This paper presents a single-phase transformerless grid-connected photovoltaic converter based on two cascaded full-bridges with different DC-link voltages. The converter can synthesize up to nine voltage levels and needs only a single DC supply bus, since one of the full bridges is supplied by a flying capacitor. The multilevel output reduces harmonic distortion and electromagnetic interference. A suitable switching strategy is employed to regulate the flying capacitor voltage, improve the efficiency (most devices switch at grid frequency) and minimize the common-mode leakage current with the help of a novel dedicated circuit (transient circuit). Simulations and experiments confirm the feasibility and good performance of the proposed converter.
A Nine-Level Grid-Connected Converter Topology for Single-Phase Transformerless PV Systems / G. Buticchi; D. Barater; E. Lorenzani; C. Concari; G. Franceschini. - In: IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS. - ISSN 0278-0046. - 61:8(2014), pp. 3951-3960. [10.1109/TIE.2013.2286562]