Power Hardware-in-the Loop Simulation ???????????? ????????? ??? ????????? ?????? ?????? ?????????

Department of Electrical EngineeringIn the prototype development process, the product functional testing could be expensive and time-consuming. In various industries such as aviation, automobiles, and electric power, Hardware-In-the-Loop Simulation (HILS) is used in the product development process. By using HILS, the system which is linked with the developed product is configured by simulation to provide a virtual operating environment. So, a variety of functions can be tested in an environment similar to the actual before the final product development stage. HILS performs simulation in real time to simulate the system same as actual operation. Various technical problems arise in this process, and a lot of research has been going on to solve the problem. In this paper, computation methods are proposed to improve the real-time simulation performance of a photovoltaic (PV) cell model for power hardware-in-the-loop simulation (PHILS) applications. In PHILS, high computation performance is required because the simulator should complete the target model calculations in a real-time manner without overrun errors. One solution is to reduce the computation time of the target model. To solve nonlinear PV cell model equations, numerical methods used for solving the nonlinear equations can be used. However, these methods can be computationally intensive. In order to optimize performance for PHILS, performance of Newton-Raphson and Halley???s numerical methods are compared and methods for choosing an initial value are proposed, which affect the computation time of the numerical iterations. Using the proposed initial value decision methods, the computation time can be drastically reduced. The target PV cell model, in which the computation time improvement method is applied, is verified in static and dynamic conditions to verify the accuracy of the model in the PHILS system. In addition, two PHILS tests were conducted to show examples of HILS for development of PV system power converter. First test is Maximum Power Point Tracking (MPPT) function test and second is to output the voltage of Differential Power Processing (DPP) converter model. Also, the real-time simulation for large-scale PV system is described to show the computation speed in extended model.ope

Effect of monovacancies on the relative stability of fcc and hcp hard-sphere crystals

The effect of monovacancies on the free energy difference of close-packed hard-sphere crystals was examined. The monovacancy free energy and concentration were obtained via Monte Carlo simulations with a biased insertion method interpreted in a grand-canonical formalism. The difference in the effect of the vacancies to the difference between the free energies of the defect-free crystalline phases was compared. It was observed that the relative stability of stress-free fcc and hcp crystals is not affected by the presence of monovacancies, and fcc remaines the more stable phase over all solid-phase densities.open5

Characterization of mono- and divacancy in fcc and hcp hard-sphere crystals

We determine and compare the thermodynamic properties of mono- and divacancies in the face-centered-cubic and hexagonal-close-packed hard-sphere crystals via a modified grand canonical ensemble. Widom-type particle insertion was employed to estimate the free energy of formation of mono- and divacancies, and the results are supported by an alternative approach, which quantifies the entropy gain of the neighbor particles. In hcp crystal, we found a strong anisotropy in the orientational distribution of vacancies and observe an eightfold increase in the number of divacancies in the hexagonal plane compared to the one in the out of plane at highest density of interest. This phenomenon is induced by the different arrangement and behavior of the shared nearest neighbor particles, which are located at the same distance from each vacant site in divacancy. The effect of divacancies on the free energy is to reduce that of the hcp crystal relative to the fcc by around 7?? 10-6 kB T at melting.open8

Surface tension and vapor-liquid phase coexistence of confined square-well fluid

Phase equilibria of a square-well fluid in planar slit pores with varying slit width are investigated by applying the grand-canonical transition-matrix Monte Carlo (GC-TMMC) with the histogram-reweighting method. The wall-fluid interaction strength was varied from repulsive to attractive such that it is greater than the fluid-fluid interaction strength. The nature of the phase coexistence envelope is in agreement with that given in literature. The surface tension of the vapor-liquid interface is calculated via molecular dynamics simulations. GC-TMMC with finite size scaling is also used to calculate the surface tension. The results from molecular dynamics and GC-TMMC methods are in very good mutual agreement. The vapor-liquid surface tension, under confinement, was found to be lower than the bulk surface tension. However, with the increase of the slit width the surface tension increases. For the case of a square-well fluid in an attractive planar slit pore, the vapor-liquid surface tension exhibits a maximum with respect to wall-fluid interaction energy. We also report estimates of critical properties of confined fluids via the rectilinear diameter approach.open312

Characterization of fluid-solid phase transition of hard-sphere fluids in cylindrical pore via molecular dynamics simulation

Equation of state and structure of hard-sphere fluids confined in a cylindrical hard pore were investigated at the vicinity of fluid-solid transition via molecular dynamics simulation. By constructing artificial closed-packed structures in a cylindrical pore, we explicitly capture the fluid-solid phase transition and coexistence for the pore diameters from 2.17?? to 15??. There exist some midpore sizes, where the phase coexistence might not exist or not clearly be observable. We found that the axial pressure including coexistence follows oscillatory behavior in different pore sizes; while the pressure tends to decrease toward the bulk value with increasing pore size, the dependence of the varying pressure on the pore size is nonmonotonic due to the substantial change of the alignment of the molecules. The freezing and melting densities corresponding to various pore sizes, which are always found to be lower than those of the bulk system, were accurately obtained with respect to the axial pressure.open9

Test Platform Development of Vessel???s Power Management System Using Hardware- in-the-Loop-Simulation Technique

A PMS (Power Management System) controls vessel's power systems to improve the system efficiency and to protect a blackout condition. The PMS should be developed with considering the type and the capacity of the vessel???s power system. It is necessary to test the PMS functions developed for vessel???s safe operations under various sailing situations. Therefore, the function tests in cooperation with practical power systems are required in the PMS development. In this paper, a hardware-in-the-loop (HIL) simulator is developed for the purposes of the PMS function tests. The HIL simulator can be more cost-effective, more time-saved, easier to reproduce, and safer beyond the normal operating range than conventional off-line simulators, especially at early stages in development processes or during fault tests. Vessel's power system model is developed by using a MATLAB/SIMULINK software and by communicating between an OPAL-RT???s OP5600 simulator. The PMS uses a Modbus communication protocol implemented using LabVIEW software. Representative tests of the PMS functions are performed to verify the validity of the proposed HIL-based test platform

Enhancing 2D Growth of Organic Semiconductor Thin Films with Macroporous Structures via a Small-Molecule Heterointerface

The physical structure of an organic solid is strongly affected by the surface of the underlying substrate. Controlling this interface is an important issue to improve device performance in the organic electronics community. Here we report an approach that utilizes an organic heterointerface to improve the crystallinity and control the morphology of an organic thin film. Pentacene is used as an active layer above, and m-bis(triphenylsilyl) benzene is used as the bottom layer. Sequential evaporations of these materials result in extraordinary morphology with far fewer grain boundaries and myriad nanometre-sized pores. These peculiar structures are formed by difference in molecular interactions between the organic layers and the substrate surface. The pentacene film exhibits high mobility up to 6.3 cm(2)V(-1)s(-1), and the pore-rich structure improves the sensitivity of organic-transistor-based chemical sensors. Our approach opens a new way for the fabrication of nanostructured semiconducting layers towards high-performance organic electronics.X116049Nsciescopu

Evaluation of bridge-function diagrams via mayer-sampling Monte Carlo simulation

We report coefficients of the h-bond expansion of the bridge function of the hard-sphere system up to order rho(4) (where rho is the density in units of the hard-sphere diameter), which in the highest-order term includes 88 cluster diagrams with bonds representing the total correlation function h(r). Calculations are performed using the recently introduced Mayer-sampling method for evaluation of cluster integrals, and an iterative scheme is applied in which the h(r) used in the cluster integrals is determined by solution of the Ornstein-Zernike equation with a closure given by the calculated clusters. Calculations are performed for reduced densities from 0.1 to 0.9 in increments of 0.1. Comparison with molecular simulation data shows that the convergence is very slow for the density expansion of the bridge function calculated this way.open9

Multi-Color Luminescence Transition of Upconversion Nanocrystals via Crystal Phase Control with SiO2 for High Temperature Thermal Labels

Upconversion nanocrystals (UCNs)-embedded microarchitectures with luminescence color transition capability and enhanced luminescence intensity under extreme conditions are suitable for developing a robust labeling system in a high-temperature thermal industrial process. However, most UCNs based labeling systems are limited by the loss of luminescence owing to the destruction of the crystalline phase or by a predetermined luminescence color without color transition capability. Herein, an unusual crystal phase transition of UCNs to a hexagonal apatite phase in the presence of SiO2 nanoparticles is reported with the enhancements of 130-fold green luminescence and 52-fold luminance as compared to that of the SiO2-free counterpart. By rationally combining this strategy with an additive color mixing method using a mask-less flow lithography technique, single to multiple luminescence color transition, scalable labeling systems with hidden letters-, and multi-luminescence colored microparticles are demonstrated for a UCNs luminescence color change-based high temperature labeling system