Flying-capacitor topology for grounding of single-phase transformer-less three-level photovoltaic inverters

This paper presents a new inverter topology named after its operating principle based on a flying capacitor. The inverter uses neither a grid transformer (50/60 Hz) nor a high frequency transformer and therefore does not provide a strict galvanic isolation. However, its innovative circuit has been designed in order to allow grounding one pole of the photovoltaic (PV) generator which is not feasible with common transformer-less PV inverters. The slight drop in efficiency and increase in size and costs due to the use of more numerous semiconductors and additional passive components is well below that of inverters using high or low frequency transformers and is fully compensated by decisive technical advantages. Indeed, the ability to ground the DC side of the inverter can be of a great interest for certain PV generators but also for other kinds of applications such as batteries.