CN113517713B - Static voltage safety domain analysis method and device suitable for alternating current-direct current hybrid system - Google Patents

Static voltage safety domain analysis method and device suitable for alternating current-direct current hybrid system Download PDF

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CN113517713B
CN113517713B CN202111069182.4A CN202111069182A CN113517713B CN 113517713 B CN113517713 B CN 113517713B CN 202111069182 A CN202111069182 A CN 202111069182A CN 113517713 B CN113517713 B CN 113517713B
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voltage
node
direct current
power
alternating current
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CN113517713A (en
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陈波
李宇骏
熊华强
程思萌
陈秋逸
陶翔
刘思宁
汪硕承
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State Grid Corp of China SGCC
Xian Jiaotong University
Electric Power Research Institute of State Grid Jiangxi Electric Power Co Ltd
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State Grid Corp of China SGCC
Xian Jiaotong University
Electric Power Research Institute of State Grid Jiangxi Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • 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
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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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Abstract

The invention discloses a static voltage safety domain evaluation method and a device suitable for an alternating current-direct current hybrid system, wherein the method comprises the steps of firstly calculating the power flow of the system in a normal state based on an alternating current-direct current system mathematical model; carrying out Taylor expansion on a system power balance equation, and neglecting a high-order term which has small influence on voltage change to obtain a rapid calculation formula of the voltage change; respectively calculating voltage changes by taking the equivalence of various serious accidents in the region as corresponding disturbances; and (4) integrating the voltage change under each accident to obtain the maximum value, and determining the static voltage security domain of each node according to the specified upper and lower voltage limits. The invention considers the operation characteristics of the AC-DC hybrid system and provides the load flow calculation method of the AC-DC system, and the load flow calculation method of the AC-DC system has the advantages that complex numerical calculation is not needed, the voltage change of the system can be calculated through a simple analytical formula, and the method can be used for online real-time monitoring.

Description

Static voltage safety domain analysis method and device suitable for alternating current-direct current hybrid system
Technical Field
The invention belongs to the technical field of electric power, and particularly relates to a static voltage safety domain analysis method and device suitable for an alternating current-direct current hybrid system.
Background
In recent years, with the development of an extra-high voltage direct current technology, a plurality of extra-high voltage direct current lines with long distance and large capacity are put into operation successively, which has a great influence on the reactive voltage of an extra-high voltage direct current near-region power grid and puts new requirements on the regulation and control of the voltage of the near-region power grid, so that the realization of safety prevention control of the power grid and the online evaluation of the safety margin of the power grid are of great importance. The concept of security region, originally introduced in the seventies of the twentieth century, is defined as a set of state variables such as injected power, voltage, phase angle, etc., that satisfy the security constraints of the system. The security domain analysis method is mainly used for obtaining the conclusion whether the system is safe or not by calculating the boundary expression of the security domain of the operating point and then comparing the position of the current operating point in the security domain.
However, the current research on the voltage safety domain mainly aims at the alternating current system, the influence of the direct current line after operation on the voltage safety domain of the power grid is less considered, and a rapid calculation and analysis method suitable for the voltage safety domain of the alternating current-direct current hybrid system is also lacked.
Disclosure of Invention
The present invention provides a static voltage safety domain analysis method and device suitable for an ac/dc hybrid system, which are used to solve at least one of the above technical problems.
In a first aspect, the present invention provides a static voltage safety domain analysis method suitable for an ac/dc hybrid system, including: respectively establishing an alternating current mathematical model and a direct current system mathematical model based on the running characteristics of an alternating current-direct current hybrid system, wherein the alternating current mathematical model comprisesThe direct current system mathematical model comprises a direct current system equation, and the direct current system equation comprises a direct current system power balance equation; correcting the power balance equation of the alternating current system according to the power balance equation of the direct current system to obtain a power balance equation of an alternating current-direct current hybrid system; expanding the power balance equation of the alternating current-direct current hybrid system according to Taylor series, and only retaining a primary term to obtain a linear analysis model, wherein the expression of the linear analysis model is as follows: Δ X ═ f' X (X)0，Y0)]-1(ΔW-f′y(X0，Y0) Δ Y), wherein X0、Y0Respectively is a state vector consisting of node voltage phase angles in the normal running state of the system and a network parameter, f 'in the normal running state of the system'x(X0，Y0) Is the derivative of the power balance equation to the node voltage, f'y(X0，Y0) The derivative of a power balance equation to the branch admittance is shown, wherein delta X is the voltage change of the AC-DC hybrid system, delta W is the power change of the AC-DC hybrid system, and delta Y is the network parameter change of the AC-DC hybrid system; correcting a Jacobian matrix of an alternating current system Newton-Raphson method according to the direct current system equation to obtain a Newton-Raphson solution of the alternating current-direct current system power flow calculation, and performing iterative convergence on the Newton-Raphson solution to obtain a power flow result under the normal operation condition of the alternating current-direct current hybrid system; calculating the voltage change of each node of a certain fault in an expected fault set according to the linear analysis model and the load flow result; and calculating a static voltage security domain by taking the maximum value based on the acquired voltage change of each node of a certain fault.
In a second aspect, the present invention provides a static voltage safety domain analyzing apparatus suitable for an ac/dc hybrid system, including: the establishing module is configured to respectively establish an alternating current mathematical model and a direct current system mathematical model based on the running characteristics of the alternating current-direct current hybrid system, wherein the alternating current mathematical model comprises an alternating current system power balance equation, the direct current system mathematical model comprises a direct current system equation, and the direct current system equation comprises direct current system powerA balance equation; the first correction module is configured to correct the alternating current system power balance equation according to the direct current system power balance equation so as to obtain a power balance equation of an alternating current-direct current hybrid system; the expansion module is configured to expand a power balance equation of the alternating current-direct current hybrid system according to a Taylor series, and only one term is reserved to obtain a linearization analysis model, wherein the expression of the linearization analysis model is as follows: Δ X ═ f'x(X0，Y0)]-1(ΔW-f′y(X0，Y0) Δ Y), wherein X0、Y0Respectively is a state vector consisting of node voltage phase angles in the normal running state of the system and a network parameter, f 'in the normal running state of the system'x(X0，Y0) Is the derivative of the power balance equation to the node voltage, f'y(X0，Y0) The derivative of a power balance equation to the branch admittance is shown, wherein delta X is the voltage change of the AC-DC hybrid system, delta W is the power change of the AC-DC hybrid system, and delta Y is the network parameter change of the AC-DC hybrid system; the second correction module is configured to correct a Jacobian matrix of an alternating current system Newton-Raphson method according to the direct current system equation, so that a Newton-Raphson solution of the alternating current-direct current system power flow calculation is obtained, iterative convergence is performed on the Newton-Raphson solution, and a power flow result under the normal operation condition of the alternating current-direct current hybrid system is obtained; the calculation module is configured to calculate the voltage change of each node of a certain fault in an expected fault set according to the linear analysis model and the load flow result; and the selecting module is used for calculating a static voltage security domain by taking the maximum value based on the acquired voltage change of each node of a certain fault.
In a third aspect, an electronic device is provided, comprising: the apparatus comprises at least one processor and a memory communicatively coupled to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executable by the at least one processor to enable the at least one processor to perform the steps of the static voltage security domain analysis method applicable to the hybrid ac/dc system according to any embodiment of the present invention.
In a fourth aspect, the present invention also provides a computer-readable storage medium, on which a computer program is stored, the computer program comprising program instructions which, when executed by a computer, cause the computer to perform the steps of the method for analyzing a static voltage safety domain applicable to an ac/dc hybrid system according to any embodiment of the present invention.
According to the static voltage safety domain analysis method and device applicable to the alternating current-direct current hybrid system, a mathematical model of the interchange and direct current system is adopted, load flow calculation is carried out on the basis to obtain the voltage of the alternating current-direct current hybrid system in a normal state, the mathematical model of the alternating current-direct current hybrid system is linearized to obtain a mathematical analytic expression for rapidly calculating the voltage change, and therefore the rapid calculation of the static voltage safety domain is achieved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flowchart of a static voltage safety domain analysis method applicable to an ac/dc hybrid system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an embodiment of the present invention for testing an AC/DC power system;
fig. 3 is a block diagram of a static voltage safety domain analysis apparatus suitable for an ac/dc hybrid system according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a flowchart of a static voltage safety domain analysis method for an ac/dc hybrid system according to the present application is shown.
As shown in fig. 1, a static voltage safety domain analysis method suitable for an ac/dc hybrid system includes the following steps:
step S101, an alternating current mathematical model and a direct current system mathematical model are respectively established based on the running characteristics of an alternating current-direct current hybrid system, wherein the alternating current mathematical model comprises an alternating current system power balance equation, the direct current system mathematical model comprises a direct current system equation, and the direct current system equation comprises a direct current voltage equation and a direct current system power balance equation.
In this embodiment, the power balance equation of the ac system is:
Figure GDA0003380197670000041
in the formula,. DELTA.PiFor node i active power correction, PGiActive power, P, generated for node i generatorLiActive power absorbed for node i load, UiIs the voltage amplitude of node i, UjIs the voltage amplitude, G, of node jijIs the real part of the ith row and jth column element of the node admittance matrix, thetaijIs the i, j voltage phase difference, BijFor the imaginary part, Δ Q, of the ith row and jth column element of the node admittance matrixiFor node i reactive power correction, QGiReactive power, Q, generated for node i generatorLiReactive power absorbed for the node i load.
Assuming that the rectifying side of the direct current circuit adopts constant current control and the inverting side adopts constant turn-off angle control, the direct current control equation is as follows: i isd＝Ids，γ＝γs (2)
In the formula IdFor direct transmission line current, IdsIs a DC current reference value, gamma is a turn-off angle, gammasIs the off angle reference value.
The dc system voltage equation can be obtained:
Udi＝Udi0cosγ-Iddxi (3)
Udr＝Udi+RdcId (4)
the power balance equation of the direct current system:
Figure GDA0003380197670000051
where γ is the off angle, dxiIs an equivalent commutation resistance, PdiFor injecting active power into the inverter station, UdiFor inverting station DC voltage, IdFor direct transmission line current, QdiIn order to inject reactive power into the inverter station,
Figure GDA0003380197670000053
for the angle of the power factor of the inverter station, Udi0For a DC no-load voltage of the inverter station, PdrFor injecting active power into the rectifying station, UdrFor a direct voltage of the rectifier station, QdrIn order to inject reactive power into the rectifying station,
Figure GDA0003380197670000054
is the power factor angle, U, of the rectifier stationdr0Is the rectifier station DC no-load voltage.
The relation of the AC-DC mathematical model is as follows:
Figure GDA0003380197670000052
in the formula of Udr0For a DC no-load voltage of the rectifier station, Udi0For DC no-load voltage of inverter station, Ui、UrRespectively being inverter stationsAnd the AC bus voltage of the rectifier station, T is the rated voltage ratio of the transformer, and c is the AC/DC voltage relation constant of the converter station.
And S102, correcting the power balance equation of the alternating current system according to the power balance equation of the direct current system to obtain the power balance equation of the alternating current-direct current hybrid system.
And S103, expanding the power balance equation of the alternating current-direct current hybrid system according to Taylor series, and only retaining a primary term to obtain a linear analysis model.
In this embodiment, the variables affecting the power balance equation include the node voltage and the admittance of each branch, which are respectively denoted by X and Y, and when the system is in normal operation, equation (1) can be expressed as:
f(X0，Y0)＝0 (11)
after the system is disturbed, equation (11) becomes:
f(X0+ΔX，Y0+ΔY)＝ΔW (12)
a taylor series expansion is performed on equation (12):
Figure GDA0003380197670000061
since the change of the node voltage X is small, it can be ignored (Δ X)2And Δ X Δ Y terms as well as higher order terms. f (X)0，Y0) Is a linear function of Y, so f ″)yy(X0，Y0)＝0。
Therefore, equation (13) can be simplified as:
f(X0，Y0)+f′x(X0，Y0)ΔX+f′y(X0，Y0)ΔY＝f(X0+ΔX，Y0+ΔY) (14)
the linear analysis model for calculating the delta X can be obtained by arranging the formula (14), and the expression is as follows:
ΔX＝[f′x(X0，Y0)]-1(ΔW-f′y(X0，Y0)ΔY) (15)
in the formula, X0、Y0Respectively is a state vector consisting of node voltage phase angles in the normal running state of the system and a network parameter, f 'in the normal running state of the system'x(X0，Y0) Is the derivative of the power balance equation to the node voltage, namely the modified Jacobian matrix f'y(X0，Y0) The derivative of the power balance equation to the branch admittance is shown, Δ X is the voltage change of the AC/DC hybrid system, Δ W is the power change of the AC/DC hybrid system, and Δ Y is the network parameter change of the AC/DC hybrid system.
And S104, correcting the Jacobian matrix of the Newton-Raphson method of the alternating current system according to the direct current system equation to obtain a Newton-Raphson solution of the tidal current calculation of the alternating current-direct current system, and performing iterative convergence on the Newton-Raphson solution to obtain a tidal current result under the normal operation condition of the alternating current-direct current hybrid system.
In this embodiment, the state quantities of the system are subjected to partial derivation based on equation (1) to obtain a jacobian matrix of the alternating-current system newton-raphson method:
Figure GDA0003380197670000062
in the formula, H is a partial derivative matrix of the active power correction amount to the voltage phase angle, N is a partial derivative matrix of the active power correction amount to the voltage amplitude, M is a partial derivative matrix of the reactive power correction amount to the voltage phase angle, L is a partial derivative matrix of the reactive power correction amount to the voltage amplitude, and HijIs the partial derivative, delta P, of the active power correction at node i to the phase angle of the voltage at node jiIs the active power correction of node i, θjIs the voltage phase angle, U, of node jjIs the voltage amplitude of node j, NijIs the partial derivative, M, of the active power correction at node i to the voltage amplitude at node jijIs the partial derivative, L, of the reactive power correction at node i to the phase angle of the voltage at node jijIs the partial derivative of the reactive power correction at node i to the voltage amplitude at node j. Delta QiThe node i reactive power correction.
For a direct current system, the converter station alternating current bus can be treated as a PQ node, and only the direct current injection power needs to be added into the balance equation of the converter station alternating current bus, namely the equation (5). The power balance equation of the alternating current bus of the converter station is as follows:
Figure GDA0003380197670000071
in the formula, i is an AC bus node of the inverter station, r is an AC bus node of the rectifier station, and delta PiFor the active power correction, Delta Q, of the AC bus node of the inverter stationiFor correction of reactive power at AC bus nodes of an inverter station, Delta QrFor the rectification station AC bus node reactive power correction, Δ PrFor the active power correction of the AC bus-bar node of the station, PdiFor injecting active power into the inverter station, PdrFor injecting active power into the rectifying station, QdiFor injecting reactive power, Q, into the inverter stationdrIs the reactive power injected into the rectifying station.
And obtaining a correction quantity according to the equation (5) by using the Jacobian matrix element corresponding to the AC bus of the converter station:
Figure GDA0003380197670000072
Figure GDA0003380197670000073
Figure GDA0003380197670000074
Figure GDA0003380197670000075
in the formula,. DELTA.NrrIs partial derivative, P, of active power injected into the station on the AC bus voltage of the stationdrFor rectifying by injectionActive power of the station, UrFor the amplitude of the AC bus voltage at the rectifying station, Δ NriIs partial derivative, U, of active power injected into the rectifying station on the AC bus voltage of the inverter stationiIs the voltage amplitude of the AC bus of the inverter station, c is the AC/DC voltage relation constant of the converter station, IdIs the current of the direct current transmission line, gamma is the turn-off angle, and delta LrrPartial derivative, Q, of reactive power injected into the station on the AC bus voltage of the stationdrFor injecting reactive power into the rectifying station, Udr0Is a DC no-load voltage of the rectifier station, Δ LriIs partial derivative, U, of reactive power injected into the rectifying station on the AC bus voltage of the inverter stationdrFor the direct voltage of the rectification station, Δ NirIs partial derivative, delta N, of active power injected into the inverter station on the AC bus voltage of the rectifier stationiiPartial derivative P of active power injected into inverter station to AC bus voltage of inverter stationdiFor injecting active power, Δ L, into the inverter stationirIs partial derivative, Q, of reactive power injected into the inverter station on the AC bus voltage of the rectifier stationdiFor injecting reactive power, Δ L, into the inverter stationiiIs partial derivative, U, of reactive power injected into the station on the AC bus voltage of the stationdiFor inverting station DC voltage, Udi0The voltage is the DC no-load voltage of the inverter station.
And (3) correcting the formula (7) based on the formula (9), and finally obtaining a Newton-Raphson solution for load flow calculation of the AC/DC system:
Figure GDA0003380197670000081
θi (k+1)＝θi (k)+Δθi (k)(i＝1，2，...，n-1)
Ui (k+1)＝Ui (k)+ΔU(k)(i＝1，2，...，m) (10)
in the formula,. DELTA.theta.(k)As a correction of the voltage phase angle in the kth iteration, H(k)Is a partial derivative matrix, N ', of the active power correction quantity to the voltage phase angle in the k iteration'(k)Is a partial derivative matrix of the active power correction quantity to the voltage amplitude in the k iteration, delta P(k)Is the correction of the active power, Δ U, in the kth iteration(k)For correction of the voltage amplitude in the kth iteration, M(k)Is a partial derivative matrix, L ', of reactive power correction quantity to voltage phase angle'(k)Is a partial derivative matrix, delta Q, of the reactive power correction to the voltage amplitude in the kth iteration(k)For the correction of reactive power in the kth iteration, θi (k+1)For the voltage phase angle, theta, of node i in the (k + 1) th iterationi (k)For the voltage phase angle, Δ θ, of node i in the kth iterationi (k)Is the correction of the voltage phase angle of node i in the kth iteration, Ui (k+1)For the voltage amplitude of node i in the (k + 1) th iteration, Ui (k)For the voltage amplitude of node i, Δ U, in the kth iteration(k)And the voltage amplitude correction quantity of the node i in the kth iteration is shown, n is the number of nodes of the system, and m is the number of PQ nodes in the system.
And (5) iteratively converging the equation (10) to obtain a power flow result under the normal operation condition of the alternating current and direct current series-parallel system.
And step S105, calculating the voltage change of each node of a certain fault in the expected fault set according to the linear analysis model and the load flow result.
In this embodiment, the anticipated failure set may include a new energy station offline failure, a high voltage dc lockout failure, and a line disconnect failure.
Specifically, the voltage change under the condition of the offline fault of the new energy station is calculated as follows:
the new energy station is connected to the power system through the converter station, and the station only affects the power of the injection node when being off-line, so that the Δ W in the formula (15) is [ 00.. -. P ═ Pw 0]T，PwFor the operating power of the new energy station before the offline, the position in Δ W corresponds to the node number of the offline new energy access, and since the network topology is not changed, Δ Y is equal to 0, then the fast calculation formula of the voltage change in the accident is:
ΔW＝[f′x(X0，Y0)]-1ΔW (16)
calculating the voltage change under the condition of the high-voltage direct-current blocking fault:
when a single-stage blocking fault occurs in an extra-high voltage direct current line, reactive power consumed by a blocking pole is instantly reduced to 0, a compensation device of the direct current line is not cut off, and the surplus of the reactive power can cause the voltage of a system to be increased, possibly causing the voltage to be out of limit. The direct current blocking influences the node injection power of load flow calculation, and delta W is [ 00.. 0.4P ]dr ... -0.4Pdi ... 0.5Qdr ... 0.5Qdi ... 0 0]TIf the position in Δ W corresponds to the node number of the converter station at the two ends of the locked dc transmission line, and the network topology is not changed, so Δ Y is equal to 0, the fast calculation formula of the voltage change in the event is still formula (15).
And calculating the voltage change under the condition of line disconnection fault:
only considering single circuit broken line trouble, after the circuit broken line takes place, Δ W is 0 when the steady state, and the quick calculation formula of voltage change under this accident is:
ΔX＝[f'x(X0,Y0)]-1(-f'y(X0,Y0)ΔY) (17)
let the total number of branches in the system be b, nodes at two ends of the disconnection branch be i and j, and only the element corresponding to the branch ij in the delta Y is a nonzero element. Assuming that the branch ij is a double-circuit line and one circuit line is disconnected, then:
Figure GDA0003380197670000091
in the formula,. DELTA.YijFor branch ij corresponding element, y in the post-fault path admittance change matrixijFor branch ij admittance modulus, GijFor branch ij admittance real part, BijThe imaginary part is admittance for branch ij.
If the total number of nodes in the system is N, fy' (X, Y) is a 2 Nxb order matrix, and the power balance equation of only the i and j nodes has a direct relationship with the admittance of the branch ij, so that the matrix has only four non-zero elements.
Figure GDA0003380197670000101
Figure GDA0003380197670000102
Figure GDA0003380197670000103
Figure GDA0003380197670000104
In the formula,. DELTA.PiFor the active power variation of node i after fault, yijFor branch ij admittance modulus, UiIs the voltage amplitude of node i, thetaijIs the voltage phase difference of the nodes i and j, BijAdmittance of the imaginary part, G, for branch ijijFor branch ij admittance real part, Δ PjIs the active power variation of the node j after the fault, UjFor the voltage amplitude of node i, Δ QiFor the post-fault node i reactive power variation, bij01/2, Δ Q accommodated for branch ij to groundjAnd the variable quantity of the reactive power of the node j after the fault. The combined formulae (18) and (19) give:
Figure GDA0003380197670000105
the voltage change amount in the case of disconnection can be obtained by substituting formula (20) for formula (17).
And step S106, based on the obtained voltage change of each node of a certain fault, calculating a static voltage security domain by taking the maximum value.
In this embodiment, GB/T12325-2008 "Power quality supply Voltage deviation" states that the sum of the absolute values of the positive and negative deviations of the supply voltage of 35kv and above does not exceed 10% of the nominal voltage, assuming that the upper and lower limits of the voltage are 1.05p.u. and 0.95 p.u.. Determining the voltage security domain of each node according to the maximum value and the minimum value of the node voltage variation obtained by the calculation in the step S105:
Figure GDA0003380197670000106
in the formula of UimaxFor node i voltage safety margin upper bound, UiminFor node i voltage safety margin lower bound, Δ XimaxIs the maximum value of voltage change, Δ X, of node iiminIs the minimum voltage change of the node i.
Referring to fig. 2, a schematic diagram of testing an ac/dc power system according to the present application is shown.
As shown in fig. 2, the tested ac/dc power system has 11 nodes, and node 3 and node 5 are high-voltage direct-current near regions. The ac grid contains four equivalent generators G1, G2, G3 and G4. The load adopts a constant power model, and the line adopts an RX model. The direct current line between the node 3 and the node 5 adopts the operation mode of constant current control at the rectifying side and constant turn-off angle control at the inverting side. And equating the three hypothetical accidents to corresponding system disturbances, and respectively testing the feasibility of the rapid calculation method provided by the invention.
Table 1 shows the absolute value of the error between the voltage change Δ U of each node of the system and the voltage change result obtained after recalculating the power flow, which is obtained by using a fast calculation method when the system has three faults, i.e., new energy station offline, high-voltage direct current blocking and line disconnection. From table 1, it can be seen that the average error of the voltage variation obtained by the fast calculation method is 0.0009p.u., and the maximum error is 0.0025p.u. The test result shows that the rapid calculation method can obtain good precision. Table 1 is as follows:
TABLE 1
Figure GDA0003380197670000111
In summary, according to the static voltage safety domain analysis method applicable to the alternating current-direct current hybrid system, the most value of the voltage change is obtained by quickly calculating various serious accidents in the region, and the static voltage safety domain is given. The rapid calculation method uses a linear analysis model based on a power balance equation, neglects high-order terms with small influence on voltage change, and obtains the rapid calculation method for voltage change with high calculation precision. And (3) equating accidents possibly occurring in the region to corresponding disturbances for quick calculation, thereby updating the voltage security domain on line in real time and avoiding the problem of voltage out-of-limit after the occurrence of the faults.
Please refer to fig. 3, which shows a block diagram of a static voltage safety domain analyzing apparatus for an ac/dc hybrid system according to the present application.
As shown in fig. 3, the static voltage security domain analyzing apparatus 200 includes an establishing module 210, a first modifying module 220, an expanding module 230, a second modifying module 240, a calculating module 250, and a selecting module 260.
The establishing module 210 is configured to respectively establish an alternating current mathematical model and a direct current system mathematical model based on the running characteristics of the alternating current-direct current hybrid system, wherein the alternating current mathematical model comprises an alternating current system power balance equation, the direct current system mathematical model comprises a direct current system equation, and the direct current system equation comprises a direct current system power balance equation; a first modification module 220 configured to modify the ac system power balance equation according to the dc system power balance equation so as to obtain a power balance equation of the ac-dc hybrid system; the expansion module 230 is configured to expand a power balance equation of the ac-dc hybrid system according to a taylor series, and only retain a primary term to obtain a linearized analysis model, where an expression of the linearized analysis model is: Δ X ═ f'x(X0，Y0)]-1(ΔW-f′y(X0，Y0) Δ Y), wherein X0，Y0Respectively is a state vector consisting of node voltage phase angles in the normal running state of the system and a network parameter, f 'in the normal running state of the system'x(X0，Y0) Is the derivative of the power balance equation to the node voltage, f'y(X0，Y0) For power balance equation derivative of branch admittance, Δ X for AC-DC hybrid systemVoltage change, wherein delta W is power change of the alternating-current and direct-current hybrid system, and delta Y is network parameter change of the alternating-current and direct-current hybrid system; the second correcting module 240 is configured to correct a Jacobian matrix of a Newton-Raphson method of the alternating current system according to the direct current system equation, so that a Newton-Raphson solution of the power flow calculation of the alternating current-direct current system is obtained, iterative convergence is performed on the Newton-Raphson solution, and a power flow result under the normal operation condition of the alternating current-direct current hybrid system is obtained; a calculation module 250 configured to calculate a voltage change of each node of a fault in the expected fault set according to the linearized analysis model and the power flow result; the selecting module 260 calculates the static voltage security domain by taking the maximum value based on the obtained voltage change of each node of a certain fault.
It should be understood that the modules depicted in fig. 3 correspond to various steps in the method described with reference to fig. 1. Thus, the operations and features described above for the method and the corresponding technical effects are also applicable to the modules in fig. 3, and are not described again here.
In other embodiments, an embodiment of the present invention further provides a computer-readable storage medium, where computer-executable instructions are stored, and the computer-executable instructions may execute the static voltage safety domain analysis method of the ac-dc hybrid system in any of the above method embodiments;
as one embodiment, the computer-readable storage medium of the present invention stores computer-executable instructions configured to:
respectively establishing an alternating current mathematical model and a direct current system mathematical model based on the running characteristics of an alternating current-direct current hybrid system, wherein the alternating current mathematical model comprises an alternating current system power balance equation, the direct current system mathematical model comprises a direct current system equation, and the direct current system equation comprises a direct current system power balance equation;
correcting the power balance equation of the alternating current system according to the power balance equation of the direct current system to obtain a power balance equation of an alternating current-direct current hybrid system;
expanding the power balance equation of the alternating current-direct current hybrid system according to Taylor series, and only retaining a primary term to obtain a linear analysis model, wherein the expression of the linear analysis model is as follows:
ΔX＝[f′x(X0，Y0)]-1(ΔW-f′y(X0，Y0)ΔY)，
in the formula, X0、Y0Respectively is a state vector consisting of node voltage phase angles in the normal running state of the system and a network parameter, f 'in the normal running state of the system'x(X0，Y0) Is the derivative of the power balance equation to the node voltage, f'y(X0，Y0) The derivative of a power balance equation to the branch admittance is shown, wherein delta X is the voltage change of the AC-DC hybrid system, delta W is the power change of the AC-DC hybrid system, and delta Y is the network parameter change of the AC-DC hybrid system;
correcting a Jacobian matrix of an alternating current system Newton-Raphson method according to the direct current system equation to obtain a Newton-Raphson solution of the alternating current-direct current system power flow calculation, and performing iterative convergence on the Newton-Raphson solution to obtain a power flow result under the normal operation condition of the alternating current-direct current hybrid system;
calculating the voltage change of each node of a certain fault in an expected fault set according to the linear analysis model and the load flow result;
and calculating a static voltage security domain by taking the maximum value based on the acquired voltage change of each node of a certain fault.
The computer-readable storage medium may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created from use of the static voltage safety domain analysis device of the ac-dc hybrid system, and the like. Further, the computer-readable storage medium may include high speed random access memory, and may also include memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some embodiments, the computer readable storage medium optionally includes memory remotely located from the processor, and the remote memory may be connected to the static voltage safety domain analysis device of the ac/dc hybrid system via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
Fig. 4 is a schematic structural diagram of an electronic device according to an embodiment of the present invention, and as shown in fig. 4, the electronic device includes: a processor 310 and a memory 320. The electronic device may further include: an input device 330 and an output device 340. The processor 310, the memory 320, the input device 330, and the output device 340 may be connected by a bus or other means, such as the bus connection in fig. 4. The memory 320 is the computer-readable storage medium described above. The processor 310 executes various functional applications and data processing of the server by running the non-volatile software programs, instructions and modules stored in the memory 320, that is, the static voltage security domain analysis method of the ac/dc hybrid system according to the above method embodiment is implemented. The input device 330 can receive input numeric or character information and generate key signal input related to user setting and function control of the static voltage safety domain analysis device of the ac/dc hybrid system. The output device 340 may include a display device such as a display screen.
The electronic device can execute the method provided by the embodiment of the invention, and has the corresponding functional modules and beneficial effects of the execution method. For technical details that are not described in detail in this embodiment, reference may be made to the method provided by the embodiment of the present invention.
As an embodiment, the electronic device is applied to a static voltage safety domain analysis apparatus of an ac-dc hybrid system, and is used for a client, and includes: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to cause the at least one processor to:
respectively establishing an alternating current mathematical model and a direct current system mathematical model based on the running characteristics of an alternating current-direct current hybrid system, wherein the alternating current mathematical model comprises an alternating current system power balance equation, the direct current system mathematical model comprises a direct current system equation, and the direct current system equation comprises a direct current system power balance equation;
correcting the power balance equation of the alternating current system according to the power balance equation of the direct current system to obtain a power balance equation of an alternating current-direct current hybrid system;
expanding the power balance equation of the alternating current-direct current hybrid system according to Taylor series, and only retaining a primary term to obtain a linear analysis model, wherein the expression of the linear analysis model is as follows:
ΔX＝[f′x(X0，Y0)]-1(ΔW-f′y(X0，Y0)ΔY)，
in the formula, X0、Y0Respectively is a state vector consisting of node voltage phase angles in the normal running state of the system and a network parameter, f 'in the normal running state of the system'x(X0，Y0) Is the derivative of the power balance equation to the node voltage, f'y(X0，Y0) The derivative of a power balance equation to the branch admittance is shown, wherein delta X is the voltage change of the AC-DC hybrid system, delta W is the power change of the AC-DC hybrid system, and delta Y is the network parameter change of the AC-DC hybrid system;
correcting a Jacobian matrix of an alternating current system Newton-Raphson method according to the direct current system equation to obtain a Newton-Raphson solution of the alternating current-direct current system power flow calculation, and performing iterative convergence on the Newton-Raphson solution to obtain a power flow result under the normal operation condition of the alternating current-direct current hybrid system;
calculating the voltage change of each node of a certain fault in an expected fault set according to the linear analysis model and the load flow result;
and calculating a static voltage security domain by taking the maximum value based on the acquired voltage change of each node of a certain fault.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods of the various embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (9)

1. A static voltage safety domain analysis method suitable for an alternating current-direct current hybrid system is characterized by comprising the following steps:
respectively establishing an alternating current mathematical model and a direct current system mathematical model based on the running characteristics of an alternating current-direct current hybrid system, wherein the alternating current mathematical model comprises an alternating current system power balance equation, the direct current system mathematical model comprises a direct current system equation, and the direct current system equation comprises a direct current voltage equation and a direct current system power balance equation;
correcting the power balance equation of the alternating current system according to the power balance equation of the direct current system to obtain a power balance equation of an alternating current-direct current hybrid system;
expanding the power balance equation of the alternating current-direct current hybrid system according to Taylor series, and only retaining a primary term to obtain a linear analysis model, wherein the expression of the linear analysis model is as follows:
ΔX＝[f′x(X0，Y0)]-1(ΔW-f′y(X0，Y0)ΔY)，
in the formula, X0、Y0Respectively is a state vector consisting of node voltage phase angles in the normal running state of the system and a network parameter, f 'in the normal running state of the system'x(X0，Y0) Is the derivative of the power balance equation to the node voltage, f'y(X0，Y0) The derivative of a power balance equation to the branch admittance is shown, wherein delta X is the voltage change of the AC-DC hybrid system, delta W is the power change of the AC-DC hybrid system, and delta Y is the network parameter change of the AC-DC hybrid system;
correcting a Jacobian matrix of an alternating current system Newton-Raphson method according to the direct current system equation to obtain a Newton-Raphson solution of the alternating current-direct current system power flow calculation, and performing iterative convergence on the Newton-Raphson solution to obtain a power flow result under the normal operation condition of the alternating current-direct current hybrid system;
calculating the voltage change of each node of a certain fault in an expected fault set according to the linear analysis model and the load flow result;
and calculating a static voltage security domain by taking the maximum value based on the acquired voltage change of each node of a certain fault.
2. The static voltage safety domain analysis method suitable for the ac-dc hybrid system according to claim 1, wherein the power balance equation of the ac system is:
Figure FDA0003337464580000011
in the formula,. DELTA.PiFor node i active power correction, PGiActive power, P, generated for node i generatorLiActive power absorbed for node i load, UiIs the voltage amplitude of node i, UjIs the voltage amplitude, G, of node jijIs the real part of the ith row and jth column element of the node admittance matrix, thetaijIs the i, j voltage phase difference, BijFor the imaginary part, Δ Q, of the ith row and jth column element of the node admittance matrixiIs a section ofPoint i reactive power correction, QGiReactive power, Q, generated for node i generatorLiReactive power absorbed for the node i load.
3. The method for analyzing the quiescent voltage safety domain of the ac-dc hybrid system according to claim 1, wherein the power balance equation of the dc system is:
Figure FDA0003337464580000021
in the formula, PdiFor injecting active power into the inverter station, UdiFor inverting station DC voltage, IdFor direct transmission line current, QdiIn order to inject reactive power into the inverter station,
Figure FDA0003337464580000022
for the angle of the power factor of the inverter station, Udi0For a DC no-load voltage of the inverter station, PdrFor injecting active power into the rectifying station, UdrFor a direct voltage of the rectifier station, QdrIn order to inject reactive power into the rectifying station,
Figure FDA0003337464580000023
is the power factor angle, U, of the rectifier stationdr0Is the rectifier station DC no-load voltage.
4. The method for analyzing the quiescent voltage safety domain of the ac-dc hybrid system according to claim 1, wherein the power balance equation of the ac-dc hybrid system is:
f(X0+ΔX，Y0+ΔY)＝ΔW，
in the formula, X0、Y0Respectively a state vector formed by node voltage phase angles in the normal operation state of the system and network parameters in the normal operation state of the system, wherein DeltaX is the voltage change of the AC-DC hybrid system, and DeltaW is the power of the AC-DC hybrid systemAnd delta Y is the network parameter change of the alternating current-direct current hybrid system.
5. The method for analyzing the static voltage safety domain of the ac-dc hybrid system as recited in claim 1, wherein the expression of the jacobian matrix of the newton-raphson method of the ac system is:
Figure FDA0003337464580000031
in the formula, H is a partial derivative matrix of the active power correction amount to the voltage phase angle, N is a partial derivative matrix of the active power correction amount to the voltage amplitude, M is a partial derivative matrix of the reactive power correction amount to the voltage phase angle, L is a partial derivative matrix of the reactive power correction amount to the voltage amplitude, and HijIs the partial derivative, delta P, of the active power correction at node i to the phase angle of the voltage at node jiIs the active power correction of node i, θjIs the voltage phase angle, U, of node jjIs the voltage amplitude of node j, NijIs the partial derivative, M, of the active power correction at node i to the voltage amplitude at node jijIs the partial derivative, L, of the reactive power correction at node i to the phase angle of the voltage at node jijIs the partial derivative, Δ Q, of the reactive power correction at node i to the voltage amplitude at node jiThe node i reactive power correction.
6. The method for analyzing the quiescent voltage safety domain of the ac-dc hybrid system according to claim 1, wherein the expression of the newton-raphson solution for the ac-dc system power flow calculation is:
Figure FDA0003337464580000032
θi (k+1)＝θi (k)+Δθi (k)(i＝1，2，…，n-1)
Ui (k+1)＝Ui (k)+ΔU(k)(i＝1，2，...，m)，
in the formula,. DELTA.theta.(k)As a correction of the voltage phase angle in the kth iteration, H(k)Is a partial derivative matrix, N ', of the active power correction quantity to the voltage phase angle in the k iteration'(k)Is a partial derivative matrix of the active power correction quantity to the voltage amplitude in the k iteration, delta P(k)Is the correction of the active power, Δ U, in the kth iteration(k)For correction of the voltage amplitude in the kth iteration, M(k)Is a partial derivative matrix, L ', of reactive power correction quantity to voltage phase angle'(k)Is a partial derivative matrix, delta Q, of the reactive power correction to the voltage amplitude in the kth iteration(k)For the correction of reactive power in the kth iteration, θi (k+1)For the voltage phase angle, theta, of node i in the (k + 1) th iterationi (k)For the voltage phase angle, Δ θ, of node i in the kth iterationi (k)Is the correction of the voltage phase angle of node i in the kth iteration, Ui (k +1)For the voltage amplitude of node i in the (k + 1) th iteration, Ui (k)For the voltage amplitude of node i, Δ U, in the kth iteration(k)And the voltage amplitude correction quantity of the node i in the kth iteration is shown, n is the number of nodes of the system, and m is the number of PQ nodes in the system.
7. The utility model provides a static voltage safety domain analytical equipment suitable for alternating current-direct current series-parallel connection system which characterized in that includes:
the system comprises an establishing module, a calculating module and a calculating module, wherein the establishing module is configured to respectively establish an alternating current mathematical model and a direct current system mathematical model based on the running characteristics of an alternating current-direct current hybrid system, the alternating current mathematical model comprises an alternating current system power balance equation, the direct current system mathematical model comprises a direct current system equation, and the direct current system equation comprises a direct current voltage equation and a direct current system power balance equation;
the first correction module is configured to correct the alternating current system power balance equation according to the direct current system power balance equation so as to obtain a power balance equation of an alternating current-direct current hybrid system;
the expansion module is configured to expand a power balance equation of the alternating current-direct current hybrid system according to a Taylor series, and only one term is reserved to obtain a linearization analysis model, wherein the expression of the linearization analysis model is as follows:
ΔX＝[f′x(X0，Y0)]-1(ΔW-f′y(X0，Y0)ΔY)，
in the formula, X0、Y0Respectively is a state vector consisting of node voltage phase angles in the normal running state of the system and a network parameter, f 'in the normal running state of the system'x(X0，Y0) Is the derivative of the power balance equation to the node voltage, f'y(X0，Y0) The derivative of a power balance equation to the branch admittance is shown, wherein delta X is the voltage change of the AC-DC hybrid system, delta W is the power change of the AC-DC hybrid system, and delta Y is the network parameter change of the AC-DC hybrid system;
the second correction module is configured to correct a Jacobian matrix of an alternating current system Newton-Raphson method according to the direct current system equation, so that a Newton-Raphson solution of the alternating current-direct current system power flow calculation is obtained, iterative convergence is performed on the Newton-Raphson solution, and a power flow result under the normal operation condition of the alternating current-direct current hybrid system is obtained;
the calculation module is configured to calculate the voltage change of each node of a certain fault in an expected fault set according to the linear analysis model and the load flow result;
and the selecting module is used for calculating a static voltage security domain by taking the maximum value based on the acquired voltage change of each node of a certain fault.
8. An electronic device, comprising: at least one processor, and a memory communicatively coupled to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any of claims 1 to 6.
9. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the method of any one of claims 1 to 6.
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