CN113346764A - Medium voltage converter topological structure based on high frequency magnetic coupling module - Google Patents

Medium voltage converter topological structure based on high frequency magnetic coupling module Download PDF

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CN113346764A
CN113346764A CN202110524475.0A CN202110524475A CN113346764A CN 113346764 A CN113346764 A CN 113346764A CN 202110524475 A CN202110524475 A CN 202110524475A CN 113346764 A CN113346764 A CN 113346764A
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phase
voltage
magnetic coupling
winding
converter
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杜思行
何思承
刘进军
张岩
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Xian Jiaotong University
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Xian Jiaotong 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
    • 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

Abstract

The invention discloses a medium-voltage converter topological structure based on a high-frequency magnetic coupling module, which comprises one or more magnetic coupling modules; the core circuit of the magnetic coupling module comprises a single-phase/multi-phase multi-winding high-frequency transformer, an LC resonance branch circuit connected with each winding in series and a single-phase/multi-phase square wave voltage source for supplying power to each winding; a direct current or alternating current interface circuit is additionally arranged at the direct current input end of the wave converter above each winding, so that a multi-port magnetic coupling sub-module capable of being packaged is formed; the plurality of magnetic coupling modules are formed by connecting a plurality of magnetic coupling modules of the same type or different types in series or in parallel through ports. The invention greatly reduces the volume and the weight of core passive elements such as a transformer, a capacitor and the like, effectively integrates power in different forms, and integrally solves the technical problems of power density, capacity and AC/DC multiport mixing.

Description

Medium voltage converter topological structure based on high frequency magnetic coupling module
Technical Field
The invention belongs to the technical field of power electronic electric energy conversion, and relates to a medium-voltage converter topological structure based on a high-frequency magnetic coupling module.
Background
The rapid development of new energy, smart grid and medium voltage motor dragging industries brings new challenges to the electric energy conversion technology, and the performance of core power equipment needs to be improved urgently. On one hand, the huge volume and weight of the medium-voltage motor dragging system bring a series of difficulties to the production, transportation, installation and maintenance of equipment, the reduction of the volume and weight of the medium-voltage motor dragging system is crucial to the development of the motor dragging technology, and the miniaturization and lightweight technology of the medium-voltage motor dragging system becomes the focus of attention in the industry. On the other hand, the new energy power generation and transmission equipment, especially offshore equipment, has high site cost, and provides extremely severe indexes in the aspects of miniaturization and light weight, and the high power density technology of the new energy power generation and transmission equipment becomes a hotspot and a difficulty of research. In addition, the smart grid and the new energy device also relate to the problem of high-low voltage, alternating current and direct current and single three-phase electric energy conversion in an alternating current and direct current hybrid power grid, new challenges are provided in the aspects of integrating various forms of electric energy and constructing various types of ports, and related technologies become difficult points of research. Therefore, the topological structure of the high-capacity, multi-port and high-power-density converter becomes a common key scientific problem in the fields of new energy, smart power grids and medium-voltage motor dragging.
In the field of medium-voltage motor drive, a medium-voltage motor drive converter which is mainly used for serially connecting an H bridge and an MMC has the excellent characteristics of low loss, low cost, high performance, high reliability and the like due to the modular structure. However, the energy fluctuation range of the sub-modules of the two modules is in reciprocal relation with the rotating speed of the motor, and a large electrolytic capacitor is required to be arranged to buffer excess energy fluctuation caused by low-speed and high-torque operation, so that the driving system is large in size and weight, and is accompanied with serious defects of short service life and the like. In addition, the series H bridge is additionally provided with an expensive phase-shifting transformer as a discrete power supply of a preceding stage rectifying circuit, and the device further increases the volume and the weight of the motor driving system. Therefore, the field of medium voltage motor drive urgently needs to develop a new generation of high power density medium voltage converter topology with smaller capacitance value and transformer size.
In the field of new energy and smart power grids, core power equipment of renewable electric energy capturing, storing and transmitting links such as alternating current-direct current converters and direct current-direct current converters is still in a primary development stage, and technical breakthroughs in the aspects of high power density, large capacity, alternating current-direct current multiport mixing and the like are urgently needed. The core carriers of the high power density technology are high-frequency transformers and soft switching technology, but the integrated mathematical analysis model and circuit construction theory based on the high-frequency transformers and the soft switching technology are still lacked. High-capacity technology relies on fully-controlled switching devices with high voltage and high current, however, the switching devices available in the market at present are still limited to withstand voltage and current. Although the switching devices connected in series or in parallel can significantly expand the capacity, serious dynamic and static voltage equalizing and current equalizing problems are caused. The AC/DC multiport mixing technology mainly integrates different forms of power in a mode of mixing modulation or bus coupling. However, mixing modulation multiplies the voltage and current stresses of the converter, and bus coupling complicates circuit design. Therefore, the new energy and smart grid field urgently need to develop a novel converter topology capable of uniformly solving the problems of high power density, large capacity and alternating current-direct current multi-port mixing.
Disclosure of Invention
Aiming at the technical problem of common core, the invention provides a medium-voltage converter topological structure based on a high-frequency magnetic coupling module. The medium-voltage high-power converter topology series based on the high-frequency magnetic coupling module aims to break through the technical bottleneck of the existing converter, greatly reduce the volume and weight of core passive elements such as a transformer and a capacitor and the like, effectively integrate different forms of power and integrally solve the technical problems in the aspects of power density, capacity and alternating current-direct current multi-port mixing.
In order to achieve the above object, the present invention provides the following technical solutions.
A medium voltage converter topological structure based on a high frequency magnetic coupling module comprises one or more magnetic coupling modules;
the core circuit of the magnetic coupling module comprises a single-phase/multi-phase multi-winding high-frequency transformer, an LC resonance branch circuit connected with each winding in series and a single-phase/multi-phase square wave voltage source for supplying power to each winding;
a direct current or alternating current interface circuit is additionally arranged at the direct current input end of the wave converter above each winding, so that a multi-port magnetic coupling sub-module capable of being packaged is formed;
the plurality of magnetic coupling modules are formed by connecting a plurality of magnetic coupling modules of the same type or different types in series or in parallel through ports.
As a further improvement of the invention, the core circuit of the magnetic coupling module is one or a plurality of magnetic coupling modules connected in parallel.
As a further improvement of the invention, the interface circuit is a direct current input port of a square wave voltage source, or a two-level, three-level or multi-level single-phase half bridge, single-phase full bridge, multi-phase half bridge, multi-phase full bridge converter constructed by silicon, silicon carbide or other switching devices, or a DC-DC or AC-DC converter.
As a further improvement of the invention, different ports of the magnetic coupling module are the same interface circuit, or two or more interface circuits are mixed for use.
As a further improvement of the invention, the frequency of the multi-winding transformer is any frequency in the range of several hundred hertz to several hundred kilohertz; the phase number of the multi-winding high-frequency transformer is from single phase, two phases to m phases, each phase is shifted by 360 degrees/m in sequence, and coils of each phase formed by each winding are connected in a star, triangle or other forms with two open ends; the winding number of the multi-winding transformer is three windings, four windings and n windings; each winding is connected with an m-phase square wave voltage source through an LC resonance branch, and each phase of the square wave voltage source is sequentially shifted by 360 degrees/m.
As a further improvement of the present invention, the square wave voltage source is an m-phase half-bridge, m-phase full-bridge converter constructed by silicon, silicon carbide or other switching devices, and the converter is two-level, three-level or multi-level.
As a further improvement of the invention, the core circuit of each magnetic coupling submodule comprises 1 m-phase n-winding high-frequency transformer, m × n LC resonance branches and n m-phase square wave voltage source half-bridge/full-bridge converters; and the m-phase winding terminals of each transformer are respectively connected with an LC branch in series, and the other end of the LC branch is connected with an m-phase square wave voltage source half-bridge/full-bridge converter.
As a further improvement of the invention, the m-phase is a single phase, two phases or multiple phases, and the n-winding is a double winding, a triple winding or a multiple winding;
if m is single phase and the converter is half bridge, the negative pole of DC side of each winding single phase half bridge converter is connected with the other connecting terminal of the winding.
As a further improvement of the present invention, the plurality of magnetic coupling modules form a three-phase ac-to-three-phase ac converter, a single-phase ac-to-single-phase ac converter, a dc-to-three-phase ac converter, a dc-to-single-phase ac converter, and a dc-to-dc two-port converter topology and a serialized converter topology having three or more ports.
Compared with the prior art, the invention has the following beneficial effects:
compared with the existing similar converters, the topological series of the converters provided by the invention has the advantages that a core circuit of the magnetic coupling module is formed by a single-phase/multiphase multi-winding high-frequency transformer, an LC resonance branch circuit connected with each winding in series and a single-phase/multiphase square wave voltage source for supplying power to each winding, the size and the weight of core passive elements such as the transformer and a capacitor are greatly reduced structurally, meanwhile, different forms of power are effectively integrated, and the technical problems in the aspects of power density, capacity and multi-port alternating current and direct current mixing are integrally solved. Technical advantages are high power density, high efficiency and multiple ports. The high power density is reflected in: the high-frequency transformer in the converter submodule has a much smaller volume and weight than a power frequency transformer with the same specification; on the basis, 2-frequency multiplication fluctuation power of three-phase alternating current is offset at the high-frequency transformer, so that the capacitance value of the module capacitor is greatly reduced, and the volume and the weight of the equipment are further reduced. The high efficiency is reflected in that: each power channel in the converter module is connected with an LC resonance branch in series, so that soft switching operation can be realized or current at hard switching-on and hard switching-off moments is forced to be close to zero, and the power loss of an energy channel is reduced; meanwhile, the serial or parallel interface circuit adopts phase shift modulation, so that the switching loss is greatly reduced while the overall frequency spectrum quality is ensured. The multi-port is embodied as: the high-frequency transformer couples the input/output ports corresponding to the plurality of windings through the magnetic circuit, so that the integrated integration of different forms of power and the magnetic isolation among any ports are realized, and the circuit topological structure is greatly simplified.
Drawings
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes, the proportional sizes, and the like of the respective members in the drawings are merely schematic for facilitating the understanding of the present invention, and do not specifically limit the shapes, the proportional sizes, and the like of the respective members of the present invention. Those skilled in the art, having the benefit of the teachings of this invention, may choose from the various possible shapes and proportional sizes to implement the invention as a matter of case. In the drawings:
fig. 1 is a single-phase multi-winding core circuit. Wherein, (a) is a single-phase n-winding core circuit schematic diagram; (b) the square wave voltage generating circuit is of a single-phase half-bridge structure; (c) the square wave voltage generating circuit is of a single-phase full-bridge structure; (d) a square wave voltage generating circuit in an m-phase half-bridge structure; (e) a square wave voltage generating circuit in a three-level single-phase half-bridge structure; (f) a square wave voltage generating circuit in a three-level single-phase full-bridge structure; (g) the square wave voltage generating circuit is a multilevel single-phase full bridge structure.
Fig. 2 is a drawing of a T-type equivalent circuit of a core circuit after conversion by winding transformation ratio, taking a single-phase 6-winding transformer as an example.
Fig. 3 shows some possible interface circuits and possible combinations with the core circuit. Wherein, (a) is an interface-less circuit; (b) an interface circuit in a single-phase half-bridge configuration; (c) the interface circuit is in a single-phase full-bridge structure; (d) an interface circuit in a three-level single-phase full-bridge structure; (e) an interface circuit in a DC/DC configuration; (f) an interface circuit that is an AC/AC architecture; (g) is a core circuit topological diagram.
The hybrid port circuit shown in fig. 4 is for illustrative purposes.
Fig. 5 is a three-phase medium voltage-three-phase medium voltage alternating current topological diagram formed by a plurality of magnetic coupling modules. Wherein, (a) is a magnetic coupling module of a three-phase medium voltage-three-phase medium voltage alternating current converter topology; (b) the ports of the modules are respectively connected in series according to A, B, C phases on the input side and a, b and c phases on the output side, star-shaped or triangular connection is carried out on the input side, and three-phase four-wire system connection is carried out on the output side, so that the medium-voltage-medium-voltage three-phase alternating current converter topology is formed.
Fig. 6 is a diagram of a magnetically coupled submodule of a three-phase low-voltage ac converter topology, wherein (a) is a magnetically coupled submodule of a three-phase medium-three-phase low-voltage ac converter topology; (b) the three-phase medium-voltage three-phase low-voltage AC topology is composed of a plurality of magnetic coupling modules.
Fig. 7 is a single-phase medium voltage to three-phase medium voltage converter topology. Wherein, (a) is a magnetic coupling module of the single-phase medium-voltage to three-phase medium-voltage converter; (b) the single-phase medium-voltage three-phase medium-voltage AC topology is composed of a plurality of magnetic coupling modules.
Fig. 8 is a single-phase low-three-phase medium voltage converter topology. Wherein, (a) is a magnetic coupling module of the single-phase low-three-phase medium voltage converter; (b) the single-phase low-voltage-three-phase medium-voltage alternating-current topology is formed by a plurality of magnetic coupling modules.
Fig. 9 is a single phase medium voltage to three phase low voltage converter topology. Wherein, (a) is a magnetic coupling module of the single-phase medium-voltage and three-phase low-voltage converter; (b) the single-phase medium-voltage three-phase low-voltage AC topology is formed by a plurality of magnetic coupling modules.
Fig. 10 is a single-phase medium voltage to single-phase medium voltage converter topology wherein (a) is the magnetic coupling module of the single-phase medium voltage to single-phase medium voltage converter; (b) the single-phase medium-voltage AC topology is a single-phase medium-voltage AC topology formed by a plurality of magnetic coupling modules.
Fig. 11 is a single-phase medium voltage to single-phase low voltage converter topology wherein (a) is a magnetic coupling module of the single-phase medium voltage to single-phase low voltage converter; (b) the single-phase medium-voltage and single-phase low-voltage alternating-current topology is formed by a plurality of magnetic coupling modules.
Fig. 12 is a dc medium voltage-three phase medium voltage converter topology. Wherein, (a) is a magnetic coupling module of the direct current medium voltage-three phase medium voltage converter; (b) the direct current medium voltage-three phase medium voltage alternating current topology is formed by a plurality of magnetic coupling modules.
Fig. 13 is a dc low-three phase medium voltage converter topology. Wherein, (a) is a magnetic coupling module of the direct current low-three-phase medium voltage converter; (b) the high-voltage DC low-voltage three-phase medium-voltage AC topology is a DC low-voltage three-phase medium-voltage AC topology formed by a plurality of magnetic coupling modules.
Fig. 14 is a dc medium voltage-three phase low voltage converter topology. Wherein, (a) is a magnetic coupling module of the direct current medium-voltage-three-phase low-voltage converter; (b) the high-voltage DC medium-voltage three-phase low-voltage AC topology is a DC medium-voltage three-phase low-voltage AC topology formed by a plurality of magnetic coupling modules.
Fig. 15 is a dc medium voltage to single phase medium voltage converter topology. Wherein, (a) is a magnetic coupling module of the direct current medium voltage-single phase medium voltage converter; (b) the high-voltage DC-single-phase medium-voltage AC topology is a DC medium-voltage-single-phase medium-voltage AC topology formed by a plurality of magnetic coupling modules.
Fig. 16 is a dc low voltage-single phase medium voltage converter topology. Wherein, (a) is a magnetic coupling module of the direct current low-voltage single-phase medium-voltage converter; (b) the high-voltage DC low-voltage single-phase medium-voltage AC topology is composed of a plurality of magnetic coupling modules.
Fig. 17 is a dc medium voltage to single phase low voltage converter topology. Wherein, (a) is a magnetic coupling module of the direct current medium-voltage single-phase low-voltage converter; fig. 17(b) shows a dc medium voltage-single phase low voltage ac topology composed of a plurality of magnetic coupling modules.
Fig. 18 is a dc medium voltage-dc medium voltage converter topology. Wherein, (a) is a magnetic coupling module of the direct current medium voltage-direct current medium voltage converter; (b) the direct current medium voltage-direct current medium voltage alternating current topology is formed by a plurality of magnetic coupling modules.
Fig. 19 is a dc medium voltage to dc low voltage converter topology. Wherein, (a) is a magnetic coupling module of the direct current medium voltage-direct current low voltage converter; (b) the direct current medium voltage-direct current low voltage alternating current topology is composed of a plurality of magnetic coupling modules.
A four-port medium-low voltage ac/dc hybrid converter circuit shown in fig. 20 will be described as an example.
FIG. 21 shows a medium-voltage three-phase AC-medium-voltage three-phase AC converter constructed based on a magnetic coupling module
Fig. 22 is a simulation waveform diagram of a Matlab/Simulink medium voltage three-phase ac-medium voltage three-phase ac converter simulation model that fully achieves the intended design objective and implements the control function. Wherein, (a) is three-phase grid voltage; (b) is three-phase grid current; (c) modulating voltage for machine side; (d) is the machine side current; (e) is the net side capacitance voltage; (f) is the machine side capacitance voltage.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.
It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a single embodiment.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The medium-voltage converter topology series based on the high-frequency magnetic coupling module comprises a core circuit consisting of a multi-winding high-frequency transformer and an LC resonant cavity; a magnetic coupling module formed by an alternating current/direct current and a single three-phase interface circuit is added in the core circuit; and a plurality of magnetic coupling modules are connected in series or in parallel through ports to form a converter topology series.
The following is a detailed description:
core circuit and basic principle
The core circuit comprises a single-phase/multi-phase multi-winding high-frequency transformer, an LC resonance branch circuit connected with each winding in series and a single-phase/multi-phase square wave voltage source for supplying power to each winding. The frequency of the multi-winding transformer may be any frequency in the range of several hundred hertz to several hundred kilohertz. The number of phases of the multi-winding high-frequency transformer is not limited, and the multi-winding high-frequency transformer can be single-phase, two-phase or m-phase, each phase is sequentially shifted by phase (360 DEG/m), and the coils of each phase formed by each winding can be open at two ends, and can also be connected in a star shape, a triangle shape or other forms. The number of windings of the multi-winding transformer is not limited, and the multi-winding transformer can be three windings, four windings or n windings, and the transformation ratio among the windings can be set arbitrarily according to needs. The connection terminals of each phase in each winding of the multi-winding transformer are connected with an LC resonance branch circuit in series, the resonance frequency of each LC branch circuit is the same value close to the frequency of the transformer, and the LC resonance branch circuits are used for assisting a switching device in a square wave voltage source to realize soft switching or forcing the current value at the moment of hard switching or hard switching to be close to a zero value, and simultaneously blocking direct current which possibly enters the winding. Each winding is connected with an m-phase square wave voltage source through an LC resonance branch, each phase of the square wave voltage source is sequentially phase-shifted (360 degrees/m), the square wave voltage source can be served by an m-phase half-bridge or an m-phase full-bridge converter constructed by silicon, silicon carbide or other switching devices, and the converter can be two-level, three-level or multi-level.
To explain the working principle of the present invention, a single-phase multi-winding core circuit shown in fig. 1 is taken as an example for explanation. It should be understood that this configuration is not intended to limit the present invention. The square-wave voltage source of each winding is served by a current transformer, the switch (S) of a single-phase full bridge in FIG. 1(c)1，S4) When the converter is conducted, the converter generates positive voltage; when switching on (S)2，S3) When the converter is conducted, the converter outputs negative voltage; two circuit states (S)1，S4) And (S)2，S3) Alternating the operation at a duty ratio of 50% to generate a square wave voltage with the amplitude of the direct current side voltage; it should be noted that the single-phase half bridge in fig. 1(b) generates a square wave voltage with dc bias, and the bias voltage can be equivalent to one half of the square wave voltage of the full bridge circuit after being blocked by the resonant cavity capacitor; a three-level or multilevel converter may generate a square wave voltage similar to a two-level converter, but with a higher voltage amplitude. When a square wave voltage with the frequency close to the resonance frequency is applied to a certain winding, due to the band-pass characteristic of the LC branch circuit, quasi-sine wave current with the same frequency as the square wave voltage is generated in the winding; partial current flows through the excitation inductor, so that voltages with the same frequency are induced in other windings; induced voltage of each winding and eachApplying the difference value of the square wave voltage to the LC branch circuit of the converter to generate quasi-sine wave current with the same frequency; the interaction of the quasi-sine wave current of each winding and the applied square wave voltage is the input power of the winding; each winding follows the principle of power conservation, and active power is freely transferred among the windings by adjusting the phase shift angle of the square wave voltage. In the power transfer process, because the square wave voltage of each winding and the quasi-sinusoidal current have a certain phase angle difference, the power semiconductor device can realize soft switching or realize that the current at the hard switching-on and hard switching-off moments is close to zero, and the electric energy conversion efficiency of a core circuit is ensured.
In order to facilitate the construction of closed-loop control, the invention develops detailed derivation on the mathematical relationship between the phase shift angle of the square wave voltage of each winding and the transfer active power according to the equivalent circuit of the core circuit. Taking a single-phase 6-winding transformer as an example, a core circuit is drawn as shown in fig. 2 according to a T-shaped equivalent circuit obtained by converting the transformation ratio of each winding. Wherein (X)m,Rm) The excitation reactance and the equivalent resistance of the multi-winding transformer; (X)i,Ri) To consider leakage inductance, resonance inductance, equivalent steady-state reactance and equivalent resistance (i.e. equivalent resistance) after resonance capacitance of each winding
Figure BDA0003065243900000081
) The set of values can be made equal among the windings by properly designing the external inductance (i.e., X)i＝X，Ri＝R)；(vi) For each winding square-wave voltage (V)i) The fundamental component of (a); (v)o) For the excitation voltage, after writing the node voltage equation of the point, the expression can be written as follows:
Figure BDA0003065243900000082
the voltage is subtracted from the fundamental component in the square wave voltage of each winding, and the equivalent reactance of each branch is divided to calculate the current flowing through each winding:
Figure BDA0003065243900000091
the conjugate of the current is multiplied by the fundamental component of the square wave voltage to obtain the apparent power (S) of each windingi) Considering that the voltage and current components involved in the calculation are both amplitude values and not significant values, the power expression needs to be multiplied by a factor of 0.5, which can be written as:
Figure BDA0003065243900000095
to facilitate characterization of the phase shift angle of the fundamental component of the square-wave voltage of each winding, each voltage variable can be expressed in complex form, i.e. (v)i＝Vdi+jVqi). Substituting the voltage expression into the apparent power equation and extracting active power components to obtain:
Figure BDA0003065243900000092
wherein the content of the first and second substances,
Figure BDA0003065243900000093
considering that the equivalent reactance of each winding is much larger than the equivalent resistance (X > R ≈ 0), and the sum of the fundamental voltage Q-axis components of each winding is approximately zero (V)∑q0), the active power of each winding is approximately calculated as:
Figure BDA0003065243900000094
in actual engineering, the sum of the D-axis components (V)∑d) The active power of each winding is approximately in a linear relation with the Q-axis component of the square wave voltage per se, and the expression can be used for designing a control strategy. The calculation method is different according to different structures of the multi-winding transformer, but the calculation method belongs to the protection scope of the invention.
Magnetic coupling module and construction method
The magnetic coupling module is characterized in that a direct current or alternating current interface circuit is additionally arranged at the direct current input end of each winding square wave converter of the core circuit, so that a multi-port magnetic coupling sub-module capable of being packaged together is formed. The core circuit in the magnetic coupling module may be one or a plurality of core circuits connected in parallel in consideration of the capacity limit of a single high-frequency transformer. The interface circuit can be a direct current input port of a square wave voltage source directly (namely, no circuit is added), can also be a two-level, three-level or multi-level single-phase half-bridge, single-phase full-bridge, multi-phase half-bridge or multi-phase full-bridge converter constructed by silicon, silicon carbide or other switching devices, and can also be other forms of DC-DC or AC-DC converters. Different ports of the magnetic coupling module can be the same interface circuit, and can also be a mixture of two or more interface circuits. Fig. 3 shows some possible interface circuits and possible combinations with the core circuit, but these interface circuits and combinations are not intended to limit the present invention.
To explain the circuit configuration of the present invention, a hybrid port circuit shown in fig. 4 is taken as an example for explanation. It should be understood that this configuration is not intended to limit the present invention. The core circuit of the hybrid multiport module adopts a 6-winding high-frequency transformer which properly sets the transformation ratio according to actual needs, a single-phase full-bridge circuit is adopted for the square wave voltage source, and a single-phase two-level full-bridge, a single-phase two-level half-bridge, a single-phase two-level full-bridge, a three-phase two-level half-bridge and a single-phase two-level half-bridge are respectively added at the direct current input port of the 6 square wave voltage sources. The module provides abundant alternating current-direct current and single three-phase interfaces, and realizes magnetic isolation between ports; the module can be used singly, or a plurality of modules can be used in series or in parallel through ports. When used alone, the device can be used as a household electric energy router, for example, a port 1 is connected with a single-phase main power of a user, a port 2 is connected with a photovoltaic panel, a port 3 is connected with a storage battery, a port 4 provides high-quality single-phase electric energy for household appliances, a port 5 provides high-quality three-phase electric energy for household appliances, and a port 6 provides adaptive direct-current electric energy for household appliances.
Thirdly, converter topology series based on magnetic coupling module
The converter topology series is a two-port converter topology formed by connecting a plurality of magnetic coupling modules of the same type or different types in series or in parallel through ports to form three-phase alternating current-three-phase alternating current, single-phase alternating current-single-phase alternating current, direct current-three-phase alternating current, direct current-single-phase alternating current and direct current-direct current, and a serialized converter topology with more than three ports. The topological series has the advantages that the fluctuating power among three phases can be partially or completely offset through a coupled magnetic circuit so as to greatly reduce the capacitance value of a capacitor used for caching the fluctuating power in the module, and then the traditional electrolytic capacitor can be replaced by the film capacitor, so that the size and the weight are reduced, and the defect of the service life is overcome. Meanwhile, the high-frequency transformer and the resonance technology further greatly reduce the volume and the weight of the magnetic element, and ensure the high power density and the high efficiency of the converter on the whole. The serialized converter topologies are introduced below according to port type:
1. two-port three-phase alternating current-three-phase alternating current converter
The three-phase AC-three-phase AC converter can be divided into a medium voltage-medium voltage and a medium voltage-low voltage according to different voltage grades, and is composed of a plurality of magnetic coupling modules which are connected in series or in parallel through ports. The magnetic coupling module of the medium-voltage to medium-voltage converter can select a single-phase half-bridge, a single-phase full-bridge or a mixed square wave voltage generating circuit according to the power requirement, and is provided with a 6-winding transformer with proper transformation ratio and single-phase full-bridge interface circuits corresponding to windings, wherein three single-phase full-bridge interfaces are marked as A, B, C phase ports on the input side, and the other three single-phase full-bridge interfaces are marked as a, b and c phase interfaces on the output side, as shown in fig. 5 (a); the ports of the modules are connected in series according to A, B, C phases on the input side and a, b and c phases on the output side respectively, and are connected in star or delta on the input side and the output side to form a medium-voltage and medium-voltage three-phase alternating current converter topology, as shown in fig. 5 (b). The medium-voltage and low-voltage converter can select a magnetic coupling module similar to the medium-voltage and medium-voltage converter and keeps the connection relation of the input side unchanged, but all modules are connected in parallel through reactors at the ports of the output side according to phases a, b and c, and are finally connected into a star shape or a triangle shape; and a magnetic coupling submodule which is similar to the medium-voltage and medium-voltage three-phase converter and is provided with a three-phase half-bridge circuit interface on the output side can be selected, and all modules are connected in parallel at the output side port through a reactor to form a medium-voltage and low-voltage three-phase alternating current converter topology.
Fig. 5 and 6 show a medium voltage-medium voltage and a medium voltage-low voltage three-phase ac converter topology, respectively. It should be understood that the structures shown in the drawings are not intended to limit the invention. The three-phase alternating current-three-phase alternating current converter can work in a power frequency and frequency conversion mode, when the frequency changes from low frequency to rated frequency, the power of three-phase fluctuation is counteracted at a coupled transformer, and the severe fluctuation of capacitance voltage in a module is not caused. When the power grid normally works, the capacitance value of the direct-current side capacitor in the topology can be reduced by more than 90% compared with that of a traditional series H bridge, and when the power grid has a single-phase earth fault, the capacitance value can be reduced by more than 60%.
2. Two-port single-phase alternating current-three-phase alternating current converter
The single-phase alternating current-three-phase alternating current converter can be divided into a single-phase medium voltage-three-phase medium voltage, a single-phase low voltage-three-phase medium voltage and a single-phase medium voltage-three-phase low voltage according to different voltage grades, and is composed of a plurality of magnetic coupling modules which are connected in series or in parallel through ports. The magnetic coupling module of the single-phase medium-voltage to three-phase medium-voltage converter can select a single-phase half-bridge, a single-phase full-bridge or a mixed square wave voltage generating circuit according to the power requirement, for example, a 6-winding transformer with proper transformation ratio and a single-phase full-bridge interface circuit corresponding to each winding are equipped, a primary side direct current capacitor is connected with the single-phase full-bridge interface circuit after being connected in parallel, the single-phase full-bridge interface is marked as an I port of an input side, a secondary side is equipped with the single-phase full-bridge interface circuit corresponding to each winding, and the three single-phase full-bridge interfaces are marked as A, B, C phase interfaces of an output side, as shown in fig. 7 (a); the ports of the modules are respectively connected in series according to A, B, C phases and I phases, the I phase after series connection is used as a medium-voltage single-phase interface, and simultaneously the A, B, C phase after series connection is connected into a star or a triangle to be used as a medium-voltage three-phase interface, so that a single-phase medium-voltage-three-phase medium-voltage converter topology is formed, as shown in fig. 7 (b). The single-phase low-voltage-three-phase medium-voltage converter can select a magnetic coupling module similar to the single-phase medium-voltage-three-phase medium-voltage converter, the connection relation of the three-phase side is kept unchanged, but the single-phase side needs to be spliced into different series-parallel arrays (the parallel connection needs inductors) according to the voltage and power requirements to form a single-phase low-voltage port, and finally a single-phase low-voltage-three-phase medium-voltage converter topology is formed. The single-phase medium-voltage and three-phase low-voltage converter can adopt a magnetic coupling module similar to the single-phase medium-voltage and three-phase medium-voltage converter, the connection relation of a single-phase side is kept unchanged, but three-phase side ports are respectively connected in parallel through reactors according to A, B, C phases, and are finally connected into a star shape or a triangle shape; and a magnetic coupling submodule which is similar to the single-phase medium-voltage to three-phase medium-voltage converter and is provided with a three-phase half-bridge circuit interface at the output side can be selected, and all modules are connected in parallel at the output side port through a reactor to form a single-phase medium-voltage to three-phase low-voltage converter topology.
Fig. 7, 8 and 9 show single-phase medium voltage-three phase medium voltage, single-phase low voltage-three phase medium voltage and single-phase medium voltage-three phase low voltage converter topologies, respectively. It should be understood that the structures shown in the drawings are not intended to limit the invention. The three-phase side of the converter can work in a power frequency, low frequency or variable frequency mode, when the frequency changes from low frequency to rated frequency, the three-phase fluctuating power is offset at the coupled transformer, and the severe fluctuation of the capacitor voltage in the module is not caused. Compared with the traditional series H bridge, the capacitance value of the direct-current side capacitor in the topology can be reduced by more than 30%.
3. Two-port single-phase alternating current-single-phase alternating current converter
The single-phase alternating current-single-phase alternating current converter can be divided into a single-phase medium voltage-single-phase medium voltage and a single-phase medium voltage-single-phase low voltage according to different voltage grades, and is composed of a plurality of magnetic coupling modules which are connected in series or in parallel through ports. The magnetic coupling module of the single-phase medium-voltage to single-phase medium-voltage converter can select a single-phase half-bridge, a single-phase full-bridge or a mixed square wave voltage generating circuit according to power requirements, taking a 6-winding transformer with proper transformation ratio and a single-phase full-bridge interface circuit corresponding to each winding as an example, wherein three single-phase full-bridge interfaces are connected in series and then marked as an I port of an input side, and the other three single-phase full-bridge interfaces are connected in series and then marked as an O interface of an output side, as shown in fig. 10 (a); the ports of the modules are respectively connected in series according to the I phase and the O phase, the I phase after the series connection is used as a medium-voltage single-phase interface, and the O phase after the series connection is used as a medium-voltage single-phase interface, so that a single-phase medium-voltage-single-phase medium-voltage converter topology is formed, as shown in fig. 10 (b). The single-phase medium-voltage and single-phase low-voltage converter can select a magnetic coupling module similar to the single-phase medium-voltage and single-phase medium-voltage converter, the connection relation of one side of the single-phase medium-voltage and single-phase medium-voltage converter is kept unchanged, but the other side of the single-phase medium-voltage and single-phase low-voltage converter is spliced into different series-parallel arrays (the parallel connection needs inductors) according to voltage and power requirements to form a single-phase low-voltage port, and finally a single-phase medium-voltage and single-phase low-voltage converter topology is formed.
Fig. 10 and 11 show single-phase medium-voltage to single-phase medium-voltage and single-phase medium-voltage to single-phase low-voltage converter topologies, respectively. It should be understood that the structures shown in the drawings are not intended to limit the invention.
4. Two-port DC-three-phase AC converter
The direct current-three phase alternating current converter can be divided into three types of direct current medium voltage-three phase medium voltage, direct current low voltage-three phase medium voltage and direct current medium voltage-three phase low voltage according to different voltage grades, and is composed of a plurality of magnetic coupling modules which are connected in series or in parallel through ports. The magnetic coupling module of the dc medium-voltage-three-phase medium-voltage converter can select a single-phase half-bridge, a single-phase full-bridge or a combination of the two square-wave voltage generating circuits according to the power requirement, taking a 5-winding transformer with proper transformation ratio as an example, a primary-side non-interface circuit is marked as an P, Q port of an input side, a secondary side is provided with a single-phase full-bridge interface circuit corresponding to each winding, and three single-phase full-bridge interfaces are marked as A, B, C phase interfaces of an output side, as shown in fig. 12 (a); the ports of the modules are respectively connected in series according to A, B, C phases and P, Q phases, the negative electrode of the finally formed P port is connected with the positive electrode of the Q port, the connection point is used as a neutral point N of a bipolar direct current bus, and meanwhile, the A, B, C phase port after being connected in series is used as a medium-voltage three-phase interface to form a direct current medium-voltage three-phase medium-voltage converter topology, as shown in fig. 12 (b). The direct-current low-voltage-three-phase medium-voltage converter can select a magnetic coupling module similar to the direct-current medium-voltage-three-phase medium-voltage converter, the connection relation of the three-phase side is kept unchanged, but the direct-current side needs to be spliced into different series-parallel arrays (parallel connection does not need inductors) according to voltage and power requirements to form a direct-current low-voltage port, and finally a direct-current low-voltage-three-phase medium-voltage converter topology is formed. The direct-current medium-voltage-three-phase low-voltage converter can select a magnetic coupling module similar to the direct-current medium-voltage-three-phase medium-voltage converter and keep the direct-current side connection relation unchanged, but the three-phase side ports are respectively connected in parallel through reactors according to A, B, C phase and are finally connected into a star shape or a triangle shape; and a magnetic coupling submodule which is similar to the direct-current medium-voltage and three-phase medium-voltage converter and is provided with a three-phase half-bridge circuit interface on the output side can be selected, and all modules are connected in parallel at the port on the output side through a reactor to form a direct-current medium-voltage and three-phase low-voltage converter topology.
Fig. 12, 13 and 14 show dc medium voltage-three phase medium voltage, dc low voltage-three phase medium voltage and dc medium voltage-three phase low voltage converter topologies, respectively. It should be understood that the structures shown in the drawings are not intended to limit the invention. The three-phase side of the converter can work in a power frequency, low frequency or variable frequency mode, when the frequency changes from low frequency to rated frequency, the three-phase fluctuating power is offset at the coupled transformer, and the severe fluctuation of the capacitor voltage in the module is not caused. When three phases are balanced, the capacitance value of a direct-current side capacitor in the topology can be reduced by more than 90% compared with that of a traditional series H bridge; when three phases are unbalanced and are power frequency, capacitance value of a direct current side capacitor in the topology can be reduced by more than 60% compared with that of a traditional series H bridge. Compared with the traditional MMC, the medium-voltage direct-medium-voltage three-phase alternating-current converter provided by the invention can greatly reduce the volume and the weight of the transformer, reduce the capacitance value of the capacitor by more than 70%, has higher equipment power density, and has more advantages than the MMC when applied to offshore direct-current transmission.
5. Two-port DC-single-phase AC converter
The direct current-single phase alternating current converter can be divided into three types of direct current medium voltage-single phase medium voltage, direct current low voltage-single phase medium voltage and direct current medium voltage-single phase low voltage according to different voltage grades, and the three types of direct current medium voltage-single phase medium voltage and direct current medium voltage-single phase low voltage are all composed of a plurality of magnetic coupling modules which are connected in series or in parallel through ports. A magnetic coupling module of the dc medium-voltage-single-phase medium-voltage converter can select a single-phase half-bridge, a single-phase full-bridge or a combination of the two square-wave voltage generating circuits according to power requirements, taking a 6-winding transformer with proper transformation ratio as an example, a primary side is provided with the single-phase half-bridge square-wave voltage generating circuit corresponding to each winding, three dc capacitors are marked as a P port of an input side after being connected in series, a secondary side is provided with the single-phase full-bridge square-wave voltage generating circuit and the single-phase full-bridge interface circuit corresponding to each winding, and three single-phase full-bridge interfaces are marked as an O port of an output side after being connected in series, as shown in fig. 15 (a); the ports of the modules are respectively connected in series according to the P and O ports, and the P port after series connection is used as a medium-voltage direct-current port, and the O port after series connection is used as a medium-voltage alternating-current port, so as to form a direct-current medium-voltage-single-phase medium-voltage converter topology, as shown in fig. 15 (b). The direct-current low-voltage-single-phase medium-voltage converter can select a magnetic coupling module similar to the direct-current medium-voltage-single-phase medium-voltage converter, the connection relation of a single-phase side is kept unchanged, but the direct-current side needs to be spliced into different series-parallel arrays according to voltage and power requirements to form a direct-current low-voltage port, and finally a direct-current low-voltage-single-phase medium-voltage converter topology is formed. The direct-current medium-voltage-single-phase low-voltage converter can select a magnetic coupling module similar to the direct-current medium-voltage-single-phase medium-voltage converter and keep the direct-current side connection relation unchanged, but a single-phase side interface is connected in parallel through a reactor to form a single-phase low-voltage port; and a magnetic coupling submodule similar to the direct-current medium-voltage single-phase medium-voltage converter but provided with a three-phase half-bridge circuit interface on the output side can be selected, and all modules are connected in parallel at the output side port through a reactor to form a direct-current medium-voltage single-phase low-voltage converter topology.
Fig. 15, 16 and 17 show dc medium voltage-single phase medium voltage, dc low voltage-single phase medium voltage and dc medium voltage-single phase low voltage converter topologies, respectively. It should be understood that the structures shown in the drawings are not intended to limit the invention.
6. Two-port DC-DC converter
The direct current-direct current converter can be divided into direct current medium voltage-direct current medium voltage and direct current medium voltage-direct current low voltage according to different voltage grades, and is composed of a plurality of magnetic coupling modules which are connected in series or in parallel through ports. The magnetic coupling module of the dc medium-voltage-single-phase medium-voltage converter can select a single-phase half-bridge, a single-phase full-bridge or a combination of both square-wave voltage generating circuits according to the power requirement, taking a 4-winding transformer equipped with an appropriate transformation ratio as an example, each winding is equipped with a single-phase full-bridge square-wave voltage generating circuit and a corresponding single-phase full-bridge interface circuit, two single-phase full-bridge interfaces are marked as P, Q phase ports on the input side, and the other two single-phase full-bridge interfaces are marked as t and s phase ports on the output side, as shown in fig. 18 (a); the ports of the modules are respectively connected in series according to P, Q phases and t and s phases, the negative electrode of the finally formed P port is connected with the positive electrode of the Q port, the connection point is used as a neutral point N of the bipolar direct current bus, the negative electrode of the finally formed t port is connected with the positive electrode of the s port, and the connection point is used as a neutral point N of the bipolar direct current bus, so that a direct current medium voltage-direct current medium voltage converter topology is formed, as shown in fig. 18 (b). The direct-current medium-voltage direct-current low-voltage converter can select a magnetic coupling module similar to the direct-current medium-voltage direct-current low-voltage converter and keep the connection relation of the medium-voltage side unchanged, but the low-voltage side needs to be spliced into different series-parallel arrays according to voltage and power requirements to form a direct-current low-voltage port, and finally a direct-current medium-voltage direct-current low-voltage converter topology is formed.
Fig. 18 and 19 show dc medium voltage-dc medium voltage and dc medium voltage-dc low voltage converter topologies, respectively. It should be understood that the structures shown in the drawings are not intended to limit the invention.
7. Multi-port AC-DC hybrid converter
The multi-port alternating current-direct current hybrid converter is provided with 3 or more than 3 alternating current, direct current or alternating current-direct current hybrid ports, covers a magnetic coupling submodule with a plurality of ports connected in series or in parallel, and has the operation capability of medium-low voltage, single multi-phase and constant/variable frequency. The magnetic coupling module can set the number of windings of the transformer to be 3 or more than 3 according to actual needs, match direct current, single-phase alternating current or three-phase alternating current ports, and connect with similar ports of other modules in series or in parallel according to the voltage and power grade needs of each port, and finally form a family of multi-port alternating current and direct current hybrid converter topology.
To explain the circuit structure of the present invention, a four-port medium-low voltage ac/dc hybrid converter circuit shown in fig. 20 will be described as an example. It should be understood that the circuit configuration of fig. 20 is not intended to limit the present invention. The converter is composed of 10 identical magnetic coupling modules, the number of transformer windings of each magnetic coupling module is set to be 10, 4 windings directly use an input port of a square wave voltage source as a direct current interface, and the other 6 windings are provided with a two-level single-phase full bridge as an alternating current interface. 2 of 4 direct current interfaces of each magnetic coupling module are provided with single-phase half-bridge square wave voltage generating circuits to respectively form a direct current H interface and a direct current L interface, and the other 2 of the 4 direct current interfaces of each magnetic coupling module are provided with single-phase full-bridge square wave voltage generating circuits to respectively form a direct current P interface and a direct current Q interface; 3 of the 6 ac interfaces are labeled as A, B, C phases, and the other 3 are labeled as a, b, c phases. H, L, P, Q ports of 10 magnetic coupling modules are respectively connected in series, the anode of the finally formed H port is connected with the cathode of the L port, the connection point is led out to be used as a neutral point N of the bipolar direct current bus, the anode of the finally formed P port is connected with the cathode of the Q port, the connection point is led out to be used as a neutral point M of the bipolar direct current bus, A, B, C phase interfaces are respectively connected in series to be connected into a star shape to form a medium voltage three-phase alternating current port, and the a, b and c phase interfaces are connected into a star shape to form a low voltage three-phase alternating current port through a three-phase four-wire system. The magnetic isolation among 4 ports of the four-port converter is realized through a high-frequency transformer, so that the volume and the weight of a magnetic core are greatly reduced; meanwhile, the power fluctuation of the three-phase alternating current port is offset at the high-frequency transformer, the capacitance value of the capacitor is reduced to the maximum extent, and the film capacitor is selected to greatly prolong the service life of the equipment. The four-port converter can be used as a medium-voltage electric energy router, is connected with active or passive networks of medium-voltage alternating current, low-voltage alternating current, medium-voltage direct current and low-voltage direct current, performs one-to-one or one-to-many power flow control, and can block fault propagation while ensuring the electric energy quality of each port.
The power frequency transformer adopted by the traditional isolated medium-voltage high-power converter has larger volume and weight. Moreover, when the converter unit of the primary side or the secondary side of the power frequency transformer processes alternating current power, power fluctuation is transferred to the direct current side, and the capacitor array which is arranged on the direct current side and used for buffering the fluctuation power further increases the size and the weight of the device. The invention aims at solving the serious power density problem caused by a power frequency transformer and a capacitor array which are arranged in a core of an isolation type converter, and constructs a multi-port magnetic coupling module which takes a multi-winding high-frequency transformer, an LC resonance branch circuit, a square wave voltage source converter and an AC/DC interface converter as a core circuit by starting from two aspects of increasing the frequency of the transformer to reduce the size and the weight of a magnetic core and canceling out fluctuating power in a magnetic coupling mode to reduce a capacitance value, and forms a topology series of a two-port DC-DC, a two-port DC-AC, a two-port AC-AC and a multi-port AC/DC hybrid converter by connecting ports among a plurality of magnetic coupling modules in series or in parallel. The core of the series of converter topologies is a magnetic coupling module, the invention develops detailed mathematical argument for the working principle of the magnetic coupling module, and mainly analyzes the mathematical relation between the phase shift angle of the square wave voltage source and the transfer active power of each winding on the basis of establishing an integrated mathematical model of the multi-winding high-frequency transformer and the LC resonance branch circuit, and obtains the proportional relation between the active power of each winding and the Q-axis fundamental wave component (indirect representation of the phase shift angle) of the square wave voltage source on the premise of following the conservation of the transformer power and reasonably using approximate conditions, thereby proving the feasibility of a magnetic circuit for counteracting the alternating current fluctuating power. The Matlab/Simulink based simulation model further demonstrates the feasibility of this family of topologies, as well as the significant advantages in power density and efficiency over conventional converters.
The present invention will be described in detail with reference to specific examples.
Examples
Fig. 21 is a medium-voltage three-phase ac-medium-voltage three-phase ac converter constructed based on a magnetic coupling module and used for four-quadrant variable frequency driving of a medium-voltage motor. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The core circuit of each magnetic coupling submodule consists of 1 six-winding high-frequency current transformer, 6 LC resonance branches and 6 square wave voltage source single-phase half bridges. In the core circuit, each transformer winding is connected with an LC branch circuit in series, the other end of the LC branch circuit is connected with a square wave voltage source half-bridge, and the negative pole of the DC side of the half-bridge is connected with the other wiring terminal of the winding. In consideration of the capacity limit of a single high-frequency transformer, each magnetic coupling sub-module can select a single core circuit or a plurality of composite core circuits connected in parallel according to the actual power requirement. Each square wave voltage source direct current end of the core circuit is provided with a high-power two-level single-phase full-bridge interface to form a complete high-power-density magnetic coupling sub-module. The modules are respectively connected in series according to 6 single-phase full-bridge interfaces, then 3 single-phase strings are selected to be connected in a star shape to form a medium-voltage three-phase power grid input port, and the other 3 single-phase strings are connected in a star shape to form a medium-voltage three-phase motor output port. The two medium-voltage ports are respectively connected with a power grid and a medium-voltage motor through two groups of single-phase discrete reactors (3 in each group), so that a main circuit of a medium-voltage motor driving system is formed.
During normal operation, the three single-phase full bridges on the input side of each module respectively generate PWM voltages which are close to one N (N is the number of the modules) of the three-phase voltage of a power grid and are used for shaping input current into sine waves with unit power factors, the sine wave currents are converted by a single-phase full bridge interface circuit on the input side to form power currents with direct current bias and double-frequency fluctuation, based on the linear relation between the power currents and the phase shift angles of the square wave voltages, a square wave voltage source half bridge circuit of each winding generates square wave voltages with specific phase shift angles, the square wave voltages generate quasi-sine wave currents of each winding according to an LC resonance branch and an energy conversion mechanism of a multi-winding high-frequency transformer, and considering that the double-frequency fluctuation of the three-phase power on the input side sequentially differs by 120 degrees, fluctuation magnetic chains generated in the input windings of the high-frequency transformer are mutually cancelled, and only average power is transmitted to the output side through a magnetic circuit, the output side receives the average power and then distributes the average power to three output windings of the transformer, based on the average power, each winding is superposed with a fluctuating magnetic circuit corresponding to the complementary fluctuating power of the three-phase output port to form a total flux linkage of each output winding, each output winding induces a quasi-sine wave current according to the flux linkage, and the current is rectified by a square wave voltage source half-bridge and then reduced into fluctuating power flow with direct current bias and transmitted to an output inverter bridge, and finally transmitted to a medium-voltage motor. It should be noted that the square wave voltage generated by each winding square wave voltage source has a certain angle difference with the winding quasi-sine wave current, so as to ensure the soft switching operation of the switching device in the square wave voltage source.
The parameters of the magnetic coupling module designed according to the above-mentioned idea are collected in table 1, and the Matlab/Simulink medium-voltage three-phase ac-medium-voltage three-phase ac converter simulation model constructed according to the above-mentioned parameters completely achieves the expected design target and realizes the control function. The simulated waveforms are compiled in fig. 22. When the three-phase output current linearly increases from 0 Hz to 50 Hz with a constant amplitude and the output voltage correspondingly increases according to the principle of constant voltage-frequency ratio, the input-side converter and the output-side converter still control the voltage fluctuation amplitude within 4 percent under the condition of selecting a minimum capacitance value. Compared with the traditional series H-bridge medium-voltage motor driving system, the converter reduces the capacitance value of the capacitor by more than 60%, and simultaneously replaces the heavy power-frequency phase-shifting transformer with a high-frequency transformer, thereby further greatly reducing the volume and the weight.
TABLE 1 converter specific parameters
Figure BDA0003065243900000181
Figure BDA0003065243900000191
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
It should be noted that, in the description of the present invention, the terms "first", "second", and the like are used for descriptive purposes only and for distinguishing similar objects, and no precedence between the two is considered as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
It is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and many applications other than the examples provided would be apparent to those of skill in the art upon reading the above description. The scope of the present teachings should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are hereby incorporated by reference for all purposes. The omission in the foregoing claims of any aspect of subject matter that is disclosed herein is not intended to forego such subject matter, nor should the applicant consider that such subject matter is not considered part of the disclosed subject matter.

Claims (9)

1. A medium voltage converter topological structure based on a high frequency magnetic coupling module is characterized by comprising one or more magnetic coupling modules;
the core circuit of the magnetic coupling module comprises a single-phase/multi-phase multi-winding high-frequency transformer, an LC resonance branch circuit connected with each winding in series and a single-phase/multi-phase square wave voltage source for supplying power to each winding;
a direct current or alternating current interface circuit is additionally arranged at the direct current input end of the wave converter above each winding, so that a multi-port magnetic coupling sub-module capable of being packaged is formed;
the plurality of magnetic coupling modules are formed by connecting a plurality of magnetic coupling modules of the same type or different types in series or in parallel through ports.
2. The medium voltage converter topology based on high frequency magnetic coupling module according to claim 1, characterized in that the core circuit of said magnetic coupling module is one or a plurality of parallel.
3. The medium voltage converter topology based on high frequency magnetic coupling module of claim 1, wherein the interface circuit is a direct current input port of a square wave voltage source, or a two-level, three-level or multi-level single-phase half-bridge, single-phase full-bridge, multi-phase half-bridge, multi-phase full-bridge converter constructed by silicon, silicon carbide or other switching devices, or a DC-DC or AC-DC converter.
4. The medium voltage converter topology structure based on high frequency magnetic coupling module according to claim 1, wherein different ports of the magnetic coupling module are the same interface circuit or two or more interface circuits are mixed.
5. The high frequency magnetic coupling module based medium voltage transformer topology of claim 1, wherein the frequency of the multi-winding transformer is any frequency in the range of several hundred hertz to several hundred kilohertz; the phase number of the multi-winding high-frequency transformer is from single phase, two phases to m phases, each phase is shifted by 360 degrees/m in sequence, and coils of each phase formed by each winding are connected in a star, triangle or other forms with two open ends; the winding number of the multi-winding transformer is three windings, four windings and n windings; each winding is connected with an m-phase square wave voltage source through an LC resonance branch, and each phase of the square wave voltage source is sequentially shifted by 360 degrees/m.
6. The high frequency magnetic coupling module based medium voltage converter topology of claim 1, wherein said square wave voltage source is served by an m-phase half bridge, m-phase full bridge converter constructed of silicon, silicon carbide or other switching devices, the converter being two-level, three-level, or multi-level.
7. The medium voltage converter topology structure based on the high frequency magnetic coupling module according to claim 1, wherein the core circuit of each magnetic coupling submodule comprises 1 m-phase n-winding high frequency transformer, m x n LC resonance branches, n m-phase square wave voltage source half-bridge/full-bridge converters; and the m-phase winding terminals of each transformer are respectively connected with an LC branch in series, and the other end of the LC branch is connected with an m-phase square wave voltage source half-bridge/full-bridge converter.
8. The medium voltage converter topology based on high frequency magnetic coupling module according to claim 7, characterized in that said m-phase is single phase, two phase or multiple phase, n-winding is double winding, triple winding or multiple winding;
if m is single phase and the converter is half bridge, the negative pole of DC side of each winding single phase half bridge converter is connected with the other connecting terminal of the winding.
9. The medium voltage converter topology based on high frequency magnetic coupling modules of claim 1, wherein said plurality of magnetic coupling modules form a three-phase ac-to-three-phase ac converter, a single-phase ac-to-single-phase ac converter, a dc-to-three-phase ac converter, a dc-to-single-phase ac converter and a dc-to-dc two-port converter topology and a serialized converter topology having more than three ports.
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CN114244139A (en) * 2021-12-23 2022-03-25 西安交通大学 Multi-winding high-frequency magnetic coupling current transformer and power decoupling control method thereof
CN114679073A (en) * 2022-05-06 2022-06-28 西安交通大学 Data center power module and modular power supply
CN115356534A (en) * 2022-10-21 2022-11-18 成都特隆美储能技术有限公司 Method for reducing frequency spectrum leakage during power grid current FFT harmonic extraction
CN114679073B (en) * 2022-05-06 2024-05-10 西安交通大学 Data center power module and modularized power supply

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CN114244139A (en) * 2021-12-23 2022-03-25 西安交通大学 Multi-winding high-frequency magnetic coupling current transformer and power decoupling control method thereof
CN114244139B (en) * 2021-12-23 2024-05-14 西安交通大学 Multi-winding high-frequency magnetic coupling converter and power decoupling control method thereof
CN114679073A (en) * 2022-05-06 2022-06-28 西安交通大学 Data center power module and modular power supply
CN114679073B (en) * 2022-05-06 2024-05-10 西安交通大学 Data center power module and modularized power supply
CN115356534A (en) * 2022-10-21 2022-11-18 成都特隆美储能技术有限公司 Method for reducing frequency spectrum leakage during power grid current FFT harmonic extraction

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