Single-Phase Transformerless Buck-Boost PV-Inverter For Leakage Current Minimization

This paper presents a novel transformerless buck-boost single-stage topology with a single energy storage inductor, designed for single-phase grid-connected PV applications. The symmetrical operation of the proposed topology, considering a single inductor, effectively minimizes the DC-current injection into the grid. The buck-boost capability of this design enables Maximum Power Point Tracking (MPPT) even under large variations in PV voltage, which make this structure applicable for wide range of input voltage variations. Operating at a frequency of 85 kHz, the topology employs five controllable devices, with only one functioning at high frequency, resulting in low switching losses. Using a single SiC fast device for high-frequency operation contributes to a cost-effective solution. Additional benefits of high switching frequency include increased power density, enhanced efficiency, and reduced filter size. MPPT, buck or boost functionality, and DC-AC inversion are all achieved within a single power stage. The proposed topology also exhibits a low leakage current. The paper provides a detailed analysis of the operating principle, supported by simulation results.