• 전력전자학회논문지
• /
• 제14권6호
• /
• pp.488-495
• /
• 2009

본 논문은 기계적 에너지를 전기에너지로 변환하는 압전소자를 이용한 에너지 수확 시스템 내에서 전력변환을 수행하는 새로운 AC/DC 공진형 자려(自勵) 부스트 컨버터를 제안한다. AC/DC 공진형 자려 부스트 컨버터의 자려 스위칭을 위한 게이트 회로는, MOSFET 특성을 이용하여 압전소자 출력전압의 최대값을 검출하고 LC 공진회로의 특성을 이용하여 영전압 스위칭을 하며, 승압형 전력변환을 수행하기 위해서 별도의 전원을 필요로 하지 않는다. 제안된 컨버터 회로의 동작원리를 설명하고, 기존 연구 개발된 토폴로지와 비교, PSPICE 시뮬레이션 및 실험을 통하여 유용성을 검증한다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• 제5B권2호
• /
• pp.181-188
• /
• 2005

In this paper, a DC smoothing filterless soft switching pulse modulated high frequency AC power conversion circuit connected to utility. frequency AC power source is proposed for consumer induction heating hot water producer, steamer and super heated steamer. The operating principle of DC link filterless utility frequency AC-high frequency AC (HF AC) power conversion circuit defined as high frequency cycloinverter is described, which can operate under a principle of ZVS/AVT and power regulation based on alternate asymmetrical PWM in synchronization with the utility frequency single phase AC positive or negative half wave voltage. The dual mode modulation control scheme based on high frequency PWM and commercial frequency AC voltage PDM for the proposed high frequency cycloinverter are discussed to enlarge its soft switching commutation operating range for wide HF AC power regulation. This high frequency cycloinverter is developed for high frequency IH Dual Packs Heater (DPH) type boiler used in consumer and industrial fluid pipeline systems. Based on the experiment and simulation results, this high frequency cycloinverter is proved to be suitable for the consumer use IH-DPH boiler and hot water producers. The cycloinverter power regulation and power conversion efficiency characteristics are evaluated and discussed.

• Carbon letters
• /
• 제3권4호
• /
• pp.187-191
• /
• 2002

In the present research, we prepared the activated carbon (AC) sorbents to remove gas-phase mercury. The mercury adsorption of virgin AC, chemically treated AC and fly ash was performed. Sulfur impregnated and sulfuric acid impregnated ACs were used as the chemically treated ACs. A simulated flue gas was made of SOx, NOx and mercury vapor in nitrogen balance. A reduced mercury adsorption capacity was obtained with the simulated gas as compared with that containing only mercury vapor in nitrogen. With the simulated gas, the sulfuric acid treated AC showed the highest performance, but it might have the problem of corrosion due to the emission of sulfuric acid. It was also found that the high sulfur impregnated AC also released a portion of sulfur at $140^{\circ}C$. Thus, it was concluded that the low sulfur impregnated AC was suitable for the treatment of flue gas in terms of stability and efficiency.

• Journal of Electrochemical Science and Technology
• /
• 제2권3호
• /
• pp.152-156
• /
• 2011

A hybrid supercapacitor is fabricated using a composite material from $LiMn_2O_4$ (LMO) and activated carbon (AC) as the positive electrode and AC as the negative electrode to form the (LMO + AC)/AC system. Volume ratio (positive : negative) of electrodes is controlled to investigate of the power and energy balance. The (LMO + AC)/AC system shows better performances than the LMO/AC system. Especially, electrochemical impedance spectra, rate charge.discharge and cycle performance testing show that the (LMO + AC)/AC system have an outstanding electrochemical performance at volume ratios of (LMO + AC)/AC = 1 : 1.7 and 1 : 2. Electric double layer capacitor (EDLC) capacitance between AC of the positive electrode and AC of the negative electrode improves power density without loss of capacitance. Stable capacitance is achieved by lowering the positive electrode resistance and balancing the energy and power densities between the positive and negative electrodes by the addition of AC to the positive electrode at high current density.

• Journal of Electrical Engineering and Technology
• /
• 제10권1호
• /
• pp.165-175
• /
• 2015

Energy storage system has been widely applied in power distribution sectors as well as in renewable energy sources to ensure uninterruptible power supply. This paper presents a model predictive algorithm to control a bidirectional AC-DC converter, which is used in an energy storage system for power transferring between the three-phase AC voltage supply and energy storage devices. This model predictive control (MPC) algorithm utilizes the discrete behavior of the converter and predicts the future variables of the system by defining cost functions for all possible switching states. Subsequently, the switching state that corresponds to the minimum cost function is selected for the next sampling period for firing the switches of the AC-DC converter. The proposed model predictive control scheme of the AC-DC converter allows bidirectional power flow with instantaneous mode change capability and fast dynamic response. The performance of the MPC controlled bidirectional AC-DC converter is simulated with MATLAB/Simulink(R) and further verified with 3.0kW experimental prototypes. Both the simulation and experimental results show that, the AC-DC converter is operated with unity power factor, acceptable THD (3.3% during rectifier mode and 3.5% during inverter mode) level of AC current and very low DC voltage ripple. Moreover, an efficiency comparison is performed between the proposed MPC and conventional VOC-based PWM controller of the bidirectional AC-DC converter which ensures the effectiveness of MPC controller.

• Journal of Power Electronics
• /
• 제13권2호
• /
• pp.197-205
• /
• 2013

In energy injection resonant AC-AC converters, due to the low frequency effect of the AC input envelope and the low energy injection losses requirement, the constant and steady control of the high frequency AC output envelope is still a problem that has not been solved very well. With the aid of system modeling, this paper analyzes the mechanism of the envelope pit on the resonant AC current. The computing methods for the critical damping point, the falling time and the bottom value of the envelope pit are presented as well. Furthermore, this paper concludes the stability precondition of the system AC output. Accordingly, an optimal control method for the AC output envelope is put forward based on the envelope prediction model. This control method can predict system responses dynamically under different series of control decisions. In addition, this control method can select best series of control decisions to make the AC output envelope stable and constant. Simulation and experimental results for a contactless power transfer system verify the control method.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
• /
• pp.1364-1367
• /
• 2005

In this paper, a novel prototype topology of soft switching PWM controlled high frequency AC power conversion circuit without DC voltage smoothing chemical capacitor filter link from the voltage grid of utility frequency AC power supply source with 60Hz-100V or 60Hz-200V is proposed and introduced for innovative consumer induction heating(IH) boiler applications as hot water producer, steamer and super heated vapor steamer.

• Journal of electromagnetic engineering and science
• /
• 제11권3호
• /
• pp.161-165
• /
• 2011

In this paper, a high-efficiency DC-AC converter is used for wireless energy transmission. The DC-AC convertter is implemented by combining the oscillator and power amplifier. Given that the conversion efficiency of a DC-AC converter is strongly affected by the efficiency of the power amplifier, a high-efficiency power amplifier is implemented using a class-E amplifier structure. Also, because of the low output power of the oscillator connected to the input stage of the power amplifier, a high-gain two-stage power amplifier using a drive amplifier is used to realize a high-output power DC-AC converter. The high-efficiency DC-AC converter is realized by connecting the oscillator to the input stage of the high-gain high-efficiency two-stage class-E power amplifier. The output power and the conversion efficiency of the DC-AC converter are 40.83 dBm and 87.32 %, respectively, at an operation frequency of 13.56 MHz.

• 전력전자학회논문지
• /
• 제10권3호
• /
• pp.274-281
• /
• 2005

압전소자를 에너지원으로 사용하여 자립형 전기전자시스템에 에너지를 공급하는 에너지 획득(Harvesting) 개념의 구현을 위하여, 새로운 AC/DC 공진형 펄스 컨버터를 제안한다. 컨버터는 정류기와 DC 컨버터의 2단계로 구성되었으며, AC/DC 변환을 위한 정류기는 MOSFET의 3상한 동작 특성을 이용하여 구현하고, N형 및 P형 MOSFETs을 사용하여 DC/DC 부스트 컨버터를 구현하였다. 제안된 컨버터 시스템의 동작원리 및 동작모드를 스위칭 소자의 기생캐패시턴스를 고려하여 해석하고, 시뮬레이션을 통하여 해석결과를 검증하였다. CMOS IC 칩으로 제작된 본 시스템의 실험 결과는 수십 uW 용량에서 에너지 획득 개념의 구현 가능성을 제시하였다.

• 전력전자학회논문지
• /
• 제15권3호
• /
• pp.207-217
• /
• 2010

현재 디지털 제품의 사용의 증가로 제품 내부의 DC 전원의 사용이 증가하는 가운데 시스템의 구동전압을 공급하기 위해 기기내부에 장착된 AC/DC컨버터로 인한 입력전류의 역률저하 및 고조파 증가, 그리고 AC/DC 컨버터에서 발생하는 변환 손실 등의 문제가 발생한다. 하이브리드 배전시스템은 기존의 AC부하(전동기 부하 및 변압기 부하)와 DC 부하(컴퓨터, TV, LED조명)에 AC 와 DC 전원을 동시에 공급하며, 직류출력 전원(신재생에너지 및 배터리뱅크)과 상용전원에서 전력을 공급받아 사용자에게 DC 및 AC 전력을 공급해주는 시스템으로 상용전원의 효율을 향상시키고 신재생에너지의 사용 편의성을 올리며 가정에 AC와 DC를 동시에 공급하는데 주목적이 있다. 본 논문을 통해 DC 및 AC 동시 배전을 위해 기존 교류부하의 직류특성에 관한 연구를 하며, 하이브리드 배전의 적절한 DC 전압레벨을 선정한다.