• Title/Summary/Keyword: Microgrid control

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Control Algorithm of Hybrid System for Feeder Flow Mode Operation in Microgrid (마이크로그리드에서 하이브리드 시스템의 Feeder Flow Mode 운영을 위한 제어 알고리즘)

  • Moon, Dae-Seong;Seo, Jae-Jin;Kim, Yun-Seong;Won, Dong-Jun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.1
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    • pp.1-7
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    • 2011
  • Active power control scheme for distributed generation in microgrid consists of feeder flow control and unit power control. Feeder flow control is more useful than the unit power control for demand-side management, because microgrid can be treated as a dispatchable load at the point of common coupling(PCC). This paper presents detailed descriptions of the feeder flow control scheme for the hybrid system in microgrid. It is divided into three parts, namely, the setting of feeder flow reference range for stable hybrid system operation, feeder flow control algorithm depending on load change in microgrid and hysteresis control. Simulation results using the PSCAD/EMTDC are presented to validate the inverter control method for a feeder flow control mode. As a result, the feeder flow control algorithm for the hybrid system in microgrid is efficient for supplying continuously active power to customers without interruption.

The Coordination Control of DC Microgrid on the Whole Operation Range (직류형 마이크로그리드의 전운전영역을 고려한 협조제어)

  • Choi, Daehee;Zhu, Shou-Zhen;Min, Yong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.6
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    • pp.864-871
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    • 2015
  • Recently, one of the main research on the power distribution system is the microgrid. The microgrid is a combination of power sources and loads, which is controllable and has separable connection. The main objective of microgrid is the deployment of the renewable clean energy and the enhancement of load-side reliability. The modern power sources and loads have DC I/O interfaces, which is the major advantage of DC microgrid compared to the conventional AC grid. The components in the microgrid have diverse features, so there is need of proper coordination control. For achieving economic feature, the active power of renewable energy resources is regarded as major control parameter and the whole operation modes of DC microgrid are defined, and the proper operations of each component are described. From the inherent characteristics of DC, there are two control variables: voltage and active power. Through analysis of operation modes, it is possible to determine exact control objectives and optimized voltage & power control strategy in each mode. Because of consideration of whole operation modes, regardless of the number and capacity of components, this coordination control method can be used without modification. This paper defines operation mode of DC microgrid with several DC sources and suggests economic and efficient coordinated control methods. Simulation with PSCAD proves effectiveness.

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.

Frequency Control of Battery Energy Storage System with a Deadband and Restoration Control in Microgrid (마이크로그리드에서의 데드 밴드와 회복 제어를 적용한 배터리 에너지저장시스템 주파수 제어)

  • Lee, Hak-Ju;Choi, Jin-Young;Choi, Jong-Chan;Won, Dong-Jun;Chae, Woo-Kyu;Park, Jung-Sung
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.11
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    • pp.1584-1589
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    • 2012
  • The grid-interconnected microgrid can be able to operate with and without the utility microgrid to supply electricity. when the microgrid operates in grid-connected mode, the frequency of the microgrid synchronizes with the system frequency. In this case, the frequency of the microgrid has small variation which is able to change the output of distributed generation with a droop controller. Thus, the small variation of frequency can make the distributed generation generate unnecessary electricity consistently. In this paper, we propose a frequency droop control with a dead band so as to prevent the distributed generations from generating unnecessary output while in grid-interconnected mode. In addition, a distributed generation can have a restoration control to restore the frequency changed by a droop control as a rated frequency. Also, we state the problem of restoration control with a dead band, and propose its solution when the microgrid operates in stand alone mode. We simulate the proposed droop control using PSCAD/EMTDC to verify the validity of the control.

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.

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.

Research on the Power Sharing Control and Stability of VSGs

  • Xie, Dong;Zang, Da-Jin;Gao, Peng;Wang, Jun-Jia
    • Journal of Power Electronics
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    • v.17 no.2
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    • pp.542-550
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    • 2017
  • Aiming at the deficiencies of power sharing control performances when a traditional droop control is adopted for microgrid inverters, this paper proposes a microgrid inverter power sharing control strategy based on a virtual synchronous generator. This control method simulates the electromechanical transient characteristics of a synchronous generator in a power system by an ontology algorithm and the control laws of a synchronous generator by control over the speed governor and excitation regulator. As a result, that the microgrid system is able to effectively retain the stability of the voltage and frequency, and the power sharing precision of the microgrid inverter is improved. Based on an analysis of stability of a microgrid system controlled by a virtual synchronous generator, design thoughts are provided for further improvement of the power sharing precision of inverters. The simulation results shows that when the virtual synchronous generator based control strategy was adopted, the power sharing performances of microgrid inverters are improved more obviously than those using the droop control strategy.

Frequency Control Method of Grid Interconnected Microgrid Operating in Stand Alone Mode (계통연계형 마이크로그리드의 독립운전시 주파수 제어에 관한 연구)

  • Chae, Woo-Kyu;Lee, Hak-Ju;Park, Jung-Sung;Cho, Jin-Tae;Won, Dong-June
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.8
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    • pp.1099-1106
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    • 2012
  • Microgrid is a new electrical energy system that composed of various generators, renewable energy, batteries and loads located near the electrical customers. When Microgrid is interconnected with large power system, Microgrid don't need to control the frequency. But in case of the outage or faults of power system, Microgrid should control the frequency to prevent the shutdown of Microgrid. This paper presents the frequency control methods using the droop function, being used by synchronous generators and EMS(Energy Management System). Using droop function, two battery systems could share the load based on locally measured signals without any communications between batteries. Also, we suggest that EMS should control the controllable distributed generators as P/Q control modes except batteries to overcome the weakness of droop function. Finally we suggest the two batteries systems to prolong the battery's life time considering the economical view. The validation of proposed methods is tested using PSCAD/EMTDC simulations and field test sites at the same time.

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.

Control Strategy for Accurate Reactive Power Sharing in Islanded Microgrids

  • Pham, Xuan Hoa Thi;Le, Toi Thanh
    • Journal of Power Electronics
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    • v.19 no.4
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    • pp.1020-1033
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    • 2019
  • This paper presents a control strategy to enhance the accuracy of reactive power sharing between paralleled three-phase inverters in an islanded microgrid. In this study, the mismatch of power sharing when the line impedances have significant differences between inverters connected to a microgrid has been solved, the accuracy of the reactive power sharing in an islanded microgrid is increased, the voltage droop slope is tuned to compensate for the mismatch of voltage drops across the line impedances by using an enhanced droop controller. The proposed method ensures accurate power sharing even if the microgrid has local loads at the output of the inverters. The control model has been simulated by MATLAB/Simulink with two or three inverters connected in parallel. Simulation results demonstrate the accuracy of the implemented control method. Furthermore, in order to validate the theoretical analysis and simulation results, an experimental setup was built in the laboratory. Results obtained from the experimental setup verify the effectiveness of the proposed method.