Fiber optic current transformer and control method based on fiber optic current transformer

Abstract

Disclosed in the embodiments of the present application are a fiber optic current transformer and a control method based on a fiber optic current transformer. The fiber optic current transformer comprises a photoelectric conversion unit, an error accumulation unit, a delay control unit and a fiber optic interferometer that comprises a variable delay unit, wherein the photoelectric conversion unit is used for converting a received light intensity signal into a proportional voltage signal; the error accumulation unit is used for performing feature analysis on the voltage signal to obtain a periodic misalignment error signal; and the delay control unit is used for performing linear adjustment processing on the periodic misalignment error signal to obtain a processed periodic misalignment error signal, and controlling the variable delay unit on the basis of the processed periodic misalignment error signal to change an intrinsic period of the fiber optic interferometer, such that the intrinsic period of the fiber optic interferometer is equal to half the period of a modulated square wave signal applied to the fiber optic interferometer.

Description

Fiber optic current transformer and control method based on fiber optic current transformer Technical Field

[0001] The present application relates to, but is not limited to, the fields of optical fiber sensing and current measurement, and in particular to an optical fiber current transformer and a control method based on the optical fiber current transformer. Background Art

[0002] The closed-loop detection type fiber optic current transformer in the related art adopts a reflective fiber optic interferometer and realizes closed-loop tracking detection of current by applying a square wave + step wave signal to the electro-optical phase modulator. Ideally, the period of the fiber optic interferometer is half of the modulated square wave. However, the modulated square wave is usually generated by a field programmable gate array (FPGA) or other digital circuits. The period of the modulated square wave is determined by the crystal oscillator frequency, which is difficult to adjust continuously, resulting in period misalignment. In practice, the period of the modulated square wave can only be adjusted to the desired size approximately through software settings, but a small amount of misalignment cannot be completely avoided. The period misalignment of the modulated square wave causes the interference light intensity to appear a positive pulse signal at the beginning or end of the square wave half-period, which will cause an additional zero-bias current error in the output signal of the fiber optic circuit transformer, affecting the measurement accuracy. Therefore, how to solve the problem of misalignment between the intrinsic period of the fiber optic interferometer and the half-period of the modulated square wave is an important topic in this field.

[0003] Summary of the Invention

[0004] To address the above problems, an embodiment of the present application provides a fiber optic current transformer and a control method based on the fiber optic current transformer, so as to achieve dynamic adjustment of the intrinsic period of the fiber optic interferometer in the fiber optic current transformer and real-time matching with the period of the modulated square wave signal.

[0005] In a first aspect, an embodiment of the present application provides a fiber optic current transformer, comprising: a photoelectric conversion unit, an error accumulation unit, a delay control unit, and a reflective fiber optic interferometer including a variable delay unit; wherein,

[0006] One end of the reflective fiber interferometer is connected to the input end of the photoelectric conversion unit, the output end of the photoelectric conversion unit is connected to the input end of the error accumulation unit, the output end of the error accumulation unit is connected to the input end of the delay control unit, and the output end of the delay control unit is connected to the input end of the reflective fiber interferometer;

[0007] The photoelectric conversion unit is used to convert the received light intensity signal into a proportional voltage signal;

[0008] The error accumulation unit is used to perform characteristic analysis on the voltage signal to obtain a period misalignment error signal;

[0009] The delay control unit is used to perform linear adjustment processing on the period misalignment error signal to obtain a processed period misalignment error signal; based on the processed period misalignment error signal, control the variable delay unit to change the intrinsic period of the fiber optic interferometer so that the intrinsic period of the fiber optic interferometer is equal to half the period of the modulated square wave signal applied to the fiber optic interferometer.

[0010] In some embodiments, the fiber interferometer further includes an electro-optical phase modulator; when the duty cycle of the modulated square wave signal applied to the electro-optical phase modulator is 50%, the intrinsic period of the fiber interferometer is equal to half the period of the modulated square wave signal.

[0011] In some embodiments, the error accumulation unit is used to integrate and accumulate the positive pulses present at the head of the modulated square wave signal to obtain a positive error signal when the intrinsic period of the fiber optic interferometer is less than half of the period of the modulated square wave signal; to integrate and accumulate the positive pulses present at the head of the modulated square wave signal to obtain a negative error signal when the intrinsic period of the fiber optic interferometer is greater than half of the period of the modulated square wave signal; to accumulate the positive error signal and the negative error signal to obtain the period misalignment error signal; and the error accumulation unit is a phase-locked integration circuit.

[0012] In some embodiments, the delay control unit is configured to invert the periodic misalignment error signal and perform PID processing on the inverted periodic misalignment error signal to obtain the processed periodic misalignment error signal. The delay control unit may be implemented using at least one of: an analog PID circuit and analog-to-digital conversion-digital signal processing-digital-to-analog conversion.

[0013] In some embodiments, the delay control unit is configured to perform PID processing on the period misalignment error signal; and perform inversion processing on the period misalignment error signal after PID processing to obtain the processed period misalignment error signal.

[0014] In some embodiments, the light wave delay time of the variable delay unit can be controlled by a control voltage; the magnitude of the light wave delay time is positively correlated with the amplitude of the control voltage; the variable delay unit is a cylindrical piezoelectric ceramic or an electrically controlled optical delay line tightly wound with an optical fiber.

[0015] In some embodiments, the fiber interferometer further includes: a light source, a coupler, a polarizer, a fixed delay fiber, a fiber measuring coil and a photodetector; wherein the light source is connected to the coupler; the coupler is connected to the polarizer; the polarizer is connected to the electro-optical phase modulator; one end of the photodetector is connected to the coupler, and the other end of the photodetector is connected to the photoelectric conversion unit; the fixed delay fiber is located between the electro-optical phase modulator and the fiber measuring coil, and the variable delay unit is located between the electro-optical phase modulator and the fiber measuring coil; the variable delay unit is located between the electro-optical phase modulator and the fixed delay fiber, or the variable delay unit is located between the fixed delay fiber and the fiber measuring coil.

[0016] In a second aspect, an embodiment of the present application provides a control method based on a fiber optic current transformer, wherein the fiber optic current transformer includes a fiber optic interferometer; the fiber optic interferometer includes a variable delay unit; the method includes: converting a received light intensity signal into a proportional voltage signal; performing characteristic analysis on the voltage signal to obtain a periodic misalignment error signal; performing linear adjustment processing on the periodic misalignment error signal to obtain a processed periodic misalignment error signal; and controlling the variable delay unit based on the processed periodic misalignment error signal to change the intrinsic period of the fiber optic interferometer so that the intrinsic period of the fiber optic interferometer is equal to half the period of the modulated square wave signal applied to the fiber optic interferometer.

[0017] In some embodiments, the characteristic analysis of the voltage signal to obtain a periodic misalignment error signal includes: when the intrinsic period of the fiber optic interferometer is less than half the period of the modulated square wave signal, integrating and accumulating the positive pulses present at the head of the modulated square wave signal to obtain a positive error signal; when the intrinsic period of the fiber optic interferometer is greater than half the period of the modulated square wave signal, integrating and accumulating the positive pulses present at the head of the modulated square wave signal to obtain a negative error signal; accumulating the positive error signal and the negative error signal to obtain the periodic misalignment error signal; and the error accumulation unit is a phase-locked integration circuit.

[0018] In some embodiments, performing linear adjustment processing on the periodic misalignment error signal to obtain a processed periodic misalignment error signal includes: performing inversion processing on the periodic misalignment error signal; and performing PID processing on the inverted periodic misalignment error signal to obtain the processed periodic misalignment error signal.

[0019] In some embodiments, performing linear adjustment processing on the periodic misalignment error signal to obtain a processed periodic misalignment error signal includes: performing PID processing on the periodic misalignment error signal; and performing inversion processing on the periodic misalignment error signal after PID processing to obtain the processed periodic misalignment error signal.

[0020] The optical fiber current transformer provided in the embodiment of the present application has a photoelectric conversion unit for converting a received light intensity signal into a proportional voltage signal; an error accumulation unit for performing feature analysis on the voltage signal to obtain a period mismatch error signal; a delay control unit for performing linear adjustment processing on the period mismatch error signal to obtain a processed period mismatch error signal; and based on the processed period mismatch error signal, a variable delay unit is controlled to change the intrinsic period of the optical fiber interferometer so that the intrinsic period of the optical fiber interferometer is equal to half the period of the modulated square wave signal applied to the optical fiber interferometer. In this way, by controlling the variable delay unit in the optical fiber interferometer, the intrinsic period of the optical fiber interferometer is changed so that the intrinsic period of the optical fiber interferometer is equal to half the period of the modulated square wave signal applied to the optical fiber interferometer, thereby eliminating the additional pulse signal introduced by the period mismatch and further eliminating the zero-bias current error of the optical fiber current transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] FIG1 is an equivalent optical path diagram of an embodiment of a fiber optic current transformer provided in an embodiment of the present application;

[0023] FIG2 is a schematic diagram showing the timing relationship of the additional pulse signal in the interference light intensity when the intrinsic period of the fiber interferometer provided by an embodiment of the present application is misaligned with the half period of the modulated square wave signal;

[0024] FIG3 is a schematic diagram of a phase-discrimination square wave used in a phase-discrimination integration circuit provided in an embodiment of the present application;

[0025] FIG4 is a schematic diagram of a circuit principle of an embodiment of an error accumulation unit provided in an embodiment of the present application;

[0026] FIG5 is a flow chart of a control method based on an optical fiber current transformer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to solve the problem that the periodic misalignment of the square wave applied to the electro-optical phase modulator causes the interference light intensity to appear a positive pulse signal at the beginning or end of the square wave half-cycle, resulting in a zero-bias current error added to the output signal of the optical fiber circuit mutual inductor, affecting the measurement accuracy, the solution of the relevant technology is to deduct this zero-bias error in the software. However, due to factors such as thermal expansion and contraction, this zero-bias error changes with temperature, which makes the error deduction method fail; or a voltage-controlled crystal oscillator is used instead of a fixed-frequency crystal oscillator to adjust the crystal oscillator frequency by voltage to eliminate the periodic misalignment problem. However, the frequency range that can be changed by the voltage-controlled crystal oscillator is usually limited, and the frequency cannot be adjusted continuously. Residual misalignment is inevitable, which cannot fundamentally solve this problem.

[0028] In order to solve the problem of misalignment between the intrinsic period of the fiber optic interferometer and the half-period of the modulated square wave, an embodiment of the present application provides a fiber optic current transformer, comprising: adding a variable delay unit, an error accumulation unit, and a delay control unit to a traditional closed-loop fiber optic current transformer. The variable delay unit is composed of a piezoelectric ceramic or an optical delay line wrapped around an optical fiber, and the error accumulation unit is composed of a phase-locked integration circuit. In the embodiment of the present application, the error accumulation unit is used to identify the difference between the intrinsic period of the fiber optic interferometer and the half-period of the square wave modulation, and the variable delay unit is used to adjust the intrinsic period of the fiber optic interferometer to be equal to the half-period of the modulation, thereby eliminating the additional pulse signal in the interference light intensity and thus eliminating the zero-bias current error of the fiber optic current transformer.

[0029] FIG1 is an equivalent optical path diagram of an embodiment of a fiber-optic current transformer according to an embodiment of the present application. As shown in FIG1 , the fiber-optic current transformer includes: a photoelectric conversion unit, an error accumulation unit, a delay control unit, and a fiber-optic interferometer. The fiber-optic interferometer includes a light source 1, a coupler 3, a polarizer 4, an electro-optical phase modulator 5, a variable delay unit, a fixed-delay optical fiber 6, an optical fiber measuring coil 7, and a photodetector 2. One end of the photodetector 2 is connected to the coupler 3, and the other end of the photodetector 2 is connected to the input end of the photoelectric conversion unit; the output end of the photoelectric conversion unit is connected to the input end of the error accumulation unit, the output end of the error accumulation unit is connected to the input end of the delay control unit, and the output end of the delay control unit is connected to the input end of the fiber-optic interferometer; the light source 1 is connected to the coupler 3; the coupler 3 is connected to the polarizer 4; the polarizer 4 is connected to the electro-optical phase modulator 5; the electro-optical phase modulator 5 is connected to the variable delay unit, and the variable delay unit is connected to the fixed-delay optical fiber 6. In this embodiment of the present application, the photoelectric conversion unit, the error accumulation unit, the delay control unit, and the variable delay unit are connected via circuits.

[0030] In the embodiment of the present application, the variable delay unit is located between the electro-optical phase modulator 5 and the fixed-delay optical fiber 6. In other embodiments, the variable delay unit may also be located between the fixed-delay optical fiber 6 and the optical fiber measurement coil 7.

[0031] In this embodiment of the present application, the photoelectric conversion unit is configured to convert a received light intensity signal into a proportional voltage signal. Here, the light intensity signal may be received by a photodetector, which then transmits the light intensity signal to the photoelectric conversion unit. In this embodiment of the present application, the output voltage of the photoelectric conversion unit is a straight line, without additional pulse signals caused by period misalignment.

[0032] In the embodiment of the present application, the error accumulation unit is used to perform characteristic analysis on the voltage signal to obtain a period misalignment error signal.

[0033] In some embodiments, the error accumulation unit can integrate and accumulate the positive pulses at the head of the modulated square wave signal when the intrinsic period of the fiber interferometer is less than half the period of the modulated square wave signal to obtain a positive error signal; when the intrinsic period of the fiber interferometer is greater than half the period of the modulated square wave signal, the error accumulation unit can integrate and accumulate the positive pulses at the head of the modulated square wave signal to obtain a negative error signal; and accumulate the positive error signal and the negative error signal to obtain a period misalignment error signal. That is, the error accumulation unit determines the period misalignment error signal based on the modulated square wave signal and the intrinsic period of the fiber interferometer shown in FIG2 . In this way, after the error accumulation unit identifies the period misalignment error signal, it outputs the period misalignment error signal to the delay control unit, and uses negative feedback to control the variable delay unit to eliminate the period misalignment.

[0034] In the embodiment of the present application, the error accumulation unit is composed of a phase-detection multiplication circuit, an addition circuit, and an integration circuit. The phase-detection multiplication circuit uses two different phase-detection square waves, as shown in Figure 3, to distinguish between positive and negative error signals. The addition circuit adds the two error signals, and the integration circuit integrates the added error signal to achieve error accumulation, as shown in Figure 4. Thus, the error accumulation unit is composed of a phase-detection integration circuit. The phase relationship between the phase-detection square wave and the modulating square wave is clear and simple, making it easy to generate. The multiplication circuit, addition circuit, and integration circuit can all be implemented using mature analog circuits.

[0035] In an embodiment of the present application, the delay control unit is used to perform linear adjustment processing on the period misalignment error signal to obtain a processed period misalignment error signal; based on the processed period misalignment error signal, the variable delay unit is controlled to change the intrinsic period of the fiber optic interferometer so that the intrinsic period of the fiber optic interferometer is equal to half the period of the modulated square wave signal applied to the fiber optic interferometer.

[0036] In some embodiments, the delay control unit obtains the processed period misalignment error signal by: the delay control unit is used to invert the period misalignment error signal; and performs PID processing on the inverted period misalignment error signal to obtain the processed period misalignment error signal.

[0037] In some embodiments, the delay control unit may obtain the processed period misalignment error signal in the following manner: the delay control unit is configured to perform PID processing on the period misalignment error signal; and the period misalignment error signal after PID processing is inverted to obtain the processed period misalignment error signal.

[0038] In some embodiments, the delay control unit may be implemented by at least one of the following: an analog PID circuit and analog-to-digital conversion-digital signal processing-digital-to-analog conversion. Here, the digital signal processing may be digital PID processing.

[0039] In some embodiments, the light wave delay time of the variable delay unit can be controlled by a control voltage; the magnitude of the light wave delay time is positively correlated with the amplitude of the control voltage; the variable delay unit is a cylindrical piezoelectric ceramic tightly wound with an optical fiber or an electrically controlled optical delay line.

[0040] In some embodiments, the variable delay unit is composed of a cylindrical piezoelectric ceramic tightly wound with an optical fiber. By applying different voltages to the piezoelectric ceramic, the tension of the piezoelectric ceramic can be changed, thereby changing the length of the optical fiber to achieve the purpose of changing the delay time of the light wave.

[0041] In some embodiments, the variable delay unit is composed of a variable optical delay line driven by a motor. By changing the stroke of the motor, the length of the optical delay line can be changed, thereby achieving the purpose of changing the delay time of the light wave.

[0042] The optical fiber current transformer provided in the embodiment of the present application is provided with a photoelectric conversion unit for converting a received light intensity signal into a proportional voltage signal; the error accumulation unit of the optical fiber current transformer is used to perform characteristic analysis on the voltage signal to obtain a period mismatch error signal; the delay control unit of the optical fiber current transformer is used to perform linear adjustment processing on the period mismatch error signal to obtain a processed period mismatch error signal; based on the processed period mismatch error signal, the variable delay unit is controlled to change the intrinsic period of the optical fiber interferometer so that the intrinsic period of the optical fiber interferometer is equal to half the period of the modulated square wave signal applied to the optical fiber interferometer. In this way, by controlling the variable delay unit in the optical fiber interferometer, the intrinsic period of the optical fiber interferometer is changed so that the intrinsic period of the optical fiber interferometer is equal to half the period of the modulated square wave signal applied to the optical fiber interferometer, thereby eliminating the additional pulse signal introduced by the period mismatch and further eliminating the zero-bias current error of the optical fiber current transformer.

[0043] FIG5 is a flow chart of a control method based on an optical fiber current transformer according to an embodiment of the present application. As shown in FIG5 , the flow chart may include:

[0044] In S501 , the received light intensity signal is converted into a proportional voltage signal.

[0045] In S502 , a characteristic analysis is performed on the voltage signal to obtain a period misalignment error signal.

[0046] In the embodiment of the present application, S502 can be implemented in the following manner:

[0047] In S521 , when the intrinsic period of the fiber interferometer is less than half the period of the modulated square wave signal, the positive pulse at the head of the modulated square wave signal is integrated and accumulated to obtain a positive error signal.

[0048] In S522, when the intrinsic period of the fiber interferometer is greater than half the period of the modulated square wave signal, the positive pulse at the head of the modulated square wave signal is integrated and accumulated to obtain a negative error signal.

[0049] In S523 , the positive error signal and the negative error signal are accumulated to obtain a period misalignment error signal; the error accumulation unit is a phase detection integration circuit.

[0050] In the embodiment of the present application, a period misalignment error signal can be obtained based on the intrinsic period of the fiber interferometer and the period of the square wave signal, so that the variable delay unit can be controlled by negative feedback to eliminate the period misalignment.

[0051] In S503, a linear adjustment process is performed on the period misalignment error signal to obtain a processed period misalignment error signal;

[0052] In the embodiment of the present application, S503 can be implemented by one of the following methods:

[0053] In S531, the period misalignment error signal is inverted; the inverted period misalignment error signal is PID processed to obtain a processed period misalignment error signal

[0054] In S532 , PID processing is performed on the period misalignment error signal; and the period misalignment error signal after PID processing is inverted to obtain a processed period misalignment error signal.

[0055] In S504, based on the processed period misalignment error signal, the variable delay unit is controlled to change the intrinsic period of the fiber interferometer so that the intrinsic period of the fiber interferometer is equal to half the period of the modulated square wave signal applied to the fiber interferometer.

[0056] In an embodiment of the present application, the received light intensity signal is first converted into a proportional voltage signal; the error accumulation unit of the optical fiber current transformer is used to perform characteristic analysis on the voltage signal to obtain a period mismatch error signal; the period mismatch error signal is then linearly adjusted to obtain a processed period mismatch error signal; and finally, based on the processed period mismatch error signal, the variable delay unit is controlled to change the intrinsic period of the optical fiber interferometer so that the intrinsic period of the optical fiber interferometer is equal to half the period of the modulated square wave signal applied to the optical fiber interferometer. In this way, by controlling the variable delay unit in the optical fiber interferometer, the intrinsic period of the optical fiber interferometer is changed so that the intrinsic period of the optical fiber interferometer is equal to half the period of the modulated square wave signal applied to the optical fiber interferometer, thereby eliminating the additional pulse signal introduced by the period mismatch and further eliminating the zero-bias current error of the optical fiber current transformer.

[0057] In some embodiments, the control method based on the optical fiber current transformer is implemented as follows:

[0058] (1) First, the error signal caused by the misalignment between the intrinsic period of the fiber interferometer and the half period of the modulated square wave is obtained, refer to Figure 2;

[0059] (2) Secondly, the period misalignment error signal is integrated and accumulated by the error accumulation unit. The specific implementation of the error accumulation unit is shown in FIG4 , and the two phase-locked square waves used in FIG4 and their phase relationship with the modulating square wave are shown in FIG3 ;

[0060] (3) The output of the error accumulation unit is then sent to the delay control unit. The control goal of the delay control unit is to make the output of the error accumulation unit zero. The delay control unit adopts a PID negative feedback regulation method, and its output acts on the variable delay unit;

[0061] (4) The variable delay unit is the final execution unit, which uses the output signal of the delay control unit to change the intrinsic period of the fiber interferometer so that it is exactly equal to the half period of the modulated square wave.

[0062] The technical solutions disclosed in the embodiments of the present application have been described above through the examples. It is believed that those skilled in the art can understand the embodiments of the present application through the description of the above embodiments. Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. However, obvious changes or modifications derived therefrom are still within the scope of protection created by the embodiments of the present application. Industrial Applicability

[0063] The present disclosure provides a fiber optic current transformer and a control method based on the fiber optic current transformer. The fiber optic current transformer includes: a photoelectric conversion unit, an error accumulation unit, a delay control unit, and a fiber optic interferometer including a variable delay unit. The photoelectric conversion unit is used to convert a received light intensity signal into a proportional voltage signal. The error accumulation unit is used to perform feature analysis on the voltage signal to obtain a period mismatch error signal. The delay control unit is used to perform linear adjustment processing on the period mismatch error signal to obtain a processed period mismatch error signal. Based on the processed period mismatch error signal, the variable delay unit is controlled to change the intrinsic period of the fiber optic interferometer so that the intrinsic period of the fiber optic interferometer is equal to half the period of the modulated square wave signal applied to the fiber optic interferometer. In this way, by controlling the variable delay unit in the fiber optic interferometer, the intrinsic period of the fiber optic interferometer is changed so that the intrinsic period of the fiber optic interferometer is equal to half the period of the modulated square wave signal applied to the fiber optic interferometer, thereby eliminating the additional pulse signal introduced by the period mismatch and further eliminating the zero-bias current error of the fiber optic current transformer.

Claims

1. A fiber optic current transformer, comprising: A photoelectric conversion unit, an error accumulation unit, a delay control unit, and a fiber interferometer including a variable delay unit; wherein, One end of the fiber interferometer is connected to the input end of the photoelectric conversion unit, the output end of the photoelectric conversion unit is connected to the input end of the error accumulation unit, the output end of the error accumulation unit is connected to the input end of the delay control unit, and the output end of the delay control unit is connected to the input end of the fiber interferometer; The photoelectric conversion unit is used to convert the received light intensity signal into a proportional voltage signal; The error accumulation unit is used to perform characteristic analysis on the voltage signal to obtain a period misalignment error signal; The delay control unit is used to perform linear adjustment processing on the period misalignment error signal to obtain a processed period misalignment error signal; based on the processed period misalignment error signal, the variable delay unit is controlled to change the intrinsic period of the fiber optic interferometer so that the intrinsic period of the fiber optic interferometer is equal to half of the period of the modulated square wave signal applied to the fiber optic interferometer.

2. The optical fiber current transformer according to claim 1, wherein: The fiber interferometer also includes an electro-optic phase modulator; when the duty cycle of the modulated square wave signal applied to the electro-optic phase modulator is 50%, the intrinsic period of the fiber interferometer is equal to half the period of the modulated square wave signal.

3. The optical fiber current transformer according to claim 1 or 2, wherein: The error accumulation unit is used to integrate and accumulate the positive pulses existing in the head of the modulated square wave signal to obtain a positive error signal when the intrinsic period of the fiber interferometer is less than half of the period of the modulated square wave signal; In the case where the intrinsic period of the fiber interferometer is greater than half of the period of the modulated square wave signal, the positive pulses existing at the head of the modulated square wave signal are integrated and accumulated to obtain a negative error signal; The positive error signal and the negative error signal are accumulated to obtain the period misalignment error signal; the error accumulation unit is a phase-detection integration circuit.

4. The optical fiber current transformer according to any one of claims 1 to 3, wherein: The delay control unit is used to invert the periodic misalignment error signal; perform PID processing on the inverted periodic misalignment error signal to obtain the processed periodic misalignment error signal; the delay control unit can be implemented by at least one of the following: analog PID circuit and analog-to-digital conversion-digital signal processing-digital-to-analog conversion.

5. The optical fiber current transformer according to any one of claims 1 to 3, wherein: The delay control unit is used to perform PID processing on the period misalignment error signal; and perform inversion processing on the period misalignment error signal after PID processing to obtain the processed period misalignment error signal.

6. The optical fiber current transformer according to any one of claims 1 to 5, wherein: The light wave delay time of the variable delay unit can be controlled by a control voltage; the magnitude of the light wave delay time is positively correlated with the amplitude of the control voltage; the variable delay unit is a cylindrical piezoelectric ceramic or an electrically controlled optical delay line tightly wound with an optical fiber.

7. The optical fiber current transformer according to claim 2, wherein: The fiber interferometer also includes: a light source, a coupler, a polarizer, a fixed delay fiber, a fiber measurement coil and a photodetector; wherein, The light source is connected to the coupler; the coupler is connected to the polarizer; the polarizer is connected to the electro-optic phase modulator; one end of the photodetector is connected to the coupler, and the other end of the photodetector is connected to the photoelectric conversion unit; The fixed delay optical fiber is located between the electro-optic phase modulator and the optical fiber measuring coil, and the variable delay unit is located between the electro-optic phase modulator and the optical fiber measuring coil; the variable delay unit is located between the electro-optic phase modulator and the fixed delay optical fiber, or the variable delay unit is located between the fixed delay optical fiber and the optical fiber measuring coil.

8. A control method based on a fiber optic current transformer, wherein the fiber optic current transformer comprises a fiber optic interferometer; The fiber interferometer includes a variable delay unit; the method includes: Convert the received light intensity signal into a proportional voltage signal; Performing characteristic analysis on the voltage signal to obtain a period misalignment error signal; Performing linear adjustment processing on the period misalignment error signal to obtain a processed period misalignment error signal; Based on the processed period misalignment error signal, the variable delay unit is controlled to change the intrinsic period of the fiber interferometer so that the intrinsic period of the fiber interferometer is equal to half the period of the modulated square wave signal applied to the fiber interferometer.

9. The method according to claim 8, wherein: The performing characteristic analysis on the voltage signal to obtain a period misalignment error signal includes: In the case where the intrinsic period of the fiber interferometer is less than half of the period of the modulated square wave signal, the positive pulses existing in the head of the modulated square wave signal are integrated and accumulated to obtain a positive error signal; In the case where the intrinsic period of the fiber interferometer is greater than half of the period of the modulated square wave signal, the positive pulses existing at the head of the modulated square wave signal are integrated and accumulated to obtain a negative error signal; The positive error signal and the negative error signal are accumulated to obtain the period misalignment error signal; the error accumulation unit is a phase-detection integration circuit.

10. The method according to claim 8 or 9, wherein: The performing linear adjustment processing on the period misalignment error signal to obtain a processed period misalignment error signal includes: The period misalignment error signal is inverted; and the inverted period misalignment error signal is PID processed to obtain the processed period misalignment error signal.

11. The method according to claim 8 or 9, wherein: The performing linear adjustment processing on the period misalignment error signal to obtain a processed period misalignment error signal includes: The period misalignment error signal is subjected to PID processing; and the period misalignment error signal subjected to PID processing is subjected to inversion processing to obtain the processed period misalignment error signal.

Images