阅读说明：本技术 混合直流换流器故障闭锁控制方法和控制装置 (Fault locking control method and control device for hybrid direct current converter ) 是由 卢东斌 赵文强 侍乔明 王永平 于 2020-05-12 设计创作，主要内容包括：本申请提供一种混合直流换流器故障闭锁控制方法和控制装置。所述混合直流换流器包括串联连接的电流源型阀组和电压源型阀组,所述电流源型阀组包括电网换相换流器,所述电压源型阀组包括电压源换流器,当直流线路发生接地故障需要退出所述电网换相换流器时,所述方法包括：控制所述电网换相换流器投入旁通对,重启对站相应极的换流器和所述混合直流换流器的电压源换流器,如果重启成功,闭合所述电流源型阀组的旁通开关,闭锁所述电网换相换流器,隔离所述电网换相换流器,如果重启失败,闭锁所述电压源换流器,发出跳所述电压源换流器的进线开关命令,所述电压源换流器的进线开关跳开后闭合所述电流源型阀组的旁通开关。(The application provides a fault lockout control method and a fault lockout control device for a hybrid direct current converter. The hybrid direct current converter comprises a current source valve group and a voltage source valve group which are connected in series, the current source valve group comprises a power grid phase-change converter, the voltage source valve group comprises a voltage source converter, and when a direct current line has a ground fault and needs to exit the power grid phase-change converter, the method comprises the following steps: controlling the power grid phase change converter to be put into a bypass pair, restarting the converter of the corresponding pole of the opposite station and the voltage source converter of the hybrid direct current converter, if the restart is successful, closing a bypass switch of the current source type valve bank, locking the power grid phase change converter, isolating the power grid phase change converter, if the restart is failed, locking the voltage source converter, sending a command of tripping an incoming line switch of the voltage source converter, and closing the bypass switch of the current source type valve bank after the incoming line switch of the voltage source converter is tripped.)

1. A method of fault lockout control for a hybrid dc converter including a current source valve bank and a voltage source valve bank connected in series, the current source valve bank including a grid commutated converter and the voltage source valve bank including a voltage source converter, for use in situations where a ground fault in a dc link requires exiting the grid commutated converter or where a ground fault in the current source valve bank requires exiting the grid commutated converter, the method comprising:

if the direct current line has a ground fault, controlling the power grid commutation converter to be put into a bypass pair, and restarting a converter of a corresponding pole of the opposite station and a voltage source converter of the hybrid direct current converter;

and if the current source type valve group has a ground fault, sending a command of tripping the incoming line switch of the power grid phase change converter, controlling the power grid phase change converter to be put into a bypass pair, locking the voltage source converter and sending the command of tripping the incoming line switch of the voltage source converter.

2. The method of claim 1, wherein, when the reboot is successful,

closing a bypass switch of the current source type valve group, locking the power grid phase-change converter and isolating the power grid phase-change converter;

or controlling the converters of the corresponding poles of the pair of stations and the voltage source converter of the hybrid direct current converter to continue to operate.

3. The method of claim 2, wherein,

and controlling bypass pairs of each bridge arm of the power grid commutation converter to be conducted in turn when the converters of the corresponding poles of the pair stations and the voltage source converter of the hybrid direct current converter are controlled to continuously operate.

4. The method of claim 1, wherein upon a restart failure, the voltage source converter is latched, a trip of a line switch command of the voltage source converter is issued, and a bypass switch of the current source valve block is closed after the line switch of the voltage source converter trips open.

5. The method of claim 1, wherein an incoming switch of the voltage source converter trips to close a bypass switch of the current source valve bank.

6. The method of claim 1, wherein a cathode of the current source valve block is connected to a positive pole of the voltage source valve block or an anode of the current source valve block is connected to a negative pole of the voltage source valve block.

7. The method of claim 1, wherein the current source valve block takes the form of either:

a power grid commutation converter;

the power grid commutation converter and the bypass switch are connected in parallel;

the power grid commutation converter is connected with the bypass switch in parallel, two ends of the power grid commutation converter after the parallel connection are respectively connected with one ends of the two isolation switches, and two ends of the bypass switch are respectively connected with the other ends of the two isolation switches.

8. The method according to claim 1, wherein the grid commutation converter adopts a six-pulse bridge circuit, a twelve-pulse bridge circuit or a circuit composed of a plurality of six-pulse bridge circuits connected in series, and the circuit is composed of non-turn-off semi-controlled power semiconductors.

9. The method of claim 8, wherein the non-turn-off, semi-controlled power semiconductor is a thyristor.

10. The method of claim 1, wherein the voltage source valve block takes the form of any one of:

type I: a single voltage source converter or two or more voltage source converters are connected in parallel;

type II: a single voltage source converter or two or more voltage source converters are connected in parallel and a bypass switch, wherein the voltage source converters are connected with the bypass switch in parallel;

type III: the device comprises a single voltage source converter or two or more voltage source converters connected in parallel, a bypass switch, a bypass disconnecting link and two isolation disconnecting links, wherein the voltage source converter is connected with the bypass switch in parallel, two ends of the voltage source converter after the voltage source converter is connected with the bypass switch in parallel are respectively connected with one ends of the two isolation disconnecting links, and two ends of the bypass disconnecting link are respectively connected with the other ends of the two isolation disconnecting links.

11. The method of claim 10, wherein the voltage source valve bank further comprises a current limiting reactor in series with the voltage source converter for type I, type II, type III, or a current limiting reactor, a bypass switch in series with the current limiting reactor for type II, type III.

12. The method of claim 1, wherein the voltage source converter employs a two-level converter, a diode-clamped multi-level converter, a modular multi-level converter, MMC, a hybrid multi-level converter, HMC, a two-level cascaded converter, CSL, or a stacked two-level converter, CTL; the modular multilevel converter MMC is a modular multilevel converter formed by half-bridge sub-modules, or a modular multilevel converter formed by full-bridge sub-modules, or a modular multilevel converter formed by mixing half-bridge sub-modules and full-bridge sub-modules.

13. The method according to claim 12, wherein the half-bridge sub-module or the full-bridge sub-module of the modular multilevel converter MMC is provided with a bypass switch or a thyristor, and the bypass switch or the thyristor is connected in parallel to two ends of the half-bridge sub-module or the full-bridge sub-module for bypassing the half-bridge sub-module or the full-bridge sub-module.

14. The method according to claim 12, wherein the half-bridge sub-modules of the modular multilevel converter MMC are further provided with protection thyristors connected in parallel across the half-bridge sub-modules protecting the inverse diodes of the turn-off fully controlled power semiconductors connected in parallel therewith.

15. The method according to claim 1, wherein the voltage source converter is made of a turn-off fully controlled Power semiconductor using insulated gate bipolar transistors IGBT, integrated gate commutated thyristors IGCT, turn-off thyristors GTO, Power field effect transistors Power MOSFET, electron injection enhanced gate transistors IEGT, gate commutated thyristors GCT or silicon carbide enhanced junction field effect transistors SiC-JFET.

16. The method of claim 1, wherein the dc link is at ground fault, as determined by a link fault amount or a traveling wave protection action.

17. The method of claim 1, wherein the current source valve set is ground faulted as determined by inverter differential protection action.

18. The method of claim 1, wherein if said hybrid dc converter includes a diode bank that prevents a voltage source converter from flowing reverse current, said diode bank that prevents a voltage source converter from flowing reverse current is engaged prior to closing a bypass switch of said current source bank if the restart is successful.

19. The method of claim 1, wherein the isolating the grid commutated converter is a bypass switch closing a current source valve set, opening two isolation switches.

20. A hybrid dc converter fault lockout control device for controlling a hybrid dc converter according to the hybrid dc converter fault lockout control method of any one of claims 1 to 19, the device comprising:

the detection unit is used for detecting the polar bus voltage, the polar bus current, the polar neutral bus voltage and the polar neutral bus current of the hybrid direct current converter and detecting the high-voltage bus current and the low-voltage bus current of the current source type valve bank;

the control unit is used for controlling the power grid commutation converter to be put into a bypass pair and restarting a converter of a corresponding pole of a station and a voltage source converter of the hybrid direct current converter when the line sudden change protection action or the traveling wave protection action of the direct current line is detected and the primary voltage restart is unsuccessful; and when detecting the converter differential protection action of the current source type valve group, sending an incoming line switch command for tripping the power grid phase change converter, controlling the power grid phase change converter to be put into a bypass pair, locking the voltage source converter and sending an incoming line switch command for tripping the voltage source converter.

21. The apparatus of claim 20, wherein upon a successful restart, closing a bypass switch of the current source valve bank, latching the grid commutated converter, isolating the grid commutated converter, upon a failed restart, latching the voltage source converter, issuing a line switch trip command to the voltage source converter, and upon a trip closing a bypass switch of the current source valve bank.

22. The apparatus of claim 20, wherein an incoming switch of the voltage source converter trips to close a bypass switch of the current source valve bank.

Technical Field

The application relates to the technical field of hybrid direct-current power transmission, in particular to a fault blocking control method and a fault blocking control device for a hybrid direct-current converter.

Background

The thyristor-based current source type high-voltage direct-current transmission has the advantages that the loss of a converter is small, and a direct-current system can be restarted by phase shifting when a direct-current line fault occurs. The inverter side converter works in active inversion and can not be connected to a passive system. The inversion side is connected into a weak alternating current system and phase commutation failure is easy to occur after disturbance occurs. The reactive power consumption is large, the harmonic content of voltage and current is high, and a filtering device is required to be installed to provide reactive power and filtering. The direct current transmission based on the voltage source converter has the advantages of high controllability, access to a passive system and no need of a reactive power compensation device. The defects are that the switching loss of the converter is large, the modularized multi-level converter adopting a half-bridge structure cannot control the fault current when the direct current side fails, and the fault can be removed only by disconnecting the circuit breaker on the alternating current side after the fault occurs.

For the direct current side fault, the ABB company adopts a direct current breaker added with a direct current line to solve the direct current side fault, but the direct current breaker has high cost and the reliability needs to be verified. For direct current side faults, siemens corporation adopts a modular multilevel converter with a full-bridge circuit structure to solve the problems, but the converter with the full-bridge circuit structure has large loss. For the direct current side fault, the alstonia company adopts a full bridge circuit and a bridge arm to be connected with a power electronic switching device in series to solve the problem, but the reliability is still to be verified. For direct current side faults, the problem is solved by serially connecting diodes in a main loop, but the diodes do not participate in power conversion and generate loss.

For direct current side faults, south rui relay protection company provides a hybrid direct current converter with a bypass branch circuit and a power grid commutation converter connected in series with a voltage source converter, the voltage source converter only needs a modular multilevel converter with a half-bridge circuit structure, the power grid commutation converter can naturally block direct current side fault current, the bypass branch circuit can reliably protect the voltage source converter, and the operation mode is more flexible. When a direct-current line ground fault occurs in a direct-current power transmission system where the hybrid direct-current converter is located and the power grid phase-change converter needs to be withdrawn, or when the current source type valve bank has a ground fault and the power grid phase-change converter needs to be withdrawn, a traditional locking strategy may have the problem that a voltage source type valve bank discharges to a fault point, so that the fault expansion risk is caused.

Disclosure of Invention

According to one aspect of the present application, there is provided a method of fault blocking control for a hybrid dc converter comprising a series connection of a current source valve bank and a voltage source valve bank, the current source valve bank comprising a grid commutated converter and the voltage source valve bank comprising a voltage source converter, the method being for use in situations where a dc link ground fault requires exiting the grid commutated converter or where the current source valve bank ground fault requires exiting the grid commutated converter, the method comprising:

if the direct current line has a ground fault, controlling the power grid commutation converter to be put into a bypass pair, and restarting a converter of a corresponding pole of the opposite station and a voltage source converter of the hybrid direct current converter;

and if the current source type valve group has a ground fault, sending a command of tripping the incoming line switch of the power grid phase change converter, controlling the power grid phase change converter to be put into a bypass pair, locking the voltage source converter and sending the command of tripping the incoming line switch of the voltage source converter.

According to some embodiments, when the restart is successful, closing a bypass switch of the current source type valve group, locking the grid commutation converter and isolating the grid commutation converter; or controlling the converters of the corresponding poles of the pair of stations and the voltage source converter of the hybrid direct current converter to continue to operate.

According to some embodiments, the voltage source converters of the station-to-station corresponding poles and the hybrid direct current converter are controlled to operate continuously, and bypass pairs of each bridge arm of the grid commutation converter are controlled to be conducted in turn. According to some embodiments, when the restart fails, the voltage source converter is locked, a trip command of the incoming line switch of the voltage source converter is sent, and the incoming line switch of the voltage source converter is tripped to close the bypass switch of the current source type valve group.

According to some embodiments, wherein the incoming switch of the voltage source converter trips to close the bypass switch of the current source valve block.

According to some embodiments, wherein the cathode of the current source valve block is connected to the anode of the voltage source valve block, or the anode of the current source valve block is connected to the cathode of the voltage source valve block.

According to some embodiments, wherein the current source valve block takes any of the following forms:

a power grid commutation converter;

the power grid commutation converter and the bypass switch are connected in parallel;

the power grid commutation converter is connected with the bypass switch in parallel, two ends of the power grid commutation converter after the parallel connection are respectively connected with one ends of the two isolation switches, and two ends of the bypass switch are respectively connected with the other ends of the two isolation switches.

According to some embodiments, the grid commutation converter adopts a six-pulse bridge circuit, a twelve-pulse bridge circuit or a circuit formed by connecting a plurality of six-pulse bridge circuits in series, and the six-pulse bridge circuit is composed of non-turn-off semi-controlled power semiconductors.

According to some embodiments, wherein the non-turn-off semi-controlled power semiconductor is a thyristor.

According to some embodiments, wherein the voltage source valve block takes any of the following forms:

type I: a single voltage source converter or two or more voltage source converters are connected in parallel;

type II: a single voltage source converter or two or more voltage source converters are connected in parallel and a bypass switch, wherein the voltage source converters are connected with the bypass switch in parallel;

type III: the device comprises a single voltage source converter or two or more voltage source converters connected in parallel, a bypass switch, a bypass disconnecting link and two isolation disconnecting links, wherein the voltage source converter is connected with the bypass switch in parallel, two ends of the voltage source converter after the voltage source converter is connected with the bypass switch in parallel are respectively connected with one ends of the two isolation disconnecting links, and two ends of the bypass disconnecting link are respectively connected with the other ends of the two isolation disconnecting links.

According to some embodiments, wherein the voltage source valve group further comprises a current limiting reactor in series with the voltage source converter for type I, type II, type III, or a current limiting reactor, a bypass switch in series with the current limiting reactor for type II, type III.

According to some embodiments, wherein the voltage source converter employs a two-level converter, a diode-clamped multi-level converter, a modular multi-level converter MMC, a hybrid multi-level converter HMC, a two-level cascaded converter CSL, or a stacked two-level converter CTL; the modular multilevel converter MMC is a modular multilevel converter formed by half-bridge sub-modules, or a modular multilevel converter formed by full-bridge sub-modules, or a modular multilevel converter formed by mixing half-bridge sub-modules and full-bridge sub-modules.

According to some embodiments, the half-bridge sub-module or the full-bridge sub-module of the modular multilevel converter MMC is provided with a bypass switch or a thyristor, and the bypass switch or the thyristor is connected in parallel with two ends of the half-bridge sub-module or the full-bridge sub-module and is used for bypassing the half-bridge sub-module or the full-bridge sub-module.

According to some embodiments, the half-bridge submodule of the modular multilevel converter MMC is further provided with a protection thyristor, the protection thyristor is connected in parallel with two ends of the half-bridge submodule to protect a reverse diode of a turn-off fully-controlled power semiconductor connected in parallel with the protection thyristor.

According to some embodiments, the voltage source converter is composed of a turn-off fully-controlled Power semiconductor using an insulated gate bipolar transistor IGBT, an integrated gate commutated thyristor IGCT, a turn-off thyristor GTO, a Power field effect transistor Power MOSFET, an electron injection enhanced gate transistor IEGT, a gate commutated thyristor GCT or a silicon carbide enhanced junction field effect transistor SiC-JFET.

According to some embodiments, wherein the dc link is at ground fault, the determination is made by a link break amount or a travelling wave protection action.

According to some embodiments, the current source valve set is grounded and judged by an inverter differential protection action.

According to some embodiments, if the hybrid dc converter comprises a diode valve set for preventing the reverse current from flowing through the voltage source converter, if the restart is successful, the diode valve set for preventing the reverse current from flowing through the voltage source converter is switched on before a bypass switch of the current source type valve set is closed.

According to some embodiments, wherein the isolating the grid commutated converter is a bypass switch closing a current source valve group, opening two isolation switches.

According to another aspect of the present application, there is provided a hybrid dc converter fault lockout control apparatus for controlling a hybrid dc converter according to a hybrid dc converter fault lockout control method, the apparatus including:

the detection unit is used for detecting the polar bus voltage, the polar bus current, the polar neutral bus voltage and the polar neutral bus current of the hybrid direct current converter and detecting the high-voltage bus current and the low-voltage bus current of the current source type valve bank;

the control unit is used for controlling the power grid commutation converter to be put into a bypass pair and restarting a converter of a corresponding pole of a station and a voltage source converter of the hybrid direct current converter when the line sudden change protection action or the traveling wave protection action of the direct current line is detected and the primary voltage restart is unsuccessful; and when detecting the converter differential protection action of the current source type valve group, sending an incoming line switch command for tripping the power grid phase change converter, controlling the power grid phase change converter to be put into a bypass pair, locking the voltage source converter and sending an incoming line switch command for tripping the voltage source converter.

According to some embodiments, when the restart is successful, the bypass switch of the current source type valve group is closed, the grid commutation converter is locked, the grid commutation converter is isolated, when the restart fails, the voltage source converter is locked, a line incoming switch command for tripping the voltage source converter is issued, and the bypass switch of the current source type valve group is closed after the line incoming switch of the voltage source converter is tripped.

According to some embodiments, wherein the incoming switch of the voltage source converter trips to close the bypass switch of the current source valve block.

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 are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1A is one of topology structures of a hybrid dc converter according to an embodiment of the present disclosure, in which a current source type valve set unit and a voltage source type valve set unit are connected;

fig. 1B is a second topology structure diagram of a hybrid dc converter according to an embodiment of the present invention, in which a current source type valve set unit and a voltage source type valve set unit are connected;

fig. 2 is a high-voltage direct-current transmission device with a current source type valve bank unit on a rectification side and two mixed direct-current converters on an inversion side;

fig. 3 is a schematic flowchart of a fault lockout control method for a hybrid dc converter in case of a dc line fault according to an embodiment of the present application;

fig. 4 is a schematic flowchart of a method for controlling a fault lockout of a hybrid dc converter when a current source valve group fails according to an embodiment of the present disclosure;

fig. 5 is another high-voltage direct-current transmission device with a current source type valve group unit on the rectifying side and a hybrid direct-current converter consisting of two types on the inverting side;

fig. 6 is a fault lockout control device for a hybrid dc converter according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be understood that the terms "first," "second," "third," and the like in the claims, the description, and the drawings of the present application are used for distinguishing between different objects and not for describing a particular order. The term "comprises/comprising" when used in the specification and claims of this application is taken to specify the presence of stated features, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Fig. 1A to fig. 1B are two topologies of a hybrid dc converter in which a current source valve group and a voltage source valve group are connected in series according to an embodiment of the present application: the hybrid direct current converter topological structure I and the hybrid direct current converter topological structure II.

Fig. 1A shows a first topology of a hybrid dc converter, in which a cathode X1 of a current source valve set is connected to an anode X3 of a voltage source valve set. The hybrid DC converter comprises a current source type valve bank and a voltage source type valve bank which are connected in series. The current source type valve group comprises a power grid commutation converter 1, a bypass switch 3, a bypass disconnecting link 4 and two isolation disconnecting links 5 and 6, wherein the power grid commutation converter 1 is connected with the bypass switch 3 in parallel, two ends of the power grid commutation converter 1 after being connected in parallel are respectively connected with one ends of the two isolation disconnecting links 5 and 6, and two ends of the bypass disconnecting link 4 are respectively connected with the other ends of the two isolation disconnecting links 5 and 6. The voltage source type valve group comprises a voltage source converter 2, a bypass switch 7, a bypass disconnecting link 8, two isolation disconnecting links 9 and 10 and a current-limiting reactor 11, wherein the voltage source converter is connected with the bypass switch 7 in parallel, two ends of the voltage source converter after being connected in parallel are respectively connected with one ends of the two isolation disconnecting links 9 and 10, and two ends of the bypass disconnecting link 8 are respectively connected with the other ends of the two isolation disconnecting links 9 and 10.

The power grid commutation converter 1 comprises at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit, wherein the pulse bridge circuit comprises a non-turn-off semi-controlled power semiconductor device, and generally adopts a thyristor.

The voltage source converter 2 comprises at least one of a two-level converter, a diode clamping type multi-level converter, a modular multi-level converter MMC, a hybrid multi-level converter HMC, a two-level cascade converter CSL and a stacking type two-level converter CTL, wherein the converter comprises a turn-off fully-controlled power semiconductor device.

If the anode X2 of the current source type valve bank is connected with the polar bus, the cathode X4 of the voltage source type valve bank is connected with the polar neutral bus; the isolation disconnecting link 5 is used for connecting the power grid commutation converter 1 and the voltage source type valve bank; the isolation disconnecting link 6 is used for connecting the power grid commutation converter 1 and the pole bus; the isolation knife switch 9 is used for connecting the voltage source converter 2 and the current source valve group; the isolation switch 10 is used to connect the voltage source converter 2 to the pole neutral bus. If the anode X2 of the current source type valve bank is connected with the polar neutral bus, the cathode X4 of the voltage source type valve bank is connected with the polar bus; the isolation disconnecting link 5 is used for connecting the power grid commutation converter 1 and the voltage source type valve bank; the isolation disconnecting link 6 is used for connecting the power grid commutation converter 1 and the polar neutral bus; the isolation knife switch 9 is used for connecting the voltage source converter 2 and the current source valve group; the isolation switch 10 is used to connect the voltage source converter 2 with the pole bus.

Fig. 1B shows a topology of a hybrid dc converter, in which an anode X2 of a current source type valve set is connected to a cathode X4 of a voltage source type valve set. The hybrid DC converter comprises a current source type valve bank and a voltage source type valve bank which are connected in series. The current source type valve group comprises a power grid commutation converter 21, a bypass switch 23, a bypass disconnecting link 24 and two isolation disconnecting links 25 and 26, wherein the power grid commutation converter 21 and the bypass switch 23 are connected in parallel, two ends of the parallel connection are respectively connected with one ends of the two isolation disconnecting links 25 and 26, and two ends of the bypass disconnecting link 24 are respectively connected with the other ends of the two isolation disconnecting links 25 and 26. The voltage source type valve group comprises a voltage source converter 22, a bypass switch 27, a bypass disconnecting link 28, two isolation disconnecting links 29 and 30 and a current-limiting reactor 31, wherein the voltage source converter and the bypass switch 27 are connected in parallel, two ends of the parallel connection are respectively connected with one ends of the two isolation disconnecting links 29 and 30, and two ends of the bypass disconnecting link 28 are respectively connected with the other ends of the two isolation disconnecting links 29 and 30.

The grid commutation converter 21 comprises at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit, wherein the pulse bridge circuit comprises a non-turn-off semi-controlled power semiconductor device, and generally adopts a thyristor.

The voltage source converter 22 includes at least one of a two-level converter, a diode-clamped multi-level converter, a modular multi-level converter MMC, a hybrid multi-level converter HMC, a two-level cascaded converter CSL, and a stacked two-level converter CTL, which includes a turn-off fully-controlled power semiconductor device.

If the cathode X1 of the current source type valve bank is connected with the polar bus, the anode X3 of the voltage source type valve bank is connected with the polar neutral bus; the isolation disconnecting link 25 is used for connecting the power grid commutation converter 21 and the voltage source type valve bank; the isolation disconnecting link 26 is used for connecting the power grid commutation converter 21 and the pole bus; the isolation knife switch 29 is used for connecting the voltage source converter 22 and the current source valve group; the isolation switch 30 is used to connect the voltage source converter 22 to the pole neutral bus. If the cathode X1 of the current source type valve bank is connected with the polar neutral bus, the anode X3 of the voltage source type valve bank is connected with the polar bus; the isolation disconnecting link 25 is used for connecting the power grid commutation converter 1 and the voltage source type valve bank; the isolation disconnecting link 26 is used for connecting the power grid commutation converter 21 and the polar neutral bus; the isolation knife switch 29 is used for connecting the voltage source converter 22 and the current source valve group; the isolation switch 30 is used to connect the voltage source converter 22 to the pole bus.

Fig. 2 is an embodiment of a high voltage direct current transmission apparatus with a current source type valve group unit on a rectification side and a hybrid direct current converter composed of the two types of the direct current converters in fig. 1 on an inversion side.

The high-voltage direct-current transmission device consists of a rectifying station 90, an inverter station 80, a pole I direct-current line 100 and a pole II direct-current line 101.

The main loop of the rectification station 90 of the high-voltage direct-current transmission device consists of a pole I40, a pole II60, a converter transformer 54, a converter transformer 55, a converter transformer 74, a converter transformer 75, an incoming line switch 56, an incoming line switch 57, an incoming line switch 76, an incoming line switch 77, an alternating-current system 91, an alternating-current filter isolating switch 97, an alternating-current filter 98 and a grounding pole line 94; the pole I40 consists of a topological structure formed by connecting two current source type valve banks in series, a smoothing reactor 52 and a direct current filter 53, the current source type valve bank positioned at the high end consists of a power grid commutation converter 41, a bypass switch 43, a bypass disconnecting link 44, an isolation disconnecting link 45 and an isolation disconnecting link 46, and the current source type valve bank positioned at the low end consists of a power grid commutation converter 42, a bypass switch 47, a bypass disconnecting link 48, an isolation disconnecting link 49 and an isolation disconnecting link 50; the pole II60 is composed of a topology structure in which two current source type valve sets are connected in series, a smoothing reactor 72 and a dc filter 73, the current source type valve set located at the high end is composed of a grid commutation converter 61, a bypass switch 63, a bypass switch 64, an isolation switch 65 and an isolation switch 66, and the current source type valve set located at the low end is composed of a grid commutation converter 62, a bypass switch 67, a bypass switch 68, an isolation switch 69 and an isolation switch 70. It is noted that the ac system is three-phase, however only one phase is shown in fig. 3 for clarity.

The inverter station 80 of the hvdc transmission system is composed of the topology shown in fig. 1A and the topology shown in fig. 1B, respectively, as a converter for pole I87 and a converter for pole II 88. The main loop of the inverter station 80 consists of a pole I87, a pole II88, a converter transformer 14, a converter transformer 15, a converter transformer 34, a converter transformer 35, a line incoming switch 16, a line incoming switch 17, a line incoming switch 36, a line incoming switch 37, an alternating current system 81 and a grounding pole line 84; the pole I87 is composed of a topological structure formed by connecting a current source type valve bank and a voltage source type valve bank in series, a smoothing reactor 12 and a direct current filter 13, the current source type valve bank is connected with the direct current filter 13 in parallel, the current source type valve bank positioned at the high end is composed of a power grid commutation converter 1, a bypass switch 3, a bypass disconnecting link 4, an isolation disconnecting link 5 and an isolation disconnecting link 6, and the voltage source type valve bank positioned at the low end is composed of a voltage source converter 2, a bypass switch 7, a bypass disconnecting link 8, an isolation disconnecting link 9, an isolation disconnecting link 10 and a current limiting reactor 11; the pole II88 is composed of a topological structure formed by connecting a current source type valve bank and a voltage source type valve bank in series, a smoothing reactor 32 and a direct current filter 33, the current source type valve bank is connected with the direct current filter 33 in parallel, the current source type valve bank positioned at the high end is composed of a power grid commutation converter 21, a bypass switch 23, a bypass disconnecting link 24, an isolation disconnecting link 25 and an isolation disconnecting link 26, and the voltage source type valve bank positioned at the low end is composed of a voltage source converter 22, a bypass switch 27, a bypass disconnecting link 28, an isolation disconnecting link 29, an isolation disconnecting link 30 and a current limiting reactor 31.

Under normal working conditions, when the bipolar full valve group operates, all the incoming switches are in the closed position, the bypass knife switch 44, the bypass knife switch 48, the bypass switch 43 and the bypass switch 47 of the first 90-pole I40 station are in the open position, and the isolating switch 45, the isolating switch 49, the isolating switch 50 and the isolating switch 46 are in the closed position; the bypass knife switch 64, the bypass knife switch 68, the bypass switch 63 and the bypass switch 67 of the station I90-pole II60 are in open positions, and the isolating switch 65, the isolating switch 69, the isolating switch 70 and the isolating switch 66 are in closed positions; the bypass knife switch 4, the bypass knife switch 8, the bypass switch 3 and the bypass switch 7 of the station two 80 poles I87 are in open positions, and the isolating switch 5, the isolating switch 9, the isolating switch 10 and the isolating switch 6 are in closed positions; the bypass knife switch 24, the bypass knife switch 28, the bypass switch 23 and the bypass switch 27 of the station two 80 poles II88 are in open positions, and the isolating switch 25, the isolating switch 29, the isolating switch 30 and the isolating switch 26 are in closed positions.

When power is transmitted positively, the power grid commutation converter of the station I90 converts alternating current of the alternating current system 91 into direct current, the direct current power is transmitted to the station II 80 through the direct current lines 100 and 101, and the power grid commutation converter and the voltage source converter of the station II 80 convert the direct current into alternating current to be output to the alternating current system 81, so that the high-voltage direct current power transmission function is realized.

The analog signals collected by the rectification station 90 are: a pole bus voltage UDL of the pole bus 92 of the pole I, a pole bus current IDL of the pole bus 92, a pole neutral bus voltage UDN of the pole neutral bus 93, and a pole neutral bus current IDNC of the pole neutral bus 93; a pole bus voltage UDL of pole bus 96 of pole II, a pole bus current IDL of pole bus 96, a pole neutral bus voltage UDN of pole neutral bus 95, and a pole neutral bus current IDNC of pole neutral bus 95. The analog signals collected by the inverter station 80 are: a pole bus voltage UDL of the pole bus 82 of pole I, a pole bus current IDL of the pole bus 82, a pole neutral bus voltage UDN of the pole neutral bus 83 and a pole neutral bus current IDNC of the pole neutral bus 83, a high voltage bus current IDC1P of the high voltage bus 18 on the dc side of the grid commutated converter and a low voltage bus current IDC1N of the low voltage bus 19; pole bus voltage UDL of pole bus 86 of pole II, pole bus current IDL of pole bus 86, pole neutral bus voltage UDN of pole neutral bus 85 and pole neutral bus current IDNC of pole neutral bus 85, high voltage bus current IDC1P of high voltage bus 38 on the dc side of the grid commutated converter and low voltage bus current IDC1N of low voltage bus 39.

Fig. 3 shows the fault lockout control method of the hybrid dc converter with the dc line having the ground fault according to the present invention.

The occurrence of the earth fault of the direct current line is judged through the line break variable or/and the traveling wave protection action. The line sudden change protection action criterion is as follows.

dUDL/dt<dUDL_set，

|UDL|<UDL_set。

And dUDL/dt is a direct-current voltage sudden change in unit time, dUDL _ set is a fixed value of the direct-current voltage sudden change, UDL is a pole bus voltage, and UDL _ set is a fixed value of the direct-current voltage.

When the pole I full valve group operates, when the direct current line 91 has an earth fault and the primary voltage restart is unsuccessful, and the voltage reduction restart of the exiting power grid commutation converter 1 is adopted, the fault locking control method of the hybrid direct current converter comprises the following procedures.

In S110, the grid commutated converter 1 is controlled to be put into the bypass pair.

Specifically, the grid commutated converter 1 is controlled to be put into a bypass pair, which is a bypass path formed by two commutation arms connecting the same ac terminal in a commutation bridge.

Optionally, the grid commutated converter 41 of control station one 90-pole I40 is taken out of operation.

In S120, the voltage source converters of the corresponding poles of the opposite station and the hybrid dc converter are restarted.

Specifically, the grid commutation converter 42 of the station I90 pole I40 is restarted, and the voltage source converter 2 of the station II 80 pole I87 is restarted in a matched mode, so that the voltage and the current are established in the pole I of the direct-current transmission system.

When the restart is successful, step S130 is performed.

In S130, the bypass switch of the current source valve block is closed.

In particular, the bypass switch 3 of the current source valve group is closed.

In S140, the grid commutated converter is blocked.

In particular, the grid commutated converter 1 is blocked, i.e. the triggering pulse of the converter is stopped.

In S150, the grid commutated converter is isolated.

Specifically, the bypass knife switch 4 of the current source type valve group is closed, and the isolation knife switch 5 and the isolation knife switch 6 are opened.

Or, when the restart is successful, the steps S130 to S150 are not executed, and the voltage source converters of the corresponding poles of the opposite station and the hybrid direct current converter are controlled to continuously operate. Specifically, bypass pairs of each bridge arm of the power grid commutation converter are controlled to be conducted in turn.

When the restart fails, step S160 is performed.

In S160, the voltage source converter is latched.

In particular, the voltage source converter 2 is latched, i.e. the trigger pulse of the converter is deactivated.

In S170, an incoming switching command to trip the voltage source converter is issued.

Specifically, the incoming switch 17 command to trip the voltage source converter 2 is issued.

In S180, the incoming switch of the voltage source converter is tripped and then the bypass switch of the current source valve set is closed.

Specifically, the incoming switch 17 of the voltage source converter 2 trips and closes the bypass switch 3 of the current source valve block.

Fig. 4 shows the fault lockout control method of the hybrid dc converter with the current source type valve set having ground fault according to the invention.

The occurrence of the ground fault of the current source type valve group is judged through the current converter differential protection action of the current source type valve group, and the criterion formula of the current converter differential protection action is as follows.

IDiff_v＝|IDC1P–IDC1N|，

IRes_v＝|IDC1P+IDC1N|/2，

IDiff_v>max(Iv_set,kv_set×IRes_v)。

The method comprises the following steps that IDC1P is high-voltage bus current on the direct current side of the power grid commutation converter, IDiff _ v is low-voltage bus current on the direct current side of the power grid commutation converter, IRes _ v is an absolute value of an average value of the high-voltage bus current and the low-voltage bus current on the direct current side of the power grid commutation converter, Iv _ set is a starting current fixed value, a value range is 0.002 times of rated high-voltage bus current or low-voltage bus current according to the fact that the value is larger than a measurement error, kv _ set is a ratio coefficient, and the value is 0.03-0.5.

When the pole I full valve group operates and when the current source type valve group has a ground fault and needs to exit the power grid phase-change converter 1, the fault locking control method of the hybrid direct current converter comprises the following procedures.

And if the current source type valve bank has a ground fault, tripping an incoming line switch of the power grid phase change converter, controlling the power grid phase change converter to be put into a bypass pair, locking the voltage source converter, tripping an incoming line switch of the voltage source converter, and closing a bypass switch of the current source type valve bank after the incoming line switch of the voltage source converter is tripped.

In S210, an incoming switching command of the grid jumper commutation converter is issued.

In particular, the incoming switch 16 command of the jumper commutation converter 1 is issued.

In S220, the grid commutated converter is controlled to be thrown into the bypass pair.

Specifically, the grid commutated converter 1 is controlled to be put into a bypass pair, which is a bypass path formed by two commutation arms connecting the same ac terminal in a commutation bridge.

In S230, the voltage source converter is latched.

In particular, the voltage source converter 2 is latched, i.e. the trigger pulse of the converter is deactivated.

In S240, an incoming switching command to trip the voltage source converter is issued.

Specifically, the incoming switch 17 command to trip the voltage source converter 2 is issued.

After S240, the bypass switch of the current source valve group may be closed after the incoming switch of the voltage source converter is tripped.

Specifically, the incoming switch 17 of the voltage source converter 2 trips and closes the bypass switch 3 of the current source valve block.

Fig. 5 is a schematic diagram of another embodiment of a high-voltage dc transmission device with a current source type valve set unit on the rectification side and a hybrid dc converter composed of the two dc converters in fig. 1 on the inversion side, wherein an inversion side pole I87 bridges an isolation switch 112 and a diode valve set 113 between a high-voltage bus 111 and a pole bus on the dc side of the voltage source converter, and a cathode of the diode valve set 113 is a common connection end with an anode of the voltage source converter 2; the inversion side pole II88 is connected across the isolation switch 122 and the diode valve set 123 between the high voltage bus 121 and the pole bus on the dc side of the voltage source converter, and the anode of the diode valve set 123 and the cathode of the voltage source converter 22 are a common connection end.

When the full valve group of the pole I operates, the isolation knife switch 112 is in the open position. When the dc line 91 has a ground fault and needs to exit the grid commutated converter 1, the hybrid dc converter fault lockout control method of fig. 3 performs the following process between S120 and S130:

a diode bank is provided for preventing the reverse current from flowing through the voltage source inverter.

Specifically, if the pole bus voltage UDL of the pole bus 82 and the high voltage bus voltage UDM on the dc side of the voltage source converter are equal to or less than the allowable closing voltage of the isolation switch 112, the isolation switch 112 is closed, separating the isolation switch 6.

Fig. 6 shows a hybrid dc converter fault blocking control apparatus 130 according to the present application, which is used for implementing hybrid dc converter fault blocking. Comprises a detection unit 131 and a control unit 132.

A detection unit 131, configured to detect a pole bus voltage UDL, a pole bus current IDL, a pole neutral bus voltage UDN, and a pole neutral bus current IDNC of the hybrid dc converter, and detect a high-voltage bus current IDC1P and a low-voltage bus current IDC1N on the dc side of the grid commutated converter;

the control unit 132 is used for controlling the power grid commutation converter to be put into a bypass pair when the line abrupt change protection action or the traveling wave protection action of the direct-current line is detected and the primary voltage restart is unsuccessful, restarting a voltage source converter of a converter and a hybrid direct-current converter of corresponding poles of the opposite station, closing a bypass switch of the current source type valve bank if the restart is successful, locking the power grid commutation converter, isolating the power grid commutation converter, locking the voltage source converter if the restart is failed, sending an incoming line switch command of a voltage source converter, and closing the bypass switch of the current source type valve bank after the incoming line switch of the voltage source converter is tripped; when the differential protection action of the current source type valve group converter is detected, an incoming line switch command of the grid-skipping phase-change current converter is sent out, the grid-skipping phase-change current converter is controlled to be put into a bypass pair, the voltage source current converter is locked, an incoming line switch command of the voltage source current converter is sent out, and a bypass switch of the current source type valve group is closed after the incoming line switch of the voltage source current converter is tripped.

The foregoing detailed description of the embodiments of the present application has been presented to illustrate the principles and implementations of the present application, and the description of the embodiments is only intended to facilitate the understanding of the methods and their core concepts of the present application. Meanwhile, a person skilled in the art should, according to the idea of the present application, change or modify the embodiments and applications of the present application based on the scope of the present application. In view of the above, the description should not be taken as limiting the application.