Hybrid hvdc valve set, hvdc system, control device and control method

Abstract

The application discloses a hybrid DC power transmission valve group, a DC power transmission system, a control device and a control method. The hybrid DC power transmission valve group comprises: a non-DC blocking valve group, the non-DC blocking valve group comprising: an uncontrolled valve group or a non-DC blocking full-controlled valve group; a DC blocking valve group, the DC blocking valve group comprising: a semi-controlled valve group or a DC blocking full-controlled valve group; and any one of the uncontrolled valve group or the non-DC blocking full-controlled valve group is connected in series with any one of the semi-controlled valve group or the DC blocking full-controlled valve group. The on-line switching of the non-DC blocking valve group is realized by connecting or disconnecting AC power, and the DC line fault ride-through is realized by controlling the DC blocking valve group to be negative pressure. The hybrid DC power transmission valve group is used to solve the problems of the existing converter structure, such as the need to be equipped with a large number of reactive power compensation devices, high loss and high cost.

Description

TECHNICAL FIELD

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

[0002] High-voltage and extra-high-voltage direct current transmission has large capacity, one of the existing technologies adopts a grid commutated converter with a twelve-pulse circuit structure, each twelve-pulse circuit has two three-phase six-bridge-arm circuits in series, and each bridge arm adopts a single large-capacity thyristor in series, since the thyristor cannot control turn-off, the existing converter structure needs to be configured with a large number of reactive power compensation devices. The second existing technology adopts a voltage source converter based on a modular multilevel converter, each bridge arm adopts a half-bridge sub-module or a full-bridge sub-module composed of IGBT or IGCT in series, the active power and the reactive power can be flexibly controlled, and the passive grid or the island new energy grid can be accessed, but the price is high and the loss is high. The third existing technology adopts a bridge-type uncontrolled rectifier circuit with a twelve-pulse circuit structure, each bridge arm adopts a single large-capacity diode in series, and has certain advantages in cost and reactive power loss, but since it is uncontrolled rectification, it cannot control power by itself and cannot suppress faults on the direct current side, and it is difficult to meet the performance requirements of the direct current transmission system.

[0003] With the development of new energy in high-altitude areas, deserts and far seas, the performance, cost and land occupation requirements of the direct current transmission system are becoming higher and higher, and the hybrid direct current transmission valve group adopting the above three existing technologies can realize complementary advantages, exert the technical advantages of each converter, make up for the shortcomings of each other, maximize the comprehensive transmission performance, and optimize the cost and land occupation of the direct current transmission system. SUMMARY

[0004] The application provides a hybrid direct current transmission valve group, a direct current transmission system, a control device and a control method, which are used to solve the problems that the existing converter structure needs to be equipped with a large number of reactive power compensation devices, the loss is high, and it is difficult to meet the direct current transmission.

[0005] Technical scheme: The application provides a hybrid direct current transmission valve group, which comprises: a non-direct-current blocking valve group, the non-direct-current blocking valve group comprises: an uncontrolled valve group or a non-direct-current blocking full-controlled valve group; a direct-current blocking valve group, the direct-current blocking valve group comprises: a semi-controlled valve group or a direct-current blocking full-controlled valve group; wherein any one of the uncontrolled valve group and the non-direct-current blocking full-controlled valve group is connected in series with any one of the semi-controlled valve group and the direct-current blocking full-controlled valve group.

[0006] In some embodiments, any one of the non-controlled valve group, the semi-controlled valve group, the non-direct-current blocking full-controlled valve group, and the direct-current blocking full-controlled valve group comprises: a converter device, a bypass switch, a bypass knife, a first isolation knife, and a second isolation knife; the bypass switch and the bypass knife are connected in parallel to form a bypass circuit; the first isolation knife and the second isolation knife are respectively arranged at a connection node of the bypass switch and the bypass knife.

[0007] In some embodiments, the converter device of the semi-controlled valve group comprises any one of a line-commutated converter, a current source converter with controllable turn-off capability.

[0008] In some embodiments, the converter device comprises a line-commutated converter, the line-commutated converter comprising: a first three-phase input, a second three-phase input, and thyristors, a plurality of the thyristors being connected in series to form a bridge arm, the first three-phase input being connected to the bridge arm, and the second three-phase input being connected to the bridge arm.

[0009] In some embodiments, the current source converter with controllable turn-off capability comprises a controllable line-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 converter device of the non-direct-current blocking full-controlled valve group and the direct-current blocking full-controlled valve group comprises a voltage source converter; wherein the voltage source converter of the non-direct-current blocking full-controlled valve group comprises a two-level converter, a three-level converter, a modular multilevel converter based on half-bridge sub-modules, a diode clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter; and the voltage source converter of the direct-current blocking full-controlled valve group comprises a modular multilevel converter based on full-bridge sub-modules 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 comprises: a third three-phase input, an isolation knife, a charging resistor, a sub-module, and a current-limiting reactor; a plurality of the sub-modules and the current-limiting reactor are connected in series to form a bridge arm; the third three-phase input is connected to a valve side of a converter transformer; the isolation knife and the charging resistor are connected in parallel and between the third three-phase input and the bridge arm; wherein the sub-module comprises a controllable module and a capacitor, and a plurality of the controllable modules and the capacitor are connected to form a full-bridge structure or a half-bridge structure.

[0012] In some embodiments, the commutating device of the uncontrolled valve group comprises a bridge uncontrolled rectifier circuit, the bridge uncontrolled rectifier circuit comprising: diodes, a fourth three-phase input and a fifth three-phase input, a plurality of the diodes connected in series to form a bridge arm, the fourth three-phase input connected to the bridge arm, and the fifth three-phase input connected to the bridge arm.

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

[0014] The 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 comprising a first DC pole, a second DC pole and a first AC system, the first AC system connected to the first DC pole and the second DC pole respectively; and an inverter station comprising a third DC pole, a fourth DC pole and a second AC system, the second AC system connected to the third DC pole and the fourth DC pole respectively.

[0015] In some embodiments, the first DC pole comprises a first high-end uncontrolled valve group, a first low-end semi-controlled valve group, a first high-end commutation transformer and a first low-end commutation transformer, the first high-end uncontrolled valve group connected in series to the first low-end semi-controlled valve group, the first high-end commutation transformer connected between the first AC system and the first high-end uncontrolled valve group, and the first low-end commutation transformer connected between the first AC system and the first low-end semi-controlled valve group; and the second DC pole comprises a second low-end semi-controlled valve group, a second high-end uncontrolled valve group, a second low-end commutation transformer and a second high-end commutation transformer, the second low-end semi-controlled valve group connected in series to the second high-end uncontrolled valve group, the second low-end commutation transformer connected between the first AC system and the second low-end semi-controlled valve group, and the second high-end commutation transformer connected between the first AC system and the second high-end uncontrolled valve group.

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

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

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

[0019] The application also provides a direct current transmission valve group control device, comprising a hybrid direct current transmission valve group or a non-direct current blocking valve group as described above, and further comprising: a first detection unit for detecting operating parameters and fault parameters of the hybrid direct current transmission valve group; a first control unit for, based on the operating parameters and fault parameters of the hybrid direct current transmission valve group or the non-direct current blocking valve group, when the non-direct current blocking valve group is online, first diverting direct current to a bridge uncontrolled rectifier circuit, a full-controlled device anti-parallel diode or a full-controlled device of the non-direct current blocking valve group, connecting an alternating current input end of the non-direct current blocking valve group to an alternating current, and / or unlocking the non-direct current blocking valve group; and when the non-direct current blocking valve group is online or fault-exits, the first control unit is used for disconnecting the alternating current input end of the non-direct current blocking valve group from the alternating current, and / or locking the non-direct current blocking valve group, and / or bypassing the non-direct current blocking valve group; or / and when the non-direct current blocking valve group fault-exits, the first control unit is used for controlling the direct current blocking valve group to present a fault point with zero voltage or a blocking state; and the first control unit is used for, when a direct current line is faulty, controlling the direct current blocking valve group to be negative, so that a direct current connected by the hybrid direct current transmission valve group to the direct current line is zero or equal to a direct current at the other end of a fault point of the direct current line, or controlling the direct current blocking valve group to present a blocking state.

[0020] The application also provides a direct current transmission valve group control method for controlling a hybrid direct current transmission valve group or a non-direct current blocking valve group as described above, comprising the steps of: obtaining operating parameters and fault parameters of the hybrid direct current transmission valve group or the non-direct current blocking valve group; in response to online input of the non-direct current blocking valve group, first diverting direct current to a bridge uncontrolled rectifier circuit, a full-controlled device anti-parallel diode or a full-controlled device of the non-direct current blocking valve group; connecting an alternating current input end of the non-direct current blocking valve group to an alternating current, and / or unlocking the non-direct current blocking valve group; in response to online exit or fault-exit of the non-direct current blocking valve group, disconnecting the alternating current input end of the non-direct current blocking valve group from the alternating current, and / or locking the non-direct current blocking valve group, and / or bypassing the non-direct current blocking valve group; or / and in response to fault-exit of the non-direct current blocking valve group, controlling the direct current blocking valve group to present a fault point with zero voltage or a blocking state;

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

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

[0023] The application also provides a direct current transmission system control method for controlling a direct current transmission system as described above, the control method comprising the steps of:

[0024] obtaining operating parameters and fault parameters of the direct current transmission system;

[0025] after the direct current blocking valve group is taken offline or fails, the station where the direct current blocking valve group is located is disconnected from the ground; when a direct current line fault occurs again in the direct current pole where the direct current blocking valve group is located, or a fault occurs again in the non-direct current blocking valve group of the direct current pole where the direct current blocking valve group is located, the direct current currents of the converters on both sides of the fault point are controlled to be equal, the direct current pole where the direct current blocking valve group is located is restarted after a de-ionization time or fault isolation, and / or the non-direct current blocking valve group of the direct current pole where the direct current blocking valve group is located is locked, and / or the alternating current input end of the direct current blocking valve group is disconnected from the alternating current, the ground is reconnected, and the direct current pole is isolated;

[0026] when a direct current line fault occurs, the direct current currents of the hybrid direct current transmission valve group and the opposite valve group of the direct current line are controlled to be equal, or the hybrid direct current transmission valve group and the opposite valve group are controlled to be zero current or in a blocking state.

[0027] Beneficial effects: Compared with the prior art, the hybrid HVDC valve group, the HVDC system, the control device and the control method provided by the application have the beneficial effects that: the hybrid HVDC valve group comprises: a non-DC blocking valve group, the non-DC blocking valve group comprises: an uncontrolled valve group or a non-DC blocking full-controlled valve group; a DC blocking valve group, the DC blocking valve group comprises: a semi-controlled valve group or a DC blocking full-controlled valve group; any one of the uncontrolled valve group or the non-DC blocking full-controlled valve group is connected in series with any one of the semi-controlled valve group or the DC blocking full-controlled valve group. The hybrid HVDC valve group of the application overcomes the problems that the existing grid commutated converter needs to be equipped with a large number of reactive power compensation devices and needs a strong AC system to provide commutation voltage support, and the existing voltage source converter has the disadvantages of high cost, high loss and difficulty in suppressing DC side faults, thereby improving the performance of HVDC. BRIEF DESCRIPTION OF DRAWINGS

[0028] The technical solutions and other beneficial effects of the application will become apparent from the following detailed description of the application, taken in conjunction with the accompanying drawings.

[0029] Figure 1 is a hybrid HVDC valve group schematic diagram provided by the embodiment of the application;

[0030] Figure 2a is a valve group structure schematic diagram of a hybrid HVDC valve group of the embodiment of the application;

[0031] Figure 2b is a valve group structure schematic diagram of a hybrid HVDC valve group of the embodiment of the application;

[0032] Figure 2c is a valve group structure schematic diagram of a hybrid HVDC valve group of the embodiment of the application;

[0033] Figure 2d is a valve group structure schematic diagram of a hybrid HVDC valve group of the embodiment of the application;

[0034] Figure 2e is a valve group structure schematic diagram of a hybrid HVDC valve group of the embodiment of the application;

[0035] Figure 2f is a valve group structure schematic diagram of a hybrid HVDC valve group of the embodiment of the application;

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

[0037] Figure 4 is a grid commutated converter using a twelve-pulse bridge circuit provided by the embodiment of the application;

[0038] Figure 5This is a schematic diagram of a fully controllable valve assembly provided in an embodiment of this application;

[0039] Figure 6 This application provides a voltage source converter employing a modular multilevel converter.

[0040] Figure 7 This application provides an embodiment of a submodule structure using a full-bridge submodule.

[0041] Figure 8 This is a schematic diagram of a half-bridge submodule structure provided in an embodiment of this application;

[0042] Figure 9 This is a schematic diagram of an uncontrolled valve assembly provided in an embodiment of this application;

[0043] Figure 10 This application provides a bridge uncontrolled rectifier circuit using a twelve-pulse bridge circuit.

[0044] Figure 11 This is a schematic diagram of a DC power transmission system according to an embodiment of this application;

[0045] Figure 12 This is a schematic diagram of another DC power transmission system according to an embodiment of this application;

[0046] Figure 13 This is a schematic diagram of another DC power transmission system according to an embodiment of this application;

[0047] Figure 14 This is a schematic diagram of another DC power transmission system according to an embodiment of this application;

[0048] Figure 15 This is a schematic flowchart of the control method for the DC transmission valve group provided in the embodiments of this application;

[0049] Figure 16 This is yet another schematic diagram of a DC transmission system applicable to the DC transmission valve group control method provided in the embodiments of this application;

[0050] Figure 17 The embodiments provided in this application are based on Figure 11 Figure showing the simulation test results of valve group commissioning in a DC transmission system;

[0051] Figure 18 The embodiments provided in this application are based on Figure 11 Figure showing the simulation results of valve group disengagement in a DC transmission system;

[0052] Figure 19 The embodiments provided in this application are based on Figure 11 Figure showing the results of a DC line fault simulation test in a DC transmission system;

[0053] Figure 20 is a schematic diagram of a control device of a direct current transmission valve group provided by an embodiment of the present application;

[0054] Figure 21 is a schematic diagram of a control method of a direct current transmission system provided by an embodiment of the present application;

[0055] Figure 22 is a schematic diagram of a control device of a direct current transmission system provided by an embodiment of the present application.

[0056] Reference numerals: 1 - line commutated converter, 3 - bypass switch, 4 - bypass pole, 5 - first isolation pole, 6 - second isolation pole, 11 - bridge uncontrolled rectifier circuit, 12 - first DC blocking voltage source converter, 13 - second bypass switch, 14 - second bypass pole, 15 - second first isolation pole, 16 - second second isolation pole, 21 - first three-phase input, 22 - second three-phase input, 23 - thyristor, 24 - third three-phase input, 25 - isolation pole, 26 - charging resistor, 27 - sub-module, 28 - current limiting reactor, 29 - first IGBT module, 30 - capacitor, 31 - second IGBT module, 32 - third IGBT module, 33 - fourth IGBT module, 42 - fourth three-phase input, 43 - fifth three-phase input, 44 - diode, 45 - third bypass switch, 46 - third bypass pole, 47 - third first isolation pole, 48 - third second isolation pole, 51, 55 - fourth bypass pole, 52, 56 - fourth bypass switch, 53 - fifth first isolation pole, 54 - fifth second isolation pole, 57 - fourth first isolation pole, 58 - fourth second isolation pole, 61 - fifth bypass pole, 62 - fifth bypass switch, 63 - sixth first isolation pole, 64 - sixth second isolation pole, 71 - seventh bypass pole, 72 - seventh bypass switch, 73 - eighth first isolation pole, 74 - eighth second isolation pole, 81 - sixth bypass pole, 82 - sixth bypass switch, 83 - seventh first isolation pole, 84 - seventh second isolation pole, 100 - rectifier station, 101 - second line commutated 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 transfer switch, 213 - second metal return transfer pole, 114 - rectifier station ground pole line, 115 - rectifier station ground pole, 116 - first high-end converter transformer, 117 - first low-end converter transformer, 119 - first pole neutral bus pole, 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 pole, 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, 143 - third low-end DC blocking fully-controlled valve group, 144 - fourth low-end DC blocking fully-controlled valve group, 145 - fifth low-end DC blocking fully-controlled valve group, 146 - sixth low-end DC blocking fully-controlled valve group, 147 - seventh low-end DC blocking fully-controlled valve group, 148 - eighth low-end DC blocking fully-controlled valve group, 149 - ninth low-end DC blocking fully-controlled valve group, 150 - tenth low-end DC blocking fully-controlled valve group, 151 - first high-end DC blocking fully-controlled valve group, 152 - second high-end DC blocking fully-controlled valve group, 153 - third high-end DC blocking fully-controlled valve group, 154 - fourth high-end DC blocking fully-controlled valve group, 155 - fifth high-end DC blocking fully-controlled valve group, 156 - sixth high-end DC blocking fully-controlled valve group, 157 - seventh high-end DC blocking fully-controlled valve group, 158 - eighth high-end DC blocking fully-controlled valve group, 159 - ninth high-end DC blocking fully-controlled valve group, 160 - tenth high-end DC blocking fully-controlled valve group, 161 - first DC circuit breaker, 162 - second DC circuit breaker, 163 - third DC circuit breaker, 164 - fourth DC circuit breaker, 165 - fifth DC circuit breaker, 166 - sixth DC circuit breaker, 167 - seventh DC circuit breaker, 168 - eighth DC circuit breaker, 169 - ninth DC circuit breaker, 170 - tenth DC circuit breaker, 171 - first DC pole, 172 - second DC pole, 173 - third DC pole, 174 - fourth DC pole, 175 - fifth DC pole, 176 - sixth DC pole, 177 - seventh DC pole, 178 - eighth DC pole, 179 - ninth DC pole, 180 - tenth DC pole, 181 - first DC pole, 182 - second DC pole, 183 - third DC pole, 184 - fourth DC pole, 185 - fifth DC pole, 186 - sixth DC pole, 187 - seventh DC pole, 188 - eighth DC pole, 189 - ninth DC pole, 190 - tenth DC pole, 191 - first DC pole, 192 - second DC pole, 193 - third DC pole, 194 - fourth DC pole, 195 - fifth DC pole, 196 - sixth DC pole, 197 - seventh DC pole, 198 - eighth DC pole, 199 - ninth DC pole, 200 - tenth DC pole, 201 - first DC pole, 202 - second DC pole, 203 - third DC pole, 204 - fourth DC pole, 205 - fifth DC pole, 206 - sixth DC pole, 207 - seventh DC pole, 208 - eighth DC pole, 209 - ninth DC pole, 210 - tenth DC pole, 211 - first DC pole, 212 - second DC pole, 214 - third DC pole, 215 - fourth DC pole, 216 - fifth DC pole, 217 - sixth DC pole, 218 - seventh DC pole, 219 - eighth DC pole, 220 - ninth DC pole, 221 - tenth DC pole, 222 - first DC pole, 223 - second DC pole, 224 - third DC pole, 225 - fourth DC pole, 226 - fifth DC pole, 227 - sixth DC pole, 228 - seventh DC pole, 229 - eighth DC pole, 230 - ninth DC pole, 231 - tenth DC pole, 232 - first DC pole, 233 - second DC pole, 234 - third DC pole, 235 - fourth DC pole, 236 - fifth DC pole, 237 - sixth DC pole, 238 - seventh DC pole, 239 - eighth DC pole, 240 - ninth DC pole, 241 - tenth DC pole, 242 - first DC pole, 243 - second DC pole, 244 - third DC pole, 245 - fourth DC pole, 246 - fifth DC pole, 247 - sixth DC pole, 248 - seventh DC pole, 249 - eighth DC pole, 250 - ninth DC pole, 251 - tenth DC pole, 252 - first DC pole, 253 - second DC pole, 254 - third DC pole, 255 - fourth DC pole, 256 - fifth DC pole, 257 - sixth DC pole, 258 - seventh DC pole, 259 - eighth DC pole, 260 - ninth DC pole, 261 - tenth DC pole, 262 - first DC pole, 263 - second DC pole, 264 - third DC pole, 265 - fourth DC pole, 266 - fifth DC pole, 267 - sixth DC pole, 268 - seventh DC pole, 269 - eighth DC pole, 270 - ninth DC pole, 271 - tenth DC pole, 272 - first DC pole, 273 - second DC pole, 274 - third DC pole, 275 - fourth DC pole, 276 - fifth DC pole, 277 - sixth DC pole, 278 - seventh DC pole, 279 - eighth DC pole, 280 - ninth DC pole, 281 - tenth DC pole, 282 - first DC pole, 283 - second DC pole, 284 - third DC pole, 285 - fourth DC pole, 286 - fifth DC pole, 287 - sixth DC pole, 288 - seventh DC pole, 289 - eighth DC pole, 290 - ninth DC pole, 291 - tenth DC pole, 292 - first DC pole, 293 - second DC pole, 294 - third DC pole, 295 - fourth DC pole, 296 - fifth DC pole, 297 - sixth DC pole, 298 - seventh DC pole, 299 - eighth DC pole, 300 - ninth DC pole, 301 - tenth DC pole, 302 - first DC pole, 303 - second DC pole, 304 - third DC pole, 305 - fourth DC pole, 306 - fifth DC pole, 307 - sixth DC pole, 308 - seventh DC pole, 309 - eighth DC pole, 310 - ninth DC pole, 311 - tenth DC pole, 312 - first DC pole, 313 - second DC pole, 314 - third DC pole, 315 - fourth DC pole, 316 - fifth DC pole, 317 - sixth DC pole, 318 - seventh DC pole, 319 -145 - first high-end non-DC blocking full-controlled valve group, 146 - second high-end non-DC blocking full-controlled valve group, 147 - first low-end non-DC blocking full-controlled valve group, 148 - second low-end non-DC blocking full-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 disconnector, 173 - first DC line isolation disconnector, 174 - first bipolar neutral zone isolation disconnector, 175 - first bipolar neutral zone isolation disconnector, 182 - second pole bus isolation disconnector, 183 - second DC line isolation disconnector, 184 - first bipolar neutral zone isolation disconnector, 185 - first bipolar neutral zone isolation disconnector, 190 - first ground return transfer switch, 200 - inverter station, 201 - third grid commutated converter, 202 - fourth grid commutated converter, 203 - sixth grid commutated converter, 204 - fifth grid commutated converter, 205 - third smoothing reactor, 206 - fourth smoothing reactor, 207 - third non-DC blocking voltage source converter, 208 - fourth non-DC blocking 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 transfer disconnector, 214 - inverter station grounding pole line, 215 - inverter station grounding pole, 216 - third high-end converter transformer, 217 - third low-end converter transformer, 219 - third pole neutral bus switch, 220 - fourth DC pole, 221 - fourth low-end semi-controlled valve group, 222 - fourth high-end semi-controlled valve group, 226 - fourth low-end converter transformer, 227 - fourth high-end converter transformer, 229 - fourth pole neutral bus switch, 231 - fifth grid side AC switch, 232 - sixth grid side AC switch, 233 - seventh grid side AC switch, 234 - eighth grid side AC switch, 235 - seventh non-DC blocking voltage source converter, 236 - eighth non-DC blocking voltage source converter, 237 - third DC circuit breaker, 238 - fourth DC circuit breaker, 240 - second AC system, 245 - third high-end non-DC blocking full-controlled valve group, 246 - fourth high-end non-DC blocking full-controlled valve group, 247 - third low-end non-DC blocking full-controlled valve group, 248 - fourth low-end non-DC blocking full-controlled valve group, 272 - third pole bus isolation disconnector, 273 - third DC line isolation disconnector, 274 - second bipolar neutral zone isolation disconnector, 275 - second bipolar neutral zone isolation disconnector, 282 - fourth pole bus isolation disconnector, 283 - fourth DC line isolation disconnector, 284 - second bipolar neutral zone isolation disconnector, 285 - second bipolar neutral zone isolation disconnector, 290 - second ground return transfer disconnector, 310 - first detection unit, 320 - first control unit, 400 - non-DC blocking valve group, 401 - uncontrolled valve group, 402 - non-DC blocking full-controlled valve group, 500 - DC blocking valve group,501-semi-controlled valve group, 502-direct current blocking type fully controlled valve group, 410-second detection unit, 420-second control unit. DETAILED DESCRIPTION

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

[0058] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or electrically connected or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In the description of the present application, the meaning of "multiple" is two or more than two, unless otherwise explicitly specified and limited. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included one or more features.

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

[0060] The present application provides a hybrid HVDC valve group, comprising: any at least two series connection of non-direct current blocking type valve group 400, direct current blocking type valve group 500, please refer to Figure 1 , Figure 1 The series connection structure of non-direct current blocking type valve group 400 and direct current blocking type valve group 500 is shown. In the embodiment of the present application, the non-direct current blocking type valve group 400 comprises: uncontrolled valve group 401 or non-direct current blocking type fully controlled valve group 402; the direct current blocking type valve group 500 comprises: semi-controlled valve group 501 or direct current blocking type fully controlled valve group 502; wherein any one of the uncontrolled valve group 401 and the non-direct current blocking type fully controlled valve group 402 is connected in series with any one of the semi-controlled valve group 501 and the direct current blocking type fully controlled valve group 502.

[0061] The hybrid HVDC valve group of the present application is combined based on the four types of valve groups described above, and has six series connection topologies: the half-controlled valve group 501 is connected in series with the non-controlled valve group 401, as shown in FIG. 1A, wherein the anode of the half-controlled valve group 501 is connected to the cathode of the non-controlled valve group 401, or as shown in FIG. 1B, wherein the cathode of the half-controlled valve group 501 is connected to the anode of the non-controlled valve group 401; or the DC blocking full-controlled valve group 502 is connected in series with the non-controlled valve group 401, as shown in FIG. 2A, wherein the negative electrode of the DC blocking full-controlled valve group 502 is connected to the cathode of the non-controlled valve group 401, or as shown in FIG. 2B, wherein the positive electrode of the DC blocking full-controlled valve group 502 is connected to the anode of the non-controlled valve group 401; or the half-controlled valve group 501 is connected in series with the non-DC blocking full-controlled valve group 402, as shown in FIG. 3A, wherein the anode of the half-controlled valve group 501 is connected to the positive electrode of the non-DC blocking full-controlled valve group 402, or as shown in FIG. 3B, wherein the cathode of the half-controlled valve group 501 is connected to the negative electrode of the non-DC blocking full-controlled valve group 402. Figure 2a Figure 2b Figure 2c Figure 2d Figure 2e Figure 2f

[0062] In some embodiments of the present application, the half-controlled valve group 501 comprises a grid commutation converter, and the grid commutation converter is connected in parallel with a bypass isolation circuit; the DC blocking full-controlled valve group 502 comprises a DC blocking voltage source converter, and the DC blocking voltage source converter is connected in parallel with a bypass isolation circuit; the non-DC blocking full-controlled valve group 402 comprises a non-DC blocking voltage source converter, and the non-DC blocking voltage source converter is connected in parallel with a bypass isolation circuit; and the non-controlled valve group 401 comprises a bridge-type non-controlled rectifier circuit, and the bridge-type non-controlled rectifier circuit 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 switching of the non-controlled valve group 401 and the non-DC blocking full-controlled valve group 402; when the DC line fails, the DC voltage or DC current control performance of the half-controlled valve group 501 or the DC blocking full-controlled valve group 502 can solve the problem that the non-controlled valve group 401 and the non-DC blocking full-controlled valve group 402 cannot pass through the DC fault, overcome the technical defects of a single valve group, effectively improve the performance of the hybrid HVDC valve group, and achieve a high-performance, low-cost and low-loss HVDC transmission scheme.

[0064] In some embodiments of the present application, the half-controlled valve group 501 is connected in series with the non-controlled valve group 401, as shown in FIG. 1A and FIG. 1B, wherein the anode of the half-controlled valve group 501 is connected to the cathode of the non-controlled valve group 401, as shown in FIG. 1A, or the cathode of the half-controlled valve group 501 is connected to the anode of the non-controlled valve group 401, as shown in FIG. 1B. Figure 2a Figure 2b Figure 2a Figure 2b ​​​​​​​​​The cathode of the half-controlled valve group 501 shown is connected to X3, and the anode of the non-controlled valve group 401 shown is connected to X2. Figure 2c and Figure 2d The non-controlled valve group 401 shown is connected in series with the direct-current blocking full-controlled valve group. Figure 2c The negative electrode of the direct-current blocking full-controlled valve group shown is connected to X6, and the cathode of the non-controlled valve group 401 shown is connected to X1. Figure 2d The positive electrode of the direct-current blocking full-controlled valve group shown is connected to X5, and the anode of the non-controlled valve group 401 shown is connected to X2. Figure 2e and Figure 2f The non-direct-current blocking full-controlled valve group 402 shown is connected in series with the half-controlled valve group 501. Figure 2e The anode of the half-controlled valve group 501 shown is connected to X4, and the positive electrode of the non-direct-current blocking full-controlled valve group 402 shown is connected to X7. Figure 2f The cathode of the half-controlled valve group 501 shown is connected to X3, and the anode of the non-direct-current blocking full-controlled valve group 402 shown is connected to X8.

[0065] In the embodiments of the present application, please refer to Figure 3 , Figure 3 The half-controlled valve group 501 shown is a structural schematic diagram of the half-controlled valve group 501, and the half-controlled valve group 501 of the present application includes a commutating device, a bypass circuit and an isolation circuit. The commutating device of the present embodiment includes a grid commutated converter 1. The bypass circuit includes a bypass switch 3 and a bypass knife switch 4, and the bypass switch 3 and the bypass knife switch 4 are arranged in parallel. The isolation circuit includes a first isolation knife switch 5 and a second isolation knife switch 6, and the first isolation knife switch 5 and the second isolation knife switch 6 are respectively arranged at the connection nodes of the bypass switch 3 and the bypass knife switch 4 in parallel. One end of the bypass knife switch 4 is connected to the end of the first isolation knife switch 5 away from the grid commutated converter 1, and the other end of the bypass knife switch 4 is connected to the end of the second isolation knife switch 6 away from the grid commutated 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-gate-controllable half-controlled power semiconductor such as a thyristor. Please refer to Figure 4 , Figure 4 The grid commutated converter 1 shown adopts a twelve-pulse bridge circuit.

[0067] In some embodiments of the present application, as shown in Figure 4 , 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 further 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 a YY-type converter transformer, and the second three-phase input 22 is connected to the valve side of a YD-type converter transformer. The first three-phase input 21 and the second three-phase input 22 are further respectively connected to the bridge arms.

[0068] In some embodiments of this application, such as Figure 5 As shown, either the non-DC blocking type fully controlled valve group 402 or the DC blocking type fully controlled valve group 502 includes a converter, an isolation circuit, and a bypass circuit. The converter 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 connected in parallel. The first isolation switch 5 is located at the connection node where the bypass switch 3 and the bypass switch 4 are connected in parallel, and the second isolation switch 6 is located at another connection node where the bypass switch 3 and the bypass switch 4 are connected in parallel. One end of the bypass switch 4 is connected to the 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 the end of the second isolation switch 6 away from the voltage source converter 2.

[0069] In some embodiments of this application, such as Figure 6 As shown, Figure 6 This is a schematic diagram of the structure of the voltage source converter 2 provided in the embodiment of this 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 isolating switch 25, and a charging resistor 26. Each bridge arm includes a sub-module 27 and a current-limiting reactor 28, which are connected in series. The third three-phase input 24 is connected to the valve side of the converter transformer. The isolating switch 25 is connected between the third three-phase input 24 and the bridge arm. The isolating switch 25 is three-phase, and a charging resistor 26 is connected in parallel across the two ends of the isolating switch 25.

[0070] In some embodiments of this application, such as Figure 7 As shown, Figure 7 This is a schematic diagram of the full-bridge submodule. Submodule 27 adopts a full-bridge submodule and includes IGBT module 1 29, IGBT module 2 31, IGBT module 32, IGBT module 4 33, and a capacitor 30. The four IGBT modules and the one 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 if more than 50% of the submodules 27 are full-bridge submodules, then... Figure 6 The voltage source converter 2 shown is a DC blocking type voltage source converter. Figure 5 The fully controlled valve assembly adopts Figure 6 The DC blocking voltage source converter shown is... Figure 6 The fully controlled valve assembly shown is a DC blocking type fully controlled valve assembly 502, wherein the DC blocking type fully controlled valve assembly 502 can adjust the DC voltage to a negative voltage.

[0072] In some embodiments of this application, such as Figure 8 As shown,Figure 8 The diagram shows the structure of the half-bridge submodule 27. The half-bridge submodule includes IGBT module 29, IGBT module 31, and capacitor 30. The two IGBT modules and one capacitor are connected to form a half-bridge structure.

[0073] It should be noted that, if Figure 6 The voltage source converter 2 shown has all its submodules 27 as half-bridge submodules. Figure 6 The voltage source converter 2 shown is a non-DC blocking voltage source converter. Figure 5 The fully controlled valve assembly shown adopts the following... Figure 6 The non-DC blocking voltage source converter shown is... Figure 6 The fully controlled valve assembly shown is a non-DC blocking type fully controlled valve assembly 402. The non-DC blocking type fully controlled valve assembly 402 cannot adjust the DC voltage to a negative value.

[0074] Please refer to some embodiments of this application. Figure 9 , Figure 9 The diagram shown is a structural schematic of an uncontrolled valve assembly. Figure 9 As shown, the uncontrolled valve group 401 includes a converter, an isolation circuit, and a bypass circuit. The converter 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 uncontrolled power semiconductors, such as diodes.

[0075] Please refer to some embodiments of this application. Figure 10 ,like Figure 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, which are connected in series to form the 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] This application also provides a DC transmission system, specifically a high-voltage current transmission system, which includes the hybrid current transmission valve assembly described above. Please refer to... Figure 11For the convenience of description, the same components in different positions will be distinguished by adding prefixes such as "first", "second", "No. two", "No. three" and the like. The DC power transmission system of the present application is an ultra-high voltage DC power transmission system. The main circuit of the DC power transmission system comprises a rectifier station 100, an inverter station 200, a first DC line 150, a second DC line 160, a rectifier station grounding pole line 114, a rectifier station grounding pole 115, an inverter station grounding pole line 214 and an inverter station grounding pole 215.

[0077] Please refer to Figure 11 , the rectifier station 100 comprises 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 switch 113, a first ground return line switch 190, a first bipolar neutral area isolation knife switch 174, a second bipolar neutral area isolation knife switch 175, a third bipolar neutral area isolation knife switch 184 and a fourth bipolar neutral area isolation knife switch 185.

[0078] 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, 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 is connected in series with the first low-end semi-controlled valve group 112.

[0079] As shown in Figure 11 , the first high-end uncontrolled valve group 111 comprises a bridge uncontrolled rectifier circuit 11, a second bypass knife switch 14, a second bypass switch 13, a No. two first isolation knife switch 15 and a No. two second isolation knife switch 16. The second bypass switch 13 is connected to the anode and cathode of the bridge uncontrolled rectifier circuit 11 respectively, and is connected to one end of the No. two first isolation knife switch 15 and the No. two second isolation knife switch 16 respectively. The second bypass knife switch 14 is connected to the other end of the No. two first isolation knife switch 15, and is connected to the other end of the No. two second isolation knife switch 16.

[0080] As shown in Figure 11 , the first low-end semi-controlled valve group 112 comprises a grid commutation converter 1, a bypass knife switch 4, a bypass switch 3, a first isolation knife switch 5 and a second isolation knife switch 6. The bypass switch 3 is connected to the anode of the grid commutation converter 1 and the cathode of the grid commutation converter 1 respectively, and is connected to one end of the first isolation knife switch 5 and one end of the second isolation knife switch 6 respectively. The bypass knife switch 4 is connected to the other end of the first isolation knife switch 5 and the other end of the second isolation knife switch 6 respectively.

[0081] AsFigure 11 As shown in FIG. 2, the second DC pole 120 comprises a second low-end half-controlled valve group 121, a second high-end non-controlled 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 switch 182 and a second DC line isolation switch 183; the second low-end half-controlled valve group 121 and the second high-end non-controlled valve group 122 are connected in series.

[0082] As shown in FIG. 3, the second high-end non-controlled valve group 122 comprises a second bridge non-controlled rectifier circuit 104, a third bypass switch 46, a third bypass switch 45, a third first isolation switch 47 and a third second isolation switch 48; the third bypass switch 45 is connected to the positive end of the second bridge non-controlled rectifier circuit 104 and the negative end of the second bridge non-controlled rectifier circuit 104 respectively, and the third bypass switch 45 is connected to one end of the third first isolation switch 47 and one end of the third second isolation switch 48 respectively; the third bypass switch 46 is connected to the other end of the third first isolation switch 47 and the other end of the third second isolation switch 48 respectively. Figure 11 As shown in FIG. 4, the second low-end half-controlled valve group 121 comprises a second line-commutated converter 101, a fourth bypass switch 55, a fourth bypass switch 56, a fourth first isolation switch 57 and a fourth second isolation switch 58; the fourth bypass switch 56 is connected to the positive end of the second line-commutated converter 101 and the negative end of the second line-commutated converter 101 respectively, and the fourth bypass switch 56 is connected to one end of the fourth first isolation switch 57 and one end of the fourth second isolation switch 58 respectively; the fourth bypass switch 55 is connected to the other end of the fourth first isolation switch 57 and the other end of the fourth second isolation switch 58 respectively.

[0083] Figure 11 As shown in FIG. 4, the second low-end half-controlled valve group 121 comprises a second line-commutated converter 101, a fourth bypass switch 55, a fourth bypass switch 56, a fourth first isolation switch 57 and a fourth second isolation switch 58; the fourth bypass switch 56 is connected to the positive end of the second line-commutated converter 101 and the negative end of the second line-commutated converter 101 respectively, and the fourth bypass switch 56 is connected to one end of the fourth first isolation switch 57 and one end of the fourth second isolation switch 58 respectively; the fourth bypass switch 55 is connected to the other end of the fourth first isolation switch 57 and the other end of the fourth second isolation switch 58 respectively.

[0084] As shown in FIG. 5, the inverter station 200 comprises 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 conversion switch 213, a second ground return line conversion 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. Figure 11 As shown in FIG. 5, the inverter station 200 comprises 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 conversion switch 213, a second ground return line conversion 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] Figure 11 ​​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 isolating switch 272, and a third DC line isolating 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 Figure 11 As shown, the third high-end semi-controlled valve group 211 includes a third grid phase-change converter 201, a fourth bypass switch 51, a fourth bypass switch 52, a fifth first isolation switch 53, and a fifth second isolation switch 54. The fourth bypass switch 52 is connected to the positive terminal and the negative terminal of the third grid phase-change converter 201, and is also connected to one end of the fifth first isolation switch 53 and one end of the fifth second isolation switch 54. The fourth bypass switch 51 is connected to the other end of the fifth first isolation switch 53 and the other end of the fifth second isolation switch 54.

[0087] like Figure 11 As shown, the third low-end semi-controlled valve group 212 includes a fourth grid phase-changing converter 202, a fifth bypass switch 61, a fifth bypass switch 62, a sixth first isolation switch 63, and a sixth second isolation switch 64. The fifth bypass switch 62 is connected to the positive terminal and the negative terminal of the fourth grid phase-changing converter 202, and is also connected to one end of the sixth first isolation switch 63 and one end of the sixth second isolation switch 64. The fifth bypass switch 61 is connected to the other end of the sixth first isolation switch 63 and the other end of the sixth second isolation switch 64.

[0088] like Figure 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 isolating switch 282, and a fourth DC line isolating 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 Figure 11As shown, the fourth high-end semi-controlled valve group 222 includes a fifth grid phase-changing converter 204, a sixth bypass switch 81, a sixth bypass switch 82, a seventh first isolation switch 83, and a seventh second isolation switch 84. The sixth bypass switch 82 is connected to the positive terminal and the negative terminal of the fifth grid phase-changing converter 204, and is also connected to one end of the seventh first isolation switch 83 and one end of the seventh second isolation switch 84. The sixth bypass switch 81 is connected to the other end of the seventh first isolation switch 83 and the other end of the seventh second isolation switch 84.

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

[0091] It should be added that the above-mentioned Figure 11 Various switches or disconnectors, including at least one of mechanical switches, disconnectors, DC circuit breakers, and thyristor valves.

[0092] like Figure 11 As shown, taking a DC 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 disconnect switch 14 of the rectifier station 100 is open, the second bypass switch 13 is open, the second first isolating disconnect switch 15 is closed, the second second isolating disconnect switch 16 is closed, the bypass disconnect switch 4 is open, the bypass switch 3 is open, the first isolating disconnect switch 5 is closed, and the second isolating disconnect switch 6 is closed; the fourth bypass disconnect switch 51 of the inverter station 200 is open, the fourth bypass switch 52 is open, the fifth first isolating disconnect switch 53 is closed, the fifth second isolating disconnect switch 54 is closed, the fifth bypass disconnect switch 61 is open, the fifth bypass switch 62 is open, the sixth first isolating disconnect switch 63 is closed, and the sixth second isolating disconnect switch 64 is closed. The rectifier station 100 is used to control the rectifier operation of the grid phase-commutation converter 1; the inverter station 200 is used to control the inverter operation of the third grid phase-commutation converter 201 and the fourth grid phase-commutation converter 202.

[0093] When the grid-side voltage of the converter transformer 116 connected with the uncontrolled valve group rises, the tap position of the converter transformer 116 is adjusted to reduce the rise of the valve-side voltage, thereby inhibiting the rise of the DC voltage; when the grid-side voltage of the converter transformer 116 connected with the uncontrolled valve group falls, the tap position of the converter transformer 116 is adjusted to reduce the fall of the valve-side voltage, thereby inhibiting the fall of the DC voltage.

[0094] Please refer to Figure 11 , Figure 12 is a schematic diagram of a DC power transmission system. As shown in Figure 12 , for the convenience of description, the same components at different positions will be distinguished by adding prefixes such as “first”, “second”, “No. 2”, “No. 3” and the like, the DC power transmission system of the embodiments of the present application is an ultra-high voltage DC power transmission system, and the main circuit of the DC power transmission system comprises: 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] As shown in Figure 12 , the rectifier station 100 comprises: 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 ground return line transfer switch 190, a first bipolar neutral area isolation knife switch 174, a second bipolar neutral area isolation knife switch 175, a third bipolar neutral area isolation knife switch 184 and a fourth bipolar neutral area isolation knife switch 185.

[0096] As shown in Figure 12 , the first DC pole 110 comprises 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 isolation knife 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] As shown in Figure 12 , the first high-end uncontrolled valve group 111 comprises: a bridge-type uncontrolled rectification circuit 11, a second bypass knife switch 14, a second bypass switch 13, a No. 2 first isolation knife switch 15, a No. 2 second isolation knife switch 16; the second bypass switch 13 is connected with the positive end of the bridge-type uncontrolled rectification circuit 11 and the negative end of the bridge-type uncontrolled rectification circuit 11 respectively, and is connected with one end of the No. 2 first isolation knife switch 15 and one end of the No. 2 second isolation knife switch 16 respectively; the second bypass knife switch 14 is connected with the other end of the No. 2 first isolation knife switch 15 and the other end of the No. 2 second isolation knife switch 16.

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

[0099] As shown in Figure 12 , the second DC pole 120 includes: a second low-end DC blocking full-control valve group 142, a second high-end non-control valve group 122, a second low-end converter transformer 126, a second high-end converter transformer 127, a second wave reactor 106, a second pole neutral bus isolation knife 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 full-control valve group 142 and the second high-end non-control valve group 122 are connected in series.

[0100] As shown in Figure 12 , the second high-end non-control valve group 122 includes: a second bridge non-control rectifier circuit 104, a third bypass knife switch 46, a third bypass switch 45, a third first isolation knife switch 47 and a third second isolation knife switch 48; the third bypass switch 45 connects the positive end of the second bridge non-control rectifier circuit 104 and the negative end of the second bridge non-control rectifier circuit 104, and the third bypass switch 45 is connected with one end of the third first isolation knife switch 47 and one end of the third second isolation knife switch 48 respectively; the third bypass knife switch 46 is connected with the other end of the third first isolation knife switch 47 and the other end of the third second isolation knife switch 48 respectively.

[0101] As shown in Figure 12 , the second low-end DC blocking full-control valve group 142 includes: a second DC blocking voltage source converter 102, a fourth bypass knife switch 51, a fourth bypass switch 52, a fourth first isolation knife switch 57 and a fourth second isolation knife switch 58; the fourth bypass switch 52 is connected with the positive end of the second DC blocking voltage source converter 102 and the negative end of the second DC blocking voltage source converter 102 respectively, and the fourth bypass switch 52 is connected with one end of the fourth first isolation knife switch 57 and one end of the fourth second isolation knife switch 58 respectively; the fourth bypass knife switch 51 and the fourth bypass switch 52 are connected with the other end of the fourth first isolation knife switch 57 and the other end of the fourth second isolation knife switch 58 respectively.

[0102] It should be noted that the DC blocking voltage source converter includes a modular multilevel converter with a full-bridge sub-module structure or a mixed structure of full-bridge and half-bridge sub-modules.

[0103] As shown in Figure 12 , 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 transfer switch 213, a second ground return line transfer switch 290, a second bipolar neutral area isolation switch 274, a second bipolar neutral area isolation switch 275, a second bipolar neutral area isolation switch 284 and a second bipolar neutral area isolation switch 285.

[0104] It should be noted that the third DC pole 210 includes: a third high-end half-controlled valve group 211, 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 switch 272 and a third DC line isolation switch 273; the third high-end half-controlled valve group 211 and the third low-end half-controlled valve group 212 are connected in series.

[0105] As shown in Figure 12 , the third high-end half-controlled valve group 211 includes: a third grid phase-change converter 201, a fourth bypass switch 51, a fourth bypass switch 52, a fifth first isolation switch 53, a fifth second isolation switch 54; the fourth bypass switch 52 is connected to the positive end of the third grid phase-change converter 201 and the negative end of the third grid phase-change converter 201 respectively, and the fourth bypass switch 52 is connected to one end of the fifth first isolation switch 53 and one end of the fifth second isolation switch 54 respectively; the fourth bypass switch 51 is connected to the other end of the fifth first isolation switch 53 and the other end of the fifth second isolation switch 54 respectively.

[0106] As shown in Figure 12 , the third low-end half-controlled valve group 212 includes: a fourth grid phase-change converter 202, a fifth bypass switch 61, a fifth bypass switch 62, a sixth first isolation switch 63, a sixth second isolation switch 64; the fifth bypass switch 62 is connected to the positive end of the fourth grid phase-change converter 202 and the negative end of the fourth grid phase-change converter 202 respectively, and the fifth bypass switch 62 is connected to one end of the sixth first isolation switch 63 and one end of the sixth second isolation switch 64 respectively; the fifth bypass switch 61 is connected to the other end of the sixth first isolation switch 63 and the other end of the sixth second isolation switch 64 respectively.

[0107] As shown in Figure 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 isolating switch 282, and a fourth DC line isolating 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 Figure 12 As shown, the fourth high-end semi-controlled valve group 222 includes: a fifth grid phase-changing converter 204, a sixth bypass switch 81, a sixth bypass switch 82, a seventh first isolation switch 83, and a seventh second isolation switch 84; the sixth bypass switch 82 is connected to the positive terminal and the negative terminal of the fifth grid phase-changing converter 204 respectively, and the sixth bypass switch 82 is connected to one end of the seventh first isolation switch 83 and one end of the seventh second isolation switch 84 respectively; the sixth bypass switch 81 is connected to the other end of the seventh first isolation switch 83 and the other end of the seventh second isolation switch 84 respectively.

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

[0110] The above-mentioned Figure 12 Various switches or disconnectors, including at least one of mechanical switches, disconnectors, DC circuit breakers, and thyristor valves.

[0111] like Figure 13As shown, taking a DC transmission system as an example, the initial state is as follows: 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; 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 disconnector 14 of the rectifier station 100 is open, the second bypass switch 13 is open, the second first isolating disconnector 15 is closed, the second second isolating disconnector 16 is closed, the bypass disconnector 4 is open, the bypass switch 3 is open, the first isolating disconnector 5 is closed, and the second isolating disconnector 6 is closed; the fourth bypass disconnector 51 of the inverter station 200 is open, the fourth bypass switch 52 is open, the fifth first isolating disconnector 53 is closed, the fifth second isolating disconnector 54 is closed, the fifth bypass disconnector 61 is open, the fifth bypass switch 62 is open, the sixth first isolating disconnector 63 is closed, and the sixth second isolating disconnector 64 is closed.

[0112] Please see Figure 13 , Figure 13 The diagram shown is a schematic representation of a DC transmission system. Figure 13 As shown, for ease of description, identical components in different locations will be distinguished by prefixes such as "first", "second", "number two", and "number three". The DC transmission system of this application is an ultra-high voltage DC transmission system, which includes: rectifier station 100, inverter station 200, first DC line 150, second DC line 160, rectifier station grounding electrode line 114, rectifier station grounding electrode 115, inverter station grounding electrode line 214, and inverter station grounding electrode 215.

[0113] like Figure 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 metallic return line changeover switch 113, a first earth return line changeover switch 190, a first bipolar neutral zone isolating switch 174, a second bipolar neutral zone isolating switch 175, a third bipolar neutral zone isolating switch 184, and a fourth bipolar neutral zone isolating switch 185.

[0114] like Figure 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 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 isolating switch 172, and a first DC line isolating switch 173; the first high-end non-DC blocking type fully controlled valve group 145 and the first low-end semi-controlled valve group 112 are connected in series.

[0115] like Figure 13As shown in the figure, the first high-end non-direct-current blocking full-control valve group 145 includes: a first non-direct-current blocking voltage source converter 107, a second bypass knife switch 14, a second bypass switch 13, a second first isolation knife switch 15, and a second second isolation knife switch 16. The second bypass switch 13 is connected to the anode of the first non-direct-current blocking voltage source converter 107 and the cathode of the first non-direct-current blocking voltage source converter 107 respectively, and is connected to one end of the second first isolation knife switch 15 and one end of the second second isolation knife switch 16 respectively. The second bypass knife switch 14 is connected to the other end of the second first isolation knife switch 15 and the other end of the second second isolation knife switch 16 respectively.

[0116] As shown in the figure, Figure 13 As shown in the figure, the first low-end semi-control valve group 112 includes: a grid commutation converter 1, a bypass knife switch 4, a bypass switch 3, a first isolation knife switch 5, and a second isolation knife switch 6. The bypass switch 3 is connected to the anode of the grid commutation converter 1 and the cathode of the grid commutation converter 1 respectively, and is connected to one end of the first isolation knife switch 5 and one end of the second isolation knife switch 6 respectively. The bypass knife switch 4 is connected to the other end of the first isolation knife switch 5 and the other end of the second isolation knife switch 6.

[0117] As shown in the figure, Figure 13 As shown in the figure, the second direct-current pole 120 includes: a second low-end semi-control valve group 121, a second high-end non-direct-current blocking full-control 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 direct-current line isolation knife switch 183. The second low-end semi-control valve group 121 and the second high-end non-direct-current blocking full-control valve group 146 are connected in series.

[0118] As shown in the figure, Figure 13 As shown in the figure, the second high-end non-direct-current blocking full-control valve group 146 includes: a second non-direct-current blocking voltage source converter 108, a third bypass knife switch 46, a third bypass switch 45, a third first isolation knife switch 47, and a third second isolation knife switch 48. The third bypass switch 45 is connected to the positive end of the second non-direct-current blocking voltage source converter 108 and the negative end of the second non-direct-current blocking voltage source converter 108 respectively, and is connected to one end of the third first isolation knife switch 47 and one end of the third second isolation knife switch 48 respectively. The third bypass knife switch 46 is connected to the other end of the third first isolation knife switch 47 and the other end of the third second isolation knife switch 48 respectively.

[0119] As shown in the figure, Figure 13As shown, the second low-end half-controlled valve group 121 comprises: a second line-commutated converter 101, a fourth bypass breaker 51, a fourth bypass switch 52, a fourth first isolation breaker 57, and a fourth second isolation breaker 58. The fourth bypass switch 52 is connected to the positive end of the second line-commutated converter 101 and the negative end of the second line-commutated converter 101 respectively, and is connected to one end of the fourth first isolation breaker 57 and one end of the fourth second isolation breaker 58 respectively. The fourth bypass breaker 51 and the fourth bypass switch 52 are connected to the other end of the fourth first isolation breaker 57 and the other end of the fourth second isolation breaker 58 respectively.

[0120] As shown in FIG. 2, the inverter station 200 comprises: 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 transfer breaker 213, a second ground return line transfer breaker 290, a second bipolar neutral zone isolation breaker 274, a second bipolar neutral zone isolation breaker 275, a second bipolar neutral zone isolation breaker 284, and a second bipolar neutral zone isolation breaker 285. Figure 13 As shown in FIG. 2, the inverter station 200 comprises: 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 transfer breaker 213, a second ground return line transfer breaker 290, a second bipolar neutral zone isolation breaker 274, a second bipolar neutral zone isolation breaker 275, a second bipolar neutral zone isolation breaker 284, and a second bipolar neutral zone isolation breaker 285.

[0121] Figure 13 As shown in FIG. 2, the inverter station 200 comprises: 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 transfer breaker 213, a second ground return line transfer breaker 290, a second bipolar neutral zone isolation breaker 274, a second bipolar neutral zone isolation breaker 275, a second bipolar neutral zone isolation breaker 284, and a second bipolar neutral zone isolation breaker 285.

[0122] As shown in FIG. 2, the inverter station 200 comprises: 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 transfer breaker 213, a second ground return line transfer breaker 290, a second bipolar neutral zone isolation breaker 274, a second bipolar neutral zone isolation breaker 275, a second bipolar neutral zone isolation breaker 284, and a second bipolar neutral zone isolation breaker 285. Figure 13 As shown in FIG. 2, the inverter station 200 comprises: 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 transfer breaker 213, a second ground return line transfer breaker 290, a second bipolar neutral zone isolation breaker 274, a second bipolar neutral zone isolation breaker 275, a second bipolar neutral zone isolation breaker 284, and a second bipolar neutral zone isolation breaker 285.

[0123] Figure 13 ​​As shown in the figure, the third low-end half-controlled valve group 212 includes: a fourth grid commutation converter 202, a fifth bypass knife switch 61, a fifth bypass switch 62, a sixth first isolation knife switch 63, and a sixth second isolation knife switch 64; the fifth bypass switch 62 is connected to the positive end of the fourth grid commutation converter 202 and the negative end of the fourth grid commutation converter 202 respectively, and is connected to one end of the sixth first isolation knife switch 63 and one end of the sixth second isolation knife switch 64 respectively; the fifth bypass knife switch 61 is connected to the other end of the sixth first isolation knife switch 63 and the other end of the sixth second isolation knife switch 64.

[0124] As shown in the figure, Figure 13 As shown in the figure, the fourth DC pole 220 includes: a fourth low-end half-controlled valve group 221, a fourth high-end half-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 isolation knife switch 229, a fourth pole bus isolation knife switch 282, and a fourth DC line isolation knife switch 283; the fourth low-end half-controlled valve group 221 and the fourth high-end half-controlled valve group 222 are connected in series.

[0125] As shown in the figure, Figure 13 As shown in the figure, the fourth high-end half-controlled valve group 222 includes: a fifth grid commutation converter 204, a sixth bypass knife switch 81, a sixth bypass switch 82, a seventh first isolation knife switch 83, and a seventh second isolation knife switch 84; the sixth bypass switch 82 is connected to the positive end of the fifth grid commutation converter 204 and the negative end of the fifth grid commutation converter 204 respectively, and is connected to one end of the seventh first isolation knife switch 83 and one end of the seventh second isolation knife switch 84 respectively; the sixth bypass knife switch 81 is connected to the other end of the seventh first isolation knife switch 83 and the other end of the seventh second isolation knife switch 84.

[0126] As shown in the figure, Figure 13 As shown in the figure, the fourth low-end half-controlled valve group 221 includes: a sixth grid commutation converter 203, a seventh bypass knife switch 71, a seventh bypass switch 72, an eighth first isolation knife switch 73, and an eighth second isolation knife switch 74; the seventh bypass switch 72 is connected to the positive end of the sixth grid commutation converter 203 and the negative end of the sixth grid commutation converter 203 respectively, and is connected to one end of the eighth first isolation knife switch 73 and one end of the eighth second isolation knife switch 74 respectively; the seventh bypass knife switch 71 is connected to the other end of the eighth first isolation knife switch 73 and the other end of the eighth second isolation knife switch 74.

[0127] It should be noted that the various switches or knife switches mentioned above in the Figure 11 include at least one of mechanical switches, knife switches, DC circuit breakers, and thyristor valves.

[0128] As shown in the figure, Figure 12As 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 semi-controlled valve group 112 of the rectifier station 100 are operated, 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 operated; the second bypass knife switch 14 of the rectifier station 100 is in the split state, the second bypass switch 13 is in the split state, the second first isolation knife switch 15 is in the closed state, the second second isolation knife switch 16 is in the closed state, the bypass knife switch 4 is in the split state, the bypass switch 3 is in the split state, the first isolation knife switch 5 is in the closed state, the second isolation knife switch 6 is in the closed state, the fourth bypass knife switch 51 of the inverter station 200 is in the split state, the fourth bypass switch 52 is in the split state, the fifth first isolation knife switch 53 is in the closed state, the fifth second isolation knife switch 54 is in the closed state, the fifth bypass knife switch 61 is in the split state, the fifth bypass switch 62 is in the split state, the sixth first isolation knife switch 63 is in the closed state, and the sixth second isolation knife switch 64 is in the closed state. The rectifier station 100 is used to control the first non-DC blocking type voltage source converter 107 and the grid commutation converter 1 to operate in rectification; the inverter station 200 is used to control the third grid commutation converter 201 and the fourth grid commutation converter 202 to operate in inversion.

[0129] Figure 13 , Figure 14 and Figure 14 In the third DC pole 210, two or any two of any one of the semi-controlled valve group, the non-DC blocking type fully controlled valve group, and the DC blocking type fully controlled valve group can be further included. In the fourth DC pole 220, two or any two of any one of the semi-controlled valve group, the non-DC blocking type fully controlled valve group, and the DC blocking type fully controlled valve group can be further included. Please refer to Figure 14 , Figure 14 It is shown that the third DC pole 210 includes a semi-controlled valve group and a non-DC blocking type fully controlled valve group; and the fourth DC pole 220 includes a semi-controlled valve group and a non-DC blocking type fully controlled valve group.

[0130] As shown in Figure 13 , for the convenience of description, the same components in different positions will be distinguished by adding prefixes such as “first”, “second”, “second”, “third”, etc. The DC power transmission system of the present application is an ultra-high voltage DC power transmission system, which includes a rectifier station 100, an inverter station 200, a first DC line 150, a second DC line 160, a rectifier station grounding pole line 114, a rectifier station grounding pole 115, an inverter station grounding pole line 214, and an inverter station grounding pole 215.

[0131] As shown in Figure 14 , the structure of the rectifier station 100 is the same as that of the rectifier station 100 in Figure 14 .

[0132] As shown in Figure 14As shown, the inverter station 200 comprises: 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 transfer switch 213, a second ground return line transfer 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] As shown, the third DC pole 210 comprises: a third high-end non-DC blocking full-control valve group 245, a third low-end half-control 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 switch 272, and a third DC line isolation switch 273; the third high-end non-DC blocking full-control valve group 245 and the third low-end half-control valve group 212 are connected in series. Figure 14 As shown, the third high-end non-DC blocking full-control valve group 245 comprises: a third non-DC blocking voltage source converter 207, a fourth bypass switch 51, a fourth bypass switch 52, a fifth first isolation switch 53, and a fifth second isolation switch 54; the fourth bypass switch 52 connects the positive end of the third non-DC blocking voltage source converter 207 and the negative end of the third non-DC blocking voltage source converter 207, and is connected with one end of the fifth first isolation switch 53 and one end of the fifth second isolation switch 54, respectively; the fourth bypass switch 51 is connected with the other end of the fifth first isolation switch 53 and the other end of the fifth second isolation switch 54, respectively.

[0134] Figure 14 As shown, the third low-end half-control valve group 212 comprises: a fourth grid commutation converter 202, a fifth bypass switch 61, a fifth bypass switch 62, a sixth first isolation switch 63, and a sixth second isolation switch 64; the fifth bypass switch 62 connects the positive end of the fourth grid commutation converter 202 and the negative end of the fourth grid commutation converter 202, respectively, and is connected with one end of the sixth first isolation switch 63 and one end of the sixth second isolation switch 64, respectively; the fifth bypass switch 61 connects the other end of the sixth first isolation switch 63 and the other end of the sixth second isolation switch 64.

[0135] As shown, the third low-end half-control valve group 212 comprises: a fourth grid commutation converter 202, a fifth bypass switch 61, a fifth bypass switch 62, a sixth first isolation switch 63, and a sixth second isolation switch 64; the fifth bypass switch 62 connects the positive end of the fourth grid commutation converter 202 and the negative end of the fourth grid commutation converter 202, respectively, and is connected with one end of the sixth first isolation switch 63 and one end of the sixth second isolation switch 64, respectively; the fifth bypass switch 61 connects the other end of the sixth first isolation switch 63 and the other end of the sixth second isolation switch 64. Figure 14 As shown, the third low-end half-control valve group 212 comprises: a fourth grid commutation converter 202, a fifth bypass switch 61, a fifth bypass switch 62, a sixth first isolation switch 63, and a sixth second isolation switch 64; the fifth bypass switch 62 connects the positive end of the fourth grid commutation converter 202 and the negative end of the fourth grid commutation converter 202, respectively, and is connected with one end of the sixth first isolation switch 63 and one end of the sixth second isolation switch 64, respectively; the fifth bypass switch 61 connects the other end of the sixth first isolation switch 63 and the other end of the sixth second isolation switch 64.

[0136] Figure 14 ​​As shown, the fourth DC pole 220 comprises: a fourth high-end non-DC blocking full-control valve group 246, a fourth low-end semi-control 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 switch 282, and a fourth DC line isolation switch 283; the fourth high-end non-DC blocking full-control valve group 246 and the fourth low-end semi-control valve group 221 are connected in series.

[0137] As shown in FIG. 1, the fourth DC pole 220 comprises: a fourth high-end non-DC blocking full-control valve group 246, a fourth low-end semi-control 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 switch 282, and a fourth DC line isolation switch 283; the fourth high-end non-DC blocking full-control valve group 246 and the fourth low-end semi-control valve group 221 are connected in series. Figure 15 As shown in FIG. 1, the fourth high-end non-DC blocking full-control valve group 246 comprises: a fourth non-DC blocking voltage source converter 208, a sixth bypass switch 81, a sixth bypass switch 82, a seventh first isolation switch 83, a seventh second isolation switch 84; the sixth bypass switch 82 is connected to the positive end of the fourth non-DC blocking voltage source converter 208 and the negative end of the fourth non-DC blocking voltage source converter 208 respectively, and the sixth bypass switch 82 is connected to one end of the seventh first isolation switch 83 and one end of the seventh second isolation switch 84 respectively; the sixth bypass switch 81 is connected to the other end of the seventh first isolation switch 83 and the other end of the seventh second isolation switch 84.

[0138] As shown in FIG. 1, the fourth high-end non-DC blocking full-control valve group 246 comprises: a fourth non-DC blocking voltage source converter 208, a sixth bypass switch 81, a sixth bypass switch 82, a seventh first isolation switch 83, a seventh second isolation switch 84; the sixth bypass switch 82 is connected to the positive end of the fourth non-DC blocking voltage source converter 208 and the negative end of the fourth non-DC blocking voltage source converter 208 respectively, and the sixth bypass switch 82 is connected to one end of the seventh first isolation switch 83 and one end of the seventh second isolation switch 84 respectively; the sixth bypass switch 81 is connected to the other end of the seventh first isolation switch 83 and the other end of the seventh second isolation switch 84. Figure 15 As shown in FIG. 1, the fourth low-end semi-control valve group 221 comprises: a sixth line-commutated converter 203, a seventh bypass switch 71, a seventh bypass switch 72, an eighth first isolation switch 73, an eighth second isolation switch 74; the seventh bypass switch 72 is connected to the positive end of the sixth line-commutated converter 203 and the negative end of the sixth line-commutated converter 203 respectively, and the seventh bypass switch 72 is connected to one end of the eighth first isolation switch 73 and one end of the eighth second isolation switch 74 respectively; the seventh bypass switch 71 is connected to the other end of the eighth first isolation switch 73 and the other end of the eighth second isolation switch 74.

[0139] It should be noted that the various switches or switches mentioned above, including at least one of mechanical switches, switches, DC circuit breakers, and thyristor valves. Figure 11

[0140] As shown in FIG. 1, the fourth high-end non-DC blocking full-control valve group 246 comprises: a fourth non-DC blocking voltage source converter 208, a sixth bypass switch 81, a sixth bypass switch 82, a seventh first isolation switch 83, a seventh second isolation switch 84; the sixth bypass switch 82 is connected to the positive end of the fourth non-DC blocking voltage source converter 208 and the negative end of the fourth non-DC blocking voltage source converter 208 respectively, and the sixth bypass switch 82 is connected to one end of the seventh first isolation switch 83 and one end of the seventh second isolation switch 84 respectively; the sixth bypass switch 81 is connected to the other end of the seventh first isolation switch 83 and the other end of the seventh second isolation switch 84. Figure 12 ​As shown, taking a DC transmission system as an example, the initial state is as follows: the first high-end non-DC blocking type fully controlled valve group 145 and the first low-end semi-controlled valve group 112 of the rectifier station 100 are in operation; the third high-end non-DC blocking type fully controlled valve group 245 and the third low-end semi-controlled valve group 212 of the inverter station 200 are in operation; the second bypass disconnector 14 of the rectifier station 100 is in the open position, the second bypass switch 13 is in the open position, the second first isolating disconnector 15 is in the closed position, the second second isolating disconnector 16 is in the closed position, the bypass disconnector 4 is in the open position, the bypass switch 3 is in the open position, the first isolating disconnector 5 is in the closed position, the second isolating disconnector 6 is in the closed position; the fourth bypass disconnector 51 of the inverter station 200 is in the open position, the fourth bypass switch 52 is in the open position, the fifth first isolating disconnector 53 is in the closed position, the fifth second isolating disconnector 54 is in the closed position, the fifth bypass disconnector 61 is in the open position, the fifth bypass switch 62 is in the open position, the sixth first isolating disconnector 63 is in the closed position, and the sixth second isolating disconnector 64 is in the closed position. The rectifier station 100 is used to control the rectification operation of the first non-DC blocking 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 voltage source converter 207 and the fourth grid commutation converter 202.

[0141] Based on the hybrid DC transmission valve group provided in the above embodiments, this application also provides a control method for the DC transmission valve group. Please refer to [link to relevant documentation]. Figure 13 ,like Figure 14 The diagram shown is a control flowchart for a DC transmission valve assembly. The control method for the DC transmission valve assembly of this application includes the following steps:

[0142] Step 110: In response to the online activation of the non-DC blocking valve group 400, the DC current is first transferred to the bridge uncontrolled rectifier circuit or the anti-parallel diode of the fully controlled device 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, and / or the non-DC blocking valve group is unlocked;

[0143] In step 110, the operating 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 online connection of the non-DC blocking valve group 400, 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. Step 111 is also included.

[0144] Close the isolating switch of the non-DC blocking valve group 400, close the bypass switch of the non-DC blocking valve group 400, open the bypass switch of the non-DC blocking valve group 400, and open the bypass switch of the non-DC blocking valve group 400, thereby transferring the DC current to the bridge uncontrolled rectifier circuit or the anti-parallel diode of the fully controlled device 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 the AC power also includes step 112: closing the valve side AC switch or the network side AC switch of the non-DC blocking valve group 400.

[0146] In some embodiments of the present application, as shown in Figure 14 In step 111, when the first high-end non-controlled valve group 111 is put into operation, the second first isolation knife switch 15 and the second second isolation knife switch 16 of the first high-end non-controlled valve group 111 are closed, the second bypass switch 13 is closed, the second bypass knife switch 14 is separated, and the second bypass switch 13 is separated, 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 non-controlled rectifier circuit 11; in step 112, the first network side AC switch 131 of the first high-end non-controlled valve group 111 is closed.

[0147] In some embodiments of the present application, as shown in Figure 16 In step 111, when the first high-end non-controlled valve group 111 is put into operation, the second first isolation knife switch 15 and the second second isolation knife switch 16 of the first high-end non-controlled valve group 111 are closed, the second bypass switch 13 is closed, the second bypass knife switch 14 is separated, and the second bypass switch 13 is separated, 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 non-controlled rectifier circuit 11; in step 112, the first network side AC switch 131 of the first high-end non-controlled valve group 111 is closed.

[0148] In some embodiments of the present application, as shown in Figure 16 and Figure 16 In step 111, when the first high-end non-DC blocking full-controlled valve group 145 is put into operation, the second first isolation knife switch 15 and the second second isolation knife switch 16 of the first high-end non-DC blocking full-controlled valve group 145 are closed, the second bypass knife switch 14 is separated, and the second bypass switch 13 is separated, so that the DC current is transferred to the anti-parallel diodes of the second IGBT module 31 of the upper and lower bridge arm sub-modules of at least one phase of the first non-DC blocking voltage source converter 107; in step 112, the first network side AC switch 131 of the first high-end non-DC blocking full-controlled valve group 145 is closed, and the first non-DC blocking voltage source converter 107 is unlocked.

[0149] In some embodiments of the present application, as shown in Figure 16As shown, when the third high-end non-DC blocking type fully controlled valve group 245 is put into operation, the fifth network side AC switch 231 is closed, the third non-DC blocking type voltage source converter 207 is charged, and after the charging is completed, the fifth network side AC switch 231 is opened, the fifth first isolation knife switch 53 and the fifth second isolation knife switch 54 of the third high-end non-DC blocking type fully controlled valve group 245 are closed, the fourth bypass knife switch 51 is separated, the fourth bypass switch 52 is closed, the IGBT of the No. 2 IGBT module 31 of the upper and lower arm sub-modules of at least one phase of the third non-DC blocking type voltage source converter 207 is controlled to be turned on, the fourth bypass switch 52 is separated, thereby transferring the DC current to the IGBT of the No. 2 IGBT module 31 of the upper and lower arm sub-modules of at least one phase of the third non-DC blocking type voltage source converter 207; the fifth network side AC switch 231 is closed, and the third non-DC blocking type voltage source converter 207 is unlocked.

[0150] The control method of the DC power transmission valve group provided in the present application is also applicable to the topology structure in which the non-DC blocking type valve group 400 is connected in series. Please refer to Figure 16 , Figure 16 As shown, the first DC pole 110 includes two non-DC blocking type fully controlled valve groups; the second DC pole 120 includes two non-DC blocking type fully controlled valve groups; the third DC pole 210 includes two non-DC blocking type fully controlled valve groups; and the fourth DC pole 220 includes two non-DC blocking type fully controlled valve groups.

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

[0152] As shown in Figure 16 , the rectifier station 100 includes a first DC pole 110, a second DC pole 120, a first AC system 140, a first network side AC switch 131, a second network side AC switch 132, a third network side AC switch 133, a fourth network side AC switch 134, a first metal return line switch 113, a first ground return line switch 190, a first bipolar neutral area isolation knife switch 174, a second bipolar neutral area isolation knife switch 175, a third bipolar neutral area isolation knife switch 184, and a fourth bipolar neutral area isolation knife switch 185.

[0153] As shown in Figure 16As shown, the first DC pole 110 comprises: a first high-end non-DC blocking full-control valve group 145, a first low-end non-DC blocking full-control 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 full-control valve group 145 and the first low-end non-DC blocking full-control valve group 147 are connected in series.

[0154] As shown in FIG. 1, the first DC pole 110 comprises: a first high-end non-DC blocking full-control valve group 145, a first low-end non-DC blocking full-control 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 full-control valve group 145 and the first low-end non-DC blocking full-control valve group 147 are connected in series. Figure 16 As shown in FIG. 1, the first high-end non-DC blocking full-control valve group 145 comprises: a first non-DC blocking voltage source converter 107, a second bypass knife switch 14, a second bypass switch 13, a second first isolation knife switch 15, a second second isolation knife switch 16; the second bypass switch 13 is connected to the anode of the first non-DC blocking voltage source converter 107 and the cathode of the first non-DC blocking voltage source converter 107 respectively, and the second bypass switch 13 is connected to one end of the second first isolation knife switch 15 and one end of the second second isolation knife switch 16 respectively; the second bypass knife switch 14 is connected to the other end of the second first isolation knife switch 15 and the other end of the second second isolation knife switch 16 respectively.

[0155] As shown in FIG. 1, the first high-end non-DC blocking full-control valve group 145 comprises: a first non-DC blocking voltage source converter 107, a second bypass knife switch 14, a second bypass switch 13, a second first isolation knife switch 15, a second second isolation knife switch 16; the second bypass switch 13 is connected to the anode of the first non-DC blocking voltage source converter 107 and the cathode of the first non-DC blocking voltage source converter 107 respectively, and the second bypass switch 13 is connected to one end of the second first isolation knife switch 15 and one end of the second second isolation knife switch 16 respectively; the second bypass knife switch 14 is connected to the other end of the second first isolation knife switch 15 and the other end of the second second isolation knife switch 16 respectively. Figure 16 As shown in FIG. 1, the first low-end non-DC blocking full-control valve group 147 comprises: a fifth non-DC blocking voltage source converter 135, a bypass knife switch 4, a bypass switch 3, a first isolation knife switch 5, a second isolation knife switch 6; the bypass switch 3 is connected to the positive end of the fifth non-DC blocking voltage source converter 135 and the negative end of the fifth non-DC blocking voltage source converter 135 respectively, and the bypass switch 3 is connected to one end of the first isolation knife switch 5 and one end of the second isolation knife switch 6 respectively; the bypass knife switch 4 is connected to the other end of the first isolation knife switch 5 and the other end of the second isolation knife switch 6.

[0156] As shown in FIG. 1, the first low-end non-DC blocking full-control valve group 147 comprises: a fifth non-DC blocking voltage source converter 135, a bypass knife switch 4, a bypass switch 3, a first isolation knife switch 5, a second isolation knife switch 6; the bypass switch 3 is connected to the positive end of the fifth non-DC blocking voltage source converter 135 and the negative end of the fifth non-DC blocking voltage source converter 135 respectively, and the bypass switch 3 is connected to one end of the first isolation knife switch 5 and one end of the second isolation knife switch 6 respectively; the bypass knife switch 4 is connected to the other end of the first isolation knife switch 5 and the other end of the second isolation knife switch 6. Figure 16 As shown in FIG. 1, the second DC pole 120 comprises: a second low-end non-DC blocking full-control valve group 148, a second high-end non-DC blocking full-control 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 full-control valve group 148 and the second high-end non-DC blocking full-control valve group 146 are connected in series.

[0157] As shown in FIG. 1, the second DC pole 120 comprises: a second low-end non-DC blocking full-control valve group 148, a second high-end non-DC blocking full-control 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 full-control valve group 148 and the second high-end non-DC blocking full-control valve group 146 are connected in series. Figure 16As shown in the figure, the second high-end non-DC blocking type fully controlled valve group 146 comprises: a second non-DC blocking type voltage source converter 108, a third bypass knife switch 46, a third bypass switch 45, a No. 3 first isolation knife switch 47, a No. 3 second isolation knife switch 48; the third bypass switch 45 is 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 respectively, and the third bypass switch 45 is connected to one end of the No. 3 first isolation knife switch 47 and one end of the No. 3 second isolation knife switch 48 respectively; the third bypass knife switch 46 is connected to the other end of the No. 3 first isolation knife switch 47 and the other end of the No. 3 second isolation knife switch 48 respectively.

[0158] As shown in the figure, Figure 16 As shown in the figure, the second low-end non-DC blocking type fully controlled valve group 148 comprises: a sixth non-DC blocking type voltage source converter 136, a fourth bypass knife switch 55, a fourth bypass switch 56, a No. 4 first isolation knife switch 57, a No. 4 second isolation knife switch 58; the fourth bypass switch 56 is 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 respectively, and the fourth bypass switch 56 is connected to one end of the No. 4 first isolation knife switch 57 and one end of the No. 4 second isolation knife switch 58 respectively; the fourth bypass knife switch 55 is connected to the other end of the No. 4 first isolation knife switch 57 and the other end of the No. 4 second isolation knife switch 58 respectively.

[0159] As shown in the figure, Figure 16 As shown in the figure, the inverter station 200 comprises: a third DC pole 210, a fourth DC pole 220, a second AC system 240, a fifth network side AC switch 231, a sixth network side AC switch 232, a seventh network side AC switch 233, an eighth network side AC switch 234, a second metal return line conversion knife switch 213, a second ground return line conversion knife switch 290, a second bipolar neutral area isolation knife switch 274, a second bipolar neutral area isolation knife switch 275, a second bipolar neutral area isolation knife switch 284 and a second bipolar neutral area isolation knife switch 285.

[0160] As shown in the figure, Figure 16 As shown in the figure, the third DC pole 210 comprises: 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] As shown in the figure, Figure 16As shown in the figure, the third high-end non-DC blocking full-control valve group 245 includes: a third non-DC blocking voltage source converter 207, a fourth bypass knife switch 51, a fourth bypass switch 52, a fifth first isolation knife switch 53, and a fifth second isolation knife switch 54; the fourth bypass switch 52 is connected to the positive end of the third non-DC blocking voltage source converter 207 and the negative end of the third non-DC blocking voltage source converter 207, and is connected to one end of the fifth first isolation knife switch 53 and one end of the fifth second isolation knife switch 54, respectively; the fourth bypass knife switch 51 is connected to the other end of the fifth first isolation knife switch 53 and the other end of the fifth second isolation knife switch 54, respectively.

[0162] As shown in the figure, Figure 16 As shown in the figure, the third low-end non-DC blocking full-control valve group 247 includes: a seventh non-DC blocking voltage source converter 235, a fifth bypass knife switch 61, a fifth bypass switch 62, a sixth first isolation knife switch 63, and a sixth second isolation knife switch 64; the fifth bypass switch 62 is connected to the positive end of the seventh non-DC blocking voltage source converter 235 and the negative end of the seventh non-DC blocking voltage source converter 235, and is connected to one end of the sixth first isolation knife switch 63 and one end of the sixth second isolation knife switch 64, respectively; the fifth bypass knife switch 61 is connected to the other end of the sixth first isolation knife switch 63 and the other end of the sixth second isolation knife switch 64.

[0163] As shown in the figure, Figure 16 As shown in the figure, the fourth DC pole 220 includes: a fourth high-end non-DC blocking full-control valve group 246, a fourth low-end non-DC blocking full-control 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 isolation knife 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 full-control valve group 246 and the fourth low-end non-DC blocking full-control valve group 248 are connected in series.

[0164] As shown in the figure, Figure 16 As shown in the figure, the fourth high-end non-DC blocking full-control valve group 246 includes: a fourth non-DC blocking voltage source converter 208, a sixth bypass knife switch 81, a sixth bypass switch 82, a seventh first isolation knife switch 83, and a seventh second isolation knife switch 84; the sixth bypass switch 82 is connected to the positive end of the fourth non-DC blocking voltage source converter 208 and the negative end of the fourth non-DC blocking voltage source converter 208, and is connected to one end of the seventh first isolation knife switch 83 and one end of the seventh second isolation knife switch 84, respectively; the sixth bypass knife switch 81 is connected to the other end of the seventh first isolation knife switch 83 and the other end of the seventh second isolation knife switch 84.

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

[0166] It should be noted that the above... Figure 17 The various switches or disconnectors mentioned include at least one of mechanical switches, disconnectors, DC circuit breakers, and thyristor valves.

[0167] like Figure 17 As shown, taking a DC transmission system as an example, in the initial state, 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 disconnector 14 of the rectifier station 100 is in the open position, the second bypass switch 13 is in the open position, and the second first isolating disconnector 15 is in the closed position. The second isolating switch 16 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 is open, the fourth bypass switch 52 is open, the fifth first isolating switch 53 is closed, the fifth second isolating switch 54 is closed, the fifth bypass switch 61 is open, the fifth bypass switch 62 is open, the sixth first isolating switch 63 is closed, and the sixth second isolating switch 64 is closed. Rectifier station 100 is used to control the rectification operation of the first non-DC interrupting voltage source converter 107 and the grid-commutated converter 1; inverter station 200 is used to control the inverter operation of the third non-DC interrupting voltage source converter 207 and the fourth grid-commutated converter 202.

[0168] In some embodiments of this application, such as Figure 11As shown, in step 111, when the first high-end non-DC blocking type fully controlled valve group 145 is put into online operation, the second first isolating switch 15 and the second second isolating 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, thereby transferring the DC current to the anti-parallel diode of the second IGBT module 31 of at least one phase upper and lower bridge arm sub-module 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 this application, such as Figure 17 As shown, when the third high-end non-DC interrupting 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 interrupting type voltage source converter 207. After charging is completed, the fifth grid-side AC switch 231 is disconnected, the fifth first isolating switch 53 and the fifth second isolating switch 54 of the third high-end non-DC interrupting type fully controlled valve group 245 are closed, the fourth bypass switch 51 is opened, and the fourth bypass switch 52 is closed to control the IGBT of the second IGBT module 31 of at least one phase upper and lower bridge arm sub-module of the third non-DC interrupting type voltage source converter 207 to conduct. The fourth bypass switch 52 is then opened, thereby transferring the DC current to the IGBT of the second IGBT module 31 of at least one phase upper and lower bridge arm sub-module of the third non-DC interrupting type voltage source converter 207. The fifth grid-side AC switch 231 is then closed to unlock the third non-DC interrupting type voltage source converter 207.

[0170] It should be noted that during online commissioning, the valve groups of the corresponding poles of rectifier station 100 and inverter station 200 are coordinated for commissioning. Please refer to [link / reference needed]. Figure 17 , Figure 11 The embodiments provided in this application are based on Figure 12 Figure 1 shows the simulation test results of valve group commissioning in a medium-voltage direct current transmission system. Figure 13 In the diagram, 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 grid-side AC voltages of the first AC system 140, IVD_L1, IVD_L2 and IVD_L3 are all valve-side AC currents of the YD type converter transformer, and DEBLOCK_IND is the operating signal of the bridge uncontrolled rectifier circuit 11. Figure 14 This 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 comprises step 120: in response to the online exit or fault exit of the non-DC blocking valve group 400, disconnecting the AC input end 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 fault exit of the non-DC blocking valve group, controlling the DC blocking valve group to realize a fault point of zero voltage or a blocking state.

[0172] In step 120, in response to the online exit or fault exit of the non-DC blocking valve group 400, disconnecting the AC input end of the non-DC blocking valve group 400 from AC power further comprises step 121: separating the valve side AC switch or the network side AC switch of the non-DC blocking valve group 400.

[0173] After disconnecting the AC input end of the non-DC blocking valve group 400 from AC power in response to the online exit or fault exit of the non-DC blocking valve group 400, it further comprises step 122: closing the bypass switch of the non-DC blocking valve group 400, closing the bypass knife switch of the non-DC blocking valve group 400, separating the bypass switch of the non-DC blocking valve group 400, separating the isolation knife switch of the non-DC blocking valve group 400, and transferring the DC current to the bypass knife switch of the non-DC blocking valve group 400, thereby isolating the full controlled device anti-parallel diode of the bridge uncontrolled rectifier circuit or the non-DC blocking voltage source converter.

[0174] In some embodiments of the present application, as shown in Figure 14 In step 121, in response to the online exit or fault exit of the first high-end uncontrolled valve group 111, the first network side AC switch 131 of the first high-end uncontrolled valve group 111 is separated, the DC current flows through the diodes of at least one upper and lower arm of the bridge uncontrolled rectifier circuit 11, in step 122, the second bypass switch 13 is closed, the second bypass knife switch 14 is closed, the second bypass switch 13 is separated, the second isolation knife switch 15 and the second isolation knife switch 16 are separated, and the DC current is transferred to the second bypass knife switch 14, thereby isolating the bridge 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 realize a fault point of zero voltage, 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, as shown in Figure 16As shown in FIG. 1, in step 121, in response to the first high-end non-DC blocking controllable valve group 111 being taken off-line or being taken off-line due to a fault, the first network-side AC switch 131 of the first high-end non-DC blocking controllable valve group 111 is opened, and the DC current flows through the diodes of at least one upper and lower arm sub-module of the bridge-type non-DC blocking rectifier circuit 11. In step 122, the second bypass switch 13 is closed, the second bypass knife switch 14 is closed, the second bypass switch 13 is opened, the second first isolation knife switch 15 and the second second isolation knife switch 16 are opened, and the DC current is transferred to the second bypass knife switch 14, thereby isolating the bridge-type non-DC blocking rectifier circuit 11. In response to the first high-end non-DC blocking controllable valve group 111 being taken off-line due to a fault, the cathode of the voltage source converter 12 of the first low-end DC blocking controllable valve group 141 is controlled to be zero voltage to realize that the fault point is zero voltage.

[0176] As shown in FIG. 1, in step 121, in response to the first high-end non-DC blocking controllable valve group 111 being taken off-line or being taken off-line due to a fault, the first network-side AC switch 131 of the first high-end non-DC blocking controllable valve group 111 is opened, and the DC current flows through the diodes of at least one upper and lower arm sub-module of the bridge-type non-DC blocking rectifier circuit 11. In step 122, the second bypass switch 13 is closed, the second bypass knife switch 14 is closed, the second bypass switch 13 is opened, the second first isolation knife switch 15 and the second second isolation knife switch 16 are opened, and the DC current is transferred to the second bypass knife switch 14, thereby isolating the bridge-type non-DC blocking rectifier circuit 11. In response to the first high-end non-DC blocking controllable valve group 111 being taken off-line due to a fault, the cathode of the voltage source converter 12 of the first low-end DC blocking controllable valve group 141 is controlled to be zero voltage to realize that the fault point is zero voltage. Figure 18 Figure 18 As shown in FIG. 1, in step 121, in response to the first high-end non-DC blocking controllable valve group 111 being taken off-line or being taken off-line due to a fault, the first network-side AC switch 131 of the first high-end non-DC blocking controllable valve group 111 is opened, and the DC current flows through the diodes of at least one upper and lower arm sub-module of the bridge-type non-DC blocking rectifier circuit 11. In step 122, the second bypass switch 13 is closed, the second bypass knife switch 14 is closed, the second bypass switch 13 is opened, the second first isolation knife switch 15 and the second second isolation knife switch 16 are opened, and the DC current is transferred to the second bypass knife switch 14, thereby isolating the bridge-type non-DC blocking rectifier circuit 11. In response to the first high-end non-DC blocking controllable valve group 111 being taken off-line due to a fault, the cathode of the voltage source converter 12 of the first low-end DC blocking controllable valve group 141 is controlled to be zero voltage to realize that the fault point is zero voltage.

[0177] As shown in FIG. 1, in step 121, in response to the first high-end non-DC blocking controllable valve group 111 being taken off-line or being taken off-line due to a fault, the first network-side AC switch 131 of the first high-end non-DC blocking controllable valve group 111 is opened, and the DC current flows through the diodes of at least one upper and lower arm sub-module of the bridge-type non-DC blocking rectifier circuit 11. In step 122, the second bypass switch 13 is closed, the second bypass knife switch 14 is closed, the second bypass switch 13 is opened, the second first isolation knife switch 15 and the second second isolation knife switch 16 are opened, and the DC current is transferred to the second bypass knife switch 14, thereby isolating the bridge-type non-DC blocking rectifier circuit 11. In response to the first high-end non-DC blocking controllable valve group 111 being taken off-line due to a fault, the cathode of the voltage source converter 12 of the first low-end DC blocking controllable valve group 141 is controlled to be zero voltage to realize that the fault point is zero voltage. Figure 11 Figure 18 As shown in FIG. 1, in step 121, in response to the first high-end non-DC blocking controllable valve group 111 being taken off-line or being taken off-line due to a fault, the first network-side AC switch 131 of the first high-end non-DC blocking controllable valve group 111 is opened, and the DC current flows through the diodes of at least one upper and lower arm sub-module of the bridge-type non-DC blocking rectifier circuit 11. In step 122, the second bypass switch 13 is closed, the second bypass knife switch 14 is closed, the second bypass switch 13 is opened, the second first isolation knife switch 15 and the second second isolation knife switch 16 are opened, and the DC current is transferred to the second bypass knife switch 14, thereby isolating the bridge-type non-DC blocking rectifier circuit 11. In response to the first high-end non-DC blocking controllable valve group 111 being taken off-line due to a fault, the cathode of the voltage source converter 12 of the first low-end DC blocking controllable valve group 141 is controlled to be zero voltage to realize that the fault point is zero voltage.

[0178] ​​It should be noted that when the valve group is disconnected online or due to a fault, the valve groups of the corresponding poles of rectifier station 100 and inverter station 200 will coordinate to perform the disconnection operation. Please refer to [link / reference]. Figure 18 ,like Figure 11 The image shown is based on an embodiment of this application. Figure 12 Figure showing the simulation results of valve group disconnection in a medium-voltage direct current transmission system; Figure 13 In the diagram, 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 operating signal of the bridge uncontrolled rectifier circuit 11. Figure 14 The diagram shows that after the first grid-side AC switch 131 of the first high-end uncontrolled valve group 111 is disconnected, the bridge uncontrolled rectifier circuit 11 is taken out of operation.

[0179] The control method for the hybrid DC transmission valve group of this application further includes step 130: in response to a DC line fault, controlling the DC blocking valve group 500 to be under negative pressure, so that the DC current at the point where the hybrid DC transmission valve group is 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 noted that the zero DC current and the equal DC current here include 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, in the event of a DC line fault, the semi-controlled valve group 501 is controlled to be under negative pressure, so that the DC current at the point where the hybrid DC transmission valve group is connected to the DC line is equal to the DC current at the other end of the DC line fault point; the grid phase-changing converter 1 of the semi-controlled valve group 501 is controlled to shift phase and present a blocking state.

[0181] like Figure 19 As shown, in response to a ground fault in a DC line, the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be under negative voltage, making the DC current IDL of the hybrid DC transmission valve group connected to the first DC line 150 equal to the DC current IDL of the third DC pole 210 at the other end of the DC line fault point, thus 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, making it in a blocking state.

[0182] In some embodiments of this 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 fault occurs, the DC blocking type fully controlled valve group 502 is controlled to be at a negative pressure, so that the DC current at the point where the hybrid DC transmission valve group is connected to the DC line is zero or equal to the DC current at the other end of the DC line fault point.

[0183] As shown in Figure 19 , when the DC line has a ground fault, the first low-end DC blocking full-controlled valve group 141 is controlled to be negative voltage by the first DC blocking voltage source converter 12, so that the DC current IDL of the hybrid HVDC 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 HVDC valve group is zero.

[0184] In response to the series connection of the non-DC blocking full-controlled valve group 402 and the semi-controlled valve group 501, when the DC line has a fault, the semi-controlled valve group 501 is controlled to be negative voltage, so that the DC current of the hybrid HVDC valve group connected to the DC line is equal to the DC current at the other end of the DC line fault point; and the grid commutation converter 1 of the semi-controlled valve group 501 is controlled to be phase-shifted and blocked.

[0185] As shown in Figure 11 and Figure 19 , in response to the ground fault of the DC line, the grid commutation converter 1 of the first low-end semi-controlled valve group 112 is controlled to be negative voltage, so that the DC current IDL of the hybrid HVDC 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 commutation converter 1 of the semi-controlled valve group 501 is controlled to be phase-shifted and blocked.

[0186] Please refer to Figure 19 , Figure 20 the simulation test result graph of the DC line fault of the HVDC system based on Figure 21 provided by the embodiment of the present application. Figure 21 The UDL is the pole bus voltage, the IDCP is the cathode DC current of the bridge uncontrolled rectifier circuit 11, the UAC_IN_L1, the UAC_IN_L2 and the UAC_IN_L3 are the grid-side AC voltages of the first AC system 140, the IVD_L1, the IVD_L2 and the IVD_L3 are the valve-side AC currents of the YD-type converter transformer, and the DEBLOCK_IND is the working signal of the bridge uncontrolled rectifier circuit 11. Figure 11 As shown in , the grid commutation converter 1 of the first low-end semi-controlled valve group 112 is controlled to be negative voltage, so that the hybrid HVDC valve group is negative voltage, and the current flowing through the fault point in the hybrid HVDC valve group is zero.

[0187] The present application also provides a DC transmission valve group control device, which comprises the hybrid HVDC valve group or the non-DC blocking valve group as described in the above embodiments, and is used to execute the control method of the DC transmission valve group as shown in Figure 12 , the control device comprises:

[0188] The first detection unit 310 is configured to detect the operating parameters and fault data of the hybrid HVDC valve group or the non-HVDC blocking valve group 400.

[0189] The first control unit 320 is configured to, based on the operating parameters and fault data detected by the first detection unit 310, when the non-HVDC blocking valve group 400 is put into operation, first transfer the DC current to the bridge uncontrolled rectifier circuit, the full-controlled device anti-parallel diode, or the full-controlled device of the non-HVDC blocking valve group 400, then connect the AC input end of the non-HVDC blocking valve group 400 to the AC power, or / and unlock the non-HVDC blocking valve group 400; when the non-HVDC blocking valve group 400 is taken out of operation or taken out of fault, disconnect the AC input end of the non-HVDC blocking valve group 400 from the AC power, or / and lock the non-HVDC blocking valve group 400, or / and bypass the non-HVDC blocking valve group 400; or / and when the non-HVDC blocking valve group 400 is taken out of fault, control the DC blocking valve group 500 to be in a zero-voltage fault point or a blocking state; and the first control unit 320 is configured to, when the DC line is in fault, control the DC blocking valve group 500 to be in a negative voltage, so that the DC current at the connection point of the hybrid HVDC valve group 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 valve group 500 to be in a blocking state.

[0190] Based on the DC power transmission system provided in the above embodiment, the application further provides a control method of the DC power transmission system, please refer to Figure 13 As shown in the control flowchart of the DC power transmission system, the control method of the DC power transmission system of the application comprises the following steps: Figure 14

[0191] In step 210, the operating parameters and fault parameters of the DC power transmission system are first obtained; and in response to the DC blocking valve group 500 being taken out of operation or taken out of fault, the station where the DC blocking valve group 500 is located is disconnected from the ground, which further comprises step 211:

[0192] In step 210, the operating parameters and fault parameters of the DC power transmission system are first obtained; and in response to the DC blocking valve group 500 being taken out of operation or taken out of fault, the station where the DC blocking valve group 500 is located is disconnected from the ground, which further comprises step 211:

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

[0194] ​In response to the DC blocking valve assembly 500 being disconnected online or due to a fault, the disconnection of the station where the DC blocking valve assembly 500 is located from the ground further includes step 212:

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

[0196] In some embodiments of this application, such as Figure 11 As shown, in step 210, in response to the online or fault exit of the first low-end semi-controlled valve group 112, the third low-end semi-controlled valve group 212 exits, the first metallic return line changeover switch 113 is disconnected, and the rectifier station 100 operates in a no-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 current 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 is controlled to be equal to the DC current of the third high-end semi-controlled valve group 211. After the deionization time, the first DC pole 110 and the third DC pole 210 are restarted. In step 212, if a fault occurs again at the first high-end uncontrolled valve group 111 at the DC pole where the first low-end semi-controlled valve group 112 is located, the first grid-side AC switch 131 is opened, the first metallic return line changeover switch 113 is closed, and the first pole neutral bus switch 119 is opened.

[0197] In some embodiments of this application, such as Figure 12 As shown, in step 210, in response to the online or fault exit of the first low-end DC blocking type fully controlled valve group 141, the third low-end semi-controlled valve group 212 exits, the first metallic return line changeover switch 113 is disconnected, and the rectifier station 100 operates in a no-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 current 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 third high-end semi-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 deionization 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 opened, the first metallic return line changeover switch 113 is closed, and the first pole neutral bus switch 119 is opened.

[0198] In some embodiments of this application, such as Figure 13 and Figure 14As shown, in step 210, in response to the online or fault exit of the first low-end semi-controlled valve group 112, the third low-end semi-controlled valve group 212 exits, the first metallic return line changeover switch 113 is disconnected, and the rectifier station 100 operates in a no-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 current of the first high-end non-DC blocking full-controlled valve group 145, the second high-end non-DC blocking full-controlled valve group 146, the second low-end semi-controlled valve group 121 at both ends of the fault point is equal to the DC current of the third high-end semi-controlled valve group 211. After the deionization time, the first DC pole 110 and the third DC pole 210 are restarted. In step 212, if the first high-end non-DC blocking type full control valve group 145 of the DC pole where the first low-end semi-control valve group 112 is located fails again, the first high-end non-DC blocking type full control valve group 145 is locked, the first grid-side AC switch 131 is opened, the first metal return line changeover switch 113 is closed, and the first pole neutral bus switch 119 is opened.

[0199] The control method for the hybrid DC transmission valve group of this application further 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 have zero current or to be in a blocking state. It should be noted that the control and measurement error of controlling the DC current to be zero, equal, or zero is allowed to be less than 0.02 times the rated DC current.

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

[0201] like Figure 22 As shown, in response to a ground fault in a DC line, the grid-commutated converter 1 of the first low-end semi-controlled valve group 112 is controlled to be under negative voltage, making the DC current IDL of the hybrid DC transmission valve group connected to the first DC line 150 equal to the DC current IDL of the third DC pole 210 at the other end of the DC line fault point, thus 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, making it in a blocking state, and the firing angles of the third grid-commutated converter 201 and the fourth grid-commutated converter 202 of the third DC pole 210 are equal to 110 degrees, also making them in a blocking state.

[0202] In some embodiments of the present application, in response to the series connection of the DC blocking full-control valve group 502 and the non-control valve group 401, when the DC line fails, the DC blocking full-control valve group 502 is controlled to be negative pressure, so that the DC current at the connection point of the hybrid DC transmission valve group and the DC line is zero or equal to the DC current at the other end of the DC line failure point.

[0203] As shown in ​ When the DC line fails, the first DC blocking voltage source converter 12 of the first low-end DC blocking full-control valve group 141 is controlled to be negative pressure, so that the DC current IDL at the connection point of the hybrid DC transmission valve group and the first DC line 150 is zero or equal to the DC current IDL at the third DC pole 210 at the other end of the DC line failure point, so that the current flowing through the failure point in the hybrid DC transmission valve group is zero.

[0204] In response to the series connection of the non-DC blocking full-control valve group 402 and the semi-control valve group 501, when the DC line fails, the semi-control valve group 501 is controlled to be negative pressure, so that the DC current at the connection point of the hybrid DC transmission valve group and the DC line is equal to the DC current at the other end of the DC line failure point; the grid commutation converter 1 of the semi-control valve group 501 is controlled to be out of phase and in blocking state.

[0205] As shown in ​ and ​ In response to the occurrence of a ground fault in the DC line, the grid commutation converter 1 of the first low-end semi-control valve group 112 is controlled to be negative pressure, so that the DC current IDL at the connection point of the hybrid DC transmission valve group and the first DC line 150 is equal to the DC current IDL at the third DC pole 210 at the other end of the DC line failure point, so that the current flowing through the failure point is zero. Alternatively, the grid commutation converter 1 of the semi-control valve group 501 is controlled to be out of phase and in blocking state.

[0206] The present application also provides a DC transmission system control device, the control device comprising a DC transmission system as described in the above embodiments, and the control device is used to execute the control method of the DC transmission system as described above, as shown in ​ The control device comprises:

[0207] A second detection unit 410 is configured to detect the operating parameters and fault data of the DC transmission system.

[0208] The second control unit 420 is configured 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 is online or faulted off; if the DC line fault occurs again in the DC pole where the DC blocking valve group 500 is located or the non-DC blocking valve group 400 in the DC pole where the DC blocking valve group 500 is located fails again, the second control unit 420 is configured to control the DC current of the converter at the fault point to be equal, to restart the DC pole where the DC blocking valve group 500 is located after the waiting ionization time or fault isolation, or / and to lock the non-DC blocking valve group 400 in the DC pole where the DC blocking valve group 500 is located or / and disconnect the AC input end of the non-DC blocking valve group 400 from the AC power, reconnect the ground and isolate the DC pole; the second control unit 420 is configured to control the DC current of the hybrid HVDC valve group and the opposite valve group on the DC line to be equal, or control the hybrid HVDC valve group and the opposite valve group to be zero current or in a blocking state when the DC line fault occurs.

[0209] The hybrid HVDC valve group, the power transmission system, the control device and the control method provided by the embodiments of the present application are described in detail above, and the principles and implementation manners of the present application are described by using specific examples; the above embodiment is only used to help understand the technical solutions and the core ideas of the present application; those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified or some technical features can be replaced by equivalents; and the 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 application.

Claims

1. A hybrid DC transmission valve assembly, characterized in that, include: A non-DC blocking valve assembly (400) includes: an uncontrolled valve assembly (401) or a non-DC blocking fully controlled valve assembly (402); A DC-blocking valve assembly (500) includes: a semi-controlled valve assembly (501) or a DC-blocking fully controlled valve assembly (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 semi-controlled valve group (501) and the DC blocking type fully controlled valve group (502); 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); Furthermore, the DC blocking valve assembly (500) is configured to output a negative DC voltage in the event of a DC line fault, thereby blocking the fault current.

2. The hybrid DC transmission valve assembly according to claim 1, characterized in that, Any 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) includes: a converter, a bypass switch (3), a bypass knife switch (4), a first isolation knife switch (5), and a second isolation knife switch (6); the bypass switch (3) and the bypass knife switch (4) are connected in parallel to form a bypass circuit; the first isolation knife switch (5) and the second isolation knife switch (6) are respectively disposed at the connection node of the bypass switch (3) and the bypass knife switch (4) connected in parallel.

3. The hybrid DC transmission valve assembly according to claim 2, characterized in that, The converter of the semi-controlled valve group (501) includes either a grid phase-commutation converter (1) or a current source converter with controllable turn-off capability.

4. The hybrid DC transmission valve assembly according to claim 3, characterized in that, The converter device includes a grid phase-commutation converter (1), which includes a first three-phase input (21), a second three-phase input (22), and thyristors (23). Multiple 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 assembly 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 assembly according to claim 2, characterized in that, The converter devices of the non-DC blocking type fully controlled valve group (402) and the DC blocking type fully controlled valve group (502) include voltage source converters (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 multilevel converter based on a half-bridge submodule, a diode clamped multilevel converter, a cascaded two-level converter, or a stacked two-level converter; the voltage source converter of the DC blocking type fully controlled valve group (502) includes a modular multilevel converter based on a full-bridge submodule or a modular multilevel converter based on a mixture of half-bridge and full-bridge submodules.

7. The hybrid DC transmission valve assembly according to claim 6, characterized in that, The voltage source converter (2) includes: a third three-phase input (24), an isolating switch (25), a charging resistor (26), a sub-module (27), and a current-limiting reactor (28); multiple sub-modules (27) and current-limiting reactors (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 switch (25) and the charging resistor (26) are connected in parallel and between the third three-phase input (24) and the bridge arm; The sub-module (27) 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.

8. The hybrid DC transmission valve assembly according to claim 2, characterized in that, The converter of the uncontrolled valve group (401) includes a bridge uncontrolled rectifier circuit (11), which includes a diode (44), a fourth three-phase input (42) and a fifth three-phase input (43). Multiple diodes (44) are connected in series to form a bridge arm. The fourth three-phase input (42) is connected to the bridge arm, and the fifth three-phase input (43) is connected to the bridge arm.

9. A DC transmission system, comprising a hybrid DC transmission valve assembly as described in any one of claims 1 to 8, characterized in that, The DC transmission system also includes: A rectifier station (100) includes a first DC pole (110), a second DC pole (120), and a first AC system (140), wherein the first AC system (140) is connected to the first DC pole (110) and the second DC pole (120) respectively. An inverter station (200) includes a third DC pole (210), a fourth DC pole (220), and a second AC system (240), wherein the second AC system (240) is connected to the third DC pole (210) and the fourth DC pole (220) respectively.

10. The DC transmission system according to claim 9, characterized in that, 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), 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). 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) 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), 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). The second high-end converter transformer (127) is connected between the first AC system (140) and the second high-end uncontrolled valve group (122).

11. The DC transmission system according to claim 9, characterized in that, The first DC pole (110) includes 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) is connected in series with the first low-end DC blocking type fully controlled valve group (141). 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) 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), and a second high-end converter transformer (127). The second low-end DC blocking type fully controlled valve group (142) is connected in series with the second high-end uncontrolled valve group (122). 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). The second high-end converter transformer (127) is connected between the second high-end uncontrolled valve group (122) and the first AC system (140).

12. The DC transmission system according to claim 9, characterized in that, The first DC pole (110) includes: a first high-end non-DC blocking type fully controlled valve group (145), 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 non-DC blocking type fully controlled valve group (145) is connected to the first low-end semi-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 semi-controlled valve group (112) and the first AC system (140); 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), 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); 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).

13. The DC transmission system according to claim 9, characterized in that, The third DC pole (210) includes: any two or any two of any one of the following: a semi-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) includes: any two or any two of the following: a semi-controlled valve group, a non-DC blocking type fully controlled valve group, and a DC blocking type fully controlled valve group.

14. A DC transmission valve group control device, comprising a hybrid DC transmission valve group as described in any one of claims 1 to 8, characterized in that, Also includes: The first detection unit (310) is used to detect the 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) is configured to, based on the operating parameters and fault parameters of the hybrid DC transmission valve group or the non-DC blocking valve group (400), 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, and then connect the AC input terminal of the non-DC blocking valve group (400) to AC power, or / and unlock the non-DC blocking valve group (400); and, the first control unit (320) is configured to, when the non-DC blocking valve group (400) is taken out of operation online or out of fault, control the non-DC blocking valve group (400) to... The AC input terminal is disconnected from the AC power supply, and / or the non-DC blocking valve group (400) is locked, and / or the non-DC blocking valve group (400) is bypassed; and / or, when the non-DC blocking valve group (400) fails out, the first control unit (320) is used to control the DC blocking valve group (500) to present a zero voltage at the fault point or to present a blocking state; and, when the DC line fails, the first control unit (320) is used to control the DC blocking valve group (500) to be at a negative voltage, 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 fault point of the DC line, or to control the DC blocking valve group (500) to present a blocking state.

15. A method for controlling a DC transmission valve group, used to control a hybrid DC transmission valve group as described in any one of claims 1 to 8, characterized in that, The control method includes the following steps: Obtain the operating parameters and fault parameters of the hybrid DC transmission valve group or the non-DC blocking valve group (400); In response to the online activation of the non-DC blocking valve group (400), the DC current is first transferred 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); the AC input terminal of the non-DC blocking valve group (400) is connected to AC power, and / or the non-DC blocking valve group (400) is unlocked; In response to the online or fault exit of the non-DC blocking valve group (400), the AC input terminal of the non-DC blocking valve group (400) is disconnected from the AC power supply, and / or the non-DC blocking valve group (400) is locked, and / or the non-DC blocking valve group (400) is bypassed; and / or in response to the fault exit of the non-DC blocking valve group (400), the DC blocking valve group (500) is controlled to present a zero-voltage fault point or a blocking state; In response to a DC line fault, the DC blocking valve group (500) is controlled to be under 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 fault point of the DC line, or the DC blocking valve group (500) is controlled to be in a blocking state.

16. A control device for a DC transmission system, comprising the DC transmission system as described in any one of claims 9 to 13, characterized in that, Also includes: The second detection unit (410) is used to detect the operating parameters and fault parameters of the DC transmission system; 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) is disconnected online or after a fault, 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 (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 second control unit (420) is used to control the DC current phase of the converters at both ends of the fault point. After waiting for the ionization time or after fault isolation, restart the DC pole of the DC blocking valve group (500), or / and lock the non-DC blocking valve group (400) of the DC pole of the DC blocking valve group (500), or / and disconnect the AC power to the AC input terminal of the DC blocking valve group (500), then connect it to the ground and isolate 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 the DC line is faulty, or to control the hybrid DC transmission valve group and the opposite valve group to be zero current or in a blocking state.

17. A control method for a DC transmission system, used to control the DC transmission system as described in any one of claims 9 to 13, characterized in that, The control method includes the following steps: Obtain the operating parameters and fault parameters of the DC transmission system; In response to the DC blocking valve group (500) being disconnected online or after 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 fault occurs again in the non-DC blocking valve group (400) at the DC pole where the DC blocking valve group (500) is located, the DC current of the converters at both ends of the fault point is equalized, and the DC pole where the DC blocking valve group (500) is located is restarted after the deionization 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 terminal 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 current of the hybrid DC transmission valve group and the opposite-end valve group of the DC line is controlled to be equal, or the hybrid DC transmission valve group and the opposite-end valve group are controlled to have zero current or be in a blocking state.

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