CN117040302A - Bridge arm multiplexing type MMC (modular multilevel converter) independent control method and system for each bridge arm - Google Patents
Bridge arm multiplexing type MMC (modular multilevel converter) independent control method and system for each bridge arm Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/49—Combination of the output voltage waveforms of a plurality of converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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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Abstract
The application discloses a bridge arm multiplexing type MMC (modular multilevel converter) bridge arm independent control method and system, which relate to the technical field of flexible direct current transmission of an electric power system and comprise the following steps: collecting data and preprocessing the data; judging the current direction of each bridge arm and multiplexing the multiplexing state of the multiplexed bridge arms; performing closed-loop control on the capacitance voltage average value difference value of each bridge arm submodule, and outputting a bridge arm submodule distribution coefficient by a controller; and distributing the input number of the sub-modules of each bridge arm according to the bridge arm current direction, the bridge arm multiplexing state and the distribution coefficient. According to the control method, the upper bridge arm, the multiplexing bridge arm and the lower bridge arm respectively have independent sub-module input numbers, so that control signals of the switching tubes of the bridge arms can be independently output through respectively configuring the controllers for the bridge arms, and control quantity interaction among the bridge arms is avoided.
Description
Technical Field
The application relates to the technical field of flexible direct current transmission of power systems, in particular to a method and a system for independently controlling each bridge arm of a bridge arm multiplexing type MMC.
Background
The modular multilevel converter (Modular Mpltilevel Converter, MMC) module has high integration level, the submodule structure is simple, the half/full-bridge submodule cascading structure is adopted, the effects of increasing the level number and equivalent switching frequency by using low-voltage-class power devices to be connected in series are achieved, meanwhile, the requirements of reducing alternating-current harmonic waves and direct-current side ripple waves are met, the transmission of active power and reactive power can be independently regulated, and the modular multilevel converter has wide application prospects in the aspects of direct-current transmission, power generation grid connection of renewable energy sources and the like.
But MMC converter station submodule quantity is more, with high costs, area is big, and the condenser is as the important component part of MMC, and investment cost and weight volume occupy more than big in the converter station, and the structure that a large amount of submodule electric capacity establish ties makes MMC reduce the appearance degree limited. The scholars propose a bridge arm multiplexing type modularized multi-level converter (Arm Mpltiplexing Modular Mpltilevel Converter, AM-MMC) structure, and the multiplexing bridge arms are configured, so that the number of sub-modules of each phase unit is reduced by 25%, the utilization rate of the sub-modules is improved to 66.7%, and the light-weight of the converter is effectively realized.
Literature proposes a modulation strategy and a control method of a bridge arm multiplexing MMC, and the multiplexing bridge arm of the AM-MMC is subjected to time division multiplexing according to the working characteristics of a conventional MMC. Specifically, the number N of submodules needed to be put into when an upper bridge arm pa And when the capacitance voltage is not less than N, the multiplexing bridge arm and the upper bridge arm are jointly formed into a composite upper bridge arm, and all the submodules of the composite upper bridge arm are subjected to comprehensive sequencing. Likewise, the number N of submodules needed to be put into the lower bridge arm na And when the capacitance voltages are more than or equal to N, the multiplexing bridge arm and the lower bridge arm are jointly formed into a composite lower bridge arm, and all the submodules of the composite lower bridge arm are subjected to comprehensive sequencing, wherein N is the number of the submodules of one bridge arm when redundancy is not considered.
When the modulation and control strategy proposed in the literature is applied to actual engineering, the capacitance voltage of the submodule of the multiplexing bridge arm is transmitted to the control units of the upper bridge arm and the lower bridge arm simultaneously due to the characteristic of time division multiplexing of the multiplexing bridge arm, the capacitance voltage sequencing is participated in time division, and the control signals of the switching tubes of the multiplexing bridge arm are extracted from the output of the two control units in time division. The control method increases the complexity of the control system and the control link delay, and reduces the portability of the control unit.
Disclosure of Invention
This section is intended to outline some aspects of embodiments of the application and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description of the application and in the title of the application, which may not be used to limit the scope of the application.
The present application has been made in view of the above-described problems.
Therefore, the technical problems solved by the application are as follows: how to realize the independent control of each bridge arm of the bridge arm multiplexing type modularized multi-level converter system.
In order to solve the technical problems, the application provides the following technical scheme: the independent control method of each bridge arm of the bridge arm multiplexing MMC comprises the following steps of; collecting data and preprocessing the data; judging the current direction of each bridge arm and multiplexing the multiplexing state of the multiplexed bridge arms; performing closed-loop control on the capacitance voltage average value difference value of each bridge arm submodule, and outputting a bridge arm submodule distribution coefficient by a controller; and distributing the input number of the sub-modules of each bridge arm according to the bridge arm current direction, the bridge arm multiplexing state and the distribution coefficient.
As a preferable scheme of the bridge arm multiplexing type MMC independent control method of each bridge arm, the application comprises the following steps: the collected data comprise current of the bridge arm during operation, capacitance voltage of the submodule and state information of the bridge arm during operation, multiplexing state of the bridge arm and current direction of the bridge arm.
As a preferable scheme of the bridge arm multiplexing type MMC independent control method of each bridge arm, the application comprises the following steps: the data preprocessing comprises the steps of removing missing values, abnormal values and invalid data in an error format from collected periodic state data, converting original format data into a format which accords with mathematical model demand analysis, and calculating capacitance voltage average values of all bridge arm submodules to perform data preprocessing.
As a preferable scheme of the bridge arm multiplexing type MMC independent control method of each bridge arm, the application comprises the following steps: judging the current direction of each bridge arm, namely judging the current direction of the upper bridge arm and the lower bridge arm, wherein when the bridge arm current is positive, the bridge arm sub-module capacitance is in a charging state, and when the bridge arm current is negative, the bridge arm sub-module capacitance is in a discharging state; the multiplexing state of the multiplexing bridge arm comprises that the multiplexing bridge arm and the upper bridge arm form a composite upper bridge arm, and the multiplexing bridge arm and the lower bridge arm form a composite lower bridge arm, and the multiplexing bridge arm is switched from multiplexing of the upper bridge arm/the lower bridge arm to multiplexing of the lower bridge arm/the upper bridge arm.
As a preferable scheme of the bridge arm multiplexing type MMC independent control method of each bridge arm, the application comprises the following steps: the distribution of the input number of the sub-modules of each bridge arm comprises setting a flag bit AM as a multiplexing state of multiplexing bridge arms, when AM=1, the multiplexing bridge arms and the upper bridge arms jointly form a composite upper bridge arm, and the input number of the sub-modules of the composite upper bridge arm is N p The input number of the lower bridge arm submodules is N n The number of the sub-modules of the composite upper bridge arm is input according to the distribution coefficient n u And the current direction I of the upper bridge arm u Respectively distributing to an upper bridge arm and a multiplexing bridge arm; when the bridge arm current is positive, the capacitance voltage of the bridge arm submodule is in a charging state, and the input number N of the submodules of the multiplexing bridge arm is made m ＝round(N p *n u ) When calculated N m >When N is set, let N m Number of upper arm submodules N =n u ＝N p -N m Number N of lower bridge arm submodules d ＝N n The method comprises the steps of carrying out a first treatment on the surface of the When the bridge arm current is negative, the capacitor voltage of the bridge arm submodule is in a discharge state, and the number N of the submodules of the upper bridge arm is input at the moment u ＝round(N p *n u ) When calculated N u >When N is set, let N u Number of multiplexing bridge arm submodules input N m ＝N p -N u Number N of lower bridge arm submodules d ＝N n Where round () is the most recent rounding function.
As a preferable scheme of the bridge arm multiplexing type MMC independent control method of each bridge arm, the application comprises the following steps: when the flag bit AM=0, the multiplexing bridge arm and the lower bridge arm jointly form a composite lower bridge arm, and the number of sub-modules of the composite lower bridge arm is inputIs N n The input number of the upper bridge arm submodules is N p The number of the sub-modules of the composite lower bridge arm is input according to the distribution coefficient n d And the current direction I of the lower bridge arm d Respectively distributing to a lower bridge arm and a multiplexing bridge arm; when the bridge arm current is positive, the capacitance voltage of the bridge arm submodule is in a charging state, and the input number N of the submodules of the multiplexing bridge arm is made m ＝round(N n *n d ) When calculated N m >When N is set, let N m Number of lower bridge arm submodules input N d ＝N n -N m The input number N of the upper bridge arm submodules u ＝N p The method comprises the steps of carrying out a first treatment on the surface of the When the bridge arm current is negative, the capacitor voltage of the bridge arm submodule is in a discharge state, and the submodule input number N of the lower bridge arm is set at the moment d ＝round(N n *n d ) When calculated N d >When N is set, let N d Number of multiplexing bridge arm submodules input N m ＝N n -N d The input number N of the upper bridge arm submodules u ＝N p Wherein round () is the nearest rounding function and N is the number of submodules of one bridge arm.
As a preferable scheme of the bridge arm multiplexing type MMC independent control method of each bridge arm, the application comprises the following steps: when the flag bit am=2, the multiplexing bridge arm is in a switching mode, and when N pa ＝N na And when the input number of the multiplexing bridge arm submodules is 0, an action instruction is sent to the bridge arm change-over switch to change the bridge arm multiplexing mode, wherein N is the number of the submodules of one bridge arm.
The application also aims to provide the bridge arm multiplexing type MMC bridge arm independent control system, which can solve the problem that the stability and efficiency of the system are difficult to guarantee when the existing modularized multi-level converter system is faced with the change of the bridge arm multiplexing state through high-precision data acquisition and processing, accurate sub-module capacitor voltage control and dynamic sub-module input number distribution.
In order to solve the technical problems, the application provides the following technical scheme: each bridge arm independent control system of bridge arm multiplexing type MMC includes: the system comprises a data collection module, a data processing module, a bridge arm current direction judging module, a bridge arm multiplexing state judging module and a bridge arm submodule input number distribution module; the data collection module is mainly used for collecting current and submodule capacitor voltage of a bridge arm during operation and state information of the bridge arm during operation, wherein the state information comprises multiplexing states of the bridge arm and current directions of the bridge arm; the data processing module is used for removing missing values, abnormal values and invalid data in an error format from the collected periodic state data, converting the original format data into a format which accords with the analysis of a mathematical model requirement, calculating the average value of the capacitance voltage of each bridge arm submodule, and carrying out data preprocessing, wherein the bridge arm current direction judging module is mainly responsible for judging the current direction of each bridge arm, when the bridge arm current is positive, the bridge arm submodule capacitance is considered to be in a charging state, and when the bridge arm current is negative, the bridge arm submodule capacitance is considered to be in a discharging state; the multiplexing state judging module is responsible for judging the multiplexing state of the multiplexing bridge arm, wherein the multiplexing state of the multiplexing bridge arm comprises that the multiplexing bridge arm and the upper bridge arm form a composite upper bridge arm, and the multiplexing bridge arm and the lower bridge arm form a composite lower bridge arm, and the multiplexing bridge arm is switched from multiplexing of the upper bridge arm/the lower bridge arm to multiplexing of the lower bridge arm/the upper bridge arm; the bridge arm submodule input number distribution module distributes the input number of each bridge arm submodule according to the bridge arm current direction, the bridge arm multiplexing state and the bridge arm submodule distribution coefficient output by the controller.
The computer equipment comprises a memory and a processor, wherein the memory stores a computer program, and the computer equipment is characterized in that the processor realizes the steps of the independent control method of each bridge arm of the bridge arm multiplexing type MMC when executing the computer program.
A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when executed by a processor, implements the steps of the bridge arm independent control method of the bridge arm multiplexing MMC as described above.
The application has the beneficial effects that: the application provides an independent control method for each bridge arm of a bridge arm multiplexing type MMC, which is characterized in that the number of sub-modules of each bridge arm is distributed and issued in a main controller, the upper/multiplexing/lower bridge arms respectively have independent control units, the capacitance voltages of the sub-modules of each bridge arm are independently participated in sequencing, and the bridge arm control units issue switching tube control signals of the respective bridge arms, so that the interaction of control links is reduced, and the complexity of the controller is reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:
fig. 1 is an overall flowchart of a method for independently controlling each bridge arm of a bridge arm multiplexing MMC according to a first embodiment of the present application;
fig. 2 is a schematic diagram of a topology structure of an AM-MMC in a method for independently controlling each bridge arm of a bridge arm multiplexing MMC according to a first embodiment of the application;
fig. 3 is a schematic structural diagram of an AM-MMC bridge arm switch in the bridge arm multiplexing type MMC bridge arm independent control method according to the first embodiment of the application;
fig. 4 is a schematic diagram of an AM-MMC valve control system in a method for independently controlling each bridge arm of a bridge arm multiplexing MMC according to a first embodiment of the application;
fig. 5 is a schematic structural diagram of an AM-MMC valve control system described in a method for independently controlling each bridge arm of a bridge arm multiplexing MMC according to a first embodiment of the application;
fig. 6 is an AM-MMC bridge arm independent control block diagram described in the bridge arm multiplexing type MMC bridge arm independent control method according to the first embodiment of the application;
fig. 7 is a flowchart of AM-MMC individual leg independent control described in the arm multiplexing type MMC individual leg independent control method according to the first embodiment of the present application;
fig. 8 is a schematic structural diagram of an independent control system of each bridge arm of a bridge arm multiplexing MMC according to a second embodiment of the application;
fig. 9 is a waveform diagram of a sub-module capacitance voltage average value difference value of upper and multiplexed bridge arms and an allocation coefficient simulation output by a controller under the independent control of each bridge arm of a bridge arm multiplexing type MMC according to a third embodiment of the present application;
fig. 10 is a simulation waveform of the number of sub-modules input to the upper and multiplexing bridge arms under the independent control of each bridge arm of the bridge arm multiplexing type MMC according to the third embodiment of the application.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present application can be understood in detail, a more particular description of the application, briefly summarized above, may be had by reference to the embodiments, some of which are illustrated in the appended drawings. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments of the present application without making any inventive effort, shall fall within the scope of the present application.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present application is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the application. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
While the embodiments of the present application have been illustrated and described in detail in the drawings, the cross-sectional view of the device structure is not to scale in the general sense for ease of illustration, and the drawings are merely exemplary and should not be construed as limiting the scope of the application. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.
Also in the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "upper, lower, inner and outer", etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first, second, or third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The terms "mounted, connected, and coupled" should be construed broadly in this disclosure unless otherwise specifically indicated and defined, such as: can be fixed connection, detachable connection or integral connection; it may also be a mechanical connection, an electrical connection, or a direct connection, or may be indirectly connected through an intermediate medium, or may be a communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
Example 1
Referring to fig. 1 to 7, for one embodiment of the present application, there is provided an independent control method for each bridge arm of a bridge arm multiplexing MMC, which is characterized in that: collecting data and preprocessing the data; judging the current direction of each bridge arm and multiplexing the multiplexing state of the multiplexed bridge arms; performing closed-loop control on the capacitance voltage average value difference value of each bridge arm submodule, and outputting a bridge arm submodule distribution coefficient by a controller; and distributing the input number of the sub-modules of each bridge arm according to the bridge arm current direction, the bridge arm multiplexing state and the distribution coefficient.
For reducing the complexity of the control unit.
Fig. 1 shows a schematic diagram of a bridge arm multiplexing type MMC topology structure suitable for the present application, where each phase unit includes an upper bridge arm, three bridge arms of a multiplexing bridge arm and a lower bridge arm, two bridge arm reactors and two sets of switches, and each bridge arm includes N half-bridge sub-modules.
As shown in fig. 2, each group of switches is composed of IGCT devices with anti-parallel diodes connected in parallel.
As shown in fig. 3, which is a schematic diagram of an AM-MMC valve control system, an upper bridge arm controller is used for controlling an upper bridge arm (or a composite upper bridge arm), a lower bridge arm controller is used for controlling a composite lower bridge arm (or a lower bridge arm), the capacitance voltages of the submodules of the multiplexed bridge arms are simultaneously transmitted to two control units, the capacitance voltages are time-division participated in the ordering of the capacitance voltages, and the PWM control signals of the multiplexed bridge arms are time-division extracted from the upper and lower controllers, so that the complexity of the control system is increased.
Wherein AM is multiplexing state of multiplexing bridge arm, U cu 、U cm 、U cd Capacitance voltages of the upper bridge arm submodule, the multiplexing submodule and the lower bridge arm submodule, N p 、N n The number of sub-modules of the upper bridge arm (or the composite upper bridge arm) and the composite lower bridge arm (or the lower bridge arm) is respectively calculated.
As shown in FIG. 4, the AM-MMC valve control system of the present application has independent controllers for the upper, multiplexing and lower bridge arms, wherein N u 、N m And N d The input numbers of the submodules are distributed and issued in advance from the valve control functional blocks, so that the interaction of PWM control signals among the bridge arms is avoided, and the complexity of a control system is reduced.
Fig. 5 is a block diagram of independent control of each bridge arm of the AM-MMC described in the present application, and fig. 6 is a flowchart of independent control of each bridge arm of the AM-MMC described in the present application. Wherein AM is multiplexing state flag bit of multiplexing bridge arm, U au_ave 、U am_ave And U ad_ave Sub-module capacitance voltage average values of an upper bridge arm, a multiplexing bridge arm and a lower bridge arm respectively, n u And n d The number distribution coefficients of the sub-modules of the composite upper bridge arm and the composite lower bridge arm are respectively input, I u And I d The current directions of the upper bridge arm and the lower bridge arm are respectively N p 、N n The number of sub-modules respectively of an upper bridge arm (or a composite upper bridge arm) and a composite lower bridge arm (or a lower bridge arm) is N u 、N m And N d The number of sub-modules of the upper bridge arm, the multiplexing bridge arm and the lower bridge arm is respectively calculated.
Collecting data and carrying out data preprocessing to calculate the capacitance voltage average value of each bridge arm submodule:
taking phase A as an example, calculating the average value U of the capacitance and voltage of the sub-module of the upper bridge arm au_ave Multiplexing bridge arm submodule capacitance-voltage average value U am_ave Capacitance voltage average value U of lower bridge arm submodule ad_ave 。
Closed-loop control is carried out on the capacitance voltage average value difference value of each bridge arm submodule:
taking phase A as an example, calculating the average value difference U of capacitance and voltage of the sub-modules of the upper bridge arm and the multiplexing bridge arm diffu Calculating the capacitance-voltage average value difference U of the sub-modules of the lower bridge arm and the multiplexing bridge arm diffd 。
Respectively U diffu And U diffd As the input quantity of the closed-loop controller, the PI controller is used for distributing the coefficient n of the input quantity of the submodule when the output quantity of the controller is am=1 and am=0 respectively u And n d 。
Judging the direction of bridge arm current:
taking phase A as an example, judging the current direction of an upper/lower bridge arm, and taking the bridge arm submodule capacitor as a charging state when the bridge arm current is positive; and when the bridge arm current is negative, the bridge arm submodule capacitor is in a discharge state. Setting the current direction zone bit of the upper bridge arm and the lower bridge arm as I respectively u And I d When the current direction of the upper bridge arm is positive I u =1, negative time I u -1; the current direction of the lower bridge arm is positive I d =1, negative time I d ＝-1。
The number of sub-modules in the bridge arm multiplexing mode is distributed:
the allocation of the input numbers of the submodules of each bridge arm is shown in table 1 under the independent control strategy of each bridge arm, wherein round () represents the latest rounding function.
TABLE 1 submodule input number Allocation Table for different bridge arm multiplexing modes
When am=1, the multiplexing bridge arm and the upper bridge arm jointly form a composite upper bridge arm, and the input number of the sub-modules of the composite upper bridge arm is N p The input number of the lower bridge arm submodules is N n Under the traditional control, the multiplexing bridge arm and the upper bridge arm participate in the sequencing of the capacitance and the voltage of the submodule together.
In order to simplify the structure of the bridge arm controller, the input number of the sub-modules of the composite upper bridge arm is calculated according to the distribution coefficient n u And the current direction I of the upper bridge arm u Respectively assigned to the upper bridge arm and the multiplexing bridge arm.
The specific distribution mode is that when the bridge arm current is positive, the capacitance voltage of the bridge arm submodule is in a charging state, and the input number N of the submodule multiplexing the bridge arm at the moment is made m ＝round(N p *n u ) When calculated N m >When N is set, let N m Number of upper arm submodules N =n u ＝N p -N m Number N of lower bridge arm submodules d ＝N n The method comprises the steps of carrying out a first treatment on the surface of the When the bridge arm current is negative, the capacitor voltage of the bridge arm submodule is in a discharge state, and the number N of the submodules of the upper bridge arm is input at the moment u ＝round(N p *n u ) When calculated N u >When N is set, let N u Number of multiplexing bridge arm submodules input N m ＝N p -N u Number N of lower bridge arm submodules d ＝N n Where round () is the most recent rounding function.
When am=0, the multiplexing bridge arm and the lower bridge arm jointly form a composite lower bridge arm, and the input number of the submodules of the composite lower bridge arm is N n The input number of the upper bridge arm submodules is N p The number of the sub-modules of the composite lower bridge arm is input according to the distribution coefficient n d And the current direction I of the lower bridge arm d Respectively assigned to the lower bridge arm and the multiplexing bridge arm.
The specific distribution mode is that when the bridge arm current is positive, the capacitance voltage of the bridge arm submodule is in a charging state, and the input number N of the submodule multiplexing the bridge arm at the moment is made m ＝round(N n *n d ) When calculated N m >When N is set, let N m Number of lower bridge arm submodules input N d ＝N n -N m The input number N of the upper bridge arm submodules u ＝N p The method comprises the steps of carrying out a first treatment on the surface of the When the bridge arm current is negative, the capacitor voltage of the bridge arm submodule is in a discharge state, and the submodule input number N of the lower bridge arm is set at the moment d ＝round(N n *n d ) When calculated N d >When N is set, let N d Number of multiplexing bridge arm submodules input N m ＝N n -N d The input number N of the upper bridge arm submodules u ＝N p Wherein round () is the nearest rounding function and N is the number of submodules of one bridge arm.
When am=2, the multiplexing bridge arm is in the switching mode, and when N, in order to ensure the safety of the on-off operation of the bridge arm switching switch when the multiplexing mode of the bridge arm is changed pa ＝N na And when the input number of the multiplexing bridge arm submodules is 0, an action instruction is sent to the bridge arm change-over switch to change the bridge arm multiplexing mode, wherein N is the number of the submodules of one bridge arm.
Example 2
Referring to fig. 8, for an embodiment of the present application, a system for an independent control method for each bridge arm of a bridge arm multiplexing MMC is provided, where: the system comprises a data collection module, a data processing module, a bridge arm current direction judging module, a bridge arm multiplexing state judging module and a bridge arm submodule input number distribution module.
The data collection module is mainly used for collecting current and submodule capacitance voltage of the bridge arm during operation and state information of the bridge arm during operation, wherein the state information comprises multiplexing states of multiplexing the bridge arm and current directions of the bridge arm.
The data processing module is used for removing missing values, abnormal values and invalid data in an error format from the collected periodic state data, converting the original format data into a format which accords with the analysis of the mathematical model requirement, and calculating the capacitance voltage average value of each bridge arm sub-module to perform data preprocessing.
The bridge arm current direction judging module is mainly responsible for judging the current direction of each bridge arm, considers the bridge arm submodule capacitor to be in a charging state when the bridge arm current is positive, and considers the bridge arm submodule capacitor to be in a discharging state when the bridge arm current is negative.
The bridge arm multiplexing state judging module is responsible for judging the multiplexing state of the multiplexing bridge arm, wherein the multiplexing state of the multiplexing bridge arm comprises that the multiplexing bridge arm and the upper bridge arm form a composite upper bridge arm, that the multiplexing bridge arm and the lower bridge arm form a composite lower bridge arm, and that the multiplexing bridge arm is switched from multiplexing of the upper bridge arm/the lower bridge arm to multiplexing of the lower bridge arm/the upper bridge arm.
The bridge arm submodule input number distribution module distributes the input number of each bridge arm submodule according to the bridge arm current direction, the bridge arm multiplexing state and the bridge arm submodule distribution coefficient output by the controller.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a usb disk, a removable hard disk, a Read-only memory (ROM), a random access memory (RAM, randomAccessMemory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
Logic and/or steps represented in the flowcharts or otherwise described herein, e.g., a ordered listing of executable instructions for implementing logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). In addition, the computer readable medium may even be paper or other suitable medium on which the program is printed, as the program may be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
It is to be understood that portions of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.
Example 3
Referring to fig. 9 to 10, in order to verify the advantageous effects of the present application, scientific demonstration is performed through economic benefit calculation and simulation experiments.
Fig. 9 is a simulation waveform of the capacitance voltage average value difference of the sub-modules of the upper and the multiplexing bridge arms and the distribution coefficient outputted by the controller under the independent control of each bridge arm of the bridge arm multiplexing type MMC, and the valve control system distributes the input number of the sub-modules of the upper and the multiplexing bridge arms according to the distribution coefficient and the current direction of the bridge arms in the current running state.
FIG. 10 is a simulation waveform of the number of sub-modules of the upper and lower legs under the independent control of each leg of the leg multiplexing type MMC, wherein the number of sub-modules of the upper and lower legs is adjusted in real time according to the current operation state when the multiplexed legs are multiplexed with the upper legs, and the number of sub-modules of the upper and lower legs is N when the multiplexed legs are multiplexed with the lower legs pa 。
It should be noted that the above embodiments are only for illustrating the technical solution of the present application and not for limiting the same, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present application may be modified or substituted without departing from the spirit and scope of the technical solution of the present application, which is intended to be covered in the scope of the claims of the present application.
Claims (10)
1. The independent control method for each bridge arm of the bridge arm multiplexing MMC is characterized by comprising the following steps:
collecting data and preprocessing the data;
judging the current direction of each bridge arm and multiplexing the multiplexing state of the multiplexed bridge arms;
performing closed-loop control on the capacitance voltage average value difference value of each bridge arm submodule, and outputting a bridge arm submodule distribution coefficient by a controller;
and distributing the input number of the sub-modules of each bridge arm according to the bridge arm current direction, the bridge arm multiplexing state and the distribution coefficient.
2. The bridge arm multiplexing type MMC individual control method of claim 1, characterized by: the collected data comprise current of the bridge arm during operation, capacitance voltage of the submodule and state information of the bridge arm during operation, multiplexing state of the bridge arm and current direction of the bridge arm.
3. The bridge arm multiplexing type MMC individual control method of claim 2, characterized by: the data preprocessing comprises the steps of removing missing values, abnormal values and invalid data in an error format from collected periodic state data, converting original format data into a format which accords with mathematical model demand analysis, and calculating capacitance voltage average values of all bridge arm submodules to perform data preprocessing.
4. The bridge arm multiplexing type MMC individual control method of claim 3, characterized by: judging the current direction of each bridge arm, namely judging the current direction of the upper bridge arm and the lower bridge arm, wherein when the bridge arm current is positive, the bridge arm sub-module capacitance is in a charging state, and when the bridge arm current is negative, the bridge arm sub-module capacitance is in a discharging state;
the multiplexing state of the multiplexing bridge arm comprises that the multiplexing bridge arm and the upper bridge arm form a composite upper bridge arm, and the multiplexing bridge arm and the lower bridge arm form a composite lower bridge arm, and the multiplexing bridge arm is switched from multiplexing of the upper bridge arm/the lower bridge arm to multiplexing of the lower bridge arm/the upper bridge arm.
5. The bridge arm multiplexing type MMC independent control method of each bridge arm of claim 4, wherein the method comprises the following steps: the distribution of the input number of the sub-modules of each bridge arm comprises setting a flag bit AM as a multiplexing state of multiplexing bridge arms, when AM=1, the multiplexing bridge arms and the upper bridge arms jointly form a composite upper bridge arm, and the input number of the sub-modules of the composite upper bridge arm is N p The input number of the lower bridge arm submodules is N n Putting the composite upper bridge arm submodules into the number N p According to the distribution coefficient n u And the current direction I of the upper bridge arm u Respectively distributing to an upper bridge arm and a multiplexing bridge arm;
when the bridge arm current is positive, the capacitance voltage of the bridge arm submodule is in a charging state, and the input number N of the submodules of the multiplexing bridge arm is made m ＝round(N p *n u ) When calculated N m >When N is set, let N m Number of upper arm submodules N =n u ＝N p -N m Number N of lower bridge arm submodules d ＝N n ；
When the bridge arm current is negative, the capacitor voltage of the bridge arm submodule is in a discharge state, and the number N of the submodules of the upper bridge arm is input at the moment u ＝round(N p *n u ) When calculated N u >When N is set, let N u =n, multiplexing bridgeNumber of arm submodules input N m ＝N p -N u Number N of lower bridge arm submodules d ＝N n Wherein round () is the nearest rounding function and N is the number of submodules of one bridge arm.
6. The bridge arm multiplexing type MMC individual control method of claim 5, characterized by: when the flag bit AM=0, the multiplexing bridge arm and the lower bridge arm jointly form a composite lower bridge arm, and the input number of the submodules of the composite lower bridge arm is N n The input number of the upper bridge arm submodules is N p The number of the sub-modules of the composite lower bridge arm is input according to the distribution coefficient n d And the current direction I of the lower bridge arm d Respectively distributing to a lower bridge arm and a multiplexing bridge arm;
when the bridge arm current is positive, the capacitance voltage of the bridge arm submodule is in a charging state, and the input number N of the submodules of the multiplexing bridge arm is made m ＝round(N n *n d ) When calculated N m >When N is set, let N m Number of lower bridge arm submodules input N d ＝N n -N m The input number N of the upper bridge arm submodules u ＝N p ；
When the bridge arm current is negative, the capacitor voltage of the bridge arm submodule is in a discharge state, and the submodule input number N of the lower bridge arm is set at the moment d ＝round(N n *n d ) When calculated N d >When N is set, let N d Number of multiplexing bridge arm submodules input N m ＝N n -N d The input number N of the upper bridge arm submodules u ＝N p Wherein round () is the nearest rounding function and N is the number of submodules of one bridge arm.
7. The bridge arm multiplexing type MMC individual control method of claim 6, characterized in that: when the flag bit am=2, the multiplexing bridge arm is in a switching mode, and when N pa ＝N na When the input number of the multiplexing bridge arm submodules is 0, an action instruction is sent to the bridge arm change-over switch to changeAnd (3) changing a bridge arm multiplexing mode, wherein N is the number of sub-modules of one bridge arm.
8. A system adopting the bridge arm multiplexing type MMC bridge arm independent control method according to any one of claims 1 to 7, characterized in that: the system comprises a data collection module, a data processing module, a bridge arm current direction judging module, a bridge arm multiplexing state judging module and a bridge arm submodule input number distribution module;
the data collection module is mainly used for collecting current and submodule capacitor voltage of a bridge arm during operation and state information of the bridge arm during operation, wherein the state information comprises multiplexing states of the bridge arm and current directions of the bridge arm;
the data processing module is used for removing missing values, abnormal values and invalid data in error format from the collected periodic state data, converting the original format data into a format conforming to the analysis required by a mathematical model, calculating the capacitance voltage average value of each bridge arm submodule and carrying out data preprocessing
The bridge arm current direction judging module is mainly responsible for judging the current direction of each bridge arm, considers the bridge arm submodule capacitor to be in a charging state when the bridge arm current is positive, and considers the bridge arm submodule capacitor to be in a discharging state when the bridge arm current is negative;
the multiplexing state judging module is responsible for judging the multiplexing state of the multiplexing bridge arm, wherein the multiplexing state of the multiplexing bridge arm comprises that the multiplexing bridge arm and the upper bridge arm form a composite upper bridge arm, and the multiplexing bridge arm and the lower bridge arm form a composite lower bridge arm, and the multiplexing bridge arm is switched from multiplexing of the upper bridge arm/the lower bridge arm to multiplexing of the lower bridge arm/the upper bridge arm;
the bridge arm submodule input number distribution module distributes the input number of each bridge arm submodule according to the bridge arm current direction, the bridge arm multiplexing state and the bridge arm submodule distribution coefficient output by the controller.
9. A computer device comprising a memory and a processor, said memory storing a computer program, characterized in that the processor, when executing said computer program, implements the steps of the individual control method of each leg of the leg multiplexing MMC of any one of claims 1 to 7.
10. A computer-readable storage medium, on which a computer program is stored, characterized in that the computer program, when executed by a processor, implements the steps of the bridge arm independent control method of the bridge arm multiplexing MMC of any one of claims 1 to 7.
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