CN102478601A - Harmonic calculation method for 64 sampling points of power quality - Google Patents

Abstract

The invention discloses a harmonic calculation method for 64 sampling points of power quality. The method comprises the following steps of: defining a reference value M; reading sampling data of five cyclic waves from a database; performing Fourier transformation on the data to acquire information, storing the information into an array and acquiring the number of harmonic data groups before the group of sampling data; judging whether the harmonic array number is more than the reference value M, if yes, entering the next step, if not, using the Vpcc value of the data as a background harmonic voltage value Vs, then ending; removing the voltage values and the fundamental current which are stored in the array in the M array number at the earliest stage, moving the voltage values and the fundamental current backwards sequentially, sequentially placing the voltage values at the first 19 positions of the array, and storing the fundamental current values in the first position of the array; acquiring the voltage values and the fundamental current values in the newest M group, sequencing the voltage values and the fundamental current values from big to small, taking the seventieth percent of big current value, finding the corresponding voltage value in the array and using the voltage value as the Vs of the data in the group; and calculating background harmonic, user harmonic, voltage ratio and harmonic power of each time. According to the invention, the number of the sampling points in the database is 64 and harmonic index calculation on five cyclic waves is realized.

Description

A kind of Harmonics Calculation method that is used for 64 sampled points of the quality of power supply

Technical field

The present invention relates to quality of power supply field, relate in particular to a kind of Harmonics Calculation method that is used for 64 sampled points of the quality of power supply.

Background technology

Along with the application of exact instrument and complex electronic equipment, the user more and more requires the supply of electrical energy of high-quality and high reliability.In recent years, along with the introduction of external sophisticated equipment and the development of application and electron trade, by power quality problem cause increasing unusually.

The quality of power supply (Power Quality) is said from universal significance to be meant quality supply, comprises quality of voltage, electric current quality, power supply quality and uses electricity quality.It can be defined as: cause the deviation of voltage, electric current or the frequency of consumer fault or cisco unity malfunction, its content comprises frequency departure, voltage deviation, voltage fluctuation and flicker, three-phase imbalance, temporary transient or transient overvoltage, wave form distortion (harmonic wave), voltage dip, interruption, rises and power supply continuity etc. temporarily.

In recent years along with rapid development of economy; Electric load increases swift and violent; Increasingly sophisticatedization of power load and variation, increasing non-linear, impact, the application apparatus that uneven harmonic is abundant insert electrical network in succession, all can have influence on the quality of power supply of power supply grid to some extent.Monitoring means imperfection and operation, extraneous interference and various failure and other reasons in addition, power quality problem becomes increasingly conspicuous.

At present; The database that all is based on PQView that a lot of Utilities Electric Co.s electric energy quality monitoring system adopts; PQView is the power quality analysis software of U.S.'s DianKeYuan development; The many electric energy quality monitoring data of storage in this database how to from this database, collecting the calculating that data are carried out harmonic wave, are that the present inventor is devoted to the problem studying and solve.

Summary of the invention

The objective of the invention is to overcome the defective of prior art and a kind of Harmonics Calculation method that is used for 64 sampled points of the quality of power supply is provided; These computing method can realize from the harmonic wave index calculating that based on sampling number the database of PQView is 64, five cycles.

The technical scheme that realizes above-mentioned purpose is: a kind of Harmonics Calculation method that is used for 64 sampled points of the quality of power supply, and wherein, it may further comprise the steps:

Step 1 defines a reference value M;

Step 2 reads the sampled data of five cycles successively from the database based on PQView, comprise three-phase voltage and three-phase current, and use k=0,1,2 this three-phase of expression, k=0 when initial;

Whether step 21 judges k less than 3, if, then get into step 3, if not, then directly finish;

Step 3; One group of data to a phase are carried out Fourier transform; Obtain voltage and voltage phase angle value and the electric current and the electric current angle values in five cycles; And the amplitude of 1 to 19 subharmonic and phase information, voltage and current is deposited in respectively among array allU_M and the allBaseI_M, obtain this group sampled data harmonic data group of having calculated before and count num;

Step 31 judges that whether the harmonic wave array count num greater than reference value M, if, then get into step 4, if not Vpcc value that then should the group data is as its background harmonics magnitude of voltage Vs, end then;

Step 4; M organized deposit pairing 1 to the 19 time magnitude of voltage of array allU_M in the number the earliest in and remove, then successively with moving behind the voltage, and 1 to 19 magnitude of voltage will organizing data is put into preceding 19 positions of array allU_M successively; For fundamental current; The electric current that deposits array allBaseI_M the earliest in is removed, and then successively with moving behind the electric current, and the fundamental current value that will organize data deposits first position of array allBaseI_M in;

Step 5 is obtained 1 to 19 magnitude of voltage and the fundamental current value of up-to-date M group;

Step 6; This M group fundamental current value is sorted from big to small; And get the 70%th big current value, and in array allU_M, find its 1 to 19 time corresponding magnitude of voltage, and with 1 to 19 the background harmonics voltage reference value Vs of this group magnitude of voltage as this group data;

Step 61, whether the background harmonics voltage reference value Vs that judges each time greater than Vpcc,

If, whether then judge power greater than 0,

If then Vs=Vpcc* (0.6+random) gets into step 7 then;

If not then Vs=Vpcc* (0.35+random) gets into step 7 then;

If not, then, get into step 7 then with the background harmonics magnitude of voltage of this background harmonics voltage reference value Vs as this this number of times of group data;

Step 7 is calculated each time background harmonics, user's harmonic wave, voltage containing ratio harmonic power, and the numerical value of k adds 1, returns step 31 then.

The above-mentioned Harmonics Calculation method that is used for 64 sampled points of the quality of power supply, wherein, in the step 7, each harmonic power calculates according to the computing formula of nth harmonic power, and formula is:

U wherein _nBe the nth harmonic voltage magnitude, I _nBe the nth harmonic current amplitude,

Be the nth harmonic voltage phase angle,

It is nth harmonic electric current phase angle;

Calculating each time background harmonics, user's harmonic wave and voltage containing ratio draws through each amplitude and phase angle of organizing each harmonic.

The above-mentioned Harmonics Calculation method that is used for 64 sampled points of the quality of power supply, wherein, when the amplitude of calculating each harmonic and phase angle, its computing formula is following:

N-th harmonic amplitude

phase angle is

Cutaway anyway.

The invention has the beneficial effects as follows: the present invention can be from based on realizing the database of PQView that sampling number is 64; The harmonic wave index of five cycles is calculated; Can access harmonic data required in the Power Quality Detection process through these computing method, for Utilities Electric Co. provides the scientific decision foundation to the improvement of the quality of power supply.

Embodiment

To be described further the present invention below.

A kind of Harmonics Calculation method that is used for 64 sampled points of the quality of power supply, it may further comprise the steps:

Step 1 defines a reference value M;

Step 2 reads the sampled data of five cycles successively from the database based on PQView, comprise three-phase voltage and three-phase current, and use k=0,1,2 this three-phase of expression, k=0 when initial;

Whether step 21 judges k less than 3, if, then get into step 3, if not, then directly finish;

Step 3; One group of data to a phase are carried out Fourier transform; Obtain voltage and voltage phase angle value and the electric current and the electric current angle values in five cycles; And the amplitude of 1 to 19 subharmonic and phase information, voltage and current is deposited in respectively among array allU_M and the allBaseI_M, obtain this group sampled data harmonic data group of having calculated before and count num;

Step 31 judges that whether the harmonic wave array count num greater than reference value M, if then get into step 4, if not Vpcc (harmonic impedance) value that then should the group data finishes as its background harmonics magnitude of voltage Vs then;

Step 4; M organized deposit pairing 1 to the 19 time magnitude of voltage of array allU_M in the number the earliest in and remove, then successively with moving behind the voltage, and 1 to 19 magnitude of voltage will organizing data is put into preceding 19 positions of array allU_M successively; For fundamental current; The electric current that deposits array allBaseI_M the earliest in is removed, and then successively with moving behind the electric current, and the fundamental current value that will organize data deposits first position of array allBaseI_M in;

Step 5 is obtained 1 to 19 magnitude of voltage and the fundamental current value of up-to-date M group;

Step 6; This M group fundamental current value is sorted from big to small; And get the 70%th big current value, and in array allU_M, find its 1 to 19 time corresponding magnitude of voltage, and with 1 to 19 the background harmonics voltage reference value Vs of this group magnitude of voltage as this group data;

Step 61, whether the background harmonics voltage reference value Vs that judges each time greater than Vpcc,

If, whether then judge power (power) greater than 0,

If then Vs=Vpcc* (0.6+random) gets into step 7 then;

If not then Vs=Vpcc* (0.35+random) gets into step 7 then;

If not, then, get into step 7 then with the background harmonics magnitude of voltage of this background harmonics voltage reference value Vs as this this number of times of group data;

Step 7 is calculated each time background harmonics, user's harmonic wave, voltage containing ratio harmonic power, and the numerical value of k adds 1, returns step 31 then.

In the step 7, each harmonic power calculates according to the computing formula of nth harmonic power, and formula is:

U wherein _nBe the nth harmonic voltage magnitude, I _nBe the nth harmonic current amplitude, Be the nth harmonic voltage phase angle,

It is nth harmonic electric current phase angle;

Calculate each time background harmonics, user's harmonic wave and voltage containing ratio and draw through each amplitude and phase angle of organizing each harmonic, the amplitude of each harmonic and the computing formula of phase angle are following:

N-th harmonic amplitude

phase angle is

Cutaway anyway.

To the Fourier transform that relate among the present invention be described below, be located in one period continuous time, voltage (or electric current) is carried out uniform sampling obtained sample sequence { f _k, therefrom take out N point in the one-period T, be designated as

For the resulting discrete-time series of sampling, its harmonic constant calculates as follows:

As if discrete time point do at this moment

(sampling time interval ), be f (k) in the sampled value of this discrete time point f (t), then

According to discrete-time series { f _kData, can by

$A_n=\frac{2}{T}{\∫}_0^{T}f\left(t\right)\cos \mathrm{n\ωtdt}$

$=\frac{1}{\mathrm{\π}}{\∫}_0^{2\mathrm{\π}}f\left(\mathrm{\ωt}\right)\cos \mathrm{n\ωtd}\left(\mathrm{\ωt}\right)$

$B_n=\frac{2}{T}{\∫}_0^{T}f\left(t\right)\sin \mathrm{n\ωtdt}$

$=\frac{1}{\mathrm{\π}}{\∫}_0^{2\mathrm{\π}}f\left(\mathrm{\ωt}\right)\sin \mathrm{n\ωtd}\left(\mathrm{\ωt}\right)$

n＝1，2，3，

Derive the coefficient a that calculates nth harmonic _nAnd b _nFormula

$a_n=\frac{2}{T}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{f}_k\cos \frac{2\mathrm{\π}}{N}\mathrm{kn}\×\frac{T}{N}$

$=\frac{2}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{f}_k\cos \frac{2\mathrm{\π}}{N}\mathrm{kn}$

$b_n=\frac{2}{T}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{f}_k\sin \frac{2\mathrm{\π}}{N}\mathrm{kn}\×\frac{T}{N}$

$=\frac{2}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{f}_k\sin \frac{2\mathrm{\π}}{N}\mathrm{kn}$

N=0 wherein, 1,2,, N-1

The amplitude c of nth harmonic then _nFor

$c_n=\sqrt{a_n^2+b_n^2}$

Once explain in the face of each property calculation formula of harmonic wave that relates among the present invention down.

(1) voltage containing ratio

U _n: nth harmonic voltage effective value (the approximate mean value that is taken as the voltage magnitude in 10 cycles of nth harmonic)

U ₁: the fundamental voltage effective value

(2) background harmonics containing ratio

Vs: background harmonics magnitude of voltage, Vpcc: the total harmonic voltage in points of common connection place

(3) user's relative harmonic content

(4) harmonic power

U _n: nth harmonic voltage effective value (the approximate mean value that is taken as the voltage magnitude in 10 cycles of nth harmonic)

I _n: nth harmonic current effective value (the approximate mean value that is taken as the current amplitude in 10 cycles of nth harmonic)

nth harmonic voltage phase angle effective value (the approximate mean value that is taken as the voltage phase angle in 10 cycles of nth harmonic)

nth harmonic electric current phase angle effective value (the approximate mean value that is taken as the electric current phase angle in 10 cycles of nth harmonic)

(5) harmonic impedance calculates

Adopt model

Adopt model

U ₁: voltage real part, U ₂: voltage imaginary part, I ₁: electric current real part, I ₂: electric current imaginary part, A: the reduction matrix of coefficients that the offset minimum binary algorithm is tried to achieve

(6) the harmonic wave admittance is calculated

Admittance is calculated in two parts

and

U ₁: voltage real part, U ₂: voltage imaginary part, I ₁: electric current real part, I ₂: electric current imaginary part, A: the reduction matrix of coefficients that the offset minimum binary algorithm is tried to achieve

(7) the user side electric current calculates

Yux: admittance real part, Yuy: admittance imaginary part, U ₁: voltage real part, U ₂: voltage imaginary part, I ₁: electric current real part, I ₂: the electric current imaginary part

More than combine embodiment that the present invention is specified, those skilled in the art can make the many variations example to the present invention according to above-mentioned explanation.Thereby some details among the embodiment should not constitute qualification of the present invention, and the scope that the present invention will define with appended claims is as protection scope of the present invention.

Claims (3)

1. Harmonics Calculation method that is used for 64 sampled points of the quality of power supply is characterized in that it may further comprise the steps:

Step 1 defines a reference value M;

Step 2 reads the sampled data of five cycles successively from the database based on PQView, comprise three-phase voltage and three-phase current, and use k=0,1,2 this three-phase of expression, k=0 when initial;

Whether step 21 judges k less than 3, if, then get into step 3, if not, then directly finish;

Step 3; One group of data to a phase are carried out Fourier transform; Obtain voltage and voltage phase angle value and the electric current and the electric current angle values in five cycles; And the amplitude of 1 to 19 subharmonic and phase information, voltage and current is deposited in respectively among array allU_M and the allBaseI_M, obtain this group sampled data harmonic data group of having calculated before and count num;

Step 31 judges that whether the harmonic wave array count num greater than reference value M, if, then get into step 4, if not Vpcc value that then should the group data is as its background harmonics magnitude of voltage Vs, end then;

Step 4; M organized deposit pairing 1 to the 19 time magnitude of voltage of array allU_M in the number the earliest in and remove, then successively with moving behind the voltage, and 1 to 19 magnitude of voltage will organizing data is put into preceding 19 positions of array allU_M successively; For fundamental current; The electric current that deposits array allBaseI_M the earliest in is removed, and then successively with moving behind the electric current, and the fundamental current value that will organize data deposits first position of array allBaseI_M in;

Step 5 is obtained 1 to 19 magnitude of voltage and the fundamental current value of up-to-date M group;

Step 6; This M group fundamental current value is sorted from big to small; And get the 70%th big current value, and in array allU_M, find its 1 to 19 time corresponding magnitude of voltage, and with 1 to 19 the background harmonics voltage reference value Vs of this group magnitude of voltage as this group data;

Step 61, whether the background harmonics voltage reference value Vs that judges each time greater than Vpcc,

If, whether then judge power greater than 0,

If then Vs=Vpcc* (0.6+random) gets into step 7 then;

If not then Vs=Vpcc* (0.35+random) gets into step 7 then;

If not, then, get into step 7 then with the background harmonics magnitude of voltage of this background harmonics voltage reference value Vs as this this number of times of group data;

Step 7 is calculated each time background harmonics, user's harmonic wave, voltage containing ratio harmonic power, and the numerical value of k adds 1, returns step 31 then.

2. the Harmonics Calculation method that is used for 64 sampled points of the quality of power supply according to claim 1 is characterized in that, in the step 7, each harmonic power calculates according to the computing formula of nth harmonic power, and formula is:

U wherein _nBe the nth harmonic voltage magnitude, I _nBe the nth harmonic current amplitude,

Be the nth harmonic voltage phase angle,

It is nth harmonic electric current phase angle;

Calculating each time background harmonics, user's harmonic wave and voltage containing ratio draws through each amplitude and phase angle of organizing each harmonic.

3. the Harmonics Calculation method that is used for 64 sampled points of the quality of power supply according to claim 2 is characterized in that, when the amplitude of calculating each harmonic and phase angle, its computing formula is following:

N-th harmonic amplitude

phase angle is

Cutaway anyway.