Hybrid direct-current power transmission valve group, direct-current power transmission system, control device and control method

Abstract

The invention discloses a hybrid direct-current power transmission valve group, a direct-current power transmission system, a control device and a control method, the hybrid direct-current power transmission valve group comprises a non-direct-current blocking type valve group, and the non-direct-current blocking type valve group comprises an uncontrolled valve group or a non-direct-current blocking type full-controlled valve group; the direct current blocking type valve group comprises a half-control valve group or a direct current blocking type full-control valve group; any one of the non-control valve group and the non-direct-current blocking type full-control valve group is connected in series with any one of the half-control valve group and the direct-current blocking type full-control valve group. On-line switching of the non-direct-current blocking type valve group is achieved by connecting or disconnecting alternating current through the alternating current end, and direct-current line fault ride-through is achieved by controlling the direct-current blocking type valve group to be in negative pressure. The hybrid direct-current power transmission valve group is used for solving the problems that an existing converter structure needs to be provided with a large number of reactive compensation devices, loss is high, and cost is high.

Description

Technical Field

[0001] The present application belongs to the technical field of high-voltage direct current transmission, and specifically relates to a hybrid direct current transmission valve group, a direct current transmission system, a control device and a control method. Background Art

[0002] High-voltage and ultra-high-voltage direct current transmission has a large capacity. One of the existing technologies uses a grid-commutated converter with a twelve-pulse circuit structure. Each twelve-pulse circuit has two three-phase six-bridge arm circuits connected in series. Each bridge arm uses a single large-capacity thyristor in series. Since the thyristor cannot be controlled to turn off, the existing converter structure needs to be equipped with a large number of reactive compensation devices. The second existing technology uses a voltage source converter based on a modular multi-level converter. Each bridge arm uses a half-bridge submodule or a full-bridge submodule composed of IGBT or IGCT in series. It can flexibly control active power and reactive power and can be connected to a passive power grid or an isolated island new energy power grid. However, it is expensive and has high losses. The third existing technology uses a bridge-type uncontrolled rectifier circuit with a twelve-pulse circuit structure. Each bridge arm uses a single large-capacity diode in series. It has certain advantages in cost and reactive loss, but due to uncontrolled rectification, it cannot control power by itself and cannot suppress DC side faults. It is difficult to meet the performance requirements of the DC transmission system.

[0003] With the development of new energy in high-altitude areas, deserts and offshore, the performance, cost and land requirements of DC transmission systems are getting higher and higher. The hybrid DC transmission valve group using the above three existing technologies can achieve complementary advantages, give full play to the technical advantages of their respective converters, make up for each other's shortcomings, maximize the comprehensive transmission performance, and optimize the cost and land occupation of the DC transmission system. Summary of the invention

[0004] Purpose of the invention: The present application provides a hybrid DC transmission valve group, a DC transmission system, a control device and a control method, which are used to solve the problem that the existing converter structure needs to be equipped with a large number of reactive compensation devices, has high losses, and is difficult to meet the requirements of DC transmission.

[0005] Technical solution: The present application provides a hybrid DC transmission valve group, including: a non-DC blocking type valve group, the non-DC blocking type valve group includes: an uncontrolled valve group or a non-DC blocking type fully controlled valve group; a DC blocking type valve group, the DC blocking type valve group includes: a semi-controlled valve group or a DC blocking type fully controlled valve group; wherein, any one of the uncontrolled valve group and the non-DC blocking type fully controlled valve group is connected in series with any one of the semi-controlled valve group and the DC blocking type fully controlled valve group.

[0006] In some embodiments, any one of the uncontrolled valve group, the semi-controlled valve group, the non-DC blocking type fully-controlled valve group, and the DC blocking type fully-controlled valve group includes: a converter, a bypass switch, a bypass knife gate, a first isolation knife gate, and a second isolation knife gate; the bypass switch and the bypass knife gate are connected in parallel to form a bypass circuit; the first isolation knife gate and the second isolation knife gate are respectively arranged at the connection node where the bypass switch and the bypass knife gate are connected in parallel.

[0007] In some embodiments, the commutation device of the semi-controlled valve group includes any one of a grid-commutated converter and a current source converter with controllable shutdown capability.

[0008] In some embodiments, the commutation device includes a grid-commutated converter, which includes: a first three-phase input, a second three-phase input and a thyristor, a plurality of the thyristors are connected in series to form a bridge arm, the first three-phase input is connected to the bridge arm, and the second three-phase input is connected to the bridge arm.

[0009] In some embodiments, the current source converter with controllable shutdown capability includes a controllable grid-commutated converter CLCC, an IGCT-based hybrid-commutated converter HCC, a controllable current source converter CSC, and a line-commutated converter LCC.

[0010] In some embodiments, the non-DC blocking type fully-controlled valve group and the conversion device of the DC blocking type fully-controlled valve group include a voltage source converter; wherein, the voltage source converter of the non-DC blocking type fully-controlled valve group includes a two-level converter, a three-level converter, a modular multilevel converter based on a half-bridge sub-module, a diode clamped multi-level converter, a cascaded two-level converter or a stacked two-level converter; the voltage source converter of the DC blocking type fully-controlled valve group includes a modular multilevel converter based on a full-bridge sub-module or a modular multilevel converter based on a mixture of half-bridge and full-bridge sub-modules.

[0011] In some embodiments, the voltage source converter includes: a third three-phase input, an isolation switch, a charging resistor, a sub-module and a current limiting reactor; multiple sub-modules and the current limiting reactor are connected in series to form a bridge arm; the third three-phase input is connected to the valve side of the converter transformer; the isolation switch and the charging resistor are connected in parallel and connected between the third three-phase input and the bridge arm; wherein the sub-module includes a full-control module and a capacitor, and multiple full-control modules are connected to the capacitor to form a full-bridge structure or a half-bridge structure.

[0012] In some embodiments, the commutation device of the uncontrolled valve group includes a bridge-type uncontrolled rectifier circuit, and the bridge-type uncontrolled rectifier circuit includes: a diode, a fourth three-phase input and a fifth three-phase input, a plurality of the diodes are connected in series to form a bridge arm, the fourth three-phase input is connected to the bridge arm, and the fifth three-phase input is connected to the bridge arm.

[0013] In some embodiments, the absolute value of the maximum negative DC voltage generated or blocked by the DC blocking valve group is greater than the rated DC voltage or the rated no-load DC voltage of the non-DC blocking valve group.

[0014] The present application also provides a DC power transmission system, comprising the hybrid DC power transmission valve group as described above, the DC power transmission system further comprising: a rectifier station, the rectifier station comprising a first DC pole, a second DC pole and a first AC system, the first AC system being connected to the first DC pole and the second DC pole respectively; an inverter station, the inverter station comprising a third DC pole, a fourth DC pole and a second AC system, the second AC system being connected to the third DC pole and the fourth DC pole respectively.

[0015] In some embodiments, the first DC pole includes a first high-end uncontrolled valve group, a first low-end semi-controlled valve group, a first high-end converter transformer, and a first low-end converter transformer. The first high-end uncontrolled valve group is connected in series with the first low-end semi-controlled valve group. The first high-end converter transformer is connected between the first AC system and the first high-end uncontrolled valve group. The first low-end converter transformer is connected between the first AC system and the first low-end semi-controlled valve group. The second DC pole includes a second low-end semi-controlled valve group, a second high-end uncontrolled valve group, a second low-end converter transformer, and a second high-end converter transformer. The second low-end semi-controlled valve group is connected in series with the second high-end uncontrolled valve group. The second low-end converter transformer is connected between the first AC system and the second low-end semi-controlled valve group. The second high-end converter transformer is connected between the first AC system and the second high-end uncontrolled valve group.

[0016] In some embodiments, the first DC pole includes a first high-end uncontrolled valve group, a first low-end DC blocking type fully-controlled valve group, a first high-end converter transformer and a first low-end converter transformer, the first high-end uncontrolled valve group is connected in series with the first low-end DC blocking type fully-controlled valve group; the first high-end converter transformer is connected between the first high-end uncontrolled valve group and the first AC system; the first low-end converter transformer is connected between the first low-end DC blocking type fully-controlled valve group and the first AC system; the second DC pole includes a second low-end DC blocking type fully-controlled valve group, a second high-end uncontrolled valve group, a second low-end converter transformer and a second high-end converter transformer, the second low-end DC blocking type fully-controlled valve group is connected in series with the second high-end uncontrolled valve group, the second low-end converter transformer is connected between the second low-end DC blocking type fully-controlled valve group and the first AC system, and the second high-end converter transformer is connected between the second high-end uncontrolled valve group and the first AC system.

[0017] In some embodiments, the first DC pole includes: a first high-end non-DC blocking type fully-controlled valve group, a first low-end half-controlled valve group, a first high-end converter transformer and a first low-end converter transformer; the first high-end non-DC blocking type fully-controlled valve group is connected to the first low-end half-controlled valve group; the first high-end converter transformer is connected between the first high-end non-DC blocking type fully-controlled valve group and the first AC system; the first low-end converter transformer is connected between the first low-end half-controlled valve group and the first AC system; the second DC pole includes: a second low-end half-controlled valve group, a second high-end non-DC blocking type fully-controlled valve group, a second low-end converter transformer and a second high-end converter transformer; the second low-end half-controlled valve group and the second high-end non-DC blocking type fully-controlled valve group are connected in series; the second low-end converter transformer is connected between the second low-end half-controlled valve group and the first AC system; the second high-end converter transformer is connected between the second high-end non-DC blocking type fully-controlled valve group and the first AC system.

[0018] In some embodiments, the third DC pole includes: two or any two of any one of a half-controlled valve group, a non-DC blocking type fully-controlled valve group, and a DC blocking type fully-controlled valve group; the fourth DC pole includes: two or any two of any one of a half-controlled valve group, a non-DC blocking type fully-controlled valve group, and a DC blocking type fully-controlled valve group.

[0019] The present application also provides a DC transmission valve group control device, comprising the hybrid DC transmission valve group or the non-DC blocking valve group as described above, and further comprising: a first detection unit, the first detection unit is used to detect the operating parameters and fault parameters of the hybrid DC transmission valve group; a first control unit, the first control unit is used to transfer the DC current to the bridge uncontrolled rectifier circuit, the fully controlled device anti-parallel diode or the fully controlled device of the non-DC blocking valve group based on the operating parameters and fault parameters of the hybrid DC transmission valve group or the non-DC blocking valve group when the non-DC blocking valve group is put into operation online, and then connect the AC input end of the non-DC blocking valve group to AC, or / and unlock the non-DC blocking valve group; and the first control unit The control unit is used to disconnect the AC power from the AC input end of the non-DC blocking type valve group, or / and lock the non-DC blocking type valve group, or / and bypass the non-DC blocking type valve group when the non-DC blocking type valve group exits online or fails; or / and when the non-DC blocking type valve group fails to exit, the first control unit is used to control the DC blocking type valve group to present a zero pressure or a blocking state at the fault point; and the first control unit is used to control the DC blocking type valve group to a negative pressure when the DC line fails, so that the DC current of the hybrid DC transmission valve group connected to the DC line is zero or equal to the DC current at the other end of the fault point of the DC line, or control the DC blocking type valve group to be in a blocking state.

[0020] The present application also provides a DC transmission valve group control method, which is used to control the hybrid DC transmission valve group or the non-DC blocking valve group as described above, and the control method includes the following steps: obtaining the operating parameters and fault parameters of the hybrid DC transmission valve group or the non-DC blocking valve group; in response to the non-DC blocking valve group being put into operation online, first transferring the DC current to the bridge uncontrolled rectifier circuit, the fully controlled device anti-parallel diode or the fully controlled device of the non-DC blocking valve group; connecting the AC input end of the non-DC blocking valve group to AC power, or / and unlocking the non-DC blocking valve group; in response to the non-DC blocking valve group exiting online or exiting due to a fault, disconnecting the AC input end of the non-DC blocking valve group from AC power, or / and locking the non-DC blocking valve group, or / and bypassing the non-DC blocking valve group; or / and in response to the non-DC blocking valve group exiting due to a fault, controlling the DC blocking valve group to achieve zero pressure or a blocking state at the fault point;

[0021] In response to a DC line fault, the DC blocking valve group is controlled to be in a negative pressure, so that the DC current of the hybrid DC transmission valve group connected to the DC line is equal to zero or equal to the DC current at the other end of the DC line fault point, or the DC blocking valve group is controlled to be in a blocking state.

[0022] The present application also provides a DC transmission system control device, comprising the DC transmission system as described above, and further comprising: a second detection unit, the second detection unit is used to detect the operating parameters and fault parameters of the DC transmission system; a second control unit, the second control unit is used to control the station where the DC blocking valve group is located to disconnect from the ground after the DC blocking valve group is online or faulty based on the operating parameters and fault parameters of the DC transmission system; when a DC line fault occurs again at the DC pole where the DC blocking valve group is located, or a non-DC blocking valve group at the DC pole where the DC blocking valve group is located occurs again In case of a fault, the second control unit is used to control the DC currents of the converters at both ends of the fault point to be equal, to restart the DC pole where the DC blocking valve group is located after the de-ionization time or fault isolation, or / and to lock the non-DC blocking valve group at the DC pole where the DC blocking valve group is located, or / and to disconnect the AC power from the AC input end of the DC blocking valve group, reconnect it to the ground and isolate the DC pole; the second control unit is used to control the DC currents of the hybrid DC transmission valve group and the opposite valve group of the DC line to be equal when the DC line fails, or to control the hybrid DC transmission valve group and the opposite valve group to be zero current or in a blocking state.

[0023] The present application also provides a DC power transmission system control method, which is used to control the DC power transmission system as described above, and the control method comprises the steps of:

[0024] Obtaining operating parameters and fault parameters of the DC power transmission system;

[0025] In response to the DC blocking valve group exiting online or exiting due to a fault, the station where the DC blocking valve group is located is disconnected from the ground; when a DC line fault occurs again at the DC pole where the DC blocking valve group is located, or a non-DC blocking valve group at the DC pole where the DC blocking valve group is located fails again, the DC currents of the converters at both ends of the fault point are controlled to be equal, and the DC pole where the DC blocking valve group is located is restarted after the de-ionizing time or fault isolation, or / and the non-DC blocking valve group at the DC pole where the DC blocking valve group is located is locked, or / and the AC input end of the DC blocking valve group is disconnected from the AC power, reconnected to the ground and the DC pole is isolated;

[0026] In response to a DC line fault, the DC currents of the hybrid DC transmission valve group and the opposite valve group of the DC line are controlled to be equal, or the hybrid DC transmission valve group and the opposite valve group are controlled to be zero current or in a blocked state.

[0027] Beneficial effect: Compared with the prior art, in the hybrid DC transmission valve group, DC transmission system, control device and control method provided by the present invention, the hybrid DC transmission valve group includes: a non-DC blocking valve group, the non-DC blocking valve group includes: an uncontrolled valve group or a non-DC blocking fully controlled valve group; a DC blocking valve group, the DC blocking valve group includes: a semi-controlled valve group or a DC blocking fully controlled valve group; any one of the uncontrolled valve group and the non-DC blocking fully controlled valve group is connected in series with any one of the semi-controlled valve group and the DC blocking fully controlled valve group. The hybrid DC transmission valve group of the present invention overcomes the problem that the existing power grid phase-changing converter needs to be equipped with a large number of reactive compensation equipment and needs a strong AC system to provide phase-changing voltage support, as well as the shortcomings of the existing voltage source converter, such as high cost, high loss, and difficulty in suppressing DC side faults, thereby improving the performance of DC transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The technical solutions and other beneficial effects of the present invention will be made apparent by describing in detail the specific embodiments of the present invention in conjunction with the accompanying drawings.

[0029] Figure 1 It is a schematic diagram of a hybrid DC transmission valve group provided in an embodiment of the present application;

[0030] Figure 2a This is a schematic diagram of the valve group structure of a hybrid DC transmission valve group according to an embodiment of the present application;

[0031] Figure 2b This is a schematic diagram of the valve group structure of a hybrid DC transmission valve group according to an embodiment of the present application;

[0032] Figure 2c This is a schematic diagram of the valve group structure of a hybrid DC transmission valve group according to an embodiment of the present application;

[0033] Figure 2d This is a schematic diagram of the valve group structure of a hybrid DC transmission valve group according to an embodiment of the present application;

[0034] Figure 2e This is a schematic diagram of the valve group structure of a hybrid DC transmission valve group according to an embodiment of the present application;

[0035] Figure 2f This is a schematic diagram of the valve group structure of a hybrid DC transmission valve group according to an embodiment of the present application;

[0036] Figure 3 This is a schematic diagram of a semi-controlled valve group provided in an embodiment of the present application;

[0037] Figure 4 A grid commutation converter using a twelve-pulse bridge circuit is provided in an embodiment of the present application;

[0038] Figure 5This is a schematic diagram of a fully controlled valve group provided in an embodiment of the present application;

[0039] Figure 6 A voltage source converter using a modular multilevel converter is provided in an embodiment of the present application;

[0040] Figure 7 The embodiment of the present application provides a submodule that adopts a full-bridge submodule structure;

[0041] Figure 8 The embodiment of the present application provides a schematic diagram of a half-bridge sub-module structure in which the sub-module is provided;

[0042] Fig. 9 This is a schematic diagram of an uncontrolled valve group provided in an embodiment of the present application;

[0043] Fig.10 A bridge-type uncontrolled rectifier circuit using a twelve-pulse bridge circuit is provided in an embodiment of the present application;

[0044] Fig.11 is a schematic diagram of a direct current transmission system according to an embodiment of the present application;

[0045] Fig.12 is another schematic diagram of a direct current transmission system according to an embodiment of the present application;

[0046] Fig.13 is a schematic diagram of another direct current transmission system according to an embodiment of the present application;

[0047] Fig.14 is another schematic diagram of a direct current transmission system according to an embodiment of the present application;

[0048] Fig.15 It is a flow chart of a control method of a DC transmission valve group provided in an embodiment of the present application;

[0049] Fig.16 is a schematic diagram of yet another DC power transmission system applicable to the DC power transmission valve group control method provided in the embodiment of the present application;

[0050] Fig.17 The embodiment of the present application provides Fig.11 The results of the simulation test on the valve group of the DC transmission system;

[0051] Fig.18 The embodiment of the present application provides Fig.11 The results of the simulation test of the valve group exiting the DC transmission system;

[0052] Fig.19 The embodiment of the present application provides Fig.11 The results of the DC line fault simulation test of the DC transmission system;

[0053] Fig. 20 It is a schematic diagram of a control device of a DC transmission valve group provided in an embodiment of the present application;

[0054] Fig.21 It is a schematic flow chart of a control method for a DC power transmission system provided in an embodiment of the present application;

[0055] Fig. 22 It is a schematic diagram of a control device for a DC power transmission system provided in an embodiment of the present application.

[0056] Figure numerals: 1-grid phase-commutating converter, 3-bypass switch, 4-bypass knife, 5-first isolating knife, 6-second isolating knife, 11-bridge uncontrolled rectifier circuit, 12-first DC blocking voltage source converter, 13-second bypass switch, 14-second bypass knife, 15-No. 2 first isolating knife, 16-No. 2 second isolating knife, 21-first three-phase input, 22-second three-phase input, 23-thyristor, 24-third three-phase input, 25-isolating knife, 26-charging resistor, 27-submodule, 28-current limiting reactor, 29-No. 1 IGBT module, 30-capacitor, 31-No. 2 IGBT module, 32-No. 3 IGBT module, 33-No. 4 IGBT module, 42-No. 43 Phase input, 43-fifth three-phase input, 44-diode, 45-third bypass switch, 46-third bypass knife, 47-No. 3 first isolation knife, 48-No. 3 second isolation knife, 51, 55-fourth bypass knife, 52, 56-fourth bypass switch, 53-No. 5 first isolation knife, 54-No. 5 second isolation knife, 57-No. 4 first isolation knife, 58-No. 4 second isolation knife, 61-fifth bypass knife, 62-fifth bypass switch, 63-No. 6 first isolation knife, 64-No. 6 second isolation knife, 71-seventh bypass knife, 72-seventh bypass switch, 73-No. 8 first isolation knife, 74-No. 8 second isolation knife, 81-sixth bypass knife, 82-sixth bypass switch, 83 - No. 7 first isolation switch, 84- No. 7 second isolation switch, 100- rectifier station, 101- second grid commutation converter, 102- second DC blocking voltage source converter, 104- second bridge uncontrolled rectifier circuit, 105- first smoothing reactor, 106- second smoothing reactor, 108- second non-DC blocking voltage source converter, 107- first non-DC blocking voltage source converter, 110- first DC pole, 111- first high-end uncontrolled valve group, 112- first low-end semi-controlled valve group, 113- first metal return line transfer switch, 213- second metal return line transfer switch, 114- rectifier station grounding pole line, 115- rectifier station grounding pole, 116- first high-end converter transformer, 117- first low-end converter transformer, 119-first pole neutral bus switch, 120-second DC pole, 121-second low-end semi-controlled valve group, 122-second high-end uncontrolled valve group, 126-second low-end converter transformer, 127-second high-end converter transformer, 129-second pole neutral bus switch, 131-first grid-side AC switch, 132-second grid-side AC switch, 133-third grid-side AC switch, 134-fourth grid-side AC switch, 135-fifth non-DC blocking voltage source converter, 136-sixth non-DC blocking voltage source converter, 137-first DC circuit breaker, 140-first AC system, 141-first low-end DC blocking fully-controlled valve group, 142-second low-end DC blocking fully-controlled valve group,145-first high-end non-DC blocking type fully controlled valve group, 146-second high-end non-DC blocking type fully controlled valve group, 147-first low-end non-DC blocking type fully controlled valve group, 148-second low-end non-DC blocking type fully controlled valve group, 116-first high-end converter transformer, 127-second high-end converter transformer, 150-first DC line, 160-second DC line, 172-first pole bus isolation knife switch, 173-first DC line isolation knife switch, 174-first bipolar neutral zone isolation knife switch, 175-first bipolar neutral zone isolation knife switch, 182-second pole bus isolation knife switch, 183-second DC line isolation knife switch, 184-first bipolar neutral zone isolation knife switch, 185-first bipolar neutral zone isolation knife switch, 190-first earth return line transfer switch, 200-inverter station, 201-third grid phase-changing converter, 202-fourth grid phase-changing converter, 203-sixth grid phase-changing converter, 204-fifth grid phase-changing converter, 205-third smoothing reactor, 206-fourth smoothing reactor, 207-third non-DC blocking type voltage source converter, 208-fourth non-DC blocking type voltage source converter, 210-third DC pole, 211-third high-end semi-controlled valve group, 212-third low-end semi-controlled valve group, 213-second metal return line conversion knife switch, 214-inverter station grounding pole line, 215-inverter station grounding pole, 216-third high-end converter transformer, 217-third low-end converter transformer, 219- The third pole neutral bus switch, 220-the fourth DC pole, 221-the fourth low-end semi-controlled valve group, 222-the fourth high-end semi-controlled valve group, 226-the fourth low-end converter transformer, 227-the fourth high-end converter transformer, 229-the fourth pole neutral bus switch, 231-the fifth grid-side AC switch, 232-the sixth grid-side AC switch, 233-the seventh grid-side AC switch, 234-the eighth grid-side AC switch, 235-the seventh non-DC blocking voltage source converter, 236-the eighth non-DC blocking voltage source converter, 237-the third DC circuit breaker, 238-the fourth DC circuit breaker, 240-the second AC system, 245-the third high-end non-DC blocking fully-controlled valve group, 246-the fourth high-end non-DC blocking fully-controlled Valve group, 247-third low-end non-DC blocking type fully controlled valve group, 248-fourth low-end non-DC blocking type fully controlled valve group, 272-third pole bus isolation knife switch, 273-third DC line isolation knife switch, 274-second bipolar neutral zone isolation knife switch, 275-second bipolar neutral zone isolation knife switch, 282-fourth pole bus isolation knife switch, 283-fourth DC line isolation knife switch, 284-second bipolar neutral zone isolation knife switch, 285-second bipolar neutral zone isolation knife switch, 290-second earth return line conversion knife switch, 310-first detection unit, 320-first control unit, 400-non-DC blocking type valve group, 401-uncontrolled valve group, 402-non-DC blocking type fully controlled valve group, 500-DC blocking type valve group,501-semi-controlled valve group, 502-DC blocking type full-controlled valve group, 410-second detection unit, 420-second control unit. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0058] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features.

[0059] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention.

[0060] The present application provides a hybrid DC power transmission valve group, including: any at least two types of non-DC blocking valve group 400 and DC blocking valve group 500 are connected in series, see Figure 1 , Figure 1 Two series connection structures of non-DC blocking valve group 400 and DC blocking valve group 500 are shown. In the embodiment of the present application, the non-DC blocking valve group 400 includes: an uncontrolled valve group 401 or a non-DC blocking fully controlled valve group 402; the DC blocking valve group 500 includes: a half-controlled valve group 501 or a DC blocking fully controlled valve group 502; wherein any one of the uncontrolled valve group 401 and the non-DC blocking fully controlled valve group 402 is connected in series with any one of the half-controlled valve group 501 and the DC blocking fully controlled valve group 502.

[0061] The hybrid DC transmission valve group of the present application is combined based on the above four types of valve groups, and has six series connection topological structures: the semi-controlled valve group 501 is connected in series with the uncontrolled valve group 401: Figure 2a The anode of the semi-controlled valve group 501 is denoted as X4 and the cathode of the uncontrolled valve group 401 is denoted as X1. Figure 2b The cathode of the semi-controlled valve group 501 is denoted as X3 and is connected to the anode of the uncontrolled valve group 401 as X2; or, the DC blocking type fully controlled valve group 502 is connected in series to the uncontrolled valve group 401: Figure 2c The negative electrode of the DC blocking type full-control valve group 502 is denoted as X6 and the cathode of the uncontrolled valve group 401 is denoted as X1, or as shown in FIG. Figure 2d The positive electrode of the DC blocking type fully controlled valve group 502 is marked as X5 and is connected to the anode of the non-controlled valve group 401 as X1; or, the semi-controlled valve group 501 is connected in series with the non-DC blocking type fully controlled valve group 402: Figure 2e The anode of the semi-controlled valve group 501 is denoted as X4 and is connected to the positive electrode of the non-DC blocking full-controlled valve group 402, denoted as X7, or as shown in FIG. Figure 2f The cathode of the semi-controlled valve group 501 is marked as X3 and is connected to the negative electrode of the non-DC blocking full-controlled valve group 402 is marked as X8.

[0062] In some embodiments of the present application, the semi-controlled valve group 501 includes a grid-commutating converter, which is connected in parallel with a bypass isolation circuit; the DC-blocking fully-controlled valve group 502 includes a DC-blocking voltage source converter, which is connected in parallel with a bypass isolation circuit; the non-DC-blocking fully-controlled valve group 402 includes a non-DC-blocking voltage source converter, which is connected in parallel with a bypass isolation circuit; the uncontrolled valve group 401 includes a bridge-type uncontrolled rectifier circuit, which is connected in parallel with a bypass isolation circuit.

[0063] It should be noted that the above-mentioned embodiments of the present application can solve the problem of online valve group insertion and withdrawal of the uncontrolled valve group 401 and the non-DC blocking type fully controlled valve group 402; when a DC line fault occurs, the DC voltage or DC current control performance of the semi-controlled valve group 501 or the DC blocking type fully controlled valve group 502 is used to solve the problem that the uncontrolled valve group 401 and the non-DC blocking type fully controlled valve group 402 cannot cross the DC fault, overcome the technical defects of the single valve group, effectively improve the performance of the hybrid DC transmission valve group, and realize a high-performance, low-cost and low-loss high-voltage DC transmission solution.

[0064] In the embodiments of the present application, Figure 2a and Figure 2b The semi-controlled valve group 501 is connected in series with the uncontrolled valve group 401, such as Figure 2a The anode of the semi-controlled valve group 501 is denoted as X4 and the cathode of the uncontrolled valve group 401 is denoted as X1. Figure 2bThe cathode of the semi-controlled valve group 501 is denoted as X3 and the anode of the uncontrolled valve group 401 is denoted as X2; Figure 2c and Figure 2d It is a DC blocking type full control valve group connected in series with the uncontrolled valve group 401 type: Figure 2c The negative electrode of the DC blocking type fully controlled valve group is denoted as X6 and the cathode of the uncontrolled valve group 401 is denoted as X1. Figure 2d The positive electrode of the DC blocking type fully controlled valve group shown is marked as X5 and is connected to the anode of the uncontrolled valve group 401 as X2; Figure 2e and Figure 2f The semi-controlled valve group 501 is connected in series with the non-DC blocking type full-controlled valve group 402: Figure 2e The anode of the semi-controlled valve group 501 is denoted as X4 and is connected to the positive electrode of the non-DC blocking full-controlled valve group 402 as X7. Figure 2f The cathode of the semi-controlled valve group 501 is marked as X3 and is connected to the anode of the non-DC blocking full-controlled valve group 402 as X8.

[0065] In the embodiments of this application, please refer to Figure 3 , Figure 3 The structure diagram of the semi-controlled valve group 501 is shown. The semi-controlled valve group 501 of the present application includes a commutation device, a bypass circuit and an isolation circuit; the commutation device of the present embodiment includes a power grid phase-commutation converter 1, the bypass circuit includes a bypass switch 3 and a bypass knife 4, and the bypass switch 3 and the bypass knife 4 are arranged in parallel; the isolation circuit includes a first isolation knife 5 and a second isolation knife 6, and the first isolation knife 5 and the second isolation knife 6 are respectively arranged at the connection node where the bypass switch 3 and the bypass knife 4 are connected in parallel, and one end of the bypass knife 4 is connected to an end of the first isolation knife 5 away from the power grid phase-commutation converter 1, and the other end of the bypass knife 4 is connected to an end of the second isolation knife 6 away from the power grid phase-commutation converter 1.

[0066] In some embodiments of the present application, the grid-commutated converter 1 includes a six-pulse bridge circuit or a twelve-pulse bridge circuit, and the grid-commutated converter 1 includes a non-disabled half-controlled power semiconductor such as a thyristor, see Figure 4 , Figure 4 The grid-commutated converter 1 shown adopts a twelve-pulse bridge circuit.

[0067] In some embodiments of the present application, such as Figure 4 As shown, the twelve-pulse bridge circuit includes thyristors 23, and the thyristors 23 are connected in series to form each bridge arm. The grid-commutated converter 1 also includes a first three-phase input 21 and a second three-phase input 22, the first three-phase input 21 is connected to the valve side of the YY type converter transformer, the second three-phase input 22 is connected to the valve side of the YD type converter transformer, and the first three-phase input 21 and the second three-phase input 22 are also connected to the bridge arms respectively.

[0068] In some embodiments of the present application, Figure 5 As shown, any one of the non-DC blocking type full-control valve group 402 and the DC blocking type full-control valve group 502 includes a commutation device, an isolation circuit and a bypass circuit; the commutation device includes a voltage source converter 2, the isolation circuit includes a first isolation switch 5 and a second isolation switch 6, and the bypass circuit includes a bypass switch 3 and a bypass switch 4; the bypass switch 3 and the bypass switch 4 are arranged in parallel; the first isolation switch 5 is arranged at a connection node where the bypass switch 3 and the bypass switch 4 are connected in parallel, and the second isolation switch 6 is arranged at another connection node where the bypass switch 3 and the bypass switch 4 are connected in parallel, and one end of the bypass switch 4 is connected to an end of the first isolation switch 5 away from the voltage source converter 2, and the other end of the bypass switch 4 is connected to an end of the second isolation switch 6 away from the voltage source converter 2.

[0069] In some embodiments of the present application, Figure 6 As shown, Figure 6 The present invention is a schematic diagram of the structure of the voltage source converter 2 provided in the embodiment of the present application. The voltage source converter 2 adopts a modular multilevel converter. The voltage source converter 2 includes multiple bridge arms, a third three-phase input 24, an isolation switch 25 and a charging resistor 26. Each bridge arm includes a sub-module 27 and a current limiting reactor 28. The sub-module 27 and the current limiting reactor 28 are connected in series; the third three-phase input 24 is connected to the valve side of the converter transformer; the isolation switch 25 is connected between the third three-phase input 24 and the bridge arm, the isolation switch 25 is three-phase, and a charging resistor 26 is connected in parallel at both ends of the isolation switch 25.

[0070] In some embodiments of the present application, Figure 7 As shown, Figure 7 It is a structural diagram of a full-bridge submodule. Submodule 27 adopts a full-bridge submodule. Submodule 27 includes IGBT module No. 1 29, IGBT module No. 2 31, IGBT module No. 32, IGBT module No. 4 33, and 1 capacitor 30. The four IGBT modules and 1 capacitor are connected to form a full-bridge structure.

[0071] It should be added that if Figure 6 If all submodules 27 of the voltage source converter 2 are full-bridge submodules, or more than 50% of the submodules 27 are full-bridge submodules, then Figure 6 The voltage source converter 2 shown is a DC blocking voltage source converter. Figure 5 The fully controlled valve group adopts Figure 6 The DC blocking voltage source converter shown in the figure has Figure 6 The fully-controlled valve group shown is a DC blocking type fully-controlled valve group 502 , wherein the DC blocking type fully-controlled valve group 502 can adjust the DC voltage to a negative pressure.

[0072] In some embodiments of the present application, Figure 8 As shown, Figure 8 The schematic diagram of the structure of the submodule 27 using a half-bridge submodule is shown. The half-bridge submodule includes a No. 1 IGBT module 29, a No. 2 IGBT module 31 and a capacitor 30. Two IGBT modules and one capacitor are connected to form a half-bridge structure.

[0073] It should be noted that if Figure 6 The submodules 27 of the voltage source converter 2 shown are all half-bridge submodule structures. Figure 6 The voltage source converter 2 shown is a non-DC blocking voltage source converter. Figure 5 The fully controlled valve group shown adopts Figure 6 For the non-DC blocking voltage source converter shown in Figure 6 The fully controlled valve group shown is a non-DC blocking type fully controlled valve group 402. The non-DC blocking type fully controlled valve group 402 cannot adjust the DC voltage to a negative pressure.

[0074] In some embodiments of this application, please refer to Fig. 9 , Fig. 9 The figure shows the structure of the uncontrolled valve group. Fig. 9 As shown, the uncontrolled valve group 401 includes a commutation device, an isolation circuit and a bypass circuit, the commutation device includes a bridge uncontrolled rectifier circuit 11, the isolation circuit includes a first isolation switch 5 and a second isolation switch 6, and the bypass circuit includes a bypass switch 3 and a bypass switch 4; the bridge uncontrolled rectifier circuit 11 includes a six-pulse bridge circuit or a twelve-pulse bridge circuit, and the bridge uncontrolled rectifier circuit 11 includes an uncontrolled power semiconductor, such as a diode.

[0075] In some embodiments of this application, please refer to Fig.10 ,like Fig.10 The bridge uncontrolled rectifier circuit 11 shown adopts a twelve-pulse bridge circuit. The bridge uncontrolled rectifier circuit 11 includes multiple bridge arms, a fourth three-phase input 42 and a fifth three-phase input 43. Each bridge arm includes multiple diodes 44, and the diodes 44 are connected in series to form a bridge arm; the fourth three-phase input 42 is connected to the valve side of the YY type converter transformer, and the fifth three-phase input 43 is connected to the valve side of the YD type converter transformer. The fourth three-phase input 42 and the fifth three-phase input 43 are also connected to the bridge arms respectively.

[0076] The present application also provides a direct current transmission system, specifically a high voltage current transmission system, the direct current transmission system comprising the hybrid current transmission valve group as described above. Fig.11For the convenience of description, the same components in different positions will be distinguished by adding prefixes such as "first", "second", "No. 2", and "No. 3". The DC transmission system of the present application is an ultra-high voltage DC transmission system. The main circuit of the DC transmission system includes: a rectifier station 100, an inverter station 200, a first DC line 150, a second DC line 160, a rectifier station grounding electrode line 114, a rectifier station grounding electrode 115, an inverter station grounding electrode line 214, and an inverter station grounding electrode 215.

[0077] See also Fig.11 The rectifier station 100 includes a first DC pole 110, a second DC pole 120, a first AC system 140, a first grid-side AC switch 131, a second grid-side AC switch 132, a third grid-side AC switch 133, a fourth grid-side AC switch 134, a first metal return line transfer switch 113, a first earth return line transfer switch 190, a first bipolar neutral zone isolation switch 174, a second bipolar neutral zone isolation switch 175, a third bipolar neutral zone isolation switch 184 and a fourth bipolar neutral zone isolation switch 185.

[0078] The first DC pole 110 includes a first high-end uncontrolled valve group 111, a first low-end semi-controlled valve group 112, a first high-end converter transformer 116, a first low-end converter transformer 117, a first smoothing reactor 105, a first pole neutral bus switch 119, a first pole bus isolation switch 172 and a first DC line isolation switch 173, wherein the first high-end uncontrolled valve group 111 and the first low-end semi-controlled valve group 112 are connected in series.

[0079] like Fig.11 As shown, the first high-end uncontrolled valve group 111 includes a bridge uncontrolled rectifier circuit 11, a second bypass knife gate 14, a second bypass switch 13, a No. 2 first isolation knife gate 15, and a No. 2 second isolation knife gate 16; the second bypass switch 13 is respectively connected to the anode and cathode of the bridge uncontrolled rectifier circuit 11, and the second bypass switch 13 is respectively connected to one end of the No. 2 first isolation knife gate 15 and the No. 2 second isolation knife gate 16; the second bypass knife gate 14 is connected to the other end of the No. 2 first isolation knife gate 15, and the second bypass knife gate 14 is connected to the other end of the No. 2 second isolation knife gate 16.

[0080] like Fig.11 As shown, the first low-end semi-controlled valve group 112 includes a grid-commutating converter 1, a bypass gate 4, a bypass switch 3, a first isolating gate 5, and a second isolating gate 6; the bypass switch 3 is respectively connected to the anode of the grid-commutating converter 1 and the cathode of the grid-commutating converter 1, and the bypass switch 3 is respectively connected to one end of the first isolating gate 5 and one end of the second isolating gate 6; the bypass gate 4 is respectively connected to the other end of the first isolating gate 5 and the other end of the second isolating gate 6.

[0081] like Fig.11 As shown, the second DC pole 120 includes a second low-end semi-controlled valve group 121, a second high-end uncontrolled valve group 122, a second low-end converter transformer 126, a second high-end converter transformer 127, a second smoothing reactor 106, a second pole neutral bus switch 129, a second pole bus isolation knife switch 182 and a second DC line isolation knife switch 183; the second low-end semi-controlled valve group 121 and the second high-end uncontrolled valve group 122 are connected in series.

[0082] like Fig.11 As shown, the second high-end uncontrolled valve group 122 includes a second bridge uncontrolled rectifier circuit 104, a third bypass knife gate 46, a third bypass switch 45, a No. 3 first isolation knife gate 47 and a No. 3 second isolation knife gate 48; the third bypass switch 45 is respectively connected to the positive end of the second bridge uncontrolled rectifier circuit 104 and the negative end of the second bridge uncontrolled rectifier circuit 104, and the third bypass switch 45 is respectively connected to one end of the No. 3 first isolation knife gate 47 and one end of the No. 3 second isolation knife gate 48; the third bypass knife gate 46 is respectively connected to the other end of the No. 3 first isolation knife gate 47 and the other end of the No. 3 second isolation knife gate 48.

[0083] like Fig.11 As shown, the second low-end semi-controlled valve group 121 includes the second grid phase-commutating converter 101, the fourth bypass knife 55, the fourth bypass switch 56, the fourth first isolation knife 57, and the fourth second isolation knife 58. The fourth bypass switch 56 is respectively connected to the positive end of the second grid phase-commutating converter 101 and the negative end of the second grid phase-commutating converter 101, and the fourth bypass switch 56 is respectively connected to one end of the fourth first isolation knife 57 and one end of the fourth second isolation knife 58; the fourth bypass knife 55 is respectively connected to the other end of the fourth first isolation knife 57 and the other end of the fourth second isolation knife 58.

[0084] like Fig.11 As shown, the inverter station 200 includes: a third DC pole 210, a fourth DC pole 220, a second AC system 240, a fifth grid-side AC switch 231, a sixth grid-side AC switch 232, a seventh grid-side AC switch 233, an eighth grid-side AC switch 234, a second metal return line switching switch 213, a second earth return line switching switch 290, a second bipolar neutral zone isolation switch 274, a second bipolar neutral zone isolation switch 275, a second bipolar neutral zone isolation switch 284 and a second bipolar neutral zone isolation switch 285.

[0085] like Fig.11As shown, the third DC pole 210 includes a third high-end semi-controlled valve group 211, a third low-end semi-controlled valve group 212, a third high-end converter transformer 216, a third low-end converter transformer 217, a third smoothing reactor 205, a third pole neutral bus switch 219, a third pole bus isolation knife switch 272 and a third DC line isolation knife switch 273; wherein the third high-end semi-controlled valve group 211 and the third low-end semi-controlled valve group 212 are connected in series.

[0086] like Fig.11 As shown, the third high-end semi-controlled valve group 211 includes a third grid phase-commutating converter 201, a fourth bypass knife gate 51, a fourth bypass switch 52, a No. 5 first isolation knife gate 53, and a No. 5 second isolation knife gate 54; the fourth bypass switch 52 is connected to the positive end of the third grid phase-commutating converter 201 and the negative end of the third grid phase-commutating converter 201, and the fourth bypass switch 52 is respectively connected to one end of the No. 5 first isolation knife gate 53 and one end of the No. 5 second isolation knife gate 54; the fourth bypass knife gate 51 is respectively connected to the other end of the No. 5 first isolation knife gate 53 and the other end of the No. 5 second isolation knife gate 54.

[0087] like Fig.11 As shown, the third low-end semi-controlled valve group 212 includes the fourth power grid phase-changing converter 202, the fifth bypass knife gate 61, the fifth bypass switch 62, the first isolation knife gate No. 6 63, and the second isolation knife gate No. 6 64; the fifth bypass switch 62 is respectively connected to the positive end of the fourth power grid phase-changing converter 202 and the negative end of the fourth power grid phase-changing converter 202, and the fifth bypass switch 62 is respectively connected to one end of the first isolation knife gate No. 6 63 and one end of the second isolation knife gate No. 6 64; the fifth bypass knife gate 61 is respectively connected to the other end of the first isolation knife gate No. 6 63 and the other end of the second isolation knife gate No. 6 64.

[0088] like Fig.11 As shown, the fourth DC pole 220 includes a fourth low-end semi-controlled valve group 221, a fourth high-end semi-controlled valve group 222, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a fourth smoothing reactor 206, a fourth pole neutral bus switch 229, a fourth pole bus isolation knife switch 282, and a fourth DC line isolation knife switch 283; the fourth low-end semi-controlled valve group 221 and the fourth high-end semi-controlled valve group 222 are connected in series.

[0089] like Fig.11As shown, the fourth high-end semi-controlled valve group 222 includes the fifth grid phase-changing converter 204, the sixth bypass knife gate 81, the sixth bypass switch 82, the seventh first isolation knife gate 83, and the seventh second isolation knife gate 84; the sixth bypass switch 82 is respectively connected to the positive end of the fifth grid phase-changing converter 204 and the negative end of the fifth grid phase-changing converter 204, and the sixth bypass switch 82 is respectively connected to one end of the seventh first isolation knife gate 83 and one end of the seventh second isolation knife gate 84; the sixth bypass knife gate 81 is respectively connected to the other end of the seventh first isolation knife gate 83 and the other end of the seventh second isolation knife gate 84.

[0090] like Fig.11 As shown, the fourth low-end semi-controlled valve group 221 includes the sixth grid phase-changing converter 203, the seventh bypass knife gate 71, the seventh bypass switch 72, the eighth first isolation knife gate 73, and the eighth second isolation knife gate 74; the seventh bypass switch 72 is respectively connected to the positive end of the sixth grid phase-changing converter 203 and the negative end of the sixth grid phase-changing converter 203, and the seventh bypass switch 72 is respectively connected to one end of the eighth first isolation knife gate 73 and one end of the eighth second isolation knife gate 74; the seventh bypass knife gate 71 is respectively connected to the other end of the eighth first isolation knife gate 73 and the other end of the eighth second isolation knife gate 74.

[0091] It should be added that the above mentioned Fig.11 The various switches or knife gates in the invention include at least one of a mechanical switch, a knife gate, a DC circuit breaker and a thyristor valve.

[0092] like Fig.11 As shown, taking the DC power transmission system as an example, the initial state is that the first high-end uncontrolled valve group 111 and the first low-end semi-controlled valve group 112 of the rectifier station 100 are in operation, and the third high-end semi-controlled valve group 211 and the third low-end semi-controlled valve group 212 of the inverter station 200 are in operation; the second bypass gate 14 of the rectifier station 100 is in position, the second bypass switch 13 is in position, the second first isolation gate 15 is in position, the second second isolation gate 16 is in position, the bypass gate 4 is in position, the bypass switch 3 is in position, the first isolation gate 5 is in position, the second isolation gate 6 is in position, the fourth bypass gate 51 of the inverter station 200 is in position, the fourth bypass switch 52 is in position, the fifth first isolation gate 53 is in position, the fifth second isolation gate 54 is in position, the fifth bypass gate 61 is in position, the fifth bypass switch 62 is in position, the sixth first isolation gate 63 is in position, and the sixth second isolation gate 64 is in position. The rectifier station 100 is used to control the rectifier operation of the grid phase-commutated converter 1 ; the inverter station 200 is used to control the inverter operation of the third grid phase-commutated converter 201 and the fourth grid phase-commutated converter 202 .

[0093] When the grid-side voltage of the converter transformer 116 connected to the uncontrolled valve group increases, the tap position of the converter transformer 116 is adjusted to reduce the increase in the valve-side voltage, thereby suppressing the increase in the DC voltage; when the grid-side voltage of the converter transformer 116 connected to the uncontrolled valve group decreases, the tap position of the converter transformer 116 is adjusted to reduce the decrease in the valve-side voltage, thereby suppressing the decrease in the DC voltage.

[0094] See also Fig.12 , Fig.12 Figure 1 is a schematic diagram of a DC transmission system. Fig.12 As shown, for the convenience of description, the same components in different positions will be distinguished by adding prefixes such as "first", "second", "No. 2", and "No. 3". The DC transmission system in the embodiment of the present application is an ultra-high voltage DC transmission system. The main circuit of the DC transmission system includes: a rectifier station 100, an inverter station 200, a first DC line 150, a second DC line 160, a rectifier station grounding electrode line 114, a rectifier station grounding electrode 115, an inverter station grounding electrode line 214, and an inverter station grounding electrode 215.

[0095] like Fig.12 As shown, the rectifier station 100 includes: a first DC pole 110, a second DC pole 120, a first AC system 140, a first grid-side AC switch 131, a second grid-side AC switch 132, a third grid-side AC switch 133, a fourth grid-side AC switch 134, a first metal return line transfer switch 113, a first earth return line transfer switch 190, a first bipolar neutral zone isolation switch 174, a second bipolar neutral zone isolation switch 175, a third bipolar neutral zone isolation switch 184 and a fourth bipolar neutral zone isolation switch 185.

[0096] like Fig.12 As shown, the first DC pole 110 includes a first high-end uncontrolled valve group 111, a first low-end DC blocking type 141, a first high-end converter transformer 116, a first low-end converter transformer 117, a first smoothing reactor 105, a first pole neutral bus switch 119, a first pole bus isolation knife switch 172 and a first DC line isolation knife switch 173; the first high-end uncontrolled valve group 111 and the first low-end DC blocking type 141 are connected in series.

[0097] like Fig.12 As shown, the first high-end uncontrolled valve group 111 includes: a bridge uncontrolled rectifier circuit 11, a second bypass knife gate 14, a second bypass switch 13, a No. 2 first isolation knife gate 15, and a No. 2 second isolation knife gate 16; the second bypass switch 13 is respectively connected to the positive end of the bridge uncontrolled rectifier circuit 11 and the negative end of the bridge uncontrolled rectifier circuit 11, and the second bypass switch 13 is respectively connected to one end of the No. 2 first isolation knife gate 15 and one end of the No. 2 second isolation knife gate 16; the second bypass knife gate 14 is connected to the other end of the No. 2 first isolation knife gate 15 and the other end of the No. 2 second isolation knife gate 16.

[0098] like Fig.12 As shown, the first low-end DC blocking type full-control valve group 141 includes: a first DC blocking type voltage source converter 12, a bypass knife gate 4, a bypass switch 3, a first isolation knife gate 5 and a second isolation knife gate 6; the bypass switch 3 connects the positive end of the first DC blocking type voltage source converter 12 and the negative end of the first DC blocking type voltage source converter 12, and the bypass switch 3 is respectively connected to one end of the first isolation knife gate 5 and one end of the second isolation knife gate 6; the bypass knife gate 4 is respectively connected to the other end of the first isolation knife gate 5 and the other end of the second isolation knife gate 6.

[0099] like Fig.12 As shown, the second DC pole 120 includes: a second low-end DC blocking type fully-controlled valve group 142, a second high-end uncontrolled valve group 122, a second low-end converter transformer 126, a second high-end converter transformer 127, a second smoothing reactor 106, a second pole neutral bus switch 129, a second pole bus isolation knife switch 182 and a second DC line isolation knife switch 183; the second low-end DC blocking type fully-controlled valve group 142 and the second high-end uncontrolled valve group 122 are connected in series.

[0100] like Fig.12 As shown, the second high-end uncontrolled valve group 122 includes: a second bridge uncontrolled rectifier circuit 104, a third bypass knife gate 46, a third bypass switch 45, a No. 3 first isolation knife gate 47, and a No. 3 second isolation knife gate 48; the third bypass switch 45 is connected to the positive end of the second bridge uncontrolled rectifier circuit 104 and the negative end of the second bridge uncontrolled rectifier circuit 104, and the third bypass switch 45 is respectively connected to one end of the No. 3 first isolation knife gate 47 and one end of the No. 3 second isolation knife gate 48; the third bypass knife gate 46 is respectively connected to the other end of the No. 3 first isolation knife gate 47 and the other end of the No. 3 second isolation knife gate 48.

[0101] like Fig.12 As shown, the second low-end DC blocking type full-control valve group 142 includes: a second DC blocking type voltage source converter 102, a fourth bypass knife gate 51, a fourth bypass switch 52, a No. 4 first isolation knife gate 57, and a No. 4 second isolation knife gate 58; the fourth bypass switch 52 is respectively connected to the positive end of the second DC blocking type voltage source converter 102 and the negative end of the second DC blocking type voltage source converter 102, and the fourth bypass switch 52 is respectively connected to one end of the No. 4 first isolation knife gate 57 and one end of the No. 4 second isolation knife gate 58; the fourth bypass knife gate 51 and the fourth bypass switch 52 are respectively connected to the other end of the No. 4 first isolation knife gate 57 and the other end of the No. 4 second isolation knife gate 58.

[0102] It should be noted that the DC blocking voltage source converter includes a modular multi-level converter with a full-bridge submodule structure or a hybrid structure of a full-bridge and half-bridge submodule structure.

[0103] like Fig.12 As shown, the inverter station 200 includes a third DC pole 210, a fourth DC pole 220 and a second AC system 240, a fifth grid-side AC switch 231, a sixth grid-side AC switch 232, a seventh grid-side AC switch 233, an eighth grid-side AC switch 234, a second metal return line switching switch 213, a second earth return line switching switch 290, a second bipolar neutral zone isolation switch 274, a second bipolar neutral zone isolation switch 275, a second bipolar neutral zone isolation switch 284 and a second bipolar neutral zone isolation switch 285.

[0104] It should be noted that the third DC pole 210 includes: a third high-end semi-controlled valve group 211, a third low-end semi-controlled valve group 212, a third high-end converter transformer 216, a third low-end converter transformer 217, a third smoothing reactor 205, a third pole neutral bus switch 219, a third pole bus isolation knife switch 272 and a third DC line isolation knife switch 273; the third high-end semi-controlled valve group 211 and the third low-end semi-controlled valve group 212 are connected in series.

[0105] like Fig.12 As shown, the third high-end semi-controlled valve group 211 includes: a third grid phase-changing converter 201, a fourth bypass knife gate 51, a fourth bypass switch 52, a No. 5 first isolation knife gate 53, and a No. 5 second isolation knife gate 54; the fourth bypass switch 52 is respectively connected to the positive end of the third grid phase-changing converter 201 and the negative end of the third grid phase-changing converter 201, and the fourth bypass switch 52 is respectively connected to one end of the No. 5 first isolation knife gate 53 and one end of the No. 5 second isolation knife gate 54; the fourth bypass knife gate 51 is respectively connected to the other end of the No. 5 first isolation knife gate 53 and the other end of the No. 5 second isolation knife gate 54.

[0106] like Fig.12 As shown, the third low-end semi-controlled valve group 212 includes: a fourth power grid phase-changing converter 202, a fifth bypass knife gate 61, a fifth bypass switch 62, a No. 6 first isolation knife gate 63, and a No. 6 second isolation knife gate 64; the fifth bypass switch 62 is respectively connected to the positive end of the fourth power grid phase-changing converter 202 and the negative end of the fourth power grid phase-changing converter 202, and the fifth bypass switch 62 is respectively connected to one end of the No. 6 first isolation knife gate 63 and one end of the No. 6 second isolation knife gate 64; the fifth bypass knife gate 61 is respectively connected to the other end of the No. 6 first isolation knife gate 63 and the other end of the No. 6 second isolation knife gate 64.

[0107] like Fig.12As shown, the fourth DC pole 220 includes: a fourth low-end semi-controlled valve group 221, a fourth high-end semi-controlled valve group 222, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a fourth smoothing reactor 206, a fourth pole neutral bus switch 229, a fourth pole bus isolation knife switch 282 and a fourth DC line isolation knife switch 283; the fourth low-end semi-controlled valve group 221 and the fourth high-end semi-controlled valve group 222 are connected in series.

[0108] like Fig.12 As shown, the fourth high-end semi-controlled valve group 222 includes: the fifth grid phase-changing converter 204, the sixth bypass knife gate 81, the sixth bypass switch 82, the seventh first isolation knife gate 83, and the seventh second isolation knife gate 84; the sixth bypass switch 82 is respectively connected to the positive end of the fifth grid phase-changing converter 204 and the negative end of the fifth grid phase-changing converter 204, and the sixth bypass switch 82 is respectively connected to one end of the seventh first isolation knife gate 83 and one end of the seventh second isolation knife gate 84; the sixth bypass knife gate 81 is respectively connected to the other end of the seventh first isolation knife gate 83 and the other end of the seventh second isolation knife gate 84.

[0109] like Fig.12 As shown, the fourth low-end semi-controlled valve group 221 includes: the sixth power grid phase-changing converter 203, the seventh bypass knife gate 71, the seventh bypass switch 72, the eighth first isolation knife gate 73, and the eighth second isolation knife gate 74; the seventh bypass switch 72 is respectively connected to the positive end of the sixth power grid phase-changing converter 203 and the negative end of the sixth power grid phase-changing converter 203, and the seventh bypass switch 72 is respectively connected to one end of the eighth first isolation knife gate 73 and one end of the eighth second isolation knife gate 74; the seventh bypass knife gate 71 is respectively connected to the other end of the eighth first isolation knife gate 73 and the other end of the eighth second isolation knife gate 74.

[0110] The above mentioned Fig.12 The various switches or knife gates in the invention include at least one of a mechanical switch, a knife gate, a DC circuit breaker and a thyristor valve.

[0111] like Fig.12As shown, taking the DC power transmission system as an example, the initial state is that the first high-end uncontrolled valve group 111 and the first low-end DC blocking type fully controlled valve group 141 of the rectifier station 100 are in operation, and the third high-end semi-controlled valve group 211 and the third low-end semi-controlled valve group 212 of the inverter station 200 are in operation; the second bypass gate 14 of the rectifier station 100 is in position, the second bypass switch 13 is in position, the second first isolation gate 15 is in position, the second second isolation gate 16 is in position, the bypass gate 4 is in position, the bypass switch 3 is in position, the first isolation gate 5 is in position, the second isolation gate 6 is in position, the fourth bypass gate 51 of the inverter station 200 is in position, the fourth bypass switch 52 is in position, the fifth first isolation gate 53 is in position, the fifth second isolation gate 54 is in position, the fifth bypass gate 61 is in position, the fifth bypass switch 62 is in position, the sixth first isolation gate 63 is in position, and the sixth second isolation gate 64 is in position.

[0112] See also Fig.13 , Fig.13 The figure shows the structural diagram of the DC transmission system. Fig.13 As shown, for the convenience of description, the same components in different positions will be distinguished by adding prefixes such as "first", "second", "No. 2", and "No. 3". The DC transmission system of the present application is an ultra-high voltage DC transmission system, and the DC transmission system includes: a rectifier station 100, an inverter station 200, a first DC line 150, a second DC line 160, a rectifier station grounding electrode line 114, a rectifier station grounding electrode 115, an inverter station grounding electrode line 214, and an inverter station grounding electrode 215.

[0113] like Fig.13 As shown, the rectifier station 100 includes: a first DC pole 110, a second DC pole 120, a first AC system 140, a first grid-side AC switch 131, a second grid-side AC switch 132, a third grid-side AC switch 133, a fourth grid-side AC switch 134, a first metal return line transfer switch 113, a first earth return line transfer switch 190, a first bipolar neutral zone isolation switch 174, a second bipolar neutral zone isolation switch 175, a third bipolar neutral zone isolation switch 184 and a fourth bipolar neutral zone isolation switch 185.

[0114] like Fig.13 As shown, the first DC pole 110 includes: a first high-end non-DC blocking type fully-controlled valve group 145, a first low-end half-controlled valve group 112, a first high-end converter transformer 116, a first low-end converter transformer 117, a first smoothing reactor 105, a first pole neutral bus switch 119, a first pole bus isolation knife switch 172 and a first DC line isolation knife switch 173; the first high-end non-DC blocking type fully-controlled valve group 145 is connected in series with the first low-end half-controlled valve group 112.

[0115] like Fig.13As shown, the first high-end non-DC blocking type full-control valve group 145 includes: a first non-DC blocking type voltage source converter 107, a second bypass gate 14, a second bypass switch 13, a No. 2 first isolation gate 15, and a No. 2 second isolation gate 16; the second bypass switch 13 is respectively connected to the anode of the first non-DC blocking type voltage source converter 107 and the cathode of the first non-DC blocking type voltage source converter 107, and the second bypass switch 13 is respectively connected to one end of the No. 2 first isolation gate 15 and one end of the No. 2 second isolation gate 16; the second bypass gate 14 is respectively connected to the other end of the No. 2 first isolation gate 15 and the other end of the No. 2 second isolation gate 16.

[0116] like Fig.13 As shown, the first low-end semi-controlled valve group 112 includes: a grid phase-commutating converter 1, a bypass gate 4, a bypass switch 3, a first isolation gate 5, and a second isolation gate 6; the bypass switch 3 is respectively connected to the anode of the grid phase-commutating converter 1 and the cathode of the grid phase-commutating converter 1, and the bypass switch 3 is respectively connected to one end of the first isolation gate 5 and one end of the second isolation gate 6; the bypass gate 4 is connected to the other end of the first isolation gate 5 and the other end of the second isolation gate 6.

[0117] like Fig.13 As shown, the second DC pole 120 includes: a second low-end semi-controlled valve group 121, a second high-end non-DC blocking type fully-controlled valve group 146, a second low-end converter transformer 126, a second high-end converter transformer 127, a second smoothing reactor 106, a second pole neutral bus switch 129, a second pole bus isolation knife switch 182, and a second DC line isolation knife switch 183; the second low-end semi-controlled valve group 121 and the second high-end non-DC blocking type fully-controlled valve group 146 are connected in series.

[0118] like Fig.13 As shown, the second high-end non-DC blocking type full-control valve group 146 includes: a second non-DC blocking type voltage source converter 108, a third bypass knife gate 46, a third bypass switch 45, a No. 3 first isolation knife gate 47, and a No. 3 second isolation knife gate 48; the third bypass switch 45 is respectively connected to the positive end of the second non-DC blocking type voltage source converter 108 and the negative end of the second non-DC blocking type voltage source converter 108, and the third bypass switch 45 is respectively connected to one end of the No. 3 first isolation knife gate 47 and one end of the No. 3 second isolation knife gate 48; the third bypass knife gate 46 is respectively connected to the other end of the No. 3 first isolation knife gate 47 and the other end of the No. 3 second isolation knife gate 48.

[0119] like Fig.13As shown, the second low-end semi-controlled valve group 121 includes: a second grid phase-commutating converter 101, a fourth bypass gate 51, a fourth bypass switch 52, a No. 4 first isolating gate 57, and a No. 4 second isolating gate 58; the fourth bypass switch 52 is respectively connected to the positive end of the second grid phase-commutating converter 101 and the negative end of the second grid phase-commutating converter 101, and the fourth bypass switch 52 is respectively connected to one end of the No. 4 first isolating gate 57 and one end of the No. 4 second isolating gate 58; the fourth bypass gate 51 and the fourth bypass switch 52 are respectively connected to the other end of the No. 4 first isolating gate 57 and the other end of the No. 4 second isolating gate 58.

[0120] like Fig.13 As shown, the inverter station 200 includes: a third DC pole 210, a fourth DC pole 220, a second AC system 240, a fifth grid-side AC switch 231, a sixth grid-side AC switch 232, a seventh grid-side AC switch 233, an eighth grid-side AC switch 234, a second metal return line switching switch 213, a second earth return line switching switch 290, a second bipolar neutral zone isolation switch 274, a second bipolar neutral zone isolation switch 275, a second bipolar neutral zone isolation switch 284 and a second bipolar neutral zone isolation switch 285.

[0121] like Fig.13 As shown, the third DC pole 210 includes: a third high-end semi-controlled valve group 211, a third low-end semi-controlled valve group 212, a third high-end converter transformer 216, a third low-end converter transformer 217, a third smoothing reactor 205, a third pole neutral bus switch 219, a third pole bus isolation knife switch 272 and a third DC line isolation knife switch 273; the third high-end semi-controlled valve group 211 and the third low-end semi-controlled valve group 212 are connected in series.

[0122] like Fig.13 As shown, the third high-end semi-controlled valve group 211 includes: a third grid phase-changing converter 201, a fourth bypass knife gate 51, a fourth bypass switch 52, a No. 5 first isolation knife gate 53, and a No. 5 second isolation knife gate 54; the fourth bypass switch 52 is connected to the positive end of the third grid phase-changing converter 201 and the negative end of the third grid phase-changing converter 201, and the fourth bypass switch 52 is respectively connected to one end of the No. 5 first isolation knife gate 53 and one end of the No. 5 second isolation knife gate 54; the fourth bypass knife gate 51 is respectively connected to the other end of the No. 5 first isolation knife gate 53 and the other end of the No. 5 second isolation knife gate 54.

[0123] like Fig.13As shown, the third low-end semi-controlled valve group 212 includes: a fourth power grid phase-changing converter 202, a fifth bypass knife gate 61, a fifth bypass switch 62, a No. 6 first isolation knife gate 63, and a No. 6 second isolation knife gate 64; the fifth bypass switch 62 is respectively connected to the positive end of the fourth power grid phase-changing converter 202 and the negative end of the fourth power grid phase-changing converter 202, and the fifth bypass switch 62 is respectively connected to one end of the No. 6 first isolation knife gate 63 and one end of the No. 6 second isolation knife gate 64; the fifth bypass knife gate 61 is connected to the other end of the No. 6 first isolation knife gate 63 and the other end of the No. 6 second isolation knife gate 64.

[0124] like Fig.13 As shown, the fourth DC pole 220 includes: a fourth low-end semi-controlled valve group 221, a fourth high-end semi-controlled valve group 222, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a fourth smoothing reactor 206, a fourth pole neutral bus switch 229, a fourth pole bus isolation knife switch 282 and a fourth DC line isolation knife switch 283; the fourth low-end semi-controlled valve group 221 and the fourth high-end semi-controlled valve group 222 are connected in series.

[0125] like Fig.13 As shown, the fourth high-end semi-controlled valve group 222 includes: the fifth grid phase-changing converter 204, the sixth bypass knife gate 81, the sixth bypass switch 82, the seventh first isolation knife gate 83, and the seventh second isolation knife gate 84; the sixth bypass switch 82 is respectively connected to the positive end of the fifth grid phase-changing converter 204 and the negative end of the fifth grid phase-changing converter 204, and the sixth bypass switch 82 is respectively connected to one end of the seventh first isolation knife gate 83 and one end of the seventh second isolation knife gate 84; the sixth bypass knife gate 81 is connected to the other end of the seventh first isolation knife gate 83 and the other end of the seventh second isolation knife gate 84.

[0126] like Fig.13 As shown, the fourth low-end semi-controlled valve group 221 includes: the sixth power grid phase-changing converter 203, the seventh bypass knife gate 71, the seventh bypass switch 72, the eighth first isolation knife gate 73, and the eighth second isolation knife gate 74; the seventh bypass switch 72 is respectively connected to the positive end of the sixth power grid phase-changing converter 203 and the negative end of the sixth power grid phase-changing converter 203, and the seventh bypass switch 72 is respectively connected to one end of the eighth first isolation knife gate 73 and one end of the eighth second isolation knife gate 74; the seventh bypass knife gate 71 is connected to the other end of the eighth first isolation knife gate 73 and the other end of the eighth second isolation knife gate 74.

[0127] It should be noted that the above Fig.13 The various switches or knife gates mentioned include at least one of a mechanical switch, a knife gate, a DC circuit breaker, and a thyristor valve.

[0128] like Fig.13As shown, taking the DC power transmission system as an example, the initial state is that the first high-end non-DC blocking type fully controlled valve group 145 and the first low-end half-controlled valve group 112 of the rectifier station 100 are in operation, and the third high-end half-controlled valve group 211 and the third low-end half-controlled valve group 212 of the inverter station 200 are in operation; the second bypass gate 14 of the rectifier station 100 is in position, the second bypass switch 13 is in position, the second first isolation gate 15 is closed, the second second isolation gate 16 is closed, the bypass gate 4 is in position, the bypass switch 3 is in position, the first isolation gate 5 is closed, the second isolation gate 6 is closed, the fourth bypass gate 51 of the inverter station 200 is in position, the fourth bypass switch 52 is in position, the fifth first isolation gate 53 is closed, the fifth second isolation gate 54 is closed, the fifth bypass gate 61 is in position, the fifth bypass switch 62 is in position, the sixth first isolation gate 63 is closed, and the sixth second isolation gate 64 is closed. The rectifier station 100 is used to control the rectifier operation of the first non-DC blocking voltage source converter 107 and the grid-commutated converter 1; the inverter station 200 is used to control the inverter operation of the third grid-commutated converter 201 and the fourth grid-commutated converter 202.

[0129] Fig.11 , Fig.12 and Fig.13 In the embodiment, the third DC pole 210 may further include: two or one of any two of a half-controlled valve group, a non-DC blocking type fully-controlled valve group, and a DC blocking type fully-controlled valve group; the fourth DC pole 220 may further include: two or one of any two of a half-controlled valve group, a non-DC blocking type fully-controlled valve group, and a DC blocking type fully-controlled valve group. Fig.14 , Fig.14 It is shown that the third DC pole 210 includes a half-controlled valve group and a non-DC blocking type fully-controlled valve group; the fourth DC pole 220 includes a half-controlled valve group and a non-DC blocking type fully-controlled valve group.

[0130] like Fig.14 As shown, for the convenience of description, the same components in different positions will be distinguished by adding prefixes such as "first", "second", "No. 2", and "No. 3". The DC transmission system of the present application is an ultra-high voltage DC transmission system, and the DC transmission system includes: a rectifier station 100, an inverter station 200, a first DC line 150, a second DC line 160, a rectifier station grounding electrode line 114, a rectifier station grounding electrode 115, an inverter station grounding electrode line 214, and an inverter station grounding electrode 215.

[0131] like Fig.14 As shown, the structure of the rectifier station 100 and Fig.13 The rectifier station 100 is the same.

[0132] like Fig.14As shown, the inverter station 200 includes: a third DC pole 210, a fourth DC pole 220, a second AC system 240, a fifth grid-side AC switch 231, a sixth grid-side AC switch 232, a seventh grid-side AC switch 233, an eighth grid-side AC switch 234, a second metal return line switching switch 213, a second earth return line switching switch 290, a second bipolar neutral zone isolation switch 274, a second bipolar neutral zone isolation switch 275, a second bipolar neutral zone isolation switch 284 and a second bipolar neutral zone isolation switch 285.

[0133] like Fig.14 As shown, the third DC pole 210 includes: a third high-end non-DC blocking type full-controlled valve group 245, a third low-end half-controlled valve group 212, a third high-end converter transformer 216, a third low-end converter transformer 217, a third smoothing reactor 205, a third pole neutral bus switch 219, a third pole bus isolation knife switch 272 and a third DC line isolation knife switch 273; the third high-end non-DC blocking type full-controlled valve group 245 and the third low-end half-controlled valve group 212 are connected in series.

[0134] like Fig.14 As shown, the third high-end non-DC blocking type full-control valve group 245 includes: a third non-DC blocking type voltage source converter 207, a fourth bypass knife gate 51, a fourth bypass switch 52, a first isolation knife gate No. 53, and a second isolation knife gate No. 54; the fourth bypass switch 52 connects the positive end of the third non-DC blocking type voltage source converter 207 and the negative end of the third non-DC blocking type voltage source converter 207, and the fourth bypass switch 52 is respectively connected to one end of the first isolation knife gate No. 53 and one end of the second isolation knife gate No. 54; the fourth bypass knife gate 51 is respectively connected to the other end of the first isolation knife gate No. 53 and the other end of the second isolation knife gate No. 54.

[0135] like Fig.14 As shown, the third low-end semi-controlled valve group 212 includes: a fourth power grid phase-changing converter 202, a fifth bypass knife gate 61, a fifth bypass switch 62, a No. 6 first isolation knife gate 63, and a No. 6 second isolation knife gate 64; the fifth bypass switch 62 is respectively connected to the positive end of the fourth power grid phase-changing converter 202 and the negative end of the fourth power grid phase-changing converter 202, and the fifth bypass switch 62 is respectively connected to one end of the No. 6 first isolation knife gate 63 and one end of the No. 6 second isolation knife gate 64; the fifth bypass knife gate 61 is connected to the other end of the No. 6 first isolation knife gate 63 and the other end of the No. 6 second isolation knife gate 64.

[0136] like Fig.14As shown, the fourth DC pole 220 includes: a fourth high-end non-DC blocking type full-controlled valve group 246, a fourth low-end half-controlled valve group 221, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a fourth smoothing reactor 206, a fourth pole neutral bus switch 229, a fourth pole bus isolation knife switch 282 and a fourth DC line isolation knife switch 283; the fourth high-end non-DC blocking type full-controlled valve group 246 and the fourth low-end half-controlled valve group 221 are connected in series.

[0137] like Fig.14 As shown, the fourth high-end non-DC blocking type full-control valve group 246 includes: a fourth non-DC blocking type voltage source converter 208, a sixth bypass gate 81, a sixth bypass switch 82, a first isolation gate No. 7 83, and a second isolation gate No. 7 84; the sixth bypass switch 82 is respectively connected to the positive end of the fourth non-DC blocking type voltage source converter 208 and the negative end of the fourth non-DC blocking type voltage source converter 208, and the sixth bypass switch 82 is respectively connected to one end of the first isolation gate No. 7 83 and one end of the second isolation gate No. 7 84; the sixth bypass gate 81 is connected to the other end of the first isolation gate No. 7 83 and the other end of the second isolation gate No. 7 84.

[0138] like Fig.14 As shown, the fourth low-end semi-controlled valve group 221 includes: the sixth power grid phase-changing converter 203, the seventh bypass knife gate 71, the seventh bypass switch 72, the eighth first isolation knife gate 73, and the eighth second isolation knife gate 74; the seventh bypass switch 72 is respectively connected to the positive end of the sixth power grid phase-changing converter 203 and the negative end of the sixth power grid phase-changing converter 203, and the seventh bypass switch 72 is respectively connected to one end of the eighth first isolation knife gate 73 and one end of the eighth second isolation knife gate 74; the seventh bypass knife gate 71 is connected to the other end of the eighth first isolation knife gate 73 and the other end of the eighth second isolation knife gate 74.

[0139] It should be noted that the above Fig.14 The various switches or knife gates mentioned include at least one of a mechanical switch, a knife gate, a DC circuit breaker, and a thyristor valve.

[0140] like Fig.14As shown, taking the DC power transmission system as an example, the initial state is that the first high-end non-DC blocking type fully-controlled valve group 145 and the first low-end half-controlled valve group 112 of the rectifier station 100 are in operation, and the third high-end non-DC blocking type fully-controlled valve group 245 and the third low-end half-controlled valve group 212 of the inverter station 200 are in operation; the second bypass gate 14 of the rectifier station 100 is in position, the second bypass switch 13 is in position, the second first isolation gate 15 is closed, the second second isolation gate 16 is closed, the bypass gate 4 is in position, the bypass switch 3 is in position, the first isolation gate 5 is closed, the second isolation gate 6 is closed, the fourth bypass gate 51 of the inverter station 200 is in position, the fourth bypass switch 52 is in position, the fifth first isolation gate 53 is closed, the fifth second isolation gate 54 is closed, the fifth bypass gate 61 is in position, the fifth bypass switch 62 is in position, the sixth first isolation gate 63 is closed, and the sixth second isolation gate 64 is closed. The rectifier station 100 is used to control the rectifier operation of the first non-DC blocking voltage source converter 107 and the grid-commutated converter 1; the inverter station 200 is used to control the inverter operation of the third non-DC blocking voltage source converter 207 and the fourth grid-commutated converter 202.

[0141] Based on the hybrid DC transmission valve group provided in the above embodiment, the present application also provides a control method for the DC transmission valve group, see Fig.15 ,like Fig.15 The control flow chart of the DC transmission valve group is shown. The control method of the DC transmission valve group of the present application includes the following steps:

[0142] Step 110: In response to the non-DC blocking valve group 400 being put into operation online, the DC current is first transferred to the bridge uncontrolled rectifier circuit or the fully controlled device anti-parallel diode of the non-DC blocking valve group 400; the AC input terminal of the non-DC blocking valve group 400 is connected to AC power, or / and the non-DC blocking valve group is unlocked;

[0143] In step 110, the operation parameters and fault parameters of the hybrid DC transmission valve group or the non-DC blocking valve group are first obtained; in response to the non-DC blocking valve group 400 being put online, the DC current is first transferred to the bridge uncontrolled rectifier circuit, the fully controlled device anti-parallel diode or the fully controlled device of the non-DC blocking valve group 400, and the step 111 is also included:

[0144] Close the isolation knife switch of the non-DC blocking valve group 400, close the bypass switch of the non-DC blocking valve group 400, separate the bypass knife switch of the non-DC blocking valve group 400, separate the bypass switch of the non-DC blocking valve group 400, so as to transfer the DC current to the bridge uncontrolled rectifier circuit or the fully controlled device anti-parallel diode of the non-DC blocking valve group 400;

[0145] In step 110 , connecting the AC input end of the non-DC blocking valve group 400 to AC power further includes step 112 : closing the valve-side AC switch or the grid-side AC switch of the non-DC blocking valve group 400 .

[0146] In some embodiments of the present application, Fig.11 As shown, in step 111, when the first high-end uncontrolled valve group 111 is put into operation online, the No. 2 first isolation switch 15 and the No. 2 second isolation switch 16 of the first high-end uncontrolled valve group 111 are closed, the second bypass switch 13 is closed, the second bypass switch 14 is opened, and the second bypass switch 13 is opened, so that the DC current is transferred to the diodes of the upper and lower bridge arms of at least one phase of the bridge uncontrolled rectifier circuit 11; in step 112, the first grid-side AC switch 131 of the first high-end uncontrolled valve group 111 is closed again.

[0147] In some embodiments of the present application, Fig.12 As shown, in step 111, when the first high-end uncontrolled valve group 111 is put into operation online, the No. 2 first isolation switch 15 and the No. 2 second isolation switch 16 of the first high-end uncontrolled valve group 111 are closed, the second bypass switch 13 is closed, the second bypass switch 14 is opened, and the second bypass switch 13 is opened, so that the DC current is transferred to the diodes of the upper and lower bridge arms of at least one phase of the bridge uncontrolled rectifier circuit 11; in step 112, the first grid-side AC switch 131 of the first high-end uncontrolled valve group 111 is closed again.

[0148] In some embodiments of the present application, Fig.13 and Fig.14 As shown, in step 111, when the first high-end non-DC blocking type fully-controlled valve group 145 is put into operation online, the No. 2 first isolation switch 15 and the No. 2 second isolation switch 16 of the first high-end non-DC blocking type fully-controlled valve group 145 are closed, the second bypass switch 14 is opened, and the second bypass switch 13 is opened, so that the DC current is transferred to the anti-parallel diode of the No. 2 IGBT module 31 of the upper and lower bridge arm sub-modules of at least one phase of the first non-DC blocking type voltage source converter 107; in step 112, the first grid-side AC switch 131 of the first high-end non-DC blocking type fully-controlled valve group 145 is closed again to unlock the first non-DC blocking type voltage source converter 107.

[0149] In some embodiments of the present application, Fig.14As shown, when the third high-end non-DC blocking type fully-controlled valve group 245 is put into operation online, the fifth grid-side AC switch 231 is closed to charge the third non-DC blocking type voltage source converter 207. After charging is completed, the fifth grid-side AC switch 231 is disconnected, the No. 5 first isolation switch 53 and the No. 5 second isolation switch 54 of the third high-end non-DC blocking type fully-controlled valve group 245 are closed, the fourth bypass switch 51 is separated, and the fourth bypass switch 52 is closed to control the IGBT of the No. 2 IGBT module 31 of the upper and lower bridge arm submodules of at least one phase of the third non-DC blocking type voltage source converter 207 to be turned on, and the fourth bypass switch 52 is separated, so as to transfer the DC current to the IGBT of the No. 2 IGBT module 31 of the upper and lower bridge arm submodules of at least one phase of the third non-DC blocking type voltage source converter 207; the fifth grid-side AC switch 231 is closed to unlock the third non-DC blocking type voltage source converter 207.

[0150] The control method of the DC transmission valve group provided in the present application is also applicable to the topological structure of the non-DC blocking valve group 400 in series. Fig.16 , Fig.16 It is shown that the first DC pole 110 includes two non-DC blocking type full-control valve groups; the second DC pole 120 includes two non-DC blocking type full-control valve groups; the third DC pole 210 includes two non-DC blocking type full-control valve groups; and the fourth DC pole 220 includes two non-DC blocking type full-control valve groups.

[0151] like Fig.16 As shown, for the convenience of description, the same components in different positions will be distinguished by adding prefixes such as "first", "second", "No. 2", and "No. 3". The DC transmission system of the present application is an ultra-high voltage DC transmission system, and the DC transmission system includes: a rectifier station 100, an inverter station 200, a first DC line 150, a second DC line 160, a rectifier station grounding electrode line 114, a rectifier station grounding electrode 115, an inverter station grounding electrode line 214, and an inverter station grounding electrode 215.

[0152] like Fig.16 As shown, the rectifier station 100 includes: a first DC pole 110, a second DC pole 120, a first AC system 140, a first grid-side AC switch 131, a second grid-side AC switch 132, a third grid-side AC switch 133, a fourth grid-side AC switch 134, a first metal return line transfer switch 113, a first earth return line transfer switch 190, a first bipolar neutral zone isolation switch 174, a second bipolar neutral zone isolation switch 175, a third bipolar neutral zone isolation switch 184 and a fourth bipolar neutral zone isolation switch 185.

[0153] like Fig.16As shown, the first DC pole 110 includes: a first high-end non-DC blocking type fully-controlled valve group 145, a first low-end non-DC blocking type fully-controlled valve group 147, a first high-end converter transformer 116, a first low-end converter transformer 117, a first DC circuit breaker 137, a first smoothing reactor 105, a first pole neutral bus switch 119, a first pole bus isolation knife switch 172 and a first DC line isolation knife switch 173; the first high-end non-DC blocking type fully-controlled valve group 145 is connected in series with the first low-end non-DC blocking type fully-controlled valve group 147.

[0154] like Fig.16 As shown, the first high-end non-DC blocking type full-control valve group 145 includes: a first non-DC blocking type voltage source converter 107, a second bypass gate 14, a second bypass switch 13, a No. 2 first isolation gate 15, and a No. 2 second isolation gate 16; the second bypass switch 13 is respectively connected to the anode of the first non-DC blocking type voltage source converter 107 and the cathode of the first non-DC blocking type voltage source converter 107, and the second bypass switch 13 is respectively connected to one end of the No. 2 first isolation gate 15 and one end of the No. 2 second isolation gate 16; the second bypass gate 14 is respectively connected to the other end of the No. 2 first isolation gate 15 and the other end of the No. 2 second isolation gate 16.

[0155] like Fig.16 As shown, the first low-end non-DC blocking type full-control valve group 147 includes: a fifth non-DC blocking type voltage source converter 135, a bypass gate 4, a bypass switch 3, a first isolation gate 5, and a second isolation gate 6; the bypass switch 3 is respectively connected to the positive end of the fifth non-DC blocking type voltage source converter 135 and the negative end of the fifth non-DC blocking type voltage source converter 135, and the bypass switch 3 is respectively connected to one end of the first isolation gate 5 and one end of the second isolation gate 6; the bypass gate 4 is connected to the other end of the first isolation gate 5 and the other end of the second isolation gate 6.

[0156] like Fig.16 As shown, the second DC pole 120 includes: a second low-end non-DC blocking type fully-controlled valve group 148, a second high-end non-DC blocking type fully-controlled valve group 146, a second low-end converter transformer 126, a second high-end converter transformer 127, a second DC circuit breaker 138, a second smoothing reactor 106, a second pole neutral bus switch 129, a second pole bus isolation knife switch 182 and a second DC line isolation knife switch 183; the second low-end non-DC blocking type fully-controlled valve group 148 and the second high-end non-DC blocking type fully-controlled valve group 146 are connected in series.

[0157] like Fig.16As shown, the second high-end non-DC blocking type full-control valve group 146 includes: a second non-DC blocking type voltage source converter 108, a third bypass knife gate 46, a third bypass switch 45, a No. 3 first isolation knife gate 47, and a No. 3 second isolation knife gate 48; the third bypass switch 45 is respectively connected to the positive end of the second non-DC blocking type voltage source converter 108 and the negative end of the second non-DC blocking type voltage source converter 108, and the third bypass switch 45 is respectively connected to one end of the No. 3 first isolation knife gate 47 and one end of the No. 3 second isolation knife gate 48; the third bypass knife gate 46 is respectively connected to the other end of the No. 3 first isolation knife gate 47 and the other end of the No. 3 second isolation knife gate 48.

[0158] like Fig.16 As shown, the second low-end non-DC blocking type full-control valve group 148 includes: a sixth non-DC blocking type voltage source converter 136, a fourth bypass gate 55, a fourth bypass switch 56, a fourth first isolation gate 57, and a fourth second isolation gate 58; the fourth bypass switch 56 is respectively connected to the positive end of the sixth non-DC blocking type voltage source converter 136 and the negative end of the sixth non-DC blocking type voltage source converter 136, and the fourth bypass switch 56 is respectively connected to one end of the fourth first isolation gate 57 and one end of the fourth second isolation gate 58; the fourth bypass gate 55 is respectively connected to the other end of the fourth first isolation gate 57 and the other end of the fourth second isolation gate 58.

[0159] like Fig.16 As shown, the inverter station 200 includes: a third DC pole 210, a fourth DC pole 220, a second AC system 240, a fifth grid-side AC switch 231, a sixth grid-side AC switch 232, a seventh grid-side AC switch 233, an eighth grid-side AC switch 234, a second metal return line switching switch 213, a second earth return line switching switch 290, a second bipolar neutral zone isolation switch 274, a second bipolar neutral zone isolation switch 275, a second bipolar neutral zone isolation switch 284 and a second bipolar neutral zone isolation switch 285.

[0160] like Fig.16 As shown, the third DC pole 210 includes: a third high-end non-DC blocking type fully-controlled valve group 245, a third low-end non-DC blocking type fully-controlled valve group 247, a third high-end converter transformer 216, a third low-end converter transformer 217, a third DC circuit breaker 237, a third smoothing reactor 205, a third pole neutral bus switch 219, a third pole bus isolation knife switch 272 and a third DC line isolation knife switch 273; the third high-end non-DC blocking type fully-controlled valve group 245 and the third low-end non-DC blocking type fully-controlled valve group 247 are connected in series.

[0161] like Fig.16As shown, the third high-end non-DC blocking type full-control valve group 245 includes: a third non-DC blocking type voltage source converter 207, a fourth bypass knife gate 51, a fourth bypass switch 52, a first isolation knife gate No. 53, and a second isolation knife gate No. 54; the fourth bypass switch 52 connects the positive end of the third non-DC blocking type voltage source converter 207 and the negative end of the third non-DC blocking type voltage source converter 207, and the fourth bypass switch 52 is respectively connected to one end of the first isolation knife gate No. 53 and one end of the second isolation knife gate No. 54; the fourth bypass knife gate 51 is respectively connected to the other end of the first isolation knife gate No. 53 and the other end of the second isolation knife gate No. 54.

[0162] like Fig.16 As shown, the third low-end non-DC blocking type full-control valve group 247 includes: the seventh non-DC blocking type voltage source converter 235, the fifth bypass knife 61, the fifth bypass switch 62, the sixth first isolation knife 63, and the sixth second isolation knife 64; the fifth bypass switch 62 is respectively connected to the positive end of the seventh non-DC blocking type voltage source converter 235 and the negative end of the seventh non-DC blocking type voltage source converter 235, and the fifth bypass switch 62 is respectively connected to one end of the sixth first isolation knife 63 and one end of the sixth second isolation knife 64; the fifth bypass knife 61 is connected to the other end of the No. 6 first isolation knife 63 and the other end of the No. 6 second isolation knife 64.

[0163] like Fig.16 As shown, the fourth DC pole 220 includes: a fourth high-end non-DC blocking type fully-controlled valve group 246, a fourth low-end non-DC blocking type fully-controlled valve group 248, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a fourth DC circuit breaker 238, a fourth smoothing reactor 206, a fourth pole neutral bus switch 229, a fourth pole bus isolation knife switch 282 and a fourth DC line isolation knife switch 283; the fourth high-end non-DC blocking type fully-controlled valve group 246 and the fourth low-end non-DC blocking type fully-controlled valve group 248 are connected in series.

[0164] like Fig.16 As shown, the fourth high-end non-DC blocking type full-control valve group 246 includes: a fourth non-DC blocking type voltage source converter 208, a sixth bypass gate 81, a sixth bypass switch 82, a first isolation gate No. 7 83, and a second isolation gate No. 7 84; the sixth bypass switch 82 is respectively connected to the positive end of the fourth non-DC blocking type voltage source converter 208 and the negative end of the fourth non-DC blocking type voltage source converter 208, and the sixth bypass switch 82 is respectively connected to one end of the first isolation gate No. 7 83 and one end of the second isolation gate No. 7 84; the sixth bypass gate 81 is connected to the other end of the first isolation gate No. 7 83 and the other end of the second isolation gate No. 7 84.

[0165] like Fig.16As shown, the fourth low-end non-DC blocking type full-control valve group 248 includes: an eighth non-DC blocking type voltage source converter 236, a seventh bypass knife gate 71, a seventh bypass switch 72, an eighth first isolation knife gate 73, and an eighth second isolation knife gate 74; the seventh bypass switch 72 is respectively connected to the positive end of the eighth non-DC blocking type voltage source converter 236 and the negative end of the eighth non-DC blocking type voltage source converter 236, and the seventh bypass switch 72 is respectively connected to one end of the eighth first isolation knife gate 73 and one end of the eighth second isolation knife gate 74; the seventh bypass knife gate 71 is connected to the other end of the eighth first isolation knife gate 73 and the other end of the eighth second isolation knife gate 74.

[0166] It should be noted that the above Fig.16 The various switches or knife gates mentioned include at least one of a mechanical switch, a knife gate, a DC circuit breaker, and a thyristor valve.

[0167] like Fig.16 As shown, taking the DC power transmission system as an example, the initial state is that the first high-end non-DC blocking type fully-controlled valve group 145 and the first low-end non-DC blocking type fully-controlled valve group 147 of the rectifier station 100 are in operation, and the third high-end non-DC blocking type fully-controlled valve group 245 and the third low-end non-DC blocking type fully-controlled valve group 247 of the inverter station 200 are in operation; the second bypass knife gate 14 of the rectifier station 100 is in the open position, the second bypass switch 13 is in the open position, the second first isolation knife gate 15 is in the closed position, and the second The second isolating switch 16 of No. 1 is closed, the bypass switch 4 is open, the bypass switch 3 is open, the first isolating switch 5 is closed, the second isolating switch 6 is closed, the fourth bypass switch 51 of the inverter station 200 is open, the fourth bypass switch 52 is open, the first isolating switch 53 of No. 5 is closed, the second isolating switch 54 of No. 5 is closed, the fifth bypass switch 61 is open, the fifth bypass switch 62 is open, the first isolating switch 63 of No. 6 is closed, and the second isolating switch 64 of No. 6 is closed. The rectifier station 100 is used to control the rectifier operation of the first non-DC blocking type voltage source converter 107 and the grid commutation converter 1; the inverter station 200 is used to control the inverter operation of the third non-DC blocking type voltage source converter 207 and the fourth grid commutation converter 202.

[0168] In some embodiments of the present application, Fig.16As shown, in step 111, when the first high-end non-DC blocking type fully-controlled valve group 145 is put into operation online, the No. 2 first isolation switch 15 and the No. 2 second isolation switch 16 of the first high-end non-DC blocking type fully-controlled valve group 145 are closed, the second bypass switch 14 is opened, the second bypass switch 13 is closed, and the second bypass switch 13 is opened, so that the DC current is transferred to the anti-parallel diode of the No. 2 IGBT module 31 of the upper and lower bridge arm sub-modules of at least one phase of the first non-DC blocking type voltage source converter 107; in step 112, the first grid-side AC switch 131 of the first high-end non-DC blocking type fully-controlled valve group 145 is closed again to unlock the first non-DC blocking type voltage source converter 107.

[0169] In some embodiments of the present application, Fig.16 As shown, when the third high-end non-DC blocking type fully-controlled valve group 245 is put into operation online, the fifth grid-side AC switch 231 is closed to charge the third non-DC blocking type voltage source converter 207. After charging is completed, the fifth grid-side AC switch 231 is disconnected, the No. 5 first isolation switch 53 and the No. 5 second isolation switch 54 of the third high-end non-DC blocking type fully-controlled valve group 245 are closed, the fourth bypass switch 51 is separated, and the fourth bypass switch 52 is closed to control the IGBT of the No. 2 IGBT module 31 of the upper and lower bridge arm submodules of at least one phase of the third non-DC blocking type voltage source converter 207 to be turned on, and the fourth bypass switch 52 is separated, so as to transfer the DC current to the IGBT of the No. 2 IGBT module 31 of the upper and lower bridge arm submodules of at least one phase of the third non-DC blocking type voltage source converter 207; the fifth grid-side AC switch 231 is closed to unlock the third non-DC blocking type voltage source converter 207.

[0170] It should be noted that when online, the valve groups of the corresponding poles of the rectifier station 100 and the inverter station 200 cooperate to perform the operation. Fig.17 , Fig.17 Based on the embodiments of the present application Fig.11 The results of the simulation test of the valve group in the DC transmission system; Fig.17 As shown in , UDL is the pole bus voltage, IDCP is the cathode DC current of the bridge uncontrolled rectifier circuit 11, UAC_IN_L1, UAC_IN_L2 and UAC_IN_L3 are all the grid-side AC voltages of the first AC system 140, IVD_L1, IVD_L2 and IVD_L3 are all the valve-side AC currents of the YD type converter transformer, and DEBLOCK_IND is the working signal of the bridge uncontrolled rectifier circuit 11; Fig.17 It shows that after the first grid-side AC switch 131 of the first high-end uncontrolled valve group 111 is closed, the bridge uncontrolled rectifier circuit 11 is put into operation.

[0171] The control method of the DC power transmission valve group of the present application further includes step 120: in response to the non-DC blocking valve group 400 exiting online or exiting due to a fault, disconnecting the AC input terminal of the non-DC blocking valve group 400 from AC power, or / and locking the non-DC blocking valve group, or / and bypassing the non-DC blocking valve group; or / and in response to the non-DC blocking valve group exiting due to a fault, controlling the DC blocking valve group to achieve zero pressure at the fault point or presenting a blocking state;

[0172] In step 120, in response to the non-DC blocking valve group 400 exiting online or exiting due to a fault, disconnecting the AC power from the AC input end of the non-DC blocking valve group 400 also includes step 121: separating the valve-side AC switch or the grid-side AC switch of the non-DC blocking valve group 400.

[0173] In response to the non-DC blocking type valve group 400 exiting online or exiting due to a fault, after the AC input end of the non-DC blocking type valve group 400 is disconnected from the AC power, it also includes step 122: closing the bypass switch of the non-DC blocking type valve group 400, closing the bypass knife gate of the non-DC blocking type valve group 400, separating the bypass switch of the non-DC blocking type valve group 400, separating the isolation knife gate of the non-DC blocking type valve group 400, and transferring the DC current to the bypass knife gate of the non-DC blocking type valve group 400, thereby isolating the anti-parallel diode of the fully controlled device of the bridge uncontrolled rectifier circuit or the non-DC blocking type voltage source converter.

[0174] In some embodiments of the present application, Fig.11 As shown, in step 121, in response to the online exit or fault exit of the first high-end uncontrolled valve group 111, the first grid-side AC switch 131 of the first high-end uncontrolled valve group 111 is separated, and the DC current flows through the diodes of the upper and lower bridge arms of at least one phase of the bridge-type uncontrolled rectifier circuit 11. In step 122, the second bypass switch 13 is closed, the second bypass knife gate 14 is closed, the second bypass switch 13 is separated, the second first isolation knife gate 15 and the second second isolation knife gate 16 are separated, and the DC current is transferred to the second bypass knife gate 14, thereby isolating the bridge-type uncontrolled rectifier circuit. In response to the fault exit of the first high-end uncontrolled valve group 111, the cathode of the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be zero voltage to achieve zero voltage at the fault point, or the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be in a blocking state relative to the fault point.

[0175] In some embodiments of the present application, Fig.12As shown, in step 121, in response to the first high-end uncontrolled valve group 111 exiting online or exiting due to a fault, the first grid-side AC switch 131 of the first high-end uncontrolled valve group 111 is separated, and the DC current flows through the diodes of the upper and lower bridge arms of at least one phase of the bridge-type uncontrolled rectifier circuit 11. In step 122, the second bypass switch 13 is closed, the second bypass knife gate 14 is closed, the second bypass switch 13 is separated, the No. 2 first isolation knife gate 15 and the No. 2 second isolation knife gate 16 are separated, and the DC current is transferred to the second bypass knife gate 14, thereby isolating the bridge-type uncontrolled rectifier circuit 11. In response to the first high-end uncontrolled valve group 111 exiting due to a fault, the cathode of the voltage source converter 12 of the first low-end DC blocking type fully controlled valve group 141 is controlled to be zero voltage to achieve zero voltage at the fault point.

[0176] In some embodiments of the present application, Fig.13 and Fig.14 As shown, in step 121, in response to the online exit or fault exit of the first high-end non-DC blocking type fully-controlled valve group 145, the first grid-side AC switch 131 of the first high-end non-DC blocking type fully-controlled valve group 145 is separated, and the DC current flows through the anti-parallel diode of the No. 2 IGBT module 31 of the upper and lower bridge arm sub-modules of at least one phase of the first non-DC blocking type voltage source converter 107. In step 122, the second bypass switch 13 is closed, the second bypass knife gate 14 is closed, the second bypass switch 13 is separated, the No. 2 first isolation knife gate 15 and the No. 2 second isolation knife gate 16 are separated, and the DC current is transferred to the second bypass knife gate 14, thereby isolating the first non-DC blocking type voltage source converter 107. In response to the failure exit of the first high-end non-DC blocking type fully-controlled valve group 145, the cathode of the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be zero voltage to achieve zero voltage at the fault point, or the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be in a blocking state relative to the fault point.

[0177] In some embodiments of the present application, Fig.14 and Fig.16 As shown, in response to the third high-end non-DC blocking type fully controlled valve group 245 being exited online or exiting due to a fault, the third non-DC blocking type voltage source converter 207 is locked, or / and the IGBT of the second IGBT module 31 of at least one phase of the upper and lower bridge arm submodules of the third non-DC blocking type voltage source converter 207 is turned on to bypass it, and the fifth grid-side AC switch 231 is separated. The fourth bypass switch 52 is closed, the fourth bypass knife 51 is closed, the fourth bypass switch 52 is separated, the fifth first isolation knife 53 and the fifth second isolation knife 54 are separated, and the DC current is transferred to the fourth bypass knife 51, thereby isolating the third non-DC blocking type voltage source converter 207.

[0178] It should be noted that when the valve group is exited online or due to a fault, the valve groups of the corresponding poles of the rectifier station 100 and the inverter station 200 cooperate to perform the exit operation. Fig.18 ,like Fig.18 The embodiment of the present application is shown based on Fig.11 The results of the simulation test of the valve group exiting the DC transmission system; Fig.18 As shown in , UDL is the pole bus voltage, IDCP is the cathode DC current of the bridge uncontrolled rectifier circuit 11, UAC_IN_L1, UAC_IN_L2 and UAC_IN_L3 are the grid-side AC voltages of the first AC system 140, IVD_L1, IVD_L2 and IVD_L3 are the valve-side AC currents of the YD type converter transformer, and DEBLOCK_IND is the working signal of the bridge uncontrolled rectifier circuit 11; Fig.18 FIG. 2 shows that after the first grid-side AC switch 131 of the first high-end uncontrolled valve group 111 is separated, the bridge uncontrolled rectifier circuit 11 stops operating.

[0179] The control method of the hybrid DC transmission valve group of the present application also includes step 130: in response to a DC line fault, controlling the DC blocking valve group 500 to be negative pressure, so that the DC current at the hybrid DC transmission valve group connected to the DC line is zero or equal to the DC current at the other end of the DC line fault point, or controlling the DC blocking valve group to be in a blocking state. It should be pointed out that the zero DC current and the equal DC current here contain certain control and measurement errors.

[0180] In step 130, when the semi-controlled valve group 501 is connected in series with the uncontrolled valve group 401, when the DC line fails, the semi-controlled valve group 501 is controlled to be negative pressure, so that the DC current at the hybrid DC transmission valve group connected to the DC line is equal to the DC current at the other end of the DC line fault point; the grid commutation converter 1 of the semi-controlled valve group 501 is controlled to shift phase and present a blocking state.

[0181] like Fig.11 As shown, in response to a ground fault in the DC line, the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be negative pressure, so that the DC current IDL of the hybrid DC transmission valve group connected to the first DC line 150 is equal to the DC current IDL of the third DC pole 210 at the other end of the DC line fault point, so that the current flowing through the fault point is zero. Alternatively, the grid-commutated converter 1 of the semi-controlled valve group 501 is controlled to shift phase to be in a blocked state.

[0182] In some embodiments of the present application, in response to the DC blocking type fully-controlled valve group 502 being connected in series with the uncontrolled valve group 401, when a DC line fails, the DC blocking type fully-controlled valve group 502 is controlled to be a negative pressure, so that the DC current at the hybrid DC transmission valve group connected to the DC line is zero or equal to the DC current at the other end of the DC line fault point.

[0183] like Fig.12 As shown, when a ground fault occurs in the DC line, the first DC blocking type voltage source converter 12 of the first low-end DC blocking type full-control valve group 141 is controlled to be negative pressure, so that the DC current IDL of the hybrid DC transmission valve group connected to the first DC line 150 is zero or equal to the DC current IDL of the third DC pole 210 at the other end of the DC line fault point, so that the current flowing through the fault point in the hybrid DC transmission valve group is zero.

[0184] In response to the non-DC blocking type fully-controlled valve group 402 being connected in series with the half-controlled valve group 501, when the DC line fails, the half-controlled valve group 501 is controlled to be a negative pressure, so that the DC current at the hybrid DC transmission valve group connected to the DC line is equal to the DC current at the other end of the DC line fault point; the grid commutation converter 1 of the half-controlled valve group 501 is controlled to shift phase and present a blocking state.

[0185] like Fig.13 and Fig.14 As shown, in response to a ground fault in the DC line, the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be negative pressure, so that the DC current IDL of the hybrid DC transmission valve group connected to the first DC line 150 is equal to the DC current IDL of the third DC pole 210 at the other end of the DC line fault point, so that the current flowing through the fault point is zero. Alternatively, the grid-commutated converter 1 of the semi-controlled valve group 501 is controlled to shift phase to be in a blocked state.

[0186] See also Fig.19 , Fig.19 Based on the embodiments of the present application Fig.11 Figure 2. Results of DC line fault simulation test of DC transmission system. Fig.19 The UDL shown in the figure is the pole bus voltage, IDCP is the cathode DC current of the bridge uncontrolled rectifier circuit 11, UAC_IN_L1, UAC_IN_L2 and UAC_IN_L3 are the grid-side AC voltages of the first AC system 140, IVD_L1, IVD_L2 and IVD_L3 are the valve-side AC currents of the YD type converter transformer, and DEBLOCK_IND is the working signal of the bridge uncontrolled rectifier circuit 11. Fig.19 It is shown that the grid commutated converter 1 controlling the first low-end semi-controlled valve group 112 is at a negative pressure, so that the hybrid DC transmission valve group is at a negative pressure, so that the current flowing through the fault point in the hybrid DC transmission valve group is zero.

[0187] The present application also provides a DC transmission valve group control device, the control device includes the hybrid DC transmission valve group or the non-DC blocking valve group as described in the above embodiment, and the control device is used to execute the control method of the DC transmission valve group, such as Fig. 20 As shown, the control device includes:

[0188] A first detection unit 310, the first detection unit 310 is used to detect operating parameters and fault data of the hybrid DC transmission valve group or the non-DC blocking valve group 400;

[0189] The first control unit 320 is used to transfer the DC current to the bridge uncontrolled rectifier circuit, the anti-parallel diode of the fully controlled device or the fully controlled device of the non-DC blocking valve group 400 when the non-DC blocking valve group 400 is put into operation online, based on the operating parameters and fault data detected by the first detection unit 310, and then connect the AC input end of the non-DC blocking valve group 400 to the AC power, or / and unlock the non-DC blocking valve group 400; the first control unit 320 is used to transfer the DC current to the non-DC blocking valve group 400 when the non-DC blocking valve group 400 is exited online or exited due to a fault. The AC input end of the hybrid DC transmission valve group is disconnected from the AC power, or / and the non-DC blocking valve group 400 is locked, or / and the non-DC blocking valve group 400 is bypassed; or / and when the non-DC blocking valve group 400 fails to exit, the DC blocking valve group 500 is controlled to achieve zero pressure at the fault point or to be in a blocking state; and the first control unit 320 is used to control the DC blocking valve group 500 to be a negative pressure when the DC line fails, so that the DC current at the hybrid DC transmission valve group connected to the DC line is zero or equal to the DC current at the other end of the DC line fault point, or the DC blocking valve group 500 is controlled to be in a blocking state.

[0190] Based on the DC power transmission system provided in the above embodiment, the present application also provides a control method for the DC power transmission system. Fig.21 ,like Fig.21 The control flow chart of the DC power transmission system is shown. The control method of the DC power transmission system of the present application includes the following steps:

[0191] Step 210: in response to the DC blocking valve group 500 exiting online or exiting due to a fault, the station where the DC blocking valve group 500 is located is disconnected from the ground;

[0192] In step 210, the operation parameters and fault parameters of the DC power transmission system are first obtained; in response to the DC blocking valve group 500 being offline or faulty, the station where the DC blocking valve group 500 is located is disconnected from the ground, and the step also includes step 211:

[0193] If the DC pole where the DC blocking valve group 500 is located has a DC line fault again or the non-DC blocking valve group 400 where the DC pole where the DC blocking valve group 500 is located has a fault again, the DC currents of the converters at both ends of the fault point are controlled to be equal, and the DC pole where the DC blocking valve group 500 is located is restarted after the de-ionization time or fault isolation;

[0194] In response to the DC blocking valve group 500 being offline or failing, disconnecting the station where the DC blocking valve group 500 is located from the ground further includes step 212:

[0195] If a DC line fault occurs again at the DC pole where the DC blocking valve group 500 is located or a fault occurs again at the non-DC blocking valve group 400 at the DC pole where the DC blocking valve group 500 is located, the non-DC blocking valve group at the DC pole where the DC blocking valve group 500 is located will be locked or / and its AC input end will be disconnected from the AC power, then connected to the ground and the DC pole will be isolated.

[0196] In some embodiments of the present application, Fig.11 As shown, in step 210, in response to the first low-end semi-controlled valve group 112 exiting online or exiting due to a fault, the third low-end semi-controlled valve group 212 exits, the first metal return line transfer switch 113 is disconnected, and the rectifier station 100 operates in a non-grounding point state. In step 211, if a DC line fault occurs again at the DC pole where the first low-end semi-controlled valve group 112 is located, the DC currents of the first high-end uncontrolled valve group 111, the second high-end uncontrolled valve group 122, and the second low-end semi-controlled valve group 121 at both ends of the fault point are controlled to be equal to the DC current of the third high-end semi-controlled valve group 211, and the first DC pole 110 and the third DC pole 210 are restarted after the de-free time. In step 212, if the first high-end uncontrolled valve group 111 of the DC pole where the first low-end semi-controlled valve group 112 is located fails again, the first grid-side AC switch 131 is disconnected, the first metal return line transfer switch 113 is closed, and the first pole neutral bus switch 119 is disconnected.

[0197] In some embodiments of the present application, Fig.12 As shown, in step 210, in response to the first low-end DC blocking type fully controlled valve group 141 exiting online or exiting due to a fault, the third low-end half-controlled valve group 212 exits, disconnects the first metal return line transfer switch 113, and the rectifier station 100 operates in a non-grounding state. In step 211, if a DC line fault occurs again at the DC pole where the first low-end DC blocking type fully controlled valve group 141 is located, the DC currents of the first high-end uncontrolled valve group 111, the second high-end uncontrolled valve group 122, the second low-end DC blocking type fully controlled valve group 142 and the DC current of the third high-end half-controlled valve group 211 at both ends of the fault point are controlled to be zero or equal, and the first DC pole 110 and the third DC pole 210 are restarted after the de-ionization time. In step 212, if the first high-end uncontrolled valve group 111 of the DC pole where the first low-end semi-controlled valve group 112 is located fails again, the first grid-side AC switch 131 is disconnected, the first metal return line transfer switch 113 is closed, and the first pole neutral bus switch 119 is disconnected.

[0198] In some embodiments of the present application, Fig.13 and Fig.14As shown, in step 210, in response to the first low-end semi-controlled valve group 112 exiting online or exiting due to a fault, the third low-end semi-controlled valve group 212 exits, disconnects the first metal return line transfer switch 113, and the rectifier station 100 operates in a non-grounding state. In step 211, if a DC line fault occurs again at the DC pole where the first low-end semi-controlled valve group 112 is located, the DC currents of the first high-end non-DC blocking type full-controlled valve group 145, the second high-end non-DC blocking type full-controlled valve group 146, and the second low-end semi-controlled valve group 121 at both ends of the fault point are controlled to be equal to the DC current of the third high-end semi-controlled valve group 211, and the first DC pole 110 and the third DC pole 210 are restarted after the de-ionization time. In step 212, if the first high-end non-DC blocking type fully-controlled valve group 145 of the DC pole where the first low-end semi-controlled valve group 112 is located fails again, the first high-end non-DC blocking type fully-controlled valve group 145 is locked and the first grid-side AC switch 131 is disconnected, the first metal return line transfer switch 113 is closed, and the first pole neutral bus switch 119 is disconnected.

[0199] The control method of the hybrid DC transmission valve group of the present application also includes step 130: in response to a DC line fault, controlling the DC current of the hybrid DC transmission valve group and the opposite valve group at both ends of the DC line to be equal, or controlling the hybrid DC transmission valve group and the opposite valve group to be zero current or to be in a blocked state. It should be noted that the control and measurement error of less than 0.02 times the rated DC current is allowed when the DC current is controlled to be zero, equal or zero.

[0200] In some embodiments of the present application, in response to the semi-controlled valve group 501 being connected in series with the uncontrolled valve group 401, when a DC line fails, the semi-controlled valve group 501 is controlled to be a negative pressure, so that the DC current at the hybrid DC transmission valve group connected to the DC line is equal to the DC current at the other end of the DC line fault point; the grid phase-commutating converter 1 of the semi-controlled valve group 501 is controlled to shift phase and present a blocked state.

[0201] like Fig.11 As shown, in response to a ground fault in the DC line, the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be negative pressure, so that the DC current IDL of the hybrid DC transmission valve group connected to the first DC line 150 is equal to the DC current IDL of the third DC pole 210 at the other end of the DC line fault point, so that the current flowing through the fault point is zero. Alternatively, the grid-commutated converter 1 of the semi-controlled valve group 501 is controlled to shift phase to present a blocking state, and the trigger angle of the third grid-commutated converter 201 and the fourth grid-commutated converter 202 of the third DC pole 210 is controlled to be equal to 110 degrees, and also present a blocking state.

[0202] In some embodiments of the present application, in response to the DC blocking type fully-controlled valve group 502 being connected in series with the uncontrolled valve group 401, when a DC line fails, the DC blocking type fully-controlled valve group 502 is controlled to be a negative pressure, so that the DC current at the hybrid DC transmission valve group connected to the DC line is zero or equal to the DC current at the other end of the DC line fault point.

[0203] like Fig.12 As shown, when a ground fault occurs in the DC line, the first DC blocking type voltage source converter 12 of the first low-end DC blocking type full-control valve group 141 is controlled to be negative pressure, so that the DC current IDL of the hybrid DC transmission valve group connected to the first DC line 150 is zero or equal to the DC current IDL of the third DC pole 210 at the other end of the DC line fault point, so that the current flowing through the fault point in the hybrid DC transmission valve group is zero.

[0204] In response to the non-DC blocking type fully-controlled valve group 402 being connected in series with the half-controlled valve group 501, when the DC line fails, the half-controlled valve group 501 is controlled to be a negative pressure, so that the DC current at the hybrid DC transmission valve group connected to the DC line is equal to the DC current at the other end of the DC line fault point; the grid commutation converter 1 of the half-controlled valve group 501 is controlled to shift phase and present a blocking state.

[0205] like Fig.13 and Fig.14 As shown, in response to a ground fault in the DC line, the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be negative pressure, so that the DC current IDL of the hybrid DC transmission valve group connected to the first DC line 150 is equal to the DC current IDL of the third DC pole 210 at the other end of the DC line fault point, so that the current flowing through the fault point is zero. Alternatively, the grid-commutated converter 1 of the semi-controlled valve group 501 is controlled to shift phase to be in a blocked state.

[0206] The present application also provides a DC power transmission system control device, the control device includes the DC power transmission system as described in the above embodiment, and the control device is used to execute the control method of the DC power transmission system as described above, such as Fig. 22 As shown, the control device includes:

[0207] A second detection unit 410, the second detection unit 410 is used to detect operating parameters and fault data of the DC power transmission system;

[0208] The second control unit 420 is used to control the station where the DC blocking valve group 500 is located to disconnect from the ground after the DC blocking valve group 500 exits online or exits due to a fault based on the operating parameters and fault data detected by the second detection unit 410; if a DC line fault occurs again at the DC pole where the DC blocking valve group 500 is located or the non-DC blocking valve group 400 at the DC pole where the DC blocking valve group 500 is located fails again, control the DC currents of the converters at both ends of the fault point to be equal, restart the DC pole where the DC blocking valve group 500 is located after the de-free time or fault isolation, or / and lock the non-DC blocking valve group 400 at the DC pole where the DC blocking valve group 500 is located or / and disconnect the AC power at its AC input end, reconnect to the ground and isolate the DC pole; the second control unit 420 is used to control the DC currents of the hybrid DC transmission valve group and the opposite valve group at both ends of the DC line to be equal when the DC line fails, or control the hybrid DC transmission valve group and the opposite valve group to be zero current or in a blocking state.

[0209] The hybrid DC transmission valve group, transmission system, control device and control method provided in the embodiments of the present invention are introduced in detail above. The principles and implementation methods of the present invention are explained by using specific examples in the present invention. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present invention. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hybrid DC transmission valve group, characterized in that: include: A non-DC blocking type valve group (400), wherein the non-DC blocking type valve group (400) comprises: an uncontrolled valve group (401) or a non-DC blocking type fully controlled valve group (402); A direct current blocking valve group (500), the direct current blocking valve group (500) comprising: a half-controlled valve group (501) or a direct current blocking fully-controlled valve group (502); wherein: Any one of the uncontrolled valve group (401) and the non-DC blocking type fully controlled valve group (402) is connected in series with any one of the half-controlled valve group (501) and the DC blocking type fully controlled valve group (502).

2. The hybrid DC transmission valve group according to claim 1, characterized in that: Any one of the uncontrolled valve group (401), the semi-controlled valve group (501), the non-DC blocking type fully-controlled valve group (402), and the DC blocking type fully-controlled valve group (502) comprises: a commutation device, a bypass switch (3), a bypass knife gate (4), a first isolating knife gate (5), and a second isolating knife gate (6); the bypass switch (3) and the bypass knife gate (4) are connected in parallel to form a bypass circuit; the first isolating knife gate (5) and the second isolating knife gate (6) are respectively arranged at a connection node where the bypass switch (3) and the bypass knife gate (4) are connected in parallel.

3. The hybrid DC transmission valve group according to claim 2, characterized in that: The commutation device of the semi-controlled valve group (501) comprises any one of a grid phase-commutation converter (1) and a current source converter with controllable shut-off capability.

4. The hybrid DC transmission valve group according to claim 3, characterized in that: The commutation device comprises a grid commutation converter (1), the grid commutation converter (1) comprising: a first three-phase input (21), a second three-phase input (22) and a thyristor (23), a plurality of the thyristors (23) are connected in series to form a bridge arm, the first three-phase input (21) is connected to the bridge arm, and the second three-phase input (22) is connected to the bridge arm.

5. The hybrid DC transmission valve group according to claim 3, characterized in that: The current source converter with controllable shutdown capability includes a controllable grid commutation converter CLCC, an IGCT-based hybrid commutation converter HCC, a controllable current source converter CSC, and a line commutation converter LCC.

6. The hybrid DC transmission valve group according to claim 2, characterized in that: The commutation devices of the non-DC blocking type fully-controlled valve group (402) and the DC blocking type fully-controlled valve group (502) include a voltage source converter (2); wherein the voltage source converter of the non-DC blocking type fully-controlled valve group (402) includes a two-level converter, a three-level converter, a modular multi-level converter based on a half-bridge submodule, a diode clamped multi-level converter, a cascaded two-level converter or a stacked two-level converter; the voltage source converter of the DC blocking type fully-controlled valve group (502) includes a modular multi-level converter based on a full-bridge submodule or a modular multi-level converter based on a mixture of half-bridge and full-bridge submodules.

7. The hybrid DC transmission valve group according to claim 6, characterized in that: The voltage source converter (2) comprises: a third three-phase input (24), an isolating knife switch (25), a charging resistor (26), a submodule (27) and a current limiting reactor (28); a plurality of the submodules (27) and the current limiting reactor (28) are connected in series to form a bridge arm; the third three-phase input (24) is connected to the valve side of the converter transformer; the isolating knife switch (25) and the charging resistor (26) are connected in parallel and connected between the third three-phase input (24) and the bridge arm; The submodule (27) comprises a full-control module and a capacitor, and a plurality of the full-control modules are connected with the capacitor to form a full-bridge structure or a half-bridge structure.

8. The hybrid DC transmission valve group according to claim 2, characterized in that: The commutation device of the uncontrolled valve group (401) comprises a bridge-type uncontrolled rectifier circuit (11), wherein the bridge-type uncontrolled rectifier circuit (11) comprises: a diode (44), a fourth three-phase input (42) and a fifth three-phase input (43), wherein a plurality of the diodes (44) are connected in series to form a bridge arm, wherein the fourth three-phase input (42) is connected to the bridge arm, and wherein the fifth three-phase input (43) is connected to the bridge arm.

9. The hybrid DC transmission valve group according to claim 1, characterized in that: The absolute value of the maximum negative DC voltage generated or blocked by the DC blocking valve group (500) is greater than the rated DC voltage or rated no-load DC voltage of the non-DC blocking valve group (400).

10. A direct current power transmission system, comprising the hybrid direct current power transmission valve group according to any one of claims 1 to 9, characterized in that: The DC power transmission system further comprises: A rectifier station (100), the rectifier station (100) comprising a first DC pole (110), a second DC pole (120) and a first AC system (140), the first AC system (140) being connected to the first DC pole (110) and the second DC pole (120) respectively; An inverter station (200), the inverter station (200) comprising a third DC pole (210), a fourth DC pole (220) and a second AC system (240), the second AC system (240) being connected to the third DC pole (210) and the fourth DC pole (220), respectively.

11. The direct current power transmission system according to claim 10, characterized in that: The first DC pole (110) comprises a first high-end uncontrolled valve group (111), a first low-end semi-controlled valve group (112), a first high-end converter transformer (116), and a first low-end converter transformer (117); the first high-end uncontrolled valve group (111) and the first low-end semi-controlled valve group (112) are connected in series; the first high-end converter transformer (116) is connected between the first AC system (140) and the first high-end uncontrolled valve group (111); and the first low-end converter transformer (117) is connected between the first AC system (140) and the first low-end semi-controlled valve group (112); The second DC pole (120) comprises a second low-end semi-controlled valve group (121), a second high-end uncontrolled valve group (122), a second low-end converter transformer (126) and a second high-end converter transformer (127); the second low-end semi-controlled valve group (121) and the second high-end uncontrolled valve group (122) are connected in series; the second low-end converter transformer (126) is connected between the first AC system (140) and the second low-end semi-controlled valve group (121); and the second high-end converter transformer (127) is connected between the first AC system (140) and the second high-end uncontrolled valve group (122).

12. The direct current transmission system according to claim 10, characterized in that: The first DC pole (110) comprises a first high-end uncontrolled valve group (111), a first low-end DC blocking type fully controlled valve group (141), a first high-end converter transformer (116) and a first low-end converter transformer (117); the first high-end uncontrolled valve group (111) and the first low-end DC blocking type fully controlled valve group (141) are connected in series; the first high-end converter transformer (116) is connected between the first high-end uncontrolled valve group (111) and the first AC system (140); the first low-end converter transformer (117) is connected between the first low-end DC blocking type fully controlled valve group (141) and the first AC system (140); The second DC pole (120) comprises a second low-end DC blocking type fully-controlled valve group (142), a second high-end uncontrolled valve group (122), a second low-end converter transformer (126) and a second high-end converter transformer (127); the second low-end DC blocking type fully-controlled valve group (142) and the second high-end uncontrolled valve group (122) are connected in series; the second low-end converter transformer (126) is connected between the second low-end DC blocking type fully-controlled valve group (142) and the first AC system (140); and the second high-end converter transformer (127) is connected between the second high-end uncontrolled valve group (122) and the first AC system (140).

13. The direct current power transmission system according to claim 10, characterized in that: The first DC pole (110) comprises: a first high-end non-DC blocking type fully-controlled valve group (145), a first low-end half-controlled valve group (112), a first high-end converter transformer (116) and a first low-end converter transformer (117); the first high-end non-DC blocking type fully-controlled valve group (145) is connected to the first low-end half-controlled valve group (112); the first high-end converter transformer (116) is connected between the first high-end non-DC blocking type fully-controlled valve group (145) and the first AC system (140); the first low-end converter transformer (117) is connected between the first low-end half-controlled valve group (112) and the first AC system (140); The second DC pole (120) comprises: a second low-end semi-controlled valve group (121), a second high-end non-DC blocking type fully-controlled valve group (146), a second low-end converter transformer (126) and a second high-end converter transformer (127); the second low-end semi-controlled valve group (121) and the second high-end non-DC blocking type fully-controlled valve group (146) are connected in series; the second low-end converter transformer (126) is connected between the second low-end semi-controlled valve group (121) and the first AC system (140); and the second high-end converter transformer (127) is connected between the second high-end non-DC blocking type fully-controlled valve group (146) and the first AC system (140).

14. The direct current power transmission system according to claim 10, characterized in that: The third DC pole (210) comprises: two of any one of a half-controlled valve group, a non-DC blocking type fully-controlled valve group, and a DC blocking type fully-controlled valve group, or one of any two of the two; The fourth DC pole (220) comprises: two of any one of a half-controlled valve group, a non-DC blocking type fully-controlled valve group, and a DC blocking type fully-controlled valve group, or one of any two of the two.

15. A DC transmission valve group control device, comprising a hybrid DC transmission valve group or a non-DC blocking valve group (400) according to any one of claims 1 to 9, characterized in that: Also includes: A first detection unit (310), the first detection unit (310) being used to detect operating parameters and fault parameters of the hybrid DC transmission valve group or the non-DC blocking valve group (400); A first control unit (320), the first control unit (320) is used for, based on the operating parameters and fault parameters of the hybrid DC transmission valve group or the non-DC blocking valve group (400), when the non-DC blocking valve group (400) is put into operation online, first transferring the DC current to the bridge uncontrolled rectifier circuit, the fully controlled device anti-parallel diode or the fully controlled device of the non-DC blocking valve group (400), and then connecting the AC input end of the non-DC blocking valve group (400) to AC power, or / and unlocking the non-DC blocking valve group (400); and the first control unit (320) is used for shutting down the non-DC blocking valve group (400) when the non-DC blocking valve group (400) is shut down online or shut down due to a fault. The AC input end of the hybrid DC power transmission valve group (400) is disconnected from the AC power supply, or / and the non-DC blocking valve group (400) is locked, or / and the non-DC blocking valve group (400) is bypassed; or / and, when the non-DC blocking valve group (400) fails and exits, the first control unit (320) is used to control the DC blocking valve group (500) to present a zero pressure at the fault point or a blocking state; and the first control unit (320) is used to control the DC blocking valve group (500) to be a negative pressure when a DC line fails, so that the DC current of the hybrid DC power transmission valve group connected to the DC line is equal to zero or equal to the DC current at the other end of the DC line at the fault point, or to control the DC blocking valve group (500) to be in a blocking state.

16. A method for controlling a DC transmission valve group, used for controlling a hybrid DC transmission valve group or a non-DC blocking valve group (400) according to any one of claims 1 to 9, characterized in that: The control method comprises the steps of: Obtaining operating parameters and fault parameters of the hybrid DC power transmission valve group or the non-DC blocking valve group (400); In response to the non-DC blocking valve group (400) being put into operation online, the DC current is first transferred to the bridge uncontrolled rectifier circuit, the fully controlled device anti-parallel diode or the fully controlled device of the non-DC blocking valve group (400); the AC input end of the non-DC blocking valve group (400) is connected to AC power, or / and the non-DC blocking valve group (400) is unlocked; In response to the non-DC blocking valve group (400) exiting online or exiting due to a fault, the AC input terminal of the non-DC blocking valve group (400) is disconnected from the AC power, or / and the non-DC blocking valve group (400) is locked, or / and the non-DC blocking valve group (400) is bypassed; or / and in response to the non-DC blocking valve group (400) exiting due to a fault, the DC blocking valve group (500) is controlled to present a fault point of zero pressure or a blocking state; In response to a DC line fault, the DC blocking valve group (500) is controlled to be in a negative pressure, so that the DC current of the hybrid DC power transmission valve group connected to the DC line is equal to zero or equal to the DC current at the other end of the DC line at the fault point, or the DC blocking valve group (500) is controlled to be in a blocking state.

17. A DC power transmission system control device, comprising the DC power transmission system according to any one of claims 10 to 14, characterized in that: Also includes: A second detection unit (410), the second detection unit (410) being used to detect operating parameters and fault parameters of the direct current power transmission system; The second control unit (420) is used for controlling the station where the DC blocking valve group (500) is located to disconnect from the ground after the DC blocking valve group (500) is offline or fails based on the operating parameters and fault parameters of the DC power transmission system; when a DC line fault occurs again at the DC pole where the DC blocking valve group (500) is located, or a non-DC blocking valve group (400) at the DC pole where the DC blocking valve group (500) is located fails again, the second control unit (420) is used for controlling the DC current phase of the converters at both ends of the fault point. and restarting the DC pole where the DC blocking valve group (500) is located after the de-free time or fault isolation, or / and locking the non-DC blocking valve group (400) at the DC pole where the DC blocking valve group (500) is located, or / and disconnecting the AC input end of the DC blocking valve group (500) from the AC power, then connecting it to the ground and isolating the DC pole; the second control unit (420) is used to control the DC current of the hybrid DC transmission valve group and the opposite valve group of the DC line to be equal when a DC line fault occurs, or to control the hybrid DC transmission valve group and the opposite valve group to be zero current or to be in a blocking state.

18. A method for controlling a DC power transmission system, for controlling the DC power transmission system according to any one of claims 10 to 14, characterized in that: The control method comprises the steps of: Obtaining operating parameters and fault parameters of the DC power transmission system; In response to the DC blocking valve group (500) exiting online or exiting due to a fault, the station where the DC blocking valve group (500) is located is disconnected from the ground; when a DC line fault occurs again at the DC pole where the DC blocking valve group (500) is located, or when a non-DC blocking valve group (400) at the DC pole where the DC blocking valve group (500) is located fails again, the DC currents of the converters at both ends of the fault point are controlled to be equal, and the DC pole where the DC blocking valve group (500) is located is restarted after a de-ionizing time or fault isolation, or / and the non-DC blocking valve group (400) at the DC pole where the DC blocking valve group (500) is located is locked, or / and the AC input end of the non-DC blocking valve group (400) is disconnected from the AC power, reconnected to the ground and the DC pole is isolated; In response to a DC line fault, the DC currents of the hybrid DC transmission valve group and the opposite valve group of the DC line are controlled to be equal, or the hybrid DC transmission valve group and the opposite valve group are controlled to be zero current or in a blocked state.

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