• 전력전자학회논문지
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• 제23권5호
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• pp.321-327
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• 2018

DC microgrid system composed of multiple converters has a tendency to make the system unstable due to the interaction of converters. To solve this problem, in this paper, the interaction between cascaded converters with LC input filter is analyzed with impedance modeling using g-parameter. The input impedance and the output impedance of the system can be obtained through this technique. The stability of the system can be determined by applying Middlebrook's stability criterion to the impedance. Virtual impedance is added to the controller to enhance stability. The validity of the analysis is verified by the result of several simulations and experiments.

• 한국초전도ㆍ저온공학회논문지
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• 제13권3호
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• pp.19-23
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• 2011

An HTS DC power cable is expected to perfectly eliminate transmission loss caused by resistance. However, when the HTS DC power cable is applied to the power system, loss of the HTS DC power cable is generated due to harmonics caused by HVDC converter. We designed and analyzed the HTS DC power cable with a critical current of 1 kA to investigate the loss characteristics using a finite element method package. In this paper, the loss characteristics caused by harmonics in the HTS DC power cable were analyzed according to order and magnitude of harmonics. Based on the analysis results, the critical current of HTS DC power cable considered with the rated current could be determined to minimize the capacity of cooling system for the design the HTS DC power cable.

• 전력전자학회논문지
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• 제23권3호
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• pp.217-224
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• 2018

In this study, the optimal design methods of soft-switching cell for high-voltage DC-DC converter (HDC) of fuel cell electric vehicles (FCEVs) is proposed for high efficiency and high power density. The appropriate soft-switching cell for FCEVs is chosen by analyzing the losses of HDC which adopts soft-switching cell. The proposed optimal design methods for the soft-switching cell are divided into two purposes which are improvement of efficiency and power density. Two kinds of design methods enable to improve fuel efficiency and cost, respectively. The proposed design methods are validated with the experimental results based on the specification and hardware used in actual FCEVs.

• 한국자기학회지
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• 제23권3호
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• pp.94-97
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• 2013

본 연구에서는 원통형 페라이트 코어와 페라이트코어를 관통하는 구리선, 그리고 검출 코일을 이용하여서 직교형 플럭스게이트 센서를 제작하고, 직류 바이어스 전류가 출력 감도에 미치는 영향에 대해서 조사하였다. 제작한 직교형 플럭스게이트 센서의 출력 및 감도는 구동주파수에 의존하였으며, 이는 검출코일 임피던스의 주파수특성이 나타내는 경향과 유사하였다. 직류 바이어스 전류가 교류 구동전류의 크기에 비해서 대략 50% 이상일 때 출력감도가 최대가 되었으며, 그 보다 큰 직류 바이어스 전류에 의해서는 출력감도가 포화되는 경향을 나타내었다.

• 전력전자학회논문지
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• 제23권1호
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• pp.32-39
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• 2018

A new dc link voltage controller for a three-phase Vienna rectifier is proposed in this study. This method uses load current and duty information to control dc link voltage. The load current affects the capacitor current and varies the output voltage. Existing methods do not perfectly consider the load current. By considering load current with duty compensation in the proposed method, the transient response is improved by the load variation regardless of the input voltage. The effectiveness of the proposed method is compared with other control methods when the load changes rapidly using PSIM simulation and experiment.

• 전력전자학회논문지
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• 제23권5호
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• pp.336-344
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• 2018

This study proposes a new PWM method for leakage current reduction and neutral point (NP) current control in three-phase three-level converter employed in bipolar DC distribution systems. The proposed PWM method uses medium vectors only when there is no need to control the NP current. Thus, common mode voltages are held constant to realize zero leakage current. Some space vectors that produce low-frequency common mode voltages are employed to minimize leakage currents when the average NP current needs to be a positive or negative value. The proposed space vector PWM is implemented based on barycentric coordinate. The validity of the proposed PWM method is verified by simulations and experiments.

• 전력전자학회논문지
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• 제23권5호
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• pp.299-304
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• 2018

An ideal circuit breaker should supply electric power to loads without losses in a conduction state and completely isolate the load from the power source by providing insulation strength in a break state. Fault current is relatively easy to break in an Alternating Current (AC) circuit breaker because the AC current becomes zero at every half cycle. However, fault current in DC circuit breaker (DCCB) should be reduced by generating a high arc voltage at the breaker contact point. Large fire may occur if the DCCB does not take sufficient arc voltage and allows the continuous flow of the arc fault current with high temperature. A semiconductor circuit breaker with a power electronic device has many advantages. These advantages include quick breaking time, lack of arc generation, and lower noise than mechanical circuit breakers. However, a large load capacity cannot be applied because of large conduction loss. An extinguishing technology of DCCB with polymeric positive temperature coefficient (PPTC) device is proposed and evaluated through experiments in this study to take advantage of low conduction loss of mechanical circuit breaker and arcless breaking characteristic of semiconductor devices.

• 전기전자학회논문지
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• 제23권3호
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• pp.1003-1014
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• 2019

본 논문에서는 PV 시스템에서 사용되는 회로들을 쉽게 해석할 수 있도록 모델링하였다. 시뮬레이션 툴은 직관적인 전기회로 시뮬레이션이 가능한 PSPICE를 이용하였다. 모델링한 라이브러리를 이용하여 태양전지의 사용에서 간과하기 쉬운 온도와 공간방사의 영향에 대해서도 시뮬레이션을 수행하였다. 이와 더불어 태양광 발전 시스템의 완전한 동작을 위해 DC-DC 벅-부스트 컨버터와 MPPT 제어 시스템에 대한 완전한 동작 시스템에 대해 모델링하고 시뮬레이션을 수행하여 양호한 동작을 확인할 수 있었다. 또한 시뮬레이션의 동작을 입증하기 위하여 시뮬레이션에서와 동일한 조건의 실제 시스템을 구성하여 실험을 수행 하였으며 실험의 결과와 시뮬레이션의 결과가 동일한 동작을 수행하는 것을 확인할 수 있었다. 또한, 단상 3[kW] 계통연계형 태양광 전력변환기를 제안하였다.

• International Journal of Computer Science & Network Security
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• 제23권9호
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• pp.162-165
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• 2023

Power can be generated from either renewable or non-renewable sources. Renewable sources are liked to maintain a strategic distance from contamination emanation and rely on upon fossil energizes which is decreasing day by day. The proposed sun powered vitality transformation unit comprises of a sun oriented exhibit, Bidirectional DC-DC converter, single stage inverter and AC. The inverter changes over DC control from the PV board into AC power and offered it to the heap which is associated with the lattice. The photovoltaic sun powered vitality (PV) is the most direct approach to change over sunlight based radiation into power and depends on the photovoltaic impact. The most extreme power point following of the PV yield for all daylight conditions is a key to keep the yield control per unit cost low for fruitful PV applications. Framework associated PV frameworks dependably have an association with people in general power matrix by means of an appropriate inverter in light of the fact that a PV module conveys just dc power. This project presents the new design, Development and Performance Analysis of a Grid Connected PV Inverter. Demonstrate that the proposed framework can lessen the Energy Consumption radically from the power board and give a solid support to the Grid.

• 한국인터넷방송통신학회논문지
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• 제23권2호
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• pp.149-155
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• 2023

태양광 발전은 신재생에너지 중 가장 친숙한 발전시설로 약 10여 년 전부터 보급이 확대되기 시작해 현재 시점에서는 시스템의 유지보수관리에 대한 해결 및 기술에 관한 관심이 높아지고 있다. 특히 태양광 발전시스템의 이상 유무 및 부품 교체시기 그리고 시스템의 종합효율을 최대화할 수 있는 대책이 필요하다. 태양광발전시스템의 한 요소인 PV 인버터는 전력용 스위칭 소자에 의존하는 전력변환 시스템으로 DC/DC 컨버터 및 DC-AC 인버터 구성에 따른 직류(DC-Link) 커패시터가 사용된다. 이러한 직류 커패시터 역시 장시간 사용에 따른 노후 및 열화로 인해 PV 인버터의 발전량 감소와 전력손실 그리고 고조파(THD, 교류출력전류 종합왜형률) 증가로 신재생에너지 설비를 통한 계통 안전성(Safety)에 영향을 미치는 요인으로 분석할 수 있다. 따라서 본 논문에서는 태양광발전시스템에서 현재 운영 중인 직류 커패시터 용량 상태에 따른 PV 인버터 동작 특성을 고찰함과 동시에 신재생에너지 설비의 안전성 및 신뢰성을 확보할 수 있도록 연구내용을 제안하였다.