• 융합신호처리학회논문지
• /
• 제5권2호
• /
• pp.143-150
• /
• 2004

In this paper, a recursive digital filter realization for an ionospheric channel model is proposed. This realization is in the form of a cascade of identical second-order all-pass filters, and is determined by only three parameters; two coefficients of an all-pass section, and the number of sections. The values of these parameters are optimized by a nonlinear optimization algorithm called the "downhill simplex method", so that the resulting time delay function closely approximates that of the ionospheric channel model. Comparing with the nonrecursive digital filter realization, it can be shown that the proposed recursive-digital-filter-realization is advantageous in points of view for the numbers of filter coefficients and the realization.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 제39회 하계학술대회
• /
• pp.1077-1078
• /
• 2008

The growing number of nonlinear loads such as static power converters has posed a problem on the quality of electric power supply. The active filters (AF) have been rapidly expanding with the advancement of power electronics technology. The purpose of the active filters is to compensate current harmonics and/or current imbalance. The authors have studied and introduced the PV-AF system; the PV power system, which is used widely as a dispersed source, including the function of active filter to compensate the harmonics caused by nonlinear loads. The PV-AF system has merits not only to compensate harmonics caused by nonlinear loads but also to increase the utilization of PCS. This paper describes the grid-connected single phase PV-AF system and the PSCAD/EMTDC simulation results.

• 전력전자학회논문지
• /
• 제12권2호
• /
• pp.131-138
• /
• 2007

본 논문은 출력단에 LC필터를 갖는 3상 PWM 인버터의 출력전압을 일정전압/일정주파수로 제어하기 위한 새로운 비선형 제어기법을 제안한다. 출력 LC필터를 포함한 비선형 모델을 궤환선형화(feedback linearization) 이론을 통하여 선형화하고 선형 제어이론에 기초하여 제어기를 설계한다. 이 제어기는 LC 출력필터를 갖는 PWM 인버터를 사용하는 독립형 풍력발전 시스템에 적용된다. 제안한 제어기법은 정상상태와 부하변동의 과도상태에 대한 실험을 통하여 검증된다.

• Journal of Positioning, Navigation, and Timing
• /
• 제9권2호
• /
• pp.99-115
• /
• 2020

Since GNSS is easily affected by jamming and/or spoofing, alternative navigation systems can be operated as backup system to prepare for outage of GNSS. Alternative navigation systems are being researched over the world, and a multi-radio integrated navigation system using alternative navigation systems such as KNSS, eLoran, Loran-C, DME, VOR has been researched in Korea. Least Square or Kalman filter can be used to estimate navigation parameters in the navigation system. A large number of measurements of the Kalman filter may lead to heavy computational load. The decentralized Kalman filter and the federated Kalman filter were proposed to handle this problem. In this paper, the decentralized Kalman filter and the federated Kalman filter are designed for the multi-radio integrated navigation system and the performance evaluation result are presented. The decentralized Kalman filter and the federated Kalman filter consists of local filters and a master filter. The navigation parameter is estimated by local filters and master filter compensates navigation parameter from the local filters. Characteristics of three Kalman filters for a linear system and nonlinear system are investigated, and the performance evaluation results of the three Kalman filters for multi-radio integrated navigation system are compared.

• 한국통신학회논문지
• /
• 제22권1호
• /
• pp.64-71
• /
• 1997

Digital communication channels are imparied by linear effects such as dispersion, ISI(intersymbol Interference), fading phenomenon etc. But, the practical channel equalization system is required to design for compensating the nonlinear distortion caused by harmonic distortion etc. This paper is a study on the performance of nonlinear channel equalization using RBF(Radial Basis Funclion) network, which has the equivalent structure to the optimal Basian filter. Expecially, the variance of RBF network is modifiedby nonlinear polynomial filters to compare the convergence characteristic of nonlinear channel equalization. Experimental results show that the modified RBF network achieves the faster convergence property than conventional RBF network. Moreover, the RBF network ofhigher order variance modified represents the better performance than that of lower order variance in the bandpass channels and second/third order polynomial channels.

• 전자공학회논문지B
• /
• 제32B권10호
• /
• pp.1326-1337
• /
• 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 Power Electronics
• /
• 제16권4호
• /
• pp.1541-1550
• /
• 2016

This paper presents a theoretical analysis and comparisons of active power filter (APF) and hybrid power filter (HPF) systems, given terminal constraints of harmonic compensations in nonlinear loads. Despite numerous publications for the two types of filters, the features and differences between them have not been clearly explained. This paper presents a detailed analysis of the operations of a HPF inverter along with those of passive power filters (PPFs). It also includes their effects on the power factor at the grid. In addition, a theoretical analysis and a systematic comparison between the APF and HPF systems are addressed based on system parameters such as the source voltage, output power, reactive component size, and power factor at the grid terminals. The converter kVA ratings and dc-link voltage requirements for both topologies are considered in the presented comparisons

• 전자공학회논문지S
• /
• 제36S권2호
• /
• pp.88-95
• /
• 1999

스텍필터는 신호복원성이 뛰어난 디지털 비선형 필터의 일종이다. 그러나 기존의 적응형 설계기법을 이요하면 순차적인 특성 때문에 윈도우의 크기가 큰 스텍필터의 설계시 많은 계산량으로 그 응용에 한계가 있었다. 본 논문에서는 평균적대오차를 최소화하는 최적의 스텍필터를 설계하기 위한 병렬구조의 기법을 제안하였고 제안된 기법을 사용하면 적응특성 즉 학습의 반복적인 특성을 가지면서 최적의 필터로 수령하는데 필요한 반복 횟수를 줄임으로써 기존의 설계기법보다 설계시간을 단축할 수 있다는 사실과 제안된 기법이 최적의 스텍필터로 수렴한다는 사실을 증명하였다.

• 전자공학회논문지B
• /
• 제29B권1호
• /
• pp.34-42
• /
• 1992

This paper presents two fast least-squares lattice algorithms for adaptive nonlinear filters equipped with bilinear system models. The lattice filters perform a Gram-Schmidt orthogonalization of the input data and have very good numerical properties. Furthermore, the computational complexity of the algorithms is an order of magnitude snaller than previously algorithm is an order of magnitude smaller than previously available methods. The first of the two approaches is an equation error algorithm that uses the measured desired response signal directly to comprte the adaptive filter outputs. This method is conceptually very simple`however, it will result in biased system models in the presence of measurement noise. The second approach is an approximate least-squares output error solution. In this case, the past samples of the output of the adaptive system itself are used to produce the filter output at the current time. Results of several experiments that demonstrate and compare the properties of the adaptive bilinear filters are also presented in this paper. These results indicate that the output error algorithm is less sensitive to output measurement noise than the squation error method.

• Journal of Electrical Engineering and information Science
• /
• 제2권5호
• /
• pp.114-120
• /
• 1997

A design method is newly presented for the creation of planar type filters which shapes will be nonuniform transmission line with continuously varying characteristic impedances. Those filters yield frequency characteristics of the bandstop filter in transmission, and have not nay discontinuities. The design is achieved by the control of wave propagation in view to both reflection an transmission properties on the dispersive nonuniform line within the desired frequency band. The developed algorithm is based on optimized perturbations of inherent nulls of lobes from the solution of first-order nonlinear differential equation for reflection coefficients of the nonuniform line, and an appropriate distribution of reflection coefficient which affects to filter length and bandwidth. Practical measurements for designed wideband microstrip and stop filter show very good agreement with theoretical results.