CN113644834A - Loss assessment method and system for modular multilevel converter - Google Patents

Loss assessment method and system for modular multilevel converter Download PDF

Info

Publication number
CN113644834A
CN113644834A CN202111195466.8A CN202111195466A CN113644834A CN 113644834 A CN113644834 A CN 113644834A CN 202111195466 A CN202111195466 A CN 202111195466A CN 113644834 A CN113644834 A CN 113644834A
Authority
CN
China
Prior art keywords
loss
converter
power
fitting
operation data
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202111195466.8A
Other languages
Chinese (zh)
Other versions
CN113644834B (en
Inventor
甘德树
陈建福
曹安瑛
丘冠新
刘尧
林桂辉
杜成涛
王超
刘行健
裴星宇
廖石江
幸旭彬
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Zhuhai Power Supply Bureau of Guangdong Power Grid Co Ltd
Original Assignee
Zhuhai Power Supply Bureau of Guangdong Power Grid Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zhuhai Power Supply Bureau of Guangdong Power Grid Co Ltd filed Critical Zhuhai Power Supply Bureau of Guangdong Power Grid Co Ltd
Priority to CN202111195466.8A priority Critical patent/CN113644834B/en
Publication of CN113644834A publication Critical patent/CN113644834A/en
Application granted granted Critical
Publication of CN113644834B publication Critical patent/CN113644834B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

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
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • 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]

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The application discloses a loss assessment method and system for a modular multilevel converter, wherein the method comprises the following steps: obtaining n groups of historical operation data of the converter at different moments, wherein the historical operation data comprises: the active power at the alternating current side, the reactive power at the alternating current side, the active power at the direct current side at the same moment and the switching frequency of a switching device at the same moment of the converter are respectively controlled by the controller, and n is a positive integer; calculating the loss of the current converter according to historical operating data, carrying out normalization processing, and then carrying out data cleaning through a Nall detection method to obtain cleaned first operating data; replacing the current variable with a power variable, and adding a power frequency fitting term to construct a loss characteristic description equation; and fitting the loss characteristic description equation through the first operation data, and solving the fitted function to obtain the loss of the converter. Therefore, the technical problems that the accuracy of the loss evaluation of the converter is poor and the loss factor is difficult to determine in the prior art are solved.

Description

Loss assessment method and system for modular multilevel converter
Technical Field
The application relates to the technical field of flexible direct current transmission, in particular to a loss evaluation method and system for a modular multilevel converter.
Background
At present, a Modular Multilevel Converter (MMC) has been widely applied to the fields of flexible direct current transmission, flexible direct current distribution, flexible interconnection of an alternating current power grid, low-voltage direct current remote supply and the like, and is a core electric energy conversion device for constructing a novel power system network frame. As the MMC sub-modules are numerous, the operation working conditions are complex, the circuit topology types are various, and the selectable types of the power switch devices are rich, the accurate loss evaluation of the MMC sub-modules is difficult. The lack of an effective quantitative evaluation method for the loss characteristics of the converter results in that the loss of the converter is difficult to reduce by a method for reasonably distributing the power flow in direct current power transmission and distribution occasions where the converter is widely applied, and the economical efficiency of system operation is influenced.
At present, the loss of the existing converter is composed of nonlinear loss, linear loss and necessary loss as in the technical scheme with the patent number of CN 109193667A. The technical scheme has the following main problems; the influence of different switching frequencies of a switching device on the loss characteristic of the converter is not considered, the loss characteristic of the power switching device under different switching frequencies cannot be reflected by representing the fixed loss of the converter by a constant, and the accuracy of loss evaluation is reduced; secondly, the loss factors are difficult to determine, various loss components need to be considered comprehensively from the aspects of topology and working principle, and the loss factors are difficult to determine accurately.
Disclosure of Invention
The application provides a loss evaluation method and system for a modular multilevel converter, which are used for solving the technical problems that the accuracy of loss evaluation of the converter in the prior art is poor and loss factors are difficult to determine.
In view of the above, a first aspect of the present application provides a modular multilevel converter loss assessment method, including:
obtaining n groups of historical operation data of the converter at different time, wherein the historical operation data comprises: the active power at the alternating current side, the reactive power at the alternating current side, the active power at the direct current side at the same moment and the switching frequency of a switching device at the same moment of the converter are respectively controlled by the controller, and n is a positive integer;
calculating the loss of the current converter according to the historical operating data, carrying out normalization processing, and then carrying out data cleaning through a Nall detection method to obtain cleaned first operating data;
replacing the current variable with a power variable, and adding a power frequency fitting term to construct a loss characteristic description equation;
and fitting the loss characteristic description equation through the first operation data, and solving the fitted function to obtain the loss of the converter.
Optionally, after calculating the converter loss according to the historical operating data and performing normalization processing, performing data cleaning by using a neel detection method to obtain cleaned first operating data, and specifically including:
respectively substituting the active power at the alternating current side and the active power at the direct current side in each group of historical operating data into a converter loss calculation formula for calculation to obtain n groups of converter losses at different moments;
on the basis of a normalization formula, after normalization processing is carried out on the losses of the n groups of converters respectively, the standard deviation of the losses of the n groups of converters is calculated;
and calculating to obtain statistic according to the standard deviation, and performing Neel detection based on the statistic to obtain the first operation data.
Optionally, the loss characteristic description equation is:
Figure 451948DEST_PATH_IMAGE002
；
in the formula (I), the compound is shown in the specification,
Figure 633531DEST_PATH_IMAGE003
in order to reduce the losses of the inverter,
Figure 698570DEST_PATH_IMAGE004
in order to fix the loss of the inverter,
Figure 536076DEST_PATH_IMAGE005
in order to be a factor of loss of the switching frequency,
Figure 977553DEST_PATH_IMAGE006
in order to obtain the power primary loss factor,
Figure 279221DEST_PATH_IMAGE007
in order to obtain the power secondary loss coefficient,
Figure 577479DEST_PATH_IMAGE008
for the purpose of said switching frequency, the switching frequency,
Figure 902281DEST_PATH_IMAGE009
for the active power on the ac side,
Figure 272082DEST_PATH_IMAGE010
and the reactive power is the reactive power of the alternating current side.
Optionally, the fitting the loss characteristic description equation through the first operation data, and solving a fitted function to obtain the loss of the converter specifically include:
fitting parameters in the loss characteristic description equation through the first operation data, determining parameters of the loss characteristic by using a least square method, and constructing to obtain a fitting function;
and respectively solving the partial derivatives of the variables in the fitting function by a method for solving the extreme value of the multivariate function, making the fitting function equal to zero to obtain a partial derivative function, and calculating the partial derivative function to obtain the loss of the converter.
Optionally, the fitting function is:
Figure 120869DEST_PATH_IMAGE011
；
in the formula (I), the compound is shown in the specification,
Figure 855606DEST_PATH_IMAGE004
in order to fix the loss of the inverter,
Figure 402125DEST_PATH_IMAGE005
in order to be a factor of loss of the switching frequency,
Figure 513301DEST_PATH_IMAGE006
in order to obtain the power primary loss factor,
Figure 523982DEST_PATH_IMAGE007
in order to obtain the power secondary loss coefficient,
Figure 429621DEST_PATH_IMAGE012
、
Figure 463436DEST_PATH_IMAGE013
a primary power variable and a secondary power variable of the equation are described for the loss characteristic,
Figure 175040DEST_PATH_IMAGE014
is the switching frequency of the i-th group,
Figure 977911DEST_PATH_IMAGE015
to the switching frequency
Figure 54452DEST_PATH_IMAGE008
Is fed by
Figure 572633DEST_PATH_IMAGE016
And (4) calculating the converter loss by using the group operation data.
Optionally, the converter loss calculation formula is:
Figure 822349DEST_PATH_IMAGE017
；
in the formula (I), the compound is shown in the specification,
Figure 745306DEST_PATH_IMAGE015
to the switching frequency
Figure 992747DEST_PATH_IMAGE008
Is fed by
Figure 1155DEST_PATH_IMAGE016
The converter losses calculated from the group historical operating data,
Figure 54561DEST_PATH_IMAGE018
、
Figure 832025DEST_PATH_IMAGE019
are respectively the first
Figure 250368DEST_PATH_IMAGE016
And active power effective values of an AC side and a DC side of the converter in the group operation data.
Optionally, the normalization formula is:
Figure 480492DEST_PATH_IMAGE020
；
in the formula (I), the compound is shown in the specification,
Figure 337589DEST_PATH_IMAGE021
is as follows
Figure 969559DEST_PATH_IMAGE016
A converter loss normalization represented by the group historical operating data,
Figure 555874DEST_PATH_IMAGE015
to the switching frequency
Figure 538873DEST_PATH_IMAGE008
Is fed by
Figure 871765DEST_PATH_IMAGE016
The converter losses calculated from the group historical operating data,
Figure 420558DEST_PATH_IMAGE018
is as follows
Figure 446283DEST_PATH_IMAGE016
And the active power effective value of the AC side of the converter in the group operation data.
A second aspect of the present application provides a modular multilevel converter loss assessment system, the system comprising:
the obtaining unit is used for obtaining n groups of historical operation data of the converter at different moments, and the historical operation data comprises: the active power at the alternating current side, the reactive power at the alternating current side, the active power at the direct current side at the same moment and the switching frequency of a switching device at the same moment of the converter are respectively controlled by the controller, and n is a positive integer;
the cleaning unit is used for calculating the loss of the converter according to the historical operating data, carrying out normalization processing, and then cleaning data through a Neel detection method to obtain cleaned first operating data;
the building unit is used for replacing the current variable with a power variable and adding a power frequency fitting term to build a loss characteristic description equation;
and the fitting unit is used for fitting the loss characteristic description equation through the first operation data and solving the fitted function to obtain the loss of the converter.
Optionally, the cleaning unit is specifically configured to:
respectively substituting the active power at the alternating current side and the active power at the direct current side in each group of historical operating data into a converter loss calculation formula for calculation to obtain n groups of converter losses at different moments;
on the basis of a normalization formula, after normalization processing is carried out on the losses of the n groups of converters respectively, the standard deviation of the losses of the n groups of converters is calculated;
and calculating to obtain statistic according to the standard deviation, and performing Neel detection based on the statistic to obtain the first operation data.
Optionally, the fitting unit is specifically configured to:
fitting parameters in the loss characteristic description equation through the first operation data, determining parameters of the loss characteristic by using a least square method, and constructing to obtain a fitting function;
and respectively solving the partial derivatives of the variables in the fitting function by a method for solving the extreme value of the multivariate function, making the fitting function equal to zero to obtain a partial derivative function, and calculating the partial derivative function to obtain the loss of the converter.
According to the technical scheme, the method has the following advantages:
the application provides a loss evaluation method of a modular multilevel converter, which solves the problem that the influence of the switching frequency of a power device on the loss characteristic of the converter is not considered in the existing loss evaluation method of the converter by adding a fitting item related to the switching frequency into a loss characteristic equation. Meanwhile, the historical operation data of the converter is used for fitting the parameters of the loss characteristic equation, a method for calculating the loss characteristic equation parameters according to topology and working principle or measuring the loss characteristic parameters through field test in the prior art is replaced, the difficulty of determining the loss factor is greatly reduced, and the method can be still used for dynamically evaluating the loss characteristic of the converter after the body parameters are changed due to long-term operation of equipment. Furthermore, after the loss characteristic fitting equation provided by the application is subjected to linearization processing, the nonlinear complexity of a fitting curve is reduced, the overall loss characteristic of the converter can be fitted by using less operation data, a new measuring device is not needed, delivery tests of various electrical quantities and non-electrical quantities are not needed, the loss evaluation process is simplified, and the method is suitable for the overall loss evaluation of converters with different sub-modules and different topological structures. Therefore, the technical problems that the accuracy of the loss evaluation of the converter is poor and the loss factor is difficult to determine in the prior art are solved.
Drawings
Fig. 1 is a schematic flowchart of a first embodiment of a loss evaluation method for a modular multilevel converter provided in an embodiment of the present application;
fig. 2 is a schematic flowchart of a second embodiment of a loss evaluation method for a modular multilevel converter provided in the embodiment of the present application;
fig. 3 is a schematic structural diagram of an embodiment of a modular multilevel converter loss evaluation system provided in an embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1, a loss evaluation method for a modular multilevel converter according to an embodiment of the present application includes:
step 101, obtaining n groups of historical operating data of the current converter at different moments, wherein the historical operating data comprises: the active power at the alternating current side, the reactive power at the alternating current side, the active power at the direct current side at the same moment and the switching frequency of a switching device at the same moment of the converter, wherein n is a positive integer.
It should be noted that, in this embodiment, historical operating data of a plurality of sets of ac ports and dc ports of a converter on a cross section at different times are acquired by a scheduling automation system, and it can be understood that the historical operating data of the same set are acquired at the same time. Specifically, the historical operating data of the present embodiment includes: the active power at the alternating current side, the reactive power at the alternating current side, the active power at the direct current side at the same moment and the switching frequency of the switching device at the same moment of the converter. According to the method and the device, the historical operation data of the current converter on different switch working frequencies and different discontinuities are collected, so that the obtained data have universal representativeness under different load rates, and the accuracy of loss assessment is improved.
102, calculating the loss of the converter according to historical operating data, carrying out normalization processing, and then cleaning data through a Neel detection method to obtain cleaned first operating data.
It should be noted that, in this embodiment, the converter loss is calculated according to the historical operating data, specifically:
for a given switching frequency
Figure 651000DEST_PATH_IMAGE008
Obtained under
Figure 787583DEST_PATH_IMAGE022
Calculating the converter loss represented by each group of operation data according to the operation data of the converter on the section of the group at different time
Figure 190882DEST_PATH_IMAGE003
：
Figure 387509DEST_PATH_IMAGE017
；
In the formula (I), the compound is shown in the specification,
Figure 79521DEST_PATH_IMAGE015
indicating switching frequency
Figure 751286DEST_PATH_IMAGE008
Is fed by
Figure 274671DEST_PATH_IMAGE016
The converter losses calculated from the group historical operating data,
Figure 642199DEST_PATH_IMAGE018
、
Figure 555928DEST_PATH_IMAGE019
respectively represent
Figure 96631DEST_PATH_IMAGE016
And active power effective values of an alternating current side and a direct current side of the converter in the group historical operation data.
The normalization process in this embodiment specifically includes:
carrying out normalization processing on the converter loss of each group of historical operating data to obtain
Figure 677785DEST_PATH_IMAGE021
。
Figure 950635DEST_PATH_IMAGE020
；
In the formula (I), the compound is shown in the specification,
Figure 679556DEST_PATH_IMAGE021
is as follows
Figure 696054DEST_PATH_IMAGE016
A converter loss normalization represented by the group historical operating data,
Figure 131714DEST_PATH_IMAGE015
to the switching frequency
Figure 575465DEST_PATH_IMAGE008
Is fed by
Figure 726436DEST_PATH_IMAGE016
The converter losses calculated from the group historical operating data,
Figure 608942DEST_PATH_IMAGE018
is as follows
Figure 899109DEST_PATH_IMAGE016
And the active power effective value of the AC side of the converter in the group operation data.
In this embodiment, data cleaning is performed by a neel detection method to obtain first operation data after cleaning, which specifically includes:
(1) computing
Figure 779340DEST_PATH_IMAGE022
Standard deviation of group loss data
Figure 154958DEST_PATH_IMAGE023
；
Figure 575575DEST_PATH_IMAGE024
；
Figure 985827DEST_PATH_IMAGE025
；
Wherein the content of the first and second substances,
Figure 771381DEST_PATH_IMAGE026
is the average of the loss sample data.
(2) Specifying maximum values in loss samples
Figure 696611DEST_PATH_IMAGE027
To assume outliers
Figure 858603DEST_PATH_IMAGE028
And calculating statistics
Figure 123362DEST_PATH_IMAGE029
；
Figure 342466DEST_PATH_IMAGE030
；
According to the detected level
Figure 754993DEST_PATH_IMAGE031
And sample volume
Figure 455096DEST_PATH_IMAGE022
Critical value table of the Charnell test
Figure 574361DEST_PATH_IMAGE032
If, if
Figure 967296DEST_PATH_IMAGE033
Judging the data to be an abnormal value, and removing the abnormal value and then continuing the neel detection on the residual data; otherwise, no outliers are found.
And 103, replacing the current variable with a power variable, and adding a power frequency fitting term to construct a loss characteristic description equation.
It should be noted that, in order to fully consider various factors affecting the loss of the converter and improve the accuracy of the loss evaluation, a power device switching frequency fitting term is added on the basis of the existing loss evaluation method in the embodiment. In addition, in order to directly employ the historical operation data, the present embodiment replaces the current variable with the power variable. Thus, the loss characteristic description equation is constructed as follows:
Figure 867119DEST_PATH_IMAGE034
；
in the formula (I), the compound is shown in the specification,
Figure 370913DEST_PATH_IMAGE003
in order to reduce the losses of the inverter,
Figure 344685DEST_PATH_IMAGE004
in order to fix the loss of the inverter,
Figure 970839DEST_PATH_IMAGE005
in order to be a factor of loss of the switching frequency,
Figure 295641DEST_PATH_IMAGE006
in order to obtain the power primary loss factor,
Figure 337546DEST_PATH_IMAGE007
in order to obtain the power secondary loss coefficient,
Figure 493721DEST_PATH_IMAGE008
for the purpose of said switching frequency, the switching frequency,
Figure 225529DEST_PATH_IMAGE009
for the active power on the ac side,
Figure 772048DEST_PATH_IMAGE010
and the reactive power is the reactive power of the alternating current side.
Furthermore, in order to reduce the nonlinearity of the loss characteristic equation and facilitate the subsequent determination of parameters by using a linear fitting method
Figure 883224DEST_PATH_IMAGE012
、
Figure 831588DEST_PATH_IMAGE013
Respectively represent the primary power variable and the secondary power variable in the above formula, and the above formula is rewritten as:
Figure 799544DEST_PATH_IMAGE035
；
and step 104, fitting the loss characteristic description equation through the first operation data, and solving the fitted function to obtain the loss of the converter.
It should be noted that, in this embodiment, the parameters in the loss characteristic equation are fitted by using the cleaned first operation data, and the parameters of the loss characteristic are determined by using the least square method, so that the fitted function is obtained as:
Figure 833359DEST_PATH_IMAGE011
；
in the formula (I), the compound is shown in the specification,
Figure 217067DEST_PATH_IMAGE004
in order to fix the loss of the inverter,
Figure 285517DEST_PATH_IMAGE005
in order to be a factor of loss of the switching frequency,
Figure 424374DEST_PATH_IMAGE006
in order to obtain the power primary loss factor,
Figure 945486DEST_PATH_IMAGE007
in order to obtain the power secondary loss coefficient,
Figure 129955DEST_PATH_IMAGE012
、
Figure 115228DEST_PATH_IMAGE013
a primary power variable and a secondary power variable of the equation are described for the loss characteristic,
Figure 362670DEST_PATH_IMAGE014
the switching frequency of the ith group,
Figure 371077DEST_PATH_IMAGE015
to the switching frequency
Figure 362167DEST_PATH_IMAGE008
Is fed by
Figure 201947DEST_PATH_IMAGE016
And (4) calculating the converter loss by using the group operation data.
Further, by using a method for solving an extreme value of a multivariate function, respectively solving partial derivatives of variables in the above formula, and making the partial derivatives equal to zero, obtaining:
Figure 620290DEST_PATH_IMAGE036
；
and solving the equation to obtain the value of each parameter in the loss characteristic equation, thereby obtaining the loss of the converter.
The first embodiment of the loss evaluation method for the modular multilevel converter provided in the embodiment of the present application is described above, and the second embodiment of the loss evaluation method for the modular multilevel converter provided in the embodiment of the present application is described below.
Referring to fig. 2, a second embodiment of the present invention provides a method for evaluating loss of a blocking multilevel converter, including:
step 201, obtaining n groups of historical operating data of the current converter at different time, wherein the historical operating data comprises: the active power at the alternating current side, the reactive power at the alternating current side, the active power at the direct current side at the same moment and the switching frequency of a switching device at the same moment of the converter, wherein n is a positive integer.
And step 202, substituting the active power of the alternating current side and the active power of the direct current side in each group of historical operating data into a converter loss calculation formula for calculation to obtain n groups of converter losses at different moments.
And 203, respectively carrying out normalization processing on the n groups of converter losses based on a normalization formula, and then calculating the standard deviation of the n groups of converter losses.
And 204, calculating to obtain statistic according to the standard deviation, and performing Neel detection based on the statistic to obtain first operation data.
And step 205, replacing the current variable with a power variable, and adding a power frequency fitting term to construct a loss characteristic description equation.
And step 206, fitting parameters in the loss characteristic description equation through the first operation data, determining the parameters of the loss characteristic by using a least square method, and constructing to obtain a fitting function.
And step 207, respectively solving the partial derivatives of the variables in the fitting function by a method for solving the extreme value of the multivariate function, making the fitting function equal to zero to obtain a partial derivative function, and calculating the partial derivative function to obtain the loss of the converter.
The steps 201-207 of the present embodiment are similar to the description of the steps 101-104 of the embodiment, please refer to the description of the steps 101-104 of the embodiment, which will not be described herein again.
The embodiment provides a loss evaluation method for a modular multilevel converter, which solves the problem that the influence of the switching frequency of a power device on the loss characteristic of the converter is not considered in the existing loss evaluation method for the converter by adding a fitting term related to the switching frequency into a loss characteristic equation. Meanwhile, the historical operation data of the converter is used for fitting the parameters of the loss characteristic equation, a method for calculating the loss characteristic equation parameters according to topology and working principle or measuring the loss characteristic parameters through field test in the prior art is replaced, the difficulty of determining the loss factor is greatly reduced, and the method can be still used for dynamically evaluating the loss characteristic of the converter after the body parameters are changed due to long-term operation of equipment. Furthermore, after the loss characteristic fitting equation provided by the application is subjected to linearization processing, the nonlinear complexity of a fitting curve is reduced, the overall loss characteristic of the converter can be fitted by using less operation data, a new measuring device is not needed, delivery tests of various electrical quantities and non-electrical quantities are not needed, the loss evaluation process is simplified, and the method is suitable for the overall loss evaluation of converters with different sub-modules and different topological structures. Therefore, the technical problems that the accuracy of the loss evaluation of the converter is poor and the loss factor is difficult to determine in the prior art are solved.
In the above, a second embodiment of the method for evaluating loss of a modular multilevel converter provided in the embodiment of the present application is described below as an embodiment of a system for evaluating loss of a modular multilevel converter provided in the embodiment of the present application.
Referring to fig. 3, an exemplary embodiment of a system for evaluating loss of a block multilevel converter includes:
an obtaining unit 301, configured to obtain n sets of historical operation data of the converter at different time instants, where the historical operation data includes: the active power at the alternating current side, the reactive power at the alternating current side, the active power at the direct current side at the same moment and the switching frequency of a switching device at the same moment of the converter, wherein n is a positive integer.
And the cleaning unit 302 is configured to calculate converter loss according to the historical operating data, perform normalization processing, and perform data cleaning by using a neel detection method to obtain cleaned first operating data.
And the constructing unit 303 is configured to replace the current variable with a power variable, and add a power frequency fitting term to construct a loss characteristic description equation.
And the fitting unit 304 is configured to fit the loss characteristic description equation through the first operation data, and solve the fitted function to obtain the loss of the converter.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The terms "first," "second," "third," "fourth," and the like in the description of the application and the above-described figures, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be understood that in the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" for describing an association relationship of associated objects, indicating that there may be three relationships, e.g., "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed 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 can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.

Claims (10)

1. A loss assessment method for a modular multilevel converter is characterized by comprising the following steps:
obtaining n groups of historical operation data of the converter at different time, wherein the historical operation data comprises: the active power at the alternating current side, the reactive power at the alternating current side, the active power at the direct current side at the same moment and the switching frequency of a switching device at the same moment of the converter are respectively controlled by the controller, and n is a positive integer;
calculating the loss of the current converter according to the historical operating data, carrying out normalization processing, and then carrying out data cleaning through a Nall detection method to obtain cleaned first operating data;
replacing the current variable with a power variable, and adding a power frequency fitting term to construct a loss characteristic description equation;
and fitting the loss characteristic description equation through the first operation data, and solving the fitted function to obtain the loss of the converter.
2. The method according to claim 1, wherein after calculating the converter loss according to the historical operating data and performing normalization processing, performing data cleaning by using a neel detection method to obtain cleaned first operating data specifically comprises:
respectively substituting the active power at the alternating current side and the active power at the direct current side in each group of historical operating data into a converter loss calculation formula for calculation to obtain n groups of converter losses at different moments;
on the basis of a normalization formula, after normalization processing is carried out on the losses of the n groups of converters respectively, the standard deviation of the losses of the n groups of converters is calculated;
and calculating to obtain statistic according to the standard deviation, and performing Neel detection based on the statistic to obtain the first operation data.
3. The modular multilevel converter loss evaluation method according to claim 1, wherein the loss characterization equation is:
Figure 392040DEST_PATH_IMAGE002
；
in the formula (I), the compound is shown in the specification,
Figure 246864DEST_PATH_IMAGE003
in order to reduce the losses of the inverter,
Figure 26601DEST_PATH_IMAGE004
in order to fix the loss of the inverter,
Figure 359493DEST_PATH_IMAGE005
in order to be a factor of loss of the switching frequency,
Figure 111549DEST_PATH_IMAGE006
in order to obtain the power primary loss factor,
Figure 871694DEST_PATH_IMAGE007
in order to obtain the power secondary loss coefficient,
Figure 76411DEST_PATH_IMAGE008
for the purpose of said switching frequency, the switching frequency,
Figure 275311DEST_PATH_IMAGE009
for the active power on the ac side,
Figure 878943DEST_PATH_IMAGE010
and the reactive power is the reactive power of the alternating current side.
4. The method according to claim 1, wherein the fitting the loss characterization equation according to the first operation data and solving the fitted function to obtain the loss of the converter specifically comprises:
fitting parameters in the loss characteristic description equation through the first operation data, determining parameters of the loss characteristic by using a least square method, and constructing to obtain a fitting function;
and respectively solving the partial derivatives of the variables in the fitting function by a method for solving the extreme value of the multivariate function, making the fitting function equal to zero to obtain a partial derivative function, and calculating the partial derivative function to obtain the loss of the converter.
5. The modular multilevel converter loss assessment method according to claim 4, wherein the fitting function is:
Figure 872307DEST_PATH_IMAGE011
；
in the formula (I), the compound is shown in the specification,
Figure 564319DEST_PATH_IMAGE004
in order to fix the loss of the inverter,
Figure 239014DEST_PATH_IMAGE005
in order to be a factor of loss of the switching frequency,
Figure 762400DEST_PATH_IMAGE006
in order to obtain the power primary loss factor,
Figure 129927DEST_PATH_IMAGE007
in order to obtain the power secondary loss coefficient,
Figure 371553DEST_PATH_IMAGE012
、
Figure 584359DEST_PATH_IMAGE013
a primary power variable and a secondary power variable of the equation are described for the loss characteristic,
Figure 165513DEST_PATH_IMAGE014
is the switching frequency of the i-th group,
Figure 500680DEST_PATH_IMAGE015
to the switching frequency
Figure 167284DEST_PATH_IMAGE008
Is fed by
Figure 183782DEST_PATH_IMAGE016
And (4) calculating the converter loss by using the group operation data.
6. The method of claim 2, wherein the converter loss calculation formula is:
Figure 616513DEST_PATH_IMAGE017
；
in the formula (I), the compound is shown in the specification,
Figure 388160DEST_PATH_IMAGE015
to the switching frequency
Figure 214164DEST_PATH_IMAGE008
Is fed by
Figure 34353DEST_PATH_IMAGE016
The converter losses calculated from the group historical operating data,
Figure 324520DEST_PATH_IMAGE018
、
Figure 204751DEST_PATH_IMAGE019
are respectively the first
Figure 642686DEST_PATH_IMAGE016
And active power effective values of an AC side and a DC side of the converter in the group operation data.
7. The modular multilevel converter loss assessment method according to claim 2, wherein the normalization formula is:
Figure 986DEST_PATH_IMAGE020
；
in the formula (I), the compound is shown in the specification,
Figure 411239DEST_PATH_IMAGE021
is as follows
Figure 459442DEST_PATH_IMAGE016
A converter loss normalization represented by the group historical operating data,
Figure 384672DEST_PATH_IMAGE015
to the switching frequency
Figure 546663DEST_PATH_IMAGE008
Is fed by
Figure 545843DEST_PATH_IMAGE016
The converter losses calculated from the group historical operating data,
Figure 767877DEST_PATH_IMAGE018
is as follows
Figure 180404DEST_PATH_IMAGE016
And the active power effective value of the AC side of the converter in the group operation data.
8. A modular multilevel converter loss assessment system, comprising:
the obtaining unit is used for obtaining n groups of historical operation data of the converter at different moments, and the historical operation data comprises: the active power at the alternating current side, the reactive power at the alternating current side, the active power at the direct current side at the same moment and the switching frequency of a switching device at the same moment of the converter are respectively controlled by the controller, and n is a positive integer;
the cleaning unit is used for calculating the loss of the converter according to the historical operating data, carrying out normalization processing, and then cleaning data through a Neel detection method to obtain cleaned first operating data;
the building unit is used for replacing the current variable with a power variable and adding a power frequency fitting term to build a loss characteristic description equation;
and the fitting unit is used for fitting the loss characteristic description equation through the first operation data and solving the fitted function to obtain the loss of the converter.
9. The modular multilevel converter loss evaluation system of claim 8, wherein the wash unit is specifically configured to:
respectively substituting the active power at the alternating current side and the active power at the direct current side in each group of historical operating data into a converter loss calculation formula for calculation to obtain n groups of converter losses at different moments;
on the basis of a normalization formula, after normalization processing is carried out on the losses of the n groups of converters respectively, the standard deviation of the losses of the n groups of converters is calculated;
and calculating to obtain statistic according to the standard deviation, and performing Neel detection based on the statistic to obtain the first operation data.
10. The modular multilevel converter loss evaluation system of claim 8, wherein the fitting unit is specifically configured to:
fitting parameters in the loss characteristic description equation through the first operation data, determining parameters of the loss characteristic by using a least square method, and constructing to obtain a fitting function;
and respectively solving the partial derivatives of the variables in the fitting function by a method for solving the extreme value of the multivariate function, making the fitting function equal to zero to obtain a partial derivative function, and calculating the partial derivative function to obtain the loss of the converter.
CN202111195466.8A 2021-10-14 2021-10-14 Loss assessment method and system for modular multilevel converter Active CN113644834B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111195466.8A CN113644834B (en) 2021-10-14 2021-10-14 Loss assessment method and system for modular multilevel converter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111195466.8A CN113644834B (en) 2021-10-14 2021-10-14 Loss assessment method and system for modular multilevel converter

Publications (2)

Publication Number Publication Date
CN113644834A true CN113644834A (en) 2021-11-12
CN113644834B CN113644834B (en) 2022-02-15

Family

ID=78426831

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111195466.8A Active CN113644834B (en) 2021-10-14 2021-10-14 Loss assessment method and system for modular multilevel converter

Country Status (1)

Country Link
CN (1) CN113644834B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115453340A (en) * 2022-09-14 2022-12-09 浙江伊控动力***有限公司 Switching loss fitting method based on least square iterative computation

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104993715A (en) * 2015-06-29 2015-10-21 中国电力工程顾问集团中南电力设计院有限公司 Quick estimation algorithm for valve loss of modularized multi-level current converter
CN104992016A (en) * 2015-06-30 2015-10-21 上海交通大学 Modular multilevel converter loss estimation method
US20170133845A1 (en) * 2014-07-22 2017-05-11 Abb Schweiz Ag Model predictive control of a modular multilevel converter
CN112362993A (en) * 2020-11-10 2021-02-12 江苏天合清特电气有限公司 Flexible direct current conversion module loss testing and evaluating method based on device parameter actual measurement
CN112990556A (en) * 2021-02-24 2021-06-18 江苏大学 User power consumption prediction method based on Prophet-LSTM model
CN113078836A (en) * 2021-05-20 2021-07-06 东南大学 Modular multilevel converter loss optimization control method based on circulation injection

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170133845A1 (en) * 2014-07-22 2017-05-11 Abb Schweiz Ag Model predictive control of a modular multilevel converter
CN104993715A (en) * 2015-06-29 2015-10-21 中国电力工程顾问集团中南电力设计院有限公司 Quick estimation algorithm for valve loss of modularized multi-level current converter
CN104992016A (en) * 2015-06-30 2015-10-21 上海交通大学 Modular multilevel converter loss estimation method
CN112362993A (en) * 2020-11-10 2021-02-12 江苏天合清特电气有限公司 Flexible direct current conversion module loss testing and evaluating method based on device parameter actual measurement
CN112990556A (en) * 2021-02-24 2021-06-18 江苏大学 User power consumption prediction method based on Prophet-LSTM model
CN113078836A (en) * 2021-05-20 2021-07-06 东南大学 Modular multilevel converter loss optimization control method based on circulation injection

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
KUN YU 等: "Comparative Analysis of Power Loss for MMC Rectifiers with NLM and CPS Modulation Schemes", 《2020 12TH IEEE PES ASIA-PACIFIC POWER AND ENERGY ENGINEERING CONFERENCE (APPEEC)》 *
谢妍 等: "模块化多电平变换器功率模块的电流与损耗", 《沈阳工业大学学报》 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115453340A (en) * 2022-09-14 2022-12-09 浙江伊控动力***有限公司 Switching loss fitting method based on least square iterative computation
CN115453340B (en) * 2022-09-14 2023-04-28 浙江伊控动力***有限公司 Switching loss fitting method based on least square iterative computation

Also Published As

Publication number Publication date
CN113644834B (en) 2022-02-15

Similar Documents

Publication Publication Date Title
CN109031184B (en) Monitoring method and system of electric energy metering device and terminal equipment
CN115237079B (en) Intelligent control system and control method for equipment for chemical production
CN107359612A (en) A kind of comprehensive estimation method of quality of power supply to power distribution network energy consumption
CN113644834B (en) Loss assessment method and system for modular multilevel converter
CN116125361B (en) Voltage transformer error evaluation method, system, electronic equipment and storage medium
US8680842B2 (en) Method for measurement of total harmonic distortion
CN110705107A (en) Power distribution network voltage evaluation method, system, equipment and storage medium
CN110045186B (en) System harmonic impedance estimation method and system at power system common connection point
CN114528951A (en) Distribution network line single line diagram abnormity diagnosis and analysis method, system and device
CN113985339A (en) Error diagnosis method, system, equipment and storage medium for intelligent electric meter
CN112305485B (en) Method and device for correcting harmonic voltage measurement error of capacitor voltage transformer
CN115618654B (en) Identification method and device for out-of-tolerance electric energy meter
CN115685046A (en) Mutual inductor metering abnormity identification method, device, equipment and storage medium
CN110929220A (en) Power distribution network index weight calculation method and device
CN109359822A (en) Electronic type voltage transformer measuring state appraisal procedure and system
CN117609904A (en) Inspection method, device and storage medium based on electricity distribution data analysis
CN109670550B (en) Power distribution terminal maintenance decision method and device
CN108229786B (en) Power grid investment distribution processing method and device
Mishra et al. Calculation of power quality factor of supply system using LabVIEW
CN111443305A (en) Method and device for detecting line fault by using electric energy deviation value
CN115051912A (en) Method, device, equipment and medium for positioning power failure user
CN110896218B (en) Harmonic modeling method and system for establishing collective residential load
CN113051741A (en) Method and device for solving reliability parameters of elements of high-voltage direct-current power transmission system
CN113435065A (en) Equivalent impedance modeling method based on 'black box' DC/DC converter
CN111007347A (en) Non-invasive load identification device and related equipment

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant