CN112653175B - Method for phase-change failure of synchronous phase modulator stable control simultaneous transmission and reception multi-circuit extra-high voltage system - Google Patents
Method for phase-change failure of synchronous phase modulator stable control simultaneous transmission and reception multi-circuit extra-high voltage system Download PDFInfo
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- H—ELECTRICITY
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- H—ELECTRICITY
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- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention discloses a method for stably controlling commutation failure of a same-transmission same-receiving multi-loop extra-high voltage system through a synchronous phase modulator, which accurately calculates the extinction angle of a receiving end of the same-transmission same-receiving system through real-time acquisition of system parameters, divides the operating area of the system by the calculated extinction angle result range, takes corresponding stable control measures according to different operating areas, and finally quantitatively analyzes and calculates the lifting degree of the extinction angle of an inversion side after a phase modulator is installed on a certain loop of direct current of the receiving end of the same-transmission same-receiving multi-loop extra-high voltage direct current transmission system based on the mechanism that the synchronous phase modulator lifts the system failure and suppresses commutation failure through voltage drop, and analyzes the lifting condition of the extinction angle and commutation failure characteristics of direct currents of other loops in the system according to the special topological structure and relevant voltage interaction factors of the same-transmission same-receiving multi-loop direct current system.
Description
Technical Field
The invention belongs to the technical field of voltage stability control, and particularly relates to a method for phase commutation failure of a synchronous phase modulator stable control co-transmitting and co-receiving multi-circuit ultrahigh voltage system.
Background
In recent years, the power grid in China has a long-distance power transmission structure which is increasingly prominent, and because two power transmission forms of alternating current and direct current are in a specific stage of unbalanced structural development, direct current active and reactive power disturbance is greatly changed to trigger strong disturbance exceeding a set fortification standard or fortification capacity, an alternating current weak link with insufficient bearing capacity is impacted, the cascading failure risk is aggravated, the global safety level is obviously reduced, and the new characteristic of 'strong direct current and weak alternating current' operation of a hybrid power grid is realized. The advantages of the large-capacity multi-feed-out and multi-feed-in ultra-high voltage direct current transmission system in the aspects of transmission distance and transmission capacity are obvious. However, such power transmission structures also present significant challenges to the operational safety and stability of the power system.
At present, aiming at the mainstream project of extra-high voltage direct current transmission, the traditional direct current transmission technology (LCC-HVDC) based on power grid commutation is still adopted, but the stability of the extra-high voltage direct current system is mainly limited by the stability of an alternating current system, especially the voltage stability of the alternating current system, when multiple direct current feed-in points and feed-out points are concentrated in certain areas, especially when a receiving end is fed into a weak alternating current system, great pressure is brought to an alternating current support network, and a series of problems are caused by insufficient support capability of the alternating current system. When a receiving end power grid has a short-circuit fault, the converter commutation fault is difficult to avoid, commutation failure of a direct current system is easily caused, even commutation failure of multiple direct currents simultaneously or sequentially is caused, a large amount of active power loss is caused, deterioration of alternating current and direct current systems can be accelerated, even stability of the systems is damaged, and great influence is caused on the transmitting end power grid and the receiving end power grid. Therefore, a method for improving the commutation failure characteristics of the same-transmission and receiving dc system is needed.
In order to improve the capability of the LCC-HVDC to resist commutation failure, a reactive power compensation device is generally arranged in the area near a commutation bus. Three reactive power compensation devices commonly used in engineering are a Static Var Compensator (SVC), a static synchronous compensator (STATCOM) and a synchronous phase modulator, wherein the reactive power output capacity of the SVC is in direct proportion to the square of voltage, the reactive power output capacity of the STATCOM is in direct proportion to the voltage, and the synchronous phase modulator has strong overcurrent capacity and is not influenced by the voltage. Compared with the other two dynamic reactive power compensation devices, the SC has advantages in capacity, transient state, and transient state reactive power support capability. In addition, the SC serving as a rotating device can provide considerable short-circuit capacity and rotational inertia for the system, so that the stability of the system is improved, when a fault occurs, the voltage of a commutation bus is reduced, the voltage of a reactive power compensation device installation node is reduced, the sub-transient characteristic of the SC enables the SC to release a large amount of reactive power, the voltage level is stabilized, and strong reactive support can be provided for the long-time fault, so that the direct-current commutation fault is effectively inhibited.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for stably controlling the commutation failure of a co-transmitting and co-receiving multi-loop extra-high voltage system through a synchronous phase modulator.
In order to achieve the aim, the invention discloses a method for stably controlling the commutation failure of a multi-loop and multi-loop extra-high voltage system which is simultaneously transmitted and received through a synchronous phase modulator, which is characterized by comprising the following steps of:
(1) calculating an inversion side arc-quenching angle gamma according to the receiving end alternating current operating condition of the co-transmission and co-reception multi-circuit ultrahigh voltage system;
(1.1) collecting alternating current voltage U of receiving end alternating current through a synchronous measuring device according to receiving end alternating current operating conditions of the co-transmission and multi-circuit extra-high voltage systemLAnd a direct current Id(ii) a Then according to the receiving end direct current operation working condition of the same-transmission same-receiving multi-circuit extra-high voltage system, reading the advanced ignition angle beta, the converter transformer transformation ratio k and the commutation reactance X of the same-transmission same-receiving multi-circuit extra-high voltage systemc;
(1.2) when the extra-high voltage system with the same transmission and reception and multiple loops operates stably, calculating a nominal arc-quenching angle gamma*;
(1.3) when the receiving end alternating current operation has asymmetric fault, acquiring a zero-crossing voltage deviation angle phi through a synchronous measurement device, and correcting a nominal arc-quenching angle gamma through phi*To obtain an inversionA side arc-extinguishing angle gamma;
(2) judging the real-time state of the co-transmitting and receiving multi-circuit extra-high voltage system according to the arc extinguishing angle gamma; when gamma is less than thetaminWhen the simultaneous transmission and receiving multi-circuit extra-high voltage system is positioned in a destabilization area, the simultaneous transmission and receiving multi-circuit extra-high voltage system fails to change the phase;
when theta isminWhen gamma is not more than or equal to theta, the co-transmitting and co-receiving multi-circuit extra-high voltage system is positioned in a risk area, and at the moment, the co-transmitting and co-receiving multi-circuit extra-high voltage system has the risk of phase commutation failure;
when theta is more than gamma and less than or equal to thetamaxMeanwhile, the extra-high voltage systems with the same transmission and reception and multiple loops are positioned in a safety area, and at the moment, the extra-high voltage systems with the same transmission and reception and multiple loops operate according to normal working conditions;
wherein, thetaminTheta and thetamaxThe values of the corresponding arc-quenching angles gamma are taken when the multi-circuit ultrahigh voltage systems which are simultaneously transmitted and received are in different states;
(3) adding a phase modulator to a multi-loop ultrahigh voltage direct current transmission system which is positioned in a destabilization area and a risk area and receives the same power;
(3.1) in the simultaneous transmission and receiving multi-loop extra-high voltage direct current transmission system, randomly selecting a certain loop direct current, installing a phase modulator on a receiving end current conversion bus, and then collecting the voltage of the receiving end alternating current bus of the simultaneous transmission and receiving multi-loop extra-high voltage direct current transmission system, wherein the direct current voltage provided with the phase modulator is recorded as U1And the residual circuit DC voltage is marked as UiI is 2,3, …, and H is the total number of direct current paths in the same-transmission and same-receiving multi-loop extra-high voltage direct current transmission system;
(3.2) collecting relevant parameters of the synchronous phase modulator, comprising the following steps: equivalent reactance X of synchronous phase modulatorTSCD-axis synchronous reactance, d-axis transient reactance and d-axis sub-transient reactance X of synchronous phase modulatorD、X'DAnd X "D(ii) a Stator winding transient time constant, d-axis transient short-circuit time constant taking system impedance into account and d-axis sub-transient short-circuit time constant T taking system impedance into accounta、T'DAnd T "D(ii) a The power angle delta of the phase modulator before failure; d-axis reactive current I of synchronous phase modulatorD0;
(3.3) calculating reactive compensation increment delta Q of synchronous phase modulatorSC;
ΔQSC=U1ΔID0-ΔU1ID0
Wherein, Delta ID0Stator current increment, AU, for synchronous phase modulators1The amplitude of the voltage drop of the alternating current bus;
(3.4) under the condition of not considering an excitation system, calculating the stator current increment delta I of the synchronous phase modulator in the sub-transient processD0;
Where, is the convolution symbol, ω is the angular frequency of the receiving end AC, t is time, Δ U1qFor the voltage drop amplitude delta U of the AC bus1Q-axis component of (a);
let delta U1q≈ΔU1Increment of stator current of synchronous phase modulator in sub-transient process by delta ID0Substituting the step (3.3) to obtain the instantaneous reactive power increment of the synchronous phase modulator in the sub-transient process
Therefore, in the sub-transient process when the fault occurs, the synchronous phase modulator generates reactive power to the extra-high voltage direct current transmission system which simultaneously transmits and receives multiple loopsThereby further reducing Δ U1;
(3.5) calculating voltage interaction factors of a transmitting end and a receiving end for the direct currents of other loops of the multi-loop ultrahigh-voltage direct-current power transmission system with the same transmission and receiving;
for the sending end, calculating the interaction factor of the multi-feed-out voltageFor the receiving end, calculating the interaction factor of the multi-feed voltageWherein i and j represent direct current numbers in a multi-circuit ultrahigh voltage direct current transmission system with transmission and reception, and i is not equal to j and delta UiAnd Δ UjRepresenting the voltage sag amplitude, Z, of the AC busbars i and jjiRepresenting the impedance between the AC busbars i and j, ZiiRepresenting the self impedance of the alternating current bus i;
when voltage interaction factors MOVIF and MIIF of a transmitting end and a receiving end of a multi-loop extra-high voltage direct current transmission system which are transmitted and received simultaneously do not change, voltage drop delta U of an alternating current bus is reduced through a synchronous phase modulator1Meanwhile, the voltage drop delta U of other alternating current buses is also reducediWherein for the voltage drop of the transmitting terminalFor receiving end voltage dropTherefore, multi-loop simultaneous adjustment of the simultaneous transmission and reception multi-loop ultrahigh voltage direct current transmission system is realized;
(4) after the synchronous phase modulator is arranged for adjustment, calculating an arc extinguishing angle gamma' on the inversion side;
wherein, VSFjiIs the voltage stability factor of the AC buses i and j;
(5) and (3) substituting the inversion side arc-extinguishing angle gamma' into the step (2) to judge the real-time state of the multi-circuit ultrahigh voltage system simultaneously transmitted and received.
The invention aims to realize the following steps:
the invention relates to a method for stably controlling commutation failure of a co-transmitting and co-receiving multi-loop extra-high voltage system through a synchronous phase modulator, which accurately calculates the extinction angle of a receiving end of the co-transmitting and co-receiving system through real-time acquisition of system parameters, divides the operating area of the system by the calculated extinction angle result range, takes corresponding stable control measures according to different operating areas, and finally quantitatively analyzes and calculates the extinction angle lifting degree of an inversion side after a phase modulator is arranged on a certain loop of direct current of the receiving end of the co-transmitting and co-receiving multi-loop extra-high voltage direct current transmission system based on the mechanism that the synchronous phase modulator lifts the system failure and suppresses commutation failure by voltage drop, and analyzes the extinction angle lifting condition and commutation failure characteristics of direct currents of other loops in the system according to the special topological structure and related voltage interaction factors of the co-transmitting and co-receiving multi-loop direct current system.
Meanwhile, the method for stably controlling the commutation failure of the extra-high voltage system with the same transmission and receiving through the synchronous phase modulator further has the following beneficial effects:
(1) the method adds a method for calculating the extinction angle aiming at a certain return direct current additionally installed synchronous phase modulator at the receiving end of the simultaneous transmission and receiving system on the basis of the original method for calculating the extinction angle, has a certain guiding function on the research on commutation failure of a novel power system topological structure of the simultaneous transmission and receiving system, is convenient and reliable in the extinction angle calculation process, improves the accuracy of operation by acquiring system parameters in real time, and can better guide a power grid to take corresponding protection actions.
(2) The invention defines the operation areas of different loop direct currents in the same-transmission and same-receiving multi-loop extra-high voltage direct current system according to the arc extinguishing angle range, and conveniently and quickly adopts corresponding stability control measures such as installing a phase modulator and enhancing the alternating current intensity of a receiving end according to the operation areas where the different direct currents are located.
Drawings
FIG. 1 is a flow chart of the method for phase commutation failure of a synchronous phase modulator for stable control and simultaneous transmission and reception of multiple extra-high voltage systems;
FIG. 2 is a schematic structural diagram of a simultaneous transmission and reception multi-circuit extra-high voltage system in a large power grid;
FIG. 3 is a schematic diagram of receiving-end direct current of a co-transmitting and receiving multi-circuit extra-high voltage system;
FIG. 4 is a waveform of a DC gamma value under a three-phase inductive load;
fig. 5 is a waveform diagram of two dc gamma values under three-phase inductive load.
Detailed Description
Specific embodiments of the present invention are described below in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It is to be expressly noted that in the following description, a detailed description of known functions and designs will be omitted when it may obscure the subject matter of the present invention.
Examples
FIG. 1 is a flow chart of the method for phase commutation failure of a synchronous phase modulator for stable control and simultaneous transmission and reception of multiple extra-high voltage systems.
In this embodiment, as shown in fig. 3, a model is built based on PSCAD/EMTDC electromagnetic transient simulation software, the model is obtained by equivalently simplifying refined operating parameters of a certain extra-high voltage direct current project, a certain two extra-high voltage direct current transmission projects and a near-area alternating current power grid of the power grid, relevant parameters of the model are shown in table 1, and drop points of transmitting and receiving ends of the model are shown in a large power grid in fig. 2, taking a co-transmitting and receiving double-circuit extra-high voltage direct current transmission system in fig. 3 as an example.
TABLE 1
Based on the model, a method for stably controlling phase commutation failure of a synchronous phase modulator and a transmitting and receiving double-circuit extra-high voltage system is explained in detail, and the method specifically comprises the following steps:
s1, calculating an inversion side arc-quenching angle gamma according to the receiving end alternating current operating condition of the co-transmission and co-reception double-circuit extra-high voltage system;
s1.1, collecting alternating current voltage U of receiving end alternating current through a synchronous measuring device according to receiving end alternating current operating conditions of a co-transmission and co-receiving double-circuit extra-high voltage systemLAnd a direct current Id(ii) a Then carrying out direct current operation according to receiving ends of the same-transmission and same-receiving double-circuit extra-high voltage systemReading the advanced ignition angle beta, the converter transformer transformation ratio k and the commutation reactance X of the same-transmission same-receiving double-circuit extra-high voltage system under the working conditionc;
In this embodiment, certain dc operating parameters are as follows: receiving end alternating voltage ULTaking 500kV and direct current Id5kA, an advance trigger angle beta of 30 degrees, a converter transformer transformation ratio k of 3.285 and a commutation reactance Xc1.9194;
some of the two dc operating parameters are as follows: receiving end alternating voltage ULTaking 500kV and direct current Id5kA, an advance trigger angle beta of 29.6 degrees, a transformation ratio k of the converter transformer of 3.166, and a commutation reactance Xc1.8984;
s1.2, when the double-circuit extra-high voltage system with the same transmission and receiving is in stable operation, calculating a nominal arc-quenching angle gamma*;
S1.3, when the receiving end alternating current operation has asymmetric faults, acquiring a zero-crossing voltage deviation angle phi through a synchronous measuring device, and correcting a nominal arc quenching angle gamma through phi*Obtaining an inversion side arc-quenching angle gamma;
in this embodiment, γ is about 17.2 ° for a direct current normal operation; gamma of about 17.4 deg. when a certain DC is normally operated
S2, judging the real-time state of the co-transmission and co-reception double-circuit extra-high voltage system according to the arc-quenching angle gamma;
generally, it is considered that the thyristor cannot recover the forward latching capability in time due to the excessively small extinction angle, and is turned on again under the action of the forward voltage, so that the valve to be turned off is turned on continuously, and the valve to be turned on is turned off, thereby causing the phase commutation failure. Therefore, the fact that the extinction angle is smaller than the inherent limit extinction angle of the valve is considered to be the root cause of commutation failure;
when gamma is less than thetaminWhile sending and receivingThe double-circuit receiving extra-high voltage system is positioned in a destabilization area, and at the moment, the same double-circuit receiving extra-high voltage system and the double-circuit receiving extra-high voltage system have phase commutation failure;
when theta isminWhen gamma is not more than or equal to theta, the co-transmitting and co-receiving dual-circuit extra-high voltage system is located in a risk area, and at the moment, the co-transmitting and co-receiving dual-circuit extra-high voltage system has the risk of phase commutation failure;
when theta is more than gamma and less than or equal to thetamaxMeanwhile, the simultaneous-transmission and simultaneous-reception double-circuit extra-high voltage system is positioned in a safety area, and at the moment, the simultaneous-transmission and simultaneous-reception double-circuit extra-high voltage system operates according to normal working conditions;
wherein, thetaminTheta and thetamaxIn order to take the corresponding extinction angle gamma values when the simultaneous transmission and reception dual-circuit extra-high voltage system is in different states, in the embodiment, theta is taken as the valuemin7 °, 15 °, 31.2 °; therefore, under normal working conditions, the direct currents at the two positions run in a safe area.
S3, adding a phase modulator to the co-transmission and co-reception double-circuit ultrahigh voltage direct current transmission system in the instability area and the risk area;
s3.1, in the co-transmission and co-reception double-circuit extra-high voltage direct current transmission system, a three-phase inductive ground fault is applied to a certain direct current receiving end converter bus, the fault occurs in 0.87S, when the inductance value is adjusted to be 0.331H, the system does not happen to phase change failure, at the moment, gamma is approximately equal to 7.6 degrees, and due to the fault propagation coupling characteristic of the co-transmission and co-reception system, phase change failure occurs in 1.0536S due to insufficient support of alternating current voltage at certain two direct current receiving ends. At the moment, a certain direct current is in a risk area, because a certain two direct currents have phase change failure, gamma is 0 degrees, namely the certain two direct currents are in a destabilization area, 2 300Mvar phase modulators are installed on a certain direct current receiving end current conversion bus, and the synchronous phase modulators can output reactive power according to the amplitude of voltage drop to achieve the purpose of supporting the bus voltage, so that the phase change failure is restrained; and then collecting the voltage of a receiving end alternating current bus of a simultaneous-transmission and simultaneous-receiving dual-circuit extra-high voltage direct current transmission system, wherein the direct current voltage provided with a phase modulator is recorded as U1The other loop DC voltage is marked as U2(ii) a S3.2, collecting relevant parameters of the synchronous phase modulator, comprising the following steps: equivalent reactance X of synchronous phase modulatorTSCD-axis synchronous reactance, d-axis transient reactance and d-axis sub-transient reactance X of synchronous phase modulatorD、X'DAnd X "D(ii) a Stator winding transient time constant, d-axis transient short-circuit time constant taking system impedance into account and d-axis sub-transient short-circuit time constant T taking system impedance into accounta、T'DAnd T'D(ii) a The power angle delta of the phase modulator before failure; d-axis reactive current I of synchronous phase modulatorD0(ii) a Wherein the d-axis synchronous reactance is 1.56 pu.; d-axis transient reactance of 0.30 pu.; d-axis sub-transient reactance of 0.28 pu.; d-axis transient time constant 1.1 s; d-axis sub-transient short circuit time constant is 0.059 s; rated line voltage of the phase modifier is 7.91kV, rated current of the phase modifier is 16.856kA and the like.
S3.3, calculating reactive compensation increment delta Q of synchronous phase modulatorSC;
ΔQSC=U1ΔID0-ΔU1ID0
Wherein, Delta ID0Stator current increment, AU, for synchronous phase modulators1The voltage drop amplitude of the alternating current bus;
s3.4, under the condition of not considering an excitation system, calculating the stator current increment delta I of the synchronous phase modulator in the sub-transient processD0;
Where, is the convolution symbol, ω is the angular frequency of the receiving end AC, t is the time, Δ U1qFor the voltage drop amplitude delta U of the AC bus1Q-axis component of (a);
let delta U1q≈ΔU1Increment of stator current of synchronous phase modulator in sub-transient process by delta ID0Substituting the obtained value into the step S3.3 to obtain the instantaneous reactive power increment of the synchronous phase modulator in the sub-transient process
Therefore, in the sub-transient process when the fault occurs, the synchronous phase modulator generates reactive power to the co-transmitting and receiving double-circuit extra-high voltage direct current transmission systemThereby further reducing Δ U1(ii) a S3.5, calculating voltage interaction factors of a transmitting end and a receiving end for the direct currents of other loops of the same-transmission and same-receiving double-loop ultrahigh-voltage direct-current power transmission system;
for the sending end, calculating the interaction factor of the multi-feed-out voltageFor the receiving end, calculating the interaction factor of the multi-feed voltageWherein 1 and 2 represent direct current numbers, delta U, in the same-transmission and same-reception double-circuit extra-high voltage direct current transmission system1And Δ U2Representing the magnitude of the voltage sag, Z, of the AC busbars 1 and 212Representing the link impedance, Z, between the converter stations 1 and 222Represents the self ac system impedance of the dc link 2;
when voltage interactive factors MOVIF and MIIF of a transmitting end and a receiving end of a co-transmitting and receiving dual-loop extra-high voltage direct current transmission system are not changed, voltage drop delta U of an alternating current bus is reduced through a synchronous phase modulator1Meanwhile, the voltage drop delta U of other alternating current buses is also reducediWherein for the voltage drop of the transmitting terminalFor receiving end voltage dropTherefore, multi-loop simultaneous adjustment of the simultaneous transmission and receiving dual-loop extra-high voltage direct current transmission system is realized;
the parameters of the phase modulator are introduced into the correlation, and the S3.2-S3.4 formula is calculated, so that the synchronous phase modulator has the reactive power output delta Q in the sub-transient processSCAbout 220Mvar, some DC is Δ U after installing synchronous phase modulator1Decrease about0.093pu。
S4, after adjusting by installing a synchronous phase modulator, calculating an arc-quenching angle gamma' of the inversion side;
wherein, VSFjiIs the voltage stability factor of the AC buses i and j;
a certain direct current inversion side gamma 'is 12.2, gamma is increased by 4.5 degrees and still is in a risk area, a synchronous phase modulator arranged on the certain direct current inversion side also has an effect of increasing the alternating current voltage drop of a certain two direct current receiving ends, the phase commutation failure characteristic of a certain two direct currents is improved, a certain two direct currents gamma' is increased from 0 to 10 degrees and is transferred to the risk area from a instability area, no phase commutation failure occurs, simulation data verification and calculation results are basically consistent, and simulation results are shown in fig. 4 and 5.
And S5, substituting the inversion side arc-quenching angle gamma' into the step S2, and judging the real-time state of the co-transmission and co-reception double-circuit extra-high voltage system.
Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, and various changes may be made apparent to those skilled in the art as long as they are within the spirit and scope of the present invention as defined and defined by the appended claims, and all matters of the invention which utilize the inventive concepts are protected.
Claims (2)
1. A method for stably controlling phase commutation failure of a multi-circuit ultrahigh voltage system with simultaneous transmission and reception through a synchronous phase modulator is characterized by comprising the following steps:
(1) calculating an inversion side arc-quenching angle gamma according to the receiving end alternating current operating condition of the co-transmission and co-reception multi-circuit ultrahigh voltage system;
(1.1) collecting alternating current voltage U of alternating current at a receiving end through a synchronous measuring device according to alternating current operating conditions at the receiving end of the co-transmission and receiving multi-circuit extra-high voltage systemLAnd a direct current Id(ii) a Then root ofAccording to the receiving end direct current operating condition of the co-transmission and co-reception multi-circuit extra-high voltage system, reading the advanced ignition angle beta, the converter transformer transformation ratio k and the commutation reactance X of the co-transmission and co-reception multi-circuit extra-high voltage systemc;
(1.2) when the extra-high voltage system with the same transmission and reception and multiple loops operates stably, calculating a nominal arc-quenching angle gamma*;
(1.3) when the receiving end alternating current operation has asymmetric faults, acquiring a zero-crossing voltage deviation angle phi through a synchronous measuring device, and correcting a nominal arc quenching angle gamma through phi*Obtaining an inversion side arc-quenching angle gamma;
(2) judging the real-time state of the co-transmitting and receiving multi-circuit extra-high voltage system according to the arc extinguishing angle gamma; when gamma is less than thetaminMeanwhile, the extra-high voltage systems with the same transmission and receiving times are positioned in a destabilization area, and at the moment, the extra-high voltage systems with the same transmission and receiving times have phase commutation failure;
when theta isminWhen gamma is not more than or equal to theta, the co-transmitting and co-receiving multi-circuit extra-high voltage system is positioned in a risk area, and at the moment, the co-transmitting and co-receiving multi-circuit extra-high voltage system has the risk of phase commutation failure;
when theta is more than gamma and less than or equal to thetamaxMeanwhile, the extra-high voltage systems with the same transmission and reception and multiple loops are positioned in a safety area, and at the moment, the extra-high voltage systems with the same transmission and reception and multiple loops operate according to normal working conditions;
wherein, thetaminTheta and thetamaxThe values of the corresponding arc-quenching angles gamma are taken when the multi-circuit ultrahigh voltage systems which are simultaneously transmitted and received are in different states;
(3) adding a phase modulator to a multi-loop ultrahigh voltage direct current transmission system which is positioned in a destabilization area and a risk area and simultaneously transmits and receives;
(3.1) in the same-transmission and same-reception multi-loop extra-high voltage direct current transmission system, randomly selecting a certain loop direct current and installing the loop direct current on a receiving end current conversion busA phase modulator, and then collecting the receiving end alternating current bus voltage of the extra-high voltage direct current transmission system which transmits and receives the extra-high voltage direct current transmission system simultaneously, wherein the direct current voltage provided with the phase modulator is recorded as U1And the residual circuit DC voltage is marked as UiI is 2,3, …, and H is the total number of direct current paths in the same-transmission and same-receiving multi-loop extra-high voltage direct current transmission system;
(3.2) collecting relevant parameters of the synchronous phase modulator, comprising the following steps: equivalent reactance X of synchronous phase modulatorTSCD-axis synchronous reactance, d-axis transient reactance and d-axis sub-transient reactance X of synchronous phase modulatorD、X'DAnd X "D(ii) a Stator winding transient time constant, d-axis transient short-circuit time constant taking system impedance into account and d-axis sub-transient short-circuit time constant T taking system impedance into accounta、T'DAnd T'D(ii) a The power angle delta of the phase modulator before failure; d-axis reactive current I of synchronous phase modulatorD0;
(3.3) calculating reactive compensation increment delta Q of the synchronous phase modulatorSC;
ΔQSC=U1ΔID0-ΔU1ID0
Wherein, Delta ID0Stator current increment, AU, for synchronous phase modulators1The amplitude of the voltage drop of the alternating current bus;
(3.4) under the condition of not considering an excitation system, calculating the stator current increment delta I of the synchronous phase modulator in the sub-transient processD0;
Where, is the convolution symbol, ω is the angular frequency of the receiving end AC, t is the time, Δ U1qFor the voltage drop amplitude delta U of the AC bus1Q-axis component of (a);
let delta U1q≈ΔU1Increment of stator current of synchronous phase modulator in sub-transient process by delta ID0Substituting the step (3.3) to obtain the instantaneous reactive power increment of the synchronous phase modulator in the sub-transient process
Therefore, in the sub-transient process, the synchronous phase modulator sends out reactive power to the co-transmission and co-reception multi-circuit extra-high voltage direct current transmission systemThereby further reducing Δ U1;
(3.5) calculating voltage interaction factors of a transmitting end and a receiving end for the direct currents of other loops of the multi-loop ultrahigh-voltage direct-current power transmission system with the same transmission and receiving;
for the sending end, calculating the interaction factor of the multi-feed-out voltageFor the receiving end, calculating the interaction factor of the multi-feed voltageWherein i and j represent direct current numbers in a multi-circuit ultrahigh voltage direct current transmission system with transmission and reception, and i is not equal to j and delta UiAnd Δ UjRepresenting the voltage sag amplitude, Z, of the AC busbars i and jjiRepresenting the impedance between the AC busbars i and j, ZiiRepresenting the self impedance of the alternating current bus i;
when voltage interaction factors MOVIF and MIIF of a transmitting end and a receiving end of a multi-loop extra-high voltage direct current transmission system which are transmitted and received simultaneously do not change, voltage drop delta U of an alternating current bus is reduced through a synchronous phase modulator1Meanwhile, the voltage drop delta U of other alternating current buses is also reducediWherein for the voltage drop of the transmitting terminalFor receiving end voltage dropTherefore, simultaneous adjustment of multiple loops of the simultaneous transmission and reception multiple-loop extra-high voltage direct current transmission system is realized;
(4) after the synchronous phase modulator is arranged for adjustment, calculating an arc extinguishing angle gamma' on the inversion side;
wherein, VSFjiVoltage stability factor, Δ Q, for AC buses i and jiThe reactive compensation quantity provided by the multi-circuit ultrahigh voltage direct current transmission system is represented by an alternating current bus i;
(5) and (3) substituting the inversion side arc-extinguishing angle gamma' into the step (2) to judge the real-time state of the multi-circuit ultrahigh voltage system simultaneously transmitted and received.
2. The method for stabilizing and controlling commutation failure of the co-transmitting and co-receiving multi-circuit extra-high voltage system through the synchronous phase modulator as claimed in claim 1, wherein the specific calculation formula of the voltage stabilization factor is as follows:
wherein, Delta UjRepresents the voltage sag amplitude, Δ Q, of the AC bus jiAnd the reactive compensation quantity provided by the multi-circuit ultrahigh voltage direct current transmission system is represented by the alternating current bus i.
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