Multi-terminal direct current system and configuration method, control method and control device thereof
By configuring AC and DC power consumption in a multi-terminal DC system and combining it with control methods, the problems of surplus power absorption and the number of circuit breakers after isolating faulty DC lines were solved, thus achieving effective control of the fault range and system stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NR ELECTRIC CO LTD
- Filing Date
- 2025-12-25
- Publication Date
- 2026-05-08
AI Technical Summary
In multi-terminal flexible DC transmission systems, the issues of absorbing surplus power after isolating faulty DC lines and configuring the number of circuit breakers lead to increased costs and expanded fault range.
In a multi-terminal DC system, AC and DC power consumption are configured. DC circuit breakers are only installed on the branch lines near the main line, while no circuit breakers are installed on the main line. The circuit breakers are tripped during a fault by a control method, and power consumption is used to absorb the surplus power. After restarting, the voltage and power are restored.
It effectively suppresses the power surplus problem of radial parallel multi-terminal flexible DC systems, reduces the number of DC circuit breakers, achieves effective isolation of faulty lines and stable operation of non-faulty stations, and reduces the scope of fault impact.
Smart Images
Figure CN122000978A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of power electronic converters, and more specifically, relates to a multi-terminal DC system and a method for configuring energy consumption and circuit breakers therein, as well as a control method and control device for a multi-terminal DC system. Background Technology
[0002] With the introduction of the "dual carbon" target and the implementation of the green and low-carbon energy development strategy, my country is facing a strategic adjustment of its energy structure and is currently comprehensively promoting the large-scale development of new energy sources such as wind power and solar energy. my country's large-scale new energy bases are mainly distributed in the "Three Norths" region (Northeast, North, and Northwest China), generally located at the end of the power grid, where the grid is relatively weak and thousands of kilometers away from the load centers in the central and eastern regions. While the central and eastern regions have great potential for offshore wind power development, their long distances from the coast and lack of grid support mean that these areas are geographically isolated. Due to the geographical location of new energy power plants, there is a concentrated connection of large-scale wind and solar power. Utilizing the voltage source characteristics of flexible DC transmission, large-scale new energy sources can be connected to the grid via multi-terminal flexible DC transmission in an islanded or interconnected manner, supplying power to multiple receiving-end converter stations. The feasibility of this has been proven by the implementation of the ±500 kV Zhangbei flexible ring network multi-terminal DC grid pilot demonstration project.
[0003] However, with the development of new energy sources in the desert and the increasing distance of power transmission, multi-terminal flexible DC transmission systems generally adopt a radial parallel configuration with a main trunk line to save costs. Furthermore, converter valves often employ a hybrid bridge structure with active voltage reduction capabilities. For example, the approved Southeast Tibet project and the Inner Mongolia West National Key Project, which is still under research, both use this multi-terminal flexible DC transmission topology and converter valve topology. While this topology, based on the advantage of the hybrid bridge, allows for the elimination of circuit breakers during DC line faults, a fault in one branch line necessitates active voltage reduction and interruption of power transmission to all converter stations, undoubtedly expanding the fault range. Relay protection in AC line protection requires isolating faulty lines and preventing the expansion of the fault range; correspondingly, optimization of DC line protection is also necessary. Considering that the power of the main line is completely interrupted during a fault, all converter stations will also stop transmitting power. The voltage reduction of all converter stations will not expand the scope of the fault. Therefore, a feasible approach is to configure DC circuit breakers at both ends of all branch lines. However, this undoubtedly increases costs and wastes the advantages of the hybrid bridge active voltage reduction. In addition, since the radial parallel system does not have a ring network, the problem of absorbing the surplus power after the faulty DC line is isolated also needs to be solved.
[0004] Therefore, there is an urgent need to study a method for absorbing surplus power after isolating a faulty DC line and a configuration method that can reduce the number of circuit breakers, which led to this case. Summary of the Invention
[0005] The purpose of this invention is to provide a multi-terminal DC system and its configuration method, control method and control device, for suppressing AC and DC overvoltages after fault ride-through or blocking of modular multilevel converters, so as to meet the operation requirements of the new energy transmission system via flexible DC islanding.
[0006] To achieve the above objectives, the solution of the present invention is:
[0007] A method for configuring energy consumption and circuit breakers in a multi-terminal DC system, wherein the multi-terminal DC system includes a main line and several branch lines respectively connected to the main line, and each branch line is connected to a sending-end converter station or a receiving-end converter station; including,
[0008] The AC energy consumption is configured at the converter station at the new energy sending end, and the capacity of the AC energy consumption is configured according to the absorption capacity of the AC power grid.
[0009] DC power consumption is configured at each receiving-end converter station, and the capacity of the DC power consumption is configured according to the capacity of the receiving-end converter station of the branch line to which it is located.
[0010] DC circuit breakers are installed on the side of each branch line close to the main line, while no circuit breakers are installed on the main line.
[0011] The capacity for AC energy consumption is configured based on the AC power grid's absorption capacity, including:
[0012] The capacity for AC energy consumption is the difference between the maximum operating power of the new energy source and the maximum power that the grid can absorb.
[0013] The DC power consumption is configured in each receiving-end converter station, including,
[0014] DC power consumption can be achieved through independent centralized or distributed power consumption, or through a self-balancing valve integrated with the flexible DC converter valve.
[0015] The DC power consumption capacity is configured based on the capacity of the receiving-end converter station of its branch line, including:
[0016] The capacity of the DC power consumption is configured to be the capacity of the receiving-end converter station of its branch line.
[0017] A multi-terminal DC system includes a main line and several branch lines respectively connected to the main line, each branch line being connected to a sending-end converter station or a receiving-end converter station; including,
[0018] When the multi-terminal DC system includes AC energy consumption, the AC energy consumption is configured on the branch line connected to the new energy sending-end converter station, and the capacity of the AC energy consumption is configured according to the AC grid absorption capacity.
[0019] When the multi-terminal DC system includes DC power consumption, the DC power consumption is configured on the branch line connected to the receiving-end converter station, and the capacity of the DC power consumption is configured according to the capacity of the receiving-end converter station on the branch line.
[0020] When the multi-terminal DC system includes DC circuit breakers, the DC circuit breakers are configured on the side of each branch line close to the main line, and no circuit breakers are configured on the main line.
[0021] The capacity for AC energy consumption is configured based on the AC power grid's absorption capacity, including:
[0022] The capacity for AC energy consumption is the difference between the maximum operating power of the new energy source and the maximum power that the grid can absorb.
[0023] The DC power consumption is configured in each receiving-end converter station, including,
[0024] DC power consumption can be achieved through independent centralized or distributed power consumption, or through a self-balancing valve integrated with the flexible DC converter valve.
[0025] The DC power consumption capacity is configured based on the capacity of the receiving-end converter station of its branch line, including:
[0026] The capacity of the DC power consumption is configured to be the capacity of the receiving-end converter station of its branch line.
[0027] A control method for a multi-terminal DC system, comprising,
[0028] When a DC line fault occurs on a branch line, the system operates according to the devices connected to that branch line. Specifically, when the branch line is connected to a new energy sending-end converter station, the system actively reduces the voltage of the converter station connected to the branch line, trips the DC circuit breaker on the main line side of the branch line, and starts AC power consumption based on the power surplus. When the branch line is connected to a receiving-end converter station, the system actively reduces the voltage of the converter station connected to the branch line, trips the DC circuit breaker on the main line side of the branch line, starts DC power consumption on the branch line connected to the receiving-end converter station outside the branch line, and controls the DC voltage.
[0029] After the DC line is extinguished, the converter station that has been actively stepped down will be restarted to step up, and the tripped circuit breaker will be reclosed.
[0030] After repeating the above operation a specified number of times, if it is determined that the converter station has failed to restart, the converter station of the branch line where the DC line fault is located is blocked, and the circuit breaker of the branch line where the DC line fault is located is disconnected.
[0031] Specifically, when a branch line connects to a converter station at the new energy sending end, the converter station connected to that branch line will be actively stepped down in voltage, including...
[0032] The valve topology of the converter station is a hybrid bridge mode constructed from full bridge and half bridge, which can output 0 voltage or even negative voltage. After the control system receives the line fault status signal sent by the DC line protection, the control system performs 0 DC current control by controlling the DC bias. During the process of controlling 0 DC current, the DC side terminals of the converter valve present 0 voltage or even negative voltage.
[0033] When a branch line connects to a receiving-end converter station, the converter station to which the branch line is connected is actively stepped down, including:
[0034] The valve topology of the converter station is a hybrid bridge mode constructed from full-bridge and half-bridge, which can output 0 voltage or even negative voltage. After the control system receives the line fault status signal sent by the DC line protection, the control system performs 0 DC current control by controlling the DC bias. During the process of controlling 0 DC current, the DC side terminals of the converter valve present 0 voltage or even negative voltage.
[0035] When a branch line connects to a new energy transmission-end converter station, the DC circuit breaker located on the main line side of that branch line is tripped, including:
[0036] When a DC line fault is detected in the branch line, the circuit breaker should be disconnected immediately without delay.
[0037] When a branch line connects to the receiving-end converter station, the DC circuit breaker on the main line side of that branch line is tripped, including:
[0038] When a DC line fault is detected in the branch line, the circuit breaker should be disconnected immediately without delay.
[0039] Among these, the allocation of AC energy based on power surplus includes,
[0040] When a single-pole DC line fault occurs during bipolar operation of the new energy sending-end converter station, the AC energy input is the power remaining after the grid has absorbed the surplus power of the single pole, i.e., the AC energy input Prt1=max{Ps11-(Pg1-(Pfy1-Ps11-Ps21)),0}, where Ps11 is the operating power of the faulty pole of the new energy sending-end converter station, Ps21 is the operating power of the other pole, Pg1 is the maximum power that the AC grid can absorb, and Pfy1 is the operating power of the new energy.
[0041] When a bipolar DC line fault occurs in the bipolar operation of the new energy sending-end converter station, the AC energy input is the power that is still surplus after the grid absorbs the bipolar surplus power, that is, the AC energy input Prt2=max{Ps12+Ps22-(Pg2-(Pfy2-Ps12-Ps22)), 0}, where Ps12 is the single-pole operating power of the new energy sending-end converter station, Ps22 is the operating power of the other pole, Pg2 is the maximum power that the AC grid can absorb, and Pfy12 is the new energy operating power;
[0042] When a single-pole DC line fault occurs during the operation of a new energy converter station, the AC energy consumption is the power remaining after the grid has absorbed the surplus power of the single pole, i.e., the AC energy consumption Prt3=max{Ps13-(Pg3-(Pfy3-Ps13)), 0}, where Ps13 is the bipolar operating power of the new energy converter station, Pg3 is the maximum power that the AC grid can absorb, and Pfy3 is the operating power of the new energy.
[0043] The DC energy consumption and DC voltage control of the branch lines connected to the receiving-end converter station outside the branch line include,
[0044] DC power consumption adopts independent distributed DC power consumption or centralized DC power consumption. When the port DC voltage UDC is greater than the first voltage setpoint UDC1, DC power consumption is activated and the DC voltage closed-loop control mode is entered. At this time, the DC voltage reference value is less than the first voltage setpoint. When the DC voltage is less than the second voltage setpoint UDC2, DC power consumption is deactivated. Wherein, the second voltage setpoint UDC2 is less than the DC voltage reference value.
[0045] The DC power consumption adopts a self-balancing valve integrated with the flexible DC converter valve. When any submodule voltage UV is greater than the third voltage setting UV1, all bridge arm submodules activate the power consumption resistor; when all submodule voltages are less than the fourth voltage setting UV2, all power consumption resistors are deactivated. Among them, the third voltage setting UV1 is greater than the fourth voltage setting UV2.
[0046] This includes restarting converter stations that have actively stepped down to boost voltage, and reclosing tripped circuit breakers, including...
[0047] Control the active step-down converter station to boost the DC voltage until it reaches the rated voltage;
[0048] When the DC voltage is maintained at the rated voltage for a set time, the circuit breaker is controlled to close.
[0049] The determination of whether the converter station restart has failed also includes,
[0050] If this station is a receiving-end converter station, the power to be withdrawn from the station is distributed equally among the other converter stations. If the power that all the remaining receiving-end converter stations can withstand is less than the sum of the power transmitted by the sending-end converter stations, then the sending-end converter stations reduce their transmission power proportionally based on the power to be withdrawn from the station. If this station is a sending-end converter station, the remaining receiving-end converter stations reduce their power proportionally based on the power to be withdrawn from the station.
[0051] A control device for a multi-terminal DC system, comprising,
[0052] The fault handling module is configured to take action based on the devices connected to the branch line when a DC line fault occurs on the branch line. Specifically, when the branch line is connected to a new energy sending-end converter station, the module will actively reduce the voltage of the converter station connected to the branch line, trip the DC circuit breaker on the main line side of the branch line, and start AC power consumption according to the power surplus. When the branch line is connected to a receiving-end converter station, the module will actively reduce the voltage of the converter station connected to the branch line, trip the DC circuit breaker on the main line side of the branch line, start DC power consumption on the branch line connected to the receiving-end converter station outside the branch line, and control the DC voltage.
[0053] The restart module, configured for DC line arc suppression, will restart the actively stepped-down converter station to boost voltage and reclose the tripped circuit breakers; and,
[0054] The judgment module is configured to, after the fault handling module and the restart module have repeated their actions a specified number of times, determine that the converter station has failed to restart, block the converter station on the branch line where the DC line fault is located, and disconnect the circuit breaker on the branch line where the DC line fault is located.
[0055] Specifically, when a branch line connects to a converter station at the new energy sending end, the converter station connected to that branch line will be actively stepped down in voltage, including...
[0056] The valve topology of the converter station is a hybrid bridge mode constructed from full bridge and half bridge, which can output 0 voltage or even negative voltage. After the control system receives the line fault status signal sent by the DC line protection, the control system performs 0 DC current control by controlling the DC bias. During the process of controlling 0 DC current, the DC side terminals of the converter valve present 0 voltage or even negative voltage.
[0057] When a branch line connects to a receiving-end converter station, the converter station to which the branch line is connected is actively stepped down, including:
[0058] The valve topology of the converter station is a hybrid bridge mode constructed from full-bridge and half-bridge, which can output 0 voltage or even negative voltage. After the control system receives the line fault status signal sent by the DC line protection, the control system performs 0 DC current control by controlling the DC bias. During the process of controlling 0 DC current, the DC side terminals of the converter valve present 0 voltage or even negative voltage.
[0059] When a branch line connects to a new energy transmission-end converter station, the DC circuit breaker located on the main line side of that branch line is tripped, including:
[0060] When a DC line fault is detected in the branch line, the circuit breaker should be disconnected immediately without delay.
[0061] When a branch line connects to the receiving-end converter station, the DC circuit breaker on the main line side of that branch line is tripped, including:
[0062] When a DC line fault is detected in the branch line, the circuit breaker should be disconnected immediately without delay.
[0063] Among these, the allocation of AC energy based on power surplus includes,
[0064] When a single-pole DC line fault occurs during bipolar operation of the new energy sending-end converter station, the AC energy input is the power remaining after the grid has absorbed the surplus power of the single pole, i.e., the AC energy input Prt1=max{Ps11-(Pg1-(Pfy1-Ps11-Ps21)),0}, where Ps11 is the operating power of the faulty pole of the new energy sending-end converter station, Ps21 is the operating power of the other pole, Pg1 is the maximum power that the AC grid can absorb, and Pfy1 is the operating power of the new energy.
[0065] When a bipolar DC line fault occurs in the bipolar operation of the new energy sending-end converter station, the AC energy input is the power that is still surplus after the grid absorbs the bipolar surplus power, that is, the AC energy input Prt2=max{Ps12+Ps22-(Pg2-(Pfy2-Ps12-Ps22)), 0}, where Ps12 is the single-pole operating power of the new energy sending-end converter station, Ps22 is the operating power of the other pole, Pg2 is the maximum power that the AC grid can absorb, and Pfy12 is the new energy operating power;
[0066] When a single-pole DC line fault occurs during the operation of a new energy converter station, the AC energy consumption is the power remaining after the grid has absorbed the surplus power of the single pole, i.e., the AC energy consumption Prt3=max{Ps13-(Pg3-(Pfy3-Ps13)), 0}, where Ps13 is the bipolar operating power of the new energy converter station, Pg3 is the maximum power that the AC grid can absorb, and Pfy3 is the operating power of the new energy.
[0067] The DC energy consumption and DC voltage control of the branch lines connected to the receiving-end converter station outside the branch line include,
[0068] DC power consumption adopts independent distributed DC power consumption or centralized DC power consumption. When the port DC voltage UDC is greater than the first voltage setpoint UDC1, DC power consumption is activated and the DC voltage closed-loop control mode is entered. At this time, the DC voltage reference value is less than the first voltage setpoint. When the DC voltage is less than the second voltage setpoint UDC2, DC power consumption is deactivated. Wherein, the second voltage setpoint UDC2 is less than the DC voltage reference value.
[0069] The DC power consumption adopts a self-balancing valve integrated with the flexible DC converter valve. When any submodule voltage UV is greater than the third voltage setting UV1, all bridge arm submodules activate the power consumption resistor; when all submodule voltages are less than the fourth voltage setting UV2, all power consumption resistors are deactivated. Among them, the third voltage setting UV1 is greater than the fourth voltage setting UV2.
[0070] The restart module will restart the converter station that has been actively stepped down and boost the voltage, and will reclose the tripped circuit breakers, including...
[0071] Control the active step-down converter station to boost the DC voltage until it reaches the rated voltage;
[0072] After a set delay time, the circuit breaker is closed.
[0073] When the judgment module determines that the converter station restart has failed, it also includes:
[0074] If this station is a receiving-end converter station, the power to be withdrawn from the station is distributed equally among the other converter stations. If the power that all the remaining receiving-end converter stations can withstand is less than the sum of the power transmitted by the sending-end converter stations, then the sending-end converter stations reduce their transmission power proportionally based on the power to be withdrawn from the station. If this station is a sending-end converter station, the remaining receiving-end converter stations reduce their power proportionally based on the power to be withdrawn from the station.
[0075] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; the processor executes the computer program to implement the steps of the control method for a multi-terminal DC system as described above.
[0076] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the steps of the control method for a multi-terminal DC system as described above.
[0077] After adopting the above scheme, the surplus power absorption method and energy consumption and circuit breaker configuration method after the faulty DC line isolation designed in this invention can, on the one hand, better suppress the power surplus problem caused by DC line isolation in radial parallel multi-terminal flexible DC lines with trunk lines, and on the other hand, better combine the advantages of DC circuit breakers and hybrid bridges, reduce the number of DC circuit breakers and achieve effective isolation of faulty lines, maintain the stable operation of non-faulty stations, reduce the impact range of DC faults, require fewer circuit breakers, have reliable principles, and are simple to implement. Attached Figure Description
[0078] Figure 1 This is a flowchart of the present invention. Detailed Implementation
[0079] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.
[0080] The invention will now be further explained with reference to the accompanying drawings.
[0081] A method for configuring energy consumption and circuit breakers in a multi-terminal DC system, wherein the configured multi-terminal DC system is as follows: Figure 1 The radial parallel configuration shown has a main line, and the control method is suitable for handling DC faults in branch lines.
[0082] The configuration method is as follows:
[0083] a) AC power consumption is configured at the converter station at the new energy sending end, and the capacity of AC power consumption is configured according to the absorption capacity of the AC power grid;
[0084] Specifically, the capacity configuration method for AC energy consumption is as follows: the maximum operating power of the new energy source is Pf, the maximum power that the AC grid can absorb is Pg, and the rated operating power of the flexible DC is Pm. Then, the capacity of AC energy consumption is the difference between the maximum operating power of the new energy source and the maximum power that the grid can absorb. That is, when the flexible DC experiences the most severe bipolar fault, the power cannot be transmitted at all, and the AC grid and AC energy consumption are required to completely absorb the power of the new energy source. This can be expressed by the formula: Pr = Pf - Pg.
[0085] b) DC circuit breakers are installed on the branch lines near the main line, and no circuit breakers are installed on the main line.
[0086] Specifically, the side of a branch line closer to the converter station is called the "branch line near converter station side," and the side of the branch line farther from the converter station is called the "branch line near main line side." One DC circuit breaker is configured on each pole on the "branch line near main line side," such as... Figure 1 The circuit breakers 1, 2, 3, and 4 are shown. For the sake of simplicity, only one bipolar circuit is drawn.
[0087] c) DC power consumption is configured at each receiving-end converter station, and the DC power consumption capacity is configured according to the capacity of the receiving-end converter station.
[0088] Specifically, the DC power consumption is configured on the receiving end branch line converter station side. Its topology can adopt independent centralized or distributed power consumption, or adopt a self-balancing valve form integrated with the flexible DC converter valve. Its total capacity is the capacity of the corresponding branch line converter station.
[0089] The control method is as follows:
[0090] d) If a DC line fault occurs in a branch line of the sending-end new energy station, the converter station of the branch line will actively reduce the voltage, the DC circuit breaker on the main line side will trip, and the AC energy consumption will be put into operation according to the power surplus.
[0091] Furthermore, the active voltage reduction method of the converter station for the branch line is as follows: the valve topology of the converter station adopts a hybrid bridge mode constructed by full bridge and half bridge, which can output 0 voltage or even negative voltage; after the control system receives the line fault status signal sent by the DC line protection, the control system performs 0 DC current control by controlling the DC bias. During the process of controlling 0 DC current, the DC side terminals of the converter valve present 0 voltage or even negative voltage.
[0092] Furthermore, the tripping method of the DC circuit breaker on the main line side is as follows: after the control system receives the line fault status signal sent by the DC line protection, the circuit breaker tripping operation is performed immediately without delay.
[0093] Specifically, the method for allocating AC energy based on power surplus is as follows:
[0094] If a single-pole DC line of a bipolar-operated renewable energy converter station fails, the surplus power is the single-pole operating power of the renewable energy converter station, Ps1. If the renewable energy operating power is Pfy and the other pole operating power is Ps2, then the AC energy consumption capacity required is the power remaining after the grid absorbs the single-pole surplus power. When the grid can fully absorb the surplus power, no AC energy consumption is required. This can be expressed by the formula: Prt=max{Ps1-(Pg-(Pfy-Ps1-Ps2)), 0}, where the remaining capacity of the AC grid to absorb surplus power is (Pg-(Pfy-Ps1-Ps2)), and Pfy-Ps1-Ps2 is the renewable energy power absorbed by the AC grid during normal operation.
[0095] If the bipolar DC line of the sending-end renewable energy converter station fails during bipolar operation, the surplus power is Ps1 + Ps2 of the renewable energy converter station's bipolar operation power. Then, the capacity required for AC energy consumption is the power that the grid still has surplus after absorbing the bipolar surplus power. When the grid can fully absorb the surplus power, no AC energy consumption is required. This can be expressed by the formula: Prt = max{Ps1 + Ps2 - (Pg - (Pfy - Ps1 - Ps2)), 0}, where the remaining capacity of the AC grid to absorb surplus power is (Pg - (Pfy - Ps1 - Ps2)), and Pfy - Ps1 - Ps2 is the renewable energy power absorbed by the AC grid during normal operation.
[0096] If a single-pole DC line fault occurs during the operation of a new energy converter station at the sending end, the surplus power is Ps1, which is the bipolar operating power of the new energy converter station. Then, the capacity required for AC energy consumption is the power that remains after the grid absorbs the single-pole surplus power. When the grid can fully absorb the surplus power, no AC energy consumption is required. This can be expressed by the formula: Prt=max{Ps1-(Pg-(Pfy-Ps1)), 0}, where the remaining capacity of the AC grid to absorb surplus power is (Pg-(Pfy-Ps1)), and Pfy-Ps1 is the new energy power absorbed by the AC grid during normal operation.
[0097] e) If a DC line fault occurs in a branch line of the receiving-end converter station, the receiving-end converter station of the branch line will actively reduce the voltage, the DC circuit breaker on the main line side will trip, and the DC power consumption of other receiving-end converter stations will be activated and the DC voltage will be controlled.
[0098] Furthermore, the active voltage reduction method of the converter station for the branch line is as follows: the valve topology of the converter station is a hybrid bridge mode constructed by full bridge and half bridge, which can output 0 voltage or even negative voltage; after the control system receives the line fault status signal sent by the DC line protection, the control system performs 0 DC current control by controlling the DC bias. During the process of controlling 0 DC current, the DC side terminals of the converter valve present 0 voltage or even negative voltage.
[0099] Furthermore, the tripping method of the DC circuit breaker on the main line side is as follows: after the control system receives the line fault status signal sent by the DC line protection, the circuit breaker tripping operation is performed immediately without delay.
[0100] Specifically, the methods for activating DC power consumption and controlling DC voltage at other receiving-end converter stations are as follows:
[0101] When DC power consumption adopts independent distributed DC power consumption or centralized DC power consumption, the control system judges the magnitude of the port DC voltage UDC. When UDC is greater than the voltage setpoint UDC1, DC power consumption is activated and enters the DC voltage closed-loop control mode, with the DC voltage reference value being UDCREF. When the DC voltage is less than the voltage setpoint UDC2, DC power consumption is deactivated. Here, UDCREF is less than UDC1, and UDC2 is less than UDCREF.
[0102] When the DC power consumption adopts a self-balancing valve integrated with the flexible DC converter valve, the valve controls the submodule voltage UV. When any submodule voltage is greater than the voltage setting UV1, all bridge arm submodules activate the power consumption resistor; when all submodule voltages are less than the voltage setting UV2, all power consumption resistors are deactivated. UV1 is greater than UV2.
[0103] f) After the DC line arc is extinguished, the converter station that actively stepped down restarts the voltage boost and the circuit breaker recloses;
[0104] Specifically, the method for restarting voltage boosting and reclosing the circuit breaker in an active step-down converter station is as follows: the active step-down converter station first boosts the voltage until the DC voltage reaches the rated voltage, at which point the circuit breaker remains open; after the DC voltage reaches the rated voltage for a certain period of time, the circuit breaker closes.
[0105] After the above process is repeated a specified number of times, if the restart is successful, the power will be restored and operation will continue. If the restart fails, the converter station will be locked, the circuit breaker will be opened, the power will be adjusted, and other converter stations will operate normally.
[0106] g) After the above process is repeated a specified number of times, if the restart is successful, the power will be restored and operation will continue. If the restart fails, the converter station will be locked, the circuit breaker will be opened, the power will be adjusted, and other converter stations will operate normally. If this station is a receiving-end converter station, the power to be withdrawn from the station will be distributed equally among the other converter stations. If the power that all remaining receiving-end converter stations can withstand is less than the sum of the power sent by the sending-end converter stations, the sending-end converter stations will reduce their power output proportionally based on the power to be withdrawn from the station. If this station is a sending-end converter station, the remaining receiving-end converter stations will reduce their power proportionally based on the power to be withdrawn from the station.
[0107] This invention also provides another computer device, including a processor and a memory configured to store a computer program capable of running on the processor; wherein, when the processor is configured to run the computer program, it performs the method steps described in the foregoing embodiments.
[0108] In practical applications, the aforementioned processor includes a Field-Programmable Gate Array (FPGA), and the processor can be a Central Processing Unit (CPU) or a Digital Signal Processor (DSP). It is understood that for different devices, the electronic devices used to implement the above-mentioned processor functions can also be other types, and this embodiment of the invention does not impose specific limitations.
[0109] The aforementioned memory can be volatile memory, such as random-access memory (RAM); or non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid-state drive (SSD); or a combination of the above types of memory, and provides instructions and data to the processor.
[0110] In an exemplary embodiment, the present invention also provides a computer-readable storage medium for storing a computer program.
[0111] Optionally, the computer-readable storage medium can be applied to any of the methods in the embodiments of the present invention, and the computer program causes the computer to execute the corresponding processes implemented by the processor in the various methods of the embodiments of the present invention. For the sake of brevity, these will not be described in detail here.
[0112] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.
[0113] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.
[0114] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.
[0115] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.
[0116] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.
[0117] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A method for configuring energy consumption and circuit breakers in a multi-terminal DC system, the multi-terminal DC system comprising a main line and several branch lines respectively connected to the main line, each branch line being connected to a sending-end converter station or a receiving-end converter station; characterized in that: include, The AC energy consumption is configured at the converter station at the new energy sending end, and the capacity of the AC energy consumption is configured according to the absorption capacity of the AC power grid. DC power consumption is configured at each receiving-end converter station, and the capacity of the DC power consumption is configured according to the capacity of the receiving-end converter station of the branch line to which it is located. DC circuit breakers are installed on the side of each branch line close to the main line, while no circuit breakers are installed on the main line.
2. The configuration method as described in claim 1, characterized in that: The capacity for AC energy consumption is configured based on the AC power grid's absorption capacity, including: The capacity for AC energy consumption is the difference between the maximum operating power of the new energy source and the maximum power that the grid can absorb.
3. The configuration method as described in claim 1, characterized in that: DC power consumption is configured in each receiving-end converter station, including, DC power consumption can be achieved through independent centralized or distributed power consumption, or through a self-balancing valve integrated with the flexible DC converter valve.
4. The configuration method as described in claim 1, characterized in that: The DC power consumption capacity is configured based on the capacity of the receiving-end converter station of its branch line, including, The capacity of the DC power consumption is configured to be the capacity of the receiving-end converter station of its branch line.
5. A multi-terminal DC system, the multi-terminal DC system comprising a main line and a plurality of branch lines respectively connected to the main line, each branch line being connected to a sending-end converter station or a receiving-end converter station; characterized in that: include, When the multi-terminal DC system includes AC energy consumption, the AC energy consumption is configured on the branch line connected to the new energy sending-end converter station, and the capacity of the AC energy consumption is configured according to the AC grid absorption capacity. When the multi-terminal DC system includes DC power consumption, the DC power consumption is configured on the branch line connected to the receiving-end converter station, and the capacity of the DC power consumption is configured according to the capacity of the receiving-end converter station on the branch line. When the multi-terminal DC system includes DC circuit breakers, the DC circuit breakers are configured on the side of each branch line close to the main line, and no circuit breakers are configured on the main line.
6. The multi-terminal DC system as described in claim 5, characterized in that: The capacity for AC energy consumption is configured based on the AC power grid's absorption capacity, including: The capacity for AC energy consumption is the difference between the maximum operating power of the new energy source and the maximum power that the grid can absorb.
7. The multi-terminal DC system as described in claim 5, characterized in that: DC power consumption is configured in each receiving-end converter station, including, DC power consumption can be achieved through independent centralized or distributed power consumption, or through a self-balancing valve integrated with the flexible DC converter valve.
8. The multi-terminal DC system as described in claim 5, characterized in that: The DC power consumption capacity is configured based on the capacity of the receiving-end converter station of its branch line, including, The capacity of the DC power consumption is configured to be the capacity of the receiving-end converter station of its branch line.
9. A control method for a multi-terminal DC system, characterized in that: include, When a DC line fault occurs on a branch line, the system operates according to the devices connected to that branch line. Specifically, when the branch line is connected to a new energy sending-end converter station, the system actively reduces the voltage of the converter station connected to the branch line, trips the DC circuit breaker on the main line side of the branch line, and starts AC power consumption based on the power surplus. When the branch line is connected to a receiving-end converter station, the system actively reduces the voltage of the converter station connected to the branch line, trips the DC circuit breaker on the main line side of the branch line, starts DC power consumption on the branch line connected to the receiving-end converter station outside the branch line, and controls the DC voltage. After the DC line is extinguished, the converter station that has been actively stepped down will be restarted to step up, and the tripped circuit breaker will be reclosed. After repeating the above operation a specified number of times, if it is determined that the converter station has failed to restart, the converter station of the branch line where the DC line fault is located is blocked, and the circuit breaker of the branch line where the DC line fault is located is disconnected.
10. The control method as described in claim 9, characterized in that: When a branch line connects to a converter station at the sending end of a new energy source, the converter station connected to that branch line is actively stepped down in voltage, including, The converter station's valve topology is a hybrid bridge mode constructed from full-bridge and half-bridge components, which can output 0 voltage or even negative voltage. After the control system receives the line fault status signal from the DC line protection, the control system performs 0 DC current control by controlling the DC bias. During the process of controlling 0 DC current, the DC side terminals of the converter valve present 0 voltage or even negative voltage. When a branch line connects to a receiving-end converter station, the converter station to which the branch line is connected is actively stepped down, including: The converter station's valve topology is a hybrid bridge mode constructed from full-bridge and half-bridge components, which can output 0 voltage or even negative voltage. After the control system receives the line fault status signal from the DC line protection, the control system performs zero DC current control by controlling the DC bias. During the process of controlling zero DC current, the DC side of the converter valve presents zero voltage or even negative voltage.
11. The control method as described in claim 9, characterized in that: When a branch line connects to a new energy transmission converter station, the DC circuit breaker on the main line side of that branch line is tripped, including: When a DC line fault is detected in the branch line, the circuit breaker should be disconnected immediately without delay. When a branch line connects to the receiving-end converter station, the DC circuit breaker on the main line side of that branch line is tripped, including: When a DC line fault is detected in the branch line, the circuit breaker should be disconnected immediately without delay.
12. The control method as described in claim 9, characterized in that: Based on the power surplus, AC energy is allocated for consumption, including: When a single-pole DC line fault occurs during bipolar operation of the new energy sending-end converter station, the AC energy input is the power remaining after the grid has absorbed the surplus power of the single pole, i.e., the AC energy input Prt1=max{Ps11-(Pg1-(Pfy1-Ps11-Ps21)), 0}, where Ps11 is the operating power of the faulty pole of the new energy sending-end converter station, Ps21 is the operating power of the other pole, Pg1 is the maximum power that the AC grid can absorb, and Pfy1 is the operating power of the new energy. When a bipolar DC line fault occurs in the bipolar operation of the new energy sending-end converter station, the AC energy consumption is the power that is still surplus after the grid absorbs the bipolar surplus power, that is, the AC energy consumption Prt2=max{Ps12+Ps22-(Pg2-(Pfy2-Ps12-Ps22)),0}, where Ps12 is the single-pole operating power of the new energy sending-end converter station, Ps22 is the operating power of the other pole, Pg2 is the maximum power that the AC grid can absorb, and Pfy12 is the new energy operating power; When a single-pole DC line fault occurs during the operation of a new energy converter station, the AC energy consumption is the power remaining after the grid has absorbed the surplus power of the single pole, i.e., the AC energy consumption Prt3=max{Ps13-(Pg3-(Pfy3-Ps13)), 0}, where Ps13 is the bipolar operating power of the new energy converter station, Pg3 is the maximum power that the AC grid can absorb, and Pfy3 is the operating power of the new energy.
13. The control method as described in claim 9, characterized in that: The DC power consumption and DC voltage control of branch lines connected to receiving-end converter stations outside this branch line include, DC power consumption adopts independent distributed DC power consumption or centralized DC power consumption. When the port DC voltage UDC is greater than the first voltage setpoint UDC1, DC power consumption is activated and the DC voltage closed-loop control mode is entered. At this time, the DC voltage reference value is less than the first voltage setpoint. When the DC voltage is less than the second voltage setpoint UDC2, DC power consumption is deactivated. Wherein, the second voltage setpoint UDC2 is less than the DC voltage reference value. The DC power consumption adopts a self-balancing valve integrated with the flexible DC converter valve. When any submodule voltage UV is greater than the third voltage setting UV1, all bridge arm submodules activate the power consumption resistor; when all submodule voltages are less than the fourth voltage setting UV2, all power consumption resistors are deactivated. Among them, the third voltage setting UV1 is greater than the fourth voltage setting UV2.
14. The control method as described in claim 9, characterized in that: Restarting the converter station that has been actively stepping down to boost voltage, and reclosing the tripped circuit breakers, including... Control the active step-down converter station to boost the DC voltage until it reaches the rated voltage; When the DC voltage is maintained at the rated voltage for a set time, the circuit breaker is controlled to close.
15. The control method as described in claim 9, characterized in that: When determining that the converter station restart has failed, the method also includes: If this station is a receiving-end converter station, the power to be withdrawn from the station is distributed equally among the other converter stations. If the power that all the remaining receiving-end converter stations can withstand is less than the sum of the power transmitted by the sending-end converter stations, then the sending-end converter stations reduce their transmission power proportionally based on the power to be withdrawn from the station. If this station is a sending-end converter station, the remaining receiving-end converter stations reduce their power proportionally based on the power to be withdrawn from the station.
16. A control device for a multi-terminal DC system, characterized in that: include, The fault handling module is configured to take action based on the devices connected to the branch line when a DC line fault occurs on the branch line. Specifically, when the branch line is connected to a new energy sending-end converter station, the module will actively reduce the voltage of the converter station connected to the branch line, trip the DC circuit breaker on the main line side of the branch line, and start AC power consumption according to the power surplus. When the branch line is connected to a receiving-end converter station, the module will actively reduce the voltage of the converter station connected to the branch line, trip the DC circuit breaker on the main line side of the branch line, start DC power consumption on the branch line connected to the receiving-end converter station outside the branch line, and control the DC voltage. The restart module, configured for DC line arc suppression, will restart the actively stepped-down converter station to boost voltage and reclose the tripped circuit breakers; and, The judgment module is configured to, after the fault handling module and the restart module have repeated their actions a specified number of times, determine that the converter station has failed to restart, block the converter station on the branch line where the DC line fault is located, and disconnect the circuit breaker on the branch line where the DC line fault is located.
17. The control device as claimed in claim 16, characterized in that: When a branch line connects to a converter station at the sending end of a new energy source, the converter station connected to that branch line is actively stepped down in voltage, including, The converter station's valve topology is a hybrid bridge mode constructed from full-bridge and half-bridge components, which can output 0 voltage or even negative voltage. After the control system receives the line fault status signal from the DC line protection, the control system performs 0 DC current control by controlling the DC bias. During the process of controlling 0 DC current, the DC side terminals of the converter valve present 0 voltage or even negative voltage. When a branch line connects to a receiving-end converter station, the converter station to which the branch line is connected is actively stepped down, including: The converter station's valve topology is a hybrid bridge mode constructed from full-bridge and half-bridge components, which can output 0 voltage or even negative voltage. After the control system receives the line fault status signal from the DC line protection, the control system performs zero DC current control by controlling the DC bias. During the process of controlling zero DC current, the DC side of the converter valve presents zero voltage or even negative voltage.
18. The control device as claimed in claim 16, characterized in that: When a branch line connects to a new energy transmission converter station, the DC circuit breaker on the main line side of that branch line is tripped, including: When a DC line fault is detected in the branch line, the circuit breaker should be disconnected immediately without delay. When a branch line connects to the receiving-end converter station, the DC circuit breaker on the main line side of that branch line is tripped, including: When a DC line fault is detected in the branch line, the circuit breaker should be disconnected immediately without delay.
19. The control device as claimed in claim 16, characterized in that: Based on the power surplus, AC energy is allocated for consumption, including: When a single-pole DC line fault occurs during bipolar operation of the new energy sending-end converter station, the AC energy input is the power remaining after the grid has absorbed the surplus power of the single pole, i.e., the AC energy input Prt1=max{Ps11-(Pg1-(Pfy1-Ps11-Ps21)), 0}, where Ps11 is the operating power of the faulty pole of the new energy sending-end converter station, Ps21 is the operating power of the other pole, Pg1 is the maximum power that the AC grid can absorb, and Pfy1 is the operating power of the new energy. When a bipolar DC line fault occurs in the bipolar operation of the new energy sending-end converter station, the AC energy consumption is the power that is still surplus after the grid absorbs the bipolar surplus power, that is, the AC energy consumption Prt2=max{Ps12+Ps22-(Pg2-(Pfy2-Ps12-Ps22)),0}, where Ps12 is the single-pole operating power of the new energy sending-end converter station, Ps22 is the operating power of the other pole, Pg2 is the maximum power that the AC grid can absorb, and Pfy12 is the new energy operating power; When a single-pole DC line fault occurs during the operation of a new energy converter station, the AC energy consumption is the power remaining after the grid has absorbed the surplus power of the single pole, i.e., the AC energy consumption Prt3=max{Ps13-(Pg3-(Pfy3-Ps13)), 0}, where Ps13 is the bipolar operating power of the new energy converter station, Pg3 is the maximum power that the AC grid can absorb, and Pfy3 is the operating power of the new energy.
20. The control device as claimed in claim 16, characterized in that: The DC power consumption and DC voltage control of branch lines connected to receiving-end converter stations outside this branch line include, DC power consumption adopts independent distributed DC power consumption or centralized DC power consumption. When the port DC voltage UDC is greater than the first voltage setpoint UDC1, DC power consumption is activated and the DC voltage closed-loop control mode is entered. At this time, the DC voltage reference value is less than the first voltage setpoint. When the DC voltage is less than the second voltage setpoint UDC2, DC power consumption is deactivated. Wherein, the second voltage setpoint UDC2 is less than the DC voltage reference value. The DC power consumption adopts a self-balancing valve integrated with the flexible DC converter valve. When any submodule voltage UV is greater than the third voltage setting UV1, all bridge arm submodules activate the power consumption resistor; when all submodule voltages are less than the fourth voltage setting UV2, all power consumption resistors are deactivated. Among them, the third voltage setting UV1 is greater than the fourth voltage setting UV2.
21. The control device as claimed in claim 16, characterized in that: The restart module will restart the converter station that has been actively stepping down to step up, and will reclose the tripped circuit breakers, including... Control the active step-down converter station to boost the DC voltage until it reaches the rated voltage; After a set delay time, the circuit breaker is closed.
22. The control device as described in claim 16, characterized in that: When the judgment module determines that the converter station restart has failed, it also includes: If this station is a receiving-end converter station, the power to be withdrawn from the station is distributed equally among the other converter stations. If the power that all the remaining receiving-end converter stations can withstand is less than the sum of the power transmitted by the sending-end converter stations, then the sending-end converter stations reduce their transmission power proportionally based on the power to be withdrawn from the station. If this station is a sending-end converter station, the remaining receiving-end converter stations reduce their power proportionally based on the power to be withdrawn from the station.
23. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, it implements the steps of the control method for a multi-terminal DC system as described in any one of claims 9 to 15.
24. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by the processor, it implements the steps of the control method for a multi-terminal DC system as described in any one of claims 9 to 15.