Research On Fault Analysis Of Photovoltaic Array

With the widely application of photovoltaic techniques, many photovoltaic systems have been in operation. In practical, when photovoltaic modules have operated for eight to ten years, the local cells will be aged and destroyed owing to the infiltrating and diffusing of air bubbles, which were caused as modules were encapsulated, and the output power of the system will lost. To this end, it is necessary and very important to develop the real-time on-line fault analysis and diagnosis methods for the photovoltaic array in high power photovoltaic generation system. By theoretical analysis and experimental verification, it is found that the surface temperatures of photovoltaic cells under different operation states are distinct different. Infrared (IR) imaging systems (cameras) now provide a convenient method for measuring both absolute and relative temperature distributions on small and large components with a high degree of temperature and spatial resolution. In this thesis, a new analysis and recognizing approach for the photovoltaic array operation state, which is based on the infrared image analysis, is proposed. At first, the infrared images of photovoltaic arrays are processed and analyzed; the abnormal areas and their features are abstracted. To deal with influences of such factors as environment temperature, wind speed and solar illumination, which affect the temperature of photovoltaic cells, a fuzzy reasoning technique based on the data fusion is employed and the fault areas are recognized automatically. The main original research of this thesis include:1. By analyzing the model, mechanism, temperature differences and infrared radiation characteristics of photovoltaic cells, the feasibility of the indirect fault diagnosis for photovoltaic arrays with the infrared image analysis method is verified.2. According to the characteristics of photovoltaic array infrared images, a series of image processing methods of gray level lengthening, de-noising,non-uniformity background correction, image segmentation for photovoltaic array infrared image are proposed, and the approaches of extracting valid information features such as aero, shape, average gray values of each area are studied and implemented.3. The influence of various environmental factors (such as environment temperature, wind speed, solar illumination) in different reasons on the characteristics of temperature differences and infrared radiation for photovoltaic cells is researched, and a fuzzy based recognition method for different operation states of photovoltaic cells such as normal, shadowed, aging and destroyed is proposed.4. The analyzing system is designed; all the proposed approaches and methods are implemented with hardware and software.The research result shows the proposed fault analysis approach for photovoltaic arrays based on infrared image analysis and data fusion is feasible and effective. The research has provided a theoretic foundation and directed basis for the real-time on-line fault diagnosis of the high power photovoltaic generation system.