• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 추계학술대회 논문집
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• pp.214-215
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• 2016

본 논문에서는 5-레벨 H-브리지 인버터에서 DC 링크 전압변화로 인하여 야기되는 출력전류 왜곡을 보상하는 기법에 대하여 연구하였다. 제안된 방식에서는 인버터로 모터를 구동할 때 일반적으로 사용되는 모터 상전류 정보를 이용하여 보상 알고리즘을 구성하였다. 또한 제안된 보상 기법은 저속운전에서 전류왜곡을 줄이고 고속운전에서 과변조 영역을 확장하기 위하여 3차 고조파를 주입하는 방식과 함께 사용되었다. 시뮬레이션 테스트 결과, 제안된 간단한 보상기법을 이용하여 전류왜곡이 상당히 줄어드는 것이 확인되었다.

• Journal of Power Electronics
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• 제17권5호
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• pp.1186-1194
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• 2017

This paper proposes an improved low frequency Selective Harmonic Mitigation-PWM (SHM-PWM) technique. The proposed method mitigates the low order harmonics of the output voltage up to the $50^{th}$ harmonic well and satisfies the grid codes EN 50160 and CIGRE-WG 36-05. Using a modified criterion for the switching angles, the range of the modulation index for non-linear SHM equations is improved, without increasing the switching frequency of the CHB converter. Due to the low switching frequency of the CHB converter, mitigating the harmonics of the converter up to the $50^{th}$ order and finding a wider modulation index range, the size and cost of the passive filters can be significantly reduced with the proposed technique. Therefore, the proposed technique is more efficient than the conventional SHM-PWM. To verify the effectiveness of the proposed method, a 7-level Cascaded H-bridge (CHB) converter is utilized for the study. Simulation and experimental results confirm the validity of the above claims.

• 전력전자학회논문지
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• 제20권4호
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• pp.321-329
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• 2015

The static synchronous compensator (STATCOM) of cascaded H-bridge configuration accompanying multiple separate DC sides is inherently subject to the problem of uneven DC voltages. These DC voltages in one leg can be controlled by adjusting the AC-side output voltage of each cell inverter, which is proportional to the active power. However, when the phase current is extremely small, large AC-side voltage is required to generate the active power to balance the cell voltages. In this study, an alternative zero-sequence current injection method is proposed, which facilitates effective cell balancing controllers at no load, and has no effect on the power grid because the injected zero sequence current only flows within the STATCOM delta circuit. The performance of the proposed method is verified through simulation and experiments.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권1호
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• pp.91-98
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• 2012

Climate change and other pollutions make a huge demand of environment friendly and high efficient motors especially Brushless DC (BLDC) motors. Generally, bidirectional energized BLDC motors are used widely; however, inverter devices used in the driver put fear of being effected by noise. This paper proposes unidirectional energized BLDC motor which utilizes asymmetrical H-bridge circuit as the driver circuit. The Minato motor is one of the pioneers in unidirectional energized system. The use of bar magnets in the rotor is one of the biggest disadvantages of the motor. We proposed using tabular magnets. The paper compares the power consumption and efficiency of the Minato motor and the proposed motor. During high speed rotation, undesirable armature current is generated that has a deceleration characteristic. This current lowers the motor's efficiency. In this paper, we propose the solutions and show comparison through equations of the copper loss ratio for the Minato and our proposed motors. The third motor, which has the highest efficiency, was discovered during examination of the equations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1126-1128
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• 2001

A single-stage high-power-factor electron ic ballast operating in critical conduction mode is presented in this paper. The proposed topology is based on integration of a boost-like converter and a LCC Type half-bridge serial resonant inverter. The power-factor-correction(PFC) stage is a boost-like converter operating in critical conduction mode for positive and negative half cycle voltage respectively at line frequency (60Hz) so that a high power factor is achieved naturally. The simulated and experimental results for 100w fluorescent lamps operating at 42kHz switching frequency and 220V line voltage have been obtained.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.616-620
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• 2003

액정 디스플레이의 백라이트에 사용되는 냉음극 방전램프(CCFL: Cold Cathode Fluorescent Lamp) 구동 인버터의 설계함에 있어 압전 변압기(Piezoelectric Transformer)를 사용하였으며, 파라미터 선정 및 최적화를 하여 실험을 통해 검증하였다. 적용한 압전 인버터로는 푸시-풀(Push-pull)과 하프-브리지(Half-bridge) 회로이며, 휘도 제어기법으로는 아날로그(Analog)와 버스트(Burst) 방법을 사용하였다. 푸시-풀 인버터의 경우 아날로그 제어방식으로 제어전압 2.5-4.5V에서 출력전류 1-6mA(최소)로 휘도 0-100$\%$ 특성을 보였다. 입출력 효율로 18.6(최소)-90.3(최대)$\%$를 얻었으며, 버스트 제어방식에서는 듀티비 50-5$\%$에서 1-6mA의 제어 성능을 보였다. 인버터의 입출력 효율은 13.6(최소)-82.1(최대)$\%$를 얻었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.464-469
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• 1998

In the conventional wire feeder drives of welding machine, one thyristor or MOSFET device was used for half-wave phase control circuit and direct EMF measurement was used for sensing the wire feed rate. But the method using one switching device has poor response for sudden disturbance and it has latent speed ripple. It can affect some welding performance such as spatter generation and irregular bead formming. Therefore, the welding performance using full-bridge PWM speed control scheme was compared with conventional driving scheme was compared with conventional driving scheme and experimented in this paper. The results of experiment confirm the posibility of welding performance improvement by proposed constant speed control scheme in wire feeding drive of welding machine.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1853-1855
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• 2002

A pulsed Nd:YAG laser is used widely in many applications such as materials processing, communications, military and medical instruments. It is important to control the laser energy in those fields with using a pulsed Nd:YAG laser. In this paper, constant-frequency current resonant half-bridge inverter and feedback control circuit are used to have output stable. This laser power supply is designed and fabri which was isolated. Also, this study is used an one-chip microprocessor, SCR, current transform A stable output of this Nd:YAG laser system investigated. The tested results are described.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.262-264
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• 2007

최근 전압 및 주파수 가변을 이용하여 전동기의 속도를 제어하여 전동기 경부하시 베인에서 소모되는 에너지 절감효과를 얻을 수 있는 인버터 시스템이 널리 사용되고 있다. 이에 전력연구원은 6.6kV, 1MVA급 인버터 개발 및 동해화력 발전처에 설치, 보일러 점화 전/후 시험, 계통 병입 후 부하 시험 등을 국내 최초로 성공적으로 완료하여 현재 이차 공기 송풍기 구동용 인버터는 상업 운전 중이다. 본 논문에서는 기존 동해화력 발전 설비와 신규 인버터 시스템의 인터페이스 부분에 해당하는 보일러 DCS 로직과 계통 병입 후 시운전 결과에 대하여 상세히 기술하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.556-559
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• 2001

In this paper, we proposed AC/DC boost converter to improve input current harmonic reduction in SMAW(shielded metal-arc welding). The proposed harmonic reduction with the boost converter design and the UC2854 integrated circuit which controls the converter, The topology of welding power supply is made of a pair of boost converter and welder half-bridge IGBT inverter. The voltage arc is modeled by a variable resistance in series with a voltage source. The results has been confirmed by PSIM simulation tool. The simulation results show that input at current is nearly sinusoidal with low harmonic contents and sinusoidal input current waveform at high power factor.