Comparison study of two cascaded configurations of PV generators-three levels inverter for a stand-alone application in South Algeria

In this paper two configurations of photovoltaic energy conversion using the NPC three levels inverter for stand-alone application are proposed and their performances compared. The first cascade uses separate PV sources and the second configuration use only one PV generator. Without a DC/DC converter used in these two studied cases, and in order to get a stable output voltage, authors propose a proportional regulator of inverter modulation index. For the second configuration proposed, we introduce in the control loops another algorithm which uses the redundant vector of the three levels inverter to stabilise the DC bus voltages. A real data of solar irradiation and temperature of Ghardaïa city in south Algeria are used to test the proposed controls. The simulation results show that the inverter output voltage is stable for the two configurations. Then, the PV cascade with separate PV sources is the best solution, seeing that we do not need to use another algorithm in the control loops.