Power system stability evaluation method and device, computer equipment and storage medium

Abstract

The invention relates to a power system stability evaluation method and device, computer equipment, a storage medium and a computer program product. The method comprises the following steps: acquiring a natural torsional vibration frequency of a target torsional vibration mode in a power system; obtaining a mode expression of an actual torsional vibration mode in the power system, wherein the mode expression of the actual torsional vibration mode is generated according to system initial parameters of the power system; performing characteristic value solution on the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain a target characteristic value of the target torsional vibration mode; and obtaining a stability evaluation result of the power system based on the target characteristic value of the target torsional vibration mode. By adopting the method, the evaluation accuracy and the evaluation efficiency of the stability evaluation of the power system can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and in particular to a method, apparatus, computer equipment, storage medium and computer program product for evaluating the stability of a power system. Background Art

[0002] With the continuous access of new energy represented by wind and solar power to the power system, the sub-synchronous resonance (SSR) problem caused by the application of series compensation equipment in the power system is also very prominent. The sub-synchronous resonance generated in the power system will cause fatigue of the unit shaft system and reduce the service life of the unit. At the same time, the sub-synchronous oscillation component introduced by the sub-synchronous resonance device to the system will reduce the power quality of the power grid and damage the safe and stable operation of the system. Therefore, how to evaluate the instability risk of the unit shaft system torsional vibration mode under different working conditions is the focus of the sub-synchronous resonance stability analysis of the power system.

[0003] The existing analysis methods commonly used in subsynchronous resonance stability assessment have the problems of insufficient assessment accuracy or large amount of calculation, which can easily lead to reduced accuracy or efficiency of power system stability assessment and make the reliability of power system operation unable to be guaranteed. Summary of the invention

[0004] Based on this, it is necessary to provide a power system stability assessment method, device, computer equipment, computer-readable storage medium and computer program product that can improve the assessment accuracy and assessment efficiency of power system stability assessment in response to the above technical problems.

[0005] In a first aspect, the present application provides a method for evaluating the stability of a power system. The method comprises:

[0006] Obtaining the natural torsional vibration frequency of the target torsional vibration mode in the power system;

[0007] Acquire a mode expression of an actual torsional vibration mode in the power system, wherein the mode expression of the actual torsional vibration mode is generated according to an initial system parameter of the power system;

[0008] Solving the eigenvalue of the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain the target eigenvalue of the target torsional vibration mode;

[0009] A stability assessment result of the electric power system is obtained based on the target characteristic value of the target torsional vibration mode.

[0010] In the above embodiment, the target eigenvalue of the target torsional vibration mode can be obtained by solving the eigenvalue of the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency of the target torsional vibration mode in the power system. There is no need to calculate all the eigenvalues ​​in the system, such as eigenvalues ​​related to the controller and line dynamics. This can greatly improve the calculation efficiency when performing stability evaluation. The obtained target eigenvalue can also accurately reflect the system state of the power system under each target torsional vibration mode. Finally, the stability evaluation result of the power system is obtained based on the target eigenvalue, which effectively improves the evaluation efficiency of the stability evaluation of the power system while obtaining accurate stability evaluation results of the power system.

[0011] In some embodiments, performing eigenvalue solving on the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain the target eigenvalue of the target torsional vibration mode includes:

[0012] Obtaining a Taylor expansion expression and a distance parameter of the mode expression according to the natural torsional vibration frequency; the distance parameter is used to characterize the distance between the characteristic value of the mode expression and the natural torsional vibration frequency;

[0013] The Taylor expansion expression is subjected to eigenvalue solution calculation based on the distance parameter to obtain a target eigenvalue of the target torsional vibration mode.

[0014] In the above embodiment, by using the natural torsional vibration frequency to perform Taylor series expansion processing on the mode expansion of the actual torsional vibration mode, the solution process of the mode display formula can be made more convenient, thereby effectively improving the evaluation efficiency of the battery system stability evaluation.

[0015] In some embodiments, the Taylor expansion expression and distance parameter of the mode expression are obtained according to the natural torsional vibration frequency, including:

[0016] Obtaining a Taylor expansion interval of the mode expression according to the natural torsional vibration frequency;

[0017] The mode expression of the actual torsional vibration mode is subjected to Taylor series expansion based on the Taylor expansion interval to obtain a Taylor expansion expression of the mode expression and a distance parameter.

[0018] In the above embodiment, the Taylor expansion interval of the mode expression is determined by the natural torsional vibration frequency, and the Taylor series expansion is performed on the mode expression in the Taylor expansion interval, so that the target eigenvalue obtained subsequently can be closer to the actual eigenvalue, thereby improving the accuracy of the power system stability assessment by improving the accuracy of the target eigenvalue.

[0019] In some embodiments, the Taylor expansion expression and distance parameter of the mode expression are obtained according to the natural torsional vibration frequency, including:

[0020] Obtaining a Taylor expansion interval of the mode expression according to the natural torsional vibration frequency;

[0021] Performing Taylor series expansion on the mode expression of the actual torsional vibration mode based on the Taylor expansion interval to obtain an initial expansion expression of the mode expression and a distance parameter;

[0022] The initial expansion expression is subjected to a high-order term ignoring process to obtain a Taylor expansion expression of the pattern expression.

[0023] In the above embodiment, based on Taylor series expansion of the mode expression, the initial expansion expression obtained after the expansion is subjected to high-order term ignoring processing, so as to further reduce the complexity of the calculation and improve the evaluation efficiency of the stability evaluation of the battery system.

[0024] In some embodiments, performing eigenvalue calculation on the Taylor expansion expression according to the distance parameter to obtain the target eigenvalue of the target torsional vibration mode includes:

[0025] Performing eigenvalue calculation on the Taylor expansion expression according to the distance parameter to obtain an iterative eigenvalue of the target torsional vibration mode;

[0026] In the case where the iterative eigenvalue of the target torsional vibration mode does not satisfy the iteration stop condition, the Taylor expansion expression and the distance parameter are updated according to the iterative eigenvalue of the target torsional vibration mode in the current iteration, and the step of performing eigenvalue solution calculation on the Taylor expansion expression according to the distance parameter to obtain the iterative eigenvalue of the target torsional vibration mode is returned until the iterative eigenvalue of the target torsional vibration mode in the current iteration satisfies the iteration stop condition;

[0027] An iterative eigenvalue satisfying the iteration stop condition is determined as a target eigenvalue of the target torsional vibration mode.

[0028] In the above embodiment, the Taylor expansion expression of the actual torsional vibration mode is iteratively calculated using the distance parameter through an iterative solution method, and the calculated iterative eigenvalue is compared with the preset iterative stop condition, so that the correct stability judgment can be made with the least number of iterations, effectively improving the evaluation efficiency of the power system stability evaluation.

[0029] In some of these embodiments, the iterative eigenvalue of the target torsional vibration mode includes a real part value of the iterative eigenvalue;

[0030] The updating of the Taylor expansion expression and the distance parameter according to the iterative eigenvalue of the target torsional vibration mode in the current iteration includes:

[0031] Obtaining an iterative eigenvalue of the target torsional vibration mode in the current iteration according to a historical iterative eigenvalue and an iterative error value of the target torsional vibration mode in the previous iteration;

[0032] Obtaining the real part value of the iterative eigenvalue in the current iteration according to the historical real part value of the historical iterative eigenvalue of the target torsional vibration mode in the previous iteration and the iterative error value;

[0033] The Taylor expansion expression and the distance parameter are updated based on the iterative eigenvalue of the target torsional vibration mode in the current iteration and the real part value of the iterative eigenvalue.

[0034] In the above embodiment, the iterative eigenvalue and the real part of the iterative eigenvalue of the target torsional vibration mode in the current iteration are obtained through the historical iterative eigenvalue and the iterative error value, so that the iterative eigenvalue and the real part of the iterative eigenvalue of the target torsional vibration mode in the current iteration are both corrected values ​​obtained after error correction of the historical iterative value and the real part of the historical iterative value. By updating the Taylor expansion expression and the distance parameter with the corrected value and then iterating, the iterative eigenvalue obtained each time can be closer to the actual eigenvalue of the target torsional vibration mode, thereby improving the assessment accuracy of the power system stability assessment.

[0035] In some embodiments, the method further comprises:

[0036] The iteration error value is obtained by differentiating the historical iteration eigenvalue of the target torsional vibration mode in the previous iteration.

[0037] In the above embodiment, the iteration error value is obtained by differentiating the historical iteration eigenvalue of the target torsional vibration mode in the previous iteration, which can provide a data basis for calculating the iteration eigenvalue in the current iteration.

[0038] In some embodiments, determining the iterative eigenvalue satisfying the iteration stop condition as the target eigenvalue of the target torsional vibration mode includes:

[0039] Determining an iteration stop threshold of the target torsional vibration mode in the current iteration according to an iteration characteristic value of the target torsional vibration mode in the current iteration and a historical iteration characteristic value of the target torsional vibration mode in the previous iteration;

[0040] When the absolute value corresponding to the real part value of the iterative eigenvalue in the current iteration is greater than or equal to the iteration stop threshold, determining that the iterative eigenvalue of the target torsional vibration mode in the current iteration satisfies the iteration stop condition;

[0041] The iterative eigenvalue of the target torsional vibration mode in the current iteration is determined as the target eigenvalue of the target torsional vibration mode.

[0042] In the above embodiment, by determining the iteration stop threshold of the target torsional vibration mode in the current iteration based on the iteration characteristic value of the target torsional vibration mode in the current iteration and the historical iteration characteristic value of the target torsional vibration mode in the previous iteration, it is possible to quickly determine whether the iteration characteristic value satisfies the iteration stop condition when the iteration characteristic value of the target torsional vibration mode in the current iteration is obtained, thereby effectively improving the evaluation efficiency of the power system stability evaluation while making a correct stability judgment with the minimum number of iterations.

[0043] In some embodiments, obtaining a stability assessment result of the power system based on the target characteristic value of the target torsional vibration mode includes:

[0044] determining a mode state of the power system in each of the target torsional vibration modes based on a target characteristic value of each of the target torsional vibration modes in the power system;

[0045] A stability evaluation result of the electric power system is determined according to a mode state of the electric power system in each of the target torsional vibration modes.

[0046] In the above embodiment, by comparing the real part of the target eigenvalue with zero, it is possible to quickly determine whether the power system has an instability risk in the target torsional vibration mode corresponding to the target eigenvalue, thereby providing a data basis for subsequently determining the stability assessment result of the power system according to the mode state of the power system in each target torsional vibration mode.

[0047] In some embodiments, the mode state includes mode instability and mode stability; and determining the mode state of the power system in each of the target torsional vibration modes based on the target characteristic value of each of the target torsional vibration modes in the power system includes:

[0048] When the real part value of the target characteristic value is greater than zero, determining that the mode state of the power system in the target torsional vibration mode corresponding to the target characteristic value is mode instability;

[0049] When the real part value of the target eigenvalue is less than zero, it is determined that the mode state of the power system in the target torsional vibration mode corresponding to the target eigenvalue is mode stable.

[0050] In the above embodiment, by comparing the real part of the target eigenvalue with zero, it is possible to quickly determine whether the power system has an instability risk in the target torsional vibration mode corresponding to the target eigenvalue, thereby providing a data basis for subsequently determining the stability assessment result of the power system according to the mode state of the power system in each target torsional vibration mode.

[0051] In some of the embodiments, the stability assessment result of the power system includes a system state of the power system, and the system state includes system instability and system stability;

[0052] The determining the stability assessment result of the power system according to the mode state of the power system in each of the target torsional vibration modes includes:

[0053] When there is a target torsional vibration mode in the power system whose mode state is mode instability, determining that a stability assessment result of the power system is system instability;

[0054] When the mode state of each of the target torsional vibration modes in the power system is mode stable, it is determined that the stability evaluation result of the power system is system stable.

[0055] In the above embodiment, even if the power system only has the risk of instability in one target torsional vibration mode, the stability assessment system can quickly determine that the stability assessment result of the battery system is system instability, effectively improving the accuracy of subsynchronous resonance risk assessment in the power system.

[0056] In some of the embodiments, the stability assessment result of the power system includes an instability level of the power system;

[0057] The determining the stability assessment result of the power system according to the mode state of the power system in each of the target torsional vibration modes includes:

[0058] The instability level of the power system is determined according to a mode state of the power system in each of the target torsional vibration modes and a preset level mapping table; the preset level mapping table includes a correspondence between the mode state of the power system in each of the target torsional vibration modes and the instability level of the power system.

[0059] In the above embodiment, the stability assessment system can not only determine whether the power system has the risk of instability, but also further determine the instability level of the power system according to the mode state of the power system under each target mode, thereby providing effective data reference value for subsequent staff to select a suppression plan for the subsynchronous resonance problem generated in the power system.

[0060] In a second aspect, the present application also provides a power system stability assessment device. The device comprises:

[0061] A torsional vibration frequency acquisition module, used to acquire the natural torsional vibration frequency of a target torsional vibration mode in the power system;

[0062] An expression acquisition module, used to acquire a mode expression of an actual torsional vibration mode in the power system, wherein the actual torsional vibration mode is generated according to an initial system parameter of the power system;

[0063] A solution module, used for performing an eigenvalue solution on the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain a target eigenvalue of the target torsional vibration mode;

[0064] A stability assessment module is used to obtain a stability assessment result of the power system based on the target characteristic value.

[0065] In a third aspect, the present application further provides a computer device, wherein the computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the above-mentioned power system stability assessment method are implemented.

[0066] In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps of the above-mentioned power system stability assessment method are implemented.

[0067] In a fifth aspect, the present application further provides a computer program product, which includes a computer program, and when the computer program is executed by a processor, the steps of the above-mentioned power system stability assessment method are implemented.

[0068] The above-mentioned power system stability assessment method, device, computer equipment, storage medium and computer program product obtain the natural torsional vibration frequency of the target torsional vibration mode in the power system, and at the same time obtain the mode expression of the actual torsional vibration mode in the power system. The mode expression of the actual torsional vibration mode is generated according to the system initial parameters of the power system, and can be used to characterize the system state of the power system under the actual torsional vibration mode. Subsequently, the mode expression of the actual torsional vibration mode is solved for the eigenvalue according to the natural torsional vibration frequency of the target torsional vibration mode in the power system, and the target eigenvalue of the target torsional vibration mode can be obtained. There is no need to calculate all the eigenvalues ​​in the system, such as the eigenvalues ​​related to the controller and line dynamics, which can greatly improve the calculation efficiency when performing stability assessment. The obtained target eigenvalue can also accurately reflect the system state of the power system under each target torsional vibration mode. Finally, the stability assessment result of the power system is obtained based on the target eigenvalue, and the assessment efficiency of the stability assessment of the power system is effectively improved while obtaining an accurate stability assessment result of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 A diagram showing an application environment of a power system stability assessment method in some embodiments;

[0070] Figure 2 is a flow chart of a method for evaluating power system stability in some embodiments;

[0071] Figure 3A schematic flow chart of a step of obtaining a Taylor expansion expression and a distance parameter of a mode expression according to a natural torsional vibration frequency in some embodiments;

[0072] Figure 4 A schematic flow chart of a step of performing eigenvalue calculation on a Taylor expansion expression according to a distance parameter to obtain a target eigenvalue of a target torsional vibration mode in some embodiments;

[0073] Figure 5 A schematic flow chart of a step of updating a Taylor expansion expression and a distance parameter according to an iterative eigenvalue of a target torsional vibration mode in a current iteration in some embodiments;

[0074] Figure 6 A schematic flow chart of a step of determining an iterative eigenvalue satisfying an iteration stop condition as a target eigenvalue of a target torsional vibration mode in some embodiments;

[0075] Figure 7 A schematic diagram of the distribution of each eigenvalue after one iteration in some embodiments;

[0076] Figure 8 is a flow chart of a method for evaluating power system stability in some other embodiments;

[0077] Fig. 9 A complex torque coefficient diagram of the first standard example of IEEE subsynchronous resonance in some embodiments;

[0078] Fig.10 is a structural block diagram of a power system stability assessment device in some embodiments;

[0079] Fig.11 1 is a diagram of the internal structure of a computer device in some embodiments. DETAILED DESCRIPTION

[0080] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0081] Sub-synchronous resonance (SSR) refers to the phenomenon that the oscillation frequency in the power system is lower than the synchronous frequency. When the generator in the power system is connected to the system through a highly compensated series compensation line or when the parameters of the direct transmission and static VAR compensation device control device are improperly set, it is easy for the electrical resonance frequency of the network to be close to the natural torsional vibration frequency of the generator shaft system, causing torsional vibration of the generator shaft and damaging the shaft. Since the oscillation frequency is lower than the grid frequency, this phenomenon is called sub-synchronous resonance.

[0082] At present, the commonly used analysis methods for subsynchronous resonance stability assessment have the problems of insufficient assessment accuracy or large amount of calculation. For example, the commonly used complex torque coefficient method, the power system stability assessment needs to identify the frequency point w through the elastic coefficient curve k(w) 0 The corresponding damping coefficient curve D(w 0 ), however, in practical applications, the complex torque coefficient method may not be able to identify all the target torsional vibration modes of interest. 0 ) to judge the stability of the power system may also lead to incorrect stability judgment results. In addition, the calculation cost required to obtain the k(w) and D(w) curves is also high. Therefore, the traditional power system stability assessment method is likely to reduce the accuracy or efficiency of power system stability assessment, making the reliability of power system unguaranteed.

[0083] Each target torsional vibration mode in the power system corresponds to a natural torsional vibration frequency. In order to accurately and efficiently evaluate the subsynchronous resonance stability in the power system, the natural torsional vibration frequency of each target torsional vibration mode in the power system can be obtained, and the mode expression of the actual torsional vibration mode in the power system can be obtained at the same time. The mode expression of the actual torsional vibration mode is generated according to the system initial parameters of the power system and can be used to characterize the system state of the power system under the actual torsional vibration mode. Subsequently, the mode expression of the actual torsional vibration mode is solved according to the natural torsional vibration frequency of the target torsional vibration mode in the power system, and the solved value is determined as the target eigenvalue of the target torsional vibration mode. The target eigenvalue can accurately reflect the system state of the power system under each target torsional vibration mode. This process does not need to calculate the eigenvalues ​​of other modes in the power system except the target torsional vibration mode, such as the eigenvalues ​​related to the controller and line dynamics, which can greatly improve the calculation efficiency when performing stability evaluation. Finally, the stability evaluation result of the power system is obtained based on the target eigenvalues ​​of each target torsional vibration mode, which effectively improves the evaluation efficiency of the stability evaluation of the power system while obtaining accurate stability evaluation results of the power system.

[0084] The power system stability assessment method provided in the embodiment of the present application can be applied to Figure 1In the application environment shown. Among them, the stability assessment system 102 communicates with the power system data source 104 through the network. The data storage system can store the data that the stability assessment system 102 needs to process. The data storage system can be integrated on the stability assessment system 102, or it can be placed on the cloud or other network servers. Based on the power system data source 104, the stability assessment system 102 obtains the natural torsional vibration frequency of the target torsional vibration mode in the power system, and at the same time obtains the mode expression of the actual torsional vibration mode in the power system. The mode expression of the actual torsional vibration mode is generated according to the system initial parameters of the power system. The stability assessment system solves the eigenvalue of the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency, obtains the target eigenvalue of the target torsional vibration mode, and obtains the stability assessment result of the power system based on the target eigenvalue of the target torsional vibration mode.

[0085] The stability assessment system 102 can be integrated on a user terminal of a technician, which can be, but is not limited to, various personal computers, laptops, smart phones, tablet computers, IoT devices, and portable wearable devices. IoT devices can be smart speakers, smart TVs, smart air conditioners, smart car-mounted devices, etc. Portable wearable devices can be smart watches, smart bracelets, head-mounted devices, etc. It can also be integrated on a server, which can be implemented as an independent server or a server cluster consisting of multiple servers.

[0086] The power system data source 104 may be any data source capable of providing the stability assessment system 102 with system data of the power system, such as a power system data storage server, or a user terminal storing system data, etc. The power system data source 104 may store various system data of the power system, such as system initial parameters, system real-time operating parameters, natural torsional vibration frequencies of torsional vibration modes in the power system, etc.

[0087] In some embodiments, Figure 2 As shown in the figure, a method for evaluating the stability of a power system is provided. Figure 1 The stability evaluation system in the example is used to illustrate, which includes the following steps:

[0088] Step 202: Acquire the natural torsional vibration frequency of the target torsional vibration mode in the power system.

[0089] Among them, the power system is an electric energy production and consumption system composed of power plants, transmission and transformation lines, power supply and distribution stations and power consumption. The function of the power system is to convert primary energy in nature into electrical energy through power generation devices, and then supply the electrical energy to various users through transmission, transformation and distribution.

[0090] Common power generation methods in power systems include thermal power generation, hydropower generation, wind power generation, nuclear power generation, etc. However, no matter which power generation method is used, the electric energy in the power system needs to be generated by the generator set. If the generator set shaft system has torsional vibration, it will directly affect the stable operation of the power system. Therefore, how to evaluate the instability risk of the torsional vibration mode of the generator set shaft system is the focus of the power system stability assessment.

[0091] The target torsional vibration mode in the power system is an interference mode that is closely related to the operational stability of the power system, that is, the torsional vibration mode of the shaft system of the generator set in the power system. It is understandable that there are multiple interference modes in the power system, such as the torsional vibration mode related to the torsional vibration of the shaft system of the generator set, the oscillation mode related to the controller, the torsional vibration mode related to the line dynamics, etc. Once the power system is generated, the types and number of interference modes therein will also be determined. When conducting a stability assessment of the power system, it is only necessary to focus on the key torsional vibration mode of the shaft system of the generator set. Therefore, the torsional vibration mode of the shaft system of the generator set is determined as the target torsional vibration mode in the power system when conducting a stability assessment.

[0092] The natural torsional vibration frequency refers to the torsional vibration frequency of the generator set shaft system in its natural state. In the power system, the generator set shaft system can be regarded as a number of elastically connected concentrated mass blocks, which rotate synchronously and also perform torsional oscillations with a frequency of the natural torsional vibration frequency. The natural torsional vibration frequency of the generator set shaft system is only related to the inherent characteristics of the generator set shaft system. Each generator set shaft system torsional vibration mode, that is, the target torsional vibration mode, in the power system has a corresponding natural torsional vibration frequency.

[0093] When actually conducting a stability assessment of a power system, the stability assessment system obtains the natural torsional vibration frequency of each target torsional vibration mode in the power system based on the power system data source.

[0094] In some of the embodiments, since the natural torsional vibration frequency is only related to the inherent characteristics of the generator set shaft system, the generator set designer can determine the natural torsional vibration frequency of the generator set shaft system torsional vibration mode as a system parameter of the power system after the generator set design is completed, and store it in the power system data source. When actually performing a stability assessment, the stability assessment system can directly obtain the natural torsional vibration frequency of the target torsional vibration mode in the power system from the power system data source.

[0095] In some of the embodiments, in order to further improve the convenience of the stability assessment of the power system, the stability assessment system can calculate the natural torsional vibration frequency of the target torsional vibration mode in the power system based on the structural parameters of the generator set in the power system. After the design of the generator set is completed, the generator set designer only needs to store the structural parameters of the generator set as the system parameters of the power system in the power system data source. The structural parameters may include the natural frequency, elastic coefficient, mass constant, etc. of the torsional vibration mode. When actually performing the stability assessment, the stability assessment system can obtain the structural parameters of the generator set from the power system data source, and based on the preset calculation method, calculate the natural torsional vibration frequency of the target torsional vibration mode in the power system according to the result parameters of the generator set.

[0096] Step 204 , obtaining a mode expression of an actual torsional vibration mode in the power system, wherein the mode expression of the actual torsional vibration mode is generated according to initial system parameters of the power system.

[0097] Among them, the actual torsional vibration mode refers to an actual manifestation of the target torsional vibration mode in the generator set after the generator set is connected to the power system. That is, the target torsional vibration mode and the actual torsional vibration mode are not two different torsional vibration modes. The actual torsional vibration mode is just a manifestation of the target torsional vibration mode under different circumstances. The natural torsional vibration mode has the same nature as the actual torsional vibration mode. The natural torsional vibration mode can be considered as a manifestation of the target torsional vibration mode in a natural state when the generator set is not connected to the power system. Therefore, each target torsional vibration mode can correspond to an actual torsional vibration mode and a natural torsional vibration mode.

[0098] In some of the embodiments, the actual torsional vibration mode corresponds to an actual eigenvalue, which is related to the actual torsional vibration frequency of the actual torsional vibration mode, and the natural torsional vibration mode corresponds to a natural eigenvalue, which is related to the natural torsional vibration frequency.

[0099] The mode expression of the actual torsional vibration mode is an expression used to characterize the system state of the power system under the actual torsional vibration mode. The mode expression of the actual torsional vibration mode can be generated according to the system initial parameters in the power system.

[0100] The system initial parameters of the power system are system parameters used to reflect the system spatial state of the power system. The system initial parameters of the power system may include synchronous machine shaft parameters, synchronous generator parameters, line parameters and system operation flow initial values.

[0101] In actual use, when obtaining the natural torsional vibration frequency of the target torsional vibration mode of the power system, the stability assessment system also needs to obtain the mode expression of the actual torsional vibration mode in the power system.

[0102] In some of the embodiments, the mode expression of the actual torsional vibration mode can be generated by the designer according to the initial system parameters of the power system and configured in the power system data source. During the actual stability assessment, the stability assessment system directly obtains the mode expression of the actual torsional vibration mode from the power system data source.

[0103] In order to further improve the ease of use and universality of the stability assessment system, in some embodiments, the mode expression of the actual torsional vibration mode in the power system is obtained, including:

[0104] Obtain the initial system parameters of the power system. Input the initial system parameters into the system space model of the power system to obtain the mode expression of the actual torsional vibration mode in the power system.

[0105] Among them, the system space model is the initial model used to describe the state space of the power system. It can be considered as a general model used in modeling the power system. The initial model can be described by differential-algebraic equations. The system space model can be pre-configured in the stability assessment system to facilitate the system to call at any time.

[0106] During the actual evaluation, after the stability evaluation system obtains the initial system parameters of the power system, it can input the initial system parameters into the universal system space model of the power system to obtain the mode expression of the actual torsional vibration mode in the power system. By pre-configuring the initial system space model, for different generator sets, only the input initial system parameters need to be changed to quickly obtain the corresponding mode expression of the actual torsional vibration mode, which effectively improves the universality and ease of use of the stability evaluation system, and also improves the evaluation efficiency of the stability evaluation of the power system.

[0107] In some of the embodiments, the process of generating the mode expression of the actual torsional vibration mode is exemplified, wherein the system space model of the power system including the synchronous generator set can be described as:

[0108]

[0109] Among them, ABCD is the coefficient matrix.

[0110] After the stability assessment system obtains the initial parameters of the power system, it inputs the initial parameters into the system space model. The initial parameters are arranged in the system matrix ABCD through the arrangement of the equations. Then the spatial model obtained after the output parameters is converted into a polynomial format. The characteristic polynomial D(s) of the system can be described as:

[0111]

[0112] As for the actual torsional vibration mode of the shaft system, its root That is, the actual characteristic value of the actual torsional vibration mode should satisfy the following formula:

[0113]

[0114] Where i represents any target torsional vibration mode in the generator shaft system. represents the actual eigenvalue of the actual torsional vibration mode corresponding to the target torsional vibration mode, By the real part and the imaginary part ω ri Composition, imaginary part ω ri That is, the actual torsional vibration frequency of the actual torsional vibration mode. The above formula is determined as the mode expression of the actual torsional vibration mode.

[0115] Step 206 , performing eigenvalue solution on the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain the target eigenvalue of the target torsional vibration mode.

[0116] The target eigenvalue of the target torsional vibration mode can be considered as an estimated eigenvalue of the actual torsional vibration frequency obtained by solving the mode expression of the actual torsional vibration mode through the natural torsional vibration frequency.

[0117] In actual engineering, the target torsional vibration mode of a generator set should meet the following constraints:

[0118]

[0119] Among them, ω ni represents the natural eigenvalue of the natural torsional vibration mode in the i-th target torsional vibration mode of the generator. Since the real part of the natural eigenvalue is 0, the natural eigenvalue of the natural torsional vibration mode can also be considered as the natural torsional vibration frequency of the natural torsional vibration mode. The above constraints reveal a very important characteristic: the natural eigenvalue of the natural torsional vibration mode Very close to the actual eigenvalues ​​of the actual torsional vibration mode That is, the natural torsional vibration frequency of the natural torsional vibration mode is very close to the actual torsional vibration frequency of the actual torsional vibration mode. Therefore, the frequency estimation of the actual torsional vibration frequency obtained by solving the eigenvalue of the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency has high accuracy.

[0120] During the actual evaluation, the stability evaluation system solves the eigenvalue of the mode expression of the actual torsional vibration mode according to the acquired natural torsional vibration frequency, and obtains the frequency estimation of the actual torsional vibration frequency of the target torsional vibration mode after the generator set is connected to the power system, that is, the target eigenvalue of the target torsional vibration mode.

[0121] In some of the embodiments, the stability assessment system may use a preset solution method to perform an eigenvalue solution on the mode expression of the actual torsional vibration mode according to the obtained natural torsional vibration frequency. The preset iterative solution method may be any solution method that can obtain an optimal solution for the mode expression of the actual torsional vibration mode, such as a gradient descent method, a Newton method, a quasi-Newton method, and the like.

[0122] Step 208 : obtaining a stability assessment result of the power system based on the target characteristic value of the target torsional vibration mode.

[0123] Among them, since the target eigenvalue is the estimated eigenvalue of the actual torsional vibration mode corresponding to the target torsional vibration mode after the generator set is connected to the power system, the target eigenvalue can reflect whether there is an instability risk after the generator set is connected to the power system. In turn, the stability assessment result of the power system can be determined.

[0124] During the actual evaluation, the stability evaluation system evaluates the stability of the power system based on the target eigenvalue of the target torsional vibration mode to obtain a stability evaluation result of the power system.

[0125] In some of the embodiments, a correspondence between target characteristic values ​​and stability values ​​of the power system is pre-configured in the stability assessment system. After obtaining the target characteristic value of the target torsional vibration mode, the stability assessment system searches for the preset correspondence based on the target characteristic value to determine the stability value of the power system, thereby obtaining a stability assessment result of the power system.

[0126] In some of the embodiments, a relationship function between a target characteristic value and a stability value of the power system is pre-configured in the stability assessment system. After obtaining the target characteristic value of the target torsional vibration mode, the stability assessment system can calculate the stability value of the power system based on the target characteristic value and the preset relationship function, and then obtain a stability assessment result of the power system.

[0127] In the above-mentioned power system stability assessment method, the natural torsional vibration frequency of the target torsional vibration mode in the power system is obtained, and at the same time, the mode expression of the actual torsional vibration mode in the power system is obtained. The mode expression of the actual torsional vibration mode is generated according to the system initial parameters of the power system, and can be used to characterize the system state of the power system under the actual torsional vibration mode. Subsequently, the mode expression of the actual torsional vibration mode is solved for the eigenvalue according to the natural torsional vibration frequency of the target torsional vibration mode in the power system, and the target eigenvalue of the target torsional vibration mode can be obtained. There is no need to calculate all the eigenvalues ​​in the system, such as the eigenvalues ​​related to the controller and line dynamics, which can greatly improve the calculation efficiency when performing stability assessment. The obtained target eigenvalue can also accurately reflect the system state of the power system under each target torsional vibration mode. Finally, the stability assessment result of the power system is obtained based on the target eigenvalue, and the assessment efficiency of the stability assessment of the power system is effectively improved while obtaining an accurate stability assessment result of the power system.

[0128] The process of solving the eigenvalue of the mode expression of the actual torsional vibration mode using the natural torsional vibration mode has an important impact on the efficiency and accuracy of power system stability assessment.

[0129] In some embodiments, performing an eigenvalue solution on the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain a target eigenvalue of the target torsional vibration mode includes:

[0130] The Taylor expansion expression and distance parameter of the mode expression are obtained according to the natural torsional vibration frequency; the distance parameter is used to characterize the distance between the eigenvalue of the mode expression and the natural torsional vibration frequency. Based on the distance parameter, the Taylor expansion expression is solved for the eigenvalue to obtain the target eigenvalue of the target torsional vibration mode.

[0131] Among them, the Taylor expansion expression and distance parameter of the mode expression are obtained by using the natural torsional vibration frequency to perform Taylor series expansion on the mode expression. Taylor series expansion refers to the method of using a polynomial function to approximate a complex function at a certain point. Polynomial functions have some good characteristics, such as it is convenient to calculate first-order, second-order, and multi-order derivatives. Therefore, by using Taylor expansion to approximate the mode expression of the actual torsional vibration mode, the obtained Taylor expansion expression can have more convenient solution characteristics, which is convenient for subsequent use of distance parameters to solve its eigenvalue.

[0132] When the Taylor series expansion of the mode expression is performed using the natural torsional frequency, in addition to obtaining the Taylor expansion expression of the mode expression, a distance parameter can also be obtained to characterize the distance between the eigenvalue of the mode expression and the natural torsional frequency, that is, the distance parameter can characterize the distance between the actual eigenvalue and the natural eigenvalue of the target torsional vibration mode. By continuing to solve and calculate the Taylor expansion expression using the distance parameter, the target eigenvalue of the target torsional vibration mode can be obtained.

[0133] During the actual evaluation, the stability evaluation system performs Taylor series expansion processing on the mode expression of the actual torsional vibration mode according to the obtained natural torsional vibration frequency, and obtains the Taylor expansion expression of the mode expression, and the distance parameter used to characterize the distance between the eigenvalue of the mode expression and the natural torsional vibration frequency. The stability evaluation system substitutes the obtained distance parameter into the Taylor display expression of the mode expression, solves the eigenvalue of the Taylor expansion expression, and obtains the target eigenvalue of the target torsional vibration mode.

[0134] In the above embodiment, by using the natural torsional vibration frequency to perform Taylor series expansion processing on the mode expansion of the actual torsional vibration mode, the solution process of the mode display formula can be made more convenient, thereby effectively improving the evaluation efficiency of the battery system stability evaluation.

[0135] The Taylor series expansion can be considered as a formula that uses the information of a function at a certain point to describe the values ​​near it. The closer the expansion obtained after Taylor series expansion is to the actual complex function, the higher the similarity between the obtained solution and the true value, that is, the more accurate the solution. Therefore, the range of Taylor series expansion will affect the convenience and accuracy of solving the obtained Taylor expansion expression.

[0136] Based on this, in some embodiments, the Taylor expansion expression and the distance parameter of the mode expression are obtained according to the natural torsional vibration frequency, including:

[0137] The Taylor expansion interval of the mode expression is obtained according to the natural torsional vibration frequency. Based on the Taylor expansion interval, the mode expression of the actual target torsional vibration mode is expanded by Taylor series to obtain the Taylor expansion expression of the mode expression and the distance parameter.

[0138] Among them, the Taylor expansion interval can be considered as the value range interval of the Taylor expansion expression. By performing Taylor series expansion on the pattern expression in the Taylor expansion interval, the value range of the obtained Taylor expansion expression can fall within the Taylor expansion interval, that is, the estimated value of the actual eigenvalue can fall within the Taylor expansion interval.

[0139] As mentioned above, in actual engineering, the shaft torsional vibration mode of the generator has a very important characteristic: the natural eigenvalue of the natural torsional vibration mode is very close to the actual eigenvalue of the actual torsional vibration mode, that is, the natural torsional vibration frequency of the natural torsional vibration mode is very close to the actual torsional vibration frequency of the actual torsional vibration mode. Therefore, by determining the Taylor expansion interval according to the natural torsional vibration frequency, the target eigenvalue obtained after the eigenvalue solution calculation of the Taylor expansion expression can be closer to the actual eigenvalue of the actual torsional vibration mode, thereby improving the accuracy of the target eigenvalue.

[0140] During the actual evaluation, the stability evaluation system takes the natural torsional vibration frequency as a specific point, and determines the Taylor expansion interval of the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency. Based on the Taylor expansion interval, the mode expression can be expanded by Taylor series near the natural torsional vibration frequency to obtain the Taylor expansion expression of the mode expression and the distance parameter used to characterize the distance between the eigenvalue of the mode expression and the natural torsional vibration frequency.

[0141] In some embodiments, the stability assessment system determines the Taylor expansion interval according to the natural torsional vibration frequency and the preset interval generation value. The preset interval generation value can be determined according to the actual solution accuracy requirements of the user, as long as the mode expression can be Taylor series expanded near the natural torsional vibration frequency.

[0142] In the above embodiment, the Taylor expansion interval of the mode expression is determined by the natural torsional vibration frequency, and the Taylor series expansion is performed on the mode expression in the Taylor expansion interval, so that the target eigenvalue obtained subsequently can be closer to the actual eigenvalue, thereby improving the accuracy of the power system stability assessment by improving the accuracy of the target eigenvalue.

[0143] In addition to performing Taylor series expansion of the mode expression near the natural torsional vibration frequency to improve the efficiency of the stability assessment of the power system, in other embodiments, such as Figure 3 As shown, the Taylor expansion expression and distance parameter of the mode expression are obtained according to the natural torsional vibration frequency, including:

[0144] Step 302: Obtain the Taylor expansion interval of the mode expression according to the natural torsional vibration frequency.

[0145] Step 304 , performing Taylor series expansion on the mode expression of the actual torsional vibration mode based on the Taylor expansion interval to obtain an initial expansion expression of the mode expression and a distance parameter.

[0146] Step 306, performing high-order term ignoring processing on the initial expansion expression to obtain a Taylor expansion expression of the pattern expression.

[0147] Among them, the high-order term ignoring process refers to the process of discarding the high-order terms in the initial expansion expression to obtain the Taylor expansion expression. As can be seen from the previous article, after the Taylor series expansion of the pattern expression, a polynomial function approximating the pattern expression is obtained, and the polynomial function is composed of multiple terms from low to high according to the order. Although the Taylor series is essentially an approximate replacement, the more terms are taken, the better the approximation effect will be, but as the order gradually increases, the corresponding calculation process becomes more complicated, and the order will have a smaller impact on the improvement of the solution accuracy during the solution process. Therefore, the method of ignoring high-order terms can be used to discard the high-order terms in the initial expansion expression obtained after the Taylor series expansion to achieve the effect of further reducing the complexity of the calculation.

[0148] During the actual evaluation, the stability evaluation system obtains the Taylor expansion interval of the mode expression according to the natural torsional vibration frequency, performs Taylor series expansion on the mode expression of the actual torsional vibration mode in the Taylor expansion interval, and obtains the initial expansion expression of the mode expression and the distance parameter. It can be understood that the specific steps of determining the Taylor expansion interval and Taylor series expansion in this step are consistent with the specific steps of determining the Taylor expansion interval and Taylor series expansion in the previous text, and will not be repeated here.

[0149] It should be noted that the high-order terms and low-order terms in the initial expanded expression are relative concepts. In some of the embodiments, the designer can determine the specific order of high-order terms that need to be discarded in the high-order term ignoring process according to the actual required solution accuracy, so as to facilitate the stable evaluation system to perform high-order term ignoring processing on the initial display expression according to the preset discarded order.

[0150] In some of the embodiments, Taylor expansion expressions and distance parameters for obtaining mode expressions based on natural torsional vibration frequencies are exemplified.

[0151] Based on the characteristics revealed by the constraints of the target torsional vibration mode, the mode expression of the actual torsional vibration mode mentioned above can be: In natural eigenvalue Perform Taylor series expansion near , and get the initial expansion expression as:

[0152]

[0153] And the distance parameter Δs:

[0154]

[0155] Ignoring the higher-order infinite terms in the initial expansion expression, the Taylor expansion expression of the mode expression can be obtained:

[0156]

[0157] In the above embodiment, based on Taylor series expansion of the mode expression, the initial expansion expression obtained after the expansion is subjected to high-order term ignoring processing, so as to further reduce the complexity of the calculation and improve the evaluation efficiency of the stability evaluation of the battery system.

[0158] After obtaining the Taylor expansion expression of the mode expression and the distance parameter, how to solve the Taylor expansion expression to obtain the target eigenvalue of the target torsional vibration mode is another important factor affecting the accuracy and efficiency of power system stability assessment.

[0159] In some embodiments, Figure 4 As shown, the Taylor expansion expression is solved and calculated according to the distance parameter to obtain the target eigenvalue of the target torsional vibration mode, including:

[0160] Step 402 , performing eigenvalue calculation on the Taylor expansion expression according to the distance parameter to obtain the iterative eigenvalue of the target torsional vibration mode.

[0161] Among them, the iteration method is a process of continuously recursively deriving new values ​​from old values ​​of variables, which can be divided into two iteration methods: precise iteration and approximate iteration. The process of solving the eigenvalue of the Taylor expansion expression according to the distance parameter can be an approximate iterative solution process. By iteratively calculating the Taylor expansion expression, the iterative eigenvalue of the target torsional vibration mode can be quickly obtained.

[0162] In some preferred embodiments, after obtaining the Taylor expansion expression of the distance parameter and the mode expression, the stability assessment system substitutes the distance parameter into the Taylor expansion expression, performs eigenvalue solution calculation on the Taylor expansion expression, and obtains the iterative eigenvalue of the target torsional vibration mode in the current iteration.

[0163] Step 404 : when the iterative eigenvalue of the target torsional vibration mode does not satisfy the iteration stop condition, the Taylor expansion expression and the distance parameter are updated according to the iterative eigenvalue of the target torsional vibration mode in the current iteration.

[0164] When using the iterative calculation method to solve the eigenvalue of the Taylor expansion expression, it is necessary to consider when to end the iteration process. Theoretically, when the number of iterations is large enough, the calculated iterative eigenvalue will be sufficiently close to the actual torsional vibration frequency. Therefore, in order to improve the calculation efficiency, it is necessary to set an iteration stop condition so that the correct stability judgment can be made with the least number of iterations.

[0165] The iteration stop condition is a preset judgment condition for determining whether the process of iteratively solving the eigenvalue of the Taylor expansion expression can be stopped. When the iterative eigenvalue of the target torsional vibration mode does not meet the iteration stop condition, it can be considered that the result obtained by solving the eigenvalue of the Taylor expansion expression at this time is greatly different from the actual torsional vibration frequency and is not accurate enough.

[0166] In order to make the calculated iterative eigenvalues ​​closer to the actual torsional vibration frequency, it is necessary to update the Taylor expansion expression and distance parameter of the mode expression according to the iterative eigenvalues ​​at the current number. This updating process can be considered as a process of narrowing the value range of the Taylor expansion, so that the iterative eigenvalues ​​calculated by solving the updated Taylor expansion expression according to the updated distance parameter can be closer to the actual torsional vibration frequency.

[0167] In some optional embodiments, the stability assessment system compares the iterative eigenvalue of the target torsional vibration mode at the current iteration with the iteration stop condition. If the iterative eigenvalue does not meet the iteration stop condition, the Taylor expansion expression and distance parameter are updated according to the iterative eigenvalue of the target torsional vibration mode at the current iteration.

[0168] Step 406, returns to the step of solving the eigenvalue of the Taylor expansion expression according to the distance parameter to obtain the iterative eigenvalue of the target torsional vibration mode, until the iterative eigenvalue of the target torsional vibration mode in the current iteration meets the iteration stop condition, and the iterative eigenvalue that meets the iteration stop condition is determined as the target eigenvalue of the target torsional vibration mode.

[0169] It can be understood that when the iterative eigenvalue of the target torsional vibration mode in the current iteration meets the iteration stop condition, it can be considered that the iterative eigenvalue obtained in the current iteration is already very close to the actual torsional vibration frequency. The subsequent stability assessment of the power system is performed based on the iterative eigenvalue obtained in the current iteration, which can improve the accuracy of the stability assessment.

[0170] In some optional embodiments, after updating the Taylor expansion expression and the distance parameter according to the iterative eigenvalue of the current iteration, the stability evaluation system re-executes the eigenvalue solution calculation of the Taylor expansion expression according to the distance parameter, that is, uses the updated distance parameter to perform the eigenvalue solution calculation on the updated Taylor expansion expression, until the iterative eigenvalue of the target torsional vibration mode in the current iteration meets the iteration stop condition. It can be considered that the iterative eigenvalue obtained in the current iteration is already very close to the actual torsional vibration frequency, and the iterative eigenvalue that meets the iteration stop condition is determined as the target eigenvalue of the target torsional vibration mode.

[0171] In the above embodiment, the Taylor expansion expression of the actual torsional vibration mode is iteratively calculated using the distance parameter through an iterative solution method, and the calculated iterative eigenvalue is compared with the preset iterative stop condition, so that the correct stability judgment can be made with the least number of iterations, effectively improving the evaluation efficiency of the power system stability evaluation.

[0172] Further, in some embodiments, the iterative eigenvalue of the target torsional vibration mode includes the real part value of the iterative eigenvalue, such as Figure 5 As shown, the Taylor expansion expression and distance parameter are updated according to the iterative eigenvalue of the target torsional vibration mode under the current iteration, including:

[0173] Step 502 : obtaining the iterative eigenvalue of the target torsional vibration mode in the current iteration according to the historical iterative eigenvalue and iterative error value of the target torsional vibration mode in the previous iteration.

[0174] The iterative error value refers to the error value that needs to be continuously corrected during the iteration process. During the iteration process, by correcting the error of each iterative eigenvalue, the final target eigenvalue can be more similar to the actual eigenvalue of the target torsional vibration mode. The historical iterative eigenvalue refers to the iterative eigenvalue obtained by the previous eigenvalue iterative calculation of the Taylor expansion expression of the actual torsional vibration mode.

[0175] In some optional embodiments, the stability evaluation system may calculate the iterative eigenvalue of the target torsional vibration mode in the current iteration based on the historical iterative eigenvalue of the target torsional vibration mode in the previous iteration and the iterative error value.

[0176] In some of the embodiments, the method for calculating the iterative error value includes: differentiating the historical iterative eigenvalue of the target torsional vibration mode in the previous iteration to obtain the iterative error value. When the stability evaluation system needs to update the Taylor expansion expression and the distance parameter to provide a calculation basis for the next eigenvalue iterative calculation, the historical iterative eigenvalue obtained in the previous iteration can be obtained, and the historical iterative eigenvalue can be differentiated based on a preset differential method. The iterative error value is obtained according to the differential calculation result. By differentiating the historical iterative eigenvalue of the target torsional vibration mode in the previous iteration to obtain the iterative error value, a data basis can be provided for the calculation of the iterative eigenvalue in the current iteration.

[0177] Step 504 , obtaining the real part value of the iterative eigenvalue in the current iteration according to the historical real part value of the historical iterative eigenvalue of the target torsional vibration mode in the previous iteration and the iterative error value.

[0178] The historical real value refers to the real value of the historical iteration eigenvalue in the previous iteration.

[0179] In some optional embodiments, the stability assessment system determines the historical real part value of the target torsional vibration mode in the previous iteration based on the historical iterative eigenvalue of the target torsional vibration mode in the previous iteration, and obtains the real part value of the iterative eigenvalue in the current iteration based on the historical real part value of the target torsional vibration mode in the previous iteration and the iterative error calculation.

[0180] Step 506: Update the Taylor expansion expression and the distance parameter based on the iterative eigenvalue of the target torsional vibration mode in the current iteration and the real part of the iterative eigenvalue.

[0181] During actual evaluation, when the stable evaluation system obtains the iterative eigenvalue of the current iteration and the real part value of the iterative eigenvalue, it updates the Taylor expansion expression and distance parameter based on the iterative eigenvalue of the current iteration and the real part value of the iterative eigenvalue to obtain the updated Taylor expansion expression and distance parameter.

[0182] In some of the embodiments, specific methods for obtaining iterative eigenvalues ​​are illustrated by way of example:

[0183] After obtaining the Taylor expansion expression and distance parameter of the mode expression, the distance parameter is entered into the Taylor expansion expression for eigenvalue iteration. After one iterative calculation, the real part of the actual torsional vibration mode can be expressed as:

[0184]

[0185] After k iterations, the output iterative eigenvalue is:

[0186]

[0187] The real part of the iterative eigenvalue is:

[0188]

[0189] According to the expressions of iterative eigenvalues ​​and real part values ​​after k iterations, it can be seen that when k→∞,

[0190] In some embodiments, based on the above reasoning and analysis results, a criterion for stability evaluation can be proposed: for the i-th target torsional vibration mode concerned by the user, if the real part after one iteration is If is negative, then the target torsional vibration mode remains stable; otherwise, the target torsional vibration mode is at risk of instability. This is the basis for stability judgment based on the eigenvalue theory.

[0191] The convergence of the above stability judgment basis is proved below. Mathematically, the above iterative method can be considered as an iterative method based on the iterative function φ(s):

[0192]

[0193] Substituting the mode expression of the actual torsional vibration mode into the above formula, we can obtain:

[0194]

[0195] Obviously, in the torsional vibration mode In a small range, there exists a constant L that satisfies the following formula:

[0196]

[0197] By deducing the above three formulas, we can get the following formula:

[0198]

[0199] Because 0<L<1, when k→∞, L k will converge to 0, so:

[0200]

[0201] The above analysis process proves that when the target eigenvalue is obtained by the iterative calculation method described above, the target eigenvalue can be obtained after one iterative calculation. This further proves that the above method of iteratively solving the pattern expression after Taylor series expansion has a faster calculation speed than other methods of solving the target eigenvalue, and can effectively improve the evaluation efficiency of power system stability assessment.

[0202] In the above embodiment, the iterative eigenvalue and the real part of the iterative eigenvalue of the target torsional vibration mode in the current iteration are obtained through the historical iterative eigenvalue and the iterative error value, so that the iterative eigenvalue and the real part of the iterative eigenvalue of the target torsional vibration mode in the current iteration are both corrected values ​​obtained after error correction of the historical iterative value and the real part of the historical iterative value. By updating the Taylor expansion expression and the distance parameter with the corrected value and then iterating, the iterative eigenvalue obtained each time can be closer to the actual eigenvalue of the target torsional vibration mode, thereby improving the assessment accuracy of the power system stability assessment.

[0203] Based on the above analysis process, in some embodiments, Figure 6 As shown, the iterative eigenvalue that satisfies the iteration stop condition is determined as the target eigenvalue of the target torsional vibration mode, including:

[0204] Step 602 : determining an iteration stop threshold of the target torsional vibration mode in the current iteration according to the iteration characteristic value of the target torsional vibration mode in the current iteration and the historical iteration characteristic value of the target torsional vibration mode in the previous iteration.

[0205] The iteration stop threshold is a preset threshold used to determine whether the iteration can be stopped. In some optional embodiments, when the stability evaluation system obtains the iteration characteristic value of the target torsional vibration mode in the current iteration, it determines the iteration stop threshold of the target torsional vibration mode in the current iteration according to the iteration characteristic value of the target torsional vibration mode in the current iteration and the historical iteration characteristic value of the target torsional vibration mode in the previous iteration. The basis for generating the iteration stop threshold is related to the basis for judging the stability of the characteristic value.

[0206] In some optional embodiments, after obtaining the iterative eigenvalue of the target torsional vibration mode in the current iteration, the stability assessment system calculates the iterative stop threshold of the target torsional vibration mode in the current iteration based on the iterative eigenvalue of the target torsional vibration mode in the current iteration and the historical iterative eigenvalue of the target torsional vibration mode in the previous iteration.

[0207] In some of the embodiments, the iteration stop threshold may be used to characterize the maximum distance between the actual eigenvalue of the actual torsional vibration mode and the iterative eigenvalue of the current iteration.

[0208] Based on the stability judgment basis of eigenvalue theory and the derivation process of the convergence of the method in the previous article, after k iterations, the following relationship will hold:

[0209]

[0210] Scaling the above formula yields:

[0211]

[0212] The above formula is rearranged, where the coefficients are defined as Represents the actual eigenvalue and the iterative eigenvalue at the current iteration Maximum distance between:

[0213]

[0214] Depend on You can get:

[0215]

[0216] Scaling the above formula, we can derive:

[0217]

[0218] based on The expression and the above formula can be obtained:

[0219]

[0220] Based on the eigenvalue stability judgment basis, The sign of can determine the mode state of the target torsional vibration mode. From the above formula, we can see that The symbol and The value of is related, so we can The iteration stop threshold of the target torsional vibration mode under k iterations is determined.

[0221] Step 604 , when the absolute value corresponding to the real part value of the iteration eigenvalue in the iteration is greater than or equal to the iteration stop threshold, it is determined that the iteration eigenvalue of the target torsional vibration mode in the iteration satisfies the iteration stop condition.

[0222] During the actual evaluation, the stability evaluation system compares the absolute value corresponding to the real part value of the iterative eigenvalue in the current iteration with the obtained iteration stop threshold. When the absolute value corresponding to the real part value of the iterative eigenvalue in the current iteration is greater than or equal to the iteration stop threshold, it is determined that the iterative eigenvalue of the target torsional vibration mode in the current iteration meets the iteration stop condition.

[0223] In some of the embodiments, the above-mentioned iteration stopping judgment basis is described:

[0224] From the reasoning process discussed above, we can see that when the condition When satisfied, and The sign of is the same. Therefore, the necessary and sufficient condition to ensure the accuracy of stable judgment with only one iteration is:

[0225]

[0226] The physical meaning of the above iteration stop condition is as follows Figure 7 As shown, Figure 7 Shown is the natural eigenvalue of the natural torsional mode after one iteration The iterative eigenvalue obtained after one iteration and the actual eigenvalues ​​of the actual torsional modes Taking the left half plane as an example, according to the above The expression can be obtained that the actual eigenvalue Located in Circle C 1 The center of the circle is the iterative eigenvalue obtained after one iteration. The radius is In order to ensure that the iterative eigenvalue estimated in one iteration and the actual eigenvalues The real part of the eigenvalue has the same sign, circle C 1 must be located in the left half plane. In the above necessary and sufficient conditions for ensuring the accuracy of stable judgment with only one iteration, the radius Compare Small, so circle C 1 It can be located in the left half plane. After each iteration, if the above necessary and sufficient conditions for ensuring the accuracy of stable judgment can be met with only one iteration, that is, when the absolute value of the iterative eigenvalue of the target torsional vibration mode in the iteration is greater than or equal to the iteration stop threshold, and The sign of will remain the same to ensure accurate stability judgment.

[0227] Step 606: determine the iterative eigenvalue of the target torsional vibration mode in the current iteration as the target eigenvalue of the target torsional vibration mode.

[0228] During actual evaluation, after determining that the iterative eigenvalue of the target torsional vibration mode in the current iteration satisfies the generation stop condition, the stability evaluation system determines the iterative eigenvalue of the target torsional vibration mode in the current iteration as the target eigenvalue of the target torsional vibration mode.

[0229] In the above embodiment, by determining the iteration stop threshold of the target torsional vibration mode in the current iteration based on the iteration characteristic value of the target torsional vibration mode in the current iteration and the historical iteration characteristic value of the target torsional vibration mode in the previous iteration, it is possible to quickly determine whether the iteration characteristic value satisfies the iteration stop condition when the iteration characteristic value of the target torsional vibration mode in the current iteration is obtained, thereby effectively improving the evaluation efficiency of the power system stability evaluation while making a correct stability judgment with the minimum number of iterations.

[0230] The above embodiments are all about how to efficiently and accurately obtain the target characteristic value of the target torsional vibration mode. After obtaining the target characteristic value of the target torsional vibration mode, how to obtain the stability evaluation result of the power system based on the target characteristic value is a crucial application step in the stability evaluation of the entire power system. The following will explain how to obtain the stability evaluation result of the power system based on the target characteristic value from several feasible evaluation schemes.

[0231] In some embodiments, obtaining a stability assessment result of the power system based on the target characteristic value of the target torsional vibration mode includes:

[0232] Based on the target characteristic values ​​of each target torsional vibration mode in the power system, the mode state of the power system in each target torsional vibration mode is determined. According to the mode state of the power system in each target torsional vibration mode, the stability assessment result of the power system is determined.

[0233] Among them, the mode state of the power system in the target torsional vibration mode is a state characterization parameter used to characterize whether the power system will become unstable in the target torsional vibration mode after the generator set is connected to the power system. The stability evaluation result of the power system can be determined by the mode state of the power system in each target torsional vibration mode.

[0234] During the actual evaluation, the stability evaluation system sequentially executes the above-mentioned specific steps of determining the target characteristic value of the target torsional vibration mode through the natural torsional vibration frequency of each target torsional vibration mode to obtain the target characteristic value corresponding to each target torsional vibration mode. Based on the target characteristic value of each target torsional vibration mode, the mode state of the power system in each target torsional vibration mode is determined, and then the stability evaluation result of the power system is determined according to the mode state of the power system in each target torsional vibration mode, so that the stability evaluation result of the power system can be determined more intuitively and quickly.

[0235] Further, in some embodiments, the mode state of the power system in the target torsional vibration mode may include two states: mode instability and mode stability. Based on the target characteristic value of each target torsional vibration mode in the power system, determining the mode state of the power system in each target torsional vibration mode includes:

[0236] When the target characteristic value of the target torsional vibration mode is greater than zero, the mode state of the power system in the target torsional vibration mode is determined to be mode instability. When the target characteristic value of the target torsional vibration mode is less than zero, the mode state of the power system in the target torsional vibration mode is determined to be mode stable.

[0237] Among them, when the mode state in the target torsional vibration mode is mode instability, it can be considered that after the generator set is connected to the power system, the power system may have subsynchronous resonance in the target torsional vibration mode, and there is a risk of instability. When the mode state in the target torsional vibration mode is mode stable, it can be considered that based on the initial parameters of the current generator set, after the generator set is connected to the power system, the possibility of subsynchronous resonance in the power system in the target torsional vibration mode is low, and the power system is relatively stable in the target torsional vibration mode.

[0238] In some optional embodiments, the target eigenvalue of the target torsional vibration mode determined by the stability evaluation system must be the iterative eigenvalue corresponding to the iteration stop condition that is satisfied during the iteration process, that is, the absolute value corresponding to the real part of the target eigenvalue. Under this necessary condition, based on the eigenvalue stability judgment criteria described above, and Figure 7 The distribution relationship between the eigenvalues ​​shown is as follows:

[0239] exist When but The mode state of the power system in the i-th target torsional vibration mode is mode instability. but The mode state of the power system in the i-th target torsional vibration mode is mode stable.

[0240] In the above embodiment, by comparing the real part of the target eigenvalue with zero, it is possible to quickly determine whether the power system has an instability risk in the target torsional vibration mode corresponding to the target eigenvalue, thereby providing a data basis for subsequently determining the stability assessment result of the power system according to the mode state of the power system in each target torsional vibration mode.

[0241] Further, after the stability assessment system obtains the mode state of the power system in each target torsional vibration mode, in some embodiments, the stability assessment result of the power system includes the system state of the power system, and the system state includes system instability and system stability. Determining the stability assessment result of the power system according to the mode state of the power system in each target torsional vibration mode includes:

[0242] When a target torsional vibration mode in the power system has a mode instability, the stability assessment result of the power system is determined to be system instability. When the mode states of the target torsional vibration modes in the power system are mode stable, the stability assessment result of the power system is determined to be system stable.

[0243] During the actual assessment, the stability assessment system determines the stability assessment result of the power system according to the mode state of the power system under each target torsional vibration mode. When the mode state of a target torsional vibration mode in the power system is mode instability, it means that when the generator set is connected to the power system, there must be an instability risk in a target torsional vibration mode. At this time, the stability assessment system determines that the stability assessment result of the power system is system instability. Only when all the mode states of the power system under each target torsional vibration mode are mode stable, can it be determined that after the generator set is connected to the power system, the instability risk value of the power system in any target torsional vibration mode is low, and the stability assessment result of the power system can be determined as system stability.

[0244] In the above embodiment, even if the power system only has the risk of instability in one target torsional vibration mode, the stability assessment system can quickly determine that the stability assessment result of the battery system is system instability, effectively improving the accuracy of subsynchronous resonance risk assessment in the power system.

[0245] In other embodiments, when the user needs to determine the instability level of the power system in addition to determining whether the power system has an instability risk, the stability assessment result of the power system may include the instability level of the power system. The stability assessment result of the power system is determined according to the mode state of the power system in each target torsional vibration mode, including:

[0246] The instability level of the power system is determined according to the mode state of the power system in each target torsional vibration mode and a preset level mapping table.

[0247] The preset level mapping table includes the corresponding relationship between the mode state of the power system in each target torsional vibration mode and the instability level of the power system.

[0248] In some of the embodiments, the designer may predetermine the correspondence between the mode state of the power system in each target torsional vibration mode and the instability level of the power system, generate a preset level mapping table based on the correspondence, and configure the preset level mapping table in the stability assessment system. After determining the mode state of the power system in each target torsional vibration mode, the stability assessment system may search the preset level mapping table based on the mode state of the power system in each target torsional vibration mode to determine the instability level that matches the mode state of the power system in each target torsional vibration mode.

[0249] In some of the embodiments, the instability level of the power system can be determined based on the number of target torsional vibration modes whose mode states are mode instability in the target torsional vibration mode of the power system. For example, in a certain power system, there are 5 target torsional vibration modes, wherein the mode states of the power system in the 5 target torsional vibration modes are all mode instability, then it can be considered that the instability level of the current power system is a high instability level. If the mode state of the power system in 3 target torsional vibration modes is mode instability, then it can be determined that the instability level of the current power system is a medium instability level. If the mode state of the power system in 1 target torsional vibration mode is mode instability, then it can be determined that the instability level of the current power system is a low instability level.

[0250] Designers can generate a level mapping table in advance based on the correspondence between the number of target torsional vibration modes with a mode instability state and the instability level of the power system, and configure it in the stability assessment system. In actual use, the stability assessment system can determine the number of mode instabilities in the power system under each target torsional vibration mode, and then search the preset level mapping table according to the number of mode instabilities to determine the instability level of the current power system.

[0251] In some of the embodiments, the instability level of the power system can be determined according to the type of target torsional vibration mode in which the power system is in a target torsional vibration mode and the mode state is mode instability. For example, there are four target torsional vibration modes A, B, C, and D in the power system. When the power system is in both target torsional vibration modes A and B and the mode state is mode instability, the instability level of the current power system can be considered to be a high instability level. When the power system is in both target torsional vibration modes C and D and the mode state is mode instability, the instability level of the current power system can be considered to be a medium instability level. When the power system is in a mode instability only in the target torsional vibration mode A, the instability level of the current power system can be considered to be a low instability level.

[0252] Designers can generate a level mapping table in advance based on the correspondence between the type of target torsional vibration mode with a mode instability state and the instability level of the power system, and configure it in the stability assessment system. In actual use, the stability assessment system can determine the type of mode instability of the power system under each target torsional vibration mode, and then search the preset level mapping table according to the type of mode instability to determine the instability level of the current power system.

[0253] In the above embodiment, the stability assessment system can not only determine whether the power system has the risk of instability, but also further determine the instability level of the power system according to the mode state of the power system under each target mode, thereby providing effective data reference value for subsequent staff to select a suppression plan for the subsynchronous resonance problem generated in the power system.

[0254] In academia and engineering application fields, the stability of the SSR of the shaft system of thermal power units can be evaluated by two methods: time domain analysis method and frequency domain analysis method. The time domain analysis method includes: eigenvalue analysis method, time domain simulation analysis method, etc.; the frequency domain analysis method includes: complex torque coefficient method (Complex Torque Coefficient Method, CTCM) and impedance analysis method. For the evaluation of the torsional vibration stability of the shaft system of thermal power units, the eigenvalue analysis method and the complex torque coefficient method are mainly used.

[0255] The characteristic analysis method requires detailed modeling of the system and global parameters. Through state-space modeling and eigenvalue calculation, it can identify the complete oscillation mode and modal information of the system. However, for SSR stability analysis, the torsional vibration mode of its shaft system is the most concerned by engineers. It is not direct to analyze SSR using the eigenvalue calculation of the whole system: on the one hand, the amount of calculation is large, and on the other hand, it is time-consuming to extract modal information related to the torsional vibration mode from a large amount of oscillation mode information. However, CTCM is actually a heuristic method with limitations. In practical applications, it may not be able to identify all the torsional vibration modes of interest, nor can it reveal the actual damping level of the torsional vibration mode. Relying solely on D(w 0 ) to judge the stability of the power system may also lead to incorrect stability judgment results. In addition, the calculation cost required to obtain the k(w) and D(w) curves is also high. Therefore, how to propose a more efficient and accurate SSR stability evaluation method to facilitate engineers to make decisions quickly and accurately is a direction worthy of attention.

[0256] Based on this, in some embodiments, such as Figure 8 As shown, a power system stability assessment method is provided, and the method is applied to a power system including a thermal power unit to illustrate the shaft system torsional vibration stability assessment process of the thermal power unit in the power system.

[0257] Step 801: The stability assessment system obtains initial system parameters of the power system and a system space model of the power system.

[0258] Step 802: inputting the initial system parameters into the system space model of the power system to obtain the mode expression of the actual torsional vibration mode in the power system.

[0259] Step 803: Acquire the natural torsional vibration frequency of each target torsional vibration mode in the power system.

[0260] Step 804 , obtaining a Taylor expansion interval of a mode expression corresponding to each target torsional vibration mode according to the natural torsional vibration frequency of each target torsional vibration mode.

[0261] Step 805, performing Taylor series expansion on the pattern expression based on the Taylor expansion interval to obtain an initial expansion expression of the pattern expression and a distance parameter.

[0262] Step 806, performing high-order term ignoring processing on the initial expansion expression to obtain a Taylor expansion expression of the pattern expression.

[0263] Step 807: Substitute the distance parameter into the Taylor expansion expression for iterative solution to obtain the iterative eigenvalue of each target torsional vibration mode.

[0264] Step 808: Determine an iteration stop threshold of the target torsional vibration mode in the current iteration according to the iteration characteristic value of the target torsional vibration mode in the current iteration and the historical iteration characteristic value of the target torsional vibration mode in the previous iteration.

[0265] Step 809, iterate the absolute value corresponding to the real part of the eigenvalue in the current iteration Greater than or equal to the iteration stop threshold In the case of , the iterative eigenvalue of the target torsional vibration mode in the current iteration is determined as the target eigenvalue of the target torsional vibration mode.

[0266] Step 810, when the absolute value corresponding to the real part of the iterative eigenvalue in the current iteration is less than the iteration stop threshold, update the Taylor expansion expression and the distance parameter according to the iterative eigenvalue of the target torsional vibration mode in the current iteration, and return to the step of substituting the distance parameter into the Taylor expansion expression for iterative solution to obtain the iterative eigenvalues ​​of each target torsional vibration mode.

[0267] Step 811 : determining a mode state of the power system in each target torsional vibration mode based on a target characteristic value of each target torsional vibration mode in the power system.

[0268] Step 812, the real part value of the target eigenvalue When is greater than zero, it is determined that the mode state of the power system in the target torsional vibration mode corresponding to the target eigenvalue is mode instability.

[0269] Step 813 : when the real part of the target eigenvalue is less than zero, determine that the mode state of the power system in the target torsional vibration mode corresponding to the target eigenvalue is mode stable.

[0270] Step 814: when there is a target torsional vibration mode in the power system whose mode state is mode instability, determine that the stability assessment result of the power system is system instability.

[0271] Step 815 : when the mode state of each target torsional vibration mode in the power system is mode stability, determining that the stability assessment result of the power system is system stability.

[0272] The above battery system stability evaluation method is verified by experiments as follows.

[0273] Appendix 1 is the eigenvalue analysis results of the first standard example of IEEE subsynchronous resonance (the series compensation degrees are 16%, 24% and 40% respectively). Appendix 1 is as follows:

[0274] Eigenvalue Series compensation degree (0.16) Series compensation degree (0.24) Series compensation degree (0.40) <![CDATA[s 1，2 (TM 1 )]]> -0.24±j99.45 -0.23±j99.53 -0.20±j99.82 <![CDATA[s 3，4 (TM 2 )]]> -0.13±j127.05 -0.13±j127.06 -0.12±j127.11 <![CDATA[s 5，6 (TM 3 )]]> -0.64±j160.72 -0.63±j160.78 0.54±j161.31 <![CDATA[s 7，8 (TM 4 )]]> -0.33±j203.24 0.25±j203.82 -0.35±j202.66 <![CDATA[s 9，10 (TM 5 )]]> -1.85±j298.17 -1.85±j298.17 -1.85±j298.17 <![CDATA[s 11,12 ]]> -0.85±j10.97 -0.91±j11.29 -1.08±j12.04 <![CDATA[s 13,14 ]]> -5.99±j242.79 -6.4±j211.92 -6.61±j164.38 <![CDATA[s 15,16 ]]> -6.59±j510.73 -6.62±j540.84 -6.67±j588.58 <![CDATA[s 17 ]]> -30.22 -30.29 -30.22 <![CDATA[s 18 ]]> -20.47 -20.48 -20.47 <![CDATA[s 19 ]]> -1.86 -1.89 -1.86 <![CDATA[s 20 ]]> -0.68 -0.71 -0.68

[0275] As can be seen from Table 1, there are 20 eigenvalues ​​in the system. In particular, s 1 ~s 5 Reflects the five torsional vibration modes (TM 1 ~TM 5 ), where TM is 24% when the series compensation is 24%. 4 and TM with 40% series compensation 3 It is an unstable mode.

[0276] Fig. 9 This is the complex torque coefficient diagram of the first standard example of IEEE subsynchronous resonance. Fig. 9 It can be seen that TM 1 ~TM 4 Identified by the k(w) curve of the complex torque coefficient method, and TM 5 The torsional vibration mode TM is not identified (omitted) at 24% and 40% series compensation. 4 and TM 3 It is judged to be unstable. It is worth noting that Fig. 9 The first part above shows that the system is unstable in the frequency range of [221.0, 264.7] rad / s. However, Appendix 1 shows that the oscillation mode (242.79 rad / s) is stable when the series compensation is 16%. In summary, the limitations of the complex torque coefficient method are: 1) it cannot identify all oscillation modes; 2) it only relies on the positive or negative sign of the D(w) curve to judge the stability of the system, and the result may be wrong; 3) the complex torque coefficient method cannot reveal the true damping level of the torsional vibration mode.

[0277] Appendix 3 shows the evaluation results of the power system stability evaluation method proposed in this application:

[0278]

[0279] First, the natural torsional vibration mode of the shaft system can be calculated using the given shaft system parameters. At the same time, the natural torsional vibration frequency of the shaft system can also be obtained from the manufacturer. The natural torsional vibration frequency of the first standard example of IEEE subsynchronous resonance is: r1 =98.65,ω r2 =126.92,ω r3 =160.22,ω r4=202.95,ω r5 =298.45rad / s. Then, according to the attached Figure 1 The algorithm flow in , the calculation results after one iteration are listed in Appendix 2. It is worth noting that the constant L is in the range of (0, 1) under all working conditions, which meets the requirements for algorithm convergence. In addition, because Under all conditions, it is greater than Therefore, the necessary and sufficient conditions for the accuracy of stable judgment are met. Obviously, σ i It can not only reveal the SSR stability of the torsional vibration mode of interest (from The sign of the positive or negative judgment) can also reflect the damping of the torsional vibration mode (from The absolute value of the complex torque coefficient method cannot be used. Among them, the unstable torsional vibration mode, that is, the TM at 24% series compensation 4 and TM at 40% series compensation 3 , were accurately identified, and other torsional vibration modes were not misjudged as unstable.

[0280] Accuracy comparison: The proposed subsynchronous resonance stability analysis method can completely detect all torsional vibration modes, while the complex torque coefficient method cannot identify TM in the example. 5 In addition, compared with the characteristic analysis method, the maximum error of the modal damping calculated by the proposed method is only 5.68%, while the value of the damping curve D(w) in the complex torque coefficient method cannot be used for stability evaluation.

[0281] Computational efficiency comparison: The complex torque coefficient method requires full-band scanning within the subsynchronous frequency band to identify the torsional vibration mode. It needs to process a series of nonlinear equations, so the computational burden is large. The eigenvalue analysis method calculates all the eigenvalues ​​of the system, including the oscillation modes we are not interested in. In contrast, the proposed method has high computational efficiency. If the necessary and sufficient conditions for the accuracy of stability judgment are met, only one iteration is required to complete the accurate stability analysis results. The proposed method can quickly calculate a single torsional vibration mode and a group of torsional vibration modes without scanning within a wide frequency band. In the numerical test conducted on a desktop computer with an Intel Core i5 CPU, the complex torque coefficient method and the eigenvalue analysis method took 1.471s and 0.223s to obtain the calculation results, respectively, while the proposed method took only 0.0511s to obtain the stability analysis results. The proposed method has certain significance for improving the efficiency of stability assessment of large power systems.

[0282] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0283] Based on the same inventive concept, the embodiment of the present application also provides a power system stability assessment device for implementing the power system stability assessment method involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in one or more power system stability assessment device embodiments provided below can refer to the limitations of the power system stability assessment method above, and will not be repeated here.

[0284] In some embodiments, Fig.10 As shown, a power system stability assessment device 1000 is provided, comprising: a torsional vibration frequency acquisition module 1001, an expression acquisition module 1002, a solution module 1003 and a stability assessment module 1004, wherein:

[0285] The torsional vibration frequency acquisition module 1001 is used to acquire the natural torsional vibration frequency of the target torsional vibration mode in the power system.

[0286] The expression acquisition module 1002 is used to acquire a mode expression of an actual torsional vibration mode in the power system, where the actual torsional vibration mode is generated according to the initial system parameters of the power system.

[0287] The solving module 1003 is used to solve the eigenvalue of the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain the target eigenvalue of the target torsional vibration mode.

[0288] The stability assessment module 1004 is used to obtain a stability assessment result of the power system based on the target characteristic value.

[0289] The above-mentioned power system stability assessment device obtains the natural torsional vibration frequency of the target torsional vibration mode in the power system, and simultaneously obtains the mode expression of the actual torsional vibration mode in the power system. The mode expression of the actual torsional vibration mode is generated based on the system initial parameters of the power system, and can be used to characterize the system state of the power system under the actual torsional vibration mode. Subsequently, the mode expression of the actual torsional vibration mode is solved for eigenvalues ​​according to the natural torsional vibration frequency of the target torsional vibration mode in the power system, and the target eigenvalue of the target torsional vibration mode can be obtained. There is no need to calculate all the eigenvalues ​​in the system, such as the eigenvalues ​​related to the controller and line dynamics, which can greatly improve the calculation efficiency when performing stability assessment. The obtained target eigenvalue can also accurately reflect the system state of the power system under each target torsional vibration mode. Finally, the stability assessment result of the power system is obtained based on the target eigenvalue, and the assessment efficiency of the stability assessment of the power system is effectively improved while obtaining an accurate stability assessment result of the power system.

[0290] In some embodiments, the solution module is also used to: obtain the Taylor expansion expression and distance parameter of the mode expression according to the natural torsional vibration frequency; the distance parameter is used to characterize the distance between the eigenvalue of the mode expression and the natural torsional vibration frequency; based on the distance parameter, the Taylor expansion expression is solved for the eigenvalue to obtain the target eigenvalue of the target torsional vibration mode.

[0291] In some embodiments, the solution module is also used to: obtain a Taylor expansion interval of the mode expression according to the natural torsional vibration frequency; perform a Taylor series expansion on the mode expression of the actual torsional vibration mode based on the Taylor expansion interval to obtain a Taylor expansion expression of the mode expression, as well as a distance parameter.

[0292] In some embodiments, the solution module is also used to: obtain the Taylor expansion interval of the mode expression according to the natural torsional vibration frequency; perform Taylor series expansion on the mode expression of the actual torsional vibration mode based on the Taylor expansion interval to obtain the initial expansion expression of the mode expression, as well as the distance parameter; and perform high-order term ignoring processing on the initial expansion expression to obtain the Taylor expansion expression of the mode expression.

[0293] In some embodiments, the solution module is also used to: perform eigenvalue solution calculation on the Taylor expansion expression according to the distance parameter to obtain the iterative eigenvalue of the target torsional vibration mode; when the iterative eigenvalue of the target torsional vibration mode does not meet the iteration stop condition, update the Taylor expansion expression and the distance parameter according to the iterative eigenvalue of the target torsional vibration mode in the current iteration, and return to the step of performing eigenvalue solution calculation on the Taylor expansion expression according to the distance parameter to obtain the iterative eigenvalue of the target torsional vibration mode, until the iterative eigenvalue of the target torsional vibration mode in the current iteration meets the iteration stop condition; determine the iterative eigenvalue that meets the iteration stop condition as the target eigenvalue of the target torsional vibration mode.

[0294] In some embodiments, the iterative eigenvalue of the target torsional vibration mode includes the real part value of the iterative eigenvalue; the solution module is also used to: obtain the iterative eigenvalue of the target torsional vibration mode in the current iteration based on the historical iterative eigenvalue and the iterative error value of the target torsional vibration mode in the previous iteration; obtain the real part value of the iterative eigenvalue in the current iteration based on the historical real part value of the historical iterative eigenvalue of the target torsional vibration mode in the previous iteration and the iterative error value; update the Taylor expansion expression and distance parameter based on the iterative eigenvalue of the target torsional vibration mode in the current iteration and the real part value of the iterative eigenvalue.

[0295] In some embodiments, the solution module is further used to: differentiate the historical iteration characteristic value of the target torsional vibration mode in the previous iteration to obtain an iteration error value.

[0296] In some embodiments, the solution module is also used to: determine the iteration stop threshold of the target torsional vibration mode in the current iteration based on the iteration eigenvalue of the target torsional vibration mode in the current iteration and the historical iteration eigenvalue of the target torsional vibration mode in the previous iteration; determine that the iteration eigenvalue of the target torsional vibration mode in the current iteration meets the iteration stop condition when the absolute value corresponding to the real part value of the iteration eigenvalue in the current iteration is greater than or equal to the iteration stop threshold; determine the iteration eigenvalue of the target torsional vibration mode in the current iteration as the target eigenvalue of the target torsional vibration mode.

[0297] In some embodiments, the stability assessment module is also used to: determine the mode state of the power system under each target torsional vibration mode based on the target characteristic value of each target torsional vibration mode in the power system; and determine the stability assessment result of the power system according to the mode state of the power system under each target torsional vibration mode.

[0298] In some embodiments, the mode state includes mode instability and mode stability; the stability assessment module is further configured to:

[0299] When the real part of the target eigenvalue is greater than zero, the mode state of the power system in the target torsional vibration mode corresponding to the target eigenvalue is determined to be mode instability; when the real part of the target eigenvalue is less than zero, the mode state of the power system in the target torsional vibration mode corresponding to the target eigenvalue is determined to be mode stable.

[0300] In some embodiments, the stability assessment result of the power system includes the system state of the power system, and the system state includes system instability and system stability; the stability assessment module is also used to: when there is a target torsional vibration mode in the power system whose mode state is mode instability, determine the stability assessment result of the power system to be system instability; when the mode state of each target torsional vibration mode in the power system is mode stability, determine the stability assessment result of the power system to be system stability.

[0301] In some embodiments, the stability assessment result of the power system includes the instability level of the power system; the stability assessment module is also used to: determine the instability level of the power system based on a mode state of the power system in each target torsional vibration mode and a preset level mapping table; the preset level mapping table includes the correspondence between the mode state of the power system in each target torsional vibration mode and the instability level of the power system.

[0302] In some embodiments, the expression acquisition module is further used to: acquire system initial parameters of the power system; input the system initial parameters into the system space model of the power system to obtain the mode expression of the actual torsional vibration mode in the power system.

[0303] Each module in the above-mentioned power system stability assessment device can be implemented in whole or in part by software, hardware and a combination thereof. Each of the above-mentioned modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute the operations corresponding to each of the above modules.

[0304] In some embodiments, a computer device is provided. The computer device may be a server integrated with a stability evaluation system. The internal structure diagram thereof may be as follows: Fig.11 As shown. The computer device includes a processor, a memory and a network interface connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store data such as the natural torsional vibration frequency of the target torsional vibration mode, the mode expression of the actual torsional vibration mode, the target characteristic value of the target torsional vibration mode, etc. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a method for evaluating the stability of a power system is implemented.

[0305] Those skilled in the art will understand that Fig.11 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0306] In some embodiments, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, specific implementation steps of the above-mentioned power system stability assessment method are implemented.

[0307] In some embodiments, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the specific implementation steps of the above-mentioned power system stability assessment method are implemented.

[0308] In some embodiments, a computer program product is provided, including a computer program, which, when executed by a processor, implements the specific implementation steps of the above-mentioned power system stability assessment method.

[0309] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0310] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but are not limited to this.

[0311] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0312] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for evaluating the stability of a power system, characterized in that: The method comprises: Obtaining the natural torsional vibration frequency of the target torsional vibration mode in the power system; Acquire a mode expression of an actual torsional vibration mode in the power system, wherein the mode expression of the actual torsional vibration mode is generated according to an initial system parameter of the power system; Solving the eigenvalue of the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain the target eigenvalue of the target torsional vibration mode; A stability assessment result of the electric power system is obtained based on the target characteristic value of the target torsional vibration mode.

2. The method according to claim 1, characterized in that The performing eigenvalue solving on the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain the target eigenvalue of the target torsional vibration mode includes: Obtaining a Taylor expansion expression and a distance parameter of the mode expression according to the natural torsional vibration frequency; the distance parameter is used to characterize the distance between the characteristic value of the mode expression and the natural torsional vibration frequency; The Taylor expansion expression is subjected to eigenvalue solution calculation based on the distance parameter to obtain a target eigenvalue of the target torsional vibration mode.

3. The method according to claim 2, characterized in that The Taylor expansion expression and distance parameter of the mode expression obtained according to the natural torsional vibration frequency include: Obtaining a Taylor expansion interval of the mode expression according to the natural torsional vibration frequency; The mode expression of the actual torsional vibration mode is subjected to Taylor series expansion based on the Taylor expansion interval to obtain a Taylor expansion expression of the mode expression and a distance parameter.

4. The method according to claim 2, characterized in that: The Taylor expansion expression and distance parameter of the mode expression obtained according to the natural torsional vibration frequency include: Obtaining a Taylor expansion interval of the mode expression according to the natural torsional vibration frequency; Performing Taylor series expansion on the mode expression of the actual torsional vibration mode based on the Taylor expansion interval to obtain an initial expansion expression of the mode expression and a distance parameter; The initial expansion expression is subjected to a high-order term ignoring process to obtain a Taylor expansion expression of the pattern expression.

5. The method according to any one of claims 2 to 4, characterized in that: The performing eigenvalue calculation on the Taylor expansion expression according to the distance parameter to obtain the target eigenvalue of the target torsional vibration mode includes: Performing eigenvalue calculation on the Taylor expansion expression according to the distance parameter to obtain an iterative eigenvalue of the target torsional vibration mode; In the case where the iterative eigenvalue of the target torsional vibration mode does not satisfy the iteration stop condition, the Taylor expansion expression and the distance parameter are updated according to the iterative eigenvalue of the target torsional vibration mode in the current iteration, and the step of performing eigenvalue solution calculation on the Taylor expansion expression according to the distance parameter to obtain the iterative eigenvalue of the target torsional vibration mode is returned until the iterative eigenvalue of the target torsional vibration mode in the current iteration satisfies the iteration stop condition; An iterative eigenvalue satisfying the iteration stop condition is determined as a target eigenvalue of the target torsional vibration mode.

6. The method according to claim 5, characterized in that The iterative eigenvalue of the target torsional vibration mode includes a real part value of the iterative eigenvalue; The updating of the Taylor expansion expression and the distance parameter according to the iterative eigenvalue of the target torsional vibration mode in the current iteration includes: Obtaining an iterative eigenvalue of the target torsional vibration mode in the current iteration according to a historical iterative eigenvalue and an iterative error value of the target torsional vibration mode in the previous iteration; Obtaining the real part value of the iterative eigenvalue in the current iteration according to the historical real part value of the historical iterative eigenvalue of the target torsional vibration mode in the previous iteration and the iterative error value; The Taylor expansion expression and the distance parameter are updated based on the iterative eigenvalue of the target torsional vibration mode in the current iteration and the real part value of the iterative eigenvalue.

7. The method according to claim 6, characterized in that The method further comprises: The iteration error value is obtained by differentiating the historical iteration eigenvalue of the target torsional vibration mode in the previous iteration.

8. The method according to claim 6, characterized in that The step of determining the iterative eigenvalue satisfying the iteration stop condition as the target eigenvalue of the target torsional vibration mode comprises: Determining an iteration stop threshold of the target torsional vibration mode in the current iteration according to an iteration characteristic value of the target torsional vibration mode in the current iteration and a historical iteration characteristic value of the target torsional vibration mode in the previous iteration; When the absolute value corresponding to the real part value of the iterative eigenvalue in the current iteration is greater than or equal to the iteration stop threshold, determining that the iterative eigenvalue of the target torsional vibration mode in the current iteration satisfies the iteration stop condition; The iterative eigenvalue of the target torsional vibration mode in the current iteration is determined as the target eigenvalue of the target torsional vibration mode.

9. The method according to claim 8, characterized in that The step of obtaining a stability assessment result of the power system based on the target characteristic value of the target torsional vibration mode includes: determining a mode state of the power system in each of the target torsional vibration modes based on a target characteristic value of each of the target torsional vibration modes in the power system; A stability evaluation result of the electric power system is determined according to a mode state of the electric power system in each of the target torsional vibration modes.

10. The method according to claim 9, characterized in that The mode state includes mode instability and mode stability; the determining the mode state of the power system in each of the target torsional vibration modes based on the target characteristic value of each of the target torsional vibration modes in the power system includes: When the real part value of the target characteristic value is greater than zero, determining that the mode state of the power system in the target torsional vibration mode corresponding to the target characteristic value is mode instability; When the real part value of the target eigenvalue is less than zero, it is determined that the mode state of the power system in the target torsional vibration mode corresponding to the target eigenvalue is mode stable.

11. The method according to claim 9 or 10, characterized in that: The stability assessment result of the power system includes a system state of the power system, and the system state includes system instability and system stability; The determining the stability assessment result of the power system according to the mode state of the power system in each of the target torsional vibration modes includes: When there is a target torsional vibration mode in the power system whose mode state is mode instability, determining that a stability assessment result of the power system is system instability; When the mode state of each of the target torsional vibration modes in the power system is mode stable, it is determined that the stability evaluation result of the power system is system stable.

12. The method according to claim 9 or 10, characterized in that: The stability assessment result of the power system includes the instability level of the power system; The determining the stability assessment result of the power system according to the mode state of the power system in each of the target torsional vibration modes includes: The instability level of the power system is determined according to a mode state of the power system in each of the target torsional vibration modes and a preset level mapping table; the preset level mapping table includes a correspondence between the mode state of the power system in each of the target torsional vibration modes and the instability level of the power system.

13. The method according to any one of claims 1 to 12, characterized in that: The method of obtaining a mode expression for an actual torsional vibration mode in the power system includes: Acquiring initial system parameters of the power system; The initial system parameters are input into the system space model of the power system to obtain a mode expression of an actual torsional vibration mode in the power system.

14. A power system stability assessment device, characterized in that: The device comprises: A torsional vibration frequency acquisition module, used to acquire the natural torsional vibration frequency of a target torsional vibration mode in the power system; An expression acquisition module, used to acquire a mode expression of an actual torsional vibration mode in the power system, wherein the actual torsional vibration mode is generated according to an initial system parameter of the power system; A solution module, used for performing an eigenvalue solution on the mode expression of the actual torsional vibration mode according to the natural torsional vibration frequency to obtain a target eigenvalue of the target torsional vibration mode; A stability assessment module is used to obtain a stability assessment result of the power system based on the target characteristic value.

15. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 13 are implemented.

16. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 13 are implemented.

17. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 13 are implemented.

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