In this paper, we first introduce a variational formulation of the Unit Commitment (UC) problem, in which generation and ramping trajectories of the generating units are continuous time signals and the generating units cost depends on the three signals: the binary commitment status of the units as well as their continuous-time generation and ramping trajectories. We assume such bids are piecewise strictly convex time-varying linear functions of these three variables. Based on this problem derive a tractable approximation by constraining the commitment trajectories to switch in a discrete and finite set of points and representing the trajectories in the function space of piece-wise polynomial functions within the intervals, whose discrete coefficients are then the UC problem decision variables. Our judicious choice of the signal space allows us to represent cost and constraints as linear functions of such coefficients, thus, our UC models preserves the MILP formulation of the UC problem. Numerical simulation over real load data from the California ISO demonstrate that the proposed UC model reduces the total dayahead and real-time operation cost, and the number of ramping scarcity events in the real-time operations.

%B 2016 49th Hawaii International Conference on System Sciences (HICSS) %I IEEE %C Koloa, HI, USA %P 2335 - 2344 %8 01/2016 %R 10.1109/HICSS.2016.292 %0 Conference Paper %B 2014 North American Power Symposium (NAPS) %D 2014 %T Generalized injection shift factors and application to estimation of power flow transients %A Chen, Yu Christine %A Alejandro D. Dominguez-Garcia %A Peter W. Sauer %K AARD %K CERTS %X This paper proposes a method to estimate transmission line flows in a power system during the transient period following a loss of generation or increase in load contingency by using linear sensitivity injection shift factors (ISFs). Traditionally, ISFs are computed from an offline power flow model of the system with the slack bus defined. The proposed method, however, relies on generalized ISFs estimated via the solution of a system of linear equations that arise from high-frequency synchronized measurements obtained from phasor measurement units. Even though the generalized ISFs are obtained at the pre-disturbance steady-state operating point, by leveraging inertial and governor power flows during appropriate time-scales, they can be manipulated to predict active transmission line flows during the post-contingency transient period. %B 2014 North American Power Symposium (NAPS) %I IEEE %C Pullman, WA, USA %P 1 - 5 %8 09/2014 %R 10.1109/NAPS.2014.6965399 %0 Journal Article %J IEEE Transactions on Industry Applications %D 2014 %T Graphical and Analytical Methods for Stalling Analysis of Engine Generator Sets %A Ajit A. Renjit %A Mahesh S. Illindala %A David A. Klapp %K MG-TB003 %XReciprocating engine driven generator sets (or “gensets”) are a leading class of distributed energy resources (DERs) from the low kilowatt up to hundreds of kilowatt ratings. Natural-gas-based DERs are more likely to be favored by both industries and utilities in the near future because of their low cost due to the newly found shale deposits at many places in the world. The DERs such as gensets when operating under islanded conditions are susceptible to stalling and can bring down the entire industrial power system, particularly if they are loaded beyond 80% of the rated engine capacity. This paper presents graphical and analytical methods to determine the stalling conditions of the most common type of gensets that have a synchronous generator as the utility interface. A systematic approach is developed from the first principles of generator electromagnetic energy conversion. The engine fuel map limits have been integrated into the generator speed versus active power characteristics for this purpose. The stalling prevention by applying an underfrequency load relief (V/Hz) scheme is also discussed.

%B IEEE Transactions on Industry Applications %V 50 %P 2967 - 2975 %8 9/2014 %N 5 %! IEEE Trans. on Ind. Applicat. %R 10.1109/TIA.2014.2305803 %0 Conference Paper %B 2013 51st Annual Allerton Conference on Communication, Control, and Computing (Allerton) %D 2013 %T A generalized battery model of a collection of Thermostatically Controlled Loads for providing ancillary service %A He Hao %A Sanandaji, Borhan M. %A Kameshwar Poolla %A Vincent, Tyrone L. %K ancillary services %K load regulation %K reliability and markets %K RM11-006 %XThe thermal storage potential of Thermostatically Controlled Loads (TCLs) is a tremendous flexible resource for providing various ancillary services to the grid. In this work, we study aggregate modeling, characterization, and control of TCLs for frequency regulation service provision. We propose a generalized battery model for aggregating flexibility of a collection of TCLs. A theoretical characterization of the aggregate power limits and energy capacity of TCLs is provided. Moreover, we propose a priority-stack-based control strategy to manipulate the power consumption of TCLs for frequency regulation, while preventing short cycling on the units. Numerical experiments are provided to show the accuracy of the proposed model and the efficacy of the developed control method.

%B 2013 51st Annual Allerton Conference on Communication, Control, and Computing (Allerton) %I IEEE %C Monticello, IL %P 551 - 558 %8 10/2013 %R 10.1109/Allerton.2013.6736573 %0 Journal Article %J Electric Power Components and Systems %D 2013 %T A Generalized Subspace Least Mean Square Method for High-resolution Accurate Estimation of Power System Oscillation Modes %A Peng Zhang %A Ning Zhou %A Ali Abdollahi %K AA09-002 %K AARD %K Automatic Switchable Network (ASN) %K oscillations %XA generalized subspace least mean square method is presented for accurate and robust estimation of oscillation modes from exponentially damped power system signals. The method is based on the orthogonality of signal and noise eigenvectors of the signal autocorrelation matrix. Performance of the proposed method is evaluated using Monte Carlo simulation and compared with the Prony method. Test results show that the generalized subspace least mean square method is highly resilient to noise and significantly dominates the Prony method in tracking power system modes under noisy environments.

%B Electric Power Components and Systems %V 41 %P 1205 - 1212 %8 09/2013 %N 12 %! Electric Power Components and Systems %R 10.1080/15325008.2013.807896 %0 Conference Paper %B 2012 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES) %D 2012 %T Graphical and analytical methods for stalling of engine generator set %A Ajit A. Renjit %A Mahesh S. Illindala %K CERTS %K distributed energy resources (der) %K MG-TB002 %K microgrid test bed %K microgrids %XNatural gas based distributed energy resources (DERs) are likely to be favored by electric utilities in the near future because of the newly found shale deposit resources. Reciprocating engine based generator sets are a leading class of energy conversion equipment from the low kW upto 100s of kW ratings. Standalone engine generator sets with isochronous governors are susceptible to stalling when they are loaded beyond 80% of the rated engine capacity. This paper presents graphical and analytical methods to determine the stalling conditions of an engine generator set. Analytical methods are developed from the first principles of electromagnetic energy conversion to establish the conditions for the synchronous generator to reach equilibrium in steady state. Active power-speed characteristics including the engine fuel map is employed together with the electrical load torque characteristics. Stalling prevention by applying an underfrequency load relief (V/Hz) scheme is also discussed.

%B 2012 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES) %I IEEE %C Bengaluru, Karnataka, India %P 1 - 6 %8 12/2012 %@ 978-1-4673-4506-4 %R 10.1109/PEDES.2012.6484436 %0 Conference Paper %B 45th International Universities Power Engineering Conference (UPEC) %D 2010 %T Geographical averaging and ancillary services for stochastic power generation %A Timothy D. Mount %A Robert J. Thomas %A Alberto J Lamadrid %K ancillary services %K reliability %K reliability and markets %K RM12-004 %K SuperOPF %K wind power %X The distribution of stochastic generation from renewables across different geographical locations can, in certain cases, help to mitigate the inherent variability in output. This variability of generation from renewables may (1) increase the operating costs of the conventional generators used to follow the net load not supplied by stochastic capacity and (2) increase the amount of reserve conventional generating capacity needed to maintain Operating Reliability. In this scenario, customers have lower wholesale prices, due to reductions in the total annual generation from fossil fuels, while generators face higher operating costs for conventional generators caused by additional ramping that partly offset the customer benefits. However, the lower wholesale prices ($/MWh) imply lower annual earnings for conventional generators that lead to higher amounts of missing money ($/MW) needed to maintain the financial adequacy of installed generating units. The objective of this paper is to determine how variability from a stochastic generation resource affects the optimal hour-to-hour dispatch of generating units and the corresponding operating costs and wholesale prices. The results show that the inclusion of ramping costs for conventional generation affect the amount of energy dispatched from the stochastic generator, and the total costs composition observed in the system. The Cornell SuperOPF is used to illustrate how the operating costs and wholesale prices can be determined for a reliable network (the amount of conventional generating capacity needed to maintain Operating Reliability is determined endogenously). The results in this paper use a typical daily pattern of load and capture the cost of ramping by including additions to the operating costs of the generating units associated with the hour-to-hour changes in their optimal dispatch. The calculations for determining endogenous up and down reserves are included, and the wind generation cost is assumed to be zero. Ad- - ditionally, the maximum and minimum available capacities for all hours in the day are constrained to the optimal capacities for the hours with the highest and the lowest loads. Different scenarios are evaluated for a given hourly realization of wind speeds using specified amounts of installed wind capacity with and without ramping costs. The analysis also evaluates the effects of eliminating network constraints, as well as the elimination of wind variability by accounting for the effects of spatial aggregation of different wind locations. %B 45th International Universities Power Engineering Conference (UPEC) %I IEEE %8 09/2010 %U http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5649447&tag=1 %0 Journal Article %J IEEE Transactions on Power Delivery %D 2009 %T GridStat: A Flexible QoS-Managed Data Dissemination Framework for the Power Grid %A Gjermundrod, H. %A Gjermundrod, H. %A David E. Bakken %A Hauser, C.H. %A Anjan Bose %K AA05-002 %K AARD %K Automatic Switchable Network (ASN) %K PSERC %X With the increase in the monitoring of operational data at very high rates in high voltage substations and the ability to time synchronize these data with global positioning systems, there is a growing need for transmitting this data for monitoring, operation, protection, and control needs. The sets of data that need to be transferred and the speed at which they need to be transferred depend on the application-for example, slow for postevent analysis, near real time for monitoring and as close to real time as possible for control or protection. In this paper, we describe GridStat, a novel middleware framework we have developed to provide flexible, robust, and secure data communications for the power grid's operations. Test results demonstrate that such a flexible framework can also guarantee latency that is suitable for fast wide-area protection and control. %B IEEE Transactions on Power Delivery %V 24 %P 136 - 143 %8 01/2009 %N 1 %! IEEE Trans. Power Delivery %R 10.1109/TPWRD.2008.917693 %0 Conference Paper %B IEEE Power Engineering Society Winter Meeting %D 2001 %T Grid Reliability Management Tools %A Joseph H. Eto %A Carlos A. Martinez %A Jim Dyer %A Vikram S. Budhraja %K Reliability Adequacy Tools %K reliability management %K RTGRM %K transmission system reliability publications %XThe U.S. electric power system is in the midst of a fundamental transition from being centrally planned and controlled to being dependent on competitive market forces for its expansion and operation. Unique features of electric power, including the need to match supply and demand in real time, the interconnectedness of the networks over which power flows, and the immediate propagation of disturbances throughout the system have always posed unique challenges for reliability. Today, these challenges are even greater and there is no prior experience to draw upon for guidance in relying on markets to manage the complexities of the electric power system. At the same time, the Nation s demands for electricity and reliable electric service are increasing. As the events of recent years demonstrate, the reliability of the grid and the integrity of the markets it supports are integral to the Nation's well-being.

%B IEEE Power Engineering Society Winter Meeting %C Columbus, Ohio %P 5 %8 01/2001 %2 LBNL-47025 %R 10.1109/PESW.2001.917068 %0 Report %D 1999 %T Grid of the Future White Papers Project Executive Summary %A Joseph H. Eto %K Grid of the Future %K transmission planning %K transmission reliability %K transmission system reliability publications %XIn 1999, the Department of Energy (DOE) tasked the Consortium for Electric Reliability Technology Solutions (CERTS) to prepare a series of white papers on federal RD&D needs to maintain or enhance the reliability of the U.S. electric power system under the emerging competitive electricity market structure.1 In so doing, the white papers build upon earlier DOE sponsored technical reviews that had been prepared prior to the Federal Energy Regulatory Commission (FERC) orders 888 and 889.

The six white papers represent the final step prior to the preparation of a multi-year research plan for DOE's Transmission Reliability program. The preparation of the white papers has benefited from substantial electricity industry review and input, culminating with a DOE/CERTS workshop in the fall of 1999 where drafts of the white papers were presented by the CERTS authors, and discussed with industry stakeholders. Taken together, the white papers are intended to lay a broad foundation for an inclusive program of federal RD&D that extends – appropriately so -- beyond the scope of the Transmission Reliability program.

With these completed white papers, DOE working in close conjunction with industry stakeholders will begin preparation a multi-year research plan for the Transmission Reliability program that is both supportive of and consistent with the needs of this critical industry in transition.

%I LBNL %C Berkelely %8 12/1999 %2 LBNL-45273