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Wang Y.P.,Electrical Industry Research Institute of Korea | Watson N.R.,University of Canterbury
International Journal of Electrical Power and Energy Systems | Year: 2013

The complexity of modern power systems often makes it impractical to model it in its entirety for electromagnetic transient studies. Therefore areas outside the immediate area of interest must be represented by some form of frequency dependent network equivalent (FDNE). The equivalent must be "frequency dependent", that is match the frequency response of the system it represents, if it is to faithfully represent it. This paper presents a z-domain rational function formulation for developing a FDNE and demonstrates the use of it for the assessment of the steady-state and transient response of the Lower South Island of New Zealand. This paper also shows the accuracy that can be expected from using FDNEs as well as providing a test system for other researchers to benchmark their work against. This is achieved by using a well publicized test system (Lower South Island of New Zealand) the parameters of which are readily available as well as providing complete information of the developed FDNE. © 2012 Elsevier Ltd. All rights reserved. Source


Ahn J.,Electrical Industry Research Institute of Korea | Kim T.W.,Hongik University | Lee W.J.,Gachon University
Journal of Ceramic Processing Research | Year: 2012

Impedance spectroscopy informs electrical properties of materials as accumulated charges, contact status between electrode and organic materials. We carried out impedance spectroscopy of organic light-emitting diodes as ITO/Alq3(60 nm)/Al on temperatures from 10 K to 300 K. The result described Z'-Z" plot, cole-cole plot and dielectric relaxation time τ. Z'-Z" plot means that real and imaginary part of materials in organic and electrode by frequencies and temperature. Z' as real part of impedance by applied frequency depending on temperature shows the plateau in low frequency region as Rs+Rp and over 100 kHz in high frequency region as Rs. Cole-cole plot shows resistance of materials in equivalent circuit of the device by temperatures. And equivalent circuit and dielectric relaxation could be accomplished by using the complex impedance analysis. Source


Kim B.-K.,Korea University | Choi S.-S.,Korea University | Wang Y.-P.,Electrical Industry Research Institute of Korea | Kim E.-S.,Korea Electric Power Research Institute | Rho D.-S.,Korea University
Journal of Electrical Engineering and Technology | Year: 2015

This paper deals with the modified modeling of PV system based on the PSCAD/EMTDC and optimal control method of customer voltages in real distribution system interconnected with the photovoltaic (PV) systems. In order to analyze voltage variation characteristics, the specific modeling of PV system which contains the theory of d-q transformation, current-control algorithm and sinusoidal PWM method is being required. However, the conventional modeling of PV system can only perform the modeling of small-scale active power of less than 60 [kW]. Therefore, this paper presents a modified modeling that can perform the large-scale active power of more than 1 [MW]. And also, this paper proposes the optimal operation method of step voltage regulator (SVR) in order to solve the voltage variation problem when the PV systems are interconnected with the distribution feeders. From the simulation results, it is confirmed that this paper is effective tool for voltage analysis in distribution system with PV systems. © 2015, The Korean Institute of Electrical Engineers. Source

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