CN108766830B - Coupling type high-voltage direct-current breaker - Google Patents
Coupling type high-voltage direct-current breaker Download PDFInfo
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- CN108766830B CN108766830B CN201810709084.4A CN201810709084A CN108766830B CN 108766830 B CN108766830 B CN 108766830B CN 201810709084 A CN201810709084 A CN 201810709084A CN 108766830 B CN108766830 B CN 108766830B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
- H01H33/02—Details
- H01H33/59—Circuit arrangements not adapted to a particular application of the switch and not otherwise provided for, e.g. for ensuring operation of the switch at a predetermined point in the ac cycle
- H01H33/596—Circuit arrangements not adapted to a particular application of the switch and not otherwise provided for, e.g. for ensuring operation of the switch at a predetermined point in the ac cycle for interrupting dc
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
- H01H9/54—Circuit arrangements not adapted to a particular application of the switching device and for which no provision exists elsewhere
- H01H9/541—Contacts shunted by semiconductor devices
- H01H9/542—Contacts shunted by static switch means
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
- H01H9/54—Circuit arrangements not adapted to a particular application of the switching device and for which no provision exists elsewhere
- H01H9/547—Combinations of mechanical switches and static switches, the latter being controlled by the former
Abstract
The invention provides a novel mechanical high-voltage direct-current breaker with a coupling reactor, which comprises: the device comprises a main loop unit, a charging converter unit, an energy consumption unit, a trigger unit and an energy absorption and voltage limiting unit; the energy-absorbing voltage-limiting unit is connected with the main loop unit in parallel, and the charging converter unit is connected with the main loop unit in parallel; the triggering unit is used for triggering the charging current converting unit when the system fails and triggering the energy consumption unit when reclosing; the charging current converting unit is used for generating high-frequency oscillation current when faults occur, reversely superposing the high-frequency oscillation current with the fault current to form zero-crossing breaking fault current, and charging the precharge capacitor after the first breaking for reclosing fault breaking; the energy-absorbing voltage-limiting unit absorbs energy stored in the inductive element of the power system after the switching-on and switching-off is finished, and limits the voltage at two ends of the mechanical switch; the energy consumption unit is used for consuming the energy of the converter capacitor when the direct current breaker is reclosed so as to quickly attenuate the closing current on the mechanical switch to zero.
Description
Technical Field
The invention belongs to the field of high-voltage direct-current circuit breakers, and particularly relates to a novel mechanical high-voltage direct-current circuit breaker with a coupling reactor.
Background
In recent years, with the continuous increase of energy demand and the rapid development of renewable energy sources, high-voltage direct-current transmission has attracted a great deal of attention at home and abroad. The direct current transmission has the advantages of large transmission energy, long transmission distance, small loss and the like, so the direct current transmission is applied to the power grids at home and abroad on a large scale. The traditional direct current transmission engineering is mostly a two-end system, only energy transmission between two points can be realized, and when direct current transmission is used for transmitting power to a plurality of load centers or direct current interconnection is adopted among a plurality of alternating current systems, a plurality of direct current transmission lines are required to be constructed, so that investment cost and operation cost are greatly increased. The multi-terminal direct current transmission system fully develops the economic advantages and the technical advantages of the high-voltage direct current transmission technology, is a more attractive transmission technology, and meets the development needs of the power industry in China. Besides the advantages of two-end direct current transmission, the multi-end direct current transmission can realize multi-power supply and multi-drop point power reception; the reliability is higher and more flexible; can be built in stages, and improves the investment benefit.
Because the impedance of the direct current side of the multi-terminal direct current transmission network is very small, when a short circuit fault occurs on the direct current side, the fault current can rise rapidly, if the fault is not timely cut off in a short time, the action of the alternating current circuit breaker on the converter side can be caused, and the converter valve block is blocked, so that the normal operation of the whole system is affected. The high-voltage direct current breaker can rapidly cut off fault current and isolate fault points in a short time, and normal operation of the system is ensured. Thus, the high voltage dc circuit breaker builds one of the key devices of a reliable multi-terminal flexible dc power grid.
At present, the main dc breakers at home and abroad are classified into mechanical dc breakers, hybrid dc breakers and all-solid-state dc breakers. The all-solid-state high-voltage direct current breaker mainly comprises power electronic devices, when the all-solid-state high-voltage direct current breaker is applied to a high-voltage direct current power grid, the number of the series devices is excessive, so that a control unit is complex, the manufacturing cost is high, and the on-state loss is large, therefore, the development of the existing high-voltage direct current breaker mainly comprises a mechanical high-voltage direct current breaker and a hybrid high-voltage direct current breaker, and for the hybrid high-voltage direct current breaker, the on-state loss and the on-state loss are high, and the control requirement is very strict because the through-current and voltage-resistant elements of the hybrid high-voltage direct current breaker are power electronic solid-state switches; in the traditional mechanical high-voltage direct current breaker, if a high-voltage ball gap is adopted as a current conversion branch control switch, spark during conduction of the high-voltage ball gap can threaten surrounding oil insulation equipment, and if a thyristor is adopted as the current conversion branch control switch, the thyristor needs to withstand higher recovery voltage in the switching-on and switching-off process, and the cost is higher.
Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, the invention provides a coupling type high-voltage direct current breaker, which solves the problems of high cost and high thyristor withstand voltage of the existing high-voltage direct current breaker on the basis of meeting the requirements of a direct current system on the high-voltage direct current breaker that the action is rapid, the high current and the low current are cut off and the high voltage is born; for the coupling type high-voltage direct current breaker, the line current is transferred to the converter branch after the circuit is opened, so that the problem of small current follow current is generated.
The invention provides a coupling type high-voltage direct-current breaker, which comprises: the device comprises a main loop unit, a charging converter unit, an energy consumption unit, a trigger unit and an energy absorption and voltage limiting unit; the main loop unit is used for being connected in series into the direct current system, the energy absorption and voltage limiting unit is connected with the main loop unit in parallel, and the charging current conversion unit is connected with the main loop unit in parallel; the first output end of the triggering unit is connected with the charging converter unit, the second output end of the triggering unit is connected with the energy consumption unit, and the triggering unit is used for triggering the charging converter unit after a system fails and triggering the energy consumption unit when reclosing; the charging current conversion unit is used for generating high-frequency oscillation current when faults occur, reversely superposing the high-frequency oscillation current with the fault current to form zero-crossing breaking fault current, and charging the precharge capacitor after the first breaking for reclosing fault breaking; the energy-absorbing voltage-limiting unit is used for absorbing energy stored in the inductive element of the power system after the power system is disconnected and limiting the voltage at two ends of the mechanical switch; the energy consumption unit is also connected with the charging converter unit, and is used for consuming the energy of the converter capacitor when the direct current breaker is reclosed so as to quickly attenuate the closing current on the mechanical switch to zero.
Still further, the main loop unit is a mechanical switch that is ignitable and can be quenched when the current crosses zero.
Still further, the charging converter unit includes: the device comprises a precharge capacitor C11, a thyristor SCR1, an energy storage capacitor C12, a charging resistor R1, a coupling reactor, a commutation capacitor C2, a mechanical switch CB2 and a lightning arrester MOV2; one end of the precharge capacitor C11 is connected with one end of the primary side L1 of the coupling reactor, and the other end of the precharge capacitor C11 is connected with one end of the thyristor SCR 1; the other end of the thyristor SCR1 is connected with the other end of the primary side L1 of the coupling reactor, and the energy storage capacitor C12 is connected with the charging resistor R1 in series and then connected with the pre-charging capacitor C11 in parallel; one end of the converter capacitor C2 is connected with one end of the secondary side L2 of the coupling reactor, the other end of the converter capacitor C2 is connected to one end of the mechanical switch CB2, the lightning arrester MOV2 is connected with the mechanical switch CB2 in parallel, and the other end of the secondary side L2 of the coupling reactor and the other end of the mechanical switch CB2 are respectively connected to two ends of the main loop unit.
Still further, the energy consumption unit includes: and the non-series connection end of the thyristor SCR2 is respectively connected with the charging converter unit and the triggering unit.
Still further, the energy-absorbing and pressure-limiting unit comprises: and the two ends of the zinc oxide lightning arrester are respectively connected with the two ends of the main loop unit.
When the system works normally, the mechanical switch CB is closed, and system current flows to a load through the mechanical switch CB, so that the on-state loss is small; when a short circuit fault occurs in the system, as the adopted breaking unit only has the capability of zero crossing breaking of current, when the fault current is broken, a contact of the mechanical switch CB is opened and burnt, after the contact opening distance of the mechanical switch CB reaches a rated opening distance and can withstand the recovery voltage after breaking, the triggering unit triggers the thyristor SCR1 to conduct the charging commutation unit, the pre-charging capacitor C11 and the primary side inductor L1 of the coupling reactor oscillate, the secondary side inductor L2 of the coupling reactor and the commutation capacitor C2 generate reverse oscillation current through the coupling reactor, and the oscillation current amplitude exceeds the maximum fault current amplitude of the system, so that the mechanical switch CB generates zero crossing arc and the fault current is broken; after the mechanical switch CB is subjected to zero crossing arc extinction, line current is transferred to a converter branch formed by the secondary side inductance L2 of the coupling reactor and the converter capacitor C2 in series, so that the voltage of the converter capacitor C2 is gradually increased and is applied to two ends of the mechanical switch CB, when the voltage amplitude is increased to the action voltage of the energy-absorbing voltage-limiting unit, the energy-absorbing voltage-limiting unit performs lightning protection, inductive energy in a line is absorbed, the mechanical switch is protected under voltage limiting, and meanwhile, the line current starts to be reduced.
If the line fault is a ground fault and the fault current amplitude is larger, the line current oscillates through the secondary side inductance L2 of the coupling reactor and the converter capacitor C2 after the line current is disconnected, and the attenuation speed is slower; if the line fault is a high-resistance ground fault, the amplitude of the fault current is smaller, the converter branch is in an over-damping state after the line fault is disconnected, and a longer tail exists in the process of reducing the line current, so that the system requirement is difficult to meet. Therefore, when the line current drops to the vicinity of zero after the disconnection, the triggering unit triggers the thyristor SCR1 again to enable the converter branch to generate an oscillating current, so that the mechanical switch CB2 disconnects the converter branch current at the zero crossing point, and the lightning arrester MOV2 plays a role in limiting the voltage across the mechanical switch CB 2.
After the first turn-off, the voltage at two ends of the precharge capacitor C11 is attenuated more, and the energy storage capacitor C12 charges the precharge capacitor through the charging resistor R1, so that the second turn-off can be satisfied.
After the primary break, the voltage of the converter capacitor C2 is consistent with the system voltage, and the converter capacitor C2 and the secondary side L2 of the coupling reactor oscillate to generate oscillation current with higher frequency and amplitude during reclosing, so that the secondary break fault current is influenced; therefore, when reclosing operation is performed, the thyristor SCR2 is turned on first, so that the high-frequency oscillation current generated on the mechanical switch is released through the energy dissipation resistor R2, and the mechanical switch current is quickly attenuated to zero.
The invention has the following advantages:
(1) The thyristor triggering unit is adopted, no arc triggering is carried out, threat to surrounding oil insulation equipment is avoided, and the operation safety of the system is ensured; meanwhile, the thyristor is arranged at the low-voltage side, so that the voltage level of the trigger unit and the difficulty of driving control are obviously reduced; the pre-charge capacitor C11 is positioned at the low voltage side, the pre-charge voltage level is lower, and the ground is not required to be insulated, so that the insulation voltage withstand requirement on a charged part is lower, and the difficult problems of high-potential and multi-potential charging are solved; the high-voltage side converter capacitor C2 is not electrified in a normal running state, and has no long-term through-current voltage-withstanding requirement, so that the cost and the size of the capacitor are greatly reduced, the switching reliability of the capacitor is improved, and the cost of the direct-current circuit breaker is reduced.
(2) The invention relates to a mechanical switch of a converter branch of a high-voltage direct current breaker, which is connected with a lightning arrester in parallel at two ends of the mechanical switch. Compared with the traditional coupling type mechanical direct current breaker, the topology can trigger the thyristor again after the switching-on and switching-off is finished to enable the mechanical switch of the converting branch to generate zero crossing points, so that the converting branch current is switched on and off, and the line current is quickly attenuated to zero. Meanwhile, the lightning arresters are connected in parallel at the two ends of the mechanical switch of the converting branch, so that the voltage at the two ends of the mechanical switch is limited, and the cost of the mechanical switch is further reduced.
(3) According to the coupling type high-voltage direct-current circuit breaker topology, the energy dissipation resistors are connected in parallel at the two ends of the primary side of the coupling reactor, so that the current on the mechanical switch can be quickly attenuated to zero during reclosing, and the negative influence of reclosing current on secondary switching-off is avoided.
(4) And the two ends of the pre-charge capacitor are connected with an energy storage capacitor in parallel, and the charging resistor is connected in series to control the charging time. When the topology is applied to the occasion with higher voltage level, the precharge capacitor loses more energy after the first turn-off, and when the precharge capacitor is turned off for the second time in the required time, if the transformer is used for charging the precharge capacitor, the power of the transformer is required to be extremely high, which puts higher requirements on the safety of the equipment. And the energy storage capacitors are connected in parallel at the two ends of the pre-charging capacitor, so that the safe and rapid charging to the required value can be ensured, and the second switching-on and switching-off can be completed.
Drawings
Fig. 1 is a schematic block diagram of a coupling type high-voltage direct current breaker provided by the invention;
fig. 2 is a specific structural block diagram of a coupling type high-voltage direct-current breaker provided by the invention;
fig. 3 is a waveform diagram of the coupled high-voltage dc breaker according to the present invention when reclosing to open and close a fault current;
fig. 4 is a waveform diagram of the coupling type high voltage dc breaker according to the present invention when the coupling type high voltage dc breaker is turned on and off;
fig. 5 is a voltage waveform diagram of a precharge capacitor in a reclosing and opening process of the coupling type high-voltage direct-current circuit breaker.
Wherein 1 is a main loop unit, 2 is a charging and converting unit, 3 is an energy consumption unit, 4 is a triggering unit, and 5 is an energy absorption and voltage limiting unit; CB is a mechanical switch, C11 is a precharge capacitor, C12 is an energy storage capacitor, R1 is a charging resistor, SCR1 and SCR2 are triggerable thyristors, L1 is a primary side of a coupling reactor, L2 is a secondary side of the coupling reactor, C2 is a current-converting loop capacitor, CB2 is a current-converting branch mechanical switch, and MOV1 and MOV2 are lightning arresters. In fig. 3 and 4, the x-axis is time t, and the unit is s; the y-axis is the current amplitude, in kA; the dashed line represents the mechanical switch CB break current and the solid line represents the line current. In fig. 5, the x-axis represents time t, in s; the y-axis is the voltage amplitude, in kV; the solid line represents the voltage of the precharge capacitor C11, and the broken line represents the voltage of the storage capacitor C12.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The invention aims to provide a coupling type high-voltage direct current breaker, which is characterized in that a trigger thyristor and a pre-charge capacitor are arranged on a low-voltage side through a coupling reactor on the basis that a direct current system acts on the high-voltage direct current breaker rapidly, a large current is cut off and a high voltage is born, so that the equipment cost is reduced, and the cut-off reliability is improved. Meanwhile, the invention also has the function of opening and closing the two-way reclosing, limits the amplitude of the line current after the opening and closing is finished, and meets the requirements of different systems.
Fig. 1 is a schematic block diagram of a coupling type high-voltage direct current breaker provided by the invention, and fig. 2 is a specific structural block diagram of the coupling type high-voltage direct current breaker provided by the invention. The invention provides a coupling type high-voltage direct-current breaker, which comprises: the energy-absorbing and voltage-limiting device comprises a main loop unit 1, a charging and current-converting unit 2, an energy-dissipating unit 3, a triggering unit 4 and an energy-absorbing and voltage-limiting unit 5; the main loop unit 1 is connected in series into a direct current system, the charging converter unit 2 and the energy-absorbing voltage-limiting unit 5 are connected in parallel with the main loop unit 1, and the triggering unit 4 is connected in parallel with the charging converter unit 2 and the energy-consuming unit 3 respectively; the main loop unit 1 is a mechanical switch CB, which is a flammable arc and can be turned off at a current zero crossing point. The charging converter unit 2 comprises a pre-charging capacitor C11, an energy storage capacitor C12, a charging resistor R1, a thyristor SCR1, a coupling reactor, a converter capacitor C2, a converter branch mechanical switch CB2 and a lightning arrester MOV2, wherein the pre-charging capacitor C11, the thyristor SCR1 and a primary inductor L1 of the coupling reactor are connected in series, the energy storage capacitor C12 is connected in series with the charging resistor R1, and the energy storage capacitor C12 and the charging resistor R1 are connected in parallel to two ends of the pre-charging capacitor C11 and are used for charging the pre-charging capacitor C11 after the primary inductor L is opened for the first time; the converter capacitor C2 is connected with the secondary side L2 of the coupling reactor in series with the converter branch mechanical switch CB2, and the lightning arrester MOV2 is connected in parallel with two ends of the converter branch mechanical switch CB2 to limit the voltage at two ends. The energy consumption unit 3 comprises a thyristor SCR2 and an energy consumption resistor R2, which are connected in series with the primary side inductance L1 of the coupling reactor and are used for consuming the energy of the converter capacitor when the direct current breaker is reclosed so as to quickly attenuate the closing current on the mechanical switch to zero. The output end of the trigger unit 4 is connected with the control ends of the charging converter unit 2 and the energy consumption unit 3, and when the power system fails, the trigger unit 4 is used for generating a trigger signal to trigger the charging converter unit 2 to conduct and generate oscillation current and fault current to be superposed to generate a zero crossing point; when reclosing, the triggering unit 4 triggers the energy consumption unit 3 to enable the energy consumption unit 3 to absorb energy and accelerate the attenuation speed of the mechanical switching current. The energy-absorbing voltage limiting unit 5 is a zinc oxide lightning arrester and is used for limiting the voltage at two ends of the mechanical switch CB of the main loop unit.
In the present example, the main function of the main loop unit 1 is to turn on and off the fault current at the current zero crossing by the mechanical switch CB; the main functions of the charging and converting unit 2 are as follows: (1) the pre-charge capacitor C11 and the coupling reactor L1 generate high-frequency oscillation current, the coupling reactor generates oscillation current in a converting branch circuit and is overlapped on the mechanical switch CB, and a zero crossing point is manufactured manually to enable the mechanical switch CB to be turned on and off; (2) triggering the thyristor SCR1 again when the switching-off is finished and the line current drops to the vicinity of zero, so that the converter branch circuit generates oscillating current, and the converter branch circuit mechanical switch CB2 is switched off, thereby switching-off the converter branch circuit current and enabling the line current to drop to zero rapidly; (3) after the first switching-on, the energy storage capacitor C12 charges the pre-charging capacitor C11 through the charging resistor R1, so that the voltage of the energy storage capacitor C meets the second switching-on requirement; the energy consumption unit 3 is used for consuming energy in the converter capacitor C2 during reclosing operation, so that the closing current is quickly attenuated to zero, and the influence on the second opening process is avoided; the main function of the energy-absorbing voltage-limiting unit 5 is to absorb the energy stored by the inductive element in the direct current system after the fault current is cut off so as to realize the voltage-limiting protection of the mechanical switch CB; the main function of the triggering unit 4 is to trigger the charging converter unit to conduct after the system fails, and trigger the energy consumption unit to absorb energy during reclosing.
In order to further explain the coupling type high-voltage direct-current breaker provided by the embodiment of the invention, the working process is described in detail as follows:
when the system works normally, the mechanical switch CB is in a closing state, system current flows to a load through the mechanical switch CB, and on-state loss is small.
When the system breaks down, the adopted breaking unit is a mature alternating current breaking unit and only has the current zero-crossing breaking capability, so that when the fault current is broken, the contacts of the mechanical switch CB are separated and burnt.
After the contact of the mechanical switch CB reaches the rated opening distance, the triggering unit sends out a signal to trigger and conduct the primary side thyristor SCR1, the pre-charge capacitor C11 and the primary side L1 of the coupling reactor generate high-frequency oscillation current, and accordingly the secondary side L2 of the coupling reactor and the converter capacitor C2 also generate high-frequency oscillation current, and the amplitude exceeds the system fault current amplitude. The current is overlapped with the fault current, so that the mechanical switch CB generates a zero crossing point, and the mechanical switch CB is arc-extinguishing and the fault current is cut off. After the mechanical switch CB is in arc extinction, line current is transferred to a converter branch circuit formed by the secondary side L2 of the coupling reactor and the converter capacitor C2, the recovery voltage of the converter capacitor C2 gradually rises, and when the recovery voltage amplitude reaches the action voltage of the energy-absorbing voltage-limiting unit lightning arrester, the energy-absorbing voltage-limiting unit lightning arrester MOV1 acts to absorb the energy of inductive elements in the system, so that the mechanical switch CB is protected in voltage limiting.
After the action of the arrester MOV1 in the energy-absorbing voltage-limiting unit 5, the line current starts to drop. The decay rate is slow when the current decays to around zero due to the small impedance in the line. At this time, the thyristor SCR1 is triggered again, so that the commutation branch circuit generates a smaller oscillating current, and the mechanical switch CB2 of the commutation branch circuit generates a zero crossing point, and the commutation branch circuit is turned on and off, so that the line current is quickly attenuated to zero, and the first fault on and off is completed. The converter limb arrester MOV2 is used to limit the voltage across the converter limb mechanical switch CB 2.
After the first turn-off, the energy of the precharge capacitor C11 is greatly consumed, and the energy storage capacitor C12 charges the precharge capacitor C11 through the charging resistor R1, so that the energy of the precharge capacitor C11 can meet the requirement of the second turn-off.
And then, performing reclosing operation. Before the first switching-off is finished, the direct current system charges the converter capacitor C2 through the converter capacitor C2 and the secondary side inductor L2 of the coupling reactor. When reclosing, the energy of the converter capacitor C2 is released through the secondary side L2 of the coupling reactor and the mechanical switch CB, and a current with high-frequency oscillation and slower attenuation is generated. Therefore, the energy dissipation resistor R2 is connected in parallel to the two ends of the primary inductor L2 of the coupling reactor, the thyristor SCR2 is turned on during reclosing, and the energy on the converter capacitor is dissipated through the energy dissipation resistor R2, so that the reclosing current is quickly attenuated to zero.
After reclosing, the second fault current breaking process is as described above, and will not be described in detail.
The present invention will be described in further detail with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The invention relates to a coupling type high-voltage direct current breaker which has the functions of bidirectionally breaking rated small current, interelectrode short-circuit large current and reclosing, and can quickly attenuate line current to zero after breaking so as to meet the requirements of different systems. For further explanation of the coupling type high voltage direct current breaker provided by the embodiment of the invention, the following details are provided with reference to the accompanying drawings and specific examples:
figure 3 is a current waveform of a coupled high voltage dc breaker when reclosing to open a 25kA high current,
FIG. 4 is a graph showing a current waveform of the HVDC circuit breaker when the circuit breaker is turned on and off for 100A small current, wherein the x-axis is time t, and unit s; the y-axis is the current amplitude, in kA; the solid line represents the line current and the dashed line represents the mechanical switching current. FIG. 5 is a waveform diagram of a pre-charge capacitor of the DC breaker according to the present invention during the turn-on and turn-off process, wherein the x-axis is time t, and the unit s; the y-axis is the voltage amplitude, in kV; the solid line represents the voltage of the precharge capacitor C11, and the broken line represents the voltage of the storage capacitor C12.
For reclosing of fig. 3 to open the 25kA fault current, the thyristor SCR1 acts at t1, opening the fault current, the current of the mechanical switch CB quickly reaches zero; then, the current is transferred to a converting branch circuit to charge a converting capacitor C2, the voltage of the converting capacitor C2 is added to two ends of a mechanical switch CB, when the voltage of the mechanical switch CB reaches the action voltage of an energy absorption and voltage limiting unit MOV, an arrester MOV acts to absorb the energy of an inductive element in the system, and the line current slowly drops to zero and continuously oscillates; at t2, the thyristor SCR1 is conducted again, the converter branch circuit generates oscillating current, the converter branch circuit mechanical switch CB2 cuts off the converter branch circuit current, and the line current is quickly attenuated to zero; at t3, the circuit breaker performs reclosing operation, at this time, the thyristor SCR2 is turned on, the energy of the converter capacitor C2 is rapidly consumed through the energy dissipation resistor R2, and the closing current of the mechanical switch rapidly decays to zero. And then reclosing for the second time according to the switching-off principle.
Fig. 4 is a waveform diagram of a small current of 100A on-off, at t1, the thyristor SCR1 acts, the primary side oscillating current causes the converter branch to generate oscillating current through the coupling reactor, the oscillating current is superimposed on the mechanical switch CB to generate zero crossing arc extinction, the line current passes through the smoothing reactor L0, the converter capacitor C2 and the secondary side inductance L2 of the coupling reactor to the load, and the converter branch is in an over-damping state of the second-order circuit due to the large load equivalent impedance, the line current slowly decays to zero exponentially, and a long tailing process exists. At t2, the thyristor SCR1 is triggered again, the converter branch circuit generates oscillating current, the converter branch circuit mechanical switch CB2 generates zero crossing point, the converter branch circuit current is disconnected, the line current is rapidly reduced, and the line current is rapidly attenuated to zero.
Fig. 5 is a voltage waveform of the precharge capacitor C11 and the storage capacitor C12 in the switching-on and switching-off process. As can be seen from the figure, after the first turn-off, the voltage of the precharge capacitor C11 is rapidly reduced from 150kV of the precharge to around 65kV, which makes it difficult to meet the second turn-off requirement. Therefore, the energy storage capacitor C12 charges the precharge capacitor C11 through the charging resistor R2, and the voltage of the two is equal to 100kV finally, so that the second switching-on and switching-off requirement can be satisfied.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (7)
1. A coupled high voltage dc circuit breaker, comprising: the energy-absorbing and voltage-limiting device comprises a main loop unit (1), a charging and current-converting unit (2), an energy-consuming unit (3), a triggering unit (4) and an energy-absorbing and voltage-limiting unit (5);
the main loop unit (1) is used for being connected into a direct current system in series, the energy absorption and voltage limiting unit (5) is connected with the main loop unit (1) in parallel, and the charging converter unit (2) is connected with the main loop unit (1) in parallel;
the first output end of the triggering unit (4) is connected with the charging converter unit (2), the second output end of the triggering unit (4) is connected with the energy consumption unit (3), and the triggering unit (4) is used for triggering the charging converter unit (2) after a system fails and triggering the energy consumption unit (3) when reclosing;
the charging current converting unit (2) is used for generating high-frequency oscillation current when faults occur, reversely superposing the high-frequency oscillation current with the fault current to form zero-crossing breaking fault current, and charging the pre-charging capacitor after the first breaking for reclosing fault breaking;
the energy-absorbing voltage-limiting unit (5) is used for absorbing energy stored in the inductive element of the power system after the switching-on and switching-off are finished and limiting the voltage at two ends of the mechanical switch;
the energy consumption unit (3) is also connected with the charging converter unit (2), and the energy consumption unit (3) is used for consuming the energy of the converter capacitor when the direct current breaker is reclosed so as to quickly attenuate the closing current on the mechanical switch to zero;
the charging converter unit (2) includes: the device comprises a precharge capacitor C11, a thyristor SCR1, an energy storage capacitor C12, a charging resistor R1, a coupling reactor, a commutation capacitor C2, a mechanical switch CB2 and a lightning arrester MOV2;
one end of the precharge capacitor C11 is connected with one end of the primary side L1 of the coupling reactor, and the other end of the precharge capacitor C11 is connected with one end of the thyristor SCR 1; the other end of the thyristor SCR1 is connected with the other end of the primary side L1 of the coupling reactor, and the energy storage capacitor C12 is connected with the charging resistor R1 in series and then connected with the pre-charging capacitor C11 in parallel;
one end of the converter capacitor C2 is connected with one end of the secondary side L2 of the coupling reactor, the other end of the converter capacitor C2 is connected to one end of the mechanical switch CB2, the lightning arrester MOV2 is connected with the mechanical switch CB2 in parallel, and the other end of the secondary side L2 of the coupling reactor and the other end of the mechanical switch CB2 are respectively connected to two ends of the main loop unit (1);
the energy consumption unit (3) comprises: the energy dissipation resistor R2 and the thyristor SCR2 are connected in series, the non-series connection end of the energy dissipation resistor R2 is grounded, and the non-series connection end of the thyristor SCR2 is respectively connected with the charging converter unit (2) and the triggering unit (4).
2. The coupled high-voltage direct-current circuit breaker according to claim 1, characterized in that the main circuit unit (1) is a mechanical switch that is ignitable and that can be put out of arc at zero crossing of the current.
3. The coupled high voltage direct current breaker according to any of the claims 1-2, characterized in that the energy absorbing and voltage limiting unit (5) comprises: and two ends of the zinc oxide lightning arrester are respectively connected with two ends of the main loop unit (1).
4. The coupling type high voltage direct current breaker according to any one of claims 1 to 2, characterized in that when the system is operating normally, the mechanical switch CB is closed, through which the system current flows to the load with small on-state losses;
when a short circuit fault occurs in the system, a contact of the mechanical switch CB is opened and burnt, after the contact opening distance of the mechanical switch CB reaches a rated opening distance and can withstand recovery voltage after opening and breaking, the trigger unit triggers the thyristor SCR1 to conduct the charging converter unit, the pre-charging capacitor C11 and the primary side inductor L1 of the coupling reactor oscillate, the secondary side inductor L2 of the coupling reactor and the converter capacitor C2 generate reverse oscillation current through the coupling reactor, and the oscillation current amplitude exceeds the maximum fault current amplitude of the system, so that the mechanical switch CB generates zero-crossing arc extinction and opens fault current;
after the mechanical switch CB is subjected to zero crossing arc extinction, line current is transferred to a converter branch formed by the secondary side inductance L2 of the coupling reactor and the converter capacitor C2 in series, so that the voltage of the converter capacitor C2 is gradually increased and is applied to two ends of the mechanical switch CB, when the voltage amplitude is increased to the action voltage of the energy-absorbing voltage-limiting unit, the energy-absorbing voltage-limiting unit performs lightning protection, inductive energy in a line is absorbed, the mechanical switch is protected under voltage limiting, and meanwhile, the line current starts to be reduced.
5. The coupling type high voltage direct current breaker according to any one of claims 1-2, wherein when the line fault is a ground fault, the line current oscillates through the secondary side inductance L2 of the coupling reactor and the commutation capacitor C2 after the line is opened, and the attenuation speed is slow;
when the line fault is a high-resistance ground fault, the converter branch is in an over-damping state after the circuit fault is opened, a longer trailing exists in the process of reducing the line current, and when the line current is reduced to be near zero, the triggering unit triggers the thyristor SCR1 again to enable the converter branch to generate oscillating current, so that the mechanical switch CB2 cuts off the converter branch current at the zero crossing point.
6. The coupling type high voltage direct current breaker according to any one of claims 1 to 2, characterized in that the voltage across the pre-charge capacitor C11 decays after the end of the first turn-off, and the energy storage capacitor C12 charges the pre-charge capacitor through the charging resistor R1 to enable the second turn-off.
7. The coupled high-voltage direct-current circuit breaker according to claim 1, wherein the thyristor SCR2 is turned on when a reclosing operation is performed, so that a high-frequency oscillating current generated on the mechanical switch is discharged through the energy dissipation resistor R2, thereby rapidly attenuating the mechanical switch current to zero.
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| CN111355213B (en) * | 2018-12-21 | 2023-09-01 | 平高集团有限公司 | Direct current breaker |
| CN109687386B (en) * | 2019-02-02 | 2020-03-06 | 四川大学 | Hybrid direct current breaker buffering branch with reclosing capability |
| CN111786355A (en) * | 2020-06-23 | 2020-10-16 | 上海电器科学研究所（集团）有限公司 | Protection device and protection method for restraining short circuit of direct current bus support capacitor |
| CN113824083B (en) * | 2021-07-09 | 2022-10-18 | 天津大学 | Hybrid direct current breaker with self-adaptive reclosing |
| CN113725831B (en) * | 2021-08-18 | 2022-05-20 | 华中科技大学 | Economical mechanical high-voltage direct-current circuit breaker |
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