Sub-Synchronous Oscillation Detection Using Adaptive Notch Filtering
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Solution Overview
Problem
Existing methods for detecting sub-synchronous oscillations in power systems are inefficient in terms of computational effort and accuracy, failing to effectively isolate the dominant SSR component and prevent generator damage.
Innovation Solution
The method employs an adaptive notch filter to calculate the amplitude of oscillation components, compares it against a threshold, and uses decision logic with transient and asymmetry checks to generate a fault signal, ensuring accurate detection and disconnection of generators from the power system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods (demodulated voltage signal with FFT or IIR filter with continuous RMS) are used to detect sub-synchronous oscillations, then detection capability is achieved, but computational effort is high and accuracy is insufficient
Solution Approach 1:
The patent extracts only the dominant SSR component from the measurement signal using an adaptive notch filter tuned to the sub-synchronous frequency range (5-55 Hz). This selective extraction isolates the relevant oscillation component while filtering out other frequency components, achieving accurate detection without the need for computationally intensive FFT analysis of the entire spectrum.
Solution Approach 2:
The patent changes the approach from using fixed filters or full-spectrum analysis to using an adaptive notch filter whose parameters (center frequency and bandwidth) are dynamically adjusted to track the dominant SSR frequency. This adaptive parameter adjustment allows the filter to maintain high selectivity and accuracy while keeping computational requirements low.
2Measurement precision
If existing methods are used to detect sub-synchronous oscillations, then detection is possible, but the dominant SSR component cannot be effectively isolated
Solution Approach 1:
The adaptive notch filter is configured to extract only the dominant SSR component by centering its notched frequency at the detected oscillation frequency and adjusting its bandwidth to pass only the sub-synchronous range (5-55 Hz). This selective extraction effectively isolates the harmful oscillation component from other signal components, enabling focused analysis and protection.
Solution Approach 2:
The patent introduces an intermediate processing stage where the adaptive notch filter acts as a mediator between the raw measurement signal and the final detection decision. This intermediary filter stage pre-processes the signal by isolating the dominant SSR component, making subsequent RMS-based detection more efficient and accurate without requiring complex multi-component analysis.
3Reliability
If existing detection methods are used, then sub-synchronous oscillations can be detected, but false detection during transient states occurs
Solution Approach 1:
The patent applies preliminary action by implementing transient detection checks before final SSR detection confirmation. The system first detects transient states in the measurement signal and blocks SSR detection during these transient periods, preventing false positive detections. Only after the transient state clears does the system proceed with SSR detection, ensuring reliable operation.
Solution Approach 2:
The patent incorporates feedback mechanisms where the detected oscillation frequency and amplitude information are continuously monitored and used to adjust the adaptive notch filter parameters and RMS window length. This feedback loop ensures that the detection system adapts to changing system conditions while maintaining reliability by comparing detected values against thresholds and blocking false detections.
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
This approach achieves high accuracy in detecting sub-synchronous oscillations with low computational burden, effectively isolating the dominant SSR component and preventing generator damage through secure decision logic and adaptive filtering.
Implementation Method 1
the dominant SSR component can be easily isolated and further analyzed... A good accuracy of the proposed solution is achieved using an AN filter, which further isolates the dominant SSR component by filtering out other components
Implementation Method 2
Then, a continuous RMS method is used to obtain the signal level for further processing
Data Source
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AI summary
A method for detection of a sub-synchronous oscillation in a power system is provided wherein the following steps are performed: measuring of a three-phase measurement signal of an electric system value, analyzing the measurement signal to detect an oscillation component of the measurement signal having an oscillation frequency that is lower than a system frequency of the power system, deciding whether the detected oscillation component at the oscillation frequency qualifies as a sub-synchronous oscillation, and disconnecting a generator from the power system that might be affected by the sub-synchronous oscillation. In order to detect sub-synchronous oscillations with low computational effort and with a good accuracy, it is proposed that an amplitude of each phase of the oscillation component is being calculated and compared against a threshold, detecting a sub-synchronous oscillation when the threshold is being exceeded during a given time delay, and generating a fault signal if a sub-synchronous oscillation has been detected. Furthermore, a device is provided containing a processing unit to perform such a method.