Impedance measurement device and method

Abstract

The invention provides an impedance measuring device and method, and relates to the technical field of electrics, and the device comprises a signal transceiver, a current injection probe and a current detection probe. The signal transceiver is used for compensating the amplitude and phase of the sweep frequency signal of each frequency point, and the compensated amplitude and phase of the sweep frequency signal of each frequency point are different; after the compensated sweep frequency signal is injected into the current injection probe through the first port, a first transmission signal fed back by the second port and a first reflection signal of the first port are obtained, and after the compensated sweep frequency signal is injected into the current detection probe through the second port, a second transmission signal fed back by the second port and a second reflection signal of the first port are obtained; acquiring a second transmission signal of the second port and a second reflection signal of the first port; and determining the impedance of the loop to be measured according to the sweep frequency signal before compensation, the first transmission signal, the second transmission signal, the first reflection signal and the second reflection signal. According to the scheme, online impedance measurement can be realized.

Description

Technical Field

[0001] The present application relates to the field of electrical technology, and in particular to an impedance measurement device and method. Background Art

[0002] Impedance is one of the important parameters of switchgear. Real-time monitoring and analysis of impedance can detect abnormal situations in time, take appropriate measures for repair or maintenance, and prevent the occurrence of faults.

[0003] In the prior art, when performing impedance measurement, it is necessary to first perform a power outage for maintenance, then directly connect the test equipment in series to the loop, and then power on again to perform impedance measurement using the test equipment.

[0004] However, the existing method of connecting the test equipment in series with the high-voltage circuit is prone to accidents during operation and has low safety. Summary of the Invention

[0005] The present application provides an impedance measurement device and method for solving the problem of poor safety of existing impedance measurement methods.

[0006] In a first aspect, an embodiment of the present application provides an impedance measurement device, comprising: a signal transceiver, a current injection probe, and a current detection probe, wherein a first port of the signal transceiver is connected to the current injection probe, a second port of the signal transceiver is connected to the current detection probe, and the current injection probe and the current detection probe are used to connect to a circuit to be measured;

[0007] The signal transceiver is used to compensate the amplitude and phase of the sweep frequency signal at each frequency point, so that the amplitude and phase of the sweep frequency signal at each frequency point after compensation are different;

[0008] The signal transceiver is further configured to, after injecting the compensated swept frequency signal into the current injection probe through the first port, obtain a first transmitted signal fed back by the second port and a first reflected signal of the first port; and, after injecting the compensated swept frequency signal into the current detection probe through the second port, obtain a second transmitted signal of the second port and a second reflected signal of the first port;

[0009] The signal transceiver is further used to determine the impedance of the circuit to be measured based on the amplitude and phase of the swept frequency signal before compensation, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal.

[0010] In a second aspect, an embodiment of the present application provides an impedance measurement method, comprising:

[0011] The amplitude and phase of the sweep signal at each frequency point are compensated, and the amplitude and phase of the sweep signal at each frequency point after compensation are different;

[0012] After injecting the compensated swept frequency signal into the current injection probe through the first port of the signal transceiver, obtaining a first transmission signal fed back by the second port of the signal transceiver and a first reflection signal of the first port; and after injecting the compensated swept frequency signal into the current detection probe through the second port, obtaining a second transmission signal of the second port and a second reflection signal of the first port;

[0013] The impedance of the circuit to be measured is determined based on the amplitude and phase of the swept frequency signal before compensation, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal.

[0014] The impedance measurement device and method provided in the embodiments of the present application achieve impedance measurement simply by comparing the excitation signal emitted by the two ports of the signal transceiver with the corresponding response signal during impedance testing, eliminating the need for power outages and maintenance, and avoiding cumbersome operational procedures. Furthermore, by transmitting and receiving amplitude- and phase-compensated swept-frequency signals, attenuation and phase shift in the current probe are offset, thereby simplifying the data processing process on the host computer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0016] Figure 1 A schematic structural diagram of an impedance measurement device provided in an embodiment of the present application;

[0017] Figure 2 This is a circuit diagram of a traditional frequency domain dual-probe online impedance measurement;

[0018] Figure 3 This is a schematic diagram of the structure of the current injection probe;

[0019] Figure 4 It is a structural diagram of the current detection probe;

[0020] Figure 5 This is the equivalent circuit diagram of the frequency domain dual-probe online impedance measurement system;

[0021] Figure 6 Schematic diagram for obtaining the S parameters of the current probe network;

[0022] Figure 7 This is a schematic diagram of the typical two-port VNA structure;

[0023] Figure 8 A waveform diagram provided for an embodiment of the present application;

[0024] Figure 9 This is a diagram showing the difference between the original frequency domain dual-probe measurement system and the hardware compensation measurement system provided in the embodiment of the present application;

[0025] Figure 10 A comparison diagram of the calculation process without compensation and with compensation provided in the embodiment of the present application;

[0026] Figure 11 A schematic structural diagram of an impedance measurement device provided in an embodiment of the present application;

[0027] Figure 12 A flow chart of the impedance measurement method provided in an embodiment of the present application.

[0028] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0030] During operation, power systems primarily rely on protective devices to ensure safety. Therefore, it's necessary to constantly monitor the electrical parameters of these devices to ensure the proper operation of the ionization system. For example, consider high-voltage switchgear circuit breakers, which are used as protective devices in power systems. These devices withstand complex operating conditions such as high voltage, high current, and high temperature. The stability and reliability of the mechanical properties of these devices are crucial for ensuring the proper operation of the power system. Real-time monitoring and analysis of the circuit breaker's contact resistance, one of the parameters that characterizes its mechanical properties, can help identify anomalies in a timely manner and enable appropriate repair or maintenance measures to prevent failures. Furthermore, through long-term analysis of monitoring data, key information such as the circuit breaker's operating mode, load conditions, and lifespan prediction can be obtained. Based on this information, equipment operation and maintenance strategies can be optimized, maintenance plans can be rationally arranged, equipment service life can be extended, and system reliability and availability can be improved.

[0031] In practical applications, traditional circuit breaker contact resistance measurement methods require the test equipment to be directly connected in series with the high-voltage circuit. This often requires power outages for maintenance during impedance measurement, making the operation cumbersome and risky. Alternatively, there are other online impedance measurement techniques, such as frequency-domain dual-probe, time-domain dual-probe, and frequency-domain single-probe impedance measurement. Of these, the frequency-domain dual-probe method is the most commonly used in practical applications. However, this method involves calculations for multiple steps, including the current injection probe, the circuit to be measured, and the current detection probe. Signal attenuation and phase shifts occur in both the current injection and detection probe stages, complicating the calculation process.

[0032] In response to the above problems, the present application provides a device and method for online impedance measurement. On the one hand, when performing impedance testing, there is no need for power outage maintenance, avoiding cumbersome operating procedures. On the other hand, by sending and receiving sweep frequency signals after amplitude and phase compensation, the attenuation and phase shift of the current probe link are offset, thereby simplifying the data processing process on the host computer side.

[0033] The technical solution of the present application is described in detail below through specific embodiments. It should be noted that the following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0034] Figure 1 A schematic diagram of the structure of the impedance measurement device provided in the embodiment of the present application is shown in FIG. Figure 1 As shown, it includes a signal transceiver 10 , a current injection probe 11 and a current detection probe 12 .

[0035] The signal transceiver 10 has two ports, namely Figure 1 The first port 101 and the second port 102 are connected to the current injection probe 11 and the second port 102 are connected to the current detection probe 12. The current injection probe 11 and the current detection probe 12 are used to connect the circuit to be tested.

[0036] The signal transceiver 10 can inject a compensated swept-frequency signal into the current injection probe through the first port 101. Alternatively, the signal transceiver 10 can also inject a compensated swept-frequency signal into the current detection probe through the second port 102. The signal transceiver 10 then obtains the response signals (specifically, including the first transmitted signal, the second transmitted signal, the first reflected signal, and the second reflected signal) generated by the first and second ports, and determines the impedance of the circuit under test based on the amplitude and phase of the uncompensated swept-frequency signal, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal.

[0037] In this embodiment, the signal transceiver 10 differs from a traditional vector network analyzer (VNA) in that it can be controlled by a digital signal processor (DSP) or field programmable gate array (FPGA) to generate stimulus signals with different waveforms. Specifically, the signal transceiver 10 compensates for the amplitude and phase of the swept-frequency signal at each frequency point and then sequentially injects the compensated swept-frequency signal into the current injection probe and the current detection probe. Different waveforms have different amplitudes and phases.

[0038] The excitation signal sent by a VNA is a constant-amplitude frequency sweep or a power sweep at a single frequency point, and the phase of each spectral component is zero. The amplitude and phase of the signal emitted at each frequency point cannot be customized. Using a VNA for online impedance measurement cannot compensate for the attenuation and phase shift caused by the current probe.

[0039] In this embodiment, the signal transceiver injects the compensated swept frequency signal into the current injection probe and the current detection probe in sequence, and can determine the impedance of the circuit to be measured based on the response signals of the current detection probe and the current injection probe.

[0040] In order to facilitate understanding of how the signal transceiver of the present application determines the impedance of the circuit to be measured, the working principle of the traditional VNA online impedance measurement is first introduced.

[0041] Figure 2 This is a circuit diagram of the traditional frequency domain dual probe online impedance measurement, such as Figure 2 As shown, it consists of a vector network analyzer 20, a current injection probe 21, and a current detection probe 22. The VNA and the probes are connected by coaxial cables. In order to measure the in-line impedance of the circuit under test powered by the power supply, the two probes are clamped on the conductor of the circuit under test. Port 1 of the VNA injects a stepped frequency swept sinusoidal signal into the circuit under test through the current injection probe, and port 2 of the VNA measures the response of the injected signal through the current detection probe. For further reference, Figure 3 The diagram below is a schematic diagram of the structure of the current injection probe. The left side of the diagram shows the overall three-dimensional structure of the current injection probe, and the right side of the diagram shows the cross-sectional structure of the current probe. The current probe mainly includes an injection head, coupling capacitors, calibration devices, and connecting wires. The injection head is the core component of the probe, responsible for effectively injecting the current signal into the cable under test. The coupling capacitor is used to isolate the DC component to ensure that only the AC signal passes through. The calibration device is used to calibrate the performance of the probe to ensure its accuracy and reliability. In addition, Figure 4This is a structural diagram of the current detection probe. The figure on the left is the overall three-dimensional structure of the current detection probe, and the figure on the right is the internal structure of the current detection probe. The current detection probe can include either a multi-turn coil or a toroidal magnetic core. The multi-turn coil is used to efficiently measure the radio frequency current, while the toroidal magnetic core is used to concentrate and guide the magnetic field to ensure the accuracy of the measurement.

[0042] Figure 5 This is the equivalent circuit diagram of the frequency domain dual-probe online impedance measurement system, as shown Figure 5 As shown in the figure, the frequency domain dual-probe online impedance measurement system can be regarded as a cascade of three two-port networks: current injection probe, circuit to be measured, and current detection probe. The three networks are represented by N IP1 , N X , N IP2 , the cascaded two-port network of the entire system is: N=N IP1 N X N IP2

[0043] In addition, since the ABCD matrix can be cascaded during calculation, it is beneficial to N IP1 With N IP2 To de-embed the impedance measurement system, the ABCD matrix is ​​used to represent the information of the impedance measurement system. The definition of the ABCD matrix is ​​as follows:

[0044]

[0045] Among them, V1 and I1 are the network input voltage and current, and their reference directions are non-correlated reference directions; V2 and I2 are the network output voltage and current, and their reference directions are correlated reference directions.

[0046] Using ABCD parameters to express the cascade relationship of the impedance measurement system, we have:

[0047]

[0048] By the ABCD matrix definition and Figure 4 The equivalent circuit of the circuit to be tested can be calculated as follows:

[0049]

[0050] From the above derivation, we can know that we only need to calculate B X The loop impedance to be measured can be obtained. To solve B x , the ABCD matrix of the system two-port network N and the two current probe networks N should be obtained IP1 , N IP2 The ABCD matrix.

[0051] Among them, the frequency domain dual-probe online impedance measurement system uses VNA as the measuring instrument, and the network parameters directly measured by VNA are S parameters, not ABCD parameters. S parameters are the ratio of the output sine wave (divided into two types: the transmitted wave from other ports and the reflected wave from this port) to the input sine wave. The amplitude is the ratio of the amplitudes of the two sine waves, and the phase is the difference between the output and input sine wave phases. In order to mark the ports where the sine wave is incident and emitted, the ports are identified with consecutive subscripts, and these subscripts are used in each S parameter. For example, the return loss S 11 is the ratio of the reflected wave to the incident wave at port 1, and the forward transmission coefficient S 21 is the ratio of the transmitted wave at port 2 to the incident wave at port 1. Both S parameters and ABCD parameters are used to describe the behavior of linear passive interconnects, but they are expressed differently, so the two can be converted to each other.

[0052] Use VNA to measure the S parameters of the system network parameter N, and obtain the ABCD parameters of the system N by the following conversion formula:

[0053]

[0054]

[0055]

[0056]

[0057] Where Z0 is the impedance of the system N. Then obtain the current injection probe network N IP1 ABCD parameters, and the current detection probe network N IP2 ABCD parameters. Figure 6 The circuit schematic diagram for obtaining the S parameters of the current probe network. Figure 6 As shown, for the current injection probe network N IP1 , VNA port 1 is connected to the probe, port 2 is connected to one side of the calibration fixture, and the other side of the calibration fixture is connected to the short-circuit element 60; for the current detection probe network N IP2 , swap the two ports of the VNA, and set the rest of the settings the same as the current injection probe. Get the two-port S parameters of the current injection probe and the current detection probe measured twice, and follow the above process of converting the S parameters of the entire system N to ABCD parameters to obtain N IP1 The ABCD parameter matrix, and N IP2 The ABCD parameter matrix.

[0058] At this point, the data required to calculate the loop impedance to be measured have been obtained, and only basic matrix operations are needed to obtain :

[0059]

[0060]

[0061] The frequency-domain dual-probe online impedance measurement method has a relatively mature application. However, as can be seen from the above calculation process, obtaining the impedance to be measured requires three S-parameter measurements, three S-parameter conversions to ABCD parameters, two matrix inversion operations, and one matrix multiplication operation, making the calculation process relatively complicated.

[0062] The overall working principle of VNA is as follows:

[0063] A VNA measures the amplitude and phase response of a device under test (DUT) by transmitting and receiving known signals. The basic principle is to input a known signal into the DUT and then measure the amplitude and phase changes of the output signal. By comparing the differences between the input and output signals, the DUT's S-parameters can be calculated.

[0064] Figure 7 This is a typical two-port VNA structure diagram, as shown in Figure 7 As shown, the VNA consists of four parts: a signal source 70, a signal separation device (not shown), a receiver, and a processing and display unit (not shown, which is a built-in processing system of the VNA and interacts through a screen and buttons).

[0065] Signal source 70 provides input signals for the circuit under test. Because the VNA tests the relationship between the transmission and reflection characteristics of the circuit under test and the operating frequency and power, the signal source within the VNA must have frequency and power sweep capabilities. The signal source sequentially transmits swept frequency signals through the VNA's first and second ports 72 and 73. The circuit under test responds to these sequentially transmitted swept frequency signal excitation waves through transmission and reflection.

[0066] The signal separation device, consisting of a power splitter and a directional coupler 71, is used to separate the incident signal at one port, the transmitted signal at the other port, and the reflected signal at this port. The VNA's internal power splitter distributes the signal source's output power to two reference receivers a1 and a2, as well as the incident signal at the two ports. The directional coupler, connected directly to the test port, separates the transmitted and reflected signals.

[0067] The receiver completes the test, comparison and analysis of the amplitude and phase parameters of the incident signal of this port, the transmitted signal of the other port and the reflected signal of this port. The display processing part completes the processing of the test results and displays the test results in the required manner.

[0068] The above article has introduced VNA online impedance measurement. In general, the signal sent by the VNA is a constant-amplitude swept frequency signal or a power sweep of a single frequency point, and the phase of each spectral component is 0. The amplitude and phase of the signal emitted at each frequency point cannot be customized. As a result, the VNA cannot compensate for the attenuation and phase shift caused by the current probe. As a result, obtaining the measured impedance requires three S-parameter measurements, three S-parameter conversions to ABCD parameters, two matrix inversion operations, and one matrix multiplication operation, resulting in a relatively complex calculation process.

[0069] Therefore, the present application provides a hardware compensation method to achieve the cancellation of current probe attenuation and phase shift, thereby simplifying the calculation process of the measured impedance. The following introduces the signal transceiver of the present application through some embodiments to illustrate how to achieve the cancellation of current probe attenuation and phase shift.

[0070] In this embodiment, the signal source of the signal transceiver can compensate the amplitude and phase of the swept frequency signal at each frequency point to achieve amplitude and phase compensation of the swept frequency signal. The compensated swept frequency signal is then injected into the current injection probe and the current detection probe in sequence. The amplitude and phase of the swept frequency signal at each frequency point after compensation are different. The impedance of the circuit under test is then determined based on the phase and amplitude of the swept frequency signal before compensation and the response signals of the current injection probe and the current detection probe.

[0071] In this embodiment, the hardware composition of the signal transceiver is substantially the same as that of the VNA. Unlike the aforementioned VNA, in order to achieve amplitude modulation and phase modulation compensation of the swept frequency signal, the signal source in the signal transceiver is controlled by a DSP or FPGA to generate different waveforms, and the amplitude and phase of each waveform are different.

[0072] Among them, after the signal transceiver compensates the swept frequency signal, the compensated swept frequency signal waveform can be customized according to the different current probe transmission networks. Therefore, the current probe network information can be burned into the ROM of the DSP or FPGA development board in advance, and the corresponding data can be called in the DSP or FPGA chip for calculation and control of waveform generation.

[0073] Regarding the specific process of compensating the swept frequency signal, in some embodiments, a processor chip (such as a DSP or FPGA chip) may be configured in the signal transceiver, and the processor chip is connected to the current injection probe and the current detection probe.

[0074] Among them, the processor chip can obtain the first reflection coefficient and the first transmission coefficient of the current injection probe, as well as the second reflection coefficient and the second transmission coefficient of the current detection probe, and then compensate the amplitude and phase of the swept frequency signal according to the first reflection coefficient, the first transmission coefficient, the second reflection coefficient and the second transmission coefficient.

[0075] In this embodiment, the first reflection coefficient and the first transmission coefficient, namely the current injection probe network N IP1 Similarly, the second reflection coefficient and the second parameter coefficient are the S parameters of the current detection network N IP2 S parameters. Among them, S parameters include S 11 、S 12 、S 21 and S 22 .

[0076] Figure 8 The waveform diagram provided in the embodiment of the present application is as follows: Figure 8 As shown in the figure, the signal transceiver generates a sweep waveform at the first port and the second port in turn. In the absence of compensation, the generated sweep signal waveform is n sine waves with different frequencies, all with amplitude A0 and phase 0 (the moment when the sine waves of the same frequency begin to be generated is defined as the starting time t i_start If the moment corresponds to sin(2πk), k=0,1,2,…, then the phase is considered to be 0), and the frequency point is set to f i , where i=1,2…n, frequency f i As i increases, linear or logarithmic frequency sweep is used. To avoid the sudden change of the output signal at the moment of frequency switching and the introduction of additional noise, the sine wave corresponding to each frequency point is repeated for several cycles (corresponding to Figure 8 The “×times” in the formula is not used, and the subsequent calculations do not use the first and last segments of the sine wave at the same frequency point and its response.

[0077] To achieve compensation, the above Figure 6 The system shown obtains the S parameters of the current injection probe network and the current detection probe network. The frequency selection settings are exactly the same as the frequency of the uncompensated waveform mentioned above. 21 , i.e. the forward transmission coefficient, which includes the amplitude attenuation and phase shift during the transmission process. The forward transmission coefficients of n frequency points are burned into the ROM of the signal transceiver provided in the embodiment of the present application. The amplitude and phase of the transmission coefficients of the two current probes are ,

[0078] Through the above operation, the compensated waveform can be obtained. For each frequency point f i , the corresponding waveform amplitude and phase (the phase is still based on the aforementioned t i_start As a benchmark) is:

[0079]

[0080]

[0081] This compensation is equivalent to inserting a "reverse current probe" link in front of the uncompensated sweep signal. The obtained signal is equivalent to the response of the uncompensated constant amplitude zero phase sweep signal passing through only the circuit under test. The above compensation only needs to be based on the original uncompensated signal divided by S 21 This can be achieved by adjusting the amplitude and adding or subtracting the phase.

[0082] The embodiment of the present application uses a hardware compensation method to compensate for the amplitude and phase of the swept frequency signal, thereby achieving the cancellation of the current probe attenuation and phase shift, which can simplify the subsequent calculation process of the loop impedance to be measured, and matrix inversion and matrix multiplication are omitted, thereby improving the efficiency of impedance measurement.

[0083] The following describes in detail how to obtain the first reflection coefficient and the first transmission coefficient of the current injection probe, and the second reflection coefficient and the second transmission coefficient of the current detection probe, ie, S parameters, through some embodiments.

[0084] For details, please refer to the above Figure 6 , in the adoption Figure 6 To obtain the S parameters of the current injection probe network and the current detection probe network using the circuit structure shown, the processor chip needs to perform the following operations:

[0085] When the first port is connected to a current injection probe and the second port is connected to a calibration fixture, a first target input signal input to the first port, a first target transmission signal fed back from the second port, and a first target reflection signal fed back from the first port are obtained, and the calibration fixture is used to connect a short-circuit component;

[0086] determining a first reflection coefficient and a first transmission coefficient based on the first target input signal, the first target transmission signal, and the first target reflection signal;

[0087] When the first port is connected to a calibration fixture and the second port is connected to a current detection probe, a second target input signal input to the second port, a second target transmission signal fed back by the first port, and a second target reflection signal fed back by the second port are obtained;

[0088] A second reflection coefficient and a second transmission coefficient are determined based on the second object input signal, the second object transmission signal, and the second object reflection signal.

[0089] For details, refer to the above Figure 6 When the first port of the signal transceiver is connected to the current injection probe, and the second port of the signal transceiver is connected to one side of the calibration fixture (the other side of the calibration fixture is connected to a short-circuit component), the signal transceiver sends the incident wave to the current injection probe through the first port. 11 It can be used to characterize the return loss, which is the ratio of the reflected wave to the incident wave when the current is injected into the probe.21 It can be used to characterize the forward transmission coefficient, which is the ratio of the transmitted wave received by the second port to the incident wave emitted by the first port.

[0090] In addition, in some embodiments, the processor chip may also calculate the impedance of the loop to be measured by performing the following operations:

[0091] Obtaining a third reflection coefficient and a third transmission coefficient of the circuit to be tested based on the amplitude and phase of the swept frequency signal before compensation, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal;

[0092] constructing a matrix based on the third reflection coefficient and the third transmission coefficient;

[0093] According to the matrix, determine the impedance of the circuit to be measured.

[0094] In this embodiment, the third reflection coefficient may include the reflection coefficient S 11 and reflection coefficient S 22 , the third transmission coefficient may include the transmission coefficient S 21 and the transmission coefficient S 12 . In addition, the matrix is ​​the ABCD matrix mentioned above.

[0095] As mentioned earlier, compensating a swept-frequency signal is equivalent to inserting a "reverse current probe" in series before the uncompensated signal. The resulting signal is equivalent to the response of an uncompensated, constant-amplitude, zero-phase swept-frequency signal passing through only the circuit under test. Therefore, when the signal response (reflected and transmitted waves) is transmitted to the receiver, it should be compared with the uncompensated signal, not the actual output signal, to determine the S-parameters of the two-port network of the circuit under test. Converting these S-parameters to ABCD parameters directly yields the loop impedance.

[0096] Figure 9 This is a diagram showing the difference between the original frequency domain dual-probe measurement system and the hardware compensation measurement system provided in the embodiment of the present application. Figure 9 As shown in the figure, after the compensation of the swept frequency signal is completed, the first port of the signal transceiver injects the compensated amplitude-modulated phase-modulated swept frequency signal into the circuit under test through the current injection probe, and the first port and the second port detect the received signal response. The ratio of the response signal received by the first port and the second port to the uncompensated constant-amplitude zero-phase swept frequency signal is the reflection coefficient S of the circuit under test. 11 and the transmission coefficient S 21 .

[0097] Similarly, the second port of the signal transceiver transmits the compensated amplitude-modulated phase-modulated frequency sweep signal. The signal transceiver receives the responses of the first port and the second port and performs comparative calculations to obtain the reflection coefficient S of the circuit to be tested. 22 and the transmission coefficient S 12 .

[0098] Among them, the reflection coefficient S of the circuit to be tested is obtained 11 and the transmission coefficient S 21 , and the reflection coefficient S 22 and the transmission coefficient S 12 Afterwards, based on the conversion formula between the S parameters and the ABCD matrix mentioned above, the ABCD matrix of the circuit to be measured can be obtained, and the impedance of the circuit to be measured can be calculated from it.

[0099] In the embodiment of the present application, by directly obtaining the third reflection coefficient and the third transmission coefficient of the circuit to be measured, the ABCD matrix of the circuit to be measured can be directly obtained, thereby directly calculating the impedance of the circuit to be measured, reducing the calculation complexity.

[0100] For example, Figure 10 The following is a comparison diagram of the calculation process without compensation and with compensation provided in the embodiment of the present application, as shown in FIG. Figure 10 As shown, after applying hardware compensation, the loop impedance measurement and calculation process is simplified. Using the original frequency-domain dual-probe impedance measurement system, obtaining the measured impedance requires three S-parameter measurements, three S-parameter conversions to ABCD parameters, two matrix inversion operations, and one matrix multiplication operation. By replacing the VNA with the swept-frequency amplitude modulation compensation signal transceiver provided in this application, obtaining the impedance of the measured loop only requires three S-parameter measurements and one S-parameter conversion to ABCD parameters, completely avoiding complex matrix operations.

[0101] Furthermore, in some embodiments, the signal transceiver further includes: a converter and a directional coupler. The processor chip is connected to the directional coupler via the converter, and the directional coupler is connected to the first port and the second port. The converter is configured to perform analog-to-digital conversion or digital-to-analog conversion. The directional coupler is configured to separate the incident signal emitted by the processor chip and the reflected and transmitted signals received by the processor chip.

[0102] In this embodiment, the operation of the receiver in the signal transceiver is also implemented in the DSP or FPGA, and the transmitted signal passes through the directional coupler and the analog-to-digital converter in sequence and is compared with the output signal.

[0103] In addition, in some embodiments, the display of data information such as the measured impedance of the circuit to be measured can be performed on the host computer, that is, the signal transceiver can also exchange data with the host computer to realize the display of data information.

[0104] In addition, in some embodiments, the signal transceiver further includes a power amplifier, and the converter is connected to the directional coupler via the power amplifier; the power amplifier is used to amplify the incident signal emitted by the processor chip, as well as the reflected signal and the transmitted signal received by the processor chip.

[0105] In this embodiment, the purpose of adding a power amplifier is to avoid inaccurate results caused by attenuation of high-frequency signals during transmission. Two additional bidirectional power amplifiers are added to amplify the output signal and the returned signal.

[0106] For example, Figure 11 A schematic diagram of the structure of the impedance measurement device provided in the embodiment of the present application is shown in FIG. Figure 11 As shown, the AM compensation signal transceiver realizes compensation of the frequency sweep signal and processing of the response signal through the processor chip, thereby calculating the impedance of the circuit to be measured.

[0107] In this embodiment, the impedance measurement device comprises an AM / PM swept frequency signal transceiver, a radio frequency current injection probe, and a current detection probe. When the impedance measurement device is in operation, the two current probes are connected to the circuit of the switchgear circuit breaker to be tested.

[0108] The AM / PM swept-frequency signal transceiver consists of a processor chip based on an FPGA / DSP, a host computer, an analog-to-digital (A / D / A) converter, a directional coupler, and a power amplifier. The processor chip is responsible for waveform generation, current probe data storage, comparison of stimulus and response signals, and data transmission to the host computer. The host computer displays data and allows for post-processing. The A / D / D / A converter converts analog and digital signals. The directional coupler separates different response waveforms. The power amplifier amplifies the transmitted and received signals.

[0109] Current injection / detection probe: used for transmitting and receiving high-frequency signals, both are composed of a magnetic core and a coil. When in use, open the probe buckle and clip the probe onto the target cable. The probe and cable then form a transformer. When a high-frequency electrical signal is injected into the current injection probe port, the signal is coupled to the cable; conversely, the original high-frequency signal on the cable can also reach the detection probe port through inductive coupling. The injection probe has limits on the losses generated during the transmission process, so a design with a large magnetic core and a small number of coil turns (1-2 turns) is adopted; the detection probe focuses on the smoothness of the transmission coefficient S21, so a design with a small magnetic core and a large number of coil turns (6-8 turns) is adopted. The application of RF current injection / detection probes enables the transmission of electrical signals without direct electrical connection, so it can be used in online impedance measurement systems.

[0110] In practical applications, the switchgear is in a high voltage and high current system, which is not conducive to direct manual measurement of impedance. Figure 11 As shown, an impedance measurement device is applied to the contact impedance measurement of switchgear circuit breakers, thus eliminating the safety hazards associated with direct manual measurement. In this embodiment, a broadband online impedance measurement solution based on amplitude and phase modulation compensation of a swept frequency signal can measure the amplitude and phase of the power system loop impedance under high voltage and high current conditions, with an upper operating frequency limit of up to 100 MHz. If the number of frequency points is set to 101, a single test is expected to take approximately one minute.

[0111] Furthermore, loop impedance includes not only the circuit breaker contact resistance but also the high-frequency parasitic resistance and inductance of the cable. However, as aging progresses, changes in impedance other than the circuit breaker contact impedance are negligible. Therefore, it is only necessary to regularly monitor changes in loop impedance and use these changes to determine the aging of the circuit breaker, providing reference information for switchgear circuit breaker maintenance.

[0112] Figure 12 The flow chart of the impedance measurement method provided in the embodiment of the present application is as follows. The method can be applied to an impedance measurement system, such as Figure 12 As shown, it may specifically include the following steps:

[0113] Step S1210: Compensate the amplitude and phase of the frequency sweep signal at each frequency point.

[0114] The amplitude and phase of the swept frequency signal at each frequency point after compensation are different.

[0115] Step S1220: After injecting the compensated swept frequency signal into the current injection probe through the first port, obtain the first transmission signal fed back by the second port and the first reflection signal of the first port, and after injecting the compensated swept frequency signal into the current detection probe through the second port, obtain the second transmission signal of the second port and the second reflection signal of the first port.

[0116] Step S1230: Determine the impedance of the circuit to be measured based on the amplitude and phase of the uncompensated swept frequency signal, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal.

[0117] Furthermore, in some embodiments, step S1230 can be specifically implemented through the following steps: obtaining the third reflection coefficient and the third transmission coefficient of the circuit to be measured based on the amplitude and phase of the swept frequency signal before compensation, the amplitude and phase of the first transmission signal, the amplitude and phase of the second transmission signal, the amplitude and phase of the first reflection signal, and the amplitude and phase of the second reflection signal; constructing a matrix based on the third reflection coefficient and the third transmission coefficient; and determining the impedance of the circuit to be measured based on the matrix.

[0118] Furthermore, in some embodiments, step S1210 can be specifically implemented by the following steps: obtaining the first reflection coefficient and the first transmission coefficient of the current injection probe, and the second reflection coefficient and the second transmission coefficient of the current detection probe; and compensating the amplitude and phase of the swept frequency signal according to the first reflection coefficient, the first transmission coefficient, the second reflection coefficient and the second transmission coefficient.

[0119] Further, in some embodiments, step S1220 can be specifically implemented by the following steps: when the first port is connected to a current injection probe and the second port is connected to a calibration fixture, obtaining a first target input signal input to the first port, a first target transmission signal fed back by the second port, and a first target reflection signal fed back by the first port, and the calibration fixture is used to connect a short-circuit component; based on the first target input signal, the first target transmission signal and the first target reflection signal, determining a first reflection coefficient and a first transmission coefficient; when the first port is connected to the calibration fixture and the second port is connected to a current detection probe, obtaining a second target input signal input to the second port, a second target transmission signal fed back by the first port, and a second target reflection signal fed back by the second port; based on the second target input signal, the second target transmission signal and the second target reflection signal, determining a second reflection coefficient and a second transmission coefficient.

[0120] The following is a detailed description of the entire impedance test process using a complete embodiment, which specifically includes the following steps:

[0121] (1) Probe data acquisition. Based on the above figure 6, two sets of current probe network S parameters are acquired, and then the S 21 The frequency, amplitude and phase of the signal are burned into the ROM of the signal transceiver processor, and the generation of the AM and PM swept frequency signal is based on this data.

[0122] (2) System Construction. Attach the current injection probe and current detection probe to the circuit to be tested and connect them to the two ports of the signal transceiver via coaxial cables. Furthermore, before this, perform a full two-port calibration (VNA calibration uses a full two-port calibration algorithm) on the signal transceiver to eliminate the attenuation and phase shift introduced by the connecting coaxial cables. Then, connect the capacitor arms between the high-voltage lines. The capacitor arms are disconnected for power frequency signals but open for high-frequency signals, so the capacitor arms are introduced to form the circuit to be tested.

[0123] (3) Signal injection. Power the system and start the signal transceiver. The first port of the signal transceiver injects the amplitude modulated phase modulated frequency sweep signal into the circuit under test through the current injection probe. At the same time, the first port and the second port detect the received RF signal response. The ratio of the signal received by the first port and the second port to the uncompensated constant amplitude zero phase frequency sweep signal is the reflection coefficient S of the circuit under test. 11 and the transmission coefficient S 21 Similarly, the second port transmits the excitation signal, and the receiver receives the responses of the two ports and performs a comparative calculation to obtain the reflection coefficient S 22 and the transmission coefficient S 12 .

[0124] (4) Data post-processing. After obtaining the individual S parameters of the circuit to be tested, substitute them into the S-to-ABCD parameter formula to directly obtain the loop impedance. Monitoring the changes in loop impedance and judging the aging of the circuit breaker based on the impedance changes can provide a reference for the maintenance of the switchgear circuit breaker.

[0125] In this application, "at least one" means one or more, and "more" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship; in a formula, the character " / " indicates that the previous and next associated objects are in a "division" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or plural.

[0126] It is understood that the various numerical numbers involved in the embodiments of the present application are only for the convenience of description and are not intended to limit the scope of the embodiments of the present application. In the embodiments of the present application, the order of the sequence numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An impedance measuring device, characterized in that: include: A signal transceiver, a current injection probe, and a current detection probe, wherein the first port of the signal transceiver is connected to the current injection probe, the second port of the signal transceiver is connected to the current detection probe, and the current injection probe and the current detection probe are used to connect the circuit to be tested; The signal transceiver is used to compensate the amplitude and phase of the sweep frequency signal at each frequency point, so that the amplitude and phase of the sweep frequency signal at each frequency point after compensation are different; The signal transceiver is further configured to, after injecting the compensated swept frequency signal into the current injection probe through the first port, obtain a first transmitted signal fed back by the second port and a first reflected signal of the first port; and, after injecting the compensated swept frequency signal into the current detection probe through the second port, obtain a second transmitted signal of the second port and a second reflected signal of the first port; The signal transceiver is further used to determine the impedance of the circuit to be measured based on the amplitude and phase of the swept frequency signal before compensation, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal.

2. The device according to claim 1, characterized in that The signal transceiver includes a processor chip, and the processor chip is connected to the first port and the second port; The processor chip is used to obtain the first reflection coefficient and the first transmission coefficient of the current injection probe, and the second reflection coefficient and the second transmission coefficient of the current detection probe; The processor chip is further configured to compensate for the amplitude and phase of the frequency sweep signal according to the first reflection coefficient, the first transmission coefficient, the second reflection coefficient, and the second transmission coefficient.

3. The device according to claim 2, characterized in that The processor chip is specifically used for: When the first port is connected to the current injection probe and the second port is connected to a calibration fixture, obtaining a first target input signal input to the first port, a first target transmission signal fed back by the second port, and a first target reflection signal fed back by the first port, wherein the calibration fixture is used to connect a short-circuit component; determining the first reflection coefficient and the first transmission coefficient based on the first target input signal, the first target transmission signal, and the first target reflection signal; When the first port is connected to the calibration fixture and the second port is connected to the current detection probe, obtaining a second target input signal input to the second port, a second target transmission signal fed back by the first port, and a second target reflection signal fed back by the second port; The second reflection coefficient and the second transmission coefficient are determined based on the second object input signal, the second object transmission signal and the second object reflection signal.

4. The device according to claim 2, characterized in that The processor chip is also used for: Obtaining a third reflection coefficient and a third transmission coefficient of the circuit to be tested based on the amplitude and phase of the swept frequency signal before compensation, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal; constructing a matrix based on the third reflection coefficient and the third transmission coefficient; The impedance of the circuit to be measured is determined according to the matrix.

5. The device according to claim 2, characterized in that The signal transceiver further includes: a converter and a directional coupler, wherein the processor chip is connected to the directional coupler via the converter, and the directional coupler is connected to the first port and the second port; The converter is used to perform analog-to-digital conversion or digital-to-analog conversion; The directional coupler is used to separate the incident signal emitted by the processor chip and the reflected signal and the transmitted signal received by the processor chip.

6. The device according to claim 5, characterized in that The signal transceiver further includes a power amplifier, and the converter is connected to the directional coupler via the power amplifier; The power amplifier is used to amplify the incident signal sent by the processor chip, and amplify the reflected signal and the transmitted signal received by the processor chip.

7. An impedance measurement method, characterized in that: include: The amplitude and phase of the sweep signal at each frequency point are compensated, and the amplitude and phase of the sweep signal at each frequency point after compensation are different; After injecting the compensated swept frequency signal into the current injection probe through the first port of the signal transceiver, obtaining a first transmission signal fed back by the second port of the signal transceiver and a first reflection signal of the first port; and after injecting the compensated swept frequency signal into the current detection probe through the second port, obtaining a second transmission signal of the second port and a second reflection signal of the first port; The impedance of the circuit to be measured is determined based on the amplitude and phase of the swept frequency signal before compensation, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal.

8. The method according to claim 7, characterized in that The determining the impedance of the circuit to be measured based on the amplitude and phase of the swept frequency signal before compensation, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal, includes: Obtaining a third reflection coefficient and a third transmission coefficient of the circuit to be tested based on the amplitude and phase of the swept frequency signal before compensation, the amplitude and phase of the first transmitted signal, the amplitude and phase of the second transmitted signal, the amplitude and phase of the first reflected signal, and the amplitude and phase of the second reflected signal; constructing a matrix based on the third reflection coefficient and the third transmission coefficient; The impedance of the circuit to be measured is determined according to the matrix.

9. The method according to claim 7, characterized in that The compensating the amplitude and phase of the frequency sweep signal at each frequency point includes: Acquire a first reflection coefficient and a first transmission coefficient of the current injection probe, and a second reflection coefficient and a second transmission coefficient of the current detection probe; The amplitude and phase of the frequency sweep signal are compensated according to the first reflection coefficient, the first transmission coefficient, the second reflection coefficient and the second transmission coefficient.

10. The method according to claim 9, characterized in that The obtaining of the first reflection coefficient and the first transmission coefficient of the current injection probe, and the second reflection coefficient and the second transmission coefficient of the current detection probe, comprises: When the first port is connected to the current injection probe and the second port is connected to a calibration fixture, obtaining a first target input signal input to the first port, a first target transmission signal fed back by the second port, and a first target reflection signal fed back by the first port, wherein the calibration fixture is used to connect a short-circuit component; determining the first reflection coefficient and the first transmission coefficient based on the first target input signal, the first target transmission signal, and the first target reflection signal; When the first port is connected to the calibration fixture and the second port is connected to the current detection probe, obtaining a second target input signal input to the second port, a second target transmission signal fed back by the first port, and a second target reflection signal fed back by the second port; The second reflection coefficient and the second transmission coefficient are determined based on the second object input signal, the second object transmission signal and the second object reflection signal.

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