The extension of active noise control (ANC) techniques to deal with nonlinear effects such as distortion and saturation requires the introduction of suitable nonlinear model classes and adaptive algorithms. Large sized models are typically used, resulting in an increased computational load, delayed convergence (and sometimes even algorithm instability), and other unwanted dynamical effects due to overparametrization. This paper discusses the usage of polynomial nonlinear autoregressive models with exogenous variables (NARX) models and model selection techniques to reduce the model size and increase its robustness, for more efficient and reliable ANC. An offline procedure is devised to identify the controller model structure, and the controller parameters are successively updated with an adaptive algorithm based on the error gradient and on the residual noise. Simulation experiments show the effectiveness of the proposed approach. A brief analysis of the involved computational complexity is also provided.

An interconnected transmission network of power system is composed of several subsystems which are jurisdictionally operated by different System Operators and exhibit global changes instantaneously as a result of local decisions of any operator related to its own grid. The complexity of the coordination and decision making of power systems, an infrastructure which can be represented as a socio-technical system, demands investigations of applicable approaches to simulate and analyze the impacts of different coordination rules on the decision making and the performance of the system, especially under emergency. In this paper, a general framework for modeling the power transmission grids as a complex socio-technical system is proposed. Under the framework, multi-agent systems are employed to simulate the decision making of each system operator and the performance of the whole interconnected system due to their interaction. Different scenarios are designed to compare and analyze the impacts of coordination rules, mainly focusing on the policy for tie-line management and on the information revealed, on the outcomes of the decision making process and on the system performance in terms of transmission network feasibility (i.e. line flow, voltage profile, generator output) with reference to the subsystem and the whole interconnected network. The approach is applied to the IEEE-30 bus system to illustrate its application and effectiveness.

The new scenarios of malicious attack prompt for their deeper consideration and mainly when critical systems are at stake. In this framework, infrastructural systems, including power systems, represent a possible target due to the huge impact they can have on society. Malicious attacks are different in their nature from other more traditional cause of threats to power system, since they embed a strategic interaction between the attacker and the defender (characteristics that cannot be found in natural events or systemic failures). This difference has not been systematically analyzed by the existent literature. In this respect, new approaches and tools are needed. This paper presents a mixed-strategy game-theory model able to capture the strategic interactions between malicious agents that may be willing to attack power systems and the system operators, with its related bodies, that are in charge of defending them. At the game equilibrium, the different strategies of the two players, in terms of attacking/protecting the critical elements of the systems, can be obtained. The information about the attack probability to various elements can be used to assess the risk associated with each of them, and the efficiency of defense resource allocation is evidenced in terms of the corresponding risk. Reference defense plans related to the online defense action and the defense action with a time delay can be obtained according to their respective various time constraints. Moreover, risk sensitivity to the defense/attack-resource variation is also analyzed. The model is applied to a standard IEEE RTS-96 test system for illustrative purpose and, on the basis of that system, some peculiar aspects of the malicious attacks are pointed out.