Wide-area Monitoring and Control of Smart Grid

Summary

A transition from the conventional grid to one of distributed resources, digital loads with solid-state power electronics, and multi-directional powerflows is well underway.  Driven by a powerful combination of technology innovation and modularity, dramatically declining costs, and policy, electric distribution systems are becoming highly dynamic systems that require sensing and control at their very edge.  Maintaining stability and realtime balance across the system is becoming much more challenging, and this is especially true in microgrids where the outsized impact of single devices puts greater emphasis on the need for resiliency and reliability.  Vastly improved monitoring is a tool to improve grid operations, and highly accurate and flexible sensor systems are becoming critical to accelerate deployments of microgrids and high penetration of renewables.
 
The changing mix and characteristics of consumer-facing energy management technologies, as well as growing opportunities for customers to participate in supply- and demand-side electricity markets, require low-cost and accurate sensing at the meter and beyond into buildings and residences.  The DOE Grid Modernization Multi-Year Program Plan states that, ”Although more observation points have been deployed with recent investments (e.g., smart meters, PMUs), very little visibility is currently available at and below the distribution level, thereby limiting the integration of distributed systems and utilization of loads to their full potential.”   Rapid deployment of new sensors in the smart grid is one potential solution to this problem, but it is not possible at present because there is:

• a pressing need for more accurate, low-cost, flexible, and secure sensor measurement systems;
• an inability of the infrastructure to accommodate large real-time data flows; and 
• a lack of interoperability among sensors and systems.

 
This project extends the capabilities of the NIST synchrometrology and smart grid testbeds for sensors to testing under real-world conditions to enable new test standards and development of new, adaptable sensor systems. This will advance and accelerate the achievement of smart grid operational priorities, including:

• Greater resilience, improved reliability for everyday operations;
• enhanced security from an increasing and evolving number of physical and cyber threats;
• additional affordability to maintain our economic prosperity;
• superior flexibility to respond to the variability and uncertainty of conditions at one or more timescales, including a range of energy futures; and
• increased sustainability through additional clean and energy-efficient resources.

Description

Objective:  To develop and verify innovative sensing systems and take full advantage of existing ones such as smart meters, PMUs, Merging Units (Mus), and other intelligent electric devices (IEDs), to enable greater electric grid resiliency, reliability, flexibility, and sustainability through comprehensive wide-area and local-area monitoring and control of the smart grid.  This is accomplished by accelerating the development and adoption of advanced sensors and measurement systems; development of conformance and interoperability tests for new standards for these devices; and development of sensor network interface specifications.

What is the Technical Idea?
This project proposes to characterize sensor systems in environments that realistically emulate real-world operating conditions. Using the advanced capabilities of the NIST SG Testbed, tests and performance requirements will be developed to characterize innovative sensors and measurement systems for the most demanding applications – in particular for dynamically changing conditions, rather than the steady-state tests primarily used to date. Innovative sensing systems will be developed and evaluated for measurement performance and interoperability.

What is the Research Plan?
Building on previous research evaluating the interoperability of PMUs and MUs, the research team will develop a logic model that is intended to provide a quantifiable metric for interoperability.  This logic model will be applied to a system using IEC 61850 GOOSE, and will conduct experiments to provide data from MUs, relays, and/or other IEDs to validate the model.  The usefulness of this work is that it will define and use logic models to calculate a quantifiable interoperability metric, an approach which stands in stark contrast to the subjective interoperability assessments used throughout industry today (e.g., the GWAC Interoperability Maturity Model).  Merging unit performance will be characterized with associated uncertainties.

As part of a longer-term effort to develop—through IEEE PES Sensors Working Group—a guide for testing smart grid sensor and intelligent electronic device systems, the group will conduct laboratory experiments to evaluate the components of dynamic uncertainty for smart measurement systems.  The group will write three chapters for this guide.

Building off of FY19 research to evaluate smart meter measurement accuracy under high levels of harmonic distortion caused by solid-state and other lighting technologies, the project will investigate the effect behind-the-meter (i.e., customer facing residential wiring) electrical circuit impedance has on the transmission of these measured harmonics to the point of common coupling (e.g., electrical meter).  This will be a substantial and innovative contribution to the research and metrology community’s understanding of how harmonics and other waveform distortions attenuate as distance from the source increases.  Use of smart meters as voltage sensors will also be characterized to include the uncertainties with sinusoidal waveforms and typical DER waveforms in the laboratory.

Major Accomplishments

Research Outcomes:

• Calibration of Phasor Measurement Units at NIST," Yi-Hua Tang, G.N. Stenbakken, and A. Goldstein, submitted to IEEE Transactions on Instrumentation and Measurement

Potential Research Impacts:

• The calibrator improves NIST PMU measurement services by better automating the process for faster turnaround times and gives NIST the ability to perform special tests of new PMU prototypes more quickly.

Potential Technology Transfer Impacts: Examples of standards/tools with dissemination and adoption with the potential to achieve significant broad-based end use for the smart grid include:  

With NIST leadership, several Phasor Measurement Unit (PMU) standards were developed over several years on an accelerated timeline and are being adopted to support interoperability and accurate testing of over 1000 new PMUs being installed with DOE American Recovery and Reinvestment Act funding. NIST support, including development of the original steady state tests and new dynamic tests, was critical to the establishment of these standards and their continued evolution. 
 

• IEEE C37.242-2013, a guide for the synchronization, calibration and installation of PMUs, was accelerated with NIST support, and is based in large part on NIST research. It supports the accelerated timeline for ARRA-funded deployments of PMUs. (FY13) 
• IEEE C37.244-2013, a guide for phasor data concentrators (PDCs) was accelerated with NIST support, and is based on NIST research. It supports the accelerated timeline for ARRA-funded deployment of PMUs and PDCs. (FY13)  
• IEC 61850-90-5 Edition 1.0 integrates the IEEE C37.118.1 data with the IEC 61850 standard. It was coordinated as part of under the NIST-led SGIP Priority Action Plan 13 and is now being implemented in ARRA-funded PMUs. This 61850 standard offers much greater functionality, flexibility, and interoperability than the original IEEE C37.118-2005 standard. (FY12) 
• IEEE1815-2012 is a standard for electric power systems communications using the Distributed Network Protocol (DNP3). It was accelerated under the NIST-led SGIP Priority Action Plan 12, and is a revision of IEEE 1815-2010 that adopts improved cybersecurity as recommended by the NIST-led SGIP cybersecurity review of the earlier standard. It is a step toward making legacy grid control systems interoperable with advanced control systems based on IEC 61850. (FY12) 
• IEEE C37.118.1-2011 covers performance requirements and testing for PMUs, and incorporates tests developed by NIST for PMU performance under dynamically changing conditions. (FY11) 
• IEEE C37.238-2011 is a guide for precision clock synchronization for electric power grid applications. It was coordinated as part of the NIST-led SGIP Priority Action Plan 13 and enables precision time synchronization among devices in substations for improved grid reliability and resilience. (FY11) 
• IEEE C37.239-2010 provides a common format for anomalous event data exchange in the grid. It was coordinated as part of the NIST-led SGIP Priority Action Plan 14 and was developed to improve interoperability of various wide-area monitoring devices and systems. (FY10) 
• IEEE1815-2010 is a standard for electric power systems communications using the Distributed Network Protocol (DNP3). It was accelerated under the NIST-led SGIP Priority Action Plan 12, and is an IEEE adoption of a widely used standard developed by the DNP users group for substation monitoring and control. It is a first step toward making legacy grid control systems interoperable with advanced control systems based on IEC 61850 for improved grid reliability and resilience. (FY10)

Phasor Measurement Units (PMU) synchrometrology laboratory, measurement service, and test tools. NIST was the first National Metrology Institute to offer traceability for PMUs through a special test calibration service, enabling vendors to verify compliance with standards and receive detailed NIST feedback to improve their products' performance. In support of this test capability, NIST installed a new three-phase PMU calibrator developed under a NIST ARRA grant in FY13, and is conducting dynamic testing according to IEEE C37.118.1-2011 for 6 commercial PMUs, with testing of a new IEC 61850-90-5-compliant PMU scheduled to begin in June 2013. The automation provided by the PMU calibrator greatly reduces the turnaround time for reporting test results to the manufacturers and accelerates product improvements. The NIST synchrometrology work has led to a suite of tests that have been adopted in IEEE and IEC standards, and the NIST-developed PMU test tools (hardware and software) have now been adopted by a commercial test laboratory, Quanta Technology. The NIST lab has also developed signal processing models for calculation of synchrophasors compliant with the IEEE standards to compare with commercially-developed models to demonstrate the validity of PMU standards and identify gaps to be addressed for improved performance and reliability.