CN117013850A - Voltage equalizing method and system for modularized multi-level medium-voltage direct-current transformer - Google Patents

Voltage equalizing method and system for modularized multi-level medium-voltage direct-current transformer Download PDF

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Publication number
CN117013850A
CN117013850A CN202311072528.5A CN202311072528A CN117013850A CN 117013850 A CN117013850 A CN 117013850A CN 202311072528 A CN202311072528 A CN 202311072528A CN 117013850 A CN117013850 A CN 117013850A
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China
Prior art keywords
switching
sub
voltage
module
sequence
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CN202311072528.5A
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Chinese (zh)
Inventor
陈勇
陈建福
杨锐雄
唐捷
曹安瑛
喻松涛
吴宏远
裴星宇
程旭
李建标
顾延勋
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CSG Electric Power Research Institute
Guangdong Power Grid Co Ltd
Zhuhai Power Supply Bureau of Guangdong Power Grid Co Ltd
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CSG Electric Power Research Institute
Guangdong Power Grid Co Ltd
Zhuhai Power Supply Bureau of Guangdong Power Grid Co Ltd
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Priority to CN202311072528.5A priority Critical patent/CN117013850A/en
Publication of CN117013850A publication Critical patent/CN117013850A/en
Pending legal-status Critical Current

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Classifications

    • 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
    • H02M3/33573—Full-bridge at primary side of an isolation transformer
    • 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
    • H02J1/002—Intermediate AC, e.g. DC supply with intermediated AC distribution
    • 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
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • 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
    • 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]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a voltage equalizing method and a system of a modularized multi-level medium-voltage direct-current transformer, which comprise the steps of determining a plurality of sub-module groups based on preset sub-module numbers in bridge arms corresponding to modularized multi-level medium-voltage direct-current transformer information; determining a plurality of switching sequence groups based on a preset switching rule and all sub-module groups; based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information, the submodules are switched according to the submodule numbering sequence of the switching sequence group corresponding to the switching period. The technical problems that in the prior art, the sub-module capacitor voltage equalizing control of a medium-voltage side MMC structure of a plurality of sub-modules is required, and the advanced controller is used for completing the calculation of a control system, so that the use cost is too high and the engineering application of a modularized multi-level medium-voltage direct-current transformer is not facilitated are solved; the voltage equalizing method provided by the invention does not need to measure the current of the bridge arm, reduces the use of a current sensor and reduces the construction cost of the medium-voltage direct-current transformer.

Description

Voltage equalizing method and system for modularized multi-level medium-voltage direct-current transformer
Technical Field
The invention relates to the technical field of modularized multi-level medium-voltage direct-current transformers, in particular to a voltage equalizing method and a voltage equalizing system for modularized multi-level medium-voltage direct-current transformers.
Background
On the power supply side of the power distribution system, the duty ratio of clean energy sources such as distributed photovoltaic and wind power is higher and higher, the matched energy storage capacity is larger and larger, and on the load side of the power distribution system, the direct current loads such as a data center and an electric vehicle charging station are also growing increasingly. This also illustrates that the dc-like character of the power distribution system is becoming more and more apparent. Under the background, in order to improve the power quality and the power supply efficiency of a power distribution system, the construction of a medium-voltage direct-current power distribution network with more flexible control, larger power supply capacity and longer power supply radius is an effective method.
In a medium-voltage direct-current distribution network, a medium-voltage direct-current transformer is a key converter device for completing electric energy transmission and voltage conversion. Although modular double-active full-bridge (Dual Active Bridge, DAB) medium voltage dc transformers based on medium voltage side series-low voltage side parallel are used for the earliest applications in medium voltage dc distribution networks, further developments of the related art have been hampered because the above-described methods fail to achieve fault isolation.
Therefore, in order to better construct a medium-voltage direct-current power distribution network, the problem of direct-current fault isolation of a medium-voltage transformer is solved, and the key of constructing a novel medium-voltage direct-current transformer is realized. Referring to fig. 1, in a modular multilevel medium voltage dc transformer based on a parallel structure of a modular multilevel converter (module multilevel converter, MMC) and a full bridge, in the modular multilevel medium voltage dc transformer, when a medium voltage dc bus fails, the MMC structure on the medium voltage side can realize isolation of branch faults through blocking, and meanwhile, in order to improve the power density of the medium voltage dc transformer, reduce the occupied area of the medium voltage dc transformer, the modular multilevel medium voltage dc transformer adopts a high frequency switching frequency above 20kHz and a high frequency isolation transformer, but the method adopts a high frequency switching frequency above 20kHz, the control period of the modular multilevel medium voltage dc transformer is usually less than 50ms, and the calculation of a control system is completed by adopting a submodule capacitor voltage equalizing control of the medium voltage side MMC structure of a plurality of submodules, so that the use cost is too high, which is unfavorable for engineering application of the modular multilevel medium voltage dc transformer.
Disclosure of Invention
The invention provides a voltage equalizing method and a system for a modularized multi-level medium voltage direct current transformer, which solve the technical problems that the prior art needs to adopt the capacitor voltage equalizing control of a sub-module capacitor with a medium voltage side MMC structure of a plurality of sub-modules and an advanced controller to finish the calculation of a control system, so that the use cost is too high and the engineering application of the modularized multi-level medium voltage direct current transformer is not facilitated.
The invention provides a voltage equalizing method of a modularized multi-level medium-voltage direct current transformer, which comprises the following steps:
responding to a voltage-sharing instruction request, and acquiring modularized multi-level medium-voltage direct-current transformer information corresponding to the voltage-sharing instruction request;
determining a plurality of sub-module groups based on preset sub-module numbers in bridge arms corresponding to the modularized multi-level medium-voltage direct-current transformer information;
determining a plurality of switching sequence groups based on a preset switching rule and all the submodule groups;
and switching the submodules according to the number sequence of the submodules of the switching sequence group corresponding to the switching period based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information.
Optionally, the step of determining a plurality of sub-module groups based on the preset sub-module numbers in the bridge arm corresponding to the modularized multi-level medium voltage dc transformer information includes:
Numbering all sub-modules in a bridge arm corresponding to the modularized multi-level medium-voltage direct current transformer information to generate a plurality of sub-module numbers;
and determining a plurality of sub-module groups based on the preset capacitor voltage requirement and the numbers of all sub-modules in each bridge arm.
Optionally, the step of determining a plurality of sub-module groups based on a preset capacitor voltage requirement and all sub-module numbers in each bridge arm includes:
acquiring a plurality of preset capacitor voltage requirements;
selecting sub-module numbers meeting the preset capacitor voltage requirements from all sub-modules in a preset target bridge arm, and generating a sub-module group;
selecting any one of the remaining bridge arms as a new target bridge arm, skipping and executing all sub-modules in the preset target bridge arm, selecting sub-module numbers meeting the preset capacitor voltage requirement, and generating a sub-module group until all sub-modules in all the bridge arms are grouped, and generating a plurality of sub-module groups.
Optionally, the method further comprises:
numbering all the sub-module groups to generate a plurality of sub-module group numbers; and the sub-module group numbers corresponding to the two different preset capacitor voltage requirements are arranged at intervals according to a preset limit.
Optionally, the step of determining a plurality of switching sequence groups based on a preset switching rule and all the submodule groups includes:
acquiring a plurality of preset switching rules;
sequencing all the sub-module groups according to a switching sequence of a target preset switching rule to generate a switching sequence group;
selecting any one of the remaining preset switching rules as a new target preset switching rule, and skipping to execute the step of sequencing all the sub-module groups according to the switching sequence of the target preset switching rule to generate a switching sequence group.
Optionally, the step of switching the sub-modules according to the sub-module numbering sequence of the switching sequence group corresponding to the switching period based on the switching period corresponding to the modularized multi-level medium voltage direct current transformer information includes:
acquiring a plurality of switching periods of the modularized multi-level medium voltage direct current transformer information, numbering all the switching periods, and generating a switching period number;
dividing each switching period into a plurality of switching stages, numbering the switching stages, and generating switching stage numbers;
acquiring a switching sequence group corresponding to each switching period according to the sequencing result of all the switching period numbers;
Determining the submodule groups required to be put into each switching stage based on the submodule group numbers and the switching stage numbers of the switching sequence groups corresponding to the switching periods;
and acquiring a submodule group of a switching stage corresponding to the switching period according to a preset sequence, and switching the submodules of the submodule group according to the serial number sequence of the submodules.
Optionally, the step of obtaining the submodule group of the switching stage corresponding to the switching period according to a preset sequence and switching the submodules of the submodule group according to the serial number sequence of the submodules includes:
acquiring a switching period corresponding to the first switching period number according to a preset sequence, and generating a first switching period;
acquiring all switching stages and switching sequence groups corresponding to the first switching period;
sequentially sequencing the numbers of the switching phases according to a preset phase sequence, and acquiring a submodule group of a switching sequence group corresponding to the current switching phase according to a sequencing result;
and switching the submodules of the submodule group according to the number sequence of the submodules.
Optionally, after the step of switching the submodules of the submodule group according to the submodule numbering sequence, the method further includes:
Judging whether the switching of the current switching period is finished;
if not, acquiring a switching stage number corresponding to the current switching submodule, determining a switching stage corresponding to the next switching stage number, and generating a target switching stage;
obtaining a submodule group of a switching sequence group corresponding to the target switching stage;
switching the submodules of the submodule group according to the number sequence of the submodules, and skipping to execute the step of judging whether the switching of the current switching period is finished or not until no residual switching stage exists in the current switching period;
if yes, judging whether the number of the switching period corresponding to the current switching period is a preset number multiple;
if yes, skipping to execute the step of acquiring all switching stages and switching sequence groups corresponding to the first switching period;
if not, acquiring a switching cycle number corresponding to the current switching cycle, determining a switching cycle corresponding to the next switching cycle number, and generating a target switching cycle;
acquiring all switching stages and switching sequence groups corresponding to the target switching period;
and skipping and executing the step of sequencing the numbers of the switching phases in turn according to the preset phase sequence and obtaining the sub-module group of the switching sequence group corresponding to the current switching phase according to the sequencing result.
Optionally, the method further comprises:
acquiring the bridge arm direct current voltage support minimum submodule number of the modularized multi-level medium voltage direct current transformer information;
and calculating the number of the submodules required to be input by the submodule group corresponding to the switching stage by adopting the least number of the submodules supported by the bridge arm direct-current voltage and the number of the submodules corresponding to the switching stage corresponding to the current switching period.
The invention provides a modular multilevel medium voltage direct current transformer voltage equalizing system, which comprises:
the voltage-sharing instruction request module is used for responding to the voltage-sharing instruction request and acquiring modularized multi-level medium-voltage direct-current transformer information corresponding to the voltage-sharing instruction request;
the submodule group module is used for determining a plurality of submodule groups based on preset submodule numbers in bridge arms corresponding to the modularized multi-level medium-voltage direct current transformer information;
the switching sequence group module is used for determining a plurality of switching sequence groups based on a preset switching rule and all the submodule groups;
and the switching module is used for switching the sub-modules according to the number sequence of the sub-modules of the switching sequence group corresponding to the switching period based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information.
From the above technical scheme, the invention has the following advantages:
according to the invention, the modularized multi-level medium-voltage direct-current transformer information corresponding to the voltage-sharing instruction request is obtained by responding to the voltage-sharing instruction request; determining a plurality of sub-module groups based on preset sub-module numbers in bridge arms corresponding to the modularized multi-level medium-voltage direct-current transformer information; determining a plurality of switching sequence groups based on a preset switching rule and all sub-module groups; based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information, the submodules are switched according to the submodule numbering sequence of the switching sequence group corresponding to the switching period. The technical problems that in the prior art, the sub-module capacitor voltage equalizing control of the medium-voltage side MMC structure of a plurality of sub-modules is required, and the advanced controller is used for completing the calculation of a control system, so that the use cost is too high and the engineering application of the modularized multi-level medium-voltage direct-current transformer is not facilitated are solved.
The voltage equalizing method provided by the invention does not need to measure the current of the bridge arm, reduces the use of a current sensor and reduces the construction cost of the medium-voltage direct-current transformer; the sequencing, addition, subtraction, multiplication and division are not needed, the time complexity of the algorithm is 0, and the calculation efficiency of the modularized multi-level medium voltage direct current transformer control system is greatly improved; the improvement of the calculation efficiency enables the modularized multi-level medium-voltage direct current transformer to adopt a marketized controller with lower cost under the algorithm of the invention, avoids the use of the customised controller, greatly reduces the hardware cost and improves the engineering application prospect of the modularized multi-level medium-voltage direct current transformer.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained from these drawings without inventive faculty for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a modular multilevel medium voltage dc transformer based on a parallel structure of a modular multilevel converter and a full bridge;
fig. 2 is a flow chart of steps of a voltage equalizing method of a modular multilevel medium voltage dc transformer according to a first embodiment of the present invention;
fig. 3 is a step flowchart of a voltage equalizing method of a modular multilevel medium voltage dc transformer according to a second embodiment of the present invention;
fig. 4 is a flowchart of a method for equalizing bridge arm capacitor voltage of a modular multilevel medium voltage dc transformer according to a second embodiment of the present invention;
fig. 5 is a block diagram of a modular multilevel medium voltage dc transformer voltage equalizing system according to a third embodiment of the present invention.
Detailed Description
The embodiment of the invention provides a voltage equalizing method and a system for a modularized multi-level medium voltage direct current transformer, which are used for solving the technical problems that in the prior art, a plurality of submodules are needed to be adopted for capacitor voltage equalizing control of a medium-voltage side MMC structure of the submodules, and an advanced controller is used for completing calculation of a control system, so that the use cost is too high, and the engineering application of the modularized multi-level medium voltage direct current transformer is not facilitated.
In order to make the objects, features and advantages of the present invention more comprehensible, the technical solutions in the embodiments of the present invention are described in detail below with reference to the accompanying drawings, and it is apparent that the embodiments described below are only some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 2, fig. 2 is a flowchart illustrating a voltage equalizing method for a modular multilevel medium voltage dc transformer according to an embodiment of the invention.
The invention provides a voltage equalizing method of a modularized multi-level medium-voltage direct current transformer, which comprises the following steps:
101. And responding to the voltage-sharing instruction request, and acquiring the modularized multi-level medium-voltage direct-current transformer information corresponding to the voltage-sharing instruction request.
The voltage equalizing command request refers to a command for equalizing control of the capacitance voltage of the submodule of each bridge arm of the modular multilevel medium voltage direct current transformer.
The modularized multi-level medium-voltage direct current transformer information comprises information such as 4 bridge arms and all sub-modules in each bridge arm.
In the implementation, when a voltage-sharing instruction request is received, the modularized multi-level medium voltage direct current transformer with the voltage-sharing instruction request is determined in response to the voltage-sharing instruction request, and information such as bridge arms of the modularized multi-level medium voltage direct current transformer and all sub-modules inside each bridge arm is acquired.
102. And determining a plurality of sub-module groups based on the preset sub-module numbers in the bridge arm corresponding to the modularized multi-level medium-voltage direct current transformer information.
It should be noted that, numbers of switching sequences are performed on all sub-modules in each bridge arm, each sub-module corresponds to a number, and the numbers are not repeated.
In specific implementation, all sub-modules in 4 bridge arms contained in the modularized multi-level medium-voltage direct-current transformer information are numbered, the sub-modules of each bridge arm are divided into a plurality of sub-module groups, and each sub-module group is numbered to generate a sub-module group number.
103. And determining a plurality of switching sequence groups based on a preset switching rule and all the sub-module groups.
It should be noted that, the preset switching rule refers to that after the sub-module group is cut off from the previous group of sub-modules according to the serial number sequence of the sub-modules, the next group of sub-modules is put into the sub-modules, and so on until the switching of all the sub-modules to be switched is finished.
In specific implementation, all the sub-module groups are sequentially switched in a plurality of sequencing modes according to a preset switching rule, and each sequencing mode is a switching sequence group.
104. Based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information, the submodules are switched according to the submodule numbering sequence of the switching sequence group corresponding to the switching period.
It should be noted that the information of the modularized multi-level medium-voltage direct current transformer includes a plurality of switching periods, and each switching period has a plurality of switching stages.
In the implementation, all switching periods in the modularized multi-level medium-voltage direct-current transformer information are acquired, each switching period is ordered according to the switching period sequence, the switching period according to the ordering sequence corresponds to one switching sequence group, and each switching stage of the switching period corresponds to one sub-module group of the switching sequence group. Starting from a first switching period according to a switching sequence, switching the submodules with the numbers of the first submodule of the submodule group corresponding to the first switching period until all the submodules of the submodule group of the first switching period are switched, namely, the next switching period can be completed, and the next switching period can be completed until all the submodules of the switching period are switched, namely, the submodules of all the switching periods are switched. In the process of inputting and cutting off the factor module, each sub-module goes through different switching stages in different switching periods, and after the sub-modules of all switching periods in the modularized multi-level medium voltage direct current transformer information are switched, the equivalent switching state and the charging and discharging state of each sub-module are completely consistent, so that the equalizing effect of capacitance voltage of the sub-modules can be realized.
According to the invention, the modularized multi-level medium-voltage direct-current transformer information corresponding to the voltage-sharing instruction request is obtained by responding to the voltage-sharing instruction request; determining a plurality of sub-module groups based on preset sub-module numbers in bridge arms corresponding to the modularized multi-level medium-voltage direct-current transformer information; determining a plurality of switching sequence groups based on a preset switching rule and all sub-module groups; based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information, the submodules are switched according to the submodule numbering sequence of the switching sequence group corresponding to the switching period. The technical problems that in the prior art, the sub-module capacitor voltage equalizing control of the medium-voltage side MMC structure of a plurality of sub-modules is required, and the advanced controller is used for completing the calculation of a control system, so that the use cost is too high and the engineering application of the modularized multi-level medium-voltage direct-current transformer is not facilitated are solved.
The voltage equalizing method provided by the invention does not need to measure the current of the bridge arm, reduces the use of a current sensor and reduces the construction cost of the medium-voltage direct-current transformer; the sequencing, addition, subtraction, multiplication and division are not needed, the time complexity of the algorithm is 0, and the calculation efficiency of the modularized multi-level medium voltage direct current transformer control system is greatly improved; the improvement of the calculation efficiency enables the modularized multi-level medium-voltage direct current transformer to adopt a marketized controller with lower cost under the algorithm of the invention, avoids the use of the customised controller, greatly reduces the hardware cost and improves the engineering application prospect of the modularized multi-level medium-voltage direct current transformer.
Referring to fig. 3-4, fig. 3 is a flowchart illustrating a voltage equalizing method for a modular multilevel medium voltage dc transformer according to a second embodiment of the present invention.
The invention provides a voltage equalizing method of a modularized multi-level medium-voltage direct current transformer, which comprises the following steps:
201. and responding to the voltage-sharing instruction request, and acquiring the modularized multi-level medium-voltage direct-current transformer information corresponding to the voltage-sharing instruction request.
In the embodiment of the present invention, the implementation process of step 201 is similar to that of step 101, and will not be repeated here.
202. Numbering all sub-modules in the bridge arm corresponding to the modularized multi-level medium-voltage direct current transformer information to generate a plurality of sub-module numbers.
In the specific implementation, four bridge arms in the modularized multi-level medium voltage direct current transformer are completely identical in structure and parameters, and the voltage equalizing algorithms of the four bridge arms are independent and identical in principle, so that all sub-modules in each bridge arm are numbered according to the switching sequence. Each sub-module corresponds to a number and is not numbered repeatedly. Meanwhile, the connection sequence of the sub-modules and the position of the sub-modules in the bridge arm do not affect the continuity of the numbers, namely, for the bridge arm containing N sub-modules, the numbers of the sub-modules are from 1 to N, but the sub-modules with the connected numbers can not be directly connected electrically. For example, sub-modules that are connected from top to bottom may be numbered 1,2,3, N; the order numbers 1, N,2, 3..n-1 can also be scrambled; and other numbering sequences until all the sub-modules are numbered to obtain N sub-module numbers.
Specifically, the numbers and the submodules only need to be in one-to-one correspondence, and the effectiveness of the algorithm is not affected.
203. And determining a plurality of sub-module groups based on the preset capacitor voltage requirement and the numbers of all sub-modules in each bridge arm.
Optionally, step 203 includes the following steps S11-S13:
s11, acquiring a plurality of preset capacitor voltage requirements;
s12, selecting sub-module numbers meeting the preset capacitor voltage requirements from all sub-modules in a preset target bridge arm, and generating a sub-module group;
s13, selecting any one of the rest bridge arms as a new target bridge arm, and jumping and executing the step of selecting the sub-module numbers meeting the preset capacitor voltage requirements from all sub-modules in the preset target bridge arm to generate a sub-module group until all the sub-modules in all the bridge arms are grouped to generate a plurality of sub-module groups.
It should be noted that the preset capacitor voltage requirement refers to a requirement of capacitor voltage consistency. Specifically, according to different working conditions of application, a designer can have a requirement index for consistency of capacitance voltage during design, and the requirement index is usually expressed by capacitance voltage dispersion, and the higher the dispersion is, the lower the consistency requirement is.
In the specific implementation, the requirement of preset capacitor voltage consistency of the current application working condition is obtained, and if the requirement of capacitor voltage consistency has a special requirement, the submodules in the same bridge arm with the capacitor voltage required to be kept at higher consistency are organized into the same group, and the like, and the submodules in each bridge arm are divided into M groups.
Specifically, a certain bridge arm of the 4 bridge arms is set as a target bridge arm, sub-modules meeting the same preset capacitor voltage consistency requirement in the target bridge arm are selected and divided into a sub-module group, and the like until all sub-modules in the target bridge arm are in the sub-module group, then a certain bridge arm of the remaining 3 bridge arms is selected and set as the target bridge arm, then the sub-modules in the target bridge arm are divided into sub-module groups, and similarly, the remaining 2 bridge arms are divided into sub-module groups until all sub-modules in all the bridge arms are divided into subgroups.
Optionally, the method further comprises the following step S21:
s21, numbering all sub-module groups to generate a plurality of sub-module group numbers; the sub-module group numbers corresponding to the two different preset capacitor voltage requirements are arranged at intervals according to the preset limit.
It should be noted that the preset limit is the maximum limit, and specifically, the maximum limit may be set according to the actual situation.
In particular implementations, each sub-module group is numbered 1-M, respectively. The numbers of the M subgroups are also arbitrary, so long as one sub-module number is guaranteed to correspond to one subgroup. Wherein each subgroup comprises at least 1 number of sub-modules, and the number n of the sub-modules comprises the largest number At most a single group The determination method of (2) is as follows: under the requirement of special requirements on the consistency of the capacitance and the voltage of the submodules, the submodules with the capacitance and the voltage required to ensure higher consistency should be organized into the same subgroup, and the two subgroup numbers with the capacitance and the voltage required to be different are separated to the greatest extent. Group n with the highest number of sub-modules contained in single group At most a single group The calculation formula of (2) is as follows:
n at most a single group ＝N-n arm minimum (1)
Wherein n is At most a single group The number of the sub-modules contained in a single group is the largest; n is n arm minimum The method is used for guaranteeing the minimum module number of the bridge arm direct-current voltage support of the modularized multi-level medium-voltage direct-current transformer.
204. And determining a plurality of switching sequence groups based on a preset switching rule and all the sub-module groups.
Optionally, step 204 includes the following steps S31-S33:
s31, acquiring a plurality of preset switching rules;
s32, sequencing all sub-module groups according to a switching sequence of a target preset switching rule to generate a switching sequence group;
s33, selecting any one of the remaining preset switching rules as a new target preset switching rule, and jumping to execute the step of sequencing all sub-module groups according to the switching sequence of the target preset switching rule to generate a switching sequence group.
It should be noted that the preset switching law is formulated based on the high-frequency switching characteristic of the modularized multi-level medium-voltage direct-current transformer and the submodule switching law of the MMC structure.
In the implementation, the voltage equalizing of the capacitance voltage of the submodule is performed based on the switching period of the modularized multi-level medium-voltage direct current transformer. Determining m groups of switching sequences according to a plurality of preset switching rules, wherein a certain preset switching rule is set as a target switching rule, and a 1 st switching sequence group is formulated according to the target switching rule, wherein the target switching rule of the 1 st switching sequence group is sequentially switched from a 1 st sub-module group, a 2 nd sub-module group. Selecting another preset switching rule as a target preset switching rule, and making a 2 nd switching sequence group by the new target preset switching rule, wherein the switching sequence of the 2 nd switching sequence group is from a 2 nd sub-module group, a 3 rd sub-module group, to an m th sub-module group, and a 1 st sub-module group; selecting another preset switching rule as a target preset switching rule, and making a 3 rd switching sequence group by the new target preset switching rule, wherein the switching sequence of the 3 rd switching sequence group is from a 3 rd sub-module group, a 4 th sub-module group, an m-th sub-module group, a 1 st sub-module group and a 2 nd sub-module group; and the like until the m groups of switching sequences are formulated.
205. Based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information, the submodules are switched according to the submodule numbering sequence of the switching sequence group corresponding to the switching period.
Optionally, step 205 includes the following steps S41-S45:
s41, acquiring a plurality of switching periods of the modularized multi-level medium-voltage direct-current transformer information, numbering all the switching periods, and generating a switching period number;
s42, dividing each switching period into a plurality of switching stages, numbering the switching stages, and generating switching stage numbers;
s43, acquiring a switching sequence group corresponding to each switching period according to the sequencing result of all the switching period numbers;
s44, determining the submodule groups required to be put into each switching stage based on the submodule group numbers and the switching stage numbers of the switching sequence groups corresponding to the switching periods;
s45, obtaining the submodule groups of the switching stages corresponding to the switching period according to a preset sequence, and switching the submodules of the submodule groups according to the serial number sequence of the submodules.
In a specific implementation, all switching periods of the modularized multi-level medium-voltage direct-current transformer information are acquired, each switching period is numbered, and the switching periods such as the 1 st switching period, the 2 nd switching period, the m th switching period and the like are numbered.
Dividing each switching period into m switching stages, numbering each switching stage, such as a 1 st switching stage and a 2 nd switching stage, wherein each switching stage number corresponds to one switching sequence group, each switching stage number of a switching period corresponds to a submodule group of the switching sequence group corresponding to the switching period, for example, a certain switching sequence group corresponding to a certain switching period number, and each switching stage of the switching period corresponds to each submodule group of the switching sequence group.
And acquiring a switching sequence group corresponding to the switching period according to the sequencing result of the switching period number, wherein the 1 st switching period corresponds to the 1 st switching sequence group, and the 2 nd switching period corresponds to the 2 nd switching sequence group. And the m-th switching period corresponds to the m-th switching sequence group, after the m-th switching period, the m-th switching sequence group needs to start from the 1-th switching sequence group again after switching is finished, and the new round of voltage equalizing control is performed, namely, the (m+1) -th switching period corresponds to the 1-th switching sequence group, and the subsequent switching periods are analogized.
In the specific implementation, the ith switching stage of the 1 st switching period adopts the submodule of the ith submodule group of the 1 st switching sequence group to switch.
Optionally, step S45 includes the following steps S51-S54:
s51, acquiring a switching period corresponding to a first switching period number according to a preset sequence, and generating a first switching period;
s52, acquiring all switching stages and switching sequence groups corresponding to a first switching period;
s53, sequentially sequencing the numbers of the switching phases according to a preset phase sequence, and acquiring a submodule group of a switching sequence group corresponding to the current switching phase according to a sequencing result;
s54, switching the sub-modules of the sub-module group according to the sub-module numbering sequence.
In specific implementation, the number of the first switching period is acquired according to the preset sequence of the number of the switching period, the number of the first switching period is set to be the 1 st switching period, the 1 st switching period corresponds to the 1 st switching sequence group and m switching stages, the 1 st switching stage of the 1 st switching period corresponds to the 1 st sub-module group of the 1 st switching sequence group, the 1 st sub-module group is switched from the 1 st switching stage corresponding to the 1 st switching period, and the sub-module numbers of the 1 st sub-module group are input into corresponding sub-modules according to the sub-module number sequence from small to large; the 2 nd switching stage of the 1 st switching period corresponds to the 2 nd sub-module group of the 1 st switching sequence group, the 2 nd sub-module group is switched from the 2 nd switching stage corresponding to the 1 st switching period, and corresponding sub-modules are input according to the sub-module numbering sequence of the 2 nd sub-module group from small to large; and by analogy, respectively inputting corresponding sub-module groups in each switching stage of the 1 st switching period.
Optionally, after step S54, the following steps S61 to S69 are further included:
s61, judging whether the switching of the current switching period is finished;
s62, if not, acquiring a switching stage number corresponding to the current switching submodule, determining a switching stage corresponding to the next switching stage number, and generating a target switching stage;
s63, obtaining a submodule group of a switching sequence group corresponding to the target switching stage;
s64, switching sub-modules of the sub-module group according to the serial number sequence of the sub-modules, and jumping to execute the step of judging whether the switching of the current switching period is finished or not until no residual switching stage exists in the current switching period;
s65, if so, judging whether the number of the switch period corresponding to the current switch period is a preset number multiple;
s66, if yes, skipping to execute the step of acquiring all switching stages and switching sequence groups corresponding to the first switching period;
s67, if not, acquiring a switching cycle number corresponding to the current switching cycle, determining a switching cycle corresponding to the next switching cycle number, and generating a target switching cycle;
s68, acquiring all switching stages and switching sequence groups corresponding to a target switching period;
s69, sequentially sequencing the numbers of the switching phases according to a preset phase sequence, and acquiring the sub-module group of the switching sequence group corresponding to the current switching phase according to the sequencing result.
It should be noted that, the preset number multiple is a multiple of the mth switching period.
In specific implementation, referring to fig. 4, after the sub-modules in the current switching stage are switched, whether the current switching period is finished is judged, if the current switching period is judged not to be finished, the switching stage number corresponding to the current switching sub-module is extracted, so that the next switching stage number and the next switching stage are determined, the next switching stage number and the next switching stage are set as target switching stages, the sub-module group of the switching sequence group corresponding to the target stage is obtained, and the sub-modules of the sub-module group are sequentially input according to the sub-module numbers from small to large. After all the sub-modules of the sub-module group in the target switching stage are switched, the step S61 is skipped again, and whether the switching of the current switching period is finished is judged again until all the switching stages in the current switching period are switched.
If the current switching period is judged to be switched to be ended, judging whether the switching period number of the current switching period is a multiple of the mth switching period or not, if the switching period number of the current switching period is judged to be just a multiple of the mth switching period, jumping to the step S51, starting with the 1 st switching period, determining the 1 st switching sequence group corresponding to the 1 st switching period, and switching the 1 st sub-module group corresponding to the 1 st switching sequence group according to the 1 st switching period of the 1 st switching period.
If it is determined that the number of the switching cycle of the current switching cycle is not a multiple of the mth switching cycle, determining the number of the next switching cycle according to the number of the switching cycle of the current switching cycle, setting the next switching cycle as a target switching cycle, acquiring a switching sequence group and all switching phases of the target switching cycle, skipping to step S53, and starting from the 1 st switching phase of the target switching cycle again, putting into the sub-module group of the corresponding switching sequence group, specifically putting into each sub-module according to the sub-module number of the sub-module group from small to large.
Optionally, the method further comprises the following steps S71-S72:
s71, acquiring the bridge arm direct current voltage support minimum submodule number of the modularized multi-level medium-voltage direct current transformer information;
s72, adopting bridge arm direct current voltage to support the least submodule number and the submodule number of the submodule group corresponding to the switching stage corresponding to the current switching period, and calculating the submodule number required to be input by the submodule group corresponding to the switching stage.
It should be noted that, because of the limitation of the subgroup with the largest number of sub-module codes in a single group, at least 1 group of sub-modules are not put into each switching stage of each switching period, and in all groups to be put into, there are cases that the sub-modules do not need to be put into in part of working conditions, so the number of sub-modules to be put into in the last of the sub-module groups corresponding to each switching stage needs to be calculated.
In the specific implementation, the least number of sub-modules for guaranteeing the direct-current voltage support of the bridge arm of the modularized multi-level medium-voltage direct-current transformer and the number of sub-modules included in the sub-module group input in the ith switching stage of the current switching period are obtained from the information of the modularized multi-level medium-voltage direct-current transformer, and the number of sub-modules which are required to be input finally of the sub-module group corresponding to the switching stage can be calculated according to the following calculation formula:
wherein n is Finally put into The number of the submodules required to be put into for the submodule group corresponding to the switching stage; n is n arm minimum The method comprises the steps of ensuring the minimum module number of the bridge arm direct-current voltage support of the modularized multi-level medium-voltage direct-current transformer; n is n i The number of the submodules included in the submodule group input in the ith switching stage in the previous (m-1) switching stage in the current switching period is the number of the submodules included in the submodule group input in the ith switching stage.
According to the invention, the modularized multi-level medium-voltage direct-current transformer information corresponding to the voltage-sharing instruction request is obtained by responding to the voltage-sharing instruction request; determining a plurality of sub-module groups based on preset sub-module numbers in bridge arms corresponding to the modularized multi-level medium-voltage direct-current transformer information; determining a plurality of switching sequence groups based on a preset switching rule and all sub-module groups; based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information, the submodules are switched according to the submodule numbering sequence of the switching sequence group corresponding to the switching period. The technical problems that in the prior art, the sub-module capacitor voltage equalizing control of the medium-voltage side MMC structure of a plurality of sub-modules is required, and the advanced controller is used for completing the calculation of a control system, so that the use cost is too high and the engineering application of the modularized multi-level medium-voltage direct-current transformer is not facilitated are solved.
The voltage equalizing method provided by the invention does not need to measure the current of the bridge arm, reduces the use of a current sensor and reduces the construction cost of the medium-voltage direct-current transformer; the sequencing, addition, subtraction, multiplication and division are not needed, the time complexity of the algorithm is 0, and the calculation efficiency of the modularized multi-level medium voltage direct current transformer control system is greatly improved; the improvement of the calculation efficiency enables the modularized multi-level medium-voltage direct current transformer to adopt a marketized controller with lower cost under the algorithm of the invention, avoids the use of the customised controller, greatly reduces the hardware cost and improves the engineering application prospect of the modularized multi-level medium-voltage direct current transformer.
Referring to fig. 5, fig. 5 is a block diagram illustrating a modular multilevel medium voltage dc transformer voltage equalizing system according to a third embodiment of the present invention.
The invention provides a modular multilevel medium voltage direct current transformer voltage equalizing system, which comprises:
the voltage-sharing instruction request module 501 is configured to respond to a voltage-sharing instruction request, and obtain information of the modular multilevel medium-voltage direct-current transformer corresponding to the voltage-sharing instruction request;
the submodule group module 502 is configured to determine a plurality of submodule groups based on a preset submodule number in a bridge arm corresponding to the modularized multi-level medium-voltage direct current transformer information;
A switching sequence group module 503, configured to determine a plurality of switching sequence groups based on a preset switching rule and all sub-module groups;
and the switching module 504 is configured to switch the sub-modules according to the sub-module numbering sequence of the switching sequence group corresponding to the switching period based on the switching period corresponding to the modularized multi-level medium voltage direct current transformer information.
Optionally, the submodule group module 502 includes:
the module coding sub-module is used for numbering all sub-modules in the bridge arm corresponding to the modularized multi-level medium-voltage direct-current transformer information to generate a plurality of sub-module numbers;
the module group submodules are used for determining a plurality of submodule groups based on preset capacitor voltage requirements and all submodule numbers in each bridge arm.
Optionally, the module group submodule includes:
the first acquisition submodule is used for acquiring a plurality of preset capacitor voltage requirements;
the first coding sub-module is used for selecting sub-module numbers meeting the preset capacitor voltage requirements from all sub-modules in a preset target bridge arm to generate a sub-module group;
and the grouping sub-module is used for selecting any one of the remaining bridge arms as a new target bridge arm, and performing the step of selecting the sub-module number meeting the preset capacitor voltage requirement from all the sub-modules in the preset target bridge arm to generate a sub-module group until all the sub-modules in all the bridge arms are grouped to generate a plurality of sub-module groups.
Optionally, the system further comprises:
the second coding sub-module is used for numbering all sub-module groups and generating a plurality of sub-module group numbers; the sub-module group numbers corresponding to the two different preset capacitor voltage requirements are arranged at intervals according to the preset limit.
Optionally, the switching order group module 503 includes:
the switching rule submodule is used for acquiring a plurality of preset switching rules;
the switching sequence group sub-module is used for sequencing all sub-module groups according to a switching sequence of a target preset switching rule to generate a switching sequence group;
and the target preset switching rule sub-module is used for selecting any one of the remaining preset switching rules as a new target preset switching rule, and performing the step of sequencing all sub-module groups according to the switching sequence of the target preset switching rule to generate a switching sequence group in a jumping manner.
Optionally, the switching module 504 includes:
the switch period coding sub-module is used for acquiring a plurality of switch periods of the modularized multi-level medium-voltage direct-current transformer information, numbering all the switch periods and generating switch period numbers;
the switching stage coding submodule is used for dividing each switching period into a plurality of switching stages, numbering the switching stages and generating switching stage numbers;
The sequencing sub-module is used for acquiring switching sequence groups corresponding to all the switching periods according to sequencing results of all the switching period numbers;
the first input submodule is used for determining submodule groups required to be input in each switching stage based on each submodule group number and each switching stage number of the switching sequence group corresponding to the switching period;
and the switching sub-module is used for acquiring the sub-module group of the switching stage corresponding to the switching period according to a preset sequence and switching the sub-modules of the sub-module group according to the serial number sequence of the sub-modules.
Optionally, the first switching submodule includes:
the first switching period submodule is used for acquiring switching periods corresponding to the first switching period numbers according to a preset sequence and generating first switching periods;
the sub-module for acquiring the first switching period is used for acquiring all switching stages and switching sequence groups corresponding to the first switching period;
the sequencing result submodule is used for sequencing the numbers of the switching phases in sequence according to a preset phase sequence and obtaining a submodule group of a switching sequence group corresponding to the current switching phase according to a sequencing result;
and the second switching sub-module is used for switching the sub-modules of the sub-module group according to the serial number sequence of the sub-modules.
Optionally, after the second switching submodule, the method further includes:
the first judging submodule is used for judging whether the switching of the current switching period is finished or not;
the target switching stage sub-module is used for acquiring the switching stage number corresponding to the current switching sub-module if not, determining the switching stage corresponding to the next switching stage number and generating a target switching stage;
the second acquisition submodule is used for acquiring a submodule group of the switching sequence group corresponding to the target switching stage;
the first rotor jumping module is used for switching the sub-modules of the sub-module group according to the serial number sequence of the sub-modules, and jumping to execute the step of judging whether the switching of the current switching period is finished or not until no residual switching stage exists in the current switching period;
the second judging submodule is used for judging whether the number of the switch period corresponding to the current switch period is a preset number multiple or not if yes;
the second rotor jumping module is used for jumping to execute the step of acquiring all switching stages and switching sequence groups corresponding to the first switching period if yes;
the target switching period submodule is used for acquiring a switching period number corresponding to the current switching period if not, determining a switching period corresponding to the next switching period number and generating a target switching period;
The third acquisition submodule is used for acquiring all switching stages and switching sequence groups corresponding to the target switching period;
and the third rotor jumping module is used for jumping and executing the steps of sequentially sequencing the numbers of the switching phases according to the preset phase sequence and obtaining the submodule group of the switching sequence group corresponding to the current switching phase according to the sequencing result.
Optionally, the system further comprises:
the least number of sub-modules is used for acquiring the bridge arm direct current voltage supporting least number of sub-modules of the modularized multi-level medium voltage direct current transformer information;
the submodule number submodule is used for supporting the least submodule number and the submodule number of the submodule group corresponding to the switching stage corresponding to the current switching period by adopting the bridge arm direct-current voltage, and calculating the submodule number required to be input by the submodule group corresponding to the switching stage.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described systems, apparatuses and units may refer to corresponding procedures in the foregoing method embodiments, which are not repeated herein.
In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices, and methods may be implemented in other manners. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of the units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional unit in the embodiments of the present invention may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in software functional units.
The integrated units, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied essentially or in part or all of the technical solution or in part in the form of a software product stored in a storage medium, including instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A modular multilevel medium voltage dc transformer voltage equalizing method, comprising:
responding to a voltage-sharing instruction request, and acquiring modularized multi-level medium-voltage direct-current transformer information corresponding to the voltage-sharing instruction request;
determining a plurality of sub-module groups based on preset sub-module numbers in bridge arms corresponding to the modularized multi-level medium-voltage direct-current transformer information;
determining a plurality of switching sequence groups based on a preset switching rule and all the submodule groups;
and switching the submodules according to the number sequence of the submodules of the switching sequence group corresponding to the switching period based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information.
2. The method for equalizing voltage of a modular multilevel medium voltage dc transformer according to claim 1, wherein the step of determining a plurality of sub-module groups based on a preset sub-module number in a bridge arm corresponding to the modular multilevel medium voltage dc transformer information comprises:
numbering all sub-modules in a bridge arm corresponding to the modularized multi-level medium-voltage direct current transformer information to generate a plurality of sub-module numbers;
and determining a plurality of sub-module groups based on the preset capacitor voltage requirement and the numbers of all sub-modules in each bridge arm.
3. The modular multilevel medium voltage dc transformer equalizing method according to claim 2, wherein said step of determining a plurality of sub-module groups based on a preset capacitor voltage requirement and all sub-module numbers in each of said bridge arms comprises:
acquiring a plurality of preset capacitor voltage requirements;
selecting sub-module numbers meeting the preset capacitor voltage requirements from all sub-modules in a preset target bridge arm, and generating a sub-module group;
selecting any one of the remaining bridge arms as a new target bridge arm, skipping and executing all sub-modules in the preset target bridge arm, selecting sub-module numbers meeting the preset capacitor voltage requirement, and generating a sub-module group until all sub-modules in all the bridge arms are grouped, and generating a plurality of sub-module groups.
4. A modular multilevel medium voltage dc transformer voltage equalizing method according to claim 3, further comprising:
numbering all the sub-module groups to generate a plurality of sub-module group numbers; and the sub-module group numbers corresponding to the two different preset capacitor voltage requirements are arranged at intervals according to a preset limit.
5. The method for equalizing voltage in a modular multilevel medium voltage dc transformer according to claim 1, wherein said step of determining a plurality of switching sequence groups based on a preset switching law and all of said sub-module groups comprises:
acquiring a plurality of preset switching rules;
sequencing all the sub-module groups according to a switching sequence of a target preset switching rule to generate a switching sequence group;
selecting any one of the remaining preset switching rules as a new target preset switching rule, and skipping to execute the step of sequencing all the sub-module groups according to the switching sequence of the target preset switching rule to generate a switching sequence group.
6. The method for equalizing voltage of a modular multilevel medium voltage dc transformer according to claim 1, wherein the step of switching the sub-modules according to the sub-module numbering sequence of the switching sequence group corresponding to the switching period based on the switching period corresponding to the modular multilevel medium voltage dc transformer information comprises:
Acquiring a plurality of switching periods of the modularized multi-level medium voltage direct current transformer information, numbering all the switching periods, and generating a switching period number;
dividing each switching period into a plurality of switching stages, numbering the switching stages, and generating switching stage numbers;
acquiring a switching sequence group corresponding to each switching period according to the sequencing result of all the switching period numbers;
determining the submodule groups required to be put into each switching stage based on the submodule group numbers and the switching stage numbers of the switching sequence groups corresponding to the switching periods;
and acquiring a submodule group of a switching stage corresponding to the switching period according to a preset sequence, and switching the submodules of the submodule group according to the serial number sequence of the submodules.
7. The method for equalizing voltage of a modular multilevel medium voltage dc transformer according to claim 6, wherein the step of obtaining the submodule group of the switching stage corresponding to the switching period according to a preset sequence and switching the submodules of the submodule group according to a submodule numbering sequence comprises:
acquiring a switching period corresponding to the first switching period number according to a preset sequence, and generating a first switching period;
Acquiring all switching stages and switching sequence groups corresponding to the first switching period;
sequentially sequencing the numbers of the switching phases according to a preset phase sequence, and acquiring a submodule group of a switching sequence group corresponding to the current switching phase according to a sequencing result;
and switching the submodules of the submodule group according to the number sequence of the submodules.
8. The method for equalizing a voltage across a modular multilevel medium voltage dc transformer according to claim 7, further comprising, after said step of switching sub-modules of said sub-module group according to a sub-module numbering sequence:
judging whether the switching of the current switching period is finished;
if not, acquiring a switching stage number corresponding to the current switching submodule, determining a switching stage corresponding to the next switching stage number, and generating a target switching stage;
obtaining a submodule group of a switching sequence group corresponding to the target switching stage;
switching the submodules of the submodule group according to the number sequence of the submodules, and skipping to execute the step of judging whether the switching of the current switching period is finished or not until no residual switching stage exists in the current switching period;
if yes, judging whether the number of the switching period corresponding to the current switching period is a preset number multiple;
If yes, skipping to execute the step of acquiring all switching stages and switching sequence groups corresponding to the first switching period;
if not, acquiring a switching cycle number corresponding to the current switching cycle, determining a switching cycle corresponding to the next switching cycle number, and generating a target switching cycle;
acquiring all switching stages and switching sequence groups corresponding to the target switching period;
and skipping and executing the step of sequencing the numbers of the switching phases in turn according to the preset phase sequence and obtaining the sub-module group of the switching sequence group corresponding to the current switching phase according to the sequencing result.
9. The modular multilevel medium voltage dc transformer voltage grading method of claim 6, further comprising:
acquiring the bridge arm direct current voltage support minimum submodule number of the modularized multi-level medium voltage direct current transformer information;
and calculating the number of the submodules required to be input by the submodule group corresponding to the switching stage by adopting the least number of the submodules supported by the bridge arm direct-current voltage and the number of the submodules corresponding to the switching stage corresponding to the current switching period.
10. A modular multilevel medium voltage dc transformer voltage equalizing system, comprising:
The voltage-sharing instruction request module is used for responding to the voltage-sharing instruction request and acquiring modularized multi-level medium-voltage direct-current transformer information corresponding to the voltage-sharing instruction request;
the submodule group module is used for determining a plurality of submodule groups based on preset submodule numbers in bridge arms corresponding to the modularized multi-level medium-voltage direct current transformer information;
the switching sequence group module is used for determining a plurality of switching sequence groups based on a preset switching rule and all the submodule groups;
and the switching module is used for switching the sub-modules according to the number sequence of the sub-modules of the switching sequence group corresponding to the switching period based on the switching period corresponding to the modularized multi-level medium-voltage direct current transformer information.
CN202311072528.5A 2023-08-23 2023-08-23 Voltage equalizing method and system for modularized multi-level medium-voltage direct-current transformer Pending CN117013850A (en)

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