Nonlinear Harmonics Research Articles

Non-linear harmonics in EIS of batteries with lithium anodes: Proper controls and analysis

Non-linear Harmonic Analysis is used to investigate the distortions accompanying the Electrochemical Impedance Spectroscopy (EIS) measurements. The distortions emerge from non-linearity and non-stationarity due to the underlying redox reactions as well as the capacitance. Identifying each response and its source is crucial to correlate the obtained harmonics to their corresponding electrochemical processes. In this study, we identify the distortions of Galvanostatic-EIS measurements of Lithium Primary Batteries by means of comparing mathematical simulations and experimental measurements. The simulations were performed on RC-based equivalent circuit models, which showed the presence of certain distortions. The experimental measurements displayed distortions in the form of both non-linearity and non-stationarity in the case of batteries. The level of the harmonics in the measurements is either similar or higher than the harmonics simulated in the RC equivalent circuits at different frequencies. The obtained harmonics compared to simulations highlights the importance of control measurements before the analysis of non-linear harmonics of EIS measurements galvanostatically excited.

Nonlinear harmonics of a seeded free-electron laser as a coherent and ultrafast probe to investigate matter at the water window and beyond

Nonlinear harmonics of a seeded free-electron laser as a coherent and ultrafast probe to investigate matter at the water window and beyond

New control strategy for multifunctional grid-connected photovoltaic systems

The main aim of this work consists of proposing a new control strategy for multifunctional grid-connected photovoltaic systems (GCPVSs) to enhance the power quality at the point of common coupling (PCC) while considering the inverter-rated capacity. In addition, an Adaptive neuro-fuzzy inference system (ANFIS) based maximum power point tracking (MPPT) controller for a two-phase interleaved boost converter is proposed to improve the dc-link voltage oscillation of the GCPVS. The control strategy takes into account the inverter's rated capacity in terms of power, which is defined by its maximal current modulus. It limits the inverter current to prevent overrating operations, and it also manages the GCPVS's functions: active power injection, reactive power compensation, and current harmonic filtering. The Active power injection into the grid takes precedence over power quality enhancement. Then, The reactive power compensation takes priority over the filtering of nonlinear load current harmonics. The proposed strategy is applied to a grid-connected PV system through an interleaved boost converter and a three-level neutral point clamped (NPC) inverter. Various scenarios with different solar irradiation levels are investigated using MATLAB/Simulink environment. Compared with another existing control strategy in terms of grid current total harmonic distortion (THD) enhancement, the simulations results indicate the superiority of the proposed method. Furthermore, the simulation results also show that the multifunctional GCPVS can perfectly perform all its functions simultaneously with up to 16.95% reduction in grid current THD.

Estimated Position Error Suppression Using Novel PLL for IPMSM Sensorless Drives Based on Full-Order SMO

To heighten the position estimation accuracy of sensorless control of interior permanent magnet synchronous motor (IPMSM), an improved full-order sliding mode observer (FSMO) based on novel phase-locked loop (PLL) is proposed in this article. By contrast with the traditional FSMO, the improved FSMO (IFSMO) with piecewise power function has merits of higher estimation accuracy and more chattering suppress capability, which is beneficial to the position sensorless drives. Based on that, to pledge the rotor position observation precision of the IFSMO during wide speed range, a variable sliding mode gain related to the rotor speed is designed. However, due to the inverter nonlinearity and rotor spatial harmonics, the extended back electromotive force contains high-order harmonics, which will reduce the estimation accuracy of PLL and cause notable position error. Therefore, a novel PLL with complex bandpass filter as the preprocessing stage that features high estimation accuracy, high filtering capability, and fast dynamic response is proposed. Meanwhile, the linearized model and parameter design of the proposed PLL is developed, and hence the stability of the designed PLL is analyzed by the derived linearized model. The availability of the proposed sensorless strategy is verified via experiments on 2-kW IPMSM drive.

Nonlinear harmonics coupled by parallel wave propagations in a time-dependent plasma flow

In a time-dependent flow, nonlinear harmonics can be excited by coupling between linear waves and flow-induced harmonic waves. Examining the dispersion relations and selection rules for the coupling, we investigate nonlinearly coupled harmonics for waves propagating along the magnetic field line in a magnetized plasma, as well as waves in an unmagnetized plasma. The coupled harmonics in a plasma flow are described by analytic dispersion relations and selection rules. This nonlinear coupling is corroborated by the particle-in-cell simulation. The coupled-harmonics model describes a mechanism for the excitation of nonlinear harmonics from linear waves in a time-dependent flow. The spectral analysis of the dispersion relation provides a useful way to evaluate the spatiotemporal behavior of a plasma flow.

Theoretical Study of the Effects of Nanoparticles on the Acoustic Performance of Microbubbles.

There are growing investigations on incorporating solid nanoparticles (NPs) into the shell of microbubbles (MBs), because NPs may endow the MBs with other bio-functions, such as multimodality imaging and drug delivery. These novel MBs have been developed as hybrid MBs' contrast agents. Generally, the shell density of hybrid MBs was assumed to be the same as water in the studies of bubble dynamics. In fact, the NPs in the layer of MBs can change the density of the shell, which leads to the change of scattering characteristics of MBs under ultrasonic excitation. Thus, it is necessary to develop a new model to simulate dynamics of the hybrid MBs. Here, we have investigated scattering characteristics of the hybrid MB embedded with NPs based on a modified Rayleigh-Plesset model. The numerical and analytical solutions to this equation are obtained for oscillation response, harmonic components, and scattered cross section of hybrid MBs at small-amplitude oscillations. The results indicated that the shell density had a greater impact on the nonlinear harmonics than fundamental ones. Considering acoustic driving frequency and pulse lengths, the largest ultraharmonic amplitude is 14 times larger than the smallest value. Considering the effects of bubble equilibrium radius, the second scattering cross section of hybrid MBs increased first and then decreased with increasing bubble equilibrium radius. Therefore, the optimal values of shell density for hybrid MBs can be predicted to obtain higher scattered signals. This also offers more accurate assessment of scattering characteristics for hybrid MB contrast agents.

Flatness-SVPWM Control for Three-Phase Shunt Active Power Filter Based on Five-Level NPC Inverter

The increasing use in the industry of nonlinear loads based on power electronic elements has introduced serious perturbation problems in the electric power distribution grids. These nonlinear loads generate non-sinusoidal currents to the mains which degrade the system's performance. Active power filters have been developed over the years to solve these problems and improve power quality. This study focuses on the use of a shunt active power filter to compensate nonlinear load's current harmonics and reactive power. To this end, a regulator based on the flatness control technique combined with an SVPWM strategy for a three-phase shunt active power filter based on a five-level neutral-point-clamped (NPC) inverter is used. The control objectives of this work are twofold: i. compensating the current harmonics and the reactive power produced by the nonlinear loads, and ii. regulating the inverter's DC capacitor voltage. To achieve these objectives, two cascaded loops are designed; an inner loop for the reactive and harmonic currents compensation based on a flatness controller and an outer loop for the DC voltage regulation based on a PI regulator. The simulation results are developed under MATLAB/Simulink environment to prove the satisfactory performance of the proposed controlled system.

Investigations of the linear and non-linear flow harmonics using the a multi-phase transport model

The multi-phase transport model (AMPT) is used to study the effects of the parton-scattering cross-sections (σ pp) and hadronic re-scattering on the linear contributions to the flow harmonic v 4, the non-linear response coefficients, and the correlations between different order flow symmetry planes in Au + Au collisions at 200 GeV. The model results, which agree with current experimental measurements, indicate that the higher-order flow harmonics are sensitive to the σ pp variations. However, the non-linear response coefficients and the correlations between different order flow symmetry planes are σ pp independent. These results suggest that further detailed experimental measurements which span a broad range of collision systems and beam energies could serve as an additional constraint for the theoretical models’ calculations.

Multiple intensity reference interferometry for the correction of sub-fringe displacement non-linearities

Displacement measuring interferometers, commonly employed for traceable measurements at the nanoscale, suffer from non-linearities in the measured displacement that limit the achievable measurement uncertainty for microscopic displacements. Two closely related novel non-linearity correction methodologies are presented here that allow for the correction of non-linearities in cases where the displacement covers much less than a full optical fringe. Both corrections have been shown, under ideal conditions, to be capable of reducing all residual non-linearity harmonics to below the 10 pm level.

Research in Nonlinearity of Surface Acoustic Wave Devices.

Surface acoustic wave (SAW) devices are one of the indispensable components in the radio frequency (RF) front-end of mobile phones. With the development of mobile communication technology, the requirements for linear specification of devices are more and more strict. Nonlinear distortions of SAW devices have a serious influence on the application of mobile RF modules. To satisfy the strict requirement of linearity of communication system, it is necessary to understand the generation mechanism of nonlinearity and study the accurate modeling, appropriate measurement methods, and nonlinear response elimination technology. In this paper, we summarize the research progress on the nonlinearity of SAW devices in recent years from four aspects: the generation mechanism, simulation methods, measurement system, and suppression technology. The nonlinear harmonics with the nonlinear Mason equivalent circuit model are simulated. Furthermore, harmonics and intermodulation signals of SAW filters are tested by the authors. Thanks to these research studies, it is of great significance to the development of future RF front-end modules with high linear SAW devices.

An efficient compensation of modified DSTATCOM for improving microgrid operation

This paper proposes a design for a modified distribution static compensator (DSTATCOM) with a proposed current controller for microgrid (MG) applications. The modified DSTATCOM is incorporated in a three-phase four-wire network system to deal accurately at grid connected mode with balanced, unbalanced and excursion load for both nonlinear and inductive loads. Moreover, it handles the stability issues of the MG at fault caused islanding incidents. The design criteria of the modified DSTATCOM parameters is presented and discussed. The hysteresis current controller is introduced to drive the voltage source converter (VSC) and its reference voltage signal is generated based on the instantaneous symmetrical components theory (ISCT). Matlab/Simulink software is used to verify the performance of the modified DSTATCOM with the proposed controller under different load types and loading conditions for grid connected mode and islanded mode of MG operation. Based on the simulation results, the power factor is improved and the non-linear harmonics currents are compensated therefore the harmonic distortion of the supply currents and voltage are reduced, moreover the stability operation at fault cause islanding is maintained. The results show the superiority of the proposed modification of DSTATCOM in dealing with unbalanced, distorted and bad power factor system in comparing with conventional DSTATCOM.

Experimental Investigation of Nonlinear Standing Waves in DC/VHF Hybrid Capacitive Discharges

It is recognized that in very-high-frequency capacitively coupled plasma (VHF CCP) reactors, the standing wave effects can be enhanced by the presence of nonlinear higher harmonics self-excited by the plasma series resonance (PSR). In this work, we investigated the influence of the dc bias on the excitation of the nonlinear standing waves in a parallel-plate capacitively coupled dc/VHF (60 MHz) hybrid discharge sustained in argon, with both the dc source and the VHF source applied to the top electrode. A hairpin probe was employed to determine the axial/radial distribution of the electron density, while a high-frequency B-dot probe was used to measure the radial distributions of the harmonic magnetic field and the harmonic current density. With no dc bias applied, the nonlinear standing wave excitation was observed to be predominant; the high-order harmonic current density exhibited a main peak at the electrode center and one or more minor peaks between the electrode center and the edge, leading to a center-high electron density profile. With the addition of the dc source, the harmonic excitations and the corresponding nonlinear standing wave effect tend to be suppressed with the increase of dc bias, resulting in improved plasma uniformities. Underlying mechanisms of the suppression effect of the dc bias on the nonlinear standing wave excitation were analyzed.

Magnetic probe diagnostics of nonlinear standing waves and bulk ohmic electron power absorption in capacitive discharges

It is recognized that standing wave effects appearing in large-area, very-high-frequency capacitively coupled plasma (CCP) reactors cause center-high plasma non-uniformity. Using a high-frequency magnetic probe, we present a direct experimental diagnostic of the nonlinear standing waves and bulk ohmic electron power absorption dynamics in low pressure CCP discharges for different driving frequencies of 13.56, 30, and 60 MHz. The design, principle, calibration, and validation of the probe are described in detail. Spatial structures of the harmonics of the magnetic field, determined by the magnetic probe, were used to calculate the distributions of the harmonic current and the corresponding ohmic electron power deposition, providing insights into the behavior of nonlinear harmonics. At a low driving frequency, i.e. 13.56 MHz, no remarkable nonlinear standing waves were identified and the bulk ohmic electron power absorption was observed to be negligible. The harmonic magnetic field/current was found to increase dramatically with the driving frequency, due to decreased sheath reactance and more remarkable nonlinear standing waves at a higher driving frequency, leading to the enhancements of the ohmic heating and the plasma density in the bulk, specifically at the electrode center. At a high driving frequency, i.e. 60 MHz, the high-order harmonic current density and the corresponding ohmic electron power absorption exhibited a similar node structure, with the main peak on axis, and one or more minor peaks between the electrode center and the edge, contributing to the center-high profile of the plasma density.

Baseband Fusion Technique for Filter-Less Wideband Transmitters

The multi-band and spectrally flexible transmission requires a wideband transmitter system to cover a wider frequency band of interest. A wideband power amplifier (PA) is required to achieve the desired signal strength for covering long-distance communication. Due to PA's nonlinear characteristics, spectral growth and harmonics occur, which may cause interference with the other band of interest. This paper presents a linearization technique, denoted as baseband fusion technique (BFT), for the wideband filter-less transmission system. The proposed method simultaneously reduces the spectral growth around the fundamental frequency and cancels out harmonics. The presented technique uses the signal cancellation approach in baseband and avoids modeling as required in digital predistortion. This method may eliminate the need for bulky filters to suppress harmonics. The proposed method has much lower complexity in digital signal processor resources than the Volterra-based models and their derivatives. We have experimentally tested with long-term-evolution (LTE), four-tone, and 256-QAM signal to validate the proposed method. This method can also be useful for cognitive radios where PA's unwanted emission interferes with the other user transmission.

Accurate and broadband manipulations of harmonic amplitudes and phases to reach 256 QAM millimeter-wave wireless communications by time-domain digital coding metasurface

We propose a theoretical mechanism and new coding strategy to realize extremely accurate manipulations of nonlinear electromagnetic harmonics in ultrawide frequency band based on a time-domain digital coding metasurface (TDCM). Using the proposed mechanism and coding strategy, we design and fabricate a millimeter-wave (mmWave) TDCM, which is composed of reprogrammable meta-atoms embedded with positive-intrinsic-negative diodes. By controlling the duty ratios and time delays of the digital coding sequences loaded on a TDCM, experimental results show that both amplitudes and phases of different harmonics can be engineered at will simultaneously and precisely in broad frequency band from 22 to 33 GHz, even when the coding states are imperfect, which is in good agreement with theoretical calculations. Based on the fabricated high-performance TDCM, we further propose and experimentally realize a large-capacity mmWave wireless communication system, where 256 quadrature amplitude modulation, along with other schemes, is demonstrated. The new wireless communication system has a much simpler architecture than the currently used mmWave wireless systems, and hence can significantly reduce the hardware cost. We believe that the proposed method and system architecture can find vast application in future mmWave and terahertz-wave wireless communication and radar systems.

Thermal stability of the electromechanical properties in acceptor-doped and composite-hardened (Na1/2Bi1/2)TiO3–BaTiO3 ferroelectrics

Lead-free relaxor ferroelectrics are promising candidates for next-generation piezoelectric high-power devices, such as ultrasonic motors, transformers, and therapeutic ultrasonics. These applications require hard ferroelectrics with a broad operating temperature range. Recently, acceptor Zn2+ doping and composite formation with ZnO were proposed to induce hardening in Na1/2Bi1/2TiO3–BaTiO3 and simultaneously increase the depolarization temperature. Here, these two strategies are compared by studying the temperature dependence of electromechanical properties, ferroelectric loops, and nonlinear polarization harmonics. In the modified compositions, depolarization is associated with the shift of the ferroelectric-to-relaxor transition to higher temperatures, while the depolarization onset remains unchanged. This leads to broadening rather than translation of the depolarization region, accompanied by decoupling of the piezoelectric d33 and d31 coefficients. The temperature-dependent electromechanical response is stable for composites, while the Zn2+-doped samples exhibit strong temperature dependence akin to acceptor-doped Pb(Zr,Ti)O3. The thermal evolution of electromechanical coefficients is not related to the thermally induced decrease of the coercive/internal bias fields but instead to the ratio of irreversible-to-reversible nonlinear dynamics arising from displacements of domain walls or similar interfaces. The results demonstrate that mechanical stress-based hardening in the composites exhibits superior thermal stability, which can considerably improve the operational range of lead-free piezoelectric materials.

Nonlinear Load Harmonic Prediction Method Based on Power Distribution Internet of Things

A large number of nonlinear loads have an impact on the stable operation of the power system. To solve this problem, this article proposes a nonlinear load harmonic prediction method based on the architecture of Power Distribution Internet of Things. Firstly, this method integrates the characteristics of edge computing technology and Power Distribution Internet of Things technology and proposes a Power Distribution Internet of Things framework applied to nonlinear load harmonic prediction, which provides top-level design for subsequent harmonic prediction methods of Power Distribution Internet of Things; then, considering the electrical characteristics of the typical nonlinear load, the mathematical model of nonlinear load data is constructed based on the harmonic coupling admittance matrix model on the edge side. At the same time, a nonlinear load harmonic prediction model based on dynamic time warping and long-term and short-term memory network (DTW-LSTM) is established in the cloud computing center to realize high accuracy and high real-time prediction and analysis of nonlinear load harmonics. Finally, the simulation results based on the general data set show that the MAE evaluation index of the proposed method is less than 5% in the experimental group, which shows good generalization ability, and has some advantages over the current method in operation efficiency.

Analysis Of 12- Level Cycloconverter To Minimize Thd (Total Harmonic Distortion) Level In 3-Phase Induction Motor

These harmonics are higher than essential frequencies and cause Total Harmonics Distortion (THD) which increases the rms current and generates more warmth in the load. Numerous techniques are used to suppress the harmonics to limit the warmth in the load. Another procedure is utilized in this work to limit THD and the method to beat the low exhibition of a traditional PWM (pulse width tweak) control. In this work, the desired output voltage is accomplished by contrasting the desired sinusoidal waveform (adjusting signal) with a high frequency three-sided waveform (transporter signal). Industrial applications demands high force and long life expectancy motor drives. Three phase motor drives have restricted force density consequently Multiphase motor drives are better solutions for high force density and substantial loads. In this work a 12 level cycloconverter is designed to drive three Phase load. The loads used in the industries almost nonlinear loads like motors. Thusly, because of these nonlinear loads extra harmonics incited at the output of the 12 level cycloconverter drive with major frequency. The harmonics and THD got using our proposed technique is thought about using Mat lab/Simulink

Application of D-STATCOM for Harmonic Reduction using Power Balance Theory

In modern power systems due to prolific use of non-linear devices harmonics are present in the distribution system. To reduce the harmonics and source neutral current D-FACT along with a star-delta transformer and Power Filter is proposed in shunt. In this article, the three phase load has been taken from NTS Industries, which deals with FMCG products. This system includes 3 phase 3 wire system having industrial load such as mixer grinder, pulverizer, packaging machine, etc. A star-delta transformer along with three leg voltage source inverter and a capacitor used to filter out harmonics present in supply current. Power balance theory is used to control the D-FACT. A MATLAB Simulink model was created and the results were discussed.

Nonlinear Adaptive Harmonics Vibration Control for Active Magnetic Bearing System With Rotor Unbalance and Sensor Runout

Rotor unbalance (RUB) and Sensor Runout (SR) are two main vibration sources for active magnetic bearing (AMB) system, and they not only produce considerable harmonic vibration but also endanger the stability of AMB system. Therefore, a nonlinear adaptive algorithm, whose asymptotic stability is guaranteed by Lyapunov's theory, is proposed in this paper to suppress the harmonic vibration. Nevertheless, RUB and the synchronous component of SR have the same frequency with the rotational frequency, and it is highly necessary to distinguish them from each other for the compensation of displacement stiffness force. Hence, the scheme of changing rotor speed is adopted for the permanent magnet biased magnetic bearing system. As a consequence, the harmonic current caused by RUB and SR is effectively attenuated and the displacement stiffness force is correctly compensated. The results of the numerical simulations and experiments demonstrate that the harmonic vibration is dramatically suppressed through the proposed method.