CN119224509B

CN119224509B - A variable frequency series resonance withstand voltage detection device and detection method

Info

Publication number: CN119224509B
Application number: CN202411776567.8A
Authority: CN
Inventors: 唐强
Original assignee: Wuhan Moen Intelligent Electric Co ltd
Current assignee: Wuhan Moen Intelligent Electric Co ltd
Priority date: 2024-12-05
Filing date: 2024-12-05
Publication date: 2025-03-14
Anticipated expiration: 2044-12-05
Also published as: CN119224509A

Abstract

The invention provides a variable-frequency series resonance withstand voltage detection device and a detection method, wherein the detection device comprises a comprehensive control box, an excitation transformer, a reactor group, a voltage divider and a compensation capacitor bank, an output end of the comprehensive control box is electrically connected with a low-voltage side of the excitation transformer, a high-voltage side of the excitation transformer is sequentially electrically connected with the reactor group, the voltage divider and the compensation capacitor bank, the compensation capacitor bank is electrically connected with a device to be detected, the comprehensive control box is directly and electrically connected with the voltage divider, the comprehensive control box is electrically connected with the low-voltage side of the excitation transformer through a shunt resistor, the comprehensive control box is used for collecting sampling voltage at the voltage divider and sampling current at the low-voltage side of the excitation transformer, the comprehensive control box is also used for predicting a resonance frequency interval where a resonance point is located by combining the sampling voltage and the sampling current, and the comprehensive control box is also used for outputting variable-frequency alternating current to the low-voltage side of the excitation transformer according to the resonance frequency interval. The invention has the effect of improving the accuracy of the voltage withstanding test result.

Description

Variable-frequency series resonance voltage withstand detection device and detection method

Technical Field

The invention belongs to the technical field of resonance withstand voltage detection, and particularly relates to a variable-frequency series resonance withstand voltage detection device and a detection method.

Background

With the continuous expansion and complexity of the power system, the requirements on the safety and reliability of the high-voltage equipment are also higher and higher. Such high voltage devices include, but are not limited to, transmission lines, transformers, switching devices, power cables, and the like. During production, installation, operation and maintenance of these devices, strict pressure tests are required to ensure that they operate safely and reliably in high pressure environments.

In the traditional testing method, three-phase traditional phase control and diode uncontrollable rectification are generally adopted, an inversion part adopts an SPWM modulation mode, in addition, the input power factor of a network side is low, the current harmonic content of an alternating current input side is high, the voltage waveform of an alternating current side power grid can generate distortion, so that the power grid generates a large amount of harmonic waves and reactive power, the power grid is polluted, the direct current voltage obtained through rectification has larger fluctuation, the voltage is unstable, the waveform smoothness of an alternating current output voltage generated by an inversion circuit is poor, and the effect of a series resonance test is influenced. On the other hand, operators often need to find the resonance point of the system through repeated experiments and manual adjustment, and the process is time-consuming and labor-consuming, and is easily affected by human factors, so that the accuracy and the repeatability of the test result are low.

Disclosure of Invention

The invention provides a variable-frequency series resonance voltage-withstanding detection device and a detection method, which are used for solving the problem of low accuracy and repeatability of voltage-withstanding test results.

In a first aspect, the invention provides a variable-frequency series resonance withstand voltage detection device, the detection device comprises a comprehensive control box, an excitation transformer, a reactor group, a voltage divider and a compensation capacitor group, the input end of the comprehensive control box is connected with an input voltage, the output end of the comprehensive control box is electrically connected with the low-voltage side of the excitation transformer, the high-voltage side of the excitation transformer is sequentially electrically connected with the reactor group, the voltage divider and the compensation capacitor group, the compensation capacitor group is electrically connected with a device to be detected, the comprehensive control box is directly electrically connected with the voltage divider, the comprehensive control box is electrically connected with the low-voltage side of the excitation transformer through a shunt resistor, the comprehensive control box is used for collecting a sampling voltage at the voltage divider and a sampling current at the low-voltage side of the excitation transformer, the comprehensive control box is also used for combining the sampling voltage and the sampling current to predict a resonance frequency range where a resonance point is located, and the comprehensive control box is also used for outputting variable-frequency alternating current to the low-voltage side of the excitation transformer according to the resonance frequency range.

The integrated control box comprises a box body, a variable frequency power supply control module, a resonant sweep prediction module and a current and voltage sampling module, wherein the variable frequency power supply control module, the resonant sweep prediction module and the current and voltage sampling module are integrated in the box body, the input end of the variable frequency power supply control module is connected with the input voltage, the output end of the variable frequency power supply control module is electrically connected with the low-voltage side of the excitation transformer, the variable frequency power supply control module is electrically connected with the resonant sweep prediction module and supplies power to the resonant sweep prediction module, the current and voltage sampling module is directly electrically connected with the voltage divider, the current and voltage sampling module is electrically connected with the low-voltage side of the excitation transformer through the shunt resistor, the current and voltage sampling module is used for collecting sampling voltage at the voltage divider and sampling current at the low-voltage side of the excitation transformer and transmitting the sampling voltage and the sampling current to the resonant sweep prediction module after filtering treatment, the variable frequency prediction module is used for combining the sampling voltage and the filtering treatment, and outputting the sampling current to the resonant sweep prediction module at the low-voltage side of the frequency conversion power supply according to the frequency conversion control section.

Optionally, the variable frequency power supply control module is directly and electrically connected with the voltage divider, and is further configured to directly collect a sampling voltage at the voltage divider, and output variable frequency ac to the low voltage side of the excitation transformer according to the sampling voltage.

Optionally, the integrated control box further includes a compensation capacitance control module, the compensation capacitance control module is integrated in the box, the compensation capacitance control module is electrically connected with the compensation capacitor bank, the variable frequency power supply control module is electrically connected with the compensation capacitance control module and supplies power to the compensation capacitance control module, the compensation capacitance control module is respectively electrically connected with the current voltage sampling module and the resonance sweep prediction module, the current voltage sampling module is further used for filtering the sampling voltage and the sampling current and then transmitting the sampling voltage and the sampling current to the compensation capacitance control module, the resonance sweep prediction module is further used for outputting the resonance frequency interval to the compensation capacitance control module, and the compensation capacitance control module is used for combining the sampling voltage, the sampling current after the filtering and the resonance frequency interval to generate a compensation capacitance control signal and transmitting the compensation capacitance control signal to the compensation capacitor bank to adjust the switching of each capacitor in the compensation capacitor bank.

Optionally, the resonance frequency sweep prediction module comprises a signal generating unit, a voltage following unit, a signal isolation unit, a resonance point prediction control unit and a phase detection unit, wherein the signal generating unit, the voltage following unit, the signal isolation unit, the resonance point prediction control unit and the phase detection unit are all electrically connected with the variable frequency power supply control module, the variable frequency power supply control module is used for supplying power to the signal generating unit, the voltage following unit, the resonance point prediction control unit and the phase detection unit, the signal generating unit is respectively electrically connected with the resonance point prediction control unit, the voltage following unit and the phase detection unit, the signal generating unit is used for generating a frequency sweep auxiliary signal according to a frequency control instruction output by the resonance point prediction control unit and outputting the frequency sweep auxiliary signal to the voltage following unit, and the signal generating unit is also used for outputting auxiliary signal information of the frequency sweep auxiliary signal to the phase detection unit;

The phase detection unit is further electrically connected with the resonance point prediction control unit and the current and voltage sampling module, and is used for receiving the auxiliary signal information output by the signal generation unit and the sampling current and the sampling voltage output by the current and voltage sampling module, combining the auxiliary signal information, the sampling current and the sampling voltage to calculate and obtain a frequency sweep detection result of the frequency sweep auxiliary signal in the main loop of the detection device, and is further used for outputting the frequency sweep detection result to the resonance point prediction control unit, and the resonance point prediction control unit is further used for generating the frequency control instruction according to the frequency sweep detection result, predicting a resonance frequency range where a resonance point is located according to the frequency sweep detection result, outputting the resonance frequency range to the frequency conversion power supply, and enabling the frequency conversion power supply module to output the frequency conversion control module to a low-voltage conversion frequency range to the resonance point prediction control unit according to the frequency conversion power supply.

The current-voltage sampling module comprises a current sampling unit, a voltage sampling unit, a first filtering unit and a second filtering unit, wherein the first filtering unit and the second filtering unit are respectively and electrically connected with the low-voltage side of the excitation transformer through a shunt resistor, the current sampling module is used for collecting sampling current from the low-voltage side of the excitation transformer, the current sampling module is respectively and electrically connected with the first filtering unit and the second filtering unit, the current sampling module is used for outputting the sampling current to the first filtering unit and the second filtering unit, the first filtering unit is electrically connected with the compensation capacitor control module, the first filtering unit is used for carrying out first filtering processing on the sampling current and outputting the sampling current after the first filtering processing to the compensation capacitor control module, the second filtering unit is electrically connected with the resonance frequency sweep prediction module, the second filtering unit is used for carrying out second filtering processing on the sampling current and outputting the sampling current to the resonance frequency sweep prediction module and the voltage from the resonance frequency prediction module to the sampling capacitor control module, and the sweep-frequency voltage prediction module respectively.

Optionally, the voltage sampling unit includes buffer amplifier, overvoltage protection circuit, voltage decay circuit and first isolation amplifier, the low pressure end of bleeder with overvoltage protection circuit in proper order buffer amplifier voltage decay circuit with first isolation amplifier electricity is connected, first isolation amplifier respectively with resonance sweep prediction module with compensation capacitance control module electricity is connected.

Optionally, the current sampling unit includes a differential amplifier and a second isolation amplifier, an input end of the differential amplifier is connected to two ends of the shunt resistor, an output end of the differential amplifier is electrically connected with the second isolation amplifier, and the second isolation amplifier is electrically connected with the first filtering unit and the second filtering unit respectively.

In a second aspect, the present invention further provides a variable frequency series resonance voltage withstand detection method, which is applied to the variable frequency series resonance voltage withstand detection device in the first aspect, where the variable frequency series resonance voltage withstand detection device includes a comprehensive control box, an excitation transformer, a reactor set, a voltage divider and a compensation capacitor set, an input end of the comprehensive control box is connected with an input voltage, an output end of the comprehensive control box is electrically connected with a low-voltage side of the excitation transformer, a high-voltage side of the excitation transformer is electrically connected with the reactor set, the voltage divider and the compensation capacitor set in sequence, the compensation capacitor set is electrically connected with a device to be detected, the comprehensive control box is directly electrically connected with the voltage divider, and the comprehensive control box is electrically connected with the low-voltage side of the excitation transformer through a shunt resistor;

The comprehensive control box comprises a box body, a variable frequency power supply control module, a resonant frequency sweep prediction module and a current and voltage sampling module, wherein the variable frequency power supply control module, the resonant frequency sweep prediction module and the current and voltage sampling module are integrated in the box body; the input end of the variable frequency power supply control module is connected with the input voltage, the output end of the variable frequency power supply control module is electrically connected with the low-voltage side of the excitation transformer, and the variable frequency power supply control module is electrically connected with the resonance sweep prediction module and supplies power to the resonance sweep prediction module;

the method comprises the following steps:

Electrically connecting a device to be detected with the compensation capacitor bank, so that the variable-frequency series resonance voltage withstand detection device and the device to be detected form a detection main loop;

Acquiring preset detection parameters and device parameters of the device to be detected;

determining an initial frequency of the resonant sweep prediction module in combination with the detection parameter and the device parameter;

Generating a frequency sweep auxiliary signal based on the initial frequency and controlling the resonant frequency sweep prediction module, and inputting the frequency sweep auxiliary signal to the variable frequency power supply control module;

The frequency conversion power supply control module is utilized to fuse the frequency sweep auxiliary signal and a preset substrate signal into a loop frequency sweep signal, and the loop frequency sweep signal is output to the detection main loop;

Collecting sampling voltage at the voltage divider by using the current-voltage sampling module, collecting sampling current at the low-voltage side of the exciting transformer by using the shunt resistor, and carrying out filtering treatment on the sampling voltage and the sampling current;

Transmitting the filtered sampling voltage and the filtered sampling current to the resonance sweep prediction module, and predicting a resonance frequency interval in which a resonance point in the detection main loop is located by the resonance sweep prediction module;

and outputting variable-frequency alternating current to the low-voltage side of the excitation transformer based on the resonance frequency interval by utilizing the variable-frequency power supply control module.

Optionally, the integrated control box further includes a compensation capacitance control module, the compensation capacitance control module is integrated in the box body, the compensation capacitance control module is electrically connected with the compensation capacitor bank, the variable frequency power supply control module is electrically connected with the compensation capacitance control module and supplies power to the compensation capacitance control module, and the compensation capacitance control module is electrically connected with the current and voltage sampling module and the resonance sweep prediction module respectively;

The method further comprises the steps of:

Estimating a loop quality factor of the detection main loop according to the resonance frequency interval;

calculating the compensation capacitance increment of the detection main loop by combining the loop quality factor and the resonance frequency interval;

Constructing an optimization constraint condition according to the capacity errors and the parallel effect of all the capacitors in the compensation capacitor bank, taking the minimized compensation capacitance increment as an optimization target, and calculating by using an optimization algorithm based on the optimization constraint condition to obtain an optimal switching scheme of the capacitors in the compensation capacitor bank;

And generating a compensation capacitance control signal based on the optimal switching scheme, and adjusting switching of each capacitor in the compensation capacitor bank through the compensation capacitance control signal.

The beneficial effects of the invention are as follows:

The device can automatically collect and analyze voltage and current data and rapidly predict the resonance frequency interval, thereby realizing accurate frequency control, greatly reducing the requirement of manual operation, reducing the risk of operation errors and improving the repeatability and consistency of the test. The device can more accurately find the resonance point, so that the required input power is greatly reduced, the energy utilization efficiency is improved, the safety of the testing process is also enhanced, and the advantage is more obvious particularly when a large-capacity sample is processed. The invention can rapidly adapt to the change of the characteristics of the test sample through real-time data analysis and automatic adjustment, and improves the flexibility and adaptability of the test. This is particularly advantageous for handling high voltage devices of different types and capacities, which can be kept efficient and accurate in different test scenarios. The invention integrates a plurality of functional modules through the comprehensive control box, realizes the compactness and integration of equipment, is beneficial to reducing the equipment cost and improves the reliability and the maintenance convenience of the system.

Drawings

Fig. 1 is a schematic circuit diagram of a variable frequency series resonance voltage withstand detection device according to one embodiment of the present application.

Fig. 2 is a schematic circuit diagram of the integrated control box according to one embodiment of the present application.

Fig. 3 is a schematic circuit diagram of a resonant sweep prediction module according to an embodiment of the present application.

Fig. 4 is a schematic circuit diagram of a current-voltage sampling module according to an embodiment of the application.

Fig. 5 is a schematic flow chart of a method for detecting voltage withstand of variable frequency series resonance in one embodiment of the application.

Reference numerals illustrate:

1. The device comprises a comprehensive control box, a exciting transformer, a 3, a reactor group, a4, a voltage divider, a 5, a compensating capacitor group, a6, a device to be detected, a 11, a variable frequency power supply control module, a 12, a resonance sweep frequency prediction module, a 13, a current and voltage sampling module, a 14, a compensating capacitor control module, a 131, a current sampling unit, a 132, a voltage sampling unit, a 133, a first filtering unit, a 134, a second filtering unit, a 121, a signal generating unit, a 122, a voltage following unit, a 123, a signal isolation unit, a 124, a phase detection unit, a 125 and a resonance point prediction control unit.

Detailed Description

The technical solutions of the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which are obtained by a person skilled in the art based on the embodiments of the present application, fall within the scope of protection of the present application.

Referring to fig. 1, the present application discloses a variable frequency series resonance voltage withstand detection device, in one embodiment, the variable frequency series resonance voltage withstand detection device is composed of an integrated control box, an exciting transformer, a reactor group, a voltage divider and a compensation capacitor group, and these components together form a highly integrated high voltage test system. The integrated control box is used as a core control unit of the whole system, and the input end of the integrated control box is connected with an external power supply, typically a three-phase 380V alternating current power supply. The input voltage is converted into alternating current with adjustable frequency and amplitude through the inside of the control box and is output to the low-voltage side of the exciting transformer. The exciting transformer adopts a specially designed high-frequency transformer, has broadband characteristic and can work in the frequency range of 20-300 Hz. The low-voltage winding is wound in multiple layers to reduce leakage inductance and improve transmission efficiency, and the high-voltage winding is wound in multiple layers to reduce interlayer capacitance and improve pressure resistance. The iron core material of the transformer can be silicon steel sheet or amorphous alloy so as to adapt to high-frequency working conditions.

In this embodiment, as shown in fig. 1, the high-voltage side of the excitation transformer is electrically connected to the reactor group, the voltage divider, and the compensation capacitor group in this order, forming a series resonant circuit. The reactor group is composed of a plurality of adjustable inductors in series-parallel connection, each inductor adopts a hollow or iron core structure, and a coil is wound by silver-plated or tinned flat copper wires so as to reduce skin effect under high frequency. The voltage divider adopts a structure of combining a capacitive voltage divider and a resistor voltage divider, the capacitive voltage divider uses a high-voltage ceramic capacitor, and the resistor voltage divider adopts a special non-inductive wire winding resistor, so that good voltage division characteristics are ensured in a wide frequency band range. The voltage division ratio can reach 1000:1 or higher, and the output signals are transmitted to the comprehensive control box through the shielded cable. The compensation capacitor group is formed by connecting a plurality of high-pressure oil immersed or SF6 gas insulation capacitors in parallel.

In one embodiment, the integrated control box contains complex circuitry, and is mainly composed of a power module, a variable frequency control module, a data acquisition module and a central processing unit. The power module is responsible for providing a stable direct current power supply for the whole control system, comprises multiple outputs, and adopts a switching power supply technology, such as an LLC resonant converter, so as to improve the efficiency and reduce the volume. The frequency conversion control module is the core of the system and adopts a framework of combining a digital signal processor DSP and a field programmable gate array. The DSP is responsible for complex mathematical operation and control algorithm realization, and the FPGA is used for high-speed data processing and PWM signal generation. The variable frequency control module realizes accurate adjustment of the frequency and amplitude of the output voltage by controlling the IGBT power module (such as FF300R12ME 4). The data acquisition module is responsible for acquiring voltage and current signals of the system.

The whole system has the working process that firstly, the comprehensive control box outputs alternating current with initial frequency to the exciting transformer through the frequency conversion control module. After the exciting transformer boosts the low-voltage alternating current, the low-voltage alternating current is transmitted to the equipment to be tested through a series resonant circuit formed by the reactor group, the voltage divider and the compensation capacitor group. Meanwhile, the voltage divider collects high-voltage side voltage signals and transmits the high-voltage side voltage signals to the comprehensive control box, and low-voltage side current is transmitted to the control box after being sampled through the shunt resistor. The data acquisition module performs high-speed sampling and digital processing on the signals. The central processing unit utilizes the collected data to analyze the characteristics of phase relation, amplitude change and the like of voltage and current through a complex digital signal processing algorithm, and rapidly estimates a possible resonant frequency interval. Based on the prediction result, the variable frequency control module adjusts the output frequency to gradually approach the real resonance point. In the process of approaching the resonance point, the system can continuously finely adjust the frequency and the voltage amplitude so as to ensure that the test voltage steadily rises and avoid the overvoltage phenomenon.

Through the technical scheme, the time for finding the resonance point is greatly shortened, and the test efficiency is improved. Secondly, because the resonant frequency can be accurately positioned, the input power required by the system when the system operates in a resonant state is greatly reduced, and the energy consumption can be saved by 30 to 50 percent. This not only reduces the testing costs, but also improves the safety of the test, especially when handling large volumes of test products, reducing the risk of overheating and dielectric breakdown of the device. On the other hand, the real-time voltage and current sampling and analysis enable the system to rapidly respond to the change of the characteristics of the sample, and adapt to the testing requirements of high-voltage equipment with different types and capacities. For example, the system can find the optimal working point in a short time for various high-voltage equipment with unequal capacities. In addition, the application of the intelligent prediction algorithm reduces the requirement of manual operation, reduces the risk of operation errors, and improves the repeatability and consistency of the test.

In one embodiment, referring to fig. 2, the integrated control box comprises a box body, a variable-frequency power supply control module, a resonant frequency sweep prediction module and a current and voltage sampling module, wherein the variable-frequency power supply control module, the resonant frequency sweep prediction module and the current and voltage sampling module are integrated in the box body, the input end of the variable-frequency power supply control module is connected with an input voltage, the output end of the variable-frequency power supply control module is electrically connected with the resonant frequency sweep prediction module and supplies power to the resonant frequency sweep prediction module, the current and voltage sampling module is directly electrically connected with a voltage divider, the current and voltage sampling module is electrically connected with the low-voltage side of the excitation transformer through a shunt resistor, the current and voltage sampling module is used for collecting sampling voltage at the voltage divider and sampling current at the low-voltage side of the excitation transformer and transmitting the sampling voltage and the sampling current to the resonant frequency sweep prediction module after filtering, and the resonant frequency sweep prediction module is used for predicting a resonance frequency range where a resonance point is located by combining the sampling voltage and the sampling current after filtering and outputting the resonance frequency range to the variable-frequency power supply control module so that the variable-frequency power supply control module outputs alternating current to the low-voltage side of the excitation transformer according to the resonance frequency range.

In the embodiment, the integrated control box is internally integrated with a variable-frequency power supply control module, a resonant sweep frequency prediction module and a current and voltage sampling module, and the three modules cooperate together to realize efficient and accurate resonance point detection and control. The box body is made of high-strength aluminum alloy materials, has good electromagnetic shielding performance, and is internally provided with a plurality of layers of partition boards, so that each functional module is effectively separated, and mutual interference is reduced. The liquid crystal display screen, the control buttons and the indicator lamps are arranged outside the box body, so that an operator can monitor the running state of the system in real time. The input end of the variable frequency power supply control module is connected with a three-phase 380V alternating current power supply. The module first suppresses grid disturbances and harmonics through an EMI filter (e.g., FN2090 series) and then converts the ac power to dc power through a three-phase rectifier bridge. The rectified direct current passes through an LC filter circuit formed by a large-capacity electrolytic capacitor and an inductor to smooth the fluctuation of the direct current voltage. The filtered direct current is converted into alternating current with adjustable frequency through an IGBT inversion module. The control signal of the IGBT is generated by a high-performance DSP, and the precise control of the frequency and the amplitude of the output voltage is realized by adopting a Space Vector Pulse Width Modulation (SVPWM) technology. The output end eliminates high-frequency switch ripple waves through an LC filter (adopting a ferro-silicon-aluminum magnetic core inductor and a polypropylene film capacitor), and finally outputs clean sine wave alternating current to the low-voltage side of the exciting transformer.

In one embodiment, as shown in fig. 2, the integrated control box further includes a compensation capacitance control module, the compensation capacitance control module is integrated in the box body, the compensation capacitance control module is electrically connected with the compensation capacitor bank, the variable frequency power supply control module is electrically connected with the compensation capacitance control module and supplies power to the compensation capacitance control module, the compensation capacitance control module is respectively electrically connected with the current-voltage sampling module and the resonance sweep prediction module, the current-voltage sampling module is further used for filtering the sampled voltage and the sampled current and then transmitting the filtered sampled voltage and the filtered current to the compensation capacitance control module, the resonance sweep prediction module is further used for outputting a resonance frequency interval to the compensation capacitance control module, and the compensation capacitance control module is used for generating a compensation capacitance control signal by combining the sampled voltage, the filtered sampled current and the resonance frequency interval and transmitting the compensation capacitance control signal to the compensation capacitor bank to adjust switching of each capacitor in the compensation capacitor bank.

In the embodiment, the compensation capacitor control module integrated in the integrated control box is a key component, and is tightly matched with the variable-frequency power supply control module, the current and voltage sampling module, the resonance sweep frequency prediction module and the compensation capacitor bank, so that the intelligent and efficient operation of the series resonance withstand voltage detection device is realized. The compensation capacitance control module is characterized by a high-performance microcontroller such as STM32F407 series, and can rapidly process complex control algorithm and data analysis tasks. The compensation capacitance control module obtains power supply from the variable frequency power supply control module through the isolated DC-DC converter. The original data acquired by the current and voltage sampling module is transmitted to the compensation capacitance control module after being subjected to digital filtering processing. The filtering algorithm adopts a Finite Impulse Response (FIR) filter, such as a low-pass filter designed by using a Kaiser window function, so that high-frequency noise can be effectively removed, and useful components of signals can be reserved. After the compensation capacitance control module receives the data, data fusion and analysis are firstly carried out. The Kalman filtering algorithm is used for further noise elimination and state estimation of the voltage and current data, and measurement accuracy is improved. Then, based on the current voltage, current values and predicted resonant frequency intervals, a complex optimization algorithm is run to determine the optimal capacitive switching scheme. The optimization algorithm adopts a self-Adaptive Particle Swarm Optimization (APSO) method, and can be used for quickly searching the optimal solution by combining with fuzzy logic control, and meanwhile, the method has good convergence and robustness. The objective function of the algorithm comprises a plurality of weight factors, such as the proximity degree of resonant frequency, system power factor, resonant current amplitude and the like, and various performance indexes of the system are comprehensively considered.

Based on the optimization result, the compensation capacitance control module generates a compensation capacitance control signal and transmits the compensation capacitance control signal to a compensation capacitor bank, wherein the compensation capacitor bank is formed by connecting a plurality of groups of high-voltage capacitors with different capacities in parallel, and each group of capacitors is controlled by an independent switch. The capacitor is a thin film type high-voltage capacitor, and the compensation capacitor control module realizes flexible switching of the capacitor by accurately controlling the on and off of the switching elements. The switching strategy adopts a progressive method, so that voltage abrupt change caused by abrupt input of the large-capacity capacitor is avoided. In addition, the compensation capacitance control module also realizes multiple protection functions. It continuously monitors the voltage, current and temperature of each set of capacitors, and immediately triggers a protection mechanism to disconnect the corresponding capacitor upon detection of an abnormality, such as overvoltage, overcurrent or overheat. The module also realizes a soft start function, gradually increases compensation capacity when the system is started, and avoids large current impact at the moment of starting.

In one embodiment, as shown in fig. 2, the variable frequency power supply control module is directly and electrically connected to the voltage divider, and is further configured to directly collect a sampling voltage at the voltage divider, and output variable frequency ac to the low voltage side of the exciting transformer according to the sampling voltage.

In this embodiment, the variable frequency power supply control module directly collects a voltage signal from the voltage divider through a high-speed analog-to-digital converter (ADC) built in the variable frequency power supply control module, and based on the collected voltage information, the DSP operates a complex control algorithm to adjust the output variable frequency alternating current. Control algorithms typically include PID (proportional-integral-derivative) control, fuzzy logic control, adaptive control, and the like. These algorithms adjust the output frequency and amplitude in real time based on the difference between the current voltage and the target voltage. In some special cases (such as abnormal faults of the resonant sweep frequency prediction module or the current and voltage sampling module), the variable-frequency power supply control module can skip the resonant point prediction stage, directly collect the voltage of the voltage divider and adjust the output frequency and amplitude in real time.

In one embodiment, referring to fig. 3, the resonant sweep prediction module is a core component in the series resonant withstand voltage detection device, and is composed of a signal generating unit, a voltage following unit, a signal isolating unit, a resonance point prediction control unit and a phase detection unit, and these units work cooperatively to realize accurate resonance frequency prediction and control. The frequency conversion power supply control module is used for supplying power to the signal generation unit, the voltage following unit, the resonance point prediction control unit and the phase detection unit, the signal generation unit is respectively and electrically connected with the resonance point prediction control unit, the voltage following unit and the phase detection unit, the signal generation unit is used for generating a frequency sweep auxiliary signal according to a frequency control instruction output by the resonance point prediction control unit and outputting the frequency sweep auxiliary signal to the voltage following unit, and the signal generation unit is also used for outputting auxiliary signal information of the frequency sweep auxiliary signal to the phase detection unit.

The phase detection unit is further electrically connected with the resonance point prediction control unit and the current and voltage sampling module, and is used for receiving auxiliary signal information output by the signal generation unit and sampling current and sampling voltage output by the current and voltage sampling module, combining the auxiliary signal information, the sampling current and the sampling voltage to calculate and obtain a frequency sweep detection result of the frequency sweep auxiliary signal in the detection device main loop, and the phase detection unit is further used for outputting the frequency sweep detection result to the resonance point prediction control unit, generating a frequency control instruction according to the frequency sweep detection result, predicting a resonance frequency interval where a resonance point is located according to the frequency sweep detection result, and outputting the resonance frequency interval to the frequency conversion power control module, so that the frequency conversion power control module outputs frequency conversion alternating current to the low-voltage side of the excitation transformer according to the resonance frequency interval, and the resonance point prediction control unit is further used for outputting the resonance frequency interval to the compensation capacitance control module.

In this embodiment, the signal generating unit may be a high-performance Direct Digital Synthesis (DDS) chip, such as AD9910. The DDS chip has a sampling rate of up to 1GSPS and 14-bit resolution, and can generate accurate sine wave sweep signals. The signal generating unit is connected with the resonance point prediction control unit through an SPI interface and receives a frequency control instruction. Based on these instructions, the DDS chip generates a swept auxiliary signal, typically set in a frequency range between 10Hz and 1MHz, covering the possible resonant frequencies of most series resonant circuits. The generated sweep auxiliary signal is first output to a voltage follower unit. The voltage follower unit uses a high-speed operational amplifier. The main function of this unit is to provide a low output impedance, ensuring that the signal is not affected by load effects during subsequent processing.

The output of the voltage follower unit is connected to the signal isolation unit. The signal isolation unit employs a high-speed digital isolator, such as Si8660, which provides data rates of up to 150Mbps and propagation delays as low as 2 ns. This isolation not only protects the low-side circuit from high voltage interference, but also eliminates ground loops, improving signal integrity. The isolated sweep frequency auxiliary signal is input to a signal output main loop of the variable frequency power supply control module. Here, the sweep assist signal is superimposed on the main control signal to collectively determine the ac characteristics of the output to the low voltage side of the excitation transformer. This design allows fine tuning of the frequency characteristics of the output signal without affecting the main control, providing a basis for accurate positioning of the resonance point. Meanwhile, the signal generating unit outputs detailed information (such as instantaneous frequency, amplitude and phase) of the sweep auxiliary signal to the phase detecting unit. The phase detection unit also receives sampling data from the current-voltage sampling module. A high-speed digital-to-analog converter (ADC), such as ADS131E08, is used here, which has 24-bit resolution and a sampling rate up to 64kSPS, enabling accurate capture of details of current and voltage waveforms.

The core of the phase detection unit is a Field Programmable Gate Array (FPGA). FPGAs implement complex digital signal processing algorithms, including Fast Fourier Transforms (FFTs) and phase comparisons. The method comprises the steps of firstly carrying out FFT analysis on sampling data, and extracting amplitude and phase information of fundamental wave components. The information is then compared with parameters of the swept auxiliary signal to calculate the phase difference between the voltage and current, and the amplitude and phase angle of the impedance. The calculation results form a sweep frequency detection result and reflect the response characteristics of the tested circuit under different frequencies. The sweep frequency detection result is transmitted to the resonance point prediction control unit. The unit adopts a high-performance microprocessor, such as STM32H743 series, has the operating frequency as high as 480MHz, and has strong floating point operation capability. The resonance point prediction control unit firstly analyzes an impedance-frequency curve in a sweep frequency detection result, finds a minimum impedance amplitude point and a point of a phase jump from inductive to capacitive, and generates a plurality of possible resonance frequency candidate values. These candidate values are evaluated and ranked to finally determine the most likely resonant frequency interval.

The resonance point prediction control unit outputs the predicted resonance frequency interval to the variable frequency power supply control module and the compensation capacitance control module. The variable frequency power supply control module utilizes the information to adjust the frequency of alternating current output to the low-voltage side of the exciting transformer so that the alternating current is closer to the actual resonant frequency, and therefore the testing efficiency and the testing precision are improved. And the compensation capacitor control module optimizes the switching strategy of the compensation capacitor according to the resonance frequency interval, and further refines the positioning of the resonance point. Meanwhile, the resonance point prediction control unit generates a new frequency control instruction according to a prediction result and feeds the new frequency control instruction back to the signal generation unit. The method forms a closed-loop control system, continuously optimizes the frequency sweep strategy and enables the frequency sweep process to be more efficient and accurate. For example, after the resonance frequency interval is initially determined, the sweep frequency range may be narrowed, and the sweep density in the interval may be increased, thereby obtaining finer resonance characteristic information.

In one embodiment, referring to fig. 4, the current-voltage sampling module includes a current sampling unit, a voltage sampling unit, a first filtering unit and a second filtering unit, where the first filtering unit and the second filtering unit respectively use different types of filters, the current sampling module is electrically connected to the low-voltage side of the excitation transformer through a shunt resistor, and the shunt resistor is usually an alloy resistor with high precision and low temperature drift. The current sampling module is used for collecting sampling current from the low-voltage side of the exciting transformer; the current sampling module is respectively and electrically connected with the first filtering unit and the second filtering unit and is used for outputting sampling current to the first filtering unit and the second filtering unit; the first filtering unit is electrically connected with the compensation capacitance control module, the first filtering unit is used for carrying out first filtering treatment on the sampling current and outputting the sampling current after the first filtering treatment to the compensation capacitance control module, the second filtering unit is electrically connected with the resonance sweep prediction module, the second filtering unit is used for carrying out second filtering treatment on the sampling current and outputting the sampling current after the second filtering treatment to the resonance sweep prediction module, the voltage sampling unit is respectively electrically connected with the voltage divider, the resonance sweep prediction module and the compensation capacitance control module, and the voltage sampling unit is used for collecting sampling voltage from the voltage divider and respectively outputting the sampling voltage to the resonance sweep prediction module and the compensation capacitance control module.

The core of the current sampling unit is a combination of a differential amplifier and an isolation amplifier. The differential amplifier adopts an instrument amplifier with high Common Mode Rejection Ratio (CMRR), can accurately amplify the tiny voltage difference at two ends of the shunt resistor, and can effectively inhibit common mode interference. The output of the differential amplifier is connected to an isolation amplifier that provides a common mode rejection ratio of up to 120 dB and a common mode transient rejection capability of 15 kV/μs, effectively isolating the high and low voltage sides, protecting the subsequent circuitry. The voltage sampling unit is directly connected with the low-voltage end of the voltage divider, and a multi-stage protection and signal conditioning circuit is adopted. Firstly, an overvoltage protection circuit uses a transient suppression diode and a gas discharge tube with quick response to prevent the damage of instantaneous high voltage to a subsequent circuit. The buffer amplifier is next, an operational amplifier with high input impedance is used, and the minimum input current can reduce the load effect on the voltage divider. The voltage decay circuit uses a precision resistor network to adjust the signal to a range suitable for subsequent processing. Finally, the isolation amplifier provides electrical isolation to ensure that the high voltage signal does not directly affect the low side control circuit.

The first filtering unit and the second filtering unit respectively adopt different types of filters so as to meet different requirements of the compensation capacitance control module and the resonance frequency sweep prediction module. The first filtering unit is mainly used for compensating capacitance control, so that a low-pass filter such as LTC1563-2 can be adopted, has linear phase response characteristics, can reserve the time domain characteristics of signals to the greatest extent, and is beneficial to quick response compensation requirements. The second filtering unit uses an elliptic filter, such as LTC1563-3, for resonance sweep prediction, which has a larger attenuation in the stop band, and can effectively suppress high-frequency noise and harmonics, and provide purer fundamental wave signals for resonance analysis. An advantage of this dual filter design is that it can meet both time and frequency domain analysis requirements. The compensation capacitor control needs to respond to the current change quickly, so that the low-pass filter adopted by the first filtering unit can effectively remove high-frequency noise while maintaining the signal integrity. And the resonance sweep frequency prediction focuses more on the frequency characteristic of the signal, and the elliptic filter of the second filtering unit can provide steeper roll-off characteristic so as to ensure the accuracy of spectrum analysis. The filtered signal is digitized by a high-speed data acquisition system. A high performance analog to digital converter (ADC) may be used here and the digitized data is transferred to a subsequent processing module.

The terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged, as appropriate, such that embodiments of the present application may be implemented in sequences other than those illustrated or described herein, and that the objects identified by "first," "second," etc. are generally of a type, and are not limited to the number of objects, such as the first object may be one or more. Furthermore, in the description and claims, "and/or" means at least one of the connected objects, and the character "/", generally means that the associated object is an "or" relationship.

The application also discloses a frequency conversion series resonance voltage withstand detection method which is applied to the frequency conversion series resonance voltage withstand detection device described in any one of the embodiments, and the frequency conversion series resonance voltage withstand detection device comprises a comprehensive control box, an excitation transformer, a reactor group, a voltage divider and a compensation capacitor group, wherein the input end of the comprehensive control box is connected with input voltage, the output end of the comprehensive control box is electrically connected with the low-voltage side of the excitation transformer, the high-voltage side of the excitation transformer is electrically connected with the reactor group, the voltage divider and the compensation capacitor group in sequence, the compensation capacitor group is electrically connected with a device to be detected, the comprehensive control box is directly electrically connected with the voltage divider, and the comprehensive control box is electrically connected with the low-voltage side of the excitation transformer through a shunt resistor.

The comprehensive control box comprises a box body, a variable-frequency power supply control module, a resonant frequency sweep prediction module and a current and voltage sampling module, wherein the variable-frequency power supply control module, the resonant frequency sweep prediction module and the current and voltage sampling module are integrated in the box body, the input end of the variable-frequency power supply control module is connected with input voltage, the output end of the variable-frequency power supply control module is electrically connected with the low-voltage side of an excitation transformer, the variable-frequency power supply control module is electrically connected with the resonant frequency sweep prediction module and supplies power to the resonant frequency sweep prediction module, the current and voltage sampling module is directly electrically connected with a voltage divider, and the current and voltage sampling module is electrically connected with the low-voltage side of the excitation transformer through a shunt resistor.

Referring to fig. 5, fig. 5 is a flow chart of a method for detecting voltage withstand of variable frequency series resonance in one embodiment. It should be understood that, although the steps in the flowchart of fig. 5 are shown in sequence as indicated by the arrows, the steps are not necessarily performed in sequence as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in fig. 5 may include multiple sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, nor do the order in which the sub-steps or stages are performed necessarily performed in sequence, but may be performed alternately or alternately with at least a portion of the sub-steps or stages of other steps or other steps. As shown in fig. 5, the method for detecting the withstand voltage of the variable frequency series resonance disclosed by the invention specifically comprises the following steps:

s101, electrically connecting a device to be detected with a compensation capacitor group, so that a detection main loop is formed by the variable-frequency series resonance voltage-withstand detection device and the device to be detected.

S102, acquiring preset detection parameters and device parameters of a device to be detected.

S103, determining the initial frequency of the resonant sweep prediction module by combining the detection parameters and the device parameters.

S104, generating a frequency sweep auxiliary signal based on the initial frequency and controlling the resonance frequency sweep prediction module, and inputting the frequency sweep auxiliary signal to the variable frequency power supply control module.

S105, utilizing a variable frequency power supply control module to fuse the frequency sweep auxiliary signal and a preset substrate signal into a loop frequency sweep signal, and outputting the loop frequency sweep signal to a detection main loop.

S106, collecting sampling voltage at the voltage divider by using a current-voltage sampling module, collecting sampling current at the low-voltage side of the exciting transformer by using a shunt resistor, and carrying out filtering treatment on the sampling voltage and the sampling current.

S107, transmitting the filtered sampling voltage and sampling current to a resonance frequency sweep prediction module, and predicting and detecting a resonance frequency interval where a resonance point in the main loop is located through the resonance frequency sweep prediction module.

S108, outputting variable-frequency alternating current to the low-voltage side of the excitation transformer based on the resonance frequency interval by utilizing a variable-frequency power supply control module.

In this embodiment, the connection terminals of the device to be inspected are first inspected to ensure that they are clean and non-destructive. The device to be tested is then connected to the compensation capacitor bank using high voltage conductors of appropriate gauge. In order to minimize parasitic inductance and capacitance, the connecting wires should be as short and straight as possible, avoiding unnecessary bending. While the spacing between the conductors needs to be considered, typically a spacing of at least 1cm per 10kV voltage should be maintained to prevent corona discharge. After the connection is completed, the insulation resistance test is carried out on the whole loop by using a high-precision megohmmeter, so that good insulation is ensured. And simultaneously, a partial discharge detector can be used for checking whether a partial discharge phenomenon exists. These precautions can greatly reduce the risk of insulation breakdown during testing, ensuring personnel and equipment safety.

The preset detection parameters generally include, but are not limited to, the following:

The target withstand voltage value is determined according to the rated voltage of the device to be detected and the relevant standard (such as IEC 60060 or IEEE Std 4). For example, a transformer rated at 220kV may have a commercial voltage withstand value of 460kV (2.1 times the phase voltage).

The boost rate, typically in kV/s, needs to be set according to the characteristics of the device to be tested and the relevant criteria. For example, for a large transformer, it may be set to 1-2kV/s.

The withstand voltage time, i.e. the duration at the target voltage, is typically 1 or 5 minutes, depending on the requirements of the relevant standard.

The frequency scanning range is usually set between 20Hz and 300Hz, and the specific range is required to be determined according to the characteristics of the device to be detected and the predicted value of the system resonance frequency.

The sweep step size can be set to a fixed value (e.g., 1 Hz) or an adaptive value (smaller step sizes are used near the predicted resonance point).

The device parameters of the device to be detected include:

rated voltage-the design operating voltage of the device.

Capacitance value can be measured by a capacitance tester under low voltage. For complex devices, measurements at different frequencies may be required to obtain more accurate values.

Induced voltage coefficient is a ratio of the induced voltage to the applied voltage at the rated frequency of the device.

Loss factor (tan delta) is a measure of the dielectric loss of a device that is measured by a dielectric loss tester.

The geometry and structural characteristics of the device such information helps to estimate the distributed capacitance and inductance of the device.

The initial frequency of the resonant sweep prediction module is determined by combining the detection parameters and the device parameters, and a plurality of factors need to be comprehensively considered and an advanced algorithm is applied. The method aims at providing a reasonable starting point for the frequency sweeping process so as to accelerate the positioning speed of the resonance point and improve the efficiency of the whole test. Specifically, an equivalent circuit model of the system needs to be built. For a typical series resonant tank circuit, its resonant frequency can be expressed by the following formula:

Wherein L is the equivalent inductance of the system, and C is the equivalent capacitance of the system. The equivalent capacitance C comprises the capacitance of the device under test Compensating capacitorIs a series combination of (a):

the equivalent inductance L is mainly from the excitation transformer, but also the stray inductances of the connecting wires need to be taken into account. The estimation can be made by the following formula:

Where V is the rated voltage of the transformer, Is the rated frequency (typically 50Hz or 60 Hz) and S is the rated capacity of the transformer.

The resonant sweep prediction module is required to generate a high quality sweep auxiliary signal based on the initial frequency. This signal is typically a sine wave with a frequency that varies linearly with time and can be described by the following mathematical expression:

where A is the signal amplitude, Is the initial frequency, k is the sweep rate (in Hz/s), and φ is the initial phase.

To generate such signals, direct Digital Synthesis (DDS) techniques may be used. The DDS technology generates sine waves with adjustable frequency and phase in a digital mode, and has the characteristics of high precision, fast switching and low phase noise.

The specific steps of signal generation are as follows:

1. and initializing the DDS chip, and setting the clock frequency and the initial phase.

2. Calculate Frequency Tuning Word (FTW): Wherein Is the system clock frequency.

3. Calculating phase increment:。

4. updating FTW every clock cycle: 。

In order to improve the accuracy and efficiency of the frequency sweep, an adaptive frequency sweep algorithm may be employed. For example, a larger frequency step is used in the region away from the estimated resonance point, while the step is automatically reduced as the resonance point is approached. This can be achieved by monitoring the voltage response of the system:

Wherein, Is the maximum step size of the step,Is the derivative of voltage with respect to frequency and k is an adjustable parameter.

In the variable frequency power supply control module, the frequency-sweeping auxiliary signal is fused with the base signal (typically a sine wave of 50Hz or 60Hz of power frequency). This may be achieved by digital signal processing techniques, for example using weighted averages or more complex signal synthesis algorithms. The fused signals are used to control a power conversion circuit (such as an IGBT inverter) to generate final high-voltage output. Specifically, a common fusion method is weighted superposition, which can be expressed as:

Wherein, Is the output signal after the fusion,Is an auxiliary signal of the frequency sweep,Is a base signal, and alpha is a weight coefficient (alpha is more than or equal to 0 and less than or equal to 1).

The weight coefficient alpha can be dynamically adjusted according to the test requirement. For example, a smaller α value may be set at the initial stage of the frequency sweep, and the α value is gradually increased as the resonance point is approached to enhance the frequency sweep effect. Alpha can be dynamically adjusted using the following formula:

After signal fusion, it is converted into a power control signal by digital Pulse Width Modulation (PWM) techniques. This is typically accomplished using a high performance Digital Signal Processor (DSP) or Field Programmable Gate Array (FPGA).

The PWM signal is generated as follows:

1. And carrying out normalization processing on the fused signals to ensure that the amplitude of the fused signals is between-1 and 1.

2. The normalized signal is compared with a high frequency triangular carrier.

3. When the signal value is greater than the carrier, the PWM output is high level, otherwise it is low level.

By means of the precise signal fusion and output control strategy, high-quality loop sweep frequency signals can be generated, and the voltage and frequency of the main loop can be accurately controlled and detected. The resonance point of the system can be accurately positioned, stable voltage output can be maintained in the withstand voltage test process, overvoltage or undervoltage caused by frequency mutation is avoided, and therefore equipment to be tested is protected.

And then, collecting the sampling voltage at the voltage divider by using the current-voltage sampling module, collecting the sampling current at the low-voltage side of the exciting transformer by using the shunt resistor, carrying out filtering treatment on the sampling voltage and the sampling current, transmitting the sampling voltage and the sampling current after the filtering treatment to the resonance frequency sweep prediction module, and predicting and detecting the resonance frequency interval where the resonance point in the main loop is located by using the module. Specifically, the resonance sweep prediction module calculates the frequency spectrum of the signal, and by analyzing the amplitude and phase characteristics of the frequency spectrum, the frequency response characteristics of the system can be primarily judged, and then the resonance points are predicted by the following steps:

finding peak points on the impedance-frequency curve, the condition that the second derivative is zero can be used to locate peaks;

searching a frequency point with zero phase difference between voltage and current, and accurately positioning the zero phase point by an interpolation method;

calculating quality factors Q of different frequency points, wherein the point with the maximum Q value is the resonance point;

the impedance-frequency curve is fitted using a polynomial or rational function and then the characteristics of the fitted curve are analyzed, for example, a higher order polynomial may be used for fitting:

Then solving for dZ/df=0 to find the resonance point;

and carrying out refined scanning on the vicinity of the resonance point so as to determine a resonance frequency interval.

And then, according to the predicted resonant frequency interval, utilizing the variable frequency power supply control module to accurately sweep the frequency in the interval, and finally determining the resonant frequency of the detection main loop. Specifically, the variable frequency power supply control module needs to formulate an accurate frequency sweep strategy according to the predicted resonance frequency interval. One common method is to use an adaptive step-by-step sweep algorithm, the basic idea of which is as follows:

1. Initializing, namely setting an initial frequency f0 as the lower limit of a prediction interval, setting a termination frequency f1 as the upper limit of the prediction interval, and setting an initial frequency step delta f.

2. Sweep frequency circulation:

a. Setting the current frequency fc=f0

B. outputting a test signal at fc, measuring the system response (voltage, current, impedance, etc.)

C. calculating the quality factor Q of the current point:

d. If the Q value exceeds a preset threshold value, entering a fine scanning mode

E. Otherwise, fc+=Δf, if fc > f1, the sweep is ended

F. Repeating steps b-e

3. Fine scanning mode:

a. Reducing the frequency step by Δfk=Δf/10

B. fine scanning in the range of [ fc- Δf, fc+Δf ]

C. finding out the point with the maximum Q value, namely the resonant frequency.

In one embodiment, the integrated control box further comprises a compensation capacitance control module, the compensation capacitance control module is integrated in the box body, the compensation capacitance control module is electrically connected with the compensation capacitor bank, the variable-frequency power supply control module is electrically connected with the compensation capacitance control module and supplies power to the compensation capacitance control module, and the compensation capacitance control module is electrically connected with the current and voltage sampling module and the resonance frequency sweep prediction module respectively. The frequency conversion series resonance withstand voltage detection method further comprises the following steps:

Detecting the loop quality factor of the main loop according to the resonant frequency interval estimation;

Calculating to obtain the compensation capacitance increment of the detection main loop by combining the loop quality factor and the resonance frequency interval;

constructing optimization constraint conditions according to capacity errors and parallel effects of all capacitors in the compensation capacitor bank, taking minimized compensation capacitance increment as an optimization target, and calculating by utilizing an optimization algorithm based on the optimization constraint conditions to obtain an optimal switching scheme of the capacitors in the compensation capacitor bank;

In this embodiment, detecting the loop quality factor of the main loop based on the resonance frequency interval estimation is a key step. The loop quality factor Q is an important parameter that measures the performance of the resonant circuit, reflecting the selectivity and energy storage capabilities of the circuit. In the known resonant frequency rangeIn the case of (2), the Q value may be estimated using a half power bandwidth method. First, the resonant frequency is determinedTaken generally as the mid-point of the interval: . Then, the half power bandwidth is calculated . Q value can be calculated by the formulaAnd (5) estimating. For example, if the resonance frequency interval is [95Hz,105Hz ], then=100 Hz, Δf=10 Hz, and q=100/10=10 is estimated. Further, a more accurate calculation can be performed by measuring the voltage and current at the resonance point using the formula q= (1/R) sqrt (L/C), wherein R, L, C are equivalent resistance, inductance and capacitance, respectively. The purpose of estimating the Q value is to provide a basis for the calculation of the subsequent compensation capacitance, meanwhile, the performance condition of the main loop can be estimated, and a higher Q value indicates that the circuit loss is small and the resonance effect is good.

The calculation of the compensation capacitance increment of the detected main loop in combination with the loop quality factor and resonance frequency interval is a key step in determining the required additional capacitance. First of all using the resonant frequencyAnd the estimated quality factor Q, the equivalent inductance L and the equivalent resistance R of the main loop can be calculated. The equivalent inductance L can be calculated by the formulaThe value of C is the currently known capacitance. The equivalent resistance R can passAnd (5) calculating. To adjust the resonant frequency to the target frequencyIt is necessary to increase the compensation capacitance deltac. The calculation formula of the compensation capacitance increment is as follows: . For example, if the current resonance frequency is 100Hz, the target frequency is 50Hz, and the current capacitance is 10 μf, Δc=10 μf ((100/50) 2-1) =30 μf. The purpose of calculating the increment of the compensation capacitor is to accurately adjust the resonant frequency to match the working frequency of the power grid, so that the optimal resonant effect and test effect are realized. The accuracy of this step directly affects the performance of the subsequent capacitor switching scheme and the overall test system.

Constructing optimization constraints based on the capacitance errors and parallel effects of all capacitors in the compensation capacitor bank to minimize the compensation capacitance increase as an optimization objective, specifically, first considering the actual capacitance of each capacitorAnd nominal capacityThere is an error between: Wherein As a percentage of the error. The parallel effect is manifested in that the total capacitance is the sum of the capacities of all the input capacitors. Optimization constraints can be expressed as: Where δ is the total error allowed. The optimization objective function may be defined as: . To solve this problem, integer programming or genetic algorithms may be employed. Taking genetic algorithm as an example, each chromosome represents a switching scheme, and the fitness function is the reciprocal of the objective function. And optimizing the switching scheme generation by generation through selection, crossing and mutation operation. The algorithm outputs an optimal switching scheme indicating the switching state of each capacitor. The optimization method can find the switching combination closest to the ideal compensation value under the condition of considering practical limitation, and improves the precision and efficiency of the system.

And generating a compensation capacitance control signal based on the optimal switching scheme, and adjusting the switching of each capacitor in the compensation capacitor bank through the compensation capacitance control signal, specifically, converting the optimal switching scheme output by the optimization algorithm into a binary control sequence, wherein each bit corresponds to the switching state (0 represents disconnection and 1 represents input) of one capacitor. These control signals are then sent to the control unit of the capacitor bank via a digital output module, such as a digital output card of a PLC or a dedicated I/O module. The control unit typically contains a relay drive circuit for controlling the high power relay or thyristor switch. In order to avoid transient impact in the switching process, a synchronous switching technology can be adopted, namely, switching operation is performed near a voltage zero crossing point. At the same time, an appropriate time delay (typically several power cycles) is set to ensure system stability. In the switching process, system parameters (such as voltage, current, power factor and the like) are monitored in real time so as to verify the switching effect and perform necessary fine adjustment. The accurate control method can realize smooth adjustment of the compensation capacitor, reduce interference to the system to the maximum extent, and improve stability and reliability of the resonance effect, thereby creating optimal conditions for subsequent withstand voltage test.

It will be appreciated by persons skilled in the art that the above discussion of any embodiment is merely exemplary and is not intended to imply that the scope of the application is limited to these examples, that combinations of technical features in the above embodiments or in different embodiments may also be implemented in any order, and that many other variations of the different aspects of one or more embodiments of the application as described above exist within the spirit of the application, which are not provided in detail for the sake of brevity.

One or more embodiments of the present application are intended to embrace all such alternatives, modifications and variations as fall within the broad scope of the present application. Accordingly, any omissions, modifications, equivalents, improvements and others which are within the spirit and principles of the one or more embodiments of the application are intended to be included within the scope of the application.

Claims

1. A variable frequency series resonant withstand voltage detection device, characterized in that the detection device comprises an integrated control box, an excitation transformer, a reactor group, a voltage divider and a compensation capacitor group, the input end of the integrated control box is connected to the input voltage, the output end of the integrated control box is electrically connected to the low voltage side of the excitation transformer, the high voltage side of the excitation transformer is electrically connected to the reactor group, the voltage divider and the compensation capacitor group in sequence, the compensation capacitor group is electrically connected to a device to be detected, the integrated control box is directly electrically connected to the voltage divider, the integrated control box is electrically connected to the low voltage side of the excitation transformer through a shunt resistor, the integrated control box is used to collect the sampled voltage at the voltage divider and the sampled current on the low voltage side of the excitation transformer, the integrated control box is also used to predict the resonant frequency interval where the resonance point is located in combination with the sampled voltage and the sampled current, and the integrated control box is also used to output variable frequency alternating current to the low voltage side of the excitation transformer according to the resonant frequency interval;

The integrated control box comprises a box body, a variable frequency power supply control module, a resonant frequency sweep prediction module and a current and voltage sampling module, wherein the variable frequency power supply control module, the resonant frequency sweep prediction module and the current and voltage sampling module are all integrated in the box body; the input end of the variable frequency power supply control module is connected to the input voltage, the output end of the variable frequency power supply control module is electrically connected to the low voltage side of the excitation transformer, the variable frequency power supply control module is electrically connected to the resonant frequency sweep prediction module and supplies power to the resonant frequency sweep prediction module; the current and voltage sampling module is directly electrically connected to the voltage divider, and the current and voltage sampling module is connected to the voltage divider through the voltage divider. The current resistor is electrically connected to the low-voltage side of the excitation transformer, the current and voltage sampling module is used to collect the sampled voltage at the voltage divider and the sampled current at the low-voltage side of the excitation transformer, and is used to transmit the sampled voltage and the sampled current to the resonant frequency sweep prediction module after filtering; the resonant frequency sweep prediction module is used to predict the resonant frequency interval where the resonant point is located in combination with the sampled voltage and the sampled current after filtering, and output the resonant frequency interval to the variable frequency power supply control module, so that the variable frequency power supply control module outputs variable frequency alternating current to the low-voltage side of the excitation transformer according to the resonant frequency interval;

The integrated control box also includes a compensation capacitor control module, which is integrated in the box body, the compensation capacitor control module is electrically connected to the compensation capacitor group, the variable frequency power supply control module is electrically connected to the compensation capacitor control module and supplies power to the compensation capacitor control module, the compensation capacitor control module is electrically connected to the current and voltage sampling module and the resonant frequency sweep prediction module respectively, the current and voltage sampling module is also used to transmit the sampled voltage and the sampled current to the compensation capacitor control module after filtering, the resonant frequency sweep prediction module is also used to output the resonant frequency interval to the compensation capacitor control module, the compensation capacitor control module is used to generate a compensation capacitor control signal in combination with the sampled voltage, the sampled current after filtering, and the resonant frequency interval, and transmit the compensation capacitor control signal to the compensation capacitor group to adjust the switching of each capacitor in the compensation capacitor group;

The resonance frequency sweep prediction module includes a signal generating unit, a voltage following unit, a signal isolating unit, a resonance point prediction control unit and a phase detection unit. The signal generating unit, the voltage following unit, the signal isolating unit, the resonance point prediction control unit and the phase detection unit are all electrically connected to the variable frequency power supply control module. The variable frequency power supply control module is used to supply power to the signal generating unit, the voltage following unit, the resonance point prediction control unit and the phase detection unit. The signal generating unit is electrically connected to the resonance point prediction control unit, the voltage following unit and the phase detection unit, respectively. The signal generating unit is used to generate a frequency sweep auxiliary signal according to a frequency control instruction output by the resonance point prediction control unit, and output the frequency sweep auxiliary signal to the voltage following unit. The signal generating unit is also used to output auxiliary signal information of the frequency sweep auxiliary signal to the phase detection unit.

The voltage following unit is electrically connected to the signal isolation unit, and the voltage following unit and the signal isolation unit are used to isolate and amplify the sweep frequency auxiliary signal and then output it to the signal output main circuit of the variable frequency power supply control module; the phase detection unit is also electrically connected to the resonance point prediction control unit and the current and voltage sampling module, and the phase detection unit is used to receive the auxiliary signal information output by the signal generation unit and the sampling current and the sampling voltage output by the current and voltage sampling module, and calculate the sweep frequency detection result of the sweep frequency auxiliary signal in the main circuit of the detection device in combination with the auxiliary signal information, the sampling current and the sampling voltage, and the phase detection unit is also used to output the sweep frequency detection result to the resonance point prediction control unit; the resonance point prediction control unit is used to generate the frequency control instruction according to the sweep frequency detection result, and is also used to predict the resonance frequency interval where the resonance point is located according to the sweep frequency detection result, and output the resonance frequency interval to the variable frequency power supply control module, so that the variable frequency power supply control module outputs variable frequency alternating current to the low voltage side of the excitation transformer according to the resonance frequency interval, and the resonance point prediction control unit is also used to output the resonance frequency interval to the compensation capacitor control module.

2. The variable frequency series resonant withstand voltage detection device according to claim 1 is characterized in that the variable frequency power supply control module is directly electrically connected to the voltage divider, and the variable frequency power supply control module is also used to directly collect the sampled voltage at the voltage divider, and output variable frequency alternating current to the low voltage side of the excitation transformer according to the sampled voltage.

3. The variable frequency series resonant withstand voltage detection device according to claim 1 is characterized in that the current and voltage sampling module includes a current sampling unit, a voltage sampling unit, a first filtering unit and a second filtering unit, the first filtering unit and the second filtering unit respectively use different types of filters, the current sampling module is electrically connected to the low-voltage side of the excitation transformer through the shunt resistor, and the current sampling module is used to collect the sampled current from the low-voltage side of the excitation transformer; the current sampling module is electrically connected to the first filtering unit and the second filtering unit respectively, and the current sampling module is used to output the sampled current to the first filtering unit and the second filtering unit; the first filtering unit is electrically connected to the compensation current The first filter unit is electrically connected to the compensation capacitor control module, the first filter unit is used to perform a first filter processing on the sampling current, and output the sampling current after the first filter processing to the compensation capacitor control module, the second filter unit is electrically connected to the resonant frequency sweep prediction module, the second filter unit is used to perform a second filter processing on the sampling current, and output the sampling current after the second filter processing to the resonant frequency sweep prediction module; the voltage sampling unit is electrically connected to the voltage divider, the resonant frequency sweep prediction module and the compensation capacitor control module respectively, the voltage sampling unit is used to collect a sampling voltage from the voltage divider, and output the sampling voltage to the resonant frequency sweep prediction module and the compensation capacitor control module respectively.

4. The variable frequency series resonant withstand voltage detection device according to claim 3 is characterized in that the voltage sampling unit includes a buffer amplifier, an overvoltage protection circuit, a voltage attenuation circuit and a first isolation amplifier, the low voltage end of the voltage divider is electrically connected to the overvoltage protection circuit, the buffer amplifier, the voltage attenuation circuit and the first isolation amplifier in sequence, and the first isolation amplifier is electrically connected to the resonant frequency sweep prediction module and the compensation capacitor control module respectively.

5. The variable frequency series resonant withstand voltage detection device according to claim 3 is characterized in that the current sampling unit includes a differential amplifier and a second isolation amplifier, the input end of the differential amplifier is connected to the two ends of the shunt resistor, the output end of the differential amplifier is electrically connected to the second isolation amplifier, and the second isolation amplifier is electrically connected to the first filtering unit and the second filtering unit respectively.

6. A variable frequency series resonant withstand voltage detection method, applied to the variable frequency series resonant withstand voltage detection device according to any one of claims 1 to 5, characterized in that the variable frequency series resonant withstand voltage detection device comprises an integrated control box, an excitation transformer, a reactor group, a voltage divider and a compensation capacitor group, the input end of the integrated control box is connected to the input voltage, the output end of the integrated control box is electrically connected to the low voltage side of the excitation transformer, the high voltage side of the excitation transformer is electrically connected to the reactor group, the voltage divider and the compensation capacitor group in sequence, the compensation capacitor group is electrically connected to the device to be detected, the integrated control box is directly electrically connected to the voltage divider, and the integrated control box is electrically connected to the low voltage side of the excitation transformer through a shunt resistor;

The integrated control box comprises a box body, a variable frequency power supply control module, a resonant frequency sweep prediction module and a current and voltage sampling module, wherein the variable frequency power supply control module, the resonant frequency sweep prediction module and the current and voltage sampling module are all integrated in the box body; the input end of the variable frequency power supply control module is connected to the input voltage, the output end of the variable frequency power supply control module is electrically connected to the low voltage side of the excitation transformer, the variable frequency power supply control module is electrically connected to the resonant frequency sweep prediction module and supplies power to the resonant frequency sweep prediction module; the current and voltage sampling module is directly electrically connected to the voltage divider, and the current and voltage sampling module is electrically connected to the low voltage side of the excitation transformer through the shunt resistor;

The integrated control box further comprises a compensation capacitor control module, which is integrated in the box, the compensation capacitor control module is electrically connected to the compensation capacitor bank, the variable frequency power supply control module is electrically connected to the compensation capacitor control module and supplies power to the compensation capacitor control module, and the compensation capacitor control module is electrically connected to the current and voltage sampling module and the resonant frequency sweep prediction module respectively;

The method comprises the following steps:

The device to be detected is electrically connected to the compensation capacitor group, so that the variable frequency series resonant withstand voltage detection device and the device to be detected form a detection main circuit;

Determining an initial frequency of the resonant frequency sweep prediction module in combination with the detection parameter and the device parameter;

Based on the initial frequency, the resonance frequency sweep prediction module is controlled to generate a frequency sweep auxiliary signal, and the frequency sweep auxiliary signal is input to the variable frequency power supply control module;

The variable frequency power supply control module is used to fuse the auxiliary frequency sweep signal and the preset base signal into a loop frequency sweep signal, and the loop frequency sweep signal is output to the main detection loop;

The current and voltage sampling module is used to collect the sampled voltage at the voltage divider, and the sampled current at the low-voltage side of the excitation transformer is collected through the shunt resistor, and the sampled voltage and the sampled current are filtered;

The filtered sampled voltage and the sampled current are transmitted to the resonance frequency sweep prediction module, and the resonance frequency sweep prediction module is used to predict the resonance frequency interval where the resonance point in the detection main loop is located;

Based on the resonant frequency range and using the variable frequency power supply control module, outputting variable frequency alternating current to the low voltage side of the excitation transformer;

The method further comprises the steps of:

estimating a loop quality factor of the detection main loop according to the resonant frequency interval;

The compensation capacitance increment of the detection main loop is calculated by combining the loop quality factor and the resonant frequency range;

According to the capacity errors and parallel effects of all the capacitors in the compensation capacitor group, an optimization constraint condition is established, with minimizing the compensation capacitance increment as the optimization goal, and based on the optimization constraint condition and using an optimization algorithm, an optimal switching scheme of the capacitors in the compensation capacitor group is calculated;

A compensation capacitor control signal is generated based on the optimal switching scheme, and the switching of each capacitor in the compensation capacitor group is adjusted by the compensation capacitor control signal.