Frequency Measurement Using PMU Phase Angle
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Solution Overview
Problem
Existing frequency measurement methods in power supply networks are complex and imprecise, leading to high costs for separate frequency measuring systems, which are often inaccurate due to significant signal noise in phasor measurement units (PMUs).
Innovation Solution
A method that calculates the frequency measurement value using the phase angle between two sampled values of a network variable, leveraging existing PMUs for precise phase angle measurement, and determining the frequency with minimal measurement effort, potentially eliminating the need for separate frequency measurement systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex frequency measurement methods (such as multiple filter stages and zero-crossing detection) are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The invention extracts only the essential information needed for frequency measurement - the phase angle between two successive sampled values - and discards the complex filtering and processing stages. By taking out just the phase angle information from the sampled values, the system achieves accurate frequency measurement without requiring multiple filter stages or complex calculation processes.
Solution Approach 2:
The invention replaces traditional mechanical/electrical frequency measurement methods (zero-crossing detection, filter stages) with a computational approach using phase angle calculation from sampled values. This substitution of computational processing for physical measurement mechanisms simplifies the device while maintaining or improving measurement precision.
2Measurement precision
If separate frequency measuring systems are maintained alongside PMUs, then measurement precision is improved, but loss of substance increases due to high costs
Solution Approach 1:
The invention makes the existing PMU system multi-functional by enabling it to perform both its original function (monitoring electrical energy supply networks) and frequency measurement function. By calculating frequency from the phase angle information already captured by the PMU, the system eliminates the need for separate frequency measuring systems, reducing costs while maintaining measurement precision.
Solution Approach 2:
The invention merges the frequency measurement function with the existing PMU system. Instead of maintaining separate frequency measuring systems, the phase angle information from the PMU's sampled values is utilized for frequency calculation, combining multiple measurement functions into a single integrated system and eliminating redundant equipment.
3Device complexity
If PMUs are used for frequency measurement, then device complexity is reduced, but measurement precision deteriorates due to high signal noise
Solution Approach 1:
The invention uses the phase angle information already captured and processed by the PMU as a copy of the essential measurement data. Rather than relying on the PMU's direct frequency measurement output (which is noisy), the system recalculates frequency from the phase angle between successive sampled values, effectively creating a cleaner, more precise frequency measurement from the same raw data source.
Data Source
Figure 1~2
AI summary
The invention relates to a method for producing a frequency measurement value that indicates a frequency of an electrical network quantity, which frequency is present at a measurement point (11) in a power supply network, wherein a signal that characterizes the network quantity is sampled by means of a measuring apparatus (14) and the frequency measurement value is determined from the sample values. In order to further develop such a method in such a way that a frequency measurement value that is as exact as possible can be produced with comparatively little measurement complexity, the phase angle between two consecutive sample values of the network quantity is determined according to the invention and the frequency measurement value is calculated on the basis of the determined phase angle. The invention further relates to a correspondingly designed measuring device (12).