Publications (20)14.88 Total impact

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    ABSTRACT: As more phasor measurement units (PMUs) are installed, portions of the power grid become observable with just phasor measurements, making feasible the estimation of the state of these observable portions at much faster rates than the traditional state estimator. Although such a linear state estimator (LSE) was proposed over a decade ago, the first field implementation was completed at Dominion Virginia Power in 2013. Although this LSE is a stand-alone function not integrated to their energy management system (EMS), it demonstrated the feasibility of the LSE. In this paper, we present the design, development, and implementation of an LSE that is fully integrated with the existing EMS and can estimate the state of the extra high voltage portion of a power system at 30 times per second. Integration of the LSE to the existing EMS environment and some of the issues in the design and testing are presented in this paper. The work paved way for LSE to supply cleansed PMU data to other synchrophasor applications that are sensitive to data quality.
    No preview · Article · Jan 2016 · IEEE Transactions on Smart Grid
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    ABSTRACT: Power grids have become more complex to plan and operate. With grid changes arise new challenges: renewable generation, energy conservation, electric vehicles, energy storage, and load growth. Challenges facing the electric industry today include balancing capacity, reliability, economics, environmental, and other public objectives. Recent cascading outages have demonstrated the challenges faced when operating a system near its limits. These outages over the last few years have had large social and economic impacts. In 2012, an outage in India affected over 620 million people. In 2009, a blackout in Brazil and Paraguay impacted 87 million. In 2011, a power blackout affecting 3 million people in Southern California and Mexico lasted 12 hours and was estimated to have cost over US$100 million in lost revenue. It is a balancing act to meet today's electricity consumer expectations in a changing landscape.
    No preview · Article · Sep 2015 · IEEE Power and Energy Magazine
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    ABSTRACT: Inherited from legacy technologies, electric distribution systems are aging infrastructures whose component failures have a significant role in customer electricity interruptions. Low visibility and controllability of the distribution grid are a common practice today across the globe. In this circumstance, elements of the distribution grid including overhead distribution lines, underground cables, breakers, sectionalizers, etc. are being operated with very limited real-time data acquisition and virtually no remote control capability. The majority of failures are not detected by system operators unless interrupted customers notify them by phone. Very often (and particularly in municipal areas with underground networks), a distribution system is scattered across a large (and cumbersome) geographical region. Therefore, fault location and service restoration by nature is a difficult and prolonged process. Most of the associated tasks such as restoration are manually implemented, which necessitates dispatching field crew to the affected regions. The lack of controllability of the distribution system, specifically, related to balancing loads with available generation, impedes islanded operation of distribution system at the event of main grid failure. For example, while transmission systems have generator inertia and governor controls which stabilize frequency during emergencies, distribution systems do not have such automated actions. As a result, during emergencies, various distributed energy resources (DERs) that might be available are most likely switched off instead of serving some portions of the affected customers.
    Full-text · Article · Jul 2015 · IEEE Transactions on Smart Grid
  • Jay Giri
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    ABSTRACT: The energy management system (EMS) at utility control centers collects real-time measurements to monitor current grid conditions. The EMS is also a suite of analytics that synthesizes these measurements to provide the grid operator with information to identify current problems and potential future problems. With evolving grid influences, such as growth of variable renewable generation resources, distributed generation, microgrids, demand response (DR), and customer engagement programs, managing the grid is becoming more challenging. Concurrently, however, there are nascent new technologies and advances in grid management schemes that will improve the ability to manage the future grid operations. These technologies include new subsecond synchrophasor measurements and analytics, advances in highperformance computing, visualization platforms, digital relays, cloud computing, and so on. Advances in grid management schemes include adding more intelligence at the substation and distribution systems, as well as microgrids and wide-area monitoring systems. One key initiative is to develop a predict-and-mitigate paradigm enabling anticipatory vision and timely decisions to mitigate potential problems before they spread to the rest of the grid. The word “proactive”means “to act now in anticipation of future problems.”Proactive grid management opportunities and solutions are described in this paper.
    No preview · Article · Jun 2015
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    ABSTRACT: The 10th anniversary of the 2003 North-East blackout reminds us the challenges faced and solutions proposed. Several converging technologies are reaching control center operations. Synchronized phasor measurements enable readings of voltages and currents across the power system and provide a more accurate state estimation than the existing Energy Management System (EMS). A synchrophasor system covering a large footprint coupled with fast sampling rates may be best served by a distributed architecture to process data for new advanced algorithms and for historical analysis. The architecture is divided into three levels for data management, functional analysis, and interface to an existing EMS. The present architecture is summarized as local substation data concentrators (PDCs) and control center PDCs that are connected to the existing EMS. Implementation experiences with the execution of state estimation at substation level, communication level, as well as the EMS level by PG&E are presented to demonstrate EMS evolution as part of technological developments.
    No preview · Conference Paper · Apr 2014
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    ABSTRACT: It is important for power grids to become flexible to accommodate diverse technologies such as intermittent renewables and power electronic conversion sources, while conventional generation resources are becoming more volatile with market forces and political directions. Environmentally, building new transmission is challenging. With smart grid technologies, there is a great deal of potential to control the power system using many widely distributed resources, but there is a considerable challenge in making use of the control capabilities in a novel way. This nascent volatility versus reliability demand makes operational decision-making and execution more challenging than in any other time in history. This chapter will explore modern techniques to improve grid reliability by enhancing and extending control center capabilities and substation capabilities. The use of automatic, wide-area protection schemes to mitigate cascading blackouts will be examined. Also explored will be the use of: wide-area control strategies, new and emerging technologies and communications, software and hardware architectures, and state-of-the art Energy Management System (EMS) technologies as the keys to more reliable operations. Additional focus will be placed on the positive impacts of synchronized phasor measurements.
    No preview · Chapter · Jan 2014
  • A.K. Jampala · J. Giri · V. Madani · M. Glavic · R. King
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    ABSTRACT: With the exploding growth of synchrophasor PMU data in utility control centers, there is an increased emphasis on successful integration of existing model-based Energy Management Systems (EMS) applications with the new complementary PMU measurement-based applications. This is necessary to gain confidence of the newly integrated data, while embracing these new measurement-based tools and techniques. These new generation of synchrophasor applications have moved beyond prototype to the Proof of Concept (PoC) stage. Once validated and accepted by end users, field installation and training, the tools will become part of the day-to-day, production EMS. The synchrophasor applications include Linear State Estimator (LSE), Oscillation Detection, Voltage Stability indicators, etc. Enhanced tools to validate results and advanced simulation tools for training are other areas for development. The integration tasks pose many challenges and are addressed in this paper.
    No preview · Conference Paper · Jan 2013
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    ABSTRACT: The modern power grid is one of the most complex engineering machines in existence. Its millions of components comprise the entire electricity supply chain, from point of generation to the end consumer. Each of these pieces must work together, reliably, 24 hours a day, seven days a week, to power our homes and businesses. In 2001, the U.S. National Academy of Engineering voted to recognize the grid as the supreme engineering achievement of the 20th century. Making matters more complex is the reality that grid conditions are continually changing every second, every minute, and every hour of the day. Changes in demand for electricity necessitate instantaneous changes in electricity production; consequently, voltages, currents, and power flows are dynamically changing at all times across the electricity supply chain.
    No preview · Article · Sep 2012 · IEEE Power and Energy Magazine
  • J. Giri
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    ABSTRACT: The recent growth in the synchrophasor measurement and communications technology has been an unprecedented change from an Energy Management System (EMS) control center perspective. For decades, traditional EMS capabilities have been based on 2-4 second SCADA measurements. As the number of milli-second rate, time-tagged synchrophasor Phasor Measurement Units (PMUs) grow in number, control centers now have the ability to monitor in greater in-depth the dynamic behavior of the grid; this leads to more advanced analysis capabilities to help monitor and control the grid to ensure enhanced grid reliability and security.
    No preview · Conference Paper · Jul 2012
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    ABSTRACT: Recent investments in the Synchrophasor technology have energized the industry and a significant number of Phasor Measurement Units (PMUs) are being deployed. By some estimates, just in North America, the number of PMU installations is expected to grow five-fold-from approximately 200 today to over a 1000. The first step in PMU deployment is a clear roadmap of the process for selecting the location of the additional PMU devices and establishing guidelines to assist with this decision-making process. Many of the existing optimal PMU placement approaches are mainly focused on a particular application (such as improving State Estimation). This paper proposes a more comprehensive, holistic set of criteria for optimizing PMU placement based on sound practical solutions by experienced industry practitioners. The methodology offers the flexibility for considering multiple, diverse factors that can influence the PMU siting decision-making process, including incorporating several practical implementation aspects (e.g. communications infrastructure, prohibitive deployment cost, etc). Application needs, reliability requirements, and infrastructure challenges that drive the overall solution for optimal PMU location selection are formulated and described.
    Full-text · Conference Paper · Apr 2011
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    ABSTRACT: PMU devices are expected to grow in number from a few to several hundreds in the next five years. Some relays are already global positioning system-capable and could provide the same type of data as any PMU. This introduces a new paradigm of very fast accurate synchrophasor measurements from across the grid in real-time that augment and parallel existing slower SCADA measurements. Control center applications will benefit from this PMU data; for example, use of PMU data in state estimation is expected to improve accuracy and robustness, which in turn will result in more timely and accurate N-1 security analysis, resulting in an overall improvement of grid system reliability and security. This paper describes results from a recent implementation of this technology, the benefits and future work.
    No preview · Conference Paper · Aug 2009
  • Jay Giri · David Sun · Rene Avila-Rosales
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    ABSTRACT: The very first large-scale North American blackout happened in 1965, disrupting the supply of electricity to 25 million people in the United States and Ontario, Canada, for 12 hours. The failure was attributed to a maintenance error. In 1978, 80 percent of France was affected by a blackout caused by the breakdown of a transmission line. In 1989, a geomagnetic storm caused an outage that left 6 million people in Quebec, Canada, without power for nine hours. And in August 2003, a wide-area power collapse in the northern United States and central Canada affected 50 million people; a thorough inquiry revealed that the causes were computer failures and power lines that came in contact with "overgrown trees." In a number of other countries, including Australia, Japan, Peru, Greece, Britain, Russia, and Italy, many other large-scale blackouts have happened since that time.
    No preview · Article · May 2009 · IEEE Power and Energy Magazine
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    ABSTRACT: The recent world-wide rash of power systems blackouts has provided an added impetus to wide-scale deployment of phasor measurement units (PMUs). Initial applications of PMUs in the late 1980s and 1990s were isolated due to the limited infrastructure availability and lack of computational support for extensive processing of the networked information. Today, networks of hundreds of PMUs are in place and more are planned.The recognition that networks of PMUs can provide greater power system reliability is based on their ability to give direct access to the state of the power system at any given instant.
    No preview · Article · Oct 2008 · IEEE Power and Energy Magazine
  • R. Avila-Rosales · J. Giri · R. Lopez
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    ABSTRACT: This paper describes the integration of stability assessment tools in the EMS. The main functions are the transient security and voltage security tools. They are invoked under several modes of operation to address the current state of the system as well as the immediate short-term planning horizons. Data exchange, preparation and output visualization are described in the context of distributed architectures and the latest user interface technology. The operators will be able to analyze transactions under various conditions and contingences that could potentially lead to insecure behavior. The dynamic tools are triggered as part of the on-line network and study network sequences. The architecture and system configuration is the key to ensuring fast, robust and accurate dynamic solutions. Several CPUs are used to reduce the execution time for day and week-ahead analysis. The user friendly data exchange setup prevents conflict between several instances of DSA users and models.
    No preview · Conference Paper · Nov 2004
  • J. Giri · R. Avila-Rosales
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    ABSTRACT: Summary form only given as follows. Security assessment has always played an important role in system operation, and has always been one of the most computationally expensive calculations in the control center. The new RTO models require the solution of very large systems of unprecedented size. Simulating systems of these sizes impose additional computational challenges and are affected by model accuracy, solution techniques and system architecture. The concept of "n-1" security is a requirement in the context of the uncertain electricity market environment. So several contingencies and monitored facilities must be included as part of the optimization techniques to guarantee "n-1" security, and to relieve constraints during the congestion management process. Model accuracy and validity becomes a major issue when dealing with very large databases. Since these databases are created by merging databases of various transmission companies, the overall model needs to be checked and validated to a greater degree than in the past. One of the basic functions of the spot/balancing and congestion management markets, is a bid-based security constrained economic dispatch, which considers real-time system balancing and re-dispatch to avoid congestion and maintain flows and constraints under several contingencies and limits. Given an operating condition, a single contingency could determine the limits on the transmission network, and branch power flows may be bound by its impact in the event the contingency takes place. Post-contingency analysis is used to identify the set of binding constraints for the optimization loop, therefore anticipated contingencies can limit the system at all times. Security assessment gets more complicated if the market deals with day-ahead hourly schedules, where participants will buy and sell energy and transmission, settle and reconfigure financial transmission rights via locational marginal prices. In general the electricity market applications are b- ased on a combination of optimization methods and efficient load flow solutions for realtime as well as day-ahead calculations. This will demand considerable computational time, paving the way to distributed and parallel processing. On-line and day-ahead voltage security has been implemented considering the use of more than one processor, but the voltage security constraints have not been implemented yet as part of the security constrained dispatch. Validity of the network models, faster algorithmic solutions, efficient data exchange and client/server distributed architecture are keys to providing security assessment in the electricity market environment.
    No preview · Conference Paper · Aug 2002
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    ABSTRACT: Transient stability assessment, preventive control measures and dynamic ATC calculations are addressed for a new deregulated EMS system. The combination of time domain analysis, SIME and optimal power flow provide a reliable solution for future transaction requirements and the current operating point
    Full-text · Conference Paper · Feb 2000
  • Jay Giri
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    ABSTRACT: The author describes how traditional energy management system (EMS) power system applications are undergoing changes, in order to adapt to the users needs of the deregulated energy markets environment
    No preview · Conference Paper · Feb 2000
  • Jay Giri · Rene Avila Rosales
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    ABSTRACT: Electric utility companies around the world are experiencing new security challenges as they move towards deregulation of power system operation. Independent power producers, distribution companies, competitive economic transactions between buyers and sellers, open access requirements and free energy routing through the transmission system are putting a greater emphasis on online transient stability assessment (TSA). Most companies with stability concerns are willing to consider online implementation of TSA and the determination of remedial and preventive control actions for the operation of their power system. This paper describes the requirements for online TSA integration from an EMS control center user's point of view. DTS and study modes of operation are also presented for planning and current operation analysis. Functional and implementation requirements are described that will enable a successful online deployment of TSA in an EMS. Voltage security assessment (VSA) is included in all figures to complete the EMS and control center picture
    No preview · Conference Paper · Feb 2000
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    ABSTRACT: An integrated scheme is proposed for computing on-line power system available transfer capability (ATC) while meeting static and transient stability constraints. The approach is based on the coupling of an OPF program with a method, called MAT (maximum allowable transfer), which relies on SIME (single machine equivalent) and its variants. The way in which this combined approach proceeds is outlined. Basically, the approach takes care of the stability constraints by (generally) decreasing active power on critical machines, then reallocating power generation on noncritical machines so as to ensure maximum allowable power transfer on the considered tie-lines. Stated otherwise, the combined use of the MAT method with the OPF program succeeds in reaching the multifold objective: to guarantee maximum power transfer on the defined tie-lines, and to meet transient stability constraints vis-a-vis all plausible contingencies, together with static constraints. The whole procedure is robust, in the sense that it converges consistently and readily to the solution. It is also compatible with real-time requirements
    No preview · Conference Paper · Aug 1999
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    Rene Avila-Rosales · Jay Giri
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    ABSTRACT: Probably the most significant development in the future is the evolution of the EMS to a more intelli-gent, automated system to analyze, predict and prevent events leading to a total system collapse. The transition to a highly automated system is possible in part by the recent advances in communication technology, hardware archi-tecture, web services and installation of synchronized phasor measurements to support wide-area system moni-toring, protection and control. This paper addresses some issues and defines a strategy towards the coordination of local and wide-area controls and protections to ensure power system grid security. The strategy relies on the integration of the latest PMU technology and data process-ing to deploy different types of control actions and special protection schemes.
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