CN110601245A - Method and system for checking transient overvoltage after extra-high voltage direct current fault - Google Patents

Method and system for checking transient overvoltage after extra-high voltage direct current fault Download PDF

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Publication number
CN110601245A
CN110601245A CN201910739488.2A CN201910739488A CN110601245A CN 110601245 A CN110601245 A CN 110601245A CN 201910739488 A CN201910739488 A CN 201910739488A CN 110601245 A CN110601245 A CN 110601245A
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China
Prior art keywords
current
direct
transient
converter station
upper limit
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CN201910739488.2A
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Chinese (zh)
Inventor
徐式蕴
于钊
王超
刘明松
邱威
黄东敏
卓谷颖
谭真
程势高
毕经天
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State Grid Corp of China SGCC
State Grid Zhejiang Electric Power Co Ltd
China Electric Power Research Institute Co Ltd CEPRI
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State Grid Corp of China SGCC
State Grid Zhejiang Electric Power Co Ltd
China Electric Power Research Institute Co Ltd CEPRI
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Priority to CN201910739488.2A priority Critical patent/CN110601245A/en
Publication of CN110601245A publication Critical patent/CN110601245A/en
Pending legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16533—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application
    • G01R19/16538—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16576—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing DC or AC voltage with one threshold
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • 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
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation
    • 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]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a method and a system for checking transient overvoltage after an extra-high voltage direct current fault, wherein the method comprises the following steps: the transient voltage rise upper limit value of a converter station bus of the alternating-current and direct-current hybrid power grid after the direct-current fault; respectively acquiring initial voltage of a converter station bus of the alternating-current and direct-current hybrid power grid before direct-current fault and maximum transient voltage of a direct-current fault period under the current direct-current power level; calculating a difference value between the maximum transient voltage and the initial voltage to serve as a current converter station bus voltage rise value, and comparing the difference value with a transient voltage rise upper limit value to obtain a checking result; and when the checking result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value, taking the current direct current power as the maximum direct current transmission power of the alternating current-direct current hybrid power grid under the transient voltage rise constraint.

Description

Method and system for checking transient overvoltage after extra-high voltage direct current fault
Technical Field
The invention relates to the field of safe and stable operation of an alternating current-direct current hybrid power grid, in particular to a method and a system for checking transient overvoltage after an extra-high voltage direct current fault.
Background
With the large-scale development of extra-high voltage direct current, power impact caused by direct current faults becomes a key factor influencing the safe and stable operation of a power system. With the continuous improvement of the extra-high voltage direct current power, the transient overvoltage problem of a power grid at the sending end after the extra-high voltage direct current disturbance is increasingly prominent, and the power transmission capacity of the extra-high voltage direct current is severely restricted.
Transient overvoltages caused by dc disturbances are mainly caused by temporary loss of work and delayed cutting off of filters. Dc blocking, commutation failure, restart and ac short circuit faults all result in temporary imbalances that are reactive, but of different durations. The dc blocking filter delay cut-off time is typically 200 ms. The power fluctuation process of one commutation failure generally lasts for 200ms, and if continuous commutation failure occurs, the duration is longer. The duration of the direct current restart process is about 300ms-1000ms according to the restart times. The short-circuit fault can cause the direct current power to drop instantly, the system voltage is recovered immediately when the fault disappears, the direct current power is gradually recovered to the initial power to cause temporary reactive surplus, the reactive surplus is similar to reactive pulse, and the duration is short. Because the proportion of the extra-high voltage direct current power is large, the power angle oscillation caused by active power impact is more severe, and the overvoltage is greatly influenced.
Therefore, research on a transient overvoltage correlation checking method after direct current disturbance of the alternating current-direct current hybrid power grid needs to be carried out.
Disclosure of Invention
The invention provides a method and a system for checking transient overvoltage after an extra-high voltage direct current fault, which are used for solving the problem of how to check the transient overvoltage of an alternating current-direct current hybrid power grid after direct current disturbance so as to determine the maximum direct current transmission power in the alternating current-direct current hybrid power grid.
In order to solve the above problem, according to an aspect of the present invention, there is provided a method for checking a transient overvoltage after an extra-high voltage dc fault, the method including:
determining the transient voltage rise upper limit value of a converter station bus of the alternating-current and direct-current hybrid power grid after the direct-current fault;
respectively acquiring initial voltage of a converter station bus of the alternating-current and direct-current hybrid power grid before direct-current fault and maximum transient voltage of the converter station bus during the direct-current fault under the current direct-current power level;
calculating a difference value between the maximum transient voltage and the initial voltage, wherein the difference value is used as a current converter station bus pressure rise value, and the current converter station bus pressure rise value is compared with the transient pressure rise upper limit value to obtain a checking result;
and when the checking result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value, taking the current direct current power as the maximum direct current transmission power of the alternating current-direct current hybrid power grid under the transient voltage rise constraint.
Preferably, the determining the transient voltage rise upper limit value of the bus of the converter station after the direct-current fault of the alternating-current/direct-current hybrid power grid includes:
wherein, the delta U is a transient state pressure rise upper limit value; u shapeEThe highest operating voltage of the direct current conversion bus; u shapeBThe reference voltage is used for simulation calculation; u shapeIThe initial voltage of the bus when calculating for the simulation.
Preferably, wherein for 500kV DC current conversion bus, the highest operation voltage UEThe value of (b) is 530kV or 550 kV.
Preferably, wherein the method further comprises:
when the check result indicates that the current converter station bus voltage rise value is smaller than the transient voltage rise upper limit value, increasing the current direct current power according to a preset power adjustment strategy, and recalculating until the check result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value; and
and when the checking result indicates that the current converter station bus voltage rise value is greater than the transient voltage rise upper limit value, reducing the current direct current power according to a preset power adjustment strategy, and recalculating until the checking result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value.
According to another aspect of the present invention, there is provided a system for checking a transient overvoltage after an extra-high voltage dc fault, the system comprising:
the transient voltage rise upper limit value determining unit is used for determining the transient voltage rise upper limit value of a converter station bus of the alternating-current and direct-current series-parallel power grid after the direct-current fault;
the transient voltage acquisition unit is used for respectively acquiring the initial voltage of a converter station bus of the alternating-current and direct-current hybrid power grid before a direct-current fault occurs and the maximum transient voltage during the direct-current fault under the current direct-current power level;
a checking result obtaining unit, configured to calculate a difference between the maximum transient voltage and the initial voltage, where the difference is used as a current converter station bus pressure rise value, and compare the current converter station bus pressure rise value with the transient pressure rise upper limit value to obtain a checking result;
and the maximum direct-current transmission power determining unit is used for taking the current direct-current power as the maximum direct-current transmission power of the alternating-current and direct-current hybrid power grid under the transient voltage rise constraint when the checking result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value.
Preferably, the transient voltage rise upper limit determining unit determines a transient voltage rise upper limit of a converter station bus of the ac-dc hybrid grid after the dc fault, and includes:
wherein, the delta U is a transient state pressure rise upper limit value; u shapeEThe highest operating voltage of the direct current conversion bus; u shapeBThe reference voltage is used for simulation calculation; u shapeIThe initial voltage of the bus when calculating for the simulation.
Preferably, wherein for 500kV DC current conversion bus, the highest operation voltage UEThe value of (b) is 530kV or 550 kV.
Preferably, wherein the system further comprises:
the direct current power adjusting unit is used for increasing the current direct current power according to a preset power adjusting strategy and entering the transient voltage obtaining unit when the checking result indicates that the current converter station bus voltage rise value is smaller than the transient voltage rise upper limit value; and
and when the checking result indicates that the current converter station bus voltage rise value is greater than the transient voltage rise upper limit value, reducing the current direct current power according to a preset power adjustment strategy, and entering a transient voltage acquisition unit.
The invention provides a method and a system for checking transient overvoltage after an extra-high voltage direct current fault, which comprises the following steps: determining the transient voltage rise upper limit value of a converter station bus of the alternating-current and direct-current hybrid power grid after the direct-current fault; respectively acquiring initial voltage of a converter station bus of the alternating-current and direct-current hybrid power grid before direct-current fault and maximum transient voltage of the converter station bus during the direct-current fault under the current direct-current power level; calculating a difference value between the maximum transient voltage and the initial voltage, wherein the difference value is used as a current converter station bus voltage rise value and is compared with the transient voltage rise upper limit value to obtain a check result; and when the checking result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value, taking the current direct current power as the maximum direct current transmission power of the alternating current-direct current hybrid power grid under the transient voltage rise constraint. The implementation method is simple and easy, the calculation efficiency can be obviously improved in the verification of the transient overvoltage after the direct current disturbance, the manpower and material resources are saved, and the obvious economic benefit is created; the method is suitable for transient voltage-rise fault checking after various direct current disturbances such as direct current bipolar locking, direct current continuous phase commutation failure, direct current bipolar twice full-voltage restart success, direct current bipolar twice full-voltage restart failure and the like.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
fig. 1 is a flowchart of a transient overvoltage checking method 100 after an extra-high voltage dc fault according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an ac/dc hybrid power grid according to an embodiment of the present invention;
fig. 3 is an equivalent circuit diagram of the ac-dc hybrid power grid after a fault and before a filter is removed according to the embodiment of the present invention;
fig. 4 is a simplified equivalent circuit diagram of the ac-dc hybrid power grid after a fault and when a filter is not cut off according to the embodiment of the present invention;
fig. 5 is a diagram of a relationship between a converter bus voltage and an equivalent reactance when a filter is not cut off after a fault occurs in the ac-dc hybrid power grid according to the embodiment of the present invention;
FIG. 6 is a flow chart of determining a DC maximum capability of a transient voltage rise constraint according to an embodiment of the present invention; and
fig. 7 is a schematic structural diagram of a transient overvoltage checking system 700 after an extra-high voltage dc fault according to an embodiment of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Fig. 1 is a flowchart of a transient overvoltage checking method 100 after an extra-high voltage dc fault according to an embodiment of the present invention. As shown in fig. 1, the method for checking the transient overvoltage after the extra-high voltage dc fault provided by the embodiment of the invention is simple and easy to implement, and can obviously improve the calculation efficiency, save manpower and material resources, and create obvious economic benefits in the checking of the transient overvoltage after the dc disturbance; the method is suitable for transient voltage-rise fault checking after various direct current disturbances such as direct current bipolar locking, direct current continuous phase commutation failure, direct current bipolar twice full-voltage restart success, direct current bipolar twice full-voltage restart failure and the like. The transient overvoltage checking method 100 after the extra-high voltage direct current fault provided by the embodiment of the invention starts from step 101, and determines the transient voltage rise upper limit value of a converter station bus of an alternating current-direct current hybrid power grid after the direct current fault in step 101.
In the embodiment of the invention, in order to determine the transient voltage rise upper limit value of the converter station bus of the alternating-current and direct-current hybrid power grid after the direct-current fault, it is required to determine the mode of the direct-current system which causes the maximum transient voltage rise after the direct-current fault when the direct-current system and the alternating-current system perform reactive power exchange.
Preferably, the determining the transient voltage rise upper limit value of the bus of the converter station after the direct-current fault of the alternating-current/direct-current hybrid power grid includes:
wherein, the delta U is a transient state pressure rise upper limit value; u shapeEThe highest operating voltage of the direct current conversion bus; u shapeBThe reference voltage is used for simulation calculation; u shapeIThe initial voltage of the bus when calculating for the simulation.
Preferably, wherein for 500kV DC current conversion bus, the highest operation voltage UEThe value of (b) is 530kV or 550 kV.
In an embodiment of the present invention, for a 500kV dc converter bus, the transient voltage rise can be calculated by the following formula:
wherein, the delta U is a transient state pressure rise upper limit value; u shapeTRepresenting a transient voltage after a fault; u0 represents the transient voltage before the fault; u shapeEThe maximum operating voltage of the 500kV direct current conversion bus; u shapeBFor simulating the reference voltage in the calculation software, UB＝525kV；UITaking the most severe condition into consideration for the initial voltage of the bus of the simulation calculation, and taking UI＝1.05*UB。
For different UEThe transient voltage rise upper limit values are also different, including:
(a) if the maximum operating voltage of the 500kV direct current conversion bus is considered to be UE530kV, then the transient voltage rise of the commutation bus after the dc fault must not exceed:
i.e. if the transient pressure rise limit is taken into account, there areTo obtain X04.8 × X. Therefore, if the extreme voltage U of the converter station is takenEWhen the equivalent reactance of the direct current filter is equal to 4.8 times of the equivalent impedance of the system, the transient voltage rise of the bus of the converter station reaches a limit value after the direct current fault.
(b) If the maximum operating voltage of the 500kV direct current conversion bus is considered to be UE550kV, then after the dc fault, the transient voltage rise of the commutation bus must not exceed:
that is, if the transient pressure rise limit is considered, there are:to obtain X04.2X. Therefore, if the extreme voltage U of the converter station is takenEWhen the equivalent reactance of the direct current filter is equal to 4.2 times of the equivalent impedance of the system, the transient voltage rise of the bus of the converter station reaches a limit value after the direct current fault.
Fig. 2 shows a schematic diagram of an ac/dc hybrid grid according to an embodiment of the present invention. After considering that the power grid has a dc blocking fault, the transient process that the filter has not been cut off, or the equivalent circuit of the system during the fault that the dc commutation fails is shown in fig. 3.
Let QrefWhich represents the reactive exchange between the dc system and the ac system. Because the reactive exchange principle in the design of the direct current system is to absorb reactive power from the system as much as possible (the reactive power can be provided by a matched power supply and the like, the filter has high manufacturing cost and is good in economic view, so that Q is goodrefTypically non-negative. At present, for different reactive power exchange modes, considering economic factors such as filter manufacturing cost and the like, the reactive power exchange between a direct current system and an alternating current system is generally determined as follows.
If the DC adopts an under-compensation mode, that is, the DC is absorbed from the AC system withoutAnd (3) power, performing reactive power exchange between the direct current system and the alternating current system: qex＝Qref+Q0Namely, the range of a group of filters is increased on the basis of the original dead zone.
If the direct current adopts an overcomplete mode, the reactive power exchange between the direct current system and the alternating current system is as follows: qex＝Qref-Q0The principle is to try not to compensate too much, especially when the dc power is large, to control within the range of a set of filters (also for economic considerations).
According to the reactive power exchange between the dc system and the ac system, the following three situations can be classified: (1) if QexThe reactive power provided by the filter is Q1(ii) a (2) If QexMore than 0, and the reactive power provided by the filter is Q in an under-compensation mode2(ii) a (3) If QexLess than 0, in the over-compensation mode, the reactive power provided by the filter is Q3(ii) a Wherein Q isexIs positive. Apparently Q3＞Q1＞Q2。
Then, the equivalent reactance X of the corresponding filter in the above three cases0(X0Positive number) is: x30＜X10＜X20。
Fig. 4 is a simplified equivalent circuit diagram of the ac/dc hybrid power grid after a fault and when the filter is not cut off. As shown in fig. 4, the overall equivalent impedance and voltage of the system are respectively:
Z＝R+j(X-X0)，
without loss of generality, R ≈ 0, then there are:
if the equivalent voltage U of the ac system is 1, there are:
thus, X0And UTThe functional relationship between them is shown in fig. 5. From the results shown in the figure, when X is present0< X and X0Greater than two intervals of X, X0Are all in harmony with UTPresenting a monotonically decreasing trend. If X0If the voltage is less than X, the capacity of the filter is very large, and the voltage of the converter station is negative at the moment, so that the situation does not exist in practice.
It can be further known that when the over-compensation mode is adopted for direct current, the equivalent reactance X of the filter is compared with the zero reactive power exchange and under-compensation mode30＜X10＜X20Then has UT3＞UT1＞UT2. Therefore, the transient voltage rise caused by the over-complement mode after the dc fault is larger than that caused by the zero reactive power exchange and the under-complement mode.
Therefore, in the embodiment of the present invention, the initial operation mode of the ac/dc hybrid grid is set to be the maximum overcomplete mode.
In step 102, an initial voltage of a converter station bus of the alternating current-direct current hybrid power grid before a direct current fault occurs and a maximum transient voltage of the converter station bus during the direct current fault are respectively obtained under the current direct current power level.
In step 103, a difference between the maximum transient voltage and the initial voltage is calculated, and the difference is used as a current converter station bus pressure rise value, and the current converter station bus pressure rise value is compared with the transient pressure rise upper limit value to obtain a check result.
In step 104, when the check result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value, taking the current direct current power as the maximum direct current transmission power of the alternating current-direct current hybrid power grid under the transient voltage rise constraint.
Preferably, wherein the method further comprises:
when the check result indicates that the current converter station bus voltage rise value is smaller than the transient voltage rise upper limit value, increasing the current direct current power according to a preset power adjustment strategy, and recalculating until the check result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value; and
and when the checking result indicates that the current converter station bus voltage rise value is greater than the transient voltage rise upper limit value, reducing the current direct current power according to a preset power adjustment strategy, and recalculating until the checking result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value.
In an embodiment of the invention, the method for determining the maximum direct-current transmission power under the constraint of the transient voltage rise upper limit of the bus of the converter station comprises the following steps: if the current converter station bus voltage rise is smaller than the transient voltage rise upper limit value under the given direct current power level, increasing the direct current power according to a preset power adjustment strategy, returning to the step 102 for recalculation until the check result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value; if the current converter station bus voltage rise is larger than the transient voltage rise upper limit value under the given direct current power level, reducing the direct current power according to a preset power adjustment strategy, returning to the step 102 for recalculation until the check result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value; and if the current bus voltage rise of the converter station is equal to the transient voltage rise upper limit value under the given direct current power level, determining the current direct current power as the maximum direct current power under the transient voltage rise constraint.
Fig. 6 is a flow chart of determining a dc maximum capability of a transient voltage rise constraint according to an embodiment of the invention. As shown in fig. 6, in the embodiment of the present invention, the process of checking the transient overvoltage after the extra-high voltage dc fault to determine the maximum dc capacity under the transient voltage rise constraint includes: determining an initial operation mode of alternating current and direct current in an alternating current and direct current hybrid power grid; determining a filter cut strategy; calculating the transient voltage rise delta U of the bus of the converter station after various direct current faults; comparing the determined transient voltage rise limit value delta Umax with the transient voltage rise delta U of the bus of the converter station; if the delta Umax-delta U is larger than a preset difference value beta under a given direct current power level, namely the current transient voltage rise delta U of the bus of the converter station is smaller than the transient voltage rise upper limit value delta Umax, the direct current power needs to be increased according to a preset power adjustment strategy; if the delta Umax-delta U is smaller than 0 under the given direct current power level, namely the current transient voltage rise delta U of the bus of the converter station is larger than the transient voltage rise upper limit value delta Umax, reducing the direct current power according to a preset power adjustment strategy; and if the value of the delta Umax-delta U is greater than or equal to 0 and less than or equal to a preset difference value beta under the given direct current power level, directly determining the current direct current power as the maximum direct current power under the transient voltage rise constraint. Among them, it should be noted that: beta should be as small as possible, generally not greater than 0.05, to reduce the error and ensure the stability of the determined dc power. The value of β can be set according to practical conditions, and is not limited to 0.05 mentioned in the present embodiment.
Fig. 7 is a schematic structural diagram of a transient overvoltage checking system 700 after an extra-high voltage dc fault according to an embodiment of the present invention. As shown in fig. 7, a transient overvoltage checking system 700 after an extra-high voltage dc fault according to an embodiment of the present invention includes: a transient voltage rise upper limit value determination unit 701, a transient voltage acquisition unit 702, a check result acquisition unit 703, and a maximum direct current transmission power determination unit 704.
Preferably, the transient voltage rise upper limit value determining unit 701 is configured to determine a transient voltage rise upper limit value of a converter station bus of the ac-dc hybrid grid after the dc fault.
Preferably, the determining unit 701 for the transient voltage rise upper limit value of the converter station bus of the ac-dc hybrid grid after the dc fault determines the transient voltage rise upper limit value of the converter station bus, including:
wherein, the delta U is a transient state pressure rise upper limit value; u shapeEThe highest operating voltage of the direct current conversion bus; u shapeBThe reference voltage is used for simulation calculation; u shapeIThe initial voltage of the bus when calculating for the simulation.
Preferably, wherein for 500kV DC current conversion bus, the highest operation voltage UEThe value of (b) is 530kV or 550 kV.
Preferably, the transient voltage obtaining unit 702 is configured to obtain, at a current dc power level, an initial voltage of a converter station bus of the ac-dc hybrid grid before a dc fault occurs and a maximum transient voltage of the converter station bus during the dc fault.
Preferably, the check result obtaining unit 703 is configured to calculate a difference between the maximum transient voltage and the initial voltage, where the difference is used as a current converter station bus voltage rise value, and compare the current converter station bus voltage rise value with the transient voltage rise upper limit value to obtain a check result.
Preferably, the maximum dc transmission power determining unit 704 is configured to, when the check result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value, use the current dc power as the maximum dc transmission power of the ac/dc hybrid grid under the transient voltage rise constraint.
Preferably, wherein the system further comprises: the direct current power adjusting unit is used for increasing the current direct current power according to a preset power adjusting strategy and entering the transient voltage obtaining unit when the checking result indicates that the current converter station bus voltage rise value is smaller than the transient voltage rise upper limit value; and when the checking result indicates that the current converter station bus voltage rise value is greater than the transient voltage rise upper limit value, reducing the current direct current power according to a preset power adjustment strategy, and entering a transient voltage acquisition unit.
The transient overvoltage checking system 700 after the extra-high voltage dc fault according to the embodiment of the present invention corresponds to the transient overvoltage checking method 100 after the extra-high voltage dc fault according to another embodiment of the present invention, and is not described herein again.
The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (8)

1. A method for checking transient overvoltage after an extra-high voltage direct current fault is characterized by comprising the following steps:
determining the transient voltage rise upper limit value of a converter station bus of the alternating-current and direct-current hybrid power grid after the direct-current fault;
respectively acquiring initial voltage of a converter station bus of the alternating-current and direct-current hybrid power grid before direct-current fault and maximum transient voltage of the converter station bus during the direct-current fault under the current direct-current power level;
calculating a difference value between the maximum transient voltage and the initial voltage, wherein the difference value is used as a current converter station bus pressure rise value, and the current converter station bus pressure rise value is compared with the transient pressure rise upper limit value to obtain a checking result;
and when the checking result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value, taking the current direct current power as the maximum direct current transmission power of the alternating current-direct current hybrid power grid under the transient voltage rise constraint.
2. The method of claim 1, wherein determining the transient voltage rise upper limit value of the converter station bus of the AC-DC hybrid power grid after the DC fault comprises:
wherein, the delta U is a transient state pressure rise upper limit value; u shapeEThe highest operating voltage of the direct current conversion bus; u shapeBThe reference voltage is used for simulation calculation; u shapeIThe initial voltage of the bus when calculating for the simulation.
3. The method of claim 2, wherein the maximum operating voltage U for a 500kV dc converter busEThe value of (b) is 530kV or 550 kV.
4. The method of claim 1, further comprising:
when the check result indicates that the current converter station bus voltage rise value is smaller than the transient voltage rise upper limit value, increasing the current direct current power according to a preset power adjustment strategy, and recalculating until the check result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value; and
and when the checking result indicates that the current converter station bus voltage rise value is greater than the transient voltage rise upper limit value, reducing the current direct current power according to a preset power adjustment strategy, and recalculating until the checking result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value.
5. A system for checking transient overvoltage after an extra-high voltage direct current fault is characterized by comprising:
the transient voltage rise upper limit value determining unit is used for determining the transient voltage rise upper limit value of a converter station bus of the alternating-current and direct-current series-parallel power grid after the direct-current fault;
the transient voltage acquisition unit is used for respectively acquiring the initial voltage of a converter station bus of the alternating-current and direct-current hybrid power grid before a direct-current fault occurs and the maximum transient voltage during the direct-current fault under the current direct-current power level;
a checking result obtaining unit, configured to calculate a difference between the maximum transient voltage and the initial voltage, where the difference is used as a current converter station bus pressure rise value, and compare the current converter station bus pressure rise value with the transient pressure rise upper limit value to obtain a checking result;
and the maximum direct-current transmission power determining unit is used for taking the current direct-current power as the maximum direct-current transmission power of the alternating-current and direct-current hybrid power grid under the transient voltage rise constraint when the checking result indicates that the current converter station bus voltage rise value is equal to the transient voltage rise upper limit value.
6. The system according to claim 5, wherein the transient voltage rise upper limit value determining unit determines a transient voltage rise upper limit value of a converter station bus of the AC/DC hybrid grid after the DC fault, and includes:
wherein, the delta U is a transient state pressure rise upper limit value; u shapeEThe highest operating voltage of the direct current conversion bus; u shapeBThe reference voltage is used for simulation calculation; u shapeIThe initial voltage of the bus when calculating for the simulation.
7. The system of claim 6, wherein the maximum operating voltage U for a 500kV DC converter busEThe value of (b) is 530kV or 550 kV.
8. The system of claim 1, further comprising:
the direct current power adjusting unit is used for increasing the current direct current power according to a preset power adjusting strategy and entering the transient voltage obtaining unit when the checking result indicates that the current converter station bus voltage rise value is smaller than the transient voltage rise upper limit value; and
and when the checking result indicates that the current converter station bus voltage rise value is greater than the transient voltage rise upper limit value, reducing the current direct current power according to a preset power adjustment strategy, and entering a transient voltage acquisition unit.
CN201910739488.2A 2019-08-12 2019-08-12 Method and system for checking transient overvoltage after extra-high voltage direct current fault Pending CN110601245A (en)

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Application publication date: 20191220