CN110581539B - Protection device and protection method for direct-current power distribution network - Google Patents
Protection device and protection method for direct-current power distribution network Download PDFInfo
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- CN110581539B CN110581539B CN201910980255.1A CN201910980255A CN110581539B CN 110581539 B CN110581539 B CN 110581539B CN 201910980255 A CN201910980255 A CN 201910980255A CN 110581539 B CN110581539 B CN 110581539B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/025—Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
- H02H9/023—Current limitation using superconducting elements
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment
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Abstract
The embodiment of the invention discloses a protection device and a protection method for a direct-current power distribution network. Wherein, this direct current distribution network includes: at least two sub-distribution networks and at least one bus bar connection line; any of the power distribution sub-networks includes: the system comprises an incoming line, at least one bus and at least one feeder line, wherein the incoming line is electrically connected with the at least one bus, the at least one bus is electrically connected with the at least one feeder line, and two ends of any bus connecting line are respectively electrically connected with the buses in the two power distribution sub-networks; this a protection device for direct current distribution network includes: and any current limiter is used for entering a current limiting mode to limit the current on the corresponding bus connecting line when the current on the corresponding bus connecting line is greater than or equal to a first preset current. According to the technical scheme of the embodiment of the invention, the fault side and the non-fault side of the direct-current power distribution network can be isolated, and the fault side can conveniently remove the fault.
Description
Technical Field
The invention relates to the technical field of power systems, in particular to a protection device and a protection method for a direct-current power distribution network.
Background
In a typical 'hand-in-hand' and double-end looped network direct current power distribution system, due to the weak damping characteristic of the direct current system, when a short-circuit fault occurs on one feeder, the direct current has the characteristics of one fault and whole network feeling because the rising speed of the direct current is higher and is far greater than that of a normal load current, so that one short-circuit fault and whole network power loss are caused, and the power supply continuity and reliability of the direct current power distribution system are directly influenced.
Disclosure of Invention
The embodiment of the invention provides a protection device and a protection method for a direct current power distribution network, wherein a current limiter is arranged on a bus connecting line, so that short-circuit fault current can be quickly inhibited when a fault occurs, a fault side and a non-fault side are quickly isolated, the influence between the fault side and the non-fault side is reduced, the impact of the fault side on the non-fault side is reduced, the non-fault side is kept in a normal operation state, the current flowing into the fault side from the non-fault side is reduced, and the cut-off current of switches such as a direct current breaker is reduced, so that the fault can be conveniently removed.
In a first aspect, embodiments of the present invention provide a protection device for a dc power distribution network,
this direct current distribution network includes: at least two sub-distribution networks and at least one bus bar connection line;
wherein, any distribution sub-network includes: the system comprises an incoming line, at least one bus and at least one feeder line, wherein the incoming line is electrically connected with the at least one bus, the at least one bus is electrically connected with the at least one feeder line, and two ends of any bus connecting line are respectively electrically connected with the buses in the two power distribution sub-networks;
this a protection device for direct current distribution network includes: the current limiters are in one-to-one correspondence with the bus connecting lines, any current limiter is arranged on the corresponding bus connecting line, and any current limiter is used for entering a current limiting mode to limit the current on the corresponding bus connecting line when the current on the corresponding bus connecting line is larger than or equal to a first preset current.
Further, the flow restrictor comprises: superconducting current limiters or liquid metal current limiters.
Furthermore, any distribution sub-network also comprises a current converter, the input end of the current converter is electrically connected with the power supply end of the distribution sub-network, the output end of the current converter is electrically connected with the inlet wire,
the protection device for the direct-current power distribution network further comprises a fault positioning module, wherein the fault positioning module is electrically connected with the current converter and is used for identifying a fault position and sending a locking signal to the current converter in the power distribution sub-network where the fault position is located.
Furthermore, the protection device for the direct-current power distribution network further comprises a plurality of switches, the fault positioning module is electrically connected with the switches, the switches are arranged on the corresponding feeder lines, and the fault positioning module is further used for sending brake-separating signals to the switches corresponding to the feeder lines where the fault positions are located;
the switch is used for disconnecting when receiving a brake separating signal sent by the fault positioning module and the current on the feeder line corresponding to the switch is less than or equal to a second preset current.
Further, the switch includes a mechanical dc breaker, a hybrid dc breaker, a solid state dc breaker, or a current injection dc breaker.
Further, the fault location module is further configured to send an unlocking signal to a current converter in the distribution sub-network where the fault location is located after the switch corresponding to the feeder where the fault location is located is switched off, and then send a control signal exiting the current limiting mode to the current limiter.
In a second aspect, an embodiment of the present invention further provides a protection method for a protection device for a dc power distribution network, where the protection method is provided in any embodiment of the present invention, and includes:
when the current of any current limiter on the corresponding bus connecting line is larger than or equal to a first preset current, the current limiter enters a current limiting mode to limit the current on the corresponding bus connecting line.
Furthermore, when any distribution sub-network also comprises an inverter, the protection device for the direct current distribution network also comprises a fault location module,
the protection method further comprises the following steps: and the fault positioning module identifies a fault position and sends a locking signal to a current converter in the power distribution sub-network where the fault position is located.
Further, when the protection device for a dc distribution network further comprises a plurality of switches,
the protection method further comprises the following steps: the fault positioning module sends a brake separating signal to a switch corresponding to a feeder line where a fault position is located;
and the switch is disconnected when receiving the opening signal sent by the fault positioning module and the current on the feeder line corresponding to the switch is less than or equal to a second preset current.
Further, the protection method further comprises: and the fault positioning module sends an unlocking signal to a current converter in the power distribution sub-network where the fault position is located, and then sends a control signal for exiting the current limiting mode to the current limiter.
According to the technical scheme of the embodiment of the invention, the current limiter is arranged on the bus connecting line connected with the power distribution sub-network, so that when the direct-current power distribution network has a fault, the fault side and the non-fault side of the direct-current power distribution network can be isolated through the current limiting effect of the current limiter, the influence between the fault side and the non-fault side is reduced, the impact of the fault side on the non-fault side is reduced, the non-fault side is kept in a normal operation state, the current flowing into the fault side from the non-fault side is reduced, the fault is conveniently cut off by the fault side, and the problems that when one feeder line has a short-circuit fault, the rising speed of the direct current is higher than that of normal load current, one fault exists, the whole network experiences the characteristics are solved, and the problems that one short-circuit fault, the whole network loses power and the power supply continuity and the reliability of the direct-current power distribution network are directly influenced are solved.
Drawings
Fig. 1 is a schematic structural diagram of a protection device for a dc power distribution network according to an embodiment of the present invention;
FIG. 2 is a cross-sectional structural diagram of a liquid metal current limiter according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a dc distribution network in case of a fault according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a dc power distribution network after a fault occurs and a current limiter limits current according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a protection device for a dc power distribution network according to another embodiment of the present invention;
fig. 6 is a schematic structural diagram of a dc power distribution network after a fault occurs and a current limiter limits current and an inverter is locked according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a dc power distribution network after a fault is removed according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of another protection device for a dc power distribution network according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of a dc power distribution network when an internal bus connection line fails according to an embodiment of the present invention;
fig. 10 is a flowchart of a protection method for a dc power distribution network according to an embodiment of the present invention;
fig. 11 is a flowchart of another protection method for a dc power distribution network according to an embodiment of the present invention;
fig. 12 is a flowchart of another protection method for a dc power distribution network according to an embodiment of the present invention;
fig. 13 is a flowchart of another protection method for a dc power distribution network according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The embodiment of the invention provides a protection device for a direct current power distribution network. Fig. 1 is a schematic structural diagram of a protection device for a dc power distribution network according to an embodiment of the present invention. This a protection device for direct current distribution network includes: at least one flow restrictor 10. Wherein, this direct current distribution network includes: at least two sub-distribution networks 20 and at least one bus bar connection 30. Fig. 1 exemplarily shows a case of two power distribution sub-networks, that is, a first power distribution sub-network 20-1 and a second power distribution sub-network 20-2, the number of the power distribution sub-networks in the embodiment of the present invention is not limited, and may be set according to needs, for example, three or more, and any two power distribution sub-networks are electrically connected through a bus bar connection line.
Wherein any one of the power distribution sub-networks 20 comprises: the power distribution system comprises an incoming line 21, at least one bus 22 and at least one feeder 23, wherein the incoming line 21 is electrically connected with the at least one bus 22, the at least one bus 22 is electrically connected with the at least one feeder 23, and two ends of any bus connecting line 30 are respectively electrically connected with the buses 22 in two power distribution sub-networks 20;
the current limiters 10 are in one-to-one correspondence with the bus connecting lines 30, any current limiter 10 is arranged on the corresponding bus connecting line 30, and any current limiter 10 is used for entering a current limiting mode to limit the current on the corresponding bus connecting line 30 when the current on the corresponding bus connecting line 30 is greater than or equal to a first preset current.
The dc distribution network may be a medium voltage dc distribution network, for example, the bus voltage may be 10 kv. The direct current distribution network can be a hand-in-hand direct current distribution network or a double-end looped network. Fig. 1 exemplarily shows a case where the dc distribution network is a hand-pulled dc distribution network. The incoming lines 21 of any of the sub-distribution networks are respectively connected with a power supply, and exemplarily, as shown in fig. 1, the incoming line 21 in the first sub-distribution network 20-1 is connected with the first power supply, and the incoming line 21 in the second sub-distribution network 20-2 is electrically connected with the second power supply. The feed line 23 may be electrically connected to a load, which may comprise a buck DC-DC switching converter. The current limiter 10 may be a bidirectional current limiter, i.e. the current limiter 10 may perform the function of limiting the fault current no matter which side of the current limiter 10 the sub-distribution network fails, whether the fault current is flowing from the first sub-distribution network 20-1 to the second sub-distribution network 20-2 or from the second sub-distribution network 20-2 to the first sub-distribution network 20-1. Optionally, the protection device for the dc power distribution network further includes at least one first current detection module, the first current detection module corresponds to the bus connection line one to one, the first current detection module is electrically connected to the corresponding current limiter, the first current detection module is configured to detect a current on the corresponding bus connection line, and when it is detected that the current on the bus connection line is greater than or equal to a first preset current, a control signal for controlling the current limiter to enter the current limiting mode is sent to the corresponding current limiter. Illustratively, the current limiter comprises a current limiting resistor and a direct current breaker which are connected in parallel, and the current limiter is controlled to enter a current limiting mode by controlling the opening of the direct current breaker, so that fault current flows through the current limiting resistor; by controlling the closing of the direct current breaker, the current limiter is controlled to exit the current limiting mode, the current limiting resistor is short-circuited, and the current in normal operation flows through the closed direct current breaker. The control signal for controlling the current limiter to enter the current limiting mode may be a signal for controlling the opening of a dc breaker of the current limiter. The control signal for controlling the current limiter to exit the current limiting mode may be a signal for controlling a dc circuit breaker of the current limiter to close. Optionally, the flow restrictor 10 comprises: superconducting current limiters or liquid metal current limiters. The current limiter can also comprise a hybrid superconducting current limiter, the hybrid superconducting current limiter comprises a superconducting current limiter and other devices, such as a fast mechanical switch and the like, a control module such as a first current detection module and the like is required to be arranged, and the on and off of the current limiting mode are realized by controlling the on and off of the fast mechanical switch. The current limiter can also comprise a hybrid liquid metal current limiter, namely the current limiter comprises a liquid metal current limiter and other devices, such as a fast mechanical switch, a resistor and the like, a control module such as a first current detection module and the like is required to be arranged, and the on and off of the fast mechanical switch are controlled to realize the on and off of the current limiting mode.
The current limiter can be an adaptive current limiter, for example, the current limiter can be a superconducting current limiter or a liquid metal current limiter, the self resistance value can be changed along with the current, and the current limiter automatically enters or exits the current limiting mode without arranging a first current detection module to control the opening and the exiting of the current limiting mode. The superconducting current limiter may include a superconductor coil, and both ends of the superconductor coil are connected to the bus bar connection lines. It should be noted that the superconductor has three basic characteristics, namely, zero resistance, Meissner (Meissner) effect and Josephson (Josephson) effect, and the critical temperature, the critical magnetic field and the critical current are three important parameters of the superconductor. When any parameter of the temperature, the magnetic field and the current exceeds a critical value, the superconducting magnet undergoes a phase change to become a constant conductor, and the process is called quench. The temperature, the magnetic field and the current need to be simultaneously less than the critical value, so that the superconducting state can be achieved. The operating temperature of the superconductor is kept constant, and the superconductor can be stably restored to a superconducting state only when the current flowing through the superconductor is reduced to be lower than a recovery current. When the current flowing through the superconducting current limiter is larger than a first preset current (which can be a current critical value), the superconductor of the superconducting current limiter is quenched, the resistance value is increased, the energy consumption is increased, the temperature is increased, the resistance value is continuously increased, the current is reduced, the energy consumption is reduced, the temperature begins to be reduced, and when the temperature is reduced to the temperature critical value, the superconductor state is recovered to a superconducting state. A temperature drop to the critical temperature value requires a temperature recovery time on the order of seconds, which is sufficient to complete the fault clearance.
Fig. 2 is a cross-sectional structural diagram of a liquid metal flow restrictor according to an embodiment of the present invention. The liquid metal current limiter can comprise a shell 1, a sealing cover 7 and two opposite electrodes 5 positioned at two ends of the shell, the two electrodes 5 can be respectively connected onto a bus connecting wire, liquid metal 4 and air 8 are contained in a cavity of the shell 1, at least one insulating partition plate 6 is arranged in the cavity, the insulating partition plate 6 is positioned between the two electrodes 5, through holes 3 are formed in the insulating partition plate 6, the liquid metal 4 is positioned between the insulating partition plate 6 and the electrodes 5, and ceramic plates 2 are arranged on at least one electrode 5. When the liquid metal current limiter does not limit current, the liquid metal 4 can flow through the through hole 3, and the two electrodes 5 are electrically connected through the liquid metal 4, so that the resistance value is smaller; when the current flowing through the liquid metal current limiter is larger than a first preset current, or the rising rate of the current flowing through the liquid metal current limiter is larger than a preset threshold value, the liquid metal 4 in the liquid metal current limiter has a self-contraction effect, the liquid metal 4 contracts, so that the liquid level of the liquid metal 4 is lowered and is lower than the height of the through hole 3, the liquid metal 4 is not arranged at the through hole 3, an air arc is formed at the through hole 3, the arc voltage has a certain current limiting function, the current can be inhibited, when the liquid metal 4 recovers the original state, the liquid level of the liquid metal 4 rises above the height of the through hole 3, and the liquid metal current limiter exits from the current limiting mode. The recovery of the liquid metal 4 to its original state requires a recovery time of the order of seconds, which is sufficient to complete the fault clearance.
When the direct current distribution network is not in fault, the current on the bus connecting line 30 is smaller than a first preset current, the current limiter 10 does not need to limit the current, the current limiter 10 is equivalent to a wire or a small resistor, and the whole direct current distribution network normally operates. The first preset current is larger than the current flowing through the bus connection line 30 when the dc distribution network is in normal operation, and the first preset current may be set as required. Fig. 3 is a schematic structural diagram of a dc power distribution network in a fault according to an embodiment of the present invention, and fig. 4 is a schematic structural diagram of a dc power distribution network in a fault after a current limiter limits a current according to an embodiment of the present invention. Fig. 3 and 4 show an exemplary situation in which the first distribution subnetwork 20-1 fails, for example, in the case of a short-circuit fault, which may be a unipolar short-circuit to earth fault or a bipolar short-circuit to earth fault, and when the dc distribution network fails at a fault point a, a fault current component I flows from the first power source and the second power source, respectivelyF1And IF2Synthesizing the fault current IFInjection into fault point a, fault current component IF1And IF2And a fault current IFRapidly increases, the fault-side short-circuit current and the busbar link current rapidly rise, so that when the current on the busbar link 30 corresponding to the current limiter 10 is greater than or equal to a first preset current, the current limiter 10 enters a current limiting mode to limit the current on the busbar link 30 (the current I is indicated by a thicker dotted line in fig. 3)F2Without being limited, the current I is represented by the thinner dotted line in FIG. 4F2Limited) to inhibit the second distribution sub-network 20-2 from injecting the first distribution sub-network 20-1 with the current, inhibit the short-circuit current peak value of the fault point, can reduce the impact of the short-circuit fault on the non-fault side, and reduce the impact of the short-circuit fault on the direct current distribution system, and the non-fault side becomes the unidirectional radiation network to continue to work normally, and simultaneously avoid the system protection from losing selectivity, thereby greatly increasing the reliability and the power supply continuity of the direct current distribution system.
According to the technical scheme, the current limiter is arranged on the bus connecting line connected with the power distribution sub-network, so that when the direct-current power distribution network fails, the fault side and the non-fault side of the direct-current power distribution network can be isolated through the current limiting effect of the current limiter, the influence between the fault side and the non-fault side is reduced, the impact of the fault side on the non-fault side is reduced, the non-fault side is kept in a normal operation state, the current flowing into the fault side from the non-fault side is reduced, the fault is conveniently cut off by the fault side, and the problems that when one feeder line has a short-circuit fault, the rising speed of the direct current is higher than that of a normal load current, one fault exists, the whole network experiences characteristics, one short-circuit fault is caused, the whole network loses power, and the power supply continuity and reliability of the direct-current power distribution system are directly influenced are solved.
The embodiment of the invention provides a protection device for a direct current distribution network. Fig. 5 is a schematic structural diagram of another protection device for a dc power distribution network according to an embodiment of the present invention. On the basis of the above embodiment, any of the distribution sub-networks 20 further includes the converter 24, the input end In1 of the converter 24 is electrically connected with the power supply end V1 of the distribution sub-network 20, and the output end Out1 of the converter 24 is electrically connected with the incoming line 21; the protection device for a dc power distribution network further comprises a fault location module 40, the fault location module 40 being electrically connected to the converter 24, the fault location module 40 being configured to identify a fault location and to send a blocking signal to the converter 24 in the power distribution sub-network 20 in which the fault location is located.
The voltage input by the power supply terminal V1 of the power distribution sub-network may be an alternating current voltage or a direct current voltage. If the voltage input from the power supply terminal V1 of the sub-distribution network is ac voltage, the inverter 24 may be a rectifier, and is configured to convert the ac voltage input from the power supply terminal V1 of the sub-distribution network into dc voltage and output the dc voltage to the incoming line 21; if the voltage input from the power supply terminal V1 of the power distribution sub-network is a DC voltage, the inverter 24 may be a DC-DC switching converter, and is configured to boost or buck the DC voltage input from the power supply terminal V1 of the power distribution sub-network, and output the DC voltage to the incoming line 21. When no fault occurs, the converter 24 outputs the required voltage and current to power the dc distribution network. When a fault occurs, the current limiter 10 can rapidly enter a current limiting mode, a certain time is needed for the fault location identification module 40 to identify the fault location, after the fault location identification module 40 identifies the fault location, a locking signal can be sent to the current converter 24 in the power distribution sub-network 20 where the fault location is located, and after the current converter 24 receives the locking signal, the output of voltage or current is stopped, so that the current flowing into the fault point can be further reduced. Fig. 6 is a schematic structural diagram of a dc power distribution network after a fault occurs, a current limiter limits current, and an inverter is locked according to an embodiment of the present invention. The fault location module 40 may be implemented by a fault location method and apparatus adopted in the prior art, for example, a fault location method and apparatus realized by a traveling wave protection principle.
Alternatively, on the basis of the above embodiments, as shown in fig. 5 and 6, the fault location module 40 may include a signal processing and control unit 41 and a plurality of second current detection modules 42 to form network protection. The signal processing and control unit 41 may be electrically connected with a plurality of second current detection modules 42. At least two second current detection modules 42 may be disposed on any one of the feeding lines 23, and illustratively, one second current detection module 42 is disposed at each of two ends of any one of the feeding lines 23. The signal processing and control unit 41 can determine whether the feeder 23 has a fault by receiving the current detected by the second current detection module 42 on each feeder according to the differential protection principle, so as to identify the fault position. For example, if the short-circuit fault does not occur on the feeder 23, the currents detected by the second current detection modules 42 at the two ends of the feeder 23 are equal; if the feeder line 23 has a short-circuit fault and current is injected into the fault point, the currents detected by the second current detection modules 42 at two sides of the fault point are not equal.
Optionally, the protection device for the dc power distribution network further includes a plurality of second switches disposed on the corresponding incoming lines 21, and the fault location module 40 is further configured to identify a fault location and send an opening signal to the second switch in the power distribution sub-network 20 where the fault location is located. The second switch is used for switching off when receiving a switching-off signal sent by the fault positioning module 40. After the fault location is identified by the fault location module 40, a blocking signal may be sent to the converter 24 in the distribution sub-network 20 in which the fault location is located, or a tripping signal may be sent to a second switch on the incoming line 21 in the distribution sub-network 20 in which the fault location is located, by which the current flowing into the fault point may be further reduced.
The embodiment of the invention provides a protection device for a direct current distribution network. On the basis of the above embodiment, as shown in fig. 5, the protection device for a dc power distribution network further includes a plurality of switches 50, the fault location module 40 is electrically connected to the plurality of switches 50, the switches 50 are disposed on the corresponding feeder lines 23, and the fault location module 40 is further configured to send a tripping signal to the switch 50 corresponding to the feeder line 23 where the fault location is located; the switch 50 is used for switching off when receiving a switching-off signal sent by the fault locating module 40 and when the current on the feeder 23 corresponding to the switch is less than or equal to a second preset current.
When no fault occurs, all the switches are conducted, and the direct-current power distribution network operates normally. When a fault occurs, the current limiter 10 limits current firstly, after the fault location module 40 identifies a fault location, the second switch is re-switched or the inverter is locked, so that the current on the feeder line where the fault point is located is reduced, so as to reduce the breaking current of the switch 50, and when a brake-switching signal sent by the fault location module 40 is received and the current on the feeder line 23 where the fault location is located is monitored to be less than or equal to a second preset current, the switch 50 on the feeder line 23 where the fault location is located is controlled to be opened, so as to clear the fault, as shown in fig. 7, fig. 7 is a schematic structural diagram of a dc power distribution network after the fault is removed according to an embodiment of the present invention. Optionally, the switch 50 comprises a mechanical dc breaker, a hybrid dc breaker, a solid state dc breaker, or a current injection dc breaker. The second preset current can be 5 times of the rated current of the feeder line, and the manufacturing cost of the direct current breaker can be reduced by reducing the breaking current of the direct current breaker.
Optionally, on the basis of the above embodiment, the fault location module 40 is further configured to send an unlocking signal to the converter 24 in the power distribution sub-network 20 in which the fault location is located after the switch 50 corresponding to the feeder 23 in which the fault location is located is opened, and then send a control signal for exiting the current limiting mode to the current limiter 10, so as to avoid that the current limiter exits the current limiting mode too early to cause impact on the power grid on the non-fault side when the pre-voltage fault still exists in the line.
After receiving the unlocking signal, the converter 24 outputs the required voltage and current to realize normal power supply. When the current limiter 10 receives a control signal to exit the current limiting mode, the current limiter 10 will no longer limit the current flowing through the busbar connection 30.
Fig. 8 is a schematic structural diagram of another protection device for a dc power distribution network according to an embodiment of the present invention. Fig. 8 exemplarily shows a case where the dc distribution network is a double-ended ring network, two distribution sub-networks may be electrically connected through at least two bus connection lines, and at least two bus connection lines are connected to different buses. It should be noted that the number of the bus bars in any distribution sub-network may be multiple, and the bus bars are electrically connected through an internal bus bar connecting line. The internal bus connecting line may be provided with a third switch 53 and a third current detection module 54, the third switch 53 and the third current detection module 54 may be electrically connected to the signal processing and control unit 41, and the signal processing and control unit 41 may determine whether the internal bus connecting line has a fault according to a differential protection principle through a current detected by the third current detection module 54 on the internal bus connecting line, and if the internal bus connecting line has a fault, send a trip signal to the third switch 53 on the internal bus connecting line, and further remove the fault. The working principle of the internal bus connecting line in the distribution sub-network is similar to the working principle of the short-circuit fault occurring on the feeder line, when the fault occurs on the internal bus connecting line, as shown in fig. 9, fig. 9 is a schematic structural diagram of the direct current distribution network when the fault occurs on the internal bus connecting line according to the embodiment of the present invention, the current limiter 10 limits the current, after the fault location module 40 identifies the fault location, the second switch 52 is opened or the converter 24 is locked, so that the current on the internal bus connecting line where the fault point is located is reduced, so as to reduce the breaking current of the third switch 53, and when the current on the internal bus connecting line where the fault location is located is monitored to be less than or equal to the second preset current, the third switch 53 on the internal bus connecting line where the fault location is controlled to be opened, so as to clear the fault. When the internal bus connecting line has a fault, the third switches 53 at both ends of the fault point are all required to be turned off, so as to prevent the buses at both sides of the internal bus connecting line from injecting fault current into the fault point. If the feeder line has a fault, the switch between the fault point and the bus needs to be disconnected. It should be noted that, in fig. 8, the second switch 52, the third switch 53, and the third current detection module 54 are all electrically connected to the signal processing and control unit 41 in the fault location module, and are not shown in the figure to avoid the influence of too many lines on the diagram. The signal processing and control unit 41 may include a processor or a logic control circuit, etc. The first current detection module, the second current detection module and the third current detection module may include a current transformer and the like.
The embodiment of the invention provides a protection method for a direct current power distribution network. Fig. 10 is a flowchart of a protection method for a dc power distribution network according to an embodiment of the present invention. The protection method for the direct-current power distribution network is realized based on the protection device for the direct-current power distribution network provided by any embodiment of the invention. The method comprises the following steps:
and 110, when the current of any current limiter on the corresponding bus connecting line is greater than or equal to a first preset current, entering a current limiting mode to limit the current on the corresponding bus connecting line.
As shown in fig. 1, 3 to 4, when no fault occurs, the current on the bus connecting line 30 is smaller than the first preset current, and the current limiter 10 does not enter the current limiting mode; when a fault occurs, the current on the bus connecting line 30 is rapidly increased, the current on the bus connecting line 30 can be detected through the first current detection module, when the first current detection module monitors that the current on the corresponding bus connecting line is greater than or equal to a first preset current, a control signal entering a current limiting mode is sent to the current limiter 10 to limit the current on the corresponding bus connecting line 30, the fault side and the non-fault side of the direct current distribution network are isolated, the influence between the fault side and the non-fault side is reduced, the impact of the fault side on the non-fault side is reduced, the non-fault side is kept in a normal operation state, the current flowing into the fault side from the non-fault side is reduced, the short-circuit current peak value of a fault point is reduced, the fault is conveniently cut off by the fault side, the characteristic of weak damping of a direct current system is solved, when a feeder line has a short-circuit fault, the rising speed of the direct current is higher, the direct current power distribution system is far larger than normal load current, and has the characteristics of one fault and whole network experience, so that the problems of one short-circuit fault, whole network power loss and direct influence on the power supply continuity and reliability of the direct current power distribution system are caused.
The protection method for the direct-current power distribution network provided by the embodiment of the invention is implemented based on the protection device for the direct-current power distribution network in the embodiment, so that the protection method for the direct-current power distribution network provided by the embodiment of the invention also has the beneficial effects described in the embodiment, and details are not repeated herein.
The embodiment of the invention provides a protection method for a direct current distribution network. Fig. 11 is a flowchart of another protection method for a dc power distribution network according to an embodiment of the present invention. On the basis of the above embodiment, when any one of the power distribution sub-networks further includes an inverter, and the protection device for the dc power distribution network further includes a fault location module, the method includes:
step 210, when the current on the corresponding bus connection line is greater than or equal to a first preset current, any current limiter enters a current limiting mode to limit the current on the corresponding bus connection line.
Step 220, the fault location module identifies the fault location and sends a blocking signal to the current converter in the distribution sub-network where the fault location is located.
When no fault occurs, the converter 24 outputs the required voltage and current to supply power to the dc distribution network. As shown in fig. 6, when a fault occurs, the inverter 24 stops outputting the voltage or current after receiving the lock signal, thereby further reducing the current flowing into the fault point.
The embodiment of the invention provides a protection method for a direct current distribution network. Fig. 12 is a flowchart of another protection method for a dc power distribution network according to an embodiment of the present invention. On the basis of the above embodiment, when the protection device for a direct current distribution network further includes a plurality of switches, the method includes:
and step 310, when the current on the corresponding bus connecting line is greater than or equal to a first preset current, any current limiter enters a current limiting mode to limit the current on the corresponding bus connecting line.
And step 320, the fault location module identifies the fault location and sends a locking signal to the current converter in the power distribution sub-network where the fault location is located.
And step 330, the fault positioning module sends a brake-off signal to a switch corresponding to the feeder line where the fault position is located.
When no fault occurs, all the switches 50 are turned on, and the direct-current power distribution network operates normally. After identifying the fault location, the fault location module 40 sends a tripping signal to the switch 50 corresponding to the feeder 23 where the fault location is located.
And step 340, the switch is disconnected when receiving the opening signal sent by the fault positioning module and the current on the feeder line corresponding to the switch is less than or equal to a second preset current.
When the switch 50 receives the opening signal sent by the fault locating module 40, which indicates that a fault occurs on the feeder 23 where the switch 50 is located, the switch 50 needs to be opened, because of the current limiting function of the current limiter 10 and the locking function of the inverter 24, the fault current on the fault feeder is greatly reduced, and when the current on the fault feeder is less than or equal to a second preset current, that is, after the current is reduced to be within the range of the opening capability of the switch 50, the switch 50 is opened, so that the current opening capability of the switch can be reduced, and the manufacturing cost of the switch is reduced.
The embodiment of the invention provides a protection method for a direct current distribution network. Fig. 13 is a flowchart of another protection method for a dc power distribution network according to an embodiment of the present invention. On the basis of the above embodiment, the method includes:
step 410, when the current on the corresponding bus connection line is greater than or equal to a first preset current, any current limiter enters a current limiting mode to limit the current on the corresponding bus connection line.
Step 420, the fault location module identifies the fault location and sends a blocking signal to the current converter in the distribution sub-network where the fault location is located.
And step 430, the fault positioning module sends a brake-off signal to a switch corresponding to the feeder line where the fault position is located.
And step 450, the switch is disconnected when receiving the opening signal sent by the fault positioning module and the current on the feeder line corresponding to the switch is less than or equal to a second preset current.
Step 450, the fault location module sends an unlocking signal to the current converter in the power distribution sub-network where the fault location is located.
Wherein after the fault is cleared, an unlock signal is sent to the converter 24 in the originally faulty distribution sub-network to cause the converter 24 to output the required voltage and current. If at this point the fault location module 40
Step 460, the fault location module sends a control signal to exit the current limiting mode to the current limiter.
After the fault is cleared and the converter 24 on the original fault side is unlocked, the current limiter 10 is controlled to exit the current limiting mode, so that the direct-current power distribution network normally works.
Compared with the scheme that the current limiter is arranged at the output end of the current converter, and when a fault occurs, due to the weak damping characteristic of a direct current system, when a feeder line has a short-circuit fault, the current limiters at the fault side and the non-fault side enter a current limiting mode together due to the fact that the rising speed of the direct current is high, the fault side and the non-fault side cannot be isolated, the non-fault side cannot normally operate, and power supply reliability and continuity of power distribution systems such as a hand-in-hand power distribution system, a double-end ring network and the like are reduced.
It should be noted that, because the short-circuit current of the dc distribution network rises fast, and the peak value is high, there is no natural zero crossing point, and the dc circuit breaker is compared with the conventional ac circuit breaker, and the design difficulty is big. Under a normal working state, the direct current circuit breaker needs to bear rated current of a system; when a short-circuit fault occurs, the fault branch circuit can be quickly disconnected, energy stored in the inductor of the fault branch circuit can be absorbed, and system overvoltage can be inhibited. The higher the on-off short-circuit current of the direct-current circuit breaker is, the higher the requirement on the device capacity of the whole direct-current circuit breaker is, the higher the manufacturing cost of the direct-current circuit breaker is, and the high construction cost of a direct-current power distribution network is caused.
The specific working process is as follows: when a short-circuit fault occurs in a certain load branch, the overcurrent protection firstly controls a current limiter on a bus connecting line to act firstly, the current of a non-fault side power supply is inhibited from injecting current to a fault point, after a short delay of 1-2ms, the current of the non-fault side is recovered to a normal level due to the action of the current limiter, and a non-fault side power distribution system is recovered to a normal operation state. After the fault point positioning is finished by the fault positioning module after 5-10ms, the fault side converter is locked, the fault network side short-circuit current begins to drop, and when the fault point short-circuit current drops to be within 5 times of rated current, the fault point direct current breaker acts to finish fault removal, the locked converter is unlocked, the normal working state is recovered, the current limiter is withdrawn from operation, and the system recovers normal power supply. When a fault occurs, the converter valve on the non-fault side is not locked, and the load power supply continuity of the non-fault side is not influenced in the whole fault process.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (3)
1. A protection device for a direct current distribution network is characterized in that,
this direct current distribution network includes: at least two sub-distribution networks and at least one bus bar connection line;
wherein any of the power distribution sub-networks comprises: the system comprises an incoming line, at least one bus and at least one feeder line, wherein the incoming line is electrically connected with the at least one bus, the at least one bus is electrically connected with the at least one feeder line, and two ends of any bus connecting line are respectively electrically connected with the buses in the two power distribution sub-networks;
this a protection device for direct current distribution network includes: the current limiters are in one-to-one correspondence with the bus connecting lines, any current limiter is arranged on the corresponding bus connecting line, and any current limiter is used for entering a current limiting mode when the current on the corresponding bus connecting line is larger than or equal to a first preset current so as to limit the current on the corresponding bus connecting line and isolate the fault side and the non-fault side of the direct current power distribution network through the current limiting effect of the current limiters; when the current on the corresponding bus connecting line is smaller than a first preset current, the bus connecting line does not enter a current limiting mode;
the flow restrictor includes: a superconducting current limiter or a liquid metal current limiter, or the current limiter comprises a current limiting resistor and a direct current breaker which are connected in parallel;
any one of the distribution sub-networks further comprises a current converter, the input end of the current converter is electrically connected with the power supply end of the distribution sub-network, the output end of the current converter is electrically connected with the incoming line,
the protection device for the direct-current power distribution network further comprises a fault positioning module, wherein the fault positioning module is electrically connected with the converter and is used for identifying a fault position and sending a locking signal to the converter in the power distribution sub-network where the fault position is located;
the protection device for the direct-current power distribution network further comprises a plurality of switches, the fault positioning module is electrically connected with the switches, the switches are arranged on corresponding feeder lines, and the fault positioning module is further used for sending brake-separating signals to the switches corresponding to the feeder lines where the fault positions are located;
the switch is used for being disconnected when the switch receives a brake-off signal sent by the fault positioning module and the current on the feeder line corresponding to the switch is smaller than or equal to a second preset current;
the fault positioning module is further used for sending an unlocking signal to a current converter in a power distribution sub-network where the fault position is located after a switch corresponding to the feeder where the fault position is located is switched off, and then sending a control signal for exiting a current limiting mode to the current limiter.
2. Protection device for a direct current distribution network according to claim 1, characterized in that the switch comprises a mechanical direct current breaker, a hybrid direct current breaker, a solid state direct current breaker or a current injection direct current breaker.
3. A protection method for a protection device for a dc power distribution network according to any one of claims 1 to 2, comprising:
when the current of any current limiter on the corresponding bus connecting line is greater than or equal to a first preset current, the current limiter enters a current limiting mode to limit the current on the corresponding bus connecting line;
when any of the distribution sub-networks further comprises an inverter, the protection arrangement for a dc distribution network further comprises a fault location module,
the protection method further comprises the following steps: the fault positioning module identifies a fault position and sends a locking signal to a current converter in a power distribution sub-network where the fault position is located;
when the protection device for a dc distribution network further comprises a plurality of switches,
the protection method further comprises the following steps: the fault positioning module sends a switching-off signal to a switch corresponding to a feeder line where the fault position is located;
the switch is disconnected when receiving a switching-off signal sent by the fault positioning module and when the current on the feeder line corresponding to the switch is less than or equal to a second preset current;
the protection method further comprises the following steps: and the fault positioning module sends an unlocking signal to a current converter in the power distribution sub-network where the fault position is located, and then sends a control signal for exiting the current limiting mode to the current limiter.
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