Modeling of photovoltaic grid connected generation system based on three level NPC converter

Abstract

Renewable energy sources have been increasing and developing continuously in the last years, due to advantages over conventional generation sources. Photovoltaic (PV) systems generate electricity from sunlight without creating any air or water pollution and in a clean, quiet and reliable way. The efficiency and performance of PV systems are still under development. As a consequence, the control structures of the PV system grid-connected are a fundamental part for its proper functioning. In this paper, a grid connected photovoltaic system based on a three-phase three-level neutral point clamped (NPC) inverter is presented. The proposed system describes in detail each stage along with the suited controllers, which operate in a proper and efficient way. In addition, the Perturbation and Observation (P&O) algorithm to get the maximum power point tracking (MPPT) of the PV system under different irradiation conditions, is proposed. In order to maximize the PV system power, a three-phase three-level NPC converter is used to achieve higher power levels, lower voltage stress on devices, lower switching frequency and reduce harmonic content. In addition, d-q reference frames are used to decouple the active and reactive power controllers. Simulations to validate the proposed procedures of the complete system are presented.