Electric Meter PPS Synchronization for Sampling Frequency Drift
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Solution Overview
Problem
Existing electric utility meters in distribution networks face challenges due to high bandwidth costs and clock oscillator degradation, which makes it impractical to implement phasor measurement units (PMUs) and maintain accurate sampling frequencies, limiting network analysis capabilities.
Innovation Solution
An electric utility meter with integrated RF communications and a controller that uses pulse-per-second signals to detect and adjust sampling frequency deviations, allowing for synchronized measurements and mitigation actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PMUs are implemented in distribution networks to enable synchronized measurements and phase angle detection, then network analysis capability is improved, but bandwidth cost and device complexity increase significantly
Solution Approach 1:
The patent replaces expensive PMU hardware with a cost-effective implementation using standard microcontroller units (MCUs) already present in smart meters. The synchronized measurement functionality is achieved through software-based phase-locked loop (PLL) algorithms and GPS-disc disciplined oscillators, eliminating the need for dedicated PMU devices in distribution networks.
Solution Approach 2:
The patent enables smart meters with existing MCUs to perform multiple functions including synchronized voltage and current measurements, phase angle detection, frequency monitoring, and communication. This multi-functionality approach allows a single device to replace specialized PMU equipment while maintaining network analysis capabilities.
2Measurement precision
If clock oscillators are used to maintain sampling frequency, then measurement synchronization is improved, but clock degradation over time causes frequency drift and reduces reliability
Solution Approach 1:
The patent implements a feedback mechanism using GPS-disc disciplined oscillators that continuously compare the local clock frequency with the GPS reference signal. The system automatically adjusts the oscillator frequency to maintain synchronization, compensating for drift caused by environmental factors and aging. This closed-loop feedback ensures long-term frequency stability without requiring manual calibration.
Solution Approach 2:
The patent introduces GPS timing signals as an intermediary reference to synchronize multiple meters across the distribution network. The GPS-disc disciplined oscillator acts as a mediator between the unstable crystal oscillator and the required sampling frequency, providing a stable reference that eliminates frequency drift issues.
3Reliability
If additional hardware is added to control sampling frequency and compensate for oscillator degradation, then frequency stability is improved, but cost increases making it impractical for widespread deployment
Solution Approach 1:
The patent enables the existing MCU to perform self-diagnosis and self-adjustment of sampling frequency using built-in peripherals and software algorithms. The system automatically detects frequency deviations and compensates through software-based PLL techniques, eliminating the need for external frequency control hardware and reducing overall system cost.
4Measurement precision
If synchronous sampling is implemented across multiple meters, then network-wide analysis accuracy is improved, but coordination complexity and communication overhead increase
Solution Approach 1:
The patent uses periodic GPS-disc synchronized timing pulses to coordinate sampling across multiple meters. Each meter samples voltage and current at precisely timed intervals based on the GPS reference, ensuring network-wide synchronization without requiring complex continuous communication protocols. The periodic synchronization approach simplifies coordination while maintaining high measurement precision.
Data Source
AI summary
A processor of an electric meter receives a measurement signal corresponding to an input electricity, initiates a first counter at a first edge of a first pulse-per-second (PPS) signal of an RF communications system, and stops the first counter at a first edge of the measurement signal. The processor determines a first counter value from the first counter and initiates a second counter at a first edge of a second PPS signal of the RF communications system. The processor stops the second counter at a second edge of the measurement signal. The processor also determines a second counter value from the second counter, determines an actual sampling frequency of the measurement signal, and compares the actual sampling frequency of the measurement signal to a predetermined sampling frequency. The controller also performs a mitigation action in response to determining that the actual sampling frequency differs from the predetermined sampling frequency.