Direct current circuit breaker, voltage source converter and control method and device, power transmission system

Abstract

The application provides a direct current circuit breaker, a voltage source valve group, a control method and device, and a power transmission system. The direct current circuit breaker comprises a main branch, a forward transfer branch, a reverse transfer branch, and an energy consumption branch. The main branch comprises a first fast isolating switch. The forward transfer branch comprises at least one diode connected in series or at least one thyristor connected in series. The reverse transfer branch comprises a first power switch and / or a first inductor and / or a first capacitor connected in series and / or a coupled negative voltage circuit. The energy consumption branch comprises a lightning arrester. The direct current circuit breaker comprises a positive terminal and a negative terminal. The main branch, the forward transfer branch, the reverse transfer branch, and the energy consumption branch are connected to the positive terminal and the negative terminal or are connected to the positive terminal and the negative terminal through a conversion switch group. Alternatively, the diodes or thyristors of the forward transfer branch, the first power switch of the reverse transfer branch, and the lightning arrester of the energy consumption branch are connected in parallel in sections and then connected in series, and then connected to the positive terminal and the negative terminal or connected to the positive terminal and the negative terminal through a conversion switch group.

Description

Technical Field

[0001] This application relates to the fields of flexible DC transmission and hybrid DC transmission technology, specifically to DC circuit breakers, voltage source valve groups and control methods and devices, 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 suitability for long-distance overhead line transmission. Flexible DC transmission uses two-level and three-level VSCs (Voltage Source Converters) or MMCs (Modular Multilevel Converters) based on half-bridge sub-modules. When a short circuit occurs on the DC side, even if all control devices are locked, the converter will still feed current to the fault point through diodes connected in anti-parallel with the control devices. Existing solutions use DC circuit breakers to clear the fault, but existing DC circuit breakers bidirectionally cut off the DC current through transfer branches. During the DC line restart process, the DC circuit breakers at the inverter station need to be turned off and on multiple times, increasing the overload stress on the energy-consuming branches. Furthermore, DC circuit breakers cannot be used to achieve online commissioning and decommissioning of the converter. Flexible DC transmission uses a hybrid MMC structure of half-bridge submodules and full-bridge submodules. Although it has DC fault ride-through capability and can realize online commissioning and decommissioning of converters, the cost of converters is increased, and the losses are greater than those of MMC based on half-bridge submodules and DC circuit breakers. Summary of the Invention

[0004] This application provides a DC circuit breaker, including a main branch, a forward transfer branch, a reverse transfer branch, and a power dissipation branch. The main branch includes a first fast disconnect switch. The forward transfer branch includes at least one diode or at least one thyristor connected in series. The reverse transfer branch includes a first power switch and / or a first inductor and / or a first capacitor and / or a coupled negative voltage circuit connected in series. The power dissipation branch includes a surge arrester. The DC circuit breaker includes a positive terminal and a negative terminal. The main branch, forward transfer branch, reverse transfer branch, and power dissipation branch are respectively connected to the positive terminal and the negative terminal, or connected to the positive terminal and the negative terminal through a group of changeover switches. Alternatively, the diode or thyristor of the forward transfer branch, and / or the first power switch of the reverse transfer branch, and / or the surge arrester of the power dissipation branch are connected in parallel in sections and then in series, and then connected to the positive terminal and the negative terminal of the main branch, or connected to the positive terminal and the negative terminal through a group of changeover switches.

[0005] According to some embodiments, the DC circuit breaker further includes a third terminal for connecting to an external circuit. The reverse transfer branch and the energy-consuming branch and / or the forward transfer branch are connected to the third terminal through a changeover switch group. Alternatively, the circuit after the diode or thyristor of the forward transfer branch is connected in antiparallel with the first power switch of the reverse transfer branch and the energy-consuming branch are connected to the third terminal through a changeover switch group.

[0006] According to some embodiments, the main branch further includes a second power switch, which is connected in series with the first fast disconnect switch. The second power switch at least unidirectionally blocks the DC current. The second power switch includes at least one of IGBT, IGCT, GTO, MOSFET, anti-parallel circuit of IGBT and diode, anti-parallel circuit of IGCT and diode, anti-parallel circuit of GTO and diode, and anti-parallel circuit of MOSFET and diode.

[0007] According to some embodiments, the forward transfer branch further includes a third power switch and / or a second fast disconnect switch, which are connected in series with at least one diode or at least one thyristor connected in series. The third power switch includes at least one of IGBT, IGCT, GTO, MOSFET, anti-parallel circuit of IGBT and diode, anti-parallel circuit of IGCT and diode, anti-parallel circuit of GTO and diode, and anti-parallel circuit of MOSFET and diode.

[0008] According to some embodiments, the reverse transfer branch further includes a resistor and / or a second inductor and / or a second capacitor connected in series, which are connected in parallel with the series circuit of the first power switch and / or the first inductor and / or the first capacitor and / or the coupling negative voltage circuit.

[0009] According to some embodiments, the transfer switch group includes a first transfer switch, a second transfer switch, a third transfer switch, and a fourth transfer switch. The first transfer switch is connected to the negative terminal of the DC circuit breaker and the negative terminal of the reverse transfer branch. The second transfer switch is connected to the positive terminal of the DC circuit breaker and the positive terminal of the reverse transfer branch. The third transfer switch is connected to the positive terminal of the DC circuit breaker and the negative terminal of the reverse transfer branch, or to the negative terminal of the DC circuit breaker and the positive terminal of the reverse transfer branch. The fourth transfer switch is connected to the third terminal of the DC circuit breaker and the positive terminal of the reverse transfer branch, or to the third terminal of the DC circuit breaker and the negative terminal of the reverse transfer branch. The third terminal of the DC circuit breaker is used to connect to an external circuit.

[0010] According to some embodiments, the DC circuit breaker further includes a residual current disconnect switch connected in series between the positive terminal of the DC circuit breaker and the parallel circuit of the main branch, the forward transfer branch, the reverse transfer branch and the energy-consuming branch.

[0011] According to some embodiments, the DC circuit breaker further includes a bypass branch, which connects the positive terminal of the DC circuit breaker to the third terminal of the DC circuit breaker or connects the negative terminal of the DC circuit breaker to the third terminal of the DC circuit breaker. The bypass branch includes at least one of a mechanical switch, a mechanical knife switch, at least one fourth power switch connected in series, or at least one diode connected in series. The first power switch and the fourth power switch include at least one of an IGBT, an IGCT, a GTO, a MOSFET, a thyristor, an anti-parallel circuit of an IGBT and a diode, an anti-parallel circuit of an IGCT and a diode, an anti-parallel circuit of a GTO and a diode, an anti-parallel circuit of a MOSFET and a diode, and an anti-parallel circuit of a thyristor and a diode.

[0012] According to some embodiments, the transfer switch group further includes a fifth transfer switch, a sixth transfer switch, a seventh transfer switch, and an eighth transfer switch. The fifth transfer switch is connected to the negative terminal of the DC circuit breaker and the negative terminal of the forward transfer branch; the sixth transfer switch is connected to the positive terminal of the DC circuit breaker and the positive terminal of the forward transfer branch; the seventh transfer switch is connected to the positive terminal of the DC circuit breaker and the negative terminal of the forward transfer branch, or connected to the negative terminal of the DC circuit breaker and the positive terminal of the forward transfer branch; the eighth transfer switch is connected to the positive terminal of the forward transfer branch and the third terminal of the DC circuit breaker, or connected to the negative terminal of the forward transfer branch and the third terminal of the DC circuit breaker.

[0013] This application embodiment also provides a voltage source type valve group, including a DC circuit breaker and a voltage source converter as described above, wherein the voltage source converter is connected in series with the main branch of the DC circuit breaker, and the voltage source converter includes at least three phases and six bridge arms.

[0014] According to some embodiments, the high-voltage terminal of the voltage source converter is connected to the main branch of the DC circuit breaker, and the high-voltage terminal of the voltage source converter is either a positive high-voltage terminal or a negative high-voltage terminal.

[0015] According to some embodiments, if the DC circuit breaker has a third terminal, the third terminal of the DC circuit breaker is connected to the low-voltage terminal of the voltage source converter, and the low-voltage terminal of the voltage source converter is either a positive low-voltage terminal or a negative low-voltage terminal.

[0016] 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 connects the positive input terminal of the voltage source valve group to the DC circuit breaker or the voltage source converter; the second isolating switch connects the negative input terminal of the voltage source valve group to the voltage source converter or the DC circuit breaker; and the bypass switch connects the positive input terminal and the negative input terminal of the voltage source valve group.

[0017] This application also provides a DC power transmission system, including the voltage source type valve group as described above.

[0018] This application embodiment also provides a control method for the voltage source valve group as described above, including: controlling the main branch and / or forward transfer branch and / or reverse transfer branch of the DC circuit breaker to conduct, and controlling the operation of the voltage source converter; when the voltage source converter experiences a DC fault, controlling the main branch of the DC circuit breaker to turn off and the reverse transfer branch to turn off, and after the fault is recovered or after a deionization time, controlling the main branch and / or forward transfer branch and / or reverse transfer branch of the DC circuit breaker to conduct; when the voltage source converter is fault-locked, controlling the main branch of the DC circuit breaker to turn off, controlling the reverse transfer branch of the DC circuit breaker to turn off, and controlling the voltage source converter to lock out.

[0019] According to some embodiments, if the DC circuit breaker further includes a bypass branch, the control method further includes: when the voltage source converter is operating in online shutdown or fault shutdown mode, controlling the bypass branch of the DC circuit breaker to be turned on, and controlling the main branch and reverse transfer branch of the DC circuit breaker to be turned off.

[0020] According to some embodiments, the DC fault includes a DC line fault. In the case of the DC line fault, after the deionization time, if the voltage source converter is operating in rectification mode, the reverse transfer branch of the DC circuit breaker is controlled to be turned on; if the voltage source converter is operating in inverter mode, the forward transfer branch of the DC circuit breaker is controlled to be turned on.

[0021] According to some embodiments, if the transfer switch group includes a first transfer switch, a second transfer switch, a third transfer switch, and a fourth transfer switch, then when the voltage source converter is operating in inverter mode, the first and second transfer switches are controlled to close, and the third and fourth transfer switches are controlled to open; when the voltage source converter is operating in online inverter mode, the following are included: controlling the first and second transfer switches to open, controlling the third and fourth transfer switches to close; controlling the voltage source converter to charge; controlling the voltage source converter to unlock; controlling the reverse transfer branch to conduct; controlling the forward transfer branch to conduct; controlling the reverse transfer branch to turn off; controlling the third and fourth transfer switches to open, controlling the first and second transfer switches to close, and controlling the main branch to conduct.

[0022] According to some embodiments, if the DC circuit breaker further includes a bypass branch, when the voltage source converter is operating in online inverter mode, after the reverse transfer branch is turned on, the bypass branch is turned off.

[0023] According to some embodiments, if the DC circuit breaker further includes a bypass branch and the bypass branch includes at least one fourth power switch or at least one diode connected in series, having forward withstand voltage and reverse conduction current capability, when the voltage source converter is operating in online rectification mode, the bypass branch is controlled to conduct in reverse, the voltage source converter is controlled to charge, the voltage source converter is controlled to unlock, the reverse transfer branch is controlled to conduct, and the main branch is controlled to conduct.

[0024] According to some embodiments, if the switching group includes a fifth switching switch, a sixth switching switch, a seventh switching switch, and an eighth switching switch, when the voltage source converter is operating in online rectification mode, the fifth and sixth switching switches are controlled to open, and the seventh and eighth switching switches are controlled to close; the voltage source converter is controlled to charge, the voltage source converter is controlled to unlock, the reverse transfer branch is controlled to conduct, and the main branch is controlled to conduct.

[0025] According to some embodiments, if the changeover switch group includes a first changeover switch, a second changeover switch, a third changeover switch, a fourth changeover switch, a fifth changeover switch, a sixth changeover switch, a seventh changeover switch, and an eighth changeover switch, when the voltage source converter is operating in inverter or rectifier mode, the first changeover switch, the second changeover switch, the fifth changeover switch, and the sixth changeover switch are controlled to close, and the third changeover switch, the fourth changeover switch, the seventh changeover switch, and the eighth changeover switch are controlled to open.

[0026] This application embodiment also provides a control device for a 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, the control unit controls the main branch and / or forward transfer branch and / or reverse transfer branch of the DC circuit breaker to conduct, and controls the operation of the voltage source converter. When the DC fault of the voltage source converter crosses through, the control unit controls the main branch of the DC circuit breaker to turn off and controls the reverse transfer branch of the DC circuit breaker to turn off. After the fault is recovered or after the deionization time, the control unit controls the main branch and / or forward transfer branch and / or reverse transfer branch of the DC circuit breaker to conduct. When the voltage source converter is fault-locked, the control unit controls the main branch of the DC circuit breaker to turn off and controls the reverse transfer branch of the DC circuit breaker to turn off, and controls the voltage source converter to lock out.

[0027] The technical solution provided in this application embodiment allows the DC circuit breaker to unidirectionally interrupt DC current. It reduces the number of load-bearing shutdowns by utilizing the reverse blocking capability of the forward transfer branch and uses the bypass branch to transfer DC current to assist in interrupting current in the other direction. At the same time, it enables online commissioning, online decommissioning, and fault decommissioning of voltage source converters that do not have full-range voltage regulation capability. This allows it to be applied to UHVDC transmission systems with multiple voltage source converters connected in series. The efficiency of the voltage source type valve group is higher than that of the existing MMC solution based on a mixture of half-bridge submodules and full-bridge submodules. Attached Figure Description

[0028] 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.

[0029] Figure 1 This is a schematic diagram of a DC circuit breaker provided in an embodiment of this application.

[0030] Figure 2a This is a schematic diagram of a main branch provided in an embodiment of this application.

[0031] Figure 2b This is another schematic diagram of the main branch provided in the embodiments of this application.

[0032] Figures 3a-3d These are schematic diagrams of various forward transfer branches provided in the embodiments of this application.

[0033] Figure 4a This is a schematic diagram of a reverse transfer branch provided in an embodiment of this application.

[0034] Figure 4bThis is a schematic diagram of another reverse transfer branch provided in an embodiment of this application.

[0035] Figure 5 This is a schematic diagram of an energy-consuming branch provided in an embodiment of this application.

[0036] Figures 6a-6c This is a schematic diagram of a segmented parallel forward transfer branch and / or reverse transfer branch and / or energy-consuming branch provided in an embodiment of this application.

[0037] Figure 7 This is a schematic diagram of another DC circuit breaker provided in an embodiment of this application.

[0038] Figures 8a-8b This is a schematic diagram of another DC circuit breaker provided in the embodiments of this application.

[0039] Figures 9a-9e These are schematic diagrams of various bypass branches provided in the embodiments of this application.

[0040] Figure 10 This is a schematic diagram of another DC circuit breaker provided in the embodiments of this application.

[0041] Figures 11a-11g This is a schematic diagram of various voltage source type valve groups provided in the embodiments of this application.

[0042] Figure 12a This is a DC power transmission system provided in the embodiments of this application.

[0043] Figure 12b This is another DC power transmission system provided in the embodiments of this application.

[0044] Figure 13 This is a schematic flowchart of a control method for a voltage source valve group provided in an embodiment of this application.

[0045] Figure 14 This is a schematic diagram of a control method for another voltage source valve group provided in an embodiment of this application.

[0046] Figure 15 This is a schematic flowchart of another control method for a voltage source type valve group provided in the embodiments of this application.

[0047] Figure 16 This is a schematic diagram of a control device for a voltage source type valve group provided in an embodiment of this application. Detailed Implementation

[0048] 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.

[0049] 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, 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.

[0050] Figure 1 This is a schematic diagram of a DC circuit breaker provided in an embodiment of this application, including a main branch 1, a forward transfer branch 2, a reverse transfer branch 3, and an energy dissipation branch 4.

[0051] like Figure 1 As shown, the DC circuit breaker has two ends, a positive terminal A and a negative terminal B. The main branch 1, the forward transfer branch 2, the reverse transfer branch 3 and the energy dissipation branch 4 are connected in parallel between the positive terminal A and the negative terminal B.

[0052] Main branch 1 includes the first fast disconnect switch 5, such as Figure 2a As shown. The two ends of the main branch 1 are A1 and B1, respectively.

[0053] Optionally, the main branch includes a second power switch 27 and a first fast disconnect switch 5 connected in series, such as... Figure 2b As shown. The second power switch 27 at least unidirectionally blocks the DC current. The second power switch 27 adopts an IGBT (Insulated Gate Bipolar Transistor) and a diode anti-parallel circuit.

[0054] Forward transfer branch 2 includes at least one diode 7 or at least one thyristor 8 connected in series, respectively as follows: Figure 3a Or as shown in 3b. The forward transfer branch 2 has at least one-way flow. The two ends of the forward transfer branch 2 are A2 and B2, respectively.

[0055] Optionally, the forward transfer branch 2 further includes a third power switch 28 and / or a second fast disconnect switch, wherein the third power switch 28 and / or the second fast disconnect switch are connected in series with at least one diode 7 or at least one thyristor 8. The third power switch 28 employs an IGBT and diode anti-parallel circuit, such as... Figure 3c As shown.

[0056] Optionally, the third power switch 28 can also be connected in parallel with the thyristor 8 and then in series with at least one diode 7, such as... Figure 3d As shown. The third power switch 28 is unidirectionally controllable to turn on and off. When the third power switch 28 is over-voltage, the thyristor 8 is forcibly triggered to protect the third power switch 28.

[0057] The reverse transfer branch 3 includes a first power switch 6 connected in series and / or a first inductor and / or a first capacitor and / or a coupling negative voltage circuit, such as Figure 4a As shown. The reverse transfer branch 3 can carry current in one or both directions, or at least be controllably shut off in one direction. The two ends of the reverse transfer branch 3 are A3 and B3, respectively.

[0058] Optionally, the reverse transfer branch 3 further includes a resistor 9 and / or a second inductor and / or a second capacitor 10 connected in series, connected in parallel with the series circuit of the first power switch 6 and / or the first inductor and / or the first capacitor and / or the coupling negative voltage circuit. The first power switch 6 adopts an IGBT and diode anti-parallel circuit, such as... Figure 4b As shown.

[0059] Energy-consuming branch 4 includes surge arrester 11, such as Figure 5 As shown. The two ends of the energy-consuming branch 4 are A4 and B4, respectively.

[0060] According to some embodiments, the diodes or thyristors of the forward transfer branch, and / or the first power switch of the reverse transfer branch, and / or the surge arresters of the energy-consuming branch are connected in parallel and then in series in sections, and then connected to the positive and negative terminals of the DC circuit breaker respectively with the main branch, or connected to the positive and negative terminals of the DC circuit breaker through a changeover switch group.

[0061] like Figure 6a As shown, the diode 7 or thyristor connected in series in the forward transfer branch 2 is connected in antiparallel to the first power switch 6 connected in series in the reverse transfer branch 3. The antiparallel circuit is connected to the positive terminal A and the negative terminal B of the DC circuit breaker. Figure 6a The first power switch 6 in the system uses IGCT (Integrated Gate Commutated Thyristors), but is not limited to this.

[0062] The first power switch 6 includes, but is not limited to, at least one of the following: IGBT, IGCT, GTO (Gate Turn-Off Thyristor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), thyristor, anti-parallel circuit of IGBT and diode, anti-parallel circuit of IGCT and diode, anti-parallel circuit of GTO and diode, and anti-parallel circuit of MOSFET and diode. The second power switch 27 and the third power switch 28 include, but are not limited to, at least one of the following: IGBT, IGCT, GTO, MOSFET, anti-parallel circuit of IGBT and diode, anti-parallel circuit of IGCT and diode, anti-parallel circuit of GTO and diode, and anti-parallel circuit of MOSFET and diode.

[0063] like Figure 6b As shown, the multiple first power switches 6 connected in series in the reverse transfer branch and the surge arresters 11 in the energy dissipation branch are connected in parallel. The parallel circuit is connected to the positive terminal A and the negative terminal B of the DC circuit breaker. Figure 6b The first power switch 6 in the circuit uses an IGCT, but is not limited to this.

[0064] like Figure 6c As shown, the diodes 7 or thyristors connected in series in the forward transfer branch 2 are respectively connected in antiparallel to the first power switch 6 connected in series in the reverse transfer branch 3. After multiple antiparallel connections, they are then connected in parallel to the surge arrester 11 of the energy dissipation branch. The parallel circuit is connected to the positive terminal A and the negative terminal B of the DC circuit breaker. Figure 6c The first power switch 6 in the circuit uses an IGBT, but this is not a limitation.

[0065] Figure 7 This is a schematic diagram of another DC circuit breaker provided in an embodiment of this application, including a main branch 1, a forward transfer branch 2, a reverse transfer branch 3, an energy dissipation branch 4, and a transfer switch group. The composition of the main branch 1, the forward transfer branch 2, the reverse transfer branch 3, and the energy dissipation branch 4 is similar to... Figure 1 The implementation methods are the same.

[0066] like Figure 7 As shown, the DC circuit breaker has three terminals: a positive terminal A, a negative terminal B, and a third terminal C. The third terminal is used to connect to an external circuit. The main branch 1, the forward transfer branch 2, the reverse transfer branch 3, and the energy-consuming branch 4 are connected to the positive terminal A, the negative terminal B, and the third terminal C through a changeover switch group.

[0067] The two ends A1 and B1 of the main branch 1 are connected to the positive terminal A and negative terminal B of the DC circuit breaker.

[0068] The two ends of the forward transfer branch 2 are A2 and B2, respectively, which are connected to the positive terminal A and the negative terminal B of the DC circuit breaker.

[0069] The reverse transfer branch 3 and the energy-consuming branch 4 are connected in parallel.

[0070] The changeover switch group includes a first changeover switch 13, a second changeover switch 14, a third changeover switch 15, and a fourth changeover switch 16.

[0071] The first changeover switch 13 connects the negative terminal B of the DC circuit breaker to the negative terminal B3 of the reverse transfer branch. The second changeover switch 14 connects the positive terminal A of the DC circuit breaker to the positive terminal A3 of the reverse transfer branch. The third changeover switch 15 connects the positive terminal A of the DC circuit breaker to the negative terminal B3 of the reverse transfer branch. The fourth changeover switch 16 connects the third terminal C of the DC circuit breaker to the positive terminal A3 of the reverse transfer branch.

[0072] Figure 8a This is a schematic diagram of another DC circuit breaker provided in the embodiments of this application.

[0073] exist Figure 7 Based on the embodiment, the DC circuit breaker also includes a bypass branch 17, which connects the positive terminal A and the third terminal C of the DC circuit breaker.

[0074] Bypass branch 17 includes, but is not limited to, at least one of a mechanical switch, a mechanical knife switch, at least one fourth power switch connected in series, or at least one diode connected in series. The fourth power switch includes, but is not limited to, at least one of an IGBT, an IGCT, a GTO, a MOSFET, a thyristor, an anti-parallel circuit of an IGBT and a diode, an anti-parallel circuit of an IGCT and a diode, an anti-parallel circuit of a GTO and a diode, an anti-parallel circuit of a MOSFET and a diode, or an anti-parallel circuit of a thyristor and a diode.

[0075] Bypass branch 17 includes mechanical switch 12, such as Figure 9a As shown, the two ends of the bypass branch 17 are A5 and B5, respectively.

[0076] Bypass branch 17 includes a fourth power switch 29 and a mechanical switch 12 connected in series, such as Figure 9b As shown.

[0077] Bypass branch 17 includes at least one diode 7 connected in series, such as Figure 9c As shown.

[0078] The bypass branch 17 includes a series circuit of the fourth power switch 29 and the mechanical switch 12, and is connected in anti-parallel to the series circuit of at least one diode 7, such as... Figure 9d As shown.

[0079] exist Figure 9dBased on the embodiment, the bypass branch 17 also includes a mechanical switch 36, which is connected in parallel with the anti-parallel circuit, such as... Figure 9e As shown.

[0080] The fourth power switch 29 includes, but is not limited to, at least one of IGBT, IGCT, GTO, MOSFET, thyristor, anti-parallel circuit of IGBT and diode, anti-parallel circuit of IGCT and diode, anti-parallel circuit of GTO and diode, anti-parallel circuit of MOSFET and diode, and anti-parallel circuit of thyristor and diode.

[0081] exist Figure 8a Based on the embodiment, the DC circuit breaker also includes a residual current disconnect switch 57, such as Figure 8b As shown, it is connected in series between the positive terminal A of the DC circuit breaker and the parallel circuit of main branch 1, forward transfer branch 2, reverse transfer branch 3 and energy-consuming branch 4.

[0082] Figure 10 This is a schematic diagram of another DC circuit breaker provided in the embodiments of this application.

[0083] exist Figure 8a Based on the embodiment, the changeover switch also includes a fifth changeover switch 18, a sixth changeover switch 19, a seventh changeover switch 20, and an eighth changeover switch 21.

[0084] The fifth changeover switch 18 connects the negative terminal B of the DC circuit breaker to the negative terminal B2 of the forward transfer branch. The sixth changeover switch 19 connects the positive terminal A of the DC circuit breaker to the positive terminal A2 of the forward transfer branch. The seventh changeover switch 20 connects the positive terminal A of the DC circuit breaker to the negative terminal B2 of the forward transfer branch. The eighth changeover switch 21 connects the positive terminal A2 of the forward transfer branch to the third terminal C of the DC circuit breaker.

[0085] Figure 11a This is one of the schematic diagrams of a voltage source valve group provided in the embodiments of this application, including a voltage source converter 22 and a DC circuit breaker 23. The DC circuit breaker 23 adopts... Figure 1 The structure of a DC circuit breaker.

[0086] The voltage source converter 22 includes, but is not limited to, at least one of a two-level converter, a three-level converter, a modular multilevel converter based on a half-bridge submodule, a diode-clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter. The voltage source converter 22 includes at least three phases and six bridge arms, and cannot regulate the DC voltage to zero or negative voltage.

[0087] Figure 11aThe positive terminal P1 of the voltage source converter 22 is the high-voltage terminal, and the negative terminal N1 is the low-voltage terminal. The positive terminal P1 of the voltage source converter 22 is connected to the negative terminal B of the DC circuit breaker 23. The positive terminal A of the DC circuit breaker 23 and the negative terminal N1 of the voltage source converter 22 are the two input terminals of the voltage source valve group: the positive input terminal P and the negative input terminal N.

[0088] Optionally, the positive terminal P1 of the voltage source converter 22 is the low-voltage end, and the negative terminal N1 is the high-voltage end. The negative terminal N1 of the voltage source converter 22 is connected to the positive terminal A of the DC circuit breaker 23. The positive terminal P1 of the voltage source converter 22 and the negative terminal B of the DC circuit breaker 23 are the two input terminals of the voltage source valve group: the positive input terminal P and the negative input terminal N, as shown below. Figure 11b As shown.

[0089] It should be noted that the aforementioned high-voltage end and low-voltage end are high-voltage and low-voltage potentials presented to ground, and the high-voltage end includes the positive high-voltage end and the negative high-voltage end.

[0090] Figure 11c This is a schematic diagram of a voltage source valve group provided in the embodiments of this application, including a voltage source converter 22 and a DC circuit breaker 23. The DC circuit breaker 23 adopts... Figure 8a The structure of a DC circuit breaker.

[0091] The voltage source converter 22 includes, but is not limited to, at least one of a two-level converter, a three-level converter, a modular multilevel converter based on a half-bridge submodule, a diode-clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter. The voltage source converter 22 includes at least three phases and six bridge arms, and cannot regulate the DC voltage to zero or negative voltage.

[0092] Figure 11c The positive terminal P1 of the voltage source converter 22 is the high-voltage terminal, and the negative terminal N1 is the low-voltage terminal. The positive terminal P1 of the voltage source converter 22 is connected to the negative terminal B of the DC circuit breaker 23, and the negative terminal N1 of the voltage source converter 22 is connected to the third terminal C of the DC circuit breaker 23. The positive terminal A of the DC circuit breaker 23 and the negative terminal N1 of the voltage source converter 22 are the two input terminals of the voltage source valve group: the positive input terminal P and the negative input terminal N. The bypass branch connects the positive terminal A of the DC circuit breaker to the third terminal C of the DC circuit breaker; positive terminal A is connected to A5, and third terminal C is connected to B5.

[0093] Optionally, the positive terminal P1 of the voltage source converter 22 is the low-voltage end, and the negative terminal N1 is the high-voltage end. The negative terminal N1 of the voltage source converter 22 is connected to the positive terminal A of the DC circuit breaker 23, and the positive terminal P1 of the voltage source converter 22 is connected to the third terminal C of the DC circuit breaker 23. The positive terminal P1 of the voltage source converter 22 and the negative terminal B of the DC circuit breaker 23 are the two input terminals of the voltage source valve group: the positive input terminal P and the negative input terminal N, as shown below. Figure 11dAs shown. The bypass branch connects the negative terminal B of the DC circuit breaker to the third terminal C of the DC circuit breaker. The negative terminal B is connected to B5, and the third terminal C is connected to A5. The third transfer switch 15 connects the negative terminal B of the DC circuit breaker 23 to the positive terminal A3 of the reverse transfer branch 3. The fourth transfer switch 16 connects the third terminal C of the DC circuit breaker 23 to the negative terminal B3 of the reverse transfer branch 3.

[0094] Figure 11e This is the fifth schematic diagram of a voltage source valve group provided in the embodiments of this application, including a voltage source converter 22 and a DC circuit breaker 23. The DC circuit breaker 23 adopts... Figure 10 The structure of a DC circuit breaker.

[0095] The voltage source converter 22 includes, but is not limited to, at least one of a two-level converter, a three-level converter, a modular multilevel converter based on a half-bridge submodule, a diode-clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter. The voltage source converter 22 includes at least three phases and six bridge arms, and cannot regulate the DC voltage to zero or negative voltage.

[0096] Figure 11e The positive terminal P1 of the voltage source converter 22 is the high-voltage terminal, and the negative terminal N1 is the low-voltage terminal. The positive terminal P1 of the voltage source converter 22 is connected to the negative terminal B of the DC circuit breaker 23, and the low-voltage terminal N1 of the voltage source converter 22 is connected to the third terminal C of the DC circuit breaker 23. The positive terminal A of the DC circuit breaker 23 and the negative terminal N1 of the voltage source converter 22 are the two input terminals of the voltage source valve group: the positive input terminal P and the negative input terminal N. The bypass branch connects the positive terminal A of the DC circuit breaker to the third terminal C of the DC circuit breaker; positive terminal A is connected to A5, and third terminal C is connected to B5.

[0097] Optionally, the positive terminal P1 of the voltage source converter 22 is the low-voltage end, and the negative terminal N1 is the high-voltage end. The negative terminal N1 of the voltage source converter 22 is connected to the positive terminal A of the DC circuit breaker 23, and the positive terminal P1 of the voltage source converter 22 is connected to the third terminal C of the DC circuit breaker 23. The positive terminal P1 of the voltage source converter 22 and the negative terminal B of the DC circuit breaker 23 are the two input terminals of the voltage source valve group: the positive input terminal P and the negative input terminal N, as shown below. Figure 11f As shown. The bypass branch connects the negative terminal B of the DC circuit breaker to the third terminal C of the DC circuit breaker. Negative terminal B is connected to B5, and third terminal C is connected to A5. The third transfer switch 15 connects the negative terminal B of the DC circuit breaker 23 to the positive terminal A3 of the reverse transfer branch 3. The fourth transfer switch 16 connects the third terminal C of the DC circuit breaker 23 to the negative terminal B3 of the reverse transfer branch 3. The seventh transfer switch 20 connects the positive terminal A2 of the forward transfer branch 2 to the negative terminal B of the DC circuit breaker. The eighth transfer switch 21 connects the negative terminal B2 of the forward transfer branch to the third terminal C of the DC circuit breaker.

[0098] Figure 11gThis is the seventh schematic diagram of a voltage source type valve group provided in the embodiments of this application, including a voltage source converter 22, a DC circuit breaker 23, a first isolating switch 24, a second isolating switch 25, and a bypass switch 26. The DC circuit breaker 23 adopts... Figure 8a The structure of a DC circuit breaker.

[0099] The voltage source converter 23 includes, but is not limited to, at least one of a two-level converter, a three-level converter, a modular multilevel converter based on a half-bridge submodule, a diode-clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter. The voltage source converter 23 includes at least three phases and six bridge arms, and cannot regulate the DC voltage to zero or negative voltage.

[0100] Figure 11g The positive terminal P1 of the voltage source converter 22 is the high-voltage terminal, and the negative terminal N1 is the low-voltage terminal. The positive terminal P1 of the voltage source converter 23 is connected to the negative terminal B of the DC circuit breaker 23, and the negative terminal N1 of the voltage source converter 23 is connected to the third terminal C of the DC circuit breaker 23. One end of the first isolating switch 24 is connected to the positive terminal A of the DC circuit breaker 23, and the other end is the positive input terminal P of the voltage source valve group. One end of the second isolating switch 25 is connected to the negative terminal N1 of the voltage source converter 22, and the other end is the negative input terminal N of the voltage source valve group. The bypass switch 26 connects the positive and negative input terminals of the voltage source valve group.

[0101] Figure 12a This application provides a DC power transmission system, including the voltage source type valve group as described above.

[0102] The main circuit of the ultra-high voltage direct current transmission system includes rectifier station 100, inverter station 200, first DC line 150, second DC line 160, rectifier station grounding electrode line 114, rectifier station grounding electrode 115, inverter station grounding electrode line 214, and inverter station grounding electrode 215.

[0103] The rectifier station 100 includes a first DC pole I110, a second DC pole II120, a first AC filter bank 118, a first AC system 140, and converter transformer incoming line switches (131, 132, 133 and 134), a DC line transfer switch 113, a ground return line transfer switch 190, and bipolar neutral zone isolating switches 174, 175, 184 and 185.

[0104] The first DC pole I110 includes a first high-side current source valve group 111, a first low-side current source valve group 112, a first high-side converter transformer 116, a first low-side converter transformer 117, a first pole neutral bus switch 119, a first DC filter 93, a first smoothing reactor 91, a first DC filter isolating switch 171, a first pole bus isolating switch 172, and a first DC line isolating switch 173. The first high-side current source valve group 111 and the first low-side current source valve group 112 are connected in series.

[0105] The first high-end current source type valve group 111 includes a first high-end grid phase-commutation converter 101, a bypass switch 36, a bypass knife switch 35, a first isolating knife switch 37, and a second isolating knife switch 38. The first low-end current source type valve group 112 includes a first low-end grid phase-commutation converter 102, a bypass switch 46, a bypass knife switch 45, a first isolating knife switch 47, and a second isolating knife switch 48.

[0106] The grid-connected phase converter includes, but is not limited to, at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit. The pulsating bridge circuit includes, but is not limited to, non-turn-off semi-controlled power semiconductor devices, typically thyristors.

[0107] The second DC pole II120 includes a second low-end current source valve group 121, a second high-end current source valve group 122, a second low-end converter transformer 126, a second high-end converter transformer 127, a second pole neutral bus switch 129, a second DC filter 94, a second smoothing reactor 92, a second DC filter isolating switch 181, a second pole bus isolating switch 182, and a second DC line isolating switch 183. The second low-end current source valve group 121 and the second high-end current source valve group 122 are connected in series.

[0108] The second low-end current source type valve group 121 includes a second low-end grid phase-commutation converter 103, a bypass switch 32, a bypass knife switch 31, a first isolating knife switch 33, and a second isolating knife switch 34. The second high-end current source type valve group 122 includes a second high-end grid phase-commutation converter 104, a bypass switch 42, a bypass knife switch 41, a first isolating knife switch 43, and a second isolating knife switch 44.

[0109] 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 and 234), a grounding electrode line isolating switch 213, a DC line isolating switch 290, and bipolar neutral zone isolating switches 274, 275, 284 and 285.

[0110] 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 pole neutral bus switch 219, a third smoothing reactor 205, 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.

[0111] The third high-end voltage source type valve group 211 includes a voltage source converter 201, a bypass switch 51, a first disconnect switch 53, a second disconnect switch 54, and a DC circuit breaker 55. The third low-end voltage source type valve group 212 includes a voltage source converter 202, a bypass switch 61, a first disconnect switch 63, a second disconnect switch 64, and a DC circuit breaker 65.

[0112] 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 fourth pole neutral bus switch 229, a fourth smoothing reactor 206, 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.

[0113] The fourth low-end voltage source type valve group 221 includes a voltage source converter 203, a bypass disconnector 71, a first disconnector 73, a second disconnector 74, and a DC circuit breaker 75. The fourth high-end voltage source type valve group 222 includes a voltage source converter 204, a bypass disconnector 81, a first disconnector 83, a second disconnector 84, and a DC circuit breaker 85.

[0114] DC circuit breakers 55, 65, 75 and 85 adopt Figure 7 , Figure 8a or Figure 8b , Figure 10 Any one of them.

[0115] The rectifier station 100 is connected to the grounding electrode 115 via grounding electrode line 114. The inverter station 200 is connected to the grounding electrode 215 via grounding electrode line 214. During power forward transmission, the first AC system 140 of the rectifier station 100 converts AC power into DC power through its first high-end grid phase-commutation converter 101, first low-end grid phase-commutation converter 102, second high-end grid phase-commutation converter 104, and second low-end grid phase-commutation converter 103, and transmits it to the inverter station 200 through DC lines 150 and 160. The inverter station 200 converts DC power into AC power through its third high-end voltage source converter 201, third low-end voltage source converter 202, fourth high-end voltage source converter 204, and fourth low-end voltage source converter 203, and sends it to the second AC system 240 of the inverter station 200, thereby achieving DC power forward transmission. The converters in the rectifier station operate under DC current control or DC power control, while the converters in the inverter station operate under DC voltage control and reactive power control.

[0116] The analog signals acquired by rectifier station 100 and inverter station 200 include: pole bus current IDL, pole-neutral bus current IDNC, grounding electrode current IDEL, pole bus voltage UDL, and pole-neutral bus voltage UDN. The acquired digital signals include: the position signals of all switches or disconnectors.

[0117] Figure 12b This is another DC power transmission system provided in this application.

[0118] The main circuit of the DC transmission system includes rectifier station 100, inverter station 200, first DC line 150, second DC line 160, rectifier station grounding electrode line 114, rectifier station grounding electrode 115, inverter station grounding electrode line 214, and inverter station grounding electrode 215.

[0119] 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 DC line transfer switch 113, a ground return line transfer switch 190, and bipolar neutral zone isolating switches 174, 175, 184 and 185.

[0120] The first DC pole I110 includes a first high-side voltage source valve group 113, a first low-side voltage source valve group 114, a first high-side converter transformer 136, a first low-side converter transformer 137, a first DC pole neutral bus switch 119, a first smoothing reactor 95, a first pole bus isolating switch 172, and a first DC line isolating switch 173. The first high-side voltage source valve group 113 and the first low-side voltage source valve group 114 are connected in series.

[0121] The first high-end voltage source type valve group 113 includes a voltage source converter 105, a bypass switch 35, a first disconnect switch 37, a second disconnect switch 38, and a DC circuit breaker 30. The first low-end voltage source type valve group 114 includes a voltage source converter 106, a bypass switch 45, a first disconnect switch 47, a second disconnect switch 48, and a DC circuit breaker 40.

[0122] The second DC pole II120 includes a second low-end voltage source valve group 123, a second high-end voltage source valve group 124, a second low-end converter transformer 138, a second high-end converter transformer 139, a second DC pole neutral bus switch 129, a second smoothing reactor 92, a second pole bus isolating switch 182, and a second DC line isolating switch 183. The second low-end voltage source valve group 123 and the second high-end voltage source valve group 124 are connected in series.

[0123] The second low-end voltage source type valve group 123 includes a voltage source converter 107, a bypass switch 31, a first disconnect switch 33, a second disconnect switch 34, and a DC circuit breaker 39. The second high-end voltage source type valve group 124 includes a voltage source converter 108, a bypass switch 41, a first disconnect switch 43, a second disconnect switch 44, and a DC circuit breaker 49.

[0124] 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 and 234), a grounding electrode line isolating switch 213, a DC line isolating switch 290, and bipolar neutral zone isolating switches 274, 275, 284 and 285.

[0125] 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 DC pole neutral bus switch 219, a third smoothing reactor 205, 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.

[0126] The third high-end voltage source type valve group 211 includes a voltage source converter 201, a bypass switch 51, a first disconnect switch 53, a second disconnect switch 54, and a DC circuit breaker 55. The third low-end voltage source type valve group 212 includes a voltage source converter 202, a bypass switch 61, a first disconnect switch 63, a second disconnect switch 64, and a DC circuit breaker 65.

[0127] 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 fourth DC pole neutral bus switch 229, a fourth smoothing reactor 206, 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.

[0128] The fourth low-end voltage source type valve group 221 includes a voltage source converter 203, a bypass disconnector 71, a first disconnector 73, a second disconnector 74, and a DC circuit breaker 75. The fourth high-end voltage source type valve group 222 includes a voltage source converter 204, a bypass disconnector 81, a first disconnector 83, a second disconnector 84, and a DC circuit breaker 85.

[0129] DC circuit breakers 30, 40, 39, 49, 55, 65, 75, and 85 adopt... Figure 7 , Figure 8a or Figure 8b , Figure 10 Any one of them.

[0130] The rectifier station 100 is connected to the grounding electrode 115 via grounding electrode line 114. The inverter station 200 is connected to the grounding electrode 215 via grounding electrode line 214. During power forward transmission, the first AC system 140 of the rectifier station 100 converts AC power into DC power through its first high-side voltage source converter 105, first low-side voltage source converter 106, second high-side voltage source converter 108, and second low-side voltage source converter 107, and transmits it to the inverter station 200 through DC lines 150 and 160. The inverter station 200 converts DC power into AC power through its third high-side voltage source converter 201, third low-side voltage source converter 202, fourth high-side voltage source converter 204, and fourth low-side voltage source converter 203, and sends it to the second AC system 240 of the inverter station 200, thereby achieving DC power forward transmission. The converters in the rectifier station operate under DC current control or DC power control, while the converters in the inverter station operate under DC voltage control and reactive power control.

[0131] The analog signals acquired by rectifier station 100 and inverter station 200 include: pole bus current IDL, pole-neutral bus current IDNC, grounding electrode current IDEL, pole bus voltage UDL, and pole-neutral bus voltage UDN. The acquired digital signals include: the position signals of all switches or disconnectors.

[0132] Figure 13 This is a schematic flowchart of a control method for a voltage source valve assembly provided in an embodiment of this application. The voltage source valve assembly is as follows: Figure 11a, 11b As shown, the control method is as follows.

[0133] In S110, the main branch 1 and / or the forward transfer branch 2 and / or the reverse transfer branch 3 of the control DC circuit breaker 23 are turned on, and the voltage source converter 22 is operated.

[0134] When the voltage source converter is inverting operation, the main branch 1 and / or the forward transfer branch 2 of the control DC circuit breaker 23 are turned on, and current flows into the positive terminal A and out the negative terminal B of the DC circuit breaker 23. When the voltage source converter is rectifying operation, the main branch 1 of the control DC circuit breaker 23 is turned on, and current flows into the negative terminal B and out the positive terminal A of the DC circuit breaker 23.

[0135] In S120, when a DC fault occurs in the voltage source converter 22, the main branch 1 of the control DC circuit breaker 23 is turned off, and the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off. After the fault is recovered or after the deionization time, the main branch 1 and / or the forward transfer branch 2 and / or the reverse transfer branch 3 of the control DC circuit breaker 23 are turned on. It should be noted that the forward transfer branch 2 and / or the reverse transfer branch 3 must be turned on before the main branch 1 is turned off.

[0136] According to some embodiments, DC faults include DC line faults. In a DC line fault, after the deionization time, if the voltage source converter 22 is operating in rectification mode, the reverse transfer branch 3 of the DC circuit breaker 23 is turned on; if the voltage source converter 22 is operating in inverter mode, the forward transfer branch 2 of the DC circuit breaker 23 is turned on.

[0137] When the voltage source converter is inverting operation, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the forward transfer branch 2 and / or the reverse transfer branch 3 of the DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the reverse current supplied by the voltage source converter 22 is blocked due to the unidirectional conduction characteristic of the forward transfer branch 2. After a deionization time, the forward transfer branch 2 of the control DC circuit breaker 23 is turned on. If the fault is recovered, the main branch 1 of the control DC circuit breaker 23 is turned on.

[0138] When the voltage source converter is operating under rectification conditions, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the reverse transfer branch 3 of the control DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the current supplied by the voltage source converter 22 is blocked. After a deionization time, the reverse transfer branch 3 of the control DC circuit breaker 23 is turned on. If the fault is recovered, the main branch 1 of the control DC circuit breaker 23 is turned on.

[0139] It should be noted that if the forward transfer branch 2 only includes diodes connected in series, the forward transfer branch 2 does not need to be controlled, and the steps of controlling the conduction of the forward transfer branch 2 in S110 and S120 can be omitted.

[0140] In S130, when the voltage source converter 22 is blocked due to a fault, the main branch 1 of the control DC circuit breaker 23 is turned off, the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, and the voltage source converter 22 is blocked.

[0141] When the voltage source converter is inverting operation, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the forward transfer branch 2 or the reverse transfer branch 3 of the control DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the control voltage source converter 22 is locked. Optionally, the incoming AC switch of the voltage source converter 22 is tripped.

[0142] When the voltage source converter is operating under rectification conditions, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the reverse transfer branch 3 or the forward transfer branch 2 of the DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the control voltage source converter 22 is locked. Optionally, the incoming AC switch of the voltage source converter 22 is tripped.

[0143] Figure 14 This is a schematic flowchart of another control method for a voltage source valve group provided in an embodiment of this application. The voltage source valve group is as follows: Figure 11c , 11d As shown, the DC circuit breaker 23 has a set of transfer switches including a first transfer switch 13, a second transfer switch 14, a third transfer switch 15 and a fourth transfer switch 16, and the control method is as follows.

[0144] In S210, the first changeover switch 13 and the second changeover switch 14 are closed, the third changeover switch 15 and the fourth changeover switch 16 are opened, the bypass switch 17 is turned off, the main branch 1 and / or the forward transfer branch 2 and / or the reverse transfer branch 3 of the DC circuit breaker 23 are turned on, and the voltage source converter 22 is operated.

[0145] When the voltage source converter 22 is in inverter operation, the main branch 1 and / or the forward transfer branch 2 of the control DC circuit breaker 23 are turned on, and the current flows into the positive terminal A and out the negative terminal B of the DC circuit breaker 23. When the voltage source converter is in rectifier operation, the main branch 1 of the control DC circuit breaker 23 is turned on, and the current flows into the negative terminal B and out the positive terminal A of the DC circuit breaker 23.

[0146] In S220, when a DC fault occurs in the voltage source converter 22, the main branch 1 of the control DC circuit breaker 23 is turned off, and the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off. After the fault is recovered or after the deionization time, the main branch 1 and / or the forward transfer branch 2 and / or the reverse transfer branch 3 of the control DC circuit breaker 23 are turned on. It should be noted that the forward transfer branch 2 and / or the reverse transfer branch 3 must be turned on before the main branch 1 is turned off.

[0147] When the voltage source converter 22 is in inverter operation, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the forward transfer branch 2 and / or the reverse transfer branch 3 of the DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the reverse current supplied by the voltage source converter 22 is blocked due to the unidirectional conduction characteristic of the forward transfer branch 2. After the deionization time, the forward transfer branch 2 of the control DC circuit breaker 23 is turned on. If the fault is recovered, the main branch 1 of the control DC circuit breaker 23 is turned on. When the voltage source converter 22 is in rectifier operation, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the reverse transfer branch 3 of the DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the current supplied by the voltage source converter 22 is blocked. After the deionization time, the reverse transfer branch 3 of the control DC circuit breaker 23 is turned on. If the fault is recovered, the main branch 1 of the control DC circuit breaker 23 is turned on.

[0148] if Figure 11c , 11d The voltage source valve group in the middle operates in rectifier mode and is also connected in series with other voltage source valve groups. The bypass switch 17 is suitable for use with Figure 9c , Figure 9d or Figure 9e The circuit.

[0149] If the voltage source valve group is operating in inverter mode and is also connected in series with other voltage source valve groups, the bypass switch 17 is suitable for use. Figure 9d or Figure 9e The circuit. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the current is continued through the diode or thyristor connected in series in the bypass switch 17 to prevent overcurrent in the energy-consuming branch 4.

[0150] In S230, when the voltage source converter 22 is blocked due to a fault, the bypass switch 17 is turned on, the main branch 1 of the DC circuit breaker 23 is turned off, the reverse transfer branch 3 of the DC circuit breaker 23 is turned off, and the voltage source converter 22 is blocked.

[0151] When the voltage source converter 22 is in inverter operation, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the forward transfer branch 2 or the reverse transfer branch 3 of the DC circuit breaker 23; after the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the current is transferred to the bypass switch 17, controlling the voltage source converter 22 to lock out; optionally, the incoming AC switch of the voltage source converter 22 is tripped. When the voltage source converter is in rectifier operation, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the reverse transfer branch 3 of the DC circuit breaker 23; after the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, controlling the voltage source converter 22 to lock out; optionally, the incoming AC switch of the voltage source converter 22 is tripped.

[0152] In S240, when the voltage source converter 22 is disconnected online or due to a fault, the bypass switch 17 is turned on, the main branch 1 of the DC circuit breaker 23 is turned off, and the reverse transfer branch 3 of the DC circuit breaker 23 is turned off.

[0153] When the voltage source converter 22 is in inverter operation and then offline, if the forward transfer branch 2 is in the off state, the forward transfer branch 2 is turned on, first controlling the main branch 1 of the DC circuit breaker 23 to turn off, controlling the reverse transfer branch 3 of the DC circuit breaker 23 to turn off, and then controlling the bypass switch 17 to turn on. When the voltage source converter 22 is in inverter operation and then out of fault, the bypass switch 17 is turned on. If the forward transfer branch 2 and / or the reverse transfer branch 3 are in the off state, the forward transfer branch 2 and / or the reverse transfer branch 3 are turned on, controlling the main branch 1 of the DC circuit breaker 23 to turn off, the current is transferred to the forward transfer branch 2 and / or the reverse transfer branch 3 of the DC circuit breaker 23, controlling the reverse transfer branch 3 of the DC circuit breaker 23 to turn off, and controlling the voltage source converter 22 to be locked out; optionally, the incoming AC switch of the voltage source converter 22 is tripped.

[0154] When the voltage source converter 22 is operating in rectification mode and then offline, if the reverse transfer branch 3 is in the off state, controlling the reverse transfer branch 3 to turn on will turn off the main branch 1 of the DC circuit breaker 23, then controlling the bypass switch 17 to turn on, and controlling the reverse transfer branch 3 of the DC circuit breaker 23 to turn off will transfer the current to the bypass switch 17. If the bypass switch 17... Figure 9c , 9d As shown in 9e, current flows through diode 7 of bypass switch 17, and the above-mentioned step of controlling bypass switch 17 to conduct can be omitted. When voltage source converter 22 is operating in rectification mode and the fault is resolved, bypass switch 17 is controlled to conduct. If reverse transfer branch 3 is in the off state, reverse transfer branch 3 is controlled to conduct. After the main branch 1 of DC circuit breaker 23 is turned off, reverse transfer branch 3 of DC circuit breaker 23 is controlled to turn off, and voltage source converter 22 is locked out. Optionally, the incoming AC switch of voltage source converter 22 is tripped.

[0155] Optionally, when the voltage source converter 22 is taken offline, the voltage source converter 22 is not locked out, but operates in reactive power compensation mode.

[0156] In S250, when the voltage source converter 22 is put into online inverter operation, the first transfer switch 13 and the second transfer switch 14 are opened, the third transfer switch 15 and the fourth transfer switch 16 are closed, the voltage source converter 22 is charged, the voltage source converter 22 is unlocked, the reverse transfer branch 3 is turned on, the bypass branch 17 is turned off, the forward transfer branch 2 is turned on, the reverse transfer branch 3 is turned off, the third transfer switch 15 and the fourth transfer switch 16 are opened, the first transfer switch 13 and the second transfer switch 14 are closed, and the main branch 1 is turned on. The bypass branch 17 is turned off by opening or closing the mechanical switch or mechanical disconnector of the bypass branch 17, or by turning off the fourth power switch connected in series.

[0157] After the aforementioned control bypass branch 17 is turned off, the current is transferred from the bypass branch 17 to the reverse transfer branch 3. After the control reverse transfer branch 3 is turned off, the current is transferred to the voltage source converter 22 and the forward transfer branch 2.

[0158] If the bypass switch 17 uses at least one diode connected in series, such as Figure 9c , 9d As shown in 9e, when the voltage source converter 22 is in online rectification operation, the bypass branch 17 is reverse-biased to control the voltage source converter 22 to charge, the voltage source converter 22 is unlocked, the reverse transfer branch 3 is turned on, and the main branch 1 is turned on.

[0159] After the aforementioned control reverse transfer branch 3 is turned on, the current is transferred from the bypass switch 17 to the voltage source converter 22 and the reverse transfer branch 3.

[0160] It should be noted that if the forward transfer branch 2 only includes diodes connected in series, the forward transfer branch 2 does not need to be controlled, and the steps of controlling the conduction and reverse conduction of the forward transfer branch 2 in S210, S220 and S250 can be omitted.

[0161] Figure 15 This is a schematic flowchart of another control method for a voltage source valve group provided in the embodiments of this application. The voltage source valve group is as follows: Figure 11e , 11f As shown, the DC circuit breaker 23 has a group of transfer switches including a first transfer switch 13, a second transfer switch 14, a third transfer switch 15, a fourth transfer switch 16, a fifth transfer switch 18, a sixth transfer switch 19, a seventh transfer switch 20, an eighth transfer switch 21, and a bypass switch 17. The control method is as follows.

[0162] In S310, the first changeover switch 13 and the second changeover switch 14 are closed, the third changeover switch 15 and the fourth changeover switch 16 are opened, the bypass switch 17 is turned off, the fifth changeover switch 18 and the sixth changeover switch 19 are closed, the seventh changeover switch 20 and the eighth changeover switch 21 are opened, the main branch 1 and / or the forward transfer branch 2 and / or the reverse transfer branch 3 of the DC circuit breaker 23 are turned on, and the voltage source converter 22 is operated.

[0163] When the voltage source converter is inverting operation, the main branch 1 and / or the forward transfer branch 2 of the control DC circuit breaker 23 are turned on, and current flows into the positive terminal A and out the negative terminal B of the DC circuit breaker 23. When the voltage source converter is rectifying operation, the main branch 1 of the control DC circuit breaker 23 is turned on, and current flows into the negative terminal B and out the positive terminal A of the DC circuit breaker 23.

[0164] Optionally, if the reverse transfer branch 3 has bidirectional current interruption capability, when the voltage source converter 22 is rectifying, it controls the first transfer switch 13 and the second transfer switch 14 to close, controls the third transfer switch 15 and the fourth transfer switch 16 to open, controls the bypass switch 17 to close, controls the fifth transfer switch 18 and the sixth transfer switch 19 to open, controls the seventh transfer switch 20 and the eighth transfer switch 21 to close, controls the main branch 1 and / or the reverse transfer branch 3 of the DC circuit breaker 23 to conduct, and controls the voltage source converter 22 to operate.

[0165] In S320, when a DC fault occurs in the voltage source converter 22, the main branch 1 of the control DC circuit breaker 23 is turned off, and the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off. After the fault is recovered or after the deionization time, the main branch 1 and / or the forward transfer branch 2 and / or the reverse transfer branch 3 of the control DC circuit breaker 23 are turned on. It should be noted that the forward transfer branch 2 and / or the reverse transfer branch 3 must be turned on before the main branch 1 is turned off.

[0166] When the voltage source converter 22 is in inverter operation, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the forward transfer branch 2 and / or the reverse transfer branch 3 of the DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, due to the unidirectional conduction characteristic of the forward transfer branch 2, the reverse current provided by the voltage source converter 22 is blocked. After the deionization time, the forward transfer branch 2 of the control DC circuit breaker 23 is turned on. If the fault is recovered, the main branch 1 of the control DC circuit breaker 23 is turned on. When the voltage source converter 22 is operating in rectification mode, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the reverse transfer branch 3 of the DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the current supplied by the voltage source converter 22 is blocked. After the deionization time, the reverse transfer branch 3 of the control DC circuit breaker 23 is turned on. If the fault is recovered, the main branch 1 of the control DC circuit breaker 23 is turned on.

[0167] In S330, when the voltage source converter 22 is blocked due to a fault, the bypass branch 17 is turned on, the main branch 1 of the DC circuit breaker 23 is turned off, the reverse transfer branch 3 of the DC circuit breaker 23 is turned off, and the voltage source converter 22 is blocked.

[0168] When the voltage source converter 22 is in inverter operation, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the forward transfer branch 2 or the reverse transfer branch 3 of the DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, the current is transferred to the bypass switch 17, controlling the voltage source converter 22 to lock out; optionally, the incoming AC switch of the voltage source converter 22 is tripped. When the voltage source converter is in rectifier operation, after the main branch 1 of the aforementioned control DC circuit breaker 23 is turned off, the current is transferred to the reverse transfer branch 3 of the DC circuit breaker 23. After the reverse transfer branch 3 of the control DC circuit breaker 23 is turned off, controlling the voltage source converter 22 to lock out; optionally, the incoming AC switch of the voltage source converter 22 is tripped.

[0169] Optionally, if the forward transfer branch 2 includes a third power switch, the forward transfer branch 2 can be turned off by controlling the third power switch.

[0170] In S340, when the voltage source converter 22 is disconnected online or due to a fault, the bypass branch 17 is turned on, and the main branch 1 and the reverse transfer branch 3 of the DC circuit breaker 23 are turned off.

[0171] When the voltage source converter 22 is in inverter operation and then offline, if the forward transfer branch 2 is in the off state, the forward transfer branch 2 is turned on, first controlling the main branch 1 of the DC circuit breaker 23 to turn off, controlling the reverse transfer branch 3 of the DC circuit breaker 23 to turn off, and then controlling the bypass switch 17 to turn on. When the voltage source converter 22 is in inverter operation and then out of fault, the bypass switch 17 is turned on. If the forward transfer branch 2 and / or the reverse transfer branch 3 are in the off state, the forward transfer branch 2 and / or the reverse transfer branch 3 is turned on, controlling the main branch 1 of the DC circuit breaker 23 to turn off, the current is transferred to the forward transfer branch 2 and / or the reverse transfer branch 3 of the DC circuit breaker 23, controlling the reverse transfer branch 3 of the DC circuit breaker 23 to turn off, and controlling the voltage source converter 22 to be locked out; optionally, the incoming AC switch of the voltage source converter 22 is tripped.

[0172] When the voltage source converter 22 is operating in rectification mode and then offline, if the reverse transfer branch 3 is in the off state, controlling the reverse transfer branch 3 to turn on will turn off the main branch 1 of the DC circuit breaker 23, then controlling the bypass switch 17 to turn on, and controlling the reverse transfer branch 3 of the DC circuit breaker 23 to turn off will transfer the current to the bypass switch 17. If the bypass switch 17... Figure 9c , 9d As shown in 9e, current flows through diode 7 of bypass switch 17, and the above-mentioned step of controlling bypass switch 17 to conduct can be omitted. When voltage source converter 22 is operating in rectification mode and the fault is resolved, bypass switch 17 is controlled to conduct. If reverse transfer branch 3 is in the off state, reverse transfer branch 3 is controlled to conduct. After the main branch 1 of DC circuit breaker 23 is turned off, reverse transfer branch 3 of DC circuit breaker 23 is controlled to turn off, and voltage source converter 22 is locked out. Optionally, the incoming AC switch of voltage source converter 22 is tripped.

[0173] Optionally, when the voltage source converter 22 is taken offline, the voltage source converter 22 is not locked out, but operates in reactive power compensation mode.

[0174] Optionally, if the reverse transfer branch 3 has bidirectional current interruption capability, the voltage source converter 22 operates in rectification mode, controlling the first transfer switch 13 and the second transfer switch 14 to close, controlling the third transfer switch 15 and the fourth transfer switch 16 to open, controlling the bypass switch 17 to close, controlling the fifth transfer switch 18 and the sixth transfer switch 19 to open, and controlling the seventh transfer switch 20 and the eighth transfer switch 21 to close. When the voltage source converter 22 is online or out of fault, the forward transfer branch 2 is controlled to conduct, and the main branch 1 and the reverse transfer branch 3 of the DC circuit breaker 23 are controlled to close.

[0175] In S350, when the voltage source converter 22 is put into online inverter operation, the first transfer switch 13 and the second transfer switch 14 are opened, the third transfer switch 15 and the fourth transfer switch 16 are closed, the fifth transfer switch 18 and the sixth transfer switch 19 are opened, the seventh transfer switch 20 and the eighth transfer switch 21 are closed, the voltage source converter 22 is charged, the voltage source converter 22 is unlocked, the reverse transfer branch 3 is turned on, the bypass branch 17 is turned off, the forward transfer branch 2 is turned on, the reverse transfer branch 3 is turned off, the third transfer switch 15 and the fourth transfer switch 16 are opened, the first transfer switch 13 and the second transfer switch 14 are closed, the fifth transfer switch 18 and the sixth transfer switch 19 are closed, the seventh transfer switch 20 and the eighth transfer switch 21 are opened, and the main branch 1 is turned on.

[0176] After the aforementioned control bypass branch 17 is turned off, the current is transferred from the bypass branch 17 to the reverse transfer branch 3. After the control reverse transfer branch 3 is turned off, the current is transferred to the voltage source converter 22 and the forward transfer branch 2.

[0177] If the bypass switch 17 uses at least one diode connected in series, such as Figure 9c , 9d As shown in 9e, when the voltage source converter 22 is in online rectification operation, the bypass branch 17 is reverse-biased to control the voltage source converter 22 to charge, the voltage source converter 22 is unlocked, the reverse transfer branch 3 is turned on, and the main branch 1 is turned on.

[0178] After the aforementioned control reverse transfer branch 3 is turned on, the current is transferred from the bypass switch 17 to the voltage source converter 22 and the reverse transfer branch 3.

[0179] It should be noted that if the forward transfer branch 2 only includes diodes connected in series, the forward transfer branch 2 does not need to be controlled, and the steps in S310, S320, S340 and S350 to control the forward transfer branch 2 to be turned on, reverse-biased, or turned off can be omitted.

[0180] by Figure 12a Taking poles I110 and I210 of the DC transmission system shown as examples, the DC circuit breaker of inverter station 200 has a bypass branch, and the bypass branch is as follows: Figure 9c , 9dOr as shown in 9e. Initially, the first high-side current source valve group 111 and the first low-side current source valve group 112 of the rectifier station 100 are operating, and the third high-side voltage source valve group 211 and the third low-side voltage source valve group 212 of the inverter station 200 are operating. The bypass switch 35 of the rectifier station 100 is open, the bypass switch 36 is open, the first isolating switch 37 is closed, the second isolating switch 38 is closed, the bypass switch 45 is open, the bypass switch 46 is open, the first isolating switch 47 is closed, and the second isolating switch 48 is closed. The bypass switch 51 of the inverter station 200 is open, the first isolating switch 53 is closed, the second isolating switch 54 is closed, the bypass switch 61 is open, the first isolating switch 63 is closed, and the second isolating switch 64 is closed.

[0181] The rectifier station 100 controls the grid commutator converter 101 and grid commutator converter 102 to operate in rectification mode. The inverter station 200 controls the main branch 1, forward transfer branch 2 and reverse transfer branch 3 of DC circuit breaker 55 and DC circuit breaker 56 to conduct, and controls the voltage source converter 201 and voltage source converter 202 to operate in inverter mode.

[0182] When a DC fault occurs in the voltage source converters 201 and 202 of the inverter station 200, such as when the first DC line 150 is grounded, the main branch 1 and the reverse transfer branch 3 of the DC circuit breakers 55 and 56 are turned off respectively. The grid phase-changing converters 101 and 102 are phase-shifted respectively. After the deionization time, the grid phase-changing converters 101 and 102 are de-phased. The forward transfer branch 2 of the DC circuit breakers 55 and 56 is turned on respectively. After the fault is restored, the main branch 1 and the reverse transfer branch 3 of the DC circuit breakers 55 and 56 are turned on.

[0183] Initially, the first high-side current source valve group 111 of the rectifier station 100 is in operation, and the third high-side voltage source valve group 211 of the inverter station 200 is in operation. When the voltage source converter 201 of the inverter station 200 is fault-locked, the main branch 1 and the reverse transfer branch 3 of the control DC circuit breaker 55 are turned off, and the voltage source converter 201 is locked. Correspondingly, the grid commutation converter 101 is locked.

[0184] Initially, the first high-side current source valve group 111 and the first low-side current source valve group 112 of the rectifier station 100 are in operation, and the third high-side voltage source valve group 211 and the third low-side voltage source valve group 212 of the inverter station 200 are in operation. When the voltage source converter 201 of the inverter station 200 performs online shutdown, the forward transfer branch 2 of the control DC circuit breaker 55 is turned on, the main branch 1 and the reverse transfer branch 3 of the control DC circuit breaker 55 are turned off, and the bypass branch 17 of the control DC circuit breaker 55 is turned on. When the voltage source converter 201 of the inverter station 200 performs fault shutdown, the bypass branch 17 of the control DC circuit breaker 55 is turned on, and the main branch 1 and the reverse transfer branch 3 of the control DC circuit breaker 55 are turned off.

[0185] The initial state is that the first low-end current 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 201 of the inverter station 200 is put into online operation, the first transfer switch 13 and the second transfer switch 14 of the DC circuit breaker 55 are opened, the third transfer switch 15 and the fourth transfer switch 16 of the DC circuit breaker 55 are closed, the voltage source converter 201 is charged, the voltage source converter 201 is unlocked, the reverse transfer branch 3 of the DC circuit breaker 55 is turned on, the bypass branch 17 of the DC circuit breaker 55 is turned off, and the current is transferred from the bypass branch 17 to the reverse transfer branch 3. The forward transfer branch 2 of the DC circuit breaker 55 is turned on, the reverse transfer branch 3 of the DC circuit breaker 55 is turned off, and the current is transferred from the reverse transfer branch to the voltage source converter 201. The third transfer switch 15 and the fourth transfer switch 16 of the DC circuit breaker 55 are opened, the first transfer switch 13 and the second transfer switch 14 of the DC circuit breaker 55 are closed, and the main branch 1 of the DC circuit breaker 55 is turned on.

[0186] 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.

[0187] by Figure 12b Taking poles I110 and I210 of the DC transmission system shown as examples, the DC circuit breakers of rectifier station 100 and inverter station 200 have bypass branches, and the bypass branches are as follows: Figure 9c , 9dOr as shown in 9e. Initially, the first high-side voltage source valve group 113 and the first low-side voltage source valve group 114 of the rectifier station 100 are operating, and the third high-side voltage source valve group 211 and the third low-side voltage source valve group 212 of the inverter station 200 are operating. The bypass switch 35 of the rectifier station 100 is open, the first isolating switch 37 is closed, the second isolating switch 38 is closed, the bypass switch 45 is open, the first isolating switch 47 is closed, and the second isolating switch 48 is closed. The bypass switch 51 of the inverter station 200 is open, the first isolating switch 53 is closed, the second isolating switch 54 is closed, the bypass switch 61 is open, the first isolating switch 63 is closed, and the second isolating switch 64 is closed.

[0188] Rectifier station 100 controls the main branch 1 and reverse transfer branch 3 of DC circuit breaker 30 to conduct, and controls voltage source converters 105 and 106 to operate in rectification mode. Inverter station 200 controls the main branch 1, forward transfer branch 2, and reverse transfer branch 3 of DC circuit breakers 30, 40, 55, and 65 to conduct, and controls voltage source converters 201 and 202 to operate in inverter mode.

[0189] When a DC fault occurs in voltage source converters 105, 106, 201, and 202, such as when the first DC line 150 is grounded, the main branch 1 and reverse transfer branch 3 of DC circuit breakers 30, 40, 55, and 65 are turned off, respectively, during rectification operation of voltage source converters 105 and 106 and inverter operation of voltage source converters 201 and 202. After deionization time, the reverse transfer branch 3 of DC circuit breakers 30 and 40 is turned on, and the forward transfer branch 2 of DC circuit breakers 55 and 65 is turned on. After the fault is recovered, the main branch 1 and reverse transfer branch 3 of DC circuit breakers 55 and 65 are turned on.

[0190] Initially, the first high-side voltage source valve group 113 of rectifier station 100 is in operation, and the third high-side voltage source valve group 211 of inverter station 200 is in operation. When the voltage source converter 105 of rectifier station 100 is fault-locked, the main branch 1 and reverse transfer branch 3 of control DC circuit breaker 30 are turned off, thus locking the voltage source converter 105. When the voltage source converter 201 of inverter station 200 is locked, the main branch 1 and reverse transfer branch 3 of control DC circuit breaker 55 are turned off, thus locking the voltage source converter 201.

[0191] Initially, the first high-side voltage source valve group 113 and the first low-side voltage source valve group 114 of the rectifier station 100 are in operation, and the third high-side voltage source valve group 211 and the third low-side voltage source valve group 212 of the inverter station 200 are in operation. When the voltage source converter 201 of the rectifier station 100 performs online or fault-free shutdown, the bypass branch 17 of the control DC circuit breaker 30 is turned on, and the main branch 1 and the reverse transfer branch 3 of the control DC circuit breaker 30 are turned off. When the voltage source converter 201 of the inverter station 200 performs online shutdown, the forward transfer branch 2 of the control DC circuit breaker 55 is turned on, the main branch 1 and the reverse transfer branch 3 of the control DC circuit breaker 55 are turned off, and the bypass branch 17 of the control DC circuit breaker 55 is turned on. When the voltage source converter 201 of the inverter station 200 performs a fault exit, the bypass branch 17 of the control DC circuit breaker 55 is turned on, and the main branch 1 and the reverse transfer branch 3 of the control DC circuit breaker 55 are turned off.

[0192] Initially, the first low-end voltage source valve group 114 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 105 of the rectifier station 100 is put into online operation, the voltage source converter 105 is controlled to charge, the voltage source converter 105 is controlled to unlock, the reverse transfer branch 3 of the DC circuit breaker 30 is controlled to conduct, and the main branch 1 of the DC circuit breaker 30 is controlled to conduct. When the voltage source converter 201 of the inverter station 200 is put into online operation, the first transfer switch 13 and the second transfer switch 14 of the DC circuit breaker 55 are opened, the third transfer switch 15 and the fourth transfer switch 16 of the DC circuit breaker 55 are closed, the voltage source converter 201 is charged, the voltage source converter 201 is unlocked, the reverse transfer branch 3 of the DC circuit breaker 55 is turned on, the bypass branch 17 of the DC circuit breaker 55 is turned off, and the current is transferred from the bypass branch 17 to the reverse transfer branch 3. The forward transfer branch 2 of the DC circuit breaker 55 is turned on, the reverse transfer branch 3 of the DC circuit breaker 55 is turned off, and the current is transferred from the reverse transfer branch to the voltage source converter 201. The third transfer switch 15 and the fourth transfer switch 16 of the DC circuit breaker 55 are opened, the first transfer switch 13 and the second transfer switch 14 of the DC circuit breaker 55 are closed, and the main branch 1 of the DC circuit breaker 55 is turned on.

[0193] 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.

[0194] Figure 16 This is a schematic diagram of a control device for a voltage source type valve group provided in an embodiment of this application. The control device 300 includes a detection unit 310 and a control unit 320.

[0195] The detection unit 310 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, the control unit 320 controls the main branch and / or forward transfer branch and / or reverse transfer branch of the DC circuit breaker to conduct, thereby controlling the operation of the voltage source converter. When the voltage source converter experiences a DC fault crossover, the control unit 320 controls the main branch and reverse transfer branch of the DC circuit breaker to close. After the fault is recovered or after a deionization time, the control unit 320 controls the main branch and / or forward transfer branch and / or reverse transfer branch of the DC circuit breaker to conduct. When the voltage source converter is fault-locked, the control unit 320 controls the main branch and reverse transfer branch of the DC circuit breaker to close, thereby controlling the voltage source converter to lock out.

[0196] The above embodiments are only for illustrating the technical concept of this application and should not be used to limit 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 DC circuit breaker, comprising: The main branch circuit includes the first fast disconnect switch; The forward transfer branch includes: a diode, or at least two diodes connected in series, with the cathodes and anodes of the at least two diodes connected in sequence; or a thyristor, or at least two thyristors connected in series, with the cathodes and anodes of the at least two thyristors connected in sequence. The reverse transfer branch includes: a first power switch or at least two first power switches connected in series; or The reverse transfer branch includes one or more of a first inductor, a first capacitor, and a coupling negative voltage circuit, and a first power switch; or The reverse transfer branch includes: one or more of a first inductor, a first capacitor, and a coupling negative voltage circuit, and at least two first power switches connected in series. The first power switch includes at least one of IGBT, IGCT, GTO, MOSFET, anti-parallel circuit of IGBT and diode, anti-parallel circuit of IGCT and diode, anti-parallel circuit of GTO and diode, and anti-parallel circuit of MOSFET and diode. Energy-consuming branches, including surge arresters; The DC circuit breaker includes a positive terminal and a negative terminal. The main branch, forward transfer branch, reverse transfer branch, and energy-consuming branch are respectively connected to the positive terminal and the negative terminal, or connected to the positive terminal and the negative terminal through a changeover switch group; or The diodes or thyristors in the forward transfer branch are respectively connected in antiparallel with the first power switch in the reverse transfer branch to form parallel branches. These parallel branches have multiple segments, which are connected in series to the positive and negative terminals or connected to the positive and negative terminals via a set of changeover switches. The main branch connects the positive and negative terminals or connects them via a set of changeover switches; or... The series-connected multiple first power switches of the reverse transfer branch are connected in parallel with a surge arrester of the energy-consuming branch to form a parallel branch. The parallel branch has multiple segments, which are connected in series and then connected to the positive and negative terminals or connected to the positive and negative terminals through a group of changeover switches. The main branch connects to the positive and negative terminals or connects to the positive and negative terminals through a group of changeover switches; or The diodes or thyristors of the forward transfer branch are respectively connected in antiparallel with the first power switch of the reverse transfer branch to form a first parallel branch. The first parallel branch has multiple segments. The multiple segments of the first parallel branch are connected in series and then connected in parallel with a surge arrester of the energy dissipation branch to form a second parallel branch. The second parallel branch has multiple segments. The multiple segments of the second parallel branch are connected in series and then connected to the positive terminal and the negative terminal or connected to the positive terminal and the negative terminal through a changeover switch group. The main branch is connected to the positive terminal and the negative terminal or connected to the positive terminal and the negative terminal through a changeover switch group.

2. The DC circuit breaker as described in claim 1, further comprising: The third terminal is used to connect to external circuitry; The reverse transfer branch and the energy-consuming branch are connected to the third terminal through a set of transfer switches, and the forward transfer branch is connected to the third terminal through a set of transfer switches. or, The circuits formed by the diodes or thyristors of the forward transfer branch being connected in antiparallel with the first power switch of the reverse transfer branch, and the energy-consuming branch, are connected to the third terminal through a group of switching devices.

3. The DC circuit breaker as described in claim 1, wherein, The main branch also includes: A second power switch is connected in series with the first fast disconnect switch. The second power switch at least unidirectionally blocks DC current. The second power switch includes at least one of the following: IGBT, IGCT, GTO, MOSFET, anti-parallel circuit of IGBT and diode, anti-parallel circuit of IGCT and diode, anti-parallel circuit of GTO and diode, and anti-parallel circuit of MOSFET and diode.

4. The DC circuit breaker as described in claim 1, wherein, The forward transfer branch also includes: A third power switch and / or a second fast disconnect switch are connected in series with at least one of the diodes or at least one of the thyristors. The third power switch includes at least one of IGBT, IGCT, GTO, MOSFET, an anti-parallel circuit of IGBT and diode, an anti-parallel circuit of IGCT and diode, an anti-parallel circuit of GTO and diode, and an anti-parallel circuit of MOSFET and diode.

5. The DC circuit breaker as described in claim 1, wherein, The reverse transfer branch also includes: A resistor and / or a second inductor and / or a second capacitor connected in series are connected in parallel with the series circuit of the first power switch and / or the first inductor and / or the first capacitor and / or the coupling negative voltage circuit.

6. The DC circuit breaker as claimed in claim 2, wherein the transfer switch group comprises: The first transfer switch connects the negative terminal of the DC circuit breaker to the negative terminal of the reverse transfer branch; The second transfer switch connects the positive terminal of the DC circuit breaker to the positive terminal of the reverse transfer branch; The third transfer switch connects the positive terminal of the DC circuit breaker to the negative terminal of the reverse transfer branch; or connects the negative terminal of the DC circuit breaker to the positive terminal of the reverse transfer branch. A fourth transfer switch connects the third terminal of the DC circuit breaker to the positive terminal of the reverse transfer branch; or connects the third terminal of the DC circuit breaker to the negative terminal of the reverse transfer branch; the third terminal of the DC circuit breaker is used to connect to an external circuit.

7. The DC circuit breaker as claimed in claim 1, further comprising: The residual current disconnect switch is connected in series between the positive terminal of the DC circuit breaker and the parallel circuit of the main branch, the forward transfer branch, the reverse transfer branch and the energy-consuming branch.

8. The DC circuit breaker as described in claim 2, further comprising: A bypass branch connects the positive terminal of the DC circuit breaker to the third terminal of the DC circuit breaker or connects the negative terminal of the DC circuit breaker to the third terminal of the DC circuit breaker. The bypass branch includes at least one of the following: a mechanical switch, a mechanical knife switch, a fourth power switch, at least two fourth power switches connected in series, a diode, and at least two diodes connected in series. The cathodes and anodes of the at least two diodes are connected in sequence. The fourth power switch includes at least one of the following: an IGBT, an IGCT, a GTO, a MOSFET, a thyristor, an anti-parallel circuit of an IGBT and a diode, an anti-parallel circuit of an IGCT and a diode, an anti-parallel circuit of a GTO and a diode, an anti-parallel circuit of a MOSFET and a diode, and an anti-parallel circuit of a thyristor and a diode.

9. The DC circuit breaker as claimed in claim 6, wherein the transfer switch group further comprises: The fifth transfer switch connects the negative terminal of the DC circuit breaker to the negative terminal of the positive transfer branch; The sixth transfer switch connects the positive terminal of the DC circuit breaker to the positive terminal of the forward transfer branch; The seventh transfer switch connects the positive terminal of the DC circuit breaker to the negative terminal of the forward transfer branch; or connects the negative terminal of the DC circuit breaker to the positive terminal of the forward transfer branch. The eighth transfer switch connects the positive terminal of the forward transfer branch to the third terminal of the DC circuit breaker; or connects the negative terminal of the forward transfer branch to the third terminal of the DC circuit breaker.

10. A voltage source type valve assembly, comprising: The DC circuit breaker as described in any one of claims 1 to 9; A voltage source converter is connected in series with the main branch of the DC circuit breaker, and the voltage source converter includes at least three phases and six bridge arms.

11. The voltage source type valve assembly as described in claim 10, wherein, The high-voltage terminal of the voltage source converter is connected to the main branch of the DC circuit breaker, and the high-voltage terminal of the voltage source converter is either a positive high-voltage terminal or a negative high-voltage terminal.

12. The voltage source type valve assembly as described in claim 10, wherein, If the DC circuit breaker has a third terminal, the third terminal of the DC circuit breaker is connected to the low-voltage terminal of the voltage source converter, and the low-voltage terminal of the voltage source converter is either a positive low-voltage terminal or a negative low-voltage terminal.

13. The voltage source type valve assembly as described in claim 10, further comprising: The first isolating switch connects the positive input terminal of the voltage source valve group to the DC circuit breaker or voltage source converter. The second isolating switch is connected to the negative input terminal of the voltage source valve group and the voltage source converter or the DC circuit breaker; A bypass switch connects the positive and negative input terminals of the voltage source valve group.

14. A DC transmission system comprising a voltage source type valve assembly as described in any one of claims 10 to 13.

15. A control method for a voltage source type valve group as described in any one of claims 10 to 13, comprising: Control the main branch and / or forward transfer branch and / or reverse transfer branch of the DC circuit breaker to conduct, and control the operation of the voltage source converter; When the DC fault of the voltage source converter passes through, the main branch of the DC circuit breaker is turned off and the reverse transfer branch is turned off. After the fault is recovered or after the deionization time, the main branch and / or the forward transfer branch and / or the reverse transfer branch of the DC circuit breaker are turned on. When the voltage source converter is fault-locked, the main branch of the DC circuit breaker is controlled to turn off, the reverse transfer branch of the DC circuit breaker is controlled to turn off, and the voltage source converter is locked.

16. The control method as described in claim 15, wherein, The DC fault includes a DC line fault. In the case of a DC line fault, after the deionization time, if the voltage source converter is operating in rectification mode, the reverse transfer branch of the DC circuit breaker is controlled to be turned on; if the voltage source converter is operating in inverter mode, the forward transfer branch of the DC circuit breaker is controlled to be turned on.

17. The control method as described in claim 15, wherein, If the changeover switch group includes a first changeover switch, a second changeover switch, a third changeover switch, and a fourth changeover switch, then When the voltage source converter is operating in inverter mode, the first and second transfer switches are closed, and the third and fourth transfer switches are opened. The voltage source converter operates in online inverter mode, including: Control the first and second changeover switches to open, and control the third and fourth changeover switches to close; Control the charging of the voltage source converter; Control the voltage source converter to unlock; Control the conduction of the reverse transfer branch; Control the conduction of the forward transfer branch; Control the shutdown of the reverse transfer branch; Control the third and fourth changeover switches to open, control the first and second changeover switches to close, and control the main branch to be connected.

18. The control method as described in claim 17, wherein, If the DC circuit breaker also includes a bypass branch, when the voltage source converter is operating in online inverter mode, after the reverse transfer branch is turned on, the bypass branch is turned off.

19. The control method as described in claim 15, wherein, If the DC circuit breaker further includes a bypass branch, the control method further includes: When the voltage source converter is in online shutdown or fault shutdown mode, the bypass branch of the DC circuit breaker is turned on, and the main branch and reverse transfer branch of the DC circuit breaker are turned off.

20. The control method as described in claim 15, wherein, If the DC circuit breaker further includes a bypass branch and the bypass branch includes: a fourth power switch, at least two fourth power switches connected in series, a diode, or at least two diodes connected in series, wherein the cathodes and anodes of the at least two diodes are connected in sequence, the control method further includes: When the voltage source converter is operating in online rectification mode, the bypass branch is controlled to conduct in reverse, the voltage source converter is controlled to charge, the voltage source converter is controlled to unlock, the reverse transfer branch is controlled to conduct, and the main branch is controlled to conduct.

21. The control method as described in claim 15, wherein, If the switching group includes a fifth switching switch, a sixth switching switch, a seventh switching switch, and an eighth switching switch, then when the voltage source converter is operating in online rectification mode, the fifth and sixth switching switches are controlled to open, and the seventh and eighth switching switches are controlled to close; the voltage source converter is controlled to charge, the voltage source converter is controlled to unlock, the reverse transfer branch is controlled to conduct, and the main branch is controlled to conduct.

22. The control method as described in claim 15, wherein, If the switching group includes a first switching switch, a second switching switch, a third switching switch, a fourth switching switch, a fifth switching switch, a sixth switching switch, a seventh switching switch, and an eighth switching switch, then when the voltage source converter is operating in inverter or rectifier mode, the first switching switch, the second switching switch, the fifth switching switch, and the sixth switching switch are controlled to close, and the third switching switch, the fourth switching switch, the seventh switching switch, and the eighth switching switch are controlled to open.

23. A control device for a voltage source type valve assembly as described in any one of claims 10 to 13, comprising: The detection unit is used to detect the operating parameters and faults of the voltage source valve group; The control unit, based on the operating parameters of the voltage source valve group, controls the main branch and / or forward transfer branch and / or reverse transfer branch of the DC circuit breaker to conduct, and controls the operation of the voltage source converter; when the voltage source converter experiences a DC fault, it controls the main branch of the DC circuit breaker to close and the reverse transfer branch of the DC circuit breaker to close; after the fault is recovered or after the deionization time, it controls the main branch and / or forward transfer branch and / or reverse transfer branch of the DC circuit breaker to conduct; when the voltage source converter is fault-locked, it controls the main branch of the DC circuit breaker to close and the reverse transfer branch of the DC circuit breaker to close, and controls the voltage source converter to lock out.

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