Parallel Load Research Articles

Designing of a multi-frequency vibrator antenna with parallel LC-circuits loads

Designing of a multi-frequency vibrator antenna with parallel LC-circuits loads

MHz-Driving Current-Fed Snubberless Soft Switching DC-DC Converter

This paper presents a novel current-fed step-up DC-DC converter that is suitable for the front-end high-frequency link DC-DC converter (DC-X) in a grid-tied inverter of a fuel cell interface. The proposed DC-DC converter features the snubberless zero current soft-switching (ZCS) commutation with high-frequency switching by adopting quasi-resonance and parallel load resonance; the multi resonance while minimizing the number of additional circuit components. The switch-mode transitions of the proposed DC-DC converter are explained in detail for revealing the principle of snubberless ZCS due the multi resonance. In order to analysis the proposed DC-DC converter more precisely, a time-domain analysis is employed to examine the high-order harmonics in the three-level stepwise voltage of the quasi-resonant high frequency inverter, which is superior to a conventional sinusoidal AC analysis. The effectiveness of the proposed converter and the analytical strategy is demonstrated by comparing the theoretical and simulation results, after which the feasibility is verified by experiment of a 1 MHz-55 W class prototype with Gallium Nitride (GaN) high-electron-mobility-transistor (HEMT).

Improving system performance in Homogeneous Multicore Systems

Allocation of parallel load in multicore systems has become a challenging task for high performance computing system. There are several parameters to evaluate the performance of a scheduling algorithm such as task imbalance and execution time. This paper proposes a task scheduling approach that targets multiple cores connected through appropriate interconnection network. The proposed approach utilizes the computing resources effectively by assigning the tasks dynamically among different cores of the system in a realistic time. Each task has its own timeline and multiple sequence of tasks are mapped on different cores of the system. In particular, performance is evaluated on n x n Mesh, DMesh, ZMesh and Torus networks. The load imbalance and execution times are considered as metrics to evaluate the performance of the proposed algorithm. Simulation results are obtained and compared with well-known minimum distance scheduling algorithm which shows reduction in execution time while maintaining the load imbalance. An improvement of 20-30% is obtained in load imbalance for considered multicore systems with improved execution time. The simulation study reveals that the proposed algorithm is best suited to take architectural benefits for mesh-based multicore systems.

EXPERIMENTS AND RELIABILITY ANALYSIS ON FRAME-TO-SHEATHING JOINTS IN LIGHT WOOD FRAMED SHEAR WALLS

To exploit the spruce-pine-fir (SPF) panel and the parallel strand bamboo (PSB) panel used in light wood framed shear wall and investigate the lateral behaviors of frame-to-sheathing joints in light wood framed shear wall with different characteristics, the experimental investigation and reliability analysis were carried out under monotonic load. The test configurations included joints with perpendicular-to-framing-grain load or parallel-to-framing-grain load, with SPF sheathing panel or PSB sheathing panel and with nail or screw. The results suggested that nailed joints with PSBpanel occurred ductile failure but other joints occurred brittle failure. Moreover, theultimate bearing capacity and the elastic stiffness of the joints under perpendicular load were higher than that ofthe joints under parallel load. The use of PSB panel and screw increased theultimate bearing capacity of the joints. Furthermore, based on Johansen yield theory and experimental results, the reliability analysis was carried out through first-order reliability methods. The results showed that the SPF-nail joints, the PSB-nail joints, and PSB-screw joints achieved the reliability requirements.

Comparison of the Performance of Prestressed Ribbed Panels and Hollow Core Panels Supported on Four-Edges

Tests of full-scale models of the precast slab with dimensions of 6.30 x 6.30 m, built of two different precast panels, were carried out under short-term load. The models were made of autoclaved aerated concrete (700 type) brick with a thickness of 240 mm and a height of 2.24 m. The slabs were supported at four edges. The first slab was precast prestressed ribbed panels with concrete overtopping. The second slab was made of prestressed hollow-core panels. The panels had the same modular width of 600 mm. Tests were carried out under load placed on the top of the slab. The short-term load was applied sequentially, and displacement measurements were measurement by the electronic method. The load was initially applied evenly distributed. In the last step, part of the load was transferred to one-half of the slabs. The obtained load was different for each half of the slab. The first part of the slab were panels 1 to 5, loaded with the value of 1.7 kN/m2, and the second part was panels 6 to 10 loaded with the value of 7.7 kN/m2. The tests allow determining the difference in slabs' performance depending on shear key construction. The panels maintained the possibility of load redistribution based on their interaction despite the longitudinal joints' work only through the concrete cross-section. The slabs had a different character of transverse displacements depending on the presence of concrete topping. The models revealed a different response to transferring part of the load to one-half of the slabs. There were no cracks in the line of longitudinal joints on the upper surface of the slabs. Also, there were no cracks on the bottom of the panels. At the panels' connection with the wall, rotation and lifting corners of the slabs were noticed. The measured displacements were significantly smaller than for the corresponding models of single-span slabs with a parallel load.

Scaling knowledge based virtual worlds: An efficiency gain through multi-core architectures

This paper investigates the impact of sequential content load algorithm on regional transfer in OpenSimulator framework. It, then, presents an abstract parallel content load algorithm, which is implemented using the basic parallel for and chunk partitioning constructs to exploit the parallelism of multi-core architectures. This work used a set of five example virtual worlds content to investigate the effectiveness of the proposed work and its impact on the reallocation process of regions in OpenSimulator. Simulation results revealed that the implementation using parallel for reduced the timings by 47% to 57% while the implementation using chunk partitioning minimized it by 63% to 72%. Time impact on regional transfer was reduced by 39% to 51% using parallel for while 52% to 66% using chunk partitioning.

0.5 V CMOS Inverter-Based Transconductance Amplifier with Quiescent Current Control

A two-stage CMOS transconductance amplifier based on the inverter topology, suitable for very low supply voltages and exhibiting rail-to-rail output capability is presented. The solution consists of the cascade of a noninverting and an inverting stage, both characterized by having only two complementary transistors between the supply rails. The amplifier provides class-AB operation with quiescent current control obtained through an auxiliary loop that utilizes the MOSFETs body terminals. Simulation results, referring to a commercial 28 nm bulk technology, show that the quiescent current of the amplifier can be controlled quite effectively, even adopting a supply voltage as low as 0.5 V. The designed solution consumes around 500 nA of quiescent current in typical conditions and provides a DC gain of around 51 dB, with a unity gain frequency of 1 MHz and phase margin of 70 degrees, for a parallel load of 1 pF and 1.5 MΩ. Settling time at 1% is 6.6 μs, and white noise is 125 nV/Hz.

Parallel Load Balancing on constrained client-server topologies

We study parallel Load Balancing protocols for the client-server distributed model defined as follows. There is a set C of n clients and a set S of n servers where each client has (at most) a constant number d⩾1 of requests that must be assigned to some server. The client set and the server one are connected to each other via a fixed bipartite graph: the requests of client v can only be sent to the servers in its neighborhood N(v). The goal is to assign every client request so as to minimize the maximum load of the servers.In this setting, efficient parallel protocols are available only for dense topologies. In particular, a simple protocol, named raes, has been recently introduced by Becchetti et al. [1] for regular dense bipartite graphs. They show that this symmetric, non-adaptive protocol achieves constant maximum load with parallel completion time O(log⁡n) and overall work O(n), w.h.p.Motivated by proximity constraints arising in some client-server systems, we analyze raes over almost-regular bipartite graphs where nodes may have neighborhoods of small size. In detail, we prove that, w.h.p., the raes protocol keeps the same performances as above (in terms of maximum load, completion time, and work complexity, respectively) on any almost-regular bipartite graph with degree Ω(log2⁡n).Our analysis significantly departs from that in [1] since it requires to cope with non-trivial stochastic-dependence issues on the random choices of the algorithmic process which are due to the worst-case, sparse topology of the underlying graph.

Silulation on Parallel Control Mthods of Isoland Microgrid Powered bylnverter and Diesel Generator

Aiming at the power quality problems caused by the large number of renewable energy access to the grid, three common parallel networking modes of inverters and diesel generators in the independent micro-grid were analyzed in this paper, this paper also makes a systematic and comprehensive comparsion from the control principle, control structure, control performance, overall resource occupation, deduced the equivalent conditions of droop control and virtual synchronous generator control. Secondly, the characteristic of different control methods was analyzed to test the stability and also point out the characteristic of voltage and current in this paper. Finally, the micro-grid model was builted on PSCAD/EMTDC platform to verify the performance of three methods from the conditions of parallel off grid switching, load mutation and three-phase short circuit fault, and also point out the application scope of different strategies, it has reference value for micro-grid engineering practice.

Design and dynamic analysis of integrated architecture for vibration energy harvesting including piezoelectric frame and mechanical amplifier

Vibration energy harvesters (VEHs) can transform ambient vibration energy to electricity and have been widely investigated as promising self-powered devices for wireless sensor networks, wearable sensors, and applications of a micro-electro-mechanical system (MEMS). However, the ambient vibration is always too weak to hinder the high energy conversion efficiency. In this paper, the integrated frame composed of piezoelectric beams and mechanical amplifiers is proposed to improve the energy conversion efficiency of a VEH. First, the initial structures of a piezoelectric frame (PF) and an amplification frame (AF) are designed. The dynamic model is then established to analyze the influence of key structural parameters on the mechanical amplification factor. Finite element simulation is conducted to study the energy harvesting performance, where the stiffness characteristics and power output in the cases of series and parallel load resistance are discussed in detail. Furthermore, piezoelectric beams with variable cross-sections are introduced to optimize and improve the energy harvesting efficiency. Advantages of the PF with the AF are illustrated by comparison with conventional piezoelectric cantilever beams. The results show that the proposed integrated VEH has a good mechanical amplification capability and is more suitable for low-frequency vibration conditions.

Robust coordination of multiple power sources for sequential service restoration of distribution systems

When a distribution system encounters a major outage due to extreme events, an efficient sequential service restoration (SSR) strategy is required to restore the outage system. However, uncertainties associated with renewable energy generation and load demands pose significant and complex challenges for the optimization of SSR strategies. This paper proposes a robust multiple power source co-optimization approach for the SSR of an outage distribution system. First, network configuration and sequential switching actions are jointly optimized to sequentially form microgrids (MGs). Second, multiple types of power sources, such as distributed generators and energy storage units, are re-energized and coordinated to pick up critical loads in parallel restored MGs. In addition, uncertainties associated with renewable energy generation and load demands are considered during the restoration process, thereby requiring a robust SSR scheme to increase the reliability of MG operations, The mathematical problem is modelled as a mixed-integer tri-level programming problem with inner-level binary variables. Thus, the extended column-and-constraint generation (EC&CG) algorithm is employed to solve the proposed robust model. The numerical results demonstrate the effective performance of the proposed approach and its robustness and advantages compared to existing models that do not consider uncertainties.

Adaptive power sharing scheme for parallel‐connected hybrid inverters in microgrid

This paper presents an adaptive power sharing control method of parallel-connected hybrid inverters in microgrid. Normally the AC microgrid is composed of hybrid inverters, other power generation equipment and some loads in parallel. Droop control or virtual synchronous generator is usually adopted to control parallel inverters, so the output power ratio between each inverter is fixed by droop parameters. The input of hybrid inverter is PV panel and battery, so the power output ability of each hybrid inverter is different because of the different PV panel capacity, illumination condition, battery capacity and battery state of charge. Hence, the output power of some hybrid inverters is short or redundant sometimes, which makes microgrid unstable or causes power generation restraints. It is necessary to recognize the actual power capacity of each inverter and control the output power reasonably. This paper analyzes the characteristics of parallel-connected hybrid inverters with droop control in microgrid. An adaptive power sharing method is developed to identify the unbalanced between the each inverter on DC bus. By adjusting the droop parameters, the output power of each inverter is regulated where the controlled parameters are defined in system transfer function with an optimal target. Experimental tests are executed following the numerical simulation. The results show that the output power of each inverter can be adjusted adaptively according to the practical needs. The excessive power from one inverter can be absorbed by the others. Therefore, the stability and the power capability in the system are both ensured by adopting the proposed methods. The outcomes of the study provide a reference to the development of the adaptive inverter in microgrid.

Wind load on façade scaffolding without protective cover – Eurocode and in-situ measurement approaches

This paper presents an analysis of scaffolding response to static wind action, based on different approaches. The static wind load was adopted according to Eurocode standard that required separate calculations for the load acting perpendicular (load case B) and parallel (load case C) to the façade of the building on which the scaffolding was attached. In the second approach, the wind load was calculated on the basis of in-situ measurements performed on scaffolding structures set on construction sites (load case A). The research was carried out on 61 façade scaffolding structures without protective covers. Models of every scaffolding were created in the Finite Element system, based on their real geometry taken from geodetic measurements. Static-strength analysis allowed comparison of the scaffolding response determined by node displacements, normal stress and axial force in structural elements. It was found that in most of the analyzed cases the wind load based on Eurocode approach resulted in the greatest axial force or normal stress in elements. In a few cases, the load based on in-situ tests caused greater response of the structures and the permissible stress and axial force value in the elements were exceeded. These scaffolding structures were usually detached from the wall and twisted out of plane. Analyses pointed out that the scaffolding during its operational use could experience a load other than perpendicular or parallel to its façade as it is given in Eurocode.

MODELING AND SIMULATION OF STATCOM FOR POWER QUALITY IMPROVEMENT

In power system, reactive power compensation is one of the important action to maintain better voltage profile, stability and decrease losses. STATCOM is feasible in terms of cost effective in wide range of problem solving capabilities among all Flexible AC Transmission system (FACTS) in both transmission and distribution levels. In this paper the synchronous rotating frame theory algorithm is used since it is easy to implement i.e. the rotating three phase quantities are converted into stationary components. So it requires less number of PI controllers and also calculations on the stationary quantities are easy than to do calculations on instantaneous quantities and the modeling of STATCOM is done. This project focuses on improvement of power quality in a three phase three wire system with a non-linear load i.e., three phase bridge rectifier and a parallel inductive load. Some power quality aspects like reactive power compensation of linear load, better Total Harmonic Distortion (THD) performance and the power factor improvement are achieved. The result shows the THD of input current achieved as per the IEEE 519-1992 standard. It is observed that STATCOM gives effective compensation for reactive power variation and hence the power quality of distribution systems improved.

Bending Characteristics of Laminated Wood Composites Made of Poplar Wood and GFRP

In this study, 4 layers of 5 mm thick slats obtained by sawing method from poplar wood were used. Plain woven GRFP with low density and grammage of 100 g/m2 (Type 1) and plain woven GRFP with high density and grammage of 200 g/m2 (Type 2) were placed and glued between each layer. Polyvinyl acetate (PVAc-D4), Polyurethane (PU) and dual-component Epoxy (L285-resin and H285-hardener) adhesives were used for gluing the layers. Strength values (bending and modulus of elasticity) between the obtained layers were investigated. As a result of the study, it was determined that epoxy glue has higher strength than polyurethane and polyvinyl acetate glues; Type 2 plain woven fabric has higher strength than Type 1 plain woven fabric; and parallel load to the glue line results in higher performance than perpendicular load to the glue line.

Parallel framework for dynamic domain decomposition of data assimilation problems: a case study on Kalman Filter algorithm

We focus on Partial Differential Equation (PDE) based Data Assimilatio problems (DA) solved by means of variational approaches and Kalman filter algorithm. Recently, we presented a Domain Decomposition framework (we call it DD-DA, for short) performing a decomposition of the whole physical domain along space and time directions, and joining the idea of Schwarz' methods and parallel in time approaches. For effective parallelization of DD-DA algorithms, the computational load assigned to subdomains must be equally distributed. Usually computational cost is proportional to the amount of data entities assigned to partitions. Good quality partitioning also requires the volume of communication during calculation to be kept at its minimum. In order to deal with DD-DA problems where the observations are nonuniformly distributed and general sparse, in the present work we employ a parallel load balancing algorithm based on adaptive and dynamic defining of boundaries of DD -- which is aimed to balance workload according to data location. We call it DyDD. As the numerical model underlying DA problems arising from the so-called discretize-then-optimize approach is the constrained least square model (CLS), we will use CLS as a reference state estimation problem and we validate DyDD on different scenarios.

Likelihood Ratio Test and Non-parametric Test for Load Sharing

In present article, we propose a likelihood ratio test and a non-parametric test for testing the load sharing effect observed in the two component parallel load sharing system. We have modeled the load sharing phenomenon observed in such system by the exponentiated conditional distribution function based load sharing model proposed by Sutar and Naik-Nimbalkar (2016). We have taken component baseline distribution as Weibull distribution and linear failure rate distribution. The simulation study to see the performance of proposed test procedures is reported. We analyze two data sets for illustrative purpose.

Wavelet-Analysis-Based Singular-Value-Decomposition Algorithm for Weak Arc Fault Detection via Current Amplitude Normalization

A wavelet-analysis-based singular-value-decomposition (WASVD) algorithm augmented by the current amplitude normalization (CAN) is proposed in this study to tackle the challenge of weak arc-fault detection. First, an experimental platform is prepared for producing bus-current data from normal operations and weak arc faults. Then, the CAN and the wavelet analysis (WA) are performed on collected signals. Moreover, the coefficients in each layer of the WA are exploited to construct a correspondent Hankel matrix for acquiring the WASVD coefficients by the singular value decomposition (SVD). In order to filter the irrelevant components automatically, the coordinates of AC/DC current components are located by the entropy index calculation on WASVD coefficients. The performances of conventional arc-fault detection algorithms with dependence on manual set-up will be severely degraded if loads, current amplitudes or working environments undergo drastic changes. The proposed algorithm avoids this dilemma by subtracting one arbitrary processed normal signal from all signals of the same system to reduce the noise floor instead of manual adjustment. In addition, signals are reconstructed to have features extracted for the support vector machine (SVM) to make the final diagnostic judgment. The effectiveness of the proposed WASVD-CAN algorithm is verified by various experiments including single load and parallel loads with different operating current amplitudes and an arc generator mounted in series with each load respectively generating series or parallel arc faults. The results show that the proposed algorithm, without manually retuning parameters, has achieved outstanding detection accuracies in comparison with traditional weak arc-fault detection methods.

Stress-stain state in elastic spherical shells under the action some asymmetrical of circular loads

The paper presents the basic differential equations for calculating shells of rotation. It is considered that the material of the shell works beyond the elastic limit. The conclusion of the resolving system of differential equations is based on the linear shell theory and the Kirchhoff-Love hypothesis. The physical correlations are based on the small elastic-plastic deformation theory. With the construction of the solution of the load function, also unknown resolving functions expand to the Fourier series along the circumferential coordinate. In the present work, the action of the asymmetrical distribution along the parallel loads is considered. The solution is approached by the elastic decisions method. The study of stress-stain state in the isotropic spherical shells is presented in the work. The results of the calculation are presented in the example of a spherical shell. The work of the material beyond the elastic limit is taken into account using assuming linear hardening of the material. The shell is loaded with ring distributed loads, and they are applied on a certain segment in a parallel circle. The diagrams of bending moments and areas of the appearance of plastic deformations along the thickness of the shell are presented. The areas of plastic deformations for ring loads distributed along the parallel relative to the zero meridian in the range of 45, 90,135 degrees are shown.

Determining potential passive islanding detection indicators for single-point single inverter, single-point multi-inverter and multi-point multi-inverter scenarios

Distributed Generation (DG) sources predominantly renewable energy-based like solar photovoltaic and wind energy sources are considerably penetrated in power system networks. This high penetration of DG sources may lead to the formation of unintentional islands which is hazardous to both the equipment and personnel, if sustained. In this paper, 46 passive parameters are considered to find out which candidate(s) are promising for detecting sustained unintentional islands and avoid false DG trips. These 46 parameters are derived from point of common coupling (PCC) voltage, DG output current, frequency, power factor angle, active and reactive powers. All these parameters are tested on standard IEEE 13 and 34 bus distribution networks integrated with inverter-interfaced DGs at different locations for different penetration levels in MATLAB/SIMULINK environment. The parameters are tested for different islanding events (comprising of various local loads such as conventional parallel RLC resonant load, R, RC, and RL loads) and for different non-islanding events. The parameters are then ranked accordingly by a suitable averaging approach based performance ranking technique. From this analysis, the best candidates are obtained for detecting inverter DG islands at single-point (or single PCC) location and multi-point (or multiple PCCs) locations. Multiple best passive candidates are obtained for different island scenarios from which a set of promising islanding detection indicators are proposed.