Rogowski Coil Integrator Circuit DC Drift Correction
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Solution Overview
Problem
Rogowski coil sensors face challenges in maintaining accurate phase information and removing DC content, leading to undesirable phase shifts and infinite amplification at DC, which affects the integration of current signals in AC power monitoring.
Innovation Solution
An integrator circuit with a high-pass filter and a feedback loop is designed to remove DC content from the signal, using three operational amplifiers to ensure the integrator output remains DC-free without requiring additional components across the feedback capacitor, and utilizing a passive first-order high-pass filter to minimize load on the high-impedance point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a basic integrator circuit is used for Rogowski coil sensors, then the voltage signal can be integrated to obtain current information, but the integrator produces substantial undesirable phase shift at line frequency and infinite amplification at DC
Solution Approach 1:
The patent implements a feedback loop that detects DC voltage at the integrator output and generates a compensating signal injected into the integrator input. This feedback mechanism automatically adjusts the input signal to counteract DC drift, eliminating the need for discharge switches while maintaining DC stability. The feedback loop ensures the integrator operates reliably without producing infinite amplification at DC frequencies.
2Reliability
If a discharge switch is added across the feedback capacitor to remove DC content, then DC stability is improved, but the device complexity increases due to timing circuitry requirements
Solution Approach 1:
The patent employs a self-regulating feedback system where the integrator's own DC output voltage serves as the error signal for correction. The circuit automatically detects its own DC drift and generates the necessary compensating signal without requiring external timing circuitry or discharge switches. This self-service approach simplifies the overall circuit design while maintaining DC stability.
3Measurement precision
If the integrator is designed for pure integration function, then phase shift accuracy is improved, but the amplification at DC becomes infinite causing undefined output level
Solution Approach 1:
The patent introduces an intermediary DC correction circuit that sits between the integrator and the output. This intermediary component detects DC voltage levels and generates compensating signals without interfering with the AC integration function. The intermediary allows the integrator to maintain its pure integration characteristics for accurate phase measurement while simultaneously preventing undefined DC output levels through automatic correction.
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 effectively removes DC content, maintains accurate phase information, and prevents infinite amplification at DC, providing a stable and phase-accurate representation of line currents for AC power monitoring, suitable for smart grid infrastructure and fault detection.
Implementation Method 1
A high-pass filter has an input coupled to the output of the integrator and has an output. The high-pass filter substantially removes a DC content from the voltage signal.
Implementation Method 2
A feedback loop has an input coupled to the output of the integrator and to the output of the high-pass filter, and has an output providing the DC content of the voltage signal to the input of the integrator.
Data Source
AI summary
An integrator circuit for a current sensor such as a Rogowski coil. The integrator circuit includes an integrator having an input for receiving a signal from a current sensor and having an output providing a voltage signal. A high-pass filter has an input coupled to the output of the integrator and substantially removes the DC content from the voltage signal. A feedback loop has an input coupled to the output of the integrator and to the high-pass filter, and has an output providing the DC content of the voltage signal back to the input of the integrator. The integrator circuit can detect large current steps in the line conductor being monitored and can be used for line fault detection.