Wavelet-Based Grid Oscillation Detection for Transient SSR
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Solution Overview
Problem
Existing methods struggle to effectively detect and interpret low-frequency oscillations in electrical supply grids, particularly those that occur transiently or are not based on resonance, due to their fleeting nature and the complexity of system observation, which can impact grid stability.
Innovation Solution
A method utilizing wavelet analysis to capture and evaluate electrical signals from the grid, creating a time-dependent frequency pattern to identify low-frequency oscillations by correlating the signals with a predetermined wavelet mother function, allowing for the detection of additional frequency components and their temporal distribution, and adapting the wavelet mother function to the expected oscillation mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional observation methods are used to monitor system characteristics, then grid stability can be assessed, but the detection becomes complicated and costly, and transient low-frequency oscillations are difficult to capture
Solution Approach 1:
The patent replaces conventional mechanical observation systems with a signal processing-based detection device that uses wavelet analysis. The detection device captures voltage signals from the grid and processes them through wavelet transformation to identify low-frequency oscillations, eliminating the need for complex physical observation systems while improving detection capability for transient phenomena
Solution Approach 2:
The patent changes the analysis parameters by applying wavelet transformation with specific mother wavelets tuned to low-frequency ranges. By transforming the voltage signal into the time-frequency domain and analyzing specific frequency bands (0.1-50 Hz), the system can detect transient oscillations that conventional methods miss, while keeping the hardware simple
2Measurement precision
If conventional frequency analysis methods are used, then ongoing oscillations can be detected, but transient low-frequency oscillations occurring briefly are difficult to capture and interpret
Solution Approach 1:
The patent applies continuous wavelet transformation that periodically analyzes the voltage signal across different time windows. This allows the system to capture transient oscillations by examining multiple time segments, identifying low-frequency components even when they occur briefly, and reconstructing their temporal characteristics through the time-dependent frequency pattern
Solution Approach 2:
The patent uses preliminary wavelet decomposition to break down the voltage signal into frequency components before detailed analysis. By pre-processing the signal through wavelet transformation and identifying potential low-frequency bands, the system prepares the data for targeted detection, enabling accurate capture of transient oscillations before they disappear
3Measurement precision
If the wavelet mother function is adapted to expected oscillation modes, then detection accuracy improves, but the system requires prior knowledge of oscillation characteristics
Solution Approach 1:
The patent implements a dynamic approach by allowing the selection of different mother wavelets based on expected oscillation modes. The system can adaptively choose appropriate wavelet functions (e.g., Morlet, Daubechies) depending on the anticipated frequency characteristics, making the detection both precise for known modes and flexible for unknown scenarios through configurable parameters
Data Source
AI summary
Provided is a method for detecting low-frequency oscillations, in particular subsynchronous resonance, in an electrical supply grid, wherein the electrical supply grid has a grid voltage at a grid nominal frequency, comprising the steps of capturing at least one electrical signal from the electrical supply grid, and evaluating the electrical signal by means of wavelet analysis, during which a time-dependent frequency pattern is created by analyzing a correlation of the captured signal with a predetermined wavelet mother function, wherein the presence of a low-frequency oscillation is assumed if at least one further low-frequency frequency component is present in the time-dependent frequency pattern in addition to a fundamental component.