• Title/Summary/Keyword: Grid connected

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Development of Low-voltage Seamless Transfer Microgrid on Grid-connected Type Islands by Autonomous Operation (자율운전에 의한 계통연계형 도서의 저압 무순단 마이크로그리드 구축)

  • Kim, Jeong Hun;Kwon, Jung-Min;Yun, Sang-Yun
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.66 no.4
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    • pp.169-176
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    • 2017
  • This paper presents research on low-voltage microgrids to maintain a continuous power supply to critical loads on grid-connected islands in Korea. The low-voltage microgrids of this paper focused on that changes public office buildings into uninterrupted microgrids by autonomous operation. For this, a microgrid controller (MGC) and a power conditioning system (PCS) that allow a seamless transfer between grid-connected and grid-isolated operation are proposed. The proposed PCS operates with a silicon controlled rectifier (SCR) switch and employs a simple structure. It supplies power continuously without operators through a coordinated operation between MGC and PCS. In addition, proposed MG has a schedule operation for minimizing electricity charges and provides ancillary services that enable the utilization of resources according to the operation purpose of utility distribution networks. To demonstrate the uninterrupted low-voltage microgrid proposed in this study, a microgrid was implemented and tested in a public office building in Anjwa Island, Jeollanam-do in Korea. A seamless, autonomous operation history, despite system disturbances, was obtained through a long-term demonstration of operation. The results showed that the proposed microgrid technology can be used to achieve energy resilience in grid-connected island areas.

Design of LCL Filter through Inductor Optimization Method in Grid-Connected Inverter (계통연계 인버터의 인덕터 최적화 기법을 통한 LCL 필터 설계)

  • Jang, Jae-Ha;Kim, Kyeong-Hwa
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.28 no.11
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    • pp.58-67
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    • 2014
  • A grid-connected inverter used for renewable energy resources produces harmonic components in the switching frequency. To effectively reduce switching harmonic components, several types of filter are generally used in the output stage of the grid-connected inverter. Many research works on LCL filter design have been done to maintain the performance with low cost. However, it is not easy to make the filter design be economical and optimal due to the varying characteristic of magnetic core and redundancy design by experience. In this paper, a design method for a LCL filter is presented through the inductor optimization scheme in view of the size and cost when the inductor is manufactured using the magnetic core. The effectiveness is verified through tests using a 3kW grid-connected inverter by simulations and experiments.

Design Factor Calculation and Analysis of Grid-Connected Photovoltaic System (계통연계형 태양광발전시스템의 설계계수 산출분석)

  • So, Jung-Hun;Hwang, Hye-Mi;Jung, Young-Seok;Ko, Suk-Whan;Ju, Young-Chul;Lim, Hyun-Mook
    • Journal of the Korean Solar Energy Society
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    • v.33 no.5
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    • pp.89-94
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    • 2013
  • This paper presents a simple but valid design factor calculation method of grid-connected photovoltaic system using normalized yield model. The proposed calculation method can be represented as a quantitative value about five design factors from irradiance to system output power. The validity of this method is identified by analyzing design factor with three years monitored data. These results will indicate that it is useful to determine the optimal design and selection of grid-connected photovoltaic system to meet different user purposes and enhance long-term reliability and stability of grid-connected photovoltaic system.

PLL Control Strategy for ZVRT(Zero Voltage Ride Through) of a Grid-connected Single-phase Inverter (계통연계형 단상 인버터의 ZVRT(Zero Voltage Ride Through)를 위한 PLL 제어 전략)

  • Lee, Tae-Il;Lee, Kyung-Soo
    • The Transactions of the Korean Institute of Power Electronics
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    • v.24 no.3
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    • pp.169-180
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    • 2019
  • Grid codes for grid-connected inverters are essential considerations for bulk grid systems. In particular, a low-voltage ride-through (LVRT) function, which can contribute to the grid system's stabilization with the occurrence of voltage sag, is required by such inverters. However, when the grid voltage is under zero-voltage condition due to a grid accident, a zero-voltage ride-through (ZVRT) function is required. Grid-connected inverters typically have phase-locked loop (PLL) control to synchronize the phase of the grid voltage with that of the inverter output. In this study, the LVRT regulations of Germany, the United States, and Japan are analyzed. Then, three major PLL methods of grid-connected single-phase inverters, namely, notch filter-PLL, dq-PLL using an active power filter, and second-order generalized integrator-PLL, are reviewed. The proposed PLL method, which controls inverter output under ZVRT condition, is suggested. The proposed PLL operates better than the three major PLL methods under ZVRT condition in the simulation and experimental tests.

Resonance Characteristics Analysis of Grid-connected Inverter Systems based on Sensitivity Theory

  • Wu, Jian;Han, Wanqin;Chen, Tao;Zhao, Jiaqi;Li, Binbin;Xu, Dianguo
    • Journal of Power Electronics
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    • v.18 no.3
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    • pp.746-756
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    • 2018
  • Harmonic resonance exists in grid-connected inverter systems. In order to determine the network components that contribute to harmonic resonance and the composition of the resonant circuit, sensitivity theory is applied to the resonance characteristic analysis. Based on the modal analysis, the theory of sensitivity is applied to derive a formula for determining the sensitivities of each network component parameter under a resonance circumstance that reflects the participation of the network component. The solving formula is derived for both parallel harmonic resonance and series harmonic resonance. This formula is adopted to a 4-node grid-connected test system. The analysis results reveal that for a certain frequency, the participation of parallel resonance and series resonance are not the same. Finally, experimental results demonstrate that the solving formula for sensitivity is feasible for grid-connected systems.

Seamless Mode Transfer of Indirect Current Controlled Parallel Grid-Connected Inverters (간접전류제어방식 병렬형 계통연계 인버터의 무순단 모드절환)

  • Song, Injong;Choi, Junsoo;Lim, Kyungbae;Choi, Jaeho
    • The Transactions of the Korean Institute of Power Electronics
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    • v.24 no.5
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    • pp.334-341
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    • 2019
  • This study proposes the control strategy for the seamless mode transfer of indirect current controlled parallel grid-connected inverters. Under the abnormal grid condition, the grid-connected inverter can convert the operation mode from grid-connected to stand-alone mode to supply power to the local load. For a seamless mode transfer, the time delay problems caused by the accumulated control variable error must be solved, and the indirect current control method has been applied as one of the solutions. In this study, the design of control parameters for the proportional-resonant-based triple-loop indirect current controller and the control strategy for the seamless mode transfer of parallel grid-connected inverters are described and analyzed. The validity of the proposed mode transfer method is verified by the PSiM simulation results.

A Study on the Characteristic Analysis of a Grid-connected Induction Generator for Wind Power Systems on Simulink (Simulink에서 계통연계 유도형 풍력발전시스템의 특성해석에 대한 연구)

  • An, Hae-Joon;Kim, Hyun-Goo;Jang, Moon-Seok;Jang, Gil-Soo
    • 한국신재생에너지학회:학술대회논문집
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    • pp.184.3-184.3
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    • 2010
  • This study suggests a modeling of grid-connected wind turbine generation systems and performs simulation according to increase/decrease of real wind speed. MATLAB & SIMULINK implemented modeling of grid-connected wind turbine generation system. Terminal voltage, grid voltage, and active/reactive power shall be observed following the performance of simulation.

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Grid-connected Wind Turbine Generation System Modeling and Simulation Using MATLAB/Simulink (MATLAB/Simulink를 이용한 계통연계 풍력발전 시스템 모델링 및 시뮬레이션)

  • An, Hae-Joon;Kim, Hyun-Goo;Jang, Gil-Soo;Jang, Moon-Seok;Ko, Seok-Whan
    • 한국신재생에너지학회:학술대회논문집
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    • pp.321-323
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    • 2008
  • This study suggests a modeling of grid-connected wind turbine generation systems and performs simulation according to increase/decrease of real wind speed. MATLAB/Simulink implemented modeling of grid-connected wind turbine generation system. Terminal voltage, grid voltage, and active/reactive power shall be observed following the performance of simulation.

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Filter Design for Grid-Connected Single-Phase Inverters

  • Kim, Hyo-Sung
    • Journal of Power Electronics
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    • v.9 no.4
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    • pp.623-630
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    • 2009
  • This paper proposes a filter design guideline for grid-connected single-phase inverters. By analyzing the instantaneous voltage applied to the filter inductor, the switching ripple current through the filter inductor can be precisely calculated. Therefore, filter inductance can be designed accurately, which guaranties that the switching ripple current will be under the target value. The proposed filter design method is verified by experiment.

Inquiry of New Topology for Grid-connected Photovoltaic Inverter (PV용 계통연계형 인버터의 새로운 Topology 고찰)

  • 정영석;유권종
    • Proceedings of the KIPE Conference
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    • pp.248-251
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    • 1999
  • Recently, according to developing industry and life style, power consumption have been increased year after year. Currently these much power demand from power consumer is weakening the allowable power reverse margin in summer. As on of the remedies about this problem, the small scale grid-connected photovoltaic system is considered for auxiliary power source. Generally, grid-connected inverter have a isolation transformer for electrical isolation from utility. This paper propose transformerless system topology an inquiry the validity using simulation.

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