CN-122000978-A - Multi-terminal direct current system, configuration method, control method and control device thereof

CN122000978ACN 122000978 ACN122000978 ACN 122000978ACN-122000978-A

Abstract

The invention discloses a multi-terminal direct current system, a configuration method, a control method and a control device thereof, wherein the configuration method comprises the steps that alternating current energy consumption is configured at a new energy source transmitting terminal converter station; the DC power consumption is configured at each receiving end converter station, the DC circuit breaker is configured at each branch line near the main line side, and the main line is not configured with the circuit breaker. The control method comprises the steps of operating according to a device connected with a branch line when the direct current line fails, restarting and boosting a converter station with active voltage reduction after arc extinction of the direct current line, reclosing a tripped breaker, locking the converter station of the branch line where the direct current line fails when the converter station fails to restart repeatedly for a designated number of times, opening the breaker of the branch line where the direct current line fails, and adjusting power. The invention is used for realizing the suppression of alternating current and direct current overvoltage after fault ride-through or locking of the modularized multi-level converter, and meets the operation requirement of a new energy source sending system through a flexible direct island.

Inventors

Xu Maoning
ZOU KAIKAI
Chang Shiyang
LU YU
JIANG CHONGXUE
LU JIANG
LU YAJUN
Zhong qidi

Assignees

南京南瑞继保电气有限公司
国网经济技术研究院有限公司
国网新疆电力有限公司经济技术研究院

Dates

Publication Date: 20260508
Application Date: 20251225

Claims (20)

1. A configuration method of energy consumption and circuit breaker in a multi-terminal direct current system comprises a main line and a plurality of branch lines connected to the main line respectively, wherein each branch line is connected with a transmitting-end converter station or a receiving-end converter station, The alternating current energy consumption is configured at a new energy source transmitting end converter station, and the capacity of the alternating current energy consumption is configured according to the consumption capacity of an alternating current power grid; the direct current energy consumption is configured at each receiving-end converter station, and the capacity of the direct current energy consumption is configured according to the capacity of the receiving-end converter station of the branch line where the direct current energy consumption is located; the direct current circuit breaker is arranged on the side of each branch line close to the main line, and the main line is not provided with the circuit breaker.
2. The method of claim 1, wherein the capacity for AC power consumption is configured according to AC grid consumption capacity, comprising, The capacity of the alternating current energy consumption is configured as the difference between the maximum running power of the new energy source and the maximum power which can be absorbed by the power grid.
3. The method of claim 1, wherein the DC power consuming configuration is performed at each of the receiving converter stations, comprising, The direct current energy consumption adopts independent centralized energy consumption and distributed energy consumption, or adopts a self-balancing valve form integrated with a soft direct current converter valve.
4. The method for configuring as recited in claim 1, wherein the capacity of the DC power consumption is configured according to the capacity of the receiving converter station of the branch line where the DC power consumption is located, comprising, The capacity of direct current energy consumption is configured as the capacity of the receiving-end converter station of the branch line where the direct current energy consumption is located.
5. A multi-terminal direct current system comprises a main line and a plurality of branch lines connected with the main line respectively, wherein each branch line is connected with a transmitting-end converter station or a receiving-end converter station, When the multi-terminal direct current system comprises alternating current energy consumption, the alternating current energy consumption is configured on a branch line connected with a new energy source transmitting-end converter station, and the capacity of the alternating current energy consumption is configured according to the consumption capacity of an alternating current power grid; When the multi-terminal direct current system comprises direct current energy consumption, the direct current energy consumption is configured on a branch line connected with a receiving-end converter station, and the capacity of the direct current energy consumption is configured according to the capacity of the receiving-end converter station of the branch line; When the multi-terminal direct current system comprises a direct current breaker, the direct current breaker is arranged on the side, close to the main line, of each branch line, and the main line is not provided with the breaker.
6. The multi-terminal DC system of claim 5, wherein the AC power dissipating capacity is configured according to AC grid consumption capabilities, comprising, The capacity of the alternating current energy consumption is configured as the difference between the maximum running power of the new energy source and the maximum power which can be absorbed by the power grid.
7. The multi-terminal DC system of claim 5, wherein the DC power consuming devices are disposed at each of the receiving converter stations comprising, The direct current energy consumption adopts independent centralized energy consumption and distributed energy consumption, or adopts a self-balancing valve form integrated with a soft direct current converter valve.
8. The multi-terminal DC system of claim 5, wherein the DC power dissipating capacity is configured based on the capacity of the receiving converter station of the branch line in which it is located, comprising, The capacity of direct current energy consumption is configured as the capacity of the receiving-end converter station of the branch line where the direct current energy consumption is located.
9. A control method of a multi-terminal direct current system is characterized by comprising the following steps of, When the branch line has a direct current line fault, the device connected with the branch line acts; when the branch line is connected with the receiving-end converter station, the converter station connected with the branch line is actively depressurized, the direct current breaker at the main line side in the branch line is disconnected, and the direct current energy consumption of the branch line connected with the receiving-end converter station is controlled; restarting the actively-reduced converter station to boost voltage after arc extinction of the direct current circuit, and reclosing the tripped circuit breaker; and after repeating the operations for a designated number of times, when judging that the restarting of the converter station fails, locking the converter station of the branch line where the direct current line fails, and opening the breaker of the branch line where the direct current line fails.
10. The control method according to claim 9, wherein when the branch line is connected to the new energy source terminal converter station, the converter station to which the branch line is connected is actively depressurized, comprising, After the control system receives the line fault state signal sent by the direct current line protection, the control system controls the direct current bias to carry out 0 direct current control, and in the process of controlling 0 direct current, the direct current side ends of the converter valves present 0 voltage or even negative voltage; when the branch line is connected with the receiving end converter station, the converter station connected with the branch line is actively depressurized, comprising, The valve topology of the converter station is a hybrid bridge mode constructed by a full bridge and a half bridge, and can output 0 voltage or even negative voltage, and after the control system receives a line fault state signal sent by a direct current line protection, the control system controls 0 direct current through controlling direct current bias, and in the process of controlling 0 direct current, the 0 voltage or even negative voltage is presented between the direct current side ends of the converter valve.
11. The control method according to claim 9, wherein when the branch line is connected to the new energy source terminal converter station, the direct current breaker on the main line side of the branch line is opened, comprising, When judging that the branch line has a direct current line fault, immediately performing breaker breaking operation without delay; when the branch line is connected with the receiving-end converter station, the direct current breaker positioned on the main line side in the branch line is tripped, which comprises, When the direct current circuit fault of the branch circuit is judged, the circuit breaker is immediately opened without delay.
12. The control method of claim 9, wherein the step of adding ac power based on the surplus power comprises, When a bipolar operation monopole direct current line of a new energy source transmitting end converter station fails, inputting alternating current energy consumption into a power grid to consume surplus monopole power, namely inputting alternating current energy consumption Prt1=max { Ps11- (Pg 1- (Pfy 1-Ps11-Ps 21)) and 0}, wherein Ps11 is the fault pole operation power of the new energy source transmitting end converter station, ps21 is the other pole operation power, pg1 is the maximum power which can be consumed by the alternating current power grid, and Pfy is the new energy source operation power; When a bipolar direct current line of a new energy source transmitting end converter station runs in a bipolar mode, alternating current energy consumption is input as power which is still surplus after the bipolar surplus power is consumed by a power grid, namely, alternating current energy consumption Prt2=max { Ps12+Ps22- (Pg2- (Pfy-Ps 12-Ps 22)) 0}, wherein Ps12 is the monopolar running power of the new energy source transmitting end converter station, ps22 is the other pole running power, pg2 is the maximum power which can be consumed by the alternating current power grid, and Pfy is the new energy source running power; When a monopole operation monopole direct current circuit of the new energy source transmitting end convertor station fails, the input alternating current energy consumption is the surplus power of the monopole consumed by the power grid, namely, the input alternating current energy consumption Prt3=max { Ps13- (Pg 3- (Pfy-Ps 13)) and 0}, wherein Ps13 is the bipolar operation power of the new energy source convertor station, pg3 is the maximum power which can be consumed by the alternating current power grid, and Pfy is the operation power of the new energy source.
13. The control method according to claim 9, wherein the step of supplying the DC power to the branch line to which the receiving-side converter station is connected outside the branch line and controlling the DC voltage includes, The direct current energy consumption adopts independent distributed direct current energy consumption or centralized direct current energy consumption, when the port direct current voltage UDC is larger than a first voltage fixed value UDC1, the direct current energy consumption is put into a direct current voltage closed-loop control mode, and at the moment, the direct current voltage reference value is smaller than the first voltage fixed value, and when the direct current voltage is smaller than a second voltage fixed value UDC2, the direct current energy consumption is withdrawn, wherein the second voltage fixed value UDC2 is smaller than the direct current voltage reference value; The direct current energy consumption is in a self-balancing valve mode integrated with the soft direct current converter valve, when the voltage UV of any submodule is larger than a third voltage fixed value UV1, all bridge arm submodules are put into energy consumption resistors, and when the voltage of all submodules is smaller than a fourth voltage fixed value UV2, all the energy consumption resistors are withdrawn, wherein the third voltage fixed value UV1 is larger than the fourth voltage fixed value UV2.
14. The control method of claim 9, wherein restarting the actively step-down converter station to step-up voltage and reclosing the tripped circuit breaker includes, Controlling the step-up of the actively step-down converter station until the direct current voltage rises to the rated voltage; and when the direct current voltage is maintained at the rated voltage within the set time, the breaker is controlled to be closed.
15. The control method according to claim 9, wherein when it is judged that the restart of the converter station has failed, further comprising, If the current transformer station is a receiving-end current transformer station, the other current transformer stations evenly distribute the exiting power, if all the remaining receiving-end current transformer stations can bear power smaller than the sum of the power sent by the sending-end current transformer stations, the sending-end current transformer stations reduce the sending-out power in proportion by taking the exiting power as a reference, and if the current transformer station is the sending-end current transformer station, the remaining receiving-end current transformer stations reduce the power in proportion by taking the exiting power as a reference.
16. A control device of a multi-terminal direct current system is characterized by comprising, The system comprises a fault processing module, a power supply module and a power supply module, wherein the fault processing module is configured to act according to a device connected with a branch circuit when the branch circuit fails and is used for actively reducing the voltage of the converter station connected with the branch circuit when the branch circuit is connected with a new energy source transmitting end converter station, and switching off a direct current breaker positioned at the main circuit side in the branch circuit and inputting alternating current energy according to the surplus power condition; A restarting module configured to restart the actively step-down converter station to step up and reclose the tripped circuit breaker after arc extinction of the DC line, and And the judging module is configured to lock the converter station of the branch line where the direct current line fault is located and disconnect the breaker of the branch line where the direct current line fault is located when judging that the restarting of the converter station fails after the fault processing module and the restarting module repeatedly act for the designated times.
17. The control device according to claim 16, wherein the step-down of the converter station to which the branch line is connected when the branch line is connected to the new energy source terminal converter station is actively performed includes, After the control system receives the line fault state signal sent by the direct current line protection, the control system controls the direct current bias to carry out 0 direct current control, and in the process of controlling 0 direct current, the direct current side ends of the converter valves present 0 voltage or even negative voltage; when the branch line is connected with the receiving end converter station, the converter station connected with the branch line is actively depressurized, comprising, The valve topology of the converter station is a hybrid bridge mode constructed by a full bridge and a half bridge, and can output 0 voltage or even negative voltage, and after the control system receives a line fault state signal sent by a direct current line protection, the control system controls 0 direct current through controlling direct current bias, and in the process of controlling 0 direct current, the 0 voltage or even negative voltage is presented between the direct current side ends of the converter valve.
18. The control device according to claim 16, wherein the direct current breaker on the main line side of the branch line is opened when the branch line is connected to the new energy source terminal converter station, When judging that the branch line has a direct current line fault, immediately performing breaker breaking operation without delay; when the branch line is connected with the receiving-end converter station, the direct current breaker positioned on the main line side in the branch line is tripped, which comprises, When the direct current circuit fault of the branch circuit is judged, the circuit breaker is immediately opened without delay.
19. The control device of claim 16, wherein the step of charging the AC power based on the surplus power comprises, When a bipolar operation monopole direct current line of a new energy source transmitting end converter station fails, inputting alternating current energy consumption into a power grid to consume surplus monopole power, namely inputting alternating current energy consumption Prt1=max { Ps11- (Pg 1- (Pfy 1-Ps11-Ps 21)) and 0}, wherein Ps11 is the fault pole operation power of the new energy source transmitting end converter station, ps21 is the other pole operation power, pg1 is the maximum power which can be consumed by the alternating current power grid, and Pfy is the new energy source operation power; When a bipolar direct current line of a new energy source transmitting end converter station runs in a bipolar mode, alternating current energy consumption is input as power which is still surplus after the bipolar surplus power is consumed by a power grid, namely, alternating current energy consumption Prt2=max { Ps12+Ps22- (Pg2- (Pfy-Ps 12-Ps 22)) 0}, wherein Ps12 is the monopolar running power of the new energy source transmitting end converter station, ps22 is the other pole running power, pg2 is the maximum power which can be consumed by the alternating current power grid, and Pfy is the new energy source running power; When a monopole operation monopole direct current circuit of the new energy source transmitting end convertor station fails, the input alternating current energy consumption is the surplus power of the monopole consumed by the power grid, namely, the input alternating current energy consumption Prt3=max { Ps13- (Pg 3- (Pfy-Ps 13)) and 0}, wherein Ps13 is the bipolar operation power of the new energy source convertor station, pg3 is the maximum power which can be consumed by the alternating current power grid, and Pfy is the operation power of the new energy source.
20. The control device according to claim 16, wherein the direct current power consumption of the branch line to which the receiving-end converter station is connected outside the branch line is input and the direct current voltage is controlled, comprising, The direct current energy consumption adopts independent distributed direct current energy consumption or centralized direct current energy consumption, when the port direct current voltage UDC is larger than a first voltage fixed value UDC1, the direct current energy consumption is put into a direct current voltage closed-loop control mode, and at the moment, the direct current voltage reference value is smaller than the first voltage fixed value, and when the direct current voltage is smaller than a second voltage fixed value UDC2, the direct current energy consumption is withdrawn, wherein the second voltage fixed value UDC2 is smaller than the direct current voltage reference value; The direct current energy consumption is in a self-balancing valve mode integrated with the soft direct current converter valve, when the voltage UV of any submodule is larger than a third voltage fixed value UV1, all bridge arm submodules are put into energy consumption resistors, and when the voltage of all submodules is smaller than a fourth voltage fixed value UV2, all the energy consumption resistors are withdrawn, wherein the third voltage fixed value UV1 is larger than the fourth voltage fixed value UV2.

Description

Multi-terminal direct current system, configuration method, control method and control device thereof Technical Field The invention belongs to the field of power electronic converters, and in particular relates to a multi-terminal direct current system, a configuration method of energy consumption and a breaker in the multi-terminal direct current system, and a control method and a control device of the multi-terminal direct current system. Background With the proposal of the 'double carbon' target and the implementation of the green low-carbon energy development strategy, china faces the strategic adjustment of the energy structure, and the large-scale development of new energy sources such as wind power, solar energy and the like is currently being comprehensively promoted. The large-scale new energy base of our country is mainly distributed in the area of 'three north', is generally at the end of the power grid, has weaker power grid, is thousands of kilometers away from the load center of the middle east, has great open sea wind power development potential in the middle east, but has long offshore distance and lacks power grid support. And the geographical position factor of the new energy power generation field shows the condition of centralized access of new energy sources such as large-scale wind power, photovoltaic and the like. By utilizing the voltage source characteristic of flexible direct current transmission, large-scale new energy can be accessed into a power grid through multi-terminal flexible direct current transmission in an island or networking mode to transmit power to a plurality of receiving-terminal converter stations, and the feasibility of the implementation of experimental demonstration engineering of the multi-terminal direct current power grid of the north flexible looped network type of +/-500 kV is proved at present. However, with the development of Sha Gehuang new energy sources, the transmission distance is further and further increased, the multi-terminal flexible direct current transmission system is generally in a radial parallel connection form with a main line for saving cost, and the converter valve is generally in a hybrid bridge structure capable of actively reducing voltage, such as the approved Tibetan southeast project and the Mongolian heavy project under study, which adopt the multi-terminal flexible direct current transmission topology and the converter valve topology. This topology is based on the advantage that the hybrid bridge can be used without a circuit breaker in case of a dc line fault, whereas when one of the branches fails, all converter stations have to actively step down and interrupt the power delivery of the faulty pole, which undoubtedly enlarges the fault range. The relay protection has the advantages that an isolated fault line is protected on an alternating current line, the requirement of a fault range is not enlarged, and correspondingly, the direct current line protection needs to be optimized. Considering that the fault power of the main line is completely interrupted, at the moment, all the converter stations interrupt power transmission, and all the converter stations step down and the fault range is not enlarged, one feasible way is to arrange direct current breakers at both ends of all branch lines, however, the cost is obviously increased, the advantage of active step down of a hybrid bridge is wasted, and in addition, the problem of surplus power dissipation after the fault direct current line is isolated is also required to be solved because of the lack of a ring network in the radial parallel system. Therefore, there is a need to develop a method for dissipating surplus power after isolating a faulty dc line and a configuration method capable of reducing the number of circuit breakers. Disclosure of Invention The invention aims to provide a multi-terminal direct current system, a configuration method, a control method and a control device thereof, which are used for realizing the suppression of alternating current and direct current overvoltage after fault ride-through or locking of a modularized multi-level converter and meeting the operation requirement of a new energy source through a flexible direct island transmission system. In order to achieve the above object, the solution of the present invention is: A configuration method of energy consumption and circuit breaker in a multi-terminal direct current system comprises a main line and a plurality of branch lines connected with the main line respectively, wherein each branch line is connected with a transmitting-end converter station or a receiving-end converter station, The alternating current energy consumption is configured at a new energy source transmitting end converter station, and the capacity of the alternating current energy consumption is configured according to the consumption capacity of an alternating current power grid; the direct current energy consumption is c