Research and Implementation of a Variable Step-Size Perturbation and Observation Algorithm for Photovoltaic System

• Main Authors: Chih-Chia Tung, 董旺洹
• Other Authors: Yi-Hua Liu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/76692537800482721297

碩士 === 國立臺灣科技大學 === 電機工程系 === 100 === Photovoltaic (PV) energy is one of the most important renewable energy sources since it is clean, free and inexhaustible. To improve the conversion efficiency, a maximum power point tracking (MPPT) technique which has quick response and is able to track the peak power generated in any weather condition is required. Many MPPT techniques have been proposed and implemented in the literatures. Among them, the perturbation and observation (P&O) method is the most common for simplicity, ease of implementation, and good performance. P&O algorithms suffer a tradeoff in choosing the increment value of the control variable; small values decrease the losses in steady state due to small perturbations around the maximum power point (MPP), while large values improve the dynamic behavior in situations involving quickly changing irradiation conditions or load. In this thesis, a variable step-size P&O method is implemented to deal with this problem. A boost converter is used as the power stage and the MPPT controller is realized using microcontroller RX62T from RENESAS corp. One of the difficulties faced in the implementation of variable step size algorithms is in finding the right value of the scaling factor M. A poor choice of M can easily lead to instability or inefficient tracking. In this thesis, the value M is selected based on intensive study of the simulation of the PV system. Simulation and experiments are carried out to validate the feasibility of the presented algorithm. According to the experimental results, the presented variable step-size algorithm can achieve high static tracking efficiency and faster tracking speed comparing to conventional P&O algorithms.