• Journal of Power Electronics
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• v.18 no.5
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• pp.1585-1594
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• 2018

The estimation of $LiFePO_4$/graphite battery states suffers from the prominent hysteresis phenomenon between the respective open-circuit voltage curves towards charging and discharging. A lot of hysteresis models have been documented to investigate the hysteresis mechanism. This paper reviews and deeply interprets four non-electrochemical hysteresis models and some improvements. These models can be conveniently incorporated into commonly used equivalent circuit models to reproduce battery behaviors. Through simulation and experimental comparisons of voltage predictions and state-of-charge estimations, the pros and cons of these models are presented.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1200-1207
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• 2008

In this paper, a novel fault detection method is proposed when the neutral-point-clamped inverter has a open-circuit fault in the switching device. This proposed method is configured with simple circuit and is achieved by a simple algorithm using the inherent characteristic of the continuous Pulse Width Modulation. Also, this method has the fast fault detection ability and is much simpler to embody, in comparison with conventional fault detection methods. This ability to detect fault minimizes harmful effect which are such as DC-link voltage unbalance and overstress to other switching devices. Therefore, this proposed fault detection method can improve reliability of NPC inverter system. Experimental results are presented to verify the validity of proposed fault detection method.

• Transactions on Electrical and Electronic Materials
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• v.17 no.1
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• pp.13-17
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• 2016

The ampere-hour integral method and the open circuit voltage method are integrated via the extended Kalman filter method so as to overcome insufficiencies of the ampere-hour integral method and the open circuit voltage method for estimating battery SOC. The process noise covariance and the measurement noise covariance of the extended Kalman filter method are simplified based on the Thevenin equivalent circuit model, with a proposed simplified SOC estimating method. Verification of DST experiments indicated that the battery SOC estimating method is simple and feasible, and the estimated SOC error is no larger than 2%.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.39-51
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• 2014

This paper deals with design of a direct-coupled, small-scaled permanent magnet generator (PMG) for wind power application. First, this paper determines rated power and speed of the PMG from measured characteristics of wind turbines. Second, we derive analytical solutions for the open-circuit field in order to determine optimum magnet thickness and pole pitch/arc ratio. Third, on the basis of open circuit field solutions, stator magnetic circuit including slot opening, teeth width and yoke thickness is designed. And then, a diameter of stator coil which agree with a required current density is calculated, and its turns are determined from the area of slot considering winding packing factor. Finally, finite element (FE) method is employed in analyzing the details of the designed PMG and, test results such as back-emf measurements are given to confirm the design.

• Bulletin of the Korean Chemical Society
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• v.21 no.10
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• pp.1047-1048
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• 2000

Dye-sensitized nanocrystalline rutile $TiO_2$ solar cells were prepared, and the influence of Li+ and 1,2-dimethyl-3-hexyl imidazolium ions in the electrolyte on the photovoltaic properties was compared. The electrolyte con-taining Li+ ions produced a lower open-circuit photovoltage than the electrolyte with 1,2-dimethyl-3-hexyl im-idazolium ions, suggesting that the adsorption of Li+ ions to the rutile $TiO_2$ surface causes a shift in the band edges toward more positive potentials. At the same time, both the short-circuit photocurrent and the maximum value of the incident-photon-current conversion efficiency (IPCE) of the electrolyte containing Li+ ions were relatively higher. Data analysis suggests that presence of adsorbed Li+ ions improves via the phenomenon of band-edge movement the charge-injection efficiency by altering both the energy and number of excited state levels of the dye that participate in electron injection.

• ETRI Journal
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• v.30 no.2
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• pp.268-274
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• 2008

This paper proposes an open-loop clock recovery circuit (CRC) using two high-Q dielectric resonator (DR) filters for 39.8 Gb/s and 42.8 Gb/s dual-mode operation. The DR filters are fabricated to obtain high Q-values of approximately 950 at the 40 GHz band and to suppress spurious resonant modes up to 45 GHz. The CRC is implemented in a compact module by integrating the DR filters with other circuits in the CRC. The peak-to-peak and RMS jitter values of the clock signals recovered from 39.8 Gb/s and 42.8 Gb/s pseudo-random binary sequence (PRBS) data with a word length of $2^{31}-1$ are less than 2.0 ps and 0.3 ps, respectively. The peak-to-peak amplitudes of the recovered clocks are quite stable and within the range of 2.5 V to 2.7 V, even when the input data signals vary from 150 mV to 500 mV. Error-free operation of the 40 Gb/s-class optical receiver with the dual-mode CRC is confirmed at both 39.8 Gb/s and 42.8 Gb/s data rates.

• Current Photovoltaic Research
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• v.6 no.1
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• pp.12-16
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• 2018

The interest in perovskite solar cells has been skyrocketed owing to their rapid progress in efficiency in recent years. Here, we report the effect of non-stoichiometry in the methylammonium lead trihalide ($MAPbI_3$) precursors used in a solution process with different MAI : $PbI_2$ ratios of 1 : 0.96, 1 : 1.10, 1 : 1.15, and 1:1.20. With an increase in the $PbI_2$ content, the $PbI_2$ secondary phase was found to form at grain boundary region of perovskite thin films, as evidenced by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In terms of device performance, open-circuit voltage in particular is significantly improved with increasing the molar ratio of $PbI_2$, which is possibly ascribed to the reduction in recombination sites at grain boundary of perovskite and hence the prolonged life time of light-generated carriers according to the reported. As a result, the $PbI_2-excess$ devices exhibited a higher power conversion efficiency compared to the MAI-excess ones.

• Journal of Power Electronics
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• v.16 no.3
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• pp.982-993
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• 2016

A method for the fault-tolerant vector control of star-connected 3-phase Induction Motor (IM) drive systems based on Field-Oriented Control (FOC) is proposed in this paper. This method enables the control of a 3-phase IM in the presence of an open-phase failure in one of its phases without the need for control structure changes to the conventional FOC algorithm. The proposed drive system significantly reduces the speed and torque pulsations caused by an open-phase fault in the stator windings. The performance of the proposed method was verified using MATLAB (M-File) simulation as well experimental tests on a 1.5kW 3-phase IM drive system. This paper experimentally compares the operation of the proposed fault-tolerant vector controller and a conventional vector controller during open-phase fault.

• Smart Structures and Systems
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• v.9 no.2
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• pp.189-206
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• 2012

This paper focuses on the actuation system combined with a piezoelectric transducer and an electric circuit, which leads to a new insight; the electric actuation system is equivalent to mechanical variable-stiffness actuation systems. By controlling the switch in the circuit, the electric status of the piezoelectric transducer is changed, and consequently a variable-stiffness mechanism is achieved on the electric actuator. This proposed actuator features a shift in the equilibrium point of force, while conventional electrically-induced variable-stiffness actuators feature the variation of the stiffness value. We intensively focus on the equilibrium shift in the actuation system, which has been neglected. The stiffness of the variable-stiffness actuator is periodically modulated by controlling the switch, to suppress the vibration of the system in an open-loop way. It is proved that this electric actuator is equivalent to its mechanical counterpart, and that the electrical version has some practical advantages over the mechanical one. Furthermore, another kind of electrically-induced variable-stiffness actuator, using an energy-recycling mechanism is also discussed from the viewpoint of open-loop vibration control. Extensive numerical simulations provide comprehensive assessment on both electrically-induced variable-stiffness actuators employed for open-loop vibration control.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.620-627
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• 2000

This paper presents a mettled to obtain line constants for a catenary system. To find them, voltages, currents and power factors according to frequencies were measured in short circuit and open circuit respectively. And front the measured data, resistances, inductances and capacitances were also calculated.