Generator field loss protection self-adaptive locking method and related device

Abstract

The invention discloses a self-adaptive locking method for excitation loss protection of a generator and a related device, and belongs to the technical field of generator protection, and the method comprises the steps: obtaining a three-phase voltage signal and a three-phase current signal of the generator; calculating to obtain a frequency domain energy ratio according to the three-phase current signal, respectively converting the three-phase current signal and the three-phase voltage signal into a current positive sequence component and a voltage positive sequence component, calculating to obtain positive sequence impedance, and calculating to obtain an impedance track slope based on the positive sequence impedance of adjacent sampling points; judging whether the positive sequence impedance is in the impedance circle or not, if so, judging whether the frequency domain energy ratio and the impedance track slope meet adaptive locking conditions or not, if so, performing adaptive locking, and otherwise, triggering field loss protection tripping action; and if outside the impedance circle, the generator operates normally. According to the method, the problem that the real field loss fault and the subsynchronous oscillation scene cannot be effectively distinguished in the prior art can be solved, so that misoperation of the generator in the subsynchronous oscillation scene is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of generator protection, and in particular relates to a generator demagnetization protection adaptive locking method and related devices. Background Art

[0002] Generator demagnetization is a common fault type in power systems. When a generator loses excitation, its reactive power output decreases, causing a drop in system voltage and, in severe cases, system instability. Traditional demagnetization protection methods are primarily based on the impedance circle principle, detecting the generator's impedance trajectory to determine if a demagnetization fault has occurred. However, with the increasing proportion of renewable energy generation, subsynchronous oscillation (SSO) in the system has become increasingly prominent. When an SSO occurs in the system, the generator-side impedance trajectory resembles a true demagnetization fault and enters the impedance circle action zone, causing the generator protection device to malfunction.

[0003] Existing solutions have the following drawbacks: fixed-delay blocking methods cannot distinguish between SSO and true demagnetization; harmonic detection methods are insensitive to low-frequency components (<30Hz); and traditional impedance protection has a false trip rate as high as 32% under SSO conditions. Therefore, how to protect generators while avoiding false trips in SSO scenarios has become an urgent challenge. Summary of the Invention

[0004] The purpose of the present invention is to provide a generator demagnetization protection adaptive locking method and related devices to solve the problem that the existing technology cannot effectively distinguish between real demagnetization faults and subsynchronous oscillation scenarios, so as to avoid the generator from malfunctioning in subsynchronous oscillation scenarios.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, a generator de-excitation protection adaptive locking method comprises the following steps: Obtain three-phase voltage signals and three-phase current signals of the generator; A frequency domain energy ratio is calculated based on the three-phase current signal, and a positive sequence impedance is calculated after converting the three-phase current signal and the three-phase voltage signal into a current positive sequence component and a voltage positive sequence component, respectively. An impedance trajectory slope is calculated based on the positive sequence impedance of adjacent sampling points; The radius and center of the preset impedance circle are used to determine whether the positive sequence impedance is within the impedance circle. If so, the adaptive locking condition is met based on the frequency domain energy ratio and the impedance trajectory slope. If so, adaptive locking is performed, otherwise the demagnetization protection tripping action is triggered; if outside the impedance circle, the generator operates normally.

[0006] In some embodiments, the step of calculating the frequency domain energy ratio according to the three-phase current signal specifically includes: After windowing the three-phase current signal, sub-synchronous frequency band energy and total energy are extracted by fast Fourier transform, and a frequency domain energy ratio is calculated based on the sub-synchronous frequency band energy and total energy.

[0007] In some implementations, the step of calculating the frequency domain energy ratio based on the subsynchronous frequency band energy and the total energy is calculated using the following formula:

[0008] in, is the frequency domain energy ratio, is the total energy, is the subsynchronous band energy, is the minimum value.

[0009] In some embodiments, the window function used in the windowing process is as follows:

[0010] in, is the window function, 、 、 and are the weight coefficients of different cosine terms, is the window function length, The index of the sampling point within the window.

[0011] In some embodiments, the adaptive locking condition is: the frequency domain energy ratio is greater than or equal to a first preset threshold, and the absolute value of the impedance trajectory slope is less than a second preset threshold.

[0012] In some embodiments, the step of calculating the impedance trajectory slope based on the positive sequence impedance at adjacent sampling points is calculated using the following formula:

[0013] in, is the impedance locus slope, and are the positive sequence reactance components at different sampling points, and are the positive sequence resistance components at different sampling points, is the change in the positive sequence reactance component, is the change in the positive sequence resistance component.

[0014] In a second aspect, a generator de-excitation protection adaptive locking system includes: A signal acquisition module is used to obtain the three-phase voltage signal and three-phase current signal of the generator; a subsynchronous oscillation feature extraction module, configured to calculate a frequency domain energy ratio based on the three-phase current signal, convert the three-phase current signal and the three-phase voltage signal into a current positive sequence component and a voltage positive sequence component, respectively, to calculate a positive sequence impedance, and calculate an impedance trajectory slope based on the positive sequence impedance of adjacent sampling points; The adaptive locking protection module is used to preset the radius and center of the impedance circle, determine whether the positive sequence impedance is within the impedance circle, and if so, determine whether the frequency domain energy ratio and the impedance trajectory slope meet the adaptive locking conditions. If so, adaptive locking is performed; otherwise, the demagnetization protection tripping action is triggered; if outside the impedance circle, the generator operates normally.

[0015] In a third aspect, an electronic device includes a memory, a processor, and a computer program stored in the memory and executable in the processor, wherein the processor implements the steps of the adaptive locking method for generator demagnetization protection when executing the computer program.

[0016] In a fourth aspect, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the generator demagnetization protection adaptive locking method are implemented.

[0017] In a fifth aspect, a computer program product is provided, comprising a computer program, wherein when the computer program is executed by a processor, the steps of the adaptive locking method for generator demagnetization protection are implemented.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention determines whether the positive-sequence impedance is within the impedance circle and performs adaptive locking condition judgment in combination with the frequency-domain energy ratio and the impedance trajectory slope. If the positive-sequence impedance is within the impedance circle and meets the adaptive locking condition, adaptive locking is performed. If the adaptive locking condition is not met, the demagnetization protection tripping action is triggered. This method can avoid single parameter misjudgment, effectively distinguish between real demagnetization faults and subsynchronous oscillation scenarios, and significantly reduce the risk of false operation in subsynchronous oscillation scenarios. In addition, if the positive-sequence impedance is outside the impedance circle, the generator is operating normally, which can quickly eliminate the normal operating state of the generator and reduce the amount of calculation.

[0019] Furthermore, after windowing the three-phase current signal, the subsynchronous frequency band energy and total energy are extracted through fast Fourier transform, which can accurately capture the subsynchronous oscillation characteristics, eliminate power frequency interference through fast Fourier transform, and introduce a minimum value when calculating the frequency domain energy ratio to avoid zero division anomaly when the total energy is close to the subsynchronous frequency band energy.

[0020] Furthermore, the specific window function used in the windowing process can reduce spectrum leakage, improve the accuracy of the fast Fourier transform, and ensure the accuracy of sub-synchronous band energy and total energy extraction.

[0021] Furthermore, the adaptive locking condition is that the frequency domain energy ratio is greater than or equal to a first preset threshold and the impedance trajectory slope is less than a second preset threshold. The frequency domain energy ratio is used to determine the presence of subsynchronous oscillation, and the impedance trajectory slope is used to distinguish between true demagnetization protection and subsynchronous oscillation, avoiding misjudgment by a single threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an overall technical flow chart of a generator de-excitation protection adaptive locking method provided by the present invention; Figure 2 A diagram showing the formation process of the final tripping decision in the embodiment; Figure 3 A flow chart of a generator de-excitation protection adaptive locking method provided in an embodiment; Figure 4 A structural diagram of a generator demagnetization protection adaptive locking system provided in an embodiment. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings. The content described is intended to explain rather than limit the present invention.

[0024] It should be noted that the terms "including" and "having" and any variations thereof in the description and claims of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, systems, products or apparatus.

[0025] like Figure 1 and Figure 3 As shown in the figure, this embodiment provides a generator de-excitation protection adaptive locking method and proposes a dual-modal feature recognition mechanism, including two modal feature quantities: frequency domain energy ratio and impedance trajectory slope. By real-time calculation of the frequency domain energy ratio (FER) and impedance trajectory slope (K z ), dynamically adjust the protection behavior, the method includes the following steps: S1, obtain the three-phase voltage signal and three-phase current signal of the generator to collect the real-time three-phase voltage of the generator 、 、 and three-phase current 、 、 .

[0026] Sampling rate: Set to 10kHz to ensure that rapid changes in electrical quantities can be accurately captured.

[0027] Simulation time: set to 2 seconds, covering the pre-fault, fault, and post-fault stages, to facilitate comprehensive observation of protection action behavior.

[0028] Base frequency: 50Hz, which is consistent with the operating frequency of conventional power systems.

[0029] S2, calculate the modal characteristic quantity: (1) Frequency domain energy ratio (FER) calculation: The three-phase current signal is windowed and then subjected to fast Fourier transform (FFT) to extract the subsynchronous frequency band energy and total energy. The frequency domain energy ratio is then calculated based on the subsynchronous frequency band energy and total energy.

[0030] The window function for windowing is:

[0031] in, is the window function, 、 、 and are the weight coefficients of different cosine terms, is the window function length, is the sampling point index within the window, , , , , n =0, 1, 2... N -1.

[0032] Applying the window function to the three-phase current signal yields:

[0033] in, is the original three-phase current signal, is the three-phase current signal after windowing.

[0034] Perform fast Fourier transform on the windowed three-phase current signal:

[0035] in, is the frequency domain signal after FFT transformation, k =0, 1, 2... N -1.

[0036] Finally, calculate the FER:

[0037]

[0038]

[0039] in, is the frequency domain energy ratio, is the total energy, is the subsynchronous band energy, is the minimum value, is the power spectrum, is the upper frequency limit, The lower frequency limit.

[0040] (2) Impedance trajectory slope K z calculate: The three-phase current signal and the three-phase voltage signal are converted into the current positive sequence component and the voltage positive sequence component respectively, and the positive sequence impedance is calculated. The impedance trajectory slope is calculated by the positive sequence impedance of adjacent sampling points, which is specifically calculated by the following formula:

[0041]

[0042]

[0043] in, is the voltage positive sequence component, is the positive sequence component of current, is the positive sequence impedance, is the resistance component, is the reactance component, is the impedance locus slope, and are the positive sequence reactance components at different sampling points, and are the positive sequence resistance components at different sampling points, is the change in the positive sequence reactance component, is the change in the positive sequence resistance component.

[0044] S3, protection logic judgment: Traditional impedance circle judgment: The radius and center of the impedance circle are preset, and the positive sequence impedance obtained in S2 is judged based on the radius and center to see whether it is within the impedance circle; if it is outside the impedance circle, the generator is operating normally.

[0045] Adaptive locking condition judgment: If it is within the impedance circle, then the frequency domain energy ratio and impedance trajectory slope obtained in S2 are used to determine whether they meet the adaptive locking condition. If the frequency domain energy ratio is greater than or equal to the first preset threshold, and the absolute value of the impedance trajectory slope is less than the second preset threshold, adaptive locking is performed; The first preset threshold is 0.8, and the second preset threshold is 0.5.

[0046] Tripping decision: If it is within the impedance circle and the adaptive blocking conditions are not met, the demagnetization protection tripping action is triggered.

[0047] Perform simulation based on the above steps: 1. Simulation working condition settings: SSO scenario simulation: The subsynchronous oscillation frequency is set to 23.8 Hz and the oscillation attenuation coefficient is set to 0.1. Three-phase voltage and current signals containing subsynchronous oscillation characteristics are generated, and appropriate noise is added to simulate actual operating conditions.

[0048] Simulating a real demagnetization fault scenario: Set the fault start time to 1.0 second and the time constant to 0.2 second, build a model for the voltage and current changes under a demagnetization fault, simulate the dynamic changes of electrical quantities during the demagnetization process, and add noise.

[0049] 2. Set up the scene: Scenario 1: Traditional SSO scenario Scenario 2: SSO scenario improvement Scenario 3: Real demagnetization fault Scenario 4: Real demagnetization fault improvement Among them, the adaptive locking method for generator demagnetization protection provided by the embodiment is not adopted in scenarios 1 and 3, while the adaptive locking method for generator demagnetization protection provided by the embodiment is adopted in scenarios 2 and 4.

[0050] 3. Simulation results: (1) The results of modal feature extraction are shown in Table 1 below

[0051] (2) Action test results like Figure 2 As shown, scenario 1: false tripping occurs at 0.78s; scenario 2: correct adaptive locking is performed but no action is taken; scenario 3: correct tripping occurs at 1.05s; scenario 4: correct tripping occurs at 1.07s.

[0052] Therefore, the adaptive locking method for generator demagnetization protection provided in this embodiment successfully solves the major technical problem of generator demagnetization protection misoperation caused by subsynchronous oscillation in high-proportion new energy power grids. By innovatively integrating frequency domain energy analysis and impedance trajectory dynamic characteristics identification, the FER-K z Dual-modal feature criteria enable precise identification and adaptive blocking of SSO conditions. Simulation experiments demonstrate that under 23.8Hz SSO conditions, the improved scheme achieves a 100% correct blocking rate and significantly reduces the false trip rate. This method is highly adaptable, accurately identifying even weak grid conditions with an SCR (Short-Circuit Ratio) ≥ 1.5, and is tolerant to 60dB noise interference, with a FER calculation error of <3%. It is also cost-effective and can be integrated into existing protection devices, requiring only a 5% increase in DSP (Digital Signal Processor) computing resources, without requiring hardware modifications. Furthermore, it is applicable to multiple scenarios, covering 300-1000MW steam turbines, 200-700MW hydro turbines, and gas turbines, providing core technical support for building a new power system security defense system.

[0053] like Figure 4 As shown, this embodiment provides a generator de-excitation protection adaptive locking system, including: A signal acquisition module is used to obtain the three-phase voltage signal and three-phase current signal of the generator; The subsynchronous oscillation feature extraction module is used to calculate the frequency domain energy ratio based on the three-phase current signal. At the same time, the three-phase current signal and the three-phase voltage signal are converted into the current positive sequence component and the voltage positive sequence component respectively to calculate the positive sequence impedance. The impedance trajectory slope is calculated based on the positive sequence impedance of adjacent sampling points. The adaptive locking protection module is used to preset the radius and center of the impedance circle, determine whether the positive sequence impedance is within the impedance circle, and if so, determine whether the frequency domain energy ratio and the impedance trajectory slope meet the adaptive locking conditions. If so, adaptive locking is performed; otherwise, the demagnetization protection tripping action is triggered; if outside the impedance circle, the generator operates normally.

[0054] The module division in the embodiments of the present invention is illustrative and represents only one logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in various embodiments of the present invention may be integrated into a single processor, exist physically as separate modules, or two or more modules may be integrated into a single module. The integrated modules may be implemented in either hardware or software functional modules.

[0055] This embodiment also provides a computer device, comprising a processor and a memory. The memory is configured to store a computer program (in this embodiment, the computer program includes a computing component and an iterative component, capable of performing model calculations and model updates). The computer program includes program instructions, and the processor is configured to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It serves as the computing and control core of the terminal and is adapted to implement one or more instructions, specifically, to load and execute one or more instructions from the computer storage medium to implement a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used to operate a method for adaptive locking of generator de-excitation protection.

[0056] This embodiment also provides a storage medium, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in a computer device, used to store programs and data. It is understood that the computer-readable storage medium herein can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides storage space, which stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for being loaded and executed by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium herein can be a high-speed RAM memory or a non-volatile memory, such as at least one disk storage device. The processor can load and execute the one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the adaptive locking method for generator demagnetization protection in the above-mentioned embodiment.

[0057] This embodiment further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the corresponding steps of the adaptive locking method for generator demagnetization protection in the above embodiment are implemented.

[0058] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0059] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, 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 produce 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 flowcharts and / or block diagrams. 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.

[0060] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work 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 The function specified in one or more boxes.

[0061] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A generator de-excitation protection adaptive locking method, characterized in that: The following steps are involved: Obtain three-phase voltage signals and three-phase current signals of the generator; A frequency domain energy ratio is calculated based on the three-phase current signal, and a positive sequence impedance is calculated after converting the three-phase current signal and the three-phase voltage signal into a current positive sequence component and a voltage positive sequence component, respectively. An impedance trajectory slope is calculated based on the positive sequence impedance of adjacent sampling points; The radius and center of the preset impedance circle are used to determine whether the positive-sequence impedance is within the impedance circle. If so, the adaptive locking condition is determined based on whether the frequency-domain energy ratio and the impedance trajectory slope meet the conditions. If so, adaptive locking is performed; otherwise, the demagnetization protection tripping action is triggered. If outside the impedance circle, the generator operates normally.

2. The method for adaptive locking of generator de-excitation protection according to claim 1, characterized in that: The step of calculating the frequency domain energy ratio according to the three-phase current signal specifically includes: After windowing the three-phase current signal, sub-synchronous frequency band energy and total energy are extracted by fast Fourier transform, and a frequency domain energy ratio is calculated based on the sub-synchronous frequency band energy and total energy.

3. The method for adaptive locking of generator de-excitation protection according to claim 2, characterized in that: The step of calculating the frequency domain energy ratio based on the sub-synchronous frequency band energy and the total energy is calculated by the following formula: in, is the frequency domain energy ratio, is the total energy, is the subsynchronous band energy, is the minimum value.

4. The method for adaptive locking of generator de-excitation protection according to claim 2, characterized in that: The window function used in the windowing process is as follows: in, is the window function, 、 、 and are the weight coefficients of different cosine terms, is the window function length, The index of the sampling point in the window.

5. The generator de-excitation protection adaptive locking method according to claim 1, characterized in that: The adaptive locking condition is: the frequency domain energy ratio is greater than or equal to a first preset threshold, and the absolute value of the impedance trajectory slope is less than a second preset threshold.

6. The generator de-excitation protection adaptive locking method according to claim 1, characterized in that: The step of calculating the impedance trajectory slope based on the positive sequence impedance of adjacent sampling points is calculated by the following formula: in, is the impedance locus slope, and are the positive sequence reactance components at different sampling points, and are the positive sequence resistance components at different sampling points, is the change in the positive sequence reactance component, is the change in the positive sequence resistance component.

7. A generator de-excitation protection adaptive locking system, characterized in that: include: A signal acquisition module is used to obtain the three-phase voltage signal and three-phase current signal of the generator; a subsynchronous oscillation feature extraction module, configured to calculate a frequency domain energy ratio based on the three-phase current signal, convert the three-phase current signal and the three-phase voltage signal into a current positive sequence component and a voltage positive sequence component, respectively, to calculate a positive sequence impedance, and calculate an impedance trajectory slope based on the positive sequence impedance of adjacent sampling points; The adaptive locking protection module is used to preset the radius and center of the impedance circle, determine whether the positive sequence impedance is within the impedance circle, and if so, determine whether the frequency domain energy ratio and the impedance trajectory slope meet the adaptive locking conditions. If so, adaptive locking is performed; otherwise, the demagnetization protection tripping action is triggered; if outside the impedance circle, the generator operates normally.

8. An electronic device, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable in the processor, wherein when the processor executes the computer program, the steps of the adaptive locking method for generator demagnetization protection according to any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the generator demagnetization protection adaptive locking method according to any one of claims 1 to 6 are implemented.

10. A computer program product, comprising a computer program, characterized in that: When the computer program is executed by a processor, the steps of the generator demagnetization protection adaptive locking method according to any one of claims 1 to 6 are implemented.

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