CN111740395A - Topological structure of inductive coupling type high-voltage direct-current limiting circuit breaker - Google Patents
Topological structure of inductive coupling type high-voltage direct-current limiting circuit breaker Download PDFInfo
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- CN111740395A CN111740395A CN202010437849.0A CN202010437849A CN111740395A CN 111740395 A CN111740395 A CN 111740395A CN 202010437849 A CN202010437849 A CN 202010437849A CN 111740395 A CN111740395 A CN 111740395A
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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
- 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
Abstract
The invention relates to an inductance coupling type high-voltage direct-current limiting circuit breaker topological structure, and belongs to the field of flexible direct-current transmission. The inductive coupling type high-voltage direct-current-limiting circuit breaker consists of a current-guiding current limiter and a fault isolation current limiter, wherein the current-guiding current limiter conducts current in an active short-circuit mode, and the fault isolation current limiter alternately inputs coupling inductors to force fault current to flow into a current-guiding branch circuit, so that the current flowing into a fault point is greatly reduced; the fault isolation current limiter is responsible for inhibiting fault point injection current and isolating the fault point, and the current guide current limiter is responsible for introducing the fault point injection current into the current guide branch circuit and reducing the fault current increase rate. The inductive coupling current-limiting circuit breaker can complete fault current conduction within 3ms and fault removal within 6ms, has good current-limiting and circuit-breaking capabilities, only needs 632 IGBT devices, and is high in economy.
Description
Technical Field
The invention relates to the field of flexible direct current transmission, in particular to an inductance coupling type high-voltage direct current limiting circuit breaker topological structure with fault current suppression capability.
Background
The high-voltage high-capacity flexible direct-current power transmission network becomes an important pillar for future energy Internet development by virtue of the advantages of controllable tide, easiness in absorbing new energy, capability of providing reactive support and the like. The modular multilevel converter has the advantages of high expandability and low harmonic content, and is a primary device for constructing a flexible direct-current network. At present, most of flexible direct power transmission systems in China are close to water sources, underwater cables are adopted for power transmission, and the cables have the advantages of stable transmission quality, low failure rate, long service life, high cable cost and difficult maintenance. With the continuous promotion of the requirement for inland new energy consumption, flexible direct-current power transmission adopting an overhead line mode is the direction of future inland direct-current network development, but the influence of natural environment on an overhead line is large, and the failure rate is high. In order to reduce the construction cost of a flexible direct current system, the MMC converter at present adopts a half-bridge submodule without fault blocking capacity, and a direct current breaker is required to be configured to cut off a fault line. However, after the high-voltage large-capacity flexible direct system is in a ground short circuit, the rising rate of the fault current is very high, and the current endurance limit of the DCCB power electronic device is greatly tested. The fault current limiter can reduce the rising rate of short-circuit current, and the direct current breaker with the fault current limiting capability becomes a hotspot developed by current equipment.
In order to ensure that a sound line can still normally transmit power after a single-pole ground fault occurs in a direct-current power grid, a direct-current circuit breaker needs to be configured on each direct-current line, the fault line is cut off before a converter is locked, and how to reduce the on-off stress of a power electronic device of the circuit breaker is a difficult point of current research. Related experts have proposed a capacitor-type and capacitor-inductor-type hybrid fault current limiting device, which can suppress the rate of fault current climbing, but still needs a fault current removing device. The current limiting capacity of the direct current circuit breaker is achieved by changing the circulation path of the fault current in the device, but the scheme is provided with more circuit breaker valve sections, each valve section comprises a large number of power electronic devices, and the construction cost is high. The direct current limiter with the DCCB function has the advantages that a bidirectional current limiter topology is effectively utilized, after the DCCB is disconnected, energy of a current-limiting inductor can be discharged through a current-limiting submodule connected in parallel with the DCCB, the impulse voltage borne by the DCCB is small, but the scheme needs to be provided with the bidirectional current limiter on each direct current bus, and the cost is high if the scheme is applied to large-scale direct current networking. How to improve the economy of the DCCB and reduce the on-off stress of the power electronic switch device is a difficult problem which is urgently needed to be solved at present.
Disclosure of Invention
The invention aims to provide an inductance coupling type high-voltage direct-current-limiting circuit breaker topological structure, which solves the problems in the prior art. The circuit breaker is divided into a current-guiding current limiter and a fault isolation current limiter, the current-guiding current limiter conducts current in an active short-circuit mode, and meanwhile, the fault isolation current limiter alternately inputs coupling inductors to force fault current to flow into a current-guiding branch circuit, so that the current flowing into a fault point is greatly reduced. The current limiter can effectively reduce the on-off stress of each power electronic device, and the power electronic devices of all parts can be mutually matched and borrowed, so that the economy of the topology is effectively improved.
The above object of the present invention is achieved by the following technical solutions:
the inductive coupling type high-voltage direct-current-limiting circuit breaker topological structure consists of a current-guiding current limiter and a fault isolation current limiter, wherein the current-guiding current limiter conducts current in an active short-circuit mode, and meanwhile, the fault isolation current limiter alternately inputs coupling inductors to force fault current to flow into a current-guiding branch circuit, so that the current flowing into a fault point is reduced to the maximum extent; the fault isolation current limiter is responsible for inhibiting fault point injection current and isolating the fault point, and the current guide current limiter is responsible for introducing the fault point injection current into the current guide branch circuit and reducing the fault current increase rate;
the current-guiding current limiter structure consists of an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy-leakage lightning arrester and a coupling inductor;
the fault isolation current limiter structure adopts an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy leakage arrester, a coupling inductor and a power electronic switch group to form the fault isolation current limiter.
SaidThe current-guiding current limiter structure consists of an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy-leakage lightning arrester and a coupling inductor, wherein T is1、T2、T3Are respectively three power electronic switch groups, LLI.e. smoothing reactors for dc lines, L0Is LLCoupling inductors connected with the different terminals; in normal operation, the ultra-fast mechanical switch is S1Open circuit state, T3The switch group is in an off state, T1、T2The IGBTs of the two switch groups are in a conducting state, and the inductor L0Is bypassed, and the current passes through the smoothing reactor LLCan be at T1、T2The branch is free to circulate.
The fault isolation current limiter consists of an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy leakage lightning arrester and a coupling inductor L1、L2Composition of T4、T5、T6Are respectively three power electronic switch groups, T5、T6Connected to L1、L2On the synonym end of (c); the fault isolation current limiter is a pass-through T5、T6The IGBTs of the two switch groups are alternately conducted to realize the positive connection and the negative connection of the coupling inductor, and are matched with the current-guiding current limiter to force fault current to flow into the current-guiding branch circuit, disconnect the ultra-fast mechanical switch and realize the physical isolation from a fault point; during normal operation, the ultra-fast mechanical switch is closed, T4Each IGBT of the switch group is in a conducting state, T5、T6The IGBTs of the two switch groups are in a turn-off state; due to the action of the current-guiding current limiter, after a fault occurs, the current flowing through the fault isolation current limiter is very small, and the energy to be released is small when the IGBT is turned off; therefore T4、T5、T6Without the need for excessive series flow of IGBT devices.
Another object of the present invention is to provide a method for implementing fault current limiting using the inductively coupled high voltage dc current limiting circuit breaker, comprising:
(1) failure to L0Throw-in period (t)0～t1)
The time interval control and protection device is responsible for detecting the current of a direct current line, and if the current risesIssuing an input L if the rate is out of limit0Instruction, the time interval is delayed by 1 ms;
at fault occurrence to L0The state of the circuit breaker in the input time period is the same as the normal state, T3、T5、T6The IGBT of (1) is in a turn-off state, no current flows through the IGBT, and fault current flows through the IGBTL、T1IGBT and T of2Diode, ultrafast mechanical switch of fault isolation current limiter and T4The IGBT of (1) flows into the fault point;
(2) current limiting period (t)1～t2)
Issuing input L of control and protection device0After the command, continuing to execute the fault positioning judgment logic, determining a fault line and a fault position, and delaying the current limiting time period by 2 ms;
during the current limiting period, the current-guiding current limiters of the fault line and the non-fault line are totally turned off T1、T2The fault current is forced to flow into the coupling inductor L0To achieve the effect of primary current limiting and simultaneously close the ultra-fast mechanical switch S1Preparing for the next period of time for putting the drainage branch into use; t is t1The fault current will suddenly change to:
in the formula i(t1-)Is L0Fault current before input, i(t1+)Is L0Fault current after input, fault current at t1There is a step decrease in time, T1、T2The lightning arrester is used for discharging overvoltage generated by current step;
(3) drainage time period (t)2～t3)
t2The time control and protection device determines a fault line, and the function part of the circuit breaker starts to be started;
a) current limiter for fault line: t is t2Instant fast trigger T2、T3Each IGBT is equivalent to that fault current is directly grounded through a series-connected coupling inductor through a current-guiding branch circuit, and the grounding impedance is extremely small; at this time, the current is changedThe discharge current of the device and the feed-in current of the non-fault line flow into the current-guiding branch circuit and the fault point, but the current flowing into the fault point can be ignored due to the action of the fault isolation current limiter;
b) current-limiting device for non-faulty line: continuously maintaining the current limiting period while tripping the mechanical switch S1By means of series-connected coupling inductors LL、L0Carrying out current limiting to reduce the feed-in current to the fault line;
c) fault isolation current limiter: t is t2Instant quick turn-off T4Is turned on alternately T at the same time5、T6IGBT of (1), keeping coupling inductance L1、L2The alternating connection reduces the current flowing into the fault point to a great extent, and forces the fault current to flow into the current-guiding branch with extremely small impedance;
(4) current limiting period (t)3～t4)
a) Fault isolation current limiter: t is t3The current injected into the fault point at the moment is almost 0, and is also T5、T6Turn off the IGBT to realize the primary isolation from the fault point, T5、T6A small part of energy is discharged through the parallel lightning arrester, and at the moment, the fault current is completely transferred to the current-guiding branch; t is t4Time ultra-fast mechanical switch S2Completely disconnecting, and establishing physical isolation between a fault point and a direct current bus;
b) current limiter for fault line: continuously keeping the working state of the drainage period;
c) current-limiting device for non-faulty line: continuously keeping the working state of the current limiting period;
(5) clearing fault current period (t)4～t5)
a) Fault isolation current limiter: after the current limiting time interval is over, the current limiter finishes the role of current limiting and fault point isolation, and S is continuously maintained2Off state, T4、T5、T6An off state;
b) current limiter for fault line: t is t4Time S2After jumping off, the drainage task is completed, and the T is quickly treated2、T3The IGBT of (1) applies a turn-off signal, and the residual energy passes through T2、T3The lightning arrester is discharged to trip off the mechanical switch S1；
c) Current-limiting device for non-faulty line: in order to ensure that the current-guiding current limiter of the fault line is smoothly switched on and off, the current limiter continuously keeps the working state of the current-limiting period;
(6) preparation for reclosing time period (t)5～t6)
Preparing a reclosing time period, namely freeing waiting time of each lightning arrester after fault current is cleared, wherein the time is usually 100 ms; during which each device will take the following actions:
a) fault isolation current limiter: closed ultra-fast mechanical switch S2And turn on T when waiting for reclosing4Is determined.
b) Current limiter for fault line: closed ultra-fast mechanical switch S1，T1、T2、T3Keeping the turn-off state to prepare for the drainage branch to be quickly put into use after the reclosing failure;
c) current-limiting device for non-faulty line: continuously keeping the working state of the current-limiting period to prevent overcurrent after reclosing failure;
(7) reclosing time period (t)6～t7)
a) Fault isolation current limiter: closed T4The direct current line is formally communicated with the IGBT device; if the current is increased slowly, the current is indicated as a clockwise fault, and reclosing is successful;
b) and (3) drainage and current limiter: if the reclosing is successful, simultaneously conducting a fault line and a non-fault line T1、T2The inductor L of0The bypass reduces the reactance value of the direct current line, ensures the dynamic characteristic of the direct current power grid, and responds to the active change more quickly and simultaneously breaks the ultra-fast mechanical switch S of the fault line1；
If closed T4After the IGBT device is started, if the current is rapidly increased, the current is indicated as a permanent fault, reclosing fails, and the whole device enters the work of the drainage time period, the fault isolation time period and the fault current clearing time period again;
cleaning outAfter fault current, the current-guiding current limiter of non-fault line is turned on1、T2The normal operation state of the IGBT is recovered; after the permanent fault is eliminated, the two current limiters of the fault line are put into normal operation again.
The invention has the beneficial effects that:
the inductive coupling current-limiting circuit breaker provided by the invention can complete fault current conduction within 3ms and fault removal within 6ms, has good current-limiting and circuit-breaking capabilities, only needs 632 IGBT devices, and has high economical efficiency.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention.
FIG. 1 is a diagram of a half-bridge sub-module topology;
FIG. 2 is a MMC direct current side fault equivalent circuit diagram;
fig. 3 is a topology structure diagram of a conventional dc circuit breaker;
FIG. 4 is a view of a layout of a flow restriction device;
FIG. 5 is a view of a drainage restrictor topology;
FIG. 6 is a diagram of a preliminary current limiting path according to the present invention;
FIG. 7 is a diagram of the fault current drainage path of the present invention;
FIG. 8 is a flow chart of the present invention.
Detailed Description
The details of the present invention and its embodiments are further described below with reference to the accompanying drawings.
Referring to fig. 1 to 8, the invention designs an inductive coupling type high-voltage direct-current-limiting circuit breaker, the direct-current circuit breaker with the fault current suppression capability is divided into a current-guiding current limiter and a fault isolation current limiter, the current-guiding current limiter conducts current in an active short-circuit mode, and the fault isolation current limiter alternately inputs coupling inductance to force fault current to flow into a current-guiding branch circuit, so that the current flowing into a fault point is greatly reduced. In order to overcome the defects of the traditional high-voltage direct-current circuit breaker, the current limiter can effectively reduce the breaking stress of each power electronic device, the power electronic devices of all parts can be mutually matched and borrowed, and the economy of the topology is effectively improved.
1. DC side fault discharge mechanism and introduction of traditional high-voltage DC circuit breaker
In the bipolar dc system, when a unipolar ground fault occurs, the HBSM does not have a fault blocking capability, and therefore, even if the inverter is locked, the three-phase short circuit is still caused on the ac side. The action targets of the current limiter and the circuit breaker of the direct current power grid are to prevent the current converter from locking, so that the sound direct current line cannot transmit power. After the unipolar short circuit is grounded, the capacitor C and the diode D are in parallel relationship for the sub-module in the on state, and the current flows directly through the diode D for the cut-off sub-module, so the discharge path is as shown in fig. 2. L isaIs bridge arm inductance, LLIs a current-limiting inductor, LeIs an equivalent inductance, ReIs an equivalent resistance, CeIs an equivalent capacitance, DeIs equivalently a diode connected in parallel with a capacitor. As can be seen from the discharge path in fig. 2, each component in the equivalent circuit is equivalent to the result of connecting the upper and lower bridge arms of each phase of the converter in series and then connecting them in parallel, that is:
in the formula RonIs the on-resistance of IGBT, RgAnd N is the number of each bridge arm submodule as a short-circuit resistor.
If the direct current system does not take any measures after the fault, waiting for CeAfter complete discharge, LeWill pass through DeFollow current, CeCan not be reversely charged and can not form LCAn oscillating circuit. However, the control and protection measures such as circuit breaker action or converter locking must be put into operation at the fault current climbing stage, and at the moment, CeStill higher voltage, DeThe back pressure is in a turn-off state, and the grounding resistance is not very large when short-circuit fault occurs, so that a loop can still be equivalent to an under-damped LC oscillating circuit before the control and protection device is put into operation, and direct short-circuit current is attenuatedThe oscillating capacitor discharge current satisfies the following formula:
in the formula uCfIs the sequential value of the equivalent capacitor voltage ifFor capacitor discharge current transients, UdcTo a rated DC voltage, Idcis rated DC current, α attenuation coefficient, omegadTo attenuate the resonance angular frequency.
The traditional high-voltage direct-current circuit breaker is composed of a main branch, a transfer branch and an energy discharge branch, and is shown in figure 3. When the inverter works normally, the main branch is connected, the transfer branch is disconnected, and power is transmitted to the inverter station through the main branch. After the fault occurs, the control protection device issues a breaker action instruction after short time delay, switches on the transfer branch IGBT device, and simultaneously switches off the main branch IGBT device to force the current to flow into the transfer branch. And after the current of the main branch circuit is reduced to 0, the ultra-fast isolating switch is switched off to realize physical isolation of a fault point, the IGBT device of the transfer branch circuit is switched off, and the generated overvoltage is discharged through the lightning arrester group of the energy discharge branch circuit.
Because the traditional high-voltage direct-current circuit breaker is directly connected in series in a direct-current line, two groups of reverse current transfer switch groups and isolation fault switch groups are required to be configured to ensure the bidirectional conduction of a direct-current system; and the circuit breaker lacks current-limiting capacity, and IGBT device breaking impulse voltage is high, need to establish ties a large amount of switch groups and equally divide this voltage, so this circuit breaker cost is higher.
2. Method for designing topological structure of fault current-limiting circuit breaker
The invention provides a direct current breaker with fault current-limiting capability, which consists of a current-guiding current limiter and a fault isolation current limiter, wherein the fault isolation current limiter is responsible for inhibiting fault point injection current and isolating a fault point, and the current-guiding current limiter is responsible for introducing the fault point injection current into a current-guiding branch circuit and reducing the fault current increase rate, as shown in figure 5. The dc current path is shown in fig. 4 and 5 for normal operation of the system.
3. Structural design method of drainage current limiter
The current limiter consists of an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy leakage lightning arrester and a coupling inductor, wherein T is1、T2、T3Are respectively three power electronic switch groups, LLI.e. smoothing reactors for dc lines, L0Is LLAnd the different-name ends are connected with the coupling inductor. In normal operation, the ultra-fast mechanical switch is S1Open circuit state, T3The switch group is in an off state, T1、T2The IGBTs of the two switch groups are in a conducting state, and the inductor L0Is bypassed, and the current passes through the smoothing reactor LLCan be at T1、T2The branch is free to circulate.
1) Current limiter for fault line: after the fault occurs, a short-circuit current flows through T1The IGBT of the switch group injects into the fault point, and the current-guiding current limiter is disconnected T at the moment1、T2Switch group IGBT to couple inductor L0A series circuit, which is turned on T simultaneously after a short judgment delay2、T3Switch group IGBT, pass T2、T3And a new low-impedance short-circuit point is formed, so that the fault current is forced to flow into the current-guiding branch circuit, and the ultra-fast mechanical switch of the fault isolation current limiter is convenient to switch off.
2) Current-limiting device for non-faulty line: after the fault occurs, a short-circuit current flows through T2The IGBT of the switch group injects into the fault point, and the current-guiding current limiter is disconnected T at the moment1、T2Switch group IGBT, hold T3The off state of the switch group forces current through L0And LLThe formed coupling inductor is fed into the fault line.
4. Method for designing fault isolation current limiter structure
The current limiter comprises an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy leakage lightning arrester and a coupling inductor L1、L2Composition of T4、T5、T6Are respectively three power electronic switch groups, T5、T6Connected to L1、L2On the synonym end of (c). The fault isolation current limiter is a pass-through T5、T6The IGBTs of the two switch groups are alternately conducted to realize positive connection and reverse connection of the coupling inductor, and are matched with the current-guiding current limiter to force fault current to flow into the current-guiding branch circuit, so that the ultra-fast mechanical switch is disconnected, and physical isolation from a fault point is realized. During normal operation, the ultra-fast mechanical switch is closed, T4Each IGBT of the switch group is in a conducting state, T5、T6The IGBTs of the two switch groups are in an off state. Due to the action of the current-guiding current limiter, after a fault occurs, the current flowing through the fault isolation current limiter is very small, and the energy needing to be discharged when the IGBT is turned off is small. Therefore T4、T5、T6Without the need for excessive series flow of IGBT devices.
5. Design of working method of fault current-limiting circuit breaker
5.1 Fault Generation to L0Throw-in period (t)0～t1)
The time period control and protection device is responsible for detecting the current of the direct current line, and issues an input L if the current rise rate exceeds the limit0The time delay is about 1 ms.
The state of the circuit breaker is the same as the normal state in the time period, T3、T5、T6The IGBT of (1) is in a turn-off state, no current flows through the IGBT, and fault current flows through the IGBTL、T1IGBT and T of2Diode, ultrafast mechanical switch of fault isolation current limiter and T4Flows into the fault point.
5.2 Current limiting time period (t)1～t2)
Issuing input L of control and protection device0And after the command, continuously executing judgment logics such as fault location and the like, and determining a fault line and a fault position, wherein the time delay is about 2 ms.
During this time period, the current-carrying current limiters of the faulty line and the non-faulty line have all been turned off T1、T2The fault current is forced to flow into the coupling inductor L0To achieve the effect of primary current limiting and simultaneously close the ultra-fast mechanical switch S1And preparing the drainage branch for the next period of time to be put into use, as shown in fig. 6. According to the principle of conservation of flux linkage, t1The fault current will suddenly change to:
in the formula i(t1-)Is L0Fault current before input, i(t1+)Is L0Fault current after input, fault current at t1There is a step decrease in time, T1、T2The arrester is used to discharge overvoltage generated by current step.
5.3 drainage time period (t)2～t3)
t2And the time control and protection device determines a fault line, and the function part of the circuit breaker starts to be started.
1) Current limiter for fault line: t is t2Instant fast trigger T2、T3Each IGBT is directly grounded through the current-guiding branch by the series-connected coupling inductor, which corresponds to a fault current, and the ground impedance is extremely small, as shown in fig. 7. The converter discharge current and the non-fault line feed current will now flow into the current-guiding branch and the fault point, but the current flow into the fault point will be almost negligible due to the effect of the fault isolation current limiter.
2) Current-limiting device for non-faulty line: continuously maintaining the current limiting period while tripping the mechanical switch S1By means of series-connected coupling inductors LL、L0And carrying out current limiting to reduce the current fed into the fault line.
3) Fault isolation current limiter: t is t2Instant quick turn-off T4Is turned on alternately T at the same time5、T6IGBT of (1), keeping coupling inductance L1、L2And the alternating connection greatly reduces the current flowing into a fault point, and forces the fault current to flow into a current-guiding branch with extremely small impedance.
5.4 Fault isolation time period (t)3～t4)
1) Fault isolation current limiter: t is t3The current injected into the fault point at the moment is almost 0, and is also T5、T6The IGBT is turned off to realize the primary isolation from the fault pointFrom, T5、T6A small part of energy is discharged through the parallel lightning arrester, and at the moment, the fault current is completely transferred to the current-guiding branch. t is t4Time ultra-fast mechanical switch S2And the direct current bus is completely disconnected, and the physical isolation between a fault point and the direct current bus is established.
2) Current limiter for fault line: and continuously keeping the working state of the drainage period.
3) Current-limiting device for non-faulty line: and continuously keeping the working state of the current limiting period.
5.5 clear Fault Current time period (t)4～t5)
1) Fault isolation current limiter: t is t4When the current limiter has completed its role of limiting current and isolating fault point, it continues to maintain S2Off state, T4、T5、T6An off state.
2) Current limiter for fault line: t is t4Time S2After jumping off, the drainage task is completed, and the T is quickly treated2、T3The IGBT of (1) applies a turn-off signal, and the residual energy passes through T2、T3The lightning arrester is discharged to trip off the mechanical switch S1。
3) Current-limiting device for non-faulty line: in order to ensure that the current-guiding current limiter of the fault line is smoothly switched on and off, the current limiter needs to continuously maintain the working state of the current-limiting period.
5.6 preparation for reclosing time period (t)5～t6)
The time period is the trip waiting time of each lightning arrester after the fault current is cleared, and is usually about 100 ms. During this period, each device will take the following actions:
1) fault isolation current limiter: closed ultra-fast mechanical switch S2And turn on T when waiting for reclosing4Is determined.
2) Current limiter for fault line: closed ultra-fast mechanical switch S1，T1、T2、T3Keeping the off state provides for the diversion branch to be quickly put into service after the reclosing failure.
3) Drainage of non-faulty linesA current limiter: and the working state of the current-limiting period is continuously kept, so that overcurrent after reclosing failure is prevented. 5.7 reclosing time period (t)6～t7)
1) Fault isolation current limiter: closed T4The direct current line is formally communicated with the IGBT device. If the current is increased slowly, the fault is indicated as a clockwise fault, and the reclosing is successful.
2) And (3) drainage and current limiter: if the reclosing is successful, simultaneously conducting a fault line and a non-fault line T1、T2The inductor L of0The bypass reduces the reactance value of the direct current line, ensures the dynamic characteristic of the direct current power grid, and responds to the active change more quickly and simultaneously breaks the ultra-fast mechanical switch S of the fault line1。
If closed T4After the IGBT device is used, if the current is rapidly increased, the permanent fault is indicated, the reclosing fails, and the whole device enters the work of the drainage time period, the fault isolation time period and the fault current clearing time period again.
After the fault current is cleared, the current-guiding current limiter of the non-fault line is conducted at the same time1、T2The normal operation state of the IGBT is recovered; after the permanent fault is eliminated, the two current limiters of the fault line are put into normal operation again.
The above description is only a preferred example of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like of the present invention shall be included in the protection scope of the present invention.
Claims (4)
1. The utility model provides an inductance coupling type high voltage direct current limiting circuit breaker topological structure which characterized in that: the inductive coupling type high-voltage direct-current-limiting circuit breaker consists of a current-guiding current limiter and a fault isolation current limiter, wherein the current-guiding current limiter conducts current in an active short-circuit mode, and the fault isolation current limiter alternately inputs coupling inductors to force fault current to flow into a current-guiding branch circuit, so that the current flowing into a fault point is greatly reduced; the fault isolation current limiter is responsible for inhibiting fault point injection current and isolating the fault point, and the current guide current limiter is responsible for introducing the fault point injection current into the current guide branch circuit and reducing the fault current increase rate;
the current-guiding current limiter structure consists of an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy-leakage lightning arrester and a coupling inductor;
the fault isolation current limiter structure adopts an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy leakage arrester, a coupling inductor and a power electronic switch group to form the fault isolation current limiter.
2. The inductively coupled high voltage direct current limiting circuit breaker topology of claim 1, wherein: the current-guiding current limiter structure consists of an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy-leakage lightning arrester and a coupling inductor, wherein T is1、T2、T3Are respectively three power electronic switch groups, LLI.e. smoothing reactors for dc lines, L0Is LLCoupling inductors connected with the different terminals; in normal operation, the ultra-fast mechanical switch is S1Open circuit state, T3The switch group is in an off state, T1、T2The IGBTs of the two switch groups are in a conducting state, and the inductor L0Is bypassed, and the current passes through the smoothing reactor LLCan be at T1、T2The branch is free to circulate.
3. The inductively coupled high voltage direct current limiting circuit breaker topology of claim 1, wherein: the fault isolation current limiter consists of an ultra-fast mechanical switch, an IGBT, an anti-parallel diode, an energy leakage lightning arrester and a coupling inductor L1、L2Composition of T4、T5、T6Are respectively three power electronic switch groups, T5、T6Connected to L1、L2On the synonym end of (c); the fault isolation current limiter is a pass-through T5、T6The IGBTs of the two switch groups are alternately switched on to realize positive connection and reverse connection of the coupling inductor, and are matched with the current-guiding current limiter to force fault current to flow into the current-guiding branch circuit to disconnect the ultra-fast mechanical switch to realize the effectPhysical isolation from the fault point; during normal operation, the ultra-fast mechanical switch is closed, T4Each IGBT of the switch group is in a conducting state, T5、T6The IGBTs of the two switch groups are in a turn-off state; due to the action of the current-guiding current limiter, after a fault occurs, the current flowing through the fault isolation current limiter is very small, and the energy to be released is small when the IGBT is turned off; therefore T4、T5、T6Without the need for excessive series flow of IGBT devices.
4. A method of achieving fault current limiting using an inductively coupled high voltage direct current limiting circuit breaker according to any of claims 1 to 3, characterized by: the method comprises the following steps:
(1) failure to L0Throw-in period (t)0～t1)
Failure to L0The switching-in time interval control and protection device is responsible for detecting the current of the direct current line, and sends a switching-in L if the current rise rate exceeds the limit0Instruction, the time interval is delayed by 1 ms;
at fault occurrence to L0The state of the circuit breaker in the input time period is the same as the normal state, T3、T5、T6The IGBT of (1) is in a turn-off state, no current flows through the IGBT, and fault current flows through the IGBTL、T1IGBT and T of2Diode, ultrafast mechanical switch of fault isolation current limiter and T4The IGBT of (1) flows into the fault point;
(2) current limiting period (t)1～t2)
Issuing input L of control and protection device0After the command, continuously executing the fault location judgment logic to determine the fault line and the fault position, t1～t2The time interval is delayed by 2 ms;
during the current limiting period, the current-guiding current limiters of the fault line and the non-fault line are totally turned off T1、T2The fault current is forced to flow into the coupling inductor L0To achieve the effect of primary current limiting and simultaneously close the ultra-fast mechanical switch S1Preparing for the next period of time for putting the drainage branch into use; t is t1The fault current will suddenly change to:
in the formula i(t1-)Is L0Fault current before input, i(t1+)Is L0Fault current after input, fault current at t1There is a step decrease in time, T1、T2The lightning arrester is used for discharging overvoltage generated by current step;
(3) drainage time period (t)2～t3)
t2The time control and protection device determines a fault line, and the function part of the circuit breaker starts to be started;
a) current limiter for fault line: t is t2Instant fast trigger T2、T3Each IGBT is equivalent to that fault current is directly grounded through a series-connected coupling inductor through a current-guiding branch circuit, and the grounding impedance is extremely small; at the moment, the discharging current of the converter and the feeding current of the non-fault line flow into the current-guiding branch circuit and the fault point, but the current flowing into the fault point can be ignored due to the action of the fault isolation current limiter;
b) current-limiting device for non-faulty line: continuously maintaining the current limiting period while tripping the mechanical switch S1By means of series-connected coupling inductors LL、L0Carrying out current limiting to reduce the feed-in current to the fault line;
c) fault isolation current limiter: t is t2Instant quick turn-off T4Is turned on alternately T at the same time5、T6IGBT of (1), keeping coupling inductance L1、L2The alternating connection reduces the current flowing into the fault point to a great extent, and forces the fault current to flow into the current-guiding branch with extremely small impedance;
(4) current limiting period (t)3～t4)
a) Fault isolation current limiter: t is t3The current injected into the fault point at the moment is almost 0, and is also T5、T6Turn off the IGBT to realize the primary isolation from the fault point, T5、T6A small part of the energy passes through the parallel lightning arresterDischarging, wherein the fault current is completely transferred to the current-guiding branch; t is t4Time ultra-fast mechanical switch S2Completely disconnecting, and establishing physical isolation between a fault point and a direct current bus;
b) current limiter for fault line: continuously keeping the working state of the drainage period;
c) current-limiting device for non-faulty line: continuously keeping the working state of the current limiting period;
(5) clearing fault current period (t)4～t5)
a) Fault isolation current limiter: after the current limiting time interval is over, the current limiter finishes the role of current limiting and fault point isolation, and S is continuously maintained2Off state, T4、T5、T6An off state;
b) current limiter for fault line: t is t4Time S2After jumping off, the drainage task is completed, and the T is quickly treated2、T3The IGBT of (1) applies a turn-off signal, and the residual energy passes through T2、T3The lightning arrester is discharged to trip off the mechanical switch S1；
c) Current-limiting device for non-faulty line: in order to ensure that the current-guiding current limiter of the fault line is smoothly switched on and off, the current limiter continuously keeps the working state of the current-limiting period;
(6) preparation for reclosing time period (t)5～t6)
Preparing a reclosing time period as the time for each lightning arrester to free after fault current is cleared, wherein the time is usually 100 ms; during which each device will take the following actions:
a) fault isolation current limiter: closed ultra-fast mechanical switch S2And turn on T when waiting for reclosing4The IGBT command of (1);
b) current limiter for fault line: closed ultra-fast mechanical switch S1，T1、T2、T3Keeping the turn-off state to prepare for the drainage branch to be quickly put into use after the reclosing failure;
c) current-limiting device for non-faulty line: continuously keeping the working state of the current-limiting period to prevent overcurrent after reclosing failure;
(7) reclosing time period (t)6～t7)
a) Fault isolation current limiter: closed T4The direct current line is formally communicated with the IGBT device; if the current is increased slowly, the current is indicated as a clockwise fault, and reclosing is successful;
b) and (3) drainage and current limiter: if the reclosing is successful, simultaneously conducting a fault line and a non-fault line T1、T2The inductor L of0The bypass reduces the reactance value of the direct current line, ensures the dynamic characteristic of the direct current power grid, and responds to the active change more quickly and simultaneously breaks the ultra-fast mechanical switch S of the fault line1；
If closed T4After the IGBT device is started, if the current is rapidly increased, the current is indicated as a permanent fault, reclosing fails, and the whole device enters the work of the drainage time period, the fault isolation time period and the fault current clearing time period again;
after the fault current is cleared, the current-guiding current limiter of the non-fault line is conducted at the same time1、T2The normal operation state of the IGBT is recovered; after the permanent fault is eliminated, the two current limiters of the fault line are put into normal operation again.
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