A multi-string photovoltaic inverter for thin-film or back-side contacted solar modules

Photovoltaic inverters are widely used to feed solar generated power into the public grid. Inverter topologies have to be carefully chosen, depending on the type and on the power of the solar generator. A new transformerless, three-level photovoltaic inverter circuit for multiple strings is investigated in this paper. It allows an individual MPP tracking of each string without needing a full scale boost converter for each input. Furthermore, either the positive poles or the negative poles of the strings can be connected to the neutral conductor N. Therefore, the topology is especially suited for thin-film or back-side contacted solar modules.