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Journal Paper Accepted: The need for holistic enterprise control assessment methods for the future electricity grid

The LIINES is happy to announce the publication of the journal article The need for holistic enterprise control assessment methods for the future electricity grid, by Prof. Amro M. Farid (Dartmouth), Bo Jiang (MIT), Aramazd Muzhikyan (Dartmouth), and Prof. Kamal Youcef-Toumi (MIT) in the journal Renewable and Sustainable Energy Reviews.

In this comprehensive literature-based study, the LIINES presents a logical case for integrating power grid assessment methods into a holistic enterprise control framework.  Such a framework is explicitly techno-economic and merges methods power systems engineering and economics.   To support the argument, the LIINES has conducted the most comprehensive review of renewable energy integration studies completed to date.

The paper discusses the need for change in the assessment of the electricity grid as a result of five driving forces.  The driving forces are identified as: decarbonization, growth of electricity demand, transportation electrification, electric power deregulation, and increasing numbers of responsive (“smart”) consumers.  These five drivers require the steadily increasing penetration of solar and wind generation as well as evolving capabilities to support demand side management for the tremendous diversity of loads that connect to the electrical grid.  The integration of these three new grid technologies of renewable energy, electric vehicles, and demand side resources ultimately imposes fundamental changes to the grid’s structure and behavior.

The paper argues that the future electric grid’s needs for reliability, cost efficiency and sustainability necessitates a holistic assessment approach.  Figure 1 shows a guiding structure that leads to five techno-economic control objectives.  This work also uses five lifecycle properties to integrate rather than decompose the engineering design.  The lifecycle properties core to the power grid are dispatchability, flexibility, forecastability, stability, and resilience. The use of these five properties avoids overlap in function of solutions.

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Figure 1: Guiding Structure of Argument

Using such a holistic paradigm for techno-economic assessment, the journal paper conducts the most comprehensive review of renewable energy studies completed to date. It found several limitations to the existing renewable energy integration studies. Firstly, in order to address the holistic nature of the power grid, the real potential of demand side resources needs to be included. Additionally, for power grid balancing, validated simulations rather than statistical methods based on questionable assumptions need to be used.  Furthermore, the consistency between future development of the real market structure and modeling methods needs to be assured. Finally, the investment costs related to the support of the future power grid need to be considered in simulation.

Thus, the paper concludes based on the defined model requirements and the assessment of the current literature, that a framework for holistic power grid enterprise control assessment needs to satisfy the following requirements:

  1. Allows for an evolving mixture of generation and demand as dispatchable energy resources
  2. Allows for an evolving mixture of generation and demand as variable energy resources
  3. Allows for the simultaneous study of transmission and distribution systems
  4. Allows for the time domain simulation of the convolution of relevant grid enterprise control functions
  5. Allows for the time domain simulation of power grid topology reconfiguration in operation time scale
  6. Specifically addresses the holistic dynamic properties of dispatchability, flexibility, forecastability, stability, and resilience
  7. Represents potential changes in enterprise grid control functions and technologies as impacts on these dynamic properties
  8. Accounts for the consequent changes in operating cost and the required investment costs.

These requirements have been realized in a power grid enterprise control simulator that was used for an extensive study of renewable energy integration in the power grid [Link 1], [Link 2].  The simulator includes the physical electrical grid layer and incorporates primary, secondary, and tertiary control functions. This model fits the requirements of the holistic enterprise control method as defined previously.

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 Figure 2: The Enterprise Control Power Grid Simulator

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LIINES Website: http://engineering.dartmouth.edu/liines

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Journal Paper Accepted: An A Priori Analytical Method for the Determination of Operating Reserve Requirements

We are happy to announce that our recent paper entitled: “An A Priori Analytical Method for the Determination of Operating Reserve Requirements”, has been accepted at the International Journal of Electrical Power & Energy Systems (IJEPES). This study comes as a result of collaboration between three universities; Masdar Institute, Dartmouth, and MIT. The work is authored by Aramazd Muzhikyan (Masdar Institute), Prof. Amro M. Farid (Dartmouth) and Prof. Kamal Youcef-Toumi (MIT).

As renewable energy becomes an ever present resource in power systems, so called “operating reserves” become increasingly important instruments for reliable power grid operations. One can think of operating reserves as additional generation capacity scheduled to compensate for real-time power supply and demand imbalances due to the existing uncertainties in forecasting not just demand but also renewable energy. On the one hand, the amount of operating reserves should be sufficient to successfully mitigate the real-time imbalances and maintain power system reliable operations. On the other hand, operating reserves are a costly commodity and they should not exceed the minimum required amount to avoid unnecessary expense. This makes accurate assessment of the operating reserve requirements vital for reliable, economic, and environmentally friendly operation of the power grid.

Currently, the necessary amount of the operating reserves is assessed based upon the power system operator experiences and the assumption that the circumstances of power system operations remain relatively unchanged. However, growing integration of renewable energy sources (RES), implementation of demand side management and transportation electrification alter the overall structure and the dynamics of the power grid. High penetration of RES brings new levels of variability and uncertainty to the grid which challenges the established practices of power system operations and the operating reserve requirement assessment methods. This newly published article provides closed-form analytical formulae that tells grid planners how much reserves to procure as they plan for more renewable energy without sacrificing economics or reliability.

While RES integration can potentially reduce the grid’s CO2 emissions and operating costs, it also brings new challenges that power grid operators need to address in order to maintain reliable operations. Wind power, for example, is known to have high intermittency; that is, the output power of a wind turbine may vary uncontrollably in a wide range. This, combined with comparably low wind forecasting accuracy, requires careful scheduling of traditional power plants and their operating reserves. Integration of solar power, on the other hand, has its own challenges. As shown in the figure below, the net load profile (the power demand minus the solar generation) of a system with integrated solar generation has a distinctive profile. It is often called the “Duck Curve” for its resemblance to the side-profile of a duck. The figure presents the net load profiles of the California Independent System Operator (CAISO) for the day of March 31 for forecasted from 2014 to 2020. The “belly” of the curve corresponds to the day time when the solar generation is at its maximum and is expected to grow with new solar power installations. With an estimated demand of 22,000MW in the year 2020, the solar generation accounts for 10,000MW or 45%; leaving only 12,000MW for the traditional generation. This situation increases the risk of overgeneration and solar generation curtailment. Another challenge is the steep jump of the net load around 6pm as solar generation wanes with the sunset and demand picks up for evening home life. Such severe variations of the net load require more careful consideration of the ramping capabilities of the scheduled generation.

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The CAISO duck chart (source: P. Denholm, M. O’Connell, G. Brinkman, and J. Jorgenson, “Overgeneration from Solar Energy in California: A Field Guide to the Duck Chart,” National Renewable Energy Laboratory, Nov. 2015)

This publication has developed analytical formulae for calculation of the requirements for each type of operating reserves; namely, load following, ramping and regulation. The derivations show that the operating reserve requirements are effectively defined by a set of dimensionless parameters related to the RES characteristics and the operations of the power grid. Those parameters are the penetration level, renewable energy capacity factor, variability, day-ahead and short-term forecast errors of the integrated RES, and the power grid day-ahead scheduling and real-time balancing time steps. Such analytical expressions reveal how the requirements of each type of reserve will change when, for instance, more renewable energy is integrated, renewable energy forecasting accuracy is improved, and the day-ahead scheduling time step is reduced. This study show that higher RES variability significantly increases the requirements of all three types of reserves. Also, while the impact of the RES forecast error on the ramping reserve requirement is negligible, its impact on the load following and regulation reserve requirements can dominate that of the variability. On the other hand, reducing the day-ahead scheduling time step can mitigate the impact of the variability on the load following reserve requirement while having negligible impact on the ramping and regulation reserve requirements. Also, changing the balancing time step has no noticeable impact on the load following reserve requirement, it has opposing impacts on the ramping and regulation reserve requirements. Reducing the balancing time step reduces the regulation reserve requirement but increases the ramping reserve requirement.

These formulae can be used for renewable energy integration studies, such as those conducted in NE-ISO and PJM-ISO, to assess the required amount of reserves for the planned RES installation. They can also be adapted by the state and federal standards organizations to establish reserve procurement standards that reflect the evolution of the power grid.

In depth materials on LIINES smart power grid research can be found on the LIINES website.

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Prof. Amro M. Farid presents at Transactive Energy Systems Conference

On Tuesday May 17, 2016, Prof. Amro M. Farid presented at the Third International Conference and Workshop on Transactive Energy Systems in Portland, Oregon.   The presentation entitled:  “Microgrids as a Key Enabling Transactive Energy Technology for Resilient Self-Healing Power Grid Operation” featured some of the LIINES’ recent research on resilience in power systems.

Building upon the recent IEEE Vision for Smart Grid Controls, the presentation advocated the concept of resilience self-healing operation in future power grids.  This continues to be an important area of LIINES research and has been the subject of several recent blogposts.  (See here, here and here).  The concept of resilient power systems effectively means that healthy regions of the grid can continue to operate while disrupted and perturbed regions bring themselves back to normal operation.   A key technology enabling this resilience is microgrids because they are often able to island themselves from the rest of the grid and continue to operate successfully.   In this presentation, the microgrids were controlled with a transactive energy control architecture that couples several control layers to achieve both technical reliability as well as cost effectiveness.  Furthermore, the presentation showed the ability for several microgrids to self-coordinate so as to demonstrate “strength-in-numbers” when adverse power grid conditions like net load ramps and variability arise.   The presentation concluded with the need for significant new research where transactive energy control concepts are intertwined with recent work on power grid enterprise control.

 

In depth materials on LIINES smart power grid research can be found on the LIINES website.

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The LIINES Commitment to Open-Information

 Good science is reproducible.   This means that it must be publicly available, its contributions transparently communicated, and its data accessible.  These are principles that drive the everyday work of every individual’s research at the LIINES.  We now wish to go further and make a commitment to Open-Information.
Beginning today, the LIINES will seek to leverage its website to make all of its research 100% reproducible by the public at large.   This includes:
  • Sharing all input datasets used to conduct the research for which no prior proprietary or security commitments have been made.
  • Producing scientific publications in such a way that scientific peers can accurately verify & validate the work.
  • Making the content of all conference, journal and book-chapter publications freely available in author preprint form.  (Note: Most publishers allow self-archiving and open-distribution of author preprints).
We believe that the LIINES’ research has broad applicability to academia, industry, government and the public at large.   However, traditional publication venues are often only subscribed by academic universities and a handful of well-funded industrial companies.   All-too-often the people that can benefit from this work, never get a chance to see it.   This slows down the work’s potential impact and is counter to the LIINES mission.   It is for these reasons, that the LIINES makes its Open-Information commitment.
While it is natural that making all of this information available will take some time, we will be sure to keep blogging to keep you up to date of new additions to the LIINES website.  For now, feel free to visit the LIINES Datasets Repository which includes both data from our publications as well as a collation of several relevant and openly available datasets.
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ESM 616: Techno-Economic Analyses in Power System Operations

To start off the new semester, we have just developed a page for the ESM 616 Techno-Economic Analyses in Power System Operations class.  The subject seeks to prepare students for the new world of “smart grid” operations.  It specifically seeks to contrast conventional paradigms of power system operations and control with those that will appear in the coming decades.   Emphasis is placed on interdisciplinary, holistic approaches founded upon industrial application and mathematical rigor.  See the LIINES Blog Keywords:  ADWEA — Abu Dhabi Water & Electricity Authority, CIGRE, Control Systems Engineering, DEWA — Dubai Water & Electricity Authority, Dynamic Systems Modeling, Enterprise Control, Graph Theory, IEEE, IEEE CSS, Large Complex Systems, Model-Based Systems Engineering, Operations Research, Power System Economics

Good luck to all as we kick off the Spring Semester.

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ESM 501 Systems Architecture

To start off the new semester, we have just developed a page for the ESM 501 System Architecture class.  The subject addresses one of the first stages of system design, analysis and engineering.  Emphasis is placed on engineering systems which include technical, economic and social aspects.  This blog does often discuss subjects related to systems architecture.  See the LIINES Blog Keywords:  Axiomatic Design, Axiomatic Design for Large Flexible Systems, Design Methodologies, Enterprise Control, Graph Theory, Life Cycle Properties, Model-Based Systems Engineering, Socio-Techno-Economic Systems, and SysML.

Additionally, a new page has been added to overview our other taught courses.

Good luck to all as we kick off the Fall Semester.

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Mendeley @ the LIINES

Reference management is a key competence in any research group or laboratory.   Think of a research workflow.

  1. Get papers
  2. Get paper reference information
  3. Read them from anywhere in the world.  Take notes.
  4. Share them with colleagues
  5. Do the research – referring to papers as required.
  6. Cite the papers easily in any document preparation system.
  7. Build the reference list easily and accurately.
  8. Be ready to change the reference list in subsequent revisions.
Reference management supports all steps of the research flow and can save dozens of hours for any given paper.  This compounds with the numbers of papers that are produced every year and the number of researchers and collaborators with whom you work.  Despite the associated controversies  journal editors and academic departments will continue to increasingly use bibliometric analysis in key decisions.  Therefore, systematic approaches to reference management is even more necessary.
At the LIINES, we use Mendeley in 2011 after a migration from EndNote.  While EndNote had been the default reference management software for many years, it did have several key disadvantages which others have also noted.
  1. Cost:  Endnote required a license for every LIINES researcher at a relatively hefty price tag.  Sharing with collaborators was an every harder proposition.  Furthermore, yearly upgrade licenses was an even tougher pill to swallow.
  2. PDF Organization:  Managing the filesystem associated with PDF files of all the references is a big challenge.  EndNote did not provide a headache-free solution to this.  Even worse, an EndNote database could lose links to PDF files making it quite difficult to find again.
  3. Collaboration & Sharing:  The above challenges were compounded when it came to share Endnote Libraries across the LIINES.  Endnote sharing through Dropbox across multiple operating systems can get quite hairy!
  4. Proprietary Platform & Database:  When reference databases get large, one increasingly becomes interested in automating tasks for its management.   While EndNote does provide plenty of built in automated functionality, the power user ultimately does need to manage records automatically.
Of course, when migrating from one reference management system to another, it is important to make an educated well-researched decision.  The folks at PhdOnTrack.net have provided an excellent introduction.  The University of Rhode Island library has made a comparison of leading options, while Wikipedia provide a comprehensive comparison
Ultimately, Mendeley did come out on top @ the LIINES for a number of reasons.
  1. Cost:  The Mendeley desktop application is free!  This meant that every LIINES researcher could work individually without paying a penny.  That said, the associated cost was in the cloud-based monthly data storage plan.   While this was a recurring cost, Mendeley’s “Solar System”, “Milky Way”, and “Big Bang” subscription plans were very much priced reasonably.   Since Elsevier’s purchase of Mendeley, the cost of new plans has risen; perhaps out of reach for many.  Fortunately, with a little computer savvy one could also use other cloud-based storage services like Dropbox or Google Drive to easily store and share reference libraries.  Alternatively, many institutions including MIT have recognized the need to provide a uniform platform for their researchers and so have purchased Mendeley Institutional Edition.
  2. PDF Organization:  Probably one of Mendeley’s strongest features is its ability to automatically name and organize PDF files based upon key reference information such as Author Name, Year, and Title.  This became a headache free solution.
  3. Collaboration & Sharing:  Another real strength of Mendeley’s is its recognition of Web 2.0 and social media.   Mendeley databases are easily shared and synchronized between multiple computers, operating systems, tablets, smart phones, and users in a seamless way.   For the LIINES, this meant native support for Windows, Mac OS X, Linux, iOS, and Android for dozens of researchers across the world.
  4. Standard Database:  Finally, Mendeley’s database is written in SQL.  This meant that for the advanced database programmer, Mendeley offers the potential to develop automated scripts to manage reference data.  This particular strength overcomes some of the feature limitations within the Mendeley desktop application itself.
And yet, the migration to Mendeley was not without its disadvantages.
  1. Integration with LatTeX/BibTex:  Mendeley is able to create and maintain an automatically synced BibTeX database file.  However, it provides no user control to the highly important Citation Key!  In the course of regular use, Mendeley can change these citation keys which will then cause LaTeX citation links to break in your document.  Make sure to keep backups of your BibTeX database unless you want to redo all the links!
  2. PDF File Import:  The jury is still out on this one. Mendeley can directly import PDF files.  It will scan the PDF for reference information and insert it into the database.  For many files of standard format (e.g. IEEE, Elsevier journals), it does this accurately.  However, for many others, it creates lots of errors; forcing the researcher to manually correct the information.  At the LIINES, we recommend going to established online reference databases (IEEE XploreScienceDirectCompendex & Google Scholar  to download the associated .ris or .bib files instead.
  3. Batched PDF Import:  Many researchers new to reference management have troves of organized pdf files.  Others are migrating to Mendeley.  Beware that a batch PDF import can create lots of duplicates in the Mendeley database!
  4. Duplicates Management:  Mendeley desktop does provide a “Check for Duplicates” feature but in then requires manual deletion of these duplicates.  For large databases, this can be very time consuming.
  5. Association with Elsevier:  Finally, some academics have chosen to boycott Elsevier’s service on ethical grounds.  Others distinguish Mendeley from its parent company, and then there is official Mendeley perspective from William Gunn   While the LIINES does not participate in this boycott, we recognize its existence out of academic respect and encourage awareness amongst our readership.  Ultimately, one must recognize that Mendeley is now a fully commercial product and service.  For those that maintain reservations, many highly functional, free and open-source reference management solutions continue to exist.
We hope to return to some of these weakness in coming blog posts.
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IEEE Statement on Appropriate use of Bibliometric Indicators

The use of bibliometric analysis has become an increasing part of scientific publishing today.   While bibliometric analysis has brought about a degree of quantified objectivity, many have raised concerns about the potential pitfalls of their usage.   We refer our LIINES readership to the recent IEEE Statement on the Appropriate use of Bibliometric Indicators.   The associated video can be found below.

 

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