Solutions to the instability problem of the DC input voltages of neutral point clamping multilevel inverter in photovoltaic chain connected to the network

Algeria has the importance´s resources of renewable energy. The solar field is the principal of these resources. Photovoltaic solar energy provides today a good energy conversion efficiency, however, the problem of coupling between a photovoltaic generator (GPV) and an AC load assured by a DC-AC converter is not yet resolved (bad adaptation). For the best quality produced by the chains of renewable energy production, we use multilevel inverters. One of the major limitations of these inverters is the instability of the DC input voltages. The Aim of this paper is to give solutions to unbalance problem of the input DC voltages of the five-level neutral point clamping (NPC) voltage source inverter (VSI). For that, we propose solutions which use a feedback loop control to regulate the total DC voltage of the inverter by using proportional integrator regulator (PI) and fuzzy logic controller (FLC). To improve the regulation of the input DC voltages, we introduce a power electronic circuit composed of a transistor in series with a resistor, called clamping bridge. The results obtained show that the use of the five-level NPC VSI in systems of renewable energy is full of promise on condition to solve the instability problem of the input voltages.