A method and system for determining state space equations of a new energy power system

Abstract

The application discloses a method and system for determining a state space equation of a new energy power system, comprising: segmenting a power system according to a power system topology, determining a main grid subsystem and at least one new energy station subsystem, and establishing interface variables between the main grid subsystem and the new energy station subsystem; determining state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem; determining state space equations corresponding to a basic loop set and a different branch set of the main grid subsystem respectively; determining a state space equation of the power system based on the state space equations corresponding to the basic loop set and the different branch set and the state variables and the input variables of the system, so as to analyze system stability based on the state space equation of the power system.

Description

Technical Field

[0001] The present invention relates to the technical field of modeling and analysis of small-disturbance stability of power systems, and more particularly, to a method and system for determining a state-space equation of a new energy power system. Background Art

[0002] (1) Introduction to state-space model

[0003] The eigenvalue analysis method is one of the effective methods for studying the stability of power systems under small disturbances. It has been widely used in the study of low-frequency oscillations, subsynchronous / supersynchronous oscillations, etc. The state space equation is the system model used in eigenvalue analysis, and its general expression is:

[0004]

[0005] Among them, X s is a column vector of state variables, U s is a column vector of input variables, Y s is a column vector of output variables, A s 、B s 、C s and D s is a real parameter matrix. In the study of low-frequency oscillations, differential equations are generally used to describe only devices such as synchronous generators, and the corresponding state-space equations are linearized. Algebraic equations are used to describe the power network equations, ignoring the influence of their dynamic characteristics. However, for broadband oscillations (generally in the 5 to 4000 Hz range) involving sub- / supersynchronous and medium- and high-frequency bands, the dynamic characteristics of the power grid have a certain impact on the oscillations, necessitating the establishment of state-space equations for the entire system, including the power network.

[0006] (2) State space model of new energy system

[0007] For complex power networks containing renewable energy sources, node voltages and branch currents are linked through the series and parallel connections of grid components, and must satisfy Kirchhoff's laws. Therefore, topological analysis of the power network is necessary to determine the system's independent state variables, eliminate all intermediate variables, and ultimately obtain a state-space model of the entire system. This process is particularly complex, as determining the state variables within the grid is complex.

[0008] A typical structure of a complex multi-new energy station grid-connected system is as follows: Figure 1 As shown in the figure, multiple new energy stations are distributed and connected to the mesh system. The grid components include resistance / inductance branches between nodes, series compensation capacitors, node-to-ground parallel resistance / inductance / capacitance branches, etc. For inductive devices, their state space equation in the dq synchronous coordinate system is:

[0009]

[0010] Among them, i L is the inductor current, which is a state variable; v L is the inductor voltage, which is the input variable; L is the inductor value; w0 is the power frequency angular frequency; J is the imaginary operation matrix, and its expression is

[0011]

[0012] For a capacitive device, its state space equation in the dq synchronous coordinate system is:

[0013]

[0014] Among them, v C is the capacitor voltage, which is a state variable; i C is the capacitor current and is the input variable; C is the capacitance value. For a renewable energy station, it consists of multiple renewable energy units connected by bus lines, usually equivalent to a single unit. The state space equation of this unit must be constructed by combining the linearized differential equations of its electrical and control links. The current of the renewable energy station is both one of the state variables and the output variable input into the AC power grid model; the voltage of the renewable energy station is one of the input variables, obtained from the AC power grid model.

[0015] In the system composed of the above-mentioned devices, the new energy station will take the port voltage obtained from the AC power grid as input and output the port current to the AC power grid; the inductor device will take the voltage difference between the two ends obtained from the AC power grid as input and output its own current to the AC power grid; the capacitor device will take its own current obtained from the AC power grid as input and output its own voltage to the AC power grid.

[0016] (3) Electrical network analysis based on graph theory

[0017] When performing topological analysis on a power grid, the association matrix A is often used to describe the association between each node and each branch. When using the loop method for analysis, the association matrix B is often used to describe the association between each basic loop and each branch. The voltage and current of the power grid satisfy Kirchhoff's law, that is,

[0018]

[0019] Among them, i b is the branch current column vector, u b is the branch voltage column vector, i lis the loop current column vector. When forming a basic loop, power grid branches are often divided into branches and interconnected branches. If the number of nodes in a grid is N+1, including N independent nodes and 1 ground node, and the number of branches is b, then the number of branches in the grid is N, and the number of interconnected branches L = bN. A loop consisting of one interconnected branch and multiple branches is called a basic loop, and its number is equal to the number of interconnected branches.

[0020] When performing eigenvalue analysis on a power system, it is necessary to establish state-space equations based on the linearization of the system. For complex power networks containing multiple renewable energy sources, topological analysis is required to determine the system's independent state variables, then eliminate all intermediate variables to ultimately obtain a state-space model of the entire system. The key challenges in modeling are determining the state variables and forming independent state-space equations. Summary of the Invention

[0021] The present invention proposes a method and system for determining a state space equation of a new energy power system to solve the problem of how to determine the state space method.

[0022] In order to solve the above problem, according to one aspect of the present invention, a method for determining a state space equation of a new energy power system is provided, the method comprising:

[0023] Segmenting the power system according to the power system topology, determining a main grid subsystem and at least one new energy station subsystem, and establishing interface variables between the main grid subsystem and the new energy station subsystem;

[0024] Determine the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem;

[0025] Determine the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem respectively;

[0026] Based on the state space equations corresponding to the basic loop set and different branch sets and the state variables and input variables of the system, the state space equations of the power system are determined, so as to analyze the system stability based on the state space equations of the power system.

[0027] Preferably, the step of segmenting the power system according to the power system topology, determining the main grid subsystem and at least one new energy station subsystem, and establishing interface variables between the main grid subsystem and the new energy station subsystem includes:

[0028] The capacitance branch between independent nodes in the power system is considered a Type I state branch; the capacitance branch between an independent node and the ground node is considered a Type II state branch; and the new energy station is considered a voltage-dependent controlled current source and is considered a Type III state branch. If there is no capacitance branch between the grid-connected node and the ground node of a new energy station, a capacitance branch is added there.

[0029] According to the power system topology, the power system is divided into a main grid subsystem and multiple new energy station subsystems. All resistance-sensitivity branches between independent nodes, type I state branches, and resistance-sensitivity branches between independent nodes and ground nodes are merged into a preliminary main grid subsystem.

[0030] Construct a basic circuit set for the main network subsystem, dividing all branches of the main network subsystem into branches and link branches. Type I state branches must be link branches, and each link branch and several branches form a basic circuit. Type II state branches are added to the main network subsystem in the form of link branches.

[0031] At the original grid-connected nodes of each new energy source in the main grid subsystem, the ground capacitor is replaced with a controlled voltage source as a new Type II state branch, and the control voltage value is equal to the voltage of the ground capacitor; at the original grid-connected nodes of each new energy station subsystem, the ground capacitor is added, and a controlled current source is added, whose current value is equal to the loop current flowing through the Type II state branch, to establish interface variables between subsystems.

[0032] Preferably, the determining of the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem includes:

[0033] The main network basic loop current i l , I-type state branch voltage v sc , Type II state branch current i G and its associated state variable X G , and the type III state branch voltage v pc , merged into the state variables of the system

[0034] Each constant frequency voltage source e s , constant frequency current source i s and / or all new energy stations’ input variables U G , combined into the system input variable U=[e s i s U G ] T .

[0035] Preferably, the determining of the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem respectively includes:

[0036] The state space equation corresponding to the basic loop set is:

[0037]

[0038] The state space equation corresponding to the type I state branch set is:

[0039]

[0040] The state space equation corresponding to the type II state branch set is:

[0041]

[0042] The state space equation corresponding to the type III state branch set is:

[0043]

[0044] Among them, Z b , L b 、R b They are the grid branch impedance, branch inductance, and branch resistance matrices respectively; B is the main network basic loop-branch correlation matrix; M b-sc is the correlation matrix of the power grid branch to the type I state branch, M b-pc is the correlation matrix of the power grid branch to the type II state branch, M b-es is the correlation matrix of the power grid branches to the branches containing voltage sources, M b-is is the correlation matrix of the power grid branches to the branches containing current sources; C pc is the capacitance coefficient matrix of the type II state branch set, M pc-G is the association matrix of type II state branches to type III state branches;

[0045] The coefficient matrix of the state space equation of the type III state branch set is:

[0046]

[0047]

[0048] The coefficient matrix is ​​composed of the internal state space equation of each new energy station.

[0049]

[0050] The coefficient matrix in is reorganized according to the sequence number of the new energy stations.

[0051] Preferably, determining the state space equation of the power system based on the state space equations corresponding to the basic loop set and different branch sets and the state variables and input variables of the system, so as to analyze the system stability based on the state space equation of the power system, includes:

[0052] The state equation of the power system is determined as:

[0053]

[0054]

[0055]

[0056] Among them, X is the state variable of the system; U is the input variable of the system; A s and B s is the coefficient matrix;

[0057] Based on the state space equation of the power system, the eigenvalues ​​and correlation factors of the matrix As are calculated, and the system stability is analyzed according to the eigenvalues ​​and correlation factors of the matrix As.

[0058] According to another aspect of the present invention, a system for determining a state-space equation of a new energy power system is provided, the system comprising:

[0059] A segmentation unit is used to segment the power system according to the power system topology, determine the main grid subsystem and at least one new energy station subsystem, and establish interface variables between the main grid subsystem and the new energy station subsystem;

[0060] A state variable and input variable determination unit, configured to determine the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem;

[0061] The first state space equation determination unit is used to determine the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem respectively;

[0062] The second state space equation determination unit is used to determine the state space equation of the power system based on the state space equations corresponding to the basic loop set and different branch sets and the state variables and input variables of the system, so as to analyze the system stability based on the state space equation of the power system.

[0063] Preferably, the segmentation unit segments the power system according to the power system topology, determines the main grid subsystem and at least one new energy station subsystem, and establishes interface variables between the main grid subsystem and the new energy station subsystem, including:

[0064] The capacitance branch between independent nodes in the power system is considered a Type I state branch; the capacitance branch between an independent node and the ground node is considered a Type II state branch; and the new energy station is considered a voltage-dependent controlled current source and is considered a Type III state branch. If there is no capacitance branch between the grid-connected node and the ground node of a new energy station, a capacitance branch is added there.

[0065] According to the power system topology, the power system is divided into a main grid subsystem and multiple new energy station subsystems. All resistance-sensitivity branches between independent nodes, type I state branches, and resistance-sensitivity branches between independent nodes and ground nodes are merged into a preliminary main grid subsystem.

[0066] Construct a basic circuit set for the main network subsystem, dividing all branches of the main network subsystem into branches and link branches. Type I state branches must be link branches, and each link branch and several branches form a basic circuit. Type II state branches are added to the main network subsystem in the form of link branches.

[0067] At the original grid-connected nodes of each new energy source in the main grid subsystem, the ground capacitor is replaced with a controlled voltage source as a new Type II state branch, and the control voltage value is equal to the voltage of the ground capacitor; at the original grid-connected nodes of each new energy station subsystem, the ground capacitor is added, and a controlled current source is added, whose current value is equal to the loop current flowing through the Type II state branch, to establish interface variables between subsystems.

[0068] Preferably, the state variable and input variable determining unit determines the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem, including:

[0069] The main network basic loop current i l , I-type state branch voltage v sc , Type II state branch current i G and its associated state variable X G , and the type III state branch voltage v pc , merged into the state variables of the system

[0070] Each constant frequency voltage source e s , constant frequency current source i s and / or all new energy stations’ input variables U G , combined into the system input variable U=[e s i s U G ] T .

[0071] Preferably, the first state space equation determination unit determines the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem respectively, including:

[0072] The state space equation corresponding to the basic loop set is:

[0073]

[0074] The state space equation corresponding to the type I state branch set is:

[0075]

[0076] The state space equation corresponding to the type II state branch set is:

[0077]

[0078] The state space equation corresponding to the type III state branch set is:

[0079]

[0080] Among them, Z b , L b 、R b They are the grid branch impedance, branch inductance, and branch resistance matrices respectively; B is the main network basic loop-branch correlation matrix; M b-sc is the correlation matrix of the power grid branch to the type I state branch, M b-pc is the correlation matrix of the power grid branch to the type II state branch, M b-es is the correlation matrix of the power grid branches to the branches containing voltage sources, M b-is is the correlation matrix of the power grid branches to the branches containing current sources; C pc is the capacitance coefficient matrix of the type II state branch set, M pc-G is the association matrix of type II state branches to type III state branches;

[0081] The coefficient matrix of the state space equation of the type III state branch set is:

[0082]

[0083]

[0084] The coefficient matrix is ​​composed of the internal state space equation of each new energy station.

[0085]

[0086] The coefficient matrix in is reorganized according to the sequence number of the new energy stations.

[0087] Preferably, the second state-space equation determining unit determines the state-space equation of the power system based on the state-space equations corresponding to the basic loop set and different branch sets and the state variables and input variables of the system, so as to analyze the system stability based on the state-space equation of the power system, including:

[0088] The state equation of the power system is determined as:

[0089]

[0090]

[0091]

[0092] Among them, X is the state variable of the system; U is the input variable of the system; A s and B s is the coefficient matrix;

[0093] Based on the state space equation of the power system, the eigenvalues ​​and correlation factors of the matrix As are calculated, and the system stability is analyzed according to the eigenvalues ​​and correlation factors of the matrix As.

[0094] The present invention provides a method and system for determining the state space equation of a new energy power system, comprising: dividing the power system according to the power system topology, determining a main grid subsystem and at least one new energy station subsystem, and establishing interface variables between the main grid subsystem and the new energy station subsystem; determining the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem; respectively determining the state space equations corresponding to the basic loop set and different branch sets of the main grid subsystem; determining the state space equations of the power system based on the state space equations corresponding to the basic loop set and different branch sets and the state variables and input variables of the system, so as to analyze the stability of the system based on the state space equations of the power system. Compared with the prior art, the present invention has the following advantages: (1) In view of the structural characteristics of the general power system which is mainly composed of series inductive devices, parallel inductive devices and parallel capacitive devices, the system is divided into the main grid subsystem and the new energy station subsystem, and the main grid basic loop and three types of state branches are used to describe the system, thereby optimizing and classifying the system state variables, and regularly and conveniently obtaining the independent state variables of the system, which facilitates the use of computer programs for state space modeling; (2) Combined with the optimization of state variables and the addition of a parallel capacitance branch to the ground at the grid-connected node of the new energy station, the decoupling of most state variables mainly based on branch current is achieved. Therefore, in the process of establishing the state space model of the power network, no intermediate variables will appear, which saves the complex calculation of eliminating intermediate variables and greatly simplifies the modeling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0096] Figure 1 This is a schematic diagram of a typical multi-renewable energy station grid connection calculation system;

[0097] Figure 2 2 is a schematic structural diagram of a method 200 for determining a state-space equation of a new energy power system according to an embodiment of the present invention;

[0098] Figure 3 A schematic diagram of determining a state space equation according to an embodiment of the present invention;

[0099] Figure 4 Schematic diagram of the main network subsystem of the example system according to an embodiment of the present invention;

[0100] Figure 5 A schematic diagram of a new energy station subsystem of an example system according to an embodiment of the present invention;

[0101] Figure 6 Schematic diagram of the structure of a system 600 for determining a state-space equation of a new energy power system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0102] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a thorough and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0103] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0104] Figure 2 FIG. 2 is a schematic diagram of a method 200 for determining a state space equation of a new energy power system according to an embodiment of the present invention. Figure 2As shown, the method for determining the state space equation of the new energy power system provided by the embodiment of the present invention has the following advantages over the existing technology: (1) In view of the structural characteristics of the general power system which is mainly composed of series inductive devices, parallel inductive devices and parallel capacitive devices, the system is divided into the main grid subsystem and the new energy station subsystem, and the main grid basic loop and three types of state branches are used to describe the system, and then the system state variables are optimized and classified, and the independent state variables of the system can be obtained regularly and conveniently, which is convenient for state space modeling using computer programs; (2) Combined with the optimization of state variables and the addition of a parallel capacitance branch to the ground at the grid-connected node of the new energy station, the decoupling of most state variables mainly based on branch current is achieved. Therefore, in the process of establishing the state space model of the power network, no intermediate variables will appear, which saves the complex calculation of eliminating intermediate variables and greatly simplifies the modeling process. The method 200 for determining the state space equation of a new energy power system provided in an embodiment of the present invention starts from step 201. In step 201, the power system is divided according to the power system topology, the main grid subsystem and at least one new energy station subsystem are determined, and interface variables are established between the main grid subsystem and the new energy station subsystem.

[0105] Preferably, the step of segmenting the power system according to the power system topology, determining the main grid subsystem and at least one new energy station subsystem, and establishing interface variables between the main grid subsystem and the new energy station subsystem includes:

[0106] The capacitance branch between independent nodes in the power system is considered a Type I state branch; the capacitance branch between an independent node and the ground node is considered a Type II state branch; and the new energy station is considered a voltage-dependent controlled current source and is considered a Type III state branch. If there is no capacitance branch between the grid-connected node and the ground node of a new energy station, a capacitance branch is added there.

[0107] According to the power system topology, the power system is divided into a main grid subsystem and multiple new energy station subsystems. All resistance-sensitivity branches between independent nodes, type I state branches, and resistance-sensitivity branches between independent nodes and ground nodes are merged into a preliminary main grid subsystem.

[0108] Construct a basic circuit set for the main network subsystem, dividing all branches of the main network subsystem into branches and link branches. Type I state branches must be link branches, and each link branch and several branches form a basic circuit. Type II state branches are added to the main network subsystem in the form of link branches.

[0109] At the original grid-connected nodes of each new energy source in the main grid subsystem, the ground capacitor is replaced with a controlled voltage source as a new Type II state branch, and the control voltage value is equal to the voltage of the ground capacitor; at the original grid-connected nodes of each new energy station subsystem, the ground capacitor is added, and a controlled current source is added, whose current value is equal to the loop current flowing through the Type II state branch, to establish interface variables between subsystems.

[0110] The state space modeling method described in the present invention is aimed at a complex AC power grid containing multiple renewable energy stations, automatically determines state variables and lists the state space equations of the entire system.

[0111] In the dq synchronous coordinate system, the current vector of the k-th branch, the voltage vector of the k-th branch, the voltage vector of the k-th node, the voltage source vector of the k-th branch, the current source vector of the k-th branch, and the current vector of the k-th new energy station are defined as follows:

[0112]

[0113] The specific process of generating the state space equation of the whole system in the present invention is as follows: Figure 3 As shown. Combined Figure 3 As shown, in the present invention, first, a main network basic circuit set and three state branch sets must be formed. Specifically, they include:

[0114] 1) The capacitance branch between independent nodes in the power grid, i.e., the series compensation capacitor, is named as type I state branch, with a total of b C The capacitance branch between the independent node and the ground node, including the equivalent capacitive reactive load of the node and the ground capacitance of the transmission line connected to the node, is named as the type II state branch, with a total of n C0 The new energy station is regarded as a voltage-dependent controlled current source and named as a type III state branch, with a total of n G If there is no capacitance branch between the grid-connected node and the ground node of a new energy station, a capacitance branch is added here, and the total capacitance of the newly added branches is n. C1 The total number of type II state branches is updated to n C =n C0 +n C1 .

[0115] 2) Based on the original power grid topology, the system is divided into the main grid subsystem (hereinafter referred to as the main grid) and multiple new energy station subsystems. All the resistance-inductive branches between independent nodes, the capacitance branches between independent nodes (i.e., type I state branches), and the resistance-inductive branches between independent nodes and ground nodes are merged into a preliminary main grid, with a total number of branches of b = b L +b C +n L; Construct a basic circuit set for the main network, that is, divide all branches of the main network into N branches and bN connecting branches, among which type I state branches must be connecting branches, and each connecting branch and several branches form a basic circuit.

[0116] 3) Add the capacitive branch between the independent node and the ground node, i.e., the type II state branch, to the main network in the form of a branch. Then, the number of basic circuits in the main network increases by n. C The total number of branches is updated to b = b L +b C +n L +n C .

[0117] 4) Establish interface variables between subsystems, that is: at the original grid-connected nodes of each new energy source in the main grid subsystem, replace the ground capacitor with a controlled voltage source as a new type II state branch, and control the voltage value to be equal to the voltage of the ground capacitor; at the original grid-connected nodes of each new energy station subsystem, add the ground capacitor and add a controlled current source, whose current value is equal to the loop current flowing through the type II state branch. Figure 4 As shown in Figure 1, it is a schematic diagram of the main grid subsystem obtained by segmenting a typical multi-new energy station grid-connected calculation system. Figure 5 As shown in Figure 1, it is a schematic diagram of the new energy station subsystem obtained by segmenting a typical multi-new energy station grid-connected calculation system. The numbers in the form of [1] represent the basic circuit numbers of the main network, and the curves represent the circuit structure and the equivalent controlled voltage source. The controlled voltage source is the interface variable between the subsystems.

[0118] In step 102, the state variables and input variables of the system are determined based on the main grid subsystem and the new energy station subsystem.

[0119] Preferably, the determining of the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem includes:

[0120] The main network basic loop current i l , I-type state branch voltage v sc , Type II state branch current i G and its associated state variable X G , and the type III state branch voltage v pc , merged into the state variables of the system

[0121] Each constant frequency voltage source e s , constant frequency current source i s and / or all new energy stations’ input variables U G , combined into the system input variable U=[e s i s UG ] T .

[0122] In the present invention, in the dq synchronous coordinate system, the following methods are used to determine the state variables and input variables:

[0123] 1) The main network basic loop current i l , I-type state branch voltage v sc , Type II state branch voltage v pc , and the type III state branch current i G and its associated state variable X G , merged into the system state variable X=[i l v sc v pc i G X G ] T .

[0124] 2) Set each constant frequency voltage source e s (if any), constant power frequency current source i s (if any), and the input variables U of all new energy stations G , combined into the system input variable U=[e s i s U G ] T .

[0125] In step 103, the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem are determined respectively.

[0126] Preferably, the determining of the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem respectively includes:

[0127] The state space equation corresponding to the basic loop set is:

[0128]

[0129] The state space equation corresponding to the type I state branch set is:

[0130]

[0131] The state space equation corresponding to the type II state branch set is:

[0132]

[0133] The state space equation corresponding to the type III state branch set is:

[0134]

[0135] Among them, Z b , L b 、R b They are the grid branch impedance, branch inductance, and branch resistance matrices respectively; B is the main network basic loop-branch correlation matrix; M b-sc is the correlation matrix of the power grid branch to the type I state branch, M b-pc is the correlation matrix of the power grid branch to the type II state branch, M b-es is the correlation matrix of the power grid branches to the branches containing voltage sources, M b-is is the correlation matrix of the power grid branches to the branches containing current sources; C pc is the capacitance coefficient matrix of the type II state branch set, M pc-G is the correlation matrix of type II state branches to type III state branches. The coefficient matrix of the state space equation of type III state branches is:

[0136]

[0137]

[0138] The coefficient matrix is ​​composed of the internal state space equation of each new energy station.

[0139]

[0140] The coefficient matrix in is reorganized according to the sequence number of the new energy stations.

[0141] In step 104, based on the state space equations corresponding to the basic loop set and different branch sets and the state variables and input variables of the system, the state space equations of the power system are determined to analyze the system stability based on the state space equations of the power system.

[0142] Preferably, determining the state space equation of the power system based on the state space equations corresponding to the basic loop set and different branch sets and the state variables and input variables of the system, so as to analyze the system stability based on the state space equation of the power system, includes:

[0143] The state equation of the power system is determined as:

[0144]

[0145]

[0146]

[0147] Among them, X is the state variable of the system; U is the input variable of the system; A s and B s is the coefficient matrix;

[0148] Based on the state space equation of the power system, the eigenvalues ​​and correlation factors of the matrix As are calculated, and the system stability is analyzed according to the eigenvalues ​​and correlation factors of the matrix As.

[0149] In the present invention, it is also necessary to list the state space equations of each part.

[0150] 1) Write the state space equation for the main network basic loop set:

[0151]

[0152] Among them, Z b , L b 、R b are the grid branch impedance, branch inductance, and branch resistance matrices respectively. B is the main network basic loop-branch association matrix, referred to as the return branch association matrix, with a dimension of 2(bN)×2b. Its calculation rule is: if loop m contains branch n and the two have the same direction, then the submatrix B of B from row 2m-1 to 2m and column 2n-1 to 2n is (mn) =E2, where E2 is the second-order identity matrix; if loop m contains branch n and the two branches are in opposite directions, then B (mn) =-E2; in other cases B (mn) is a zero matrix. M b-sc is the correlation matrix of the power grid branch to the type I state branch, M b-pc is the correlation matrix of the power grid branch to the type II state branch, M b-es is the correlation matrix of the power grid branches to the branches containing voltage sources, M b-is is the correlation matrix of the power grid branch to the branch containing the current source. These types of correlation matrices (general code M b-Q ) is calculated as follows: if branch m is equal to the nth element of a branch set Q, then the matrix M b-Q The submatrix M of rows 2m-1 to 2m and columns 2n-1 to 2n b-Q(mn) =E2, otherwise M b-Q(mn) is a zero matrix.

[0153] The final expression of this part of the state space equation is:

[0154]

[0155] 2) Write the state space equation for the type I state branch set:

[0156]

[0157] Among them, C sc is the capacitance coefficient matrix of the type I state branch set. The final expression of this part of the state space equation is

[0158]

[0159] 3) Write the state space equation for the type II state branch set:

[0160]

[0161] Among them, C pc is the capacitance coefficient matrix of the type II state branch set, M pc-G is the correlation matrix of type II state branches to type III state branches (new energy stations), and its calculation rule is: if a certain grid node is connected to a ground capacitance branch m and the nth new energy station, then the matrix M pc-G The submatrix M of rows 2m-1 to 2m and columns 2n-1 to 2n pc-G(mn) =E2, otherwise M pc-G(mn) is a zero matrix. The final expression of this part of the state space equation is

[0162]

[0163] 4) Write the state space equation for the type III state branch set:

[0164]

[0165] The coefficient matrix in the formula is composed of the internal state space equation of each new energy station

[0166]

[0167] The coefficient matrix in is reorganized according to the sequence number of the new energy station, that is,

[0168]

[0169] (4) The system state space equation is obtained by combining equations (8), (10), (12), and (13):

[0170]

[0171] In short:

[0172]

[0173] Based on the state space equation, the system stability can be analyzed by calculating the eigenvalues ​​and correlation factors of the matrix As.

[0174] The following examples illustrate the embodiments of the present invention.

[0175] by Figure 1For example, a case study of 2 wind farms and 5 nodes is given. The independent nodes are marked in the form of "①" and the branches are marked in the form of "(1)". The number of independent nodes in the power grid in this case is N = 5 (excluding ground nodes); the number of new energy stations is n G =2; number of resistance-inductive branches between independent nodes b L =4, number of independent node-to-node capacitance (i.e. series compensation capacitance) branches b C =1; resistance-inductive branch n between independent node and ground L =2, the number of capacitance branches between an independent node and ground is n C0 =1.

[0176] The specific process of generating the state space equations of the entire system includes:

[0177] (1) Forming the main network basic circuit and three state branches

[0178] 1) Type I state branches in the power grid include branch 6, number of branches b C =1; Type II state branch includes branch C n3 、C n1 , total n C0 =2; Type III state branches include G1 and G2 branches, number n G =2; the newly added Type II state branches due to the new energy station include branch C n2 , number n C1 =1, the total number of final type II state branches is n C =n C0 +n C1 =3.

[0179] 2) According to the original power grid topology, establish the main grid subsystem such as Figure 4 As shown, the total number of branches is b = b L +b C +n L =7, the total number of its branches is bN=2, including branch 6 and branch 4, of which the type I state branch includes branch 6, the number of branches is b C =1, the basic loop [1] to basic loop 2 formed in this step are as follows Figure 4 shown.

[0180] 3) Add the type II state branch to the main network in the form of a branch, and the total number of branches in the main network is updated to b = b L +b C +n L +n C =10, the number of basic circuits in the main network has increased by n C =3, the newly added basic circuits [3] to [5] are as follows Figure 4 shown.

[0181] (2) Determine state variables and input variables

[0182] 1) The state variables of this example are expressed as follows:

[0183]

[0184] 2) In this example, there is no current source branch. The input variables include the voltage source and the auxiliary input variables of the new energy stations G1 and G2, namely:

[0185]

[0186] (3) Write down the state space equations for each part

[0187] 1) State space equation of the main network basic loop. For this example, the expressions of each term in equation (8) are

[0188]

[0189] Where E2 is the 2nd-order identity matrix and O2 is the 2×2 zero matrix.

[0190] 2) State space equation of type I state branch. For this example, the expressions in equation (10) are

[0191] C sc =C6E2 (22)

[0192] 3) State space equation of type II state branch. For this example, the expressions in equation (12) are

[0193]

[0194] 4) State space equations for type III state branches. For this example, the expressions in equation (13) are

[0195]

[0196] (4) The system state space equation is obtained by combining the equations.

[0197] Substituting Equations (18)-(24) into Equation (16), we can obtain the system state-space equation for this example, which is shown in Equation (17). Based on this state-space equation, we can analyze the system stability by calculating the eigenvalues ​​and correlation factors of the matrix As.

[0198] Figure 6 FIG. 6 is a schematic diagram of a system 600 for determining a state space equation of a new energy power system according to an embodiment of the present invention. Figure 6As shown, the system 600 for determining the state space equation of the new energy power system provided by the embodiment of the present invention includes: a segmentation unit 601, a state variable and input variable determination unit 602, a first state space equation determination unit 603 and a second state space equation determination unit 604.

[0199] Preferably, the segmentation unit 601 is used to segment the power system according to the power system topology, determine the main grid subsystem and at least one new energy station subsystem, and establish interface variables between the main grid subsystem and the new energy station subsystem.

[0200] Preferably, the segmentation unit 601 segments the power system according to the power system topology, determines the main grid subsystem and at least one new energy station subsystem, and establishes interface variables between the main grid subsystem and the new energy station subsystem, including:

[0201] The capacitance branch between independent nodes in the power system is considered a Type I state branch; the capacitance branch between an independent node and the ground node is considered a Type II state branch; and the new energy station is considered a voltage-dependent controlled current source and is considered a Type III state branch. If there is no capacitance branch between the grid-connected node and the ground node of a new energy station, a capacitance branch is added there.

[0202] According to the power system topology, the power system is divided into a main grid subsystem and multiple new energy station subsystems. All resistance-sensitivity branches between independent nodes, type I state branches, and resistance-sensitivity branches between independent nodes and ground nodes are merged into a preliminary main grid subsystem.

[0203] Construct a basic circuit set for the main network subsystem, dividing all branches of the main network subsystem into branches and link branches. Type I state branches must be link branches, and each link branch and several branches form a basic circuit. Type II state branches are added to the main network subsystem in the form of link branches.

[0204] At the original grid-connected nodes of each new energy source in the main grid subsystem, the ground capacitor is replaced with a controlled voltage source as a new Type II state branch, and the control voltage value is equal to the voltage of the ground capacitor; at the original grid-connected nodes of each new energy station subsystem, the ground capacitor is added, and a controlled current source is added, whose current value is equal to the loop current flowing through the Type II state branch, to establish interface variables between subsystems.

[0205] Preferably, the state variable and input variable determining unit 602 is used to determine the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem.

[0206] Preferably, the state variable and input variable determining unit 602 determines the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem, including:

[0207] The main network basic loop current i l , I-type state branch voltage v sc , Type II state branch current i G and its associated state variable X G , and the type III state branch voltage v pc , merged into the state variables of the system

[0208] Each constant frequency voltage source e s , constant frequency current source i s and / or all new energy stations’ input variables U G , combined into the system input variable U=[e s i s U G ] T .

[0209] Preferably, the first state-space equation determining unit 603 is used to respectively determine the state-space equations corresponding to the basic loop set and different branch sets of the main network subsystem.

[0210] Preferably, the first state space equation determination unit 603 determines the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem, respectively, including:

[0211] The state space equation corresponding to the basic loop set is:

[0212]

[0213] The state space equation corresponding to the type I state branch set is:

[0214]

[0215] The state space equation corresponding to the type II state branch set is:

[0216]

[0217] The state space equation corresponding to the type III state branch set is:

[0218]

[0219] Among them, Z b , L b 、R bThey are the grid branch impedance, branch inductance, and branch resistance matrices respectively; B is the main network basic loop-branch correlation matrix; M b-sc is the correlation matrix of the power grid branch to the type I state branch, M b-pc is the correlation matrix of the power grid branch to the type II state branch, M b-es is the correlation matrix of the power grid branches to the branches containing voltage sources, M b-is is the correlation matrix of the power grid branches to the branches containing current sources; C pc is the capacitance coefficient matrix of the type II state branch set, M pc-G is the correlation matrix of type II state branches to type III state branches. The coefficient matrix of the state space equation of type III state branches is:

[0220]

[0221]

[0222] The coefficient matrix is ​​composed of the internal state space equation of each new energy station.

[0223]

[0224] The coefficient matrix in is reorganized according to the sequence number of the new energy stations.

[0225] Preferably, the second state-space equation determination unit 604 is configured to determine the state-space equation of the power system based on the state-space equations corresponding to the basic loop set and different branch sets, as well as the state variables and input variables of the system, so as to analyze the system stability based on the state-space equation of the power system. Preferably, the second state-space equation determination unit, which determines the state-space equation of the power system based on the state-space equations corresponding to the basic loop set and different branch sets, as well as the state variables and input variables of the system, so as to analyze the system stability based on the state-space equation of the power system, includes:

[0226] The state equation of the power system is determined as:

[0227]

[0228]

[0229]

[0230] Among them, X is the state variable of the system; U is the input variable of the system; A s and B s is the coefficient matrix;

[0231] Based on the state space equation of the power system, the eigenvalues ​​and correlation factors of the matrix As are calculated, and the system stability is analyzed according to the eigenvalues ​​and correlation factors of the matrix As.

[0232] The system 600 for determining the state-space equation of a new energy power system according to the embodiment of the present invention corresponds to the method 200 for determining the state-space equation of a new energy power system according to another embodiment of the present invention, and will not be described in detail here.

[0233] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0234] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / the [means, component, etc.]" are to be interpreted openly as referring to at least one instance of the means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily need to be performed in the exact order disclosed, unless explicitly stated otherwise.

[0235] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0236] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0237] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0238] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0239] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for determining the state space equation of a new energy power system, characterized in that: The method comprises: Segmenting the power system according to the power system topology, determining a main grid subsystem and at least one new energy station subsystem, and establishing interface variables between the main grid subsystem and the new energy station subsystem; Determine the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem; Determine the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem respectively; Determining a state-space equation of the power system based on the state-space equations corresponding to the basic loop set and different branch sets and the state variables and input variables of the system, so as to analyze the system stability based on the state-space equation of the power system; The step of segmenting the power system according to the power system topology, determining a main grid subsystem and at least one new energy station subsystem, and establishing interface variables between the main grid subsystem and the new energy station subsystem includes: The capacitance branch between independent nodes in the power system is considered a Type I state branch; the capacitance branch between an independent node and the ground node is considered a Type II state branch; and the new energy station is considered a voltage-dependent controlled current source and is considered a Type III state branch. If there is no capacitance branch between the grid-connected node and the ground node of a new energy station, a capacitance branch is added there. According to the power system topology, the power system is divided into a main grid subsystem and multiple new energy station subsystems. All resistance-sensitivity branches between independent nodes, type I state branches, and resistance-sensitivity branches between independent nodes and ground nodes are merged into a preliminary main grid subsystem. Construct a basic circuit set for the main network subsystem, dividing all branches of the main network subsystem into branches and link branches. Type I state branches must be link branches, and each link branch and several branches form a basic circuit. Type II state branches are added to the main network subsystem in the form of link branches. At the original grid-connected nodes of each new energy source in the main grid subsystem, the ground capacitor is replaced with a controlled voltage source as a new Type II state branch, and the control voltage value is equal to the voltage of the ground capacitor; at the original grid-connected nodes of each new energy station subsystem, the ground capacitor is added, and a controlled current source is added, whose current value is equal to the loop current flowing through the Type II state branch, to establish interface variables between subsystems.

2. The method according to claim 1, characterized in that The determining of the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem includes: The main network basic loop current i l , I-type state branch voltage v sc , Type II state branch voltage v pc , and the type III state branch current i G and its associated state variable X G , merged into the system state variable X=[i l v sc v pc i G X G ] T ; Each constant frequency voltage source e s , constant frequency current source i s and / or all new energy stations’ input variables U G , combined into the system input variable U=[e s i s U G ] T .

3. The method according to claim 2, characterized in that The state space equations corresponding to the basic loop set and different branch sets of the main network subsystem are determined separately, including: The state space equation corresponding to the basic loop set is: The state space equation corresponding to the type I state branch set is: The state space equation corresponding to the type II state branch set is: The state space equation corresponding to the type III state branch set is: Among them, Z b , L b 、R b They are the grid branch impedance, branch inductance, and branch resistance matrices respectively; B is the main network basic loop-branch correlation matrix; M b-sc is the correlation matrix of the power grid branch to the type I state branch, M b-pc is the correlation matrix of the power grid branch to the type II state branch, M b-es is the correlation matrix of the power grid branches to the branches containing voltage sources, M b-is is the correlation matrix of the power grid branches to the branches containing current sources; C pc is the capacitance coefficient matrix of the type II state branch set, M pc-G is the incidence matrix of type II state branches to type III state branches; The coefficient matrix of the state space equation of the type III state branch set is: The coefficient matrix is ​​composed of the internal state space equation of each new energy station. The coefficient matrix in is reorganized according to the sequence number of the new energy stations.

4. The method according to claim 3, characterized in that The determining of the state space equation of the power system based on the state space equations corresponding to the basic loop set and different branch sets and the state variables and input variables of the system, and performing system stability analysis based on the state space equation of the power system, includes: The state equation of the power system is determined as: Among them, X is the state variable of the system; U is the input variable of the system; A s and B s is the coefficient matrix; Based on the state space equation of the power system, the eigenvalues ​​and correlation factors of the matrix As are calculated, and the system stability is analyzed according to the eigenvalues ​​and correlation factors of the matrix As.

5. A system for determining the state space equation of a new energy power system, characterized in that: The system comprises: A segmentation unit is used to segment the power system according to the power system topology, determine the main grid subsystem and at least one new energy station subsystem, and establish interface variables between the main grid subsystem and the new energy station subsystem; A state variable and input variable determination unit, configured to determine the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem; The first state space equation determination unit is used to determine the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem respectively; a second state-space equation determining unit, configured to determine a state-space equation of the power system based on the state-space equations corresponding to the basic loop set and different branch sets, as well as the state variables and input variables of the system, so as to analyze system stability based on the state-space equation of the power system; The segmentation unit segments the power system according to the power system topology, determines the main grid subsystem and at least one new energy station subsystem, and establishes interface variables between the main grid subsystem and the new energy station subsystem, including: The capacitance branch between independent nodes in the power system is considered a Type I state branch; the capacitance branch between an independent node and the ground node is considered a Type II state branch; and the new energy station is considered a voltage-dependent controlled current source and is considered a Type III state branch. If there is no capacitance branch between the grid-connected node and the ground node of a new energy station, a capacitance branch is added there. According to the power system topology, the power system is divided into a main grid subsystem and multiple new energy station subsystems. All resistance-sensitivity branches between independent nodes, type I state branches, and resistance-sensitivity branches between independent nodes and ground nodes are merged into a preliminary main grid subsystem. Construct a basic circuit set for the main network subsystem, dividing all branches of the main network subsystem into branches and link branches. Type I state branches must be link branches, and each link branch and several branches form a basic circuit. Type II state branches are added to the main network subsystem in the form of link branches. At the original grid-connected nodes of each new energy source in the main grid subsystem, the ground capacitor is replaced with a controlled voltage source as a new Type II state branch, and the control voltage value is equal to the voltage of the ground capacitor; at the original grid-connected nodes of each new energy station subsystem, the ground capacitor is added, and a controlled current source is added, whose current value is equal to the loop current flowing through the Type II state branch, to establish interface variables between subsystems.

6. The system according to claim 5, characterized in that The state variable and input variable determination unit determines the state variables and input variables of the system based on the main grid subsystem and the new energy station subsystem, including: The main network basic loop current i l , I-type state branch voltage v sc , Type II state branch voltage v pc , and the type III state branch current i G and its associated state variable X G , merged into the system state variable X=[i l v sc v pc i G X G ] T ; Each constant frequency voltage source e s , constant frequency current source i s and / or all new energy stations’ input variables U G , combined into the system input variable U=[e s i s U G ] T .

7. The system according to claim 6, characterized in that The first state space equation determination unit determines the state space equations corresponding to the basic loop set and different branch sets of the main network subsystem, respectively, including: The state space equation corresponding to the basic loop set is: The state space equation corresponding to the type I state branch set is: The state space equation corresponding to the type II state branch set is: The state space equation corresponding to the type III state branch set is: Among them, Z b , L b 、R b They are the grid branch impedance, branch inductance, and branch resistance matrices respectively; B is the main network basic loop-branch correlation matrix; M b-sc is the correlation matrix of the power grid branch to the type I state branch, M b-pc is the correlation matrix of the power grid branch to the type II state branch, M b-es is the correlation matrix of the power grid branches to the branches containing voltage sources, M b-is is the correlation matrix of the power grid branches to the branches containing current sources; C pc is the capacitance coefficient matrix of the type II state branch set, M pc-G is the incidence matrix of type II state branches to type III state branches; The coefficient matrix of the state space equation of the type III state branch set is: The coefficient matrix is ​​composed of the internal state space equation of each new energy station. The coefficient matrix in is reorganized according to the sequence number of the new energy stations.

8. The system according to claim 7, characterized in that The second state-space equation determining unit determines the state-space equation of the power system based on the state-space equations corresponding to the basic loop set and different branch sets, as well as the state variables and input variables of the system, so as to analyze the system stability based on the state-space equation of the power system, including: The state equation of the power system is determined as: Among them, X is the state variable of the system; U is the input variable of the system; A s and B s is the coefficient matrix; Based on the state space equation of the power system, the eigenvalues ​​and correlation factors of the matrix As are calculated, and the system stability is analyzed according to the eigenvalues ​​and correlation factors of the matrix As.

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