Electric Meter Offset Correction for Asymmetrical Current Signals
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Solution Overview
Problem
Electricity meters face challenges in accurately calculating apparent power consumption when dealing with asymmetrical current signals, as existing methods fail to account for the intrinsic DC component, leading to incorrect calculations and the need for additional processing steps to correct for this component.
Innovation Solution
The method involves measuring the effective current value, obtaining a current offset value by identifying a 'flat zone' in the signal where samples have minimal deviation, and using this offset to correct the RMS current value for accurate apparent power calculation, thereby accounting for the intrinsic DC component in asymmetrical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the average of the electrical current signal is determined and subtracted during apparent power calculation, then the intrinsic DC component of the electric meter is removed, but the continuous component intrinsic to the signal is incorrectly excluded from the calculation
Solution Approach 1:
The patent extracts and removes only the intrinsic DC component of the electric meter through a dedicated offset determination process, while preserving the continuous component intrinsic to the signal. This is achieved by separately identifying and eliminating the meter's inherent offset without affecting the signal's continuous component, thus resolving the contradiction between removing meter bias and preserving signal information.
Solution Approach 2:
The patent performs preliminary determination of the offset value before the apparent power calculation. By pre-calculating and storing the offset value in a non-volatile memory, the system prepares the correction data in advance, allowing the actual power calculation to proceed without needing to re-process the entire signal, thereby maintaining accuracy while reducing computational burden.
2Measurement precision
If additional processing steps are added to correct for the DC component, then measurement accuracy improves, but device complexity and processing time increase
Solution Approach 1:
The offset value is determined in advance and stored in non-volatile memory, eliminating the need for complex real-time correction calculations. This preliminary preparation simplifies the main calculation process while maintaining high accuracy, as the correction factor is already pre-computed and readily available during normal operation.
Solution Approach 2:
The system uses the signal's own characteristics (flat zones with minimal deviation) to automatically determine the offset value without requiring external reference signals or complex calibration procedures. This self-determination mechanism reduces device complexity by eliminating the need for additional calibration hardware or manual configuration.
3Measurement precision
If the entire current signal is processed to determine offset, then accurate correction is achieved, but memory usage and processing time increase
Solution Approach 1:
The patent segments the current signal into identifiable flat zones characterized by minimal deviation, and processes only these representative segments to determine the offset value. This segmentation approach allows accurate offset determination while significantly reducing the amount of data that needs to be stored and processed, as only the characteristic flat zone samples are retained rather than the entire signal waveform.
Solution Approach 2:
The patent focuses analysis on specific local regions (flat zones) of the signal that possess distinctive characteristics (minimal deviation), rather than processing the entire signal uniformly. This localized approach concentrates computational resources on the most informative portions of the signal, achieving accurate offset determination with reduced memory and processing requirements.
Data Source
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AI summary
An electric current signal is observed by an electric meter to determine the apparent electrical power consumed by an electrical installation. The apparent electrical power is calculated from an RMS current value corrected using an offset value. Determining the offset value involves a search (501) in the electric current signal over a period, called the flat zone, comprising samples of the electric current signal. The flat zone has a duration at least equal to a predefined duration and is such that, among the samples included in the flat zone, a percentage of samples, called non-singular samples, is greater than or equal to a detection threshold. A non-singular sample is a sample having a current value deviation less than a predefined deviation from at least one temporally adjacent sample.When a flat area is identified, the electric meter calculates (502) the offset value from at least one non-singular sample belonging to the flat area.