1,721,086 research outputs found
Generalized Power Flow Analysis of Electrical Power Systems Modeled as Mixed Single-Phase/Three-Phase Sub-Systems
Full text linkElectrical power generation, transmission and distribution systems are often simulated through the single-phase equivalent model by assuming the presence of only the positive sequence in the real system. The well known power flow (pf) analysis is typically used to determine the steady state solution of these single-phase models. After the pf solution was determined, other elements, such as for example synchronous generators and controllers, are initialised. This provides the initial conditions to subsequent transient stability analyses. Nowadays, this simulation approach may be no longer feasible due to the large penetration of unbalanced and/or electronic elements in the power systems. In this paper we present a novel numerical method that allows to freely compute the steady state solution of complex power systems made up of a 'mixing' of conventional single-phase models and more complex, detailed three-phase models, for example of some portions of the transmission system and of the distribution ones. This steady state solution can be viewed as a generalization and/or an extension of the conventional pf
A parameter-dependent approximation of the Hindmarsh-Rose neuron model suitable for analog circuit implementation
No full textPWL approximation of the Hindmarsh-Rose neuron model in view of its circuit implementation
No full textDecision Making in Networks: A Model of Awareness Raising
Full text linkThis work investigates how interpersonal interactions among individuals could affect the dynamics of awareness raising. Even though previous studies on mathematical models of awareness in the decision making context demonstrate how the level of awareness results from self-observation impinged by optimal decision selections and external uncertainties, an explicit accounting of interaction among individuals is missing. Here we introduce for the first time a theoretical mathematical framework to evaluate the effect on individual awareness exerted by the interaction with neighbor agents. This task is performed by embedding the single agent model into a graph and allowing different agents to interact by means of suitable coupling functions. The presence of the network allows, from a global point of view, the emergence of diffusion mechanisms for which the population tends to reach homogeneous attractors, and, among them, the one with the highest level of awareness. The structural and behavioral patterns, such as the initial levels of awareness and the relative importance the individual assigns to their own state with respect to others’, may drive real actors to stress effective actions increasing individual and global awareness
Analog-mixed-signal simulation of DC-DC Boost-Based MPPT system taking into account weather conditions variations
No full textDC-DC converters are widely used as interfaces between photovoltaic (PV) sources and loads in different applications. These devices use inductors as energy storage elements for controlling the power flow from the PV source to the load. These systems are usually designed using conventional linear small-signal approaches in the vicinity of an operating point. However, the operating point of a PV system is highly dependent on the environmental conditions such as the irradiance and the temperature. Irradiance and temperature changes make the system work at different power and current levels. The inductance of a nonlinear real inductor strongly depends on the operating current. In this paper, a study of a boost converter used for maximum power point tracking is presented by taking into account the inductor nonlinearity till saturation and the variation of its inductance with the weather conditions. To this end analog-mixed-signal circuit simulations are used to show the effects of the weather conditions on the dynamical behavior of the overall PV system
Discrete Programming Entailing Circulant Quadratic Forms: Refinement of a Heuristic Approach Based on ΔΣ Modulation
Full text linkA recent result on the potential of Delta !Sigma modulators ( Delta !Sigma Ms) as heuristic optimizers for circulant unconstrained discrete quadratic programming (C-UDQP) is revisited, bridging it with current developments on the design of Delta !Sigma Ms by semi-definite programming (SDP). This provides an efficient strategy by which one can design a Delta !Sigma ext{M} and its input signal from a C-UDQP specification so that the solution of the C-UDQP problem can be found in the Delta !Sigma ext{M} output, all with almost no manual intervention. The proposed concept is validated by simulation-based experiments on a benchmark case, comparing the new strategy to previous results and exact optimization techniques
Load Transient Response Analysis of Constant On-Time DC-DC Converters Using a State-Variables Approach
No full textIn the design of constant-on-time buck converters, prediction of the onset of subharmonics, at steady-state working conditions, and prediction of the saturation of the controller, i.e., the occurrence of at least one switching cycle at minimum off-time, after a dynamic step variation of the load are relevant aspects. By starting from the design parameters of a constant-on-time buck converter and grounding on a state-variables approach, we consider these aspects and develop a reliable and efficient approach to determine both limits. The proposed approach, despite having rigorous mathematical basis, is sufficiently simple. Thus it can be easily applied to predict results in designing constant-on time buck converters. The accuracy and effectiveness of the proposed approach is tested versus experimental results. This article is accompanied by a MATLAB live script that allows the reader to reproduce the proposed results and create new case studies
Closed-Form Operational Boundaries for Buck Converters with Constant On-Time Control
Full text linkIn this brief, we provide three operational boundaries in closed analytical form for a Constant ON-Time buck converter working in continuous current mode. Two of these boundaries are related to the sudden appearance of pulse-bursting induced by either (i) the hysteresis of the comparator that drives the input of the block implementing the circuit control algorithm (hysteresis condition), or (ii) by a period doubling bifurcation (bouncing condition). The third operational boundary corresponds to the saturation condition of the circuit controller which does no longer guarantee an OFF-time larger than the minimum allowed one. These stability boundaries are provided both for the adaptive and the fixed ON-time working modes
Cellular non-linear networks for minimization of functionals. Part 2: Examples
No full textA method for the definition of cellular non-linear networks able to find approximate minima of rather a large class of continuous functionals is illustrated through three examples. The method, based on the spatial discretization of continuous functionals and on the theory of potential functions for resistive circuits, has been presented in Part 1 of this paper. The first example (related to electromagnetic-field theory) has the main purpose to show some aspects of the application procedure. The other two examples concern, respectively, a possible image-processing application of the method (where a parallel processing is highly desirable) and a comparison with another method proposed in the literature on CNNs
Shooting by a Two-Step Galerkin Method
No full textThe shooting method employed to compute the steady-state solution of circuits in the time domain is well known, largely used, and has been intensely studied in the literature. During these last decades, the large penetration of radio-frequency devices in the everyday activities has renewed some interest in this method, but the renewed interest is mainly focused on the simulation of large or very large circuits composed of thousands of transistors. The original formulation of the shooting method, despite being formally adequate, is unfeasible to handle this target. The introduction of iterative methods such as for example GMRES has largely pushed up the maximum size of the circuits that can be considered. Nevertheless, this may be not enough. We present an approach that faces the curse of dimensionality suffered by the original method. It allows both saving memory occupation and tackling circuits (or systems) with a number of differential and algebraic variables well above those managed by GMRES. Dimensionality is reduced by exploiting Galerkin projections
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