CN105425036A - Method and system for acquiring reduction frequency cosine function sequence of electric power signal - Google Patents

Abstract

The invention discloses a method and system for acquiring a reduction frequency cosine function sequence of an electric power signal. The method comprises: acquiring an electric power signal preliminary sequence length and a preliminary sequence; performing preliminary test of frequency for the preliminary sequence, and setting a reference frequency; acquiring an electric power signal unit periodic sequence length and a preset sequence length, and further obtaining a preliminary forward/deconvolution sequence; according to the preliminary forward/deconvolution sequence, acquiring a preliminary average initial phase; according to the preliminary average initial phase, the initial phase comparative value of +-Pi/4 and a new initial point, acquiring a secondary forward/deconvolution sequence and a secondary average initial phase; according to the secondary forward/deconvolution sequence and the secondary average initial phase, acquiring a cosine/sine function modulation sequence; according to the preset fine modulation frequency and the cosine/sine function modulation sequence, acquiring a third/fourth multiplication sequence, and at last according to the third/fourth multiplication sequence, acquiring a reduction frequency cosine function sequence. The method and system for acquiring a reduction frequency cosine function sequence of an electric power signal can improve the accuracy for sine parameter calculation and is suitable for application.

Description

Obtain the method and system of the reduction frequency cosine function sequence of electric power signal

Technical field

The present invention relates to technical field of electric power, particularly relate to a kind of method and system obtaining the reduction frequency cosine function sequence of electric power signal.

Background technology

The frequency measurement, phase measurement, amplitude measurement etc. of electric system are the measurement of sine parameter in itself.Fast Fourier Transform (FFT) and discrete Fourier transformation are the basic skills realizing sine parameter measurement, are widely used in electric system.But said method blocks at the non-integer of signal sampling process, causes spectrum leakage, and spectrum leakage can produce corresponding error.

In the measurement of electric system sine parameter, there is many measuring methods, as added window functional based method, adopting interpolation correcting method etc., reduce the impact of spectrum leakage problem.But above-mentioned measuring method measuring accuracy is low, is not suitable for the measurement of pin-point accuracy sine parameter.

Summary of the invention

Based on above-mentioned situation, the present invention proposes a kind of method and system obtaining the reduction frequency cosine function sequence of electric power signal, improve the accuracy that sine parameter is measured.

To achieve these goals, the embodiment of technical solution of the present invention is:

Obtain a method for the reduction frequency cosine function sequence of electric power signal, comprise the following steps:

According to the lower limit of frequency power signal scope, default sample frequency and default integer signal period number, obtain the preliminary sequence length of described electric power signal;

According to described preliminary sequence length, described electric power signal is sampled, obtain the preliminary sequence of described electric power signal;

Frequency preliminary survey is carried out to described preliminary sequence, generates the first synchronizing frequency of described electric power signal, and according to described preliminary frequency setting the reference frequency of electric power signal;

According to described default sample frequency and described reference frequency, obtain the unit period sequence length of described electric power signal;

According to described default integer signal period number and described unit period sequence length, obtain the predetermined sequence length of described electric power signal;

According to default starting point and described predetermined sequence length, from described preliminary sequence, obtain the first forward sequence of described electric power signal;

The first anti-pleat sequence of described electric power signal is obtained according to described first forward sequence;

Obtain the first positive phase of described electric power signal according to described first forward sequence, and obtain the first antiphase of described electric power signal according to described first anti-pleat sequence;

The first average initial phase of described electric power signal is obtained according to described first positive phase and described first antiphase;

Described first average initial phase and ± π/4 are compared, obtains the first phase compare value compared with described ± π/4, and according to described first phase compare value and described default starting point, obtain new starting point;

According to described new starting point and described predetermined sequence length, from described preliminary sequence, obtain the sequence of forward again of described electric power signal, and obtain the again anti-pleat sequence of described electric power signal according to the described sequence of forward again;

Obtain the positive phase again of described electric power signal according to the described sequence of forward again, and obtain the antiphase again of described electric power signal according to described anti-pleat sequence again;

The again average initial phase of described electric power signal is obtained according to described positive phase again and described antiphase again;

The described sequence of forward again and described anti-pleat sequence are again added, and according to the result after addition and described average initial phase again, obtain the cosine function modulation sequence of described electric power signal;

The described sequence of forward again and described anti-pleat sequence are again subtracted each other, and according to the result after subtracting each other and described average initial phase again, obtains the sine function modulation sequence of described electric power signal;

The discrete sine function of default fine setting frequency be multiplied with described sine function modulation sequence and obtain the 3rd multiplication sequence of described electric power signal, being multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency obtains the 4th multiplication sequence of described electric power signal;

Described 4th multiplication sequence is added with described 3rd multiplication sequence, obtains the reduction frequency cosine function sequence of described electric power signal.

Obtain a system for the reduction frequency cosine function sequence of electric power signal, comprising:

Preliminary sequence length modules, for the lower limit according to frequency power signal scope, presets sample frequency and default integer signal period number, obtains the preliminary sequence length of described electric power signal;

Preliminary sequence module, for sampling to described electric power signal according to described preliminary sequence length, obtains the preliminary sequence of described electric power signal;

Frequency preliminary survey module, for carrying out frequency preliminary survey to described preliminary sequence, generates the first synchronizing frequency of described electric power signal, and according to described preliminary frequency setting the reference frequency of electric power signal;

Unit period sequence length module, for according to described default sample frequency and described reference frequency, obtains the unit period sequence length of described electric power signal;

Predetermined sequence length modules, for according to described default integer signal period number and described unit period sequence length, obtains the predetermined sequence length of described electric power signal;

First forward block, for according to presetting starting point and described predetermined sequence length, obtains the first forward sequence of described electric power signal from described preliminary sequence;

First anti-pleat block, for obtaining the first anti-pleat sequence of described electric power signal according to described first forward sequence;

First phase module, for obtaining the first positive phase of described electric power signal according to described first forward sequence, and obtains the first antiphase of described electric power signal according to described first anti-pleat sequence;

First average initial phase module, for obtaining the first average initial phase of described electric power signal according to described first positive phase and described first antiphase;

Phase compare module, for described first average initial phase and ± π/4 being compared, obtaining the first phase compare value compared with described ± π/4, and according to described first phase compare value and described default starting point, obtaining new starting point;

Block again, for according to described new starting point and described predetermined sequence length, obtains the sequence of forward again of described electric power signal, and obtains the again anti-pleat sequence of described electric power signal according to the described sequence of forward again from described preliminary sequence;

Phase module again, for obtaining the positive phase again of described electric power signal according to the described sequence of forward again, and obtains the antiphase again of described electric power signal according to described anti-pleat sequence again;

Average initial phase module again, for obtaining the again average initial phase of described electric power signal according to described positive phase again and described antiphase again;

Cosine function modulation sequence module, for the described sequence of forward again and described anti-pleat sequence being again added, and according to the result after addition and described average initial phase again, obtains the cosine function modulation sequence of described electric power signal;

Sine function modulation sequence module, for the described sequence of forward again and described anti-pleat sequence again being subtracted each other, and according to the result after subtracting each other and described average initial phase again, obtains the sine function modulation sequence of described electric power signal;

Multiplication sequence module, obtain the 3rd multiplication sequence of described electric power signal for the discrete sine function of default fine setting frequency being multiplied with described sine function modulation sequence, being multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency obtains the 4th multiplication sequence of described electric power signal;

Reducing frequency cosine function block, for being added with described 3rd multiplication sequence by described 4th multiplication sequence, obtaining the reduction frequency cosine function sequence of described electric power signal.

Compared with prior art, beneficial effect of the present invention is: the present invention obtains the method and system of the reduction frequency cosine function sequence of electric power signal, according to the lower limit of frequency power signal scope, preset sample frequency and just establish integer signal period number, obtain preliminary sequence length, and electric power signal is tentatively sampled, obtain preliminary sequence; Frequency preliminary survey is carried out to preliminary sequence, generates just synchronizing frequency, setting reference frequency; According to default sample frequency and reference frequency, obtain unit period sequence length; According to default integer signal period number and unit period sequence length, obtain predetermined sequence length; From preliminary sequence, obtain first forward sequence, obtain first anti-pleat sequence further; Obtain first positive phase, first antiphase according to first forward sequence, first anti-pleat sequence, obtain first average initial phase further; Compare obtain first phase compare value with ± π/4, obtain new starting point further; According to new starting point and predetermined sequence length, obtain again forward sequence, again anti-pleat sequence, obtain again positive phase, again antiphase, again average initial phase further; According to positive phase, again antiphase, again average initial phase obtain cosine function modulation sequence, sine function modulation sequence again; Obtain reduce frequency cosine function sequence according to default fine setting frequency, cosine function modulation sequence, sine function modulation sequence, by reducing the fundamental frequency of burst, can realize blocking the number of cycles of fundamental signal, with the amplitude maximum of first-harmonic composition in electric power signal, solve the number of cycles truncated problem of fundamental signal, improve the accuracy that sine parameter calculates, be applicable to practical application.

Accompanying drawing explanation

Fig. 1 is the method flow diagram of the reduction frequency cosine function sequence obtaining electric power signal in an embodiment;

Fig. 2 is first forward sequence and first anti-pleat sequence diagram in an embodiment;

Fig. 3 is the system architecture schematic diagram of the reduction frequency cosine function sequence obtaining electric power signal in an embodiment.

Embodiment

In order to make the object, technical solutions and advantages of the present invention clearly, below in conjunction with accompanying drawing, the present invention is described in further detail.

Although the step in the present invention arranges with label, and be not used in and limit the precedence of step, the order of step or the execution of certain step need based on other steps unless expressly stated, otherwise the relative rank of step is adjustable.

Obtain the method for the reduction frequency cosine function sequence of electric power signal in an embodiment, as shown in Figure 1, comprise the following steps:

Step S101: according to the lower limit of frequency power signal scope, default sample frequency and default integer signal period number, obtain the preliminary sequence length of described electric power signal;

Step S102: according to described preliminary sequence length, described electric power signal is sampled, obtain the preliminary sequence of described electric power signal;

Step S103: carry out frequency preliminary survey to described preliminary sequence, generates the first synchronizing frequency of described electric power signal, and according to described preliminary frequency setting the reference frequency of electric power signal;

Step S104: according to described default sample frequency and described reference frequency, obtains the unit period sequence length of described electric power signal;

Step S105: according to described default integer signal period number and described unit period sequence length, obtain the predetermined sequence length of described electric power signal;

Step S106: according to default starting point and described predetermined sequence length, obtains the first forward sequence of described electric power signal from described preliminary sequence;

Step S107: the first anti-pleat sequence obtaining described electric power signal according to described first forward sequence;

Step S108: the first positive phase obtaining described electric power signal according to described first forward sequence, and the first antiphase obtaining described electric power signal according to described first anti-pleat sequence;

Step S109: the first average initial phase obtaining described electric power signal according to described first positive phase and described first antiphase;

Step S110: described first average initial phase and ± π/4 are compared, obtains the first phase compare value compared with described ± π/4, and according to described first phase compare value and described default starting point, obtain new starting point;

Step S111: according to described new starting point and described predetermined sequence length, obtains the sequence of forward again of described electric power signal from described preliminary sequence, and obtains the again anti-pleat sequence of described electric power signal according to the described sequence of forward again;

Step S112: the positive phase again obtaining described electric power signal according to the described sequence of forward again, and obtain the antiphase again of described electric power signal according to described anti-pleat sequence again;

Step S113: the again average initial phase obtaining described electric power signal according to described positive phase again and described antiphase again;

Step S114: the described sequence of forward again and described anti-pleat sequence are again added, and according to the result after addition and described average initial phase again, obtain the cosine function modulation sequence of described electric power signal;

Step S115: the described sequence of forward again and described anti-pleat sequence are again subtracted each other, and according to the result after subtracting each other and described average initial phase again, obtain the sine function modulation sequence of described electric power signal;

Step S116: the discrete sine function of default fine setting frequency is multiplied with described sine function modulation sequence and obtains the 3rd multiplication sequence of described electric power signal, being multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency obtains the 4th multiplication sequence of described electric power signal;

Step S117: be added with described 3rd multiplication sequence by described 4th multiplication sequence, obtains the reduction frequency cosine function sequence of described electric power signal.

Known from the above description, the present invention obtains and reduces frequency cosine function sequence, and improve the accuracy that sine parameter calculates, actual application value is high.

Wherein, for step S101, according to the lower limit of frequency power signal scope, default sample frequency and default integer signal period number, obtain the preliminary sequence length of described electric power signal;

Described electric power signal is a kind of first-harmonic composition is main sinusoidal signal.Sinusoidal signal is extensively made a comment or criticism string function signal and cosine function signal.

In one embodiment, power system frequency scope at 45Hz-55Hz, power taking force signal lower-frequency limit f _minfor 45Hz; Described default integer signal period number C is set according to actual needs _{2 π}, in one embodiment, get C _{2 π}be 13.

In one embodiment, obtaining described preliminary sequence length is formula (1):

$N_{start}=\left(\mathrm{int}\right)\frac{C_{2\mathrm{\π}}f}{f_{\min }}---\left(1\right);$

In formula, N _startfor preliminary sequence length; (int) expression rounds; C _{2 π}for default integer signal period number; f _minfor the lower limit of frequency power signal scope, unit Hz; F is for presetting sample frequency, unit Hz.

For step S102, according to described preliminary sequence length, described electric power signal is sampled, obtain the preliminary sequence of described electric power signal;

In one embodiment, described electric power signal is the cosine function signal of single fundamental frequency, and the preliminary sequence obtaining described electric power signal is formula (2):

Wherein, X _startn () is described preliminary sequence; A is signal amplitude, unit v; ω _ifor signal frequency, T is sampling interval duration, and f is for presetting sample frequency, and unit Hz, n are series of discrete number, for preliminary sequence initial phase, N _startfor preliminary sequence length.

For step S103, frequency preliminary survey is carried out to described preliminary sequence, generates the first synchronizing frequency of described electric power signal, and according to described preliminary frequency setting the reference frequency of electric power signal;

By zero friendship method, based on the algorithm of filtering, based on Wavelet Transformation Algorithm, the algorithm based on neural network, the frequency algorithm based on DFT conversion or carry out frequency preliminary survey based on the frequency algorithm of phase differential to described preliminary sequence, obtain described just synchronizing frequency.

In one embodiment, generating described just synchronizing frequency is formula (3):

ω _o(3)；

Preferably, described reference frequency equals described just synchronizing frequency is formula (4):

ω _s＝ω _o(4)；

Wherein, ω _sfor reference frequency, ω _ofor first synchronizing frequency.

For step S104, according to described default sample frequency and described reference frequency, obtain the unit period sequence length of described electric power signal;

In one embodiment, the unit period sequence length obtaining described electric power signal is formula (5):

$N_{2\mathrm{\π}}=\left(\mathrm{int}\right)\frac{2\mathrm{\π}f}{{\mathrm{\ω}}_s}---\left(5\right);$

In formula, N _{2 π}for described unit period sequence length; (int) be round numbers; F is for presetting sample frequency, unit Hz; ω _sfor reference frequency.There is the error in 1 sampling interval in unit period sequence length integer.

For step S105, according to described default integer signal period number and described unit period sequence length, obtain the predetermined sequence length of described electric power signal;

In one embodiment, obtaining described predetermined sequence length is formula (6):

N＝(int)[(C _2π-1)N _2π](6)；

Wherein, N is predetermined sequence length, and (int) is round numbers, N _{2 π}for described unit period sequence length, C _{2 π}for default integer signal period number.

For step S106, according to default starting point and described predetermined sequence length, from described preliminary sequence, obtain the first forward sequence of described electric power signal;

In one embodiment, default starting point is 0.5 times of described unit period sequence length;

In one embodiment, obtaining described first forward sequence is formula (7):

Wherein, X _startn () is preliminary sequence, X _{+ start}n () is first forward sequence, P _startpreset starting point, N _{2 π}for described unit period sequence length, (int) is round numbers, and A is signal amplitude, unit v, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, for first forward sequence initial phase, N predetermined sequence length.First forward sequence pattern is expressed, shown in Fig. 2.

For step S107, obtain the first anti-pleat sequence of described electric power signal according to described first forward sequence;

In one embodiment, obtaining first anti-pleat sequence is formula (8):

$\begin{array}{c}{X}_{-\mathrm{start}}(-n)=X_{+\mathrm{start}}(N-n)=A\cos (-{\mathrm{\ω}}_i\mathrm{Tn}+\mathrm{\β}1)\\ n=\mathrm{0,1,2},...,N-1\end{array}---\left(8\right);$

Wherein, X _-start(-n) is first anti-pleat sequence, X _{+ start}(n) for first forward sequence, A be signal amplitude, unit v, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, and β 1 is first anti-pleat sequence initial phase, N predetermined sequence length.The avatars of described first anti-pleat sequence, as shown in Figure 2.

For step S108, obtain the first positive phase of described electric power signal according to described first forward sequence, and obtain the first antiphase of described electric power signal according to described first anti-pleat sequence;

In one embodiment, first positive phase and first antiphase are the results based on quadrature downconvert and integral and calculating, when not considering the mixing interfering frequency of quadrature downconvert, quadrature downconvert is expressed as formula (9), and integral and calculating is expressed as formula (10):

Wherein, R _{+ start}n () is the first positive real sequence of mixing frequently, I _{+ start}n () is first weakened body resistance frequency mixing sequence, R _-start(-n) is the first anti-real sequence of mixing frequently, I _-start(-n) is the first anti-empty sequence of mixing frequently, cos (ω _sor cos (-ω Tn) _stn) be the discrete cosine function of reference frequency, sin (ω _sor sin (-ω Tn) _stn) be the discrete sine function of reference frequency, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, for first forward sequence initial phase, β 1 is first forward sequence initial phase, and N is predetermined sequence length.

In formula, R _{+ start}first positive real integrated value, unit dimensionless frequently, I _{+ start}for first weakened body resistance frequency integrated value, unit dimensionless, R _-startfor first anti-real integrated value, unit dimensionless frequently, I _-startfor the first anti-empty integrated value of mixing frequently, unit dimensionless, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, T is sampling interval duration, and n is series of discrete number, and N is predetermined sequence length, for first forward sequence initial phase, β 1 is first forward sequence initial phase.

In one embodiment, the expression formula of first positive phase and first antiphase is obtained for (11):

In formula, PH _{+ start}for first positive phase, PH _-startfor first antiphase, R _{+ start}first positive real integrated value, unit dimensionless frequently, I _{+ start}for first weakened body resistance frequency integrated value, unit dimensionless, R _-startfor first anti-real integrated value, unit dimensionless frequently, I _-startfor the first anti-empty integrated value of mixing frequently, unit dimensionless, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, T is sampling interval duration, and N is predetermined sequence length, for first forward sequence initial phase, β 1 is first anti-pleat sequence initial phase.

For step S109, obtain the first average initial phase of described electric power signal according to described first positive phase and described first antiphase;

In one embodiment, the expression formula obtaining first average initial phase is (12):

In formula, PH _start-avgfor first average initial phase, PH _{+ start}for first positive phase, PH _-startfor first antiphase, for first forward sequence initial phase, β 1 is first anti-pleat sequence initial phase.

For step S110, described first average initial phase and ± π/4 are compared, obtains the first phase compare value compared with described ± π/4, and according to described first phase compare value and described default starting point, obtain new starting point;

In one embodiment, by described first average initial phase and PH _start-avgwith ± π/4 compare as formula (13):

${\mathrm{\&Delta;PH}}_{com}=\left\{\begin{array}{cc}\frac{\mathrm{\&pi;}}{4}-{\mathrm{PH}}_{start-avg}& 0\&le;{\mathrm{PH}}_{start-avg}\&le;\frac{\mathrm{\&pi;}}{4},\frac{\mathrm{\&pi;}}{4}<{\mathrm{PH}}_{start-avg}\&le;\frac{\mathrm{\&pi;}}{2}\\ -\frac{\mathrm{\&pi;}}{4}-{\mathrm{PH}}_{start-avg}& -\frac{\mathrm{\&pi;}}{2}\&le;{\mathrm{PH}}_{start-avg}<-\frac{\mathrm{\&pi;}}{4},-\frac{\mathrm{\&pi;}}{4}<{\mathrm{PH}}_{start-avg}\&le;0\\ 0& {\mathrm{PH}}_{start-avg}=\&PlusMinus;\frac{\mathrm{\&pi;}}{4}\end{array}\right.---\left(13\right);$

In formula, Δ PH _comfor first phase compare value, unit rad, PH _start-avgfor first average initial phase.

In one embodiment, obtaining described new starting point is formula (14):

$P_{new}=P_{start}+\left(\mathrm{int}\right)\left(\frac{{\mathrm{\&Delta;PH}}_{com}}{2\mathrm{\&pi;}}{N}_{2\mathrm{\&pi;}}\right)---\left(14\right);$

In formula, P _newfor new starting point, unit dimensionless, P _startfor default starting point, Δ PH _comfor first phase compare value, unit rad, N _{2 π}for unit periodic sequence length, (int) is round numbers.

For step S111, according to described new starting point and described predetermined sequence length, from described preliminary sequence, obtain the sequence of forward again of described electric power signal, and obtain the again anti-pleat sequence of described electric power signal according to the described sequence of forward again;

In one embodiment, again forward sequence and again anti-pleat sequence be formula (15):

In formula, X _{+ end}n () is again forward sequence, X _-end(-n) is again anti-pleat sequence, P _newfor new starting point, unit dimensionless, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, and N is predetermined sequence length.

For step S112, obtain the positive phase again of described electric power signal according to the described sequence of forward again, and obtain the antiphase again of described electric power signal according to described anti-pleat sequence again;

In one embodiment, again positive phase and again antiphase be the result calculated based on quadrature downconvert and digital filtering.Described digital filtering is made up of 6 grades of rectangular window arithmetic mean filter of 2 kinds of filtering parameters.

When not considering the mixing interfering frequency of quadrature downconvert, quadrature downconvert is expressed as formula (16), and 6 grades of rectangular window arithmetic mean filter filtering calculation expressions of 2 kinds of filtering parameters are formula (17):

In formula, R _{+ end}n () is again the positive real sequence of mixing frequently, I _{+ end}n () is again weakened body resistance frequency mixing sequence, R _-end(-n) is again the anti-real sequence of mixing frequently, I _-end(-n) is again the anti-empty sequence of mixing frequently, cos (ω _sor cos (-ω Tn) _stn) be the discrete cosine function of reference frequency, sin (ω _sor sin (-ω Tn) _stn) be the discrete sine function of reference frequency, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase, and N is predetermined sequence length.

In formula, R _{+ end}for positive real digital filtering final value frequently again, unit dimensionless; I _{+ end}for weakened body resistance frequency digital filtering final value again, unit dimensionless; R _-endfor anti-digital filtering final value again, unit dimensionless; I _-endfor anti-empty digital filtering final value frequently again, unit dimensionless; Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference; K (Ω) for digital filtering is in the amplitude gain of frequency difference Ω, unit dimensionless; T is sampling interval duration; for forward sequence initial phase again; β 2 is again anti-pleat sequence initial phase; N _d1for filtering parameter 1, namely to N _d1individual continuous discrete value is added, and then gets its arithmetic mean and exports as this filter value; N _d2for filtering parameter 2, namely to N _d2individual continuous discrete value is added, and then gets its arithmetic mean and exports as this filter value; N _dfor digital filtering uses sequence length, be quantitatively the summation of 6 grades of rectangular window arithmetic mean filter filtering parameters, be less than or equal to predetermined sequence length N.

In one embodiment, filtering parameter N _d1value is 1.5 times of the unit period sequence length of described reference frequency, and object carries out degree of depth suppression to the mixing interfering frequency that 1/3 subharmonic produces; Filtering parameter N _d2value is 2 times of the unit period sequence length of described reference frequency, and object carries out degree of depth suppression to the mixing interfering frequency that direct current, 1/2 gradation, subharmonic etc. produce.6 grades of rectangular window arithmetic mean filter filtering of 2 kinds of filtering parameters calculate 10.5 times that need to use signal period sequence length.

Filtering parameter N _d1with filtering parameter N _d2expression formula is formula (18):

$\begin{array}{c}{N}_{D1}=\left(\mathrm{int}\right)\left(1.5N_{2\mathrm{\&pi;}}\right)\\ N_{D2}=2N_{2\mathrm{\&pi;}}\end{array}---\left(18\right);$

In formula, N _d1for digital filter parameters 1, unit dimensionless, (int) is round numbers, N _d2for digital filter parameters 2, unit dimensionless, N _{2 π}for unit periodic sequence length.

In one embodiment, again positive phase and again antiphase expression formula be (19):

In formula, PH _{+ end}for positive phase again, PH _-endfor antiphase again, R _{+ end}for positive real integrated value frequently again, unit dimensionless, I _{+ end}for weakened body resistance frequency integrated value again, unit dimensionless, R _-endfor anti-real integrated value frequently again, unit dimensionless, I _-endfor the anti-empty integrated value of mixing frequently again, unit dimensionless, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, T is sampling interval duration, N _dfor digital filtering uses sequence length, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase.

For step S113, obtain the again average initial phase of described electric power signal according to described positive phase again and described antiphase again;

In one embodiment, the expression formula obtaining again average initial phase is (20):

In formula, PH _end-avgfor average initial phase again, PH _{+ end}for positive phase again, PH _-endfor antiphase again, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase.

For step S114, the described sequence of forward again and described anti-pleat sequence are again added, and according to the result after addition and described average initial phase again, obtain the cosine function modulation sequence of described electric power signal;

In one embodiment, obtaining cosine function modulation sequence expression formula is (21):

In formula, X _cosn () is cosine function modulation sequence; A is cosine function modulation sequence amplitude, unit v; for cosine function modulation sequence initial phase, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, and N is predetermined sequence length, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase.

For step S115, the described sequence of forward again and described anti-pleat sequence are again subtracted each other, and according to the result after subtracting each other and described average initial phase again, obtain the sine function modulation sequence of described electric power signal;

In one embodiment, obtaining sine function modulation sequence expression formula is (22):

In formula, X _sinn () is sine function modulation sequence, A is sine function modulation sequence amplitude, unit v, for cosine function modulation sequence initial phase, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, and N is predetermined sequence length, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase.

For step S116, the discrete sine function of default fine setting frequency be multiplied with described sine function modulation sequence and obtain the 3rd multiplication sequence of described electric power signal, being multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency obtains the 4th multiplication sequence of described electric power signal;

In one embodiment, described default fine setting frequency is the arithmetic number being less than or equal to actual signal frequency 1%, and unit rad/s is expressed as formula (23):

$\begin{array}{c}{\mathrm{\&Omega;}}_{\mathrm{set}}\\ {\mathrm{\&Omega;}}_{\mathrm{set}}\&le;0.01{\mathrm{\&omega;}}_i\end{array}---\left(23\right)$

In formula, Ω _setfor fine setting frequency, unit rad/s, Ω _set≤ 0.01 ω _i.

The 3rd multiplication sequence obtaining described electric power signal that the discrete sine function of default fine setting frequency is multiplied with described sine function modulation sequence is formula (24):

The 4th multiplication sequence obtaining described electric power signal that is multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency is formula (25):

In formula, X3 (n) is the first multiplication sequence, and X4 (n) is the second multiplication sequence, sin (Ω _settn) be the discrete sine function of described fine setting frequency, cos (Ω _settn) be the discrete cosine function of described fine setting frequency.

For step S117, described 4th multiplication sequence is added with described 3rd multiplication sequence, obtains the reduction frequency cosine function sequence of described electric power signal;

In one embodiment, obtaining reduction frequency cosine function sequence is formula (26):

In formula, X _cos+fn (), for reducing frequency cosine function sequence, sequence frequency reduces Ω _set.

Obtain the system of the reduction frequency cosine function sequence of electric power signal in an embodiment, as shown in Figure 3, comprising:

Preliminary sequence length modules 301, for the lower limit according to frequency power signal scope, presets sample frequency and default integer signal period number, obtains the preliminary sequence length of described electric power signal;

Preliminary sequence module 302, for sampling to described electric power signal according to described preliminary sequence length, obtains the preliminary sequence of described electric power signal;

Frequency preliminary survey module 303, for carrying out frequency preliminary survey to described preliminary sequence, generates the first synchronizing frequency of described electric power signal, and according to described preliminary frequency setting the reference frequency of electric power signal;

Unit period sequence length module 304, for according to described default sample frequency and described reference frequency, obtains the unit period sequence length of described electric power signal;

Predetermined sequence length modules 305, for according to described default integer signal period number and described unit period sequence length, obtains the predetermined sequence length of described electric power signal;

First forward block 306, for according to presetting starting point and described predetermined sequence length, obtains the first forward sequence of described electric power signal from described preliminary sequence;

First anti-pleat block 307, for obtaining the first anti-pleat sequence of described electric power signal according to described first forward sequence;

First phase module 308, for obtaining the first positive phase of described electric power signal according to described first forward sequence, and obtains the first antiphase of described electric power signal according to described first anti-pleat sequence;

First average initial phase module 309, for obtaining the first average initial phase of described electric power signal according to described first positive phase and described first antiphase;

Phase compare module 310, for described first average initial phase and ± π/4 being compared, obtaining the first phase compare value compared with described ± π/4, and according to described first phase compare value and described default starting point, obtaining new starting point;

Block 311 again, for according to described new starting point and described predetermined sequence length, obtains the sequence of forward again of described electric power signal, and obtains the again anti-pleat sequence of described electric power signal according to the described sequence of forward again from described preliminary sequence;

Phase module 312 again, for obtaining the positive phase again of described electric power signal according to the described sequence of forward again, and obtains the antiphase again of described electric power signal according to described anti-pleat sequence again;

Average initial phase module 313 again, for obtaining the again average initial phase of described electric power signal according to described positive phase again and described antiphase again;

Cosine function modulation sequence module 314, for the described sequence of forward again and described anti-pleat sequence being again added, and according to the result after addition and described average initial phase again, obtains the cosine function modulation sequence of described electric power signal;

Sine function modulation sequence module 315, for the described sequence of forward again and described anti-pleat sequence again being subtracted each other, and according to the result after subtracting each other and described average initial phase again, obtains the sine function modulation sequence of described electric power signal;

Multiplication sequence module 316, obtain the 3rd multiplication sequence of described electric power signal for the discrete sine function of default fine setting frequency being multiplied with described sine function modulation sequence, being multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency obtains the 4th multiplication sequence of described electric power signal;

Reducing frequency cosine function block 317, for being added with described 3rd multiplication sequence by described 4th multiplication sequence, obtaining the reduction frequency cosine function sequence of described electric power signal.

Known from the above description, the present invention obtains and reduces frequency cosine function sequence, improves the accuracy that sine parameter calculates, meets actual needs.

Wherein, preliminary sequence length modules 301, according to the lower limit of frequency power signal scope, default sample frequency and default integer signal period number, obtains the preliminary sequence length of described electric power signal;

Described electric power signal is a kind of first-harmonic composition is main sinusoidal signal.Sinusoidal signal is extensively made a comment or criticism string function signal and cosine function signal.

In one embodiment, power system frequency scope at 45Hz-55Hz, power taking force signal lower-frequency limit f _minfor 45Hz; Described default integer signal period number C is set according to actual needs _{2 π}, in one embodiment, get C _{2 π}be 13.In one embodiment, obtaining described preliminary sequence length is formula (1):

$N_{start}=\left(\mathrm{int}\right)\frac{C_{2\mathrm{\&pi;}}f}{f_{\min }}---\left(1\right);$

In formula, N _startfor preliminary sequence length; (int) expression rounds; C _{2 π}for default integer signal period number; f _minfor the lower limit of frequency power signal scope, unit Hz; F is for presetting sample frequency, unit Hz.

Preliminary sequence module 302 is sampled to described electric power signal according to described preliminary sequence length, obtains the preliminary sequence of described electric power signal;

In one embodiment, described electric power signal is the cosine function signal of single fundamental frequency, and the preliminary sequence obtaining described electric power signal is formula (2):

Wherein, X _startn () is described preliminary sequence; A is signal amplitude, unit v; ω _ifor signal frequency, T is sampling interval duration, and f is for presetting sample frequency, and unit Hz, n are series of discrete number, for preliminary sequence initial phase, N _startfor preliminary sequence length.

Frequency preliminary survey module 303 is by zero friendship method, based on the algorithm of filtering, based on Wavelet Transformation Algorithm, the algorithm based on neural network, the frequency algorithm based on DFT conversion or carry out frequency preliminary survey based on the frequency algorithm of phase differential to described preliminary sequence, obtain described just synchronizing frequency.

In one embodiment, generating described just synchronizing frequency is formula (3):

ω _o(3)；

Preferably, described reference frequency equals described just synchronizing frequency is formula (4):

ω _s＝ω _o(4)；

Wherein, ω _sfor reference frequency, ω _ofor first synchronizing frequency.

Unit period sequence length module 304, according to described default sample frequency and described reference frequency, obtains the unit period sequence length of described electric power signal;

In one embodiment, the unit period sequence length obtaining described electric power signal is formula (5):

$N_{2\mathrm{\&pi;}}=\left(\mathrm{int}\right)\frac{2\mathrm{\&pi;}f}{{\mathrm{\&omega;}}_s}---\left(5\right);$

In formula, N _{2 π}for described unit period sequence length; (int) be round numbers; F is for presetting sample frequency, unit Hz; ω _sfor reference frequency.There is the error in 1 sampling interval in unit period sequence length integer.

Predetermined sequence length modules 305, according to described default integer signal period number and described unit period sequence length, obtains the predetermined sequence length of described electric power signal;

In one embodiment, obtaining described predetermined sequence length is formula (6):

N＝(int)[(C _2π-1)N _2π](6)；

Wherein, N is predetermined sequence length, and (int) is round numbers, N _{2 π}for described unit period sequence length, C _{2 π}for default integer signal period number.

First forward block 306, according to default starting point and described predetermined sequence length, obtains the first forward sequence of described electric power signal from described preliminary sequence;

In one embodiment, default starting point is 0.5 times of described unit period sequence length;

In one embodiment, obtaining described first forward sequence is formula (7):

Wherein, X _startn () is preliminary sequence, X _{+ start}n () is first forward sequence, P _startpreset starting point, N _{2 π}for described unit period sequence length, (int) is round numbers, and A is signal amplitude, unit v, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, for first forward sequence initial phase, N predetermined sequence length.First forward sequence pattern is expressed, shown in Fig. 2.

First anti-pleat block 307 obtains the first anti-pleat sequence of described electric power signal according to described first forward sequence; In one embodiment, obtaining first anti-pleat sequence is formula (8):

$\begin{array}{c}{X}_{-\mathrm{start}}(-n)=X_{+\mathrm{start}}(N-n)=A\cos (-{\mathrm{\&omega;}}_i\mathrm{Tn}+\mathrm{\&beta;}1)\\ n=\mathrm{0,1,2},...,N-1\end{array}---\left(8\right);$

Wherein, X _-start(-n) is first anti-pleat sequence, X _{+ start}(n) for first forward sequence, A be signal amplitude, unit v, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, and β 1 is first anti-pleat sequence initial phase, N predetermined sequence length.The avatars of described first anti-pleat sequence, as shown in Figure 2.

First phase module 308 obtains the first positive phase of described electric power signal according to described first forward sequence, and obtains the first antiphase of described electric power signal according to described first anti-pleat sequence;

In one embodiment, first positive phase and first antiphase are the results based on quadrature downconvert and integral and calculating, when not considering the mixing interfering frequency of quadrature downconvert, quadrature downconvert is expressed as formula (9), and integral and calculating is expressed as formula (10):

Wherein, R _{+ start}n () is the first positive real sequence of mixing frequently, I _{+ start}n () is first weakened body resistance frequency mixing sequence, R _-start(-n) is the first anti-real sequence of mixing frequently, I _-start(-n) is the first anti-empty sequence of mixing frequently, cos (ω _sor cos (-ω Tn) _stn) be the discrete cosine function of reference frequency, sin (ω _sor sin (-ω Tn) _stn) be the discrete sine function of reference frequency, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, for first forward sequence initial phase, β 1 is first forward sequence initial phase, and N is predetermined sequence length.

In formula, R _{+ start}first positive real integrated value, unit dimensionless frequently, I _{+ start}for first weakened body resistance frequency integrated value, unit dimensionless, R _-startfor first anti-real integrated value, unit dimensionless frequently, I _-startfor the first anti-empty integrated value of mixing frequently, unit dimensionless, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, T is sampling interval duration, and n is series of discrete number, and N is predetermined sequence length, for first forward sequence initial phase, β 1 is first forward sequence initial phase.

In one embodiment, the expression formula of first positive phase and first antiphase is obtained for (11):

In formula, PH _{+ start}for first positive phase, PH _-startfor first antiphase, R _{+ start}first positive real integrated value, unit dimensionless frequently, I _{+ start}for first weakened body resistance frequency integrated value, unit dimensionless, R _-startfor first anti-real integrated value, unit dimensionless frequently, I _-startfor the first anti-empty integrated value of mixing frequently, unit dimensionless, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, T is sampling interval duration, and N is predetermined sequence length, for first forward sequence initial phase, β 1 is first anti-pleat sequence initial phase.

First average initial phase module 309 obtains the first average initial phase of described electric power signal according to described first positive phase and described first antiphase;

In one embodiment, the expression formula obtaining first average initial phase is (12):

In formula, PH _start-avgfor first average initial phase, PH _{+ start}for first positive phase, PH _-startfor first antiphase, for first forward sequence initial phase, β 1 is first anti-pleat sequence initial phase.

Described first average initial phase and ± π/4 compare by phase compare module 310, obtain the first phase compare value compared with described ± π/4, and according to described first phase compare value and described default starting point, obtain new starting point; In one embodiment, by described first average initial phase and PH _start-avgwith ± π/4 compare as formula (13):

${\mathrm{\&Delta;PH}}_{com}=\left\{\begin{array}{cc}\frac{\mathrm{\&pi;}}{4}-{\mathrm{PH}}_{start-avg}& 0\&le;{\mathrm{PH}}_{start-avg}\&le;\frac{\mathrm{\&pi;}}{4},\frac{\mathrm{\&pi;}}{4}<{\mathrm{PH}}_{start-avg}\&le;\frac{\mathrm{\&pi;}}{2}\\ -\frac{\mathrm{\&pi;}}{4}-{\mathrm{PH}}_{start-avg}& -\frac{\mathrm{\&pi;}}{2}\&le;{\mathrm{PH}}_{start-avg}<-\frac{\mathrm{\&pi;}}{4},-\frac{\mathrm{\&pi;}}{4}<{\mathrm{PH}}_{start-avg}\&le;0\\ 0& {\mathrm{PH}}_{start-avg}=\&PlusMinus;\frac{\mathrm{\&pi;}}{4}\end{array}\right.---\left(13\right);$

In formula, Δ PH _comfor first phase compare value, unit rad, PH _start-avgfor first average initial phase.

In one embodiment, obtaining described new starting point is formula (14):

$P_{new}=P_{start}+\left(\mathrm{int}\right)\left(\frac{{\mathrm{\&Delta;PH}}_{com}}{2\mathrm{\&pi;}}{N}_{2\mathrm{\&pi;}}\right)---\left(14\right);$

In formula, P _newfor new starting point, unit dimensionless, P _startfor default starting point, Δ PH _comfor first phase compare value, unit rad, N _{2 π}for unit periodic sequence length, (int) is round numbers.

Block 311 is according to described new starting point and described predetermined sequence length again, obtains the sequence of forward again of described electric power signal from described preliminary sequence, and obtains the again anti-pleat sequence of described electric power signal according to the described sequence of forward again;

In one embodiment, again forward sequence and again anti-pleat sequence be formula (15):

In formula, X _{+ end}n () is again forward sequence, X _-end(-n) is again anti-pleat sequence, P _newfor new starting point, unit dimensionless, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, and N is predetermined sequence length.

Phase module 312 obtains the positive phase again of described electric power signal according to the described sequence of forward again again, and obtains the antiphase again of described electric power signal according to described anti-pleat sequence again;

In one embodiment, again positive phase and again antiphase be the result calculated based on quadrature downconvert and digital filtering.Described digital filtering is made up of 6 grades of rectangular window arithmetic mean filter of 2 kinds of filtering parameters.

When not considering the mixing interfering frequency of quadrature downconvert, quadrature downconvert is expressed as formula (16), and 6 grades of rectangular window arithmetic mean filter filtering calculation expressions of 2 kinds of filtering parameters are formula (17):

In formula, R _{+ end}n () is again the positive real sequence of mixing frequently, I _{+ end}n () is again weakened body resistance frequency mixing sequence, R _-end(-n) is again the anti-real sequence of mixing frequently, I _-end(-n) is again the anti-empty sequence of mixing frequently, cos (ω _sor cos (-ω Tn) _stn) be the discrete cosine function of reference frequency, sin (ω _sor sin (-ω Tn) _stn) be the discrete sine function of reference frequency, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase, and N is predetermined sequence length.

In formula, R _{+ end}for positive real digital filtering final value frequently again, unit dimensionless; I _{+ end}for weakened body resistance frequency digital filtering final value again, unit dimensionless; R _-endfor anti-digital filtering final value again, unit dimensionless; I _-endfor anti-empty digital filtering final value frequently again, unit dimensionless; Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference; K (Ω) for digital filtering is in the amplitude gain of frequency difference Ω, unit dimensionless; T is sampling interval duration; for forward sequence initial phase again; β 2 is again anti-pleat sequence initial phase; N _d1for filtering parameter 1, namely to N _d1individual continuous discrete value is added, and then gets its arithmetic mean and exports as this filter value; N _d2for filtering parameter 2, namely to N _d2individual continuous discrete value is added, and then gets its arithmetic mean and exports as this filter value; N _dfor digital filtering uses sequence length, be quantitatively the summation of 6 grades of rectangular window arithmetic mean filter filtering parameters, be less than or equal to predetermined sequence length N.

In one embodiment, filtering parameter N _d1value is 1.5 times of the unit period sequence length of described reference frequency, and object carries out degree of depth suppression to the mixing interfering frequency that 1/3 subharmonic produces; Filtering parameter N _d2value is 2 times of the unit period sequence length of described reference frequency, and object carries out degree of depth suppression to the mixing interfering frequency that direct current, 1/2 gradation, subharmonic etc. produce.6 grades of rectangular window arithmetic mean filter filtering of 2 kinds of filtering parameters calculate 10.5 times that need to use signal period sequence length.

Filtering parameter N _d1with filtering parameter N _d2expression formula is formula (18):

$\begin{array}{c}{N}_{D1}=\left(\mathrm{int}\right)\left(1.5N_{2\mathrm{\&pi;}}\right)\\ N_{D2}=2N_{2\mathrm{\&pi;}}\end{array}---\left(18\right);$

In formula, N _d1for digital filter parameters 1, unit dimensionless, (int) is round numbers, N _d2for digital filter parameters 2, unit dimensionless, N _{2 π}for unit periodic sequence length.

In one embodiment, again positive phase and again antiphase expression formula be (19):

In formula, PH _{+ end}for positive phase again, PH _-endfor antiphase again, R _{+ end}for positive real integrated value frequently again, unit dimensionless, I _{+ end}for weakened body resistance frequency integrated value again, unit dimensionless, R _-endfor anti-real integrated value frequently again, unit dimensionless, I _-endfor the anti-empty integrated value of mixing frequently again, unit dimensionless, Ω is signal frequency ω _iwith reference frequency ω _sfrequency difference, T is sampling interval duration, N _dfor digital filtering uses sequence length, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase.

Average initial phase module 313 obtains the again average initial phase of described electric power signal according to described positive phase again and described antiphase again again;

In one embodiment, the expression formula obtaining again average initial phase is (20):

In formula, PH _end-avgfor average initial phase again, PH _{+ end}for positive phase again, PH _-endfor antiphase again, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase.

The described sequence of forward again and described anti-pleat sequence are again added by cosine function modulation sequence module 314, and according to the result after addition and described average initial phase again, obtain the cosine function modulation sequence of described electric power signal; In one embodiment, obtaining cosine function modulation sequence expression formula is (21):

In formula, X _cosn () is cosine function modulation sequence; A is cosine function modulation sequence amplitude, unit v; for cosine function modulation sequence initial phase, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, and N is predetermined sequence length, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase.

The described sequence of forward again and described anti-pleat sequence are again subtracted each other by sine function modulation sequence module 315, and according to the result after subtracting each other and described average initial phase again, obtain the sine function modulation sequence of described electric power signal; In one embodiment, obtaining sine function modulation sequence expression formula is (22):

In formula, X _sinn () is sine function modulation sequence, A is sine function modulation sequence amplitude, unit v, for cosine function modulation sequence initial phase, ω _ifor signal frequency, T is sampling interval duration, and n is series of discrete number, and N is predetermined sequence length, for forward sequence initial phase again, β 2 is again anti-pleat sequence initial phase.

The discrete sine function of default fine setting frequency is multiplied with described sine function modulation sequence and obtains the 3rd multiplication sequence of described electric power signal by multiplication sequence module 316, and being multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency obtains the 4th multiplication sequence of described electric power signal;

In one embodiment, described default fine setting frequency is the arithmetic number being less than or equal to actual signal frequency 1%, and unit rad/s is expressed as formula (23):

$\begin{array}{c}{\mathrm{\&Omega;}}_{\mathrm{set}}\\ {\mathrm{\&Omega;}}_{\mathrm{set}}\&le;0.01{\mathrm{\&omega;}}_i\end{array}---\left(23\right)$

In formula, Ω _setfor fine setting frequency, unit rad/s, Ω _set≤ 0.01 ω _i.

The 3rd multiplication sequence obtaining described electric power signal that the discrete sine function of default fine setting frequency is multiplied with described sine function modulation sequence is formula (24):

The 4th multiplication sequence obtaining described electric power signal that is multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency is formula (25):

In formula, X3 (n) is the first multiplication sequence, and X4 (n) is the second multiplication sequence, sin (Ω _settn) be the discrete sine function of described fine setting frequency, cos (Ω _settn) be the discrete cosine function of described fine setting frequency.

Reduce frequency cosine function block 317 described 4th multiplication sequence is added with described 3rd multiplication sequence, obtain the reduction frequency cosine function sequence of described electric power signal;

In one embodiment, obtaining reduction frequency cosine function sequence is formula (26):

In formula, X _cos+fn (), for reducing frequency cosine function sequence, sequence frequency reduces Ω _set.

Each technical characteristic of the above embodiment can combine arbitrarily, for making description succinct, the all possible combination of each technical characteristic in above-described embodiment is not all described, but, as long as the combination of these technical characteristics does not exist contradiction, be all considered to be the scope that this instructions is recorded.

The above embodiment only have expressed several embodiment of the present invention, and it describes comparatively concrete and detailed, but can not therefore be construed as limiting the scope of the patent.It should be pointed out that for the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection domain of patent of the present invention should be as the criterion with claims.

Claims (10)

1. obtain a method for the reduction frequency cosine function sequence of electric power signal, it is characterized in that, comprise the following steps:

According to the lower limit of frequency power signal scope, default sample frequency and default integer signal period number, obtain the preliminary sequence length of described electric power signal;

According to described preliminary sequence length, described electric power signal is sampled, obtain the preliminary sequence of described electric power signal;

Frequency preliminary survey is carried out to described preliminary sequence, generates the first synchronizing frequency of described electric power signal, and according to described preliminary frequency setting the reference frequency of electric power signal;

According to described default sample frequency and described reference frequency, obtain the unit period sequence length of described electric power signal;

According to described default integer signal period number and described unit period sequence length, obtain the predetermined sequence length of described electric power signal;

According to default starting point and described predetermined sequence length, from described preliminary sequence, obtain the first forward sequence of described electric power signal;

The first anti-pleat sequence of described electric power signal is obtained according to described first forward sequence;

Obtain the first positive phase of described electric power signal according to described first forward sequence, and obtain the first antiphase of described electric power signal according to described first anti-pleat sequence;

The first average initial phase of described electric power signal is obtained according to described first positive phase and described first antiphase;

Described first average initial phase and ± π/4 are compared, obtains the first phase compare value compared with described ± π/4, and according to described first phase compare value and described default starting point, obtain new starting point;

According to described new starting point and described predetermined sequence length, from described preliminary sequence, obtain the sequence of forward again of described electric power signal, and obtain the again anti-pleat sequence of described electric power signal according to the described sequence of forward again;

Obtain the positive phase again of described electric power signal according to the described sequence of forward again, and obtain the antiphase again of described electric power signal according to described anti-pleat sequence again;

The again average initial phase of described electric power signal is obtained according to described positive phase again and described antiphase again;

The described sequence of forward again and described anti-pleat sequence are again added, and according to the result after addition and described average initial phase again, obtain the cosine function modulation sequence of described electric power signal;

The described sequence of forward again and described anti-pleat sequence are again subtracted each other, and according to the result after subtracting each other and described average initial phase again, obtains the sine function modulation sequence of described electric power signal;

The discrete sine function of default fine setting frequency be multiplied with described sine function modulation sequence and obtain the 3rd multiplication sequence of described electric power signal, being multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency obtains the 4th multiplication sequence of described electric power signal;

Described 4th multiplication sequence is added with described 3rd multiplication sequence, obtains the reduction frequency cosine function sequence of described electric power signal.

2. the method for the reduction frequency cosine function sequence of acquisition electric power signal according to claim 1, it is characterized in that, described electric power signal is the cosine function signal of single fundamental frequency, according to expression formula obtain described preliminary sequence X _start(n), wherein n=0,1,2,3 ..., N _start-1, A is signal amplitude, ω _ifor signal frequency, for the initial phase of described preliminary sequence, T is sampling interval duration, and f is described default sample frequency, and n is series of discrete number, N _startfor described preliminary sequence length.

3. the method for the reduction frequency cosine function sequence of acquisition electric power signal according to claim 2, is characterized in that, according to expression formula obtain described cosine function modulation sequence X _cos(n), wherein n=0,1,2 ..., N-1, X _{+ end}n () is the described sequence of forward again, X _-end(-n) is described anti-pleat sequence again, PH _end-avgfor described average initial phase again, n is series of discrete number, and N is described predetermined sequence length.

4. the method for the reduction frequency cosine function sequence of the acquisition electric power signal according to Claims 2 or 3, is characterized in that, according to expression formula obtain described sine function modulation sequence X _sin(n), wherein n=0,1,2 ..., N-1, X _{+ end}n () is the described sequence of forward again, X _-end(-n) is described anti-pleat sequence again, PH _end-avgfor described average initial phase again, n is series of discrete number, and N is described predetermined sequence length.

5. the method for the reduction frequency cosine function sequence of acquisition electric power signal according to claim 1, is characterized in that, according to expression formula X3 (n)=X _sin(n) sin (Ω _settn) described 3rd multiplication sequence X3 (n) is obtained, according to expression formula X4 (n)=X _cos(n) cos (Ω _settn) described 4th multiplication sequence X4 (n), wherein n=0 is obtained, 1,2 ..., N-1, X _cosn () is described cosine function modulation sequence, X _sinn () is described sine function modulation sequence, sin (Ω _settn) be the discrete sine function of described default fine setting frequency, cos (Ω _settn) be the discrete cosine function of described default fine setting frequency, Ω _setfor described default fine setting frequency, T is sampling interval duration, and n is series of discrete number, and N is described predetermined sequence length.

6. obtain a system for the reduction frequency cosine function sequence of electric power signal, it is characterized in that, comprising:

Preliminary sequence length modules, for the lower limit according to frequency power signal scope, presets sample frequency and default integer signal period number, obtains the preliminary sequence length of described electric power signal;

Preliminary sequence module, for sampling to described electric power signal according to described preliminary sequence length, obtains the preliminary sequence of described electric power signal;

Frequency preliminary survey module, for carrying out frequency preliminary survey to described preliminary sequence, generates the first synchronizing frequency of described electric power signal, and according to described preliminary frequency setting the reference frequency of electric power signal;

Unit period sequence length module, for according to described default sample frequency and described reference frequency, obtains the unit period sequence length of described electric power signal;

Predetermined sequence length modules, for according to described default integer signal period number and described unit period sequence length, obtains the predetermined sequence length of described electric power signal;

First forward block, for according to presetting starting point and described predetermined sequence length, obtains the first forward sequence of described electric power signal from described preliminary sequence;

First anti-pleat block, for obtaining the first anti-pleat sequence of described electric power signal according to described first forward sequence;

First phase module, for obtaining the first positive phase of described electric power signal according to described first forward sequence, and obtains the first antiphase of described electric power signal according to described first anti-pleat sequence;

First average initial phase module, for obtaining the first average initial phase of described electric power signal according to described first positive phase and described first antiphase;

Phase compare module, for described first average initial phase and ± π/4 being compared, obtaining the first phase compare value compared with described ± π/4, and according to described first phase compare value and described default starting point, obtaining new starting point;

Block again, for according to described new starting point and described predetermined sequence length, obtains the sequence of forward again of described electric power signal, and obtains the again anti-pleat sequence of described electric power signal according to the described sequence of forward again from described preliminary sequence;

Phase module again, for obtaining the positive phase again of described electric power signal according to the described sequence of forward again, and obtains the antiphase again of described electric power signal according to described anti-pleat sequence again;

Average initial phase module again, for obtaining the again average initial phase of described electric power signal according to described positive phase again and described antiphase again;

Cosine function modulation sequence module, for the described sequence of forward again and described anti-pleat sequence being again added, and according to the result after addition and described average initial phase again, obtains the cosine function modulation sequence of described electric power signal;

Sine function modulation sequence module, for the described sequence of forward again and described anti-pleat sequence again being subtracted each other, and according to the result after subtracting each other and described average initial phase again, obtains the sine function modulation sequence of described electric power signal;

Multiplication sequence module, obtain the 3rd multiplication sequence of described electric power signal for the discrete sine function of default fine setting frequency being multiplied with described sine function modulation sequence, being multiplied with described cosine function modulation sequence by the discrete cosine function of described default fine setting frequency obtains the 4th multiplication sequence of described electric power signal;

Reducing frequency cosine function block, for being added with described 3rd multiplication sequence by described 4th multiplication sequence, obtaining the reduction frequency cosine function sequence of described electric power signal.

7. the system of the reduction frequency cosine function sequence of acquisition electric power signal according to claim 6, is characterized in that, described electric power signal is the cosine function signal of single fundamental frequency, and described preliminary sequence module is according to expression formula obtain described preliminary sequence X _start(n), wherein n=0,1,2,3 ..., N _start-1, A is signal amplitude, ω _ifor signal frequency, for the initial phase of described preliminary sequence, T is sampling interval duration, and f is described default sample frequency, and n is series of discrete number, N _startfor described preliminary sequence length.

8. the system of the reduction frequency cosine function sequence of acquisition electric power signal according to claim 7, is characterized in that, described cosine function modulation sequence module is according to expression formula obtain described cosine function modulation sequence X _cos(n), wherein n=0,1,2 ..., N-1, X _{+ end}n () is the described sequence of forward again, X _-end(-n) is described anti-pleat sequence again, PH _end-avgfor described average initial phase again, n is series of discrete number, and N is described predetermined sequence length.

9. the system of the reduction frequency cosine function sequence of the acquisition electric power signal according to claim 7 or 8, is characterized in that, described sine function modulation sequence module is according to expression formula obtain described sine function modulation sequence X _sin(n), wherein n=0,1,2 ..., N-1, X _{+ end}n () is the described sequence of forward again, X _-end(-n) is described anti-pleat sequence again, PH _end-avgfor described average initial phase again, n is series of discrete number, and N is described predetermined sequence length.

10. the system of the reduction frequency cosine function sequence of acquisition electric power signal according to claim 6, it is characterized in that, described multiplication sequence module is according to expression formula X3 (n)=X _sin(n) sin (Ω _settn) described 3rd multiplication sequence X3 (n) is obtained, according to expression formula X4 (n)=X _cos(n) cos (Ω _settn) described 4th multiplication sequence X4 (n), wherein n=0 is obtained, 1,2 ..., N-1, X _cosn () is described cosine function modulation sequence, X _sinn () is described sine function modulation sequence, sin (Ω _settn) be the discrete sine function of described default fine setting frequency, cos (Ω _settn) be the discrete cosine function of described default fine setting frequency, Ω _setfor described default fine setting frequency, T is sampling interval duration, and n is series of discrete number, and N is described predetermined sequence length.