Direct-current power transmission valve group, series circuit, system, control method and control device

Abstract

The invention discloses a direct-current power transmission valve group, a series circuit, a system, a control method and a control device. Different connection modes of a voltage source converter or a bridge type uncontrolled rectifying circuit, a direct-current circuit breaker, a first valve, an energy consumption circuit and a bypass switch are configured; on-line input, on-line quit and fault quit of the voltage source converter without full-range voltage regulation capability are realized, meanwhile, the follow current of the first valve is utilized to reduce the stress when the direct-current circuit breaker is cut off when a fault occurs, and the direct-current power transmission valve group formed by the direct-current circuit breakers with low voltage levels is serially connected and applied to an extra-high-voltage direct-current power transmission system. Compared with a half-bridge sub-module and full-bridge sub-module mixed MMC structure, loss is reduced, fault isolation performance is better, and the MMC structure is more suitable for a multi-terminal extra-high voltage flexible or mixed direct current power transmission system and a long-distance power transmission direct current power grid.

Description

Technical Field

[0001] This invention belongs to the field of flexible DC power transmission and hybrid DC power transmission technology, and specifically relates to a DC power transmission valve group, series circuit, system, control method and control device. Background Technology

[0002] Compared with traditional DC transmission technology, flexible DC transmission technology has the following advantages: there are no reactive power compensation and commutation failure problems, it can supply power to passive systems, it can simultaneously and independently adjust active and reactive power, it has low harmonic levels, it is suitable for forming multi-terminal DC systems, and it occupies a small area.

[0003] Flexible DC transmission also has shortcomings compared to traditional DC transmission, mainly in the following aspects: higher losses, higher equipment costs, relatively smaller capacity, and less suitable for long-distance overhead line transmission.

[0004] Currently, flexible DC transmission systems employ two-level or three-level VSCs (Voltage Source Converters) or multilevel MMCs (Modular Multilevel Converters) based on half-bridge submodules. When a short circuit occurs on the DC side, even if all controlled devices are turned off, the converter will still feed current to the fault point through diodes connected in anti-parallel with the controlled devices. Existing solutions use DC circuit breakers to clear the fault, but the shutdown stress is very high for long lines, and the limited voltage regulation range prevents online connection and disconnection of the converter. Flexible DC transmission systems use a hybrid MMC structure of half-bridge and full-bridge submodules. While this provides DC fault ride-through capability and allows for online connection and disconnection of the converter, its losses are higher than those of MMCs based on half-bridge submodules and DC circuit breakers, and it is not suitable for DC power grids. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by this application is to overcome the defects of the prior art and provide a DC transmission valve group, series circuit, system, control method and control device that are more suitable for multi-terminal ultra-high voltage flexible or hybrid DC transmission systems and DC power grids for long-distance power transmission.

[0006] Technical solution: This application provides a DC transmission valve group, including a voltage source converter or bridge uncontrolled rectifier circuit, a DC circuit breaker, a first valve, and an energy dissipation circuit.

[0007] Specifically, the voltage source converter or the bridge uncontrolled rectifier circuit is connected in series with the main branch of the DC circuit breaker and then connected in antiparallel with the series circuit of the first valve and the energy consumption circuit; or the voltage source converter is connected in series with the series circuit of the first valve and the energy consumption circuit and then connected in parallel with the DC circuit breaker.

[0008] In some embodiments, the voltage source converter or the bridge uncontrolled rectifier circuit each includes at least three phases and six bridge arms; the DC circuit breaker includes a first two-port DC circuit breaker or a multi-port DC circuit breaker; the first valve includes a first diode valve, a first thyristor valve, or a first fully controlled valve, wherein the first diode valve includes at least one diode connected in series, the first thyristor valve includes at least one thyristor connected in series, and the first fully controlled valve includes at least one fully controlled device connected in series, and the fully controlled device includes anti-parallel diodes; the energy dissipation circuit includes a surge arrester or a resistor.

[0009] In some embodiments, the voltage source converter includes at least one of the following: a two-level converter, a three-level converter, a modular multilevel converter, a diode-clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter.

[0010] In some embodiments, the bridge uncontrolled rectifier circuit includes a six-pulse bridge circuit or a twelve-pulse bridge circuit, and is composed of uncontrolled power semiconductors.

[0011] In some embodiments, the DC circuit breaker is at least one of a hybrid DC circuit breaker, a solid-state DC circuit breaker, or a mechanical DC circuit breaker, wherein the DC circuit breaker comprises: a main branch, wherein the first two-port DC circuit breaker includes the main branch, and the multi-port DC circuit breaker includes one or more of the main branches, and all main branches have a common terminal, the main branch including a fast disconnecting switch and / or a first power switch connected in series; and / or a transfer branch, the transfer branch including a second power switch and / or an LC resonant circuit and / or a coupled negative voltage circuit connected in series; and an energy-dissipating branch, the energy-dissipating branch being connected in parallel with the transfer branch, the energy-dissipating branch including a surge arrester.

[0012] In some embodiments, the system further includes a transfer switch group, through which the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in anti-parallel with the first valve, for rectifier or inverter operation of the voltage source converter; or through the transfer switch group, the voltage source converter is connected in series with the first valve and then connected in parallel with the transfer branch of the DC circuit breaker, for inverter operation or online inversion of the voltage source converter; or through the transfer switch group, the voltage source converter is connected in parallel with the transfer branch of the DC circuit breaker, for online inversion of the voltage source converter.

[0013] In some embodiments, the transfer switch group includes: a first transfer switch, a second transfer switch, and a third transfer switch; wherein the first transfer switch is connected to the positive terminal of the voltage source converter and a first terminal of the DC circuit breaker, the second transfer switch is connected to the negative terminal of the voltage source converter and a first terminal of the DC circuit breaker, and the third transfer switch is connected to the positive terminal of the voltage source converter and a second terminal of the DC circuit breaker; or, the first transfer switch is connected to the negative terminal of the voltage source converter and a second terminal of the DC circuit breaker, the second transfer switch is connected to the positive terminal of the voltage source converter and a second terminal of the DC circuit breaker, and the third transfer switch is connected to the negative terminal of the voltage source converter and a first terminal of the DC circuit breaker.

[0014] In some embodiments, the transfer switch group includes: a fourth transfer switch, a fifth transfer switch, and a sixth transfer switch; wherein the fourth transfer switch is connected to the positive terminal of the DC transmission valve group and the second terminal of the DC circuit breaker, the fifth transfer switch is connected to the positive terminal of the DC transmission valve group and the first terminal of the DC circuit breaker, and the sixth transfer switch is connected to the negative terminal of the DC transmission valve group and the second terminal of the DC circuit breaker; or, the fourth transfer switch is connected to the negative terminal of the DC transmission valve group and the first terminal of the DC circuit breaker, the fifth transfer switch is connected to the negative terminal of the DC transmission valve group and the second terminal of the DC circuit breaker, and the sixth transfer switch is connected to the positive terminal of the DC transmission valve group and the first terminal of the DC circuit breaker.

[0015] In some embodiments, the transfer switch group includes: a first transfer switch, a seventh transfer switch, an eighth transfer switch, a ninth transfer switch, and a tenth transfer switch; wherein, the first transfer switch is connected to the positive terminal of the voltage source converter and the first terminal of the DC circuit breaker, the seventh transfer switch is connected to the positive terminal of the DC transmission valve group and the cathode of the first valve, the eighth transfer switch is connected to the negative terminal of the DC transmission valve group and the anode of the first valve, the ninth transfer switch is connected to the positive terminal of the voltage source converter and the cathode of the first valve, and the tenth transfer switch is connected to the positive terminal of the DC transmission valve group and the anode of the first valve; or, the first transfer switch is connected to the negative terminal of the voltage source converter and the second terminal of the DC circuit breaker, the seventh transfer switch is connected to the negative terminal of the DC transmission valve group and the anode of the first valve, the eighth transfer switch is connected to the positive terminal of the DC transmission valve group and the cathode of the first valve, the ninth transfer switch is connected to the negative terminal of the voltage source converter and the anode of the first valve, and the tenth transfer switch is connected to the negative terminal of the DC transmission valve group and the cathode of the first valve.

[0016] In some embodiments, the transfer switch group includes: a first transfer switch, a second transfer switch, a seventh transfer switch, an eighth transfer switch, a ninth transfer switch, and a tenth transfer switch; wherein, the first transfer switch is connected to the positive terminal of the voltage source converter and the first terminal of the DC circuit breaker; the second transfer switch is connected to the negative terminal of the voltage source converter and the first terminal of the DC circuit breaker; the seventh transfer switch is connected to the positive terminal of the DC transmission valve group and the cathode of the first valve; the eighth transfer switch is connected to the negative terminal of the DC transmission valve group and the anode of the first valve; and the ninth transfer switch is connected to the positive terminal of the voltage source converter and the cathode of the first valve. The tenth changeover switch is connected to the positive terminal of the DC transmission valve group and the anode of the first valve; or, the first changeover switch is connected to the negative terminal of the voltage source converter and the second terminal of the DC circuit breaker, the second changeover switch is connected to the positive terminal of the voltage source converter and the second terminal of the DC circuit breaker, the seventh changeover switch is connected to the negative terminal of the DC transmission valve group and the anode of the first valve, the eighth changeover switch is connected to the positive terminal of the DC transmission valve group and the cathode of the first valve, the ninth changeover switch is connected to the negative terminal of the voltage source converter and the anode of the first valve, and the tenth changeover switch is connected to the negative terminal of the DC transmission valve group and the cathode of the first valve.

[0017] In some embodiments, the voltage source converter is connected in series with the first valve, including: the positive terminal of the voltage source converter is connected to the cathode of the anti-parallel diode of the diode, thyristor, or fully controlled device of the first valve; or the negative terminal of the voltage source converter is connected to the anode of the anti-parallel diode of the diode, thyristor, or fully controlled device of the first valve.

[0018] In some embodiments, the DC transmission valve group further includes at least one residual current disconnect switch. When the voltage source converter or the bridge uncontrolled rectifier circuit is connected in series with the DC circuit breaker and then connected in antiparallel with the first valve, the residual current disconnect switch is connected in series between the voltage source converter and the DC circuit breaker, and / or, connected in series between the DC circuit breaker and the first valve. When the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker, the residual current disconnect switch is first connected in series with the DC circuit breaker, and then connected in parallel with the circuit after the voltage source converter and the first valve are connected in series.

[0019] In some embodiments, the DC transmission valve group further includes a bypass switch, which is connected to the positive and negative terminals of the DC transmission valve group; the bypass switch includes at least one of a mechanical switch, a mechanical knife switch, and a third power switch connected in series.

[0020] In some embodiments, the DC transmission valve group further includes: a positive isolating switch connected to the positive terminal and the first positive input terminal of the DC transmission valve group; a negative isolating switch connected to the negative terminal and the first negative input terminal of the DC transmission valve group; and a bypass switch connected to the first positive input terminal and the first negative input terminal of the DC transmission valve group.

[0021] In some embodiments, the DC circuit breaker is a multi-port DC circuit breaker, and the DC transmission valve group further includes: a second valve, the second valve including a second diode valve or a second thyristor valve, the second diode valve including at least one diode connected in series, the second thyristor valve including at least one thyristor connected in series, the cathode of the second valve being the second positive input terminal of the DC transmission valve group, and the anode of the second valve being the second negative input terminal of the DC transmission valve group; one DC transmission valve group constitutes a DC pole, and the voltage source converter is connected in series with the main branch of the multi-port DC circuit breaker and then connected in anti-parallel with the second valve.

[0022] In some embodiments, the DC circuit breaker is a first two-port DC circuit breaker, and the DC transmission valve group further includes: a second two-port DC circuit breaker; a second valve, the second valve including a second diode valve or a second thyristor valve, the second diode valve including at least one diode connected in series, the second thyristor valve including at least one thyristor connected in series, the cathode of the second valve being the second positive input terminal of the DC transmission valve group, and the anode of the second valve being the second negative input terminal of the DC transmission valve group; one DC transmission valve group constitutes a DC pole, and the voltage source converter is connected in series with the second two-port DC circuit breaker and / or the first two-port DC circuit breaker and then connected in anti-parallel with the second valve.

[0023] In some embodiments, the DC transmission valve group further includes a bypass switch, which is connected in parallel with the energy-consuming circuit; the bypass switch includes a mechanical switch and / or a mechanical knife switch.

[0024] This application embodiment also provides a DC transmission valve group series circuit, including at least two DC transmission valve groups as described in any of the foregoing embodiments; the DC transmission valve group series circuit includes at least a first DC transmission valve group and a second DC transmission valve group, wherein the first negative input terminal of the first DC transmission valve group and the first positive input terminal of the second DC transmission valve group are connected.

[0025] In some embodiments, both the first DC transmission valve group and the second DC transmission valve group include a multi-port DC circuit breaker and a second valve, or both the first DC transmission valve group and the second DC transmission valve group include a second two-port DC circuit breaker and a second valve, wherein the second negative input terminal of the first DC transmission valve group is connected to the second positive input terminal of the second DC transmission valve group, and the first negative input terminal of the first DC transmission valve group is connected to the first positive input terminal of the second DC transmission valve group.

[0026] In some embodiments, the first DC transmission valve group includes a second two-port DC circuit breaker and a second valve. The first negative input terminal of the first DC transmission valve group is connected to the first positive input terminal of the second DC transmission valve group. The second negative input terminal of the first DC transmission valve group is connected to the first negative input terminal of the second DC transmission valve group or connected through a disconnect switch. Alternatively, the second positive input terminal of the first DC transmission valve group is connected to the first positive input terminal of the second DC transmission valve group or connected through a disconnect switch.

[0027] This application also provides a DC power transmission system, including a DC power transmission valve group as described in any of the foregoing embodiments or a DC power transmission valve group series circuit as described in any of the foregoing embodiments; a neutral bus switch is connected in series between the DC power transmission valve group or the DC power transmission valve group series circuit and the ground; the neutral bus switch includes at least one of a mechanical switch, a mechanical disconnect switch, and a fourth power switch connected in series.

[0028] A control method for a DC transmission valve group, applied to a DC transmission valve group as described in any of the foregoing embodiments; the control method includes:

[0029] If the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in antiparallel with the series circuit of the first valve and the energy consumption circuit, during normal operation, the DC circuit breaker is controlled to be turned on, the first valve is controlled to be turned off, and the voltage source converter is controlled to operate in rectification or inversion mode.

[0030] If the voltage source converter is connected in series with the first valve, the energy-consuming circuit, and the bypass switch, and then connected in parallel with the DC circuit breaker, during normal operation, the DC circuit breaker is controlled to turn off, the first valve is controlled to turn on, the bypass switch is controlled to close, and the voltage source converter is controlled to operate in inverter mode.

[0031] In some embodiments, if the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in antiparallel with the series circuit of the first valve and the energy-consuming circuit, the control method further includes:

[0032] When the voltage source converter is in online rectification operation, control the voltage source converter to charge, control the voltage source converter to unlock, and control the DC circuit breaker to turn on;

[0033] When the voltage source converter is in rectifier operation and is offline, the bypass switch is closed, the DC circuit breaker is turned off, and the first valve is turned on.

[0034] When the voltage source converter is in rectifier operation and a fault is resolved, the DC circuit breaker is controlled to turn off and the first valve is controlled to open; when the fault is resolved, the voltage source converter is also controlled to lock out.

[0035] When the voltage source converter is operating in rectification or inversion mode and a DC fault occurs, the DC circuit breaker is controlled to turn off, and the first valve is controlled to turn on. After the fault is recovered or after the deionization time, the DC circuit breaker is controlled to turn on. The DC fault includes DC line faults.

[0036] In some embodiments, if the voltage source converter is connected in series with the parallel circuit of the first valve, the energy-consuming circuit, and the bypass switch, and then connected in parallel with the DC circuit breaker, the control method further includes:

[0037] When the voltage source converter is put into inverter operation online, the system controls the voltage source converter to charge, controls the voltage source converter to unlock, controls the DC circuit breaker to turn off, and controls the first valve to turn on.

[0038] When the voltage source converter is in inverter operation and is shut down online or out of fault, the DC circuit breaker is controlled to be turned on; or if the DC transmission valve group also includes a bypass switch, the bypass switch is controlled to be turned on and / or the DC circuit breaker is controlled to be turned on.

[0039] When the voltage source converter is in inverter operation and a DC fault occurs, the first valve is turned on after the fault is recovered or after the deionization time; the DC fault includes DC line faults.

[0040] In some embodiments, if the DC transmission valve assembly further includes a bypass switch,

[0041] When the voltage source converter is in rectifier operation and then shuts down online or shuts down due to a fault, after controlling the first valve to turn on, the bypass switch is also controlled to turn on.

[0042] When the voltage source converter is in inverter operation and is shut down online or due to a fault, the bypass switch is turned on and the DC circuit breaker is turned off; when the fault is shut down, the voltage source converter is also locked.

[0043] In some embodiments, if the DC transmission valve group further includes a disconnect switch, or the DC transmission system in which the DC transmission valve group is located further includes a neutral bus switch, when the voltage source converter is operating in rectification or inversion mode and a DC fault occurs, after the first valve is turned on, the disconnect switch or the neutral bus switch is disconnected, and after the fault is recovered or after the deionization time, the disconnect switch or the neutral bus switch is reclosed.

[0044] In some embodiments, if the first fully controlled valve of the DC transmission valve group adopts a fully controlled device, when the voltage source converter or bridge uncontrolled rectifier circuit cannot deliver energy normally and generates AC or DC overvoltage, the fully controlled device of the first valve is turned on to dissipate energy in the energy-consuming circuit. When the voltage source converter or bridge uncontrolled rectifier circuit can deliver energy normally, the fully controlled device of the first valve is turned off.

[0045] If the first diode valve of the DC transmission valve group adopts an anti-parallel circuit of at least one diode and thyristor, when the voltage source converter or bridge uncontrolled rectifier circuit cannot deliver energy normally and generates AC or DC overvoltage, the thyristor controlling the first valve is turned on to dissipate the energy in the energy-consuming circuit.

[0046] A control device for a DC transmission valve group, applied to a DC transmission valve group as described in any of the foregoing embodiments; the control device includes: a detection unit for detecting the operating parameters and faults of the DC transmission valve group; and a control unit, which, based on the operating parameters of the DC transmission valve group, controls the DC circuit breaker to conduct, controls the first valve to close, and controls the voltage source converter to operate in rectification or inversion mode during normal operation if the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in antiparallel with the series circuit of the first valve and the energy dissipation circuit; and controls the voltage source converter to operate in inversion mode during normal operation if the voltage source converter is connected in series with the first valve and the parallel circuit of the energy dissipation circuit and the bypass switch and then connected in parallel with the DC circuit breaker.

[0047] Beneficial Effects: The embodiments of this application provide a DC transmission valve group, series circuit, system, control method, and control device. The DC transmission valve group includes a voltage source converter or bridge uncontrolled rectifier circuit, a DC circuit breaker, a first valve, and an energy dissipation circuit. The voltage source converter or bridge uncontrolled rectifier circuit is connected in series with the main branch of the DC circuit breaker and then connected in antiparallel with the series circuit of the first valve and the energy dissipation circuit. Alternatively, the voltage source converter is connected in series with the series circuit of the first valve and the energy dissipation circuit and then connected in parallel with the DC circuit breaker. This application enables online commissioning, online decommissioning, and fault exit of voltage source converters without full-range voltage regulation capabilities by configuring a DC circuit breaker, a first valve, an energy dissipation circuit, and a bypass switch. At the same time, the follow current of the first valve reduces the stress of the DC circuit breaker during interruption in the event of a fault. This allows the DC transmission valve group composed of low-voltage DC circuit breakers to be connected in series in UHVDC transmission systems. Compared with the MMC structure that uses a mixture of half-bridge and full-bridge sub-modules, the loss is reduced and the fault isolation performance is better, making it more suitable for multi-terminal UHV flexible or hybrid DC transmission systems and long-distance DC power grids. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of the first type of DC transmission valve group according to an embodiment of this application;

[0050] Figure 2 This is a schematic diagram of a second type of DC transmission valve assembly according to an embodiment of this application;

[0051] Figure 3 This is a schematic diagram of a third type of DC transmission valve assembly according to an embodiment of this application;

[0052] Figure 4 This is a schematic diagram of the fourth type of DC transmission valve group according to an embodiment of this application;

[0053] Figure 5 This is a schematic diagram of the fifth type of DC transmission valve assembly according to an embodiment of this application;

[0054] Figure 6 This is a schematic diagram of the sixth type of DC transmission valve assembly according to an embodiment of this application;

[0055] Figure 7 This is a schematic diagram of the first type of DC transmission valve group suitable for inverter operation according to an embodiment of this application;

[0056] Figure 8 This is a schematic diagram of a second type of DC transmission valve group suitable for inverter operation according to an embodiment of this application;

[0057] Figure 9 This is a schematic diagram of a third type of DC transmission valve group suitable for inverter operation according to an embodiment of this application;

[0058] Figure 10 This is a schematic diagram of the fourth type of DC transmission valve group suitable for inverter operation according to the embodiments of this application;

[0059] Figure 11 This is a schematic diagram of the fifth type of DC transmission valve group suitable for inverter operation according to the embodiments of this application;

[0060] Figure 12 This is a schematic diagram of the DC transmission valve group using fully controlled devices in the first valve of this application;

[0061] Figure 13 This is a schematic diagram of a DC transmission valve group with a first configuration of the changeover switch group according to an embodiment of this application;

[0062] Figure 14 This is a schematic diagram of a DC transmission valve group with a second configuration of the switching group according to an embodiment of this application;

[0063] Figure 15 This is a schematic diagram of a DC transmission valve group with a third configuration of the switching group according to an embodiment of this application;

[0064] Figure 16This is a schematic diagram of a DC transmission valve group with a fourth configuration of the switching group according to an embodiment of this application;

[0065] Figure 17 This is a schematic diagram of a DC transmission valve group with a fifth configuration of the switching group according to an embodiment of this application;

[0066] Figure 18 This is a schematic diagram of a DC transmission valve group with a sixth configuration of the switching group according to an embodiment of this application;

[0067] Figure 19 This is a schematic diagram of a DC transmission valve group with a seventh configuration of the switching group according to an embodiment of this application;

[0068] Figure 20 This is a schematic diagram of a DC transmission valve group with an eighth configuration of a switching group according to an embodiment of this application;

[0069] Figure 21 This is a schematic diagram of a DC transmission valve group configured with a changeover switch group and a bypass switch according to an embodiment of this application;

[0070] Figure 22 This is a schematic diagram of a DC transmission valve group configured with a changeover switch group, a bypass switch, and a knife switch, according to an embodiment of this application.

[0071] Figure 23 This is a schematic diagram of a DC transmission valve group configured with a multi-port DC circuit breaker according to an embodiment of this application;

[0072] Figure 24 This is a schematic diagram of a DC transmission valve group with another configuration of a multi-port DC circuit breaker according to an embodiment of this application;

[0073] Figure 25 This is a schematic diagram of a DC transmission valve group configured with a second two-port DC circuit breaker according to an embodiment of this application;

[0074] Figure 26 This is a schematic diagram of a DC transmission valve group with another configuration of the second two-port DC circuit breaker according to an embodiment of this application;

[0075] Figure 27 This is a schematic diagram of a first type of DC transmission valve group series circuit according to an embodiment of this application;

[0076] Figure 28 This is a schematic diagram of a second type of DC transmission valve group series circuit according to an embodiment of this application;

[0077] Figure 29 This is a schematic diagram of a third type of DC transmission valve group series circuit according to an embodiment of this application;

[0078] Figure 30 This is a schematic diagram of a fourth type of DC transmission valve group series circuit according to an embodiment of this application;

[0079] Figure 31 This is a schematic diagram of the first type of two-port DC circuit breaker according to an embodiment of this application;

[0080] Figure 32 This is a schematic diagram of a second type of two-port DC circuit breaker according to an embodiment of this application;

[0081] Figure 33 This is a schematic diagram of a third type of two-port DC circuit breaker according to an embodiment of this application;

[0082] Figure 34 This is a schematic diagram of a multi-port DC circuit breaker according to an embodiment of this application;

[0083] Figure 35 This is a schematic diagram of the first type of bypass switch or bypass switch according to an embodiment of this application;

[0084] Figure 36 This is a schematic diagram of a second type of bypass switch or bypass switch according to an embodiment of this application;

[0085] Figure 37 This is a schematic diagram of a third type of bypass switch or bypass switch according to an embodiment of this application;

[0086] Figure 38 This is a schematic diagram of a voltage source converter according to an embodiment of this application;

[0087] Figure 39 This is a schematic diagram of a bridge uncontrolled rectifier circuit according to an embodiment of this application;

[0088] Figure 40 This is a schematic flowchart of a control method for a DC transmission valve group according to an embodiment of this application;

[0089] Figure 41 This is a schematic flowchart of another control method for a DC transmission valve group according to an embodiment of this application;

[0090] Figure 42 This is a schematic diagram of a first type of DC power transmission system according to an embodiment of this application;

[0091] Figure 43 This is a schematic diagram of a second type of DC transmission system according to an embodiment of this application;

[0092] Figure 44 This is a schematic diagram of a third type of DC power transmission system according to an embodiment of this application;

[0093] Figure 45 This is a schematic diagram of a fourth type of DC transmission system according to an embodiment of this application;

[0094] Figure 46 This is a schematic diagram of the fifth type of DC transmission system according to an embodiment of this application;

[0095] Figure 47 This is a schematic diagram of a control device for a DC transmission valve group according to an embodiment of this application. Detailed Implementation

[0096] The following is a detailed description. It should be noted that the order in which the embodiments are described is not intended to limit the preferred order of the embodiments.

[0097] Please refer to the following: Figures 1-6 , Figures 1-6 This is a schematic diagram of various DC transmission valve assemblies according to embodiments of this application.

[0098] like Figure 1 As shown, a DC transmission valve group according to an embodiment of this application includes a voltage source converter or a bridge uncontrolled rectifier circuit, a DC circuit breaker 2, a first valve 3, and an energy dissipation circuit 10, wherein the positive terminal P1 of the voltage source converter or the bridge uncontrolled rectifier circuit is the high voltage terminal.

[0099] In this embodiment, the voltage source converter includes at least three phases and six bridge arms, and cannot adjust the DC voltage to zero or negative voltage. The voltage source converter includes, but is not limited to, at least one of a two-level converter, a three-level converter, a modular multilevel converter, a diode-clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter. The modular multilevel converter is based on a half-bridge submodule. The DC circuit breaker 2 has at least unidirectional DC current interruption capability. The DC circuit breaker 2 includes, but is not limited to, at least one of a hybrid DC circuit breaker, a solid-state DC circuit breaker, or a mechanical DC circuit breaker. The DC circuit breaker 2 is a first two-port DC circuit breaker or a multi-port DC circuit breaker. The first valve 3 includes, but is not limited to, a first diode valve, a first thyristor valve, or a first fully controlled valve. The first diode valve includes at least one diode connected in series or an anti-parallel circuit of at least one diode and a thyristor. The first thyristor valve includes at least one thyristor connected in series. The first fully controlled valve includes at least one fully controlled device connected in series, and the fully controlled device includes an anti-parallel diode. The energy-consuming circuit 10 includes a surge arrester or a resistor.

[0100] A bridge uncontrolled rectifier circuit also includes at least three phases and six arms, including a six-pulse bridge circuit or a twelve-pulse bridge circuit, which is composed of uncontrolled power semiconductors, such as diodes.

[0101] Specifically, the voltage source converter or bridge uncontrolled rectifier circuit is connected in series with the main branch of the DC circuit breaker 2, and then connected in antiparallel with the series circuit of the first valve 3 and the energy-consuming circuit 10, such as... Figure 1As shown, the aforementioned anti-parallel connection involves the positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit being connected to the cathode K of the first valve 3 via the DC circuit breaker 2, and the negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit being connected to one end of the energy-consuming circuit 10. Specifically, the positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to the first terminal C of the DC circuit breaker 2, the second terminal D of the DC circuit breaker 2 is connected to the cathode K of the anti-parallel diode of the diode, thyristor, or fully controlled device of the first valve 3, and the negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to one end of the first energy-consuming circuit 10.

[0102] In this embodiment, when the DC circuit breaker 2 is turned off, the first valve 3 transfers the current flowing through the voltage source converter or the bridge uncontrolled rectifier circuit via a freewheeling current transfer, reducing the stress on the DC circuit breaker 2. The energy dissipation circuit 10 is used to rapidly attenuate the fault current during a fault.

[0103] like Figure 2 As shown, in some embodiments, the DC transmission valve group includes a bypass switch 20, and the bypass switch 20 and the energy dissipation circuit 10 are connected in parallel to bypass the energy dissipation circuit 10 when the DC transmission valve group is put into operation or deactivated.

[0104] In some embodiments, the DC transmission valve assembly further includes at least one residual current disconnect switch, wherein at least one of the residual current disconnect switches is connected in series between the voltage source converter or bridge uncontrolled rectifier circuit and the DC circuit breaker 2 and / or connected in series between the DC circuit breaker 2 and the first valve 3. Specifically, as shown in the figure... Figure 3 As shown, the DC transmission valve group also includes a first residual current disconnect switch 60 and / or a second residual current disconnect switch 70. The first residual current disconnect switch 60 is connected in series between the voltage source converter or bridge uncontrolled rectifier circuit and the DC circuit breaker 2, and / or the second residual current disconnect switch 70 is connected in series between the DC circuit breaker 2 and the first valve 3.

[0105] Furthermore, such as Figure 4 As shown, the aforementioned anti-parallel connection connects the positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit to the cathode K of the first valve 3, and the negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to one end of the energy-consuming circuit 10 through the DC circuit breaker 2. This connection is suitable when the negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit is the high-voltage end. Specifically, the negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to the second terminal D of the DC circuit breaker 2, the first terminal C of the DC circuit breaker 2 is connected to one end of the energy-consuming circuit 10, and the positive terminal P1 of the voltage source converter is connected to the cathode K of the first valve 3.

[0106] In some embodiments, the DC transmission valve assembly further includes a bypass switch 12, which connects the positive terminal P2 and the negative terminal N2 of the DC transmission valve assembly, such as... Figure 5As shown. The bypass switch 12 includes at least one of a mechanical switch, a mechanical knife switch, and a third power switch connected in series. The third power switch includes a power device, which includes at least one of the following: IGCT (Integrated Gate Commutated Thyristors), IGBT (Insulated Gate Bipolar Transistor), GTO (Gate Turn-Off Thyristor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and thyristors, but is not limited thereto. Further, the third power switch includes the power device and an uncontrolled device connected in antiparallel to it.

[0107] In some embodiments, the DC transmission valve assembly further includes a positive isolating switch 13, a negative isolating switch 14, and a bypass switch 11, such as Figure 6 As shown. Positive isolating switch 13 connects the positive terminal P2 of the DC transmission valve group to the first positive input terminal P. Negative isolating switch 14 connects the negative terminal N2 of the DC transmission valve group to the first negative input terminal N. Bypass switch 11 connects the first positive input terminal P and the first negative input terminal N of the DC transmission valve group.

[0108] This application also provides a DC transmission valve group suitable for inverter operation in a voltage source converter, specifically as follows: Figure 7 As shown, the DC transmission valve group includes a voltage source converter 1, a DC circuit breaker 2, a first valve 3, and an energy dissipation circuit 10, which is suitable for the positive terminal P1 of the voltage source converter 1 to be the high voltage end.

[0109] In this embodiment, the voltage source converter 1 includes at least three phases and six bridge arms, and cannot adjust the DC voltage to zero or negative voltage. The voltage source converter 1 includes, but is not limited to, at least one of a two-level converter, a three-level converter, a modular multilevel converter, a diode-clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter, wherein the modular multilevel converter is based on a half-bridge submodule. The DC circuit breaker 2 has at least unidirectional DC current interruption capability, and includes, but is not limited to, a first two-port DC circuit breaker or a multi-port DC circuit breaker. The first valve 3 includes, but is not limited to, a first diode valve, a first thyristor valve, or a first fully controlled valve. The first diode valve includes at least one diode connected in series, the first thyristor valve includes at least one thyristor connected in series, and the first fully controlled valve includes at least one fully controlled device connected in series, and the fully controlled device includes anti-parallel diodes.

[0110] In some embodiments, the DC transmission valve group suitable for inverter operation of the voltage source converter further includes a bypass switch 20. The voltage source converter 1, the first valve 3, and the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20 are connected in series and then connected in parallel with the DC circuit breaker 2. Figure 7 As shown. The series connection described above connects the positive terminal P1 of the voltage source converter 1 to one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20. Specifically, the negative terminal N1 of the voltage source converter 1 is connected to the second terminal D of the DC circuit breaker 2, the first terminal C of the DC circuit breaker 2 is connected to the anode A of the first valve 3, and the positive terminal P1 of the voltage source converter 1 is connected to one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20.

[0111] In this embodiment, during normal operation, the bypass switch 20 is in the closed position; during a DC fault, the unidirectional conduction characteristic of the first valve 3 is used to block the reverse DC current flowing into the fault point from the voltage source converter 1.

[0112] Furthermore, the negative terminal N1 of the voltage source converter 1 is connected to one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20, and the other end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20 is connected to the anode A of the first valve 3. The positive terminal P1 of the voltage source converter 1 is connected to the first terminal C of the DC circuit breaker 2, and the second terminal D of the DC circuit breaker 2 is connected to the cathode K of the first valve 3. Figure 8 As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0113] In some embodiments, the DC transmission valve assembly further includes at least one residual current disconnect switch, which is first connected in series with the DC circuit breaker, and then connected in parallel with the circuit after the voltage source converter and the first valve are connected in series. Figure 9 As shown, specifically, the DC transmission valve group also includes a third residual current disconnect switch 80 and / or a fourth residual current disconnect switch 90. The third residual current disconnect switch 80 and / or the fourth residual current disconnect switch 90 are first connected in series with the DC circuit breaker 2, and then connected in parallel with the circuit after the voltage source converter 1, the first valve 3, the energy consumption circuit 10 and the bypass switch 20 are connected in series.

[0114] In some embodiments, the DC transmission valve assembly further includes a second bypass switch 52, which connects the positive terminal P2 and the negative terminal N2 of the DC transmission valve assembly, such as... Figure 10 As shown.

[0115] In some embodiments, the DC transmission valve assembly further includes a third isolating switch 53, a fourth isolating switch 54, and a second bypass switch 51, such as Figure 11As shown. The third isolating switch 53 connects the positive terminal P2 and the positive input terminal P of the DC transmission valve group. The fourth isolating switch 54 connects the negative terminal N2 and the negative input terminal N of the DC transmission valve group. The second bypass switch 51 connects the positive input terminal P and the negative input terminal N of the DC transmission valve group.

[0116] This application embodiment also provides a DC transmission valve assembly where the first valve employs fully controllable devices, specifically as follows: Figure 12 As shown, the DC transmission valve group includes a voltage source converter or bridge uncontrolled rectifier circuit, a DC circuit breaker 2, a first valve 3, and an energy dissipation circuit 10, suitable for the positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit to be the high voltage end.

[0117] In this embodiment, the voltage source converter includes at least three phases and six bridge arms, and cannot adjust the DC voltage to zero or negative voltage. The voltage source converter includes, but is not limited to, at least one of a two-level converter, a three-level converter, a modular multilevel converter, a diode-clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter. The modular multilevel converter is based on a half-bridge submodule. The DC circuit breaker 2 has at least unidirectional DC current interruption capability, and includes, but is not limited to, at least one of a hybrid DC circuit breaker, a solid-state DC circuit breaker, or a mechanical DC circuit breaker. The DC circuit breaker 2 is a first two-port DC circuit breaker or a multi-port DC circuit breaker. The first valve 3 includes a first fully controlled valve, which includes at least one fully controlled device connected in series, and the fully controlled device includes anti-parallel diodes.

[0118] A bridge uncontrolled rectifier circuit includes at least three phases and six bridge arms, including a six-pulse bridge circuit or a twelve-pulse bridge circuit, which is composed of uncontrolled power semiconductors, such as diodes.

[0119] The voltage source converter or bridge uncontrolled rectifier circuit is connected in series with the main branch of the DC circuit breaker 2, and then connected in antiparallel with the series circuit of the first valve 3 and the energy dissipation circuit 10, such as... Figure 12 As shown, the aforementioned anti-parallel connection involves the positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit being connected to the cathode K of the first valve 3 via the DC circuit breaker 2, and the negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit being connected to one end of the energy-consuming circuit 10. Specifically, the positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to the first terminal C of the DC circuit breaker 2, the second terminal D of the DC circuit breaker 2 is connected to the cathode K of the anti-parallel diode of the first valve 3, and the negative terminal N1 of the voltage source converter 1 is connected to one end of the energy-consuming circuit 10.

[0120] In this embodiment, when the DC circuit breaker 2 is turned off, the first valve 3 transfers the current flowing through the voltage source converter or the bridge uncontrolled rectifier circuit via a freewheeling current transfer, reducing the stress on the DC circuit breaker 2. The energy dissipation circuit 10 is used to rapidly attenuate the fault current during a fault.

[0121] When the voltage source converter or bridge uncontrolled rectifier circuit cannot deliver energy normally, such as when a three-phase short circuit fault occurs on the inverter side, the fully controlled device of the first valve 3 is turned on, dissipating the energy in the energy dissipation circuit 10. When the voltage source converter or bridge uncontrolled rectifier circuit can deliver energy normally, the fully controlled device of the first valve 3 is turned off.

[0122] In some embodiments, the first valve includes a first diode valve, which includes an anti-parallel circuit of at least one diode and a thyristor. When the voltage source converter or bridge uncontrolled rectifier circuit cannot deliver energy normally, such as when a three-phase short circuit fault occurs on the inverter side, the thyristor controlling the first valve 3 is turned on, dissipating the energy in the energy dissipation circuit 10.

[0123] In some embodiments, a DC transmission valve group configured with a switching group is also provided, specifically as follows: Figure 13 As shown. The DC transmission valve group includes a voltage source converter 1, a DC circuit breaker 2, a first valve 3, an energy consumption circuit 10, a bypass switch 20, a first changeover switch 4, a second changeover switch 5, and a third changeover switch 6, which is suitable for the positive terminal P1 of the voltage source converter 1 to be the high-voltage end.

[0124] Specifically, this embodiment is in Figure 2 Based on the previous embodiment, three transfer switches were added: a first transfer switch 4, a second transfer switch 5, and a third transfer switch 6, which are used to switch the connection relationship of the DC circuit breaker 2 so that the voltage source converter 1 can operate in rectification mode, inverting mode, or be put into inverting mode online.

[0125] The first transfer switch 4 connects the positive terminal P1 of the voltage source converter 1 to the first terminal C of the DC circuit breaker 2. The second transfer switch 5 connects the negative terminal N1 of the voltage source converter 1 to the first terminal C of the DC circuit breaker 2. The third transfer switch 6 connects the positive terminal P1 of the voltage source converter 1 to the second terminal D of the DC circuit breaker 2.

[0126] Furthermore, an embodiment with the following connection method can also exist: The first changeover switch 4 connects the negative terminal N1 of the voltage source converter 1 to the second terminal D of the DC circuit breaker 2. The second changeover switch 5 connects the positive terminal P1 of the voltage source converter 1 to the second terminal D of the DC circuit breaker 2. The third changeover switch 6 connects the negative terminal N1 of the voltage source converter 1 to the first terminal C of the DC circuit breaker 2, specifically as follows... Figure 14 As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0127] like Figure 13 and Figure 14 As shown, when the voltage source converter is running in rectification mode, the bypass switch 20 is open, the first changeover switch 4 is closed, and the second changeover switch 5 and the third changeover switch 6 are open.

[0128] When the voltage source converter is inverting, the bypass switch 20 is closed, the first transfer switch 4 is closed, and the second transfer switch 5 and the third transfer switch 6 are separated.

[0129] When the voltage source converter is put into online inverter operation, the bypass switch 20 is closed, the first transfer switch 4 is open, and the second transfer switch 5 and the third transfer switch 6 are closed.

[0130] In some embodiments, there is also another configuration of the DC transmission valve group with the switching group, specifically as follows: Figure 15 As shown, the DC transmission valve group includes a voltage source converter 1, a DC circuit breaker 2, a first valve 3, an energy consumption circuit 10, a bypass switch 20, a fourth changeover switch 7, a fifth changeover switch 8, and a sixth changeover switch 9, which is suitable for the positive terminal P1 of the voltage source converter 1 to be the high voltage end.

[0131] This embodiment is also in Figure 2 Based on the previous embodiment, three additional switching switches were added: a fourth switching switch 7, a fifth switching switch 8, and a sixth switching switch 9, to switch the connection relationship of the DC circuit breaker 2, so that the voltage source converter 1 can operate in rectification mode, inverting mode, or be put into inverting mode online.

[0132] One embodiment is as follows: Figure 15 As shown, the fourth changeover switch 7 connects the second terminal D of the DC circuit breaker 2 to the positive terminal P2 of the DC transmission valve group. The fifth changeover switch 8 connects the positive terminal P2 of the DC transmission valve group to the first terminal C of the DC circuit breaker 2. The sixth changeover switch 9 connects the second terminal D of the DC circuit breaker 2 to the negative terminal N2 of the DC transmission valve group.

[0133] Another embodiment is as follows: the fourth changeover switch 7 connects the first terminal C of the DC circuit breaker 2 to the negative terminal N2 of the DC transmission valve group. The fifth changeover switch 8 connects the negative terminal N2 of the DC transmission valve group to the second terminal D of the DC circuit breaker 2. The sixth changeover switch 9 connects the first terminal C of the DC circuit breaker 2 to the positive terminal P2 of the DC transmission valve group, specifically as follows. Figure 16 As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0134] like Figure 15 and Figure 16 As shown, when the voltage source converter is running in rectification mode, the bypass switch 20 is open, the fourth transfer switch 7 is closed, and the fifth transfer switch 8 and the sixth transfer switch 9 are open.

[0135] When the voltage source converter is inverting, the bypass switch 20 is closed, the fourth transfer switch 7 is closed, and the fifth transfer switch 8 and the sixth transfer switch 9 are open.

[0136] When the voltage source converter is put into online inverter operation, the bypass switch 20 is closed, the fourth transfer switch 7 is open, and the fifth transfer switch 8 and the sixth transfer switch 9 are closed.

[0137] In some embodiments, a DC transmission valve group configured with a switching group is also provided, specifically as follows: Figure 17 As shown, the DC transmission valve group includes a voltage source converter 1, a DC circuit breaker 2, a first valve 3, an energy-consuming circuit 10, a bypass switch 20, a first changeover switch 4, a second changeover switch 5, a seventh changeover switch 15, an eighth changeover switch 16, a ninth changeover switch 17, and a tenth changeover switch 18, which is suitable for the positive terminal P1 of the voltage source converter 1 to be the high-voltage end.

[0138] This embodiment is... Figure 2 Based on the previous embodiment, six additional switching switches were added: first switching switch 4, second switching switch 5, seventh switching switch 15, eighth switching switch 16, ninth switching switch 17, and tenth switching switch 18, which are used to switch the connection relationship between voltage source converter 1, DC circuit breaker 2 and first valve 3, so that voltage source converter 1 can operate in rectification mode, inverter mode or online inverter mode.

[0139] One embodiment is as follows: A first changeover switch 4 connects the positive terminal P1 of the voltage source converter 1 to the first terminal C of the DC circuit breaker 2. A second changeover switch 5 connects the negative terminal N1 of the voltage source converter 1 to the first terminal C of the DC circuit breaker 2. A seventh changeover switch 15 connects the cathode K of the first valve 3 to the positive terminal P2 of the DC transmission valve group. An eighth changeover switch 16 connects one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20 to the negative terminal N2 of the DC transmission valve group. A ninth changeover switch 17 connects the cathode K of the first valve 3 to the positive terminal P1 of the voltage source converter. A tenth changeover switch 18 connects the positive terminal P2 of the DC transmission valve group to one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20.

[0140] Another embodiment is as follows: The first changeover switch 4 connects the negative terminal N1 of the voltage source converter 1 to the second terminal D of the DC circuit breaker 2. The second changeover switch 5 connects the positive terminal P1 of the voltage source converter 1 to the second terminal D of the DC circuit breaker 2. The seventh changeover switch 15 connects one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20 to the negative terminal N2 of the DC transmission valve group. The eighth changeover switch 16 connects the cathode K of the first valve 3 to the positive terminal P2 of the DC transmission valve group. The ninth changeover switch 17 connects one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20 to the negative terminal N1 of the voltage source converter. The tenth changeover switch 18 connects the negative terminal N2 of the DC transmission valve group to the cathode K of the first valve 3, specifically as follows... Figure 18 As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0141] like Figure 17and Figure 18 As shown, when the voltage source converter is running in rectification mode, the bypass switch 20 is open, the first changeover switch 4, the seventh changeover switch 15 and the eighth changeover switch 16 are closed, and the second changeover switch 5, the ninth changeover switch 17 and the tenth changeover switch 18 are open.

[0142] When the voltage source converter is in inverter operation, the bypass switch 20 is closed, the first transfer switch 4, the seventh transfer switch 15 and the eighth transfer switch 16 are closed, and the second transfer switch 5, the ninth transfer switch 17 and the tenth transfer switch 18 are open.

[0143] Optionally, when the voltage source converter is inverting, the bypass switch 20 is closed, the first transfer switch 4, the seventh transfer switch 15 and the eighth transfer switch 16 are opened, and the second transfer switch 5, the ninth transfer switch 17 and the tenth transfer switch 18 are closed.

[0144] When the voltage source converter is put into online inverter operation, the bypass switch 20 is closed, the first transfer switch 4, the seventh transfer switch 15 and the eighth transfer switch 16 are opened, and the second transfer switch 5, the ninth transfer switch 17 and the tenth transfer switch 18 are closed.

[0145] In some embodiments, a DC transmission valve group with a configuration of a switching group is also provided. The DC transmission valve group includes a voltage source converter 1, a DC circuit breaker 2, a first valve 3, a first switching switch 4, a fourth switching switch 7, a fifth switching switch 8, a sixth switching switch 9, a seventh switching switch 15, an eighth switching switch 16, a ninth switching switch 17, and a tenth switching switch 18, suitable for the positive terminal P1 of the voltage source converter 1 to be the high-voltage end.

[0146] This embodiment is Figure 15 Based on the previous embodiment, five additional switching switches were added: first switching switch 4, fourth switching switch 7, fifth switching switch 8, sixth switching switch 9, seventh switching switch 15, eighth switching switch 16, ninth switching switch 17, and tenth switching switch 18. These switches are used to switch the connection relationship between voltage source converter 1, DC circuit breaker 2, and first valve 3, enabling voltage source converter 1 to operate in rectification mode, inverter mode, or online inverter mode.

[0147] One embodiment of the connection method is as follows: First changeover switch 4 connects the positive terminal P1 of voltage source converter 1 to the first terminal C of DC circuit breaker 2. Fourth changeover switch 7 connects the second terminal D of DC circuit breaker 2 to the positive terminal P2 of DC transmission valve group. Fifth changeover switch 8 connects the positive terminal P2 of DC transmission valve group to the first terminal C of DC circuit breaker 2. Sixth changeover switch 9 connects the second terminal D of DC circuit breaker 2 to the negative terminal N2 of DC transmission valve group. Seventh changeover switch 15 connects the cathode K of first valve 3 to the positive terminal P2 of DC transmission valve group. Eighth changeover switch 16 connects one end of the parallel circuit of energy dissipation circuit 10 and bypass switch 20 to the negative terminal N2 of DC transmission valve group. Ninth changeover switch 17 connects the cathode K of first valve 3 to the positive terminal P1 of voltage source converter. Tenth changeover switch 18 connects the positive terminal P2 of DC transmission valve group to one end of the parallel circuit of energy dissipation circuit 10 and bypass switch 20.

[0148] Another embodiment of the connection method is as follows: First changeover switch 4 connects the negative terminal N1 of voltage source converter 1 to the second terminal D of DC circuit breaker 2. Fourth changeover switch 7 connects the first terminal C of DC circuit breaker 2 to the negative terminal N2 of DC transmission valve group. Fifth changeover switch 8 connects the negative terminal N2 of DC transmission valve group to the second terminal D of DC circuit breaker 2. Sixth changeover switch 9 connects the first terminal C of DC circuit breaker 2 to the positive terminal P2 of DC transmission valve group. Seventh changeover switch 15 connects one end of the parallel circuit of energy dissipation circuit 10 and bypass switch 20 to the negative terminal N2 of DC transmission valve group. Eighth changeover switch 16 connects the cathode K of first valve 3 to the positive terminal P2 of DC transmission valve group. Ninth changeover switch 17 connects one end of the parallel circuit of energy dissipation circuit 10 and bypass switch 20 to the negative terminal N1 of voltage source converter. Tenth changeover switch 18 connects the negative terminal N2 of DC transmission valve group to the cathode K of first valve 3. Specifically, as follows... Figure 20 As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0149] like Figure 19 and Figure 20 As shown, when the voltage source converter is running in rectification mode, the bypass switch 20 is open, the first changeover switch 4, the fourth changeover switch 7, the seventh changeover switch 15 and the eighth changeover switch 16 are closed, and the fifth changeover switch 8, the sixth changeover switch 9, the ninth changeover switch 17 and the tenth changeover switch 18 are open.

[0150] When the voltage source converter is inverting, the bypass switch 20 is closed, the first transfer switch 4, the fourth transfer switch 7, the seventh transfer switch 15 and the eighth transfer switch 16 are closed, and the fifth transfer switch 8, the sixth transfer switch 9, the ninth transfer switch 17 and the tenth transfer switch 18 are open.

[0151] Optionally, when the voltage source converter is inverting, the bypass switch 20 is closed, the first transfer switch 4, the fourth transfer switch 7, the seventh transfer switch 15 and the eighth transfer switch 16 are opened, and the fifth transfer switch 8, the sixth transfer switch 9, the ninth transfer switch 17 and the tenth transfer switch 18 are closed.

[0152] When the voltage source converter is put into online inverter operation, the bypass switch 20 is closed, the first transfer switch 4, the fourth transfer switch 7, the seventh transfer switch 15 and the eighth transfer switch 16 are opened, and the fifth transfer switch 8, the sixth transfer switch 9, the ninth transfer switch 17 and the tenth transfer switch 18 are closed.

[0153] It should be noted that if the connection relationship of the residual current disconnect switch is the same as that of the transfer switch mentioned above, then the residual current disconnect switch and the transfer switch share the same switch.

[0154] exist Figure 19 Based on the illustrated embodiment, the DC transmission valve group further includes a bypass switch 12, which connects the positive terminal P2 and the negative terminal N2 of the DC transmission valve group, as shown below. Figure 21 As shown.

[0155] Furthermore, in Figure 21 Based on the illustrated embodiment, the DC transmission valve group further includes a positive isolating switch 13, a negative isolating switch 14, and a bypass switch 11, as shown below. Figure 22 As shown. Positive isolating switch 13 connects the positive terminal P2 of the DC transmission valve group to the first positive input terminal P. Negative isolating switch 14 connects the negative terminal N2 of the DC transmission valve group to the first negative input terminal N. Bypass switch 11 connects the first positive input terminal P and the first negative input terminal N of the DC transmission valve group.

[0156] In some embodiments, the DC circuit breaker of the DC transmission valve group is a multi-port DC circuit breaker. In this case, the DC transmission valve group includes a voltage source converter or a bridge uncontrolled rectifier circuit, a multi-port DC circuit breaker 19, a first valve 3, an energy dissipation circuit 10, a bypass switch 20, a second valve 28, a second energy dissipation circuit 30, and a second bypass switch 96. The positive terminal P1 of the voltage source converter or the bridge uncontrolled rectifier circuit is the high-voltage terminal.

[0157] This embodiment is... Figure 2A further improvement based on the embodiment is made: the DC circuit breaker 19 is a multi-port DC circuit breaker, possessing at least a unidirectional DC current interruption capability. The first valve 3 includes a first diode valve, a first thyristor valve, or a first fully controlled valve. The first diode valve includes at least one diode connected in series or an anti-parallel circuit of at least one diode and a thyristor. The first thyristor valve includes at least one thyristor connected in series. The second valve 28 includes a second diode valve or a second thyristor valve. The second diode valve includes at least one diode connected in series or an anti-parallel circuit of at least one diode and a thyristor. The second thyristor valve includes at least one thyristor connected in series.

[0158] In this embodiment, the voltage source converter or bridge uncontrolled rectifier circuit is connected in series with the main branch of the multi-port DC circuit breaker 19, then in series with the parallel circuit of the first valve 3, the energy dissipation circuit 10, and the bypass switch 20, and then connected in antiparallel. The voltage source converter or bridge uncontrolled rectifier circuit is connected in series with the main branch of the multi-port DC circuit breaker 19, then in series with the parallel circuit of the second valve 28, the second energy dissipation circuit 30, and the second bypass switch 96, and then connected in antiparallel. In the antiparallel connection, the positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to the cathode K of the first valve 3 or the second valve 28 through the multi-port DC circuit breaker 19, and the negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20, or one end of the parallel circuit of the second energy dissipation circuit 30 and the second bypass switch 96.

[0159] Specifically, such as Figure 23 As shown, the positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to the first terminal C of the multi-port DC circuit breaker 19. The second terminal D of the multi-port DC circuit breaker 19 is connected to the cathode K of the first valve 3. The negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20. The third terminal E of the multi-port DC circuit breaker 19 is connected to the cathode K of the second valve 28. The negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to one end of the parallel circuit of the second energy dissipation circuit 30 and the second bypass switch 96.

[0160] Optionally, the negative terminal N1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to the second terminal D of the multi-port DC circuit breaker 19. The first terminal C of the multi-port DC circuit breaker 19 is connected to one end of the parallel circuit of the energy dissipation circuit 10 and the bypass switch 20. The positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to the cathode K of the first valve 3. The third terminal E of the multi-port DC circuit breaker 19 is connected to one end of the parallel circuit of the second energy dissipation circuit 30 and the second bypass switch 96. The positive terminal P1 of the voltage source converter or bridge uncontrolled rectifier circuit is connected to the cathode K of the second valve 28, as detailed below. Figure 24As shown, the negative terminal N1 of a voltage source converter or bridge uncontrolled rectifier circuit is the high-voltage terminal.

[0161] Figure 25 This is a schematic diagram of a DC transmission valve group with a second two-port DC circuit breaker configured according to an embodiment of this application. It is applicable to voltage source converters or bridge uncontrolled rectifier circuits where the positive terminal P1 is the high-voltage terminal.

[0162] exist Figure 2 Based on this, the DC transmission valve group also includes a second two-port DC circuit breaker 27, a second valve 28, a second energy dissipation circuit 30, and a second bypass switch 96. A voltage source converter or bridge uncontrolled rectifier circuit is connected in series with the second two-port DC circuit breaker 27 and the first two-port DC circuit breaker 2, then connected in series with the parallel circuit of the second valve 28, the second energy dissipation circuit 30, and the second bypass switch 96, and then connected in anti-parallel.

[0163] Specifically, such as Figure 25 As shown, the first positive input terminal P of the DC transmission valve group is connected to the first terminal C of the second two-port DC circuit breaker 27, the second terminal D of the second two-port DC circuit breaker 27 is connected to the cathode K of the second valve 28, and the first negative input terminal N of the DC transmission valve group is connected to one end of the parallel circuit of the second energy dissipation circuit 30 and the bypass switch 96.

[0164] Optionally, in Figure 3 Based on this, the first negative input terminal N of the DC transmission valve group is connected to the second terminal D of the second two-port DC circuit breaker 27, the first terminal C of the second two-port DC circuit breaker 27 is connected to one end of the parallel circuit of the second energy dissipation circuit 30 and the second bypass switch 96, and the first positive input terminal P of the DC transmission valve group is connected to the cathode K of the second valve 28, as detailed below. Figure 26 As shown, the negative terminal N1 of a voltage source converter or bridge uncontrolled rectifier circuit is the high-voltage terminal.

[0165] Figure 27 This is a schematic diagram of a DC transmission valve group series circuit according to an embodiment of this application, including two... Figure 2 The DC transmission valve groups shown are connected in series. Specifically, the first negative input terminal N of the first DC transmission valve group 29 and the first positive input terminal P of the second DC transmission valve group 37 are connected.

[0166] Figure 28 This is a schematic diagram of another DC transmission valve group series circuit according to an embodiment of this application, including two... Figure 23The DC transmission valve groups shown are connected in series. Specifically, the first negative input terminal N of the third DC transmission valve group 38 is connected to the first positive input terminal P of the fourth DC transmission valve group 39, the second negative input terminal N3 of the third DC transmission valve group 38 is connected to the second positive input terminal P3 of the fourth DC transmission valve group 39, and the first negative input terminal N and the second negative input terminal N3 of the third DC transmission valve group 38 are separated.

[0167] Figure 29 This is a schematic diagram of another DC transmission valve group series circuit according to an embodiment of this application, including two... Figure 25 The DC transmission valve groups shown are connected in series. Specifically, the first negative input terminal N of the fifth DC transmission valve group 47 is connected to the first positive input terminal P of the sixth DC transmission valve group 48, and the second negative input terminal N3 of the fifth DC transmission valve group 47 is connected to the second positive input terminal P3 of the sixth DC transmission valve group 48. The first negative input terminal N and the second negative input terminal N3 of the fifth DC transmission valve group 47 are separate.

[0168] Figure 30 This is a schematic diagram of another DC transmission valve group series circuit according to an embodiment of this application, including... Figure 23 The DC transmission valve assembly shown is Figure 2 The DC transmission valve groups shown are connected in series. Specifically, the first negative input terminal N of the seventh DC transmission valve group 40 is connected to the first positive input terminal P of the eighth DC transmission valve group 50, and the second negative input terminal N3 of the seventh DC transmission valve group 40 is connected to the first negative input terminal N of the eighth DC transmission valve group 50.

[0169] The DC circuit breakers in the embodiments of this application include, but are not limited to, hybrid DC circuit breakers, solid-state DC circuit breakers, or mechanical DC circuit breakers. Figure 31 This is a schematic diagram of a two-port DC circuit breaker according to an embodiment of this application. The DC circuit breaker is a hybrid DC circuit breaker, including a main branch 49, a transfer branch 57 and an energy-dissipating branch 58 connected in parallel.

[0170] Main branch 49 includes, but is not limited to, a fast disconnect switch and / or a first power switch connected in series. For example... Figure 31 As shown, the main branch 49 includes a fast disconnect switch 59 and a first power switch connected in series, used to conduct steady-state current and reduce losses. The first power switch employs a first power device 67 with a forward and reverse series structure, possessing bidirectional DC current interruption capability. The first power device 67 includes, but is not limited to, a forward IGBT and a reverse IGBT connected in series, with the forward and reverse IGBTs respectively connected in anti-parallel diodes. The transfer branch 57 includes, but is not limited to, a second power switch and / or an LC resonant circuit and / or a coupling negative voltage circuit connected in series. Figure 31As shown, the transfer branch 57 includes a second power switch and a diode 69, used to interrupt DC current under high-voltage operating conditions. It should be noted that the diode 69 allows current from the DC circuit breaker to flow unidirectionally into the second power switch, and the second power switch, when open, can interrupt current from the DC circuit breaker in either direction. The second power switch in the transfer branch 57 uses a second power device 68 with a forward series structure, possessing unidirectional DC current interruption capability. The second power device 68 includes, but is not limited to, IGBTs and anti-parallel diodes. The energy dissipation branch 58 includes, but is not limited to, a surge arrester 77, used to suppress overvoltage and absorb energy.

[0171] The first power switch includes at least one first power device 67 connected in series, the first power device 67 including at least one of IGCT, IGBT, GTO, and MOSFET, but not limited thereto.

[0172] The second power switch includes at least one second power device 68 connected in series. The second power device 68 includes at least one of IGCT, IGBT, GTO, MOSFET, and thyristor, but is not limited thereto.

[0173] Optionally, the first power switch and the second power switch include at least one power device connected in series and an uncontrolled device connected in antiparallel with it.

[0174] Figure 32 This is a schematic diagram of another two-port DC circuit breaker according to an embodiment of this application. The DC circuit breaker is a hybrid DC circuit breaker, including a main branch 49, a transfer branch 57 and an energy-dissipating branch 58 connected in parallel.

[0175] Main branch 49 includes, but is not limited to, a fast disconnect switch and / or a first power switch connected in series. For example... Figure 32 As shown, the main branch 49 includes a fast disconnect switch 59 and a first power switch connected in series for conducting steady-state current and reducing losses. The first power switch of the main branch 49 adopts a third power device 78 with a forward series structure, which has the ability to unidirectionally interrupt DC current. The third power device 78 includes, but is not limited to, an IGBT and diode anti-parallel circuit. The transfer branch includes, but is not limited to, a second power switch and / or an LC resonant circuit and / or a coupling negative voltage circuit connected in series. Figure 32 As shown, the transfer branch 57 includes a second power switch for interrupting DC current under high-voltage operating conditions. The second power switch employs a second power device 68 with a forward series structure, possessing unidirectional DC current interruption capability. The second power device 68 includes, but is not limited to, IGBTs and anti-parallel diodes. The energy dissipation branch 58 includes, but is not limited to, a surge arrester 77 for suppressing overvoltage and absorbing energy.

[0176] Figure 33This is a schematic diagram of another two-port DC circuit breaker according to an embodiment of this application. The DC circuit breaker is a solid-state DC circuit breaker, including a transfer branch 57 and an energy dissipation branch 58 connected in parallel. The transfer branch 57 includes, but is not limited to, a second power switch and / or an LC resonant circuit and / or a coupling negative voltage circuit connected in series. Figure 33 As shown, the transfer branch 57 includes, but is not limited to, a second power switch connected in series, used to interrupt DC current under high-voltage operating conditions. The second power switch of the transfer branch 57 adopts a second power device 68 with a forward series structure, which has the ability to unidirectionally interrupt DC current. The second power device 68 includes, but is not limited to, an IGBT and an anti-parallel diode. The energy dissipation branch 58 includes, but is not limited to, a surge arrester 77, used to suppress overvoltage and absorb energy.

[0177] Multi-port DC circuit breakers include multi-port hybrid DC circuit breakers or multi-port mechanical DC circuit breakers. Figure 34 This is a schematic diagram of a multi-port DC circuit breaker according to an embodiment of this application. The multi-port DC circuit breaker is a hybrid multi-port DC circuit breaker, including a main branch 49, a second main branch 79, a third main branch 87, a first selector switch 88, a second selector switch 89, a third selector switch 91, a transfer branch 57, and a power dissipation branch 58. The main branch 49, the second main branch 79, and the third main branch 87 include, but are not limited to, a fast-disconnecting switch and / or a first power switch connected in series. Figure 31 As shown, main branch 49, second main branch 79, and third main branch 87 each include a fast disconnect switch 59 and a first power switch connected in series, used to conduct steady-state current and reduce losses. The first power switches in main branch 49, second main branch 79, and third main branch 87 each employ a first power device 67 with a forward and reverse series structure, possessing bidirectional DC current interruption capability. The first power switch includes, but is not limited to, a forward IGBT and a reverse IGBT connected in series, with the forward and reverse IGBTs respectively connected in anti-parallel diodes. First selection switch 88, second selection switch 89, and third selection switch 91 include, but are not limited to, at least one of a mechanical switch, a mechanical knife switch, and a third power switch connected in series. Transfer branch 57 includes, but is not limited to, a second power switch connected in series and / or an LC resonant circuit and / or a coupling negative voltage circuit. Figure 33 As shown, the transfer branch 57 includes a second power switch and a diode 69, used to interrupt DC current under high-voltage operating conditions. It should be noted that the diode 69 allows current from the DC circuit breaker to flow unidirectionally into the second power switch, and the second power switch, when open, can interrupt current from the DC circuit breaker in either direction. The second power switch in the transfer branch 57 uses a second power device 68 with a forward series structure, possessing the capability to unidirectionally interrupt DC current. The second power device 68 includes, but is not limited to, an anti-parallel circuit of an IGBT and a diode.

[0178] The energy-dissipating branch 58 includes, but is not limited to, surge arrester 77, used to suppress breaking overvoltage and absorb energy.

[0179] Figures 35-37 This is a schematic diagram of various bypass switches or bypass switches according to embodiments of this application. The bypass switches or bypass switches include, but are not limited to, at least one of mechanical switches, mechanical knife switches, or at least one third power switch connected in series.

[0180] like Figure 35 As shown, the bypass switch or bypass switch includes a first mechanical switch 92. For example... Figure 36 As shown, the bypass switch or bypass switch includes a third power switch and a first mechanical switch 92 connected in series. (As...) Figure 37 As shown, the bypass switch or bypass switch includes a third power switch and a first mechanical switch 92 connected in series, and a second mechanical switch 94 connected in parallel with this series circuit. The third power switch includes a fourth power device 93 connected in series, which includes, but is not limited to, a thyristor. The third power switch includes at least one fourth power device 93 connected in series, which includes, but is not limited to, at least one of IGCT, IGBT, GTO, MOSFET, and thyristor.

[0181] Figure 38 This is a schematic diagram of a voltage source converter according to an embodiment of this application. The voltage source converter adopts a modular multilevel converter, and each sub-module adopts a half-bridge structure. Figure 39 This is a schematic diagram of a bridge uncontrolled rectifier circuit according to an embodiment of this application. The bridge uncontrolled rectifier circuit adopts a twelve-pulse bridge circuit, with each bridge arm consisting of diodes connected in series.

[0182] Accordingly, this application provides a control method for a DC transmission valve group, applied to the DC transmission valve group of the aforementioned embodiments; the control method includes:

[0183] If the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in antiparallel with the series circuit of the first valve and the energy consumption circuit, during normal operation, the DC circuit breaker is controlled to conduct, the first valve is controlled to close, and the voltage source converter is controlled to operate in rectification or inversion mode.

[0184] If the voltage source converter is connected in series with the first valve, the energy consumption circuit, and the bypass switch, and then connected in parallel with the DC circuit breaker, during normal operation, the DC circuit breaker is controlled to turn off, the first valve is controlled to turn on, the bypass switch is controlled to close, and the voltage source converter is controlled to operate in inverter mode.

[0185] In some embodiments, if the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in antiparallel with the series circuit of the first valve and the energy-consuming circuit, the control method further includes:

[0186] When the voltage source converter is in online rectification operation, control the voltage source converter to charge, control the voltage source converter to unlock, and control the DC circuit breaker to turn on;

[0187] When the voltage source converter is in rectifier operation and is offline, the control bypass switch is closed, the control DC circuit breaker is turned off, and the control first valve is turned on.

[0188] When the voltage source converter is in rectifier operation and the fault is resolved, the DC circuit breaker is controlled to turn off and the first valve is controlled to turn on; when the fault is resolved, the voltage source converter is also locked.

[0189] When the voltage source converter is operating in rectification or inversion mode and a DC fault occurs, the DC circuit breaker is controlled to turn off and the first valve is controlled to turn on. After the fault is recovered or after the deionization time, the DC circuit breaker is controlled to turn on. DC faults include DC line faults.

[0190] In some embodiments, if the voltage source converter is connected in series with the parallel circuit of the first valve, the energy dissipation circuit, and the bypass switch, and then connected in parallel with the DC circuit breaker, the control method further includes:

[0191] When the voltage source converter is put into inverter operation online, the system controls the voltage source converter to charge, unlock, turn off the DC circuit breaker, and open the first valve.

[0192] When the voltage source converter is in inverter operation and is shut down online or out of fault, the DC circuit breaker is turned on, or if the DC transmission valve group also includes a bypass switch, the bypass switch is turned on and / or the DC circuit breaker is turned on.

[0193] When the voltage source converter is in inverter operation and a DC fault occurs, the first control valve is turned on after the fault is recovered or after the deionization time; DC faults include DC line faults.

[0194] In some embodiments, if the DC transmission valve assembly further includes a bypass switch,

[0195] When the voltage source converter is in rectifier operation and then shuts down online or due to a fault, after the first control valve is turned on, the bypass switch is also turned on.

[0196] When the voltage source converter is in inverter operation and is shut down online or due to a fault, the bypass switch is turned on and the DC circuit breaker is turned off; when it is shut down due to a fault, the voltage source converter is also locked out.

[0197] In some embodiments, if the DC transmission valve group further includes a disconnect switch, or the DC transmission system in which the DC transmission valve group is located further includes a neutral bus switch, when the voltage source converter is operating in rectification or inversion mode and a DC fault crosses through, after the control first valve is turned on, the disconnect switch or the neutral bus switch is disconnected, and after the fault is recovered or after the deionization time, the disconnect switch or the neutral bus switch is reclosed.

[0198] In some embodiments, if the first fully controlled valve of the DC transmission valve group adopts a fully controlled device, when the voltage source converter or bridge uncontrolled rectifier circuit cannot deliver energy normally and generates AC or DC overvoltage, the fully controlled device of the first valve is turned on to dissipate energy in the energy-consuming circuit. When the voltage source converter or bridge uncontrolled rectifier circuit can deliver energy normally, the fully controlled device of the first valve is turned off.

[0199] If the first diode valve of the DC transmission valve group adopts an anti-parallel circuit of at least one diode and thyristor, when the voltage source converter or bridge uncontrolled rectifier circuit cannot deliver energy normally and generates AC or DC overvoltage, the thyristor controlling the first valve will be turned on to dissipate the energy in the energy-consuming circuit.

[0200] Figure 40 This is a schematic flowchart of a control method for a DC transmission valve assembly according to an embodiment of this application. The DC transmission valve assembly is as follows: Figures 1-6 , Figures 13-20 , Figures 21-22 As shown, the voltage source converter is connected in series with the main branch of the DC circuit breaker, and then connected in antiparallel with the series circuit of the first valve and the energy consumption circuit. The control method is as follows.

[0201] In S110, the DC circuit breaker 2 is turned on and the first valve 3 is turned off. If the DC transmission valve group includes a bypass switch 20, the bypass switch 20 is closed and the voltage source converter 1 is rectified. Alternatively, the DC circuit breaker 2 is turned on and the first valve 3 is turned off. If the DC transmission valve group includes a bypass switch 20, the bypass switch 20 is opened and the voltage source converter 1 is inverted.

[0202] In S120, when the voltage source converter 1 is operating in rectification or inversion mode and a DC fault occurs, the DC circuit breaker 2 is controlled to turn off and the first valve 3 is controlled to turn on. After the fault is recovered or after the deionization time has elapsed, the DC circuit breaker 2 is controlled to turn on.

[0203] The aforementioned DC faults include DC line faults.

[0204] In S130, when the voltage source converter 1 is in rectifier operation and is either offline or out of fault, the DC circuit breaker 2 is controlled to turn off and the first valve 3 is controlled to turn on. If the DC transmission valve group includes a bypass switch 20, the bypass switch 20 is controlled to close. When out of fault, the voltage source converter 1 is also controlled to lock out.

[0205] If the DC transmission valve group also includes a first residual current disconnect switch 60 and a second residual current disconnect switch 70, after the DC circuit breaker 2 is turned off, the first residual current disconnect switch 60 and the second residual current disconnect switch 70 are separated.

[0206] If the DC transmission valve group also includes a bypass switch 12, when the voltage source converter 1 is operating in rectification mode and then shut down online, the DC circuit breaker 2 is controlled to turn off, the first valve 3 is controlled to open, and the bypass switch 12 is controlled to close. When the voltage source converter 1 is operating in rectification mode and then shuts down due to a fault, the bypass switch 12 is controlled to close, the DC circuit breaker 2 is controlled to turn off, and the voltage source converter 1 is controlled to lock out.

[0207] If the DC transmission valve group also includes a bypass switch 12, when the voltage source converter 1 is in inverter operation and is shut down online or after a fault, the bypass switch 12 is closed to control the DC circuit breaker 2 to turn off; when the fault is shut down, the bypass switch 1 is also locked.

[0208] Optionally, voltage source converter 1 is not locked when it is taken out online, but operates in reactive power compensation mode.

[0209] In S140, when the voltage source converter 1 is in online rectification operation, if the DC transmission valve group includes a bypass switch 20, the bypass switch 20 is closed to control the voltage source converter 1 to charge, the voltage source converter 1 is unlocked to control the DC circuit breaker 2 to conduct.

[0210] If the first valve 3 only includes diodes connected in series, then the first valve 3 does not need to be controlled, and the above steps for controlling the first valve 3 to be turned on or off can be omitted.

[0211] Figure 41 This is a schematic flowchart of another control method for a DC transmission valve assembly according to an embodiment of this application. The DC transmission valve assembly is as follows... Figures 7-11 As shown, the voltage source converter 1 is connected in series with the first valve 3, the energy consumption circuit 10, and the bypass switch 20, and then connected in parallel with the DC circuit breaker 2. The control method is as follows.

[0212] In S210, the DC circuit breaker 2 is turned off, the first valve 3 is turned on, the bypass switch 20 is closed, and the voltage source converter 1 is turned on for inverter operation.

[0213] If the DC transmission valve group also includes a third residual current disconnect switch 80 and a fourth residual current disconnect switch 90, after the DC circuit breaker 2 is turned off, the third residual current disconnect switch 80 and the fourth residual current disconnect switch 90 are separated.

[0214] In S220, when the voltage source converter 1 is in inverter operation and a DC fault occurs, the first valve 3 is turned on after the fault is recovered or after the deionization time.

[0215] In S230, when the voltage source converter 1 is in inverter operation and is either offline or out of fault, the DC circuit breaker 2 is turned on; when out of fault, the voltage source converter 1 is also locked.

[0216] Alternatively, if the DC transmission valve group also includes a bypass switch 12, when the voltage source converter 1 is in inverter operation and is out of service online or out of fault, the DC circuit breaker 2 is turned on and / or the bypass switch 12 is turned on; when out of fault, the voltage source converter 1 is also turned off.

[0217] Optionally, voltage source converter 1 is not locked when it is taken out online, but operates in reactive power compensation mode.

[0218] If the DC transmission valve group also includes a third residual current disconnect switch 80 and a fourth residual current disconnect switch 90, before the DC circuit breaker 2 is turned on, the third residual current disconnect switch 80 and the fourth residual current disconnect switch 90 are closed.

[0219] In S240, when the voltage source converter 1 is put into online inverter operation, the voltage source converter 1 is controlled to charge, the voltage source converter 1 is controlled to unlock, the DC circuit breaker 2 is controlled to turn off, and the first valve 3 is controlled to open.

[0220] If the DC transmission valve group also includes a third residual current disconnect switch 80 and a fourth residual current disconnect switch 90, after the DC circuit breaker 2 is turned off, the third residual current disconnect switch 80 and the fourth residual current disconnect switch 90 are separated.

[0221] If the DC transmission valve group also includes a bypass switch 12, the bypass switch 12 is opened before the DC circuit breaker 2 is turned off.

[0222] Figures 13-20 The DC transmission valve group, after adding a changeover switch group, has the function of online inverter operation. For example... Figure 13 and Figure 14 In the DC transmission valve group, when the voltage source converter 1 is put into online inverter operation, the bypass switch 20 is closed, the second transfer switch 5 and the third transfer switch 6 are closed, the first transfer switch 4 is opened, the DC circuit breaker 2 is turned on, the current is transferred to the DC circuit breaker 2, the voltage source converter 1 is charged, the voltage source converter 1 is unlocked, the DC circuit breaker 2 is turned off, the first valve 3 is turned on, and the current is transferred to the voltage source converter 1.

[0223] like Figure 15 and Figure 16In the DC transmission valve group, when the voltage source converter 1 is put into online inverter operation, the bypass switch 20 is closed, the fifth changeover switch 8 and the sixth changeover switch 9 are closed, the fourth changeover switch 7 is opened, the DC circuit breaker 2 is turned on, the current is transferred to the DC circuit breaker 2, the voltage source converter 1 is charged, after charging, the voltage source converter 1 is unlocked, the DC circuit breaker 2 is turned off, the first valve 3 is turned on, and the current is transferred to the voltage source converter 1.

[0224] like Figure 17 and Figure 18 In the DC transmission valve group, when the voltage source converter 1 is put into online inverter operation, the bypass switch 20 is closed, the second transfer switch 5, the ninth transfer switch 17 and the tenth transfer switch 18 are closed, the first transfer switch 4, the seventh transfer switch 15 and the eighth transfer switch 16 are opened, the DC circuit breaker 2 is turned on, the current is transferred to the DC circuit breaker 2, the voltage source converter 1 is charged, after charging, the voltage source converter 1 is unlocked, the DC circuit breaker 2 is turned off, the first valve 3 is turned on, and the current is transferred to the voltage source converter 1.

[0225] like Figure 19 and Figure 20 In the DC transmission valve group, when the voltage source converter 1 is put into online inverter operation, the bypass switch 20 is closed, the fifth changeover switch 8, the sixth changeover switch 9, the ninth changeover switch 17 and the tenth changeover switch 18 are closed, the first changeover switch 4, the fourth changeover switch 7, the seventh changeover switch 15 and the eighth changeover switch 16 are opened, the DC circuit breaker 2 is turned on, the current is transferred to the DC circuit breaker 2, the voltage source converter 1 is charged, after charging, the voltage source converter 1 is unlocked, the DC circuit breaker 2 is turned off, the first valve 3 is turned on, and the current is transferred to the voltage source converter 1.

[0226] If the first valve 3 only includes diodes connected in series, then the first valve 3 does not need to be controlled, and the above steps for controlling the first valve 3 to be turned on or off can be omitted.

[0227] This application also provides a DC power transmission system. For example... Figure 42 As shown, the DC transmission system is an ultra-high voltage flexible DC transmission system. The main circuit of the ultra-high voltage flexible DC transmission system includes a rectifier station 100, an inverter station 200, a first DC line 150, a second DC line 160, a rectifier station grounding electrode line 114, a rectifier station grounding electrode 115, an inverter station grounding electrode line 214, and an inverter station grounding electrode 215.

[0228] The rectifier station 100 includes a first DC pole 110, a second DC pole 120, a first AC system 140, and a converter transformer incoming line switch (e.g., Figure 42(as shown by reference numerals 131, 132, 133, and 134), first metallic return changeover switch 113, first earth return changeover switch 190, and bipolar neutral zone isolating switch ( Figure 42 (As shown in reference numbers 174, 175, 184, and 185).

[0229] The first DC pole 110 includes a first high-end DC transmission valve group 111, a first low-end DC transmission valve group 112, a first high-end converter transformer 116, a first low-end converter transformer 117, a first smoothing reactor 105, a first pole neutral bus switch 119, a first pole bus isolating switch 172, and a first DC line isolating switch 173. The first high-end DC transmission valve group 111 and the first low-end DC transmission valve group 112 are connected in series.

[0230] Both the first high-end DC transmission valve group 111 and the first low-end DC transmission valve group 112 include a voltage source converter, a DC circuit breaker, a first valve, an energy-consuming circuit, a bypass switch 20, a bypass knife switch, a bypass switch, a positive isolation knife switch, and a negative isolation knife switch.

[0231] The first high-end DC transmission valve group 111 includes a voltage source converter 1, a DC circuit breaker 2, a first valve 3, an energy-consuming circuit 10, a bypass switch 20, a bypass knife switch 11, a bypass switch 12, a positive isolation knife switch 13, and a negative isolation knife switch 14. The bypass switch 12 is connected to the positive and negative terminals of the first high-end DC transmission valve group 111. The positive isolation knife switch 13 is connected to the positive terminal and the first positive input terminal of the first high-end DC transmission valve group 111. The negative isolation knife switch 14 is connected to the negative terminal and the first negative input terminal of the first high-end DC transmission valve group 111. The bypass knife switch 11 is connected to the first positive input terminal and the first negative input terminal of the first high-end DC transmission valve group 111.

[0232] The first low-end DC transmission valve group 112 includes a first low-end voltage source converter 102, a first low-end DC circuit breaker 25, a first low-end valve 26, a first low-end energy dissipation circuit 191, a first low-end bypass switch 192, a first low-end bypass knife switch 21, a first low-end bypass switch 22, a first low-end positive isolation knife switch 23, and a first low-end negative isolation knife switch 24. The first low-end bypass switch 22 is connected to the positive and negative terminals of the first low-end DC transmission valve group 112. The first low-end positive isolation knife switch 23 is connected to the positive terminal and the first positive input terminal of the first low-end DC transmission valve group 112. The first low-end negative isolation knife switch 24 is connected to the negative terminal and the first negative input terminal of the first low-end DC transmission valve group 112. The first low-end bypass knife switch 21 is connected to the first positive input terminal and the first negative input terminal of the first low-end DC transmission valve group 112.

[0233] The voltage source converter, DC circuit breaker, and first valve of the first high-end DC transmission valve group 111 and the first low-end DC transmission valve group 112 are connected in the following manner: Figure 2The structure shown.

[0234] Voltage source converters include, but are not limited to, at least one of two-level converters, three-level converters, modular multilevel converters, diode-clamped multilevel converters, cascaded two-level converters, or stacked two-level converters. The aforementioned modular multilevel converters include, but are not limited to, modular multilevel converters (MMCs) with a half-bridge sub-module structure.

[0235] The second DC pole 120 includes a second low-end DC transmission valve group 121, a second high-end DC transmission valve group 122, a second low-end converter transformer 126, a second high-end converter transformer 127, a second smoothing reactor 106, a second pole neutral bus switch 129, a second pole bus isolating switch 182, and a second DC line isolating switch 183. The second low-end DC transmission valve group 121 and the second high-end DC transmission valve group 122 are connected in series.

[0236] The second high-end DC transmission valve group 122 and the second low-end DC transmission valve group 121 both include a voltage source converter, a DC circuit breaker, a first valve, an energy-consuming circuit, a bypass switch, a bypass knife switch, a positive isolation knife switch, and a negative isolation knife switch.

[0237] The second high-end DC transmission valve group 122 includes a second high-end voltage source converter 104, a second high-end DC circuit breaker 45, a second high-end valve 46, a second high-end energy consumption circuit 195, a second high-end bypass switch 196, a second high-end bypass knife switch 41, a second high-end bypass switch 42, a second high-end positive isolation knife switch 43, and a second high-end negative isolation knife switch 44. The second high-end bypass switch 42 is connected to the positive and negative terminals of the second high-end DC transmission valve group 122. The second high-end positive isolation knife switch 43 is connected to the positive terminal and the first positive input terminal of the second high-end DC transmission valve group 122. The second high-end negative isolation knife switch 44 is connected to the negative terminal and the first negative input terminal of the second high-end DC transmission valve group 122. The second high-end bypass knife switch 41 is connected to the first positive input terminal and the first negative input terminal of the second high-end DC transmission valve group 122.

[0238] The second low-end DC transmission valve group 121 includes a second low-end voltage source converter 103, a second low-end DC circuit breaker 35, a second low-end valve 36, a second low-end energy dissipation circuit 193, a second low-end bypass switch 194, a second low-end bypass knife switch 31, a second low-end bypass switch 32, a second low-end positive isolation knife switch 33, and a second low-end negative isolation knife switch 34. The second low-end bypass switch 32 is connected to the positive and negative terminals of the second low-end DC transmission valve group 121. The second low-end positive isolation knife switch 33 is connected to the positive terminal and the first positive input terminal of the second low-end DC transmission valve group 121. The second low-end negative isolation knife switch 34 is connected to the negative terminal and the first negative input terminal of the second low-end DC transmission valve group 121. The second low-end bypass knife switch 31 is connected to the first positive input terminal and the first negative input terminal of the second low-end DC transmission valve group 121.

[0239] The voltage source converter, DC circuit breaker, and first valve of the second high-end DC transmission valve group 122 and the second low-end DC transmission valve group 121 are connected in the following manner: Figure 4 The structure shown.

[0240] Inverter station 200 includes a third DC pole 210, a fourth DC pole 220, a second AC system 240, and a converter transformer incoming line switch. Figure 42 (as shown by reference numerals 231, 232, 233, and 234), second metallic return line switching switch 213, second earth return line switching switch 290, bipolar neutral zone isolating switch ( Figure 42 (As shown by reference numerals 274, 275, 284, and 285).

[0241] The third DC pole 210 includes a third high-end DC transmission valve group 211, a third low-end DC transmission valve group 212, a third high-end converter transformer 216, a third low-end converter transformer 217, a third smoothing reactor 205, a third pole neutral bus switch 219, a third pole bus isolating switch 272, and a fifth DC line isolating switch 273. The third high-end DC transmission valve group 211 and the third low-end DC transmission valve group 212 are connected in series.

[0242] Both the third high-end DC transmission valve group 211 and the third low-end DC transmission valve group 212 include a voltage source converter, a DC circuit breaker, a first valve, an energy-consuming circuit, a bypass switch 20, a bypass knife switch, a bypass switch, a positive isolating knife switch, and a negative isolating knife switch.

[0243] The third high-end DC transmission valve group 211 includes a third high-end voltage source converter 201, a third high-end DC circuit breaker 55, a third high-end valve 56, a third high-end energy consumption circuit 297, a third high-end bypass switch 298, a second bypass knife switch 51, a second bypass switch 52, a third isolating knife switch 53, and a fourth isolating knife switch 54. The third high-end bypass switch 52 is connected to the positive and negative terminals of the third high-end DC transmission valve group 211. The third isolating knife switch 53 is connected to the positive terminal and the first positive input terminal of the third high-end DC transmission valve group 211. The fourth isolating knife switch 54 is connected to the negative terminal and the first negative input terminal of the third high-end DC transmission valve group 211. The second bypass knife switch 51 is connected to the first positive input terminal and the first negative input terminal of the third high-end DC transmission valve group 211.

[0244] The third low-end DC transmission valve group 212 includes a third low-end voltage source converter 202, a third low-end DC circuit breaker 65, a third low-end valve 66, a third low-end energy dissipation circuit 291, a third low-end bypass switch 292, a third low-end bypass knife switch 61, a third low-end bypass switch 62, a third low-end positive isolation knife switch 63, and a third low-end negative isolation knife switch 64. The third low-end bypass switch 62 is connected to the positive and negative terminals of the third low-end DC transmission valve group 212. The third low-end positive isolation knife switch 63 is connected to the positive terminal and the first positive input terminal of the third low-end DC transmission valve group 212. The third low-end negative isolation knife switch 64 is connected to the negative terminal and the first negative input terminal of the third low-end DC transmission valve group 212. The third low-end bypass knife switch 61 is connected to the first positive input terminal and the first negative input terminal of the third low-end DC transmission valve group 212.

[0245] The voltage source converter, DC circuit breaker, and first valve of the third high-end DC transmission valve group 211 and the third low-end DC transmission valve group 212 are connected in the following manner: Figure 2 The structure shown.

[0246] The fourth DC pole 220 includes a fourth low-end DC transmission valve group 221, a fourth high-end DC transmission valve group 222, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a fourth smoothing reactor 206, a fourth pole neutral bus switch 229, a fourth pole bus isolating switch 282, and a sixth DC line isolating switch 283. The fourth low-end DC transmission valve group 221 and the fourth high-end DC transmission valve group 222 are connected in series.

[0247] Both the fourth high-end DC transmission valve group 222 and the fourth low-end DC transmission valve group 221 include a voltage source converter, a DC circuit breaker, a first valve, an energy-consuming circuit, a bypass switch 20, a bypass knife switch, a bypass switch, a positive isolation knife switch, and a negative isolation knife switch.

[0248] The fourth high-end DC transmission valve group 222 includes a fourth high-end voltage source converter 204, a fourth high-end DC circuit breaker 85, a fourth high-end valve 86, a fourth high-end energy consumption circuit 295, a fourth high-end bypass switch 296, a fourth high-end bypass knife switch 81, a fourth high-end bypass switch 82, a fourth high-end positive isolation knife switch 83, and a fourth high-end negative isolation knife switch 84. The fourth high-end bypass switch 82 is connected to the positive and negative terminals of the fourth high-end DC transmission valve group 222. The fourth high-end positive isolation knife switch 83 is connected to the positive terminal and the first positive input terminal of the fourth high-end DC transmission valve group 222. The fourth high-end negative isolation knife switch 84 is connected to the negative terminal and the first negative input terminal of the fourth high-end DC transmission valve group 222. The fourth high-end bypass knife switch 81 is connected to the first positive input terminal and the first negative input terminal of the fourth high-end DC transmission valve group 222.

[0249] The fourth low-end DC transmission valve group 221 includes a fourth low-end voltage source converter 203, a fourth low-end DC circuit breaker 75, a fourth low-end valve 76, a fourth low-end energy dissipation circuit 293, a fourth low-end bypass switch 294, a fourth low-end bypass knife switch 71, a fourth low-end bypass switch 72, a fourth low-end positive isolation knife switch 73, and a fourth low-end negative isolation knife switch 74. The fourth low-end bypass switch 72 is connected to the positive and negative terminals of the fourth low-end DC transmission valve group 221. The fourth low-end positive isolation knife switch 73 is connected to the positive terminal and the first positive input terminal of the fourth low-end DC transmission valve group 221. The fourth low-end negative isolation knife switch 74 is connected to the negative terminal and the first negative input terminal of the fourth low-end DC transmission valve group 221. The fourth low-end bypass knife switch 71 is connected to the first positive input terminal and the first negative input terminal of the fourth low-end DC transmission valve group 221.

[0250] The voltage source converter, DC circuit breaker, and first valve of the fourth high-end DC transmission valve group 222 and the fourth low-end DC transmission valve group 221 are connected as follows: Figure 4 The structure is shown. The various switches mentioned above include at least one of mechanical switches, knife switches, DC circuit breakers, and thyristor valves.

[0251] It should be noted that the first valve 3, the first low-end valve 26, the second high-end valve 46, the second low-end valve 36, the third high-end valve 56, the third low-end valve 66, the fourth high-end valve 86, and the fourth low-end valve 76 mentioned above are all on / off valves. The on / off valve can be a first diode valve, a first thyristor valve, or a first fully controllable valve. The first diode valve includes at least one diode connected in series or at least one diode and a thyristor in anti-parallel circuit. The first thyristor valve includes at least one thyristor connected in series. The first fully controllable valve includes at least one fully controllable device connected in series and the fully controllable device includes a diode connected in anti-parallel.

[0252] like Figure 42As shown, taking pole I of the UHV flexible DC transmission system as an example, the initial state is that the first high-end DC transmission valve group 111 and the first low-end DC transmission valve group 112 of the rectifier station 100 are in operation, and the third high-end DC transmission valve group 211 and the third low-end DC transmission valve group 212 of the inverter station 200 are in operation. The rectifier station 100 has the following circuits: bypass switch 20 (open position), bypass knife switch 11 (open position), bypass switch 12 (open position), positive isolating knife switch 13 (closed), negative isolating knife switch 14 (closed), first low-end bypass switch 192 (open position), first low-end bypass knife switch 21 (open position), first low-end bypass switch 22 (open position), first low-end positive isolating knife switch 23 (closed), first low-end negative isolating knife switch 24 (closed). The inverter station 200 has the following circuits: third high-end bypass switch 298 (open position), second bypass knife switch 51 (open position), second bypass switch 52 (open position), third isolating knife switch 53 (closed), fourth isolating knife switch 54 (closed), third low-end bypass switch 292 (open position), third low-end bypass knife switch 61 (open position), third low-end bypass switch 62 (open position), third low-end positive isolating knife switch 63 (closed), third low-end negative isolating knife switch 64 (closed).

[0253] Rectifier station 100 controls the DC circuit breaker 2 of the first high-end DC transmission valve group 111 to be turned on and the first valve 3 to be turned off. It also controls the first low-end DC circuit breaker 25 of the first low-end DC transmission valve group 112 to be turned on and the first low-end valve 26 to be turned off, so that voltage source converter 1 and first low-end voltage source converter 102 can operate in rectification mode. Inverter station 200 controls the third high-end DC circuit breaker 55 of the third high-end DC transmission valve group 211 to be turned on and the third high-end valve 56 to be turned off. It also controls the third low-end DC circuit breaker 65 of the third low-end DC transmission valve group 212 to be turned on and the third low-end valve 66 to be turned off, so that the third high-end voltage source converter 201 and third low-end voltage source converter 202 can operate in inverter mode.

[0254] When a DC fault occurs in the voltage source converter of the first high-end DC transmission valve group 111 and the first low-end DC transmission valve group 112 of the rectifier station 100, the DC circuit breaker 2 of the first high-end DC transmission valve group 111 and the first low-end DC circuit breaker 25 of the first low-end DC transmission valve group 112 are turned off, and the first valve 3 of the first high-end DC transmission valve group 111 and the first low-end valve 26 of the first low-end DC transmission valve group 112 are turned on. The energy consumption circuit 10 can suppress the fault current oscillation. After the fault is recovered or after the deionization time, the DC circuit breaker 2 of the first high-end DC transmission valve group 111 and the first low-end DC circuit breaker 25 of the first low-end DC transmission valve group 112 are turned on. When a DC fault occurs in the voltage source converter of the third high-end DC transmission valve group 211 and the third low-end DC transmission valve group 212 of the inverter station 200, the third high-end DC circuit breaker 55 of the third high-end DC transmission valve group 211 and the third low-end DC circuit breaker 65 of the third low-end DC transmission valve group 212 are turned off, and the third high-end valve 56 of the third high-end DC transmission valve group 211 and the third low-end valve 66 of the third low-end DC transmission valve group 212 are turned on. After the fault is recovered or after the deionization time, the third high-end DC circuit breaker 55 of the third high-end DC transmission valve group 211 and the third low-end DC circuit breaker 65 of the third low-end DC transmission valve group 212 are turned on.

[0255] When the voltage source converter 1 of rectifier station 100 is disconnected from the line, the bypass switch 20 in rectifier station 100 is closed, the DC circuit breaker 2 in rectifier station 100 is turned off, the first valve 3 in rectifier station 100 is opened, and the bypass switch 12 in rectifier station 100 is closed. When the voltage source converter 1 of rectifier station 100 fails and disconnects, the bypass switch turns off the DC circuit breaker 2 in rectifier station 100, opens the first valve 3 in rectifier station 100, and locks the voltage source converter 1 in rectifier station 100. When the third high-side voltage source converter 201 of inverter station 200 is disconnected from the line, the third high-side bypass switch 298 in inverter station 200 is closed, the second bypass switch 52 in inverter station 200 is closed, and the third high-side DC circuit breaker 55 in inverter station 200 is turned off. When the third high-side voltage source converter 201 of inverter station 200 fails and disconnects, the second bypass switch 52 within inverter station 200 is closed, the third high-side DC circuit breaker 55 within inverter station 200 is turned off, the third high-side valve 56 within inverter station 200 is opened, and the third high-side voltage source converter 201 within inverter station 200 is locked. Inverter station 200 of the aforementioned UHV flexible DC transmission system requires a transfer switch group to enable online connection. Coordination between rectifier station 100 and inverter station 200 is required to achieve the desired online connection of the voltage source converter, whether it is online, disconnected due to a fault, or connected online.

[0256] Figure 43This is a schematic diagram of another DC transmission system according to an embodiment of this application. Figure 42 Based on the embodiment, the voltage source converter, DC circuit breaker, and first valve of the third high-end DC transmission valve group 211 and the third low-end DC transmission valve group 212 are connected in the following manner: Figure 7 The structure shown; the voltage source converter, DC circuit breaker, and first valve of the fourth high-end DC transmission valve group 222 and the fourth low-end DC transmission valve group 221 are connected as follows: Figure 8 The structure shown.

[0257] like Figure 43 As shown, taking pole I of the DC transmission system as an example, the initial state is that the first high-end DC transmission valve group 111 and the first low-end DC transmission valve group 112 of the rectifier station 100 are in operation, and the third high-end DC transmission valve group 211 and the third low-end DC transmission valve group 212 of the inverter station 200 are in operation. The bypass switch of rectifier station 100 is in position 20, the bypass knife switch is in position 11, the bypass switch is in position 12, the positive isolating knife switch is in position 13, the negative isolating knife switch is in position 14, the first low-end bypass switch is in position 192, the first low-end bypass knife switch is in position 21, the first low-end bypass switch is in position 22, and the first low-end positive isolating knife switch is in position 23. The third high-end bypass switch of inverter station 200 is in position 298, the second bypass knife switch is in position 51, the second bypass switch is in position 52, the third isolating knife switch is in position 53, the fourth isolating knife switch is in position 54, the third low-end bypass switch is in position 292, the third low-end bypass knife switch is in position 61, the third low-end bypass switch is in position 62, the third low-end positive isolating knife switch is in position 63, and the third low-end negative isolating knife switch is in position 64.

[0258] Rectifier station 100 controls the DC circuit breaker 2 and first valve 3 of the first high-end DC transmission valve group 111 to close, and controls the first low-end DC circuit breaker 25 of the first low-end DC transmission valve group 112 to open, and the first low-end valve 26 to close, so that voltage source converter 1 and first low-end voltage source converter 102 can operate in rectification mode. Inverter station 200 controls the third high-end DC circuit breaker 55 of the third high-end DC transmission valve group 211 to close, and the third high-end valve 56 to open, and controls the third low-end DC circuit breaker 65 of the third low-end DC transmission valve group 212 to close, and the third low-end valve 66 to open, so that the third high-end voltage source converter 201 and third low-end voltage source converter 202 can operate in inverter mode.

[0259] When a DC fault occurs in the voltage source converter of rectifier station 100, DC circuit breakers 2 and 25 are turned off, and the first valve 3 and the first low-end valve 26 are turned on. Energy dissipation circuit 10 and the first low-end energy dissipation circuit 191 suppress fault current oscillations. After the fault is recovered or after a deionization time, DC circuit breakers 2 and 25 are turned on again. When a DC fault occurs in the voltage source converter of inverter station 200, the third high-end valve 56 and the third low-end valve 66 reverse-block the fault current. After the fault is recovered or after a deionization time, the third high-end valve 56 and the third low-end valve 66 are turned on again.

[0260] When the voltage source converter 1 of rectifier station 100 is taken offline, the bypass switch 20 is closed, the DC circuit breaker 2 is turned off, the first valve 3 is turned on, and the bypass switch 20 controls the bypass switch 12 to close. When the voltage source converter 1 of rectifier station 100 is taken offline due to a fault, the bypass switch 12 controls the first valve 3 to open, the DC circuit breaker 2 to close, the voltage source converter 1 to be locked, and the bypass switch 12 to close. When the third high-side voltage source converter 201 of inverter station 200 is taken offline or due to a fault, the third high-side DC circuit breaker 55 is turned on and / or the second bypass switch 52 is closed.

[0261] The initial state is that the first low-end DC transmission valve group 112 of the rectifier station 100 is in operation, and the third low-end DC transmission valve group 212 of the inverter station 200 is in operation. When the voltage source converter 1 of the first high-end DC transmission valve group 111 of the rectifier station 100 is put into online operation, the voltage source converter 1 of the first high-end DC transmission valve group 111 is charged, the bypass switch 20 of the first high-end DC transmission valve group 111 is closed, the first valve 3 of the first high-end DC transmission valve group 111 is turned on, the bypass switch 20 controls the bypass switch 12 of the first high-end DC transmission valve group 111 to open, the current is transferred from the bypass switch 12 of the first high-end DC transmission valve group 111 to the first valve 3 of the first high-end DC transmission valve group 111, the voltage source converter 1 of the first high-end DC transmission valve group 111 is unlocked, the DC circuit breaker 2 of the first high-end DC transmission valve group 111 is turned on, and the current is transferred from the first valve 3 of the first high-end DC transmission valve group 111 to the voltage source converter 1 of the first high-end DC transmission valve group 111. When the voltage source converter of the third high-end DC transmission valve group 211 of the inverter station 200 is put into online operation, the third high-end bypass switch 298 of the third high-end DC transmission valve group 211 is closed, the third high-end voltage source converter 201 of the third high-end DC transmission valve group 211 is charged, the third high-end voltage source converter 201 of the third high-end DC transmission valve group 211 is unlocked, the third high-end DC circuit breaker 55 of the third high-end DC transmission valve group 211 is turned on, and the second bypass of the third high-end DC transmission valve group 211 is turned on. When switch 52 is open, current is transferred from the second bypass switch 52 of the third high-end DC transmission valve group 211 to the third high-end DC circuit breaker 55 of the third high-end DC transmission valve group 211, controlling the third high-end valve 56 of the third high-end DC transmission valve group 211 to conduct, and controlling the third high-end DC circuit breaker 55 of the third high-end DC transmission valve group 211 to turn off, and current is transferred from the third high-end DC circuit breaker 55 of the third high-end DC transmission valve group 211 to the third high-end voltage source converter 201 of the third high-end DC transmission valve group 211. When the voltage source converter is online, out of service due to a fault, or put into operation, coordination between rectifier station 100 and inverter station 200 is required.

[0262] It should be pointed out that, Figure 42 and Figure 43 The rectifier station 100 or inverter station 200 can also use valve groups of grid-commutated converters or valve groups of voltage source converters based on a hybrid half-bridge and full-bridge submodule, in combination with the aforementioned DC transmission valve groups. The voltage source converter of the DC transmission valve group of the aforementioned rectifier station 100 can be replaced with a bridge uncontrolled rectifier circuit.

[0263] Figure 44This is a schematic diagram of another DC transmission system according to an embodiment of this application. The DC transmission system is a four-terminal DC grid, including Station 1 310, Station 2 320, Station 3 330, Station 4 340, Third DC Line 351, Fourth DC Line 352, Fifth DC Line 353, Sixth DC Line 354, First Metallic Return Line 411, Second Metallic Return Line 412, Third Metallic Return Line 413, and Fourth Metallic Return Line 414. Station 1 310 includes... Figure 23 The DC transmission valve assembly shown includes a fifth-pole neutral bus switch 315 and a sixth-pole neutral bus switch 316. The DC transmission valve assembly also includes a first disconnect switch 317. Station 2 320 includes... Figure 23 The DC transmission valve assembly shown includes a seventh-pole neutral bus switch 325 and an eighth-pole neutral bus switch 326. The DC transmission valve assembly also includes a second disconnector 327. Station 330 includes... Figure 23 The DC transmission valve assembly shown includes the ninth-pole neutral bus switch 335 and the tenth-pole neutral bus switch 336. The DC transmission valve assembly also includes a third disconnector 337. Station 4 340 includes... Figure 23 The DC transmission valve group shown includes the eleventh-pole neutral bus switch 345 and the twelfth-pole neutral bus switch 346. The DC transmission valve group also includes a fourth disconnect switch 347.

[0264] like Figure 44 As shown, during normal operation, the control multi-port DC circuit breaker 19, the second multi-port DC circuit breaker 322, the third multi-port DC circuit breaker 332, and the fourth multi-port DC circuit breaker 342 are turned on, the control first valve 3, the eleventh valve 323, the twelfth valve 333, and the thirteenth valve 343 are turned off, the control second valve 28, the twenty-first valve 324, the twenty-second valve 334, and the twenty-third valve 344 are turned off, the control voltage source converter 1, the second voltage source converter 321, the third voltage source converter 331, and the fourth voltage source converter 341 are turned on, and the control bypass switch 20 and the second bypass switch 96 of station 1 310, the third bypass switch 329 and the fourth bypass switch 314 of station 2 320, the fifth bypass switch 339 and the sixth bypass switch 319 of station 330, and the seventh bypass switch 349 and the eighth bypass switch 362 of station 4 340 are turned off.

[0265] It should be noted that valves 28, 324, 334, 344, and 308 are all on / off valves.

[0266] Taking a momentary fault in the third DC line 351 as an example, when the DC fault crosses through the voltage source converter 1 and the second voltage source converter 321, the first terminal C and the second terminal D, the second terminal D and the third terminal E of the multi-port DC circuit breaker 19 are controlled to close, the first valve 3 is controlled to open, the first terminal C and the third terminal E, the second terminal D and the third terminal E of the second multi-port DC circuit breaker 322 are controlled to close, the twenty-first valve 324 is controlled to open, and optionally, the fifth pole neutral bus switch 315 and the first disconnecting switch 3 are disconnected. 17. The eighth pole neutral bus switch 326 and the second disconnect switch 327 rapidly attenuate the fault current. After the fault is recovered or after the deionization time, the fifth pole neutral bus switch 315, the first disconnect switch 317, the eighth pole neutral bus switch 326, and the second disconnect switch 327 are reclosed to control the first terminal C and the second terminal D, the second terminal D and the third terminal E of the multi-port DC circuit breaker 19 to conduct, and to control the first terminal C and the third terminal E, the second terminal D and the third terminal E of the second multi-port DC circuit breaker 322 to conduct.

[0267] Taking a permanent fault in the third DC line 351 as an example, when the voltage source converter 1 and the second voltage source converter 321 are blocked and isolated, the first terminal C and the second terminal D, the second terminal D and the third terminal E of the multi-port DC circuit breaker 19 are controlled to be turned off, the first valve 3 is controlled to be turned on, the first terminal C and the third terminal E, the second terminal D and the third terminal E of the second multi-port DC circuit breaker 322 are controlled to be turned off, and the twenty-first valve 324 is controlled to be turned on. Optionally, the fifth pole neutral bus switch 315, the first disconnect switch 317, the eighth pole neutral bus switch 326 and the second disconnect switch 327 are disconnected to isolate the faulty third DC line 351.

[0268] When the voltage source converter 1 is blocked due to a fault, the first terminal C and the second terminal D, the first terminal C and the third terminal E of the multi-port DC circuit breaker 19 are turned off, and the voltage source converter 1 is blocked. Optionally, the first valve 3 is turned on.

[0269] Figure 45 This is a schematic diagram of another DC transmission system according to an embodiment of this application. The DC transmission system is a four-terminal ultra-high voltage flexible DC transmission system, including Station 5 360, Station 6 370, Station 7 380, Station 8 390, DC line 7 355, DC line 8 356, and DC line 9 357. Station 5 360 includes... Figure 27 The circuit shown is a series circuit of a DC transmission valve group equipped with a bypass switch 12, a first low-side bypass switch 22, and a first-pole neutral bus switch 119. Station 6 370 includes... Figure 27 The DC transmission valve group series circuit shown includes a fifth bypass switch 374, a sixth bypass switch 378, and a fourteenth-pole neutral bus switch 379, and also includes a first high-speed switch 301, a second high-speed switch 302, and a third high-speed switch 303. Station 7 380 includes... Figure 27The DC transmission valve group series circuit shown includes a third bypass switch 384, a seventh bypass switch 388, and a fifteenth-pole neutral bus switch 389, and also includes a fourth high-speed switch 304, a fifth high-speed switch 305, and a sixth high-speed switch 306. Station 8 390 includes... Figure 27 The circuit shown is a series circuit of DC transmission valve group equipped with a fourth bypass switch 394, an eighth bypass switch 398 and a sixteenth-pole neutral bus switch 399.

[0270] like Figure 45 As shown, during normal operation, the first high-speed switch 301, the second high-speed switch 302, the third high-speed switch 303, the fourth high-speed switch 304, the fifth high-speed switch 305, and the sixth high-speed switch 306 are closed, controlling the DC circuit breaker 2, the first low-end DC circuit breaker 25, the second DC circuit breaker 372, the third DC circuit breaker 376, the fourth DC circuit breaker 382, ​​the fifth DC circuit breaker 386, the sixth DC circuit breaker 392, and the seventh DC circuit breaker 396 to conduct, controlling the first valve 3, the first low-end valve 26, the fourteenth valve 373, the fifteenth valve 377, the sixteenth valve 383, the seventeenth valve 387, and the eighteenth valve. 393. When the nineteenth valve 397 is closed, the bypass switch 12 and the first low-end bypass switch 22 of station 5 360, the fifth bypass switch 374 and the sixth bypass switch 378 of station 6 370, the third bypass switch 384 and the seventh bypass switch 388 of station 7 380, and the fourth bypass switch 394 and the eighth bypass switch 398 of station 8 390 are separated, thus controlling the operation of voltage source converter 1, the first low-end voltage source converter 102, the fifth voltage source converter 371, the sixth voltage source converter 375, the seventh voltage source converter 381, the eighth voltage source converter 385, the ninth voltage source converter 391, and the tenth voltage source converter 395.

[0271] It should be noted that DC circuit breaker 2, first low-end DC circuit breaker 25, second DC circuit breaker 372, third DC circuit breaker 376, fourth DC circuit breaker 382, ​​fifth DC circuit breaker 386, sixth DC circuit breaker 392 and seventh DC circuit breaker 396 have the same structure; first valve 3, first low-end valve 26, eleventh valve 323, twelfth valve 333, thirteenth valve 343, fourteenth valve 373, fifteenth valve 377, sixteenth valve 383, seventeenth valve 387, eighteenth valve 393 and nineteenth valve 397 are all on / off valves.

[0272] Taking a momentary fault in the seventh DC line 355 as an example, when the DC fault crosses through the voltage source converter, the control DC circuit breakers 2, 25, 372, 376, 382, ​​386, 392, and 396 are shut down, while the control valves 3, 26, 373, 377, 383, 387, 393, and 397 are turned on. This achieves the series shutdown of the high-voltage DC line by low-voltage DC circuit breakers, while simultaneously reducing the stress on the DC circuit breakers. Optionally, the first-pole neutral bus switch 119, the fourteenth-pole neutral bus switch 379, the fifteenth-pole neutral bus switch 389, and the sixteenth-pole neutral bus switch 399 are disconnected to rapidly attenuate the fault current. After the fault is recovered or after the deionization time, the first-pole neutral bus switch 119, the fourteenth-pole neutral bus switch 379, the fifteenth-pole neutral bus switch 389, and the sixteenth-pole neutral bus switch 399 are reclosed to control the DC circuit breaker 2, the first low-end DC circuit breaker 25, the second DC circuit breaker 372, the third DC circuit breaker 376, the fourth DC circuit breaker 382, ​​the fifth DC circuit breaker 386, the sixth DC circuit breaker 392, and the seventh DC circuit breaker 396 to conduct.

[0273] When the DC fault of the voltage source converter 1 is blocked, if the blocking of this pole is selected, the DC circuit breaker 2 and the first low-end DC circuit breaker 25 are turned off, the voltage source converter 1 is blocked, the first high-speed switch 301 is opened, and optionally, the first pole neutral bus switch 119 is disconnected.

[0274] Taking the rectification operation of Station 5 (360) and Station 6 (370), and the inverter operation of Station 7 (380) and Station 8 (390) as an example, when the voltage source converter 1 of Station 5 (360) is taken offline, the bypass switch 20 of Station 5 (360) is closed, the third bypass switch 384 and the fourth bypass switch 394 are closed, the DC circuit breaker 2, the second DC circuit breaker 372, the fourth DC circuit breaker 382 and the sixth DC circuit breaker 392 are turned off, the first valve 3 and the fourteenth valve 373 are turned on, and the bypass switch 12 and the fifth bypass switch 374 are closed. Optionally, the voltage source converter 1, the fifth voltage source converter 371, the seventh voltage source converter 381 and the voltage source converter 391 are locked. When voltage source converter 1 fails and exits, the bypass switch 12 is closed, the DC circuit breaker 2 is turned off, the third bypass switch 384 and the fourth bypass switch 394 are closed, the second DC circuit breaker 372, the fourth DC circuit breaker 382 and the sixth DC circuit breaker 392 are turned off, the fourteenth valve 373 is turned on, the fifth bypass switch 374 is closed, and voltage source converter 1 is locked. Optionally, the fifth voltage source converter 371, the seventh voltage source converter 381 and the voltage source converter 391 are locked.

[0275] The aforementioned four-terminal UHV flexible DC transmission system requires the configuration of transfer switch sets at stations 7380 and 8390 to enable online commissioning.

[0276] Figure 45 This is a schematic diagram of another DC transmission system according to an embodiment of this application. The DC transmission system is a four-terminal ultra-high voltage flexible DC transmission system, including Station 5 360, Station 6 370, Station 7 380, Station 8 390, DC line 7 355, DC line 8 356, and DC line 9 357. Station 5 360 includes... Figure 27 The DC transmission valve group series circuit shown includes a bypass switch 12, a first low-side bypass switch 22, and a first-pole neutral bus switch 119; Station 6 370 includes Figure 30 The circuit shown includes a DC transmission valve group series circuit with a fifth bypass switch 374, a sixth bypass switch 378, a fifth disconnect switch 311, and a fourteenth-pole neutral bus switch 379; Station 7 380 includes... Figure 30 The circuit shown includes a DC transmission valve group series circuit with a third bypass switch 384, a seventh bypass switch 388, a sixth disconnect switch 312, and a fifteenth-pole neutral bus switch 389; Station 8 390 includes Figure 27 The circuit shown is a series circuit of DC transmission valve group equipped with a fourth bypass switch 394, an eighth bypass switch 398 and a sixteenth-pole neutral bus switch 399.

[0277] like Figure 46As shown, during normal operation, the following DC circuit breakers are controlled to conduct: DC circuit breaker 2, first low-end DC circuit breaker 25, second DC circuit breaker 372, third DC circuit breaker 376, second two-port DC circuit breaker 27, fourth DC circuit breaker 382, ​​fifth DC circuit breaker 386, third two-port DC circuit breaker 307, sixth DC circuit breaker 392, and seventh DC circuit breaker 396. This controls the following valves to close: first valve 3, first low-end valve 26, fourteenth valve 373, fifteenth valve 377, second valve 28, sixteenth valve 383, seventeenth valve 387, twenty-fourth valve 308, eighteenth valve 393, and nineteenth valve 397. Bypass switch 20 and first low-end bypass switch 192 of station 5 360, ninth bypass switch 364 and tenth bypass switch 366 of station 6 370, eleventh bypass switch 368 and twelfth bypass switch 402 of station 7 380, and thirteenth bypass switch 404 and fourteenth bypass switch 406 of station 8 390 are separated to control the operation of voltage source converter 1, first low-end voltage source converter 102, fifth voltage source converter 371, sixth voltage source converter 375, seventh voltage source converter 381, eighth voltage source converter 385, ninth voltage source converter 391, and tenth voltage source converter 395.

[0278] Taking a momentary fault on the seventh DC line 355 as an example, when the DC fault crosses through the voltage source converter, the DC circuit breaker 2 and the first low-end DC circuit breaker 25 in station 5 360 and the second two-port DC circuit breaker 27 in station 6 370 are turned off, and the first valve 3, the first low-end valve 26, and the second valve 28 are turned on. Optionally, the first neutral bus switch 119 and the fifth disconnect switch 311 are disconnected to quickly attenuate the fault current. After the deionization time, the first neutral bus switch 119 is reclosed, and the DC circuit breaker 2 and the first low-end DC circuit breaker 25 are turned on. If the fault is recovered, the fifth disconnect switch 311 is reclosed, and the second two-port DC circuit breaker 27 is turned on. During the DC fault crossing process, stations 6 370, 7 380, and 8 390 are isolated from the fault point through the second two-port DC circuit breaker 27, and their transmission power is not affected.

[0279] When a DC fault occurs in voltage source converter 1, if that pole is selected for blocking, the control DC circuit breaker 2, the first low-end DC circuit breaker 25, and the second two-port DC circuit breaker 27 will be turned off, and voltage source converter 1 and the first low-end voltage source converter 102 will be blocked. Optionally, the first pole neutral bus switch 119 and the fifth disconnect switch 311 can be used. During the DC fault blocking process, stations 6 (370), 7 (380), and 8 (390) are isolated from the fault point through the second two-port DC circuit breaker 27, and their power transmission is not affected.

[0280] Taking the rectification operation of station 5 (360) and station 6 (370) and the inverter operation of station 7 (380) and station 8 (390) as an example, when voltage source converter 1 is taken offline, the third bypass switch 384 and the fourth bypass switch 394 are closed, the first valve 3 and the fourteenth valve 373 are turned on, the DC circuit breaker 2, the second DC circuit breaker 372, the fourth DC circuit breaker 382 and the sixth DC circuit breaker 392 are turned off, and the bypass switch 12 and the fifth bypass switch 374 are closed. Optionally, voltage source converter 1, the fifth voltage source converter 371, the seventh voltage source converter 381 and the ninth voltage source converter 391 are locked. When voltage source converter 1 fails and exits, the bypass switch 12 is turned on, the DC circuit breaker 2 is turned off, the third bypass switch 384 and the fourth bypass switch 394 are closed, the second DC circuit breaker 372, the fourth DC circuit breaker 382 and the sixth DC circuit breaker 392 are turned off, the fourteenth valve 373 is turned on, the fifth bypass switch 374 is closed, and voltage source converter 1 is locked. Optionally, the fifth voltage source converter 371, the seventh voltage source converter 381 and the ninth voltage source converter 391 are locked.

[0281] The aforementioned four-terminal UHV flexible DC transmission system, stations 7 (380) and 8 (390) require transfer switch sets to enable online connection. The second two-port DC circuit breaker 27 and the third two-port DC circuit breaker 307 need to meet the voltage level requirements of a DC transmission valve group series circuit.

[0282] Figure 47 This is a schematic diagram of the structure of a control device 400 for a DC transmission valve group provided in this application. The control device includes a detection unit 410 and a control unit 420.

[0283] The detection unit 410 is used to detect the operating parameters and faults of the DC transmission valve group as described above, including the AC voltage, DC voltage, DC current, operating status of the voltage source converter, operating status of the DC circuit breaker, operating status of the first valve, and the positions of the switch and disconnector.

[0284] Based on the operating parameters of the DC transmission valve group, the control unit 420 controls the DC circuit breaker to turn on, the first valve to turn off, and the voltage source converter to operate in rectification or inversion mode during normal operation if the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in antiparallel with the series circuit of the first valve and the energy dissipation circuit. If the voltage source converter is connected in series with the first valve, the energy dissipation circuit and the bypass switch and then connected in parallel with the DC circuit breaker, the DC circuit breaker is controlled to turn off, the first valve to turn on, the bypass switch to close, and the voltage source converter to operate inversion mode during normal operation.

Claims

1. A DC power transmission valve group, characterized by: The voltage source converter or the bridge-type uncontrolled rectifier circuit, the DC circuit breaker, the first valve, and the energy dissipation circuit are connected in series. The voltage source converter or the bridge-type uncontrolled rectifier circuit is connected in series with the main branch of the DC circuit breaker, and then connected in anti-parallel with the series circuit of the first valve and the energy dissipation circuit, or the voltage source converter is connected in series with the series circuit of the first valve and the energy dissipation circuit, and then connected in parallel with the DC circuit breaker.

2. The DC power transmission valve group according to claim 1, wherein: The voltage source converter or the bridge-type uncontrolled rectifier circuit comprises at least three phases and six bridge arms respectively; The DC circuit breaker comprises a first two-port DC circuit breaker or a multi-port DC circuit breaker; The first valve comprises a first diode valve, a first thyristor valve, or a first fully-controlled valve, the first diode valve comprises at least one diode connected in series or at least one diode and a thyristor connected in anti-parallel, the first thyristor valve comprises at least one thyristor connected in series, and the first fully-controlled valve comprises at least one fully-controlled device connected in series, and the fully-controlled device comprises a diode connected in anti-parallel; The energy dissipation circuit comprises a surge arrester or a resistor.

3. The valve set for direct current power transmission according to claim 2, characterized in that: The voltage source converter comprises at least one of a two-level converter, a three-level converter, a modular multi-level converter, a diode clamped multi-level converter, a cascaded two-level converter, or a stacked two-level converter.

4. The valve set for direct current power transmission according to claim 2, characterized by: The bridge-type uncontrolled rectifier circuit comprises a six-pulse bridge circuit or a twelve-pulse bridge circuit and is composed of uncontrolled power semiconductors.

5. The valve set for direct current power transmission according to claim 2, characterized by: The DC circuit breaker is at least one of a hybrid DC circuit breaker, a solid-state DC circuit breaker, or a mechanical DC circuit breaker, wherein the DC circuit breaker comprises: a main branch comprising a fast disconnector and / or a first power switch connected in series, wherein the first two-port DC circuit breaker comprises the main branch, the multi-port DC circuit breaker comprises one or more main branches, and all the main branches have a common terminal; and / or a transfer branch comprising a second power switch, an LC resonant circuit, and / or a coupled negative voltage circuit connected in series; an energy dissipation branch connected in parallel with the transfer branch, the energy dissipation branch comprising a surge arrester.

6. The valve set for direct current power transmission according to claim 1, wherein: The DC power transmission valve group further comprises a switch group, the voltage source converter is connected in series with the main branch of the DC circuit breaker through the switch group, and then connected in anti-parallel with the first valve, for rectification operation or inversion operation of the voltage source converter; or the voltage source converter is connected in series with the first valve through the switch group, and then connected in parallel with the transfer branch of the DC circuit breaker, for inversion operation or online inversion operation of the voltage source converter; or the voltage source converter is connected in parallel with the transfer branch of the DC circuit breaker through the switch group, for online inversion operation of the voltage source converter.

7. The valve set for direct current power transmission according to claim 6, characterized by: The switch group comprises a first switch, a second switch, and a third switch. The first switch is connected in series with the main branch of the DC circuit breaker, and then connected in anti-parallel with the first valve; The first transfer switch connects a positive pole of the voltage source converter and a first end of the DC circuit breaker, The second transfer switch connects a negative pole of the voltage source converter and the first end of the DC circuit breaker, The third transfer switch connects the positive pole of the voltage source converter and a second end of the DC circuit breaker; or, The first transfer switch connects the negative pole of the voltage source converter and the second end of the DC circuit breaker, The second transfer switch connects the positive pole of the voltage source converter and the second end of the DC circuit breaker, The third transfer switch connects the negative pole of the voltage source converter and the first end of the DC circuit breaker. The transfer switch group comprises a fourth transfer switch, a fifth transfer switch and a sixth transfer switch; 8. The valve set for direct current power transmission according to claim 6, characterized by: The fourth transfer switch connects a positive end of the DC transmission valve group and the second end of the DC circuit breaker, The fifth transfer switch connects the positive end of the DC transmission valve group and the first end of the DC circuit breaker, The sixth transfer switch connects a negative end of the DC transmission valve group and the second end of the DC circuit breaker; or, The fourth transfer switch connects the negative end of the DC transmission valve group and the first end of the DC circuit breaker, The fifth transfer switch connects the negative end of the DC transmission valve group and the second end of the DC circuit breaker, The sixth transfer switch connects the positive end of the DC transmission valve group and the first end of the DC circuit breaker. The transfer switch group comprises a first transfer switch, a seventh transfer switch, an eighth transfer switch, a ninth transfer switch and a tenth transfer switch; The first transfer switch connects a positive pole of the voltage source converter and a first end of the DC circuit breaker, The seventh transfer switch connects a positive end of the DC transmission valve group and a cathode of the first valve, 9. The valve set for direct current power transmission according to claim 6, characterized by: The eighth transfer switch connects a negative end of the DC transmission valve group and an anode of the first valve, The ninth transfer switch connects the positive pole of the voltage source converter and the cathode of the first valve, The tenth transfer switch connects the positive end of the DC transmission valve group and the anode of the first valve; or, The first transfer switch connects a negative pole of the voltage source converter and a second end of the DC circuit breaker, The seventh transfer switch connects a negative end of the DC transmission valve group and the anode of the first valve, The eighth transfer switch connects the positive end of the DC transmission valve group and the cathode of the first valve, The ninth transfer switch connects the negative pole of the voltage source converter and the anode of the first valve, The tenth transfer switch connects the negative end of the DC transmission valve group and the cathode of the first valve. The transfer switch group comprises a first transfer switch, a second transfer switch, a seventh transfer switch, an eighth transfer switch, a ninth transfer switch and a tenth transfer switch; The first transfer switch connects a positive pole of the voltage source converter and a first end of the DC circuit breaker, The second transfer switch connects a negative pole of the voltage source converter and the first end of the DC circuit breaker, The seventh transfer switch connects a positive end of the DC transmission valve group and a cathode of the first valve, 10. The DC power delivery valve bank of claim 6, wherein: The eighth transfer switch connects a negative end of the DC transmission valve group and an anode of the first valve, The ninth transfer switch connects the positive pole of the voltage source converter and the cathode of the first valve, The tenth transfer switch connects the positive end of the DC transmission valve group and the anode of the first valve; or, The first transfer switch connects the negative pole of the voltage source converter and a second end of the DC circuit breaker, The seventh transfer switch connects the negative end of the DC transmission valve group and the anode of the first valve, The eighth transfer switch connects the positive end of the DC transmission valve group and the cathode of the first valve, The ninth transfer switch connects the negative pole of the voltage source converter and the anode of the first valve, The tenth transfer switch connects the negative end of the DC transmission valve group and the cathode of the first valve. The ninth switch connects the positive pole of the voltage source converter and the cathode of the first valve, The tenth switch connects the positive end of the DC transmission valve group and the anode of the first valve. Or, The first switch connects the negative pole of the voltage source converter and the second end of the DC circuit breaker, The second switch connects the positive pole of the voltage source converter and the second end of the DC circuit breaker, The seventh switch connects the negative end of the DC transmission valve group and the anode of the first valve, The eighth switch connects the positive end of the DC transmission valve group and the cathode of the first valve, The ninth switch connects the negative pole of the voltage source converter and the anode of the first valve, The tenth switch connects the negative end of the DC transmission valve group and the cathode of the first valve.

11. The valve set for direct current power transmission according to claim 2, characterized by: The voltage source converter is connected in series with the first valve, comprising: The positive pole of the voltage source converter is connected with the cathode of the diode, the anti-parallel diode of the thyristor or the full-controlled device of the first valve; or the negative pole of the voltage source converter is connected with the anode of the diode, the anti-parallel diode of the thyristor or the full-controlled device of the first valve.

12. The valve set for direct current power transmission according to claim 1, characterized by: Further comprising: At least one residual current disconnector, when the voltage source converter or the bridge uncontrolled rectifier circuit is connected in series with the DC circuit breaker and then connected in anti-parallel with the first valve, the residual current disconnector is connected in series between the voltage source converter and the DC circuit breaker, and / or connected in series between the DC circuit breaker and the first valve; when the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker, the residual current disconnector is first connected in series with the DC circuit breaker, and then connected in parallel with the circuit after the voltage source converter and the first valve are connected in series.

13. The valve set for direct current power transmission according to claim 1, characterized by: Further comprising: A bypass switch, the bypass switch connects the positive end and the negative end of the DC transmission valve group; the bypass switch comprises at least one of a mechanical switch, a mechanical knife switch, and a series-connected third power switch.

14. The direct current transmission valve group of claim 1, wherein: Further comprising: A positive isolation knife switch, the positive isolation knife switch connects the positive end of the DC transmission valve group and a first positive input end; A negative isolation knife switch, the negative isolation knife switch connects the negative end of the DC transmission valve group and a first negative input end; A bypass knife switch, the bypass knife switch connects the first positive input end and the first negative input end of the DC transmission valve group.

15. The valve set for direct current power transmission according to claim 2, characterized by: The DC circuit breaker is a multi-port DC circuit breaker, and the DC transmission valve group further comprises: A second valve, the second valve comprises a second diode valve or a second thyristor valve, the second diode valve comprises at least one diode connected in series, and the second thyristor valve comprises at least one thyristor connected in series, the cathode of the second valve is a second positive input end of the DC transmission valve group, and the anode of the second valve is a second negative input end of the DC transmission valve group; One DC pole is formed by one DC transmission valve group, and the voltage source converter is connected in series with a main branch of the multi-port DC circuit breaker and then connected in anti-parallel with the second valve.

16. The valve set for direct current power transmission according to claim 2, wherein: The DC circuit breaker is a first two-port DC circuit breaker, and the DC transmission valve group further comprises: A second two-port DC circuit breaker; A second valve, the second valve comprising a second diode valve or a second thyristor valve, the second diode valve comprising at least one diode connected in series, the second thyristor valve comprising at least one thyristor connected in series, a cathode of the second valve being a second positive input end of the DC transmission valve group, an anode of the second valve being a second negative input end of the DC transmission valve group; One of the DC transmission valve groups constitutes a DC pole, the voltage source converter being connected in series with the second two-port DC circuit breaker and / or the first two-port DC circuit breaker and then connected in anti-parallel with the second valve.

17. The valve set for direct current power transmission according to claim 6, characterized by: A bypass switch is further included, the bypass switch being connected in parallel with the energy dissipation circuit; the bypass switch comprising a mechanical switch and / or a mechanical knife switch.

18. A DC power transmission valve group series circuit, characterized by: The DC transmission valve group as claimed in any one of claims 1-17 is included at least twice; the series circuit of the DC transmission valve groups at least comprising a first DC transmission valve group and a second DC transmission valve group, a first negative input end of the first DC transmission valve group and a first positive input end of the second DC transmission valve group being connected.

19. The direct current transmission valve string series circuit of claim 18, wherein: The first DC transmission valve group and the second DC transmission valve group both comprise a multi-port DC circuit breaker and a second valve, or the first DC transmission valve group and the second DC transmission valve group both comprise a second two-port DC circuit breaker and a second valve, wherein a second negative input end of the first DC transmission valve group and a second positive input end of the second DC transmission valve group are connected, and a first negative input end of the first DC transmission valve group and a first positive input end of the second DC transmission valve group are connected.

20. The direct current transmission valve string series circuit of claim 18, wherein: The first DC transmission valve group comprises a second two-port DC circuit breaker and a second valve, a first negative input end of the first DC transmission valve group and a first positive input end of the second DC transmission valve group are connected, and a second negative input end of the first DC transmission valve group and a first negative input end of the second DC transmission valve group are connected or connected through a disconnection switch, or a second positive input end of the first DC transmission valve group and a first positive input end of the second DC transmission valve group are connected or connected through a disconnection switch.

21. A direct current power transmission system characterised by: The DC transmission valve group as claimed in any one of claims 1-17 or the series circuit of the DC transmission valve groups as claimed in any one of claims 18-20 is included; a pole neutral bus switch is connected in series between the DC transmission valve group or the series circuit and the ground; the pole neutral bus switch comprises at least one of a mechanical switch, a mechanical knife switch, and a fourth power switch connected in series.

22. A method of controlling a DC power transmission valve group, characterized by: The control method is applied to the DC transmission valve group as claimed in any one of claims 1-17; the control method comprises: If the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in anti-parallel with the series circuit of the first valve and the energy dissipation circuit, in normal operation, the DC circuit breaker is controlled to be turned on, the first valve is controlled to be turned off, and the voltage source converter is controlled to be operated in rectification or inversion; If the voltage source converter is connected in series with the first valve and the parallel circuit of the energy dissipation circuit and the bypass switch and then connected in parallel with the DC circuit breaker, in normal operation, the DC circuit breaker is controlled to be off, the first valve is controlled to be on, and the bypass switch is controlled to be on.

23. The DC power transmission valve group control method of claim 22, wherein: If the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in anti-parallel with the series circuit of the first valve and the energy dissipation circuit, the control method further comprises: When the voltage source converter is online and rectifying, the voltage source converter is controlled to be charged, the voltage source converter is controlled to be unlocked, and the DC circuit breaker is controlled to be on; When the voltage source converter is rectifying and online, the bypass switch is controlled to be on, the DC circuit breaker is controlled to be off, and the first valve is controlled to be on; When the voltage source converter is rectifying and offline due to a fault, the DC circuit breaker is controlled to be off, the first valve is controlled to be on, and the voltage source converter is controlled to be blocked; When the voltage source converter is rectifying or inverting and DC fault ride through, the DC circuit breaker is controlled to be off, the first valve is controlled to be on, and the DC circuit breaker is controlled to be on after fault recovery or deionization time; the DC fault includes DC line fault.

24. The DC power transmission valve group control method of claim 22, wherein: If the voltage source converter is connected in series with the first valve and the parallel circuit of the energy dissipation circuit and the bypass switch and then connected in parallel with the DC circuit breaker, the control method further comprises: When the voltage source converter is online and inverting, the voltage source converter is controlled to be charged, the voltage source converter is controlled to be unlocked, the DC circuit breaker is controlled to be off, and the first valve is controlled to be on; When the voltage source converter is inverting and offline or offline due to a fault, the DC circuit breaker is controlled to be on, or if the DC power transmission valve group further comprises a bypass switch, the bypass switch is controlled to be on and / or the DC circuit breaker is controlled to be on; When the voltage source converter is inverting and DC fault ride through, the first valve is controlled to be on after fault recovery or deionization time; the DC fault includes DC line fault.

25. The DC power transmission valve group control method of claim 23, wherein: If the DC power transmission valve group further comprises a bypass switch, When the voltage source converter is rectifying and offline or offline due to a fault, after the first valve is controlled to be on, the bypass switch is further controlled to be on; When the voltage source converter is inverting and offline or offline due to a fault, the bypass switch is controlled to be on, and the DC circuit breaker is controlled to be off; the voltage source converter is controlled to be blocked when offline due to a fault.

26. The DC power transmission valve group control method of claim 23, wherein: If the DC power transmission valve group further comprises a disconnection switch, or the DC power transmission system further comprises a pole neutral bus switch, when the voltage source converter rectifies or inverts and DC fault passes through, the control of the first valve is turned on, the disconnection switch or the pole neutral bus switch is disconnected, and after fault recovery or de-ionization time, the disconnection switch or the pole neutral bus switch is reclosed.

27. The DC power transmission valve group control method according to claim 22, characterized in that: If the first fully controlled valve of the DC power transmission valve group adopts a fully controlled device, when the voltage source converter or the bridge uncontrolled rectifier circuit energy cannot be normally sent out to generate AC or DC overvoltage, the fully controlled device of the first valve is controlled to be turned on, and the energy is dissipated in the energy dissipation circuit; when the voltage source converter or the bridge uncontrolled rectifier circuit energy can be normally sent out, the fully controlled device of the first valve is controlled to be turned off. If the first diode valve of the DC power transmission valve group adopts at least one diode and a thyristor anti-parallel circuit, when the voltage source converter or the bridge uncontrolled rectifier circuit energy cannot be normally sent out to generate AC or DC overvoltage, the thyristor of the first valve is controlled to be turned on, and the energy is dissipated in the energy dissipation circuit.

28. A DC power transmission valve group control apparatus characterized by: The control device is applied to the DC power transmission valve group according to any one of claims 1-17, and the control device comprises: a detection unit configured to detect an operating parameter and a fault of the DC power transmission valve group; a control unit configured to, based on the operating parameter of the DC power transmission valve group, control the DC circuit breaker to be turned on, control the first valve to be turned off, and control the voltage source converter to rectify or invert when the voltage source converter is connected in series with a main branch of the DC circuit breaker and then connected in anti-parallel with a series circuit of the first valve and the energy dissipation circuit in a normal operation; and control the DC circuit breaker to be turned off, control the first valve to be turned on, control the bypass switch to be reclosed, and control the voltage source converter to invert when the voltage source converter is connected in series with a parallel circuit of the first valve and the energy dissipation circuit and a bypass switch and then connected in parallel with the DC circuit breaker in a normal operation.

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