CN110048377B - Multi-port hybrid direct-current circuit breaker applicable to direct-current power distribution network and control method - Google Patents

Multi-port hybrid direct-current circuit breaker applicable to direct-current power distribution network and control method Download PDF

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CN110048377B
CN110048377B CN201910243369.8A CN201910243369A CN110048377B CN 110048377 B CN110048377 B CN 110048377B CN 201910243369 A CN201910243369 A CN 201910243369A CN 110048377 B CN110048377 B CN 110048377B
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branch
current
direct
main branch
transfer
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CN110048377A (en
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邹贵彬
张烁
孙增献
魏秀燕
杜肖功
佀庆华
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Shandong Xunfeng Electronics Co ltd
Shandong University
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Shandong Xunfeng Electronics Co ltd
Shandong University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
    • Y04S10/52—Outage or fault management, e.g. fault detection or location

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Driving Mechanisms And Operating Circuits Of Arc-Extinguishing High-Tension Switches (AREA)

Abstract

The invention discloses a multi-port hybrid direct-current circuit breaker applicable to a direct-current power distribution network and a control method, wherein the control method comprises the following steps: the main branch, the transfer branch and the energy consumption branch are connected in parallel; the main branch path includes: the main branch units are connected in parallel, and each main branch unit is connected between the direct current bus and the outgoing line of the direct current bus; each main tributary unit includes: the isolating switch, the quick mechanical switch and the load transfer switch are sequentially connected in series; the isolating switch is connected with an outlet wire of the direct current bus, and the load transfer switch is connected with the direct current bus; each main branch unit is connected with the transfer branch through a diode, and the direct-current bus is connected with the transfer branch through the diode. The invention has the beneficial effects that: the multi-port hybrid direct-current circuit breaker can realize normal circuit opening and closing and isolation of fault circuits or buses, and has the rapid mechanical switch failure protection capability.

Description

Multi-port hybrid direct-current circuit breaker applicable to direct-current power distribution network and control method
Technical Field
The invention relates to the technical field of fault clearing and isolation of a direct current side of a flexible direct current power distribution network, in particular to a multi-port hybrid direct current circuit breaker suitable for a direct current power distribution network and a control method.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
With the large-scale access of distributed power sources, the increase of direct current loads and the requirement of high-reliability power supply, a flexible direct current power distribution network based on a modular multilevel converter becomes a hot spot of domestic and foreign research.
In order to improve the reliability of power supply, the flexible direct-current power distribution network is mainly of a symmetrical monopole structure and adopts a non-grounding operation mode. When a single-pole ground fault occurs on the direct current side of the direct current distribution network, the fault current is mainly the charge and discharge current of the distributed capacitor of the direct current line due to the large resistance in the fault path, the amplitude is small, and the fault current is attenuated to zero quickly, so that the direct current distribution network can operate with the fault in a short time. However, when an inter-pole short-circuit fault occurs on the DC side, parallel capacitors of the DC/AC converters, the DC/DC converters, and the converter stations in the DC power distribution network are simultaneously discharged to a fault point, and a fault current rises to a large value in a very short time (millisecond). Therefore, in order to ensure continued operation of sound lines in a dc distribution network and to avoid damage to fragile power electronics in the converter station, the fault must be cleared and isolated within a few milliseconds. This characteristic of flexible dc distribution networks determines the great difference in dc breakers required in comparison to ac breakers.
At present, the direct current circuit breaker mainly comprises a mechanical direct current circuit breaker, an all-solid-state direct current circuit breaker and a hybrid direct current circuit breaker. The mechanical direct current circuit breaker has the characteristics of low investment and low running loss, but the mechanical direct current circuit breaker adopts a mechanical device and needs arc extinction, so that the action speed is low, and the reliability is low. The all-solid-state direct current circuit breaker adopts power electronic devices to break fault current, breaking electric arcs are not generated, the action speed is very high, and the load current needs to flow through a large number of power electronic devices during normal operation, so the operation loss is large. The concept of the hybrid direct current circuit breaker is originally proposed by ABB corporation, which combines the advantages of the mechanical direct current circuit breaker and the all-solid-state direct current circuit breaker and has the characteristics of small operation loss and high action speed. In the field of high-voltage flexible direct-current transmission, a 500kV hybrid direct-current circuit breaker developed by Nanrui relay protection company can cut off 25kA of fault current within 3 ms.
The inventor finds that although the hybrid direct current circuit breaker has a plurality of excellent characteristics, the hybrid direct current circuit breaker is high in cost because a large number of power electronic devices are required to bear transient breaking voltage, and is difficult to apply to a direct current distribution network in a large scale.
Disclosure of Invention
In order to solve the problems, the invention fully utilizes the forced commutation characteristic of the branch of the hybrid direct current breaker, provides a novel multiport hybrid direct current breaker and a control method, and analyzes the action process of the multiport hybrid direct current breaker under various working conditions; the primary equipment investment of the direct current circuit breaker is greatly reduced by sharing the transfer branch and the energy consumption branch by all lines.
In some embodiments, the following technical scheme is adopted:
a multi-port hybrid dc circuit breaker suitable for use in a dc power distribution network, comprising: the main branch, the transfer branch and the energy consumption branch are connected in parallel; the main branch path includes: the main branch units are connected in parallel, and each main branch unit is connected between the direct current bus and the outgoing line of the direct current bus; each main tributary unit includes: the isolating switch, the quick mechanical switch and the load transfer switch are sequentially connected in series; the isolating switch is connected with an outlet wire of the direct current bus, and the load transfer switch is connected with the direct current bus; each main branch unit is connected with the transfer branch through a diode, and the direct-current bus is connected with the transfer branch through the diode.
When the system normally operates, load current flows through each main branch path, and no current flows through each diode. When a line or bus fails, after the load transfer switches of the main branches are latched, the fault current will be commutated to the transfer branches via the diodes D1-D6 connected to each main branch unit and the diode D7 connected to the dc bus.
In other embodiments, the following technical scheme is adopted:
a control method of a multi-port hybrid direct current breaker applicable to a direct current power distribution network is characterized in that when an ith outgoing line connected with the multi-port hybrid direct current breaker breaks down or the ith outgoing line needs to be normally cut off, the action process of the multi-port hybrid direct current breaker is as follows:
(1) controlling each IGBT sub-module of the transfer branch circuit to be unlocked, and controlling a load transfer switch of the ith main branch circuit unit to be locked, so that the fault current flowing through the isolating switch and the quick mechanical switch of the main branch circuit unit is reduced, and the fault current is converted to the transfer branch circuit through a diode;
(2) when the current flowing through the main branch unit fast mechanical switch is close to zero, the fast mechanical switch is switched off;
(3) and locking each IGBT submodule in the transfer branch, charging each IGBT submodule capacitor by fault current, conducting the energy consumption branch to start energy release when the capacitor voltage reaches the starting voltage of the MOV of the energy consumption branch, and disconnecting the isolating switch of the ith main branch unit to realize the complete isolation of the ith outgoing line after the fault current drops to zero.
As a further technical solution, in the step (2), if the fast mechanical switch of the ith main branch unit fails to perform the opening operation, the load transfer switches of the main branch unit are unlocked again, and the load transfer switches of the remaining main branch units are locked, at this time, the fault current flowing through the remaining main branch units is reduced, and the fault current is converted to the transfer branch through the diode;
the fast mechanical switches of the remaining main branching units open when the current through them is close to zero.
As a further technical solution, when the multi-port hybrid dc breaker needs to remove a bus fault, the action process of the multi-port hybrid dc breaker is as follows:
unlocking each IGBT sub-module of the transfer branch, locking load transfer switches of the main branch units on all outgoing lines, gradually reducing fault current flowing through the quick mechanical switches of each main branch unit, and converting the fault current to the transfer branch through the diodes;
when the fault current flowing through the quick mechanical switch of each main branch unit is close to zero, the quick mechanical switch of each main branch unit is switched off;
and locking each IGBT submodule of the transfer branch, transferring the fault current to the energy consumption branch, and removing the fault current by the multi-port hybrid direct current circuit breaker after the energy in the fault current is released.
In other embodiments, the following technical scheme is adopted:
the controller of the multi-port hybrid direct current circuit breaker applicable to the direct current power distribution network comprises a server, wherein the server comprises a memory, a processor and a computer program which is stored on the memory and can run on the processor, and the processor executes the program to realize the control method of the multi-port hybrid direct current circuit breaker applicable to the direct current power distribution network.
In other embodiments, the following technical scheme is adopted:
a computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the above-mentioned method of controlling a multi-port hybrid dc breaker suitable for a dc power distribution network.
Compared with the prior art, the invention has the beneficial effects that:
(1) the multi-port hybrid direct-current circuit breaker greatly reduces the primary equipment investment of the direct-current circuit breaker by sharing the transfer branch and the energy consumption branch by each line, and is an economic and feasible scheme under the condition of limited investment of a direct-current power distribution network;
(2) the multi-port hybrid direct-current circuit breaker can realize normal circuit switching-on and switching-off and fault circuit or bus isolation, and has the rapid mechanical switch failure protection capability;
(3) the multi-port hybrid direct current circuit breaker has the characteristics of simple control, high modularization degree and easiness in expansion.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
Fig. 1 is a schematic topology diagram of a two-port hybrid dc circuit breaker according to an embodiment;
fig. 2(a) shows current waveforms of branches of a hybrid dc circuit breaker according to a first embodiment;
FIG. 2(b) is a voltage waveform across the hybrid DC circuit breaker according to the first embodiment;
FIG. 3 is a multi-port hybrid DC circuit breaker topology according to an embodiment I;
FIG. 4 is a fault current flow path according to the second embodiment;
FIG. 5 is a fault current flow path according to the second embodiment;
FIG. 6 is a fault current flow path according to the second embodiment;
fig. 7 is a simulation model of a dc distribution network in the third embodiment;
FIG. 8 illustrates the line current and DC bus voltage waveforms in the third embodiment;
FIG. 9 shows an example III MP-HCB1Current waveforms of all branches;
FIGS. 10(a) - (b) are graphs of the line current and bus voltage waveforms of the third embodiment;
FIG. 11 shows an example III MP-HCB1Current waveforms of all branches;
FIGS. 12(a) - (b) are graphs of the line current and bus voltage waveforms of the third embodiment;
FIG. 13 shows MP-HCB of example III1Current waveforms of all branches;
fig. 14(a) - (b) show the line current and bus voltage waveforms in the third embodiment.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Example one
A two-port hybrid DC circuit breaker (TP-HCB) combines the advantages of a mechanical DC circuit breaker and an all-solid-state DC circuit breaker, and utilizes a forced commutation principle to realize the breaking of fault current, and a topological structure of the TP-HCB circuit breaker is shown in fig. 1 and includes a main branch, a transfer branch and an energy consumption branch.
The two-port hybrid direct-current circuit breaker main branch is composed of a fast-mechanical switch (FMS) and a Load Communication Switch (LCS), and is responsible for conducting normal load current and transferring fault current in the action process of the direct-current circuit breaker; the transfer branch is formed by connecting a large number of IGBT sub-modules (SM) in series, is used for bearing fault current for a short time and establishing transient breaking voltage, and is the part with the largest equipment investment in the hybrid direct current breaker; the energy consumption branch is formed by connecting Metal Oxide Varistors (MOVs) in series and in parallel and is used for limiting transient breaking voltage and consuming energy stored in fault current. The timing of the operation of the two-port hybrid DC circuit breaker is shown in FIG. 2, where imain、itransferAnd iMOVRespectively representing the current in the main branch, the transfer branch and the energy consumption branch.
As shown in FIG. 2, t0At the moment, a line fails, and the fault current begins to rise; t is t1At the moment, the direct current breaker receives a tripping command, unlocks each IGBT submodule in the transfer branch and locks a load transfer switch in the main branch, fault current starts to flow from the main branch to the transfer branch, and the first current-flowing process starts; t is t2At the moment, the first commutation process is finished, the fault current in the main branch is close to zero, and the rapid mechanical switch starts the opening; t is t3At the moment, the main branch circuit is opened by the rapid mechanical switch, each IGBT sub-module of the transfer branch circuit is locked, the fault current starts to charge the capacitor of each IGBT sub-module, and the second commutation process starts; t is t4Constantly transferring the capacitance voltage of the IGBT sub-module of the branch circuit to reach the starting voltage of the MOV of the energy consumption branch circuit, starting energy release when the energy consumption branch circuit is conducted, and finishing the second commutation process; t is t5Energy in time of day fault currentAnd after the discharge is finished, the fault current is cleared, and the voltage at the two ends of the direct current circuit breaker is maintained at the system voltage.
In one or more embodiments, a multi-port hybrid dc circuit breaker suitable for a dc power distribution network is disclosed, which provides a novel multi-port hybrid dc circuit breaker by using a branch circuit forced commutation characteristic according to a characteristic that a plurality of outgoing lines are present on a dc bus of the dc power distribution network, and a topology structure of the novel multi-port hybrid dc circuit breaker is shown in fig. 3, and includes: the main branch, the transfer branch and the energy consumption branch are connected in parallel; the main branch road includes: the main branch units are connected in parallel, and each main branch unit is connected between the direct current bus and the outgoing line of the direct current bus; each main tributary unit includes: the isolating switch, the quick mechanical switch and the load transfer switch are sequentially connected in series; the isolating switch is connected with an outlet wire of the direct current bus, and the load transfer switch is connected with the direct current bus; the direct current bus is connected with the transfer branch through a diode D7;
referring to fig. 3, after connecting wires are respectively led out to two ends between the isolating switch and the fast mechanical switch of each main branch unit and connected with diodes, the connecting wires are respectively connected with two ends of the transfer branch, and the direct current bus is connected with the transfer branch through a diode D7. When the system normally operates, load current flows through each main branch path, and no current flows through each diode. When a line or bus fails, after the load transfer switches of the main branches are latched, the fault current will be commutated to the transfer branches via the diodes D1-D6 connected to each main branch unit and the diode D7 connected to the dc bus.
In FIG. 3, FMSiFor quick mechanical switching, LCSiBeing load-transfer switches, DiIs a diode series branch, DSiFor the isolating switch, all IGBT submodules of a transfer branch of the multi-port hybrid direct-current circuit breaker are locked during normal operation, and all load current flows through a rapid mechanical switch FMS on each lineiAnd load transfer switch LCSi。
Example two
In one or more embodiments, a method for controlling a multi-port hybrid dc circuit breaker for a dc distribution network is disclosed, comprising:
a line fault circuit interrupter control strategy. When a Line connected to the multi-port hybrid dc circuit breaker fails or a Line needs to be normally cut off (taking Line 1 in fig. 3 as an example), the operation process of the multi-port hybrid dc circuit breaker is as follows:
1) control transfer branch IGBT submodule unlocking and LCS1Block when flowing through the FMS1And LCS1The fault current starts to decrease and the fault current commutates to the diode branch D2～D4And a transfer branch;
2) when flowing through FMS1When the current of (2) is close to zero, the FMS1Starting the brake separating;
3) after a certain time (typically 2ms), the FMS is started1The opening is completed, the circulation path of the fault current is shown as the dotted line part in fig. 4, and the light color part shows the area without current circulation;
4) each IGBT submodule in the locking transfer branch circuit, the fault current is converted to the energy consumption branch circuit, the energy consumption branch circuit is conducted to discharge energy, and the disconnecting switch DS on the fault line can be disconnected after the fault current is reduced to zero1Complete isolation of the faulty line is achieved.
And a circuit breaker failure protection control strategy. When the Line 1 is in fault, after the direct current breaker receives a tripping command, the direct current breaker firstly carries out the isolation operation process of the normal fault Line and sequentially controls the load transfer switch LCS1Locking, quick mechanical switch FMS1And (7) opening the gate. When FMS is used1After the opening is started, the control system detects FMS after a short time (set to 0.5ms in the invention)1Failure of action, FMS is judged1And (4) failure, wherein the rapid mechanical switch failure protection starts to act, and the action process is as follows:
1) re-unlocking LCS1After locking of LCS2、LCS3Now flows through DS2-FMS2-LCS2And DS3-FMS3-LCS3The fault current in (1) starts to decrease and the fault current starts to commutate to the diode branch D2～D4、D7And branch of metastasisIn the road;
2) when flowing through FMS2And FMS3When the fault current is close to zero, the FMS2And FMS3Starting the brake separating;
3) FMS after 2ms2And FMS3The opening is completed and the path of the fault current is shown in phantom in fig. 5. Then, the fault current can be converted to an energy consumption branch by locking each IGBT submodule of the transfer branch, and the fault current is eliminated by the energy consumption branch;
4) as can be seen from FIG. 5, after the rapid mechanical switch fails to protect, the FMS is activated2And FMS3Is in the open state, and therefore the power exchange between Line 2 and Line 3 is interrupted. The disconnecting switch DS on the faulty Line 1 should be disconnected at this time1Sequentially closing FMS after completely isolating fault Line 12And FMS3Unlocking LCS2And LCS3And normal operation of Line 2 and Line 3 is resumed.
And (4) a bus fault circuit breaker control strategy. When the multi-port hybrid direct current breaker needs to remove bus faults, the action process of the multi-port hybrid direct current breaker is as follows:
1) unlocking all IGBT sub-modules of the transfer branch and locking load transfer switches (LCS) on all lines1～LCS3Then flows through the FMS1～FMS3The fault current is gradually reduced and the fault current is converted to the diode branch D1～D3D7 and a transfer branch;
2) when flowing through FMS1～FMS3When the fault current is close to zero, the FMS1～FMS3Starting the opening, and completing the opening of the quick mechanical switch after about 2 ms. The circulation path of the fault current at this time is shown by the broken line region in fig. 6;
3) and locking each IGBT submodule of the transfer branch, transferring the fault current to the energy consumption branch, and removing the fault current by the multi-port hybrid direct current circuit breaker after the energy in the fault current is released.
EXAMPLE III
A4-node flexible direct-current power distribution network simulation model based on the modular multilevel converter is constructed in PSCAD/EMTDC software, and the feasibility of the multi-port hybrid direct-current circuit breaker is subjected to simulation verification:
1) modeling
In order to verify the feasibility of the multi-port hybrid direct-current circuit breaker provided by the invention, a 4-node +/-10 kV direct-current power distribution network model based on the modular multi-level converter is built on a PSCAD/EMTDC simulation platform, as shown in FIG. 7. The voltage class of each converter station of the direct-current power distribution network, which is connected to an alternating-current power grid, is 110kV, the MMC converter stations are of a symmetrical monopole structure, and a mode that a converter transformer neutral point is grounded through a high resistance is adopted. Each pole of the outlet of the converter station is connected with a 10mH current-limiting reactor in series, and the current-limiting reactor is used for inhibiting the rising speed of fault current and striving for time for protection and action of a direct current breaker. The MMC1 converter station uses a constant dc voltage control mode and the MMC2 and MMC3 converter stations use a constant active power control mode, the main parameters of which are shown in table 1. The DC/DC converter is in a double-active full-bridge structure, adopts a single phase-shifting control mode, has the rated voltage of 20kV/1.5kV and carries the rated power of a direct current load of 4 MW. The dc lines employ a distributed frequency dependent model, with the line lengths shown in fig. 7. MP-HCBiThe multi-port hybrid direct-current circuit breaker is shown, is respectively arranged at each direct-current bus and is responsible for cutting off corresponding fault elements when an MMC converter station, a direct-current line or a bus fails, so that the safe and stable operation of the system is guaranteed, and the main parameters of the multi-port hybrid direct-current circuit breaker are shown in Table 2.
TABLE 1 DC POWER DISTRIBUTION NETWORK CONVERTER STATION PRE-PARAMETERS
Figure BDA0002010353280000071
TABLE 2 multiport hybrid DC breaker principal parameters
Figure BDA0002010353280000072
2) Analysis of economics
The following scheme compares the economy of the multi-line centralized multi-port hybrid direct-current circuit breaker of the direct-current distribution network with the scheme of dispersedly configuring two-port hybrid direct-current circuit breakers of all lines. For the sake of simplicity of comparison, analyses were performed by taking Line 1 to Line 3 in fig. 7 as examples. Because the manufacturing cost of the direct current circuit breaker is greatly influenced by the maximum transient voltage and the maximum fault current which are required to be borne by the transfer branch, each fault point is simulated on the PSCAD/EMTDC simulation platform, and the maximum fault current which can possibly appear on each line after a fault current breaking period (including fault detection time and circuit breaker action time, the fault detection time in the invention is 1ms, and the circuit breaker action time is 2.5ms) is obtained, as shown in Table 3.
TABLE 3 maximum Fault Current for each line
Figure BDA0002010353280000073
Table 4 shows the number of load transfer switches, fast mechanical switches and the maximum transient breaking voltage and maximum fault current to which the transfer branch is subjected for two different scenarios. Through comparison, the numbers of the quick mechanical switches and the load transfer switches required by the two schemes are the same, but the maximum transient voltage and fault current required to be borne by the transfer branch of the multi-port hybrid direct-current circuit breaker are far smaller than those of the two-port hybrid direct-current circuit breaker respectively configured for each line, three groups of transfer branches and energy consumption branches are required for distributed configuration, and one group of transfer branch and energy consumption branch is shared for centralized configuration, so that the equipment cost is greatly reduced.
TABLE 4 comparison of device requirements for different protocols
Figure BDA0002010353280000081
3) Normal line brake-separating simulation
Taking Line 1 in fig. 7 as an example, normal Line opening simulation is performed. The multi-port hybrid direct current breaker starts to perform the opening operation at 1 second, the operation process is as described above, and the MP-HCB performs the opening operation1The current of each line connected and the dc bus voltage are shown in fig. 8(a) - (b). For clarity of presentation, e.g. noneIn the following figures, the current waveform is a positive electrode current waveform.
As can be seen from fig. 8(a) - (b), after the dc circuit breaker operates for 1 second, the Line 1 current rapidly drops to zero, the non-faulty lines Line 2 and Line 3 maintain normal current flow, and the normal Line opening process has little effect on the system voltage stability.
4) Line fault simulation
Because the direct-current power distribution network is an ungrounded system, the fault current is very small when the single-pole grounding fault occurs, and the fault transient current is quickly attenuated to zero, so that the process of isolating the single-pole grounding fault line and the process of opening the brake transient state of the normal line are the same, and the details are not repeated.
When an inter-electrode short-circuit fault occurs in the system, the fault generates a very large fault current in a short time. Assuming that the fault occurrence time is 1 second, the dc circuit breaker starts to operate when receiving a trip command at 1.001 second, the detailed operation process is as described above, and the simulation waveforms are shown in fig. 9 and fig. 10(a) - (b). FIG. 9 shows MP-HCB1The respective branch current waveforms are Line 1 to Line 3 Line currents and dc bus voltage waveforms in fig. 10(a) to (b).
As can be seen from fig. 9 and fig. 10(a) - (b), the dc circuit breaker cuts off the fault line within 3 milliseconds, the cutting process of the fault line does not affect the normal operation of the healthy line, the current of the non-fault line is stable after 1.3 seconds after the short fluctuation, and the voltage of the dc distribution network is quickly restored to be stable after the short fluctuation.
5) Switch failure protection simulation
When a certain quick mechanical switch of the multi-port hybrid direct current circuit breaker fails, the quick mechanical switch fails to protect and acts, and the quick mechanical switch on each sound line replaces the failure switch to complete the fault current transfer function. When the Line 1 generates an inter-electrode short-circuit fault at the set time of 1 second, the 1.001 second direct current breaker receives a tripping command and starts to act on tripping. And sequentially locking a load transfer switch on the fault Line 1 and starting a rapid mechanical switch to open. And the control system detects that the rapid mechanical switch does not act after 0.5 milliseconds, judges that the rapid mechanical switch fails, and at the moment, performs protection action on the failure of the rapid mechanical switch, wherein the specific action process is as described above. The transient state of the system during the action of the dc breaker is shown in fig. 11 and fig. 12(a) - (b).
As can be seen from fig. 11 and fig. 12(a) - (b), failure of the mechanical switch of the circuit breaker results in a slight increase in the fault clearing time. When the fault line is completely isolated, the non-fault line is put into operation again, the non-fault line is kept stable after the transient process of about 0.25 second, and the system voltage is recovered to the normal state about 0.1 second after the direct current breaker acts.
6) DC bus fault simulation
Setting MP-HCB at 1 second1When an inter-electrode short circuit fault occurs in the medium direct current bus, the fault current rapidly rises, and all lines inject the fault current into the direct current bus, which is the most severe working state for the multi-port hybrid direct current circuit breaker. The 1.001 second dc breaker starts to operate after receiving the trip command, and the detailed operation process is as described above. The current and voltage waveforms during the system transient are shown in fig. 13 and fig. 14(a) - (b).
It can be seen from fig. 14(a) - (b) that the system voltage of the dc distribution network tends to be off-rated because of the MP-HCB1After the direct current bus is cut off by action, the MMC1 converter station is isolated from a direct current power distribution network, and the MMC1 converter station is a constant voltage converter station, so that the system voltage is increased due to the fact that the power generated in the direct current power distribution network is larger than the power consumed by a load after the direct current bus is cut off. In order to maintain the system voltage stable, the control mode of the converter station MMC2 or MMC3 should be adjusted from constant active power control to constant voltage control.
The rapid development of the dc distribution network urgently needs a dc circuit breaker with good performance in the aspects of reliability, quick action, economy and the like. In order to solve the problem, the invention provides a multi-port hybrid direct-current circuit breaker topology with normal circuit switching-on and switching-off, fault circuit or bus isolation and rapid mechanical switch failure protection capabilities. The topology has the advantages of simple control, high modularization degree and easy expansion, and the equipment investment of one time is greatly reduced compared with the scheme that each line is independently provided with the two-port hybrid direct current circuit breaker, and the topology is an economic and feasible scheme particularly under the condition that the direct current distribution network investment is limited.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.

Claims (5)

1. The control method of the multi-port hybrid direct-current circuit breaker suitable for the direct-current power distribution network is characterized in that when the ith outgoing line connected with the multi-port hybrid direct-current circuit breaker breaks down or the ith outgoing line needs to be normally cut off, the action process of the multi-port hybrid direct-current circuit breaker is as follows:
(1) controlling each IGBT sub-module of the transfer branch circuit to be unlocked, and controlling a load transfer switch of the ith main branch circuit unit to be locked, so that the fault current flowing through the isolating switch and the quick mechanical switch of the main branch circuit unit is reduced, and the fault current is converted to the transfer branch circuit through a diode;
(2) when the current flowing through the main branch unit fast mechanical switch is close to zero, the fast mechanical switch is switched off;
(3) each IGBT submodule in the transfer branch is locked, fault current charges each IGBT submodule capacitor, when the capacitor voltage reaches the starting voltage of an MOV (metal oxide varistor) of the energy consumption branch, the energy consumption branch is conducted to start energy release, and after the fault current drops to zero, an isolating switch of the ith main branch unit is disconnected to realize the complete isolation of the ith outgoing line;
in the step (2), if the fast mechanical switch of the ith main branch unit fails to open, it is determined that the fast mechanical switch of the ith main branch unit fails, and at this time, the fast mechanical switch failure protection starts to operate, and the operation process is as follows:
the load transfer switches of the main branch unit are unlocked again, and the load transfer switches of the other main branch units are locked, at the moment, the fault current flowing through the other main branch units is reduced, and the fault current is converted to the transfer branch circuit through the diode;
the diodes comprise diodes connected with the rest main branch units and diodes connected with the direct current bus;
when the current flowing through the fast mechanical switches of the rest main branch units is close to zero, the fast mechanical switches are switched off;
the fault current can be converted to the energy consumption branch by locking each IGBT submodule of the transfer branch, and the fault current is eliminated by the energy consumption branch;
when the multi-port hybrid direct current breaker needs to remove bus faults, the action process of the multi-port hybrid direct current breaker is as follows: unlocking each IGBT sub-module of the transfer branch, locking load transfer switches of the main branch units on all outgoing lines, gradually reducing fault current flowing through the quick mechanical switches of each main branch unit, and converting the fault current to the transfer branch through the diodes; when the fault current flowing through the quick mechanical switch of each main branch unit is close to zero, the quick mechanical switch of each main branch unit is switched off;
and locking each IGBT submodule of the transfer branch, transferring the fault current to the energy consumption branch, and removing the fault current by the multi-port hybrid direct current circuit breaker after the energy in the fault current is released.
2. The method of claim 1, wherein after the ith outgoing line is isolated, the fast mechanical switches of the remaining main branch units are sequentially closed, the load transfer switches of the remaining main branch units are unlocked, and normal operation of the remaining outgoing lines is resumed.
3. A multiport hybrid dc breaker for a dc distribution network, based on a method for controlling a multiport hybrid dc breaker for a dc distribution network according to any of claims 1-2, comprising: the main branch, the transfer branch and the energy consumption branch are connected in parallel; characterized in that the main branch comprises: the main branch units are connected in parallel, and each main branch unit is connected between the direct current bus and the outgoing line of the direct current bus; each main tributary unit includes: the isolating switch, the quick mechanical switch and the load transfer switch are sequentially connected in series; the isolating switch is connected with an outlet wire of the direct current bus, and the load transfer switch is connected with the direct current bus; each main branch unit is connected with the transfer branch through a diode, and the direct-current bus is connected with the transfer branch through the diode.
4. A controller for a multi-port hybrid dc circuit breaker adapted for use in a dc power distribution network, comprising a server, the server comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method for controlling a multi-port hybrid dc circuit breaker adapted for use in a dc power distribution network as claimed in any one of claims 1-2 when executing the program.
5. A computer-readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, performs the method of controlling a multi-port hybrid dc breaker adapted for a dc distribution network according to any one of claims 1-2.
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