Multilevel DC-Link Inverter and Control Algorithm to Overcome the PV Partial Shading

This letter presents for the first time the application of multilevel dc-link inverter to overcome the problem of partial shading of individual photovoltaic (PV) sources which are connected in series. The PV permutation algorithm, as a new method, is developed for the control of the inverter so as to extract the maximum power form each PV source under partial shading and to deliver all that power to the load. The algorithm is based on combination of the direct pulsewidth modulation, the sequential permutation PV sources, and the output generation to control the multilevel dc-link inverter. The algorithm is applied successfully to a seven-level inverter with separate maximum power point tracking algorithm for each PV source and under nonuniform irradiance (partial shading). Digital processing unit F28335 eZdsp is used to control the PV system in the real-time mode, and MATLAB-Simulink real-time data exchange is employed to display the extracted power and to control the system parameters via a designed graphical user interface window. The implementation and experimental results are presented.