• Journal of the Korea Convergence Society
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• v.2 no.4
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• pp.21-27
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• 2011

Recently, new distributed power sources such as photovoltaic, wind power, fuel cell systems etc. are energetically interconnected and operated in the distribution feeders, as one of the national projects for alternative energy. When new power sources are considered to be interconnected to distribution systems, bi-directional power flow and interconnection conditions of new power sources may cause several power quality problems like voltage sag, voltage swell, harmonics, since new power sources can change typical characteristics of distribution systems. Under these situations, this paper deals with the analysis the power quality problems at primary and secondary feeders in distribution systems, when new power sources like photovoltaic (PV) systems are interconnected, by using the test devices for PV systems based on the LabVIEW S/W. This paper presents the test device which is consisted with model distribution system and model PV systems. By performing the simulation for power quality operation characteristic based on the test facilities, this paper presents the optimal countermeasures for power quality.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.640-642
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• 2008

This paper presents the design, development and performance of a 250kW power conditioning system(PCS) for large scale photovoltaic power plant. The PV inverter consists of a three phase IGBT stack, L-C filter, transformer and HMI unit for monitoring. To verify the performance of the PV inverter a testing facility was designed and constructed to simulate the characteristics of the solar cell and grid.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.474-483
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• 1996

In this paper, as a part of the method improving stability, the load-flow calculation in D.C. power system and the models for stability analysis are studied with A.C-D.C. interconnected power systems transmission performed. Moreover, the theory is established in relation to each control method of D.C. power systems. Then the stability of A.C-D.C.interconnected power systems is compared and considered by the way of dividing the operating control method of the rectifier inverter converter into ACR-AVR, APR-A.gamma.R, A.alpha.R-ACR. The dynamics characteristic of terminal voltage, frequency, active-reactive power and rotor angle of the generator with disturbances and load fluctuations is considered. In addition, the characteristic of direct voltage, direct current, power and control systems. From this the comparative analysis of the direct current control method, the possibility of the stability analysis of A.C.-D.C. interconnected power system is considered. (author). refs., figs., tabs.

• Journal of Power Electronics
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• v.11 no.5
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• pp.767-777
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• 2011

Power electronic systems such as switching power supplies are accounted as noise sources for other sensitive circuits. EMI caused by power converters can disturb the normal operation of the converter and other adjacent systems. Major research is concentrated on EMI mitigation for power converters in which the main concern is compliance with EMC standards to ensure proper operation of converters and nearby systems. This paper reviews EMI reduction techniques related to switching power converters with emphasis on the conducted EMI. A comprehensive review of significant research works is performed and various methods are thoroughly discussed and compared. Also, a classification of methods is presented. Moreover, converter prototypes are realized which contain several EMI mitigation techniques and their effects are presented via experimental results.

• Journal of Advanced Navigation Technology
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• v.17 no.1
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• pp.56-62
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• 2013

Recently with smart phones and tablets, next generation mobile communication systems have supported various multimedia contents services. Thus, multimedia communication systems have been gradually increased compared to voice communication systems. Since the growth of multimedia services has increased users' duration on systems and decreased systems' effectiveness on power, a study on effective usage of power needs to be researched. Furthermore, radio shadow areas under heavy urban environments have generated unnecessary power consumption which reduces the usage duration of power on next generation mobile communication systems. This paper has reviewed the communication network architecture on next generation mobile communication systems and the unnecessary power consumption in radio shadow areas. This paper has also proposed the method of the effective power usage and analyzed the effective power usage on next generation mobile communication systems with simulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1512-1518
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• 2009

Recently, new dispersed power sources such as photovoltaics, wind power, fuel cell etc. are energetically interconnected and operated in the distribution systems, as one of the national projects for alternative energy. This paper deals with the optimal countermeasures for the mal-function of protective devices at primary feeder in distribution systems when new power sources like photovoltaic (PV) systems are interconnected, based on the symmetrical components of short circuit studies. When new power sources are considered to be interconnected to distribution systems, bi-directional power flow and interconnection transformer connection of new power sources may cause the operation problems of protective devices (mainly re-closer), since new power sources can change typical characteristics of distribution systems. Therefore, this paper shows an analysis skill of the mal-functional mechanism of protective relay and proposes the optimal solution for the mal-function problem using the symmetrical components of fault analysis. And, this paper also shows the effectiveness of proposed method by the simulation at the field distribution systems.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.790-802
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• 2017

This paper proposes the modeling and control strategy to track the MPPs of hybrid PV and Wind power systems, using a new dual input boost converter. The dual input power conditioning system with an independent MPPT control scheme is introduced with minimum number of circuit elements in order to reduce the switching loss, size and cost of the system. Since the operating conditions for the PV and Wind power systems are very distinct from each other, an efficient and superior control system is required to track the MPPs of both renewable sources with the use of a simply-structured single-ended single-inductor converter. The design of Power-Conditioning System (PCS) and detail control strategy are presented in this paper. To provide independent tracking of MPPs, a variable duty-cycle control strategy is employed for the wind system and a variable frequency strategy is employed for the PV system. Finally, the proposed dual-input converter for hybrid power conditioning system is implemented and the hardware test results are presented. From the hardware experiment, it is concluded that the proposed system successfully tracks the MPPs of both of the renewable power systems independently.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.172-183
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• 2006

This paper analyzes instantaneous power compensation theory through comparing p-q theory and cross-vector theory which were proposed by Akagi and Nabae respectively in three-phase four-wire systems. The two compensation theories are identical when there is no zero-sequence voltage component in three-phase three-wire systems, However, when the zero-sequence voltage and/or current components exist in three-phase four-wire systems, the two compensation theories we different in definition on instantaneous real power and instantaneous imaginary power. Based on the analysis, this paper presents instantaneous power compensation method that can eliminate neutral current completely without using energy storage element when the zero-sequence current and voltage components exist in three-phase four-wire systems.

• Transactions on Electrical and Electronic Materials
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• v.17 no.1
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• pp.1-6
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• 2016

Ensuring the secure operation of power systems has become an important and critical matter during the present time, along with the development of large, complex and load-increasing systems. Security constraints such as the thermal limits of transmission lines and bus-voltage limits must be satisfied under all of a system’s operational conditions. An alternative solution to improve the security of a power system is the employment of Flexible Alternating-Current Transmission Systems (FACTS). FACTS devices can reduce the flows of heavily loaded lines, maintain the bus voltages at desired levels, and improve the stability of a power network. The Unified Power Flow Controller (UPFC) is a versatile FACTS device that can independently or simultaneously control the active power, the reactive power and the bus voltage; however, to achieve such functionality, it is very important to determine the optimal location of the UPFC device, with the appropriate parameter setting, in the power system. In this paper, a genetic algorithm (GA) method is applied to determine the optimal location of the UPFC device in a network for the enhancement of the power-system loadability and the minimization of the active power loss in the transmission line. To verify our approach, simulations were performed on the IEEE 14 Bus, 30 Bus, and 57 Bus test systems. The proposed work was implemented in the MATLAB platform.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1245-1255
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• 2016

The single resonant inverter is widely employed in typical inductive power transfer (IPT) systems to generate a high-frequency current in the primary side. However, the power capacity of a single resonant inverter is limited by the constraints of power electronic devices and the relevant cost. Consequently, IPT systems fail to meet high-power application requirements, such as those in rail applications. Total harmonic distortion (THD) may also violate the standard electromagnetic interference requirements with phase shift control under light load conditions. A power regulation approach with selective harmonic elimination is proposed on the basis of a parallel multi-inverter to upgrade the power levels of IPT systems and suppress THD under light load conditions by changing the output voltage pulse width and phase shift angle among parallel multi-inverters. The validity of the proposed control approach is verified by using a 1,412.3 W prototype system, which achieves a maximum transfer efficiency of 90.602%. Output power levels can be dramatically improved with the same semiconductor capacity, and distortion can be effectively suppressed under various load conditions.