• Journal of the Korean Solar Energy Society
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• v.32 no.6
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• pp.106-112
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• 2012

As a fuel cell converts the chemical energy of the fuel cell into electrical energy by electrochemical reaction, the fuel cell system is uniquely integrated technique including fuel processor, fuel cell stack, power conditioning system. The residential fuel cell-PCS(Power Conditioning System) needs to convert efficiently the DC current produced by the fuel cell into AC current using single-phase DC-AC inverter. A single-phase DC-AC inverter has naturally low frequency ripple which is twice frequency of the output current. This low frequency(120Hz) ripple reduces the efficiency of the fuel cell. This paper presents notch filter with IP voltage controller to reject specific 120Hz current ripple in single-phase inverter. The notch filter is designed that suppress just only specific frequency component and no phase delay. Finally, the proposed notch filter design method has been verified with computer simulation and experimentation.

• Journal of Power Electronics
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• v.15 no.4
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• pp.1066-1073
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• 2015

This paper proposes a control strategy based on the frequency detection method, comprising a current control and a feed-forward voltage control loop, is proposed for grid-interactive power conditioning systems (PCS). For continuous provision of power to critical loads, PCS should be able to check grid outages instantaneously. Hence, proposed in the present paper are a frequency detection method for detecting abnormal grid conditions and a controller, which consists of a current controller and a feedforward voltage controller, for different operation modes. The frequency detection method can detect abnormal grid conditions accurately and quickly. The controller which has current and voltage control loops rapidly helps in load voltage regulation when grid fault occurs by changing reference and control modes. The proposed seamless transfer control strategy is confirmed by experimental results.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.41-44
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• 2009

본 논문에서는 태양광발전이 본격적으로 보급 활성화 되기 전인 1999년 4월에 50 kVA 계통연계형 태양광 발전시스템 개발과제로 구축된 50kWp급 중규모의 계통연계 태양광 발전시스템의 약 10년간의 장기 실증운전을 통하여 취득한 자료를 기반으로 장기운전에 따른 운전특성 변화를 분석하였다. 본 설비는 50kVA급 PCS, 3kVA급 PCS 및 모듈 50kWp의 용량으로 1999년도에 한전 전력연구원 구내에서 실증시험용으로 구축되었으며, 장기운전에 따른 출력감소율은 10년간 전년도 대비 연 2.73% 이며, 발전설비 이용율은 11.04% 로 분석되었다

• Journal of Power Electronics
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• v.10 no.3
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• pp.328-333
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• 2010

A photovoltaic power conditioning system (PV PCS) that contains single-phase dc/ac inverters tends to draw an ac ripple current at twice the output frequency. Such a ripple current perturbs the operating points of solar cells continuously and it may reduce the efficiency of the current based maximum power point tracking technique (CMPPT). In this paper, the ripple current generation in a dc link and boost inductor is analyzed using the ac equivalent circuit of a dc/dc boost converter. A new feed-forward ripple current compensation method to incorporate a current control loop into a dc/dc converter for ripple reduction is proposed. The proposed feed-forward compensation method is verified by simulation and experimental results. These results show a 41.8 % reduction in the peak-to peak ac ripple. In addition, the dc/ac inverter control system uses an automatic voltage regulation (AVR) function to mitigate the ac ripple voltage effect in the dc link. A 3kW PV PCS prototype has been built and its experimental results are given to verify the effectiveness of the proposed method.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.65.2-65.2
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• 2010

Currently the variety of governmental business support and research for supplying solar energy have been actively progressed. As of now, however, There are no practical testing infrastructures of grid-connected photovoltaic system which test performance of solar power facility in domestic. Therefore, in KEPRI, there is in progress construction of practical testing ground of 500 kW class grid-connected PV System for developing the evaluation of the performance technology including the Module, PCS, and etc, that is the important instrument of the PV System, in Gochang area. It analyzed the site creation work for constructing the practical testing ground and new construction of control room and the unit standards, specifications and capacity of required equipment. For the system detailed design, configuration, instrument-specific parameters established, power generation predictions of Array Type and the components of testing ground are needed to build.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.253-257
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• 2016

This paper analyzes voltage control method in order to supply high-quality power for stand-alone microgrid. Stand-alone microgrid is composed of battery bank, stand-alone PCS and controllable loads. The main role of stand-alone PCS is to supply high-quality power to loads as main source by using stable voltage method regardless of load conditions. In particularly, output voltage of stand-alone PCS gets severely unbalanced voltage under unbalanced loads. Fundamental positive and negative sequences are transformed by two coordinates transformation which are rotated in each opposite direction, respectively. Each fundamental d-q voltage is regulated by each fundamental PI control. In addition, low-order harmonics are compensated through resonant controllers. Performance of stand-alone microgrid is tested for feasibility, and it is verified that output voltage of THD is improved to 1% from 2.2% under 50 kW balanced load, and is improved to 1.1% from 2.6% under 50 kW unbalanced load.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1174-1180
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• 2018

In December 2017, the government announced plans to increase the current proportion of renewable energy from 7% to 20% by 2030 through a plan called the Renewable Energy 3020 Implementation Plan. Therefore, the demand for installation of photovoltaic(PV), wind turbine(WT) and battery energy storage system(BESS) is expected to increase. In particular, the system combined with energy storage system(ESS) is expected to take up a large portion since PV and WT can receive high renewable energy certificates(REC) weights when combined with ESS. In this study, we calculate the optimal capacity of the power conditioning system(PCS) and the BESS by comparing the economical efficiency and maximize the efficiency of the PV-BESS system in which the PV and the BESS are connected. By analyzing the system marginal price(SMP) and REC, it maximize profits through application of REC weight 5.0 and optimal charge-discharge scheduling according to the SMP changes.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.449-450
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• 2017

본 논문은 계통연계 10kW급 3레벨 태양광 PCS(Power Conditioning System) 게이트 드라이버 설계에 대해 서술하였다. 게이트 드라이버는 DSP로부터 신호를 받아 정해진 시간에 IGBT의 게이트에 문턱전압 이상의 전압을 공급하여 IGBT의 게이트를 구동해 주는 역할을 한다. 게이트 드라이버는 간결한 회로의 사용으로 에너지 손실과 제작비용을 최소한으로 저감해야한다. 설계된 10kW급 3레벨 태양광 PCS 게이트 드라이버의 파워부는 15V 전압을 받아 PSIM 시뮬레이션을 통해 확인하였고 이를 실험하여 이상 없이 동작함을 검증하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.94-100
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• 2018

Generally, in a single-phase energy storage system (ESS) for households, AC ripple component with twice the fundamental frequency exists inevitably in the DC link voltage of single-phase PCS. In the grid-connected mode of a single-phase inverter, the AC ripple component in the DC link voltage causes low-order harmonics on grid-side current that deteriorates power quality on an AC grid. In this work, a control system adopting a feedforward controller is established to eliminate the AC ripple interference on the DC link side. Optimal battery nominal voltage design method is also proposed by considering the voltage loss and AC ripple voltage on DC link side in a single-phase ESS. Finally, the control system and battery nominal voltage design method are verified through simulations and experiments.

• 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.