신재생에너지원이 연계된 배전계통의 전력품질 향상을 위한 ESS의 전력 제어 기법

다국어 초록 (Multilingual Abstract)

As the depletion of fossil fuels, safety issues of nuclear power, and environmental pollution is coming for the fore, the interest in Renewable Energy Sources (RES) is also increasing. Thanks to the advancement of renewable energy technique like power-electronics and electrical and electronic materials, the RESs have been commercialized successfully. Especially, after RESs are adopted Distributed Generation (DG) as a substitute to motor generator, energy supply structures are also changed to inverter-based Power Conditioning Systems (PCS).
However, this change has serious impact on the conventional power systems and transmission lines due to designs for constant power. There are different types of RESs like photovoltaic array and wind turbine. What all these things have in common is that the generation quantity is influenced by environmental factor such as instantaneous changes of weather. These heavy fluctuations of output power will give rise to irregular voltage variation at Point of Common Coupling (PCC) and frequency fluctuation. From the point of view of Power System Operator (PSO), these cases become harder to maintain the optimum level of power quality. The solution to the problem is the use of ESS which can implement 'Power Smoothing Control'.
ESS has been used for various purposes like electric supply reserve capacity, time-of-use based electricity demand response, and uninterrupted power supply. In these methods, Power Smoothing is one of the purposes of ESS be able to respond to output power fluctuation of RESs. For implementation of Power smoothing, it is necessary for ESS to calculate the reference of ESS according to output power of RESs. In general, prediction of power generation using weather forecasting or signal smoothing using Low Pass Filter (LPF) are used for the method of calculating reference of ESS.
However, these methods have weaknesses. First, it incurs the loss caused by inaccurate calculation. The method of prediction using weather forecasting needs to produce a tried and true data, and the method of LPF can generate error due to excessive damping or phase delay. It means that these methods might be a cause of output of unnecessary power. Second, it has little effect on the improvement of stability in power system. For better performance of power quality maintenance, ESS should control the active power as well as reactive power.
In this paper, the improved power control method of ESS is introduced. Two points of control method are minimizing the error of active power calculation and adding the reactive power calculation. Also, simulation is presented using PSCAD/EMTDC by modeling all the power system consisting of RES and ESS.

목차 (Table of Contents)

• I. 서 론 1
• 1.1 연구배경 1
• 1.2 연구목적 3
• 1.3 논문구성 4
• Ⅱ. 신재생에너지원의 출력 평활을 위한 ESS의 유무효전력 제어 5
• 2.1 신재생에너지원이 배전계통에 미치는 영향 5
• 2.1.1 연계 계통의 전압 변동 6
• 2.1.2 연계 계통의 주파수 변동 9
• 2.2 출력 평활을 위한 ESS의 유무효전력 제어 12
• 2.2.1 신재생에너지원에 연계된 ESS의 제어 형태 13
• 2.2.2 출력 평활을 위한 ESS의 유무효전력 제어 방법 16
• 2.2.3 저역통과필터를 이용한 출력 평활화 기법과 문제점 18
• 2.2.3.1 저역통과필터의 주파수 응답 18
• 2.2.3.2 위상지연과 감쇠효과의 트레이드오프 21
• 2.2.3.3 전압 변동 완화 효과의 경미함 24
• Ⅲ. 제안하는 ESS의 유무효전력 제어 기법 28
• 3.1 유효전력 제어 기법 29
• 3.1.1 유효전력 제어 시스템의 주파수 특성 29
• 3.1.2 파라미터 변동에 따른 성능 비교 32
• 3.2 무효전력 제어 기법 35
• Ⅳ. 시뮬레이션을 통한 모의분석 및 고찰 37
• 4.1 전체 시스템 구성 37
• 4.2 시나리오 구성 40
• 4.3 모의분석 43
• 4.3.1 유효전력 제어 시뮬레이션 분석 43
• 4.3.2 무효전력 제어 시뮬레이션 분석 47
• 4.4 비교분석 및 고찰 53
• Ⅴ. 결 론 55
• 참고 문헌 57