Wind Turbine Grid Oscillation Detection Using Sinusoidal Correlation
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Solution Overview
Problem
Existing electrical supply grids face challenges in detecting low-frequency oscillations, particularly subsynchronous resonances, due to their low amplitude and frequency, which can lead to instability and interference, especially with regenerative power units like wind turbines that lack inherent damping properties.
Innovation Solution
A method involving recording series of measurements of grid variables and multiplying them by a time-dependent sinusoidal test function to identify low-frequency oscillations through frequency and phase analysis, using a process control computer to vary test frequencies and angles to determine product sums, allowing for the detection of low-frequency oscillations with improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a longer measurement time period is used to detect low-frequency oscillations accurately, then detection precision improves, but detection speed decreases
Solution Approach 1:
The patent applies periodic action by using a sinusoidal test function that is multiplied with the measured signal at different frequencies and phases. This periodic multiplication allows the system to identify low-frequency oscillations by detecting correlated patterns without requiring extremely long measurement periods, thus balancing detection accuracy with detection speed
Solution Approach 2:
The patent implements preliminary action by pre-defining a range of test frequencies and phases before actual detection. The control unit systematically varies these parameters in advance according to a predetermined sequence, allowing the evaluation unit to quickly compare measured signals against pre-prepared reference patterns, thereby reducing the time needed for accurate detection
2Manufacturing precision
If wind turbines use full-power converter concept with precise presets for injected power, then control precision improves, but ability to react to grid phenomena physically decreases
Solution Approach 1:
The patent implements feedback by continuously monitoring grid variables (voltage, frequency, power) and using this information to adjust the injected power through the converter. The control unit compares measured grid conditions with reference values and dynamically modifies control parameters, enabling wind turbines to physically respond to grid phenomena like low-frequency oscillations while maintaining precise control through the full-power converter concept
Solution Approach 2:
The patent applies dynamics by enabling the converter to dynamically adjust its operation based on real-time grid conditions. The control parameters (amplitude, frequency, phase of injected current) are no longer fixed presets but are continuously adapted based on detected oscillations and their characteristics, allowing the system to maintain both control precision and physical adaptability
3Measurement precision
If detection method uses multiplication by sinusoidal test function with varied frequencies and phases, then detection accuracy improves, but computational complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the detection process into distinct functional units: a control unit that manages the variation of test parameters, a multiplication unit that performs the signal processing, and an evaluation unit that analyzes results. This segmentation allows complex computations to be organized efficiently and implemented in real-time without overwhelming computational demands
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 quick and accurate detection of low-frequency oscillations, enhancing system stability and allowing for timely countermeasures, even in noisy environments, by correlating measurement data with a sinusoidal test function to determine frequency and phase of oscillations.
Implementation Method 1
multiplying them by a time-dependent sinusoidal test function to identify low-frequency oscillations through frequency and phase analysis
Data Source
AI summary
A method for detecting low-frequency oscillations, in particular subsynchronous resonances, in a grid is provided. The method includes recording a series of measurements, having measurement points, of a grid variable over a measurement time period, for performing a frequency analysis and multiplying the series a time-dependent sinusoidal test function for the same measurement time period. The test function is characterized by a test frequency and a test angle as phase angle. The series for each measurement point is multiplied by the test function in order to obtain a test product for each measurement point. The method includes adding the test products taking into consideration the mathematical sign thereof to give a product sum, and evaluating, depending on the product sum, whether the series of measurements has a low-frequency oscillation having a frequency in the region of the test frequency and a phase angle in the region of the test angle.