CN106921172B - Topological structure of flexible ring network controller - Google Patents
Topological structure of flexible ring network controller Download PDFInfo
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- CN106921172B CN106921172B CN201511001333.7A CN201511001333A CN106921172B CN 106921172 B CN106921172 B CN 106921172B CN 201511001333 A CN201511001333 A CN 201511001333A CN 106921172 B CN106921172 B CN 106921172B
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- 239000004973 liquid crystal related substance Substances 0.000 description 4
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
Abstract
The invention provides a topological structure of a flexible ring network controller, which comprises a converter transformer, a first converter and a second converter; the first converter is connected to the alternating current system through a converter transformer, and the second converter is directly connected to the alternating current system; the grid side winding of the converter transformer is in star connection, and the valve side winding is in triangular connection; each phase bridge arm of the first current converter is formed by connecting half-bridge submodules in series; each phase bridge arm of the second converter is formed by connecting half-bridge submodules and full-bridge submodules in series, and the number ratio of the half-bridge submodules to the full-bridge submodules is 1: 1. compared with the prior art, the topological structure of the flexible ring network controller provided by the invention omits a group of converter transformers and a one-end grounding system, saves the floor area of the flexible ring network controller, and realizes compact design; the converter transformer on one side is utilized to block the passage of zero sequence current and direct current magnetic bias current in normal operation, and the reliability of the flexible ring network controller is improved.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a topological structure of a flexible ring network controller.
Background
With the continuous increase of transmission load and the development and construction of a high-level power grid, an electromagnetic ring network is continuously formed. The existing general method for disconnecting the electromagnetic ring network is to add an alternating current breaker at a disconnecting point or implement the partitioned operation of the power grid, but the precondition of the method is that the power grid has the basic condition of the open-loop operation. When the electromagnetic ring network is difficult to operate in an open loop mode and meets the condition of safety constraint, technologies such as a unified power flow controller, a phase shifter, an interphase power controller, a controllable series compensation and the like can be adopted, and voltage phase angles are adjusted through an FACTS device, so that circulation currents in the electromagnetic ring network are eliminated, short-circuit currents are limited, power distribution between high/low voltage networks is optimized, and the operation reliability and economy of a system are improved. The flexible ring network controller is back-to-back flexible direct current, and can realize the rapid independent control of active power and reactive power; when the alternating current system breaks down, the flexible direct current does not provide short-circuit current, the fault can be isolated rapidly, and the device has a black start function, and provides a choice for solving the problem of the electromagnetic looped network.
At present, the universal flexible ring network controller topology is a flexible ring network controller with converter transformers on two sides, symmetrical monopoles and half-bridge sub-module converters, but the topology structure has two groups of converter transformers and two groups of grounding systems, occupies a large area, considers the actual installation position and space limitation factors of an urban power grid and is difficult to apply. The other flexible ring network controller without the converter transformer adopts a mixed sub-module converter for symmetrical single poles, although two groups of converter transformers and a grounding system are removed, the topology has strict requirements on the symmetrical operation degree of the converter, once the operation deviation of direct currents at two poles of the converter exists, direct current magnetic biasing components appear in alternating currents output by the flexible ring network controller, the direct currents are injected into the autotransformer to form direct current circulating currents in an alternating current bus, the autotransformer in the alternating current system has poor tolerance capability on long-term direct current magnetic biasing, and potential safety hazards exist. Therefore, it is desirable to provide a flexible looped network controller that saves floor space and has high reliability.
Disclosure of Invention
To meet the needs of the prior art, the present invention provides a topology for a flexible ring network controller.
The technical scheme of the invention is as follows:
the controller comprises a converter transformer, a first converter and a second converter; the first converter is connected to the alternating current system through a converter transformer, and the second converter is directly connected to the alternating current system; the grid side winding of the converter transformer is in star connection, and the valve side winding is in triangular connection;
each phase of bridge arm of the first converter is formed by connecting half-bridge sub-modules in series;
each phase bridge arm of the second converter is formed by connecting half-bridge submodules and full-bridge submodules in series, and the number ratio of the half-bridge submodules to the full-bridge submodules is 1: 1.
preferably, the first and second liquid crystal materials are,
when an asymmetric fault occurs at the AC side connected with the converter transformer, the converter transformer isolates the asymmetric fault;
and when the asymmetrical fault occurs on the accessed alternating current side of the second converter, the second converter isolates the asymmetrical fault.
Preferably, the first and second liquid crystal materials are,
when an asymmetric fault occurs at the AC side connected with the converter transformer, the converter transformer carries out magnetic coupling power transmission through a primary side winding and a secondary side winding to realize the electrical insulation of an AC system and a DC system;
when the asymmetric fault occurs on the AC side connected with the second converter, the second converter is controlled to output negative voltage, and the distortion-free symmetric output of the AC voltage and the AC current of the second converter is realized.
Preferably, the first and second liquid crystal materials are,
when a direct current line has a fault, the converter transformer and the second converter bear direct current fault overvoltage.
Preferably, the first and second liquid crystal materials are,
when a direct current line has a fault, the converter transformer carries out magnetic coupling power transmission through a primary side winding and a secondary side winding to realize the electrical insulation of an alternating current system and a direct current system;
when a direct current line has a fault, the second converter restrains direct current fault current through the full-bridge submodule, so that direct current voltage drop output by the second converter is zero, and direct current fault ride-through or rapid locking is realized.
Compared with the closest prior art, the excellent effects of the invention are as follows:
1. compared with the topological structure of the existing flexible ring network controller, the topological structure of the flexible ring network controller provided by the invention omits a group of converter transformers and a one-end grounding system, saves the floor area of the topological structure of the flexible ring network controller, and realizes compact design;
2. according to the topological structure of the flexible ring network controller, the converter transformer on one side is utilized, the path of zero sequence current and direct current magnetic biasing current in normal operation is blocked, and the reliability of the topological structure of the flexible ring network controller is improved;
3. according to the topological structure of the flexible ring network controller, the second converter adopts a mixed bridge arm structure formed by connecting 50% of full-bridge submodules and 50% of half-bridge submodules in series, and after an alternating current fault occurs, the distortion-free symmetrical output of alternating current voltage and current of the converter is realized by utilizing the negative voltage output capacity of the mixed submodule structure; when a direct current system fault occurs, the full-bridge submodule in the hybrid submodule structure is used for restraining fault current flowing through a diode of the hybrid submodule, the direct current voltage drop output by the second converter is controlled to be zero, fault ride-through or rapid locking can be achieved, and the fault is isolated.
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1: a topological structure schematic diagram of a common flexible ring network controller;
FIG. 2: the topological structure schematic diagram of a flexible ring network controller in the embodiment of the invention;
FIG. 3: the permanent bias current generated by the flexible ring network controller in the embodiment of the invention is shown schematically;
FIG. 4: the direct current magnetic bias current path of the converter-less transformer in the embodiment of the invention is schematically shown;
FIG. 5: in the embodiment of the invention, the single-side converter transformer blocks the direct current magnetic bias current path;
FIG. 6: the embodiment of the invention is a schematic diagram of single-phase earth fault of an alternating current system;
FIG. 7: the embodiment of the invention provides a schematic diagram of the occurrence of the positive metal ground fault of a direct current line.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The embodiment of the topology structure of the flexible ring network controller provided by the present invention is shown in fig. 2, and specifically includes:
the topology of the flexible ring network controller in this embodiment includes a converter transformer, a first converter, and a second converter. Wherein the content of the first and second substances,
1. first inverter
In this embodiment, the first converter is connected to the ac system through the converter transformer, and each phase bridge arm of the first converter is formed by connecting half-bridge sub-modules in series.
2. Second inverter
In this embodiment, the second converter is directly connected to the ac system, each phase of the bridge arm of the second converter is formed by connecting a half-bridge submodule and a full-bridge submodule in series, and the number ratio of the half-bridge submodule to the full-bridge submodule is 1: 1. namely, each phase bridge arm is formed by connecting 50% of full-bridge submodules and 50% of half-bridge submodules in series.
3. Converter transformer
In this embodiment, the network side winding of the converter transformer is connected in a star shape, and the valve side winding is connected in a delta shape.
When the power grid of the invention is in normal operation, the two-pole direct current of the current converter has operation deviation delta Id，ΔId＝Id2-Id1In which Id2Is a negative direct current, Id1Is positive direct current. But since the converter transformer corresponds to a disconnection for direct current. Therefore, no dc loop exists, and no dc bias component is caused to be present in the ac current output by the flexible loop network controller, as shown in fig. 3-5. When the power grid fails, the flexible ring network controller works in the following modes:
1. fault of ac system
As shown in fig. 6:
①, when the AC side connected with the converter transformer has an asymmetric fault, the converter transformer isolates the asymmetric fault.
In this embodiment, the converter transformer performs magnetic coupling power transmission by the primary side winding and the secondary side winding, thereby achieving electrical insulation between the ac system and the dc system.
②, when the asymmetrical fault occurs on the AC side connected with the second converter, the second converter isolates the asymmetrical fault.
In this embodiment, the second converter is controlled to output a negative voltage, so that the distortion-free symmetrical output of the ac voltage and the ac current of the second converter is realized.
2. Fault of dc system
As shown in fig. 7, when the dc line fails, the converter transformer and the second converter are subjected to a dc fault overvoltage.
① when the DC line has fault, the converter transformer transmits power by magnetic coupling through the primary side winding and the secondary side winding, thus realizing the electric insulation of the AC system and the DC system and preventing the DC fault from being transmitted to the AC side.
②, when the DC line has fault, the second converter restrains the DC fault current through the full bridge submodule, so that the DC voltage drop output by the second converter is zero, and the DC fault ride-through or fast locking is realized.
Compared with the topological structure of the common flexible ring network controller shown in fig. 1, the topological structure of the flexible ring network controller in the embodiment eliminates a group of converter transformers and grounding systems, so that the occupied area is saved, and on one hand, the reliability of the flexible ring network control is improved by using single-side converter transformers and adopting the design of a converter with a hybrid sub-module structure.
Finally, it should be noted that: the described embodiments are only some embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Claims (1)
1. A topological structure of a flexible ring network controller is characterized in that the controller comprises a converter transformer, a first converter and a second converter; the first converter is connected to the alternating current system through a converter transformer, and the second converter is directly connected to the alternating current system; the grid side winding of the converter transformer is in star connection, and the valve side winding is in triangular connection;
each phase of bridge arm of the first converter is formed by connecting half-bridge sub-modules in series;
each phase bridge arm of the second converter is formed by connecting half-bridge submodules and full-bridge submodules in series, and the number ratio of the half-bridge submodules to the full-bridge submodules is 1: 1;
when an asymmetric fault occurs at the AC side connected with the converter transformer, the converter transformer isolates the asymmetric fault;
when the asymmetric fault occurs at the AC side connected with the second converter, the second converter isolates the asymmetric fault;
when an asymmetric fault occurs at the AC side connected with the converter transformer, the converter transformer carries out magnetic coupling power transmission through a primary side winding and a secondary side winding to realize the electrical insulation of an AC system and a DC system;
when the asymmetrical fault occurs on the AC side connected with the second converter, the second converter is controlled to output negative voltage, and the distortion-free symmetrical output of the AC voltage and the AC current of the second converter is realized;
when a direct current line has a fault, the converter transformer and the second converter bear direct current fault overvoltage;
when a direct current line has a fault, the converter transformer carries out magnetic coupling power transmission through a primary side winding and a secondary side winding to realize the electrical insulation of an alternating current system and a direct current system;
when a direct current line has a fault, the second converter restrains direct current fault current through the full-bridge submodule, so that direct current voltage drop output by the second converter is zero, and direct current fault ride-through or rapid locking is realized.
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| CN108963988B (en) * | 2018-06-25 | 2024-01-16 | 全球能源互联网研究院有限公司 | Looped network controller and power distribution network |
| WO2020000528A1 (en) * | 2018-06-25 | 2020-01-02 | 全球能源互联网研究院有限公司 | Ring network controller and power distribution network |
| CN109711089B (en) * | 2019-01-15 | 2021-02-02 | 清华大学 | Simplified modeling simulation method for four-port electric energy router |
| CN112187396B (en) * | 2019-07-05 | 2022-10-25 | 许继集团有限公司 | Communication system and method suitable for flexible direct current converter valve |
| CN110492477A (en) * | 2019-08-02 | 2019-11-22 | 全球能源互联网研究院有限公司 | A kind of loop network control device and control method |
| CN113595128B (en) * | 2021-08-10 | 2023-08-22 | 东南大学 | Flexible ring network controller topology without coupling transformer |
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