CN107482928B - A kind of D.C. high voltage transmission modularization multi-level converter and its control method - Google Patents

A kind of D.C. high voltage transmission modularization multi-level converter and its control method Download PDF

Info

Publication number
CN107482928B
CN107482928B CN201710675899.0A CN201710675899A CN107482928B CN 107482928 B CN107482928 B CN 107482928B CN 201710675899 A CN201710675899 A CN 201710675899A CN 107482928 B CN107482928 B CN 107482928B
Authority
CN
China
Prior art keywords
submodule
voltage
sub
modules
submodules
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.)
Expired - Fee Related
Application number
CN201710675899.0A
Other languages
Chinese (zh)
Other versions
CN107482928A (en
Inventor
冯轩
冯一轩
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Priority to CN201710675899.0A priority Critical patent/CN107482928B/en
Publication of CN107482928A publication Critical patent/CN107482928A/en
Application granted granted Critical
Publication of CN107482928B publication Critical patent/CN107482928B/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

Links

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
    • 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
    • H02M7/42—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
    • H02M7/487—Neutral point clamped inverters
    • 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
    • H02M7/53—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 using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • 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)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a kind of D.C. high voltage transmission modularization multi-level converter and its control methods, including：Three phase elements, each phase element include two symmetrically upper bridge arm, lower bridge arms；Bridge arm, including N number of submodule and with the concatenated reactor of submodule；Submodule, for double Clamp submodules.The D.C. high voltage transmission modularization multi-level converter and its control method of the present invention, MMC can be equivalent at two independent subtopology structures, realize that double-throw enters, double excisions, single-throw list is cut and the working conditions such as single singulation is thrown, and submodule is ranked up using the electric voltage frequency method of weighting, keep the switching frequency of the IGBT of submodule uniform.

Description

Modularized multi-level converter for high-voltage direct-current transmission and control method thereof
Technical Field
The invention relates to the field of high-voltage direct-current transmission. More particularly, the present invention relates to a modular multilevel converter for high voltage direct current transmission and a control method thereof.
Background
In recent years, Modular Multilevel Converters (MMC) are widely applied to high-voltage direct-current transmission systems, so that a multi-terminal high-voltage direct-current transmission technology is easy to implement. However, in actual operation, the capacitor voltage of the power module is easy to fluctuate, and the capacitor voltage of the modular multilevel converter for high-voltage direct-current transmission must be balanced and controlled to be controlled within a certain fluctuation range as much as possible, so that the influence on the system is reduced.
In the process of controlling the balance of the capacitor voltage, the switching frequency of the switching device is too high, and the use frequencies of different switches are uneven, which easily causes the reduction of the stability and reliability of the system.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a modular multilevel converter for a high-voltage direct-current transmission system, wherein sub-modules can be equivalent to two independent sub-topology structures, and the working states of double input, double cutting, single input and single cut, single input and the like are realized.
The invention also aims to provide a capacitance-voltage balance control method of the modular multilevel converter for the high-voltage direct-current transmission system, which sequences the submodule by adopting a voltage-frequency weight method so as to ensure that the switching frequency of the IGBT of the submodule is uniform.
To achieve these objects and other advantages in accordance with the invention, a modular multilevel converter for high voltage direct current transmission comprises:
each phase unit comprises an upper bridge arm and a lower bridge arm which are symmetrical;
the bridge arm comprises N sub-modules and a reactor connected with the sub-modules in series;
a sub-module which is a doubly clamped sub-module.
Preferably, the double-clamping sub-module comprises 5 IGBTs, two diodes and two independent capacitors C; wherein the IGBT has a diode connected in anti-parallel therewith.
The object of the invention is also achieved by a method for controlling a modular multilevel converter for high voltage direct current transmission, comprising:
step 1, collecting sub-module quantity N input by an upper bridge arm and a lower bridge arm in a control period before collecting by a controlleron-1And the number of excised submodules Noff-1；
Step 2, in the period, the number N of submodules required to be put into the controlleron-2Or the number of cut-out sub-modules Noff-2Judging the operating mode of execution by the current direction of the bridge arm;
step 3, sequencing the sub-modules by using a voltage-frequency weight method;
step 4, the MMC enters a corresponding working mode, the sub-modules carry out switching-in or switching-out state conversion according to the sequence until the voltage difference value delta U of the sub-modules is smaller than the set allowable deviation U of the capacitor voltagez。
Preferably, the voltage-frequency weighting method comprises calculating voltage-frequency weightsThe steps of (1):
wherein U is the capacitance voltage value of the ith sub-module; f is the switching frequency of the ith sub-module; λ is a current influence factor; w is a1iThe voltage weight coefficient of the ith sub-module; w is a2iIs the frequency weight coefficient of the ith sub-module.
Preferably, the method further comprises the following steps: sub-module weighting according to voltage-frequencyThe values are sorted in order from large to small.
Preferably, the operation modes include:
when the number of the submodules needing to be switched in or out is not changed, the bridge arm current is greater than zero, and the first mode is adopted;
when the number of the submodules needing to be switched in or out is not changed, the bridge arm current is smaller than zero, and the mode is a second mode;
when the number of the submodules needing to be put into the converter is increased, the bridge arm current is greater than zero, and the mode is a third mode;
when the number of the submodules needing to be put into the converter is increased, the bridge arm current is smaller than zero, and the fourth mode is adopted;
when the number of the submodules needing to be put into the converter is reduced, the number of the submodules needing to be cut is increased, and the bridge arm current is greater than zero, so that the converter is in a fifth mode;
and when the number of the submodules needing to be put into the converter is reduced, the number of the submodules needing to be cut is increased, the bridge arm current is smaller than zero, and the sixth mode is adopted.
Preferably, the first mode will have been engagedLargest submodule and in cut-out stateThe smallest submodule starts to exchange and will be put intoSubmodule of the second largest size and in the switched-out stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the input submodule and the voltage of the submodule in the cut-out state is smaller than the set allowable deviation U of the capacitor voltagez；
When executing the second mode, will be switched outLargest submodule and in input stateThe smallest submodule starts to exchange and is cut outSubmodule second largest and in input stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the cut-out submodule and the voltage of the submodule in the switching-in state is smaller than the set allowable deviation U of the capacitor voltagez。
Preferably, in the third mode, the number m of the submodules to be newly input is calculated, and the submodules in the switching-out state are selectedThe m sub-modules at the lowest are switched to the input state; and then, switching the sub-modules which are put into and switched out until the difference value delta U between the voltage of the put-in sub-module and the voltage of the switched-out sub-module is smaller than the set allowable deviation U of the capacitor voltagez；
When the fourth mode is executed, the number m of the submodules needing to be newly input is calculated, and the submodules in the switching-out state are selectedThe m highest submodules are switched into the input state; and then, switching the switched-in sub-modules and the switched-out sub-modules until the voltage difference delta U between the switched-out sub-modules and the switched-in sub-modules is smaller than the set capacitor voltage allowable deviation Uz。
Preferably, the fifth mode is: calculating the number k of the submodules needing to be newly cut out, and selecting the submodules in the input stateThe highest k number of sub-modules,switching k submodules into a switching-out state; and then, switching the sub-modules which are put into and switched out until the difference value delta U between the voltage of the put-in sub-module and the voltage of the switched-out sub-module is smaller than the set allowable deviation U of the capacitor voltagez；
When the sixth mode is executed, the number k of the sub-modules needing to be newly switched out is calculated, and the sub-modules in the input state are selectedThe lowest k sub-modules switch the k sub-modules into a switching-out state; and then, switching the switched-in sub-modules and the switched-out sub-modules until the voltage difference delta U between the switched-out sub-modules and the switched-in sub-modules is smaller than the set capacitor voltage allowable deviation Uz。
Preferably, when the current impact factor lambda is equal to 1,when the current influencing factor lambda is equal to-1,wherein,is the average voltage.
The invention has the beneficial effects that: 1. MMC topological structure can be equivalent to two ordinary MMC topological structure of independent operation, and two submodule piece electric capacity mutually independent charge, put the point, can realize two input, two excision, single input single-cutting and single-cutting four kinds of states, and operating mode is various, realizes more performances. 2. According to the capacitance voltage balance control method, the switching frequency and the capacitance voltage value of the IGBT of the submodule are calculated according to a certain weight by adopting a voltage-frequency weight method, then are sequenced according to the weight calculated values, the influence of the switching frequency is taken into consideration, and the switching frequency of the IGBT of the submodule is uniform on the basis of ensuring the capacitance voltage balance.
Drawings
Fig. 1 is a block diagram of a Modular Multilevel Converter (MMC) for a high voltage direct current transmission system according to the invention.
Fig. 2 is a sub-module structure diagram of a Modular Multilevel Converter (MMC) of the present invention.
Fig. 3 is a flow chart of a method of controlling the capacitor voltage balance of a modular multilevel converter for a high voltage direct current transmission system according to the invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
Fig. 1-3 show a Modular Multilevel Converter (MMC) for a hvdc transmission system according to an implementation form of the invention, which comprises three identical phase cells as shown in fig. 1, each phase cell comprising two fully symmetrical upper and lower legs, each leg comprising N sub-modules and a reactor connected in series, each phase cell being fed with N sub-modules, U, in steady state operationdThe bridge arm reactor is the direct-current side voltage of the MMC, can inhibit interphase circulating current, reduce the harmonic distortion rate of bridge arm current, and can inhibit the rise of fault current under serious faults so as to protect the power electronic device of the MMC.
The specific structure of a submodule of the MMC is shown in fig. 2, and comprises 5 IGBTs, a diode switch group, two diodes and two independent capacitors C, as shown in table 1, when the submodule normally operates, T5 keeps an on state, D6 and D7 are reversely cut off, the whole topological structure can be equivalent to two common MMC topological structures which independently operate, the two submodule capacitors can be mutually independently charged and discharged, four states of double input, double cut, single input, single cut and single cut can be realized, the operating modes are various, more performances are realized, and the defect that other submodules cannot cut off direct-current fault short-circuit current can be overcome,
when the direct current fault occurs, the MMC is integrally locked, all IGBTs are locked, as shown in Table 1, when the current is positive, T1, T2, T3, T4 and T5 are all locked, namely, the current flows through D1, D4, D5 and two capacitors C which are connected in series and are charged, when the alternating current voltage and the capacitor voltage of a submodule in the MMC are clamped with each other, the charging is stopped, the direct current short-circuit current is cut off, and the output voltage is 2UC in different current directions after locking; when the current is negative, the current flows through the D3, the D5, the D6 and the D7 and the two capacitors, and the two capacitors are connected in parallel and charged. When the alternating voltage and the capacitance voltage of the MMC neutron module are clamped mutually, the charging is stopped, the direct short-circuit current is cut off, and the output voltage is U in different current directions after lockingC。
TABLE 1 summary of sub-module operating conditions
Compared with a universal MMC topological structure, the MMC provided by the invention has the advantages that the added switching device enhances the control flexibility of the sub-module, and the MMC has the direct-current fault short-circuit current cutting-off capability.
The invention also discloses a capacitance voltage balance control method of the modular multilevel converter for the high-voltage direct-current transmission system, which comprises the following steps as shown in figure 3:
step 1, collecting sub-module quantity N input by an upper bridge arm and a lower bridge arm in a control period before collecting by a controlleron-1And the number of excised submodules Noff-1；
Step 2, in the period, the number N of submodules required to be put into the controlleron-2Or number of submodules cut outNoff-2Judging the operating mode of execution by the current direction of the bridge arm; (ii) a The working modes comprise six working modes which are respectively a first mode, a second mode, a third mode, a fourth mode, a fifth mode and a sixth mode;
when the number of the submodules needing to be switched in or out is not changed, and the bridge arm current is greater than zero, executing a first mode;
when the number of the submodules needing to be switched in or out is not changed, and the bridge arm current is less than zero, executing a second mode;
when the number of the submodules needing to be put into the converter is increased and the bridge arm current is greater than zero, executing a third mode;
when the number of the submodules needing to be put into the converter is increased and the bridge arm current is less than zero, executing a fourth mode;
when the number of the submodules needing to be put into is reduced, the number of the submodules needing to be cut out is increased, and the bridge arm current is greater than zero, a fifth mode is executed;
when the number of the submodules needing to be input is reduced, the number of the submodules needing to be cut is increased, and the bridge arm current is smaller than zero, a sixth mode is executed;
step 3, sequencing the sub-modules by using a voltage-frequency weight method;
the voltage-frequency weight method comprises the following steps: calculating voltage-frequency weights
Wherein, U is the capacitance voltage value of the ith sub-module, and the unit is volt; f is the switching frequency of the ith sub-module; lambda [ alpha ]iIs a current influence factor and has no dimension; w is a1iThe voltage weight coefficient of the ith sub-module is zero dimension; w is a2iIs the ithFrequency weight coefficient of the sub-module, no dimension. In practical use, neglecting the influence of environmental factors on the voltage weight, the voltage weight coefficient w of the sub-module1iIs constant and takes value as 1; current influencing factor lambdaiWhen is coming into contact withλi-1; when in useλi1, average voltage
Preferably, the frequency weight coefficient w of the ith sub-module2iAs a piecewise function:
when f isi＜1/4fDIV，w2i＝0.138；
Wherein f isDIVThe average value of the switching frequency of the IGBTs of the sub-modules within 0.1s is 336/N times, wherein N is the number of the sub-modules contained in a certain bridge arm in the MMC, and each bridge arm contains 20 sub-modules in general;
when 1/4fDIV≤fi＜2/3fDIV，w2i＝0.276；
When 2/3fDIV≤fi≤fDIV，w2i＝0.38；
Step 4, the MMC enters a corresponding working mode, the sub-module is switched into a switching-in state or a switching-out state until the voltage difference value delta U of the sub-module is smaller than the set allowable deviation U of the capacitor voltagezAt this time, the sub-module switching-in and switching-out adjustment is completed, and one level step change is completed.
The specific work flow under the six modes is as follows:
when the first mode is executed: first, it is judgedλi-1; when in useλi1 is ═ 1; secondly, the voltage-frequency weight is calculated according to a voltage-frequency weight methodWeighting the sub-modules by voltage-frequencySorting the values; finally, the already inputLargest submodule and in cut-out stateThe smallest submodule starts to exchange and will be put intoSubmodule of the second largest size and in the switched-out stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the input submodule and the voltage of the submodule in the cut-out state is smaller than the set allowable deviation U of the capacitor voltagezAt this time, the sub-module input/output adjustment is completed.
When executing the second mode, firstly, the first mode is judgedλi-1; when in useλi1 is ═ 1; secondly, the voltage-frequency weight is calculated according to a voltage-frequency weight methodWeighting the sub-modules by voltage-frequencySorting is carried out; finally, the cut-outLargest submodule and in input stateThe smallest submodule starts to exchange and is cut outSubmodule second largest and in input stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the cut-out submodule and the voltage of the submodule in the switching-in state is smaller than the set allowable deviation U of the capacitor voltagezAt this time, the sub-module input/output adjustment is completed.
When the third mode is executed, it is first judgedλi-1; when in useλi1 is ═ 1; secondly, the voltage-frequency weight is calculated according to a voltage-frequency weight methodWeighting the sub-modules by voltage-frequencySorting is carried out; thirdly, calculating the number m of the submodules needing to be newly input, wherein m is equal to Non-2-Non-1(ii) a Is selected in a cut-out shapeIn submodules of stateThe m sub-modules at the lowest are switched to the input state; finally, the submodules which are put into and cut out are exchanged, and the principle is as follows: will be thrown intoLargest submodule and remaining in switched-out stateThe smallest submodule starts to exchange and will be put intoThe second largest submodule is switched out of the restThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the input submodule and the voltage of the submodule in the cut-out state is smaller than the set allowable deviation U of the capacitor voltagezAt this time, the sub-module input/output adjustment is completed.
When the fourth mode is executed, it is first judgedλi-1; when in useλi1 is ═ 1; secondly, the voltage-frequency weight is calculated according to a voltage-frequency weight methodWeighting the sub-modules by voltage-frequencySorting is carried out; thirdly, calculating the number m of the submodules needing to be newly input, wherein m is equal to Non-2-Non-1(ii) a Selecting sub-modules in a switched-out stateThe m highest submodules are switched into the input state; finally, the submodules which are put into and cut out are exchanged, and the principle is as follows: cutting out the remainingLargest submodule and in input stateThe smallest submodule is exchanged and the rest is cut outSubmodule second largest and in input stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the cut-out submodule and the voltage of the submodule in the switching-in state is smaller than the set allowable deviation U of the capacitor voltagezAt this time, the sub-module input/output adjustment is completed.
When the fifth mode is executed, it is first judgedλi-1; when in useλi1 is ═ 1; secondly, the voltage-frequency weight is calculated according to a voltage-frequency weight methodWeighting the sub-modules by voltage-frequencySorting is carried out; thirdly, calculateNumber k of newly cut-out submodules, where k is Noff-2-Noff-1(ii) a Selecting sub-modules in the input stateThe highest k sub-modules switch the k sub-modules into a switching-out state; finally, the remaining submodules which are put into and switched out are exchanged, and the principle is as follows: the rest of the chargedLargest submodule and in cut-out stateThe smallest submodule starts to exchange, and the rest is put intoSubmodule of the second largest size and in the switched-out stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the input submodule and the voltage of the submodule in the cut-out state is smaller than the set allowable deviation U of the capacitor voltagezAt this time, the sub-module input/output adjustment is completed.
When the sixth mode is executed, it is first judgedλi-1; when in useλi1 is ═ 1; secondly, the voltage-frequency weight is calculated according to a voltage-frequency weight methodWeighting the sub-modules by voltage-frequencySorting is carried out; thirdly, calculating the number k of the sub-modules to be cut out newly, wherein k is Noff-2-Noff-1(ii) a Selecting sub-modules in the input stateThe lowest k sub-modules switch the k sub-modules into a switching-out state; finally, the remaining submodules which are put into and switched out are exchanged, and the principle is as follows: will be cut outThe largest submodule and the rest are in the input stateThe smallest submodule is exchanged and the switched-out submodule is switchedThe second largest submodule is put into operation with the remainderThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the cut-out submodule and the voltage of the submodule in the switching-in state is smaller than the set allowable deviation U of the capacitor voltagezAt this time, the sub-module input/output adjustment is completed.
The voltage-frequency weight method is optimized and improved based on a common sorting algorithm, and solves the problem that the switching frequency of the IGBT is overlarge due to continuous change of the switching state of the sub-modules caused by frequent sorting of the MMC. The voltage value is often used for sequencing in a common sequencing algorithm, so that the switching frequency of the IGBTs of the sub-modules is uneven, the switching frequency of the IGBTs of part of the sub-modules is overlarge, the switching frequency and the capacitance voltage value of the IGBTs of the sub-modules are calculated according to a certain weight by a voltage-frequency weight method, sequencing is carried out according to weight calculation values, the influence of the switching frequency influence is taken into consideration, on the basis of ensuring the capacitance voltage balance, the switching frequency of the IGBTs of the sub-modules is uniform, the sequencing speed is remarkably improved, the switching loss is remarkably reduced, and the performance and the safety of the converter are ensured.
While embodiments of the invention have been disclosed above, it is not intended to be limited to the uses set forth in the specification and examples. It can be applied to all kinds of fields suitable for the present invention. Additional modifications will readily occur to those skilled in the art. It is therefore intended that the invention not be limited to the exact details and illustrations described and illustrated herein, but fall within the scope of the appended claims and equivalents thereof.

Claims (1)

1. A control method of a modular multilevel converter for high-voltage direct-current transmission is characterized by comprising the following steps:
step 1, collecting sub-module quantity N input by an upper bridge arm and a lower bridge arm in a control period before collecting by a controlleron-1And the number of excised submodules Noff-1；
Step 2, in the period, the controller puts in the number N of the submodules according to the requirementon-2And the number of sub-modules cut out Noff-2Judging the operating mode of execution by the current direction of the bridge arm; the working modes comprise: when needing to put in or cut out sub-diesThe number of blocks is unchanged, the bridge arm current is greater than zero, and the first mode is adopted; when the number of the submodules needing to be switched in or out is not changed, the bridge arm current is smaller than zero, and the mode is a second mode; when the number of the submodules needing to be put into the converter is increased, the bridge arm current is greater than zero, and the mode is a third mode; when the number of the submodules needing to be put into the converter is increased, the bridge arm current is smaller than zero, and the fourth mode is adopted; when the number of the submodules needing to be put into the converter is reduced, the number of the submodules needing to be cut is increased, and the bridge arm current is greater than zero, so that the converter is in a fifth mode; when the number of the submodules needing to be put into the converter is reduced, the number of the submodules needing to be cut is increased, the bridge arm current is smaller than zero, and the sixth mode is adopted;
step 3, weighting the submodule according to the voltage-frequencyThe values are sorted in descending order, and the voltage-frequency weight method comprises the calculation of voltage-frequency weightThe steps of (1):
wherein, UiThe voltage value of the capacitor of the ith sub-module is obtained; f. ofiThe switching frequency of the ith sub-module; lambda [ alpha ]iIs a current influencing factor; w is a1iThe voltage weight coefficient of the ith sub-module; w is a2iThe frequency weight coefficient of the ith sub-module; when the current influencing factor lambda is equal to 1,when the current influencing factor lambda is equal to-1,wherein the average voltage
And 4, enabling the modular multilevel converter to enter a corresponding working mode:
the first mode to be put intoLargest submodule and in cut-out stateThe smallest submodule starts to exchange and will be put intoSubmodule of the second largest size and in the switched-out stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the input submodule and the voltage of the submodule in the cut-out state is smaller than the set allowable deviation U of the capacitor voltagez；
When executing the second mode, will be switched outLargest submodule and in input stateThe smallest submodule starts to exchange and is cut outSubmodule second largest and in input stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the cut-out submodule and the voltage of the submodule in the switching-in state is smaller than the set allowable deviation U of the capacitor voltagez；
In the third mode, a new child is calculatedThe number m of modules, selecting the sub-modules in the cut-out stateThe m sub-modules at the lowest are switched to the input state; then the added sub-modules and the sub-modules in the cut-out state are exchanged, and the added sub-modules are usedLargest submodule and remaining in switched-out stateThe smallest submodule starts to exchange and will be put intoThe second largest submodule is switched out of the restThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the input submodule and the voltage of the submodule in the cut-out state is smaller than the set allowable deviation U of the capacitor voltagez；
When the fourth mode is executed, the number m of the submodules needing to be newly input is calculated, and the submodules in the switching-out state are selectedThe m highest submodules are switched into the input state; then the sub-modules which are put into and switched out are exchanged, and the rest switched out areLargest submodule and in input stateThe smallest submodule is exchanged and the rest is cut outSubmodule second largest and in input stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the cut-out submodule and the voltage of the submodule in the switching-in state is smaller than the set allowable deviation U of the capacitor voltagez；
The fifth mode is: calculating the number k of the submodules needing to be newly cut out, and selecting the submodules in the input stateThe highest k sub-modules switch the k sub-modules into a switching-out state; then the added sub-modules and the sub-modules in the cut-out state are exchanged, and the rest added sub-modules are addedLargest submodule and in cut-out stateThe smallest submodule starts to exchange, and the rest is put intoSubmodule of the second largest size and in the switched-out stateThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the input submodule and the voltage of the submodule in the cut-out state is smaller than the set allowable deviation U of the capacitor voltagez；
When the sixth mode is executed, the number k of the sub-modules needing to be newly switched out is calculated, and the sub-modules in the input state are selectedThe lowest k sub-modules switch the k sub-modules into a switching-out state; then the sub-modules which are put into and switched out are exchanged, and the switched-out sub-modules are switched outThe largest submodule and the rest are in the input stateThe smallest submodule is exchanged and the switched-out submodule is switchedThe second largest submodule is put into operation with the remainderThe submodules with the second smallest number are exchanged in sequence until the difference value delta U between the voltage of the cut-out submodule and the voltage of the submodule in the switching-in state is smaller than the set allowable deviation U of the capacitor voltagez。
CN201710675899.0A 2017-08-09 2017-08-09 A kind of D.C. high voltage transmission modularization multi-level converter and its control method Expired - Fee Related CN107482928B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201710675899.0A CN107482928B (en) 2017-08-09 2017-08-09 A kind of D.C. high voltage transmission modularization multi-level converter and its control method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201710675899.0A CN107482928B (en) 2017-08-09 2017-08-09 A kind of D.C. high voltage transmission modularization multi-level converter and its control method

Publications (2)

Publication Number Publication Date
CN107482928A CN107482928A (en) 2017-12-15
CN107482928B true CN107482928B (en) 2018-08-24

Family

ID=60599942

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201710675899.0A Expired - Fee Related CN107482928B (en) 2017-08-09 2017-08-09 A kind of D.C. high voltage transmission modularization multi-level converter and its control method

Country Status (1)

Country Link
CN (1) CN107482928B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109274285B (en) * 2018-10-24 2020-04-03 南方电网科学研究院有限责任公司 Capacitance voltage balancing method of hybrid modular multilevel converter
CN110988742A (en) * 2019-10-31 2020-04-10 东南大学 Open-circuit fault diagnosis method for modular multilevel converter based on quartile

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103427692B (en) * 2013-07-30 2015-08-26 浙江大学 A kind of modulator approach of the modularization multi-level converter based on deque
CN103683995B (en) * 2013-09-25 2016-04-06 浙江大学 A kind of balance control method of full-bridge MMC capacitance voltage
CN103956925B (en) * 2014-04-28 2016-04-06 浙江大学 A kind of balance control method of confusion type MMC capacitance voltage
CN105576691B (en) * 2016-03-01 2018-07-03 西安许继电力电子技术有限公司 Modularization multi-level converter DC Line Fault ride-through capability evaluation method and system
CN106505641B (en) * 2016-10-18 2019-03-05 华中科技大学 The AC/DC decoupling control method of modularization multi-level converter and its application

Also Published As

Publication number Publication date
CN107482928A (en) 2017-12-15

Similar Documents

Publication Publication Date Title
JP6526344B2 (en) Power converter and power system
CN103095167B (en) Three-phase modulation multi-level converter energy balance control method
KR101983524B1 (en) Voltage Balancing in Modular Multilevel Converters with Delta Configuration
Xu et al. Active capacitor voltage control of flying capacitor multilevel converters
KR20190089053A (en) Charging method of sub module based hybrid converter
CN106030955A (en) Energy storage system comprising a modular multi-level converter
CN109256964B (en) MMC model prediction control method for mixing half-bridge submodule and full-bridge submodule
CN111541362B (en) Switching control method and system for MMC redundancy sub-module
CN109586328B (en) Economical single-end cascade hybrid direct-current power transmission system with bidirectional flowing power flow
RU2649888C2 (en) Assembly for compensating reactive power and active power in a high-voltage network
CN107482928B (en) A kind of D.C. high voltage transmission modularization multi-level converter and its control method
Geng et al. A switching times reassignment-based voltage balancing strategy for submodule capacitors in modular multilevel HVDC converters
Long et al. Noninteger lexicographic-optimization-based sequential model-predictive fault-tolerant control of T-type shunt active power filter
Xia et al. A distributed voltage balancing method for modular multilevel converter
CN112087134A (en) Energy storage type direct coupling type direct current transformer and control method
CN114553020B (en) Capacitor multiplexing type modular multilevel converter and control method thereof
Kamran et al. Study of a state-of-the art M-STATCOM
CN115395549A (en) Modular multi-level hybrid energy storage system and implementation method, device and equipment thereof
Yalla et al. A new three-phase multipoint clamped 5L-HPFC with reduced PSD count and switch stress
Peng et al. Capacitor voltage balancing control algorithm for modular multilevel converter based on the dynamic tiered sorting
Zhao et al. Capacitor voltage ripples characterization and reduction of hybrid modular multilevel converter with circulating current injection
CN115001297A (en) Improved carrier phase-shifting capacitance voltage balancing method suitable for direct-current fault ride-through
Zhang et al. A strategy of DC fault ride through and capacitor voltage balancing for hybrid modular multilevel converter (MMC)
Hasegawa et al. Voltage control of common flying capacitors in 5-level converter with capacitor current estimation
Chen et al. A capacitor voltage balancing control method for modular multilevel converter based on variable threshold interval sub-modules grouping

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
CF01 Termination of patent right due to non-payment of annual fee

Granted publication date: 20180824

Termination date: 20210809

CF01 Termination of patent right due to non-payment of annual fee