WO2020101320A1 - Procédé de commande de tension de condensateur de sous-module de convertisseur multiniveau modulaire, et support d'enregistrement dans lequel un programme lisible par ordinateur pour exécuter ledit procédé est enregistré - Google Patents

Procédé de commande de tension de condensateur de sous-module de convertisseur multiniveau modulaire, et support d'enregistrement dans lequel un programme lisible par ordinateur pour exécuter ledit procédé est enregistré Download PDF

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Publication number
WO2020101320A1
WO2020101320A1 PCT/KR2019/015329 KR2019015329W WO2020101320A1 WO 2020101320 A1 WO2020101320 A1 WO 2020101320A1 KR 2019015329 W KR2019015329 W KR 2019015329W WO 2020101320 A1 WO2020101320 A1 WO 2020101320A1
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WO
WIPO (PCT)
Prior art keywords
capacitor voltage
capacitor
submodule
short
modular multilevel
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Ceased
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PCT/KR2019/015329
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English (en)
Korean (ko)
Inventor
강대욱
이종필
이준민
김태진
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Korea Electrotechnology Research Institute KERI
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Korea Electrotechnology Research Institute KERI
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
    • H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
    • H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
    • H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels

Definitions

  • the present invention relates to a power conversion system, and more particularly, to a method for effectively adjusting the capacitor voltage of a modular multilevel converter submodule.
  • Modular multi-level converter is easy to expand the voltage level because a large number of sub-modules are connected in series, high voltage direct current (HVDC) transmission and invalidation with the advantage of obtaining excellent output due to high voltage level even at low switching frequency It is used in power compensators (STATCOM) and motor drives.
  • FIG. 1 is a circuit diagram of a half-bridge converter for explaining a sub-module of a modular multilevel converter (MMC).
  • MMC modular multilevel converter
  • the half-bridge converter consists of two IGBT switches operating complementarily and a capacitor to store energy.
  • the capacitor is discharged when the dark current flows to the capacitor when the switch S1 is turned on, and when the switch S2 is turned on, the dark current flows to the reflux diode D2 to bypass the capacitor. There is no change in capacitor voltage. Therefore, when the switch S1 is turned on, charging and discharging of the capacitor is determined according to the direction of the dark current.
  • FIG. 2 is a circuit diagram for explaining the configuration of a modular multi-level converter (MMC).
  • MMC modular multi-level converter
  • N sub-modules 11 connected in series and the female inductor 12 are connected to constitute an arm (A-B-B), and two arms are connected based on the AC output terminal to form one leg (Node A-C).
  • the female inductor 12 serves to prevent a sudden increase in the short circuit current in case of a short circuit accident.
  • Each sub-module capacitor voltage has a size equal to N of the DC link voltage, and the voltage output from one arm is equal to the sum of the output voltages of each sub-module constituting the arm.
  • the converter control system adjusts the voltage of the submodule capacitors to perform voltage balancing of the capacitors, and for this, aligns capacitor voltages.
  • FIG. 3 is a schematic flowchart illustrating an example of a conventional capacitor voltage alignment method for voltage balancing of a submodule capacitor.
  • the method shown in FIG. 3 is a full sorting method, which is a method of continuously sorting voltages of all submodule capacitors by size and performing switching of a switch that performs charging and discharging of capacitors according to the sorted order.
  • the present invention has been devised to solve the above-mentioned conventional problems, and modular multi-level converters can maintain a voltage balancing between sub-module capacitors while protecting expensive capacitors while maintaining a high power conversion efficiency of the converter. It is an object of the present invention to provide a method for adjusting the capacitor voltage of a level converter submodule.
  • the capacitor voltage adjustment method of the submodule performed by the capacitor voltage adjustment system of the modular multilevel converter submodule is within a preset allowable range. Determining whether the capacitor voltage is outside the allowable range, opening the charging and discharging switch of all submodules that perform charging and discharging, the preset number of reference switch short circuits, and the current short circuit of the submodules currently being shorted. Steps to compare the number.
  • the selected switches are short-circuited according to a preset short-circuit criterion equal to the difference between the current switch short-circuit number from the reference switch short-circuit number among the currently open submodule's charge / discharge switches. If the number of short-circuits is smaller than the number of short-circuits of the current switch, opening and closing selected switches according to a preset opening criterion equal to a difference between the current switch short-circuit number and the reference switch short-circuit number among the current short-circuit sub-modules.
  • the preset short circuit criterion may be a sequence in which the capacitor voltage is small when the dark current of the modular multilevel converter is in the direction of charging the capacitor, and a sequence in which the capacitor voltage is large when the dark current of the modular multilevel converter is in the direction of discharging the capacitor.
  • the preset open criterion may be a sequence in which the capacitor voltage is in a large order when the dark current of the modular multilevel converter is a direction in which the capacitor is charged, and a capacitor voltage in a small order when the dark current of the modular multilevel converter is in the direction of discharging the capacitor.
  • the allowable range may be set using the size of the maximum value of the capacitor voltage, and in particular, may be further set using the size of the minimum value of the capacitor voltage.
  • the capacitor voltage may be set using a difference between a maximum value and a preset comparison value, and the comparison value may be an average value of the capacitor voltages.
  • the number of short circuits of the reference switch may be a value calculated by the control system of the modular multilevel converter for controlling the output voltage of the modular multilevel converter.
  • the present invention while setting the allowable range for the capacitor voltage to limit the voltage applied to the capacitor, voltage adjustment is performed only for some capacitors corresponding to certain conditions, not all. Accordingly, while protecting expensive capacitors, the overall switching frequency can be reduced to maintain the converter's power conversion efficiency high.
  • voltage balancing can be performed even within an allowable range by opening or shorting an appropriate switch according to the direction of the dark current.
  • FIG. 1 is a circuit diagram of a half-bridge converter for explaining a sub-module of a modular multi-level converter (MMC).
  • MMC modular multi-level converter
  • MMC modular multi-level converter
  • Figure 3 is a schematic flow diagram showing an example of a conventional capacitor voltage alignment method for voltage balancing of the sub-module capacitor.
  • FIG. 4 is a schematic flow chart for performing a method of adjusting a capacitor voltage of a modular multilevel converter submodule according to an embodiment of the present invention.
  • FIG. 5 is a schematic flow diagram of one implementation of FIG. 4;
  • FIG. 6 is a diagram illustrating an example in which the number of short circuits of a reference switch for power conversion in a converter is transmitted.
  • FIGS. 7 to 14 are diagrams showing waveforms implemented by implementing the conventional ATB method and the method of the present invention in an MMC Hardware In the Loop Simulation (HILS) system having 432 submodules per arm.
  • HILS Loop Simulation
  • 15 is a graph showing the average switching frequency according to the% band for the ATB scheme and the scheme proposed in the present invention.
  • 16 and 17 are enlarged views of sub-module capacitor voltage waveforms using the ATB method and the method proposed in the present invention.
  • FIG. 4 is a schematic flowchart for performing a method of adjusting a capacitor voltage of a modular multilevel converter submodule according to an embodiment of the present invention
  • FIG. 5 is a schematic flowchart of an embodiment of FIG. 4. 4 and 5, capacitor voltage regulation may be performed by a capacitor voltage regulation system included in a modular multilevel converter control system.
  • the capacitor voltage regulation system may be implemented only with hardware, or may be implemented together with hardware and software operating on hardware.
  • V cap _max is Maximum Voltage of SM (Sub-Module) Capacitors
  • V cap _avr is Average Voltage of SM Capacitors
  • % band is Percentage of Tolerance Band
  • N is Number of SM
  • N on is Number of SM for Switching on
  • N on_old is Previous number of SM for Switching on
  • i arm (t) means Current of Arm, respectively.
  • the capacitor voltage adjustment system of the modular multilevel converter submodule arranges the capacitor voltage of the submodule according to its size (S110), and determines whether the capacitor voltage is within a preset allowable range (S120).
  • a specific operation value of the capacitor voltage is illustrated as a decision value that is compared with the allowable range, the decision value may be determined in advance by any other singular or plural values, and a different allowable range may be set correspondingly.
  • the allowable range may be set using the size of the maximum value of the capacitor voltage, and in particular, may be set using the size of the minimum value of the capacitor voltage.
  • the capacitor voltage may be set to a range greater than a preset minimum value and smaller than a preset maximum value.
  • the capacitor voltage may be set using a difference between a maximum value and a preset comparison value, and the comparison value may be an average value of the capacitor voltages. That is, as in the example shown in FIG. 5, a band using an average voltage may be used as the allowable range, but a band having other specific values may also be used.
  • the charging / discharging switches of all submodules performing charging and discharging are opened (S130), and the number of currently shorted switches is set to '0' (S140).
  • the preset reference switch short circuit number is compared with the current short circuit switch number of the submodules currently being short-circuited (S150), and it is determined which is greater (S160).
  • the charge / discharge switch is a switch for performing direct charge / discharge among switches located in the submodule, and in FIG. 1 , means S 1 of two switches S 1 and S 2 that operate complementarily.
  • the number of short circuits of the reference switch may be a value calculated by the control system of the modular multilevel converter for controlling the output voltage of the modular multilevel converter.
  • 6 is a diagram illustrating an example in which the number of short circuits of a reference switch for power conversion in a converter is transmitted.
  • FIG. 6 shows an example in which the control system of the modular multilevel converter calculates the number of short circuits of the reference switch and transmits it to the capacitor voltage adjustment system, and generates the gating signal of the submodule switch using the number information transmitted by the capacitor voltage adjustment system. It is.
  • the reference switch short circuit generation module Phase-Shifted Carrier or NLC
  • N on a reference switch short circuit number
  • An example is shown in which a selection algorithm of the capacitor voltage adjustment system, which receives the received signal, transmits a gating signal by selecting a switch of a submodule to be shorted or opened.
  • the selected switches are short-circuited according to a preset short circuit criterion equal to the difference between the number of short circuits of the current switch and the number of short circuits of the current switch among the currently open submodules. .
  • the direction of the dark current of the modular multi-level converter is determined (S170), and when the dark current of the modular multi-level converter is the direction of charging the capacitor, the switch is shorted in order of small capacitor voltage (S180), and the modular multi-level converter When the dark current in the direction of discharging the capacitor, the switch is shorted in the order of the highest capacitor voltage (S190).
  • the direction of the dark current of the modular multi-level converter is determined (S200), and when the dark current of the modular multi-level converter is the direction of charging the capacitor, the switch is opened in the order of the highest capacitor voltage (S210), and the When the dark current is in the direction of discharging the capacitor, the switches are opened in the order of small capacitor voltage (S220).
  • FIGS. 7 to 14 are diagrams showing the waveforms tested by implementing the conventional ATB method and the method of the present invention in an MMC Hardware In the Loop Simulation (HILS) system having 432 submodules per arm.
  • HILS Loop Simulation
  • FIGS. 7 and 8 are diagrams showing sub-module capacitor voltage waveforms according to the ATB method and the method of the present invention, respectively, when the tolerance band is 4%
  • FIGS. 9 and 10 respectively show cyclic current waveforms. It is a drawing shown.
  • FIGS. 11 and 12 are diagrams showing sub-module capacitor voltage waveforms according to the ATB method and the method of the present invention, respectively, when the tolerance band is 8%, and FIGS. 13 and 14 respectively show cyclic current waveforms. It is a drawing.
  • the ATB (Average Tolerance) method is also a method proposed to improve the conventional full sorting method.
  • the submodule capacitor voltage is out of a specific band, it is sorted and switched using a new sorting list. Otherwise, switching is performed using an existing sorting list.
  • the ATB method has the advantage of reducing the switching frequency while limiting the ripple of the capacitor voltage by placing a tolerance band, but when the capacitor voltage is within the allowable band, the existing sorting list is used, so it reflects the current voltage value. This has the disadvantage that the number of times the capacitor voltage of the submodule that is switched on reaches the allowable band is relatively increased.
  • 15 is a graph showing the average switching frequency according to the% band for the ATB scheme and the scheme proposed in the present invention. 15, in the method of the present invention, it can be seen that the switching frequency is reduced by approximately 20% around the conventional ATB method.
  • the sorting list is not updated when the capacitor voltage is within the allowable band, but in the proposed method, the sorting list is updated even when within the allowable band to continue switching according to the current direction and switching state.
  • 16 and 17 are enlarged diagrams of sub-module capacitor voltage waveforms using the ATB method and the method proposed in the present invention. 16 and 17, it can be seen that the number of occurrences of alignment in the case of the present invention decreases.
  • the capacitor voltage is switched from the smallest SM or the largest SM through sorting, and when the band is not out of the band, the sorting is performed without sorting.
  • the proposed method continuously sorts the capacitor voltage among SMs that must be turned on or off even when it does not leave the band to sub-module the smallest voltage (SM) or the largest sub-module (SM). Switch from.
  • the voltage balancing is more evenly compared to the conventional method, the size of the circulating current and the DC-link ripple can be reduced, and the switching frequency is reduced because the speed of reaching the band is relatively slow. In addition, it is possible to reduce the switching frequency, thereby reducing the loss of the system.

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

Abstract

La présente invention concerne un procédé comprenant les étapes consistant à : déterminer si des tensions de condensateur des sous-modules d'un convertisseur multiniveau modulaire sont comprises dans une plage admissible prédéterminée ; lorsque les tensions de condensateur se trouvent hors de la plage admissible, mettre hors tension les commutateurs de charge/décharge pour tous les sous-modules à charger/décharger ; comparer un nombre prédéterminé de référence mis sous tension avec un nombre actuellement mis sous tension, qui est le nombre de commutateurs actuellement mis sous tension parmi les commutateurs de charge/décharge pour les sous-modules ; et lorsque le nombre de référence mis sous tension est supérieur au nombre actuellement mis sous tension, allumer des commutateurs sélectionnés parmi les commutateurs de charge/décharge actuellement mis hors tension pour les sous-modules correspondants sur une base de mise sous tension prédéterminée de la différence obtenue en soustrayant le nombre actuellement mis sous tension du nombre de référence mis sous tension, et lorsque le nombre de référence mis sous tension est inférieur au nombre actuellement mis sous tension sélectionnés parmi des commutateurs de charge/décharge actuellement mis sous tension pour les sous-modules correspondants sur une base de mise hors tension prédéterminée de la différence obtenue en soustrayant le nombre de référence mis sous tension du nombre actuellement mis sous tension.
PCT/KR2019/015329 2018-11-14 2019-11-12 Procédé de commande de tension de condensateur de sous-module de convertisseur multiniveau modulaire, et support d'enregistrement dans lequel un programme lisible par ordinateur pour exécuter ledit procédé est enregistré Ceased WO2020101320A1 (fr)

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KR1020180139549A KR102086530B1 (ko) 2018-11-14 2018-11-14 모듈러 멀티레벨 컨버터 서브모듈의 커패시터 전압 조정 방법 및 상기 방법을 실행시키기 위한 컴퓨터 판독 가능한 프로그램을 기록한 기록 매체
KR10-2018-0139549 2018-11-14

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CN113364022A (zh) * 2021-05-18 2021-09-07 中国南方电网有限责任公司超高压输电公司 柔性直流输电系统功率子模块开关损耗的优化方法及系统
WO2022191384A1 (fr) * 2021-03-08 2022-09-15 엘에스일렉트릭 주식회사 Dispositif de commande vbe servant à commander la commutation de sous-modules et système statcom basé sur un mmc comprenant un dispositif de commande vbe

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EP3890178A1 (fr) * 2020-04-02 2021-10-06 General Electric Technology GmbH Perfectionnements apportés ou se rapportant ou des convertisseurs chain-link
CN117977919B (zh) * 2024-03-29 2024-06-04 南昌工程学院 模块化多电平换流器高频抑制方法和柔性直流输电系统

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US20140354248A1 (en) * 2013-05-28 2014-12-04 Lsis Co., Ltd. Method for controlling multilevel converter
KR20160008754A (ko) * 2014-07-15 2016-01-25 전남대학교산학협력단 하프 레벨 그룹을 포함하는 모듈형 멀티레벨 컨버터의 스위칭 방법
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KR20170004345A (ko) * 2015-07-02 2017-01-11 엘에스산전 주식회사 모듈형 멀티 레벨 컨버터 및 모듈형 멀티 레벨 컨버터의 전압 밸런싱 제어 방법

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WO2022191384A1 (fr) * 2021-03-08 2022-09-15 엘에스일렉트릭 주식회사 Dispositif de commande vbe servant à commander la commutation de sous-modules et système statcom basé sur un mmc comprenant un dispositif de commande vbe
CN113364022A (zh) * 2021-05-18 2021-09-07 中国南方电网有限责任公司超高压输电公司 柔性直流输电系统功率子模块开关损耗的优化方法及系统
CN113364022B (zh) * 2021-05-18 2022-05-17 中国南方电网有限责任公司超高压输电公司 柔性直流输电系统功率子模块开关损耗的优化方法及系统

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