• Journal of Power Electronics
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• 제15권6호
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• pp.1609-1618
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• 2015

DC microgrids are considered as prospective systems because of their easy connection of distributed energy resources (DERs) and electric vehicles (EVs), reduction of conversion loss between dc output sources and loads, lack of reactive power issues, etc. These features make them very suitable for future industrial and commercial buildings' power systems. In addition, the bipolar-type dc system structure is more popular, because it provides two voltage levels for different power converters and loads. To keep voltage balanced in such a dc system, a bidirectional dual buck-boost voltage balancer with direct coupling is introduced based on P-cell and N-cell concepts. This results in greatly enhanced system reliability thanks to no shoot-through problems and lower switching losses with the help of power MOSFETs. In order to increase system efficiency and reliability, a novel burst-mode control strategy is proposed for the dual buck-boost voltage balancer. The basic operating principle, the current relations, and a small-signal model of the voltage balancer are analyzed under the burst-mode control scheme in detail. Finally, simulation experiments are performed and a laboratory unit with a 5kW unbalanced ability is constructed to verify the viability of the bidirectional dual buck-boost voltage balancer under the proposed burst-mode control scheme in low-voltage bipolar-type dc microgrids.

• 전기학회논문지P
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• 제67권3호
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• pp.119-124
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• 2018

Recently, LVDC distribution network and DC microgrid with many advantages are being built. However, this LVDC distribution is an IT grounded or ungrounded system, and it is difficult to detect a ground fault because the fault current is small. In this paper, we propose a signal injection method for unipolar LVDC distribution network to detect ground fault in ungrounded LVDC distribution, and various analyzes were performed for ground fault detection.

• 전력전자학회논문지
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• 제27권2호
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• pp.157-164
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• 2022

This study proposes an enhanced quadruple-Active-Bridge (QAB) converter that can solve power coupling problems. By adopting a multiple winding transformer, the equivalent circuit of a conventional QAB converter has power couplings between arbitrary output ports. This coupling is an unintended power relationship that complicates the regulation of output voltage of the multiple ports. The proposed converter can carry out power decoupling by changing the arrangement of the coupling inductor. Power transfer equations for the proposed converter and its operating principles are analyzed in detail. The power coupling caused by the transformer's leakage inductance is verified by using a proposed coupling factor that presents the relationship between inductance ratio and coupling power. In addition, the decoupling power control performance of the proposed converter is verified by simulation and a 3 kW prototype converter.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.782-785
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• 2011

최근 세계적으로 에너지원의 고갈, 전력 수요 증가, 기후 환경 변화에 대처하기 위해 신재생에너지원을 활용한 마이크로그리드 개발의 필요성이 점증하고 있다. 특히 태양광 발전은 댁내에 설치하기 용이한 가장 일반적인 신재생에너지원의 하나로써 각광받고 있다. 하지만 태양광은 기후 변화(일사량 및 일조량의 변화)에 따라 출력이 불안정하다는 단점으로 인해, 균일한 전력품질을 제공하기 위해 해결해야 할 기술적인 과제를 가지고 있다. 이 문제의 해결책으로써 에너지저장장치(ESS)이 고려되고 있지만, 이것도 용량이란 한계점을 가지고 있다. 이 문제를 해결하는 방법으로써 본 논문에서는 2가지 기후 요소인 일조량과 일사량에 따른 태양광 발전량을 추정하는 복합적인 방법을 제안한다. 이 연구 결과는 ESS의 정적 용량을 설계하는데 도움을 줄 수 있으며, 댁내 전력 IT 시스템에서 DC/AC 전력 스위칭의 적절한 타이밍을 제공하는데 도움을 줌으로써 전력품질의 균일성을 유지할 수 있도록 해줄 것으로 기대된다.

• 한국산업융합학회 논문집
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• 제23권6_2호
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• pp.989-998
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• 2020

Recently, demands for large-capacity electronic loads are increasing in various industries such as a reliability test for the performance of a DC power supply device or a dummy-load for improving the stability of an independent microgrid to be actively built in the future. The electronic load required in these various fields requires an operation such as a continuously variable resistance load while minimizing the switching harmonic component generated in the electric load current in order to reduce the influence of interference from the load peripheral device. Electronic loads require a system that minimizes switching current ripple for load control. Therefore, in this paper, we propose a three-level module converter structure to reduce the current ripple of an electronic load, and a multilevel interleaved power converter topology to reduce the current ripple. The validity of the proposed electronic load, 3-level 6 interleaver converter, was verified by simulation and experiment. In addition, the user's convenience was provided by applying the emotional command curve interface method.

• 한국정보전자통신기술학회논문지
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• 제13권6호
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• pp.590-596
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• 2020

상용전력망과 계통연계가 어려운 도서지역에서는 독립적인 마이크로그리드로 생산된 에너지를 효율적으로 관리할 수 있는 방법을 찾는 것은 매우 중요한 일이다. 본 논문에서는 태양광과 풍력의 하이브리드 모델을 적용한 소규모 마이크로그리드에서 생산된 전력을 전력계측기와 수집된 데이터의 응답속도 테스트를 거쳐 P2P전력거래를 위한 프로슈머관리시스템을 구현하였다. 마이크로그리드 프로슈머 관리시스템의 전력망은 Mesh구조로 이루어져 있으며 P2P전력거래는 3곳의 독립적으로 구축된 off-grid 사이트에서 전력계측기와 DC전력전송기를 이용하여 테스트하였고, 이때 전력계측기의 측정값은 전압(평균값) : 380V + 0.9V, 전류(평균값) : + 0.01A, 전력 : 1000W ( - 1W)로 오차 허용범위인 ±1%이내로 나타나 그 유의성을 확인하였다. 실시간으로 50개의 데이터를 동시 전송하여 메인화면 0.32초, 일 발전량 2.61초, 누적발전량 2.77초, 전력거래 0.11초 등의 응답속도가 나타나 서버의 안정화를 확인하였다. 따라서 본 시스템은 한국전력의 중계 없이 독립적인 망으로 활용될 수 있는 P2P 전력거래시스템으로서 그 타당성이 입증되었다.