Rogowski Coil Integrator Circuit Attenuation Factor
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Solution Overview
Problem
Existing electrical interfaces for Rogowski coils face challenges in maintaining accuracy and stability at high sampling frequencies, often leading to saturation and increased error in measuring primary current, especially when dealing with decaying or steady-state currents.
Innovation Solution
An electrical interface with an integrator circuit that employs a transfer function including an attenuation factor, down-sampling, and averaging modules to stabilize operation and reduce distortion, while a disturbance detector and reconstruction module ensure accurate primary current derivation and compensation for errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high sampling frequency is used to improve measurement accuracy, then measurement precision is improved, but integrator stability deteriorates and saturation occurs
Solution Approach 1:
The patent applies parameter changes by introducing an attenuation factor A in the transfer function and implementing down-sampling with scale Nd. These parameter modifications allow the integrator to operate stably at high sampling frequencies while maintaining measurement accuracy. The attenuation factor reduces the gain to prevent saturation, and down-sampling adjusts the feedback signal frequency to match the integrator's stable operating range.
2Stability of the object's composition
If attenuation factor is increased to improve integrator stability, then integrator stability is improved, but measurement accuracy deteriorates
Solution Approach 1:
The patent uses feedback by incorporating a down-sampled previous output voltage signal back into the integrator module through the transfer function. This feedback mechanism allows the system to maintain stability while compensating for the attenuation effect. The feedback loop continuously adjusts the integration based on past outputs, ensuring both stability and accuracy are maintained despite the attenuation factor.
3Reliability
If down-sampling is applied to reduce distortion, then integrator saturation is reduced, but sampling frequency is affected
Solution Approach 1:
The patent applies segmentation by separating the sampling process into two distinct stages: high-frequency input sampling at frequency fs for accurate signal capture, and down-sampled feedback sampling at reduced frequency fs/Nd for stable integration. This segmentation allows each stage to operate at its optimal frequency, maintaining both input signal fidelity and integrator stability without mutual interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution maintains high accuracy and stability at very high sampling frequencies, limiting error to less than 10% for decaying currents and 0.3% for steady-state currents, preventing saturation and ensuring reliable DC offset removal and temperature compensation.
Implementation Method 1
The voltage induced in the coil 12 is proportional to the rate of change, i.e. the derivative, of the primary current i p flowing through the primary conductor 16
Data Source
Figure 1~2
AI summary
In the field of Rogowski coils for the measurement of current within a conductor there is provided an electrical interface (30) for connection to a Rogowski coil (10) arranged around a primary conductor (16). The electrical interface (30) includes an input (32) that is configured to sample an input voltage signal (us(n)) from the Rogowski coil (10). The electrical interface (30) also has an integrator circuit (34) which includes an integrator module (36) that is configured to integrate the sampled input voltage signal (us(n)) to provide an output voltage signal (uINT(n)) from which can be derived a primary current (ip(n)) flowing through the primary conductor (16). The integrator module (36) employs a transfer function that includes an attenuation factor (A).