HHT Voltage Disturbance Detection via Mode Mixing Prevention
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Solution Overview
Problem
Existing HHT-based methods for voltage quality disturbance detection suffer from mode mixing, which prevents accurate time-frequency characterization of signals and hampers the detection of voltage quality disturbances.
Innovation Solution
The method involves transforming the original voltage signal into a Hankel matrix, performing singular value decomposition and reconstruction to remove interference signals, and then applying frequency modulation and empirical mode decomposition to prevent mode mixing and improve detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If HHT method is used for disturbance detection, then computation speed is fast and it is appropriate for non-stationary signal detection, but mode mixing occurs which prevents accurate time-frequency characterization
Solution Approach 1:
The patent segments the voltage signal into multiple intrinsic mode functions through empirical mode decomposition, then applies Hilbert transform to each segment separately. This segmentation allows accurate time-frequency characterization of each mode while maintaining the computational efficiency of HHT method.
Solution Approach 2:
The patent introduces an intermediary processing step between EMD and Hilbert transform, where mode filtering and signal reconstruction are performed. This intermediary process eliminates mode mixing while preserving the fast computation speed and non-stationary signal handling capabilities of the original HHT method.
2Adaptability or versatility
If EMD is applied to decompose the signal, then the signal is transformed into mode functions, but different IMFs are distributed at different time scales causing mode mixing
Solution Approach 1:
The patent applies local quality by analyzing each intrinsic mode function individually after decomposition, applying Hilbert transform and mode filtering specific to each IMF's local characteristics. This allows accurate time-frequency characterization while maintaining the versatile decomposition capability of EMD.
Solution Approach 2:
The patent performs preliminary mode filtering and signal reconstruction before applying Hilbert transform. This preliminary action prevents mode mixing from occurring in the first place, ensuring that each IMF maintains its temporal localization properties while enabling accurate time-frequency analysis.
3Device complexity
If traditional HHT method is used, then the system structure is simple, but it cannot accurately detect voltage quality disturbances due to mode mixing
Solution Approach 1:
The patent extracts and removes the harmful mode mixing effect through additional filtering and reconstruction steps. By taking out the mode mixing problem systematically, the method maintains relatively simple system structure while significantly improving disturbance detection accuracy through precise time-frequency characterization.
Data Source
AI summary
A HHT-based voltage quality disturbance detection method, including: obtaining frequency spectrum information of an original voltage signal, and determining whether the original voltage signal is a closely spaced mode signal; based on the frequency spectrum information, performing a singular value decomposition on the original voltage signal and performing a reconstruction to obtain a reconstructed voltage signal with an interference signal removed; if the original voltage signal is the closely spaced mode signal, performing a frequency modulation on the reconstructed voltage signal to obtain a frequency-modulated signal; adding white noise to the reconstructed voltage signal or the frequency-modulated signal, and then performing an empirical mode decomposition; and performing a Hilbert transform on each intrinsic mode function obtained by the empirical mode decomposition to obtain an amplitude and frequency information of a corresponding intrinsic mode function.