A transformerless grid connected inverter for solar photovoltaic systems having capability to negotiate DC loads

This paper presents a multipurpose converter for solar photovoltaic (PV) systems. The main purpose of this converter is to serve as a transformerless grid connected inverter having solar PV array at its input. In addition to this the same converter can be employed for catering to dc load simultaneously. The aforementioned dc load can be supplied from the PV array and/or the grid. Thus the proposed converter can serve as dc to ac inverter, dc to dc converter, and ac to dc converter. The converter operates in buck-boost mode which allows wide variation in PV array voltage. Further, the structure of the converter is based on neutral point clamped structure which eliminates concerns pertaining to leakage current issue in grid connected transformerless PV systems. The converter is free from shoot through fault and does not require grid current sensing for its operation. The principle of operation of the converter and its control structure is presented. The scheme is validated through detailed simulation results.