• JSTS:Journal of Semiconductor Technology and Science
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• 제16권4호
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• pp.451-462
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• 2016

Photovoltaic energy conversion becomes main focus of many researches due to its promising potential as source for future electricity and has many advantages than the other alternative energy sources like wind, solar, ocean, biomass, geothermal etc. In Photovoltaic power generation multilevel inverters play a vital role in power conversion. The three different topologies, diode-clamped (neutral-point clamped) inverter, capacitor-clamped (flying capacitor) inverter and cascaded h-bridge multilevel inverter are widely used in these multilevel inverters. Among the three topologies, cascaded h-bridge multilevel inverter is more suitable for photovoltaic applications since each pv array can act as a separate dc source for each h-bridge module. This paper presents a single phase Cascaded H-bridge five level inverter for grid-connected photovoltaic application using sinusoidal pulse width modulation technique. This inverter output voltage waveform reduces the harmonics in the generated current and the filtering effort at the input. The control strategy allows the independent control of each dc-link voltages and tracks the maximum power point of PV strings. This topology can inject to the grid sinusoidal input currents with unity power factor and achieves low harmonic distortion. A PID control algorithm is implemented in Arm Processor LPC2148. The validity of the proposed inverter is verified through simulation and is implemented in a single phase 100W prototype. The results of hardware are compared with simulation results. The proposed system offers improved performance over conventional three level inverter in terms of THD.

• 한국HCI학회논문지
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• 제12권4호
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• pp.37-44
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• 2017

Eye-typing은 인간-컴퓨터 상호작용의 일종으로 시선의 위치 정보를 기반으로 하는 입력 체계이다. 눈동자의 움직임 이외의 물리적 행위를 필요로 하지 않아 거동이 어려운 전신마비 환자들을 위한 입력 수단으로 널리 사용된다. 하지만 eye-typing을 위한 한글 기반의 인터페이스는 거의 제시되지 않은 것이 현실이다. 이에 본 연구에서는 한글 입력에 최적화된 eye-typing 입력 체계를 구현하였다. 우선 큰 잡음과 Midas touch problem으로 대표되는 eye-typing의 특성을 고려하여 설계 목표를 정립하였다. 잡음 문제를 해결하기 위해 개별 버튼의 크기를 극대화하기 위해 단계식 입력 체계를 도입하였고 Midas touch problem을 해결하기 위해 입력 영역 중간에 시선 보류 영역을 두었다. 다음으로 각 음절이 자음과 모음의 조합으로 생성되는 한글의 언어학적 특성에 대한 고찰을 바탕으로 두 종류의 eye-typing 인터페이스를 설계하였다. 각각 자모 일체형, 자모 분리형 인터페이스로 정의한 두 인터페이스는 한글의 자모음을 유형화하여 단계적으로 입력하도록 구현되었다. 그리고 이들의 성능을 검증하기위해 한글 두벌식자판과 비교하고 입력 과정에서 시선의 동선을 분석하는 실험을 수행하였다. 그 결과, 제시한 인터페이스가 실용적인 eye-typing 수단으로 활용될 가능성이 충분함을 확인하였다.

• 대한전자공학회논문지TC
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• 제40권11호
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• pp.17-26
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• 2003

시간영역 확산을 하는 순방향 링크 OFCDM 시스템에서 고출력 증폭기의 비선형 왜곡을 경감시키고자 IFFT단 부반송파의 다중레벨 입력신호를 clipping을 한 후 MPSK(Multilevel-PSK) 신호로 전송하는 기술을 적용한다. AWGN 채널에서 고출력 증폭기의 비선형 왜곡이 고려된 경우 extended m 부호열을 사용한 clipping OFCDM 시스템이 extended m 부호열을 사용한 OFCDM 시스템에 비해 N이 8, 16명인 경우 2.2㏈ 이상 성능이 우수하였다. Quasi-static 채널에서 고출력 증폭기의 비선형 왜곡이 고려된 경우 extended m 부호열을 사용한 clipping OFCDM 시스템이 extended m 부호열을 사용한 OFCDM 시스템에 비해 N이 8, 16명인 경우는 2㏈ 이상 우수하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.618-621
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• 2002

This paper proposes a static vu compensator using hybrid cascade 5-level PWM inverter, Circuit DQ transformation is used for modeling and analysis of the system, and it reveals the important characteristics and related equations of the system. Also, a multilevel PWM technique suitable to hybrid structure Is proposed for less harmonics in the input currents of the system. Finally, the validity of tile characteristics analysis is shown through PSIM simulations.

• 조명전기설비학회논문지
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• 제28권10호
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• pp.16-26
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• 2014

This paper proposes new 13-level inverter topology and DC/DC converter buck-boost structure topology for multilevel, compounding uni-directional and bi-directional switches, and proposes high-efficient multilevel inverter system in which the proposed two PCS(Power Conditioning System) was connected in series. In proposed multilevel inverter of forming a output 13-level phase voltage by using total 18 switching parts, Then bi-directional switch has a characteristic of reducing conduction loss and controlling the reactive power effectively by separating electrically from the neutral point. DC/DC converter for supplying in dependent 3 DC voltage to the proposed multi-level inverter generates 180-degree phase shifted PWM by the symmetrically combined structure of 2 buck-boost converter and twice switching frequency efficiency can be obtained, meanwhile, the converter can step up/down the output voltage and 20% output can be generated comparing the input voltage. This proposed system is verified with the simulation and laboratory test.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.261-270
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• 2015

In this paper, the Optimal Harmonic Stepped Waveform (OHSW) method is proposed in order to eliminate the selective harmonic orders available at the output of cascaded multilevel inverter (CMLI) fed by solar photovoltaic (SPV). This technique is used to solve the harmonic elimination equations based on stepped waveform analysis in order to obtain the optimal switching angles which in turn reduce the Total Harmonic Distortion (THD). The OHSW method considers the output voltage waveform as four equal symmetries in each half cycle. In the proposed method, a solar fed fifteen level cascaded multilevel is considered where the magnitude of six numbers of harmonic orders is reduced. A programmable pulse generator is developed to carry the switching angles directly to the semiconductor switches obtained as a result of OHSW analysis. Simulations are carried out in MATLAB/Simulink in which a separate model is developed for solar photovoltaic which serves as the input for cascaded multilevel inverter. A 3kWp solar plant with multilevel inverter system is implemented in hardware to show the effectiveness of the proposed system. Based on the observation the OHSW method provides the reduced THD thereby improving power quality in renewable energy applications.

• Journal of information and communication convergence engineering
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• 제1권3호
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• pp.163-168
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• 2003

This paper presents a cascade multilevel PWM rectifier without the isolation transformers for energy build-up at each inverter modules. The features and advantages of the proposed PWM rectifier can be summarized as follows; I) It realizes the high power high voltage AC/DC power conversion, 2) It uses no transformer which is bulky and heavy, 3) It has hybrid structure so that switching devices can be effectively utilized, 4) It produces high quality AC current even in high power high voltage applications, 5) The input power factor remains unity by simple modulation index control. The multilevel rectifier is analyzed by using the circuit DQ transformation whereby the characteristics and control equations are obtained. Finally, it will be shown that the system simulation reveals the validity of analyses.

• Journal of Power Electronics
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• 제16권6호
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• pp.2272-2283
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• 2016

This paper proposes a power conditioning system (PCS) for distributed photovoltaic (PV) applications using an asymmetric cascaded multilevel inverter with a single PV source. One of the main disadvantages of the cascaded multilevel inverters in PV systems is the requirement of multiple isolated DC sources. Using multiple PV strings leads to a compromise in either the voltage balance of individual H-bridge cells or the maximum power point tracking (MPPT) operation due to localized variations in atmospheric conditions. The proposed PCS uses a single PV source with a flyback DC-DC converter to facilitate a reduction of the required DC sources and to maintain the voltage balance during MPPT operation. The flyback converter is used to provide input for low-voltage H-bridge cells which processes only 20% of the total power. This helps to minimize the losses occurring in the proposed PCS. Furthermore, transient analyses and controller design for the proposed PCS in both the stand-alone mode and the grid-connection mode are presented. The feasibility of the proposed PCS and its control scheme have been tested using a 1kW hardware prototype and the obtained results are presented.

• 전력전자학회논문지
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• 제8권1호
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• pp.9-16
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• 2003

본 논문에서는 출력 고조파 성분을 억제하기 위한 한 방법으로 변압기의 조합에 의한 멀티 레벨 인버터를 제안한다. 제안된 인버터의 구조는 요구하는 멀티 레벨의 출력 생성을 위한 단상 풀-브리지 인버터 모듈과 이와 동일한 수의 변압기로 구성되며, 변압기의 권수비를 적절히 선택하여 직류 전원에 대한 정수비의 연속적인 전압 레벨의 발생이 가능한 새로운 멀티 레벨 인버터이다. 제안하는 인버터는 변압기의 직렬 운전으로 출력단의 필터용 인덕터가 필요 없다. 제안된 멀티 레벨 인버터의 타당성을 입증하기 위해 24[V] 직류 전원에서 220 [V] 교류 전원을 발생시킬 수 있는 인버터에 대하여 1.5 [kW]급 시작품을 제작하고 실험을 행하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.576-580
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• 2001

This paper presents a casca multilevel PWM rectifier without the isolation transformers for energy build-up at each inverter modules; The features and advantages of the proposed PWM rectifier can be summarized as follows; 1) It realizes the high power high voltage AC/DC power conversion, 2) It uses no transformer which is bulky and heavy, 3) It has hybrid structure so that switching devices can be effectively utilized, 4) It produces high quality AC current even in high power high voltage applications, 5) The input power factor remains unity by simple modulation index control. The multilevel rectifier is analyzed by using the circuit DQ transformation whereby the characteristics and control equations are obtained. Finally, it will be shown that the system simulation reveals the validity of analyses