CN115603255A - Ice melting circuit of extra-high voltage direct current transmission system and control method and control device thereof - Google Patents

Abstract

The application provides an ice melting circuit of an extra-high voltage direct-current transmission system, and a control method and a control device of the ice melting circuit. The extra-high voltage direct current transmission system comprises at least two converter stations, wherein each converter station comprises double direct current poles, each direct current pole comprises at least two valve groups, each valve group comprises at least one converter, each circuit comprises a first current path and a second current path, a direct current pole of the station forms the first current path through two direct current lines and a metal bus of the station or two direct current poles connected with the station, any converter station serves as the station, the other converter station corresponding to the station serves as the station, and the two valve groups of one direct current pole of the two direct current poles of the station are isolated through a bypass knife switch; the cathodes and anodes of the converters of the two valve groups of the other direct current pole of the local station are reversely connected, and the other direct current pole of the local station is connected to the two direct current lines in parallel to form the second current path.

Description

Ice melting circuit of extra-high voltage direct-current transmission system and control method and control device thereof

Technical Field

The application relates to the technical field of high-voltage direct-current transmission, in particular to an ice melting circuit of an extra-high voltage direct-current transmission system, and a control method and a control device thereof.

Background

The extra-high voltage direct current transmission line has long distance, and needs to have the functions of ice prevention and ice removal when crossing an area which is easy to have ice coating disasters. The ice melting of the extra-high voltage direct current transmission line is divided into two modes of ice resistance and ice melting: the ice blocking is to apply direct current near the rated value of a direct current transmission system on a direct current line to prevent the formation of line ice coating; the ice melting is to apply a direct current exceeding a rated value within a certain range to a direct current line to quickly melt the formed ice on the line.

The direct-current line ice melting scheme adopted by the current extra-high voltage direct-current transmission project is as follows: a small number of connecting wires and isolating switches are added in a transmitting end converter station and a receiving end converter station respectively, and the converters which normally run in series are switched into a plurality of converters to run in parallel through the operation of a direct current switch field, so that the current running of multiple rated values is realized, and the aim of deicing a direct current line is fulfilled. Under the parallel ice-melting operation mode, special connecting wires and isolating switches are required to be configured at two stations, the ice-melting can be carried out only by the fact that the direct-current transmission system needs to transmit enough direct-current power, and power fluctuation can be caused if a fault occurs during the ice-melting period, so that the safety of a power grid is influenced.

Because icing disasters can only happen under specific climatic conditions, the actual occurrence probability is not high, and the economical efficiency of the scheme is not high in consideration of the construction cost and the later maintenance cost increased by the special connecting lines and the switch disconnecting links which are arranged at the two stations.

Disclosure of Invention

The embodiment of the application provides an ice melting circuit for an extra-high voltage direct current transmission system, which comprises at least two converter stations, wherein each converter station comprises double direct current poles, each direct current pole comprises at least two valve groups, each valve group comprises at least one converter, the circuit comprises a first current path and a second current path, a direct current pole of the station forms the first current path through two direct current lines and a metal bus of the opposite station or the two direct current poles of the opposite station, any converter station serves as the station, the other converter station corresponding to the station serves as the opposite station, and the two valve groups of one direct current pole of the two direct current poles of the opposite station are isolated through a bypass knife switch; the converter cathodes and anodes of the two valve groups of the other direct current pole of the own station are connected in reverse, the other direct current pole of the own station is connected in parallel to the two direct current lines, and the metal bus of the pair of stations or the two direct current poles of the pair of stations constitute the second current path.

According to some embodiments, one and only one of said own station or said pair of stations is connected to ground.

According to some embodiments, the two dc lines include a dc line of one dc pole of the station and a dc line of another dc pole of the station.

According to some embodiments, the second current path comprises a valve area ice melting disconnecting link, a first pole area ice melting disconnecting link and a third pole area ice melting disconnecting link, and inverter cathodes and anodes of two valve groups of another direct current pole of the local station are reversely connected through the valve area ice melting disconnecting link; the first pole area ice melting disconnecting link is connected with a pole bus of the other direct current pole of the station and a direct current line of the direct current pole of the station; and the third pole ice melting disconnecting link is connected with the DC line and the pole neutral bus of the other DC pole of the station.

According to some embodiments, a dc pole of the local station constitutes the first current path through two dc lines and a metal bus of a docking station, and the first current path includes two valve groups of one dc pole of the local station, a connection line of the two valve groups of one dc pole of the local station, a pole bus of one dc pole of the local station, a pole neutral bus, a dc line, and a metal bus of two dc poles of the docking station; the direct current utmost point of this station constitutes through two direct current circuit with two direct current utmost point of counterpointing first electric current route, then first electric current route includes two valves of a direct current utmost point of this station, the connecting wire of two valves of a direct current utmost point of this station, the utmost point generating line of a direct current utmost point of this station, utmost point neutral bus, direct current circuit, the bypass knife brake of two valves of one of them direct current utmost point of two direct current utmost point of counterpointing, one or two valves of another direct current utmost point of two direct current utmost points of counterpointing.

According to some embodiments, the other dc pole of the local station is connected in parallel to the two dc lines, and the metal bus of the opposite station forms the second current path, and the second current path includes two valve groups of the other dc pole of the local station, a connection line of the two valve groups of the other dc pole of the local station, a pole bus of the other dc pole of the local station, a pole neutral bus, an ice melting connection line formed by the valve zone ice melting disconnecting link, the first pole zone ice melting disconnecting link and the third pole zone ice melting disconnecting link, a dc line, and the metal bus of the two dc poles of the opposite station; the other direct current pole of the local station is connected to the two direct current lines in parallel, and the two direct current poles of the opposite station form the second current path, and the second current path includes the two valve groups of the other direct current pole of the local station, a connecting line of the two valve groups of the other direct current pole of the local station, a pole bus and a pole neutral bus of the other direct current pole of the local station, the valve zone ice melting disconnecting link, the first pole zone ice melting disconnecting link and the third pole zone ice melting disconnecting link, a direct current line, a bypass disconnecting link of the two valve groups of one direct current pole of the two direct current poles of the opposite station, and one or two valve groups of the other direct current pole of the two direct current poles of the opposite station.

According to some embodiments, the valve pack is a current source valve pack comprising a grid commutated converter or a voltage source valve pack comprising a voltage source converter.

The embodiment of the present application further provides a control method for an ice melting circuit of an extra-high voltage direct current transmission system, where the extra-high voltage direct current transmission system includes at least two converter stations, each converter station includes a double direct current pole, each direct current pole includes at least two valve banks, each valve bank includes at least one converter, and the control method includes: controlling a direct current pole of the current station to form the first current path through two direct current lines and a metal bus of the opposite station or two direct current poles of the opposite station, wherein any one converter station is used as the current station, and the other converter station corresponding to the current station is used as the opposite station, wherein two valve groups of one direct current pole of the two direct current poles of the opposite station are isolated through a bypass disconnecting link, and the bypass disconnecting link is controlled to be conducted; the cathodes and anodes of the converters of the two valve groups controlling the other direct current pole of the local station are reversely connected, and the other direct current pole of the local station is connected in parallel to the two direct current lines and the metal bus of the opposite station or the two direct current poles of the opposite station form the second current path; and controlling the converter of the first current path and the converter of the second current path to work, and generating direct current in the first current path and the second current path respectively to melt the ice on the direct current line.

According to some embodiments, if the direct current required for ice melting is larger than the maximum allowable current of a switch, a disconnecting link or a connecting line for the metal buses of the two direct current poles of the pair station, controlling the metal buses of the pair station and the two direct current poles of the pair station to simultaneously flow current.

According to some embodiments, the controlling of the converter operation of the first current path and the converter operation of the second current path comprises controlling a dc pole of a local station to form the first current path by two dc lines and a metal bus of a counter station, and controlling another dc pole of the local station to be connected in parallel to the two dc lines and the metal bus of the counter station to form the second current path, the controlling of the converter operation of the first current path and the converter operation of the second current path comprising: controlling the converters of the two valve banks of the DC pole of the station to respectively operate in a rectification state and an inversion state, and controlling the DC currents of the converters of the two valve banks of the DC pole of the station; and controlling the converters of the two valve banks of the other direct current pole of the station to respectively operate in a rectification state and an inversion state, and controlling the direct current of the converters of the two valve banks of the other direct current pole of the station.

According to some embodiments, the controlling of the converter operation of the first current path and the converter operation of the second current path comprises controlling a dc pole of a local station to constitute the first current path through two dc lines and a metal bus of a counter station and another dc pole of the local station to be connected in parallel to the two dc lines and the two dc poles of the counter station to constitute the second current path, or controlling a dc pole of a local station to constitute the first current path through two dc lines and the two dc poles of the counter station and another dc pole of the local station to be connected in parallel to the two dc lines and the metal bus of the counter station to constitute the second current path, the controlling of the converter operation of the first current path and the converter operation of the second current path comprises: controlling the converters of the two valve banks of the DC pole of the station to respectively operate in a rectification state and an inversion state, and controlling the DC currents of the converters of the two valve banks of the DC pole of the station; controlling the converters of the two valve groups of the other direct current pole of the local station to respectively operate in a rectification state and an inversion state, and controlling the direct current of the converters of the two valve groups of the other direct current pole of the local station; and controlling the converters of the two valve banks of the other non-isolated direct current pole of the station pair to respectively operate in a rectification state and an inversion state, and controlling the direct current of the converters of the two valve banks of the other non-isolated direct current pole of the station pair.

The embodiment of the application also provides a control device of the ice melting circuit of the extra-high voltage direct current transmission system, which applies the control method of the ice melting circuit of the extra-high voltage direct current transmission system, and the device comprises a detection unit and a control unit, wherein the detection unit is used for detecting the operation parameters of the extra-high voltage direct current transmission system; the control unit controls a direct current pole of a station to form the first current path through two direct current lines and a metal bus of the opposite station or two connected direct current poles of the opposite station based on operation parameters of the high-voltage direct current transmission system, the any converter station serves as the station, another converter station corresponding to the station serves as the opposite station, two valve groups of one direct current pole of the two direct current poles of the opposite station are isolated through a bypass knife switch, the bypass knife switch is controlled to be conducted, converter cathodes and anodes of two valve groups of the other direct current pole of the station are controlled to be reversely connected, the other direct current pole of the station is connected in parallel to the two direct current lines and the metal bus of the opposite station or the two direct current poles of the opposite station to form the second current path, converter work of the first current path and converter work of the second current path are controlled, direct currents are generated in the first current path and the second current path respectively, and ice melting of the direct current lines is performed.

According to some embodiments, the operating parameters of the extra-high voltage direct current transmission system comprise position signals of switches or disconnecting links, direct current, direct voltage and alternating voltage.

According to some embodiments, if the direct current required for ice melting is larger than the maximum allowable current of the switch, the knife switch or the connecting line for the metal bus of the two direct current poles of the pair station, the control unit controls the metal bus of the pair station and the two direct current poles of the pair station to flow current at the same time.

According to the technical scheme provided by the embodiment of the application, the direct-current field switch or the disconnecting link for ice melting is only added to a single station of the ultra-high voltage direct-current transmission system, direct-current power does not need to be transmitted in the ice melting process, and the ice melting function of the ultra-high voltage direct-current transmission system can be realized by controlling the operation modes of the current converters of the two stations.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a schematic diagram of a main loop of an extra-high voltage direct current transmission system provided by the application.

Fig. 2 is a schematic diagram of an ice melting circuit of an extra-high voltage direct current transmission system provided by the application.

Fig. 3 is a schematic diagram of an ice melting circuit of another extra-high voltage direct-current transmission system provided by the application.

Fig. 4 is a schematic flow chart of a control method for an ice melting circuit of an extra-high voltage direct-current transmission system provided by the application.

Fig. 5 is a schematic flow chart of another control method for an ice melting circuit of an extra-high voltage direct-current transmission system provided by the application.

Fig. 6 is a schematic diagram of a control device of an ice melting circuit of an extra-high voltage direct-current transmission system provided in the present application.

Detailed Description

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, and it is obvious that the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Fig. 1 is a schematic diagram of a main loop of an extra-high voltage direct current transmission system provided by the present application.

The extra-high voltage direct current transmission system main loop comprises, but is not limited to, a rectifying station 100, an inverter station 200, a first direct current line 150, a second direct current line 160, a rectifying station grounding electrode line 114, a rectifying station grounding electrode 115, an inverter station grounding electrode line 214 and an inverter station grounding electrode 215. The rectifying station 100 is connected in parallel with the inverter station 200 through a first direct current line and a second direct current line. The rectifier station 100 is connected to a rectifier station earth 115 by a rectifier station earth line 114. The rectifier station 200 is connected to an inverter station ground 215 by an inverter station ground line 214.

The rectification station 100 comprises a first dc pole I110, a second dc pole II120, a first ac filter bank 118, a first ac system 140 and a converter transformer incoming line switch, a metallic return line transfer switch 113, an earth return line transfer switch 190, bipolar neutral zone isolation switches 174, 175, 184 and 185, valve zone ice melting switches 35, 36, 45 and 46, first pole zone ice melting switches 191, 192 and a third pole zone ice melting switch 193. The first ac system 140 is connected to the first ac filter bank 118. The first dc pole I110 is connected to the first ac system 140 via the incoming line switches 131, 132 of the converter transformer. The second dc pole II120 is connected to the first ac system 140 via the incoming line switches 133, 134 of the converter transformer. The rectifier station 100 is connected to the rectifier station ground line 114 through bipolar neutral zone isolation switchgears 174, 175, 184 and 185 and the dc line transfer switch 113. The station 100 is connected to the dc link through bipolar neutral isolation switches 174, 175, 184 and 185 and a ground return switch 190.

The first dc pole I110 includes a first high-side valve group 111, a first low-side valve group 112, a first high-side converter transformer 116, a first low-side converter transformer 117, a first dc pole neutral bus switch 119, a first dc filter 93, a first smoothing reactor 91, a first dc filter isolation switch 171, a first pole bus isolation switch 172, and a first metal return isolation switch 173. First high side valve block 111 and first low side valve block 112 are connected in series. The first high-side valve group 111 is connected to the converter transformer incoming line switch 131 through the first high-side converter transformer 116. The first low side valve set 112 is connected to the converter transformer inlet switch 132 via a first low side converter transformer 117. The first high-side valve block 111 is connected to the first dc link 150 via the first smoothing reactor 91 and the first pole bus isolation switch 172. The first low side valve set 112 is connected to bipolar neutral zone isolation switches 174, 175 through a first dc pole neutral bus switch 119. The first smoothing reactor 91 is connected with the first direct current filter 93 through a first direct current filter isolation disconnecting link 171 between one end of the first high-end valve group 111 which is not connected with the first direct current pole neutral bus switch 119 and one end of the first low-end valve group 112 which is not connected with the first direct current pole neutral bus switch 119. The first dc link 150 and the second dc link 160 are connected by a first dc link isolation switch 173 and a second dc link isolation switch 183.

The first high-end valve group 111 includes a first high-end converter 1, a first high-end valve group first bypass switch 11, a first high-end valve group second bypass switch 12, a first high-end valve group bus switch 13, and a first high-end valve group switch 14. The first low side valve block 112 includes a first low side inverter 2, a first low side valve block first bypass switch 21, a first low side valve block second bypass switch 22, a first low side valve block switch 23, and a first low side valve block bus switch 24. The first high-side inverter 1 is connected in parallel with the first high-side valve group second bypass switch 12. Two ends of the first high-end valve bank first bypass switch 11 are connected to the first high-end valve bank bus switch 13 and the first high-end valve bank switch 14 respectively and then connected to the first high-end valve bank second bypass switch 12 in parallel. The first low side inverter 2 is connected in parallel with a first low side bank of second bypass switches 22. Two ends of the first low-end valve bank first bypass switch 21 are connected to the first low-end valve bank switch 23 and the first low-end valve bank bus switch 24 respectively and then connected to the first low-end valve bank second bypass switch 22 in parallel.

The first high side converter 1 and the first low side converter 2 comprise at least one of a grid commutated converter or a voltage source converter. The grid commutation converter comprises at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit. The ripple bridge circuit includes, but is not limited to, a non-turn-off semi-controlled power semiconductor device, typically a thyristor device.

The voltage source converter comprises at least one of but not limited to a two-level converter, a diode clamping type multi-level converter, a modular multi-level converter MMC, a hybrid multi-level converter HMC, a two-level cascade converter CSL and a stacking type two-level converter CTL, and the converters comprise but not limited to turn-off fully-controlled power semiconductor devices. The modular multilevel converter MMC includes, but is not limited to, at least one of a modular multilevel converter MMC of a half-bridge sub-module structure, a modular multilevel converter MMC of a full-bridge sub-module structure, and a modular multilevel converter MMC of a half-bridge and full-bridge hybrid sub-module structure.

The second dc pole II120 includes a second low-side valve group 121, a second high-side valve group 122, a second low-side converter transformer 126, a second high-side converter transformer 127, a second dc pole neutral bus switch 129, a second dc filter 94, a second smoothing reactor 92, a second dc filter isolation switch 181, a second pole bus isolation switch 182, and a second metallic return isolation switch 183. The second low side valve block 121 and the second high side valve block 122 are connected in series. The second high-side valve bank 122 is connected to the converter transformer incoming line switch 134 via a second high-side converter transformer 127. The second low side valve set 121 is connected to the incoming converter transformer switch 133 through the second low side converter transformer 126. The first high-side valve set 122 is connected to the second dc link 160 through the second smoothing reactor 92 and the second pole bus isolation switch 182. The second low side valve set 121 is connected to bipolar neutral zone isolation switches 184, 185 through a second dc pole neutral bus switch 129. And a second direct current filter 94 is connected between one end of the second smoothing reactor 92, which is not connected with the second high-end valve bank 122, and one end of the second direct current pole neutral bus switch 129, which is not connected with the second low-end valve bank 121, through a second direct current filter isolation knife switch 181.

The second low side valve block 121 includes a second low side inverter 3, a second low side valve block first bypass switch 31, a second low side valve block second bypass switch 32, a second low side valve block bus switch 33, and a second low side valve block switch 34. The second high-side valve group 122 includes a second high-side converter 4, a second high-side valve group first bypass switch 41, a second high-side valve group second bypass switch 42, a second high-side valve group switch 43, and a second high-side valve group bus switch 44. The second low side converter 3 and the second high side converter 4 comprise at least one of a grid commutated converter or a voltage source converter. The second high side inverter 4 is connected in parallel with a second high side bank second bypass switch 42. Two ends of the second high-end valve bank first bypass switch 41 are connected to the second high-end valve bank bus switch 44 and the second high-end valve bank switch 43 respectively and then connected to the second high-end valve bank second bypass switch 42 in parallel. The second low side inverter 3 is connected in parallel with a second low side bank of second bypass switches 32. Two ends of the second low-end valve bank second bypass switch 31 are connected to the second low-end valve bank switch 34 and the first low-end valve bank bus switch 33, respectively, and then connected to the second low-end valve bank second bypass switch 32 in parallel.

The inverter station 200 comprises a third dc pole I210, a fourth dc pole II220, a second ac filter bank 218, a second ac system 240, a converter transformer incoming line switch, a ground line isolation switch 213, a metal return isolation switch 290, a bipolar neutral zone isolation switch 274, 275, 284 and 285. The second ac system 240 is connected to the second ac filter bank 218. The third dc pole I210 is connected to the second ac system 240 via the converter transformer inlet switches 231, 232. The fourth dc pole II220 is connected to the second ac system 240 via the converter transformer inlet switches 233, 234. The inverter station 200 is connected to the rectifier station ground line 214 through bipolar neutral zone isolation switches 274, 275, 284 and 285 and a dc line transfer switch 213.

The third dc pole I210 includes a third high-side valve group 211, a third low-side valve group 212, a third high-side converter transformer 216, a third low-side converter transformer 217, a third dc pole neutral bus switch 219, a third dc filter 97, a third smoothing reactor 95, a third dc filter isolation switch 271, a third pole bus isolation switch 272, and a third metal return isolation switch 273. The first high side valve set 111 and the first low side valve set 112 are connected in series. The third high end valve bank 211 and the third low end valve bank 212 are connected in series. The third high-side valve group 211 is connected with the incoming converter transformer switch 231 through the third high-side converter transformer 216. The third low-side valve set 212 is connected to the incoming line switch 232 of the converter transformer via a third low-side converter transformer 217. The third high-side valve set 211 is connected to the first dc line 150 through a third smoothing reactor 95 and a third pole bus isolation switch 272. The third low side valve bank 212 is connected to the bipolar neutral zone isolation switches 274, 275 through a third dc neutral bus switch 219. And a third direct current filter 97 is connected between one end of the third smoothing reactor 91, which is not connected with the third high-end valve group 211, and one end of the third direct current pole neutral bus switch 219, which is not connected with the third low-end valve group 212, through a third direct current filter isolation disconnecting link 271. The first dc link 150 and the second dc link 160 are connected by a third dc link isolation switch 273 and a fourth dc link isolation switch 283.

The third high side valve group 211 includes a third high side converter 5, a third high side valve group first bypass switch 51, a third high side valve group second bypass switch 52, a third high side valve group bus switch 53, and a third high side valve group switch 54. The third low side valve block 212 includes a third low side inverter 6, a third low side valve block first bypass switch 61, a third low side valve block second bypass switch 62, a third low side valve block switch 63, and a third low side valve block bus switch 64. The third high-side converter 5 and the third low-side converter 6 comprise at least one of a grid commutated converter or a voltage source converter. The third high side inverter 5 is connected in parallel with the third high side valve block second bypass switch 52. Both ends of the third high-side valve group first bypass switch 51 are connected to a third high-side valve group bus switch 53 and a third high-side valve group switch 54, respectively, and then connected in parallel to a third high-side valve group second bypass switch 52. The third low side inverter 6 is connected in parallel with a third low side bank of second bypass switches 62. Both ends of the third low-side valve bank first bypass switch 61 are connected to a third low-side valve bank switch 63 and a third low-side valve bank bus switch 64, respectively, and then connected in parallel to a third low-side valve bank second bypass switch 62.

The fourth dc pole II220 includes a fourth low-side valve group 221, a fourth high-side valve group 222, a fourth low-side converter transformer 226, a fourth high-side converter transformer 227, a fourth dc pole neutral bus switch 229, a fourth dc filter 98, a fourth smoothing reactor 96, a fourth dc filter isolation disconnecting link 281, a fourth pole bus isolation disconnecting link 282, and a fourth metal return isolation disconnecting link 283. The fourth low side valve block 221 and the fourth high side valve block 222 are connected in series. The fourth high-side valve group 222 is connected with the incoming converter transformer switch 234 through the fourth high-side converter transformer 227. The fourth low side valve group 221 is connected to the converter transformer incoming line switch 233 through the fourth low side converter transformer 226. The fourth high side valve set 222 is connected to the second dc link 160 via a fourth smoothing reactor 96 and a fourth pole bus isolation switch 282. The fourth low side valve set 221 is connected to the bipolar neutral zone isolation switches 284, 285 through a fourth dc neutral bus switch 229. And a fourth smoothing reactor 96 is connected with the fourth direct-current filter 98 through a fourth direct-current filter isolation disconnecting link 281 between one end of the fourth smoothing reactor 96, which is not connected with the fourth high-end valve bank 222, and one end of the fourth direct-current pole neutral bus switch 229, which is not connected with the fourth low-end valve bank 221.

The fourth low side bank 221 includes a fourth low side inverter 7, a fourth low side bank first bypass switch 71, a fourth low side bank second bypass switch 72, a fourth low side bank bus switch 73, and a fourth low side bank switch 74. The fourth high-side valve group 222 includes a fourth high-side converter 8, a fourth high-side valve group first bypass switch 81, a fourth high-side valve group second bypass switch 82, a fourth high-side valve group switch 83, and a fourth high-side valve group bus switch 84. The fourth low-side converter 7 and the fourth high-side converter 8 comprise at least one of a grid commutated converter or a voltage source converter. The fourth high side inverter 8 is connected in parallel with a fourth high side valve set second bypass switch 82. The two ends of the fourth high-end valve bank first bypass switch 81 are connected to the fourth high-end valve bank bus switch 84 and the second high-end valve bank switch 83 respectively and then connected to the fourth high-end valve bank second bypass switch 82 in parallel. The fourth low side inverter 7 is connected in parallel with a fourth low side bank second bypass switch 72. Both ends of the fourth low end valve group second bypass switch 71 are connected to the fourth low end valve group switch 74 and the fourth low end valve group bus switch 73, respectively, and then connected in parallel to the fourth low end valve group second bypass switch 72.

The above mentioned switches include, but are not limited to, at least one of mechanical switches, knife switches, dc breakers, and thyristor valve blocks.

If the high-end converter and the low-end converter of the direct current pole of the rectifying station 100 and the inverting station 200 are both grid commutation converters, the system is a conventional extra-high voltage direct current transmission system.

If the high-side converter and the low-side converter of the direct current pole of the rectifying station 100 and the inverting station 200 are both voltage source converters, the system is a flexible extra-high voltage direct current transmission system.

If the first high-side converter 1, the first low-side converter 2, the second high-side converter 4 and the second low-side converter 3 of the first dc pole I110 and the second dc pole II120 of the rectifying station 100 are all grid commutated converters, and the third high-side converter 5, the third low-side converter 6, the fourth high-side converter 8 and the fourth low-side converter 7 of the third dc pole I210 and the fourth dc pole II220 of the inverting station 200 are all voltage source converters, the hybrid extra-high voltage dc transmission system between stations is obtained.

If the first high-side converter 1, the first low-side converter 2, the second high-side converter 4 and the second low-side converter 3 of the first dc pole I110 and the second dc pole II120 of the rectifying station 100 are all grid commutation converters, the third high-side converter 5 and the fourth high-side converter 8 of the third dc pole I210 and the fourth dc pole II220 of the inverting station 200 are grid commutation converters, and the third low-side converter 6 and the fourth low-side converter 7 are voltage source converters, an intra-pole hybrid ultra-high voltage dc transmission system is provided.

The rectifier station 100 is connected to an earth 115 via an earth line 114. The inverter station 200 is connected to a ground 215 via a ground line 214. When power is being transmitted, the first ac system 140 of the rectifying station 100 converts ac power into dc power through the first high-side converter 1, the first low-side converter 2, the second high-side converter 4 and the second low-side converter 3, and transmits the dc power to the inverter station 200 through the dc lines 150 and 160, and the inverter station 200 converts dc power into ac power through the third high-side converter 5, the third low-side converter 6, the fourth high-side converter 8 and the fourth low-side converter 7, and transmits the ac power to the second ac system 240 of the inverter station 200, thereby realizing the direct power transmission. The converters of the rectifier stations generally operate in current control, and the converters of the inverter stations generally operate in voltage control or maximum firing angle control (AMAX). It is noted that the maximum firing angle control (AMAX) is only applicable to grid commutated converters and not to voltage source converters.

The analog quantity signals collected by the rectification station 100 and the inversion station 200 comprise: high-voltage bus current IDC1P and low-voltage bus current IDC1N on the direct current side of a high-end converter, high-voltage bus current IDC2P and low-voltage bus current IDC2N on the direct current side of a low-end converter, pole bus current IDL, pole neutral bus current IDNC, head end current IZT1 of a direct current filter, grounding pole current IDEL, pole bus voltage UDL and pole neutral bus voltage UDN; optionally, the analog signal collected by the rectification station 100 or the inversion station 200 further includes an extreme midpoint voltage UDM. The acquired digital quantity signals comprise: position signals of all switches or knife switches.

Fig. 2 is a schematic diagram of an ice melting circuit of an extra-high voltage direct current transmission system provided by the application.

The ultrahigh voltage direct current transmission system comprises at least two converter stations, each converter station comprises double direct current poles, each direct current pole comprises at least two valve groups, each valve group comprises at least one converter, and the parallel ice melting circuit of the high voltage direct current transmission system comprises a first current path and a second current path.

A direct current pole of the station forms a first current path through two direct current lines and a metal bus of the opposite station, any converter station is used as the station, the other converter station corresponding to the station is the opposite station, and two valve groups of one direct current pole of the two direct current poles of the opposite station are isolated through a bypass disconnecting link. The cathodes and the anodes of the current converters of the two valve groups of the other direct current pole of the station are reversely connected, the other direct current pole of the station is connected to the two direct current lines in parallel, and a metal bus of the opposite station forms a second current path.

The own station or the counter station has one and only one converter station connected to ground. The two dc lines include a dc line of one dc pole of the station and a dc line of the other dc pole of the station. The second current path comprises a valve area ice melting disconnecting link, a first pole area ice melting disconnecting link and a third pole area ice melting disconnecting link, and the cathodes and the anodes of the current converters of the two valve groups of the other direct current pole of the station are reversely connected through the valve area ice melting disconnecting link. And the first pole area ice melting disconnecting link is connected with a pole bus of the other direct current pole of the station and a direct current circuit of the other direct current pole of the station. And the third pole ice melting disconnecting link is connected with a direct current line and a pole neutral bus of the other direct current pole of the station.

In this embodiment, the first current path includes two valve groups of one dc pole of the station, a connection line of two valve groups of one dc pole of the station, a pole bus of one dc pole of the station, a pole neutral bus, a dc line, and a metal bus of two dc poles of the opposite station.

Taking fig. 2 as an example, the first high-end valve group 111 and the first low-end valve group 112 of the first dc pole I110 of the rectifier station 100, the connection lines of the two valve groups, the pole bus (including the first pole bus isolation switch 172), the pole neutral bus (including the first dc pole neutral bus switch 119), the metal return connection lines (including the bipolar neutral isolation switch 175, the ground return transfer switch 190, and the second metal return isolation switch 183), the dc line 150, the dc line 160, and the metal buses (including the third metal return isolation switch 273 and the fourth metal return isolation switch 283) of the two dc poles of the inverter station 200 form a first current path.

In this embodiment, the second current path includes two valve groups of another dc pole of the station, a connection line of two valve groups of another dc pole of the station, a pole bus of another dc pole of the station, a pole neutral bus, a deicing switch of the valve area, a deicing connection line of the deicing switch of the first pole area and the deicing switch of the third pole area, a dc line, and a second current path of a metal bus of two dc poles of the opposite station.

Taking fig. 2 as an example, the second high-end valve group 121 and the second low-end valve group 122 of the second dc pole II120, the connection lines of the two valve groups, the pole bus (including the second pole bus isolation switch 182), the pole neutral bus (including the second dc pole neutral bus switch 129), the ice-melting connection line (which implements the cathode and anode reverse connection of the inverter 3 and the inverter 4) composed of the valve-zone ice- melting switches 35, 36, 45, and 46, the ice-melting connection line (which implements the cathode and anode reverse connection of the inverter 3 and the inverter 4) composed of the first pole-zone ice-melting switch 191 and the third pole-melting switch 193, the dc lines 150 and 160, and the metal bus (including the third metal loop isolation switch 273 and the fourth metal loop isolation switch 283) of the two dc poles of the inverter station 200 constitute a second current path.

Optionally, the valve set is a current source type valve set or a voltage source type valve set, the current source type valve set includes a grid phase-change converter, and the voltage source type valve set includes a voltage source converter, but not limited thereto.

The pole bus connecting lines of the two dc poles of the inverter station 200 (including the third metallic return line isolating switch 273 and the fourth metallic return line isolating switch 283) constitute the only branches of the ice melting circuit.

Fig. 3 is a schematic diagram of an ice melting circuit of another extra-high voltage direct-current transmission system provided by the application.

The ultrahigh-voltage direct-current transmission system comprises at least two converter stations, the converter stations comprise double direct-current poles, the direct-current poles comprise at least two valve groups, each valve group comprises at least one converter, and the high-voltage direct-current transmission system parallel ice melting circuit comprises a first current path and a second current path.

A direct current pole of the station forms a first current path through two direct current lines and a metal bus of the opposite station, any converter station is used as the station, the other converter station corresponding to the station is the opposite station, and two valve groups of one direct current pole of the two direct current poles of the opposite station are isolated through a bypass disconnecting link. The cathodes and the anodes of the current converters of the two valve groups of the other direct current pole of the station are reversely connected, the other direct current pole of the station is connected to the two direct current lines in parallel, and the two direct current poles of the opposite station form a second current path. The own station or the counter station has one and only one converter station connected to ground. The two dc lines include a dc line of one dc pole of the station and a dc line of the other dc pole of the station. The second current path comprises a valve area ice melting disconnecting link, a first pole area ice melting disconnecting link and a third pole area ice melting disconnecting link, and the cathodes and the anodes of the current converters of the two valve groups of the other direct current pole of the station are reversely connected through the valve area ice melting disconnecting link; the ice melting disconnecting link of the first pole area is connected with a pole bus of the other direct current pole of the station and a direct current circuit of the other direct current pole of the station; and the third pole ice melting disconnecting link is connected with a direct current line and a pole neutral bus of the other direct current pole of the station.

In this embodiment, the first current path includes two valve groups of one dc pole of the station, a connection line of two valve groups of one dc pole of the station, a pole bus of one dc pole of the station, a pole neutral bus, a dc line, and a metal bus of two dc poles of the opposite station.

Taking fig. 3 as an example, the first high-end valve group 111 and the first low-end valve group 112 of the first dc pole I110 of the rectification station 100, the connection lines of the two valve groups, the pole bus (including the first pole bus isolation switch 172), the pole neutral bus (including the first dc pole neutral bus switch 119), the metal return connection line (including the bipolar neutral isolation switch 175, the earth return switch 190, and the second metal return isolation switch 183), and the metal bus (including the third metal return isolation switch 273 and the fourth metal return isolation switch 283) of the two dc poles of the inverter station 200 constitute a first current path.

In this embodiment, the second current path includes two valve groups of another dc pole of the station, a connection line of two valve groups of another dc pole of the station, a pole bus of another dc pole of the station, a pole neutral bus, a valve area deicing switch, a first pole area deicing switch, a third pole area deicing switch deicing connection line, a dc line, a bypass switch of two valve groups of one dc pole of two dc poles of the opposite station, and one or two valve groups of another dc pole of two dc poles of the opposite station.

Taking fig. 3 as an example, the second high-end valve group 121 and the second low-end valve group 122 of the second dc pole II120, the connection lines of the two valve groups, the pole bus (including the second pole bus isolation disconnecting switch 182), the pole neutral bus (including the second dc pole neutral bus switch 129), the valve zone ice-melting disconnecting switches 35, 36, 45, and 46 (to realize the cathode and anode reverse connection of the inverter 3 and the inverter 4), the first pole zone ice-melting disconnecting switch 191 and the third pole zone ice-melting disconnecting switch 193, the dc lines 150 and 160, the fourth low-end valve group 221 and the fourth high-end valve group 222 of the fourth dc pole II220 of the inverter station 200, the connection lines of the two valve groups, the pole bus (including the fourth pole bus isolation disconnecting switch 282) and the pole neutral bus connection line (including the fourth dc pole neutral bus switch 229), and the third high-end first bypass switch 51, the third low-end valve group first bypass switch 71, the pole bus (including the fourth bus isolation switch 272) and the pole neutral switch connection line (including the fourth dc pole neutral switch 219) of the third dc pole I210 constitute a second four pole bypass path.

Fig. 4 is a schematic flow chart of a control method of an ice melting circuit of an extra-high voltage direct-current transmission system, which is applicable to the ice melting circuit shown in fig. 2.

In S110, one dc pole of the own station is controlled to be connected to the dc line.

Taking the rectifying station 100 as an example, the first dc pole I110 of the rectifying station 100 is controlled to be connected to a dc line. Specifically, the bipolar neutral isolation switch 175, the second metallic return isolation switch 183, the earth return switch 190, the first dc neutral bus switch 119, and the first dc bus isolation switch 172 are closed, and the first dc I110 is connected to the dc line.

Before connecting the direct current line, the valve bank needs to be charged and connected. Specifically, the first high-side converter transformer inlet switch 131 is closed, and the first high-side valve bank 111 is charged; the first high-end valve bank bus switch 13 and the first high-end valve bank switch 14 are closed, the first high-end valve bank first bypass switch 11 and the first high-end valve bank second bypass switch 12 are separated, and the first high-end valve bank 111 is connected. Closing the first low-side converter transformer inlet switch 132, charging the first low-side valve bank 112; the first low-side valve block bus switch 23 and the first low-side valve block switch 24 are closed, the first low-side valve block first bypass switch 21 and the first low-side valve block second bypass switch 22 are separated, and the first low-side valve block 112 is connected.

After the dc line is connected, the first dc filter 93 is connected. Specifically, the first dc filter isolation switch 171 is closed.

In S120, the cathodes and anodes of the inverters of the two valve groups controlling the other dc pole of the local station are connected in reverse, and the other dc pole of the local station is controlled to be connected in parallel to the dc line of the one dc pole of the local station.

Taking the rectifying station 100 as an example, the valve area ice melting disconnecting switches 35, 36, 45 and 46 are closed, and the second low-end valve group bus switch 33, the second low-end valve group switch 34, the second high-end valve group switch 43 and the second high-end valve group bus switch 44 are separated; and (3) separating the second pole zone ice-melting disconnecting link 192 and closing the first metal loop isolation disconnecting link 173, the second direct-current pole neutral bus switch 129, the first pole zone ice-melting disconnecting link 191 and the third pole zone ice-melting disconnecting link 193.

Before the above operation, the valve block is charged and connected. Specifically, the second high-side converter transformer incoming line switch 134 is closed, and the second high-side valve bank 122 is charged; the second high-end valve group bus switch 44 and the second high-end valve group switch 43 are closed, the second high-end valve group first bypass switch 41 and the second high-end valve group second bypass switch 42 are separated, and the second high-end valve group 122 is connected. The second low-side converter transformer incoming switch 133 is closed, and the second low-side valve bank 121 is charged; the second low side valve group bus switch 33 and the second low side valve group switch 34 are closed, the second low side valve group first bypass switch 31 and the second low side valve group second bypass switch 32 are separated, and the fourth low side valve group 121 is connected.

In S130, the metal bus of the control counter station connects the two dc poles. The local station or the opposite station is controlled, and only one station is connected with the ground.

Taking the inverter station 200 as an example, the third and fourth metallic return isolation switches 273 and 283 are closed.

After the metal bus connects the two direct current poles, the rectifier station 100 or the inverter station 200 can be connected to a grounding pole or an in-station ground. For the example of the rectifier station 100 connected to ground, the bipolar neutral isolation switch 174 and the metallic return transfer switch 113 are closed.

It should be noted that the sequence of S110 to S130 is not strict, and the sequence provided in this embodiment is better; the sequence of closing the switch or knife switch in each step can be adjusted.

In S140, the converters of the two valve banks controlling one dc pole of the station operate in rectification and inversion states, respectively, and the converters of the two valve banks controlling the other dc pole of the station operate in rectification and inversion states, respectively.

Taking the rectifying station 100 as an example, the first low-side converter 2 controlling the first dc pole I110 of the rectifying station 100 operates in a rectifying state, and the first high-side converter 1 operates in an inverting state. The second low-side converter 3 controlling the second dc pole I120 of the rectifying station 100 operates in a rectifying state and the second high-side converter 4 operates in an inverting state.

Before unlocking, the ac filter 118 is also connected.

In S150, the dc currents of the converters of the two valve banks of the dc pole of the local station are controlled, the dc currents of the converters of the two valve banks of the other dc pole of the local station are controlled, and the ice melting is performed on the dc line between the local station and the opposite station.

Specifically, the direct current of the first direct current pole I110 of the rectifying station 100 is controlled, the direct current of the second direct current pole I120 of the rectifying station 100 is controlled, and the direct current of the fourth direct current pole II220 of the inverter station 200 is controlled, so that ice melting is performed. One preferred working condition is that the dc current of the first dc pole I110 of the rectifying station 100 is 0.8pu, the dc current of the second dc pole I120 of the rectifying station 100 is 0.8pu, and the current of the metal bus of the inverter station 200 is 1.6pu, which requires that the maximum allowable current flowing through the third metal loop isolation switch 273, the fourth metal loop isolation switch 283 and the connecting line thereof is greater than or equal to 1.6pu.

The DC current measurement can be high voltage bus current IDC1P and low voltage bus current IDC1N on the DC side of the high side converter, high voltage bus current IDC2P and low voltage bus current IDC2N on the DC side of the low side converter, pole bus current IDL or pole neutral bus current IDNC.

Fig. 5 is a schematic flow chart of another control method for an ice melting circuit of an extra-high voltage direct-current transmission system, which illustrates an ice melting control method that a direct current required for ice melting is larger than a maximum allowable current of a switch, a disconnecting link or a connecting wire for metal busbars of two direct-current poles of a station, and is suitable for the ice melting circuit shown in fig. 3.

Taking the main loop shown in fig. 1 as an example, the dc current required for ice melting is greater than the third and fourth metallic return line isolation switches 273 and 283 for the metallic bus.

In S210, one dc pole of the station is controlled to be connected to the dc line.

Taking the rectifying station 100 as an example, the first dc pole I110 of the rectifying station 100 is controlled to be connected to a dc line. Specifically, the bipolar neutral zone isolation switch 175, the second metallic return isolation switch 183, the earth return transfer switch 190, the first dc neutral bus switch 119 and the first dc bus isolation switch 172 are closed, and the first dc I110 is connected to the dc line.

Before connecting the direct current line and the ground, the valve bank needs to be charged and connected. Specifically, the first high-side converter transformer inlet switch 131 is closed, and the first high-side valve bank 111 is charged; the first high-end valve bank bus switch 13 and the first high-end valve bank switch 14 are closed, the first high-end valve bank first bypass switch 11 and the first high-end valve bank second bypass switch 12 are separated, and the first high-end valve bank 111 is connected. Closing the first low-side converter transformer inlet switch 132, charging the first low-side valve bank 112; the first low side valve bank bus switch 23 and the first low side valve bank switch 24 are closed, the first low side valve bank first bypass switch 21 and the first low side valve bank second bypass switch 22 are separated, and the first low side valve bank 112 is connected.

After connecting the dc line to the ground, the first dc filter 93 is connected. Specifically, the first dc filter isolation knife-switch 171 is closed.

In S220, the cathodes and anodes of the inverters of the two valve groups controlling the other dc pole of the local station are connected in reverse, and the other dc pole of the local station is controlled to be connected in parallel to the dc line of one dc pole of the local station.

Taking the rectifying station 100 as an example, the valve area ice melting disconnecting switches 35, 36, 45 and 46 are closed, and the second low-end valve group bus switch 33, the second low-end valve group switch 34, the second high-end valve group switch 43 and the second high-end valve group bus switch 44 are separated; and (3) separating the second pole zone ice-melting disconnecting link 192 and closing the first metal loop isolation disconnecting link 173, the second direct-current pole neutral bus switch 129, the first pole zone ice-melting disconnecting link 191 and the third pole zone ice-melting disconnecting link 193.

Before the operation, the valve group is charged and connected. Specifically, the second high-side converter transformer incoming line switch 134 is closed, and the second high-side valve group 122 is charged; and closing the second high-end valve bank bus switch 44 and the second high-end valve bank switch 43, separating the second high-end valve bank first bypass switch 41 and the second high-end valve bank second bypass switch 42, and connecting the second high-end valve bank 122. The second low-side converter transformer incoming switch 133 is closed, and the second low-side valve bank 121 is charged; the second low side valve group bus switch 33 and the second low side valve group switch 34 are closed, the second low side valve group first bypass switch 31 and the second low side valve group second bypass switch 32 are separated, and the fourth low side valve group 121 is connected.

In S230, the metal bus of the control pair station connects the two dc poles.

Taking the inverter station 200 as an example, the third and fourth metallic return isolation switches 273 and 283 are closed.

In S240, the local station or the opposite station is controlled to have one and only one station connected to the ground. And controlling the connection of the two direct current poles of the docking station, and isolating the two valve banks of one of the two direct current poles of the docking station.

Taking the inverter station 200 as an example, the third dc pole I210 and the fourth dc pole II220 of the inverter station 200 are controlled to be connected to the ground return line. Specifically, the closed earth electrode line isolation disconnecting link 213, the bipolar neutral isolation disconnecting link 274, the fourth dc electrode neutral bus switch 219, the fourth pole bus isolation disconnecting link 272, and the third dc electrode I210 are connected to the earth return line; the closed earth pole line isolation disconnecting link 213, the bipolar neutral isolation disconnecting link 284, the fourth direct current pole neutral bus switch 229 and the fourth pole bus isolation disconnecting link 282, and the fourth direct current pole II220 is connected with the earth return line.

Isolating the third dc pole II120 of the inverter station 200. Specifically, third high-side group first bypass switch 51 is closed, third high-side group switch 54 and third high-side group bus switch 53 are separated, and third high-side group 211 is isolated. The third low side valve block first bypass switch 61 is closed, the third low side valve block bus switch 64, the third low side valve block switch 63 are opened, and the third low side valve block 212 is isolated.

Before the ground return wire is connected, the valve group without the isolated pole needs to be charged and connected. Specifically, the fourth high-side converter transformer inlet switch 234 is closed, and the fourth high-side valve bank 222 is charged; the fourth high-end valve bank bus switch 84 and the fourth high-end valve bank switch 83 are closed, the fourth high-end valve bank first bypass switch 81 and the fourth high-end valve bank second bypass switch 82 are separated, and the fourth high-end valve bank 222 is connected. Closing the fourth low-side converter transformer inlet switch 233, and charging the fourth low-side valve bank 221; the fourth low side valve group bus switch 73 and the fourth low side valve group switch 74 are closed, the fourth low side valve group first bypass switch 71 and the fourth low side valve group second bypass switch 72 are separated, and the fourth low side valve group 221 is connected.

It should be noted that the sequence from S210 to S240 is not strict, and the sequence provided in this embodiment is preferred; the sequence of closing the switch or knife switch in each step can be adjusted.

In S250, the converters of the two valve banks controlling one dc pole of the station operate in rectification and inversion states, respectively, and the converters of the two valve banks controlling the other dc pole of the station operate in rectification and inversion states, respectively.

Taking the rectifying station 100 as an example, the first low-side converter 2 controlling the first dc pole I110 of the rectifying station 100 operates in a rectifying state, and the first high-side converter 1 operates in an inverting state. The second low-side converter 3 controlling the second dc pole I120 of the rectifying station 100 operates in a rectifying state and the second high-side converter 4 operates in an inverting state.

Before unlocking, the ac filter 118 is also connected.

In S260, the inverters of the two valve banks controlling the other of the two dc poles of the docking station are operated in rectification and inversion states, respectively.

Taking the inverter station 200 as an example, the fourth low-side converter 7 controlling the fourth dc pole II220 of the inverter station 200 operates in a rectifying state, and the fourth high-side converter 8 operates in an inverting state.

Before unlocking, the ac filter 218 is also connected.

In S270, the dc currents of the converters of the two valve banks of the dc pole of the current station are controlled, the dc currents of the converters of the two valve banks of the other dc pole of the opposite station that are not isolated are controlled, and the ice melting is performed on the dc line between the current station and the opposite station.

Specifically, the direct current of the first direct current pole I110 of the rectifying station 100 is controlled, the direct current of the second direct current pole I120 of the rectifying station 100 is controlled, and the direct current of the fourth direct current pole II220 of the inverter station 200 is controlled, so that ice melting is performed. One preferred working condition is that the dc current of the first dc pole I110 of the rectifying station 100 is 0.8pu, the dc current of the second dc pole I120 of the rectifying station 100 is 0.8pu, and the dc current of the fourth dc pole II220 of the inverting station 200 is 0.8pu. Because the direct current of the fourth direct current pole II220 of the inverter station 200 is 0.8pu, and the current of the metal bus of the inverter station 200 is also 0.8pu, the direct current controllability of the two parallel branches is realized.

The DC current measurement can be high voltage bus current IDC1P and low voltage bus current IDC1N on the DC side of the high side converter, high voltage bus current IDC2P and low voltage bus current IDC2N on the DC side of the low side converter, pole bus current IDL or pole neutral bus current IDNC.

Fig. 6 is a schematic structural diagram of an ice melting control apparatus 300 for an extra-high voltage direct-current transmission system, where the apparatus includes a detection unit 310 and a control unit 320.

The detection unit 310 is used for detecting the operation parameters of the high-voltage direct-current transmission system, and comprises a high-voltage bus current IDC1P and a low-voltage bus current IDC1N on the direct-current side of a high-end converter, a high-voltage bus current IDC2P and a low-voltage bus current IDC2N on the direct-current side of a low-end converter, an electrode bus current IDL, an electrode neutral bus current IDNC, a head-end current IZT1 of a direct-current filter, an earth electrode current IDEL, an electrode bus voltage UDL, an electrode neutral bus voltage UDN, a switch and a knife switch position signal.

The control unit 320 controls one direct current pole of the station to be connected with a direct current line based on the operation parameters of the high-voltage direct current transmission system, controls the cathodes and the anodes of the two valve banks of the other direct current pole of the station to be reversely connected, controls the other direct current pole of the station to be connected in parallel with the direct current line of the one direct current pole of the station, controls a metal bus of the opposite station to be connected with the two direct current poles, controls the current converters of the two valve banks of the one direct current pole of the station to respectively operate in a rectification state and an inversion state, controls the current converters of the two valve banks of the other direct current pole of the station to respectively operate in the rectification state and the inversion state, and controls the direct current of the station or/and the opposite station to melt ice on the direct current line between the station and the opposite station. The control of the local station or the opposite station has only one station connected with the ground, and the connection of the ground is the connection of a grounding electrode or the in-station grounding. If the direct current required by ice melting is larger than the maximum allowable current of a switch, a disconnecting link or a connecting line for the metal bus of the two direct current poles of the docking station, controlling the connection of the two direct current poles of the docking station, and isolating two valve groups of one of the two direct current poles of the docking station; the current converters controlling the two valve groups of the other one of the two direct current poles of the station respectively operate in a rectification state and an inversion state.

The above embodiments are only for illustrating the technical idea of the present application, and the protection scope of the present application is not limited thereby, and any modification made on the basis of the technical solution according to the technical idea proposed in the present application falls within the protection scope of the present application.

Claims (14)

1. An extra-high voltage direct current transmission system ice melting circuit, the extra-high voltage direct current transmission system comprises at least two converter stations, the converter stations comprise double direct current poles, the direct current poles comprise at least two valve groups, each valve group comprises at least one converter, and the circuit comprises:

a first current path, a direct current pole of the current station forms the first current path through two direct current lines and a metal bus of a station pair or two direct current poles of the station pair, any converter station serves as the current station, the other converter station corresponding to the current station serves as the station pair, and two valve groups of one direct current pole of the two direct current poles of the station pair are isolated through a bypass disconnecting link;

and a second current path, wherein the cathodes and anodes of the converters of the two valve groups of the other direct current pole of the local station are reversely connected, the other direct current pole of the local station is connected to the two direct current lines in parallel, and the metal bus of the pair of stations or the two direct current poles of the pair of stations form the second current path.

2. The circuit of claim 1, wherein one and only one of the local station or the pair of stations is grounded.

3. The circuit of claim 1, wherein the two dc lines include a dc line of one dc pole of the station and a dc line of another dc pole of the station.

4. The circuit of claim 1, wherein the second current path comprises:

the valve area ice melting disconnecting link is used for realizing the reverse connection of the cathodes and the anodes of the converters of the two valve groups of the other direct current pole of the current station;

the first pole area ice melting disconnecting link is connected with a pole bus of the other direct current pole of the station and a direct current circuit of the direct current pole of the station;

and the third pole region ice melting disconnecting link is connected with the DC line and the pole neutral bus of the other DC pole of the station.

5. The circuit of claim 1, wherein a dc pole of the local station forms the first current path through two dc lines and a metal bus of the opposite station, and the first current path includes two valve groups of a dc pole of the local station, a connection line of the two valve groups of a dc pole of the local station, a pole bus of a dc pole of the local station, a pole neutral bus, a dc line, and a metal bus of two dc poles of the opposite station;

the direct current pole of this station constitutes through two direct current circuits with two direct current poles to the station first electric current route, then first electric current route includes two valves of a direct current pole of this station, the connecting wire of two valves of a direct current pole of this station, the utmost point generating line, utmost point neutral bus, direct current circuit of a direct current pole of this station, the bypass knife brake of two valves of one of them direct current pole of two direct current poles to the station, one or two valves of another direct current pole of two direct current poles to the station.

6. The circuit of claim 1, wherein the other dc pole of the local station is connected in parallel to the two dc lines, and the metal bus of the opposite station forms the second current path, and then the second current path includes two valve groups of the other dc pole of the local station, a connection line of the two valve groups of the other dc pole of the local station, a pole bus of the other dc pole of the local station, a pole neutral bus, a deicing connection line formed by the valve zone deicing switch, the first pole zone deicing switch and the third pole zone deicing switch, a dc line, and the metal bus of the two dc poles of the opposite station;

the other direct current pole of the local station is connected to the two direct current lines in parallel, and the two direct current poles of the opposite station form the second current path, and the second current path includes the two valve groups of the other direct current pole of the local station, a connecting line of the two valve groups of the other direct current pole of the local station, a pole bus and a pole neutral bus of the other direct current pole of the local station, the valve zone ice melting disconnecting link, the first pole zone ice melting disconnecting link and the third pole zone ice melting disconnecting link, a direct current line, a bypass disconnecting link of the two valve groups of one direct current pole of the two direct current poles of the opposite station, and one or two valve groups of the other direct current pole of the two direct current poles of the opposite station.

7. The circuit of claim 1, wherein the valve bank is a current source valve bank comprising a grid commutated converter or a voltage source valve bank comprising a voltage source converter.

8. A control method for an ice melting circuit of an extra-high voltage direct current transmission system, wherein the extra-high voltage direct current transmission system comprises at least two converter stations, each converter station comprises a double direct current pole, each direct current pole comprises at least two valve groups, each valve group comprises at least one converter, and the control method comprises the following steps:

controlling a direct current pole of the current station to form the first current path through two direct current lines and a metal bus of the opposite station or two direct current poles of the opposite station, wherein any one converter station is used as the current station, and the other converter station corresponding to the current station is used as the opposite station, wherein two valve groups of one direct current pole of the two direct current poles of the opposite station are isolated through a bypass disconnecting link, and the bypass disconnecting link is controlled to be conducted;

the cathodes and anodes of the converters of the two valve groups controlling the other direct current pole of the local station are reversely connected, and the other direct current pole of the local station is connected in parallel to the two direct current lines and the metal bus bar of the pair station or the two direct current poles of the pair station to form the second current path;

and controlling the converter of the first current path and the converter of the second current path to work, and generating direct current in the first current path and the second current path respectively to melt the ice on the direct current line.

9. The control method according to claim 8, wherein if the DC current required for melting ice is larger than the maximum allowable current of a switch, a knife switch or a connecting wire for the metal bus of the two DC poles of the pair station, the metal bus of the pair station and the two DC poles of the pair station are controlled to flow current at the same time.

10. The control method according to claim 8, wherein the controlling of the first current path is performed by a dc pole of a local station being connected in parallel to two dc lines and a metal bus bar of a counter station or the second current path is performed by another dc pole of the local station being connected in parallel to the two dc lines and the metal bus bar of the counter station, and the controlling of the converter operation of the first current path and the converter operation of the second current path includes:

controlling the converters of the two valve banks of the DC pole of the local station to respectively operate in a rectification state and an inversion state, and controlling the DC currents of the converters of the two valve banks of the DC pole of the local station;

and controlling the converters of the two valve banks of the other direct current pole of the local station to respectively operate in a rectification state and an inversion state, and controlling the direct current of the converters of the two valve banks of the other direct current pole of the local station.

11. The control method according to claim 8, wherein the controlling of the first current path is performed by two dc lines and a metal bus bar of a station pair, and the first current path is performed by connecting a dc pole of the station pair in parallel to the two dc lines and the second current path is performed by connecting another dc pole of the station pair in parallel to the two dc lines and the metal bus bar of the station pair, or the controlling of the first current path is performed by two dc lines and the two dc poles of the station pair, and the second current path is performed by connecting another dc pole of the station pair in parallel to the two dc lines and the metal bus bar of the station pair, and the controlling of the converter operation of the first current path and the converter operation of the second current path includes:

controlling the converters of the two valve banks of the DC pole of the station to respectively operate in a rectification state and an inversion state, and controlling the DC currents of the converters of the two valve banks of the DC pole of the station;

controlling the converters of the two valve groups of the other direct current pole of the local station to respectively operate in a rectification state and an inversion state, and controlling the direct current of the converters of the two valve groups of the other direct current pole of the local station;

and controlling the converters of the two valve banks of the other non-isolated direct current pole of the station pair to respectively operate in a rectification state and an inversion state, and controlling the direct current of the converters of the two valve banks of the other non-isolated direct current pole of the station pair.

12. An apparatus for controlling an ice melting circuit of an extra-high voltage direct current transmission system, applying the method for controlling the ice melting circuit of the extra-high voltage direct current transmission system according to any one of claims 8 to 11, the apparatus comprising:

the detection unit is used for detecting the operation parameters of the extra-high voltage direct current transmission system;

and a control unit, configured to control a dc pole of a local station to form the first current path through two dc lines and a metal bus of a peer station or two connected dc poles of the peer station based on an operating parameter of the high-voltage dc transmission system, where any one of the two converter stations serves as the local station, and another converter station corresponding to the local station serves as the peer station, where two valve banks of one of the two dc poles of the peer station are isolated by a bypass switch, the bypass switch is controlled to be turned on, and a converter cathode and an anode of two valve banks of another dc pole of the local station are controlled to be connected in reverse, and another dc pole of the local station is connected in parallel to the two dc lines and the metal bus of the peer station or the two dc poles of the peer station to form the second current path, and a converter operation of the first current path and a converter operation of the second current path are controlled to generate dc currents in the first current path and the second current path, respectively, so as to melt ice on the dc lines.

13. The control apparatus of claim 12, wherein the operating parameters of the extra-high voltage direct current transmission system include position signals of switches or disconnecting links, direct current, direct voltage and alternating voltage.

14. The control device of claim 12, wherein if the direct current required for melting ice is larger than the maximum allowable current of a switch, a knife switch or a connecting wire for the metal bus of the two direct current poles of the pair station, the control unit controls the metal bus of the pair station and the two direct current poles of the pair station to flow current at the same time.

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