• 전력전자학회논문지
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• 제25권6호
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• pp.433-441
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• 2020

This study proposes a constant power tracking algorithm to compensate for the intermittent characteristics of Photovoltaic connected to a DC micro grid. A PV-ESS integrated module in which distributed ESS is additionally connected is utilized for the proposed algorithm. PV performs P&O MPPT control at all times. To supplement the intermittent characteristics of PV, the proposed constant power tracking algorithm maintains constant power by operating the distributed ESS of the PV-ESS integrated module in accordance with the output state of the PV. By performing PSIM simulation and an experiment, this study verifies the performance of the integrated module of PV-ESS for DC micro grids applying the constant power tracking algorithm.

• 한국전자통신학회논문지
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• 제11권4호
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• pp.395-402
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• 2016

DC ${\mu}$-Grid 기반의 충/방전 시스템에서 배터리의 동작 변환 시, 망 전압의 fluctuation이 발생하게 되며, 과다한 fluctuation은 충/방전 시스템의 손상 및 고장을 일으킬 수 있다. 따라서 본 논문에서는 DC ${\mu}$-Grid 기반의 충/방전 시스템에서 fluctuation 완화용 커패시터의 적용 및 설계 포인트에 대하여 연구하였다. 컴퓨터 시뮬레이션 결과, 3개의 충전 배터리 set와 5개의 방전 배터리 set의 조건으로 운영되는 DC ${\mu}$-Grid 기반 충/방전 시스템에서 600V/35mF의 초기 값을 갖는 fluctuation 완화용 커패시터를 적용하였을 때 충/방전에 의한 fluctuation을 약 66.3% 감소시킬 수 있었으며, 추가적으로 초기 망 전압 안정화 시 발생하는 fluctuation 또한 약 73% 감소시킬 수 있었다.

• 전기학회논문지
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• 제65권11호
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• pp.1800-1805
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• 2016

The micro-grid designed as bipolar ${\pm}750V$ low-voltage DC power distribution system demonstrated by KEPRI, demands interconnection of a number of small decentralized power source including variable renewable generator. Therefore, variable researches for the influence of interconnection with the bipolar typed DC grid and these variable power sources are required for superior quality of power distribution. Renewable power generation simulators for the bipolar ${\pm}750V$ low-voltage DC power distribution system are necessary for such researches. In this paper, we carry out a research on the photovoltaic simulator that be actually able to interconnect with a bipolar ${\pm}750V$ low-voltage micro-grid. Simulator for this research is not only able to simulate photovoltaic generation according to weather informations and PV modules characteristics, but also contribute to stabilization of bipolar ${\pm}750V$ low-voltage of the system. Therefore, the simulator was designed to develop a system that can situationally respond to variable control algorithms such as the MPPT control, droop control, EMS power control, etc.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.151-153
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• 2008

DC 마이크로그리드는 태양광과 연료전지와 같은 DC 출력의 분산전원, 풍력이나 가스엔진과 같은 AC 출력의 분산전원이 이차전지나 수퍼커패시터와 같은 에너지 저장장치와 직류로 결합되어 있는 구조로, 최근 급증하고 있는 디지털부하에 고품질, 고신뢰도 전력을 공급하는 새로운 직류배전시스템이다. 본 연구에서는, 먼저 DC 마이크로그리드의 한 시스템 구성을 가정하고, 이들 분산전원과 에너지저장의 컨버터를 제어하는 기법을 제안하였다. 또한 PSCAD/EMTDC 소프트웨어를 사용하여 각각의 분산전원의 세부모델을 구현하고, 이를 DC 마이크로그리드로 구성한 후 분산전원의 생산량, 에너지저장의 저장량, 부하의 소모량, 연계 계통의 공급량을 타당한 시나리오로 가정하여 전체 마이크로그리드의 동작을 분석하였다.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권2호
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• pp.225-231
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• 2013

Low voltage ride through capability augmentation of a hybrid micro-grid system is presented in this paper which reflects enhanced reliability in the system. The control scheme involves parallel connected multiple ac-dc bidirectional converters. When the micro-grid system is subjected to a severe voltage dip by any transient fault single power converter may not be able to provide necessary reactive power to overcome the severe voltage dip. This paper discusses the control strategy of additional power converter connected in parallel with main converter to support extra reactive power to withstand the severe voltage dip. During transient fault, when the terminal voltage crosses 90% of its pre-fault value, additional converter comes into operation. With the help of additional power converter, the micro-grid system withstands the severe voltage fulfilling the grid code requirements. This multiple converter scheme provides the micro-grid system the capability of low voltage ride through which makes the system more reliable and stable.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1123-1130
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• 2018

Voltage stabilization is an essential component of power quality in low voltage DC (LVDC) microgrid. The microgrid demands the interconnection of a number of small distributed power resources, including variable renewable generators. Therefore, the voltage can be maintained in a stable manner through the control of these distributed generators. In this study, we did research on the new advanced operating method for a photovoltaic (PV) simulator in order to achieve interconnection to a bipolar LVDC microgrid. The validity of this voltage stabilization method, using the distributed generators, is experimentally verified. The test LVDC microgrid is configured by connecting the developed PV simulator and DC load, DC line, and AC/DC rectifier for connecting the main AC grid. The new advanced control method is applied to the developed PV simulator for the bipolar LVDC grid in order to stabilize the gird voltage. Using simulation results, the stabilization of the grid voltage by PV simulator using the proposed control method is confirmed the through the simulation results in various operation scenarios.

• 한국전자통신학회논문지
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• 제10권12호
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• pp.1337-1344
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• 2015

Li-ion 배터리를 생산하는데 있어서 충/방전을 통한 formation 과정이 필요하다. 이 과정에서 방전기의 부하 저항을 통해 방전하게 되는데 이때 에너지 손실이 발생한다. 따라서 본 논문에서는 DC ${\mu}-Grid$ 기반의 충/방전 시스템에서 배터리를 효율적으로 운영하는 방안에 대해 연구하였다. 컴퓨터 시뮬레이션 결과, DC ${\mu}-Grid$ 기반의 충/방전 시스템에서 충전 배터리 set 3개 기준 대비 방전 배터리 set의 수가 133%를 초과하게 되면 망 전압이 안정화되는 과정에서 발생하는 전압 fluctuation 폭을 초과하기 때문에 시스템에 치명적인 손상을 야기한다. 따라서 충전 배터리 set 3개 기준 대비 방전 배터리 set의 수를 133%까지 운영할 수 있으며 획기적인 에너지 절감 효과를 확인할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.137-139
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• 2003

Micro-Sources arc emerging as a providing environmentally friendly and reliable and effective solution. Micro-Source converter DC voltage of prime mover to AC voltage using voltage source inverter for interjecting with AC grid system. This paper studies optimal series inductance size for interjecting with AC grid system.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.839-847
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• 2016

Energy recovery battery testing systems (ERBTS) have been widely used in battery manufactures. All the ERBTS are connected in parallel which forms a special and complicated micro-grid system, which has the shortcomings of low energy recovery efficiency, complex grid-connected control algorithms issues for islanded detection, and complicated power circuit topology issues. To solve those shortcomings, a DC micro-grid system is proposed, the released testing energy has the priority to be reutilized between various testing system within the local grid, Compared to conventional scheme, the proposed system has the merits of a simplified power circuit topology, no needs for synchronous control, and much higher testing efficiency. The testing energy can be cycle-used inside the local micro-grid. The additional energy can be recovered to AC-grid. Numerous experimental comparison results between conventional and proposed scheme are provided to demonstrate the validity and effectiveness of the proposed technique.

• 전기학회논문지
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• 제62권6호
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• pp.737-743
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• 2013

This paper describes the overvoltage through lightning surge analysis on underground system in DC combined distribution systems. It is considered that operating micro grid including distributed generation with smart grid can make possibility of composing new distribution system different from existing one. However, there are many papers about low voltage DC distribution in grids or buildings but not many about replacement or distributing 22.9kV AC distribution system to DC system. Among many research need for DC system development, overvoltage is studied in this paper. Overvoltage is simulated on DC cable when lightning strikes to overhead grounding wire which is installed at the nearest location from power cable section. Analysis as well as modeling is performed in EMTP/ATPDraw. It is evaluated that analysis results can be used to design of DC underground distribution power cable system.