Asynchronous Load Research Articles

Automatic control system of the reactive power factor of the power supply system of the industrial enterprise

Considered is the control of the reactive power factor of the power supply system of an industrial enterprise, which includes: electrical receivers with asynchronous load; workshop transformer substations with and without regulated capacitor units, as well as the main step-down substation with synchronous motors powered from it. It is proposed to consider electrical receivers with capacitor units and a transformer substation as an object of reactive power factor control, on the basis of which the corresponding automatic control system (ACS) is built. An ACS with an algorithm formed as a function of active and reactive power of electrical receivers is considered. The ACS was developed by the reactive power factor of the power supply system of the entire enterprise with shop combined loads. A method is given for calculating the capacity of capacitor units of shop substations. The use of this control system will allow meeting the regulatory requirements for ensuring the limiting values of the reactive power coefficients and thereby reducing losses during the transportation of electricity and increasing the throughput of the electrical network.

Effect of Loading Frequency Ratio on Multiaxial Asynchronous Fatigue Failure of 30CrMnSiA Steel.

Multiaxial asynchronous fatigue experiments were carried out on 30CrMnSiA steel to investigate the influence of frequency ratio on fatigue crack initiation and propagation. Test results show that the surface cracks initiate on the maximum shear stress amplitude planes with larger normal stress, propagate approximately tens of microns, and then propagate along the maximum normal stress planes. The frequency ratio has an obvious effect on the fatigue life. The variation of normal and shear stress amplitudes on the maximum normal stress plane induces the crack retardation, and results in that the crack growth length is longer for the constant amplitude loading than that for the asynchronous loading under the same fatigue life ratio. A few fatigue life prediction models were employed and compared. Results show that the fatigue life predicted by the model of Bannantine-Socie cycle counting method, section critical plane criterion and Palmgren-Miner’s cumulative damage rule were more applicable.

Three-Level Inverter Control Techniques: Design, Analysis, and Comparisons

This work addresses the analysis and design of various Proportional-Integral-Derivative (PID) control techniques for a three-level inverter. Multilevel power converters are modern and basic elements of high-voltage electric drive and power supply systems. By using simulations and specific computer-aided design tools, the overall functional characteristics of multilevel converters, as well as the electrical demands of the components, can be accurately assessed to obtain an appropriate control solution. An innovative and detailed software model of a three-level inverter is developed and then used for the implementation of control techniques. Several tuning methods are used to tune PID controllers for two specific cases: the multilevel inverter with a linear load and with an asynchronous motor load, respectively. A detailed analysis and comparisons of the quality criteria and control performance are achieved. This analysis shows that the choice of controller type depends on the inverter load. For the linear load, proper results are obtained with a PI Nichols-tuned controller, and for the asynchronous load, with a PI controller tuned via a modified Hokushin method. The computer-aided design tools can be further used for the simulation of the equipment in various operating conditions, normal and fault, following all functional parameters.

CMCSF: a collaborative service framework for mobile web augmented reality base on mobile edge computing

Mobile web-based augmented reality (MWAR) provides users with quick richer information interaction forms due to its convenience and universality. However, the 3D model data service for MWAR is a type of centralized file-based data service, which cannot simultaneously meet diverse user and response delay requirements in large-scale and complex applications. This affects the application and promotion of large-scale and complex MWAR application. To this end, this paper proposes a collaborative model data computing service framework (CMCSF) for MWAR between Mobile Edge Servers (MES), Cloud Servers (CS), and mobile devices. The main contributions of this paper include: (1) The CMCSF converts the file-based 3D model data service in MWAR to a computing-based and interfaced data service to meet the diverse service requirements of users; (2) The CMCSF establishes a collaborative computing model data service between the MES and the CS, and it computes a control and deployment strategy for the collaborative computing model data service in order to reduce the response delay of 3D model data; and (3) The CMCSF optimizes the loading method of the WebGL engine (for example, three.js) and applies the asynchronous loading method of the JSON interface data on the http protocol for browsers to get persistent model data services. An experimental evaluation shows the CMCSF improves the response efficiency of the 3D model data file Significantly when compared with the original centralized file-based 3D model file service.

Simulation of Gas Turbine Plant Modes with Prognostic Controllers in an Isolated Power Supply System with Asynchronous Load

Simulation of Gas Turbine Plant Modes with Prognostic Controllers in an Isolated Power Supply System with Asynchronous Load

SEM analysis of PA38-T6 aluminum alloy thin-walled tubular specimen fatigue fracture, and comparison to surface replication results

The paper presents results of SEM analysis of fatigue fracture surface of thin-walled tubular specimen manufactured from PA38-T6 aluminum alloy. In the previous research specimens were subjected to multiaxial loadings. They were axial, torsional, in-phase, 90º out-of-phase and asynchronous loadings. During the fatigue experiments, the process of initiation and development of cracks was tracked using the surface replication technique, using cellulose acetate thin foils. In the present work, SEM observations of fatigue fracture surface were conducted and compared to previously obtained data. It was confirmed, that the dominating mechanism of fatigue crack formation was the coalescence of small crack, regardless of loading type and level.

Multiaxial fatigue tests under variable strain paths and asynchronous loading and assessment of fatigue life using critical plane models

In the present work, axial-torsion fatigue tests were performed under two loading categories, (i) variable strain paths sequential loading and (ii) asynchronous (different loading frequencies) conditions on low C-Mn steel. Variable strain paths tests brought out that saturated cyclic stress-strain behaviour under a given strain path, is insignificantly affected by loading history. However, transient material behaviour is history dependent.Three different critical plane models, Fatemi-Socie (FS), Smith-Watson-Topper (SWT) and Arora et al. (bi-axial SWT) along with linear damage accumulation rule were used to predict fatigue life. FS and Arora et al. model resulted in accurate assessments under both loading categories.

Fatigue of four metallic materials under asynchronous loadings: Small cracks observation and fatigue life prediction

This paper is a continuation of previously published work. It presents the results of small cracks observation on the surfaces of fatigued specimens subjected to multiaxial loadings. Specimens were manufactured from four materials: PA38-T6 aluminum alloy, E235 and E355 non-alloy steels, and X5CrNi18-10 austenitic steel. Based on the cracking analysis, it was found that the aluminum alloy and low-alloy steels exhibited shear damage mechanism, while the austenitic steel showed the tensile damage mechanism. Fatigue life prediction was performed based on six popular damage parameters. A correlation between the observed damage mechanism and the fatigue life prediction quality was noted.

A novel technique for determining the dynamic Bauschinger effect by electromagnetic Hopkinson bar

Dynamic mechanical behavior of metallic materials under complicated loading conditions has attracted much attention. However, it is hard to obtain the dynamic Bauschinger effect of metallic materials due to the limitation of loading equipment. In order to investigate the relationship between the Bauschinger effect and strain rate effect of metallic materials, this paper proposes an asynchronous loading technique based on electromagnetic split Hopkinson bar system, which could provide an effective way to study the Bauschinger effect of metallic materials under high strain rate loading. We first introduce the main characteristics of the asynchronous loading device, that is, the specimen can be loaded by one cycle of continuous dynamic tension-compression loading pulse in which the two separate stress waves are created by electromagnetic pulse generators and prove to maintain their consistency. The propagation of stress waves was analyzed to ensure the continuity of the loading process. Then the dynamic loading process and the methods of data processing and stress wave separation are presented. Stress equilibrium was also analyzed in order to demonstrate the reliability of the equipment. Finally, the Bauschinger effect of 6061 aluminum alloy at 5% pre-strain during the process of dynamic compression to dynamic tension loading was studied using this method, and the corresponding quasi-static tests were also conducted for comparison. It was found that the material shows less strain-rate sensitivity under axial compression loading, while its Bauschinger stress parameter increases from 0.07 in quasi-static loading to 0.17 in dynamic loading. The results indicate that the Bauschinger effect of 6061 aluminum alloys depends on the strain rate and can be significantly enhanced under dynamic loading. This conclusion presents a challenge to the traditional conception that aluminum alloys are insensitive to strain rate.

Dynamic modeling and validation of a micro-combined heat and power system with integrated thermal energy storage

The operation of combined heat and power systems is inherently challenging due to the fact that they synchronously generate power and heat while being tasked to meet asynchronous loads. By integrating thermal storage into the system, these loads can be temporally decoupled, albeit at the cost of a more complex dynamical system. In this paper we present a nonlinear, reduced order dynamic model of a small-scale, proton exchange membrane fuel cell combined heat and power system with sensible thermal energy storage in the form of a stratified hot water tank. By modeling the thermal stratification dynamics within the thermal storage, its storage capacity, and the temperature of water that will be discharged from the tank, can be accurately quantified. A quasi-static approach is used to couple the dynamic components without increasing the model order, thereby minimizing computational burden. The resulting system model is fully parameterized by the system temperatures and model inputs, making it well suited for use as a faster than real-time, simulated testbed. The model’s empirical parameters are identified from experimental data, and the resulting system model is validated against an experimental testbed over a wide operating range. The results of the experimental validation show that the model is able to predict the electrical power and temperature of hot water provided to the end user within a normalized root mean square error of 1.58% and 8.34%, respectively. The presented model is available for download from a public repository through the URL provided at the end of the manuscript.

A Cut-Out Strategy for Wind Turbines that Ensures Low-Voltage Ride-Through Capability

To ensure the dynamic stability of the system and improve low-voltage ride-through (LVRT) capability, this study presents a cut-out strategy for doubly-fed induction generator (DFIG) wind turbines that combines reactive power output with asynchronous load reduction. This strategy reduces the risk of the large-scale disconnection of DFIGs in a wind farm by regulating the reactive power output of DFIGs in the wind farm and removing DFIGs in an asynchronous state based on the reduction ratio. Simulation results demonstrate that the implementation of this strategy can help increase the voltage at the point of common coupling and the LVRT time for a wind farm.

Studies of Current Modulation in the DC Voltage Link of the Frequency Converter during its Operation with Asynchronous Load

The paper discusses current issues on the inverters peculiarities in the frequency converter. Theoretical studies have been carried out to determine the influence of the induction motor mode on the current modulation in the DC link. The authors suggest a calculation technique to determine the form of transient current characteristics when exposed to a single pulse of the inverter. Model studies of the system, calculation and construction of current characteristics proved the correspondence of theoretical and practical results. The research results determined the relationship between the current modulation in the DC link and the induction motor mode of operation.

Investigation to the torsion generation of spatial tubes in bending-twisting process

Bending-twisting process can be used for manufacturing complex spatial tube products. To describe the relationship between the torsion of tube axis and the twisting angle, torsion adjustment index is introduced in existing literatures. However, a puzzling problem is that the torsion adjustment index varies nonlinearly in a large range. Until now, this phenomenon has not been explained properly. In this paper, three loading models are introduced to investigate the springback behavior of tube element in bending-twisting deformation, including synchronous loading model, asynchronous loading model, and multiple loading model. Equations are established to describe the relationship between torsion and twisting angle for the three loading models separately. By comparison, it is found that the relationships among bending radii, twisting angles, residual radii, and residual angles are only a little different for the three loading models above, while a distinguished relationship between torsion and twisting angle exists obviously. The multiple loading model is better for describing the inconformity between twisting angle and torsion in bending-twisting process. The executed work shows that the inconformity between twisting angle and torsion occurs before springback. There exists twisting deformation in feeding phase, but no torsion is generated. Twisting deformation in feeding phase only influences the torsion during springback. The enhanced twisting angle in bending phase is a key factor in torsion generation. The enhanced twisting angle can be influenced by the mobile die position and torque on clamp. Finally, the springback is also a factor in torsion variation.

Identification of fatigue damage mechanism in PA38-T6 aluminum alloy under multiaxial loadings – initial research

This paper presents results of the initial research which originated from previous work, which was aimed to study the effect of asynchronous loadings in elastic-plastic strain range. Among the others, a study of fatigue cracks on the fatigued specimens’ surfaces, was performed.The aim of the present work is to identify the mechanisms of initiation and propagation of small fatigue cracks in selected materials under multiaxial loadings, including asynchronous cases. To study the evolution of small cracks and main crack formation, the cellulose acetate thin foil replication technique was utilized. Fatigue tests were performed on thin-walled tubular specimens, which were mirror-polished after CNC machining, to avoid the influence of unwanted factors.This paper presents the first part of fatigue tests, performed on specimens manufactured from PA38-T6 (AW 6060-T6) aluminum alloy. Fully reversed axial, torsional and 90º out-of-phase loadings were applied in elastic-plastic strain regime, with strain control. For these loading cases a shear damage mechanism was identified, based on the observation of small cracks. The small cracks initiated ate grew on maximum shear strain planes. The main crack formed at the very end of fatigue life by coalescence of small cracks of high density, regardless the applied loading case and level. An interesting difference in cracking behavior was observed in case of out-of-phase loading, on the low loading level. Small cracks propagated, and the main crack formed by linking of a few propagating cracks.The research is in progress and will be extended to the lower levels of strain as well as other cases of loadings, including asynchronous loadings. It is planned to conduct the research using other materials, for example non-alloy steel and austenitic stainless steel.

Fatigue Life Prediction Under Multiaxial Variable Amplitude Loading Using A Stress-Based Criterion

This article presents fatigue life calculations for metals under different multiaxial variable amplitude loading patterns. Developed from a stress-based multiaxial fatigue criterion, a damage parameter used in the fatigue life prediction method can capture correctly different damage mechanisms (proportional and non-proportional multiaxiality, mean stress, asynchronous and variable amplitude) of fatigue loading in the high cycle fatigue domain. The method is based on a reference S-N curve and a cumulative damage law. Assessment of the accuracy of the proposed method is carried out with three different materials from literature (EN-GS800-2 cast iron, 39NiCrMo3 steel and SAE 1045 steel) subjected to different patterns of variable amplitude loading (blocks, non-proportional asynchronous and proportional random loading). Results reveal that the prediction method is in good accordance with the experimental data.

Strength Check of Aircraft Parts Based on Multi-GPU Clusters for Fast Calculation of Sparse Linear Equations

In order to improve the cost-effectiveness ratio, the next-generation vehicle needs to meet the requirements of reuse, while adopting a lighter structural weight, so it is necessary to realize the strength calculation and condition monitoring of key components in the digital twin. Most of the current monitoring methods are based on the characteristics of various data acquisition systems, but they need the support of a large number of flight data. The disadvantages of the above strategy can be avoided by reducing the structure of aircraft components to a finite element model and quickly checking the key components in the health management system. In order to solve the problem of fast calculation of the finite element model of the key components of the aircraft, a parallel algorithm and framework of large-scale sparse matrix preprocessing conjugate gradient method based on CUDA(Compute Unified Device Architecture) technology is proposed in the multi GPU(Graphics Processing Unit) workstation cluster environment. Once the sparse matrix is too large to be processed in a single workstation, this paper discusses how to realize the optimized data segmentation in the distributed multi-GPU computing environment. For the problem of iterative solution of matrix preprocessing, two preprocessing strategies of matrix bandwidth reduction parallelization and incomplete Cholesky decomposition are proposed, and asynchronous task concurrency and load balancing strategies are designed on the architecture. The calculation of some examples in the standard sparse matrix database shows that the algorithm and architecture proposed in this paper have the ability to solve large-scale sparse matrix quickly and efficiently, and can complete the fast strength verification of vehicle components.

Detection of Security Threats to Modern Websites

The problem of the dynamic analysis of website security using asynchronous content loading technologies is considered. The possibility of solving the problem of detecting scan input vectors using the technology of interpreting JavaScript scripts is considered.

Probabilistic optimal design of cleanroom air-conditioning systems facilitating optimal ventilation control under uncertainties

Buildings with spaces requiring strict temperature and humidity controls, such as pharmaceutical cleanrooms and semiconductor/microchip factories, have been growing very quickly in terms of total floor area and energy consumption. In such buildings, much of the energy is unnecessarily wasted due to the incoordination of system design and operation/control, especially under “off-design” and ever-changing ambient and load conditions. This paper, therefore, proposes a probabilistic optimal design method for cleanroom air-conditioning systems facilitating optimal ventilation control under uncertainties. To consider the effects of asynchronous loads in different zones/spaces with reduced computation demand, a probabilistic diversity factor method is proposed which is a simplified method to quantify the effects of uncertainties of space load diversities in multiple zones/spaces using diversity factors. The proposed design method is implemented and validated in the design optimization of air-conditioning systems for implementing four different ventilation control strategies considering possible and uncertain off-design conditions. The energy and economic performance as well as service satisfaction of the air-conditioning systems are also evaluated and compared. Results show that the proposed design method can obtain the optimal air-conditioning systems with minimum life-cycle cost and superior satisfaction of service.

Stress-strain response and fatigue life of four metallic materials under asynchronous loadings: Experimental observations

In this work, axial-torsional fatigue tests were carried out on four materials: PA38-T6 aluminium alloy, E235 and E355 non-alloy steels and X5CrNi18-10 austenitic steel. Applied loadings included axial, torsional, in-phase, 90° out-of-phase loading as well as several types of asynchronous loadings. All tests were strain-controlled. The results reported include the stress-strain response (hysteresis loops, equivalent stress histories and cyclic hardening/softening). Fatigue life has been studied taking into account the problem of the loadings’ cycle definition. The results show that this type of loading cause high non-proportional hardening and strongly influence fatigue life. The materials’ response was both path- and material-dependent.

Simultaneously enhanced strength and ductility of FGH4097 nickel-based alloy via a novel hot isostatic pressing strategy

Hot isostatic pressing (HIP) of nickel-based superalloys still suffer from some detrimental carbides precipitated along the prior particle boundaries (PPBs), resulting in the degradation of mechanical properties of superalloy parts. In this study, a novel asynchronous loading HIP strategy, elevating temperature to the highest value first and then raising pressure, was proposed for FGH4097 to overcome this industrial challenge. The results manifest this novel strategy paves the way for fabricating nickel-based superalloys with both significantly enhanced strength and ductility by in-situ eliminating carbides precipitated along PPBs during HIP process, further boosting HIP process as a potential technology for the near-net manufacturing of key components in aerospace field.