Analytic method and device for space charge measurement in extremely non-uniform electric field

Abstract

The invention discloses an analytic method and device for space charge measurement in an extremely non-uniform electric field. The analytic method comprises the following steps: S1, acquiring an actual measurement signal of space charges in the extremely non-uniform electric field; s2, establishing a simulation model of the space charge measurement process, and based on the simulation model, obtaining simulation output signals of the unit charge at different positions in the extremely non-uniform electric field simulation domain; and S3, through frequency domain analysis, according to the simulation output signal, analyzing electric charge quantities at different positions forming the actual measurement signal. According to the invention, reduction and analysis of a space charge measurement signal in an extremely non-uniform electric field by adopting an electro-acoustic pulse method can be realized, so that development of a dielectric space charge measurement technology is promoted, and a measurement method is provided for researching a space charge transport mechanism in the extremely non-uniform electric field.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric charge distribution measurement, and in particular to an analytical method and device for measuring space charge in an extremely non-uniform electric field. Background Art

[0002] The development of space charge measurement technology has not only strongly supported theoretical research on space charge phenomena in solid dielectrics, but also provided important tools for insulation design and reliability assessment. Space charge measurement devices developed based on various technical solutions have been widely used in scientific research. Common non-destructive space charge measurement techniques include the Pulsed Electro-Acoustic method, the Pressure Wave Propagation method, and the Thermal Step method. Although these three methods implement the measurement in different ways, their principles are essentially similar. They all use external electrical, mechanical, or thermal stimuli to generate a force or electric displacement response in the dielectric being measured that is affected by the space charge. Post-processing methods such as deconvolution and calibration of the measured signal are then used to eliminate the influence of the measurement system response and infer the magnitude and distribution of the space charge. Therefore, space charge measurement technology is essentially an indirect measurement technique, and its measurement of the space charge distribution relies on the restoration and analysis of the measurement signal. The implementation principle of space charge measurement technology determines that its measurement in the thickness direction of flat samples is the most direct and simple. This is also the fundamental reason why most space charge measurement devices are only used for flat samples of thin films and thick plates.

[0003] In the highly divergent electric field (i.e., extremely nonuniform) generated by sharp electrodes such as needles and wires, the response signal generated by the applied excitation source is more complex and influenced by the spatial position of the charge itself. This makes it difficult to directly remove the influence of the system response from the measured signal and recover the spatial charge information. Therefore, analytical methods for recovering the measured signal are the main technical bottleneck limiting the application of spatial charge measurement methods in highly nonuniform electric fields, such as those generated by needle electrodes. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for analyzing space charge measurement under extremely non-uniform electric fields, so as to solve the current problem of restoring and analyzing space charge measurement signals under extremely non-uniform electric fields.

[0005] To solve the above technical problems, in a first aspect, the present invention provides an analytical method for measuring space charge in a highly non-uniform electric field, comprising the steps of:

[0006] S1: Obtain the actual measurement signal of space charge in a highly inhomogeneous electric field;

[0007] S2: Establish a simulation model for the space charge measurement process, and based on the simulation model, obtain the simulated output signals of the unit charge at different positions in the extremely non-uniform electric field simulation domain;

[0008] S3: Analyze the charge amounts at different locations that constitute the actual measurement signal based on the simulated output signal through frequency domain analysis.

[0009] Furthermore, according to the linear time-invariant system theory, the output function corresponding to the actual measurement signal of space charge in a highly inhomogeneous electric field is expressed as:

[0010] H(ρ)=∑h i,j (ρ i,j )=∑h i,j (W i,j ·e)=∑W i,j ·h i,j (e) (1)

[0011] Where H(ρ) is the actual measurement signal of space charge; ρ is the space charge density; h i,j (e) is the measurement response of unit charge e at measurement section position i, j; W i,j is the charge at the measurement section position i, j.

[0012] Furthermore, step S3 includes: performing frequency domain analysis on the actual measurement signal to obtain a frequency domain structure of the actual measurement signal represented as:

[0013] f(ρ)=A1f1+A2f2+···+A n f n (2)

[0014] Where A is the spectrum amplitude of the actual measured signal at frequency f.

[0015] Furthermore, step S3 includes: performing frequency domain analysis on the simulation output signal, and obtaining a frequency domain structure of the simulation output signal represented as:

[0016]

[0017] Where a is the spectrum amplitude of the simulated output signal at frequency f, i, j are the positions of the unit charge, It is the frequency domain characteristic array of the unit charge at all positions in the extremely inhomogeneous electric field simulation domain in the measured output.

[0018] Furthermore, the method for calculating the amount of charge at different positions constituting the actual measurement signal includes: decomposing the frequency domain structure of the actual measurement signal into the superposition of unit charges in each region at the system output, and obtaining:

[0019]

[0020] Combining equations (2) and (4), we can obtain W for solving the charge at different positions: i,j The system of equations:

[0021]

[0022] Furthermore, an extremely non-uniform electric field is generated by the dielectric to be measured with an embedded sharp electrode. Then, the electroacoustic pulse method is used to apply high-voltage electric pulses to the sharp electrode to excite space charges to generate stress waves, and the stress wave signals are received by the piezoelectric sensor as actual measurement data.

[0023] Furthermore, before performing frequency domain analysis on the actual measurement signal, the actual measurement signal is preprocessed, and the preprocessing includes denoising and signal simplification.

[0024] Furthermore, the simulation model includes: modeling the generation, propagation and acoustic-electrical signal conversion process of stress waves under non-uniform electric fields, and verifying the parameters of the simulation model by comparing with actual measurement signals.

[0025] Furthermore, by placing unit charges e in the simulation model one by one ij , and obtain the simulated output signals of the charges at different positions as the simulated output signals.

[0026] In a second aspect, the present invention further provides an analytical device for measuring space charge under extremely non-uniform electric fields, comprising an actual measurement signal acquisition module, a simulation output signal acquisition module, and an analytical module;

[0027] An actual measurement signal acquisition module, used to obtain actual measurement signals of space charges in an extremely non-uniform electric field;

[0028] A simulation output signal acquisition module is used to establish a simulation model of the space charge measurement process and obtain the simulation output signals of the unit charge at different positions in the extremely non-uniform electric field simulation domain based on the simulation model;

[0029] The analyzing module is used to analyze the charge amounts at different positions constituting the actual measurement signal according to the simulation output signal through frequency domain analysis.

[0030] The beneficial effects of the present invention are: obtaining the response of the unit charge in the measurement output at each position in the measurement domain through the simulation model; then tracing back the composition of the actual measurement signal through means such as frequency domain analysis to obtain the spatial charge distribution information (position and relative charge amount) represented by the actual measurement signal; realizing the restoration and analysis of the spatial charge measurement signal in an extremely non-uniform electric field using, for example, the electroacoustic pulse method, which can promote the development of dielectric space charge measurement technology and provide a measurement method for studying the mechanism of space charge transport under extremely non-uniform electric fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The same reference numerals are used in these drawings to represent the same or similar parts. The exemplary embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0032] Figure 1 This is a schematic diagram of actual measurement signals according to an embodiment of the present invention;

[0033] Figure 2 A flowchart for obtaining the frequency domain composition of a simulation output signal according to an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of the frequency domain composition of an actual measurement signal according to an embodiment of the present invention;

[0035] Figure 4 A schematic diagram of spatial charge distribution characteristics corresponding to a measurement signal according to an embodiment of the present invention;

[0036] Figure 5 FIG. 4 is a schematic diagram of a space charge measurement device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] like Figure 1 The analytical method for measuring space charge in a highly non-uniform electric field includes the following steps:

[0038] S1: Obtain the actual measurement signal of space charge in a highly inhomogeneous electric field;

[0039] S2: Establish a simulation model for the space charge measurement process, and based on the simulation model, obtain the simulated output signals of the unit charge at different positions in the extremely non-uniform electric field simulation domain;

[0040] S3: Analyze the charge amounts at different locations that constitute the actual measurement signal based on the simulated output signal through frequency domain analysis.

[0041] The present invention obtains the response of a unit charge in the measurement output at each position within the measurement domain through a simulation model; then, through means such as frequency domain analysis, the composition of the actual measurement signal is traced back to obtain the spatial charge distribution information (position and relative charge amount) represented by the actual measurement signal; and realizes the restoration and analysis of the spatial charge measurement signal in an extremely non-uniform electric field using, for example, the electroacoustic pulse method, which can promote the development of dielectric space charge measurement technology and provide a measurement method for studying the mechanism of space charge transport in extremely non-uniform electric fields.

[0042] According to one embodiment of the present application, the space charge measurement system is a linear time-invariant system. According to the linear time-invariant system theory, the output function corresponding to the actual measurement signal of the space charge in a highly non-uniform electric field is expressed as:

[0043] H(ρ)=∑h i,j (ρ i,j )=∑h i,j (W i,j ·e)=∑W i,j ·h i,j (e) (1)

[0044] Where H(ρ) is the actual measurement signal of space charge; ρ is the space charge density; h i,j (e) is the measurement response of unit charge e at measurement section position i, j; W i,j is the charge at the measurement section position i, j.

[0045] Furthermore, step S3 includes: performing frequency domain analysis on the actual measurement signal to obtain a frequency domain structure of the actual measurement signal represented as:

[0046] According to one embodiment of the present application, step S3 includes: performing frequency domain analysis on the actual measurement signal (discrete Fourier transform may be used), and obtaining the frequency domain structure of the actual measurement signal represented as:

[0047] f(ρ)=A1f1+A2f2+···+A n f n (2)

[0048] Where A is the spectrum amplitude of the actual measured signal at frequency f.

[0049] According to one embodiment of the present application, step S3 includes: performing frequency domain analysis on the simulation output signal (discrete Fourier transform may be used), and obtaining a frequency domain structure of the simulation output signal represented as:

[0050]

[0051] Where a is the spectrum amplitude of the simulated output signal at frequency f; i, j are the positions of the unit charge, The purpose is to obtain the frequency domain characteristic array of the unit charge at all positions in the extremely non-uniform electric field simulation domain in the measurement output by simulating the electroacoustic pulse measurement of the assumed unit charge at each position.

[0052] According to one embodiment of the present application, a method for calculating the charge amount at different locations includes: the measurement signal is the superposition of the responses of the space charge as the "source" in the measurement system; therefore, this embodiment decomposes the frequency domain structure of the actual measurement signal into the superposition of the unit charges in each region at the system output, and obtains:

[0053]

[0054] Combining equations (2) and (4), we can obtain W for solving the charge at different positions: i,j The system of equations:

[0055]

[0056] The frequency domain characteristic array of the measured response at different positions in formula (3) is Substitute into equation (5) to solve the charge W at each position i,j , obtain the spatial charge distribution characteristics corresponding to the measurement signal, that is, the two-dimensional spatial position and relative charge amount, such as Figure 4 shown.

[0057] In addition to using the method disclosed in the above solution to form a solution to the equation group through (discrete) Fourier transform, other time-frequency analysis methods such as wavelet transform can also be used to form a solution to the equation group.

[0058] According to one embodiment of the present application, this embodiment is based on the modification of a traditional space charge measurement device and sample. Taking the electroacoustic pulse method as an example, a highly non-uniform electric field is generated by a dielectric to be measured with an embedded sharp electrode, and then a high-voltage electric pulse is applied to the sharp electrode to excite the space charge to generate a stress wave, and the stress wave signal is received by a piezoelectric sensor as actual measurement data. Among them, the sharp electrode can be a stainless steel blade or a thin tungsten wire. After the piezoelectric sensor receives the stress wave signal, it converts the received stress wave signal into a time domain electrical signal as the actual measurement data.

[0059] According to an embodiment of the present application, the actual measurement signal is preprocessed before frequency domain analysis is performed on the actual measurement signal, and the preprocessing includes denoising and signal simplification. By preprocessing the actual measurement signal, environmental interference can be eliminated.

[0060] According to one embodiment of the present application, a simulation model includes modeling the generation, propagation, and acoustic-to-electrical signal conversion process of stress waves in a non-uniform electric field, and verifying the parameters of the simulation model by comparing them with actual measurement signals. During the modeling process, the simulation model calculation domain and parameter settings need to be adjusted according to the dimensions and parameters of the actual measurement device and sample. By comparing the measured and simulated output signals of the electrode interface charge under low pressure, the simulation parameters (such as sound velocity and sensor sensitivity) are verified and adjusted to obtain a simulation model that reflects the system response of the actual measurement device.

[0061] According to one embodiment of the present application, by placing unit charges e in the simulation model one by one ij(where i and j are position coordinates), and the simulated output signals of the charges at different positions are obtained as the simulated output signals.

[0062] In a second aspect, the present invention further discloses an analytical device for measuring space charge under extremely non-uniform electric fields, comprising an actual measurement signal acquisition module, a simulation output signal acquisition module, and an analytical module;

[0063] An actual measurement signal acquisition module, used to obtain actual measurement signals of space charges in an extremely non-uniform electric field;

[0064] A simulation output signal acquisition module is used to establish a simulation model of the space charge measurement process and obtain the simulation output signals of the unit charge at different positions in the extremely non-uniform electric field simulation domain based on the simulation model;

[0065] The analyzing module is used to analyze the charge amounts at different positions constituting the actual measurement signal according to the simulation output signal through frequency domain analysis.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An analytical method for measuring space charge in a highly non-uniform electric field, characterized in that: Including steps: S1: Obtain the actual measurement signal of space charge in a highly inhomogeneous electric field; S2: Establishing a simulation model of the space charge measurement process, and based on the simulation model, obtaining simulation output signals of a unit charge at different positions in the extremely non-uniform electric field simulation domain; S3: analyzing the amount of charge at different positions constituting the actual measurement signal based on the simulated output signal through frequency domain analysis.

2. The analytical method for measuring space charge under extremely non-uniform electric field according to claim 1, characterized in that: According to the linear time-invariant system theory, the output function corresponding to the actual measurement signal of the space charge in the extremely non-uniform electric field is expressed as: H(ρ)=∑h i,j (r i,j )=∑h i,j (W i,j ·e)=∑W i,j ·h i,j (e) (1) Where H(ρ) is the actual measurement signal of space charge; ρ is the space charge density; h i,j (e) is the measurement response of unit charge e at measurement section position i, j; W i,j is the charge at the measurement section position i, j.

3. The analytical method for measuring space charge under extremely non-uniform electric field according to claim 2, characterized in that: The step S3 includes: performing frequency domain analysis on the actual measurement signal to obtain a frequency domain structure of the actual measurement signal represented as: f(ρ)=A1f1+A2f2+…+A n f n (2) Where A is the spectrum amplitude of the actual measured signal at frequency f.

4. The analytical method for measuring space charge under extremely non-uniform electric field according to claim 3, characterized in that: The step S3 further includes: performing frequency domain analysis on the simulation output signal to obtain a frequency domain structure of the simulation output signal represented as: Where a is the spectrum amplitude of the simulated output signal at frequency f, i, j are the positions of the unit charge, It is the frequency domain characteristic array of the unit charge at all positions in the extremely inhomogeneous electric field simulation domain in the measured output.

5. The analytical method for measuring space charge under extremely non-uniform electric field according to claim 4, characterized in that: The calculation method of the charge amount at different positions constituting the actual measurement signal includes: decomposing the frequency domain structure of the actual measurement signal into the superposition of the unit charges of each region at the system output, and obtaining: Combining equations (2) and (4), we can obtain W for solving the charge at different positions: i,j The system of equations:

6. The analytical method for measuring space charge under extremely non-uniform electric field according to claim 3, characterized in that: The extremely non-uniform electric field is generated by the dielectric to be measured with a sharp electrode embedded in it. Then, the electroacoustic pulse method is used to apply high-voltage electric pulses to the sharp electrode to excite space charges to generate stress waves, and the stress wave signals are received by the piezoelectric sensor as actual measurement data.

7. The analytical method for measuring space charge under extremely non-uniform electric field according to claim 3, characterized in that: Before performing frequency domain analysis on the actual measurement signal, the actual measurement signal is preprocessed, and the preprocessing includes denoising and signal simplification.

8. The analytical method for measuring space charge under extremely non-uniform electric field according to claim 4, characterized in that: The simulation model includes: modeling the generation, propagation and acoustic-electrical signal conversion process of stress waves under a non-uniform electric field, and verifying the parameters of the simulation model by comparing with actual measurement signals.

9. The analytical method for measuring space charge under extremely non-uniform electric field according to claim 4, characterized in that: By placing unit charges e in the simulation model one by one ij , and obtain the simulated output signals of the charges at different positions as the simulated output signals.

10. An analytical device for measuring space charge in an extremely non-uniform electric field, characterized in that: include An actual measurement signal acquisition module, used to obtain actual measurement signals of space charges in an extremely non-uniform electric field; A simulation output signal acquisition module is used to establish a simulation model of the space charge measurement process and obtain the simulation output signals of the unit charge at different positions in the extremely non-uniform electric field simulation domain based on the simulation model; The analyzing module is used to analyze the charge amounts at different positions constituting the actual measurement signal according to the simulation output signal through frequency domain analysis.

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