Characterization Forms of Inertial Spatiotemporal Distribution Characteristics of Power Systems under Large Disturbances

Abstract

The present invention provides a characterization form of the inertial spatio-temporal distribution characteristics of a power system under large disturbances, belonging to the technical field of power systems. The spatial distribution characteristics of the power system inertia are analyzed, the concept of system node inertia is proposed and discriminated, and the inertial spatio-temporal distribution characteristics are comprehensively and normatively described through the system node inertia and the node inertia matrix composed of it; furthermore, the related concepts of system inertia are systematically sorted out and discriminated; the property description parameters of the system node inertia are given, including the instantaneous inertia of the system node, the average inertia of the node, the inertia-time differential rate of the node, and the inertia-node source inertia differential rate of the node, and the quantitative analysis methods of these parameters are given. The present invention can comprehensively and normatively characterize the spatio-temporal distribution characteristics of system inertia, and depict the inertial properties in detail from different angles, so as to provide an accurate basis for system operation control.

Description

Technical Field

[0001] The invention belongs to the technical field of power systems, and in particular relates to a representation form of the temporal and spatial distribution characteristics of inertia of a power system under large disturbances. Background Art

[0002] Inertia can slow down the frequency deviation rate after the power system is subjected to a large disturbance, buying time for the start of other subsequent frequency regulation measures (such as primary and secondary frequency regulation, etc.), thereby maintaining the smooth operation of the system and ensuring the safety of the system operation.

[0003] As the proportion of renewable energy power generation capacity continues to increase, synchronous generators, which are the main source of inertia, are gradually replaced. Not only does the overall level of system inertia continue to decline, but the uneven distribution characteristics of the system's inertia resources, that is, the spatial distribution characteristics, are also becoming increasingly significant. This leads to a significant enhancement of the frequency-spatial distribution characteristics of the system after disturbance.

[0004] Frequency stability control is based on the frequency dynamic indicators of the system after the disturbance, such as: frequency drop rate for relay protection setting, frequency minimum point for low-frequency load reduction setting, etc. In the case of significant frequency spatial distribution, if the existing system inertia based on the centralized parameter model and estimation principle is used for frequency stability analysis, and this is used as the basis for operation plan formulation and control decision-making, it may cause misjudgment of instability and bury safety hazards. Therefore, it is necessary to conduct a refined analysis of the system's inertia level to fully characterize its response characteristics and provide accurate basic data for planning, planning and operation control for system frequency stability.

[0005] However, most of the current research on the spatial distribution characteristics of inertia in power systems focuses on inertia estimation. There is no unified concept for the characterization of the spatial and temporal distribution of system inertia, and there is a lack of in-depth analysis of its properties and systematic sorting and analysis of related concepts. Therefore, it is necessary to explore the spatial and temporal distribution characteristics of inertia in power systems in order to comprehensively and normatively characterize the spatial and temporal distribution characteristics of system inertia.

[0006] The present invention proposes and analyzes the concept of system node inertia, and comprehensively and normatively describes the spatiotemporal distribution characteristics of inertia through the system node inertia and the node inertia matrix it constitutes, and then systematically sorts out and analyzes the concepts related to system inertia, and further provides the property description parameters of system node inertia and its quantitative analysis method. The present invention can comprehensively and normatively characterize the spatiotemporal distribution characteristics of system inertia, and carefully characterize the inertial properties from different angles to provide an accurate basis for system operation control. Summary of the invention

[0007] In view of the problems existing in the above-mentioned prior art, the present invention analyzes the spatial distribution characteristics of the inertia of the power system, proposes and differentiates the concept of the inertia of system nodes, and comprehensively and normatively describes the spatio-temporal distribution characteristics of inertia through the inertia of system nodes and the node inertia matrix composed thereof. Furthermore, the concepts related to system inertia are systematically sorted out and differentiated, and the property description parameters of the inertia of system nodes are further given, including the instantaneous inertia of system nodes, the average inertia of nodes, the micro-increment rate of node inertia-time, and the micro-increment rate of node inertia-node source inertia. And the quantitative analysis methods of these parameters are given. The present invention can comprehensively and normatively characterize the spatio-temporal distribution characteristics of system inertia, and carefully depict the inertia properties from different angles, so as to provide an accurate basis for system operation control.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A characterization form of the spatio-temporal distribution characteristics of the inertia of a power system under large disturbances, comprising the following steps:

[0010] S1: Analyze the spatial distribution characteristics of the inertia of the power system, and propose and differentiate the concept of the inertia of system nodes.

[0011] When the frequency spatial distribution of the system after the disturbance is significant, that is, the frequency dynamic processes between different nodes are quite different, the inertia energy releases of the inertia resource components connected to different nodes will show different output modes. This not only causes the overall effect of system inertia to be different, but also leads to differences in the presentation of inertia at different nodes:

[0012] a) When the same number of disturbances occur at different nodes, the system inertia observed at the disturbed nodes is not the same. That is, when the same amount of power disturbances occur at different nodes, the system will show different inertia levels respectively;

[0013] b) When a disturbance occurs at a certain node, the system inertia observed at different nodes of the system is not the same. That is, after the disturbance occurs, the system inertia shows different inertia levels at different nodes.

[0014] This is the spatial distribution characteristic of the inertia of the power system, and its manifestation is that generally, the inertia quantities observed at different nodes after the system is disturbed are not equal. These observed quantities are called the inertia of system nodes, or simply node inertia for short.

[0015] S2: Propose a node inertia matrix of the system to comprehensively and normatively describe the spatio-temporal distribution characteristics of the system inertia.

[0016] When a certain node is disturbed, the node inertia observed at all nodes can be described by a row vector; when the disturbance traverses all nodes, the spatial distribution characteristics of the system inertia can be completely described by using all the observed row vectors.

[0017] Therefore, the air-variable characteristics of the power system can be described in a standardized manner by the following system node inertia matrix H,

[0018]

[0019] The i-th row in the matrix corresponds to the system inertia observed from each node after node i is disturbed. That is, H ii and H ij are the system inertia observed from node i and node j respectively after node i is disturbed, and can be called the system node self-inertia coefficient and mutual-inertia coefficient, s. N is the number of system nodes. In the formula,

[0020]

[0021]

[0022] In the formula: f i and f j are the frequency values observed at node i and node j respectively, in per-unit value; ΔP e-i represents the magnitude of the disturbance power at node i, in per-unit value; t represents time, in s.

[0023] The magnitude of the node inertia depends on the amount of unbalanced power caused by the disturbance and the dynamic change of the node frequency. Since the rate of change of the node frequency is not uniform along the time axis, the node inertia will change continuously over time and is not a fixed value. This is the time distribution characteristic of the power system inertia, simply referred to as the time-varying characteristic.

[0024] Therefore, the time-varying characteristic of the power system can be described in a standardized manner by the following system node inertia matrix H(t),

[0025]

[0026] In the formula: H ii (t) and H ij (t) are the system inertia observed from node i and node j respectively t seconds after the disturbance occurs at node i, in s. Among them,

[0027]

[0028]

[0029] In the formula: f i (t) and f j (t) are the frequency values observed at node i and node j at time t respectively, in per-unit value.

[0030] S3: Sort out and distinguish the concepts related to system inertia.

[0031] Based on the system node inertia and the system node inertia matrix composed of it, the relevant concepts of system inertia are systematically sorted out and discriminated as follows: The inertia of the power system is an inherent property of the power system itself, which refers to the property of the system to suppress energy fluctuations, manifested as the property of reducing the rate of frequency deviation, and its external manifestation of the action is the throughput of the overall energy of the system after a disturbance. The inertia of the power system is a physical quantity that measures the magnitude of this property, and its quantity can be perceived through node parameters.

[0032] To understand the spatio-temporal distribution characteristics of system inertia vividly, the power system can be compared to a sphere. When it is a rigid sphere or a non-rigid sphere but with a uniform and symmetric distribution of rigidity, when a force is applied at any point, the inertial response of the sphere is the same, and this situation can correspond to the case without frequency spatial distribution. Then the inertia felt at all nodes after the system is disturbed is equal, and at this time, the system's inherent inertia H s is uniformly characterized.

[0033]

[0034] In the formula, H s is the equivalent inertia time constant of the system, that is, the system's inherent inertia, used to characterize the inertia of the system, s. h i is the equivalent inertia time constant of the inertia resources directly connected to node i, abbreviated as the node source inertia (if a node has no directly connected inertia resources, the node source inertia is zero), s.

[0035] If the sphere is non-rigid and the rigidity degree is unevenly distributed, when a force is applied at different points, the inertial response of the sphere may not be the same, which corresponds to the situation with frequency spatial distribution. At this time, the system node inertia needs to be used for detailed description.

[0036] When there is a frequency spatial distribution in the system, the responses of inertial components are not synchronous. It may occur that some inertial components do not respond sufficiently while some inertial components respond excessively and reach their capacity limits. Therefore, the system node inertia will be less than the system's inherent inertia. In other words, the spatio-temporal distribution characteristics of frequency will affect the full play of the inertia resource capacity.

[0037] S4: Give a quantization method for the spatio-temporal distribution characteristics of system inertia. The specific steps are as follows:

[0038] S4-1: Obtain the data required for calculation.

[0039] The basic data on which the spatio-temporal distribution characteristics of system inertia are described include the node where the disturbance occurs, the quantity of unbalanced power generated by the disturbance, and the dynamic change parameters of the frequencies of each node, etc. These data can be obtained through simulation, or using the actual system operation data, such as historical data or real-time collected data.

[0040] Compared with using the actual system operation data, the advantage of obtaining data through simulation is that the disturbances can traverse all nodes, thus obtaining a complete picture of the relationship characteristics, while the former can only obtain the relevant data of the nodes where disturbances have occurred. Of course, the advantage of using actual data is obvious, which is real and reliable.

[0041] For real-time acquisition of data, since PMU devices are basically installed at 500 kV nodes, it is relatively easy to obtain the node frequencies; due to the rapid operation of the relay protection system, the disturbed nodes can be quickly locked. However, relatively speaking, it is relatively difficult to determine the disturbance amount.

[0042] Therefore, the methods for obtaining the elements of the node inertia matrix are given respectively for the two cases where the disturbance amount is known and unknown.

[0043] S4-2: Calculate the elements of the node inertia matrix in the case where the disturbance is known.

[0044] In the case where the disturbance is known, the elements of the node inertia matrix can be conveniently calculated using equations (5) and (6).

[0045] At present, the frequency of the multi-machine system cannot be analytically described, so its derivative value cannot be directly obtained. The difference method can be used to obtain it. Then,

[0046]

[0047]

[0048] In the formula: Δt is the difference time step, s;

[0049] This method is applicable to the off-line analysis of inertia, with simple calculation and clear principle; another advantage is that it does not require knowing the quantity of inertia resources connected to each node.

[0050] S4-3: Calculate the elements of the node inertia matrix in the case where the disturbance is unknown.

[0051] In the case where the disturbance is unknown, for a power system with a frequency spatial distribution, for convenient analysis, it can be simplified to a lumped parameter model, that is,

[0052]

[0053]

[0054] In the formula: H s represents the equivalent inertia time constant of the system, s; f coi (t) is the frequency of the equivalent inertia center of the system, per unit value; h m represents the node source inertia of node m, s; f m (t) represents the frequency of node m at time t;

[0055] By combining equations (5), (10), and (11), it can be obtained that

[0056]

[0057] After simplification, it can be obtained that

[0058]

[0059] where μ m (t) is the node source inertia correction coefficient,

[0060]

[0061] By combining equations (6), (10), and (11), similarly, it can be obtained that

[0062]

[0063] where h j represents the node source inertia of node j, s; h n represents the node source inertia of node n, s; μ n (t) is also the node source inertia correction coefficient,

[0064]

[0065] where f n (t) represents the frequency of node n at time t; using the difference method to calculate, then

[0066]

[0067] where μ m-d (t) is the node source inertia difference correction coefficient,

[0068]

[0069]

[0070] where μ n-d (t) is also the node source inertia difference correction coefficient,

[0071]

[0072] S5: The property description parameters of the system node inertia and its quantitative analysis method are given. The specific steps are as follows.

[0073] S5-1: The node instantaneous inertia refers to the immediate node inertia of the system at time t after being disturbed, which can be characterized by equation (4), and its element values can be calculated using the formula in S4-2.

[0074] As can be seen from Eqs. (14), (16), (18), and (20), when the frequencies of all nodes change synchronously, the correction factors in Eqs. (13), (15), (17), and (19) are all 1. At this time, whether it is the self-inertia or the mutual inertia of the nodes is equal to the inherent inertia H of the system characterized by lumped parameters. s .

[0075] Using this parameter, the inertia level shown by any node of the system at any time after being disturbed can be obtained.

[0076] S5-2: The average node inertia refers to the overall inertia level shown by the node from the occurrence of the disturbance to time t, which represents the average value of the node inertia during this time period.

[0077] Similar to the instantaneous node inertia, the average node inertia at time t can also be represented in matrix form.

[0078]

[0079] In the formula, H v-ii (t) and H v-ij (t) are the average node inertias of the system observed by node i and node j respectively s seconds after the disturbance occurs at node i.

[0080]

[0081]

[0082] Or by combining Eqs. (5), (6), (10), and (11), we can get:

[0083]

[0084] In the formula, μ v-m-d (t) is the correction factor of the average node source inertia.

[0085]

[0086]

[0087] In the formula, μ v-n-d (t) is also the correction factor of the average node source inertia.

[0088]

[0089] S5-3: The node inertia-time differential rate, abbreviated as the time differential rate, refers to the change rate of the node inertia with time, which can reflect the change trend of the node inertia with time after the system is disturbed. Based on this parameter, the operator can predict the trend of the system inertia to serve as the basis for control decisions.

[0090] From formula (4), we can get:

[0091]

[0092] In the formula,

[0093]

[0094]

[0095] Using the difference method, we can calculate:

[0096]

[0097]

[0098] Or by combining equations (5), (10) and (11), we can get:

[0099]

[0100] In the formula, γ m (t) is the time increment rate correction coefficient at time t

[0101]

[0102] Combining equations (6), (10) and (11), we can also obtain:

[0103]

[0104] In the formula, γ n (t) is the time increment rate correction coefficient at time t

[0105]

[0106] Formula (34) and formula (36) are calculated by difference method, and we can get:

[0107]

[0108]

[0109] S5-4: Node inertia-node source inertia slight increase rate, referred to as source inertia slight increase rate, refers to the rate of change of node inertia with the change of node source inertia h, which can be represented by the source inertia slight increase rate matrix. This characteristic parameter can provide a basis for the optimization decision of system inertia source supplement.

[0110] It can be imagined that when node i is disturbed, the change of any node source inertia will affect the value of node inertia. Therefore, the matrix is a three-dimensional matrix, that is, the node source inertia dimension is added on the basis of formula (8). If the situation after node i is disturbed is taken as the analysis object, then,

[0111]

[0112] wherein,

[0113]

[0114]

[0115]

[0116]

[0117] Calculated using the difference method, equations (41) and (42) are

[0118]

[0119]

[0120] Through the above description of the parameters of the system node inertia properties and their quantization calculations, the inertia properties can be characterized in detail from different angles, thus providing an accurate basis for the system operation control.

[0121] The beneficial effects of the present invention are as follows: The present invention can comprehensively and normatively characterize the spatio-temporal distribution characteristics of the system inertia, and can characterize the inertia properties in detail from different angles, thus providing an accurate basis for the system operation control. BRIEF DESCRIPTION OF THE DRAWINGS

[0122] Figure 1 is the structure diagram of IEEE 10-machine 39-bus system;

[0123] Figure 2 is the map of the spatial variation of the instantaneous inertia of the system nodes 0.1 s after the disturbance occurs; Figure 2 (a) is the instantaneous inertia observed by each node when the disturbance occurs at node 1; Figure 2 (b) is the instantaneous inertia observed at node 1 when the disturbance occurs at each node; Figure 2 (c) is the instantaneous self-inertia coefficient when the disturbance occurs at each node;

[0124] Figure 3 is the map of the time variation of the instantaneous inertia of the system nodes after the disturbance at node 39;

[0125] Figure 4 is the map of the spatial variation of the average inertia of the system nodes 0.3 s after the disturbance occurs; Figure 4 (a) is the average inertia observed by each node when the disturbance occurs at node 1; Figure 4 (b) is the average inertia observed at node 1 when the disturbance occurs at each node; Figure 4 (c) is the average self-inertia coefficient when the disturbance occurs at each node;

[0126] Figure 5 It is the time-varying graph of the average inertia of system nodes after the perturbation of node 39;

[0127] Figure 6 It is the bar graph of the incremental rate of system node inertia-time after 0.1 s when the perturbation occurs; Figure 6 (a) is the incremental rate of inertia-time of each node when node 1 is perturbed; Figure 6 (b) is the incremental rate of inertia-time of node 2 when each node is perturbed; Figure 6 (c) is the incremental rate of inertia-time of the perturbed node when each node is perturbed;

[0128] Figure 7 It is the bar graph of the incremental rate of system node inertia-source inertia after 0.5 s when the perturbation of node 1 occurs. Specific implementation manner

[0129] The present invention will be further described below in conjunction with specific embodiments.

[0130] To make the technical solutions and advantages of the present invention clearer, the IEEE 10-machine 39-node system shown as Figure 1 is introduced as a test system. The parameters of each generator are shown in Table 1. There are 10 generators and 39 buses in total, with a rated frequency of 50 Hz, a main voltage level of 345 kV, and a total load of 6150 MW in the system.. A simulation model is built on PSASP, and the perturbation is realized by sequentially applying an impact load of 300 MW (about 5% of the load power) to each node. The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments and the accompanying drawings.

[0131] Table 1 Generator parameters of IEEE 10-machine 39-node system

[0132]

[0133] The characterization form of the inertial spatio-temporal distribution characteristics of a power system under large disturbances includes the following steps:

[0134] S1: Analyze the inertial spatial distribution characteristics of the power system, and propose and distinguish the concept of system node inertia.

[0135] When the frequency space distribution of the post-disturbance system is significant, the inertial energy release of the inertial resource components connected to different nodes will exhibit different output modes. This not only results in different overall effects of system inertia but also causes differences in the manifestation of inertia at different nodes. That is, the system inertia observed at different nodes after the system is disturbed is not the same, which is the spatial distribution characteristic of the power system inertia; its manifestation is that the inertial quantities observed at different nodes after the system is disturbed are generally not equal. These observed quantities are called system node inertia, abbreviated as node inertia.

[0136] S2: Propose a system node inertia matrix to comprehensively and normatively describe the spatio-temporal distribution characteristics of system inertia.

[0137] When a certain node is disturbed, the node inertia observed at all nodes can be described by a row vector; when the disturbance traverses all nodes, the spatial distribution characteristics of system inertia can be completely described by using all the observed row vectors.

[0138] Therefore, the space-varying characteristics of the power system can be normatively described by the following system node inertia matrix H,

[0139]

[0140] The i-th row in the matrix corresponds to the system inertia observed from each node after node i is disturbed, that is, H ii and H ij are the system inertia observed from node i and j respectively after node i is disturbed, which can be called the system node self-inertia coefficient and mutual-inertia coefficient respectively, s. N is the number of system nodes. In the formula,

[0141]

[0142]

[0143] In the formula: f i and f j are the frequency values observed at nodes i and j respectively, per unit value; ΔP e-i represents the magnitude of the disturbance power at node i, per unit value; t represents time, s.

[0144] The magnitude of node inertia depends on the amount of unbalanced power caused by the disturbance and the dynamic change of node frequency. Since the rate of change of node frequency is not uniform along the time axis, node inertia will change continuously over time and is not a fixed value. This is the time distribution characteristic of the power system inertia, abbreviated as the time-varying characteristic.

[0145] Therefore, the time-varying characteristics of the power system can be normatively described by the following system node inertia matrix H(t),

[0146]

[0147] Where: H ii (t) and H ij (t) are the system inertias observed from nodes i and j respectively at t seconds after the disturbance occurs, s. Among them,

[0148]

[0149]

[0150] Where: f i (t) and f j (t) are the frequency values observed at nodes i and j at time t respectively, in per-unit value.

[0151] S3: Sort out and distinguish the concepts related to system inertia.

[0152] Based on the proposed system node inertia and the system node inertia matrix composed of it, the concepts related to system inertia are systematically sorted out and distinguished as follows:

[0153] To understand the spatio-temporal distribution characteristics of system inertia vividly, the power system can be compared to a sphere. When it is a rigid sphere or a non-rigid sphere but with a uniform and symmetric distribution of rigidity, if a force is applied at any point, the inertial response of the sphere will be the same, and this situation can correspond to the case without frequency spatial distribution. Then the inertia felt at all nodes after the system is disturbed is equal, and at this time, the system inherent inertia H s is used for unified characterization.

[0154]

[0155] Where, H s is the equivalent inertia time constant of the system, that is, the system inherent inertia, used to characterize the inertia of the system, s. h i is the equivalent inertia time constant of the inertia resources directly connected to node i, abbreviated as the node source inertia (if a node has no directly connected inertia resources, the node source inertia is zero), s.

[0156] If the sphere is non-rigid and the distribution of rigidity is uneven, when a force is applied at different points, the inertial response of the sphere may not be the same, which corresponds to the case with frequency spatial distribution. At this time, the system node inertia needs to be used for detailed description.

[0157] When there is a frequency spatial distribution in the system, the responses of inertial elements are not synchronous. It is possible that some inertial elements respond insufficiently while some inertial elements respond excessively and reach their capacity limits. Therefore, the system node inertia will be less than the system inherent inertia. In other words, the spatio-temporal distribution characteristics of frequency will affect the full play of the inertia resource capacity.

[0158] S4: Give a quantization method for the characteristics of the spatio-temporal distribution of system inertia. The specific steps are as follows:

[0159] S4-1: Obtain the data required for calculation.

[0160] The basic data on which the description of the spatio-temporal distribution characteristics of system inertia is based, including the nodes where disturbances occur, the amount of unbalanced power generated by the disturbances, and the dynamic change parameters of the frequencies of each node, etc. These data can be obtained through simulation, or using the actual system operation data, such as: historical data, or real-time collected data.

[0161] Compared with using the actual system operation data, the advantage of obtaining data through simulation is that the disturbances can traverse all nodes, so as to obtain the whole picture of the relationship characteristics, while the former can only obtain the relevant data of the nodes where disturbances have occurred. Of course, the advantage of using actual data is obvious, which is real and reliable.

[0162] For real-time collection and acquisition of data, since PMU devices are basically installed at 500 kV nodes, it is relatively easy to obtain the node frequencies; due to the rapid action of the relay protection system, the disturbance nodes can be quickly locked. However, relatively speaking, it is relatively difficult to determine the amount of disturbance.

[0163] Therefore, the method for obtaining the elements of the node inertia matrix is given respectively for the two cases where the amount of disturbance is known and unknown.

[0164] S4-2: Calculate the elements of the node inertia matrix when the disturbance is known.

[0165] When the disturbance is known, the elements of the node inertia matrix can be conveniently calculated using equations (5) and (6).

[0166] At present, the frequency of the multi-machine system cannot be analytically described, so the derivative value cannot be directly obtained. The difference method can be used to obtain it. Then,

[0167]

[0168]

[0169] In the formula: Δt is the difference time step, s;

[0170] This method is applicable to the offline analysis of inertia, with simple calculation and clear principle; another advantage is that it does not require the number of inertia resources connected to each node to be known.

[0171] S4-3: Calculate the elements of the node inertia matrix when the disturbance is unknown.

[0172] In the case of unknown disturbances, for a power system with a frequency spatial distribution, for the convenience of analysis, it can be simplified to a lumped parameter model, that is,

[0173]

[0174]

[0175] where: H s represents the equivalent inertia time constant of the system, s; f coi (t) is the frequency of the equivalent inertia center of the system, per unit value; h m represents the nodal source inertia of node m, s; f m (t) represents the frequency of node m at time t;.

[0176] By combining equations (5), (10) and (11), it can be obtained that

[0177]

[0178] After simplification, it can be obtained that

[0179]

[0180] where, μ m (t) is the nodal source inertia correction coefficient,

[0181]

[0182] By combining equations (6), (10) and (11), similarly, it can be obtained that

[0183]

[0184] where, h j represents the nodal source inertia of node j, s; h n represents the nodal source inertia of node n, s; μ n (t) is also the nodal source inertia correction coefficient,

[0185]

[0186] where, f n (t) represents the frequency of node n at time t; Using the difference method to calculate, then

[0187]

[0188] where, μ m-d (t) is the nodal source inertia difference correction coefficient,

[0189]

[0190]

[0191] In the formula, μ n-d (t) is also the node source inertia difference correction coefficient,

[0192]

[0193] In this example, the calculation data is obtained by simulating and modeling on PSASP, and the disturbance is realized by sequentially applying a 300 MW (about 5% of the load power) impact load to each node.

[0194] S5: The property description parameters of the system node inertia and its quantitative analysis method are given. The specific steps are as follows.

[0195] S5-1: The node instantaneous inertia refers to the instantaneous node inertia of the system at time t after being disturbed, which can be characterized by Equation (4), and its element values can be calculated using the formula in S4-2.

[0196] It can be seen from Equations (14), (16), (18) and (20) that when the frequencies of all nodes change synchronously, the correction coefficients in Equations (13), (15), (17) and (19) are all 1. At this time, whether it is the self-inertia or the mutual inertia of the nodes is equal to the system inherent inertia H characterized by lumped parameters s .

[0197] Using this parameter, the inertia level shown by any node of the system at any time after being disturbed can be obtained.

[0198] In this example, the spatial distribution of the system node instantaneous inertia after 0.1 s of the disturbance is as Figure 2 shown, and the time distribution of the system node instantaneous inertia after the disturbance of node 39 is as Figure 3 shown. It can be analyzed that the node instantaneous inertia matrix proposed by the present invention can effectively characterize the inertial spatio-temporal distribution characteristics of the system.

[0199] S5-2: The node average inertia refers to the overall inertia level shown by the node from the occurrence of the disturbance to time t, and it represents the mean value of the node inertia during this time period.

[0200] Similar to the node instantaneous inertia, the node average inertia at time t can also be characterized in matrix form.

[0201]

[0202] In the formula, H v-ii (t) and H v-ij (t) are the system node average inertia observed by node i and node j respectively at t seconds after the disturbance of node i, s,

[0203]

[0204]

[0205] Or by combining equations (5), (6), (10), and (11), we can obtain:

[0206]

[0207] where μ v-m-d (t) is the average node source inertia correction coefficient,

[0208]

[0209]

[0210] where μ v-n-d (t) is also the average node source inertia correction coefficient,

[0211]

[0212] In this example, the spatial distribution of the average inertia of system nodes 0.3 seconds after the disturbance is as Figure 4 shown, and the temporal distribution of the average inertia of system nodes after the disturbance at node 39 is as Figure 5 shown. It can be analyzed that the average node inertia matrix proposed in the present invention can also effectively characterize the spatio-temporal distribution characteristics of the system inertia.

[0213] S5-3: The node inertia-time incremental rate, abbreviated as the time incremental rate, refers to the change rate of the node inertia with time and can reflect the change trend of the node inertia with time after the system is disturbed. Based on this parameter, the operator can predict the trend of the system inertia to serve as the basis for control decisions.

[0214] From equation (4), we can obtain

[0215]

[0216] where

[0217]

[0218]

[0219] Using the difference method to calculate, then

[0220]

[0221]

[0222] Or by combining equations (5), (10), and (11), we can obtain

[0223]

[0224] where γ m (t) is the correction coefficient of the time differential increase rate at time t

[0225]

[0226] By combining equations (6), (10), and (11), it can also be obtained that

[0227]

[0228] where γ n (t) is the correction coefficient of the time differential increase rate at time t

[0229]

[0230] By calculating equations (34) and (36) using the difference method, it can be obtained that

[0231]

[0232]

[0233] In this example, the node inertia - time differential increase rate of the system after 0.1 s of the disturbance is as Figure 6 shown

[0234] S5 - 4: The node inertia - node source inertia differential increase rate, abbreviated as the source inertia differential increase rate, refers to the change rate of the node inertia with respect to the change in the node source inertia h, and it can be characterized by the source inertia differential increase rate matrix. This characteristic parameter can provide a basis for the optimization decision of the system inertia source supplement

[0235] It can be imagined that when node i is disturbed, the change in the inertia of any node source will affect the value of the node inertia. Therefore, this matrix is a three - dimensional solid matrix, that is, the node source inertia dimension is added based on equation (8). If the situation after node i is disturbed is taken as the analysis object, then

[0236]

[0237] where

[0238]

[0239]

[0240]

[0241]

[0242] By calculating using the difference method, equations (41) and (42) are

[0243]

[0244]

[0245] In this example, after 0.5 s of the disturbance at Node 1, the incremental rate of the system node inertia - node source inertia is as Figure 7 shown.

[0246] Through the property description parameters and their quantitative calculations of the system node inertia above, the inertia properties can be described in detail from different perspectives, thus providing an accurate basis for the system operation control.

[0247] It can be seen from the analysis of the calculation results that the system node inertia and the property description parameters proposed in the present invention can comprehensively and normatively describe the characteristics of the system inertia spatio - temporal distribution and its properties from different perspectives.

[0248] Therefore, the present invention analyzes the spatial distribution characteristics of the power system inertia, proposes and differentiates the concept of the system node inertia, and comprehensively and normatively describes the spatio - temporal distribution characteristics of inertia through the system node inertia and the node inertia matrix composed of it; furthermore, it systematically sorts out and differentiates the related concepts of the system inertia; gives the property description parameters of the system node inertia, including the system node instantaneous inertia, node average inertia, incremental rate of node inertia - time, and incremental rate of node inertia - node source inertia, and gives the quantitative analysis methods of these parameters. The present invention can comprehensively and normatively characterize the spatio - temporal distribution characteristics of the system inertia, and describe the inertia properties in detail from different perspectives, thus providing an accurate basis for the system operation control.

[0249] The above - described embodiments only represent the implementation manners of the present invention, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for characterizing the inertial spatio-temporal distribution characteristics of a power system under large disturbances, characterized in that, The following steps are involved: S1: Analyze the spatial distribution characteristics of power system inertia, propose and analyze the concept of system node inertia; S2: The system node inertia matrix H is proposed to describe the spatiotemporal distribution characteristics of the system inertia; The space-variable characteristics of the power system are described by the following system node inertia matrix H: The i-th row in the matrix corresponds to the system inertia observed from each node after the disturbance of node i, i.e., H ii and H ij are the system inertia observed from nodes i and j respectively after the disturbance of node i, and can be called the system node self-inertia coefficient and the mutual-inertia coefficient, s; N is the number of system nodes; The time-varying characteristics of the power system can be described by the following system node inertia matrix H(t): Where: H ii (t) and H ij (t) are the system inertias observed from node i and node j respectively, s, t seconds after the disturbance occurs at node i; S3: Analyze concepts related to system inertia; S4: Provide a quantitative method for the spatial and temporal distribution characteristics of the system inertia; S5: Based on the system node inertia matrix, describe and quantify the parameters of the system node inertia.

2. The characterization method of the inertial spatio-temporal distribution characteristics of a power system under large disturbances according to claim 1, characterized in that, The specific steps are as follows: S1: Analyze the spatial distribution characteristics of power system inertia, propose and analyze the concept of system node inertia; The spatial distribution characteristics of the power system inertia are that the amount of inertia observed at different nodes after the system is disturbed is not equal. The observed amount is called the system node inertia, or node inertia for short. S2: The system node inertia matrix is proposed to describe the spatiotemporal distribution characteristics of system inertia; In formula (1), where: f i and f j are the frequency values observed at nodes i and j, respectively, in per-unit; ΔP e-i represents the magnitude of the disturbance power at node i, in per-unit; t represents time, in s; In formula (2), where: f i (t) and f j (t) are the frequency values observed at nodes i and j at time t, respectively, in per-unit values; S3: Based on the proposed system node inertia and its system node inertia matrix, the concepts related to system inertia are analyzed; Compare the power system to a sphere: When it is a rigid sphere or a non-rigid sphere with a uniformly symmetric rigidity distribution, the system's inherent inertia H s is used for unified characterization. Where, H s is the equivalent inertia time constant of the system, i.e., the inherent inertia of the system, used to characterize the inertia of the system, s; h i is the equivalent inertia time constant of the inertia resources directly connected to node i, abbreviated as the node source inertia, s; When the sphere is non-rigid and the degree of rigidity is unevenly distributed, the system node inertia is used for detailed description; S4: A quantitative method for the spatiotemporal distribution characteristics of the system inertia is given; the specific steps are as follows: S4-1: Obtain data required for calculation; The basic data used to describe the spatial and temporal distribution characteristics of the system inertia include the nodes where the disturbance occurs, the amount of unbalanced power generated by the disturbance, and the dynamic change parameters of the frequency of each node. These data can be obtained through simulation or using actual system operation data; The methods for obtaining the elements of the node inertia matrix are given for the two cases of known and unknown disturbances. S4-2: Calculate the nodal inertia matrix elements when the disturbance is known; When the disturbance is known, the elements of the node inertia matrix can be calculated using equations (5) and (6); S4-3: Calculate the nodal inertia matrix elements when the disturbance is unknown; When the disturbance is unknown, for the power system with frequency spatial distribution, it is simplified to a lumped parameter model, that is, Where: H s represents the equivalent inertia time constant of the system, s; f coi (t) is the equivalent inertia center frequency of the system, per unit value; h m represents the nodal source inertia of node m, s; f m (t) represents the frequency of node m at time t; Combining equations (5), (10) and (11) we can obtain: where μ m (t) is the node source inertia correction coefficient, Combining equations (6), (10) and (11), we can also obtain: where h j represents the nodal source inertia of node j, s; h n represents the nodal source inertia of node n, s; μ n (t) is also the nodal source inertia correction factor, where f n (t) represents the frequency of node n at time t; calculated using the difference method, then, where μ m-d (t) is the inertia difference correction coefficient of the node source, where μ n-d (t) is also the node source inertia difference correction coefficient, S5: Provide the property description parameters of the system node inertia and its quantitative analysis method; the specific steps are as follows; S5-1: Node instantaneous inertia, which refers to the instantaneous node inertia of the system at time t after the disturbance, can be represented by formula (4), and its element value can be calculated using the formula in S4-2; As can be seen from Eqs. (14), (16), (18), and (20), when the frequencies of all nodes change synchronously, the correction factors in Eqs. (13), (15), (17), and (19) are all 1. At this time, whether it is the self-inertia or the mutual inertia of the nodes is equal to the inherent inertia H of the system characterized by lumped parameters s ; This parameter can be used to obtain the inertia level of any node in the system at any time after being disturbed; S5-2: Node average inertia, which refers to the mean value of the node inertia from the occurrence of the disturbance to time t; The node average inertia can also be represented in matrix form, where H v-ii (t) and H v-ij (t) are the average inertia of the system nodes observed by node i and node j respectively t seconds after the disturbance occurs at node i, s, Or combining equations (5), (6), (10) and (11) we can get: where μ v-m-d (t) is the average nodal source inertia correction factor, where μ v-n-d (t) is also the average nodal source inertia correction factor, S5-3: Node inertia-time slight increase rate refers to the rate of change of node inertia over time, which is used to predict the trend of system inertia and serve as the basis for control decision-making. From formula (4), we can get: In the formula, Using the difference method, we can calculate: Or by combining equations (5), (10) and (11), we can get: where γ m (t) is the correction coefficient of the time increment rate at time t; Combining equations (6), (10) and (11), we can also obtain: where γ n (t) is the time increment rate correction factor at time t; Formula (34) and formula (36) are calculated by difference method, and we can get: S5-4: Node inertia-node source inertia slight increase rate, referred to as source inertia slight increase rate, refers to the rate of change of node inertia with the change of node source inertia h. It can be represented by the source inertia slight increase rate matrix. When node i is disturbed, the matrix is a three-dimensional matrix, that is, the node source inertia dimension is added on the basis of formula (8); if the situation after node i is disturbed is taken as the analysis object, then, In the formula, Using the difference method, equations (41) and (42) are: The properties of the system node inertia are described by the parameters and their quantitative calculation, providing a basis for system operation control.

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