CN113659604A - Electromechanical transient simulation method and device for LCC-VSC hybrid direct-current power grid and storage medium - Google Patents

Electromechanical transient simulation method and device for LCC-VSC hybrid direct-current power grid and storage medium Download PDF

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CN113659604A
CN113659604A CN202110806544.7A CN202110806544A CN113659604A CN 113659604 A CN113659604 A CN 113659604A CN 202110806544 A CN202110806544 A CN 202110806544A CN 113659604 A CN113659604 A CN 113659604A
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direct current
current
lcc
direct
vsc
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张金龙
鲍颜红
徐泰山
徐伟
查显煜
罗峰
杨君军
郭剑
吴峰
任先成
阮晶晶
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Nari Technology 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
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • 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
    • 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]

Abstract

The invention discloses an LCC-VSC hybrid direct current power grid electromechanical transient simulation method, a device and a storage medium, wherein the method comprises the following steps: constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology; constructing a difference equation set corresponding to the hybrid direct-current power grid dynamic model according to a preset simulation step length; constructing a Jacobian matrix according to the partial derivative terms of the state variables of the mixed direct current network of the differential equation set; performing iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence; and obtaining the state variable of the hybrid direct-current power grid at the next simulation time according to the solving result of the differential equation set at the current simulation time. The method can improve the calculation precision and the calculation efficiency of the electromechanical transient simulation of the LCC-VSC hybrid direct current power grid on the whole, and meet the engineering application requirements.

Description

Electromechanical transient simulation method and device for LCC-VSC hybrid direct-current power grid and storage medium
Technical Field
The invention relates to an LCC-VSC hybrid direct current power grid electromechanical transient simulation method, device and storage medium, and belongs to the technical field of power system automation.
Background
The high-voltage direct-current transmission system (LCC-HVDC) of the power grid commutation converter has the advantages of large transmission capacity, low operation loss, mature and reliable technology and the like, but has the defects of failed commutation of an inverter station, incapability of supplying power to a weak alternating-current system, large reactive power consumption in the operation process and the like; the voltage source type converter high-voltage direct-current transmission system (VSC-HVDC, wherein MMC-HVDC is widely applied) has the advantages of flexible control, small compensation and filtering capacity, no commutation failure, easy formation of a multi-terminal network and the like; but has the defects of lower transmission capacity, higher running loss, high manufacturing cost and the like. The LCC-VSC hybrid direct-current power grid is constructed, stable transmission of long-distance large-capacity electric energy is achieved through the LCC-HVDC, collection of distributed renewable energy sources is achieved through the VSC-HVDC, and the LCC-HVDC hybrid direct-current power grid and the VSC-HVDC are mutually connected and fused and have complementary advantages, so that the LCC-VSC hybrid direct-current power grid becomes an expression form with great development prospects in the future.
Limited by computing power and data parameters, compared with electromagnetic transient simulation, electromechanical transient simulation is a main means for analyzing the safety and stability of the large power grid at present. Because the dynamic response speed of the capacitor and the inductor on the direct current side is high, the alternating current and direct current hybrid power grid has obvious response speed difference, in order to take account of calculation efficiency and accuracy, the alternating current power grid adopts a large step length (h is 0.01 s), the direct current power grid adopts a small step length (h/10-h/4), and alternating current and direct current power grid alternating iterative solution is the mainstream method for the electromechanical transient simulation calculation of the alternating current and direct current hybrid power grid at present.
Aiming at the simulation calculation in the direct current power grid, because the interface of a converter and the direct current network contains a nonlinear equation, the solving steps of the existing method are as follows:
1) suppose a DC voltage UdCalculating the current I of the converter injected into the DC network without changingd；
2) Solving a direct current network difference equation set according to the Id, and updating the Ud；
3) The steps 1) and 2) are circulated until the U is reacheddThe iteration error is less than the threshold value.
The existing method is to carry out linearization processing on the original equation and adopt a simple iteration method to alternately solve the dynamic equations at two sides of the interface, but the convergence error caused by alternate iteration under the complex multi-terminal direct-current power network can cause too slow convergence or even incapability of convergence.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides an LCC-VSC hybrid direct current power grid electromechanical transient simulation method, device and storage medium, and solves the technical problem that convergence is too slow or even can not be converged due to handover errors caused by alternate iteration under a complex multi-terminal direct current power grid when a nonlinear equation of the direct current power grid is solved in electromechanical transient simulation.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
in a first aspect, the invention provides an LCC-VSC hybrid dc grid electromechanical transient simulation method, which includes:
constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;
constructing a difference equation set corresponding to the hybrid direct-current power grid dynamic model according to a preset simulation step length;
constructing a Jacobian matrix according to the partial derivative terms of the state variables of the mixed direct current network of the differential equation set;
performing iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;
and obtaining the state variable of the hybrid direct-current power grid at the next simulation time according to the solving result of the differential equation set at the current simulation time.
Further, before the dynamic model of the hybrid direct-current power grid is constructed, circuit equivalent transformation is carried out on the hybrid direct-current power grid.
Further, the hybrid direct-current power grid dynamic model comprises a direct-current line dynamic model, an LCC converter direct-current side dynamic model and a VSC converter direct-current side dynamic model.
Further, the dc link dynamic model is described by equation (1):
Figure BDA0003166574180000031
wherein R isi,j、Li,j、Ii,jThe equivalent resistance and the equivalent inductance of the direct current line and the current flowing through the direct current line are respectively; t represents time; vi、VjThe direct current voltages of nodes i and j at two ends of a direct current line are respectively direct current voltages; the positive direction of the direct current line current flows from i to j, wherein i is less than j;
the direct current side dynamic model of the LCC converter is described by equations (2) to (4):
Figure BDA0003166574180000032
Figure BDA0003166574180000033
Figure BDA0003166574180000034
wherein, UiThe voltage is the direct current side voltage of the LCC converter; l isiIs a smoothing reactor; xiIs the LCC converter equivalent impedance; i isiInjecting the current of the direct current line into the LCC converter; ci、Ic,iNode i is equivalent to earth capacitance and current flowing through the node i; siThe direct current lines connected with the node i are collected;
Figure BDA0003166574180000035
gi、hiare respectively SiCurrent, head end node, tail end node, g, of medium DC linei＜hi；
Figure BDA0003166574180000036
Is an orientation factor, if i ═ giThen
Figure BDA0003166574180000037
Otherwise
Figure BDA0003166574180000038
The VSC converter direct current side dynamic model is described by equations (5) to (7):
VjIj＝Pj (5)
Figure BDA0003166574180000039
Figure BDA00031665741800000310
wherein: cj、Ic,jRespectively node j equivalent earth capacitance and current flowing through the node j equivalent earth capacitance; i isjInjecting the current of the direct current line into the VSC converter; sjIs a direct current line set connected with the node j;
Figure BDA00031665741800000311
gj、hjare respectively SjCurrent, head end node, tail end node, g, of medium DC linej＜hj；
Figure BDA0003166574180000041
Is a direction factor, if j is gjThen, then
Figure BDA0003166574180000042
Otherwise
Figure BDA0003166574180000043
PjAnd injecting the power of the direct current line for the VSC converter.
Further, the system of difference equations includes:
direct current line differential equation:
Figure BDA0003166574180000044
LCC converter direct current side difference equation set:
Figure BDA0003166574180000045
Figure BDA0003166574180000046
Figure BDA0003166574180000047
VSC converter direct current side difference equation set:
Figure BDA0003166574180000048
Figure BDA0003166574180000049
Figure BDA00031665741800000410
in the formula, Δ t is a preset time interval, and n +1 respectively represent n time and n +1 time; the superscripts n and n +1 are added to each parameter to respectively represent the values of the parameter corresponding to the time n and the time n + 1.
Further, when the jacobian matrix is constructed, the following method is adopted for row sorting and column sorting:
sequencing the corresponding differential equation sets in a row sequence, namely sequentially sequencing a direct-current line differential equation (8), an LCC converter direct-current side differential equation (9), an LCC converter direct-current side differential equation (10), a VSC converter direct-current side differential equation (13), an LCC converter direct-current side differential equation (11), a VSC converter direct-current side differential equation (14) and a VSC converter direct-current side differential equation (12);
the column sequence corresponds to the mixed direct current network state variable sequence and sequentially comprises current flowing through a direct current circuit, direct current voltage of a side end node connected with the direct current circuit and the LCC converter, direct current circuit node ground capacitance branch current, current injected into the direct current circuit by the LCC converter, current injected into the direct current circuit by the VSC converter and direct current voltage of a side end node connected with the direct current circuit and the VSC converter.
Further, the DC side voltage U of the LCC converteriObtaining by calculation using equation (15):
Figure BDA0003166574180000051
in the formula, EiMeasuring the voltage, alpha, for the LCC converter ACiThe control trigger angle of the LCC converter.
In a second aspect, an LCC-VSC hybrid dc grid electromechanical transient simulation apparatus includes:
a dynamic model construction unit: the system is used for constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;
a difference equation set construction unit: the system comprises a simulation step length generation unit, a difference equation set and a difference equation set, wherein the simulation step length generation unit is used for generating a difference equation set corresponding to a dynamic model of the hybrid direct-current power grid according to a preset simulation step length;
a jacobian matrix construction unit: the method comprises the steps of constructing a Jacobian matrix according to a partial derivative term of a state variable of a mixed direct current network of a difference equation set;
an iteration solving unit: the method is used for carrying out iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;
an acquisition unit: and the method is used for obtaining the state variable of the hybrid direct-current power grid at the next simulation moment according to the solving result of the differential equation set at the current simulation moment.
In a third aspect, the invention further provides an LCC-VSC hybrid direct current grid electromechanical transient simulation device, which includes a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate according to the instructions to perform the steps of the LCC-VSC hybrid direct current grid electromechanical transient simulation method of any one of the first aspect.
In a fourth aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored, wherein the program is executed by a processor to implement the steps of the LCC-VSC hybrid direct current grid electromechanical transient simulation method according to any one of the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the LCC-VSC hybrid direct current power grid electromechanical transient simulation method, the difference equation set at the current simulation moment is iteratively solved by adopting a Newton-Raphson method, variable elements in the difference equation set and a Jacobian matrix are continuously updated in the iteration process, and the convergence stability is improved; the Jacobian matrix is constructed and obtained according to the partial derivatives of the state variables of the hybrid direct current power grid of the differential equation set, only a small number of matrix elements are used as variables, so that only a small number of variable elements in the Jacobian matrix need to be updated in each iterative solution process, the calculated amount is greatly reduced, the calculation accuracy and the calculation efficiency of the electromechanical transient simulation of the LCC-VSC hybrid direct current power grid can be integrally improved, and the engineering application requirements are met.
Drawings
Fig. 1 is a flowchart of an LCC-VSC hybrid dc power grid electromechanical transient simulation method according to an embodiment of the present invention;
fig. 2 is an equivalent circuit diagram of an LCC-VSC hybrid dc power grid according to an embodiment of the present invention;
fig. 3 is a circuit diagram of an LCC-VSC three-terminal hybrid dc grid according to an embodiment of the present invention;
fig. 4 is a ranking diagram of a jacobian matrix constructed from the circuit diagram provided in fig. 3.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The first embodiment is as follows:
referring to fig. 1, an embodiment of the present invention provides an LCC-VSC hybrid dc power grid electromechanical transient simulation method, which is used for obtaining state variables of a next simulation time hybrid dc power grid in a simulation manner, and specifically includes the following steps:
step A: constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;
in the embodiment of the present invention, before constructing the dynamic model of the hybrid dc power grid, equivalent transformation may be performed on the circuit of the hybrid dc power grid, and the circuit structure is divided into three parts, i.e., a dc side of the LCC converter, a dc line and a dc side of the VSC converter, as shown in fig. 2, which is an equivalent circuit diagram of the hybrid dc power grid provided in the embodiment of the present invention. Corresponding dynamic models can be respectively constructed for the direct current side of the LCC converter, the direct current line and the direct current side of the VSC converter.
As shown in fig. 2, the dc link dynamics model can be described using equation (1):
Figure BDA0003166574180000071
wherein R isi,j、Li,j、Ii,jThe equivalent resistance and the equivalent inductance of the direct current line and the current flowing through the direct current line are respectively; t represents time; vi、VjThe direct current voltages of nodes i and j at two ends of the direct current line are respectively direct current voltages, and the positive direction of the direct current line current flows from i to j.
The direct current side dynamic model of the LCC converter can be described by equations (2) to (4):
Figure BDA0003166574180000072
Figure BDA0003166574180000073
Figure BDA0003166574180000074
wherein, UiThe voltage is the direct current side voltage of the LCC converter; l isiIs a smoothing reactor; xiIs the LCC converter equivalent impedance; i isiInjecting the current of the direct current line into the LCC converter; ci、Ic,iNode i is equivalent to earth capacitance and current flowing through the node i; siThe direct current lines connected with the node i are collected;
Figure BDA0003166574180000081
gi、hiare respectively SiCurrent, head end node, tail end node, g, of medium DC linei＜hi；
Figure BDA0003166574180000082
Is an orientation factor, if i ═ giThen
Figure BDA0003166574180000083
Otherwise
Figure BDA0003166574180000084
The direct current side dynamic model of the VSC can be described by equations (5) to (7):
VjIj＝Pj (5)
Figure BDA0003166574180000085
Figure BDA0003166574180000086
wherein: cj、Ic,jRespectively node j equivalent earth capacitance and current flowing through the node j equivalent earth capacitance; i isjInjecting the current of the direct current line into the VSC converter; sjIs a direct current line set connected with the node j;
Figure BDA0003166574180000087
gj、hjare respectively SjCurrent, head end node, tail end node, g, of medium DC linej＜hj；
Figure BDA0003166574180000088
Is a direction factor, if j is gjThen, then
Figure BDA0003166574180000089
Otherwise
Figure BDA00031665741800000810
PjAnd injecting the power of the direct current line for the VSC converter.
And B: constructing a difference equation set corresponding to the hybrid direct-current power grid dynamic model according to a preset simulation step length;
corresponding direct current circuit dynamic model, LCC transverter direct current side dynamic model and VSC transverter direct current side dynamic model, corresponding difference equation set includes: the direct current circuit differential equation, the LCC converter direct current side differential equation set and the VSC converter direct current side differential equation set. The embodiment of the invention adopts an implicit trapezoidal integral method to convert a direct current power grid dynamic differential equation into a differential equation set, and specifically comprises the following steps:
direct current line differential equation:
Figure BDA0003166574180000091
LCC converter direct current side difference equation set:
Figure BDA0003166574180000092
Figure BDA0003166574180000093
Figure BDA0003166574180000094
VSC converter direct current side difference equation set:
Figure BDA0003166574180000095
Figure BDA0003166574180000096
Figure BDA0003166574180000097
in the formula, Δ t is a preset time interval (i.e. simulation step length), and n +1 respectively represent n time and n +1 time; the superscripts n and n +1 are added to each parameter to respectively represent the values of the parameter corresponding to the time n and the time n + 1.
And C: constructing a Jacobian matrix according to the partial derivative terms of the state variables of the mixed direct current network of the differential equation set;
in vector calculus, the jacobian matrix is a matrix in which the first-order partial derivatives are arranged in a certain way, the determinant of which is called jacobian, and the significance of the jacobian matrix is that it embodies an optimal linear approximation of a given point to a micro equation, and therefore, the jacobian matrix is similar to the derivative of a multi-element function.
As an embodiment of the present invention, when constructing the jacobian matrix, the following method may be adopted for row sorting and column sorting:
sequencing the corresponding differential equation sets in a row sequence, namely sequentially sequencing a direct-current line differential equation (8), an LCC converter direct-current side differential equation (9), an LCC converter direct-current side differential equation (10), a VSC converter direct-current side differential equation (13), an LCC converter direct-current side differential equation (11), a VSC converter direct-current side differential equation (14) and a VSC converter direct-current side differential equation (12);
the column sequence corresponds to the mixed direct current network state variable sequence and sequentially comprises current flowing through a direct current circuit, direct current voltage of a side end node connected with the direct current circuit and the LCC converter, direct current circuit node ground capacitance branch current, current injected into the direct current circuit by the LCC converter, current injected into the direct current circuit by the VSC converter and direct current voltage of a side end node connected with the direct current circuit and the VSC converter.
As shown in fig. 3, taking an LCC-VSC three-terminal hybrid dc grid as an example, the three-terminal hybrid dc grid includes a dc network, an LCC converter and two VSC converters; the direct current network comprises three direct current lines, three nodes are corresponding to the three direct current lines, and the nodes can be respectively marked as nodes 1, 2 and 3, wherein the node 1 is connected with the LCC converter, and the nodes 2 and 3 are respectively and correspondingly connected with the two VSC converters. For the hybrid dc power grid shown in fig. 3, the jacobian matrix may be sorted in rows and columns by the following method:
the row ordering is:
group 1: lines (1) - (3) correspond to equation (8);
group 2: line (4) corresponds to equation (9);
group 3: lines (5) - (7) correspond to equation (10) and equation (13);
group 4: lines (8) - (10) correspond to equation (11) and equation (14);
group 5: lines (11) to (12) correspond to equation (12);
the column ordering is:
group 1: the columns (1) to (3) correspond to DC line currents
Figure BDA0003166574180000101
A partial derivative term;
group 2: column (4) corresponds to LCC converter DC point voltage
Figure BDA0003166574180000102
A partial derivative term;
group 3: the line (5) to (7) corresponds to the branch current of the converter to the ground capacitor
Figure BDA0003166574180000103
A partial derivative term;
group 4: injecting DC network current into the LCC converter corresponding to the column (8)
Figure BDA0003166574180000111
A partial derivative term;
group 5: injecting direct current network current into VSC converter corresponding to columns (9) - (10)
Figure BDA0003166574180000112
A partial derivative term;
group 6: the rows (11) to (12) correspond to the DC point voltage of the VSC converter
Figure BDA0003166574180000113
And (4) a partial derivative item.
It should be noted that: the row sorting and the column sorting described above are only one preferred sorting method of the jacobian matrix in the present embodiment, and the jacobian matrix may be another sorting method in the present invention.
As shown in FIG. 4, three constructed for FIG. 3A jacobian matrix of the end hybrid direct-current power grid, wherein a main diagonal element of the jacobian matrix is shown in a box a in fig. 4, and the value of the main diagonal element is relatively large; except for the matrix elements circled by the box b in fig. 4
Figure BDA0003166574180000114
Except for the variables, the other matrix elements are all constants.
Step D: performing iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;
the newton-raphson method is a method of solving equations approximately in the real and complex domains, using the first terms of the taylor series of functions to find the root of the equation, with the greatest advantage of square convergence near a single root of the equation.
It should be noted that the value of the principal diagonal elements of the jacobian matrix generated according to the sorting method of step C is relatively large; only the first calculation needs full matrix LU factorization; subsequent calculations need only update the jacobian matrix part elements (matrix elements as circled by the lower right corner box b in fig. 4)
Figure BDA0003166574180000115
) And its corresponding LU factor.
In this embodiment, the "next simulation time" may be understood as n +1 time, where n time is denoted as the current simulation time, and the time interval between n +1 time and n time is Δ t.
Step E: and obtaining the state variable of the hybrid direct-current power grid at the next simulation time according to the solving result of the differential equation set at the current simulation time.
According to the LCC-VSC hybrid direct current power grid electromechanical transient simulation method, the difference equation set at the current simulation moment is iteratively solved by adopting a Newton-Raphson method, variable elements in the difference equation set and a Jacobian matrix are continuously updated in the iteration process, and the convergence stability is improved; the Jacobian matrix is constructed and obtained according to the partial derivatives of the state variables of the hybrid direct current power grid of the differential equation set, only a small number of matrix elements are used as variables, so that only a small number of variable elements in the Jacobian matrix need to be updated in each iterative solution process, the calculated amount is greatly reduced, the calculation accuracy and the calculation efficiency of the electromechanical transient simulation of the LCC-VSC hybrid direct current power grid can be integrally improved, and the engineering application requirements are met.
Example two:
the embodiment of the invention provides an LCC-VSC hybrid direct current power grid electromechanical transient simulation device, which comprises:
a dynamic model construction unit: the system is used for constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;
a difference equation set construction unit: the system comprises a simulation step length generation unit, a difference equation set and a difference equation set, wherein the simulation step length generation unit is used for generating a difference equation set corresponding to a dynamic model of the hybrid direct-current power grid according to a preset simulation step length;
a jacobian matrix construction unit: the method comprises the steps of constructing a Jacobian matrix according to a partial derivative term of a state variable of a mixed direct current network of a difference equation set;
an iteration solving unit: the method is used for carrying out iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;
an acquisition unit: and the method is used for obtaining the state variable of the hybrid direct-current power grid at the next simulation moment according to the solving result of the differential equation set at the current simulation moment.
The device provided by the embodiment of the present invention can be used to implement the simulation method described in the first embodiment, and the specific implementation method for implementing the corresponding function by each unit in the device may refer to the description of the corresponding part of the first embodiment.
Example three:
the embodiment of the invention also provides an LCC-VSC hybrid direct current power grid electromechanical transient simulation device, which comprises a processor and a storage medium;
a storage medium to store instructions;
the processor is used for operating according to the instructions to execute the steps of the LCC-VSC hybrid direct current grid electromechanical transient simulation method according to the first embodiment.
Example four:
the embodiment of the invention provides a computer-readable storage medium, on which a computer program is stored, wherein the program is executed by a processor to implement the steps of the LCC-VSC hybrid direct current grid electromechanical transient simulation method according to the first embodiment.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (10)

1. An LCC-VSC hybrid direct current grid electromechanical transient simulation method is characterized by comprising the following steps:
constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;
constructing a difference equation set corresponding to the hybrid direct-current power grid dynamic model according to a preset simulation step length;
constructing a Jacobian matrix according to the partial derivative terms of the state variables of the mixed direct current network of the differential equation set;
performing iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;
and obtaining the state variable of the hybrid direct-current power grid at the next simulation time according to the solving result of the differential equation set at the current simulation time.
2. The LCC-VSC hybrid direct current grid electromechanical transient simulation method of claim 1, wherein a circuit equivalent transformation is performed on the hybrid direct current grid before the hybrid direct current grid dynamic model is constructed.
3. The LCC-VSC hybrid direct current grid electromechanical transient simulation method according to claim 1 or 2, characterized in that the hybrid direct current grid dynamic models comprise a direct current line dynamic model, an LCC converter direct current side dynamic model and a VSC converter direct current side dynamic model.
4. The LCC-VSC hybrid direct current grid electromechanical transient simulation method of claim 3, wherein the direct current line dynamic model is described with equation (1):
Figure FDA0003166574170000011
wherein R isi,j、Li,j、Ii,jThe equivalent resistance and the equivalent inductance of the direct current line and the current flowing through the direct current line are respectively; t represents time; vi、VjThe direct current voltages of nodes i and j at two ends of a direct current line are respectively direct current voltages; the positive direction of the direct current line current flows from i to j, wherein i is less than j;
the direct current side dynamic model of the LCC converter is described by equations (2) to (4):
Figure FDA0003166574170000021
Figure FDA0003166574170000022
Figure FDA0003166574170000023
wherein, UiThe voltage is the direct current side voltage of the LCC converter; l isiIs a smoothing reactor; xiIs the LCC converter equivalent impedance; i isiInjecting the current of the direct current line into the LCC converter; ci、Ic,iNode i is equivalent to earth capacitance and current flowing through the node i; siThe direct current lines connected with the node i are collected;
Figure FDA0003166574170000024
gi、hiare respectively SiCurrent, head end node, tail end node, g, of medium DC linei＜hi；
Figure FDA0003166574170000025
Is an orientation factor, if i ═ giThen
Figure FDA0003166574170000026
Otherwise
Figure FDA0003166574170000027
The VSC converter direct current side dynamic model is described by equations (5) to (7):
VjIj＝Pj (5)
Figure FDA0003166574170000028
Figure FDA0003166574170000029
wherein: cj、Ic,jRespectively node j equivalent earth capacitance and current flowing through the node j equivalent earth capacitance; i isjInjecting the current of the direct current line into the VSC converter; sjIs a direct current line set connected with the node j;
Figure FDA00031665741700000210
gj、hjare respectively SjCurrent, head end node, tail end node, g, of medium DC linej＜hj；
Figure FDA00031665741700000211
Is a direction factor, if j is gjThen, then
Figure FDA00031665741700000212
Otherwise
Figure FDA00031665741700000213
PjAnd injecting the power of the direct current line for the VSC converter.
5. The LCC-VSC hybrid direct current grid electromechanical transient simulation method of claim 4, wherein the set of differential equations comprises:
direct current line differential equation:
Figure FDA0003166574170000031
LCC converter direct current side difference equation set:
Figure FDA0003166574170000032
Figure FDA0003166574170000033
Figure FDA0003166574170000034
VSC converter direct current side difference equation set:
Figure FDA0003166574170000035
Figure FDA0003166574170000036
Figure FDA0003166574170000037
in the formula, Δ t is a preset time interval, and n +1 respectively represent n time and n +1 time; the superscripts n and n +1 are added to each parameter to respectively represent the values of the parameter corresponding to the time n and the time n + 1.
6. The LCC-VSC hybrid direct current grid electromechanical transient simulation method of claim 5, wherein the Jacobian matrix is constructed by row ordering and column ordering using the following method:
sequencing the corresponding differential equation sets in a row sequence, namely sequentially sequencing a direct-current line differential equation (8), an LCC converter direct-current side differential equation (9), an LCC converter direct-current side differential equation (10), a VSC converter direct-current side differential equation (13), an LCC converter direct-current side differential equation (11), a VSC converter direct-current side differential equation (14) and a VSC converter direct-current side differential equation (12);
the column sequence corresponds to the mixed direct current network state variable sequence and sequentially comprises current flowing through a direct current circuit, direct current voltage of a side end node connected with the direct current circuit and the LCC converter, direct current circuit node ground capacitance branch current, current injected into the direct current circuit by the LCC converter, current injected into the direct current circuit by the VSC converter and direct current voltage of a side end node connected with the direct current circuit and the VSC converter.
7. The LCC-VSC hybrid direct current grid electromechanical transient simulation method according to claim 4, characterized in that the LCC converter direct current side voltage UiObtaining by calculation using equation (15):
Figure FDA0003166574170000041
in the formula, EiMeasuring the voltage, alpha, for the LCC converter ACiThe control trigger angle of the LCC converter.
8. An LCC-VSC hybrid direct current grid electromechanical transient simulation device is characterized by comprising:
a dynamic model construction unit: the system is used for constructing a hybrid direct-current power grid dynamic model according to the characteristics of the hybrid direct-current power grid dynamic elements and the network topology;
a difference equation set construction unit: the system comprises a simulation step length generation unit, a difference equation set and a difference equation set, wherein the simulation step length generation unit is used for generating a difference equation set corresponding to a dynamic model of the hybrid direct-current power grid according to a preset simulation step length;
a jacobian matrix construction unit: the method comprises the steps of constructing a Jacobian matrix according to a partial derivative term of a state variable of a mixed direct current network of a difference equation set;
an iteration solving unit: the method is used for carrying out iterative solution on the differential equation set at the current simulation time by adopting a Newton-Raphson method, and continuously updating variable elements in the differential equation set and the Jacobian matrix in the iterative process until convergence;
an acquisition unit: and the method is used for obtaining the state variable of the hybrid direct-current power grid at the next simulation moment according to the solving result of the differential equation set at the current simulation moment.
9. An LCC-VSC hybrid direct current power grid electromechanical transient simulation device is characterized by comprising a processor and a storage medium;
the storage medium is used for storing instructions; the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any one of claims 1 to 7.
10. Computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 7.
CN202110806544.7A 2021-07-16 2021-07-16 Electromechanical transient simulation method and device for LCC-VSC hybrid direct-current power grid and storage medium Pending CN113659604A (en)

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WO2024037429A1 (en) * 2022-08-17 2024-02-22 国网经济技术研究院有限公司 Method and system for calculating main-loop parameters of slcc, and readable medium
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