• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.6
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• pp.292-298
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• 2006

Because of the high cost for the active power filter, passive filters have been widly used to eliminate harmonic currents of nonlinear load and can also improve the power factor. They are not often optimal filters because the passive filters are designed under the fixed load conditions. In this paper we proposed the method which only the necessary harmonic filters are operated by detecting the various harmonic current components. We presents the new control method of passive filter selection type with the relay control circuit which is consist of analog GIC, comparater, flip-flop and etc. By the experimental results using the proposed system for the rectifier load, we concluded that the researched method is cost effective and the performance is better than the passive filter.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.850-853
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• 1991

This paper suggests a triple laminated piezoelectric ceramic filter composed of three piezoelectric ceramic vibrators and two sheets of thin insulator, and an equivalent circuit of the filter and several expressions for the resonant frequency; voltage, current, and power gains under the various loads and frequencies; and phase differences between the input and the output voltages are introduced and simulated from its equivalent circuit when two outputs from the side vibrators are connected in series. Those expressions show that this filter has not only a filtering function but also an amplifying function.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.4
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• pp.44-55
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• 1993

In this paper, we proposed a new optical method for the efficient recognition of Korean characters. There are six filters in the proposed method which employed the concepts of amplitude-modulated phase-only filter(AMPOF) and spatial frequency modulation(SFM). Here, amplitude modulation is used to achieve improved correlation discrimination and SFM is to reduce the number of filters. We also used a simplified synthetic discriminant function(SDF) for distortion invariance of input image. In order to recognize the partial rotation invariant Korean characters, the proposed distortion invariant minimum average correlation energy (MACE) filter is synthesized SFM, partial rotation invariant filter (PRIF), AMPOF and MACE for partial rotation invariance in the frequency domain. The advantage of the proposed filters is to supress the sidelobes of cross correlation peak away from the autocorrelation peak and to produce sharp correlation peaks. We performed simulation and optical experiment for some of Korea characters using the proposed method. The results show that the proposed method has more improved discriminant ability and reduced processing time than the conventional methods.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.249-253
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• 2006

Because of the high cost for the active power filter, passive filters have been widly used to absorb harmonic currents of nonlinear loads and can also improve the power factor. They are not often optimal filters because the passive filters are designed with the fixed load conditions. In this paper we proposed the method which only the necessary harmonic filters are operated by detecting the various harmonic current components. By the experimental results using the proposed system for the 500VA rectifier load, we concluded that the researched hybrid filter is cost effective and the performance is better than the passive filter.

• The Journal of the Acoustical Society of Korea
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• v.15 no.1E
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• pp.84-88
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• 1996

In this paper, we propose a novel adaptive digital filter for tonal noise cancellation, with a frequency tracking capability. The proposed algorithm not only estimates the magnitude and phase of the tonal disturbance but also tracks its frequency, which changes in quasi-static manner. The algorithm uses the steepest descent method and the instantaneous frequency approach for the phase/magnitude estimation and frequency tracking, respectively. A number of computer simulations have been carried out in order to demonstrate the feasibility of the proposed ANC algorithm under various conditions.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.103-106
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• 1989

A method of adaptive formation of the synthetic discriminant function(SDF) both in image plane and spatial frequency plane by using the Widrow-Hoff learning rule is proposed. The proposed method uses minimum number of interconnections between neurons so it can reduce the time for learning the neural net. Also complex valued interconnection weights are introduced for the purposes of handling the phase objects or Fourier transformed spatial frequency objects which usually have complex values for the representation of not only amplitude but also phase information. Also methods of optical implementation for the complex valued interconnection weights are discussed.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.495-497
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• 1994

Given the constraint of the AC input power factor and the DC-link voltage and current ripple in voltage source inverter, minimizing the size and cost of the DC-link fitter components is very important. This paper presents a procedure for the selection of DC-link filler element values in a three-phase PWM voltage source inverter-fed induction motor drive system, which can not only satisfy the requirements for the system performance but also minimize the filter size.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.739-743
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• 2000

With significant development of power electronics technology the proliferation of nonlinear loads such as such as static power converters has deteriorated power quality in power transmission distribution systems. Notably voltage harmonics resulting from current harmonies produced by the nonlinear loads have become a serious problem in many systems Moreover momentary interruptions and voltage sags are responsible for many of the power quality problems found in typical industrial plants. Int his paper proposed 3 phase hybrid series active power filter is not only for harmonic compensation but also for harmonic isolation between supply and load and for voltage regulation and imbalance compensation Through computer simulations we have verified the effectiveness of the proposed system.

• Journal of Power Electronics
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• v.11 no.6
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• pp.904-913
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• 2011

Previous publications regarding the design and specifications of input filters for STATCOMs usually deal with the input filter only, and seldom pay any attention to the influence of the input filters on the performance of the STATCOM systems. A detailed analysis of the influences of input filters on the stability of STATCOM systems and the corresponding design considerations are presented in this paper. Three types of input filters, L filters, LC filters, and LCL filters, are examined separately. The influences of the parameters of input filters on system stability are investigated through frequency domain methods. With direct current control taken as the major control strategy for the STATCOMs, the different situations when adopting different current detection points are covered in this analysis. A comparison between LC filters and LCL filters is also presented with optimized filter parameters. Based on the analysis, the phase margin, as one of the design considerations for the different types of input filters under different current detection schemes, is discussed. This leads to filter parameters that are different than those of the traditional design. Hardware experimental results verify the validity of the above analysis and design.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1247-1249
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• 2003

Despite many advantages, d-q theory was available only for three phase system. But recently, some papers proposed the application methods of d-a theory or similar theories for single phase systems. This paper presents the control method of the utility-connected single-phase inverter using d-q theory. The suggested method gives single-phase system instantaneous controllability and also makes the realization of APF(Active Power Filter) without DFT operation and PFC(Power Factor Controller) possible. This paper deals with utility-connected single phase inverter with PFC function. The controller was verified by simulation tool.