Ultralow-frequency sine high-voltage generator

Abstract

The utility model provides an ultralow-frequency sine high-voltage generator. The ultralow-frequency sine high-voltage generator comprises a flyback switching power supply circuit, an ultralow-frequency signal generator and a cascade linear amplification circuit, the flyback switching power supply circuit comprises a driving circuit, a switching device and a reaction isolation transformer. The driving circuit is connected with the switching device, the switching device is connected with the counterattack isolation transformer, and the driving circuit drives the switching device to be regularly switched on and off to form a square wave signal to be output to the rectification side of the counterattack isolation transformer; the counterattack isolation transformer is also connected with the cascade linear amplification circuit and supplies power to the cascade linear amplification circuit; according to the technical scheme, electrical isolation and cascade linear amplification of ultralow-frequency sinusoidal signals can be achieved, and a foundation is laid for research of a high-voltage cable ultralow-frequency dielectric loss device.

Description

Technical Field

[0001] This utility model relates to the field of high-voltage electrical testing technology, and in particular to an ultra-low frequency sinusoidal high-voltage generator. Background Technology

[0002] Ultra-low frequency dielectric loss testing technology for high-voltage cables is a non-destructive testing method for evaluating the insulation performance of cables. As a new type of non-destructive diagnostic technology, it has advantages such as low applied voltage, convenient operation, strong anti-interference ability, accurate information acquisition, and no damage to insulation materials.

[0003] The energy loss of cable insulation materials due to conductivity and polarization under alternating electric fields is called dielectric loss, which is an important indicator for evaluating insulation performance. In engineering, the dielectric loss tangent (tan φ) under ultra-low frequency 0.1Hz sinusoidal voltage excitation is often used. δ The overall insulation thermal aging, moisture absorption, and water treeing degradation characteristics of XLPE cables were evaluated. δ The higher the value, the worse the insulation performance. However, due to the small insulation margin of high-voltage cables, applying excessively high ultra-low frequency voltages can lead to the risk of space charge injection accumulation. Furthermore, there is a lack of testing equipment development and insulation condition assessment criteria. As a result, this technology has not yet been applied in 110 kV and above high-voltage cable lines in China. The technical specifications of products from foreign brands such as B2, Megger, and Baur also focus on medium and low voltage cables, with few application cases in high-voltage cables.

[0004] With the increase in urban power supply and offshore wind power capacity, the use of high-voltage cables has surged, becoming the lifeline of the power grid. Research on ultra-low frequency dielectric loss measurement methods and devices for high-voltage cables, and the assessment of their aging conditions, to accurately determine the aging status of in-service XLPE cables, is of great significance for clean energy transmission and improving the reliability of power supply systems. Current high-voltage cable ultra-low frequency dielectric loss detection devices lack a mechanism capable of providing stable power supply and reliable ultra-low frequency signal transmission to the dielectric loss measurement device. Utility Model Content

[0005] In view of this, the purpose of this utility model is to provide an ultra-low frequency sinusoidal high voltage generator that can realize electrical isolation and cascaded linear amplification of ultra-low frequency sinusoidal signals, ensuring safe, stable and reliable output of linear sinusoidal high voltage ultra-low frequency signals, and laying the foundation for the research of ultra-low frequency dielectric loss devices for high voltage cables.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an ultra-low frequency sinusoidal high voltage generator, comprising a flyback switching power supply circuit, an ultra-low frequency signal generator, and a cascaded linear amplifier circuit;

[0007] The flyback switching power supply circuit includes a drive circuit, a switching device, and a flyback isolation transformer. The drive circuit is connected to the switching device, and the switching device is connected to the flyback isolation transformer. The drive circuit drives the switching device to switch regularly to form a square wave signal, which is output to the rectifier side of the flyback isolation transformer. The flyback isolation transformer is also connected to the cascaded linear amplifier circuit to supply power to the cascaded linear amplifier circuit.

[0008] The ultra-low frequency signal generator includes a low-voltage side main control chip, an optical fiber transmitter, a high-voltage side main control chip, and an optical fiber receiver. The low-voltage side main control chip is connected to the optical fiber transmitter, the optical fiber transmitter is connected to the optical fiber receiver through an optical fiber channel, and the optical fiber receiver is connected to the high-voltage side main control chip. The low-voltage side main control chip outputs sinusoidal waveform data to the optical fiber transmitter and converts the electrical signal into an optical signal for transmission to the optical fiber receiver. The optical fiber receiver converts the optical signal back into an electrical signal for transmission to the high-voltage side main control chip.

[0009] The cascaded linear amplifier circuit includes six operational amplifiers. The cascaded linear amplifier circuit amplifies the signal received by the high-voltage side main control chip and outputs a 0-50kV high voltage.

[0010] In a preferred embodiment, the primary winding of the counter-current isolation transformer is provided with one set; each set is provided with 8-15 turns of enameled wire.

[0011] In a preferred embodiment, the secondary winding of the counter-current isolation transformer is provided with four sets; each set of secondary windings is provided with three units, which are respectively provided with 3-6 turns of enameled wire and 8-15 turns of enameled wire.

[0012] In a preferred embodiment, the backflash isolation transformer is connected to an RCD spike absorption circuit; the RCD spike absorption circuit includes a transient suppression diode, a resistor, a capacitor, and a diode; the transient suppression diode, resistor, and capacitor are connected in parallel, and the negative terminal of the diode is connected to one end of the resistor.

[0013] In a preferred embodiment, both the low-voltage side main control chip and the high-voltage side main control chip are STM32F103VET6 chips.

[0014] In a preferred embodiment, all operational amplifiers are OPA454 operational amplifiers.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The use of flyback isolation transformers and ultra-low frequency signal fiber optic communication achieves electrical isolation between the high and low voltage ends, ensuring safe and efficient power supply and stable and reliable ultra-low frequency signal transmission.

[0017] 2. The cascaded linear amplifier circuit structure can not only achieve good linearity, but also output ultra-low frequency sinusoidal signals with higher voltage amplitude through multi-unit cascading.

[0018] 3. This ultra-low frequency sinusoidal high voltage generator can apply ultra-low frequency detection technology to equipment of 110 kV and above high voltage cables, and has the characteristics of independent and controllable technology and domestic production capability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of an ultra-low frequency sinusoidal high voltage generator according to a preferred embodiment of the present invention;

[0020] Figure 2 This is a flowchart illustrating the operation of an ultra-low frequency sinusoidal high voltage generator, which is a preferred embodiment of the present invention.

[0021] Figure 3 This is a circuit diagram of a flyback switching power supply for an ultra-low frequency sinusoidal high voltage generator, which is a preferred embodiment of the present invention.

[0022] Figure 4 This invention provides a preferred embodiment of the UF80 magnetic core for an ultra-low frequency sinusoidal high voltage generator, with physical images and a schematic diagram of the core dimensions in mm.

[0023] Figure 5 This is a diagram of the transformer winding of an ultra-low frequency sinusoidal high voltage generator according to a preferred embodiment of the present invention.

[0024] Figure 6 This is a schematic diagram of the RCD spike absorption circuit of an ultra-low frequency sinusoidal high voltage generator according to a preferred embodiment of the present invention.

[0025] Figure 7 This is a schematic diagram illustrating the generation and transmission of low-frequency signals in an ultra-low frequency sinusoidal high-voltage generator according to a preferred embodiment of the present invention.

[0026] Figure 8 This is a schematic diagram of a cascaded linear amplifier circuit for an ultra-low frequency sinusoidal high voltage generator, which is a preferred embodiment of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0029] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] An ultra-low frequency sinusoidal high voltage generator, reference Figure 1-8 This includes a flyback switching power supply circuit, an ultra-low frequency signal generator, and a cascaded linear amplifier circuit.

[0031] The flyback switching power supply circuit includes a drive circuit, a switching device, and a flyback isolation transformer. The drive circuit is connected to the switching device, and the switching device is connected to the flyback isolation transformer. The drive circuit drives the switching device to switch regularly to form a square wave signal, which is output to the rectifier side of the flyback isolation transformer. The flyback isolation transformer is also connected to the cascaded linear amplifier circuit to supply power to the cascaded linear amplifier circuit. The switching device is specifically a MOS switch.

[0032] The ultra-low frequency signal generator includes a low-voltage side main control chip, an optical fiber transmitter, a high-voltage side main control chip, and an optical fiber receiver. The low-voltage side main control chip is connected to the optical fiber transmitter, the optical fiber transmitter is connected to the optical fiber receiver through an optical fiber channel, and the optical fiber receiver is connected to the high-voltage side main control chip. The low-voltage side main control chip outputs sinusoidal waveform data to the optical fiber transmitter and converts the electrical signal into an optical signal for transmission to the optical fiber receiver. The optical fiber receiver converts the optical signal back into an electrical signal for transmission to the high-voltage side main control chip.

[0033] The cascaded linear amplifier circuit includes six operational amplifiers, which amplify the signal received by the high-voltage side main control chip.

[0034] refer to Figure 2The working process of an ultra-low frequency sinusoidal high-voltage generator is as follows: A DC power supply is used as the input source. The input DC signal is converted into a square wave signal for output through the switching function of a MOSFET. The switching function of the MOSFET is implemented using a drive circuit. Changing the duty cycle of the drive circuit adjusts the duty cycle of the square wave output signal, thereby adjusting the output amplitude. A flyback isolation transformer outputs the square wave signal to the rectifier side according to the turns ratio. After diode rectification, the final output is a DC voltage used to power the operational amplifier devices in the cascaded linear amplifier circuit. Adjusting the duty cycle changes the output voltage amplitude. The flyback isolation transformer completes the tasks of energy transfer and isolation between different voltage levels throughout the entire process. The amplitude and frequency of the ultra-low frequency signal are set. The signal generation module outputs the ultra-low frequency signal and completes the conversion from electrical signal to optical signal. This signal is then transmitted through an optical fiber channel to the high-voltage cascaded linear amplifier circuit, where it is amplified to a specified factor.

[0035] Specifically, a flyback switching power supply is used as the power supply circuit. The secondary and primary sides of the flyback switching power supply share a single magnetic core, with corresponding terminals facing each other. The basic schematic diagram is as follows. Figure 3 As shown. The flyback switching power supply mainly achieves energy conversion and transfer through the inductive characteristics of the flyback isolation transformer TB and the switching characteristics of the switching device T. The switching device T is an IRBUGG30PBF type MOSFET, which can quickly switch the circuit under the control of the drive signal, has a drain-source voltage of 1000 V, and can carry a maximum current of 3.1 A. The MOSFET drive circuit is implemented using the IR2113 driver chip. If the duty cycle of the drive signal is too large, it will cause instability in the control circuit; if it is too small, it will cause the MOSFET to withstand too large an impulse voltage, which may break down the MOSFET. The duty cycle selected in the design is 0.4.

[0036] The flyback isolation transformer uses a UF80 core, and the core structure is as follows: Figure 4 As shown. The magnetic material selected is DMR40 manganese-zinc high-permeability ferrite, which has high permeability, low remanence, high saturation flux density, and a high Curie temperature.

[0037] The final design of the flyback isolation transformer winding connection is as follows: Figure 5 As shown, the transformer's primary winding has 8-15 turns, and the enameled wire diameter is 0.7mm. The secondary winding has four sets, as shown... Figure 5 As shown, one set consists of 3-6 turns, 8-15 turns, and 8-15 turns, with an enameled wire diameter of 0.5mm. The 3-6 turn coil powers the ultra-low frequency receiving module, and the 8-15 turn coil powers the high-voltage amplifier circuit.

[0038] Specifically, the designed flyback isolation transformer has a stable output voltage during normal operation. However, during the switching process, the transformer's leakage inductance creates a freewheeling circuit, resulting in voltage spikes in the transformer waveform. Excessive voltage spikes can damage the switching devices, thus requiring a spike suppression circuit. The designed RCD snubber circuit effectively suppresses backlash voltage and signal oscillations, without affecting the normal operation of the switching devices. The circuit structure is as follows: Figure 6 As shown.

[0039] Specifically Figure 7 This diagram illustrates the control of the high and low voltage sides of an ultra-low frequency (ULF) signal. In the ULF signal generator, the low-voltage side uses an STM32F103VET6 as the main control chip, and a corresponding USB-to-serial communication unit and a multi-channel fiber optic signal transmission circuit are designed. The USB-to-serial communication unit primarily handles data exchange and command parsing between the PC and the low-voltage control end to configure the period and amplitude information of the output sinusoidal signal and to provide feedback on the start signal of the positive period of the sinusoidal signal. The multi-channel fiber optic signal transmission circuit mainly converts the sinusoidal waveform data output by the STM32F103VET6 into optical signals for transmission to the high-voltage side. The multi-channel fiber optic signal transmission circuit uses an HFBR1521 fiber optic module, with a transmission rate of 5 Mbit / s and a normal transmission length of 20 m, reliably ensuring the stability and integrity of signal transmission.

[0040] The high-voltage output communication unit also uses the STM32F103VCT6 as the main control chip, and is equipped with an optical fiber signal analysis circuit and a signal conditioning unit. The optical fiber signal analysis circuit is designed using the HFBR2521 optical fiber module paired with the HFBR1521 to ensure reliable signal reception. The main controller converts the received sinusoidal waveform data into corresponding analog signals through its built-in DAC, and then transmits the corresponding signals to the input side of the analog amplifier circuit at the high-voltage end through the signal conditioning unit, ultimately realizing the transmission and amplification of ultra-low frequency 0.01-0.1Hz sinusoidal signals.

[0041] Specifically Figure 8 The circuit diagram shows the main amplifier circuit, which can accept arbitrary voltage waveform signals as input, with the input voltage signal output from an optocoupler-isolated backend. The circuit consists of six high-voltage, high-output-current OPA454 operational amplifiers. The OPA454 offers stable gain and a slew rate as high as 13V / μs, with a gain-bandwidth product of 2.5 MHz. The amplifier circuit has a wide power supply range, capable of supplying ±5V to ±50V bipolar power or 10V to 100V unipolar power. Figure 8The output voltage on one side can reach 200Vpp. Since the output voltage on the other side has the same amplitude but a 180° phase difference, the total output of each unit, when superimposed from both sides, can reach 400Vpp. Each unit circuit can achieve a 40x amplification. By cascading multiple of the above unit circuits, a peak voltage output of 0-50kV can be achieved, and the output bandwidth does not change with the increase of the cascading factor.

Claims

1. An ultra-low frequency sinusoidal high voltage generator, characterized in that... This includes a flyback switching power supply circuit, an ultra-low frequency signal generator, and a cascaded linear amplifier circuit. The flyback switching power supply circuit includes a drive circuit, switching devices, and a flyback isolation transformer. The drive circuit is connected to the switching devices, which are connected to the flyback isolation transformer. The drive circuit drives the switching devices to switch on and off regularly, generating a square wave signal that is output to the rectifier side of the flyback isolation transformer. The output voltage side of the flyback isolation transformer is also connected to the cascaded linear amplifier circuit, providing power to the cascaded linear amplifier circuit. Electrical isolation between the high and low voltage ends is achieved through the flyback isolation transformer. The ultra-low frequency signal generator includes a low-voltage side main control chip, an optical fiber transmitter, a high-voltage side main control chip, and an optical fiber receiver. The low-voltage side main control chip and the high-voltage side main control chip transmit signals via optical fiber. The low-voltage side main control chip is connected to the optical fiber transmitter, the optical fiber transmitter is connected to the optical fiber receiver via an optical fiber channel, and the optical fiber receiver is connected to the high-voltage side main control chip. The low-voltage side main control chip outputs sinusoidal waveform data to the optical fiber transmitter and converts the electrical signal into an optical signal for transmission to the optical fiber receiver. The optical fiber receiver converts the optical signal back into an electrical signal for transmission to the high-voltage side main control chip. The cascaded linear amplifier circuit includes six operational amplifiers. The cascaded linear amplifier circuit amplifies the signal received by the high-voltage side main control chip and outputs a 0-50kV high voltage.

2. The ultra-low frequency sinusoidal high voltage generator according to claim 1, characterized in that, The primary winding of the counter-attack isolation transformer is provided in one set; each set is provided with 8-15 turns of enameled wire.

3. The ultra-low frequency sinusoidal high voltage generator according to claim 1, characterized in that, The secondary winding of the counter-attack isolation transformer is provided in four groups, and each group of secondary windings is provided in three units, which are respectively provided with 3-6 turns of enameled wire and 8-15 turns of enameled wire.

4. The ultra-low frequency sinusoidal high voltage generator according to claim 1, characterized in that, The counter-current isolation transformer is connected to an RCD spike absorption circuit; the RCD spike absorption circuit includes a transient suppression diode, a resistor, a capacitor, and a diode; the transient suppression diode, resistor, and capacitor are connected in parallel, and the negative terminal of the diode is connected to one end of the resistor.

5. The ultra-low frequency sinusoidal high voltage generator according to claim 1, characterized in that, Both the low-voltage side main control chip and the high-voltage side main control chip use the STM32F103VET6 chip.

6. The ultra-low frequency sinusoidal high voltage generator according to claim 1, characterized in that, All operational amplifiers used are OPA454 operational amplifiers.

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