Load Phase Angle Research Articles

WAMS Based Real-Time Voltage Stability Monitoring for Various Load Models in the Presence of a DFIG Integrated Wind Farm

With rising global energy demand, transmission lines are operated at their limits, causing electrical grids to operate under extreme voltage instability conditions. To meet the increased load-demand and the forced tendency across the globe of tilting towards even more renewable generation, solar and wind farms are integrated with increased size and capacity. These uncontrolled natural power injection again may affect the system’s voltage stability. To avoid blackouts and to achieve the maximum voltage stability of power systems, operators need to do effective real-time grid monitoring and control at load terminals. Load models are important in the analysis of voltage stability, and accurate load models are useful in analysing the voltage stability conditions. Phasor-measurement-unit (PMU) based wide-area monitoring and smart-automation is an innovative technology for measuring load voltage magnitude, phase angle, and frequency variations in a DFIG integrated large wind power system. This research paper focuses on estimating the real-time voltage stability through the use of linear, nonlinear, and dynamic load models in presence of a DFIG based wind-farm in WSCC three-machine nine-bus power network using PMU data. This study is carried out using MATLAB-Simulink software.

On the flow field induced by two counter-rotating propellers at varying load conditions

The hydrodynamics of the flow between and in the wake of contra-rotating propellers is investigated experimentally via Particle Image Velocimetry (PIV) at different advanced coefficients. Results show that the flow dynamics is deeply influenced by the interplay between the two systems of helical vorticity that develop in the wake. The forward and aft propellers’ slipstream structure is analyzed in terms of blade loading and relative phase angle. The onset of tip vortex break-up, reconnection and pairing processes occurring within the wake is discussed with a focus on instability mechanisms. Flow field measurements between propellers highlight that the distribution of the tangential component is balanced more effectively by the aft propeller at specific loading conditions.

Thermomechanical fatigue damage development of continuous carbon fiber-reinforced ceramic-matrix composites subjected to different loading sequences and phase angles

Under thermomechanical fatigue (TMF) loading of fiber-reinforced ceramic-matrix composites (CMCs), the multiple TMF damage mechanisms of matrix multicracking, fiber/matrix interface debonding, and sliding are affected by the loading sequence and phase angle. In this paper, the TMF damage development of carbon fiber-reinforced CMCs is investigated corresponding to different loading sequences and phase angles. The TMF damage evolution subjected to different loading sequences (i.e., constant fatigue peak stress, low-high fatigue peak stress, and high-low fatigue peak stress) and phase angles (i.e., θ = 0, π/3, π/2, and π) are analyzed. The effects of fiber volume fraction, matrix crack spacing, fiber/matrix interface debonded energy, initiate/steady-state fiber/matrix interface shear stress, and thermal cycle temperature on the TMF damage evolution are discussed. The experimental TMF damage evolution of fatigue peak strain and hysteresis modulus versus applied cycles curves of 2D and 2.5D C/SiC composites at elevated temperatures of 550 and 800 °C in air condition are predicted.

Contactless power transfer system for sealed lead acid battery charging

In this paper, an experimental study is carried out while charging the sealed lead acid battery bank using a series-parallel (SP) compensated contactless power transfer (CPT) system. Constant current (CC) and constant voltage (CV) modes are used for charging the battery bank. An expression of optimum operating frequency is derived to maintain the maximum compensated coil efficiency throughout the load variation in charging process. An experimental setup of SP compensated CPT system is built for charging the battery bank. The variation of compensated coil efficiency and the load phase angle with respect to different operating frequencies in CC and CV modes is verified with the measurement. Based on the analysis, the control parameters are identified.

A comparative study on different walking load models

Excessive vibrations can occur in long-span structures such as floors or footbridges due to occupant\'s daily activity like walking and cause a so-called vibration serviceability issue. Since 1970s, researchers have proposed many human walking load models, and some of them have even been adopted by major design guidelines. Despite their wide applications in structural vibration serviceability problems, differences between these models in predicting structural responses are not clear. This paper collects 19 popular walking load models and compares their effects on structure\'s responses when subjected to the human walking loads. Model parameters are first compared among all these models including orders of components, dynamic load factors, phase angles and function forms. The responses of a single-degree-of-freedom system with various natural frequencies to the 19 load models are then calculated and compared in terms of peak values and root mean square values. Case studies on simulated structures and an existing long-span floor are further presented. Comparisons between predicted responses, guideline requirements and field measurements are conducted. All the results demonstrate that the differences among all the models are significant, indicating that in a practical design, choosing a proper walking load model is crucial for the structure\'s vibration serviceability assessment.

Analysis based on the energy release rate criterion of a dynamically growing crack approaching an interface

A problem of a dynamically growing crack, which is approaching an interface between the two elastic isotropic materials at an arbitrary angle, is considered in this paper. That crack could behave in three ways: (i) it can arrest at contact with the interface, (ii) it can deflect into the interface and continue to propagate along it or (iii) the crack can penetrate the interface and continue to propagate in the material across it. The competition between the latter two cases can be estimated by considering the ratio of the energy release rates necessary for the crack penetrating the interface and for the crack deflecting into the interface. A concept that the criterion for the dynamic crack growth in homogeneous solids could be based on the static stress field, with addition of the stress intensity factor dependent on time, is used here to explain the behavior of the crack approaching the interface in dynamic loading conditions. Obtained results enable comparison of the interface dynamic fracture toughness to the fracture toughness of the base material (without the interface), to determine whether the incoming crack would deflect into or would penetrate the interface. If the ratio between the dynamic fracture toughness of the interface and the dynamic fracture toughness of the material into which the crack continues to propagate was less than the ratio of the dynamic release rates for the deflecting and penetrating crack, the incoming crack would deflect into the interface. If the case was reversed, the crack would cross the interface and continue to propagate in the material across it. Comparison of results for the load phase angle dependence on the crack tip propagation speed and on the approaching angle, obtained by this criterion and by the maximum stress direction criterion, proves the validity of the energy release rate concept adopted in this analysis.

Switching Frequency Analysis of Staircase-Modulated Modular Multilevel Converters and Equivalent PWM Techniques

The large number of voltage levels in a modular multilevel converter (MMC) make staircase modulation a feasible alternative, particularly in high-power applications. However, staircase waveforms do not necessarily mean operation of the MMC submodules (SMs) at the fundamental frequency. This paper presents an analysis of SM switching frequencies in staircase-modulated MMCs and their correlation to the modulation index and load phase angle. A carrier-based pulsewidth-modulation (CB-PWM) equivalent technique is also developed. This analysis demonstrates that CB-PWM techniques provide a similar switching frequency with superior harmonic performance and improved voltage balancing characteristics at all modulation indices compared to staircase modulation. The theoretical analysis is verified with extensive simulation results for MMCs with different SMs and experimental results from a laboratory prototype.

Testing and assessment of fatigue life prediction models for Indian PHWRs piping material under multi-axial load cycling

In the present paper, experimental and analytical fatigue studies on primary piping material of Indian PHWRs, have been carried out under multi-axial loading with an aim to assess the adequacy of currently used fatigue life models based on ASME B&PV Sec-III procedure and plastic strain energy density. The experiments were conducted under axial, torsion and combined axial–torsion loading with different loading waveforms, phase angle and strain ratio (shear to axial). The tests under varying principal directions loading resulted in shorter fatigue lives. The orientations of crack initiation plane were measured and found dependent on the loading parameters which supports the idea of critical plane based fatigue models.

Comparison of solder joint fracture behavior in Arcan and DCB specimens

The mixed-mode fracture energies of copper–SAC305–copper solder joints were measured using both an Arcan-type specimen and a double-cantilever beam (DCB) specimen. The critical strain energy release rate, Jci, values obtained from Arcan-type specimens were in the range of 10–80J/m2, depending on the strain rate and phase angle of loading, while those obtained from DCB specimens were much higher, in the range of 380–2300J/m2. This large difference in the measured Jci values, which is consistent with the literature, was explained in terms of the stress distributions, constraint and plastic zone sizes in the solder layers in these two specimens.

A molecular dynamics study of nanofracture in monolayer boron nitride

In this paper, we use molecular dynamics (MD) modeling to study the fracture properties of monolayer hexagonal boron nitride (h-BN) under mixed mode I and II loading. We investigate the impact of crack edge chirality, crack tip configuration and loading phase angle on the crack propagation path and critical stress intensity factors. The MD results predict that under all the loading phase angles cracks prefer to propagate along a zigzag direction and the critical stress intensity factors of zigzag cracks are higher than those of armchair cracks. Under mixed mode loading, the h-BN sheets can undergo out-of-plane deformations due to the buckling induced by compressive stresses. The out-of-plane deformations can be significant when mode II loading is dominant. An excessive amount of out-of-plane deformation can induce buckling cracks. Depending on the loading phase angle and crack configurations, buckling cracks can nucleate before or after the propagation of the original cracks.

Walking load model for single footfall trace in three dimensions based on gait experiment

This paper investigates the load model for single footfall trace of human walking. A large amount of single person walking load tests were conducted using the three-dimensional gait analysis system. Based on the experimental data, Fourier series functions were adopted to model single footfall trace in three directions, i.e. along walking direction, direction perpendicular to the walking path and vertical direction. Function parameters such as trace duration time, number of Fourier series orders, dynamic load factors (DLFs) and phase angles were determined from the experimental records. Stochastic models were then suggested by treating walking rates, duration time and DLFs as independent random variables, whose probability density functions were obtained from experimental data. Simulation procedures using the stochastic models are presented with examples. The simulated single footfall traces are similar to the experimental records.

Effect of processing parameters on fracture toughness of lead-free solder joints

Solder joint fracture toughness was measured using double-cantilever-beam specimens over a range of strain rates and mode ratios as a function of five key processing parameters: the type of lead-free solder alloy, solder thickness, time above liquidus, aging time, and the geometry of the end of the solder layer. Although the toughness was a strong function of the loading phase angle and strain rate, relatively small differences were due to the solder composition, time above liquidus, and aging. The effects of solder thickness and local end geometry were found to be significant only at the higher strain rates.

Fracture mechanics of monolayer molybdenum disulfide

Molecular dynamics (MD) modeling is used to study the fracture toughness and crack propagation path of monolayer molybdenum disulfide (MoS2) sheets under mixed modes I and II loading. Sheets with both initial armchair and zigzag cracks are studied. The MD simulations predict that crack edge chirality, tip configuration and the loading phase angle influence the fracture toughness and crack propagation path of monolayer MoS2 sheets. Furthermore, under all loading conditions, both armchair and zigzag cracks prefer to extend along a zigzag path, which is in agreement with the crack propagation path in graphene. A remarkable out-of-plane buckling can occur during mixed mode loading which can lead to the development of buckling cracks in addition to the propagation of the initial cracks.

IJARCCE - Computer and Communication Engineering

2 Abstract: Power factor is most important for all industrial as well as domestic sectors. In this research paper present the comparative study and analyzes the power factor variation due to loading effect. For this comparison we take different values of inductance, three different range of capacitor and two range of resistance and their total impedance is calculated. The calculated theoretical and practical values of power factor on the basis of different combination loads. Pure sinusoidal sine waves are displayed in computer through sound card and calculate the load phase angle between the fundamental components of the load voltage and current.

Determination of interfacial adhesion energies of thermal barrier coatings by compression test combined with a cohesive zone finite element model

Determination of interfacial adhesion energies of thermal barrier coatings is important for understanding failure mechanisms and predicting their lifetime. Combined compression test with a cohesive zone finite element model, it is shown that the interfacial adhesion energy is in the range of 100–130J/m2. Based on the nonlinear delamination theory, the critical interfacial adhesion energy of delamination is 120J/m2 and the corresponding loading phase angle is −56°. With the increase of the half-length of the crack, the crack propagation tends to be steady with a steady-state interface energy release rate of 150J/m2, and delamination experiences almost pure mode II. These results obtained from finite element simulations and theoretical analyses are in good agreement with the available values determined by other testing methods reported in the literatures, which confirms the validity of this method.

Performance Analysis of DVR Using ANN Controller for Voltage Quality Enhancement

This paper presents a Dynamic Voltage Restorer to mitigate power quality disturbances such as voltage sag, swell and harmonics. The compensation strategy is based on pre-sag compensation. Controller based on dq0 transformation technique and ANN is implemented in order to maintain the nominal load voltage and phase angle. Simulation studies under three phase rectifier with parallel resistive/capacitive dc load as a non linear load is carried out. Also the system is investigated under voltage sag and swells on source side using programmable AC source. Simulation results show that DVR performs accurately in mitigating disturbances with minimum Total Harmonic Distortion. The performance of DVR is verified using Matlab / Simulink Environment.

Contour-Based Dead-Time Harmonic Analysis in a Three-Level Neutral-Point-Clamped Inverter

The term dead time refers to a prime safety factor for most power electronic converter topologies, and it is included either in the control software or in the gate/base driver hardware, depending on the application as well as the control requirements. In this paper, the authors present a comprehensive numerical analysis of dead-time effects on the output voltage of a three-level neutral-point-clamped (NPC) inverter. To incorporate the dead-time effect in the output voltage, 3-D models of three-level carrier pulse width modulation (PWM) methods are modified for two dead-time implementations. Closed-form expressions of inverter phase voltage harmonics for phase opposition disposition (POD) PWM are derived based on the double Fourier series approach and modified contour plots. The harmonic spectra from numerical evaluations, simulations, and experiments for natural sampling (NS), symmetrical regular sampling (SRS), and asymmetrical regular sampling (ARS) are compared to validate the mathematical models. In addition, the fundamental voltage with respect to the dead time and the load phase angle is presented based on analytical results and simulation.

Investigation of interfacial properties of atmospheric plasma sprayed thermal barrier coatings with four-point bending and computed tomography technique

A modified four-point bending test has been employed to investigate the interfacial toughness of atmospheric plasma sprayed (APS) yttria stabilised zirconia (YSZ) thermal barrier coatings (TBCs) after isothermal heat treatments at 1150°C. The delamination of the TBCs occurred mainly within the TBC, several to tens of microns above the interface between the TBC and bond coat. X-ray diffraction analysis revealed that the TBC was mainly tetragonal in structure with a small amount of the monoclinic phase. The calculated energy release rate increased from ~50J/m−2 for as-sprayed TBCs to ~120J/m−2 for the TBCs exposed at 1150°C for 200h with a loading phase angle about 42°. This may be attributed to the sintering of the TBC. X-ray micro-tomography was used to track in 3D the evolution of the TBC microstructure non-destructively at a single location as a function of thermal exposure time. This revealed how various types of imperfections develop near the interface after exposure. The 3D interface was reconstructed and showed no significant change in the interfacial roughness after thermal exposure.

Prediction of flow rutting in asphalt concrete layers

This paper evaluates an approach for predicting rut formation in asphalt concrete (AC) layers. The approach is based on a linear viscoelastic model for predicting permanent vertical strain in AC layers subjected to a moving load. The input data are tyre pressure, loading speed, lateral wandering of loading wheel, shear modulus and phase angle of AC layer. The analytical approach takes into consideration the change in material characteristics in respect of temperature and changes in the air void content of AC layers due to repeated loading. The approach is verified by a full-scale accelerated loading test at different temperatures. The approach has shown good agreement as regards the prediction of flow rutting in AC layers. In addition, the approach is capable of calculating rutting profiles including the upheaval, which is important for estimating rut depth.

A Power-Recycling Technique for Improving Power Amplifier Efficiency Under Load Mismatch

This letter presents a method for improving the efficiency of a power amplifier (PA) under load mismatch by recycling the reflected power. By configuring the PA as a balanced PA, the reflected power will be directed to the isolation port of a 90° hybrid coupler. The reflected power can then by rectified and converted back to dc power to assist in supplying the PA. A prototype system was built to validate the concept and tested under various load phase angles with 2:1 and 4:1 VSWR using a W-CDMA voice signal at 836.5 MHz. Measurement results show that the power recycling technique improves the overall efficiency by as much as 22.1% when the output power level is 25 dBm. Under load conditions and power levels where the rectifier cannot provide sufficient output voltage level to supply the PA, the proposed technique simply maintains the original PA efficiency with no degradation.