IEEE TRANSACTIONS ON POWER SYSTEMS, VOL. 35, NO. 3, MAY 2020 1707 PMU Signals Responses-Based RAS for Instability Mitigation Through On-The Fly Identification and Shedding of the Run-Away Generators Avishek Paul , Innocent Kamwa, Fellow, IEEE, and Geza Joos, Fellow, IEEE Abstract—This paper presents a new method of instability de- tection and subsequent stabilization of the power system network using a proposed multi-shot remedial action scheme (RAS) that can extemporaneously detect critical generators based on the dy- namic states of generator computed from the terminal phasor measurement units. The instability detector is a moving window classifier that predicts impending instability using rate of change of individual generator transient energy indices evaluated from the d–q axis voltage as well as conventional severity indices based on generator angle and frequency. A comparative performance analy- sis of a spectral feature based ensemble decision tree classifier with a multivariate long short-term memory network is also presented. The proposed RAS identifies critical generators through individual machine transient energy formulation and recursive coherency ma- trix, evaluated solely from system-wide generator dynamic states, and maintains stability by tripping adaptively the run-away gen- erators. Performance evaluation of the proposed scheme has been made on IEEE 39-bus network and it has been demonstrated that the proposed RAS is robust with regards to instability prediction and it can effectively identify critical generators and stabilize the network by tripping the same. Index Terms—Decision tree, long short term memory network, phasor measurement unit, dynamic state estimation, remedial action scheme, transient stability assessment. NOMENCLATURE u: Column Vector of Inputs to the System Consists of V t Voltage of terminal bus in p.u. V ref Voltage Reference to exciter P ref Active Power Reference to Governor x: Column Vector of State Consists of δ Rotor angle Δω Rotor speed deviation e ′ d ,e ′ q d & q axis transient electromotive force (emf) Manuscript received October 5, 2018; revised March 8, 2019 and May 5, 2019; accepted June 16, 2019. Date of publication July 1, 2019; date of current version April 22, 2020. This work was supported by the Natural Sciences and Engineering Research Council of Canada. Paper no. TPWRS-01500-2018. (Corresponding author: Avishek Paul.) A. Paul and G. Joos are with the Department of Electrical and Computer Science Engineering, McGill University, Montreal, QC H3A 0G4, Canada (e-mail: avishek.paul@mail.mcgill.ca; geza.joos@mail.mcgill.ca). I. Kamwa is with the Department of Power Systems and Mathematics, Research Institute of Hydro-Quebec/IREQ, Varennes, QC J3X 1S1, Canada (e-mail: kamwa.innocent@ireq.ca). 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.2019.2926243 E fd Exciter field voltage T m Governor Mechanical Input y: Column Vector of Measured Output P t ,Q t Active and Reactive Power at terminal bus in p.u. f r Rotor Frequency in Hz I t Current at terminal bus in p.u. α: Other Parameter Definitions x d ,x q Direct(d) and quadrature(q) axis reactance x ′ d ,x ′ q Direct(d) and quadrature(q) axis transient re- actance T ′ d0 ,T ′ q0 D and q transient open circuit time constant i d ,i q Direct and quadrature axis current D, M Damping factor and Inertia constant on p.u. Instability Indices and Energy terms γ COP ,κ COP Instability Index w.r.t Centre of Power (COP) W d Rate of change of Transient Energy W KE ,W PE ,W T Kinetic, Potential, Total Transient Energy of generator P L ,Q L Active and Reactive Power at load buses I. INTRODUCTION T HERE is a growing risk of grid vulnerability resulting from an aggregated effect of increasing demand, delayed trans- mission construction and rapid permeation of renewable energy sources. All these factors cause the grid to operate at reduced op- erating margins, thereby requiring implementation of automatic system wide mitigation action, following a contingency, without operator intervention. This functionality is incorporated through Remedial Action Scheme (RAS), sometimes loosely referred to as System Integrity Protection System (SIPS) [1]. RAS is defined by North American Electric Reliability Corporation (NERC) [2] as ‘an automatic protection scheme that detects abnormal or predetermined system conditions and takes corrective actions other than and in addition to faulted component isolation in form of changes in generation and/or demand, system configuration to maintain system reliability. One of the earliest formal works on RAS [3], presents an algorithm for automatically identifying constraint violations and deploying mitigation actions while addressing computational constraints. In conventional RAS and SIPS design, critical contingencies and control actions for corresponding cases are 0885-8950 © 2019 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See https://www.ieee.org/publications/rights/index.html for more information. Authorized licensed use limited to: BIBLIOTHEQUE DE L'UNIVERSITE LAVAL. Downloaded on January 30,2022 at 01:02:20 UTC from IEEE Xplore. Restrictions apply.