Photovoltaic power conditioning units

A photovoltaic (PV) panel system comprising:

• a PV panel in combination with a power conditioning unit for providing ac power from the PV panel,
• wherein the PV panel comprises a string of series connected solar cells having first and second connections to either end of the string and having at least one tap connection between first and second connections to define a plurality sub-strings of the string, each sub-string having an electrical connection at either end, and
• wherein the power conditioning unit comprises:
• a set of input power converters, one for each of the plurality of sub-strings, each having a pair of dc input connections connected to either end of a sub-string, each of the set of input power converters having a power output;
• and
• a common output power conversion stage coupled to the set of input power converters to provide an ac output from the power conditioning unit.