each rectifier circuit also corresponds one-to-one with a regulating circuit. In some embodiments, the output terminals of the regulating circuits are either independent or at least partially connected in parallel. The output terminals of the regulating circuits are connected to an electrolytic cell. Each rectifier circuit includes a first rectifier branch and a second rectifier branch. Each regulating circuit includes a voltage regulating module and an output module. The output terminal of the voltage regulating module is connected to the input terminal of the output module. The output terminal of the first rectifier branch is connected to the output module of the corresponding regulating circuit. The output terminal of the second rectifier branch is connected to the input terminal of the voltage regulating module, and the output terminal of the voltage regulating module is connected to the output module. With this configuration, the first rectifier branch of the quasi-single-stage DC transformer is directly connected to the output module, i.e., single-stage conversion. The second rectifier branch is connected to the output module through a voltage regulation module, and the output is regulated by the voltage regulation module before being sent to the output module, i.e., two-stage conversion. This configuration balances efficiency and performance, possessing the advantages of fast response and low loss of a single-stage structure while retaining the voltage regulation flexibility of a two-stage structure. At the same time, the output of the regulation circuit adopts an independent output mode or at least a partial parallel output mode, meeting the requirements of different electrolyzer capacities and voltage levels. It can support power conversion from medium-voltage DC to low-voltage various types of electrolyzers, significantly increasing the capacity of DC hydrogen production power supplies and adapting to the application requirements of renewable energy with fluctuations and intermittency.

[0024] The quasi-single-stage DC transformer coupling provided in the embodiments of this application will be described below.

[0025] like Figure 1 As shown, the quasi-single-stage DC transformer may include: an inverter circuit 1, multiple isolation transformers 2, multiple rectifier circuits 3, and multiple regulating circuits 4 connected in sequence. The input terminals of the multiple isolation transformers 2 are connected in parallel. Each isolation transformer 2 corresponds to one of the multiple rectifier circuits 3, and each rectifier circuit 3 corresponds to one of the multiple regulating circuits 4. The output terminal of the regulating circuit 4 adopts an independent output mode or at least a partially parallel output mode. The output terminal of the regulating circuit 4 is connected to the electrolytic cell. Each rectifier circuit 3 may include a first rectifier branch 31 and a second rectifier branch 32. Each regulating circuit 4 may include a voltage regulating module 41 and an output module 42. The output terminal of the voltage regulating module 41 is connected to the input terminal of the output module 42. The output terminal of the first rectifier branch 31 is connected to the output module 42 of the corresponding regulating circuit 4. The output terminal of the second rectifier branch 32 is connected to the input terminal of the voltage regulating module 41, and the output terminal of the voltage regulating module 41 is connected to the output module 42.

[0026] Inverter circuit 1 is used to realize the voltage level conversion from medium-voltage DC bus to low-voltage bus.

[0027] The isolation transformer 2 achieves electrical isolation between the primary and secondary sides through electromagnetic induction, cutting off the direct current path between them, and also functions as a voltage converter. The input terminals of multiple isolation transformers 2 are all connected to the output terminal of the inverter circuit 1, and the multiple isolation transformers 2 are connected in parallel. Different turns ratios and capacities can be used for the isolation transformers to meet the voltage levels of different electrolytic cells.

[0028] The rectifier circuit 3 is connected one-to-one with the isolation transformer 2, and is used to convert the AC voltage output by the isolation transformer 2 into DC voltage. The output terminal of the rectifier circuit 3 is connected to the input terminal of the regulating circuit 4.

[0029] The connection method of the output terminal of the regulating circuit 4 is determined by the required capacity of the electrolyzer. For example, proton exchange membrane (PEM) electrolyzers typically have lower capacity and voltage levels, below 1MW. In this case, the capacity of a single output terminal of the regulating circuit 4 is sufficient, and the output terminal of the regulating circuit 4 can be used independently, with each output terminal of the regulating circuit 4 serving as an output port connected to the PEM electrolyzer. On the other hand, for alkaline electrolyzers, where a single unit can reach 5MW or even 10MW or more, the output terminals of multiple regulating circuits 4 can be connected in parallel, with each output terminal connected to the electrolyzer through a single output port to meet the requirements of the alkaline electrolyzer.

[0030] For example, such as Figure 1 As shown, the quasi-single-stage DC transformer includes multiple regulating circuits 4. One of the regulating circuits 4 adopts an independent output mode and is used to connect to a low-capacity, low-voltage electrolytic cell (e.g., a PEM electrolytic cell). The output terminals of the remaining regulating circuits 4 adopt a parallel output mode and are used to connect to a high-capacity, high-voltage electrolytic cell (e.g., an alkaline electrolytic cell).

[0031] It should be noted that, Figure 1 This example only illustrates that one regulating circuit 4 has an independent output, while the remaining regulating circuits 4 have parallel outputs. This does not constitute a limitation on the quasi-single-stage DC transformer provided in this embodiment. In other embodiments, all regulating circuits 4 may have independent outputs, and the quasi-single-stage transformer may have multiple output ports; alternatively, all regulating circuits 4 may have their outputs connected in parallel, and the quasi-single-stage transformer may have only one output port; or, as needed, a preset number of regulating circuits 4 may be connected in parallel, which can be two, three, or more, and is not limited here.

[0032] This quasi-single-stage DC transformer, by setting the output terminal of the regulating circuit 4, can output independently or at least in parallel, meeting the requirements of different electrolyzer capacities and voltage levels. It can support power conversion of various types of electrolyzers from medium-voltage DC to low-voltage DC, avoid the manufacturing difficulties of large-capacity AC transformers, significantly increase the capacity of DC hydrogen production power supply, and adapt to the application requirements of the volatility and intermittency of renewable energy.

[0033] The output terminal of output module 42 is the same as the output terminal of adjustment circuit 4.

[0034] The output of the first rectifier branch 31 is connected to the output module 42. The first rectifier branch 31 converts the AC power output from the isolation transformer 2 into DC power and directly transmits the DC power to the output module 42, undergoing only one AC-to-DC conversion, i.e., single-stage conversion. The second rectifier branch 32 converts the AC power output from the isolation transformer 2 into DC power and transmits the DC power to the voltage regulation module 41. After voltage regulation by the voltage regulation module 41, the DC power is output to the output module 42, undergoing two conversions, i.e., two-stage conversion. This quasi-single-stage DC transformer achieves single-stage conversion through the first rectifier branch 31, which has the advantages of fast response speed and low loss. It achieves two-stage conversion through the second rectifier branch 32 and the voltage regulation module 41, which has the flexibility of voltage regulation and can adapt to a wide range of voltage loads.

[0035] As an example, the AC output of isolation transformer 2 varies periodically, with each cycle including a positive half-cycle and a negative half-cycle. The first rectifier branch 31 and the second rectifier branch 32 are activated in different cycles, for example, the first rectifier branch 31 is activated in the positive half-cycle and the second rectifier branch is activated in the negative half-cycle, or the first rectifier branch 31 is activated in the negative half-cycle and the second rectifier branch is activated in the positive half-cycle. This configuration achieves full-cycle activation of rectifier circuit 3, ensuring that the electrolytic cell connected to the output of regulating circuit 4 receives unidirectional DC power throughout the entire AC cycle, which is beneficial for improving energy utilization and output stability. Simultaneously, during the half-cycle in which the first rectifier branch 31 is activated, the energy is output after only a single-stage conversion, which helps reduce losses and improve response speed; during the half-cycle in which the second rectifier branch 32 is activated, the energy is output after two-stage conversion, resulting in a wider voltage regulation range.

[0036] This application provides a quasi-single-stage DC transformer. The first rectifier branch 31 of the quasi-single-stage DC transformer is directly connected to the output module 42, i.e., single-stage conversion. The second rectifier branch 32 is connected to the output module 42 through the voltage regulation module 41. After voltage regulation by the voltage regulation module 41, the output is sent to the output module 42, i.e., two-stage conversion. It can balance efficiency and performance, possessing the advantages of fast response and low loss of single-stage structure, while retaining the voltage regulation flexibility of two-stage structure. At the same time, the output terminal of the regulation circuit adopts an independent output mode or at least a partial parallel output mode, which meets the requirements of different electrolyzer capacities and voltage levels. It can support power conversion of various types of electrolyzers from medium-voltage DC to low-voltage, significantly improving the capacity of DC hydrogen production power supply and adapting to the application requirements of renewable energy with fluctuations and intermittency.

[0037] In some embodiments, such as Figure 2 As shown, the first rectifier branch includes a first conducting module 311 and a first returning module 312. The output terminal of the isolation transformer 2 is connected to the first conducting module 311 and the first returning module 312 respectively. The output module 42 is connected between the first conducting module 311 and the first returning module 312. The second rectifier branch includes a second conducting module 321, a second returning module 322 and a charging energy storage module 323. The output terminal of the isolation transformer 2 is connected to the second conducting module 321 and the second returning module 322 respectively. The charging energy storage module 323 is connected between the second conducting module 321 and the second returning module 322. The output terminal of the charging energy storage module 323 is connected to the input terminal of the voltage regulation module 41.

[0038] In this embodiment, the isolation transformer 2, the first conducting module 311, the output module 42, and the first return module 312 constitute a closed first loop. During the half-cycle of the first rectifier branch being turned on, the first loop is conducting, and the current flow path is: isolation transformer 2 → first conducting module 311 → output module 42 → first return module 312 → isolation transformer 2. The output terminal of the output module 42 is the output terminal of the regulating circuit 4, which can supply power to the electrolytic cell.

[0039] The isolation transformer 2, the second conducting module 321, the charging energy storage module 323, and the second return module 322 constitute a closed second circuit. During the half-cycle of the second rectifier branch being turned on, the second circuit is turned on, and the current flow path is: isolation transformer 2 → second conducting module 321 → charging energy storage module 323 → second return module 322 → isolation transformer 2; the charging energy storage module 323 provides a first voltage to the voltage regulation module 41, the voltage regulation module 41 regulates the first voltage to a second voltage, and the second voltage is output to the electrolytic cell via the output module 42.

[0040] In some embodiments, such as Figure 3As shown, the first conducting module includes a first diode 3111, the second return module includes a second diode 3121, the second conducting module includes a third diode 3211, the second return module includes a fourth diode 3221, and the charging energy storage module includes a first capacitor 3231.

[0041] In this embodiment, the isolation transformer 2, the first diode 3111, the output module 42, and the second diode 3121 form a closed first circuit. During the half-cycle when the first rectifier branch is conducting, the first circuit is active, and the current flow path is: isolation transformer 2 → first diode 3111 → output module 42 → second diode 3121 → isolation transformer 2. The output terminal of the output module 42 is the output terminal of the regulating circuit 4, which can supply power to the electrolytic cell.

[0042] The isolation transformer 2, the third diode 3211, the first capacitor 3231, and the fourth diode 3221 form a closed second circuit. During the half-cycle of the second rectifier branch being turned on, the second circuit is turned on, and the current flow path is: isolation transformer 2 → third diode 3211 → first capacitor 3231 → fourth diode 3221 → isolation transformer 2; the first capacitor 3231 provides a first voltage to the voltage regulation module 41, the voltage regulation module 41 regulates the first voltage to a second voltage, and the second voltage is output to the electrolytic cell via the output module 42.

[0043] In this embodiment, a rectifier module is constructed using four diodes and one capacitor, which has the advantages of low cost and high reliability, and does not require the setting of a control circuit.

[0044] It should be noted that at least one of the first diode 3111, the second diode 3121, the third diode 3211, and the fourth diode 3221 can be replaced with a switching transistor, which is beneficial for improving efficiency and controllability. However, this requires the inclusion of a phase detection module, a gate drive circuit, and a protection circuit, increasing cost and complexity. The switching transistor includes all types known to those skilled in the art, such as transistors, metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), and silicon-controlled thyristors (SCRs), and is not limited herein.

[0045] In some embodiments, such as Figure 4As shown, the isolation transformer 2 includes a primary winding 21; a first diode 3111 is connected between the first end 211 of the primary winding 21 and the output module 42, a second diode 3121 is connected between the second end 212 of the primary winding 21 and the output module 42; a third diode 3211 is connected between the first end 211 of the primary winding 21 and the first capacitor 3231, and a fourth diode 3221 is connected between the second end 212 of the primary winding 21 and the first capacitor 3231; the conduction direction of the first diode 3111 is opposite to the conduction direction of the third diode 3211, and the conduction direction of the second diode 3121 is opposite to the conduction direction of the fourth diode 3221.

[0046] In this embodiment, the secondary side of the isolation transformer 2 is provided with a secondary winding, namely the primary winding 21. One of the first end 211 and the second end 212 of the primary winding 21 is a terminal with the same name, and the other is an unnamed terminal.

[0047] For example, such as Figure 4As shown, the anode of the first diode 3111 is connected to the first end 211 of the first primary winding 21, and the cathode of the first diode 3111 is connected to the output module 42. The cathode of the second diode 3121 is connected to the second end 212 of the first primary winding 21, and the anode of the second diode 3121 is connected to the output module 42. The first primary winding 21, the first diode 3111, the output module 42, and the second diode 3121 form a closed first circuit. The cathode of the third diode 3211 is connected to the first end 211 of the first primary winding 21, and the anode of the third diode 3211 is connected to the first capacitor 3231. The anode of the fourth diode 3221 is connected to the second end 212 of the first primary winding 21, and the cathode of the fourth diode 3221 is connected to the first capacitor 3231. The first primary winding 21, the third diode 3211, the first capacitor 3231, and the fourth diode 3221 form a closed second circuit. The isolation transformer 2 outputs a periodically varying alternating current. During the positive half-cycle, the first diode 3111 and the second diode 3121 are turned on, while the third diode 3211 and the fourth diode 3221 are turned off, meaning the first circuit is open. Current flows from the first terminal 211 of the primary winding 21, through the first diode 3111, the output module 42, and the second diode 3121, before flowing back to the second terminal 212 of the primary winding 21. During this period, the output module 42 is charged, and the output module 42 supplies power to the electrolytic cell. During the negative half-cycle, the first and second diodes 3111 and 3121 are turned on, while the third diode 3211 and the fourth diode 3221 are turned off. When diode 3111 and second diode 3121 are turned off, and third diode 3211 and fourth diode 3221 are turned on, current flows out from the second end 212 of the first winding 21, and flows back to the first end 211 of the first winding 21 after passing through fourth diode 3221, first capacitor 3231 and third diode 3211. During this period, first capacitor 3231 stores electrical energy and outputs DC voltage to voltage regulation module 41. After voltage regulation by voltage regulation module 41, the voltage is output to output module 42, which supplies power to electrolytic cell.

[0048] The quasi-single-stage DC transformer provided in this application embodiment adopts an isolation transformer and rectifier circuit in the form of a single-input single-output winding, and the circuit structure is simple.

[0049] To improve the transmission capacity of quasi-single-stage DC transformers, in some embodiments, such as Figure 5As shown, the isolation transformer 2 includes a secondary winding 22 and a third winding 23, which share a common terminal 222. A first diode 3111 is connected between the first terminal 221 of the secondary winding 22 and the output module 42, and a second diode 3121 is connected between the common terminal 222 and the output module 42. A third diode 3211 is connected between the first terminal 231 of the third winding 23 and the first capacitor 3231, and a fourth diode 3221 is connected between the common terminal 222 and the first capacitor 3231. The conduction direction of the first diode 3111 is opposite to that of the third diode 3211, and the conduction direction of the second diode 3121 is opposite to that of the fourth diode 3221.

[0050] In this embodiment, the secondary side of the isolation transformer 2 has two secondary windings, namely the second secondary winding 22 and the third secondary winding 23. The second secondary winding 22 is connected to the third secondary winding 23, and they share a common terminal 222. The common terminal 222 can be an unnamed terminal, corresponding to the first terminal 221 of the second secondary winding 22 and the first terminal 231 of the third secondary winding 23 being the same-named terminal; the common terminal 222 can also be a terminal with the same name, corresponding to the first terminal 221 of the second secondary winding 22 and the first terminal 231 of the third secondary winding 23 being the unnamed terminal.

[0051] For example, such as Figure 5As shown, the anode of the first diode 3111 is connected to the first terminal 221 of the second winding 22, and the cathode of the first diode 3111 is connected to the output module 42. The cathode of the second diode 3121 is connected to the common terminal 222, and the anode of the second diode 3121 is connected to the output module 42. The second winding 22, the first diode 3111, the output module 42, and the second diode 3121 form a closed first circuit. The cathode of the third diode 3211 is connected to the common terminal 222, and the anode of the third diode 3211 is connected to the first capacitor 3231. The anode of the fourth diode 3221 is connected to the common terminal 222, and the cathode of the fourth diode 3221 is connected to the first capacitor 3231. The third winding 23, the third diode 3211, the first capacitor 3231, and the fourth diode 3221 form a closed second circuit. The isolation transformer 2 outputs a periodically varying alternating current. During the positive half-cycle, the first diode 3111 and the second diode 3121 are turned on, while the third diode 3211 and the fourth diode 3221 are turned off, meaning the first circuit is open. Current flows out from the first terminal 221 of the secondary winding 22, passes through the first diode 3111, the output module 42, and the second diode 3121, and then flows back to the common terminal 222. During this period, the output module 42 is charged, and the output module 42 supplies power to the electrolytic cell. During the negative half-cycle, the first diode 3111, the second diode 3121, the third diode 3121, the fourth diode 3221, and the fifth diode 3221 are turned off. When diodes 111 and 3121 are turned off, diodes 3211 and 3221 are turned on. Current flows out from the common terminal of the third winding 23, passes through diode 3221, capacitor 3231 and diode 3211 and flows back to the first terminal 231 of the third winding 23. During this period, capacitor 3231 stores electrical energy and outputs DC voltage to voltage regulation module 41. After voltage regulation by voltage regulation module 41, the voltage is output to output module 42, which supplies power to the electrolytic cell.

[0052] The quasi-single-stage DC transformer provided in this application adopts an isolation transformer 2 with a single-input dual-output winding, which can increase the capacity of the isolation transformer 2 and reduce the number of isolation converter rectifier circuits (i.e., isolation transformer 2 + rectifier circuit 3), thereby reducing costs.

[0053] In some embodiments, the voltage regulation module may include a two-level multi-phase interleaved regulation module or a three-level multi-phase interleaved regulation module.

[0054] For example, such as Figures 4-7 As shown in any figure, the voltage regulation module 41 may include a two-level multi-phase interleaved regulation module 411. The two-level multi-phase interleaved regulation module 411 includes multiple switching transistors, multiple diodes, and multiple filter reactances. The multiple switching transistors, multiple diodes, and multiple filter reactances constitute a non-isolated topology, which is connected to the output module 42.

[0055] For example, the voltage regulation module may include a three-level multi-phase interleaved regulation module. The two-level multi-phase interleaved regulation module 411 includes a flying capacitor, a filter reactor, and multiple switching transistors. The multiple flying capacitors, filter reactors, and multiple switching transistors constitute a non-isolated topology, which is connected to the output module.

[0056] In this embodiment, closed-loop control of the voltage / current of each output port is achieved by adjusting the duty cycle of the voltage regulation module 41. That is, each voltage regulation module 41 is equipped with a controller. The controller detects the output current of the voltage regulation module 41. If the output current does not reach the preset current value, the duty cycle is increased by adjusting the switching transistor to increase the output voltage of the voltage regulation module 41, thereby increasing the output current to reach the preset current value.

[0057] In some embodiments, such as Figures 4-7 As shown in any figure, the output module 42 may include an output capacitor 421.

[0058] In some embodiments, such as Figure 6 or Figure 7 As shown, the quasi-single-stage DC transformer may further include: multiple resonant circuits, each corresponding to a multiple isolation transformer 2; each resonant circuit includes a resonant inductor 51 and a resonant capacitor 52, the resonant inductor 51 being located between the output terminal of the inverter circuit 1 and the isolation transformer 2, and the resonant capacitor 52 being located between the output terminal of the inverter circuit 1 and the isolation transformer 2, or connected between the isolation transformer 2 and the voltage regulation module 41.

[0059] The resonant inductor 51 can be externally supplied (as shown in the figure) or replaced by the leakage inductance of the isolation transformer 2 itself, thereby reducing the system cost and size.

[0060] The resonant capacitor 52 can be placed on the primary side of the isolation transformer 2 or on the secondary side of the isolation transformer 2. As an example, such as... Figure 6 Or, as shown in Figure 7, the resonant capacitor 52 is located on the secondary side of the isolation transformer 2 and connected between the common terminal 222 and the fourth diode 3221.

[0061] In some embodiments, the resonant circuit further includes a magnetizing inductor 53, which is connected in parallel with the primary winding of the isolation transformer 2.

[0062] Among them, the magnetizing inductor 53 can be externally supplied, or the magnetizing inductor of the isolation transformer 2 itself can be used to reduce the system cost and size.

[0063] In some embodiments, such as Figure 6 or Figure 7As shown, the inverter circuit may include a full-bridge inverter circuit, which may include four bridge arms connected in an H-shape. Each bridge arm may include at least one switch module 11. When the number of switch modules 11 is greater than or equal to two, the switch modules 11 are connected in series.

[0064] In this embodiment, by setting multiple series-connected switch modules 11 on each bridge arm, the voltage withstand requirements of a single switch module can be reduced by having multiple switch modules share the voltage withstand, which is beneficial to reducing device cost and selection difficulty.

[0065] In some embodiments, such as Figure 5 or Figure 6 As shown, each switching module may include a switching transistor, a fifth diode, a first voltage equalization unit, and a second voltage equalization unit; the fifth diode, the first voltage equalization unit, and the second voltage equalization unit are all connected in parallel across the two ends of the switching transistor, and the conduction direction of the fifth diode is opposite to the conduction direction of the switching transistor.

[0066] The switching transistor 111 may include a gate turn-off thyristor, a high-power transistor, a power MOSFET, and an insulated-gate bipolar transistor. The types of switching transistors 111 in different switching modules 11 may be the same or different.

[0067] The fifth diode 112 is used to provide a reverse freewheeling path for the switching transistor 111.

[0068] The first voltage equalization unit may include a first resistor 1131 and a second capacitor 1132, forming a dynamic RC voltage equalization unit, which is used for dynamic voltage equalization of the switching transistor 111 during the switching dynamic process.

[0069] The second voltage equalization unit 114 may include a second resistor to form a static voltage equalization unit for static voltage equalization of the switching transistor 111.

[0070] For example, when the quasi-single-stage DC transformer is used as a hydrogen production power source, the inverter circuit is controlled to output with a duty cycle of 50% by controlling the on or off of the switch tube 111 on the corresponding bridge arm, so as to control the establishment of each voltage in multiple isolation rectifier conversion circuits (isolation transformer 2 + rectifier circuit 3), thereby realizing the voltage level conversion from medium voltage DC bus to low voltage bus.

[0071] In some embodiments, such as Figure 6 or Figure 7 As shown, the quasi-single-stage DC transformer also includes a clamping circuit, the output of which is connected to the input of the inverter circuit. The clamping circuit includes an anode reactor 61, a clamping diode 62, a clamping resistor 63, and a clamping capacitor 64. The clamping diode 62 is connected between the anode reactor 61 and the clamping capacitor 64. The series connection between the clamping diode 62 and the anode reactor 61 is connected in parallel with the clamping resistor 63.

[0072] In this embodiment, the clamping circuit is used to limit the rate of change of current when the switching transistor is turned on, and to limit the oscillation amplitude of the AC output port voltage of the inverter circuit.

[0073] Specifically, the anode reactance 61 is used to suppress the sudden current when the switch 111 is turned on and the diode is turned off, and together with the clamping diode 62, the clamping resistor 63 and the clamping capacitor 64, they form a clamping circuit to suppress the voltage spikes caused by the anode reactance 61 and the stray inductance of the circuit when the switch 111 is turned off.

[0074] For example, such as Figure 6 or Figure 7 As shown, the clamping circuit includes multiple clamping diodes 62 connected in series.

[0075] In some embodiments, the clamping circuit may further include a third capacitor 65 and a third resistor 66, both of which are connected in parallel with the clamping diode 62.

[0076] The third capacitor 65 is a dynamic voltage equalization circuit used to dynamically equalize the voltage of the clamping diode 62 during the switching process. The third resistor 66 is a static voltage equalization unit used to statically equalize the voltage of the clamping diode 62.

[0077] It should also be noted that the exemplary embodiments mentioned in this application describe methods or systems based on a series of steps or apparatus. However, this application is not limited to the order of the above steps; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0078] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific operation processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A quasi-single-stage DC transformer, characterized in that, The quasi-single-stage DC transformer includes: An inverter circuit, multiple isolation transformers, multiple rectifier circuits, and multiple regulating circuits are connected in sequence. The input terminals of the multiple isolation transformers are connected in parallel. Each of the multiple isolation transformers corresponds to one of the multiple rectifier circuits. Each of the multiple rectifier circuits corresponds to one of the multiple regulating circuits. The output terminals of the regulating circuits are either independent outputs or at least partially parallel outputs. The output terminals of the regulating circuits are connected to the electrolytic cell. Each of the rectifier circuits includes a first rectifier branch and a second rectifier branch, and each of the regulating circuits includes a voltage regulating module and an output module, wherein the output terminal of the voltage regulating module is connected to the input terminal of the output module; The output terminal of the first rectifier branch is connected to the output module of the corresponding regulating circuit. The output terminal of the second rectifier branch is connected to the input terminal of the voltage regulation module, and the output terminal of the voltage regulation module is connected to the output module.

2. The quasi-single-stage DC transformer according to claim 1, characterized in that, The first rectifier branch includes a first conducting module and a first returning module. The output terminal of the isolation transformer is connected to the first conducting module and the first returning module respectively. The output module is connected between the first conducting module and the first returning module. The second rectifier branch includes a second conduction module, a second return module, and a charging energy storage module. The output terminal of the isolation transformer is connected to the second conduction module and the second return module, respectively. The charging energy storage module is connected between the second conduction module and the second return module. The output terminal of the charging energy storage module is connected to the input terminal of the voltage regulation module.

3. The quasi-single-stage DC transformer according to claim 2, characterized in that, The first conducting module includes a first diode, the second return module includes a second diode, the second conducting module includes a third diode, the second return module includes a fourth diode, and the charging energy storage module includes a first capacitor.

4. The quasi-single-stage DC transformer according to claim 3, characterized in that, The isolation transformer includes a primary winding; The first diode is connected between the first end of the first primary winding and the output module, and the second diode is connected between the second end of the first primary winding and the output module; The third diode is connected between the first end of the first primary winding and the first capacitor, and the fourth diode is connected between the second end of the first primary winding and the first capacitor. The conduction direction of the first diode is opposite to that of the third diode, and the conduction direction of the second diode is opposite to that of the fourth diode.

5. The quasi-single-stage DC transformer according to claim 3, characterized in that, The isolation transformer includes a second-stage winding and a third-stage winding, wherein the second-stage winding and the third-stage winding share a common terminal; The first diode is connected between the first end of the second stage winding and the output module, and the second diode is connected between the common terminal and the output module; The third diode is connected between the first end of the third winding and the first capacitor, and the fourth diode is connected between the common terminal and the first capacitor; The conduction direction of the first diode is opposite to that of the third diode, and the conduction direction of the second diode is opposite to that of the fourth diode.

6. The quasi-single-stage DC transformer according to any one of claims 1-5, characterized in that, The voltage regulation module includes a two-level multi-phase interleaved regulation module or a three-level multi-phase interleaved regulation module; And / or, the output module includes an output capacitor.

7. The quasi-single-stage DC transformer according to any one of claims 1-5, characterized in that, Also includes: Multiple resonant circuits, each corresponding to one of the multiple isolation transformers; Each of the resonant circuits includes a resonant inductor and a resonant capacitor, wherein the resonant inductor is located in the circuit between the output terminal of the inverter circuit and the isolation transformer; The resonant capacitor is located in the circuit between the output terminal of the inverter circuit and the isolation transformer, or in the circuit between the isolation transformer and the voltage regulation module.

8. The quasi-single-stage DC transformer according to any one of claims 1-5, characterized in that, The inverter circuit includes a full-bridge inverter circuit, which includes four bridge arms connected in an H-shape. Each bridge arm includes at least one switching module. When the number of switching modules is greater than or equal to two, the switching modules are connected in series.

9. The quasi-single-stage DC transformer according to claim 8, characterized in that, Each switching module includes a switching transistor, a fifth diode, a first voltage equalization unit, and a second voltage equalization unit; The fifth diode, the first voltage equalization unit, and the second voltage equalization unit are all connected in parallel across the two ends of the switching transistor, and the conduction direction of the fifth diode is opposite to that of the switching transistor.

10. The quasi-single-stage DC transformer according to any one of claims 1-5, characterized in that, It also includes a clamping circuit, the output of which is connected to the input of the inverter circuit; The clamping circuit includes an anode reactor, a clamping diode, a clamping resistor, and a clamping capacitor. The clamping diode is connected between the anode reactor and the clamping capacitor, and the series connection of the clamping diode and the anode reactor is connected in parallel with the clamping resistor.

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