• Title/Summary/Keyword: Distributed Generators

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A Distributed Control Method based on Voltage Sensitivity Matrix in DC Microgrids for Improvement of Power Sharing Accuracy and Voltage Regulation Performance (직류 마이크로그리드의 전력 공유 정확도 및 전압 제어 성능 향상을 위한 전압 민감도 행렬 기반의 분산 제어 방법)

  • Lee, Gi-Young;Ko, Byoung-Sun;Lee, Jae-Suk;Kim, Rae-Young
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.5
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    • pp.345-351
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    • 2018
  • A distributed control method is proposed to improve the power sharing performance of bidirectional distributed generators and the voltage regulation performance of a DC bus in a DC microgrid. Voltage sensitivity analysis based on power flow analysis is conducted to analyze the structural characteristics of a DC microgrid. A distributed control method using a voltage sensitivity matrix is proposed on the basis of this analysis. The proposed method uses information received through the communication system and performs the droop gain variation method and voltage shift method without additional PI controllers. This approach achieves improved power sharing and voltage regulation performance without output transient states. The proposed method is implemented through a laboratory-scaled experimental system consisting of two bidirectional distributed generators, namely, a load and a non-dispatchable distributed generator in a four-bus ring-type model. The experimental results show improved power sharing accuracy and voltage regulation performance.

Study on the Voltage Stabilization Technology Using Photovoltaic Generation Simulator in Three-Level Bipolar Type DC Microgrid

  • Kim, Taehoon;Kim, Juyong;Cho, Jintae;Jung, Jae-Seung
    • Journal of Electrical Engineering and Technology
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    • v.13 no.3
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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.

A Study on Simplified Robust Optimal Operation of Microgrids Considering the Uncertainty of Renewable Generation and Loads (신재생에너지와 부하의 불확실성을 고려한 마이크로그리드의 단순화된 강인최적운영 기법에 관한 연구)

  • Lee, Byung Ha
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.3
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    • pp.513-521
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    • 2017
  • Robust optimal operation of a microgrid is required since the increase of the penetration level of renewable generators in the microgrid raises uncertainty due to their intermittent power output. In this paper, an application of probabilistic optimization method to economical operation of a microgrid is studied. To simplify the treatment of the uncertainties of renewable generations and load, the new 'band of virtual equivalent load variation' is introduced considering their uncertainties. A simplified robust optimization methodology to generate the scenarios within the band of virtual equivalent load variation and to obtain the optimal solution for the worst scenario is presented based on Monte Carlo method. The microgrid to be studied here is composed of distributed generation system(DGs), battery systems and loads. The distributed generation systems include combined heat and power(CHP) and small generators such as diesel generators and the renewable energy generators such as photovoltaic(PV) systems and wind power systems. The modeling of the objective function for considering interruption cost by the penalty function is presented. Through the case study for a microgrid with uncertainties, the validity of proposed robust optimization methodology is evaluated.

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.

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.

Review of Multifunctional Inverter Topologies and Control Schemes Used in Distributed Generation Systems

  • Teke, Ahmet;Latran, Mohammad Barghi
    • Journal of Power Electronics
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    • v.14 no.2
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    • pp.324-340
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    • 2014
  • Recent developments in power electronics technology have spurred interest in the use of renewable energy sources as distributed generation (DG) generators. The key component in DG generators is a grid-connected inverter that serves as an effective interface between the renewable energy source and the utility grid. The multifunctional inverter (MFI) is special type of grid-connected inverter that has elicited much attention in recent years. MFIs not only generate power for DGs but also provide increased functionality through improved power quality and voltage and reactive power support; thus, the capability of the auxiliary service for the utility grid is improved. This paper presents a comprehensive review of the various MFI system configurations for single-phase (two-wire) and three-phase (three- or four-wire) systems and control strategies for the compensation of different power quality problems. The advances in practical applications and recent research on MFIs are presented through a review of nearly 200 papers.

A Study on the SVR Optimal Placement in Distribution System with Distributed Generators (분산전원이 연계된 배전 계통의 SVR 최적 설치위치 선정)

  • Lee, Hyun-Ok;Huh, Jae-Sun;Kim, Chan-Hyeok;Kim, Jae-Chul
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.11
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    • pp.69-75
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    • 2013
  • This paper proposes a new algorithm for the optimal placement of a step voltage regulator(SVR) in distribution system with Distributed Generators(DG) using a Particle Swarm Optimization(PSO). The objective function of this algorithm is to find optimal placement for minimum loss while maintaining each node voltage fluctuations within upper and lower limits. In the objective function of proposed algorithm, the deviations to reference voltage and the distribution loss are considered. To verify effectiveness of the proposed method, simulation is implemented using MATLAB.

Feeder Loop Line Control for the Voltage Stabilization of Distribution Network with Distributed Generators

  • Jeong, Bong-Sang;Chun, Yeong-Han
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.1-5
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    • 2014
  • When renewable sources are connected to the distribution network in the form of a distributed generators(DGs), the effect of intermittent output appears as voltage fluctuation. The surplus power at the consumer ends results in the reverse power flow to the distribution network. This reverse power flow causes several problems to the distribution network such as overvoltage. Application of the reactive power control equipment and power flow control by means of BTB inverter have been suggested as the general solutions to overcome the overvoltage, but they are not economically feasible since they require high cost devices. Herein, we suggest the feeder loop line switch control method to solve the problem.

A New Islanding Detection Method using Phase-Locked Loop for Inverter-Interfaced Distributed Generators

  • Chung, Il-Yop;Moon, Seung-Il
    • Journal of Electrical Engineering and Technology
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    • v.2 no.2
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    • pp.165-171
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    • 2007
  • This paper proposes a new islanding detection method for inverter-interfaced distributed generators (DG). To detect islanding conditions, this paper calculates the phase angle variation of the system voltage by using the phase-locked loop (PLL) in the inverter controllers. Because almost all inverter systems are equipped with the PLL, the implementation of this method is fairly simple and economical for inverter-interfaced DGs. The detection time can also be shortened by reducing communication delay between the relays and the DGs. The proposed method is based on the fact that islanding conditions result in the frequency and voltage variation of the islanded area. The variation depends on the amount of power mismatch. To improve the accuracy of the detection algorithm, this paper injects small low-frequency reactive power mismatch to the output power of DG.

A Study on Probabilistic Reliability Evaluation of Power System Considering Wind Turbine Generators (풍력발전기를 고려한 전력계통의 확률론적인 신뢰도 평가에 관한 연구)

  • Park, Jeong-Je;Wu, Liang;Choi, Jae-Seok;Moon, Seung-Il
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.9
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    • pp.1491-1499
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    • 2008
  • This paper presents a study on reliability evaluation of a power system considering wind turbine generators (WTG) with multi-state. Renewable energy resources such as wind, wave, solar, micro hydro, tidal and biomass etc. are becoming importance stage by stage because of considering effect of the environment. Wind energy is one of the most successful sources of renewable energy for the production of electrical energy. But, reliability evaluation of generating system with wind energy resources is a complex process. While the wind turbine generators can not modelled as two-state model as like as conventional generators, they should be modelled as multi-state model due to wind speed random variation. The methodology for obtaining reliability evaluation index of wind turbine generators is different from it of the conventional generators. A method for making outage capacity probability table of WTG for reliability is proposed in this paper. The detail process is presented using case study of simple system.