A power grid transient stability quantitative evaluation method based on voltage phasor trajectory fitting

Abstract

This invention discloses a method for quantitatively assessing the transient stability of a power grid based on voltage phasor trajectory fitting, comprising: acquiring real-time measurement information of each generator in the power grid from a wide-area power grid measurement system; calculating the rate of change of angle values ​​of each generator at two different times, identifying the generator with the largest rate of change as the stable unit and the generator with the smallest rate of change as the unstable unit; calculating the equivalent mechanical power and equivalent electromagnetic power of the unstable unit based on the real-time measurement information of the stable unit and the unstable unit; calculating the transient stability assessment index of the power grid based on the equivalent mechanical power and equivalent electromagnetic power, and determining the stable state of the power grid based on the transient stability assessment index.

Description

Technical Field

[0001] This invention relates to the field of power grid steady-state technology, and more specifically, to a quantitative assessment method for power grid transient stability based on voltage phasor trajectory fitting. Background Technology

[0002] With the continuous expansion of AC / DC hybrid power system integration, the increasing proportion of renewable energy grid connection, and the growing trend of power electronics, the development pattern and operating conditions of the power grid exhibit greater complexity, variability, and randomness, posing significant challenges to power system stability analysis and control. Transient stability analysis, as a crucial component of power system security and stability analysis, will also face significant challenges under these new power grid development trends.

[0003] Traditional transient stability assessment methods mostly employ an "offline simulation + online matching" model. This model is no longer sufficient to meet the current changes in the power grid structure. Therefore, there is an urgent need for a more accurate, faster, and less model-dependent online transient stability assessment method. From the perspective of power grid operating state trajectory and information-driven analysis, in-depth exploration of the dynamic process evolution mechanism of the power grid and transient stability assessment methods has gradually become a research hotspot in the field of large power grid online security defense due to its good timeliness and applicability. Currently, methods for spatiotemporal trajectory analysis include: ① using extended phase trajectories composed of generalized angular velocity and angular acceleration; ② analyzing transient stability through trajectory concavity and convexity, which is a derivative method; ③ obtaining system stability through trajectory integration by analyzing voltage and power angle; ④ analyzing structural distribution based on differential equation theory by studying the saddle point decomposition and infinity morphology of fault points, and exploring transient stability boundaries by combining simulation theory; ⑤ exploring system stability by obtaining the potential energy difference from the power angle curve integral starting from the trajectory potential energy surface. The methods described above offer valuable insights into trajectory characterization, but in practice, data often contains significant noise, and the use of differentiation and integration can have a substantial impact on sharp curve changes. Therefore, from an engineering perspective, these studies cannot effectively differentiate between specific situations and lack broad applicability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a quantitative evaluation method for power grid transient stability based on voltage phasor trajectory fitting.

[0005] According to one aspect of the present invention, a method for quantitative evaluation of power grid transient stability based on voltage phasor trajectory fitting is provided, comprising:

[0006] Real-time measurement information of each generator in the power grid is obtained from the power grid wide-area measurement system.

[0007] Calculate the rate of change of angle values ​​for each generator at two different times. Determine the generator with the largest rate of change as the stable generator and the generator with the smallest rate of change as the unstable generator.

[0008] Based on the real-time measurement information of the stable unit and the unstable unit, calculate the equivalent mechanical power and equivalent electromagnetic power of the unstable unit;

[0009] The transient stability assessment index of the power grid is calculated based on the equivalent mechanical power and equivalent electromagnetic power, and the stable state of the power grid is determined based on the transient stability assessment index.

[0010] Optionally, the operation of calculating the transient stability assessment index of the power grid based on the equivalent mechanical power and the equivalent electromagnetic power includes:

[0011] Calculate the virtual stable equilibrium point of the unstable unit based on the equivalent mechanical power and equivalent electromagnetic power;

[0012] Construct the voltage vector trajectory of the unstable unit pair, and calculate the real and imaginary parts of the voltage vector trajectory;

[0013] Calculate the phase trajectory arc length under the ultimate stability state of the unstable unit based on the voltage vector trajectory and the virtual stable equilibrium point;

[0014] Calculate the arc length of the actual motion trajectory of the unstable unit based on the voltage vector trajectory, the real part of the voltage vector trajectory, and the imaginary part of the voltage vector trajectory.

[0015] The transient stability assessment index of the power grid is calculated based on the phase trajectory arc length and the actual motion trajectory arc length.

[0016] Optionally, the operation of determining the steady state of the power grid based on transient stability assessment indicators includes:

[0017] When 0 < ρ < 1, the power grid is determined to be in a transient stable state;

[0018] When 1 = ρ, the power grid is determined to be in a critical transient stable state;

[0019] When 1 < ρ, the power grid is determined to be in a transient unstable state, where

[0020] ρ is the transient stability evaluation index.

[0021] Optionally, it also includes:

[0022] Based on the phase trajectory arc length and the actual motion trajectory arc length, the stability margin or instability degree of the power grid is calculated, whereby...

[0023]

[0024] When the power grid is in a transiently stable state, 0 < ψ < 1, where ψ represents the stability margin; the larger the value, the more stable the system.

[0025] When the power grid is in a state of transient instability, 0 < ψ, where ψ represents the degree of instability. The larger the value, the more severe the system instability.

[0026] According to another aspect of the present invention, a power grid transient stability quantitative evaluation system based on voltage phasor trajectory fitting is provided, comprising:

[0027] The acquisition module is used to acquire real-time measurement information of each generator in the power grid from the power grid wide-area measurement system.

[0028] The determination module is used to calculate the rate of change of the angle value of each generator at two different times, and to determine the generator with the largest rate of change among all generators as the stable unit and the generator with the smallest rate of change as the unstable unit.

[0029] The first calculation module is used to calculate the equivalent mechanical power and equivalent electromagnetic power of the unstable unit based on the real-time measurement information of the stable unit and the real-time measurement information of the unstable unit.

[0030] The second calculation module is used to calculate the transient stability assessment index of the power grid based on the equivalent mechanical power and the equivalent electromagnetic power, and to determine the stable state of the power grid based on the transient stability assessment index.

[0031] According to another aspect of the present invention, a computer-readable storage medium is provided, the storage medium storing a computer program for performing the methods described in any of the above aspects of the present invention.

[0032] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the method described in any of the preceding aspects of the present invention.

[0033] Therefore, based on the principle of equal area, this application mathematically characterizes the voltage phasor trajectory curve in a relative power angle coordinate system by constructing unit pairs. Then, by analyzing the geometric characteristics of the voltage phasor trajectory, it completes a quantitative assessment of power grid transient stability based on phase trajectory analysis. This method can be fitted and calculated using a small amount of real-time voltage measurement data, resulting in fast calculations and accurate results. It meets the timeliness and applicability requirements of new power systems for power grid transient stability analysis and effectively supplements existing transient stability analysis theories. Furthermore, it constructs generator voltage phase trajectories in fault conditions using a trajectory fitting method based on the alternating direction multiplier method, achieving high fitting accuracy with limited data. This enables a quantitative assessment of power grid transient stability, with fast calculations and accurate results, meeting the timeliness and applicability requirements of power grid transient stability analysis. Attached Figure Description

[0034] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0035] Figure 1 This is a flowchart illustrating a quantitative evaluation method for power grid transient stability based on voltage phasor trajectory fitting, provided by an exemplary embodiment of the present invention.

[0036] Figure 2 This is another flowchart illustrating a quantitative evaluation method for power grid transient stability based on voltage phasor trajectory fitting provided in an exemplary embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram of a unit pair formed by a stable unit (or reference unit) and an unstable unit, provided in an exemplary embodiment of the present invention.

[0038] Figure 4a This is a schematic diagram of a voltage vector trajectory provided in an exemplary embodiment of the present invention;

[0039] Figure 4b This is a schematic diagram of voltage amplitude versus time curves provided in an exemplary embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the limiting arc length and the actual motion arc length provided in an exemplary embodiment of the present invention;

[0041] Figure 6 This is a diagram of an IEEE 39-node system provided in an exemplary embodiment of the present invention;

[0042] Figure 7a This is a schematic diagram of the generator power angle curve of a system provided in an exemplary embodiment of the present invention;

[0043] Figure 7b This is a schematic diagram of the evaluation index curve provided by an exemplary embodiment of the present invention;

[0044] Figure 8a This is a phase trajectory fitting accuracy diagram provided by an exemplary embodiment of the present invention;

[0045] Figure 8b This is a comparison chart of fitting times provided by an exemplary embodiment of the present invention;

[0046] Figure 9 This is a schematic diagram of the structure of a power grid transient stability quantitative evaluation system based on voltage phasor trajectory fitting provided in an exemplary embodiment of the present invention;

[0047] Figure 10 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. Detailed Implementation

[0048] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is obvious that the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0049] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0050] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0051] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0052] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0053] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0054] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0055] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0056] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0057] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0058] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0059] The embodiments of this invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate together with a wide range of other general-purpose or special-purpose computing system environments or configurations. Well-known examples of terminal devices, computing systems, environments, and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, and servers include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments including any of the above systems, etc.

[0060] Electronic devices such as terminal devices, computer systems, and servers can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Typically, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in distributed cloud computing environments, where tasks are executed by remote processing devices linked through communication networks. In distributed cloud computing environments, program modules can reside on local or remote computing system storage media, including storage devices.

[0061] Exemplary methods

[0062] Figure 1 This is a flowchart illustrating a quantitative evaluation method for power grid transient stability based on voltage phasor trajectory fitting, provided by an exemplary embodiment of the present invention. This embodiment can be applied to electronic devices, such as… Figure 1 As shown, the power grid transient stability quantitative evaluation method 100 based on voltage phasor trajectory fitting includes the following steps:

[0063] Step 101: Obtain real-time measurement information of each generator in the power grid from the power grid wide-area measurement system;

[0064] Step 102: Calculate the rate of change of angle values ​​for each generator at two different times. Determine the generator with the largest rate of change as the stable generator and the generator with the smallest rate of change as the unstable generator.

[0065] Step 103: Calculate the equivalent mechanical power and equivalent electromagnetic power of the unstable unit based on the real-time measurement information of the stable unit and the real-time measurement information of the unstable unit.

[0066] Step 104: Calculate the transient stability assessment index of the power grid based on the equivalent mechanical power and equivalent electromagnetic power, and determine the stable state of the power grid based on the transient stability assessment index.

[0067] Optionally, the operation of calculating the transient stability assessment index of the power grid based on the equivalent mechanical power and the equivalent electromagnetic power includes:

[0068] Calculate the virtual stable equilibrium point of the unstable unit based on the equivalent mechanical power and equivalent electromagnetic power;

[0069] Construct the voltage vector trajectory of the unstable unit pair, and calculate the real and imaginary parts of the voltage vector trajectory;

[0070] Calculate the phase trajectory arc length under the ultimate stability state of the unstable unit based on the voltage vector trajectory and the virtual stable equilibrium point;

[0071] Calculate the arc length of the actual motion trajectory of the unstable unit based on the voltage vector trajectory, the real part of the voltage vector trajectory, and the imaginary part of the voltage vector trajectory.

[0072] The transient stability assessment index of the power grid is calculated based on the phase trajectory arc length and the actual motion trajectory arc length.

[0073] Optionally, the operation of determining the steady state of the power grid based on transient stability assessment indicators includes:

[0074] When 0 < ρ < 1, the power grid is determined to be in a transient stable state;

[0075] When 1 = ρ, the power grid is determined to be in a critical transient stable state;

[0076] When 1 < ρ, the power grid is determined to be in a transient unstable state, where

[0077] ρ is the transient stability evaluation index.

[0078] Optionally, it also includes:

[0079] Based on the phase trajectory arc length and the actual motion trajectory arc length, the stability margin or instability degree of the power grid is calculated, whereby...

[0080]

[0081] When the power grid is in a transiently stable state, 0 < ψ < 1, where ψ represents the stability margin; the larger the value, the more stable the system.

[0082] When the power grid is in a state of transient instability, 0 < ψ, where ψ represents the degree of instability. The larger the value, the more severe the system instability.

[0083] Specifically, this invention proposes a quantitative assessment method for power grid transient stability based on voltage phasor trajectory fitting. This method can convert changes in angle of attack into changes in voltage dynamic phasor trajectory, and then judge the transient stability state of the power grid through the proposed index. It has good robustness and strong applicability.

[0084] like Figure 2 As shown, the specific steps are as follows:

[0085] Step (1) Obtain the power angle δ of each generator in the power grid in real time from the wide area measurement system (WAMS). i angular velocity ω i Terminal voltage U i ∠θ i Mechanical power P Mi Electromagnetic power P Ei Real-time measurement information, etc.

[0086] Step (2) Calculate the rate of change η of the angular velocity values ​​of each generator at the two time points before and after using formula (1). i Compare the angular velocity change rates of all generators in the system. The two generators with the largest and smallest angular velocity change rates are defined as the pair of generators with the most severe relative disturbance (the reference or stable generator is defined as generator S, and the unstable generator is defined as generator A, such as...). Figure 3 As shown):

[0087]

[0088] Step (3) calculates the equivalent mechanical power P of the unit pair obtained in step (2) using formulas (2) and (3) respectively. Meq and equivalent electromagnetic power P Eeq :

[0089]

[0090]

[0091] P EM E and E are the equivalent parameters after the formula is simplified, and can be calculated by formulas (4) and (5).

[0092]

[0093]

[0094] Where G and H are obtained from equations (6) and (7), respectively:

[0095]

[0096]

[0097] Among them, M S and M A The inertia of unit S and unit A are respectively, P MS and P MA The mechanical power of unit S and unit A are respectively, P ES and P EA The electromagnetic power of unit S and unit A are respectively, δ SA The power angle δ of unit S S The power angle δ of unit A A The difference, E S and E A θ represents the virtual internal electromotive force of unit S and unit A, respectively. S and θ A These are the phase angles of the grid-connected bus voltages of unit S and unit A, respectively, U S and U A X represents the amplitude of the grid-connected bus voltage of unit S and unit A, respectively. S and X A These are the internal reactances of unit S and unit A to their respective grid-connected busbars.

[0098] Step (4) Calculate the virtual stable equilibrium point δ of the equivalent unit pair using formula (8). Seq :

[0099]

[0100] Step (5) calculates the real part X of the voltage phasor trajectory of unstable unit A using formulas (9) and (10). A And the imaginary part Y A E A It is the voltage amplitude of unstable unit A, δ A The voltage phase angle of unstable unit A:

[0101] X A =E A cosδ A (9)

[0102] Y A =E A sinδA (10)

[0103] Step (6) Construct the voltage phasor trajectory model of unit A. Using the Alternating Direction Method of Multipliers (ADMM), combined with the decomposability of the dual rising method and the easy convergence of the augmented Lagrange multiplier method, the standard trajectory equations are established as follows:

[0104]

[0105] In the above formula, u and v are the coordinates of the model center point, where r a ,r b The lengths of the major and minor semi-axis are given. Further, based on the voltage and power angle information of unit A obtained from PMU and other measurement data, the training value X of the voltage phasor trajectory information is obtained using formulas (9) and (10). A and Y A The trajectory parameters are substituted into the equation, and the method for obtaining the trajectory is as follows:

[0106] The standard equation is transformed into the general equation as follows:

[0107] Ax 2 +By 2 +Cx+Dy+E=0 (13)

[0108] in,

[0109] Multiply both sides of the general equation The following equations are obtained.

[0110] ax 2 +by 2 +cx+dy+e=0 (14)

[0111] in:

[0112] a = 1, b = r a 2 / r b 2 c = -2u, d = -2r a 2 v / r b 2 e = u 2 +r a 2 v 2 / r b 2 -r a 2 (15)

[0113] The fitting values ​​of the initial A, B, C, D, E are reduced to b, c, d, e, which speeds up the fitting process. Based on historical data, the ADMM algorithm is used to iteratively revise the parameters in equation (15), thereby obtaining two unconstrained optimization problems. Solving these problems allows for fitting the voltage trajectory, obtaining the parameters in the fitted equation (15), and thus obtaining the voltage trajectory equation (14).

[0114] Step (7) Based on the evolution law of transient voltage phasor trajectory, and using the sudden change in trajectory radius as the identification criterion for method initiation, further determine the fault occurrence time T1 and the fault clearing time T2 (e.g., Figure 2 (As shown). The trajectory radius has the following characteristics:

[0115] 1) When a system fault occurs, the system voltage level drops, the generator terminal voltage will drop, the trajectory radius will suddenly become smaller, and the system is at the moment of fault occurrence.

[0116] 2) Conversely, when the trajectory radius suddenly increases, it indicates that the fault has been cleared and the system is in the fault clearing moment.

[0117] Therefore, the moment when the system fails is defined as T1, at which point the voltage phasor trajectory radius will drop rapidly, due to U A Reduce to U B1 During the fault, the voltage amplitude does not change significantly, as shown in Figure 4(b) from B1 to B2, and the trajectory radius does not change much. The fault end time is defined as T2, at which point the trajectory radius suddenly increases but does not return to its initial size, as shown in Figure 4(a) from B2 to C. The trajectory reversal time is defined as T3, at which point the trajectory radius does not change much.

[0118] Step (8) The formula for calculating the arc length between any two points on the voltage phasor trajectory of unstable unit A:

[0119]

[0120]

[0121] Where X1 and X2 are the real parts of point 1 and point 2, Y1 and Y2 are the imaginary parts of point 1 and point 2, and the solution method for the real and imaginary parts is referred to step (5), and r is the inner radius of the voltage phasor trajectory model obtained in step (6).

[0122] Therefore, as Figure 5 As shown, the arc length of the phase trajectory in the ultimate stable state can be obtained as:

[0123]

[0124] The actual arc length of the motion trajectory of the unstable unit A is:

[0125]

[0126] Where θ2 is the difference between the phase angle at the time of trajectory reversal and the phase angle at the time of fault termination.

[0127] Step (9) Calculate the transient stability assessment index ρ using formula (17).

[0128]

[0129] When 0 < ρ < 1, the power grid is in a transient stable state;

[0130] When 1 = ρ, the power grid is in a critical transient stable state;

[0131] When 1 < ρ, the power grid is in a transient unstable state.

[0132] The stability margin or degree of instability of the unstable unit A can be further calculated using formula (18).

[0133]

[0134] When the power grid is in a steady state, 0 < ψ < 1, where ψ represents the stability margin. The larger the value, the more stable the system.

[0135] When the power grid is in an unstable state, 0 < ψ, where ψ represents the degree of instability. The larger the value, the more severe the system instability.

[0136] In addition, such as Figure 6 As shown, in order to more clearly illustrate the optimal effect of implementing the present invention, the technical solution of the present invention will be further described in detail with reference to the IEEE-39 node system example.

[0137] The system uses a fourth-order model for the generators and a constant power model for the loads. The system includes 10 generators, 46 lines, and 19 loads. The simulation step size is 0.02s, the fault occurrence time is 0s, the fault location is set at node 15, the fault type is a three-phase short circuit fault, and the fault end time is 0.44s.

[0138] (2) Validation of indicator effectiveness

[0139] As shown in Figure 7(a) of the system generator power angle curve, the system is in a transient stable state under this fault condition. Through steps 1 and 2 of the method proposed in this patent, generator 30 and generator 36 are selected as equivalent unit pairs. Then, through steps 3-9 of the method proposed in this patent, the transient stability evaluation index and stability margin of generator 36 under this fault scenario are calculated. The calculated index curve results are shown in Figure 7(b).

[0140] As shown in Figure 7(b), after the fault is cleared in 0.4s, the calculated transient evaluation index of the system is approximately 0.6. According to the stability criteria provided in step 9, the system is in a transient stable state. At the same time, the transient stability margin of the system is approximately 40%, that is, after the system fault, the system is in a stable state with a stability margin of approximately 40%.

[0141] Therefore, the transient assessment method proposed in this patent can effectively obtain quantitative assessment results of system transient stability, guiding dispatchers to conduct transient stability analysis and handling.

[0142] (3) Verification of method accuracy and timeliness

[0143] To verify the accuracy and timeliness of the fitting method proposed in this patent, comparative tests were conducted using measured data, the least squares method, and the fitting method proposed in this patent.

[0144] As shown in Figure 8(a), the black line represents the least squares fitting, the hollow circle represents the actual data, and the dashed line represents the fitting method used in this paper. Generator 36 and a stable generator group were selected for fitting analysis. The fitting results show that the method proposed in this patent is closer to the actual curve than the least squares method, indicating that its fitting accuracy is relatively high.

[0145] As shown in Figure 8(b), nine generators were selected for fitting speed tests. By comparing the method proposed in this patent with the least squares method, it can be seen that the fitting method proposed in this patent consumes less time than the least squares method and is about 50% faster than the traditional least squares method, which saves nearly half the time and has better timeliness.

[0146] This invention provides a method for fitting the voltage phasor trajectory of a power grid and constructing transient stability prediction indices based on the alternating direction multiplier method. It has the following advantages: 1. For a single-machine infinite bus system model, by combining the voltage trajectory with energy conversion relationships, the differences between the generator when it loses stability and when it remains stable are obtained; the evolution law of the voltage trajectory under relative power angle is deduced from a geometric perspective. Its physical characteristics are obvious and possess strong physical properties. 2. A generator voltage phase trajectory under fault conditions is constructed using a trajectory fitting method based on the alternating direction multiplier method, and fitting can be performed with a small amount of data, achieving high fitting accuracy. 3. This method has been verified through the IEEE 39-bus system and a provincial power grid system, demonstrating its good applicability.

[0147] (1) The method provided by this invention is mainly applied to the field of online safety analysis of large power grids. It can be based entirely on real-time online measurement data of generators. Through the transient assessment method proposed in this patent, the quantitative assessment of power grid transient stability can be realized. The calculation is fast and the results are accurate, meeting the timeliness and applicability requirements of power grid transient stability analysis.

[0148] (2) The method provided by the present invention, which involves the voltage phasor trajectory alternating direction multiplier fitting technique, can effectively avoid the problem of trajectory fitting difficulties caused by abnormalities such as missing or incorrect measured data, and provides a simple, efficient and reliable trajectory fitting method.

[0149] (3) The method provided by this invention is essentially an analysis method based on the information-driven mode, but its voltage phase trajectory motion characteristics have the same motion characteristics as the generator equal area law. That is, the method proposed in this patent is essentially based on the energy function, and has both speed and interpretability, which can effectively support the construction of the future power grid online security defense system.

[0150] Therefore, this application, focusing on a single-machine infinite bus system model, combines the voltage trajectory with energy conversion relationships to obtain the similarities and differences between the generator when it loses stability and when it remains stable. From a geometric perspective, it derives the voltage trajectory evolution law under relative power angles, revealing clear physical characteristics and strong physical properties. A trajectory fitting method based on the alternating direction multiplier method is used to construct the generator voltage phase trajectory during a fault. This method can fit the data with high accuracy using limited data, enabling quantitative assessment of grid transient stability. The calculation is fast and the results are accurate, meeting the timeliness and applicability requirements of grid transient stability analysis.

[0151] Exemplary System

[0152] Figure 9 This is a schematic diagram of the structure of a power grid transient stability quantitative evaluation system based on voltage phasor trajectory fitting, provided in an exemplary embodiment of the present invention. Figure 9 As shown, system 900 includes:

[0153] The acquisition module 910 is used to acquire real-time measurement information of each generator in the power grid from the power grid wide-area measurement system.

[0154] The module 920 is used to calculate the rate of change of the angle value of each generator at two different times, and to determine the generator with the largest rate of change among all generators as the stable unit and the generator with the smallest rate of change as the unstable unit.

[0155] The first calculation module 930 is used to calculate the equivalent mechanical power and equivalent electromagnetic power of the unstable unit based on the real-time measurement information of the stable unit and the real-time measurement information of the unstable unit.

[0156] The second calculation module 940 is used to calculate the transient stability assessment index of the power grid based on the equivalent mechanical power and the equivalent electromagnetic power, and to determine the stable state of the power grid based on the transient stability assessment index.

[0157] Optionally, the second computing module 940 includes:

[0158] The first calculation submodule is used to calculate the virtual stable equilibrium point of the unstable unit based on the equivalent mechanical power and the equivalent electromagnetic power.

[0159] The second calculation submodule is used to construct the voltage vector trajectory of the unstable unit pair and calculate the real and imaginary parts of the voltage vector trajectory.

[0160] The third calculation submodule is used to calculate the phase trajectory arc length of the unstable unit under the ultimate stability state based on the voltage vector trajectory and the virtual stable equilibrium point.

[0161] The fourth calculation submodule is used to calculate the arc length of the actual motion trajectory of the unstable unit based on the voltage vector trajectory, the real part of the voltage vector trajectory, and the imaginary part of the voltage vector trajectory.

[0162] The fifth calculation submodule is used to calculate the transient stability assessment index of the power grid based on the phase trajectory arc length and the actual motion trajectory arc length.

[0163] Optionally, the second computing module 940 includes:

[0164] The first determination submodule is used to determine that the power grid is in a transient stable state when 0 < ρ < 1.

[0165] The second determination submodule is used to determine that the power grid is in a critical transient stable state when 1 = ρ.

[0166] The third determination submodule is used to determine whether the power grid is in a transient unstable state when 1 < ρ.

[0167] ρ is the transient stability evaluation index.

[0168] Optionally, system 900 also includes:

[0169] The third calculation module is used to calculate the stability margin or instability degree of the power grid based on the phase trajectory arc length and the actual motion trajectory arc length.

[0170]

[0171] When the power grid is in a transiently stable state, 0 < ψ < 1, where ψ represents the stability margin; the larger the value, the more stable the system.

[0172] When the power grid is in a state of transient instability, 0 < ψ, where ψ represents the degree of instability. The larger the value, the more severe the system instability.

[0173] Exemplary electronic devices

[0174] Figure 10 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. For example... Figure 10As shown, the electronic device 100 includes one or more processors 101 and memory 102.

[0175] The processor 101 may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0176] The memory 102 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 101 may execute the program instructions to implement the methods of the software programs of the various embodiments of the present invention described above, and / or other desired functions. In one example, the electronic device may also include an input device 103 and an output device 104, these components being interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0177] In addition, the input device 103 may also include, for example, a keyboard, a mouse, etc.

[0178] The output device 104 can output various information to the outside. The output device 104 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0179] Of course, for the sake of simplicity, Figure 10 Only some of the components of the electronic device relevant to the present invention are shown, omitting components such as buses, input / output interfaces, etc. In addition, the electronic device may include any other suitable components depending on the specific application.

[0180] Exemplary computer program products and computer-readable storage media

[0181] In addition to the methods and apparatus described above, embodiments of the present invention may also be computer program products, which include computer program instructions that, when executed by a processor, cause the processor to perform the steps of the methods according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0182] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of the present invention. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0183] Furthermore, embodiments of the present invention may also be computer-readable storage media storing computer program instructions thereon, which, when executed by a processor, cause the processor to perform the steps of the methods for information mining of historical change records according to various embodiments of the present invention as described in the "Exemplary Methods" section above.

[0184] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or any combination thereof. More specific examples (a non-exhaustive list) of readable storage media include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof.

[0185] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0186] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0187] The block diagrams of devices, systems, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, systems, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0188] The methods and systems of the present invention may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of the present invention are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, the present invention may also be implemented as a program recorded on a recording medium, the program comprising machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers recording media storing programs for performing the methods according to the present invention.

[0189] It should also be noted that in the systems, apparatus, and methods of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered equivalents of the present invention. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0190] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A quantitative assessment method for power grid transient stability based on voltage phasor trajectory fitting, characterized in that, include: Real-time measurement information of each generator in the power grid is obtained from the power grid wide-area measurement system. Calculate the rate of change of the angle value of each generator at two different times, and determine the generator with the largest rate of change as the stable unit and the generator with the smallest rate of change as the unstable unit. Based on the real-time measurement information of the stable unit and the real-time measurement information of the unstable unit, calculate the equivalent mechanical power and equivalent electromagnetic power of the unstable unit; The transient stability assessment index of the power grid is calculated based on the equivalent mechanical power and the equivalent electromagnetic power, and the stable state of the power grid is determined based on the transient stability assessment index. The operation of calculating the transient stability assessment index of the power grid based on the equivalent mechanical power and the equivalent electromagnetic power includes: Calculate the virtual stable equilibrium point of the unstable unit based on the equivalent mechanical power and the equivalent electromagnetic power; Construct the voltage vector trajectory of the unstable generator pair, and calculate the real and imaginary parts of the voltage vector trajectory; Based on the voltage vector trajectory and the virtual stable equilibrium point, calculate the phase trajectory arc length under the ultimate stability state of the unstable unit. l 1; Based on the voltage vector trajectory, its real part, and its imaginary part, calculate the arc length of the actual motion trajectory of the unstable generator unit. l 2; According to the phase trajectory arc length l 1 and the actual arc length of the motion trajectory l 2. Calculate the transient stability assessment index of the power grid. , .

2. The method according to claim 1, characterized in that, The operation of determining the stable state of the power grid based on the transient stability assessment index includes: when When this occurs, the power grid is determined to be in a transient stable state; when When the power grid is in a critical transient stable state, it is determined that the power grid is in a critical transient stable state. when When the power grid is in a transient unstable state, it is determined that the power grid is in a transient unstable state. It serves as a transient stability assessment indicator.

3. The method according to claim 2, characterized in that, Also includes: According to the phase trajectory arc length l 1 and the actual arc length of the motion trajectory l 2. Calculate the stability margin or instability degree of the power grid, wherein... When the power grid is in a transient stable state , This represents the stability margin; the larger the value, the more stable the system. When the power grid is in a state of transient instability , This indicates the degree of instability; the larger the value, the more severe the system instability.

4. A power grid transient stability quantitative evaluation system based on voltage phasor trajectory fitting, used to implement the method described in any one of claims 1-3, characterized in that, include: The acquisition module is used to acquire real-time measurement information of each generator in the power grid from the power grid wide-area measurement system. The determination module is used to calculate the rate of change of the angle value of each generator at two different times, and to determine the generator with the largest rate of change among all generators as the stable unit and the generator with the smallest rate of change as the unstable unit. The first calculation module is used to calculate the equivalent mechanical power and equivalent electromagnetic power of the unstable generator unit based on the real-time measurement information of the stable generator unit and the real-time measurement information of the unstable generator unit. The second calculation module is used to calculate the transient stability assessment index of the power grid based on the equivalent mechanical power and the equivalent electromagnetic power, and to determine the stable state of the power grid based on the transient stability assessment index.

5. The system according to claim 4, characterized in that, The second calculation module includes: The first calculation submodule is used to calculate the virtual stable equilibrium point of the unstable unit based on the equivalent mechanical power and the equivalent electromagnetic power. The second calculation submodule is used to construct the voltage vector trajectory of the unstable generator pair and calculate the real part and imaginary part of the voltage vector trajectory. The third calculation submodule is used to calculate the phase trajectory arc length of the unstable unit under the ultimate stability state based on the voltage vector trajectory and the virtual stable equilibrium point. l 1; The fourth calculation submodule is used to calculate the arc length of the actual motion trajectory of the unstable unit based on the voltage vector trajectory, the real part of the voltage vector trajectory, and the imaginary part of the voltage vector trajectory. l 2; The fifth calculation submodule is used to calculate the phase trajectory arc length. l 1 and the actual arc length of the motion trajectory l 2. Calculate the transient stability assessment index of the power grid. , .

6. The system according to claim 4, characterized in that, The second calculation module includes: The first decision submodule is used when... When this occurs, the power grid is determined to be in a transient stable state; The second decision submodule is used when... When the power grid is in a critical transient stable state, it is determined that the power grid is in a critical transient stable state. The third decision submodule is used when... When the power grid is in a transient unstable state, it is determined that the power grid is in a transient unstable state. It serves as a transient stability assessment indicator.

7. The system according to claim 6, characterized in that, Also includes: The third calculation module is used to calculate based on the phase trajectory arc length. l 1 and the actual arc length of the motion trajectory l 2. Calculate the stability margin or instability degree of the power grid, wherein... When the power grid is in a transient stable state , This represents the stability margin; the larger the value, the more stable the system. When the power grid is in a state of transient instability , This indicates the degree of instability; the larger the value, the more severe the system instability.

8. A computer-readable storage medium, characterized in that, The storage medium stores a computer program for performing the method described in any one of claims 1-3.

9. An electronic device, characterized in that, The electronic device includes: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method described in any one of claims 1-3.

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