A hybrid new energy collection and transmission system

Abstract

This application provides a hybrid renewable energy collection and transmission system, comprising a first collection subsystem, a second collection subsystem, and a transmission subsystem. The first collection subsystem converts AC power from a wind farm into DC power and transmits it to the transmission subsystem. The second collection subsystem converts DC power from a photovoltaic power plant into DC power and transmits it to the transmission subsystem. The transmission subsystem converts the first and third DC power into a fourth DC power and transmits it. The hybrid renewable energy collection and transmission system provided by this application can take into account the technical characteristics of different renewable energy types, improve the transmission efficiency and stability of DC collection and long-distance power transmission, and reduce the cost of the hybrid renewable energy collection and transmission system, thus achieving economic efficiency.

Description

Technical Field

[0001] This application relates to the field of new energy technology, specifically to a hybrid new energy collection and transmission system. Background Technology

[0002] Line commutator-based HVDC (LCC-HVDC) technology, with its advantages of large capacity, low cost, and mature reliability, has been widely used in large-scale, long-distance power transmission. Large-scale renewable energy power plants generally use AC aggregation, multi-stage voltage boosting, and then transmit power via LCC-HVDC. However, as the scale of renewable energy transmission continues to expand in weak grid scenarios such as deserts and Gobi, LCC-HVDC exhibits technical limitations such as low aggregation efficiency, low system short-circuit capacity, poor synchronization stability, and significant transient overvoltage risks. To meet operational stability requirements, additional reactive power and inertia support devices such as synchronous condensers are needed, resulting in large equipment investment and high overall project costs.

[0003] Voltage source converters (VSCs), with their ability to independently regulate active and reactive power, support four-quadrant operation, and provide excellent grid control capabilities, have become an important technical means to enhance the grid connection capability of new energy sources. For wind farms, using VSCs for DC aggregation can provide the necessary voltage and frequency support for connected wind turbines without changing the original AC interfaces of the wind turbines, thereby improving the grid connection adaptability of wind farms under weak grid or islanded operation conditions. Photovoltaic farms, which output DC, can effectively reduce the number of energy conversion stages and improve the efficiency of the transmission system by using DC aggregation and boosting methods, while avoiding the synchronization stability constraints of AC aggregation methods.

[0004] Compared with AC aggregation technology, DC aggregation technology has significant advantages in aggregation capacity, system stability, and economy, and has gradually become an important development direction for the aggregation and transmission of isolated new energy bases. However, how to achieve efficient, stable, and economical DC aggregation and long-distance transmission while taking into account the technical characteristics of different new energy types remains a key problem that urgently needs to be solved. Summary of the Invention

[0005] This application provides a hybrid new energy collection and transmission system, which may include a first collection subsystem, a second collection subsystem, and a transmission subsystem.

[0006] The first collection subsystem is used to convert AC power from the wind farm into DC power and transmit it to the sending subsystem.

[0007] The second collection subsystem is used to convert the second DC power from the photovoltaic power station into a third DC power and transmit it to the sending subsystem.

[0008] The output subsystem is used to convert the first and third DC currents into a fourth DC current and then output it.

[0009] In some possible implementations, the first aggregation subsystem includes multiple voltage source converters. These multiple voltage source converters are connected one-to-one with multiple wind farms.

[0010] The input terminal of each voltage source converter is connected to the wind farm station, the first output terminal of each voltage source converter is connected to the first DC port of the transmission subsystem, and the second output terminal of each voltage source converter is connected to the second DC port of the transmission subsystem.

[0011] Optionally, the voltage source converter may employ a modular multilevel converter. A modular multilevel converter comprises multiple cascaded sub-modules. These sub-modules may employ a half-bridge or full-bridge structure.

[0012] In some other possible implementations, the second collection subsystem includes multiple first DC-DC converters. These multiple first DC-DC converters are connected one-to-one with multiple photovoltaic power stations.

[0013] The input terminal of each first DC converter is connected to the photovoltaic power station, the first output terminal of each first DC converter is connected to the third DC port of the transmission subsystem, and the second output terminal of each first DC converter is connected to the fourth DC port of the transmission subsystem.

[0014] For example, the first DC-DC converter includes an inverter module, a transformer module, and a rectifier module.

[0015] The input terminals of the inverter modules are all connected to the photovoltaic power station, the output terminals of the inverter modules are connected to the input terminals of the transformer modules, the output terminals of the transformer modules are connected to the input terminals of the rectifier modules, the first output terminal of the rectifier modules serves as the first output terminal of the first DC-DC converter, and the second output terminal of the rectifier modules serves as the second output terminal of the first DC-DC converter.

[0016] The inverter module uses a diode-clamped converter. The transformer module uses a three-winding isolation transformer. The rectifier module uses a twelve-pulse uncontrolled rectifier bridge structure.

[0017] Furthermore, the transformer module includes a primary winding, a first secondary winding, and a second secondary winding.

[0018] The primary winding and the first secondary winding are connected in a star configuration, while the second secondary winding is connected in a delta configuration.

[0019] In some other possible implementations, the output subsystem includes a second DC-DC converter.

[0020] The first positive input terminal of the second DC-DC converter serves as the first DC port of the transmission subsystem, the first negative input terminal serves as the second DC port of the transmission subsystem, the second positive input terminal serves as the third DC port of the transmission subsystem, and the second negative input terminal serves as the fourth DC port of the transmission subsystem. The first output terminal of the second DC-DC converter serves as the first output terminal of the hybrid new energy collection and transmission system, and the second output terminal serves as the second output terminal of the hybrid new energy collection and transmission system.

[0021] Furthermore, the second DC-DC converter includes a first low-voltage bridge arm, a second low-voltage bridge arm, a third low-voltage bridge arm, a fourth low-voltage bridge arm, a first common bridge arm, a second common bridge arm, a first high-voltage bridge arm, and a second high-voltage bridge arm.

[0022] The first end of the first low-voltage bridge arm serves as the first positive input terminal, the first end of the second low-voltage bridge arm serves as the second positive input terminal, the first end of the third low-voltage bridge arm serves as the second negative input terminal, and the first end of the fourth low-voltage bridge arm serves as the first negative input terminal.

[0023] The second end of the first low-voltage bridge arm, the second end of the second low-voltage bridge arm, the first end of the first common bridge arm, and the first end of the first high-voltage bridge arm are connected. The second ends of the third low-voltage bridge arm, the fourth low-voltage bridge arm, the second end of the second common bridge arm, and the first end of the second high-voltage bridge arm are connected. The second end of the first common bridge arm and the first end of the second common bridge arm are both connected to the ground terminal. The second end of the first high-voltage bridge arm serves as the first output terminal of the second DC-DC converter, and the second end of the second high-voltage bridge arm serves as the second output terminal of the second DC-DC converter.

[0024] Furthermore, each of the aforementioned bridge arms includes multiple cascaded sub-modules, making it suitable for high-voltage, high-capacity DC-DC conversion applications at voltage levels of hundreds of kilovolts and capacity levels of gigawatts, taking into account both technical feasibility and engineering economics.

[0025] Compared with the prior art, the beneficial effects of this application are as follows: The hybrid renewable energy collection and transmission system provided in this application includes a first collection subsystem, a second collection subsystem, and a transmission subsystem. The first collection subsystem converts AC power from wind farms into first DC power and transmits it to the transmission subsystem. The second collection subsystem converts second DC power from photovoltaic (PV) farms into third DC power and transmits it to the transmission subsystem. The transmission subsystem converts the first and third DC power into fourth DC power and transmits it. This application combines the AC collection from wind farms with the DC collection from PV farms through the first and second collection subsystems, and boosts and transmits the power through the transmission subsystem, achieving efficient collection and long-distance transmission of multiple types of renewable energy in isolated scenarios. It can be seen that the hybrid renewable energy collection and transmission system provided in this application can take into account the technical characteristics of different renewable energy types, improve the transmission efficiency and stability of DC collection and long-distance power transmission, and reduce the cost of the hybrid renewable energy collection and transmission system, thus achieving economic efficiency.

[0026] The hybrid new energy collection and transmission system provided in this application has strong collection capabilities, does not have problems with AC synchronization stability and frequency stability, and does not rely on strong grid support. It is easy to form a cluster for external transmission and can effectively solve the core problems of low inertia, low damping, and weak voltage support of long-distance new energy power stations, and realize long-distance and efficient external transmission of isolated new energy power stations.

[0027] In this application, the photovoltaic power station connected to the second collection subsystem adopts a full DC collection and boost method to realize direct collection and boosting of the DC side of the photovoltaic power station, avoid the synchronization stability problem under the AC collection method, and improve the efficiency of new energy collection and the operational stability of the hybrid new energy collection and transmission system.

[0028] In this application, the second DC converter achieves a combined voltage boost through the transformer module and the rectifier module, thereby obtaining a higher DC voltage boost ratio and further improving the operating efficiency of the hybrid new energy collection and transmission system.

[0029] The second DC converter in the transmission subsystem of this application adopts a multi-low-voltage port topology, with wind power DC and photovoltaic DC connected to different ports respectively, realizing the separate collection of new energy sources. This eliminates the need for a DC collection bus and DC circuit breakers, ensuring fault isolation between different new energy branches, improving the safety of the hybrid new energy collection and transmission system, and reducing engineering costs. Furthermore, it is applicable to high-voltage, high-capacity DC conversion applications at the 100 kV and gigawatt capacity levels, balancing technical feasibility and engineering economics. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic structural diagram of a hybrid new energy collection and transmission system in an embodiment of this application; Figure 2 This is a schematic structural diagram of a first DC-DC converter in an embodiment of this application; Figure 3 This is a schematic structural diagram of a second DC-DC converter in an embodiment of this application. Detailed Implementation

[0032] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0033] The terms "first," "second," etc., used in the specification, embodiments, claims, and drawings of this application are for distinguishing purposes only and should not be construed as indicating or implying relative importance or order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as including a series of steps or units. A method, system, product, or apparatus is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0034] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0035] This application provides a hybrid new energy collection and transmission system, such as... Figure 1As shown. The hybrid renewable energy collection and transmission system 100 can be connected to the receiving-end converter station via a DC transmission line. The hybrid renewable energy collection and transmission system 100 may include a first collection subsystem 1, a second collection subsystem 2, and a transmission subsystem 3.

[0036] The first collection subsystem 1 can be connected to multiple wind farms (including wind farms WF1 to WFn) and also to the transmission subsystem 3. The second collection subsystem 2 can be connected to multiple photovoltaic farms (including photovoltaic farms PV1 to PVm) and also to the transmission subsystem 3.

[0037] The first collection subsystem 1 is used to convert the AC power from the wind farm into a first DC power and transmit it to the sending subsystem 3.

[0038] The second collection subsystem 2 is used to convert the second DC power from the photovoltaic power station into a third DC power and transmit it to the sending subsystem 3.

[0039] The transmitting subsystem 3 is used to convert the first DC power and the third DC power into a fourth DC power and transmit it.

[0040] In one possible implementation, such as Figure 1 As shown, the first aggregation subsystem 1 may include multiple voltage source converters (i.e., multiple VSCs, which may include VSC1 to VSCn). The multiple voltage source converters are connected to multiple wind farms in a one-to-one correspondence.

[0041] like Figure 1 As shown, the input terminal of each voltage source converter is connected to the wind farm station, and the first output terminal DC11 of each voltage source converter is connected to the first DC port P1 of the transmission subsystem 3 (which serves as the first positive input terminal, i.e., ...). Figure 3 The DC1+ of each voltage source converter is connected to the second DC port P2 of the output subsystem 3 (which serves as the first negative input terminal, i.e., ...). Figure 3 Connect DC1- in the middle.

[0042] Optionally, the voltage source converter can be a modular multilevel converter, etc. A modular multilevel converter consists of multiple cascaded sub-modules. The sub-modules adopt a half-bridge or full-bridge structure.

[0043] In this embodiment, the voltage source converter can realize the DC collection of the AC output of the wind farm. At the same time, the voltage source converter has grid control capability and provides voltage and frequency support for the wind farm under islanded operation conditions.

[0044] In some other possible implementations, the second collection subsystem 2 includes multiple first DC-DC converters (which may include DC / DC11 to DC / DC1m). The multiple first DC-DC converters are connected one-to-one with multiple photovoltaic power stations.

[0045] refer to Figure 1 The input terminal of each first DC converter is connected to the photovoltaic power station, and the first output terminal DC21 of each first DC converter is connected to the third DC port P3 of the transmission subsystem 3 (as the second positive input terminal, i.e. Figure 3 The DC2+ of the first DC converter is connected to the fourth DC port P4 of the output subsystem 3 (which serves as the second negative input terminal, i.e., ...). Figure 3 The DC2-) connection is in the middle.

[0046] For example, such as Figure 2 As shown, the first DC-DC converter (taking DC / DC11 as an example) includes an inverter module 21, a transformer module 22, and a rectifier module 23.

[0047] The input terminals (IN+ and IN-) of the inverter module 21 are both connected to the photovoltaic power station. The output terminal of the inverter module 21 is connected to the input terminal of the transformer module 22. The output terminal of the transformer module 22 is connected to the input terminal of the rectifier module 23. The first output terminal of the rectifier module 23 serves as the first output terminal OUT+ of the first DC-DC converter DC / DC11, and the second output terminal of the rectifier module 23 serves as the second output terminal OUT- of the first DC-DC converter DC / DC11.

[0048] Inverter module 21 can employ a diode-clamped converter, etc. Transformer module 22 employs a three-winding isolation transformer, etc. Rectifier module 23 employs a twelve-pulse uncontrolled rectifier bridge structure, etc.

[0049] In this embodiment, the inverter module 21 can be called a low-voltage side three-level intermediate frequency inverter. The transformer module 22 can be called a three-winding intermediate frequency transformer. The rectifier module 23 can be called a high-voltage side twelve-pulse uncontrolled rectifier bridge structure. This can meet the high step-up ratio requirement while significantly reducing the number of fully controlled power devices used, thus improving the system's economy and reliability.

[0050] Furthermore, such as Figure 2 As shown, the transformer module 22 includes a primary winding 221, a first secondary winding 222, and a second secondary winding 223.

[0051] The primary winding 221 and the first secondary winding 222 are connected in a star configuration, while the second secondary winding 223 is connected in a delta configuration.

[0052] Of course, the transformer module 22 can also adopt other structures, which are not limited in this application embodiment.

[0053] In some other possible implementations, the output subsystem 3 includes a second DC-DC converter (i.e., DC / DC2).

[0054] The first positive input terminal DC1+ of the second DC-DC converter DC / DC2 serves as the first DC port P1 of the output subsystem 3; the first negative input terminal DC1- of the second DC-DC converter DC / DC2 serves as the second DC port P2 of the output subsystem 3; the second positive input terminal DC2+ of the second DC-DC converter DC / DC2 serves as the third DC port P3 of the output subsystem 3; and the second negative input terminal DC2- of the second DC-DC converter DC / DC2 serves as the fourth DC port P4 of the output subsystem 3. The first output terminal DC3+ of the second DC-DC converter DC / DC2 serves as the first output terminal of the hybrid new energy collection and transmission system 100; and the second output terminal DC3- of the second DC-DC converter DC / DC2 serves as the second output terminal of the hybrid new energy collection and transmission system 100.

[0055] Furthermore, such as Figure 3 The second DC / DC converter includes a first low-voltage bridge arm, a second low-voltage bridge arm, a third low-voltage bridge arm, a fourth low-voltage bridge arm, a first common bridge arm, a second common bridge arm, a first high-voltage bridge arm, and a second high-voltage bridge arm.

[0056] The first end of the first low-voltage bridge arm serves as the first positive input terminal DC1+, the first end of the second low-voltage bridge arm serves as the second positive input terminal DC2+, the first end of the third low-voltage bridge arm serves as the second negative input terminal DC2-, and the first end of the fourth low-voltage bridge arm serves as the first negative input terminal DC1-.

[0057] The second end of the first low-voltage bridge arm, the second end of the second low-voltage bridge arm, the first end of the first common bridge arm, and the first end of the first high-voltage bridge arm are connected. The second end of the third low-voltage bridge arm, the second end of the fourth low-voltage bridge arm, the second end of the second common bridge arm, and the first end of the second high-voltage bridge arm are connected. The second end of the first common bridge arm and the first end of the second common bridge arm are both connected to the ground terminal. The second end of the first high-voltage bridge arm serves as the first output terminal DC3+ of the second DC / DC converter, and the second end of the second high-voltage bridge arm serves as the second output terminal DC3- of the second DC / DC converter.

[0058] Of course, the second DC converter, in addition to using Figure 3 The structure shown can be adapted to other structures, and this application does not limit the specific embodiments. In this application embodiment, the second DC converter can be a high-voltage, high-capacity DC transformer.

[0059] The hybrid renewable energy collection and transmission system provided in this application combines the AC collection of wind farms with the DC collection of photovoltaic farms, and uses a high-voltage, high-capacity DC transformer to boost and transmit the voltage, thereby achieving efficient collection and long-distance transmission of multiple types of renewable energy in isolated scenarios.

[0060] The above are merely embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application shall be included within the scope of the claims of this application pending approval.

Claims

1. A hybrid new energy collection and transmission system, characterized in that, It includes a first collection subsystem, a second collection subsystem, and an output subsystem; The first collection subsystem is used to: convert AC power from the wind farm into DC power and transmit it to the sending subsystem; The second collection subsystem is used to: convert the second direct current from the photovoltaic power station into a third direct current and transmit it to the sending subsystem; The output subsystem is used to convert the first DC power and the third DC power into a fourth DC power and output it.

2. The hybrid new energy collection and transmission system according to claim 1, characterized in that, The first aggregation subsystem includes multiple voltage source converters; each of the multiple voltage source converters is connected to a corresponding wind farm station. The input terminal of each voltage source converter is connected to the wind farm, the first output terminal of each voltage source converter is connected to the first DC port of the transmission subsystem, and the second output terminal of each voltage source converter is connected to the second DC port of the transmission subsystem.

3. The hybrid new energy collection and transmission system according to claim 2, characterized in that, The voltage source converter adopts a modular multilevel converter.

4. The hybrid new energy collection and transmission system according to claim 1, characterized in that, The second collection subsystem includes multiple first DC converters; each of the multiple first DC converters is connected to a corresponding photovoltaic power station. The input terminal of each first DC converter is connected to the photovoltaic power station, the first output terminal of each first DC converter is connected to the third DC port of the transmission subsystem, and the second output terminal of each first DC converter is connected to the fourth DC port of the transmission subsystem.

5. The hybrid new energy collection and transmission system according to claim 4, characterized in that, The first DC-DC converter includes an inverter module, a transformer module, and a rectifier module; The input terminals of the inverter modules are all connected to the photovoltaic power station, the output terminals of the inverter modules are connected to the input terminals of the transformer modules, the output terminals of the transformer modules are connected to the input terminals of the rectifier modules, the first output terminal of the rectifier modules serves as the first output terminal of the first DC-DC converter, and the second output terminal of the rectifier modules serves as the second output terminal of the first DC-DC converter.

6. The hybrid new energy collection and transmission system according to claim 5, characterized in that, The inverter module uses a diode-clamped converter. The transformer module uses a three-winding isolation transformer; The rectifier module adopts a twelve-pulse uncontrolled rectifier bridge structure.

7. The hybrid new energy collection and transmission system according to claim 6, characterized in that, The transformer module includes a primary winding, a first secondary winding, and a second secondary winding; The primary winding and the first secondary winding are connected in a star configuration, while the second secondary winding is connected in a delta configuration.

8. The hybrid new energy collection and transmission system according to claim 1, characterized in that, The output subsystem includes a second DC-DC converter; The first positive input terminal of the second DC-DC converter serves as the first DC port of the transmission subsystem, the first negative input terminal of the second DC-DC converter serves as the second DC port of the transmission subsystem, the second positive input terminal of the second DC-DC converter serves as the third DC port of the transmission subsystem, and the second negative input terminal of the second DC-DC converter serves as the fourth DC port of the transmission subsystem; the first output terminal of the second DC-DC converter serves as the first output terminal of the hybrid new energy collection and transmission system, and the second output terminal of the second DC-DC converter serves as the second output terminal of the hybrid new energy collection and transmission system.

9. The hybrid new energy collection and transmission system according to claim 8, characterized in that, The second DC-DC converter includes a first low-voltage bridge arm, a second low-voltage bridge arm, a third low-voltage bridge arm, a fourth low-voltage bridge arm, a first common bridge arm, a second common bridge arm, a first high-voltage bridge arm, and a second high-voltage bridge arm. The first end of the first low-voltage bridge arm serves as the first positive input terminal, the first end of the second low-voltage bridge arm serves as the second positive input terminal, the first end of the third low-voltage bridge arm serves as the second negative input terminal, and the first end of the fourth low-voltage bridge arm serves as the first negative input terminal. The second end of the first low-voltage bridge arm, the second end of the second low-voltage bridge arm, the first end of the first common bridge arm, and the first end of the first high-voltage bridge arm are connected; the second end of the third low-voltage bridge arm, the second end of the fourth low-voltage bridge arm, the second end of the second common bridge arm, and the first end of the second high-voltage bridge arm are connected; the second end of the first common bridge arm and the first end of the second common bridge arm are both connected to the ground terminal; the second end of the first high-voltage bridge arm serves as the first output terminal of the second DC-DC converter, and the second end of the second high-voltage bridge arm serves as the second output terminal of the second DC-DC converter.

10. The hybrid new energy collection and transmission system according to claim 3, characterized in that, The modular multilevel converter includes multiple cascaded sub-modules; The submodule adopts a half-bridge structure or a full-bridge structure.

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