Nonlinear Voltage Research Articles

Wavelet analysis of a memristor emulated model proposed for compact fluorescent lamp operated systems

Compact fluorescent lamps (CFLs) are widely employed in lighting systems thanks to their energy efficient characteristics. In contrast to incandescent lamps, CFLs have highly non-linear current–voltage characteristics and exhibit harmonic distortions during their operation. Although nonlinearity and accelerated harmonic effects may cause disturbance in power networks, CFLs are frequently preferred due to their low energy consumption. In this study a test set-up is operated for investigating non-linear characteristics of commercially available CFLs. During these tests non-linear current and voltage waveforms of CFLs are analyzed via oscilloscope and compared with the proposed memristor emulator circuit output waveforms. The non-linear characteristics of CFLs are accurately modelled by proposed memristor emulator circuit, which has a tunable threshold property. To obtain proper comparison wavelet analysis is conducted for current waveforms of CFLs and memristor emulator circuit. The wavelet analysis is an efficient tool for processing non-linear signals, which are prone to display high frequency distortions. In addition to wavelet analysis, the Fourier Transform (FFT) characteristics and total harmonic distortion (THD) levels are also analyzed for correlation of CFLs and proposed memristor.

Magnetic Skyrmion as a Nonlinear Resistive Element: A Potential Building Block for Reservoir Computing

Inspired by the human brain, there is a strong effort to find alternative models of information processing capable of imitating the high energy efficiency of neuromorphic information processing. One possible realization of cognitive computing are reservoir computing networks. These networks are built out of non-linear resistive elements which are recursively connected. We propose that a skyrmion network embedded in frustrated magnetic films may provide a suitable physical implementation for reservoir computing applications. The significant key ingredient of such a network is a two-terminal device with non-linear voltage characteristics originating from single-layer magnetoresistive effects, like the anisotropic magnetoresistance or the recently discovered non-collinear magnetoresistance. The most basic element for a reservoir computing network built from "skyrmion fabrics" is a single skyrmion embedded in a ferromagnetic ribbon. In order to pave the way towards reservoir computing systems based on skyrmion fabrics, here we simulate and analyze i) the current flow through a single magnetic skyrmion due to the anisotropic magneto-resistive effect and ii) the combined physics of local pinning and the anisotropic magneto-resistive effect.

Mathematical modelling and parametric resonances of a nonlinear RLC series circuit

In order to study nonlinear parametric oscillations of a RLC series circuit consisting of a nonlinear resistor, a nonlinear inductor and a nonlinear capacitor subjected to mixed-frequency voltage, a class of nonlinear ordinary differential equations is generated. From this class, a generalised mixed Rayleigh-Lienard oscillator used to describe the steady-state oscillations is derived. Applying the method of multiple scales to this specific equation, six resonances states are obtained whose four cases of resonances such as Ω = 3 ω0, Ω = 5 ω0, Ω = 7 ω0 and 2Ω = ω0 are studied. The modulation equations in the amplitude and the phase of these four cases of resonances are determined. The corresponding frequency-response equations and stability analysis of steady-state solutions are investigated. The frequency response curves and stability analysis of each steady-state solution are plotted. As results, bistability, hysteresis, bifurcation and jump phenomena are obtained. Finally, some effects of the nonlinear damping parameters and excitation voltage amplitudes are investigated numerically and results are presented graphically and discussed.

Mathematical modelling and parametric resonances of a nonlinear RLC series circuit

In order to study nonlinear parametric oscillations of a RLC series circuit consisting of a nonlinear resistor, a nonlinear inductor and a nonlinear capacitor subjected to mixed-frequency voltage, a class of nonlinear ordinary differential equations is generated. From this class, a generalised mixed Rayleigh-Liénard oscillator used to describe the steady-state oscillations is derived. Applying the method of multiple scales to this specific equation, six resonances states are obtained whose four cases of resonances such as Ω = 3 ω0, Ω = 5 ω0, Ω = 7 ω0 and 2Ω = ω0 are studied. The modulation equations in the amplitude and the phase of these four cases of resonances are determined. The corresponding frequency-response equations and stability analysis of steady-state solutions are investigated. The frequency response curves and stability analysis of each steady-state solution are plotted. As results, bistability, hysteresis, bifurcation and jump phenomena are obtained. Finally, some effects of the nonlinear damping parameters and excitation voltage amplitudes are investigated numerically and results are presented graphically and discussed.

Investigation of mechanochemical green synthesis of exfoliated graphite nano-platelets on conductivity and its nonlinear properties based on zinc oxide

We investigated the effect of water and its amount on conductivity of exfoliated graphite nano-platelets (XGnP) under mechanochemical methods. Results showed that, by increasing water content in the system, conductivity of the product increased from 109 to 219 S/cm and the nonlinear coefficient decreased from 14.5 to 10.5. Electrophysical studies of the samples prepared from zinc oxide-XGnP-high density polyethylene showed strong dependency of nonlinearity and breakdown voltage to the XGnP and zinc oxide content in the mixture. Accordingly, by increasing the XGnP content from 1 to 4% at a constant zinc oxide content (80%), the nonlinear coefficient decreased from 10.5 to 4.1.

Solving OPF using linear approximations: fundamental analysis and numerical demonstration

Due to the unique advantages in computational robustness and convergence, the linear approximation approach is and will remain to be an important method to solve the optimal power flow (OPF) problem, especially for industrial applications. The DC power flow method, which is currently used in the majority of power industries, is the representative. Many studies extend the DC power flow method by including voltage magnitude, reactive power, and losses. This study provides a detailed analysis and breakdown investigation of existing linear approximations of the OPF problem. The formulation and accuracy of existing linear approximations are compared. Taking advantage of the decoupled formulation of linear approximations, the property of power flow equations is illustrated from a new perspective. Why reactive power flow equations are hard to linearise is explained theoretically. The numerical performance of existing linear approximations is demonstrated in IEEE and Polish test systems. Evidence from the theoretical analysis and numerical studies shows that the accuracy of linear approximations could be substantially improved using a mathematical transformation of the non-linear voltage magnitude term. This finding provides a new research direction for solving the OPF problem using linear approximations.

Reduced-Order Averaged Model and Non-Linear Control of a Dual Active Bridge DC-DC Converter for Aerospace Applications

The paper presents a generalized averaged model and a reduced-order averaged model of a dual active bridge bidirectional dc-dc converter, taking into account parasitic components. On the basis of these models, a particular non-linear voltage control scheme is suggested using an integral sliding mode control approach for driving the adopted single phase shift modulation technique. The main operative conditions of the converter have been examined through extensive simulations. The numerical results confirm the effectiveness of the proposed strategy. The suggested control exhibits a strong robustness against parameters variations and disturbances and presents a very simple implementation.

Optimal sizing of distribution network transformers considering power quality problems of non-linear loads

Transformers are important equipment in distribution networks which their optimal siting and sizing is one the important issues in planning and operation of distribution networks. In traditional methods, the optimal capacity of transformers is determined considering the average load consumption and temperature. In the presence of non-linear loads, the current and voltage distortions are increased which increase the power losses of transformers, increase their temperature and decrease their lifetime. Therefore, in this study, a new method is proposed to determine the optimal size of distribution transformers in the presence of non-linear loads. To evaluate the effectiveness of the proposed method, it is applied on two commercial complexes with high non-linear loads.

Comparative Analysis of Various MPPT-Techniques for Optimization of Solar-PVEC System

<p>The paper aims to provide a comprehensive analysis of various MPPT Technique under various environmental condition. The photovoltaic array having non-linear power voltage characteristic and under non-uniform irradiances. It shows a many peaks which have many local peaks and one global peak. For getting a global peak among all local peaks, MPPT play an important role in PV system. Therefore a technique like maximum power point tracking (MPPT) is required to optimize the performance. Here the comparison of hill climbing perturb and observe (P&O) algorithm technique, incremental and conductance (I&C) control algorithm, the drift free P&O algorithm technique are discussed in detail with simulation and simultaneously some other intelligent control techniques comparison are given briefly which help the researcher to ease in selecting the appropriate algorithm for specific application.</p>

Using Volt-Second Sensing to Directly Improve Torque Accuracy and Self-Sensing at Low Speeds

As a result of dead-time, device on-state voltage drop, dc bus voltage measurement error, etc., volt-second errors degrade precise control of torque and flux linkage, particularly at low speeds. This is true for deadbeat-direct torque and flux control (DB-DTFC), which directly manipulates the volt-second vector sourced by inverters as well as for indirect field oriented control (IFOC) drives. This paper introduces a real-time sensing scheme to measure the motor terminal volt-second vectors for each switching period with negligible phase lag. Based on the volt-second sensing, a model reference adaptive system (MRAS)-based approach is developed to decouple the volt-second errors from inverter nonlinearity and dc bus voltage fluctuation and measurement error. By delivering an accurate volt-second vector for each switching period, torque and flux control accuracy, self-sensing performance and parameter estimation accuracy are significantly enhanced.

An improved optimization technique for estimation of solar photovoltaic parameters

Abstract The nonlinear current vs voltage (I-V) characteristics of solar PV make its modelling difficult. Optimization techniques are the best tool for identifying the parameters of nonlinear models. Even though, there are different optimization techniques used for parameter estimation of solar PV, still the best optimized results are not achieved to date. In this paper, Wind Driven Optimization (WDO) technique is proposed as the new method for identifying the parameters of solar PV. The accuracy and convergence time of the proposed method is compared with results of Pattern Search (PS), Genetic Algorithm (GA), and Simulated Annealing (SA) for single diode and double diode models of solar PV. Furthermore, for performance validation, the parameters obtained through WDO are compared with hybrid Bee Pollinator Flower Pollination Algorithm (BPFPA), Flower Pollination Algorithm (FPA), Generalized Oppositional Teaching Learning Based Optimization (GOTLBO), Artificial Bee Swarm Optimization (ABSO), and Harmony Search (HS). The obtained results clearly reveal that WDO algorithm can provide accurate optimized values with less number of iterations at different environmental conditions. Therefore, the WDO can be recommended as the best optimization algorithm for parameter estimation of solar PV.

A nonlinear electromagnetics model of an asymmetrically-driven, low pressure capacitive discharge

It is well-known that standing waves having radially center-high voltage profiles exist in high frequency driven capacitive discharges. Capacitive sheaths can also nonlinearly excite driving frequency harmonics near the series resonance that can be spatially near-resonant, and therefore enhance the on-axis power deposition. The powered-electrode/plasma/grounded-electrode sandwich structure of an asymmetrically excited cylindrical discharge forms a three electrode system in which both z-symmetric and z-antisymmetric radially propagating wave modes can exist. We develop a nonlinear electromagnetics model for this system with radially- and time-varying sheath widths, incorporating both symmetric and antisymmetric modes, and the plasma skin effect. Waves generated in the electrostatic wave limit are also treated. The discharge is modeled as a uniform density bulk plasma with either homogeneous or Child law sheaths at the electrodes, incorporating their nonlinear voltage versus charge relations. The model includes a finite power source resistance and a self-consistent calculation of the dc bias voltages. The resulting set of nonlinear partial differential equations is solved numerically to determine the symmetric and antisymmetric mode amplitudes and the nonlinearly-excited radially-varying harmonics. Two examples driven at lower frequency (30 MHz) or at higher frequency (60 MHz) are examined. The first case displays the excited dominant ninth harmonic near the series resonance frequency with the fundamental frequency having a weak standing wave. The higher frequency case shows a more obvious standing wave effect, enhanced by the nonlinear harmonics. The symmetric and antisymmetric modes are of similar amplitudes over the driving electrode, summing to give a larger bottom sheath.

Nonlinear data-driven identification of polymer electrolyte membrane fuel cells for diagnostic purposes: A Volterra series approach

In this work, a data-driven identification method, based on polynomial nonlinear autoregressive models with exogenous inputs (NARX) and the Volterra series, is proposed to describe the dynamic and nonlinear voltage and current characteristics of polymer electrolyte membrane fuel cells (PEMFCs). The structure selection and parameter estimation of the NARX model is performed on broad-band voltage/current data. By transforming the time-domain NARX model into a Volterra series representation using the harmonic probing algorithm, a frequency-domain description of the linear and nonlinear dynamics is obtained. With the Volterra kernels corresponding to different operating conditions, information from existing diagnostic tools in the frequency domain such as electrochemical impedance spectroscopy (EIS) and total harmonic distortion analysis (THDA) are effectively combined. Additionally, the time-domain NARX model can be utilized for fault detection by evaluating the difference between measured and simulated output. To increase the fault detectability, an optimization problem is introduced which maximizes this output residual to obtain proper excitation frequencies. As a possible extension it is shown, that by optimizing the periodic signal shape itself that the fault detectability is further increased.

High-Performance Adaptive Torque Control for an IPMSM With Real-Time MTPA Operation

In this paper, a high-performance torque control scheme of an interior permanent magnet synchronous machine (IPMSM) is introduced, which focuses on both steady state and transient torque dynamics of the IPMSM under the maximum torque per ampere (MTPA) condition. For the proposed control scheme with model-based torque correction, an accurate and efficient torque control with robust torque response can be achieved for the MPTA operation. Global stability and performance of the proposed torque control scheme are theoretically guaranteed. The current limitation of the IPMSM is easily handled without anti-windup and without degrading the torque dynamics or stability even the torque demand is beyond the maximum reachable torque. Implementation issues of the proposed control scheme to the real IPMSM plant with parameter variation are discussed. With the compensation of the linear and nonlinear inverter voltage drop, a robust and accurate torque response for the real-time MTPA operation can be achieved by an adaptive current control and online parameter estimation. The simulation and experimental results validate the safety and high performance of the proposed torque control scheme.

Implementation of artificial neural network based controller for a five-level converter based UPQC

To reduce the cost and complexity of the system, ANN controller is proposed for a five-level converter based UPQC which eliminates mathematical operations such as a-b-c to d-q-0 transformation and complex controllers such as DSP’s and FPGA’s,. This paper proposes a five-level DCC based UPQC with ANN based controller and its performance is tested with nonlinear unbalanced loads and harmonic supply voltage. In addition, voltage related issues such as sag and swell are also considered. ANN control scheme trained with Levenberg-Marquardt backpropagation algorithm is used in this paper for effective generation of reference signals and also for maintaining desired dc link capacitor voltage. Simulations are carried out in Matlab/Simulink software with two-level UPQC, and three-level and five-level diode clamped converter based UPQC using SRF based control and ANN control schemes. The results showed better performance with the proposed concept and are discussed in this paper. The response of dc link capacitor voltage with two-level, three-level and five-level converter based UPQC and its effect on supply currents are discussed. Comparison of %THD in load voltage and supply current with two-level, three-level and five-level converter based UPQC using SRF based control and ANN control schemes is presented to show the superiority of the proposed controller.

A Low Power Bandgap Voltage Reference with Nonlinear Voltage Curvature Compensation

The reference voltage source is the main part both in the analog and mixed-signal integrated circuits. A good reference voltage source can provide a stable voltage for the circuit, so that the system can work stable accurately. This paper describes a low power bandgap voltage reference with second order compensated, which utilizes a Kujik bandgap reference as the first order curvature correction and adding second order non-linear voltage compensation. The presented circuit is implemented in a 0.18μm CMOS technology, and the voltage supply (VDD) is 1.8V. Piecewise curvature compensation is employed to reduce the temperature coefficient of the bandgap reference from 465ppm/°C to 5.5ppm/°C, with a temperature range –45~85°C. The circuit works under the condition of 27 °C, the output of the reference voltage is 1.207 V. The total current consumption of the whole bandgap is 11.69μA, the total area of the layout is 0.10132mm2 and the power supply rejection ratio is -63dB.

Harmonic Suppression of Shunt Hybrid Filter Using LQR-PSO based

In linear quadratic regulator (LQR), two different weighting matrices play an important role in presenting the performance of this controller. Instead of using classic common approach, which is trial and error method, this study proposes a particle swarm optimization (PSO) algorithm to track the best solution of the weighting matrices. The proposed algorithm is tested on shunt hybrid active power filter (APF) to mitigate the harmonic contents in voltage and current signals in a nonlinear load system. The modeling work of this proposed system is simulated using MATLAB/Simulink software. From the simulation, the obtained results proved that using PSO in tuning the LQR controller produce smoother nonlinear voltage and current signals. In fact, the amount of current to be injected into network can be reduced up to 95%. Besides, less time is consumed during searching the optimum weighting matrices using the proposed approach.

Теоретичне обгрунтування методів реалізації вимог нормативної бази з якості електроенергії

. У наш час важко уявити собі своє життя без електрики. У квартирі, заміському будинку, офісі від наявності та якості електроенергії залежить все. На жаль, коли електроенергію стабільно подається в наші будинки і квартири, це ще не означає, що розрахункові параметри електроенергії саме такі, які необхідні для живлення побутової техніки та різних електроприладів, від яких безпосередньо залежить якість нашого життя, а іноді і саме життя. У даній роботі проведено аналіз проблематики дослідження та контролю якості електроенергії у мережах постачання споживачів. Поставлено головні задачі, які полягають у встановленні причин погіршення якості електроенергії та визначенні місця появи негативного процесу у мережі. Виходячи із класифікації видів навантажень та споживання ними електроенергії, запропоновані розвиток методики виконання вимірювань показників якості електроенергії та нові показники, що дозволять отримати додаткову інформацію для розв’язання вказаних задач.

POD-DEIM reduction of computational EMG models

This article presents an application of model order reduction techniques to a numerical model computing electromyographic (EMG) signals. The considered EMG model is a combination of the extracellular bidomain equation with a parameterized nonlinear membrane voltage source. Key ingredients for the proposed reduction methodology are Galerkin projection via proper orthogonal decomposition and application of the discrete empirical interpolation method to the nonlinear source term. The computational efficiency of the approach is demonstrated by numerical examples comparing the reduced model to the full (non-reduced) model. In detail, a high-fidelity model of ≈100000 degrees of freedom is successfully reduced by several orders of magnitude whilst preserving accuracy and gaining a computational speedup of up to 180. Thus, using the proposed method a realistic number of muscle fibres and motor units can be considered in numerical EMG simulations, which is not feasible using full models due to their high computational cost.

Finite-Element Analysis of Coupled Electro-Thermal Problems With Strong Scale Separation

We present a finite-element analysis of the coupled electro-thermal behavior of a mm $^2$ -sized power DMOS device, with a focus on resolving µm-sized structures. For a reliable power technology, the predictions of current and temperature distributions under self-heating are vital for reaching long device lifetime. Two aspects of our approach are unique: First, we have integrated the active region of the DMOS into the finite-element program code as a nonlinear voltage and temperature dependent tripole , incorporating local biasing and temperature conditions. Second, to model small features like defects or process-induced imperfections in sufficient detail, we use the Nitsche -type nonmatching grid technique to include the substantially finer meshed microscale geometry. This allows us to study very local changes in temperature and biasing conditions, which are normally not accessible. The methodology is applied to a state-of-the-art power technology device with integrated current sensor to validate the methodology. Good agreement is found between results and experiments.