This paper describes an air-conditioner (A/C) compressor single phase induction motor (SPIM) model for use in an electro-magnetic transients (EMTs) simulation. The system of differential equations representing the SPIM model is developed and formulated. The angular position of the rotor shaft is retained in the electrical and mechanical equations of the model so that position dependence of the driven-load torque can be explicitly recognized. The equivalent circuit of the proposed model is represented as an interface to the external electric network in the EMTs simulator. Motor dynamic response to voltage dip at different points on the voltage waveform has been studied. The rationale of motor stalling is explored. Multiple aggregate units of the proposed model have been implemented on a distribution feeder to test and verify the motor dynamics in an EMTs simulation.

%B IEEE Transactions on Power Systems %I IEEE %V 28 %P 4528-4536 %8 11/2013 %N 4 %& 4528 %R 10.1109/TPWRS.2013.2275256 %0 Journal Article %J IEEE Power and Energy Magazine %D 2012 %T The Big Picture: Smart Research for Large-Scale Integrated Smart Grid Solutions %A Mladen Kezunovic %A Vijay Vittal %A Meliopoulos, S. %A Timothy D. Mount %K AA05-003 %K power system economics %K power system security %K reliability and markets %K smart grid %X This article represents an edited version of opinions expressed in an extensive white paper created by many individuals associated with the Power Systems Engineering Research Center (PSERC) of the National Science Foundation (NSF) and posted on PSERC's Web site, www.pserc. org. The four tasks described above are considered crucial to smart grid R&D, demonstration, and eventual deployment. As learning and innovation occur during the course of a demonstration, changes may be needed in the architecture, the components, and the way they are integrated operationally. The goal is to acquire the best information possible for the eventual decisions on whether and how an integrated smart grid solution should be implemented, so adjusting demonstrations as needed to provide that information is very appropriate. It is also important that demonstrations be designed and implemented to gain the knowledge needed for a system wide deployment of a smart grid. The bulk transmission system should be included in the design. There are a great number of unknowns in moving toward the national goal of a low-carbon economy. That uncertainty can be reduced by effectively designed large-scale demonstrations drawing on the results of prior R&D efforts. %B IEEE Power and Energy Magazine %V 10 %P 22 - 34 %8 07/2012 %N 4 %! IEEE Power and Energy Mag. %R 10.1109/MPE.2012.2196335 %0 Journal Article %J IEEE Transactions on Power Systems %D 2011 %T Controlled Islanding Demonstrations on the WECC System %A Xu, Guangyue %A Vijay Vittal %A Meklin, Anatoliy %A Thalman, Jon Eric %K AA05-001 %K AARD %K CERTS %K dynamic simulations %X Cascading outages have resulted in significant disruptions to power systems all over the world. Controlled islanding can provide a corrective measure of last resort to alleviate the impact of large disturbances. This paper provides detailed demonstrations of using controlled islanding to prevent cascading outages in bulk power systems. To test the islanding performance, four extreme contingencies under two different operating conditions of the WECC system are tested using time domain simulations. The cutsets used in the controlled islanding cases are obtained from a software package developed in earlier work by the authors. Time domain simulation results for the four contingencies with controlled islanding and uncontrolled islanding are shown, and the dynamic performance in each case is analyzed. Further analyses are conducted to examine the amount of load shed in each case, and a discussion of the cutset sensitivity and time sensitivity of islanding is provided. Finally, the discussion of practical implementation issues and conclusions is provided. %B IEEE Transactions on Power Systems %V 26 %P 334 - 343 %8 02/2011 %N 1 %! IEEE Trans. Power Syst. %R 10.1109/TPWRS.2010.2047413 %0 Journal Article %J IEEE Transactions on Power Systems %D 2010 %T Slow Coherency Based Cutset Determination Algorithm for Large Power Systems %A Xu, Guangyue %A Vijay Vittal %K AA05-001 %K AARD %K cascading outages %K controlled islanding %K distributed generation %X This paper provides an integrated algorithm to identify a cutset for a large power system for the application of a slow coherency based controlled islanding scheme. Controlled islanding is employed as a corrective measure of last resort to prevent cascading outages caused by large disturbances. The large scale power system is represented as a graph and a simplification algorithm is used to reduce the complexity of the system. Generators belonging to the same slowly coherent group are collapsed into a dummy node, and a graph partition library is used to split the graph into a given number of parts. Some extra islands formed by the partition library are merged into their adjacent large islands and the original cutset of the actual power system is recovered from the highly simplified graph. A software package was developed to test the efficiency of the algorithm, and dynamic simulations were run on the WECC system to verify the effectiveness of the cutset obtained. The WECC system has more than 15 000 buses and 2300 generators. Detailed steps to develop an islanding strategy for a specified contingency for a large system are described in this paper. %B IEEE Transactions on Power Systems %V 25 %P 877 - 884 %8 05/2010 %N 2 %! IEEE Trans. Power Syst. %R 10.1109/TPWRS.2009.2032421 %0 Conference Paper %B 2009 IEEE/PES Power Systems Conference and Exposition (PSCE) %D 2009 %T Decision tree assisted controlled islanding for preventing cascading events %A Ruisheng Diao %A Vijay Vittal %A Sun, Kai %A Kolluri, Sharma %A Mandal, S. %A Galvan, F. %K AA05-001 %K AARD %K Automatic Switchable Network (ASN) %K distributed generation %K phasor measurement units (PMUs) %XAt stressed operating conditions, critical contingencies can initiate loss of synchronism and trigger cascading events. Controlled islanding is the last line of defense to stabilize the whole system. This paper presents a decision tree assisted scheme to determine the timing of controlled islanding in real time by using phasor measurements. In addition, a slow coherency based approach is used to determine where to island. This scheme is tested on the operational model of the Entergy system and a severe N-2 outage case is used to demonstrate the phenomenon of cascading events due to protective relay actions. The results show that training one decision tree only for a specified critical contingency that can potentially cause cascading events can yields high prediction accuracy. Being aware of loss of synchronism in real time, operators can implement controlled islanding at carefully designed transmission interfaces and rapidly stabilize each island. Thus a significant amount of load is still served compared to uncontrolled system islanding.

%B 2009 IEEE/PES Power Systems Conference and Exposition (PSCE) %I IEEE %C Seattle, WA, USA %P 1 - 8 %8 03/2009 %@ 978-1-4244-3810-5 %R 10.1109/PSCE.2009.4839985 %0 Conference Paper %B 2009 IEEE/PES Power Systems Conference and Exposition (PSCE) %D 2009 %T The problem of initiating controlled islanding of a large interconnected power system solved as a Pareto optimization %A Vijay Vittal %A Gerald T. Heydt %K AA05-001 %K AARD %K Automatic Switchable Network (ASN) %K controlled islanding %K electricity markets %K Power system dynamics %K power system economics %XControlled islanding of a large electric power system is proposed under rare circumstances as a measure of last resort to avoid a catastrophic blackout. Controlled islanding appears to be more desirable than uncontrolled islanding. A separate power system operating objective is the retention of synchronous operation of the entire system to ensure the viability of power markets. The problem of when to initiate controlled islanding, accounting for power marketing objectives is formulated as a multiobjective optimization. Pareto optimization is applied in the form of the calculation of a Pareto surface. This formulation may allow power system operators to manage the multiobjectives of mitigating the possibility of a blackout versus the full enabling of power markets. This is a conceptual paper in which the analytical basis and the main points of the solution of when to initiate controlled islanding are outlined. The objective function recommended for the capture of transient stability is the transient stability load margin.

%B 2009 IEEE/PES Power Systems Conference and Exposition (PSCE) %I IEEE %C Seattle, WA, USA %P 1 - 7 %8 03/2009 %@ 978-1-4244-3810-5 %R 10.1109/PSCE.2009.4839928 %0 Journal Article %J IEEE Transactions on Power Systems %D 2006 %T Slow Coherency Based Controlled Islanding - A Demonstration of the Approach on the August 14, 2003 Blackout Scenario %A Bo Yang %A Vijay Vittal %A Gerald T. Heydt %K AA05-001 %K AARD %K CERTS %K System Security Tools %XThis paper demonstrates the use of a slow coherency based generator grouping algorithm and a graph theoretic approach to form controlled islands as a last resort to prevent cascading outages following large disturbances. The proposed technique is applied to a 30,000-bus, 5000-generator, 2004 summer peak load, Eastern Interconnection data and demonstrated on the August 14, 2003 blackout scenario. Adaptive rate of frequency decline based load shedding schemes are used in the load rich islands to control frequency. The simulation results presented show the advantage of the proposed method in containing the impact of the disturbance within the islands formed and in preventing the impact of the disturbance from propagating to the rest of the system. This is demonstrated by the significant reduction in line flows in the rest of the system and by improved voltage and relative angle characteristics. Based on the suggestion in the joint US-Canadian task force final report on the blackout, load shedding without any islanding is also performed and results obtained are compared with the proposed controlled islanding method. The islanding method outperforms the load shedding only method in reducing the transmission line flows but both methods have similar effects on voltage and relative angle behavior.

%B IEEE Transactions on Power Systems %V 21 %P 9 %8 11/2006 %N 4 %& 1840 %R 10.1109/TPWRS.2006.881126 %0 Conference Paper %B Power Systems Conference and Exposition %D 2004 %T System Islanding Using Minimal Cutsets with Minimum Net Flow %A Xiaoming Wang %A Vijay Vittal %K AA05-001 %K AARD %K CERTS %K System Security Tools %XSlow coherency has effectively proved its capability in determining sets of generator groups among weak connections in any given power system. In this paper, we provide two comprehensive approaches to deal with islanding the actual system based on the grouping information, by using the minimal cutsets technique in graph theory. The issue of minimal cutsets has been widely discussed in areas related to network topology determination, reliability analysis, etc. The results of this paper also show potential in application to power system islanding. The verification of the islanding scheme is provided based on a WECC 179-Bus, 29-Generator test system.

%B Power Systems Conference and Exposition %I IEEE %P 6 %8 10/2004 %R 10.1109/PSCE.2004.1397589