CN112398323A - High-frequency chain direct-current transformer with short-circuit current blocking and fault tolerance functions and control method - Google Patents

High-frequency chain direct-current transformer with short-circuit current blocking and fault tolerance functions and control method Download PDF

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CN112398323A
CN112398323A CN202011214023.4A CN202011214023A CN112398323A CN 112398323 A CN112398323 A CN 112398323A CN 202011214023 A CN202011214023 A CN 202011214023A CN 112398323 A CN112398323 A CN 112398323A
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frequency
hvdc
module
lvdc
port
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CN112398323B (en
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文武松
赵争鸣
袁立强
姬世奇
莫昕
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Tsinghua University
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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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • 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
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • 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
    • H02M3/33569—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 several active switching elements
    • H02M3/33576—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 several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • 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
    • H02M3/33569—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 several active switching elements
    • H02M3/33576—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 several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33592—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 several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/325—Means for protecting converters other than automatic disconnection with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention discloses a high-frequency chain direct current transformer with short-circuit current blocking and fault tolerance and a control method, and belongs to the technical field of power electronic equipment. The high-frequency chain direct current transformer is provided with two ports, namely an HVDC port and an LVDC port, and adopts a common high-frequency bus structure, wherein the ports are interconnected through a high-frequency bus; and the method has a plurality of operation modes, and adopts a phase shift control method based on a global synchronous clock. The topological structure has high modularization degree and simple control, is beneficial to improving the power density and reducing the design difficulty and the device volume of the high-frequency transformer, thereby optimizing the cost; each port has short-circuit current blocking capability and high recovery speed; the operation of each port submodule is independent, when a certain module of one port breaks down, the operation of all submodules of the other port is not influenced, and the method is very suitable for application occasions of flexible interconnection of a plurality of direct current ports.

Description

High-frequency chain direct-current transformer with short-circuit current blocking and fault tolerance functions and control method
Technical Field
The invention relates to the technical field of power electronic equipment, in particular to a high-frequency chain direct-current transformer with short-circuit current blocking and fault tolerance and a control method.
Background
With the increasing demand of distributed new energy grid connection, the wide application of direct current loads and the development of flexible direct current transmission technology, a direct current micro-grid/direct current distribution network becomes a hot point of current research. In order to realize the connection of dc sub-networks of various voltage classes, energy conversion is inevitable and must be realized by means of dc transformers (DCT) based on power electronics technology.
In the field of low voltage and small capacity, the DC/DC converter is used for accessing direct current loads, energy storage, distributed power supplies and the like in a low voltage direct current micro-grid, generally does not meet the requirement of power bidirectional transmission, is inconvenient for system structure modularization and capacity expansion, and is difficult to apply to the field of medium and high voltage direct current power grids. Due to the advantages of high modularity and high redundancy, the application of MMC (Modular Multi-level Converter) technology in medium voltage DCT is concerned, and research on MMC type DCT generally focuses on voltage balancing strategy, pulse modulation strategy, efficiency and loss analysis of sub-module capacitors. The MMC type DCT has the defects of excessive sub-module quantity, larger device volume, low power density and the like, so the MMC type DCT has no obvious advantages in the application occasions of medium-voltage direct-current power distribution networks. Therefore, it is rarely adopted in practical engineering. The modular topology based on the Dual Active Bridge (DAB) converter has the advantages of low voltage stress requirement, high modularization degree, high power density, good redundancy design and the like, and is widely applied to medium-high voltage DCT at present, wherein the high-voltage sides of the modular topology are connected in series to improve the voltage level, and the low-voltage sides of the modular topology are connected in parallel to improve the power level. Referred to herein as a conventional DCT (the traditional DAB-based DCT), the topology of which is shown in fig. 1. There have been many researches on the voltage equalization control technology of the sub-module capacitor of the TDCT, and the engineering application difficulties of the TDCT mainly include the following aspects:
(1) when an external direct current short-circuit fault occurs to a port, the TDCT cannot be cut off from the fault without overcurrent quickly, and cannot be put into operation again quickly after the fault disappears.
(2) When the port has an internal sub-module fault, the TDCT cannot realize redundant operation.
(3) From the application scenario of the medium voltage DCT, the number of modules of the medium voltage port is mainly related to the voltage class, and the number of modules of the low voltage port is mainly related to the port power class. If the number of the modules of the two ports can be independently adjusted, the number of the modules is favorable for optimizing, system structure reconstruction is convenient to carry out according to voltage and power levels, and system power density is improved. However, in the TDCT, two H-bridges in each DAB are respectively located in the medium voltage port and the low voltage port, and the numbers of sub-modules of the two ports cannot be independent and must be kept equal. Therefore, flexibility in adjusting the number of port modules is limited.
(4) When a module of one port of the TDCT fails, not only the failed module needs to be bypassed, but also the power transmission of the module corresponding to the other port fails.
(5) The TDCT topology only has two direct current ports, and cannot be suitable for application occasions of flexible interconnection and power mutual transmission of a plurality of direct current ports.
These disadvantages and shortcomings limit the application of TDCT in practical engineering to a great extent, and are urgently to be solved.
Disclosure of Invention
The invention aims to provide a high-frequency chain direct-current transformer with short-circuit current blocking and fault tolerance and a control method. A high-frequency chain direct current transformer with short-circuit current blocking and fault tolerance is characterized in that: the direct current transformer is composed of a high voltage direct current port (HVDC port) and a low voltage direct current port (LVDC port); HVDC port and LVDC port through high frequency bus HFB1-HFB2Connecting; the direct current transformer adopts a phase shift control method based on a global synchronous clock, has multiple operation modes, and has short-circuit current blocking capability and redundant fault-tolerant capability under different operation modes.
The HVDC port is composed of multiple HVDC modules of the same structure in series, and each HVDC module comprises 1 HVDC module composed of T1/D1、T2/D2、T3/D3And T4/D4Formed high-frequency H bridge and 1 high-frequency transformer M h1 DC bus capacitor ChAnd 1 is composed of T5/D5And T6/D6A bypass switch; high-frequency H-bridge and DC bus capacitor ChAnd the bypass switch is connected in parallel; bridge arm midpoint A of high-frequency H bridgehAnd BhConnecting a high-frequency transformer MhBoth ends of the primary coil of (1); high-frequency transformer MhSecondary winding terminal Hh1And Hh2As a high frequency output of the HVDC module; midpoint a of the bypass switchhAnd negative electrode node b of direct current bus capacitorhAs low frequency input of the HVDC module.
High-frequency output ends of HVDC modules are connected in parallel and then connected with a high-frequency bus HFB1-HFB2(ii) a The low-frequency input ends of the HVDC modules are connected in series with each other and then connected with the reactor LphConnected in series to form the input H of the HVDC port1-H2。
The LVDC port is formed by connecting a plurality of LVDC modules with the same structure in parallel; the LVDC module comprises 1S1/Q1、S2/Q2、S3/Q3And S4/Q4Formed high-frequency H bridge and 2 high-frequency reactors LL1And L L21 DC bus capacitor CLAnd 1 is composed of S5/Q5And Q6A bypass switch; high-frequency H-bridge and DC bus capacitor CLAnd the bypass switch is connected in parallel; bridge arm midpoint A of high-frequency H bridgeLAnd BLAre respectively connected with high-frequency reactors LL1And LL2One end of (a); high-frequency reactor LL1And LL2The other end of the LVDC module is used as a high-frequency output end of the LVDC module; midpoint a of the bypass switchLAnd negative electrode node b of direct current bus capacitorLAs the low frequency input of the LVDC module.
High-frequency output ends of the LVDC modules are connected in parallel and then connectedConnect high frequency generating line HFB1-HFB2(ii) a The low-frequency input ends of the LVDC modules are connected in parallel with each other and then connected with the reactor LpLConnected in series to form the input terminal L of the LVDC port1-L2。
The control method of the high-frequency chain direct current transformer with short-circuit current blocking and fault tolerance is characterized by comprising the following steps of: the signal of the global synchronous clock is 1 path of high-frequency square wave signal, and the duty ratio is 50%; t in HVDC Module1、T2、T3And T4The driving pulses are all high-frequency square wave signals, the duty ratios are all 50%, and the frequencies are all the same as the signal frequency of the global synchronous clock; t in HVDC Module1And T4Are in the same phase as the drive pulse of (T)2And T3Are in the same phase as the drive pulse of (T)1Drive pulse of (1) and T2The phase of the drive pulse is 180 degrees different; LVDC module inner S1、S2、S3And S4The driving pulses of the clock signal are all high-frequency square wave signals, the duty ratios of the driving pulses are all 50%, and the frequencies of the driving pulses are all the same as the frequencies of the global synchronous clock signals; LVDC module inner S1And S4Are in the same phase as the drive pulse of S2And S3Are in the same phase as the drive pulse of S1Of (d) and (S)2The phase of the drive pulse is 180 degrees different; t in HVDC Module1The phase difference between the driving pulse and the global synchronous clock is called HVDC module phase shift angle, S in LVDC module1The phase difference between the driving pulse and the global synchronous clock is called as LVDC module phase shift angle, and the port voltage, the port current and the transmission power of the direct current transformer are controlled by changing the magnitude of the HVDC module phase shift angle and the LVDC module phase shift angle.
The direct-current transformer has two typical operation modes, namely an operation mode 1 and an operation mode 2; in operation mode 1, the HVDC port operates in power following mode, with its input H1-H2Receiving a voltage source, wherein the phase shift angle of each HVDC module is equal to the sum of a reference phase shift angle and a deviation phase shift angle, the reference phase shift angle of each HVDC module is equal to 0, the magnitude of the deviation phase shift angle is changed for balancing the direct-current side voltage of each HVDC module, the magnitude of the phase shift angle of each LVDC module is consistent, and the phase shift angles of the HVDC modules are adjusted to be consistentThe phase shift angle of the LVDC module realizes the control of the voltage or current of the LVDC port of the direct current transformer; in run mode 2, the LVDC port is run in power following mode with input L1-L2And the phase shift angle of each LVDC module is equal to 0, the phase shift angle of each HVDC module is equal to the sum of the reference phase shift angle and the deviation phase shift angle, the reference phase shift angle of each HVDC module is consistent in size, the control of the total voltage or the current of the HVDC port of the direct current transformer is realized by adjusting the size of the reference phase shift angle of the HVDC module, and the size of the deviation phase shift angle of the HVDC module is changed to balance the voltage on the direct current side of each HVDC module.
When the input end L of the LVDC port is detected1-L2When short-circuit fault occurs, the high-frequency H-bridge power tubes S in all the LVDC modules are locked simultaneously1、S2、S3And S4And the upper tube S of the bypass switch5(ii) a When the input end L of the LVDC port is detected1-L2When the short-circuit fault is eliminated, the high-frequency H-bridge power tubes S in all the LVDC modules are unlocked1、S2、S3And S4And the upper tube S of the bypass switch5；
When detecting the input H of the HVDC port1-H2When short-circuit fault occurs, high-frequency H-bridge power tubes T in all HVDC modules are locked simultaneously1、T2、T3And T4And upper tube T of bypass switch5When detecting the input H of the HVDC port1-H2When the short-circuit fault is eliminated, the high-frequency H-bridge power tubes T in all the HVDC modules are unlocked1、T2、T3And T4And upper tube T of bypass switch5。
When a LVDC module of the LVDC port is detected to be out of order (referred to as an LVDC failure module herein), the high-frequency H-bridge power tube S of the LVDC failure module is immediately and simultaneously locked1、S2、S3And S4And the upper tube S of the bypass switch5；
When a fault is detected in one of the HVDC modules of the HVDC port (referred to herein as HVDC fault module), it is immediately closed at the same timeHigh-frequency H-bridge power tube T for locking HVDC fault module1、T2、T3And T4And upper tube T of bypass switch5And unlocking a lower tube T of a bypass switch of the HVDC fault module after 2-3 us of interval6。
The invention has the beneficial effects that:
(1) the system adopts a common high-frequency bus structure, and the electric coupling relationship between the ports is changed into a magnetic coupling relationship, thereby being beneficial to improving the system efficiency.
(2) The number of the sub-modules of each port can be independently configured, which is beneficial to optimizing the number of modules, improving the power density, reducing the design difficulty of the high-frequency transformer and the device volume and optimizing the cost.
(3) Each port has short-circuit current blocking capacity, when a short-circuit fault occurs outside the port, the short-circuit current can be blocked quickly, and the voltage of the port is kept unchanged; when the short-circuit fault is recovered, each port can quickly recover to normal operation.
(4) Each port has redundant fault-tolerant capability, when the port submodule has internal fault, the fault module can be shielded in time, and other submodules can continue to work normally. And the operation of each port submodule is independent, when a certain module of one port has a fault, only the fault module is shielded, and the operation of all submodules of the other port is not influenced.
(5) Theoretically any number of dc ports can be extended. The port submodule consists of a high-frequency transformer, a port reactor, a high-frequency H bridge and a bypass switch. The high-frequency sides of the submodules are connected in parallel and then connected to a high-frequency bus, the direct-current sides are connected in series to obtain a high-voltage port with any voltage grade, and the direct-current sides are connected in parallel to obtain a low-voltage port with any power grade.
(6) The phase-shifting control strategy based on the global synchronous clock is adopted, the control method is simple, multiple operation modes are provided, and the actual application requirements can be met.
Drawings
FIG. 1 is a topological structure of a conventional DC transformer TDCT;
FIG. 2 is a topology of a high frequency chain DC transformer HFL-DCT;
FIG. 3 is a schematic diagram illustrating normal operation of the HFL-DCT;
FIG. 4 is a schematic diagram of the blocking of the short circuit current of the HFL-DCT when an external short circuit fault occurs at the LVDC port;
FIG. 5 is a schematic diagram of the short circuit current blocking of the HFL-DCT in the event of an external short circuit fault at the HVDC port;
FIG. 6 is a schematic diagram of redundant operation of the HFL-DCT when the LVDC port transmits active power to the outside and a fault occurs inside the sub-module;
FIG. 7 is a schematic diagram of the redundant operation of the HFL-DCT when the LVDC port absorbs active power from the outside and a sub-module fails inside;
FIG. 8 is a schematic diagram of the redundant operation of the HFL-DCT when the HVDC port delivers active power to the outside and a fault occurs inside the sub-module;
fig. 9 is a schematic diagram of the redundant operation of the HFL-DCT when the HVDC port absorbs active power from the outside and a fault occurs inside the sub-module.
Detailed Description
The invention provides a high-frequency chain direct current transformer with short-circuit current blocking and fault tolerance and a control method thereof, and the invention is further explained by combining the attached drawings and the specific embodiment.
(1) Topological structure
The topology of the HFL-DCT is shown in fig. 2. The HFL-DCT comprises a high-voltage direct current (HVDC) port and a low-voltage direct current (LVDC) port, and the HVDC port and the LVDC port are connected through a high-frequency bus HFB1-HFB2Are connected. Fig. a and b in fig. 2 are circuit diagrams of the high voltage dc port and low voltage dc port sub-modules of fig. c, respectively.
The HVDC port is composed of multiple HVDC modules of the same structure in series, each HVDC module contains 1 module of T1/D1、T2/D2、T3/D3And T4/D4Formed high-frequency H bridge and 1 high-frequency transformer M h1 DC bus capacitor ChAnd 1 is composed of T5/D5And T6/D6A bypass switch is formed. High-frequency H-bridge and DC bus capacitor ChAnd a bypassThe switches are connected in parallel, and the middle point A of the bridge arm of the high-frequency H bridgehAnd BhConnecting a high-frequency transformer MhBoth ends of the primary coil of (1); high-frequency transformer MhSecondary winding terminal Hh1And Hh2As a high frequency output of the HVDC module; midpoint a of the bypass switchhAnd negative electrode node b of direct current bus capacitorhAs low frequency input of the HVDC module. The high-frequency output ends of all HVDC modules are connected in parallel and then connected with a high-frequency bus HFB1-HFB2The low-frequency input ends are connected in series and then connected with the reactor LphConnected in series to form the input H of the HVDC port1-H2。
The LVDC port is formed by connecting a plurality of LVDC modules with the same structure in parallel. Each LVDC module comprises 1S1/Q1、S2/Q2、S3/Q3And S4/Q4Formed high-frequency H bridge and 2 high-frequency reactors LL1And L L21 DC bus capacitor CLAnd 1 is composed of S5/Q5And Q6A bypass switch is formed. High-frequency H-bridge and DC bus capacitor CLAnd a bypass switch connected in parallel, and a bridge arm midpoint A of the high-frequency H bridgeLAnd BLAre respectively connected with high-frequency reactors LL1And LL2One end of (a); high-frequency reactor LL1And LL2The other end of the LVDC module is used as a high-frequency output end of the LVDC module; midpoint a of the bypass switchLAnd negative electrode node b of direct current bus capacitorLAs the low frequency input of the LVDC module. The high-frequency output ends of all LVDC modules are connected in parallel and then connected with a high-frequency bus HFB1-HFB2The low-frequency input ends are connected in parallel with the reactor LpLConnected in series to form the input terminal L of the LVDC port1-L2。
In theory this topology can extend any number of dc ports. The sub-module of the expansion port is composed of 1 high-frequency transformer, 1 high-frequency H bridge, 1 bypass switch and 1 port reactor, and the connection of the devices is consistent with the internal connection condition of the HVDC sub-module. The high-frequency side of each submodule of the expansion port is connected with a high-frequency bus after being connected in parallel, the direct-current side can obtain a high-voltage port with any voltage grade through series connection, and the direct-current side can obtain a low-voltage port with any power grade through parallel connection.
(2) Control method and operating mode
The HFL-DCT shown in fig. 2 employs a phase shift control strategy based on a global synchronous clock, the global synchronous clock signal is a 1-path high-frequency square wave signal, the duty ratio is 50%, and the signal is used as a phase shift reference for all sub-modules. T in HVDC Module1、T2、T3And T4The driving pulses of the clock are all high-frequency square wave signals, the duty ratios of the driving pulses are all 50%, and the frequencies of the driving pulses are all the same as the frequency of the global synchronous clock signal; t in HVDC Module1And T4Are in the same phase as the drive pulse of (T)2And T3Are in the same phase as the drive pulse of (T)1Drive pulse of (1) and T2Are 180 degrees out of phase. LVDC module inner S1、S2、S3And S4The driving pulses of the clock are all high-frequency square wave signals, the duty ratios of the driving pulses are all 50%, and the frequencies of the driving pulses are all the same as the frequency of the global synchronous clock signal; LVDC module inner S1And S4Are in the same phase as the drive pulse of S2And S3Are in the same phase as the drive pulse of S1Of (d) and (S)2Are 180 degrees out of phase. T in HVDC Module1The phase difference between the driving pulse and the global synchronous clock signal is called HVDC module phase shift angle, S in LVDC module1The phase difference between the driving pulse and the global synchronous clock signal is called LVDC module phase shift angle, and the port voltage, the port current and the transmission power of the HFL-DCT can be controlled by changing the magnitude of the HVDC module phase shift angle and the LVDC module phase shift angle.
The HFL-DCT has two typical modes of operation-mode 1 and mode 2. In operation mode 1, the HVDC port operates in power following mode, with its input H1-H2Receiving a voltage source, wherein the phase shift angle of each HVDC module is equal to the sum of a reference phase shift angle and a deviation phase shift angle, the reference phase shift angle of each HVDC module is equal to 0, the magnitude of the deviation phase shift angle is changed to balance the direct-current side voltage of each HVDC module, and each LVThe phase shift angles of the DC modules are consistent, and the voltage or current of the LVDC port is controlled by adjusting the phase shift angle of the LVDC module. In run mode 2, the LVDC port is run in power following mode with input L1-L2And when the HVDC module is connected with a voltage source, the phase shift angle of each LVDC module is equal to 0, the phase shift angle of each HVDC module is equal to the sum of the reference phase shift angle and the deviation phase shift angle, the reference phase shift angle of each HVDC module is consistent in size, the total voltage or current of the HVDC port is controlled by adjusting the size of the reference phase shift angle of the HVDC module, and the size of the deviation phase shift angle of the HVDC module is changed to balance the direct-current side voltage of each HVDC module.
(3) Short circuit current blocking control
The normal operation topology of the HFL-DCT is shown in figure 3, and the upper tube of each sub-module bypass switch is unlocked. The dashed line represents the tube in the locked state and the solid line represents the tube in the unlocked state.
As shown in fig. 4, when the input terminal L of the LVDC port is detected1-L2When short-circuit fault occurs, the high-frequency H-bridge power tubes S in all the LVDC modules are locked simultaneously1、S2、S3And S4And the upper tube S of the bypass switch5. When the input end L of the LVDC port is detected1-L2When the short-circuit fault is eliminated, the high-frequency H-bridge power tubes S in all the LVDC modules are unlocked1、S2、S3And S4And the upper tube S of the bypass switch5。
When the input H of the HVDC port is detected, as shown in fig. 51-H2When short-circuit fault occurs, high-frequency H-bridge power tubes T in all HVDC modules are locked simultaneously1、T2、T3And T4And upper tube T of bypass switch5. When detecting the input H of the HVDC port1-H2When the short-circuit fault is eliminated, the high-frequency H-bridge power tubes T in all HVDC modules are unlocked1、T2、T3And T4And upper tube T of bypass switch5。
(4) Redundant operation control
As shown in fig. 6 and 7, when LVDC is detectedWhen one LVDC module of the port fails (referred to as an LVDC fault module), the high-frequency H-bridge power tube S of the LVDC fault module is immediately and simultaneously locked1、S2、S3And S4And the upper tube S of the bypass switch5。
As shown in fig. 8 and 9, when a fault is detected in one of the HVDC modules of the HVDC port (referred to herein as an HVDC fault module), the high-frequency H-bridge power tube T of the HVDC fault module is immediately and simultaneously locked1、T2、T3And T4And upper tube T of bypass switch5And unlocking a lower tube T of a bypass switch of the HVDC fault module after 2-3 us of interval6。
The present invention is not limited to the above embodiments, and any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (9)

1. A high-frequency chain direct current transformer with short-circuit current blocking and fault tolerance is characterized in that: the direct current transformer consists of an HVDC port and an LVDC port; HVDC port and LVDC port through high frequency bus HFB1-HFB2Connecting; the direct current transformer adopts a phase shift control strategy based on a global synchronous clock, has multiple operation modes, and has short-circuit current blocking capability and redundant fault-tolerant capability under different operation modes.
2. The high frequency link dc transformer with short circuit current blocking and fault tolerance of claim 1, wherein: the HVDC port is formed by connecting a plurality of HVDC modules with the same structure in series, and each HVDC module comprises 1 HVDC module with T1/D1、T2/D2、T3/D3And T4/D4Formed high-frequency H bridge and 1 high-frequency transformer Mh1 DC bus capacitor ChAnd 1 is composed of T5/D5And T6/D6A bypass switch; high-frequency H-bridge and DC bus capacitor ChAnd the bypass switch is connected in parallel; bridge arm midpoint A of high-frequency H bridgehAnd BhConnecting a high-frequency transformer MhBoth ends of the primary coil of (1); high-frequency transformer MhSecondary winding terminal Hh1And Hh2As a high frequency output of the HVDC module; midpoint a of the bypass switchhAnd negative electrode node b of direct current bus capacitorhAs low frequency input of the HVDC module.
3. The high frequency link dc transformer with short circuit current blocking and fault tolerance of claim 2, wherein: the high-frequency output ends of the HVDC modules are connected in parallel and then connected with a high-frequency bus HFB1-HFB2(ii) a The low-frequency input ends of the HVDC modules are connected in series with each other and then connected with the reactor LphConnected in series to form the input H of the HVDC port1-H2。
4. The high frequency link dc transformer with short circuit current blocking and fault tolerance of claim 1, wherein: the LVDC port is formed by connecting a plurality of LVDC modules with the same structure in parallel; the LVDC module comprises 1S1/Q1、S2/Q2、S3/Q3And S4/Q4Formed high-frequency H bridge and 2 high-frequency reactors LL1And LL21 DC bus capacitor CLAnd 1 is composed of S5/Q5And Q6A bypass switch; high-frequency H-bridge and DC bus capacitor CLAnd the bypass switch is connected in parallel; bridge arm midpoint A of high-frequency H bridgeLAnd BLAre respectively connected with high-frequency reactors LL1And LL2One end of (a); high-frequency reactor LL1And LL2The other end of the LVDC module is used as a high-frequency output end of the LVDC module; midpoint a of the bypass switchLAnd negative electrode node b of direct current bus capacitorLAs the low frequency input of the LVDC module.
5. The method of claim 4The high-frequency chain direct current transformer with short-circuit current blocking and fault tolerance is characterized in that: the high-frequency output ends of the LVDC modules are connected in parallel and then connected with a high-frequency bus HFB1-HFB2(ii) a The low-frequency input ends of the LVDC modules are connected in parallel with each other and then connected with the reactor LpLConnected in series to form the input terminal L of the LVDC port1-L2。
6. A control method of a high frequency chain DC transformer with short circuit current blocking and fault tolerance as claimed in claim 1, 2 or 4, characterized in that: the signal of the global synchronous clock is 1 path of high-frequency square wave signal, and the duty ratio is 50%; t in the HVDC module1、T2、T3And T4The driving pulses are all high-frequency square wave signals, the duty ratios are all 50%, and the frequencies are all the same as the signal frequency of the global synchronous clock; t in HVDC Module1And T4Are in the same phase as the drive pulse of (T)2And T3Are in the same phase as the drive pulse of (T)1Drive pulse of (1) and T2The phase of the drive pulse is 180 degrees different; s in the LVDC module1、S2、S3And S4The driving pulses of the clock signal are all high-frequency square wave signals, the duty ratios of the driving pulses are all 50%, and the frequencies of the driving pulses are all the same as the frequencies of the global synchronous clock signals; LVDC module inner S1And S4Are in the same phase as the drive pulse of S2And S3Are in the same phase as the drive pulse of S1Of (d) and (S)2The phase of the drive pulse is 180 degrees different; t in HVDC Module1The phase difference between the driving pulse and the global synchronous clock is called HVDC module phase shift angle, S in LVDC module1The phase difference between the driving pulse and the global synchronous clock is called as LVDC module phase shift angle, and the port voltage, the port current and the transmission power of the direct current transformer are controlled by changing the magnitude of the HVDC module phase shift angle and the LVDC module phase shift angle.
7. The method according to claim 6, wherein the method comprises the steps of: the DC transformer is provided withTwo typical modes of operation — mode 1 and mode 2; in operation mode 1, the HVDC port operates in power following mode, with its input H1-H2Receiving a voltage source, wherein the phase shift angle of each HVDC module is equal to the sum of a reference phase shift angle and a deviation phase shift angle, the reference phase shift angle of each HVDC module is equal to 0, the magnitude of the deviation phase shift angle is changed to balance the direct current side voltage of each HVDC module, the magnitude of the phase shift angle of each LVDC module is consistent, and the magnitude of the voltage or the current of an LVDC port of a direct current transformer is controlled by adjusting the magnitude of the phase shift angle of the LVDC module; in run mode 2, the LVDC port is run in power following mode with input L1-L2And the phase shift angle of each LVDC module is equal to 0, the phase shift angle of each HVDC module is equal to the sum of the reference phase shift angle and the deviation phase shift angle, the reference phase shift angle of each HVDC module is consistent in size, the control of the total voltage or the current of the HVDC port of the direct current transformer is realized by adjusting the size of the reference phase shift angle of the HVDC module, and the size of the deviation phase shift angle of the HVDC module is changed to balance the voltage on the direct current side of each HVDC module.
8. The method according to claim 6, wherein the method comprises the steps of: when the input end L of the LVDC port is detected1-L2When short-circuit fault occurs, the high-frequency H-bridge power tubes S in all the LVDC modules are locked simultaneously1、S2、S3And S4And the upper tube S of the bypass switch5(ii) a When the input end L of the LVDC port is detected1-L2When the short-circuit fault is eliminated, the high-frequency H-bridge power tubes S in all the LVDC modules are unlocked1、S2、S3And S4And the upper tube S of the bypass switch5；
When detecting the input H of the HVDC port1-H2When short-circuit fault occurs, high-frequency H-bridge power tubes T in all HVDC modules are locked simultaneously1、T2、T3And T4And upper tube T of bypass switch5When detecting the input H of the HVDC port1-H2When the short-circuit fault is eliminated, the high-frequency H-bridge power tubes T in all the HVDC modules are unlocked1、T2、T3And T4And upper tube T of bypass switch5。
9. The method according to claim 6, wherein the method comprises the steps of: when a certain LVDC module of the LVDC port is detected to be in fault, the high-frequency H-bridge power tube S of the LVDC fault module is immediately and simultaneously locked1、S2、S3And S4And the upper tube S of the bypass switch5；
When a certain HVDC module of the HVDC port is detected to have a fault, the high-frequency H-bridge power tube T of the HVDC fault module is immediately and simultaneously locked1、T2、T3And T4And upper tube T of bypass switch5And unlocking a lower tube T of a bypass switch of the HVDC fault module after 2-3 us of interval6。
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