CN111244909A - Modularized mechanical direct current circuit breaker and switching-on and switching-off method thereof - Google Patents
Modularized mechanical direct current circuit breaker and switching-on and switching-off method thereof Download PDFInfo
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- CN111244909A CN111244909A CN202010057801.7A CN202010057801A CN111244909A CN 111244909 A CN111244909 A CN 111244909A CN 202010057801 A CN202010057801 A CN 202010057801A CN 111244909 A CN111244909 A CN 111244909A
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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
- 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
- H01H9/56—Circuit arrangements not adapted to a particular application of the switching device and for which no provision exists elsewhere for ensuring operation of the switch at a predetermined point in the ac cycle
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/021—Details concerning the disconnection itself, e.g. at a particular instant, particularly at zero value of current, disconnection in a predetermined order
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- Driving Mechanisms And Operating Circuits Of Arc-Extinguishing High-Tension Switches (AREA)
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Abstract
The present disclosure discloses a modularized mechanical dc circuit breaker and a switching method thereof, including: the on-line monitoring system comprises a main current loop, a current transfer branch, an overvoltage limiting branch, an on-line monitoring system, a control system, a first wire inlet/outlet end and a second wire inlet/outlet end, wherein the main current loop is connected with the current transfer branch and the overvoltage limiting branch in parallel; the main current loop comprises a high-speed mechanical switch, one side of the high-speed mechanical switch is connected to the first wire inlet/outlet end, and the other side of the high-speed mechanical switch is connected to the second wire inlet/outlet end; the current transfer branch circuit comprises a control module, a transfer capacitor module and an inductor which are connected in series; the transfer capacitor module comprises n oscillation units which are connected in series, each oscillation unit comprises a pre-charge transfer capacitor, an oscillation inductor and a control device, and the oscillation inductor and the control device are connected in series and then connected in parallel with the pre-charge transfer capacitor. The circuit breaker scheme provided by the disclosure has the advantages of low cost, high breaking speed in a full current range, good fracture insulation recovery and the like.
Description
Technical Field
The present disclosure relates to a dc circuit breaker, and more particularly, to a modular mechanical dc circuit breaker.
Background
The mechanical direct current circuit breaker has the advantages of stable operation, high reliability, small on-state loss and the like, and is widely concerned by the researchers in the industry. With the further development of the dc power supply system, most loads in the new dc system have the characteristics of dual attributes of load and power supply. The characteristic causes uncertain current and energy flow direction in the direct current power grid, thereby providing the requirement of bidirectional breaking for the direct current breaker. The direct current circuit breaker working in the direct current system has no definite characteristic in the current direction of the power supply system in which the traditional circuit breaker works. Most of the mechanical direct current circuit breakers at the present stage realize artificial zero crossing points by manufacturing oscillating current opposite to short-circuit current, so that the purpose of direct current breaking is realized. Meanwhile, the traditional mechanical direct current circuit breaker has the defects of long on-off time of low current, poor insulation recovery capability of a fracture and the like due to the requirement of breaking short circuit and high current, and higher capacitor pre-charging voltage of a current transfer branch circuit. Under the application background, a direct current breaker applied to a bidirectional direct current power supply system must have the capacity of identifying the current flow direction and making corresponding breaking action according to the current flow direction when the breaker is opened, so that bidirectional opening and closing are realized; meanwhile, the current amplitude is identified, and the transfer capacity of the current transfer branch is matched according to the amplitude of the required switching-on and switching-off current, so that the rapid switching-on and switching-off in the full current range are realized.
The above information disclosed in this background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
Disclosure of Invention
Aiming at the defects in the prior art, the disclosed object is to provide a modularized mechanical direct current circuit breaker, which can effectively adjust the voltage amplitude and the voltage polarity of a pre-charging capacitor through the modularized design of a current transfer branch, and make the mechanical direct current circuit breaker have the capability of good fracture insulation recovery and rapid full current range disconnection while realizing the bidirectional conduction and breaking functions.
In order to achieve the above purpose, the present disclosure provides the following technical solutions:
a modular mechanical dc circuit breaker comprising: a main current loop, a current transfer branch, an overvoltage limiting branch, a first inlet/outlet terminal and a second inlet/outlet terminal, wherein the main current loop is connected in parallel with the current transfer branch and the overvoltage limiting branch,
the main current loop comprises a high-speed mechanical switch, one side of the high-speed mechanical switch is connected to the first wire inlet/outlet end, and the other side of the high-speed mechanical switch is connected to the second wire inlet/outlet end;
the current transfer branch circuit comprises a control module, a transfer capacitor module and an inductor which are connected in series;
the transfer capacitor module comprises n oscillation units which are connected in series, each oscillation unit comprises a pre-charge transfer capacitor, an oscillation inductor and a control device, and the oscillation inductor and the control device are connected in series and then connected in parallel with the pre-charge transfer capacitor.
Preferably, the cathode of the pre-charge transfer capacitor of the first oscillation unit of the n series-connected oscillation units is connected with the cathode of the control device of the first oscillation unit and with the control module, and the anode of the pre-charge transfer capacitor of the first oscillation unit is connected with the anode of the control device of the first oscillation unit and with the cathode of the pre-charge transfer capacitor of the second oscillation unit through the oscillation inductor of the first oscillation unit; and the positive electrode of the pre-charging transfer capacitor of the nth oscillating unit is connected to one side of the second wire inlet/outlet end close to the high-speed mechanical switch through an inductor.
Preferably, the control device is a voltage control device or a current control device.
Preferably, the control module includes a first control device and a second control device, the first control device and the second control device are connected in parallel in an opposite direction, an anode of the first control device and a cathode of the second control device are connected to one side of the high-speed mechanical switch close to the first wire inlet/outlet terminal, and a cathode of the first control device and an anode of the second control device are connected to one side of the high-speed mechanical switch close to the second wire inlet/outlet terminal after passing through the transfer capacitor module and the inductor.
Preferably, the dc circuit breaker is externally connected with an online monitoring system, which is used for:
monitoring the current state of the power system current, the main current loop, the overvoltage limiting branch and the current transfer branch,
monitoring the break voltage and the movement state of the high-speed mechanical switch, an
And monitoring the terminal voltage of the pre-charging capacitor in the transfer capacitor module and the n series-connected oscillation units and the ambient temperature of the circuit breaker.
Preferably, the dc circuit breaker is further externally connected with a control system, which:
controlling the high speed mechanical switching action based on the current magnitude and rate of change of the main current loop,
controlling the conduction state of a first control device and a second control device in the control module based on the direction of the power system current, an
And controlling the conduction number of the control device in the transfer capacitance module based on the magnitude and the direction of the current of the power system.
Preferably, the control system comprises a processor, the processor comprising any one of: general purpose processors, digital signal processors, application specific integrated circuits ASIC and field programmable gate arrays FPGA.
Preferably, the overvoltage limiting branch comprises any one of: the lightning arrester comprises a line type metal oxide lightning arrester, a gapless line type metal oxide lightning arrester, a full-insulation composite jacket metal oxide lightning arrester and a detachable lightning arrester.
The present disclosure also provides a method for switching on and off a modular mechanical dc circuit breaker, including the steps of:
s100: when the current of the power system flows in from the first wire inlet/outlet end and flows out of the second wire inlet/outlet end through the high-speed mechanical switch, if the on-line monitoring system monitors that the power system has a short-circuit fault, the control system judges the polarity of the current of the power system flowing through the main current loop and calculates the current amplitude and the current change rate of the main current loop;
s200: the control system controls the conduction of a controller in the transfer capacitance module according to the current amplitude and the current change rate, and the conduction quantity is less than half;
s300: the control system sends a brake-separating instruction, the high-speed mechanical switch starts to act, a first control device in the control module is controlled to be conducted according to the current direction of the power system, the current transfer branch circuit injects reversed-phase high-frequency oscillation current into the main current loop to force the current of the main current loop to zero, and the high-speed mechanical switch is quenched due to the zero crossing of the current;
s400: the current of the power system is continuously charged to the transfer capacitor module, when the voltage at two ends of the circuit breaker is higher than the conduction threshold value of the overvoltage limiting branch circuit, the overvoltage limiting branch circuit is conducted, and the current of the power system is transferred to the overvoltage limiting branch circuit from the current transfer branch circuit;
s500: and when the overvoltage limiting branch circuit current is subjected to zero crossing and the high-impedance state is recovered, the breaker is switched on and off.
The present disclosure also provides a method for switching on and off a modular mechanical dc circuit breaker, including the steps of:
s1000: when the current of the power system flows in from the second wire inlet/outlet end and flows out of the first wire inlet/outlet end through the high-speed mechanical switch, if the on-line monitoring system monitors that the power system has a short-circuit fault, the control system judges the polarity of the current of the power system flowing through the main current loop and calculates the current amplitude and the current change rate of the main current loop;
s2000: the control system controls the conduction of a controller in the transfer capacitance module according to the current amplitude and the current change rate, and the conduction number is more than half;
s3000: the control system sends a brake-separating instruction, the high-speed mechanical switch starts to act, a second control device in the control module is controlled to be conducted according to the current direction of the power system, the current transfer branch circuit injects reversed-phase high-frequency oscillation current into the main current loop to force the current of the main current loop to zero, and the high-speed mechanical switch is quenched due to the zero crossing of the current;
s4000: the current of the power system is continuously charged to the transfer capacitor module, when the voltage at two ends of the circuit breaker is higher than the conduction threshold value of the overvoltage limiting branch circuit, the overvoltage limiting branch circuit is conducted, and the current of the power system is transferred to the overvoltage limiting branch circuit from the current transfer branch circuit;
s5000: and when the overvoltage limiting branch circuit current returns to a high-impedance state after zero crossing, the breaker completes the on-off.
Compared with the prior art, the beneficial effect that this disclosure brought does: the current transfer branch circuit is subjected to modular design, and the voltage amplitude and the voltage polarity of the transfer capacitor module are changed by adjusting the conduction number of a plurality of control devices in the transfer capacitor module, so that the bidirectional conduction and breaking of the circuit breaker are realized, and the circuit breaker has the advantages of good fracture insulation recovery and quick breaking in a full current range.
Drawings
The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the disclosure. It is apparent that the drawings described below are only some embodiments of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without inventive effort. Also, like parts are designated by like reference numerals throughout the drawings.
Fig. 1 is a schematic structural diagram of a modular mechanical dc circuit breaker according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of the distribution of the sensors of the online monitoring system inside the circuit breaker according to one embodiment of the present disclosure;
fig. 3(a) to 3(f) are schematic diagrams illustrating the operation of the circuit breaker when the system current flows from the first inlet/outlet terminal a1 to the second inlet/outlet terminal a2 according to an embodiment of the present disclosure;
fig. 4(a) to 4(f) are schematic diagrams illustrating the operation of the circuit breaker when the system current flows from the second inlet/outlet terminal a2 to the first inlet/outlet terminal a1 according to an embodiment of the present disclosure;
fig. 5 is a waveform diagram of the currents flowing through the system, the main current loop, the current diverting branch and the overvoltage limiting branch during short circuit current breaking and low current breaking of the modular mechanical dc circuit breaker according to one embodiment of the present disclosure.
Detailed Description
Specific embodiments of the present disclosure will be described in more detail below with reference to fig. 1 to 5. While specific embodiments of the disclosure are shown in the drawings, it should be understood that the disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
It should be noted that certain terms are used throughout the description and claims to refer to particular components. As one skilled in the art will appreciate, various names may be used to refer to a component. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The description which follows is a preferred embodiment of the disclosure, but is made for the purpose of illustrating the general principles of the disclosure and not for the purpose of limiting the scope of the disclosure. The scope of the present disclosure is to be determined by the terms of the appended claims.
To facilitate an understanding of the embodiments of the present disclosure, the following detailed description is to be considered in conjunction with the accompanying drawings, and the drawings are not to be construed as limiting the embodiments of the present disclosure.
In one embodiment, fig. 1 is a modular mechanical dc circuit breaker provided by the present disclosure, including: a main current loop, a current transfer branch, an overvoltage limiting branch, a first inlet/outlet terminal and a second inlet/outlet terminal, wherein the main current loop is connected in parallel with the current transfer branch and the overvoltage limiting branch,
the main current loop comprises a high-speed mechanical switch, one side of the high-speed mechanical switch is connected to the first wire inlet/outlet end, and the other side of the high-speed mechanical switch is connected to the second wire inlet/outlet end;
the current transfer branch circuit comprises a control module, a transfer capacitor module and an inductor which are connected in series;
the transfer capacitor module comprises n oscillation units which are connected in series, each oscillation unit comprises a pre-charge transfer capacitor, an oscillation inductor and a control device, and the oscillation inductor and the control device are connected in series and then connected in parallel with the pre-charge transfer capacitor.
Compared with the traditional mechanical direct current circuit breaker, only one transfer capacitor module is adopted, the charging voltage amplitude of the transfer capacitor module cannot be changed, the small current breaking time is long, and the defect of poor fracture insulation recovery is overcome.
In another embodiment, the cathode of the pre-charge transfer capacitor of the first oscillation unit of the n series oscillation units is connected with the cathode of the control device of the first oscillation unit and with the control module, and the anode of the pre-charge transfer capacitor of the first oscillation unit is connected with the anode of the control device of the first oscillation unit and with the cathode of the pre-charge transfer capacitor of the second oscillation unit through the oscillation inductor of the first oscillation unit; and the positive electrode of the pre-charging transfer capacitor of the nth oscillating unit is connected to one side of the second wire inlet/outlet end close to the high-speed mechanical switch through an inductor.
In this embodiment, the negative charged end of the precharge transfer capacitor C1 in the first oscillation cell is connected to the control module K, the negative charged end of the precharge transfer capacitor C2 in the second oscillation cell is connected to the positive charged end of the precharge transfer capacitor C1 in the first oscillation cell, and so on to the nth oscillation cell, that is, the negative charged end of the precharge transfer capacitor Cn in the nth oscillation cell is connected to the positive charged end of the precharge transfer capacitor Cn-1 in the nth-1 oscillation cell. The positive charging end of the pre-charging transfer capacitor Cn in the nth oscillating unit is connected to one end of the high-speed mechanical switch close to the second incoming/outgoing line A2 through the oscillating inductor L.
In another embodiment, the control module includes a first control device V1 and a second control device V2, the first control device V1 and the second control device V2 are connected in parallel in reverse, an anode of the first control device V1 and a cathode of the second control device V2 are connected to a side of the high-speed mechanical switch close to the first incoming/outgoing line terminal a1, and a cathode of the first control device V1 and an anode of the second control device V2 are connected to a side of the high-speed mechanical switch close to the second incoming/outgoing line terminal a2 through a transfer capacitor module and an inductor.
In this embodiment, the first control device V1 and the second control device V2 are voltage control devices or current control devices, where the commonly used voltage control devices include IGBTs, IEGTs, and the like, and the current control devices include GTOs, IGCTs, thyristors, and the like.
In another embodiment, the dc circuit breaker is externally connected with an online monitoring system, which is configured to:
monitoring the current state of the power system current, the main current loop, the overvoltage limiting branch and the current transfer branch,
for monitoring the break voltage and the movement state of the high-speed mechanical switch, an
The device is used for monitoring the terminal voltage of the pre-charging capacitor in the transfer capacitor module and the n series-connected oscillation units and the ambient temperature of the circuit breaker.
In this embodiment, as shown in fig. 2, the online monitoring system includes a first current sensor D0, a second current sensor D1, a third current sensor D2, a fourth current sensor D3, a first voltage sensor vhs, a second voltage sensor Vc, third to n +2 voltage sensors, a displacement sensor P, and a temperature sensor T1; the first current sensor D0 is used for measuring the current state of the power system, the second current sensor D1 is used for measuring the current state of the main current loop, the third current sensor D2 is used for measuring the current state of the current transfer branch, the fourth current sensor D3 is used for measuring the current state of the overvoltage limiting branch, the first voltage sensor vhs is used for measuring the break voltage of the high-speed mechanical switch, the second voltage sensor Vc is used for measuring the voltage state of the two ends of the transfer capacitor module, the third to n +2 voltage sensors are used for measuring the voltage state of the two ends of each pre-charged transfer capacitor in the transfer capacitor module C, the displacement sensor P is used for measuring the motion state of the high-speed mechanical switch, and the temperature sensor T1 is used for measuring the ambient temperature of the circuit breaker.
In another embodiment, the dc circuit breaker is further externally connected with a control system, which:
controlling the high speed mechanical switching action based on the current magnitude and rate of change of the main current loop,
controlling the conduction state of a first control device and a second control device in the control module based on the direction of the power system current, an
And controlling the conduction number of the control device in the transfer capacitance module based on the magnitude and the direction of the current of the power system.
In this embodiment, the control system includes a signal conditioning circuit, a high-speed digital-to-analog converter, a processor, a human-computer interaction interface, and a communication module, where the processor may be any one of a general processor, a digital signal processor, an application specific integrated circuit ASIC, and a field programmable gate array FPGA.
Further, the processor includes a memory, which may include one or more of a read only memory ROM, a random access memory RAM, a flash memory, or an electronically erasable programmable read only memory EEPROM.
The magnitude and the flow direction of the current of the power system, the current of a main current loop, the current of an overvoltage limiting branch circuit, the voltage amplitude and the voltage polarity of a transfer capacitor module, the voltage amplitude and the voltage polarity of a pre-charging transfer capacitor, the fracture voltage of a high-speed mechanical switch and/or the numerical value of the displacement of the high-speed mechanical switch are input into a processor for calculation after being filtered and amplified by a signal conditioning circuit and a high-speed digital-to-analog converter, the processor calculates the current amplitude and the change rate di/dt of the main current loop, controls the high-speed mechanical switch and a control device based on the calculation result, displays the state and the calculation result of the circuit breaker in real time by a human-computer interaction interface, and sends a fault waveform to a superior system and receives a control command of the.
Under the normal current flowing state of the power system, the current of the power system flows through the main current loop, the transfer capacitors C1 to Cn have certain pre-charging voltage, all control devices of the current transfer branch circuit are not triggered, no current flows through the current transfer branch circuit, the conduction threshold value of the overvoltage limiting branch circuit is higher than the system voltage, and no current flows through the overvoltage limiting branch circuit.
When the on-line monitoring system monitors that the electric power system has a short-circuit fault, and the control system receives a short-circuit signal or a switching-off instruction, the control system controls the circuit breaker according to the current flow direction of the system, and the specific process is as follows:
1. when the power system current flows from the first inlet/outlet terminal A1 to the second inlet/outlet terminal A2, the control system calculates the current amplitude and the change rate of the main current loop, controls the conduction number of the control devices VT1 to VTn in the transfer capacitor module based on the calculation result, the conduction number corresponds to the number of the voltage polarities of the pre-charge transfer capacitors C1 to Cn changed to be reversed, so as to change the voltage amplitude of the transfer capacitor module C without changing the voltage polarity, and then controls the high-speed mechanical switch action based on the calculation result of the main current loop.
2. When the electric system current flows from the second inlet/outlet terminal A2 to the first inlet/outlet terminal A1, the control system calculates the current amplitude and the change rate of the main current loop, controls the action number of the control devices VT1 to VTn in the transfer capacitor module based on the calculation result, the action number corresponds to the number of the voltage polarities of the transfer capacitors C1 to Cn changed to be opposite, so as to change the voltage amplitude and the voltage polarity of the transfer capacitor module C, and then controls the high-speed mechanical switch action based on the calculation result of the main current loop.
In another embodiment, the overvoltage limiting branch comprises any one of: the lightning arrester comprises a line type metal oxide lightning arrester, a gapless line type metal oxide lightning arrester, a full-insulation composite jacket metal oxide lightning arrester and a detachable lightning arrester.
In another embodiment, fig. 3(a) to 3(f) illustrate a method for opening a modular mechanical dc circuit breaker according to the present disclosure, which includes the following steps:
1. in the normal current flowing state, as shown in fig. 3(a), the power system current flows from the first inlet/outlet terminal a1 and flows from the second inlet/outlet terminal a2 through the high-speed mechanical switch, corresponding to the time T0 before the short-circuit current is turned on and the time T0 before the small-current is turned on in fig. 5.
2. As shown in fig. 3(b), when the on-line monitoring system monitors that the power system has a short-circuit fault, the control system determines the polarity of the power system current flowing through the main current loop, calculates the current amplitude and the current change rate of the main current loop, and determines the number of breakthroughs of the control devices VT1 to VTn in the transfer capacitor module C according to the polarity of the power system current, the current amplitude and the current change rate of the main current loop, and triggers the breakthroughs.
In this step, the control system determines the conducting number of the control devices VT1 to VTn in the transfer capacitor module and controls the conducting thereof according to the polarity, the current amplitude and the current change rate of the power system current flowing through the main current loop, under the actual working condition, the pre-charge transfer capacitor in the transfer capacitor module needs to have the pre-charge voltage to ensure the rapid disconnection when the power system has a short-circuit fault, the present embodiment assumes that the polarity of the pre-charge voltage in the transfer capacitor module is determined by the power system current flowing from the first inlet/outlet terminal a1 to the second inlet/outlet terminal a2, when the power system current that needs to be cut off flows from the first inlet/outlet terminal a1 to the second inlet/outlet terminal a2, only the voltage amplitude of the transfer capacitor module is changed but the voltage polarity thereof is not required to be changed, and thus, the turn-on number of the control devices VT1 to VTn does not exceed a half.
3. As shown in fig. 3(c), the control system issues a switching-off command, the high-speed mechanical switch starts to operate, and triggers the control device V1 in the control module K to operate according to the current direction of the power system, and the high-speed mechanical switch receives the operation command, and does not open at this time according to the response characteristic of the high-speed mechanical switch, and current still flows through the main current loop.
The above steps 2 and 3 correspond to the time T0 to T1 when the short-circuit current is turned off and the time T0 to T1 when the small current is turned off in fig. 5.
4. As shown in fig. 3(d), since the current transfer branch injects the inverted high-frequency oscillating current into the main current loop to force the main current loop to pass through zero, the high-speed mechanical switch extinguishes the arc due to the current passing through zero, and the high-speed mechanical switch completes the opening, which corresponds to the time T1 to T2 when the short-circuit current is opened and the time T1 to T2 when the small current is opened in fig. 5.
5. As shown in fig. 3(e), the transfer capacitor C is charged with the power system current continuously, which corresponds to the time T2 to T3 when the short-circuit current is turned on and the time T2 to T3 when the small current is turned on in fig. 5. When the voltage at two ends of the circuit breaker exceeds the conduction threshold value of the overvoltage limiting branch circuit, the overvoltage limiting branch circuit conducts, and as the on-state resistance of the overvoltage limiting branch circuit is far smaller than the on-state resistance of the current transfer branch circuit, the current is rapidly transferred to the overvoltage limiting branch circuit, which corresponds to the time from T3 to T4 when the short-circuit current is switched on and the time from T3 to T4 when the small current is switched on in fig. 5.
6. As shown in fig. 3(f), after the current of the overvoltage limiting branch passes zero, since the voltage of the power system is smaller than the turn-on threshold of the overvoltage limiting branch, the overvoltage limiting branch recovers to the high impedance state, and the switching-off process is completed, which corresponds to the time T4 to T5 when the short-circuit current is switched off and the time T4 to T5 when the small current is switched off in fig. 5.
In another embodiment, fig. 4(a) to 4(f) illustrate another method for opening a modular mechanical dc circuit breaker according to the present disclosure, which includes the following steps:
1. in the normal current flowing state, as shown in fig. 4(a), the power system current flows in from the second inlet/outlet terminal a2, passes through the high-speed mechanical switch, and flows out from the first inlet/outlet terminal a 1.
2. As shown in fig. 4(b), when the on-line monitoring system monitors that the power system has a short-circuit fault, the control system determines the polarity of the power system current flowing through the main current loop, calculates the current amplitude and the current change rate of the main current loop, and determines the number of breakthroughs of the control devices VT1 to VTn in the transfer capacitor module C according to the polarity of the power system current, the current amplitude and the current change rate of the main current loop, and triggers the breakthroughs.
In this step, the control system determines the conducting number of the control devices VT1 to VTn in the transfer capacitor module and controls the conducting thereof according to the polarity, the current amplitude and the current change rate of the power system current flowing through the main current loop, under the actual working condition, the pre-charge transfer capacitor in the transfer capacitor module needs to have the pre-charge voltage to ensure the rapid disconnection when the power system has a short-circuit fault, the present embodiment assumes that the polarity of the pre-charge voltage in the transfer capacitor module is determined by the power system current flowing from the first inlet/outlet terminal a1 to the second inlet/outlet terminal a2, when the power system current which needs to be cut off flows from the second inlet/outlet line A2 to the first inlet/outlet line A1, not only the voltage amplitude of the transfer capacitor module needs to be changed, and it is necessary to change the polarity of the voltage thereof, the turn-on number of the control devices VT1 to VTn should exceed a half.
3. As shown in fig. 4(c), the control system issues a switching-off command, the high-speed mechanical switch starts to operate, and triggers the control device V2 in the control module K to operate according to the current direction of the power system, and the high-speed mechanical switch receives the operation command, and does not open at this time according to the response characteristic of the high-speed mechanical switch, and current still flows through the main current loop.
4. As shown in fig. 4(d), since the current transfer branch injects the inverted high-frequency oscillating current into the main current loop to force the main current loop to pass through zero, the high-speed mechanical switch completes opening due to arc extinction caused by the current passing through zero.
5. As shown in fig. 4(e), the current of the power system is continuously charged to the transfer capacitor C, when the voltage across the circuit breaker exceeds the turn-on threshold of the overvoltage limiting branch, the overvoltage limiting branch is turned on, and the current is rapidly transferred to the overvoltage limiting branch because the on-state resistance of the overvoltage limiting branch is much smaller than the on-state resistance of the current transfer branch.
6. As shown in fig. 4(f), after the current of the overvoltage limiting branch passes zero, the overvoltage limiting branch recovers to a high impedance state because the voltage of the power system is smaller than the turn-on threshold of the overvoltage limiting branch, and the switching-off process is completed.
It should be noted that, in the above steps, during the switching process of the power system current flowing from the second inlet/outlet terminal a1 to the first inlet/outlet terminal a2 via the high-speed mechanical switch, the current waveform of each branch is consistent with the current waveform of each branch during the switching process of the power system current flowing from the first inlet/outlet terminal a1 to the second inlet/outlet terminal a2 via the high-speed mechanical switch, and therefore, the description is omitted here.
According to the mechanical direct current circuit breaker, the voltage amplitude and the voltage polarity of the pre-charging capacitor can be effectively adjusted through the modular design of the current transfer branch, and the mechanical direct current circuit breaker has the capacity of good fracture insulation recovery and quick full current range opening and closing while the bidirectional conduction and breaking functions are realized.
While the embodiments of the disclosure have been described above in connection with the drawings, the disclosure is not limited to the specific embodiments and applications described above, which are intended to be illustrative, instructive, and not restrictive. Those skilled in the art, having the benefit of this disclosure, may effect numerous modifications thereto and changes may be made without departing from the scope of the disclosure as set forth in the claims that follow.
Claims (10)
1. A modular mechanical dc circuit breaker comprising: a main current loop, a current transfer branch, an overvoltage limiting branch, a first inlet/outlet terminal and a second inlet/outlet terminal, wherein the main current loop is connected in parallel with the current transfer branch and the overvoltage limiting branch,
the main current loop comprises a high-speed mechanical switch, one side of the high-speed mechanical switch is connected to the first wire inlet/outlet end, and the other side of the high-speed mechanical switch is connected to the second wire inlet/outlet end;
the current transfer branch circuit comprises a control module, a transfer capacitor module and an inductor which are connected in series;
the transfer capacitor module comprises n oscillation units which are connected in series, each oscillation unit comprises a pre-charge transfer capacitor, an oscillation inductor and a control device, and the oscillation inductor and the control device are connected in series and then connected in parallel with the pre-charge transfer capacitor.
2. The direct current breaker according to claim 1, wherein preferably, a negative electrode of a pre-charge transfer capacitor of a first oscillating unit of the n oscillating units connected in series is connected to a negative electrode of a control device of the first oscillating unit and to the control module, and a positive electrode of the pre-charge transfer capacitor of the first oscillating unit is connected to a positive electrode of the control device of the first oscillating unit and to a negative electrode of a pre-charge transfer capacitor of a second oscillating unit through an oscillating inductor of the first oscillating unit; and the positive electrode of the pre-charging transfer capacitor of the nth oscillating unit is connected to one side of the second wire inlet/outlet end close to the high-speed mechanical switch through an inductor.
3. The direct current circuit breaker according to claim 1 or 2, wherein the control device is a voltage control device or a current control device.
4. The direct current circuit breaker according to claim 1,
the control module comprises a first control device and a second control device,
the first control device and the second control device are connected in anti-parallel, and:
the positive pole of the first control device and the negative pole of the second control device are connected to one side, close to the first wire inlet/outlet end, of the high-speed mechanical switch, and the negative pole of the first control device and the positive pole of the second control device are connected to one side, close to the second wire inlet/outlet end, of the high-speed mechanical switch after passing through the transfer capacitor module and the inductor.
5. The dc circuit breaker of claim 1, wherein the dc circuit breaker is externally connected with an online monitoring system for:
monitoring the current state of the power system current, the main current loop, the overvoltage limiting branch and the current transfer branch,
monitoring the break voltage and the movement state of the high-speed mechanical switch, an
And monitoring the terminal voltage of the pre-charging capacitor in the transfer capacitor module and the n series-connected oscillation units and the ambient temperature of the circuit breaker.
6. The dc circuit breaker of claim 1, wherein the dc circuit breaker is further externally connected with a control system that:
controlling the high speed mechanical switching action based on the current magnitude and rate of change of the main current loop,
controlling the conduction state of a first control device and a second control device in the control module based on the direction of the power system current, an
And controlling the conduction number of the control device in the transfer capacitance module based on the magnitude and the direction of the current of the power system.
7. The direct current circuit breaker of claim 6, wherein the control system comprises a processor, the processor comprising any of: general purpose processors, digital signal processors, application specific integrated circuits ASIC and field programmable gate arrays FPGA.
8. The direct current circuit breaker according to claim 1, wherein the overvoltage limiting branch comprises any one of: the lightning arrester comprises a line type metal oxide lightning arrester, a gapless line type metal oxide lightning arrester, a full-insulation composite jacket metal oxide lightning arrester and a detachable lightning arrester.
9. Method for opening a modular mechanical dc circuit breaker according to any of claims 1-8, comprising the steps of:
s100: when the current of the power system flows in from the first wire inlet/outlet end and flows out of the second wire inlet/outlet end through the high-speed mechanical switch, if the on-line monitoring system monitors that the power system has a short-circuit fault, the control system judges the polarity of the current of the power system flowing through the main current loop and calculates the current amplitude and the current change rate of the main current loop;
s200: the control system controls the conduction of a controller in the transfer capacitance module according to the current amplitude and the current change rate, and the conduction quantity is less than half;
s300: the control system sends a brake-separating instruction, the high-speed mechanical switch starts to act, a first control device in the control module is controlled to be conducted according to the current direction of the power system, the current transfer branch circuit injects reversed-phase high-frequency oscillation current into the main current loop to force the current of the main current loop to zero, and the high-speed mechanical switch is quenched due to the zero crossing of the current;
s400: the current of the power system is continuously charged to the transfer capacitor module, when the voltage at two ends of the circuit breaker is higher than the conduction threshold value of the overvoltage limiting branch circuit, the overvoltage limiting branch circuit is conducted, and the current of the power system is transferred to the overvoltage limiting branch circuit from the current transfer branch circuit;
s500: and when the overvoltage limiting branch circuit current is subjected to zero crossing and the high-impedance state is recovered, the breaker is switched on and off.
10. Method for opening a modular mechanical dc circuit breaker according to any of claims 1-8, comprising the steps of:
s1000: when the current of the power system flows in from the second wire inlet/outlet end and flows out of the first wire inlet/outlet end through the high-speed mechanical switch, if the on-line monitoring system monitors that the power system has a short-circuit fault, the control system judges the polarity of the current of the power system flowing through the main current loop and calculates the current amplitude and the current change rate of the main current loop;
s2000: the control system controls the conduction of a controller in the transfer capacitance module according to the current amplitude and the current change rate, and the conduction number is more than half;
s3000: the control system sends a brake-separating instruction, the high-speed mechanical switch starts to act, a second control device in the control module is controlled to be conducted according to the current direction of the power system, the current transfer branch circuit injects reversed-phase high-frequency oscillation current into the main current loop to force the current of the main current loop to zero, and the high-speed mechanical switch is quenched due to the zero crossing of the current;
s4000: the current of the power system is continuously charged to the transfer capacitor module, when the voltage at two ends of the circuit breaker is higher than the conduction threshold value of the overvoltage limiting branch circuit, the overvoltage limiting branch circuit is conducted, and the current of the power system is transferred to the overvoltage limiting branch circuit from the current transfer branch circuit;
s5000: and when the overvoltage limiting branch circuit current returns to a high-impedance state after zero crossing, the breaker completes the on-off.
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| CN116908675A (en) * | 2023-09-08 | 2023-10-20 | 清华四川能源互联网研究院 | Circuit breaker post-arc current measurement system and method |
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