Voltage source type valve group and control method and device, series circuit, power transmission system

Abstract

This application provides a voltage source type valve group and control method and device, a series circuit, and a power transmission system. The voltage source type valve group includes a voltage source converter, a DC circuit breaker, and a first valve. The voltage source converter 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 or a first thyristor valve. The first diode valve includes at least one diode connected in series, and the first thyristor valve includes at least one thyristor connected in series. 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; or the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker.

Description

Technical Field

[0001] This application relates to the fields of flexible DC transmission and hybrid DC transmission technology, specifically to voltage source type valve groups and control methods and devices, series circuits, and transmission systems. 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 switching 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 using a hybrid MMC structure of half-bridge and full-bridge submodules, while possessing DC fault ride-through capability and enabling online connection and disconnection of the converter, suffer from higher losses than the half-bridge submodule-based MMC and DC circuit breaker solutions, and are unsuitable for DC power grids. Summary of the Invention

[0005] This application provides a voltage source valve group, including a voltage source converter, a DC circuit breaker, and a first valve. The voltage source converter 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 or a first thyristor valve. The first diode valve includes at least one diode connected in series, and the first thyristor valve includes at least one thyristor connected in series. 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; or the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker.

[0006] According to some embodiments, the voltage source converter includes 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 DC circuit breaker includes 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 includes a main branch, or includes a main branch, a transfer branch, and a power dissipation branch; the first two-port DC circuit breaker includes the main branch; 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 includes a series-connected fast disconnect switch and / or a first power switch; the transfer branch includes a series-connected second power switch and / or an LC resonant circuit and / or a coupled negative voltage circuit; the power dissipation branch is connected in parallel with the transfer branch, and the power dissipation branch includes a surge arrester.

[0007] According to some embodiments, the voltage source valve group further includes a changeover 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 rectification or inversion operation of the voltage source converter; or through the changeover 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 inversion operation or online inversion operation of the voltage source converter; or through the changeover switch group, the voltage source converter is connected in parallel with the transfer branch of the DC circuit breaker, for online inversion operation of the voltage source converter.

[0008] According to some embodiments, the transfer switch group includes a first transfer switch, a second transfer switch, and a third transfer switch. 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; and the third transfer switch is connected to the positive terminal of the voltage source converter and the second terminal of the DC circuit breaker.

[0009] According to some embodiments, the transfer switch group includes a first transfer switch, a second transfer switch, and a third transfer switch. 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 second transfer switch is connected to the positive terminal of the voltage source converter and the second terminal of the DC circuit breaker; and the third transfer switch is connected to the negative terminal of the voltage source converter and the first terminal of the DC circuit breaker.

[0010] According to some embodiments, the transfer switch group includes a fourth transfer switch, a fifth transfer switch, and a sixth transfer switch. The fourth transfer switch is connected to the positive terminal of the voltage source valve group and the second terminal of the DC circuit breaker; the fifth transfer switch is connected to the positive terminal of the voltage source valve group and the first terminal of the DC circuit breaker; and the sixth transfer switch is connected to the negative terminal of the voltage source valve group and the second terminal of the DC circuit breaker.

[0011] According to some embodiments, the transfer switch group includes a fourth transfer switch, a fifth transfer switch, and a sixth transfer switch. The fourth transfer switch is connected to the negative terminal of the voltage source valve group and the first terminal of the DC circuit breaker; the fifth transfer switch is connected to the negative terminal of the voltage source valve group and the second terminal of the DC circuit breaker; and the sixth transfer switch is connected to the positive terminal of the voltage source valve group and the first terminal of the DC circuit breaker.

[0012] According to some embodiments, the transfer switch group further includes 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 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 voltage source valve group and the cathode of the first valve; the eighth transfer switch is connected to the negative terminal of the voltage source 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 voltage source valve group and the anode of the first valve.

[0013] According to some embodiments, the transfer switch group further includes 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 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 voltage source valve group and the anode of the first valve; the eighth transfer switch is connected to the positive terminal of the voltage source 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 voltage source valve group and the cathode of the first valve.

[0014] According to 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. 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 voltage source valve group and the cathode of the first valve; the eighth transfer switch is connected to the negative terminal of the voltage source 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 voltage source valve group and the anode of the first valve.

[0015] According to 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. 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 second transfer switch is connected to the positive 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 voltage source valve group and the anode of the first valve; the eighth transfer switch is connected to the positive terminal of the voltage source 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 voltage source valve group and the cathode of the first valve.

[0016] According to 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 first valve; or the negative terminal of the voltage source converter is connected to the anode of the first valve.

[0017] According to some embodiments, the voltage source valve group further includes a residual current disconnect switch. When the voltage source converter is connected in series with the main branch of 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, or / and 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.

[0018] According to some embodiments, the voltage source valve group further includes a bypass switch, which is connected to the positive and negative terminals of the voltage source 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.

[0019] According to some embodiments, the voltage source valve group further includes a first isolating switch, a second isolating switch, and a bypass switch. The first isolating switch is connected to the positive terminal and the first positive input terminal of the voltage source valve group; the second isolating switch is connected to the negative terminal and the first negative input terminal of the voltage source valve group; and the bypass switch is connected to the first positive input terminal and the first negative input terminal of the voltage source valve group.

[0020] According to some embodiments, if the DC circuit breaker is a multi-port DC circuit breaker, the voltage source 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 voltage source valve group, and the anode of the second valve being the second negative input terminal of the voltage source valve group; if one of the voltage source valve groups constitutes a DC pole, 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.

[0021] According to some embodiments, the voltage source valve group further includes a second two-port DC circuit breaker and a second valve. The second valve includes a second diode valve or a second thyristor valve. The second diode valve includes at least one diode connected in series, and the second thyristor valve includes at least one thyristor connected in series. The cathode of the second valve is the second positive input terminal of the voltage source valve group, and the anode of the second valve is the second negative input terminal of the voltage source valve group.

[0022] If one of the voltage source valve groups constitutes a DC pole, 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] According to some embodiments, the voltage source valve group further includes a resistor and / or a disconnecting switch, the resistor and / or the disconnecting switch being connected in series with the first valve and / or the second valve; or / and connected in series between the first negative input terminal and the second negative input terminal or between the first positive input terminal and the second positive input terminal of the voltage source valve group; the disconnecting switch includes at least one of a mechanical switch, a mechanical knife switch, and a fourth power switch connected in series.

[0024] This application embodiment also provides a voltage source valve group series circuit, including at least two voltage source valve groups as described above, wherein the first negative input terminal of one voltage source valve group is connected to the first positive input terminal of the other voltage source valve group.

[0025] According to some embodiments, if both voltage source valve groups include a multi-port DC circuit breaker or a second two-port DC circuit breaker and a second valve, the second negative input terminal of one voltage source valve group is connected to the second positive input terminal of the other voltage source valve group.

[0026] According to some embodiments, if the voltage source valve group includes a second two-port DC circuit breaker and a second valve, the second negative input terminal of the voltage source valve group is connected to the first negative input terminal of the other voltage source valve group, or the second positive input terminal of the voltage source valve group is connected to the first positive input terminal of the other voltage source valve group.

[0027] This application also includes a DC power transmission system, comprising the voltage source valve group as described above or the voltage source valve group series circuit as described above.

[0028] According to some embodiments, a neutral bus switch is connected in series between the voltage source valve group or the series circuit of the voltage source valve group and the ground; the neutral bus switch includes at least one of a mechanical switch, a mechanical knife switch, and a fourth power switch connected in series.

[0029] This application embodiment also includes a control method for the voltage source valve group as described above, comprising: 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 first valve, during normal operation, controlling the DC circuit breaker to conduct, controlling the first valve to close, and controlling the voltage source converter to operate in rectification or inversion mode; if the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker, during normal operation, controlling the DC circuit breaker to close, controlling the first valve to conduct, and controlling the voltage source converter to operate inversion mode.

[0030] According to some embodiments, 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 first valve, the control method further includes: when the voltage source converter is in online rectification operation, controlling the voltage source converter to charge, controlling the voltage source converter to unlock, and controlling the DC circuit breaker to turn on; when the voltage source converter is in rectification operation and then exits online or exits due to a fault, controlling the DC circuit breaker to turn off and controlling the first valve to turn on; when exiting due to a fault, the method further includes controlling the voltage source converter to lock out; when the voltage source converter is in rectification or inverter operation and a DC fault crosses through, controlling the DC circuit breaker to turn off and controlling the first valve to turn on, and after the fault is recovered or after a deionization time, controlling the DC circuit breaker to turn on; the DC fault includes a DC line fault.

[0031] According to some embodiments, if the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker, the control method further includes: when the voltage source converter is in online inverter operation, controlling the voltage source converter to charge, controlling the voltage source converter to unlock, controlling the DC circuit breaker to turn off, and controlling the first valve to turn on; when the voltage source converter is in inverter operation and is offline or fault-exited, controlling the DC circuit breaker to turn on, or if the voltage source valve group further includes a bypass switch, controlling the bypass switch to turn on and / or controlling the DC circuit breaker to turn on; when the voltage source converter is in inverter operation and a DC fault crosses, controlling the first valve to turn on after fault recovery or after a deionization time; the DC fault includes a DC line fault.

[0032] According to some embodiments, if the voltage source valve group further includes a bypass switch, when the voltage source converter is operating in rectification mode and is shut down online or after a fault, after controlling the first valve to open, the bypass switch is also controlled to open; when the voltage source converter is operating in inverter mode and is shut down online or after a fault, the bypass switch is controlled to open, and the DC circuit breaker is controlled to close; when the fault occurs, the voltage source converter is also controlled to lock out.

[0033] According to some embodiments, if the voltage source valve group further includes a disconnect switch or the DC transmission system in which the voltage source 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. After the fault is recovered or after the deionization time, the disconnect switch or the neutral bus switch is reclosed.

[0034] This application embodiment also provides a control device for the voltage source valve group as described above, including a detection unit and a control unit. The detection unit is used to detect the operating parameters and faults of the voltage source valve group. Based on the operating parameters of the voltage source valve group, 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 first valve, during normal operation, the control unit 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. If the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker, during normal operation, the control unit controls the DC circuit breaker to close, controls the first valve to conduct, and controls the voltage source converter to operate inversion mode.

[0035] The technical solution provided in this application embodiment enables the online commissioning, online decommissioning, and fault exit of voltage source converters that do not have full-range voltage regulation capabilities by configuring DC circuit breakers and a first valve. At the same time, the follow current of the first valve reduces the stress of the DC circuit breaker when interrupting current during a fault. This allows the voltage source 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 sub-modules and full-bridge sub-modules, the loss is reduced and the fault isolation performance is better. It is more suitable for multi-terminal UHV flexible or hybrid DC transmission systems and long-distance DC power grids. Attached Figure Description

[0036] 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.

[0037] Figures 1a-1f This is a schematic diagram of various voltage source type valve groups according to embodiments of this application.

[0038] Figure 1g-Figure 1k These are schematic diagrams of various voltage source valve groups suitable for inverter operation according to embodiments of this application.

[0039] Figures 2a-2h This is a schematic diagram of a voltage source type valve group with various configurations of switching groups according to embodiments of this application.

[0040] Figure 3a This is a schematic diagram of a voltage source valve group configured with a changeover switch group and a bypass switch according to an embodiment of this application.

[0041] Figure 3b This is a schematic diagram of a voltage source valve group configured with a changeover switch group, a bypass switch, and a knife switch, according to an embodiment of this application.

[0042] Figure 4a This is a schematic diagram of a voltage source valve group configured with a multi-port DC circuit breaker according to an embodiment of this application.

[0043] Figure 4b This is a schematic diagram of a voltage source type valve group with another configuration of a multi-port DC circuit breaker according to an embodiment of this application.

[0044] Figure 4c This is a schematic diagram of a voltage source valve group configured with a second two-port DC circuit breaker according to an embodiment of this application.

[0045] Figure 4d This is a schematic diagram of a voltage source valve group with another configuration of the second two-port DC circuit breaker according to an embodiment of this application.

[0046] Figures 5a-5d This is a schematic diagram of a series circuit of various voltage source type valve groups according to an embodiment of this application.

[0047] Figures 6a-6c This is a schematic diagram of various two-port DC circuit breakers according to embodiments of this application.

[0048] Figure 6d This is a schematic diagram of a multi-port DC circuit breaker according to an embodiment of this application.

[0049] Figures 7a-7c This is a schematic diagram of various bypass switches according to embodiments of this application.

[0050] Figure 8a This is a schematic diagram of a disconnect switch according to an embodiment of this application.

[0051] Figure 8b This is a schematic diagram of another disconnect switch according to an embodiment of this application.

[0052] Figure 9 This is a schematic flowchart of a control method for a voltage source type valve group according to an embodiment of this application.

[0053] Figure 10 This is a schematic flowchart of another voltage source valve group control method according to an embodiment of this application.

[0054] Figures 11-15 These are schematic diagrams of various DC power transmission systems according to embodiments of this application.

[0055] Figure 16 This is a schematic diagram of a control device for a voltage source type valve group according to an embodiment of this application. Detailed Implementation

[0056] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0057] It should be understood that the terms "first," "second," "third," "fourth," "fifth," "sixth," "seventh," and "eighth," etc., used in the claims, specification, and drawings of this application are used to distinguish different objects and not to describe a specific order. The terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0058] Figures 1a-1f This is a schematic diagram of various voltage source type valve groups according to embodiments of this application.

[0059] like Figure 1a As shown, the voltage source type valve group includes a voltage source converter 1, a DC circuit breaker 2, and a first valve 3, which is suitable for the positive terminal P1 of the voltage source converter 1 to be the high voltage end.

[0060] The voltage source converter 1 includes at least three phases and six bridge arms, and cannot regulate 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, but is not limited to, a first diode valve or a first thyristor valve; the first diode valve includes at least one diode connected in series, and the first thyristor valve includes at least one thyristor connected in series.

[0061] The voltage source converter 1 is connected in series with the main branch of the DC circuit breaker 2, and then connected in anti-parallel with the first valve 3, such as... Figure 1a As shown, the aforementioned anti-parallel connection involves the positive terminal P1 of the voltage source converter 1 being connected to the cathode K of the diode 3 via the DC circuit breaker 2, and the negative terminal N1 of the voltage source converter 1 being connected to the anode A of the diode 3. Specifically, the positive terminal P1 of the voltage source converter 1 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 first valve 3, and the negative terminal N1 of the voltage source converter 1 is connected to the anode A of the first valve 3.

[0062] When DC circuit breaker 2 is turned off, the first valve 3 transfers the current flowing through the voltage source converter through freewheeling, thereby reducing the stress on DC circuit breaker 2.

[0063] According to some embodiments, the voltage source type valve assembly also includes a resistor and / or a disconnect switch, connected in series with the first valve, such as... Figure 1b As shown, the voltage source valve group includes a resistor 10 and a first valve 3 connected in series, which is used to quickly attenuate the fault current in the event of a fault.

[0064] According to some embodiments, the voltage source valve group further includes a residual current disconnect switch connected in series between the voltage source converter 1 and the DC circuit breaker 2, or / and connected in series between the DC circuit breaker 2 and the first valve 3, such as... Figure 1cAs shown, the voltage source type valve group also includes residual current disconnect switches 60 and 70. The residual current disconnect switch 60 is connected in series between the voltage source converter 1 and the DC circuit breaker 2, and the residual current disconnect switch 70 is connected in series between the DC circuit breaker 2 and the first valve 3.

[0065] Optionally, such as Figure 1d As shown, the above anti-parallel connection connects the positive terminal P1 of the voltage source converter 1 to the cathode K of the diode 3, and the negative terminal N1 of the voltage source converter 1 to the anode A of the diode 3 through the DC circuit breaker 2. This is suitable when the negative terminal N1 of the voltage source converter 1 is the high-voltage end. 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 the cathode K of the first valve 3.

[0066] According to some embodiments, the voltage source valve assembly also includes a bypass switch 12, which connects the positive terminal P2 and the negative terminal N2 of the voltage source valve assembly, such as... Figure 1e As shown. The bypass switch 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 Thyristor), IGBT (Insulated Gate Bipolar Transistor), GTO (Gate Turn-Off Thyristor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and thyristor, but is not limited thereto. Optionally, the third power switch includes a power device and an uncontrolled device connected in antiparallel to it.

[0067] According to some embodiments, the voltage source type valve group further includes a first isolating switch 13, a second isolating switch 14, and a bypass switch 11, such as Figure 1f As shown. The first isolating switch 13 connects the positive terminal P2 and the positive input terminal P of the voltage source type valve group. The second isolating switch 14 connects the negative terminal N2 and the negative input terminal N of the voltage source type valve group. The bypass switch 11 connects the positive input terminal P and the negative input terminal N of the voltage source type valve group.

[0068] Figure 1g This is a schematic diagram of a voltage source type valve group suitable for inverter operation of a voltage source converter according to an embodiment of this application, including a voltage source converter 1, a DC circuit breaker 2, and a first valve 3, with the positive terminal P1 of the voltage source converter 1 being the high-voltage end.

[0069] The voltage source converter 1 includes at least three phases and six bridge arms, and cannot regulate 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, 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 or a first thyristor valve; the first diode valve includes at least one diode connected in series, and the first thyristor valve includes at least one thyristor connected in series.

[0070] The voltage source converter 1 is connected in series with the first valve 3, and then connected in parallel with the DC circuit breaker 2, such as... Figure 1g As shown. The above series connection connects the positive terminal P1 of the voltage source converter 1 to the cathode K of the first valve 3. 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 the cathode K of the first valve 3.

[0071] In the event of 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.

[0072] Optionally, the negative terminal N1 of the voltage source converter 1 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, as shown below. Figure 1h As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0073] According to some embodiments, the voltage source valve group also includes a 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, such as... Figure 1i As shown, the voltage source type valve group also includes residual current disconnect switches 80 and 90, which 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 and the first valve 3 are connected in series.

[0074] According to some embodiments, the voltage source valve assembly also includes a bypass switch 52, which connects the positive terminal P2 and the negative terminal N2 of the voltage source valve assembly, such as... Figure 1j As shown.

[0075] According to some embodiments, the voltage source type valve group further includes a first isolating switch 53, a second isolating switch 54, and a bypass switch 51, such as Figure 1kAs shown. The first isolating switch 53 connects the positive terminal P2 and the positive input terminal P of the voltage source valve group. The second isolating switch 54 connects the negative terminal N2 and the negative input terminal N of the voltage source valve group. The bypass switch 51 connects the positive input terminal P and the negative input terminal N of the voltage source valve group.

[0076] Figure 2a This is a schematic diagram of a voltage source valve group with a configuration of a switching group according to an embodiment of this application, including a voltage source converter 1, a DC circuit breaker 2, a first valve 3, a first switching switch 4, a second switching switch 5, and a third switching switch 6, suitable for the positive terminal P1 of the voltage source converter 1 to be the high voltage end.

[0077] exist Figure 1a 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. These switches are used to change the connection relationship of the DC circuit breaker 2, enabling the voltage source converter 1 to operate in rectifier mode, inverter mode, or be put into inverter mode online.

[0078] The 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. The 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. The third changeover switch 6 connects the positive terminal P1 of the voltage source converter 1 to the second terminal D of the DC circuit breaker 2.

[0079] Optionally, 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, as shown below. Figure 2b As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0080] When the voltage source converter is in rectification or inverting operation, the first changeover switch 4 is closed, and the second changeover switch 5 and the third changeover switch 6 are open.

[0081] When the voltage source converter is put into online inverter operation, the first transfer switch 4 is open, and the second transfer switch 5 and the third transfer switch 6 are closed.

[0082] Figure 2c This is a schematic diagram of a voltage source valve group with a configuration of a switching group according to an embodiment of this application, including a voltage source converter 1, a DC circuit breaker 2, a first valve 3, a fourth switching switch 7, a fifth switching switch 8, and a sixth switching switch 9, suitable for the positive terminal P1 of the voltage source converter 1 to be the high voltage end.

[0083] exist Figure 1aBased on the previous embodiment, three additional transfer switches were added: a fourth transfer switch 7, a fifth transfer switch 8, and a sixth transfer switch 9. These switches are used to change the connection relationship of the DC circuit breaker 2, enabling the voltage source converter 1 to operate in rectifier mode, inverter mode, or be put into inverter mode online.

[0084] The fourth changeover switch 7 connects the second terminal D of the DC circuit breaker 2 to the positive terminal P2 of the voltage source valve group. The fifth changeover switch 8 connects the positive terminal P2 of the voltage source 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 voltage source valve group.

[0085] Optionally, the fourth changeover switch 7 connects the first terminal C of the DC circuit breaker 2 to the negative terminal N2 of the voltage source valve group. The fifth changeover switch 8 connects the negative terminal N2 of the voltage source 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 voltage source valve group, as shown below. Figure 2d As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0086] When the voltage source converter is in rectification or inverting operation, the fourth changeover switch 7 is closed, and the fifth changeover switch 8 and the sixth changeover switch 9 are open.

[0087] When the voltage source converter is put into online inverter operation, the fourth transfer switch 7 is open, and the fifth transfer switch 8 and the sixth transfer switch 9 are closed.

[0088] Figure 2e This is a schematic diagram of a voltage source valve group with a configuration of a switching group according to an embodiment of this application. It includes a voltage source converter 1, a DC circuit breaker 2, a first valve 3, a first switching switch 4, a second switching switch 5, a seventh switching switch 15, an eighth switching switch 16, a ninth switching switch 17, and a tenth switching switch 18, which is suitable for the positive terminal P1 of the voltage source converter 1 to be the high voltage end.

[0089] exist Figure 1a Based on the previous embodiment, six additional switching switches were added.

[0090] First changeover switch 4, second changeover switch 5, seventh changeover switch 15, eighth changeover switch 16, ninth changeover switch 17, and tenth changeover switch 18 are used to change 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, inverting mode, or online inverting mode.

[0091] The 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. The 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. The seventh changeover switch 15 connects the cathode K of the first valve 3 to the positive terminal P2 of the voltage source valve assembly. The eighth changeover switch 16 connects the anode A of the first valve 3 to the negative terminal N2 of the voltage source valve assembly. The ninth changeover switch 17 connects the cathode K of the first valve 3 to the positive terminal P1 of the voltage source converter. The tenth changeover switch 18 connects the positive terminal P2 of the voltage source valve assembly to the anode A of the first valve 3.

[0092] Optionally, 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 the anode A of the first valve 3 to the negative terminal N2 of the voltage source valve group. The eighth changeover switch 16 connects the cathode K of the first valve 3 to the positive terminal P2 of the voltage source valve group. The ninth changeover switch 17 connects the anode A of the first valve 3 to the negative terminal N1 of the voltage source converter. The tenth changeover switch 18 connects the negative terminal N2 of the voltage source valve group to the cathode K of the first valve 3, as shown in Figure 2f, suitable when the negative terminal N1 of the voltage source converter 1 is the high-voltage end.

[0093] When the voltage source converter is in rectification or inverting operation, 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.

[0094] Optionally, during the inverter operation of the voltage source converter, the first transfer switch 4, the seventh transfer switch 15 and the eighth transfer switch 16 are open, and the second transfer switch 5, the ninth transfer switch 17 and the tenth transfer switch 18 are closed.

[0095] When the voltage source converter is put into online inverter operation, the first transfer switch 4, the seventh transfer switch 15 and the eighth transfer switch 16 are open, and the second transfer switch 5, the ninth transfer switch 17 and the tenth transfer switch 18 are closed.

[0096] Figure 2g This is a schematic diagram of a voltage source valve group with a configuration of a switching group according to an embodiment of this application. It 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, which is suitable for the positive terminal P1 of the voltage source converter 1 to be the high voltage end.

[0097] exist Figure 2c Based on the previous implementation, five additional switching switches were added.

[0098] The first changeover switch 4, the fourth changeover switch 7, the fifth changeover switch 8, the sixth changeover switch 9, the seventh changeover switch 15, the eighth changeover switch 16, the ninth changeover switch 17, and the tenth changeover switch 18 are used to change the connection relationship between the voltage source converter 1, the DC circuit breaker 2, and the first valve 3, so that the voltage source converter 1 can operate in rectification mode, inverting mode, or be put into inverter mode online.

[0099] The 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. The fourth changeover switch 7 connects the second terminal D of the DC circuit breaker 2 to the positive terminal P2 of the voltage source valve group. The fifth changeover switch 8 connects the positive terminal P2 of the voltage source 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 voltage source valve group. The seventh changeover switch 15 connects the cathode K of the first valve 3 to the positive terminal P2 of the voltage source valve group. The eighth changeover switch 16 connects the anode A of the first valve 3 to the negative terminal N2 of the voltage source valve group. The ninth changeover switch 17 connects the cathode K of the first valve 3 to the positive terminal P1 of the voltage source converter. The tenth changeover switch 18 connects the positive terminal P2 of the voltage source valve group to the anode A of the first valve 3.

[0100] Optionally, 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 fourth changeover switch 7 connects the first terminal C of the DC circuit breaker 2 to the negative terminal N2 of the voltage source valve group. The fifth changeover switch 8 connects the negative terminal N2 of the voltage source 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 voltage source valve group. The seventh changeover switch 15 connects the anode A of the first valve 3 to the negative terminal N2 of the voltage source valve group. The eighth changeover switch 16 connects the cathode K of the first valve 3 to the positive terminal P2 of the voltage source valve group. The ninth changeover switch 17 connects the anode A of the first valve 3 to the negative terminal N1 of the voltage source converter. The tenth changeover switch 18 connects the negative terminal N2 of the voltage source valve group to the cathode K of the first valve 3, and so on. Figure 2h As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0101] When the voltage source converter is in rectification or inverting operation, 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.

[0102] Optionally, during the inverter operation of the voltage source converter, the first transfer switch 4, the fourth transfer switch 7, the seventh transfer switch 15 and the eighth transfer switch 16 are separated, and the fifth transfer switch 8, the sixth transfer switch 9, the ninth transfer switch 17 and the tenth transfer switch 18 are closed.

[0103] When the voltage source converter is put into online inverter operation, the first transfer switch 4, the fourth transfer switch 7, the seventh transfer switch 15 and the eighth transfer switch 16 are open, and the fifth transfer switch 8, the sixth transfer switch 9, the ninth transfer switch 17 and the tenth transfer switch 18 are closed.

[0104] 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.

[0105] According to some embodiments, the voltage source valve assembly also includes a bypass switch 12, which connects the positive terminal P2 and the negative terminal N2 of the voltage source valve assembly, such as... Figure 3a As shown.

[0106] According to some embodiments, the voltage source type valve group further includes a first isolating switch 13, a second isolating switch 14, and a bypass switch 11, such as Figure 3b As shown. The first isolating switch 13 connects the positive terminal P2 and the positive input terminal P of the voltage source type valve group. The second isolating switch 14 connects the negative terminal N2 and the negative input terminal N of the voltage source type valve group. The bypass switch 11 connects the positive input terminal P and the negative input terminal N of the voltage source type valve group.

[0107] Figure 4a This is a schematic diagram of a voltage source type valve group including a multi-port DC circuit breaker according to an embodiment of this application. It includes a voltage source converter 1, a multi-port DC circuit breaker 19, a first valve 3, and a second valve 28, and is suitable for the positive terminal P1 of the voltage source converter 1 to be the high-voltage end.

[0108] exist Figure 1a Based on the embodiments, the DC circuit breaker 19 is a multi-port DC circuit breaker, having at least a unidirectional DC current interruption capability. The first valve 3 includes a first diode valve or a first thyristor valve; the first diode valve includes at least one diode connected in series, and 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, and the second thyristor valve includes at least one thyristor connected in series.

[0109] The voltage source converter 1 is connected in series with the main branch of the multi-port DC circuit breaker 19, and then connected in anti-parallel with the first valve 3. The voltage source converter 1 is also connected in series with the main branch of the multi-port DC circuit breaker 19, and then connected in anti-parallel with the second valve 28. In this anti-parallel connection, the positive terminal P1 of the voltage source converter 1 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 1 is connected to the anode A of the first valve 3 or the second valve 28, or connected through a resistor or a disconnect switch.

[0110] Specifically, such as Figure 4a As shown, the positive terminal P1 of the voltage source converter 1 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, and the negative terminal N1 of the voltage source converter 1 is connected to the anode A of the first valve 3. The third terminal E of the multi-port DC circuit breaker 19 is connected to the cathode K of the second valve 28, and the negative terminal N1 of the voltage source converter 1 is connected to the anode A of the second valve 28.

[0111] Optionally, the negative terminal N1 of the voltage source converter 1 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 the anode A of the first valve 3, and the positive terminal P1 of the voltage source converter 1 is connected to the cathode K of the first valve 3. The third terminal E of the DC circuit breaker 19 is connected to the anode A of the second valve 28, and the positive terminal P1 of the voltage source converter 1 is connected to the cathode K of the second valve 28, as shown below. Figure 4b As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0112] Figure 4c This is a schematic diagram of a voltage source valve group with a second two-port DC circuit breaker configured according to an embodiment of this application, which is suitable for the positive terminal P1 of the voltage source converter 1 as the high-voltage end.

[0113] exist Figure 1a Based on this, the voltage source type valve group also includes a second two-port DC circuit breaker 27 and a second valve 28. The voltage source converter 1 is connected in series with the second two-port DC circuit breaker 27 and the first two-port DC circuit breaker 2, and then connected in anti-parallel with the second valve 28.

[0114] Specifically, such as Figure 4c As shown, the first positive input terminal P of the voltage source type 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 voltage source type valve group is connected to the anode A of the second valve 28.

[0115] Optionally, in Figure 1c Based on this, the first negative input terminal N of the voltage source 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 the anode A of the second valve 28, and the first positive input terminal P of the voltage source valve group is connected to the cathode K of the second valve 28, as follows. Figure 4d As shown, the negative terminal N1 of the voltage source converter 1 is the high-voltage terminal.

[0116] Figure 5a This is a schematic diagram of a voltage source type valve group series circuit according to an embodiment of this application, including two... Figure 1aThe voltage source valve groups 29 and 37 shown are connected in series. The first negative input terminal N of the voltage source valve group 29 is connected to the first positive input terminal P of the voltage source valve group 37.

[0117] Figure 5b This is a schematic diagram of another voltage source type valve group series circuit according to an embodiment of this application, including two... Figure 4a The voltage source valve groups 38 and 39 shown are connected in series. The first negative input terminal N of the voltage source valve group 38 is connected to the first positive input terminal P of the voltage source valve group 39, the second negative input terminal N3 of the voltage source valve group 38 is connected to the second positive input terminal P3 of the voltage source valve group 39, and the first negative input terminal N and the second negative input terminal N3 of the voltage source valve group 39 are connected.

[0118] Figure 5c This is a schematic diagram of another voltage source type valve group series circuit according to an embodiment of this application, including two... Figure 4c The voltage source valve groups 47 and 48 shown are connected in series. The first negative input terminal N of the voltage source valve group 47 is connected to the first positive input terminal P of the voltage source valve group 48, and the second negative input terminal N3 of the voltage source valve group 47 is connected to the second positive input terminal P3 of the voltage source valve group 48. The first negative input terminal N and the second negative input terminal N3 of the voltage source valve group 48 are connected.

[0119] Figure 5d This is a schematic diagram of another voltage source type valve group series circuit according to an embodiment of this application, including... Figure 4a The voltage source type valve group 40 shown and Figure 1a The voltage source valve group 50 shown is connected in series. The first negative input terminal N of the voltage source valve group 40 is connected to the first positive input terminal P of the voltage source valve group 50, and the second negative input terminal N3 of the voltage source valve group 40 is connected to the first negative input terminal N of the voltage source valve group 50.

[0120] DC circuit breakers include, but are not limited to, hybrid DC circuit breakers, solid-state DC circuit breakers, or mechanical DC circuit breakers. Figure 6a 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.

[0121] The main branch includes, but is not limited to, a series-connected fast disconnect switch and / or a first power switch. For example... Figure 6aAs 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 employs a power device 67 with a forward and reverse series structure, possessing bidirectional DC current interruption capability. The 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 6a 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 power device 68 with a forward series structure, possessing the capability to unidirectionally interrupt DC current. The 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.

[0122] The first power switch includes at least one power device connected in series, which includes at least one of IGCT, IGBT, GTO, and MOSFET, but is not limited thereto.

[0123] The second power switch includes at least one power device connected in series, which includes at least one of IGCT, IGBT, GTO, MOSFET, and thyristor, but is not limited thereto.

[0124] 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.

[0125] Figure 6b 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.

[0126] The main branch includes, but is not limited to, a series-connected fast disconnect switch and / or a first power switch. For example... Figure 6b 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 uses a power device 78 with a forward series structure and has the ability to unidirectionally interrupt DC current. The power device 78 includes, but is not limited to, an IGBT and a diode anti-parallel circuit. The transfer branch 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 6bAs 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 power device 68 with a forward series structure, possessing unidirectional DC current interruption capability. The 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.

[0127] Figure 6c 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 solid-state DC circuit breaker, including a transfer branch 57 and an energy dissipation branch 58 connected in parallel. 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 6c 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 power device 68 with a forward series structure and has the ability to unidirectionally interrupt DC current. The 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.

[0128] Multi-port DC circuit breakers include multi-port hybrid DC circuit breakers or multi-port mechanical DC circuit breakers. Figure 6d 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 6a 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 power devices 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 6cAs 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 adopts a forward series structure switch 68, which has the capability to unidirectionally interrupt DC current. The power device 68 includes, but is not limited to, an anti-parallel circuit of IGBTs and diodes.

[0129] The energy-dissipating branch 58 includes, but is not limited to, surge arrester 77, used to suppress breaking overvoltage and absorb energy.

[0130] Figures 7a-7c This is a schematic diagram of various bypass switches according to embodiments of this application. The bypass switches include, but are not limited to, at least one of a mechanical switch, a mechanical knife switch, or at least one third power switch connected in series.

[0131] like Figure 7a As shown, the bypass switch includes a mechanical switch 92. (As indicated...) Figure 7b As shown, the bypass switch includes a third power switch and a mechanical switch 92 connected in series. (As...) Figure 7c As shown, the bypass switch includes a third power switch and a mechanical switch 92 connected in series, and also includes a mechanical switch 94 connected in parallel with this series circuit. The third power switch includes a power device 93 connected in series, which includes, but is not limited to, a thyristor. The third power switch includes at least one power device connected in series, which includes, but is not limited to, at least one of IGCT, IGBT, GTO, MOSFET, and thyristor.

[0132] Figures 8a-8b This is a schematic diagram of a disconnecting switch according to an embodiment of this application. The disconnecting switch includes, but is not limited to, at least one type of mechanical switch, mechanical knife switch, or fourth power switch. Figure 8a As shown, the disconnect switch includes a mechanical switch 94. (As indicated...) Figure 8b As shown, the disconnecting switch includes a fourth power switch and a mechanical switch 94 connected in series. The fourth power switch includes a power device 95 connected in series, which includes, but is not limited to, an anti-parallel circuit of an IGBT and a diode. The fourth power switch includes at least one power device connected in series, which includes, but is not limited to, at least one of IGCT, IGBT, GTO, and MOSFET.

[0133] Figure 9 This is a schematic flowchart of a control method for a voltage source valve assembly according to an embodiment of this application. The voltage source valve assembly is as follows: Figures 1a-1fAs shown in Figures 2a-2h and 3a-3b, the voltage source converter and the main branch of the DC circuit breaker are connected in series and then connected in anti-parallel with the first valve. The control method is as follows.

[0134] In S110, the DC circuit breaker 2 is turned on, the first valve 3 is turned off, and the voltage source converter 1 is controlled to operate in rectification or inversion mode.

[0135] 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.

[0136] The aforementioned DC faults include DC line faults.

[0137] 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 open; when out of fault, the voltage source converter 1 is also controlled to lock out.

[0138] If the voltage source valve group also includes a residual current disconnect switch, after the DC circuit breaker 2 is turned off, the residual current disconnect switches 60 and 70 are separated.

[0139] If the voltage source 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 turned off, the first valve 3 is turned on, and the bypass switch 12 is turned on. When the voltage source converter 1 is operating in rectification mode and then shut down due to a fault, the bypass switch 12 is turned on, the DC circuit breaker 2 is turned off, and the voltage source converter 1 is locked out.

[0140] If the voltage source type 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 turned on to control the DC circuit breaker 2 to turn off; when the fault occurs, the bypass switch 1 is also locked.

[0141] Optionally, voltage source converter 1 is not locked when it is taken out online, but operates in reactive power compensation mode.

[0142] In S140, when the voltage source converter 1 is in online rectification operation, the voltage source converter 1 is controlled to charge, the voltage source converter 1 is controlled to unlock, and the DC circuit breaker 2 is controlled to turn on.

[0143] 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.

[0144] Figure 10 This is a schematic flowchart of a control method for another voltage source valve assembly according to an embodiment of this application. The voltage source valve assembly is as follows: Figure 1g-1k As shown, the voltage source converter 1 is connected in series with the first valve 3 and then in parallel with the DC circuit breaker 2. The control method is as follows.

[0145] In S210, the DC circuit breaker 2 is turned off, the first valve 3 is turned on, and the voltage source converter 1 is turned on for inverter operation.

[0146] If the voltage source valve group also includes a residual current disconnect switch, after the DC circuit breaker 2 is turned off, the residual current disconnect switches 80 and 90 are separated.

[0147] In S220, when the voltage source converter 1 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.

[0148] 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.

[0149] Alternatively, if the voltage source 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 service due to a fault, the DC circuit breaker 2 is turned on and / or the bypass switch 12 is turned on; when out of service due to a fault, the voltage source converter 1 is also turned off.

[0150] Optionally, voltage source converter 1 is not locked when it is taken out online, but operates in reactive power compensation mode.

[0151] If the voltage source valve group also includes a residual current disconnect switch, before the DC circuit breaker 2 is turned on, the residual current disconnect switches 80 and 90 are closed.

[0152] 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.

[0153] If the voltage source valve group also includes a residual current disconnect switch, after the DC circuit breaker 2 is turned off, the residual current disconnect switches 80 and 90 are separated.

[0154] If the voltage source valve group also includes a bypass switch 12, the bypass switch 12 is turned off before the DC circuit breaker 2 is turned off.

[0155] Figures 2a-2h The voltage source valve group, after adding a changeover switch group, has the function of online inverter operation. For example... Figure 2a and Figure 2bIn the voltage source type valve group, when the voltage source converter 1 is put into online inverter operation, the second changeover switch 5 and the third changeover switch 6 are closed, the first changeover 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.

[0156] like Figure 2c and Figure 2d In the voltage source type valve group, when the voltage source converter 1 is put into online inverter operation, 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, the voltage source converter 1 is unlocked after charging, 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.

[0157] like Figure 2e and Figure 2f In the voltage source type valve group, when the voltage source converter 1 is put into online inverter operation, the second changeover switch 5, the ninth changeover switch 17 and the tenth changeover switch 18 are closed, the first changeover switch 4, 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.

[0158] like Figure 2g and Figure 2h In the voltage source type valve group, when the voltage source converter 1 is put into online inverter operation, 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.

[0159] 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.

[0160] Figure 11 This is a schematic diagram of a DC power transmission system according to an embodiment of this application.

[0161] like Figure 11As 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.

[0162] The rectifier station 100 includes a first DC pole I110, a second DC pole II120, a first AC system 140, and converter transformer incoming line switches (131, 132, 133 and 134), a metallic return line changeover switch 113, a ground return line changeover switch 190, and bipolar neutral zone isolating switches 174, 175, 184 and 185.

[0163] The first DC pole I110 includes a first high-side voltage source valve group 111, a first low-side voltage source valve group 112, a first high-side converter transformer 116, a first low-side 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-side voltage source valve group 111 and the first low-side voltage source valve group 112 are connected in series.

[0164] The first high-side voltage source valve group 111 includes a voltage source converter 1, a DC circuit breaker 2, a first valve 3, a bypass switch 11, a bypass switch 12, a first isolating switch 13, and a second isolating switch 14. The bypass switch 12 connects the positive and negative terminals of the first high-side voltage source valve group 111. The first isolating switch 13 connects the positive terminal and the first positive input terminal of the first high-side voltage source valve group 111. The second isolating switch 14 connects the negative terminal and the first negative input terminal of the first high-side voltage source valve group 111. The bypass switch 11 connects the first positive input terminal and the first negative input terminal of the first high-side voltage source valve group 111. The first low-side voltage source valve group 112 includes a voltage source converter 102, a DC circuit breaker 25, a first valve 26, a bypass switch 21, a bypass switch 22, a first isolating switch 23, and a second isolating switch 24. Bypass switch 22 connects to the positive and negative terminals of the first low-end voltage source valve group 112, first isolating switch 23 connects to the positive terminal and the first positive input terminal of the first low-end voltage source valve group 112, second isolating switch 24 connects to the negative terminal and the first negative input terminal of the first low-end voltage source valve group 112, and bypass switch 21 connects to the first positive input terminal and the first negative input terminal of the first low-end voltage source valve group 112.

[0165] The voltage source converter, DC circuit breaker, and first valve of the first high-end voltage source valve group 111 and the first low-end voltage source valve group 112 are connected in the following manner: Figure 1a The structure shown.

[0166] 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.

[0167] The second DC pole II120 includes a second low-end voltage source valve group 121, a second high-end voltage source 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 voltage source valve group 121 and the second high-end voltage source valve group 122 are connected in series.

[0168] The second high-end voltage source type valve group 122 includes a voltage source converter 104, a DC circuit breaker 45, a first valve 46, a bypass switch 41, a bypass switch 42, a first isolating switch 43, and a second isolating switch 44. The bypass switch 42 connects to the positive and negative terminals of the second high-end voltage source type valve group 122. The first isolating switch 43 connects to the positive terminal and the first positive input terminal of the second high-end voltage source type valve group 122. The second isolating switch 44 connects to the negative terminal and the first negative input terminal of the second high-end voltage source type valve group 122. The bypass switch 41 connects to the first positive input terminal and the first negative input terminal of the second high-end voltage source type valve group 122. The second low-end voltage source type valve group 121 includes a voltage source converter 103, a DC circuit breaker 35, a first valve 36, a bypass switch 31, a bypass switch 32, a first isolating switch 33, and a second isolating switch 34. Bypass switch 32 connects to the positive and negative terminals of the second low-end voltage source valve group 121. First isolating switch 33 connects to the positive terminal and the first positive input terminal of the second low-end voltage source valve group 121. Second isolating switch 34 connects to the negative terminal and the first negative input terminal of the second low-end voltage source valve group 121. Bypass switch 31 connects to the first positive input terminal and the first negative input terminal of the second low-end voltage source valve group 121. The voltage source converter, DC circuit breaker, and first valve of the second high-end voltage source valve group 122 and the second low-end voltage source valve group 121 are connected as follows: Figure 1c The structure shown.

[0169] The inverter station 200 includes a third DC pole I210, a fourth DC pole II220, a second AC system 240, and converter transformer incoming line switches (231, 232, 233, 234), a metallic return line switching switch 113, a ground return line switching switch 290, and bipolar neutral zone isolating switches 274, 275, 284, and 285.

[0170] The third DC pole I210 includes a third high-side voltage source valve group 211, a third low-side voltage source valve group 212, a third high-side converter transformer 216, a third low-side converter transformer 217, a third smoothing reactor 205, a third pole neutral bus switch 219, a third pole bus isolating switch 272, and a third DC line isolating switch 273. The third high-side voltage source valve group 211 and the third low-side voltage source valve group 212 are connected in series.

[0171] The third high-end voltage source type valve group 211 includes a voltage source converter 201, a DC circuit breaker 55, a first valve 56, a bypass switch 51, a bypass switch 52, a first isolating switch 53, and a second isolating switch 54. The bypass switch 52 connects to the positive and negative terminals of the third high-end voltage source type valve group 211; the first isolating switch 53 connects to the positive terminal and the first positive input terminal of the third high-end voltage source type valve group 211; the second isolating switch 54 connects to the negative terminal and the first negative input terminal of the third high-end voltage source type valve group 211; and the bypass switch 51 connects to the first positive input terminal and the first negative input terminal of the third high-end voltage source type valve group 211. The third low-end voltage source type valve group 212 includes a voltage source converter 202, a DC circuit breaker 65, a first valve 66, a bypass switch 61, a bypass switch 62, a first isolating switch 63, and a second isolating switch 64. Bypass switch 62 connects to the positive and negative terminals of the third low-end voltage source valve group 212; first isolating switch 63 connects to the positive terminal and the first positive input terminal of the third low-end voltage source valve group 212; second isolating switch 64 connects to the negative terminal and the first negative input terminal of the third low-end voltage source valve group 212; and bypass switch 61 connects to the first positive input terminal and the first negative input terminal of the third low-end voltage source valve group 212. The voltage source converter, DC circuit breaker, and first valve of the third high-end voltage source valve group 211 and the third low-end voltage source valve group 212 are connected as follows: Figure 1a The structure shown.

[0172] The fourth DC pole II 220 includes a fourth low-end voltage source valve group 221, a fourth high-end voltage source valve group 222, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a second smoothing reactor 206, a fourth pole neutral bus switch 229, a fourth pole bus isolating switch 282, and a fourth DC line isolating switch 283. The fourth low-end voltage source valve group 221 and the fourth high-end voltage source valve group 222 are connected in series.

[0173] The fourth high-side voltage source type valve group 222 includes a voltage source converter 204, a DC circuit breaker 85, a first valve 86, a bypass switch 81, a bypass switch 82, a first isolating switch 83, and a second isolating switch 84. The bypass switch 82 connects to the positive and negative terminals of the fourth high-side voltage source type valve group 222. The first isolating switch 83 connects to the positive terminal and the first positive input terminal of the fourth high-side voltage source type valve group 222. The second isolating switch 84 connects to the negative terminal and the first negative input terminal of the fourth high-side voltage source type valve group 222. The bypass switch 81 connects to the first positive input terminal and the first negative input terminal of the fourth high-side voltage source type valve group 222. The fourth low-side voltage source type valve group 221 includes a voltage source converter 203, a DC circuit breaker 75, a first valve 76, a bypass switch 71, a bypass switch 72, a first isolating switch 73, and a second isolating switch 74. Bypass switch 72 connects to the positive and negative terminals of the fourth low-end voltage source valve group 221, first isolating switch 73 connects to the positive terminal and the first positive input terminal of the fourth low-end voltage source valve group 221, second isolating switch 74 connects to the negative terminal and the first negative input terminal of the fourth high-end voltage source valve group 221, and bypass switch 71 connects to the first positive input terminal and the first negative input terminal of the fourth low-end voltage source valve group 221.

[0174] The voltage source converter, DC circuit breaker, and first valve of the fourth high-end voltage source valve group 222 and the fourth low-end voltage source valve group 221 are connected as follows: Figure 1c The structure is shown. The various switches mentioned above include at least one of mechanical switches, knife switches, DC circuit breakers, and thyristor valves.

[0175] like Figure 11 As shown, taking pole I of the DC transmission system as an example, the initial state is that the first high-end voltage source valve group 111 and the first low-end voltage source valve group 112 of the rectifier station 100 are in operation, and the third high-end voltage source valve group 211 and the third low-end voltage source valve group 212 of the inverter station 200 are in operation. The bypass switch 11 of the rectifier station 100 is open, the bypass switch 12 is open, the first isolating switch 13 is closed, the second isolating switch 14 is closed, the bypass switch 21 is open, the bypass switch 22 is open, the first isolating switch 23 is closed, and the second isolating switch 24 is closed. The bypass switch 51 of the inverter station 200 is open, the bypass switch 52 is open, the first isolating switch 53 is closed, the second isolating switch 54 is closed, the bypass switch 61 is open, the bypass switch 62 is open, the first isolating switch 63 is closed, and the second isolating switch 64 is closed.

[0176] Rectifier station 100 controls DC circuit breakers 2 and 25 to conduct, controls first valves 3 and 26 to close, and controls voltage source converters 1 and 102 to operate in rectification mode. Inverter station 200 controls DC circuit breakers 55 and 65 to conduct, controls first valves 56 and 66 to close, and controls voltage source converters 201 and 202 to operate in inverter mode.

[0177] When a DC fault occurs at voltage source converters 1 and 102 of rectifier station 100, DC circuit breakers 2 and 25 are turned off, and first valves 3 and 26 are turned on. To suppress fault current follow current, the first-pole neutral bus switch 119 may be switched off. After the fault is recovered or after the deionization time, the first-pole neutral bus switch 119 is reclosed, and DC circuit breakers 2 and 25 are turned on. When a DC fault occurs at voltage source converters 201 and 202 of inverter station 200, DC circuit breakers 55 and 65 are turned off, and first valves 56 and 66 are turned on. To suppress fault current follow current, the third-pole neutral bus switch 219 may be switched off. After the fault is recovered or after the deionization time, the third-pole neutral bus switch 219 is reclosed, and DC circuit breakers 55 and 65 are turned on.

[0178] When voltage source converter 1 of rectifier station 100 is taken offline, the control DC circuit breaker 2 is turned off, the control first valve 3 is turned on, and the control bypass switch 12 is turned on. When voltage source converter 1 of rectifier station 100 fails and is taken offline, the control bypass switch 12 is turned on, the control DC circuit breaker 2 is turned off, and the control voltage source converter 1 is locked. When voltage source converter 201 of inverter station 200 is taken offline or fails and is taken offline, the control bypass switch 52 is turned on, the control DC circuit breaker 55 is turned off, and the control voltage source converter 201 is locked. The inverter station 200 of the above-mentioned UHV flexible DC transmission system needs to be equipped with a transfer switch group to have the online connection function. When the voltage source converter is taken offline or fails and is put online, the rectifier station 100 and the inverter station 200 need to coordinate to achieve this.

[0179] Figure 12 This is a schematic diagram of another DC power transmission system according to an embodiment of this application.

[0180] exist Figure 11 Based on the embodiment, the voltage source converter, DC circuit breaker, and first valve of the third high-end voltage source valve group 211 and the third low-end voltage source valve group 212 are connected in the following manner: Figure 1g The structure shown; the voltage source converter, DC circuit breaker, and first valve of the fourth high-end voltage source valve group 222 and the fourth low-end voltage source valve group 221 are connected as follows: Figure 1h The structure shown.

[0181] like Figure 12 As shown, taking pole I of the DC transmission system as an example, the initial state is that the first high-end voltage source valve group 111 and the first low-end voltage source valve group 112 of the rectifier station 100 are in operation, and the third high-end voltage source valve group 211 and the third low-end voltage source valve group 212 of the inverter station 200 are in operation. The bypass switch 11 of the rectifier station 100 is open, the bypass switch 12 is open, the first isolating switch 13 is closed, the second isolating switch 14 is closed, the bypass switch 21 is open, the bypass switch 22 is open, the first isolating switch 23 is closed, and the second isolating switch 24 is closed. The bypass switch 51 of the inverter station 200 is open, the bypass switch 52 is open, the first isolating switch 53 is closed, the second isolating switch 54 is closed, the bypass switch 61 is open, the bypass switch 62 is open, the first isolating switch 63 is closed, and the second isolating switch 64 is closed.

[0182] Rectifier station 100 controls DC circuit breakers 2 and 25 to be turned on, controls first valve 3 and first valve 26 to be turned off, and controls voltage source converter 1 and voltage source converter 102 to operate in rectification mode. Inverter station 200 controls DC circuit breakers 55 and 65 to be turned off, controls first valve 56 and first valve 66 to be turned on, and controls voltage source converter 201 and voltage source converter 202 to operate in inverter mode.

[0183] When a DC fault occurs in voltage source converter 1 and voltage source converter 102 of rectifier station 100, DC circuit breakers 2 and 25 are turned off, and first valves 3 and 26 are turned on. To suppress the follow current of the fault, the polarity neutral bus switch 119 can be optionally turned on. After the fault is recovered or after the deionization time, the polarity neutral bus switch 119 is reclosed, and DC circuit breakers 2 and 25 are turned on. When a DC fault occurs in voltage source converter 201 and voltage source converter 202 of inverter station 200, first valves 56 and 66 reverse the fault current. After the fault is recovered or after the deionization time, first valves 56 and 66 are turned on.

[0184] When the voltage source converter 1 of rectifier station 100 is taken offline, the control DC circuit breaker 2 is turned off, the control first valve 3 is turned on, and the control bypass switch 12 is turned on. When the voltage source converter 1 of rectifier station 100 is taken offline due to a fault, the control bypass switch 12 is turned on, the control DC circuit breaker 2 is turned off, and the control voltage source converter 1 is locked. When the voltage source converter 201 of inverter station 200 performs online or fault-based offline operation, the control DC circuit breaker 55 is turned on and / or the control bypass switch 52 is turned on.

[0185] Initially, the first low-end voltage source valve group 112 of the rectifier station 100 is in operation, and the third low-end voltage source valve group 212 of the inverter station 200 is in operation. When the voltage source converter 1 of the rectifier station 100 is put into operation, the voltage source converter 1 is charged, the first valve 3 is turned on, the bypass switch 12 is turned off, and the current is transferred from the bypass switch 12 to the first valve 3. The voltage source converter 1 is then unlocked, and the DC circuit breaker 2 is turned on, transferring the current from the first valve 3 to the voltage source converter 1. When the voltage source converter 201 of the inverter station 200 is put into operation, the voltage source converter 201 is charged, the voltage source converter 201 is unlocked, the DC circuit breaker 55 is turned on, the bypass switch 52 is turned off, and the current is transferred from the bypass switch 52 to the DC circuit breaker 55. The DC circuit breaker 55 is then turned off, the first valve 56 is turned on, and the current is transferred from the DC circuit breaker 55 to the voltage source converter 201. When the voltage source converter is online, out of service due to a fault, or put into operation, the rectifier station 100 and the inverter station 200 need to coordinate to achieve this.

[0186] Figure 13 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 DC grid, including Station 1 310, Station 2 320, Station 3 330, Station 4 340, a first DC line 351, a second DC line 352, a third DC line 353, and a fourth DC line 354. Station 1 310 includes... Figure 4a The voltage source type valve assembly and neutral bus switches 315 and 316 shown in Figure 4a are included. The voltage source type valve assembly also includes a disconnecting switch 317. Station 2 320 includes the voltage source type valve assembly and neutral bus switches 325 and 326 shown in Figure 4a. The voltage source type valve assembly also includes a disconnecting switch 327. Station 330 includes... Figure 4a The voltage source type valve assembly and polarity bus switches 335 and 336 are shown. The voltage source type valve assembly also includes a disconnect switch 337. Station 4 340 includes... Figure 4a The voltage source type valve group and polarity bus switch 345 and 346 shown are included. The voltage source type valve group also includes disconnect switch 347.

[0187] like Figure 13 As shown, during normal operation, the DC circuit breakers 19, 322, 332, and 342 are controlled to be turned on, the first valves 3, 323, 333, and 343 are controlled to be turned off, the second valves 28, 324, 334, and 344 are controlled to be turned off, and the voltage source converters 1, 321, 331, and 341 are controlled to operate.

[0188] Taking a momentary fault in the first DC line 351 as an example, when the DC fault crosses through voltage source converter 1 and voltage source converter 321, the first terminal C and the second terminal D, the second terminal D and the third terminal E of the 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 DC circuit breaker 322 are controlled to be turned off, and the second valve 324 is controlled to be turned on. Optionally, the polarized neutral bus switch 315, the disconnect switch 317, the polarized neutral bus switch 326, and the disconnect switch 327 are used to quickly attenuate the fault current. After the fault is recovered or after the deionization time, the polarized neutral bus switch 315, the disconnect switch 317, the polarized neutral bus switch 326, and the disconnect switch 327 are reclosed, the first terminal C and the second terminal D, the second terminal D and the third terminal E of the DC circuit breaker 19 are controlled to be turned on, and the first terminal C and the third terminal E, the second terminal D and the third terminal E of the DC circuit breaker 322 are controlled to be turned on.

[0189] Taking a permanent fault in the first DC line 351 as an example, when the voltage source converter 1 and the 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 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 DC circuit breaker 322 are controlled to close, and the second valve 324 is controlled to open. Optionally, the polarity neutral bus switch 315, the disconnect switch 317, the polarity neutral bus switch 326, and the disconnect switch 327 are also controlled.

[0190] When the DC fault of the voltage source converter 1 is blocked, the first terminal C and the second terminal D, the first terminal C and the third terminal E of the DC circuit breaker 19 are turned off, and the voltage source converter 1 is blocked. Optionally, the first valve 3 is turned on.

[0191] Figure 14 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 1 360, Station 2 370, Station 3 380, Station 4 390, a first DC line 355, a second DC line 356, and a third DC line 357. Station 1 360 includes... Figure 5a The voltage source type valve group series circuit shown is equipped with a bypass switch and a neutral bus switch 369. Station 2 370 includes... Figure 5a The circuit shown is a voltage source type valve group series circuit equipped with bypass switches and polarity bus switches 379 and 358, and high-speed switches 301, 302, and 303. Station 380 includes... Figure 5a The circuit shown is a voltage source type valve group series circuit equipped with bypass switches and polarity bus switches 389 and 359, and high-speed switches 304, 305, and 306. Station 4 390 includes... Figure 5a The voltage source type valve group series circuit shown is equipped with a bypass switch and a neutral bus switch 399.

[0192] like Figure 14 As shown, during normal operation, high-speed switches 301, 302, 303, 304, 305, and 306 are closed, controlling DC circuit breakers 2, 366, 372, 376, 382, ​​386, 392, and 396 to conduct, controlling first valves 3, 367, 373, 377, 383, 387, 393, and 397 to close, and controlling voltage source converters 1, 365, 371, 375, 381, 385, 391, and 395 to operate.

[0193] Taking a momentary fault in the first DC line 355 as an example, when the DC fault crosses through the voltage source converter, the control circuit breakers 2, 366, 372, 376, 382, ​​386, 392, and 396 are turned off, while the control valves 3, 367, 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 reducing the stress on the DC circuit breakers. Optionally, the polarity neutral bus switch 369, polarity neutral bus switch 358, polarity neutral bus switch 379, polarity neutral bus switch 359, and polarity neutral bus switch 389 are also connected. The neutral bus switch 399 rapidly attenuates the fault current. After the fault is recovered or after the deionization time, the neutral bus switches 369, 358, 379, 389, and 399 are reclosed to control the conduction of DC circuit breakers 2, 366, 372, 376, 382, ​​386, 392, and 396.

[0194] When the DC fault of voltage source converter 1 is blocked, if the blocking of that pole is selected, the control of DC circuit breakers 2, 366, 372, 376, 382, ​​386, 392, and 396 will be turned off, the control of voltage source converter 1 will be blocked, the control of high-speed switch 301 will be opened, and the control of DC circuit breakers 372, 376, 382, ​​386, 392, and 396 will be turned on. Optionally, the polarity neutral bus switch 369 and polarity neutral bus switch 358 will be turned on.

[0195] Taking station 1 (360) and station 2 (370) as rectifiers and station 3 (380) and station 4 (390) as inverters as an example, when voltage source converter 1 is taken offline, bypass switches 384 and 394 are turned on, DC circuit breakers 2, 372, 382, ​​and 392 are turned off, first valve 3 and first valve 373 are turned on, and bypass switches 12 and 374 are turned on. Optionally, voltage source converters 1, 371, 381, and 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 bypass switches 384 and 394 are turned on, the DC circuit breakers 372, 382, ​​and 392 are turned off, the first valve 373 is turned on, the bypass switch 374 is turned on, and the voltage source converter 1 is locked. Optionally, the voltage source converters 371, 381, and 391 are locked.

[0196] The above-mentioned four-terminal UHV flexible DC transmission system requires the configuration of transfer switch groups at stations 380 and 390 to enable online commissioning.

[0197] Figure 15 This is a schematic diagram of yet 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 1 360, Station 2 370, Station 3 380, Station 4 390, a first DC line 355, a second DC line 356, and a third DC line 357. Station 1 360 includes... Figure 5a The voltage source type valve group series circuit shown is equipped with a bypass switch and a polarity bus switch 369; Station 2 370 includes Figure 5d The voltage source type valve group series circuit shown is equipped with a bypass switch, disconnect switch 311, and polarity bus switches 379 and 358; Station 380 includes Figure 5d The circuit shown includes a voltage source type valve group series circuit with bypass switch, disconnect switch 312, neutral bus switch 389, 359; Station 4 390 includes Figure 5a The voltage source type valve group series circuit shown is equipped with a bypass switch and a neutral bus switch 399.

[0198] like Figure 15 As shown, during normal operation, the following control functions are implemented: DC circuit breaker 2, DC circuit breaker 366, DC circuit breaker 372, DC circuit breaker 376, DC circuit breaker 27, DC circuit breaker 382, ​​DC circuit breaker 386, DC circuit breaker 307, DC circuit breaker 392, and DC circuit breaker 396 are turned on; the following control functions are implemented: first valve 3, first valve 367, first valve 373, first valve 377, second valve 28, first valve 383, first valve 387, second valve 308, first valve 393, and first valve 397 are turned off; and voltage source converters 1, 365, 371, 375, 381, 385, 391, and 395 are operated.

[0199] Taking a momentary fault in the first DC line 355 as an example, when the DC fault crosses through the voltage source converter, the control DC circuit breakers 2, 366, and 27 are turned off, and the control valves 3, 367, and 28 are turned on. Optionally, the polarity neutral bus switch 369, polarity neutral bus switch 358, and disconnector 311 are activated to rapidly attenuate the fault current. After the deionization time, the polarity neutral bus switch 369 is reclosed, and the control DC circuit breakers 2 and 366 are turned on. If the fault is recovered, the polarity neutral bus switch 358 and disconnector 311 are closed, and the control DC circuit breaker 27 is turned on. During the DC fault crossing process, stations 2 (370), 3 (380), and 4 (390) are isolated from the fault point through the DC circuit breaker 27, and their transmission power is not affected.

[0200] When a DC fault occurs in voltage source converter 1, if that pole is selected for blocking, control DC circuit breakers 2, 366, and 27 to turn off, and control voltage source converter 1 and voltage source converter 365 to be blocked. Optionally, the polarity neutral bus switch 369, polarity neutral bus switch 358, and trip switch 311 can be used. During the DC fault blocking process, stations 2 (370), 3 (380), and 4 (390) are isolated from the fault point through DC circuit breaker 27, and their power transmission is not affected.

[0201] Taking station 1 (360) and station 2 (370) as rectifiers and station 3 (380) and station 4 (390) as inverters as an example, when voltage source converter 1 is taken offline, bypass switches 384 and 394 are turned on, DC circuit breakers 2, 372, 382, ​​and 392 are turned off, first valve 3 and first valve 373 are turned on, and bypass switches 12 and 374 are turned on. Optionally, voltage source converters 1, 371, 381, and 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 bypass switches 384 and 394 are turned on, the DC circuit breakers 372, 382, ​​and 392 are turned off, the first valve 373 is turned on, the bypass switch 374 is turned on, and the voltage source converter 1 is locked. Optionally, the voltage source converters 371, 381, and 391 are locked.

[0202] The aforementioned four-terminal UHV flexible DC transmission system requires the configuration of transfer switch groups at stations 380 and 390 to enable online connection. DC circuit breakers 27 and 307 must meet the voltage rating requirements for voltage source type valve group series circuits.

[0203] Figure 16 This is a schematic diagram of a control device 400 for a voltage source type valve group provided in this application. The control device includes a detection unit 410 and a control unit 420.

[0204] The detection unit 410 is used to detect the operating parameters and faults of the voltage source valve group as described above, including the AC voltage, DC voltage, DC current, operating status of the voltage source converter 1, operating status of the DC circuit breaker 2, operating status of the first valve 3, and the positions of the switch and disconnector.

[0205] Based on the operating parameters of the voltage source valve group, 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 first valve, the control unit 420 controls the DC circuit breaker to turn on and the first valve to turn off during normal operation, thus controlling the voltage source converter to operate in rectification or inversion mode. The control unit 420 also controls the DC circuit breaker to turn off and the first valve to turn on during normal operation, based on the operating parameters of the voltage source valve group, if the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker, thus controlling the voltage source converter to operate inversion mode or to be put into online inversion mode.

[0206] The above embodiments are merely illustrative of the technical concept of this application and should not be construed as limiting the scope of protection of this application. Any modifications made to the technical solution based on the technical concept proposed in this application shall fall within the scope of protection of this application.

Claims

1. A voltage source type valve assembly, comprising: Voltage source converter, comprising at least three phases and six bridge arms; A DC circuit breaker, including a first two-port DC circuit breaker or a multi-port DC circuit breaker, wherein the DC circuit breaker includes: Main branch; the first two-port DC circuit breaker includes the main branch, 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; or / and The transfer branch includes a second power switch and / or an LC resonant circuit and / or a coupled negative voltage circuit connected in series; An energy-consuming branch is connected in parallel with the transfer branch, and the energy-consuming branch includes a surge arrester; The first valve includes a first diode valve or a first thyristor valve, wherein the first diode valve includes at least one diode connected in series, and the first thyristor valve includes at least one thyristor connected in series. The switching group allows the voltage source converter to be connected in series with the main branch of the DC circuit breaker and then anti-parallel with the first valve, for rectification or inversion operation of the voltage source converter; or the switching group allows the voltage source converter to be connected in series with the first valve and then parallel with the transfer branch of the DC circuit breaker, for inversion operation or online inversion operation of the voltage source converter; or the switching group allows the voltage source converter to be connected in parallel with the transfer branch of the DC circuit breaker, for online inversion operation of the voltage source converter.

2. The voltage source type valve assembly as described in claim 1, wherein, The voltage source converter includes 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 DC circuit breaker includes at least one of a hybrid DC circuit breaker, a solid-state DC circuit breaker, or a mechanical DC circuit breaker.

3. The voltage source type valve assembly as described in claim 1, wherein, The changeover switch group includes: The first transfer switch connects the positive terminal of the voltage source converter to 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 third transfer switch connects the positive terminal of the voltage source converter to the second terminal of the DC circuit breaker.

4. The voltage source type valve assembly as described in claim 1, wherein, The changeover switch group includes: The first transfer switch connects the negative terminal of the voltage source converter to the second terminal of the DC circuit breaker; The second transfer switch is connected to the positive terminal of the voltage source converter and the second terminal of the DC circuit breaker; The third transfer switch connects the negative terminal of the voltage source converter to the first terminal of the DC circuit breaker.

5. The voltage source type valve assembly as described in claim 1, wherein, The changeover switch group includes: The fourth changeover switch connects the positive terminal of the voltage source valve group to the second terminal of the DC circuit breaker; The fifth changeover switch connects the positive terminal of the voltage source valve group to the first terminal of the DC circuit breaker; The sixth changeover switch connects the negative terminal of the voltage source valve group to the second terminal of the DC circuit breaker.

6. The voltage source type valve assembly as described in claim 1, wherein, The changeover switch group includes: The fourth changeover switch connects the negative terminal of the voltage source valve group to the first terminal of the DC circuit breaker; The fifth changeover switch connects the negative terminal of the voltage source valve group to the second terminal of the DC circuit breaker; The sixth changeover switch connects the positive terminal of the voltage source valve group to the first terminal of the DC circuit breaker.

7. The voltage source type valve assembly as described in claim 5, wherein, The changeover switch group also includes: The first transfer switch connects the positive terminal of the voltage source converter to the first terminal of the DC circuit breaker; The seventh changeover switch connects the positive terminal of the voltage source valve assembly to the cathode of the first valve; The eighth changeover switch connects the negative terminal of the voltage source valve assembly to the anode of the first valve; The ninth changeover switch is connected to the positive terminal of the voltage source converter and the cathode of the first valve; The tenth changeover switch connects the positive terminal of the voltage source valve assembly to the anode of the first valve.

8. The voltage source type valve assembly as described in claim 6, wherein, The changeover switch group also includes: The first transfer switch connects the negative terminal of the voltage source converter to the second terminal of the DC circuit breaker; The seventh changeover switch connects the negative terminal of the voltage source valve assembly to the anode of the first valve; The eighth changeover switch connects the positive terminal of the voltage source valve assembly to the cathode of the first valve; The ninth changeover switch connects the negative terminal of the voltage source converter to the anode of the first valve; The tenth changeover switch connects the negative terminal of the voltage source valve assembly to the cathode of the first valve.

9. The voltage source type valve assembly as described in claim 1, wherein, The changeover switch group includes: The first transfer switch connects the positive terminal of the voltage source converter to 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 changeover switch connects the positive terminal of the voltage source valve assembly to the cathode of the first valve; The eighth changeover switch connects the negative terminal of the voltage source valve assembly to the anode of the first valve; The ninth changeover switch is connected to the positive terminal of the voltage source converter and the cathode of the first valve; The tenth changeover switch connects the positive terminal of the voltage source valve assembly to the anode of the first valve.

10. The voltage source type valve assembly as described in claim 1, wherein, The changeover switch group includes: The first transfer switch connects the negative terminal of the voltage source converter to the second terminal of the DC circuit breaker; The second transfer 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 connects the negative terminal of the voltage source valve assembly to the anode of the first valve; The eighth changeover switch connects the positive terminal of the voltage source valve assembly to the cathode of the first valve; The ninth changeover switch connects the negative terminal of the voltage source converter to the anode of the first valve; The tenth changeover switch connects the negative terminal of the voltage source valve assembly to the cathode of the first valve.

11. The voltage source type valve assembly as described in claim 1, wherein, 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 first valve; or the negative terminal of the voltage source converter is connected to the anode of the first valve.

12. The voltage source type valve assembly as described in claim 1, further comprising: The residual current disconnect switch is connected in series between the voltage source converter and the DC circuit breaker when the voltage source converter is connected in series with the main branch of the DC circuit breaker and then connected in antiparallel with the first valve, or / and 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.

13. The voltage source type valve assembly as described in claim 1, further comprising: A bypass switch is connected to the positive and negative terminals of the voltage source 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.

14. The voltage source type valve assembly as described in claim 1, further comprising: The first isolating switch connects the positive terminal of the voltage source valve group to the first positive input terminal; The second isolating switch is connected to the negative terminal of the voltage source valve group and the first negative input terminal; A bypass switch is connected to the first positive input terminal and the first negative input terminal of the voltage source valve group.

15. The voltage source type valve assembly as described in claim 1, wherein, If the DC circuit breaker is a multi-port DC circuit breaker, the voltage source valve group further includes: The second valve includes a second diode valve or a second thyristor valve. The second diode valve includes at least one diode connected in series, and the second thyristor valve includes at least one thyristor connected in series. The cathode of the second valve is the second positive input terminal of the voltage source valve group, and the anode of the second valve is the second negative input terminal of the voltage source valve group. If one of the voltage source valve groups constitutes a DC pole, 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.

16. The voltage source type valve assembly as described in claim 1, further comprising: Second two-port DC circuit breaker; The second valve includes a second diode valve or a second thyristor valve. The second diode valve includes at least one diode connected in series, and the second thyristor valve includes at least one thyristor connected in series. The cathode of the second valve is the second positive input terminal of the voltage source valve group, and the anode of the second valve is the second negative input terminal of the voltage source valve group. If one of the voltage source valve groups constitutes a DC pole, 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.

17. The voltage source type valve assembly as described in claim 15 or 16, further comprising: A resistor and / or a disconnecting switch are connected in series with the first valve and / or the second valve; or / and connected in series between the first negative input terminal and the second negative input terminal or between the first positive input terminal and the second positive input terminal of the voltage source valve group. The disconnecting switch includes at least one of a mechanical switch, a mechanical knife switch, and a fourth power switch connected in series.

18. A voltage source type valve group series circuit, comprising at least two of the voltage source type valve groups as described in any one of claims 1 to 17, wherein, The first negative input terminal of one voltage source valve group is connected to the first positive input terminal of another voltage source valve group.

19. The voltage source type valve group series circuit as described in claim 18, wherein, If both voltage source valve groups include a multi-port DC circuit breaker or a second two-port DC circuit breaker and a second valve, the second negative input terminal of one voltage source valve group is connected to the second positive input terminal of the other voltage source valve group.

20. The voltage source type valve group series circuit as described in claim 18, wherein, If the voltage source valve group includes a second two-port DC circuit breaker and a second valve, the second negative input terminal of the voltage source valve group is connected to the first negative input terminal of the other voltage source valve group, or the second positive input terminal of the voltage source valve group is connected to the first positive input terminal of the other voltage source valve group.

21. A DC transmission system comprising a voltage source valve group as described in any one of claims 1 to 17 or a voltage source valve group series circuit as described in any one of claims 18 to 20.

22. The DC transmission system as described in claim 21, wherein, The voltage source valve group or the series circuit of the voltage source valve group is connected in series with the neutral bus switch to the ground; the neutral bus switch includes at least one of a mechanical switch, a mechanical knife switch, and a fourth power switch connected in series.

23. A control method for a voltage source type valve group, wherein, The voltage source valve group includes: a voltage source converter, including at least three phases and six bridge arms; a DC circuit breaker, including a first two-port DC circuit breaker or a multi-port DC circuit breaker; a first valve, including a first diode valve or a first thyristor valve, wherein the first diode valve includes at least one diode connected in series, and the first thyristor valve includes at least one thyristor connected in series; 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; or the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker, and the control method includes: 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 first valve, 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. 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 first valve, when the voltage source converter is put into rectification operation online, the voltage source converter is controlled to charge, the voltage source converter is controlled to unlock, and the DC circuit breaker is controlled to turn on. When the voltage source converter is in rectifier operation and is either offline or out of fault, the DC circuit breaker is controlled to turn off and the first valve is controlled to open; when the fault is out, the voltage source converter is also controlled to lock out. 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. If the voltage source converter is connected in series with the first valve 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, and the voltage source converter is controlled to operate in inverter mode. If the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker, when the voltage source converter is put into online inverter operation, the voltage source converter is controlled to charge, the voltage source converter is controlled to unlock, the DC circuit breaker is controlled to turn off, and the first valve is controlled to turn on. 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 voltage source 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. 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.

24. The control method as described in claim 23, wherein, If the voltage source valve assembly also includes a bypass switch 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. 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.

25. The control method as described in claim 23, wherein, If the voltage source valve group further includes a disconnect switch or the DC transmission system in which the voltage source 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 control valve is turned on, the disconnect switch or the neutral bus switch is disconnected. After the fault is recovered or after the deionization time, the disconnect switch or the neutral bus switch is reclosed.

26. A control device for a voltage source type valve assembly as described in any one of claims 1 to 17, comprising: The detection unit is used to detect the operating parameters and faults of the voltage source valve group; Based on the operating parameters of the voltage source valve group, 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 first valve, during normal operation, the control unit 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; if the voltage source converter is connected in series with the first valve and then connected in parallel with the DC circuit breaker, during normal operation, the control unit controls the DC circuit breaker to close, controls the first valve to conduct, and controls the voltage source converter to operate inversion mode.

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