• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.688-698
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• 2018

Quasi Z-Source Multilevel Inverter (QZMLI) topology has attracted grid connected Photovoltaic (PV) systems in recent days. So there is a remarkable research thrust in switching techniques and control strategies of QZMLI. This paper presents the mathematical analysis of Phase shift- Pulse Width Amplitude Modulation (PS-PWAM) for QZMLI and emphasizes on the advantages of the technique. The proposed technique uses the maximum and minimum envelopes of the reference waves for generation of pulses and proportion of it to generate shoot-through pulses. Hence, it results in maximum utilization of input voltage, lesser switching loss, reduced Total Harmonic Distortion (THD) of the output voltage, reduced inductor current ripple and capacitor voltage ripple. Due to these qualities, the QZMLI with PS-PWAM emerges to be the best suitable for PV based grid connected applications compared to Phase shift-Pulse Width Modulation (PS-PWM). The detailed math analysis of the proposed technique has been disclosed. Simulation has been performed for the proposed technique using MATLAB/Simulink. A prototype has been built to validate the results for which the pulses were generated using FPGA /SPARTAN 3E.

• Geomechanics and Engineering
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• 제31권3호
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• pp.281-289
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• 2022

Bio-CaCO₃ is a blowout environment-friendly materials for soil improvement and sealing of rock fissures. To evaluate the chemical characteristics, shape, size and productivity of soybean urease induced CaCO₃ precipitates (SUICP), experimental studies were conducted via EDS, XRD, FT-IR, TGA, BET, and SEM. Also, the conversion rate of SUICP reaction at different time were determined and analyzed. The Bio-CaCO₃ product obtained by SUICP is comprehensively judged as calcite based on the results of EDS, XRD and FT-IR. The SUICP calcite precipitates are detected as spherical or ellipsoidal particles 3-6 ㎛ in diameter with nanoscale pores on their surface, and this morphology is novel. The median secondary particle size d₅₀ is 39-88 ㎛, indicating the agglomeration of the primary calcite particles. The Bio-calcite decomposes at 650-780℃, representing a medium thermal stability. The conversion rate of SUICP reaction can reach 80% in 24h, which is much more efficient than microbially induced CaCO₃ precipitation. These results reveal the knowledges of SUICP, and further direct its engineering applications. Moreover, we show an economic channel to obtain porous spherical calcite.

• 센서학회지
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• 제24권4호
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• pp.219-223
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• 2015

Indium free consisting of three alternating layers GTO/Ag/GTO has been fabricated by radio-frequency (RF) sputtering for the applications as transparent conducting electrodes and the structural, electrical and optical properties of the gallium tin oxide (GTO) films were carefully studied. The gallium tin oxide thin films deposited at room temperature are found to have an amorphous structure. Hall Effect measurements show a strong influence on the conductivity type where it changed from n-type to p-type at $700^{\circ}C$. GTO/Ag/GTO multilayer structured electrode with a few nm of Ag layer embedded is fabricated and show the optical transmittance of 86.48% in the visible range (${\lambda}$ = 380~770 nm) and quite low electrical resistivity of ${\sim}10^{-5}{\Omega}cm$. The resultant power conversion efficiency of 2.60% of the multilayer based OPV (GAG) is lower than that of the reference commercial ITO. GTO/Ag/GTO multilayer is a promising transparent conducting electrode material due to its low resistivity, high transmittance, low temperature deposition and low cost components.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1997년도 추계학술발표회논문집
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• pp.88-92
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• 1997

Power conversion system must be increased swiching frequency in order to achieve a small size, a light weight and a low noise, However, the swiches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. In this paper, the authors propose a DC-DC boost converter of high power by partial resonant switch method (PRSM). The switching devices in a proposed circuit are operated with soft swiching and the control technique of those is simplified for switch to drive in constant duty cycle. The partial resonant circuit makes use of a inductor suing step up and a condenser of loss-less snubber. Also the circuit has a merit which is taken to increase of efficiency, as if makes to a regeneration at input source of accumulated energy in snubber condenser without loss of snubber in conventional cirvuit. The result is the the switching loss is very low and the efficiency of system is high. The proposed converter is deemed the most suitable for high power applications where the power switching devices are used.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.262-263
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• 2005

Pt counter electrode based on flexible metal for dye-sensitized solar cells(DSCs) has been investigated. Photovoltaic structures on lightweight substrates have several advantages over the heavy glass-based structures in both terrestrial and space applications. Cyclic voltammetry and impedance spectroscopy were used to investigate electrochemical properties of Pt counter electrode both FTO glass and SUS sheet substrate. The DSCs composed of the counter electrode based on a stainless steel substrate has obtained conversion efficiencies comparable to that based on the conducting glass. The counter electrode based on the stainless steel substrate has the merit of improving the fill factor and conversion efficiency of the DSCs by reducing its internal resistance.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권4호
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• pp.451-462
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• 2016

Photovoltaic energy conversion becomes main focus of many researches due to its promising potential as source for future electricity and has many advantages than the other alternative energy sources like wind, solar, ocean, biomass, geothermal etc. In Photovoltaic power generation multilevel inverters play a vital role in power conversion. The three different topologies, diode-clamped (neutral-point clamped) inverter, capacitor-clamped (flying capacitor) inverter and cascaded h-bridge multilevel inverter are widely used in these multilevel inverters. Among the three topologies, cascaded h-bridge multilevel inverter is more suitable for photovoltaic applications since each pv array can act as a separate dc source for each h-bridge module. This paper presents a single phase Cascaded H-bridge five level inverter for grid-connected photovoltaic application using sinusoidal pulse width modulation technique. This inverter output voltage waveform reduces the harmonics in the generated current and the filtering effort at the input. The control strategy allows the independent control of each dc-link voltages and tracks the maximum power point of PV strings. This topology can inject to the grid sinusoidal input currents with unity power factor and achieves low harmonic distortion. A PID control algorithm is implemented in Arm Processor LPC2148. The validity of the proposed inverter is verified through simulation and is implemented in a single phase 100W prototype. The results of hardware are compared with simulation results. The proposed system offers improved performance over conventional three level inverter in terms of THD.

• Journal of Power Electronics
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• 제13권3호
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• pp.339-348
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• 2013

Multiphase dc-dc converters are widely used in modern power electronics applications due to their advantages over single-phase converters. Such advantages include reduced current stress in both the switching devices and passive elements, reduced output current ripple, and so on. Although the output current ripple of a converter can be significantly reduced by virtue of the interleaving effect, the inductor current ripple cannot be reduced even with the interleaving PWM method. One way to solve this problem is to use a coupled inductor. However, care must be taken in designing the coupled inductor to maximize its performances. In this paper, a detailed analysis of a coupled inductor is conducted and the effect of a coupled inductor on current ripple reduction is investigated extensively. From this analysis, a UU core based coupled inductor structure is proposed to maximize the performance of the coupled inductor.

• Current Photovoltaic Research
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• 제10권4호
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• pp.107-110
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• 2022

Lightweight and flexible photovoltaic (PV) modules are attractive for building-integrated photovoltaic (BIPV) applications because of their easy construction and applicability. In this study, we fabricated lightweight and flexible c-Si PV modules using ethylene tetrafluoroethylene (ETFE) front cover and shingled design string cells. The ETFE front cover instead of glass made the PV modules lighter in weight, and the shingled design string cells increased the flexibility. Finally, we fabricated a PV module with a conversion power of 240.08 W at an area of 1.25 m² and weighed only 2 kg/m². Moreover, to check the PV module's flexibility, we conducted a bending test. The difference of conversion power between the modules before and after bending shown was only 1.7 W, which showed a power reduction rate of about 0.7%.

• 한국전기전자재료학회논문지
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• 제31권2호
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• pp.117-121
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• 2018

Perovskite solar cells have received increasing attention in recent years because of their outstanding power conversion efficiency (exceeding 22%). However, they typically contain toxic Pb, which is a limiting factor for industrialization. We focused on preparing Pb-free perovskite films of Ag-Bi-I trivalent compounds. Perovskite thin films with improved optical properties were obtained by applying an anti-solvent (toluene) washing technique during the spin coating of perovskites. In addition, the surface condition of the perovskite film was optimized using a multi-step thermal annealing treatment. Using the optimized process parameters, $AgBi_2I_7$ perovskite films with good absorption and improved planar surface topography (root mean square roughness decreased from 80 to 26 nm) were obtained. This study is expected to open up new possibilities for the development of high performance $AgBi_2I_7$ perovskite solar cells for applications in Pb-free energy conversion devices.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2057-2061
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• 2015

This paper describes analysis and experimental characterization of low speed direct drive fractional slot concentrated winding (FSCW) surface permanent magnet synchronous motor (SPMSM) with consequent pole (CP) rotor, for which studies have been recently performed. The proposed motor, which consists of 30 poles and 36 slots, is analyzed and characterized by extensive 2D finite element analysis (FEA) and together with 3D FEA for an appropriate PM overhang length design. The validity of the analysis is confirmed by the corresponding experiments which fully characterize the proposed motor with excellent agreement between the FEA and the experiments. Thermal stability is also experimentally examined to determine continuous operating points and instantaneous operating points of the proposed motor. It is highly expected that the proposed motor is applicable for low speed direct drive applications.