• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1334-1339
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• 2004

This paper proposes transformerless power conversion system consisting of a single-phase diode rectifier and a shunt hybrid filter for the electric-railway system. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multi-level inverter. Compared with conventional active filters. Transformers are not used. Also, LC filter works as not only a harmonic filter tuned at the 5th harmonic frequency but also a switching-ripple filter. The rating of the active filter can be decreased by using a NPC type multi-level inverter. The simulation results confirm the validity of the system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1427-1432
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• 2004

This paper proposes transformerless power conversion system consisting of a single-phase diode rectifier and a shunt hybrid filter for the electric-railway system. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multi-level inverter. Compared with conventional active filters. Transformers are not used. Also, LC filter works as not only a harmonic filter tuned at the 5th harmonic frequency but also a switching-ripple filter. The rating of the active filter can be decreased by using a NPC type multi-level inverter. The simulation results confirm the validity of the system

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권5호
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• pp.265-270
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• 2006

In this paper EMI problems with induction motor drive system using multi-level inverters are investigated. The high power multi-level inverter usually operates with low switching frequency and produces large noises. Generally, EMI consists of the conduction component through source lines and emission component emitted to the space. This conduction component can be classified to the common-mode between source line and ground, and the normal-mode between lines. The EMI filters for the induction motor drive system are designed and implemented to reduce EMI noise. Finally the designed system is verified by the experiment. The experimental results show that both the normal mode and common mode noises are greatly reduced compared to the system without filters.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.215-218
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• 2001

This paper is proposed a sinusoidal input current multi-level ac-dc converter using transformer. The multi-level converter which controls input current by combining Buck converter to Improve input current characteristics. This method, which is multiplying and duplicating output of converter of equal capacity, is able to control unit power factor of input current, reduce the problem caused by high frequency switching, and apply to high power converter because filter is not necessary The feasibility of the circuit is verified by computer simulation using PSIM

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.651-654
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• 2005

In this paper, an efficient switching pattern to equalize the size of transformer is proposed for a multi-level inverter employing cascaded transformers. It is based on the prior selected harmonic elimination PWM(SHEPWM) method. Because the maximum magnetic flux imposed on each transformer becomes exactly equal each to each, all transformers can be designed with the same size regardless of their position. Therefore, identical full-bridge inverter units can be utilized, thus improving modularity and manufacturability. The fundamental idea of the proposed switching pattern is illustrated and the analyzed theoretically. The validity of the proposed switching strategy is verified by experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.515-517
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• 1989

This PWM inverter are used bridge circuit of two pair complementary transistor at each phase. The operation signals are 3 level PWM wave of W type and M type modulation, Which were obtained from switching time data by switching position calculation of triangular and sine wave. The output voltage waveforms of this inverter have the 5 level phase voltage and the 9 level line voltage of PWM.

• 대한전기학회논문지
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• 제39권2호
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• pp.157-163
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• 1990

The PWM inverter investigated in this paper utilizes a bridge type current sharing reactor circuit with tow pairs of complementary transistor at each phase. The driving signals for this inverter are 3 level PWM waves of W type an M type modulation, which are obtained from a microprocessor based on the switching time data obtained by switching position calculation of triangular and sine modulation wave. The output voltage waveforms of this inverter have 5 level phase voltage and 9 level line voltage of PWM. The harmonics of the output voltage are reduced to half when it is compared with single CTI, and the occurrence of harmonics is also reduced.

• 대한전자공학회논문지SD
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• 제46권11호
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• pp.84-91
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• 2009

본 논문은 multi-level signaling을 이용한 high speed serial link transmitter에 관하여 제안하였다. High speed serial link에서 수 Gb/s를 달성하기 위해 4-pulse amplitude modulation (PAM) 을 사용하였다. 4-PAM은 4개의 level로 한 symbol time에 2 bit data를 전송함으로써 binary signaling보다 2배 빠른 data 전송이 가능해졌다. 제안된 4-PAM transmitter는 전압 output 대신 전류 output을 생성하며 이로 인해 driver의 switching time이 빨라져서 더 높은 속도의 transmitter를 구현할 수 있었다. $2^5-1$ pseudo-random bit sequence (PRBS) 생성기는 built-in self test (BIST)를 하기 위해 on-chip으로 설계되었다. 본 연구는 동부 하이텍 $0.18{\mu}m$ CMOS 공정을 통하여 설계되었으며 1.8 V supply voltage에서 eye 크기가 160 mV 이고 최대 동작 속도는 8 Gb/s이다. 칩 전체 면적은 $0.7\times0.6mm^2$이며 전력 소모는 98 mW이다.

• 정보과학회지
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• 제5권2호
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• pp.94-98
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• 1987

本 論文에서는 多値論理回路를 實現함에 있어서 發生하는 Hazard를 2가 지, 卽 Function Hazard와 Logic Hazard로 分類하였고 이의 解決方案으로 入力 信號가 Switching하여 最終 安定 level에 到達했을 때 Switching函數를 決定하고 이 函數로써 Switching函數의 Unate性을 試圖하였다. 그리고 內部回路에서 信號 가 遷移될 때 內部回路의 遲延 遲延時間으로 말미암아 發生되는 Hazard狀態를 Redundant回路를 實現하였다. 또 이 論理回路를 基本으로한 N値 Flip-flop N과 Shift Register, Counter等의 順序論理回路를 構成하였다.

• Journal of Power Electronics
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• 제16권2호
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• pp.464-472
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• 2016

This study applies the selective harmonic elimination (SHE) technique to design and operate a regulated AC/DC/AC power supply suitable for maritime military applications and underground trains. The input is a single 50/60 Hz AC voltage, and the output is a 400 Hz regulated voltage. The switching angles for a multi-level inverter and transformer turns ratio are determined to operate with special connected transformers with equal power ratings and produce an almost sinusoidal current. As a result of its capability of directly controlling harmonics, the SHE technique is applicable to apparatus with congenital immunity to specific harmonics, such as series-connected transformers, which are specially designed to equally share the total load power. In the present work, a single-phase 50/60 Hz input source is rectified via a semi-controlled bridge rectifier to control DC voltage levels and thereby regulate the output load voltage at a constant level. The DC-rectified voltage then supplies six single-phase quazi-square H-bridge inverters, each of which supplies the primary of a single-phase transformer. The secondaries of the six transformers are connected in series. Through off-line calculation, the switching angles of the six inverters and the turns ratios of the six transformers are designed to ensure equal power distribution for the transformers. The SHE technique is also employed to eliminate the higher-order harmonics of the output voltage. A digital implementation is carried out to determine the switching angles. Theoretical results are demonstrated, and a scaled-down experimental 600 VA prototype is built to verify the validity of the proposed system.