CN109038580B - Method for solving APF fault caused by sliding dft abnormity caused by load sudden change - Google Patents
Method for solving APF fault caused by sliding dft abnormity caused by load sudden change Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/20—Active power filtering [APF]
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Abstract
The invention discloses a solutionThe method for solving the problem that the load sudden change causes the sliding dft abnormality to cause the APF fault comprises the following steps: a. will load current iL(t) calculating a positive-sequence active current direct current component i as a study objectpThe array P for calculation result1To record; b. extracting each harmonic component in the load current by a sliding dft algorithm, and using an array P as a calculation result2To record; c. calculating a multiple actual value S 'and a difference actual value T'; d. determining a multiple threshold S and a difference threshold T; e. if S '> S and T' > T are established, determining that the load current is mutated; if not, the load current does not have mutation; f. when the load current is judged to be suddenly changed, the harmonic command current of the APF in the future period adopts the value of each harmonic component calculated by the sliding dft of the previous power frequency period. The invention can still realize the stable operation of the APF when the load is suddenly changed, is convenient and reliable, and can not influence the work of the power grid.
Description
Technical Field
The invention relates to the technical field of circuits, in particular to the technical field of circuit fault processing in a power system and automation thereof, and more particularly relates to a method for solving APF faults caused by sliding dft abnormity caused by sudden load change.
Background
In a low voltage 400V grid system, due to the presence of non-linear loads, distortions, i.e. harmonics, of the sinusoidal waveform of the power system voltage or current may be caused, which in the case of asymmetric loads may even result in unbalanced currents. The APF is a novel power electronic device for dynamically inhibiting harmonic waves and compensating reactive power, can quickly track and compensate harmonic waves with different sizes and frequencies, can sample load current and separate each harmonic wave from reactive power to control and actively output the size, frequency and phase of the current, can quickly respond and offset corresponding current in the load and realizes dynamic tracking compensation compared with a passive LC filter which can only passively absorb the harmonic waves with fixed frequency and size. To compensate the load harmonics, an effective harmonic extraction method is necessary, and the slip DFT can accurately separate specific sub-harmonics, but when the load current suddenly changes, the DFT separation result generates a large spike, that is, a small number of points in the DFT calculation result are obviously far larger or far smaller than the values of the nearby points, and in a serious case, the APF fails to operate stably and continuously.
For example, patent application No. cn201510616390.x, publication date 2015, 12, month 9, and patent name "a method for designing a nonlinear controller of a hybrid active filter", includes: a nonlinear control strategy based on the Lyapunov function is provided, decoupling control of reactive compensation current is achieved, and harmonic reference current is tracked rapidly; the method aims at enhancing the anti-interference performance of the system, obtains the optimal gain of the controller, and ensures that the system can still stably operate when the system parameters are perturbed or the load demand is changed in a step mode. The voltage ring adopts a sliding mode nonlinear control method, so that the voltage of the capacitor is kept stable, dynamic adjustment during sudden load change is realized, and the disturbance resistance of the system is enhanced. Although the controller designed by the above patent has the anti-interference capability of a system, the system can be quickly recovered and stabilized when the parameters are perturbed and the load current is subjected to step change, and the controller has the characteristics of high robustness, the method structure is complex, and the hardware cost is high.
Disclosure of Invention
In order to overcome the defects and shortcomings in the prior art, the invention provides a method for solving the problem of APF faults caused by abnormal sliding ft caused by sudden change of load.
In order to achieve the above object, the technical solution of the present invention is as follows:
a method for solving APF faults caused by sliding dft abnormity caused by load sudden change comprises the following steps:
a. load current i sampled by current CTL(t) as a research object, calculating a positive sequence active current direct current component i according to a three-phase circuit instantaneous reactive power theorypThe result is set P1Recording, recording the calculation result of this time as a new value A', and recording the adjacent calculation result of the last time as an old value A;
b. load current i sampled by current CTL(t) extracting the harmonic components of the load current by sliding dft algorithm, and using the result as an array P2To record;
c. calculating a multiple actual value S ' and a difference actual value T ' according to the new value A ' and the old value A in the step a;
d. determining a multiple threshold S and a difference threshold T according to the old value A in the step a;
e. if S '> S and T' > T are established, determining that the load current is mutated; if not, the load current does not have mutation;
f. when the load current is judged to be suddenly changed, the harmonic command current of the APF in the future period adopts the value of each harmonic component calculated by the sliding dft of the previous power frequency period.
In the step a, the positive sequence active current direct current component is calculated according to the following formula:
wherein iα，iβTwo axes representing a stationary coordinate system, C and C32Is a constant matrix, ia、ib、icThree phases of load current a, b and c, omega is angular frequency, t is time variable, ipAnd iqPositive sequence active current direct current components and positive sequence reactive current direct current components are respectively.
In the step b, the algorithm for extracting each subharmonic component in the load current is as follows:
according to Fourier decomposition, load current iL(t) is expressed as follows:
wherein: a is0Is a direct current component; t is iL(t) period; omega is angular frequency; t is a time variable; n is 0, 1, 2 …; when n is 3, 5, 7, 9 …, etc, the harmonics in the load current can be obtainedA wave component.
The calculation method of the multiple actual value S' in the step c comprises the following steps:
if A' > A is added to the mixture,
if A' < A,
the calculation method of the actual difference value T' in the step c comprises the following steps:
T′＝abs(A′-A)。
the array P1And array P2The number of the sampling points is one power frequency period sampling point number.
The invention has the beneficial effects that:
the method comprises the steps of detecting the load of the power grid in real time, taking the load current sampled by current CT as a research object, processing the load current in a power frequency period through a three-phase circuit instantaneous reactive power theory and a sliding dft algorithm to respectively obtain a positive sequence active current direct current component and a load current harmonic component in the power frequency period, and analyzing the change condition of the positive sequence active current direct current component to judge whether the load current changes suddenly so as to further obtain whether the load of the power grid changes suddenly. For the power grid with sudden load change, the command current of the APF adopts the value of each harmonic component calculated by the sliding dft of the last power frequency cycle, namely, the response of one power frequency cycle is delayed to avoid that the stable operation of the APF is influenced by the sharp spike generated by the sudden load change on the calculation result of the sliding dft so as to cause the failure of the APF. The invention can still realize the stable operation of the APF when the load of the power grid system is suddenly changed, prevents the resonance from damaging equipment, is convenient to realize, has high reliability and cannot influence the work of the power grid system.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
Example 1
A method for solving APF faults caused by sliding dft abnormity caused by load sudden change comprises the following steps:
a. load current i sampled by current CTL(t) as a research object, calculating a positive sequence active current direct current component i according to a three-phase circuit instantaneous reactive power theorypThe result is set P1Recording, recording the calculation result of this time as a new value A', and recording the adjacent calculation result of the last time as an old value A;
b. load current i sampled by current CTL(t) extracting the harmonic components of the load current by sliding dft algorithm, and using the result as an array P2To record;
c. calculating a multiple actual value S ' and a difference actual value T ' according to the new value A ' and the old value A in the step a;
d. determining a multiple threshold S and a difference threshold T according to the old value A in the step a;
e. if S '> S and T' > T are established, determining that the load current is mutated; if not, the load current does not have mutation;
f. when the load current is judged to be suddenly changed, the harmonic command current of the APF in the future period adopts the value of each harmonic component calculated by the sliding dft of the previous power frequency period.
Example 2
A method for solving APF faults caused by sliding dft abnormity caused by load sudden change comprises the following steps:
a. load current i sampled by current CTL(t) as a research object, calculating a positive sequence active current direct current component i according to a three-phase circuit instantaneous reactive power theorypThe result is set P1Recording, recording the calculation result of this time as a new value A', and recording the adjacent calculation result of the last time as an old value A;
b. load current i sampled by current CTL(t) extracting the harmonic components of the load current by sliding dft algorithm, and using the result as an array P2To record;
c. calculating a multiple actual value S ' and a difference actual value T ' according to the new value A ' and the old value A in the step a;
d. determining a multiple threshold S and a difference threshold T according to the old value A in the step a;
e. if S '> S and T' > T are established, determining that the load current is mutated; if not, the load current does not have mutation;
f. when the load current is judged to be suddenly changed, the harmonic command current of the APF in the future period adopts the value of each harmonic component calculated by the sliding dft of the previous power frequency period.
In the step a, the positive sequence active current direct current component is calculated according to the following formula:
wherein iα，iβTwo axes representing a stationary coordinate system, C and C32Is a constant matrix, ia、ib、icThree phases of load current a, b and c, omega is angular frequency, t is time variable, ipAnd iqPositive sequence active current direct current components and positive sequence reactive current direct current components are respectively.
In the step b, the algorithm for extracting each subharmonic component in the load current is as follows:
according to Fourier decomposition, load current iL(t) is expressed as follows:
wherein: a is0Is a direct current component; t is iL(t) period; omega is angular frequency; t is a time variable; n is 0, 1, 2 …; when n is 3, 5, 7, 9 …, the harmonic components in the load current can be obtained.
The calculation method of the multiple actual value S' in the step c comprises the following steps:
if A' > A is added to the mixture,
if A' < A,
the calculation method of the actual difference value T' in the step c comprises the following steps:
T′＝abs(A′-A)。
the array P1And array P2The number of the sampling points is one power frequency period sampling point number.
The specific implementation mode is as follows:
the load current sampled by current CT is used for calculating the positive sequence active current direct current component i according to the three-phase circuit instantaneous reactive power theorypThe array P for calculation result1Recording, recording the calculation result of this time as a new value A ', recording the adjacent calculation result as an old value A, and recording the logarithm group P when each new value A' is calculated1An update is performed, i.e. the new value A' is put into the array P1In, truncate the array P1Before updating, whether the load current is suddenly changed needs to be judged; extracting each harmonic component in the load current by the load current sampled by the current CT through a sliding dft algorithm, and using an array P2To record, every time a value is calculated, for the array P2Making one update, i.e. discarding the array P2The first calculated value in (1) is put into an array, array P1And P2The number of the sampling points is the number of sampling points in one power frequency period; calculating a multiple actual value S ' and a difference actual value T ' according to the new value A ' and the old value A; determining a multiple threshold S and a difference threshold T according to the old value A; if S '> S and T' > T are true, namely the multiple actual value is greater than the multiple threshold value, and under the condition that the difference actual value is greater than the difference threshold value, the load current is judged to be mutated, and if not, the load current is not mutated; when the load current is judged to be suddenly changed, the instruction current of one future period of the APF adopts the last power frequency period to slide dftAnd calculating the value of each harmonic component, namely delaying a power frequency period response. Wherein, the multiple threshold and the difference threshold are determined by a simulation experiment method, and the change range of the old value A is marked as 0-A3The unevenness is divided into 3 segments, and the range of the first segment is described as 0 to A1And the range of the second paragraph is denoted A1～A2And the range of the third segment is marked as A2～A3When the size of the old value A is in the first segment range, the threshold value is determined by the following steps: (1) inputting fundamental wave active current A by adopting relay protection tester1The magnitude of the harmonic current is the upper limit value of the first section of variation range, and in addition, a certain value of harmonic current is arbitrarily input; (2) increasing fundamental wave active current, keeping harmonic current unchanged, performing sliding dft processing on current in the circuit, checking whether a calculation result of dft generates spikes, and if not, returning the fundamental wave active current to A1Increasing the fundamental wave active current again, checking whether the calculation result of the dft generates the spine, and repeating the operation until the calculation result of the dft generates the spine; (3) when the magnitude of the fundamental active current is A'1Then, the calculation result of dft is found to generate a spike, and the actual value of the multiple at the moment is calculated
Difference actual value T '═ abs (A'i-A1) (ii) a (4) The fundamental wave active current input by the relay protection tester is modified into a1Optionally inputting a constant value of harmonic current, a1Is close to the lower limit value of the first section variation range; (5) the active current of the fundamental wave is increased, the harmonic current is kept unchanged, and the value of the increased fundamental wave current is a'1Start, a'1Is less than A'1But far greater than a1If the calculation result of the sliding dft does not have the spine, determining the multiple threshold value
Difference threshold value T ═ abs (A'1-A1) (ii) a (6) If the fundamental wave active current is a'1When the calculation result of the dft generates the spike, the active current of the fundamental wave is reduced, and the current is straightThe calculation result to the dft has no sharp prick, and the fundamental current at the moment is a ″)1Then, the difference threshold is determined to be T ═ abs (a ″)1-a′1) Actual value of the multiple at that time
The magnitudes of S 'and S' are compared, and the multiplier threshold is the greater of the two. If the size of the old value A is in the second section or the third section variation range, the threshold value is determined by adopting the same step method as that when the old value A is in the first section variation range. It should be noted that, when the magnitude of the threshold is determined by a simulation experiment, the fundamental active current in the circuit is increased or decreased to discrete discontinuity, that is, after the fundamental active current is increased or decreased, if no spike appears in the calculation result of dft, the fundamental active current needs to be adjusted back to the value before the increase or decrease, and then the magnitude of the fundamental active current needs to be adjusted again.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.
Claims (3)
1. A method for solving APF (active power filter) faults caused by sliding dft abnormity caused by sudden load change is characterized by comprising the following steps:
a. load current i sampled by current CTL(t) as a research object, calculating a positive sequence active current direct current component i according to a three-phase circuit instantaneous reactive power theorypThe result is set P1Recording, recording the calculation result of this time as a new value A', and recording the adjacent calculation result of the last time as an old value A;
b. load current i sampled by current CTL(t) extracting the harmonic components of the load current by sliding dft algorithm, and using the result as an array P2To record;
c. calculating a multiple actual value S ' and a difference actual value T ' according to the new value A ' and the old value A in the step a;
d. determining a multiple threshold S and a difference threshold T according to the old value A in the step a;
e. if S '> S and T' > T are established, determining that the load current is mutated; if not, the load current does not have mutation;
f. when the load current is judged to be suddenly changed, the harmonic command current of the APF in the future period adopts the value of each subharmonic component calculated by the sliding dft of the previous power frequency period;
in the step a, the positive sequence active current direct current component is calculated according to the following formula:
wherein iα，iβTwo axes representing a stationary coordinate system, C and C32Is a constant matrix, ia、ib、icThree phases of load current a, b and c, omega is angular frequency, t is time variable, ipAnd iqPositive sequence active current direct current components and positive sequence reactive current direct current components are respectively;
the calculation method of the multiple actual value S' in the step c comprises the following steps:
if A' > A is added to the mixture,
if A' < A,
the calculation method of the actual difference value T' in the step c comprises the following steps:
T′＝abs(A′-A)。
2. the method for solving the problem of APF fault caused by sliding dft abnormity caused by load sudden change is disclosed by claim 1, wherein the method comprises the following steps: in the step b, the load current i is extractedLThe algorithm of each harmonic component in (t) is:
according to Fourier decompositionApplying a load current iL(t) is expressed as follows:
wherein: a is0Is a direct current component; t is iL(t) period; omega is angular frequency; t is a time variable; n is 0, 1, 2 …; when n is 3, 5, 7, 9 …, the harmonic components in the load current can be obtained.
3. The method for solving the problem of APF fault caused by sliding dft abnormity caused by load sudden change is disclosed by claim 1, wherein the method comprises the following steps: the array P1And array P2The number of the sampling points is one power frequency period sampling point number.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104113052A (en) * | 2014-06-30 | 2014-10-22 | 浙江大学 | Method for protecting active power filter (APF) |
| CN106253279A (en) * | 2016-08-23 | 2016-12-21 | 南京亚派科技股份有限公司 | A kind of anti-resonance control algolithm being applied to active filter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104113052A (en) * | 2014-06-30 | 2014-10-22 | 浙江大学 | Method for protecting active power filter (APF) |
| CN106253279A (en) * | 2016-08-23 | 2016-12-21 | 南京亚派科技股份有限公司 | A kind of anti-resonance control algolithm being applied to active filter |
Non-Patent Citations (1)
| Title |
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| 基于APF的地铁供配电系统谐波补偿研究;宋平岗等;《科学技术与工程》;20160808;第16卷(第22期);第69-75页 * |
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