CN108155825B - Isolated modular multilevel converter - Google Patents

Isolated modular multilevel converter Download PDF

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Publication number
CN108155825B
CN108155825B CN201810076176.3A CN201810076176A CN108155825B CN 108155825 B CN108155825 B CN 108155825B CN 201810076176 A CN201810076176 A CN 201810076176A CN 108155825 B CN108155825 B CN 108155825B
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active
switch tube
active switch
tube
diode
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CN108155825A (en
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刘闯
蔡国伟
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Northeast Electric Power University
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Northeast Dianli 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
    • H02M7/42—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
    • H02M7/4807—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 having a high frequency intermediate AC stage
    • 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
    • H02H7/122—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 inverters, i.e. dc/ac converters
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • 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
    • 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
    • H02M7/493—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 the static converters being arranged for operation in parallel

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

Abstract

The invention discloses an isolated modular multilevel converter, which comprises three high-voltage direct-current ports (P) H、N H) Each phase unit consists of an upper bridge arm and a lower bridge arm, and the electrical connection points (N) of the upper bridge arm and the lower bridge arm of the three phase units 1、N 2、N 3) The outgoing line is connected with a filter inductor in series and then is provided with high-voltage alternating current ports (a, b and c), each bridge arm consists of n single-stage high-frequency isolation type sub-modules with high-voltage direct current side fault current blocking capacity and a bridge arm reactor L mComposition is carried out; the single-stage high-frequency isolation type submodule comprises a front-stage part, a high-frequency transformer part and a rear-stage part; the rear-stage part can block fault current when a short-circuit fault occurs on the high-voltage direct-current side, and fault clearing on the direct-current side is achieved. The converter provided by the invention has a simple structure, has the advantages of no high-voltage side capacitor, voltage-sharing control and the like of the isolated modular multilevel converter, and can quickly cut off the high-voltage direct-current side fault current.

Description

Isolated modular multilevel converter
Technical Field
The invention relates to the technical field of isolated modular multilevel power conversion, in particular to an isolated modular multilevel converter with high-voltage direct-current side fault current blocking capability.
Background
The isolated modular multilevel converter has the advantages of no need of high-voltage side capacitor support, voltage-sharing control and the like, but when a high-voltage direct-current side has a short-circuit fault, even if the active switching tube of the rear-stage part is completely turned off, a short-circuit current can still be fed into a fault point through a diode which is reversely connected with the active switching tube on the high-voltage alternating-current side in parallel, which is equivalent to a three-phase alternating-current short-circuit fault, and the switching tube can be seriously damaged, so that the converter cannot normally work.
Disclosure of Invention
In order to solve the problems, the invention provides an isolated modular multilevel converter, and by introducing a reverse fault current blocking switch module, a signal can be switched off for the fault current blocking switch module when a short-circuit fault occurs on a high-voltage direct-current side on the premise of not influencing the normal work of a circuit, so that the short-circuit current is blocked.
The invention is realized by the following technical scheme:
an isolated modular multilevel converter is of a three-phase system structure and comprises three high-voltage direct-current ports (P) H、N H) BetweenEach phase unit consists of an upper bridge arm and a lower bridge arm, and the electrical connection points (N) of the upper bridge arm and the lower bridge arm of the three phase units 1、N 2、N 3) The outgoing line is connected with a filter inductor in series and then is provided with high-voltage alternating current ports (a, b and c), each bridge arm consists of n single-stage high-frequency isolation type sub-modules with high-voltage direct current side fault current blocking capacity and a bridge arm reactor L mComposition is carried out; positive pole terminals (P) of upper bridge arms of three phase units Ha、P Hb、P Hc) Connected as positive pole P of high voltage DC port of the converter HNegative terminal (N) of lower arm of three-phase unit Ha、N Hb、N Hc) Negative pole N connected as high voltage DC port of the converter H；
The single-stage high-frequency isolation type submodule with the high-voltage direct-current side fault current blocking capacity comprises a preceding stage part, a high-frequency transformer part and a subsequent stage part, wherein the alternating current side of the preceding stage part is connected with the primary side of the high-frequency transformer, the alternating current side of the subsequent stage part is connected with the secondary side of the high-frequency transformer, and the positive and negative electrode ports of the preceding stage part of each submodule are respectively connected in parallel to be used as a common low-voltage direct current port (P) L、N L) The ports of the rear stage part are connected in series to form a high-voltage direct current side port (P) H、N H)。
Further, the front stage part of the submodule comprises a low-voltage side direct current capacitor C dcLAnd an active H-bridge consisting of four active switches (such as IGBTs, etc.) with anti-parallel diodes; the rear-stage part comprises a voltage clamping circuit, an active H-bridge consisting of four active switches with anti-parallel diodes and a fault current blocking switch module reversely connected on a bridge arm.
Further, the active H-bridge of the front stage part comprises a first active switch tube Q 1A second active switch tube Q 2A third active switch tube Q 3And a fourth active switch tube Q 4The collector of each active switch tube is respectively connected with the cathode of the corresponding freewheeling diode, and the emitter of each active switch tube is respectively connected with the anode of the corresponding freewheeling diode;
first active switch tube Q 1And thirdActive switch tube Q 3After being connected in series with the low-voltage side direct current capacitor C dcLParallel connection, a first active switch tube Q 1Emitter and third active switching tube Q 3Is connected with the collector and serves as a primary side E of the high-frequency transformer, and a second active switch tube Q 2Emitter and fourth active switching tube Q 4The collector of the first active switch tube Q is connected with the other end F which is the primary side of the high-frequency transformer 1Collector electrode and C dcLIs connected with the positive pole of the third active switch tube Q 3Emitter and C dcLThe negative electrodes are connected; second active switch tube Q 2And a fourth active switch tube Q 4After being connected in series with the low-voltage side direct current capacitor C dcLParallel second active switch tube Q 2Collector electrode and C dcLIs connected with the positive pole of the fourth active switch tube Q 4Emitter and C dcLThe negative electrodes are connected; first active switch tube Q 1And a second active switch tube Q 2Collector electrode of (1) and (C) dcLIs connected with the positive pole of the sub-module and is used as the positive pole A of the front stage part of the sub-module, and a third active switch tube Q 3And a fourth active switch tube Q 4Emitter and C of dcLIs connected with and serves as the cathode B of the preceding part of the submodule.
Furthermore, the sub-modules can be divided into a first sub-module and a second sub-module according to different connection points of the fault current blocking switch module at the rear stage part;
the rear-stage part of the first submodule comprises a fifth active switching tube Q 5A sixth active switch tube Q 6A seventh active switch tube Q 7An eighth active switch tube Q 8A ninth active switch tube Q 9A tenth active switch tube Q 10The collector of each active switch tube is respectively connected with the cathode of the corresponding freewheeling diode, and the emitter of each active switch tube is respectively connected with the anode of the corresponding freewheeling diode; the fault current blocking switch module is composed of a ninth active switch tube Q 9And a tenth active switching tube Q 10Composition of a ninth active switch tube Q 9Emitter and seventh active switching tube Q 7OfEmitter-connected tenth active switching tube Q 10Emitter and eighth active tube Q 8The emitting electrodes are connected; fifth active switch tube Q 5Emitter and seventh active switching tube Q 7Is connected with the collector and serves as a secondary side end G of the high-frequency transformer, and a sixth active switching tube Q 6Emitter and eighth active switching tube Q 8The collector of the transformer is connected with the other end H which is used as the secondary side of the high-frequency transformer; fifth active switch tube Q 5And a sixth active switch tube Q 6And a ninth active switching tube Q, and a positive electrode C connected with the collector and serving as a post-stage part of the submodule 9And a tenth active switch tube Q 10The collector electrodes of the sub-modules are connected and used as a negative electrode D of the post-stage part of the sub-modules;
the rear-stage part of the second submodule comprises an eleventh active switching tube Q 11A twelfth active switch tube Q 12A thirteenth active switch tube Q 13A fourteenth active switch tube Q 14A fifteenth active switch tube Q 15A sixteenth active switch tube Q 16The collector of each active switch tube is respectively connected with the cathode of the corresponding freewheeling diode, and the emitter of each active switch tube is respectively connected with the anode of the corresponding freewheeling diode; the fault current blocking switch module is composed of a fifteenth active switch tube Q 15And sixteenth active switch tube Q 16Composition of an eleventh active switching tube Q 13Collector and fifteenth active switch tube Q 15Is connected with the collector of the twelfth active switching tube Q 12Collector electrode of and sixteenth active tube Q 16The collector electrodes are connected; eleventh active switch tube Q 11Emitter and thirteenth active switching tube Q 13Is connected with the collector and serves as a secondary side end G of the high-frequency transformer and a twelfth active switching tube Q 12Emitter and fourteenth active switching tube Q 14The collector of the transformer is connected with the other end H which is used as the secondary side of the high-frequency transformer; fifteenth active switch tube Q 15And a sixteenth active switch tube Q 16Is connected with the emitter and serves as the anode C of the post-stage part of the submodule, and an eleventh active switching tube Q 11And a twelfth active switch tube Q 12Collector electrode ofAnd the negative electrode D is connected with the negative electrode D and serves as a post-stage part of the submodule.
Further, the voltage clamping circuit includes a first diode D 1A second diode D 2A third diode D 3A fourth diode D 4A first capacitor C 1A first resistor R 1First diode D 1And a second diode D 3Are respectively connected with the first capacitor C after being connected in series 1A first resistor R 1Parallel, a second diode D 2And a fourth diode D 4Are respectively connected with the first capacitor C after being connected in series 1A first resistor R 1Parallel, first diode D 1A second diode D 2Cathode and first capacitor C 1A first resistor R 1Is connected to the anode of a second diode D 2A fourth diode D 4Anode and first capacitor C 1A first resistor R 1Is connected to the negative electrode of a first diode D 1Anode of and a third diode D 3Is connected with the secondary side end G of the high-frequency transformer, and a second diode D 2Anode of and a fourth diode D 4The cathode of the transformer is connected with the other end H of the secondary side of the high-frequency transformer.
Furthermore, the high-frequency transformer part is composed of a high-frequency transformer T which can realize the functions of power transmission, electrical isolation, voltage grade conversion and the like on the high-voltage side and the low-voltage side; bridge arm reactor L mBesides reducing harmonic distortion rate of bridge arm current, the converter can also inhibit interphase circulation and short-circuit circulation generated by short-circuit fault on a direct current side, and protect a power electronic switch of the converter.
The invention has the following beneficial effects:
(1) the high-voltage direct current short-circuit fault current blocking circuit has the capability of rapidly blocking the short-circuit fault current on the high-voltage direct current side. Because the fault current blocking switch module is added at the rear-stage part, when a short-circuit fault occurs at the high-voltage direct-current side, the short-circuit current can be blocked by a switching-off signal of the active switch tube of the fault current blocking switch module while the active switch tube of the H bridge of the rear-stage part is locked, and the action is rapid and the reliability is high.
(2) The high-voltage side of each submodule is not provided with a direct current capacitor. The structure adopts a high-frequency chain technology, the high-voltage side pulse width modulation is realized through the switch combination of the front-stage driving H-bridge power tube and the rear-stage driving H-bridge power tube of the submodule, and the pulse width modulation voltage wave is directly supported by the low-voltage side direct current capacitor of the front-stage part through the high-frequency transformer, so that the high-voltage side of the rear-stage part does not need to be supported by the capacitor any more.
(3) No separate voltage balancing control is required. The terminal voltage of each submodule is directly clamped by the bus voltage at the low-voltage direct-current side through a high-frequency transformer, the stable state and the dynamic characteristic of the output voltage of the upper bridge arm terminal and the lower bridge arm terminal are consistent, voltage-sharing control is not needed, the complexity of control is reduced, and the reliability and the economical efficiency of a system are improved.
(4) The converter does not require a bidirectional switching tube. Because the voltage of the high-voltage side port of each submodule is always positive, the converter does not need a bidirectional switch tube, and the problems of secondary side current conversion and voltage peak caused by leakage inductance of the traditional single-stage converter are avoided.
Drawings
Fig. 1 is a three-phase topology structure diagram of an isolated modular multilevel converter with high-voltage direct-current side fault current blocking capability according to the present invention;
FIG. 2 is a first sub-module topology structure of the present invention;
FIG. 3 is a second sub-module topology of the present invention;
in the figure:
P H-a high voltage dc positive port;
N H-a high voltage dc negative port;
P L-a low voltage dc positive port;
N L-a low voltage dc negative port;
a-a high voltage alternating current phase A port;
b-a high voltage alternating current phase B port;
c-a high voltage alternating current (C) phase port;
SM n-submodules, n being their number;
L m-bridge arm reactors;
L f-an ac side filter inductance;
N 1-a phase upper and lower bridge arm connection points;
N 2-phase b upper and lower bridge arm connection points;
N 3-c phase upper and lower bridge arm connection points;
C dcL-a low voltage dc capacitor;
a T-high frequency transformer;
A. b-positive and negative electrode ports of the front part of the submodule;
C. d-positive and negative electrode ports of the rear part of the submodule;
E. f, a primary side port of the high-frequency transformer;
G. an auxiliary side port of the H-high frequency transformer;
Q 1～Q 4-a front-end part active switching transistor, such as an Insulated Gate Bipolar Transistor (IGBT);
Q 5～Q 16-a post-stage partially active switching transistor, such as an Insulated Gate Bipolar Transistor (IGBT);
D 1～D 4-a post-stage partial voltage clamping circuit diode;
C 1-a post-stage partial voltage clamping circuit capacitance;
R 1-a voltage clamp circuit resistance in the post-stage section;
P Ha、P Hb、P Hc-a positive port of the upper leg;
N Ha、N Hb、N Hc-the negative terminal of the lower leg;
P c、N c-voltage clamping circuit positive and negative terminals for the sub-module back-stage part.
Detailed Description
In order that the objects and advantages of the invention will be more clearly understood, the invention is further described in detail below with reference to examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, an embodiment of the present invention provides an isolated modular multilevel converter with a fault current blocking capability on a high-voltage dc side, where the converter 1 includes three isolated modular multilevel converters connected in parallel at a high-voltage dc port (P) of the converter H、N H) Each phase unit 2 consists of an upper bridge arm and a lower bridge arm, and the electrical connection points (N) of the upper bridge arm and the lower bridge arm of the three phase units 1、N 2、N 3) The outgoing lines are connected with filter inductors in series and then are high-voltage alternating-current ports (a, b and c), each bridge arm consists of n single-stage high-frequency isolation type sub-modules 3 with high-voltage direct-current side fault current blocking capacity and a bridge arm reactor L mComposition is carried out; positive terminal (P) of upper arm of three phase units 2 Ha、P Hb、P Hc) Connected as positive pole P of high voltage DC port of the converter HNegative terminal (N) of lower arm of three phase unit 2 Ha、N Hb、N Hc) Negative pole N connected as high voltage DC port of the converter H；
Each single-stage high-frequency isolation type submodule 3 with high-voltage direct-current side fault current blocking capacity comprises a front-stage part 4, a high-frequency transformer part 5 and a rear-stage part 6, can be divided into a first submodule and a second submodule according to different connection positions of a fault current blocking switch module 8 in the rear-stage part, and is topological in a structure shown in figures 2 and 3, wherein the high-frequency alternating current side of the front-stage part is connected with the primary side of a high-frequency transformer T, the high-frequency alternating current side of the rear-stage part is connected with the secondary side of the high-frequency transformer T, and the front-stage side ports of all the submodules form a common low-voltage direct-current side port ( L、N L) The rear stage side ports are connected in series to form a high-voltage direct-current side port (P) H、N H) Positive terminal (P) of arm on three phase unit Ha、P Hb、P Hc) Connected as positive pole P of high voltage DC port of the converter HSimilarly, the negative terminal (N) of the lower arm of the three-phase unit Ha、N Hb、N Hc) Negative pole N connected as high voltage DC port of the converter H。
The front stage part comprises 4 active switching tubes (such as IGBT) Q with anti-parallel diodes 1-Q 4Composed H bridge and low-voltage side DC capacitor C dcLThe latter part comprises 6 active switching tubes (such as IGBT) Q with anti-parallel diodes 5～Q 10(first submodule) or comprising 6 active switching tubes (e.g. IGBT) Q with antiparallel diodes 11～Q 16(second submodule) and voltage clamp circuit, said active tube Q with anti-parallel diode 1～Q 16The collectors of which are respectively connected with the cathodes of the respective freewheeling diodes and the emitters of which are respectively connected with the anodes of the respective freewheeling diodes.
Q in preceding stage part 1And Q 3After being connected in series with the low-voltage side direct current capacitor C dcLIn parallel, said Q 1Emitter and Q 3Are connected and used as primary terminals E, Q of the high-frequency transformer 2Emitter and Q 4Is connected with the collector and serves as the other end F, Q of the primary side of the high-frequency transformer 1Collector electrode and C dcLAre connected to the positive pole of Q 3Emitter and C dcLThe negative electrodes are connected; said Q 2And Q 4After being connected in series with the low-voltage side direct current capacitor C dcLParallel connection, Q 2Collector electrode and C dcLAre connected to the positive pole of Q 4Emitter and C dcLThe negative electrodes are connected; said Q 1、Q 2Collector electrode of (1) and (C) dcLIs connected with the positive pole and is used as the positive pole port A, Q of the front stage part of the submodule 3、Q 4Emitter and C of dcLIs connected with the negative pole and is used as the negative pole port B of the front stage part of the submodule.
As shown in FIG. 2, the rear stage of the first sub-module includes a fifth active switch transistor Q 5A sixth active switch tube Q 6A seventh active switch tube Q 7An eighth active switch tube Q 8A ninth active switch tube Q 9A tenth active switch tube Q 10The collector of each active switch tube is connected with the cathode of the free-wheeling diode, and the emitter is connected with the free-wheeling diodeThe anodes of the diodes are connected; the fault current blocking switch module is composed of a ninth active switch tube Q 9And a tenth active switching tube Q 10Composition of a ninth active switch tube Q 9Emitter and seventh active switching tube Q 7Is connected with the emitting electrode of the tenth active switching tube Q 10Emitter and eighth active tube Q 8The emitting electrodes are connected; fifth active switch tube Q 5Emitter and seventh active switching tube Q 7Is connected with the collector and serves as a secondary side end G of the high-frequency transformer, and a sixth active switching tube Q 6Emitter and eighth active switching tube Q 8The collector of the transformer is connected with the other end H which is used as the secondary side of the high-frequency transformer; fifth active switch tube Q 5And a sixth active switch tube Q 6And a ninth active switching tube Q, and a positive electrode C connected with the collector and serving as a post-stage part of the submodule 9And a tenth active switch tube Q 10The collector electrodes of the sub-modules are connected and used as a negative electrode D of the post-stage part of the sub-modules;
as shown in FIG. 3, the rear stage of the second sub-module includes an eleventh active switch transistor Q 11A twelfth active switch tube Q 12A thirteenth active switch tube Q 13A fourteenth active switch tube Q 14A fifteenth active switch tube Q 15A sixteenth active switch tube Q 16The collector of each active switch tube is respectively connected with the cathode of the corresponding freewheeling diode, and the emitter of each active switch tube is respectively connected with the anode of the corresponding freewheeling diode; the fault current blocking switch module is composed of a fifteenth active switch tube Q 15And sixteenth active switch tube Q 16Composition of an eleventh active switching tube Q 13Collector and fifteenth active switch tube Q 15Is connected with the collector of the twelfth active switching tube Q 12Collector electrode of and sixteenth active tube Q 16The collector electrodes are connected; eleventh active switch tube Q 11Emitter and thirteenth active switching tube Q 13Is connected with the collector and serves as a secondary side end G of the high-frequency transformer and a twelfth active switching tube Q 12Emitter and fourteenth active switching tube Q 14Connected to collector electrodes and serving as secondary side of high-frequency transformerThe other end H; fifteenth active switch tube Q 15And a sixteenth active switch tube Q 16Is connected with the emitter and serves as the anode C of the post-stage part of the submodule, and an eleventh active switching tube Q 11And a twelfth active switch tube Q 12And the collector of the sub-module is connected with the anode D and used as the cathode of the next stage part of the sub-module.
The voltage clamp circuit 7 in the latter part comprises a capacitor C 1Resistance R 14 diodes D 1～D 4Said D is 1And D 3After being connected in series, are respectively connected with C 1、R 1In parallel, said D 2And D 4After being connected in series, are respectively connected with C 1、R 1Parallel connection, D 1、D 2And C 1、R 1Are connected to the positive electrode of D 2、D 4With C and an anode of 1、R 1Is connected to the negative electrode of D 1And D 3The cathode and the secondary side end G of the high-frequency transformer are connected, D 2And D 4The cathode of the transformer is connected with the other end H of the secondary side of the high-frequency transformer.
In normal operation, the fault current blocks 2 active switching tubes (Q) of the switching module 8 9、Q 10Or Q 15、Q 16) The active switch tube (Q) of the H-bridge at the rear stage part is locked when the short circuit fault occurs at the high-voltage direct-current side 5、Q 6、Q 7、Q 8Or Q 11、Q 12、Q 13、Q 14) Simultaneously and rapidly providing 2 active switch tubes (Q) of fault current blocking switch module 9、Q 10Or Q 15、Q 16) The reverse fault current blocking switch module blocks the active switch tube (Q) of the H bridge of the rear stage part due to the turn-off signal 5、Q 6、Q 7、Q 8Or Q 11、Q 12、Q 13、Q 14) An energy feed loop of an alternating current side and a fault point formed by the anti-parallel diodes can block short-circuit fault current of a high-voltage direct current side, so that fault isolation of the direct current side is realized.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.

Claims (3)

1. The isolated modular multilevel converter is characterized in that: the converter (1) is of a three-phase system structure and comprises three high-voltage direct-current ports (P) connected in parallel H、N H) Each phase unit (2) consists of an upper bridge arm and a lower bridge arm, and the electrical connection points (N) of the upper bridge arm and the lower bridge arm of the three phase units 1、N 2、N 3) The outgoing lines are connected with filter inductors in series and then are high-voltage alternating-current ports (a, b and c), each bridge arm consists of n single-stage high-frequency isolation type sub-modules (3) with high-voltage direct-current side fault current blocking capacity and a bridge arm reactor L mComposition is carried out; positive pole ends (P) of upper bridge arms of three phase units (2) Ha、P Hb、P Hc) Connected as positive pole P of high voltage DC port of the converter HNegative pole end (N) of lower bridge arm of three phase units (2) Ha、N Hb、N Hc) Negative pole N connected as high voltage DC port of the converter H；
The single-stage high-frequency isolation type submodule (3) with the high-voltage direct-current side fault current blocking capacity comprises a preceding stage part (4), a high-frequency transformer part (5) and a subsequent stage part (6), wherein the alternating current side of the preceding stage part is connected with the primary side of the high-frequency transformer, the alternating current side of the subsequent stage part is connected with the secondary side of the high-frequency transformer, and the positive and negative electrode ports of the preceding stage part of each submodule (3) are respectively connected in parallel to serve as a common low-voltage direct-current port (P) L、N L) The ports of the rear stage part are connected in series to form a high-voltage direct current side port (P) H、N H)；
The preceding stage part (4) comprises a low-voltage side direct current capacitor C dcLAnd an active H-bridge consisting of four active switches with anti-parallel diodes; the rear-stage part (6) comprises a voltage clamping circuit (7), an active H bridge consisting of four active switches with anti-parallel diodes and a fault current blocking switch module (8) reversely connected on a bridge arm;
according to the fact that connection points of a rear-stage part (6) of a fault current blocking switch module (8) are different, a single-stage high-frequency isolation type sub-module (3) is divided into a first sub-module and a second sub-module;
the rear-stage part of the first submodule comprises a fifth active switching tube Q 5A sixth active switch tube Q 6A seventh active switch tube Q 7An eighth active switch tube Q 8A ninth active switch tube Q 9A tenth active switch tube Q 10The collector of each active switch tube is respectively connected with the cathode of the corresponding freewheeling diode, and the emitter of each active switch tube is respectively connected with the anode of the corresponding freewheeling diode; the fault current blocking switch module is composed of a ninth active switch tube Q 9And a tenth active switching tube Q 10Composition of a ninth active switch tube Q 9Emitter and seventh active switching tube Q 7Is connected with the emitting electrode of the tenth active switching tube Q 10Emitter and eighth active tube Q 8The emitting electrodes are connected; fifth active switch tube Q 5Emitter and seventh active switching tube Q 7Is connected with the collector and serves as a secondary side end G of the high-frequency transformer, and a sixth active switching tube Q 6Emitter and eighth active switching tube Q 8The collector of the transformer is connected with the other end H which is used as the secondary side of the high-frequency transformer; fifth active switch tube Q 5And a sixth active switch tube Q 6And a ninth active switching tube Q, and a positive electrode C connected with the collector and serving as a post-stage part of the submodule 9And a tenth active switch tube Q 10The collector electrodes of the sub-modules are connected and used as a negative electrode D of the post-stage part of the sub-modules;
the rear stage part of the second submodule comprises an eleventh active switching tube Q 11A twelfth active switch tube Q 12A thirteenth active switch tube Q 13A fourteenth active switch tube Q 14A fifteenth active switch tube Q 15A sixteenth active switch tube Q 16The collector of each active switch tube is respectively connected with the cathode of the corresponding freewheel diode, and the emitter of each active switch tube is respectively connected with the anode of the corresponding freewheel diodeConnecting; the fault current blocking module is composed of a fifteenth active switching tube Q 15And sixteenth active switch tube Q 16Composition of an eleventh active switching tube Q 11Collector and fifteenth active switch tube Q 15Is connected with the collector of the twelfth active switching tube Q 12Collector electrode of and sixteenth active tube Q 16The collector electrodes are connected; eleventh active switch tube Q 11Emitter and thirteenth active switching tube Q 13Is connected with the collector and serves as a secondary side end G of the high-frequency transformer and a twelfth active switching tube Q 12Emitter and fourteenth active switching tube Q 14The collector of the transformer is connected with the other end H which is used as the secondary side of the high-frequency transformer; fifteenth active switch tube Q 15And a sixteenth active switch tube Q 16And as the positive pole C of the sub-module rear-stage part, and the thirteenth active switching tube Q13 is connected to the emitter of the fourteenth active switching tube Q14 and as the negative pole D of the sub-module rear-stage part.
2. The isolated modular multilevel converter of claim 1, wherein: the active H-bridge of the preceding stage part (4) comprises a first active switching tube Q 1A second active switch tube Q 2A third active switch tube Q 3And a fourth active switch tube Q 4The collector of each active switch tube is respectively connected with the cathode of the corresponding freewheeling diode, and the emitter of each active switch tube is respectively connected with the anode of the corresponding freewheeling diode;
first active switch tube Q 1And a third active switch tube Q 3After being connected in series with the low-voltage side direct current capacitor C dcLParallel connection, a first active switch tube Q 1Emitter and third active switching tube Q 3Is connected with the collector and serves as a primary side E of the high-frequency transformer, and a second active switch tube Q 2Emitter and fourth active switching tube Q 4The collector of the first active switch tube Q is connected with the other end F which is the primary side of the high-frequency transformer 1Collector electrode and C dcLIs connected with the positive pole of the third active switch tube Q 3Emitter and C dcLIs connected to the negative electrode(ii) a Second active switch tube Q 2And a fourth active switch tube Q 4After being connected in series with the low-voltage side direct current capacitor C dcLParallel second active switch tube Q 2Collector electrode and C dcLIs connected with the positive pole of the fourth active switch tube Q 4Emitter and C dcLThe negative electrodes are connected; first active switch tube Q 1And a second active switch tube Q 2Collector electrode of (1) and (C) dcLIs connected with the positive pole of the sub-module and is used as the positive pole A of the front stage part of the sub-module, and a third active switch tube Q 3And a fourth active switch tube Q 4Emitter and C of dcLIs connected with and serves as the cathode B of the preceding part of the submodule.
3. The isolated modular multilevel converter of claim 1, wherein: the voltage clamping circuit (7) comprises a first diode D 1A second diode D 2A third diode D 3A fourth diode D 4A first capacitor C 1A first resistor R 1First diode D 1And a third diode D 3Are respectively connected with the first capacitor C after being connected in series 1A first resistor R 1Parallel, a second diode D 2And a fourth diode D 4Are respectively connected with the first capacitor C after being connected in series 1A first resistor R 1Parallel, first diode D 1A second diode D 2Cathode and first capacitor C 1A first resistor R 1The anodes of the third diode D3 and the fourth diode D4 are connected with the cathodes of the first capacitor C1 and the first resistor R1, and the first diode D 1Anode of and a third diode D 3Is connected with the secondary side end G of the high-frequency transformer, and a second diode D 2Anode of and a fourth diode D 4The cathode of the transformer is connected with the other end H of the secondary side of the high-frequency transformer.
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