CN110718909A - Method for analyzing influence of commutation failure of high-voltage direct-current transmission system on voltage of sending terminal - Google Patents

Method for analyzing influence of commutation failure of high-voltage direct-current transmission system on voltage of sending terminal Download PDF

Info

Publication number
CN110718909A
CN110718909A CN201910969196.8A CN201910969196A CN110718909A CN 110718909 A CN110718909 A CN 110718909A CN 201910969196 A CN201910969196 A CN 201910969196A CN 110718909 A CN110718909 A CN 110718909A
Authority
CN
China
Prior art keywords
voltage
current
failure
commutation failure
analyzing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN201910969196.8A
Other languages
Chinese (zh)
Inventor
朱丽萍
刘文颖
王维洲
王方雨
张柏林
夏鹏
邵冲
张雨薇
拜润卿
张尧翔
陈仕彬
曾贇
许春蕾
聂雅楠
冉忠
李宛齐
胡阳
李潇
陈鑫鑫
郇悦
刘紫东
张雯程
杨美颖
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
State Grid Corp of China SGCC
North China Electric Power University
State Grid Gansu Electric Power Co Ltd
Electric Power Research Institute of State Grid Gansu Electric Power Co Ltd
Original Assignee
State Grid Corp of China SGCC
North China Electric Power University
State Grid Gansu Electric Power Co Ltd
Electric Power Research Institute of State Grid Gansu Electric Power Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by State Grid Corp of China SGCC, North China Electric Power University, State Grid Gansu Electric Power Co Ltd, Electric Power Research Institute of State Grid Gansu Electric Power Co Ltd filed Critical State Grid Corp of China SGCC
Priority to CN201910969196.8A priority Critical patent/CN110718909A/en
Publication of CN110718909A publication Critical patent/CN110718909A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • 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
    • 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]

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a method for analyzing the influence of commutation failure of a high-voltage direct-current power transmission system on voltage at a sending end. The method comprises the following steps: analyzing a failure mechanism of the inversion side commutation failure and a current replacement rule of the converter valve during the commutation failure; drawing an equivalent circuit during the phase change failure according to the current replacement rule of the converter valve, and analyzing the influence mechanism of the phase change failure on the direct-current voltage of a sending end system; researching the reactive power characteristic of the rectifier, and analyzing the influence mechanism of the commutation failure on the alternating voltage of the sending end system based on the reactive power characteristic; and finally, building a simulation model and verifying the practicability and effectiveness of the analysis method by adopting electromagnetic transient simulation software. The method for analyzing the influence of the commutation failure of the high-voltage direct-current power transmission system on the voltage of the sending end reveals the cause of the commutation failure and how to influence the voltages of the direct-current side and the alternating-current side of the sending end system, and has important theoretical and practical significance for providing a control strategy aiming at the commutation failure in the sending end system in future.

Description

Method for analyzing influence of commutation failure of high-voltage direct-current transmission system on voltage of sending terminal
Technical Field
The invention belongs to the field of analysis of a fault influence mechanism of an alternating current-direct current hybrid system, and particularly relates to a method for analyzing influence of commutation failure of a high-voltage direct current transmission system on voltage at a sending end.
Background
At present, ultra-high voltage alternating current and direct current hybrid connection and large-scale trans-regional power transmission become typical characteristics of power grids in China. Among various types of direct current faults, commutation failure is one of the most common faults of a direct current transmission system, and may cause overvoltage of a direct current transmission end system, even cause large-scale grid disconnection of a new energy source unit in a direct current near region due to high-voltage protection action. If the control is improper after the commutation failure, the subsequent continuous commutation failure is also caused, which is a fault that the overvoltage duration of the sending end system is longest and finally causes the interruption of the direct current transmission power. Therefore, the analysis and the clear analysis of the reason of the commutation failure and how to influence the voltages of the direct current side and the alternating current side of the sending end system have important theoretical and practical significance for proposing a control strategy of the sending end system side for the commutation failure in the future.
Many experts and scholars have studied the cause and influence of commutation failure, but most of them focus on the receiving end system, and the influence on the sending end voltage during the period of direct current commutation failure is less studied.
Disclosure of Invention
The invention aims to provide a method for analyzing the influence of commutation failure of a high-voltage direct-current transmission system on the voltage of a transmitting terminal, which is used for solving the problems existing in the existing method. In order to achieve the purpose, the technical scheme provided by the invention is a method for analyzing the influence of commutation failure of a high-voltage direct-current transmission system on the voltage of a sending end, and the method is characterized by comprising the following steps:
the method for analyzing the influence of the commutation failure of the high-voltage direct-current transmission system on the voltage of a sending end is characterized by comprising the following steps of:
s1: analyzing a phase change failure fault mechanism and a current replacement rule of the converter valve during phase change failure;
s2: analyzing the influence mechanism of the commutation failure on the direct-current voltage of the sending-end system based on the equivalent circuit during the commutation failure;
s3: analyzing the influence mechanism of commutation failure on alternating voltage of a sending end system based on the reactive power characteristic of a rectifier;
s4: and building a simulation model to verify the analysis method.
1. The S1 includes the steps of:
s101: setting up definition and analysis of commutation failure, and analyzing common reasons causing commutation failure and failure mechanism of commutation failure on an inversion side;
s102: taking the phase change failure caused by the single-phase earth fault of the receiving-end alternating-current system as an example, analyzing the replacement rule of the inverter valve current to obtain the conclusion that the short circuit of the direct-current side and the open circuit of the alternating-current side of the inverter occur in the phase change failure period.
2. The S2 includes the steps of:
s201: drawing an equivalent circuit diagram during the commutation failure as shown in FIG. 8 according to the conclusion of S1;
s202: and analyzing an influence mechanism of the commutation failure on the direct-current voltage of the sending-end system according to a relational expression between the electric quantities of the rectification side and a change process during the commutation failure based on the equivalent circuit of S201. The numerical relationship between the electrical quantities on the rectification side is expressed as follows
Figure BDA0002231520350000021
UdR＝URcosα-IdR·dR(2)
In the formula IdRIs a rectifier polar DC current; u shapedRIs a rectifier polar DC voltage; u shapedIFor inverter pole line DC voltage, during commutation failure period UdI＝0V；URThe voltage is the rectifier polar line no-load direct current voltage, and is determined by the effective value of the converter transformer valve side winding no-load line voltage; dRThe unit direct current is the direct current voltage drop caused in the phase commutation process, and is determined by equivalent commutation reactance; r is the equivalent resistance of a direct current line.
United vertical type (1) and (2) to obtain UdRExpressions during commutation failure
Figure BDA0002231520350000031
At the initial stage of commutation failure, α has not changed, and U is analyzed from the influence on the ac side voltage in S3RAt a descent, and R, dRIs constant, so that the DC voltage U of the transmitting end systemdRIs decreasing. After 20ms-100ms of delay, the rectifier current regulator acts to increase the trigger angle alpha to limit the direct current IdRIncrease of cos alpha, decrease of UdRThe decrease continues. At the end of the phase change failure, U is analyzed from the influence on the AC side voltage in S3RWill riseHigh, so UdRDoes not decrease continuously but follows URThe increase in (c) is in a rising trend.
Therefore, the conclusion that the DC voltage of the sending-end system is reduced in the initial phase of commutation failure and increased in the later phase of commutation failure is obtained.
3. The S3 includes the steps of:
s301: analyzing the reactive power characteristic of the rectifier, and setting the active power at the AC side of the rectifier as P1Angle of power factor of
Figure BDA0002231520350000032
Can write the reactive power consumed by the rectifier as
Figure BDA0002231520350000033
Active power P on the AC side of the rectifier under the condition of neglecting the loss and the commutation angle of the rectifier1About DC power PdRAngle of power factor
Figure BDA0002231520350000034
About the trigger angle alpha of the rectifier, the reactive power Q consumed by the rectifierRCan be approximated as
QR＝PdRtanα＝UdRIdRtanα (5)
During operation of the hvdc transmission system, the rectifier station and the ac system must maintain a balance of reactive power, and fig. 9 shows the exchange of reactive power in the rectifier station. When the AC system provides the reactive power to the rectifying station in the positive direction, the system has
Qac＝QR-QC(6)
In the formula QacReactive, Q, exchange for DC and AC systemsCThe reactive power is compensated by a reactive power compensation device in the rectifier station;
s302: and analyzing the influence mechanism of the reduction of the alternating current voltage caused by the phase change failure in the first stage according to the relation between the electric quantities at the rectification side and the change process of the reactive power consumption of the rectification station during the phase change failure based on the reactive power characteristics obtained in the step S301.
In the initial stage of phase change failure, the DC current I is firstly changed on the rectifying sidedRAnd (4) rising. When Q is known from the formula (5)RIncrease, i.e. increase of reactive power consumed by the rectifier, resulting in a sending-end system alternating voltage URAnd (4) descending. After the action of the current regulator at the rectifying side increases the trigger angle alpha to limit the direct current, QRThe increase amplitude of the voltage is larger, more reactive power needs to be absorbed from the system, and the alternating voltage U of the system at the transmitting end is largerRFurther decrease;
s303: and analyzing an influence mechanism of the phase change failure in the second stage to increase the alternating-current voltage according to a relational expression between the electric quantities on the rectification side and a change process of reactive power consumption of the rectification station during the phase change failure based on the reactive power characteristics obtained in the step S301.
Substituting the formula (1) or (3) with the formula (5), and eliminating QRIn the expression IdRAnd UdRSettling to obtain a commutation failure period QRIs another expression of
When in normal operation, the working range of alpha is 5-20 degrees. After commutation failure, an increase in α will bring sin2 α to a monotonically decreasing interval. If the voltage U at the AC side is presentRWhen the alpha is continuously increased and continuously decreased, the reactive Q consumed by the converter can be causedRAnd decreases rapidly. Simultaneous vertical (1) and (2) to obtain IdRIs expressed as follows
Figure BDA0002231520350000042
When alpha increases above 90 deg., the direct current will drop to 0. The direct current no longer transmits power, and the reactive power consumed by the direct current is reduced to 0. However, the reactive power compensation device of the rectifier station does not adapt to the change of the running mode of the alternating current and direct current system to change the magnitude of the reactive power compensation capacity, the compensation capacity of the reactive power compensation device is not changed, and the reverse alternating current system of the rectifier station injects reactive power, so that the alternating current voltage U of the sending end system is increasedRIs increased.
Even if the duration of the commutation failure exceeds the protection setting threshold value to cause the locking of the direct current system, the phenomenon of the rise of the alternating current voltage of the sending end system can be caused due to the time delay of communication and device action. Specifically, the pole control system will operate to remove all ac filters of the converter station (delay time is about 200ms), and the safety control system will remove the sending terminal set according to the policy table (delay time is about 300 ms). In a short time from the locking of the direct current to the cutting off of the filter, the transmitting end and the receiving end are not mutually coupled, and meanwhile, the transmitting end converter does not consume reactive power, so that reactive power provided by the reactive power compensation device and the transmitting end alternating current power supply can generate a large surplus, and the alternating voltage of a transmitting end system is increased.
4. The S4 includes the steps of:
s401: building a high-voltage direct-current power transmission model shown in FIG. 10 and verifying the technical effect of the invention by adopting electromagnetic transient simulation software;
s402: obtaining a transient curve change diagram of each electrical quantity before and after the fault occurs, as shown in fig. 11-15;
s403: the consistency of the simulation result and the analysis method provided by the invention is verified.
Drawings
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Fig. 1 is a flow chart of a method for analyzing a sending end voltage in a commutation failure of a high-voltage direct-current power transmission system according to the invention;
fig. 2 is a schematic wiring diagram of a high voltage direct current transmission system according to the present invention;
FIG. 3 is a rectifier and inverter valve voltage waveform according to the present invention;
FIG. 4 is a schematic diagram of a three-phase 6-ripple inverter according to the present invention;
FIG. 5 is a waveform diagram of the main electrical quantity of the inverter side during a commutation failure period according to the present invention;
FIG. 6 is a diagram of the normal V2 → V4 commutation process of the inverter according to the present invention;
FIG. 7 is an equivalent circuit diagram of an inverter with a short circuit at the DC side and an open circuit at the AC side due to a phase change failure according to the present invention;
FIG. 8 is an equivalent circuit diagram of the inverter side phase commutation failure according to the present invention;
fig. 9 is a schematic diagram of reactive power exchange of the rectifier station according to the present invention;
fig. 10 is a diagram of a high voltage dc transmission model according to an embodiment of the invention;
FIG. 11 is a DC voltage variation graph of the sending end system before and after a fault according to the embodiment of the present invention;
FIG. 12 is a graph of the AC voltage variation of the sending end system before and after a fault according to the embodiment of the present invention;
FIG. 13 is a graph of DC current change before and after a fault according to an embodiment of the present invention;
FIG. 14 is a graph of rectifier firing angle changes before and after a fault according to an embodiment of the present invention;
fig. 15 is a graph illustrating a change in reactive power consumed by the rectifying station before and after a fault according to an embodiment of the present invention.
Detailed Description
In order to clearly understand the technical solution of the present invention, a detailed structure thereof will be set forth in the following description. It is apparent that the specific implementation of the embodiments of the present invention is not limited to the specific details familiar to those skilled in the art. The preferred embodiments of the present invention are described in detail below, and other embodiments are possible in addition to the embodiments described in detail.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Examples
In the embodiment of the invention, a 500kV high-voltage direct-current power transmission model shown in fig. 10 is adopted to verify the mechanism analysis method provided by the invention, and a thyristor is used as a converter device. The length of the high-voltage direct-current transmission line is 300km, the resistance is 0.015 omega/km, the capacitance is 1.44 multiplied by 10 < -8 > F/km, and two ends of the high-voltage direct-current transmission line are respectively provided with a 0.5H inductance simulation direct-current smoothing reactor. The rectification side adopts a constant current control mode, and the inversion side adopts a constant voltage control mode. Fig. 1 is a flow chart of a method for analyzing a sending end voltage in a commutation failure of a high-voltage direct-current power transmission system according to the invention. In fig. 1, the analysis method provided by the present invention comprises the following steps:
s1: analyzing a phase change failure fault mechanism and a current replacement rule of the converter valve during phase change failure;
s2: analyzing the influence mechanism of the commutation failure on the direct-current voltage of the sending-end system based on the equivalent circuit during the commutation failure;
s3: analyzing the influence mechanism of commutation failure on alternating voltage of a sending end system based on the reactive power characteristic of a rectifier;
s4: and building a simulation model to verify the analysis method.
The S1 includes the steps of:
s101: the definition and analysis of the commutation failure are explained, and the common reasons causing the commutation failure and the failure mechanism of the commutation failure on the inversion side are analyzed.
Fig. 2 is a schematic wiring diagram of a hvdc transmission system, and fig. 3(a) and (b) are rectifier and inverter valve voltage waveforms, respectively. It can be seen from fig. 3(a) that after the commutation phase, the rectifier valve exiting the commutation is subjected to a long reverse voltage immediately after the current is turned off; as can be seen from fig. 3(b), the inverter valve receives a forward voltage immediately after receiving a short reverse voltage after the current is turned off. If the time from current cut-off to zero-crossing time when the anode voltage of the inverter valve arm exiting the commutation is changed from negative to positive is too short, the valve arm exiting the commutation still has residual current carriers, and the valve arm exiting the commutation can be switched on again without adding trigger pulse under the action of forward voltage, the commutation phase occurs, and the valve expected to be switched on is switched off again, and the phenomenon is commutation failure.
The commutation failure is a common fault of the inverter, and the commutation failure is caused by short circuit of a converter valve of the inverter, loss of trigger pulse of the inverter, fault of an inverter side alternating current system and the like. Taking an inverter side alternating current system fault as an example, when an alternating current side short circuit occurs, the inverter side direct current voltage is reduced, the direct current is increased, the phase change time is prolonged, and the gamma angle is reduced. Generally, when the gamma angle is less than 7 degrees, the commutation failure occurs, and then the AC/DC protection device acts. Under the condition that the commutation failure duration time does not exceed the protection fixed value and locking is triggered, the pole control system and the safety control system cannot act to cut off an alternating current filter and a sending end unit of the converter station; however, when the ac system fails to clear the fault in time or the dc protection system has poor performance, a continuous commutation failure occurs, and at this time, the dc system is locked and the safety control system is switched off.
S102: taking the phase change failure caused by the single-phase earth fault of the receiving-end alternating-current system as an example, the replacement rule of the current of the inverter valve is analyzed.
FIG. 4 is a schematic diagram of a three-phase 6-pulse inverter, in which the DC voltage and current adopt the inverter station reference direction, the common end of the anodes of the valves 4, 6 and 2 is the DC voltage anode, the current flowing into the valve is the DC current reference direction, and U in the diagram isabcIFor inverting side commutation, the phase voltage on the high voltage side is changed, Lr is equivalent commutation inductance, iSw1,2,3,4,5,6 is converter valve current, uSw1,2,3,4,5,6 is converter valve voltage, UdIFor inverting the side pole DC voltage, IdIThe direct current of the inversion side pole line is adopted.
And c-phase metal grounding faults are set in an inverter side alternating current system, the voltage of the c-phase commutation phase is reduced to 0, the fault starts from 1s, the alternating current circuit breaker trips off the fault after 0.08s, and the far-end instantaneous fault is simulated.
Fig. 5 is a waveform of main electrical quantities of the inverter side during a fault, and a current replacement law of the converter valve during a phase change failure is analyzed as follows:
① at time A, a short-circuit fault occurs to the phase-c metal ground, resulting in a bus voltage UcIDrops to 0 and generates waveform distortion. At this time, the phase-change state is being conducted at the same time of V2, V3 and V4, as shown in FIG. 6, the solid line is DC current IdIThe two-phase short-circuit current i when the dotted line is V2 → V4 for the phase change is formed by the current paths formed by V2 and V3 which are turned on at this timescThe current path of (1).
② at time B, the V2 valve current drops to 0 and is subject to UaI-UcIThe voltage of (c). Due to UaI> 0 and U cI0, so UaI-UcIGreater than 0, resulting in V2 still being subjected to the forward voltage at this time, V2 fails to turn off, and a reverse phase occurs from V4 to V2. The current at V4 gradually becomes 0, and is turned off at V4 by time C. After the switching phase, V2 and V3 continue to conduct.
③ at time D, V5 is triggered, the DC current is shorted via V2 and V5, the DC current rises rapidly, the DC voltage drops rapidly, and V3 is subjected to UbI-UcIVoltage of UbI< 0 and UcI＝0，
④ to E, V3 is closed, and the system on the AC side of the inverter is equivalently open, and the current path is as shown in FIG. 7.
⑤ at time F, V6 is triggered and experiences UcI-UbIThe voltage of (c). Due to UbIThe positive voltage at V6 is too short to be applied from positive values quickly, and is turned on briefly and then turned off immediately.
⑥ F, the continuous commutation failure occurs because the ac side protection device fails to timely remove the short-circuit fault and the dc protection device has poor performance, and the current path is still as shown in fig. 7.
⑦ at time G, the DC system voltage and current regulator is operated to reduce the DC voltage, DC current and valve current to 0.
⑧ at time H, the fault is removed and the DC system gradually resumes the normal commutation process.
From the above described commutation valve current replacement during a commutation failure it follows: after an alternating current system at the inversion side has a ground fault, the inverter may have continuous phase commutation failure; the commutation failure period corresponds to the occurrence of a short circuit on the dc side and an open circuit on the ac side of the inverter.
The S2 includes the steps of:
s201: from the conclusion of S1, the equivalent circuit shown in fig. 8 can be obtained, and the inverter station has a dc side short circuit after the commutation failure. The dc current begins to increase due to the loss of the inverter side back emf. Although the reactor arrangement on the dc transmission line, the increase of the current cannot be completely suppressed due to the limited inductance of the dc reactor.
S202: and analyzing the influence mechanism of the commutation failure on the direct-current voltage of the sending-end system according to the relation between the electric quantities of the rectification side and the change process during the commutation failure.
The numerical relationship between the electrical quantities on the rectification side is expressed as follows
Figure BDA0002231520350000101
UdR＝URcosα-IdR·dR(2)
In the formula IdRIs a rectifier polar DC current; u shapedRIs a rectifier polar DC voltage; u shapedIFor inverter pole line DC voltage, during commutation failure period UdI＝0V；URThe voltage is the rectifier polar line no-load direct current voltage, and is determined by the effective value of the converter transformer valve side winding no-load line voltage; dRThe unit direct current is the direct current voltage drop caused in the phase commutation process, and is determined by equivalent commutation reactance; r is the equivalent resistance of a direct current line.
United vertical type (1) and (2) to obtain UdRExpressions during commutation failure
Figure BDA0002231520350000102
At the initial stage of commutation failure, α has not changed, and U is analyzed from the influence on the ac side voltage in S3RAt a descent, and R, dRIs constant, so that the DC voltage U of the transmitting end systemdRIs decreasing. After 20ms-100ms of delay, the rectifier current regulator acts to increase the trigger angle alpha to limit the direct current IdRIncrease of cos alpha, decrease of UdRThe decrease continues.
At the end of the phase change failure, U is analyzed from the influence on the AC side voltage in S3RWill rise so that UdRDoes not decrease continuously but follows URThe increase in (c) is in a rising trend.
The S3 includes the steps of:
s301: and analyzing the reactive power characteristic of the rectifier. Unlike the analysis of the dc voltage in S2, the ac voltage is strongly coupled to the reactive power. The variation of reactive power is limited by various factors. When a direct current system breaks down, various parameters in the system can change, and the reactive power consumption of the current exchange station is influenced. Therefore, when a commutation failure fault occurs in the direct current system, the reactive power balance in the converter station is broken, and the reactive power maintains the constant voltage of the system, which inevitably has a certain influence on the stable operation of the system.
The ac system is a constant power source for the dc system, and the dc system not only obtains active power from the ac system, but also obtains enough reactive power to support the operation of the converter valve. Let the active power on the AC side of the rectifier be P1Angle of power factor ofCan write the reactive power consumed by the rectifier as
Active power P on the AC side of the rectifier under the condition of neglecting the loss and the commutation angle of the rectifier1About DC power PdRAngle of power factor
Figure BDA0002231520350000113
About the trigger angle alpha of the rectifier, the reactive power Q consumed by the rectifierRCan be approximated as
QR＝PdRtanα＝UdRIdRtanα (5)
During operation of the hvdc transmission system, the rectifier station and the ac system must maintain a balance of reactive power, and fig. 9 shows the exchange of reactive power in the rectifier station.
When the AC system provides the reactive power to the rectifying station in the positive direction, the system has
Qac＝QR-QC(6)
In the formula QacReactive, Q, exchange for DC and AC systemsCIs reactive power compensated by a reactive power compensation device in the rectifying station.
S302: and analyzing the influence mechanism of the reduction of the alternating current voltage caused by the phase change failure in the first stage according to the relation between the electric quantities at the rectification side and the change process of the reactive power consumption of the rectification station during the phase change failure.
In the initial stage of phase change failure, the DC current I is firstly changed on the rectifying sidedRAnd (4) rising. When Q is known from the formula (5)RIncrease, i.e. increase of reactive power consumed by the rectifier, resulting in a sending-end system alternating voltage URAnd (4) descending.
After the action of the current regulator at the rectifying side increases the trigger angle alpha to limit the direct current, QRThe increase amplitude of the voltage is larger, more reactive power needs to be absorbed from the system, and the alternating voltage U of the system at the transmitting end is largerRFurther decreases.
S303: substituting the formula (1) or (3) with the formula (5), and eliminating QRIn the expression IdRAnd UdRSettling to obtain a commutation failure period QRIs another expression of
Figure BDA0002231520350000114
When in normal operation, the working range of alpha is 5-20 degrees. After commutation failure, an increase in α will bring sin2 α to a monotonically decreasing interval. If the voltage U at the AC side is presentRWhen the alpha is continuously increased and continuously decreased, the reactive Q consumed by the converter can be causedRAnd decreases rapidly.
Simultaneous vertical (1) and (2) to obtain IdRIs expressed as follows
Figure BDA0002231520350000121
When alpha increases above 90 deg., the direct current will drop to 0. The direct current no longer transmits power, and the reactive power consumed by the direct current is reduced to 0. However, the reactive power compensation device of the rectifier station does not adapt to the change of the running mode of the alternating current and direct current system to change the magnitude of the reactive power compensation capacity, the compensation capacity of the reactive power compensation device is not changed, and the reverse alternating current system of the rectifier station injects reactive power, so that the alternating current voltage U of the sending end system is increasedRIs increased.
Even if the duration of the commutation failure exceeds the protection setting threshold value to cause the locking of the direct current system, the phenomenon of the rise of the alternating current voltage of the sending end system can be caused due to the time delay of communication and device action. Specifically, the pole control system will operate to remove all ac filters of the converter station (delay time is about 200ms), and the safety control system will remove the sending terminal set according to the policy table (delay time is about 300 ms). In a short time from the locking of the direct current to the cutting off of the filter, the transmitting end and the receiving end are not mutually coupled, and meanwhile, the transmitting end converter does not consume reactive power, so that reactive power provided by the reactive power compensation device and the transmitting end alternating current power supply can generate a large surplus, and the alternating voltage of a transmitting end system is increased.
The S4 includes the steps of:
s401: a500 kV high-voltage direct-current power transmission model shown in figure 10 is established by adopting electromagnetic transient simulation software MATLAB/Simulink to verify the technical effect of the invention, and a thyristor is used as a converter device. The length of the high-voltage direct-current transmission line is 300km, the resistance is 0.015 omega/km, and the capacitance is 1.44 multiplied by 10-8F/km, and 0.5H inductance simulation direct current smoothing reactors are respectively arranged at two ends of the reactor. The rectification side adopts a constant current control mode, and the inversion side adopts a constant voltage control mode. Setting the total simulation duration to be 1.5s, setting a C-phase metal grounding fault lasting for 0.05s in an inverter side alternating current system at 1s, and checking the response characteristic of a sending end system when the inverter side fails to change phase in a simulation model. The minimum γ angle is set to 0 °, i.e., when the γ angle becomes 0 °, it indicates that commutation failure occurs;
s402: and obtaining a transient curve change diagram of each electrical quantity before and after the fault occurs. FIGS. 11-15 show the DC voltage U of the sending end system, respectivelydRSending end system alternating current voltage URD.c. current IdRRectifier firing angle alpha and reactive power Q consumed by rectifier stationRChange before and after a fault. Fig. 11-fig. 15 show the whole process of the conversion of the inversion side of the direct current system when a commutation failure occurs. At 0.6s, the direct voltage and the direct current reach rated values, and the whole system enters a stable operation state. And in 1s, the alternating current side of the inverter station fails, and the direct current side of the inverter station fails to change the phase.
S403: and analyzing the consistency of the simulation result and the analysis method provided by the invention. From the simulation result of S402, it can be seen that: at the initial stage of phase change failure, the direct current rises suddenly to cause the reactive power consumed by the rectifying station to increase suddenly, the reactive power compensated by the reactive power compensation device of the rectifying station is unchanged, the voltage of a sending end alternating current system is reduced due to insufficient reactive power, and the sending end direct current voltage begins to be reduced along with the reduction of the alternating current voltage; the action of the current regulator on the rectifying side increases the trigger angle alpha to limit direct current, the reduction of alternating current voltage and the increase of alpha can reduce reactive power consumed by the rectifying station, when the alpha is increased to about 90 degrees, the direct current can be attenuated to 0, the direct current system can not consume the reactive power, reactive power surplus of reactive power compensation equipment of the rectifying station starts to be injected into the alternating current system, the voltage of the alternating current system at the transmitting end rises due to the surplus of the reactive power, and the direct current voltage at the transmitting end also starts to rise along with the rise of the alternating current voltage.
The simulation result is basically consistent with the result obtained by the analysis method provided by the invention, and the practicability and effectiveness of the invention are verified.
Finally, it should be noted that: although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is set forth in the claims appended hereto.

Claims (5)

1. The method for analyzing the influence of the commutation failure of the high-voltage direct-current transmission system on the voltage of a sending end is characterized by comprising the following steps of:
s1: analyzing a phase change failure fault mechanism and a current replacement rule of the converter valve during phase change failure;
s2: analyzing the influence mechanism of the commutation failure on the direct-current voltage of the sending-end system based on the equivalent circuit during the commutation failure;
s3: analyzing the influence mechanism of commutation failure on alternating voltage of a sending end system based on the reactive power characteristic of a rectifier;
s4: and building a simulation model to verify the analysis method.
2. The method of analyzing the effect of commutation failure on the voltage at the transmitting end of the HVDC transmission system of claim 1, wherein S1 comprises the steps of:
s101: setting up definition and analysis of commutation failure, and analyzing common reasons causing commutation failure and failure mechanism of commutation failure on an inversion side;
s102: taking the phase change failure caused by the single-phase earth fault of the receiving-end alternating-current system as an example, analyzing the replacement rule of the inverter valve current to obtain the conclusion that the short circuit of the direct-current side and the open circuit of the alternating-current side of the inverter occur in the phase change failure period.
3. The method of analyzing the effect of commutation failure on the voltage at the transmitting end of the HVDC transmission system of claim 1, wherein S2 comprises the steps of:
s201: drawing an equivalent circuit during the phase commutation failure according to the conclusion of S1;
s202: based on the equivalent circuit of S201, the relation between the electric quantities of the rectification side and the change process during the commutation failure, the influence mechanism of the commutation failure on the direct-current voltage of the sending-end system is analyzed, and the conclusion that the initial phase commutation failure is reduced and the later phase commutation failure is increased is obtained.
4. The method of analyzing the effect of commutation failure on the voltage at the transmitting end of the HVDC transmission system of claim 1, wherein S3 comprises the steps of:
s301: analyzing the reactive power characteristic of the rectifier;
s302: analyzing an influence mechanism of the reduction of the alternating current voltage caused by the phase change failure in the first stage according to a relational expression between the electric quantities at the rectification side and a change process of the reactive power consumption of the rectification station during the phase change failure based on the reactive power characteristics obtained in the step S301;
s303: and analyzing an influence mechanism of the phase change failure in the second stage to increase the alternating-current voltage according to a relational expression between the electric quantities on the rectification side and a change process of reactive power consumption of the rectification station during the phase change failure based on the reactive power characteristics obtained in the step S301.
5. The method of analyzing the effect of commutation failure on the voltage at the transmitting end of the HVDC transmission system of claim 1, wherein S4 comprises the steps of:
s401: a high-voltage direct-current power transmission model test is established, and electromagnetic transient simulation software is adopted to verify the technical effect of the invention;
s402: obtaining a transient curve change diagram of each electrical quantity before and after a fault occurs;
s403: the consistency of the simulation result and the analysis method provided by the invention is verified.
CN201910969196.8A 2019-10-12 2019-10-12 Method for analyzing influence of commutation failure of high-voltage direct-current transmission system on voltage of sending terminal Pending CN110718909A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201910969196.8A CN110718909A (en) 2019-10-12 2019-10-12 Method for analyzing influence of commutation failure of high-voltage direct-current transmission system on voltage of sending terminal

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201910969196.8A CN110718909A (en) 2019-10-12 2019-10-12 Method for analyzing influence of commutation failure of high-voltage direct-current transmission system on voltage of sending terminal

Publications (1)

Publication Number Publication Date
CN110718909A true CN110718909A (en) 2020-01-21

Family

ID=69211481

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201910969196.8A Pending CN110718909A (en) 2019-10-12 2019-10-12 Method for analyzing influence of commutation failure of high-voltage direct-current transmission system on voltage of sending terminal

Country Status (1)

Country Link
CN (1) CN110718909A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112383079A (en) * 2020-11-19 2021-02-19 国网浙江省电力有限公司经济技术研究院 Direct-current system control method and device of extra-high voltage direct-current transmission system
CN113517712A (en) * 2021-05-17 2021-10-19 国网甘肃省电力公司电力科学研究院 Direct-current system commutation method for improving success rate based on self-adaptive threshold of prediction link
CN114362572A (en) * 2022-01-13 2022-04-15 国网江苏省电力有限公司 Method for calculating maximum temporary overvoltage of parallel MMC under AC short-circuit fault
CN114389297A (en) * 2020-10-19 2022-04-22 湖南大学 Commutation failure suppression method and system based on mutual coordination of STATCOM and HVDC predictive control

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114389297A (en) * 2020-10-19 2022-04-22 湖南大学 Commutation failure suppression method and system based on mutual coordination of STATCOM and HVDC predictive control
CN114389297B (en) * 2020-10-19 2024-04-30 湖南大学 Commutation failure suppression method and system based on mutual coordination of STATCOM and HVDC predictive control
CN112383079A (en) * 2020-11-19 2021-02-19 国网浙江省电力有限公司经济技术研究院 Direct-current system control method and device of extra-high voltage direct-current transmission system
CN113517712A (en) * 2021-05-17 2021-10-19 国网甘肃省电力公司电力科学研究院 Direct-current system commutation method for improving success rate based on self-adaptive threshold of prediction link
CN113517712B (en) * 2021-05-17 2022-10-25 国网甘肃省电力公司电力科学研究院 Direct current system commutation method for improving success rate based on self-adaptive threshold of prediction link
CN114362572A (en) * 2022-01-13 2022-04-15 国网江苏省电力有限公司 Method for calculating maximum temporary overvoltage of parallel MMC under AC short-circuit fault
CN114362572B (en) * 2022-01-13 2024-02-09 国网江苏省电力有限公司 Calculation method for maximum temporary overvoltage of parallel MMC under alternating current short circuit fault

Similar Documents

Publication Publication Date Title
CN110718909A (en) Method for analyzing influence of commutation failure of high-voltage direct-current transmission system on voltage of sending terminal
CN108808718B (en) Method for determining direct current operation range of high-voltage direct current transmission system in alternating current fault
CN108493977B (en) Transient reactive coordination control method for series hybrid direct-current power transmission system
CN103066557B (en) Modular multi-level flexible direct current system direct current fault overvoltage restraining method
CN111769586B (en) Commutation failure suppression method for non-fault layer converter of layered access UHVDC system
WO2023029813A1 (en) Control method for suppressing overvoltage under fault of receiving-end power grid of hybrid direct-current power transmission system
Zhou et al. Coordinated power control of electrochemical energy storage for mitigating subsequent commutation failures of HVDC
Zheng et al. Research on DC power control strategy for mitigating the continuous commutation failure
CN111628507A (en) Novel phase modulator and SVG coordinated control method for suppressing transient overvoltage
CN112688288A (en) Overvoltage control protection method for submodule of symmetrical bipolar flexible direct-current power transmission system
Liu et al. Study on transient overvoltage of wind farm caused by fault of HVDC system and its suppression measures
CN111463816A (en) Phase modulator fast forced excitation-based method and system for inhibiting direct current continuous commutation failure
CN114884112B (en) Receiving end alternating current fault ride-through control method of hybrid cascade direct current transmission system
CN113765107A (en) Method for analyzing influence of high-voltage direct-current fault on voltage of direct-current transmission end power grid
Ouyang et al. Fault security region modeling and adaptive current control method for the inverter station of DC transmission system
CN114447927A (en) VDCOL control improvement method for suppressing sending end overvoltage during commutation failure
Yang et al. Simulation analysis of split connection mode system control for XiMeng to TaiZhou UHVDC project
Wang et al. Study on AC Transient Overvoltage Suppression of LCC-HVDC Sending End System Based on DC Current Control Optimization
CN112994065A (en) Method for inhibiting continuous commutation failure of direct current transmission system based on phase modulation operation of photovoltaic power station
Xu et al. Impact of the UHVDC on Performance Characteristics of Power Grid
Han et al. Research on grounding mode of AC-AC converter system
Yang et al. Bipolar fault analysis and protection method of AC/DC power electronic transformer in microgrid
Xue et al. Strategy of Voltage Stress Supression and Dynamic Simulation Experiments of MMC Sub-Module on Hybrid Cascaded Multi-Terminal UHVDC Transmisson System
Hong et al. The Influence of VDCOL Parameters on the Recovery Characteristic after Commutation Failures of HVDC Links Fed into Weak AC Systems
CN113241749B (en) Virtual resistor-based transient overvoltage suppression method for transmission-end power grid during commutation failure

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination