Power system dynamic broadband signal measurement method and system based on time-frequency domain analysis

Abstract

The present invention discloses a method and system for measuring dynamic broadband signals of an electric power system based on time-frequency domain analysis, including: using trigonometric functions to describe the dynamic change characteristics of the dynamic broadband signals of the electric power system, and constructing a dynamic broadband signal measurement model of the electric power system; using the Prony algorithm in the time domain to extract the fundamental wave, harmonic and interharmonic signals of the electric power system; using the dynamic broadband signal measurement model of the electric power system, screening the real frequency components in the fundamental wave, harmonic and interharmonic signals of the electric power system, and extracting their frequency parameters; using a variable-length sampling window to adjust the signal sampling window length to capture the dynamic change characteristics of the broadband signal, and constructing a dynamic broadband signal frequency domain model; and solving the dynamic broadband signal frequency domain model to obtain the amplitude and phase of the broadband signal of the electric power system. The present invention can overcome the problems of failure of existing methods when the amplitude of harmonics or interharmonics fluctuates and difficulty in selecting real harmonic / interharmonic signals, and realize accurate measurement of dynamic broadband signals of the electric power system.

Description

Technical Field

[0001] The present invention relates to the field of power system signal measurement, and in particular to a method and system for measuring dynamic broadband signals of a power system based on time-frequency domain analysis. Background Art

[0002] With the large-scale access of a high proportion of renewable energy generation to the power grid and the widespread application of power electronic equipment, the harmonic and interharmonic content in the power system has increased year by year, which will lead to a series of problems such as increased network losses, communication interference and harmonic resonance. At the same time, when the power system load fluctuates, sub / supersynchronous oscillations, harmonic / interharmonic oscillations or harmonic resonances occur, the amplitudes of the fundamental wave, harmonics and interharmonics no longer remain constant. Accurately measuring the dynamic broadband signal of the power system is crucial for the management and control of harmonic and interharmonic problems.

[0003] At present, the commonly used harmonic / interharmonic estimation methods can be divided into two categories: fast Fourier analysis (FFT) and its improved methods and modern spectrum analysis methods. Existing method 1: Fast Fourier transform is the most common harmonic / interharmonic parameter estimation method, but it is only applicable to signals with constant amplitude and spectrum, and is often affected by spectrum leakage and fence effect. Its improved methods include multi-layer interpolation method, full-phase Fourier method and adjacent interharmonic estimation method. Among them, the multi-layer interpolation method uses an appropriate window function to suppress spectrum leakage, and then uses three or five spectrum lines to interpolate and fit the real spectrum line to estimate the harmonic / interharmonic parameters; the full-phase Fourier method superimposes multiple monitoring data to eliminate the phase change caused by Fourier transform and suppress spectrum leakage interference. The adjacent interharmonic estimation method uses the amplitude difference of the spectrum lines on both sides of the main spectrum line to judge the category of the adjacent interharmonic and estimate its parameters. However, these methods fail when the amplitude of the harmonic or interharmonic fluctuates. Existing method 2: Modern spectral analysis methods mainly include rotational invariance method and matrix bundle method. These methods often decompose power system signals into many frequency signals, but cannot determine which signals are real. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing methods fail when the amplitude of harmonics or interharmonics fluctuates, and the real harmonic / interharmonic signals are difficult to select, the dynamic broadband signal of the power system is difficult to be accurately measured, and the dynamic signal cannot be measured; the purpose of the present invention is to provide a method and system for measuring dynamic broadband signals of a power system based on time-frequency domain analysis. The present invention is a method for measuring dynamic broadband signals of a power system based on synchronous analysis of time-frequency domains, which can overcome the problems of the existing methods failing when the amplitude of harmonics or interharmonics fluctuates, and the real harmonic / interharmonic signals are difficult to select, and realize the accurate measurement of dynamic broadband signals of the power system. The present invention can help the staff to further carry out the management and control of harmonics and interharmonics, and the research has practical engineering significance.

[0005] The present invention is achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for measuring dynamic broadband signals of a power system based on time-frequency domain analysis, the method comprising:

[0007] The dynamic characteristics of the dynamic broadband signal of the power system are described by using trigonometric functions, and the measurement model of the dynamic broadband signal of the power system is constructed;

[0008] The Prony algorithm is used in the time domain to extract the fundamental wave, harmonic and interharmonic signals of the power system; the dynamic broadband signal measurement model of the power system is used to screen the real frequency components in the fundamental wave, harmonic and interharmonic signals of the power system, and extract their frequency parameters;

[0009] The signal sampling window length is adjusted using a variable-length sampling window to capture the dynamic change characteristics of the broadband signal and to construct a frequency domain model of the dynamic broadband signal. The frequency domain model of the dynamic broadband signal is then solved to obtain the amplitude and phase parameters of the broadband signal of the power system.

[0010] Furthermore, a dynamic broadband signal measurement model for the power system is constructed, including:

[0011] A1: When the power system has subsynchronous / supersynchronous oscillation, harmonic / interharmonic oscillation or harmonic resonance, the amplitude of harmonics and interharmonics changes. At this time, the dynamic broadband signal expression of the power system containing harmonics and interharmonics is expressed as:

[0012]

[0013] In the formula, x h [n] is the fundamental wave, harmonic or interharmonic; a h [n] is x h The amplitude of the dynamic change of h For x h The frequency of h is the sampling frequency; For x h phase angle; in particular, x1[n] is the fundamental wave, a1[n], f1 and are the amplitude, frequency and phase angle of the fundamental wave respectively.

[0014] A2: Use trigonometric functions to convert the dynamic amplitude a in the dynamic broadband signal of the power system h [n] is modulated to obtain the modulated dynamic amplitude; the modulation formula is:

[0015]

[0016] In the formula, F 0,h , and is the fitting coefficient, is the fitting frequency, and Δt is the sampling time interval;

[0017] A3: Substitute the modulated dynamic amplitude into the expression of the dynamic broadband signal of the power system to obtain the measurement model of the dynamic broadband signal of the power system; the expression of the measurement model x[n] of the dynamic broadband signal of the power system is:

[0018]

[0019] Furthermore, each frequency component in the power system dynamic broadband signal measurement model x[n] is:

[0020]

[0021] Where:

[0022]

[0023]

[0024]

[0025] In the formula, x h [n] is the fundamental wave, harmonic or interharmonic; a h [n] is x h The amplitude of the dynamic change of h For x h The frequency of h is the sampling frequency; For x h The phase angle of 0,h , and is the fitting coefficient, is the fitting frequency, and Δt is the sampling time interval; F * for and function.

[0026] Furthermore, the dynamic broadband signal measurement model of the power system is used to screen the real frequency components in the fundamental wave, harmonic and interharmonic signals of the power system, and extract their frequency parameters, including:

[0027] According to the dynamic broadband signal measurement model of the power system, if the amplitudes of the fundamental wave, harmonics and interharmonics change, they are mathematically decomposed into three frequency components with constant amplitude and symmetrical frequency;

[0028] The estimated frequency {f est,1 ,...,f est,6H} Every three are screened and judged, if they meet f est,i-1 +f est,i+1 =2fest,i , then it means f est,i is the true frequency; and the estimated frequency {f est,1 ,...,f est,6H The true positive frequency in} is denoted as {f real,1 ,...,f real,H}.

[0029] Furthermore, a variable-length sampling window is used to adjust the signal sampling window length to capture the dynamic change characteristics of the broadband signal, and a dynamic broadband signal frequency domain model is constructed, including:

[0030] Construct a variable-length sampling window function W(n,λ), and construct a column vector L that is consistent with the length of the sampling window W(n,λ);

[0031] Perform sliding window sampling on the dynamic broadband signal x[n] of the power system, and determine the window length N of the variable length sampling window by the dynamic factor η;

[0032] Perform Fourier transform on the dynamic broadband signal x[n] of the power system and convert the dynamic amplitude a h [n] Using Taylor formula expansion, the frequency domain model of dynamic broadband signal is obtained; the frequency domain model of dynamic broadband signal is:

[0033]

[0034] Where H is the total number of frequency components in the sampled signal, I is the Taylor expansion order, and f s is the sampling rate, N is the number of sampling points, is the phase parameter of the fundamental wave, harmonic or interharmonic, f h is the frequency parameter of the fundamental wave, harmonic or interharmonic, is the amplitude fitting coefficient.

[0035] Furthermore, the frequency domain model of the dynamic broadband signal is solved to obtain the amplitude and phase parameters of the broadband signal of the power system, including:

[0036] According to the extracted true positive frequency {f real，1 , ..., f real，H}, rewrite the frequency domain model of dynamic broadband signal into equation; the form is:

[0037] x[k]=AB+CD

[0038] Where:

[0039]

[0040]

[0041]

[0042] In the formula, A, B, C, and D are all vectors, and f real,1 ,...,f real,H is the true frequency screened out, f s is the sampling rate, N is the number of sampling points, is the phase parameter, and is the amplitude fitting coefficient, H is the total number of frequency components in the sampled signal, and I is the Taylor expansion order.

[0043] Solve the equations to obtain the phase and dynamically changing amplitude of the fundamental wave, harmonics, and interharmonics.

[0044] Furthermore, the amplitude of the dynamic change a h The calculation formula for [n] is:

[0045] In a second aspect, the present invention further provides a power system dynamic broadband signal measurement system based on time-frequency domain analysis, the system using the above-mentioned power system dynamic broadband signal measurement method based on time-frequency domain analysis; the system comprises:

[0046] A dynamic broadband signal measurement model building unit is used to describe the dynamic change characteristics of the dynamic broadband signal of the power system by using trigonometric functions, and to build a dynamic broadband signal measurement model of the power system;

[0047] The real frequency screening unit is used to extract the fundamental wave, harmonic and interharmonic signals of the power system using the Prony algorithm in the time domain; the real frequency components in the fundamental wave, harmonic and interharmonic signals of the power system are screened using the dynamic broadband signal measurement model of the power system, and their frequency parameters are extracted;

[0048] The amplitude and phase parameter calculation unit is used to adjust the signal sampling window length using a variable length sampling window to capture the dynamic change characteristics of the broadband signal, build a dynamic broadband signal frequency domain model; and solve the dynamic broadband signal frequency domain model to obtain the amplitude and phase parameters of the broadband signal of the power system.

[0049] Furthermore, the execution process of the dynamic broadband signal measurement model building unit is:

[0050] When the power system experiences subsynchronous / supersynchronous oscillation, harmonic / interharmonic oscillation or harmonic resonance, the amplitude of harmonics and interharmonics changes. At this time, the dynamic broadband signal expression of the power system containing harmonics and interharmonics is expressed as:

[0051]

[0052] In the formula, x h [n] is the fundamental wave, harmonic or interharmonic; a h [n] is xh The amplitude of the dynamic change of h For x h The frequency of h is the sampling frequency; For x h phase angle; in particular, x1[n] is the fundamental wave, a1[n], f1 and are the amplitude, frequency and phase angle of the fundamental wave respectively.

[0053] The dynamic amplitude a in the dynamic broadband signal of the power system is converted into h [n] is modulated to obtain the modulated dynamic amplitude; the modulation formula is:

[0054]

[0055] In the formula, F 0,h , and is the fitting coefficient, f h (*) is the fitting frequency, Δt is the sampling time interval;

[0056] Substitute the modulated dynamic amplitude into the expression of the dynamic broadband signal of the power system to obtain the dynamic broadband signal measurement model of the power system; the expression of the dynamic broadband signal measurement model x[n] of the power system is:

[0057]

[0058] Furthermore, the execution process of the real frequency screening unit is:

[0059] According to the dynamic broadband signal measurement model of the power system, if the amplitudes of the fundamental wave, harmonics and interharmonics change, they are mathematically decomposed into three frequency components with constant amplitude and symmetrical frequency;

[0060] The estimated frequency {f est,1 ,...,f est,6H} Every three are screened and judged, if they meet f est,i-1 +f est,i+1 =2f est,i , then it means f est,i is the true frequency; and the estimated frequency {f est,1 ,...,f est,6H The true positive frequency in} is denoted as {f real,1 ,...,f real,H}.

[0061] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0062] The present invention is based on a method and system for measuring dynamic broadband signals of an electric power system based on time-frequency domain analysis. First, the present invention uses trigonometric functions to modulate the signal amplitude, and constructs a dynamic broadband signal measurement model for an electric power system that can characterize changes in signal amplitude, thereby overcoming the defect that existing methods cannot measure dynamic signals; then, the Prony algorithm is used to decompose the signal to be measured, and it is proposed to use trigonometric function modulation rules to screen the real frequency components, thereby solving the problem that existing methods cannot distinguish whether the frequency components actually exist; finally, a variable-length sampling window is proposed to capture the dynamic change characteristics of broadband signals, and a dynamic broadband signal frequency domain model is constructed, thereby further improving the accuracy of the method of the present invention, and the measurement results are more real, objective and reasonable. The present invention can overcome the problems that the existing methods fail when the harmonic or interharmonic amplitude fluctuates, and that the real harmonic / interharmonic signals are difficult to select, thereby realizing the accurate measurement of dynamic broadband signals of the electric power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0064] Figure 1 This is a flow chart of a method for measuring dynamic broadband signals in a power system based on time-frequency domain analysis according to the present invention;

[0065] Figure 2 A schematic diagram of relative error and error distribution of the parameters of each frequency component estimated by the method of the present invention and other methods;

[0066] Figure 3 The present invention is a structural block diagram of the power system dynamic broadband signal measurement system based on time-frequency domain analysis. DETAILED DESCRIPTION

[0067] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0068] Based on the defects of the existing harmonic / interharmonic measurement method that strictly requires the amplitude of the signal to be measured to be constant and cannot determine whether the separated frequency components actually exist, the existing method fails when the harmonic or interharmonic amplitude fluctuates, and the real harmonic / interharmonic signal is difficult to select, the dynamic broadband signal of the power system is difficult to be accurately measured, and the dynamic signal cannot be measured; the present invention designs a power system dynamic broadband signal measurement method and system based on time-frequency domain analysis. The present invention is a power system dynamic broadband signal measurement based on time-frequency domain synchronous analysis, which can overcome the problems of the existing method failing when the harmonic or interharmonic amplitude fluctuates and the real harmonic / interharmonic signal is difficult to select, and realize the accurate measurement of the dynamic broadband signal of the power system. The present invention can help the staff to further carry out the management and control of harmonics and interharmonics, and the research has practical engineering significance.

[0069] Firstly, the present invention uses trigonometric function to modulate the signal amplitude and constructs a dynamic broadband signal measurement model for the power system which can characterize the change of signal amplitude, thereby overcoming the defect that the existing method cannot measure dynamic signals; then, the Prony algorithm is used to decompose the signal to be measured and the trigonometric function modulation rule is proposed to screen the real frequency components, thereby solving the problem that the existing method cannot distinguish whether the frequency components actually exist; finally, a variable length sampling window is proposed to capture the dynamic change characteristics of broadband signals and construct a frequency domain model of dynamic broadband signals, thereby further improving the accuracy of the method of the present invention and making the measurement results more real, objective and reasonable.

[0070] Example 1

[0071] like Figure 1 As shown, the present invention provides a method for measuring dynamic broadband signals in a power system based on time-frequency domain analysis, the method comprising:

[0072] Step A: Use trigonometric functions to describe the dynamic change characteristics of the dynamic broadband signal of the power system and construct a dynamic broadband signal measurement model for the power system;

[0073] Step A specifically includes:

[0074] A1: When the power system has subsynchronous / supersynchronous oscillation, harmonic / interharmonic oscillation or harmonic resonance, the amplitude of harmonics and interharmonics changes. At this time, the dynamic broadband signal expression of the power system containing harmonics and interharmonics is expressed as:

[0075]

[0076] In the formula, x h [n] is the fundamental wave, harmonic or interharmonic; a h [n] is x h The amplitude of the dynamic change of h For x h The frequency ofh is the sampling frequency; For x h phase angle; in particular, x1[n] is the fundamental wave, a1[n], f1 and are the amplitude, frequency and phase angle of the fundamental wave respectively.

[0077] A2: Use trigonometric functions to convert the dynamic amplitude a in the dynamic broadband signal of the power system h [n] is modulated to obtain the modulated dynamic amplitude; the modulation formula is:

[0078]

[0079] In the formula, F 0,h , and is the fitting coefficient, f h (*) is the fitting frequency, Δt is the sampling time interval;

[0080] A3: Substitute the modulated dynamic amplitude into the expression of the dynamic broadband signal of the power system to obtain the measurement model of the dynamic broadband signal of the power system; the expression of the measurement model x[n] of the dynamic broadband signal of the power system is:

[0081]

[0082] Simplifying equation (3), each frequency component in the power system dynamic broadband signal measurement model x[n] is:

[0083]

[0084] Where:

[0085]

[0086]

[0087]

[0088] In the formula, x h [n] is the fundamental wave, harmonic or interharmonic; a h [n] is x h The amplitude of the dynamic change of h For x h The frequency of h is the sampling frequency; For x h The phase angle of 0,h , and is the fitting coefficient, f h (*)is the fitting frequency, Δt is the sampling time interval; F * for and function.

[0089] Step B: Using the Prony algorithm in the time domain to extract the fundamental wave, harmonic and interharmonic signals of the power system; using the dynamic broadband signal measurement model of the power system to screen the real frequency components in the fundamental wave, harmonic and interharmonic signals of the power system, and extract their frequency parameters;

[0090] Step B specifically includes:

[0091] Using Euler's formula, we write equation (4) in complex signal form and consider noise interference, and the amplitude is uniformly recorded as A h , the frequency is uniformly recorded as f h , the phase is unified as have:

[0092]

[0093] In the formula, ξ is the noise. Also note:

[0094]

[0095] Formula (9) is the homogeneous solution of the linear difference equation with constant coefficients, and the polynomial is defined as:

[0096]

[0097] According to formula (10), we have:

[0098]

[0099] Multiply both sides of equation (11) by b i And the sum is:

[0100]

[0101] Rewrite equation (12) into the matrix form shown in equation (13) and solve to obtain the parameters {b1,...,b 6H};

[0102]

[0103] Using the solved parameters {b1,...,b 6H}Construct characteristic polynomial (14) and solve it to obtain the frequencies of fundamental wave, harmonics and interharmonics in power system signal {f est,1 ,...,f est,6H}.

[0104] 1+b1z -1+…+b 2M z -2M =0 (14)

[0105] According to the dynamic broadband signal measurement model of the power system (Equation (4)), if the amplitudes of the fundamental wave, harmonics and interharmonics change, they are mathematically decomposed into three frequency components with constant amplitude and symmetrical frequency. Therefore, the estimated frequency {f est,1 ,...,f est,6H} Every three are screened and judged, if they meet f est,i-1 +f est,i+1 =2f est,i , then it means f est,i is the true frequency; and the estimated frequency {f est,1 ,...,f est,6H The true positive frequency in} is denoted as {f real,1 ,...,f real,H}.

[0106] Step C: Use a variable-length sampling window to adjust the signal sampling window length to capture the dynamic change characteristics of the broadband signal, and construct a dynamic broadband signal frequency domain model; and solve the dynamic broadband signal frequency domain model to obtain the amplitude and phase parameters of the power system broadband signal.

[0107] Step C specifically includes:

[0108] Construct a variable length sampling window function W(n,λ);

[0109]

[0110] In the above formula, N0 represents the initial sampling window length. The scaling factor λ is used to control the length N of the window function W(n,λ). When a fast signal change is detected, the scaling factor λ is used to reduce the sampling window length to ensure that formula (2) is sufficient to describe the dynamic characteristics of the dynamic harmonics.

[0111] Construct a column vector L with the same length as the sampling window W(n,λ):

[0112] L=[e -100πΔt·0 ,e -100πΔt·1 ,...,e -100πΔt·(N-1) ] T (16)

[0113] Sliding window sampling is performed on the dynamic broadband signal x[n] of the power system, and the initial window length is N0. Then the first frame signal x (1) [n] The number of steps from time n=0 to time n=N0-1. The second frame signal x (2) [n] The order starts from time n=N0 / 2 to time n=3N0 / 2-1. The third frame signal is the same, denoted by x(3) [n].

[0114] Define the dynamic factor as η:

[0115]

[0116] In the formula, [W(n,λ)x (1) [n]] represents the conversion of W(n,λ)x (1) [n] is written as a column vector.

[0117] The present invention defines a dynamic factor η that can be used to characterize the speed of the dynamic deviation change between two frame signals. If the dynamic factor is greater than a threshold σ (recommended to be 0.3), it means that the current frame signal changes at a faster rate, and the scale expansion factor λ should be increased to avoid errors. Until the dynamic factor is greater than the threshold σ, the window length N of the variable length sampling window is determined.

[0118] Perform Fourier transform on equation (1) and convert the dynamic amplitude a h [n] Using Taylor formula expansion, the frequency domain model of dynamic broadband signal is obtained; the frequency domain model of dynamic broadband signal is:

[0119]

[0120] Where H is the total number of frequency components in the sampled signal, I is the Taylor expansion order, and f s is the sampling rate, N is the number of sampling points, is the phase parameter of the fundamental wave, harmonic or interharmonic, f h is the frequency parameter of the fundamental wave, harmonic or interharmonic, is the amplitude fitting coefficient.

[0121] According to the real positive frequency {f real,1 ,...,f real,H}, rewrite equation (18) into equation form:

[0122] x[k]=AB+CD (19)

[0123] Where:

[0124]

[0125]

[0126]

[0127]

[0128] In the formula, A, B, C, and D are all vectors, and f real,1 ,...,f real,His the true frequency screened out, f s is the sampling rate, N is the number of sampling points, is the phase parameter, and is the amplitude fitting coefficient, H is the total number of frequency components in the sampled signal, and I is the Taylor expansion order.

[0129] Solve equation (19) to obtain the phase of the fundamental wave, harmonics and interharmonics and amplitude fitting coefficient and the amplitude of dynamic changes.

[0130] Dynamically changing amplitude a h The calculation formula for [n] is:

[0131]

[0132] In specific implementation, if the power oscillation signal monitored in the power system is expressed by equation (25) and equation (26):

[0133]

[0134]

[0135] The amplitude and frequency parameters of each frequency component in the monitoring signal are shown in Table 1. For no loss of generality, the phase is set to 0.

[0136] Table 1 Frequency component parameters

[0137]

[0138] The parameters of each frequency component are estimated using the method proposed in the present invention, the interpolation Fourier method, the matrix bundle method and the multi-layer interpolation method. Since the amplitude of the dynamic broadband signal is changing, the vector relative error between the estimated signal and the actual signal is used as an indicator to measure the accuracy of the algorithm. The relative errors of the seven frequency components calculated by each method are as follows: Figure 2 The error distribution of each method is shown in Figure a-g. Figure 2 Obviously, the method proposed by the present invention has the smallest overall error and can measure dynamic broadband signals more accurately and effectively.

[0139] Example 2

[0140] like Figure 3 As shown, the difference between this embodiment and embodiment 1 is that this embodiment further provides a power system dynamic broadband signal measurement system based on time-frequency domain analysis, and the system uses the power system dynamic broadband signal measurement method based on time-frequency domain analysis in embodiment 1; the system includes:

[0141] A dynamic broadband signal measurement model building unit is used to describe the dynamic change characteristics of the dynamic broadband signal of the power system by using trigonometric functions, and to build a dynamic broadband signal measurement model of the power system;

[0142] The real frequency screening unit is used to extract the fundamental wave, harmonic and interharmonic signals of the power system using the Prony algorithm in the time domain; the real frequency components in the fundamental wave, harmonic and interharmonic signals of the power system are screened using the dynamic broadband signal measurement model of the power system, and their frequency parameters are extracted;

[0143] The amplitude and phase parameter calculation unit is used to adjust the signal sampling window length using a variable length sampling window to capture the dynamic change characteristics of the broadband signal, build a dynamic broadband signal frequency domain model; and solve the dynamic broadband signal frequency domain model to obtain the amplitude and phase parameters of the broadband signal of the power system.

[0144] As a further implementation, the execution process of the dynamic broadband signal measurement model building unit is:

[0145] When the power system experiences subsynchronous / supersynchronous oscillation, harmonic / interharmonic oscillation or harmonic resonance, the amplitude of harmonics and interharmonics changes. At this time, the dynamic broadband signal expression of the power system containing harmonics and interharmonics is expressed as:

[0146]

[0147] In the formula, x h [n] is the fundamental wave, harmonic or interharmonic; a h [n] is x h The amplitude of the dynamic change of h For x h The frequency of h is the sampling frequency; For x h phase angle; in particular, x1[n] is the fundamental wave, a1[n], f1 and are the amplitude, frequency and phase angle of the fundamental wave respectively.

[0148] The dynamic amplitude a in the dynamic broadband signal of the power system is converted into h [n] is modulated to obtain the modulated dynamic amplitude; the modulation formula is:

[0149]

[0150] In the formula, F 0,h , and is the fitting coefficient, f h (*) is the fitting frequency, Δt is the sampling time interval;

[0151] Substitute the modulated dynamic amplitude into the expression of the dynamic broadband signal of the power system to obtain the dynamic broadband signal measurement model of the power system; the expression of the dynamic broadband signal measurement model x[n] of the power system is:

[0152]

[0153] As a further implementation, the execution process of the real frequency screening unit is:

[0154] According to the dynamic broadband signal measurement model of the power system, if the amplitudes of the fundamental wave, harmonics and interharmonics change, they are mathematically decomposed into three frequency components with constant amplitude and symmetrical frequency;

[0155] The estimated frequency {f est,1 ,...,f est,6H} Every three are screened and judged, if they meet f est,i-1 +f est,i+1 =2f est,i , then it means f est,i is the true frequency; and the estimated frequency {f est,1 ,...,f est,6H The true positive frequency in} is denoted as {f real,1 ,...,f real,H}.

[0156] The execution process of each unit can be performed according to the process steps of the power system dynamic broadband signal measurement method based on time-frequency domain analysis in Example 1, and will not be described one by one in this embodiment.

[0157] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0158] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0159] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0160] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0161] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for measuring dynamic broadband signals in a power system based on time-frequency domain analysis, characterized in that: The method includes: The dynamic characteristics of the dynamic broadband signal of the power system are described by using trigonometric functions, and the measurement model of the dynamic broadband signal of the power system is constructed; The Prony algorithm is used in the time domain to extract the fundamental wave, harmonic and interharmonic signals of the power system; the dynamic broadband signal measurement model of the power system is used to screen the real frequency components in the fundamental wave, harmonic and interharmonic signals of the power system, and extract their frequency parameters; The signal sampling window length is adjusted by using a variable length sampling window to capture the dynamic change characteristics of the broadband signal, and a dynamic broadband signal frequency domain model is constructed; and the dynamic broadband signal frequency domain model is solved to obtain the amplitude and phase parameters of the broadband signal of the power system; The power system dynamic broadband signal measurement model is used to screen the real frequency components in the power system fundamental wave, harmonic and interharmonic signals, and extract their frequency parameters, including: According to the power system dynamic broadband signal measurement model, if the amplitudes of the fundamental wave, harmonics and interharmonics change, they are mathematically decomposed into three frequency components with constant amplitudes and symmetrical frequencies; The estimated frequency {f est,1 ,...,f est,6H } Every three are screened and judged, if they meet f est,i-1 +f est,i+1 =2f est,i , then it means f est,i is the true frequency; and the estimated frequency {f est,1 ,...,f est,6H The true positive frequency in} is denoted as {f real,1 ,...,f real,H }; The signal sampling window length is adjusted using a variable-length sampling window to capture the dynamic change characteristics of broadband signals and to construct a dynamic broadband signal frequency domain model, including: Construct a variable-length sampling window function and construct a column vector that is consistent with the sampling window length; Perform sliding window sampling on the dynamic broadband signal of the power system and determine the window length of the variable length sampling window through the dynamic factor; Perform Fourier transform on the dynamic broadband signal of the power system, and expand the dynamic amplitude using Taylor formula to obtain the frequency domain model of the dynamic broadband signal; The frequency domain model of the dynamic broadband signal is solved to obtain the amplitude and phase parameters of the broadband signal of the power system, including: According to the extracted real frequency {f real，1 , ..., f real，H } The dynamic broadband signal frequency domain model Rewritten as an equation; the equation is in the form: x[k]=AB+CD Where: In the formula, A, B, C, and D are all vectors, and f real,1 ,...,f real,H is the true frequency screened out, f s is the sampling rate, N is the number of sampling points, is the phase parameter, and is the amplitude fitting coefficient, H is the total number of frequency components in the sampled signal, and I is the Taylor expansion order; The equations are solved to obtain the phases and dynamically changing amplitudes of the fundamental wave, harmonics, and interharmonics.

2. The method for measuring dynamic broadband signals of a power system based on time-frequency domain analysis according to claim 1, characterized in that: Construct a dynamic broadband signal measurement model for power systems, including: A1: When the power system has subsynchronous / supersynchronous oscillation, harmonic / interharmonic oscillation or harmonic resonance, the amplitude of harmonics and interharmonics changes. At this time, the dynamic broadband signal expression of the power system containing harmonics and interharmonics is expressed as: In the formula, x h [n] is the fundamental wave, harmonic or interharmonic; a h [n] is x h The amplitude of the dynamic change of h For x h The frequency of h is the sampling frequency; For x h The phase angle of A2: Use trigonometric functions to convert the dynamic amplitude a in the dynamic broadband signal of the power system h [n] is modulated to obtain the dynamic amplitude after modulation; the modulation formula is: In the formula, F 0,h , and is the fitting coefficient, f h (*) is the fitting frequency, Δt is the sampling time interval; A3: Substitute the modulated dynamic amplitude into the power system dynamic broadband signal expression to obtain the power system dynamic broadband signal measurement model; the power system dynamic broadband signal measurement model x[n] expression is:

3. The method for measuring dynamic broadband signals of a power system based on time-frequency domain analysis according to claim 2, characterized in that: Each frequency component in the power system dynamic broadband signal measurement model x[n] is: Where: In the formula, x h [n] is the fundamental wave, harmonic or interharmonic; a h [n] is x h The amplitude of the dynamic change of h For x h The frequency of h is the sampling frequency; For x h The phase angle of 0,h , and is the fitting coefficient, f h (*) is the fitting frequency, Δt is the sampling time interval; F * for and function.

4. The method for measuring dynamic broadband signals in a power system based on time-frequency domain analysis according to claim 1, characterized in that: The amplitude of the dynamic change a h The calculation formula for [n] is:

5. The power system dynamic broadband signal measurement system based on time-frequency domain analysis is characterized by: The system uses the power system dynamic broadband signal measurement method based on time-frequency domain analysis as described in any one of claims 1 to 4; the system comprises: A dynamic broadband signal measurement model building unit is used to describe the dynamic change characteristics of the dynamic broadband signal of the power system by using trigonometric functions, and to build a dynamic broadband signal measurement model for the power system; A real frequency screening unit is used to extract the fundamental wave, harmonic and interharmonic signals of the power system by using the Prony algorithm in the time domain; the real frequency components in the fundamental wave, harmonic and interharmonic signals of the power system are screened by using the power system dynamic broadband signal measurement model, and the frequency parameters thereof are extracted; The amplitude and phase parameter calculation unit is used to adjust the signal sampling window length using a variable length sampling window to capture the dynamic change characteristics of the broadband signal, build a dynamic broadband signal frequency domain model; and solve the dynamic broadband signal frequency domain model to obtain the amplitude and phase parameters of the broadband signal of the power system.

6. The power system dynamic broadband signal measurement system based on time-frequency domain analysis according to claim 5, characterized in that: The execution process of the dynamic broadband signal measurement model construction unit is as follows: When the power system experiences subsynchronous / supersynchronous oscillation, harmonic / interharmonic oscillation or harmonic resonance, the amplitude of harmonics and interharmonics changes. At this time, the dynamic broadband signal expression of the power system containing harmonics and interharmonics is expressed as: In the formula, x h [n] is the fundamental wave, harmonic or interharmonic; a h [n] is x h The amplitude of the dynamic change of h For x h The frequency of h is the sampling frequency; For x h The phase angle of The dynamic amplitude a in the dynamic broadband signal of the power system is converted into h [n] is modulated to obtain the dynamic amplitude after modulation; the modulation formula is: In the formula, F 0,h , and is the fitting coefficient, f h (*) is the fitting frequency, Δt is the sampling time interval; Substitute the modulated dynamic amplitude into the power system dynamic broadband signal expression to obtain the power system dynamic broadband signal measurement model; the power system dynamic broadband signal measurement model x[n] expression is:

7. The power system dynamic broadband signal measurement system based on time-frequency domain analysis according to claim 5, characterized in that: The execution process of the real frequency screening unit is: According to the power system dynamic broadband signal measurement model, if the amplitudes of the fundamental wave, harmonics and interharmonics change, they are mathematically decomposed into three frequency components with constant amplitudes and symmetrical frequencies; The estimated frequency {f est,1 ,...,f est,6H } Every three are screened and judged, if they meet f est,i-1 +f est,i+1 =2f est,i , then it means f est,i is the true frequency; and the estimated frequency {f est,1 ,...,f est,6H The true positive frequency in} is denoted as {f real,1 ,...,f real,H }.

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