Method and system for analyzing influence of network following type new energy power change on transient power angle stability

Abstract

The invention discloses a method and a system for analyzing the influence of network following type new energy power change on transient power angle stability. The method comprises the following steps: calculating an initial power flow of a power system; shrinking the system admittance matrix to a synchronous machine node and a to-be-analyzed wind turbine generator grid-connected node; calculating an instant electrical quantity after the power of the wind turbine generator changes; calculating a synchronous torque coefficient between each synchronous machine node and a wind turbine generator grid-connected node in the system; calculating and analyzing a power change influence coefficient corresponding to the wind turbine generator and an electromagnetic power variable quantity of an equivalent single-machine infinite bus system; and judging the influence of the wind turbine generator power change on the transient power angle stability according to the positive and negative electromagnetic power variation.

Description

Technical Field

[0001] The present invention relates to a method for analyzing the transient power angle stability of an electric power system, and in particular to a method and system for analyzing the influence of power changes of grid-following new energy sources on the transient power angle stability. Background Art

[0002] With the rapid increase in the proportion of wind power access to the power system, the transient stability characteristics of the system have changed significantly. When the system encounters an emergency such as a short circuit fault or DC lockout, it is necessary to include wind farms in the control resources of emergency control, and consider using a machine cut-off or emergency power reduction strategy in wind farms in emergency situations to ensure the safety and stability of the system. From the system level, the sudden drop in power of wind farms during emergency control may not necessarily have a positive effect on the transient power angle stability of the system. When wind power is in the critical group, its power drop is conducive to the transient power angle stability of the system. When wind power is in the remaining group, its power drop is not conducive to the transient power angle stability of the system. However, grid-following wind turbines are not the main body of the system power angle stability and do not directly participate in the system power angle stability movement. There is no clear definition of whether wind turbines belong to the critical group or the remaining group. At present, in engineering applications, wind farms are often divided into groups based on the electrical distance between the critical and remaining groups of synchronous units, and then the transient power angle stability of the system is empirically judged. However, the impact of wind turbine power change on system transient stability is not only affected by the system structure, but also by other types of parameters. Currently, there is no research on this issue, so the existing grouping and judgment methods are not accurate and are only used as engineering references. Therefore, an analysis method is needed to accurately judge the system transient power angle stability of wind farms. Summary of the invention

[0003] Purpose of the invention: In view of the above problems, the present invention proposes a method and system for analyzing the impact of power changes of grid-following renewable energy on transient power angle stability, which can quickly determine the sensitivity, advantages and disadvantages and impact intensity of the impact of power reduction of grid-following renewable energy on transient power angle stability under a specific grid structure operation mode, and improve the accuracy of transient power angle stability analysis of power grid systems containing grid-following renewable energy.

[0004] Technical solution: The technical solution adopted by the present invention is a method for analyzing the influence of the power change of grid-following renewable energy on the transient power angle stability, including:

[0005] Based on the power system and its initial operation mode, the initial power flow of the power system is calculated to obtain the initial value of the power flow and the system admittance matrix when the power system is in a synchronous stable state before the output of the wind turbines changes;

[0006] According to the preset fault, calculate the system disturbance 0 + The electrical quantity at each moment is calculated, and the synchronous machines in the system are grouped based on the extended equal area criterion EEAC to obtain the grouping results;

[0007] According to the system admittance matrix, shrinking the system admittance matrix to the synchronous machine node and the grid-connected node of the wind turbine to be analyzed, to obtain a shrunken system admittance matrix;

[0008] According to the initial value of the power flow, the system admittance matrix after contraction and the system disturbance 0 + The electrical quantity at each moment is used to calculate the angle transfer coefficient and the voltage transfer coefficient; based on the angle transfer coefficient and the voltage transfer coefficient, the synchronous torque coefficient between each synchronous machine node in the system and the grid-connected node of the wind turbine to be analyzed is calculated;

[0009] According to the synchronous torque coefficient between each synchronous machine node and the wind turbine grid-connected node in the system and the grouping result, the influence coefficient of the power change of the wind turbine to be analyzed on the power change of the equivalent single-machine infinite system is calculated; according to the influence coefficient of the power change of the wind turbine to be analyzed on the power change of the equivalent single-machine infinite system, the change of the electromagnetic power of the equivalent single-machine infinite system is calculated;

[0010] The influence of wind turbine power change on transient power angle stability is judged based on the change of electromagnetic power of the equivalent single-machine infinite system.

[0011] As a preferred solution of the method for analyzing the impact of grid-following renewable energy power changes on transient power angle stability described in the present invention, the initial value of the power flow includes the electromotive force in each synchronous machine, the synchronous machine power angle, and the voltage and phase angle of each node.

[0012] As a preferred solution of the analysis method of the influence of the power change of the grid-following new energy on the transient power angle stability described in the present invention, the preset fault is a three-phase short circuit fault occurring on any transmission line of the system; the system disturbance 0+ moment is the moment when the preset fault occurs and causes a sudden change of the non-state quantity in the system; the system disturbance 0 + The electrical quantities at each moment include: voltage amplitude at the wind turbine grid-connected node, voltage phase angle, active power and reactive power of the wind turbine.

[0013] As a preferred scheme of the analysis method of the influence of the change of the power of the grid-following new energy on the transient power angle stability described in the present invention, the grouping of the synchronous machines in the system based on EEAC includes: dividing the synchronous machines into two groups, namely a critical group and a remaining group, based on the power angle trajectory after the disturbance, the critical group represents a combination of synchronous machines whose power angle increases when the system state changes, and the remaining group represents a combination of synchronous machines whose power angle decreases when the system state changes; based on the judgment of the disturbed trajectory of the whole process after the system is disturbed, all the disturbed trajectories are randomly divided into two groups, each of the two groups is fitted with a disturbed trajectory, and then the angle difference of this grouping method is obtained by difference, and the enumeration method is used to make all possible angle differences of the grouping, and the one with the largest angle difference is selected as the grouping method.

[0014] As a preferred solution of the analysis method of the influence of the change of grid-following renewable energy power on the transient power angle stability described in the present invention, the contraction system admittance matrix eliminates the tie line nodes in the system admittance matrix output by the power flow calculation, so that each node in the admittance matrix is ​​a synchronous machine node containing injected power and a grid-connected node of the wind turbine to be analyzed;

[0015] The synchronous machine node is a node with the internal potential of the generator as voltage and the active power of the generator as injection power. The generator transient reactance x' d connect;

[0016] The wind turbine grid-connected node to be analyzed is a wind turbine grid-connected node for performing synchronous machine power distribution and equivalent single-machine system power change calculation, and the node is retained during the admittance array contraction.

[0017] As a preferred solution of the analysis method of the influence of the change of grid-following renewable energy power on the transient power angle stability described in the present invention, the calculation of the equivalent admittance of the wind turbine generator set includes:

[0018]

[0019] Among them, Y w represents wind power equivalent admittance, P w Indicates the active power of wind turbine, Q w Indicates the reactive power of wind turbine.

[0020] As a preferred solution of the analysis method of the influence of the change of grid-following renewable energy power on the transient power angle stability described in the present invention, wherein: the synchronous torque coefficient between each synchronous machine node and the wind turbine grid-connected node in the calculation system includes:

[0021]

[0022] Where N is the number of nodes in the admittance array after contraction, node k is the wind turbine grid-connected node, and the remaining nodes are synchronous machine nodes. ik (or T kk ) is the synchronous torque coefficient between nodes i (or k) and k, C ik (or C kk ) is the angle transfer coefficient between nodes i (or k) and k, D ik (or D kk ) is the voltage transfer coefficient between nodes i (or k), k.

[0023] As a preferred solution of the analysis method of the influence of the power change of the grid-following new energy on the transient power angle stability described in the present invention, wherein: the angle transfer coefficient includes:

[0024]

[0025] Among them, E i represents the internal potential of the generator at node i of the synchronous machine, U k represents the voltage of the wind turbine grid-connected node k, G ik represents the mutual conductance between nodes i and k, B ik represents the mutual susceptance between nodes i and k, B kk represents the self-susceptance of node k, θ ik represents the angle difference between nodes i and k, Q k Indicates the reactive power injected by the wind turbine.

[0026] As a preferred solution of the analysis method of the influence of the power change of the grid-following new energy on the transient power angle stability described in the present invention, wherein: the voltage transfer coefficient includes:

[0027]

[0028] Among them, G kk represents the self-conductance of node k, P k Indicates the active power injected by the wind turbine.

[0029] As a preferred solution of the analysis method of the influence of the power change of the grid-following new energy on the transient power angle stability described in the present invention, the influence coefficient of the power change of the wind turbine set on the power change of the equivalent single-machine infinite system (hereinafter referred to as the power change influence coefficient) is:

[0030]

[0031] Among them, E k represents the influence coefficient of wind turbine power change at node k, that is, the influence coefficient of power change at node k on the equivalent electromagnetic power of the equivalent single-machine infinite system. The subscript S represents the critical group of the system, the subscript A represents the remaining group, and M S (or M A ) represents the equivalent inertia of the S (or A) group, T ik (or T jk ) represents the synchronous torque coefficient of the synchronous machine of the S (or A) group. The larger the absolute value of the influence coefficient is, the greater the change in the equivalent electromagnetic power of the equivalent single-machine infinite system caused by the change in unit wind power is.

[0032] As a preferred solution of the analysis method of the influence of the power change of the grid-following new energy on the transient power angle stability described in the present invention, the change amount of the electromagnetic power of the equivalent single-machine infinite system is,

[0033] ΔP e =E k ΔP k

[0034] Where ΔP e Indicates the change in electromagnetic power of an equivalent single-machine infinite system, ΔP k It represents the change of active power injected at the grid-connected node k of the wind turbine. The equivalent single-machine infinite system is a single-machine infinite system equivalent to the actual system through the complementary group inertia center relative motion (CCCOI-RM) transformation.

[0035] As a preferred solution of the analysis method of the influence of the power change of the grid-following renewable energy on the transient power angle stability described in the present invention, the influence of the power change of the wind turbine on the transient power angle stability is judged based on the electromagnetic power change, including:

[0036] The influence of wind turbine power change on transient power angle stability is judged based on the positive and negative value of electromagnetic power change: when the electromagnetic power change of the equivalent single-machine infinite system is positive, the wind turbine power change has a positive effect on transient power angle stability; when the electromagnetic power change of the equivalent single-machine infinite system is negative, the wind turbine power change has a negative effect on transient power angle stability;

[0037] The absolute value of the electromagnetic power change reflects the intensity of the impact of wind turbine power change on transient power angle stability.

[0038] When analyzing the influence of wind turbine power change of a node on transient power angle stability, the method converts wind turbines of other grid-connected nodes into admittance equivalent to the system admittance matrix before contraction, and eliminates the tie line node when contracting the system admittance matrix. As a preferred solution of the analysis method of the influence of grid-connected new energy power change on transient power angle stability described in the present invention, the wind turbines of other grid-connected nodes are converted into admittance equivalent to the system admittance matrix before contraction, and the wind turbine equivalent admittance calculation formula is:

[0039]

[0040] Among them, Y w Represents the equivalent admittance of the wind turbine, P w Indicates the active power of wind turbine, Q w Indicates the reactive power of wind turbine, U w Indicates the voltage of the wind turbine grid-connected node.

[0041] A second aspect of the present invention provides an analysis system for the impact of grid-connected renewable energy on transient power angle stability in a power angle stability scenario, comprising:

[0042] A power flow calculation unit is used to calculate the initial power flow of the power system based on the power system and its initial operation mode, and obtain the initial value of the power flow and the system admittance matrix when the power system is in a synchronous stable state before the output of the wind turbine generator set changes;

[0043] A system admittance matrix contraction unit is used to contract the system admittance matrix to the synchronous machine node and the wind turbine grid-connected node to be analyzed according to the system admittance matrix, so as to obtain a contracted system admittance matrix;

[0044] The electrical quantity calculation unit is used to calculate the system disturbance according to the preset fault. + Electrical quantity at every moment;

[0045] A synchronous machine grouping unit is used to group synchronous machines in the system according to preset faults and based on the extended equal area criterion EEAC to obtain a grouping result;

[0046] The synchronous torque coefficient calculation unit is used to calculate the synchronous torque coefficient according to the initial value of the power flow, the system admittance matrix after contraction and the system disturbance 0 + The electrical quantity at each moment is used to calculate the angle transfer coefficient and the voltage transfer coefficient; based on the angle transfer coefficient and the voltage transfer coefficient, the synchronous torque coefficient between each synchronous machine node in the system and the grid-connected node of the wind turbine to be analyzed is calculated;

[0047] The transient power variation calculation unit is used to calculate the influence coefficient of the power variation of the wind turbine to be analyzed on the power variation of the equivalent single-machine infinite system according to the synchronous torque coefficient between each synchronous machine node and the wind turbine grid-connected node in the system and the grouping result; and calculate the electromagnetic power variation of the equivalent single-machine infinite system according to the influence coefficient of the power variation of the wind turbine to be analyzed on the power variation of the equivalent single-machine infinite system;

[0048] The transient power angle stability judgment unit is used to judge the influence of wind turbine power change on transient power angle stability according to the change of electromagnetic power of equivalent single machine infinite system.

[0049] A third aspect of the present invention provides a computer device, the computer device comprising:

[0050] processor;

[0051] a memory for storing processor-executable instructions;

[0052] The processor is configured to call the instructions stored in the memory to execute the analysis method of the impact of grid-following new energy power changes on transient power angle stability described in the present invention.

[0053] A fourth aspect of the present invention provides a computer-readable storage medium having computer program instructions stored thereon, comprising:

[0054] When the computer program instructions are executed by the processor, the method for analyzing the influence of the power change of the grid-following renewable energy on the transient power angle stability as described in the present invention is implemented.

[0055] A fifth aspect of the present invention provides a computer program product, including a computer program and / or instructions, which, when executed by a processor, implements the method for analyzing the impact of grid-following new energy power changes on transient power angle stability.

[0056] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0057] The present invention aims to analyze the pros and cons and strength of the impact of wind power participating in emergency control power changes on transient power angle stability, and proposes a method for analyzing the impact of grid-following new energy power changes on transient power angle stability. The method analyzes and calculates the impact of sudden power drop of wind turbines on the active output changes of each synchronous machine in the system. The present invention groups synchronous machines according to the EEAC theory into critical groups and remaining groups, and performs subsequent calculations of synchronous torque coefficients and power change influence coefficients based on the grouping results. It further determines the impact of wind farm power changes on the system transient power angle stability by calculating the equivalent single-machine infinite system electromagnetic power change, and can make a more accurate judgment on the system transient power angle stability. Compared with the prior art, the present invention can effectively evaluate the pros and cons and strength of the impact of power changes of different new energy sites on the system transient power angle stability characteristics, which is conducive to improving the effectiveness and economy of emergency control strategies involving new energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is an overall flow chart of the analysis method of the influence of the power change of the grid-following new energy on the transient power angle stability described in the present invention;

[0059] Figure 2 It is a module diagram of the analysis system of the influence of grid-connected renewable energy on transient power angle stability in the power angle stability scenario described in the present invention;

[0060] Figure 3 A schematic diagram of a derived scenario of a power grid in a certain region for analyzing the influence of power changes of grid-following renewable energy on transient power angle stability according to the present invention;

[0061] Figure 4 It is the transient power angle curve of the synchronous machine in the analysis method of the influence of the power change of the grid-following new energy on the transient power angle stability described in the present invention. DETAILED DESCRIPTION

[0062] In order to more clearly illustrate the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0063] Example 1

[0064] The analysis method of the influence of the power change of the grid-following new energy on the transient power angle stability described in the present invention is referred to Figure 1This is an embodiment of the present invention, including the following parts S1 to S6:

[0065] S1: Calculate the initial power flow of the power system.

[0066] Calculating the initial power flow of the power system is to use the power flow calculation method to calculate the initial value of the power flow when the power system is in a synchronous stable state before the output of the wind turbine group changes. In this patent, the synchronous machine adopts a second-order model, and outputs the electromotive force amplitude of each synchronous machine, the synchronous machine power angle, the active power of each wind power grid-connected node, the system admittance matrix, etc. when the system is in a steady state according to the power flow calculation results.

[0067] S2: According to the preset fault, calculate the electrical quantity of the system disturbance 0+, and group the synchronous machines in the system based on EEAC. Including:

[0068] The preset fault is a three-phase short circuit fault occurring on any transmission line of the system;

[0069] The system disturbance 0+ moment is the moment when a preset fault occurs, resulting in a sudden change in non-state quantities in the system. The electrical quantities include the voltage amplitude and voltage phase angle of the wind turbine grid-connected node, and the active power and reactive power of the wind turbine;

[0070] The EEAC is the extended equal area criterion. The synchronous machine grouping in the system is to divide the synchronous machine into two groups, namely the critical group and the remaining group, based on the power angle trajectory after the disturbance. The critical group represents the combination of synchronous machines whose power angle increases upward when the system state changes, and the remaining group represents the combination of synchronous machines whose power angle decreases downward when the system state changes. Synchronous machines are grouped according to the EEAC theory. The grouping is based on the judgment of the disturbed trajectory of the whole process after the system is disturbed. For example, there are n disturbed trajectories for n synchronous machines. The n disturbed trajectories are randomly divided into two groups. Each of the two groups is fitted with a trajectory, and then the angle difference of this grouping method is obtained by difference. The enumeration method is used to make all possible angle differences of the grouping, and the one with the largest angle difference is selected as the grouping method.

[0071] S3: Contract the system admittance matrix to the synchronous machine node and the grid-connected node of the wind turbine to be analyzed.

[0072] The contraction system admittance matrix to the synchronous machine node and the wind turbine grid connection node to be analyzed includes:

[0073] The shrinking system admittance matrix is ​​to eliminate the tie line nodes (nodes without power injection) in the system admittance matrix output by the power flow calculation, so that each node in the admittance matrix is ​​a synchronous machine node with injected power and a grid-connected node of the wind turbine to be analyzed;

[0074] The synchronous machine node is a node with the internal potential of the generator as voltage and the active power of the generator as injection power. The generator transient reactance x' dconnect;

[0075] The wind turbine grid-connected node to be analyzed is a wind turbine grid-connected node for performing synchronous machine power distribution and equivalent single-machine system power change calculation, and the node is retained during the admittance array contraction.

[0076] S4: Calculate the synchronous torque coefficient between each synchronous machine node and the wind turbine grid-connected node in the system.

[0077] The calculation of instantaneous electrical quantities after the wind turbine power changes includes:

[0078] The instantaneous electrical quantity after the wind turbine power changes is the voltage amplitude of the wind turbine grid-connected node, the voltage phase angle, the active power and the reactive power of the wind turbine after the wind turbine power changes suddenly.

[0079] The synchronous torque coefficient between each synchronous machine node and the wind turbine grid-connected node in the calculation system includes:

[0080]

[0081] Where N is the number of nodes in the admittance array after contraction, node k is the wind turbine grid-connected node, and the remaining nodes are synchronous machine nodes. ik (or T kk ) is the synchronous torque coefficient between nodes i (or k) and k, C ik (or C kk ) is the angle transfer coefficient between nodes i (or k) and k, D ik (or D kk ) is the voltage transfer coefficient between nodes i (or k), k.

[0082] The angle transfer coefficient includes,

[0083]

[0084] Among them, E i represents the internal potential of the generator at node i of the synchronous machine, U k represents the voltage of the wind turbine grid-connected node k, G ik represents the mutual conductance between nodes i and k, B ik represents the mutual susceptance between nodes i and k, B kk represents the self-susceptance of node k, θ ik represents the angle difference between nodes i and k, Q k Indicates the reactive power injected by the wind turbine.

[0085] The voltage transfer coefficient includes,

[0086]

[0087] Among them, Gkk represents the self-conductance of node k, P k Indicates the active power injected by the wind turbine.

[0088] S5: Calculate the influence coefficient of wind turbine power change on the power change of the equivalent single-machine infinite system and the change of electromagnetic power of the equivalent single-machine infinite system.

[0089] The power change influence coefficient is,

[0090]

[0091] Among them, E k represents the influence coefficient of wind turbine power change at node k, that is, the influence coefficient of power change at node k on the equivalent electromagnetic power of the equivalent single-machine infinite system. The subscript S represents the critical group of the system, that is, the combination of synchronous machines whose power angle increases upward when the system state changes. The subscript A represents the remaining group, that is, the combination of synchronous machines whose power angle decreases downward when the system state changes. M S (or M A ) represents the equivalent inertia of the S (or A) group, T ik (or T jk ) represents the synchronous torque coefficient of the synchronous machine of the S (or A) group;

[0092] The equivalent single-machine infinite system is a single-machine infinite system equivalent to the actual system through the complementary group inertia center relative motion (CCCOI-RM) transformation;

[0093] The equivalent single-machine infinite system electromagnetic power change is:

[0094] ΔP e =E k ΔP k

[0095] Where ΔP e Indicates the change in electromagnetic power of an equivalent single-machine infinite system, ΔP k It represents the change of active power injected into the wind turbine grid-connected node k.

[0096] S6: Determine the impact of wind turbine power changes on transient power angle stability based on the positive and negative changes in electromagnetic power.

[0097] The influence of wind turbine power change on transient power angle stability is judged based on the positive or negative value of electromagnetic power change. When the electromagnetic power change of the equivalent single-machine infinite system is positive, the wind turbine power change has a positive effect on transient power angle stability. When the electromagnetic power change of the equivalent single-machine infinite system is negative, the wind turbine power change has a negative effect on transient power angle stability. The numerical value (absolute value) of the electromagnetic power change reflects the influence intensity. The sensitivity index is Ek .

[0098] This method only analyzes the impact of wind turbine power changes at one node at a time. In the analysis of the wind turbine to be analyzed, the wind turbines at other grid-connected nodes need to be equivalent to admittances and included in the system admittance matrix before contraction, and converted into tie-line nodes, which are eliminated when the nodes are contracted.

[0099] The preferred method for calculating the equivalent admittance of a wind turbine is:

[0100]

[0101] Among them, Y w represents wind power equivalent admittance, P w Indicates the active power of wind turbine, Q w Indicates the reactive power of wind turbine.

[0102] Example 2

[0103] The analysis system of the influence of grid-connected renewable energy on transient power angle stability in the power angle stability scenario of the present invention has a schematic diagram as shown in FIG. Figure 2 As shown, including:

[0104] The power flow calculation unit is used to calculate the initial value of the power flow when the power system is in a synchronous and stable state before the output of the wind turbine generator set changes;

[0105] The system admittance matrix contraction unit is used to eliminate the tie line nodes in the system admittance matrix output by the power flow calculation, and contract the admittance matrix to the synchronous machine nodes and the wind turbine grid-connected nodes to be analyzed;

[0106] Electrical quantity calculation unit, used to calculate system disturbance t 0+ All electrical quantities in the system at all times;

[0107] Synchronous machine grouping unit, used to group synchronous machines according to expected faults;

[0108] A synchronous torque coefficient calculation unit is used to calculate the angle transfer coefficient, voltage transfer coefficient and synchronous torque coefficient between each synchronous machine node and the wind turbine grid connection node;

[0109] The transient power variation calculation unit is used to calculate the electromagnetic power variation of the equivalent single-machine infinite system under the influence of wind turbine power variation;

[0110] The transient power angle stability judgment unit is used to judge the influence of wind turbine power change on transient power angle stability according to the change of electromagnetic power of equivalent single machine infinite system.

[0111] Figure 4A synchronous machine power allocation and equivalent single-machine system power change calculation method taking into account the impact of new energy power changes and system verification test results are provided to verify and illustrate the technical effects used in this method.

[0112] This example verifies the validity and applicability of the calculation of the equivalent single-machine system power change when the wind power changes. Figure 3 Take a two-machine system derived scenario as an example, the system base power is 100MW. The fault is set to the double-circuit transmission line L 1 A three-phase metallic ground short circuit occurred on the synchronous machine side of the middle circuit, and the fault line was cut off after 0.1s. The generating capacity of synchronous machine 1 is 70MW, and the inertia is M 1 =2, synchronous machine 2 generates 50MW, inertia M 2 =10, double-fed wind power generation 30MW. The double-fed wind turbine enters the low voltage ride-through state during the fault, and the active output is instantly reduced. The electrical parameters of the two-machine system are shown in Table 1;

[0113] Table 1: Equivalent single-machine infinite system electrical parameters.

[0114]

[0115] The specific implementation process of this embodiment is as follows:

[0116] S1: Calculate the initial power flow of the power system;

[0117] S2: Calculate the instantaneous electrical quantity after the wind turbine power changes, which is the system grouping. Synchronous machine 1 is group S, and synchronous machine 2 is group A.

[0118] S3: shrink the system admittance matrix to the synchronous machine node and the grid-connected node of the wind turbine to be analyzed;

[0119] S4: Calculate the synchronous torque coefficient between each synchronous machine node and the wind turbine grid-connected node in the system;

[0120] S5: Calculate the power change influence coefficient corresponding to the analyzed wind turbine and the equivalent single-machine infinite system electromagnetic power change;

[0121] S6: Determine the impact of wind turbine power changes on transient power angle stability based on the positive and negative changes in electromagnetic power.

[0122] Step 1: Calculate the initial power flow of the power system;

[0123] Step 2: Shrink the system admittance matrix to the synchronous machine node and the wind turbine grid-connected node to be analyzed:

[0124]

[0125] Step 3: Calculate the change in injected power ΔP at the wind turbine grid connection node 3 3 =-0.191, the instantaneous grid-connected node voltage amplitude U after the wind power changes k =0.619, angle θ k =-25.53°;

[0126] Step 4: Calculate the synchronous torque coefficient T between each synchronous machine node and the wind turbine grid-connected node in the system 13 =-0.018, T 23 =-1.8031, T 33 =1.8210;

[0127] Step 5: Calculate the power change influence coefficient E corresponding to the wind turbine 3 =0.4901, equivalent to the change in electromagnetic power of a single machine infinite system ΔP e =0.2016;

[0128] Step 6: Due to the change in electromagnetic power ΔP of the equivalent single-machine infinite system e >0, so it is judged that the decrease of wind power is conducive to the stability of the transient power angle of the system. The transient power angle curve of the synchronous machine before and after the wind turbine adopts the low voltage ride-through strategy is as follows Figure 4 As shown in the figure, the power angle stability of wind turbines entering the low-penetrator is better than that of those not entering the low-penetrator, which is consistent with the calculated results.

[0129] It can be seen from the above steps that the synchronous machine power distribution and equivalent single-machine system power change calculation method and system taking into account the impact of new energy power changes proposed in the present invention can accurately evaluate the impact of new energy power reduction on the transient power angle stability level, which is beneficial to improving the effectiveness and economy of the emergency control strategy involving new energy.

[0130] Example 3

[0131] The present invention provides a computer device, comprising: a processor; a memory for storing instructions executable by the processor; wherein the processor is configured to call the instructions stored in the memory to execute the aforementioned analysis method of the impact of grid-following new energy power changes on transient power angle stability.

[0132] Example 4

[0133] The present invention provides a computer-readable storage medium having computer program instructions stored thereon, including: when the computer program instructions are executed by a processor, a method for analyzing the influence of the aforementioned grid-following new energy power change on the transient power angle stability is implemented.

[0134] Example 5

[0135] The present invention provides a computer program product, including a computer program and / or instructions, which, when executed by a processor, implements the method for analyzing the impact of grid-following renewable energy power changes on transient power angle stability.

[0136] The present invention may be a method, an apparatus, a system and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for executing various aspects of the present invention.

[0137] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

Claims

1. A method for analyzing the influence of power changes of grid-following renewable energy on transient power angle stability, characterized in that: include: Based on the power system and its initial operation mode, the initial power flow of the power system is calculated to obtain the initial value of the power flow and the system admittance matrix when the power system is in a synchronous stable state before the output of the wind turbines changes; According to the preset fault, calculate the system disturbance 0 + The electrical quantity at each moment is calculated, and the synchronous machines in the system are grouped based on the extended equal area criterion EEAC to obtain the grouping results; According to the system admittance matrix, shrinking the system admittance matrix to the synchronous machine node and the grid-connected node of the wind turbine to be analyzed, to obtain a shrunken system admittance matrix; According to the initial value of the power flow, the system admittance matrix after contraction and the system disturbance 0 + The electrical quantity at each moment is used to calculate the angle transfer coefficient and the voltage transfer coefficient; based on the angle transfer coefficient and the voltage transfer coefficient, the synchronous torque coefficient between each synchronous machine node in the system and the grid-connected node of the wind turbine to be analyzed is calculated; According to the synchronous torque coefficient between each synchronous machine node and the wind turbine grid-connected node in the system and the grouping result, the influence coefficient of the power change of the wind turbine to be analyzed on the power change of the equivalent single-machine infinite system is calculated; according to the influence coefficient of the power change of the wind turbine to be analyzed on the power change of the equivalent single-machine infinite system, the change of the electromagnetic power of the equivalent single-machine infinite system is calculated; The influence of wind turbine power change on transient power angle stability is judged based on the change of electromagnetic power of the equivalent single-machine infinite system.

2. The method for analyzing the influence of power changes of grid-connected renewable energy on transient power angle stability as claimed in claim 1, characterized in that: The initial value of the power flow includes the electromotive force in each synchronous machine, the synchronous machine power angle, and the voltage and phase angle of each node.

3. The analysis method of the influence of the change of grid-following renewable energy power on the transient power angle stability as claimed in claim 1, wherein the preset fault is a three-phase short circuit fault occurring on any transmission line of the system; the system disturbance 0+ moment is the moment when the preset fault occurs and causes a sudden change in the non-state quantity in the system; the system disturbance 0 + The electrical quantities at each moment include: Voltage amplitude and voltage phase angle of wind turbine grid-connected nodes, as well as active and reactive power of wind turbines.

4. The method for analyzing the influence of power change of grid-connected renewable energy on transient power angle stability as claimed in claim 1, characterized in that: The method of grouping synchronous machines in the system based on EEAC includes: dividing the synchronous machines into two groups, namely a critical group and a remaining group, based on the power angle trajectory after the disturbance, wherein the critical group represents a combination of synchronous machines whose power angle increases when the system state changes, and the remaining group represents a combination of synchronous machines whose power angle decreases when the system state changes; based on the judgment of the disturbed trajectory of the whole process after the system is disturbed, all disturbed trajectories are randomly divided into two groups, each of the two groups is fitted with a disturbed trajectory, and then the angle difference of this grouping method is obtained by difference, and the enumeration method is used to make all possible angle differences for grouping, and the one with the largest angle difference is selected as the grouping method.

5. The method for analyzing the influence of power change of grid-connected renewable energy on transient power angle stability as claimed in claim 1, characterized in that: The shrinking of the system admittance matrix to the synchronous machine node and the wind turbine grid-connected node to be analyzed comprises: eliminating the tie line nodes in the system admittance matrix so that each node in the admittance matrix is ​​a synchronous machine node containing injected power and a wind turbine grid-connected node to be analyzed; The synchronous machine node is a node with the internal potential of the generator as voltage and the active power of the generator as injected power, and the synchronous machine node is connected to the original generator node by the transient reactance of the generator; The wind turbine grid-connected node to be analyzed is a wind turbine grid-connected node for performing synchronous machine power allocation and equivalent single-machine system power change calculation.

6. The method for analyzing the influence of power change of grid-connected renewable energy on transient power angle stability as claimed in claim 1, characterized in that: The calculation formula for the synchronous torque coefficient between each synchronous machine node and the grid-connected node of the wind turbine to be analyzed in the calculation system is: Where N is the number of nodes in the admittance array after contraction, node k is the wind turbine grid-connected node, and the remaining nodes are synchronous machine nodes. ik is the synchronous torque coefficient between nodes i and k, T kk is the synchronous torque coefficient between nodes k and k, C ik is the angle transfer coefficient between nodes i and k, C kk is the angle transfer coefficient between nodes k and k, D ik is the voltage transfer coefficient between nodes i and k, D kk is the voltage transfer coefficient between nodes k and k.

7. The method for analyzing the influence of power change of grid-connected new energy on transient power angle stability as claimed in claim 6, characterized in that: The angle transfer coefficient includes, Among them, E i represents the internal potential of the generator at node i of the synchronous machine, U k represents the voltage of the wind turbine grid-connected node k, G ik represents the mutual conductance between nodes i and k, B ik represents the mutual susceptance between nodes i and k, B kk represents the self-susceptance of node k, θ ik represents the angle difference between nodes i and k, Q k Indicates the reactive power injected by the wind turbine.

8. The method for analyzing the influence of power changes of grid-connected renewable energy on transient power angle stability as claimed in claim 6, characterized in that: The voltage transfer coefficient includes, Among them, E i represents the internal potential of the generator at node i of the synchronous machine, U k represents the voltage of the wind turbine grid-connected node k, G ik represents the mutual conductance between nodes i and k, B ik represents the mutual susceptance between nodes i and k, θ ik represents the angle difference between nodes i and k, G kk represents the self-conductance of node k, P k Indicates the active power injected by the wind turbine.

9. The method for analyzing the influence of power change of grid-connected renewable energy on transient power angle stability as claimed in claim 1, characterized in that: The calculation formula for calculating the influence coefficient of the power change of the wind turbine to be analyzed on the power change of the equivalent single-machine infinite system is: Among them, E k represents the influence coefficient of the wind turbine power change at node k on the equivalent electromagnetic power of the equivalent single-machine infinite system. The subscript S represents the critical group of the system, the subscript A represents the remaining group, and M S represents the equivalent inertia of the S group, M A represents the equivalent inertia of group A, T ik The synchronous torque coefficient of the synchronous machine of the S group, T jk Indicates the synchronous torque coefficient of the synchronous machines in group A.

10. The method for analyzing the influence of power change of grid-connected renewable energy on transient power angle stability according to claim 1, characterized in that: The equivalent single-machine infinite system electromagnetic power change is: ΔP e =E k ΔP k Among them, ΔP e Indicates the change in electromagnetic power of an equivalent single-machine infinite system, ΔP k represents the change in active power injected into the wind turbine grid-connected node k, E k It represents the influence coefficient of the wind turbine power change at node k on the equivalent electromagnetic power of the equivalent single-machine infinite system.

11. The method for analyzing the influence of power change of grid-connected renewable energy on transient power angle stability according to claim 1, characterized in that: The method of judging the influence of wind turbine power change on transient power angle stability based on electromagnetic power change includes: The influence of wind turbine power change on transient power angle stability is judged based on the positive and negative value of electromagnetic power change: when the electromagnetic power change of the equivalent single-machine infinite system is positive, the wind turbine power change has a positive effect on transient power angle stability; when the electromagnetic power change of the equivalent single-machine infinite system is negative, the wind turbine power change has a negative effect on transient power angle stability; The absolute value of the electromagnetic power change reflects the intensity of the impact of wind turbine power change on transient power angle stability.

12. The method for analyzing the influence of power change of grid-connected renewable energy on transient power angle stability according to claim 1, characterized in that: When analyzing the impact of wind turbine power changes at a node on transient power angle stability, the method treats wind turbines at other grid-connected nodes as equivalent admittances and includes them in the system admittance matrix before contraction, converting them into tie-line nodes, and eliminating the tie-line nodes when contracting the system admittance matrix.

13. The method for analyzing the influence of power change of grid-connected renewable energy on transient power angle stability as claimed in claim 12, characterized in that: The wind turbines at other grid-connected nodes are equivalent to admittance and included in the system admittance matrix before contraction. The calculation formula for the equivalent admittance of the wind turbines is: Among them, Y w Represents the equivalent admittance of the wind turbine, P w Indicates the active power of wind turbine, Q w Indicates the reactive power of wind turbine, U w Indicates the voltage of the wind turbine grid-connected node.

14. An analysis system for the impact of grid-connected renewable energy on transient power angle stability in a power angle stability scenario, characterized in that: include: A power flow calculation unit is used to calculate the initial power flow of the power system based on the power system and its initial operation mode, and obtain the initial value of the power flow and the system admittance matrix when the power system is in a synchronous stable state before the output of the wind turbine generator set changes; A system admittance matrix contraction unit is used to contract the system admittance matrix to the synchronous machine node and the wind turbine grid-connected node to be analyzed according to the system admittance matrix, so as to obtain a contracted system admittance matrix; The electrical quantity calculation unit is used to calculate the system disturbance according to the preset fault. + Electrical quantity at every moment; A synchronous machine grouping unit is used to group synchronous machines in the system according to preset faults and based on the extended equal area criterion EEAC to obtain a grouping result; The synchronous torque coefficient calculation unit is used to calculate the synchronous torque coefficient according to the initial value of the power flow, the system admittance matrix after contraction and the system disturbance 0 + The electrical quantity at each moment is used to calculate the angle transfer coefficient and the voltage transfer coefficient; based on the angle transfer coefficient and the voltage transfer coefficient, the synchronous torque coefficient between each synchronous machine node in the system and the grid-connected node of the wind turbine to be analyzed is calculated; The transient power variation calculation unit is used to calculate the influence coefficient of the power variation of the wind turbine to be analyzed on the power variation of the equivalent single-machine infinite system according to the synchronous torque coefficient between each synchronous machine node and the wind turbine grid-connected node in the system and the grouping result; and calculate the electromagnetic power variation of the equivalent single-machine infinite system according to the influence coefficient of the power variation of the wind turbine to be analyzed on the power variation of the equivalent single-machine infinite system; The transient power angle stability judgment unit is used to judge the influence of wind turbine power change on transient power angle stability according to the change of electromagnetic power of equivalent single machine infinite system.

15. A computer device, characterized in that: The device comprises, processor; a memory for storing processor-executable instructions; The processor is configured to call the instructions stored in the memory to execute the method for analyzing the influence of the change of grid-following new energy power on the transient power angle stability according to any one of claims 1 to 13.

16. A computer-readable storage medium having computer program instructions stored thereon, characterized in that: When the computer program instructions are executed by the processor, the method for analyzing the influence of the change of grid-connected renewable energy power on the transient power angle stability according to any one of claims 1 to 13 is implemented.

17. A computer program product comprising a computer program and / or instructions, characterized in that When the computer program and / or instruction is executed by a processor, the method for analyzing the influence of the change of grid-following renewable energy power on the transient power angle stability as described in any one of claims 1 to 13 is implemented.

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