A method and system for self-compensation of ratio error of an optical fiber current transformer

Abstract

The application discloses a kind of optical fiber current transformer ratio difference error self-compensation method and system, belong to optical fiber current transformer technical field.The method is by constructing "wavelength drift→Verdet constant change and half-wave voltage change→ratio difference offset→temperature compensation", the ratio difference error caused by wavelength drift is self-compensated using temperature regulation.Specifically includes: establishing the linear model of half-wave voltage and wavelength, temperature, and the correlation model of Verdet constant and wavelength, temperature.Through real-time detection wavelength drift and ambient temperature, compensation temperature value is dynamically solved by calculation module, the temperature of phase modulator is adjusted to change half-wave voltage and Verdet constant, offset the ratio difference change caused by wavelength drift.The system does not need to add additional hardware, with the advantages of low cost, fast response, effectively improve the measurement accuracy and environmental adaptability of optical fiber current transformer, suitable for smart grid, high-voltage transmission and other scenes.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic current transformers, specifically relating to a self-compensation method and system for the ratio error of fiber optic current transformers. Background Technology

[0002] Fiber optic current transformers (FOCTs) are widely used in power systems such as smart grids, high-voltage direct current transmission, and new energy power generation due to their advantages such as high precision, resistance to electromagnetic interference, and wide dynamic range, becoming an important alternative to traditional electromagnetic current transformers. However, in actual operation, factors such as changes in ambient temperature and light source aging can cause the output wavelength of the light source to drift, which in turn causes changes in the Verdet constant in the Faraday rotation effect (the Verdet constant is inversely proportional to the square of the wavelength). Ultimately, this leads to a significant change in the ratio error (relative error) of the FOCT, seriously affecting measurement accuracy and system reliability. Traditional compensation methods are mainly divided into two categories: one is to directly stabilize the light source wavelength through hardware means (such as optical path adjustment, wavelength locking devices, etc.), but this method is costly and increases system complexity; the other is error correction based on software algorithms (such as neural networks, least squares methods, etc.), which avoids hardware modifications, but the algorithm complexity is high, the real-time performance is poor, and it relies on a large amount of experimental data for training, making it difficult to adapt to complex and changing field environments. Therefore, there is an urgent need for a low-cost, simple-to-implement, and fast-dynamic-response wavelength drift compensation method to solve this technical problem. Summary of the Invention

[0003] This invention addresses the problems existing in the prior art by providing a self-compensation method and system for the ratio difference error of fiber optic current transformers, which can achieve dynamic response, correct errors caused by wavelength drift in real time, and ensure measurement accuracy.

[0004] To solve the above technical problems, the present invention provides the following technical solution: a self-compensation method for the ratio error of an optical fiber current transformer, comprising the following steps:

[0005] S1. Establish a linear relationship model between half-wave voltage and wavelength: In the formula, It is a half-wave voltage. As a scaling factor, It is the wavelength of the incident light. This is the error constant term;

[0006] S2. Establish a model showing the inverse relationship between Verdet constant and wavelength: In the formula, It is a Verdet constant. Here, n is a constant, and n is the refractive index.

[0007] S3. Establish a linear relationship model between half-wave voltage and temperature: In the formula, As a scaling factor, For temperature, For constant terms;

[0008] S4. Establish a linear relationship model between Verdet constant and temperature: In the formula, This is the Verdet constant at standard temperature;

[0009] S5. Real-time detection of light source wavelength drift. and ambient temperature The ratio change is calculated by combining the linear relationship model of half-wave voltage and wavelength, the inverse relationship model of Verdet constant and wavelength, the linear relationship model of half-wave voltage and temperature, and the linear relationship model of Verdet constant and temperature. and temperature compensation value, by adjusting the temperature Reverse ratio change , making This achieves error compensation.

[0010] Furthermore, the aforementioned ratio difference is calculated as follows:

[0011] ,

[0012] Where N is the number of sensing rings, Here, m represents the modulation coefficient of the phase modulator, and m represents the number of bits in the digital-to-analog converter. It is a Verdet constant.

[0013] Furthermore, the aforementioned temperature compensation value is calculated based on the following relationship:

[0014] ,

[0015] in, , For the Verdet constant and half-wave voltage after wavelength shift, , For the temperature-compensated Verdet constant and half-wave voltage, , These are the Verdet constant and half-wave voltage under standard conditions.

[0016] The present invention also provides a self-compensation system for the ratio difference error of an optical fiber current transformer, for implementing the aforementioned method, comprising:

[0017] The wavelength detection module is used to detect the output wavelength of the light source in real time and acquire wavelength drift data;

[0018] Temperature sensing module is used to collect ambient temperature data from the phase modulator and sensing fiber.

[0019] The model building module is used to build linear relationship models between half-wave voltage and wavelength, inverse relationship models between Verdet constant and wavelength, linear relationship models between half-wave voltage and temperature, and linear relationship models between Verdet constant and temperature.

[0020] The temperature self-compensation calculation module is used to calculate the temperature compensation value based on the wavelength drift data detected by the wavelength detection module and the temperature data collected by the temperature sensing module, combined with the linear relationship model between half-wave voltage and wavelength, the inverse proportional relationship model between Verdet constant and wavelength, the linear relationship model between half-wave voltage and temperature, and the linear relationship model between Verdet constant and temperature.

[0021] The temperature control module is used to dynamically adjust the temperature of the phase modulator based on the compensation value output by the temperature compensation calculation module.

[0022] The verification and feedback module is used to monitor the difference after compensation in real time and provide feedback adjustments until the error stabilizes within the allowable range.

[0023] Furthermore, the aforementioned temperature regulation module achieves temperature control of the phase modulator through a thermoelectric cooler (TEC) or a heating element.

[0024] Furthermore, the aforementioned verification and feedback module adopts a closed-loop feedback mechanism. If the difference after compensation does not meet the standard, the temperature compensation value is recalculated and iteratively optimized.

[0025] Compared with the prior art, the beneficial technical effects of the present invention using the above technical solution are as follows:

[0026] The wavelength drift error self-compensation system provided by this invention achieves dynamic response through a closed-loop control chain (wavelength drift → Verdet constant change → ratio shift → temperature compensation), enabling real-time correction of errors caused by wavelength drift and ensuring measurement accuracy. Compared to traditional methods, this system requires no additional hardware (such as a wavelength locking device), and compensation is completed solely through temperature adjustment, significantly reducing system complexity and cost. Furthermore, this solution possesses excellent adaptability, capable of handling complex and changing field environments and effectively overcoming the effects of light source aging or ambient temperature fluctuations. In addition, the system's built-in verification module continuously monitors the compensation effect, ensuring long-term operational stability and reliability, thereby significantly improving the overall performance of the fiber optic current transformer. Attached Figure Description

[0027] Figure 1 This is a flowchart of a self-compensation method for the ratio difference error of an optical fiber current transformer, provided as an embodiment of the present invention.

[0028] Figure 2This is a structural block diagram of a fiber optic current transformer ratio error self-compensation system provided in an embodiment of the present invention. Detailed Implementation

[0029] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0030] In this invention, various aspects of the invention are described with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. Embodiments of the invention are not limited to those depicted in the drawings. It should be understood that the invention is implemented through any of the various concepts and embodiments described above, as well as the concepts and embodiments described in detail below, because the concepts and embodiments disclosed herein are not limited to any particular implementation. Furthermore, some aspects of the invention disclosed may be used alone or in any suitable combination with other aspects of the invention disclosed.

[0031] like Figure 1 The flowchart of a self-compensation method for the ratio error of an optical fiber current transformer according to the present invention is shown, including the following steps:

[0032] S1. Based on the theoretical formula of half-wave voltage and the wavelength dependence of each parameter of the modulator, establish a mathematical model of the half-wave voltage of the fiber optic current transformer and the center wavelength and temperature of the light source, or change the wavelength and temperature of the light source experimentally and record the corresponding half-wave voltage data, and fit the polynomial.

[0033] In this step, a linear relationship between half-wave voltage and wavelength is established. There are two methods to obtain this relationship: First, experimentally, the wavelength of the light source is changed, and the corresponding half-wave voltage values ​​are recorded. Using the experimental data, a polynomial is fitted to the relationship between half-wave voltage and wavelength to establish the relationship. Second, theoretical derivation is used. The half-wave voltage formula is derived, and fitting the half-wave voltage shows a good linear function relationship with wavelength, with a correlation coefficient reaching 0.9984. Combining experimental data fitting and theoretical derivation can mutually verify and prove the linear relationship. The linear relationship model between half-wave voltage and wavelength is constructed as follows:

[0034] ,

[0035] In the formula: It is a half-wave voltage. It is a scaling factor (positive number). It is the wavelength of the incident light. The term is the error constant, which can be seen from the formula. The half-wave voltage of the phase modulator increases with increasing temperature. The half-wave voltage and wavelength exhibit an approximately linear relationship, with a positive correlation between them. That is, as temperature increases, the half-wave voltage will also increase.

[0036] S2. Analyze the wavelength dependence of the Verdet constant in the sensing fiber and establish an inverse relationship model between the Verdet constant and the wavelength. In this step, the wavelength dependence of the Verdet constant in the sensing fiber is analyzed using dispersion theory and the Sellmeir dispersion formula: In the formula, It is a Verdet constant. Let n be a constant and n be the refractive index of the magneto-optical glass. From this formula, we can see that the Verdet constant is inversely proportional to the square of the wavelength, that is, the Verdet constant decreases as the wavelength increases.

[0037] S3. Based on the theoretical formula of half-wave voltage and the dependence of modulator parameters on temperature, half-wave voltage and temperature data are obtained experimentally, and a correlation model between half-wave voltage and temperature is established through polynomial fitting of the data:

[0038] Temperature correlation study of half-wave voltage

[0039] The electrode length L of LiNbO3 crystal changes with temperature due to thermal expansion:

[0040] ,

[0041] Where L is the electrode length. When hour, , ,Pick .

[0042] After simplification, we can obtain

[0043] ,

[0044] Between -40 and +70°C, the electrode length L changes as a quadratic function with temperature, but the change is only 0.002%, which is extremely small and has a negligible effect on the modulator half-wave voltage.

[0045] Ordinary optical refractive index of LiNbO3 crystal and very light refractive index It is relatively sensitive to temperature, and the relationship it satisfies when the incident light wavelength is 1310nm is as follows:

[0046] ,

[0047] Where T is the thermodynamic temperature, and the unit is K.

[0048] According to the literature, the refractive index of light is... It increases with increasing temperature, and when the temperature increases from -40℃ to +70℃ (233.15~343.15K), It increased by 0.62%. Therefore, when the external temperature changes, the refractive index of light... Corresponding changes will occur, and since there is a significant relationship between temperature and crystal refractive index, it will inevitably affect the phase modulator. Therefore, combining this with the half-wave voltage formula, we know that as temperature increases... If the voltage increases, the half-wave voltage will decrease.

[0049] In summary, within the temperature range of -40 to +70℃, the half-wave voltage of the phase modulator exhibits an approximately linear relationship with temperature, and the expression of its model is as follows: ,

[0050] In the formula: The scaling factor is negative, and T is the temperature. The term is the error constant, which, according to the formula, is... The half-wave voltage of the phase modulator decreases with increasing temperature. The half-wave voltage and temperature exhibit an approximately linear relationship, but they are negatively correlated; that is, as temperature increases, the half-wave voltage will decrease.

[0051] S4. The Verdet constant in sensing optical fibers is an important parameter used to measure their ability to reflect their own magnetic field. The Verdet constant, which changes with temperature, affects the measurement accuracy of fiber optic current transformers. The value of the Verdet constant changes with temperature. Further experimental methods are used to establish the Verdet constant-temperature characteristics:

[0052] The classical theoretical expression for the Verdet constant is:

[0053] ,

[0054] Where e / m is the charge-to-mass ratio of electrons. Permeability in vacuum Let λ be the wavelength of the incident light, c be the speed of light in a vacuum, and n be the wavelength of the optical fiber. The refractive index under certain conditions. From the above equation, it can be seen that the Verdet constant is related to the refractive index n of the optical fiber. Since the refractive index of the optical fiber is affected by the ambient temperature, the Verdet constant is also a function of temperature. The Verdet constant of fused fiber can be expressed as:

[0055] ,

[0056] Further simplification is performed to establish a linear relationship model between the Verdet constant and temperature:

[0057] ,

[0058] In the formula: when the ambient temperature is the standard 25°C, the Verdet constant is used. This indicates that T represents the current temperature. When the ambient temperature is a standard 25°C, the Verdet constant is typically [value missing]. Therefore, it can be seen that the relationship between the Verdet constant and temperature is approximately linear.

[0059] S5, the half-wave voltage and Verdet constant change with wavelength, and both changes cause the ratio difference to change in the same way. Simultaneously, the half-wave voltage and Verdet constant also change with temperature, and both cause the ratio difference to change in the same way with temperature. By converting temperature and wavelength into a related function, adjusting the temperature can compensate for the ratio difference error caused by wavelength drift. In the embodiment, the wavelength drift of the light source is detected in real time. and ambient temperature The ratio change is calculated by combining the linear relationship model of half-wave voltage and wavelength, the inverse relationship model of Verdet constant and wavelength, the linear relationship model of half-wave voltage and temperature, and the linear relationship model of Verdet constant and temperature. and temperature compensation value, by adjusting the temperature Reverse ratio change , making This achieves error compensation.

[0060] By establishing the characteristics between the ratio difference and half-wave voltage, Verdet constant and wavelength, and temperature, we can further analyze the relationship between wavelength and temperature influencing the ratio difference by affecting the half-wave voltage and Verdet constant.

[0061] ,

[0062] ,

[0063] In the formula: For the ratio (absolute error); This refers to the difference (relative error). These are measured values; The actual value;

[0064] Building Model Relationships: Finding T , and The relationship between (comparison and difference) is used to realize the comparison and difference. Compensation;

[0065] ,

[0066] Variable ratio: ,

[0067] In the formula: Verdet constant; N: Number of sensing loops; : Modulation coefficient of the phase modulator; m: Number of bits in the digital-to-analog converter;

[0068] Therefore, the difference is:

[0069] ,

[0070] According to the fundamental theory of the photoelectric effect, the power attenuation of a light source will cause a decrease in the center wavelength of the light source. A drift occurs; the wavelength was analyzed earlier. and temperature For Verdet constant With half-wave voltage The dependence on [something] causes changes in the ratio.

[0071] Wavelength drift causes changes in the Verdet constant and half-wave voltage, which in turn causes a change in the ratio c, resulting in a As the formula shows, increasing the wavelength increases the half-wave voltage and decreases the Verdet constant, thus decreasing the specific difference. Conversely, increasing the temperature decreases the half-wave voltage and increases the Verdet constant, thus increasing the specific difference. When wavelength drift occurs, the Verdet constant and half-wave voltage can be changed by adjusting the temperature T, thereby controlling the change in specific difference caused by wavelength drift. Compensation is performed, compensating with an equal and opposite amount. The change in ratio difference is caused by wavelength drift in the fiber optic current transformer.

[0072] When the wavelength is Become At that time, the half-wave voltage is from Become The Verdet constant is derived from Become At this point, the difference is determined by... , become ,

[0073] Right now ,

[0074] At this point, compensation is made using temperature changes; when the temperature changes from... Become At that time, the half-wave voltage is from Become The Verdet constant is derived from Become At this point, the difference is determined by... , become ,

[0075] Right now ;

[0076] make Compensation can be achieved, therefore ,

[0077] ,

[0078] ,

[0079] ,

[0080] Will ; ; ; Substituting the four formulas, we get:

[0081] ,

[0082] set up ; ; ,

[0083] We can obtain:

[0084] ,

[0085] As can be seen from the above formula, there are only two variables: wavelength. and temperature Since all other quantities are constants or fixed values, a certain functional relationship can be constructed as shown in the above equation. When wavelength drift causes a contrast difference and an error occurs, there must be a corresponding temperature. Compensate for the error caused by the difference.

[0086] In summary, the method of this application first analyzes the influence of wavelength drift and temperature change on the ratio error of the fiber optic current transformer. Through mathematical derivation, it quantitatively analyzes the influence of wavelength drift and temperature change on the ratio error of the fiber optic current transformer, explores the mapping relationship between wavelength and Verdet constant, wavelength and half-wave voltage, temperature and Verdet constant, and temperature and half-wave voltage, and constructs a compensation model for the error caused by temperature change due to wavelength drift. By adjusting the temperature, the error caused by the ratio error due to wavelength drift can be self-compensated. In this way, the ratio error caused by wavelength drift can be effectively compensated, and the measurement performance of the fiber optic current transformer can be improved.

[0087] Please see Figure 2 The diagram shows a structural block diagram of a fiber optic current transformer ratio error self-compensation system according to this application.

[0088] like Figure 2As shown, the fiber optic current transformer ratio error self-compensation system includes a wavelength detection module, a temperature sensing module, a model building module, a temperature compensation calculation module, a temperature adjustment module, and a verification and feedback module.

[0089] Wavelength detection module: configured to detect the output wavelength of the light source in real time, acquire wavelength drift data, and transmit the data to the calculation module;

[0090] Temperature sensing module is used to collect ambient temperature data from the phase modulator and sensing fiber.

[0091] The model building module is used to build linear relationship models between half-wave voltage and wavelength, inverse relationship models between Verdet constant and wavelength, linear relationship models between half-wave voltage and temperature, and linear relationship models between Verdet constant and temperature.

[0092] The temperature self-compensation calculation module is used to calculate the temperature compensation value based on the wavelength drift data detected by the wavelength detection module and the temperature data collected by the temperature sensing module, combined with the linear relationship model between half-wave voltage and wavelength, the inverse proportional relationship model between Verdet constant and wavelength, the linear relationship model between half-wave voltage and temperature, and the linear relationship model between Verdet constant and temperature. This module is configured to perform real-time calculations based on wavelength drift data and temperature data, combined with the following models:

[0093] Linear relationship model between half-wave voltage and wavelength: ,

[0094] The inverse relationship model between Verdet constant and wavelength: ,

[0095] Linear relationship model between half-wave voltage and temperature: ,

[0096] Linear relationship model between Verdet constant and temperature: ,

[0097] Using the above model, the calculation module determines the change in ratio caused by wavelength drift and solves for the corresponding temperature compensation value to achieve error compensation.

[0098] The temperature control module is used to dynamically adjust the temperature of the phase modulator based on the compensation value output by the temperature compensation calculation module.

[0099] The verification and feedback module is used to monitor the difference after compensation in real time and provide feedback adjustments until the error stabilizes within the allowable range.

[0100] While the present invention has been described above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A self-compensation method for ratio error in an optical fiber current transformer, characterized in that, The steps are as follows: S1. Establish a linear relationship model between half-wave voltage and wavelength: In the formula, It is a half-wave voltage. As a scaling factor, It is the wavelength of the incident light. This is the error constant term; S2. Establish a model showing the inverse relationship between Verdet constant and wavelength: In the formula, It is a Verdet constant. Here, n is a constant, and n is the refractive index. S3. Establish a linear relationship model between half-wave voltage and temperature: In the formula, As a scaling factor, For temperature, For constant terms; S4. Establish a linear relationship model between Verdet constant and temperature: In the formula, This is the Verdet constant at standard temperature; S5. Real-time detection of light source wavelength drift. and ambient temperature The ratio change is calculated by combining the linear relationship model of half-wave voltage and wavelength, the inverse relationship model of Verdet constant and wavelength, the linear relationship model of half-wave voltage and temperature, and the linear relationship model of Verdet constant and temperature. and temperature compensation value, by adjusting the temperature Reverse ratio change , making To achieve error compensation; The temperature compensation value is calculated based on the following formula: ， in, , For the Verdet constant and half-wave voltage after wavelength shift, , For the temperature-compensated Verdet constant and half-wave voltage, , These are the Verdet constant and half-wave voltage under standard conditions.

2. The self-compensation method for ratio error of an optical fiber current transformer according to claim 1, characterized in that, The ratio difference is calculated as follows: ， Where N is the number of sensing rings, Here, m represents the modulation coefficient of the phase modulator, and m represents the number of bits in the digital-to-analog converter. It is a Verdet constant.

3. A self-compensation system for ratio error of an optical fiber current transformer, characterized in that, include: The wavelength detection module is used to detect the output wavelength of the light source in real time and acquire wavelength drift data; Temperature sensing module is used to collect ambient temperature data from the phase modulator and sensing fiber. The model building module is used to build the linear relationship model between half-wave voltage and wavelength, the inverse proportional relationship model between Verdet constant and wavelength, the linear relationship model between half-wave voltage and temperature, and the linear relationship model between Verdet constant and temperature in the self-compensation method for ratio error of fiber optic current transformer as described in claim 1. The temperature self-compensation calculation module is used to calculate the temperature compensation value based on the wavelength drift data detected by the wavelength detection module and the temperature data collected by the temperature sensing module, combined with the linear relationship model between half-wave voltage and wavelength, the inverse proportional relationship model between Verdet constant and wavelength, the linear relationship model between half-wave voltage and temperature, and the linear relationship model between Verdet constant and temperature in the fiber optic current transformer ratio error self-compensation method described in claim 1. The temperature control module is used to dynamically adjust the temperature of the phase modulator based on the compensation value output by the temperature compensation calculation module. The verification and feedback module is used to monitor the difference after compensation in real time and provide feedback adjustments until the error stabilizes within the allowable range.

4. The fiber optic current transformer ratio error self-compensation system according to claim 3, characterized in that, The temperature control module achieves temperature control of the phase modulator through a thermoelectric cooler (TEC) or a heating element.

5. The fiber optic current transformer ratio error self-compensation system according to claim 4, characterized in that, The verification and feedback module adopts a closed-loop feedback mechanism. If the difference after compensation does not meet the standard, the temperature compensation value is recalculated and iteratively optimized.

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