Control Strategy of Cascaded H-Bridge Multilevel Inverter with PV System as Separate DC Source

Abstract: The integration of solar energy to the power grid is a challenging topic nowadays. Many topologies and control methods have already been proposed. In this thesis, the cascaded H-bridge (CHB) multilevel inverter is adopted for the photovoltaic (PV) energy integration. The purpose of this thesis is to develop a control strategy for the CHB multilevel inverter with PV array as separate DC source. The thesis first gives a short review of the three commonly used multilevel inverter topologies. Then the PV array with maximum power point tracker (MPPT) is modeled. The selection mechanism with some improvements is chosen as the control and modulation method for the CHB inverter with PV system. Real and reactive power exchange between the inverter and grid are also discussed. Finally, the simulation results are presented to verify the control methods. The software for the simulation is PSCAD/EMTDC and all the figures are plotted in MATLAB.