RMS Metering Using Segmented Frequency Paths
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Solution Overview
Problem
Traditional metering systems fail to accurately calculate root-mean-square (RMS) values of alternating current (AC) signals due to the exclusion of high frequency components, leading to errors in power management, particularly in environments like data centers where accuracy is critical.
Innovation Solution
A method and device that separate high and low frequency components of AC signals, using filters and waveform factors to approximate RMS values without the need for high-speed analog-to-digital converters (ADCs), allowing for accurate RMS calculations with cost-effective circuit architectures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high speed ADC is used to convert high frequency components into the digital domain, then measurement precision of RMS voltage and current levels is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent segments the current measurement into two separate paths: a high frequency current path that captures high frequency components (including harmonics and switching currents) and a low frequency current path that captures fundamental frequency components. Each path uses its own ADC and processing chain, allowing the system to measure high frequency components without requiring a single high-speed ADC, thus reducing overall device complexity while maintaining measurement precision
Solution Approach 2:
The patent introduces an intermediary approach by using a current transformer and separate measurement paths with individual ADCs operating at different sampling rates. This intermediary structure allows high frequency components to be captured without requiring the main ADC to operate at extremely high speeds, thereby reducing device complexity while preserving measurement accuracy
2Measurement precision
If a high speed ADC is used to convert high frequency components, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent divides the ADC operation into separate channels with different sampling rates: a first ADC samples at a lower rate for fundamental frequency components while a second ADC samples at a higher rate for high frequency components. This segmentation allows the system to achieve comprehensive measurement precision without having a single ADC consume excessive power by operating at maximum speed continuously
Solution Approach 2:
The patent changes the sampling rate parameter of different ADCs according to their specific measurement needs. The first ADC operates at a lower sampling rate suitable for fundamental frequency, while the second ADC operates at a higher sampling rate for high frequency components. This parameter optimization reduces overall power consumption while maintaining measurement precision across all frequency ranges
3Device complexity
If high frequency components are ignored in RMS calculations, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements segmentation by creating separate measurement paths for high frequency and low frequency current components. Each path processes its frequency range independently and contributes to the overall RMS calculation. This ensures that high frequency components are not ignored, maintaining measurement precision while avoiding the need for a single complex high-speed ADC system
4Measurement precision
If separate high frequency and low frequency current paths are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the results from separate high frequency and low frequency current measurement paths into a unified RMS calculation. The squared currents from both paths are summed and processed together to generate the final RMS current value. This merging approach maintains measurement precision by capturing all frequency components while managing device complexity through shared processing resources
Data Source
AI summary
Embodiments of the present invention provide systems, devices and methods for efficiently calculating a true RMS values (either voltage or current) of an AC signal. The RMS value is generated from both high and low frequency components of the AC signal without a high speed ADC being integrated within the system. The high frequency component is processed by calculating an average current waveform of the high frequency component and approximating a corresponding RMS value using a waveform factor. The waveform factor is effectively a scalar that relates the average current waveform of the high frequency component to an appropriate RMS value.