• Journal of the Korean Society of Radiology
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• v.5 no.3
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• pp.127-134
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• 2011

In this paper we propose an improved PV generation systems. Improved systems for temperature and humidity controlled heating and air conditioning offers a pleasant environment within the building, set up chopper and consists of a PWM voltage type inverter. The proposed system is stable modulation for a one-chip microprocessor using the synchronous signal and control signals was treated. The proposed system is a PWM voltage type inverter and phase of the synchronous to the grid voltage to detect the system voltage and inverter output to drive the statue, so surplus power to connection was able to, certain buildings such as buildings or hospitals, temperature and humidity sensor is applied to the good dynamic characteristic could be obtained. In addition, the system was applied to the high power factor and low-frequency harmonics by maintaining the output load and grid to power to be supplied to a stable control could get a good result.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.6
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• pp.55-64
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• 2007

This paper represents characteristics and design example of series loaded LCC type high frequency resonant DC-DC converter with variable parallel capacitor in the secondary side of inductive power transformer. In this converter, ZVS(zero voltage switching) technique is applied to reduce turn-off switching losses, and the applied converter used the PFM switching pattern to control output voltage. The operating characteristics of the proposed converter is analyzed using nomalized parameter such as switching frequency and load factor with varing the secondary parallel resonant capacitor. The results of analysis show the operating characteristics and design method of the proposed converter using characteristic values. And the proposed converter can be applied for the contactless power supply with linear transfer system such as dean room facilities of semiconductor and Flat Panel Display.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.145-151
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• 2010

Voltage unbalance is regarded as a power quality problem of significant at the user application. Although the voltages are quite well balanced at the transmission system, the voltage level of utilization can be unbalanced due to the unequal system impedances and the unequal distribution of single phase loads. Capacitor is generally used for power-factor compensation and reducing harmonics of non linear load with reactor. If voltage unbalance exists, current unbalance is generated and it will be reflected in the capacity variance. When the reactor and condenser are used at the same location, generally its trouble rate is high. And it is very important checking out that how the variance of voltage, current and capacity of condenser is proceeded by the voltage unbalance. In this paper, we calculated that voltage, current and capacity of condenser are within the tolerance limit of official regulations in the event of voltage unbalance with/without reactor.

• Journal of Electrical Engineering and Technology
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• v.5 no.2
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• pp.179-190
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• 2010

This paper describes a new stochastic heuristic algorithm in engineering problem optimization especially in power system applications. An improved particle swarm optimization (PSO) called adaptive particle swarm optimization (APSO), mixed with simulated annealing (SA), is introduced and referred to as APSO-SA. This algorithm uses a novel PSO algorithm (APSO) to increase the convergence rate and incorporate the ability of SA to avoid being trapped in a local optimum. The APSO-SA algorithm efficiency is verified using some benchmark functions. This paper presents the application of APSO-SA to find the optimal location, type and size of flexible AC transmission system devices. Two types of FACTS devices, the thyristor controlled series capacitor (TCSC) and the static VAR compensator (SVC), are considered. The main objectives of the presented method are increasing the voltage stability index and over load factor, decreasing the cost of investment and total real power losses in the power system. In this regard, two cases are considered: single-type devices (same type of FACTS devices) and multi-type devices (combination of TCSC, SVC). Using the proposed method, the locations, type and sizes of FACTS devices are obtained to reach the optimal objective function. The APSO-SA is used to solve the above non.linear programming optimization problem for better accuracy and fast convergence and its results are compared with results of conventional PSO. The presented method expands the search space, improves performance and accelerates to the speed convergence, in comparison with the conventional PSO algorithm. The optimization results are compared with the standard PSO method. This comparison confirms the efficiency and validity of the proposed method. The proposed approach is examined and tested on IEEE 14 bus systems by MATLAB software. Numerical results demonstrate that the APSO-SA is fast and has a much lower computational cost.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.1
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• pp.30-40
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• 2002

This paper studies the electronic ballast development for 250w MH lamps. We have improved the input power factor using a PFC IC. To provide the rating voltage required In the lamps, we have used the buck type dc-dc converter By this method, the stress of switching devices in inverter can be reduced. The inverter is the Full-Bridge type. To eliminate the acoustic resonance phenomena of MH lamps, we have added the high frequency sinewave voltage to the low frequency square-wave voltage to the lamp. We hove developed the igniter circuit using the L, C devices. We could control dimming of the lamp by varying the output voltage of the buck converter. The time of illuminating lamps and luminous intensity could be adjusted by season and time band. The buck converter output voltage can be controlled and the no load and over current situation were Protected by the development of the microprocessor Program.

• Journal of Korean Society of Transportation
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• v.20 no.2
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• pp.17-26
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• 2002

Driver's psychophysiological load is one of the key measures for evaluating the safety of the highway. The purpose of this study is to propose and to test the methodology of evaluating the length limit of tangent section using driver's psychophysiological load. Driver's psychophysiological data is represented by the data acquire by frontal and occipital lobe. In order to compare the differences between tangent segments and the orders, real road driving experiments were performed. We collected psychophysiological data during the operation of vehicles. The experimental data were analyzed using FFT (Fast Fourier Transform) and relative power spectrum tools. These routine produces the beta value which is a major factor in consideration of driver's condition. The results in this study are summarized as follows: (1) A new methodology of evaluating the length limit in tangent section of highway using driver's psychophysiological load was proposed. (2) It was observed that driver's work load at tangent section was three times lower than that at the other section types. The beta value at tangent section is 2.219, while that at general section is 0.821. (3) It was observed that the driver's work load was significantly dropped to 0.428 after the continuous driving of 4.2km tangent section. (4) Based on the experimental subjects(from 27 Years to 31). we suggest that 30 times of design speed(3.0 km) could be acceptable as the length limit of tangent section in highway rather than the Previous limit which is 20 times of design speed(2.0km).

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1124-1128
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• 2021

As regulations of emissions from ships become more stringent, electric propulsion systems have been increasingly used to solve this problem in vessels ranging from large merchant ships to small and medium-sized ships. Methods for improving the efficiency of the electric propulsion system include the improvement of power sources; the use of a system linked to environmentally friendly power sources, such as batteries, fuel cells, and solar power; and the development of hardware and control methodology for rectifiers, power conversion devices, and propulsion motors. The method using a phase-shifting transformer with diodes has been widely used for rectification. Power semiconductor devices with grid connection to an environmentally friendly power source using DC distribution, a variable speed power source, and the application of small and medium-sized electric propulsion systems have been developed. Accordingly, the demand for active front-end (AFE) rectifiers is increasing. In this study, a method using a neural network rather than a conventional proportional-integral controller was proposed to control the AFE rectifier. Tested controller data were used to design a neural network controller trained through MATLAB/Simulink. The neural network controller was applied to a rectification system designed using PSIM software. The results indicated the effectiveness of improving the waveform and power factor DC output stage according to the load variation. The proposed system can be applied as a rectification system for small and medium-sized environmentally friendly ships.

• Journal of the Korea Society of Computer and Information
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• v.14 no.2
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• pp.157-168
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• 2009

In this paper, a photovoltaic system is designed with a step up chopper and single phase PWM(Pulse Width Modulation) voltage source inverter. Where proposed Synchronous signal and control signal was processed by one-chip microprocessor for stable modulation. The step up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature because solar cell has typical voltage and current dropping character. The single phase PWM voltage source the inverter using inverter consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be developed continuously by connecting with the source of electric power for ordinary use. It can cause the effect of saving electric power. from 10 to 20[%]. The single phase PWM voltage source inverter operates in situation that its output voltage is in same phase with the utility voltage. In order to enhance the efficiency of photovoltaic cells, photovoltaic positioning system using sensor and microprocessor was design so that the fixed type of photovoltaic cells and photovoltaic positioning system were compared. In result, photovoltaic positioning system can improved 5% than fixed type of photovoltaic cells. In addition, I connected extra power to the system through operating the system voltage and inverter power in a synchronized way by extracting the system voltage so that the phase of the system and the phase of single-phase inverter of PWM voltage type can be synchronized. And, It controlled in order to provide stable pier to the load and the system through maintaining high lurer factor and low output power of harmonics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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• pp.263-269
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• 2017

A piezoelectric cantilever energy harvester (PCEH) driven in longitudinal (3-3) vibration mode was fabricated, and its electrical properties were evaluated by varying the resistive load. A commercial PZT piezoelectric ceramic with a high piezoelectric charge constant ($d_{33}$) of 520 pC/N and the interdigitated (IDT) electrode pattern was used to fabricate the PCEH driven in longitudinal vibration. The IDT Ag electrode embedded piezoelectric laminates were co-fired at $850^{\circ}C$ for 2 h. The 3-3 mode PCEH was successfully fabricated by attaching the piezoelectric laminates to a SUS304 elastic substrate. The PCEH exhibited a high output power of 3.8 mW across the resistive load of $100k{\Omega}$ at 100 Hz and 1.5 G. This corresponds to a power density of $10.3mW/cm^3$ and a normalized global power factor of $4.56mW/g^2{\cdot}cm^3$. Given the other PCEH driven in transverse (3-1) vibration mode, the 3-3 mode PCEH could be better for vibration energy harvesting applications.

• Journal of the Korean Society of Safety
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• v.12 no.3
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• pp.166-172
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• 1997

The BEF on the radial distribution line refers to a class of ground faults in which the load-side power line only is grounded, with the distribution line broken into two parts, the source-side and the load-side. Because its mechanism is remarkably different from that of other earth faults, the fault current is very low, and then difficult to detect the BEF. Thus, it is necessary to analyze its properties and to find an appropriate method that can economically protect the BEF of nonautomation area in the substation. As a result of analyzing the BEF data obtained by the RTDS, EMTP simulation, and the field test data of ETSA, we believe that it is the dominant factor in distinguishing the BEF from normal conditions by a criterion value that is appropriately handled from the zero-sequence current. Thus, with this criterion value, a BEF detecting algorithm is constructed which measures the variations of the zero-sequence current and processes then properly so as to make the fault decision. To prove the accuracy of this algorithm, it is compared with the field test data of ETSA under various conditions. The results show that the proposed algorithm is accurate.