CN202757996U - System for power factor measurement - Google Patents

Abstract

The utility model relates to a system for power factor measurement and an integral method using the system. According to the system for power factor measurement, a sinusoidal voltage is input from a U end positive pole and undergoes the voltage dividing of a resistor Ru and a resistor R0 to be used as a voltage signal, and the voltage signal is divided into three channels; the first channel of voltage signal is connected with a negative input pole of a comparison amplifier A1 through a resistor R10; an output pole of the comparison amplifier A1 is connected with an electronic switch KU; a second channel of voltage signal is connected with a negative input end of a proportional integral amplifier A3 successively through a resistor R1 and a resistor R2; and a third channel of voltage signal is connected with a negative input end of a proportional integral amplifier A4 successively through a resistor R3 and a resistor R4. According to the utility model, an accurate and stable measurement result is acquired; if the sampling width of a current signal is shortened, a specified harmonic can be removed.

Description

Measure the system of power factor

Technical field

The utility model relates to a kind of integration method of measuring the system of power factor and adopting this system.

Background technology

In the prior art, power-factor measurement generally has two kinds of methods, and is a kind of with electrodynamic type meter test, and this method can only direct-reading can not become electric signal and control; Another kind is the phase place of at first measuring between electric current and the voltage, then calculates power factor value with single-chip microcomputer.This method can be used for controlling, but is easy to be subject to the impact of voltage clutter and higher hamonic wave, can not obtain high-precision measurement.

The utility model content

Technique effect of the present utility model can overcome defects, and a kind of system of measuring power factor is provided, and it is simple in structure, cost is low, realization is easy.

For achieving the above object, the utility model adopts following technical scheme: it comprises from U rectifies utmost point input sinusoidal voltage, and as voltage signal, voltage signal is divided into three the tunnel through resistance R u and resistance R 0 dividing potential drop:

First via voltage signal is by the negative input utmost point of resistance R 10 connection comparison amplifier A1, the output stage connecting electronic K switch of comparison amplifier A1 _U

The the second road voltage signal is successively by resistance R 1, resistance R 2 connects the negative input end of proportional integral amplifier A3, the negative input end of proportional integral amplifier A3 is contact resistance R5 respectively, capacitor C 2, resistance R 5, the other end of capacitor C 2 connects proportional integral amplifier A3 output terminal, proportional integral amplifier A3 output terminal connects stepless electronic potentiometer RW1, the middle sliding end of stepless electronic potentiometer RW1 connects the positive input terminal of error amplifier A5, the negative input end of error amplifier A5 connects voltage-reference diode VE, voltage-reference diode VE, the stepless electronic potentiometer RW1 other end, electronic switch K _U, comparison amplifier A1, A3 positive input terminal connect respectively U end negative pole;

The Third Road voltage signal connects the negative input end of proportional integral amplifier A4, connecting electronic K switch between resistance R 3, the resistance R 4 successively by resistance R 3, resistance R 4 _IThe negative input end of proportional integral amplifier A4 is contact resistance R7, capacitor C 3 respectively, resistance R 7, the other end of capacitor C 3 connects proportional integral amplifier A4 output terminal, proportional integral amplifier A4 output terminal connects stepless electronic potentiometer RW2, the middle sliding end of stepless electronic potentiometer RW2 connects the negative input end of error amplifier A6 through resistance R 6, be connected the stepless electronic potentiometer RW2 other end, the positive input terminal of amplifier A6, electronic switch K by resistance R 8 between the negative input end of error amplifier A6 and the output terminal _IConnect respectively U end negative pole;

Electronic switch K _IThe output terminal that connects comparison amplifier A2, the negative input end of comparison amplifier A2 connects respectively capacitor C 1, resistance R 1, Current Mutual Inductance T, the respectively connection U end negative pole of the positive input terminal of capacitor C 1 other end, resistance R 1 other end, the Current Mutual Inductance T other end, comparison amplifier A2.

Another purpose of the present utility model provides a kind of normalizing integration method that adopts this system, and it comprises the steps:

(1) voltage signal drives electronic switch Ku through comparison amplifier device A1, when voltage signal be on the occasion of the time, electronic switch Ku turn-offs, and voltage signal is sent into proportional integral amplifier A3 through resistance R 1, resistance R 2, and the output of proportional integral amplifier A3 is 0 phase integral of voltage signal U0

$\mathrm{Uv}=\frac{\sqrt{2}*U*{\∫}_0^{\mathrm{\π}}\sin \mathrm{\ωt}}{2\mathrm{\π}}=\frac{\sqrt{2}*U}{\mathrm{\π}};$

When voltage signal is negative value, the electronic switch conducting, proportional integral amplifier A3 is input as 0;

(2) effect of error amplifier A5 output terminal is exactly that the current potential of controlling the intermediate ends of the stepless potentiometer RW1 of electronics equals voltage Ve all the time, and intrinsic standoff ratio at this moment is k;

(3) input current drives electronic switch KI through comparison amplifier device A2 the voltage signal U0 on the resistance R 0 is sampled through Current Mutual Inductance T generation current signal on secondary resistance, works as K _IVoltage during shutoff on the resistance R 0 is sent into proportional integral amplifier A4 through resistance R 3, resistance R 4, and the voltage when electronic switch KI conducting on the resistance R 0 is by short circuit, and the output of proportional integral amplifier A4 is the φ phase integral of voltage signal U0:

$\mathrm{Ui}=\frac{\sqrt{2}*U*{\∫}_{\mathrm{\φ}}^{\mathrm{\π}+\mathrm{\φ}}\sin \mathrm{\ωt}}{2\mathrm{\π}}=\frac{\sqrt{2}*U*\mathrm{Cos\φ}}{\mathrm{\π}}$

Wherein: φ is the phase differential of electric current and voltage signal;

(4) because the output terminal of proportional integral amplifier A4 links to each other with stepless potentiometer RW2, and stepless potentiometer RW2 is with stepless potentiometer RW1 synchronous operation, and k is identical for its intrinsic standoff ratio,

And order

Uv*k＝Ve＝1

So, output end voltage in the middle of the electrodeless potentiometer RW2 of electronics

Ui*k＝Uv*k*Cosφ＝Cosφ

；

(5) error amplifier A6 is a phase inverter, and the output of error amplifier A6 is exactly the power factor (PF) of circuit, and when power factor (PF) was 1, voltage was Ve.

The utility model provides a kind of new method for the power-factor measurement in the electrotechnical measurement, and it is with the current signal offset of sinusoidal voltage integration of sampling.Obtain the cosine function of sinusoidal voltage.Then, again the cosine function of voltage is carried out normalized.Obtain the power factor value of circuit.Owing to adopt integral way, can effectively remove impact and the impact of various voltage clutter of higher hamonic wave.Obtain high precision, stable measurement result, if shorten the sampling width of current signal, can also eliminate a certain appointment harmonic wave.

Description of drawings

Fig. 1 is electrical block diagram of the present utility model;

Fig. 2 is B1 point voltage waveform synoptic diagram among the utility model Fig. 1;

Fig. 3 is B2 point voltage waveform synoptic diagram among the utility model Fig. 1.

Embodiment

As shown in Figure 1, the system of measurement power factor of the present utility model comprises from U and rectifies utmost point input sinusoidal voltage, and as voltage signal, voltage signal is divided into three the tunnel through resistance R u and resistance R 0 dividing potential drop:

First via voltage signal is by the negative input utmost point of resistance R 10 connection comparison amplifier A1, the output stage connecting electronic K switch of comparison amplifier A1 _U

The the second road voltage signal is successively by resistance R 1, resistance R 2 connects the negative input end of proportional integral amplifier A3, the negative input end contact resistance R5 of proportional integral amplifier A3, capacitor C 2, resistance R 5, the other end of capacitor C 2 connects proportional integral amplifier A3 output terminal, proportional integral amplifier A3 output terminal connects stepless electronic potentiometer RW1, the middle sliding end of stepless electronic potentiometer RW1 connects the positive input terminal of error amplifier A5, the negative input end of error amplifier A5 connects voltage-reference diode VE, voltage-reference diode VE, the stepless electronic potentiometer RW1 other end, electronic switch K _U, comparison amplifier A1 positive input terminal connects respectively U end negative pole;

The Third Road voltage signal is successively by resistance R 3, resistance R 4 connects the negative input end of proportional integral amplifier A4, resistance R 3, connecting electronic K switch I between the resistance R 4, the negative input end of proportional integral amplifier A4 is contact resistance R7 respectively, capacitor C 3, resistance R 7, the other end of capacitor C 3 connects proportional integral amplifier A4 output terminal, proportional integral amplifier A4 output terminal connects stepless electronic potentiometer RW2, the middle sliding end of stepless electronic potentiometer RW2 connects the negative input end of error amplifier A6 through resistance R 6, be connected the positive input terminal of error amplifier A6 by resistance R 8 between the negative input end of error amplifier A6 and the output terminal, the stepless electronic potentiometer RW2 other end, electronic switch K _IConnect respectively U end negative pole;

The intermediate ends of stepless electronic potentiometer RW1, RW2 is with the control that is subjected to the A5 output terminal.

Electronic switch K _IThe output terminal that connects comparison amplifier A2, the negative input end of comparison amplifier A2 connects respectively capacitor C 1, resistance R 1, Current Mutual Inductance T, the respectively connection U end negative pole of the positive input terminal of capacitor C 1 other end, resistance R 1 other end, the Current Mutual Inductance T other end, comparison amplifier A2.

The system of measurement power factor of the present utility model comprise sinusoidal voltage from U end input through resistance R U and resistance R 0 dividing potential drop as voltage signal, voltage signal drives electronic switch Ku through comparison amplifier A1, when voltage signal be on the occasion of the time, electronic switch Ku shutoff.Voltage signal is sent into proportional integral amplifier A3 through resistance R 1, resistance R 2.Proportional integral amplifier A 3 is 0 phase integral of voltage signal U0.

$\mathrm{Uv}=\frac{\sqrt{2}*U*{\∫}_0^{\mathrm{\π}}\sin \mathrm{\ωt}}{2\mathrm{\π}}=\frac{\sqrt{2}*U}{\mathrm{\π}}$

Proportional integral amplifier A3 output terminal connects stepless electronic potentiometer RW1.The middle sliding end of stepless electronic potentiometer RW1 connects the input end of error amplifier A5, and another input end of error amplifier A5 connects voltage-reference diode VE.The effect of error amplifier A5 output terminal is exactly to control the voltage Ve that the current potential of the intermediate ends of the electrodeless potentiometer RW1 of electronics equals voltage-reference diode VE.At this moment intrinsic standoff ratio is k.

Input current is through Current Mutual Inductance T generation current signal on secondary resistance.(effect of capacitor C 1 is the phase shift that the compensation mutual inductor produces, and also can consider simultaneously except the current impulse interference.) through comparison amplifier A2 driving electronic switch KI the voltage signal U0 on the R0 is sampled.Voltage when electronic switch KI turn-offs on the R0 is sent into proportional integral amplifier A4, error amplifier A6 through resistance R 3, resistance R 4, and the voltage when electronic switch KI conducting on the R0 is by short circuit.The output of proportional integral amplifier A4 is the φ phase integral of voltage signal U0.

$\mathrm{Ui}=\frac{\sqrt{2}*U*{\∫}_{\mathrm{\φ}}^{\mathrm{\π}+\mathrm{\φ}}\sin \mathrm{\ωt}}{2\mathrm{\π}}=\frac{\sqrt{2}*U*\mathrm{Cos\φ}}{\mathrm{\π}}$

Wherein: φ is the phase differential of electric current and voltage signal

Such as Fig. 2, shown in Figure 3, be B1, B2 point voltage waveform synoptic diagram.

Because the output terminal of proportional integral amplifier A4 links to each other with stepless potentiometer RW2.Stepless potentiometer RW2 is with stepless potentiometer RW1 synchronous operation.K is identical for its intrinsic standoff ratio.

And order

Uv*k＝Ve＝1

So, output end voltage in the middle of the electrodeless potentiometer RW2 of electronics

Ui*k＝Uv*k*Cosφ＝Cosφ

Error amplifier A6 is that an enlargement factor is 1 reverser, and the output of error amplifier A6 is exactly the power factor of circuit, and when power factor was 1, the voltage of voltage-reference diode VE was Ve.

Claims (1)

1. a system of measuring power factor is characterized in that, comprises from U rectifying utmost point input sinusoidal voltage, and as voltage signal, voltage signal is divided into three the tunnel through resistance R u and resistance R 0 dividing potential drop:

First via voltage signal is by the negative input utmost point of resistance R 10 connection comparison amplifier A1, the output stage connecting electronic K switch of comparison amplifier A1 _U

The the second road voltage signal is successively by resistance R 1, resistance R 2 connects the negative input end of proportional integral amplifier A3, the negative input end contact resistance R5 of proportional integral amplifier A3, capacitor C 2, resistance R 5, the other end of capacitor C 2 connects proportional integral amplifier A3 output terminal, proportional integral amplifier A3 output terminal connects stepless electronic potentiometer RW1, the middle sliding end of stepless electronic potentiometer RW1 connects the positive input terminal of error amplifier A5, the negative input end of error amplifier A5 connects voltage-reference diode VE, voltage-reference diode VE, the stepless electronic potentiometer RW1 other end, electronic switch K _U, comparison amplifier A1 positive input terminal connects respectively U end negative pole;

The Third Road voltage signal connects the negative input end of proportional integral amplifier A4, connecting electronic K switch between resistance R 3, the resistance R 4 successively by resistance R 3, resistance R 4 _IThe negative input end of proportional integral amplifier A4 is contact resistance R7, capacitor C 3 respectively, the other end of resistance R 7, capacitor C 3 connects proportional integral amplifier A4 output terminal, proportional integral amplifier A4 output terminal connects stepless electronic potentiometer RW2, the middle sliding end of stepless electronic potentiometer RW2 connects the negative input end of error amplifier A6 through resistance R 6, be connected the positive input terminal of error amplifier A6, the stepless electronic potentiometer RW2 other end, electronic switch K by resistance R 8 between the negative input end of error amplifier A6 and the output terminal _IConnect respectively U end negative pole;

The intermediate ends of stepless electronic potentiometer RW1, RW2 is with the control that is subjected to the A5 output terminal.Electronic switch K _IThe output terminal that connects comparison amplifier A2, the negative input end of comparison amplifier A2 connects respectively capacitor C 1, resistance R 1, Current Mutual Inductance T, the respectively connection U end negative pole of the positive input terminal of capacitor C 1 other end, resistance R 1 other end, the Current Mutual Inductance T other end, comparison amplifier A2.

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