A transient instability pattern recognition method and terminal for power system

Abstract

The present invention discloses a transient instability mode recognition method and terminal for an electric power system, calculates a transient power angle instability index and a transient voltage instability index, establishes a hierarchical model according to the quantitative index, and respectively constructs a power angle instability index judgment matrix and a voltage instability index judgment matrix, calculates the power angle instability and voltage instability evaluation index scores, and then recognizes the dominant instability mode of the actual electric power system according to the score difference. In this way, the accuracy of the recognition of the dominant instability mode in the AC / DC hybrid power system can be improved, and the calculation process is simpler and more practical than the existing recognition method based on dynamic theory.

Description

Technical Field

[0001] The present invention relates to the field of electrical technology, and in particular to a method and a terminal for identifying a transient instability pattern of an electric power system. Background Art

[0002] With the widespread commissioning of DC transmission projects, my country has formed a large number of AC / DC hybrid power systems, among which the DC transmission system has a fast dynamic response characteristic, which significantly affects the transient stability process of the power system. Therefore, compared with the traditional AC power system, the transient stability problem of the AC / DC hybrid power system is more complicated. According to existing theories, the transient stability of the power system is often presented in two forms: transient voltage stability and transient power angle stability. Transient voltage instability will cause the node voltage in the power system to collapse, while transient power angle instability will cause the generator power angle to oscillate greatly. When the transient power angle is unstable, there is a certain probability of causing voltage instability, and when the system voltage is unstable, there is also a certain probability of causing power angle oscillation. The two types of transient instability phenomena are often intertwined and jointly affect the instability mode of the power system. Correctly distinguishing the dominant instability mode is an important prerequisite for improving the safety level of the power system.

[0003] At present, the physical characteristics identification methods based on voltage instability and power angle instability include: the method based on the oscillation center, the method based on the Thevenin equivalent, and the method based on the difference of the interconnection line power. However, the above methods are directly extended from the two-machine system to the multi-machine system. When the system does not have obvious characteristics of the two types of instability, the analysis results may not be reliable. In addition, there is an identification method based on dynamic theory. This method is difficult to calculate and requires more simplification of the system model. It is often not adopted in engineering. Moreover, most of the current power system transient instability identification methods only identify a single instability situation in voltage instability or power angle instability. Therefore, the accuracy of identifying the dominant instability mode of the AC / DC hybrid power system is low. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and a terminal for identifying transient instability modes of an electric power system, which can improve the accuracy of identifying the dominant instability modes in an AC / DC hybrid electric power system.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for identifying transient instability patterns of a power system comprises the following steps:

[0007] Calculate transient power angle instability index and transient voltage instability index;

[0008] A hierarchical structure model is established according to the transient power angle instability index and the transient voltage instability index, a power angle instability index judgment matrix and a voltage instability index judgment matrix are constructed respectively, and an evaluation index score reflecting power angle instability and an evaluation index score reflecting voltage instability are calculated;

[0009] A dominant instability mode is identified according to a difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability.

[0010] In order to solve the above technical problems, another technical solution adopted by the present invention is:

[0011] A transient instability mode recognition terminal for a power system includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the following steps when executing the computer program:

[0012] Calculate transient power angle instability index and transient voltage instability index;

[0013] A hierarchical structure model is established according to the transient power angle instability index and the transient voltage instability index, a power angle instability index judgment matrix and a voltage instability index judgment matrix are constructed respectively, and an evaluation index score reflecting power angle instability and an evaluation index score reflecting voltage instability are calculated;

[0014] A dominant instability mode is identified according to a difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability.

[0015] The beneficial effects of the present invention are: calculating the transient power angle instability index and the transient voltage instability index, establishing a hierarchical model according to the quantitative index, and constructing the power angle instability index judgment matrix and the voltage instability index judgment matrix respectively, calculating the power angle instability and voltage instability evaluation index scores, and then identifying the dominant instability mode of the actual power system according to the score difference. In this way, the accuracy of the dominant instability mode identification in the AC / DC hybrid power system can be improved, and the calculation process is simpler and more practical than the existing identification method based on dynamic theory. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flowchart of a method for identifying transient instability patterns of a power system according to an embodiment of the present invention;

[0017] Figure 2 A schematic diagram of a transient instability mode recognition terminal for a power system according to an embodiment of the present invention;

[0018] Figure 3 A schematic diagram of a transient instability mode hierarchical structure identification model of a method for identifying transient instability modes of a power system according to an embodiment of the present invention;

[0019] Figure 4 This is a single line diagram of the Fujian-Guangdong cross-region asynchronous interconnection network in the second embodiment of the present invention;

[0020] Figure 5 is a curve diagram of power angle and bus voltage amplitude in the second embodiment of the present invention;

[0021] Description of labels:

[0022] 1. A transient instability pattern recognition terminal for a power system; 2. A memory; 3. A processor. DETAILED DESCRIPTION

[0023] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in combination with the implementation modes and the accompanying drawings.

[0024] Please refer to Figure 1 The embodiment of the present invention provides a method for identifying a transient instability pattern of a power system, comprising the steps of:

[0025] Calculate transient power angle instability index and transient voltage instability index;

[0026] A hierarchical structure model is established according to the transient power angle instability index and the transient voltage instability index, a power angle instability index judgment matrix and a voltage instability index judgment matrix are constructed respectively, and an evaluation index score reflecting power angle instability and an evaluation index score reflecting voltage instability are calculated;

[0027] A dominant instability mode is identified according to a difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability.

[0028] From the above description, it can be seen that the beneficial effects of the present invention are: calculating the transient power angle instability index and the transient voltage instability index, establishing a hierarchical model based on the quantitative index, and constructing the power angle instability index judgment matrix and the voltage instability index judgment matrix respectively, calculating the power angle instability and voltage instability evaluation index scores, and then identifying the dominant instability mode of the actual power system based on the score difference. In this way, the accuracy of the identification of the dominant instability mode in the AC / DC hybrid power system can be improved, and the calculation process is simpler and more practical than the existing identification method based on dynamic theory.

[0029] Furthermore, the transient power angle instability index includes the generator instability index K i , power angle stability margin index A and DC active power stability margin index PM;

[0030] The transient voltage instability index includes a network transmission margin index Voltage recovery critical index T VC .

[0031] From the above description, it can be seen that the power angle stability and voltage stability of the actual power system can be quantified through the generator instability index, power angle stability margin index, DC active power stability margin index, network transmission margin index and voltage recovery critical index.

[0032] Furthermore, the respectively constructing of the power angle instability index judgment matrix and the voltage instability index judgment matrix comprises:

[0033] Establishing a power angle instability index judgment matrix according to the relative importance of each of the transient power angle instability indexes and the weight of each of the transient power angle instability indexes;

[0034] A voltage instability index judgment matrix is ​​established according to the relative importance of each of the transient voltage instability indicators and the weight of each of the transient voltage instability indicators.

[0035] From the above description, it can be seen that according to the relative importance and weights between transient instability indicators, the power angle instability indicator judgment matrix and the voltage instability indicator judgment matrix are established respectively, which is convenient for the subsequent evaluation of the scores of power angle instability and voltage instability.

[0036] Further, the calculation of the evaluation index score reflecting the power angle instability and the evaluation index score reflecting the voltage instability includes:

[0037] Normalizing the transient power angle instability index and the transient voltage instability index;

[0038] Calculate the evaluation index score reflecting the power angle instability according to the normalized values ​​and weights of each of the transient power angle instability indicators;

[0039] Calculating an evaluation index score reflecting voltage instability according to normalized values ​​of each transient voltage instability index and its weight;

[0040] According to the difference between the power angle instability evaluation index score and the voltage instability evaluation index score, identifying the dominant instability mode includes:

[0041] If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is greater than a first critical value, the dominant mode is the power angle instability;

[0042] If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is less than a second critical value, the dominant mode is voltage instability;

[0043] If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is greater than or equal to the second critical value and less than or equal to the first critical value, the power angle instability mode is strongly coupled with the voltage instability mode;

[0044] The second critical value is smaller than the first critical value.

[0045] From the above description, it can be seen that after normalizing each transient instability index, the evaluation index scores reflecting power angle instability and voltage instability are calculated respectively according to the normalized values ​​and their weights, and the dominant instability mode is determined according to the score difference, which can improve the recognition speed of the instability mode while ensuring the recognition accuracy.

[0046] Furthermore, normalizing the transient power angle instability index and the transient voltage instability index includes:

[0047] If the transient instability index to be normalized is a positive index, the positive index is normalized:

[0048]

[0049] In the formula, x i It indicates a positive indicator of transient instability;

[0050] If the transient instability index to be normalized is a reverse index, the reverse index is normalized:

[0051]

[0052] In the formula, x j It indicates the reverse indicator of transient instability.

[0053] From the above description, it can be seen that the accuracy of instability mode recognition can be further improved by performing corresponding normalization processing on the positive and reverse indicators of transient instability respectively.

[0054] Please refer to Figure 2 Another embodiment of the present invention provides a transient instability pattern recognition terminal for a power system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the following steps when executing the computer program:

[0055] Calculate transient power angle instability index and transient voltage instability index;

[0056] A hierarchical structure model is established according to the transient power angle instability index and the transient voltage instability index, a power angle instability index judgment matrix and a voltage instability index judgment matrix are constructed respectively, and an evaluation index score reflecting power angle instability and an evaluation index score reflecting voltage instability are calculated;

[0057] A dominant instability mode is identified according to a difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability.

[0058] From the above description, it can be seen that by calculating the transient power angle instability index and the transient voltage instability index, the power angle stability and voltage stability of the actual power system can be quantified; a hierarchical model is established based on the quantitative indexes, and the power angle instability index judgment matrix and the voltage instability index judgment matrix are constructed respectively, and the power angle instability and voltage instability evaluation index scores are calculated, so as to identify the dominant instability mode of the actual power system according to the score difference. In this way, the accuracy of the identification of the dominant instability mode in the AC / DC hybrid power system can be improved, and the calculation process is simpler and more practical than the existing identification method based on dynamic theory.

[0059] Furthermore, the transient power angle instability index includes the generator instability index K i , power angle stability margin index A and DC active power stability margin index PM;

[0060] The transient voltage instability index includes a network transmission margin index Voltage recovery critical index T VC .

[0061] From the above description, it can be seen that the power angle stability and voltage stability of the actual power system can be quantified through the generator instability index, power angle stability margin index, DC active power stability margin index, network transmission margin index and voltage recovery critical index.

[0062] Furthermore, the respectively constructing of the power angle instability index judgment matrix and the voltage instability index judgment matrix comprises:

[0063] Establishing a power angle instability index judgment matrix according to the relative importance of each of the transient power angle instability indexes and the weight of each of the transient power angle instability indexes;

[0064] A voltage instability index judgment matrix is ​​established according to the relative importance of each of the transient voltage instability indicators and the weight of each of the transient voltage instability indicators.

[0065] From the above description, it can be seen that according to the relative importance and weights between transient instability indicators, the power angle instability indicator judgment matrix and the voltage instability indicator judgment matrix are established respectively, which is convenient for the subsequent evaluation of the scores of power angle instability and voltage instability.

[0066] Further, the calculation of the evaluation index score reflecting the power angle instability and the evaluation index score reflecting the voltage instability includes:

[0067] Normalizing the transient power angle instability index and the transient voltage instability index;

[0068] Calculate the evaluation index score reflecting the power angle instability according to the normalized values ​​and weights of each of the transient power angle instability indicators;

[0069] Calculating an evaluation index score reflecting voltage instability according to normalized values ​​of each transient voltage instability index and its weight;

[0070] According to the difference between the power angle instability evaluation index score and the voltage instability evaluation index score, identifying the dominant instability mode includes:

[0071] If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is greater than a first critical value, the dominant mode is the power angle instability;

[0072] If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is less than a second critical value, the dominant mode is voltage instability;

[0073] If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is greater than or equal to the second critical value and less than or equal to the first critical value, the power angle instability mode is strongly coupled with the voltage instability mode;

[0074] The second critical value is smaller than the first critical value.

[0075] From the above description, it can be seen that after normalizing each transient instability index, the evaluation index scores reflecting power angle instability and voltage instability are calculated respectively according to the normalized values ​​and their weights, and the dominant instability mode is determined according to the score difference, which can improve the recognition speed of the instability mode while ensuring the recognition accuracy.

[0076] Furthermore, normalizing the transient power angle instability index and the transient voltage instability index includes:

[0077] If the transient instability index to be normalized is a positive index, the positive index is normalized:

[0078]

[0079] In the formula, x i It indicates a positive indicator of transient instability;

[0080] If the transient instability index to be normalized is a reverse index, the reverse index is normalized:

[0081]

[0082] In the formula, x j It indicates the reverse indicator of transient instability.

[0083] From the above description, it can be seen that the accuracy of instability mode recognition can be further improved by performing corresponding normalization processing on the positive and reverse indicators of transient instability respectively.

[0084] The above-mentioned method and terminal for identifying transient instability modes of a power system of the present invention are suitable for identifying the dominant transient instability modes in an AC / DC hybrid power system, and can improve the accuracy and efficiency of identification. The following is an explanation through specific implementation methods:

[0085] Embodiment 1

[0086] Please refer to Figure 1 , a method for identifying transient instability patterns of a power system, comprising the steps of:

[0087] S1. Calculate the transient power angle instability index and transient voltage instability index.

[0088] Among them, the transient power angle instability index includes the generator instability index K i , power angle stability margin index A and DC active power stability margin index PM; transient voltage instability index includes network transmission margin index Voltage recovery critical index T VC .

[0089] S11. Calculate the power angle stability margin index A.

[0090] The power angle stability margin index A, its physical meaning is to characterize the power angle stability margin of the generator in the power system, and the calculation formula is:

[0091]

[0092] In the formula, A acc represents the acceleration area of ​​the generator, A dec Indicates the deceleration area of ​​the generator.

[0093] When the acceleration area A acc Greater than the maximum deceleration area A dec When A is less than 0, it indicates that the power angle of the power system is unstable. The closer A is to -1, the higher the degree to which the acceleration area of ​​the generator is greater than the deceleration area, and the more unstable the transient power angle of the power system. acc Less than the maximum deceleration area A dec When A is close to 0+, the power angle of the power system is stable.

[0094] S12. Calculate the generator instability index K i .

[0095] Generator instability index K i , its physical meaning is to consider whether the generator will cause transient instability of the power system from the perspective of energy. The calculation formula is:

[0096]

[0097] Where t0 represents the generator instability time; t i It is expressed as the moment when the kinetic energy of the i-th generator is the smallest, represents the rotor speed at time t, represents the rotor angle of the i-th generator at time t;

[0098] Among them, V KEi (t i ) represents the minimum kinetic energy of the i-th generator related to the inertia center, and its calculation formula is:

[0099]

[0100] Where, T j represents the inertia time constant of the i-th generator;

[0101] When K i When it is less than or equal to 0, it indicates that the generator power angle lags behind the inertia center, indicating that the power angle of the power system is stable, and the smaller the value, the more stable it is; when K i When it is greater than 0, the power system power angle is unstable.

[0102] S13. Calculate network transmission margin index

[0103] definition and Its physical meaning is the transmission capacity of the power system network, the ratio of the change in reactive power emitted by all generators to the change in active power and reactive power of the load, and is a sensitivity indicator.

[0104] The calculation formula is:

[0105]

[0106]

[0107]

[0108] Where ΣΔQ Gi Represents the increment of all reactive power in the system, corresponding to the change in reactive output of the generator and reactive power compensation equipment; ΔP Li represents the active power increment of the i-th load node; ΔQ Li represents the reactive power increment of the i-th load node;

[0109] When the power system voltage is stable tends to 1, when the power system voltage instability occurs Tends to 0.

[0110] S14. Calculate the voltage recovery critical index T VC .

[0111] According to existing engineering standards, when the system is in a transient state after a large disturbance, if the load bus voltage can recover to above 0.8pu within 10s, it means that the system transient voltage is stable. Therefore, the voltage recovery critical index T is proposed. VC This indicator indicates the time required for the load bus voltage to recover to 0.8pu after the system suffers a large disturbance. The calculation method is as follows:

[0112] T vc =max{t i-re -t i-str};

[0113] Among them, t i-re It represents the time point when the voltage of the ith load bus recovers to above 0.8 pu level, t i-str Indicates the time when the fault started.

[0114] When T VC When it is greater than 10s, it indicates that the system transient voltage is unstable; when T VC When it is less than 10s, it means that the system transient voltage is stable.

[0115] S15. Calculate the DC active power stability margin PM.

[0116] When an AC system fails, the active power on the DC line will fluctuate accordingly. If the DC power exceeds the static stability limit power P lim , the DC system is in an unstable state, and the DC system will also affect the transient power angle stability of the AC system. The calculation method of DC active power stability margin is as follows:

[0117] PM=P lim -ΔP first-impact ;

[0118] Where PM is the DC active power stability margin, P lim is the static stability limit power after fault removal, ΔP first-impact It is the active power impulse amount of the first swing of active power.

[0119] The method for obtaining the static stability limit power in the above is as follows:

[0120]

[0121] In the formula, U1 and U2 represent the equivalent voltage of the sending and receiving end systems, X ∑ It represents the equivalent reactance of the equivalent system at the sending and receiving ends, and δ represents the power angle.

[0122] From the above formula, we can see that when δ = 90°, the exchange power P reaches the static stability limit value P lim :

[0123]

[0124] S2. Establish a hierarchical structure model according to the transient power angle instability index and the transient voltage instability index, construct a power angle instability index judgment matrix and a voltage instability index judgment matrix respectively, and calculate an evaluation index score reflecting power angle instability and an evaluation index score reflecting voltage instability.

[0125] S21. Establish a hierarchical identification model for transient stability modes of actual power systems.

[0126] For details, please refer to Figure 3 , according to the relationship between the target layer and the evaluation indicators at each level, the hierarchical model of the transient instability mode evaluation system can be obtained.

[0127] S22, establishing a power angle instability index judgment matrix according to the relative importance of each of the transient power angle instability indicators and the weight of each of the transient power angle instability indicators;

[0128] A voltage instability index judgment matrix is ​​established according to the relative importance of each of the transient voltage instability indicators and the weight of each of the transient voltage instability indicators.

[0129] Specifically, according to the hierarchical evaluation system model, the relative importance of the above five evaluation indicators is compared to construct a judgment matrix. ij Indicates transient instability analysis, P i Relative to P j The importance of; and the elements in the matrix satisfy: P ij >0,P ii =1,P ij =1 / P ji .P ij The size of refers to the "1-9 scale method" proposed by Satie, as shown in Table 1.

[0130] Table 1 Satie scale and its meaning

[0131]

[0132]

[0133] In this embodiment, the relative weight of the indicator w i The calculation method is:

[0134] Please refer to Table 2 and Table 3, and establish a power angle instability index judgment matrix and a voltage instability index judgment matrix according to the relative importance and weight of each transient instability index.

[0135] Table 2 Power angle instability index judgment matrix

[0136] Power angle instability index A <![CDATA[K i ]]> PM <![CDATA[Weight w i > A 1 3 5 0.6413 <![CDATA[K i ]]> 1 / 3 1 2 0.2375 PM 1 / 5 1 / 2 1 0.1211

[0137] Table 3 Voltage instability index judgment matrix

[0138]

[0139] Compute the consistency index of the matrix According to the average random consistency index Calculate the test coefficient CR.

[0140] Calculate the λ of the power angle instability index judgment matrix max =3.0037, CI = 0.00185, CR = 0.00356 < 0.1. The λ of the voltage instability index judgment matrix max =2.000, CI=0, CR=0<0.1.

[0141] The average random consistency index RI data is shown in Table 4.

[0142] Table 4 Average random consistency index RI

[0143] Matrix order 1 2 3 4 RI 0 0 0.52 0.89

[0144] S3. Identify a dominant instability mode according to a difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability.

[0145] S31, according to the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability

[0146] Specifically, the uniform range normalization method is used to normalize the positive index (i.e., the larger the data, the more dangerous it is) and the reverse index (i.e., the smaller the data, the more dangerous it is). According to step S1, the generator instability index K i , voltage recovery critical index T VC It is a positive indicator, power angle stability margin indicator A, network transmission margin indicator The DC active power stability margin PM is a reverse indicator. The processing formula is as follows:

[0147] Positive indicators:

[0148]

[0149] Contrarian Indicators:

[0150]

[0151] The indicator score is calculated according to the indicator weight. The calculation formula is as follows:

[0152]

[0153]

[0154] According to the power angle index score y1 and the voltage index score y2, the transient instability identification function Z is solved, and the formula is as follows:

[0155] Z(y1,y2)=y1-y2;

[0156] The values ​​of y1 and y2 are in the range of [0,1], and the value of Z is in the range of [-1,1].

[0157] S32. Identification of the dominant instability mode.

[0158] In this embodiment, Z=-0.3 and Z=0.3 are determined as critical points for instability mode identification. If the Z value is greater than 0.3, the system is more prone to power angle instability; if the Z value is less than -0.3, the system is more prone to voltage instability. If the Z value is between -0.3 and 0.3, power angle instability and voltage instability are strongly coupled.

[0159] Embodiment 2

[0160] Compared with the first embodiment, this embodiment provides a specific application scenario, which is as follows:

[0161] On the PSCAD / EMTDC platform, the example used is the simulation model of the cross-regional asynchronous interconnection between Fujian and Guangdong. The Fujian-Guangdong interconnection project adopts a conventional DC back-to-back interconnection method. The DC transmission capacity is 2×1 million kilowatts and the DC voltage is ±100 kV. Please refer to the example network single-line diagram Figure 4 .

[0162] A three-phase short-circuit fault is set near the DC feed-in bus 2, and the fault time is 0.23s / 0.3s / 0.5s, respectively, recorded as Case 1 / 2 / 3. Power angle instability and voltage instability occur simultaneously in the system. Using a single power angle stability evaluation index or voltage stability evaluation index can only lead to the conclusion that both power angle instability and voltage instability occur in the system, and it is not possible to identify which instability form is dominant. The hierarchical evaluation method proposed in this embodiment can provide such dominant stability identification. The evaluation values ​​calculated based on the identification method of this embodiment are shown in Table 5.

[0163] Table 5 Indicator recognition results

[0164]

[0165] Please refer to Figure 5 , (a) represents the power angle and bus voltage amplitude curves in the voltage instability mode in case 1, (b) represents the power angle and bus voltage amplitude curves in the coupling situation in case 2, and (a) represents the power angle and bus voltage amplitude curves in the power angle instability mode in case 3.

[0166] Therefore, as the fault duration increases, the system instability mode gradually evolves from voltage instability to power angle instability. During this change process, the power angle instability gradually increases, while the voltage instability gradually decreases.

[0167] Embodiment 3

[0168] Please refer to Figure 2 A transient instability pattern recognition terminal 1 for an electric power system includes a memory 2, a processor 3, and a computer program stored in the memory 2 and executable on the processor 3. When the processor 3 executes the computer program, each step of a method for transient instability pattern recognition for an electric power system in embodiment one or two is implemented.

[0169] In summary, the present invention provides a method and terminal for identifying transient instability patterns of power systems. By calculating transient power angle instability indicators and transient voltage instability indicators, the power angle stability and voltage stability of the actual power system can be quantified. A hierarchical model is established based on the quantitative indicators, and a power angle instability indicator judgment matrix and a voltage instability indicator judgment matrix are constructed respectively, and the power angle instability and voltage instability evaluation indicator scores are calculated, so as to identify the dominant instability pattern of the actual power system based on the score difference. In this way, the accuracy of identifying the dominant instability pattern in the AC / DC hybrid power system can be improved, and the calculation process is simpler and more practical than the existing identification method based on dynamic theory.

[0170] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for identifying transient instability patterns of a power system, characterized in that: Applicable to AC / DC hybrid power system, including the following steps: Calculate the transient power angle instability index and the transient voltage instability index, wherein the transient power angle instability index includes the generator instability index K i , power angle stability margin index A and DC active power stability margin index PM, the transient voltage instability index includes network transmission margin index Voltage recovery critical index T VC ; The DC active power stability margin calculation method is as follows: PM=P lim -ΔP first-impact ; Where PM is the DC active power stability margin, P lim is the static stability limit power after fault removal, ΔP first-impact It is the active power impulse of the first swing of active power; Network transmission margin index Where ΣΔQ Gi Represents the increment of all reactive power in the system, corresponding to the change in reactive output of the generator and reactive power compensation equipment; ΔP Li represents the active power increment of the i-th load node; ΔQ Li represents the reactive power increment of the i-th load node; When the power system voltage is stable tends to 1, when the power system voltage instability occurs tends to 0; Calculate the voltage recovery critical index T VC : T vc =max{t i-re -t i-str }; Among them, t i-re It represents the time point when the voltage of the ith load bus recovers to above 0.8 pu level, t i-str Indicates the time point when the fault starts. When T VC When it is greater than 10s, it indicates that the system transient voltage is unstable; when T VC When it is less than 10s, it means that the system transient voltage is stable; A hierarchical structure model is established according to the transient power angle instability index and the transient voltage instability index, and a power angle instability index judgment matrix and a voltage instability index judgment matrix are constructed respectively: Establishing a power angle instability index judgment matrix according to the relative importance of each of the transient power angle instability indexes and the weight of each of the transient power angle instability indexes; Establishing a voltage instability index judgment matrix according to the relative importance of each of the transient voltage instability indicators and the weight of each of the transient voltage instability indicators; Weight w i The calculation method is: Where P ij Indicates the importance of evaluation index i relative to evaluation index j; And calculate the evaluation index score reflecting power angle instability and the evaluation index score reflecting voltage instability; identifying a dominant instability mode according to a difference between the power angle instability evaluation index score and the voltage instability evaluation index score; The calculation of the evaluation index score reflecting the power angle instability and the evaluation index score reflecting the voltage instability includes: Normalizing the transient power angle instability index and the transient voltage instability index; Calculate the evaluation index score reflecting the power angle instability according to the normalized values ​​and weights of each of the transient power angle instability indicators; Calculating an evaluation index score reflecting voltage instability according to normalized values ​​of each transient voltage instability index and its weight; According to the difference between the power angle instability evaluation index score and the voltage instability evaluation index score, identifying the dominant instability mode includes: If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is greater than a first critical value, the dominant mode is the power angle instability; If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is less than a second critical value, the dominant mode is voltage instability; If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is greater than or equal to the second critical value and less than or equal to the first critical value, the power angle instability mode is strongly coupled with the voltage instability mode; The second critical value is smaller than the first critical value.

2. According to the method for identifying transient instability patterns of a power system according to claim 1, normalizing the transient power angle instability index and the transient voltage instability index comprises: If the transient instability index to be normalized is a positive index, the positive index is normalized: In the formula, x i It indicates a positive indicator of transient instability; If the transient instability index to be normalized is a reverse index, the reverse index is normalized: In the formula, x j It indicates the reverse indicator of transient instability.

3. A transient instability pattern recognition terminal for a power system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: Applicable to an AC / DC hybrid power system, the processor implements the following steps when executing the computer program: Calculate the transient power angle instability index and the transient voltage instability index, wherein the transient power angle instability index includes the generator instability index K i , power angle stability margin index A and DC active power stability margin index PM, the transient voltage instability index includes network transmission margin index Voltage recovery critical index T VC ; The DC active power stability margin calculation method is as follows: PM=P lim -ΔP first-impact ; Where PM is the DC active power stability margin, P lim is the static stability limit power after fault removal, ΔP first-impact It is the active power impulse of the first swing of active power; Network transmission margin index Where ΣΔQ Gi Represents the increment of all reactive power in the system, corresponding to the change in reactive output of the generator and reactive power compensation equipment; ΔP Li represents the active power increment of the i-th load node; ΔQ Li represents the reactive power increment of the i-th load node; When the power system voltage is stable tends to 1, when the power system voltage instability occurs tends to 0; Calculate the voltage recovery critical index T VC : T vc =max{t i-re -t i-str }; Among them, t i-re It represents the time point when the voltage of the ith load bus recovers to above 0.8 pu level, t i-str Indicates the time point when the fault starts. When T VC When it is greater than 10s, it indicates that the system transient voltage is unstable; when T VC When it is less than 10s, it means that the system transient voltage is stable; A hierarchical structure model is established according to the transient power angle instability index and the transient voltage instability index, and a power angle instability index judgment matrix and a voltage instability index judgment matrix are constructed respectively: Establishing a power angle instability index judgment matrix according to the relative importance of each of the transient power angle instability indexes and the weight of each of the transient power angle instability indexes; Establishing a voltage instability index judgment matrix according to the relative importance of each of the transient voltage instability indicators and the weight of each of the transient voltage instability indicators; Weight w i The calculation method is: Where P ij Indicates the importance of evaluation index i relative to evaluation index j; And calculate the evaluation index score reflecting power angle instability and the evaluation index score reflecting voltage instability; identifying a dominant instability mode according to a difference between the power angle instability evaluation index score and the voltage instability evaluation index score; The calculation of the evaluation index score reflecting the power angle instability and the evaluation index score reflecting the voltage instability includes: Normalizing the transient power angle instability index and the transient voltage instability index; Calculate the evaluation index score reflecting the power angle instability according to the normalized values ​​and weights of each of the transient power angle instability indicators; Calculating an evaluation index score reflecting voltage instability according to normalized values ​​of each transient voltage instability index and its weight; According to the difference between the power angle instability evaluation index score and the voltage instability evaluation index score, identifying the dominant instability mode includes: If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is greater than a first critical value, the dominant mode is the power angle instability; If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is less than a second critical value, the dominant mode is voltage instability; If the difference between the evaluation index score of the power angle instability and the evaluation index score of the voltage instability is greater than or equal to the second critical value and less than or equal to the first critical value, the power angle instability mode is strongly coupled with the voltage instability mode; The second critical value is smaller than the first critical value.

4. According to the transient instability pattern recognition terminal of the power system of claim 3, the normalization processing of the transient power angle instability index and the transient voltage instability index comprises: If the transient instability index to be normalized is a positive index, the positive index is normalized: In the formula, x i It indicates a positive indicator of transient instability; If the transient instability index to be normalized is a reverse index, the reverse index is normalized: In the formula, x j It indicates the reverse indicator of transient instability.

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