SiC Switch based Single-Stage Buck-Boost Transformerless Mini Inverter with Low Leakage Current and Negligible DC Injection

Abstract

A novel buck-boost type single-stage transformerless topology with one energy storage inductor is proposed in this paper for single-phase grid-connected PV applications. The symmetrical operation of the topology with only one inductor minimises dc current injection into the grid. The buck-boost ability of this topology helps in achieving MPPT operation even under large variation of PV voltage. This topology, with an operating frequency of 100 kHz, uses five controllable devices out of which only one operates at high-frequency. Thus, the proposed topology has low switching losses. Only one SiC device is used to incorporate high frequency operation leading to a cost-effective solution. Other advantages of the high switching frequency include high power density, high efficiency and reduced filter size. MPPT, buck or boost operation, and dc-ac inversion are all implemented in a single power stage only. The proposed topology incurs very low leakage current. The working principle has been analysed and discussed in detail, and the simulation and experimental results are presented.