CN102095925A - 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 crucial electrical parameter, and idle size directly influences 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 constitute 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 at 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 based on wavelet transformation need 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 one 16 point sequence (DFT) needs 16 ²The multiplying of=256 complexity and 16 * 15=240 complicated additive operation.Yet, still very complicated on computation process based on the algorithm of Fourier transform.

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 simple relatively.

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+Q sin 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 p (n) is by formula (7)

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, zero crossing with p (n) is a starting point, two cycles of p (n) are equally divided into four parts, 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;

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 Be the phasing degree between the voltage and current waveform, w=2 π/T, T are the cycle periods of 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 that sampling period i is the exponent number of walsh function, i=0,1,2, K, 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 the Walsh 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, the code generator, zero crossing detector produces pulse and inputs to the steering logic device, the cycle of the cycle period of this pulse and input 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 generator of binary storage counter, continuously be input to binary counter by steering logic device time clock, code comparator is made comparisons the output binary storage counter and line output and binary counter.

The beneficial effect that the present invention reached: among the present invention, the Walsh conversion becomes square wave rather than sinusoidal waveform to the signal decomposition 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 simplified the hardware of reactive power measurement greatly; 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 composition 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 ₂The time representation method and the discrete walsh function Wal in three rank (3, β _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, comprise with the analog and digital signal Processing Algorithm being the Walsh conversion of basic calculation reactive power, the reactive volt-ampere meter that utilizes the Walsh mapping algorithm to realize based on the Walsh mapping algorithm.

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

p(t)＝P-[Pcos2wt+Q?sin?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)-P cos 2wtWal (3, t)-Q sin 2wtWal (3, t) sequential chart on (2) equation (2) right side is seen shown in the accompanying drawing 3, it should be noted that since walsh function be have only+1 and the complete system of orthogonal function of-1 two value, Wal (3 is multiply by on (1) formula both sides, t) waveform of back gained is the full-wave rectification of reactive power among the instantaneous power p (t), as the curve in the accompanying drawing 31.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 and 3 from accompanying drawing 3 as can be seen, (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 character (4) formula can be written as by Qsin 2wt Wal

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

Can solve reactive power by following formula:

Examine curve 1 (accompanying drawing 3) and formula (5) as can be seen, 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.

Walsh transform based on digital signal processing.Use digitizing algorithm computation reactive power, (1) formula cocoa is write as following form:

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

N=0 in the formula, 1,2 ..., N-1.N is a 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:

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

Wherein i is the exponent number of walsh function, i=0,1,2, K, N-1, β _kBe the parameter of walsh function, with the formal definition of binary code β _kPotential coefficient, β=(β ₁, β ₂Λ β _k) ₂, β _k=0,1, w _mBe potential coefficient with the binary code definition, w=(w ₀, w ₁, Λ w _m) ₂, w _m=0,1, m is meant 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, have only 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, Λ, 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 that from accompanying drawing 5 value of three rank walsh functions on a normal period disperses, definition expression formula below having:

${(-1)}^{{\mathrm{\&beta;}}_2}=\left\{\begin{array}{cc}+1,& [0,\frac{N}{4})Y[\frac{N}{2},\frac{3N}{4}]\\ -1,& [\frac{N}{4},\frac{N}{2})Y[\frac{3N}{4},N-1]\end{array}\right.---\left(12\right)$

Consider

With

Be that following formula is expressed as with negative just together:

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

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 digitizing algorithm computation 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, outputing to adding counting end or subtracting counting end of up-down counter of multiplier connection mode number converter, purpose are to be consistent with wattless power measurement algorithm based on DISCRETE W alsh 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 according to numeral remaining in formula (14) up-down counter to end second round of input signal, display has shown that the scale-of-two of up-down counter exports.

The key component of electronic type reactive volt-ampere meter is a digital sampler, and under 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 period T of the cycle period of this pulse and input voltage signal u (t) is proportional.In first period 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 comparator is made comparisons the output binary storage counter and line output and binary counter.When the umber of pulse of time clock counter generation equaled M, code comparator just had pulse output, and this pulse makes binary counter be reset to zero, also was simultaneously first sampled signal of digital sampler output.In second complete period T, time clock continuously is input to binary counter.When the number of pulses by binary counter equaled M once more, steering logic produced second output pulse, and the output pulse of digital sampler resets binary counter once more.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 _sBe the 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 period T of input signal p (t).

Can draw from formula (17) and (18), the electronic wattmeter that design need satisfy the requirement of data continuous acquisition.When because during the frequency change of the input signal that causes of distribution system instability, the requirement of this continuous sampling can solve the loss of energy in the wave spectrum composition.When needing emphasis to consider influencing 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 of the present invention based on the Walsh mapping algorithm, 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 W alsh 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 (5)

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.

2. the electronic type reactive volt-ampere meter based on the Walsh mapping algorithm according to claim 1, 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+Q sin 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 p (n) is by formula (7)

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, zero crossing with p (n) is a starting point, two cycles of p (n) are equally divided into four parts, 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;

According to formula (14) 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

Be the phasing degree between the voltage and current waveform, w=2 π/T, T are the cycle periods of 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 that sampling period i is the exponent number of walsh function, i=0,1,2, K, N-1, β _kIt is the parameter of walsh function.

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

4. the electronic type reactive volt-ampere meter based on the Walsh mapping algorithm according to claim 1 and 2 is characterized in that: the frequency of the sampled signal that described digital sampler produces is corresponding with frequency input signal.

5. the electronic type reactive volt-ampere meter based on the Walsh mapping algorithm according to claim 1 and 2, 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, the code generator, zero crossing detector produces pulse and inputs to the steering logic device, the cycle of the cycle period of this pulse and input 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 generator of binary storage counter, continuously be input to binary counter by steering logic device time clock, code comparator is made comparisons the output binary storage counter and line output and binary counter.

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