| Summary: | 碩士 === 龍華科技大學 === 電機工程系碩士班 === 102 === In recent years, the series problem of carbon dioxide emissions contributes to climate change and the earth's increased temperature. It also led to a number of serious natural disasters. In order to avoid energy depletion and environmental degradation, seeking for clean alternative energies is a global trend. The solar power is a clean, inexhaustible and convenient technology, therefore, is greatly concerned in the field of renewable energy.
Since the amount of electric power generated by solar cells always varies with irradiance and cell temperatures. Therefore, maximum power point tracking (MPPT) technique is necessary to ensure the solar cells operate at their optimum output power. Traditional MPPT algorithms used a fixed step size, which is determined by the tracking speed and steady state oscillations, to track the maximum power of the solar cells. The corresponding design should achieve the tradeoff between the dynamic responses and steady state oscillations.
Three modified MPPT algorithms with variable step size are proposed in this thesis. They used the slop of the tangent for the P-V curve or P-D curve as the judging conditions in order to improve the MPPT performance of the photovoltaic system. The Matlab/Simulink is used to perform the modeling and simulation tasks. The system was developed by combining the models of a established solar module and a DC-DC boost converter with the proposed modified variable step size MPPT algorithm. The system will be simulated with fixed and variable step size MPPT algorithms, respectively, under different weather conditions in order to observe and analyze the improvements of the variable step size MPPT algorithms on dynamic response and steady state oscillation issues. From the simulation results, the proposed modified MPPT algorithms with variable step size spent less time than the fixed ones to achieve the maximum power point tracking. It also showed similar oscillation magnitudes to those of the traditional fixed ones when the operating point is near to the MPP. The corresponding results validate that the proposed modified MPPT algorithms with variable step size can effectively improve the dynamic and steady state performance simultaneously.
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