الفهرس 
AbstractOnly 14 pages are availabe for public view
 |  | from | 110 |  |  |
| | | from | 110 | | |
Abstract
Not only are small photovoltaic (PV) systems widely used in poor countries and rural areas where the electrical loads are low, but they can also be integrated into the national electricity grid to save electricity costs and reduce CO2 emissions. Partial shading (PS) is one of the phenomena that leads to a sharp decrease in the performance of PV systems. This thesis firstly provides a comprehensive performance investigation of small systems (consisting of ten modules or fewer) under all possible shading patterns that result from one shading level (300 W/m2 is chosen). The most common configurations are considered for which a performance comparison is presented. Five small systems of different sizes are studied under PS. A new simplifying method is proposed to identify the distinct PS patterns under study. Consequently, the number of cases to be studied is significantly reduced from 1862 to 100 cases only. Also, a new reconfigurable total-cross-tied (RTCT) method is introduced. The simulation results demonstrate the most outperformed configuration in each case of PS pattern and the amount of improvement for each configuration. The configurations include static series-parallel (SP), static total-cross-tied (TCT), dynamic switching between SP and TCT, and TCT-reconfiguration. The study provides PV systems’ owners with a set of guidelines to opt for the best configuration of their PV systems. The optimum recommended configuration is TCT reconfiguration, rather than dynamic switching between SP and TCT.
Secondly, three different approaches of boosting output power under the influence of the PS circumstances are compared. The three approaches are based on different techniques; static, column reconfiguration, and array reconfiguration. The three methodologies are represented by the TCT, CWR, and RTCT methods, respectively. Each of which proved previously superior to its counterparts using the same methodology. The three methods are tested in two parts. The first part included five different static shading patterns and have been tested on a 5x5 system. RTCT showed superior results compared to the other two methods. It has improved the output power in the all five patterns, with rates ranging between 1.45% and 32.49%. While the CWR method achieved improvement in four patterns with lower percentages (between 1.68% and 27.81%), and one pattern is lower than the static TCT. In the second part, the three methods are tested on a system of one hundred modules, arranged in 10x10 array, and under a dynamic solar radiation pattern that changes over time within ten minutes. RTCT provides the highest improvement rate for all cases with 9.5% for the mean of the total period and CWR achieved 6.9%. Therefore, direct development of static systems into array reconfiguration using RTCT is highly recommended if the goal is to obtain the maximum possible power. Simulation results are carried out using MATLAB/Simulink environment.