Analysis and Performance Evaluation of Single-Stage Three-Phase SEPIC Differential Inverter with Continuous Input Current for PV Grid-Connected Applications

Abstract

Renewable energy sources (RESs) such as Photovoltaics (PV) often experience a significant change in the output voltage terminals due to partial shading scenarios and other atmospheric conditions. This paper focuses on the performance and evaluation of SEPIC-based differential inverter (SEPIC-BDI) when used as single-stage three-phase grid-connected inverter for PV energy harvesting. The continuous input current of the SEPIC-BDI, which validated by small input film capacitor, is crucial to get high performed maximum power points tracking (MPPT) control. By integrating HFT in the utilized SEPIC converters, the inverter realizes galvanic isolation and provide high power density with low leakage current, which is essential for safety requirements at advanced PV architectures. Moreover, the design criteria accompanied by a two-loop-based d-q synchronous frame grid-current control for SEPIC-BDI are presented. The proposed control has effectively achieved grid-current management and negative sequence harmonic component (NSHC) compensation and obtained a small computational burden. Theoretical analysis is validated by building an experimental setup (0.2-1.6kW) to examine inverter capability to cope with PV variations. The THD over the recommended power range of SEPIC-BDI is also provided.