Amplitude Of AC Voltage Research Articles

Fault-ride Through Control Strategy of Multi-terminal High Voltage DC Systems

Abstract A coordinate control strategy is proposed to secure fault-ride through (FRT) for voltage source converter (VSC) based multi-terminal high voltage dc transmissions (MTDC) integrating the offshore wind farms (OWFs). The short circuit fault in the ac grid obviously reduces the voltage at the connection point which, in turn, block the power output of MTDC systems instantaneously. The resulting power imbalance in MTDC system correspondingly charge the DC capacitors. In the absence of suitable countermeasures, this would lead to increased dc voltage, which would further lead to potential equipment damage in the installation. Therefore, for the OWF-integrated MTDC systems, keep ing the dc voltage within a reasonable value is the key to achieving the fault-ride through. The grid side converters (GSCs), wind farm side converters (WFCs), and doubly fed induction generators (DFIGs) will operate under the fault operation mode when there is a three-phase symmetrical fault. An improved reactive power compensation method is applied to GSCs’ controllers to enhance the stability of the ac grid. The controllers of WFCs reduce the ac voltage amplitude of OWFs according to the dc voltage signal, which correspondingly decreases the power transmitted to the MTDC system. As a result, the increase in dc voltage is restrained. Since the degree of voltage decline for WFCs is limited by the over-current capability of the power electronics, an active power reduction control of DFIG is used to complement with this method. Different simulation scenarios are presented by DIgSILENT PowerFactory to verify the effectiveness of the proposed control strategy.

A Robust Flywheel Energy Storage System Discharge Strategy for Wide Speed Range Operation

Wide speed range operation in discharge mode is essential for ensuring discharge depth and energy storage capacity of a flywheel energy storage system (FESS). However, for a permanent magnet synchronous motor/generator-based FESS, the wide-range speed variation in a short discharge period causes consecutive decreases in ac voltage frequency and amplitude. As a result, operation point shift leads to performance deterioration of the conventional local linearization based dc-link voltage control strategies. This study aims to realize a consistent robust discharge performance within the entire available operation range for FESS. We propose a robust discharge strategy that incorporates the speed variation to the dc-link voltage controller. A speed-dependent extended state observer is designed to realize global linearization and enhance the robustness. A speed adaptive feedback control law is designed to ensure consistent dynamic performance within the entire available operation range. Finally, the discharge strategy is validated at different speeds on a high-speed FESS test bench.

A modelling of AC voltage stabilizer based on a hybrid transformer with matrix converter

AbstractThis article presents a study of an AC voltage stabilizer based on a three-phase hybrid transformer combined with a matrix converter. The proposed solution is used to control AC voltage amplitude and phase shift. By adjustment of these voltage parameters we can reduce the effects of overvoltage, voltage dips or lamp flicker. Such negative phenomena are very significant, particularly from the perspective of the final consumer and sensitive loads connected to the power network. Often the voltage in the power system can be adjusted using a mechanical or thyristor controlled regulator, which in a stepwise manner switches the taps of the electromagnetic transformer. The method for obtaining continuous control of the voltage magnitude and phase shift with the use of a conventional transformer with two output windings and a matrix converter is presented in this paper. The operating principles, mathematical model and properties of the proposed voltage stabilizers are discussed in this paper. The main part of the article will be devoted to the mathematical model which is based on an averaged equation. Computer simulation results are presented and compared with the results of a mathematical study.

Dielectric relaxation process of a partially unwound helical structure in ferroelectric liquid crystals.

The fluctuations of unwound helical structure have been observed in deformed helix ferroelectric liquid crystal (DHFLC) and conventional FLC sample cells. The helix is partially unwound by strong anchoring on the substrates. In such sample cells, the helical decarlization lines are not observed in the texture under crossed polarized microscope. The dielectric spectroscopy is employed to observe the behavior of dielectric relaxation processes in these sample cells. A dielectric relaxation process is observed at a lower frequency than the Goldstone mode processes in DHFLC and FLC, which we call partially unwound helical mode (p-UHM). However, the p-UHM process is not observed in the sample cell in which the helical lines appear. The application of various amplitudes of probing ac voltages on this mode has shown the higher frequency shift, i.e., the larger the amplitude of ac voltage, the higher is the relaxation frequency of p-UHM. At sufficient amplitude of applied probing ac voltage, the p-UHM merges with the Goldstone mode process and is difficult to detect. However, the Goldstone mode relaxation frequency is almost independent of the cell geometry and sample configuration. The electro-optical behavior of the p-UHM has also been confirmed by electro-optical technique. The dielectric relaxation of UHM at a frequency lower than the Goldstone mode is interpreted as the fluctuation of partially unwound helix.

A control strategy for a multi-terminal HVDC network integrating wind farms to the AC grid

This paper describes a novel control strategy of voltage source converters (VSC) in large-scale wind farm applications, in order to achieve a constant DC voltage for connecting to the long transmission system based on multi-terminal high voltage direct current (HVDC) technology. The control strategy is based on a multi-loop current and voltage control for tracking the predetermined value of the DC link voltage in the rectifier side station to achieve proper performance in the irregular circumstances of wind farm operation. In addition, the control strategy is able to transmit the maximum input power to the consumption side in different situations in grid side converter. Grid connection of the HVDC system is analysed under two conditions: balanced AC grid, and connection of unbalanced nonlinear load into the AC grid. The control strategy guarantees injection of minimum harmonic current components from the grid to the loads. MATLAB simulation results are presented to demonstrate the effectiveness of the proposed strategy for different types of variations in AC voltage amplitude and frequency of wind turbines output voltage.

Droplet condensation on superhydrophobic surfaces with enhanced dewetting under a tangential AC electric field

In this Letter, the dewetting behavior of superhydrophobic condensing surfaces under a tangential AC electric field is reported. The surface coverage of condensed droplets only exhibits a negligible increase with time. The jumping frequency of droplets is enhanced. The AC electric field motivates the dynamic transition of droplets from stretch to recoil, resulting in the counterforce propelling droplet jumping. The considerable horizontal component of jumping velocity facilitates droplet departure from superhydrophobic surfaces. Both the amplitude and frequency of AC voltage are important factors for droplet departure and dewetting effect. Thereby, the tangential electric field provides a unique and easily implementable approach to enhance droplet removal from superhydrophobic condensing surfaces.

Low Voltage Electrowetting on Ferroelectric PVDF-HFP Insulator with Highly Tunable Contact Angle Range.

We demonstrate a consistent electrowetting response on ferroelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) insulator covered with a thin Teflon AF layer. This bilayer exhibits a factor of 3 enhancement in the contact angle modulation compared to that of conventional single-layered Teflon AF dielectric. On the basis of the proposed model the enhancement is attributed to the high value of effective dielectric constant (εeff ≈ 6) of the bilayer. Furthermore, the bilayer dielectric exhibits a hysteresis-free contact angle modulation over many AC voltage cycles. But the contact angle modulation for DC voltage shows a hysteresis because of the field-induced residual polarization in the ferroelectric layer. Finally, we show that a thin bilayer exhibits contact angle modulation of Δθ (U) ≈ 60° at merely 15 V amplitude of AC voltage indicating a potential dielectric for practical low voltage electrowetting applications. A proof of concept confirms electrowetting based rapid mixing of a fluorescent dye in aqueous glycerol solution for 15 V AC signal.

Current-Based Resonant Power Delivery With Multi-Cycle Switching for Extended-Range Inductive Power Transmission

A current-based resonant power delivery (CRPD) technique with multi-cycle switching has been presented that enables efficient inductive power transmission at large distances. Unlike the conventional inductive link, in which the receiver (Rx) LC-tank is utilized as a voltage source, the proposed CRPD switches the Rx LC-tank for several cycles in a novel fashion to utilize it as a current source. Therefore, the voltage across the load $(R_{L})$ can be significantly higher than the Rx LC-tank voltage. This eliminates the need for DC-DC charge pumps or AC-DC voltage multipliers, which require several capacitors and diodes. In CRPD, the energy is first stored in the Rx coil by shorting the Rx LC-tank for several power carrier cycles. At the peak of Rx coil current, the coil energy is then transferred to $R_{L}$ for a quarter of the power carrier cycle. The circuit theory behind CRPD has been developed and verified with simulation results. A proof-of-concept CRPD was also characterized in measurements to demonstrate its feasibility. In measurements, CRPD was capable of achieving the DC voltage of 3.1 V across an $R_{L}$ of 100 $\text{k}\Omega$ , by switching the Rx LC-tank at 50 kHz with an AC voltage amplitude of 1 V across the Rx coil at the operation frequency of 1 MHz. Moreover, compared to a conventional inductive link followed by a passive rectifier, to achieve a minimum DC voltage of 2.8 V across an $R_{L}$ of 100 $\text{k}\Omega$ the proposed CRPD extended the range from 7 cm to 13 cm for the same voltage across the transmitter coil.

Stochastic resonance in MEMS capacitive sensors

The paper presents a theory for stochastic resonance in MEMS capacitive chemical sensors and lays a framework for the calculation of sensor response. A parallel plate capacitive MEMS sensor biased to a fixed DC voltage and driven by a small amplitude AC voltage is considered in the presence of inherent cantilever noise sources. The stochastic resonance occurs due to correlation between the cantilever oscillations and the noise spectral components in the presence of dynamic nonlinearity. The noise power is transferred resonantly to the cantilever oscillations under certain conditions that are determined by the noise correlation rate, damping loss and AC drive frequency. The traditional strategies for enhancing sensor responses explore the optimization of cantilever geometry, DC bias level and AC drive amplitude and frequency. The present work provides theoretical framework for harnessing the noise power for enhancing the amplitude response of capacitive MEMS chemical sensors. The occurrence and usefulness of stochastic resonance in MEMS chemical sensor has been demonstrated by generating simulation results pertaining to explore the dependencies on various sensor parameters such as noise power and correlation rate, damping loss and polymer thickness.

High Frequency Sensing with Enhanced Sensitivity in Graphene Nanogrid FET Immunosensor

:-FET based charge detection sensing mechanism with various nanostructures has many advantages like label free detection, femtomolar sensitivity and compatibility with electronic interface. However detecting charges in high ionic strength solution is a challenge due to the inherent problem of ionic screening beyond the Debye length.To overcome this effect, high frequency signal has been applied in single walled carbon nanotube structures which has enabled detection of biotin in presence of 100mM buffer solution [1]. But the limit of detection achieved is not satisfactory. In this work we superimpose a high frequency ac signal in the range of 100KHz to 10MHz across the drain and source terminal in a graphene nanogrid structure and applied it for detection of IgG-protein A binding in sub femtomolar regime. The graphene nanogrid structure has been developed on a nanoporous silicon oxide template as shown in Fig.1 and is an interconnected grid structure of bilayer reduced graphene oxide(RGO) which is composed of long and narrow strips alternating with series combination of short and narrow strips on planar regions and within pores.The long and short strips are interconnected during the deposition stage and hence the structure is expected to have fewer edges. Such a structure is expected to possess certain advantages in addition to the improved binding efficiency of the biomolecules due to large surface area to volume ratio. Firstly, in the nanopores, the biomolecules usually reside within a distance shorter than the original pore radius which statistically raises the charge transfer probability between the biomolecules and the surface even at high ionic strength of buffer. As a consequence, the heterogeneous charge transfer gets facilitated and the electrode potential reaches equilibrium faster for a given electrochemical system [2]. Secondly, such a graphene nanostructure has a size dependent effective energy gap which increases the transconductance of the device [3]. Due to the absence of edges, the conductance of the fabricated smooth nanogrid structure will be contributed by every section of the device and hence all the antigen molecules that get captured at any location contribute towards the change in conductance. Also there is a probable localization effect of the charge modulation after antigen capture within the corresponding quantum dots, which can result in an enhanced change of the overall carrier transport. Fabrication of the nanoporous silicon oxide template has been carried out by anodic etching of p-type silicon<100> wafers of 10–20 Ω-cm resistivity in a double pond electrochemical bath for 30 minute using a constant current density of 2.35 mA/cm2 with an electrolyte mixture of 48% hydrofluoric acid and dimethyl sulfoxide in the ratio of 1:9 by volume. The nanopores formed are of about 30nm thickness and 100 nm length. The silicon substrates have been oxidized for subsequent graphene deposition. Graphene has been deposited by electrophoretic method[4] and after that antibody has been immobilized through poly-l-lysine (PLL). Raman spectroscopic measurements have been performed for characterization of deposited graphene[Fig:2] and the spectra of the graphene shows three Raman bands at 1195,1590 and 2670 cm-1that assigned to the well-documented D,G, and 2D bands respectively in RGO. The bilayer thickness has been confirmed by the presence of a symmetric 2D band and 2D/G intensity ratio of around 1.4. The two lateral electrodes used for RGO deposition act as the drain and source electrodes. Graphene based FET has been realized with a platinum top gate electrode suspended in buffer. Protein A has been selected as the antigen and its different concentration has been listed using 100mM buffer in the range of 100KHz to 10MHz. An ac voltage of amplitude 20 mV has been fed between the drain-source terminal. The gate potential has been fixed at 0.2 V. It has been observed [Fig:3] that the drain current (Id ) decreases with frequency for 100mM which may be attributed to the slow decay of the surface potential resulting in effective increase of the Debye length and hence the capacitive impedance. We further plotted the sensitivity [Fig.:4], calculated as the fractional change in Id before and after Protein A attachment. A peak in sensitivity has been observed at a frequency of around 8MHz which corresponds to the optimum interaction of the antigen molecules with the graphene nanostructure. The intrinsic advantages of the graphene nanogrids(as discussed above) enable detection down to 0.1 fg/ml antigen in a high ionic strength buffer which has significant impact in point-of care applications. Figure 1

Microstructure and corrosion model of MAO coating on nano grained AA2024 pretreated by ultrasonic cold forging technology

In order to study the effect of surface nano-structuring of aluminum alloy on the corrosion performance of MAO coating, ultrasonic cold forging technology (UCFT) was used as a pretreatment to produce a refined layer before a MAO coating was prepared on the surface of 2024 Al alloy (AA2024). The surface roughness was evaluated by atomic force microscope (AFM), and the average surface roughness value of the 5.00 × 5.00 μm area of UCFT treated sample is 7.477 nm. The grain size of the modified layer were observed by transmission electron microscope (TEM). The result showed that UCFT can refine the grains. The microstructure and phase component of the coated samples were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The observations showed that the micro-pore size of the MAO coating on UCFT treated Al alloy is smaller than that of MAO coating on untreated alloy. The phases of the coated samples with and without UCFT remain the same. The hardness of the samples measured by the micro-hardness tester showed that the UCFT-MAO sample possesses the highest micro-hardness among all the samples. The potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were employed to characterize the corrosion rate and the electrochemical impedance in a 3.5% NaCl solution. For the PDP testing, the sweep rate was 5 mV/s starting from −1.4 V to 0 V, while the EIS tests were carried out in the range of 0.01 Hz–100 kHz with AC voltage amplitude of 10 mV. The PDP and EIS results show that the UCFT-MAO sample has the best corrosion resistance with the lowest corrosion current density, 0.412 A/cm2. The largest electrochemical impedance is attributed to UCFT pretreatment prior to MAO process on aluminum alloys. The corrosion model of MAO coated AA2024 pretreated by UCFT was proposed.

Electrical characteristics and rectification performance of wet chemically synthesized vertically aligned n-ZnO nanowire/p-Si heterojunction

Vertically well-aligned n-ZnO nanowire (NW) thin films were deposited onto p-Si substrates by a two-step wet chemical technique to form a p–n heterojunction diode. The morphological and structural characteristics of the ZnO NW performed by scanning electron microscopy (SEM) and x-ray diffraction (XRD) revealed well-aligned h-ZnO NW with a wurtzite structure. A direct optical band gap of 3.30 eV was calculated from the transmittance trace obtained using a UV–VIS–NIR spectrophotometer. The electrical characteristics of the heterojunction diode were studied by capacitance–voltage (C–V) measurement at room temperature, and current–voltage–temperature (I–V–T) measurements performed in the 300–400 K range. The C–V measurements yield a carrier concentration of 1.3 × 1016 c.c.−1 for the ZnO NW thin film. The ideality factor (n) was found to decrease, while the barrier height (φb0) increased with the increase in temperature, when calculated using a thermionic emission model from the non-linear I–V–T plots. The series resistance (Rs) calculated by the Cheung–Cheung method decreased with the increase in temperature. The mean barrier height (0.718 eV) and modified Richardson constant (28.4 A cm−2 K−2) calculated using a Gaussian distribution of barrier heights (considering barrier height inhomogeneity) were closer to the theoretical value than those calculated from the linear approximation of the ln(Is/T2) versus 1000/T plot. The variation of the density of interface states with interface state energy was also studied. The n-ZnO NW/p-Si heterojunction diode performed very good half wave rectification in the frequency range 50 Hz–10 kHz, when a sinusoidal ac voltage of amplitude 4.5 V was applied across it.

DEVELOPMENT OF A LOW VOLTAGE AC TO DC CONVERTER FOR MESO AND MICRO ENERGY HARVESTERS

Energy harvesting is widely used for the operation of wireless sensor nodes. Most of the energy harvesters gen- erated voltage levels are sinusoidal or random in nature, moreover, the output voltage levels these produce are in low (in mV range). For sensor operation, in order to convert this low AC voltage levels into relatively high DC voltage DC, a three stage Cockcroft Walton converter is developed. The paper presents fabrication and characteri- zation of a 3 stage Low Voltage Cockcroft-Walton converter in an area of 5.5 x 3.3 cm 2 . The converter was capable of converting a minimum AC voltage amplitude of 10 mV with a transformation factor of 6.5. The variation in the input frequency had almost no effect on the DC output voltage of the converter. Upon integration of the converter to different energy harvesters, the converter successfully rectified the AC or random output voltage signals of the harvesters into corresponding DC voltage.

Characterization of the dielectric endurance of reinforced recycled PET using electro-thermal aging test

This paper presents the advantages of dielectric characterization by electro-thermal aging testing in the durability analysis of reinforced recycled polyethylene terephthalate (PET), as compared to short-term dielectric breakdown strength measurements. Dielectric breakdown strength measurements were carried out at room temperature according to ASTM D149-a, while electro-thermal aging tests were conducted in air at different constant temperatures ranging from 140 to 170 °C, using an experiment setup comprising a cell test arranged in a point-to-plane configuration, with a very small air gap of 50±1 μm. The tests were conducted at an AC voltage of amplitude 7 kV rms on eight different reinforced recycled PET samples. The degradation of recycled PET-based composites during exposure to corona discharges at elevated temperatures was characterized by optical microscopy and scanning electron microscopy (SEM). The main goal of this study is to characterize and to determine the relationship between the addition of different inorganic reinforcements, such as mica and glass fibers, to a recycled PET matrix, as well as the resistance to dielectric failure during electro-thermal aging. The effect of plasticizers on the dielectric endurance of recycled PET-based composites was also investigated. Results obtained showed that glass fibers contribute to the enhancement of the resistance to dielectric failure. Our experiments also revealed that the dielectric behaviour of these composites can be affected by the presence of plasticizers. In addition, the size of additives such as mica can greatly improve the resistance to the dielectric breakdown caused by electrothermal aging.

Kelvin Probe Force Microscopy by Dissipative Electrostatic Force Modulation

We report a new experimental technique for Kelvin probe force microscopy (KPFM) using the dissipation signal of frequency modulation atomic force microscopy for bias voltage feedback. It features a simple implementation and faster scanning as it requires no low frequency modulation. The dissipation is caused by the oscillating electrostatic force that is coherent with the tip oscillation, which is induced by a sinusoidally oscillating voltage applied between the tip and sample. We analyzed the effect of the phase of the oscillating force on the frequency shift and dissipation and found that the relative phase of 90$^\circ$ that causes only the dissipation is the most appropriate for KPFM measurements. The present technique requires a significantly smaller ac voltage amplitude by virtue of enhanced force detection due to the resonance enhancement and the use of fundamental flexural mode oscillation for electrostatic force detection. This feature will be of great importance in the electrical characterizations of technically relevant materials whose electrical properties are influenced by the externally applied electric field as is the case in semiconductor electronic devices.

Moderately nonlinear diffuse-charge dynamics under an ac voltage.

The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of V_{o}/(k_{B}T/e), where V_{o} is the amplitude of the driving voltage and k_{B}T/e is the thermal voltage with k_{B} as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D/λ_{D}L, where D is the ion diffusivity, λ_{D} is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O(V_{o}^{3}) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in V_{o}. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing V_{o}. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

Instability in Nonlinear Oscillation of Dielectric Elastomers

A membrane of a dielectric elastomer oscillates when subject to AC voltage. Its oscillation is nonlinear due to large deformation and nonlinear electromechanical coupling. Dynamic instability in dielectric elastomers—the oscillation with an unbounded amplitude—is investigated in this paper. The critical amplitude of AC voltage for dynamic instability varies with the frequency of AC voltage and reaches a valley when the superharmonic, harmonic, or subharmonic resonance is excited. Prestretches can improve dielectric elastomer actuators' capabilities to resist dynamic instability. The critical deformation at the onset of dynamic instability can be much larger than that at the onset of static instability. Oscillation of dielectric elastomers can be used for applications, such as vibration shakers for haptic feedback, soft loudspeakers, soft motors, and soft pumps. We hope that the current analyses can improve the understanding of dynamic behavior of dielectric elastomers and enhance their stability and reliability.

Characterization of electrical properties of n-conducting barium titanate as a function of dc-bias and ac-voltage amplitude by application of impedance spectroscopy

The electrical properties of bulk and grain boundaries of donor-doped barium titanate ceramics have been characterized as a function of temperature (50–350 °C) and voltage load (up to 140 V) by application of impedance spectroscopy. Both the grain boundary resistivities and the steepness of the R-T characteristics are diminished significantly with increasing voltage load. While the grain boundary resistances are strongly affected by the applied electric field, the grain boundary capacitance is almost independent of the dc-bias. The non-linearity of the resistivity of n-conducting BaTiO3 has been investigated in detail by impedance spectroscopy as a function of dc-bias and a small ac-voltage signal as well as impedance measurements with high ac-voltage amplitudes (zero bias). The non-linear current response to high ac-voltage amplitudes at low frequencies (0.01 Hz) has been determined experimentally and analyzed by means of fast Fourier transform (FFT) as well as Lissajous analyses. Moreover, a finite element model (FEM) has been developed for the simulation of the ac-current response. The FEM calculations are in close agreement with the experimentally determined data for the variation of the grain boundary resistance with ac-voltage amplitude.

Harmonic estimation using RLS algorithm and elimination with improved current control technique based SAPF in a distribution network

Abstract This paper presents the application of well known recursive least square (RLS) harmonic estimation technique and its elimination with improved current control technique based shunt active power filter (SAPF) in a distorted power network. The estimation of amplitude and phase angle of fundamental and harmonics is performed using RLS algorithm, known for their simplicity of computation, accuracy and good convergence properties. The estimates are updated recursively as samples of the harmonic signals are received. In order to eliminate harmonics produced by the nonlinear load connected in the distribution network, a three-phase SAPF with modified current control technique is employed. In this paper, based on the analysis and modeling of SAPF with closed-loop control, a feed forward compensation path of load current and a new pulse width modulation (PWM) control scheme is proposed to improve the dynamic performance of the SAPF. In this case the amplitude and phase angle of the converter AC voltage should be adjusted using PWM, thus producing either leading or lagging reactive power. Harmonic contented in the signal is estimated at the point of common coupling (PCC) with and without SAPF. The comparative results of amplitude and phase angle of fundamental and selected harmonics are determined considering installation of SAPF in the distribution network. The system is studied using MATLAB environment to justify the effectiveness of proposed control technique in comparison to the other techniques discussed in the recent literature.

A low-cost acceleration monitoring system based on dual fiber Bragg gratings

In this paper, we constructed a low-cost acceleration monitoring system based on a rectangle cantilever beam (RCB), two fiber Bragg gratings and the light intensity measurement method. To do this, we investigated the minimum natural frequency of RCB and the dependence relationship of the strain of the measurement point and its change rate with respect to the acceleration amplitude upon the inclination angle of the sensor, and given the quantitative relationship between the amplitude of AC voltage of monitoring system versus the acceleration amplitude and the inclination angle of the sensor. Finally, we have finished a series of vibration monitoring experiments, and the experiment data are consistent with the theoretical equations.