Capacitor assisted off-grid converter and control method and device and system thereof

Abstract

The application provides a capacitor-assisted off-grid commutation converter and a control method and device thereof and system, and relates to the technical field of high-voltage direct current transmission.The capacitor-assisted off-grid commutation converter provided by the application comprises a main circuit, at least one upper bridge arm circuit and at least one lower bridge arm circuit; an auxiliary circuit, at least one upper bridge transfer circuit, one upper bridge off-grid circuit, one upper bridge energy storage circuit, at least one upper bridge pumping circuit, at least one lower bridge transfer circuit, one lower bridge off-grid circuit, one lower bridge energy storage circuit and at least one lower bridge pumping circuit.The application can inhibit the occurrence of commutation failure and improve the reliability of high-voltage direct current transmission.

Description

Technical Field

[0001] This invention relates to the field of high voltage direct current transmission technology, and in particular to a capacitor-assisted grid-shutdown phase-commutation converter and its control method, device, and system. Background Technology

[0002] With the increasing number of high-voltage and ultra-high-voltage direct current (HVDC) transmission systems connected to the grid, multi-feed HVDC transmission systems have been formed in multiple regional power grids. When multiple HVDC lines fail to commutate simultaneously, it may pose a threat to the safe operation of the AC power grid in that region. Furthermore, as the proportion of renewable energy generation increases, the AC voltage support capacity decreases, placing higher demands on the stable operation of HVDC transmission systems and their ability to suppress commutation failures.

[0003] Existing DC transmission technologies mainly employ grid-commutated converters with a twelve-pulse circuit structure and voltage source converters with a modular multilevel circuit structure for high-voltage and ultra-high-voltage DC transmission. In the twelve-pulse grid-commutated converter, each twelve-pulse circuit consists of two three-phase six-arm bridge circuits connected in series or parallel, with each arm using a single high-capacity thyristor connected in series. In the modular multilevel voltage source converter, the modular multilevel circuit is a three-phase six-arm bridge circuit, with each arm using a half-bridge submodule structure and / or a full-bridge submodule structure connected in series. Furthermore, addressing commutation failure issues by replacing existing grid-commutated converters with fully controlled devices and adding auxiliary circuits to create controllable turn-off grid-commutated converters has become an important research direction in DC transmission technology.

[0004] However, existing grid-commutated converters with a twelve-pulse circuit structure suffer from commutation failure; existing voltage source converters with a modular multilevel circuit structure suffer from small device capacity, high cost, and high losses. Existing grid-commutated converters that use fully controlled device replacement to suppress commutation failure have small device capacity and their reliability still needs verification; existing grid-commutated converters that use more auxiliary circuits to suppress commutation failure have complex structures and reduced reliability; both of the above two types of grid-commutated converters rely on surge arresters to absorb energy during forced shutdown, requiring each bridge arm to be equipped with an equivalent surge arrester. In the case of faults with a high probability such as single-phase grounding, only the surge arrester of the faulty phase operates, resulting in low surge arrester utilization. Summary of the Invention

[0005] In order to suppress the occurrence of commutation failure in high-voltage direct current transmission, reduce the cost of controllable shutdown grid commutation converters, and improve the reliability of high-voltage direct current transmission, this invention provides a capacitor-assisted shutdown grid commutation converter and its control method, device, and system.

[0006] This invention provides a capacitor-assisted grid-connected phase-commutation converter, employing the following technical solution:

[0007] A capacitor-assisted grid-connected phase-commutator includes:

[0008] The main circuit includes 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 to the anode bus of the main circuit, the other end of the at least one upper bridge arm circuit is connected to 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 to the cathode bus of the main circuit.

[0009] The auxiliary circuit includes at least one phase upper bridge transfer circuit, one upper bridge turn-off circuit, one upper bridge energy storage circuit, at least one upper bridge pumping circuit, at least one phase lower bridge transfer circuit, one lower bridge turn-off circuit, one lower bridge energy storage circuit, and at least one lower bridge pumping circuit.

[0010] One end of the at least one phase upper bridge transfer circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the at least one phase upper bridge transfer circuit is connected to the at least one phase upper bridge arm circuit.

[0011] One end of the upper bridge shutdown circuit is connected to the anode bus of the upper bridge transfer circuit; the other end of the upper bridge shutdown circuit is connected to one end of the upper bridge energy storage circuit; the other end of the upper bridge energy storage circuit is connected to the anode bus of the main circuit; or, one end of the upper bridge energy storage circuit is connected to the anode bus of the upper bridge transfer circuit, the other end of the upper bridge energy storage circuit is connected to one end of the upper bridge shutdown circuit, and the other end of the upper bridge shutdown circuit is connected to the anode bus of the main circuit.

[0012] One end of the upper bridge pump circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the upper bridge pump circuit is connected to the upper bridge arm circuit.

[0013] One end of the at least one phase lower bridge transfer circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the at least one phase lower bridge transfer circuit is connected to the at least one phase lower bridge arm circuit.

[0014] One end of the lower bridge shutdown circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the lower bridge shutdown circuit is connected to one end of the lower bridge energy storage circuit; the other end of the lower bridge energy storage circuit is connected to the cathode bus of the main circuit; or, one end of the lower bridge energy storage circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the lower bridge energy storage circuit is connected to one end of the lower bridge shutdown circuit, and the other end of the lower bridge shutdown circuit is connected to the cathode bus of the main circuit.

[0015] One end of the lower bridge pump circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the lower bridge pump circuit is connected to the lower bridge arm circuit.

[0016] According to some embodiments, both the at least one phase upper arm circuit and the at least one phase lower arm circuit include: a first semi-controlled valve and a second semi-controlled valve;

[0017] The first semi-controlled valve and the second semi-controlled valve are connected in series; one end of the first semi-controlled valve of the at least one phase upper bridge arm circuit is connected to the anode bus of the main circuit, one end of the second semi-controlled valve of the at least one phase upper bridge arm circuit is connected to one end of the second semi-controlled valve of the at least one phase lower bridge arm circuit; one end of the first semi-controlled valve of the at least one phase lower bridge arm circuit is connected to the cathode bus of the main circuit.

[0018] According to some embodiments, the connection point between the first half-control valve and the second half-control valve of the at least one phase upper bridge arm circuit is connected to one end of the at least one phase upper bridge transfer circuit, and the connection point between the first half-control valve and the second half-control valve of the at least one phase lower bridge arm circuit is connected to one end of the at least one phase lower bridge transfer circuit.

[0019] According to some embodiments, the pressure resistance ratio of the first semi-controlled valve and the second semi-controlled valve ranges from 0.2 to 5.

[0020] According to some embodiments, both the at least one phase upper bridge transfer circuit and the at least one phase lower bridge transfer circuit include: a third semi-controlled valve or a first uncontrolled valve;

[0021] One end of the third half-controlled valve or the first uncontrolled valve of the at least one phase upper bridge transfer circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the third half-controlled valve or the first uncontrolled valve of the at least one phase upper bridge transfer circuit is connected to the connection point between the first half-controlled valve and the second half-controlled valve of the at least one phase upper bridge arm circuit; one end of the third half-controlled valve or the first uncontrolled valve of the at least one phase lower bridge transfer circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the third half-controlled valve or the first uncontrolled valve of the at least one phase upper bridge transfer circuit is connected to the connection point between the first half-controlled valve and the second half-controlled valve of the at least one phase lower bridge arm circuit.

[0022] According to some embodiments, the first semi-controlled valve, the second semi-controlled valve, and the third semi-controlled valve all include a semi-controlled switch; the first uncontrolled valve includes an uncontrolled switch.

[0023] The semi-controlled switch is composed of semiconductor devices that can be controlled to turn on but not controlled to turn off, and the semiconductor devices that can be controlled to turn on but not controlled to turn off include, but are not limited to, thyristors.

[0024] The uncontrolled switch is composed of semiconductor devices that are connected in series for uncontrolled on and off, including but not limited to diodes.

[0025] According to some embodiments, the first semi-controlled valve, and / or the second semi-controlled valve, and / or the third semi-controlled valve or the first uncontrolled valve are connected in parallel with surge arresters.

[0026] According to some embodiments, the first semi-controlled valve, and / or the second semi-controlled valve, and / or the third semi-controlled valve, or the first uncontrolled valve further includes a reactor.

[0027] According to some embodiments, the circuit consisting of the upper bridge shutdown circuit and the upper bridge energy storage circuit connected in series in the auxiliary circuit and the anode bus of the main circuit are connected through a disconnecting switch and / or a knife switch; the circuit consisting of the lower bridge shutdown circuit and the lower bridge energy storage circuit connected in series in the auxiliary circuit and the cathode bus of the main circuit are connected through a disconnecting switch and / or a knife switch.

[0028] According to some embodiments, both the upper bridge shutdown circuit and the lower bridge shutdown circuit include a first fully controlled valve;

[0029] One end of the first fully controlled valve of the upper bridge shutdown circuit is connected to one end of the upper bridge energy storage 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 energy storage 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.

[0030] One end of the first fully controlled valve of the lower bridge shutdown circuit is connected to one end of the lower bridge energy storage 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 energy storage 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.

[0031] According to some embodiments, both the upper bridge shutdown circuit and the lower bridge shutdown circuit further include a fourth semi-controlled valve, which is connected in series with the first fully controlled valve.

[0032] According to some embodiments, the first fully controlled valve is connected in parallel with a surge arrester.

[0033] According to some embodiments, the first fully controlled valve includes at least one of a one-way fully controlled switch, a two-way fully controlled switch, and a submodule series switch.

[0034] According to some embodiments, the unidirectional fully controlled switch is composed of semiconductor devices with unidirectional turn-off capability connected in series. The semiconductor devices with unidirectional turn-off capability include, but are not limited to, insulated gate bipolar transistors, integrated gate commutated thyristors, and reverse-resistance integrated gate commutated thyristors.

[0035] The bidirectional fully controlled switch is composed of semiconductor devices with bidirectional turn-off capability connected in series. The semiconductor devices with bidirectional turn-off capability include, but are not limited to, anti-parallel reverse-resistance integrated gate commutated thyristors and anti-connected insulated gate bipolar transistors.

[0036] The sub-module series switch is composed of sub-modules connected in series. The sub-modules include, but are not limited to, half-bridge sub-modules, full-bridge sub-modules, near-full-bridge sub-modules, and clamped double sub-modules. The semiconductor devices of the half-bridge sub-modules, full-bridge sub-modules, near-full-bridge sub-modules, and clamped double sub-modules include, but are not limited to, insulated-gate bipolar transistors and integrated gate commutated thyristors.

[0037] According to some embodiments, both the upper-bridge energy storage circuit and the lower-bridge energy storage circuit include: a capacitor or a sub-module series switch; one end of the capacitor or sub-module series switch of the upper-bridge energy storage circuit is connected to the anode bus of the main circuit, and the other end of the capacitor or sub-module series switch of the upper-bridge energy storage circuit is connected to the upper-bridge shutdown circuit; or, one end of the capacitor or sub-module series switch of the upper-bridge energy storage circuit is connected to the anode bus of the upper-bridge transfer circuit, and the other end of the capacitor or sub-module series switch of the upper-bridge energy storage circuit is connected to the upper-bridge shutdown circuit; one end of the capacitor or sub-module series switch of the lower-bridge energy storage circuit is connected to the cathode bus of the main circuit, and the other end of the capacitor or sub-module series switch of the lower-bridge energy storage circuit is connected to the lower-bridge shutdown circuit; or, one end of the capacitor or sub-module series switch of the lower-bridge energy storage circuit is connected to the cathode bus of the lower-bridge transfer circuit, and the other end of the capacitor or sub-module series switch of the lower-bridge energy storage circuit is connected to the lower-bridge shutdown circuit.

[0038] According to some embodiments, both the upper bridge energy storage circuit and the lower bridge energy storage circuit include a resistor or an inductor; the resistor or inductor is connected in series with the capacitor or submodule series switch.

[0039] According to some embodiments, the capacitor or submodule is connected in series with a surge arrester in parallel.

[0040] According to some embodiments, both the at least one upper bridge pump circuit and the at least one lower bridge pump circuit include a fifth semi-controlled valve and / or a second uncontrolled valve; one end of the fifth semi-controlled valve and / or the second uncontrolled valve of the at least one upper bridge pump circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the fifth semi-controlled valve and / or the second uncontrolled valve of the at least one upper bridge pump circuit is connected to one end of the second semi-controlled valve of the upper bridge arm circuit; one end of the fifth semi-controlled valve and / or the second uncontrolled valve of the at least one lower bridge pump circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the fifth semi-controlled valve and / or the second uncontrolled valve of the at least one lower bridge pump circuit is connected to one end of the second semi-controlled valve of the lower bridge arm circuit; or,

[0041] Each of the at least one upper bridge pump circuit and the at least one lower bridge pump circuit includes a first sub-semi-controlled valve and a second sub-semi-controlled valve; the first and second sub-semi-controlled valves of the at least one upper bridge pump circuit are connected in series, one end of the first sub-semi-controlled valve of the at least one upper bridge pump circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the first sub-semi-controlled valve of the at least one upper bridge pump circuit is connected to one end of the third sub-semi-controlled valve or the first uncontrolled valve of the upper bridge transfer circuit; one end of the second sub-semi-controlled valve of the at least one upper bridge pump circuit is connected to one end of the second sub-semi-controlled valve of the upper bridge arm circuit; the first and second sub-semi-controlled valves of the at least one lower bridge pump circuit are connected in series, one end of the first sub-semi-controlled valve of the at least one lower bridge pump circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the first sub-semi-controlled valve of the at least one lower bridge pump circuit is connected to one end of the third sub-semi-controlled valve or the first uncontrolled valve of the lower bridge transfer circuit; one end of the second sub-semi-controlled valve of the at least one lower bridge pump circuit is connected to one end of the second sub-semi-controlled valve of the lower bridge arm circuit; or...

[0042] The at least one upper bridge pump circuit and the at least one lower bridge pump circuit each include a first sub-semi-controlled valve and a second sub-semi-controlled valve; the first sub-semi-controlled valve of the at least one upper bridge pump circuit is integrated with the third semi-controlled valve or the first uncontrolled valve of the upper bridge transfer circuit, and the two are connected in parallel as devices, valve segments, or valves; the second sub-semi-controlled valve of the at least one upper bridge pump circuit is integrated with the second semi-controlled valve of the upper bridge arm circuit, and the two are connected in parallel as devices, valve segments, or valves; the first sub-semi-controlled valve of the at least one lower bridge pump circuit is integrated with the third semi-controlled valve or the first uncontrolled valve of the lower bridge transfer circuit, and the two are connected in parallel as devices, valve segments, or valves; the second sub-semi-controlled valve of the lower bridge pump circuit is integrated with the second semi-controlled valve of the lower bridge arm circuit, and the two are connected in parallel as devices, valve segments, or valves.

[0043] This invention provides a control method for a capacitor-assisted power grid commutator switch, employing the following technical solution:

[0044] A control method for a capacitor-assisted grid-connected phase-commutator, used to control the capacitor-assisted grid-connected phase-commutator, includes:

[0045] Upon obtaining the operating parameter information of the capacitor-assisted grid-connected phase converter, inverter state control information is generated based on the parameter information, and the main circuit is controlled to operate in inverter state based on the inverter state control information.

[0046] When the negative pressure of the energy storage circuit is lower than the rated value and exceeds the first threshold, and the commutation bridge arm of the main circuit ends the commutation to the commutation bridge arm circuit and bears the negative pressure, an auxiliary circuit control command is generated, and the corresponding pump pressure circuit of the corresponding auxiliary circuit is controlled to be turned on based on the auxiliary circuit control command. The energy storage circuit is an upper bridge energy storage circuit or a lower bridge energy storage circuit.

[0047] Upon receiving commutation fault information, a circuit turn-on command is generated, and based on the circuit turn-on command, the transfer circuit and turn-off circuit in the auxiliary circuit corresponding to the commutation bridge arm are controlled to turn on; wherein, the commutation bridge arm is the upper bridge arm circuit and / or the lower bridge arm circuit.

[0048] When the first half-control valve of the commutation bridge arm in the main circuit is restored to shutdown, a circuit shutdown command is generated to control the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm to shut down.

[0049] According to some embodiments, when the commutation bridge arm is an upper bridge arm circuit, the transfer circuit in the auxiliary circuit corresponding to the commutation bridge arm is an upper bridge transfer circuit of the same phase, and the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm is an upper bridge shutdown circuit.

[0050] When the commutation bridge arm is a lower bridge arm circuit, the transfer circuit in the auxiliary circuit corresponding to the commutation bridge arm is a lower bridge transfer circuit of the same phase, and the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm is a lower bridge shutdown circuit.

[0051] According to some embodiments, the first half-controlled valve of the commutation bridge arm of the main circuit resumes shutdown based on the reverse recovery time of the first half-controlled valve, wherein the reverse recovery time is greater than or equal to the reverse recovery time of the thyristor included in the first half-controlled valve.

[0052] According to some embodiments, the circuit after the upper bridge shutdown circuit and the upper bridge energy storage circuit of the auxiliary circuit are connected in series with the anode bus of the main circuit through a disconnecting switch and / or a knife switch, and the circuit after the lower bridge shutdown circuit and the lower bridge energy storage circuit of the auxiliary circuit are connected in series with the cathode bus of the main circuit through a disconnecting switch and / or a knife switch. When the fault information of the auxiliary circuit is obtained, a switch separation command is generated, and the disconnecting switch and / or knife switch are controlled to separate based on the switch separation command.

[0053] This invention provides a capacitor-assisted grid-connected phase-commutator control device, which adopts the following technical solution:

[0054] A capacitor-assisted grid-connected phase-commutator control device is provided for controlling the capacitor-assisted grid-connected phase-commutator, comprising: a first control module, a second control module, a third control module, and a fourth control module, wherein...

[0055] The first control module is used to generate inverter state control information based on the operating parameter information of the capacitor-assisted grid-connected phase converter when it obtains the operating parameter information, and to control the main circuit to operate in inverter state based on the inverter state control information.

[0056] The second control module is used to generate an auxiliary circuit control command when the negative pressure of the energy storage circuit is lower than the rated value and exceeds the first threshold, and the commutation bridge arm of the main circuit ends the commutation to the commutation bridge arm circuit and bears the negative pressure, and to control the corresponding pump pressure circuit of the corresponding auxiliary circuit to be turned on based on the auxiliary circuit control command. The energy storage circuit is an upper bridge energy storage circuit or a lower bridge energy storage circuit.

[0057] The third control module is used to generate a circuit turn-on command when a commutation fault information is obtained, and to control the transfer circuit and the turn-off circuit in the auxiliary circuit corresponding to the commutation bridge arm to turn on based on the circuit turn-on command; wherein, the commutation bridge arm is an upper bridge arm circuit or a lower bridge arm circuit.

[0058] The fourth control module is used to generate a circuit shutdown command when the first half-control valve of the commutation bridge arm of the main circuit is restored to shutdown, and to control the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm to shut down.

[0059] The present invention provides a high voltage direct current transmission system, including the aforementioned capacitor-assisted grid-shutdown phase-commutation converter.

[0060] 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 or the multi-terminal direct current transmission system respectively includes a unipolar direct current transmission system, a bipolar direct current transmission system or a back-to-back direct current system.

[0061] According to some embodiments, some or all of the converters in the two-terminal or multi-terminal DC transmission system that require inverter operation adopt the capacitor-assisted grid-shutdown phase-commutation converter.

[0062] In summary, the present invention has the following beneficial technical effects:

[0063] During normal operation, when the commutation arm of the main circuit is subjected to negative pressure after commutation to the arm to be commutated, the corresponding pump circuit of the control auxiliary circuit is turned on, and the capacitor of the corresponding energy storage circuit is reverse-charged, causing the capacitor to present a negative voltage. In the event of an AC system fault leading to natural commutation failure, the corresponding transfer circuit and shut-off circuit of the control auxiliary circuit are turned on, forming a parallel current with the commutation arm of the main circuit. The current is transferred to the auxiliary circuit. After the first half-controlled valve of the commutation arm of the main circuit is restored to shutdown, the shut-off circuit of the control auxiliary circuit is turned off, thereby shutting off the commutation arm and suppressing the occurrence of commutation failure. Compared with the prior art, the auxiliary circuit structure of this invention is simple, reducing the cost of controllable shutdown grid commutation converters and improving the reliability of high-voltage direct current transmission. Attached Figure Description

[0064] Figure 1 This is one of the schematic diagrams of a capacitor-assisted grid-connected phase-commutation converter according to an embodiment of the present invention;

[0065] Figure 2 This is the second schematic diagram of the capacitor-assisted power grid-connected phase-commutation converter according to an embodiment of the present invention;

[0066] Figure 3 This is the third schematic diagram of the capacitor-assisted power grid-connected phase-commutation converter according to an embodiment of the present invention;

[0067] Figure 4 This is one of the circuit diagrams of a capacitor-assisted power grid commutator converter including a surge arrester in the embodiments of the present invention;

[0068] Figure 5 This is the second embodiment of the capacitor-assisted shutdown power grid commutator circuit diagram including a surge arrester in this invention.

[0069] Figure 6 This is the third embodiment of the capacitor-assisted shutdown power grid commutator circuit diagram of the present invention, which includes a surge arrester.

[0070] Figure 7A , Figure 7B , Figure 7C , Figure 7D , Figure 7E , Figure 7F , Figure 7G , Figure 7H , Figure 7I , Figure 7J as well as Figure 7K This is a schematic diagram of the valve structure according to an embodiment of the present invention;

[0071] Figure 8 This is a block diagram of the control method for a capacitor-assisted shutdown grid commutator converter according to an embodiment of the present invention;

[0072] Figure 9This is a schematic flowchart of the control method for a capacitor-assisted shutdown grid commutator converter according to an embodiment of the present invention;

[0073] Figure 10 This is a block diagram of the control device for the capacitor-assisted shutdown grid commutator converter according to an embodiment of the present invention;

[0074] Figure 11 This is a schematic diagram of a single pole of a bipolar DC transmission system according to an embodiment of the present invention.

[0075] Explanation of reference numerals in the attached diagram: 1. Upper bridge arm circuit; 2. Lower bridge arm circuit; 3. Upper bridge transfer circuit; 4. Upper bridge turn-off circuit; 5. Lower bridge transfer circuit; 6. Lower bridge turn-off circuit; 7. Upper bridge energy storage circuit; 8. Lower bridge energy storage circuit; 9. Upper bridge pump circuit; 10. Lower bridge pump circuit; 11. First grid commutation converter; 12. Second grid commutation converter; 13. First converter transformer; 14. Second converter transformer; 15. First AC system; 16. DC line; 17. First capacitor-assisted grid turn-off converter; 18. Second capacitor-assisted grid turn-off converter; 19. Third converter transformer; 21. Fourth converter transformer; 22. Second AC system; 201. First control module; 202. Second control module; 203. Third control module; 204. Fourth control module. Detailed Implementation

[0076] The following is in conjunction with the appendix Figure 1-11 The present invention will be described in further detail below.

[0077] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0078] This invention provides a capacitor-assisted grid-connected phase-switching converter, comprising: a main circuit, including at least one phase upper arm circuit and at least one phase lower arm circuit, one end of the at least one phase upper arm circuit being connected to the anode bus of the main circuit, the other end of the at least one phase upper arm circuit being connected to one end of the at least one phase lower arm circuit, and the other end of the at least one phase lower arm circuit being connected to the cathode bus of the main circuit.

[0079] At least one phase upper arm circuit and at least one phase lower arm circuit each include: 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 phase upper arm circuit is connected to the anode bus of the main circuit, one end of the second half-controlled valve of the at least one phase upper arm circuit is connected to one end of the second half-controlled valve of the at least one phase lower arm circuit; one end of the first half-controlled valve of the at least one phase lower arm circuit is connected to the cathode bus of the main circuit.

[0080] Reference Figure 1 The main circuit can be a three-phase six-arm circuit, including: three upper arm circuits 1 and three lower arm circuits 2. There is a one-to-one correspondence between the three upper arm circuits 1 and the three lower arm circuits 2, and each corresponding upper arm circuit 1 and lower arm circuit 2 corresponds to one phase. One end of each upper arm circuit 1 is connected to the anode bus of the main circuit, and the other end of each upper arm circuit 1 is connected to one end of its corresponding lower arm circuit 2. The other end of its corresponding lower arm circuit 2 is connected to the cathode bus of the main circuit. Each upper arm circuit 1 and lower arm circuit 2 includes a first semi-controlled valve and a second semi-controlled valve. The first semi-controlled valve and the second semi-controlled valve are connected in series. One end of the first semi-controlled valve of each upper arm circuit 1 is connected to the anode bus of the main circuit, and one end of the second semi-controlled valve of each upper arm circuit 1 is connected to one end of the second semi-controlled valve of its corresponding lower arm circuit 2. One end of the first semi-controlled valve of each lower arm circuit 2 is connected to the cathode bus of the main circuit.

[0081] In some embodiments, refer to Figure 1 Phase A upper arm circuit 1 includes a first half-control valve V42 and a second half-control valve V43, which are connected in series. One end of the first half-control valve V42 is connected to the anode bus P1 of the main circuit, and one end of the second half-control valve V43 is connected to the lower arm circuit 2 of phase A. Phase B upper arm circuit 1 includes a first half-control valve V62 and a second half-control valve V63, which are connected in series. One end of the first half-control valve V62 is connected to the anode bus P1 of the main circuit, and one end of the second half-control valve V63 is connected to the lower arm circuit 2 of phase B. Phase C upper arm circuit 1 includes a first half-control valve V22 and a second half-control valve V23, which are connected in series. One end of the first half-control valve V22 is connected to the anode bus P1 of the main circuit, and one end of the second half-control valve V23 is connected to the lower arm circuit 2 of phase C.

[0082] Phase A lower bridge arm circuit 2 includes a first semi-controlled valve V12 and a second semi-controlled valve V13, which are connected in series. One end of the first semi-controlled valve V12 is connected to the cathode bus N1 of the main circuit, and one end of the second semi-controlled valve V13 is connected to one end of the second semi-controlled valve V43 of Phase A upper bridge arm circuit 1. Phase B lower bridge arm circuit 2 includes a first semi-controlled valve V32 and a second semi-controlled valve V33, which are connected in series. One end of the semi-controlled valve V32 is connected to the cathode bus N1 of the main circuit, and one end of the second semi-controlled valve V33 is connected to one end of the second semi-controlled valve V63 of the upper bridge arm circuit 1 of phase B; the lower bridge arm circuit 2 of phase C includes a first semi-controlled valve V52 and a second semi-controlled valve V53, which are connected in series. One end of the first semi-controlled valve V52 is connected to the cathode bus N1 of the main circuit, and one end of the second semi-controlled valve V53 is connected to the second semi-controlled valve V23 of the upper bridge arm circuit 1 of phase C.

[0083] The auxiliary circuit includes at least one phase upper bridge transfer circuit, one upper bridge turn-off circuit, one upper bridge energy storage circuit, at least one upper bridge pump circuit, at least one phase lower bridge transfer circuit, one lower bridge turn-off circuit, one lower bridge energy storage circuit, and at least one lower bridge pump circuit; one end of the at least one phase upper bridge transfer circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the at least one phase upper bridge transfer circuit is connected to the at least one phase upper bridge arm circuit; one end of the upper bridge turn-off circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the upper bridge turn-off circuit is connected to one end of the upper bridge energy storage circuit; the other end of the upper bridge energy storage circuit is connected to the anode bus of the main circuit; or, one end of the upper bridge energy storage circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the upper bridge energy storage circuit is connected to one end of the upper bridge turn-off circuit, and the other end of the upper bridge turn-off circuit is connected to the anode bus of the main circuit; one end of the upper bridge pump circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the upper bridge pump circuit is connected to the upper bridge arm circuit.

[0084] One end of the at least one phase downbridge transfer circuit is connected to the cathode bus of the downbridge transfer circuit, and the other end of the at least one phase downbridge transfer circuit is connected to the at least one phase downbridge arm circuit; one end of the downbridge turn-off circuit is connected to the cathode bus of the downbridge transfer circuit, and the other end of the downbridge turn-off circuit is connected to one end of the downbridge energy storage circuit; the other end of the downbridge energy storage circuit is connected to the cathode bus of the main circuit; or, one end of the downbridge energy storage circuit is connected to the cathode bus of the downbridge transfer circuit, and the other end of the downbridge energy storage circuit is connected to one end of the downbridge turn-off circuit, and the other end of the downbridge turn-off circuit is connected to the cathode bus of the main circuit; one end of the downbridge pump circuit is connected to the cathode bus of the downbridge transfer circuit, and the other end of the downbridge pump circuit is connected to the downbridge arm circuit.

[0085] In some embodiments, the connection point between the first half-control valve and the second half-control valve of at least one phase upper bridge arm circuit is connected to one end of at least one phase upper bridge transfer circuit, and the connection point between the first half-control valve and the second half-control valve of at least one phase lower bridge arm circuit is connected to one end of at least one phase lower bridge transfer circuit.

[0086] Reference Figure 1 The auxiliary circuit may include: three upper-bridge transfer circuits 3, one upper-bridge shutdown circuit 4, one upper-bridge energy storage circuit 7, at least one upper-bridge pump circuit 9, three lower-bridge transfer circuits 5, one lower-bridge shutdown circuit 6, one lower-bridge energy storage circuit 8, and at least one lower-bridge pump circuit 10; wherein, the three upper-bridge transfer circuits 3 correspond one-to-one with the three upper-bridge arm circuits 1, the three lower-bridge transfer circuits 5 correspond one-to-one with the three lower-bridge arm circuits 2, the upper-bridge shutdown circuit 4 corresponds to the three upper-bridge arm circuits 1, the lower-bridge shutdown circuit 6 corresponds to the three lower-bridge arm circuits 2, the upper-bridge energy storage circuit 7 corresponds to the three upper-bridge arm circuits 1, the lower-bridge energy storage circuit 8 corresponds to the three lower-bridge arm circuits 2, and at least one upper-bridge pump circuit 10. 9 corresponds to three upper bridge arm circuits 1, and at least one lower bridge pump circuit 10 corresponds to three lower bridge arm circuits 2; one end of each upper bridge transfer circuit 3 is connected to the anode bus of the upper bridge transfer circuit, and the other end of each upper bridge transfer circuit 3 is connected to its corresponding upper bridge arm circuit 1; one end of the upper bridge shutdown circuit 4 is connected to one end of the upper bridge energy storage circuit 7, and the other end of the upper bridge shutdown circuit 4 is connected to the anode bus of the upper bridge transfer circuit; one end of each lower bridge transfer circuit 5 is connected to the cathode bus of the lower bridge transfer circuit, and the other end of each lower bridge transfer circuit 5 is connected to its corresponding lower bridge arm circuit 2; one end of the lower bridge shutdown circuit 6 is connected to one end of the lower bridge energy storage circuit 8, and the other end of the lower bridge shutdown circuit 6 is connected to the cathode bus of the lower bridge transfer circuit.

[0087] In some embodiments, the circuit of the upper bridge shutdown circuit 4 and the upper bridge energy storage circuit 7 connected in series in the auxiliary circuit and the anode bus of the main circuit are connected through a disconnecting switch and / or a knife switch; the circuit of the lower bridge shutdown circuit 6 and the lower bridge energy storage circuit 8 connected in series in the auxiliary circuit and the cathode bus of the main circuit are connected through a disconnecting switch and / or a knife switch.

[0088] Reference Figure 1Each upper bridge transfer circuit 3 and each lower bridge transfer circuit 5 includes: a third semi-controlled valve or a first uncontrolled valve; one end of the third semi-controlled valve or the first uncontrolled valve of each upper bridge transfer circuit 3 is connected to the anode bus of the upper bridge transfer circuit, and the other end of the third semi-controlled valve or the first uncontrolled valve of each upper bridge transfer circuit 3 is connected to the connection point between the first semi-controlled valve and the second semi-controlled valve of its corresponding upper bridge arm circuit 1; one end of the third semi-controlled valve or the first uncontrolled valve of each lower bridge transfer circuit 5 is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the third semi-controlled valve or the first uncontrolled valve of each lower bridge transfer circuit 5 is connected to the connection point between the first semi-controlled valve and the second semi-controlled valve of its corresponding lower bridge arm circuit 2, wherein the first semi-controlled valve, the second semi-controlled valve and the third semi-controlled valve all include a semi-controlled switch, and the first uncontrolled valve includes an uncontrolled 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, and the first semi-controlled valve needs to be able to withstand the commutation voltage provided by the first fully controlled valve when it is shut down in case of a fault after being turned off, therefore, the preferred value is 1.5.

[0089] In some embodiments, refer to Figure 1 Phase A upper bridge transfer circuit 3 includes a third semi-controlled valve or a first uncontrolled valve V44. One end of the third semi-controlled valve or the first uncontrolled valve V44 is connected to the anode bus P2 of the upper bridge transfer circuit, and the other end of the third semi-controlled valve or the first uncontrolled valve V44 is connected to the connection point of the first semi-controlled valve V42 and the second semi-controlled valve V43 of the phase A upper bridge arm circuit 1. Phase B upper bridge transfer circuit 3 includes a third semi-controlled valve or a first uncontrolled valve V64. One end of the third semi-controlled valve or the first uncontrolled valve V64 is connected to the anode bus P2 of the upper bridge transfer circuit. 2. The other end of the third semi-controlled valve or the first uncontrolled valve V64 is connected to the connection point of the first semi-controlled valve V62 and the second semi-controlled valve V63 of the upper bridge arm circuit 1 of phase B; the upper bridge transfer circuit 3 of phase C includes a third semi-controlled valve or the first uncontrolled valve V24, one end of the third semi-controlled valve or the first uncontrolled valve V24 is connected to the anode bus P2 of the upper bridge transfer circuit, and the other end of the third semi-controlled valve or the first uncontrolled valve V24 is connected to the connection point of the first semi-controlled valve V22 and the second semi-controlled valve V23 of the upper bridge arm circuit 1 of phase C.

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

[0091] Both the upper bridge shutdown circuit 4 and the lower bridge shutdown circuit 6 include a first full control valve; one end of the first full control valve of the upper bridge shutdown circuit 4 is connected to the upper bridge energy storage circuit 7, and the other end of the first full control valve of the upper bridge shutdown circuit 4 is connected to the anode bus P2 of the upper bridge transfer circuit; one end of the first full control valve of the lower bridge shutdown circuit 6 is connected to the lower bridge energy storage circuit 8, and the other end of the first full control valve of the lower bridge shutdown circuit 6 is connected to the cathode bus N2 of the lower bridge transfer circuit; wherein, the first full control valve includes at least one of a one-way full control switch, a two-way full control switch, and a sub-module series switch.

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

[0093] In some embodiments, both the upper bridge shutdown circuit and the lower bridge shutdown circuit further include a fourth semi-controlled valve, which is connected in series with the first fully controlled valve; the cathode of the fourth semi-controlled valve is connected to the positive terminal of the first fully controlled valve or the anode of the fourth semi-controlled valve is connected to the negative terminal of the first fully controlled valve; the fourth semi-controlled valve includes a semi-controlled switch with bidirectional flow capability.

[0094] Both the upper bridge energy storage circuit 7 and the lower bridge energy storage circuit 8 include capacitors or sub-module series switches; one end of the capacitor or sub-module series switch of the upper bridge energy storage circuit 7 is connected to the anode bus of the main circuit, and the other end of the capacitor or sub-module series switch of the upper bridge energy storage circuit 7 is connected to one end of the upper bridge shutdown circuit 4; one end of the capacitor or sub-module series switch of the lower bridge energy storage circuit 8 is connected to the cathode bus of the main circuit, and the other end of the capacitor or sub-module series switch of the lower bridge energy storage circuit 8 is connected to one end of the lower bridge shutdown circuit 6.

[0095] In some embodiments, refer to Figure 1 One end of the capacitor or submodule series switch C81 of the upper bridge energy storage circuit 7 is connected to the anode bus P1 of the main circuit, and the other end of the capacitor or submodule series switch C81 of the upper bridge energy storage circuit 7 is connected to one end of the first full control valve V71 of the upper bridge shutdown circuit 4; one end of the capacitor or submodule series switch of the lower bridge energy storage circuit 8 is connected to the cathode bus N1 of the main circuit, and the other end of the capacitor or submodule series switch C82 of the lower bridge energy storage circuit 8 is connected to one end of the first full control valve V72 of the lower bridge shutdown circuit 6.

[0096] In some embodiments, the positions of the upper bridge shutdown circuit and the upper bridge energy storage circuit can be interchanged; the positions of the lower bridge shutdown circuit and the lower bridge energy storage circuit can be interchanged.

[0097] In some embodiments, refer to Figure 1 Both the upper bridge pump circuit 9 and the lower bridge pump circuit 10 include a fifth semi-controlled valve and / or a second uncontrolled valve; one end of the fifth semi-controlled valve and / or the second uncontrolled valve of the upper bridge pump circuit 9 is connected to the anode bus of the upper bridge transfer circuit, and the other end of the fifth semi-controlled valve and / or the second uncontrolled valve of the upper bridge pump circuit 9 is connected to one end of the second semi-controlled valve of the upper bridge arm circuit; one end of the fifth semi-controlled valve and / or the second uncontrolled valve of the lower bridge pump circuit 10 is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the fifth semi-controlled valve and / or the second uncontrolled valve of the lower bridge pump circuit 10 is connected to one end of the second semi-controlled valve of the lower bridge arm circuit.

[0098] Reference Figure 1 One end of the fifth semi-controlled valve and / or the second uncontrolled valve V41 of the upper bridge pump circuit 9 is connected to the anode bus P2 of the upper bridge transfer circuit, and the other end of the fifth semi-controlled valve and / or the second uncontrolled valve V41 of the upper bridge pump circuit 9 is connected to one end of the second semi-controlled valve V43 of the upper bridge arm circuit 1; one end of the fifth semi-controlled valve and / or the second uncontrolled valve V11 of the lower bridge pump circuit 10 is connected to the cathode bus N2 of the lower bridge transfer circuit, and the other end of the fifth semi-controlled valve and / or the second uncontrolled valve V11 of the lower bridge pump circuit 10 is connected to one end of the second semi-controlled valve V13 of the lower bridge arm circuit 2.

[0099] In some embodiments, both the upper bridge pump circuit 9 and the lower bridge pump circuit 10 include a first sub-semi-controlled valve and a second sub-semi-controlled valve. The first and second sub-semi-controlled valves of the upper bridge pump circuit 9 are connected in series. One end of the first sub-semi-controlled valve of the upper bridge pump circuit 9 is connected to the anode bus of the upper bridge transfer circuit, and the other end of the first sub-semi-controlled valve of the upper bridge pump circuit 9 is connected to one end of the third sub-semi-controlled valve or the first uncontrolled valve of the upper bridge transfer circuit 3. One end of the second sub-semi-controlled valve of the upper bridge pump circuit 9 is connected to one end of the second sub-semi-controlled valve of the upper bridge arm circuit 1. The first and second sub-semi-controlled valves of the lower bridge pump circuit 10 are connected in series. One end of the first sub-semi-controlled valve of the lower bridge pump circuit 10 is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the first sub-semi-controlled valve of the lower bridge pump circuit 10 is connected to one end of the third sub-semi-controlled valve or the first uncontrolled valve of the lower bridge transfer circuit 5. One end of the second sub-semi-controlled valve of the lower bridge pump circuit 10 is connected to one end of the second sub-semi-controlled valve of the lower bridge arm circuit 2.

[0100] Reference Figure 2 The first sub-semi-controlled valve V411 and the second sub-semi-controlled valve V412 of the upper bridge pump circuit 9 are connected in series. One end of the first sub-semi-controlled valve V411 of the upper bridge pump circuit 9 is connected to the anode bus P2 of the upper bridge transfer circuit, and the other end of the first sub-semi-controlled valve V411 of the upper bridge pump circuit 9 is connected to one end of the third semi-controlled valve or the first uncontrolled valve V44 of the upper bridge transfer circuit 3. One end of the second sub-semi-controlled valve V412 of the upper bridge pump circuit 9 is connected to one end of the second semi-controlled valve V43 of the upper bridge arm circuit 1; The first sub-semi-controlled valve V111 and the second sub-semi-controlled valve V112 of the bridge pump circuit 10 are connected in series. One end of the first sub-semi-controlled valve V111 of the lower bridge pump circuit 10 is connected to the cathode bus N2 of the lower bridge transfer circuit. The other end of the first sub-semi-controlled valve V111 of the lower bridge pump circuit 10 is connected to one end of the third semi-controlled valve or the first uncontrolled valve V14 of the lower bridge transfer circuit 5. One end of the second sub-semi-controlled valve V112 of the lower bridge pump circuit 10 is connected to one end of the second semi-controlled valve V13 of the lower bridge arm circuit 2.

[0101] In some embodiments, both the upper bridge pump circuit 9 and the lower bridge pump circuit 10 include a first sub-semi-controlled valve and a second sub-semi-controlled valve; the first sub-semi-controlled valve of the upper bridge pump circuit 9 is integrated with the third semi-controlled valve or the first uncontrolled valve of the upper bridge transfer circuit 3, and the two are connected in parallel as devices, valve segments, or valves; the second sub-semi-controlled valve of the upper bridge pump circuit 9 is integrated with the second semi-controlled valve of the upper bridge arm circuit 1, and the two are connected in parallel as devices, valve segments, or valves; the first sub-semi-controlled valve of the lower bridge pump circuit 10 is integrated with the third semi-controlled valve or the first uncontrolled valve of the lower bridge transfer circuit 5, and the two are connected in parallel as devices, valve segments, or valves; the second sub-semi-controlled valve of the lower bridge pump circuit 10 is integrated with the second semi-controlled valve of the lower bridge arm circuit 2, and the two are connected in parallel as devices, valve segments, or valves.

[0102] Reference Figure 3The first sub-semi-controlled valve V411 of the upper bridge pump circuit 9 is integrated with the third semi-controlled valve or the first uncontrolled valve V44 of the upper bridge transfer circuit 3, and the two are connected in parallel; the second sub-semi-controlled valve V412 of the upper bridge pump circuit 9 is integrated with the second semi-controlled valve V43 of the upper bridge arm circuit 1, and the two are connected in parallel; the first sub-semi-controlled valve V111 of the lower bridge pump circuit 10 is integrated with the third semi-controlled valve or the first uncontrolled valve V14 of the lower bridge transfer circuit 5, and the two are connected in parallel; the second sub-semi-controlled valve V112 of the lower bridge pump circuit 10 is integrated with the second semi-controlled valve V13 of the lower bridge arm circuit 2, and the two are connected in parallel; wherein, the parallel connection includes parallel connection by device, parallel connection by valve segment, or parallel connection by valve; after parallel connection, it can be bidirectionally controlled to open, and has bidirectional flow capability.

[0103] Reference Figure 4 Each first fully controlled valve's unidirectional fully controlled switch is composed of at least one IGBT (Insulated Gate Bipolar Transistor) connected in series. Each first half-controlled valve, each second half-controlled valve, and each fifth half-controlled valve's half-controlled switch is composed of at least one thyristor connected in series. Each first uncontrolled valve's uncontrolled switch is composed of at least one diode connected in series. For example, the unidirectional fully controlled switches of the first fully controlled valve V71 in the upper bridge turn-off circuit and the first fully controlled valve V72 in the lower bridge turn-off circuit are composed of multiple IGBT modules connected in series; the first half-controlled valve V42 and the second half-controlled valve V72 in the A-phase upper bridge arm circuit... The semi-controlled switches of the first semi-controlled valve V12 and the second semi-controlled valve V13 in the lower bridge arm circuit of phase A are all composed of multiple thyristors connected in series; the uncontrolled switches of the first uncontrolled valve V44 in the upper bridge transfer circuit of phase A and the first uncontrolled valve V14 in the lower bridge transfer circuit of phase A are composed of multiple diodes connected in series; the upper bridge energy storage circuit and the lower bridge energy storage circuit use capacitor C81; the semi-controlled switches of the fifth semi-controlled valve V41 in the upper bridge pump circuit and the fifth semi-controlled valve V11 in the lower bridge pump circuit are all composed of multiple thyristors connected in series.

[0104] In addition, phases B and C share the first full control valve with phase A; the half-control switches of the first and second half-control valves corresponding to phases B and C are the same as the half-control switches of the first and second half-control valves corresponding to phase A; the uncontrollable switches of the first uncontrollable valves corresponding to phases B and C are the same as the uncontrollable switches of the first uncontrollable valves corresponding to phase A.

[0105] Reference Figure 5 The semi-controlled switches of the first sub-semi-controlled valve V411 and the second sub-semi-controlled valve V412 in the upper bridge pump circuit, and the first sub-semi-controlled valve V111 and the second sub-semi-controlled valve V112 in the lower bridge pump circuit are all composed of multiple thyristors connected in series.

[0106] Reference Figure 6The first semi-controlled valve V411 of the upper bridge pump circuit and the first uncontrolled valve V44 of the upper bridge transfer circuit are integrated in parallel to form a bidirectional semi-controlled switch; the second semi-controlled valve V412 of the upper bridge pump circuit and the second semi-controlled valve V43 of the upper bridge arm circuit are integrated in parallel to form a bidirectional semi-controlled switch; the first semi-controlled valve V111 of the lower bridge pump circuit and the third semi-controlled valve or the first uncontrolled valve V14 of the lower bridge transfer circuit are integrated in parallel to form a bidirectional semi-controlled switch; the second semi-controlled valve V112 of the lower bridge pump circuit and the second semi-controlled valve V13 of the lower bridge arm circuit are integrated in parallel to form a bidirectional semi-controlled switch. The bidirectional semi-controlled switches are composed of multiple thyristors connected in anti-parallel and then connected in series.

[0107] In some embodiments, refer to Figure 4 , Figure 5 as well as Figure 6 Each first fully controlled valve, each first partially controlled valve, each second partially controlled valve, each first uncontrolled valve or third partially controlled valve, and the capacitor are all connected in parallel with surge arresters to protect each first fully controlled valve, each first partially controlled valve, each second partially controlled valve, each third partially controlled valve or first uncontrolled valve, and the capacitor for normal operation. For example, in the upper bridge arm circuit 1 of phase A, the first partially controlled valve V42 is connected in parallel with the second surge arrester F42, and the second partially controlled valve V43 is connected in parallel with the third surge arrester F43. In the lower bridge arm circuit 2 of phase A, the first partially controlled valve V12 is connected in parallel with the second surge arrester F12, and the second partially controlled valve V13 is connected in parallel with the third surge arrester. F13; The first half-controlled valve V62 of the upper bridge arm circuit 1 of phase B is connected in parallel with the second surge arrester F62, and the second half-controlled valve V63 is connected in parallel with the third surge arrester F63; The first half-controlled valve V32 of the lower bridge arm circuit 2 of phase B is connected in parallel with the second surge arrester F32, and the second half-controlled valve V33 is connected in parallel with the third surge arrester F33; The first half-controlled valve V22 of the upper bridge arm circuit 1 of phase C is connected in parallel with the second surge arrester F22, and the second half-controlled valve V23 is connected in parallel with the third surge arrester F23; The first half-controlled valve V52 of the lower bridge arm circuit 2 of phase C is connected in parallel with the second surge arrester F52, and the second half-controlled valve V53 is connected in parallel with the third surge arrester F53.

[0108] The first uncontrolled valve V44 of the A-phase upper bridge transfer circuit 3 is connected in parallel with the fourth surge arrester F44; the first uncontrolled valve V14 of the A-phase lower bridge transfer circuit 5 is connected in parallel with the fourth surge arrester F14; the first uncontrolled valve V64 of the B-phase upper bridge transfer circuit 3 is connected in parallel with the fourth surge arrester F64; the first uncontrolled valve V34 of the B-phase lower bridge transfer circuit 5 is connected in parallel with the fourth surge arrester F34; the first uncontrolled valve V24 of the C-phase upper bridge transfer circuit 3 is connected in parallel with the fourth surge arrester F24; the first uncontrolled valve V54 of the C-phase lower bridge transfer circuit 5 is connected in parallel with the fourth surge arrester F54; the first fully controlled valve V71 of the upper bridge shutdown circuit 4 is connected in parallel with the fifth surge arrester F71; the first fully controlled valve V72 of the lower bridge shutdown circuit 6 is connected in parallel with the fifth surge arrester F72.

[0109] The capacitor C81 of the upper bridge energy storage circuit 7 is connected in parallel with the sixth surge arrester F81, and the capacitor C82 of the lower bridge energy storage circuit 8 is connected in parallel with the sixth surge arrester F82.

[0110] In some embodiments, the first semi-controlled valve, and / or the second semi-controlled valve, and / or the third semi-controlled valve, and / or the first uncontrolled valve further includes a reactor. Optionally, the first fully controlled valve further includes a reactor.

[0111] In some embodiments, a fully controlled switch includes at least one fully controlled device connected in series, the fully controlled device including at least one of IGCT (Integrated Gate Commutated Thyristors), reverse-resistance IGCT, IGBT, GTO (Gate Turn-Off Thyristor), and MOSFET (Metal Oxide Semiconductor Field Effect Transistor); a semi-controlled switch includes at least one semi-controlled device connected in series, the semi-controlled device including a thyristor; and an uncontrolled switch includes at least one uncontrolled device connected in series, the uncontrolled device including a diode.

[0112] Reference Figure 7A An uncontrolled switch includes at least one diode connected in series, which cannot be controlled to turn on or off, and has unidirectional current-carrying capability and unidirectional voltage-blocking capability; (Refer to...) Figure 7B A semi-controlled switch includes thyristors connected in series. It only controls the turn-on process and cannot control the turn-off process. It has unidirectional current-carrying capability and bidirectional voltage-blocking capability. Optionally, the semi-controlled switch is composed of thyristors and diodes connected in series or parallel; see reference. Figure 7C The unidirectional fully controlled switch includes an IGBT module connected in series. The IGBT module includes an IGBT and a diode connected in antiparallel. It controls the on / off state in only one direction and has bidirectional current-carrying and unidirectional voltage-blocking capabilities. (Refer to...) Figure 7D A unidirectional fully controlled switch includes a series-connected IGCT, which controls only one-way switching on and off, and has unidirectional current-carrying and voltage-blocking capabilities. When it is a series-connected reverse-resistance type IGCT, it has unidirectional current-carrying and bidirectional voltage-blocking capabilities; refer to... Figure 7E A unidirectional fully controlled switch includes an IGBT module and a diode connected in series. It controls the on and off states in only one direction, and has the capability of unidirectional current carrying and bidirectional voltage blocking. (Refer to...) Figure 7F The unidirectional fully controlled switch includes a reverse-resistance IGCT and a thyristor anti-parallel followed by a series circuit. It features bidirectional control for turn-on and unidirectional control for turn-off, and has bidirectional current-carrying and bidirectional voltage-blocking capabilities; (Refer to...) Figure 7GThe bidirectional fully controlled switch includes a forward IGBT module and a reverse IGBT module connected in series. It can be bidirectionally controlled to turn on and off, and has bidirectional current carrying capacity and bidirectional voltage blocking capacity; (Refer to...) Figure 7H The bidirectional fully controlled switch includes a series circuit after the anti-parallel connection of a reverse-resistance IGCT, which can be bidirectionally controlled to turn on and off, and has bidirectional current-carrying capacity and bidirectional voltage-blocking capacity; refer to Figure 7I The sub-module series switch includes a series-connected half-bridge sub-module. Each half-bridge sub-module comprises two IGBT modules and a capacitor. The connection point of the two IGBT modules serves as the positive terminal of the half-bridge sub-module, and the other end of one IGBT module serves as the negative terminal. The series-connected half-bridge sub-modules provide unidirectional control for switching on and off, possessing bidirectional current-carrying capability and unidirectional voltage-blocking capability. (Refer to...) Figure 7J The sub-module series switch includes a full-bridge sub-module connected in series. Each full-bridge sub-module comprises four IGBT modules and a capacitor. The IGBT modules are connected in series in pairs and then in parallel, and also in parallel with the capacitor. The connection points of the series-connected IGBT modules serve as the positive and negative terminals of the full-bridge sub-module, respectively. This series connection of sub-modules allows for bidirectional control of switching on and off, providing bidirectional current carrying capacity and bidirectional voltage blocking capability. (Refer to...) Figure 7K The sub-module series switch includes a series-connected full-bridge sub-module. The full-bridge sub-module includes two IGBT modules, two diodes, and a capacitor. The IGBT modules and diodes are connected in series and then in parallel, and are also connected in parallel with the capacitor. The connection points of the IGBT modules and diodes in series serve as the positive and negative terminals of the full-bridge sub-module, respectively. The series-connected full-bridge sub-modules can unidirectionally control the opening and closing, and have bidirectional current carrying capacity and bidirectional voltage blocking capacity.

[0113] 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-resistance IGCT is configured with a corresponding drive circuit and a buffer circuit; the buffer circuit consists of at least a capacitor, or a resistor and a capacitor in series circuit.

[0114] It should be pointed out that, Figure 4 , Figure 5 and Figure 6 The capacitor in the energy storage circuit can also be used Figure 7I , Figure 7J or Figure 7K Submodules connected in series, such as using Figure 7I The half-bridge sub-module has its negative terminal connected to the anode busbar of the main circuit via a series switch.

[0115] This invention provides a capacitor-assisted shutdown control method for a grid-connected commutator converter, executed by an electronic device. The 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 invention does not impose specific limitations.

[0116] Reference Figure 8 A capacitor-assisted grid-connected phase-commutator control method includes steps S101, S102, S103, and S104, wherein...

[0117] S101. After obtaining the operating parameter information of the capacitor-assisted grid-connected phase 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.

[0118] In some embodiments, the electronic device monitors the operating status of the capacitor-assisted grid-connected phase-commutator in real time and acquires operating parameter information of the capacitor-assisted grid-connected phase-commutator, such as AC voltage and DC current. When the electronic device acquires the operating status of the capacitor-assisted grid-connected phase-commutator, it generates inverter state control information, such as a trigger pulse. Based on the inverter state control information, the capacitor-assisted grid-connected phase-commutator operates in inverter state according to the six-pulse inverter operating mode. For example, the electronic device controls the first half-control valve V42 and the second half-control valve V43 of the upper bridge arm circuit of phase A, the first half-control valve V12 and the second half-control valve V13 of the lower bridge arm of phase A, the first half-control valve V62 and the second half-control valve V63 of the upper bridge arm of phase B, the first half-control valve V32 and the second half-control valve V33 of the lower bridge arm of phase B, the first half-control valve V22 and the second half-control valve V23 of the upper bridge arm of phase C, and the first half-control valve V52 and the second half-control valve V53 of the lower bridge arm of phase C to operate in inverter state according to the six-pulse inverter operating mode.

[0119] S102. When the negative pressure of the energy storage circuit is lower than the rated value and exceeds the first threshold, and the commutation bridge arm of the main circuit ends the commutation to the bridge arm circuit to be commutated and bears the negative pressure, an auxiliary circuit control command is generated, and the corresponding pump pressure circuit of the corresponding auxiliary circuit is controlled to be turned on based on the auxiliary circuit control command.

[0120] In some embodiments, the energy storage circuit is an upper bridge energy storage circuit or a lower bridge energy storage circuit; the corresponding pumping circuit of the auxiliary circuit is a pumping circuit connected to the same busbar as the commutation bridge arm of the main circuit, and the corresponding energy storage circuit of the auxiliary circuit is an energy storage circuit connected to the same busbar as the commutation bridge arm of the main circuit; when the negative voltage of the energy storage circuit is lower than the rated value and exceeds the first threshold, and the commutation bridge arm of the main circuit ends its commutation to another bridge arm, the commutation bridge arm bears the negative voltage, the electronic device controls the corresponding pumping circuit of the auxiliary circuit to be turned on, and the capacitor or sub-module series switch of the corresponding energy storage circuit is reverse-charged, so that the capacitor or sub-module series switch presents a negative voltage; Example For example, when the commutation from the upper bridge arm circuit of phase A to the upper bridge arm circuit of phase B ends and it experiences negative pressure, the fifth semi-controlled valve V41 (including V411 and V412) of the upper bridge pump circuit of the electronic control auxiliary circuit is turned on, reversing the charging of the capacitor or sub-module series switch C81 of the upper bridge energy storage circuit, causing it to exhibit negative pressure; when the commutation from the lower bridge arm circuit of phase A to the lower bridge arm circuit of phase B ends and it experiences negative pressure, the fifth semi-controlled valve V11 (including V111 and V112) of the lower bridge pump circuit of the electronic control auxiliary circuit is turned on, reversing the charging of the capacitor or sub-module series switch C82 of the lower bridge energy storage circuit, causing it to exhibit negative pressure. Optionally, the semiconductor device in the sub-module series switch is turned on to reverse charge the capacitor in the sub-module series switch.

[0121] In some embodiments, the first threshold value ranges from 0.01 to 0.5 times the rated voltage of the energy storage circuit.

[0122] S103. Upon obtaining commutation fault information, generate a circuit turn-on command and control the transfer circuit and turn-off circuit in the auxiliary circuit corresponding to the commutation bridge arm to turn on based on the circuit turn-on command.

[0123] In some embodiments, commutation fault information includes fault information that causes the commutation bridge arm of the main circuit to fail to commutate naturally; commutation fault information includes AC system faults or DC system faults connected to the capacitor-assisted grid-connected commutation converter. AC system faults can be judged based on the increase of AC voltage zero-sequence component, AC voltage sudden change, AC voltage amplitude drop, increase of AC voltage harmonics, and increase of DC current. DC system faults can be judged based on the drop of DC voltage and increase of DC current, but are not limited thereto.

[0124] In some embodiments, the aforementioned natural commutation failure refers to commutation failure that occurs when commutation is performed solely by the commutation voltage provided by the AC system. Whether a natural commutation failure occurs can be determined based on the closing time of the first half-controlled valve of the commutation bridge arm, the AC current and AC voltage on the grid side or valve side. If the first half-controlled valve of the commutation bridge arm has not closed by the time it begins to bear positive pressure under normal AC voltage, it is judged that a commutation fault has occurred, but this is not a limitation; the commutation bridge arm is the upper bridge arm circuit or the lower bridge arm circuit.

[0125] When the electronic device obtains the commutation fault information of the capacitor-assisted grid-connected commutator, the electronic device generates a circuit turn-on command. The capacitor-assisted grid-connected commutator responds to the circuit turn-on command, causing the transfer circuit and turn-off circuit in the auxiliary circuit corresponding to the commutation arm of the capacitor-assisted grid-connected commutator to turn on. For example, if the A-phase upper bridge arm circuit commutates to the B-phase upper bridge arm circuit and a fault occurs, and if natural commutation will cause the first half-controlled valve V42 and the second half-controlled valve V43 of the A-phase upper bridge arm circuit of the main circuit to fail to commutate, the third half-controlled valve or the first uncontrolled valve V44 of the A-phase upper bridge transfer circuit and the first fully controlled valve V71 of the upper bridge turn-off circuit of the auxiliary circuit will turn on. Since the capacitor or the sub-module series switch C81 presents a negative voltage, the current of the A-phase upper bridge arm circuit is transferred to the A-phase upper bridge transfer circuit and the upper bridge turn-off circuit of the auxiliary circuit.

[0126] S104. 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 shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm to shut off.

[0127] In some embodiments, when the electronic device detects that the first half-controlled valve of the commutation bridge arm of the main circuit has resumed shutdown, a circuit shutdown command is generated. The capacitor-assisted shutdown grid commutation converter responds to the circuit shutdown command and controls the shutdown circuit corresponding to the commutation bridge arm to shut down, so that the current is transferred from the phase where the commutation bridge arm is located to the phase to be commutated, effectively suppressing the occurrence of commutation failure. For example, when the electronic device detects that the first half-controlled valve of the upper bridge arm circuit of phase A of the main circuit has resumed shutdown, a circuit shutdown command is generated. The capacitor-assisted shutdown grid commutation converter responds to the circuit shutdown command and controls the first fully controlled valve V71 of the upper bridge shutdown circuit corresponding to the upper bridge arm circuit of phase A to shut down, so that the current is transferred from the upper bridge arm circuit of phase A to the upper bridge arm circuit of phase B. The corresponding transfer circuit of the auxiliary circuit is the bridge arm connected to the same phase as the commutation bridge arm of the main circuit, and the shutdown circuit corresponding to the auxiliary circuit is the shutdown circuit connected to the same bus as the commutation bridge arm of the main circuit.

[0128] In some embodiments, refer to Figure 9 When the main circuit is in inverter operation, the control pump circuit is turned on to supply power to the energy storage circuit, so that it is charged in reverse. Then, it is determined whether the commutation bridge arm may fail to commutate naturally. If the commutation bridge arm fails to commutate naturally, the corresponding transfer circuit and shutdown circuit of the control auxiliary circuit are turned on. After the commutation bridge arm is turned off again, the corresponding shutdown circuit of the control auxiliary circuit is turned off.

[0129] In some embodiments, the first half-controlled valve of the commutation bridge arm of the main circuit resumes shutdown based on the reverse recovery time of the first half-controlled valve. The reverse recovery time is greater than or equal to the reverse recovery time of the thyristor included in the first half-controlled valve. The typical reverse recovery time of the thyristor is 200 to 800 μs, and the typical reverse recovery time of the first half-controlled valve is 200 μs to 1.5 ms.

[0130] In some embodiments, when the electronic device obtains auxiliary circuit fault information, a switch disconnection command is generated, and the corresponding isolating switch and / or knife switch of the auxiliary circuit is disconnected based on the switch disconnection command, thereby reducing the occurrence of main circuit damage due to auxiliary circuit faults.

[0131] In some embodiments, the above-mentioned auxiliary circuit fault information includes auxiliary circuit device or submodule failures affecting normal operation, but is not limited thereto.

[0132] Reference Figure 10 The capacitor-assisted grid-connected phase-commutator control device 20 may specifically include: a first control module 201, a second control module 202, a third control module 203, and a fourth control module 204, wherein,

[0133] The first control module 201 is used to generate inverter state control information based on the operating parameter information of the capacitor-assisted grid-connected phase converter when it obtains the operating parameter information, and to control the main circuit to operate in inverter state based on the inverter state control information.

[0134] The second control module 202 is used to generate an auxiliary circuit control command when the negative pressure of the energy storage circuit is lower than the rated value and exceeds the first threshold, and the commutation bridge arm of the main circuit ends the commutation to the bridge arm circuit to be commutated and bears the negative pressure, and control the corresponding pump pressure circuit of the corresponding auxiliary circuit to be turned on based on the auxiliary circuit control command. The energy storage circuit is an upper bridge energy storage circuit or a lower bridge energy storage circuit.

[0135] The third control module 203 is used to generate a circuit turn-on command when fault information is obtained, and to control the transfer circuit and turn-off circuit in the auxiliary circuit corresponding to the commutation bridge arm to turn on based on the circuit turn-on command; wherein, the commutation bridge arm is the upper bridge arm circuit or the lower bridge arm circuit.

[0136] The fourth control module 204 is used to generate a circuit shutdown command when the first half-control valve of the commutation bridge arm of the main circuit is restored to shutdown, and to control the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm to shut down.

[0137] In some embodiments, the first control module 201 may include logic circuits, or may be implemented by a central processing unit, microprocessor, digital signal processor or field programmable gate array included in the device;

[0138] The second control module 202 may include logic circuits or may be implemented by a central processing unit, microprocessor, digital signal processor or field programmable gate array included in the device;

[0139] The third control module 203 may include logic circuits or may be implemented by a central processing unit, microprocessor, digital signal processor or field programmable gate array included in the device.

[0140] The fourth control module 204 may include logic circuits or be implemented by a central processing unit, microprocessor, digital signal processor or field programmable gate array included in the device.

[0141] This invention provides a high-voltage direct current transmission system, including a capacitor-assisted grid-shutdown phase-commutation converter.

[0142] In 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. The two-terminal direct current transmission system or the multi-terminal direct current transmission system respectively includes a unipolar direct current transmission system, a bipolar direct current transmission system or a back-to-back direct current system.

[0143] In some embodiments, some or all of the converters in a two-terminal or multi-terminal DC transmission system that require inverter operation employ the aforementioned capacitor-assisted grid-shutdown phase-commutation converter.

[0144] Reference Figure 11 , Figure 11 The structure of a single pole of a bipolar DC transmission system is shown. A single pole includes a first AC system 15, a first grid-commutated converter 11, a second grid-commutated converter 12, a first converter transformer 13, a second converter transformer 14, a DC line 16, a second AC system 22, a first capacitor-assisted grid-shutdown converter 17, a second capacitor-assisted grid-shutdown converter 18, a third converter transformer 19, and a fourth converter transformer 21. When power is being transmitted in the forward direction, the AC power from the first AC system 15 is rectified into DC power by the first grid phase-commutation converter 11 and the second grid phase-commutation converter 12 after passing through the first converter transformer 13 and the second converter transformer 14. This DC power is then transmitted through the DC line 16 to the first capacitor-assisted grid-off phase-commutation converter 17 and the second capacitor-assisted grid-off phase-commutation converter 18, where it is inverted back into AC power. After passing through the third converter transformer 19 and the fourth converter transformer 21, the DC power is transmitted to the second AC system 22, thus realizing the transmission of DC power. The first capacitor-assisted grid-off phase-commutation converter 17 and the second capacitor-assisted grid-off phase-commutation converter 18 have the ability to suppress commutation failures, ensuring the reliability of DC power transmission.

[0145] The above are only some embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A capacitor-assisted grid-connected phase-commutator, characterized in that, include: The main circuit includes 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 to the anode bus of the main circuit, and the other end of the at least one upper bridge arm circuit is connected to one end of the at least one lower bridge arm circuit. The other end of the at least one lower bridge arm circuit is connected to the cathode bus of the main circuit. Each of the at least one upper bridge arm circuit and the at least one lower bridge arm circuit includes a first semi-controlled valve and a second semi-controlled valve, which are connected in series. One end of the first semi-controlled valve of the at least one upper bridge arm circuit is connected to the anode bus of the main circuit, and one end of the second semi-controlled valve of the at least one upper bridge arm circuit is connected to one end of the second semi-controlled valve of the at least one lower bridge arm circuit. One end of the first semi-controlled valve of the at least one lower bridge arm circuit is connected to the cathode bus of the main circuit. The auxiliary circuit includes at least one phase upper bridge transfer circuit, one upper bridge turn-off circuit, one upper bridge energy storage circuit, at least one upper bridge pumping circuit, at least one phase lower bridge transfer circuit, one lower bridge turn-off circuit, one lower bridge energy storage circuit, and at least one lower bridge pumping circuit. One end of the at least one phase upper bridge transfer circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the at least one phase upper bridge transfer circuit is connected to the connection point between the first half-control valve and the second half-control valve of the at least one phase upper bridge arm circuit. One end of the upper bridge shutdown circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the upper bridge shutdown circuit is connected to one end of the upper bridge energy storage circuit; the other end of the upper bridge energy storage circuit is connected to the anode bus of the main circuit; or, one end of the upper bridge energy storage circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the upper bridge energy storage circuit is connected to one end of the upper bridge shutdown circuit, and the other end of the upper bridge shutdown circuit is connected to the anode bus of the main circuit. One end of the upper bridge pump circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the upper bridge pump circuit is connected to the other end of the upper bridge arm circuit. One end of the at least one phase lower bridge transfer circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the at least one phase lower bridge transfer circuit is connected to the connection point between the first half-control valve and the second half-control valve of the at least one phase lower bridge arm circuit. One end of the lower bridge shutdown circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the lower bridge shutdown circuit is connected to one end of the lower bridge energy storage circuit; the other end of the lower bridge energy storage circuit is connected to the cathode bus of the main circuit; or, one end of the lower bridge energy storage circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the lower bridge energy storage circuit is connected to one end of the lower bridge shutdown circuit, and the other end of the lower bridge shutdown circuit is connected to the cathode bus of the main circuit. One end of the lower bridge pump circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the lower bridge pump circuit is connected to one end of the lower bridge arm circuit.

2. The capacitor-assisted grid-connected phase-commutator according to claim 1, characterized in that, The pressure resistance ratio of the first semi-controlled valve and the second semi-controlled valve ranges from 0.2 to 5.

3. The capacitor-assisted grid-connected phase-commutator according to claim 1, characterized in that, Both the at least one phase upper bridge transfer circuit and the at least one phase lower bridge transfer circuit include: a third semi-controlled valve or a first uncontrolled valve; One end of the third half-controlled valve or the first uncontrolled valve of the at least one phase upper bridge transfer circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the third half-controlled valve or the first uncontrolled valve of the at least one phase upper bridge transfer circuit is connected to the connection point between the first half-controlled valve and the second half-controlled valve of the at least one phase upper bridge arm circuit; one end of the third half-controlled valve or the first uncontrolled valve of the at least one phase lower bridge transfer circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the third half-controlled valve or the first uncontrolled valve of the at least one phase lower bridge transfer circuit is connected to the connection point between the first half-controlled valve and the second half-controlled valve of the at least one phase lower bridge arm circuit.

4. The capacitor-assisted grid-connected phase-commutator according to claim 3, characterized in that, The first semi-controlled valve, the second semi-controlled valve, and the third semi-controlled valve all include a semi-controlled switch; the first uncontrolled valve includes an uncontrolled switch. The semi-controlled switch is composed of semiconductor devices that can be controlled to turn on but not controlled to turn off, and the semiconductor devices that can be controlled to turn on but not controlled to turn off include thyristors. The uncontrolled switch is composed of semiconductor devices that are connected in series for uncontrolled on and off, including diodes.

5. The capacitor-assisted grid-connected phase-commutator according to claim 3, characterized in that, The first semi-controlled valve, and / or the second semi-controlled valve, and / or the third semi-controlled valve or the first uncontrolled valve are connected in parallel with surge arresters.

6. The capacitor-assisted grid-connected phase-commutator according to claim 3, characterized in that, The first semi-controlled valve, and / or the second semi-controlled valve, and / or the third semi-controlled valve, or the first uncontrolled valve, further includes a reactor.

7. The capacitor-assisted grid-connected phase-commutator according to claim 1, characterized in that, The circuit consisting of the upper bridge shutdown circuit and the upper bridge energy storage circuit connected in series in the auxiliary circuit and the anode bus of the main circuit are connected through a disconnecting switch and / or a knife switch; the circuit consisting of the lower bridge shutdown circuit and the lower bridge energy storage circuit connected in series in the auxiliary circuit and the cathode bus of the main circuit are connected through a disconnecting switch and / or a knife switch.

8. The capacitor-assisted grid-connected phase-commutator according to claim 1, characterized in that, Both the upper bridge shutdown circuit and the lower bridge shutdown circuit include a first full control valve. One end of the first fully controlled valve of the upper bridge shutdown circuit is connected to one end of the upper bridge energy storage 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 energy storage 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. One end of the first fully controlled valve of the lower bridge shutdown circuit is connected to one end of the lower bridge energy storage 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 energy storage 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.

9. The capacitor-assisted grid-connected phase-commutator according to claim 8, characterized in that, Both the upper bridge shutdown circuit and the lower bridge shutdown circuit further include a fourth semi-control valve, which is connected in series with the first fully control valve.

10. The capacitor-assisted grid-connected phase-commutator according to claim 8, characterized in that, The first fully controlled valve is connected in parallel with a surge arrester.

11. The capacitor-assisted grid-connected phase-commutator according to claim 8, characterized in that, The first fully controlled valve includes at least one of a one-way fully controlled switch, a two-way fully controlled switch, and a sub-module series switch.

12. The capacitor-assisted grid-connected phase-commutator according to claim 11, characterized in that, The unidirectional fully controlled switch is composed of semiconductor devices with unidirectional turn-off capability connected in series. The semiconductor devices with unidirectional turn-off capability include insulated gate bipolar transistors, integrated gate commutated thyristors, and reverse-resistance integrated gate commutated thyristors. The bidirectional fully controlled switch is composed of semiconductor devices with bidirectional turn-off capability connected in series. The semiconductor devices with bidirectional turn-off capability include anti-parallel reverse-resistance integrated gate commutator thyristors and anti-connected insulated gate bipolar transistors. The sub-module series switch is composed of sub-modules connected in series. The sub-modules include half-bridge sub-modules, full-bridge sub-modules, near-full-bridge sub-modules, and clamped double sub-modules. The semiconductor devices of the half-bridge sub-modules, full-bridge sub-modules, near-full-bridge sub-modules, and clamped double sub-modules include insulated-gate bipolar transistors and integrated gate commutated thyristors.

13. The capacitor-assisted grid-connected phase-commutator according to claim 1, characterized in that, Both the upper-bridge energy storage circuit and the lower-bridge energy storage circuit include: a capacitor or a sub-module series switch; one end of the capacitor or sub-module series switch of the upper-bridge energy storage circuit is connected to the anode bus of the main circuit, and the other end of the capacitor or sub-module series switch of the upper-bridge energy storage circuit is connected to the upper-bridge shutdown circuit; or, one end of the capacitor or sub-module series switch of the upper-bridge energy storage circuit is connected to the anode bus of the upper-bridge transfer circuit, and the other end of the capacitor or sub-module series switch of the upper-bridge energy storage circuit is connected to the upper-bridge shutdown circuit; one end of the capacitor or sub-module series switch of the lower-bridge energy storage circuit is connected to the cathode bus of the main circuit, and the other end of the capacitor or sub-module series switch of the lower-bridge energy storage circuit is connected to the lower-bridge shutdown circuit; or, one end of the capacitor or sub-module series switch of the lower-bridge energy storage circuit is connected to the cathode bus of the lower-bridge transfer circuit, and the other end of the capacitor or sub-module series switch of the lower-bridge energy storage circuit is connected to the lower-bridge shutdown circuit.

14. The capacitor-assisted grid-connected phase-commutator according to claim 13, characterized in that, Both the upper bridge energy storage circuit and the lower bridge energy storage circuit include a resistor or an inductor; the resistor or inductor is connected in series with the capacitor or submodule series switch.

15. The capacitor-assisted grid-connected phase-commutator according to claim 13, characterized in that, The capacitor or submodule is connected in series with a switch and a surge arrester is connected in parallel.

16. The capacitor-assisted grid-connected phase-commutator according to any one of claims 1-15, characterized in that, Both the at least one upper bridge pump circuit and the at least one lower bridge pump circuit include a fifth semi-controlled valve and / or a second uncontrolled valve; one end of the fifth semi-controlled valve and / or the second uncontrolled valve of the at least one upper bridge pump circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the fifth semi-controlled valve and / or the second uncontrolled valve of the at least one upper bridge pump circuit is connected to one end of the second semi-controlled valve of the upper bridge arm circuit; one end of the fifth semi-controlled valve and / or the second uncontrolled valve of the at least one lower bridge pump circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the fifth semi-controlled valve and / or the second uncontrolled valve of the at least one lower bridge pump circuit is connected to one end of the second semi-controlled valve of the lower bridge arm circuit; or, Each of the at least one upper bridge pump circuit and the at least one lower bridge pump circuit includes a first sub-semi-controlled valve and a second sub-semi-controlled valve; the first and second sub-semi-controlled valves of the at least one upper bridge pump circuit are connected in series, one end of the first sub-semi-controlled valve of the at least one upper bridge pump circuit is connected to the anode bus of the upper bridge transfer circuit, and the other end of the first sub-semi-controlled valve of the at least one upper bridge pump circuit is connected to one end of the third sub-semi-controlled valve or the first uncontrolled valve of the upper bridge transfer circuit; one end of the second sub-semi-controlled valve of the at least one upper bridge pump circuit is connected to one end of the second sub-semi-controlled valve of the upper bridge arm circuit; the first and second sub-semi-controlled valves of the at least one lower bridge pump circuit are connected in series, one end of the first sub-semi-controlled valve of the at least one lower bridge pump circuit is connected to the cathode bus of the lower bridge transfer circuit, and the other end of the first sub-semi-controlled valve of the at least one lower bridge pump circuit is connected to one end of the third sub-semi-controlled valve or the first uncontrolled valve of the lower bridge transfer circuit; one end of the second sub-semi-controlled valve of the at least one lower bridge pump circuit is connected to one end of the second sub-semi-controlled valve of the lower bridge arm circuit; or... The at least one upper bridge pump circuit and the at least one lower bridge pump circuit each include a first sub-semi-controlled valve and a second sub-semi-controlled valve; the first sub-semi-controlled valve of the at least one upper bridge pump circuit is integrated with the third semi-controlled valve or the first uncontrolled valve of the upper bridge transfer circuit, and the two are connected in parallel as devices, valve segments, or valves; the second sub-semi-controlled valve of the at least one upper bridge pump circuit is integrated with the second semi-controlled valve of the upper bridge arm circuit, and the two are connected in parallel as devices, valve segments, or valves; the first sub-semi-controlled valve of the at least one lower bridge pump circuit is integrated with the third semi-controlled valve or the first uncontrolled valve of the lower bridge transfer circuit, and the two are connected in parallel as devices, valve segments, or valves; the second sub-semi-controlled valve of the lower bridge pump circuit is integrated with the second semi-controlled valve of the lower bridge arm circuit, and the two are connected in parallel as devices, valve segments, or valves.

17. A method for controlling a capacitor-assisted grid-connected phase-commutator, characterized in that, Controlling the capacitor-assisted grid-connected phase-commutator according to any one of claims 1-16, comprising: Upon obtaining the operating parameter information of the capacitor-assisted grid-connected phase converter, inverter state control information is generated based on the parameter information, and the main circuit is controlled to operate in inverter state based on the inverter state control information. When the negative pressure of the energy storage circuit is lower than the rated value and exceeds the first threshold, and the commutation bridge arm of the main circuit ends the commutation to the commutation bridge arm circuit and bears the negative pressure, an auxiliary circuit control command is generated, and the corresponding pump pressure circuit of the corresponding auxiliary circuit is controlled to be turned on based on the auxiliary circuit control command. The energy storage circuit is an upper bridge energy storage circuit or a lower bridge energy storage circuit. Upon receiving commutation fault information, a circuit turn-on command is generated, and based on the circuit turn-on command, the transfer circuit and turn-off circuit in the auxiliary circuit corresponding to the commutation bridge arm are controlled to turn on; wherein, the commutation bridge arm is an upper bridge arm circuit or a lower bridge arm circuit. When the first half-control valve of the commutation bridge arm in the main circuit is restored to shutdown, a circuit shutdown command is generated to control the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm to shut down.

18. The method according to claim 17, characterized in that, When the commutation bridge arm is an upper bridge arm circuit, the transfer circuit in the auxiliary circuit corresponding to the commutation bridge arm is an upper bridge transfer circuit of the same phase, and the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm is an upper bridge shutdown circuit. When the commutation bridge arm is a lower bridge arm circuit, the transfer circuit in the auxiliary circuit corresponding to the commutation bridge arm is a lower bridge transfer circuit of the same phase, and the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm is a lower bridge shutdown circuit.

19. The method according to claim 17, characterized in that, The shutdown of the first semi-controlled valve of the commutation bridge arm of the main circuit is determined based on the reverse recovery time of the first semi-controlled valve, wherein the reverse recovery time is greater than or equal to the reverse recovery time of the thyristor contained in the first semi-controlled valve.

20. The method according to any one of claims 17-19, characterized in that, The circuit consisting of the upper bridge shutdown circuit and the upper bridge energy storage circuit in series in the auxiliary circuit is connected to the anode bus of the main circuit via a disconnecting switch and / or a knife switch. The circuit consisting of the lower bridge shutdown circuit and the lower bridge energy storage circuit in series in the auxiliary circuit is connected to the cathode bus of the main circuit via a disconnecting switch and / or a knife switch. When fault information of the auxiliary circuit is obtained, a switch separation command is generated, and the disconnecting switch and / or knife switch are controlled to separate based on the switch separation command.

21. A capacitor-assisted power grid commutator control device, characterized in that, Controlling the capacitor-assisted grid-connected phase-commutator according to any one of claims 1-16, comprising: The first control module is used to generate inverter state control information based on the operating parameter information of the capacitor-assisted grid-connected phase converter when it obtains the operating parameter information, and to control the main circuit to operate in inverter state based on the inverter state control information. The second control module is used to generate an auxiliary circuit control command when the negative pressure of the energy storage circuit is lower than the rated value and exceeds the first threshold, and the commutation bridge arm of the main circuit ends the commutation to the commutation bridge arm circuit and bears the negative pressure, and to control the corresponding pump pressure circuit of the corresponding auxiliary circuit to be turned on based on the auxiliary circuit control command. The energy storage circuit is an upper bridge energy storage circuit or a lower bridge energy storage circuit. The third control module is used to generate a circuit turn-on command when a commutation fault information is obtained, and to 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 command; wherein, the commutation bridge arm is an upper bridge arm circuit or a lower bridge arm circuit. The fourth control module is used to generate a circuit shutdown command when the first half-control valve of the commutation bridge arm of the main circuit is restored to shutdown, and to control the shutdown circuit in the auxiliary circuit corresponding to the commutation bridge arm to shut down.

22. A high-voltage direct current transmission system, comprising the capacitor-assisted grid-connected phase-commutator as described in any one of claims 1-16.

23. The system according to claim 22, characterized in that, The high-voltage direct current transmission system is a two-terminal direct current transmission system or a multi-terminal direct current transmission system. The two-terminal direct current transmission system or the multi-terminal direct current transmission system includes a single-pole direct current transmission system, a bipolar direct current transmission system or a back-to-back direct current transmission system.

24. The system according to claim 23, characterized in that, Some or all of the converters in the two-terminal or multi-terminal DC transmission system that require inverter operation adopt the capacitor-assisted grid-shutdown phase-commutation converter.

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