A medium and low voltage two-stage direct current ring network system

Abstract

The application provides a kind of middle-low voltage two-stage direct current ring network system, comprising: middle voltage direct current ring network system, the middle voltage direct current ring network system includes middle voltage AC / DC converter, middle voltage AC bus and middle voltage AC power equipment;Wherein, the middle voltage AC / DC converter is connected with the middle voltage AC bus, and the middle voltage AC bus is connected with middle voltage AC power equipment;Low voltage direct current ring network system, the low voltage direct current ring network system includes low voltage AC / DC converter, low voltage AC bus and low voltage distribution equipment;Wherein, the low voltage AC / DC converter is connected with the low voltage AC bus, and the low voltage AC bus is connected with low voltage distribution equipment;Direct current ring network contact system, the direct current ring network contact system is connected with the middle voltage direct current ring network system and the low voltage direct current ring network system respectively.The application solves the technical problems of narrow power allocation range and poor reliability in the prior art.

Description

Technical Field

[0001] This invention relates to the field of power distribution technology, and in particular to a medium- and low-voltage two-stage DC ring network system. Background Technology

[0002] DC distribution grids are one of the important directions for the future development of distribution grids due to their advantages such as flexible power allocation, high system efficiency, large power supply capacity, low line loss and good power quality, as well as their suitability for flexible access to distributed new energy sources, energy storage devices and DC loads.

[0003] However, the existing DC distribution network has many problems, such as rapid growth and high load density in regional distribution loads, uneven distribution of regional loads, long-term heavy and light loads on feeders / transformers, high requirements for the power flow regulation capability of the distribution network by distributed new energy sources, and high requirements for the reliability of power supply by sensitive loads.

[0004] Therefore, overcoming the technical problems of narrow power distribution range and poor reliability of existing DC power distribution networks is an urgent issue to be addressed. Summary of the Invention

[0005] This invention provides a medium- and low-voltage two-stage DC ring network system to at least partially solve the technical problems of narrow power distribution range and poor reliability in the prior art.

[0006] To address the aforementioned technical problems, the present invention provides the following technical solution:

[0007] A medium-low voltage two-stage DC ring network system includes:

[0008] A medium-voltage DC ring network system, comprising a medium-voltage AC / DC converter, a medium-voltage AC bus, and medium-voltage AC transformer equipment; wherein the medium-voltage AC / DC converter is connected to the medium-voltage AC bus, and the medium-voltage AC bus is connected to the medium-voltage AC transformer equipment;

[0009] A low-voltage DC ring network system, comprising a low-voltage AC / DC converter, a low-voltage AC bus, and low-voltage power distribution equipment; wherein the low-voltage AC / DC converter is connected to the low-voltage AC bus, and the low-voltage AC bus is connected to the low-voltage power distribution equipment.

[0010] A DC ring network interconnection system is connected to both the medium-voltage DC ring network system and the low-voltage DC ring network system.

[0011] In some embodiments, there are multiple medium-voltage AC / DC converters and multiple medium-voltage AC buses;

[0012] The output terminals of the multiple medium-voltage AC / DC converters are interconnected;

[0013] The input terminals of the multiple medium-voltage AC / DC converters are connected one-to-one with the output terminals of the multiple medium-voltage AC buses, and the input terminals of the multiple medium-voltage AC buses are connected one-to-one with the multiple medium-voltage AC power equipment.

[0014] In some embodiments, the medium-voltage AC / DC converter includes a first medium-voltage AC / DC converter, a second medium-voltage AC / DC converter, and a third medium-voltage AC / DC converter;

[0015] The medium-voltage AC busbar includes a first medium-voltage AC busbar, a second medium-voltage AC busbar, and a third medium-voltage AC busbar;

[0016] The output terminals of any two of the first medium-voltage AC / DC converter, the second medium-voltage AC / DC converter, and the third medium-voltage AC / DC converter are interconnected.

[0017] The input terminal of the first medium-voltage AC / DC converter is connected to the output terminal of the first medium-voltage AC bus, and the input terminal of the first medium-voltage AC bus is connected to the first medium-voltage AC transformer.

[0018] The input terminal of the second medium-voltage AC / DC converter is connected to the output terminal of the second medium-voltage AC bus, and the input terminal of the second medium-voltage AC bus is connected to the second medium-voltage AC transformer.

[0019] The input terminal of the third medium-voltage AC / DC converter is connected to the output terminal of the third medium-voltage AC bus, and the input terminal of the third medium-voltage AC bus is connected to the third medium-voltage AC substation.

[0020] In some embodiments, the outputs of the plurality of medium-voltage AC / DC converters are connected via a first medium-voltage DC bus.

[0021] In some embodiments, a DC circuit breaker is configured on the first medium-voltage DC bus.

[0022] In some embodiments, there are multiple low-voltage AC / DC converters and multiple low-voltage AC buses;

[0023] The outputs of the multiple low-voltage AC / DC converters are interconnected;

[0024] The input terminals of the multiple low-voltage AC / DC converters and the output terminals of the multiple low-voltage AC buses are connected one-to-one, and the input terminals of the multiple low-voltage AC buses are connected one-to-one with the multiple low-voltage power distribution equipment.

[0025] In some embodiments, the low-voltage AC / DC converter includes a first low-voltage AC / DC converter, a second low-voltage AC / DC converter, a third low-voltage AC / DC converter, and a fourth low-voltage AC / DC converter.

[0026] The low-voltage AC busbar includes a first low-voltage AC busbar, a second low-voltage AC busbar, a third low-voltage AC busbar, and a fourth low-voltage AC busbar.

[0027] The output terminals of any two of the first, second, third, and fourth low-voltage AC / DC converters are interconnected.

[0028] The input terminal of the first low-voltage AC / DC converter is connected to the output terminal of the first low-voltage AC bus, and the input terminal of the first low-voltage AC bus is connected to the first low-voltage power distribution equipment.

[0029] The input terminal of the second low-voltage AC / DC converter is connected to the output terminal of the second low-voltage AC bus, and the input terminal of the second low-voltage AC bus is connected to the second low-voltage power distribution equipment.

[0030] The input terminal of the third low-voltage AC / DC converter is connected to the output terminal of the third low-voltage AC bus, and the input terminal of the third low-voltage AC bus is connected to the third low-voltage power distribution equipment.

[0031] The input terminal of the fourth low-voltage AC / DC converter is connected to the output terminal of the fourth low-voltage AC bus, and the input terminal of the fourth low-voltage AC bus is connected to the fourth low-voltage power distribution equipment.

[0032] In some embodiments, the outputs of the plurality of low-voltage AC / DC converters are connected via a first low-voltage DC bus.

[0033] In some embodiments, a DC circuit breaker is configured on the first low-voltage DC bus.

[0034] In some embodiments, the DC ring network interconnection system includes a DC transformer;

[0035] The medium-voltage side of the DC transformer is connected to the medium-voltage DC ring network system, and the low-voltage side of the DC transformer is connected to the low-voltage DC ring network system.

[0036] In some embodiments, the DC ring network interconnection system further includes a second medium-voltage DC bus;

[0037] The medium-voltage side of the DC transformer is connected to the second medium-voltage DC bus, and the second medium-voltage DC bus is connected to the medium-voltage DC ring network system.

[0038] In some embodiments, a DC circuit breaker is configured on the second medium-voltage DC bus.

[0039] In some embodiments, the DC ring network interconnection system further includes a second low-voltage DC bus;

[0040] The low-voltage side of the DC transformer is connected to the second low-voltage DC bus, and the second low-voltage DC bus is connected to the low-voltage DC ring network system.

[0041] In some embodiments, a DC circuit breaker is configured on the second low-voltage DC bus.

[0042] In some embodiments, the DC ring network interconnection system further includes a third low-voltage DC bus, and the second low-voltage DC bus is connected to distributed new energy sources, distributed energy storage, and new DC loads respectively through the third low-voltage DC bus and a DC transformer.

[0043] In some embodiments, the distributed new energy source includes photovoltaics; and / or, the distributed energy storage includes energy storage batteries; and / or, the novel DC load includes charging piles.

[0044] This invention provides a medium- and low-voltage dual-stage DC ring network system, comprising a medium-voltage DC ring network system, a low-voltage DC ring network system, and a DC ring network interconnection system, which is connected to both the medium-voltage and low-voltage DC ring network systems. By constructing the medium-voltage DC ring network system, asynchronous loop operation of AC feeders is achieved, improving the reliability of the distribution network, adjusting load balancing between feeders, and providing distributed renewable energy AC / DC access and control capabilities. By constructing the low-voltage DC ring network system, flexible access to high-proportion distributed renewable energy, high-proportion distributed energy storage, and new DC loads can be supported. It offers advantages such as a wider power distribution range, higher reliability, stronger scalability, and more flexible control. The DC ring network interconnection system enables power exchange between the medium-voltage and low-voltage DC ring network systems, power exchange between medium-voltage AC transformers, and power exchange between low-voltage distribution equipment. This solves the technical problems of narrow power distribution range and poor reliability in existing technologies. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in this invention 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 invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0046] Figure 1 The diagram shows the topology of a medium- and low-voltage dual-stage DC ring network system provided in an embodiment of the present invention.

[0047] Explanation of reference numerals in the attached figures:

[0048] 11-First medium-voltage AC / DC converter, 12-Second medium-voltage AC / DC converter, 13-Third medium-voltage AC / DC converter;

[0049] 21-First medium-voltage AC busbar, 22-Second medium-voltage AC busbar, 23-Third medium-voltage AC busbar;

[0050] 31-First low-voltage AC / DC converter, 32-Second low-voltage AC / DC converter, 33-Third low-voltage AC / DC converter, 34-Fourth low-voltage AC / DC converter;

[0051] 41-First low-voltage AC busbar, 42-Second low-voltage AC busbar, 43-Third low-voltage AC busbar, 44-Fourth low-voltage AC busbar;

[0052] 51-First low-voltage DC bus, 52-Second low-voltage DC bus, 53-Third low-voltage DC bus;

[0053] 61 - First medium-voltage DC bus, 62 - Second medium-voltage DC bus;

[0054] 71-First DC / DC transformer, 72-Second DC / DC transformer, 73-Third DC / DC transformer, 74-Fourth DC / DC transformer. Detailed Implementation

[0055] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] In this document, the terms "first," "second," and other similar words are not intended to imply any order, quantity, or importance, but are merely used to distinguish different elements. The terms "one," "a," and other similar words are not intended to indicate the existence of only one of the stated things, but rather that the description refers only to one of the stated things, which may have one or more. The terms "comprising," "including," and other similar words are intended to indicate a logical relationship, not a spatial relationship. For example, "A includes B" means that logically B belongs to A, not that spatially B is located inside A. Furthermore, the meanings of the terms "comprising," "including," and other similar words should be considered open-ended, not closed. For example, "A includes B" means that B belongs to A, but B does not necessarily constitute all of A; A may also include other elements such as C, D, and E.

[0057] In this document, the terms "embodiment," "this embodiment," "preferred embodiment," and "one embodiment" do not imply that the description applies only to one specific embodiment, but rather that such description may also be applicable to one or more other embodiments. Those skilled in the art will understand that any description made herein with respect to one embodiment can be substituted, combined, or otherwise incorporated with the descriptions in one or more other embodiments. Such substitutions, combinations, or other incorporations resulting in new embodiments are readily conceived by those skilled in the art and fall within the scope of protection of this invention.

[0058] In this description, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0059] In one specific embodiment, the medium- and low-voltage dual-stage DC ring network system provided by the present invention includes a medium-voltage DC ring network system, a low-voltage DC ring network system, and a DC ring network interconnection system, wherein the DC ring network interconnection system is connected to the medium-voltage DC ring network system and the low-voltage DC ring network system. The medium-voltage DC ring network system includes a medium-voltage AC / DC converter, a medium-voltage AC bus, and medium-voltage AC transformer equipment; wherein the medium-voltage AC / DC converter is connected to the medium-voltage AC bus, and the medium-voltage AC bus is connected to the medium-voltage AC transformer equipment. The low-voltage DC ring network system includes a low-voltage AC / DC converter, a low-voltage AC bus, and low-voltage distribution equipment; wherein the low-voltage AC / DC converter is connected to the low-voltage AC bus, and the low-voltage AC bus is connected to the low-voltage distribution equipment.

[0060] In this way, by constructing a medium-voltage DC ring network system, asynchronous loop operation of AC feeders is achieved, improving the reliability of power distribution network supply, regulating load balance between feeders, and providing distributed new energy AC / DC access and control capabilities. By constructing a low-voltage DC ring network system, flexible access to high-proportion distributed new energy sources, high-proportion distributed energy storage, and new DC loads can be supported. It has advantages such as a wider power distribution range, higher reliability, stronger scalability, and more flexible control. The DC ring network interconnection system realizes power exchange between the medium-voltage and low-voltage DC ring network systems, power exchange between medium-voltage AC transformers, and power exchange between low-voltage distribution equipment. This solves the technical problems of narrow power distribution range and poor reliability in existing technologies.

[0061] Please refer to Figure 1 , Figure 1 The diagram shows the topology of a medium- and low-voltage dual-stage DC ring network system provided in an embodiment of the present invention.

[0062] like Figure 1 As shown, one embodiment of the present invention provides a medium- and low-voltage two-stage DC ring network system, including a medium-voltage DC ring network system. The medium-voltage DC ring network system includes a medium-voltage AC / DC converter, a medium-voltage AC bus, and medium-voltage AC transformer equipment. The medium-voltage AC / DC converter is connected to the medium-voltage AC bus, and the medium-voltage AC bus is connected to the medium-voltage AC transformer equipment.

[0063] Specifically, multiple medium-voltage AC / DC converters and multiple medium-voltage AC buses are used. The outputs of the multiple medium-voltage AC / DC converters are interconnected, the inputs of the multiple medium-voltage AC / DC converters are connected one-to-one with the outputs of the multiple medium-voltage AC buses, and the inputs of the multiple medium-voltage AC buses are connected one-to-one with the multiple medium-voltage AC power transmission devices.

[0064] Multiple medium-voltage AC / DC converters and multiple medium-voltage AC buses are used to interconnect multiple medium-voltage power equipment. There are no specific requirements for the selection of the medium-voltage AC / DC converters, as long as they can interconnect with the medium-voltage AC buses. In this embodiment, voltage source type AC / DC converters are preferred. The voltage level of the medium-voltage AC bus can be set by those skilled in the art according to actual needs; preferably, the voltage level of the medium-voltage AC bus is 10kV. Medium-voltage AC power equipment includes, but is not limited to, medium-voltage AC substations and medium-voltage AC transformers.

[0065] In this embodiment, the output terminals of multiple medium-voltage AC / DC converters are connected through a first medium-voltage DC bus 61, and the voltage level of the medium-voltage DC bus can be selected as ±5kV, ±10kV, etc.

[0066] Furthermore, in order to provide fault protection for the first medium-voltage DC bus 61, in some embodiments, a DC circuit breaker may be configured on the first medium-voltage DC bus 61.

[0067] The above-mentioned construction of a medium-voltage DC ring network system can realize asynchronous closed-loop operation of AC feeders, improve the reliability of power supply in the distribution network, adjust the load balance between feeders, and provide distributed new energy AC / DC access and control capabilities.

[0068] As a preferred embodiment, the medium-low voltage dual-stage DC ring network system provided by the present invention further includes a low-voltage DC ring network system. The low-voltage DC ring network system includes a low-voltage AC / DC converter, a low-voltage AC bus, and low-voltage power distribution equipment. The low-voltage AC / DC converter is connected to the low-voltage AC bus, and the low-voltage AC bus is connected to the low-voltage power distribution equipment.

[0069] Specifically, multiple low-voltage AC / DC converters and multiple low-voltage AC buses are used. The output terminals of the multiple low-voltage AC / DC converters are interconnected, the input terminals of the multiple low-voltage AC / DC converters are connected to the output terminals of the multiple low-voltage AC buses in a one-to-one correspondence, and the input terminals of the multiple low-voltage AC buses are connected to multiple low-voltage power distribution equipment in a one-to-one correspondence.

[0070] Multiple low-voltage power distribution devices are interconnected by employing multiple low-voltage AC / DC converters and multiple low-voltage AC buses. There are no specific requirements for the selection of the low-voltage AC / DC converters, as long as they can interconnect with the low-voltage AC buses. In this embodiment, voltage source type AC / DC converters are preferred. The voltage level of the low-voltage AC bus can be set by those skilled in the art according to actual needs; preferably, the voltage level of the low-voltage AC bus is 380V. The low-voltage power distribution devices include, but are not limited to, low-voltage distribution substations.

[0071] In this embodiment, the output terminals of multiple low-voltage AC / DC converters are connected through a first low-voltage DC bus 51. The low-voltage DC bus can be selected with voltage levels of ±375V, ±750V, ±1500V, etc.

[0072] Furthermore, in order to provide fault protection for the first low-voltage DC bus 51, in this embodiment, a DC circuit breaker is configured on the first low-voltage DC bus 51.

[0073] The aforementioned low-voltage DC ring network system can support flexible access for high-proportion distributed renewable energy sources (such as photovoltaics), high-proportion distributed energy storage (such as energy storage batteries), and new DC loads (such as charging piles). It offers advantages such as a wider power distribution range, higher reliability, stronger scalability, and more flexible control.

[0074] Furthermore, as a preferred embodiment, the medium- and low-voltage dual-stage DC ring network system of the present invention also includes a DC ring network interconnection system. The DC ring network interconnection system includes a DC transformer, the medium-voltage side of which is connected to the aforementioned medium-voltage DC ring network system, and the low-voltage side of which is connected to the aforementioned low-voltage DC ring network system.

[0075] Specifically, to connect the medium-voltage side of the DC transformer to the aforementioned medium-voltage DC ring network system, and the low-voltage side of the DC transformer to the aforementioned low-voltage DC ring network system, the DC ring network interconnection system also includes a second medium-voltage DC bus 62 and a second low-voltage DC bus 52. The medium-voltage side of the DC transformer is connected to the input terminal of the second medium-voltage DC bus 62, and the output terminal of the second medium-voltage DC bus 62 is connected to the aforementioned medium-voltage DC ring network system, specifically, the output terminal of the second medium-voltage DC bus 62 is connected to the first medium-voltage DC bus 61 of the aforementioned medium-voltage DC ring network system. The low-voltage side of the DC transformer is connected to the input terminal of the second low-voltage DC bus 52, and the output terminal of the second low-voltage DC bus 52 is connected to the aforementioned low-voltage DC ring network system, specifically, the output terminal of the second low-voltage DC bus 52 is connected to the first low-voltage DC bus 51 of the aforementioned low-voltage DC ring network system.

[0076] In order to provide fault protection for the second medium-voltage DC bus 62 and the second low-voltage DC bus 52, in this embodiment, a DC circuit breaker is configured on the second medium-voltage DC bus 62 and a DC circuit breaker is configured on the second low-voltage DC bus 52.

[0077] Similarly, there are no specific requirements for the selection of the DC transformer mentioned above, as long as it can be connected to the low-voltage DC ring network system and the medium-voltage DC ring network system. In this embodiment, a DC / DC DC transformer is preferred.

[0078] Furthermore, the low-voltage DC bus in this embodiment is also used to connect to distributed renewable energy sources, distributed energy storage, and novel DC loads. Distributed renewable energy sources include, but are not limited to, photovoltaics; distributed energy storage includes, but is not limited to, energy storage batteries; and novel DC loads include, but are not limited to, charging piles.

[0079] A low-voltage DC microgrid system is formed by connecting distributed new energy sources, distributed energy storage, and new DC loads to the low-voltage side of the DC transformer via a low-voltage DC bus.

[0080] The aforementioned DC ring network interconnection system enables power exchange between the medium-voltage DC ring network system and the low-voltage DC ring network system, power exchange between medium-voltage AC power equipment, and power exchange between low-voltage power distribution equipment.

[0081] The following section provides a detailed supplementary explanation of the medium- and low-voltage two-stage DC ring network system, taking it as an example. The system includes a medium-voltage DC ring network system, a low-voltage DC ring network system, and a DC ring network interconnection system. Specifically... Figure 1 As shown, the medium- and low-voltage dual-stage DC ring network system includes a medium-voltage DC ring network system, a low-voltage DC ring network system, and a DC ring network interconnection system.

[0082] The medium-voltage DC ring network system includes a medium-voltage AC / DC converter and a medium-voltage AC bus. The medium-voltage AC / DC converter includes a first medium-voltage AC / DC converter 11, a second medium-voltage AC / DC converter 12, and a third medium-voltage AC / DC converter 13. The medium-voltage AC bus includes a first medium-voltage AC bus 21, a second medium-voltage AC bus 22, and a third medium-voltage AC bus 23.

[0083] The output terminals of any two of the first medium-voltage AC / DC converter 11, the second medium-voltage AC / DC converter 12, and the third medium-voltage AC / DC converter 13 are interconnected via the first medium-voltage DC bus 61.

[0084] The input terminal of the first medium-voltage AC / DC converter 11 is connected to the output terminal of the first medium-voltage AC bus 21, and the input terminal of the first medium-voltage AC bus 21 is used to connect to the first medium-voltage AC substation.

[0085] The input terminal of the second medium-voltage AC / DC converter 12 is connected to the output terminal of the second medium-voltage AC bus 22, and the input terminal of the second medium-voltage AC bus 22 is used to connect to the second medium-voltage AC substation.

[0086] The input terminal of the third medium-voltage AC / DC converter 13 is connected to the output terminal of the third medium-voltage AC bus 23, and the input terminal of the third medium-voltage AC bus 23 is used to connect to the third medium-voltage AC substation.

[0087] The low-voltage DC ring network system includes a low-voltage AC / DC converter and a low-voltage AC bus. The low-voltage AC / DC converter includes a first low-voltage AC / DC converter 31, a second low-voltage AC / DC converter 32, a third low-voltage AC / DC converter 33, and a fourth low-voltage AC / DC converter 34. The low-voltage AC bus includes a first low-voltage AC bus 41, a second low-voltage AC bus 42, a third low-voltage AC bus 43, and a fourth low-voltage AC bus 44.

[0088] The output terminals of any two of the first low-voltage AC / DC converter 31, the second low-voltage AC / DC converter 32, the third low-voltage AC / DC converter 33, and the fourth low-voltage AC / DC converter 34 are interconnected via the first low-voltage DC bus 51.

[0089] The input terminal of the first low-voltage AC / DC converter 31 is connected to the output terminal of the first low-voltage AC bus 41, and the input terminal of the first low-voltage AC bus 41 is used to connect to the first low-voltage distribution station area.

[0090] The input terminal of the second low-voltage AC / DC converter 32 is connected to the output terminal of the second low-voltage AC bus 42, and the input terminal of the second low-voltage AC bus 42 is used to connect to the second low-voltage distribution substation.

[0091] The input terminal of the third low-voltage AC / DC converter 33 is connected to the output terminal of the third low-voltage AC bus 43, and the input terminal of the third low-voltage AC bus 43 is used to connect to the third low-voltage distribution station area.

[0092] The input terminal of the fourth low-voltage AC / DC converter 34 is connected to the output terminal of the fourth low-voltage AC bus 44, and the input terminal of the fourth low-voltage AC bus 44 is used to connect to the fourth low-voltage distribution substation.

[0093] The DC ring network interconnection system includes a DC transformer (i.e., the first DC / DC transformer 71), a second medium-voltage DC bus 62, and a second low-voltage DC bus 52.

[0094] The medium-voltage side of the DC transformer is connected to the input terminal of the second medium-voltage DC bus 62, and the output terminal of the second medium-voltage DC bus 62 is connected to the first medium-voltage DC bus 61 of the aforementioned medium-voltage DC ring network system.

[0095] The low-voltage side of the DC transformer is connected to the input terminal of the second low-voltage DC bus 52, and the output terminal of the second low-voltage DC bus 52 is connected to the first low-voltage DC bus 51 of the aforementioned low-voltage DC ring network system via the third low-voltage DC bus 53.

[0096] The low-voltage side of the DC transformer is connected to energy storage batteries, photovoltaic systems, and charging piles via the second low-voltage DC bus 52. Figure 1 The diagram illustrates that the second low-voltage DC bus 52 is connected to the energy storage battery through the third low-voltage DC bus 53 and the second DC / DC transformer 72, connected to the charging pile through the third low-voltage DC bus 53 and the third DC / DC transformer 73, and connected to the photovoltaic system through the third low-voltage DC bus 53 and the fourth DC / DC transformer 74.

[0097] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0098] This invention provides a medium- and low-voltage two-stage DC ring network system, including a medium-voltage DC ring network system. Specifically, the medium-voltage DC ring network system includes a medium-voltage AC / DC converter, a medium-voltage AC bus, and medium-voltage AC transformer equipment. The medium-voltage AC / DC converter and the medium-voltage AC bus are connected, and the medium-voltage AC bus is used to connect to the medium-voltage transformer equipment. By constructing a medium-voltage DC ring network system, asynchronous loop operation of AC feeders can be achieved, improving the reliability of power distribution network supply, regulating load balancing between feeders, and providing distributed new energy AC / DC access and control capabilities.

[0099] Furthermore, the medium- and low-voltage dual-stage DC ring network system also includes a low-voltage DC ring network system. Specifically, the low-voltage DC ring network system includes a low-voltage AC / DC converter, a low-voltage AC bus, and low-voltage power distribution equipment. The low-voltage AC / DC converter is connected to the low-voltage AC bus, which is used to connect to the low-voltage power distribution equipment. By constructing a low-voltage DC ring network system, it is possible to support flexible access for high-proportion distributed new energy sources (such as photovoltaics), high-proportion distributed energy storage (such as energy storage batteries), and new DC loads (such as charging piles). It has advantages such as a wider power distribution range, higher reliability, stronger scalability, and more flexible control.

[0100] Furthermore, the medium- and low-voltage dual-stage DC ring network system of this invention also includes a DC ring network interconnection system. Specifically, the DC ring network interconnection system includes a DC transformer, with its medium-voltage side connected to the medium-voltage DC ring network system and its low-voltage side connected to the low-voltage DC ring network system. The DC ring network interconnection system enables power exchange between the medium-voltage and low-voltage DC ring network systems, power exchange between medium-voltage AC transformers, and power exchange between low-voltage distribution equipment.

[0101] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A medium-low voltage two-stage DC ring network system, characterized in that, include: A medium-voltage DC ring network system, comprising a medium-voltage AC / DC converter, a medium-voltage AC bus, and medium-voltage AC transformer equipment; wherein the medium-voltage AC / DC converter is connected to the medium-voltage AC bus, and the medium-voltage AC bus is connected to the medium-voltage AC transformer equipment; A low-voltage DC ring network system, comprising a low-voltage AC / DC converter, a low-voltage AC bus, and low-voltage power distribution equipment; wherein the low-voltage AC / DC converter is connected to the low-voltage AC bus, and the low-voltage AC bus is connected to the low-voltage power distribution equipment. A DC ring network interconnection system is provided, which is connected to both a medium-voltage DC ring network system and a low-voltage DC ring network system. The DC ring network interconnection system includes a DC transformer; the medium-voltage side of the DC transformer is connected to the medium-voltage DC ring network system, and the low-voltage side of the DC transformer is connected to the low-voltage DC ring network system. The DC ring network interconnection system also includes a second medium-voltage DC bus; the medium-voltage side of the DC transformer is connected to the second medium-voltage DC bus, and the second medium-voltage DC bus is connected to the medium-voltage DC ring network system. A DC circuit breaker is configured on the second medium-voltage DC bus. The DC ring network interconnection system also includes a second low-voltage DC bus; the low-voltage side of the DC transformer is connected to the second low-voltage DC bus, and the second low-voltage DC bus is connected to the low-voltage DC ring network system. A DC circuit breaker is configured on the second low-voltage DC bus. The DC ring network interconnection system further includes a third low-voltage DC bus; the second low-voltage DC bus is connected to distributed new energy sources, distributed energy storage, and new DC loads via the third low-voltage DC bus and the DC transformer.

2. The medium-low voltage dual-stage DC ring network system according to claim 1, characterized in that, There are multiple medium-voltage AC / DC converters and multiple medium-voltage AC buses; The output terminals of the multiple medium-voltage AC / DC converters are interconnected; The input terminals of the multiple medium-voltage AC / DC converters are connected one-to-one with the output terminals of the multiple medium-voltage AC buses, and the input terminals of the multiple medium-voltage AC buses are connected one-to-one with the multiple medium-voltage AC power equipment.

3. The medium-low voltage two-stage DC ring network system according to claim 1 or 2, characterized in that, The medium-voltage AC / DC converter includes a first medium-voltage AC / DC converter, a second medium-voltage AC / DC converter, and a third medium-voltage AC / DC converter; The medium-voltage AC busbar includes a first medium-voltage AC busbar, a second medium-voltage AC busbar, and a third medium-voltage AC busbar; The output terminals of any two of the first medium-voltage AC / DC converter, the second medium-voltage AC / DC converter, and the third medium-voltage AC / DC converter are interconnected. The input terminal of the first medium-voltage AC / DC converter is connected to the output terminal of the first medium-voltage AC bus, and the input terminal of the first medium-voltage AC bus is connected to the first medium-voltage AC transformer. The input terminal of the second medium-voltage AC / DC converter is connected to the output terminal of the second medium-voltage AC bus, and the input terminal of the second medium-voltage AC bus is connected to the second medium-voltage AC transformer. The input terminal of the third medium-voltage AC / DC converter is connected to the output terminal of the third medium-voltage AC bus, and the input terminal of the third medium-voltage AC bus is connected to the third medium-voltage AC substation.

4. The medium-low voltage dual-stage DC ring network system according to claim 2, characterized in that, The output terminals of the plurality of medium-voltage AC / DC converters are connected via a first medium-voltage DC bus.

5. The medium-low voltage two-stage DC ring network system according to claim 4, characterized in that, A DC circuit breaker is installed on the first medium-voltage DC bus.

6. The medium-low voltage two-stage DC ring network system according to claim 1, characterized in that, There are multiple low-voltage AC / DC converters and multiple low-voltage AC buses; The outputs of the multiple low-voltage AC / DC converters are interconnected; The input terminals of the multiple low-voltage AC / DC converters and the output terminals of the multiple low-voltage AC buses are connected one-to-one, and the input terminals of the multiple low-voltage AC buses are connected one-to-one with the multiple low-voltage power distribution equipment.

7. The medium-low voltage two-stage DC ring network system according to claim 5 or 6, characterized in that, The low-voltage AC / DC converter includes a first low-voltage AC / DC converter, a second low-voltage AC / DC converter, a third low-voltage AC / DC converter, and a fourth low-voltage AC / DC converter. The low-voltage AC busbar includes a first low-voltage AC busbar, a second low-voltage AC busbar, a third low-voltage AC busbar, and a fourth low-voltage AC busbar. The output terminals of any two of the first, second, third, and fourth low-voltage AC / DC converters are interconnected. The input terminal of the first low-voltage AC / DC converter is connected to the output terminal of the first low-voltage AC bus, and the input terminal of the first low-voltage AC bus is connected to the first low-voltage power distribution equipment. The input terminal of the second low-voltage AC / DC converter is connected to the output terminal of the second low-voltage AC bus, and the input terminal of the second low-voltage AC bus is connected to the second low-voltage power distribution equipment. The input terminal of the third low-voltage AC / DC converter is connected to the output terminal of the third low-voltage AC bus, and the input terminal of the third low-voltage AC bus is connected to the third low-voltage power distribution equipment. The input terminal of the fourth low-voltage AC / DC converter is connected to the output terminal of the fourth low-voltage AC bus, and the input terminal of the fourth low-voltage AC bus is connected to the fourth low-voltage power distribution equipment.

8. The medium-low voltage two-stage DC ring network system according to claim 6, characterized in that, The outputs of the plurality of low-voltage AC / DC converters are connected via a first low-voltage DC bus.

9. The medium-low voltage two-stage DC ring network system according to claim 8, characterized in that, A DC circuit breaker is configured on the first low-voltage DC bus.

10. The medium-low voltage two-stage DC ring network system according to claim 1, characterized in that, The distributed new energy source includes photovoltaics; and / or, The distributed energy storage includes energy storage batteries; and / or, The new type of DC load includes a charging pile.

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