• Journal of Power Electronics
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• v.13 no.2
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• pp.287-295
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• 2013

The use of LCL filters in pulse width modulation voltage source converters is a standard solution for providing proper attenuation of high-order grid-current harmonics. However, these filters can cause the undesired effect of resonance. This paper proposes an active damping strategy with harmonics compensation. It can alleviate the harmonics around the resonance frequency caused by the LCL filters. The proposed strategy is attractive since it is simple, does not depend on grid parameters and does not increase the number of sensors. Simulation and experimental results verify the effectiveness of the proposed active damping strategy.

• Journal of Power Electronics
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• v.15 no.3
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• pp.786-795
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• 2015

In this paper, an active damping control scheme for LLCL filters based on the PR (proportional-resonant) regulator is proposed for grid-connected three-level T-type PWM converter systems. The PR controller gives an infinite gain at the resonance frequency. As a result, the oscillation can be suppressed at that frequency. In order to improve the stability of the system in the case of grid impedance variations, online grid impedance estimation is applied. Simulation and experimental results have verified the effectiveness of the proposed scheme for three-phase T-type AC/DC PWM converters.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2299-2304
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• 2011

In this paper, we propose the methodology to make the bandpass filters for the Smart Grid IED(Intelligent Electronic Device) smaller than the conventional bandpass filters. The size-reduction of the filters and the filter performances are indebted to devising small CRLH(composite right- and left-handed) resonators and coupling them as the metamaterial structures. The design methodology is validated by the equivalent circuit to be compared with the reliable full-wave EM simulation, and the proposed metamaterial filter outperforms the standard parallel-edge coupled filter with respect to the miniaturization and frequency response.

• ETRI Journal
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• v.25 no.2
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• pp.133-139
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• 2003

We studied how the passive intermodulation (PIM) power arising in air cavity filters could be calculated and how the design of the filter could be optimized in order to reduce the amplitude of the PIM signal. To do this, using simulated results, we optimized the various parameters of a filter. PIM in an air cavity filter depends on the power dissipated in its cavities. A reduction of this power loss therefore decreases the PIM power in the air cavity filter. Our experimental results confirm that it is possible to design and produce air cavity filters that generate low PIM signals.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.559-564
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• 2003

Recently, particle filters have attracted attentions for nonlinear state estimation. They evaluate a posterior probability distribution of the state variable based on observations in simulation using so-called importance sampling. However, degeneracy phenomena in the importance weights deteriorate the filter performance. A new filter, Evolution Strategies Based Particle Filter, is proposed to circumvent this difficulty and to improve the performance. Numerical simulation results illustrate the applicability of the proposed idea.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.10
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• pp.1326-1337
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• 1995

In this paper, we transformed the bilinear filter into an equivalent linear multichannel filter and derived QR decomposition based recursive least squares algorithms for bilinear lattice filters. We also defined order update relation of the forward and the backward input vectors by using the channel decomposition. The forward and the backward data matrices were defined by using the forward and the backward input vectors and orthogonalized with the QR decomposition. we can obtain the lattice equations of the bilinear filters by using the channel decomposition. we can be derived the lattice equations of the bilinear filters using this decomposition process which are the same as the lattice equations derived by Baik, we can use the coefficient transformation algorithm proposed by Baik. We derived the equation error and the output error algorithm of the QRD based RLS bilinear lattice algorithm. Also, we evaluated the performance of the proposed algorithms through the system identification of the bilinear system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.11
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• pp.954-962
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• 1998

Energy-trapped thickness vibrations of piezoelectric substrates are utilized in fabricating resonators and filters which have their operating frequencies in HF band. Normalized particle displacement distributions of the fundamental thickness shear vibration mode and overtone modes into the thickness direction in energy-trapped resonators and double-coupled filters were obtained by solving the wave equation and calculating the solved equations. These results show that as the number order of the harmonic mode in a energy-trapped resonator becomes larger, the degree of energy-trapping in the resonator increase, and if the conditions for energy-trapping become sufficiently weak, the energy-trapping effect of the harmonic mode which has the lower order disappears the earlier. Above simulation results were proved by the experiments.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.5
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• pp.249-257
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• 2002

In this paper, a novel control scheme compensating source voltage unbalance and harmonic currents for the combined system of series active and shunt passive power filter is proposed, where no low/high-pass filters are used in deriving the reference voltage for compensation. The phase angle and the reference voltages compensating for harmonic current and unbalanced voltage are derived from the positive sequence component of the unbalanced voltage set, which is simply obtained by using digital all-pass filters. In order to remove the phase delay in generating the reference voltage for compensation, the reference of 5th and 7th harmonic components is predicted one-sampling ahead. The validity of the proposed scheme has been verified for 3[kVA] proto-type active power filter system.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.9
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• pp.389-401
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• 2002

To complement the conventional fusion methodologies of state fusion and measurement fusion, a time-propagated measurement fusion methodology is proposed. Various aspects of common process noise are investigated regarding information preservation. Based on time-propagated measurement fusion methodology, four compression filters are derived. The derived compression filters are efficient in asynchronous sensor fusion and fault detection since they maintain correct statistical information. A new batch Kalman recursion is proposed to show the optimality under the time-propagated measurement fusion methodology. A simple simulation result evaluates estimation efficiency and characteristic.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.25-34
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• 2001

There are many kinds of dielectric materials in microwave dielectric filters for mobile telecomunication. But It is need to new dielectric materials for IMT200O, Bluetooth, wireless LAN to miniaturize the dielectric filters. These kinds of materials should have high dielectric constants, high Q, and low firing sintering temperature(<900˚C ). Multilayer monolithic dielectric filters are manufactured by BiNb04, dielectric ceramics cofired at 875˚C .