CN102435829B - Self-calibration method for optical voltage sensor - Google Patents

Abstract

The invention relates to a self-calibration method for realizing an optical voltage sensor, which relates to a self-calibration method for a sensor. A reference voltage source is designed to realize a self-calibration function of the optical voltage sensor. By using the current optical voltage sensor, measurement precision and temperature stability are low. By using the optical voltage sensor of the invention, the above problem can be solved. In the invention, a discrete Fourier algorithm is used to acquire an effective value of a voltage signal. Through adding a calculation sample number and windowing processing, influence of frequency fluctuation on effective value calculation can be reduced and the stability of a self-calibration coefficient can be increased. An optical voltage sensor measurement result is affected by a temperature. By using an optical current sensor in the invention, the above problem can be solved. Through testing, the measurement precision reaches an IEC 0.2 grade measuring requirement in a temperature scope of minus 40-60 DEG C. The sensor and the method are suitable for designing a voltage transformer.

Description

Self-calibration method of optical voltage sensor

technical field

The invention relates to a self-calibration method of a sensor.

Background technique

Voltage transformer is an important equipment for voltage measurement in power system, and its measurement accuracy and operation reliability are closely related to the safe, reliable and economical operation of power system. The voltage transformers currently used mainly include electromagnetic voltage transformers, capacitive voltage divider voltage transformers and electronic voltage transformers. With the development of smart grids, electronic voltage transformers have received more and more attention and applications. The optical voltage transformer adopts the principle of Pockels electro-optic effect. It has no frequency band measurement limit, can accurately reflect the full voltage information including non-periodic components, and is the most ideal electronic voltage transformer. It is the development of electronic voltage transformers. main direction.

The optical voltage sensor is the core component of the optical voltage transformer, and the temperature drift problem of its measurement accuracy has always been one of the main reasons why the optical voltage transformer is difficult to be practical. According to the principle of optical voltage sensing, the optical voltage sensor belongs to the open-loop measurement system. The high measurement accuracy of the open-loop measurement system depends on the high stability of the parameters of each part of the sensing system. Any part of the sensing system that is affected by temperature will inevitably cause a drift in the output signal of the voltage sensor, resulting in measurement errors.

The most direct way to improve the measurement accuracy of optical voltage sensors is to use structures and materials with stable parameters, but due to technical and cost reasons, this method is still difficult to achieve. At present, the method to improve the measurement accuracy of the optical voltage sensor is mainly the compensation method. These compensation methods generally take temperature compensation measures for a certain link of the sensing system. Although these compensation methods improve the measurement accuracy of optical sensors to some extent, there is a large dispersion and uncertainty in the influence of temperature on the sensing system.

To sum up, the consistency of measurement accuracy and long-term temperature stability of existing optical voltage sensors are difficult to meet the requirements of power systems for voltage measurement accuracy.

Contents of the invention

The object of the present invention is to solve the problem of poor temperature stability of the measurement accuracy of the existing optical voltage sensor, thereby providing a self-calibration method of the optical voltage sensor.

An optical voltage sensor, which includes an optical voltage sensing unit, a reference voltage source and a remote acquisition module, the upper electrode of the optical voltage sensing unit is connected to a voltage signal input terminal of the optical voltage sensor, the input terminal is a Ground terminal, the ground terminal of the reference voltage source is another voltage input terminal to be measured of the optical voltage sensor, the input terminal is the ground terminal, and the reference voltage signal output terminal of the reference voltage source is connected to the lower electrode of the optical voltage sensing unit; The frequency of the voltage signal output by the voltage source is greater than the frequency of the voltage signal to be measured; the remote acquisition module collects the reference voltage signal output by the reference voltage source, and the remote acquisition module converts the collected voltage signal into an optical pulse signal and outputs it to the optical The calibration voltage output terminal of the voltage sensor; the light source input terminal of the optical voltage sensing unit is the light source input terminal of the optical voltage sensor; the induction signal output terminal of the optical voltage sensing unit is the optical voltage sensing signal output terminal of the optical voltage sensor ; The reference voltage output terminal of the remote acquisition module is the reference voltage output terminal of the optical voltage sensor.

To realize the self-calibration method of the above-mentioned optical voltage sensor, one input terminal of the voltage signal to be measured of the optical voltage sensor is connected to the non-ground terminal of the output voltage signal _U1 of the voltage source under test; the ground terminal of the reference voltage source is connected to the ground terminal of the voltage source under test connection; the remote acquisition module collects the output voltage signal U ₂ of the reference voltage source, and the remote acquisition module converts the collected voltage signal into an optical pulse signal, and then transmits it to the secondary converter of the voltage transformer through an optical fiber; The light source emitted by the secondary converter of the above-mentioned voltage transformer is transmitted to the light source input end of the optical voltage sensing unit through the optical fiber, and the optical voltage sensing unit simultaneously senses the voltage signals U ₁ and U ₂ and transmits them to the voltage transformer through the optical fiber Secondary converter: The secondary converter of the voltage transformer processes the received analog optical signal to obtain the induced measured voltage signal and the induced reference voltage signal;

The secondary converter also receives the optical pulse signal output by the calibration voltage output terminal of the optical voltage sensor, and obtains the reference voltage signal after digital demodulation;

The secondary converter also uses the discrete Fourier algorithm to realize the calculation of the effective value of the obtained induction reference voltage signal and the reference voltage signal. By comparing the calculated induction reference voltage signal and the effective value of the reference voltage signal in real time, an optical voltage sensor is obtained. The output self-calibration coefficient; then, use this self-calibration coefficient to correct the sensed voltage signal of the optical voltage sensing unit, and obtain the measured voltage output signal that is not affected by the ambient temperature;

The secondary converter will also frame the measured voltage signal according to the FT3 format, and send it to the merging unit through the optical fiber in an asynchronous manner.

Described method is specifically:

The reference voltage source generates a voltage signal with a frequency of _f2 and an effective value of _U2 . After the reference voltage signal received by the secondary converter from the reference voltage output terminal of the optical voltage sensor is demodulated, the obtained voltage signal is expressed as:

Among them: n is the count of data samples; t _n is the sampling time of the nth data; is the initial phase of the reference voltage signal collected by the remote collection module;

The secondary converter receives the optical voltage sensing signal output from the optical voltage sensor The optical voltage sensing unit is sensitive to the sensed measured voltage signal and the sensed reference voltage signal, and performs data processing on the signal to obtain the sensed measured voltage as:

The induced reference voltage is obtained as:

为光学电压传感单元敏感的感应被测电压信号的初始相位；U₁为被测电压源输出电压信号的有效值，为光学电压传感单元敏感的感应基准电压信号的初始相位；f₁为被测电压源输出电压信号的频率；Among them: Δk is the change in the output coefficient of the optical voltage sensing unit caused by external factors such as ambient temperature, which has nothing to do with the frequency of the sensitive voltage signal;

_U1 is the effective value of the output voltage signal of the measured voltage source, is the initial phase of the induced reference voltage signal sensitive to the optical voltage sensing unit; _f1 is the frequency of the output voltage signal of the measured voltage source;

The output coefficient change Δk of the optical voltage sensing unit caused by external factors such as ambient temperature is calculated by the following formula:

$\mathrm{<span\; class="notranslate">\; \&Delta;k</span>}<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Among them: U ₂ ′ is the effective value of the induced reference voltage signal sensitively obtained by the optical voltage sensing unit;

The above coefficients are used to correct the sensed voltage signal of the optical voltage sensing unit to obtain an output voltage signal that is not affected by the ambient temperature:

Where: (1+Δk) is the self-calibration coefficient of the output signal of the optical voltage sensor.

The optical voltage sensing unit is based on the principle of Pockels electro-optic effect and simultaneously sensitively senses the measured voltage signal and the reference voltage signal.

Beneficial effects: the present invention realizes the self-calibration function of the optical voltage sensor by designing the reference voltage source, and solves the problem of poor temperature stability of measurement accuracy of the existing optical voltage sensor. After testing, the measurement accuracy in the temperature range of -40 ~ 60 ° C has reached the measurement requirements of IEC0.2 level.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Detailed ways

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. This specific embodiment is described in conjunction with FIG. 1. An optical voltage sensor includes an optical voltage sensing unit 2-1, a reference voltage source 2-2, and a remote acquisition module 2-3. The optical voltage sensing The upper electrode of the unit 2-1 is connected to a voltage signal input terminal to be measured of the optical voltage sensor 2, the input terminal is a non-ground terminal, and the ground terminal of the reference voltage source 2-2 is another terminal to be measured of the optical voltage sensor 2 A voltage input terminal, the input terminal is a ground terminal, and the reference voltage signal output terminal of the reference voltage source 2-2 is connected to the lower electrode of the optical voltage sensing unit 2-1; the frequency of the voltage signal output by the reference voltage source 2-2 is greater than that to be Measure the frequency of the voltage signal; the remote acquisition module 2-3 collects the reference voltage signal output by the reference voltage source 2-2, and the remote acquisition module 2-3 converts the collected voltage signal into an optical pulse signal and outputs it to the optical voltage The calibration voltage output end of the sensor; the light source input end of the optical voltage sensing unit 2-1 is the light source input end of the optical voltage sensor 2; the induction signal output end of the optical voltage sensing unit 2-1 is the optical voltage sensor 2 The optical voltage sensing signal output terminal; the reference voltage output terminal of the remote acquisition module 2-3 is the reference voltage output terminal of the optical voltage sensor 2 .

Embodiment 2. Realize the self-calibration method of an optical voltage sensor described in Embodiment 1. An input terminal of a voltage signal to be measured of the optical voltage sensor 2 is connected to a non-ground terminal of the output voltage signal U1 of the voltage source ₁ under test. connection; the ground terminal of the reference voltage source 2-2 is connected to the ground terminal of the measured voltage source 1; the remote acquisition module 2-3 collects the output voltage signal U ₂ of the reference voltage source 2-2, and the remote acquisition module 2- 3 Convert the collected voltage signal into an optical pulse signal, and then transmit it to the secondary converter 3 of the voltage transformer through an optical fiber; the light source emitted by the secondary converter 3 of the voltage transformer is transmitted to the optical voltage sensor through an optical fiber The light source input end of unit 2-1, the optical voltage sensing unit 2-1 simultaneously senses the voltage signals U ₁ and U ₂ , and transmits them to the secondary converter 3 of the voltage transformer through optical fiber; the secondary converter of the voltage transformer 3 Process the received analog optical signal to obtain the induced measured voltage signal and the induced reference voltage signal;

The secondary converter 3 also receives the optical pulse signal output by the calibration voltage output end of the optical voltage sensor 2, and obtains a reference voltage signal after digital demodulation;

The secondary converter 3 also uses the discrete Fourier algorithm to calculate the effective value of the obtained induced reference voltage signal and the reference voltage signal, and obtains the optical voltage by comparing the calculated induced reference voltage signal and the effective value of the reference voltage signal in real time. The output self-calibration coefficient of the sensor 2; then, the self-calibration coefficient is used to correct the sensed measured voltage signal sensitive to the optical voltage sensing unit 2-1 to obtain a measured voltage output signal that is not affected by the ambient temperature;

The secondary converter 3 will also frame the measured voltage signal according to the FT3 format, and send it to the merging unit 4 through the optical fiber in an asynchronous manner.

The calculation of the correction coefficient and the method of realizing the self-calibration function will be further described below.

The reference voltage source 2-2 generates a voltage signal with a frequency of f ₂ and an effective value of U ₂ , the remote acquisition module 2-3 collects the voltage signal and converts it into an optical pulse signal and sends it to the secondary converter 3 for demodulation After that, the obtained voltage signal can be expressed as:

in:

为远端采集模块2-3采集的电压信号U₂的初始相位。n is the count of data samples; t _n is the sampling time of the nth data;

is the initial phase of the voltage signal U ₂ collected by the remote collection module 2-3.

The frequency _f2 of the voltage signal generated by the reference voltage source 2-2 is known, and the effective value _U2 is calculated using the discrete Fourier algorithm. During the calculation, the number of calculation samples and windowing are increased to reduce the influence of frequency fluctuations on the calculation of the effective value. Since the voltage signal collected by the remote acquisition module 2-3 is not affected by external factors such as environmental problems, it can be considered that the voltage signal acquired by the remote acquisition module 2-3 is the voltage signal U produced by the reference voltage source 2-2. ₂ .

The optical voltage sensing unit 2-1 simultaneously senses the voltage signal U ₁ and the voltage signal U ₂ , and transmits them to the secondary converter 3 through an optical fiber. After data processing, the obtained voltage signals can be expressed as:

为光学电压传感单元2-1敏感的电压信号U₁的初始相位；

为光学电压传感单元2-1敏感的电压信号U₂的初始相位；f₁为被测电压源1输出电压信号U₁的频率。Among them: Δk is the variation of the output coefficient of the optical voltage sensing unit 2-1 caused by external factors such as ambient temperature, which has nothing to do with the frequency of the sensitive voltage signal;

is the initial phase of the voltage signal _U1 sensitive to the optical voltage sensing unit 2-1;

is the initial phase of the voltage signal _U2 sensitive to the optical voltage sensing unit 2-1; _f1 is the frequency of the voltage signal _U1 output by the voltage source 1 under test.

The effective value U ₂ ′ of the voltage signal obtained by the sensitive voltage signal U ₂ of the optical voltage sensing unit 2-1 is calculated by using the discrete Fourier algorithm. In the calculation, increasing the number of calculation samples and adding window processing are used to reduce the frequency fluctuation and affect the effective value calculation Impact.

The output coefficient variation Δk of the optical voltage sensing unit 2-1 caused by external factors such as ambient temperature can be calculated by the following formula:

$\mathrm{<span\; class="notranslate">\; \&Delta;k</span>}<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="u"\; filenames="HDA0000103369460000011.png"\; state="\{\{state\}\}">u</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Wherein: U ₂ ′ is the effective value of the induced reference voltage signal sensitively obtained by the optical voltage sensing unit (2-1);

By correcting the voltage signal u ₁ ′ obtained by the optical voltage sensing unit 2-1 sensitive to the voltage signal U ₁ at the same time, an output voltage signal that is not affected by external factors such as ambient temperature can be obtained:

In the formula: (1+Δk) is the self-calibration coefficient of the output signal of the optical voltage sensor (2);

If the output voltage signal U ₁ of the voltage source 1 under test includes not only the fundamental frequency but also other higher harmonic frequencies, the above calculation method is also applicable.

Compared with the prior art, the optical voltage sensor of the present invention has the following characteristics and advantages:

1. The present invention realizes the self-calibration function of the optical voltage sensor by designing the reference voltage source, and solves the problem of poor temperature stability of the measurement accuracy of the existing optical voltage sensor.

2. The present invention adopts the discrete Fourier algorithm to obtain the effective value of the voltage signal, reduces the influence of frequency fluctuation on the effective value calculation by increasing the number of calculation samples and adding window processing, and improves the stability of the self-calibration coefficient.

The optical current sensor of the invention solves the disadvantage that the measurement results of the optical voltage sensor are affected by temperature, and after testing, the measurement accuracy in the temperature range of -40-60°C meets the measurement requirements of IEC0.2 level.

Claims (3)

1. The self-calibration method of the optical voltage sensor, the optical voltage sensor includes an optical voltage sensing unit (2-1), a reference voltage source (2-2) and a remote acquisition module (2-3), the optical voltage sensing unit ( 2-1), the upper electrode of the optical voltage sensor (2) is connected to a voltage signal input terminal to be measured, the input terminal is a non-ground terminal, and the ground terminal of the reference voltage source (2-2) is the optical voltage sensor (2) ), the input terminal is a ground terminal, and the reference voltage signal output terminal of the reference voltage source (2-2) is connected to the lower electrode of the optical voltage sensing unit (2-1); the reference voltage source ( 2-2) the frequency of the output voltage signal is greater than the frequency of the voltage signal to be measured; the remote acquisition module (2-3) collects the reference voltage signal output by the reference voltage source (2-2), and the remote acquisition module (2 -3) Convert the collected voltage signal into an optical pulse signal and output it to the calibration voltage output end of the optical voltage sensor; the light source input end of the optical voltage sensing unit (2-1) is the light source input of the optical voltage sensor (2) end; the induction signal output end of the optical voltage sensing unit (2-1) is the optical voltage sensing signal output end of the optical voltage sensor (2); the reference voltage output end of the remote acquisition module (2-3) is the The reference voltage output terminal of the optical voltage sensor (2); It is characterized in that the self-calibration method of the optical voltage sensor is: A voltage signal input terminal to be measured of the optical voltage sensor (2) is connected to a non-ground terminal of the output voltage signal _U1 of the voltage source under test (1); the ground terminal of the reference voltage source (2-2) is connected to the voltage source under test ( 1) ground connection; the remote acquisition module (2-3) collects the output voltage signal U ₂ of the reference voltage source (2-2), and the remote acquisition module (2-3) converts the collected voltage signal into The light pulse signal is then transmitted to the secondary converter (3) of the voltage transformer through an optical fiber; the light source sent by the secondary converter (3) of the voltage transformer is transmitted to the optical voltage sensing unit (2-1) through an optical fiber ), the optical voltage sensing unit (2-1) simultaneously senses the voltage signals U ₁ and U ₂ , and transmits them to the secondary converter (3) of the voltage transformer through an optical fiber; the secondary conversion of the voltage transformer The device (3) processes the received analog optical signal to obtain an induced measured voltage signal and an induced reference voltage signal; The secondary converter (3) also receives the optical pulse signal output by the calibration voltage output terminal of the optical voltage sensor (2), and obtains a reference voltage signal after digital demodulation; The secondary converter (3) also uses the discrete Fourier algorithm to realize the calculation of the effective value of the obtained induced reference voltage signal and the reference voltage signal, and through the real-time comparison of the calculated induced reference voltage signal and the effective value of the reference voltage signal, it is obtained The output self-calibration coefficient of the optical voltage sensor (2); then, use this self-calibration coefficient to correct the sensed voltage signal sensitive to the optical voltage sensing unit (2-1) to obtain a measured voltage that is not affected by the ambient temperature output signal; The secondary converter (3) also performs data framing on the measured voltage signal according to the FT3 format, and sends it to the merging unit (4) through an optical fiber in an asynchronous manner. 2. The self-calibration method of optical voltage sensor according to claim 1, is characterized in that described method is specially: The reference voltage source (2-2) generates a voltage signal with frequency _f2 and effective value _U2 , and the reference voltage signal received by the secondary converter (3) from the reference voltage output terminal of the optical voltage sensor (2) is demodulated After processing, the obtained voltage signal is expressed as:

Among them: n is the count of data samples; t _n is the sampling time of the nth data;

The initial phase of the reference voltage signal collected for the remote acquisition module (2-3); The secondary converter (3) receives the induced measured voltage signal and the induced reference voltage signal sensitively obtained by the optical voltage sensing unit (2-1) from the optical voltage sensing signal output end of the optical voltage sensor (2), and The signal is processed for data, and the induced measured voltage is obtained as: The induced reference voltage is obtained as:

Among them: Δk is the variation of the output coefficient of the optical voltage sensing unit (2-1) caused by external factors such as ambient temperature, which has nothing to do with the frequency of the sensitive voltage signal; is the initial phase of the optical voltage sensing unit (2-1) sensitively sensing the measured voltage signal; U ₁ is the effective value of the output voltage signal of the measured voltage source (1),

is the initial phase of the induced reference voltage signal sensitive to the optical voltage sensing unit (2-1); _f1 is the frequency of the output voltage signal of the measured voltage source (1); The output coefficient variation Δk of the optical voltage sensing unit (2-1) caused by external factors such as ambient temperature is calculated by the following formula: $\mathrm{<span\; class="notranslate">\; \&Delta;k</span>}<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}$ Wherein: U ₂ ′ is the effective value of the induced reference voltage signal sensitively obtained by the optical voltage sensing unit (2-1); The above-mentioned coefficients are used to correct the sensed and measured voltage signal sensitive to the optical voltage sensing unit (2-1) to obtain an output voltage signal that is not affected by the ambient temperature:

In the formula: (1+Δk) is the self-calibration coefficient of the output signal of the optical voltage sensor (2). 3. The self-calibration method of the optical voltage sensor according to claim 1, characterized in that the optical voltage sensing unit (2-1) is based on the Pockels electro-optic effect principle and sensitively obtains the induced measured voltage signal and the reference voltage signal simultaneously.

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