• 제목/요약/키워드: multi-level

검색결과 4,734건 처리시간 0.029초

이진 레벨 클리핑 multi-code PW-CDMA 시스템을 위한 적응역확산수신기 (Adaptive Despreading Receiver for Multi-Code PW-CDMA System with Binary-Level Clipping)

  • 최정민;이재홍
    • 대한전자공학회:학술대회논문집
    • /
    • 대한전자공학회 2002년도 하계종합학술대회 논문집(1)
    • /
    • pp.13-16
    • /
    • 2002
  • In this paper, we propose adaptive despreading receiver for multi-code PW-CDMA system with binary-level clipping. The distortion due to clipping the multi-level signal causes the performance degradation. Adaptive despreading alleviates the effect of clipping. It is shown that the proposed adaptive despreading receiver achieves smaller BER than conventional despreading receiver for multi-code PW-CDMA system with binary-level clipping.

  • PDF

양방향 스위치를 이용한 H-bridge 구조의 새로운 멀티레벨 인버터 (A New Multilevel Inverter of H-bridge Topology using Bidirection Switch)

  • 이상혁;강성구;이태원;허민호;박성준
    • 전력전자학회논문지
    • /
    • 제17권4호
    • /
    • pp.291-297
    • /
    • 2012
  • Recently, Switching devices become cheaper, depending on the multi-level inverters are considered as the power-conversion systems for high-power and power-quality demanding applications. The multi-level inverters can reduce the THD(Total Harmonic Distortion) as the output which is similar sinusoidal waveform by synthesizing several capacitor DC voltages. However it has some disadvantages such as increased number of components, complex PWM control method. Therefore, this paper is proposed the new multi-level inverter topology using an new H-bridge output stage with a bidirectional auxiliary switch. The proposed topology is the 4-level 3-phase PWM inverter with less switching part than conventional multi-level inverters and reactive power control possible. In order to understand the new multi-level inverter, topology analysis and switching patterns and modes according to the current loop are described in this paper. The proposed multi-level inverter topology is validated through PSIM simulation and the experimental results are provided from a prototype.

Road Damage Detection and Classification based on Multi-level Feature Pyramids

  • Yin, Junru;Qu, Jiantao;Huang, Wei;Chen, Qiqiang
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • 제15권2호
    • /
    • pp.786-799
    • /
    • 2021
  • Road damage detection is important for road maintenance. With the development of deep learning, more and more road damage detection methods have been proposed, such as Fast R-CNN, Faster R-CNN, Mask R-CNN and RetinaNet. However, because shallow and deep layers cannot be extracted at the same time, the existing methods do not perform well in detecting objects with fewer samples. In addition, these methods cannot obtain a highly accurate detecting bounding box. This paper presents a Multi-level Feature Pyramids method based on M2det. Because the feature layer has multi-scale and multi-level architecture, the feature layer containing more information and obvious features can be extracted. Moreover, an attention mechanism is used to improve the accuracy of local boundary boxes in the dataset. Experimental results show that the proposed method is better than the current state-of-the-art methods.

자동미분을 이용한 뼈대구조의 다단계 다목적 최적설계 (Multi-Level and Multi-Objective Optimization of Framed Structures Using Automatic Differentiation)

  • Cho, Hyo-Nam;Min, Dae-Hong;Lee, Kwang-Min;Kim, Hoan-Kee
    • 한국전산구조공학회:학술대회논문집
    • /
    • 한국전산구조공학회 2000년도 봄 학술발표회논문집
    • /
    • pp.177-186
    • /
    • 2000
  • An improved multi-level(IML) optimization algorithm using automatic differentiation (AD) for multi-objective optimum design of framed structures is proposed in this paper. In order to optimize the steel frames under seismic load, two main objective functions need to be considered for minimizing the structural weight and maximizing the strain energy. For the efficiency of the proposed algorithm, multi-level optimization techniques using decomposition method that separately utilizes both system-level and element-level optimizations and an artificial constraint deletion technique are incorporated in the algorithm. And also to save the numerical efforts, an efficient reanalysis technique through approximated structural responses such as moments, frequencies, and strain energy with respect to intermediate variables is proposed in the paper. Sensitivity analysis of dynamic structural response is executed by AD that is a powerful technique for computing complex or implicit derivatives accurately and efficiently with minimal human effort. The efficiency and robustness of the IML algorithm, compared with a plain multi-level (PML) algorithm, is successfully demonstrated in the numerical examples.

  • PDF

Multi-level PDP 구동회로를 위한 Gate driver의 Boot-strap chain에 관한 연구 (A Study on Gate driver with Boot-strap chain to Drive Multi-level PDP Driver Application)

  • 남원석;홍성수;사공석진;노정욱
    • 전력전자학회논문지
    • /
    • 제11권2호
    • /
    • pp.120-126
    • /
    • 2006
  • 본 논문에서는 Multi-level PDP 구동회로의 Sustain 스위치를 구동하기 위해 Boot-strap chain 방식의 Gate driver를 제안한다. 제안된 Gate driver는 한 개의 High-side N-MOSFETS를 구동하기 위해 별도의 Floating power supply 가 필요치 않고 한 쌍의 다이오드와 캐패시터만을 사용한다. 제안 Gate driver 회로를 적용함으로서, Multi-level PDP driver의 가격과 무게 및 부피를 줄일 수 있다.

직렬형 3상 변압기를 이용한 다중레벨 PV-PCS (A Study on the Multi-level PV-PCS Using Cascade 3-Phase Transformer)

  • 김기선;송성근;조수억;최준호;김광헌;박성준
    • 전기학회논문지
    • /
    • 제58권12호
    • /
    • pp.2359-2369
    • /
    • 2009
  • The study on the multi-level inverter has been increasingly progressing to reduce the switching loss and improve the THD of output current in photovoltaic inverter. Recently, the main topics of multi-level inverter are to reduce the number of devices maintaining the power quality. Therefore, the novel topology was proposed for these problem which is composed of the isolated H-bridge multi-level inverter using the three phase low frequency transformer. The proposed multi-level inverter may not be need for a independent DC power, diode and capacitor. Specially, It has a advantage in generating high voltage source. The proposed approach is verified through simulation and experiment.

TOPSIS와 전산직교배열을 적용한 자동차 로워암의 다수준 형상최적설계 (Multi-level Shape Optimization of Lower Arm by using TOPSIS and Computational Orthogonal Array)

  • 이광기;한승호
    • 한국정밀공학회지
    • /
    • 제28권4호
    • /
    • pp.482-489
    • /
    • 2011
  • In practical design process, designer needs to find an optimal solution by using full factorial discrete combination, rather than by using optimization algorithm considering continuous design variables. So, ANOVA(Analysis of Variance) based on an orthogonal array, i.e. Taguchi method, has been widely used in most parts of industry area. However, the Taguchi method is limited for the shape optimization by using CAE, because the multi-level and multi-objective optimization can't be carried out simultaneously. In this study, a combined method was proposed taking into account of multi-level computational orthogonal array and TOPSIS(Technique for Order preference by Similarity to Ideal Solution), which is known as a classical method of multiple attribute decision making and enables to solve various decision making or selection problems in an aspect of multi-objective optimization. The proposed method was applied to a case study of the multi-level shape optimization of lower arm used to automobile parts, and the design space was explored via an efficient application of the related CAE tools. The multi-level shape optimization was performed sequentially by applying both of the neural network model generated from seven-level four-factor computational orthogonal array and the TOPSIS. The weight and maximum stress of the lower arm, as the objective functions for the multi-level shape optimization, showed an improvement of 0.07% and 17.89%, respectively. In addition, the number of CAE carried out for the shape optimization was only 55 times in comparison to full factorial method necessary to 2,401 times.

멀티레벨 인버터와 다상 유도기를 이용한 견인기용 대전력 VSI의 구조와 특성 (Configurations of High Power VSI Drives for Traction Applications Using Multi Level Inverters and Multi Phase Induction Motors)

  • ;류홍제;김종수;임근희
    • 대한전기학회:학술대회논문집
    • /
    • 대한전기학회 1997년도 추계학술대회 논문집 학회본부
    • /
    • pp.500-504
    • /
    • 1997
  • Current source inverter drives of auto sequentially commutated type are very popular in high power applications, because of simple power circuit configuration with four quadrant operation. But the six-step current output create harmonic problems and the input power factor of such a drive is not always good. In this respect pulse width modulated drives using gate turn off thyristors ( GTO ) are finding application, especially in traction drives. However the switching and snubber loses of a GTO do not permit the inverter switching frequency go beyond a few hundred hertz.This will again introduce low frequency harmonic problems. Multi level inverters of the 3-level and 5-level can be considered as an alternative to overcome the low switching frequency harmonic problem of the 2-level GTO inverters. But with multi level inverters the complexity of the power circuit increases. In this paper a combination of multi level ( 2-level and 3-level ) inverters and multi phase induction motor ( 3-phase and 6-phase) configurations are presented for high power VSI drives for traction applications with reduced inverter switching frequency requirements coupled with reduced voltage rating for the power switch.

  • PDF

출력전압 레벨 수와 전류정격을 고려한 PWM 다중레벨 인버터 (Multi-level PWM Inverter Considering the number of Output Voltage level and Current rating)

  • 박노식;서종준;박성준;김광헌;조수억;김철우
    • 전력전자학회:학술대회논문집
    • /
    • 전력전자학회 2005년도 전력전자학술대회 논문집
    • /
    • pp.659-662
    • /
    • 2005
  • In this paper, we proposed the novel hybrid multi-level inverter using combination of the output voltage of transformers to reduce the THD(Total Harmonic Distortion) and improve the waveform of output voltage. The proposed multi-level inverter used the output of transformer which is 1times, 2times, 4times of input of the transformers. So we increased the output voltage from the reduce the number of switching component and transformer. Also, we tested the proposed prototype 15-level inverter to clarify the proposed electric circuit and reasonableness of control signal for the proposed multi -level PWM inverter.

  • PDF

계통연계형 멀티스트링 3상 3레벨 태양광 인버터의 MPPT 제어방법에 관한 연구 (A Study on the MPPT Control Method for Grid-connected Multi-String Three-Phase Three-Level PV Inverter)

  • 김진수;양오
    • 반도체디스플레이기술학회지
    • /
    • 제13권4호
    • /
    • pp.43-48
    • /
    • 2014
  • Two-level inverter has some disadvantages like high harmonics contained in the output current, efficiency limit and stress to switching device as IGBT and FET. Many researches have reported multi-level inverter to complement two-level inverter of problems. In this paper, we suggest MPPT algorithm of multi-string three-level solar inverter that considered nowadays. We added midpoint controller in order to implement the MPPT algorithm because the three-level inverter has to need midpoint controller and procured the stability of direct current link. We verify the superiority of multi-string T-Type inverter and the algorithm we suggested with solar irradiance variation experiment and MPPT efficiency measurement. The MPPT efficiency was confirmed with a high efficiency more than 99.97%.