CN108761262A - A kind of short circuit current zero passage prediction technique - Google Patents
A kind of short circuit current zero passage prediction technique Download PDFInfo
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- CN108761262A CN108761262A CN201810399760.2A CN201810399760A CN108761262A CN 108761262 A CN108761262 A CN 108761262A CN 201810399760 A CN201810399760 A CN 201810399760A CN 108761262 A CN108761262 A CN 108761262A
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- circuit current
- short circuit
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/175—Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero
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Abstract
The invention discloses a kind of short circuit current zero passage prediction techniques, include the following steps：Short circuit current when first to short trouble is sampled and is filtered, then Numerical Value Derivative operation is carried out to filtered short circuit current, calculate separately out short circuit current first derivative and second dervative, and it carries out a series of operations in conjunction with short circuit current angular frequency and constructs the short-circuit current forecast value that phase is ahead of former short circuit current a quarter cycle, by detecting the zero crossing of the short-circuit current forecast value of construction, the zero crossing of actual short electric current is predicted.The present invention can accurately and reliably predict short circuit current zero crossing, have stronger anti-interference ability, technical solution is simple and effective and practicability is stronger.
Description
Technical field
The present invention relates to technical field of power systems, and in particular to a kind of short circuit current zero passage prediction technique.
Background technology
With the continuous development of modern power systems, the short circuit current level in power grids at different levels is continuously improved, once occur
Short trouble, it will cause extremely serious consequence, it is therefore necessary to limit to system short-circuit electric current.In various short circuit currents
In restriction, the fault current limiter based on fast chopper is a kind of effective technological means.Fault current limiter controls
System is other than being required to quickly recognize short trouble, while in order to improve the energy that fast chopper cut-offs short circuit current
Power, the transient state impact for reducing system, control system should be provided simultaneously with that short circuit current is phased to cut-off function, i.e. fast prediction goes out short circuit
Current zero-crossing point.Prior art means generally use point of safes algorithm, adaptive algorithm, half-wave Fourier algorithms, total regression to calculate
Method etc. carries out current over-zero prediction, however these method predicted times cannot meet fault current limiter typically each in 10ms or more
The requirement of quick acting, while these methods implement more complicated, and accuracy in computation is difficult to ensure.For the prior art
Deficiency, the present invention provide it is a kind of simply and effectively be suitable for fault current limiter short circuit current zero passage prediction technique.
Invention content
To solve deficiency in the prior art, the present invention provides a kind of short circuit current zero passage prediction technique, solves existing
The problem of prediction technique time is longer, realizes complexity, and accuracy in computation is difficult to ensure.
In order to realize that above-mentioned target, the present invention adopt the following technical scheme that：A kind of short circuit current zero passage prediction technique, it is special
Sign is：Include the following steps：
(1) by short trouble short circuit current when samples, and obtains short circuit current instantaneous value i (k), and wherein k is
Current sample time point；
(2) first derivation operation is carried out to short circuit current instantaneous value, the short circuit current single order for obtaining current sample time is led
Number i'(k)；
(3) second order derivative operation is carried out to short circuit current instantaneous value, the short circuit current second order for obtaining current sample time is led
Number i " (k)；
(4) pass through short circuit current instantaneous value i (k), short circuit current first derivative i'(k) and short circuit current second dervative i "
(k) following operation is carried out, current time short-circuit current forecast value i is constructedp(k), expression formula is：
Wherein, ω is short circuit current angular frequency；
(5) to the short-circuit current forecast value i of constructionp(k) zero-crossing examination is carried out, if short-circuit current forecast value ip(k) meet
ip(k)×ip(k-1)≤0, then it is assumed that short-circuit current forecast value ip(k) in current sample time point k zero passages, ip(k-1) it is previous
Sampling instant point short-circuit current forecast value.
A kind of short circuit current zero passage prediction technique above-mentioned, it is characterized in that：Further include to after sampling in the step (1)
Short circuit current is filtered.
3. a kind of short circuit current zero passage prediction technique according to claim 1, it is characterized in that：The sampling instant
Short circuit current first derivative i'(k) it is sought using numerical differentiation method, expression formula is：
I'(k)=[i (k)-i (k-1)]/Ts (1)
Wherein, TsFor the sampling period, k-1 is previous sampling instant point, and i (k-1) is previous sampling instant point short circuit current
Instantaneous value.
A kind of short circuit current zero passage prediction technique above-mentioned, it is characterized in that：Current sample time is short in the step (3)
Road electric current second dervative i " (k) is sought using numerical differentiation method, and expression formula is：
I " (k)=[i (k)+i (k-2) -2 × i (k-1)]/Ts 2 (2)
Wherein, TsFor the sampling period, k-1 is previous sampling instant point, and i (k-1) is previous sampling instant point short circuit current
Instantaneous value, k-2 are the first two sampling instant point, and i (k-2) is the first two sampling instant point short circuit current instantaneous value.
A kind of short circuit current zero passage prediction technique above-mentioned, it is characterized in that：The short circuit current angular frequency=2 π f, f are
System frequency takes f=50Hz in engineering.
A kind of short circuit current zero passage prediction technique above-mentioned, it is characterized in that：The short-circuit current forecast value i of the constructionp(k)
It is ahead of current short-circuit current value i (k) a quarter cycle.
The advantageous effect that the present invention is reached：
(1) present invention, which utilizes short circuit current and its differentiates, constructs another electric current, and the electric current is made to surpass in phase
It is preceding that the zero crossing of electric current is constructed by detection in former short circuit current certain time, it is short to predict original after the set time
Road current zero-crossing point, due to only shifting to an earlier date short circuit current in time, prediction result is accurate and reliable；
(2) present invention is filtered short circuit current, to reduce the interference of high-frequency signal, improves system
Reliability；
(3) due to the present invention only with simple arithmetical operation and square, the operations such as evolution, reduce software and hardware and open
Pin, technical solution are implemented simple and effective.
Description of the drawings
Fig. 1 is flow chart of the present invention.
Specific implementation mode
The invention will be further described below in conjunction with the accompanying drawings.Following embodiment is only used for clearly illustrating the present invention
Technical solution, and not intended to limit the protection scope of the present invention.
Embodiment：
As shown in Figure 1, a kind of short circuit current zero passage prediction technique, includes the following steps：
(1) by short trouble short circuit current when carries out high frequency sampling, obtains short circuit current instantaneous value i (k), wherein
K is current sample time point, simultaneously because high-frequency interferencing signal may be superimposed in short circuit current, before carrying out data processing
It is necessary to be filtered to short circuit current；
(2) first derivation operation is carried out to short circuit current instantaneous value, the short circuit current single order for obtaining current sample time is led
Number i'(k)；In the present embodiment, short circuit current first derivative i'(k is sought using numerical differentiation method), i'(k can be obtained)
Discrete expression is：
I'(k)=[i (k)-i (k-1)]/Ts (1)
Wherein, TsFor the sampling period, k-1 is previous sampling instant point, and i (k-1) is previous sampling instant point short circuit current
Instantaneous value；
(3) second order derivative operation is carried out to short circuit current instantaneous value, the short circuit current second order for obtaining current sample time is led
Number i " (k) seeks short circuit current second dervative i " (k) using numerical differentiation method, can obtain i " (k) in the present embodiment
Discrete expression is：
I " (k)=[i (k)+i (k-2) -2 × i (k-1)]/Ts 2 (2)
Wherein, k-2 is the first two sampling instant point, and i (k-2) is the first two sampling instant point short circuit current instantaneous value；
(4) pass through short circuit current instantaneous value i (k), short circuit current first derivative i'(k) and short circuit current second dervative i "
(k) following operation is carried out, current time short-circuit current forecast value i is constructedp(k), expression formula is：
Wherein, short circuit current angular frequency=2 π f, f is system frequency, and f=50Hz is taken in engineering；
(5) to the short-circuit current forecast value i of constructionp(k) zero-crossing examination is carried out, if short-circuit current forecast value ip(k) meet
ip(k)×ip(k-1)≤0, then it is assumed that short-circuit current forecast value ip(k) in current sample time point k zero passages, ip(k-1) it is previous
Sampling instant point short-circuit current forecast value.Due to the short-circuit current forecast value i of constructionp(k) it is ahead of practical (current) short circuit electricity
Flow valuve i (k) a quarter cycles, therefore pass through short-circuit current forecast value ip(k) zero crossing can predict four/
The zero crossing of actual short electric current after one cycle.
According to experiment results proved, above method can fast and effeciently predict short circuit current zero crossing, protect in order to control
The action policy of protecting system provides reliable foundation.
The present invention first to short trouble when short circuit current sample and be filtered, then to filtered short circuit
Electric current carries out Numerical Value Derivative operation, calculates separately out short circuit current first derivative and second dervative, and combine short circuit current angular frequency
Rate carries out a series of operations and constructs the short-circuit current forecast value that phase is ahead of former short circuit current a quarter cycle, passes through
The zero crossing of the short-circuit current forecast value of construction is detected, predicts the zero crossing of actual short electric current.The present invention can be accurate and reliable
Ground predicts short circuit current zero crossing, has stronger anti-interference ability, technical solution is simple and effective and practicability is stronger.
The above is only a preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art
For member, without departing from the technical principles of the invention, several improvement and deformations can also be made, these improvement and deformations
Also it should be regarded as protection scope of the present invention.
Claims (6)
1. a kind of short circuit current zero passage prediction technique, it is characterised in that：Include the following steps：
(1) by short trouble short circuit current when samples, and obtains short circuit current instantaneous value i (k), and wherein k is current
Sampling instant point；
(2) first derivation operation is carried out to short circuit current instantaneous value, obtains the short circuit current first derivative i' of current sample time
(k)；
(3) second order derivative operation is carried out to short circuit current instantaneous value, obtains the short circuit current second dervative i " of current sample time
(k)；
(4) pass through short circuit current instantaneous value i (k), short circuit current first derivative i'(k) and short circuit current second dervative i " (k) into
The following operation of row, constructs current time short-circuit current forecast value ip(k), expression formula is：
Wherein, ω is short circuit current angular frequency；
(5) to the short-circuit current forecast value i of constructionp(k) zero-crossing examination is carried out, if short-circuit current forecast value ip(k) meet ip
(k)×ip(k-1)≤0, then it is assumed that short-circuit current forecast value ip(k) in current sample time point k zero passages, ip(k-1) it is previous adopt
Sample moment point short-circuit current forecast value.
2. a kind of short circuit current zero passage prediction technique according to claim 1, it is characterized in that：It is also wrapped in the step (1)
It includes and the short circuit current after sampling is filtered.
3. a kind of short circuit current zero passage prediction technique according to claim 1, it is characterized in that：The short circuit of the sampling instant
Electric current first derivative i'(k) it is sought using numerical differentiation method, expression formula is：
I'(k)=[i (k)-i (k-1)]/Ts (1)
Wherein, TsFor the sampling period, k-1 is previous sampling instant point, and i (k-1) is that previous sampling instant point short circuit current is instantaneous
Value.
4. a kind of short circuit current zero passage prediction technique according to claim 1, it is characterized in that：It is current in the step (3)
The short circuit current second dervative i " (k) of sampling instant is sought using numerical differentiation method, and expression formula is：
I " (k)=[i (k)+i (k-2) -2 × i (k-1)]/Ts 2 (2)
Wherein, TsFor the sampling period, k-1 is previous sampling instant point, and i (k-1) is that previous sampling instant point short circuit current is instantaneous
Value, k-2 are the first two sampling instant point, and i (k-2) is the first two sampling instant point short circuit current instantaneous value.
5. a kind of short circuit current zero passage prediction technique according to claim 1, it is characterized in that：The short circuit current angular frequency
The π of ω=2 f, f are system frequency, and f=50Hz is taken in engineering.
6. a kind of short circuit current zero passage prediction technique according to claim 1, it is characterized in that：The short circuit current of the construction
Predicted value ip(k) it is ahead of current short-circuit current value i (k) a quarter cycle.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112260390A (en) * | 2020-10-12 | 2021-01-22 | 宁夏凯晨电气集团有限公司 | Electrical phase prediction device based on second derivative algorithm |
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| CN112260390A (en) * | 2020-10-12 | 2021-01-22 | 宁夏凯晨电气集团有限公司 | Electrical phase prediction device based on second derivative algorithm |
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Application publication date: 20181106 |