• Journal of Energy Engineering
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• v.11 no.3
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• pp.230-236
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• 2002

In real-time power system control, it is essential to measure the power system variables which are voltage, current, real and reactive power, power factor, system frequency and etc. These variables can be estimated or calculated by the synchronized phasor informations of voltage and current. Therefore, the synchronized phasor measurement of voltage and current is very important to real-time power system control. So, we develop SPMD (Synchronized Phasor Measurement Device) for synchronized phasor measurement of voltage and current. In this paper, we present the design and implementation of SPMD for real-time phasor measurement and the test results of developed SPMD on 380 V 3 phase distribution line in laboratory with resistor load and RTDS (Real Time Digital Simulator).

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.268-274
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• 1999

The problem of power factor and hmmonics are occurred in convelter system which used to SCRs and diodes as p power semiconductor devices. IGBT power device with selh:ommutation type was solved that problem. maintain the l input line current with sinusoidal wave CUlTent of input power source voltage. It was estimated that improvement of t transient state characteristics with feedfolward compensator added in the diode rectifier with single phase voltage type i inverter was used to simulation load. As a results it was verified that the transient state characteristics with voltage t type PWM convelter control was improved.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1830-1843
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• 2018

In this paper, the generation of a reference current and voltage signal based on a Kalman filter is offered for a 3-phase 4wire UPQC (Unified Power Quality Conditioner). The performance of the UPQC is improved with source voltages that are distorted due to harmonic components. Despite harmonic and frequency variations, the Kalman filter is capable enough to determine the amplitude and the phase angle of load currents and source voltages. The calculation of the first state is sufficient to identify the fundamental components of the current, voltage and angle. Therefore, the Kalman state estimator is fast and simple. A Kalman based control strategy is proposed and implemented for a UPQC in a distribution system. The performance of the proposed control strategy is assessed for all possible source conditions with varying nonlinear and linear loads. The functioning of the proposed control algorithm with a UPQC is scrutinized and validated through simulations employing MATLAB/Simulink software. Using a FPGA SPATRAN 3A DSP board, the proposed algorithm is developed and implemented. A small-scale laboratory prototype is built to verify the simulation results. The stated control scheme for the UPQC reduces the following issues, voltage sags, voltage swells, harmonic distortions (voltage and current), unbalanced supply voltage and unbalanced power factor under dynamic and steady-state operating conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.655-661
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• 2006

Dielectric and piezoelectric properties of PMN-PZT ceramics with a high mechanical quality factor$(Q_m)$ and a low temperature sintering temperature were investigated as a function of PZN substitution in order to develop multilayer piezoelectric transformer for AC-DC converter. Multilayer piezoelectric transformers were subsequently manufactured using the PMN-PZN-PZT ceramic offering the optimal behavior and then the electrical performance were invetigated. At the sintering temperature of $940^{\circ}C$, density, electromechanical coupling factor$(k_p)$, mechanical qualify factor$(Q_m)$ and dielectric constant$(\varepsilon_r)$ of 8 mol% PZN substituted specimen were $7.73g/cm^3$, 0.524, 1573 and 1455, respectively. The PZN substitution caused a increase in the dielectric constant and the electromechnical coupling factor. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at near the resonant frequency of 76.55 kHz and increased according to the increase of load resistance. The multilayer piezoelectric transformer with the output impedance coincided with the load resistance showed the temperature increase of less than $20^{\circ}C$ at the output power of 10 W. Based on the results, the manufactured multilayer transformer using the low temperature sintered PMN-PZN-PZT ceramics can be stably driven for both step-up and down transformers.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.2
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• pp.127-132
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• 2010

The standards of demand, diversity and load density are necessary to create the design of a transformer capacity that is seldom presented in terms for academic study. At the moment, both legal and institutional standards for such a transformer are insufficient both at home and abroad. The works described in this thesis strongly support more reasonable standards for calculating transformer capacity by correlating the analysis between the maximum utilization factors of a given transformer with those of a transformer capacity whose power consumption has been investigated within a lease apartment. In this dissertation, it is necessary to analyze the key features and general trend from the investigated data. It made an analysis of the feature parameters, such as average, standard deviation, median, maximum, minimun and thus it was carried by the linear and nonlinear regression analysis.

• Journal of IKEEE
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• v.15 no.1
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• pp.96-103
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• 2011

This paper deals with the characteristic analysis of the integrated power system applied for the electric propulsion ships. This includes the electric power system modeling which is accomplished with the electric power network mainly composed of generators, switchboards, variable frequency devices, electric motors, and etc. In addition, performance comparison between the permanent magnet synchronous motor (PMSM) and the induction motor (IM) for 3.7MW ship propulsion has been done. In order to investigated the main performance of propulsion motor, a coupled model taking into account torque density, copper loss, iron loss, efficiency, power factor, and torque ripple using finite element analysis (FEA) has been employed.

• Tribology and Lubricants
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• v.21 no.6
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• pp.249-255
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• 2005

In this paper, the friction characteristic of engine bearings has been analyzed in terms of a friction loss power, a minimum film thickness and an oil film pressure. This analysis has been focused on the fuel economy improvement with a low viscosity engine oil such as SAE 0W-40, which is used for a friction loss reduction and increased for a Diesel fuel economy. The friction loss power, the minimum oil film thickness and oil film pressure distribution for plain bearings of a Diesel engine are analyzed using an AVL's EXCITE program with a conventional engine oils of SAE 5W-40 and 10W-40, and a low viscosity engine oil of SAE 0W-40. The computed results indicate that a viscosity of engine oils is closely related to the friction loss power and the decreased minimum film thickness in which is a key parameter of a load carrying capacity of an oil film pressure distribution. When the low viscosity engine oil is supplied to engine bearings, it does not affect to the formation of a minimum oil film thickness. But the friction loss power has been significantly affected by low viscosity engine oil at a low operating temperature of 0. Based on the FEM computed results, the low viscosity engine oil at a low temperature range will be an important factor for an improvement of the fuel economy improvement.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.2
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• pp.151-160
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• 2010

Particles emitted from three coal-fired power plants burning bituminous and sub-bituminous coals were examined for PM and size fractions PM>2.5 and PM2.5. The ratio of PM2.5/PM was ranged from 10 to 62%, and PM emission increased with the amount of coal feed, which was 7.23~15.66 kg/h. The emission range of PM2.5 from three power plants was 1.24~4.48 kg/h (dry), which was function of the mixed rate of viscous sub-bituminous coal in feed. Of course such effect should be examined by further tests in details. Based on the consumed coal and thermal load, the emission factors averaged were shown as 59.03 g-PM/ton-coal, 14.79 g-PM2.5/ton-coal and 22.51 g-PM/MWh, 5.54 g-PM2.5/MWh, respectively.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.804-811
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• 2015

The presence of responsive loads in the promising active distribution networks (ADNs) would definitely affect the power system problems such as distributed generations (DGs) studies. Hence, an optimal procedure is proposed herein which takes into account the simultaneous placement of DGs and smart meters (SMs) in ADNs. SMs are taken into consideration for the sake of successful implementing of demand response programs (DRPs) such as direct load control (DLC) with end-side consumers. Seeking to power loss minimization, the optimization procedure is tackled with genetic algorithm (GA) and tested thoroughly on 69-bus distribution test system. Different scenarios including variations in the number of DG units, adaptive power factor (APF) mode for DGs to support reactive power, and individual or simultaneous placing of DGs and SMs have been established and interrogated in depth. The obtained results certify the considerable effect of DRPs and APF mode in determining the optimal size and site of DGs to be connected in ADN resulting to the lowest value of power losses as well.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.233-236
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• 2002

The solution for PFC(Power Factor Correction), as a regulation in energy Policy, is becoming a hot Issue in every country because of the shortage of electrical energy. Therefore, a new improved idea for PFC problem has been introduced in this study. A lot of merits, effective cost by simple circuit, reduced PCB size, lighter than reactor in the view of weight, lower level of screen noise by leakage inductance in CTV applications, have been stated by comparing to the earlier method of using a Reactor. All test results in this statement were done by using a power device of STR-G9600 series based on the real load condition of color television. furthermore, the study shows that the test results also meets the IEC-1000-3-2 class D, which regulates the PFC when input power of a set is more than 75watts. More improved PFC in other applications hopes to be implemented by using the proposed method.