Showing papers on "Electrical network published in 2017"

Mathematical Models of Electrical Activity in Plants

Abstract: Electrical activity plays an important role in plant life; in particular, electrical responses can participate in the reception of the action of stressors (local electrical responses and oscillations) and signal transduction into unstimulated parts of the plant (action potential, variation potential and system potential). Understanding the mechanisms of electrical responses and subsequent changes in physiological processes and the prediction of plant responses to stressors requires the elaboration of mathematical models of electrical activity in plant organisms. Our review describes approaches to the simulation of plant electrogenesis and summarizes current models of electrical activity in these organisms. It is shown that there are numerous models of the generation of electrical responses, which are based on various descriptions (from modifications of the classical Hodgkin-Huxley model to detailed models, which consider ion transporters, regulatory processes, buffers, etc.). A moderate number of works simulate the propagation of electrical signals using equivalent electrical circuits, systems of excitable elements with local electrical coupling and descriptions of chemical signal propagation. The transmission of signals from a plasma membrane to intracellular compartments (endoplasmic reticulum, vacuole) during the generation of electrical responses is much less modelled. Finally, only a few works simulate plant physiological changes that are connected with electrical responses or investigate the inverse problem: reconstruction of the type and parameters of stimuli through the analysis of electrical responses. In the conclusion of the review, we discuss future perspectives on the simulation of electrical activity in plants.

Optimization of Electrical Energy Storage System Sizing for an Accurate Energy Management in an Aircraft

Abstract: The development of More Electrical Aircraft has lead to the adaptation of their electrical architecture and their capacity of power generation and storage. Therefore, generation and storage systems must be well sized to match their energetic performances versus the vehicle requirements. This paper deals with the optimal sizing of storage systems (secondary batteries and supercapacitors) for an aircraft. In this particular application, the global weight of the whole storage system must be minimized. An optimal sizing tool has been developed to reach this objective by acting on setting parameters that are the cut-off frequency of the low-pass filter (to share out the mission profile between storage systems according to an energy management based on a frequency approach), the discharge ratio for storage components (in relation with their technological limits and the electrical network specifications), and temperature (which can be seen as an environmental constraint as well). The optimization results, which are obtained with the simulated annealing method implemented in MATLAB, are presented and assessed throughout the whole temperature range. Finally, the impact of setting parameters on the global storage system weight is studied, and an adaptation of the energy management strategy is presented to take into account the temperature influence on battery performances.

Optimal charging for general equivalent electrical battery model, and battery life management

Abstract: The contributions of this paper are threefold. First, we present the linear quadratic solution to optimally charge a Li-ion battery in a general form. Although the battery model considered here is a circuit comprised of an open-circuit voltage (OCV), a series resistance, and an RC circuit, the methodology is applicable to any electrical circuit model of a battery. A combination of different cost functions is considered including: time-to-charge, energy loss, and temperature rise index. We discuss the effect of different weightings in the cost functions on the current and voltage profiles. Second, we present two models for normalized battery capacity as a function of the number of cycles and two charge control parameters, viz., maximum terminal voltage of the battery and maximum charge current. These models are compared to a bi-exponential capacity model. The effectiveness of the proposed models for forecasting the battery capacity is validated using the experimental data. Third, these models are used for battery life management by developing an optimal charging parameter selection method which provides the best setpoint values for the control variables to achieve a pre-specified desired “useful cycle life” while attaining the fastest possible time-to-charge. The proposed optimal charging parameter selection method is illustrated via numerical results.

Biosensors, memristors and actuators in electrical networks of plants

Abstract: Electrical circuits connect biosensors and actuators in plants and trees. There are many electrochemical components and devices in plants created by nature. Memristors participate in the electrical signal transduction between phytosensors and actuators. Electrical processes play important roles in the physiology of plants, trees, fruits and seeds. Electrical form of energy has no entropy content that can be used to do work, information transfer, computing and analysis. These signals propagate along sophisticated electrical circuitry of plants consisting of many electrical components and cell computing system for decision-making processes. Action potentials are the mediators for intercellular and intracellular communication in response to environmental stresses.

Enhanced Equivalent Electrical Circuit Model of Lithium-Based Batteries Accounting for Charge Redistribution, State-of-Health, and Temperature Effects

Abstract: Accurate models capable to predict the dynamic behavior, and the state of charge of battery energy storage systems (BESSs) is a key aspect for the definition of model-based controls in electric vehicles and in power grid applications of these energy storage systems. In this context, this paper presents an enhanced electrical BESS model capable to accurately represent the effects of charge redistribution in lithium-based cells. In fact, this phenomenon is the main source of nonlinearity in the behavior of such devices. The improvement of the proposed model is achieved by a virtual dc current generator accounting for the internal charge transfer. The behavior of this virtual generator is inferred from experimental results describing the effects of the charge redistribution during different subphases, namely, charge, discharge, and rest phases. The proposed model, along with its parameter assessment, has been experimentally validated for: 1) two types of Li-ion chemistry; 2) aged cells; 3) different cell operating temperatures ranging from −20 °C up to 55 °C; and 4) a complex battery cell pack of 25-kWh rated energy.

Behavioral Device-Level Modeling of Modular Multilevel Converters in Real Time for Variable-Speed Drive Applications

Abstract: This paper presents the real-time hardware-in-the-loop (HIL) emulation of an induction machine (IM) driven by a modular multilevel converter (MMC) on the field-programmable gate array (FPGA). The insulated gate bipolar transistors and antiparallel diodes of the MMC are modeled with nonlinear static and dynamic characteristics to provide not only accurate system-level performance of the converter but also insight into the power losses under different operation conditions. Due to the large network size of the MMC, its solution in conjunction with the IM fifth-order model proved to be a significant computational challenge. Therefore, circuit partitioning based on the transmission line modeling is proposed, which introduced an interface to the electrical network for the IM as well as split the multiloop MMC into several smaller subcircuits in terms of matrix size, and consequently enabled a fully parallel implementation on the FPGA. Control strategies for the MMC and IM are also emulated in hardware, and due to the large latency difference between subcircuits and controllers, the overall system hardware design is divided into several layers, each having an independent time step ranging from 500 ns to $4~\mu \text{s}$ so as to attain the goal of real-time execution. A comparison of transient and steady-state results from the HIL emulation and offline simulation tools shows high accuracy of the modeling approach as well as the efficacy of proposed multiple time steps in achieving real time.

Equivalent Electrical Circuits of Thermoelectric Generators under Different Operating Conditions

Abstract: Energy harvesting has become a promising and alternative solution to conventional energy generation patterns to overcome the problem of supplying autonomous electrical systems. More particularly, thermal energy harvesting technologies have drawn a major interest in both research and industry. Thermoelectric Generators (TEGs) can be used in two different operating conditions, under constant temperature gradient or constant heat flow. The commonly used TEG electrical model, based on a voltage source in series with an electrical resistance, shows its limitations especially under constant heat flow conditions. Here, the analytical electrical modeling, taking into consideration the internal and contact thermal resistances of a TEG under constant temperature gradient and constant heat flow conditions, is first given. To give further insight into the electrical behavior of a TEG module in different operating conditions, we propose a new and original way of emulating the above analytical expressions with usual electronics components (voltage source, resistors, diode), whose values are determined with the TEG’s parameters. Note that such a TEG emulation is particularly suited when designing the electronic circuitry commonly associated to the TEG, to realize both Maximum Power Point Tracking and output voltage regulation. First, the proposed equivalent electrical circuits are validated through simulation with a SPICE environment in static operating conditions using only one value of either temperature gradient or heat flow. Then, they are also analyzed in dynamic operating conditions where both temperature gradient and heat flow are considered as time-varying functions.

Lithium-ion battery dynamic model for wide range of operating conditions

Abstract: In order to analyze the dynamic behavior of a Lithium-ion (Li-ion) battery and to determine their suitability for various applications, battery models are needed. An equivalent electrical circuit model is the most common way of representing the behavior of a Li-ion battery. There are different circuit models proposed and various techniques for parameterization of these models available in literature. Nevertheless, in this paper a second order equivalent circuit is proposed and the current pulse technique is used for its parameterization. This study shows results of extensive experimental characterization tests performed for a wide range of operating conditions (temperature, load current and state-of-charge) on a commercial available 13Ah high-power lithium titanate oxide battery cell. The obtained results were used to parametrize the proposed dynamic model of the battery cell. To assess the accuracy of the proposed dynamic model, simulation results are presented and compared against laboratory measurements, performed for different conditions.

Sub-cycle average models with integrated diodes for real-time simulation of power converters

Abstract: Real-time simulators for electrical circuits typically employ a fixed time-step solver, where the computation time determines the simulation step size. If forced-commutated power converters are simulated and the controlling PWM signals are sampled once per simulation step the simulation may become inaccurate as the pulses do not naturally coincide with the simulation steps. To improve the accuracy of the simulation results the PWM signal can be averaged over one simulation step and fed into an average model of the converter. In this paper, high-fidelity converter models are presented that can be controlled with instantaneous and averaged signals. The models are based on the time-average method using variable transformers. To obtain general applicability for real-time and offline simulations the average models have been extended with diodes to operate accurately under various conditions, such as continuous/discontinuous conduction mode, commutation blanking-time and rectifier operation of half-bridges.

Voltage stability assessment and identification of important nodes in power transmission network through network response structural characteristics

Abstract: Electrical power grids are often susceptible to voltage instability and have been a growing concern. In this study, the authors propose techniques based on network response structural characteristics for voltage stability assessment and for the identification of important nodes in electrical power grids. First, the network response structural characteristic indices (NRSCIs) which are inherent in the conventional power grids in terms of the Kirchhoff matrix is formulated. The eigenvalue decomposition (ED) technique is then applied to a submatrix of the Kirchhoff matrix to determine the topological strength of the electrical network graph. The vertex (node) that has a minimum eigenvalue is taken as the critical mode, from which its contributions to the entire graph is identified using the proposed network response structural characteristics theory participation factor (NRSCTPF). To demonstrate the magnitude of the concept formulated, the known degree centrality is modified in terms of the established NRSCI, which are then used to determine the important nodes of the network graph. The results obtained show that the proposed NRSCTPF and the degree centrality based on the NRSCI can be used for voltage stability assessment and identification of important nodes. The proposed approach is also less computationally intensive compared with the traditional approach.

PV Based Microgrid with Grid-Support Grid-Forming Inverter Control-(Simulation and Analysis)

Abstract: Microgrid (MG) is a small entity of electrical network which comprises of various Distributed Generation (DG) sources, storage devices, and group of loads in various classes. MG provides reliable and secure energy supply to the critical loads of communities while operating either in on-grid or off-grid mode. In this study, a coordinated power management control strategy for a typical low voltage (LV) MG network with integration of solar Photovoltaic (PV) and storage facility has been developed and analysed in Matlab-Simu-link software environment at various modes (on-grid, off-grid, and on-grid to off-grid transition) of MG operation. Solar PV and battery power inverters are considered as grid-support grid-forming (GsGfm) Voltage Source Inverter (VSI) with the implementation of modified droop and virtual output impedance control strategies. Proposed control strategy supports coordinated control operation between PV units and battery storage, equal power sharing among the DG sources, and smooth MG mode transition with regulation of voltage and frequency level in MG network. In addition, voltage and current THD level were analysed and verified as per the standard of AS4777.

Efficient quantum algorithms for analyzing large sparse electrical networks

Abstract: Analyzing large sparse electrical networks is a fundamental task in physics, electrical engineering and computer science. We propose two classes of quantum algorithms for this task. The first class is based on solving linear systems, and the second class is based on using quantum walks. These algorithms compute various electrical quantities, including voltages, currents, dissipated powers and effective resistances, in time poly(d,c,log(N),1/λ,1/e), where N is the number of vertices in the network, d is the maximum unweighted degree of the vertices, c is the ratio of largest to smallest edge resistance, λ is the spectral gap of the normalized Laplacian of the network, and e is the accuracy. Furthermore, we show that the polynomial dependence on 1/λ is necessary. This implies that our algorithms are optimal up to polynomial factors and cannot be significantly improved.

Automatic EMI Filter Design Through Particle Swarm Optimization

Abstract: The design of electrical filters for the suppression of electromagnetic interferences is a complex multiconstrained problem. The solution to such a problem aims to identify the suitable electrical circuit and components taking in consideration the nonidealities of the hardware as well as the parasitic phenomena. A customized optimization strategy is proposed for the automatic design of a ready-to-build filter solution. The design procedure integrates a circuital simulator and a library of electrical models to simulate the behavior of commercially available passive components. The obtained filter is designed to fit the end-user requirements (such as the common mode and the differential mode insertion losses) and the filter layout is automatically identified for simple prototyping on a printed circuit board. A selected set of filters have been simulated and developed to numerically and experimentally assess the effectiveness and show the flexibility of the proposed methodology.

Circuit synthesis of electrochemical supercapacitor models

Abstract: This paper considers the synthesis of RC electrical circuits from physics-based supercapacitor models that describe conservation and diffusion relationships. The proposed synthesis procedure uses model discretisation, linearisation, balanced model order reduction and passive network synthesis to form the circuits. Circuits with different topologies are synthesized from physical models. Because the synthesized impedance functions are generated by considering the physics, rather than from experimental fitting which may ignore dynamics, this work provides greater understanding of the physical interpretation of electrical circuits and will enable the development of more generalised circuits.

Hybrid Circuits with Nanofluidic Diodes and Load Capacitors

Abstract: The chemical and physical input signals characteristic of micro- and nanofluidic devices operating in ionic solutions should eventually be translated into output electric currents and potentials that are monitored with solid-state components. This crucial step requires the design of hybrid circuits showing robust electrical coupling between ionic solutions and electronic elements. We study experimentally and theoretically the connectivity of the nanofluidic diodes in single-pore and multipore membranes with conventional capacitor systems for the cases of constant, periodic, and white-noise input potentials. The experiments demonstrate the reliable operation of these hybrid circuits over a wide range of membrane resistances, electrical capacitances, and solution pH values. The model simulations are based on empirical equations that have a solid physical basis and provide a convenient description of the electrical circuit operation. The results should contribute to advance signal transduction and processing using nanopore-based biosensors and bioelectronic interfaces.

A Consistent Simulation of Electrothermal Transients in Accelerator Circuits

Abstract: Transient effects occurring in a superconducting accelerator circuit can be correctly simulated only if the models consistently account for the electrothermodynamic coupling between the magnets, the protection systems, and the remaining network. We present a framework based on the idea of cosimulation. The core component is a coupling interface exchanging information between the independent models. Within the framework, we simulate selected parts of a magnet and the electrical network, combining appropriately different commercial tools. This modularity gives the possibility of integrating new tools in the framework, to provide further insights on different physical domains as mechanics or fluid dynamics. The workflow is applied to the field-circuit coupling of an LHC main dipole magnet.

Analysis of electrical circuits including fractional order elements

Abstract: This paper deals with the analysis of electrical circuits with classical one-port elements including two novel defined one-port fractional order elements: fractional-order resistive-capacitive RC-α and fractional-order inductive RL-α element. The definitions and analytical relations between current, voltage and power of introduced fractional elements are provided. An example of fractional element realization via ladder electrical circuit composed of classical resistors, capacitors and/or inductors is presented. Several examples are analyzed to illustrate the behavior of electrical circuit with fractional order elements for different values of fractional order α including differentiator/integrator circuits as well as complex circuits without accumulated energy.

Hand Drawn Optical Circuit Recognition

Abstract: Electrical diagram is foundation of studies in electrical science. A circuit diagram convey many information about the system. Behind any device there are plenty of electrical ingredients which perform their specific tasks, today all the electrical software tools failed to effectively convert the information automatically from a circuit image diagram to digital form. Hence electrical engineers should manually enter all information into computers, and this process takes time and bring errors with high probability. Moreover, when the diagram is hand drawn, the problem is more complicated for any electrical analysis. Thus, in this paper we propose a new method using Artificial Neural Network (ANN) to make a machine that can directly read the electrical symbols from a hand drawn circuit image. The recognition process involves two steps: first step is feature extraction using shape based features, and the second one is a classification procedure using ANN through a back propagation algorithm. The ANN was trained and tested with different hand drawn electrical images. The results show that our proposal is viable and brings good performances.

A modeling and simulation of optimized interconnection between DC microgrids with novel strategies of voltage, power and control

Abstract: The interconnection between DC microgrids has been studied through the modeling and simulation of two DC microgrids and utility network with independent connection to each microgrid. Each microgrid has generation sources, storage source, electrical charges, two points of common coupling (one with the utility network and other with the neighboring microgrid) and a central controller. By performing the simulations and searching for new ways in which the interconnection can be made, the following contributions are reached: (a) although a nominal voltage is present on the DC microgrid bus, it becomes necessary to have three mini-voltage scales (one for the micro-sources, another for the storage sources and a third for AC/DC converter output that connects the utility supply and DC microgrid bus); (b) the power to avoid being heavily dependent on random variables requires temporary storage at the generation sources and that electrical loads define a very stable demand and clearance for certain period of time (of a few minutes), said period would be a new time scale of microgrid operation; (c) the cost associated with generation and storage sources must be optimized for the microgrids operation on the new unit of measurement and for which linear programming techniques have been used, and (d) it representing new coordination actions for tertiary control among central controllers of the microgrids. The new strategies of control, voltage and power will serve to propose and study new designs of: topologies of the electrical network, interconnection devices between microredes and other topics.

Fractional derivatives in electrical circuit theory – critical remarks

Abstract: A number of critical remarks related to the application of fractional derivatives in electrical circuit theory have been presented in this paper. Few cases have been pointed out that refer to observed in selected publications violations of dimensional uniformity of physical equation rules as well as to a potential impact on the Maxwell equations.