WO2023217221A1

WO2023217221A1 - Bridge arm circuit having capacitor-assisted turn-off, converter, method, apparatus, and system

Info

Publication number: WO2023217221A1
Application number: PCT/CN2023/093466
Authority: WO
Inventors: 卢东斌; 李海英; 柏传军; 刘磊
Original assignee: 南京南瑞继保工程技术有限公司; 南京南瑞继保电气有限公司; 常州博瑞电力自动化设备有限公司
Priority date: 2022-05-12
Filing date: 2023-05-11
Publication date: 2023-11-16
Also published as: CN117097119A

Abstract

The present application provides a bridge arm circuit having capacitor-assisted turn-off, a converter, a method, an apparatus and a system. The bridge arm circuit having capacitor-assisted turn-off comprises a main branch and an assisted turn-off branch. The main branch comprises a first semi-controlled valve. The assisted turn-off branch is connected in parallel with the main branch, the assisted turn-off branch comprising a power electronic switch and a first capacitor, connected in series; the power electronic switch bidirectionally conducts current, is bidirectionally controllable to turn on, and unidirectionally controllable to turn off.

Description

Bridge arm circuit, converter, method, device and system for capacitor-assisted turn-off

Technical field

This application relates to the technical field of high-voltage direct current transmission, specifically to capacitor-assisted turn-off bridge arm circuits, converters, methods, devices, and systems.

Background technique

Converters in high-voltage and ultra-high voltage DC transmission systems generally use twelve-pulse circuits as the basic unit. Each twelve-pulse circuit has two three-phase six-arm circuits connected in series, and each bridge arm uses thyristors in series. Since the thyristor cannot be controlled to turn off, the existing converter structure has the problem of commutation failure. Voltage source converters for flexible DC transmission and hybrid DC transmission generally use modular multi-level converters. Each bridge arm is connected in series by half-bridge or full-bridge sub-modules. The sub-modules use full control devices and capacitors. Although there is no switching Phase failure problem, but the cost is high, the loss is large, and there is a risk of oscillation.

With the increasing number of high-voltage and ultra-high voltage DC transmission systems connected, multi-feed DC transmission systems have been formed in multiple regional power grids. When multiple DC lines fail to commutate at the same time, it may pose a threat to the safe operation of the regional AC power grid. threaten. As the proportion of new energy power generation increases, the AC voltage support capacity decreases, which places higher requirements on the stable operation of the DC transmission system and the ability to suppress commutation failure and oscillation. Existing high-voltage DC transmission, flexible DC transmission, and hybrid DC transmission technologies are difficult to meet the stringent cost and performance requirements of DC transmission systems.

Contents of the invention

The embodiment of the present application provides a capacitor-assisted turn-off bridge arm circuit, which includes a main branch and an auxiliary turn-off branch connected in parallel. The main branch includes a first half-control valve, and the first half-control valve includes Semi-controlled switch; the auxiliary shutdown branch includes a power electronic switch and a first capacitor connected in series. The power electronic switch has bidirectional flow, bidirectional controllable opening, and unidirectional controllable shutdown.

According to some embodiments, the main branch further includes a first full control valve connected in series with the first half control valve; lightning arresters are connected in parallel at both ends of the first half control valve and the first full control valve, A second half-control valve is connected in parallel at both ends of the first full-control valve. The second half-control valve includes a half-control switch, and the first full-control valve includes a full-control switch.

According to some embodiments, the auxiliary shutdown branch further includes a resistance or/and reactance, the resistance or/and reactance is connected in series with the power electronic switch and the first capacitor; the power electronic switch, the Lightning arresters are connected in parallel at both ends of the first capacitor, and the first capacitor includes at least one capacitive element connected in series.

According to some embodiments, the power electronic switch includes at least one switch group connected in series, and the switch group includes full control switches and half control switches connected in anti-parallel.

According to some embodiments, the power electronic switch includes at least one switch group connected in series, the switch group includes a fully controlled switch, an uncontrolled switch and a semi-controlled switch, and the uncontrolled switch is connected in series with the fully controlled switch; The half-controlled switch is connected in anti-parallel with the series circuit of the full-controlled switch and the uncontrolled switch.

According to some embodiments, the power electronic switch includes at least one switch group connected in series, the switch group including fully controlled switches connected in anti-parallel.

According to some embodiments, the power electronic switch includes a first half-controlled switch group and a full-controlled switch group connected in series. The first half-controlled switch group includes at least one switch group connected in series. The switch group includes an anti-parallel connected switch group. connected half-controlled switches; the full-controlled switch group includes at least one switch group connected in series, the switch group includes a fully-controlled switch and an uncontrolled switch connected in anti-parallel, and is connected in series with the first half-controlled switch group; The first capacitor is connected in series between the first half-controlled switch group and the full-controlled switch group or between the main branch and the first half-controlled switch group or the full-controlled switch group. . According to some embodiments, the power electronic switch includes a second half-controlled switch group and a full-controlled switch group connected in series, the second half-controlled switch group includes at least one switch group connected in series, and the switch group includes an anti-parallel connected half-controlled switches and uncontrolled switches; the fully controlled switch group includes at least one switch group connected in series, and the switch group includes a fully controlled switch and an uncontrolled switch connected in anti-parallel, and the second half-controlled switch groups are connected in series; the first capacitor is connected in series between the second half-controlled switch group and the full-controlled switch group or between the main branch and the second half-controlled switch group or the full-controlled switch group. between switch groups.

According to some embodiments, the power electronic switch includes at least one switch group connected in series. The switch group includes a fully controlled switch, an uncontrolled switch, a first half-controlled switch and a second half-controlled switch. The first half-controlled switch The switch is connected in series with the fully controlled switch and the uncontrolled switch; the second half controlled switch is connected in anti-parallel with the series circuit of the full controlled switch, the uncontrolled switch and the first half controlled switch.

According to some embodiments, the power electronic switch includes at least one switch group connected in series. The switch group includes: a fully controlled switch, a first half-controlled switch and a second half-controlled switch. The first half-controlled switch is connected to the first half-controlled switch and the second half-controlled switch. The full control switch is connected in series; the second half control switch is connected in anti-parallel with the series circuit of the full control switch and the first half control switch.

According to some embodiments, the fully controlled switch includes at least one fully controlled device connected in series, and the fully controlled device includes at least one of IGCT, IGBT, GTO, and MOSFET; the half controlled switch includes at least one half controlled device connected in series. The semi-controlled device includes a thyristor; the uncontrolled switch includes at least one uncontrolled device connected in series, and the uncontrolled device includes a diode.

According to some embodiments, the auxiliary shutdown branch further includes a fast isolating switch, and the fast isolating switch is connected in series with the power electronic switch.

An embodiment of the present application also provides a capacitor-assisted turn-off inverter. The converter includes a three-phase six bridge arm, at least one of which is a capacitor-assisted turn-off bridge arm circuit as described above.

According to some embodiments, the auxiliary turn-off branches of the three upper arms of the converter share a first capacitor, and the auxiliary turn-off branches of the three lower arms of the converter share another first capacitor. capacitor.

An embodiment of the present application also provides a high-voltage direct current transmission system, which includes a capacitor-assisted turn-off inverter as described above.

Embodiments of the present application also provide a control method for a capacitor-assisted turn-off inverter as described above, including: controlling the main branch of the bridge arm circuit of the inverter to operate in an inverter state; When the bridge arm circuit ends commutation to the other bridge arm, the power electronic switch controlling the auxiliary shutdown branch of the bridge arm circuit is reversely conducted, and the first capacitor of the auxiliary shutdown branch is reversely charged, causing The first capacitor presents a negative voltage; when a fault occurs that may cause commutation failure of the bridge arm circuit, the power electronic switch that controls the auxiliary shutdown branch of the bridge arm circuit is forward-conducted, causing the bridge arm circuit to The current of the main branch is transferred to the auxiliary turn-off branch; after the main branch of the bridge arm circuit is turned off, the power electronic switch of the auxiliary turn-off branch of the bridge arm circuit is controlled to turn off in the forward direction, realizing Current is transferred from one phase of the bridge arm circuit to another phase.

According to some embodiments, the main branch of the bridge arm circuit is turned off when the forward current of the first half-controlled valve of the main branch of the bridge arm circuit is less than the maintaining current and the forward blocking capability is restored.

An embodiment of the present application also provides a control device for a capacitor-assisted turn-off inverter as described above, including a detection unit and a control unit. The detection unit is used to detect the operation of the capacitor-assisted turn-off inverter. Parameters and faults; the control unit controls the main branch of the bridge arm circuit of the converter to run in an inverter state based on the operating parameters of the capacitor-assisted turn-off converter; in the bridge arm When the circuit ends commutation to the other bridge arm, the power electronic switch that controls the auxiliary shutdown branch of the bridge arm circuit conducts in the reverse direction, and the auxiliary shutdown branch The first capacitor of the branch is reversely charged, causing the first capacitor to present a negative voltage; when a fault occurs that may cause the commutation failure of the bridge arm circuit, the power electronics of the auxiliary shutdown branch of the bridge arm circuit are controlled. The switch is forward-conducting, causing the current of the main branch of the bridge arm circuit to be transferred to the auxiliary shutdown branch. After the main branch of the bridge arm circuit is turned off, the auxiliary shutdown branch of the bridge arm circuit is controlled. The power electronic switch is turned off in the forward direction, realizing the current transfer from the phase where the bridge arm circuit is located to another phase.

The technical solution provided by the embodiment of the present application is that when the bridge arm commutates, the negative voltage generated during the commutation is used to reversely charge the capacitor of the auxiliary branch of the bridge arm circuit. When a fault occurs, the negative pressure of the capacitor is used to reverse the capacitor of the bridge arm circuit. The main branch is turned off, and then the power electronic switch of the auxiliary turn-off branch is turned off, forcing the current to transfer from the phase where the bridge arm circuit is located to another phase, realizing controllable commutation of the power grid phase commutation converter based on semi-controlled devices. phase, effectively suppressing commutation failure and ensuring reliable operation of the converter.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

FIG. 1 is one of the schematic diagrams of a capacitor-assisted turn-off bridge arm circuit provided by an embodiment of the present application.

FIG. 2 is the second schematic diagram of a capacitor-assisted turn-off bridge arm circuit provided by an embodiment of the present application.

FIG. 3 is the third schematic diagram of a capacitor-assisted turn-off bridge arm circuit provided by an embodiment of the present application.

Figures 4a-4h are schematic diagrams of power electronic switches provided by embodiments of the present application.

FIG. 5 is one of the schematic diagrams of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

FIG. 6 is a second schematic diagram of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

FIG. 7 is a third schematic diagram of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

Figure 8 is a schematic diagram of a capacitor-assisted turn-off inverter provided by an embodiment of the present application. Four.

Figure 9 is a fifth schematic diagram of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

Figure 10 is a sixth schematic diagram of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

Figure 11 is a seventh schematic diagram of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

Figure 12 is an eighth schematic diagram of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

Figure 13 is a ninth schematic diagram of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

Figure 14a is a single-phase ground fault test result of a capacitor-assisted turn-off converter according to an embodiment of the present application; Figure 14b is a three-phase ground fault test result of a capacitor-assisted turn-off converter according to an embodiment of the present application. test results.

FIG. 15 is a schematic flowchart of a control method for a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

Figure 16 is a schematic diagram of a control device of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of this application.

It should be understood that the terms "first", "second", "third", etc. in the claims, description, and drawings of this application are used to distinguish different objects, rather than describing a specific sequence. The terms "comprising" and "comprising" used in the description and claims of this application indicate the presence of described features, integers, steps, operations, elements and/or components but do not exclude one or more other features, integers , the presence or addition of steps, operations, elements, components and/or collections thereof.

The bridge arm circuit of capacitor-assisted turn-off includes a main branch 1 and an auxiliary turn-off branch 2 connected in parallel.

As shown in Figure 1, the main branch 1 includes a first half-control valve V41. The auxiliary shutdown branch 2 includes a power electronic switch 3 and a first capacitor C42 connected in series. The power electronic switch 3 has bidirectional flow, bidirectional controllable opening, and unidirectional controllable shutdown.

According to some embodiments, the main branch 1 further includes a first full control valve V411, which is connected in series with the first half control valve V41, as shown in Figure 2.

According to some embodiments, the first half-control valve V41, the first full-control valve V411, the power electronic switch 3, and the first capacitor C42 are respectively connected in parallel with lightning arresters, and both ends of the first full-control valve V411 are connected in parallel with the second half-control valve V412. The first half-control valve V41 and the second half-control valve V412 respectively include a half-control switch, and the first full-control valve V411 includes a full-control switch.

According to some embodiments, the auxiliary shutdown branch 2 also includes a resistor R42 or/and a reactance L42, which is connected in series with the power electronic switch 3 and the first capacitor C42. As shown in Figure 3, the auxiliary shutdown In branch 2, resistor R42, reactance L42, power electronic switch 3 and first capacitor C42 are connected in series.

According to some embodiments, the first capacitor C42 includes at least one capacitive element connected in series, and the at least one capacitive element of the first capacitor C42 is respectively connected in parallel with a voltage-sharing resistor.

According to some embodiments, the power electronic switch 3 includes at least one switch group connected in series. The switch group includes a fully controlled switch and a half-controlled switch connected in anti-parallel. As shown in Figure 4a, the full-controlled switch includes an IGCT6 and the half-controlled switch includes a thyristor. 4. It is not limited to this.

According to some embodiments, the power electronic switch 3 includes at least one switch group connected in series. The switch group includes a fully controlled switch, an uncontrolled switch and a half-controlled switch. The fully controlled switch and the uncontrolled switch are connected in series and then connected in anti-parallel with the half-controlled switch. , as shown in Figure 4b, the fully controlled switch includes an IGBT 5 and a diode 7 connected in anti-parallel, the uncontrolled switch includes a diode 7, and the half-controlled switch includes a thyristor 4, which is not limited thereto. It should be pointed out that the diode 7 in the fully controlled switch is not necessary.

According to some embodiments, the power electronic switch 3 includes at least one switch group connected in series, and the switch group includes a fully controlled switch connected in anti-parallel. As shown in Figure 4c, the fully controlled switch includes an IGCT 6, but is not limited thereto.

According to some embodiments, the power electronic switch 3 includes a first half-controlled switch group 9 and a full-controlled switch group 8. The first half-controlled switch group 9 and the full-controlled switch group 8 are connected in series. The first half-controlled switch group 9 is connected in series with the full-controlled switch group 8. The switch group 9 includes at least one switch group connected in series. The switch group includes two half-controlled switches connected in anti-parallel. The full-controlled switch group 8 includes at least one switch group connected in series. The switch group includes a fully-controlled switch connected in anti-parallel. Without controlled switches, as shown in Figure 4d, a switch group of the first half-controlled switch group 9 includes two thyristors 4, and a switch group of the fully controlled switch group 8 includes an IGBT 5 and a diode 7 connected in anti-parallel with it. This is the limit.

According to some embodiments, the power electronic switch 3 includes a second half-controlled switch group 10 and a full-controlled switch group 8. The second half-controlled switch group 10 is connected in series with the full-controlled switch group 8. The second half-controlled switch group 10 includes at least one The switch group is connected in series. The switch group includes half-controlled switches and uncontrolled switches connected in anti-parallel. The full-controlled switch group 8 includes at least one switch group connected in series. The switch group includes fully-controlled switches and uncontrolled switches connected in anti-parallel. As shown in Figure 4e, a switch group of the second half-controlled switch group 10 includes a thyristor 4 and a diode 7 connected in anti-parallel thereto, and a switch group of the full-controlled switch group 8 includes an IGBT 5 and a diode 7 connected in anti-parallel thereto. The power electronic switch 3 of this embodiment can also be connected in series with the fully controlled switch after the half-controlled switch and the uncontrolled switch are connected in anti-parallel as shown in Figure 4f.

According to some embodiments, the power electronic switch 3 includes at least one switch group connected in series. The switch group includes a fully controlled switch 11, an uncontrolled switch 13, a first half-controlled switch 12 and a second half-controlled switch 14. The fully controlled switch 11, The uncontrolled switch 13 and the first half-controlled switch 12 are connected in series, and the second half-controlled switch 14 is connected in anti-parallel with the series circuit of the above-mentioned full-controlled switch 11, the uncontrolled switch 13 and the first half-controlled switch 12, as shown in Figure 4g , the fully controlled switch 11 includes an IGBT 5 connected in series and a diode 7 connected in anti-parallel with it, the uncontrolled switch 13 includes a diode 7 connected in series, the first half-controlled switch 12 includes a thyristor 4 connected in series, and the second half-controlled switch 14 includes The thyristors 4 connected in series are not limited to this.

According to some embodiments, the power electronic switch 3 includes at least one switch group connected in series. The switch group includes a full control switch 11 , a first half control switch 12 and a second half control switch 14 . The full control switch 11 and the first half control switch 12 are connected in series, and the second half-controlled switch 14 is connected in anti-parallel with the series circuit of the above-mentioned full-controlled switch 11 and the first half-controlled switch 12. As shown in Figure 4h, the full-controlled switch 11 includes an IGBT 5 connected in series and an anti-parallel connection with it. The diode 7 , the first half-controlled switch 12 includes a series-connected thyristor 4 , and the second half-controlled switch 14 includes a series-connected thyristor 4 , but is not limited thereto.

The fully controlled switch includes at least one fully controlled device connected in series. The fully controlled device includes IGCT (Integrated Gate Commutated Thyristors), IGBT (Insulated Gate Bipolar Transistor, insulated gate bipolar transistor), GTO (Gate At least one of Turn-Off Thyristor (gate turn-off thyristor) and MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The half-controlled switch includes at least one half-controlled device connected in series, and the half-controlled device includes a thyristor. The uncontrolled switch consists of at least one connected in series Uncontrolled devices include, but are not limited to, diodes. Optionally, the fully controlled switch includes at least one fully controlled device connected in series and an uncontrolled device connected in anti-parallel.

Thyristor 4 is configured with corresponding trigger circuit and buffer circuit. IGBT5 is configured with corresponding drive circuit and buffer circuit. IGCT6 is configured with corresponding drive circuit and buffer circuit. The buffer circuit consists of at least a capacitor, or a series circuit of a resistor and a capacitor.

According to some embodiments, the auxiliary shutdown circuit 2 further includes a fast isolating switch. The fast isolating switch is a mechanical switch and is connected in series with the power electronic switch 3 .

Figure 5 is one of the schematic diagrams of a capacitor-assisted turn-off converter provided by an embodiment of the present application. The capacitor-assisted turn-off converter has three phases and six bridge arms, and each bridge arm is composed of a bridge as shown in Figure 1 arm circuit.

Each bridge arm circuit includes a main branch and an auxiliary shutdown branch connected in parallel. The main branch includes the first semi-controlled valve. The auxiliary shutdown branch includes a power electronic switch and a first capacitor connected in series. The power electronic switch has bidirectional flow, bidirectional controllable opening, and unidirectional controllable shutdown.

The main branch of the A-phase upper bridge arm is composed of the first half-control valve V41, and the auxiliary shutdown branch is composed of the power electronic switch 3 and the first capacitor C42 connected in series.

The main branch of the B-phase upper bridge arm is composed of the first half-control valve V61, and the auxiliary shutdown branch is composed of the power electronic switch 3 and the first capacitor C62 connected in series.

The main branch of the C-phase upper bridge arm is composed of the first half-control valve V21, and the auxiliary shutdown branch is composed of the power electronic switch 3 and the first capacitor C22 connected in series.

The main branch of the A-phase lower bridge arm is composed of the first half-controlled valve V11, and the auxiliary shutdown branch is composed of the power electronic switch 3 and the first capacitor C12 connected in series.

The main branch of the B-phase lower bridge arm is composed of the first half-control valve V31, and the auxiliary shutdown branch is composed of the power electronic switch 3 and the first capacitor C32 connected in series.

The main branch of the C-phase lower bridge arm is composed of the first half-control valve V51, and the auxiliary shutdown branch is composed of the power electronic switch 3 and the first capacitor C52 connected in series.

Based on the embodiment in Figure 5, the power electronic switch adopts the structure as shown in Figure 4a, including multiple switch groups connected in series. The switch group includes a full control switch and a half control switch connected in anti-parallel. The full control switch includes IGCT6, and the half control switch The switch includes a thyristor 4. The first semi-controlled valve, electric The force electronic switch and the first capacitor are respectively connected in parallel with lightning arresters to protect the device.

As shown in Figure 6, the first half-controlled valve V41 is connected in parallel to the arrester F41, the power electronic switch V42 is connected in parallel to the arrester F42, and the first capacitor C42 is connected in parallel to the arrester F74. The first semi-controlled valve V61 is connected in parallel to the arrester F61, the power electronic switch V62 is connected in parallel to the arrester F62, and the first capacitor C62 is connected in parallel to the arrester F76. The first semi-controlled valve V21 is connected in parallel to the arrester F21, the power electronic switch V22 is connected in parallel to the arrester F22, and the first capacitor C22 is connected in parallel to the arrester F72. The first semi-controlled valve V11 is connected in parallel to the arrester F11, the power electronic switch V12 is connected in parallel to the arrester F12, and the first capacitor C12 is connected in parallel to the arrester F71. The first semi-controlled valve V31 is connected in parallel to the arrester F31, the power electronic switch V32 is connected in parallel to the arrester F32, and the first capacitor C32 is connected in parallel to the arrester F73. The first semi-controlled valve V51 is connected in parallel to the arrester F51, the power electronic switch V52 is connected in parallel to the arrester F52, and the first capacitor C52 is connected in parallel to the arrester F75.

According to some embodiments, the power electronic switch adopts the structure as shown in Figure 4a, which only includes a series-connected switch group. The switch group includes a full-control switch and a half-control switch connected in anti-parallel. As shown in Figure 7, the full-control switch includes a series-connected switch. The connected IGCT6, half-controlled switch includes thyristors 4 connected in series.

As shown in Figure 7, the first half-controlled valve V41 is connected in parallel to the arrester F41, the power electronic switch includes a full-controlled switch V43 and a half-controlled switch V44 connected in anti-parallel, the power electronic switch is connected in parallel to the arrester F43, and the first capacitor C42 is connected in parallel to the arrester F74. The first half-controlled valve V61 is connected in parallel to the arrester F61, the power electronic switch includes a full-controlled switch V63 and a half-controlled switch V64 connected in anti-parallel, and the arrester F63 is connected in parallel, and the first capacitor C62 is connected in parallel to the arrester F76. The first half-controlled valve V21 is connected in parallel to the arrester F21, the power electronic switch includes a full-controlled switch V23 and a half-controlled switch V24 connected in anti-parallel, and the arrester F23 is connected in parallel, and the first capacitor C22 is connected in parallel to the arrester F72. The first half-controlled valve V11 is connected in parallel to the arrester F11. The power electronic switch includes a full-controlled switch V13 and a half-controlled switch V14 connected in anti-parallel, and the arrester F13 is connected in parallel. The first capacitor C12 is connected in parallel to the arrester F71. The first half-controlled valve V31 is connected in parallel with the arrester F31. The power electronic switch includes a full-controlled switch V33 and a half-controlled switch V34 connected in anti-parallel, and the arrester F33 is connected in parallel. The first capacitor C32 is connected in parallel with the arrester F73. The first half-controlled valve V51 is connected in parallel to the arrester F51. The power electronic switch includes a full-controlled switch V53 and a half-controlled switch V54 connected in anti-parallel, and the arrester F53 is connected in parallel. The first capacitor C52 is connected in parallel to the arrester F75.

FIG. 8 is the fourth schematic diagram of a capacitor-assisted turn-off inverter provided by an embodiment of the present application.

Based on the embodiment of Figure 5, the power electronic switch adopts the structure shown in Figure 4d, including a first half-controlled switch group and a full-controlled switch group connected in series. The first half-controlled switch group includes at least one switch group connected in series. , the switch group includes half-controlled switches connected in anti-parallel, half The controlled switch includes a thyristor, the fully controlled switch group includes at least one switch group connected in series, the switch group includes a fully controlled switch and an uncontrolled switch connected in series, the fully controlled switch includes an IGBT, and the uncontrolled switch includes a diode. The first half-controlled valve, the first half-controlled switch group, the full-controlled switch group, and the first capacitor are respectively connected in parallel with lightning arresters to protect the device. The first capacitor is connected in series between the main branch and the full control switch group.

In the upper bridge arm of phase A, the first half-controlled valve V41 is connected in parallel with the arrester F41. The first half-controlled switch group V45 includes at least one switch group connected in series. The switch group includes half-controlled switches connected in anti-parallel. The first half-controlled switch group V45 is connected in parallel with arrester F44, the fully controlled switch group V46 includes at least one switch group connected in series, the switch group includes fully controlled switches and uncontrolled switches connected in anti-parallel, the fully controlled switch group V46 is connected in parallel with arrester F45, and the first capacitor C42 is connected in parallel with arrester F74 .

In the upper bridge arm of phase B, the first half-controlled valve V61 is connected in parallel with the arrester F61. The first half-controlled switch group V65 includes at least one switch group connected in series. The switch group includes half-controlled switches connected in anti-parallel. The first half-controlled switch group V65 parallel arrester F64, fully controlled switch group V66 includes at least one switch group connected in series, the switch group includes fully controlled switches and uncontrolled switches connected in anti-parallel, fully controlled switch group V66 connected in parallel with arrester F65, first capacitor C62 connected in parallel with arrester F76 .

In the phase C upper bridge arm, the first half-controlled valve V21 is connected in parallel with the arrester F21. The first half-controlled switch group V25 includes at least one switch group connected in series. The switch group includes half-controlled switches connected in anti-parallel. The first half-controlled switch group V25 is connected in parallel to the arrester F24, the fully controlled switch group V26 includes at least one switch group connected in series, the switch group includes fully controlled switches and uncontrolled switches connected in anti-parallel, the fully controlled switch group V26 is connected in parallel to the arrester F25, and the first capacitor C22 is connected in parallel to the arrester F72 .

In the lower bridge arm of phase A, the first half-controlled valve V11 is connected in parallel with the arrester F11. The first half-controlled switch group V15 includes at least one switch group connected in series. The switch group includes half-controlled switches connected in anti-parallel. The first half-controlled switch group V15 is connected in parallel to the arrester F14, the fully controlled switch group V16 includes at least one switch group connected in series, the switch group includes fully controlled switches and uncontrolled switches connected in anti-parallel, the fully controlled switch group V16 is connected in parallel to the arrester F15, and the first capacitor C12 is connected in parallel to the arrester F71 .

In the lower bridge arm of phase B, the first half-controlled valve V31 is connected in parallel with the arrester F31. The first half-controlled switch group V35 includes at least one switch group connected in series. The switch group includes half-controlled switches connected in anti-parallel. The first half-controlled switch group V35 is connected in parallel to the arrester F34, the fully controlled switch group V36 includes at least one switch group connected in series, the switch group includes fully controlled switches and uncontrolled switches connected in anti-parallel, the fully controlled switch group V36 is connected in parallel to the arrester F35, and the first capacitor C32 is connected in parallel to the arrester F73 .

In the C-phase lower bridge arm, the first half-controlled valve V51 is connected in parallel with the arrester F51. The first half-controlled switch group V55 includes at least one switch group connected in series. The switch group includes half-controlled switches connected in anti-parallel. The first half-controlled switch group V55 parallel arrester F54, fully controlled switch group V56 includes at least one switch group connected in series, the switch group includes fully controlled switches and uncontrolled switches connected in anti-parallel, fully controlled switch group V56 connected in parallel with arrester F55, first capacitor C52 connected in parallel with arrester F75 .

Based on the embodiment of Figure 5, the power electronic switch adopts the structure shown in Figure 4e, including a second half-controlled switch group and a full-controlled switch group connected in series. The second half-controlled switch group includes at least one switch group connected in series. , the switch group includes a semi-controlled switch and an uncontrolled switch connected in anti-parallel, the semi-controlled switch includes a thyristor, the uncontrolled switch includes a diode, the fully controlled switch group includes at least one switch group connected in series, and the switch group includes a fully controlled switch connected in series Unlike uncontrolled switches, fully controlled switches include IGBTs, and uncontrolled switches include diodes. The first half-controlled valve, the second half-controlled switch group, the full-controlled switch group, and the first capacitor are respectively connected in parallel with lightning arresters to protect the device. The first capacitor is connected in series between the main branch and the full control switch group.

In the upper bridge arm of phase A, the first half-controlled valve V41 is connected in parallel with the arrester F41. The second half-controlled switch group V47 includes at least one switch group connected in series. The switch group includes an uncontrolled switch and a half-controlled switch connected in anti-parallel. The semi-controlled switch group V47 is connected in parallel with the arrester F44, the fully controlled switch group V46 includes at least one switch group connected in series, the switch group includes a fully controlled switch and an uncontrolled switch connected in anti-parallel, the fully controlled switch group V46 is connected in parallel with the arrester F46, and the first capacitor C42 parallel arrester F74.

In the upper bridge arm of phase B, the first half-controlled valve V61 is connected in parallel with the arrester F61. The second half-controlled switch group V67 includes at least one switch group connected in series. The switch group includes an uncontrolled switch and a half-controlled switch connected in anti-parallel. The semi-controlled switch group V67 is connected in parallel with the arrester F64, the fully controlled switch group V66 includes at least one switch group connected in series, the switch group includes a fully controlled switch and an uncontrolled switch connected in anti-parallel, the fully controlled switch group V66 is connected in parallel with the arrester F66, the first capacitor C62 parallel arrester F76.

In the upper bridge arm of phase C, the first half-controlled valve V21 is connected in parallel with the arrester F21, and the second half-controlled switch group V27 includes at least one switch group connected in series. The switch group includes an uncontrolled switch and a half-controlled switch connected in anti-parallel. The semi-controlled switch group V27 is connected in parallel with the arrester F24. The fully controlled switch group V26 includes at least one switch group connected in series. The switch group includes a fully controlled switch and an uncontrolled switch connected in anti-parallel. The fully controlled switch group V26 is connected in parallel with the arrester F26 and the first capacitor. C22 parallel arrester F72.

In the lower bridge arm of phase A, the first half-controlled valve V11 is connected in parallel with the arrester F11. The second half-controlled switch group V17 includes at least one switch group connected in series. The switch group includes an uncontrolled switch and a half-controlled switch connected in anti-parallel. The semi-controlled switch group V17 is connected in parallel with the arrester F14. The fully controlled switch group V16 includes at least one switch group connected in series. The switch group includes a fully controlled switch and an uncontrolled switch connected in anti-parallel. The fully controlled switch group V16 is connected in parallel with the arrester F16 and the first capacitor. C12 parallel arrester F71.

In the lower bridge arm of phase B, the first half-controlled valve V31 is connected in parallel with the arrester F31. The second half-controlled switch group V37 includes at least one switch group connected in series. The switch group includes an uncontrolled switch and a half-controlled switch connected in anti-parallel. The semi-controlled switch group V37 is connected in parallel with the arrester F34, the fully controlled switch group V36 includes at least one switch group connected in series, the switch group includes a fully controlled switch and an uncontrolled switch connected in anti-parallel, the fully controlled switch group V36 is connected in parallel with the arrester F36, the first capacitor C32 parallel arrester F73.

In the C-phase lower bridge arm, the first half-controlled valve V51 is connected in parallel with the arrester F51. The second half-controlled switch group V57 includes at least one switch group connected in series. The switch group includes an uncontrolled switch and a half-controlled switch connected in anti-parallel. The semi-controlled switch group V57 is connected in parallel with the arrester F54, the fully controlled switch group V56 includes at least one switch group connected in series, the switch group includes a fully controlled switch and an uncontrolled switch connected in anti-parallel, the fully controlled switch group V56 is connected in parallel with the arrester F56, the first capacitor C52 parallel arrester F75.

According to some embodiments, the first capacitor may also be connected in series between the second half-controlled switch group and the full-controlled switch, as shown in FIG. 10 .

Based on the embodiment of Figure 5, the auxiliary shutdown branch includes a power electronic switch, a resistor and a first capacitor connected in series. The power electronic switch adopts the structure shown in Figure 4a, including multiple switch groups connected in series. The switch group Including anti-parallel connected full control switch and half control switch, the full control switch includes IGCT6, and the half control switch includes thyristor 4. The first semi-controlled valve, the power electronic switch, and the first capacitor are connected in parallel with the arrester. The three upper bridge arms share the first capacitor and the resistor, and the three lower bridge arms share the first capacitor and the resistor.

In the upper bridge arm of phase A, the first half-controlled valve V41 is connected in parallel to the arrester F41, the power electronic switch V42 is connected in parallel to the arrester F42, and the first capacitor C42 is connected in parallel to the arrester F74.

In the upper bridge arm of phase B, the first half-controlled valve V61 is connected in parallel to the arrester F61, the power electronic switch V62 is connected in parallel to the arrester F62, and the first capacitor C42 is connected in parallel to the arrester F74.

In the C-phase upper bridge arm, the first half-controlled valve V21 is connected in parallel with the arrester F21 and the power electronic switch V22 is connected in parallel with arrester F22, and the first capacitor C42 is connected in parallel with arrester F74.

In the lower bridge arm of phase A, the first half-controlled valve V11 is connected in parallel to the arrester F11, the power electronic switch V12 is connected in parallel to the arrester F12, and the first capacitor C12 is connected in parallel to the arrester F71.

In the lower bridge arm of phase B, the first half-controlled valve V31 is connected in parallel to the arrester F31, the power electronic switch V32 is connected in parallel to the arrester F32, and the first capacitor C12 is connected in parallel to the arrester F71.

In the C-phase lower bridge arm, the first half-controlled valve V51 is connected in parallel to the arrester F51, the power electronic switch V52 is connected in parallel to the arrester F52, and the first capacitor C12 is connected in parallel to the arrester F71.

The three upper bridge arms share the first capacitor V42 and resistor R42, and the power electronic switches of the three upper bridge arms are connected to the same bus P2; the three lower bridge arms share the first capacitor V12 and resistor R12, and the power electronic switches of the three lower bridge arms are connected to the same bus P2. The switch is connected to the same bus N2.

Based on the embodiment of Figure 5, the power electronic switch adopts the structure shown in Figure 4d, including a first half-controlled switch group and a full-controlled switch group connected in series. The first half-controlled switch group includes at least one switch group connected in series. , the switch group includes half-controlled switches connected in anti-parallel, the half-controlled switches include thyristors, the fully-controlled switch group includes at least one switch group connected in series, the switch group includes fully-controlled switches and uncontrolled switches connected in series, and the full-controlled switch includes IGBT , the uncontrolled switch includes a diode. The first half-controlled valve, the first half-controlled switch group, the full-controlled switch group, and the first capacitor are respectively connected in parallel with lightning arresters to protect the device. The three upper bridge arms share the first capacitor and the full control switch group, and the three lower bridge arms share the first capacitor and the full control switch group.

In the upper bridge arm of phase A, the first half-controlled valve V41 is connected in parallel to the arrester F41, the first half-controlled switch group V45 is connected in parallel to the arrester F44, the full-controlled switch group V46 is connected in parallel to the arrester F45, and the first capacitor C42 is connected in parallel to the arrester F74.

In the upper bridge arm of phase B, the first half-controlled valve V61 is connected in parallel with arrester F61, the first half-controlled switch group V65 is connected in parallel with arrester F64, the full-controlled switch group V46 is connected in parallel with arrester F45, and the first capacitor C42 is connected in parallel with arrester F74.

In the phase C upper bridge arm, the first half-controlled valve V21 is connected in parallel to the arrester F21, the first half-controlled switch group V25 is connected in parallel to the arrester F24, the full-controlled switch group V46 is connected in parallel to the arrester F45, and the first capacitor C42 is connected in parallel to the arrester F74.

In the lower bridge arm of phase A, the first half-controlled valve V11 is connected in parallel to the arrester F11, the first half-controlled switch group V15 is connected in parallel to the arrester F14, the full-controlled switch group V16 is connected in parallel to the arrester F15, and the first capacitor C12 is connected in parallel to the arrester F71.

In the lower bridge arm of phase B, the first half-controlled valve V31 is connected in parallel to the arrester F31, the first half-controlled switch group V35 is connected in parallel to the arrester F34, the full-controlled switch group V16 is connected in parallel to the arrester F15, and the first capacitor C12 is connected in parallel to the arrester F71.

In the C-phase lower bridge arm, the first half-controlled valve V51 is connected in parallel to the arrester F51, the first half-controlled switch group V55 is connected in parallel to the arrester F54, the full-controlled switch group V16 is connected in parallel to the arrester F15, and the first capacitor C12 is connected in parallel to the arrester F71.

The three upper bridge arms share the full control switch V46 and the first capacitor V42, and the first half control switch group of the three upper bridge arms is connected to the same bus P2. The three lower bridge arms share the full control switch V16 and the first capacitor V12, and the first half control switch group of the three lower bridge arms is connected to the same bus N2.

Based on the embodiment of Figure 5, the power electronic switch adopts the structure shown in Figure 4g, including a switch group connected in series. The switch group includes a fully controlled switch, an uncontrolled switch, a first half-controlled switch and a second half-controlled switch. , the full control switch, the uncontrolled switch and the first half-controlled switch are connected in series, the second half-controlled switch is connected in anti-parallel with the series circuit of the above-mentioned full control switch, the uncontrolled switch and the first half-controlled switch, and the full-controlled switch includes a series connection The IGBT and the diode connected in anti-parallel with it, the uncontrolled switch includes a diode 7 connected in series, the first half-controlled switch includes a thyristor 4 connected in series, and the second half-controlled switch includes a thyristor 4 connected in series. The first half-controlled valve, the fully controlled switch, the uncontrolled switch, the first half-controlled switch, the second half-controlled switch and the first capacitor are respectively connected in parallel to the lightning arrester.

In the upper bridge arm of phase A, the first half-controlled valve V41 is connected in parallel to the arrester F41, the fully controlled switch V46 is connected in parallel to the arrester F45, the uncontrolled switch V48 is connected in parallel to the arrester F47, the first half-controlled switch V49 is connected in parallel to the arrester F48, and the first capacitor C42 is connected in parallel to the arrester F74. .

In the B-phase upper bridge arm, the first half-controlled valve V61 is connected in parallel with the arrester F61, and the uncontrolled switch V68 is connected in parallel with the arrester F67.

In the C-phase upper bridge arm, the first half-controlled valve V21 is connected in parallel with the arrester F21, and the uncontrolled switch V28 is connected in parallel with the arrester F27.

In the lower bridge arm of phase A, the first half-controlled valve V11 is connected in parallel to the arrester F11, the fully controlled switch V16 is connected in parallel to the arrester F15, the uncontrolled switch V18 is connected in parallel to the arrester F17, the first half-controlled switch V19 is connected in parallel to the arrester F18, and the first capacitor C12 is connected in parallel to the arrester F71. .

In the lower bridge arm of phase B, the first half-controlled valve V31 is connected in parallel with the arrester F31, and the uncontrolled switch V38 is connected in parallel with the arrester F37.

In the C-phase lower bridge arm, the first half-controlled valve V51 is connected in parallel with the arrester F51, and the uncontrolled switch V58 is connected in parallel with the arrester F57.

The three upper arms share the full control switch V46, the first half control switch V49 and the first capacitor C42, and the uncontrolled switches of the three upper arms are connected to the same bus P2. The three lower bridge arms share the fully controlled switch V16, the first half controlled switch V19 and the first capacitor C12, and the uncontrolled switches of the three lower bridge arms are connected to the same bus N2.

In this embodiment, only the A-phase upper bridge arm and the A-phase lower bridge arm are respectively configured with the second half-controlled switch V40 and the second half-controlled switch V10.

Figure 14a shows the single-phase ground fault test results of the capacitor-assisted turn-off converter shown in Figure 13. UAC_IN_L1, UAC_IN_L2 and UAC_IN_L3 are three-phase AC voltage; IVY_L1_SCA, IVY_L2_SCA and IVY_L3_SCA are three-phase valve side AC current; UDL_IN is DC voltage; IDNC is DC current; CPRY is the first half-controlled valve V11, V21, V31, V41, V51 and V61 trigger flag, such as CPRY=12, converted to binary is 0x1001, then the first half control valve V41 and V11 are connected; MAIN_BRANCH_CP1 is the pulse of the full control switch V16 and the first half control switch V19, MAIN_BRANCH_CP4 is the full control The pulses of switch V46 and the first half-controlled switch V49, CHARGE_BRANCH_CP1 is the pulse of the second half-controlled switch V10, CHARGE_BRANCH_CP2 is the pulse of the second half-controlled switch V40; UCAP_YUP is the voltage of the first capacitor C42, and UCAP_YDOWN is the voltage of the first capacitor C12 Voltage. After a ground fault occurs in phase A of the AC system, the AC voltage UAC_IN_L1 becomes 0. When it is detected that the first half-controlled valve V41, V61 or V21 may have commutation failure, the full control switch V46 and the first half-controlled switch V49 are controlled to be turned on. , correspondingly, the current is transferred to the full control switch V46, the first half control switch V49 and the uncontrolled switch V48, V68 or V28. When the first half control valve V41, V61 or V21 is turned off, the full control switch V46 is controlled to turn off. ; When it is detected that the first half control valve V11, V31 or V51 may have commutation failure, the full control switch V16 and the first half control switch V19 are controlled to be turned on. Correspondingly, the current is transferred to the full control switch V16 and the first half control switch V16. The control switch V19 and the non-control switch V18, V38 or V58, when the first half control valve V11, V31 or V51 is turned off, control the full control switch V16 to turn off. During the entire fault period, the valve-side AC currents IVY_L1_SCA, IVY_L2_SCA and IVY_L3_SCA can still be commutated successfully. The negative voltage of the voltage UCAP_YUP of the first capacitor C42 and the voltage UCAP_YDOWN of the first capacitor C12 decreases. The DC voltage UDL_IN maintains about 50%. Current IDNC can also maintain fluctuations at pre-fault levels. Test results show that this topology can achieve self-commutation during a single-phase AC fault, maintain a certain power transmission, and will not cause commutation failure. Figure 14b shows the three-phase ground fault test results of the capacitor-assisted turn-off converter shown in Figure 13. After a ground fault occurs in the three phases of the AC system, the AC voltages UAC_IN_L1, UAC_IN_L2 and UAC_IN_L3 are all 0. During the entire fault period, the valve side AC currents IVY_L1_SCA, IVY_L2_SCA and IVY_L3_SCA can still be commutated successfully, achieving automatic switching that does not depend on the AC voltage during the fault. commutation and can provide Controlled short circuit current.

Embodiments of the present application also provide a high-voltage direct current transmission system. The high-voltage direct current transmission system includes a capacitor-assisted turn-off inverter as described above.

In S110, the main branch of the bridge arm circuit that controls the converter operates in the inverter state.

The first half-controlled valves V11, V21, V31, V41, V51 and V61 that control the main branch 1 of the converter shown in Figures 6-13 above operate in the inverter state.

In S120, when the bridge arm circuit ends commutation to the other bridge arm, the power electronic switch controlling the auxiliary shutdown branch of the bridge arm circuit is reversely conducted, and the first capacitor of the auxiliary shutdown branch is reversely charged. causing the first capacitor to present a negative voltage.

Taking the A-phase upper arm as shown in Figure 6 and Figure 11 as an example, when the A-phase upper arm of the converter finishes commutation to the B-phase upper arm, the auxiliary shutdown branch 2 of the A-phase upper arm is controlled. The power electronic switch V42 is reversely conductive, and the first capacitor C42 of the auxiliary shutdown branch 2 is charged in the reverse direction, causing the first capacitor C42 to present a negative voltage.

Taking the A-phase upper arm in Figure 7 as an example, when the A-phase upper arm of the converter finishes commutation to the B-phase upper arm, the half control of the auxiliary shutdown branch 2 of the A-phase upper arm is controlled. The switch V44 is reversely conductive, and the first capacitor C42 of the auxiliary shutdown branch 2 is charged in the reverse direction, causing the first capacitor C42 to present a negative voltage.

Taking the A-phase upper arm as shown in Figure 8 and Figure 12 as an example, when the A-phase upper arm of the converter finishes commutation to the B-phase upper arm, the auxiliary shutdown branch 2 of the A-phase upper arm is controlled. The first half-controlled switch group V45 is reversely conductive, and the first capacitor C42 of the auxiliary shutdown branch 2 is charged in the reverse direction, causing the first capacitor C42 to present a negative voltage.

Taking the A-phase upper arm as shown in Figure 9 and Figure 10 as an example, when the A-phase upper arm of the converter finishes commutation to the B-phase upper arm, the auxiliary shutdown branch 2 of the A-phase upper arm is controlled. The second half-controlled switch group V47 is reversely conductive, and the first capacitor C42 of the auxiliary shutdown branch 2 is charged in the reverse direction, causing the first capacitor C42 to present a negative voltage.

Taking the A-phase upper arm in Figure 13 as an example, when the phase A upper arm of the converter finishes commutation to the B-phase upper arm, the second phase of the auxiliary shutdown branch 2 of the A-phase upper arm is controlled. The half-controlled switch V40 is reversely conductive, and the first capacitor C42 of the auxiliary shutdown branch 2 is charged in the reverse direction, causing the first capacitor C42 to present a negative voltage.

The positive direction of the voltage of the upper arm is directed from the positive pole of the DC bus of the converter to the AC phase. Taking the A-phase upper arm shown in Figure 6 as an example, the positive direction of the voltage of the first capacitor C42 is directed from the positive pole of the DC bus P1 of the converter. Pointing to the A-phase end point A1, taking the A-phase lower bridge arm shown in Figure 6 as an example, the positive direction of the voltage of the first capacitor C12 points from the A-phase end point A1 to the DC bus negative electrode N1 of the converter.

In S130, when a fault occurs that may cause commutation failure of the bridge arm circuit of the converter with capacitor-assisted shutdown, the power electronic switch of the auxiliary shutdown branch of the commutation bridge arm circuit is forward-conducted to cause commutation. The current of the main branch of the bridge arm circuit is transferred to the auxiliary turn-off branch.

The above-mentioned commutation bridge arm circuit is the bridge arm that commutates to the other bridge arm during normal operation.

The above faults include but are not limited to AC system faults or DC system faults connected to the inverter. AC system faults can be caused by an increase in the zero sequence component of the AC voltage, a sudden change in the AC voltage, a drop in the amplitude of the AC voltage, an increase in the harmonics of the AC voltage, or a DC fault. The fault of the DC system can be judged based on the drop of DC voltage and the increase of DC current. The commutation failure of the bridge arm circuit of the converter that may cause capacitor-assisted shutdown is determined based on the turn-off time of the first half-controlled valve of the main branch of the bridge arm circuit and the AC voltage. If the first half-controlled valve of the main branch of the bridge arm circuit If the semi-controlled valve has not turned off at the turn-off time under normal AC voltage, it is judged that it may cause the commutation failure of the bridge arm circuit of the converter, but it is not limited to this.

Taking the A-phase upper arm in Figure 6 and Figure 11 as an example, when the A-phase first upper arm commutates to the B-phase first upper arm, at this time, if a fault occurs, the commutation may cause the capacitor auxiliary shutdown. When the commutation of the A-phase upper arm of the current converter fails, the power electronic switch V42 that controls the auxiliary shutdown branch 2 of the A-phase upper arm is forward-conducted, and the first switch of the auxiliary shutdown branch 2 of the A-phase upper arm Capacitor C42 applies a back voltage to main branch 1, and the current of main branch 1 is transferred to auxiliary shutdown branch 2.

Take the A-phase upper arm as shown in Figure 7 as an example. When the A-phase first upper arm commutates to the B-phase first upper arm, at this time, if a fault occurs, it may cause the capacitor-assisted shutdown of the converter. When the phase A upper bridge arm commutation fails, the fully controlled switch V43 that controls the auxiliary shutdown branch 2 of the A phase upper bridge arm is forward-conducted, and the first capacitor C42 of the auxiliary shutdown branch 2 of the A phase upper bridge arm applies Back pressure is applied to main branch 1, and the current of main branch 1 is transferred to auxiliary shutdown branch 2.

Take the A-phase upper arm in Figure 8 and Figure 12 as an example. When the A-phase first upper arm commutates to the B-phase first upper arm, at this time, if a fault occurs, the commutation may cause the capacitor auxiliary shutdown. When the commutation of the A-phase upper arm of the current converter fails, the first half-controlled switch group V45 and the full-controlled switch group V46 of the auxiliary shutdown branch 2 of the A-phase upper arm are forward-conducted, and the A-phase upper arm The first capacitor C42 of the auxiliary shutdown branch 2 applies a back pressure to the main branch 1 , and the current of the main branch 1 is transferred to the auxiliary shutdown branch 2 .

Take the A-phase upper arm in Figure 9 and Figure 10 as an example. When the A-phase first upper arm commutates to the B-phase first upper arm, at this time, if a fault occurs, the commutation may cause the capacitor auxiliary shutdown. When the commutation of the A-phase upper arm of the current converter fails, the second half-controlled switch group V47 and the full-controlled switch group V46 of the auxiliary shutdown branch 2 of the A-phase upper arm are forward-conducted, and the A-phase upper arm The first capacitor C42 of the auxiliary shutdown branch 2 applies a back pressure to the main branch 1 , and the current of the main branch 1 is transferred to the auxiliary shutdown branch 2 .

Take the A-phase upper arm as shown in Figure 13 as an example. When the A-phase first upper arm commutates to the B-phase first upper arm, at this time, if a fault occurs, it may cause the capacitor-assisted shutdown of the converter. When the phase A upper bridge arm commutation fails, the full control switch V46 and the first half control switch V49 that control the auxiliary shutdown branch 2 shared by the three upper bridge arms are forward-conducted, and the auxiliary shutdown shared by the three upper bridge arms The first capacitor C42 of branch 2 applies a back voltage to the main branch 1 of the A-phase upper arm, and the current of the main branch 1 of the A-phase upper arm is transferred to the auxiliary turn-off branch 2. Take the B-phase upper arm in Figure 13 as an example. When the B-phase first upper arm commutates to the C-phase first upper arm, at this time, if a fault occurs, the capacitor-assisted shutdown of the converter may occur. When the phase B upper bridge arm commutation fails, the full control switch V46 and the first half control switch V49 that control the auxiliary shutdown branch 2 shared by the three upper bridge arms are forward-conducted, and the auxiliary shutdown shared by the three upper bridge arms The first capacitor C42 of branch 2 applies a back voltage to the main branch 1 of the B-phase upper arm, and the current of the main branch 1 of the B-phase upper arm is transferred to the auxiliary turn-off branch 2.

In S140, after the main branch of the bridge arm circuit is turned off, the power electronic switch that controls the auxiliary shutdown branch of the bridge arm circuit is turned off in the forward direction, realizing the current transfer from the phase where the bridge arm circuit is located to another phase.

Taking the A-phase upper arm in Figure 6 and Figure 11 as an example, after the first half control valve V41 of the A-phase upper arm is turned off, it controls the power electronic switch V42 of the auxiliary shutdown branch 2 of the A-phase upper arm. Forward shutdown forces the current to change from phase A to phase B.

Taking the A-phase upper arm in Figure 7 as an example, after the first half-control valve V41 of the A-phase upper arm is turned off, the full control switch V43 of the auxiliary shutdown branch 2 of the A-phase upper arm is controlled to close forward. It cuts off and forces the current to change from phase A to phase B.

Taking the A-phase upper arm as shown in Figure 8, Figure 9, Figure 10, Figure 12 and Figure 13 as an example, after the first half control valve V41 of the A-phase upper arm is turned off, the auxiliary switch of the A-phase upper arm is controlled. The fully controlled switch V46 of branch 2 is turned off in the forward direction, forcing the current to change from phase A to phase B.

When the main branch of the bridge arm circuit is turned off, the forward current of the first half-controlled valve of the main branch of the bridge arm circuit is less than the maintaining current and the forward blocking capability is restored. Specifically, restoring the forward blocking capability refers to restoring the forward blocking capability after the forward current is less than the holding current and the shutdown time is delayed. The shutdown time is less than 700us, but it is not limited to this.

FIG. 16 is a schematic diagram of a control device of a capacitor-assisted turn-off inverter provided by an embodiment of the present application. The control device 300 includes a detection unit 310 and a control unit 320 .

The detection unit 310 is used to detect the operating parameters of the capacitor-assisted turn-off converter.

The control unit 320 controls the main branch of the bridge arm circuit of the converter to operate in the inverter state based on the operating parameters of the capacitor-assisted turn-off converter. When the bridge arm circuit ends commutation to the other bridge arm, the control unit 320 controls the bridge arm. The power electronic switch of the auxiliary shutdown branch of the circuit is reversely conductive, and the first capacitor of the auxiliary shutdown branch is reversely charged, causing the first capacitor to present a negative voltage. When a fault occurs that may cause commutation failure of the bridge arm circuit, the control unit 320 controls the power electronic switch of the auxiliary shutdown branch of the bridge arm circuit to conduct forward, so that the current of the main branch of the bridge arm circuit is transferred to the auxiliary shutdown branch. After the main branch of the bridge arm circuit is turned off, the power electronic switch that controls the auxiliary shutdown branch of the bridge arm circuit is turned off in the forward direction, realizing the current transfer from the phase where the bridge arm circuit is located to another phase.

The above embodiments are only used to illustrate the technical ideas of the present application and cannot be used to limit the scope of protection of the present application. Any changes made based on the technical ideas proposed in the present application and on the basis of the technical solutions will fall within the scope of protection of the present application. Inside.

Claims

A bridge arm circuit with capacitor-assisted turn-off, including:

The main branch includes a first semi-controlled valve, and the first semi-controlled valve includes a semi-controlled switch;

An auxiliary shutdown branch is connected in parallel with the main branch. The auxiliary shutdown branch includes a power electronic switch and a first capacitor connected in series. The power electronic switch has bidirectional flow, bidirectional controllable opening, and unidirectional flow. Controlled shutdown.
The bridge arm circuit of claim 1, wherein the main branch further includes:

The first full control valve is connected in series with the first half control valve; the first half control valve and the first full control valve are connected in parallel with arresters at both ends, and the two ends of the first full control valve are connected in parallel with the second A semi-controlled valve, the second semi-controlled valve includes a semi-controlled switch, and the first full-controlled valve includes a fully controlled switch.
The bridge arm circuit of claim 1, wherein the auxiliary turn-off branch further includes:

Resistance or/and reactance, connected in series with the power electronic switch and the first capacitor; lightning arresters are connected in parallel at both ends of the power electronic switch and the first capacitor, and the first capacitor includes at least one capacitor connected in series. element.
The bridge arm circuit of claim 1, wherein the power electronic switch includes:

At least one switch group connected in series, the switch group including a full control switch and a half control switch connected in anti-parallel.
The bridge arm circuit of claim 1, wherein the power electronic switch includes:

At least one switch group connected in series, said switch group including:

Full control switch;

An uncontrolled switch is connected in series with the fully controlled switch;

A half-controlled switch is connected in anti-parallel with the series circuit of the full-controlled switch and the uncontrolled switch.
The bridge arm circuit of claim 1, wherein the power electronic switch includes:

At least one switch group connected in series, said switch group including fully controlled switches connected in anti-parallel.
The bridge arm circuit of claim 1, wherein the power electronic switch includes:

The first semi-controlled switch group includes at least one switch group connected in series, and the switch group includes semi-controlled switches connected in anti-parallel;

A fully controlled switch group, including at least one switch group connected in series, the switch group including a fully controlled switch and an uncontrolled switch connected in anti-parallel, connected in series with the first half-controlled switch group;

The first capacitor is connected in series between the first half-controlled switch group and the full-controlled switch group or between the main branch and the first half-controlled switch group or the full-controlled switch group. .
The bridge arm circuit of claim 1, wherein the power electronic switch includes:

The second half-controlled switch group includes at least one switch group connected in series, and the switch group includes half-controlled switches and uncontrolled switches connected in anti-parallel;

A fully controlled switch group, including at least one switch group connected in series, the switch group including a fully controlled switch and an uncontrolled switch connected in anti-parallel, connected in series with the second half-controlled switch group;

The first capacitor is connected in series between the second half-controlled switch group and the full-controlled switch group or between the main branch and the second half-controlled switch group or the full-controlled switch group. .
The bridge arm circuit of claim 1, wherein the power electronic switch includes:

At least one switch group connected in series, said switch group including:

Full control switch;

No control switch;

A first semi-controlled switch is connected in series with the fully controlled switch and the uncontrolled switch;

The second half-controlled switch is connected in anti-parallel with the series circuit of the full-controlled switch, the uncontrolled switch and the first half-controlled switch.
The bridge arm circuit of claim 1, wherein the power electronic switch includes:

At least one switch group connected in series, said switch group including:

Full control switch;

The first half-controlled switch is connected in series with the full-controlled switch;

The second half-controlled switch is connected in anti-parallel with the series circuit of the full-controlled switch and the first half-controlled switch.
The bridge arm circuit of claim 5, wherein the fully controlled switch includes at least one fully controlled device connected in series, and the fully controlled device includes at least one of IGCT, IGBT, GTO, and MOSFET; and the half controlled switch The switch includes at least one semi-controlled device connected in series, and the semi-controlled device includes a thyristor; the uncontrolled switch includes at least one uncontrolled device connected in series, and the uncontrolled device includes a diode.
The bridge arm circuit of claim 1, wherein the auxiliary turn-off branch further includes:

A fast isolating switch is connected in series with the power electronic switch.
A capacitor-assisted turn-off inverter. The converter includes three-phase six bridge arms, at least one of which is the capacitor-assisted turn-off bridge arm circuit described in any one of rights 1 to 12.
The converter of claim 13, wherein the auxiliary turn-off branches of the three upper arms of the converter share a first capacitor, and the auxiliary turn-off branches of the three lower arms of the converter share a first capacitor. The broken branch circuit shares another first capacitor.
A high-voltage direct current transmission system, the high-voltage direct current transmission system comprising the capacitor-assisted turn-off inverter according to claim 13 or 14.
A control device for a capacitor-assisted turn-off converter according to claim 13 or 14. Preparation methods include:

Control the main branch of the bridge arm circuit of the converter to operate in an inverter state;

When the bridge arm circuit ends commutation to the other bridge arm, the power electronic switch controlling the auxiliary shutdown branch of the bridge arm circuit is reversely conductive, and the first capacitor of the auxiliary shutdown branch is reversely charged. , causing the first capacitor to present a negative voltage;

When a fault occurs that may cause commutation failure of the bridge arm circuit, the power electronic switch that controls the auxiliary shutdown branch of the bridge arm circuit is forward-conducted, causing the current of the main branch of the bridge arm circuit to be transferred to the auxiliary branch. Turn off the branch;

After the main branch of the bridge arm circuit is turned off, the power electronic switch that controls the auxiliary shutdown branch of the bridge arm circuit is turned off in the forward direction, realizing the current transfer from the phase where the bridge arm circuit is located to another phase. .
The control method according to claim 16, wherein the main branch of the bridge arm circuit is turned off when the forward current of the first half-controlled valve of the main branch of the bridge arm circuit is less than the maintaining current and returns to normal. blocking ability.
A control device for a capacitor-assisted turn-off inverter as claimed in claim 13 or 14, comprising:

A detection unit used to detect operating parameters and faults of the capacitor-assisted shutdown converter;

A control unit, based on the operating parameters of the capacitor-assisted turn-off converter, controls the main branch of the bridge arm circuit of the converter to operate in an inverter state; when the bridge arm circuit switches to another bridge When the arm commutation is completed, the power electronic switch controlling the auxiliary shutdown branch of the bridge arm circuit is reversely conductive, and the first capacitor of the auxiliary shutdown branch is reversely charged, causing the first capacitor to present a negative voltage. ; When a fault occurs that may cause the commutation failure of the bridge arm circuit, the power electronic switch that controls the auxiliary shutdown branch of the bridge arm circuit is forward-conducting, so that the current of the main branch of the bridge arm circuit is transferred to Auxiliary turn-off branch, after the main branch of the bridge arm circuit is turned off, the power electronic switch of the auxiliary turn-off branch of the bridge arm circuit is controlled to turn off in the forward direction, realizing that the current flows from the location of the bridge arm circuit. Phase transfer to another phase.