Analysis and Development of new strategies for solar energy conversion: New systems of integration, topologies and control

Abstract

In the recent past, energy and environment have played opposite roles in human progress. Energy has been as an engine for the development and the environment has been as the breaker of it. Only after a more conscious and rigorous international policy on environment protection, not opposed to the development, energy and environmental matters have become unified behind a new sustainable model. This has determined new strategies in the energy sector. Hence, renewable sources have become a must in this new sustainable model. The key role in the last decade has been played by the Distributed Power Generation Systems (DPGS) which present an efficient and economic way of generating electricity closer to the load(s). The DPGS can contribute to an efficient and renewable electricity future by potentially: increasing the use of renewable sources of energy; improving the efficiency of the electricity system by reducing transmission and distribution losses; improving the security of the electricity supply through increased diversity of supply and reduced vulnerability to simultaneous system failures. However, the new trend of using DPGS comes also with a suite of new challenges. One of the challenges is the interaction between the DPGS and the utility grid. As a consequence, grid interconnection requirements applied to the distributed generation are continuously updated in order to maintain the quality and the stability of the utility grid. Consequently, the major tasks of this thesis were to analyze and to develop new strategies for solar energy conversion addressing efficiency and quality in order to allow the DPGS not only to deliver power with high efficiency to the utility grid but also to sustain it. This thesis was divided into three main parts, as follows: à ¢ Small Photovoltaic System: AC moduleà ¢ , à ¢ Control of DPGSà ¢ and à ¢ New Topologies and Devices, technologies for multilevel inverter addressing grid connectionà ¢ . 8 In the first part, the main focus was on topologies for module integration. Additionally, a new topology has been proposed and developed and successfully tested. In the second part, the main focus was c on Control, PWM techniques and ancillary function as grid-connection algorithms. In the third part, the main reported research was concentrated around the role of multilevel inverter in the next future of DPGS. Focusing on topologies and technologies device.