CN114156846B - Low-loss multi-terminal direct current circuit breaker and control method thereof - Google Patents
Low-loss multi-terminal direct current circuit breaker and control method thereof Download PDFInfo
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- CN114156846B CN114156846B CN202111460731.0A CN202111460731A CN114156846B CN 114156846 B CN114156846 B CN 114156846B CN 202111460731 A CN202111460731 A CN 202111460731A CN 114156846 B CN114156846 B CN 114156846B
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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
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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
- H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
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- 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 belongs to the field of multi-terminal direct current circuit breakers, particularly relates to a low-loss multi-terminal direct current circuit breaker and a control method thereof, and aims to solve the problems of high loss and high cost of the existing bridge type multi-terminal direct current circuit breaker. The invention comprises the following steps: the positive end of the main circuit breaker is connected to a direct current bus and connected with the positive end of the mechanical switch group, the negative end of the main circuit breaker is connected to the positive end of the resonant circuit, the negative end of the mechanical switch group is connected to the negative end of the resonant circuit, and the output end of the mechanical switch group serves as the output end of the low-loss multi-end direct current circuit breaker and is used for supplying power to the positive electrode of a corresponding direct current circuit. The mechanical switches are mutually backed up, and a multiplex resonance circuit formed by the resonance inductor, the resonance capacitor, the switch and the diode is utilized to generate high-frequency resonance current to guide the current of the mechanical switches to perform zero-crossing arc extinguishing, so that the mechanical switch has the advantages of high switching reliability, small volume, low loss and low cost.
Description
Technical Field
The invention belongs to the field of multi-terminal direct current circuit breakers, and particularly relates to a low-loss multi-terminal direct current circuit breaker and a control method thereof.
Background
In some application scenarios, one dc bus of the dc power grid has a plurality of dc outgoing lines. In order to selectively cut off a faulty line, each dc line port needs to be configured with a dc breaker, however, this configuration is too costly to build. A single multi-terminal direct-current circuit breaker is used for replacing a plurality of direct-current circuit breakers, so that a plurality of ports share expensive breaking equipment, the construction cost can be effectively reduced, and the line breaking efficiency is improved.
A bridge type multi-terminal direct current breaker is characterized in that a main breaker part with the highest cost is shared. The method has a strong economic application prospect in a direct current power grid. However, such a bridge-type multi-terminal dc breaker has some drawbacks: firstly, the redundancy is low, a self-protection function is not provided, and once faults such as short circuit of a positive bus and a negative bus or faults of a mechanical switch occur, the circuit breaker cannot work and even threatens the stability of a direct current network; secondly, the existing bridge type multi-terminal direct current circuit breaker carries out short-circuit current transfer by depending on a load transfer switch, and the loss is high.
Disclosure of Invention
In order to solve the above problems in the prior art, namely the problems of large loss and high cost of the existing bridge type multi-terminal direct current circuit breaker, the invention provides a low-loss multi-terminal direct current circuit breaker, which comprises a main circuit breaker, a resonance circuit and a mechanical switch group;
the positive end of the main breaker is connected to the direct-current bus and is connected with the positive end of the mechanical switch group, and the negative end of the main breaker is connected to the positive end of the resonant circuit;
the negative end of the mechanical switch group is connected to the negative end of the resonant circuit;
and the output end of the mechanical switch group is used as the output end of the low-loss multi-end direct current circuit breaker and used for supplying power to the positive pole of the corresponding direct current circuit.
In some preferred embodiments, the mechanical switch group includes N upper and lower mechanical switch pairs; wherein N is a positive integer;
the connection point of the upper mechanical switch and the lower mechanical switch in the N upper mechanical switch and lower mechanical switch pairs is the output end of the mechanical switch group;
the positive terminals of the upper mechanical switches of the N upper mechanical switch pairs and the upper mechanical switch of the lower mechanical switch pairs are used as the positive terminals of the mechanical switch groups;
and the negative electrode ends of the lower mechanical switches of the N upper mechanical switch pairs and the lower mechanical switch pairs are used as the negative electrode ends of the mechanical switch groups.
In some preferred embodiments, the resonant circuit includes a resonant inductor, a resonant capacitor, a resonant switch 1, a resonant switch 2, and N upper bridge arm switch and lower bridge arm switch pairs in one-to-one correspondence with the N upper mechanical switch and lower mechanical switch pairs;
the positive pole of the resonance inductor is used as the positive pole end of the resonance circuit, and the negative pole of the resonance inductor is connected to the cathode of the resonance switch 1 and the anode of the resonance switch 2;
the anode of the resonance switch 1 is connected to the anode of the resonance capacitor and the anodes of the upper bridge arm switches of the N upper bridge arm switches and the lower bridge arm switches;
the cathode of the resonance switch 2 is connected to the cathode of the resonance capacitor and the cathodes of the lower bridge arm switches of the N upper bridge arm switches and the lower bridge arm switches;
and the connection point of the upper bridge arm switches and the lower bridge arm switches in the N pairs of upper bridge arm switches and lower bridge arm switches is used as the negative pole end of the resonant circuit.
In some preferred embodiments, the negative terminals of the N-th pair of lower and upper mechanical switches of the N pairs of lower and upper mechanical switches are connected to the connection point of the N-th pair of upper and lower bridge arm switches of the N pairs of lower and upper bridge arm switches; wherein N is more than or equal to 1 and less than or equal to N.
In some preferred embodiments, the resonant switch 1, the resonant switch 2, and the N upper arm switch and lower arm switch pairs are all fully-controlled electronic devices.
In some preferred embodiments, the fully-controlled electronic device is one of an insulated gate bipolar transistor, an integrated gate commutated thyristor, and an injection enhanced gate transistor.
On the other hand, the invention provides an external line fault blocking control method of a low-loss multi-terminal direct current circuit breaker, which is based on the low-loss multi-terminal direct current circuit breaker and comprises the following steps:
when the external line has short-circuit fault, the short-circuit current flows through the upper mechanical switches of all lines, the lower mechanical switch connected with the fault line is not switched on or off by an arc, and the upper mechanical switches of other non-fault lines are switched on or off by an arc; wherein the arc is a unipolar arc;
switching on a lower bridge arm switch corresponding to the main breaker and the fault line and an upper bridge arm switch connected with the resonant inductor;
the upper mechanical switch, the pre-charged resonant capacitor, the resonant inductor and the main breaker of the non-fault line form a high-frequency current oscillation circuit;
the high-frequency current generated by the high-frequency current oscillation circuit is superposed on the unipolar electric arc in the upper mechanical switch corresponding to the non-fault line, so that the electric arc is extinguished in a zero-crossing manner;
after the mechanical switch is completely opened, fault current is transferred to the main circuit breaker, the main circuit breaker IGBT breaks the current, and residual current is transferred to a lightning arrester in the main circuit breaker to be consumed.
The third aspect of the present invention provides a method for controlling a dc bus fault of a low-loss multi-terminal dc circuit breaker, based on the above-mentioned low-loss multi-terminal dc circuit breaker, the method includes:
when the direct current bus has short-circuit fault, short-circuit current flows through the upper mechanical switches of all lines, and all the mechanical switches are switched on and off with arcs; wherein the arc is a unipolar arc;
a lower bridge arm switch connected with the main circuit breaker and the lower mechanical switch and an upper bridge arm switch connected with the resonant inductor are conducted;
all the upper mechanical switches, the pre-charged resonant capacitors, the resonant inductors and the main circuit breaker form a plurality of high-frequency current oscillation circuits;
the high-frequency currents generated by the high-frequency current oscillating circuits are respectively superposed on the unipolar arcs in the corresponding upper mechanical switches, so that the arcs are extinguished at zero passage;
after the mechanical switch is completely opened, fault current is transferred to the main circuit breaker, the main circuit breaker breaks the current, and residual current is transferred to a lightning arrester in the main circuit breaker to be consumed.
In a fourth aspect of the present invention, a method for controlling a mechanical switch fault of a low-loss multi-terminal dc circuit breaker is provided, where based on the low-loss multi-terminal dc circuit breaker, the method includes:
when the mechanical switch has short-circuit fault, short-circuit current flows through the upper mechanical switches of all lines, the lower mechanical switch connected with the fault line is not switched on and off by an arc, and the upper mechanical switches of other non-fault lines are switched on and off by an arc; wherein the arc is a unipolar arc;
if the failure circuit is detected to be corresponding to the lower mechanical switch to be refused, the upper mechanical switch connected with the failure circuit is continuously switched on and off in an arc manner, and the lower mechanical switches of other non-failure circuits are not switched on and off in an arc manner;
switching on an upper bridge arm switch corresponding to the main breaker and the fault line and a lower bridge arm switch connected with the resonant inductor;
the upper mechanical switch, the pre-charged resonant capacitor, the resonant inductor and the main breaker of the fault line form a high-frequency current oscillation circuit;
the high-frequency current generated by the high-frequency current oscillation circuit is superposed on the unipolar electric arc in the upper mechanical switch corresponding to the fault line, so that the electric arc is extinguished in a zero-crossing manner;
after the mechanical switch is completely opened, the fault current is transferred to the main circuit breaker, the main circuit breaker IGBT breaks the current, the residual current is transferred to the lightning arrester in the main circuit breaker to be consumed, and at the moment, the arc of the upper mechanical switch corresponding to the non-fault line is extinguished.
In a fifth aspect of the present invention, a method for controlling a capacitor pre-charge of a low-loss multi-terminal dc circuit breaker is provided, where based on the low-loss multi-terminal dc circuit breaker, the method includes:
when the low-loss multi-terminal direct current circuit breaker is used, all the lower mechanical switches, the upper bridge arm switches and the lower bridge arm switches are closed, and then the resonant capacitors in the resonant circuit are charged to a rated value by controlling the upper bridge arm switches and the lower bridge arm switches to be alternately conducted.
The invention has the beneficial effects that:
(1) the low-loss multi-terminal direct current breaker provided by the invention utilizes the double mechanical switches with arc extinguishing functions as a main loop structure, can realize low loss of the multi-terminal direct current breaker and mutual backup of the mechanical switches, and has reliable equipment and high safety.
(2) The low-loss multi-terminal direct current circuit breaker provided by the invention utilizes the resonant inductor, the resonant capacitor, the mechanical switch and the bridge arm switch to generate high-frequency resonant current, guides the current of the mechanical switch to zero-cross to extinguish electric arc, and further improves the switching reliability of the multi-terminal direct current circuit breaker.
(3) According to the low-loss multi-terminal direct current breaker, the resonance circuit can be multiplexed, the size of the multi-terminal direct current breaker is further reduced, and the cost is reduced.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:
fig. 1 is a schematic circuit diagram of a low loss multi-terminal dc circuit breaker according to the present invention;
fig. 2 is a schematic diagram of a circuit structure for protecting only the load transfer switch and the positive and negative buses in the system according to an embodiment of the low-loss multi-terminal dc circuit breaker of the present invention.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the related invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
The invention provides a low-loss multi-terminal direct current breaker, when a short-circuit fault occurs in a line, short-circuit current flows through upper mechanical switches of all lines, after the short-circuit fault is detected, the upper mechanical switch connected with the fault line is switched on and off by an electric arc, and lower mechanical switches of other non-fault lines are switched on and off by no electric arc, so that the electric arc is always kept and is unipolar because a direct current power grid does not have a zero crossing point; at the moment, an upper bridge arm switch corresponding to the main circuit breaker and the fault line is switched on, an upper mechanical switch, a pre-charged resonant capacitor, a resonant inductor and the main circuit breaker of the fault line form a high-frequency current oscillation circuit, high-frequency current is superposed on unipolar electric arcs in the upper mechanical switch corresponding to the fault line, so that zero crossing of the electric arcs is extinguished, the standby mechanical switch is completely opened, after the fault current is transferred to the main circuit breaker, the IGBT of the main circuit breaker breaks the current, and residual current is transferred to a lightning arrester in the main circuit breaker to be consumed.
The invention discloses a low-loss multi-terminal direct current breaker, which comprises a main breaker, a resonant circuit and a mechanical switch group, wherein the main breaker is connected with the resonant circuit;
the positive end of the main breaker is connected to the direct-current bus and is connected with the positive end of the mechanical switch group, and the negative end of the main breaker is connected to the positive end of the resonant circuit;
the negative end of the mechanical switch group is connected to the negative end of the resonant circuit;
and the output end of the mechanical switch group is used as the output end of the low-loss multi-end direct current circuit breaker and used for supplying power to the positive pole of the corresponding direct current circuit.
In order to more clearly describe the low-loss multi-terminal dc circuit breaker of the present invention, details of the modules in the embodiment of the present invention are described below with reference to fig. 1.
The low-loss multi-terminal direct current circuit breaker in the first embodiment of the invention comprises a main circuit breaker, a resonance circuit and a mechanical switch group, wherein each module is described in detail as follows:
the positive terminal of the main breaker is connected to the direct current bus and connected with the positive terminal of the mechanical switch group, and the negative terminal of the main breaker is connected to the positive terminal of the resonant circuit.
And the negative end of the mechanical switch group is connected to the negative end of the resonant circuit.
The mechanical switch group comprises N upper mechanical switch pairs and N lower mechanical switch pairs; wherein N is a positive integer;
the connection point of the upper mechanical switch and the lower mechanical switch in the N upper mechanical switch and lower mechanical switch pairs is the output end of the mechanical switch group;
the positive terminals of the upper mechanical switches of the N upper mechanical switch pairs and the upper mechanical switch of the lower mechanical switch pairs are used as the positive terminals of the mechanical switch groups;
and the negative electrode ends of the lower mechanical switches of the N upper mechanical switch and lower mechanical switch pairs are used as the negative electrode ends of the mechanical switch groups.
The resonance circuit comprises a resonance inductor, a resonance capacitor, a resonance switch 1, a resonance switch 2, and N upper bridge arm switches and lower bridge arm switches which are in one-to-one correspondence with the N upper mechanical switches and the N lower mechanical switches;
the positive pole of the resonance inductor is used as the positive pole end of the resonance circuit, and the negative pole of the resonance inductor is connected to the cathode of the resonance switch 1 and the anode of the resonance switch 2;
the anode of the resonance switch 1 is connected to the anode of the resonance capacitor and the anodes of the upper bridge arm switches of the N upper bridge arm switches and the lower bridge arm switches;
the cathode of the resonance switch 2 is connected to the cathode of the resonance capacitor and the cathodes of the lower bridge arm switches of the N upper bridge arm switches and the lower bridge arm switches;
and the connection point of the upper bridge arm switches and the lower bridge arm switches in the N pairs of upper bridge arm switches and lower bridge arm switches is used as the negative pole end of the resonant circuit.
The negative pole ends of the lower mechanical switches of the nth pair of the N upper mechanical switches and the lower mechanical switches are connected to the connection points of the upper bridge arm switches and the lower bridge arm switches of the nth pair of the N upper bridge arm switches and the lower bridge arm switches corresponding to the N lower bridge arm switches; wherein N is more than or equal to 1 and less than or equal to N.
And the output end of the mechanical switch group is used as the output end of the low-loss multi-end direct current circuit breaker and used for supplying power to the positive pole of the corresponding direct current circuit.
The resonance switch 1, the resonance switch 2 and the N pairs of upper bridge arm switches and lower bridge arm switches are all fully-controlled electronic devices.
In one embodiment of the present invention, the fully-controlled electronic device is an IGBT (insulated gate bipolar transistor), and in other application scenarios, different fully-controlled electronic devices, such as an IGCT thyristor (integrated gate commutated thyristor) or an IEGT transistor (injection enhanced gate transistor), may be selected according to current and voltage levels.
As shown in fig. 2, a schematic diagram of a circuit structure for protecting only the load transfer switch and the positive and negative buses in the system according to an embodiment of the low-loss multi-terminal dc circuit breaker of the present invention is shown, and in an actual use process, costs and functions can be balanced to a certain extent, for example, backup of a mechanical switch is not considered, only protection of the load transfer switch and the positive and negative buses is considered, a lower bridge arm switch in a protection switch can be replaced by a diode, a resonance switch is cancelled, and the above effects can also be achieved.
The external line fault blocking control method of the low-loss multi-terminal dc circuit breaker according to the second embodiment of the present invention is based on the above-mentioned low-loss multi-terminal dc circuit breaker, and the method includes:
when the short-circuit fault occurs to the external line, the short-circuit current flows through the upper mechanical switches of all lines, when the short-circuit fault is detected, the lower mechanical switch connected with the fault line is not switched on or off in an arc way, and the upper mechanical switches of other non-fault lines are switched on or off in an arc way; wherein, the electric arc can be always maintained and is a unipolar electric arc because the direct current power grid has no zero crossing point;
at the moment, a lower bridge arm switch corresponding to the fault line and an upper bridge arm switch connected with the resonant inductor of the main circuit breaker are switched on;
under the condition that the corresponding switch is switched on and switched off, the upper mechanical switch, the pre-charged resonant capacitor, the resonant inductor and the main circuit breaker of the non-fault line form a high-frequency current oscillation circuit;
the high-frequency current generated by the high-frequency current oscillation circuit is superposed on the unipolar electric arc in the upper mechanical switch corresponding to the non-fault line, so that the electric arc is extinguished in a zero-crossing manner;
after the mechanical switch is completely opened, the fault current is transferred to the main circuit breaker, the main circuit breaker breaks the current, and the residual current is transferred to the lightning arrester in the main circuit breaker for consumption. The main breaker is also used for breaking current by adopting a fully-controlled electronic device, and similarly, different fully-controlled electronic devices can be selected according to current and voltage levels, such as an IGBT transistor (insulated gate bipolar transistor), an IGCT thyristor (integrated gate commutated thyristor) or an IEGT transistor (injection enhanced gate transistor), and the like.
A dc bus fault control method of a low-loss multi-terminal dc circuit breaker according to a third embodiment of the present invention is based on the above-mentioned low-loss multi-terminal dc circuit breaker, and the method includes:
when the direct current bus has short-circuit fault, short-circuit current flows through the upper mechanical switches of all lines, and when the short-circuit fault is detected, all the mechanical switches are switched off with arcs; wherein, the electric arc can be always maintained and is a unipolar electric arc because the direct current power grid has no zero crossing point;
at the moment, a lower bridge arm switch connected with the main circuit breaker and the lower mechanical switch and an upper bridge arm switch connected with the resonant inductor are switched on;
under the condition that the corresponding switches are switched on and off, all the upper mechanical switches, the pre-charged resonant capacitors, the resonant inductors and the main circuit breaker form a plurality of high-frequency current oscillation circuits;
high-frequency currents generated by the high-frequency current oscillating circuits are respectively superposed on unipolar arcs in the corresponding upper mechanical switches, so that the arcs are extinguished in a zero-crossing mode;
after the mechanical switch is completely opened, the fault current is transferred to the main circuit breaker, the main circuit breaker IGBT breaks the current, and the residual current is transferred to the arrester in the main circuit breaker for consumption.
A mechanical switch fault control method for a low-loss multi-terminal dc circuit breaker according to a fourth embodiment of the present invention is based on the above-mentioned low-loss multi-terminal dc circuit breaker, and the method includes:
when the mechanical switch has short-circuit fault, short-circuit current flows through the upper mechanical switches of all lines, and after the short-circuit fault is detected, the lower mechanical switch connected with the fault line is not switched on or off in an arc manner, and the upper mechanical switches of other non-fault lines are switched on or off in an arc manner; wherein, the electric arc can be always maintained and is a unipolar electric arc because the direct current power grid has no zero crossing point;
if the failure circuit is detected to be corresponding to the lower mechanical switch to be refused, the upper mechanical switch connected with the failure circuit is continuously switched on and off in an arc manner, and the lower mechanical switches of other non-failure circuits are not switched on and off in an arc manner;
at the moment, an upper bridge arm switch corresponding to the fault line and a lower bridge arm switch connected with the resonant inductor of the main circuit breaker are switched on;
under the condition that the corresponding switches are switched on and off, the upper mechanical switch, the pre-charged resonant capacitor, the resonant inductor and the main circuit breaker of the fault line form a high-frequency current oscillation circuit;
the high-frequency current generated by the high-frequency current oscillation circuit is superposed on the unipolar electric arc in the upper mechanical switch corresponding to the fault line, so that the electric arc is extinguished in a zero-crossing manner;
and after the mechanical switch is completely opened, the fault current is transferred to the main circuit breaker, the main circuit breaker IGBT breaks the current, the residual current is transferred to a lightning arrester in the main circuit breaker to be consumed, and at the moment, the electric arc of the upper mechanical switch corresponding to the non-fault line is extinguished.
A capacitor precharge control method for a low-loss multi-terminal dc circuit breaker according to a fifth embodiment of the present invention is based on the low-loss multi-terminal dc circuit breaker, and the method includes:
before the low-loss multi-terminal direct current breaker is put into use, all the mechanical switches are in an on-off state; when the low-loss multi-terminal direct current circuit breaker is used, all the lower mechanical switches, the upper bridge arm switches and the lower bridge arm switches are closed, and then the resonant capacitors in the resonant circuit are charged to a rated value by controlling the upper bridge arm switches and the lower bridge arm switches to be alternately conducted.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process and related descriptions of the method described above may refer to the corresponding process in the foregoing system embodiment, and are not described herein again.
It should be noted that, the low-loss multi-terminal dc circuit breaker and the control method thereof provided in the foregoing embodiments are only illustrated by the division of the functional modules, and in practical applications, the functions may be distributed by different functional modules according to needs, that is, the modules or steps in the embodiments of the present invention are further decomposed or combined, for example, the modules in the foregoing embodiments may be combined into one module, or may be further split into multiple sub-modules, so as to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only for distinguishing the modules or steps, and are not to be construed as unduly limiting the present invention.
The terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing or implying a particular order or sequence.
The terms "comprises," "comprising," or any other similar term are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can be within the protection scope of the invention.
Claims (7)
1. A low-loss multi-terminal direct current breaker is characterized by comprising a main breaker, a resonant circuit and a mechanical switch group;
the positive end of the main breaker is connected to the direct-current bus and is connected with the positive end of the mechanical switch group, and the negative end of the main breaker is connected to the positive end of the resonant circuit;
the mechanical switch group comprises N upper mechanical switch pairs and N lower mechanical switch pairs, wherein N is a positive integer, the connection point of the upper mechanical switch pairs and the lower mechanical switch pairs in the N upper mechanical switch pairs and the lower mechanical switch pairs is the output end of the mechanical switch group, the positive terminals of the upper mechanical switches of the N upper mechanical switch pairs and the upper mechanical switch pairs of the N lower mechanical switch pairs are used as the positive terminals of the mechanical switch group, the negative terminals of the lower mechanical switches of the N upper mechanical switch pairs and the lower mechanical switch pairs are used as the negative terminals of the mechanical switch group, and the negative terminals of the mechanical switch group are connected to the negative terminal of the resonant circuit;
the output end of the mechanical switch group is used as the output end of the low-loss multi-end direct current circuit breaker and used for supplying power to the positive pole of the corresponding direct current circuit
The resonance circuit comprises a resonance inductor, a resonance capacitor, a resonance switch 1, a resonance switch 2, and N upper bridge arm switches and lower bridge arm switches which are in one-to-one correspondence with the N upper mechanical switches and lower mechanical switches, the positive pole of the resonance inductor is used as the positive pole end of the resonance circuit, the negative pole of the resonance inductor is connected to the cathode of the resonance switch 1 and the anode of the resonance switch 2, the anode of the resonance switch 1 is connected to the anode of the resonance capacitor and the anodes of the upper arm switches of the N upper arm switch and lower arm switch pairs, the cathode of the resonance switch 2 is connected to the cathode of the resonance capacitor and the cathodes of the lower arm switches of the N upper arm switch and lower arm switch pairs, the connection point of the upper bridge arm switch and the lower bridge arm switch in the N pairs of upper bridge arm switches and lower bridge arm switches is used as the negative pole end of the resonant circuit;
and the negative pole ends of the N-th pair of lower mechanical switches in the N upper mechanical switches and the N-th pair of lower mechanical switches are connected to the connecting points of the N-th pair of upper bridge arm switches and the N-th pair of lower bridge arm switches corresponding to the N upper bridge arm switches and the N-th pair of lower bridge arm switches, and N is more than or equal to 1 and less than or equal to N.
2. The low-loss multi-terminal direct current circuit breaker according to claim 1, wherein the resonant switch 1, the resonant switch 2 and the N upper and lower bridge arm switch pairs are all fully-controlled electronic devices.
3. The low-loss multi-terminal dc circuit breaker according to claim 2, wherein the fully-controlled electronic device is one of an insulated gate bipolar transistor, an integrated gate commutated thyristor, and an injection enhanced gate transistor.
4. An external line fault blocking control method of a low loss multi-terminal dc circuit breaker, characterized in that, based on the low loss multi-terminal dc circuit breaker of any of claims 1-3, the method comprises:
when the external line has short-circuit fault, the short-circuit current flows through the upper mechanical switches of all lines, the lower mechanical switch connected with the fault line is not switched on or off by an arc, and the upper mechanical switches of other non-fault lines are switched on or off by an arc; wherein the arc is a unipolar arc;
switching on a lower bridge arm switch corresponding to the main breaker and the fault line and an upper bridge arm switch connected with the resonant inductor;
the upper mechanical switch, the pre-charged resonant capacitor, the resonant inductor and the main breaker of the non-fault line form a high-frequency current oscillation circuit;
the high-frequency current generated by the high-frequency current oscillation circuit is superposed on the unipolar electric arc in the upper mechanical switch corresponding to the non-fault line, so that the electric arc is extinguished at zero passage;
after the mechanical switch is completely opened, fault current is transferred to the main circuit breaker, the main circuit breaker breaks the current, and residual current is transferred to a lightning arrester in the main circuit breaker to be consumed.
5. A method for controlling a dc bus fault of a low-loss multi-terminal dc circuit breaker, the method being based on any one of claims 1-3, the method comprising:
when the direct current bus has short-circuit fault, short-circuit current flows through the upper mechanical switches of all lines, and all the mechanical switches are switched on and off with arcs; wherein the arc is a unipolar arc;
a lower bridge arm switch connected with the lower mechanical switch and an upper bridge arm switch connected with the resonant inductor are conducted;
all the upper mechanical switches, the pre-charged resonant capacitors, the resonant inductors and the main circuit breaker form a plurality of high-frequency current oscillation circuits;
high-frequency currents generated by the high-frequency current oscillating circuits are respectively superposed on unipolar arcs in the corresponding upper mechanical switches, so that the arcs are extinguished in a zero-crossing mode;
after the mechanical switch is completely opened, fault current is transferred to the main circuit breaker, the IGBT of the main circuit breaker breaks the current, and residual current is transferred to the lightning arrester in the main circuit breaker to be consumed.
6. A method for controlling a mechanical switch fault of a low-loss multi-terminal dc circuit breaker, the method being based on any one of claims 1-3, the method comprising:
when the mechanical switch has short-circuit fault, short-circuit current flows through the upper mechanical switches of all lines, the lower mechanical switch connected with the fault line is not subjected to arc disconnection, and the upper mechanical switches of other non-fault lines are subjected to arc disconnection; wherein the arc is a unipolar arc;
if the failure circuit is detected to be corresponding to the lower mechanical switch to be refused, the upper mechanical switch connected with the failure circuit is continuously switched on and off in an arc manner, and the lower mechanical switches of other non-failure circuits are not switched on and off in an arc manner;
switching on an upper bridge arm switch corresponding to the main breaker and the fault line and a lower bridge arm switch connected with the resonant inductor;
the upper mechanical switch, the pre-charged resonant capacitor, the resonant inductor and the main breaker of the fault line form a high-frequency current oscillation circuit;
the high-frequency current generated by the high-frequency current oscillation circuit is superposed on the unipolar electric arc in the upper mechanical switch corresponding to the fault line, so that the electric arc is extinguished in a zero-crossing manner;
after the mechanical switch is completely opened, the fault current is transferred to the main circuit breaker, the main circuit breaker IGBT breaks the current, the residual current is transferred to the lightning arrester in the main circuit breaker to be consumed, and at the moment, the arc of the upper mechanical switch corresponding to the non-fault line is extinguished.
7. A method for controlling the capacitor pre-charging of a low-loss multi-terminal dc circuit breaker, the method being based on any one of claims 1-3, the method comprising:
when the low-loss multi-terminal direct current circuit breaker is used, all the lower mechanical switches, the upper bridge arm switches and the lower bridge arm switches are closed, and then the upper bridge arm switches and the lower bridge arm switches are controlled to be alternately conducted to charge the resonant capacitors in the resonant circuit to rated values.
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