6,694 research outputs found
Geometry-based Estimation of Stability Region for A Class of Structure Preserving Power Grids
The increasing development of the electric power grid, the largest engineered
system ever, to an even more complicated and larger system requires a new
generation of stability assessment methods that are computationally tractable
and feasible in real-time. In this paper we first extend the recently
introduced Lyapunov Functions Family (LFF) transient stability assessment
approach, that has potential to reduce the computational cost on large scale
power grids, to structure-preserving power grids. Then, we introduce a new
geometry-based method to construct the stability region estimate of power
systems. Our conceptual demonstration shows that this new method can certify
stability of a broader set of initial conditions compared to the
minimization-based LFF method and the energy methods (closest UEP and
controlling UEP methods)
A Framework for Robust Assessment of Power Grid Stability and Resiliency
Security assessment of large-scale, strongly nonlinear power grids containing
thousands to millions of interacting components is a computationally expensive
task. Targeting at reducing the computational cost, this paper introduces a
framework for constructing a robust assessment toolbox that can provide
mathematically rigorous certificates for the grids' stability in the presence
of variations in power injections, and for the grids' ability to withstand a
bunch sources of faults. By this toolbox we can "off-line" screen a wide range
of contingencies or power injection profiles, without reassessing the system
stability on a regular basis. In particular, we formulate and solve two novel
robust stability and resiliency assessment problems of power grids subject to
the uncertainty in equilibrium points and uncertainty in fault-on dynamics.
Furthermore, we bring in the quadratic Lyapunov functions approach to transient
stability assessment, offering real-time construction of stability/resiliency
certificates and real-time stability assessment. The effectiveness of the
proposed techniques is numerically illustrated on a number of IEEE test cases
Large-Eddy Simulations of Flow and Heat Transfer in Complex Three-Dimensional Multilouvered Fins
The paper describes the computational procedure and
results from large-eddy simulations in a complex three-dimensional
louver geometry. The three-dimensionality in the
louver geometry occurs along the height of the fin, where the
angled louver transitions to the flat landing and joins with the
tube surface. The transition region is characterized by a swept
leading edge and decreasing flow area between louvers.
Preliminary results show a high energy compact vortex jet
forming in this region. The jet forms in the vicinity of the louver
junction with the flat landing and is drawn under the louver in
the transition region. Its interaction with the surface of the
louver produces vorticity of the opposite sign, which aids in
augmenting heat transfer on the louver surface. The top surface
of the louver in the transition region experiences large velocities
in the vicinity of the surface and exhibits higher heat transfer
coefficients than the bottom surface.Air Conditioning and Refrigeration Project 9
Conic Optimization Theory: Convexification Techniques and Numerical Algorithms
Optimization is at the core of control theory and appears in several areas of
this field, such as optimal control, distributed control, system
identification, robust control, state estimation, model predictive control and
dynamic programming. The recent advances in various topics of modern
optimization have also been revamping the area of machine learning. Motivated
by the crucial role of optimization theory in the design, analysis, control and
operation of real-world systems, this tutorial paper offers a detailed overview
of some major advances in this area, namely conic optimization and its emerging
applications. First, we discuss the importance of conic optimization in
different areas. Then, we explain seminal results on the design of hierarchies
of convex relaxations for a wide range of nonconvex problems. Finally, we study
different numerical algorithms for large-scale conic optimization problems.Comment: 18 page
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