A method and system for calculating power system power angle stability margin

Abstract

The present invention proposes a method and system for calculating the power angle stability margin of an electric power system. The method includes: extracting the first data of a multi-machine system required for calculating the power angle stability margin, normalizing the first data, and using the normalized first data to divide the multi-machine system into complementary groups; calculating the equivalent parameters of the complementary groups, using the size of the equivalent parameters to further divide the complementary groups into single-machine systems after secondary division, and calculating the equivalent parameters of the single-machine system. The swing modes are classified according to the changes in the equivalent electromagnetic power and the equivalent mechanical power in the equivalent parameters of the single-machine system; and the stability margins under different swing modes are calculated. Based on this method, a system for calculating the power angle stability margin of an electric power system is also proposed. The present invention classifies the swing modes using the aggregated power curve, and provides corresponding stability margin calculation methods for different swing modes, which can improve the accuracy of stability judgment and provide a basis for stable control of the electric power system.

Description

Technical Field

[0001] The invention belongs to the technical field of power system stability analysis and control, and in particular relates to a method and system for calculating power system power angle stability margin. Background Art

[0002] The safety and stability of the power system refers to the ability of the system to recover to its original state or transition to a new stable state after being disturbed. Among them, the power angle stability refers to the ability of the synchronous generator to maintain synchronous operation after the system is disturbed, which is an important part of the safety and stability of the power system. Accurately assessing the power angle stability margin of the power system and then supporting accurate and reliable stability control decisions is the key to ensuring the safe operation of the power system.

[0003] The EEAC method is a classic method for calculating the power angle stability margin. It combines the universality of the time domain analysis method and the simplicity of the classic direct method, and is widely used in engineering practice. However, the accurate application of the EEAC method to calculate the power angle stability margin of the power system requires accurate identification of the cumulative energy change process of the equivalent system, and the acceleration and deceleration process of the equivalent system under different working conditions may present different characteristics. The traditional EEAC method assumes that the power exchange of the equivalent system is blocked during the fault and tends to separate (that is, the equivalent system accelerates first), and after the fault is removed, the equivalent system approaches under the action of the restoring force (that is, the equivalent system enters the deceleration state) and enters the swing state. On this basis, the acceleration area and the deceleration area are calculated to form the stability margin index. However, the diverse operating modes of complex power systems lead to diverse transient swing modes. For example, changes in ground resistance and voltage-power coupling may cause the equivalent system to approach rather than separate during the fault, and changes in operating modes may cause it to still separate after the fault is removed rather than approaching first and then swinging. The change in the swing mode causes the assumption of the traditional EEAC method to no longer hold, and the accuracy of the results calculated by the original stability margin calculation method will be significantly reduced. How to classify the swing modes of power system under different operating conditions and then provide the corresponding stability margin calculation method is an urgent problem to be solved when using the extended equal area rule to evaluate and quantify stability. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a method and system for calculating the power angle stability margin of an electric power system, which can effectively improve the accuracy of the stability margin calculation results under complex working conditions and provide a more accurate basis for the safe and stable control of the electric power system.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for calculating a power angle stability margin of an electric power system comprises: extracting first data of a multi-machine system required for calculating a power angle stability margin, and performing standardization processing on the first data; wherein the first time series data comprises a power angle, a rotation speed, an electromagnetic power and a mechanical power; the first model parameter comprises a generator capacity and an inertia; and further comprising:

[0007] Using the normalized first data to divide the multi-machine system into complementary groups; calculating the equivalent parameters of the complementary groups, using the size of the equivalent parameters to further divide the complementary groups into equivalent single-machine systems, and calculating the equivalent parameters of the single-machine systems;

[0008] Determine the acceleration power of the single-machine system according to the equivalent electromagnetic power and equivalent mechanical power in the equivalent parameters of the single-machine system, and classify the swing mode according to the change of the acceleration power;

[0009] Calculate the stability margin under different swing modes; specifically include: first find the key moment for judging stability under different modes, use the change of acceleration power to judge the stability at the key moment, then calculate the acceleration and deceleration areas under stable and unstable conditions respectively, and finally calculate the stability margin using the acceleration and deceleration areas according to the result of stability judgment.

[0010] A calculation system for power angle stability margin of an electric power system, comprising a data preprocessing module, the data preprocessing module being used to extract first data of a multi-machine system required for power angle stability margin calculation, and to perform standardization processing on the first data; wherein the first time series data comprises power angle, rotation speed, electromagnetic power and mechanical power; the first model parameter comprises generator capacity and inertia; and further comprising an equivalent value determination module, a classification module and a calculation module;

[0011] The determining equivalent module is used to divide the multi-machine system into complementary groups once using the normalized first data; calculate the equivalent parameters of the complementary groups, divide the complementary groups into equivalent single-machine systems after secondary division using the size of the equivalent parameters, and calculate the equivalent parameters of the single-machine system;

[0012] The classification module is used to determine the acceleration power of the single-machine system according to the equivalent electromagnetic power and the equivalent mechanical power in the equivalent parameters of the single-machine system, and classify the swing mode according to the change of the acceleration power;

[0013] The calculation module is used to calculate the stability margin under different swing modes; specifically, it includes: firstly finding the key moment for judging stability under different modes, using the change of acceleration power to judge the stability at the key moment, then respectively calculating the acceleration and deceleration areas under stable and unstable conditions, and finally calculating the stability margin using the acceleration and deceleration areas according to the result of the stability judgment.

[0014] The effects provided in the content of the invention are only the effects of the embodiments, not all the effects of the invention. One of the above technical solutions has the following advantages or beneficial effects:

[0015] The present invention proposes a method and system for calculating the power angle stability margin of an electric power system. The method comprises the following steps: extracting first data of a multi-machine system required for calculating the power angle stability margin, and performing per-unit processing on the first data; wherein the first time series data comprises power angle, rotation speed, electromagnetic power and mechanical power; the first model parameter comprises generator capacity and inertia; using the per-unit first data to divide the multi-machine system into complementary groups once; calculating equivalent parameters of the complementary groups, using the size of the equivalent parameters to further divide the complementary groups into single-machine systems after secondary division, and calculating equivalent parameters of the single-machine systems;

[0016] Determine the acceleration power of the single-machine system according to the equivalent electromagnetic power and equivalent mechanical power in the equivalent parameters of the single-machine system, and classify the swing mode according to the change of the acceleration power; calculate the stability margin under different swing modes; specifically include: first find the key moment of stability judgment under different modes, use the change of the acceleration power to judge the stability at the key moment of stability judgment, then calculate the acceleration and deceleration areas under stable and unstable conditions respectively, and finally calculate the stability margin according to the result of stability judgment using the acceleration and deceleration areas. Based on a method for calculating the power angle stability margin of an electric power system, a calculation system for the power angle stability margin of an electric power system is also proposed. The present invention classifies the swing modes using the aggregated power curve, and provides a corresponding stability margin calculation method for different swing modes. The present invention can adjust the application mode of the EEAC method according to different swing modes, enhance the applicability of the extended equal area law, improve the accuracy of stability judgment, and provide an accurate basis for the stability control of the electric power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the overall flow chart for stability margin calculation using EEAC;

[0018] Figure 2 This is a flow chart of calculating the power angle stability margin under multiple working conditions proposed in Example 1 of the present invention;

[0019] Figure 3 A schematic diagram of a multi-machine system trajectory aggregation process proposed in Example 1 of the present invention;

[0020] Figure 4 It is the instability trajectory on the external force-position plane under the first swaying mode proposed in Example 1 of the present invention;

[0021] Figure 5 It is a stable trajectory on the external force-position plane in the first swing mode proposed in Example 1 of the present invention;

[0022] Figure 6 It is the instability trajectory on the external force-position plane in the second swing mode proposed in Example 1 of the present invention;

[0023] Figure 7 It is a stable trajectory on the external force-position plane in the second swing mode proposed in Example 1 of the present invention;

[0024] Figure 8 It is the instability trajectory on the external force-position plane under the third swing mode proposed in Example 1 of the present invention;

[0025] Fig. 9 This is a diagram of the 10,000-node system structure and fault location proposed in Example 1 of the present invention;

[0026] Fig.10 The diagrams of initial power angles and equivalent power angles of two groups under different conditions proposed in Embodiment 1 of the present invention;

[0027] Fig.11 It is a graph of external force-work angle curves under different conditions proposed in Example 1 of the present invention;

[0028] Fig.12 This is a fitting curve diagram of the external force-power angle under situation 3 proposed in embodiment 1 of the present invention;

[0029] Fig.13 This is a schematic diagram of a system for calculating the power angle stability margin of an electric power system proposed in Example 2 of the present invention. DETAILED DESCRIPTION

[0030] In order to clearly illustrate the technical features of the present solution, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings. The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. In addition, the present invention may repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. It should be noted that the components illustrated in the accompanying drawings are not necessarily drawn to scale. The present invention omits the description of known components and processing techniques and processes to avoid unnecessary limitations on the present invention.

[0031] Example 1

[0032] A method for calculating the power angle stability margin of an electric power system proposed in Embodiment 1 of the present invention is used to solve the technical problem of how to improve the accuracy of stability judgment and stability margin calculation in the prior art.

[0033] The present invention is applicable to the calculation of stability margin of power system with complex operating conditions, including three parts: multi-machine system equivalence, transient process swing mode identification, and stability margin calculation under different swing modes. The first part first reads simulation data or real-time measurement data sequence and model parameters to obtain system data such as power angle, speed, electromagnetic power, mechanical power, generator inertia, etc. required for calculation; then uses kmeans clustering to group the multi-machine system into leading group and lagging group; finally, the two-machine system is equivalent to a single-machine system, and the power angle, inertia, mechanical power and electromagnetic power of the single-machine equivalent system are calculated. The second part first calculates the key characteristic quantity of the swing mode, calculates the acceleration power based on the equivalent system electromagnetic power and mechanical power, and then divides the transient process swing mode into three categories according to the change relationship of the acceleration power sign. The third part jumps to the stability margin method under the corresponding mode according to the swing mode; for each swing mode, the P-δ plane is used to determine the acceleration and deceleration process, and the acceleration area, deceleration area, and potential deceleration area are calculated in combination with the power angle, speed and power curve to calculate the power angle stability margin index.

[0034] Figure 2 This is a flow chart of calculating the power angle stability margin under multiple working conditions proposed in Example 1 of the present invention;

[0035] In step 1, the first data of the multi-machine system required for calculating the power angle stability margin is extracted, and the first data is normalized; wherein the first time series data includes the power angle, the rotation speed, the electromagnetic power and the mechanical power; the first model parameters include the generator capacity and inertia;

[0036] Using the normalized first data to divide the multi-machine system into complementary groups; calculating the equivalent parameters of the complementary groups, using the size of the equivalent parameters to further divide the complementary groups into equivalent single-machine systems, and calculating the equivalent parameters of the single-machine systems;

[0037] Figure 3 A schematic diagram of a multi-machine system trajectory aggregation process proposed in Example 1 of the present invention;

[0038] Step 1.1: Sort the first time series data of each generator in the system in time series, with each row representing a time point. Horizontally connect the first time series data column matrix of each generator to form a first time series data matrix, with each column representing the first time series data of a generator. Sort the first model parameters according to the order of any first time series data of the generator recorded in the first time series data matrix to generate the capacity matrix and the inertia matrix.

[0039] Specifically, read the simulation or measured data, sort the power angle data of each generator in the system in time series, each row represents a time point, and connect the power angle data column matrix of each generator horizontally to form the power angle matrix δ, each column represents the power angle data of a generator. The same operation is used to form the speed matrix w and the electromagnetic power matrix p e and the mechanical power matrix p m , where the power angle, electromagnetic power, and mechanical power are nominal values, and the speed value is the per unit value based on the rated synchronous angular velocity of the system. According to the order in which the generator records the power angle in the first time series data, the capacity and inertia data are sorted to generate the capacity matrix S N and the inertia matrix m.

[0040] The specific process of normalizing the first data is as follows:

[0041]

[0042] Among them, p e is the electromagnetic power; S B is the base capacity value; P e is the normalized electromagnetic power matrix; p m is the mechanical power; P m is the normalized mechanical power matrix; m i is the i-th value in the inertia matrix m, i.e., the inertia of the i-th machine; M i is the ith value in the normalized system inertia matrix M, i.e., the normalized inertia matrix of the ith machine; S Ni is the i-th value in the capacity matrix, that is, the capacity of the i-th machine.

[0043] Step 1.2: Group the multi-machine system based on the acquired time series data. The process of using the normalized first data to divide the multi-machine system into complementary groups includes:

[0044] The power angle data of all generators within a period of time after the system is disturbed are selected to form the power angle curves of each generator. Two power angle curves are randomly selected from all the curves as cluster centers, denoted as C1 and C2; the power angle curves of the remaining generators are calculated to cluster center C k distance;

[0045]

[0046] δ i is the sequential power angle data of the i-th machine; δ im is δ i The mth data of km C kThe mth data of the power angle curve; each power angle curve time series data contains n elements in total, and n depends on the time length of the selected power angle curve;

[0047] The power angle curves of each generator are classified according to the Euclidean distance D and divided into the clusters with the closest distance. Then the cluster centers of the two clusters are calculated and replaced with the randomly selected power angle curves as the new cluster centers. The above classification and calculation processes are repeated until the cluster centers no longer change. The final classification results are obtained, and all generators are divided into the first group G1 and the second group G2.

[0048] The process of calculating the equivalence parameters of the complementation group involves:

[0049] The calculation formula of the equivalent rotor angle is:

[0050]

[0051] Among them, δ1 is the equivalent rotor angle of the first group G1; δ2 is the equivalent rotor angle of the second group G2; M i is the normalized inertia matrix of the i-th machine; M j is the normalized inertia matrix of the jth machine;

[0052] Then, the normalized mechanical power matrix and the normalized inertia matrix are used to calculate the equivalent inertia, equivalent mechanical power, equivalent electromagnetic power and equivalent speed of the first group G1 and the second group G2 respectively; the specific process is:

[0053]

[0054] Where M1 is the equivalent inertia of the first group G1; M2 is the equivalent inertia of the second group G2; P m1 is the equivalent mechanical power of the first group G1; P m2 is the equivalent mechanical power of the second group G2; w1 is the equivalent speed of the first group G1; w2 is the equivalent speed of the second group G2; P mi is the mechanical power of the i-th machine; P mj is the mechanical power of the jth machine; P ei is the electromagnetic power of the i-th machine; P ej is the electromagnetic power of the jth machine; w i is the speed of the i-th machine; w j is the speed of the jth machine;

[0055] The first group G1 and the second group G2 are judged according to the size of the equivalent rotor angle, and the two groups of equivalent rotor angles are summed from the time of fault onset to the time of fault removal. The summed values ​​are compared. The larger sum of equivalent rotor angles is the third group S, and the other is the fourth group A. The equivalent rotor angles δ of the third group S and the fourth group A are calculated again according to formula (8) and formula (9): S and δ A , equivalent inertia M S and M A , equivalent mechanical power P mS and P mA , equivalent electromagnetic power P eS and P eA , equivalent speed w S and w A .

[0056] Step 1.3: Treat the two clusters as single machines and calculate the equivalent parameters of the single machine system.

[0057] The process of further converting the complementary group into a single-machine system by dividing it twice using the size of the equivalent parameter includes: converting the third group S and the fourth group A into a single-machine system, and calculating the equivalent rotor angle of the single-machine system:

[0058]

[0059] Among them, δ E is the equivalent rotor angle of the single-machine system;

[0060] Calculate the equivalent speed, equivalent inertia, equivalent mechanical power and equivalent electromagnetic power of a single machine system;

[0061]

[0062] Among them, w E is the equivalent speed of a single-machine system; M E is the equivalent inertia of the single-machine system; P mE is the equivalent mechanical power of the single-machine system; P eE is the equivalent electromagnetic power of a single-machine system.

[0063] Step 2: Determine the acceleration power of the single-machine system according to the equivalent electromagnetic power and equivalent mechanical power in the equivalent parameters of the single-machine system, and classify the swing mode according to the change of the acceleration power.

[0064] Step 2.1 Calculation of key characteristic quantities of the swing mode

[0065] (1) Subtract the equivalent electromagnetic power from the equivalent mechanical power of the single-machine system after aggregation to obtain the acceleration power P a .

[0066] (2) P a An appropriate zero-crossing threshold is selected so that it is neither too small to record data caused by errors nor too large to miss the moment when the mechanical power and the electromagnetic power actually intersect.

[0067] (3) After the system is disturbed, once P a If the change exceeds the positive value of the threshold or is less than the negative value of the threshold and the current state is different from the state at the previous moment, it is considered that the acceleration and deceleration state of the system has changed, and the current moment is recorded in P a List of change points middle.

[0068] Step 2.2 Divide the swing mode according to the acceleration power Pa change table

[0069] (1) P a List of change points To calculate the length, if If the list length is 0, the current swing mode is judged to be mode 3, the mechanical power is always greater than the electromagnetic power, there is no deceleration, and there is no deceleration area, and the current swing mode division program ends; if P a If the list length is not 0, go to (2) to continue the judgment.

[0070] (2) Compare P from the time the fault started a With the size of the zero-crossing threshold, once P a If the positive value is greater than the threshold, the current swing mode is judged to be mode 2. After the fault occurs, the mechanical power is greater than the electromagnetic power first, and the system accelerates first and then decelerates; or once P a If the negative value is less than the threshold, the current swing mode is judged to be mode 1. After the fault occurs, the mechanical power is first less than the electromagnetic power, and the system first decelerates, then accelerates, and then decelerates.

[0071] Step 3: Calculate the stability margin according to different swing modes. The present invention considers three different swing modes: acceleration first and then deceleration, deceleration first and then acceleration and deceleration again, and deceleration all the time.

[0072] The Extended Equal Area Criterion (EEAC) is a mature scheme for stability margin calculation and the basis for the implementation of this method.

[0073] Figure 1 This is the overall flow chart for stability margin calculation using EEAC;

[0074] The EEAC theory divides the generator into a critical group S and a residual group A, and performs single-machine equivalence. The model after equivalence is:

[0075]

[0076] In formula (1), w E is the equivalent speed of a single-machine system; M E is the equivalent inertia of the single-machine system; P mE is the equivalent mechanical power of the single-machine system; P eE is the equivalent electromagnetic power of a single-machine system; δ E is the equivalent power angle of a single-machine system.

[0077] For the obtained equivalent single-machine system, quantitative analysis is performed on the P-δ plane to obtain the stability margin. The fault is divided into two cases: instability and stability. During the simulation time, if the system has no dynamic saddle point DSP and only the farthest point FEP of the swing, the system is stable; if the system reaches the DSP point, the system is generally unstable. The system stability criterion and margin expression are as follows.

[0078] (1) System instability criterion:

[0079]

[0080] In the formula, t u is the moment when the system reaches the DSP point after EEAC equalization. At this time, the stability margin is defined as

[0081]

[0082] In the formula, A dec is the deceleration area on the P-δ plane, A inc is the acceleration area on the P-δ plane.

[0083] (2) The stability criterion for the system to maintain a stable power angle is:

[0084]

[0085] In the formula, t r It is the moment when the system reaches the FEP point for the first time after the EEAC is equal. At this time, the stability margin is defined as

[0086]

[0087] In the formula, A dec.pot is the potential deceleration area.

[0088] The EEAC theory is based on the complete multi-machine disturbed trajectory. It maps the multi-machine disturbed trajectory section by time section onto a series of aggregated single-machine planes through the complementary group center of inertia-relative motion (CCCOI-RM) transformation. The plane has the equivalent power angle as the horizontal axis and the equivalent power as the vertical axis (i.e., the P-δ plane), and then uses an appropriate area to quantify the stability of the system.

[0089] The above method of using EEAC to calculate the power angle stability margin of the power system has the following problems: the initial unbalanced force caused by the fault or disturbance is assumed to be positive, the power angle and the speed both increase in the initial stage, and the equivalent system enters a deceleration state and a swinging state after the fault or disturbance disappears. On this basis, the acceleration area and the deceleration area are calculated to form a stability margin index. However, changes in the operating mode may cause the transient process of the equivalent system to not meet the above assumptions. For example, even after the fault is removed, the system remains separated rather than converging first and then swinging. Changes in grounding resistance and the coupling between voltage and power may cause the equivalent behavior of the system during the fault to be more consistent rather than separated. At this time, the original stability criterion is no longer applicable, and the power system power angle stability margin cannot be calculated, resulting in a significant reduction in the accuracy of the stability results obtained according to the original criterion and the stability margin calculation method under certain operating modes.

[0090] Therefore, the overall implementation process of the stability margin calculation in this application includes: first, finding the critical moment for judging stability under different methods, using the change in acceleration power to make a stability judgment at the critical moment for judging stability, and then respectively calculating the acceleration and deceleration areas under stable and unstable conditions, and finally calculating the stability margin using the acceleration and deceleration areas according to the result of the stability judgment.

[0091] P mE With P eE The intersection point is P a The zero crossing point determines the increase or decrease of the speed, and the zero crossing point of the speed determines the increase or decrease of the power angle. By comparing the order of these moments with the arrival time of the farthest power angle point, stability judgment can be made and the starting and ending points of the acceleration and deceleration area can be determined, thereby calculating the stability margin. Specifically, it includes: finding the key moments for stability judgment under different methods, then making stability judgments, and finally calculating the acceleration and deceleration areas, and using the acceleration and deceleration areas to calculate the stability margin according to the results of the stability judgment.

[0092] The process of calculating the stability margin for the first sway mode includes:

[0093] (1) Search for critical moments in determining stability

[0094] Find the system equivalent power angle δ E The moment when the farthest point is reached for the first time. The maximum power angle is initialized to the power angle value at the time when the fault starts, and the state variable is initialized to 0; the power angle curve after the equal value is iterated from the time when the fault occurs, and the power angle values ​​are compared one by one. If the current power angle value is greater than the maximum power angle value, the current power angle value is updated to the maximum power angle value, and the current moment is the moment of maximum power angle, and the state variable is changed to 1; when the state variable is 1 and the power angle begins to decrease, the loop is terminated, and the moment T at which the power angle is maximum is output at this time. δ .

[0095] Find the equivalent speed w EThe zero-crossing moment of E Select a suitable zero-crossing threshold. After the fault starts, once w E If the change of exceeds the positive value of the threshold or is less than the negative value of the threshold and the current state is different from the state at the previous moment, the system speed is considered to change from positive to negative or from negative to positive, and the current moment is recorded in w E List of change points T w middle;

[0096] (2) Stability judgment

[0097] Figure 4 It is the instability trajectory on the external force-position plane under the first swaying mode proposed in Example 1 of the present invention; Figure 5 It is a stable trajectory on the external force-position plane in the first swing mode proposed in Example 1 of the present invention;

[0098] Use the system instability criterion and system stability criterion to determine whether the system is stable; if the system stability criterion is met, the system is stable, otherwise the system is unstable;

[0099] The criterion for system instability is:

[0100] The criterion for system stability is:

[0101] in, P a List of change points The third value in w E (T δ ) is T δ The equivalent speed of the single-machine system at the moment w E The value of

[0102] (3) Acceleration and deceleration area calculation

[0103] First, determine the starting and ending points of the acceleration and deceleration area. After determining the starting and ending points of the acceleration and deceleration area, calculate the acceleration and deceleration area by integration.

[0104] Calculate the acceleration and deceleration areas in stable and unstable conditions respectively. In the unstable condition, the starting point of the acceleration area is the zero crossing point T of the speed. w [0], the end point of the acceleration area and the end point of the deceleration area are P a The moment from positive to negative The end point of the deceleration area is P a The second moment from negative to positive Under stable conditions, the acceleration and deceleration areas of the system are equal, and the starting point of the acceleration area is the zero-crossing point T of the speed. w [0], the end point of the acceleration area and the end point of the deceleration area are P a The moment from positive to negative The end point of the deceleration area is the farthest point T when the kinetic energy is reduced to zero. δ .

[0105] After determining the starting and ending points of the acceleration and deceleration area, the acceleration and deceleration area is calculated by integration. Through slicing operations, the angle values ​​in the acceleration and deceleration ranges of the power angle curve and the power values ​​in the acceleration and deceleration ranges of the power curve are obtained. The power in the acceleration range and the power in the deceleration range are respectively integrated in a trapezoidal manner. The power angle in the acceleration range and the power angle in the deceleration range are respectively used as the independent variables of the integration to obtain the acceleration area A. inc and deceleration area A dec . Add a minus sign in front of the integral result of the deceleration area.

[0106] (4) Stability margin calculation

[0107] If it is unstable, the formula Calculate the stability margin and end the current stability margin calculation program; where A dec is the deceleration area on the P-δ plane, A inc is the acceleration area on the P-δ plane;

[0108] If instability does not occur, the acceleration area is equal to the deceleration area in a stable condition. The P-δ curve after the farthest power corner point is fitted, and the potential deceleration area is used to characterize the stability margin.

[0109] Then use the formula Calculate the stability margin; where A dec.pot is the potential deceleration area.

[0110] The process of calculating the stability margin in the second swing mode includes:

[0111] (1) Search for critical moments in determining stability

[0112] Find the equivalent rotor angle δ for a single-machine system E The first time to reach the farthest point is T δ ;

[0113] (2) Stability judgment

[0114] Figure 6 It is the instability trajectory on the external force-position plane in the second swing mode proposed in Example 1 of the present invention; Figure 7 It is a stable trajectory on the external force-position plane in the second swing mode proposed in Example 1 of the present invention;

[0115] Use the system instability criterion and system stability criterion to determine whether the system is stable; if the system stability criterion is met, the system is stable, otherwise the system is unstable;

[0116] The criterion for system instability is:

[0117] The criterion for system stability is: in, P a List of change points The second value in

[0118] (3) Acceleration and deceleration area calculation

[0119] First, the acceleration and deceleration areas in stable and unstable conditions are calculated respectively. After determining the starting and ending points of the acceleration and deceleration areas, the acceleration and deceleration areas are calculated by integration.

[0120] Calculate the acceleration and deceleration areas in stable and unstable conditions respectively. In the unstable condition, the starting point of the acceleration area is the moment of fault occurrence, and the end point of the acceleration area and the starting point of the deceleration area are P a The moment from positive to negative The end point of the deceleration area is P a The moment from negative to positive Under stable conditions, the acceleration and deceleration areas of the system are equal. The starting point of the acceleration area is the moment of fault occurrence, and the end point of the acceleration area and the end point of the deceleration area are P a The moment from positive to negative The end point of the deceleration area is the farthest point T when the kinetic energy is reduced to zero. δ .

[0121] After determining the starting and ending points of the acceleration and deceleration area, the acceleration and deceleration area is calculated by integration. Through slicing operations, the angle values ​​in the acceleration and deceleration ranges of the power angle curve and the power values ​​in the acceleration and deceleration ranges of the power curve are obtained. The power in the acceleration range and the power in the deceleration range are respectively integrated in a trapezoidal manner. The power angle in the acceleration range and the power angle in the deceleration range are respectively used as the independent variables of the integration to obtain the acceleration area A. inc and deceleration area A dec . Add a minus sign in front of the integral result of the deceleration area.

[0122] (4) Stability margin calculation

[0123] If it is unstable, the formula Calculate the stability margin and end the current stability margin calculation program; where A dec is the deceleration area on the P-δ plane, A inc is the acceleration area on the P-δ plane; if instability does not occur, the formula is used Calculate the stability margin; where A dec.pot is the potential deceleration area.

[0124] The process of calculating the stability margin under the third swing mode includes:

[0125] Figure 8 This is the instability trajectory on the external force-position plane under the third swing mode proposed in Example 1 of the present invention; under the third swing mode, the mechanical power is always greater than the electromagnetic power, the speed keeps increasing under the action of the acceleration force, the power angle keeps increasing, and the system is in an extremely unstable state. Therefore, under the third swing mode, the system does not have a deceleration area, and the stability margin is -1 at this time.

[0126] A method for calculating the power angle stability margin of a power system proposed in Example 1 of the present invention uses aggregated power curves to classify swing modes, and provides corresponding stability margin calculation methods for different swing modes. The present invention can adjust the application mode of the EEAC method according to different swing modes, enhance the applicability of the extended equal area law, improve the accuracy of stability judgment, and provide an accurate basis for power system stability control.

[0127] This application takes a large system with 10,000 AC nodes (hereinafter referred to as a 10,000-node system) as an example to further illustrate the application process of the method proposed in this application.

[0128] Based on the 10,000-node system, it adopts various operating modes, faults and emergency control to perform electromechanical transient simulation to obtain various time series data, and further uses the method proposed in this application to calculate the stability margin. Fig. 9 This is the 10,000-node system structure and fault location diagram proposed in Example 1 of the present invention; considering three situations: fault in a certain operation mode, fault in a certain operation mode and emergency control, and fault in another operation mode and emergency control. The stability margin calculation steps are:

[0129] Step 1: Multi-machine system equivalence

[0130] The simulation data files and model parameter files of the three cases are processed to obtain the trajectory data, generator capacity and inertia data of the system synchronous units in the three cases.

[0131] The synchronous units in each case are divided into two groups according to the power angle curve, and the leading and lagging groups are judged according to the equivalent power angle from the beginning of the fault to the fault removal. The initial power angles and equivalent power angles of the two groups in the three cases are obtained as follows: Fig.10 As shown, Fig.10 The initial power angle and equivalent power angle diagram of the two groups under different conditions proposed in Example 1 of the present invention are given.

[0132] The two-machine system is equivalent to a single-machine system, and the external force-power angle curves under three conditions are obtained as follows: Fig.11 As shown, Fig.11 This is a graph of external force-work angle curves under different conditions proposed in Example 1 of the present invention.

[0133] Step 2: Swing Pattern Classification

[0134] The process of calculating the key characteristic quantity of the swing mode is as follows: Calculate P for three cases a List of change points Situation 1 Empty, case 2 Case 3

[0135] The process of swing mode division is as follows: The list length is 0, and its swing mode is mode 3; P of cases 2 and 3 a The length of the list is not 0. In case 2, P a First, the positive value is greater than the threshold, and the current swing mode is judged to be mode 2; in case 3, P a First, if the negative value is smaller than the threshold, the current swing mode is determined to be mode 1.

[0136] Step 3: Stability Margin Calculation

[0137] In the third case: there is no deceleration area in the system and the stability margin is -1.

[0138] In the second case: Find the time T when the system equivalent power angle δ first reaches the farthest point δ 899; P a The moment from negative to positive is 176, The instability criterion is met and the system is generally unstable. In this case, the starting point of the acceleration area is 100 when the fault occurs, and the end point of the acceleration area is the starting point of the deceleration area. 148, the end point of the deceleration area =176, and the acceleration area A is obtained by integral calculation inc is 28.38, the deceleration area A dec is 7.41; then substitute into the formula:

[0139] The calculated stability margin is -0.739.

[0140] In the first case: Find the time T when the system equivalent power angle δ first reaches the farthest point δ is 240, find the zero-crossing time T of the speed w after equalization w =[118,226,505,648,911]; P a The second moment from negative to positive is 352, which meets the stability criterion and the system is stable. Under this stable condition, the starting point T of the acceleration area w [0] is 118, the end point of the acceleration area and the end point of the deceleration area is 141, the end point of the deceleration area is T δ is 240, and the integral calculation gives the acceleration area and deceleration area A dec Equal; fit the P-δ curve after the farthest power corner point, and its image is as follows Fig.12 As shown, Fig.12 The external force-power angle fitting curve diagram under case 3 is given, and the formula is substituted:

[0141] The stability margin of the system under calculated stable conditions is 0.378.

[0142] The above examples illustrate that the method for calculating the power system power angle stability margin proposed in Embodiment 1 of the present invention enhances the applicability of the extended equal area rule and can improve the accuracy of stability judgment.

[0143] Example 2

[0144] Based on the method for calculating the power angle stability margin of a power system proposed in Embodiment 1 of the present invention, Embodiment 2 of the present invention further proposes a system for calculating the power angle stability margin of a power system. Fig.13 A schematic diagram of a calculation system for power angle stability margin of an electric power system proposed in Embodiment 2 of the present invention, the system comprising a data preprocessing module, the data preprocessing module being used to extract first data of a multi-machine system required for power angle stability margin calculation, and to perform standardization processing on the first data; wherein the first time series data comprises power angle, rotation speed, electromagnetic power and mechanical power; the first model parameter comprises generator capacity and inertia;

[0145] It also includes an equivalence determination module, a classification module and a calculation module;

[0146] The determining equivalent module is used to divide the multi-machine system into complementary groups once using the normalized first data; calculate the equivalent parameters of the complementary groups, divide the complementary groups into equivalent single-machine systems after secondary division using the size of the equivalent parameters, and calculate the equivalent parameters of the single-machine system;

[0147] The classification module is used to determine the acceleration power of the single-machine system according to the equivalent electromagnetic power and the equivalent mechanical power in the equivalent parameters of the single-machine system, and classify the swing mode according to the change of the acceleration power;

[0148] The calculation module is used to calculate the stability margin under different swing modes; specifically, it includes: firstly finding the key moment for judging stability under different modes, using the change of acceleration power to judge the stability at the key moment, then respectively calculating the acceleration and deceleration areas under stable and unstable conditions, and finally calculating the stability margin using the acceleration and deceleration areas according to the result of the stability judgment.

[0149] In the data preprocessing module, after extracting the first data of the multi-machine system required for the power angle stability margin calculation, it also includes preprocessing the first data, wherein the preprocessing process includes: sorting the first time series data of each generator of the system according to the time series, each row represents a time point, horizontally connecting the first time series data column matrix of each generator to form a first time series data matrix, each column represents the first time series data of a generator; sorting the first model parameters according to the order of any first time series data of the generator recorded in the first time series data matrix to generate a capacity matrix and an inertia matrix;

[0150] The specific process of normalizing the first data is as follows:

[0151]

[0152]

[0153]

[0154] Among them, p e is the electromagnetic power; S B is the base capacity value; P e is the normalized electromagnetic power matrix; p m is the mechanical power; P m is the normalized mechanical power matrix; m i is the inertia of the i-th machine; M i is the normalized inertia matrix of the i-th machine; S Ni is the capacity of the i-th machine

[0155] In the determination module of equivalent value, the process of dividing the multi-machine system into complementary groups by using the normalized first data includes: selecting the power angle data of all generators within a period of time after the system is disturbed to form the power angle curve of each generator, randomly selecting two power angle curves from all the curves as cluster centers, denoted as C1 and C2; calculating the power angle curves of the remaining generators to the cluster center C k distance;

[0156]

[0157] δ i is the sequential power angle data of the i-th machine; δ im is δ i The mth data of km C k The mth data of the power angle curve; each power angle curve time series data contains n elements in total, and n depends on the time length of the selected power angle curve; the power angle curves of each generator are classified according to the Euclidean distance D, and the kmeans clustering method is used to divide the generator into the first group G1 and the second group G2.

[0158] The process of calculating the equivalent parameters of the complementation group includes:

[0159] The calculation formula of the equivalent rotor angle is:

[0160]

[0161] Among them, δ1 is the equivalent rotor angle of the first group G1; δ2 is the equivalent rotor angle of the second group G2; M i is the normalized inertia matrix of the i-th machine; M j is the normalized inertia matrix of the jth machine; then, the normalized mechanical power matrix and the normalized inertia matrix are used to calculate the equivalent inertia, equivalent mechanical power, equivalent electromagnetic power and equivalent speed of the first group G1 and the second group G2 respectively; the specific process is:

[0162]

[0163] Where M1 is the equivalent inertia of the first group G1; M2 is the equivalent inertia of the second group G2; P m1 is the equivalent mechanical power of the first group G1; P m2 is the equivalent mechanical power of the second group G2; w1 is the equivalent speed of the first group G1; w2 is the equivalent speed of the second group G2; P mi is the mechanical power of the i-th machine; P mj is the mechanical power of the jth machine; P ei is the electromagnetic power of the i-th machine; P ej is the electromagnetic power of the jth machine; w i is the speed of the i-th machine; w j is the speed of the jth machine;

[0164] The first group G1 and the second group G2 are judged according to the size of the equivalent rotor angle, and are divided into the third group S and the fourth group A. The equivalent rotor angle δ of the third group S and the fourth group A is calculated again according to formula (8) and formula (9): S and δ A , equivalent inertia M S and M A , equivalent mechanical power P mS and P mA , equivalent electromagnetic power P eS and P eA , equivalent speed w S and w A .

[0165] The process of further converting the complementary group into a single-machine system by dividing it twice using the size of the equivalent parameter includes: converting the third group S and the fourth group A into a single-machine system, and calculating the equivalent rotor angle of the single-machine system:

[0166]

[0167] where δ E is the equivalent rotor angle of the single-machine system;

[0168] Calculate the equivalent speed, equivalent inertia, equivalent mechanical power and equivalent electromagnetic power of a single machine system;

[0169]

[0170] Among them, w E is the equivalent speed of a single-machine system; M E is the equivalent inertia of the single-machine system; P mE is the equivalent mechanical power of the single-machine system; P eE is the equivalent electromagnetic power of a single-machine system.

[0171] In the classification module, the process of classifying the swing mode according to the changes of equivalent electromagnetic power and equivalent mechanical power in the equivalent parameters of the single-machine system includes:

[0172] The acceleration power P is obtained by subtracting the equivalent electromagnetic power of the single-machine system from the equivalent mechanical power of the single-machine system. a ; is the acceleration power P a Set the zero-crossing threshold at P a When the change exceeds the positive value of the zero-crossing threshold or is less than the negative value of the zero-crossing threshold and the current state is different from the state at the previous moment, the current moment is recorded in P a List of change points middle;

[0173] For the P a List of change points To calculate the length, if If the list length is 0, the swing mode is judged to be the third swing mode: that is, the mechanical power is always greater than the electromagnetic power, there is no deceleration, and there is no deceleration area;

[0174] like The list length is not 0, and P is compared from the moment the fault starts. a With the size of the zero-crossing threshold, once P a If the positive value is greater than the zero-crossing threshold, the swing mode is judged to be the second swing mode: that is, after the fault occurs, the mechanical power is first greater than the electromagnetic power, and the system accelerates first and then decelerates;

[0175] If P a If the value is less than the negative value of the zero-crossing threshold, the swing mode is judged to be the first swing mode: that is, after the fault occurs, the mechanical power is first less than the electromagnetic power, and the system first decelerates, then accelerates, and then decelerates.

[0176] In the calculation module, the process of calculating the stability margin under the first swing mode includes:

[0177] Find the equivalent rotor angle δ for a single-machine system E The first time to reach the farthest point is T δ , and find the equivalent speed w of a single-machine system E At the zero-crossing moment, w E The zero-crossing moment is recorded in w E List of change points T w middle;

[0178] Use the system instability criterion and system stability criterion to determine whether the system is stable; if the system stability criterion is met, the system is stable, otherwise the system is unstable;

[0179] The criterion for system instability is:

[0180] The criterion for system stability is:

[0181] in, P a List of change points The third value in w E (T δ ) is T δ The equivalent speed of the single-machine system at the moment w E The value of

[0182] First, determine the starting and ending points of the acceleration and deceleration area. After determining the starting and ending points of the acceleration and deceleration area, calculate the acceleration and deceleration area by integration.

[0183] If it is unstable, the formula Calculate the stability margin and end the current stability margin calculation program; where A dec is the deceleration area on the P-δ plane, A inc is the acceleration area on the P-δ plane; if instability does not occur, the formula is used Calculate the stability margin; where A dec.pot is the potential deceleration area.

[0184] The process of calculating the stability margin in the second swing mode includes:

[0185] Find the equivalent rotor angle δ for a single-machine system E The first time to reach the farthest point is T δ ;

[0186] Use the system instability criterion and system stability criterion to determine whether the system is stable; if the system stability criterion is met, the system is stable, otherwise the system is unstable;

[0187] The criterion for system instability is:

[0188] The criterion for system stability is:

[0189] in, P a List of change points The second value in

[0190] First, determine the starting and ending points of the acceleration and deceleration area. After determining the starting and ending points of the acceleration and deceleration area, calculate the acceleration and deceleration area by integration.

[0191] If it is unstable, the formula Calculate the stability margin and end the current stability margin calculation program; where A dec is the deceleration area on the P-δ plane, A inc is the acceleration area on the P-δ plane; if instability does not occur, the formula is used Calculate the stability margin; where A dec.pot is the potential deceleration area.

[0192] The process of calculating the stability margin in the third swing mode is as follows: in the third swing mode, the mechanical power is always greater than the electromagnetic power, the speed keeps increasing under the action of the acceleration force, the power angle keeps increasing, and the system is in an extremely unstable state; at this time, the stability margin is -1.

[0193] A calculation system for the power angle stability margin of a power system proposed in Example 2 of the present invention uses aggregated power curves to classify swing modes and provides corresponding stability margin calculation methods for different swing modes. The present invention can adjust the application mode of the EEAC method according to different swing modes, enhance the applicability of the extended equal area law, improve the accuracy of stability judgment, and provide an accurate basis for power system stability control.

[0194] The description of the relevant parts of a calculation system for the power angle stability margin of an electric power system provided in Example 2 of the present application can be found in the detailed description of the corresponding parts of a calculation method for the power angle stability margin of an electric power system provided in Example 1 of the present application, and will not be repeated here.

[0195] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment that includes a series of elements are inherent to the elements. In the absence of more restrictions, the elements limited by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or equipment that includes the elements. In addition, the above-mentioned technical solution provided in the embodiment of the present application is consistent with the corresponding technical solution in the prior art in principle, and the part is not described in detail, so as not to repeat too much.

[0196] Although the above describes the specific implementation of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. For those skilled in the art, other different forms of modifications or deformations can be made on the basis of the above description. It is not necessary and impossible to list all the implementation methods here. On the basis of the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A method for calculating the power angle stability margin of an electric power system, comprising: Extracting first data of a multi-machine system required for calculating a power angle stability margin, and performing standardization processing on the first data; the first data includes first time series data and first model parameters; wherein the first time series data includes power angle, rotation speed, electromagnetic power and mechanical power; the first model parameters include generator capacity and inertia; characterized in that it also includes: Read the simulation or measured data, sort the power angle data of each generator in the system in time series, each row represents a time point, connect the power angle data column matrix of each generator horizontally to form the power angle matrix δ, each column represents the power angle data of a generator; follow the same operation to form the speed matrix w and electromagnetic power matrix p e and the mechanical power matrix p m ; The method comprises the following steps: using the normalized first data to divide the multi-machine system into complementary groups; calculating the equivalent parameters of the complementary groups, using the size of the equivalent parameters to further divide the complementary groups into equivalent single-machine systems, and calculating the equivalent parameters of the single-machine systems; and using the normalized first data to divide the multi-machine system into complementary groups. Select the power angle data of all generators within a period of time after the system is disturbed to form the power angle curve of each generator. Randomly select two power angle curves from all the curves as cluster centers, denoted as C1 and C2; calculate the power angle curves of the remaining generators to the cluster center C k distance; δ i is the sequential power angle data of the i-th machine; δ im is δ i The mth data of km C k The mth data of the power angle curve; each power angle curve time series data contains n elements in total, and n depends on the time length of the selected power angle curve; The power angle curves of each generator are classified according to the Euclidean distance D, and the generators are divided into the first group G1 and the second group G2 by using the kmeans clustering method; The process of calculating the equivalent parameters of the complementation group includes: The calculation formula of the equivalent rotor angle is: Among them, δ1 is the equivalent rotor angle of the first group G1; δ2 is the equivalent rotor angle of the second group G2; M i is the normalized inertia matrix of the i-th machine; M j is the normalized inertia matrix of the jth machine; Then, the normalized mechanical power matrix and the normalized inertia matrix are used to calculate the equivalent inertia, equivalent mechanical power, equivalent electromagnetic power and equivalent speed of the first group G1 and the second group G2 respectively; the specific process is: Where M1 is the equivalent inertia of the first group G1; M2 is the equivalent inertia of the second group G2; P m1 is the equivalent mechanical power of the first group G1; P m2 is the equivalent mechanical power of the second group G2; w1 is the equivalent speed of the first group G1; w2 is the equivalent speed of the second group G2; P mi is the mechanical power of the i-th machine; P mj is the mechanical power of the jth machine; P ei is the electromagnetic power of the i-th machine; P ej is the electromagnetic power of the jth machine; w i is the speed of the i-th machine; w j is the speed of the jth machine; P e1 is the equivalent electromagnetic power of the first group G1; P e2 is the equivalent electromagnetic power of the second group G2; The first group G1 and the second group G2 are judged according to the size of the equivalent rotor angle, and are divided into the third group S and the fourth group A. The equivalent rotor angle δ of the third group S and the fourth group A is calculated again according to formula (8) and formula (9): S and δ A , equivalent inertia M S and M A , equivalent mechanical power P mS and P mA , equivalent electromagnetic power P eS and P eA , equivalent speed w S and w A ; The acceleration power of the single-machine system is determined according to the equivalent electromagnetic power and the equivalent mechanical power in the equivalent parameters of the single-machine system, and the swing mode is classified according to the change of the acceleration power; the process of determining the acceleration power of the single-machine system according to the equivalent electromagnetic power and the equivalent mechanical power in the equivalent parameters of the single-machine system, and classifying the swing mode according to the change of the acceleration power includes: The acceleration power P is obtained by subtracting the equivalent electromagnetic power of the single-machine system from the equivalent mechanical power of the single-machine system. a ; is the acceleration power P a Set the zero-crossing threshold at P a When the change exceeds the positive value of the zero-crossing threshold or is less than the negative value of the zero-crossing threshold and the current state is different from the state at the previous moment, the current moment is recorded in P a List of change points middle; For the P a List of change points To calculate the length, if If the list length is 0, the swing mode is judged to be the third swing mode: that is, the mechanical power is always greater than the electromagnetic power, there is no deceleration, and there is no deceleration area; like The list length is not 0, and P is compared from the moment the fault starts. a With the size of the zero-crossing threshold, once P a If the positive value is greater than the zero-crossing threshold, the swing mode is judged to be the second swing mode: that is, after the fault occurs, the mechanical power is first greater than the electromagnetic power, and the system accelerates first and then decelerates; If P a If the negative value is less than the zero-crossing threshold, the swing mode is judged to be the first swing mode: that is, after the fault occurs, the mechanical power is first less than the electromagnetic power, and the system first decelerates, then accelerates, and then decelerates; Calculate the stability margin under different swing modes; specifically, first find the key moments for judging stability under different modes, use the change of acceleration power to judge the stability at the key moments, then calculate the acceleration and deceleration areas under stable and unstable conditions respectively, and finally calculate the stability margin using the acceleration and deceleration areas according to the results of the stability judgment; The process of calculating the stability margin for the first sway mode includes: Find the equivalent rotor angle δ for a single-machine system E The first time to reach the farthest point is T δ , and find the equivalent speed w of a single-machine system E At the zero-crossing moment, w E The zero-crossing moment is recorded in w E List of change points T w middle; Use the system instability criterion and system stability criterion to determine whether the system is stable; if the system stability criterion is met, the system is stable, otherwise the system is unstable; The criterion for system instability is: T δ >T Pa [2];(12) The criterion for system stability is: in, P a List of change points The third value in w E (T δ ) is T δ The equivalent speed of the single-machine system at the moment w E The value of Determine the starting and ending points of the acceleration and deceleration areas in stable and unstable conditions respectively, and then calculate the acceleration and deceleration areas by integration; If it is unstable, the formula Calculate the stability margin and end the current stability margin calculation program; where A dec is the deceleration area on the P-δ plane, A inc is the acceleration area on the P-δ plane; if instability does not occur, the formula is used Calculate the stability margin; where A dec.pot is the potential deceleration area; The process of calculating the stability margin in the second swing mode includes: Find the equivalent rotor angle δ for a single-machine system E The first time to reach the farthest point is T δ ; Use the system instability criterion and system stability criterion to determine whether the system is stable; if the system stability criterion is met, the system is stable, otherwise the system is unstable; The criterion for system instability is: T δ >T Pa [1](14) The criterion for system stability is: in, P a List of change points The second value in Determine the starting and ending points of the acceleration and deceleration areas in stable and unstable conditions respectively, and then calculate the acceleration and deceleration areas by integration; If it is unstable, the formula Calculate the stability margin and end the current stability margin calculation program; where A dec is the deceleration area on the P-δ plane, A inc is the acceleration area on the P-δ plane; if instability does not occur, the formula is used Calculate the stability margin; where A dec.pot is the potential deceleration area; The process of calculating the stability margin in the third swing mode is as follows: in the third swing mode, the mechanical power is always greater than the electromagnetic power, the speed keeps increasing under the action of the acceleration force, the power angle keeps increasing, and the system is in an extremely unstable state; at this time, the stability margin is -1.

2. The method for calculating the power system power angle stability margin according to claim 1, characterized in that: The process of extracting the first data of the multi-machine system required for calculating the power angle stability margin and performing standardization processing on the first data includes: Sort the first time series data of each generator in the system in time series, with each row representing a time point, and horizontally connect the first time series data column matrix of each generator to form a first time series data matrix, with each column representing the first time series data of a generator; sort the first model parameters according to the order of any first time series data of the generator recorded in the first time series data matrix to generate a capacity matrix and an inertia matrix; The formula for normalizing the first data is: Among them, p e is the electromagnetic power; S B is the base capacity value; P e is the normalized electromagnetic power matrix; p m is the mechanical power; P m is the normalized mechanical power matrix; m i is the inertia of the i-th machine; M i is the normalized inertia matrix of the i-th machine; S Ni is the capacity of the i-th machine.

3. The method for calculating the power system power angle stability margin according to claim 1, characterized in that: The process of further converting the complementary group into a single-machine system by dividing it into two parts using the size of the equivalent parameter comprises: converting the third group S and the fourth group A into a single-machine system, and calculating the equivalent rotor angle of the single-machine system: where δ E is the equivalent rotor angle of the single-machine system; Calculate the equivalent speed, equivalent inertia, equivalent mechanical power and equivalent electromagnetic power of a single machine system; Among them, w E is the equivalent speed of a single-machine system; M E is the equivalent inertia of the single-machine system; P mE is the equivalent mechanical power of the single-machine system; P eE is the equivalent electromagnetic power of a single-machine system.

4. A calculation system for power system power angle stability margin, used to execute a calculation method for power system power angle stability margin according to any one of claims 1 to 3, comprising a data preprocessing module, the data preprocessing module is used to extract first data of a multi-machine system required for power angle stability margin calculation, and perform standardization processing on the first data; the first data includes first time series data and first model parameters; wherein, The first time series data includes power angle, rotation speed, electromagnetic power and mechanical power; the first model parameters include generator capacity and inertia; the model is characterized in that it also includes an equivalent value determination module, a classification module and a calculation module; The determining equivalent module is used to divide the multi-machine system into complementary groups once using the normalized first data; calculate the equivalent parameters of the complementary groups, divide the complementary groups into equivalent single-machine systems after secondary division using the size of the equivalent parameters, and calculate the equivalent parameters of the single-machine system; The classification module is used to determine the acceleration power of the single-machine system according to the equivalent electromagnetic power and the equivalent mechanical power in the equivalent parameters of the single-machine system, and classify the swing mode according to the change of the acceleration power; The calculation module is used to calculate the stability margin under different swing modes; specifically, it includes: firstly finding the key moment for judging stability under different modes, using the change of acceleration power to judge the stability at the key moment, then respectively calculating the acceleration and deceleration areas under stable and unstable conditions, and finally calculating the stability margin using the acceleration and deceleration areas according to the result of the stability judgment.

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