CN107658842B - DC side fault protection system and method based on MMC submodule topology - Google Patents

DC side fault protection system and method based on MMC submodule topology Download PDF

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Publication number
CN107658842B
CN107658842B CN201711091438.5A CN201711091438A CN107658842B CN 107658842 B CN107658842 B CN 107658842B CN 201711091438 A CN201711091438 A CN 201711091438A CN 107658842 B CN107658842 B CN 107658842B
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fault
mmc
submodule
current
module
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CN107658842A (en
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马静
项晓强
康文博
李沛
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North China Electric Power University
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North China Electric Power University
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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
    • 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
    • H02H7/10—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 converters; for rectifiers
    • H02H7/12—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 converters; for rectifiers for static converters or rectifiers
    • H02H7/125—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 converters; for rectifiers for static converters or rectifiers for rectifiers
    • 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]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Rectifiers (AREA)
  • Inverter Devices (AREA)

Abstract

The invention belongs to MMC-HVDC system dc side technical field of relay protection more particularly to a kind of DC side fault protection systems and method based on MMC submodule topology.The system comprises the connected MMC-HVDC system inverter of sequence, data to read in module, logic judgment module and protection act module；Wherein MMC-HVDC system inverter is made of MMC submodule and additional resistance module, additional resistance module by inverse parallel IGBT it is in parallel with additional resistance after be connected on DC side route；MMC submodule installs a resistance-capacitance absorption device additional between multiple series thyristors, and one group of antiparallel IGBT and diode are added in submodule.The method includes acquisition data, low pressure overcurrent protection logic judgment and fault current decaying judgements; the invention efficiently solve double-thyristor method cause thyristor to be surprisingly connected when removing MMC-HVDC system dc side failure, diode damage, and Fault Isolation time long the problem of causing system security and stability to reduce.

Description

DC side fault protection system and method based on MMC submodule topology
Technical field
The invention belongs to MMC-HVDC system dc side technical field of relay protection, more particularly to one kind to be based on MMC submodule The DC side fault protection system and method for block topology.
Background technique
It is difficult to quickly locate when by serious impact from DC side failure based on the MMC topological structure of half-bridge submodule Reason, to cause serious impact to two side system of alternating current-direct current.Therefore, dealing carefully with DC line fault is engineering circles and academia Critical issue urgently to be resolved.
Currently, carrying out correlative study, most representative master for the inverter topology with DC Line Fault isolating power Will be there are two types of type: the first be using full-bridge submodule and clamper Shuangzi module as representative, will be sub after DC line breaks down It puts into fault paths to module capacitance reversed polarity, to eliminate fault current.Second mainly using double-thyristor method as representative, After DC line breaks down, to avoid the occurrence of uncontrollable rectifier bridge, by opening inverse parallel double-thyristor, arteface bridge Arm access, cutting exchange short circuit current of the side power supply to DC line feed-in, realizes Failure elimination.Inverter is based on the first kind Failure separation method compare, double-thyristor method cost of investment, additional power losses, in terms of all have compared with Big advantage.
However double-thyristor method there are still some drawbacks, one is system operate normally when, thyristor will bear by High forward voltage change rate caused by IGBT switching submodule capacitor may cause the unexpected conducting of thyristor.The second is locking Inverter and after submodule double-thyristor is connected, diode must share short circuit current, still there is the possibility of damage.The third is the time is normal When number is excessive, DC line fault current attenuation is slow, is unfavorable for Fault Isolation and system safety and stability.
Summary of the invention
In view of the above-mentioned problems, the present invention provides a kind of DC side fault protection system based on MMC submodule topology and side Method causes thyristor to be surprisingly connected, diode damage to solve double-thyristor method when removing MMC-HVDC system dc side failure It is bad, and Fault Isolation time long the problem of causing system security and stability to reduce.
A kind of DC side fault protection system based on MMC submodule topology, comprising:
The connected MMC-HVDC system inverter of sequence, data read in module, logic judgment module and protection act module；
The MMC-HVDC system inverter is by the MMC submodule that is connected on bridge arm and is connected on the attached of DC side route Resistive module is added to form；Wherein, each MMC submodule configures antiparallel double-thyristor S1, S2, with thyristor S1 instead simultaneously A resistance-capacitance absorption device in parallel between multiple concatenated thyristor S2 of connection, the resistance-capacitance absorption device is by resistance RnAnd capacitor CnIt is composed in series, the high forward voltage change rate generated when for inhibiting submodule switching causes thyristor S2 to mislead；In son One end differential concatenation one group of antiparallel IGBT3 and diode D3 of the IGBT2 and diode D2 of module, for blocking short-circuit electricity The access on diode D2 is flowed, protection diode D2 is not damaged；The additional resistance module is by one group of antiparallel IGBT With additional resistance RaddIt composes in parallel, for accelerating direct fault current to decay；
The data read in DC side electric current, the voltage signal that module is used to acquire MMC-HVDC system inverter, concurrently It send to logic judgment module；
The logic judgment module carries out low pressure overcurrent protection according to DC side fault current, the voltage signal of acquisition Logic judgment, and obtained fault message is sent to protection act module；
The protection act module sends block signal according to fault message, to corresponding inverter and breaker.
The working method of the MMC-HVDC system inverter are as follows:
When MMC-HVDC system operates normally, the IGBT3 in MMC submodule is in the conductive state always, inverse parallel twin crystal Brake tube S1, S2 are in blocking always；Inverse parallel IGBT in additional resistance module is in the conductive state, additional resistance Radd It is short-circuited；
When DC side breaks down, the IGBT3 in MMC submodule is turned off, blocks short circuit current in sustained diode 2 Access, it is not damaged with protection diode；Meanwhile the characteristic that resistance-capacitance absorption device utilizes capacitor both end voltage that cannot be mutated, Inhibit the high forward voltage change rate generated when submodule switching, prevents antiparallel thyristor S2 from misleading；Turn off additional electrical Hinder the inverse parallel IGBT, additional resistance R in moduleaddFault loop is accessed, direct fault current decaying is accelerated.
A kind of DC side fault protecting method based on MMC submodule topology, comprising the following steps:
Step 1: acquisition data, including DC side positive and negative electrode transmission route survey voltage signal, DC side positive and negative electrode are defeated Electric line measures current signal；
Step 2: low pressure overcurrent protection logic judgment is carried out according to the collected data, if it is determined that DC side breaks down, Then low pressure overcurrent protection acts and sends block signal to corresponding converter station；
Step 3: after converter station receives block signal, each bridge arm submodule of inverter is latched rapidly, by additional resistance RaddIt throws Enter in discharge loop, triggers inverse parallel double-thyristor in submodule, short circuit current is made to enter the decling phase；
Step 4: judge whether fault current decays and finish, if it is determined that fault current decaying finishes, reopens inverter, IGBT on the inverse parallel double-thyristor being latched on submodule, and locking DC line, makes additional resistance RaddIn circuit, Permanent fault is avoided to cause large impact；
Step 5: return step 2 re-starts low pressure overcurrent protection logic judgment, if low pressure overcurrent protection acts, Block signal is sent to inverter rapidly, is latched submodule again, and send trip signal to breaker, if protection is failure to actuate, Then system is restored to operate normally, and exits additional resistance Radd。
The determination method of the low pressure overcurrent protection logic judgment are as follows:
When DC side positive and negative electrode transmission route survey difference in voltage absolute value is less than under-voltage protection setting valve, at the same it is straight It flows side transmission line of electricity positive or negative pole measurement current absolute value and is greater than overcurrent protection setting valve, be then determined as that event occurs for DC side Barrier.
It is described to judge whether fault current decays the judgment basis finished are as follows: when the survey of DC side transmission of electricity positive and negative electrode route When amount electric current is respectively less than current attenuation setting valve, then it is determined as that fault current decaying finishes.
The beneficial effects of the present invention are:
A kind of DC side fault protection system and method based on MMC submodule topology proposed by the present invention efficiently solves Double-thyristor method causes thyristor to be surprisingly connected when removing MMC-HVDC system dc side failure, diode damages, and failure The problem of isolation time length causes system security and stability to reduce.It specifically includes:
1) MMC submodule proposed by the present invention, which can effectively avoid thyristor and mislead, causes the danger of the system failure, simultaneously Access of the short circuit current on freewheeling diode can be blocked, protection diode is not damaged.
2) resistance-capacitance absorption device proposed by the present invention, the characteristic that cannot be mutated using capacitor both end voltage inhibit submodule The high forward voltage change rate generated when switching, can effectively prevent thyristor S2 to mislead, and do not influence MMC-HVDC system just Often operation.
3) present invention additional resistance module concatenated on DC side route, when system dc side failure, by additional electrical Resistance access fault loop, can accelerate direct fault current to decay, and then solve since Fault Isolation time length causes system to be pacified The problem of total stability reduces.
Detailed description of the invention
Attached drawing 1 is the DC side fault protection system structural schematic diagram based on MMC submodule topology；
Attached drawing 2 is MMC-HVDC system inverter topological diagram；
Attached drawing 3 is MMC submodule topological diagram；(Figure of abstract)
Attached drawing 4 is the DC side fault protecting method flow chart based on MMC submodule topology；
Attached drawing 5 is MMC-HVDC analogue system schematic diagram in embodiment 1；
Attached drawing 6 is that thyristor S2 bears voltage change ratio simulation result in embodiment 1；
Attached drawing 7 is 1 Neutron module switching voltage change simulation result of embodiment；
Attached drawing 8a is the transient fault short circuit current simulation result of fault distance x=0 in embodiment 1；
Attached drawing 8b is the transient fault short circuit current simulation result of fault distance x=50 in embodiment 1；
Attached drawing 8c is the transient fault short circuit current simulation result of fault distance x=150 in embodiment 1；
Attached drawing 9a is the transient fault capacitance voltage simulation result of fault distance x=0 in embodiment 1；
Attached drawing 9b is the transient fault capacitance voltage simulation result of fault distance x=50 in embodiment 1；
Attached drawing 9c is the transient fault capacitance voltage simulation result of fault distance x=150 in embodiment 1；
Attached drawing 10a is the permanent fault short circuit current simulation result of fault distance x=0 in embodiment 1；
Attached drawing 10b is the permanent fault short circuit current simulation result of fault distance x=50 in embodiment 1；
Attached drawing 10c is the permanent fault short circuit current simulation result of fault distance x=150 in embodiment 1；
Attached drawing 11a is the permanent fault capacitance voltage simulation result of fault distance x=0 in embodiment 1；
Attached drawing 11b is the permanent fault capacitance voltage simulation result of fault distance x=50 in embodiment 1；
Attached drawing 11c is the permanent fault capacitance voltage simulation result of fault distance x=150 in embodiment 1；
Specific embodiment
The present invention is described in detail with reference to the accompanying drawings and examples.
Thyristor is caused surprisingly to be connected when removing MMC-HVDC system dc side failure to solve double-thyristor method, two poles Pipe damage, and Fault Isolation time long the problem of causing system security and stability to reduce, the present invention propose a kind of based on MMC submodule The DC side fault protection system of block topology, the structural schematic diagram of the DC side fault protection system is as shown in Figure 1, include suitable The connected MMC-HVDC system inverter of sequence, data read in module, logic judgment module and protection act module；Data read in mould DC side electric current, the voltage signal of the MMC-HVDC system inverter of acquisition are sent to logic judgment module, logic first by block Judgment module according to DC side fault current, the voltage signal of acquisition, sentence by the low pressure overcurrent protection logic exported through inverter It is disconnected, fault message is obtained, and fault message is sent to protection act module；Protection act module is according to fault message, Xiang Xiang The inverter answered sends block signal, and sends block signal to corresponding breaker；
Attached drawing 2 is MMC-HVDC system inverter topological diagram, as shown in Fig. 2, the MMC-HVDC system inverter is by even It connects the MMC submodule on bridge arm and is connected on the additional resistance module composition of DC side route；Since down slope time is normal Number τ directly affects Fault Isolation and system safety and stability, and down slope time constant, τ is bigger, DC line fault current attenuation It is slower, remove failure when it is longer to the system overcurrent attack time, be more unfavorable for the safety and relaying configuration of AC system.And pass through The method of loop inductance can reduce timeconstantτ after increasing loop resistance after failure or reducing failure.Therefore, the present invention is in direct current Side line road series connection one is by inverse parallel IGBT and additional resistance RaddThe additional resistance module composed in parallel, system operate normally When, antiparallel IGBT is in the conductive state, parallel resistance RaddIt is short-circuited, therefore not will increase system running wastage, system is straight Antiparallel IGBT is turned off after flowing side failure, parallel resistance RaddFault loop is accessed, direct fault current decaying is accelerated.
Attached drawing 3 is MMC submodule topological diagram, as shown in figure 3, each MMC submodule configures antiparallel double-thyristor S1, S2 (convenient for the sake of, S2 will be referred to as with the antiparallel thyristor of S1), with the antiparallel multiple concatenated crystalline substances of thyristor S1 A resistance-capacitance absorption device in parallel, the resistance-capacitance absorption device are composed in series by resistance Rn and capacitor Cn, are used between brake tube S2 Inhibit the high forward voltage change rate generated when submodule switching that thyristor S2 is caused to mislead；In the IGBT2 of submodule and two One end differential concatenation one group of antiparallel IGBT3 and diode D3 of pole pipe D2, for blocking short circuit current in diode D2 Access, protection diode D2 is not damaged；The additional resistance module is by one group of antiparallel IGBT and additional resistance RaddAnd Connection composition, for accelerating direct fault current to decay；
When MMC-HVDC system operates normally, IGBT3 is in the conductive state always, thyristor S1, antiparallel brilliant lock Pipe system S2 is in blocking always, and the circulation path of electric current is as shown in Figure 1.Submodule need to be latched when DC side breaks down When, turn off the trigger signal of IGBT3, can block access of the short circuit current in sustained diode 2, protection diode not by Damage.The characteristic that resistance-capacitance absorption device utilizes capacitor both end voltage that cannot be mutated inhibits the height generated when submodule switching positive Voltage change ratio du/dt, even if du/dt makes the thyristor of top half mislead, shunt capacitance still can effectively protect lower half Divide thyristor unaffected, therefore thyristor S2 can be effectively prevent to mislead, and does not influence MMC-HVDC system normal operation.
Attached drawing 4 is the DC side fault protecting method flow chart based on MMC submodule topology, as shown in figure 4, the method Include:
Step 1: acquisition data, including DC side positive and negative electrode transmission route survey voltage signal, DC side positive and negative electrode are defeated Electric line measures current signal；
Step 2: after DC side failure occurs, the low pressure overcurrent protection for being installed on converter station outlet detects DC side After fault current raising and voltage landing, acts and issues converter station block signal, operation equation are as follows:
In formula: UdP、UdNIt is the measurement voltage of DC side positive and negative electrode transmission line of electricity, I respectivelydP、IdNIt is that DC side is defeated respectively The measurement electric current of electric positive and negative electrode route, Uset、Iset1It is low-voltage, overcurrent protection setting valve respectively；
Step 3: according to fault message, if it is determined that DC side breaks down, Xiang Xiangying converter station sends block signal, the change of current Station receives block signal, is latched each bridge arm submodule rapidly, by submodule capacitive bypass, while being latched in each submodule IGBT3 blocks short circuit current circulation path in diode D2.The IGBT being latched on DC line, makes additional resistance RaddInvestment In discharge loop, inverse parallel double-thyristor in submodule is triggered, so that short circuit current is entered the decling phase, whether judges fault current Decaying finishes, criterion are as follows:
|IdP|and|IdN| < Iset2 (2)
I in formulaset2For current attenuation setting valve；
Step 4: when DC side measurement electric current meets formula (2), reopening MMC-HVDC inverter, be latched on submodule Inverse parallel double-thyristor, while IGBT being kept on DC line to be latched, makes additional resistance RaddStill in circuit, avoid permanent Property failure caused large impact；
Step 5: low pressure overcurrent protection logic judgment is re-started, if low pressure overcurrent protection acts, and rapidly to changing It flows device and sends block signal, be latched submodule again, and send trip signal to breaker, if low pressure overcurrent protection is not again Movement, then prove that failure has disappeared, can exit the additional resistance on DC line.
Embodiment 1
Exist for DC side fault protection system of the verifying based on MMC submodule topology and the validity of method, the present embodiment MMC-HVDC system simulation model is built on RTDS platform carries out simulating, verifying, it is imitative using MMC-HVDC system as shown in Figure 5 True mode carry out respectively thyristor S2 bear forward voltage change rate emulation, abort situation apart from converter station outlet 0km, 50km, The emulation of 150km transient fault, abort situation is apart from converter station outlet 0km, 50km, 150km permanent fault emulation.
(1) when systems are functioning properly, the voltage change ratio emulation knot thyristor S2 in sub- module topology born Fruit is as shown in fig. 6, when switching submodule capacitor caused high forward voltage change rate carries out simulation result as shown in fig. 7, comparison For Fig. 6 and 7 it is found that in submodule topology, the order of magnitude for the voltage change ratio that thyristor S2 is born is 10-3, much smaller than switching Caused high forward voltage change rate when module capacitance, it can be seen that, the present invention can avoid thyristor S2 when system operates normally Logical danger is misled into because bearing high forward voltage change rate.
(2) when transient fault occurs for system, it is assumed that transient fault, fault bit occur in t=3s for DC line It is set at converter station outlet xkm.After failure occurs, transient fault when fault distance is respectively 0km, 50km, 150km is short Transient fault capacitance voltage of the road current simulations result as shown in Fig. 8 a~8c, when fault distance is respectively 0km, 50km, 150km For simulation result as shown in Fig. 9 a~9c, whole process can be divided into 3 stages:
(I) fault current ascent stage
It is fault current ascent stage from the failure generation moment to the converter station locking moment, i.e. t in Fig. 8 a~8c1-t2When Section, whole process last about greatly 10ms.At this stage, fault current according to the discharge current of order Oscillating circuit capacitance variation Rule rises, and different fault distances corresponds to different fault current maximum values: fault distance is remoter, and fault current maximum value is got over It is small；Fault distance is closer, and fault current maximum value is bigger.Meanwhile the capacitance voltage of each submodule drops rapidly from voltage rating It falls, such as t in Fig. 9 a~9c1-t2Shown in period.
(II) fault current removing stage
After failure occurs, overcurrent under-voltage protection starts rapidly, block signal is issued to converter station, into fault current Removing stage, i.e. t in Fig. 8 a~8c2-t3Period.Under the action of submodule topology, after converter station locking, exchange side system feedback The electric current entered flows in bridge arm using the double-thyristor in each submodule as access, eliminates the uncontrollable rectifier bridge effect of diode It answers, the fault current facilitated in DC line is removed.Meanwhile diode D2 no longer shares short circuit current, avoids damage It may.By Fig. 8 a~8c it is found that fault current decays to zero according to curent change rule in First Order Circuit, die-away time is A few tens of milliseconds, decaying speed depend on the total resistance value in entire circuit, additional series resistance RaddBigger, die-away time is normal Number is smaller, is more conducive to system safety and stability.Such as t in Fig. 9 a~9c2-t3It is at this stage, each after converter station locking shown in period Submodule capacitor is in bypass condition, no longer discharges to fault point, and voltage remains unchanged.
(III) the fault recovery stage
After detecting that DC side fault current decays to zero, inverter is reopened and by the twin crystal lock in each submodule It is latched, i.e. t in Fig. 8 a~8c3-t4Period.For transient fault, fault point has disappeared after DC side fault current decays to zero It loses, short circuit current does not occur again.Such as t in Fig. 9 a~9c3-t4Shown in period, due to converter station quick lock after failure, each submodule Block capacitance voltage still keeps higher level, and after reopening converter station, capacitance voltage can rise to specified within a few tens of milliseconds Level, MMC-HVDC system can resume operation rapidly, improve system availability.
(3) when permanent fault occurs for system, if permanent fault, abort situation occur in t=3s for DC line To be exported at xkm apart from converter station.Permanent fault short circuit after failure occurs, when fault distance is respectively 0km, 50km, 150km Permanent fault capacitance voltage of the current simulations result as shown in Figure 10 a~10c, when fault distance is respectively 0km, 50km, 150km Simulation result is as shown in Figure 11 a~11c, and whole process can equally be divided into fault current rising, fault current is removed and failure is extensive Multiple three phases, wherein fault current ascent stage and fault current removing stage are similar with transient fault, no longer superfluous herein It states.The difference is that the fault recovery stage, such as t in Figure 10 a~10c3-t4Shown in period, when detecting DC side fault current After decaying to zero, reopens inverter and be latched the double-thyristor in each submodule.Such as t in 11a~11c3-t4Period institute Show, for permanent fault, reopening after inverter fault point, there are still therefore fault current will occur again, each submodule Block capacitance voltage further decreases.But due to after open inverter not by additional resistance RaddExcision, therefore coincide with permanent event The secondary pulse of short circuit current when barrier is simultaneously little, such as t in Figure 10 a~10c4-t5Shown in period.When overcurrent, low-voltage protection After monitoring failure again, it is latched inverter rapidly, fault current will gradually decay.To further ensure that system safety, disconnect Side breaker is exchanged, direct current system is isolated.
Verification result show a kind of DC side fault protection system based on MMC submodule topology proposed by the present invention and Method is avoided that thyristor misleads and causes the danger of the system failure, while short circuit current can be blocked logical on freewheeling diode Road, protection diode are not damaged.For transient fault, since submodule capacitor voltage is still protected after reopening converter station Higher level is held, therefore MMC-HVDC system can resume operation rapidly after failure.For permanent fault, after open converter station Short circuit current impacts less secondary system when additional resistance not being cut off, therefore coinciding with permanent fault, can still pass through Locking converter station rapidly disconnects AC circuit breaker, isolated fault.
This embodiment is merely preferred embodiments of the present invention, but scope of protection of the present invention is not limited thereto, In the technical scope disclosed by the present invention, any changes or substitutions that can be easily thought of by anyone skilled in the art, It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with scope of protection of the claims Subject to.

Claims (1)

1. a kind of DC side fault protecting method based on MMC submodule topology, is used for the direct current based on MMC submodule topology Side fault protection system, the system comprises:
The connected MMC-HVDC system inverter of sequence, data read in module, logic judgment module and protection act module；
The MMC-HVDC system inverter is by the MMC submodule that is connected on bridge arm and the additional electrical for being connected on DC side route Hinder module composition；Wherein, each MMC submodule configures antiparallel double-thyristor S1, S2, antiparallel with thyristor S1 A resistance-capacitance absorption device in parallel between multiple concatenated thyristor S2, the resistance-capacitance absorption device is by resistance RnWith capacitor CnString Connection composition, the high forward voltage change rate generated when for inhibiting submodule switching cause thyristor S2 to mislead；In submodule IGBT2 and diode D2 one end differential concatenation one group of antiparallel IGBT3 and diode D3, for blocking short circuit current to exist Access on diode D2, protection diode D2 are not damaged；The additional resistance module by one group of antiparallel IGBT with it is attached Power-up resistance RaddIt composes in parallel, for accelerating direct fault current to decay；
The data read in DC side electric current, the voltage signal that module is used to acquire MMC-HVDC system inverter, and are sent to Logic judgment module；
The logic judgment module carries out low pressure overcurrent protection logic according to DC side fault current, the voltage signal of acquisition Judgement, and obtained fault message is sent to protection act module；
The protection act module sends block signal according to fault message, to corresponding inverter and breaker；The MMC- The working method of HVDC system inverter are as follows: when MMC-HVDC system operates normally, the IGBT3 in MMC submodule is in always On state, inverse parallel double-thyristor S1, S2 are in blocking always；Inverse parallel IGBT in additional resistance module, which is in, to be led Logical state, additional resistance RaddIt is short-circuited；
When DC side breaks down, the IGBT3 in MMC submodule is turned off, blocks short circuit current logical in sustained diode 2 Road, it is not damaged with protection diode；Meanwhile the characteristic that resistance-capacitance absorption device utilizes capacitor both end voltage that cannot be mutated, inhibit The high forward voltage change rate generated when submodule switching, prevents antiparallel thyristor S2 from misleading；Turn off additional resistance mould Inverse parallel IGBT in block, additional resistance RaddFault loop is accessed, direct fault current decaying is accelerated；
It is characterized in that, the guard method the following steps are included:
Step 1: acquisition data, including DC side positive and negative electrode transmission route survey voltage signal, DC side positive and negative electrode power transmission line Drive test amount current signal；
Step 2: low pressure overcurrent protection logic judgment is carried out according to the collected data, if it is determined that DC side breaks down, then it is low It presses through current protection movement and sends block signal to corresponding converter station；The judgement side of the low pressure overcurrent protection logic judgment Method are as follows: when DC side positive and negative electrode transmission route survey difference in voltage absolute value is less than under-voltage protection setting valve, while DC side Transmission line of electricity positive or negative pole measures current absolute value and is greater than overcurrent protection setting valve, then is determined as that DC side breaks down；
In formula: UdP、UdNIt is the measurement voltage of DC side positive and negative electrode transmission line of electricity, I respectivelydP、IdNBe respectively DC side transmission of electricity just, The measurement electric current of anode circuit, Uset、Iset1 is low-voltage, overcurrent protection setting valve respectively；
Step 3: after converter station receives block signal, each bridge arm submodule of inverter is latched rapidly, by additional resistance RaddInvestment is put In electrical circuit, inverse parallel double-thyristor in submodule is triggered, short circuit current is made to enter the decling phase；
Step 4: judging whether fault current decays and finish, if it is determined that fault current decaying finishes, reopen inverter, be latched IGBT on inverse parallel double-thyristor on submodule, and locking DC line, makes additional resistance RaddIn circuit, avoid Permanent fault caused large impact；It is described to judge whether fault current decays the judgment basis finished are as follows: when DC side is transmitted electricity When the measurement electric current of positive and negative electrode route is respectively less than current attenuation setting valve, then it is determined as that fault current decaying finishes；
Its criterion are as follows:
|IdP|and|IdN| < Iset2 (2)
I in formulaset2For current attenuation setting valve；
Step 5: return step 2 re-starts low pressure overcurrent protection logic judgment, if low pressure overcurrent protection acts, rapidly Block signal is sent to inverter, submodule is latched again, and send trip signal to breaker, if protection is failure to actuate, is System restores to operate normally, and exits additional resistance Radd。
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CN108448542A (en) * 2018-02-07 2018-08-24 许继集团有限公司 Sub-modular structure with alternating current-direct current fault clearance ability and MMC topological structures
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WO2015074689A1 (en) * 2013-11-20 2015-05-28 Siemens Aktiengesellschaft A high voltage converter circuit equipped with a voltage monitoring device
CN104953571A (en) * 2015-07-03 2015-09-30 天津大学 Improved MMC (modular multi-level converter) structure with direct current fault clearing capacity
CN106058824A (en) * 2016-05-26 2016-10-26 华北电力大学 MMC topology having DC fault removing capability
CN206211517U (en) * 2016-12-05 2017-05-31 国网浙江临海市供电公司 A kind of overvoltage protective system of silicon controlled rectifier

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Publication number Priority date Publication date Assignee Title
WO2015074689A1 (en) * 2013-11-20 2015-05-28 Siemens Aktiengesellschaft A high voltage converter circuit equipped with a voltage monitoring device
CN104953571A (en) * 2015-07-03 2015-09-30 天津大学 Improved MMC (modular multi-level converter) structure with direct current fault clearing capacity
CN106058824A (en) * 2016-05-26 2016-10-26 华北电力大学 MMC topology having DC fault removing capability
CN206211517U (en) * 2016-12-05 2017-05-31 国网浙江临海市供电公司 A kind of overvoltage protective system of silicon controlled rectifier

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