CN111463819A - Energy absorption circuit and energy absorption method - Google Patents

Energy absorption circuit and energy absorption method Download PDF

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Publication number
CN111463819A
CN111463819A CN202010295134.6A CN202010295134A CN111463819A CN 111463819 A CN111463819 A CN 111463819A CN 202010295134 A CN202010295134 A CN 202010295134A CN 111463819 A CN111463819 A CN 111463819A
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China
Prior art keywords
fault
diode
current
point
direct current
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Withdrawn
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CN202010295134.6A
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Chinese (zh)
Inventor
苏麟
王尉
闫安心
卫银忠
张曌
马亚林
何梦雪
蒋科
梅军
葛锐
范光耀
朱鹏飞
田济源
姜华
裴昌盛
王旗
蔡博戎
王政高
鹿峪宁
史洋
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China Energy Engineering Group Jiangsu Power Design Institute Co Ltd
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China Energy Engineering Group Jiangsu Power Design Institute Co Ltd
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Priority to CN202010295134.6A priority Critical patent/CN111463819A/en
Publication of CN111463819A publication Critical patent/CN111463819A/en
Withdrawn legal-status Critical Current

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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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • 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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H02J2003/365—Reducing harmonics or oscillations in HVDC
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention discloses an energy absorption circuit, wherein the circuit topology is composed of a parallel energy absorption module and a quick isolating switch. The parallel energy absorption module is composed of an absorption capacitor, a fully-controlled switch tube, a diode and the like and is positioned between the anode circuit and the cathode circuit. The quick isolating switches are respectively connected in parallel to two sides of the current-limiting reactor on the positive line and two sides of the current-limiting reactor on the negative line. The energy absorption module can effectively absorb fault energy on the current-limiting reactor and the direct current line, and energy required to be absorbed by the energy consumption branch of the direct current breaker is reduced. Meanwhile, the fault can be secondarily detected by controlling the on-off of the switch tube and the quick isolating switch, so that the judgment of the fault property and the accurate positioning of the fault are realized.

Description

Energy absorption circuit and energy absorption method
Technical Field
The invention belongs to the technical field of flexible direct current transmission, and particularly relates to an energy absorption circuit and an energy absorption method.
Background
With the development of the Modular Multilevel Converter (MMC) technology, the high-voltage direct-current transmission (VSC-HVDC) based on the voltage source converter technology gradually replaces the traditional high-voltage direct-current transmission (L CC-HVDC) based on the thyristor technology, and has the characteristics of independent active and reactive control, no commutation failure, low harmonic level and the like.
However, due to the particularity of the control mode and the self topological structure of the HB-MMC flexible direct current system, when a direct current side short circuit fault occurs, the system inertia is small, the fault current rising speed is very high, the amplitude is very high, and the fault current often exceeds the tolerance capability of a device within a few milliseconds, so that the fault must be quickly isolated by a direct current breaker. The direct current circuit breaker needs to bear huge voltage and current stress caused by rapid discharging of HB-MMC on one hand, and needs to absorb huge fault energy including magnetic field energy stored in a current-limiting reactor and a system equivalent inductor and energy provided by a power supply on the other hand, which provides challenges for the design of voltage resistance, current resistance and energy consumption branches of the direct current circuit breaker. Meanwhile, after fault isolation, in order to reduce loss caused by power transmission interruption, the direct-current circuit breaker needs to be superposed as soon as possible to restore system operation. Due to the low damping characteristic of the direct current system, once the direct current breaker is superposed on a permanent fault, the direct current system suffers secondary fault impact in a short time, and therefore secondary detection needs to be carried out on the fault so as to judge the fault property.
At present, fault energy absorption methods in the existing flexible direct current transmission system are a series connection type absorption method and a converter side absorption method. The series absorption method comprises a Metal Oxide Arrester (MOA) energy consumption branch of the hybrid direct current circuit breaker, a resistance type fault current limiter and the like. However, the absorption energy of the MOA monomer is very limited, a complicated water cooling system needs to be configured for the resistance type fault current limiter, the loss is large during normal work, and the MOA monomer is not suitable for engineering. The converter side absorption method needs to modify the sub-module of the MMC and is not suitable for pure half-bridge sub-module MMC topology. Meanwhile, the existing direct current system superposition method is direct superposition of direct current circuit breakers, and the problem of secondary impact cannot be completely avoided.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides an energy absorption circuit which can absorb fault energy and simultaneously realize secondary fault detection.
The technical scheme adopted by the invention is as follows:
in a first aspect, an energy absorption circuit is provided, comprising:
an energy absorption module: for absorbing fault energy;
the energy absorption module comprises a diode T1Diode T2Diode T3Capacitor C and switch tube T4Switch tube T5Diode T6Diode T7(ii) a The diode T6And a switching tube T4Antiparallel, diode T1The cathode and anode DC lines of the transformer are connected to a point A between a DC circuit breaker and a current-limiting reactor, and the anode of the transformer is connected with a switch tube T4Emitter, diode T6Anode of (2), diode T2The cathode of (A) is connected to the point B; switch tube T4Collector and diode T6Cathode, diode T2The cathode of the capacitor C and the anode of the capacitor C are connected with the point D; diode T3Anode and switch tube T5Emitter, diode T7The anode of the capacitor C and the cathode of the capacitor C are connected with a point E; diode T2Anode and switch tube T5Collector electrode of (2), diode T7Is connected to point F; the point F and the cathode direct current circuit are connected to a point G between the direct current breaker and the current-limiting reactor.
An isolation module: the energy absorption module is used for matching with the energy absorption module to carry out secondary diagnosis on the fault.
The isolating module comprises an isolating switch QS1、QS2QS isolator switch1Current limiting reactor L in direct current connection with anodex1Parallel isolating switch QS2Current limiting reactor L x connected to cathode DC line2And (4) connecting in parallel.
In combination with the first aspect, in order to better withstand the interelectrode voltage between the positive electrode line and the negative electrode line, further, the diode T1The diode group is formed by connecting a plurality of diodes in series.
In combination with the first aspect, further, the switch tube T4、T5Are all IGBT.
In a second aspect, there is provided a method of energy absorption comprising:
when a direct current circuit fault is detected and a main circuit breaker branch in the direct current circuit breaker is switched off, current flowing through the current limiting reactor automatically flows after passing through the energy absorption module, and fault current sequentially passes through the current limiting reactor on the anode direct current circuit, a fault point, the cathode direct current circuit, the current limiting reactor on the cathode direct current circuit and the diode T2Capacitor C and diode T3Diode T1And the current limiting reactor is arranged on the anode direct current lower path, the current in the follow current path is gradually attenuated to zero, and the fault energy absorption is finished.
In combination with the second aspect, further, when the fault energy absorption is completed, the voltage of the capacitor C is charged from 0 to UcClosing L in parallel with a current limiting reactorx1、Lx2Isolating switch QS1、QS2Simultaneously controlling the switch tube T4、T5Conduction, duration of conduction tmRear-turn-off switch tube T4、T5Recording switch tube T4、T5The starting conduction time is t0And then executing a fault judgment step to finish fault judgment.
With reference to the second aspect, further, the step of executing the fault determination specifically includes:
for permanent faults, voltage incident traveling waves are refracted and reflected at fault points, corresponding reverse voltage traveling waves can be detected at voltage detection points after a period of time, and the time for detecting the reverse voltage traveling waves for the first time is recorded as t1According to t0、t1The specific position of a reflection point is calculated according to the propagation velocity v of the traveling wave, and then the reflection of the fault point is judged according to the polarity of the reverse voltage traveling wave, namely the fault property is a permanent fault, and meanwhile, the fault point is accurately positioned;
for temporary faults, voltage incident travelling wave is reflected at the tail end of a direct current line, after a fixed time, corresponding reverse voltage travelling wave can be detected at a voltage detection point, and the time t of detecting the reverse voltage travelling wave for the first time is recorded2Because the length of the line is known, the theoretical time of arrival of the reverse voltage traveling wave can be calculated, and whether the theoretical time is matched with the actually detected time or not is compared, so that whether the fault point disappears or not can be judged; the direct current breaker is disconnected at the tail end of the line, the voltage traveling wave is approximately totally reflected at the tail end, and the fault point can be further judged to disappear according to the fact that the polarity of the reverse voltage traveling wave is opposite to that of the incident wave.
With reference to the second aspect, further, if it is determined that the fault point has disappeared and the dc fault is a temporary fault, the QS is turned off1And QS2Then, the direct-current circuit breaker is superposed, the system operates again, and power transmission is recovered; if the fault point still exists, the fault judging step is executed again to confirm that the fault point is a permanent fault, and after the fault processing is finished, the QS (fast isolating switch) is switched off1And QS2And then the direct current circuit breaker is superposed, the system operates again, and power transmission is recovered.
The beneficial effects are as follows:
(1) the invention can absorb the fault energy of the current-limiting reactor and the line, does not need to carry out structural modification on the traditional direct current breaker and HB-MMC, and is convenient to apply.
(2) The invention can not only reduce the requirement on the absorption capacity of the energy consumption branch of the direct current breaker, but also shorten the time of the direct current breaker for bearing the great voltage stress, and does not increase any loss during normal work.
(3) The fault energy absorbed by the invention can be used for carrying out secondary detection on the fault, thereby realizing the functions of judging the nature of the fault and positioning the fault and realizing the function of self-adaptive reclosing.
Drawings
FIG. 1 is a topology diagram of an energy absorption circuit of the present invention;
FIG. 2 is a schematic diagram of a fault current freewheel path in accordance with the present invention;
FIG. 3 is a waveform of current decay in the freewheel path in accordance with the present invention;
FIG. 4 is a waveform of the voltage rise of the absorption capacitor according to the present invention;
fig. 5 is a diagram of the fault energy absorbed by the energy-consuming branch of the dc circuit breaker according to the present invention;
fig. 6 is a diagram of the fault energy absorbed by the energy-consuming branch of the dc circuit breaker after the energy absorption circuit is removed in the present invention;
FIG. 7 is a waveform diagram of voltage stress applied to two ends of the DC circuit breaker according to the present invention;
FIG. 8 is a waveform of the voltage stress across the DC chopper after the energy absorption circuit is removed in accordance with the present invention;
FIG. 9 is a waveform diagram of forward voltage traveling waves under permanent fault in the present invention;
FIG. 10 is a waveform diagram of a reverse voltage traveling wave in the case of a permanent fault in the present invention;
FIG. 11 is a diagram of forward voltage traveling waveforms under a temporary fault in the present invention;
fig. 12 is a waveform diagram of a reverse voltage traveling wave in a temporary fault.
Detailed Description
The invention is further described with reference to the accompanying drawings.
As shown in FIGS. 1-12, the invention provides a topology of a fault energy absorption circuit suitable for a half-bridge multilevel converter, which comprises a half-bridge modular multilevel converter HB-MMC, an anode direct current line, a cathode direct current line, a direct current breaker DCCB1 and a current limiting reactor L x, wherein the direct current breaker DCCB1 and the current limiting reactor L x are positioned on the anode direct current line1A DC breaker DCCB2 and a current limiting reactor L x on the cathode DC line2Parallel energy absorption modules between the positive and negative electrode lines and L parallel to the positive and negative electrode lines respectivelyx1、Lx2Isolation modules on both sides (fast isolating switch QS)1And QS2). The HB-MMC adopts a pseudo bipolar structure, and the grounding mode adopts a direct current side to be grounded through a clamping resistor. The parallel energy absorption module includes a first freewheeling diode T1A second freewheeling diode T2A third freewheeling diode T3An absorption capacitor C, a first active control switch tube T4A second active control switch tube T5A first anti-parallel diode T6A second anti-parallel diode T7(ii) a First active control switch tube T4A second active control switch tube T5All are fully-controlled power electronic devices IGBT; first freewheeling diode T1The diode group is formed by connecting a plurality of diodes in series; first freewheeling diode T1The cathode and the anode direct current circuit are connected to the point A; first freewheeling diode T1Anode and first active control switch tube T4Emitter, anti-parallel diode T6The anode of the first freewheeling diode and the cathode of the second freewheeling diode are connected to the point B; first active control switch tube T4Collector of and first anti-parallel diode T6Cathode of (2), second freewheeling diode T2The cathode of the absorption capacitor C and the anode of the absorption capacitor C are connected with the point D; third freewheeling diode T3Anode and second active control switch tube T5Emitter of (2), second antiparallel diode T7The anode of the absorption capacitor C and the cathode of the absorption capacitor C are connected with a point E; second freewheeling diode T2Anode and second active control switch tube T5Collector electrode of, and a second anti-parallel diode T7Is connected to point F; the point F and the cathode direct current line are connected with a point G between the direct current breaker and the current-limiting reactor.
The embodiment also provides an energy absorption method:
when a bipolar short-circuit fault occurs in a direct-current line, the direct-current breaker detects the fault and starts to act. When a main breaker branch in the direct current breaker is switched off, current flowing through the current-limiting reactor automatically flows through the parallel energy absorption module. The fault current freewheel path is shown in fig. 2. The current flowing through the current-limiting reactor sequentially passes through the current-limiting reactor on the anode line, the anode direct-current line, the fault point, the cathode direct-current line, the current-limiting reactor on the cathode direct-current line, the anode of the second fly-wheel diode, the cathode of the second fly-wheel diode, the anode of the absorption capacitor, the cathode of the absorption capacitor, the anode of the third fly-wheel diode, the cathode of the third fly-wheel diode, the anode of the first fly-wheel diode, the cathode of the first fly-wheel diode and the current-limiting reactor to form a closed fly-wheel loop.
The fault energy absorption principle of the parallel energy absorption topology provided by the invention is verified by applying a PSCAD/EMTDC simulation experiment platform, and simulation results are shown in FIGS. 3 to 8. And when a bipolar short-circuit fault occurs in 1.8s, the main breaker branch of the 1.802s direct-current breaker starts to be switched off, and the parallel energy absorption topology automatically starts to absorb fault energy.
Fig. 3 shows the current waveform in the freewheel path, and fig. 4 shows the capacitor voltage waveform of the snubber capacitor C. As can be seen from a comparison of fig. 3 and 4, the 1.802s fault current begins to decrease and the capacitor begins to charge. At 1.853s, the current flowing through the current-limiting reactor decays to 0, and the voltage at the two ends of the absorption capacitor reaches the maximum value, i.e. the energy absorption is finished.
Fig. 5 shows fault energy absorbed by the energy consumption branch of the direct current circuit breaker, which absorbs 1631.82kJ in total. Fig. 6 shows the fault energy absorbed by the energy-consuming branch of the dc circuit breaker after the parallel energy absorption topology is removed, and 4230.01kJ of energy is absorbed in total. After the parallel energy absorption topology is added, the fault energy required to be absorbed by the energy consumption branch of the direct current circuit breaker is effectively reduced, the requirement on the absorption capacity of the energy consumption branch of the direct current circuit breaker is reduced, and the design difficulty of the direct current circuit breaker is reduced.
Fig. 7 is a variation of voltage stress at two ends of the dc circuit breaker, and fig. 8 is a variation of voltage stress at two ends of the dc circuit breaker after the parallel energy absorption topology is removed. The time that the two ends of the direct current circuit breaker bear the maximum voltage stress lasts 7.1ms after the parallel energy absorption topology is removed, the time that the two ends of the direct current circuit breaker bear the maximum voltage stress lasts 2.7ms after the parallel energy absorption topology is increased, the time of bearing the maximum voltage stress is greatly shortened, the safety and reliability of the direct current circuit breaker are improved to a certain extent, and the service life is prolonged.
The secondary fault detection function of the parallel energy absorption topology provided by the invention is verified, and the simulation result is shown in fig. 9 and 10. After the fault energy is absorbed completely, the QS fast isolating switches connected in parallel with the two sides of the current-limiting reactor are closed after a certain free time, and meanwhile, the T first active control switch tube is controlled4A second active control switch tube T5Conducting for 0.2ms, and then turning off the first active control switch tube T4A second active control switch tube T5Recording the first active control switch tube T4A second active control switch tube T5Time 2.2s at which conduction begins.
Assuming a permanent bipolar short fault at 150km of the line, the waveforms of the forward voltage traveling wave and the reverse voltage traveling wave are shown in fig. 9 and 10, respectively. The forward voltage traveling wave is sent out at 2.2s, the wave head of the first reverse voltage traveling wave is detected at 2.201s, and the reflecting point position is 150km through calculation because the wave speed of traveling wave propagation is close to the light speed. And judging the reverse voltage traveling wave as the reflection of the fault point according to the fact that the reverse voltage traveling wave is opposite to the forward voltage traveling wave in polarity.
Assuming that a temporary bipolar short-circuit fault occurs at 150km of the line, the overall length of the line is 300km, and the waveforms of the forward voltage traveling wave and the reverse voltage traveling wave are shown in fig. 10 and 11, respectively. The forward voltage traveling wave is sent out at 2.2s, the wave head of the first reverse voltage traveling wave is detected at 2.202s, and the position of the reflection point can be calculated to be 300km as the wave speed of traveling wave propagation is close to the light speed. And judging the reverse voltage traveling wave as the reflection of the line tail end boundary according to the same polarity of the reverse voltage traveling wave and the forward voltage traveling wave.
Through the detailed description of each specific embodiment, the parallel energy absorption topology suitable for the half-bridge modular multilevel converter provided by the invention can effectively absorb fault energy on a current-limiting reactor and a line, thereby reducing the requirement on the absorption capacity of an energy-consuming branch of a direct current breaker and reducing the design difficulty. Meanwhile, by utilizing the parallel energy absorption topology provided by the invention, the secondary detection of the fault can be realized, the secondary impact problem caused by the permanent fault of the direct current system is thoroughly avoided, and the self-adaptive reclosing is realized.
The embodiments are only for illustrating the technical idea of the present invention, and the technical idea of the present invention is not limited thereto, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the scope of the present invention.

Claims (9)

1. An energy absorbing circuit, comprising:
an energy absorption module: for absorbing fault energy;
an isolation module: the energy absorption module is used for matching with the energy absorption module to carry out secondary diagnosis on the fault.
2. The energy absorbing circuit of claim 1, wherein the energy absorbing module comprises a diode T1Diode T2Diode T3Capacitor C and switch tube T4Switch tube T5Diode T6Diode T7(ii) a The diode T6And a switching tube T4Antiparallel, diode T1The cathode and anode DC lines of the transformer are connected to a point A between a DC circuit breaker and a current-limiting reactor, and the anode of the transformer is connected with a switch tube T4Emitter, diode T6Anode of (2), diode T2The cathode of (A) is connected to the point B; switch tube T4Collector and diode T6Cathode, diode T2The cathode of the capacitor C and the anode of the capacitor C are connected with the point D; diode T3Anode and switch tube T5Emitter, diode T7The anode of the capacitor C and the cathode of the capacitor C are connected to the point E; diode T2Anode and switch tube T5Collector electrode of (2), diode T7Is connected to point F; the point F and the cathode direct current circuit are connected to a point G between the direct current breaker and the current-limiting reactor.
3. The energy absorbing circuit of claim 2, wherein the first and second conductive layers are formed of a material selected from the group consisting of copper, aluminum, and combinations thereofIn that the isolating module comprises an isolating switch QS1、QS2QS isolator switch1Current limiting reactor L in direct current connection with anodex1Parallel isolating switch QS2Current limiting reactor L x connected to cathode DC line2And (4) connecting in parallel.
4. The energy absorbing circuit of claim 2, wherein the diode T1The diode group is formed by connecting a plurality of diodes in series.
5. The energy absorbing circuit of claim 4, wherein the switch tube T4、T5Are all IGBT.
6. A method of energy absorption, comprising:
when a direct current circuit fault is detected and a main circuit breaker branch in the direct current circuit breaker is switched off, current flowing through the current limiting reactor automatically flows after passing through the energy absorption module, and fault current sequentially passes through the current limiting reactor on the anode direct current circuit, a fault point, the cathode direct current circuit, the current limiting reactor on the cathode direct current circuit and the diode T2Capacitor C and diode T3Diode T1And the current limiting reactor is arranged on the anode direct current lower path, the current in the follow current path is gradually attenuated to zero, and the fault energy absorption is finished.
7. The energy absorbing method of claim 6, wherein the voltage of the capacitor C is charged from 0 to U when the absorption of the fault energy is completedcClosing L in parallel with a current limiting reactorx1、Lx2Isolating switch QS1、QS2Simultaneously controlling the switch tube T4、T5Conduction, duration of conduction tmRear-turn-off switch tube T4、T5Recording switch tube T4、T5The starting conduction time is t0And then executing a fault judgment step to finish fault judgment.
8. The energy absorption method according to claim 7, wherein the step of performing a fault determination is specifically:
for permanent faults, voltage incident traveling waves are refracted and reflected at fault points, corresponding reverse voltage traveling waves can be detected at voltage detection points after a period of time, and the time for detecting the reverse voltage traveling waves for the first time is recorded as t1According to t0、t1The specific position of a reflection point is calculated according to the propagation velocity v of the traveling wave, and then the reflection of the fault point is judged according to the polarity of the reverse voltage traveling wave, namely the fault property is a permanent fault, and meanwhile, the fault point is accurately positioned;
for temporary faults, voltage incident travelling wave is reflected at the tail end of a direct current line, after a fixed time, corresponding reverse voltage travelling wave can be detected at a voltage detection point, and the time t of detecting the reverse voltage travelling wave for the first time is recorded2Because the length of the line is known, the theoretical time of arrival of the reverse voltage traveling wave can be calculated, and whether the theoretical time is matched with the actually detected time or not is compared, so that whether the fault point disappears or not can be judged; the direct current breaker is disconnected at the tail end of the line, the voltage traveling wave is approximately totally reflected at the tail end, and the fault point can be further judged to disappear according to the fact that the polarity of the reverse voltage traveling wave is opposite to that of the incident wave.
9. The energy absorption method according to claim 8, wherein if it is determined that the fault point has disappeared and the dc fault is a temporary fault, the QS is turned off1And QS2Then, the direct-current circuit breaker is superposed, the system operates again, and power transmission is recovered; if the fault point still exists, the fault judging step is executed again to confirm that the fault point is a permanent fault, and after the fault processing is finished, the QS (fast isolating switch) is switched off1And QS2And then the direct current circuit breaker is superposed, the system operates again, and power transmission is recovered.
CN202010295134.6A 2020-06-04 2020-06-04 Energy absorption circuit and energy absorption method Withdrawn CN111463819A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112039354A (en) * 2020-09-11 2020-12-04 华北电力大学 Parallel hybrid MMC topology suitable for flexible direct-current power grid fault clearing
CN112421585A (en) * 2020-10-27 2021-02-26 国网江苏省电力有限公司扬州供电分公司 Parallel fault energy recycling device and direct-current line bipolar short-circuit fault detection method
CN113629680A (en) * 2021-08-18 2021-11-09 华北电力大学（保定） MMC-HVDC bipolar short-circuit fault current limiting method combining active current limiting and capacitance current conversion

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112039354A (en) * 2020-09-11 2020-12-04 华北电力大学 Parallel hybrid MMC topology suitable for flexible direct-current power grid fault clearing
CN112421585A (en) * 2020-10-27 2021-02-26 国网江苏省电力有限公司扬州供电分公司 Parallel fault energy recycling device and direct-current line bipolar short-circuit fault detection method
CN113629680A (en) * 2021-08-18 2021-11-09 华北电力大学（保定） MMC-HVDC bipolar short-circuit fault current limiting method combining active current limiting and capacitance current conversion

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Application publication date: 20200728