CN112310994B - Method for evaluating influence of power grid line outage on harmonic stability of alternating current-direct current system - Google Patents

Method for evaluating influence of power grid line outage on harmonic stability of alternating current-direct current system Download PDF

Info

Publication number
CN112310994B
CN112310994B CN202011181483.1A CN202011181483A CN112310994B CN 112310994 B CN112310994 B CN 112310994B CN 202011181483 A CN202011181483 A CN 202011181483A CN 112310994 B CN112310994 B CN 112310994B
Authority
CN
China
Prior art keywords
admittance
alternating current
direct current
line
equivalent
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.)
Active
Application number
CN202011181483.1A
Other languages
Chinese (zh)
Other versions
CN112310994A (en
Inventor
毛炽祖
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.)
Maintenance and Test Center of Extra High Voltage Power Transmission Co
Original Assignee
Maintenance and Test Center of Extra High Voltage Power Transmission Co
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 Maintenance and Test Center of Extra High Voltage Power Transmission Co filed Critical Maintenance and Test Center of Extra High Voltage Power Transmission Co
Priority to CN202011181483.1A priority Critical patent/CN112310994B/en
Publication of CN112310994A publication Critical patent/CN112310994A/en
Application granted granted Critical
Publication of CN112310994B publication Critical patent/CN112310994B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

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
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations
    • G06F17/15—Correlation function computation including computation of convolution operations
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/18—Network design, e.g. design based on topological or interconnect aspects of utility systems, piping, heating ventilation air conditioning [HVAC] or cabling
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/30—Circuit design
    • G06F30/36—Circuit design at the analogue level
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
    • G06Q50/00—Systems or methods specially adapted for specific business sectors, e.g. utilities or tourism
    • G06Q50/06—Electricity, gas or water supply
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/04—Power grid distribution networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H02J2003/365—Reducing harmonics or oscillations in HVDC
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics
    • 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]
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications

Abstract

The invention discloses an evaluation method for influence of power grid line outage on harmonic stability of an alternating current-direct current system, which comprises the following steps: taking a node of a flexible direct current system accessed to a transformer substation as a starting point, and layering an alternating current-direct current hybrid power grid; carrying out transfer function derivation on each layer of power grid obtained after layering under the condition of single flexible direct current system access and power grid N-1 faults; and calculating the sensitivity of each line parameter according to the closed loop transfer function expression of the single flexible direct current system accessed to the alternating current network with any port obtained by calculation, and screening out the maximum line link which is the weakest line link after the sensitivity is sorted. The invention has the beneficial effects that: by taking a node of a flexible direct current system accessed to a transformer substation as a starting point, the alternating current-direct current hybrid power grid is layered, the line parameter sensitivity and weak link identification are calculated, the weak link in the alternating current-direct current system is finally screened out, and a theoretical basis is provided for power grid operation mode management and power equipment model selection.

Description

Method for evaluating influence of power grid line outage on harmonic stability of alternating current-direct current system
Technical Field
The invention relates to the technical field of harmonic stability analysis of an alternating current-direct current hybrid power grid, in particular to an evaluation method for influence of power grid line outage on harmonic stability of an alternating current-direct current system.
Background
In recent years, broadband harmonic oscillation occurs in a plurality of flexible direct-current transmission projects based on Modular Multilevel Converters (MMC) at home and abroad in the debugging or running process, and the safe and stable running of an alternating-current and direct-current system is seriously threatened. With the wide-range popularization of flexible direct current engineering in different application occasions, a large number of power electronic devices and equipment are introduced into an alternating current-direct current system. In the current multi-terminal direct current transmission project, a transmitting-end Converter station usually adopts a thyristor-type power grid phase-change Converter (LCC), and a receiving end usually adopts a topological structure of two full-bridge and half-bridge mixed type MMC Converter stations. The MMC converter station comprises hundreds of high-capacity fully-controlled power semiconductor devices and a suspended direct-current energy storage capacitor, and the converter valve generally adopts a nonlinear modulation strategy and capacitor voltage balance based on a sequencing algorithm, so that the flexible direct-current converter station has strong nonlinearity and strong coupling characteristics. Therefore, when the flexible direct current converter station is under a certain control strategy or operation condition, certain specific frequency resonance points may exist with line impedance, series-parallel compensation devices and the like in the alternating current system, so that oscillation of the alternating current-direct current system is caused. Although resonance can be avoided when the flexible circuit is connected into the alternating current power grid, when N-1 disconnection fault occurs in the alternating current power grid to cause parameter change on the alternating current side, resonance can still be caused at certain frequency to threaten safe operation of the power grid.
Disclosure of Invention
The invention provides an evaluation method for the influence of power grid line outage on the harmonic stability of an alternating current-direct current system, which aims at solving the problem of the harmonic stability of the existing alternating current-direct current hybrid power grid and mainly solves the problem of the background technology.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a method for evaluating influence of power grid line outage on harmonic stability of an alternating current-direct current system comprises the following steps:
step S1: taking a node of a flexible direct current system accessed to a transformer substation as a starting point, and layering an alternating current-direct current hybrid power grid;
step S2: carrying out transfer function derivation on each layer of power grid obtained after S1 layering under the condition of single flexible direct current system access and power grid N-1 faults;
step S3: and (4) calculating the sensitivity of each line parameter according to a closed loop transfer function expression of the single flexible direct current system accessed to the alternating current network with any port obtained by calculation of S2, and sorting the sensitivity to obtain the largest link which is the weakest link.
The invention has the beneficial effects that: by taking a node of a flexible direct current system accessed to a transformer substation as a starting point, the alternating current-direct current hybrid power grid is layered, the line parameter sensitivity and weak link identification are calculated, the weak link in the alternating current-direct current system is finally screened out, and a theoretical basis is provided for power grid operation mode management and power equipment model selection.
Drawings
Fig. 1 is a flowchart of a method for evaluating influence of power grid line outage on harmonic stability of an ac/dc system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a three-port equivalent circuit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an equivalent admittance circuit of the AC/DC system disclosed in the embodiments of the present invention;
FIG. 4 is a schematic diagram of a single flexible line accessing a three-port equivalent circuit according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a single flexible line access multiport network according to an embodiment of the present invention;
fig. 6 is a schematic diagram of an equivalent circuit of a single flexible line access multiport network according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer and clearer, the following detailed description of the present invention is provided with reference to the accompanying drawings and detailed description. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some but not all of the relevant aspects of the present invention are shown in the drawings.
As shown in fig. 1, the present embodiment provides a method for evaluating an influence of a power grid line outage on harmonic stability of an ac/dc system, including the following steps:
step S1: taking a node of a flexible direct current system accessed to a transformer substation as a starting point, and layering an alternating current-direct current hybrid power grid;
step S1 specifically includes: taking a node of a flexible direct current system accessed to a transformer substation as a starting point, and taking a network formed by a simplest loop where the node of the transformer substation is located and a tail end node connected to the simplest loop as a first-layer network; then taking the nodes of the first layer network as first layer generalized nodes, a first layer simplest loop where the first layer generalized nodes are located, and a network formed by end nodes connected to the first layer simplest loop as a second layer network; and taking the nodes of the second-layer network as second-layer generalized nodes, the simplest loop of the second layer where the second-layer generalized nodes are located, and a network formed by the end nodes connected to the simplest loop of the second layer as a third-layer network, and so on to obtain the N-layer network.
Step S2: carrying out transfer function derivation on each layer of power grid obtained after S1 layering under the condition of single flexible direct current system access and power grid N-1 faults;
step S2 specifically includes: as shown in fig. 2, the harmonic stability analysis model for accessing the flexible dc system to the ac power grid is equivalent to a three-port equivalent circuit, one port of the three-port equivalent circuit is equivalent to the flexible dc system, and the other two ports are equivalent to the corresponding ac power grid 1 and ac power grid 2, respectively. The other two ports in the power grid can be simply regarded as a Thevenin branch equivalent circuit with a voltage source and impedance connected in series by using an alternating current system equivalent method; the ports for accessing the two alternating current systems are also connected with loads, and the loads are represented in the form of admittances. Meanwhile, in order to better analyze the problem, all impedances and admittances in the three-port equivalent circuit are uniformly expressed in an admittance form by using the KCL, KVL and norton equivalent theorem, so as to obtain the flexible direct current grid-connected alternating current and direct current system equivalent admittance circuit, as shown in fig. 3; in fig. 3, after all impedances in the ac/dc system are converted into admittance forms, the ac/dc system equivalent admittance circuit includes two naturally formed admittance matrices, where the first admittance matrix is a system network side admittance matrix that does not include power supply equivalent admittance, and the second admittance matrix is a total admittance matrix that includes power supply equivalent admittance, and a closed-loop transfer function of the ac/dc system is obtained according to the first admittance matrix and the second admittance matrix; solving an equivalent admittance transfer function at an alternating current side in the alternating current-direct current system, solving a closed-loop transfer function expression of the alternating current-direct current system according to the equivalent admittance transfer function, solving a closed-loop transfer function expression of a single flexible linear circuit accessed to an alternating current network with any port according to the closed-loop transfer function expression of the alternating current-direct current system, and further obtaining an open-loop transfer function expression.
Second layer admittance matrix YncComprises the following steps:
Figure BDA0002750318310000031
the result of the conversion is that,
Figure BDA0002750318310000032
first layer admittance matrix YnoComprises the following steps:
Figure BDA0002750318310000033
the result of the conversion is that,
Figure BDA0002750318310000034
and determining the total impedance matrix Znc：
Figure BDA0002750318310000035
Wherein, Yg1For AC systems 1 equivalent admittance, Vg1For an equivalent voltage, V, of the AC system 1b1For the voltage at the 1-port of the AC system, Ig1For an equivalent output current of the ac system 1,Yl1load equivalent admittance, Y, for access to port 1 of AC systemg2For AC system 2 equivalent admittance, Vg2For an equivalent voltage, V, of the AC system 2b2For an AC system 2-port voltage, Ig2For an equivalent output current, Y, of the AC system 2l2Equivalent admittance of load, G, for access to port 2 of AC systemclFor a flexible DC closed loop transfer function, IrefIs a reference value of current of a flexible direct current system, Vb3For a flexible DC system port voltage, YinvFor flexible DC system equivalent admittance, Ig3For flexible DC system output current, Yc1For line admittance, Y, between ports of AC system 1 and ports of AC system 2c2For line admittance, Y, between the 2-port and the flexible DC-port of the AC systemc3Is a line admittance between the port of the alternating current system 1 and the flexible direct current port; z11For the bus node self-impedance, Z, of the AC system 112And Z21Is the mutual impedance between the bus node of the alternating current system 1 and the bus node of the alternating current system 2, Z13And Z31Is the mutual impedance between the bus node of the alternating current system 1 and the bus node of the alternating current system 3, Z22For the self-impedance of the bus-bar node 2 of the AC system, Z23And Z32Is the mutual impedance between the bus node of the alternating current system 2 and the bus node of the alternating current system 3.
The method for calculating the closed loop transfer function expression of the flexible direct current system comprises the following steps: the formula (3) is converted into a formula,
Figure BDA0002750318310000041
the closed loop transfer function is obtained according to the equation (6), as shown in the equation (7), and the corresponding equivalent circuit is shown in fig. 4.
Figure BDA0002750318310000042
In the formula, YgridIs the equivalent impedance transfer function on the alternating current side.
The calculation method of the closed-loop transfer function expression comprises the following steps:listing the equivalent impedance Z from the power supply end of the flexible direct system to the AC-DC hybrid system33As can be seen in FIG. 4, Z33Actually, the equivalent impedance from the power supply end of the flexible direct system to the alternating current-direct current hybrid system is YinvAnd YgridInverse of the parallel admittance value of (a):
Figure BDA0002750318310000043
deriving Z from the matrix transformation relationship33The expression of (a) is, in order,
Figure BDA0002750318310000044
in the formula, YnomIs a matrix YncDeterminant of (4);
the expression (7) is calculated to obtain a closed-loop transfer function expression shown in the expression (10),
Figure BDA0002750318310000051
for an alternating current network with any port, a single flexible line access is considered, a network schematic diagram when a connection line of a node I and a node j is disconnected is shown in fig. 5, in the diagram, k represents a flexible line access substation node number, I and j are node numbers at two ends of a disconnected line, and Iref,kFor accessing a k-node flexible DC system current reference value, Yinv,kFor accessing k-node flexible DC system equivalent admittance, YcijFor line admittance between nodes i, j, m1+1 to m1+m2Numbering the nodes of the AC substation, Yg,m1+1Is an equivalent admittance, V, of an AC system m1+1g,m1+1Is an equivalent voltage of m1+1 of an AC system, Yg,m1+m2Is an equivalent admittance, V, of an alternating current system m1+ m2g,m1+m2Is the equivalent voltage of an alternating current system m1+ m 2. The equivalent circuit of the multiport network obtained by the same analysis method as that of the three-port network is shown in FIG. 6, in which IgkFor access to k-node flexibilityOutput current of DC system, VbkFor accessing the port voltage, Y, of the k-node flexible direct current systemgrid,kAnd connecting the k node into the flexible direct current system and then performing equivalent impedance transfer function on the alternating current side. And when the connection lines of the nodes i and j are disconnected, a single flexible direct access multiport network is established, a multiport network equivalent circuit is obtained by applying the analysis methods from (1) to (10), and a closed-loop transfer function expression of the single flexible direct access arbitrary port alternating-current network is calculated.
The method for calculating the closed-loop transfer function expression of the single flexible linear path accessing to the alternating current network with any port specifically comprises the following steps:
when the line between nodes i and j is down, Ycij0, pair admittance matrix YncThe influence of (a) is that,
diagonal line element
Figure BDA0002750318310000052
In the formula: y'iiFor node i self-admittance, Y after disconnectioniiIs self-admittance of node i before disconnection, Y'jjFor node j self-admittance, Y after disconnectionjjFor node j self-admittance, Y before disconnectioncijIs the line admittance between the nodes i and j;
off diagonal elements
Y′ij＝Y′ji＝Yij+Ycij (12)
In the formula: y'ijAnd Y'jiFor mutual admittance between nodes i, j after disconnection, YijMutual admittance between nodes i and j before disconnection;
solving the equivalent admittance transfer function Y of the multiport network equivalent circuitgrid,k，
Figure BDA0002750318310000053
In the formula: y isgrid,kThe k node is connected into the equivalent impedance transfer function, Z, of the alternating current side of the flexible direct current systemkkIs the self-impedance of node k, Yinv,kFor accessing the k-node flexible dc system equivalent admittance, and,
Figure BDA0002750318310000061
in the formula: mkkIs Ync,kMiddle element ZkkThe remainder type of (1);
the expression form of the closed loop transfer function of the single flexible line access to the alternating current network with any port is the same as that of the expression (10), as shown in the expression (15),
Figure BDA0002750318310000062
in the formula, k represents the node number of the flexible line access substation, I and j are the node numbers of two ends of a disconnected line, and Iref,kFor accessing a k-node flexible DC system current reference value, IgkAnd outputting current for connecting a k-node flexible direct current system.
Further obtaining an open-loop transfer function expression of the single flexible line access to the alternating current network with any port, as shown in formula (16),
Figure BDA0002750318310000063
step S3: and (4) calculating the sensitivity of each line parameter according to a closed loop transfer function expression of the single flexible direct current system accessed to the alternating current network with any port obtained by calculation of S2, and sorting the sensitivity to obtain the largest link which is the weakest link.
Step S3 specifically includes: the relative sensitivity of the parameters of the lines connected with the nodes i and j in the system is calculated by adopting the following formula
Figure BDA0002750318310000064
In the formula: rcijIs a line resistance, X, between nodes i, jcijIs a node i,A line reactance between j, which is used to connect the line R when a line break accident occurscijAnd XcijThe value of (d) is a positive real number between 600 and 1000;
and (3) calculating the relative sensitivity value of each line after a certain line in the alternating current power grid is disconnected by adopting the formula (17) under different frequencies, sorting the lines from large to small according to the magnitude relation of the relative sensitivity values, and screening the line with the highest sorting.
According to the method, the flexible direct-current system is accessed to the transformer substation node as a starting point, the alternating-current and direct-current series-parallel power grid is layered, the line parameter sensitivity and weak link identification are calculated, the weak link in the alternating-current and direct-current system is finally screened, and a theoretical basis is provided for power grid operation mode management and power equipment model selection.
The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention accordingly, and not to limit the protection scope of the present invention accordingly. All equivalent changes or modifications made in accordance with the spirit of the present disclosure are intended to be covered by the scope of the present disclosure.

Claims (7)

1. A method for evaluating the influence of power grid line outage on harmonic stability of an alternating current-direct current system is characterized by comprising the following steps:
step S1: taking a node of a flexible direct current system accessed to a transformer substation as a starting point, and layering an alternating current-direct current hybrid power grid;
step S2: carrying out transfer function derivation on each layer of power grid obtained after S1 layering under the condition of single flexible direct current system access and power grid N-1 faults;
step S3: according to a closed loop transfer function expression of a single flexible direct current system accessed to an alternating current network with any port obtained by calculation of S2, calculating the sensitivity of each line parameter, and screening out the maximum one after the sensitivity is sorted, namely the weakest link;
the step S1 specifically includes: taking a node of the flexible direct current system accessed to a transformer substation as a starting point, and taking a network formed by a simplest loop where the node of the transformer substation is located and a tail end node connected to the simplest loop as a first-layer network; then taking the nodes of the first-layer network as first-layer generalized nodes, a first-layer simplest loop where the first-layer generalized nodes are located, and a network formed by end nodes connected to the first-layer simplest loop as a second-layer network; taking the nodes of the second-layer network as second-layer generalized nodes, taking a network formed by a second-layer simplest loop where the second-layer generalized nodes are located and end nodes connected to the second-layer simplest loop as a third-layer network, and so on to obtain an N-layer network;
the step S2 specifically includes: the harmonic stability analysis model of the flexible direct current system accessed to the alternating current power grid is equivalent to a three-port equivalent circuit, one port of the three-port equivalent circuit is equivalent to the flexible direct current system, and the other two ports are equivalent to the corresponding alternating current power grid 1 and the corresponding alternating current power grid 2 respectively; uniformly expressing all impedance and admittance in the three-port equivalent circuit into an admittance form to obtain an AC/DC system equivalent admittance circuit of a flexible DC grid connection; the alternating current and direct current system equivalent admittance circuit comprises two layers of admittance matrixes which are naturally formed, wherein the first layer of admittance matrix is a system network side admittance matrix which does not contain power supply equivalent admittance, the second layer of admittance matrix is a total admittance matrix which contains power supply equivalent admittance, and a closed-loop transfer function of the alternating current and direct current system is obtained according to the first layer of admittance matrix and the second layer of admittance matrix; and solving an equivalent admittance transfer function at the AC side in the AC-DC system, solving a closed-loop transfer function expression of the AC-DC system according to the equivalent admittance transfer function, and solving a closed-loop transfer function expression of a single flexible linear path accessed to an AC network with any port according to the closed-loop transfer function expression of the AC-DC system, so as to obtain an open-loop transfer function expression.
2. The method of claim 1, wherein the second layer admittance matrix Y is a measure of the effect of grid line outages on harmonic stability of the ac/dc systemncComprises the following steps:
Figure FDA0003238842750000011
the result of the conversion is that,
Figure FDA0003238842750000021
the first layer admittance matrix YnoComprises the following steps:
Figure FDA0003238842750000022
the result of the conversion is that,
Figure FDA0003238842750000023
and determining the total impedance matrix Znc：
Figure FDA0003238842750000024
Wherein, Yg1For AC systems 1 equivalent admittance, Vg1For an equivalent voltage, V, of the AC system 1b1For the voltage at the 1-port of the AC system, Ig1For an equivalent output current, Y, of the AC system 1l1Load equivalent admittance, Y, for access to port 1 of AC systemg2For AC system 2 equivalent admittance, Vg2For an equivalent voltage, V, of the AC system 2b2For an AC system 2-port voltage, Ig2For an equivalent output current, Y, of the AC system 2l2Equivalent admittance of load, G, for access to port 2 of AC systemclFor a flexible DC closed loop transfer function, IrefIs a reference value of current of a flexible direct current system, Vb3For a flexible DC system port voltage, YinvFor flexible DC system equivalent admittance, Ig3Outputting current for flexible DC system，Yc1For line admittance, Y, between ports of AC system 1 and ports of AC system 2c2For line admittance, Y, between the 2-port and the flexible DC-port of the AC systemc3Is a line admittance between the port of the alternating current system 1 and the flexible direct current port; z11For the bus node self-impedance, Z, of the AC system 112And Z21Is the mutual impedance between the bus node of the alternating current system 1 and the bus node of the alternating current system 2, Z13And Z31Is the mutual impedance between the bus node of the alternating current system 1 and the bus node of the alternating current system 3, Z22For the self-impedance of the bus-bar node 2 of the AC system, Z23And Z32Is the mutual impedance between the bus node of the alternating current system 2 and the bus node of the alternating current system 3, Z33The equivalent impedance is seen from the power supply end of the flexible direct current system to the alternating current-direct current hybrid system.
3. The method for evaluating the influence of the line outage of the power grid on the harmonic stability of the alternating current-direct current system as claimed in claim 2, wherein the method for calculating the closed-loop transfer function expression of the flexible direct current system comprises the following steps: the formula (3) is converted into a formula,
Figure FDA0003238842750000025
obtaining the closed loop transfer function according to the formula (6), as shown in the formula (7)
Figure FDA0003238842750000031
In the formula, YgridIs the equivalent impedance transfer function on the alternating current side.
4. The method for evaluating the influence of the line outage of the power grid on the harmonic stability of the alternating current-direct current system according to claim 3, wherein the calculation method of the closed-loop transfer function expression comprises the following steps: listing the equivalent impedance Z from the power supply end of the flexible direct system to the AC-DC hybrid system33：
Figure FDA0003238842750000032
Deriving Z from the matrix transformation relationship33The expression of (a) is, in order,
Figure FDA0003238842750000033
in the formula, YnomIs a matrix YncDeterminant of (4);
the expression (7) is calculated to obtain a closed-loop transfer function expression shown in the expression (10),
Figure FDA0003238842750000034
5. the method for evaluating the influence of the outage of the power grid line on the harmonic stability of the alternating current-direct current system according to claim 4, wherein a single flexible line access is considered for the alternating current network with any port, a single flexible line access multi-port network is established when the connection lines of the nodes i and j are disconnected, the multi-port network equivalent circuit is obtained by applying the analysis methods from (1) to (10), and a closed-loop transfer function expression of the single flexible line access alternating current network with any port is calculated.
6. The method for evaluating the influence of the line outage of the power grid on the harmonic stability of the alternating current-direct current system according to claim 5, wherein the calculation method of the closed-loop transfer function expression of the single flexible line accessing the alternating current network with any port specifically comprises the following steps:
when the line between nodes i and j is down, Ycij0, pair admittance matrix YncThe influence of (a) is that,
diagonal line element
Figure FDA0003238842750000035
In the formula: y'iiFor node i self-admittance, Y after disconnectioniiIs self-admittance of node i before disconnection, Y'jjFor node j self-admittance, Y after disconnectionjjFor node j self-admittance, Y before disconnectioncijIs the line admittance between the nodes i and j;
off diagonal elements
Y′ij＝Y′ji＝Yij+Ycij (12)
In the formula: y'ijAnd Y'jiFor mutual admittance between nodes i, j after disconnection, YijMutual admittance between nodes i and j before disconnection;
solving an equivalent admittance transfer function Y of the multiport network equivalent circuitgrid,k，
Figure FDA0003238842750000041
In the formula: y isgrid,kThe k node is connected into the equivalent impedance transfer function, Z, of the alternating current side of the flexible direct current systemkkIs the self-impedance of node k, Yinv,kFor accessing the k-node flexible dc system equivalent admittance, and,
Figure FDA0003238842750000042
in the formula: mkkIs Ync,kMiddle element ZkkThe remainder type of (1);
the expression form of the closed loop transfer function of the single flexible line access to the alternating current network with any port is the same as that of the expression (10), as shown in the expression (15),
Figure FDA0003238842750000043
in the formula, k represents the flexible line access substation node number, i and j are disconnectedNode numbers at both ends of the line, Iref,kFor accessing a k-node flexible DC system current reference value, IgkOutputting current for accessing a k-node flexible direct current system;
further obtaining an open-loop transfer function expression of the single flexible line access to the alternating current network with any port, as shown in formula (16),
Figure FDA0003238842750000044
7. the method for evaluating the influence of the grid line outage on the harmonic stability of the ac-dc system according to claim 6, wherein the step S3 specifically comprises: the relative sensitivity of the parameters of the lines connected with the nodes i and j in the system is calculated by adopting the following formula
Figure FDA0003238842750000045
In the formula: rcijIs a line resistance, X, between nodes i, jcijIs a line reactance between nodes i and j, and when a line disconnection accident occurs, the line R is connectedcijAnd XcijThe value of (d) is a positive real number between 600 and 1000;
and calculating the relative sensitivity value of each line after a certain line in the alternating current power grid is disconnected by adopting the formula (17) under different frequencies, sorting the lines from large to small according to the magnitude relation of the relative sensitivity values, and screening the line with the highest sorting.
CN202011181483.1A 2020-10-29 2020-10-29 Method for evaluating influence of power grid line outage on harmonic stability of alternating current-direct current system Active CN112310994B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202011181483.1A CN112310994B (en) 2020-10-29 2020-10-29 Method for evaluating influence of power grid line outage on harmonic stability of alternating current-direct current system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202011181483.1A CN112310994B (en) 2020-10-29 2020-10-29 Method for evaluating influence of power grid line outage on harmonic stability of alternating current-direct current system

Publications (2)

Publication Number Publication Date
CN112310994A CN112310994A (en) 2021-02-02
CN112310994B true CN112310994B (en) 2021-11-16

Family

ID=74331469

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202011181483.1A Active CN112310994B (en) 2020-10-29 2020-10-29 Method for evaluating influence of power grid line outage on harmonic stability of alternating current-direct current system

Country Status (1)

Country Link
CN (1) CN112310994B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113364007B (en) * 2021-06-07 2023-06-23 广东电网有限责任公司 Two-dimensional admittance model construction method, device, terminal and readable storage medium
CN117728478B (en) * 2024-02-08 2024-04-19 四川大学 Harmonic wave transmission analysis method for line segment of parallel three-terminal direct current transmission system

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108667027A (en) * 2018-05-15 2018-10-16 四川大学 Ac and dc systems power flow transfer search containing flexible direct current and quantitative analysis method
CN109802406A (en) * 2019-04-01 2019-05-24 云南电网有限责任公司 A method of analysis flexible DC transmission access system resonance stability
CN110783968A (en) * 2019-10-09 2020-02-11 深圳供电局有限公司 Alternating current-direct current power grid fragile line analysis method and system
CN111652469A (en) * 2020-04-29 2020-09-11 国网河南省电力公司电力科学研究院 Weak link identification method and system for alternating current-direct current hybrid power grid

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108667027A (en) * 2018-05-15 2018-10-16 四川大学 Ac and dc systems power flow transfer search containing flexible direct current and quantitative analysis method
CN109802406A (en) * 2019-04-01 2019-05-24 云南电网有限责任公司 A method of analysis flexible DC transmission access system resonance stability
CN110783968A (en) * 2019-10-09 2020-02-11 深圳供电局有限公司 Alternating current-direct current power grid fragile line analysis method and system
CN111652469A (en) * 2020-04-29 2020-09-11 国网河南省电力公司电力科学研究院 Weak link identification method and system for alternating current-direct current hybrid power grid

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Research on fault location method of VSC-MTDC power grid;Kun Zhao 等;《2017 China International Electrical and Energy Conference (CIEEC)》;20171027;754-760 *

Also Published As

Publication number Publication date
CN112310994A (en) 2021-02-02

Similar Documents

Publication Publication Date Title
CN112310994B (en) Method for evaluating influence of power grid line outage on harmonic stability of alternating current-direct current system
CN104281979B (en) Distribution transformer platform area low voltage failure type detection method and system
CN105977934B (en) A kind of power distribution network intelligence Sofe Switch service restoration method for considering load importance
CN107086591A (en) A kind of three-phase imbalance adjuster based on reactive-load compensation and intelligent commutation
CN108226713A (en) A kind of concentric relaxation sag exposed areas analysis method of voltage dip
CN108233383A (en) A kind of economic load dispatching method of AC-DC interconnecting power network
CN105095590B (en) A kind of modeling method of the electromechanical transient simulation system based on three sequence equivalent impedances
CN106229970A (en) Micro-capacitance sensor method for estimating state based on converter Control characteristic
CN110780132B (en) Method for detecting reliability of alternating current and direct current power system node containing multi-terminal direct current system
CN105762845B (en) ± 10kV flexible direct current power distribution network incoming transport power grid modes determine method
CN110768285A (en) Method for obtaining strength of alternating current-direct current hybrid direct current multi-feed-in receiving-end power grid
CN108599226B (en) True bipolar MMC-HVDC system line overload emergency control method
Li et al. Evaluation of critical node groups in cyber-physical power systems based on pinning control theory
Zhang et al. Calculation and analysis of total supply capability of AC/DC hybrid distribution network considering load balance
CN110048427A (en) A kind of multiterminal flexible direct current distribution power flow protection fixed value calculation method
Chen et al. Summary of research on multi-infeed short circuit ratio in AC and DC systems
Yi et al. An unified power flow method of hybrid AC/DC power system with VSC-MTDC
CN110661260B (en) Power grid load flow calculation method based on four-winding induction filter transformer equivalent model
CN106291207A (en) A kind of chain type SVG module test system, platform and method
CN106786498A (en) A kind of main website substation data cooperative identification method and its device
CN113125882A (en) Power line route loss real-time monitoring system based on Internet of things
CN114362181B (en) Uniform harmonic state estimation method suitable for alternating current-direct current hybrid power grid
Lu et al. A unified power flow model for three-phase transformers in medium and low voltage distribution networks
CN114243711B (en) Large-scale power grid voltage sag evaluation method based on change branch influence domain
Zhang et al. Electromechanical Transient Simulation of AC-DC Hybrid Power System Considering MMC Model

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
GR01 Patent grant
GR01 Patent grant