Commutation failure warning method and system based on identification of time-varying harmonics of commutation voltage

Abstract

The present invention discloses a commutation failure warning method and system based on the identification of time-varying harmonics of commutation voltage, which relates to the broadband measurement technology and application field of power system. The theoretical functional relationship between the frequency deviation identification value and the true value of the frequency deviation when the harmonic frequency deviates from the center frequency of the Taylor Fourier transform filter passband is given, and then a nonlinear equation between the frequency deviation identification value and the true value is constructed. The nonlinear equation is solved by Newton iteration to obtain the true value of the frequency deviation, thereby achieving high-precision identification of the time-varying harmonic frequency, amplitude, phase, and damping ratio coefficient. Based on the harmonic identification results, the commutation voltage harmonic identification data is used to calculate and predict the maximum commutation area change trend that the commutation voltage can supply, thereby achieving commutation failure warning. The proposed method has extremely high engineering application value in the high-precision real-time identification of time-varying harmonics and commutation failure warning of high-voltage direct current transmission systems.

Description

Technical Field

[0001] The present invention relates to a wideband measurement technology for power systems and its application field, and in particular to a commutation failure early warning method and system based on identification of time-varying harmonics of commutation voltage. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Because the thyristors used in commutation converters lack self-shutoff capability, insufficient AC system voltage support on the inverter side can easily lead to commutation failures. Repeated commutation failures can also cause DC lockout, severely disturbing the active power of both the transmitting and receiving grids. In grids with insufficient physical inertia support, this can trigger cascading failures, threatening the safe and stable operation of AC / DC hybrid power grids. The nonlinear characteristics of power electronic devices are influenced by a variety of factors, including the operating environment, control method, and fault type. The harmonics they generate have time-varying characteristics. Therefore, the rapid and precise identification of time-varying harmonics is a critical prerequisite for commutation failure analysis, early warning, and mitigation.

[0004] Currently, the Discrete Fourier Transform (DFT) method has become the most commonly used harmonic identification method for converter station power fault recording and monitoring devices due to its simplicity and ease of implementation. However, DFT suffers from spectrum leakage in the presence of frequency offsets, which significantly reduces identification accuracy, particularly in weak inertia systems with large frequency offsets. Improved DFT methods using adaptive sampling interval adjustment technology based on phase-locked loops, adaptive soft synchronization technology based on sampling sequence interpolation, and spectrum leakage suppression technology based on frequency domain interpolation can improve identification accuracy in the presence of frequency offsets to a certain extent, but cannot fundamentally solve the spectrum leakage problem. In addition to the aforementioned Fourier transform-based methods, there are also parameter-based identification methods, such as the Prony method and the Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT) method. These methods use linear combinations of exponential functions to establish a signal model. They first estimate the frequency using techniques such as autocorrelation, covariance, autocorrelation, and singular value decomposition. Then, they solve for the phasor by solving a linear regression model that establishes the relationship between the phasor and the signal. These methods can identify not only the frequency, amplitude, and phase, but also the damping ratio coefficient, providing predictive information for analyzing the impact of harmonic variations on commutation failure. However, the identification performance of the Prony and ESPRIT methods is closely related to the choice of model order and noise level. It should be noted that both Fourier transform-based methods and parameter-based identification methods assume a stationary signal using a windowed sampling sequence. They require dividing the signal into a series of continuous short windows, but the signal within each short window is still approximately assumed to be stationary, and approximate tracking of time-varying harmonics can only be achieved by sliding the window.

[0005] The Taylor Fourier Transform (TFT) method directly incorporates the time-varying characteristics of the signal into the signal identification model by performing a Taylor series expansion on the harmonic phasors. The TFT filter bank is solved using the least squares (LS) method, leveraging its bandpass filtering properties to approximate the variation trends of each frequency component in the frequency domain, thereby identifying the harmonic frequencies and phasors. To further suppress interference from stopband components, the sampling sequence in the observation window can be weighted using a window function with low sidelobe levels, significantly attenuating the stopband sidelobe levels. However, due to the limited flatness of the TFT filter passband, the center frequency of the filter passband must be iteratively adjusted using feedback from the frequency identification results to gradually approximate the true frequency, achieving high-precision identification in the presence of frequency offsets and dynamic frequency variations. However, each iteration requires recalculating the TFT filter bank, calculating multiple intermediate variable matrices, and performing complex matrix multiplication and inversion. The heavy computational burden and memory overhead are major obstacles to the engineering application of the TFT method.

[0006] Therefore, it is very necessary to design a high-precision and fast identification method for time-varying harmonics of commutation voltage and apply it to commutation failure warning. Summary of the Invention

[0007] To address the shortcomings of the existing technology, the present invention aims to provide a commutation failure warning method and system based on the identification of time-varying harmonics in commutation voltage. This method can achieve high-precision harmonic identification in frequency offset scenarios, as well as dynamic scenarios with frequency ramps and frequency oscillations. Based on the harmonic identification results, the commutation voltage harmonic identification data is used to calculate and predict the maximum commutation area variation trend that the commutation voltage can supply, thereby providing commutation failure warning. The proposed method obtains the required parameters through offline calculation, eliminating the need to store any intermediate variables. This method requires minimal memory and computational complexity, and possesses high engineering application value for high-precision, real-time identification of time-varying harmonics and commutation failure warning in HVDC transmission systems.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] A first aspect of the present invention provides a commutation failure warning method based on identification of time-varying harmonics of commutation voltage, comprising the following steps:

[0010] Acquire a signal sampling sequence to obtain preliminary identification values of harmonic parameters; the preliminary identification values of harmonic parameters include amplitude identification values, phase identification values, and frequency deviation identification values;

[0011] According to the frequency response function of the Taylor Fourier transform filter bank, a functional relationship between the frequency deviation identification value and the true value of the frequency deviation is constructed;

[0012] The frequency deviation identification value is updated through the frequency deviation iterative correction process;

[0013] The frequency identification value is obtained according to the updated frequency deviation identification value, the amplitude identification value and the phase identification value are updated according to the frequency identification value, and the damping ratio coefficient identification value is obtained. The commutation failure risk is warned according to the commutation area prediction formula.

[0014] Furthermore, a functional relationship between the frequency deviation identification value and the true value of the frequency deviation is constructed in an offline manner.

[0015] Furthermore, preliminary identification values of harmonic parameters are obtained according to the signal sampling sequence and the calculation formula of harmonic phasor and its derivative.

[0016] Furthermore, a functional relationship between the frequency deviation identification value and the true value of the frequency deviation is constructed, specifically a theoretical functional relationship between the frequency deviation identification value and the true value of the frequency deviation when the harmonic frequency deviates from the center frequency of the Taylor Fourier transform filter passband.

[0017] Furthermore, the preliminary identification value of the harmonic parameter is updated according to the updated frequency deviation identification value. The specific process is to set the center frequency of the harmonic filter passband of the Taylor Fourier transform filter group, and obtain the updated frequency identification value according to the sum of the updated frequency deviation identification value and the center frequency of the harmonic filter passband of the Taylor Fourier transform filter group, and then obtain the updated amplitude identification value and phase identification value.

[0018] Furthermore, the commutation area prediction formula takes into account the harmonic amplitude, frequency, phase and damping ratio coefficient identification value. When the shutdown angle is taken as the minimum shutdown angle required for the converter valve to restore the forward blocking capability, the commutation area that can be supplied by the commutation voltage is the maximum commutation area.

[0019] Furthermore, when the maximum commutation area is smaller than the required commutation area, it is determined that there is a risk of commutation failure.

[0020] A second aspect of the present invention provides a commutation failure warning system based on identification of time-varying harmonics of commutation voltage, comprising:

[0021] The data acquisition module is configured to acquire a signal sampling sequence to obtain preliminary identification values of harmonic parameters; the preliminary identification values of harmonic parameters include amplitude identification values, phase identification values, and frequency deviation identification values;

[0022] The first data processing module is configured to construct a functional relationship between the frequency deviation identification value and the true value of the frequency deviation according to the frequency response function of the Taylor Fourier transform filter bank;

[0023] a second data processing module configured to update the frequency deviation identification value through a frequency deviation iterative correction process;

[0024] The commutation failure warning module is configured to obtain a frequency identification value based on the updated frequency deviation identification value, update the amplitude identification value and the phase identification value based on the frequency identification value, and obtain a damping ratio coefficient identification value, and warn of the commutation failure risk based on the commutation area prediction formula.

[0025] A third aspect of the present invention provides a medium having a program stored thereon, which, when executed by a processor, implements the steps of the commutation failure warning method based on identification of time-varying harmonics of commutation voltage as described in the first aspect of the present invention.

[0026] The fourth aspect of the present invention provides a device comprising a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, the steps of the commutation failure warning method based on identification of time-varying harmonics of commutation voltage as described in the first aspect of the present invention are implemented.

[0027] One or more of the above technical solutions have the following beneficial effects:

[0028] The present invention provides a commutation failure warning method based on the identification of time-varying harmonics in commutation voltage. It presents a theoretical functional relationship between the identified frequency deviation value and the true value of the frequency deviation when the harmonic frequency deviates from the center frequency of the Taylor Fourier transform filter passband. This relationship then constructs a nonlinear equation between the identified frequency deviation value and the true value. This nonlinear equation is solved via Newton iteration to obtain the true value of the frequency deviation, thereby achieving high-precision identification of the time-varying harmonic frequency, amplitude, phase, and damping ratio coefficient. The parameters required for this proposed method for rapid identification of time-varying harmonics in commutation voltage are obtained through offline calculation, eliminating the need to store any intermediate variables, resulting in minimal memory requirements. Furthermore, the Taylor Fourier transform filter bank does not need to be recalculated, resulting in extremely low computational complexity.

[0029] Based on harmonic identification results, this invention provides a commutation area prediction formula that takes into account harmonic frequency, amplitude, phase, and damping ratio. Using commutation voltage harmonic identification data, this method calculates and predicts the maximum commutation area trend that can be supplied by the commutation voltage, providing a warning of commutation failure. Therefore, this invention has high engineering application value in high-precision, real-time identification of time-varying harmonics and commutation failure warning in HVDC transmission systems.

[0030] Advantages of additional aspects of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] Figure 1This is a flow chart of a commutation failure warning method based on identification of time-varying harmonics of commutation voltage according to a first embodiment of the present invention. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "comprising" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations;

[0035] Example 1:

[0036] A first embodiment of the present invention provides a commutation failure warning method based on identification of time-varying harmonics of commutation voltage, comprising the following steps:

[0037] Acquire a signal sampling sequence to obtain preliminary identification values of harmonic parameters; the preliminary identification values of harmonic parameters include amplitude identification values, phase identification values, and frequency deviation identification values;

[0038] According to the frequency response function of the Taylor Fourier transform filter bank, a functional relationship between the frequency deviation identification value and the true value of the frequency deviation is constructed;

[0039] The frequency deviation identification value is updated through the frequency deviation iterative correction process;

[0040] The frequency identification value is obtained according to the updated frequency deviation identification value, the amplitude identification value and the phase identification value are updated according to the frequency identification value, and the damping ratio coefficient identification value is obtained. The commutation failure risk is warned according to the commutation area prediction formula.

[0041] As a further technical solution, in this embodiment, there is no order relationship between the step of obtaining the preliminary identification value of the harmonic parameter and the step of constructing the functional relationship between the frequency deviation identification value and the true value of the frequency deviation. Figure 1 As shown, in some embodiments, a functional relationship between the frequency deviation identification value and the true value of the frequency deviation can be constructed offline first, and then the signal sampling sequence can be obtained.

[0042] As a further technical solution, preliminary identification values of harmonic parameters are obtained based on the signal sampling sequence and the calculation formula of the harmonic phasor and its derivative.

[0043] The specific steps are: obtain the signal sampling sequence S = [s0, s1, s2, ..., s N-1 ] T , the calculation formula for the kth derivative of the mth harmonic phasor is Initially obtain the amplitude identification value Phase recognition value Frequency deviation identification value

[0044]

[0045]

[0046]

[0047] Among them, abs[] means taking the amplitude, angle[] means taking the phase, and imag[] means taking the imaginary part. is the Taylor Fourier transform filter bank parameter of the kth derivative of the mth harmonic phasor, which comes from: Initialize the Taylor Fourier transform filter bank parameter matrix It is a matrix of M(K+1) rows and N columns; The parameters of the (m-1)(K+1)+k+1th row are the parameters of the Taylor Fourier transform filter bank of the kth derivative of the mth harmonic phasor, expressed as

[0048] As a further technical solution, a functional relationship between the frequency deviation identification value and the true value of the frequency deviation is constructed, specifically a theoretical functional relationship between the frequency deviation identification value and the true value of the frequency deviation when the harmonic frequency deviates from the center frequency of the Taylor Fourier transform filter passband.

[0049] A frequency identification value is obtained according to the updated frequency deviation identification value, and the amplitude identification value and the phase identification value are updated according to the frequency identification value. The specific process is to set the center frequency of the harmonic filter passband of the Taylor Fourier transform filter group, and obtain the frequency identification value according to the sum of the updated frequency deviation identification value and the center frequency of the harmonic filter passband of the Taylor Fourier transform filter group, and then obtain the updated amplitude identification value and the phase identification value according to the frequency identification value.

[0050] The specific steps are:

[0051] Set the Taylor Fourier transform filter bank harmonic filter passband center frequency ω Cm , where m = 1, 2, ..., M, m represents the mth harmonic, and M represents the maximum harmonic order; set the signal sampling rate to F s , the sampling interval is The filter window length is N and the Taylor expansion order is K. Offline calculation of Taylor Fourier transform filter bank parameter matrix

[0052] Offline calculation of Taylor Fourier transform filter bank frequency response function: The Taylor Fourier transform filter bank frequency response function of the k-th derivative of the m-th harmonic phasor is

[0053]

[0054] Among them, E FR Represents the frequency rotation factor column vector, E FR =[1,e jω , e j2ω ,…,e j(N-1)ω ] T , [] T represents the matrix transpose, represents the amplitude-frequency response, represents the phase-frequency response, and ω is the frequency.

[0055] Frequency deviation identification value The actual value of the frequency deviation Δω m The functional relationship is

[0056]

[0057] right Perform polynomial fitting and get Among them, Q is the fitting order, u q is the qth order fitting parameter.

[0058] Construct frequency deviation nonlinear equation based on preliminary frequency deviation identification value and its derivatives initialization The frequency deviation iterative correction process is shown below, and the number of iterations is J. is the result of the jth iteration;

[0059]

[0060] Update frequency deviation identification value Obtain the frequency identification value based on the updated frequency deviation identification value Update the amplitude identification value according to the frequency identification value and phase identification value

[0061]

[0062]

[0063]

[0064]

[0065] As a further technical solution, the damping ratio coefficient identification value is Among them, ln[] is the natural logarithm function, is the recognition result of the previous window, T report is the identification window time interval.

[0066] The commutation area prediction formula takes into account harmonic amplitude, frequency, phase, and the identified damping ratio coefficient. When the shutdown angle is set to the minimum required for the converter valve to restore forward blocking capability, the commutation area that can be supplied by the commutation voltage is the maximum commutation area. If the maximum commutation area is less than the required commutation area, there is a risk of commutation failure.

[0067] Specifically, the commutation area prediction formula considering the harmonics and their damping ratio coefficient identification values is:

[0068]

[0069] in, α is the trigger advance angle, and γ is the shut-off angle. When γ is the minimum shut-off angle required for the converter valve to restore its forward blocking capability, min When Y ca is the maximum commutation area that the commutation voltage can supply, denoted as T pred The warning duration;

[0070] if If it is smaller than the required commutation area, it is judged to be T pred There is a risk of commutation failure. The required commutation area can be obtained by manual setting.

[0071] Example 2:

[0072] A second embodiment of the present invention provides a commutation failure warning system based on identification of time-varying harmonics of commutation voltage, including:

[0073] The data acquisition module is configured to acquire a signal sampling sequence to obtain preliminary identification values of harmonic parameters; the preliminary identification values of harmonic parameters include amplitude identification values, phase identification values, and frequency deviation identification values;

[0074] The first data processing module is configured to construct a functional relationship between the frequency deviation identification value and the true value of the frequency deviation according to the frequency response function of the Taylor Fourier transform filter bank;

[0075] a second data processing module configured to update the frequency deviation identification value through a frequency deviation iterative correction process;

[0076] The commutation failure warning module is configured to obtain a frequency identification value based on the updated frequency deviation identification value, update the amplitude identification value and the phase identification value based on the frequency identification value, and obtain a damping ratio coefficient identification value, and warn of the commutation failure risk based on the commutation area prediction formula.

[0077] Example 3:

[0078] A third embodiment of the present invention provides a medium having a program stored thereon. When the program is executed by a processor, the steps of the commutation failure warning method based on identification of time-varying harmonics of commutation voltage as described in the first embodiment of the present invention are implemented.

[0079] Example 4:

[0080] Embodiment 4 of the present invention provides a device, including a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, the steps of the commutation failure warning method based on identification of time-varying harmonics of commutation voltage as described in embodiment 1 of the present invention are implemented.

[0081] The steps involved in the apparatuses of Examples 2, 3, and 4 above correspond to those of Method Example 1. For detailed implementations, please refer to the relevant description of Example 1. The term "computer-readable storage medium" should be understood to mean a single medium or multiple media containing one or more instruction sets; it should also be understood to include any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and causing the processor to perform any method of the present invention.

[0082] Those skilled in the art will appreciate that the modules or steps of the present invention described above can be implemented using a general-purpose computer device. Alternatively, they can be implemented using program code executable by a computing device, which can then be stored in a storage device and executed by the computing device. Alternatively, they can be fabricated into separate integrated circuit modules, or multiple modules or steps can be fabricated into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0083] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A commutation failure warning method based on identification of time-varying harmonics of commutation voltage, characterized in that: The following steps are involved: Obtain the signal sampling sequence and obtain the preliminary identification value of the harmonic parameters; The preliminary identification values of harmonic parameters include amplitude identification value, phase identification value and frequency deviation identification value; According to the frequency response function of the Taylor Fourier transform filter bank, a functional relationship between the frequency deviation identification value and the true value of the frequency deviation is constructed; The frequency deviation identification value is updated through the frequency deviation iterative correction process; The frequency identification value is obtained according to the updated frequency deviation identification value, the amplitude identification value and the phase identification value are updated according to the frequency identification value, and the damping ratio coefficient identification value is obtained. The commutation failure risk is warned according to the commutation area prediction formula.

2. The commutation failure warning method based on identification of time-varying harmonics of commutation voltage according to claim 1, characterized in that: The functional relationship between the frequency deviation identification value and the true value of the frequency deviation is constructed in an offline manner.

3. The commutation failure warning method based on identification of time-varying harmonics of commutation voltage according to claim 1, characterized in that: The preliminary identification value of harmonic parameters is obtained according to the signal sampling sequence and the calculation formula of harmonic phasor and its derivative.

4. The commutation failure warning method based on identification of time-varying harmonics of commutation voltage according to claim 1, characterized in that: A functional relationship between the frequency deviation identification value and the true value of the frequency deviation is constructed, specifically a theoretical functional relationship between the frequency deviation identification value and the true value of the frequency deviation when the harmonic frequency deviates from the center frequency of the Taylor Fourier transform filter passband.

5. The commutation failure warning method based on identification of time-varying harmonics of commutation voltage according to claim 4, characterized in that: The preliminary identification value of the harmonic parameter is updated according to the updated frequency deviation identification value. The specific process is to set the center frequency of the harmonic filter passband of the Taylor Fourier transform filter group, and obtain the updated frequency identification value according to the sum of the updated frequency deviation identification value and the center frequency of the harmonic filter passband of the Taylor Fourier transform filter group, and then obtain the updated amplitude identification value and phase identification value.

6. The commutation failure warning method based on identification of time-varying harmonics of commutation voltage according to claim 1, characterized in that: The commutation area prediction formula takes into account the harmonic amplitude, frequency, phase and damping ratio coefficient identification value. When the turn-off angle is taken as the minimum turn-off angle required for the converter valve to restore the forward blocking capability, the commutation area that can be supplied by the commutation voltage is the maximum commutation area.

7. The commutation failure warning method based on identification of time-varying harmonics of commutation voltage according to claim 6, characterized in that: When the maximum commutation area is smaller than the required commutation area, it is determined that there is a risk of commutation failure.

8. A commutation failure warning system based on identification of time-varying harmonics of commutation voltage, characterized in that: include: A data acquisition module is configured to acquire a signal sampling sequence and obtain a preliminary identification value of a harmonic parameter; The first data processing module is configured to construct a functional relationship between the frequency deviation identification value and the true value of the frequency deviation according to the frequency response function of the Taylor Fourier transform filter bank; a second data processing module configured to update the frequency deviation identification value through a frequency deviation iterative correction process; The commutation failure warning module is configured to update the preliminary identification value of the harmonic parameter according to the updated frequency deviation identification value, obtain the damping ratio coefficient identification value, and warn of the commutation failure risk according to the commutation area prediction formula.

9. A computer-readable storage medium, characterized in that Multiple instructions are stored therein, and the instructions are suitable for being loaded by a processor of a terminal device and executing the commutation failure warning method based on identification of time-varying harmonics of commutation voltage according to any one of claims 1-7.

10. A terminal device, characterized in that: The method comprises a processor and a computer-readable storage medium, wherein the processor is used to implement various instructions; and the computer-readable storage medium is used to store multiple instructions, wherein the instructions are suitable for being loaded by the processor and executing the commutation failure warning method based on the identification of time-varying harmonics of the commutation voltage according to any one of claims 1 to 7.

Images