https://research.vu.nl/ws/files/118938525/State_of_the_art_of_cyberphysical_systems_security.pdf

State of the art of cyber-physical systems security : An automatic control perspective

The Unit Commitment problem in energy management aims at finding the optimal production schedule of a set of generation units, while meeting various system-wide constraints. It has always been a large-scale, non-convex, difficult problem, especially in view of the fact that, due to operational requirements, it has to be solved in an unreasonably small time for its size. Recently, growing renewable energy shares have strongly increased the level of uncertainty in the system, making the (ideal) Unit Commitment model a large-scale, non-convex and uncertain (stochastic, robust, chance-constrained) program. We provide a survey of the literature on methods for the Uncertain Unit Commitment problem, in all its variants. We start with a review of the main contributions on solution methods for the deterministic versions of the problem, focussing on those based on mathematical programming techniques that are more relevant for the uncertain versions of the problem. We then present and categorize the approaches to the latter, while providing entry points to the relevant literature on optimization under uncertainty. This is an updated version of the paper “Large-scale Unit Commitment under uncertainty: a literature survey” that appeared in 4OR 13(2):115–171 (2015); this version has over 170 more citations, most of which appeared in the last 3 years, proving how fast the literature on uncertain Unit Commitment evolves, and therefore the interest in this subject.

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Large-scale unit commitment under uncertainty: an updated literature survey

Recent work has studied the impact caused by attackers that compromise pricing signals used in the emerging retail electricity market and send false prices to a subset of consumers. In this paper, we extend previous work by considering a more realistic adversary model that is not arbitrarily tied to scaling and delay attacks, but that can generate any arbitrary pricing signal and show how to keep the problem tractable with a new analysis based on sensitivity functions. In addition, we extend previous work by proposing countermeasures to mitigate the negative impact of these attacks. Countermeasures include selecting parameters of the controller, designing robust control algorithms, and by detecting anomalies in the behavior of the system.

Integrity Attacks on Real-Time Pricing in Smart Grids: Impact and Countermeasures

The ability to maintain the system frequency within specified operating limits is crucial for the stability and proper operation of power systems. Any small deviation out of the permissible frequency range must be well-mitigated by the automatic generation control (AGC) system, otherwise it may result in disruption of operation and/or damage to the power grid equipment. The data required by the AGC control system is sent to the control center through communication links which are susceptible to cyber attacks. Therefore, such AGC systems have to be well-protected against false data injection (FDI) attacks. In this paper, the use of a simultaneous input and state estimation based algorithm to detect and concurrently compensate for FDI attacks against the measurements of AGC systems is investigated. Throughout the use of this algorithm, the FDI attack signal is dealt with as an unknown input and its value is estimated accordingly. Then, the estimated value for the FDI is used to compensate for the effect of the attack so that the control center makes its decision based on the corrected sensor signals, and not the manipulated ones. The proposed approach is tested under different types of FDI attacks and the simulation results for a 2-area and a 4-area practical system confirm its ability to detect, estimate FDI attacks and successfully compensate for it.

Joint Detection and Mitigation of False Data Injection Attacks in AGC Systems

Load frequency control (LFC) is widely employed to regulate power plants in modern power generation systems of smart grids. This paper presents a simple and yet powerful type of attacks, referred to as resonance attacks, on LFC power generation systems. Specifically, in a resonance attack, an adversary craftily modifies the input of a power plant according to a resonance source (e.g., rate of change of frequency) to produce a feedback on LFC power generation system, such that the state of the power plant quickly becomes instable. Extensive computer simulations on popular LFC power generation system models which consist of linear, non-linear, and/or high-order items clearly demonstrate the effectiveness of the proposed attacks. As the attack has very low computational cost and communication overhead, it is easy to launch in resource-limited devices such as intelligent electronic devices. In our simulations, the attacker keeps modified input within the normal operating range so as to invade plausibility and consistency based attack detection methods and yet the modifications can quickly drive the system beyond the admissible boundary. Another interesting finding is that by maliciously modifying the input such as power load and tie-line signal over multi-area interconnection channels, a multi-area LFC power generation system could become unreliable more quickly than a single-area system. Finally, we propose countermeasures on the proposed attacks.

https://ink.library.smu.edu.sg/cgi/viewcontent.cgi?article=5149&context=sis_research

Resonance Attacks on Load Frequency Control of Smart Grids

Power systems are traditionallymonitored and controlled by an IT infrastructure, referred to as Supervisory Control and Data Acquisition (SCADA) system. The cyber-physical interaction of power systems (physical) and SCADA systems (cyber) rises security issues, since the links between those systems are vulnerable to cyber-attacks that can potentially lead to catastrophic economical and societal effects. In this chapter we focus on a specific cyber-physical link, the Automatic Generation Control (AGC), which is an automatic frequency control loop closed over the SCADA system. We provide an impact analysis in case of a cyber-attack on the AGC signal. We first carry out a feasibility analysis based on reachability and optimal control theory, that provides an information regarding the existence of an attack pattern that can disturb the power system. We then deal with the problem of synthesizing an attack signal and treat it as a nonlinear control synthesis problem. Third, performance of our methodologies are illustrated by means of dynamic simulations on IEEE-118 bus network.

Goeran Andersson

Papers

Cyber-Attacks in the Automatic Generation Control

Stochastic security constrained unit commitment and non-spinning reserve allocation with performance guarantees