Dynamic Phasor Filter Cascade for Frequency-Adaptive Signal Processing
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Solution Overview
Problem
Existing methods for phaser determination of current or voltage signals are limited in filtering out undesirable signal parts below a static, predefined frequency, leading to potential loss of necessary signal components and reduced output quality, especially when network frequency changes.
Innovation Solution
A filter cascade with multiple levels is used to filter out signal components at specified multiples of a basic frequency, allowing for dynamic adaptation of filter levels based on changes in the basic frequency, thereby improving phaser determination accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a static, predefined frequency filter is used to remove unwanted signal components, then filtering of decaying DC and AC components below the defined mains frequency is achieved, but signal components required for correct phasor determination may be lost when the line frequency drops
Solution Approach 1:
The filter cascade dynamically adapts its filtering characteristics by adjusting the multiple factor k based on the detected fundamental frequency. When the fundamental frequency changes, the filter stages recalculate their cutoff frequencies using the updated fundamental frequency, ensuring that harmful harmonics are always filtered at the correct frequencies while preserving the fundamental component for accurate phasor determination.
Solution Approach 2:
The filter parameters (cutoff frequencies) are changed based on the detected fundamental frequency. The system calculates new filter parameters using the relationship f Harmonic = k × f Fundamental, where k is the harmonic order. This parameter adaptation ensures that the filter always targets the correct harmonic frequencies regardless of fundamental frequency variations.
2Object-affected harmful factors
If the filter cascade removes signal components below a static frequency threshold, then unwanted low-frequency components are filtered out, but the filter cannot adapt when the fundamental frequency changes
Solution Approach 1:
The system employs feedback by continuously detecting the fundamental frequency and using this information to adjust the filter cascade parameters. The detected fundamental frequency feeds back into the filter configuration, allowing the system to automatically adapt to frequency changes and maintain optimal filtering performance without manual intervention.
Solution Approach 2:
The filter cascade transitions from a static filtering system to a dynamic one that automatically adjusts its characteristics based on the detected fundamental frequency. The filter stages recalculate their cutoff frequencies in real-time based on the updated fundamental frequency, enabling the system to adapt to varying operating conditions while effectively suppressing harmful harmonics.
3Measurement precision
If filter stages are added to improve phasor determination by removing more harmonics, then filtering accuracy is improved, but the complexity of the filter cascade increases
Solution Approach 1:
The filter cascade is segmented into multiple independent filter stages, each targeting a specific harmonic order k. This segmentation allows the system to selectively filter only the most significant harmonics rather than implementing a single complex wideband filter. Each stage can be independently configured and optimized, reducing overall system complexity while maintaining high filtering effectiveness.
Data Source
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AI summary
A method for determining the phasor of a current or voltage signal is described, wherein the current or voltage signal is sampled and the time-discrete samples are fed to a multi-stage filter cascade (4), after which the parameters of the phasor are determined and output from the filtered samples transformed into the frequency domain. To design a method of the type described above in such a way that reliable and fast determination of the phasor is possible even in the case of a frequency change of the current or voltage signal, it is proposed that the filter cascade (4) comprise several filter stages (5), wherein in each filter stage (5) a signal component with a predetermined multiple of a fundamental frequency stored in a frequency memory (3) is filtered out from the samples, and successive input values are temporarily stored to determine an output value.