A Transformerless Three-Level Flying-Capacitor Step-up PV Micro-Inverter without Electrolytic Capacitors

Voltage step-up, DC/AC inversion, and active pulsating-power-buffering are three indispensable functions of next-generation PV micro-inverters. Conventionally, these three functions are realized by separate power-conversion stages, resulting in lower conversion efficiency and a higher cost. In this paper, a new hybrid topology capable of merging all three functions into a single power-conversion stage is proposed. The topology enjoys all the benefits of system integration, including simple circuit structure and low bill-of-materials. It also features low voltage stresses, significantly reduced energy storage requirement of the passive components, and low leakage current, potentially leading to highly compact and high efficiency design. A 60-W hardware prototype is built to demonstrate the feasibility of the proposed inverter. An efficiency over 95% across a wide load range has been experimentally obtained.