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.  Additionally, the project provides insight into user application requirement specification, precision timing characterization, guidance for monitoring time synchronized networks as well as effects of timing uncertainty on grid operations under a distributed services 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 explore computational algorithms for predicting and managing timing uncertainty.

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. 

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. Integrate timing measurement and monitoring system into other collaborative Smart Grid testbed experiments to study the effects of timing error on wide area measurement and control. 

Wireless (RF), Metrology and Documentary standards