CN1034772C - Method for solving the contradiction between watt-hour operation precision and speed in digit electron watt-hour meter - Google Patents

Abstract

The present invention relates to a sampling and operating method for solving the contradiction between electrical degree operation precision and speed in a digital electronic watt meter. The method comprises an asynchronous sampling method, a power-electrical degree radix converting method and a positive and negative power method which is used for operating wattless electrical degrees. The asynchronous sampling method is used for reducing sampling phase angle step distances in a sampling cycle, the secondary multiply operation in the electric energy increment operation in each sampling step distance is simplified into an add operation, and instantaneous power values in the process of operating wattful electrical degrees are utilized to estimate the wattless electrical degrees. The method can also be applied to metering devices, such as high-accuracy phase or phase meters, power factor meters, etc.

Description

Solve the method for electric degree operational precision and speed contradiction in the digital and electronic watt-hour meter

The present invention relates to the digital electronic watt hour meter making, especially relate to the sampling and the operational method of contradiction between solution electric degree operational precision in the digital electronic watt-hour meter and the arithmetic speed.

In existing various microcomputerization (intellectuality) watt-hour meter and electronic type (solid-state) watt-hour meter, its watt metering system all adopts one of following two classes:

(1) mechanical rotating disk type watt-hour meter adds detecting devices such as light one electricity, will become umber of pulse with the proportional capstan revolution of electricity, again by microcomputer or this umber of pulse of counter accumulative total, to realize electric energy metrical.

(2) convert voltage, current signal to the output pulses string with dissimilar analog multiplier units and voltage-frequency converter, again by microcomputer or counter integral power umber of pulse, to realize electric energy metrical.

The digitizing full-electronic watt hour meter making that has occurred recently is as the inventor's Chinese utility model patent " electric spoon type intelligent kilowatt-hour meter ".In (ZL92209607.4 authorizes), its metering system be by the microcomputer in the watt-hour meter will take a sample and analog to digital conversion after the digitizing electric current and voltage signal carries out digitized power and the electric degree computing realizes electric energy metrical.Its advantage is, mechanical watt-hour meter of the prior art or analog multiplier and voltage-frequency converter have not only been saved, give full play to the potentiality of microcomputer in the intelligent electric meter, make it can hold a concurrent post the electric degree calculation function, thereby reduce cost, and can also realize automatic phase compensation and amplitude compensation with microcomputer software.Therefore, can under the hardware condition that adopts low precision, make high-precision watt-hour meter.In addition, can also realize the fast automatic table of electronics.

About how carrying out the compensation of automatic phase and range error, and technology contents how to realize the electronics auto-adjustment, the Chinese patent application that proposes the inventor is made detailed description among CN94100987.4 and the CN94101541.6.

The objective of the invention is to, propose three methods with the contradiction between the two of the electric degree operational precision that solves digital full-electronic watt-hour meter in the prior art and hardware effort speed.

The meritorious of digital electronic watt-hour meter with the compensation of automatic phase and amplitude comprises following four fundamental operation steps with idle electric degree computing:

(1) phase compensation factor under evaluation work voltage and the working current and amplitude penalty coefficient.

(2) to the line phase compensation of going forward side by side of electric current and voltage sampling.

(3) current/voltage sampling (phase compensation) is multiplied each other and multiply by the amplitude penalty coefficient, the sampling instantaneous power after phase, the width of cloth compensation: $P\left(n\right)=\frac{(1+\mathrm{gr})(1+\mathrm{hr})}{(1+\mathrm{gN})}.\mathrm{dx}\left(n\right).d^{\′}y\left(n\right)$

P (n)--the power an of-Di n sample moment, unit are LSB ²

Dx (n)--n current sampling value, Dan Weiwei is LSB

Dy ' is (n)--n voltage sampling value, done phase compensation, and unit is LSB

The amplitude penalty coefficient that gr--is relevant with operating voltage

The amplitude penalty coefficient that hr--is relevant with working current

Amplitude penalty coefficient under gN--nominal voltage and the nominal current

Above-mentioned ' LSB ' is the unit of digitized electric current and voltage signal, and promptly the lowest order of binary number (Least Significant Bit) is 1 unit.

(4) electric energy calculates

With the instantaneous power P (n) of each sampling multiply by this ammeter proportionality constant Kwp and sample time step pitch Δ t get electric flux in the time Δ t, again this electric flux and the electric energy that adds up are in the past added up, obtain up to now the accumulative total electricity W (N) of (to N sampling):

The unit of Kwp is: kilovolt-ampere-hour/LSB ²Second

LSB is the digitizing electric current, the unit of voltage.

More than basic electric energy arithmetic expression be the approximate treatment formula of following integral operation:

In order to improve the electric degree operational precision, just should reduce sample interval Δ t as far as possible, but Δ t is placed restrictions on by the slewing rate of analog to digital converter and microcomputer arithmetic speed, and Δ t obtains the more little analog to digital converter and the microcomputer that will adopt more at a high speed, and these device cost are increased significantly.

The present invention proposes to solve with following three methods the contradiction of electric degree operational precision and hardware speed, can under the velocity conditions that does not increase hardware, significantly improve the precision of ammeter thus, or can price lower (or speed is lower) microcomputer and the analog to digital converter watt-hour meter of realizing obtaining to have certain accuracy class.

Three methods that the present invention proposes are respectively:

(1) asynchronous sampling method

This method is chosen step pitch Δ t sample time according to the present invention's following ' asynchronous sampling criterion ', to shorten ' sampling phase angle step pitch ', reach under the condition of the arithmetic speed of slewing rate that does not need to improve analog to digital converter and microcomputer, significantly reduce ' sampling phase angle step pitch ' in the sampling circulation, thereby reach the precision that under the condition that does not increase hardware effort speed, improves the electric degree computing.

(2) power-electric degree radix transformation approach

This method is with the secondary multiplying in the electric energy incremental computations in each sampling step pitch Δ t:

Kwp * P (n) * Δ t (kilowatt-time) is reduced to and whenever goes out the additive operation that an output pulses (generally will just go out an output pulses through many Δ t) is done once ' power-electric degree radix conversion '.Thus, saved the secondary multiplying of above-mentioned each Δ t, the computing workload of microcomputer is greatly reduced.

(3) ' the positive and negative power method ' of the idle electric degree of calculating

The calculating of idle electric degree can be adopted the method that is similar to mechanical watt-hour meter, as 90 ° of phase shift killovar-hour meter algorithms of 60 ° of phase shifts of phase three-wire three two unit watt-hour meter or 90 ° of phase shift killovar-hour meter algorithms and three-phase and four-line three unit watt-hour meter.Calculation procedure is similar with amount of calculation and active electrical degree calculating, and difference only is to calculate idle used voltage, the collocation of electric current is different from meritorious.

Meritorious and killovar-hour meter amount can be realized by same set of hardware, for example can survey simultaneously and remember meritorious and idle requirement meritorious and idle electric degree and derivation thereof, the multi-function watt-hour meter of functions such as taking is remembered in timesharing, measure the digital and electronic watt-hour meter of meritorious and idle electric degree simultaneously for this need, can adopt ' positive and negative power method ' of the present invention to calculate idle electric degree, these characteristics of calculating idle electric degree method are: can utilize the instantaneous power value of calculating gained in the active electrical degree process, by simple calculations, extrapolate idle electric degree.Do not need each phase current, voltage are arranged in pairs or groups separately, combination is calculated the calculating (aforementioned 1,2,3,4 steps) of carrying out a whole set of similar active electrical degree for killovar-hour meter and therefore can significantly be saved microcomputer operation time meritorious and idle dual-purpose watt-hour meter.

The method of contradiction between the present invention is proposed below in conjunction with accompanying drawing three speed that is used for solving electronic electric meter electric degree operational precision, promptly, asynchronous sampling method, the positive and negative power method that power-electric degree radix conversion method and killovar-hour meter are calculated is made detailed description respectively.

Fig. 1 represents one-phase digital full-electronic watt-hour meter hardware block diagram.

Fig. 2 represents the digital full-electronic watt-hour meter of three-phase and four-line hardware block diagram.

Fig. 3 represents the main program flow chart of digital electronic watt-hour meter.

Fig. 4 represents regularly break in service process flow diagram of digital electronic watt-hour meter microcomputer.

Fig. 5 represents regularly to calculate in the interrupt service routine program circuit (with " power-electric degree radix transformation approach ") of active electrical degree.

Fig. 6 represents regularly to calculate in the interrupt service routine program circuit of idle electric degree (reaching " radix transformation approach " with " positive and negative area-method ").

Referring to accompanying drawing, wherein Fig. 1 is an one-phase digital full-electronic watt-hour meter hardware block diagram.Digital and electronic watt-hour meter 100 in the figure is connected with the power transmission line of powering to load 99, to measure the electric degree that this load consumes.

The chief component of described watt-hour meter 100 comprises:

Current channel I-CH 104, it comprises current sensor CT 121 again, low-pass amplifier X1 122 and delay network X2 123;

Voltage channel U-CH 105, it comprises voltage sensor VT124 again, low-pass amplifier Y1 125, and delay network Y2 216;

Sample-and-hold circuit, multicircuit switch and analog to digital converter unit 106;

Single chip microcomputer MCU 107;

Active power pulse delivery outlet PP 112;

Reactive power pulse delivery outlet QP 113;

Non-volatile storage EEPROM 108;

Asynchronous Serial Interface driving circuit 108;

Liquid crystal display drive circuit 110 and LCDs 111;

Among the figure, the effect of electric current and voltage channel 104,105 is that the weak current part for forceful electric power electric current, voltage and instrument provides and isolates and signal amplitude is transformed to the level suitable with appliance circuit.Low-pass amplifier X1122 in these two signalling channels and Y1125 are higher than the harmonic wave composition elimination of 1/2 sampling frequency in order to avoid ' fold and obscure ' error occurs in signal is done also to play electric current, voltage signal the necessary amplification.X2-123 in this two passage, Y2126 is the time-delay network that cooperates the sampling time difference range to use, and this is that the road has this and needs (consulting first kind of mode of operation among the aforementioned Chinese patent CN94101541.6) adopting time-sharing work and carrying out the sampling of phase compensation and analog to digital conversion circuit with the sampling time difference.

The explanation of the electric current of each link and voltage sign among Fig. 1:

I _s(t) load current, that is the measured electric current of this ammeter 100, the unit peace is doubly;

U _s(t) load voltage, that is the measured voltage of this ammeter 100, the unit volt;

I _x(t) output signal of current channel, unit is a volt;

U _y(t) output signal of voltage channel, unit is a volt;

d _x(n) current channel output signal I _x(t) keep and the later digitized current signal of analog to digital conversion through sampling, n is the sequence number of sampling, n=0, and 1,2,3,

D ' _y(n) voltage channel output signal U _y(t) keep and analog to digital conversion through sampling, the digitized voltage signal in back, n is the sequence number of sampling.D ' _y(n) and be the voltage sampling signal of phase compensation.

Fig. 2 is the hardware block diagram of a three-phase and four-line digital electronic watt-hour meter.Described watt-hour meter 200 mainly is made up of following each several part:

A phase current passage I-CH-A 201

B phase current passage I-CH-B 202

C phase current passage I-CH-C 203

A phase voltage passage U-CH-A 204

B phase voltage passage U-CH-B 205

C phase voltage passage U-CH-C 206

The sampling maintenance of multichannel timesharing and analog to digital conversion circuit unit 220

Single chip microcomputer MCU 207

Non-volatile storage 208

Asynchronous go here and there driving circuit 209

Active power delivery outlet 212

Reactive power delivery outlet 213

Liquid crystal display drive circuit 210 and LCDs 211

In above-mentioned each phase current, voltage channel, current sensor CTA 221 is arranged respectively, CTB 227, CTC 233 and voltage sensor VTA 224, VTB 230, and VTC 236, voltage sensor is a star connection, and promptly the voltage sensor of each produces and the proportional voltage signal of load phase voltage; Each phase current sensor is through external impressed current mutual inductor XCTA 251, and XCTB 252, and XCTB 253 obtains and the proportional signal of each phase load electric current, but also can be directly with each mutually supply lines directly connect.Low-pass amplifier XA1 222 in each phase current and the voltage channel, XB1228, XC1234, YA1225, YB1231, the effect of YC1237 and phase shift network XA2 223, XB2 229, and XC2 235, and YA2 226, YB2 232, YC2.238, effect respectively with the X1 122 of aforementioned single-phase table, Y1 125 and X2 123, Y2126 is identical, and electric current, the voltage sign of these three phase watt-hour meter 200 each links are as follows:

i _SA(t), i _SB(t), i _SC(t) be A, B, the input current instantaneous value of each phase current passage of C,

u _SA(t), u _SB(t), u _SC(t) be A, B, the input voltage instantaneous value of each phase voltage passage of C;

i _XA(t), i _XB(t), i _XC(t) be A, B, the output signal instantaneous value of each phase current passage.So for ease of explanation and memory still with the symbolic representation of electric current, but in fact these signals are the amplifier output voltage signal, and unit is volt.

u _YA(t), u _YB(t), u _YC(t) be A, B, the input voltage instantaneous value of each phase voltage passage of C, unit is volt, because the aforesaid voltage sensor is taked star connection, u _YA, u _YB, u _YCProportional with each phase voltage of load.

d _XA(n), d _XB(n), d _XC(n) be through sampling keep and analog to digital conversion after A, B, the current signal of C phase, they are (sampling keep after) and the digitized signals that disperse.

D ' _YA(n), d ' _YB(n), d ' _YC(n) be to keep through sampling, the A that phase compensation and analog to digital conversion are later, B, the voltage signal of C phase is discrete digitized signal.

Fig. 3 is a three-phase and four-line digital and electronic watt-hour meter main program flow chart.Wherein, Δ t in sample interval carries out the timing interrupt control by the timer in the microcomputer (Timer).

Fig. 4 is the main flow process of relevant watt metering in the service routine that regularly interrupts, and it comprises, the time of resetting and interrupting next time, and electric current, voltage sampling, phase, width of cloth compensation, and electric degree calculates.

Fig. 5 is the process flow diagram (three-phase and four-line adopts power of the present invention-electric degree radix transformation approach) that the active electrical degree in the described timing interrupt service routine of Fig. 4 calculates.

Fig. 6 is that the killovar-hour meter in the described timing interrupt service routine of Fig. 4 is calculated process flow diagram (adopting ' positive and negative power method ' of the present invention).

Details are as follows for the sampling of solution electric degree operational precision and speed contradiction and operational method in the digital and electronic watt-hour meter that the present invention proposes:

(1) asynchronous sampling method.

If tested voltage, electric current are the identical periodic signal of frequency, voltage can be different with the waveform of electric current.If represent the cycle of voltage, electric current with T, again with voltage and the current sampling of identical sampling frequency to each phase, but and do not require simultaneously voltage, the current sampling of each phase, do not require simultaneously the voltage of same phase and current sampling (about the sampling of same phase voltage and electric current relation and used automatic phase compensation method the Chinese patent CN94100877.4 and the CN94101541.6 that can apply for referring to the inventor constantly) yet.If to the sample time each time of same voltage or current signal and next time the time interval Δ t between sample time be called step pitch sample time, and all be identical and fixing Δ t to step pitch sample time of all each phase voltages, electric current.

The sequence number of sampling is represented with n, now considers the n=0 of any voltage or current signal, 1,2 ..., (N _S-1) is total to N _SIf individual sampling is this N _SThe phase value of the measured signal that each sampling of individual sampling is got has nothing in common with each other, and n=N _S+ 0, N _S+ 1, N _S+ 2 ... 2N _S-1 sampling value respectively according to the order of sequence with n=0,1,2 ... the phase value correspondent equal of the measured signal that individual sampling value is got, then N _SIndividual sampling value constitutes a sampling circulation, and this sampling round-robin cycle is (N _S. Δ t)=T _S, sampling round-robin period T _SCan equal the circle phase T of measured signal, also can be the integral multiple of T $C_S=\frac{T_S}{T}$ , as multiple C _S=1 o'clock, i.e. T _SDuring=T, below will be called ' synchronized sampling.As multiple C _SDuring＞1 (positive integer), below will be called ' asynchronous sampling.Sample time step pitch Δ t, measured signal period T, the sampling number N in the sampling circulation _SAnd sampling cycle period T _SMultiple C to the measured signal period T _S(being the number of the contained measured signal period T of each sampling circulation) their mutual relationship is as follows: $\frac{T}{\mathrm{\Δt}}=\frac{N_S}{C_S}----\left(1\right)$ In this formula, N _SWith C _S, the two is not for there being the positive integer of the common factor beyond 1.Under above-mentioned constraint condition, if T/ Δ t=integer, i.e. C _S=1, at this moment ' synchronized sampling ', a sampling cycle period equals a measured signal period T _S=T, the phase place of each sampling spot equals the phase place of each sampling spot in the next cycle T successively respectively in each tested period T.In this case, have only and reduce step pitch Δ t sample time, just can dwindle the phase angle step pitches of adjacent two samplings.Mean and to adopt higher analog to digital converter of speed and microcomputer that cost will increase thereupon and reduce Δ t.In the measured signal frequency stabilization, and under the situation of all non-frequent fast speed change of amplitude, power factor (meeting the electric power system actual conditions), choose by above relational expression (1) and to make C _S＞1, Δ t, even sampling cycle period T _SBe the several times in measured signal cycle, i.e. ' asynchronous sampling '.Under asynchronous sampling situation, have $N_S=\frac{C_{S}T}{\mathrm{\Δt}}$ The phase place of the measured signal that individual sampling spot is got has nothing in common with each other.Therefore, this N _SAfter individual sampling was got up by the phase arrangement of the measured signal of being got, the phase angle difference of adjacent two samplings was exactly

Because C during asynchronous sampling _S＞1, C during synchronized sampling _S=1, obviously, when Δ t keeps constant substantially, the sampling angle step pitch under the asynchronous sampling condition With C _SBe inversely proportional to C _SBig more, Δ _ _SMore little, i.e. sampling is meticulous more, makes the electric degree operational precision also high more.

Below single simple numerical example the effect of asynchronous sampling is described:

Tested electric current, voltage cycle 20,000 microseconds (being the 50HZ frequency)

If get Δ t=1500 microsecond, $\frac{T}{\mathrm{\Δt}}=\frac{20000}{1500}=\frac{40}{3}$ Because 40 and 3 do not have the common divisor beyond 1, by above-mentioned differentiation sampling circulation N _S, C _SCriterion, N as can be known _S=40, C _S=3, i.e. sampling circulation comprises 3 measured signal period T, in each sampling circulation 40 sampling spots is arranged, and each and every one obtains the different phase place of measured signal, and like this, sampling angle step pitch is:

Or the number of degrees represent:

More than be C _S=3 asynchronous sampling situation.

As if being changed, Δ t is taken as Δ t=1250 microsecond (less than above-mentioned 1500 microseconds) $\frac{T}{\mathrm{\Δt}}=\frac{20000}{1250}=\frac{16}{1}$

Be C _S=1, N _S=16, this is a synchronized sampling, and sampling angle step pitch is:

By above two examples as seen, when synchronized sampling, even Δ t=1250ms also less than 1500 microseconds of asynchronous sampling, but resulting sampling angle step pitch 22.50 is on the contrary greater than 9 ° of asynchronous sampling, the electric degree computational accuracy just instead is not so good as asynchronous sampling.

Above-mentioned method of dwindling the sampling phase angle step pitch in the sampling circulation with asynchronous sampling not only can be used for the digital and electronic watt-hour meter, also can be used for high-resolution phasometer or phasometer, the instrument that power factor meter etc. are relevant.Note the sampling phase angle step pitch of each sampling spot in ' the one sampling circulation ' be not the phase angle difference that refers to adjacent two sampling spots, and be meant the phase step distance of adjacent two sampling spots after the phase place ordering of the measured signal that each sampling spot in the sampling circulation is got by them, for watt-hour meter, because the electric energy computing is an integral operation, the addition order of its each integration unit and addition result are irrelevant, so calculate electric degree again after when carrying out the electric degree computing, need not rearranging (this will expend a large amount of storage elements) by phase sequence, and can still directly carry out the electric degree computing in proper order by temporal sampling to each sampling spot of asynchronous sampling.

2, power-electric degree radix transformation approach

The general formula that the active electrical degree of digitalized electron watt-hour meter calculates is:

For single-phase table: $P\left(n\right)=\mathrm{dx}\left(n\right).d^{\′}y\left(n\right).\frac{(1+\mathrm{gr})(1+\mathrm{hr})}{(1+\mathrm{gN})}----\left(4\right)$ Dx in the formula (n), dy ' (n) be respectively n the sampling electric current, instantaneous voltage, the phase compensation of this voltage sampling.

Gr, hr, gN are the amplitude penalty coefficients, (referring to Chinese patent application CN941015141.6).For phase three-wire three ammeter (Unit two)) $P\left(n\right)=(d_{\mathrm{XA}}\left(n\right).{d^{\′}}_{\mathrm{yAB}}).\left(\frac{(1+g_{\mathrm{rAB}})(1+h_{\mathrm{rA}})}{1+g_{\mathrm{NAB}}}\right)$ $+(d_{\mathrm{XC}}\left(n\right).{d^{\′}}_{\mathrm{yCB}}).\left(\frac{(1+g_{\mathrm{rCB}})(1+h_{\mathrm{rC}})}{1+g_{\mathrm{NAB}}}\right)----\left(5\right)$ In the formula: d _XA(n), d _XC(n) be respectively A, C phase current sampling value; D ' _YAB(n), d ' _YCB(n) be AB, CB voltage between phases sampling value sampling value, phase compensation; g _RAB, g _RCB, g _NAB, g _NCB, h _RA, h _RCBe the amplitude penalty coefficient.For three-phase and four-line $P\left(n\right)=d_{\mathrm{XA}}\left(n\right).{d^{\′}}_{\mathrm{yA}}\left(n\right)\left[\frac{(1+h_{\mathrm{rA}})(1+g_{\mathrm{rA}})}{(1+g_{\mathrm{NA}})}\right]$ $+d_{\mathrm{XB}}\left(n\right).{d^{\′}}_{\mathrm{yB}}\left(n\right)\left[\frac{(1+h_{\mathrm{rB}})(1+g_{\mathrm{rB}})}{1+g_{\mathrm{NB}}}\right]$ $+d_{\mathrm{XC}}\left(n\right).{d^{\′}}_{\mathrm{yC}}\left(n\right)\left[\frac{(1+h_{\mathrm{rC}})(1+g_{\mathrm{rC}})}{1+g_{\mathrm{NC}}}\right]----\left(6\right)$ In the formula: d _XA(n), d _XB(n), d _XC(n) be respectively A, B, C phase current sampling value;

D ' _YA(n), d ' _YB(n), d ' _YC(n) be respectively A, B, C phase voltage sampling value, phase compensation;

h _RA, h _RB, h _RC, g _Ra, g _Rb, g _Rc, g _NA, g _NB, g _NCBe the amplitude penalty coefficient.The general formula that the killovar-hour meter of digitalized electron watt-hour meter is calculated is:

For three-phase and four-line three unit ammeters, 90 ° of idle calculating of phase-shifting method: $q\left(n\right)=d_{\mathrm{XA}}\left(n\right).{d^{\′}}_{\mathrm{yCB}}\left[\frac{(1+g_{\mathrm{rCB}})(1+h_{\mathrm{rA}})}{(1+g_{\mathrm{NCB}})}\right]$ $+d_{\mathrm{XB}}\left(n\right).{d^{\′}}_{\mathrm{yAC}}\left[\frac{(1+g_{\mathrm{rAC}})(1+h_{\mathrm{rB}})}{1+g_{\mathrm{NAC}}}\right]$ $+d_{\mathrm{XC}}\left(n\right).{d^{\′}}_{\mathrm{yBA}}\left[\frac{(1+G_{\mathrm{rAB}})(1+h_{\mathrm{rC}})}{1+g_{\mathrm{NBA}}}\right]----\left(8\right)$ In the formula: d _XA(n), d _XB(n), d _XC(n) be respectively A, B, C phase current sampling value;

D ' _YCB(n), d ' _YAC(n), d ' _BA(n) be respectively CB, AC, BA voltage between phases sampling value (having done phase compensation);

h _RA, h _RB, h _RCB, g _RCB, g _RAC, g _RBA, g _NCB, g _NAC, g _NBABe the amplitude penalty coefficient.

Subscript about more used symbols among last is described as follows:

During with the work of subscript ' r ' expression ammeter, the penalty coefficient under the real work curtage in ought be is for the previous period represented voltage amplitude penalty coefficient under the work at present voltage as gr, and hr represents the current magnitude compensation coefficient under the current working current.

With subscript ' A ', ' B ', the phase name of ' C ' expression voltage or electric current, for example, g _RABe the voltage amplitude penalty coefficient under the work at present voltage of A phase, g _RABFor to the voltage amplitude penalty coefficient under the alternate operating voltage of AB (current) because of subscript r is arranged.

Being illustrated in amplitude penalty coefficient under nominal voltage and the nominal current with ' N ', is mutually a certain as for this voltage and electric current, or certain is two alternate, by the g of correspondence _r, h _rPhase name subscript decision.

Voltage and current magnitude compensation coefficient are respectively electric current and are fixed on nominal value, making the electric degree range error under the different voltages is that zero required amplitude penalty coefficient and voltage is fixed on nominal value, and making the electric degree range error under the different electric currents is zero required amplitude penalty coefficient (seeing patent CN94100987.4 and CN94101541.6 that the inventor has applied for for details).

Below, will be example with single-phase active electrical degree, illustrate that ' power-electric degree radix transformation approach ' that the present invention proposes is used to calculate the method step of electricity.The calculating of and idle electric degree meritorious for phase three-wire three and three-phase and four-line and single-phase similar, its difference only is that used power-electric degree radix value is different.

The method step of ' power-radix transformation approach ' proposed by the invention can be made an explanation in conjunction with program circuit shown in Figure 5.

Referring to Fig. 5, ' power-electric degree radix transformation approach ' comprises following method step:

1, the hardware that will realize electric degree computing integral operation is divided into two parts, promptly one ' power-electric degree radix conversion totalizer WHR1 and output pulses summary counter WHR2, the RAM storage element in all available single chip microcomputer of these two totalizers.When having a power failure, interior storage data are write in the table in the non-volatile storage.The effect of WHR1 is that each sample moment power p (n) is added up, and when the electricity of being accumulated is the pairing electricity of output pulses, the output pulses delivery outlet of microcomputer produces an output pulses, the effect of WHR2 is the output pulses number that accumulative total WHR1 sends, because each output pulses is represented the electric degree increment of a unit, so WHR2 accumulation electricity.

2, for a new ammeter when the electric degree of microcomputer calculates program initialization, WHR1, put with one ' power-electric degree conversion radix ' BWHR, the carry digit WHR1-CARRY zero clearing of WHR1 most significant digit, the WHR2 zero clearing, for the ammeter that has moved, the data of WHR1 and WHR2 write non-volatile storage in the table when having a power failure; In when telegram in reply, in the program initialization process with the WHR1 in the non-volatile storage, the WHR2 data WHR1 that reads back, WHR2; WHR1, WHR2 are multibyte ram cell.

3, carrying out electric current, voltage sampling every a Δ t, phase, width of cloth compensation and voltage, electric current multiplies each other and obtains after the instantaneous power p (n), the number that this p (n) and WHR1 is interior adds up, if the most significant digit no-carry of WHR1 then finishes the electric degree computing of this sampling, heavily cover this step in next sampling.

If WHR1 C Δ ARRY=1, get back to this step in next sampling again after then carrying out following 4,5,6,7 earlier.

4, when WHR1-CARRY=1, WHR2 increases 1

5, when WHR1-CARRY=1, make output pulses of output pulses delivery outlet output of microcomputer

6, add a power-electric degree conversion cardinal B WHR, that is: WHR1=WHR1+BWHR to WHR1

7, remove WHR1-CARRY

Used in the 2nd step that above-mentioned electric degree calculates and the 6th step ' power-electric degree conversion cardinal B WHR (single-phase, meritorious) is as follows with the relation of every constant of this ammeter: $\mathrm{BWHR}=2^L-\frac{1}{K_{\mathrm{WP}}.\mathrm{\Δt}.\mathrm{Cp}}----\left(9\right)$ In the formula: L is the number of bits of WHR1

Cp is every kilowatt-hour an output pulses number of this watt-hour meter

Unit is: umber of pulse/kilowatt-hour

K _WPBe the electric degree proportionality constant of this watt-hour meter, unit is kilowatt hour/LSB ². second

Its size is relevant with the analog to digital conversion scale-up factor of electric current, voltage signal.LSB is the unit of digitized voltage, current signal, and promptly the lowest order of binary number is 1 LSB unit.

Δ t is step pitch sample time, unit: a second above BWHR computing formula is applicable to single-phase, and the active electrical degree of phase three-wire three (Unit two) and three-phase and four-line ammeter calculates.Killovar-hour meter for phase three-wire three two cell lists that adopt 90 ° of phase shifts is calculated, and uses following conversion radix: $\mathrm{BQHR}=2^L-\frac{2}{\sqrt{3}{K}_{\mathrm{WQ}}.\mathrm{\Δt}.C_Q}----\left(10\right)$ Three-phase and four-line (Unit three) is shown with 90 ° of conversion radixes that the phase-shifting method killovar-hour meter is used: $\mathrm{BQHR}=2^L-\frac{\sqrt{3}}{K_{\mathrm{WQ}}.C_Q.\mathrm{\Δt}}----\left(11\right)$ In the formula: Δ t step pitch sample time, unit: second

C _QReactive power pulse constant, unit is: umber of pulse/kilovar-hour

K _WQIdle electric degree proportionality constant, its unit are kilovar-hour/LSB ²-second, LSB herein is the unit of digitized electric current and voltage, promptly the lowest order of binary number is a unit, K _WQSize relevant with the analog to digital conversion scale-up factor of electric current and voltage signal.Notice that above the used conversion radix of 90 ° of phase-shifting method killovar-hour meters is different from the conversion radix that following ' positive and negative power method ' killovar-hour meter is calculated.

3, ' positive and negative power method '

This method is used to simplify the calculating of idle electric degree.Before address, survey the three-phase multifunctional digital and electronic watt-hour meter of active electrical degree and idle electric degree for holding concurrently, can utilize the used instantaneous power of calculating active electrical degree to extrapolate idle electric degree, promptly utilize described the asking of this section to calculate idle electric degree with ' positive and negative power method '.

The method step of ' positive and negative power method ' that the present invention proposes can be made an explanation in conjunction with program flow diagram shown in Figure 6.Program circuit shown in this figure is exactly the final stage content of timing interrupt service routine among Fig. 4.

Described timing is interrupted, every Δ t master routine interrupted once, and the timing interrupt service routine of execution graph 4, it comprises sampling, compensation, power calculation, active electrical degree calculate and killovar-hour meter is calculated.

Three-phase and four-line (Unit three) watt-hour meter, and the idle electric degree of single-phase each phase of table can calculate (subscript of expression A, B, C phase is omitted) by following formula: $W_Q\left(N_S\right)=\frac{\mathrm{\π}}{N_S}\{N\_W_{P+}\left(N_S\right)+N_{+}.W_{P-}.(N_S\}$ (kilovar-time) (12)

In the formula: W _Q(NS)--the interior idle electric degree of sampling circulation

N _S--the sampling number of times in----sampling circulation

The electric current and the voltage contrary sign of same phase in one of the N_------sampling circulation, i.e. this phase power sampling number of times that is negative value

N ₊--in----one sampling circulation, the electric current of same phase and voltage jack per line, promptly this phase power be on the occasion of the sampling number of times $W_{P+}\left(N_S\right)=\underset{n=0}{\overset{N_S-1}{\mathrm{\Σ}}}{K}_{\mathrm{WP}}{P}_{+}\left(n\right).\mathrm{\Δt}----\left(13\right)$ Wherein

P ₊(n) $W_{P-}\left(N_S\right)=\underset{n=0}{\overset{N_S-1}{\mathrm{\Σ}}}{K}_{\mathrm{WP}}|p\_\left(n\right)|.\mathrm{\Δt}----\left(14\right)$ P_ (n) wherein

Because dx (n), d ' y (n) is the phase current of same phase, phase voltage, p when active electrical degree calculates (n) calculates, so calculating with said method does not need that voltage, the electric current to collocation again multiplies each other and compensation operation as 90 ° of phase-shifting methods when idle, and idle electric degree computing and compensated curve are greatly simplified.The cost of being paid is to count N respectively _-With N ₊Can in last circulation, add up, be used for current sampling circulation.Simultaneously at the used N of next circulation of current sampling circle statistics _-With N ₊

Carrying out three-phase killovar-hour meter calculation (three phase watt-hour meter of Unit three, phase current and phase voltage are surveyed in every unit) used ' power-electric degree conversion radix ' with above-mentioned ' positive and negative power method ' in conjunction with aforementioned ' power-electric degree radix transformation approach ' is: $\mathrm{BQHR}=2^L-\frac{N_S}{\mathrm{\π}{K}_{\mathrm{WP}}\·\mathrm{\Δt}.C_Q}----\left(15\right)$ In the formula: 1--is the ' number of bits (word length) of power-electric degree conversion totalizer QHR1 of the idle electric degree of metering

C _Q--be the reactive power pulse constant of this ammeter, unit is the umber of pulse of every kilovar-hour: umber of pulse/kilovar. the time

K _WP--be the electric degree proportionality constant of this ammeter, its proportionality constant used with calculating active electrical degree is identical, and its unit is: kilovar a period of time/LSB ². second

Δ t--is step pitch sample time, unit second

N _S--be a sampling number of times in the sampling circulation.

π--be circular constant

What Fig. 6 represented is the program circuit that calculates the idle electric degree of three-phase and four-line with ' positive and negative power method ' in conjunction with ' power-electric degree radix transformation approach '.The convection current flow process is summarized as follows:

P _A(n) be A phase instantaneous power (A phase phase current and A be the product of phase voltage mutually, has done phase place, amplitude compensation and zero correction),

If P _A(n)＞0, then

QHR1＝QHR1＋(N _-A)P _A(n)

If P _A(n)＜0, then

QHR1=QHR1+ (N _{+ A}) | P _A(n) | wherein, | P _A(n) | be P _A(n) absolute value, N _-A, N _{+ A}Be respectively A in a sampling circulation, the number of times of negative power or positive occurs.

If above-mentioned operation result does not produce the carry of QHR1, then just directly be P _B(n) and P _C(n) relevant computing, on the contrary if the most significant digit of QHR1 has carry, then to carry out being P again after following each step _B(n) and P _C(n) relevant computing:

. reactive power pulse delivery outlet is exported a pulse

. the output pulses summary counter QHR2 of idle electric degree increases 1

. with idle electric degree ' power-electric degree conversion cardinal B QHR is added among the QHR1 and goes:

QHR1＝QHR1＋BQHR

. remove the carry of QHR1: the B that QHR1-CARRY=0. follows is all mutually similar to A with the relevant computing of C phase, repeats no more.

Said method of the present invention can solve electric degree computing commentaries on classics degree and contradiction between speed in the digital and electronic watt-hour meter effectively; above-mentioned method of dwindling sampling phase angle step pitch in the sampling circulation with asynchronous sampling not only can be used for the digital and electronic watt-hour meter; also can be used for high-resolution phasometer or phasometer; the instrument that power factor meter etc. are relevant, technical scheme that every the present invention of belonging to proposes and the operational method in the scope thereof all are protection contents of the present invention.

Claims (5)

1, a kind of method that is used for digital and electronic watt-hour meter electric degree solution electric degree operational precision and speed contradiction is characterized in that described method comprises:

To ' the asynchronous sampling method ' of electric current, voltage signal, that is, choose with sampling circulation T _SThe number C of contained measured signal period T _SSampling step pitch Δ t greater than 1 (positive integer) carries out the asynchronous sampling of curtage each time,

' power-electric degree radix transformation approach ' of computing electric energy increment, that is, and with the secondary multiplying in the electric energy incremental computations in each the step pitch Δ t: K sample time _WP* P (N) * Δ t is reduced to and whenever goes out an output pulses and do once ' additive operation of power-electric degree radix conversion ', saving the secondary multiplying of above-mentioned each Δ t,

Calculate ' the positive and negative power method ' of idle electric degree, that is, utilize and calculate the instantaneous power value that obtains in the active electrical degree process, extrapolate idle electric degree, not needing each phase current, voltage are arranged in pairs or groups separately and made up, is that killovar-hour meter is calculated and carried out the calculating of a whole set of similar active electrical degree.

2, the method for claim 1 is characterized in that, described ' asynchronous sampling method ', wherein, sample time step pitch Δ t, measured signal period T, the sampling number N in the sampling circulation _SAnd sampling cycle period T _SMultiple C to the measured signal period T _SPass between them is: $\frac{T}{\mathrm{\Δt}}=\frac{N_S}{C_S}$

N in the formula _SWith C _SFor there not being the positive integer of the common factor beyond 1, work as C ₃＞1 o'clock is asynchronous sampling.

3, the method for claim 1 is characterized in that, described ' power-electric degree radix transformation approach ' comprises the steps:

(1) hardware that will realize electric degree computing, integral operation is divided into two parts, promptly one ' power-electric degree radix conversion totalizer WHR1 and output pulses summary counter WHR2;

(2) to a new ammeter when the electric degree of microcomputer calculates program initialization, put with one ' power-electric degree conversion cardinal B WHR, the carry digit WHR1-CARRY zero clearing of WHR1 most significant digit, WHR2 zero clearing; To the ammeter that has moved, when having a power failure, the data of WHR1 and WHR2 write volatile storage in the table; In when telegram in reply, in the program initialization process with the WHR1 in the non-volatile storage, WHR2 data read back WHR1, WHR2.

(3) carrying out electric current, voltage sampling every a Δ t, phase place and amplitude compensation, and voltage, electric current multiply each other and obtain instantaneous power P (n) afterwards, the number that this P (n) and WHR1 is interior adds up, if the most significant digit no-carry of WHR1, then finish the electric degree computing of this sampling, repeat this step in next one sampling

If WHR1-CARRY=1 then carries out following 4-7 earlier after the step, get back to this step in next sampling again.

(4) when WHR1-CARRY=1, make WHR2 increase 1,

(5) when WHR1-CARRY=1, make output pulses of output pulses delivery outlet output of microcomputer;

(6) add ' power-electric degree conversion radix ' BWHR to WHR1, that is, and WHR1=WHR1+BWHR,

(7) remove WHR1-CARRY.

4, the method for claim 1 is characterized in that, described positive and negative power method is that following column count formula calculates:

The time)

Calculate when idle with said method, do not need as 90 ° of jayrators again that voltage, the electric current of collocation multiply each other and compensation operation, idle electric degree computing and compensated curve are simplified.

5, the method for claim 1 is characterized in that, it is as follows that described ' positive and negative power method ' is used for the program circuit of the idle electric degree of computing triple-phase line in conjunction with ' power-electric degree radix transformation approach ':

A phase instantaneous power P _A(n)

If P _A(n)＞0, QHR1=QHR1+ (N then _-A) P _A(n)

If P _A(n)＜0, QHR1=QHR1+ (N then _{+ A}) | P _A(n) | if above-mentioned operation result do not produce the QHR1 carry, then directly carry out to B mutually with C instantaneous power P mutually _B(n) and P _C(n) carry out the computing similar with A, otherwise, if the most significant digit of QHR1 has carry, then to carry out following each step and be P again _B(n) and P _C(n) relevant computing:

. reactive power pulse delivery outlet is exported a pulse

. the output pulses summary counter QHR2 of idle electric degree increases 1

. ' power-electric degree conversion radix ' BQHR of idle electric degree is added among the QHR1 and goes, be i.e. QHR1=QHR1+BQHR

. remove the carry of QHR1, that is, and QHR1_CARRY=0

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