Digital design and validation of GC-VSI control for Photovoltaic(PV) systems
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- Institutt for elkraftteknikk 
Solar power is one of the most promising renewable energy in future. Nevertheless,the increasing PV penetration rates could lead to many problems. For example, when the local PV generation is higher than the demand in distribution systems, power will flow to higher voltage levels, which will cause the increase of voltage. Also, the fluctuating generation brings challenge to the stability of the grid. To deal with the above mentioned challenges, power electronics equipment have been increasingly employed in the electric grid worldwide. More accurate modeling and digital design of the control systems for PV systems is necessary. This thesis is structured as the follows: In the first chapter, the background of PV generation, the structure of PV systems and its working principles are introduced. Background knowledge of converters are introduced in Chapter2. Common used 3 phase inverter control strategies and the coordinate transformation method for single phase systems are detailed. Based on a typical PV systems structure, the grid side, the DC bus, the PV side mathematical models are built in synchronous frame respectively in Chapter3. Chapter4 focuses on the control design principle. The Grid Synchronization problem is roughly discussed and a concept of Multiple Maximum Power Point Tracking(MMPPT) is came up. Conclusion and future work are stated in the last chapter.