Simulation Model and Simulation Test Method of All-Fiber Optic Current Transformer

Abstract

A simulation model and simulation testing method for an all-fiber optic current transformer are disclosed. The simulation model includes: a fiber sensing module, a phase modulator module, a photodetector module, a filter module, a signal demodulation module, an integrator module, and a closed-loop feedback module. Using the simulation model and simulation testing method provided by this invention, the transmission performance of the all-fiber optic current transformer can be tested by inputting different current signals. This simulation model can analyze the influence of multiple parameters on the frequency characteristics of the all-fiber optic current transformer and system optimization issues such as the joint tuning of multiple parameters, providing strong guidance for the selection of hardware for harmonic measurement in all-fiber optic current transformers.

Description

Technical Field

[0001] This invention relates to the field of intelligent device simulation technology, and more specifically, to a simulation model and simulation testing method for an all-fiber current transformer. Background Technology

[0002] As power systems develop towards higher voltage and larger capacity, the proportion of ultra-high voltage (UHV) transmission lines is increasing, leading to a rise in lightning strike accidents. The resulting transient high-frequency components can easily cause malfunctions in the protection systems of high-voltage direct current (HVDC) transmission lines. Accurate measurement of transient current is fundamental and a prerequisite for surge arrester design. Traditional electromagnetic current transformers have limitations such as small dynamic range and waveform distortion, which can lead to serious consequences such as maloperation or failure to operate in line relay protection and transformer protection systems based on differential measurement of instantaneous current values.

[0003] With social development and progress, new power systems based on new energy sources are widely used. The large number of power electronic devices connected to the power grid has led to increasingly serious problems with the safe and stable operation of the grid caused by power harmonics. Accurate measurement of high-frequency current waveforms is crucial for research on system control and protection. However, traditional current transformers, due to limitations in their operating principles, are technically unable to meet the harmonic measurement requirements of these new power systems.

[0004] As the primary sensor for acquiring analog information in DC engineering control and protection systems, the operational reliability of DC current transformers directly affects the safety and stability of the power grid. The all-fiber optic current transformer (FOCT) is a novel electronic current transformer based on the Faraday magneto-optical effect. Compared with traditional electromagnetic current transformers, it offers advantages such as high measurement accuracy, large dynamic range, simple insulation structure, good electromagnetic compatibility, and flexible installation.

[0005] All-fiber current transformers are important primary equipment in DC transmission systems, and their structure contains a large number of optical and electronic components. In actual engineering operation, all-fiber current transformers are susceptible to the effects of external factors such as temperature and the aging of internal optical and electronic components, which can lead to deterioration of their measurement performance or even failure, seriously affecting the safe and stable operation of the converter station.

[0006] Current research on the frequency characteristics of all-fiber current transformers mainly focuses on analyzing the transfer function and bandwidth, neglecting the analysis of factors affecting system response speed. Therefore, it is necessary to build upon existing research to study the dynamic simulation model of all-fiber current transformers and analyze the factors influencing system response speed.

[0007] Currently, there are two main approaches to studying the frequency characteristics of all-fiber current transformers. One approach is to treat the optical path and circuit as equivalent and establish a transfer function model. Since the optical path is the main cause of measurement error in FOCT, noise and nonlinearity of electronic components in the circuit are often ignored during modeling and analysis. The transfer function model of FOCT can be equivalent to a first-order inertial system. By using the transfer function of a linear system, its dynamic response characteristics and steady-state characteristics, including frequency response characteristics, can be analyzed.

[0008] Another approach is to experimentally study the frequency characteristics. This usually involves building a prototype of the FOCT in the laboratory, measuring the output of the FOCT under different frequency inputs, and obtaining the frequency characteristics of the FOCT based on the input-output characteristics.

[0009] The frequency characteristics of FOCT obtained by the current two research schemes on the frequency characteristics of all-fiber current transformers are equivalent to treating FOCT as a completely linear system. They cannot reflect the output response of FOCT to input currents of different frequencies under small current conditions, and can only reflect the frequency characteristics of FOCT to a certain extent.

[0010] Research on the frequency characteristics of FOCT mainly focuses on the accuracy of power frequency and low frequency measurements, and pays attention to the working stability and error compensation of optical path and optical devices. It ignores the influence of noise and nonlinear factors in the circuit. Due to experimental limitations, current experimental research on the frequency characteristics of FOCT can only reflect the transmission characteristics of large current to a certain extent, and cannot comprehensively evaluate the frequency characteristics of FOCT. Summary of the Invention

[0011] In view of this, the present invention proposes a simulation model and simulation test method for an all-fiber current transformer, aiming to solve the problem that the existing technology cannot fully evaluate the frequency characteristics of the all-fiber current transformer.

[0012] In a first aspect, embodiments of the present invention provide a simulation model of an all-fiber current transformer. The simulation model is used to test the transmission performance of the all-fiber current transformer and includes: an optical fiber sensing module for receiving a current signal to be measured, converting the current signal into a Faraday phase shift of a light beam for measurement, obtaining and transmitting the Faraday phase shift; a phase modulator module for modulating the Faraday phase shift and transmitting the modulated optical signal, and applying a feedback phase shift to the current Faraday phase shift based on the transmission characteristic signal fed back by a closed-loop feedback module; and a photodetector module for converting the modulated optical signal into an electrical signal and transmitting... The system includes: a conversion module for transmitting the converted electrical signal; a filtering module for de-DC processing the converted electrical signal and transmitting the de-DC processed signal; a signal demodulation module for demodulating the useful signal from the de-DC processed signal and transmitting the useful signal; an integration module for accumulating the useful signal to obtain and output a transmission characteristic signal for analyzing the transmission characteristics of the all-fiber current transformer for time-domain and frequency-domain signals, and for sending the transmission characteristic signal to a closed-loop feedback module; and a closed-loop feedback module for feeding back the transmission characteristic signal to the phase modulator module so that the simulation model always operates at the 0-phase point.

[0013] Furthermore, the integration module is also used to send the transmission characteristic signal to the D / A module. The simulation model further includes: a preamplifier module, used to amplify the DC-DC-de-processed signal with low noise and then send it to the A / D module; an A / D module, used to convert the low-noise amplified signal into a digital signal and then send it to the signal demodulation module; and a D / A module, used to convert the transmission characteristic signal into an electrical signal and then send it to the closed-loop feedback module.

[0014] Furthermore, the simulation model also includes a noise module for simulating noise factors in an all-fiber current transformer.

[0015] Further, the measurement of the Faraday phase shift of the beam is converted from the measured current signal, including: obtaining the Faraday phase shift based on the measured current signal using the following formula: Where N is the number of turns of the fiber optic ring, V is the Wilder constant of the optically active medium, and I is the current signal to be measured.

[0016] Furthermore, the fiber optic sensing module is also used to: adjust the Wilder constant to simulate the transmission performance of the all-fiber current transformer when the temperature changes.

[0017] Furthermore, the Faraday phase shift is modulated by using a periodic square wave signal to process the Faraday phase shift by ±π / 2.

[0018] Furthermore, the phase modulator module is also used to: adjust the frequency of the square wave signal to simulate the transmission performance of the all-fiber current transformer when the frequency of the square wave signal changes.

[0019] Further, the modulated optical signal is converted into an electrical signal, including: converting the modulated optical signal into an electrical signal based on the following formula: Where K is the optical path loss coefficient, P i To output light intensity from the light source, For the Faraday effect phase shift, For feedback phase shift.

[0020] Furthermore, the current signal to be measured includes: steady-state power frequency current signal, transient current signal, impulse current signal and / or step current signal.

[0021] Furthermore, the transmission characteristics include: amplitude error, phase error, simulation model bandwidth, and / or simulation model response time.

[0022] Secondly, embodiments of the present invention also provide a simulation testing method for an all-fiber current transformer, wherein the simulation testing method utilizes the simulation model provided in each embodiment to simulate and test the transmission performance of the all-fiber current transformer.

[0023] The simulation model and simulation testing method for an all-fiber optic current transformer provided in this invention include an optical fiber sensing module, a phase modulator module, a photodetector module, a filtering module, a signal demodulation module, an integration module, and a closed-loop feedback module. The model can test the transmission performance of the all-fiber optic current transformer by inputting different current signals. It can analyze the influence of multiple parameters on the frequency characteristics of the all-fiber optic current transformer and system optimization issues such as the joint tuning of multiple parameters. This provides strong guidance for the selection of hardware for measuring harmonics in all-fiber optic current transformers. Furthermore, the model can also discover potential major quality hazards in all-fiber optic current transformers through simulation, which is of great significance for improving power grid safety. Attached Figure Description

[0024] Figure 1 A schematic diagram of the structure of a simulation model of an all-fiber current transformer according to an embodiment of the present invention is shown;

[0025] Figure 2 A schematic diagram of the equivalent simulation model of an all-fiber current transformer according to another embodiment of the present invention is shown;

[0026] Figure 3 A schematic diagram of the structure of an all-fiber current transformer according to another embodiment of the present invention is shown;

[0027] Figure 4The steady-state test results of the simulation model according to an embodiment of the present invention are shown in the figure.

[0028] Figure 5 A transient test result diagram of the simulation model according to an embodiment of the present invention is shown. Detailed Implementation

[0029] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0030] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0031] Figure 1 A schematic diagram of the structure of a simulation model of an all-fiber current transformer according to an embodiment of the present invention is shown.

[0032] like Figure 1 As shown, this simulation model is used to test the transmission performance of an all-fiber current transformer, including:

[0033] The fiber optic sensing module 101 is used to receive the current signal to be measured, convert the current signal to be measured into the Faraday phase shift of the beam for measurement, and send the Faraday phase shift to the phase modulator module 102.

[0034] The phase modulator module 102 is used to modulate the Faraday phase shift and send the modulated optical signal to the photodetector module 103, and to apply a feedback phase shift to the current Faraday phase shift based on the transmission characteristic signal fed back by the closed-loop feedback module.

[0035] The photodetector module 103 is used to convert the modulated optical signal into an electrical signal and send it to the filter module 104.

[0036] The filtering module 104 is used to de-DC process the electrical signal sent by the photodetector module before sending it to the signal demodulation module 105;

[0037] The signal demodulation module 105 is used to demodulate the useful signal from the signal after DC removal and send the useful signal to the integration module 106.

[0038] The integration module 106 is used to accumulate the useful signal, obtain and output the transmission characteristic signal for analyzing the transmission characteristics of the all-fiber current transformer for time-domain and frequency-domain signals, and to send the transmission characteristic signal to the closed-loop feedback module 107.

[0039] The closed-loop feedback module 107 is used to feed back the transmission characteristic signal to the phase modulator module 102 so that the simulation model always works at the 0 phase point.

[0040] Specifically, the all-fiber current transformer is the Sagnac reflective all-fiber current transformer.

[0041] Figure 2 A schematic diagram of the equivalent simulation model of an all-fiber current transformer according to another embodiment of the present invention is shown.

[0042] like Figure 2 As shown, the simulation model includes:

[0043] The fiber optic sensing module 201 is used to receive the current signal to be measured, convert the current signal to be measured into the Faraday phase shift of the beam for measurement, obtain and send the Faraday phase shift;

[0044] The phase modulator module 202 is used to modulate the Faraday phase shift and send the modulated optical signal, as well as to apply a feedback phase shift to the current Faraday phase shift based on the transmission characteristic signal fed back by the closed-loop feedback module 210.

[0045] The photodetector module 203 is used to convert the modulated optical signal into an electrical signal and send the converted electrical signal.

[0046] The filter module 204 is used to perform DC-DC de-processing on the converted electrical signal and send the DC-DC de-processed signal.

[0047] The preamplifier module 205 is used to amplify the DC-de-DC processed signal with low noise before sending it to the A / D module 206.

[0048] A / D module 206 is used to convert the low-noise amplified signal into a digital signal and send it to signal demodulation module 207;

[0049] The signal demodulation module 207 is used to demodulate the useful signal from the converted digital signal and transmit the useful signal.

[0050] The integration module 208 is used to accumulate the useful signal, obtain and output the transmission characteristic signal for analyzing the transmission characteristics of the all-fiber current transformer for time-domain and frequency-domain signals, and to send the transmission characteristic signal to the D / A module.

[0051] D / A module 209 is used to convert the transmission characteristic signal into an electrical signal and send it to the closed-loop feedback module;

[0052] The closed-loop feedback module 210 is used to feed back the transmission characteristic signal converted into an electrical signal to the phase modulator module 202 so that the simulation model always works at the 0 phase point.

[0053] Figure 3 A schematic diagram of an all-fiber current transformer according to another embodiment of the present invention is shown. Figure 2 To and Figure 3 The equivalent simulation model of the corresponding all-fiber current transformer. For example... Figure 2 As shown, the fiber optic sensing module simulates the sensing part of an all-fiber optic current transformer. The photodetector module simulates not only the physical detector structure but also other parts of the optical path besides the sensing structure. The filtering module removes DC components from the detected signal that are irrelevant to the desired Faraday phase shift, facilitating subsequent processing. The signal demodulation module demodulates the useful signal from the noisy actual signal. Since the useful signal changes regularly while the noise signal is random, coherent demodulation can be used to demodulate the system input signal. The closed-loop feedback module adds a feedback phase shift equal in magnitude and opposite in direction to the current Faraday phase shift, ensuring the simulation model system always operates at the 0-phase point, maximizing sensitivity and effectively improving the system's linearity and measurement range.

[0054] Furthermore, the simulation model also includes:

[0055] Noise module used to simulate the noise factor in an all-fiber current transformer.

[0056] The noise module can use a Gaussian white noise module to simulate the noise factors that may exist in the electronic components of the all-fiber current transformer, such as the noise of electronic components such as photodetectors, preamplifiers, and AD components.

[0057] Furthermore, the measured current signal is converted into a Faraday phase shift of the light beam for measurement, including:

[0058] Based on the current signal to be measured, the Faraday phase shift is obtained using the following formula:

[0059]

[0060] Where N is the number of turns of the fiber optic ring, V is the Wilder constant of the optically active medium, and I is the current signal to be measured.

[0061] Furthermore, the fiber optic sensing module is also used for:

[0062] The Wilder constant was adjusted to simulate the transmission performance of the all-fiber current transformer under temperature variations.

[0063] The fiber optic sensing module is a Simulink simulation model built based on mathematical formulas of the Faraday effect and Ampere's circuital law. It is used to convert the current signal to be measured into the Faraday phase shift of the light beam for measurement. The magnitude of the generated Faraday phase shift is:

[0064]

[0065] In the formula: V represents the Wilder constant of the optically active medium, A vector representing magnetic field strength. Let L represent a linear element along the path of light propagation, and let L represent the total path length of light propagation in the medium.

[0066] The magnitude of the magnetic flux density at the sensing fiber loop is:

[0067]

[0068] Where: μ0 is the vacuum permeability, I is the current signal to be measured, and R is the radius of the sensing fiber loop;

[0069] Combining the two formulas above, we obtain the relationship between the magnitude of the Faraday phase shift and the input current as follows:

[0070]

[0071] In the formula: N is the number of turns of the fiber optic ring.

[0072] Because temperature changes affect the Wilder constant of optical fiber, the impact of parameter variations caused by temperature on the transmission performance of an all-fiber current transformer can be simulated by adjusting the Wilder constant in real time. The Wilder constant of the sensing fiber is affected by ambient temperature and the center wavelength of the light source as follows:

[0073]

[0074] In the formula: V0 is the initial Wilder constant of the sensing fiber, K ΔT ΔT is the temperature coefficient of the sensing fiber, ΔT is the change in ambient temperature, Δλ is the change in center wavelength, and λ0 is the initial center wavelength of the light source.

[0075] Furthermore, the Faraday phase shift is modulated, including:

[0076] The Faraday phase shift is processed by ±π / 2 using a periodic square wave signal.

[0077] The system uses a periodic square wave signal to modulate the input signal, and processes the Faraday phase shift by ±π / 2 to change the system's static operating point and improve system sensitivity.

[0078] Furthermore, the phase modulator module is also used for:

[0079] The frequency of the square wave signal is adjusted to simulate the transmission performance of the all-fiber current transformer when the frequency of the square wave signal changes.

[0080] The phase modulator module can adjust the frequency of the modulated square wave in real time to simulate the impact of changes in the modulated square wave frequency on the transmission performance of the all-fiber current transformer. The magnitude of the modulated square wave frequency is related to the transit time τ of the optical fiber in the sensing fiber, and the transit time τ is:

[0081]

[0082] Where: n l L is the refractive index of the optical fiber; L is the length of the optical fiber; C is the speed of light in a vacuum, C = 3 × 10⁻⁶. 8 m / s.

[0083] Further, the modulated optical signal is converted into an electrical signal, including:

[0084] The modulated optical signal is converted into an electrical signal based on the following formula:

[0085]

[0086] Where K is the optical path loss coefficient, P i To output light intensity from the light source, For the Faraday effect phase shift, For feedback phase shift.

[0087] The photodetector module is structurally an integration of a photodiode and an amplifier. The mathematical relationship between the light intensity signal detected by the photodetector and the Faraday rotation angle is derived based on the Jones matrix, and the relationship is as follows:

[0088]

[0089] In the formula: K is the optical path loss coefficient, P i To output light intensity from the light source, For the Faraday effect phase shift, For feedback phase shift.

[0090] Furthermore, the current signal to be measured includes: steady-state power frequency current signal, transient current signal, impulse current signal and / or step current signal.

[0091] Furthermore, the transmission characteristics include: amplitude error, phase error, simulation model bandwidth, and / or simulation model response time.

[0092] The simulation model also includes an oscilloscope, which is used to receive the current signal under test and the output transmission characteristic signal, and display them in real time.

[0093] The input current signal to be measured can be one type of current signal, or two or more types of current signals. Figure 4 and Figure 5 Steady-state test results and transient test results of the simulation model according to an embodiment of the present invention are shown respectively. It can be seen that... Figure 4 and Figure 5 The input current signals to be measured are steady-state power frequency current signal and impulse current signal, respectively. The output transmission characteristic signal can be one type, or two or more types.

[0094] The above embodiments provide a simulation model of an all-fiber optic current transformer, which can simulate the output characteristics of the all-fiber optic current transformer and test its transmission performance by inputting different current signals. This simulation model can analyze the influence of multiple parameters on the frequency characteristics of the all-fiber optic current transformer and system optimization issues such as the joint adjustment between multiple parameters. It provides strong guidance for the selection of hardware for measuring harmonics in all-fiber optic current transformers. Furthermore, the model can also discover potential major quality hazards in all-fiber optic current transformers through simulation, which is of great significance for improving power grid safety.

[0095] This invention also provides a simulation testing method for an all-fiber current transformer, which uses the simulation model provided in the above embodiments to simulate and test the transmission performance of the all-fiber current transformer.

[0096] By setting specific parameters of the simulation model and associating them with the relevant parameters of the target all-fiber current transformer, the transmission performance of the all-fiber current transformer can be tested by inputting different current signals. Based on the simulation model, different parameters can be adjusted to discover and analyze the influence of relevant factors on the frequency characteristics of the all-fiber current transformer. This allows for the simulation of the performance of the target all-fiber current transformer and improves the accuracy of high-frequency and small-amplitude current measurements.

[0097] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0098] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

[0099] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0100] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0101] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0102] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A simulation model of an all-fiber current transformer, characterized in that, The simulation model is used to test the transmission performance of the all-fiber current transformer, including: The fiber optic sensing module is used to receive the current signal to be measured, convert the current signal to be measured into the Faraday phase shift of the light beam for measurement, obtain and send the Faraday phase shift; The phase modulator module is used to modulate the Faraday phase shift and send the modulated optical signal, as well as to apply a feedback phase shift to the current Faraday phase shift based on the transmission characteristic signal fed back by the closed-loop feedback module. A photodetector module is used to convert the modulated optical signal into an electrical signal and to send the converted electrical signal. The filtering module is used to perform DC-DC de-DC processing on the converted electrical signal and send the DC-DC de-DC processed signal. The signal demodulation module is used to demodulate the useful signal from the DC-de-processed signal and transmit the useful signal. An integration module is used to accumulate the useful signal, obtain and output a transmission characteristic signal for analyzing the transmission characteristics of the all-fiber current transformer for time-domain and frequency-domain signals, and to send the transmission characteristic signal to a closed-loop feedback module. A closed-loop feedback module is used to feed back the transmission characteristic signal to the phase modulator module so that the simulation model always works at the 0 phase point; The simulation model further includes: Noise module, used to simulate the noise factor in an all-fiber current transformer; The process of converting the current signal under test into a Faraday phase shift of a light beam for measurement includes: Based on the measured current signal, the Faraday phase shift is obtained using the following formula: ； in, N This represents the number of turns in the fiber optic ring. V For optically active media, the Wilder constant is given. I The signal is the current to be measured. The fiber optic sensing module is further used for: The Wilder constant is adjusted to simulate the transmission performance of the all-fiber current transformer under temperature changes.

2. The simulation model according to claim 1, characterized in that, The integration module is also used to send the transmission characteristic signal to the D / A module, and the simulation model further includes: The preamplifier module is used to amplify the DC-DC-de-processed signal with low noise before sending it to the A / D module; The A / D module is used to convert the low-noise amplified signal into a digital signal and then send it to the signal demodulation module. The D / A module is used to convert the transmission characteristic signal into an electrical signal and then send it to the closed-loop feedback module.

3. The simulation model according to claim 1, characterized in that, Modulation processing of the Faraday phase shift includes: The Faraday phase shift is performed using a periodic square wave signal. The processing.

4. The simulation model according to claim 3, characterized in that, The phase modulator module is also used for: The frequency of the square wave signal is adjusted to simulate the transmission performance of the all-fiber current transformer when the frequency of the square wave signal changes.

5. The simulation model according to claim 1, characterized in that, Converting the modulated optical signal into an electrical signal includes: The modulated optical signal is converted into an electrical signal based on the following formula: ； in, K This is the optical path loss coefficient. P i To output light intensity from the light source, For the Faraday effect phase shift, For feedback phase shift.

6. The simulation model according to any one of claims 1-5, characterized in that, The current signal to be measured includes: steady-state power frequency current signal, transient current signal, impulse current signal and / or step current signal.

7. The simulation model according to any one of claims 1-5, characterized in that, The transmission characteristics include: amplitude error, phase error, simulation model bandwidth, and / or simulation model response time.

8. A simulation test method for an all-fiber optic current transformer, characterized in that, The simulation test method uses the simulation model described in any one of claims 1-7 to simulate and test the transmission performance of the all-fiber current transformer.

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