Dynamic performance analysis of a PV-SEPIC-based grid-forming converter

This paper analyses the dynamic performance of a grid-forming (GFM) converter supplied by a photovoltaic (PV) source through a Single-Ended Primary Inductor Converter (SEPIC). For the analysis, the conventional MATLAB/Simulink “Design and Analyse Grid-Forming Converter” model is modified by replacing the ideal DC source with a SEPIC-interfaced PV source controlled via an incremental-conductance (InC) maximum power point tracking (MPPT) algorithm. The modified configuration enables evaluation of the GFM inverter response under predefined frequency test conditions specified in the Great Britain Grid-Forming (GBGF) specification. Three frequency-ramp test scenarios are investigated in the simulations to evaluate the dynamic performance of the SEPIC-PV and ideal DC-source setups. The results demonstrate that the PV–SEPIC system presents low-frequency oscillations (1–3 Hz) and longer rise times due to finite input power and converter dynamics, while still maintaining stable voltage and frequency regulation within the GBGF limits. This work provides new insights into the use of a PV-SEPIC-based GFM converter, which has not been previously reported in the literature. Additionally, it highlights the importance of accurately modelling DC-side dynamics in renewable-fed GFM converters and offers guidance on testing and design considerations for GFM technologies used in PV-integrated power systems.