CN114050727A - Circuit topology structure of LCC-MMC mixed type AC-AC converter - Google Patents
Circuit topology structure of LCC-MMC mixed type AC-AC converter Download PDFInfo
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- CN114050727A CN114050727A CN202111397781.9A CN202111397781A CN114050727A CN 114050727 A CN114050727 A CN 114050727A CN 202111397781 A CN202111397781 A CN 202111397781A CN 114050727 A CN114050727 A CN 114050727A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
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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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/145—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/155—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M7/162—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/145—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/155—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M7/19—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only arranged for operation in series, e.g. for voltage multiplication
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/25—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only arranged for operation in series, e.g. for multiplication of voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/505—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
- H02M7/515—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
- H02M7/521—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P80/00—Climate change mitigation technologies for sector-wide applications
- Y02P80/20—Climate change mitigation technologies for sector-wide applications using renewable energy
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- Engineering & Computer Science (AREA)
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Abstract
The invention discloses a circuit topology structure of an LCC-MMC hybrid alternating current converter, which comprises an anode part and a cathode part, wherein the anode part comprises a first LCC-MMC rectifying module and a first LCC-MMC inverting module; the negative part comprises a second LCC-MMC rectifying module and a second LCC-MMC inverting module; wherein, first LCC-MMC rectifier module, first LCC-MMC contravariant module, second LCC-MMC contravariant module and second LCC-MMC rectifier module connect gradually and constitute the series circuit, external first system is connected with first LCC-MMC rectifier module and second LCC-MMC rectifier module, external second system is connected with first LCC-MMC contravariant module and second LCC-MMC contravariant module, this structure can the independent control active and idle, and the cost is lower.
Description
Technical Field
The invention belongs to the field of topological structures of high-voltage and high-power conversion devices, and relates to a circuit topological structure of an LCC-MMC hybrid alternating current converter.
Background
The high-voltage high-power AC/AC converter has very wide practical engineering application and plays a very important role in asynchronous networking, offshore wind power, long-distance frequency division transmission, ocean oil and gas exploitation, future seabed power transmission and distribution system construction and the like. In addition, the high-power alternating-current converter is also indispensable in the fields of electric transmission such as rail transit, mining, smelting and steel rolling and the high-voltage high-power supply industry.
The AC-AC converter is a core device of a flexible frequency division power transmission system, and the current mainstream converter topology adopts a modular multilevel technology. The technology can rapidly and independently control active power and reactive power in an operation range, a receiving end system can be a passive network, and the technology has the advantages of low loss, high waveform quality, strong fault handling capacity and the like, but the investment cost is overhigh due to the fact that a large number of IGBT elements are needed.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a circuit topology structure of an LCC-MMC hybrid AC-AC converter, which can independently control active power and reactive power and has low cost.
In order to achieve the above purpose, the circuit topology structure of the LCC-MMC hybrid ac/ac converter of the present invention includes an anode portion and a cathode portion, wherein the anode portion includes a first LCC-MMC rectifying module and a first LCC-MMC inverting module; the negative part comprises a second LCC-MMC rectifying module and a second LCC-MMC inverting module; wherein, first LCC-MMC rectifier module, first LCC-MMC contravariant module, second LCC-MMC contravariant module and second LCC-MMC rectifier module connect gradually and constitute the series circuit, and external first system is connected with first LCC-MMC rectifier module and second LCC-MMC rectifier module, and external second system is connected with first LCC-MMC contravariant module and second LCC-MMC contravariant module.
The first system is used as an input side system, the second system is used as an output side system, and one of the first system and the second system is an active system.
The first LCC-MMC rectifying module, the second LCC-MMC rectifying module, the first LCC-MMC inverter module and the second LCC-MMC inverter module are formed by connecting a 6-pulse wave 3-phase full-bridge LCC converter based on a semi-control device and a modular multi-level converter based on a full-control device in series.
The 6-pulse 3-phase full-bridge LCC converter consists of 6 thyristors, 3 phase-change inductors and a smoothing reactor;
the modularized multi-level converter is composed of 6 bridge arms, and each bridge arm is formed by connecting an inductor, an equivalent resistor and N half-bridge sub-modules in series.
The half-bridge submodule structure comprises a power electronic device and a direct current capacitor, wherein the power electronic device comprises two full-control type power electronic devices which are connected in series, and the direct current capacitor is connected with the power electronic devices in parallel.
The number N of the half-bridge sub-modules is determined by the voltage of a direct current bus, the voltage-resistant level of the 6-pulse 3-phase full-bridge LCC converter and the power optimization coordination condition of the MMC and the LCC converter.
The invention has the following beneficial effects:
when the circuit topology structure of the LCC-MMC hybrid AC-AC converter is specifically operated, a first LCC-MMC rectifying module, a first LCC-MMC inverting module, a second LCC-MMC inverting module and a second LCC-MMC rectifying module are sequentially connected to form a series circuit, an externally connected first system is connected with the first LCC-MMC rectifying module and the second LCC-MMC rectifying module, and an externally connected second system is connected with the first LCC-MMC inverting module and the second LCC-MMC inverting module, namely, the circuit topology structure not only can be directly connected with two three-phase AC systems with different frequencies and amplitudes in a grid-connected mode, but also can be directly connected with a passive load in a power mode, has the advantages of a modular multilevel technology and the traditional LCC, is widely applied to high-voltage and high-power conversion application occasions, and is compared with the existing converter topology based on the modular multilevel technology, the volume and the cost of the system can be obviously reduced, and the reliability is improved. In addition, compared with the traditional LCC converter, the invention can supply power to a passive system, the MMC can temporarily maintain the voltage of the alternating-current bus when in alternating-current fault, and the MMC can still transmit power when in LCC commutation failure, thus the reliability is higher.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic structural diagram of an LCC-MMC rectifier module;
FIG. 3 is a schematic structural diagram of an LCC-MMC inverter module;
fig. 4 is a main circuit structure diagram of a 6-pulse 3-phase full-bridge LCC converter in an LCC-MMC rectifier module;
fig. 5 is a structure diagram of a main circuit of a 6-pulse 3-phase full-bridge LCC converter in an LCC-MMC inverter module;
fig. 6 is a main circuit block diagram of a modular multilevel converter;
FIG. 7 is a circuit block diagram of a submodule of the modular multilevel converter;
FIG. 8 is a diagram of a system for interconnecting a frequency-divided power grid and a power frequency power grid according to the present invention;
fig. 9 is a structural diagram of a frequency division offshore wind power grid-connected system according to the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure. 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 invention.
There is shown in the drawings a schematic block diagram of a disclosed embodiment in accordance with the invention. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, according to actual needs.
Referring to fig. 1, the circuit topology of the LCC-MMC hybrid ac/ac converter according to the present invention includes an anode portion and a cathode portion, wherein the anode portion includes a first LCC-MMC rectifying module and a first LCC-MMC inverting module; the negative part comprises a second LCC-MMC rectifying module and a second LCC-MMC inverting module; the first LCC-MMC rectifier module, the first LCC-MMC inverter module, the second LCC-MMC inverter module and the second LCC-MMC rectifier module sequentially form a series circuit, an external first system is connected with the first LCC-MMC rectifier module and the second LCC-MMC rectifier module, and an external second system is connected with the first LCC-MMC inverter module and the second LCC-MMC inverter module.
Referring to fig. 2 and 3, x is 1,2, the first LCC-MMC rectifying module, the first LCC-MMC inverting module, the second LCC-MMC rectifying module, and the second LCC-MMC inverting module are each formed by connecting a 6-pulse 3-phase full-bridge LCC converter based on a half-controlled device and a Modular Multilevel Converter (MMC) based on a full-controlled device in series, and an ac side of the converter is connected to a corresponding ac system through a converter transformer.
Referring to fig. 4 and 5, the 6-pulse 3-phase full-bridge LCC converter is composed of 6 half-controlled power electronic devices VT1～VT63 phase-change inductors LcrAnd a smoothing reactor LdcThe semi-Controlled power electronic device is a Thyristor (Thyristor), also called Silicon Controlled Rectifier (Silicon Controlled Rectifier). Optionally, the smoothing reactors of the LCC converters may be equivalent and integrated into one or more smoothing reactors connected in series to the dc bus.
The circuit structures of the 6-pulse wave 3-phase full-bridge LCC current converter in the first LCC-MMC rectification module and the second LCC-MMC rectification module are shown in FIG. 4, and the thyristor VT1、VT3、VT5Positive electrode of (2)dcA thyristor VT connected to the positive electrode of the DC side1、VT3、VT5Negative pole phase-change inductor LcrThe A, B, C three phases of the first system are respectively connected; thyristor VT4、VT6、VT2Positive pole phase-change inductor LcrConnected to A, B, C three phases of the first system, respectively, thyristor VT4、VT6、VT2Is connected with the direct current side negative electrode.
The circuit structure of the 6-pulse wave 3-phase full-bridge LCC converter in the first LCC-MMC inverter module and the second LCC-MMC inverter module is shown in FIG. 5, and the thyristorVT1、VT3、VT5Negative electrode lead wire LdcA thyristor VT connected to the positive electrode of the DC side1、VT3、VT5Positive pole phase-change inductor LcrRespectively connected with U, V, W three phases of the second system; thyristor VT4、VT6、VT2Negative pole phase-change inductor LcrConnected to U, V, W three phases of the second system, respectively, thyristor VT4、VT6、VT2The positive electrode of the anode is connected with the direct current side negative electrode.
As shown in fig. 6, the topology of the modular multilevel converter is similar between the rectifier module and the inverter module, and the modular multilevel converter is composed of 6 bridge arms, and each bridge arm is formed by connecting an inductor L, an equivalent resistor R, and N half-bridge sub-modules in series.
In the first LCC-MMC rectifier module and the second LCC-MMC rectifier module, the anodes of three upper main bridge arms are connected with the anode of a direct current side, and the cathodes of the three upper main bridge arms are respectively connected with A, B, C three phases of a first system; the negative poles of the three lower main bridge arms are connected with the negative pole on the direct current side, and the positive poles of the three lower main bridge arms are respectively connected with A, B, C three phases of the first system.
In the first LCC-MMC inverter module and the second LCC-MMC inverter module, the anodes of three upper main bridge arms are connected with the anode of a direct current side, and the cathodes of the three upper main bridge arms are respectively connected with U, V, W three phases of the second system 2; and the cathodes of the three lower main bridge arms are connected with the cathode of the direct current side, and the anodes of the three lower main bridge arms are respectively connected with U, V, W three phases of the second system.
As shown in fig. 7, the half-bridge submodule structure includes a power electronic device and a dc capacitor, where the power electronic device includes two fully-controlled power electronic devices T connected in series1And T2And the direct current capacitor C is connected with the power electronic device in parallel. The fully-controlled power electronic device comprises an insulated gate bipolar transistor and a back pressure diode connected with the insulated gate bipolar transistor in parallel. Meanwhile, the power electronic device may be a metal-oxide-semiconductor (semiconductor) field effect Transistor (MOS) Transistor, a Bipolar Junction Transistor (BJT) Transistor, or the like.
The number N of the half-bridge sub-modules is determined by the voltage of a direct current bus and the voltage-resistant level of the 6-pulse 3-phase full-bridge LCC converter, and meanwhile, the power optimization matching condition of the MMC and the LCC converter needs to be considered.
According to the difference between the types of the first system and the second system, the application scenarios of the invention can be divided into:
scene 1
The first system is an active system, the second system is a passive system, the high-voltage high-power supply system is suitable for power transmission and serves as a high-voltage high-power supply, the first system is a distribution station and/or a transformer substation and/or a power station, and the second system is a passive load such as a passive power grid, rail transit, mining, smelting, steel rolling and the like.
Scene 2
The system is suitable for a scene that frequency division new energy power sources such as frequency division offshore wind power, frequency division onshore wind power, frequency division photovoltaic and the like are connected to a power grid.
Scene 3
The invention is suitable for scenes such as asynchronous alternating current system networking, new energy system access containing power supply, frequency division power system networking and power frequency power system networking.
Example one
Referring to fig. 8, the present invention is applied to a scenario where a frequency-division power grid is connected to a power-frequency power grid.
The frequency division power grid and the power frequency power grid are both active networks, and the neutral point on the direct current side of the LCC-MMC hybrid AC-AC converter is not grounded, namely n in figure 111Dot is only with p21Point to point, n12Dot is only with p22The dots are connected. For a scene with lower power and lower direct voltage, only the positive electrode part or the negative electrode part can be provided to improve the economy of the whole system.
For the LCC, the LCC is connected with an active network, so that the phase change of the 3-phase full-bridge LCC converter can be realized, and under the normal condition, the rectification side adopts constant direct current control and the inversion side adopts constant turn-off angle control. In addition, the rectification side and the inversion side are respectively provided with auxiliary control strategies such as minimum trigger angle control and low-voltage current limiting control.
For MMC, a control mode of fixed direct current voltage and fixed alternating current voltage is adopted on a rectifying side, and a control mode of fixed direct current and fixed alternating current voltage is adopted on an inverting side, so that the adjustment capability of the MMC on the alternating current bus voltage is utilized, the operation characteristic of LCC and even the whole system is improved, and meanwhile, the control mode can be coordinated with the fixed direct current control of the LCC.
Meanwhile, the harmonic component output by the LCC is compensated, and optionally, when the compensation capability is insufficient, PCC (point of common coupling control) can be performed on the point of common coupling1And PCC2Reactive compensation equipment is added respectively to improve the quality of output waveforms.
Example two
Referring to fig. 9, the present invention is applied to a scenario of frequency division offshore wind power integration.
The low-frequency power of 50/3Hz is generated by the frequency-dividing offshore wind turbine, is collected to the frequency-dividing offshore booster station through the current collecting circuit, and is transmitted to the land through the frequency-dividing submarine cable. The neutral point on the DC side of the invention is grounded, i.e. n in FIG. 111Dot, n12Dot, p21Point and p22The point is grounded.
For the rectifier module, since the offshore wind farm adopts a Maximum Power Point Tracking (MPPT) mode, a converter is required to provide voltage for the wind farm, and since the LCC does not have a voltage providing capability, the wind farm voltage needs to be provided by the MMC. Therefore, the LCC may adopt constant dc current control, assisted by other control methods such as minimum trigger angle control and low voltage current limiting control. The MMC can adopt constant voltage and constant frequency control (V/f control) or introduce droop control to provide voltage for the wind power plant. In order to realize V/f control, a grid-connected point PCC is needed on a frequency division side1Is connected in parallel with a capacitor C.
For the inversion module, because the power frequency side is directly connected with the power frequency power grid, similar to the inversion module in the first embodiment, the LCC can adopt a constant turn-off angle control mode, and the MMC adopts a control mode of constant direct current voltage and constant alternating current voltage.
Like the first embodiment, the MMC may compensate the output harmonic component of the LCC through an appropriate control strategy, and optionally, when compensatingWhen the compensation capacity is insufficient, PCC can be arranged at the point of connection1、PCC2Reactive compensation equipment is added respectively to improve the quality of output waveforms.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (7)
1. A circuit topology structure of an LCC-MMC hybrid AC-AC converter is characterized by comprising an anode part and a cathode part, wherein the anode part comprises a first LCC-MMC rectifying module and a first LCC-MMC inverting module; the negative part comprises a second LCC-MMC rectifying module and a second LCC-MMC inverting module; wherein, first LCC-MMC rectifier module, first LCC-MMC contravariant module, second LCC-MMC contravariant module and second LCC-MMC rectifier module connect gradually and constitute the series circuit, and external first system is connected with first LCC-MMC rectifier module and second LCC-MMC rectifier module, and external second system is connected with first LCC-MMC contravariant module and second LCC-MMC contravariant module.
2. The circuit topology of an LCC-MMC hybrid ac-dc converter according to claim 1, wherein the first system is an input-side system and the second system is an output-side system, and wherein one of the first system and the second system is an active system.
3. The circuit topology of LCC-MMC hybrid AC-AC converter according to claim 1, wherein said first LCC-MMC rectifier module, said second LCC-MMC rectifier module, said first LCC-MMC inverter module and said second LCC-MMC inverter module are each composed of a 6-pulse 3-phase full-bridge LCC converter based on half-controlled devices and a modular multi-level converter based on full-controlled devices connected in series.
4. The circuit topology of the LCC-MMC hybrid ac-dc converter according to claim 1, wherein the 6-pulse 3-phase full-bridge LCC converter consists of 6 thyristors, 3 phase-change inductors and a smoothing reactor.
5. The circuit topology of an LCC-MMC hybrid ac-dc converter according to claim 1, wherein the modular multilevel converter consists of 6 legs, each leg being composed of an inductor, an equivalent resistor, and N half-bridge sub-modules connected in series.
6. The circuit topology of an LCC-MMC hybrid AC-AC converter of claim 5, wherein the half-bridge sub-module structure comprises a power electronics device comprising two fully-controlled power electronics devices in series and a DC capacitor connected in parallel with the power electronics device.
7. The circuit topology of an LCC-MMC hybrid ac/dc converter according to claim 1, wherein the number N of half-bridge sub-modules is determined by the dc bus voltage and the withstand voltage level and power optimization coordination of a 6-pulse 3-phase full-bridge LCC converter.
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