CN111244957B - Active power filter control algorithm based on voltage closed-loop control - Google Patents
Active power filter control algorithm based on voltage closed-loop control Download PDFInfo
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- CN111244957B CN111244957B CN202010162492.XA CN202010162492A CN111244957B CN 111244957 B CN111244957 B CN 111244957B CN 202010162492 A CN202010162492 A CN 202010162492A CN 111244957 B CN111244957 B CN 111244957B
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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]
Abstract
The invention relates to an active power filter control algorithm based on voltage closed-loop control, which comprises the following steps: obtaining input non-sinusoidal alternating current; obtaining a first voltage of an input non-sinusoidal alternating current; carrying out Fourier series decomposition on the input non-sinusoidal alternating current quantity to obtain fundamental waves and harmonic waves; classifying according to the frequency of the harmonic wave; obtaining one or more first waveforms of non-sinusoidal alternating flow corresponding to harmonic waves in a Cartesian coordinate system; respectively outputting a second waveform opposite to each first waveform to offset the corresponding first waveform; obtaining a second voltage of the output non-sinusoidal alternating current in a Cartesian coordinate system; and comparing the difference value between the second voltage and the first voltage, and if the difference value exceeds the allowable range, adjusting the second waveform to enable the difference value between the second voltage and the first voltage to fall back into the allowable range. The method is used for strategy control of the active power filter, can perform dynamic adjustment based on the output result, and improves the output precision of the filter.
Description
Technical Field
The invention relates to the technical field of filter algorithm control, in particular to an active power filter control algorithm based on voltage closed-loop control.
Background
The filter is used for filtering a frequency point of a specific frequency in a power supply or an unexpected frequency of the frequency point to obtain a power supply signal of the specific frequency or eliminate the power supply signal of the specific frequency, and can be divided into a passive type and an active type according to the working principle of the filter.
The core of the active filter lies in a built-in algorithm which determines the processing process of input voltage and also determines the final power output precision.
Most of the existing algorithms are based on open-loop control, that is, corresponding adjustment is started after input electric signals are detected, the adjustment mode is relatively fixed, the adjusted output result cannot be fed back to the adjustment process, and when the input power supply fluctuates, the output result also fluctuates.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an active power filter control algorithm based on voltage closed-loop control, which can dynamically adjust the adjustment process based on the output result and improve the output precision of the filter.
The above object of the present invention is achieved by the following technical solutions:
an active power filter control algorithm based on voltage closed-loop control comprises the following steps:
obtaining input non-sinusoidal alternating current;
obtaining a first voltage of an input non-sinusoidal alternating current;
carrying out Fourier series decomposition on the input non-sinusoidal alternating current quantity to obtain fundamental waves and harmonic waves;
classifying according to the frequency of the harmonic wave;
obtaining one or more first waveforms of non-sinusoidal alternating flow corresponding to harmonic waves in a Cartesian coordinate system;
respectively outputting a second waveform opposite to each first waveform to offset the corresponding first waveform;
obtaining a second voltage of the output non-sinusoidal alternating current in a Cartesian coordinate system; and
and comparing the difference value between the second voltage and the first voltage, and if the difference value exceeds the allowable range, adjusting the second waveform to enable the difference value between the second voltage and the first voltage to fall back into the allowable range.
By adopting the technical scheme, after voltage detection and Fourier series decomposition are carried out on the input non-sinusoidal alternating current, the first voltage and the corresponding fundamental wave and harmonic wave are obtained, then the obtained harmonic wave is classified and the first waveform in a Cartesian coordinate system is obtained, finally, filtering is carried out according to the first waveform, in the filtering process, the second waveform opposite to the first waveform is generated and used for offsetting the first waveform, and in the adjusting process, the second waveform is dynamically adjusted according to the difference value of the output second voltage and the first voltage. In the adjustment mode, the harmonics are classified, and each type of harmonics is eliminated, so that the output precision can be further improved, the process of eliminating the harmonics can be dynamically adjusted according to the output second voltage, the fluctuation characteristic of the input non-sinusoidal alternating flow is fitted, the output precision can be further improved, and the influence of input fluctuation on the output precision is reduced.
In a preferred embodiment of the invention: after Fourier series decomposition is carried out on the input non-sinusoidal alternating current quantity, classification is carried out according to harmonic frequencies, and in the classification process, the number of the harmonics with different frequencies in each class is 3-5.
By adopting the technical scheme, the number of the harmonic waves in each group is limited, the number comprehensively considers the precision and the control cost, the control strategy complication caused by too many groups is avoided, and the output precision reduction caused by too few groups is also avoided.
In a preferred embodiment of the invention: in a cartesian coordinate system, the second waveform is discontinuous, and each second waveform segment is located between two intersection points of the corresponding first waveform segment and the coordinate axis.
By adopting the technical scheme, a specific form of the second waveform is provided, the length of the second waveform section is smaller than that of the corresponding first waveform section, namely the appearance time of the second waveform section lags behind the appearance time of the corresponding first waveform section or the appearance time of the first waveform section lags behind the appearance time of the corresponding first waveform section or the appearance time of the second waveform section and the disappearance time of the second waveform section lags behind the disappearance time of the corresponding first waveform section or the disappearance time of the first waveform section and the disappearance time of the second waveform section and the disappearance time of the first waveform section and the disappearance time of the second waveform section, so that the length of each second waveform section is smaller than that of the corresponding first waveform section, the ratio of the processing capacity of the first waveform section to.
In a preferred embodiment of the invention: and the intersection point of each second waveform segment and the coordinate axis is positioned between the two corresponding intersection points of the first waveform segment and the coordinate axis.
By adopting the technical scheme, the appearance time of each second waveform segment lags behind the appearance time of the corresponding first waveform segment, and the disappearance time is earlier than the disappearance time of the corresponding first waveform segment, so that the increase of the numerical control difficulty of the corresponding second waveform segment caused by the small numerical value of the first waveform segment at the position close to the coordinate axis can be avoided.
In a preferred embodiment of the invention: the distance between the intersection point of the second waveform section and the coordinate axis and the intersection point of the corresponding first waveform section and the coordinate axis is 5-8% of the distance between the two intersection points of the first waveform section and the coordinate axis.
By adopting the technical scheme, the appearance time and the disappearance time of the second waveform segment are further given.
In a preferred embodiment of the invention: the absolute value of the minimum distance between the point on the second waveform segment and the coordinate axis is smaller than the absolute value of the minimum distance between the point on the first waveform segment and the coordinate axis corresponding to the absolute value.
By adopting the technical scheme, the numerical value of the second waveform segment is limited, so that a new interference waveform cannot be generated when the second waveform segment is offset with the corresponding first waveform segment, and the output precision can be further improved.
In a preferred embodiment of the invention: the absolute value of the minimum distance between the point on the second waveform section and the coordinate axis is 95% -99% of the absolute value of the minimum distance between the point on the first waveform section and the coordinate axis.
By adopting the technical scheme, the difference between the second waveform segment and the corresponding first waveform segment is further limited, and the final output precision is properly reduced by reducing the numerical value of the point on the second waveform segment, so that on one hand, the output precision of the second waveform segment can be reduced, and on the other hand, the difference can be used as the accommodation of the output fluctuation error of the second waveform segment, and the influence of the difference on the final output precision is reduced.
In a preferred embodiment of the invention: the preferred range of the absolute value of the minimum distance between the point on the second waveform segment and the coordinate axis is 97% -98% of the absolute value of the minimum distance between the point on the corresponding first waveform segment and the coordinate axis.
In conclusion, the beneficial technical effects of the invention are as follows:
1. in the working process, after voltage detection and Fourier series decomposition are carried out on input non-sinusoidal alternating current, first voltage and corresponding fundamental waves and harmonic waves are obtained, then the obtained harmonic waves are classified, first waveforms in a Cartesian coordinate system are obtained, finally filtering is carried out according to the first waveforms, second waveforms opposite to the first waveforms are generated in the filtering process and used for offsetting the first waveforms, and dynamic adjustment is carried out on the second waveforms according to the difference value of the output second voltage and the first voltage in the adjusting process. In the adjustment mode, the harmonics are classified, and each type of harmonics is eliminated, so that the output precision can be further improved, the process of eliminating the harmonics can be dynamically adjusted according to the output second voltage, the fluctuation characteristic of the input non-sinusoidal alternating flow is fitted, the output precision can be further improved, and the influence of input fluctuation on the output precision is reduced.
2. In the process of grouping the harmonic waves, the number of the harmonic waves in each group is limited, the number comprehensively considers the precision and the control cost, the control strategy complication caused by too many groups is avoided, and the output precision reduction caused by too few groups is also avoided.
3. The length of the second waveform segment is smaller than that of the corresponding first waveform segment, namely the appearance time lags behind the appearance time of the corresponding first waveform segment or the appearance time and the disappearance time of the second waveform segment are simultaneously shown, and the disappearance time is earlier than the disappearance time of the corresponding first waveform segment or the disappearance time and the disappearance time of the first waveform segment are simultaneously shown, so that the length of each second waveform segment is smaller than that of the corresponding first waveform segment, the occupation ratio of the processing amount of the first waveform segment in the total amount can be effectively improved, and the output precision is improved.
4. The appearance time of each second waveform segment lags behind the appearance time of the corresponding first waveform segment, and the disappearance time of each second waveform segment is ahead of the disappearance time of the corresponding first waveform segment, so that the numerical control difficulty of the corresponding second waveform segment caused by the small numerical value of the first waveform segment at the position close to the coordinate axis can be avoided.
5. In the filtering process, the absolute value of the numerical value on the second waveform segment is always smaller than the absolute value of the numerical value on the corresponding first waveform segment, so that in the process of offsetting the absolute value of the numerical value on the second waveform segment and the absolute value of the numerical value on the corresponding first waveform segment, a new interference waveform cannot be generated, and the output precision can be further improved.
Drawings
Fig. 1 is a schematic block diagram of a process provided by an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Referring to fig. 1, an active power filter control algorithm based on voltage closed-loop control disclosed in an embodiment of the present invention includes the following steps:
s101, obtaining input non-sinusoidal alternating current.
In this step, the non-sinusoidal ac power to be processed is input to the active power filter.
Conventional power supplies for production or life are all three-phase power, theoretically, the waveform of any phase point in the three-phase power is a sine function, but in practice, various interference factors such as manufacturing errors and loss need to be considered, the actual waveform is the superposition of a plurality of waveforms, and the superposed waveform comes in and comes out of the required waveform, so that the required waveform needs to be filtered, and the unnecessary waveform is filtered.
This superimposed waveform is commonly referred to as a non-sinusoidal alternating current.
S102, obtaining a first voltage of the input non-sinusoidal alternating current.
The purpose of this step is to obtain an initial voltage of the input for comparison with the output voltage obtained subsequently, and to perform dynamic adjustment according to the difference between the two voltages, so as to form a closed-loop control strategy based on the voltage.
And S103, carrying out Fourier series decomposition on the input non-sinusoidal alternating current quantity to obtain fundamental waves and harmonic waves.
The step is to process the input non-sinusoidal alternating current, because the input non-sinusoidal alternating current is formed by overlapping a plurality of waveforms, the processing cannot be directly performed, the original waveforms need to be obtained, and then different processing strategies are adopted according to different waveforms.
After fourier series decomposition, several waveforms are obtained, and the frequency of each waveform is different. In general, the frequency of the desired waveform is 50 hz, and a wave having a frequency of 50 hz is referred to as a fundamental wave, and a wave having a frequency other than 50 hz is referred to as a harmonic wave.
The fundamental wave is a wave that meets the use requirement, and the harmonic wave is an interference wave, so the harmonic wave needs to be removed.
And S104, classifying according to the frequency of the harmonic waves.
In this step, the harmonics in step S103 are classified because the harmonics are of a large frequency, and if the harmonics of each frequency are individually processed, the processing equipment and the processing strategy will be inevitably complicated, and on the premise of comprehensively considering the final output accuracy and the processing cost, the harmonics are processed in a grouping manner, that is, one control strategy is used for a certain group of harmonics, so that the processing cost can be reduced as much as possible on the premise of satisfying the output accuracy.
And S105, one or more first waveforms of the non-sinusoidal alternating flow corresponding to the harmonic waves in a Cartesian coordinate system are obtained.
The purpose of this step is to obtain a waveform that can be parameterized so that an appropriate control strategy can be selected based on the waveform. Here the parameterized waveform is chosen to be generated in a cartesian coordinate system.
A parameterized waveform generated in a Cartesian coordinate system by a non-sinusoidal alternating flow corresponding to a harmonic is called a first waveform.
S106, outputting a second waveform opposite to each first waveform respectively to cancel the corresponding first waveform.
This step is to process the obtained first waveforms and customize each first waveform with its opposite second waveform. In a cartesian coordinate system, when two waveforms are both located on the same side of a coordinate axis, the two waveforms are superimposed together, and when the two waveforms are divided to be located on both sides of the coordinate axis, the two waveforms are cancelled out. Therefore, by outputting the second waveform opposite to the first waveform, the first waveform can be eliminated, and the purpose of weakening or removing can be achieved.
And S107, obtaining a second voltage of the output non-sinusoidal alternating current in a Cartesian coordinate system.
The purpose of this step is to obtain the final output voltage for comparison with the input voltage obtained as described above, and to perform dynamic adjustment according to the difference between the two voltages, so as to form a closed-loop control strategy based on voltage.
S108, comparing the difference value between the second voltage and the first voltage, and if the difference value exceeds the allowable range, adjusting the second waveform to enable the difference value between the second voltage and the first voltage to fall back to the allowable range.
This step is based on step S107, comparing the difference between the first voltage and the second voltage, and then dynamically adjusting the output second waveform according to the difference, so that the actual output voltage fluctuates within an allowable range.
In the processing process, the processing precision and the actual processing cost need to be considered at the same time, and the higher the processing precision is, the higher the corresponding processing cost is, so that on the premise of meeting the processing precision, a proper strategy needs to be used for reducing the processing cost.
Therefore, when the harmonics are classified in step S104, the number of the harmonic frequency frequencies in each class is controlled to be 3-5, and the classification method processes the waveforms obtained by superimposing a plurality of harmonics as an integral waveform, so that the processing difficulty can be reduced, and the processing cost can be reduced after the opposition difficulty is reduced, thereby better meeting the requirements of actual production.
In order to further improve the output accuracy and reduce the control cost, in step S106, the waveform of the second waveform is changed to be discontinuous, that is, the second waveform is composed of a plurality of second waveform segments, each of which corresponds to a first waveform segment, and the first waveform segment is a portion between the first waveform and two adjacent intersection points of the coordinate axis.
Therefore, the overlapping part of the first waveform and the second waveform can be reduced, and new interference at the overlapping part is avoided. Because the waveform fed back from the Cartesian coordinate system is fluctuant, the second waveform is fluctuant, the numerical values of the two waveforms are very small at the position close to the coordinate axis, the numerical equality difficulty is very high, and the realization cost is very high, so that the part is omitted, the secondary interference caused by insufficient precision control is avoided, and the control cost can be effectively reduced.
Furthermore, the intersection point of each second waveform segment and the coordinate axis is located between the two corresponding intersection points of the first waveform segment and the coordinate axis, and the distance between the intersection point of the second waveform segment and the coordinate axis and the intersection point of the corresponding first waveform segment and the coordinate axis is 5-8% of the distance between the two intersection points of the first waveform segment and the coordinate axis.
Meanwhile, considering the fluctuation of the second waveform segment in the value, if the value corresponding to a certain point is equal to the value corresponding to the first waveform segment at the point, the difficulty is considerable, so that the second waveform segment is properly adjusted in a specific way: and the absolute value of the minimum distance between the point on the second waveform segment and the coordinate axis is smaller than the absolute value of the minimum distance between the point on the first waveform segment corresponding to the absolute value and the coordinate axis, and the reserved partial difference value is used as buffer to absorb the numerical fluctuation of the second waveform segment.
Further, the absolute value of the minimum distance between a point on the second waveform segment and the coordinate axis is 95% -99% of the absolute value of the minimum distance between a point on the corresponding first waveform segment and the coordinate axis.
At the same time, in order to improve the accuracy again, a further limitation is made to this preferred range, that is, the preferred range in which the absolute value of the minimum distance between a point on the second waveform segment and the coordinate axis is 97% to 98% of the absolute value of the minimum distance between a corresponding point on the first waveform segment and the coordinate axis corresponding thereto.
The embodiments of the present invention are preferred embodiments of the present invention, and the scope of the present invention is not limited by these embodiments, so: all equivalent changes made according to the structure, shape and principle of the invention are covered by the protection scope of the invention.
Claims (6)
1. An active power filter control algorithm based on voltage closed-loop control is characterized by comprising the following steps:
obtaining input non-sinusoidal alternating current;
obtaining a first voltage of an input non-sinusoidal alternating current;
carrying out Fourier series decomposition on the input non-sinusoidal alternating current quantity to obtain fundamental waves and harmonic waves;
classifying according to the frequency of the harmonic wave;
obtaining one or more first waveforms of non-sinusoidal alternating flow corresponding to harmonic waves in a Cartesian coordinate system;
respectively outputting a second waveform opposite to each first waveform to offset the corresponding first waveform;
obtaining a second voltage of the output non-sinusoidal alternating current in a Cartesian coordinate system; and
comparing the difference value of the second voltage and the first voltage, if the difference value exceeds the allowable range, adjusting the second waveform to enable the difference value of the second voltage and the first voltage to fall back to the allowable range;
after Fourier series decomposition is carried out on the input non-sinusoidal alternating current, classification is carried out according to harmonic frequencies, and in the classification process, the number of the harmonics with different frequencies in each class is 3-5;
in a cartesian coordinate system, the second waveform is discontinuous, and each second waveform segment is located between two intersection points of the corresponding first waveform segment and the coordinate axis.
2. The active power filter control algorithm based on voltage closed-loop control according to claim 1, wherein: and the intersection point of each second waveform segment and the coordinate axis is positioned between the two corresponding intersection points of the first waveform segment and the coordinate axis.
3. The active power filter control algorithm based on voltage closed-loop control according to claim 2, wherein: the distance between the intersection point of the second waveform section and the coordinate axis and the intersection point of the corresponding first waveform section and the coordinate axis is 5-8% of the distance between the two intersection points of the first waveform section and the coordinate axis.
4. The active power filter control algorithm based on voltage closed-loop control according to any one of claims 1 to 3, characterized in that: the absolute value of the minimum distance between the point on the second waveform segment and the coordinate axis is smaller than the absolute value of the minimum distance between the point on the first waveform segment and the coordinate axis corresponding to the absolute value.
5. The active power filter control algorithm based on voltage closed-loop control according to claim 4, wherein: the absolute value of the minimum distance between the point on the second waveform section and the coordinate axis is 95% -99% of the absolute value of the minimum distance between the point on the first waveform section and the coordinate axis.
6. The active power filter control algorithm based on voltage closed-loop control according to claim 5, wherein: the preferred range of the absolute value of the minimum distance between the point on the second waveform segment and the coordinate axis is 97% -98% of the absolute value of the minimum distance between the point on the corresponding first waveform segment and the coordinate axis.
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| US7834643B2 (en) * | 2008-03-28 | 2010-11-16 | Baker Hughes Incorporated | Systems and methods for reducing distortion in a power source using an active harmonics filter |
| CN101572535A (en) * | 2008-04-01 | 2009-11-04 | 硅谷实验室公司 | System and method of changing a PWM power spectrum |
| CN110707698A (en) * | 2019-11-04 | 2020-01-17 | 四川英杰电气股份有限公司 | Method, device and equipment for compensating harmonic current and readable storage medium |
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