In recent years, the transformerless photovoltaic (PV) systems are receiving more and more attentions in both academic and industrial fields. The main advantages of these kinds of systems are small size, low cost and high efficiency. However, there are several technical challenges, such as dc injection, leakage current, which should be dealt with before successfully integrating them into the grid. The objective of this special session is to focus on the related issues regarding the transformerless PV systems, to provide an open opportunity for presentation and discussion of recently advanced technologies, while promoting academic and industrial interaction and cooperation.