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1. Cyber-Physical Attack Leveraging Subsynchronous Resonance

   Li, Bosong; Zhang, Baosen; Kirschen, Daniel S. (January 2022, IREP 2022 Symposium)

   This paper discusses how a cyber attack could take advantage of torsional resonances in the shaft of turbo-generators to inflict severe physical damage to a power system. If attackers were able to take over the control of a battery energy storage device, they could modulate the injection of this device at a frequency that matches one of the sub-synchronous resonance frequencies of a generator. Small changes in injection might be sufficient to excite one of these mechanical resonances, resulting in metal fatigue and ultimately a catastrophic failure in the shaft of the generator. Using a state-space model of the electromechanical system, the paper develops transfer functions linking the magnitude of the malicious injections to the magnitude of oscillations in the speed and angle of the various masses connected to the shaft. Numerical results from a two-area power system demonstrate the existence of vulnerable frequencies and show that damaging mechanical oscillations can be triggered without causing easily detectable signals at the generator terminals. 

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2. Stability Analysis of Real-World Subsynchronous Oscillations via Black-Box EMT Models

   https://doi.org/10.1109/TPWRD.2024.3447463  

   Ramakrishna, Rahul Halugudde; Miao, Zhixin; Fan, Lingling (October 2024, IEEE Transactions on Power Delivery)

   In this paper, we demonstrate methods to extract dq admittance for a solar photovoltaic (PV) farm from its black-box model used for electromagnetic transient (EMT) simulation. Each dq admittance corresponds to a certain operating condition. Based on the dq admittance, analysis is carried out to evaluate how grid strength and solar irradiance may influence stability. Two types of stability analysis methods (open-loop system based and closed-loop system based) are examined and both can deal with dq admittance's frequency-domain measurements directly and produce graphics for stability analysis. The findings based on dq admittance-based analysis are shown to corroborate EMT simulation results. 

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3. Frequency Scan–Based Mitigation Approach of Subsynchronous Control Interaction in Type-3 Wind Turbines

   https://doi.org/10.3390/en14154626  

   Alatar, Faris; Mehrizi-Sani, Ali (August 2021, Energies)

   null (Ed.)

   Integration of wind energy resources into the grid creates several challenges for power system dynamics. More specifically, Type-3 wind turbines are susceptible to subsynchronous control interactions (SSCIs) when they become radially connected to a series-compensated transmission line. SSCIs can cause disruptions in power generation and can result in significant damage to wind farm (WF) components and equipment. This paper proposes an approach to mitigate SSCIs using an online frequency scan, with optimized phase angles of voltage harmonic injection to maintain steady-state operation, to modify the controllers or the operating conditions of the wind turbine. The proposed strategy is simulated in PSCAD/EMTDC software on the IEEE second benchmark model for subsynchronous resonance. Simulation results demonstrate the effectiveness of this strategy by ensuring oscillations do not grow. 

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4. Subsynchronous Control Interaction Analysis and Trigger-based Damping Control for Doubly Fed Induction Generator-based Wind Turbines

   https://doi.org/10.1080/15325008.2015.1131768  

   Zhang, Jian; Xiao, Xiangning; Zhang, Peng; Lu, Jingjing; Orekan, Taofeek (April 2016, Electric Power Components and Systems)