CN112165074A - Transformer neutral point protection device, system and circuit breaker - Google Patents
Transformer neutral point protection device, system and circuit breaker Download PDFInfo
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- CN112165074A CN112165074A CN202010986520.XA CN202010986520A CN112165074A CN 112165074 A CN112165074 A CN 112165074A CN 202010986520 A CN202010986520 A CN 202010986520A CN 112165074 A CN112165074 A CN 112165074A
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- 239000003990 capacitor Substances 0.000 claims abstract description 71
- 230000000903 blocking effect Effects 0.000 claims abstract description 28
- 238000002955 isolation Methods 0.000 claims description 17
- 238000001914 filtration Methods 0.000 claims description 16
- 238000004804 winding Methods 0.000 claims description 8
- 239000002689 soil Substances 0.000 abstract description 10
- 230000000694 effects Effects 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 3
- 230000000712 assembly Effects 0.000 description 2
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- 230000009286 beneficial effect Effects 0.000 description 2
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- 238000005516 engineering process Methods 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 230000008054 signal transmission Effects 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
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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
- H02H7/04—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 transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
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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
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The application relates to a transformer neutral point protection device, system and circuit breaker, transformer neutral point protection device includes: the device comprises a blocking capacitor, a current detector, a three-level inverter and a controller. This can effectively separate the direct current in the soil through being provided with blocking condenser, simultaneously through setting up the current detector detects and flows in from the soil blocking condenser's first harmonic current, then through controller control three level inverter produce with first harmonic current size the same, the opposite direction's second harmonic current for flow in transformer neutral point first harmonic current with second harmonic current superposes each other in order to offset, thereby solved the technical problem that the present harmonic that flows in alternating current transformer neutral point that exists can't be eliminated among the prior art, reached the technological effect of eliminating the harmonic that flows in alternating current transformer neutral point.
Description
Technical Field
The application relates to the technical field of electrical equipment, in particular to a transformer neutral point protection device, a transformer neutral point protection system and a breaker.
Background
An alternating current Transformer (Transformer) is a device that changes an alternating current voltage by using the principle of electromagnetic induction, and main components thereof are a primary coil, a secondary coil, and an iron core (magnetic core), and is generally used in an environment such as a substation to perform voltage conversion of an input voltage and an output voltage of the substation. The neutral point of the alternating current transformer needs to be grounded when in use, but external currents such as direct current and harmonic waves can be generated in soil due to the existence of a nearby high-voltage direct current transmission system or other nonlinear systems, and when the external currents flow into the neutral point of the alternating current transformer along with a grounding device, the working stability of the alternating current transformer can be seriously affected. At present, a passive filter and the like are mainly adopted for external current to filter the external current, but the current passive filter can only remove direct current in the external current, but cannot eliminate harmonics in the external current, so that the harmonics flowing into a neutral point of an alternating current transformer cannot be eliminated at present.
Disclosure of Invention
In view of the above, it is necessary to provide a transformer neutral point protection device, a transformer neutral point protection system, and a circuit breaker, which can solve the problem that the harmonic waves flowing into the neutral point of the ac transformer cannot be eliminated.
A transformer neutral point protection device comprising:
the blocking capacitor comprises a first polar plate and a second polar plate which are opposite, the first polar plate is used for connecting a neutral point of the transformer, and the second polar plate is grounded;
a current detector having an input electrically connected to the second plate, the current detector for detecting a first harmonic current flowing into the second plate;
the input end of the three-level inverter is used for connecting power supply equipment, and the output end of the three-level inverter is electrically connected with the second plate;
the input end of the controller is electrically connected with the output end of the current detector, the output end of the controller is electrically connected with the control end of the three-level inverter, the controller is used for controlling the three-level inverter to output second harmonic current according to the first harmonic current, and the second harmonic current is equal to the first harmonic current in magnitude and is mutually reverse current.
In one embodiment, the three-level inverter includes:
a first clamping loop, a first end of which is used for connecting the anode of the power supply device, a second end of which is used for connecting the cathode of the power supply device, and a third end of which is electrically connected with the second pole plate;
a second clamping loop, a first end of which is electrically connected with a first end of the first clamping loop, a second end of which is electrically connected with a second end of the first clamping loop, a third end of which is electrically connected with an input end of the current detector, and a fourth end of which is electrically connected with a fourth end of the first clamping loop;
the control ends of the first clamping loop and the second clamping loop are electrically connected with the output end of the controller;
a first end of the capacitor assembly is electrically connected to the first end of the second clamping loop, a second end of the capacitor assembly is electrically connected to the second end of the second clamping loop, and a third end of the capacitor assembly is electrically connected to the fourth end of the second clamping loop.
In one embodiment, the first clamping loop comprises:
the emitter of the first IGBT tube is used for being connected with the anode of the power supply equipment;
the emitter of the second IGBT tube is electrically connected with the collector of the first IGBT tube;
the emitter of the third IGBT tube is respectively and electrically connected with the collector of the second IGBT tube and the second diode plate;
an emitter of the fourth IGBT tube is electrically connected with a collector of the third IGBT tube, and the collector of the fourth IGBT tube is used for being connected with a negative electrode of the power supply equipment;
the gate electrodes of the first IGBT tube, the second IGBT tube, the third IGBT tube and the fourth IGBT tube are electrically connected with the output end of the controller;
a first diode, wherein the cathode of the first diode is electrically connected with the collector electrode of the first IGBT tube;
and the cathode of the second diode is respectively and electrically connected with the anode of the first diode and the fourth end of the second clamping loop, and the anode of the second diode is electrically connected with the collector of the third IGBT tube.
In one embodiment, the second clamping loop comprises:
an emitter of the fifth IGBT tube is electrically connected with the emitter of the first IGBT tube and the first end of the capacitor assembly respectively;
an emitter of the sixth IGBT tube is electrically connected with a collector of the fifth IGBT tube;
an emitter of the seventh IGBT tube is electrically connected with a collector of the sixth IGBT tube and the input end of the current detector respectively;
an emitter of the eighth IGBT tube is electrically connected with a collector of the seventh IGBT tube, and collectors of the eighth IGBT tube are respectively electrically connected with a collector of the fourth IGBT tube and the second end of the capacitor assembly;
a cathode of the third diode is electrically connected with a collector of the fifth IGBT tube, and an anode of the third diode is electrically connected with an anode of the first diode and a third end of the capacitor assembly respectively;
and the cathode of the fourth diode is electrically connected with the anode of the third diode, and the anode of the fourth diode is electrically connected with the collector of the seventh IGBT tube.
In one embodiment, the capacitive assembly comprises:
a first end of the first capacitor is electrically connected with an emitter of the fifth IGBT tube, and a second end of the first capacitor is electrically connected with an anode of the third diode;
and a first end of the second capacitor is electrically connected with a second end of the first capacitor, and a second end of the second capacitor is electrically connected with a collector electrode of the eighth IGBT tube.
In one embodiment, the method further comprises the following steps:
and the input end of the passive filter is electrically connected with the output end of the three-level inverter.
In one embodiment, the method further comprises the following steps:
and an input winding of the isolation transformer is electrically connected with the passive filter, one end of an output winding of the isolation transformer is electrically connected with the second pole plate, and the other end of the output winding of the isolation transformer is electrically connected with the input end of the current detector.
In one embodiment, the method further comprises the following steps:
and the first end of the alternating current filtering component is grounded, and the second end of the alternating current filtering component is electrically connected with the input end of the current detector.
A transformer neutral protection system comprising:
the transformer neutral point protection device as described above;
and the power supply equipment is electrically connected with the input end of the three-level inverter.
A circuit breaker comprising a transformer neutral protection arrangement as described above.
The embodiment of the application provides a transformer neutral point protection device, includes: the device comprises a blocking capacitor, a current detector, a three-level inverter and a controller. This can effectively separate the direct current in the soil through being provided with blocking condenser, simultaneously through setting up the current detector detects and flows in from the soil blocking condenser's first harmonic current, then through controller control three level inverter produce with first harmonic current size the same, the opposite direction's second harmonic current for flow in transformer neutral point first harmonic current with second harmonic current superposes each other in order to offset, thereby solved the technical problem that the present harmonic that flows in alternating current transformer neutral point that exists can't be eliminated among the prior art, reached the technological effect of eliminating the harmonic that flows in alternating current transformer neutral point.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a transformer neutral point protection device and an application environment according to an embodiment of the present application;
fig. 2 is a circuit diagram of a three-level inverter of a transformer neutral point protection device according to an embodiment of the present application;
fig. 3 is a schematic diagram of a first clamping loop of a transformer neutral point protection apparatus according to an embodiment of the present application;
fig. 4 is a schematic diagram of a second clamping loop of a transformer neutral point protection apparatus according to an embodiment of the present application;
fig. 5 is a circuit diagram of a three-level inverter of a transformer neutral point protection device according to an embodiment of the present application;
fig. 6 is a schematic structural diagram of a transformer neutral point protection device and an application environment according to an embodiment of the present application;
fig. 7 is a schematic structural diagram of a transformer neutral point protection system according to an embodiment of the present application;
fig. 8 is a schematic structural diagram of a power supply device of a transformer neutral point protection system according to an embodiment of the present application;
fig. 9 is a schematic structural diagram of a circuit breaker according to an embodiment of the present application.
Description of reference numerals:
10. a transformer neutral point protection device; 100. a blocking capacitor; 110. a first electrode plate; 120. a second polar plate; 200. a current detector; 300. a three-level inverter; 310. a first clamping loop; 311. a first IGBT tube; 312. a second IGBT tube; 313. a third IGBT tube; 314. a fourth IGBT tube; 315. a first diode; 316. a second diode; 320. a second clamping loop; 321. a fifth IGBT tube; 322. a sixth IGBT tube; 323. a seventh IGBT tube; 324. an eighth IGBT tube; 325. a third diode; 326. a fourth diode; 330. a capacitive component; 331. a first capacitor; 332. a second capacitor; 400. a controller; 500. a passive filter; 600. an isolation transformer; 700. an AC filtering component; 20. a transformer neutral point protection system; 21. a power supply device; 21a, an alternating current power supply; 21b, a rectifying component; 30. a circuit breaker; 40. a transformer.
Detailed Description
In order to make the purpose, technical solution and advantages of the present application more apparent, the transformer neutral point protection device, system and circuit breaker of the present application are further described in detail by embodiments and with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings). In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present application and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be considered as limiting the present application.
In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
Referring to fig. 1, the transformer neutral point protection device 10 according to the embodiment of the present application may be applied to a transformer 40, and is used for blocking direct current and harmonic current flowing into a neutral point of the transformer 40, so as to achieve the purpose of protecting the neutral point of the transformer 40.
The embodiment of the present application provides a transformer neutral point protection device 10, including: a blocking capacitor 100, a current detector 200, a three-level inverter 300, and a controller 400.
The dc blocking capacitor 100 includes a first plate 110 and a second plate 120 opposite to each other, the first plate 110 is connected to a neutral point of the transformer 40, and the second plate 120 is grounded. The blocking capacitor 100 is used to isolate the direct current flowing into the transformer 40, the blocking capacitor 100 may include a plurality of capacitors, the plurality of capacitors may be connected in parallel or in series, and the blocking capacitor 100 may be a common capacitor or an adjustable capacitor, so as to conveniently block direct currents with different strengths. The blocking capacitor can block direct current flowing into the transformer 40, and has a signal transmission function, and the larger the capacitance of the blocking capacitor is, the smaller the signal loss is, the larger the capacity is, the more favorable the transmission of low-frequency signals is, and the blocking performance is better. The dc blocking capacitor 100 of this embodiment is not particularly limited, and may be specifically selected according to actual situations, and only needs to satisfy the function of blocking the dc current flowing into the neutral point of the transformer 40.
The input terminal of the current detector 200 is electrically connected to the second plate 120, and the current detector 200 is used for detecting the first harmonic current flowing into the second plate 120. The first harmonic refers to a harmonic flowing from soil into the transformer 40, and the first harmonic current may be any one or a combination of zero sequence harmonic and positive sequence harmonic. The current detector 200 may be an ammeter, and is low in cost and easy to obtain, so that the cost of the transformer neutral point protection device 10 of the present embodiment can be effectively reduced. The current detector 200 may also be a current transformer, which does not need to directly contact the second plate 120, but only needs to be sleeved on a lead of the ground terminal of the second plate 120, and can detect the first harmonic current by electromagnetic induction, and thus, the flexibility is high. The current detector 200 may also be any other electronic device with a current detection function, and in this embodiment, the current detector 200 is not limited at all, and may be specifically selected according to actual situations, and only needs to satisfy the function of detecting the first harmonic current.
The input end of the three-level inverter 300 is used for connecting the power supply device 21, and the output end of the three-level inverter 300 is electrically connected with the second plate 120. The three-level inverter 300 is configured to generate a second harmonic current, which is a reverse current to the first harmonic current. The reverse current means that the second harmonic current and the first harmonic current are complementary currents, the magnitudes of the currents are the same, the directions are opposite, the vector sum of the first harmonic current and the second harmonic current is zero, and the first harmonic current and the second harmonic current can be mutually eliminated by superposition. The three-level inverter 300 may generate voltage currents of various waveforms other than sine waves. In this embodiment, the specific type, model, etc. of the three-level inverter 300 are not limited at all, and may be specifically selected or set according to the actual situation, and only the function of generating the second harmonic current may be satisfied. The main circuit of the three-level inverter 300 adopts a diode-clamped three-level circuit, and is respectively connected with the diodes connected in series with the upper and lower bridge arms through a pair of neutral point phase diodes, the switching devices are connected in series, the voltage value borne by each switching device is equal to half of the input voltage, the output states are various, especially when an alternating-current three-phase power supply is adopted, 27 output states can be generated, and meanwhile, the voltage borne by the internal switching devices and the switching loss can be reduced by half, so that the waveform of the output second harmonic current is more stable. In this embodiment, the type, specific model, etc. of the three-level inverter 300 are not limited at all, and may be specifically selected according to actual situations.
The input end of the controller 400 is electrically connected to the output end of the current detector 200, the output end of the controller 400 is electrically connected to the control end of the three-level inverter 300, the controller 400 is configured to control the three-level inverter 300 to output a second harmonic current according to the first harmonic current, and the second harmonic current is equal to the first harmonic current in magnitude and is a reverse current. The controller 400 is not only used to control the operation state of the three-level inverter 300, such as the start or the shut-down of the three-level inverter 300, but also the controller 400 is used to control the type and intensity of the second harmonic current outputted by the three-level inverter 300. The controller 400 may be connected to the current detector 200 and the three-level inverter 300 by wires, and has high signal transmission stability, or may be connected wirelessly, and field wiring is not required, so that flexibility is high. The controller 400 may be any one of a microprocessor, a control chip, and the like, and this embodiment is not limited in any way, and may be specifically selected or set according to actual situations.
The working principle of the transformer neutral point protection device 10 provided by the embodiment of the application is as follows:
the transformer neutral point protection device 10 provided by the embodiment of the application includes: a blocking capacitor 100, a current detector 200, a three-level inverter 300, and a controller 400.
The neutral point of the transformer 40 is grounded, the direct current in the soil is blocked when passing through the blocking capacitor 100, and when a harmonic current, that is, the first harmonic current, in the soil flows into the neutral point of the transformer 40, the current detector 200 transmits the collected first harmonic current signal to the controller 400. The controller 400 controls the three-level inverter 300 to output a second harmonic current, which is a reverse current to the first harmonic current, according to the type and intensity of the first harmonic current, and the first harmonic current and the second harmonic current flow into the second plate 120 of the blocking capacitor 100 together. The first harmonic current and the second harmonic current are mutually superposed and cancelled at the second plate 120 of the blocking capacitor 100, so that the current flowing into the neutral point of the transformer 40 through the blocking capacitor 100 does not include harmonic current and direct current, and the purpose of protecting the neutral point of the transformer 40 is achieved.
The present embodiment provides a transformer neutral point protection device 10, including: the blocking capacitor 100, the current detector 200, the three-level inverter 300, and the controller 400. The direct current in the soil can be effectively blocked by arranging the blocking capacitor 100, meanwhile, the current detector 200 is arranged to detect the first harmonic current flowing into the blocking capacitor 100 from the soil, and then the controller 400 controls the three-level inverter 300 to generate the second harmonic current which has the same magnitude and the opposite direction with the first harmonic current, so that the first harmonic current flowing into the neutral point of the transformer 40 and the second harmonic current are mutually superposed to offset, the technical problem that the harmonic wave flowing into the neutral point of the alternating current transformer 40 in the prior art cannot be eliminated at present is solved, and the technical effect of eliminating the harmonic wave flowing into the neutral point of the alternating current transformer 40 is achieved.
Referring to fig. 2, in one embodiment, the three-level inverter 300 includes: a first clamping loop 310, a second clamping loop 320, and a capacitive component 330.
A first end of the first clamping loop 310 is used for connecting the positive pole of the power supply device 21, a second end of the first clamping loop 310 is used for connecting the negative pole of the power supply device 21, and a third end of the first clamping loop 310 is electrically connected with the second pole plate 120. A first end of the second clamping loop 320 is electrically connected to a first end of the first clamping loop 310, a second end of the second clamping loop 320 is electrically connected to a second end of the first clamping loop 310, a third end of the second clamping loop 320 is electrically connected to an input of the current detector 200, and a fourth end of the second clamping loop 320 is electrically connected to a fourth end of the first clamping loop 310. The control terminals of the first clamping loop 310 and the second clamping loop 320 are electrically connected to the output terminal of the controller 400.
Referring to fig. 3, the first clamping loop 310 includes: first IGBT tube 311, second IGBT tube 312, third IGBT tube 313, fourth IGBT tube 314, first diode 315, and second diode 316. The emitter of the first IGBT tube 311 is used to connect the positive electrode of the power supply device 21. The emitter of the second IGBT tube 312 is electrically connected to the collector of the first IGBT tube 311. The emitter of the third IGBT tube 313 is electrically connected to the collector of the second IGBT tube 312 and the second plate 120, respectively. The emitter of the fourth IGBT tube 314 is electrically connected to the collector of the third IGBT tube 313, and the collector of the fourth IGBT tube 314 is used for connecting to the cathode of the power supply device 21. The gates of the first IGBT tube 311, the second IGBT tube 312, the third IGBT tube 313 and the fourth IGBT tube 314 are all electrically connected to the output terminal of the controller 400.
The cathode of the first diode 315 is electrically connected to the collector of the first IGBT 311. The cathode of the second diode 316 is electrically connected to the anode of the first diode 315 and the fourth end of the second clamping circuit 320, respectively, and the anode of the second diode 316 is electrically connected to the collector of the third IGBT tube 313. A first terminal of the capacitor element 330 is electrically connected to a first terminal of the second clamping loop 320, a second terminal of the capacitor element 330 is electrically connected to a second terminal of the second clamping loop 320, and a third terminal of the capacitor element 330 is electrically connected to a fourth terminal of the second clamping loop 320.
Referring to fig. 4 and 5, the second clamping loop 320 includes: fifth IGBT transistor 321, sixth IGBT transistor 322, seventh IGBT transistor 323, eighth IGBT transistor 324, third diode 325, and fourth diode 326. The emitter of the fifth IGBT tube 321 is electrically connected to the emitter of the first IGBT tube 311 and the first end of the capacitor assembly 330, respectively, the emitter of the sixth IGBT tube 322 is electrically connected to the collector of the fifth IGBT tube 321, the emitter of the seventh IGBT tube 323 is electrically connected to the collector of the sixth IGBT tube 322 and the input end of the current detector 200, the emitter of the eighth IGBT tube 324 is electrically connected to the collector of the seventh IGBT tube 323, and the collector of the eighth IGBT tube 324 is electrically connected to the collector of the fourth IGBT tube 314 and the second end of the capacitor assembly 330, respectively.
The cathode of the third diode 325 is electrically connected to the collector of the fifth IGBT tube 321, the anode of the third diode 325 is electrically connected to the anode of the first diode 315 and the third end of the capacitor component 330, respectively, the cathode of the fourth diode 326 is electrically connected to the anode of the third diode 325, and the anode of the fourth diode 326 is electrically connected to the collector of the seventh IGBT tube 323. The first capacitor 331 and the second capacitor 332 share half of the input voltage respectively, and the voltage borne by each switching device is limited to half of the voltage of one capacitor by the clamping action of the clamping diodes, namely the first diode 315 and the second diode 316, and the third diode 325 and the fourth diode 326, so that the voltage stress of the switching devices, namely 8 IGBT transistors, is greatly reduced, and the operation stability of the three-level inverter 300 is improved.
Referring to fig. 5, the capacitor assembly 330 includes a first capacitor 331 and a second capacitor 332. A first end of the first capacitor 331 is electrically connected to the emitter of the fifth IGBT tube 321, and a second end of the first capacitor 331 is electrically connected to the anode of the third diode 325. A first terminal of the second capacitor 332 is electrically connected to a second terminal of the first capacitor 331, and a second terminal of the second capacitor 332 is electrically connected to a collector of the eighth IGBT tube 324. The first capacitor 331 and the second capacitor 332 share half of the input voltage respectively, and the voltage borne by each switching device is limited to half of the voltage of one capacitor by the clamping action of the clamping diodes, namely the first diode 315 and the second diode 316, and the third diode 325 and the fourth diode 326, so that the voltage stress of the switching devices, namely 8 IGBT transistors, is greatly reduced, and the operation stability of the three-level inverter 300 is improved.
Referring to fig. 6, in an embodiment, the transformer neutral point protection device 10 further includes: passive filter 500, isolation transformer 600, and ac filtering assembly 700.
The input end of the passive filter 500 is electrically connected to the output end of the three-level inverter 300, the passive filter 500 is configured to filter a harmonic current generated by the three-level inverter 300 during operation, so as to prevent a harmonic wave generated in a working circuit of the three-level inverter 300 from affecting the working stability of a grounding circuit of the transformer 40, and the working stability of the transformer neutral point protection device 10 is greatly improved by the passive filter 500. In this embodiment, the number, the type, and the like of the passive filters 500 are not limited, and may be specifically selected according to actual situations, and only the function of filtering the harmonic current generated by the three-level inverter 300 during operation needs to be satisfied.
The input winding of the isolation transformer 600 is electrically connected to the passive filter 500, one end of the output winding of the isolation transformer 600 is electrically connected to the second plate 120, and the other end is electrically connected to the input end of the current detector 200. The isolation transformer 600 is used for isolating the passive filter 500 from the ground loop of the transformer 40, so as to prevent overcurrent from breaking down the ground loop of the transformer 40 when the three-level inverter 300 fails, thereby ensuring the working stability of the ground loop of the transformer 40 and improving the safety of the neutral point of the transformer 40. The isolation transformer 600 may be any one or any combination of a common isolation transformer, a shielding isolation transformer, a double shielding isolation transformer, and a triple shielding isolation transformer, and the present embodiment does not make any limitation on the type, model, and the like of the isolation transformer 600, and may be specifically selected or set according to actual situations.
A first terminal of the ac filter assembly 700 is grounded, and a second terminal of the ac filter assembly 700 is electrically connected to the input terminal of the current detector 200. The number of the ac filtering components 700 may be one, each of the ac filtering components 700 includes an LC oscillating circuit, such as a reactor, a capacitor, a resistor, and the like, and a capacitor with a specific size is connected in series with the resistor and then connected in parallel with the reactor to form a first-stage band-stop filter for filtering ac current with a frequency equal to the oscillation frequency of the reactor. The number of the ac filtering assemblies 700 may also be multiple, the multiple ac filtering assemblies 700 are connected in series, and the oscillation frequency of each ac filtering assembly 700 is different, so as to form a multi-stage series ac filtering assembly group, so as to filter the ac flow in the ground current and the excitation current with multiple frequencies. In this embodiment, the number, the model, and the like of the ac filtering components 700 are not limited, and may be specifically selected according to actual conditions, and only the function of filtering the ac flow in the ground current is required.
Referring to fig. 7, an embodiment of the present application provides a transformer neutral point protection system 20, including: transformer neutral point protection 10 and power supply equipment 21.
The beneficial effects of the transformer neutral point protection device 10 are described in detail in the above embodiments, and will not be described herein again.
Referring to fig. 8, the power supply device 21 is electrically connected to an input terminal of the three-level inverter 300. The power supply device 21 may be a dc power supply or an ac power supply 21a, and when the power supply device 21 is the ac power supply 21a, the power supply device 21 includes: the input end of the rectifying component 21b is electrically connected with the alternating current power supply 21a, the output end of the rectifying component 21b is electrically connected with the input end of the three-level inverter 300, and the rectifying component 21b converts the alternating current output by the alternating current power supply 21a into direct current to be supplied to the three-level inverter 300 for use. In the present embodiment, the type of the power supply device 21 and the like are not limited at all, and only the function of supplying dc power to the three-level inverter 300 needs to be satisfied.
Referring to fig. 9, the present embodiment provides a circuit breaker 30 including the transformer neutral point protection device 10 as described above.
The beneficial effects of the transformer neutral point protection device 10 are described in detail in the above embodiments, and will not be described herein again.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A transformer neutral point protection device, comprising:
the blocking capacitor comprises a first polar plate and a second polar plate which are opposite, the first polar plate is used for connecting a neutral point of the transformer, and the second polar plate is grounded;
a current detector having an input electrically connected to the second plate, the current detector for detecting a first harmonic current flowing into the second plate;
the input end of the three-level inverter is used for connecting power supply equipment, and the output end of the three-level inverter is electrically connected with the second plate;
the input end of the controller is electrically connected with the output end of the current detector, the output end of the controller is electrically connected with the control end of the three-level inverter, the controller is used for controlling the three-level inverter to output second harmonic current according to the first harmonic current, and the second harmonic current is equal to the first harmonic current in magnitude and is mutually reverse current.
2. The transformer neutral point protection device of claim 1, wherein the three-level inverter comprises:
a first clamping loop, a first end of which is used for connecting the anode of the power supply device, a second end of which is used for connecting the cathode of the power supply device, and a third end of which is electrically connected with the second pole plate;
a second clamping loop, a first end of which is electrically connected with a first end of the first clamping loop, a second end of which is electrically connected with a second end of the first clamping loop, a third end of which is electrically connected with an input end of the current detector, and a fourth end of which is electrically connected with a fourth end of the first clamping loop;
the control ends of the first clamping loop and the second clamping loop are electrically connected with the output end of the controller;
a first end of the capacitor assembly is electrically connected to the first end of the second clamping loop, a second end of the capacitor assembly is electrically connected to the second end of the second clamping loop, and a third end of the capacitor assembly is electrically connected to the fourth end of the second clamping loop.
3. The transformer neutral protection device of claim 2, wherein the first clamping loop comprises:
the emitter of the first IGBT tube is used for being connected with the anode of the power supply equipment;
the emitter of the second IGBT tube is electrically connected with the collector of the first IGBT tube;
the emitter of the third IGBT tube is respectively and electrically connected with the collector of the second IGBT tube and the second diode plate;
an emitter of the fourth IGBT tube is electrically connected with a collector of the third IGBT tube, and the collector of the fourth IGBT tube is used for being connected with a negative electrode of the power supply equipment;
the gate electrodes of the first IGBT tube, the second IGBT tube, the third IGBT tube and the fourth IGBT tube are electrically connected with the output end of the controller;
a first diode, wherein the cathode of the first diode is electrically connected with the collector electrode of the first IGBT tube;
and the cathode of the second diode is respectively and electrically connected with the anode of the first diode and the fourth end of the second clamping loop, and the anode of the second diode is electrically connected with the collector of the third IGBT tube.
4. The transformer neutral protection device of claim 3, wherein the second clamping loop comprises:
an emitter of the fifth IGBT tube is electrically connected with the emitter of the first IGBT tube and the first end of the capacitor assembly respectively;
an emitter of the sixth IGBT tube is electrically connected with a collector of the fifth IGBT tube;
an emitter of the seventh IGBT tube is electrically connected with a collector of the sixth IGBT tube and the input end of the current detector respectively;
an emitter of the eighth IGBT tube is electrically connected with a collector of the seventh IGBT tube, and collectors of the eighth IGBT tube are respectively electrically connected with a collector of the fourth IGBT tube and the second end of the capacitor assembly;
a cathode of the third diode is electrically connected with a collector of the fifth IGBT tube, and an anode of the third diode is electrically connected with an anode of the first diode and a third end of the capacitor assembly respectively;
and the cathode of the fourth diode is electrically connected with the anode of the third diode, and the anode of the fourth diode is electrically connected with the collector of the seventh IGBT tube.
5. The transformer neutral point protection device of claim 4, wherein the capacitive assembly comprises:
a first end of the first capacitor is electrically connected with an emitter of the fifth IGBT tube, and a second end of the first capacitor is electrically connected with an anode of the third diode;
and a first end of the second capacitor is electrically connected with a second end of the first capacitor, and a second end of the second capacitor is electrically connected with a collector electrode of the eighth IGBT tube.
6. The transformer neutral point protection device of claim 1, further comprising:
and the input end of the passive filter is electrically connected with the output end of the three-level inverter.
7. The transformer neutral point protection device of claim 6, further comprising:
and an input winding of the isolation transformer is electrically connected with the passive filter, one end of an output winding of the isolation transformer is electrically connected with the second pole plate, and the other end of the output winding of the isolation transformer is electrically connected with the input end of the current detector.
8. The transformer neutral point protection device of claim 1, further comprising:
and the first end of the alternating current filtering component is grounded, and the second end of the alternating current filtering component is electrically connected with the input end of the current detector.
9. A transformer neutral point protection system, comprising:
a transformer neutral point protection arrangement according to any one of claims 1-8;
and the power supply equipment is electrically connected with the input end of the three-level inverter.
10. A circuit breaker comprising a transformer neutral point protection arrangement according to any one of claims 1-9.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010986520.XA CN112165074A (en) | 2020-09-18 | 2020-09-18 | Transformer neutral point protection device, system and circuit breaker |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010986520.XA CN112165074A (en) | 2020-09-18 | 2020-09-18 | Transformer neutral point protection device, system and circuit breaker |
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| CN102157940A (en) * | 2011-03-28 | 2011-08-17 | 荣信电力电子股份有限公司 | Device for eliminating voltage harmonics of power system |
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| US20140119088A1 (en) * | 2012-10-29 | 2014-05-01 | Huawei Technologies Co., Ltd. | Three-level inverter and power supply equipment |
| CN107147095A (en) * | 2017-05-25 | 2017-09-08 | 华中科技大学 | A kind of direct current and spuious harmonic current of suppressing is into the device of transformer neutral point |
| CN108233402A (en) * | 2018-01-11 | 2018-06-29 | 上海交通大学 | Suitable for coal mine it is remote pressure DC transmission system |
| CN109066624A (en) * | 2018-08-13 | 2018-12-21 | 广州供电局有限公司 | Inhibit the device of AC transformer neutral point direct current and alternating current |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102157940A (en) * | 2011-03-28 | 2011-08-17 | 荣信电力电子股份有限公司 | Device for eliminating voltage harmonics of power system |
| US20140119088A1 (en) * | 2012-10-29 | 2014-05-01 | Huawei Technologies Co., Ltd. | Three-level inverter and power supply equipment |
| CN103023033A (en) * | 2013-01-07 | 2013-04-03 | 曹一家 | Transformerless hybrid active power amplifier and implementation and control methods thereof |
| CN107147095A (en) * | 2017-05-25 | 2017-09-08 | 华中科技大学 | A kind of direct current and spuious harmonic current of suppressing is into the device of transformer neutral point |
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Application publication date: 20210101 |