CN110045252B - Series direct current arc detection method utilizing frequency spectrum energy integration - Google Patents
Series direct current arc detection method utilizing frequency spectrum energy integration Download PDFInfo
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- CN110045252B CN110045252B CN201910371739.6A CN201910371739A CN110045252B CN 110045252 B CN110045252 B CN 110045252B CN 201910371739 A CN201910371739 A CN 201910371739A CN 110045252 B CN110045252 B CN 110045252B
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Abstract
The invention discloses a series direct current arc detection method by utilizing frequency spectrum energy integration, which is characterized in that in a direct current system, loop current is measured, the measured loop current is subjected to band-pass filtering, and the pass band range is 1-100 kHz. And performing Fast Fourier Transform (FFT) on the loop current after the band-pass filtering in a certain time window to obtain the frequency spectrum of the loop current. And performing the square sum calculation of the loop current frequency domain amplitude value within the range of the series arc fault specific frequency band (1-100kHz), namely calculating the energy integral value within the range of the fault specific frequency band. When a series arc fault occurs in a direct current system, the energy integral value in the specific frequency band before and after the fault is increased. If the energy integral value in the fault specific frequency band range increases and exceeds a threshold value, the series direct current arc fault is considered to occur.
Description
Technical Field
The invention belongs to the field of electrical engineering, and relates to a series direct current arc fault detection method.
Background
With the further development of modern industry, direct current systems are widely applied in the fields of aerospace, electric vehicles and the like. In a dc system, series dc arc faults can occur due to loose connectors and cable degradation. Because the direct current does not have the zero crossing point, after the series direct current arc fault is generated, the arc cannot be naturally extinguished, and the dangers such as fire disasters are more easily caused.
When a series direct current arc fault occurs in a direct current system, the amplitude of direct current in the system is reduced, which is equivalent to connecting a nonlinear resistor in series in the system, and a high-frequency component is generated along with the series direct current arc fault. The main detection mode of the series direct current arc fault is an indirect detection mode by detecting the time domain change and the frequency domain amplitude change of the loop current. The current probe is used for measuring the loop current, the frequency domain in the loop current is further analyzed, the fault characteristic frequency band is extracted, and the generation of the fault is represented by the change of the amplitude value of the specific frequency in the characteristic frequency band. Taufik et al studied the detection methods of series and parallel arc faults generated in dc systems of 80V and below, and proposed a dc arc detection method based on the amplitude change of the frequency domain within the frequency band range of 24.4-100kHz in the current, and made a dc arc fault detection device according to the method.
However, since electromagnetic interference in an actual environment is severe, and high-frequency signals are generated in an electrical circuit due to normal operations such as normal switching and load switching in an electrical system, a method for detecting a series dc arc fault based on a frequency domain amplitude of a characteristic frequency band of the series dc arc fault has a small degree of discrimination, and a new detection method with a larger degree of discrimination is required to be provided.
Disclosure of Invention
In view of the above, the present invention is directed to a method for detecting a series-connected dc arc by integrating spectral energy. By utilizing the frequency spectrum energy integration, the distinguishing degree of the characteristic signals of the series direct current arc fault and the normal operation in the electrical system can be improved, and the generation of the series direct current arc fault can be effectively detected.
In order to achieve the purpose, the invention provides the following technical scheme:
a series direct current arc detection method using spectral energy integration includes the following steps:
1) in a direct current system, measuring the loop current of a direct current output side, and performing band-pass filtering on the measured loop current;
2) performing Fast Fourier Transform (FFT) on the loop current after the band-pass filtering in a time window of 1-20 ms to obtain a frequency spectrum of the loop current;
3) and performing square sum calculation of loop current frequency domain amplitude in the range of 1-100kHz of the specific frequency band of the series arc fault, namely calculating an energy integral value in the range of the specific frequency band of the fault, wherein when the series arc fault occurs in the direct current system, the energy integral value in the specific frequency band before and after the fault is increased, and if the energy integral value in the range of the specific frequency band of the fault is increased and exceeds a threshold value, the series direct current arc fault is considered to occur.
The measured loop current needs to be subjected to band-pass filtering, and the pass band range is 1-100 kHz.
The integral value of the detected energy is the square sum of the amplitude of the frequency domain of the loop current in the frequency band range of 1-100 kHz.
The detection criterion is that when the energy integral value increases and exceeds a threshold value within the frequency band range of 1-100kHz, the series direct current arc fault is considered to occur.
The invention has the beneficial effects that:
1. the method comprises the steps of detecting the generation of a series direct current arc fault by using a spectrum energy integration principle, wherein the principle is simple and easy to implement, and the method comprises the steps of performing energy integration on a fault characteristic frequency band in a current spectrum and comparing the energy integration with a preset threshold;
2. the detection area graduation can be improved by utilizing the frequency spectrum energy integration, the interference of normal operation and environmental factors in the system is avoided, and the misjudgment omission are prevented.
Drawings
FIG. 1 is a flow chart of the present invention for detecting a DC arc fault using spectral energy integration;
FIG. 2 is a graph of the spectra before and after a series DC arc fault occurs;
FIG. 3 is a graph of spectral energy integral versus frequency before and after a series DC arc fault in accordance with the present invention;
FIG. 4 is a graph of the integral of spectral energy over time before and after a series DC arc fault in accordance with the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
The invention relates to a series direct current arc detection method utilizing frequency spectrum energy integration, which is characterized in that in a direct current system, loop current is measured, the measured loop current is subjected to band-pass filtering, and the pass band range is 1-100 kHz. And performing Fast Fourier Transform (FFT) on the loop current after the band-pass filtering in a certain time window to obtain the frequency spectrum of the loop current. And performing the square sum calculation of the loop current frequency domain amplitude value within the range of the series arc fault specific frequency band (1-100kHz), namely calculating the energy integral value within the range of the fault specific frequency band. When a series arc fault occurs in a direct current system, the energy integral value in the specific frequency band before and after the fault is increased. If the energy integral value in the fault specific frequency band range increases and exceeds a threshold value, the series direct current arc fault is considered to occur.
According to the prior frequency domain spectrum analysis of the arc current, the characteristic frequency band of the arc current is mainly 1-100kHz, so that the frequency band range of 1-100kHz is selected as a detection range;
as shown in fig. 1, the series dc arc fault detection process using spectral energy integration can be divided into the following steps:
1) detecting the loop current of the direct current output side by using a current probe;
2) band-pass filtering is carried out on the measured loop current, and the pass band range is 1-100 kHz;
3) for a time window tNPerforming FFT on the loop current after internal filtering;
as shown in FIG. 2, after the series DC arc fault is generated, the loop current increases in magnitude in the 1-100kHz frequency band.
4) Calculating tNThe sum of the squares of the amplitudes of the inner frequency domain in the characteristic frequency band (1-100kHz) of the inner loop currentN(i.e., energy integration);
as shown in fig. 3, after the series direct current arc fault occurs, the sum of squares of the frequency domain amplitude values in the loop current characteristic frequency band is much larger than the sum of squares of the frequency domain amplitude values before the arc fault occurs, the range of the distinguishing interval is large, and the influence of interference factors can be effectively avoided.
5) If SNGreater than SN-1And SNGreater than a threshold value StThis indicates a series arc fault in the circuit. Wherein the threshold value StThe selection is based on data detected in the actual electrical circuit and is related to the particular electrical circuit.
In the embodiment, a 48V lithium battery is selected as a direct-current power supply, a 12.5 omega resistor is selected as a direct-current load, and an arc generating device is used for generating a series direct-current arc;
in the embodiment, a TCPA300 type current probe of Thake is used for data acquisition, the bandwidth of the current probe is DC-100MHz, the sampling frequency f of an oscilloscope is 200MHz, the sampling time is 100ms, and the number of sampling points is 20M;
in the embodiment, the current probe is used for detecting the current of the positive electrode output side of the lithium battery;
in the embodiment, the arc generating device is manually operated at 10ms, so that a series direct current arc fault is generated in a direct current loop;
in the embodiment, the band-pass filter passband range is 1-100 kHz;
in the embodiment, the time window is selected to be 5ms, and the sum of squares of the frequency domain amplitude of the loop current in the frequency band range of 1-100kHz is calculated from 0 ms;
as shown in fig. 4, a significant increase in the loop current 1-100kHz energy integral at 15ms compared to 10ms is considered a series dc arc fault during 10-15 ms.
Claims (2)
1. A series direct current arc detection method using spectral energy integration is characterized by comprising the following steps:
1) in a direct current system, measuring the loop current of a direct current output side, and performing band-pass filtering on the measured loop current;
2) performing Fast Fourier Transform (FFT) on the loop current after the band-pass filtering in a time window of 1-20 ms to obtain a frequency spectrum of the loop current;
3) and performing square sum calculation of loop current frequency domain amplitude in the range of 1-100kHz of the specific frequency band of the series arc fault, namely calculating an energy integral value in the range of the specific frequency band of the fault, wherein when the series arc fault occurs in the direct current system, the energy integral value in the specific frequency band before and after the fault is increased, and if the energy integral value in the range of the specific frequency band of the fault is increased and exceeds a threshold value, the series direct current arc fault is considered to occur.
2. The method of claim 1, wherein the measured loop current is bandpass filtered and the passband is in the range of 1-100 kHz.
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| CN111983402A (en) * | 2020-08-20 | 2020-11-24 | 阳光电源股份有限公司 | Direct-current arc fault detection method and photovoltaic inversion system |
| CN112067961B (en) * | 2020-10-13 | 2023-08-15 | 哈尔滨工业大学（深圳） | Arc fault detection method, system and storage medium |
| CN112363021B (en) * | 2020-11-13 | 2022-05-17 | 重庆大学 | Distributed line fault detection and positioning system and method |
| CN114252669B (en) * | 2021-12-22 | 2024-04-26 | 江苏格澜得智能电气有限公司 | Device for generating series arc harmonic signals |
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| CN109560770B (en) * | 2018-10-29 | 2020-03-13 | 西安交通大学 | Photovoltaic system fault arc detection method based on self-adaptive kernel function and instantaneous frequency estimation |
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