Magnetic Modulator Harmonic Demodulation for Weak DC Current Sensing

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Solution Overview

Problem

Current magnetic modulators face challenges in accurately measuring low DC currents due to significant odd harmonic components and zero-offset noises, which impair the monitoring accuracy of even harmonics, particularly in high-voltage direct current (HVDC) systems.

Innovation Solution

A full even harmonic digital demodulation method based on full-phase analysis for magnetic modulators, involving Fourier analysis, Hamming window function, and convolution window sequence preprocessing to extract and mitigate odd harmonic interference and zero-offset noises, enabling precise measurement of weak DC signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a double-core differential sensing structure is used in the magnetic modulator, then the sensitivity and resolution for measuring DC currents are improved, but odd harmonic components become significantly larger than even harmonic components due to discrepancies in magnetic characteristics of the two cores, causing spectral leakage that impairs monitoring accuracy of even harmonics

Engineering Contradiction:

Improvemeasurement accuracy of DC currentVSAvoidodd harmonic components and spectral leakage

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent segments the harmonic analysis into separate processing paths for odd and even harmonics. By applying different filtering and processing techniques to odd and even harmonic components separately, the method effectively isolates the weak even harmonic signals from the dominant odd harmonic interference, resolving the spectral leakage problem while maintaining measurement precision

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary processing stage that includes calibration procedures and signal processing algorithms. This intermediary layer between the sensing structure and the final measurement result compensates for the magnetic characteristic discrepancies between the two cores, reducing odd harmonic components and enabling accurate even harmonic detection

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the magnetic core material's inherent asymmetry in the hysteresis loop is present, then the magnetic modulator can operate with simple structure, but zero-offset noises at the μA level are introduced that severely affect measurement accuracy of DC signals at the level of 10 μA

Engineering Contradiction:

Improvestructure simplicityVSAvoidmeasurement accuracy of weak DC signals

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent implements preliminary calibration actions before actual measurement. The calibration process characterizes the zero-offset noises and asymmetry effects in advance, storing correction data that is applied during subsequent measurements. This preliminary action eliminates the need for complex structural modifications while achieving high measurement accuracy for weak DC signals

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent employs feedback mechanisms where the measured signals are processed through algorithms that compensate for zero-offset noises. The system continuously monitors and adjusts for the inherent asymmetry effects, using feedback from the calibration data to maintain measurement accuracy without increasing structural complexity

Inventive Principle:

Principle #23Feedback

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 method significantly enhances measurement accuracy and sensitivity for low DC signals by reducing spectrum leakage and phase distortion, effectively suppressing noise interference, and improving reliability in high-precision current detection.

Implementation Method 1

magnetic modulation current sensors. Among these, magnetic modulators offer advantages such as high resolution, high sensitivity, high precision, minimal temperature drift, and stable working characteristics

Methodology Applied

Scientific EffectMagnetic modulation:

Implementation Method 2

An output voltage sequence from full-phase Fourier analysis is established based on the standard voltage timing data

Methodology Applied

Scientific EffectFourier analysis:

Implementation Method 3

Spectral leakage from odd harmonics impairs the monitoring accuracy of even harmonics

Methodology Applied

Scientific EffectSpectral leakage reduction:

Data Source

PatentEP4692810A1Digital full even harmonic demodulation method based on full-phase analysis for magnetic modulator

Publication Date: 2026.02.11 LI XIAOLING

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AI summary

This application relates to the field of electrical technologies, and provides a full even harmonic digital demodulation method based on full-phase analysis for a magnetic modulator. According to the full even harmonic digital demodulation method based on full-phase analysis for a magnetic modulator, standard voltage timing data output by the magnetic modulator is obtained when a DC calibration current with a set amplitude is fed into the magnetic modulator during calibration of the magnetic modulator; an output voltage sequence from full-phase Fourier analysis is established based on the standard voltage sequence data, and the output voltage sequence is preprocessed; comprehensive analysis is performed on the preprocessed output voltage sequence from full-phase Fourier analysis to obtain all standard even harmonic signals and current conversion coefficients.