Showing papers on "Electrical network published in 2013"

Assessment and Optimization of the Transient Response of Proportional-Resonant Current Controllers for Distributed Power Generation Systems

Abstract: The increasing number of distributed power generation systems (DPGSs) is changing the traditional organization of the electrical network. An important part of these DPGSs is based on renewable energy sources. In order to guarantee an efficient integration of renewable-based generation units, grid codes must be fulfilled. Their most demanding requirements, such as low-voltage ride-through and grid support, need a really fast transient response of the power electronics devices. In this manner, the current controller speed is a key point. This paper proposes a methodology to assess and optimize the transient response of proportional-resonant current controllers. The proposed methodology is based on the study of the error signal transfer function roots by means of pole-zero plots. Optimal gains are set to achieve fast and nonoscillating transient responses, i.e., to optimize the settling time. It is proved that optimal gain selection results from a tradeoff between transients caused by reference changes and transients caused by changes at the point of common coupling. Experimental results obtained by means of a three-phase voltage source converter prototype validate the approach. Short transient times are achieved even when tests emulate very demanding realistic conditions: a +90° phase-angle jump in the current reference and a “type C” voltage sag at the point of common coupling.

Voltage stabilization in microgrids via quadratic droop control

Abstract: Motivated by the growing interest in energy technology and smart grid architectures, we consider the problem of voltage stability and reactive power balancing in low-voltage electrical networks equipped with DC/AC inverters (“microgrids”). It is generally believed that high-voltage equilibria of such networks are stable, but the locations of these equilibria are unknown, as is the critical network load where stability is lost. Inspired by the “control by interconnection” paradigm developed for port-Hamiltonian systems, we propose a novel droop-like inverter controller which is quadratic in the local voltage magnitude. Remarkably, under this controller the closed-loop network is again a well-posed electrical circuit. We find that the equilibria of the quadratic droop-controlled network are in exact correspondence with the solutions of a reduced power flow equation. For general network topologies, we study some simple yet insightful solutions of this equation, and for the frequently-encountered case of a parallel microgrid, we present a concise and closed-form condition for the existence of an exponentially stable high-voltage network equilibrium. Our condition establishes the existence of a critical inductive load for the network, which depends only on the network topology, admittances, and controller gains. We compare and contrast our design with the conventional droop controller, investigate the relationship between the two, and validate the robustness of our design through simulation.

Control of PV generation systems using the synchronous power controller

Abstract: The high penetration of distributed generation, as PV or wind power, has forced the Transmission System Operators (TSOs) to set restrictive requirements for the operation of such systems. As it can be extracted from the forthcoming grid codes drafts, the future distributed generation systems will be requested to have the equivalent performance of a synchronous generator, which is seen from the TSOs as the only solution if a massive integration of renewable in the electrical network should be achieved. In this paper a method for controlling PV grid connected power converters as a synchronous generator, namely Synchronous Power Controller (SPC), is presented. As a difference with previous works this method permits to take advantage of emulating the synchronous behavior meanwhile it is able to get rid of its drawbacks. The main concept of the SPC, as well as some simulation and experimental results will be shown in this paper considering a PV power plant as a study case.

Control of grid-connected power converters based on a virtual admittance control loop

Abstract: The connection of electronic power converters to the electrical network is increasing mainly due to massive integration of renewable energy systems. However, the electrical dynamic performance of these converters does not match the behavior of the network, which is mainly formed by generation facilities based on big synchronous generation systems. Depending on the desired electrical operation mode different control structures can be implemented in the converters in order to get adapted with the grid conditions. However, changing between different control structures and operation is not an optimal solution, as the resulting system results complex and is not highly robust. As an alternative, this paper presents a new control technique for grid connected power converters based on the concept of virtual admittance. The proposed control permits to emulate the electrical performance of generation facilities based on classical synchronous generators with a power converter, with no need of implementing different control structures, giving rise to a system that provides a friendly and robust operation with the network.

Online SOC and SOH estimation for multicell lithium-ion batteries based on an adaptive hybrid battery model and sliding-mode observer

Abstract: This paper proposes an adaptive hybrid battery model-based high-fidelity state of charge (SOC) and state of health (SOH) estimation method for rechargeable multicell batteries. The hybrid battery model consists of an enhanced Coulomb counting algorithm for SOC estimation and an electrical circuit battery model. A variable-length sliding window least squares (VSWLS)-based online parameter identification algorithm is designed to estimate the electrical parameters of the electrical battery model, which are then used as the parameters of an adaptive discrete-time sliding-mode observer (ADSMO) for terminal and open-circuit voltage estimation of a battery cell. The error of the SOC estimated from the enhanced Coulomb counting algorithm is then corrected by using the SOC obtained from the ADSMO-estimated open-circuit voltage. This leads to an accurate, robust real-time SOC estimation. In addition, the maximum capacity of the cell is estimated to determine the SOH of the cell. The proposed method is validated by simulation and experimental results for a four-cell cylindrical lithium-ion battery pack.

Types-1 and -2 fuzzy logic controllers-based shunt active filter I d -I q control strategy with different fuzzy membership functions for power quality improvement using RTDS hardware

Abstract: This research paper proposes the shunt active filter (SHAF), which is used to improve the power quality of the electrical network by mitigating the harmonics with the help of Types-1 and -2 fuzzy logic controllers (Types-1 and -2 FLC) using different fuzzy membership functions (MFs). To carry out this analysis, active and reactive current (I d -I q ) control strategy is chosen. Threephase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the proposed control strategy has been evaluated in terms of harmonic mitigation and DC-link voltage regulation under various source conditions. To maintain DC-link voltage constant and to generate the compensating reference currents, the authors have developed Types-1 and -2 FLC with different fuzzy MFs (trapezoidal, triangular and Gaussian). The I d -I q control strategy with proposed Type-2 FLC is able to eliminate the uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed real-time results using real-time digital simulator are presented to support the feasibility of proposed control strategy.

Synchronization of Nonlinear Circuits in Dynamic Electrical Networks with General Topologies

Abstract: Sufficient conditions are derived for global asymptotic synchronization in a system of identical nonlinear electrical circuits coupled through linear time-invariant (LTI) electrical networks. In particular, the conditions we derive apply to settings where: i) the nonlinear circuits are composed of a parallel combination of passive LTI circuit elements and a nonlinear voltage-dependent current source with finite gain; and ii) a collection of these circuits are coupled through either uniform or homogeneous LTI electrical networks. Uniform electrical networks have identical per-unit-length impedances. Homogeneous electrical networks are characterized by having the same effective impedance between any two terminals with the others open circuited. Synchronization in these networks is guaranteed by ensuring the stability of an equivalent coordinate-transformed differential system that emphasizes signal differences. The applicability of the synchronization conditions to this broad class of networks follows from leveraging recent results on structural and spectral properties of Kron reduction---a model-reduction procedure that isolates the interactions of the nonlinear circuits in the network. The validity of the analytical results is demonstrated with simulations in networks of coupled Chua's circuits.

Directly writing resistor, inductor and capacitor to composite functional circuits: a super-simple way for alternative electronics.

Abstract: Background The current strategies for making electronic devices are generally time, water, material and energy consuming. Here, the direct writing of composite functional circuits through comprehensive use of GaIn10-based liquid metal inks and matching material is proposed and investigated, which is a rather easy going and cost effective electronics fabrication way compared with the conventional approaches. Methods Owing to its excellent adhesion and electrical properties, the liquid metal ink was demonstrated as a generalist in directly making various basic electronic components such as planar resistor, inductor and capacitor or their combination and thus composing circuits with expected electrical functions. For a precise control of the geometric sizes of the writing, a mask with a designed pattern was employed and demonstrated. Mechanisms for justifying the chemical components of the inks and the magnitudes of the target electronic elements so as to compose various practical circuits were disclosed. Results Fundamental tests on the electrical components including capacitor and inductor directly written on paper with working time up to 48 h and elevated temperature demonstrated their good stability and potential widespread adaptability especially when used in some high frequency circuits. As the first proof-of-concept experiment, a typical functional oscillating circuit including an integrated chip of 74HC04 with a supply voltage of 5 V, a capacitor of 10 nF and two resistors of 5 kΩ and 1 kΩ respectively was directly composed on paper through integrating specific electrical elements together, which presented an oscillation frequency of 8.8 kHz. Conclusions The present method significantly extends the roles of the metal ink in recent works serving as only a single electrical conductor or interconnecting wires. It opens the way for directly writing out complex functional circuits or devices on different substrates. Such circuit composition strategy has generalized purpose and can be extended to more areas, even daily pervasive electronics.

Resistance-Based Performance Analysis of the Consensus Algorithm over Geometric Graphs

Abstract: The performance of the linear consensus algorithm is studied by using a linear quadratic (LQ) cost. The objective is to understand how the communication topology influences this algorithm. This is achieved by exploiting the analogy between Markov chains and electrical resistive networks. Indeed, this allows us to uncover the relation between the LQ performance cost and the average effective resistance of a suitable electrical network and, moreover, to show that if the communication graph fulfills some local properties, then its behavior can be approximated by that of a grid, which is a graph whose associated LQ cost is well known.

Modeling of Switched Reluctance Linear Launcher

Abstract: A nonlinear simulation model of switched reluctance linear launcher drive based on MATLAB platform is presented in this paper. It consists of a three-phase 6/4 structure simple side switched reluctance linear motor, a three-phase asymmetric bridge power converter, and a closed-loop velocity controller, which is integrated with the magnetization curves of the switched reluctance linear motor obtained by the two-dimension finite-element electromagnetic field calculation, the nonlinear electrical network model of the power converter, and the excitation/commutation/velocity control algorithms. Those include mover relative position calculation module, controller module, power converter module, phase winding modules, and velocity calculation module. The simulated phase current waveforms and velocity curves agree well with the tested phase current waveforms and velocity curves experimentally. It is shown that the proposed nonlinear simulation model of the three-phase 6/4 structure switched reluctance linear launcher system is valid.

Formalization of Laplace Transform Using the Multivariable Calculus Theory of HOL-Light

Abstract: Algebraic techniques based on Laplace transform are widely used for solving differential equations and evaluating transfer of signals while analyzing physical aspects of many safety-critical systems. To facilitate formal analysis of these systems, we present the formalization of Laplace transform using the multivariable calculus theories of HOL-Light. In particular, we use integral, differential, transcendental and topological theories of multivariable calculus to formally define Laplace transform in higher-order logic and reason about the correctness of Laplace transform properties, such as existence, linearity, frequency shifting and differentiation and integration in time domain. In order to demonstrate the practical effectiveness of this formalization, we use it to formally verify the transfer function of Linear Transfer Converter (LTC) circuit, which is a commonly used electrical circuit.

Analysis on the time and frequency domain for the RC electric circuit of fractional order

Abstract: This paper provides an analysis in the time and frequency domain of an RC electrical circuit described by a fractional differential equation of the order 0 < α≤ 1. We use the Laplace transform of the fractional derivative in the Caputo sense. In the time domain we emphasize on the delay, rise and settling times, while in the frequency domain the interest is in the cutoff frequency, the bandwidth and the asymptotes in low and high frequencies. All these quantities depend on the order of differential equation.

An automated framework for generating variable-accuracy battery models from datasheet information

Abstract: Models based on an electrical circuit equivalent have become the most popular choice for modeling the behavior of batteries, thanks to their ease of co-simulation with other parts of a digital system. Such circuit models are actually model templates: the specific values of their electrical elements must be derived by the analysis of the specific battery devices to be modeled. This process requires either to measure the battery characteristics or to derive them from the datasheet. In the latter case, however, very often not all information are available and the model fitting becomes then unfeasible. In this paper we present a methodology for deriving, in a semi-automatic way, circuit equivalent battery models solely from data available in a battery datasheet. In order to account for the different amount of information available, we introduce the concept of “level” of a model, so that models with different accuracy can be derived depending on the available data. The methodology requires only minimal intervention by the designer and it automatically generates MATLAB models once the required data for the corresponding model level are transcribed from the datasheet. Simulation results show that our methodology allows to accurately reconstruct the information reported in the datasheet as well as to derive missing ones.

A Voltage-Behind-Reactance Model of Five-Phase Induction Machines Considering the Effect of Magnetic Saturation

Abstract: Five-phase induction machines are generally modeled using multiple dq planes or using a phase variable model. This paper considers modeling five-phase induction machines using a voltage-behind-reactance (VBR) configuration. This configuration lends itself suitable for time-domain circuit-based simulators as the MATLAB/Simulink SimPowerSystems (SPS) toolbox. The stator electrical dynamics are represented in five-phase coordinates, while the rotor electrical circuit is modeled using rotor flux linkage as the state variable and expressed in the dq stator reference frame. The VBR model is equivalent to a conventional dq model; however, it facilitates the connection of an external inductance without affecting numerical accuracy and calculation efficiency. It also facilitates the simulation of different winding connections, series-connected multimotors, and open phase(s) conditions. The model is, first, derived for a magnetically linear system and then it is extended to include the effect of magnetic saturation. The flux correction method is used to represent the effect of magnetic saturation with a simple modification to represent the effect of cross coupling between fundamental and third sequence planes due to saturation effect. The dynamic cross saturation is considered by adding compensating terms that depend on magnetizing inductance variation. The proposed model is experimentally verified using a prototype 1.5-hp five-phase induction machine under different operating conditions.

Non-stationary multi-frequency vibration energy harvesting with tunable electrical impedance

Abstract: The present application relates to energy harvesting. More particularly, the present application relates to harvesting energy from non-stationary, multi-frequency mechanical vibrations using a tunable electrical circuit.

Equivalent Electrical Model of a Ferrite Core Inductor Excited by a Square Waveform Including Saturation and Power Losses for Circuit Simulation

Abstract: We propose a model of an equivalent electrical circuit specifically designed for a ferrite inductor excited by a nonsinusoidal waveform valid for use in an electronic circuit simulator. We estimate the model parameters by means of Finite Elements in 2-D which leads to significant computational advantages over the 3-D model. We carry out the validation of the procedure for an RM14/I core by comparing the experimental and simulated output waveforms obtained at different frequencies and levels of excitation from the linear to the saturation regions. In addition, we consider the effect of power losses in the core.

Real-time state of charge and electrical impedance estimation for lithium-ion batteries based on a hybrid battery model

Abstract: This paper proposes a real-time state of charge (SOC) and electrical impedance estimation method for lithium-ion batteries based on a hybrid battery model. The hybrid battery model consists of an enhanced Coulomb counting algorithm for SOC estimation and an electrical circuit battery model. A particle swarm optimization (PSO)-based online parameter identification algorithm is designed to estimate the electrical impedances and open-circuit voltage of the electrical circuit battery model. A SOC compensator is designed to correct the error of the Coulomb counting-based SOC estimation, leading to a closed-loop, accurate, robust real-time SOC estimation. The proposed method is validated by using experimental data collected from a battery tester for a polymer lithium-ion battery cell. The proposed method is applicable to other types of electrochemical battery cells.

Modeling of Li $_{x}$ FePO $_{4}$ Cathode Li-Ion Batteries Using Linear Electrical Circuit Model

Abstract: It is demonstrated that a physical-based equivalent electrical circuit could be developed based on electrochemical impedance spectroscopy (EIS) to describe electrochemical performance of a commercial Li1-xPO4-cathode, Li-ion cell. This model uses only EIS modeling and Fourier transform techniques to provide reasonably accurate voltage performance characteristics while providing insight into the physical processes at work in the cell.

Method and apparatus for controlling operations and signaling at times dependent on clock, calendar and geographic location

Abstract: Techniques are provided for inhibiting changes in the operational state of electrical circuits for lights, appliances and other devices by controlling the effect of manual actuation of an electrical switch in an electrical circuit. A normal mode is established in which manual actuation of the switch effects a change in a state of current flow in the circuit. An alternative holiday mode is also established in which manual actuation of the switch has no effect on current flow in the circuit. Automatic switching occurs between the normal mode and the holiday mode at specific times corresponding to specific events dependent on the time of year, a time of day and a geographic location of the circuit.

Positive fractional linear electrical circuits

Abstract: The positive fractional linear systems and electrical circuits are addressed. New classes of fractional asymptotically stable and unstable electrical circuits are introduced. The Caputo and Riemann-Liouville definitions of fractional derivatives are used to analysis of the positive electrical circuits composed of resistors, capacitors, coils and voltage (current) sources. The positive fractional electrical and specially unstable different types electrical circuits are analyzed. Some open problems are formulated.

Electrical energy management and monitoring system, and method

Abstract: A system and method are provided for managing electrical power consumption by individual electrical circuits in a building. The system includes a power control device in electrical communication with a multi-circuit power infeed and a multi-circuit power output, each of which includes at least two electrical conductors on separate circuits. The power control device includes respective electrical switches associated with the conductors of the power infeed and power output, an electronic communications module, and a computer processor in communication with the switches and the communications module. The processor is operable to open and close the electrical switches independently, in response to an occupancy signal and/or a trigger or scheduled event stored by the power control device. When a period of non-use is detected or anticipated, the power control device de-energizes one or more circuits, to limit unnecessary energy consumption within the system. A receptacle-level power control is also disclosed.

Simulation of Higher-Order Electrical Circuits with Stochastic Parameters via SDEs

Abstract: The paper deals with a technique for the simulation of higher-order electrical circuits with parameters varying randomly. The principle consists in the utilization of the theory of sto ...

On-line inter-turn short-circuit detection in permanent magnet synchronous generators

Abstract: This paper focus on inter-turn short-circuit detection in Permanent Magnet Synchronous Generators (PMSG). Inter-turn short-circuit current are among the most critical in the PMSG. For safety considerations, a fast detection is required when a fault occurs. In this work, a fault indicator for on-line diagnosis is proposed. Based on a faulty PMSG model expressed in Park's reference frame, the number of short-circuited turns is estimated using Extended Kalman Filter (EKF). Simulation and experimental results are provided to demonstrate the quickness and the robustness of the fault indicator with regards to various operating points on an electrical network.

An electrical circuit for performance analysis of polymer electrolyte fuel cell stacks using electrochemical impedance spectroscopy

Abstract: In this study, a new electrical equivalent circuit is developed to evaluate the performance of polymer electrolyte fuel cell (PEFC) stacks using electrochemical impedance spectroscopy (EIS). Experimental EIS measurements were carried out in an open-cathode PEFC stack to validate the new electrical equivalent circuit. The electrical equivalent circuit developed in the authors’ previous study, which simulates the impedance response of a single PEFC, is applied to EIS measurements carried out in the open-cathode PEFC stack. However, it cannot reproduce EIS measurements with positive imaginary components at low frequencies. Thus, in this study, the electrical equivalent circuit is modified by adding electrical components which represent intermediate adsorbed species in a two-step electrochemical reaction as reported in the literature. The results show that the new electrical equivalent circuit can accurately reproduce the experimental EIS measurements and can give an insight into the factors that limit the performance of the PEFC stack. This new electrical equivalent circuit can enable an assessment of the state of health and performance of the fuel cell stacks.