Journal of the Korea Academia-Industrial cooperation Society (한국산학기술학회논문지)

The Korea Academia-Industrial cooperation Society (한국산학기술학회)
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Implementation and Characteristic Analysis of DC/DC Voltage Regulator for Operation Efficiency Improvement in PV system

태양광발전의 운용효율 향상을 위한 DC/DC 전압 레귤레이터의 구현 및 특성분석

  • Kim, Chanhyeok (Dept. of Electrical Engineering, Korea University of Technology & Education) ;
  • Choi, Sungsik (Dept. of Electrical Engineering, Korea University of Technology & Education) ;
  • Kang, Minkwan (Dept. of Electrical Engineering, Korea University of Technology & Education) ;
  • Jung, Youngmun (Dept. of Electrical Engineering, Korea University of Technology & Education) ;
  • Rho, Daeseok (Dept. of Electrical Engineering, Korea University of Technology & Education)
  • 김찬혁 (한국기술교육대학교 전기전자통신공학부) ;
  • 최성식 (한국기술교육대학교 전기전자통신공학부) ;
  • 강민관 (한국기술교육대학교 전기전자통신공학부) ;
  • 정영문 (한국기술교육대학교 전기전자통신공학부) ;
  • 노대석 (한국기술교육대학교 전기전자통신공학부)
  • Received : 2017.02.28
  • Accepted : 2017.04.07
  • Published : 2017.04.30
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Abstract

Recently, the installation of photovoltaic(PV) systems has been increasing due to the worldwide interest in eco-friendly and abundant solar energy. On the other hand, a PV system has approximately 25% power loss while the energy generated from solar cells is transformed to the power coupling point through a power conversion system (DC/AC). If the output voltage of a string in the PV system is lower than the operating range of the inverter when a part of module in the string has a shadow due to weather conditions, the string is not synchronized and the whole efficiency of output power in a PV system may be reduced significantly. Therefore, to overcome this problem, this paper proposes a novel control method to compensate for the lower voltage by introducing a DC/DC voltage regulator for each string in a PV system, which adopts a concept for MPPT (Maximum Power Point Tracking) control function using the P&O algorithm and adopts constant voltage control method used in an existing inverter. This paper also implements a 2kW DC/DC voltage regulator based on the proposed algorithm and performs a variety of scenario-based experiments. From the simulation result, it was confirmed that the operation efficiency in the proposed method is improved compared to the existing method.

최근, 전 세계적으로 신 재생에너지에 대한 관심이 증가됨에 따라 친환경적이고 무한한 태양에너지를 이용하는 태양광 발전의 설치가 매년 급증하고 있다. 그러나, 태양광발전시스템은 일반적으로 태양광 전지에서 발생한 에너지로부터 전력변환장치(DC/AC)를 거쳐 계통연계 지점까지 약 25[%]의 전력손실을 발생시키고 있다. 이 전력손실 가운데, 일부 태양광 모듈에 음영이나 환경변화(일사량, 온도, 습도 등)로 인해 스트링의 출력 전압이 인버터의 동작전압보다 낮아지면 해당 스트링이 동작하지 않아 전체의 발전효율이 감소하거나, 최악의 경우 인버터가 탈락되어 계통의 출력 전력이 저하되는 등의 손실이 큰 부분을 차지하고 있다. 따라서, 본 논문에서는 상기의 문제점을 개선하기 위하여, 각각의 스트링별로 DC/DC 전압 레귤레이터를 도입하여 환경변화에 따른 전압 저하로 발생하는 스트링의 탈락을 방지하는 제어방식을 제시하였고, 기존 인버터의 MPPT(P&O) 제어와 정전압 제어기능을 전압 레귤레이터에서 수행하는 방식을 채택하였다. 또한, 제안한 알고리즘을 바탕으로 2kW급의 전압 레귤레이터를 구현하여 기존의 운용방식과 비교, 분석한 결과, 환경변화에 따른 다양한 시나리오에서 제안한 운용방식의 운용효율이 크게 향상됨을 확인하였다.

Keywords

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