Wind Turbine Converter ROCOF Measurement Under Noise and Response Trade-Off
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Solution Overview
Problem
Existing methods for measuring the rate of change of frequency in wind turbine converter units are prone to noise interference and face a trade-off between accuracy and time response, with relays being sensitive to noise and phase-locked loops amplifying noise, making it difficult to achieve both high accuracy and quick time response.
Innovation Solution
A method and module that calculate two filtered values of the rate of change of frequency, one with higher accuracy and slower time response, and another with faster time response but lower accuracy, using a comparison value to select the output based on a predetermined threshold, along with noise reduction techniques like filtering and rate limiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If filtering is applied to improve measurement accuracy, then measurement precision is improved, but time response becomes slower
Solution Approach 1:
The patent applies dynamics by making the filter characteristics adaptive rather than fixed. The system dynamically adjusts between a first filter with higher accuracy and slower response, and a second filter with lower accuracy but faster response, based on real-time operating conditions. This allows the measurement system to optimize its performance characteristics dynamically rather than being constrained by a static filter design.
Solution Approach 2:
The patent changes the filter parameters dynamically by selecting between different filter configurations. When grid conditions are stable, the system uses the first filter with higher measurement accuracy. When rapid changes occur, the system switches to the second filter with faster time response, effectively changing the operational parameters to match the current situation.
2Measurement precision
If derivative calculation is used to measure rate of change of frequency, then measurement precision is improved, but noise amplification increases
Solution Approach 1:
The patent introduces an intermediary filtering stage between the derivative calculation and the final output. By applying filters to the frequency measurement before calculating the derivative, the system eliminates harmful high-frequency noise components that would otherwise be amplified by the differentiation operation. This intermediary filtering step protects the system from noise amplification while preserving the essential frequency change information.
Solution Approach 2:
The patent converts the harmful effect of noise into a beneficial selection criterion. By analyzing the characteristics of the filtered signals and comparing them, the system can identify when noise is present and switch to the more robust filter configuration. The noise that would normally degrade measurement quality becomes a trigger for adapting the measurement strategy.
3Device complexity
If relay-based frequency measurement is used, then device complexity is reduced, but measurement precision deteriorates due to noise sensitivity
Solution Approach 1:
The patent replaces the mechanical relay-based measurement system with an electronic/digital filtering and calculation system. Instead of using physical relays that detect zero crossings and are inherently noisy, the system uses electronic filters and mathematical operations on the voltage waveform. This substitution eliminates the mechanical limitations and noise sensitivity of relay-based systems while achieving the desired measurement accuracy.
Data Source
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AI summary
Method and module for measuring the rate of change of frequency of a waveform related to a converter unit of a wind turbine generator, comprising: measuring an instantaneous value of said rate of change of frequency of the waveform, calculating a first filtered value of said rate of change of frequency, said first filtered value having good accuracy but low time response, and calculating a second filtered value of said rate of change of frequency said second filtered value having a good time response but low accuracy, comparing said first and second filtered values and selecting that an output value of said measured rate of change is based on said first or second filtered values depending on said comparison,