Broadband impedance multichannel synchronous test method and system

Abstract

The invention discloses a broadband impedance multichannel synchronous test method and system, relates to the technical field of power systems, and solves the problem of low impedance measurement precision during multichannel parallel impedance test in the prior art. The method comprises the following steps: respectively generating a corresponding discrete frequency point set for each test channel; generating an excitation signal based on the discrete frequency point set; injecting the excitation signal into the to-be-tested equipment through the corresponding test channel; acquiring a response signal generated by the to-be-tested equipment based on the excitation signal; and calculating a broadband impedance spectrum of the to-be-tested device based on the response signal. Through a mode of generating mutually exclusive discrete frequency point sets for different test channels or adding quadrature phase offset to the same test frequency points of the different test channels, non-target signals can be filtered in a demodulation process, so that mutual interference among response signals of multi-channel test is effectively inhibited; and the impedance measurement precision during multi-channel parallel impedance testing can be improved.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and in particular to a wideband impedance multi-channel synchronous testing method and system. Background Technology

[0002] In the field of impedance testing of power equipment, accurately measuring the impedance characteristics of the equipment at different frequencies is the core basis for analyzing the equivalent circuit model of the equipment, evaluating the insulation status, and diagnosing faults.

[0003] The traditional single-sinusoidal frequency sweep method is the most basic technique in impedance testing. Its principle is to apply a sinusoidal excitation signal of a single frequency point by point, measure the voltage and current response of the equipment, and then calculate the impedance value at that frequency point. However, this method requires traversing each frequency point at fixed intervals within the target frequency band. The wider the frequency band, the more scans are required, and the test time increases linearly. This excessively long test cycle not only reduces engineering efficiency but also makes it difficult to meet the impedance testing needs of power equipment under dynamic operating conditions. Because the frequency sweep method can only reflect the impedance characteristics of the equipment in a steady state, it cannot capture the transient impedance changes exhibited by the equipment during fault transients, lightning strikes, and other transient processes, resulting in a critical deficiency in the evaluation of the equipment's dynamic impedance characteristics.

[0004] To improve impedance testing efficiency, multi-frequency synchronous excitation technology has been introduced into the field of impedance testing. This method improves impedance testing efficiency and significantly shortens testing time by simultaneously applying excitation signals of multiple frequency components in a single test. However, in multi-channel parallel impedance testing scenarios, the signal faces severe spectral interference problems, directly affecting the accuracy of impedance measurements.

[0005] Therefore, a wideband impedance multi-channel synchronous testing method and system are needed. Summary of the Invention

[0006] To address the problem of low impedance measurement accuracy in existing technologies for multi-channel parallel impedance testing, this invention provides a wideband multi-channel synchronous impedance testing method and system, which can improve the impedance measurement accuracy during multi-channel parallel impedance testing. The specific technical solution is as follows: In a first aspect, embodiments of this application provide a broadband impedance multi-channel synchronous testing method, including: Based on the multi-channel testing requirements of the device under test (DUT), a corresponding discrete frequency point set is generated for each test channel. The intersection of discrete frequency point sets from different test channels is an empty set, and the inner product of two frequency points belonging to different discrete frequency point sets is zero. Alternatively, when different discrete frequency point sets include the same frequency point, the phase difference between the excitation signals generated based on the same frequency point is 90°, 180°, or 270°. An excitation signal is generated based on this discrete frequency point set. This excitation signal is injected into the DUT through the corresponding test channel. The response signal generated by the DUT based on the excitation signal is acquired. The broadband impedance spectrum of the DUT is calculated based on the response signal.

[0007] Preferably, the multi-channel test requirement includes a target frequency band corresponding to the test channel; the multi-channel test requirement based on the device under test generates a corresponding discrete frequency point set for each test channel, including: generating candidate frequency points based on the target frequency band; generating the discrete frequency point set based on the candidate frequency points; the calculation formula for generating the candidate frequency points includes: ; in, The baseband selected based on the target frequency band. Here, k is the frequency scaling factor, and k is the candidate frequency point number. Let be the frequency value at the k-th frequency point.

[0008] Preferably, generating the excitation signal based on the discrete frequency point set includes: calculating the duration of the corresponding excitation signal based on the frequency points in the discrete frequency point set; the formula for calculating the duration includes: ; ; in, The frequency is The duration corresponding to the first frequency point, It is the smallest frequency interval in the set of discrete frequency points where the first frequency point is located. It is the frequency of any frequency point in the discrete frequency point set containing the first frequency point. Except for the set of discrete frequency points where the first frequency point is located The frequency of any point outside the range; The excitation signal is generated based on the duration and the frequency of the frequency point.

[0009] Preferably, the calculation of the broadband impedance spectrum of the device under test based on the response signal includes: separating the in-phase component and the quadrature component in the response signal; the calculation formula for separating the response signal includes: ; in, The frequency injected into test channel i is The response signal corresponding to the excitation signal, where T is the signal duration, t is time, and v(t) is the time-domain signal. It is an in-phase carrier. Orthogonal carriers, The initial phase is given; the broadband impedance spectrum of the device under test is calculated based on the in-phase component and the quadrature component.

[0010] Preferably, after calculating the broadband impedance spectrum of the device under test based on the response signal, the method further includes: extracting the impedance amplitude and phase corresponding to different frequencies from the broadband impedance spectrum; performing an inverse Fourier transform based on the impedance amplitude and phase to obtain a time-domain response curve; mapping the time-domain response curve to a distance curve; and locating the fault point of the device under test based on the distance curve.

[0011] Preferably, after obtaining the time-domain response curve, the method further includes: marking outliers in the time-domain response curve; and calculating the location of impedance discontinuities and the magnitude of reflection coefficients based on the data of the outliers.

[0012] Preferably, the device under test includes a single-phase cable, a three-phase cable, a three-phase transformer, and / or a parallel capacitor bank.

[0013] Secondly, embodiments of this application provide a wideband impedance multi-channel synchronous test system, applied to the method described in the first aspect, the system including an encoder, a signal source circuit, a signal injection module, a signal acquisition module and a digital signal processing module; This encoder is used to generate a set of discrete frequency points for each test channel based on the multi-channel testing requirements of the device under test. Wherein, the intersection between discrete frequency point sets of different test channels is an empty set, and the inner product of two frequency points belonging to different discrete frequency point sets is zero; or, when different discrete frequency point sets include the same frequency point, the phase difference of the excitation signal generated based on the same frequency point is 90°, 180° or 270°. This signal source circuit is used to generate an excitation signal based on this discrete frequency point set; This signal injection module is used to inject the excitation signal into the device under test through the corresponding test channel; The signal acquisition module is used to acquire the response signal generated by the device under test based on the excitation signal; The digital signal processing module is used to calculate the broadband impedance spectrum of the device under test based on the response signal.

[0014] Thirdly, embodiments of this application provide a computing device, including: a memory for storing a program; and a processor for loading the program to execute the method as described in the first aspect.

[0015] Fourthly, embodiments of this application provide a computer-readable storage medium including a stored program, wherein, when the program is executed, it controls the device where the computer-readable storage medium is located to perform the method described in the first aspect.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: by generating mutually exclusive discrete frequency point sets for different test channels, or by adding orthogonal phase offsets to the same test frequency points of different test channels, non-target signals can be filtered out during demodulation, thereby effectively suppressing mutual interference between response signals of multi-channel tests and improving impedance measurement accuracy during multi-channel parallel impedance testing. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0018] Figure 1 A system architecture diagram of a wideband impedance multi-channel synchronous test system provided in this application embodiment; Figure 2 A flowchart illustrating a wideband impedance multi-channel synchronous testing method provided in this application embodiment; Figure 3 This is a schematic diagram of the structure of a computing device provided in an embodiment of this application. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0021] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0022] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0023] To address the issue of low impedance measurement accuracy in traditional methods for multi-channel parallel impedance testing, this invention provides a wideband impedance multi-channel synchronous testing method and system, which can improve impedance measurement accuracy during multi-channel parallel impedance testing.

[0024] To better understand the embodiments of this application, the system architecture used in the embodiments of this application will be described below.

[0025] Please see Figure 1 , Figure 1 A system architecture diagram of a wideband impedance multi-channel synchronous test system provided in this application embodiment is shown below. Figure 1 As shown, the system 10 includes an encoder 101, a signal source circuit 102, a signal injection module 103, a signal acquisition module 104, and a digital signal processing module 105; wherein, the encoder 101, the signal source circuit 102, and the signal injection module 103 are connected in sequence, the signal injection module 103 and the signal acquisition module 104 are respectively connected to the device under test 90, and the signal acquisition module 104 is connected to the digital signal processing module 105.

[0026] The signal source circuit 102 is used to generate high-precision, high-resolution discrete frequency points through digital control, and can quickly switch frequencies and support arbitrary frequency steps. More specifically, the signal injection module 103 includes multiple test channels, each of which is used to test the impedance spectrum of different parts or components of the device under test 90 in different target frequency bands. The signal source circuit 102 can generate discrete frequency points for impedance testing for different test channels within a pre-set target frequency band.

[0027] Preferably, the signal source circuit 102 includes a Direct Digital Synthesizer (DDS) signal source. For example, the DDS signal source is an AD9854 module used to generate signals with frequencies ranging from 0.01 Hz to 30 MHz.

[0028] The encoder 101 is used to perform orthogonal encoding on these discrete frequency point sets, so that the digital signal processing module 105 can separate the response signals of each frequency point through orthogonal decoding and avoid mutual interference.

[0029] Optionally, the encoder 101 can encode the discrete frequency point sets corresponding to the multiple test channels into mutually exclusive discrete frequency point sets, that is, the intersection between discrete frequency point sets of different test channels is an empty set; at the same time, the inner product of two frequency points belonging to different discrete frequency point sets is zero, satisfying the orthogonality condition.

[0030] Optionally, encoder 101 can also be used to add quadrature phase shift to excitation signals of the same frequency but different test channels, so that the response signals corresponding to the excitation signals of the same frequency can be distinguished.

[0031] Preferably, encoder 101 includes an orthogonal Walsh function encoder and a field-programmable gate array (FPGA); the Walsh code generated by the FPGA controls the phase of the signal.

[0032] By encoding discrete frequency point sets, each test channel can only perform measurements at its assigned key frequency points. This not only allows for targeted acquisition of impedance data of the test object at important frequencies, but also avoids the time wastage caused by measuring the entire frequency band in a continuous frequency range. Thus, while ensuring test accuracy, the overall test efficiency of the system 10 is improved.

[0033] The signal source circuit 102 is also used to generate an excitation signal based on a discrete frequency point set, and inject the excitation signal into the device under test 90 through the test channel corresponding to the signal injection module 103. It can be understood that there is a one-to-one correspondence between the test channel, the target frequency band, the discrete frequency point set, the excitation signal, and the response signal.

[0034] Preferably, the system 10 also includes a multiplier (not shown in the figure) for conditioning the signal, specifically for amplifying, modulating, mixing or demodulating the signal so that the conditioned signal is better suited to the needs of acquisition and analysis.

[0035] For example, the multiplier is an AD835 module with a slew rate ≤0.3V / μs.

[0036] The signal injection module 103 includes multiple test channels, each of which can be connected to different objects under test, such as different cables, PCB lines, or electronic components in the device under test 90. Since the impedance characteristics of different objects under test may vary at different frequencies, it is necessary to allocate a discrete set of frequency points suitable for its testing requirements to each test channel.

[0037] The signal acquisition module 104 is used to synchronously acquire the response signals corresponding to the multiple excitation signals injected by the signal injection module 103; the response signals may include voltage and / or current signals.

[0038] Preferably, the signal acquisition module 104 includes an analog-to-digital converter and a controller. For example, the analog-to-digital converter is an AD7862 module with a sampling rate of 900 MSPS; the controller is a C8051f010 microcontroller used to control multi-channel synchronous sampling with a delay error of <900 ns.

[0039] The digital signal processing module 105 is used to calculate the broadband impedance spectrum of the device under test 90 based on the response signal.

[0040] Preferably, the digital signal processing module 105 includes a digital signal processor or an FPGA.

[0041] Among them, device under test 90 is the device whose impedance needs to be tested.

[0042] Preferably, the device under test 90 includes a single-phase cable, a three-phase cable, a three-phase transformer, and / or a parallel capacitor bank; the system 10 can be applied to the synchronous testing of single-phase or three-phase cables; the parallel measurement of the winding impedance of a three-phase transformer; and the multi-terminal impedance spectrum analysis of a parallel capacitor bank.

[0043] It should be noted that, in the specific implementation, the system architecture can be any, including... Figure 1 A similar architecture to that in [the text]. The embodiments of this application do not limit the specific composition of this system architecture. Furthermore, Figure 1 The architectural components shown do not constitute a limitation on the system architecture, except... Figure 1 In addition to the devices shown, the system architecture may include more or fewer devices than illustrated.

[0044] Please see Figure 2 , Figure 2 This application provides a flowchart illustrating a wideband impedance multi-channel synchronous testing method, which is applied to the aforementioned wideband impedance multi-channel synchronous testing system. Figure 2 As shown, the method includes: Step 201: Based on the multi-channel testing requirements of the device under test, the encoder generates a corresponding discrete frequency point set for each test channel.

[0045] Among them, the multi-channel test requirement of the device under test refers to the requirement information for multi-channel impedance testing of the device under test that is preset in the test system, including the test object, target frequency band, and number of discrete frequency points for each test channel.

[0046] Preferably, the multi-channel test requirement includes a target frequency band corresponding to the test channel; the encoder can select a frequency point from the target frequency band as the base frequency, and then generate candidate frequency points corresponding to the test channel based on the base frequency in an exponential generation manner; then orthogonal coding is performed based on these candidate frequency points to obtain the discrete frequency point set.

[0047] For example, the encoder can select the starting frequency in the target frequency band as the base frequency.

[0048] The formula for generating the frequency points in this discrete frequency set, that is, the formula for calculating the exponentially generated frequency, includes: ; in, The baseband selected based on the target frequency band. Here, k is the frequency scaling factor, and k is the frequency point index. Let be the frequency value at the k-th frequency point.

[0049] It is understandable that the step of generating alternative frequency points can be performed by the encoder or by the signal source circuit.

[0050] In one possible implementation, the encoder can orthogonally encode the candidate frequency points of each test channel to obtain the discrete frequency point set corresponding to each test channel, such that the intersection between the discrete frequency point sets of different test channels is an empty set, and the inner product of two frequency points belonging to different discrete frequency point sets is zero.

[0051] Among them, the discrete frequency point sets corresponding to any two different test channels satisfy the following conditions: ; ; in, , Let i and j be the frequency points in the discrete frequency point set i and j, respectively, n be the number of single-channel frequencies, and t be the time variable.

[0052] In another possible implementation, the encoder can directly construct a discrete frequency point set based on the candidate frequency points corresponding to each test channel; then, when the frequency points of different discrete frequency point sets partially overlap, an orthogonal phase offset is added to the co-frequency signals generated corresponding to the overlapping frequency points, so that the phase difference between the excitation signals generated based on the same frequency points is 90°, 180° or 270°.

[0053] In another possible implementation, the encoder can directly construct a discrete frequency point set based on the candidate frequency points corresponding to each test channel; then, when the frequency points of different discrete frequency point sets partially overlap, an orthogonal phase offset is added to all excitation signals corresponding to the relevant test channels, so that the phase difference between the excitation signals generated based on the same frequency point is 90°, 180° or 270°.

[0054] The formula for calculating the additional orthogonal phase offset can be as follows: ; m=1,2,3; in, Let n be the final synthesized time-domain signal for test channel i, and n be the total number of frequency points corresponding to test channel i. Let be the amplitude at the k-th frequency point. The quadrature phase shift is added to the excitation signal corresponding to test channel i.

[0055] By generating candidate frequency points based on the logarithmic distribution principle, and constructing a discrete frequency point set based on the candidate frequency points, the discrete frequency point set is dense in the low-frequency region and sparse in the high-frequency region, which adapts to the cable impedance characteristics.

[0056] For example, the discrete frequency point set corresponding to each phase of the cable in the three-phase cable test is shown in Table 1 below: Table 1 Step 202: The signal source circuit generates an excitation signal based on the discrete frequency point set.

[0057] The signal source circuit generates the excitation signal to be injected into the corresponding test channel based on the discrete frequency point set corresponding to different test channels.

[0058] The excitation signal is the signal input to the device under test (DUT). Its function is to excite the DUT to generate a response signal, which can then be used to analyze the impedance of the DUT.

[0059] Specifically, for a discrete frequency point set of a test channel, the signal source circuit generates an excitation signal of the corresponding frequency based on each frequency point; then, all the excitation signals corresponding to the discrete frequency point set can be spliced ​​together to obtain the total excitation signal of the corresponding test channel, or all the excitation signals can be injected into the device under test sequentially through the test channel.

[0060] Specifically, the duration and amplitude of the excitation signal can be preset or determined based on its frequency. For example, it can be based on expert evaluation or signal-to-noise ratio calibration based on experimental results.

[0061] Preferably, the signal source circuit calculates the duration of the corresponding excitation signal based on the frequency points in the discrete frequency point set; the formula for calculating the duration includes: ; ; in, The frequency is The duration corresponding to the first frequency point, It is the smallest frequency interval in the set of discrete frequency points where the first frequency point is located. It is the frequency of any frequency point in the discrete frequency point set containing the first frequency point. Except for the set of discrete frequency points where the first frequency point is located The frequency of any frequency point outside the specified duration is used; then, an excitation signal is generated based on the duration and the frequency of the corresponding frequency point.

[0062] Specifically, the minimum interval between the actual frequency components in the excitation signal injected into a test channel is... To distinguish excitation signals of different frequencies and prevent them from overlapping into a single peak in the spectrum, the calculation formula for this duration can be used. This ensures that the frequency resolution is sufficient to identify the frequency components of the excitation signal, avoiding the situation where a short observation time leads to poor frequency resolution and the misidentification of excitation signals of different frequencies as the same signal. Simultaneously, it also ensures testing speed, achieving a balance between frequency resolution and testing speed.

[0063] By calculating the duration of the corresponding frequency point, it can be ensured that each excitation signal can achieve a balance between frequency resolution and test speed, thereby achieving a balance between test accuracy and test efficiency.

[0064] Step 203: The signal injection circuit injects the excitation signal into the device under test through the corresponding test channel.

[0065] The signal injection circuit can perform impedance matching through matching resistors or impedance transformation circuits, and then inject the excitation signal into the device under test through the corresponding test channel.

[0066] Specifically, the signal injection power can be selected according to the type of input port of the device under test, such as DC coupling, AC coupling, differential input, etc., to inject the signal by selecting the appropriate coupling method.

[0067] Step 204: The signal acquisition module acquires the response signal generated by the device under test based on the excitation signal.

[0068] The signal acquisition module can directly acquire voltage signals by connecting sensors or probes to the output of the device under test; alternatively, it can convert the acquired voltage signal into a current signal by connecting a series sampling resistor. Then, components such as multipliers, filters, and amplifiers are used to filter, amplify, and isolate the sensed signal, addressing issues such as noise, amplitude mismatch, and common-mode interference. Finally, the conditioned analog signal is converted into a digital signal for analysis by the subsequent digital signal processing module.

[0069] Step 205: The digital signal processing module calculates the broadband impedance spectrum of the device under test based on the response signal.

[0070] The digital signal processing module can calculate the broadband impedance spectrum of the device under test based on the response signal in digital signal form.

[0071] Specifically, the response signal may include voltage and current signals. The digital signal processing module may use Ohm's law for testing, the reflection method, or a simple voltage-current FFT to calculate the impedance of the device under test (DUT) at a single frequency point, and then generate a broadband impedance spectrum of the DUT based on the impedance at multiple frequency points. This application does not impose specific limitations on the impedance calculation method used here.

[0072] Preferably, the digital signal processing module can separate the in-phase component and the quadrature component in the response signal; the calculation formula for separating the response signal includes: ; in, The frequency injected into test channel i is The response signal corresponding to the excitation signal, where T is the signal duration, t is time, j is the imaginary unit, and v(t) is the time-domain signal. It is an in-phase carrier. Orthogonal carriers, The initial phase is given; the broadband impedance spectrum of the device under test is calculated based on the in-phase component and the quadrature component.

[0073] Specifically, the initial phase refers to the phase value of the corresponding periodic physical quantity when time t=0.

[0074] Specifically, the first term in the formula is the in-phase component, and the second term is the quadrature component; in essence, the in-phase component is the real part of the response signal, and the quadrature component is the imaginary part of the response signal.

[0075] By using imaginary parts to separate out-of-phase signals, channel crosstalk can be suppressed.

[0076] Preferably, after calculating the broadband impedance spectrum of the device under test based on the response signal, the digital signal processing module can further extract the impedance amplitude corresponding to different frequencies from the broadband impedance spectrum. and phase Based on the impedance amplitude and phase, an inverse Fourier transform is performed to obtain the time-domain response curve; the time-domain response curve is mapped to a distance curve; based on the distance curve, the fault point of the device under test is located.

[0077] The formula for calculating the time-domain response curve obtained by the inverse Fourier transform includes: ; Where z(t) represents the time-domain response curve, This is an inverse Fourier transform. Specifically, the time-domain response curve is essentially a dynamic representation of the impedance characteristics in the time dimension. It describes the response process of the system's impedance as a function of time when the device under test is subjected to an "ideal broadband excitation signal" (such as an impulse signal whose spectrum covers all analysis frequencies). Specifically, each point on the curve (the impedance value at time t) represents the instantaneous value of the system impedance after time t following the excitation; the trend of the curve reflects the dynamic characteristics of the system.

[0078] Then, the time-domain response curve is further mapped to a distance curve using the formula L=vt / 2. Here, L represents the distance between the device under test and the excitation source, v represents the electromagnetic wave propagation speed, t is the time variable in the time-domain response curve, and the division by 2 is because the signal usually needs to "propagate back and forth" (from the excitation source to the target location, and then reflected back to the receiver), so the one-way distance is half of the total propagation distance.

[0079] The distance curve here represents the "impedance characteristic distribution at different locations in the system under test". In the scenario of detecting faults in transmission lines such as cables and PCBs, the time domain variable t reflects the time difference of signal reflection. The farther away the fault point is, the greater the time delay of the reflected signal return. L is the distance between the impedance point and the excitation source.

[0080] Therefore, the digital signal processing module determines the peak value of the distance curve as an impedance anomaly point or impedance discontinuity point, and directly determines the physical distance L of the fault point based on the coordinates of the peak value, thus locating the fault point.

[0081] Preferably, after obtaining the time-domain response curve, the digital signal processing module can also mark the outliers of the time-domain response curve; and calculate the location of the impedance discontinuity and the amplitude of the reflection coefficient based on the data of the outliers.

[0082] Outliers are isolated data points that deviate significantly from the overall trend of the curve, adjacent data points, or theoretical expectations. Marking these outliers facilitates curve observation and helps determine the cable's condition. Specifically, a cable may not have only one outlier. By marking these outliers on the time-domain curve, the entire cable under test can be viewed globally. For example, when there are multiple peaks, impedance discontinuities can be observed through the connection curve between the peaks: small and short faults appear as peaks on the curve, while large and long faults are not a single point. Small peaks have high reflection coefficients, while long outliers have low reflection coefficients but large distance spans. These characteristics facilitate further in-depth analysis by researchers.

[0083] In this embodiment, by generating mutually exclusive discrete frequency point sets for different test channels or by adding orthogonal phase offsets to the same test frequency points of different test channels, non-target signals can be filtered out during demodulation, thereby effectively suppressing mutual interference between response signals of multi-channel tests and improving impedance measurement accuracy during multi-channel parallel impedance testing.

[0084] The following describes the effects of the embodiments of this application using the testing process of the system provided in this application for three-phase cables: First, the system provided in this application injects a first excitation signal in the 10Hz-10kHz frequency band into phase A. The first excitation signal has a different frequency from the second excitation signal injected into phase B and the third excitation signal injected into phase C, and satisfies the orthogonality condition. The overlapping frequency bands of the second excitation signal and the third excitation signal have an additional 90° phase difference.

[0085] Then, the three-channel synchronous sampling response signal is controlled by the C8051f020 microcontroller, with a time delay error of <100ns.

[0086] Then, the impedance amplitude and phase of the response signal at each frequency point are extracted to locate the fault point of the three-phase cable.

[0087] Then, the test results of this test procedure were compared with the test results of other methods, and the results are shown in Table 2 below (signal-to-noise ratio unit: dB): Table 2 Among them, the non-orthogonal coding scheme refers to the Multisine signal scheme. Although the Multisine signal can suppress harmonics, the lack of orthogonal constraints between multiple channels leads to severe cross-interference.

[0088] Among them, the pure frequency orthogonal scheme refers to the scheme in which different excitation signals are injected into each phase of the three-phase cable and the orthogonal condition is met; the hybrid orthogonal scheme is the test scheme performed on the three-phase cable by the system provided in this application in the above test process.

[0089] As can be seen, compared with the traditional scheme without orthogonal coding, the pure frequency orthogonal and hybrid orthogonal schemes provided in this application embodiment can significantly improve the signal-to-noise ratio of the test results.

[0090] like Figure 3 As shown, Figure 3 This is a schematic diagram of a possible logical structure of a computing device provided in an embodiment of this application. The computing device 30 includes a processor 301, a communication interface 302, a memory 303, and a bus 304. The processor 301, the communication interface 302, and the memory 303 are interconnected via the bus 304. In an embodiment of this application, the processor 301 is used to control and manage the operation of the computing device 30. For example, the processor 301 is used to execute... Figure 2 The steps in the embodiments and / or other processes used in the techniques described herein. Communication interface 302 is used to support communication by computing device 30. Memory 303 is used to store program code and data of computing device 30.

[0091] The processor 301 can be a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a digital signal processor and a microprocessor, etc. The bus 304 can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 3 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0092] In another embodiment of this application, a computer-readable storage medium is also provided, the computer-readable storage medium including instructions that, when executed on a computer, cause the computer to perform the above-described... Figure 2 The method described in the embodiments.

[0093] Those skilled in the art will recognize that the units of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of the invention.

[0094] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0095] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0096] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0097] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0098] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A broadband impedance multi-channel synchronous testing method, characterized in that, The method includes: Based on the multi-channel testing requirements of the device under test, a corresponding discrete frequency point set is generated for each test channel. Wherein, the intersection of discrete frequency point sets of different test channels is an empty set, and the inner product of two frequency points belonging to different discrete frequency point sets is zero; or, when different discrete frequency point sets include the same frequency point, the phase difference between multiple excitation signals generated based on the same frequency point is 90°, 180° or 270°. An excitation signal is generated based on the discrete frequency point set; The excitation signal is injected into the device under test through the corresponding test channel; Collect the response signal generated by the device under test based on the excitation signal; The broadband impedance spectrum of the device under test is calculated based on the response signal.

2. The method according to claim 1, characterized in that, The multi-channel test requirements include the target frequency band corresponding to the test channel; the multi-channel test requirements based on the device under test generate a corresponding discrete frequency point set for each test channel, including: Based on the target frequency band, candidate frequency points are generated; Based on the candidate frequency points, the discrete frequency point set is generated; The formula for generating the candidate frequency points includes: ； in, The baseband selected based on the target frequency band. Here, k is the frequency scaling factor, and k is the candidate frequency point number. Let be the frequency value at the k-th frequency point.

3. The method according to claim 1, characterized in that, The generation of the excitation signal based on the discrete frequency point set includes: Based on the frequency points in the discrete frequency point set, the duration of the corresponding excitation signal is calculated; the formula for calculating the duration includes: ； ； in, It is a frequency of The duration corresponding to the first frequency point, It is the smallest frequency interval in the set of discrete frequency points where the first frequency point is located. It is the frequency of any frequency point in the discrete frequency point set containing the first frequency point. Except for the set of discrete frequency points where the first frequency point is located The frequency of any point outside the range; The excitation signal is generated based on the duration and the frequency of the frequency point.

4. The method according to claim 1, characterized in that, The calculation of the broadband impedance spectrum of the device under test based on the response signal includes: Separate the in-phase and quadrature components in the response signal; the formula for separating the response signal includes: ； in, The frequency injected into test channel i is The response signal corresponding to the excitation signal, where T is the signal duration, t is time, j is the imaginary unit, and v(t) is the time-domain signal. It is an in-phase carrier. Orthogonal carriers, This is the initial phase; The broadband impedance spectrum of the device under test is calculated based on the in-phase component and the quadrature component.

5. The method according to any one of claims 1-4, characterized in that, After calculating the broadband impedance spectrum of the device under test based on the response signal, the method further includes: Extract the impedance amplitude and phase corresponding to different frequencies from the broadband impedance spectrum; Based on the impedance amplitude and phase, an inverse Fourier transform is performed to obtain the time-domain response curve; Map the time-domain response curve to a distance curve; Based on the distance curve, the fault point of the device under test is located.

6. The method according to claim 5, characterized in that, After obtaining the time-domain response curve, the method further includes: Mark the outliers in the time-domain response curve; The location of the impedance discontinuity and the magnitude of the reflection coefficient are calculated based on the data from the anomaly points.

7. The method according to any one of claims 1-4, characterized in that, The device under test includes single-phase cables, three-phase cables, three-phase transformers, and / or parallel capacitor banks.

8. A wideband impedance multi-channel synchronous testing system, characterized in that, The system applied to the method of any one of claims 1-7 includes an encoder, a signal source circuit, a signal injection module, a signal acquisition module, and a digital signal processing module; The encoder is used to generate a corresponding discrete frequency point set for each test channel based on the multi-channel test requirements of the device under test. Wherein, the intersection of discrete frequency point sets of different test channels is an empty set, and the inner product of two frequency points belonging to different discrete frequency point sets is zero; or, when different discrete frequency point sets include the same frequency point, the phase difference between the excitation signals generated based on the same frequency point is 90°, 180° or 270°. The signal source circuit is used to generate an excitation signal based on the discrete frequency point set; The signal injection module is used to inject the excitation signal into the device under test through the corresponding test channel; The signal acquisition module is used to acquire the response signal generated by the device under test based on the excitation signal; The digital signal processing module is used to calculate the broadband impedance spectrum of the device under test based on the response signal.

9. A computing device, characterized in that, include: Memory, used to store programs; A processor for loading the program to perform the method as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored program, wherein, when the program is executed, it controls the device on which the computer-readable storage medium is located to perform the method of any one of claims 1-7.

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