CN108418448B - MMC transverter submodule circuit with direct current fault self-clearing capability - Google Patents

MMC transverter submodule circuit with direct current fault self-clearing capability Download PDF

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CN108418448B
CN108418448B CN201810054213.0A CN201810054213A CN108418448B CN 108418448 B CN108418448 B CN 108418448B CN 201810054213 A CN201810054213 A CN 201810054213A CN 108418448 B CN108418448 B CN 108418448B
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diode
circuit
igbt
capacitor
fault
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CN108418448A (en
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薛士敏
崔淼
廉杰
范勃旸
齐金龙
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Tianjin University
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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
    • H02M7/02—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
    • H02M7/219—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 in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/125—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for rectifiers
    • 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
    • H02M7/2173—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 in a biphase or polyphase circuit arrangement

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

Abstract

The invention belongs to the field of relay protection and automation of a power system, and relates to an MMC converter submodule circuit with direct-current fault self-clearing capability, wherein two submodules SM1 and SM2 in half-bridge structures are reversely connected in series to form a structural unit, each submodule in half-bridge structure comprises three parallel circuits, one circuit is a capacitor C, the other circuit is two diodes D1 and D2 which are connected in series, the other circuit is two IGBTs which are connected in series, the cathode of a first diode D1 is connected with the anode of a second diode D2, the emitter of the first IGBT is connected with the collector of the second IGBT, and the anode of a first diode D1 and the collector of the first IGBT are connected with the anode of the capacitor C; the capacitor voltage rating of one of the submodules is 2UdcAnother submodule has a capacitor voltage rating of UdcThe two directions are opposite, so that a back pressure is formed for the cut-off diode.

Description

MMC transverter submodule circuit with direct current fault self-clearing capability
Technical Field
The invention relates to the field of relay protection of a power system, in particular to an MMC direct-current side fault isolation technology.
Background
In recent years, the installed capacity of renewable energy sources such as wind power generation, photovoltaic power generation and the like in China is continuously enlarged, so that a power generation center is far away from a load center. The high-voltage direct-current transmission mode is suitable for long-distance large-capacity power transmission, and therefore great attention and development are obtained. At present, the VSC with the independent control attribute of active power and reactive power is widely applied to the actual flexible direct-current transmission engineering. The MMC current converter is a novel VSC structure, has a modular topology, and has the advantages of high output voltage level, low switching loss and good output voltage waveform, and is the development direction of future flexible direct current transmission.
At present, research on direct current power grid protection based on MMC is still in a starting stage. After the flexible direct-current power grid has a direct-current side fault, the fault damage is large and the development is rapid. However, the technology for clearing the fault on the dc side is still incomplete, on one hand, the research on the high-voltage large-capacity dc circuit breaker is not mature, and on the other hand, most of the MMC converters in the actual engineering are in a half-bridge topology structure, and when the dc side has a fault, the fault current cannot be completely cleared even though all the MMC converters are locked. It is therefore often necessary to open the ac side breaker after a dc side fault to clear the fault, which greatly increases the fault clearing time and the post fault recovery time. In recent years, many experts and scholars propose novel topological structures, which can reversely block a diode connected in parallel with a capacitor in a submodule by means of voltage of the capacitor, further cut off a fault path and realize fault arc quenching. These structures usually increase the amount of switching power devices used, and make the sub-module circuit structure more complex, increase the control complexity of the system, and reduce the reliability of the system. Especially for the already established half-bridge based MMC dc transmission systems, these methods all require a thorough replacement of the MMC converter station, which is not economically and engineering-wise feasible.
Disclosure of Invention
The invention provides a novel MMC submodule topological circuit with direct-current fault self-clearing capability, which can reduce the number of additional devices as much as possible, does not increase the complexity of a system, ensures that the structure can quickly and reliably automatically cut off direct-current fault current by means of locking action after a direct-current side fault, and can be conveniently applied to an established half-bridge structure MMC converter station. The technical scheme is as follows:
a submodule circuit of an MMC converter with direct current fault self-clearing capability is characterized in that two submodules SM1 and SM2 of a half-bridge structure are connected in series in a reverse direction to form a structural unit, each submodule of the half-bridge structure comprises three parallel circuits, one circuit is a capacitor C, the other circuit is two diodes D1 and D2 which are connected in series, the other circuit is two IGBTs which are connected in series, the anode of a first diode D1 is connected with the cathode of a second diode D2, the emitter of the first IGBT is connected with the collector of the second IGBT, and the cathode of a first diode D1 and the collector of the first IGBT are connected with the anode of the capacitor C; the capacitor voltage rating of one of the submodules is 2UdcCapacitive powering of another submoduleRated voltage of UdcThe two directions are opposite, so that a back pressure is formed for the cut-off diode.
Compared with the prior art, the invention has the following advantages:
(1) during normal operation, the current converter is similar to a traditional half-bridge structure, the controller does not need to be completely changed, and the normal operation can be realized by slightly changing the original controller;
(2) when a direct current side fault occurs, the fault can be quickly isolated through locking action, the fault current is eliminated, the method is suitable for a multi-end MMC direct current power grid, and the use of a high-capacity direct current breaker is omitted;
(3) compared with the conventional sub-modules with direct-current fault self-clearing capability, such as a full-bridge structure, a clamping dual-sub-module structure and the like, the power semiconductor devices used under the same voltage level are fewer, and through calculation, the number of the power devices required by the converter is half of that of the full-bridge structure and two thirds of that of the clamping dual-sub-module structure, and the fault clearing time is shorter than that of the other two structures;
(4) the topological structure is convenient for reforming the established MMC actual engineering based on the half-bridge structure, and the reliability and the economy of the converter station can be greatly improved.
Drawings
FIG. 1 is a schematic diagram of an inverse series connection dual sub-module topology;
FIG. 2 is a schematic view of a bipolar short-circuit fault converter current path of an MMC DC power transmission system;
fig. 3 is a schematic diagram of a switch signal controller for a converter submodule, (a) a trigger signal additional control part of a forward throw submodule (SM2) and (b) a trigger signal additional control part of a reverse throw submodule (SM 1).
Detailed Description
The invention provides a novel MMC sub-module circuit with direct-current fault self-clearing capability, which can ensure that the structure can quickly and reliably automatically cut off direct-current fault current by means of locking action after a direct-current side fault while reducing the number of additional devices as much as possible and not increasing the complexity of a system, and can be conveniently applied to an established half-bridge structure MMC converter station. Therefore, the reliability of the MMC converter station is improved, and the economy of the MMC converter station can be improved. The invention can be realized by the following technical scheme:
the specific topology is shown in fig. 1.
The topology is based on a traditional half-bridge MMC structure, two sub-modules SM1 and SM2 of the half-bridge structure are connected in series in an inverted mode to form a structural unit, and therefore the structure is named as an inverted series double sub-module (RSDSM) structure. One of them half-bridge structure is connected in parallel by a electric capacity C, two diodes and two IGBT and constitutes: the anode of D1 is connected to the cathode of D2, the emitter of T1 is connected to the collector of T2, and the cathode of D1, the collector of T1 and the anode of capacitor C are connected. The RSDSM structure contains two capacitors, four diodes, and four IGBTs in total. The capacitor voltage rating of one of the submodules is 2UdcAnother submodule has a capacitor voltage rating of UdcThe two directions are opposite, so that a back pressure is formed for the cut-off diode.
An anode of the first diode D1 is connected with a cathode of the second diode D2, an emitter of the first IGBT is connected with a collector of the second IGBT, and a cathode of the first diode D1 and a collector of the first IGBT are connected with an anode of the capacitor C;
the operating principle of the MMC current converter is as follows:
in normal operation, two sub-modules connected in series in opposite directions can generate 2U by controlling the switching states of T1-T4 to be the conditions shown in the first three kinds of table 1c、UcAnd 0 three voltage levels to achieve normal voltage output of the MMC.
TABLE 1 converter submodule trigger signal and output voltage indication table
Figure GDA0002326785420000021
Figure GDA0002326785420000031
When a fault occurs on the DC side, the control is performed by controlling T1-T4On and off, bypassing SM1 in the RSDSM topology, SM2 is put into what is called a latch-up state. As is clear from Table 1, the voltage value of-NU is applied to each armcAnd/2 capacitance (N is the number of submodules per bridge arm). The bridge arm circuit is equivalent to reverse series connection of a diode and a capacitor, and the conducted diode can be forced to be cut off in a reverse direction by using the voltage of the capacitor, so that a path of fault current on a direct current side is cut off. Bridge arm currents in different directions correspond to different fault current clearing equivalent circuits, and fig. 2 shows the equivalent circuit of the post-fault MMC, which includes two current flowing directions. Each current path has 2N diodes connected in series, and the cathode of the diode is just connected with the anode of the sub-module capacitor. It can be seen that, after the RSDSM structure enters a locked state, the diodes on the bridge arms are cut off due to the back voltage, no matter what the direction of the bridge arm current, so that the bridge arm current is rapidly attenuated to zero, and the reliability of the operation of the converter station is ensured.
In terms of control, compared with the conventional half-bridge structure, a part of additional controllers needs to be added on the basis of the original control circuit, and the additional controllers are shown in fig. 3. T1A1 and T1A2 are trigger signals of TI in two adjacent sub-modules output by an original controller respectively, T1A1D and T2A1D are trigger signals of T3 and T4 of an SM2 part in an RSDSM structure respectively, and T1A2D and T2A2D are trigger signals of an SM1 part T1 and T2 in the RSDSM structure respectively.

Claims (1)

1. A MMC converter submodule circuit with direct-current fault self-clearing capability is characterized in that intermediate terminals of two half-bridge submodules SM1 and SM2 are connected to form a structural unit in reverse series connection, wherein each half-bridge submodule comprises three parallel circuits, one circuit is a capacitor C, the other circuit is two diodes in series connection, namely a first diode and a second diode, the other circuit is two IGBTs in series connection, and the anode of the first diode is connected with the cathode of the second diode; the connection mode of each device pin in the submodule is as follows: the emitter of the first IGBT is connected with the collector of the second IGBT and the anode of the first diode, the cathode of the first diode and the collector of the first IGBT are connected with the anode of the capacitor C, and the anode of the second diodeAn emitter of the IGBT is connected with a cathode of the capacitor C; the connection mode of device pins between two submodules in one structural unit is as follows: anodes of the two first diodes are connected with emitters of the two first IGBTs; the capacitor voltage is set as: capacitor voltage rating of one submodule of 2U dcThe capacitor voltage rating of the other sub-module isU dcThe polarity directions of the voltages of the two sub-modules connected into the loop are opposite, so that back voltage is formed for cutting off the diode; after the occurrence of a fault, the blocking path of the fault current is set to: SM1 capacitance-SM 1 first IGBT-SM2 second IGBT; or the capacitance of the first diode-SM 1 of the second diode-SM 1 of SM2, serves to isolate the fault by blocking the conduction of the diodes in the path with the SM1 capacitance voltage.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103066551A (en) * 2012-12-13 2013-04-24 国网智能电网研究院 Fault protective system for short-circuit current testing apparatus
CN103219738A (en) * 2013-03-29 2013-07-24 浙江大学 Direct current transmission system based on three-pole type structure
CN103633872A (en) * 2013-12-17 2014-03-12 山东大学 Capacitor voltage self-balancing circuit of modularized multi-level converter
CN105406743A (en) * 2015-09-22 2016-03-16 华南理工大学 Hybrid modular multi-level converter with asymmetric bridge arms

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015113033A1 (en) * 2014-01-27 2015-07-30 Elserougi Ahmed Dc side fault isolator for high voltage dc converters

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103066551A (en) * 2012-12-13 2013-04-24 国网智能电网研究院 Fault protective system for short-circuit current testing apparatus
CN103219738A (en) * 2013-03-29 2013-07-24 浙江大学 Direct current transmission system based on three-pole type structure
CN103633872A (en) * 2013-12-17 2014-03-12 山东大学 Capacitor voltage self-balancing circuit of modularized multi-level converter
CN105406743A (en) * 2015-09-22 2016-03-16 华南理工大学 Hybrid modular multi-level converter with asymmetric bridge arms

Non-Patent Citations (1)

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Title
用于 MMC-HVDC 直流故障保护的新型拓扑及;王一，等;《电网技术》;20150831;全文 *

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