• Wind and Structures
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• 제8권2호
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• pp.89-106
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• 2005

For estimating the vortex excited vibrations of overhead transmission lines, the Energy Balance Principle (EBP) is well established for spans damped near the ends. Although it involves radical simplifications, the method is known to give useful estimates of the maximum vibration levels. For very long spans, there often is the need for a large number of in-span fittings, such as in-span Stockbridge dampers, aircraft warning spheres etc. This adds complexity to the problem and makes the energy balance principle in its original form unsuitable. In this paper, a modified version of EBP is described taking into account in-span damping and in particular also aircraft warning spheres. In the first step the complex transcendental eigenvalue problem is solved for the conductor with in-span fittings. With the thus determined complex eigenvalues and eigenfunctions a modified energy balance principle is then used for scaling the amplitudes of vibrations at each resonance frequency. Bending strains are then estimated at the critical points of the conductor. The approach has been used by the authors for studying the influence of in-span Stockbridge dampers and aircraft warning spheres; and for optimizing their positions in the span. The modeling of the aircraft warning sphere is also described in some detail.

• Journal of Power Electronics
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• 제16권5호
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• pp.1735-1742
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• 2016

This paper proposes an interleaved five-level boost converter based on a switched-capacitor network. The operating principle of the converter under the CCM mode is analyzed. A high voltage gain, low component stress, small input current ripple, and self-balancing function for the capacitor voltages in the switched-capacitor networks are achieved. In addition, a three-loop control strategy including an outer voltage loop, an inner current loop and a voltage-balance loop has been researched to achieve good performances and voltage-balance effect. An experimental study has been done to verify the correctness and feasibility of the proposed converter and control strategy.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.424-428
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• 2007

In the current most tool using heat and mass balance in a coal gasifier is dependent on commercial code such as STANJAN, CHEMKIN. However, in order to keep the self-reliance technology, it is necessary to develop the original design tool available for comprehension and analysis on the spot. So in this study, its own heat and mass balance program is developed on the assumption that the process in a coal gasifier is adiabatic and quasi-equilibrium. The mass balance is calculated by using the chemical equilibrium principle. Also the heat and mass balance according to main operating factors such as temperature, pressure and O2/Coal ratio, was carried in this tool. This heat and mass balance was verified on the basis of the results simulated in STANJAN, commercial codes using similar logic.

• Structural Engineering and Mechanics
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• 제63권1호
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• pp.23-35
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• 2017

A nonlinear static procedure considering work-energy principle and global failure mechanism to estimate base shears of reinforced concrete (RC) frame-type structures is presented. The relative energy equation comprising of elastic vibrational energy, plastic strain energy and seismic input energy is obtained. The input energy is modified with a factor depending on damping ratio and ductility, and the energy that contributes to damage is obtained. The plastic energy is decreased with a factor to consider the reduced hysteretic behavior of RC members. Given the pre-selected failure mechanism, the modified energy balance equality is written using various approximations for modification factors of input energy and plastic energy in scientific literature. External work done by the design lateral forces distributed to story levels in accordance with Turkish Seismic Design Code is calculated considering the target plastic drift. Equating the plastic energy obtained from energy balance to external work done by the equivalent inertia forces considering, a total of 16 energy-based base shears for each frame are derived considering different combinations of modification factors. Ductility related parameters of modification factors are determined from pushover analysis. Relative input energy of multi degree of freedom (MDOF) system is approximated by using the modal-energy-decomposition approach. Energy-based design base shears are compared with those obtained from nonlinear time history (NLTH) analysis using recorded accelerograms. It is found that some of the energy-based base shears are in reasonable agreement with the mean base shear obtained from NLTH analysis.

• 한국안전학회지
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• 제15권1호
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• pp.93-99
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• 2000

This paper presents a study on the assessment of electrical fire hazards by electric circuits with leakage. The hazards are evaluated with the energy supplied by earth-leakage currents which flow in the circuits simulating the actual circuit of domestic premises. Also, operating time and current of ELB are measured by an experimental approach. A common specification of ELB used in this paper has a sensitivity of 30[mA] for leakage current working on the current-balance principle. Total charges and energy of leakage currents are calculated quantitatively by a theoretical approach and compared with the results obtained from experiments.

• Wind and Structures
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• 제6권4호
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• pp.307-324
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• 2003

The paper presents results of studies concerning wind-induced aeolian vibration and fatigue of a 110 kV covered conductor overhead line. Self-damping measurement techniques are discussed: power method is found to be the most reliable technique. A method for compensating tension variations during the self-damping test is presented. Generally used empirical self-damping power models are enhanced and the different models are compared with each other. The Energy Balance Analysis (EBR) is used to calculate the aeolian vibration amplitudes, which thereafter are converted to bending stress for the calculation of conductor lifetime estimate. The results of EBA are compared with field measurements, Results indicate that adequate lifetime estimates are produced by EBA as well as field measurements. Generally the EBA gives more conservative lifetime expectancy. This is believed to result from the additional damping existing in true suspension structures not taken into account by EBA. Finally, the correctness of the line design is verified using Cigre's safe design tension approach.

• Journal of Power Electronics
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• 제16권3호
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• pp.925-935
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• 2016

This paper proposes a new interleaved double-input three-level Boost (DITLB) converter, which is composed of two boost converters indirectly in series. Thus, a high voltage gain, together with a low component stress and a small input current ripple due to the interleaved control scheme, is achieved. The operating principle of the DITLB converter under the individual supplying power (ISP) and simultaneous supplying power (SSP) mode is analyzed. In addition, closed-loop control strategies composed of a voltage-current loop and a voltage-balance loop, have been researched to make the converter operate steadily and to alleviate the neutral-point imbalance issue. Experimental results verify correctness and feasibility of the proposed topology and control strategies.

• 전력전자학회논문지
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• 제26권1호
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• pp.66-73
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• 2021

This study presents a novel four-channel light-emitting diode (LED) current balancing topology using a current-fed hybrid quasi-Z-source converter. With the proposed structure, currents flowing through four LED strings are automatically balanced owing to the charge (amp-sec) balance condition on capacitors. Thus, automatic current balancing of the proposed driver is simple and precise. In addition, the proposed LED driver uses only one active switch and three diodes. The operating principle and characteristics of the proposed four-channel LED driver are analyzed in detail. To verify the operation of the proposed LED driver, a prototype is built and tested with different numbers of LEDs.

• 에너지공학
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• 제9권1호
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• pp.47-53
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• 2000

This paper is to propose the concept and performance of a gravity engine which could extract energy from sea or river as a clean. renewable and sustainable power. the vertical motion of the buoyancy cylinder of the present gravity engine is converted to the mechanical work directly without any hydraulic loss. The positive net energy between the imposed and harnessed one is achieved by the specific operating procedure. The detailed derivation of the energy balance is made based on the first principle of thermodynamics. The calculation demonstrates that the present gravity engine could harness more energy than the conventional turbine system in the same basin area because of the relatively high efficiency in the energy conversion system and added mass from the buoyancy cylinder.

• Journal of Power Electronics
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• 제14권3호
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• pp.499-506
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• 2014

This paper proposes a 3 kW single-phase bi-directional multi-level converter for energy storage applications. The proposed topology is based on the H-bridge structure with four switches connected to the DC-link. A simple phase opposition disposition PWM method that requires only one carrier signal is also suggested. The switching sequence to balance the capacitor voltage is considered. The topology can be extended to a nine-level converter or a three-phase system. The operating principle of the proposed converter is verified through a simulation and an experiment.