CN117175490A - Bidirectional AC/DC hybrid circuit breaker and control method - Google Patents
Bidirectional AC/DC hybrid circuit breaker and control method Download PDFInfo
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Abstract
The invention discloses a bidirectional AC/DC universal hybrid circuit breaker and a control method thereof, wherein the bidirectional AC/DC universal hybrid circuit breaker comprises a mechanical switch branch, a power electronic switch branch, a protection buffer unit, an energy absorption unit, a detection unit and a control unit; the mechanical switch branch, the power electronic switch branch, the protection buffer unit, the energy absorption unit and the detection unit are all connected with the control unit; the detection unit is used for detecting voltage and current signals of the input side and the output side of the circuit breaker and sending the voltage and current signals to the control unit, and the control unit controls the on and off of the mechanical switch branch and the power electronic switch branch and controls the protection actions of the protection buffer unit and the energy absorption unit according to the voltage and current signals. The invention greatly shortens the action time of the whole switch, digitally controls the switch opening and closing time interval, is compatible with an AC/DC circuit loop, and can carry out high-speed effective protection.
Description
Technical Field
The invention mainly relates to the technical field of circuit breakers, in particular to a bidirectional alternating current-direct current universal hybrid circuit breaker and a control method.
Background
The existing electric components, namely the circuit breaker, can be divided into an alternating current circuit breaker and a direct current circuit breaker according to the type of an application circuit, and the alternating current circuit breaker and the direct current circuit breaker can not be used in a mutually replaced mode; the setting value of the protection parameters of the circuit breaker can be set only In the range close to rated current, for example, 0.5-1 time of In (rated current), and the setting gear is limited, so that the overload protection of light load current is unfavorable; the input voltage and the output voltage (for the direct current reverse application working condition) cannot be effectively detected and the protection value can be set; the control command of the circuit breaker is to introduce a switching-on/off coil of the circuit breaker (through an intermediate relay) into a control loop, and introduce an operation state into signal acquisition equipment (such as a PLC or a distributed slave station) through auxiliary contact signals of the circuit breaker, so as to enter an internal signal system; the normal switching-on and switching-off time delay of the circuit breaker is large (a control command is sent from a controller, and the command is transmitted to the final circuit breaker to complete switching-on through an intermediate relay), and even for a high-speed direct current circuit breaker, the time delay from receiving the switching-on command to completing switching-on is 30 ms-80 ms.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: aiming at the problems existing in the prior art, the invention provides the bidirectional AC/DC universal hybrid circuit breaker and the control method, which can greatly shorten the action time of the whole switch, digitally control the switch-on/off time interval of the switch, be compatible with an AC/DC circuit loop and perform high-speed effective protection.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a bidirectional AC/DC universal hybrid circuit breaker comprises a mechanical switch branch, a power electronic switch branch, a protection buffer unit, an energy absorption unit, a detection unit and a control unit; the mechanical switch branch, the power electronic switch branch, the protection buffer unit, the energy absorption unit and the detection unit are all connected with the control unit; the detection unit is used for detecting voltage and current signals of the input side and the output side of the circuit breaker and sending the voltage and current signals to the control unit, and the control unit controls the on and off of the mechanical switch branch and the power electronic switch branch and controls the protection actions of the protection buffer unit and the energy absorption unit according to the voltage and current signals.
Preferably, the mechanical switch branch, the power electronic switch branch, the energy absorbing unit and the protection buffer unit are mutually connected in parallel; the power electronic switching branch comprises two switching elements connected in reverse series.
Preferably, the switching element is an IGBT or an IGCT, and a plurality of power electronic devices may be used in parallel to increase the current of the application circuit.
Preferably, the mechanical switch branch, the power electronic switch branch and the energy absorbing unit are connected in parallel;
the power electronic switch branch comprises diodes D1-D4 and a full-control power electronic device V1 (such as IGBT), wherein the positive electrode of the D1 is connected with the negative electrode of the D2, the positive electrode of the D3 is connected with the negative electrode of the D4, the negative electrode of the D3 of the D1 is connected with the negative electrode of the D3, and the positive electrode of the D4 of the D2 is connected with the positive electrode; and two ends of the protection buffer unit and the full-control power electronic device V1 are respectively connected with the cathodes of the D1 and the D3 and the anodes of the D2 and the D4.
Preferably, the detection unit includes a voltage sensor and a current sensor, which are mounted to an input side and an output side of the circuit breaker.
The invention also discloses an application method of the bidirectional AC/DC hybrid circuit breaker, which is used for accurately controlling the interruption time of the DC power supply interruption test by arranging the bidirectional AC/DC hybrid circuit breaker between the DC output voltage and the tested inverter in the DC power supply interruption test.
The invention also discloses an application method of the bidirectional AC/DC hybrid circuit breaker, wherein in the AC power supply interruption test, the bidirectional AC/DC hybrid circuit breaker is arranged between the AC output voltage and the tested inverter and is used for precisely controlling the interruption time of the AC power supply interruption test.
The invention also discloses an application method of the bidirectional AC/DC hybrid circuit breaker, wherein the bidirectional AC/DC hybrid circuit breaker is directly used for replacing a pre-charging loop in the frequency conversion loop.
The invention also discloses an application method of the bidirectional AC/DC universal hybrid circuit breaker, which adopts a plurality of bidirectional AC/DC universal hybrid circuit breakers, and the synchronous clocks and the corresponding delays of a plurality of control units are popularized to a three-phase AC application circuit to realize interrupt control; wherein phase B is delayed by one third of the period relative to phase A, corresponding to 2π/3 electrical angles, and phase C is delayed by two thirds of the period relative to phase A, corresponding to 4π/3 electrical angles.
The invention also discloses a control method based on the bidirectional AC/DC universal hybrid circuit breaker, which comprises the following steps:
t0 to t1: before t0, the mechanical switch branch flows normal current; short-circuit fault occurs at time t0, current starts to rise, and time t 0-t 1 is the fault detection time of the control unit; after confirming detection faults, the control unit sends out a mechanical switch branch switching-off command at the time t1, and starts to execute switching-off operation, and mechanical switches in the mechanical switch branch start switching-off; at the same time, the power electronic switch branch is triggered to be conducted at the moment t 1;
t1 to t2: the mechanical switch executes a brake separating operation at the moment t1, and the distance between the contacts is gradually increased; the main circuit part current starts to be transferred to the power electronic switch branch circuit in the process, and the voltage drop of the input end and the output end of the corresponding circuit breaker is gradually increased;
t2 to t3: when the mechanical switch contact is separated to a certain distance, the current starts to be converted to the power electronic switch branch by the self-heating of the arc voltage generated by the mechanical switch at the moment t2 until the current is completely converted to the power electronic switch branch at the moment t 3;
t3 to t4: the power electronic switch branch conducts current, and the distance between the mechanical switch contacts continues to increase; before the time t4, the contact gap establishes an insulation gap capable of bearing the breaking overvoltage;
t4 to t5: the switching-off process of the branch power electronic switch has extremely short switching-off time, the output wire part of the input and output end of the hybrid circuit breaker switches off overvoltage, and the current is firstly transferred to the parallel protection buffer unit; when the voltage of the protection buffer unit exceeds the action voltage of the lightning arrester of the energy absorption unit, current is converted to the energy absorption unit;
t5 to t6: the short-circuit current flows through the energy absorption unit, the residual voltage of the energy absorption unit is higher than the running voltage of the system, the fault current is gradually attenuated, the current is attenuated to be near 0A at the time t6, and the fault is cleared;
t6 to t7: the breaker keeps on-off state; receiving a reclosing instruction at the moment t7, starting to execute reclosing operation, triggering and conducting a power electronic switch branch, and generating current in a circuit;
t7 to t8: the current rises, if the system fault is eliminated, the current is maintained at a lower level, and after judging that the system is normal and has no fault, the mechanical switch is switched on; after the mechanical switch finishes closing, the power electronic switch branch is turned off, and the current is transferred to the main current branch; if the system fault is not eliminated, the current rises to be above a setting value, a reclosing failure instruction is received at a time t8, the power electronic switch branch switching-off operation is started to be executed, and the fault current is switched off;
t8 to t9: after the power electronic switch branch is turned off, the current is transferred to the parallel protection buffer unit, and when the energy absorption unit exceeds the action voltage of the lightning arrester of the energy absorption unit, the current is converted to the energy absorption and gradually decays to zero.
Compared with the prior art, the invention has the advantages that:
the hybrid circuit breaker adopts the forms of a high-speed power electronic switch branch and a quick mechanical switch branch, so that the action time of the whole switch can be greatly shortened, the switch-on and switch-off time interval of the switch can be digitally controlled, an alternating current/direct current circuit loop can be compatible, the high-speed effective protection can be carried out, the circuit loss can be reduced, and the heat dissipation requirement can be furthest reduced.
The hybrid circuit breaker can be suitable for direct current and alternating current power supply loops with rated voltage/current and below, opens real-time protection (setting) data through a communication interface, provides corresponding current circuit parameters, protection states and data and linkage protection with a system-level circuit, and finally achieves dynamic setting of protection action parameters, digital visualization of the circuit parameters and seamless open access to a circuit system.
The high-speed bidirectional AC/DC universal hybrid circuit breaker has the advantages of universal AC/DC circuit, settable protection action current and current digitalization, control by using an Ethernet communication interface, replacement of a precharge loop, accurate interruption control of power supply and high-speed and effective protection action in the rated voltage range and below.
Drawings
Fig. 1 is a schematic structural diagram of a hybrid circuit breaker according to an embodiment of the present invention.
Fig. 2 is one of the circuit schematic diagrams of the hybrid circuit breaker of the present invention in an embodiment.
Fig. 3 is a logic diagram of the overall shutdown process in the control method of the present invention.
Fig. 4 is a diagram showing the application of the hybrid circuit breaker of the present invention in a dc power interruption test.
Fig. 5 is a reference waveform diagram of the hybrid circuit breaker of the present invention in a dc power interruption test.
Fig. 6 is a diagram of the application of the hybrid circuit breaker of the present invention in an ac power interruption test.
Fig. 7 is a reference waveform diagram of the hybrid circuit breaker of the present invention in an ac power interruption test.
Fig. 8 is a schematic diagram of a general inverter circuit precharge circuit according to the present invention.
Fig. 9 is a waveform diagram of the precharge of the hybrid circuit breaker of the present invention.
Fig. 10 is a schematic block diagram of circuit parameter protection according to the present invention.
Fig. 11 is an application diagram of the hybrid circuit breaker of the present invention in a three-phase ac power interruption test.
Fig. 12 is a reference waveform diagram of the hybrid circuit breaker of the present invention in a three-phase ac power interruption test.
Fig. 13 is a second schematic circuit diagram of a hybrid circuit breaker according to an embodiment of the invention.
Detailed Description
The invention is further described below with reference to the drawings and specific examples.
As shown in fig. 1 and fig. 2, the bidirectional ac/dc hybrid circuit breaker according to the embodiment of the present invention includes a mechanical switching branch, a power electronic switching branch, a protection buffer unit, an energy absorption unit, a detection unit, and a control unit; the mechanical switch branch, the power electronic switch branch, the protection buffer unit, the energy absorption unit and the detection unit are all connected with the control unit; the detection unit is used for detecting voltage and current signals of the input side and the output side of the circuit breaker and sending the voltage and current signals to the control unit, and the control unit controls the on and off of the mechanical switch branch and the power electronic switch branch and controls the protection actions of the protection buffer unit and the energy absorption unit according to the voltage and current signals. The detection unit comprises a voltage sensor and a current sensor, wherein the voltage sensor and the current sensor are arranged on the input side and the output side of the circuit breaker.
The hybrid circuit breaker adopts the forms of a high-speed power electronic switch branch and a quick mechanical switch branch, so that the action time of the whole switch can be greatly shortened, the switch-on and switch-off time interval of the switch can be digitally controlled, an alternating current/direct current circuit loop can be compatible, the high-speed effective protection can be carried out, the circuit loss can be reduced, and the heat dissipation requirement can be furthest reduced.
In a specific embodiment, as shown in fig. 2, the mechanical switch branch, the power electronic switch branch and the energy absorbing unit are connected in parallel; the power electronic switch branch comprises diodes D1-D4 and a full-control power electronic device (such as IGBT) V1, wherein the positive electrode of the D1 is connected with the negative electrode of the D2, the positive electrode of the D3 is connected with the negative electrode of the D4, the negative electrode of the D3 of the D1 is connected with the negative electrode of the D3, and the positive electrode of the D4 of the D2 is connected with the positive electrode; and two ends of the protection buffer unit and the full-control power electronic device V1 are respectively connected with the cathodes of the D1 and the D3 and the anodes of the D2 and the D4.
In another embodiment, as shown in fig. 13, the mechanical switch branch, the power electronic switch branch, the energy absorbing unit and the protection buffer unit are connected in parallel; the power electronic switching branch comprises two switching elements which are connected in reverse series, wherein the switching elements are IGBT modules. As shown in fig. 13, the two IGBT modules have anti-parallel diodes therein, and the function of the hybrid circuit breaker (control and triggering are consistent with the following description) is realized by anti-series connection, and the corresponding one of the two IGBTs is automatically turned on by the direction of the current of the circuit itself (voltage difference on the input-output side). Of course, the power electronics IGBTs in fig. 2 and 13 may be replaced by fully controlled IGCTs, or may be implemented by multiple IGBTs or IGCTs in series due to high voltage, or by multiple IGBTs or IGCTs in parallel due to high current.
In normal operation, the contact resistance of the quick mechanical switch branch of the hybrid circuit breaker is small, so that better heat loss is achieved, and therefore the quick mechanical switch branch is used as a normal use branch. The user sends out the protection data of overvoltage, undervoltage and overcurrent through the communication interface according to the load characteristics of the circuit, and the protection data is stored in the central control board (as a given signal). The central control board collects the input/output side voltage and current sensor electric signals at high speed and is used as a trigger signal (closed loop electric parameter feedback signal) for overvoltage, undervoltage and overcurrent protection. When the closed-loop electric parameter feedback signal triggers a protection threshold value (such as an overvoltage value, an undervoltage value, an overcurrent timing limit value, an overcurrent reverse timing limit value and an overcurrent instantaneous break value), the protection mechanism of the corresponding central control board is triggered, and the corresponding protection action is correspondingly completed by the central control board.
The hybrid circuit breaker can be suitable for direct current and alternating current power supply loops with rated voltage/current and below, opens real-time protection (setting) data through a communication interface, provides corresponding current circuit parameters, protection states and data and linkage protection with a system-level circuit, and finally achieves dynamic setting of protection action parameters, digital visualization of the circuit parameters and seamless open access to a circuit system.
The high-speed bidirectional AC/DC universal hybrid circuit breaker has the advantages of universal AC/DC circuit, settable protection action current and current digitalization, control by using an Ethernet communication interface, replacement of a precharge loop, accurate interruption control of power supply and high-speed and effective protection action in the rated voltage range and below.
As shown in fig. 3, the embodiment of the invention further provides a control method based on the bidirectional ac/dc universal hybrid circuit breaker, which comprises the following steps:
t0 to t1: before t0, the fast mechanical switching branch of the hybrid circuit breaker flows through the normal current of the system. A short-circuit fault occurs at time t0, the current starts to rise, and the time t0 to t1 is the system fault detection time of the control unit (central control board in fig. 1). After confirming detection faults, the central control board sends out a rapid mechanical switch branch switching-off command at the time t1, switching-off operation starts to be executed, and the main branch rapid mechanical switch starts to switch off; and at the same time, the power electronic switch branch is triggered to be conducted at the moment t 1. Since the conduction voltage drop of the power electronic switching branch is large (compared with mechanical contact), substantially all current still flows through the fast mechanical switching branch at this time;
t1 to t2: the main branch quick mechanical switch at time t1 performs a switching-off operation, and contacts start to move and separate after a certain time delay due to mechanical inertia, and the distance between the contacts is gradually increased. The main circuit part current starts to be transferred to the power electronic switch branch circuit in the process, and the voltage drop of the input end and the output end of the corresponding hybrid circuit breaker is gradually increased;
t2 to t3: when the main branch quick mechanical switch contact is separated to a certain distance, the current starts to be commutated to the power electronic switch branch by self-heating (with large equivalent current resistance value) of arc voltage generated by the mechanical switch at the moment t2 until the current is commutated to the power electronic switch branch completely at the moment t 3;
t3 to t4: the power electronic switch branch conducts current, and the distance between the main branch mechanical switch contacts continues to increase. the contact gap establishes an insulation gap that can withstand the breaking overvoltage before time t 4. the power electronic switch branch circuit continues to be increased due to the detection current at the time t4, so that the circuit protection is carried out and the power electronic switch branch circuit starts to be turned off;
t4 to t5: and in the switching-off process of the branch power electronic switch, the switching-off time is extremely short, the output wire part of the input end and the output end of the hybrid circuit breaker is switched off to overvoltage (UMS), and the current is firstly transferred to a protection buffer unit (RC branch) connected in parallel. When the voltage of the protection buffer unit exceeds the action voltage of the lightning arrester of the energy absorption unit, current is converted to the energy absorption unit;
t5 to t6: short-circuit current flows through the lightning arrester branch, residual voltage of the lightning arrester is higher than system operation voltage, fault current is gradually attenuated, current is attenuated to be near 0A at a time t6 (about 100 ms), and the fault is cleared;
t6 to t7: the hybrid circuit breaker remains in an open state. Receiving a reclosing instruction at the moment t7, starting to execute reclosing operation, triggering and conducting a power electronic switch branch, and generating current in a circuit;
t7 to t8: and when the system fault is eliminated, the current is maintained at a lower level (Io), and the mechanical switch is closed after the system is judged to be normal and fault-free. And after the mechanical switch is switched on, the power electronic transfer branch is switched off, and the current is transferred to the main current branch. If the system fault is not eliminated, the current rises to be above a setting value (Id), a reclosing failure instruction is received at a time t8, the switching-off operation of the transfer branch power electronic switch is started to be executed, and the fault current is switched off;
t8 to t9: after the transfer branch power electronic switch is turned off, the current is transferred to the parallel buffer capacitor, and when the voltage of the buffer capacitor exceeds the action voltage of the lightning arrester of the energy absorption branch, the current is converted to the energy absorption branch and gradually decays to zero.
The switch protection operation is quick (within 10 ms) and is far lower than the operation time (30 ms-80 ms) of the high-speed direct current breaker. The current can be cut off rapidly before the fault current is rapidly deteriorated, and the requirements of the hybrid circuit breaker on arc extinguishing performance are greatly reduced. The adoption of the mode of quick branch current conversion reduces the requirements on heat dissipation design and improves the adaptability to the environment.
In a specific embodiment, the protection parameters can be set, the parameter protection setting of the upper computer is directly accepted through the communication function of the central control board, the protection parameter digital quantity can be set, and the central control board automatically triggers whether to execute long delay protection, short delay protection and instantaneous interruption protection in parallel or not through detecting the output parameters of the circuit sensor and comparing the protection threshold value, and the protection device is particularly suitable for the circuit protection of variable load (such as a test system, a load system and the like). And the protection parameters are complete, including overvoltage protection, overcurrent protection and external interlocking protection (interlocking nodes are externally provided through a central controller), without adding new hardware.
Based on the design of the high-speed switch, compared with a high-speed direct current breaker with uncertain action time, the high-speed direct current breaker is particularly suitable for occasions with accurate requirements on power interruption and settable interruption time.
As shown in fig. 4, the embodiment of the present invention further provides an application method of a bidirectional ac/dc hybrid circuit breaker, for a dc power interruption test, the hybrid circuit breaker is placed between a dc output voltage and a tested inverter, for precisely controlling an interruption time to of the dc power interruption test, the time to can be set within a wide range of time from 10ms to 10s, the interruption time can also be precisely controlled, and the requirement of energy bidirectional flow is met, and an interruption time waveform is shown in fig. 5 (to is the interruption time).
As shown in fig. 6, the embodiment of the invention further provides an application method of the bidirectional ac/dc hybrid circuit breaker, for the ac power supply interruption test, the hybrid circuit breaker is placed between the single-phase ac power supply and the tested inverter, for precisely controlling the interruption time to of the ac power supply interruption test, the time to range can be set within a wide range of time from 10ms to 10s, the interruption time starting point (such as zero crossing point and zero crossing point delay td) and the interruption time can be precisely controlled, the requirement of energy bidirectional flow is met, and the waveform of the interruption time is shown in fig. 7 (the broken line is the interruption process in the time to period).
As shown in fig. 8, the embodiment of the invention also provides an application method of the bidirectional ac/dc hybrid circuit breaker, which can directly replace a precharge circuit in a frequency conversion circuit. Taking the single-phase precharge of fig. 8 as an example, since a large capacitor exists in the line (the voltage across the initial capacitor is 0), the direct current breaker is closed to cause a large line surge current (similar to a short circuit), and therefore, it is necessary to add the circuit breaker, and the structure in the dashed line box of fig. 8 is replaced with a hybrid breaker to perform the line precharge and protection. The method comprises the steps of controlling the conduction time of alternating current incoming line voltage in a positive half period through a hybrid circuit breaker (a power electronic switch branch), gradually increasing the opening time in the positive half period until full conduction in the positive half period is completed, exiting a precharge mode, and entering a circuit breaker line protection function.
As shown in fig. 11, the embodiment of the invention also provides an application method of the bidirectional ac/dc universal hybrid circuit breaker, which adopts a plurality of hybrid circuit breakers, and the hybrid circuit breaker can be popularized to a three-phase ac application circuit through synchronous clocks and corresponding delays (corresponding to the phase delays of the three-phase circuit) of a plurality of central control boards. Taking phase A as an example, the control boards receive commands of the upper computer through communication, and the interrupt time waveform is shown in FIG. 12 (td is delay time, to is interrupt time) through clock synchronization and delay between the central control boards (phase B is delayed by one third of a period corresponding to 2 pi/3 electrical angle, phase C is delayed by two thirds of a period corresponding to 4 pi/3 electrical angle relative to phase A).
Based on the analysis, when the main circuit current of the hybrid breaker is completely transferred to the power electronic switch branch, the hybrid breaker is particularly suitable for simulating interruption test of a power supply grid (alternating current or direct current) or precise test control based on interruption, such as loss of a certain phase in a three-phase power grid, unbalance of the three phases and the like, and has the incomparable advantage of the traditional mechanical high-speed direct current breaker.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and all technical solutions belonging to the concept of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to the invention without departing from the principles thereof are intended to be within the scope of the invention as set forth in the following claims.
Claims (10)
1. The bidirectional AC/DC universal hybrid circuit breaker is characterized by comprising a mechanical switch branch, a power electronic switch branch, a protection buffer unit, an energy absorption unit, a detection unit and a control unit; the mechanical switch branch, the power electronic switch branch, the protection buffer unit, the energy absorption unit and the detection unit are all connected with the control unit; the detection unit is used for detecting voltage and current signals of the input side and the output side of the circuit breaker and sending the voltage and current signals to the control unit, and the control unit controls the on and off of the mechanical switch branch and the power electronic switch branch and controls the protection actions of the protection buffer unit and the energy absorption unit according to the voltage and current signals.
2. The bi-directional ac/dc hybrid circuit breaker according to claim 1, wherein the mechanical switching leg, the power electronic switching leg, the energy absorbing unit and the protection buffer unit are connected in parallel with each other; the power electronic switching branch comprises two switching elements connected in reverse series.
3. The bi-directional ac/dc hybrid circuit breaker according to claim 2, wherein the switching element is an IGBT or an IGCT.
4. The bi-directional ac/dc hybrid circuit breaker according to claim 1, wherein the mechanical switching branch, the power electronic switching branch and the energy absorbing unit are connected in parallel; the power electronic switch branch comprises diodes D1-D4 and a full-control power electronic device V1, wherein the positive electrode of the D1 is connected with the negative electrode of the D2, the positive electrode of the D3 is connected with the negative electrode of the D4, the negative electrode of the D1 is connected with the negative electrode of the D3, and the positive electrode of the D4 of the D2 is connected; and two ends of the protection buffer unit and the full-control power electronic device V1 are respectively connected with the cathodes of the D1 and the D3 and the anodes of the D2 and the D4.
5. The bi-directional ac/dc hybrid circuit breaker according to any one of claims 1 to 4, wherein the detection unit includes a voltage sensor and a current sensor, which are installed on an input side and an output side of the circuit breaker.
6. The application method of the bidirectional AC/DC hybrid circuit breaker is characterized in that in a DC power supply interruption test, the bidirectional AC/DC hybrid circuit breaker is arranged between a DC output voltage and a tested inverter and is used for precisely controlling the interruption time of the DC power supply interruption test.
7. The application method of the bidirectional AC/DC hybrid circuit breaker is characterized in that in an AC power supply interruption test, the bidirectional AC/DC hybrid circuit breaker is arranged between an AC output voltage and a tested inverter and is used for accurately controlling the interruption time of the AC power supply interruption test.
8. The application method of the bidirectional AC/DC hybrid circuit breaker is characterized in that the bidirectional AC/DC hybrid circuit breaker is directly used for replacing a pre-charging loop in a frequency conversion loop.
9. The application method of the bidirectional AC/DC universal hybrid circuit breaker is characterized in that a plurality of bidirectional AC/DC universal hybrid circuit breakers are adopted, and the synchronous clocks and the corresponding delays of a plurality of control units are popularized to a three-phase AC application circuit to realize interrupt control; wherein phase B is delayed by one third of the period relative to phase A, corresponding to 2π/3 electrical angles, and phase C is delayed by two thirds of the period relative to phase A, corresponding to 4π/3 electrical angles.
10. A control method based on the bi-directional ac/dc hybrid circuit breaker according to any one of claims 1 to 5, comprising:
t0 to t1: before t0, the mechanical switch branch flows normal current; short-circuit fault occurs at time t0, current starts to rise, and time t 0-t 1 is the fault detection time of the control unit; after confirming detection faults, the control unit sends out a mechanical switch branch switching-off command at the time t1, and starts to execute switching-off operation, and mechanical switches in the mechanical switch branch start switching-off; at the same time, the power electronic switch branch is triggered to be conducted at the moment t 1;
t1 to t2: the mechanical switch executes a brake separating operation at the moment t1, and the distance between the contacts is gradually increased; the main circuit part current starts to be transferred to the power electronic switch branch circuit in the process, and the voltage drop of the input end and the output end of the corresponding circuit breaker is gradually increased;
t2 to t3: when the mechanical switch contact is separated to a certain distance, the current starts to be converted to the power electronic switch branch by the self-heating of the arc voltage generated by the mechanical switch at the moment t2 until the current is completely converted to the power electronic switch branch at the moment t 3;
t3 to t4: the power electronic switch branch conducts current, and the distance between the mechanical switch contacts continues to increase; before the time t4, the contact gap establishes an insulation gap capable of bearing the breaking overvoltage;
t4 to t5: the switching-off process of the branch power electronic switch has extremely short switching-off time, the output wire part of the input and output end of the hybrid circuit breaker switches off overvoltage, and the current is firstly transferred to the parallel protection buffer unit; when the voltage of the protection buffer unit exceeds the action voltage of the lightning arrester of the energy absorption unit, current is converted to the energy absorption unit;
t5 to t6: the short-circuit current flows through the energy absorption unit, the residual voltage of the energy absorption unit is higher than the running voltage of the system, the fault current is gradually attenuated, the current is attenuated to be near 0A at the time t6, and the fault is cleared;
t6 to t7: the breaker keeps on-off state; receiving a reclosing instruction at the moment t7, starting to execute reclosing operation, triggering and conducting a power electronic switch branch, and generating current in a circuit;
t7 to t8: the current rises, if the system fault is eliminated, the current is maintained at a lower level, and after judging that the system is normal and has no fault, the mechanical switch is switched on; after the mechanical switch finishes closing, the power electronic switch branch is turned off, and the current is transferred to the main current branch; if the system fault is not eliminated, the current rises to be above a setting value, a reclosing failure instruction is received at a time t8, the power electronic switch branch switching-off operation is started to be executed, and the fault current is switched off;
t8 to t9: after the power electronic switch branch is turned off, the current is transferred to the parallel protection buffer unit, and when the energy absorption unit exceeds the action voltage of the lightning arrester of the energy absorption unit, the current is converted to the energy absorption and gradually decays to zero.
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| CN202210576429.XA CN117175490A (en) | 2022-05-25 | 2022-05-25 | Bidirectional AC/DC hybrid circuit breaker and control method |
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