This paper presents a polynomial dimensional decomposition (PDD) method for global sensitivity analysis of stochastic systems subject to independent random input following arbitrary probability distributions. The method involves Fourier-polynomial expansions of lower-variate component functions of a stochastic response by measure-consistent orthonormal polynomial bases, analytical formulae for calculating the global sensitivity indices in terms of the expansion coefficients, and dimension-reduction integration for estimating the expansion coefficients. Due to identical dimensional structures of PDD and analysis-of-variance decomposition, the proposed method facilitates simple and direct calculation of the global sensitivity indices. Numerical results of the global sensitivity indices computed for smooth systems reveal significantly higher convergence rates of the PDD approximation than those from existing methods, including polynomial chaos expansion, random balance design, state-dependent parameter, improved Sobol’s method, and sampling-based methods. However, for non-smooth functions, the convergence properties of the PDD solution deteriorate to a great extent, warranting further improvements. The computational complexity of the PDD method is polynomial, as opposed to exponential, thereby alleviating the curse of dimensionality to some extent. Mathematical modeling of complex systems often requires sensitivity analysis to determine how an output variable of interest is influenced by individual or subsets of input variables. A traditional local sensitivity analysis entails gradients or derivatives, often invoked in design optimization, describing changes in the model response due to the local variation of input. Depending on the model output, obtaining gradients or derivatives, if they exist, can be simple or difficult. In contrast, a global sensitivity analysis (GSA), increasingly becoming mainstream, characterizes how the global variation of input, due to its uncertainty, impacts the overall uncertain behavior of the model. In other words, GSA constitutes the study of how the output uncertainty from a mathematical model is divvied up, qualitatively or quantitatively, to distinct sources of input variation in the model [1].

Reliability Engineering and System Safety

This paper reports on the development and subsequent use of the electric power and communication synchronizing simulator (EPOCHS), a distributed simulation environment. Existing electric power simulation tools accurately model power systems of the past, which were controlled as large regional power pools without significant communication elements. However, as power systems increasingly turn to protection and control systems that make use of computer networks, these simulators are less and less capable of predicting the likely behavior of the resulting power grids. Similarly, the tools used to evaluate new communication protocols and systems have been developed without attention to the roles they might play in power scenarios. EPOCHS integrates multiple research and commercial off-the-shelf systems to bridge the gap.

EPOCHS: a platform for agent-based electric power and communication simulation built from commercial off-the-shelf components

Today's electricity grid is transitioning to a so-called smart grid. The associated challenges and funding initiatives have spurred great efforts from the research community to propose innovative smart grid solutions. To assess the performance of possible solutions, simulation tools offer a cost effective and safe approach. In this paper we will provide a comprehensive overview of various tools and their characteristics, applicable in smart grid research: we will cover both the communication and associated ICT infrastructure, on top of the power grid. First, we discuss the motivation for the development of smart grid simulators, as well as their associated research questions and design challenges. Next, we discuss three types of simulators in the smart grid area: power system simulators, communication network simulators, and combined power and communication simulators. To summarize the findings from this survey, we classify the different simulators according to targeted use cases, simulation model level of detail, and architecture. To conclude, we discuss the use of standards and multi-agent based modeling in smart grid simulation.

Combining Power and Communication Network Simulation for Cost-Effective Smart Grid Analysis

SCADA systems are nowadays exposed not only to traditional safety and availability problems, but also to new kinds of security threats. These are mainly due to the large number of new vulnerabilities and architectural weaknesses introduced by the extensive use of ICT and networking technologies into such complex systems. The analysis of the effects of these new threats is a mandatory activity to ensure the security of critical installation relying on SCADA systems. In this paper, after describing an experimental platform developed for studying the effects of ICT attacks against SCADA systems, we present some attack scenarios successfully exploited in this experimental platform, taking as reference the SCADA system of a typical Turbo-Gas Power Plant. Moreover we present a brief overview of the possible countermeasures for enhancing the security of SCADA systems.

An experimental platform for assessing SCADA vulnerabilities and countermeasures in power plants

This paper presents a study of wide area agents based on communication for primary and backup coordinated protection Agents are used to give each protection component control capacity as well as the ability to communicate with other agents We feel that this method naturally points toward a new philosophy for primary and backup protection Simulations are used to illustrate concepts, using a simulation engine called EPOCHS that combines the EMTDC/PSCAD power simulator with the NS2 network communications simulator Results show the improved performance of our protection scheme In this new protection system, agents were embedded in each of the conventional protection components to construct an IED relay The agent searches for relevant information by communicating with other agents Agent communication can take place at the same substation or at remote substations This information can be used to detect primary and remote faults, relay misoperation, breaker failures, and to compensate such problems with a much better performance than can be done in traditional schemes Preliminary results give us hope that the proposed protection scheme may be able to contribute toward the mitigation of wide-area disturbances and the power blackouts that frequently follow them

A primary and backup cooperative protection system based on wide area agents

We report on the development of the Electric Power and Communication Synchronizing Simulator (EPOCHS), a distributed simulation environment. Existing electric power simulation tools accurately model power systems of the past, which were controlled as large regional power pools without significant communication elements. However, as power systems increasingly turn to protection and control systems that make use of computer networks, these simulators are less and less capable of predicting the likely behavior of the resulting power grids. Similarly, the tools used to evaluate new communication protocols and systems have been developed without attention to the roles they might play in power scenarios. EPOCHS utilizes multiple research and commercial off-the-shelf (COTS) systems to bridge the gap. EPOCHS is also notable for allowing users to transparently encapsulate complex system behavior that bridges multiple domains through the use of a simple agent-based framework.

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Birman

Papers

EPOCHS: integrated commercial off-the-shelf software for agent-based electric power and communication simulation