• 전력전자학회논문지
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• 제17권3호
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• pp.274-280
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• 2012

In this paper, three current controllers for a grid-connected PCS using an LCL filter are compared and analyzed. Current controllers discussed in this paper are linear controllers such as PI (proportional-integral), PR (proportional-resonant), and DB (deadbeat) controller. Both transient and steady state responses of each controller are compared through both simulation and experiment. Although the DB controller has the fastest transient response and the lowest THD in the steady state, the DB controller has two cycles delay of current response in the steady state and has the stability problem which can be occurred due to variation of the system parameters. On the one hand the responses of PR controller are not much different from that of DB controller but the other hand that are not only strong to noise of grid current but also have smaller THD than PI controller. Considering the response time and stability issue of three controllers, the PR controller has the best performance among three controllers and thus can be strongly recommended as a current controller for a grid-connected PCS.

• 한국수소및신에너지학회논문집
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• 제19권5호
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• pp.417-422
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• 2008

In this paper, a novel DC/DC low-voltage high-current converter circuit is proposed to improve the efficiency of power converter used in the grid-connected fuel-cell generator system. We proposed a novel high efficiency grid-connected power conditioning system for RPG fuel cell. On the result of that, the loss of system was decreased rapidly by driving stack within the condition of maximum efficiency. The peak currents of the current-type inductor and the transformer's coil are reduced by synchronizing switching frequency of Buck-type converter is increased twice as the Push-Pull converter's switching frequency. The novel structure of DC/DC converter is able to realize ZVS-ZCS in fuel-cell system is proposed. The proposed switching component of Push-Pull converter has the ZVS and ZCS function by using the circuit of new passive clamp.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.516-519
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• 2003

3kW photovoltaic (PV) systems and data acquisition system are constructed for performance analysis of PV system at field demonstration test center (FDTC) of Korea. As climatic and irradiation conditions are varied, the performance characteristics of PV system are collected and analyzed in data acquisition system. From these results, the performances of gird-connected power conditioning system (PCS) fur PV system have been evaluated and analyzed. Furthermore, performance indices of grid-connected PCS e.g. output power, efficiency, loss factor, and the other index at the site are reviewed.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.341-344
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• 2009

In this paper, protective function evaluation was conducted to determine the performance and safety of a power conditioning system(PCS) for 1kW residential fuel cell system. It is essential to have a power quality, grid-connection and safety of PCS. Even though it is under 500ms by KGS-A410 standard, it is shown a rapid response time of 25ms from input under-voltage test. In terms of output over/under-voltage test, it is shown 29.15 and 79.4ms. Especially using anti-islanding test, it is shown all times under 100ms for combination cases of real and reactive power. We confirmed a rapid response characteristics and safety of PCS. The results of this evaluation are being used to develop a new test protocols of PCS.

• 한국태양에너지학회 논문집
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• 제37권3호
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• pp.13-22
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• 2017

Anti-islanding scheme of grid-connected inverter is a key function of standards compliance, since unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, many anti-islanding schemes have been researched, however, most of them have problems, which deteriorate performance of islanding detection under parallel-operation. Therefore, this paper proves the reason of problems and proposes a new anti-islanding scheme that has precise islanding detection under parallel-operation in single-phase and three-phase system. Finally, both simulation and experimental result validate the proposed scheme.

• Journal of Power Electronics
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• 제17권3호
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• pp.756-765
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• 2017

The control of the power conversion system (PCS) in a battery energy storage system has a challenge due to the existence of grid impedance. This paper studies an impedance model of an LCL-based PCS in the d-q domain. The feature of a PCS connected to a weak grid is unveiled by use of an impedance model and a generalized Nyquist criterion. It is shown that the interaction between grid impedance and the PCS destabilizes the cascaded system in certain cases. Therefore, this paper proposes a novel control method that adopts virtual resistors to overcome this issue. The improvement in the control loop leads the PCS to a more stable condition than the conventional method. Impedance measurement is implemented to verify the correctness of the theoretical analysis. Experimental results obtained from a down-scaled prototype indicate that the proposed control method can improve the performance of the PCS under a weak grid.

• 한국태양에너지학회 논문집
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• 제35권2호
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• pp.11-19
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• 2015

Islanding is a phenomenon that EPS(Electric Power System) is continuously energized by PV PCS(Photovoltaic Power Conditioning System) even when EPS is isolated from the grid. Unintentional islanding will result in safety hazard, power quality degradation and many other issues. So, islanding protection of grid-connected PV PCS is a key function for standards compliance. Nowadays, many anti-islanding schemes are researched. But existing anti-islanding schemes used in PV PCS have power quality degradation and non-detection zone issues. This paper analyses not only detection performance of existed anti-islanding schemes using active frequency drift but also THD of PCS output current according to each value disturbance for anti-islanding. In addition, the lowest value of disturbance in each scheme was tabulated under guarantee of anti-islanding condition.

• 한국가스학회지
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• 제22권5호
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• pp.124-132
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• 2018

파리협정의 체결로 신 재생에너지 보급이 활발해지고 있다. 국내의 경우 공공건물 중심으로 신 재재생에너지 보급 정책이 진행되고 있으며, 건물 내에 설치가 비교적 수월한 연료전지 시스템의 보급이 확대될 전망이여서 계통연계형 연료전지 전력변환장치의 단독운전방지 평가 연구가 중요하다. 본 연구에서는 연료전지 전력변환장치의 국내 인증기준 KGS AB934 PC53이 해외 규격과 부합하는지 검토해보고 계통연계 시 중요한 안전성능인 단독운전방지 평가에 대해 분석하였다. 또한, 병렬로 연결된 두 대의 전력변환장치의 단독운전방지 평가를 위한 시작품을 제작하고 실증 평가를 통해 여러 대의 연료전지 시스템이 설치되고 있는 상황에 맞는 안전성능 확보 방안을 연구하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.761-764
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• 2003

Islanding phenomenon of a grid-connected photovoltaic (PV) power conditioning system (PCS) is said to occur if the PCS continues to power a section of the utility system after that section has been disconnected from the utility source. Since islanding creates hazards for personnel and equipment, PCSs are required to detect and prevent Et. In this paper, several islanding detection methods (IDMs) and reactive power variation method are described. Islanding test results for 9kW PCS are presented for verification.

• 전력전자학회논문지
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• 제13권3호
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• pp.206-212
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• 2008

본 논문에서는 계통 연계형 태양광 발전 시스템의 새로운 FFT에 의한 위상추종 알고리즘을 제안한다. 신재생 에너지 분야에 적용되는 계통연계형 인버터에서는 계통과 동기를 위해서 반드시 계통의 위상 정보가 필요하다. 일반적으로 사용하는 3상 D-Q 변환에 의한 위상 추종과 달리 새롭게 제안하는 FFT를 사용하는 알고리즘은 게인튜닝 부분이 필요 없어 직접제어가 가능하며, FFT의 특성상 기본주파수 이외의 성분을 제외한 강력한 노이즈 제거효과로 인해 노이즈에 강한 특징을 가지고 있다. 시뮬레이션과 실험을 통하여 제안한 알고리즘의 성능이 만족함을 보였다.