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Smart Grid Communication Networks

Summary:

While there is a clear need for communication networks supporting reliable information transfer between the various entities in the electric grid, there are many issues related to network performance, suitability, interoperability, and security that need to be resolved. This project will focus on identifying opportunities to tailor communication protocols that have been designed for network traffic control to provide quality of service (QoS) to smart grid applications and to manage power flows in the smart grid between traditional and renewable generation sources and between utility-owned and customer-owned assets. By creating collaborative links between the stakeholders, users, and standard developing organizations (SDOs) working on telecommunications, this project will promote the use and deployment of interoperable communication protocols for smart grid. In addition, the analytical and simulation tools and the published research findings that will be produced by this project will foster the development of new areas of inquiry into smart grid specific communication technologies.

Description:

Objective - To accelerate the development of scalable, reliable, secure, and interoperable communications and standards for smart grid applications; and to enable informed decision making by smart grid operators by developing measurement science-based guidelines and tools.

What is the new technical idea? Traditionally, technology decisions have been dictated by offerings of system vendors, while business decisions are regulated by federal, state, and regional regulatory commissions and organizations (e.g. the Federal Energy Regulatory Commission, state Public Utility Commissions, and the North American Electric Reliability Corporation). While there are many choices of communications and networking standards, most of these standards were not developed specifically for smart grid applications. The new technical idea is to work directly with the smart grid stakeholders (utilities, regulators and consumers) and the telecommunication industry (vendors, SDOs, service providers) to identify communication requirements for smart grid applications, evaluate and develop communication standards, and develop guidelines and recommendations on their use and deployment. Also, the introduction of new power distribution technologies will transform the electrical network so that it will resemble regional and continental high speed telecommunications networks, although the transported commodity will be electrical power rather than data. This creates an opportunity to apply well-established analysis and optimization techniques from the telecommunications field to aid in the design of future electrical networks.

What is the research plan? Our research plan is focused on understanding and modeling the power grid user and system behaviors and developing control and communication strategies for achieving the smart grid vision of a more efficient and dynamic electric grid. Our research in FY15 comprises two main thrusts:

1) Algorithms to enforce QoS in electrical networks: Microgrid ScenarioSince the electrical distribution network has structural similarities to wired communications networks, several modeling and analysis techniques that have been traditionally used in communications networks, such as routing algorithms, traffic analysis, and call admission control, may be applied for controlling and characterizing the electric grid. In FY14, we examined how storage devices can be positioned to mitigate the effect of network failures. In FY15, are applying techniques developed to guarantee quality of service (QoS) for data traffic flows in communications networks to manage power flows in microgrid networks. This work consists of applying modifications to admission control algorithms to optimize them for use in a microgrid, combined with use of a the co-simulation system platform described below to examine the admission control algorithm performance. As part of the study, we are considering tradeoffs between centralized, distributed, and hybrid approaches. We are using the MATPOWER toolbox in Matlab to study the effect of the grid when additional customer load is requested. To make a good admission decision for load request, it is critical to find the maximum extra load that can be allowed in the grid. We are developing an analysis method, in which we determine the optimal flow through a test network, in this case the IEEE 14-bus, and then successively recompute the optimal flow as the load on the system increases.

Algorithms that enforce QoS in electrical networks will perform two functions: admission control and policing of admitted flows. Historically, power flows traveled from generators (sources) to customers (sinks). The growing use of distributed power generation using renewable resources (e.g. wind and solar) that fluctuate over time, combined with increasing use of renewable sources located at the customer premises, means that there are additional sources of power flows that an operator must contend with. To assess control algorithms that perform admission and policing of flows from operator­ owned or customer ­owned sources, we need accurate models of user behavior. Previously, we used real­world data to characterize customer usage patterns. In FY15, are extending this work by developing and examining stochastic models that capture the arrival and departure behavior of power flows in a grid that incorporates intermittent sources, based on electrical generation and consumption statistics. This work leverages network calculus theory to mathematically describe the characteristics of power flows and uses the concept of a "service curve" to model the ability of a network with limited transmission capabilities to transmit power, and to model flow policing functions (e.g. electrical analogues to the leaky bucket function that is used to police traffic flows in packet-switched networks). Properly tuned electrical flow policing will further provide guaranteed levels of performance for electrical distribution networks. I

n FY14, we used GridLAB­D to simulate failures in power distribution networks, including integrating of distributed energy resources and cascading failures. We developed and tested a co-simulation framework using GRIDLAB-D/NS3/ MATLAB that we used to examine interactions between the electrical generation/distribution network and the communications network. This work leverages the GridMat Toolbox to develop a co-simulation platform that connects GRIDLAB-D to Matlab/Simulink We used the SGIP PAP2-developed use cases as example scenarios, and we documented the results of the performance evaluation in a journal article that has been submitted for review. We modeled element failures that occur in the electrical distribution network, the communications network, as well as correlated failures that affect both networks, and applied protection and restoration strategies to mitigate their effects. In FY15, we are extending this work by examining the behavior of adapted QoS algorithms and the communications network traffic that they generate. We are developing models for the timing of arrivals and departures of power flows in microgrids based on electrical generation and consumption statistics. In FY16, we will use system­level simulation models (1) to support SG testbed specific-scenarios more specifically to help plan experiments to be conducted on the testbed and validate results obtained from testbed experiments, (2) investigate the use of shared communication network resources to support SG-specific applications.    

2) Improvements to the smart grid communications network: Wide Area Measurement Systems ScenarioSmart grid traffic is structurally different from Internet traffic, as revealed by the use cases developed for PAP 2. The delay and loss requirements for smart grid applications vary widely; some are very tolerant of long delays or lost information (metering), while others demand near instantaneous data delivery with virtually no loss (wide area measurement systems). Also, the amount of data exchanged can grow very large as in the case of wide area measurement systems. As these systems scale up to a large number of Phasor Measurement Units (PMU), the centralized super­Phasor Data Collector (PDC) architecture becomes untenable.

In FY15 we continued our efforts to expand the testbed by implementing a hierarchical synchrophasor network.  In addition, a novel scheme that would considerably reduce the bandwidth needed to transmit aggregated data at each PDC level has been designed. In FY16, we plan to expand the synchrophasor testbed to include Distributed Generation (DG) grid systems and examine developing a multihop wireless mesh routing protocol suitable for radial and loop feeders. As a new milestone, additional efforts will be dedicated to developing a visualization framework for an interactive real-time display of the measured phase, frequency, voltage, current, and power factor, as well as displaying packet exchanges at the application, network, and physical layers. Furthermore, to overcome the current limitations of the Emulab system (where virtual nodes can only be created on a single host computer), we envision a rather ambitious plan to expand the operational capabilities of the testbed under more realistic environments. If funded, this new intuitive can lead to the development of a flexible Software Defined Testbed where nodes can be dispersed throughout a NIST-wide network. This would enable PMU's and PDC's to be located at different test sites. Such a testbed would allow us to put theory into practice towards fast deployment of novel techniques, as well as testing and verifying various communication protocols and standards.    

ITL will continue to lead and contribute to the activities of the SGIP related to wireless and powerline communications. In addition ITL staff will continue to participate in international standard activities (ITU, IEEE 802 and IETF) related to smart grid communications.

Major Accomplishments:

Research Outcomes: A list of ERB-approved papers submitted for publication in the identified list of peer-reviewed, archival journals in 2012-2013 is provided below, along with project name(s) in brackets:
  • “On Statistical Modeling and Forecasting of Energy Usage in Smart Grid,” W. Yu, D. An, D. Griffith, Q. Yang, and G. Xu, submitted to IEEE Transactions on Smart Grid 
  • “Guest Editorial – Smart Grid Communications,” N. Golmie, A. Scaglione, L. Lumpe, E. Yeh, Lang Tong, and Sean Smith, submitted to IEEE Journal on Selected Areas in Communications 
A few additional ERB-approved papers submitted for publications in other journals are listed below for reference:  
  • '4-Way Handshaking Protection for Wireless Mesh Network Security in Smart Grid,” H. Gharavi and B. Hu, submitted to IEEE GLOBECOM 2013. [Smart Grid Communication Networks, FY13] 
  • “Adaptive Key Management for Wireless Sensor Networks,” T. Cheneau and M. Ranganatha, submitted to IEEE GLOBECOM 2013. 
Realized Research Impacts: A list of published papers in peer-reviewed, archival journals is provided below, in brackets, fiscal year of acceptance and number of citations (as of May 2013):
  • “Multigate Communication Network for Smart Grid” Hamid Gharavi and Bin Hu, Proceedings of the IEEE (June 2011) 99 (6) 1028-1045.  
  • “Smart Grid: The Electric Energy System of the Future” Hamid Gharavi and Reza Ghafurian, Proceedings of the IEEE (June 2011) 99 (6) 917-921.