# A Software-based Low-Jitter Servo Clock for Inexpensive Phasor Measurement Units

## TL;DR

This paper introduces a low-cost, software-based servo clock for PMUs that achieves accurate synchronization using a PI controller and minimal hardware, suitable for inexpensive and scalable deployment.

## Contribution

It presents a novel software servo clock implementation for PMUs that maintains synchronization without specialized hardware, using only a PPS input and a co-processor.

## Key findings

- Achieves good long-term stability in tracking PPS signals
- Requires only a single PPS input and minimal hardware
- Demonstrated on a BeagleBone Black platform

## Abstract

This paper presents the design and the implementation of a servo-clock (SC) for low-cost Phasor Measurement Units (PMUs). The SC relies on a classic Proportional Integral (PI) controller, which has been properly tuned to minimize the synchronization error due to the local oscillator triggering the on-board timer. The SC has been implemented into a PMU prototype developed within the OpenPMU project using a BeagleBone Black (BBB) board. The distinctive feature of the proposed solution is its ability to track an input Pulse-Per-Second (PPS) reference with good long-term stability and with no need for specific on-board synchronization circuitry. Indeed, the SC implementation relies only on one co-processor for real-time application and requires just an input PPS signal that could be distributed from a single substation clock.