• Title/Summary/Keyword: Grid-connected system

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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 Seamless and Autonomous Mode Transfer Method of Grid-connected Inverter in Microgrid (마이크로그리드에서 계통연계 인버터의 자율적이며 끊김없는 모드전환 기법)

  • Park, Sung-Youl;Kwon, Min-Ho;Choi, Se-Wan
    • The Transactions of the Korean Institute of Power Electronics
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    • v.24 no.5
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    • pp.349-355
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    • 2019
  • A grid-connected inverter with critical loads should be able to supply a stable voltage to critical loads at mode change and during clearing time while detecting unintentional islanding. This study proposes a mode transfer method for a grid-connected inverter with critical loads. The proposed method, which integrates the grid-connected and islanded mode control loops into one control block, provides an autonomous and seamless mode transfer from the current control to the voltage control. Therefore, the proposed scheme can supply a stable voltage to critical loads at mode change and during clearing time. Experimental results are provided to validate the proposed method.

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.

Economic analysis on Sustainable Photovoltaic Systems (지속가능한 태양광발전시스템의 경제성 분석)

  • Park, Soo-Uk;Lee, Deok-Ki
    • New & Renewable Energy
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    • v.1 no.3 s.3
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    • pp.35-41
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    • 2005
  • This paper analyses the economics of grid-connected photovoltaic systems. With the 2003 cost of photovoltaic systems, under prevailing capital market conditions, with a system lifetime of 30 years, and under the best climatic conditions, it appears that the cost of production of grid-connected electricity could be of 0.21 US $/kWh, and under medium climatic conditions, European locations, Switzerland, Japan and South Korean could be of 0.28$/kWh. If the lifetime if the system goes up, due to future technological improvements, to a very large value such as 50 years, these costs can be lowered by 10-20%. Competitiveness of grid-connected photovoltaic electricity, while it still cannot be taken for granted, is a possibility, especially if major technological advances further lowers the costs of photo cells and increases their lifetimes.

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Bus Voltage Analysis of Substation Connected to the Wind Generation Farm (풍력발전단지와 연계된 변전소의 모선전압 분석)

  • Kim Young Hwan;Hyun Gil Ju;Ko Seok Bum;Yang Ik Jun;Na Kyoung Yun;Kim Se Ho
    • Proceedings of the KIEE Conference
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    • summer
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    • pp.236-238
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    • 2004
  • In recent years wind turbine technology has undergone the rapid development in response to the demands for increased use of renewable sources of energy. Using wind turbines for production of electrical energy requires reliable operation. The increased share of wind power in electrical system makes it necessary to have grid-friendly interfaces between the wind turbines and the grid in order to maintain power quality. Increasingly wind turbines are being connected into electricity distribution system. The grid-connected wind power stations have many impacts on power systems such as voltage variations, harmonics. The paper investigates the influences of grid-connected wind power generation system on substation bus voltage.

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Grid Connected Photovoltaic Inverter System Using a New Zero-Current- Transition Scheme (새로운 Zero-Current-Transition 기법을 이용한 계통 연계형 태양광 발전 인버터 시스템)

  • Choi, Young-Deok;Lee, Dong-Yun;Hyun, Dong-Seok
    • Proceedings of the KIEE Conference
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    • 2002.04a
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    • pp.213-215
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    • 2002
  • This paper presents grid connected photovoltaic inverter system using a new Zero-Current-Transition(ZCT) technique. The main switches of the proposed grid connected inverter are turned off under the zero current condition by operating the auxiliary circuit and also all semiconductor devices, switches and diodes, are applied to low rated voltage regardless of the load condition. In additionally, the proposed ZCT scheme has advantages, which are without the additional current stresses and the conduction losses on the main switches during the resonance period of the auxiliary circuit. The simulation was performed to verify the validity of the proposed grid connected photovoltaic ZCT inverter system.

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New MPPT Control Strategy for Two-Stage Grid-Connected Photovoltaic Power Conditioning System

  • Bae, Hyun-Su;Park, Joung-Hu;Cho, Bo-Hyung;Yu, Gwon-Jong
    • Journal of Power Electronics
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    • v.7 no.2
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    • pp.174-180
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    • 2007
  • In this paper, a simple control method for two-stage utility grid-connected photovoltaic power conditioning systems (PCS) is proposed. This approach enables maximum power point (MPP) tracking control with post-stage inverter current information instead of calculating solar array power, which significantly simplifies the controller and the sensor. Furthermore, there is no feedback loop in the pre-stage converter to control the solar array voltage or current because the MPP tracker drives the converter switch duty cycle. This simple PCS control strategy can reduce the cost and size, and can be utilized with a low cost digital processor. For verification of the proposed control strategy, a 2.5kW two-stage photovoltaic grid-connected PCS hardware which consists of a boost converter cascaded with a single-phase inverter was built and tested.

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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    • 1999.07a
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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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A Study on the Harmonics and Flicker Measurements and Analysis of the Grid Connected Photovoltaic Power System (전력계통 연계형 태양광 발전시스템의 고조파 및 플리커의 측정 및 분석에 관한 연구)

  • Kim, Kyung-Chul;Kim, Yong-Kwan
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.26 no.5
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    • pp.48-57
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    • 2012
  • This paper analyzes the characteristic of gird connected photovoltaic power generation system which is available to connect the utility. Renewable energy photovoltaic power system has been linked to the system to analyze the impact of photovoltaic system. It is measured that power data for the Grid connected photovoltaic power plant with instantaneous measuring and 3-sec measuring for 7 days. Harmonic field measurements have shown that the harmonic contents of a waveform varies with time. A cumulative probability approach is the most commonly used method to solve time varying harmonics. So, it is used 50[%] cumulative probability approach. This paper provides an in depth analysis on power quality field measurement of the Grid connected photovoltaic power plant.

A Development of Smart Black Box for Grid-connected Solar Power System (계통 연계형 태양광 발전 시스템의 스마트 블랙박스의 개발)

  • Park, Sung-Won;Kim, Dong-Wan;Lee, Jin-Woo
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.12
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    • pp.2119-2126
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    • 2016
  • In this paper, we developed a smart black box that can monitor and record the information of the sensor from subsystem in the smart grid system. The plant is the complex power system which is integrated by solar power system, grid-connected power systems, and BESS(battery energy storage system). The black box with the web-server application can connect and synchronize to an external monitoring system and a smart phone. We hope that this system is to contribute to improve operational efficiency, reliability, and stability for the smart grid power system.