Variable Acquisition Buffer Length for Energy Measurement Precision
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Solution Overview
Problem
Current energy measurement devices face inaccuracies and inconsistencies due to the use of fixed acquisition buffer times that accommodate fractional line cycles, leading to fluctuations in metrological measurements, and sigma-delta ADCs are limited by frequency changes, resulting in costly and slow solutions.
Innovation Solution
Implementing a variable acquisition buffer length to minimize partial line cycles and using an asynchronous sigma-delta ADC with multiple filter sets to synchronize samples with line frequency and phase changes, allowing for accurate and consistent measurements without requiring extensive reconfiguration of ADCs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed acquisition buffer time is used for sampling voltage and current signals, then the device structure is simple, but measurement precision deteriorates due to fluctuations caused by fractional line cycles
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed acquisition buffer time to a variable acquisition buffer time that adapts to changing line frequencies. The buffer length is dynamically adjusted based on detected frequency deviations, allowing the system to maintain integer line cycle boundaries despite frequency variations. This resolves the contradiction by making the buffer structure flexible rather than rigid, improving measurement precision without requiring complex hardware changes.
Solution Approach 2:
The patent changes the parameter of acquisition buffer time from a fixed value to a variable value that is adjusted based on line frequency detection. When frequency deviations are detected, the buffer length is modified to compensate, ensuring that the buffer always contains an integer number of line cycles. This parameter change allows the system to maintain high measurement precision while keeping the overall device structure relatively simple.
2Adaptability or versatility
If sigma-delta ADC frequency rate is changed to accommodate line frequency variations, then adaptability improves, but measurement precision deteriorates due to errors from internal modulators and filters
Solution Approach 1:
The patent applies dynamics by detecting line frequency changes in real-time and dynamically adjusting the acquisition buffer length to match the varying frequency conditions. This allows the system to adapt to frequency variations without changing the ADC operating frequency, thereby maintaining measurement precision while achieving the needed adaptability.
Solution Approach 2:
The patent introduces an intermediary mechanism (the variable acquisition buffer with integer line cycle synchronization) between the ADC and the measurement processing. This intermediary absorbs the frequency variations, allowing the ADC to operate at a stable frequency while still accommodating line frequency changes. The buffer acts as a mediator that decouples the ADC's fixed frequency requirement from the variable line frequency conditions.
3Measurement precision
If averaging several successive time periods is used to remedy measurement fluctuations, then measurement precision improves, but productivity deteriorates due to additional computation and memory requirements
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing the acquisition buffer to contain exactly an integer number of line cycles. This preliminary synchronization prevents measurement fluctuations from occurring in the first place, eliminating the need for subsequent averaging operations. By addressing the root cause before measurement takes place, the system achieves consistent measurements without requiring additional computation or memory for post-processing averaging.
4Measurement precision
If windowing is applied to the Fourier transform to improve measurement accuracy, then measurement precision improves, but device complexity increases due to additional computation
Solution Approach 1:
The patent applies preliminary action by ensuring the acquisition buffer contains an integer number of line cycles before performing the Fourier transform. This preliminary setup eliminates spectral leakage and measurement fluctuations, making windowing functions unnecessary. By preparing the data correctly in advance, the system achieves high measurement precision without adding the computational complexity of windowing operations.
Data Source
AI summary
A system and method for determining an acquisition buffer size for use in processing signals, the method including determining a number of samples obtained for a predetermined number of line cycles based on digital signals received from an analog-to-digital converter (106), determining an integer number of line cycles needed for a predetermined target number of samples, and determining an acquisition buffer length based on the integer number of line cycles, as a length of time that can accommodate the determined integer number of line cycles while minimizing or avoiding partial line cycles. The method can further include determining whether the determined acquisition buffer length is within a threshold range, and when not within the threshold, continuing to store a previously determined acquisition buffer length instead of the determined acquisition buffer length. The method may be repeated to continually adjust the acquisition buffer length to minimize or avoid partial line cycles.