A Novel Battery-Integrated Transformer-Less Microinverter for Solar PV Applications

Solar PV micro-inverters are typically designed to be operated in grid-connected mode. By interfacing a battery with a micro-inverter, it is possible to minimize the wide variations in power drawn from solar PV module. In this article a battery-integrated transformer-less solar PV micro-inverter is proposed which can integrate a battery having voltage lower than that of the PV module. Depending on the available solar irradiation and the battery's state of charge, it simultaneously regulates the battery current and the current drawn from the PV module. Although it is suitable for getting interfaced with a 220 V ac grid, it can also operate in a standalone mode in the absence of the grid. The proposed micro-inverter has inherent power decoupling capability, and the existence of double grounding ensures that there is no leakage current flow. In-depth analysis of the proposed scheme is carried out. An appropriate control algorithm is developed for operating the micro-inverter under different conditions. The feasibility of the proposed scheme is validated by performing detailed experimental studies on the prototype developed for the purpose.