CN1356556A - 90-deg phose-lock phase shifter for measuring true reactive power - Google Patents

Abstract

A 90-deg. phase-locked phase shifter for measuring true reactive power is composed of PT secondary filter, cross-zero comparator, 90-deg phase-locked electronic phase shifter, phase detector, two-order active filter, DC reference, error integrator and voltage-controlled varistor, and features SMT thick-film circuit and integral temp compensation. It is used in electric power system.

Description

90-deg phose-lock phase shifter for measuring true reactive power

90-deg phose-lock phase shifter for measuring true reactive power of the present invention relates to fields of measurement such as reactive energy, capacity of idle power, reactive-load compensation, particularly the automatic dispatching of electric system and control, state estimation etc. all be unable to do without idle correct measurement, it has signal filtering, cross zero balancing, phase bit comparison, frequency multiplier, error intergal amplifier, phase compensation adjustment, particularly with 90 ° of phase shift angles of signal center frequency, reach the feature of setting by regulating DC reference voltage.

Existing phase shift technology state is: with RC rc phase shifter circuit, general electronics phase-shift circuit and integration, derivative compensation formula phase-shift circuit, its amplitude versus frequency characte and phase-frequency characteristic are respectively

KF(ω)＝1 (1)

φ(ω)＝-[π+2tg ^-1(ω/ω ₀)] (2)

ω in its Chinese style ₀=2 л f ₀ω ₀Be centre frequency angle f ₀Be centre frequency

And measure f for power frequency ₀=50Hz is not difficult to calculate with signal frequency to centre frequency f from formula (2) ₀Change circuit phase shift in ± 5% o'clock to 90 ° of variations can reach ± 2.8 °, this will cause 5% additive error.

For integration, 90 ° of phase-shift circuits of derivative compensation formula, the characteristic of its output and input as shown in the formula:

U _o=1/2 (ω RC+1/ ω RC) sin (ω t+90 °) (3) by (3) though formula has been taked compensation in the circuit as can be known, but owing to can not definitely equate with the parameter of differential RC element as integration, change less occasion so can only be fit to frequency input signal, can not satisfy the requirement of wide model usefulness, high-acruracy survey.

90-deg phose-lock phase shifter for measuring true reactive power of the present invention is exactly 90 ° of phase-locked phase shift technologies of design in order to overcome above-mentioned several phase shift technology deficiency.Input, output signal carried out respectively zero balancing, phase bit comparison, frequency multiplication, dc reference, error ratio, a series of technical measures such as integration amplification, phase compensation adjustment, reach 90 ° phase-locked.

90-deg phose-lock phase shifter for measuring true reactive power of the present invention, its circuit is reliable, especially adopts current high-tech surface mounting technique (SMT technology), and institute is so that reactive power measurement is correct, reliable as meritorious.

Below in conjunction with accompanying drawing the present invention is further described:

Fig. 1 for measuring true reactive power with 90 ° of phase-locked phase-shift circuit block schemes

Fig. 2 is the second-order active filter device

Fig. 3 is phase detecting principle figure

Fig. 4 is an oscillogram

Fig. 5 is 90 ° of phase shifters

Fig. 6 is the circuit analysis of Fig. 5

Fig. 7 is the normalization phase-shift characterisitc

Fig. 8 is among way circuit figure Fig. 1: A be PT, B be secondary filtering active power filtering, C be 90 ° of phase shifters of phase-locking type,

D be error integrator, E be dc reference, F be the second-order active filter device,

G is that phase-sensitive detector, H are that zero balancing, I are voltage-controlled rheostat.

Its course of work is as follows:

The U of input voltage after the PT conversion _IEnter that second harmonic active filter filtering secondary is above humorously to divide two road signals after involving undesired signal, the one tunnel sends into 90 ° of electronic phase shifters, produces one and input signal U _IThe amplitude equal phase differs from 90 ° phase-locked phase shift signal, and also divides two tunnel, one tunnel voltage end that is input to multiplier, transfers bandwidth signals usefulness as multiplier, and another road is input to feedback comparer 2 and produces the zero passage comparison signals.The Jia Yilu of active filter output sends into comparer 1 and produces zero passage benchmark signal.Two-way zero passage comparison signal is through phase-sensitive detector, be smoothed to DC voltage through second-order active filter after detecting phase differential, and amplify back control variable resistor parts through integral error with the sum voltages of reference dc voltage E after relatively, make the phase place maintenance of electronic phase shifter constant.Concrete feedback control procedure is as follows:

Active filter (Fig. 2)

The parameter of active filter is selected correctness, will directly influence the response time of circuit, amplitude-frequency, phase-frequency characteristic.By the second order filter transport function as can be known, have only the choose reasonable component parameters just can make the gain of circuit, quality factor, cutoff frequency is guaranteed.Its transport function is: $H\left(S\right)=\frac{\left(\frac{R_3+R_2}{R_3}\right)\&times;\frac{1}{R_1{R}_2{C}_1{C}_2}}{{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="A0012782100101.png,A0012782100111.png"\; state="\{\{state\}\}">S</figure-callout>}}^2+[\frac{1}{R_1{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A0012782100092.png,A0012782100101.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}+\frac{1}{R_2{C}_2}-\frac{R_4}{R_2{R}_3{C}_2}]S+\frac{1}{R_1{R}_2{C}_1{C}_2}}----\left(4\right)$ With the second order filter normal formula $H\left(S\right)=\frac{H_0{\mathrm{\&omega;}}_0^2}{S^2(\mathrm{\&omega;}/R)S+{\mathrm{\&omega;}}_0^2}----\left(5\right)$ Compare ${\mathrm{<figure-callout\; id="0"\; label="H"\; filenames="A0012782100101.png,A0012782100102.png"\; state="\{\{state\}\}">H</figure-callout>}}_0=\frac{R_3+R_4}{R_3}----\left(6\right)$ ${\mathrm{\&omega;}}_0=\sqrt{-\frac{1}{R_1{R}_2{C}_1{C}_2}}----\left(7\right)$ $Q=[\sqrt{\frac{R_2{C}_2}{R_1{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A0012782100092.png,A0012782100101.png"\; state="\{\{state\}\}">C</figure-callout>}}_1}}+\sqrt{\frac{R_1{C}_2}{R_2{C}_1}}-\frac{R_1}{R_3}\&CenterDot;\sqrt{\frac{R_1{C}_1}{R_2{C}_2}}]----\left(8\right)$ Make R ₁=R ₂=R C ₁=C ₂=C then has ${\mathrm{\&omega;}}_0=\frac{1}{\mathrm{RC}}----\left(7\right)$ $H_0=\frac{R_3+R_4}{R_4}----\left(9\right)$

I/Q＝3-H ₀ (10)

ω ₀Cutoff frequency H ₀Gain Q quality factor

Zero balancing, phase-detecting, integrating circuit (Fig. 3, Fig. 4)

UA, UB, through I _C1, I _C2Become square wave, again by with or the door carry out becoming and the proportional duty square wave of phase place after the logical process.As Fig. 4, output V after active filter is level and smooth ₁Again with the V of E summation after error intergal is amplified ₄Voltage removes to control voltage-controlled rheostat. $V_2=\frac{\mathrm{Tw}}{T}----\left(11\right)$ $V_3=\frac{1}{\mathrm{R\; C}}{\&Integral;v}_3\mathrm{dt}----\left(12\right)$

90 ° of phase shifters (Fig. 5)

So-called phase shifter is exactly under the constant condition of gain, the circuit that the phase-shift phase of frequency input signal or other circuit parameter is changed.

Ui=U _msinωt

U ₀=Umsin(ωt+90°) $V_G={\mathrm{<figure-callout\; id="4"\; label="V"\; filenames="A0012782100101.png,A0012782100111.png"\; state="\{\{state\}\}">V</figure-callout>}}_4=\frac{1}{\mathrm{RC}}\&Integral;{\mathrm{<figure-callout\; id="3"\; label="v"\; filenames="A0012782100111.png"\; state="\{\{state\}\}">v</figure-callout>}}_3\mathrm{dt}$ 90 ° of phase shifters, analysis chart 5, by Fig. 6 analysis as can be known:

V ₀=V ₀₁+ V ₀₂Its amplitude-frequency and phase-frequency characteristic are

R ₁=R ₂Amplitude-frequency V _F(ω)=1 phase frequency _ (ω)=-| π+2tg ^-1(ω/ω ₀) | (13)

Wherein Be centre frequency (14)

With normalized output phase shift characteristic (Fig. 7)

Phase-shift phase

Voltage-controlled rheostat

The rheostat of being controlled by FEEDBACK CONTROL voltage is the JFET field effect transistor of a controllable transconductance, and when frequency changed, the voltage of phase-sensitive detector output changed thereupon.

Make γ _DsThereby the phase-frequency characteristic that changes obtains adjusting, and certainly, the change resistance of JFET and input control voltage are the relations of a linear change. $r_{\mathrm{DS}}=\frac{r_0{\mathrm{<figure-callout\; id="0"\; label="s"\; filenames="A0012782100101.png,A0012782100102.png"\; state="\{\{state\}\}">s</figure-callout>}}_0}{1-\frac{U_{\mathrm{GS}}}{V_P}}----\left(16\right)$

V in the formula _pFor r is pressed in outage _DsBe U _GS=0 o'clock dynamic resistance

The following formula explanation With U _GSFor linear relationship is to realize the key of voltage-controlled change resistance.By above analysis, adopt the SMT thick film circuit, and carry out the bulk temperature compensation, being configured in the true reactive power transmitter is the accurate measurement that electric system realizes reactive power, has improved the reliability of Operation of Electric Systems.

Claims (3)

1. 90-deg phose-lock phase shifter for measuring true reactive power of the present invention, it is by PT secondary filter L ₀, zero-crossing comparator L ₃: C, L ₃: D, 90 ° of phase-locked electronic phase shifter L ₁: A, phase-sensitive detector, L ₂Second-order active filter L ₀, dc reference L ₁: D, error intergal L ₁: D, voltage-controlled rheostat J ₂Form in circuit.The phase place that it is characterized in that 90 ° of phase-locked phase shifters is adjusted into voltage-controlled rheostat, J ₂Phase-sensitive detector, with logical and or the door realize that wave filter realizes that with the quick active filter of second order the control of centre frequency angle is provided with dc reference.

2. according to claim 1,90-deg phose-lock phase shifter for measuring true reactive power is characterized in that through zero-crossing comparator L ₃: C, L ₃: two waveforms of D are input to L ₂Logical and or door, through this with or the frequency of door phase-detecting output be two times signal frequency, the adjusting of centre frequency is by dc reference L ₁: output to totalizer R after D is anti-phase ₁₄, among the R15, active filter has L3:B and Resistor-Capacitor Unit to constitute, phase-shift compensation is adjusted L ₁: A, J ₂Finish.

3. according to claim 1,2 described, phase-sensitive detector L ₂, three control ends inputs of A, B, C relatively square wave and threshold voltage, output terminal X, Y, Z be input with or relation, phase shifter compensation J ₂The input control voltage scope is-9V～-1V, centre frequency 50Hz, the frequency compensation scope is 43Hz-57Hz.

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