Photovoltaic system optimization through distributed maximum power point tracking techniques and power delivery strategies in distribution networks

Abstract

In this thesis, di erent strategies that improve the integration of photovoltaic (PV) systems into the grid are discussed. First, the interaction of PV installations and the distribution network is addressed. A management system in charge of controlling the di erent PV units is implemented in real hardware. The management system deals with the grid-voltage issues caused by the distributed PV generation thanks to the contribution of all the inverters connected to the same network. In the second part, the strategy is focused on the DC side of the PV system. Distributed maximum power point (DMPPT) architectures are adopted as an alternative to the classical PV systems, that show improved performance in mismatch conditions when compared to the classical approach. The coordination of the DMPPT functions with a central MPPT function in charge of tracking the DC-bus voltage VDC is proposed and safe VDC operating areas are identiffied. The advantages of having an adaptive VDC control in partially shaded conditions is studied and demonstrated. Besides, the dynamic performance in DMPPT systems is improved, enhancing system stability. Alternative control strategies consider the integration of batteries at module level. The batteries provide support to the PV generation and act as a backup system to compensate large mismatch conditions in systems adopting a constant VDC or if the joint operation of DMPPT and CMPPT functions is not e ective. Overall, the proposed control strategies enhance the integration of PV systems, increase the PV generation and improve system stability, compared to other control strategies for PV DMPPT systems.