Enhancing PV system through CSI-based topology and grid-forming control

This paper proposes a novel topology for photovoltaic (PV) systems in grid-connected applications utilizing current source inverters (CSIs). In the proposed topology, a DC-DC Buck converter is employed between the PV array and the CSI to enhance the low voltage ride-through (LVRT) capabilities in compliance with grid code requirements. By leveraging the fast and linear control of the DC inductor current in the Buck converter, along with current setting in the CSI, the system enables direct power control of the grid. Additionally, a novel Maximum Power Point Tracking (MPPT) algorithm is introduced, allowing the PV array to generate the maximum active power in response to grid voltage dips, while maintaining power balance between the converter’s input and output according to the power rating of the grid inverter. Furthermore, both grid-following and grid-forming control strategies are implemented in the system and compared under severe LVRT scenarios in a strong grid environment. The system is also evaluated for LVRT and phase jump performance using grid-forming control in a weak grid condition. The test results are derived from simulations performed using Plecs software.