• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.829-833
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• 2007

In this paper, the RCF method is applied to analyze small signal stability of power systems including GTO controlled parallel FACTS equipments such as STATCOM. To apply the RCF method in power system small signal stability problems, state transition equations of generator, controllers and STATCOM are presented. In eigenvalue analysis of power systems, STATCOM is modelled as the equivalents voltage source model and the PWM switching circuit model. As a result of simulation, the RCF method is very powerful to calculate the oscillation modes exactly after the switching operations, and useful to analyze the small signal stability of power systems with periodically operated switching devices such as STATCOM.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.139-141
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• 2002

This paper describes a new contingency analysis methods for small signal security assessment based on the eigenvalue perturbation. The eigenvalue perturbation with respect to MW changes can be used to find possible sources of the low frequency oscillation, and to select contingency for small signal stability. The proposed algorithm has been successfully tested on the KEPCO systems.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.365-366
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• 2017

LLC resonant DC-DC converter is widely used in many kinds of applications such as battery energy storage systems, wireless power transfer and high voltage power supply. It is because of characteristics like high efficiency, power density, isolation, wide power level and stability enhancement at high switching frequency. Small signal modeling helps to design controller of the converter by approximating the behavior of nonlinear system with linear state equations. This paper presents comparison between small signal modeling analysis and experimental results of LLC resonant converter.

• 전자공학회논문지 IE
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• v.44 no.2
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• pp.1-7
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• 2007

The increasing high frequency capabilities of CMOS have resulted in increased RF and analog design in CMOS. Design of RF and analog circuits depends critically on device S-parameter characteristics, magnitude of real and imaginary components and their behavior as a function of frequency. Utilization of scaled high performance CMOS technologies poses challenges as concerns for reliability degradation mechanisms increase. It is important to understand and quantify the effects of the reliability degradation mechanisms on the S-parameters and in turn on small signal model parameters. Various physical effects influencing small-signal parameters, especially the transconductance and capacitances and their degradation dependence, are discussed in detail. The measured S-parameters of H-gate and T-gate devices in a frequency range from 0.5GHz to 40GHz. All intrinsic and extrinsic parameters are extracted from S-parameters measurements at a single bias point in saturation. In this paper we discuss the analysis of the small signal equivalent circuits of RF SOI MOSFET's verificated for the purpose of exacting the change of parameter of small signal equivalent model followed by device flame.

• Journal of Power Electronics
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• v.12 no.1
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• pp.164-171
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• 2012

Variable step size maximum power point trackers (MPPTs) are widely used in photovoltaic (PV) systems to extract the peak array power which depends on solar irradiation and array temperature. One essential factor which judges system dynamics and steady state performances is the scaling factor (N), which is used to update the controlling equation in the tracking algorithm to determine a new duty cycle. This paper proposes a novel stability study of variable step size incremental resistance maximum power point tracking (INR MPPT). The main contribution of this analysis appears when developing the overall small signal model of the PV system. Therefore, by using linear control theory, the boundary value of the scaling factor can be determined. The theoretical analysis and the design principle of the proposed stability analysis have been validated using MATLAB simulations, and experimentally using a fixed point digital signal processor (TMS320F2808).

• Design & Manufacturing
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• v.9 no.2
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• pp.1-5
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• 2015

Recently, as small-sized display products such as mobile phones and digital cameras have become lighter and smaller, the size of electric signal delivery part, connector for the mobile display products, also, needs to become smaller, so high-density integration like shortening the distance between signal delivery media, conductors is necessary. With the micro and high-density integration of the connector, it is necessary to maintain contact to a certain degree for keeping intensity and delivering electric signal smoothly to prevent a defect with a specific impact. Accordingly, this study carried out a structural analysis according to the operating mechanisms of 0.16CHP Class Bottom Contact FPC Connector and 0.24CHP Class BTB Connector mostly used in small-sized mobile display products such as mobile phones and digital cameras. As a result of the analysis, both connectors had lower than 997MPa, yield strength of connector material C5240-XSH, so it is judged that permanent plastic deformation would not occur, and that a contact force between the connector and FPC film occurs to a certain degree, so that there would not be any defect in electric signal delivery.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.4
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• pp.168-176
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• 2000

This paper presents the Hessenberg method, a new sparsity-based small signal stability analysis program for large interconnected power systems. The Hessenberg method as well as the Arnoldi method computes the partial eigen-solution of large systems. However, the Hessenberg method with pivoting is numerically very stable comparable to the Householder method and thus re-orthogonalization of the krylov vectors is not required. The fractional transformation with a complex shift is used to compute the modes around the shift point. If only the dominant electromechanical oscillation modes are of concern, the modes can be computed fast with the shift point determined by Fourier transforming the time simulation results for transient stability analysis, if available. The program has been successfully tested on the New England 10-machine 39-bus system and Korea Electric Power Co. (KEPCO) system in the year of 2000, which is comprised of 791-bus, 1575-branch, and 215-machines. The method is so efficient that CPU time for computing five eigenvalues of the KEPCO system is 3.4 sec by a PC with 400 MHz Pentium IIprocessor.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.3
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• pp.886-900
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• 2015

Small cells are deployed in Heterogeneous Networks (HetNet) to improve overall performance. These access points can provide high-rate mobile services at hotspots to users. In a Small Cell Network (SCN), the good deployment of small cells can guarantee the performance of users on the basis of average and cell edge spectrum efficiency. In this paper, the performance of small cell deployment is analyzed by using system-level simulations. The positions of small cells can be adjusted according to the deployment radius and angle. Moreover, different Inter-Cell Interference Coordination (ICIC) techniques are also studied, which can be implemented either in time domain or in frequency domain. The network performances are evaluated under different ICIC techniques when the locations of Small evolved Nodes (SeNBs) vary. Simulation results show that the average throughput and cell edge throughput can be greatly improved when small cells are properly deployed with the certain deployment radius and angle. Meanwhile, how to optimally configure the parameters to achieve the potential of the deployment is discussed when applying different ICIC techniques.

• Journal of Power Electronics
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• v.16 no.3
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• pp.849-860
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• 2016

The high-switching-frequency operation of power converters can achieve high power density through size reduction of passive components, such as capacitors, inductors, and transformers. However, a small-output capacitor that has small capacitance and low effective series resistance changes the small-signal model of the converter power stage. Such a capacitor can make the converter unstable by increasing the crossover frequency in the transfer function of the small-signal model. In this paper, the design and implementation of a high-frequency LLC resonant converter are presented to verify the power density enhancement achieved by decreasing the size of passive components. The effect of small output capacitance is analyzed for stability by using a proper small-signal model of the LLC resonant converter. Finally, proper design methods of a feedback compensator are proposed to obtain a sufficient phase margin in the Bode plot of the loop gain of the converter for stable operation at 500 kHz switching frequency. A theoretical approach using MATLAB, a simulation approach using PSIM, and experimental results are presented to show the validity of the proposed analysis and design methods with 100 and 500 kHz prototype converters.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.3
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• pp.219-225
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• 2005

In this paper, a new discrete-time small signal model of an average current mode control is proposed to predict the inductor current responses. Compared to the peak current mode control, the analysis of the average current mode control is difficult because of its presence of an compensation network. By utilizing sampler model, a new discrete-time small signal model is derived and used to predict the behaviors of an inductor current of average current mode control employing generalized compensation networks. In order to show the usefulness of the proposed model, prediction results of the proposed model are compared to those of the circuit level simulator, PSIM and experiment.