Optimal design and research on multi objective control strategy for multilevel multifunctional inverter in large scale grid connected photovoltaic system

This thesis focuses on the multilevel multifunctional grid connected inverter architecture, taking into account how to interconnect photovoltaic (PV) systems into the future smart microgrid with maximizes efficiency, power quality (PQ) and reliability of the power system. The desirable approach should be capable to sustain high quality energy transfer between PV power plants and utility grid and to enhance the PQ at the both consumers and source side. This thesis presents investigations into issues of PQ and reliability of grid connected inverters and offers advanced topological and sophisticated control solutions to significantly improve performance of these systems. In this context, a PV based multilevel inverter proposed to simultaneously maintain high-quality power exchange between PV systems and the utility grid in disturbed grids and perform simultaneous mitigation of PQ problems using novel control algorithm. Furthermore, to produce optimum power and operate at the maximum proficiency a maximum power point tracking method proposed to extract maximum power of the PV system when the PV system receives uniform and non-uniform irradiance or subjected to partial shading. Additionally a wavelet transform based voltage sag/swell detectıon algorithm is proposed to detect voltage sag/swell disturbances.