A Transformer-less Hybrid PV Inverter with Integrated Battery Energy Storage

In this paper a transformer-less hybrid PV inverter with integrated battery energy storage is proposed. The proposed converter integrates both solar PV and battery sources with the ability to control for maximum power transfer as well as control the charge discharge functions of a battery energy storage system. The proposed control employs a single current and single voltage sensor with perturb and observe based method to achieve maximum solar power and battery state of charge control. The proposed interleaved modular multilevel converter boosts the dc link voltage to suitable value to enable transformer-less interface to the electric commercial utility grid. It is shown that ZVS operation will yield higher conversion efficiency. Simulation results validate the concept over a wide operation range. Preliminary experimental results are discussed.