CN113626971A - Direct-current transformer simulation modeling method and system based on alternating current-direct current decoupling - Google Patents

Direct-current transformer simulation modeling method and system based on alternating current-direct current decoupling Download PDF

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CN113626971A
CN113626971A CN202010387165.4A CN202010387165A CN113626971A CN 113626971 A CN113626971 A CN 113626971A CN 202010387165 A CN202010387165 A CN 202010387165A CN 113626971 A CN113626971 A CN 113626971A
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CN113626971B (en
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赵彪
安峰
宋强
余占清
曾嵘
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Tsinghua University
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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
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    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter

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Abstract

The invention discloses a direct current transformer simulation modeling method and a direct current transformer simulation modeling system based on alternating current-direct current decoupling, wherein the method comprises the steps of firstly, carrying out equivalent decoupling on the input side and the output side of each submodule of a combined direct current transformer based on the connection mode of the input side and the output side of each submodule in the combined direct current transformer to obtain a first decoupling equivalent model; then, based on the first decoupling equivalent model, performing equivalent decoupling on a double-active full-bridge DC-DC converter in any sub-module of the modular combined direct current transformer to obtain a second decoupling equivalent model; and finally, combining one or more module sets composed of all sub-modules based on the first decoupling equivalent model and the second decoupling equivalent model to obtain a modular combined direct-current transformer rapid equivalent model. The modeling method is suitable for any large-scale modular combined direct-current transformer with high voltage and large capacity, has strong universality, and improves the simulation precision and the simulation efficiency.

Description

Direct-current transformer simulation modeling method and system based on alternating current-direct current decoupling
Technical Field
The invention belongs to the technical field of direct-current transformers, and particularly relates to a direct-current transformer simulation modeling method and system based on alternating current and direct current decoupling.
Background
The high-voltage direct-current transmission technology has the advantages of large transmission capacity, long transmission distance, small loss and the like, so that the high-voltage direct-current transmission technology is applied in China on a large scale. The complementary characteristics of various energy sources can be fully utilized by constructing the high-voltage direct-current power grid, and the optimization configuration of resources in a large range, the reliable access of large-scale new energy sources and the improvement of the operation stability of the existing power system are realized. The high-voltage high-capacity direct-current transformer is a key link for realizing the high-efficiency access of renewable energy sources and the interconnection of direct-current systems with different voltage levels.
The topology types of the existing high-voltage large-capacity direct-current transformer mainly include: thyristor resonant type, modular multilevel type, switched capacitor type, and modular combination type dc transformers, and the like. The modular combined type direct current transformer can effectively avoid the direct series connection of power devices, has a modular structure, and is convenient for standardized production, debugging and redundancy design, so that the modular combined type direct current transformer is widely adopted. Meanwhile, the double-active full-bridge DC-DC converter is used as a basic power unit of the DC transformer, so that the DC transformer has the advantages of electrical isolation, bidirectional power flow, high power density and the like, and the application requirements of the DC transformer under the scenes of DC system interconnection and new energy access are met.
The external operation working condition of the direct current transformer is complex, and electromagnetic transient simulation analysis under various working conditions is indispensable before actual production, installation and debugging. However, in order to construct a dc port of a transmission voltage class, a modular combined dc transformer generally requires hundreds of sub-modules to be combined in series and parallel, which greatly increases the number of system network nodes and power devices, so that the simulation process is very slow. The existing rapid electromagnetic transient modeling method mainly comprises an equivalent modeling method based on a controlled source and a Thevenin equivalent modeling method. Compared with Thevenin equivalent modeling, the physical concept of the equivalent modeling method based on the controlled source is clearer, and meanwhile, complex formula derivation is avoided, and the method is easy to realize. However, the existing fast electromagnetic transient simulation method mainly focuses on the modular multilevel converter, and compared with the modular multilevel converter, the structure of the dc transformer is more complex, all sub-modules of the dc transformer are not singly connected in series, and each sub-module internally includes eight switching devices, and elements such as an inductor, a capacitor, and a transformer, which makes the modeling method of the dc transformer difficult to be equivalent to the modular multilevel converter.
Therefore, how to implement equivalent modeling for the dc transformer becomes an urgent technical problem to be solved.
Disclosure of Invention
Aiming at the problems, the invention provides a direct current transformer simulation modeling method and system based on alternating current-direct current decoupling.
The invention aims to provide a direct current transformer simulation modeling method based on alternating current-direct current decoupling, which comprises the following steps,
performing equivalent decoupling on the input side and the output side of each submodule of the modular combined direct-current transformer based on the connection mode of the input side and the output side of each submodule in the modular combined direct-current transformer to obtain a first decoupling equivalent model;
performing equivalent decoupling on a double-active full-bridge DC-DC converter in any sub-module of the modular combined direct-current transformer based on the first decoupling equivalent model to obtain a second decoupling equivalent model;
and combining one or more module sets composed of all sub-modules based on the first decoupling equivalent model and the second decoupling equivalent model to obtain a modular combined direct-current transformer rapid equivalent model.
Further, the obtaining of the first decoupling equivalent model includes performing equivalent decoupling on the input side and the output side of each sub-module of the modular combined direct current transformer based on the connection mode of the input side and the output side of each sub-module of the modular combined direct current transformer,
when the input side of each submodule in the modular combined direct current transformer is a serial connection port:
the input side currents of the submodules are equal, and the input sides of the submodules are equivalent to a controlled current source; wherein the current value of each controlled current source is the input current I of the power supply side of the modular combined direct current transformerin；
Each series sub-module in the modular combined direct current transformer is equivalent to a controlled voltage source, and the voltage value of the controlled voltage source is the sum U of the input side voltages of each sub-modulein；
When the output side of each submodule in the modularized combined direct current transformer is a parallel connection port:
the output side voltages of the sub-modules are equal, and the output side of each sub-module is equivalent to a controlled voltage source; wherein the voltage value of the controlled voltage source is the output voltage U of the modularized combined type direct current transformero；
Each parallel sub-module in the modular combined direct current transformer is equivalent to a controlled current source, and the current value of the controlled current source is the sum I of the currents at the output sides of the sub-moduleso。
Further, the air conditioner is provided with a fan,
the sum U of the input side voltages of the submodulesinAnd sum of output side current IoThe following relation is satisfied:
Figure BDA0002484211630000031
wherein M is the total number of any module centralized sub-modules in the modularized combined direct current transformer, i belongs to M and UiniRepresents the voltage value at the input side of the ith sub-module, IoiIndicating the current value at the output side of the i-th sub-module.
Further, the equivalently decoupling the dual-active full-bridge DC-DC converter in any sub-module of the modular combined type direct current transformer based on the first decoupling equivalent model to obtain a second decoupling equivalent model comprises,
equivalently decoupling the dual-active full-bridge DC-DC converter into three parts comprises: an input side dc port, an intermediate ac link, and an output side dc port, wherein,
the method comprises the steps that a direct current port on the input side of a double-active full-bridge DC-DC converter is equivalent to an input controlled current source, and the current of the input controlled current source is the input current of the double-active full-bridge DC-DC converter;
the method comprises the steps that an intermediate alternating current link of a double-active full-bridge DC-DC converter is equivalent to a primary full-bridge controlled voltage source, an isolation transformer and a secondary full-bridge controlled voltage source, wherein the voltages of the primary full-bridge controlled voltage source and the secondary full-bridge controlled voltage source are the alternating current output voltages of the primary full-bridge and the secondary full-bridge respectively;
and (2) equating a direct current port at the output side of the double-active full-bridge DC-DC converter to be an output controlled current source, wherein the current of the output controlled current source is the output current of the double-active full-bridge DC-DC converter.
Further, the equivalently decoupling the dual-active full-bridge DC-DC converter in any sub-module of the modular combined direct current transformer based on the first decoupling equivalent model to obtain a second decoupling equivalent model further comprises,
determining the current of the input controlled current source, the voltage of the primary full-bridge controlled voltage source, the voltage of the secondary full-bridge controlled voltage source and the current of the output controlled current source in any second decoupling equivalent model based on three working states of the primary full-bridge and the secondary full-bridge of the double-active full-bridge DC-DC converter under single-phase shift control; wherein the content of the first and second substances,
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S11And S14Conducting and switching tube S12And S13When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (1):
Figure BDA0002484211630000041
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S12And S13Conducting and switching tube S11And S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (2):
Figure BDA0002484211630000042
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S11～S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (3):
Figure BDA0002484211630000051
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefdRepresenting the conduction voltage drop of the diode, iLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S15And S18Conducting and switching tube S16And S17When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (4):
Figure BDA0002484211630000052
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S16And S17Conducting and switching tube S15And S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (5):
Figure BDA0002484211630000053
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S15～S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (6):
Figure BDA0002484211630000061
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefdRepresenting the conduction voltage drop of the diode, iLiTo representAnd the inductance current of the primary side full bridge of the ith sub-module is n, and the transformation ratio of the isolation transformer is represented.
Further, based on the formulas (1) - (6), I in the ith sub-modulepi、Uabi、UcdiAnd IsiSatisfies the following conditions:
Figure BDA0002484211630000062
or the like, or, alternatively,
Figure BDA0002484211630000063
wherein S is11-S18The switching signals of the switching tubes in the ith sub-module are represented; u shapeabiAnd UcdiAlternating current output voltages of a primary side full bridge and a secondary side full bridge of the isolation transformer are respectively; i.e. iLiRepresents the inductor current of the ith module; u shapeiniAnd UoiRespectively representing the input voltage and the output voltage of the ith module; u shapefgAnd UfdRespectively representing the conduction voltage drops of the switch tube and the diode; i ispiAnd IsiRespectively representing the input current and the output current of the ith sub-module; n represents the transformation ratio of the isolation transformer; sign represents a sign function and a V-shaped represents a logic or gate.
Another objective of the present invention is to provide a dc transformer simulation modeling system based on ac/dc decoupling, which includes a first decoupling equivalent model, a second decoupling equivalent model, and a modular combined dc transformer fast equivalent model, wherein,
the first decoupling equivalent model comprises an input side model and an output side model of a neutron module of the modular combined direct-current transformer;
the second decoupling equivalent model comprises a double-active full-bridge DC-DC converter input side direct current port model, an intermediate alternating current link model and an output side direct current port model in any submodule of the modular combined direct current transformer;
the modular combined type direct current transformer rapid equivalent model is an equivalent model formed by combining one or more module sets composed of sub-modules based on a first decoupling equivalent model and a second decoupling equivalent model.
Further, an input side model and an output side model of the neutron module of the modular combined direct current transformer are equivalently decoupled based on the connection mode of the input side and the output side of the modular combined direct current transformer; wherein the content of the first and second substances,
when the input side of the modular combined direct current transformer is a serial connection port:
the input side currents of each submodule are equal, and the input side of each submodule is equivalent to a controlled current source; wherein the current value of the controlled current source is the input current I of the power supply side of the modularized combined direct current transformerinEach series sub-module in the modular combined dc transformer is equivalent to a controlled voltage source, and the voltage value of the controlled voltage source is the sum U of the input side voltages of each sub-modulein；
When the output side of the modularized combined direct current transformer is a parallel connection port:
the output side voltages of the sub-modules are equal, and the output side of each sub-module is equivalent to a controlled voltage source; wherein the voltage value of the controlled voltage source is the output voltage U of the modularized combined type direct current transformero(ii) a Each parallel sub-module in the modular combined direct current transformer is equivalent to a controlled current source, and the current value of the controlled current source is the sum I of the currents at the output sides of the sub-moduleso；
The sum U of the input side voltages of the submodulesinAnd sum of output side current IoThe following relation is satisfied:
Figure BDA0002484211630000071
wherein M is the total number of any module centralized sub-modules in the modularized combined direct current transformer, i belongs to M and UiniRepresents the ith sub-moduleVoltage value of input side, IoiIndicating the current value at the output side of the i-th sub-module.
Further, the air conditioner is provided with a fan,
the double-active full-bridge DC-DC converter input side direct current port model is that the double-active full-bridge DC-DC converter input side direct current port is equivalent to an input controlled current source, and the current of the input controlled current source is the input current of the double-active full-bridge DC-DC converter;
the intermediate alternating current link model of the double-active full-bridge DC-DC converter is characterized in that the intermediate alternating current link of the double-active full-bridge DC-DC converter is equivalent to a primary full-bridge controlled voltage source, an isolation transformer and a secondary full-bridge controlled voltage source, wherein the voltage values of the primary full-bridge controlled voltage source and the secondary full-bridge controlled voltage source are the alternating current output voltages of the primary full-bridge and the secondary full-bridge respectively;
the output side direct current port model of the double-active full-bridge DC-DC converter is that the output side direct current port of the double-active full-bridge DC-DC converter is equivalent to an output controlled current source, and the current of the output controlled current source is the output current of the double-active full-bridge DC-DC converter.
Further, the system also comprises a parameter obtaining model for obtaining the current of the input controlled current source, the voltage of the primary side full-bridge controlled voltage source, the voltage of the secondary side full-bridge controlled voltage source and the current of the output controlled current source in the input side direct current port model, the intermediate alternating current link model and the output side direct current port model of the double-active full-bridge DC-DC converter based on three working states of the primary side full-bridge and the secondary side full-bridge of the double-active full-bridge DC-DC converter under single-phase shift control, wherein,
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S11And S14Conducting and switching tube S12And S13When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (1):
Figure BDA0002484211630000081
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S12And S13Conducting and switching tube S11And S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (2):
Figure BDA0002484211630000091
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S11～S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (3):
Figure BDA0002484211630000092
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefdRepresenting the conduction voltage drop of the diode, iLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S15And S18Conducting and switching tube S16And S17When the double-active full-bridge DC-DC converter is turned off, the alternating current output voltage U of the double-active full-bridge DC-DC convertercdiAnd an input side current IsiSatisfies formula (4):
Figure BDA0002484211630000093
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S16And S17Conducting and switching tube S15And S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (5):
Figure BDA0002484211630000094
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S15～S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (6):
Figure BDA0002484211630000101
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefdIndicating the on-voltage of the diodeDecrease, iLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
i in the ith sub-module based on the formulas (1) - (6)pi、Uabi、UcdiAnd IsiSatisfies the following conditions:
Figure BDA0002484211630000102
or the like, or, alternatively,
Figure BDA0002484211630000103
wherein S is11-S18The switching signals of the switching tubes in the ith sub-module are represented; u shapeabiAnd UcdiAlternating current output voltages of a primary side full bridge and a secondary side full bridge of the isolation transformer are respectively; i.e. iLiRepresents the inductor current of the ith module; u shapeiniAnd UoiRespectively representing the input voltage and the output voltage of the ith module; u shapefgAnd UfdRespectively representing the conduction voltage drops of the switch tube and the diode; i ispiAnd IsiRespectively representing the input current and the output current of the ith sub-module; n represents the transformation ratio of the isolation transformer; sign represents a sign function and a V-shaped represents a logic or gate.
The invention has the beneficial effects that:
1. the rapid equivalent model decomposes all high-order admittance matrixes in the detailed model of the original modular combined direct-current transformer into low-order subsystems, so that the simulation speed is accelerated by solving the low-order matrixes simultaneously, and the modeling method is suitable for establishing rapid equivalent modeling for large-scale modular combined direct-current transformers in any high-voltage large-capacity occasions and has strong universality.
2. Aiming at a modular combined direct current transformer taking a double-active full-bridge DC-DC converter as a basic power unit, each submodule in the direct current transformer is decomposed into a corresponding number of alternating current and direct current ports by an alternating current and direct current decoupling and node equivalence method, so that the simulation efficiency can be greatly improved while the simulation precision is ensured.
3. The three parts of the double-active full-bridge DC-DC converter after decoupling are not electrically connected any more, secondary information is transmitted only through a controlled source (a controlled current source or a controlled voltage source), all switching devices are omitted, simultaneously, the method is equivalent to reducing the admittance matrix of the node network again to improve the simulation speed, and all characteristics of an original detailed model can be effectively reserved, such as voltage and current characteristics of an alternating-current link, loss characteristics of a transformer and the switching devices and the like.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 shows a topological structure diagram of a modular combined dc transformer according to an embodiment of the present invention;
FIG. 2 shows an equivalent decoupling schematic diagram of a series-parallel sub-module in the embodiment of the present invention;
FIG. 3 shows an equivalent model of a dual-active full-bridge DC-DC converter in an embodiment of the present invention;
fig. 4 shows a fast equivalent model of a modular combined dc transformer according to an embodiment of the present invention;
FIG. 5 shows the voltage U of the MVDC port of the rapid equivalent model FEM of the modular combined DC transformer and the detailed model DM of the conventional modular combined DC transformer in the start-up phase according to the embodiment of the present inventionMVComparing the simulation waveform with a schematic diagram;
FIG. 6 shows a primary side full bridge AC output voltage U of the fast equivalent model FEM of the modular combined DC transformer and the detailed model DM of the conventional modular combined DC transformer in the start-up phase according to the embodiment of the present inventionab1Inductor current iL1And secondary side full bridge AC output voltage Ucd1A simulation comparison schematic diagram;
FIG. 7 shows a primary side full bridge AC output voltage U of the steady-state stage modular combined DC transformer rapid equivalent model FEM and the conventional modular combined DC transformer detailed model DM in the embodiment of the present inventionab1Inductor current iL1And secondary side full bridge AC output voltage Ucd1A simulation comparison schematic diagram;
fig. 8 shows a trend diagram of the operating time of the modular combined dc transformer fast equivalent model FEM and the conventional modular combined dc transformer detailed model DM according to the embodiment of the present invention as a function of the number of sub-modules.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 some, but not all, embodiments of the present invention. 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.
The implementation of the invention introduces a direct current transformer simulation modeling method based on alternating current-direct current decoupling, which is characterized by comprising the following steps of firstly, carrying out equivalent decoupling on the input side and the output side of each submodule of a combined direct current transformer based on the connection mode of the input side and the output side of each submodule in the combined direct current transformer to obtain a first decoupling equivalent model; then, based on the first decoupling equivalent model, performing equivalent decoupling on a double-active full-bridge DC-DC converter in any sub-module of the modular combined direct current transformer to obtain a second decoupling equivalent model; and finally, combining one or more module sets composed of all sub-modules based on the first decoupling equivalent model and the second decoupling equivalent model to obtain a modular combined direct-current transformer rapid equivalent model. The fast equivalent model FEM (model built according to an electromagnetic transient modeling algorithm) decomposes all high-order admittance matrixes in a detailed model DM (model built by a switching device) of an original modularized combined type direct current transformer into low-order subsystems, so that the low-order matrixes are solved simultaneously, the simulation speed is accelerated, and the modeling method is suitable for fast equivalent modeling of large-scale modularized combined type direct current transformers in any high-voltage large-capacity occasions and has strong universality.
Illustratively, a DAB (Dual Active Bridge) type modular combined direct current transformer using the Dual Active full-Bridge DC-DC converter shown in fig. 1 as a basic power unit is exemplified.
The structure of the DAB type modularized combined dc transformer shown in fig. 1 includes 1-N DAB module sets, N is greater than or equal to 1, that is, DAB module set 1, DAB module set 2, … … and DAB module set N in fig. 1. Because all the DAB module sets are connected in series by input and output, the equivalent decoupling methods at the two ends of all the DAB module sets are consistent. A DAB module set internally comprises a plurality of DAB modules, namely a DAB module 1, a DAB module 2, … … and a DAB module M (also called DAB #1 and DAB #2 … … DAB # M), wherein M is more than or equal to 1. The input side of the DAB type modularized combined Direct Current transformer is an HVDC (High Voltage Direct Current) port, and the Voltage of the port is UHVThe output side is MVDC (medium voltage direct current) port, and the voltage of the port is UMV. Now, only one DAB module with an internal input series output parallel connection of a DAB module set is taken as an example for analysis, and the specific equivalent decoupling method is as follows:
equivalently decoupling the input side of the DAB module: because the input sides of all the DAB modules in the DAB module set are connected in series and the input currents of all the DAB modules are equal, the input sides of all the DAB modules can be equivalent to a controlled current source, and the current value of each controlled current source is the input current of the power supply sideIin(ii) a Viewed from the input side of the DAB module set, each series-connected DAB module can be equivalent to a controlled voltage source, and the voltage value of the controlled voltage source is the sum U of the input side terminal voltages of each DAB moduleinAs shown in fig. 2.
Equivalently decoupling the output side of the DAB module: because the output sides of all the DAB modules are connected in parallel, the output voltages of all the DAB modules are equal, so that the output sides of all the DAB modules can be equivalent to a controlled voltage source, and the voltage value of each controlled voltage source is the output voltage Uo(ii) a Viewed from the output side of the DAB module set, each DAB module connected in parallel can be equivalent to a controlled current source, and the current value of the controlled current source is the sum I of the currents on the output sides of the DAB modulesoAs shown in fig. 2.
Specifically, as shown in fig. 2, in the DAB module set 1, the input side currents of DAB #1 to DAB # M are all IinThe voltages at the input sides of DAB #1-DAB # M are Uin1-UinM。
The voltages at the output sides of DAB #1-DAB # M are all UoThe currents at the output sides of DAB #1-DAB # M are Io1-IoM,. Furthermore, the sum U of the voltages of the concentrated input terminals of any DAB moduleinAnd sum of output side current IoThe requirements are met,
Figure BDA0002484211630000141
wherein M is the total number of any DAB module in the DAB module set, i belongs to M and UiniIndicating the voltage value at the input side of the ith DAB module, IoiIndicating the current value at the output side of the ith DAB module.
By decoupling the input side and the output side of the DAB module set, the electrical decoupling among the DAB modules in the modular combined direct current transformer can be realized, and the transmission of secondary information among ports is ensured, so that the decoupled model has the same simulation precision as the original detailed model.
In this embodiment, the dual-active full-bridge DC-DC converter in any DAB module in the combined DC transformer is subjected to equivalent decoupling modeling, because the dual-active full-bridge DC-DC converter has a completely symmetrical topology structure, the support capacitors at the input side and the output side of the dual-active full-bridge DC-DC converter respectively form two DC ports, and the two H bridges (the primary full-bridge and the secondary full-bridge), together with the auxiliary inductor and the isolation transformer, form an intermediate ac link to transfer energy, thereby equivalently decoupling the dual-active full-bridge DC-DC converter into three parts including the input side DC port, the intermediate ac link, and the output side DC port. As shown in fig. 3, the dual-active full-bridge DC-DC converter in the DAB module 1 in the DAB module set is used for exemplary illustration, but the invention is not limited to the DAB module 1, and any other DAB module is applicable.
The direct current port at the input side of the double-active full-bridge DC-DC converter is equivalent to an input controlled current source with the current Ip1；
The middle alternating current link of the double-active full-bridge DC-DC converter is equivalent to a primary full-bridge controlled voltage source, an isolation transformer and a secondary full-bridge controlled voltage source, wherein the voltage values of the primary full-bridge controlled voltage source and the secondary full-bridge controlled voltage source are the alternating current output voltage U of the primary full-bridge and the secondary full-bridge respectivelyab1And Ucd1；
The direct current port at the output side of the double-active full-bridge DC-DC converter is equivalent to an output controlled current source with the current Is1。
Compared with the existing modular combined direct current transformer average value model, discrete time model and the like, the modeling method in the embodiment of the invention not only omits all switching devices, but also equivalently reduces the admittance matrix of the node network again to improve the simulation speed, and can effectively retain all characteristics of the original detailed model, such as the voltage and current characteristics of an alternating current link, the loss characteristics of the transformer and the switching devices and the like.
In this embodiment, I also needs to be determinedp1、Uab1、Ucd1And Is1Wherein Ip1、Uab1、Ucd1And Is1Value of (2)In relation to the operation state of each H-bridge of the dual-active full-bridge DC-DC converter under the single-phase-shift control, specifically, each H-bridge includes three operation states. Taking the primary side full bridge of the dual-active full bridge DC-DC converter in the DAB module 1 in FIG. 1 as an example, the working states are respectively the switch tube S11And S14Conducting and switching tube S12And S13Switch-off and switch tube S12And S13Conducting and switching tube S11And S14Switch-off and switch tube S11～S14Are off, i.e., latched. In each operating state, the relationship between the voltage and the current on the alternating current side and the relationship between the voltage and the current on the direct current side of the converter are different, specifically:
in the primary side full bridge of the double-active full bridge DC-DC converter, the switch tube S11And S14Conducting and switching tube S12And S13When the power is turned off, the voltage U of the primary side full-bridge controlled voltage sourceab1And a current I input to the controlled current sourcep1Satisfies the following conditions:
Figure BDA0002484211630000151
wherein, Uin1Representing the voltage value, U, at the input side of the DAB module 1fgIs the voltage drop on the switch tubes from S11 to S18, UfdIs the voltage drop across the diode connected in anti-parallel with S11-S18, iL1The output current of the primary side full bridge in the dual active full bridge DC-DC converter in the DAB module 1 is shown.
In the primary side full bridge of the double-active full bridge DC-DC converter, the switch tube S12And S13Conducting and switching tube S11And S14When the power is turned off, the voltage U of the primary side full-bridge controlled voltage sourceab1And a current I input to the controlled current sourcep1Satisfies the following conditions:
Figure BDA0002484211630000161
Uin1representing the voltage value, U, at the input side of the DAB module 1fgIs the voltage drop on the switch tubes from S11 to S18,Ufdis the voltage drop across the diode connected in anti-parallel with S11-S18, iL1The output current of the primary side full bridge in the dual active full bridge DC-DC converter in the DAB module 1 is shown.
In the primary side full bridge of the double-active full bridge DC-DC converter, the switch tube S11～S14When the power is turned off, the voltage U of the primary side full-bridge controlled voltage sourceab1And a current I input to the controlled current sourcep1Satisfies the following conditions:
Figure BDA0002484211630000162
wherein, Uin1Representing the voltage value, U, at the input side of the DAB module 1fdIs the voltage drop across the diode connected in anti-parallel with S11-S18, iL1The method comprises the steps of representing output current of a primary full bridge in a double-active full bridge DC-DC converter in a DAB module 1;
similarly, the ac side voltage to current and the DC side voltage to current of the secondary side full bridge (H-bridge) of the dual active full bridge DC-DC converter are as follows:
in the secondary side full bridge of the double-active full bridge DC-DC converter, the switch tube S15And S18Conducting and switching tube S16And S17When the circuit is turned off, the voltage U of the secondary side full-bridge controlled voltage sourcecd1And outputting the current I of the controlled current sources1Satisfies the following conditions:
Figure BDA0002484211630000163
wherein, Uo1Representing the voltage value, U, at the output side of the DAB module 1fgIs the voltage drop on the switch tubes from S11 to S18, UfdIs the voltage drop across the diode connected in anti-parallel with S11-S18, iL1The method comprises the steps that the inductive current of a primary side full bridge in a double-active full bridge DC-DC converter in a DAB module 1 is shown, and n represents the transformation ratio of an isolation transformer;
in the secondary side full bridge of the double-active full bridge DC-DC converter, the switch tube S16And S17Conducting and switching tube S15And S18When the circuit is turned off, the voltage U of the secondary side full-bridge controlled voltage sourcecd1And outputting the current I of the controlled current sources1Satisfies the following conditions:
Figure BDA0002484211630000171
wherein, Uo1Representing the voltage value, U, at the output side of the DAB module 1fgIs the voltage drop on the switch tubes from S11 to S18, UfdIs the voltage drop across the diode connected in anti-parallel with S11-S18, iL1The method comprises the steps that the inductive current of a primary side full bridge in a double-active full bridge DC-DC converter in a DAB module 1 is shown, and n represents the transformation ratio of an isolation transformer;
in the secondary side full bridge of the double-active full bridge DC-DC converter, the switch tube S15～S18When the circuit is turned off, the voltage U of the secondary side full-bridge controlled voltage sourcecd1And outputting the current I of the controlled current sources1Satisfies the following conditions:
Figure BDA0002484211630000172
wherein, Uo1Representing the voltage value, U, at the output side of the DAB module 1fdIs the voltage drop across the diode connected in anti-parallel with S11-S18, iL1The inductance current of a primary side full bridge in a double-active full bridge DC-DC converter in the DAB module 1 is shown, and n represents the transformation ratio of an isolation transformer.
Based on the relation between the alternating-current side voltage and current and the direct-current side voltage and current of the primary full bridge and the secondary full bridge of the double-active full-bridge DC-DC converter, I in the second decoupling equivalent modelp1、Uab1、Ucd1And Is1The parameter values of (A) satisfy:
Figure BDA0002484211630000173
or the like, or, alternatively,
Figure BDA0002484211630000174
wherein S is11-S18A switching signal representing a switching tube in the DAB module 1; u shapeab1And Ucd1The AC output voltages of the H bridges on the two sides of the isolation transformer are respectively; i.e. iL1Represents the inductor current in the DAB module 1; u shapein1And Uo1Respectively representing the input voltage and the output voltage in the DAB module 1; u shapefgAnd UfdRespectively representing the conduction voltage drops of the switch tube and the diode; i isp1And Is1Respectively representing the input current and the output current in the DAB module 1; n represents the transformation ratio of the transformer; sign represents a sign function and a V-shaped represents a logic or gate.
Preferably, the input sides of the DAB module sets in the DAB type modular combined dc transformer are also connected in series, and the output sides are also connected in parallel.
In addition, under the single-phase shift operating module, the double-active full-bridge DC-DC converter in any submodule has only three states in one cycle, wherein the on and off timings of S11 and S14 are consistent, the on and off timings of S12 and S13 are consistent, namely the on and off timings of S15 and S18 are consistent, and the on and off timings of S16 and S17 are consistent, so that only one switch in the two switches is required to be selected for representation in the primary full-bridge and the secondary full-bridge.
By combining the equivalent decoupling methods shown in fig. 2 and fig. 3, all the DAB module sets and DAB modules in the DAB module sets are equivalently decoupled, and the modular combined dc transformer shown in fig. 1 can be completely decomposed into low-order subsystems, so that only the low-order matrix needs to be solved simultaneously, and the simulation speed is increased. The final fast equivalent model of the high-voltage high-capacity modular combined type dc transformer is shown in fig. 4.
As can be seen from fig. 5, after the DAB type modular combined dc transformer is started, the medium voltage side voltage reaches the given value of 40kV for about 0.05s, and the fast equivalent model FEM of the DAB type modular combined dc transformer can accurately and equivalently obtain the average value of the detailed model DM, and the voltage ripples of the two models almost completely coincide (the two curves in the figure coincide), and the harmonic characteristics are completely consistent. Therefore, the fast equivalent model is only the segmentation and equivalence of the nodes of the electrical network, and the order of the fast equivalent model is not reduced compared with the original detailed model, so that the fast equivalent model has very high accuracy.
As shown in fig. 6, 0.03s after the DAB type modular dc transformer is started, the controller operates to start outputting the control pulse, and the primary side full bridge ac output voltage U is exemplified by the DAB module 1ab1Under the action of (i), the inductive current iL1Starting to charge the capacitor in the secondary side full bridge, and outputting the voltage Ucd1Starts to increase and all three have very high coincidence with the corresponding parameters in the DM detailed model.
As shown in fig. 7, the DAB type modular combined dc transformer takes the DAB module 1 as an example, and its primary side full-bridge ac output voltage U is in the steady stateab1Inductor current iL1And secondary side full bridge AC output voltage Ucd1The model has very high coincidence degree with corresponding parameters in the DM detailed model, so that the rapid equivalent model of the DAB type modularized combined direct-current transformer has higher precision.
As shown in fig. 8, when the number of DAB modules of the DAB-type modular combined dc transformer is 200, the calculation efficiency of the fast equivalent model FEM is two orders of magnitude higher than that of the DM detailed model, and the actual speed-up multiple reaches 270 times. With the increase of the number of direct current transformer sub-modules (DAB models), the simulation time of the detailed model increases exponentially, while the simulation time of the fast equivalent model increases linearly, so that the speed-up multiple also increases exponentially.
The invention takes the interconnection of direct current systems as an application background, and aims at a modular combined direct current transformer taking a double-active full-bridge DC-DC converter as a basic power unit, and decomposes each submodule in the direct current transformer into a corresponding number of alternating current and direct current ports by an alternating current and direct current decoupling and node equivalence method, thereby greatly improving the simulation efficiency while ensuring the simulation precision. The rapid equivalent modeling method of the large-scale modular combined direct-current transformer suitable for the high-voltage large-capacity occasions provided by the embodiment of the invention has extremely high simulation precision under various operating conditions. Meanwhile, compared with the original detailed model, the simulation efficiency of the rapid equivalent model can be 1-2 orders of magnitude higher. In addition, the method is simultaneously suitable for the control and real-time digital simulation of series-parallel combined converters of other topological types, and has strong practicability.
The embodiment of the invention also discloses a direct current transformer simulation modeling system based on alternating current-direct current decoupling, which can execute the modeling method, wherein the system comprises a first decoupling equivalent model, a second decoupling equivalent model and a modular combined direct current transformer rapid equivalent model, wherein the first decoupling equivalent model comprises an input side model and an output side model of a submodule of the modular combined direct current transformer; the second decoupling equivalent model comprises a double-active full-bridge DC-DC converter input side direct current port model, an intermediate alternating current link model and an output side direct current port model in any submodule of the modular combined direct current transformer; the modular combined type direct current transformer rapid equivalent model is an equivalent model formed by combining one or more module sets composed of sub-modules based on a first decoupling equivalent model and a second decoupling equivalent model.
The input side model and the output side model of the neutron module of the modular combined direct-current transformer are equivalently decoupled based on the connection mode of the input side and the output side of the modular combined direct-current transformer; wherein the content of the first and second substances,
when the input side of the modular combined direct current transformer is a serial connection port:
the input side currents of each submodule are equal, and the input side of each submodule is equivalent to a controlled current source; wherein the current value of the controlled current source is the input current I of the power supply side of the modularized combined direct current transformerinEach series sub-module in the modular combined dc transformer is equivalent to a controlled voltage source, and the voltage value of the controlled voltage source is the sum U of the input side voltages of each sub-modulein；
When the output side of the modularized combined direct current transformer is a parallel connection port:
output side voltage of each submoduleThe output sides of the submodules are equivalent to a controlled voltage source; wherein the voltage value of the controlled voltage source is the output voltage U of the modularized combined type direct current transformero(ii) a Each parallel sub-module in the modular combined direct current transformer is equivalent to a controlled current source, and the current value of the controlled current source is the sum I of the currents at the output sides of the sub-moduleso；
The sum U of the input side voltages of the submodulesinAnd sum of output side current IoThe following relation is satisfied:
Figure BDA0002484211630000201
wherein M is the total number of any module centralized sub-modules in the modularized combined direct current transformer, i belongs to M and UiniRepresents the voltage value at the input side of the ith sub-module, IoiIndicating the current value at the output side of the i-th sub-module.
The double-active full-bridge DC-DC converter input side direct current port model is that the double-active full-bridge DC-DC converter input side direct current port is equivalent to an input controlled current source, and the current of the input controlled current source is the input current of the double-active full-bridge DC-DC converter;
the intermediate alternating current link model of the double-active full-bridge DC-DC converter is characterized in that the intermediate alternating current link of the double-active full-bridge DC-DC converter is equivalent to a primary full-bridge controlled voltage source, an isolation transformer and a secondary full-bridge controlled voltage source, wherein the voltage values of the primary full-bridge controlled voltage source and the secondary full-bridge controlled voltage source are the alternating current output voltages of the primary full-bridge and the secondary full-bridge respectively;
the output side direct current port model of the double-active full-bridge DC-DC converter is that the output side direct current port of the double-active full-bridge DC-DC converter is equivalent to an output controlled current source, and the current of the output controlled current source is the output current of the double-active full-bridge DC-DC converter.
The system also comprises a parameter acquisition model for acquiring the current of the input controlled current source, the voltage of the primary side full-bridge controlled voltage source, the voltage of the secondary side full-bridge controlled voltage source and the current of the output controlled current source in the input side direct current port model, the intermediate alternating current link model and the output side direct current port model of the double-active full-bridge DC-DC converter based on the relation between the alternating current side voltage and the current and the relation between the direct current side voltage and the current of the primary side full-bridge and the secondary side full-bridge under the single-phase shift control of the double-active full-bridge DC-DC converter,
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, a switching tube S11And S14Conducting and switching tube S12And S13When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (1):
Figure BDA0002484211630000211
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgIs a conduction voltage drop on the switching tubes from S11 to S18, UfdIs the conduction voltage drop across the diode connected in anti-parallel with S11-S18, iLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, a switching tube S12And S13Conducting and switching tube S11And S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (2):
Figure BDA0002484211630000212
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgIs a conduction voltage drop on the switching tubes from S11 to S18, UfdIs the conduction voltage drop across the diode connected in anti-parallel with S11-S18, iLiRepresents the ith submodeThe inductance current of a block primary side full bridge;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, a switching tube S11～S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (3):
Figure BDA0002484211630000221
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefdIs the conduction voltage drop across the diode connected in anti-parallel with S11-S18, iLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, a switching tube S15And S18Conducting and switching tube S16And S17When the double-active full-bridge DC-DC converter is turned off, the alternating current output voltage U of the double-active full-bridge DC-DC convertercdiAnd an input side current IsiSatisfies formula (4):
Figure BDA0002484211630000222
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgIs a conduction voltage drop on the switching tubes from S11 to S18, UfdIs the conduction voltage drop across the diode connected in anti-parallel with S11-S18, iLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, a switching tube S16And S17Conducting and switching tube S15And S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (5):
Figure BDA0002484211630000223
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefgIs a conduction voltage drop on the switching tubes from S11 to S18, UfdIs the conduction voltage drop across the diode connected in anti-parallel with S11-S18, iLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, a switching tube S15～S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (6):
Figure BDA0002484211630000231
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefdIs the conduction voltage drop across the diode connected in anti-parallel with S11-S18, iLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
i in the ith sub-module based on the formulas (1) - (6)pi、Uabi、UcdiAnd IsiSatisfies the following conditions:
Figure BDA0002484211630000232
or the like, or, alternatively,
Figure BDA0002484211630000233
wherein S is11-S18The switching signals of the switching tubes in the ith sub-module are represented; u shapeabiAnd UcdiThe AC output voltages of the H bridges on the two sides of the isolation transformer are respectively; i.e. iLiRepresents the inductor current of the ith module; u shapeiniAnd UoiRespectively representing the input voltage and the output voltage of the ith module; u shapefgIs the voltage drop on the switch tubes from S11 to S18, UfdIs the conduction voltage drop across the diodes connected in anti-parallel with S11-S18; i ispiAnd IsiRespectively representing the input current and the output current of the ith sub-module; n represents the transformation ratio of the isolation transformer; sign represents a sign function and a V-shaped represents a logic or gate.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (10)

1. A simulation modeling method of a direct current transformer based on alternating current-direct current decoupling is characterized by comprising the following steps,
performing equivalent decoupling on the input side and the output side of each submodule of the modular combined direct-current transformer based on the connection mode of the input side and the output side of each submodule in the modular combined direct-current transformer to obtain a first decoupling equivalent model;
performing equivalent decoupling on a double-active full-bridge DC-DC converter in any sub-module of the modular combined direct-current transformer based on the first decoupling equivalent model to obtain a second decoupling equivalent model;
and combining one or more module sets composed of all sub-modules based on the first decoupling equivalent model and the second decoupling equivalent model to obtain a modular combined direct-current transformer rapid equivalent model.
2. The AC-DC decoupling-based DC transformer simulation modeling method according to claim 1, wherein the equivalent decoupling of the input side and the output side of each submodule of the modular combined DC transformer based on the connection mode of the input side and the output side of each submodule in the modular combined DC transformer comprises the steps of,
when the input side of each submodule in the modular combined direct current transformer is a serial connection port:
the input side currents of the submodules are equal, and the input sides of the submodules are equivalent to a controlled current source; wherein the current value of each controlled current source is the input current I of the power supply side of the modular combined direct current transformerin；
Each series sub-module in the modular combined direct current transformer is equivalent to a controlled voltage source, and the voltage value of the controlled voltage source is the sum U of the input side voltages of each sub-modulein；
When the output side of each submodule in the modularized combined direct current transformer is a parallel connection port:
the output side voltages of the sub-modules are equal, and the output side of each sub-module is equivalent to a controlled voltage source; wherein the voltage value of the controlled voltage source is the output voltage U of the modularized combined type direct current transformero；
Each parallel sub-module in the modular combined direct current transformer is equivalent to a controlled current source, and the current value of the controlled current source is the sum I of the currents at the output sides of the sub-moduleso。
3. The AC-DC decoupling-based DC transformer simulation modeling method according to claim 2,
the sum U of the input side voltages of the submodulesinAnd sum of output side current IoThe following relation is satisfied:
Figure FDA0002484211620000021
wherein M is the total number of any module centralized sub-modules in the modularized combined direct current transformer, i belongs to M and UiniRepresents the voltage value at the input side of the ith sub-module, IoiIndicating the current value at the output side of the i-th sub-module.
4. The AC-DC decoupling-based direct current transformer simulation modeling method according to claim 2, wherein the step of equivalently decoupling the dual-active full-bridge DC-DC converter in any sub-module of the modular combined direct current transformer based on the first decoupling equivalent model to obtain a second decoupling equivalent model comprises the steps of,
equivalently decoupling the dual-active full-bridge DC-DC converter into three parts comprises: an input side dc port, an intermediate ac link, and an output side dc port, wherein,
the method comprises the steps that a direct current port on the input side of a double-active full-bridge DC-DC converter is equivalent to an input controlled current source, and the current of the input controlled current source is the input current of the double-active full-bridge DC-DC converter;
the method comprises the steps that an intermediate alternating current link of a double-active full-bridge DC-DC converter is equivalent to a primary full-bridge controlled voltage source, an isolation transformer and a secondary full-bridge controlled voltage source, wherein the voltages of the primary full-bridge controlled voltage source and the secondary full-bridge controlled voltage source are the alternating current output voltages of the primary full-bridge and the secondary full-bridge respectively;
and (2) equating a direct current port at the output side of the double-active full-bridge DC-DC converter to be an output controlled current source, wherein the current of the output controlled current source is the output current of the double-active full-bridge DC-DC converter.
5. The AC-DC decoupling-based direct current transformer simulation modeling method according to claim 4, wherein the equivalent decoupling of the dual-active full-bridge DC-DC converter in any sub-module of the modular combined direct current transformer based on the first decoupling equivalent model to obtain a second decoupling equivalent model further comprises,
determining the current of the input controlled current source, the voltage of the primary full-bridge controlled voltage source, the voltage of the secondary full-bridge controlled voltage source and the current of the output controlled current source in any second decoupling equivalent model based on three working states of the primary full-bridge and the secondary full-bridge of the double-active full-bridge DC-DC converter under single-phase shift control; wherein the content of the first and second substances,
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S11And S14Conducting and switching tube S12And S13When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (1):
Figure FDA0002484211620000031
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S12And S13Conducting and switching tube S11And S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (2):
Figure FDA0002484211620000032
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S11～S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (3):
Figure FDA0002484211620000033
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefdRepresenting the conduction voltage drop of the diode, iLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S15And S18Conducting and switching tube S16And S17When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (4):
Figure FDA0002484211620000041
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S16And S17Conducting and switching tube S15And S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (5):
Figure FDA0002484211620000042
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
dual active in ith sub-moduleIn the secondary side full bridge of the full bridge DC-DC converter, the working state is the switch tube S15～S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (6):
Figure FDA0002484211620000043
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefdRepresenting the conduction voltage drop of the diode, iLiThe inductance current of the primary side full bridge of the ith sub-module is shown, and n represents the transformation ratio of the isolation transformer.
6. The AC-DC decoupling-based direct current transformer simulation modeling method according to claim 5, wherein I in the ith sub-module is determined based on the formulas (1) - (6)pi、Uabi、UcdiAnd IsiSatisfies the following conditions:
Figure FDA0002484211620000051
or the like, or, alternatively,
Figure FDA0002484211620000052
wherein S is11-S18The switching signals of the switching tubes in the ith sub-module are represented; u shapeabiAnd UcdiAlternating current output voltages of a primary side full bridge and a secondary side full bridge of the isolation transformer are respectively; i.e. iLiRepresents the inductor current of the ith module; u shapeiniAnd UoiRespectively representing the input voltage and the output voltage of the ith module; u shapefgAnd UfdRespectively representing the conduction voltage drops of the switch tube and the diode; i ispiAnd IsiRespectively representing the input current and the output current of the ith sub-module; n represents an isolation transformerThe transformation ratio of (a); sign represents a sign function and a V-shaped represents a logic or gate.
7. A direct current transformer simulation modeling system based on alternating current-direct current decoupling is characterized by comprising a first decoupling equivalent model, a second decoupling equivalent model and a modular combined direct current transformer rapid equivalent model, wherein,
the first decoupling equivalent model comprises an input side model and an output side model of a neutron module of the modular combined direct-current transformer;
the second decoupling equivalent model comprises a double-active full-bridge DC-DC converter input side direct current port model, an intermediate alternating current link model and an output side direct current port model in any submodule of the modular combined direct current transformer;
the modular combined type direct current transformer rapid equivalent model is an equivalent model formed by combining one or more module sets composed of sub-modules based on a first decoupling equivalent model and a second decoupling equivalent model.
8. The direct current transformer simulation modeling system based on alternating current-direct current decoupling as claimed in claim 7, wherein an input side model and an output side model of a submodule in the modular combined direct current transformer are equivalently decoupled based on a connection mode of the input side and the output side of the modular combined direct current transformer; wherein the content of the first and second substances,
when the input side of the modular combined direct current transformer is a serial connection port:
the input side currents of each submodule are equal, and the input side of each submodule is equivalent to a controlled current source; wherein the current value of the controlled current source is the input current I of the power supply side of the modularized combined direct current transformerinEach series sub-module in the modular combined dc transformer is equivalent to a controlled voltage source, and the voltage value of the controlled voltage source is the sum U of the input side voltages of each sub-modulein；
When the output side of the modularized combined direct current transformer is a parallel connection port:
the output side voltages of the sub-modules are equal, and the output side of each sub-module is equivalent to a controlled voltage source; wherein the voltage value of the controlled voltage source is the output voltage U of the modularized combined type direct current transformero(ii) a Each parallel sub-module in the modular combined direct current transformer is equivalent to a controlled current source, and the current value of the controlled current source is the sum I of the currents at the output sides of the sub-moduleso；
The sum U of the input side voltages of the submodulesinAnd sum of output side current IoThe following relation is satisfied:
Figure FDA0002484211620000061
wherein M is the total number of any module centralized sub-modules in the modularized combined direct current transformer, i belongs to M and UiniRepresents the voltage value at the input side of the ith sub-module, IoiIndicating the current value at the output side of the i-th sub-module.
9. The AC-DC decoupling based DC transformer simulation modeling system according to claim 7,
the double-active full-bridge DC-DC converter input side direct current port model is that the double-active full-bridge DC-DC converter input side direct current port is equivalent to an input controlled current source, and the current of the input controlled current source is the input current of the double-active full-bridge DC-DC converter;
the intermediate alternating current link model of the double-active full-bridge DC-DC converter is characterized in that the intermediate alternating current link of the double-active full-bridge DC-DC converter is equivalent to a primary full-bridge controlled voltage source, an isolation transformer and a secondary full-bridge controlled voltage source, wherein the voltage values of the primary full-bridge controlled voltage source and the secondary full-bridge controlled voltage source are the alternating current output voltages of the primary full-bridge and the secondary full-bridge respectively;
the output side direct current port model of the double-active full-bridge DC-DC converter is that the output side direct current port of the double-active full-bridge DC-DC converter is equivalent to an output controlled current source, and the current of the output controlled current source is the output current of the double-active full-bridge DC-DC converter.
10. The AC-DC decoupling-based DC transformer simulation modeling system according to claim 9, further comprising a parameter obtaining model for obtaining the current of the input controlled current source, the voltage of the primary side full-bridge controlled voltage source, the voltage of the secondary side full-bridge controlled voltage source and the current of the output controlled current source in the input side DC port model, the intermediate AC link model and the output side DC port model of the dual-active full-bridge DC-DC converter based on three operating states of the primary and secondary side full-bridges under single-phase shift control, wherein,
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S11And S14Conducting and switching tube S12And S13When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (1):
Figure FDA0002484211620000071
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S12And S13Conducting and switching tube S11And S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (2):
Figure FDA0002484211620000072
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the primary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is the switching tube S11～S14When the power is turned off, the voltage U of the original side full-bridge controlled voltage source in the ith sub-moduleabiAnd a current I input to the controlled current sourcepiSatisfies formula (3):
Figure FDA0002484211620000081
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefdRepresenting the conduction voltage drop of the diode, iLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S15And S18Conducting and switching tube S16And S17When the double-active full-bridge DC-DC converter is turned off, the alternating current output voltage U of the double-active full-bridge DC-DC convertercdiAnd an input side current IsiSatisfies formula (4):
Figure FDA0002484211620000082
wherein, UiniRepresenting the voltage value, U, at the input side of the i-th sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductive current of the primary side full bridge of the ith sub-module is represented;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S16And S17Conducting and switchingPipe S15And S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (5):
Figure FDA0002484211620000083
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefgAnd UfdRespectively representing the conduction voltage drops, i, of the switching tube and the diodeLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
in the secondary side full bridge of the double-active full bridge DC-DC converter in the ith sub-module, the working state is a switching tube S15～S18When the power supply is turned off, the voltage U of the secondary side full-bridge controlled voltage source in the ith sub-modulecdiAnd outputting the current I of the controlled current sourcesiSatisfies formula (6):
Figure FDA0002484211620000091
wherein, UoiRepresenting the voltage value, U, at the output side of the ith sub-modulefdRepresenting the conduction voltage drop of the diode, iLiThe inductance current of a primary side full bridge of the ith sub-module is represented, and n represents the transformation ratio of the isolation transformer;
i in the ith sub-module based on the formulas (1) - (6)pi、Uabi、UcdiAnd IsiSatisfies the following conditions:
Figure FDA0002484211620000092
or the like, or, alternatively,
Figure FDA0002484211620000093
wherein S is11-S18The switching signals of the switching tubes in the ith sub-module are represented; u shapeabiAnd UcdiAlternating current output voltages of a primary side full bridge and a secondary side full bridge of the isolation transformer are respectively; i.e. iLiRepresents the inductor current of the ith module; u shapeiniAnd UoiRespectively representing the input voltage and the output voltage of the ith module; u shapefgAnd UfdRespectively representing the conduction voltage drops of the switch tube and the diode; i ispiAnd IsiRespectively representing the input current and the output current of the ith sub-module; n represents the transformation ratio of the isolation transformer; sign represents a sign function and a V-shaped represents a logic or gate.
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