CN102095925B - Electronic reactive power meter based on Walsh transformation algorithm - Google Patents

Abstract

The invention discloses an electronic reactive power meter based on a Walsh transformation algorithm, comprising an analog multiplier, an analog-to-digital converter, a reversible counter and a display which are orderly connected, wherein a control logic device is respectively connected with the analog multiplier, the analog-to-digital converter, the reversible counter and the display. In the invention, the to-be-analyzed signals are decomposed into rectangular wave but not sine wave form by the Walsh transformation algorithm; the calculation speed is faster; and the algorithm taking the Walsh transformation as base only comprises addition operation and subtraction operation, thereby greatly simplifying reactive power measurement hardware implementation; and the Walsh transformation algorithm does not need phase-shifting pi/2 between voltage signals and current signals.

Description

Electronic type reactive volt-ampere meter based on the Walsh mapping algorithm

Technical field

The present invention relates to a kind of electronic type reactive volt-ampere meter, belong to the electric energy meter technical field.

Background technology

In electric system, reactive power is very important electrical parameter, and idle size directly affects the transfer efficiency of electric system and the quality of the quality of power supply.The core of traditional electronic type reactive energy measurement technology is to adopt electron device and circuit thereof to consist of the metering link, and the method for taking has phase-shifting method, the indirect method of measurement, and integral method etc., these measuring methods have adopted Analog Electronics Technique or Digital Electronic Technique.The ten years in past has been studied the method for many different measurement reactive powers for the electric system under sinusoidal and multiple-harmonic (the having harmonic distortion) condition.Article " adopting the power measurement method of wavelet transformation " (" metering journal " the 1st phase in 2003) proposes a kind of power calculation method based on wavelet transformation, and this power measuring system take wavelet transformation as the basis need to carry out the phase shift operation to input voltage signal.Although can calculate reactive power and not need the phase shift operation based on the Fourier transform of numeral or analog filter algorithm, when utilizing Fourier algorithm to calculate reactive power, need a large amount of multiplication and additive operation.For example, the discrete Fourier transformation of 16 point sequences (DFT) needs 16 ²The multiplying of=256 complexity and 16 * 15=240 complicated additive operation.Yet, still very complicated on computation process take Fourier transform as the algorithm on basis.

Summary of the invention

Technical matters to be solved by this invention is to obtain the reactive power composition in the instantaneous power and do not need phase shift pi/2 between voltage waveform and the current waveform, and computation process is relatively simple.

For solving the problems of the technologies described above, the invention provides a kind of electronic type reactive volt-ampere meter based on the Walsh mapping algorithm, comprise the analog multiplier, analog to digital converter, multiplier, up-down counter and the display that link to each other successively, steering logic links to each other with analog to digital converter, multiplier, up-down counter and display, digital sampler respectively.

Aforesaid electronic type reactive volt-ampere meter based on the Walsh mapping algorithm, it is characterized in that: voltage signal u (t) and current signal i (t) input to analog multiplier, the power waveform that analog multiplier output is continuous, this waveform and formula (1) p (t)=P-[Pcos2wt+Qsin2wt] middle instantaneous power p (t) is proportional;

Analog multiplier export to analog to digital converter;

Digital sampler changes the analog voltage signal of input into digital voltage signal, and analog to digital converter changes into digital output signal p (n) to input signal p (t), and digital output signal p (n) is by formula (7) $P\left(n\right)=P-[P\cos (\frac{4\mathrm{\π}}{N}\·n)+Q\sin (\frac{4\mathrm{\π}}{N}\·n)]$ Provide;

The output signal of analog to digital converter is supplied with up-down counter by multiplier, the output of analog to digital converter is connected to adding counting end or subtracting counting end of up-down counter by multiplier, take the zero crossing of digital output signal p (n) as starting point, two cycles of digital output signal p (n) are equally divided into four parts, first and the 3rd four/part of digital output signal p (n) is input to and adds counting end, and second and the 4th four/part of digital output signal p (n) is input to the counting end that subtracts of up-down counter;

According to formula (14)

Calculate the second round of input signal when terminal in the up-down counter remainder just equal the reactive power of the circuit of study, utilize the scale-of-two of display demonstration up-down counter to export,

Wherein

Reactive power

Be the phasing degree between the voltage and current waveform, w=2 π/T, T are the cycle periods of voltage signal u (t), and t is the arbitrary instantaneous moment in the cycle, n=0,1,2 ... N-1, N are hits, and N is determined by sampling theorem, N=T/Ts, Ts are the sampling periods, and i is the exponent number of walsh function, i=0,1,2,, N-1, β _kIt is the parameter of walsh function.

Aforesaid electronic type reactive volt-ampere meter based on the Walsh mapping algorithm is characterized in that: described analog multiplier adopts AD633, and analog to digital converter adopts ADC0804.

Aforesaid electronic type reactive volt-ampere meter based on the Walsh mapping algorithm is characterized in that: the frequency of the sampled signal that described digital sampler produces is corresponding with frequency input signal.

Aforesaid electronic type reactive volt-ampere meter based on Wal sh mapping algorithm, it is characterized in that: digital sampler comprises zero crossing detector, logic controller, clock-signal generator, the scale-of-two ripple counter, binary storage device, binary counter, code produces and comparer, zero crossing detector produces pulse and inputs to the steering logic device, the cycle of the cycle period of this pulse and voltage signal u (t) is proportional, the steering logic device makes the output pulse of clock output to the binary storage counter by the scale-of-two ripple counter, the output termination code of binary storage counter produces and comparer, continuously be input to binary counter by steering logic device time clock, code produces and comparer is made comparisons the output of the parallel output of binary storage counter and binary counter.

The beneficial effect that the present invention reaches: among the present invention, the Walsh conversion is the orthogonal ripple of signal decomposition rather than the sinusoidal waveform that will analyze, computing velocity is faster, and includes only addition and subtraction with the algorithm that Walsh is transformed to the basis, realizes so greatly simplified the hardware of reactive power measurement; The Walsh mapping algorithm does not need phase shift pi/2 between voltage signal, the current signal.

Description of drawings

Fig. 1 is the diagram of the power Components of (1) formula definition, u (t)=2.4sin wt, i (t)=0.5sin (wt-0.5);

Fig. 2 is three rank Walsh function waveforms.

Fig. 3 is the every waveform in equation (2) the right.

Fig. 4 is β _kThe time representation method of last three potential coefficients.

Fig. 5 is β ₂Time representation method and discrete walsh function Wal (3, the β in three rank _k).

Fig. 6 is the structured flowchart of electronic type reactive volt-ampere meter.

Fig. 7 is the digital sampler cut-away view.

Embodiment

The invention provides a kind of electronic type reactive volt-ampere meter based on the Walsh mapping algorithm, comprise the Walsh conversion take the analog and digital signal Processing Algorithm as the basic calculation reactive power, the reactive volt-ampere meter that utilizes the Walsh mapping algorithm to realize.

Take the Walsh conversion of analog signal processing as the basis.The current i (t) of supposing voltage u (t) in the single-phase circuit and flowing through load all is sinusoidal signal, and then instantaneous power is

p(t)=P-[Pcos2wt+Qsin 2wt] （1）

In the formula

Be the phasing degree between the voltage and current waveform, w=2 π/T, T are the cycle periods of u (t).The sequential chart on equation (1) the right is seen accompanying drawing 1.Accompanying drawing 2 be three rank walsh function Wal (3, the t) waveform in a normal period T, (1) formula both sides multiply by respectively three rank walsh function Wal (3, t)

p(t)Wal(t)=PWal(3,t)-Pcos2wtWal(3,t)-Qsin2wtWal(3,t) （2）

The sequential chart on equation (2) right side is seen shown in the accompanying drawing 3, it should be noted that, since walsh function be only have+1 and the complete system of orthogonal function of-1 two value, (1) Wal (3 is multiply by on the formula both sides, t) waveform of gained is the full-wave rectification of reactive power among the instantaneous power p (t) after, such as the curve 1 in the accompanying drawing 3.Integration is carried out simultaneously in following formula (2) both sides in a period of time T, as follows:

$\frac{1}{T}\underset{0}{\overset{T}{\&Integral;}}P\left(t\right)\&CenterDot;\mathrm{Wal}(3,t)\mathrm{dt}=\frac{1}{T}\underset{0}{\overset{T}{\&Integral;}}\mathrm{PWal}(3,t)\mathrm{dt}-\frac{1}{T}\underset{0}{\overset{\mathrm{<figure-callout\; id="2"\; label="T\; P\; cos"\; filenames="101231175501.png"\; state="\{\{state\}\}">T</figure-callout>}}{\&Integral;}}P\cos 2\mathrm{wt}\&CenterDot;\mathrm{Wal}(3,t)\mathrm{dt}-\frac{1}{T}\underset{0}{\overset{T}{\&Integral;}}Q\sin 2\mathrm{wt}\&CenterDot;\mathrm{Wal}(3,t)\mathrm{dt}---\left(3\right)$

Curve 2 from accompanying drawing 3 and 3 can find out, (3, t) (3, t) mean value in one-period T all equals zero product P Wal with product Pcos2wtWal.Therefore first on the right of the formula (3) and second integration in one-period T are zero.Therefore formula (3) formula can be write as following form:

$\frac{1}{T}\underset{0}{\overset{T}{\&Integral;}}P\left(t\right)\&CenterDot;\mathrm{Wal}(3,t)\mathrm{dt}=-\frac{1}{T}\underset{0}{\overset{T}{\&Integral;}}Q\sin 2\mathrm{wt}\&CenterDot;\mathrm{Wal}(3,t)\mathrm{dt}---\left(4\right)$

Examine the curve 1 in the accompanying drawing 3, (3, t) Curve Property (4) formula can be written as by Qsin2wtWal

$\frac{1}{T}\underset{0}{\overset{T}{\&Integral;}}P\left(t\right)\&CenterDot;\mathrm{Wal}(3,t)\mathrm{dt}=-\frac{1}{T}\underset{0}{\overset{T}{\&Integral;}}\left|Q\sin 2\mathrm{wt}\right|\mathrm{dt}---\left(5\right)$

Can solve reactive power by following formula: $Q=\frac{\mathrm{\&pi;}}{2T}\underset{0}{\overset{T}{\&Integral;}}P\left(t\right)\&CenterDot;\mathrm{Wal}(3,t)\mathrm{dt}---\left(6\right)$

Examine curve 1(accompanying drawing 3) and formula (5) can find out, adopt said method can measure the mean value of pulsation reactive power, and this algorithm does not need phase shift pi/2 between the voltage and current signal.

Take the Walsh transform of digital signal processing as the basis.Use Digital Algorithm to calculate reactive power, (1) formula cocoa is write as following form:

$P\left(n\right)=P-[P\cos (\frac{4\mathrm{\&pi;}}{N}\&CenterDot;n)+Q\sin \left(\frac{4\mathrm{\&pi;}}{N}\&CenterDot;n\right)]---\left(7\right)$

N=0 in the formula, 1,2 ..., N-1.N is hits, and N is by the sampling theorem decision, and N=T/Ts, Ts are the sampling periods.For expressing the digital algorithm of reactive power, walsh function is expressed as following discrete form:

$\mathrm{Wal}(i,{\mathrm{\&beta;}}_k)={(-1)}^{\underset{k}{\mathrm{\&Sigma;}}(w_{m-k+1}\&CirclePlus;w_{m-k}){\mathrm{\&beta;}}_k}---\left(8\right)$

Wherein i is the exponent number of walsh function, i=0, and 1,2 ..., N-1, β _kThe parameter of walsh function, with the formal definition of binary code β _kPotential coefficient, β=(β ₁, β ₂β _k) ₂, β _k=0,1, w _mThe potential coefficient with the binary code definition, w=(w ₀, w ₁... w _m) ₂, w _m=0,1, m refers to the sequence number of higher-order function in the walsh function system, with binary representation.We use three rank walsh function Wal(3, β _k) calculating reactive power composition.Three rank walsh function w=3 are because 3=(0000011) ₂, only have w ₆=1 and w ₅=1, w _mRemaining potential coefficient, m=1,2,3,4 all equal zero.Therefore three rank Walsh functions are write

$w(3,{\mathrm{\&beta;}}_2)={(-1)}^{({\mathrm{\&omega;}}_5\&CirclePlus;{\mathrm{\&omega;}}_4){\mathrm{\&beta;}}_2}={(-1)}^{(1\&CirclePlus;0){\mathrm{\&beta;}}_2}={(-1)}^{{\mathrm{\&beta;}}_2}---\left(9\right)$

Parameter beta _kChange depend on standard time T=0.2s, accompanying drawing 4 and accompanying drawing 5 are β ₂And Wal (3, β _k) oscillogram.(7) sue for peace from n=0 to n=N-1 with multiply by (9) formula in the formula both sides again,

$\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}p\left(n\right){(-1)}^{{\mathrm{\&beta;}}_k}=\frac{1}{N}\underset{N-0}{\overset{N-1}{\mathrm{\&Sigma;}}}P{(-1)}^{{\mathrm{\&beta;}}_2}-\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}P\cos (4\mathrm{\&pi;n}/N){(-1)}^{{\mathrm{\&beta;}}_2}-\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}Q\sin (4\mathrm{\&pi;n}/N){(-1)}^{{\mathrm{\&beta;}}_2}---\left(10\right)$

In fact, because at n=0,1,2 ..., on the N-1,

Be change in the cycle and and cos (4 π n/N) quadrature, first and second vanishing in the right of (10) formula.Therefore (10) can be write as

$\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}p\left(n\right){(-1)}^{{\mathrm{\&beta;}}_2}=-\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}Q\sin \left(\frac{4\mathrm{\&pi;n}}{N}\right){(-1)}^{{\mathrm{\&beta;}}_2}---\left(11\right)$

Find out from accompanying drawing 5, the value of three rank walsh functions on a normal period disperses, definition expression formula below having:

${(-1)}^{{\mathrm{\&beta;}}_2}=\left\{\begin{array}{cc}+1,& [0,\frac{N}{4})\&cup;[\frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="101231175501.png"\; state="\{\{state\}\}">N</figure-callout>}}{2},\frac{3N}{4}]\\ -1,& [\frac{N}{4},\frac{N}{2})\&cup;[\frac{3N}{4},N-1]\end{array}\right.---\left(12\right)$

Consider

With

That following formula is expressed as with just same negative:

$\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}p\left(n\right){(-1)}^{{\mathrm{\&beta;}}_2}=\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}\left|Q\sin (4\mathrm{\&pi;n}/N)\right|---\left(13\right)$

Similar with (4), can solve

$Q=\frac{\mathrm{\&pi;}}{2N}\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}p\left(n\right){(-1)}^{{\mathrm{\&beta;}}_2}---\left(14\right)$

The reactive power of Digital Algorithm calculating that Here it is.

The realization of electronic type reactive volt-ampere meter.Accompanying drawing 6 is realization block diagrams of electronic type reactive volt-ampere meter.The voltage and current signal inputs to analog multiplier, the waveform that analog multiplier output is continuous, and instantaneous power p (t) is proportional in this waveform and the definition (1).Analog multiplier export to analog to digital converter, steering logic control analog to digital converter.In order to reach the purpose of the insensitive measurement of frequency, digital sampler changes the analog voltage signal of input into digital voltage signal, and analog to digital converter changes into digital output signal p (n) to input signal p (t), and p (n) is provided by (7) formula.The output signal p of analog to digital converter (n) supplies with up-down counter by multiplier, multiplier connection mode number converter output to adding counting end or subtracting counting end of up-down counter, purpose is to be consistent with wattless power measurement algorithm based on discrete Walsh function.Therefore first and the 3rd four/part of p (n) is input to " adding " input end, and second and the 4th four/part of P (n) is input to " subtracting " input end of up-down counter.Therefore, just equal the reactive power of the circuit of studying to end second round of input signal according to numeral remaining in formula (14) up-down counter, display has shown the scale-of-two output of up-down counter.

The key component of electronic type reactive volt-ampere meter is digital sampler, in the situation that frequency input signal changes, it provides the measurement result (Fig. 7) of relative variation.The frequency of the sampled signal that digital sampler produces is corresponding with frequency input signal.In Fig. 7, zero crossing detector produces pulse, and the cycle T of the cycle period of this pulse and input voltage signal u (t) is proportional.In first cycle T the inside, the output pulse of steering logic control clock outputs to the binary storage counter after by the scale-of-two ripple counter again.According to the Shannon's sampling theorem of instantaneous power signal p (t) sampling, the counter capacity N of scale-of-two ripple counter is defined as, N=2 ^m, m is the figure place of scale-of-two ripple counter, count pulse is stored in the binary storage counter until preparation period T finishes, and following formula is arranged,

M=(f _cT)/N (15)

F wherein _cIt is clock frequency.

From second period T, steering logic makes the output pulse of clock only pass through binary counter.Code produces and comparer is made comparisons the output of the parallel output of binary storage counter and binary counter.When the umber of pulse of time clock counter generation equaled M, code produced and comparer just has pulse output, and this pulse makes binary counter be reset to zero, also is simultaneously first sampled signal that digital sampler is exported.In second complete cycle T, time clock continuously is input to binary counter.When the number of pulses by binary counter equaled M again, steering logic produced second output pulse, and the output pulse of digital sampler resets binary counter again.The time interval between adjacent twice output pulse of digital sampler is defined as

T _s=M/f _s （16）

T wherein _sThe expression sampling interval, f _s=1/T _sBe sample frequency, (15) brought into (16) draw sampling interval T _sAnd the relation between the input signal cycle T:

T _s=T/N (17)

So repetition interval T of digital sampler output pulse _sThe 1/T in the one-period, the form that following formula also can frequency in and out be expressed:

f _s=N·f （18）

Here f=1/T is the frequency of input signal.Therefore, sampling period T _sBecome the function of the cycle T of input signal p (t).

Can draw from formula (17) and (18), the electronic wattmeter that design need to satisfy the requirement of data continuous acquisition.When because during the frequency change of the unstable input signal that causes of distribution system, the requirement of this continuous sampling can solve the loss of energy in the wave spectrum composition.When needing emphasis to consider affecting of elimination frequency input signal variation, the way of this digital sample can be widely used.

As shown in Figure 6, a kind of electronic type reactive volt-ampere meter based on the Walsh mapping algorithm of the present invention, structure mainly comprises analog multiplier, analog to digital converter, multiplier, bi-directional counter, digital sampler, steering logic and display.Wherein analog multiplier adopts AD633, and analog to digital converter adopts ADC0804.

Voltage signal u (t) and current signal i (t) input to analog multiplier AD633, the power waveform that analog multiplier output is continuous, and instantaneous power p (t) is proportional in this waveform and the definition (1).AD633 exports to analog to digital converter ADC0804.In order to reach the purpose of the insensitive measurement of frequency, digital sampler changes the analog voltage signal of input into digital voltage signal, and analog to digital converter changes into digital output signal p (n) to input signal p (t), and p (n) is provided by (7) formula.The output signal of analog to digital converter is supplied with up-down counter by multiplier, the output of analog to digital converter ADC0804 is to be connected to adding counting end or subtracting counting end of up-down counter by multiplier, and purpose is to be consistent with wattless power measurement algorithm based on discrete Walsh function.Two cycles of p (n) are equally divided into four parts, and first and the 3rd four/part of p (n) is input to and adds counting end, and second and the 4th four/part of p (n) is input to the counting end that subtracts of up-down counter.Therefore, according to formula (14) calculate the second round of input signal when terminal in the up-down counter remainder just equal the reactive power of the circuit of studying, display has shown that the scale-of-two of up-down counter exports.

Claims (4)

1. electronic type reactive volt-ampere meter based on the Walsh mapping algorithm, comprise the analog multiplier, analog to digital converter, multiplier, up-down counter and the display that link to each other successively, steering logic links to each other with analog to digital converter, multiplier, up-down counter and display, digital sampler respectively, voltage signal u (t) and current signal i (t) input to analog multiplier, the power waveform that analog multiplier output is continuous, described power waveform and formula p (t)=P-[Pcos(2wt)+Qsin(2wt)] middle instantaneous power p (t) is proportional;

Analog multiplier export to analog to digital converter;

Digital sampler changes the analog voltage signal of input into digital voltage signal, and analog to digital converter changes into digital output signal p (n) to input signal p (t), and digital output signal p (n) is by formula $P\left(n\right)=P-[P\cos (\frac{4\mathrm{\&pi;}}{N}\&CenterDot;n)+Q\sin (\frac{4\mathrm{\&pi;}}{N}\&CenterDot;n)]$ Provide;

The output signal of analog to digital converter is supplied with up-down counter by multiplier, the output of analog to digital converter is connected to adding counting end or subtracting counting end of up-down counter by multiplier, take the zero crossing of digital output signal p (n) as starting point, two cycles of digital output signal p (n) are equally divided into four parts, first and the 3rd four/part of digital output signal p (n) is input to and adds counting end, and second and the 4th four/part of digital output signal p (n) is input to the counting end that subtracts of up-down counter;

According to formula

, calculate the second round of input signal when terminal in the up-down counter remainder equal the reactive power of the circuit of study, utilize the scale-of-two of display demonstration up-down counter to export,

Wherein

Reactive power

Be the phasing degree between the voltage and current waveform, w=2 π/T, T are the cycle periods of voltage signal u (t), and t is the arbitrary instantaneous moment in the cycle, n=0,1,2 ..., N-1, N are hits, N is by the sampling theorem decision, and N=T/Ts, Ts are the sampling periods, β ₂It is the parameter of walsh function.

2. the electronic type reactive volt-ampere meter based on the Walsh mapping algorithm according to claim 1 is characterized in that: described analog multiplier employing AD633, analog to digital converter employing ADC0804.

3. the electronic type reactive volt-ampere meter based on the Walsh mapping algorithm according to claim 1 is characterized in that: the frequency of the sampled signal that described digital sampler produces is corresponding with frequency input signal.

4. the electronic type reactive volt-ampere meter based on the Walsh mapping algorithm according to claim 1, it is characterized in that: digital sampler comprises zero crossing detector, logic controller, clock-signal generator, the scale-of-two ripple counter, binary storage device, binary counter, code produces and comparer, zero crossing detector produces pulse and inputs to logic controller, the cycle of the cycle period of this pulse and voltage signal u (t) is proportional, logic controller makes the output pulse of clock output to binary storage device by the scale-of-two ripple counter, the output termination code of binary storage device produces and comparer, continuously be input to binary counter by the logic controller time clock, code produces and comparer is made comparisons the output of the parallel output of binary storage device and binary counter.

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