• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.490-498
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• 2002

In this paper, a design method of LCL filter at the AC input side of a voltage source PWM converter is proposed. Effective method to prevent pollution of the utility caused by high frequency current ripple is to use a AC input LCL filter, The C elements in the filter provide a low impedance path for the high frequency component, preventing them from entering the utility. The resistors In series with the capacitors are used for damping the resonance in the filter The design examples are shown and the validity of the proposed design method is verified through the PSIM simulation.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.506-509
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• 2002

In this paper, a design method of LCL filter at the AC input side of a voltage source PWM converter is proposed. Effective method to prevent pollution of the utility caused by high frequency current ripple is to use a LCL filter instead of the L filter The C elements in the filter provide a low impedance path for the high frequency component, preventing them from entering the utility. A resistor in series with a capacitor is used for damping the resonance in the filter. The design examples are shown and the validity of the proposed design method is verified through the PSIM simulation.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.234-236
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• 2002

The Co-Gen System which maximize energy efficiency was installed at the industrial plants at the initial stage. However Small Scale Co-Gen System was expanded even to the general end-users such as housing and building owing to ESCO business recently. For this SSC, inter-connected operation to the utility is desirable due to voltage and frequency fluctuation following to unbalance between power output and load. Then voltage unbalance with utility system, frequency, increase of short circuit capacity, reclosing, and ALTS etc. should be fully considered for the inter-connected operation. Voltage variation, protection coordination, Co-Generators single running, and short circuit capacity should also be solved. To research the method and solve the problems through the field test and application, we study individual customers Co-Gen System as a case study.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.478-480
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• 1998

We develops a simulator to evaluate the performance of the autosyncronizer. The autosyncronizer is used to automatically syncronize magnitude, frequency, and phase of 3 phase signals of generator with respect to those of the utility grid. This autosyncronizer needs to be evaluated its performance to prevent malfunctions. To do this, 3 phase signals of generator and the utility grid are simulated and signals of the generator should be changed by ouput of the autosyncronizer with high precision. In this paper, we uses TMS320C31 to generate high precision sinusoidal 3 phase signals using Table Lookup method. In this process, it is very desirable to control magnitude, frequency, and phase of the signal with high precision and this is achieved by appropriate interpolation method. The resulted signal is well controlled and has low THD and could be used to evaluate the performance of the autosyncronizer.

• Proceedings of the KIEE Conference
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• summer
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• pp.276-279
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• 2004

The purpose of this paper is to describe and demonstrate how a utility-connectable inverter for photovoltaic or fuel-cell applications can be well modeled using PSCAD/EMTDC. In this paper, a single-phase IGBT inverter using SPWM is modeled. Simple voltage magnitude and phase controls are implemented using PSCAD's Pl controller, PLL, and a 'user defined' component called Modulo (found in their extensive collection of example circuits). The circuit model also takes advantage of PSCAD's interpolated firing pulse option, which provides improved simulation results by preventing errors from being introduced when switches fire between time simulation steps. Additionally, SCAD's Online Frequency Scanner for FFT is utilized for a demonstration of PSCAD's frequency-domain analysis capabilities.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.721-725
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• 2014

In this paper, we propose a fast adaptive power allocation method for an orthogonal frequency division multiple access (OFDMA) system that employs an adaptive modulation and coding (AMC) scheme. The proposed scheme aims to reduce the calculation complexity of greedy adaptive power allocation (APA), which is known as the optimal algorithm for maximizing the utility argument of power. Unlike greedy APA, which starts power allocation from "0", the proposed algorithm initially allocates a certain level of power determined by the water-filling scheme. We theoretically demonstrate that the proposed algorithm has almost the same capability of maximizing the utility argument as the greedy APA while reducing the number of operations by 2M, where M is the number of AMC levels.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.72_73
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• 2009

The industrial power system has the radial plant distribution system and domestic generators to supply the essential loads. When the system is isolated from the utility tie line, the system frequency drops resulting in the trip of generators. The load shedding scheme shall be properly designed to secure the essential load. In this paper two kinds of load shedding schemes, those are, the Fast Act Load Shedding(FALS) and Under Frequency Load Shedding(UFLS) are simulated and compared taking an example of petrochemical gas separation plant.

• ETRI Journal
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• v.33 no.6
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• pp.957-960
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• 2011

We present a fair and efficient solution for selfish readers with the Nash bargaining solution (NBS) to mitigate the effects of RFID frequency interference. We compare the NBS with a solution derived by the max log-sum scheme that maximizes total utility and show that for selfish and rational readers, the NBS brings success in bargaining on resource allocation between readers unlike the max log-sum scheme, although the NBS has less total payoff compared to the max log-sum scheme.

• Journal of Sensor Science and Technology
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• v.24 no.3
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• pp.181-187
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• 2015

The magnetoelectric characteristics on layered $Fe_{78}B_{13}Si_9/PZT$ and $Fe_{78}B_{13}Si_9/PZT/Fe_{78}B_{13}Si_9$($t_m=0.017$, 0.034mm) composites by epoxy bonding for magnetic field sensor were investigated in the low-frequency range and resonance frequency range. The optimal bias magnetic field $H_{dc}$ of these samples was about 23~63 Oe range. The Me coefficient of $Fe_{78}B_{13}Si_9/PZT/Fe_{78}B_{13}Si_9(t_m=0.034mm)$ composites reaches a maximum of $186mV/cm{\cdot}Oe$ at $H_{dc}=63Oe$, f=50 Hz and a maximum of $1280mV/cm{\cdot}Oe$ at $H_{dc}=63Oe$, resonance frequency $f_r=95.5KHz$. The output voltage shows linearity proportional to ac fields $H_{ac}$ and is about U=0~130.6 mV at $H_{ac}=0{\sim}7Oe$, f=50 Hz, U=0~12.4 V at $H_{ac}=0{\sim}10Oe$, $f_r=95.5KHz$(resonance frequency). The optimal frequency(f=50 Hz) of this sample is around the utility ac frequency(f=60 Hz). Therefore, this sample will allow for ac magnetic field sensor at utility frequency and low bias magnetic fields $H_{dc}$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.219-225
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• 2007

The frequency and phase angle of utility voltage represent very important information fur applications such as AC/DC converters and Uninterruptible Power Supplies(UPS). In a three-phase system, the utility voltage information can be easily obtained by using a utility voltage vector. However, in the case of a single-phase system. the utility voltage information is much harder to obtain. This paper presents a comparative study of single-phase PLL algorithms using virtual 2-phase strategy. Simulation and experimental results, including operation of the PLL structures introduced in reference papers, are presented to allow a performance comparison of the PLL algorithms.