• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1261-1268
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• 2013

This study proposes a voltage and reactive coordinative control strategy with distributed generator (DG) in a distribution power system. The aim is to determine the optimum dispatch schedules for an on-load tap changer (OLTC), distributed generator settings and all shunt capacitor switching on the load and DG generation profile in a day. The proposed method minimizes the real power losses and improves the voltage profile using squared deviations of bus voltages. The results indicate that the proposed method reduces the real losses and voltage fluctuations and improve receiving power factor. This paper proposes coordinated voltage and reactive power control methods that adjust optimal control values of capacitor banks, OLTC, and the AVR of DGs by using a voltage sensitivity factor (VSF) and dynamic programming (DP) with branch-and-bound (B&B) method. To avoid the computational burden, we try to limit the possible states to 24 stages by using a flexible searching space at each stage. Finally, we will show the effectiveness of the proposed method by using operational cost of real power losses and voltage deviation factor as evaluation index for a whole day in a power system with distributed generators.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.648-653
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• 1998

The conventional three-phase rectifier with bulky LC output filter has been widely used in the industry because of its distinctive advantages over the active power factor correction rectifier such as simple circuit, high reliability, and low cost. Over than 0.9 power factor can be achieved, which is acceptable in most of industry applications. This rectifier, however, is not easy to use for high power density applications since the LC filter is bulky and heavy. To solve this problem, a new simple rectifier is presented in this paper. By eliminating the bulky LC filter from the conventional diode rectifier without losing most of the advantages of the conventional rectifier, very high power density power conversion with high power factor can be achieved. Operation principle and design considerations are illustrated and verified by Pspice simulation and experimental results from a prototype of 3.3 kW rectifier followed by 100KHz zero voltage switching full bridge PWM converter

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1999.10a
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• pp.153-161
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• 1999

For composing the structure model of national maritime power system by system structural modelling, in this study, the 50 basic factors are selected by survey of the extensive and thorough literatures on maritime, sea, maritime power and sea power. And the basic factors are classified into 36 component factors by cluster method. The 9 attributes are extracted by the application of the principle component analysis method, one of the factor analysis method in system engineering, to component factors. We defined the attributes composing the national maritime power system by integration the result of this study and existed our studies relate to this topic. Which are showed in table 8. and we showed the structure model of national maritime power system in figure 3. In table 8, the 9 attributes are as follows: the fundamental power of maritime, shipping and port power, naval power, fishing power, shipbuilding power, the power of ocean research and development, dependency on seaborne trade, the protection power of ocean environment and the will and inclination of government.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.214-217
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• 2003

The connectorless power supply system on that multi-contact causes confidence when the wiring reconstructed in the rear. As you see above, contact points between sets and indoor space cause inferior function of audio frequency so it needs to be eliminated. This paper explains the structure of connectorless power supply to supply the system with power crossing the air gap in the part of inductively in the connectorless power supply of both magnetic and electrical model. To get maximum output of electrical load, compensating capacitor compensates to show inter-inductance, lequeage-inductance reducing the track-inductance and access the conditions for resonance. At that time it accesses the maximum electric power. The small change of the value of compensating capacitor causes the changes of maximum electric power. Here the power electronics technology is used not only in the industrial machinery but also in the home appliances so the switching power supply is used to actualize the miniaturization, lightweight, and high efficiency. Generally the condenser input methods are widely used in the rectification circuit of switching power supply, but condenser input method generate great quantity of high frequency components because with this method the current flows in the power input filtering condenser only around value of peak of ac input voltage. To solve these problems, installation of power factor improve circuit on the front of filtering capacitence was considered. Several methods were suggested regarding, but the active filter method which makes smalliging and highly power factor possible are the produce main stream. IC for power factor improvement can be utilized by CMOS process proposing low power consumption. When the high power factor is considered seriously in the power factor improvement circuit, active filter method is selected. In the active filter method, the boost converter is used. Regarding this ·the boost converter is needed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1467-1475
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• 2007

This paper investigates the modal acoustic power by a cascade of flat-plate airfoils interacting with homogeneous, isotropic turbulence. Basic formulation for the acoustic power upstream and downstream is based on the analytical theory of Smith and its generalization due to Cheong et al. The acoustic power spectrum has been expressed as the sum of cut-on acoustic modes, whose modal power is the product of three terms: a turbulence series, an upstream or downstream power factor and an upstream or downstream acoustic response function. The effect of these terms in the modal acoustic power has been examined. For isotropic turbulence gust, the turbulent series are only reducing factor of the modal acoustic power. The power factor tends to reduce the modal acoustic power in the upstream direction, although the power factor is liable to increase the modal acoustic power in the downstream direction. The modes close to cut-off are decreasing strongly, especially in the downstream direction. Therefore the modes close to cut-off don't contribute highly to the radiated acoustic power in the downstream direction, although the modal acoustic pressure is high for these modes.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.61-70
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• 2008

This paper investigates the modal acoustic power by a cascade of flat-plate airfoils interacting with homogeneous, isotropic turbulence. Basic formulation for the acoustic power upstream and downstream is based on the analytical theory of Smith and its generalization due to Cheong et al. The acoustic power spectrum has been expressed as the sum of cut-on acoustic modes, whose modal power is the product of three terms: a turbulence series, an upstream or downstream power factor and an upstream or downstream acoustic response function. The effect of these terms in the modal acoustic power has been examined. For isotropic turbulence gust, the turbulent series are only reducing factor of the modal acoustic power. The power factor tends to reduce the modal acoustic power in the upstream direction, although the power factor is liable to increase the modal acoustic power in the downstream direction. The modes close to cut-off are decreasing strongly, especially in the downstream direction. Therefore the modes close to cut-off don't contribute highly to the radiated acoustic power in the downstream direction, although the modal acoustic pressure is high for these modes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.8
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• pp.18-26
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• 2012

Recently, there have been suggestions that power factor should be considered to increase the efficiency of electric power supply when evaluating the performance of the electric appliances in standby mode and the related studies have been conducted to improve the efficiency standard of standby power. But, they lack the analysis of the standby power characteristics with the changes of power factor. This study is conducted to analyze the standby power characteristics of TV which is a typical home appliance and reaches a conclusion that the apparent power can be a more reasonable index which reflects the efficiency of electric power supply. It is also found that LED TVs show the best performance in standby mode. Moreover, an example to set standby power standards on TVs to be applied in the future is suggested, considering the energy efficiency policies for appliances.

• Journal of Power Electronics
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• v.11 no.4
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• pp.561-567
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• 2011

This paper presents a high-efficiency power conditioning system (PCS) for grid-connected photovoltaic (PV) modules. The proposed PCS consists of a step-up DC-DC converter and a single-phase DC-AC inverter for the grid-connected PV modules. A soft-switching step-up DC-DC converter is proposed to generate a high DC-link voltage from the low PV module voltage with a high-efficiency. A DC-link voltage controller is presented for constant DC-link voltage regulation. A half-bridge inverter is used for the single-phase DC-AC inverter for grid connection. A grid current controller is suggested to supply PV electrical power to the power grid with a unity power factor. Experimental results are obtained from a 180 W grid-connected PV module system using the proposed PCS. The proposed PCS achieves a high power efficiency of 93.0 % with an unity power factor for a 60 Hz / 120 Vrms AC power grid.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.1
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• pp.9-13
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• 1996

The high precision of electrical power and energy measurements with wide range of frequency and power factor can be achieved by using the thermo-electrical power comparators. The paper describes the development of a precision power measuring system by using a ac/dc power comparator for measurement of power. Based on a thermal principle, the instrument performs ac-dc transfer for ac power measurements in the range of currents from 0 to 5 $A_{ms}$ , voltages from 0 to 240 $V_{ms}$ , power factors from 0 to 1 and frequencies from 0 to 1000 Hz. Two thermal converters with two heater are used in the functional element of the comparators. The ac-dc transfer accuracy is better than 20 ppm at unity power factor and better than 50 ppm at 0.5 power factor. (author). 8 refs., 5 figs., 3 tabs.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2121-2125
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• 2003

This paper proposes a fast distributed constrained power control (FDCPC) with non-stationary relaxation factor to next power update in CDMA cellular power control system. We review unconstrained control algorithms, the distributed power control (DPC), unconstrained second order power control (USOPC) and DPC with stationary relaxation factor (DPCSRF). Under the unconstrained condition, the convergence analysis shows theoretically that the convergence rate of DPC is the fastest one. However, under the constrained control algorithms, DCPC is not the fastest one any more because of transmission power constraint. To improve the convergence speed, the DCPC with non-stationary relaxation factor (FDCPC) are proposed. Under the constrained condition, the convergence rate of FDCPC outperforms that of DCPC and CSOPC.