High-voltage broadband pulsating direct current system and method for insulation degradation experiment

Abstract

The invention discloses a high-voltage broadband pulsating direct current system and method for an insulation degradation experiment, and relates to the technical field of voltage generators, and the method comprises the steps: obtaining three-phase current sampling values of two sides of a doubly-fed wind power plant sending-out line; and judging whether a pilot protection criterion is met or not according to the three-phase current sampling value. According to the system, superposition output of high-frequency harmonic waves and direct-current voltage can be achieved within the frequency range of 50 Hz to 2500 Hz, the limitation that traditional equipment can only generate single-frequency signals is overcome, experiment conditions closer to actual operation working conditions are provided, and comprehensive evaluation of the performance of an insulating material under multi-frequency harmonic waves is facilitated. Through the arrangement of the protection resistor and the coupling resistor, the breakdown risk caused by high-frequency signal superposition in the circuit is effectively controlled, the experiment safety is improved, and the reliability and stability of equipment under the high-voltage condition are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of voltage generators, in particular to a high-voltage, wide-frequency pulsating direct current system and method for insulation degradation experiments. Background Art

[0002] Harmonics in the DC transmission system of the power grid refer to voltage or current components with frequencies that are integer multiples of the base frequency of the power grid (50Hz) that appear during the transmission process. These harmonics are mainly caused by factors such as nonlinear loads in the power grid, power electronic equipment in the DC transmission system, and system operation. Harmonics contain many high-frequency components, which are often accompanied by related insulation problems of power equipment, which may cause accidents such as premature damage to the equipment. Therefore, studying the impact of the insulation of power equipment in the environment of power frequency superimposed high-frequency harmonics, especially the insulation life and reliability of power cables, is of great significance for timely judging the insulation status of cables, preventing accidents, and ensuring the safe and reliable operation of the power grid.

[0003] At present, there are some harmonics with a frequency range of about 50Hz to 2500Hz in the power grid operation environment. Under this condition, it becomes difficult to use experimental equipment to simultaneously generate high frequency and high voltage. For the simulation and application of this kind of waveform, domestic research mainly uses high-frequency high-voltage generators. This kind of equipment can generally only simulate and generate single-frequency voltage excitation. Compared with the waveform after the superposition of DC and high-frequency harmonics, the single harmonic frequency wave can only detect the material performance at a specific frequency in the insulation material experiment, and cannot more scientifically and appropriately reflect the role of harmonics under power frequency operation conditions in terms of material dielectric loss. Therefore, there is an urgent need for a broadband pulsating voltage waveform generator that can effectively generate high voltage. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is: how to effectively simulate the influence of broadband harmonics on the insulation performance of power equipment in an experimental environment, especially to evaluate the insulation life and reliability of power equipment such as cables under complex voltage waveforms containing power frequency and broadband high-frequency harmonics. The current experimental equipment can usually only generate high-voltage excitation of a single frequency, and it is difficult to achieve the superposition of multi-frequency harmonics in the range of 50Hz to 2500Hz, resulting in limited research on the influence of harmonics on insulation loss under power frequency conditions, and unable to fully reflect the comprehensive effect of harmonics on the insulation materials of power equipment.

[0006] In order to solve the above technical problems, the present invention provides the following technical solution: a high-voltage broadband pulsating DC system for insulation degradation experiment, which comprises the following steps:

[0007] Coupling resistor, high frequency signal generator, amplifier, transformer group, high voltage DC power supply, protection resistor and coupling capacitor.

[0008] As a preferred solution of the high-voltage, wide-frequency pulsating DC system for insulation degradation experiment described in the present invention, wherein: the coupling resistor couples the DC voltage to the output end.

[0009] The high-frequency signal generator is responsible for generating a high-frequency analog signal.

[0010] The amplifier is responsible for boosting high frequency analog signals.

[0011] The transformer group is responsible for voltage step-up.

[0012] The high-voltage DC power supply is responsible for generating DC high voltage.

[0013] The protection resistor is responsible for preventing breakdown phenomena.

[0014] The coupling capacitor is responsible for adjusting the output impedance and high frequency harmonics.

[0015] As a preferred solution of the high-voltage, wide-band pulsating DC system for insulation degradation experiments described in the present invention, the capacity of the AC transformer 1 in the transformer group is 500VA, the input is 380V, the output voltage is 25kV, and the frequency range is 50Hz-500Hz; the capacity of the AC transformer 2 is 500VA, the input is 380V, the rated output voltage is 25kV, and the frequency range is 500Hz-1000Hz; the capacity of the AC transformer 3 is 500VA, the input is 380V, the rated output voltage is 25kV, and the frequency range is 1000Hz-1500Hz; the capacity of the AC transformer 4 is 500VA, the input is 380V, the rated output voltage is 20kV, and the frequency range is 1500Hz-2500Hz.

[0016] As a preferred solution of the high-voltage, wide-frequency pulsating DC system for insulation degradation experiments described in the present invention, wherein: among the coupling capacitors, C1=12.7nF, C2=22nF, C3=42.7nF, and C4=500nF.

[0017] As a preferred solution of the high-voltage wide-frequency pulsating DC system for insulation degradation experiment described in the present invention, the high-voltage DC power supply is responsible for generating an output voltage of 50kV and an output current of 20mA.

[0018] Another object of the present invention is to provide a high-voltage broadband pulsating DC method for insulation degradation experiments, which can simulate the harmonic superposition effect under actual power grid conditions in an experimental environment by generating a broadband pulsating voltage waveform containing power frequency and multi-frequency high-frequency harmonic components, thereby comprehensively evaluating the insulation performance of cables and other power equipment. This solves the limitation that existing experimental devices can only generate single-frequency or low-frequency harmonic excitation.

[0019] In order to solve the above technical problems, the present invention provides the following technical solutions: a high-voltage broadband pulsating DC method for insulation degradation experiment, comprising:

[0020] Obtain the three-phase current sampling values ​​on both sides of the doubly-fed wind farm transmission line.

[0021] Determine whether the three-phase current sampling values ​​meet the longitudinal protection criteria.

[0022] As a preferred solution of the high-voltage, wide-frequency pulsating DC method for insulation degradation experiment described in the present invention, the longitudinal protection criterion includes a start-up criterion and an in-zone and out-of-zone fault identification criterion.

[0023] The start-up criterion includes that when three consecutive sampling values ​​of any phase current or zero-sequence current meet any one of the start-up criterion, the protection is started and the corresponding protection action is performed, otherwise the protection is reset.

[0024] As a preferred solution of the high-voltage, wide-frequency, pulsating DC system for insulation degradation experiments described in the present invention, the in-zone and out-of-zone fault identification criteria include: after the current sampling data in the data window is transmitted to the opposite protection device through the communication channel, the protection devices on both sides respectively use the current sampling data on both sides to calculate the Wasserstein distance of each phase current.

[0025] Determine whether the Wasserstein distance result meets the internal and external fault criteria. If so, it is determined to be an internal fault and a trip command is sent. Otherwise, it is determined to be an external fault and protection restoration is executed.

[0026] A computer device comprises a memory and a processor, wherein the memory stores a computer program and the processor implements the steps of the high-voltage, wide-frequency pulsating direct current method for insulation degradation experiment as described above when executing the computer program.

[0027] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the high-voltage, wide-frequency, pulsating direct current method for insulation degradation experiments as described above.

[0028] Beneficial effects of the present invention: The system can realize the superposition output of high-frequency harmonics and DC voltage in the frequency range of 50Hz to 2500Hz, overcome the limitation that traditional equipment can only generate single frequency signals, provide experimental conditions closer to actual operating conditions, and help to comprehensively evaluate the performance of insulating materials under multi-frequency harmonics. By setting protection resistors and coupling resistors, the breakdown risk caused by the superposition of high-frequency signals in the circuit is effectively controlled, the safety of the experiment is improved, and the reliability and stability of the equipment under high-voltage conditions are ensured. The system adopts four AC transformer groups, covering a wide frequency range of 50Hz to 2500Hz. Each group of transformers has a specific frequency band range, which ensures the accuracy and diversity of the output signal and avoids the deficiency that a single device cannot cover the full frequency band, thereby simulating the harmonic environment more accurately. The setting of coupling capacitors (C1=12.7nF, C2=22nF, C3=42.7nF, C4=500nF) can not only perform impedance matching, but also effectively adjust and control the distribution of high-frequency harmonics, thereby stabilizing the output signal, further enhancing the controllability of the experiment and the reliability of the data. Combined with the current sampling value of the doubly-fed wind farm, the longitudinal protection criteria can be used to identify faults inside and outside the area, quickly determine the insulation status, and provide reliable protection measures. The startup criteria and fault identification criteria ensure accurate protection of power equipment under wide-band and high-voltage conditions, help to quickly discover and handle potential faults, and reduce the risk of insulation failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0030] Figure 1 A schematic diagram of the current flow of various functional components in a high-voltage, wide-frequency pulsating DC system for insulation degradation experiments provided in the first embodiment of the present invention.

[0031] Figure 2 A physical diagram of a high-voltage, wide-frequency pulsating DC system for insulation degradation experiments provided in accordance with the second embodiment of the present invention.

[0032] Figure 3 An overall flow chart of a high voltage, wide frequency, pulsating DC method for insulation degradation experiments provided in accordance with the second embodiment of the present invention.

[0033] Figure 4 The output result of the high-voltage, wide-frequency pulsating DC system used for insulation degradation experiment provided by the third embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0035] Example 1, reference Figure 1-2 , which is an embodiment of the present invention, provides a high voltage broadband pulsating DC system for insulation degradation experiment, characterized in that:

[0036] like Figure 1 As shown, the system includes a coupling resistor, a high-frequency signal generator, an amplifier, a transformer group, a high-voltage DC power supply, a protection resistor and a coupling capacitor.

[0037] like Figure 2 Shown is a physical picture of this system.

[0038] The coupling resistor couples the DC voltage to the output.

[0039] The high frequency signal generator is responsible for generating high frequency analog signals.

[0040] Amplifiers are responsible for boosting high-frequency analog signals.

[0041] The transformer group is responsible for stepping up the voltage.

[0042] The high voltage DC power supply is responsible for generating DC high voltage.

[0043] The protection resistor is responsible for preventing breakdown.

[0044] The coupling capacitor is responsible for adjusting the output impedance and high-frequency harmonics.

[0045] The capacity of AC transformer 1 in the transformer group is 500VA, the input is 380V, the output voltage is 25kV, and the frequency range is 50Hz-500Hz. The capacity of AC transformer 2 is 500VA, the input is 380V, the rated output voltage is 25kV, and the frequency range is 500Hz-1000Hz. The capacity of AC transformer 3 is 500VA, the input is 380V, the rated output voltage is 25kV, and the frequency range is 1000Hz-1500Hz. The capacity of AC transformer 4 is 500VA, the input is 380V, the rated output voltage is 20kV, and the frequency range is 1500Hz-2500Hz.

[0046] Among the coupling capacitors, C1=12.7nF, C2=22nF, C3=42.7nF, and C4=500nF.

[0047] The high voltage DC power supply is responsible for generating an output voltage of 50kV and an output current of 20mA.

[0048] Example 2, reference Figure 3 , as one embodiment of the present invention, provides a method for a high voltage broadband pulsating DC system for insulation degradation experiment, characterized in that:

[0049] S1: Obtain the three-phase current sampling values ​​on both sides of the doubly-fed wind farm transmission line.

[0050] This method first obtains the three-phase current sampling values ​​on both sides of the transmission line of the doubly-fed wind farm, and uses the adaptive sampling rate technology to automatically increase the sampling frequency when a current mutation or power fluctuation occurs, ensuring that the data sampling at the critical fault moment is more accurate. In addition, by introducing a dynamic filtering algorithm, interference noise is removed in real time to enhance the reliability of the sampled data.

[0051] S2: Determine whether the three-phase current sampling values ​​meet the longitudinal protection criteria.

[0052] This method uses intelligent judgment logic to determine whether the longitudinal protection criteria are met, including the following two modules: startup criteria and in-zone and out-of-zone fault identification criteria.

[0053] Start criteria

[0054] The startup criterion of the present invention innovatively combines continuous sampling with machine learning algorithms. When three consecutive sampling values ​​of any phase current or zero-sequence current meet any of the startup criteria, the protection will start immediately. If the continuous sampling values ​​do not meet the startup conditions, the protection state will be restored. In addition, a machine learning model based on historical data is introduced to dynamically adjust the startup threshold and sampling frequency through an adaptive algorithm, further improving the startup sensitivity of the system under different working conditions.

[0055] In-zone and out-zone fault identification criteria

[0056] The in-zone and out-of-zone fault identification criterion of the present invention proposes a fault identification method based on multi-dimensional data fusion, including current sampling data within a time window and real-time communication channel transmission data, to enhance the accuracy and real-time performance of fault identification. The method includes the following steps:

[0057] The protection devices on both sides synchronously receive the current sampling data on their respective sides and transmit the data to the protection device on the other side through a dedicated communication channel. The multi-data source fusion technology is used to achieve real-time synchronization of the current sampling data of each phase, avoiding the impact of communication delay on fault identification.

[0058] The present invention proposes an improved dynamic distance calculation method, which not only considers the current amplitude, but also combines the current phase and waveform characteristics to ensure accurate calculation of the distance of each phase current under various power operation conditions. If the distance calculation result meets the internal and external fault judgment criteria, the system immediately determines it as an internal fault and sends a trip command; otherwise, it is determined as an external fault and executes protection restoration.

[0059] Adaptive identification of fault types: By inputting the sampled data into the fault type classification model, the system can automatically identify different fault types (such as short circuit, open circuit, etc.), and automatically select the most suitable protection action and reclosing strategy in the execution of the tripping command, thereby reducing the fault recovery time and the risk of secondary impact.

[0060] The present invention also introduces a self-learning module, which automatically optimizes the longitudinal protection criteria based on past fault data and equipment operating status data. Through the deep learning algorithm, the thresholds of the startup criteria and the in-zone and out-of-zone fault identification criteria are gradually adjusted, so that the protection system can adapt to the changes in the operating environment of the power grid and the aging of the equipment, thereby improving the accuracy and timeliness of the criteria.

[0061] After the fault identification is completed, the present invention will start the intelligent alarm system, send alarm information to the operation and maintenance personnel in real time, and upload key data to the cloud database through the remote diagnosis system. The operation and maintenance personnel can view the fault location, type and corresponding protection action in real time through the visualization platform, providing a scientific basis for subsequent fault analysis and maintenance.

[0062] In summary, the present invention realizes the intelligentization and precision of protection actions such as current sampling, fault identification, and tripping decision by introducing adaptive sampling, machine learning, dynamic distance calculation, and self-learning modules, ensuring the efficient operation and reliability of the double-fed wind farm transmission line in a wide-band harmonic environment. This innovative method provides the power grid with higher stability and risk resistance, and fills the technical deficiencies of traditional protection systems in complex operating environments.

[0063] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program code.

[0064] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0065] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0066] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0067] Example 3: In this example, in order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments. In the method for building a high-voltage broadband pulsating DC system for insulation degradation experiments in the present invention, the following functions can be finally achieved: the input voltage is 50Hz, 380V three-phase AC. The output voltage is a single-phase DC superimposed harmonic voltage: U=U0+U n ·sin 2πf n t. Among them, the harmonic frequency f n 50Hz-2500Hz adjustable, harmonic voltage U n 0-25kV adjustable, DC voltage U00-50kV adjustable, such as Figure 4 shown.

[0068] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A high voltage, wide frequency, pulsating DC system for insulation degradation experiments, characterized in that: include: Coupling resistor, high frequency signal generator, amplifier, transformer group, high voltage DC power supply, protection resistor and coupling capacitor.

2. The high voltage, wide frequency, pulsating DC system for insulation degradation test according to claim 1, characterized in that: The coupling resistor couples the DC voltage to the output terminal; The high-frequency signal generator is responsible for generating a high-frequency analog signal; The amplifier is responsible for enhancing high-frequency analog signals; The transformer group is responsible for voltage boosting; The high-voltage DC power supply is responsible for generating DC high voltage; The protection resistor is responsible for preventing breakdown; The coupling capacitor is responsible for adjusting the output impedance and high frequency harmonics.

3. The high voltage, wide frequency, pulsating DC system for insulation degradation test according to claim 2, characterized in that: The capacity of AC transformer 1 in the transformer group is 500VA, the input is 380V, the output voltage is 25kV, and the frequency range is 50Hz-500Hz. The capacity of AC transformer 2 is 500VA, the input is 380V, the rated output voltage is 25kV, and the frequency range is 500Hz-1000Hz. The capacity of AC transformer 3 is 500VA, the input is 380V, the rated output voltage is 25kV, and the frequency range is 1000Hz-1500Hz. The capacity of AC transformer 4 is 500VA, the input is 380V, the rated output voltage is 20kV, and the frequency range is 1500Hz-2500Hz.

4. The high voltage, wide frequency, pulsating DC system for insulation degradation test according to claim 3, characterized in that: Among the coupling capacitors, C1=12.7nF, C2=22nF, C3=42.7nF, and C4=500nF.

5. The high voltage, wide frequency, pulsating DC system for insulation degradation test according to claim 4, characterized in that: The high voltage DC power supply is responsible for generating an output voltage of 50 kV and an output current of 20 mA.

6. A method for using the high voltage wide frequency pulsating DC system for insulation degradation test as claimed in any one of claims 1 to 5, characterized in that: include: Obtain the three-phase current sampling values ​​on both sides of the double-fed wind farm transmission line; Determine whether the three-phase current sampling values ​​meet the longitudinal protection criteria.

7. The high voltage, wide frequency, pulsating direct current method for insulation degradation test according to claim 6, characterized in that: The longitudinal protection criterion includes a start-up criterion and an in-zone and out-of-zone fault identification criterion; The start-up criterion includes that when three consecutive sampling values ​​of any phase current or zero-sequence current meet any one of the start-up criterion, the protection is started and the corresponding protection action is performed, otherwise the protection is reset.

8. The method of the high voltage wide frequency pulsating DC system for insulation degradation test according to claim 7, characterized in that: The fault identification criteria for the zone include: after the current sampling data in the data window is transmitted to the opposite protection device through the communication channel, the protection devices on both sides respectively use the current sampling data on both sides to calculate the Wasserstein distance of each phase current; Determine whether the Wasserstein distance result meets the internal and external fault criteria. If so, it is determined to be an internal fault and a trip command is sent. Otherwise, it is determined to be an external fault and protection restoration is executed.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the high-voltage, wide-frequency, pulsating DC system for insulation degradation experiment described in any one of claims 6 to 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the high-voltage, wide-frequency, pulsating DC system for insulation degradation experiments described in any one of claims 6 to 8 are implemented.

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