• Title, Summary, Keyword: Microgrid

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Design and Dynamic Performance Analysis of a Stand-alone Microgrid - A Case Study of Gasa Island, South Korea

  • Husein, Munir;Hau, Vu Ba;Chung, Il-Yop;Chae, Woo-Kyu;Lee, Hak-Ju
    • Journal of Electrical Engineering and Technology
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    • v.12 no.5
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    • pp.1777-1788
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    • 2017
  • This paper presents the design and dynamic analysis of a stand-alone microgrid with high penetration of renewable energy. The optimal sizing of various components in the microgrid is obtained considering two objectives: minimization of levelized cost of energy (LCOE) and maximization of renewable energy penetration. Integrating high renewable energy in stand-alone microgrid requires special considerations to assure stable dynamic performance, we therefore develop voltage and frequency control method by coordinating Battery Energy Storage System (BESS) and diesel generators. This approach was applied to the design and development of Gasa Island microgrid in South Korea. The microgrid consists of photovoltaic panels, wind turbines, lithium-ion batteries and diesel generators. The dynamic performance of the microgrid during different load and weather variations is verified by simulation studies. Results from the real microgrid were then presented and discussed. Our approach to the design and control of microgrid will offer some lessons in future microgrid design.

A Microgrid Operation based on a Power Market Environment

  • Kim, Hak-Man;Kinoshita, Tetsuo
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.23 no.11
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    • pp.61-68
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    • 2009
  • A Microgrid is a private small-scale power system composed of distributed energy resources (DERs), storage devices and loads. And it is expected that the Microgrid will come into wide use in the near future. For this, the establishment of the Microgrid operation methodology is a very important problem. Especially, the Microgrid is greatly different from existing private small-scale power systems because of the multiple participants. Therefore, the Microgrid operation considered various requirements according to multiple participants is more complicated than the operation of existing private small-scale power systems. In this paper, Microgrid operation methodology based on a market environment is suggested. Through case studies, the effectiveness of the suggested methodology is verified.

Supervisory Protection System of Microgird Interconnected to Low Voltage Grids (저압계통 연계형 마이크로그리드의 보호감시 시스템)

  • Jyung, Tae-Young;Baek, Young-Sik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.1
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    • pp.36-42
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    • 2011
  • This paper mainly proposes the protective coordination scheme of the microgrid system. The microgrid protection is identical to the conventional protection system separating the normal part and contingency part to reduce damage when the contingency occur at power cables, facilities. But they are different in the protection type. The conventional protection system only considers unidirectional current. However the microgrid protection should be considered not only unidirectional current but also backfeed current because various microsources and loads are installed in the microgrid system. In case the contingency occurs in microsource, when microgrid is interconnected to grid, the protection system should be configured to not separate microgrid from grid before the microsource is isolated to microgrid. And in case of fault occur in power system, the microsources should not isolated to microgrid before the static switch at PCC is tripped to separate from power system. Considering these characteristic of microgird, this paper proposes the protective coordination scheme of microgrid and implemented the on-line real time monitoring system. Especially in case the microgrid is connected to low voltage distribution system with 220/380V voltage level, the proposed protection method with power IT technology can solve the problems when the existing protective devices only applied to the microgrid system.

Study on the Dynamic Synchronizing Control of An Islanded Microgrid (독립운전 마이크로그리드의 능동형 동기 투입 제어에 관한 연구)

  • Cho, Chang-Hee;Jeon, Jin-Hong;Kim, Jong-Yul;Kwon, Soon-Man;Kim, Sung-Shin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.6
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    • pp.1112-1121
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    • 2011
  • A microgrid is an aggregation of multiple distributed generators (DGs) such as renewable energy sources, conventional generators, and energy storage systems that provide both electric power and thermal energy. Generally, a microgrid operates in parallel with the main grid. However, there are cases in which a microgrid operates in islanded mode, or in a disconnected state. Islanded microgrid can change its operational mode to grid-connected operation by reconnection to the grid, which is referred to as synchronization. Generally, a single machine simply synchronizes with the grid using a synchronizer. However, the synchronization of microgrid that operate with multiple DGs and loads cannot be controlled by a traditional synchronizer, but needs to control multiple generators and energy storage systems in a coordinated way. This is not a simple job, considering that a microgrid consists of various power electronics-based DGs as well as alternator-based generators that produce power together. This paper introduces the results of research examining an active synchronizing control system that consists of the network-based coordinated control of multiple DGs. Consequently, it provides the microgrid with a deterministic and reliable reconnection to the grid. The proposed method is verified by using the test cases with the experimental setup of a microgrid pilot plant.

Optimal Microgrid Operation Considering Fuel Cell and Combined Heat and Power Generation (연료전지와 열병합 발전을 고려한 마이크로그리드의 최적 운용)

  • Lee, Ji-Hye;Lee, Byung Ha
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.5
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    • pp.596-603
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    • 2013
  • The increase of distributed power generation is closely related to interest in microgird including renuable energy sources such as photovoltaic (PV) systems and fuel cell. By the growing interest of microgrid all over the world, many studies on microgrid operation are being carried out. Especially operation technique which is core technology of microgrid is to supply heat and electricity energy simultaneously. Optimal microgrid scheduling can be established by considering CHP (Combined Heat and Power) generation because it produce both heat and electricity energy and its total efficiency is high. For this reason, CHP generation in microgrid is being spotlighted. In the near future, wide application of microgrid is also anticipated. This paper proposes a mathematical model for optimal operation of microgrid considering both heat and power. To validate the proposed model, the case study is performed and its results are analyzed.

A Novel Frequency Tracker for Islanded-Mode Operation in Microgrid (마이크로그리드 독립운전모드를 위한 주파수 추종에 관한 연구)

  • Jeon, Jin-Hong;Kim, Kyoung-Hoon;Hwang, Chul-Sang;Kim, Jang-Mok
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.7
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    • pp.1331-1338
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    • 2011
  • This paper proposes a method for frequency control of islanded microgrid with battery energy storage system. For frequency control of islanded microgrid, battery energy storage system uses a phase locked loop algorithm with positive sequence components for a fast frequency estimation. Microgrid is a power system with small inertia because it has small capacity generators and inverter systems for renewable energy. So, Islanded microgrid's frequency varies fast and large as small generation and load changes. To reduce frequency variation of islanded microgrid, it needs a device with fast frequency response. For fast frequency response, a fast frequency tracking is important. To show the validation of proposed fast frequency tracking algorithm, battery energy storage system with proposed algorithm is tested in microgrid pilot plant.

Linear Programming based Optimal Scheduling for Grid-connected Microgrid (선형계획법에 의한 계통연계형 마이크로그리드의 최적 운용에 관한 연구)

  • Park, Jae-Sae
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.8
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    • pp.1622-1626
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    • 2011
  • Recently, interests on microgrids have been growing as clean power systems. Microgrids include small scaled distributed generation such as wind and solar power as well as diesel generators as main power sources. To operate a microgrid effectively, optimal scheduling for the microgrid is important. Especially, in the grid-connected mode, power trades between the microgrid and the power grid should be considered in optimal scheduling. In this paper, mathematic models for optimal operation of a microgrid were established based on the linear programming. In particular, the shiftable load was considered in the models to optimize it in microgrid operation. To show feasibility of the proposed models, they were applied to optimal microgrid operation and the results were discussed.

A Study on Simulation of Dynamic Characteristics in Prototype Microgrid (Prototype Microgrid의 동특성 모의에 관한 연구)

  • Choi, Eun-Sik;Choi, Heung-Kwan;Jeon, Jin-Hong;Ahn, Jong-Bo
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.12
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    • pp.2157-2164
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    • 2010
  • Microgrid is generally defined as cluster of small distributed generators, energy storages and loads. Through monitoring and coordinated control, microgrid can provide various benefits such as reduction of energy cost, peak shaving and power quality improvement. In design stage of microgrid, system dynamic simulation is necessary for optimizing of sizing and siting of DER(distributed energy resources). As number of the system components increases, simulation time will be longer. This problem can restrict optimal design. So we used simplified modeling on energy sources and average switching model on power converters to reduce simulation time. The effectiveness of this method is verified by applying to prototype microgrid system, which is consist of photovoltaic, wind power, diesel engine generators, battery energy storage system and loads installed in laboratory. Simulation by Matlab/Simulink and measurements on prototype microgrid show that the proposed method can reduce simulation time not sacrificing dynamic characteristics.

Studies of Switching Transients and Power Quality Improvement in Microgrid PCC Switch (마이크로그리드 계통연계 스위치의 스위칭 과도상태 해석과 전력품질 향상을 위한 연구)

  • Jyung, Tae-Young;Baek, Young-Sik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.11
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    • pp.2142-2148
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    • 2009
  • A microgrid is defined as two or more distributed generation or storage assets configured in a networks and capable of operation in parallel or independently form a larger electric gird, while providing continuous power to one or more end users. And when microgrid are separated from grid oprating protection devices by faults of the grid side, microsources should charge electrical power needs of loads in microgrid and operate maintaining power quality. The magnitude of the switching transients will vary based on voltage phase difference between microgrid and grid, when the microgrid is resynchronized to grid. In this paper, when microgrid is resynchronized to grid, we analyzed the existing problems for reducing switching transients of SS(Static Switch).

Power Sharing Method for a Grid connected Microgrid with Multiple Distributed Generators

  • Nguyen, Khanh-Loc;Won, Dong-Jun;Ahn, Seon-Ju;Chung, Il-Yop
    • Journal of Electrical Engineering and Technology
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    • v.7 no.4
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    • pp.459-467
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    • 2012
  • In this paper, a grid connected microgrid with multiple inverter-based distributed generators (DGs) is considered. DG in FFC mode regulates the microgrid as a controllable load from the utility point of view as long as its output is within the capacity limit. The transition mode causes a change in frequency of microgrid due to the loss of power transferred between main grid and microgrid. Frequency deviation from the nominal value can exceed the limit if the loss of power is large enough. This paper presents a coordinated control method for inverter-based DGs so that the microgrid is always regulated as a constant load from the utility viewpoint during grid connected mode, and the frequency deviation in the transition mode is minimized. DGs can share the load by changing their control modes between UPC and FFC and stabilize microgrid during transition.