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A Discrimination Method for Low-Frequency Oscillation and Forced Oscillation of Power System Negative Damping Mechanism
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A technology of low-frequency oscillation and forced oscillation, applied in the direction of measuring electricity, measuring electrical variables, measuring devices, etc., can solve problems such as misjudgment and uncertainty of disturbance sources, and achieve the effects of convenient suppression, high discrimination ability, and strong adaptability
Active Publication Date: 2017-11-28
SOUTHEAST UNIV
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However, the existing methods have certain problems in the adaptability of the criterion. The uncertainty of the disturbance source makes the forced oscillation manifest in various forms, which may be very similar to other types of faults. For example, when the forced oscillation is a beat frequency oscillation, its The characteristics of the start-up waveform are similar to those of the negatively damped oscillation. At this time, the discrimination method based on the waveform of the start-up section is likely to be misjudged.
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Embodiment 1
[0065] Figure 4 It is the waveform diagram of the active power signal output by the generator of Embodiment 1, and the specific steps of discrimination are as follows:
[0066] Step 1: Obtain the active power signal S1 of the generator from the synchronous measurement unit, the sampling time is 20s, and the sampling frequency is 50Hz;
[0067] Step 2: Filter the low-frequency oscillation signal S1 with a low-pass filter, set the cutoff frequency to 2.5 Hz, and filter out noise components higher than 2.5 Hz in the signal. Transfer Function of Low Pass Filter s is the Laplacian operator. The filtered signal is S2, and its waveform is as Figure 4 shown;
[0068] Step 3: Zeroize the signal S2 in step 2. First, the average value of the signal S2 is obtained as 0.85, and then subtract 0.85 from the original value of S2 to obtain the zeroed signal S3. Its waveform is as follows Figure 5 shown;
[0069] Step 4: Perform spectrum analysis on the signal S3 in the frequency rang...
Embodiment 2
[0075] Figure 8 It is the waveform diagram of the active power signal output by the generator of Embodiment 2, and the specific identification steps are as follows:
[0076] Step 1: Obtain the active power signal S1 of the generator from the synchronous measurement unit, the sampling time is 20s, and the sampling frequency is 50Hz;
[0077] Step 2: Filter the signal S1 in step 1 with a low-pass filter, set the cutoff frequency to 2.5 Hz, and filter out noise components higher than 2.5 Hz in the signal. Transfer Function of Low Pass Filter s is the Laplacian operator. The waveform of the filtered signal S2 is as follows Figure 9 shown;
[0078] Step 3: Zeroize the signal S2 in step 2, that is, subtract the mean value 0.85 of the signal S2 from the original value of S2 to obtain the zeroed signal S3, whose waveform is as follows Figure 9 shown;
[0079] Step 4: Perform spectrum analysis on the signal S3 in step 3 in the frequency range of 0.1-2.6 Hz using the fast Four...
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Abstract
The invention provides a method for determining low-frequency oscillating and mandatory oscillating through a negative damping mechanism of a power system. The method comprises the steps of performing low-pass filter and zeroing a low-frequency oscillating signal; solving a spectrum analysis value of the signals obtained after the low-pass filter and the zeroing processing by the fast fourier decomposition method; performing interpolating fitting based on the spectrum analysis value; calculating determining indexes according to the interpolating fitting value and the spectrum analysis value; comparing the determining index and the threshold to determine the oscillating type. With the adoption of the method, the oscillating type can be accurately determined without being influenced by the waveform variation; the method is relatively high in adaptability; meanwhile, the forced oscillating frequency time can be provided, which facilitates the inhibition of forced oscillating.
Description
technical field [0001] The invention relates to a method for discriminating low-frequency oscillation and forced oscillation of a negative damping mechanism in a power system, and belongs to the technical field of power system analysis. Background technique [0002] Under the basic pattern of west-to-east power transmission and north-south interconnection, my country will gradually form a large-scale national interconnected power grid, which makes the low-frequency oscillation problem of the power system increasingly prominent. At present, the low-frequency oscillations that occur in the system are mainly divided into two types, one is the low-frequency oscillation caused by the negative damping mechanism caused by insufficient system damping, and the other is the forced oscillation caused by the periodic power disturbance. The two oscillations have very similar manifestations, but due to their different mechanisms, the suppression methods that need to be adopted are also ve...
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