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1. Analyzing Mutual Influences of Conventional and Distributed FACTS via Stochastic Co-optimization

   https://doi.org/10.1109/PMAPS.2018.8440367  

   Sang, Yuanrui; Sahraei-Ardakani, Mostafa (June 2018, 2018 IEEE International Conference on Probabilistic Methods Applied to Power Systems (PMAPS))

   Distributed flexible AC transmission systems (D-FACTS) is an attractive power flow control technology, featuring low cost and flexibility for re-deployment. Optimal allocation of D-FACTS and the mutual influence between existing FACTS and newly planned D-FACTS are challenging but important issues that need to be addressed. This paper proposes a co-optimization model of FACTS and D-FACTS based on stochastic optimization, considering the uncertainties caused by fluctuating load and renewable energy generation. Using this model, the location and set points of FACTS and D-FACTS can be co-optimized; in a system with existing FACTS, the locations of FACTS can be predetermined and the locations of D-FACTS can be optimized. The study shows that existing FACTS affects the optimal locations of D-FACTS and adding D-FACTS into the system affects the optimal set points of existing FACTS. Thus, it is essential to co-optimize the two technologies to maximize their economic benefits. 

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2. Moving-Target Defense for Detecting Coordinated Cyber-Physical Attacks in Power Grids

   https://doi.org/10.1109/SmartGridComm.2019.8909767  

   Lakshminarayana, Subhash; Belmega, E. Veronica; Poor, H. Vincent (October 2019, Proceedings of the 10th IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm 2019))

   This work proposes a moving target defense (MTD) strategy to detect coordinated cyber-physical attacks (CCPAs) against power grids. A CCPA consists of a physical attack, such as disconnecting a transmission line, followed by a coordinated cyber attack that injects false data into the sensor measurements to mask the effects of the physical attack. Such attacks can lead to undetectable line outages and cause significant damage to the grid. The main idea of the proposed approach is to invalidate the knowledge that the attackers use to mask the effects of the physical attack by actively perturbing the grid’s transmission line reactances using distributed flexible AC transmission system (D-FACTS) devices. We identify the MTD design criteria in this context to thwart CCPAs. The proposed MTD design consists of two parts. First, we identify the subset of links for D-FACTS device deployment that enables the defender to detect CCPAs against any link in the system. Then, in order to minimize the defense cost during the system’s operational time, we use a game-theoretic approach to identify the best subset of links (within the D-FACTS deployment set) to perturb which will provide adequate protection. Extensive simulations performed using the MATPOWER simulator on IEEE bus systems verify the effectiveness of our approach in detecting CCPAs and reducing the operator’s defense cost. 

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3. Systematic planning of moving target defence for maximising detection effectiveness against false data injection attacks in smart grid

   https://doi.org/10.1049/cps2.12012  

   Liu, Bo; Wu, Hongyu (May 2021, IET Cyber-Physical Systems: Theory & Applications)

   Abstract Moving target defence (MTD) has been gaining traction to thwart false data injection attacks against state estimation (SE) in the power grid. MTD actively perturbs the reactance of transmission lines equipped with distributed flexible AC transmission system (D‐FACTS) devices to falsify the attacker's knowledge about the system configuration. However, the existing literature has not systematically studied what influences the detection effectiveness of MTD and how it can be improved based on the topology analysis. These problems are tackled here from the perspective of an MTD plan in which the D‐FACTS placement is determined. We first exploit the relation between the rank of the composite matrix and the detecting effectiveness. Then, we rigorously derive upper and lower bounds on the attack detecting probability of MTDs with a given rank of the composite matrix. Furthermore, we analyse existing planning methods and highlight the importance of bus coverage by D‐FACTS devices. To improve the detection effectiveness, we propose a novel graph theory–based planning algorithm to retain the maximum rank of the composite matrix while covering all necessary buses. Comparative results on multiple systems show the high detecting effectiveness of the proposed algorithm in both DC‐ and AC‐SE. 

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4. Unconventional High Surge Impedance Loading (HSIL) Lines and Transmission Expansion Planning

   https://doi.org/10.1109/NAPS58826.2023.10318813  

   Dhamala, Bhuban; Ghassemi, Mona (October 2023, IEEE)

   Transmission expansion planning (TEP) is crucial for maintaining the reliable and efficient operation of the power systems, particularly in the face of increasing electricity demand and the integration of renewable energy sources. This paper aims to investigate the application of unconventional high surge impedance loading (HSIL) lines in TEP and presents a comparative analysis of their outcomes against conventional line-based TEP approaches. Starting with a 17-bus 500 kV test system, which can operate well under normal operating condition as well as all single contingency conditions, the objective is to connect a new load located in a new bus, bus #18, to the existing test system via two approaches: using conventional lines and incorporating unconventional HSIL lines. By comparing the number of lines required for the conventional and unconventional approaches, maintaining identical conductor weight per circuit, the effectiveness of unconventional HSIL lines in TEP is evaluated where using only two unconventional HSIL lines is sufficient to connect 1250 MW load demand at bus 18 while three transmission lines are required when using the conventional line. Finally, a thorough economic analysis has been conducted on both TEP scenarios, revealing that implementing unconventional HSIL lines leads to remarkable cost savings and thus can be considered a promising option for TEP studies. 

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5. Data-Driven Phase-Based Control of a Powered Knee-Ankle Prosthesis for Variable-Incline Stair Ascent and Descent

   https://doi.org/10.1109/TMRB.2023.3328656  

   Cortino, Ross J.; Best, T. Kevin; Gregg, Robert D. (January 2023, IEEE Transactions on Medical Robotics and Bionics)

   Powered knee-ankle prostheses can offer benefits over conventional passive devices during stair locomotion by providing biomimetic net-positive work and active control of joint angles. However, many modern control approaches for stair ascent and descent are often limited by time-consuming hand-tuning of user/task-specific parameters, predefined trajectories that remove user volition, or heuristic approaches that cannot be applied to both stair ascent and descent. This work presents a phase-based hybrid kinematic and impedance controller (HKIC) that allows for semi-volitional, biomimetic stair ascent and descent at a variety of step heights. We define a unified phase variable for both stair ascent and descent that utilizes lower-limb geometry to adjust to different users and step heights. We extend our prior data-driven impedance model for variable-incline walking, modifying the cost function and constraints to create a continuously-varying impedance parameter model for stair ascent and descent over a continuum of step heights. Experiments with above-knee amputee participants (N=2) validate that our HKIC controller produces biomimetic ascent and descent joint kinematics, kinetics, and work across four step height configurations. We also show improved kinematic performance with our HKIC controller in comparison to a passive microprocessor-controlled device during stair locomotion. 

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