CN114709800A - Compact direct-current circuit breaker sharing branch circuit and control method thereof - Google Patents

Compact direct-current circuit breaker sharing branch circuit and control method thereof Download PDF

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Publication number
CN114709800A
CN114709800A CN202210462451.1A CN202210462451A CN114709800A CN 114709800 A CN114709800 A CN 114709800A CN 202210462451 A CN202210462451 A CN 202210462451A CN 114709800 A CN114709800 A CN 114709800A
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current
branch
fault
mechanical switch
switch
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CN114709800B (en
Inventor
刘思远
陈金超
金敬勇
刘志远
耿英三
王建华
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Xian Jiaotong University
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Xian Jiaotong University
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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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/02—Details
    • H02H3/06—Details with automatic reconnection
    • H02H3/066—Reconnection being a consequence of eliminating the fault which caused disconnection
    • 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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Abstract

The invention provides a compact direct current breaker sharing a branch circuit and a control method thereof, when the breaker is in normal through-current, the current is conducted through a main mechanical switch of a through-current loop, and the loss of the direct current breaker is extremely low; the direct current circuit breaker of the invention adopts the quick operating mechanism to drive the mechanical switch, can cut off the fault current in a short time, realizes the reclosing function, isolates the fault and protects the flexible direct current system. The control method can generate oscillation current with gradually increased amplitude by sharing the current conversion branch and the energy absorption branch, the oscillation current is superposed on the current of the main loop to generate a current zero crossing point, and finally the current is switched off by the mechanical switch. The circuit breaker is used for breaking and isolating fault current of all external lines on one bus. And each direct-current bus is only provided with one direct-current breaker, so that the cost and the volume of the direct-current breaker in a direct-current power grid are greatly reduced, and the technical support is provided for the construction of the direct-current power grid.

Description

Compact direct-current circuit breaker sharing branch circuit and control method thereof
Technical Field
The invention belongs to the technical field of power equipment, and particularly belongs to a compact direct current breaker sharing a branch circuit and a control method thereof.
Background
At present, a direct current circuit breaker mainly has two implementation modes of a mechanical direct current circuit breaker and a hybrid direct current circuit breaker, wherein the mechanical circuit breaker becomes an optimal technical scheme of the direct current circuit breaker by the advantage of small on-state loss of the mechanical circuit breaker. With the great increase of the demand of a distributed direct current power supply system of new energy, especially in an offshore wind power flexible multi-terminal direct current system, the power grid has limited erection space resources, limited offshore platform bearing capacity, large fault current and high rise rate, so that the requirements on the volume space, weight, on-off capacity, on-off speed and cost of the high-voltage direct current circuit breaker are extremely high. As shown in fig. 1, the conventional dc circuit breaker can only break fault current on one incoming line and one outgoing line, and if the conventional mechanical dc circuit breaker is applied to a dc power grid, the number of the dc circuit breakers installed on each dc bus is the same as the number of the external lines of the dc bus. The number of the direct-current circuit breakers to be configured in the direct-current power grid is large, the direct-current circuit breakers are expensive in manufacturing cost and large in size and space, and further the construction cost of the direct-current power grid is greatly increased, so that the direct-current circuit breakers cannot be applied to a flexible multi-terminal direct-current system.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a compact direct current breaker sharing a branch and a control method thereof, which ensure that only one direct current breaker is required to be configured for each direct current bus, greatly reduce the cost and the volume of the direct current breaker in a direct current power grid, and provide technical support for the construction of the direct current power grid.
In order to achieve the purpose, the invention provides the following technical scheme:
a compact direct current breaker sharing a branch circuit comprises a wiring terminal, a through-current branch circuit, an isolation branch circuit, a breaking unit, a direct current bus, an online monitoring system and a control system;
the number of the wiring ends, the number of the through-current branches and the number of the isolation branches are multiple and are connected in a one-to-one correspondence manner;
one end of the through-current branch is connected with the wiring terminal through a mechanical switch, and the other end of the through-current branch is connected with a direct-current bus;
one end of the through-current branch is connected with one end of the isolation branch, the other ends of the isolation branches are connected with one end of the cut-off unit, and the other end of the cut-off unit is connected with a line outlet end bus;
the through-flow branch comprises a main mechanical switch; the main mechanical switch comprises one or more vacuum switches connected in series; the isolation branch comprises an auxiliary isolation switch and a thyristor module; the auxiliary isolating switch is connected with the thyristor module in series;
the online monitoring system is used for measuring the current magnitude and the current direction flowing through the current conversion switch module, the current and the direction flowing through the lightning arrester, the voltage and the temperature at two ends of the lightning arrester, the current magnitude and the current direction flowing through the mechanical switch of the through-current branch circuit, the voltage and the switch stroke at two ends and the voltage at two ends of the energy storage capacitor;
the control system is connected with the online monitoring system and is used for controlling the main mechanical switch of the through-flow branch, the thyristor and the auxiliary isolating switch of the isolating branch, the commutation switch module and the quick mechanical switch.
Preferably, the switching unit comprises a commutation switch module, an oscillating capacitor, an oscillating inductor and a lightning arrester; the current conversion switch module is connected with the oscillating capacitor and the oscillating inductor in series to form a current conversion branch, and the lightning arrester is connected with the current conversion branch in parallel.
Preferably, the switching unit comprises a commutation switch module, an oscillating capacitor, an oscillating inductor and a lightning arrester; the current conversion switch module is connected with the oscillating capacitor in series, the lightning arrester is connected with a branch formed by connecting the lightning arrester and the oscillating capacitor in series in parallel, the branch formed by connecting the lightning arrester and the oscillating capacitor in parallel is connected with one end of the oscillating inductor, and the other end of the oscillating inductor is connected with a wire outlet end bus.
Preferably, the commutation switch module of the switching-on/off unit includes an energy storage capacitor, a charging branch and a power electronic power device;
the power electronic power device comprises a fully-controlled power electronic power device ES1, a fully-controlled power electronic power device ES2, a fully-controlled power electronic power device ES3 and a fully-controlled power electronic power device ES 4;
the cathode of the fully-controlled power electronic power device ES1 and the anode of the fully-controlled power electronic power device ES3 are connected to N1, and N1 is connected with the isolation branch; the cathode of the fully-controlled power electronic power device ES2 and the anode of the fully-controlled power electronic power device ES4 are connected to N2, and N2 is connected to one end of an oscillation capacitor C;
the anode of the fully-controlled power electronic power device ES1 and the anode of the fully-controlled power electronic power device ES2 are connected to N3, and the cathode of the fully-controlled power electronic power device ES3 and the cathode of the fully-controlled power electronic power device ES4 are connected to N4;
n3 is connected with one end of the energy storage capacitor, and N4 is connected with the other end of the energy storage capacitor; the charging direction of the energy storage capacitor is the same as or opposite to the current direction of the main loop; the charging branch circuit is connected with the energy storage capacitor in parallel.
Further, the power electronic power device is a series-parallel combination of one or more of GTO, thyristor, MOSFET, IGBT and IGCT.
Preferably, the mechanical switch is a mechanical switch driven by explosion, a mechanical switch driven by electromagnetic repulsion, a mechanical switch driven by permanent magnet repulsion, a mechanical switch driven by a spring actuator, or a mechanical switch driven by a motor.
Preferably, the online monitoring system comprises a voltage measuring module, a current measuring module, a temperature measuring module, a sound measuring module, an X-ray measuring module and a magnetic field measuring module, and each measuring module of the online monitoring system is used for monitoring the state of the dc breaker and determining the time for the control system to send the instruction signal according to the monitored state of the dc breaker.
A control method of a compact DC breaker sharing a branch is characterized in that based on any one of the above-mentioned compact DC breakers sharing a branch, the method comprises the following processes,
under the normal through-current state of the system, the main mechanical switches and the mechanical switches of the multiple through-current branches are in a closing state; thyristors in the plurality of isolation branches are in an off state; the switching-off unit is in a switching-off state; the line current is converged to the direct current bus by the through-current branch where part of the terminals are located, and then flows out from the direct current bus through the through-current branches where the rest of the terminals are located;
under the fault state, when a fault of a certain terminal is detected, the direct current breaker sends a brake-off command to a main mechanical switch of a through-flow branch where the fault terminal is located and an auxiliary isolating switch of an isolating branch where other terminals are located, arcing starts between contacts, when the main mechanical switch and the auxiliary isolating switch reach a preset opening distance, a conducting command is sent to a thyristor and a full-bridge converter in the isolating branch where the fault terminal is located, two bridge arms of the full-bridge converter are conducted alternately, pre-charged energy storage capacitors are discharged through oscillating capacitors and oscillating inductors, oscillating currents with gradually increasing amplitudes are generated until the oscillating currents are superposed on fault currents to generate current zero crossing points, the fault currents enable voltages at two ends of the oscillating capacitors to rise until the action voltages of an arrester are reached, the fault currents are transferred to an energy-absorbing branch, when the fault currents drop to 0, electric arcs are extinguished, and the quick mechanical switch of the fault terminal is used for brake-off residual currents, and the fault current is cut off.
Preferably, for a permanent fault, waiting for a preset time after the fault current is cut off, conducting a main mechanical switch of the through-flow branch and a quick mechanical switch connected with the main mechanical switch, detecting the fault current again, repeating the cut-off process of the direct-current circuit breaker, after the fault current drops to zero, switching off the quick mechanical switch connected with the fault terminal and an auxiliary isolating switch in the isolating branch, and switching on the auxiliary isolating switches in the isolating branch where the other normal terminals are located, so as to isolate a fault line, and resetting the direct-current circuit breaker to wait for the next operation;
for a temporary fault, after the on-off unit is switched on, the fault current is not detected, and all the quick mechanical switches and the auxiliary isolating switches are switched on, so that the direct-current circuit breaker is reset to wait for the next operation.
Preferably, the commutation comprises a stage 1 and a stage 2;
the stage 1 is as follows: the ES1 and ES4 in the commutation switch module are turned on, the ES2 and ES3 are turned off, the energy storage capacitor is discharged through the oscillation capacitor and the oscillation inductor after the ES1 and ES4 are turned on, a sinusoidal oscillation current is generated, when the sinusoidal oscillation current finishes oscillation of a sinusoidal half-wave and the oscillation current reaches a zero crossing point, the control system sends out a control signal, and the phase 2 is executed: ES1 and ES4 are closed, ES2 and ES3 are conducted, the polarity of the energy storage capacitor is consistent with the discharge current direction, the energy storage capacitor continues to discharge through the oscillation capacitor and the oscillation inductor, the amplitude of the generated sinusoidal oscillation current is higher than that of the first sinusoidal half-wave, when the current of the second sinusoidal half-wave reaches the zero-crossing point, the control system sends out a control signal, the phase 1 is executed, and then the phase 2 and the phase 1 are executed alternately.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention provides a compact direct current breaker sharing a branch, when the direct current is normally conducted, the current is conducted through a main mechanical switch of a through-current loop, and the loss of the direct current breaker is extremely low; the direct current circuit breaker of the invention adopts the quick operating mechanism to drive the mechanical switch, can cut off the fault current in a short time, realizes the reclosing function, isolates the fault and protects the flexible direct current system.
According to the control method of the compact direct current breaker sharing the branch circuit, the current conversion branch circuit can generate the oscillating current with the amplitude gradually increasing through sharing the current conversion branch circuit and the energy absorption branch circuit, the oscillating current is superposed on the current of the main loop to generate the current zero crossing point, and finally the current is switched off through the mechanical switch. The circuit breaker is small in occupied area and low in construction cost, and is beneficial to construction of a multi-end flexible direct current system.
Drawings
Fig. 1 shows a configuration diagram of a conventional dc circuit breaker in four-terminal engineering;
figure 2 shows a schematic structural view of a particular embodiment of the compact circuit breaker of the present invention;
fig. 3 is a schematic view showing a sensor mounting position of the compact circuit breaker of the present invention;
fig. 4 shows a schematic structural view of a particular embodiment of the breaking unit in the compact circuit breaker of the present invention;
fig. 5 shows a schematic structural view of another embodiment of the breaking unit in the compact circuit breaker of the present invention.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
Examples
As shown in fig. 2, the present invention discloses a compact dc circuit breaker sharing a branch, which includes n terminals, n through-current branches, n isolation branches, a disconnection unit, a dc bus, a set of online monitoring system and a set of control system.
One end of each through-current branch and one end of each isolation branch are correspondingly connected with the wiring terminals through a rapid mechanical switch RCB, the other end of each through-current branch is connected with a direct-current bus, the other end of each isolation branch and one end of the on-off unit are connected with N1, and the other end of the on-off unit is connected with a bus at the wire outlet end. The through-flow branch comprises a main mechanical switch CB which is formed by connecting one vacuum switch or a plurality of vacuum switches in series. The isolation branch comprises an auxiliary isolating switch S and a thyristor module T.
As shown in fig. 4, the switching unit includes a commutation switch module and an oscillation capacitor CPAnd an oscillating inductor LPAnd a lightning arrester SA. Current conversion switch module and oscillation capacitor CpThe lightning arrester SA is connected in parallel with a branch formed by connecting the lightning arrester SA and the lightning arrester SA in series, and the branch formed by connecting the lightning arrester SA and the branch in parallel is connected with the oscillating inductor LpOne terminal of (1), oscillation inductance LpThe other end of the connecting wire is connected with a wire outlet end bus. Or, as shown in FIG. 5, the commutation switch module and the oscillation capacitor CPAnd an oscillating inductor LPThe series connection forms a current conversion branch circuit, and the lightning arrester is connected with the current conversion branch circuit in parallel.
The commutation switch module comprises an energy storage capacitor CDCThe charging branch circuit and the power electronic power device; the charging branch comprises a DC power supply VDCCharging resistor RCHCharging switch SCH(ii) a Power electronic powerThe device comprises a fully-controlled power electronic power device ES1, a fully-controlled power electronic power device ES2, a fully-controlled power electronic power device ES3 and a fully-controlled power electronic power device ES 4.
The cathode of the fully-controlled power electronic power device ES1 and the anode of the fully-controlled power electronic power device ES3 are connected to N1, and N1 is connected with the isolation branch; the cathode of the fully-controlled power electronic power device ES2 and the anode of the fully-controlled power electronic power device ES4 are connected with N2, and N2 is connected with an oscillation capacitor CpOne end of (a);
the anode of the fully-controlled power electronic power device ES1 and the anode of the fully-controlled power electronic power device ES2 are connected to N3, and the cathode of the fully-controlled power electronic power device ES3 and the cathode of the fully-controlled power electronic power device ES4 are connected to N4;
n3 and energy storage capacitor CDCIs connected with one end of the energy storage capacitor C, N4DCThe other ends of the two are connected; energy storage capacitor CDCThe charging direction is the same as or opposite to the main loop current direction; charging branch and energy storage capacitor CDCAre connected in parallel.
The line current is converged to the direct current bus by the current branch circuits connected with one or some terminals, and then flows out from the direct current bus through the current branch circuits connected with the other terminals.
As shown in FIG. 3, the on-line detection system comprises current sensor groups D11-D1 n for measuring the current state of the terminal outgoing line, current sensor groups D21-D2 n for measuring the current state of the current branch, a current sensor D3 for measuring the current conversion switch module, a current sensor D4 for measuring the current state of the lightning arrester, voltage sensor groups V11-V1 n for measuring the voltage state of the two ends of a main mechanical switch CB of the current branch, a voltage sensor V2 for measuring the voltage state of the two ends of the lightning arrester, and an energy storage capacitor CDCThe lightning arrester temperature monitoring system comprises a voltage sensor V3 for measuring the voltage state of two ends, displacement sensor groups W11-W1 n for measuring the motion state of a main mechanical switch CB of a current-passing path, a temperature sensor M1 for measuring the temperature state of a lightning arrester SA, and a necessary signal processing circuit, an A/D conversion module and a communication module.
The control system is connected with the on-line detection system, and the on-line detection system is used for measuring the current amplitude, the current zero crossing point and the current change rate of the through-flow branch and the current amplitude, the current zero crossing point and the current change rate of the current conversion switch module to control the main mechanical switch CB, the quick mechanical switch RCB, the current conversion switch module, the auxiliary isolating switch S and the thyristor T, so that the fault current with different amplitudes can be quickly and reliably turned off.
Under the normal through-current state of the system, the main mechanical switches CB of the n through-current branches and the rapid mechanical switches RCB connected with the main mechanical switches CB are in a switch-on state; the thyristors T in the n isolating branches are in a turn-off state; the cut-off unit is in a cut-off state; at the moment, the line current is converged to the direct current bus by the current branch connected with one or some of the terminals, and then flows out from the direct current bus through the current branch with the rest terminals, and no current flows through the cut-off unit.
In a fault state, when the on-line detection system detects a fault of a certain terminal, the control system provides a main mechanical switch CB of a through-flow branch connected with the fault terminal1An auxiliary isolating switch S of the isolating branch connected with other terminals sends a switching-off command, and a mechanical switch CB sends a switching-off command after a certain delay1The electrode contacts start to separate, arcing between the electrode contacts, when the main mechanical switch CB is opened1And an auxiliary isolating switch S1After reaching a certain opening distance, the thyristor T in the isolation branch connected with the fault wiring terminal1And the full-bridge converter sends a conduction command, two bridge arms of the full-bridge converter are conducted alternately, and the conduction time sequence comprises: in the first stage, the ES1 and the ES4 in the commutation switch module are switched on, the ES2 and the ES3 are switched off, and the ES1 and the ES4 are switched on to form the energy storage capacitor CDCBy oscillating a capacitor CpAnd an oscillating inductor LpDischarging to generate sinusoidal oscillation current, when the sinusoidal oscillation current completes oscillation of a sinusoidal half wave and the oscillation current reaches a zero crossing point, sending a control signal by the control system, executing the stage 2, closing the ES1 and the ES4, conducting the ES2 and the ES3, and then conducting the energy storage capacitor CDCThe polarity is consistent with the discharge current direction, and the energy storage capacitor CDCContinues through the oscillating capacitor CpAnd an oscillating inductor LpDischarging to generate sinusoidal oscillation current with amplitude higher than that of the first sinusoidal half wave,when the second sinusoidal half-wave current reaches the zero crossing point, the control system sends out a control signal, and the phase 1 is executed, and then the phase 2 and the phase 1 are executed alternately. Pre-charged energy storage capacitor CDCThe capacitor C and the inductor L are discharged to generate oscillation current with gradually increasing amplitude until the oscillation current is superposed on fault current to generate a current zero crossing point, electric arc is extinguished, the fault current is transferred to a branch where the commutation switch is located, the voltage at two ends of the capacitor C is increased until the voltage reaches the action voltage of the lightning arrester SA, due to the nonlinear resistance characteristic of the lightning arrester SA, the lightning arrester SA is converted from a high-resistance state to a low-resistance state, the fault current is transferred to the branch where the lightning arrester SA is located, the electromagnetic energy of the system is converted into the heat energy of the lightning arrester SA, the fault current is gradually reduced, and when the fault current drops to be close to 0, the RCB of the fault terminal is switched off to cut off residual current, so that the fault current is quickly and reliably cut off.
The online monitoring system comprises a voltage measuring module, a current measuring module, a temperature measuring module, a sound measuring module, an X-ray measuring module and a magnetic field measuring module.
The mechanical switch is a mechanical switch based on explosion driving, a mechanical switch based on electromagnetic repulsion, a mechanical switch based on permanent magnet repulsion, a mechanical switch based on a spring operating mechanism and a mechanical switch based on motor driving.
When the power electronic device is a fully-controlled power electronic device, a single device or a plurality of devices are combined in series and parallel in the following period, such as GTO, a thyristor, a MOSFET, an IGBT and an IGCT.
The arrester SA comprises a metal oxide arrester, a gas insulated metal oxide arrester, a ceramic shell insulated metal oxide arrester and a gapless metal oxide arrester which are connected in series and in parallel.
In order to achieve the above object, an embodiment of an aspect of the present invention discloses a method for opening a shared branch compact dc circuit breaker, including the above-mentioned shared branch compact dc circuit breaker, further including the following steps:
in a first step, the system current passes from the terminal 1 through the mechanical switch RCB1And CB1Rear inflow direct currentThe bus bar flows out from the direct current bus bar through the cables where the other wiring terminals are located;
in the second step, when the on-line monitoring system detects that the system has a fault, a trigger signal is sent to the control system, the control system immediately sends a brake-separating instruction after receiving the trigger signal, and a main mechanical switch CB of a through-flow branch circuit connected with a fault terminal is connected with a main mechanical switch CB of the through-flow branch circuit1The auxiliary isolating switches S of the isolating branches connected with the other terminals start to open the brake and burn after receiving the brake opening instruction with a certain delay;
in a third step, a mechanical switch CB1The thyristor T in the isolation branch connected with the fault terminal is connected when the switching-off time reaches a certain time or the switching-off distance of the electrode contact reaches a certain distance1And the energy storage capacitor C which is triggered to be switched on and precharged by the current conversion switch moduleDCBy oscillating a capacitor CpAnd an oscillating inductor LpThe discharge generates an oscillating current that is generated,
the online monitoring system detects the zero crossing point of the oscillating current, the control system controls the commutation switch module to alternately execute the stage 1 and the stage 2 at each zero crossing point of the oscillating current, and the amplitude of the oscillating current is increased once every half of a sinusoidal oscillation period until the oscillating current is connected with a main mechanical switch CB of a through-current branch circuit1The medium current arc is superposed to generate a zero crossing point, and a main mechanical switch CB1The arc in (2) is extinguished.
In the fourth step, a main mechanical switch CB1The electric arc in the system is extinguished and stops conducting, the system current is transferred to the branch where the current conversion switch module is positioned, and the oscillating capacitor C is connectedpCharging and oscillating capacitor CpThe voltage at both ends rises rapidly until the oscillating capacitor CpWhen the voltage reaches the action voltage of the arrester connected with the voltage in parallel, the arrester SA acts to start conducting current, and the system current is transferred to the energy absorption branch where the arrester SA is located. The arrester SA absorbs residual energy in the system, and along with the gradual absorption of the energy, the current of the arrester SA gradually decreases until the current drops to 0, so that the current is cut off, and a fault line is isolated.
Realize quick reclosing lock, specifically include: for permanent faults, a main mechanical switch CB for conducting a through-current branch is turned on after a fault current is cut off for a certain time1And withConnected fast mechanical switch RCB1When the fault current is detected again, the direct current breaker repeats the breaking process, and after the fault current drops to zero, the rapid mechanical switch RCB of the opening fault terminal1And an auxiliary isolating switch S in the isolating branch1Switching on the auxiliary isolating switches S in the isolating branch circuits where the other normal wiring terminals are located, so as to isolate a fault line and reset the direct current circuit breaker to wait for the next operation; for a temporary fault, after the start-up unit is switched on, no fault current is detected, and all the rapid mechanical switches RCB and the auxiliary isolating switch S are switched on, so that the direct-current circuit breaker is reset to wait for the next operation.
The invention provides a compact direct current breaker sharing a branch, when the direct current is normally conducted, the current is conducted through a mechanical switch of a through-current branch, and the loss of the direct current breaker is extremely low; the direct current circuit breaker adopts the quick operating mechanism to drive the mechanical switch, so that the fault current can be switched off in a short time, the reclosing function is realized, the fault is isolated, and the flexible direct current system is protected; the invention can realize the on-off and the isolation of the fault current of all external circuits on one bus by sharing the current conversion branch and the energy absorption branch, has small floor area and low construction cost, and is beneficial to the construction of a multi-end flexible direct current system.

Claims (10)

1. A compact direct current breaker sharing a branch circuit is characterized by comprising a wiring terminal, a through-current branch circuit, an isolation branch circuit, a breaking unit, a direct current bus, an online monitoring system and a control system;
the number of the wiring ends, the number of the through-current branches and the number of the isolation branches are multiple and are connected in a one-to-one correspondence manner;
one end of the through-current branch is connected with the wiring terminal through a mechanical switch, and the other end of the through-current branch is connected with a direct-current bus;
one end of the through-current branch is connected with one end of the isolation branch, the other ends of the isolation branches are connected with one end of the cut-off unit, and the other end of the cut-off unit is connected with a line outlet end bus;
the through-flow branch comprises a main mechanical switch; the main mechanical switch comprises one or more vacuum switches connected in series; the isolation branch comprises an auxiliary isolation switch and a thyristor module; the auxiliary isolating switch is connected with the thyristor module in series;
the online monitoring system is used for measuring the current magnitude and the current direction flowing through the current conversion switch module, the current and the direction flowing through the lightning arrester, the voltage and the temperature at two ends of the lightning arrester, the current magnitude and the current direction flowing through the mechanical switch of the through-current branch circuit, the voltage and the switch stroke at two ends and the voltage at two ends of the energy storage capacitor;
the control system is connected with the online monitoring system and is used for controlling the main mechanical switch of the through-flow branch, the thyristor and the auxiliary isolating switch of the isolating branch, the commutation switch module and the quick mechanical switch.
2. The compact direct current circuit breaker of a shared branch circuit of claim 1, wherein the breaking unit comprises a commutation switch module, an oscillating capacitor, an oscillating inductor and a lightning arrester; the current conversion switch module is connected with the oscillating capacitor and the oscillating inductor in series to form a current conversion branch, and the lightning arrester is connected with the current conversion branch in parallel.
3. The compact direct current circuit breaker of a shared branch circuit of claim 1, wherein the breaking unit comprises a commutation switch module, an oscillating capacitor, an oscillating inductor and a lightning arrester; the current conversion switch module is connected with the oscillating capacitor in series, the lightning arrester is connected with a branch formed by connecting the lightning arrester and the oscillating capacitor in series in parallel, the branch formed by connecting the lightning arrester and the oscillating capacitor in parallel is connected with one end of the oscillating inductor, and the other end of the oscillating inductor is connected with a wire outlet end bus.
4. The compact direct current circuit breaker sharing branch circuit according to claim 1, wherein the commutation switch module of the breaking unit comprises an energy storage capacitor, a charging branch circuit and a power electronic power device;
the power electronic power device comprises a fully-controlled power electronic power device ES1, a fully-controlled power electronic power device ES2, a fully-controlled power electronic power device ES3 and a fully-controlled power electronic power device ES 4;
the cathode of the fully-controlled power electronic power device ES1 and the anode of the fully-controlled power electronic power device ES3 are connected to N1, and N1 is connected with the isolation branch; the cathode of the fully-controlled power electronic power device ES2 and the anode of the fully-controlled power electronic power device ES4 are connected to N2, and N2 is connected to one end of an oscillation capacitor C;
the anode of the fully-controlled power electronic power device ES1 and the anode of the fully-controlled power electronic power device ES2 are connected to N3, and the cathode of the fully-controlled power electronic power device ES3 and the cathode of the fully-controlled power electronic power device ES4 are connected to N4;
n3 is connected with one end of the energy storage capacitor, and N4 is connected with the other end of the energy storage capacitor; the charging direction of the energy storage capacitor is the same as or opposite to the current direction of the main loop; the charging branch circuit is connected with the energy storage capacitor in parallel.
5. The compact direct current circuit breaker sharing a branch circuit according to claim 4, wherein the power electronic power device is a series-parallel combination of one or more devices including GTO, thyristor, MOSFET, IGBT, IGCT.
6. The compact direct current circuit breaker sharing a branch according to claim 1, wherein the mechanical switch is an explosion-driven mechanical switch, an electromagnetic repulsion-based mechanical switch, a permanent magnet repulsion-based mechanical switch, a spring-operated mechanical switch, or a motor-driven mechanical switch.
7. The compact direct current circuit breaker of claim 1, wherein the online monitoring system comprises a voltage measuring module, a current measuring module, a temperature measuring module, a sound measuring module, an X-ray measuring module, and a magnetic field measuring module, and each measuring module of the online monitoring system is configured to monitor a state of the direct current circuit breaker and determine a time for the control system to send a command signal according to the monitored state of the direct current circuit breaker.
8. A control method of a branch-sharing compact DC breaker, characterized in that, based on the branch-sharing compact DC breaker of any one of claims 1 to 7, the method comprises the following procedures,
under the normal through-current state of the system, the main mechanical switches and the mechanical switches of the multiple through-current branches are in a closing state; thyristors in the plurality of isolation branches are in an off state; the switching-off unit is in a switching-off state; the line current is converged to the direct current bus by the through-current branch where part of the terminals are located, and then flows out from the direct current bus through the through-current branches where the rest of the terminals are located;
under the fault state, when a fault of a certain terminal is detected, the direct current breaker sends a brake-off command to a main mechanical switch of a through-flow branch where the fault terminal is located and an auxiliary isolating switch of an isolating branch where other terminals are located, arcing starts between contacts, when the main mechanical switch and the auxiliary isolating switch reach a preset opening distance, a conducting command is sent to a thyristor and a full-bridge converter in the isolating branch where the fault terminal is located, two bridge arms of the full-bridge converter are conducted alternately, pre-charged energy storage capacitors are discharged through oscillating capacitors and oscillating inductors, oscillating currents with gradually increasing amplitudes are generated until the oscillating currents are superposed on fault currents to generate current zero crossing points, the fault currents enable voltages at two ends of the oscillating capacitors to rise until the action voltages of an arrester are reached, the fault currents are transferred to an energy-absorbing branch, when the fault currents drop to 0, electric arcs are extinguished, and the quick mechanical switch of the fault terminal is used for brake-off residual currents, and the fault current is cut off.
9. The method as claimed in claim 8, wherein for a permanent fault, waiting for a preset time after the fault current is cut off, turning on the main mechanical switch of the current branch and the fast mechanical switch connected thereto, detecting the fault current again, repeating the cut-off process of the dc circuit breaker, waiting for the fault current to drop to zero, opening the fast mechanical switch connected to the fault terminal and the auxiliary isolating switch in the isolating branch, and closing the auxiliary isolating switches in the isolating branch where the other normal terminals are located, thereby isolating the fault line and resetting the dc circuit breaker for the next operation;
for temporary faults, after the on-off unit is switched on, fault current is not detected, and all the quick mechanical switches and the auxiliary isolating switches are switched on, so that the direct-current circuit breaker is reset to wait for the next operation.
10. The method of claim 8, wherein the commutation comprises a phase 1 and a phase 2;
the stage 1 is as follows: the ES1 and ES4 in the commutation switch module are turned on, the ES2 and ES3 are turned off, the energy storage capacitor is discharged through the oscillation capacitor and the oscillation inductor after the ES1 and ES4 are turned on, a sinusoidal oscillation current is generated, when the sinusoidal oscillation current finishes oscillation of a sinusoidal half-wave and the oscillation current reaches a zero crossing point, the control system sends out a control signal, and the phase 2 is executed: ES1 and ES4 are closed, ES2 and ES3 are conducted, the polarity of the energy storage capacitor is consistent with the discharge current direction, the energy storage capacitor continues to discharge through the oscillation capacitor and the oscillation inductor, the amplitude of the generated sinusoidal oscillation current is higher than that of the first sinusoidal half-wave, when the current of the second sinusoidal half-wave reaches the zero-crossing point, the control system sends out a control signal, the phase 1 is executed, and then the phase 2 and the phase 1 are executed alternately.
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