Dual inverter system with integrated energy storage for grid connected photovoltaic systems

Smooth and fluctuation free power dispatch is strongly encouraged by grid operators and therefore energy storage is becoming an indispensable part in modern large scale grid connected photovoltaic (PV) systems. As a result, associated power converter topologies and energy storage interfacing technologies are currently receiving unprecedented attention. The most common energy storage interfacing technique used in grid connected PV systems is the use of an additional power electronic converter between the energy storage system and the grid connecting inverter. Taking the disadvantages of this implementation into account this paper proposes a dual inverter based battery direct integration scheme for grid connected PV systems. In this approach, the generation of proper multilevel voltage waveforms is a complicated process, particularly when the battery is charging. A modified space vector modulation method and switching strategy are proposed in this paper to address this issue. Simulation results are presented to prove the efficacy of the proposed topology and the modulation technique.