CN107046271A - A kind of low-pass digital filter method suitable for DC line protection - Google Patents
A kind of low-pass digital filter method suitable for DC line protection Download PDFInfo
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- CN107046271A CN107046271A CN201611257437.9A CN201611257437A CN107046271A CN 107046271 A CN107046271 A CN 107046271A CN 201611257437 A CN201611257437 A CN 201611257437A CN 107046271 A CN107046271 A CN 107046271A
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- window
- digital filter
- line protection
- protection
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0092—Details of emergency protective circuit arrangements concerning the data processing means, e.g. expert systems, neural networks
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
- H02H7/226—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices for wires or cables, e.g. heating wires
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
Abstract
The present invention relates to a kind of low-pass digital filter method suitable for DC line protection, its technical characterstic is：Comprise the following steps：Step 1, research choose with triumphant plucked instrument window design low pass filter as DC line protection lowpass digital filter；Step 2, β=7.865, N=21 is taken in Keyser window function, calculate the coefficient of triumphant plucked instrument window lowpass digital filter；Step 3, it is multiplied by with the sampled value ordered series of numbers x (n) of DC line protection after ω (n) ordered series of numbers and is added successively, calculating obtains the filtered output ordered series of numbers of triumphant plucked instrument window lowpass digital filter；The program that step 4, the ordered series of numbers y (n) for obtaining filtering send into DC line protection can carry out the calculating of Protection criteria.The present invention can be from the sampled signal containing DC component, transient high frequency oscillating component and noise; the flip-flop in voltage and current is extracted exactly; correct measurement amount is provided for the back-up protection of DC line, it is ensured that the selectivity of DC power transmission line back-up protection action.
Description
Technical field
The invention belongs to DC line protection technical field, especially a kind of Low pass digital suitable for DC line protection
Filtering method.
Background technology
Direct current transportation has obvious in terms of long-distance and large-capacity power transmission, submarine cable power transmission and power system interconnection
Advantage.Realize that Asynchronous Interconnection can both obtain networking income using direct current transportation, the problem of bulk power grid is brought is avoided that again, can be with
Improve the runnability of former AC network.DC line protection carries the task of quick detection and process circuit failure, its energy
The no quick, action message in failure, concerns the safe and stable operation of whole power system.
At present, the domestic widely used traveling-wave protection of DC transmission engineering put into operation is adopted as the main protection of DC line
Protected with voltage Sudden Changing Rate, under-voltage protection and DC line longitudinal difference protection are used as standby.That is, the standby of DC line
Protection is all constituted based on DC voltage or DC current.But, it is contemplated that during DC line fault, stored up by system
The influence of the factors such as energy element charge and discharge process, circuit distributed constant and voltage current transformer progress of disease error, sampled voltage
With not only include DC component in electric current, also containing substantial amounts of transient high frequency oscillating component, and voltage jump amount protection by
It is very sensitive for noise in the inherent characteristic differentiated.Therefore, DC line protection in order to extract voltage and electricity exactly
Flip-flop in stream is, it is necessary to using lowpass digital filter.
The basic function of lowpass digital filter is exactly to be extracted the signal of some frequencies in signal, and by other one
The signal of a little frequencies is suppressed, i.e., obtain by certain computing or conversion or strengthen desired signal, filter out unwanted letter
Number.But if the filtering characteristic of lowpass digital filter is undesirable, the back-up protection misoperation of DC power transmission line can be caused, is drawn
Play unnecessary power outage.
In summary, research is applied to the low-pass digital filter new method of DC line protection, for ensureing DC line
The correct operation of back-up protection is significant.
The content of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide reasonable in design, convenient and practical and extract exactly
The low-pass digital filter method suitable for DC line protection of the flip-flop gone out in voltage and current.
The present invention solves its technical problem and takes following technical scheme to realize：
A kind of low-pass digital filter method suitable for DC line protection, comprises the following steps：
Step 1, research choose with triumphant plucked instrument window design low pass filter as DC line protection low-pass digital filter
Device；
Step 2, β=7.865, N=21 is taken in Keyser window function, calculate 20 of triumphant plucked instrument window lowpass digital filter
Coefficient ω (n), n=1,2,3 ... 20；
The expression formula of the Keyser window function is：
Wherein, I0[x] is first kind zeroth order modification Bessel function, can use such as following formula series expression：
In above formula, β for triumphant plucked instrument window parameter,
Step 3, it is multiplied by with the sampled value ordered series of numbers x (n) of DC line protection after ω (n) ordered series of numbers and is added successively, calculating is obtained
The triumphant filtered output ordered series of numbers of plucked instrument window lowpass digital filter；
The program that step 4, the ordered series of numbers y (n) for obtaining filtering send into DC line protection can carry out the meter of Protection criteria
Calculate.
Moreover, the specific method of the step 1 is：By contrast the rectangular window in window function metht, Hanning window, hamming code window,
Bartlett window, Blackman window, the time-domain shape graph and amplitude-versus-frequency curve figure of quarter window and Kai Se windows, choose main lobe wide
The low pass filter that narrow, secondary lobe the peak value of degree is small with respect to main lobe pad value and the fireballing triumphant plucked instrument window of side lobe attenuation is designed is as straight
The lowpass digital filter of Flow Line protection.
Advantages and positive effects of the present invention are：
1st, the invention provides a kind of low-pass digital filter new method suitable for DC line protection.When DC line event
During barrier, from the sampled signal containing DC component, transient high frequency oscillating component and noise, voltage and current is extracted exactly
In flip-flop, provide correct measurement amount for the back-up protection of DC line, it is ensured that DC power transmission line back-up protection move
The selectivity of work.
2nd, the present invention can obtain narrow mistake by studying the low pass filter that the triumphant plucked instrument window in discovery window function metht is designed
Band is crossed, energy can be made preferably to concentrate in main lobe, preferable stopband attenuation and relatively more stable passband can be obtained.So, this
Invention proposes that triumphant plucked instrument window applies to the best lowpass digital filter of DC line protection first.
3rd, the present invention is had found by multiple research practice, and β=7.865, N=is taken in triumphant plucked instrument window expression formula is formula (9)
When 21, the best results of LPF.
Brief description of the drawings
Fig. 1 (a) is the time-domain shape graph and amplitude-versus-frequency curve figure of the rectangular window of the present invention；
Fig. 1 (b) is the time-domain shape graph and amplitude-versus-frequency curve figure of the Hanning window of the present invention；
Fig. 1 (c) is the time-domain shape graph and amplitude-versus-frequency curve figure of the hamming code window of the present invention；
Fig. 1 (d) is the time-domain shape graph and amplitude-versus-frequency curve figure of the bartlett window of the present invention；
Fig. 1 (e) is the time-domain shape graph and amplitude-versus-frequency curve figure of the Blackman window of the present invention；
Fig. 1 (f) is the time-domain shape graph and amplitude-versus-frequency curve figure of the quarter window of the present invention；
Fig. 1 (g) is the time-domain shape graph and amplitude-versus-frequency curve figure of the triumphant plucked instrument window of the present invention；
Fig. 2 be the present invention embodiment in Kai Se in triumphant plucked instrument window expression formula when taking β=7.865, N=21
The amplitude-frequency response figure of window.
Embodiment
The embodiment of the present invention is described in further detail below in conjunction with accompanying drawing：
A kind of low-pass digital filter method suitable for DC line protection, comprises the following steps：
Step 1, research choose with triumphant plucked instrument window design low pass filter as DC line protection low-pass digital filter
Device；
It is most widely used digital filter in relay protection, its design method to have limit for length's impulse responding digital filter
There are window function metht, Frequency Sampling Method and Constraint least square algorithm.Wherein, window function metht principle is more simple, it is easier to realize.Allusion quotation
The window function metht of type includes rectangular window, Hanning window, hamming code window, bartlett window, Blackman window, quarter window and Kai Se windows.
The specific method of the step 1 is：By contrasting the rectangular window in window function metht, Hanning window, hamming code window, Ba Teli
Special window, Blackman window, the time-domain shape graph and amplitude-versus-frequency curve figure of quarter window and Kai Se windows, choose main lobe width it is narrow,
The peak value of secondary lobe is small with respect to main lobe pad value and the low pass filter of the fireballing triumphant plucked instrument window design of side lobe attenuation is used as AC line
The lowpass digital filter of road protection.
(a) rectangular window
The function expression of rectangular window is：
Its time-domain shape graph and amplitude versus frequency characte such as Fig. 1 (a) are shown (N=21), and main lobe is a width ofFirst secondary lobe is relative
Main lobe decay -13dB.
(b) Hanning window
The function expression of Hanning window is：
Its time-domain shape graph and amplitude versus frequency characte such as Fig. 1 (b) are shown (N=21), and main lobe is a width ofFirst secondary lobe is relative
Main lobe decay -31dB.
(c) hamming code window
The expression formula of Hamming window function is：
Its time-domain shape graph and amplitude versus frequency characte such as Fig. 1 (c) are shown (N=21), and main lobe is a width ofFirst secondary lobe is relative
Main lobe decay -41dB.
(d) bartlett window
The function expression of bartlett window is：
When N is odd number：
When N is even number：
Its time-domain shape graph and amplitude versus frequency characte such as Fig. 1 (d) are shown (N=21), and main lobe is a width ofFirst secondary lobe is relative
Main lobe decay -25dB.
(e) Blackman window
The function expression of Blackman window is：
Its time-domain shape graph and amplitude versus frequency characte such as Fig. 1 (e) are shown (N=21), and main lobe is a width ofFirst secondary lobe is relative
Main lobe decay -57dB.
(f) quarter window
The function expression of quarter window is：
When N is odd number：
When N is even number：
Its time-domain shape graph and amplitude versus frequency characte such as Fig. 1 (f) (N=21), main lobe is a width ofFirst secondary lobe is with respect to main lobe
Decay -25dB.
(g) triumphant plucked instrument window
The function expression of triumphant plucked instrument window is：
In above formula, β is the parameter of triumphant plucked instrument window, influences the attenuation rate of window secondary lobe amplitude, it can adjust main lobe width simultaneously
With secondary lobe amplitude.β is bigger, and the main lobe width of frequency spectrum can be bigger, and secondary lobe amplitude can decline.Therefore, changing β value just can be to main lobe
Width is selected with side lobe attenuation.I0[x] is first kind zeroth order modification Bessel function function, can use following series table
Show.
Shown in the time-domain shape graph and amplitude versus frequency characte such as Fig. 1 (g) of triumphant plucked instrument window (N=21, β=4), main lobe width and first
Secondary lobe can be adjusted with respect to main lobe pad value according to β.
It can be drawn by Fig. 1 (a) to Fig. 1 (g)：
Rectangular window has most narrow main lobe, but also has the side lobe peak of maximum, and minimum stop-band attenuation is also worst.
Hanning window and hamming code window are single order raised cosine windows, and Hanning window side lobe peak is small compared with rectangular window, energy can be made effective
Concentrate in main lobe, but the width of main lobe increases one times compared with rectangular window.In addition, the minimum stop-band attenuation of Hanning window is compared
Small, side lobe attenuation speed is also more preferable compared with rectangular window.
Hamming code window can concentrate on 99.963% ability in main lobe, and compared with Hanning window, main lobe width is identical, and other
Valve peak value is smaller, but side lobe attenuation speed is poor, it is impossible to obtain preferable stop band attenuation.
Bartlett window and quarter window effect are essentially identical, all have the effect of more preferable suppressed sidelobes than rectangular window, still
Main lobe width adds one times than rectangular window, and filter effect is poor.
Blackman window is second order raised cosine, and amplitude function is made up of five parts, and their displacement and amplitude are not
Together, thus secondary lobe can be made further to offset, stopband attenuation is further increased, thus it has minimum side lobe peak, but
Its main lobe width is 3 times of rectangular window, it is meant that need to increase filter data window to shorten intermediate zone, poor real.
When triumphant plucked instrument window parameter beta takes 7.865, triumphant plucked instrument window has identical side lobe peak, but triumphant plucked instrument window with Blackman window
Main lobe width it is narrower than Blackman window, and side lobe attenuation speed is also more preferable.
As the above analysis, various window functions all have obvious main lobe and secondary lobe.The amplitude of main lobe frequency range and secondary lobe
Attenuation characteristic determines the application scenario of window function.The window function of ideal low-pass filter should possess following characteristics：(1) main lobe is most
Measure narrow, can so obtain narrow intermediate zone；(2) peak value of secondary lobe is small as best one can with respect to main lobe pad value so that
The energy of frequency domain is concentrated mainly in main lobe；(3) secondary lobe decrease speed is fast, in favor of increasing the decay of stopband.
Step 2, β=7.865, N=21 is taken in Keyser window function, calculate 20 of triumphant plucked instrument window lowpass digital filter
Coefficient ω (n), n=1,2,3 ... 20；
The expression formula of the Keyser window function is：
In above formula, β is the parameter of triumphant plucked instrument window, influences the attenuation rate of window secondary lobe amplitude, it can adjust main lobe width simultaneously
With secondary lobe amplitude.β is bigger, and the main lobe width of frequency spectrum can be bigger, and secondary lobe amplitude can decline.Therefore, changing β value just can be to main lobe
Width is selected with side lobe attenuation.
Wherein, I0[x] is first kind zeroth order modification Bessel function, can use such as following formula series expression：
Shown in the time-domain shape graph and amplitude versus frequency characte such as Fig. 1 (g) of triumphant plucked instrument window (N=21, β=4), main lobe width and first
Secondary lobe can be adjusted with respect to main lobe pad value according to β.
The characteristic of each window function of Integrated comparative is drawn：When triumphant plucked instrument window parameter beta takes 7.865, the side lobe peak of triumphant plucked instrument window is most
Small, side lobe attenuation speed is also more preferable, and main lobe relative narrower.Therefore the low pass filter designed with triumphant plucked instrument window can be compared
Narrow intermediate zone；Energy can be made preferably to concentrate in main lobe；Preferable stopband attenuation and relatively more stable passband can be obtained.Institute
With, compare under, triumphant plucked instrument window applies to the best lowpass digital filter of DC line protection.
Triumphant plucked instrument window amplitude versus frequency characte when triumphant plucked instrument window parameter beta=7.865, N=21 is as shown in Figure 2.As can be seen that triumphant plucked instrument
Window is unattenuated to pure direct current, and static error is 0 in theory, and because main lobe is narrower, side lobe attenuation fast, rapid dynamic response speed.
Step 3, it is multiplied by with the sampled value ordered series of numbers x (n) of DC line protection after ω (n) ordered series of numbers and is added successively, calculating is obtained
The triumphant filtered output ordered series of numbers of plucked instrument window lowpass digital filter：
The program that step 4, the ordered series of numbers y (n) for obtaining filtering send into DC line protection can carry out the meter of Protection criteria
Calculate.
It is emphasized that embodiment of the present invention is illustrative, rather than it is limited, therefore present invention bag
Include and be not limited to embodiment described in embodiment, it is every by those skilled in the art's technique according to the invention scheme
The other embodiment drawn, also belongs to the scope of protection of the invention.
Claims (2)
1. a kind of low-pass digital filter method suitable for DC line protection, it is characterised in that：Comprise the following steps：
Step 1, research choose with triumphant plucked instrument window design low pass filter as DC line protection lowpass digital filter；
Step 2, β=7.865, N=21 is taken in Keyser window function, calculate 20 coefficients of triumphant plucked instrument window lowpass digital filter
ω (n), n=1,2,3 ... 20；
The expression formula of the Keyser window function is：
Wherein, I0[x] is first kind zeroth order modification Bessel function, can use such as following formula series expression：
In above formula, β is the parameter of triumphant plucked instrument window；
Step 3, it is multiplied by with the sampled value ordered series of numbers x (n) of DC line protection after ω (n) ordered series of numbers and is added successively, calculating obtains Kai Se
The filtered output ordered series of numbers of window lowpass digital filter；
The program that step 4, the ordered series of numbers y (n) for obtaining filtering send into DC line protection can carry out the calculating of Protection criteria.
2. a kind of low-pass digital filter method suitable for DC line protection according to claim 1, it is characterised in that：
The specific method of the step 1 is：By contrasting the rectangular window in window function metht, Hanning window, hamming code window, bartlett window, cloth
The time-domain shape graph and amplitude-versus-frequency curve figure of the graceful window in Rec, quarter window and Kai Se windows, selection main lobe width is narrow, secondary lobe peak
The low pass filter for being worth the fireballing triumphant plucked instrument window design of and side lobe attenuation small with respect to main lobe pad value is used as DC line protection
Lowpass digital filter.
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| CN201611257437.9A CN107046271A (en) | 2016-12-30 | 2016-12-30 | A kind of low-pass digital filter method suitable for DC line protection |
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| CN201611257437.9A CN107046271A (en) | 2016-12-30 | 2016-12-30 | A kind of low-pass digital filter method suitable for DC line protection |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109871575A (en) * | 2018-12-29 | 2019-06-11 | 陕西海泰电子有限责任公司 | A kind of design method of the electromagnetic interference receiver window function based on time domain FFT |
| CN112564670A (en) * | 2020-11-20 | 2021-03-26 | 核工业二〇八大队 | Filtering method for power frequency noise interference of audio magnetotelluric data |
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| CN201352236Y (en) * | 2008-12-02 | 2009-11-25 | 湖南海兴电器有限责任公司 | Harmonic power meter based on Kaiser window double-spectrum-line interpolation FFT |
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2016
- 2016-12-30 CN CN201611257437.9A patent/CN107046271A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201352236Y (en) * | 2008-12-02 | 2009-11-25 | 湖南海兴电器有限责任公司 | Harmonic power meter based on Kaiser window double-spectrum-line interpolation FFT |
Non-Patent Citations (1)
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109871575A (en) * | 2018-12-29 | 2019-06-11 | 陕西海泰电子有限责任公司 | A kind of design method of the electromagnetic interference receiver window function based on time domain FFT |
| CN109871575B (en) * | 2018-12-29 | 2022-12-20 | 陕西海泰电子有限责任公司 | Electromagnetic interference receiver window function design method based on time domain FFT |
| CN112564670A (en) * | 2020-11-20 | 2021-03-26 | 核工业二〇八大队 | Filtering method for power frequency noise interference of audio magnetotelluric data |
| CN112564670B (en) * | 2020-11-20 | 2023-11-21 | 核工业二〇八大队 | Filtering method for power frequency noise interference of audio magnetotelluric data |
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