Full-bridge circuit off-grid converter and control method and device and system thereof

Abstract

The application provides a full-bridge circuit off-grid commutation converter and a control method and device thereof, and relates to the technical field of high-voltage direct current transmission.The full-bridge circuit off-grid commutation converter comprises at least one upper bridge arm circuit and at least one lower bridge arm circuit, at least one upper bridge transfer circuit, an upper bridge off circuit, an upper bridge full-bridge circuit, at least one lower bridge transfer circuit, a lower bridge off circuit and a lower bridge full-bridge circuit; the upper bridge off circuit and the upper bridge full-bridge circuit are connected in series, and one end of the series-connected circuit is connected with the upper bridge transfer circuit anode bus; the lower bridge off circuit and the lower bridge full-bridge circuit are connected in series, and one end of the series-connected circuit is connected with the lower bridge transfer circuit cathode bus.The application has the effects of inhibiting the occurrence of commutation failure, improving the reliability of high-voltage direct current transmission, reducing the off-angle reference value and reducing the reactive power consumed by the converter.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-voltage direct current transmission, in particular to a full-bridge circuit turn-off grid commutated converter and a control method and device and system thereof. BACKGROUND

[0002] With the gradual increase of high-voltage and ultra-high-voltage direct current transmission systems connected, a multi-infeed direct current transmission system has been formed in multiple regional power grids. When multiple direct currents simultaneously fail to commutate, it may pose a threat to the safe operation of the regional alternating current power grid. Moreover, with the increasing proportion of new energy power generation, the alternating current voltage support capability decreases, and higher requirements are put forward for the stable operation of the direct current transmission system and the ability to suppress commutation failure.

[0003] The existing direct current transmission technology mainly uses a grid commutated converter with a twelve-pulse circuit structure and a voltage source converter with a modular multilevel circuit structure for high-voltage and ultra-high-voltage direct current transmission. In the grid commutated converter with a twelve-pulse circuit structure, each twelve-pulse circuit has two three-phase six-bridge-arm bridge circuits connected in series or parallel, and each bridge arm uses a single large-capacity thyristor in series. In the voltage source converter with a modular multilevel circuit structure, the modular multilevel circuit is a three-phase six-bridge-arm bridge circuit, and each bridge arm uses a half-bridge sub-module structure and / or a full-bridge sub-module structure in series. In addition, replacing and adding auxiliary circuits to form a controllable turn-off grid commutated converter based on the existing grid commutated converter to solve the commutation failure problem has also become an important direction of direct current transmission technology research.

[0004] However, the existing grid commutated converter with a twelve-pulse circuit structure has a commutation failure problem; the existing voltage source converter with a modular multilevel circuit structure has the problems of small device capacity, high cost, and large loss. The existing controllable turn-off grid commutated converter that uses full-controlled devices to suppress commutation failure has a small device capacity and its reliability needs to be verified. The existing controllable turn-off grid commutated converter that suppresses commutation failure by adding auxiliary circuits has a complex structure and reduced reliability. The above two kinds of controllable turn-off grid commutated converters rely on lightning arresters to absorb energy when forced to turn off, and each bridge arm needs to be equipped with an equal amount of lightning arresters. In the case of single-phase grounding faults with a high probability, only the lightning arresters of the faulty phase act, resulting in low utilization of lightning arresters. Since lightning arresters can only absorb energy for a short time, they cannot act in steady-state operation, so the alternating current system voltage still needs to be relied on for commutation, making it impossible to control the minimum turn-off angle too small, and still consuming a large amount of reactive power. SUMMARY

[0005] In order to inhibit the commutation failure from occurring, reduce the cost of the controllable turn-off grid commutated converter, improve the reliability of the high-voltage direct current transmission, and reduce the turn-off angle reference value and the consumed reactive power, the application provides a full-bridge circuit turn-off grid commutated converter and a control method and device and system thereof.

[0006] The application provides a full-bridge circuit turn-off grid commutated converter, which adopts the following technical scheme:

[0007] The full-bridge circuit turn-off grid commutated converter comprises:

[0008] A main circuit comprises at least one upper bridge arm circuit and at least one lower bridge arm circuit, one end of the at least one upper bridge arm circuit is connected with a main circuit anode bus, the other end of the at least one upper bridge arm circuit is connected with one end of the at least one lower bridge arm circuit, and the other end of the at least one lower bridge arm circuit is connected with a main circuit cathode bus;

[0009] An auxiliary circuit comprises at least one upper bridge transfer circuit, one upper bridge turn-off circuit, one upper bridge full-bridge circuit, at least one lower bridge transfer circuit, one lower bridge turn-off circuit, and one lower bridge full-bridge circuit;

[0010] One end of the at least one upper bridge transfer circuit is connected with an upper bridge transfer circuit anode bus, the other end of the at least one upper bridge transfer circuit is connected with the at least one upper bridge arm circuit, the upper bridge turn-off circuit and the upper bridge full-bridge circuit are connected in series, one end of the series-connected circuit is connected with the upper bridge transfer circuit anode bus, and the other end is connected with the main circuit anode bus;

[0011] One end of the at least one lower bridge transfer circuit is connected with a lower bridge transfer circuit cathode bus, the other end of the at least one lower bridge transfer circuit is connected with the at least one lower bridge arm circuit, the lower bridge turn-off circuit and the lower bridge full-bridge circuit are connected in series, one end of the series-connected circuit is connected with the lower bridge transfer circuit cathode bus, and the other end is connected with the main circuit cathode bus.

[0012] According to some embodiments, the at least one upper bridge arm circuit and the at least one lower bridge arm circuit comprise a first half-controlled valve and / or a second half-controlled valve;

[0013] In the case that the at least one upper bridge arm circuit and the at least one lower bridge arm circuit both comprise the first half-controlled valve and the second half-controlled valve, the first half-controlled valve and the second half-controlled valve are connected in series, one end of the first half-controlled valve of the at least one upper bridge arm circuit is connected with the main circuit anode bus, one end of the second half-controlled valve of the at least one upper bridge arm circuit is connected with one end of the second half-controlled valve of the at least one lower bridge arm circuit, one end of the first half-controlled valve of the at least one lower bridge arm circuit is connected with the main circuit cathode bus, or,

[0014] In the case that the at least one upper bridge arm circuit and the at least one lower bridge arm circuit comprise the first half-controlled valve, one end of the first half-controlled valve of the at least one upper bridge arm circuit is connected with the main circuit anode bus, and the other end of the first half-controlled valve of the at least one upper bridge arm circuit is connected with one end of the first half-controlled valve of the at least one lower bridge arm circuit; and the other end of the first half-controlled valve of the at least one lower bridge arm circuit is connected with the main circuit cathode bus.

[0015] According to some embodiments, the at least one upper bridge transfer circuit and the at least one lower bridge transfer circuit each comprise: a third half-controlled valve or a first non-controlled valve;

[0016] In the case that the at least one upper bridge arm circuit and the at least one lower bridge arm circuit comprise the first half-controlled valve and the second half-controlled valve, one end of the third half-controlled valve or the first non-controlled valve of the at least one upper bridge transfer circuit is connected with the upper bridge transfer circuit anode bus, and the other end of the third half-controlled valve or the first non-controlled valve of the at least one upper bridge transfer circuit is connected with a connection point between the first half-controlled valve and the second half-controlled valve of the at least one upper bridge arm circuit; one end of the third half-controlled valve or the first non-controlled valve of the at least one lower bridge transfer circuit is connected with the lower bridge transfer circuit cathode bus, and the other end of the third half-controlled valve or the first non-controlled valve of the at least one lower bridge transfer circuit is connected with a connection point between the first half-controlled valve and the second half-controlled valve of the at least one lower bridge arm circuit; or,

[0017] In the case that the at least one upper bridge arm circuit and the at least one lower bridge arm circuit comprise the first half-controlled valve, one end of the third half-controlled valve or the first non-controlled valve of the at least one upper bridge transfer circuit is connected with the upper bridge transfer circuit anode bus, and the other end of the third half-controlled valve or the first non-controlled valve of the at least one upper bridge transfer circuit is connected with one end of the first half-controlled valve of the at least one upper bridge arm circuit; one end of the third half-controlled valve or the first non-controlled valve of the at least one lower bridge transfer circuit is connected with one end of the first half-controlled valve of the at least one lower bridge arm circuit, and the other end of the third half-controlled valve or the first non-controlled valve of the at least one lower bridge transfer circuit is connected with the lower bridge transfer circuit cathode bus.

[0018] According to some embodiments, the first half-controlled valve, the second half-controlled valve and the third half-controlled valve each comprise a half-controlled switch; and the first non-controlled valve comprises a non-controlled switch.

[0019] The half-controlled switch is composed of controllable turn-on but uncontrollable turn-off semiconductor devices, which include but are not limited to thyristors; and the non-controlled switch is composed of non-controlled turn-on and turn-off semiconductor devices, which include but are not limited to diodes.

[0020] According to some embodiments, the first semi-controlled valve, and / or the second semi-controlled valve, and / or the third semi-controlled valve or first uncontrolled valve is connected in parallel with a lightning arrester.

[0021] According to some embodiments, in the case that the at least one upper bridge arm circuit and the at least one lower bridge arm circuit comprise a first semi-controlled valve and a second semi-controlled valve, the withstand voltage ratio of the first semi-controlled valve and the second semi-controlled valve is in the range of 0.2-5.

[0022] According to some embodiments, the first semi-controlled valve, and / or the second semi-controlled valve, and / or the third semi-controlled valve or first uncontrolled valve further comprises a reactor.

[0023] According to some embodiments, the upper bridge shutdown circuit of the auxiliary circuit and the circuit after the upper bridge full-bridge circuit is connected in series, and the anode bus of the main circuit is connected through an isolating switch or a knife switch; the lower bridge shutdown circuit of the auxiliary circuit and the circuit after the lower bridge full-bridge circuit is connected in series, and the cathode bus of the main circuit is connected through an isolating switch or a knife switch.

[0024] According to some embodiments, the upper bridge shutdown circuit and the lower bridge shutdown circuit each comprise a first fully-controlled valve;

[0025] One end of the first fully-controlled valve of the upper bridge shutdown circuit is connected to one end of the upper bridge full-bridge circuit, and the other end of the first fully-controlled valve of the upper bridge shutdown circuit is connected to the anode bus of the upper bridge transfer circuit; or, one end of the first fully-controlled valve of the upper bridge shutdown circuit is connected to one end of the upper bridge full-bridge circuit, and the other end of the first fully-controlled valve of the upper bridge shutdown circuit is connected to the anode bus of the main circuit.

[0026] One end of the first fully-controlled valve of the lower bridge shutdown circuit is connected to one end of the lower bridge full-bridge circuit, and the other end of the first fully-controlled valve of the lower bridge shutdown circuit is connected to the cathode bus of the lower bridge transfer circuit; or, one end of the first fully-controlled valve of the lower bridge shutdown circuit is connected to one end of the lower bridge full-bridge circuit, and the other end of the first fully-controlled valve of the lower bridge shutdown circuit is connected to the cathode bus of the main circuit.

[0027] According to some embodiments, the upper bridge shutdown circuit and the lower bridge shutdown circuit each further comprise a fourth semi-controlled valve connected in series with the first fully-controlled valve.

[0028] According to some embodiments, the first fully-controlled valve is connected in parallel with a lightning arrester.

[0029] According to some embodiments, the first fully-controlled valve comprises at least one of a unidirectional fully-controlled switch, a bidirectional fully-controlled switch, and a sub-module series switch.

[0030] According to some embodiments, the unidirectional fully controlled switch is composed of semiconductor devices with unidirectional blocking capability in series, including but not limited to insulated gate bipolar transistors, integrated gate-commutated thyristors, reverse blocking integrated gate-commutated thyristors;

[0031] The bidirectional fully controlled switch is composed of semiconductor devices with bidirectional blocking capability in series, including but not limited to reverse-parallel reverse blocking integrated gate-commutated thyristors, reverse series insulated gate bipolar transistors;

[0032] The sub-module series switch is composed of sub-modules in series, including but not limited to half-bridge sub-modules, full-bridge sub-modules, full-bridge-like sub-modules, clamped double sub-modules, and semiconductor devices of the half-bridge sub-modules, full-bridge sub-modules, full-bridge-like sub-modules, and clamped double sub-modules including but not limited to insulated gate bipolar transistors and integrated gate-commutated thyristors.

[0033] According to some embodiments, the upper bridge full-bridge circuit and the lower bridge full-bridge circuit each include a second fully controlled valve; one end of the second fully controlled valve of the upper bridge full-bridge circuit is connected with the main circuit anode bus, and the other end of the second fully controlled valve of the upper bridge full-bridge circuit is connected with the upper bridge shutdown circuit; or, one end of the second fully controlled valve of the upper bridge full-bridge circuit is connected with the upper bridge transfer circuit anode bus, and the other end of the second fully controlled valve of the upper bridge full-bridge circuit is connected with the upper bridge shutdown circuit.

[0034] One end of the second fully controlled valve of the lower bridge full-bridge circuit is connected with the main circuit cathode bus, and the other end of the second fully controlled valve of the lower bridge full-bridge circuit is connected with the lower bridge shutdown circuit; or, one end of the second fully controlled valve of the lower bridge full-bridge circuit is connected with the lower bridge transfer circuit cathode bus, and the other end of the second fully controlled valve of the lower bridge full-bridge circuit is connected with the lower bridge shutdown circuit.

[0035] According to some embodiments, the second fully controlled valve includes at least one of a full-bridge sub-module, a full-bridge-like sub-module, a midpoint clamped sub-module, a double half-bridge series sub-module, a double full-bridge series sub-module, a clamped double sub-module, a cross-connected double sub-module, a self-blocking sub-module, or a diode clamped sub-module connected in series.

[0036] According to some embodiments, the upper bridge full-bridge circuit and the lower bridge full-bridge circuit further include a resistance or an inductance; the resistance or the inductance is connected in series with the sub-module.

[0037] According to some embodiments, the second fully controlled valve is connected in parallel with a lightning arrester.

[0038] In normal operation, if a continuous commutation voltage is provided by the full-bridge circuit, the higher the turn-off voltage of the full-bridge circuit is, the smaller the turn-off angle of the full-bridge circuit turn-off grid commutation converter can be set, and the less the reactive power consumption is. In commutation failure, the turn-off circuit provides a transient commutation voltage. Therefore, the turn-off voltage of the full-bridge circuit is lower than that of the turn-off circuit, and the ratio of the turn-off voltages of the two circuits is in the range of 0.01 to 0.5.

[0039] The application provides a control method of a full-bridge circuit turn-off grid commutation converter.

[0040] The application provides a control method of a full-bridge circuit turn-off grid commutation converter.

[0041] In the case that the operation parameter information of the full-bridge circuit turn-off grid commutation converter is obtained, the inverter state control information is generated based on the parameter information, and the main circuit is controlled to operate in the inverter state based on the inverter state control information.

[0042] In the case that the turn-off angle reference value is less than the minimum turn-off angle constant value or the commutation failure information is obtained, the circuit conduction instruction and the negative voltage control information are generated during commutation, the transfer circuit and the turn-off circuit in the auxiliary circuit corresponding to the commutation bridge arm are controlled to be turned on based on the circuit conduction instruction, and the full-bridge circuit of the auxiliary circuit corresponding to the commutation bridge arm is controlled to present a negative voltage based on the negative voltage control information.

[0043] In the case that the first half-controlled valve of the commutation bridge arm of the main circuit recovers turn-off, the circuit turn-off instruction is generated, and the full-bridge circuit and / or the turn-off circuit corresponding to the commutation bridge arm are controlled to be turned off.

[0044] According to some embodiments, in the case that the full-bridge circuit turn-off grid commutation converter operates normally, the turn-off angle reference value is set to be less than the minimum turn-off angle constant value; in the case that the turn-off angle reference value is less than the minimum turn-off angle constant value and the first half-controlled valve of the commutation bridge arm of the main circuit recovers turn-off, the circuit turn-off instruction is generated, and the full-bridge circuit corresponding to the commutation bridge arm is controlled to be turned off based on the circuit turn-off instruction.

[0045] According to some embodiments, in the case that the capacitance voltage of the sub-module of the full-bridge circuit of the auxiliary circuit is lower than the rated value and exceeds the first threshold value, and the first half-controlled valve of the commutation bridge arm of the main circuit recovers turn-off, the circuit turn-off instruction is generated in advance; and / or, the number of sub-modules of the full-bridge circuit is increased; and / or, the circuit conduction instruction for controlling the corresponding transfer circuit and turn-off circuit to be turned on and the negative voltage control information for controlling the sub-module of the full-bridge circuit to present a negative voltage are generated in advance; the value of the first threshold value is in the range of 0.01 to 0.6 times the rated capacitance voltage.

[0046] Optionally, in a case that the sub-module capacitor voltage is greater than or equal to a rated value and exceeds a second threshold value, and in a case that the first half-controlled valve of the commutation bridge arm of the main circuit recovers off, the circuit off instruction is generated in a delayed manner; and / or, the number of sub-modules of the full-bridge circuit is reduced; and / or, the circuit on instruction for controlling the corresponding transfer circuit and off circuit to be turned on and the negative voltage control information for controlling the sub-modules of the full-bridge circuit to present negative voltage are generated in a delayed manner; the second threshold value ranges from 0.01 to 0.6 times the rated capacitor voltage.

[0047] According to some embodiments, the control of the full-bridge circuit to present negative voltage is achieved by controlling the switch device in the sub-module of the third fully-controlled valve to be turned on so that the sub-module presents capacitor negative voltage in the current flow direction.

[0048] According to some embodiments, the recovery off of the first half-controlled valve of the commutation bridge arm of the main circuit is determined according to the reverse recovery time of the first half-controlled valve, and the reverse recovery time is greater than or equal to the reverse recovery time of the thyristor contained in the first half-controlled valve.

[0049] According to some embodiments, in a case that the circuit obtained by connecting the upper bridge off circuit and the upper bridge full-bridge circuit of the auxiliary circuit in series and the anode bus of the main circuit are connected through a disconnecting switch or a knife switch, the circuit obtained by connecting the lower bridge off circuit and the lower bridge full-bridge circuit of the auxiliary circuit in series and the cathode bus of the main circuit are connected through a disconnecting switch and / or a knife switch, and the auxiliary circuit fault information is obtained, a switch separation instruction is generated, and the disconnecting switch or the knife switch is controlled to be separated based on the switch separation instruction.

[0050] The application provides a full-bridge circuit off grid commutation converter control device, which adopts the following technical scheme:

[0051] A full-bridge circuit off grid commutation converter control device is used for controlling the full-bridge circuit off grid commutation converter, comprising a first control module, a second control module and a third control module, wherein,

[0052] The first control module is used for, in a case that the operating parameter information of the full-bridge circuit off grid commutation converter is obtained, generating the inverter state control information based on the parameter information, and controlling the main circuit to operate in the inverter state based on the inverter state control information.

[0053] The second control module is used for, in a case that the off angle reference value is less than the minimum off angle constant value or the commutation fault information is obtained, generating the circuit on instruction and the negative voltage control information during commutation, controlling the transfer circuit and the off circuit in the corresponding auxiliary circuit of the commutation bridge arm to be turned on based on the circuit on instruction, and controlling the full-bridge circuit of the corresponding auxiliary circuit of the commutation bridge arm to present negative voltage based on the negative voltage control information.

[0054] The third control module is configured to generate a circuit shutdown instruction to control the full-bridge circuit and / or the shutdown circuit to shut down in the case that the first semi-controlled valve included in the commutation bridge arm of the main circuit recovers from shutdown.

[0055] The application provides a high-voltage direct current transmission system, which comprises the full-bridge circuit shutdown grid commutation converter.

[0056] According to some embodiments, the high-voltage direct current transmission system is a two-terminal direct current transmission system or a multi-terminal direct current transmission system, and the two-terminal direct current transmission system comprises a single-pole direct current transmission system, a bipolar direct current transmission system or a back-to-back direct current system.

[0057] According to some embodiments, the two-terminal direct current transmission system or the multi-terminal direct current transmission system requires that the converter part of the inverter operation adopts the full-bridge circuit shutdown grid commutation converter.

[0058] In summary, the application has the following beneficial technical effects:

[0059] When the AC system failure may cause commutation failure, the full-bridge circuit of the auxiliary circuit is controlled to present negative pressure, the corresponding transfer circuit and the shutdown circuit are turned on to form parallel conduction with the commutation bridge arm of the main circuit, the current is transferred to the auxiliary circuit, and after the first semi-controlled valve of the commutation bridge arm of the main circuit recovers from shutdown, the full-bridge circuit and / or the shutdown circuit of the auxiliary circuit are controlled to shut down, the commutation bridge arm is shut down, the commutation failure is effectively suppressed, the controllable shutdown of the full-bridge circuit shutdown grid commutation converter is realized, the continuous shutdown capability of the full-bridge circuit is used to reduce the reference value of the shutdown angle and reduce the consumed reactive power. Compared with the prior art, the circuit structure of the application is simple, the reactive power compensation equipment can be reduced, the cost of the high-voltage direct current transmission system with controllable shutdown capability is reduced, and the reliability of the system is improved. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is one of the full-bridge circuit shutdown grid commutation converter schematic diagrams of the embodiments of the application;

[0061] Figure 2 is the second full-bridge circuit shutdown grid commutation converter schematic diagram of the embodiments of the application;

[0062] Figure 3 is the third full-bridge circuit shutdown grid commutation converter schematic diagram of the embodiments of the application;

[0063] Figure 4 is one of the full-bridge circuit shutdown grid commutation converter circuit diagrams of the embodiments of the application comprising a lightning arrester;

[0064] Figure 5Figure 2 is a circuit diagram of a full-bridge circuit shutdown grid commutation converter containing a surge arrester according to an embodiment of the present application;

[0065] Figure 6 Figure 3 is a circuit diagram of a full-bridge circuit shutdown grid commutation converter containing a surge arrester according to an embodiment of the present application;

[0066] Figure 7A 、 Figure 7B 、 Figure 7C 、 Figure 7D 、 Figure 7E 、 Figure 7F 、 Figure 7G 、 Figure 7H 、 Figure 7I and Figure 7J Figure 7 is a schematic diagram of a valve structure according to an embodiment of the present application;

[0067] Figure 8A Figure 8 is a schematic diagram of a full-bridge sub-module according to an embodiment of the present application;

[0068] Figure 8B Figure 9 is a schematic diagram of a quasi-full-bridge sub-module according to an embodiment of the present application;

[0069] Figure 9 Figure 10 is a block schematic diagram of a control method of a full-bridge circuit shutdown grid commutation converter according to an embodiment of the present application;

[0070] Figure 10 Figure 11 is a flow schematic diagram of a control method of a full-bridge circuit shutdown grid commutation converter according to an embodiment of the present application;

[0071] Figure 11 Figure 12 is a block schematic diagram of a control device of a full-bridge circuit shutdown grid commutation converter according to an embodiment of the present application;

[0072] Figure 12 Figure 13 is a schematic diagram of a structure of a single pole of a bipolar direct current transmission system according to an embodiment of the present application.

[0073] BRIEF DESCRIPTION OF DRAWINGS 1, upper bridge arm circuit; 2, lower bridge arm circuit; 3, upper bridge transfer circuit; 4, upper bridge shutdown circuit; 5, lower bridge transfer circuit; 6, lower bridge shutdown circuit; 7, upper bridge full-bridge circuit; 8, lower bridge full-bridge circuit; 9, first grid commutation converter; 10, second grid commutation converter; 11, first converter transformer; 12, second converter transformer; 13, first alternating current system; 14, direct current line; 15, first full-bridge circuit shutdown grid commutation converter; 16, second full-bridge circuit shutdown grid commutation converter; 17, third converter transformer; 18, fourth converter transformer; 19, second alternating current system; 201, first control module; 202, second control module; 203, third control module. DETAILED DESCRIPTION

[0074] The following will be described in conjunction with the drawingsFigures 1-12 The application will be further described in detail.

[0075] In order to make the purposes, technical solutions and advantages of the embodiments of the application clearer, the following will combine the drawings in the embodiments of the application to clearly and completely describe the technical solutions in the embodiments of the application. Obviously, the described embodiments are some but not all of the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the application.

[0076] The embodiment of the application provides a full-bridge circuit off-grid phase-change converter, which comprises a main circuit, wherein the main circuit comprises at least one upper bridge arm circuit and at least one lower bridge arm circuit, one end of the at least one upper bridge arm circuit is connected with a main circuit anode bus, the other end of the at least one upper bridge arm circuit is connected with one end of the at least one lower bridge arm circuit, and the other end of the at least one lower bridge arm circuit is connected with a main circuit cathode bus.

[0077] The at least one upper bridge arm circuit and the at least one lower bridge arm circuit each comprise a first half-controlled valve and a second half-controlled valve; the first half-controlled valve and the second half-controlled valve are connected in series; one end of the first half-controlled valve of the at least one upper bridge arm circuit is connected with the main circuit anode bus, and one end of the second half-controlled valve of the at least one upper bridge arm circuit is connected with one end of the second half-controlled valve of the at least one lower bridge arm circuit; one end of the first half-controlled valve of the at least one lower bridge arm circuit is connected with the main circuit cathode bus; or, the at least one upper bridge arm circuit and the at least one lower bridge arm circuit each comprise a first half-controlled valve; one end of the first half-controlled valve of the at least one upper bridge arm circuit is connected with the main circuit anode bus, and the other end of the first half-controlled valve of the at least one upper bridge arm circuit is connected with one end of the first half-controlled valve of the at least one lower bridge arm circuit; the other end of the first half-controlled valve of the at least one lower bridge arm circuit is connected with the main circuit cathode bus.

[0078] Referring to Figure 1 , the main circuit can be a three-phase six-bridge-arm circuit, which comprises three upper bridge arm circuits 1 and three lower bridge arm circuits 2, the three upper bridge arm circuits 1 and the three lower bridge arm circuits 2 have one-to-one correspondence, and the upper bridge arm circuit 1 and the lower bridge arm circuit 2 in each correspondence correspond to one phase of electricity; one end of each upper bridge arm circuit 1 is connected with the main circuit anode bus, the other end of each upper bridge arm circuit 1 is connected with one end of the corresponding lower bridge arm circuit 2, and the other end of the corresponding lower bridge arm circuit 2 is connected with the main circuit cathode bus.

[0079] Each of the upper bridge arm circuit 1 and the lower bridge arm circuit 2 comprises a first half-controlled valve and a second half-controlled valve; wherein the first half-controlled valve and the second half-controlled valve are connected in series; one end of the first half-controlled valve of each upper bridge arm circuit 1 is connected with the main circuit anode bus, and one end of the second half-controlled valve of each upper bridge arm circuit 1 is connected with one end of the second half-controlled valve of the corresponding lower bridge arm circuit 2; one end of the first half-controlled valve of each lower bridge arm circuit 2 is connected with the main circuit cathode bus.

[0080] In some embodiments, with reference to Figure 1 , the A-phase upper bridge arm circuit 1 comprises a first half-controlled valve V42 and a second half-controlled valve V43, the first half-controlled valve V42 and the second half-controlled valve V43 are connected in series, one end of the first half-controlled valve V42 is connected with the main circuit anode bus P1, and one end of the second half-controlled valve V43 is connected with the A-phase lower bridge arm circuit; the B-phase upper bridge arm circuit 1 comprises a first half-controlled valve V62 and a second half-controlled valve V63, the first half-controlled valve V62 and the second half-controlled valve V63 are connected in series, one end of the first half-controlled valve V62 is connected with the main circuit anode bus P1, and one end of the second half-controlled valve V63 is connected with the B-phase lower bridge arm circuit 2; the C-phase upper bridge arm circuit 1 comprises a first half-controlled valve V22 and a second half-controlled valve V23, the first half-controlled valve V22 and the second half-controlled valve V23 are connected in series, one end of the first half-controlled valve V22 is connected with the main circuit anode bus P1, and one end of the second half-controlled valve V23 is connected with the C-phase lower bridge arm circuit 2.

[0081] The A-phase lower bridge arm circuit 2 comprises a first half-controlled valve V12 and a second half-controlled valve V13, the first half-controlled valve V12 and the second half-controlled valve V13 are connected in series, one end of the first half-controlled valve V12 is connected with the main circuit cathode bus N1, and one end of the second half-controlled valve V13 is connected with one end of the second half-controlled valve V43 of the A-phase upper bridge arm circuit 1; the B-phase lower bridge arm circuit 2 comprises a first half-controlled valve V32 and a second half-controlled valve V33, the first half-controlled valve V32 and the second half-controlled valve V33 are connected in series, one end of the first half-controlled valve V32 is connected with the main circuit cathode bus N1, and one end of the second half-controlled valve V33 is connected with one end of the second half-controlled valve V63 of the B-phase upper bridge arm circuit 1; the C-phase lower bridge arm circuit 2 comprises a first half-controlled valve V52 and a second half-controlled valve V53, the first half-controlled valve V52 and the second half-controlled valve V53 are connected in series, one end of the first half-controlled valve V52 is connected with the main circuit cathode bus N1, and one end of the second half-controlled valve V53 is connected with the second half-controlled valve V23 of the C-phase upper bridge arm circuit 1.

[0082] The auxiliary circuit comprises at least one upper bridge transfer circuit, one upper bridge off circuit, one upper bridge full bridge circuit, at least one lower bridge transfer circuit, one lower bridge off circuit and one lower bridge full bridge circuit; one end of the at least one upper bridge transfer circuit is connected with the upper bridge transfer circuit anode bus, and the other end of the at least one upper bridge transfer circuit is connected with the at least one upper bridge arm circuit; the upper bridge off circuit and the upper bridge full bridge circuit are connected in series, and one end of the series-connected circuit is connected with the upper bridge transfer circuit anode bus, and the other end is connected with the main circuit anode bus; one end of the at least one lower bridge transfer circuit is connected with the lower bridge transfer circuit cathode bus, and the other end of the at least one lower bridge transfer circuit is connected with the at least one lower bridge arm circuit; the lower bridge off circuit and the lower bridge full bridge circuit are connected in series, and one end of the series-connected circuit is connected with the lower bridge transfer circuit cathode bus, and the other end is connected with the main circuit cathode bus.

[0083] Referring to Figure 1 The auxiliary circuit can comprise three upper bridge transfer circuits 3, one upper bridge off circuit 4, one upper bridge full bridge circuit 7, three lower bridge transfer circuits 5, one lower bridge off circuit 6 and one lower bridge full bridge circuit 8; wherein the three upper bridge transfer circuits 3 correspond to the three upper bridge arm circuits 1 one by one, the three lower bridge transfer circuits 5 correspond to the three lower bridge arm circuits 2 one by one, the upper bridge off circuit 4 corresponds to the three upper bridge arm circuits 1, the lower bridge off circuit 6 corresponds to the three lower bridge arm circuits 2, the upper bridge full bridge circuit 7 corresponds to the three upper bridge arm circuits 1, and the lower bridge full bridge circuit 8 corresponds to the three lower bridge arm circuits 2.

[0084] One end of each upper bridge transfer circuit 3 is connected with the upper bridge transfer circuit anode bus, and the other end of each upper bridge transfer circuit 3 is connected with the corresponding upper bridge arm circuit 1; one end of the upper bridge off circuit 4 is connected with one end of the upper bridge full bridge circuit 7, and the other end of the upper bridge off circuit 4 is connected with the upper bridge transfer circuit anode bus.

[0085] One end of each lower bridge transfer circuit 5 is connected with the lower bridge transfer circuit cathode bus, and the other end of each lower bridge transfer circuit 5 is connected with the corresponding lower bridge arm circuit 2; one end of the lower bridge off circuit 6 is connected with one end of the lower bridge full bridge circuit 8, and the other end of the lower bridge off circuit 6 is connected with the lower bridge transfer circuit cathode bus.

[0086] In some embodiments, the circuit obtained by connecting the upper bridge off circuit 4 and the upper bridge full bridge circuit 7 of the auxiliary circuit in series is connected with the main circuit anode bus through an isolation switch or a knife switch; and the circuit obtained by connecting the lower bridge off circuit 6 and the lower bridge full bridge circuit 8 of the auxiliary circuit in series is connected with the main circuit cathode bus through an isolation switch or a knife switch.

[0087] In some embodiments, the at least one upper bridge transfer circuit and the at least one lower bridge transfer circuit each comprise: a third semi-controlled valve or a first non-controlled valve; in the case where the at least one upper bridge arm circuit and the at least one lower bridge arm circuit comprise a first semi-controlled valve and a second semi-controlled valve, one end of the third semi-controlled valve or the first non-controlled valve of the at least one upper bridge transfer circuit is connected to the upper bridge transfer circuit anode bus, and the other end of the third semi-controlled valve or the first non-controlled valve of the at least one upper bridge transfer circuit is connected to a connection point between the first semi-controlled valve and the second semi-controlled valve of the at least one upper bridge arm circuit; one end of the third semi-controlled valve or the first non-controlled valve of the at least one lower bridge transfer circuit is connected to the lower bridge transfer circuit cathode bus, and the other end of the third semi-controlled valve or the first non-controlled valve of the at least one lower bridge transfer circuit is connected to a connection point between the first semi-controlled valve and the second semi-controlled valve of the at least one lower bridge arm circuit.

[0088] Referring to Figure 1 , each upper bridge transfer circuit 3 and each lower bridge transfer circuit 5 comprises: a third semi-controlled valve or a first non-controlled valve; one end of the third semi-controlled valve or the first non-controlled valve of each upper bridge transfer circuit 3 is connected to the upper bridge transfer circuit anode bus, and the other end of the third semi-controlled valve or the first non-controlled valve of each upper bridge transfer circuit 3 is connected to a connection point between the first semi-controlled valve and the second semi-controlled valve of the corresponding upper bridge arm circuit 1; one end of the third semi-controlled valve or the first non-controlled valve of each lower bridge transfer circuit 5 is connected to the lower bridge transfer circuit cathode bus, and the other end of the third semi-controlled valve or the first non-controlled valve of each lower bridge transfer circuit 5 is connected to a connection point between the first semi-controlled valve and the second semi-controlled valve of the corresponding lower bridge arm circuit 2, wherein the first semi-controlled valve, the second semi-controlled valve and the third semi-controlled valve each comprise a semi-controlled switch, and the first non-controlled valve comprises a non-controlled switch; the withstand voltage ratio of the first semi-controlled valve and the second semi-controlled valve is in the range of 0.2-5.

[0089] In some embodiments, referring to Figure 1 , the A-phase upper bridge transfer circuit 3 comprises a third semi-controlled valve or a first non-controlled valve V44, one end of the third semi-controlled valve or the first non-controlled valve V44 is connected to the upper bridge transfer circuit anode bus P2, and the other end of the third semi-controlled valve or the first non-controlled valve V44 is connected to a connection point of the first semi-controlled valve V42 and the second semi-controlled valve V43 of the A-phase upper bridge arm circuit 1; the B-phase upper bridge transfer circuit 3 comprises a third semi-controlled valve or a first non-controlled valve V64, one end of the third semi-controlled valve or the first non-controlled valve V64 is connected to the upper bridge transfer circuit anode bus P2, and the other end of the third semi-controlled valve or the first non-controlled valve V64 is connected to a connection point of the first semi-controlled valve V62 and the second semi-controlled valve V63 of the B-phase upper bridge arm circuit 1; the C-phase upper bridge transfer circuit 3 comprises a third semi-controlled valve or a first non-controlled valve V24, one end of the third semi-controlled valve or the first non-controlled valve V24 is connected to the upper bridge transfer circuit anode bus P2, and the other end of the third semi-controlled valve or the first non-controlled valve V24 is connected to a connection point of the first semi-controlled valve V22 and the second semi-controlled valve V23 of the C-phase upper bridge arm circuit 1.

[0090] The A-phase lower bridge transfer circuit 5 includes a third half-controlled valve or a first uncontrolled valve V14, one end of the third half-controlled valve or the first uncontrolled valve V14 is connected with the lower bridge transfer circuit cathode bus N2, and the other end of the third half-controlled valve or the first uncontrolled valve V14 is connected with the connection point of the first half-controlled valve V12 and the second half-controlled valve V13 of the A-phase lower bridge arm circuit 2; the B-phase lower bridge transfer circuit 5 includes a third half-controlled valve or a first uncontrolled valve V34, one end of the third half-controlled valve or the first uncontrolled valve V34 is connected with the lower bridge transfer circuit cathode bus N2, and the other end of the third half-controlled valve or the first uncontrolled valve V34 is connected with the connection point of the first half-controlled valve V32 and the second half-controlled valve V33 of the B-phase lower bridge arm circuit 2; the C-phase lower bridge transfer circuit 5 includes a third half-controlled valve or a first uncontrolled valve V54, one end of the third half-controlled valve or the first uncontrolled valve V54 is connected with the lower bridge transfer circuit cathode bus N2, and the other end of the third half-controlled valve or the first uncontrolled valve V54 is connected with the connection point of the first half-controlled valve V52 and the second half-controlled valve V53 of the C-phase lower bridge arm circuit 5.

[0091] The upper bridge shutdown circuit 4 and the lower bridge shutdown circuit 6 each include a first fully-controlled valve; one end of the first fully-controlled valve of the upper bridge shutdown circuit 4 is connected with the upper bridge full-bridge circuit 7, and the other end of the first fully-controlled valve of the upper bridge shutdown circuit 4 is connected with the upper bridge transfer circuit anode bus; one end of the first fully-controlled valve of the lower bridge shutdown circuit 6 is connected with the lower bridge full-bridge circuit 8, and the other end of the first fully-controlled valve of the lower bridge shutdown circuit 6 is connected with the lower bridge transfer circuit cathode bus; wherein the first fully-controlled valve includes at least one of a unidirectional fully-controlled switch, a bidirectional fully-controlled switch, and a sub-module series switch.

[0092] In some embodiments, with reference to Figure 1 The upper bridge shutdown circuit 4 includes a first fully-controlled valve V71, one end of the first fully-controlled valve V71 is connected with the upper bridge full-bridge circuit 7, and the other end of the first fully-controlled valve V71 is connected with the upper bridge transfer circuit anode bus P2; the lower bridge shutdown circuit 6 includes a first fully-controlled valve V72, one end of the first fully-controlled valve V72 is connected with the lower bridge full-bridge circuit 8, and the other end of the first fully-controlled valve V72 is connected with the lower bridge transfer circuit cathode bus N2.

[0093] The upper bridge full-bridge circuit 7 and the lower bridge full-bridge circuit 8 each include a second fully-controlled valve; one end of the second fully-controlled valve of the upper bridge full-bridge circuit 7 is connected with the main circuit anode bus, and the other end of the second fully-controlled valve of the upper bridge full-bridge circuit 7 is connected with one end of the first fully-controlled valve of the upper bridge shutdown circuit 4; one end of the second fully-controlled valve of the lower bridge full-bridge circuit 8 is connected with the main circuit cathode bus, and the other end of the second fully-controlled valve of the lower bridge full-bridge circuit 8 is connected with one end of the first fully-controlled valve of the lower bridge shutdown circuit 6.

[0094] In some embodiments, with reference to Figure 1The other end of the second controllable valve V81 of the upper bridge full-bridge circuit 7 is connected with the first controllable valve V71 of the upper bridge off-circuit 4.

[0095] In some embodiments, the positions of the upper bridge off-circuit and the upper bridge full-bridge circuit can be interchanged; the positions of the lower bridge off-circuit and the lower bridge full-bridge circuit can be interchanged.

[0096] In some embodiments, the at least one phase upper bridge arm circuit and the at least one phase lower bridge arm circuit only include the first half-controlled valve but do not include the second half-controlled valve, one end of the first half-controlled valve of the at least one phase upper bridge arm circuit is connected with the main circuit anode bus, and the other end of the first half-controlled valve of the at least one phase upper bridge arm circuit is connected with one end of the first half-controlled valve of the at least one phase lower bridge arm circuit; the other end of the first half-controlled valve of the at least one phase lower bridge arm circuit is connected with the main circuit cathode bus.

[0097] Referring to Figure 2 In the case that each upper bridge arm circuit 1 and each lower bridge arm circuit 2 include the first half-controlled valve but do not include the second half-controlled valve, one end of the first half-controlled valve of each upper bridge arm circuit 1 is connected with the main circuit anode bus, and the other end of the first half-controlled valve of each upper bridge arm circuit 1 is connected with one end of the first half-controlled valve of its corresponding lower bridge arm circuit 2; the other end of the first half-controlled valve of each lower bridge arm circuit 2 is connected with the main circuit cathode bus.

[0098] In some embodiments, in the case that the at least one phase upper bridge arm circuit and the at least one phase lower bridge arm circuit include the first half-controlled valve but do not include the second half-controlled valve, one end of the third half-controlled valve or the first non-controlled valve of the at least one phase upper bridge transfer circuit is connected with the upper bridge transfer circuit anode bus, and the other end of the third half-controlled valve or the first non-controlled valve of the at least one phase upper bridge transfer circuit is connected with one end of the first half-controlled valve of the at least one phase upper bridge arm circuit; one end of the third half-controlled valve or the first non-controlled valve of the at least one phase lower bridge transfer circuit is connected with one end of the first half-controlled valve of the at least one phase lower bridge arm circuit, and the other end of the third half-controlled valve or the first non-controlled valve of the at least one phase lower bridge transfer circuit is connected with the lower bridge transfer circuit cathode bus.

[0099] Referring to Figure 2the third half-controlled valve or first uncontrolled valve V44 of the upper bridge transfer circuit of phase A is connected at one end with the anode bus P2 of the upper bridge transfer circuit, and at the other end with one end of the first half-controlled valve V41 of the upper bridge arm circuit 1 of phase A; the third half-controlled valve or first uncontrolled valve V14 of the lower bridge transfer circuit of phase A is connected at one end with the cathode bus N2 of the lower bridge transfer circuit, and at the other end with one end of the first half-controlled valve V11 of the lower bridge arm circuit 2 of phase A;

[0100] the third half-controlled valve or first uncontrolled valve V64 of the upper bridge transfer circuit of phase B is connected at one end with the anode bus P2 of the upper bridge transfer circuit, and at the other end with one end of the first half-controlled valve V61 of the upper bridge arm circuit 1 of phase B; the third half-controlled valve or first uncontrolled valve V34 of the lower bridge transfer circuit of phase B is connected at one end with the cathode bus N2 of the lower bridge transfer circuit, and at the other end with one end of the first half-controlled valve V31 of the lower bridge arm circuit 2 of phase B;

[0101] the third half-controlled valve or first uncontrolled valve V24 of the upper bridge transfer circuit of phase C is connected at one end with the anode bus P2 of the upper bridge transfer circuit, and at the other end with one end of the first half-controlled valve V21 of the upper bridge arm circuit 1 of phase C; the third half-controlled valve or first uncontrolled valve V54 of the lower bridge transfer circuit of phase C is connected at one end with the cathode bus N2 of the lower bridge transfer circuit, and at the other end with one end of the first half-controlled valve V51 of the lower bridge arm circuit 2 of phase C.

[0102] In some embodiments, the first half-controlled valve, and / or the second half-controlled valve, and / or the third half-controlled valve or first uncontrolled valve further comprises a reactor. Optionally, the first fully-controlled valve further comprises a reactor.

[0103] In some embodiments, the upper bridge shutdown circuit and the lower bridge shutdown circuit each further comprises a fourth half-controlled valve connected in series with the first fully-controlled valve; the cathode of the fourth half-controlled valve and the anode of the first fully-controlled valve are connected or the anode of the fourth half-controlled valve and the cathode of the first fully-controlled valve are connected.

[0104] Referring to Figure 3 The upper bridge shutdown circuit 4 further comprises a fourth half-controlled valve V73 connected in series with the first fully-controlled valve V71, and the anode of the fourth half-controlled valve V73 and the cathode of the first fully-controlled valve V71 are connected; the lower bridge shutdown circuit 6 further comprises a fourth half-controlled valve V74 connected in series with the first fully-controlled valve V72, and the cathode of the fourth half-controlled valve V74 and the anode of the first fully-controlled valve V72 are connected.

[0105] Referring to Figure 4The unidirectional full-control switch of each first full-control valve is composed of at least one IGBT (Insulated Gate Bipolar Transistor) in series, the half-control switch of each first half-control valve and each second half-control valve is composed of at least one thyristor in series, the non-control switch of each first non-control valve is composed of at least one diode in series, and each second full-control valve is composed of full-bridge sub-modules in series. For example, the unidirectional full-control switch of the first full-control valve V71 of the A-phase upper bridge turn-off circuit and the first full-control valve V72 of the A-phase lower bridge turn-off circuit are composed of a plurality of IGBT modules in series; the half-control switch of the first half-control valve V42 and the second half-control valve V43 of the A-phase upper bridge arm circuit and the first half-control valve V12 and the second half-control valve V13 of the A-phase lower bridge arm circuit are composed of a plurality of thyristors in series; the non-control switch of the first non-control valve V44 of the A-phase upper bridge transfer circuit and the first non-control valve V14 of the A-phase lower bridge transfer circuit are composed of a plurality of diodes in series, and the second full-control valve V81 of the A-phase upper bridge full-bridge circuit and the second full-control valve V82 of the A-phase lower bridge full-bridge circuit are composed of full-bridge sub-modules in series.

[0106] In addition, the first full-control valves of the B-phase and the C-phase are shared with the A-phase; the unidirectional half-control switch of the first half-control valve and the second half-control valve corresponding to the B-phase and the C-phase is the same as the unidirectional half-control switch of the first half-control valve and the second half-control valve corresponding to the A-phase; the non-control switch of the first non-control valve corresponding to the B-phase and the C-phase is the same as the non-control switch of the first non-control valve corresponding to the A-phase; and the second full-control valves of the B-phase and the C-phase are shared with the A-phase.

[0107] In some embodiments, referring to Figure 4 Each first full-control valve, each first half-control valve, each second half-control valve, each first non-control valve, and each second full-control valve are connected in parallel with lightning arresters to protect normal use of each first full-control valve, each first half-control valve, each second half-control valve, each first non-control valve, and each second full-control valve. For example, the first half-control valve V42 of the A-phase upper bridge arm circuit is connected in parallel with a second lightning arrester F42, the second half-control valve V43 is connected in parallel with a third lightning arrester F43, the first half-control valve V12 of the A-phase lower bridge arm circuit is connected in parallel with a second lightning arrester F12, and the second half-control valve V13 is connected in parallel with a third lightning arrester F13; the first half-control valve V62 of the B-phase upper bridge arm circuit is connected in parallel with a second lightning arrester F62, the second half-control valve V63 is connected in parallel with a third lightning arrester F63, the first half-control valve V32 of the B-phase lower bridge arm circuit is connected in parallel with a second lightning arrester F32, and the second half-control valve V33 is connected in parallel with a third lightning arrester F33; the first half-control valve V22 of the C-phase upper bridge arm circuit is connected in parallel with a second lightning arrester F22, the second half-control valve V23 is connected in parallel with a third lightning arrester F23, the first half-control valve V52 of the C-phase lower bridge arm circuit is connected in parallel with a second lightning arrester F52, and the second half-control valve V53 is connected in parallel with a third lightning arrester F53.

[0108] The first non-controlled valve V44 of the upper bridge transfer circuit is connected in parallel with the fourth lightning arrester F44, and the first non-controlled valve V14 of the lower bridge transfer circuit is connected in parallel with the fourth lightning arrester F14; the first non-controlled valve V64 of the upper bridge transfer circuit of phase B is connected in parallel with the fourth lightning arrester F64, and the first non-controlled valve V34 of the lower bridge transfer circuit of phase B is connected in parallel with the fourth lightning arrester F34; the first non-controlled valve V24 of the upper bridge transfer circuit of phase C is connected in parallel with the fourth lightning arrester F24, and the first non-controlled valve V54 of the lower bridge transfer circuit of phase C is connected in parallel with the fourth lightning arrester F54; the first controlled valve V71 of the upper bridge shutdown circuit is connected in parallel with the fifth lightning arrester F71, and the first controlled valve V72 of the lower bridge shutdown circuit is connected in parallel with the fifth lightning arrester F72.

[0109] The second controlled valve V81 of the upper bridge full-bridge circuit is connected in parallel with the sixth lightning arrester F81, and the second controlled valve V82 of the lower bridge full-bridge circuit is connected in parallel with the sixth lightning arrester F82.

[0110] Reference Figure 5 Each upper bridge arm circuit and each lower bridge arm circuit includes a first semi-controlled valve but does not include a second semi-controlled valve, and the semi-controlled switch of each first semi-controlled valve is composed of at least one thyristor in series.

[0111] In some embodiments, with reference to Figure 5 Each first semi-controlled valve is connected in parallel with a lightning arrester to protect normal use of each first semi-controlled valve, for example, the first semi-controlled valve V41 of the upper bridge arm circuit of phase A is connected in parallel with the first lightning arrester F41, and the first semi-controlled valve V11 of the lower bridge arm circuit of phase A is connected in parallel with the first lightning arrester F11; the first semi-controlled valve V61 of the upper bridge arm circuit of phase B is connected in parallel with the first lightning arrester F61, and the first semi-controlled valve V31 of the lower bridge arm circuit of phase B is connected in parallel with the first lightning arrester F31; the first semi-controlled valve V21 of the upper bridge arm circuit of phase C is connected in parallel with the first lightning arrester F21, and the first semi-controlled valve V51 of the lower bridge arm circuit of phase C is connected in parallel with the first lightning arrester F51.

[0112] Reference Figure 6 The upper bridge shutdown circuit further includes a fourth semi-controlled valve V73 connected in series with the first controlled valve V71, and the anode of the fourth semi-controlled valve V73 is connected with the negative electrode of the first controlled valve V71; the lower bridge shutdown circuit further includes a fourth semi-controlled valve V74 connected in series with the first controlled valve V72, and the cathode of the fourth semi-controlled valve V74 is connected with the positive electrode of the first controlled valve V72; the semi-controlled switch of each fourth semi-controlled valve is composed of at least one thyristor in series.

[0113] In some embodiments, with reference to Figure 6 Each fourth semi-controlled valve is connected in parallel with a lightning arrester to protect normal use of each fourth semi-controlled valve, for example, the fourth semi-controlled valve V73 is connected in parallel with the seventh lightning arrester F73, and the fourth semi-controlled valve V74 is connected in parallel with the seventh lightning arrester F74.

[0114] In some embodiments, the fully-controlled switch comprises at least one fully-controlled device connected in series, the fully-controlled device comprising at least one of an IGCT (Integrated Gate Commutated Thyristor), an IGBT, an inverse-IGCT, a GTO (Gate Turn-Off Thyristor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor); the semi-controlled switch comprises at least one semi-controlled device connected in series, the semi-controlled device comprising a thyristor; the uncontrolled switch comprises at least one uncontrolled device connected in series, the uncontrolled device comprising a diode.

[0115] With reference to Figure 7A the uncontrolled switch comprises at least one diode D1 connected in series, which cannot be controlled to turn on and off, has a unidirectional current flow capability and a unidirectional blocking voltage capability; with reference to Figure 7B the semi-controlled switch comprises a thyristor T1 connected in series, which can only be controlled to turn on, cannot be controlled to turn off, has a unidirectional current flow capability and a bidirectional blocking voltage capability, optionally, the semi-controlled switch is composed of a thyristor and a diode connected in series or in parallel; with reference to Figure 7C the unidirectional fully-controlled switch comprises an IGBT module connected in series, the IGBT module comprising an IGBT (T2) and a diode D2 anti-parallel thereto, which can only be controlled to turn on and off in one direction, has a bidirectional current flow capability and a unidirectional blocking voltage capability; with reference to Figure 7D the unidirectional fully-controlled switch comprises an IGCT (T3) connected in series, which can only be controlled to turn on and off in one direction, has a unidirectional current flow capability and a unidirectional blocking voltage capability, if it is an inverse-IGCT connected in series, has a unidirectional current flow capability and a bidirectional blocking voltage capability; with reference to Figure 7E the unidirectional fully-controlled switch comprises an IGBT module and a diode D1 connected in series, which can only be controlled to turn on and off in one direction, has a unidirectional current flow capability and a bidirectional blocking voltage capability; with reference to Figure 7F the unidirectional fully-controlled switch comprises an inverse-IGCT (T3) and a thyristor T1 connected in series after being anti-parallel, which can be controlled to turn on in both directions and to turn off in one direction, has a bidirectional current flow capability and a bidirectional blocking voltage capability; with reference to Figure 7G the bidirectional fully-controlled switch comprises a forward IGBT module and a reverse IGBT module connected in series, which can be controlled to turn on and off in both directions, has a bidirectional current flow capability and a bidirectional blocking voltage capability; with reference to Figure 7H the bidirectional fully-controlled switch comprises an inverse-IGCT (T3) connected in series after being anti-parallel, which can be controlled to turn on and off in both directions, has a bidirectional current flow capability and a bidirectional blocking voltage capability; with reference to Figure 7IThe sub-module series switch includes series-connected half-bridge sub-modules, the half-bridge sub-module includes two IGBT modules M1, M2 and a capacitor C1, the connection point of the two IGBT modules M1, M2 is the positive pole of the sub-module, and the other end of the IGBT module M2 is the negative pole of the sub-module, the half-bridge sub-modules are series-connected, and the half-bridge sub-modules are unidirectionally controlled to be turned on and turned off, have bidirectional current flow capability and unidirectional blocking voltage capability; refer to Figure 7J The sub-module series switch includes series-connected full-bridge sub-modules, the full-bridge sub-module includes four IGBT modules M3, M4, M5 and M6 and a capacitor C1, the IGBT modules M3 and M4 are series-connected, the IGBT modules M5 and M6 are series-connected, and the series-connected IGBT modules M3 and M4 and the series-connected IGBT modules M5 and M6 are parallel-connected, and the parallel-connected IGBT modules and the capacitor C1 are also parallel-connected, the connection point of the series-connected IGBT modules M3 and M4 is the positive pole of the sub-module, the connection point of the series-connected IGBT modules M5 and M6 is the negative pole of the sub-module, and the full-bridge sub-modules are series-connected and can be bidirectionally controlled to be turned on and turned off, have bidirectional current flow capability and bidirectional blocking voltage capability.

[0116] In some embodiments, the thyristor is configured with a corresponding trigger circuit and a buffer circuit; the IGBT is configured with a corresponding drive circuit and a buffer circuit; the IGCT or reverse blocking IGCT is configured with a corresponding drive circuit and a buffer circuit; and the buffer circuit is at least composed of a capacitor or a series circuit of a resistor and a capacitor.

[0117] In some embodiments, the second full-controlled valve includes at least one of a full-bridge sub-module, a full-bridge-like sub-module, a midpoint clamping sub-module, a double-half-bridge series sub-module, a double-full-bridge series sub-module, a clamping double sub-module, a cross-connection double sub-module, a self-blocking sub-module or a diode clamping sub-module. Refer to Figure 8A The full-bridge sub-module includes four IGBT modules M7, M8, M9 and M10 and a capacitor C2, the IGBT module includes an IGBT and a diode; the IGBT modules M7 and M8 are series-connected, the IGBT modules M9 and M10 are series-connected, and the series-connected IGBT modules M7 and M8 and the series-connected IGBT modules M9 and M10 are parallel-connected, and the parallel-connected IGBT modules and the capacitor C2 are also parallel-connected, the connection point of the series-connected IGBT modules M7 and M8 is the positive pole of the sub-module, and the connection point of the series-connected IGBT modules M9 and M10 is the negative pole of the sub-module; and when the current flows through the IGBT modules M8 and M9, the full-bridge sub-module presents a negative voltage.

[0118] In some embodiments, refer to Figure 8BThe near-full-bridge submodule includes two IGBT modules M11 and M12, two diodes D3 and D4, and a capacitor C2. Each IGBT module consists of an IGBT and a diode. Diode D3 and IGBT module M11 are connected in series, and diode D4 and IGBT module M12 are connected in series and then in parallel, and are also connected in parallel with capacitor C2. The connection point of diode D3 and IGBT module M11 in series serves as the positive terminal of the near-full-bridge submodule, and the connection point of diode D4 and IGBT module M12 in series serves as the negative terminal of the near-full-bridge submodule. When current flows through IGBT modules M11 and M12, the near-full-bridge submodule exhibits a negative voltage.

[0119] In some embodiments, Figure 8A and Figure 8B The IGBT module can be replaced by the IGCT module.

[0120] This invention provides a method for controlling a full-bridge circuit to shut down a grid-connected commutator converter, executed by an electronic device. This electronic device can be a control unit, a server, or a terminal device. The control unit is an independent physical controller. The server can be an independent physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing cloud computing services. The terminal device can be a smartphone, tablet, laptop, desktop computer, etc., but is not limited to these. The control unit, server, and terminal device can be directly or indirectly connected via wired or wireless communication; this embodiment of the invention does not impose specific limitations.

[0121] Reference Figure 9 A method for controlling a full-bridge circuit to shut down a grid-connected commutator includes steps S101, S102, and S103, wherein...

[0122] S101. After obtaining the operating parameter information of the full-bridge circuit shut-off grid commutator converter, generate inverter state control information based on the parameter information, and control the main circuit to operate in inverter state based on the inverter state control information.

[0123] In some embodiments, the electronic device monitors the operating state of the full-bridge circuit off-grid phase commutated converter in real time, and obtains operating parameter information of the operating state of the full-bridge circuit off-grid phase commutated converter, such as AC voltage, DC current, etc. When the electronic device obtains the operating state of the full-bridge circuit off-grid phase commutated converter, the electronic device generates inverter state control information, such as a trigger pulse, and the full-bridge circuit off-grid phase commutated converter operates in an inverter state based on the inverter state control information. For example, the electronic device controls the first half-controlled valve V42 and the second half-controlled valve V43 of the A-phase upper bridge arm circuit 1, the first half-controlled valve V12 and the second half-controlled valve V13 of the A-phase lower bridge arm circuit 2, the first half-controlled valve V62 and the second half-controlled valve V63 of the B-phase upper bridge arm circuit 1, the first half-controlled valve V32 and the second half-controlled valve V33 of the B-phase lower bridge arm circuit 2, the first half-controlled valve V22 and the second half-controlled valve V23 of the C-phase upper bridge arm circuit 1, and the first half-controlled valve V52 and the second half-controlled valve V53 of the C-phase lower bridge arm circuit 2 to operate in an inverter state according to a six-pulse inverter working mode.

[0124] S102, generating circuit conduction instructions and negative voltage control information during commutation in the case of obtaining a turn-off angle reference value less than a minimum turn-off angle set value or phase commutation failure information, and controlling the transfer circuit and the turn-off circuit in the auxiliary circuit corresponding to the commutation bridge arm to be conductive based on the circuit conduction instructions, and controlling the full-bridge circuit of the auxiliary circuit corresponding to the commutation bridge arm to present negative voltage based on the negative voltage control information.

[0125] In some embodiments, the phase commutation bridge arm is an upper bridge arm circuit or a lower bridge arm circuit; the electronic device obtains an off-angle reference value, and compares the off-angle reference value with a preset minimum off-angle setting value; in the case where the off-angle reference value is less than the minimum off-angle setting value, the electronic device generates a circuit conduction instruction and negative voltage control information during phase commutation, and then controls the third half-controlled valve or the first uncontrolled valve of the transfer circuit in the auxiliary circuit corresponding to the phase commutation bridge arm and the first fully-controlled valve of the off circuit to be conductive based on the circuit conduction instruction, and controls the second fully-controlled valve of the full-bridge circuit of the auxiliary circuit corresponding to the phase commutation bridge arm to present negative voltage based on the negative voltage control information, so as to transfer the current of the phase commutation bridge arm to the transfer circuit, the off circuit and the full-bridge circuit of the auxiliary circuit. For example, when the A-phase upper bridge arm circuit 1 commutates to the B-phase upper bridge arm circuit 1, if the off-angle reference value is less than the minimum off-angle setting value (e.g. 3°), the electronic device controls the third half-controlled valve or the first uncontrolled valve V44 of the A-phase upper bridge transfer circuit 1 and the first fully-controlled valve V71 of the upper bridge off circuit 4 to be conductive based on the circuit conduction instruction, and controls the second fully-controlled valve V81 of the upper bridge full-bridge circuit 7 to present negative voltage based on the negative voltage control information, so as to transfer the current of the A-phase upper bridge arm circuit 1 to the A-phase upper bridge transfer circuit 3, the upper bridge off circuit 4 and the upper bridge full-bridge circuit 7 of the auxiliary circuit. When the A-phase lower bridge arm circuit 2 commutates to the B-phase lower bridge arm circuit 2, if the off-angle reference value is less than the minimum off-angle setting value (e.g. 3°), the electronic device controls the third half-controlled valve or the first uncontrolled valve V14 of the A-phase lower bridge transfer circuit 5 and the first fully-controlled valve V72 of the lower bridge off circuit 6 to be conductive based on the circuit conduction instruction, and controls the second fully-controlled valve V82 of the lower bridge full-bridge circuit 8 to present negative voltage based on the negative voltage control information, so as to transfer the current of the A-phase lower bridge arm circuit 2 to the A-phase lower bridge transfer circuit 5, the lower bridge off circuit 6 and the lower bridge full-bridge circuit 8 of the auxiliary circuit. In the case where the phase commutation fault information is obtained, the control method is the same as described above. The minimum off-angle setting value is in the range of -30° to 10°.

[0126] In some embodiments, the phase commutation fault information includes fault information causing the phase commutation bridge arm of the main circuit to fail in natural phase commutation or the full-bridge circuit to fail in auxiliary phase commutation. The phase commutation fault information includes AC system fault or DC system fault of the full-bridge circuit off-grid phase commutated converter connection. The AC system fault can be determined according to the increase of the zero sequence component of the AC voltage, the sudden change of the AC voltage, the drop of the AC voltage amplitude, the increase of the AC voltage harmonic, and the increase of the DC current. The DC system fault can be determined according to the drop of the DC voltage and the increase of the DC current, but is not limited thereto. The phase commutation fault information also includes determination according to the off time of the first half-controlled valve of the phase commutation bridge arm, the grid-side or valve-side AC current and AC voltage. If the first half-controlled valve of the phase commutation bridge arm has not been turned off at the time when it starts to bear positive voltage under normal AC voltage, it is determined that the phase commutation fault information occurs, but is not limited thereto.

[0127] S103. When the first half-control valve of the commutation bridge arm in the main circuit is restored to shut off, a circuit shutdown command is generated to control the full-bridge circuit and / or shutdown circuit corresponding to the commutation bridge arm to shut off.

[0128] In some embodiments, when the electronic device detects that the first half-controlled valve of the commutation arm of the main circuit has resumed shutdown, a circuit shutdown command is generated. The full-bridge circuit shuts down, and the grid commutation converter responds to the circuit shutdown command, controlling the full-bridge circuit and / or shutdown circuit corresponding to the commutation arm to shut down, thereby transferring the current from the phase power where the commutation arm is located to the phase power to be commutated, effectively suppressing commutation failure, reducing the shutdown angle reference value, and thus reducing reactive power consumption. For example, when the electronic device detects that the first half-controlled valve V42 of the upper bridge arm circuit 1 of phase A in the main circuit has resumed shutdown, a circuit shutdown command is generated. The full-bridge circuit shuts down, and the grid commutation converter responds to the circuit shutdown command, controlling the upper full-bridge circuit 7 and / or upper shutdown circuit 4 corresponding to the upper bridge arm circuit 1 of phase A to shut down, thereby transferring the current from the phase A power where the upper bridge arm circuit 1 is located to the phase B power; wherein, the upper full-bridge circuit 7 is controlled to present a negative voltage, for Figure 8A The full-bridge submodule, through control Figure 8A The conduction of IGBT modules M8 and M9 in the full-bridge submodule is achieved, for Figure 8B The full-bridge submodule controls Figure 8B The IGBT modules M11 and M12 of the full-bridge submodule are turned on; when the A-phase upper bridge transfer circuit is the first uncontrolled valve V44, it can be turned on without applying a trigger pulse.

[0129] In some embodiments, refer to Figure 10 When the main circuit is in inverter operation, the system determines whether the commutation bridge arm has failed to commutate naturally based on the turn-off angle reference value or commutation fault information. If there is no natural commutation failure of the commutation bridge arm, the system continues to control the main circuit to operate in inverter mode. If there is a possibility of commutation failure of the commutation bridge arm, the system controls the negative voltage of the full-bridge circuit and controls the corresponding transfer circuit and turn-off circuit of the auxiliary circuit to be turned on. Subsequently, when the commutation bridge arm is turned off again, the system controls the full-bridge circuit and / or turn-off circuit of the auxiliary circuit to be turned off.

[0130] In some embodiments, when the full-bridge circuit is shut down and the grid commutator inverter is in operation, the shut-off angle reference value is set to be less than the minimum shut-off angle setting value; when the shut-off angle reference value is found to be less than the minimum shut-off angle setting value, and the first half-control valve of the commutation bridge arm of the main circuit is restored to shut-off, a circuit shutdown command is generated, and based on the circuit shutdown command, only the full-bridge circuit corresponding to the commutation bridge arm is controlled to shut down.

[0131] In some embodiments, the circuit shutdown instruction is generated in advance in the case that the sub-modules of the full-bridge circuit of the auxiliary circuit are in the off-grid phase of the phase-change converter, the capacitor voltage of the sub-modules is lower than the rated value and exceeds a first threshold value, and the first half-controlled valve of the phase-change bridge arm of the main circuit is restored to be off; and / or, the number of sub-modules of the full-bridge circuit is increased; and / or, the circuit conduction instruction for controlling the corresponding transfer circuit and shutdown circuit to be turned on and the negative voltage control information for controlling the sub-modules of the full-bridge circuit to present negative voltage are generated in advance; and the first threshold value is in the range of 0.01-0.6 times the rated capacitor voltage.

[0132] In some embodiments, the circuit shutdown instruction is generated in delay in the case that the capacitor voltage of the sub-modules is greater than or equal to the rated value and exceeds a second threshold value, and the first half-controlled valve of the phase-change bridge arm of the main circuit is restored to be off; and / or, the number of sub-modules of the full-bridge circuit is reduced; and / or, the circuit conduction instruction for controlling the corresponding transfer circuit and shutdown circuit to be turned on and the negative voltage control information for controlling the sub-modules of the full-bridge circuit to present negative voltage are generated in delay; and the second threshold value is in the range of 0.01-0.6 times the rated capacitor voltage.

[0133] In some embodiments, the first half-controlled valve of the phase-change bridge arm of the main circuit contains a reverse recovery time greater than or equal to the reverse recovery time of the thyristor contained in the first half-controlled valve, and the reverse recovery time of the thyristor is typically in the range of 200-800us, and the reverse recovery time of the second half-controlled valve is typically in the range of 200us-1.5ms.

[0134] In some embodiments, the circuit after the series connection of the upper bridge shutdown circuit and the upper bridge full-bridge circuit of the auxiliary circuit and the anode bus of the main circuit are connected through a disconnecting switch and / or a knife switch, the circuit after the series connection of the lower bridge shutdown circuit and the lower bridge full-bridge circuit of the auxiliary circuit and the cathode bus of the main circuit are connected through a disconnecting switch and / or a knife switch, and the switch separation instruction is generated in the case that the auxiliary circuit failure information is obtained, and the disconnecting switch and / or the knife switch are separated based on the switch separation instruction.

[0135] In some embodiments, the auxiliary circuit failure information includes the impact of the failure of the auxiliary circuit device or sub-module on the operation, but is not limited thereto.

[0136] In some embodiments, in the case that the full-bridge circuit is in the off-grid phase of the phase-change converter, the auxiliary phase-change voltage can also be provided by the full-bridge circuit, the trigger angle reference value is reduced, and thus the consumption of reactive power is reduced and the power factor is improved.

[0137] Reference Figure 11The full-bridge circuit off-grid phase commutated converter control device 20 can specifically include a first control module 201, a second control module 202, and a third control module 203, wherein

[0138] The first control module 201 is configured to, when the operating parameter information of the full-bridge circuit off-grid phase commutated converter is acquired, generate inverter state control information based on the parameter information, and control the main circuit to operate in an inverter state based on the inverter state control information.

[0139] The second control module 202 is configured to, when the off-grid angle reference value is less than the minimum off-grid angle reference value or the phase commutation fault information is acquired, generate a circuit conduction instruction and negative voltage control information during phase commutation, and control the transfer circuit and the off-grid circuit in the auxiliary circuit corresponding to the phase commutation bridge arm to be conductive based on the circuit conduction instruction, and control the full-bridge circuit of the auxiliary circuit corresponding to the phase commutation arm to present a negative voltage based on the negative voltage control information.

[0140] The third control module 203 is configured to, when the first half-controlled valve of the phase commutation bridge arm of the main circuit recovers off-grid, generate a circuit off-grid instruction, and control the full-bridge circuit and / or the off-grid circuit corresponding to the phase commutation bridge arm to be off-grid.

[0141] In some embodiments, the first control module 201 can include a logic circuit, or be implemented by a central processor, a microprocessor, a digital signal processor, a field programmable gate array, or the like included in the device.

[0142] The second control module 202 can include a logic circuit, or be implemented by a central processor, a microprocessor, a digital signal processor, a field programmable gate array, or the like included in the device.

[0143] The third control module 203 can include a logic circuit, or be implemented by a central processor, a microprocessor, a digital signal processor, a field programmable gate array, or the like included in the device.

[0144] The embodiment of the present application provides a high-voltage direct-current power transmission system, including a full-bridge circuit off-grid phase commutated converter.

[0145] In some embodiments, the high-voltage direct-current power transmission system is a two-terminal direct-current power transmission system or a multi-terminal direct-current power transmission system, and the two-terminal direct-current power transmission system or the multi-terminal direct-current power transmission system respectively includes a single-pole direct-current power transmission system, a bipolar direct-current power transmission system, or a back-to-back direct-current system.

[0146] The part or all of the inverters required to operate in the two-terminal direct-current power transmission system or the multi-terminal direct-current power transmission system adopt the full-bridge circuit off-grid phase commutated converter.

[0147] Reference Figure 12 , Figure 12The structure of one pole of bipolar DC power transmission system is shown, one pole includes first AC system 13, first grid commutation converter 9, second grid commutation converter 10, first converter transformer 11, second converter transformer 12, DC line 14, second AC system 19, first full-bridge circuit shutdown grid commutation converter 15, second full-bridge circuit shutdown grid commutation converter 16, third converter transformer 17 and fourth converter transformer 18. When power is sent positively, the AC power of the first AC system 13 is rectified into DC power by the first grid commutation converter 9 and the second grid commutation converter 10 after the first converter transformer 11 and the second converter transformer 12, transmitted to the first full-bridge circuit shutdown grid commutation converter 15 and the second full-bridge circuit shutdown grid commutation converter 16 through the DC line 14, and inverted into AC power, transmitted to the second AC system 19 after the third converter transformer 17 and the fourth converter transformer 18, realizing the transmission of DC power. The first full-bridge circuit shutdown grid commutation converter 15 and the second full-bridge circuit shutdown grid commutation converter 16 have the ability to suppress commutation failure, ensuring the reliability of DC power transmission.

[0148] The above is only part of the embodiments of the present application, it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can also be made, which should be considered as the protection scope of the present application.

Claims

1. A full-bridge circuit off-grid phase commutated converter, characterized in that, The application relates to a main circuit, an auxiliary circuit, and a main circuit and an auxiliary circuit. The main circuit comprises at least one upper bridge arm circuit and at least one lower bridge arm circuit, one end of the at least one upper bridge arm circuit is connected with a main circuit anode bus, the other end of the at least one upper bridge arm circuit is connected with one end of the at least one lower bridge arm circuit, and the other end of the at least one lower bridge arm circuit is connected with a main circuit cathode bus. The auxiliary circuit comprises at least one upper bridge transfer circuit, an upper bridge off circuit, an upper bridge full bridge circuit, at least one lower bridge transfer circuit, a lower bridge off circuit and a lower bridge full bridge circuit. One end of the at least one upper bridge transfer circuit is connected with an upper bridge transfer circuit anode bus, the other end of the at least one upper bridge transfer circuit is connected with the at least one upper bridge arm circuit, the upper bridge off circuit and the upper bridge full bridge circuit are connected in series, and one end of the series-connected circuit is connected with the upper bridge transfer circuit anode bus and the other end is connected with the main circuit anode bus. One end of the at least one lower bridge transfer circuit is connected with a lower bridge transfer circuit cathode bus, the other end of the at least one lower bridge transfer circuit is connected with the at least one lower bridge arm circuit, the lower bridge off circuit and the lower bridge full bridge circuit are connected in series, and one end of the series-connected circuit is connected with the lower bridge transfer circuit cathode bus and the other end is connected with the main circuit cathode bus. The at least one upper bridge arm circuit and the at least one lower bridge arm circuit comprise first half-controlled valves and second half-controlled valves. In the case that the at least one upper bridge arm circuit and the at least one lower bridge arm circuit both comprise first half-controlled valves and second half-controlled valves, the first half-controlled valves and the second half-controlled valves are connected in series, one end of the first half-controlled valve of the at least one upper bridge arm circuit is connected with the main circuit anode bus, one end of the second half-controlled valve of the at least one upper bridge arm circuit is connected with one end of the second half-controlled valve of the at least one lower bridge arm circuit, and one end of the first half-controlled valve of the at least one lower bridge arm circuit is connected with the main circuit cathode bus. The at least one upper bridge transfer circuit and the at least one lower bridge transfer circuit both comprise third half-controlled valves or first non-controlled valves.

2. The line commutated converter according to claim 1, characterized in that The first half-controlled valves, the second half-controlled valves and the third half-controlled valves all comprise half-controlled switches, and the first non-controlled valves comprise non-controlled switches. The half-controlled switch is composed of controllable turn-on but uncontrollable turn-off semiconductor devices in series, and the controllable turn-on but uncontrollable turn-off semiconductor devices include thyristors. The uncontrolled switch is composed of uncontrollable turn-on and turn-off semiconductor devices in series, and the uncontrollable turn-on and turn-off semiconductor devices include diodes.

3. The line commutated force commutated converter of claim 1, wherein, The first half-controlled valve, and / or the second half-controlled valve, and / or the third half-controlled valve or the first uncontrolled valve are connected in parallel with a lightning arrester.

4. The line commutated force commutated converter of claim 1, wherein, In the case that the upper bridge arm circuit and the lower bridge arm circuit of the at least one phase include the first half-controlled valve and the second half-controlled valve, the voltage withstand ratio of the first half-controlled valve and the second half-controlled valve is in the range of 0.2-5.

5. The line commutated force commutated converter of claim 1, wherein, The first half-controlled valve, and / or the second half-controlled valve, and / or the third half-controlled valve or the first uncontrolled valve further include an electric reactor.

6. The full-bridge circuit off-grid phase commutated converter of claim 1, wherein, The upper bridge turn-off circuit of the auxiliary circuit is connected to the circuit obtained by connecting the upper bridge full-bridge circuit in series and the main circuit anode bus through an isolating switch or a knife switch; the lower bridge turn-off circuit of the auxiliary circuit is connected to the circuit obtained by connecting the lower bridge full-bridge circuit in series and the main circuit cathode bus through an isolating switch or a knife switch.

7. The full-bridge circuit off-grid phase commutated converter of claim 1, wherein, The upper bridge turn-off circuit and the lower bridge turn-off circuit each include a first fully-controlled valve; One end of the first fully-controlled valve of the upper bridge turn-off circuit is connected to one end of the upper bridge full-bridge circuit, and the other end of the first fully-controlled valve of the upper bridge turn-off circuit is connected to the upper bridge transfer circuit anode bus; or, one end of the first fully-controlled valve of the upper bridge turn-off circuit is connected to one end of the upper bridge full-bridge circuit, and the other end of the first fully-controlled valve of the upper bridge turn-off circuit is connected to the main circuit anode bus. One end of the first fully-controlled valve of the lower bridge turn-off circuit is connected to one end of the lower bridge full-bridge circuit, and the other end of the first fully-controlled valve of the lower bridge turn-off circuit is connected to the lower bridge transfer circuit cathode bus; or, one end of the first fully-controlled valve of the lower bridge turn-off circuit is connected to one end of the lower bridge full-bridge circuit, and the other end of the first fully-controlled valve of the lower bridge turn-off circuit is connected to the main circuit cathode bus.

8. The line commutated force commutated converter of claim 7, wherein, The upper bridge turn-off circuit and the lower bridge turn-off circuit each further include a fourth half-controlled valve connected in series with the first fully-controlled valve.

9. The line commutated force commutated converter of claim 7, wherein, The first fully-controlled valve is connected in parallel with a lightning arrester.

10. The line commutated force commutated converter of claim 7, wherein, The first fully-controlled valve includes at least one of a unidirectional fully-controlled switch, a bidirectional fully-controlled switch and a sub-module series switch.

11. The line commutated force commutated converter of claim 10, wherein, The unidirectional fully-controlled switch is composed of semiconductor devices with unidirectional turn-off capability in series, and the semiconductor devices with unidirectional turn-off capability include insulated gate bipolar transistors, integrated gate-commutated thyristors, reverse blocking integrated gate-commutated thyristors; The bidirectional fully-controlled switch is composed of semiconductor devices with bidirectional turn-off capability in series, and the semiconductor devices with bidirectional turn-off capability include reverse-parallel reverse blocking integrated gate-commutated thyristors and reverse series insulated gate bipolar transistors; The sub-module series switch is composed of sub-modules in series, and the sub-modules include half-bridge sub-modules, full-bridge sub-modules, quasi-full-bridge sub-modules and clamped double sub-modules, and the semiconductor devices of the half-bridge sub-modules, the full-bridge sub-modules, the quasi-full-bridge sub-modules and the clamped double sub-modules include insulated gate bipolar transistors and integrated gate-commutated thyristors.

12. The line commutated force commutated converter of any of claims 1-11, wherein, The upper bridge full-bridge circuit and the lower bridge full-bridge circuit each include a second fully-controlled valve. One end of the second controllable valve of the upper bridge full-bridge circuit is connected with the anode bus of the main circuit, and the other end of the second controllable valve of the upper bridge full-bridge circuit is connected with the upper bridge shutdown circuit; or one end of the second controllable valve of the upper bridge full-bridge circuit is connected with the anode bus of the upper bridge transfer circuit, and the other end of the second controllable valve of the upper bridge full-bridge circuit is connected with the upper bridge shutdown circuit. One end of the second controllable valve of the lower bridge full-bridge circuit is connected with the cathode bus of the main circuit, and the other end of the second controllable valve of the lower bridge full-bridge circuit is connected with the lower bridge shutdown circuit; or one end of the second controllable valve of the lower bridge full-bridge circuit is connected with the cathode bus of the lower bridge transfer circuit, and the other end of the second controllable valve of the lower bridge full-bridge circuit is connected with the lower bridge shutdown circuit.

13. The line commutated force commutated converter of claim 12, wherein, The second controllable valve comprises at least one of a full-bridge sub-module, a full-bridge-like sub-module, a midpoint clamping sub-module, a double-half-bridge series sub-module, a double-full-bridge series sub-module, a clamping double sub-module, a cross-connection double sub-module, a self-resistance sub-module or a diode clamping sub-module connected in series.

14. The line commutated force commutated converter of claim 12, wherein, The upper bridge full-bridge circuit and the lower bridge full-bridge circuit further comprise a resistor or an inductor; the resistor or the inductor is connected in series with the sub-module.

15. The line commutated force commutated converter of claim 12, wherein, The second controllable valve is connected in parallel with a lightning arrester.

16. A method of controlling a line-commutated converter with a full-bridge circuit for switching off, characterized by A method for controlling the full-bridge circuit shutdown grid commutated converter according to any one of claims 1-15, comprising: In the case that the operating parameter information of the full-bridge circuit shutdown grid commutated converter is obtained, generating the inverter state control information based on the parameter information, and controlling the main circuit to operate in the inverter state based on the inverter state control information; In the case that the shutdown angle reference value is less than the minimum shutdown angle constant value or the commutation fault information is obtained, generating the circuit conduction instruction and the negative voltage control information during commutation, and controlling the transfer circuit and the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm to be turned on based on the circuit conduction instruction, and controlling the full-bridge circuit of the auxiliary circuit corresponding to the commutation bridge arm to present negative voltage based on the negative voltage control information; In the case that the first half-controlled valve of the commutation bridge arm of the main circuit recovers shutdown, generating the circuit shutdown instruction to control the full-bridge circuit and / or the shutdown circuit corresponding to the commutation bridge arm to be turned off.

17. The method of claim 16, wherein, In the case that the full-bridge circuit shutdown grid commutated converter operates normally, setting the shutdown angle reference value to be less than the minimum shutdown angle constant value; in the case that the shutdown angle reference value is less than the minimum shutdown angle constant value and the first half-controlled valve of the commutation bridge arm of the main circuit recovers shutdown, generating the circuit shutdown instruction based on the circuit shutdown instruction, and controlling only the full-bridge circuit corresponding to the commutation bridge arm to be turned off.

18. The method of claim 16, wherein, In a case that the full-bridge circuit of the auxiliary circuit is normally operating, the capacitor voltage of the sub-module of the full-bridge circuit of the auxiliary circuit is lower than the rated value and exceeds a first threshold value, and the first semi-controlled valve of the commutation bridge arm of the main circuit is recovered to be turned off, the circuit turn-off instruction is generated in advance; and / or, the number of the sub-modules of the full-bridge circuit is increased; and / or, the circuit turn-on instruction for controlling the corresponding transfer circuit and turn-off circuit to be turned on and the negative voltage control information for controlling the sub-module of the full-bridge circuit to present negative voltage are generated in advance; the first threshold value is in a range of 0.01-0.6 times of the rated capacitor voltage.

19. The method of claim 18, wherein, In a case that the capacitor voltage of the sub-module is greater than or equal to the rated value and exceeds a second threshold value, and the first semi-controlled valve of the commutation bridge arm of the main circuit is recovered to be turned off, the circuit turn-off instruction is generated in a delayed manner; and / or, the number of the sub-modules of the full-bridge circuit is reduced; and / or, the circuit turn-on instruction for controlling the corresponding transfer circuit and turn-off circuit to be turned on and the negative voltage control information for controlling the sub-module of the full-bridge circuit to present negative voltage are generated in a delayed manner; the second threshold value is in a range of 0.01-0.6 times of the rated capacitor voltage.

20. The method of claim 16, wherein, The negative voltage of the full-bridge circuit is presented by controlling the switch device in the sub-module of the third fully-controlled valve to be turned on so that the sub-module presents capacitor negative voltage in the current flow direction.

21. The method of claim 16, wherein, The recovery of the first semi-controlled valve of the commutation bridge arm of the main circuit to be turned off is determined according to the reverse recovery time of the first semi-controlled valve, and the reverse recovery time is greater than or equal to the reverse recovery time of the thyristor contained in the first semi-controlled valve.

22. The method according to any one of claims 16-21, characterized by, In a case that the circuit obtained by connecting the upper bridge turn-off circuit and the upper bridge full-bridge circuit of the auxiliary circuit in series and the anode bus of the main circuit are connected through a disconnecting switch or a knife switch, the circuit obtained by connecting the lower bridge turn-off circuit and the lower bridge full-bridge circuit of the auxiliary circuit in series and the cathode bus of the main circuit are connected through a disconnecting switch and / or a knife switch, and the auxiliary circuit fault information is obtained, a switch separation instruction is generated, and the disconnecting switch or the knife switch is separated based on the switch separation instruction.

23. A full-bridge circuit turn-off line-commutated converter control device, characterized by A control method for the full-bridge circuit turn-off line-commutated converter according to any one of claims 1-15, comprising: a first control module configured to, in a case that the operating parameter information of the full-bridge circuit turn-off line-commutated converter is obtained, generate inverter state control information based on the parameter information, and control the main circuit to operate in an inverter state based on the inverter state control information; a second control module configured to, in a case that the turn-off angle reference value is less than the minimum turn-off angle constant value or the commutation fault information is obtained, generate a circuit turn-on instruction and negative voltage control information during commutation, control the transfer circuit and the turn-off circuit in the auxiliary circuit corresponding to the commutation bridge arm to be turned on based on the circuit turn-on instruction, and control the full-bridge circuit of the auxiliary circuit corresponding to the commutation bridge arm to present negative voltage based on the negative voltage control information; a third control module configured to, in a case that the first semi-controlled valve of the commutation bridge arm of the main circuit is recovered to be turned off, generate a circuit turn-off instruction, and control the full-bridge circuit and / or the turn-off circuit corresponding to the commutation bridge arm to be turned off.

24. A high voltage direct current transmission system comprising the full-bridge circuit blocked grid commutated converter of any one of claims 1-15.

25. The system of claim 24, wherein, The high voltage direct current transmission system is a two-terminal direct current transmission system or a multi-terminal direct current transmission system, which respectively comprises a single-pole direct current transmission system, a bipolar direct current transmission system or a back-to-back direct current system.

26. The system of claim 25, wherein, The full-bridge circuit blocked grid commutated converter is used in part or all of the inverter operating converter of the two-terminal direct current transmission system or the multi-terminal direct current transmission system.

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