Multi-stage series high-voltage alternating current and direct current connection system based on direct current-direct current converter
By adopting a multi-stage series high-voltage AC-DC connection system based on DC-DC converters in large-scale fixed high-voltage AC-DC connection systems, the problems of high manufacturing costs and poor system reliability in the prior art are solved, and flexible selection of power supplies and direct incorporation of high-voltage outputs into the power grid are realized, which reduces system costs and improves reliability.
Patent Information
- Application Number
- CN202510103009.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-22
- Publication Date
- 2025-05-27
AI Technical Summary
In the existing large-scale fixed high-voltage AC-DC connection systems, multiple systems are connected in parallel and power frequency boost isolation transformers are used, resulting in high manufacturing costs, poor system reliability, and the inability to flexibly select power supplies.
A multi-stage series high-voltage AC-DC connection system based on DC-DC converters is adopted, and multiple DC-DC converters are connected one by one to multiple DC load subunits in parallel, achieving flexible selection of power supplies, and forming a high-voltage output through series superposition of power generation modules to directly merge into the power grid.
It reduces the manufacturing cost of high-voltage connection systems, improves the reliability of the system, avoids the high cost problems caused by the power frequency boost isolation transformer, and realizes flexible selection of power supplies.
Smart Images
Figure CN120049478A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of power generation equipment, and particularly relates to a multi-stage series high-voltage AC-DC connection system based on a DC-DC converter. Background Art
[0002] In large-scale fixed high-voltage AC-DC connection systems, multiple sets of systems are usually connected in parallel to achieve high-power high-voltage connection. For high-power high-voltage AC-DC grid connection systems, as Figure 1 shown, the currently adopted method is to add a power frequency step-up transformer between the inverter and the high-voltage power grid to meet the requirements of different voltage power grids. This power frequency step-up isolation transformer is mainly made of metal copper or aluminum alloy and silicon steel sheets, with a high cost and large size. When generating electricity using this method, the manufacturing cost of the system itself is relatively high.
[0003] Meanwhile, the power supply is connected to the DC-DC converter through one link to transmit current to the inverter, and the power supply cannot be flexibly selected, resulting in poor system reliability. Summary of the Invention
[0004] In view of this, an embodiment of the present application provides a multi-stage series high-voltage AC-DC connection system based on a DC-DC converter, which is convenient for reducing manufacturing costs and improving system reliability.
[0005] In a first aspect, an embodiment of the present application provides a multi-stage series high-voltage AC-DC connection system based on a DC-DC converter, including: at least two DC load sub-units and at least two DC-DC converters; the at least two DC load sub-units are connected to the at least two DC-DC converters in a one-to-one correspondence; the at least two DC-DC converters are connected in parallel to the input end of the converter; the converters in each phase power generation sub-system are connected in series in sequence; each phase power generation sub-system includes a first power generation module and a second power generation module; the first power generation module includes a first converter, and the second power generation module includes a second converter; the first converter is at one end of the link in which the converters in its own phase power generation sub-system are connected in series, and the second converter is at the other end of the link in which the converters in its own phase power generation sub-system are connected in series; the first converter in each phase power generation sub-system is used to connect to the power grid; the second converters in each phase power generation sub-systems are connected.
[0006] According to a specific implementation manner of an embodiment of the present application, each power generation module of each phase power generation sub-system further includes a third power generation module, a fourth power generation module, and a fifth power generation module; the first output end of the converter in the fourth power generation module is connected to the second output end of the converter in the third power generation module, and the second output end of the converter in the fourth power generation module is connected to the first output end of the converter in the fifth power generation module.
[0007] According to a specific implementation manner of an embodiment of the present application, it further includes a controller; on the output ends of at least one converter in at least one of the first-phase power generation subsystem, the second-phase power generation subsystem, and the third-phase power generation subsystem, a bypass circuit is connected in parallel; the bypass circuit is connected to the controller.
[0008] According to a specific implementation manner of an embodiment of the present application, the bypass circuit includes a bypass switch.
[0009] According to a specific implementation manner of an embodiment of the present application, the DC load sub-unit includes a fuel cell, an energy storage power supply, or a DC load electrolyzer.
[0010] According to a specific implementation manner of an embodiment of the present application, the converter is a bidirectional converter.
[0011] According to a specific implementation manner of an embodiment of the present application, the controller is further respectively connected to the DC-DC converter and the DC load sub-unit.
[0012] According to a specific implementation manner of an embodiment of the present application, the number of power generation modules included in each of the first-phase power generation subsystem, the second-phase power generation subsystem, and the third-phase power generation subsystem is equal.
[0013] The multi-stage series high-voltage AC-DC connection system based on a DC-DC converter provided in this embodiment includes a first-phase power generation subsystem, a second-phase power generation subsystem, and a third-phase power generation subsystem; each phase power generation subsystem includes at least two power generation modules; each power generation module includes: at least two DC load sub-units, at least two DC-DC converters; at least two DC load sub-units are connected to at least two DC-DC converters in one-to-one correspondence; at least two DC-DC converters are connected in parallel to the input end of the converter; the converters in each phase power generation subsystem are connected in series in sequence; each phase power generation subsystem includes a first power generation module and a second power generation module; the first power generation module includes a first converter, and the second power generation module includes a second converter; the first converter is at one end of the link in which the converters in its own power generation subsystem are connected in series, and the second converter is at the other end of the link in which the converters in its own power generation subsystem are connected in series; the first converter in each phase power generation subsystem is used to connect to the power grid; the second converters in each phase power generation subsystem are connected. In this way, by connecting multiple DC-DC converters in parallel to multiple DC load sub-units in one-to-one correspondence, the power supply can be flexibly selected, improving the reliability of the system; since each phase power generation subsystem includes at least two power generation modules, the converters in each power generation module are connected in series and superimposed, and then the high voltage obtained by series connection and superimposition can be directly incorporated into the power grid, which is convenient for reducing the manufacturing cost of the high-voltage connection system and avoiding the problem of high manufacturing cost caused by the three-phase circuit cascade passing through the industrial frequency step-up isolation transformer in the prior art. Description of the Drawings
[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0015] Figure 1 It is a schematic structural diagram of a multi-stage series high-voltage AC-DC connection system based on a DC-DC converter in the prior art of the present application; Figure 2 It is a schematic structural diagram of a multi-stage series high-voltage AC-DC connection system based on a DC-DC converter provided in an embodiment of the present application; Figure 3 It is a schematic structural diagram of a power generation module provided in an embodiment of the present application. Detailed Embodiments
[0016] The embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.
[0017] As mentioned in the background art, referring to Figure 1 , taking a fuel cell as an example, in a 1.5 MW fuel cell stationary power generation system with a grid-connected voltage of 10 kV, 10 sets of 150 kW fuel cell power generation units are required for this system. Each unit needs to be equipped with an isolated DC-DC converter. After the outputs of the isolated DC-DC converters are connected in parallel, they are connected to a 1.5 MW grid-connected inverter. The output of the inverter is connected to a 1.5 MW power frequency isolation transformer, and the secondary side output of the transformer is connected to the 10 kV AC grid. If larger power grid-connected power generation is to be achieved, multiple sets of the above 1.5 MW systems are connected in parallel. The power frequency step-up isolation transformer system has a high cost, and the efficiency loss affects the overall power generation system efficiency. The occupied volume is relatively large. Using this technology in the power generation system will result in a lower power generation efficiency and an increase in cost. Connecting the power source to the DC-DC converter through a single link to transmit current to the inverter cannot flexibly select the power source (such as a fuel cell, photovoltaic power generation, etc.). If the power source fails, high-power power generation cannot be achieved, and the system reliability is poor.
[0018] Based on this, the inventors found during the research process that the three-phase circuit can be directly connected to the grid without passing through a step-up transformer, and each phase of the system can be formed by connecting several energy storage converter units in series and superimposing them to form a high-voltage output. The new solution is applied to the high-voltage AC-DC connection system, which can effectively solve the existing technical problems.
[0019] To enable those skilled in the art to better understand the technical concept, implementation solution, and beneficial effects of the embodiments of the present application, the following will be described in detail through specific embodiments.
[0020] A multi-stage series high-voltage AC-DC connection system based on a DC-DC converter provided by an embodiment of the present application is convenient for reducing costs and improving the system applicability and reliability.
[0021] Figure 2 FIG. is a schematic structural diagram of a multi-stage series high-voltage AC-DC connection system based on a DC-DC converter provided by an embodiment of the present application. Figure 3 FIG. is a schematic structural diagram of a power generation module provided by an embodiment of the present application, as shown in Figure 2 and Figure 3As shown in the figure, the multi-stage series high-voltage AC-DC connection system based on a DC-DC converter in this embodiment includes: a first-phase power generation subsystem 1, a second-phase power generation subsystem 2, and a third-phase power generation subsystem 3; each phase power generation subsystem includes at least two power generation modules; each power generation module includes: at least two DC load sub-units, at least two DC-DC converters; the at least two DC load sub-units are connected to the at least two DC-DC converters in a one-to-one correspondence; the at least two DC-DC converters are connected in parallel to the input end of the converter; the converters in each phase power generation subsystem are connected in series in sequence; each phase power generation subsystem includes a first power generation module and a second power generation module; the first power generation module includes a first converter, and the second power generation module includes a second converter; the first converter is at one end of the link in which the converters in its own power generation subsystem are connected in series, and the second converter is at the other end of the link in which the converters in its own power generation subsystem are connected in series; the first converter in each phase power generation subsystem is used to connect to the power grid; the second converters in each phase power generation subsystem are connected to each other.
[0022] This embodiment is a three-phase circuit system, including a first-phase power generation subsystem 1, a second-phase power generation subsystem 2, and a third-phase power generation subsystem 3. Each phase power generation subsystem includes two or more power generation modules, and the number of power generation modules in each phase power generation subsystem can be the same or different.
[0023] Each power generation module includes a DC power generation unit and a converter. The DC power generation unit includes two or more DC load sub-units and two or more DC-DC converters. Each DC load sub-unit is connected to each DC-DC converter in a one-to-one correspondence. Among them, the DC-DC converters are connected in parallel, and the DC load sub-units can be the same or different types of power supplies. See Figure 3 In the shown embodiment, the power generation module in the first-phase power generation subsystem 1 includes a DC load sub-unit 11a and a DC-DC converter 11b. Multiple DC-DC converters are connected in parallel. The output end of the DC load sub-unit 11a is connected to the input end of the parallel-connected DC-DC converters 11b. The first voltage value output from the output end of the DC load sub-unit 11a is converted to a second voltage value through the parallel-connected DC-DC converters 11b. In some examples, the second voltage value is greater than the first voltage value. According to the type and control mode of the DC load sub-unit and the different loads, the type and parallel connection quantity of the DC-DC converters are adjusted, that is, the parallel connection quantity and type of the DC-DC converters are determined by the actual situation. The parallel-connected DC-DC converters expand the system application by connecting different DC load sub-units and are not limited to connecting one type of power supply.
[0024] The output terminals of two or more DC-DC converters connected in parallel are connected to the input terminals of the converter, as Figure 3 shown in the embodiment. The power generation module in the first-phase power generation subsystem 1 includes a DC power generation unit 11 and a converter 12. The output terminal of the DC power generation unit 11 is connected to the input terminal of the converter 12. Through the converter 12, the DC voltage output by the DC power generation unit 11 can be converted into an AC voltage. By connecting the converters of multiple power generation modules in series in sequence, multiple power generation modules are connected in series to form each phase power generation subsystem. The voltage of each phase circuit module can be adjusted according to the number of power generation modules connected in series, and it can be used for cascading of multiple voltage platforms. The voltage between adjacent two-phase power generation subsystems is determined by the grid voltage.
[0025] As can be seen from the above, each phase power generation subsystem is a series link, including the converters of multiple power generation modules and the output terminals of the converters of multiple power generation modules are connected in series. The power generation modules at both ends of the link are the first power generation module and the second power generation module respectively. The converters of the first power generation module and the second power generation module are the first converter and the second converter respectively.
[0026] See Figure 2 the embodiment shown. The first converter 12a in the first-phase power generation subsystem 1 is connected to the grid, and the second converter 12b can be connected to the second converters in other phase power generation subsystems.
[0027] Connecting each phase power generation subsystem together constitutes the multi-stage series high-voltage AC-DC connection system based on DC-DC converters of this embodiment. Among them, the first converter of each phase power generation subsystem is used to be directly connected to the high-voltage grid in the target range, and the second converters of each phase power generation subsystem are connected to each other.
[0028] The multi-stage series high-voltage AC-DC connection system based on a DC-DC converter provided in this embodiment includes a first-phase power generation subsystem, a second-phase power generation subsystem, and a third-phase power generation subsystem; each phase power generation subsystem includes at least two power generation modules; each power generation module includes: at least two DC load subunits, at least two DC-DC converters; at least two DC load subunits are connected to at least two DC-DC converters in one-to-one correspondence; at least two DC-DC converters are connected in parallel to the input end of the converter; the converters in each phase power generation subsystem are connected in series in sequence; each phase power generation subsystem includes a first power generation module and a second power generation module; the first power generation module includes a first converter, and the second power generation module includes a second converter; the first converter is at one end of the link in which the converters in its own power generation subsystem are connected in series, and the second converter is at the other end of the link in which the converters in its own power generation subsystem are connected in series; the first converter in each phase power generation subsystem is used to connect to the power grid; the second converters in each phase power generation subsystem are connected. In this way, by connecting in parallel multiple DC-DC converters in one-to-one correspondence with multiple DC load subunits, the power source can be flexibly selected, improving the reliability of the system; since each phase power generation subsystem includes at least two power generation modules, and the converters in each power generation module are connected in series and superimposed, the high voltage obtained by series connection and superposition can be directly incorporated into the power grid, facilitating the reduction of the manufacturing cost of the high-voltage connection system and avoiding the problem of high manufacturing cost caused by the three-phase circuit cascade passing through the industrial frequency step-up isolation transformer in the prior art.
[0029] The multi-stage series high-voltage AC-DC connection system based on a DC-DC converter in this embodiment can modularize the DC-DC converter and the power generation module. The parallel connection method of the DC-DC converter module allows the system to safely access both the DC load and the DC power supply without an industrial frequency step-up transformer. Each phase power generation subsystem can output different voltages by using power generation modules with different series numbers, and then the corresponding number of power generation modules can be configured according to the requirements of the power grid to improve the system applicability.
[0030] In some embodiments, each of the power generation modules in each phase power generation subsystem further includes a third power generation module, a fourth power generation module, and a fifth power generation module; the first output end of the converter in the fourth power generation module is connected to the second output end of the converter in the third power generation module, and the second output end of the converter in the fourth power generation module is connected to the first output end of the converter in the fifth power generation module.
[0031] Each phase of the power generation subsystem is a series link. When there are more than two power generation modules in each phase, the power generation modules are the third power generation module, the fourth power generation module, and the fifth power generation module. The output terminals of each power generation module are led out by two wires from the converter, and these two wires are the first output terminal and the second output terminal respectively. The connection method of the third power generation module, the fourth power generation module, and the fifth power generation module is that the first output terminal of the converter in the fourth power generation module is connected to the second output terminal of the converter in the third power generation module, and the second output terminal of the converter in the fourth power generation module is connected to the first output terminal of the converter in the fifth power generation module. Each power generation module is connected in sequence, and a high-voltage output can be formed. By using power generation modules with different series numbers, different voltage outputs can be applied, improving the applicability of the system.
[0032] In some embodiments, a controller is further included; a bypass circuit is connected in parallel to the output terminal of at least one converter in at least one of the first-phase power generation subsystem, the second-phase power generation subsystem, and the third-phase power generation subsystem; the bypass circuit is connected to the controller.
[0033] In the first-phase power generation subsystem, the second-phase power generation subsystem, and the third-phase power generation subsystem, two or more power generation subsystem circuit modules include a bypass circuit, and the output terminals of one or more converters in each phase of the power generation subsystem are connected in parallel with the bypass circuit. Since the converter circuit includes a controller for controlling the bypass circuit, the bypass circuit is connected to the controller.
[0034] In the embodiment as Figure 3 shown, the converter is a bridge circuit, and two wires are led out from the upper bridge arm as the output terminals, then the two ports of the bypass circuit are connected to the two wires.
[0035] In some embodiments, the bypass circuit includes a bypass switch.
[0036] The bypass switch can be a relay, a thyristor, or an insulated gate bipolar transistor. In the case of a converter failure or a DC power generation unit failure, the corresponding bypass switch can be closed, thereby short-circuiting the faulty power generation module and enabling other power generation modules in the same-phase power generation subsystem to operate normally.
[0037] In some embodiments, the DC load sub-unit includes a fuel cell, an energy storage power source, or a DC load electrolyzer.
[0038] In this embodiment, the DC load sub-unit includes a fuel cell, an energy storage power source, or a DC load electrolyzer connected thereto. Among them, the fuel used in the fuel cell can be hydrogen. In some examples, the energy storage power source can be a DC source such as a lithium battery or a flow battery. During operation, each DC-DC converter is connected to each DC load sub-unit in a one-to-one correspondence. Each DC-DC converter can be connected to different DC load sub-units (such as a fuel cell, an energy storage power source, or a DC load electrolyzer) respectively, or can be connected to the same DC load sub-unit respectively. Depending on different DC load sub-units, control methods, and load requirements, the DC load sub-units may work simultaneously or may not work simultaneously.
[0039] In some embodiments, the converter is a bidirectional converter.
[0040] The bidirectional converter can transmit electric power from the power grid to the energy storage system for storage, and can also reverse-transmit the electric power stored in the energy storage system to the power grid for use.
[0041] In some embodiments, the controller is also connected to the DC-DC converter and the DC load sub-unit respectively.
[0042] The DC-DC converter can boost and stabilize the voltage output by the DC load sub-unit and transmit it to the next stage. In some examples, the DC-DC converter can be isolated, non-isolated, or a combination of isolated and non-isolated, depending on specific input and output parameters and system design requirements. In this embodiment, an isolated DC-DC converter is used. The parallel DC-DC converters can be of the same type or different types, which is determined by the connected DC load sub-units. For example, if the DC load sub-unit is an energy storage power source, the DC-DC converter operates in a bidirectional dual-voltage power supply mode.
[0043] When each DC load sub-unit has the ability to generate electricity simultaneously, all converters are turned on and the converters are in the rectification mode. In a multi-stage series high-voltage AC-DC connection system based on a DC-DC converter, the DC power generation unit includes a controller, and the output end of the controller is connected to the input end of the DC-DC converter. The controller sends a control instruction to the DC-DC converter. The control instruction includes the power generation power of the DC load sub-unit system. According to the control instruction, the input current of the DC-DC converter and the turned-on converter are synchronized in real time to boost the voltage, and an amplified DC current is obtained. The converter inversely converts the DC current to obtain an AC current. According to the magnitude of the grid voltage output, the output ends of the converter modules are connected in series and directly connected in parallel to the target range high-voltage power grid. In some examples, the target range high-voltage power grid can be a 6-35 kV AC power grid.
[0044] In some embodiments, the number of power generation modules included in each of the first-phase power generation subsystem, the second-phase power generation subsystem, and the third-phase power generation subsystem is equal.
[0045] In this embodiment, each phase power generation subsystem is formed by connecting power generation modules in series. The power generation modules have the same constitution and the number of series-connected power generation modules is equal.
[0046] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.
[0047] Each embodiment in this specification is described in a related manner. For the same or similar parts among the embodiments, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments.
[0048] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims
1. A multi-stage series high voltage AC / DC connection system based on DC-DC converter, characterized in that: include: a first phase power generation subsystem, a second phase power generation subsystem, and a third phase power generation subsystem; Each phase power generation subsystem includes at least two power generation modules; each power generation module includes: at least two DC load subunits and at least two DC-DC converters; the at least two DC load subunits are connected to the at least two DC-DC converters in a one-to-one correspondence; the at least two DC-DC converters are connected in parallel to the input end of the converter; The converters in each phase power generation subsystem are connected in series in sequence; Each phase power generation subsystem includes a first power generation module and a second power generation module; the first power generation module includes a first converter, and the second power generation module includes a second converter; the first converter is located at one end of a link in which the converters of the power generation subsystem are connected in series, and the second converter is located at the other end of a link in which the converters of the power generation subsystem are connected in series; The first converter in each phase power generation subsystem is used to connect to the power grid; the second converters in each phase power generation subsystem are connected.
2. The multi-stage series high-voltage AC-DC connection system based on DC-DC converter according to claim 1 is characterized in that: Each phase power generation subsystem also includes a third power generation module, a fourth power generation module and a fifth power generation module; the first output end of the inverter in the fourth power generation module is connected to the second output end of the inverter in the third power generation module, and the second output end of the inverter in the fourth power generation module is connected to the first output end of the inverter in the fifth power generation module.
3. The multi-stage series high-voltage AC-DC connection system based on DC-DC converter according to claim 1 is characterized in that: Also comprising a controller; a bypass circuit is connected in parallel to the output end of at least one of the converters in at least one of the first phase power generation subsystem, the second phase power generation subsystem and the third phase power generation subsystem; The bypass circuit is connected to the controller.
4. The multi-stage series high-voltage AC-DC connection system based on DC-DC converter according to claim 4 is characterized in that: The bypass circuit includes a bypass switch.
5. The multi-stage series high-voltage AC-DC connection system based on DC-DC converter according to claim 2 is characterized in that: The DC load subunit includes a fuel cell, an energy storage power supply or a DC load electrolyzer.
6. The multi-stage series high-voltage AC-DC connection system based on DC-DC converter according to claim 1 is characterized in that: The converter is a bidirectional converter.
7. The multi-stage series high-voltage AC-DC connection system based on DC-DC converter according to claim 4 is characterized in that: The controller is also connected to the DC-DC converter and the DC load subunit respectively.
8. The multi-stage series high-voltage AC-DC connection system based on DC-DC converter according to claim 1, characterized in that: Each of the first phase power generation subsystem, the second phase power generation subsystem and the third phase power generation subsystem includes an equal number of power generation modules.