Converter station optical CT maloperation prevention method and system based on frequency spectrum energy

Abstract

The invention provides a frequency spectrum energy-based converter station optical CT maloperation prevention method and system. The method comprises the following steps of: S1, acquiring real-time unbalanced current data on a line in real time; s2, the starting unit judges whether the three-phase unbalanced current characteristic quantity is larger than a current starting threshold value or not; if not, entering S3; otherwise, returning to S1; s3, the locking unit performs frequency spectrum energy difference calculation on adjacent windows in each phase according to a preset time interval; s4, if a plurality of continuous frequency spectrum energy differences of one phase are all smaller than a three-phase unbalanced current frequency spectrum energy difference threshold value, entering S5; if not, the locking unit acts, the protection is locked, and the step S1 is returned; and S5, the locking unit does not act, the protection unit sends out a signal, and protection measures are started. Through spectrum energy analysis, fault signals can be accurately identified, misoperation is reduced, the reliability of a protection system is improved, and the method has good applicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical CT operation status control and monitoring, and in particular relates to a method and system for preventing misoperation of an optical CT in a converter station based on spectrum energy. Background Art

[0002] The converter station is a key facility in the HVDC transmission system. Its main function is to convert AC to DC or DC to AC to meet the safety, stability and power quality requirements of the power system. In recent years, with the continuous improvement of the voltage level of HVDC transmission, the number and capacity of power equipment in the converter station have continued to increase, and the protection requirements for the converter station have become higher and higher. With the rapid growth of economic strength and the rapid development of the power industry, the widespread application of UHVDC transmission technology has put forward higher requirements for the reliability of power equipment. With the continuous expansion and upgrading of the power grid, the expectations for relay protection systems are also gradually increasing. The power industry's requirements for relay protection systems are gradually increasing with the continuous expansion and upgrading of the power grid. The power transmission and fault detection of the power grid face more stringent requirements in the rapid development of modern industry, which poses new challenges to traditional high-voltage and high-current measurement methods. In recent years, optical current transformers (optical CTs) have been widely used in power system relay protection to meet the requirements for high-precision current measurement, and have faster response speeds and wider measurement ranges.

[0003] The application of optical CT has gradually become a key means to improve the reliability of relay protection systems. Its excellent safety in high voltage environments is also one of the reasons for its popularity. The requirements for the reliability and measurement accuracy of optical CT in power systems are also increasing with the continuous development of technology. This reflects the urgent need for the power industry to meet the needs of efficient, safe and sustainable operation, and actively adopt innovative technologies to improve overall performance and reliability when meeting future challenges. Optical CT is different from other electrical equipment. Due to the presence of sensing optical fiber and optical circuit, the transmitted signal of optical CT is easily distorted by the natural aging of semiconductor optoelectronic devices and the temperature, humidity and vibration changes in the on-site operating environment. According to the actual on-site engineering, the optical CT measurement data is transmitted to the protection unit through a longer optical fiber. The three-phase polarization-maintaining optical fiber transmission of optical CT is relatively close. When the environment is disturbed or the same vibration source exists, its waveform will be severely distorted and mostly irregular. Unlike line faults, the waveforms of the three-phase unbalanced currents of A, B, and C are quite different, and there will be phase differences.

[0004] When an AC filter fails, its three-phase unbalanced current has a phase difference, but its frequency is always equal. However, after being disturbed by the environment, the AC filter optical CT output waveform has no fixed frequency, and its frequency at each moment is different. In actual engineering, when an AC filter fails, the three-phase unbalanced current is transmitted to the protection unit through optical fiber. When the amplitude of these unbalanced currents exceeds the set protection threshold, the AC filter protection device will act. However, when the transmission optical fiber is disturbed by the environment, the transmission signal may be distorted, resulting in an increase in the amplitude of the three-phase unbalanced current received by the protection unit, causing the protection to malfunction. The existing AC filter controls it through a control algorithm and then performs a protection action. However, when the current AC filter is subjected to environmental disturbances, it may cause frequency instability and signal distortion of the AC filter, resulting in insufficient accuracy and effectiveness of its control, which may affect the stability of the protection system. Summary of the invention

[0005] The present invention provides a method and system for preventing false operation of an optical CT in a converter station based on spectrum energy, aiming to solve the problem that the current AC filter may cause frequency instability and signal distortion when responding to environmental disturbances, resulting in insufficient accuracy and effectiveness of its control, which may affect the stability of the protection system.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] The present invention provides a method for preventing malfunction of an optical CT in a converter station based on spectrum energy, which is characterized by comprising the following steps:

[0008] S1, real-time collection of three-phase unbalanced current at the AC filter end to obtain real-time unbalanced current data on the line;

[0009] S2, the starting unit presets the current starting threshold value. The starting unit determines whether the three-phase unbalanced current characteristic quantity is greater than the current starting threshold value based on the real-time unbalanced current data on the line; if it is greater than or equal to the current starting threshold value, enter S3; otherwise return to S1;

[0010] S3, the starting unit sends the real-time unbalanced current data on the line to the locking unit, and the locking unit calculates the spectrum energy difference of adjacent windows in each phase according to a preset time interval to obtain spectrum capacity difference data;

[0011] S4, the locking unit sets the three-phase unbalanced current spectrum energy difference threshold. If the continuous spectrum energy differences of one phase are all less than the three-phase unbalanced current spectrum energy difference threshold, then enter S5; if not, the locking unit will be activated to protect the lock and return to S1;

[0012] S5. The locking unit does not operate, and the protection unit sends a signal to start protection.

[0013] In some implementations, in S1 , the three-phase unbalanced current at the AC filter end is collected in real time through a current transformer.

[0014] Furthermore, in S2, a preset current starting threshold value of the starting unit is calculated according to the following formula (1):

[0015] I set =K C I max (1);

[0016] Among them, I set is the preset current starting threshold value, K C is the current setting factor, I max It is the maximum value of the three-phase unbalanced current under normal operation.

[0017] Further, in S2, the starting unit determines whether the three-phase unbalanced current characteristic quantity is greater than the current starting threshold value according to the following formula (2):

[0018] I(t)>I set (2);

[0019] Among them, I(t) is the characteristic quantity of three-phase unbalanced current.

[0020] In some embodiments, in S3, the three-phase unbalanced current spectrum energy difference threshold is calculated by the following formula (3):

[0021] M set =KM max (3);

[0022] Among them, M set is the three-phase unbalanced current spectrum energy difference threshold, K is the distance setting coefficient, M max It is the maximum value of the spectrum energy difference between two adjacent windows of the three-phase unbalanced current of the optical CT under fault conditions.

[0023] In some implementations, in S3, the locking unit collects unbalanced currents in real time at a preset time before and after the starting unit is started.

[0024] Furthermore, in S3, the locking unit performs window processing on the real-time unbalanced current data on the line. During the window processing, the locking unit divides the real-time unbalanced current data on the line into sliding windows with a preset time interval as a window and a preset time as a sliding step.

[0025] Furthermore, in S4, the locking unit first performs Fourier transform on the waveform between two adjacent windows in each phase, obtains the main frequency components in each window, and calculates the frequency energy; and then calculates the spectrum energy difference by subtracting the frequency energy between the two windows.

[0026] In some implementations, in S4, the signal waveform in each window is analyzed using Fourier transform, specifically as follows:

[0027]

[0028] Among them, X(k) is the window spectrum after Fourier transformation, and x(n) is the original signal of the window;

[0029] Calculate the spectrum energy. The spectrum energy is calculated as follows:

[0030]

[0031] Where, E is the spectrum energy;

[0032] Perform difference processing on the spectrum energy difference between two adjacent windows.

[0033] The present invention also provides a system for preventing misoperation of optical CT in a converter station based on spectrum energy, the system comprising a current acquisition module, a current start determination module and a protection control module; wherein:

[0034] The current acquisition module is used to collect the three-phase unbalanced current at the AC filter end in real time through the current transformer, and obtain the real-time unbalanced current data on the line;

[0035] The current start judgment module is used to judge whether the three-phase unbalanced current characteristic quantity is greater than the current start threshold value based on the real-time unbalanced current data on the line, and then choose to continue to collect the unbalanced current data in real time or send the real-time unbalanced current data on the line to the locking unit;

[0036] The protection control module is used to calculate the spectrum capability difference data, and to determine whether the control locking unit is actuated, and then choose to continue to collect unbalanced current data in real time or to start protection measures.

[0037] Compared with the prior art, the method and system for preventing misoperation of optical CT in a converter station based on spectrum energy of the present invention have the following beneficial effects:

[0038] The present invention discloses a method for preventing misoperation of an optical CT in a converter station based on spectrum energy, comprising the following steps: S1, real-time acquisition of three-phase unbalanced current at an AC filter end to obtain real-time unbalanced current data on the line; S2, a starting unit presets a current starting threshold value, and the starting unit determines whether a characteristic quantity of the three-phase unbalanced current is greater than the current starting threshold value based on the real-time unbalanced current data on the line; if greater than or equal to, then enter S3; otherwise, return to S1; S3, the starting unit sends the real-time unbalanced current data on the line to a locking unit, and the locking unit calculates the spectrum energy difference for adjacent windows in each phase according to a preset time interval to obtain spectrum capability difference data; S4, the locking unit sets a three-phase unbalanced current spectrum energy difference threshold value, and if a plurality of continuous spectrum energy differences of one phase meet the requirement of being less than the three-phase unbalanced current spectrum energy difference threshold value, then enter S5; if not, the locking unit acts to lock the protection and returns to S1; S5, the locking unit does not act, and the protection unit sends a signal to start the protection. Based on the above, the present invention aims to prevent the AC filter protection from malfunctioning due to the environmental disturbance of the optical CT. When the AC filter fails, the waveform of the three-phase unbalanced current will show a phase difference, but the frequency remains equal. When the optical CT of the AC filter is disturbed by the environment, the current waveform output by it will lose its fixed frequency, showing that the frequency at each moment is different. The fault data is processed by windowing, and when the frequencies of adjacent windows are the same, it is considered that the AC filter fault occurs at this time, and the protection needs to be activated at this time. When the frequencies of adjacent windows are greatly different, it is considered that the transmission optical fiber is disturbed by the environment at this time. The present invention uses a locking unit to identify the abnormal output of the optical CT under forced vibration conditions, thereby distinguishing whether the system has failed. When the transmission optical fiber is disturbed by the environment, the locking unit can accurately identify and lock the protection in time. Through spectrum energy analysis, the present invention can more accurately identify fault signals, reduce the possibility of malfunction, improve the accuracy and reliability of the protection system, and can timely and accurately identify and isolate faults, which is helpful to maintain the stable operation of the power system and reduce the risk of system fluctuations and power outages caused by malfunctions. The automated monitoring and analysis process improves the operation and maintenance efficiency and reduces the operation and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0040] Figure 1 A schematic diagram of a method for preventing misoperation of an optical CT in a converter station based on spectrum energy and a flow chart of the method in the system of the present invention;

[0041] Figure 2It is a schematic diagram of the principle of a method for preventing misoperation of an optical CT in a converter station based on spectrum energy and a method in a system of the present invention;

[0042] Figure 3 A schematic diagram of a method for preventing malfunction of an optical CT in a converter station based on spectrum energy and waveforms of three unbalanced currents of the optical CT under forced vibration conditions in the system according to the present invention;

[0043] Figure 4 A method for preventing malfunction of an optical CT in a converter station based on spectrum energy of the present invention and a schematic diagram of a three-phase unbalanced current waveform of an optical CT in a system under an AC filter fault;

[0044] Figure 5 A schematic diagram of the spectrum of adjacent windows under forced conditions in a method for preventing malfunction of an optical CT in a converter station based on spectrum energy of the present invention and a system;

[0045] Figure 6 The present invention provides a method for preventing malfunction of an optical CT in a converter station based on spectrum energy and a schematic diagram of adjacent window spectra under AC filter fault in the system. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0049] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0050] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0051] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] How to provide an algorithm that is accurate and has a short calculation time, which can make the converter station protection action reliable and ensure the safe and reliable operation of the converter station AC filter.

[0053] like Figure 1 , Figure 2 and Figure 3 As shown, the present invention provides a method for preventing malfunction of an optical CT in a converter station based on spectrum energy, comprising the following steps:

[0054] S1, real-time collection of three-phase unbalanced current at the AC filter end to obtain real-time unbalanced current data on the line;

[0055] S2, the starting unit presets the current starting threshold value. The starting unit determines whether the three-phase unbalanced current characteristic quantity is greater than the current starting threshold value based on the real-time unbalanced current data on the line; if it is greater than or equal to the current starting threshold value, enter S3; otherwise return to S1;

[0056] S3, the starting unit sends the real-time unbalanced current data on the line to the locking unit, and the locking unit calculates the spectrum energy difference of adjacent windows in each phase according to a preset time interval to obtain spectrum capacity difference data;

[0057] S4, the locking unit sets the three-phase unbalanced current spectrum energy difference threshold. If the continuous spectrum energy differences of one phase are all less than the three-phase unbalanced current spectrum energy difference threshold, then enter S5; if not, the locking unit will be activated to protect the lock and return to S1;

[0058] S5. The locking unit does not operate, and the protection unit sends a signal to start protection.

[0059] In the method of the present invention, when the optical CT transmission fiber of the converter station AC filter is disturbed, the protection device can be accurately identified and locked; the frequency distribution of the three-phase unbalanced quantity can be accurately identified, and the spectrum differences of adjacent windows can be distinguished; the rapid response requirements of the protection device can be met. The method of the present invention has high accuracy and high calculation efficiency, which can improve the accuracy of the converter station protection action and ensure the reliability of the converter station AC filter.

[0060] Specifically, as an important component of AC filters, high-voltage capacitors are prone to failure due to insulation material breakdown or degradation caused by overvoltage and voltage fluctuations, overheating caused by long-term operation or excessive ambient temperature, dielectric breakdown or damage caused by current shock, adverse effects of environmental humidity, pollution and salt spray on insulation performance, loosening or damage of internal connection parts caused by mechanical stress, aging effects over time, defects in the manufacturing process, and improper maintenance or lack of regular inspections. These factors make high-voltage capacitors face a higher risk of failure during operation. The reason why AC filters need to be equipped with optical CT protection is that optical CT has high precision and anti-electromagnetic interference capabilities, can accurately measure current, and needs to promptly identify and lock abnormal outputs caused by environmental disturbances to prevent misoperation and ensure the safe and stable operation of the filter and the overall system.

[0061] In a specific embodiment, the present invention uses a current transformer (CT) as a sensor to collect the three-phase current at the AC filter end in real time, and obtain the three-phase unbalanced current data by calculation. The current transformer can reflect the current changes in real time to ensure the timeliness and accuracy of the data. The current transformer has high measurement accuracy and can accurately reflect the true value of the current.

[0062] like Figure 2 As shown, the circuit system based on the present invention is mainly divided into a merging unit, a starting unit, a locking unit and a protection unit. The merging unit is an important component in the power protection system, responsible for receiving unbalanced current signals from three phases A, B and C. The merging unit fuses the electrical signals transmitted by the three phases and outputs the three-phase unbalanced current to the protection unit, using the transmission optical fiber to achieve fast and lossless transmission of the signal.

[0063] The protection unit of the present invention has a built-in start unit, which is used to determine whether the magnitude of the unbalanced current of the three phases A, B, and C reaches the set start threshold value. If the unbalanced current reaches the preset threshold value, the start unit will immediately send a signal to the locking unit to trigger the subsequent protection mechanism. If the unbalanced current does not reach the threshold value, the protection unit will continue to measure the magnitude of the three-phase unbalanced current to ensure continuous monitoring and accurate analysis.

[0064] In some embodiments, after receiving the signal from the start-up unit, the locking unit of the present invention will immediately collect the unbalanced current 20ms before and 20ms after the start-up unit is started in real time. The locking unit performs window processing on the 40ms data to more accurately analyze the current change. During the window processing, the locking unit divides the 40ms data into sliding windows with 10ms as a window and 1ms as a sliding step to ensure detailed and accurate data analysis.

[0065] The locking unit will perform spectrum energy difference analysis on each phase. First, perform Fourier transform on the waveform between two adjacent windows of each phase, obtain the main frequency components in each window, and calculate its frequency energy. The spectrum energy difference is determined by calculating the frequency energy difference between the two windows. When the energy difference is small, it indicates that the frequency difference between adjacent windows is small. At this time, an AC filter failure may have occurred, and the protection unit will take protection action; when the energy difference is large, it indicates that the spectrum difference between adjacent windows is large. At this time, it is believed that it is caused by environmental disturbances in the transmission optical fiber. The locking unit will take locking action, and the protection unit will not act to ensure that the system does not malfunction.

[0066] Based on the above method, the present invention also provides a system for preventing misoperation of optical CT in a converter station based on spectrum energy, the system comprising a current acquisition module, a current start determination module and a protection control module; wherein:

[0067] The current acquisition module is used to collect the three-phase unbalanced current at the AC filter end in real time through the current transformer, and obtain the real-time unbalanced current data on the line; the current start judgment module is used to judge whether the three-phase unbalanced current characteristic quantity is greater than the current start threshold value based on the real-time unbalanced current data on the line, and then choose to continue to collect the unbalanced current data in real time or send the real-time unbalanced current data on the line to the locking unit; the protection control module is used to calculate the spectrum capability difference data, and by judging whether the control locking unit is actuated, it is selected to continue to collect the unbalanced current data in real time or start the protection measures. The present invention realizes a fully automated process from data acquisition to fault identification through the collaborative work of various modules, improves the system's integration and automation level, and improves the quality of operation and maintenance.

[0068] In some embodiments, the present invention calculates the preset current startup threshold value of the startup unit according to the following formula (1):

[0069] I set =K C I max (1);

[0070] Among them, I set is the preset current starting threshold value, K C is the current setting factor, I max It is the maximum value of the three-phase unbalanced current under normal operation.

[0071] Further, in S2, the starting unit determines whether the three-phase unbalanced current characteristic quantity is greater than the current starting threshold value according to the following formula (2):

[0072] I(t)>I set (2);

[0073] Among them, I(t) is the characteristic quantity of three-phase unbalanced current.

[0074] The present invention determines whether to enter the subsequent analysis process by determining whether the characteristic quantity of the three-phase unbalanced current is greater than the current starting threshold value, and can quickly determine whether the current is abnormal, providing timely data support for the subsequent spectrum energy analysis. In actual working conditions, the present invention can flexibly set the starting threshold value according to the actual operating conditions by adjusting the current setting coefficient, thereby improving the adaptability and flexibility of the system. Reasonable setting of the starting threshold value helps to reduce false alarms caused by non-fault factors and improve reliability.

[0075] In some embodiments, the three-phase unbalanced current spectrum energy difference threshold of the present invention is calculated by the following formula (3):

[0076] M set =KM max (3);

[0077] Among them, M set is the three-phase unbalanced current spectrum energy difference threshold, K is the distance setting coefficient, M max It is the maximum value of the spectrum energy difference between two adjacent windows of the three-phase unbalanced current of the optical CT under fault conditions.

[0078] The present invention calculates the three-phase unbalanced current spectrum energy difference threshold value, which is based on the maximum value of the spectrum energy difference between two adjacent windows of the optical CT three-phase unbalanced current under the fault state and the distance setting coefficient. Through spectrum energy difference analysis, the fault signal can be identified more accurately and the accuracy of the protection action can be improved.

[0079] like Figure 5 and 6As shown, in some embodiments, the present invention first uses Fourier transform to analyze the signal waveform in each window, as shown in the following formula (4):

[0080]

[0081] Among them, X(k) is the window spectrum after Fourier transformation, and x(n) is the original signal of the window;

[0082] The present invention then calculates the spectrum energy, and the spectrum energy E of each window shows the energy distribution of the signal at each frequency. The high-energy frequency component plays a leading role in the formation of the signal, while the low-energy frequency component has a smaller impact. The specific calculation formula of the spectrum energy E is as follows: t <M set

[0083]

[0084] Perform difference processing on the spectrum energy difference between two adjacent windows.

[0085] The present invention utilizes 40ms data points, where 5 consecutive spectrum energy differences are all less than the set threshold. At this time, the AC filter is determined to be faulty and the protection device is activated. If the above conditions are not met, the locking unit is locked and the protection does not operate.

[0086] The present invention performs window processing on real-time unbalanced current data, calculates the spectrum energy of each window using Fourier transform, and calculates the spectrum energy difference between adjacent windows. If several consecutive spectrum energy differences are less than a preset threshold, it is judged that there is no fault; otherwise, the protection measures are activated. The spectrum energy analysis of the present invention can reflect the changing characteristics of the current signal more finely, improve the accuracy of fault identification, and through spectrum analysis, can effectively filter out noise and interference signals, and improve anti-interference ability.

[0087] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the specification and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A method for preventing malfunction of optical CT in a converter station based on spectrum energy, characterized in that: The steps include: S1, real-time collection of three-phase unbalanced current at the AC filter end to obtain real-time unbalanced current data on the line; S2, the starting unit presets the current starting threshold value. The starting unit determines whether the three-phase unbalanced current characteristic quantity is greater than the current starting threshold value based on the real-time unbalanced current data on the line; if it is greater than or equal to the current starting threshold value, enter S3; Otherwise return to S1; S3, the starting unit sends the real-time unbalanced current data on the line to the locking unit, and the locking unit calculates the spectrum energy difference of adjacent windows in each phase according to a preset time interval to obtain spectrum capacity difference data; S4, the locking unit sets the three-phase unbalanced current spectrum energy difference threshold. If the continuous spectrum energy differences of one phase are all less than the three-phase unbalanced current spectrum energy difference threshold, then enter S5; if not, the locking unit will be activated to protect the lock and return to S1; S5. The locking unit does not operate, and the protection unit sends a signal to start protection.

2. The method for preventing malfunction of converter station optical CT based on spectrum energy according to claim 1 is characterized in that: In S1, the three-phase unbalanced current at the AC filter end is collected in real time through the current transformer.

3. The method for preventing malfunction of converter station optical CT based on spectrum energy according to claim 1, characterized in that: In S2, the preset current starting threshold value of the starting unit is calculated according to the following formula (1): I set =K C I max (1); Among them, I set is the preset current starting threshold value, K C is the current setting factor, I max It is the maximum value of the three-phase unbalanced current under normal operation.

4. The method for preventing malfunction of converter station optical CT based on spectrum energy according to claim 3 is characterized in that: In S2, the starting unit determines whether the three-phase unbalanced current characteristic quantity is greater than the current starting threshold value according to the following formula (2): I(t)>I set (1); Among them, I(t) is the characteristic quantity of three-phase unbalanced current.

5. The method for preventing malfunction of converter station optical CT based on spectrum energy according to claim 1, characterized in that: In S3, the three-phase unbalanced current spectrum energy difference threshold is calculated by the following formula (2): M set =KM max (2); Among them, M set is the three-phase unbalanced current spectrum energy difference threshold, K is the distance setting coefficient, M max It is the maximum value of the spectrum energy difference between two adjacent windows of the three-phase unbalanced current of the optical CT under fault conditions.

6. The method for preventing malfunction of converter station optical CT based on spectrum energy according to claim 1, characterized in that: In S3, the locking unit collects the unbalanced current in real time at a preset time before and after the starting unit is started.

7. The method for preventing malfunction of converter station optical CT based on spectrum energy according to claim 6, characterized in that: In S3, the locking unit performs window processing on the real-time unbalanced current data on the line. During the window processing, the locking unit divides the real-time unbalanced current data on the line into sliding windows with a preset time interval as a window and a preset time as a sliding step.

8. The method for preventing malfunction of converter station optical CT based on spectrum energy according to claim 7, characterized in that: In S4, the locking unit first performs Fourier transform on the waveform between two adjacent windows in each phase to obtain the main frequency components in each window and calculate the frequency energy; then subtracts the frequency energy between the two windows to calculate the spectrum energy difference.

9. The method for preventing malfunction of converter station optical CT based on spectrum energy according to claim 1, characterized in that: In S4, the signal waveform in each window is analyzed using Fourier transform, specifically as follows: Among them, X(k) is the window spectrum after Fourier transformation, and x(n) is the original signal of the window; Calculate the spectrum energy. The spectrum energy is calculated as follows: Where, E is the spectrum energy; Perform difference processing on the spectrum energy difference between two adjacent windows.

10. A system based on the method for preventing misoperation of optical CT in a converter station based on spectrum energy as described in any one of claims 1 to 9, characterized in that: The system includes a current acquisition module, a current start determination module and a protection control module; wherein: The current acquisition module is used to collect the three-phase unbalanced current at the AC filter end in real time through the current transformer, and obtain the real-time unbalanced current data on the line; The current start determination module is used to determine whether the three-phase unbalanced current characteristic quantity is greater than the current start threshold value based on the real-time unbalanced current data on the line, and then choose to continue to collect the unbalanced current data in real time or send the real-time unbalanced current data on the line to the locking unit; The protection control module is used to calculate the spectrum capability difference data, and to determine whether the control locking unit is actuated, and then to choose to continue to collect the unbalanced current data in real time or to start the protection measures.

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