• 전기학회논문지
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• 제64권2호
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• pp.228-231
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• 2015

In power system research fields, one of current key issues is the construction and commercialization of micro grid site which is called green island, carbon zero island, energy independent island, building micro grid, etc. and various affiliated technologies have been being vigorously developed to realize. In addition, various researches about electric vehicles (EVs) are in progress and it is expected to penetrate rapidly with the next a few years. Some new load models should be developed integrating with electric vehicle loads because the EVs' deployment could cause the change of load composition rate on power system planning and operations. EVs are also resources for micro grid as well as distributed generation and demand response so that various supply and demand side resources should be considered for micro grid researches. In this paper, the load composition rate of residential sectors is prospected considering the deployment of EVs and the resource configuration of micro grid is optimized based on net present cost. In the optimization, the load patten of case studies includes EV's charging characteristics and various cases are simulated comparing micro grid environment and normal condition. HOMER is used to compare various cases and economic effects.

• 한국산학기술학회논문지
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• 제20권10호
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• pp.18-25
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• 2019

최근, 도서지역의 신재생에너지전원 및 ESS의 도입이 확대되면서, 이산화탄소 배출의 저감을 위하여, 디젤발전기 대신 CVCF 인버터가 주 전원인 Micro-grid를 안정적으로 운용하는 방안들이 연구되고 있다. 그러나, CVCF 인버터 기반의 Micro-grid에서는 전체 부하보다 신재생에너지전원의 출력이 큰 경우에 에너지 Sinking(과도상태) 현상이 발생하게 된다. 이 때, CVCF 인버터용 배터리의 SOC 상태에 따라, 배터리 전압이 급격히 상승하여, 인버터의 과전압 보호동작에 의해 CVCF 인버터가 탈락되어 Micro-grid 전체 계통에 정전을 유발할 수 있다. 따라서, 본 논문에서는 CVCF 인버터를 기반으로 한 도서지역용 Micro-grid의 안정적인 운용을 위하여, 에너지 Sinking이 발생한 경우의 운용특성을 분석하고, CVCF 인버터가 에너지 Sinking 시에 탈락되는 것을 사전에 방지할 수 있는 Micro-grid의 과도상태 운용전략을 제안한다. 또한, CVCF 인버터, 태양광전원, 수용가부하로 구성된 30kW급 Micro-grid 시험장치를 구현하여, 실 계통에서의 에너지 Sinking에 의한 CVCF 인버터 기반 Micro-grid의 과도상태 시 운용특성을 제시한다. 한편, 30kW급 시험장치와 제안한 운용전략을 바탕으로 Micro-grid의 과도상태 운용특성을 분석한 결과, CVCF 인버터용 배터리의 전압과 SOC에 따라 인버터가 탈락하는 과도상태를 사전에 방지할 수 있어, 본 논문의 유용성을 확인하였다.

• 한국산학기술학회논문지
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• 제10권1호
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• pp.81-90
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• 2009

전력산업의 구조개편과 더불어 분산전원의 배전계통연계운용 및 전력품질이 전력회사의 배전사업자, 구역전기사업자, 전기공급 신뢰도와 밀접한 관계에 있는 산업용 수용가들에게 많은 관심을 불러일으키고 있다. 이러한 주변정세는 차세대의 배전계통이 다수의 Micro-grid들로 구성될 것이라고 하는 예상을 전문가들로부터 제기되기에 이르렀다. 그러나, 제안된 Micro-grid는 몇몇의 분산전원과 전력품질을 보상하는 기기, 그리고 통신제어설비와 부하들로 구성된다는 기본적인 내용에 지나지 않는다 따라서, 본 논문에서는 수용가에 고신뢰 고품질의 전력공급을 가능하게 하는 차세대 전력공급네트워크인 Micro-grid의 적정전압유지를 위한 자율분산협조 운용제어 알고리즘을 제안한다.

• 조명전기설비학회논문지
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• 제20권3호
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• pp.12-19
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• 2006

마이크로소스는 1[kW]${\sim}$수[MW] 사이의 전력을 공급하고, 기존의 대규모 발전설비보다 높은 신뢰도와 에너지 효율을 가지는 고품질의 전력을 공급할 수 있다. 본 논문에서는 마이크로소스의 스위칭레벨 모델을 개발하였으며, 다수의 마이크로소스가 전력시스템과 연계되어 마이크로그리드를 형성할 경우의 특성에 대하여 연구하였다. 마이크로소스는 인버터의 효율을 극대화 할 수 있도록 공간벡터 펄스폭변조(Space Vector PWM, SVPWM) 기법을 채용하였으며, 마이크로소스의 제어시스템 파라미터 특성 및 마이크로소스 상호작용에 관하여 연구하였다. 마이크로소스는 PSCAD/EMTDC를 이용하여 구현하였으며 이를 이용해 마이크로그리드를 구성하여 시뮬레이션하였다. 사례 연구를 통하여 제안된 모델의 효용성을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.533-534
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• 2006

Micro-source units having power ratings in thousands of watts can provide power quality with higher reliability and efficiency than the conventional large scale units. This paper develops switching level model of micro-source and studies the characteristics of the micro-grid consisting of multiple micro-sources and interfaced with electric power system. The developed model adopts the space vector PWM to fully utilize the capacity of inverter. The interaction of the grid connected micro-sources and the characteristics of the control system parameters are investigated. Micro-sources and micro-grid are implemented using PSCAD/EMTDC. Simulation results show that the proposed model is efficient for studying micro-grid system.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.1072-1079
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• 2014

This paper introduces a coordinated droop control for the stand-alone DC micro-grid, which is composed of photo-voltaic generator, wind power generator, engine generator, and battery storage with SOC (state of charge) management system. The operation of stand-alone DC micro-grid with the coordinated droop control was analyzed with computer simulation. Based on simulation results, a hardware simulator was built and tested to analyze the performance of proposed system. The developed simulation model and hardware simulator can be utilized to design the actual stand-alone DC micro-grid and to analyze its performance. The coordinated droop control can improve the reliability and efficiency of the stand-alone DC micro-grid.

• 전기학회논문지
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• 제58권11호
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• pp.2175-2184
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• 2009

This paper describes operational analysis results of the DC micro-grid using detailed model of distributed generation. Detailed model of wind power generation, photo-voltaic generation, fuel-cell generation was implemented with the user-defined model of PSCAD/EMTDC software that is coded with C-language. The operation analysis was carried out using PSCAD/EMTDC software, in which the power circuit is implemented by built-in model and the controller is modelled by user-defined model that is also coded with C-language. Various simulation results confirm that the DC micro-grid can operate without any problem in both the interconnected mode and the islanded mode. The operation analysis result confirms that the DC micro-grid make it feasible to provide power to the load stably. And it can be utilize to develop the actual system design and building.

• 전기학회논문지P
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• 제67권4호
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• pp.175-182
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• 2018

In recent years, micro-grid has been widely focused on the fields of renewal energy systems. This paper proposes a novel robust power converter control against arbitrary electric load changes for islanded micro-grid topology. First, we provide a state-space representation of our micro-grid model including power converter and electric load circuit. And then a state feedback control method is applied to construct a nominal control framework. Next, we propose a robust adaptive control law to enhance a control performance against unexpected load perturbation. In addition, we analytically investigate a passivity property for the micro-grid model and carry out computer simulation to demonstrate superiority and reliability of the proposed control methodology.

• 전기학회논문지
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• 제63권2호
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• pp.205-210
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• 2014

The micro grid considered in this paper consists of a diesel generator, a photovoltaic array, a wind turbine, a fuel cell, and a energy storage system. This paper explains and simulates the micro grid components in terms of accuracy and efficiency of having a system model based on the costs of fuel as well as operation and maintenance. For operational efficiency, the objective function in a diesel generator consists of the fuel cost function similar to the cost functions used for the conventional fossil-fuel generating plants. The wind turbine generator is modeled by the characteristics of variable output. The optimization is aimed at minimizing the cost function of the system while constraining it to meet the customer demand and safety of micro grid. The operating cost in fuel-cell system includes the fuel costs and the efficiency for fuel to generate electric power. To develop the overall system model gives a possibility to minimize of the total cost of micro grid. The application of optimal operation can save the interruption costs as well as the operating costs, and improve reliability index in micro grid.

• 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.