High frequency signal detection system

Abstract

The application provides a high-frequency signal detection system, comprising: a Rogowski coil type current sensor; a first circuit, the first circuit comprising a first resistor, one end of the first resistor being connected with a coil of the Rogowski coil type current sensor, and the other end of the first resistor being grounded; a second circuit, the second circuit comprising: a delay circuit and a second resistor, one end of the delay circuit being connected with one end of the first resistor, the other end of the delay circuit being connected with one end of the second resistor, and the other end of the second resistor being grounded; one end of the first resistor serving as a first output end of the high-frequency signal detection system, one end of the second resistor serving as a second output end of the high-frequency signal detection system, and a voltage difference between the first output end and the second output end serving as an output signal, and a high-frequency signal being obtained according to the output signal. Through a proper delay circuit, the electromagnetic waves before and after the delay are differentiated, and the power frequency is filtered out without affecting the output of the high-frequency signal, so that the high-frequency signal required to be analyzed can be conveniently obtained.

Description

Technical Field

[0001] This invention relates to the field of electrical technology, and more specifically to a high-frequency signal detection system. Background Technology

[0002] Currently, offline detection methods in power grids can no longer meet the current safety and reliability requirements, making online monitoring imperative. One of the key challenges in online monitoring is how to accurately acquire frequency response signals.

[0003] In related technologies, current sensors are generally used to collect current signals for online monitoring. However, the field test environment has a lot of power frequency interference. The current signal collected by the current sensor is a superposition of power frequency signal and high frequency signal of 1kHz-1MHz. Therefore, high-pass filtering is required to obtain the 1kHz-1MHz high frequency signal required for the research.

[0004] In related technologies, active filtering is generally used for high-pass filtering. However, the power frequency voltage input to the filter will exceed the power supply voltage of the active filter, which will cause the active filter to malfunction and thus fail to effectively acquire high-frequency signals. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a high-frequency signal detection system.

[0006] The technical solution adopted in this invention is as follows:

[0007] An embodiment of the present invention provides a high-frequency signal detection system, comprising: a Rogowski coil current sensor; a first circuit, the first circuit including a first resistor, one end of the first resistor being connected to the coil of the Rogowski coil current sensor, and the other end of the first resistor being grounded; a second circuit, the second circuit including: a delay circuit and a second resistor, one end of the delay circuit being connected to one end of the first resistor, the other end of the delay circuit being connected to one end of the second resistor, and the other end of the second resistor being grounded; wherein, one end of the first resistor serves as a first output terminal of the high-frequency signal detection system, one end of the second resistor serves as a second output terminal of the high-frequency signal detection system, the voltage difference between the first output terminal and the second output terminal serves as an output signal, and the high-frequency signal is acquired based on the output signal.

[0008] The high-frequency signal detection system proposed above in this invention may also have the following additional technical features:

[0009] According to an embodiment of the present invention, the delay time of the delay circuit T Based on the following formula: ;in, T The delay time of the delay circuit is...f 0 The power frequency of the output signal of the Rogowski coil current sensor is [the frequency of the power supply frequency]. f The high frequency of the output signal of the Rogowski coil current sensor.

[0010] According to one embodiment of the present invention, the delay circuit is composed of a capacitor-inductor chain.

[0011] According to one embodiment of the present invention, the resistance value of the second resistor is equal to the wave impedance of the delay circuit.

[0012] According to one embodiment of the present invention, the resistance value of the first resistor is equal to the wave impedance of the delay circuit.

[0013] According to one embodiment of the present invention, the wave impedance of the delay circuit satisfies the self-integrating circuit condition of the high-frequency range of the Rogowski coil current sensor.

[0014] The beneficial effects of this invention are:

[0015] This invention uses a suitable delay circuit to filter out the power frequency signal by subtracting the electromagnetic waves before and after the delay, without affecting the output of the high-frequency signal, thus making it easy to obtain the high-frequency signal to be analyzed.

[0016] Electromagnetic wave delay can be achieved with a very short circuit length by using a capacitor-inductor chain composed of several capacitors and inductors, saving space and improving the feasibility of the detection scheme. Furthermore, the capacitors and inductors used in the delay circuit are commercially available, eliminating the need for custom-made components and significantly reducing costs. Attached Figure Description

[0017] Figure 1 This is a circuit topology diagram of a high-frequency signal detection system according to the first embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the delay circuit according to the first embodiment of the present invention. Detailed Implementation

[0019] This invention was made by the inventor based on research and understanding of the following issues:

[0020] In experiments, the power frequency signal is particularly strong. Another method to eliminate the power frequency magnetic field is to connect a power frequency load to the sensor. This load must exhibit highly nonlinear characteristics, with near-zero impedance at power frequency and very high impedance at high frequencies. An ideal load is a power frequency resonant load, because it should not affect the operation of the integrating resistor. Otherwise, within the measurement frequency band, the output voltage amplitude will vary with frequency, which does not meet the requirement that the output voltage and the measured current amplitude are in a fixed proportion. Taking a second-order resonance as an example, if the impedance of a resonant circuit at 50Hz is required to be 100... Reaching 200k at 10kHz above:

[0021] ;

[0022] ;

[0023] Solving the above equation yields... , .

[0024] Therefore, filtering a power frequency load with prominent nonlinear characteristics requires a very large inductor, which is difficult to manufacture. At the same time, eliminating power frequency magnetic fields in this way is uneconomical.

[0025] 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 embodiments of the present invention, and not all embodiments. 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.

[0026] Figure 1 This is a circuit topology diagram of a high-frequency signal detection system according to the first embodiment of the present invention, such as... Figure 1 As shown, the high-frequency signal detection system includes: a Rogowski coil current sensor 1, a first line 2, and a second line 3.

[0027] The first circuit 2 includes a first resistor R1, one end of which is connected to the coil of the Rogowski coil current sensor 1, and the other end of which is grounded. The second circuit 3 includes a delay circuit 4 and a second resistor R2, one end of which is connected to one end of the first resistor R1, and the other end of which is connected to one end of the second resistor R2, and the other end of the second resistor R2 is grounded. One end of the first resistor R1 serves as the first output terminal of the high-frequency signal detection system, and one end of the second resistor R2 serves as the second output terminal of the high-frequency signal detection system. The voltage difference u2 between the first and second output terminals serves as the output signal, and the high-frequency signal is obtained based on the output signal.

[0028] In one embodiment of the present invention, such as Figure 2 As shown, the delay circuit can be composed of a capacitor-inductor chain. L is the inductor, and C is the capacitor.

[0029] Specifically, according to the wave process principle, the wave speed v of electromagnetic wave propagation is: Assuming the length of the delay circuit is S Then the delay T of the electromagnetic wave passing through this line is: 。 The wave impedance of this section of the line, i.e., the wave impedance Z of the delay circuit, is: .

[0030] To prevent electromagnetic wave reflection, R2 needs to be matched with the impedance Z of the delay circuit 4. Simultaneously, it must be ensured that the current amplitude flowing through the first line 2 and the second line 3 is equal, and the first resistor R1 should also be matched with the impedance Z of the delay circuit 4. That is, the resistance value of the second resistor R2 is equal to the impedance Z of the delay circuit. The resistance value of the first resistor R1 is equal to the impedance Z of the delay circuit, i.e. .

[0031] like Figure 1 As shown, the measured current (output current of the Rogowski coil current sensor) I1 is:

[0032] ;

[0033] in, The signal is the current signal corresponding to the measured current I1 (output signal of a Rogowski coil current sensor), and t is time. For power frequency signal current, This refers to the high-frequency signal current (i.e., the high-frequency signal that needs to be acquired). f 0 The power frequency is the output signal frequency of the Rogowski coil current sensor. f This refers to the high-frequency output signal of the Rogowski coil current sensor.

[0034] resistance R voltage on 1 (The voltage at the first output terminal) is:

[0035] ;

[0036] N is the number of turns of the coil in the Rogowski coil current sensor.

[0037] resistance R2 The voltage on the second output terminal, i.e. After passing through delay circuit 4, the result is... :

[0038] T is the delay time of the delay circuit. for The corresponding voltage signal.

[0039] The pressure difference between the first output terminal and the second output terminal ,Right now:

[0040] ;

[0041] According to the rules of trigonometric function operations ,get:

[0042] As can be seen from the above formula, The value of will affect the strength of the two frequency signals on the differential voltage u2. According to the properties of trigonometric functions, the ideal state to eliminate the power frequency signal while retaining the high-frequency signal is... At this point, the power frequency signal will be completely eliminated, while the high-frequency signal will be fully preserved.

[0043] Based on the above derivation, the appropriate delay time can be determined by constructing a suitable delay circuit according to the desired high-frequency signal. T This makes it easy to reduce the power frequency signal in the measurement signal, thereby obtaining the high-frequency signal that you want to analyze.

[0044] In delay circuit 4, the values ​​of the capacitors and inductors in the capacitor-inductor chain need to be determined based on the delay time. T and the length of the delay circuit S The decision is made by 、 Therefore, by selecting appropriate L and C values ​​for the delay circuit, the delay time can be made to meet the requirements as much as possible. Meanwhile, the impedance Z of the delay circuit needs to satisfy Z=R1=R2. In practical applications of the experiment, multi-level delay circuits can be made according to commonly used frequency response signals, and adjustable resistors are required to match the impedance of the delay circuit.

[0045] In other words, considering practical considerations, the above is theoretically satisfied. The conditions described represent the ideal state, but achieving this ideal state may be difficult in engineering applications. Therefore, the conditions can be relaxed to simply require... As close to 0 as possible Ideally, the delay time should be equal to 1. Therefore, in one specific embodiment of the invention, the delay time of the delay circuit is... T It can be set according to the following formula: ;in, T The delay time of the delay circuit. f 0The power frequency is the output signal frequency of the Rogowski coil current sensor. f This refers to the high-frequency output signal of the Rogowski coil current sensor.

[0046] The real-time performance of the high-frequency signal detection system described above is illustrated below through two specific examples:

[0047] 1) If the output current of the Rogowski coil sensor is the superposition of a 50Hz power frequency signal and a 1MHz frequency response signal, then if we take... , We obtain:

[0048] For power frequency signals ,but .

[0049] For high-frequency signals, ,but .

[0050] At this time, the voltage power frequency signal output by u2 is the original... The signal attenuates by a factor of 1, while a 1MHz signal (high-frequency signal) does not attenuate.

[0051] 2) If the output current of the Rogowski coil sensor is the superposition of a 50Hz power frequency signal and a 1.5MHz frequency response signal, then if we take... , We obtain:

[0052] For power frequency signals ,but .

[0053] For high-frequency signals, ,but .

[0054] At this time, the voltage power frequency signal output by u2 is the original... The signal is 0.707 times stronger than the original signal, while the 1.5MHz signal is 0.707 times stronger. Parameter adjustments in subsequent circuits can ensure normal signal output.

[0055] As can be seen from the above examples, different delay circuits can be designed according to the frequency of the frequency response signal to be analyzed, which can effectively filter out power frequency signals. The capacitors and inductors used in the delay circuits are readily available on the market and do not need to be specially customized, which greatly reduces costs.

[0056] In summary, the high-frequency signal detection system according to embodiments of the present invention, through a suitable delay circuit, allows the difference between the electromagnetic waves before and after the delay to filter out the power frequency signal without affecting the output of the frequency response signal, thus conveniently obtaining the high-frequency signal to be analyzed. The delay of the electromagnetic wave can be achieved with a very short circuit length using a capacitor-inductor chain composed of several capacitors and inductors, saving space and improving the feasibility of the detection scheme. Furthermore, the capacitors and inductors used in the delay circuit are commercially available, eliminating the need for custom-made components and significantly reducing costs.

[0057] In this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples and features described in this specification without contradiction. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described herein, as well as the features of the different embodiments or examples, without contradiction.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-frequency signal detection system, characterized in that, include: Rogowski coil current sensor; A first circuit, the first circuit including a first resistor, one end of the first resistor being connected to the coil of the Rogowski coil current sensor, and the other end of the first resistor being grounded; The second line includes: a delay circuit and a second resistor, one end of the delay circuit is connected to one end of the first resistor, the other end of the delay circuit is connected to one end of the second resistor, and the other end of the second resistor is grounded; Wherein, one end of the first resistor serves as the first output terminal of the high-frequency signal detection system, one end of the second resistor serves as the second output terminal of the high-frequency signal detection system, the voltage difference between the first output terminal and the second output terminal serves as the output signal, and the high-frequency signal is obtained based on the output signal; Delay time of delay circuit T Based on the following formula: ； in, T The delay time of the delay circuit is... f 0 The power frequency of the output signal of the Rogowski coil current sensor is [the frequency of the power supply frequency]. f The high frequency of the output signal of the Rogowski coil current sensor; The delay circuit is composed of a capacitor-inductor chain; The resistance value of the second resistor is equal to the wave impedance of the delay circuit; The resistance value of the first resistor is equal to the wave impedance of the delay circuit; The wave impedance of the delay circuit satisfies the self-integrating circuit conditions for the high-frequency range of the Rogowski coil current sensor.

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