• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.188-190
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• 2006

본 논문에서는 국내최초로 개발에 성공한 단일용량의120kW급 계통연계형 태양광발전용 PCS에 관한 내용을 설명하고 있다. 120kW급 계통연계형 태양광발전시스템은 22.9kV의 특고압 계통전원에 연계되도록 설계되었으며, 삼상 380V를 22.9kV로 승압 연계하는 2단 절연방식을 채택하였다. 120kW급 PCS는 상용주파수 변압기 절연방식으로 3상4선식 380v 60H2 출력을 가지고 있으며, PCS 내부에 120kVA급 변압기와 리액터를 포함하고 있다. 최대출력점추종(MPPT)제어 기법으로 P&O 알고리즘을 적용하였으며, 3상 IGBT 인버터를 DSP로 제어하였다. 본 논문에서는 120kW급 단일용량 PC를 개발함에 있어, 계통연계 시험, 유,무효 전류제어 시험, 단독운전 검출 및 방지시험, 출력전류의 THD 측정 등의 결과를 보이고 있다.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.6
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• pp.563-569
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• 2002

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency DC-DC converter, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter, and an AC filter. The 20kHz switched high frequency converter is used to generate bipolar PWM pulse, and the high frequency transformer transforms its voltage twice, which is subsequently rectified by diode bridge rectifiers for a full-wave rectified 60 Hz sine wave power output. Even though the high frequency link system needs more power semiconductors, a reduced size, light weight, and saved parts cost make this system more comparative than other power conditioning systems due to elimination of 60Hz transformer.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.247-254
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• 2015

Unintentional islanding results in safety hazards, power quality degradation, and many other issues. Thus, islanding detection of grid-connected distributed generation system is a key function for standards compliance. Many anti-islanding schemes are currently being studied; however, existing anti-islanding schemes used in inverters have power quality degradation and non-detection zone issues. Therefore, this paper analyzes existing anti-islanding schemes by using frequency drift in accordance with both islanding detection performance and power quality. This paper also proposes a new anti-islanding scheme by using frequency drift. Both simulation and experimental results show that the proposed scheme has negligible power quality degradation and no non-detection zones compared with other existing schemes.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.1
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• pp.20-29
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• 2011

This paper proposes critical load following back-up system using MCFC stack. This system enables MCFC generation system to supply power to critical load without UPS and to generate rated power under grid fault state. This back-up system includes 'Load Leveler' that is connected with 3-phase inverter and is controlled by additional algorithm that includes critical load following. The proposed system and algorithm are verified by computer simulation based on 5kW system.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.1
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• pp.79-87
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• 2011

The fault detection technique of the grid-connected photovoltaic system using wavelet transform has been suggested in this paper. The additional hardware and sensors are required to detect the inverter failure in the conventional method, and it has the disadvantage of high cost and re-design problem if the inverter specification has been changed. The suggested method used the inverter voltage and current waveform to detect the failure and the location by the wavelet coefficients variations. The prompt and accurate diagnostic function is possible using the normalized standard deviation method. The merit of the proposed method is the simple calculation and precise diagnostic capabilities of the fault detection. The computer simulation is performed and the experimental result verifies the validity of the proposed method.

• Journal of the Korean Solar Energy Society
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• v.39 no.2
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• pp.81-92
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• 2019

When Photovoltaic inverter is connected to grid and used as PVPCS (Photovoltaic Power Conditioning System), 120 Hz AC ripple occurs at the dc-link capacitor voltage. This AC ripple reduces the efficiency of PVPCS and shortens the lifetime of the capacitor. In this paper, we design a notch filter to remove AC ripple. As a result, the AC voltage ripple was removed from the dc link and the THD of the PVPCS output current with the notch filter was lowered. This notch filter is determined by the damping coefficient, the bandwidth coefficient, and the switching frequency. Among these, the switching frequency determines the switching loss and the size of the LC filter, and the PVPCS with the high switching frequency has a greater efficiency loss due to the switching loss than the efficiency improvement by the notch filter. Therefore, it is important to set the optimum switching frequency in the PVPCS with the notch filter applied. In this paper, THD and switching loss of PVPCS output current with notch filter are calculated through simulation, and cost function to calculate optimum switching frequency through data is proposed.

• Journal of Power Electronics
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• v.18 no.4
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• pp.997-1006
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• 2018

This paper proposes a transformerless photovoltaic (PV) power converter system based on the DC/AC boost inverter, which can solve the leakage current and second-order ripple power issues in single-phase grid-connected PV inverters. In the proposed topology, the leakage current can be decreased remarkably since most of the common-mode currents flow through the output capacitor, by-passing parasitic capacitors, and grounding resistors. In addition, the inherent ripple power component in the single-phase grid inverter can be suppressed without adding any extra components. Therefore, bulky electrolytic capacitors can be replaced by small film capacitors. The effectiveness of the proposed topology has been verified by simulation and experimental results for a 1-kW PV PCS.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.346-347
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• 2018

본 논문은 Grid, PV(Photovoltaic), BESS(Battery Energy Stroage System), DC Load로 구성된 DC 마이크로그리드를 국내 사이트에 적용한 사례 및 실증 결과에 대해 기술하고 있다. 또한 DC 마이크로그리드 시스템의 구성과 함께 Destin Power사가 개발하여 적용한 125kW급 PCS(Power Conditioning System)의 기술을 소개하였다. 마지막으로 시스템의 운영 타당성을 체계적으로 검증하기 위해 진행했던 시험 항목과 결과를 서술하였으며 그 결과를 바탕으로 DC 마이크로 그리드 시스템 실증을 검증하였다.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1781-1783
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• 2005

To evaluate the grid-connected Photovoltaic(PV) system performance, as a medium size, a 120 kW PV system which was consisted of solar cells, PCS, 150kVA transformer station and utility grid was designed and constructed.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.3
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• pp.235-243
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• 2010

This paper describes a design method of LCL filter for grid-connected three-phase PWM inverter. First, by analyzing the ripple component of phase voltages and currents according to the PWM pattern of grid-connected three-phase inverter, the RMS value of the current ripple can be calculated. Then based on the analysis, the current THD in the inverter-side can be defined. After that by analyzing the dependency between the current THD of the system and the current ripple attenuation, the parameter of LCL filter can be designed. Finally, the described LCL filter design method is verified by showing a good agreement between the target current $THD_g$ and the actual one through the simulation and experiment.