• Nuclear Engineering and Technology
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• 제42권3호
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• pp.305-312
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• 2010

The protection sequence of an AC/DC converter for an ITER PF coil system is developed in this study. Possible faults in the coil system are simulated and the results reflected in the design of a sequence to protect the coil and converter. The inductances of the current sharing reactors and thyristor numbers in parallel with the bridge arms are optimized with the designed protection sequence.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1226-1228
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• 2004

A novel lossless passive snubber is proposed for soft switching the boost type converters. The proposed snubber does not use any auxiliary switches. but uses two identical snubber capacitors which are charged in parallel at turn off of the main switch and discharged in series at turn on automatically, and the discharged energy is recovered effectively (more than $95[\%]$ recovery) into the output capacitor. Thus, the snubber provides zero voltage switching for the converter main switch, reducing both the turn off losses and the electromagnetic interference(EMI) noise, whitch improves the converter performance. The experimental results of a 20[kHz] 600[W] DC-DC boost converter and a single-phase AC-DC boost rectifier with the new snubber are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.1022-1024
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• 1992

The multiple poly-phase converters to be overcome the current limits of switching devices have the merits of the lessen weight and ripple. This paper deals with the circuit analysis of the poly-phase buck converters with discontinuous inductor current. The dc and ac models are obtained by the average method of the state equations.

• 전력전자학회논문지
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• 제18권2호
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• pp.169-177
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• 2013

This paper proposes a new configuration of bidirectional intelligent semiconductor transformer with rating of 1.9kV/127V, 2kVA. The proposed transformer consists of high-voltage high-frequency AC-DC rectifier, and low-voltage DC-DC and DC-AC converters. The operational feasibility of proposed transformer was verified by computer simulation with PSCAD/EMTDC software. Based on the simulation results, a hardware prototype with rating of 1.9kV/127V, 2kVA was built and tested in the lab to confirm the feasibility of hardware implementation. Using three units of this transformer, a 3-phase transformer with rating of 3.3kV/220V, 6kVA can be built.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.1035-1037
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• 1992

Generally, fuel cell has characteristics of low voltage, large current and voltage variation under load change. Therefore, DC output voltage of fuel cell is too low to convert into AC with high efficiency and good performance. For this reason, fuel cell generating system is composed of DC-DC converter and inverter in cascade. This paper used 2-phase boost DC-DC converter to obtain low distortion waveform and reduce input-output current ripple, and discussed inverter which can be operated in independent drive mode and utility line interface drive mode. Then, the change of modes can be achived smoothly.

• 전력전자학회논문지
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• 제16권3호
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• pp.293-301
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• 2011

본 논문에서는 정류용 브릿지 다이오드가 없는 고효율 하프 브릿지 AC-DC 컨버터를 제안한다. 제안하는 컨버터는 비대칭 펄스 폭 변조 방식의 하프 브릿지 DC-DC 컨버터와 정류용 브릿지 다이오드가 없는 역률 개선 회로가 통합된 회로 구조를 지닌다. 제안하는 컨버터는 정류용 브릿지 다이오드를 사용하지 않고 교류 입력 전압으로부터 절연된 직류 출력 전압을 공급한다. 간단한 회로 구조와 함께 도통 손실을 줄일 수 있다. 또한 스위칭 소자들의 영전압 스위칭을 통하여 스위칭 손실을 줄일 수 있다. 두 개의 직렬 연결된 트랜스포머를 구비함으로서 프로파일을 낮추고 전력밀도를 높일 수 있다. 250 W (48 V / 5.2 A) 회로 설계 및 실험을 통하여 제안된 컨버터의 성능을 $90 \;V_{rms}$ 교류 입력 전압에 대하여 입증하였다.

• Journal of Power Electronics
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• 제14권6호
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• pp.1166-1177
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• 2014

A new type of topology with medium-frequency-transformer (MFT) isolation for medium voltage wind power generation systems is proposed in this paper. This type of converter is a high density power conversion system, with high performance features suitable for next generation wind power systems in either on-shore or off-shore applications. The proposed topology employs single-phase cascaded multi-level AC-AC converters on the grid side and three phase matrix converters on the generator side, which are interfaced by medium frequency transformers. This avoids DC-Link electrolytic capacitors and/or resonant L-C components in the power flow path thereby improving the power density and system reliability. Several configurations are given to fit different applications. The modulation and control strategy has been detailed. As two important part of the whole system, a novel single phase AC-AC converter topology with its reliable six-step switching technique and a novel symmetrical 11-segment modulation strategy for two stage matrix converter (TSMC) is proposed at the special situation of medium frequency chopping. The validity of the proposed concept has been verified by simulation results and experiment waveforms from a scaled down laboratory prototype.

• Journal of Electrical Engineering and Technology
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• 제2권1호
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• pp.68-80
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• 2007

This paper covers switched reluctance generator (SRG) and its comparison with induction and synchronous machines for distributed generation. The SRG is simple in design, robust in construction, and fault tolerant in operation; it can also withstand very high temperatures. However, the performance and cost of the SRG power electronics driver are highly affected by the topology and design of the converter. IGBT and MOSFET based converters are not suitable for very high power applications. This paper presents thyristor-based resonant converters which are superior candidates for very high power applications. Operations of the converters are analyzed and their characteristics and dynamics are determined in terms of the system parameters. The resonant converters are capable of handling high currents and voltages; these converters are highly efficient and reliable as well. Therefore, they are suitable for high power applications in the range of 1MW or larger for distributed generation.

• Journal of Power Electronics
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• 제19권5호
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• pp.1153-1161
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• 2019

A current sharing controller is proposed in this paper for parallel-connected converters. The proposed controller is based on the calculation of the magnitudes of system current space vectors. Good current distribution between parallel converters is achieved with only one Proportional-Integral (PI) compensator. The proposed controller is analyzed and the circulating current impedance is derived for paralleled systems. The performance of the new control strategy is experimentally verified using two parallel connected converters employing Space Vector Pulse Width Modulation (SVPWM) feeding a passive RL load and a 2.2 kW three-phase induction motor load. The obtained test results show a reduction in the current imbalance ratio between the converters in the experimental setup from 53.9% to only 0.2% with the induction motor load.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권4호
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• pp.483-491
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• 2012

It is expected that, in the future, DC power service will be widely used for photovoltaic home power generation systems, since DC consuming devices are ever increasing. Instead of using multiple converters to convert DC to AC and then AC to DC, the power service could solely be based on DC. This would eliminate the need for converters, reducing the cost, complexity, and possibly increasing the efficiency. However, configuration of direct DC power service with mechanical contacts can cause spark voltage or an electric shock when the switch is turned on and off. To solve these problems, in this paper, a contactless power supply for a DC power service that can transfer electric power produced by photovoltaics to the home electric system using magnetic coupling instead of mechanical contacts has been proposed. The proposed system consists of a ZVS boost converter, a half-bridge LLC resonant converter, and a contactless transformer. This proposed contactless system eliminates the use of DC switches. To reduce the stress and loss of the boost converter switching devices, a lossless snubber with coupled inductor is applied. In this paper, a switching frequency control technique using the contactless voltage sensing circuit is also proposed and implemented for the output voltage control instead of using additional power regulators. Finally, a prototype consisted of 150W boost converter has been designed and built to demonstrate the feasibility of the proposed contactless photovoltaic DC power service. Experimental results show that 74~83% overall system efficiency is obtained for the 10W~80W load.