Signal processing circuit for Rogowski coil

Abstract

The utility model discloses a signal processing circuit for a Rogowski coil, and belongs to the field of intelligent power grids. The signal processing circuit used for the Rogowski coil has the characteristics of real-time measurement, fast response speed and wide current measurement range, and especially can ensure the metering precision under a small current working condition. The Rogowski coil converts a primary side current value into a current-to-time differential signal, the passive RC integrating circuit reduces the turning frequency of the differential signal, the low-pass filtering circuit effectively attenuates a high-frequency signal, the T-type integrating circuit integrates the differential signal to restore an original signal, and the blocking circuit filters and blocks the integrated signal. The adjustable proportion amplification circuit performs in-phase amplification on the integral signal and adjusts the amplitude of the output signal as required, and the anti-aliasing filter circuit filters the amplified integral signal and finally inputs the integral signal to the sampling chip for current metering.

Description

Technical Field

[0001] The utility model relates to the technical field of smart grid, in particular to a signal processing circuit for Rogowski coil. Background Art

[0002] At present, for the construction of smart grid, it is mostly necessary to externally connect current transformers to monitor, collect and process line current data. Traditional current transformers have low measurement accuracy and are greatly affected by load changes. Rogowski coil has the characteristics of high precision and sensitivity, and is not affected by load changes, and can measure very small current changes. However, the signal processing circuit of Rogowski coil in the current industry is not perfect enough for the acquisition and processing of small current, and cannot guarantee the metering accuracy requirements when measuring small current. Therefore, a signal processing solution for Rogowski coil that can measure in real time, has a fast response speed, a wide current measurement range, especially to ensure metering accuracy under small current conditions is needed. Summary of the Utility Model

[0003] Aiming at the deficiencies and defects existing in the prior art, the utility model provides a signal processing circuit for Rogowski coil. The purpose of the utility model is to provide a signal processing circuit for Rogowski coil with high precision, high sensitivity and wide measurement range.

[0004] The purpose of the utility model can be achieved by the following technical solutions:

[0005] A signal processing circuit for Rogowski coil includes a passive RC integration circuit, a low-pass filter circuit, a T-type integration circuit, a DC blocking circuit, an adjustable proportional amplification circuit, and an anti-aliasing filter circuit:

[0006] The passive RC integration circuit includes resistors R1, R2, and capacitor C1, and is used to increase the resistance value and reduce the corner frequency of the Rogowski coil at the same time, so as to attenuate high-frequency signals.

[0007] The low-pass filter circuit includes resistor R3 and capacitor C2, and is used to reduce the noise of the input signal of the operational amplifier and the intensity of impact signals such as surges, and effectively attenuate high-frequency signals.

[0008] The T-type integration circuit includes resistors R4, R5, R6, capacitors C3, C4, and operational amplifier D1, and is used to integrate the differential signal output by the Rogowski coil to restore the original signal. Resistors R4, R6, and capacitor C4 form a DC feedback loop to provide a feedback channel for the DC bias of the operational amplifier. Compared with ordinary integrators, the T-type integrator has a stronger attenuation ability for ultra-low frequency signals and has a stronger anti-interference ability while ensuring steady-state performance.

[0009] The DC blocking circuit includes resistor R7 and capacitor C5, and is used to filter and block DC for the output of the T-type integration circuit and input it to the subsequent amplification circuit.

[0010] An adjustable ratio amplification circuit, including resistor R8, R10, adjustable potentiometer R9, capacitor C6, and operational amplifier D2, is used for in-phase amplification of the integration signal. By adjusting the adjustable potentiometer R9, the amplification factor of the circuit is changed, and the amplitude of the final output signal is adjusted to achieve adjustable output.

[0011] An anti-aliasing filter circuit, including resistors R11, R12, capacitor C7, and TVS tube VP1, is used to filter out the high-frequency part of the output signal, prevent high-frequency signals from being aliased into low-frequency signals and input into the sampling chip for primary side current measurement.

[0012] The beneficial technical effects of the present invention: Through continuous exploration and experiments, the signal processing circuit of the Rogowski coil has the characteristics of real-time measurement, fast response speed, and wide current measurement range. Especially, the measurement accuracy can be guaranteed under low-current conditions. Description of the Drawings

[0013] Figure 1 It is the working principle block diagram of the signal processing circuit for the Rogowski coil of the present invention.

[0014] Figure 2 It is the specific circuit diagram of the signal processing circuit for the Rogowski coil of the present invention. Detailed Embodiments

[0015] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the present invention.

[0016] On the contrary, the present invention covers any alternatives, modifications, equivalent methods and solutions made within the essence and scope of the present invention defined by the claims. Further, in order to enable the public to have a better understanding of the present invention, some specific details are described in detail in the following detailed description of the present invention. Those skilled in the art can fully understand the present invention without the description of these details.

[0017] As Figure 1-2 shown, a signal processing circuit for a Rogowski coil includes a passive RC integration circuit, a low-pass filter circuit, a T-type integration circuit, a DC blocking circuit, an adjustable ratio amplification circuit, and an anti-aliasing filter circuit:

[0018] The passive RC integration circuit includes resistors R1 (100 kΩ), R2 (5.1 kΩ), and capacitor C1 (1 nF), and is used to increase the resistance value and at the same time reduce the corner frequency of the Rogowski coil to achieve attenuation of high-frequency signals. The approximate equivalent calculation formula for the cut-off frequency of the passive RC integration circuit is:

[0019]

[0020] A low-pass filter circuit, including a resistor R3 (15.1 kΩ) and a capacitor C2 (1 nF), is used to reduce the noise of the input signal of the operational amplifier and the intensity of impact signals such as surges, and effectively attenuate high-frequency signals. The approximate equivalent calculation formula for the cut-off frequency of the low-pass filter circuit is:

[0021]

[0022] A T-type integrating circuit, including resistors R4 (100 kΩ), R5 (20 kΩ), R6 (1 MΩ), capacitors C3 (20 nF), C4 (4.7 μF), and an operational amplifier D1 (SGM8249-1), is used to integrate the differential signal output by the Rogowski coil to restore the original signal. Resistors R4, R6, and capacitor C4 form a DC feedback loop to provide a feedback channel for the DC bias of the operational amplifier. Compared with a common integrator, the T-type integrator has a stronger attenuation ability for ultra-low-frequency signals and stronger anti-interference ability while ensuring steady-state performance. The approximate equivalent calculation formula for the integration amplification factor of the T-type integrating circuit is:

[0023]

[0024] A DC blocking circuit, including a resistor R7 (62 kΩ) and a capacitor C5 (44 μF), is used to filter and block DC from the output of the T-type integrating circuit and input it to the subsequent amplifier circuit.

[0025] An adjustable proportional amplifier circuit, including resistors R8 (5.1 kΩ), R10 (2 kΩ), an adjustable potentiometer R9 (≤10 kΩ), a capacitor C6 (3.3 nF), and an operational amplifier D2 (SGM8249-2), is used to amplify the integration signal in-phase. By adjusting the adjustable potentiometer R9, the amplification factor of the circuit is changed to adjust the amplitude of the final output signal to achieve adjustable output. The approximate equivalent calculation formula for the amplification factor of the adjustable proportional amplifier circuit is:

[0026]

[0027] An anti-aliasing filter circuit, including resistors R11 (2 kΩ), R12 (2 kΩ), a capacitor C7 (16.5 nF), and a TVS tube VP1 (WPE5V0D3ULA), is used to filter the high-frequency part of the output signal to prevent high-frequency signals from being aliased into low-frequency signals and input to the sampling chip for primary side current measurement. The approximate equivalent calculation formula for the cut-off frequency of the anti-aliasing filter circuit is:

[0028]

[0029] The specific working process of the utility model is as follows: The Rogowski coil converts the primary side current value into a differential signal of current with respect to time. The passive RC integration circuit reduces the turning frequency of the differential signal. The low-pass filter circuit effectively attenuates high-frequency signals. The T-type integration circuit integrates the differential signal to restore the original signal. The DC blocking circuit filters and blocks the DC component of the integrated signal. The adjustable proportional amplification circuit amplifies the integrated signal in phase and adjusts the amplitude of the output signal according to requirements. The anti-aliasing filter circuit filters the amplified integrated signal and finally inputs it to the sampling chip for current measurement.

[0030] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0031] 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 above embodiments, those of ordinary skill in the art should understand that: still can modify the specific implementation manners of the present invention or make equivalent substitutions, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A signal processing circuit for a Rogowski coil, characterized in that: Including passive RC integration circuit, low-pass filter circuit, T-type integration circuit, DC isolation circuit, adjustable ratio amplifier circuit, anti-aliasing filter circuit; The passive RC integration circuit comprises: resistors R1, R2, and capacitor C1; The low-pass filter circuit comprises: a resistor R3 and a capacitor C2; The T-type integration circuit includes: resistors R4, R5, R6, capacitors C3, C4, and an operational amplifier D1; The DC blocking circuit includes: a resistor R7 and a capacitor C5; The adjustable proportional amplification circuit includes: resistors R8, R10, an adjustable potentiometer R9, a capacitor C6, and an operational amplifier D2; The anti-aliasing filter circuit includes: resistors R11, R12, capacitor C7, and TVS tube VP1.

2. A signal processing circuit for a Rogowski coil according to claim 1, characterized in that: The passive RC integration circuit is used to increase the resistance value and reduce the turning frequency of the Rogowski coil, thereby achieving attenuation of high-frequency signals.

3. The signal processing circuit for a Rogowski coil according to claim 1, characterized in that: The low-pass filter circuit is used to reduce the noise of the operational amplifier input signal and the strength of the surge impact signal, and effectively attenuate the high-frequency signal.

4. The signal processing circuit for a Rogowski coil according to claim 1, characterized in that: The T-type integrator circuit is used to integrate the differential signal output by the Rogowski coil to restore the original signal. Resistors R4, R6, and capacitor C4 form a DC feedback loop to provide a feedback channel for the DC bias of the operational amplifier. Compared with ordinary integrators, the T-type integrator has a stronger attenuation capability for ultra-low frequency signals and has a stronger anti-interference capability while ensuring steady-state performance.

5. The signal processing circuit for a Rogowski coil according to claim 1, characterized in that: The DC isolation circuit is used to filter and isolate the output of the T-type integration circuit and input it to the back-end amplifier circuit.

6. The signal processing circuit for a Rogowski coil according to claim 1, characterized in that: The adjustable proportional amplifier circuit is used to perform in-phase amplification on the integrated signal. By adjusting the adjustable potentiometer R9, the amplification factor of the circuit is changed, and the final output signal amplitude is adjusted to achieve output adjustment.

7. The signal processing circuit for a Rogowski coil according to claim 1, characterized in that: The anti-aliasing filter circuit is used to filter out the high-frequency part of the output signal to prevent the high-frequency signal from being aliased into a low-frequency signal and input into the sampling chip for measuring the primary side current.

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