Precision Timing for Smart Grid Systems

Summary

This project supports the power systems industry by developing an in-depth understanding of timing performance and metrology necessary to achieve the precision timing requirements for grid data acquisition, communications, and computational analytics. Through exploration, research and applications development, the project provides insight into user application requirement specification for synchronization and timeliness of grid measurement networks and systems, deployment of secure and resilient timing infrastructure, and guidance for monitoring time synchronized networks, under a distributed environment. The project will survey the precision time system performance metrics for assurance requirements specification, continued guidance for online monitoring of timing performance relevant to the power systems domain, and engage with stakeholders on methods for assured and resilient timing networks.

Description

Objective: The key objective is to support the power sector industry through research and development in the metrology for online and predictive precision timing characterization necessary for grid monitoring and control applications.

This project strives to support to the Smart Grid Testbed and the power systems industry in developing an assured time synchronization infrastructure, state-of-the-art online measurement and monitoring capabilities, test methods, tools, and performance characterization and metrics for time synchronization of system and devices to achieve assured precision time, phase, and frequency synchronization necessary for grid data and communications applications. This project will continue to engage with on user time synchronization and time stamping requirements and evaluate selected tests in the NIST-supported Precision Time Protocol (PTP) test suite specification (TSS) as well as the responsible use of Global Positioning System (GPS) for time and frequency synchronization.

The project ties to the Integrated Smart Grid Framework 4.0 by striving to support systems interoperability through (1) a trustworthy precision time synchronization infrastructure to support synchronized measurement functions, (2) conformance test method development and validation for the reference clock, network switches, and end devices for testing and certification, as well as (3) systems monitoring design and application development towards secure, timely information exchange.

What is the new technical idea?
Increased integration of renewables and reliance on microgrids lead to temporal challenges driving the need for improved precision timing.  Power system signals are subject to faster dynamics, especially with the increase of renewable generation sources and load demands. Enabling intelligent automation in power generation and management will require correct timing and timeliness. Emerging grid sensing technologies, such as Merging Units (MUs), used to sample local currents and voltages for automated grid applications, is projected to require sub-microsecond synchronization capabilities. Existing grid sensing applications such as voltage and frequency regulation as well as traveling wave fault detection require clock synchronization on the order of a microsecond.

Timing accuracy is critical for accurate data fusion from heterogeneous sources (diagnostics), to make accurate estimates of state (situational awareness) and to ensure safety of decentralized control schemes (situational intelligence). Practical timing considerations are rarely considered during design but pose a significant challenge at the time of implementation.

In additional, scalable implementation of control and estimation algorithms for large power networks depend on their amenability to decentralization and parallelization, thus requiring precise synchronization between the various interacting components.

Precisely synchronized clocks are needed to:
1)  ensure fidelity of error and event logs used for diagnosis;
2)  accurately estimate the state of the system based on its time stamped measurements; and
3)  develop control algorithms that can apply corrective action in a timely manner.

For safety reasons, engineered systems go through the verification process during design phase and are tested after manufacturing. However, anomalous environmental conditions and aging of devices can still lead to unpredictable system behavior. Furthermore, the complexity and scale of power systems drives the computational complexity, sometimes rendering the analytical computations intractable to verify in a timely manner.  We propose to research and develop an experimental system to monitor the performance metrics of pertinent system components from the time server down to the device (sensing and control) level to better understand the variability over time.  
 

What is the research plan?
The research plan is to (1) based on literature review, empirical data from our testbed devices and industry input, develop a report for specifying user application requirements for timing and (2) to continue to develop an experimental end-to-end real-time automated monitoring system augmented with computational estimation and prediction algorithms to provide end applications with uncertainty values on timestamps and other time dependent attributes/measurements robust to a variety of environmental conditions, including loss of a time reference.

The plan also includes benchmarking the analysis against highly dynamic aspects of the power network. Specifically, the project will focus on applications requiring clock accuracy at the sub-microsecond level and timeliness to a few milliseconds.

The plan can be organized into the following steps to address some of the timing challenges listed in the NIST report on “Technology, Measurement, and Standards Challenges for the Smart Grid.”

1. Literature review of user temporal requirements for Smart Grid and other CPS applications. 
2. Co-chair “User Requirements for Assured Timing” working group as part of the Department of Homeland Security (DHS) effort to develop a framework to specify user requirements for assured timing. 
3. Integrate new equipment capabilities, specifically the Paragon-X, into the testbed time measurement and monitoring system. 
4. Design and conduct an experiment to determine important factors contributing to time server and end device errors in commercially available devices.
5. Based on the literature review, working group input and empirical data, develop a framework on specification of user timing requirements.
6. Continued support of the IEEE C37.238 Conformity Assessment effort for 61850-9-3 (2016) and IEEE C37.238 (2017).
7. Continued development of a cyber testbed environment that enables conformance / interoperability test validation as well as real­time simulation and research in a time­aware network for measurement and control.
8. Augment online monitoring system with estimation and predictive capabilities using environmental data from IoT devices and computational learning algorithms.
9. Support the development of a cybersecurity framework profile for responsible use of PNT. 

Wireless (RF), Metrology and Documentary standards