Energy management and power quality enhancement in grid-tied single-phase PV system using modified PUC converter

摘要

Pack U-Cell (PUC) multi-level inverter is an attractive topology which widely investigated in the past few years for renewable energy conversion systems. This study introduces a modified five-level packed Unit-cell converter (MPUC5) for single-phase double stage grid-tied photovoltaic (PV) system with unity power factor. The proposed system operates as a single-phase active power filter able to compensate reactive power generated by non-linear loads connected to the point of common coupling, feeds the non-linear load by the generated PV power, and injects the extra power into the grid. The MPUC5 inverter has a special topology with two DC-link capacitors and six switches. One DC-link of the inverter is connected to the PV arrays through DC/DC Cuk converter to draw the maximum power. Therefore, finite-control-set model predictive control (FCS-MPC) for such configuration appears as a promising alternative for this inverter to work properly. Where the proposed FCS-MPC algorithm is designed to ensure a high grid current quality, taking into consideration the issue of the capacitor voltages balancing and the switching frequency minimisation. Both simulation results and experimental validation through real-time hardware in the loop system prove the validity and feasibility of the proposed control scheme, regarding PV power management and quality enhancement.