2604 IEEE TRANSACTIONS ONPOWER SYSTEMS, VOL. 32, NO. 4, JULY 2017 Real-Time Contingency Analysis With Corrective Transmission Switching Xingpeng Li, Student Member, IEEE, Pranavamoorthy Balasubramanian, Student Member, IEEE, Mostafa Sahraei-Ardakani, Member, IEEE, Mojdeh Abdi-Khorsand, Student Member, IEEE, Kory W. Hedman, Member, IEEE, and Robin Podmore, Fellow, IEEE Abstract—Transmission switching (TS) has gained significant attention recently. However, barriers still remain and must be over- come before the technology can be adopted by the industry. The state-of-the-art challenges include AC feasibility, computational complexity, the ability to handle large-scale real power systems, and dynamic stability. This paper investigates these challenges by developing an AC corrective TS (CTS) based real-time contingency analysis (RTCA) tool that can handle large-scale systems within a reasonable time. The tool quickly proposes multiple high-quality corrective switching actions for contingencies with potential viola- tions. To reduce the computational complexity, three heuristic algo- rithms are proposed to generate a small set of candidate switching actions. Parallel computing is implemented to further speed up the solution time. Moreover, time-domain simulations are performed to check for dynamic stability of the proposed CTS solutions. The promising results, tested on the Tennessee Valley Authority (TVA) system and actual energy management system snapshots from the PJM Interconnection (PJM) and the Electric Reliability Council of Texas (ERCOT), show that the tool effectively reduces post- contingency violations. It is concluded that CTS is ripe for industry adoption for RTCA application. Index Terms—Corrective transmission switching, energy man- agement systems, high performance computing, large-scale power systems, power system operation, power system reliability, power system stability, real-time contingency analysis. I. INTRODUCTION M AINTAINING a reliable power system is of utmost im- portance. The North American Electric Reliability Cor- poration (NERC) requires systems to withstand the loss of a single bulk element (N-1) [1]. While reserves are acquired, re- liable operation is not always achieved. Real-time contingency analysis (RTCA) is frequently repeated for this purpose. In the Midcontinent Independent System Operator (MISO) system, the RTCA package simulates more than 11,500 Manuscript received November 10, 2015; revised March 6, 2016, June 27, 2016, and September 22, 2016; accepted October 7, 2016. Date of publication October 18, 2016; date of current version June 16, 2017. This work was supported by the Department of Energy Advanced Projects Agency – Energy under the Green Electricity Network Integration program. Paper no. TPWRS- 01607-2015. X. Li, P. Balasubramanian, M. Sahraei-Ardakani, M. Abdi-Khorsand, and K. W. Hedman are with the School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, AZ 85287 USA (e-mail: xingpeng.li@asu.edu; pbalasu3@asu.edu; mostafa.ardakani@utah.edu; mabdikho@asu.edu; kwh@myuw.net). R. Podmore is with IncSys, Bellevue, WA 98007 USA (e-mail: robin@incsys.com). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TPWRS.2016.2616903 contingency scenarios every four minutes [2]. RTCA utilizes data from the state estimator and contingency analysis is per- formed by successively solving AC power flows. Line flow and bus voltage violations corresponding to different contingencies are determined [3] by analyzing the power flow results. PJM Interconnection (PJM) runs AC real-time contingency analysis to identify the contingencies that cause violations in the system [4]. Approximately 6,000 contingencies are assessed every minute at PJM [4]. Although there is a list of all contin- gencies in PJM’s database, not all contingencies in that list are evaluated at all times [5]. The Electric Reliability Council of Texas (ERCOT) uses a two-phase procedure to perform breaker-to-breaker con- tingency analysis [6]. A heuristic screening procedure is performed in the first phase to identify the most severe contingencies based on the post-contingency violations. Pre- viously, ERCOT had approximately 3938 contingencies, in- cluding 2958 single branch contingencies, 375 double branch contingencies, and 605 generator contingencies, modeled in its system [7]. The RTCA in ERCOT executes every five minutes [7]. If a contingency with post-contingency violations is detected, appropriate actions will be taken to ensure reliable operations. These actions may include: 1) Sending constraints to security-constrained economic dis- patch to move away from a vulnerable state. 2) Commitment of fast-start units to provide local reserves. 3) Adjustment of transmission assets (e.g., transformer taps, switchable shunts, adjustment of flexible AC transmission systems (FACTS) devices). 4) Transmission switching (TS) to enhance deliverability of reserves and reroute the network power flow. Corrective transmission switching (CTS) is shown to be a viable solution for handling contingencies, which is also signif- icantly cheaper than many alternatives [8]–[10]. CTS is already being used in normal and post-contingency operation, though to a very limited extent, at PJM [11]. Despite the vast body of literature that has been dedicated to TS over the last decade, im- portant challenges remain for more systematic adoption of the technology. The challenges include the following: 1) computa- tional complexity, 2) unknown or poor AC performance, 3) con- cerns regarding the stability of switching actions, 4) and limited insight on performance of the technology on actual large-scale power system data. 0885-8950 © 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications standards/publications/rights/index.html for more information.