AC Current Waveform Phase Correction via FFT
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Solution Overview
Problem
Accurate measurement of current waveforms in relation to voltage waveforms in distribution boards is challenging due to the need for precise phase delay analysis, which is often hindered by the difficulty of non-contact voltage measurement and environment-dependent stray capacitance variations, leading to increased calculation costs and decreased accuracy.
Innovation Solution
A measurement apparatus and method that apply a Fourier Transform to AC current waveforms, adjust phase components to zero the AC power supply frequency phase, and then perform an inverse Fourier Transform to obtain current waveforms in the time domain, allowing analysis without the need for voltage measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-contact type voltage sensor is used to measure voltage waveform, then voltage measurement can be performed without touching power wiring, but measurement accuracy decreases due to environment-dependent stray capacitance variations
Solution Approach 1:
The patent introduces a calibration process using a known reference voltage waveform as an intermediary to correct the measurements from the non-contact voltage sensor. The calibration voltage waveform, which has a known phase relationship with the current waveform, serves as a mediator to determine and compensate for the phase delay introduced by stray capacitance, thereby improving measurement accuracy without requiring direct contact with power wiring.
2Loss of information
If phase delay measurement is performed using non-contact sensor, then voltage measurement can be obtained, but calculation cost increases and accuracy decreases due to environment-dependent phase delay
Solution Approach 1:
The patent employs a feedback mechanism where the measured current waveform and calibration voltage waveform are used to calculate the actual phase delay, which then feeds back into the phase correction process. By continuously using the measured phase delay to adjust and correct subsequent measurements, the system compensates for environment-dependent variations and improves the accuracy of phase delay determination.
3Measurement precision
If voltmeter is installed in distribution board to measure voltage, then accurate voltage measurement can be obtained, but construction by qualified electrician is required and installation becomes complex
Solution Approach 1:
The patent enables the measurement system to perform its own calibration and phase correction using the non-contact voltage sensor and the available current waveform information. By making the system self-calibrating through the use of calibration voltage waveforms and automatic phase delay calculation, it eliminates the need for complex manual installation and calibration by qualified electricians, while still achieving accurate measurements.
4Measurement precision
If current waveform measurement is performed with phase delay correction, then accurate current waveform estimation can be achieved, but calculation cost increases
Solution Approach 1:
The patent applies partial phase correction by focusing the calculation effort on determining and correcting only the dominant phase delay component using calibration waveforms, rather than performing exhaustive calculations for all possible phase relationships. This selective approach to phase correction reduces the overall calculation cost while still achieving sufficient accuracy for practical current waveform estimation.
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
Enables accurate analysis and synchronization of current waveforms with AC voltage waveforms, reducing the reliance on voltage measurement and improving estimation accuracy while simplifying installation by eliminating the need for voltage measurement cables.
Implementation Method 1
an FFT operation part that performs a Fast Fourier Transform (FFT) on a measured Alternating-Current (AC) current waveform to perform conversion to a frequency domain
Implementation Method 2
a phase adjustment part that adjusts entire phase components of frequency spectra obtained as a result of the FFT, so that a phase component of an AC power supply frequency becomes zero
Implementation Method 3
an IFFT operation part that performs an Inverse Fast Fourier Transform (IFFT) on the frequency spectra with the entire phase components adjusted to obtain a current waveform in a time domain
Data Source
AI summary
Provided a method including applying a Fourier Transform to an AC current waveform measured to perform conversion thereof to a frequency domain; adjusting entire phase components of frequency spectra obtained as a result of the Fourier Transform, such that a phase component of an AC power supply frequency becomes zero; and applying an inverse Fourier Transform to the frequency spectra with the entire phase components thereof adjusted to obtain a current waveform in a time domain.