A distributed power harvesting system comprising: a plurality of DC power sources (301,401,301,601,701); a plurality of converters (305,405,505,605,705), and wherein each of the converters (305,405,505,605,705) comprises: i input terminals (614,616,716) coupled to a respective DC power source (301,401,301,601,701); ii output terminals (610,612,712) coupled in series to the other converters (305,405,505,605,705), thereby forming a serial string; and iii a power conversion portion for converting the power received at the input terminals (614,616) to an output power at the output terminals (610,612,712); and a power delivery device (304,404,504) coupled to the serial string, characterized in that the converters (305,405,505,605,705) are buck plus boost converters each comprising a buck converter, a boost converter, a controller and a circuit loop (608,708) setting the voltage and current at the input terminals (614,616,716) of the buck plus boost converters (305,405,505,605,705) according to predetermined criteria; wherein, in response to the MPPT part and current or voltage at the output terminals (610,612), the controller either selectively activates either the buck converter or the boost converter or activates the buck converter and the boost converter together, and that the power delivery device (304,404,504) comprises a control part maintaining the input voltage to the power delivery device (304,404,504) at a predetermined value. a plurality of DC power sources (301,401,301,601,701); a plurality of converters (305,405,505,605,705), and wherein each of the converters (305,405,505,605,705) comprises: i input terminals (614,616,716) coupled to a respective DC power source (301,401,301,601,701); ii output terminals (610,612,712) coupled in series to the other converters (305,405,505,605,705), thereby forming a serial string; and iii a power conversion portion for converting the power received at the input terminals (614,616) to an output power at the output terminals (610,612,712); and i input terminals (614,616,716) coupled to a respective DC power source (301,401,301,601,701); ii output terminals (610,612,712) coupled in series to the other converters (305,405,505,605,705), thereby forming a serial string; and iii a power conversion portion for converting the power received at the input terminals (614,616) to an output power at the output terminals (610,612,712); and a power delivery device (304,404,504) coupled to the serial string, characterized in that the converters (305,405,505,605,705) are buck plus boost converters each comprising a buck converter, a boost converter, a controller and a circuit loop (608,708) setting the voltage and current at the input terminals (614,616,716) of the buck plus boost converters (305,405,505,605,705) according to predetermined criteria; wherein, in response to the MPPT part and current or voltage at the output terminals (610,612), the controller either selectively activates either the buck converter or the boost converter or activates the buck converter and the boost converter together, and that the power delivery device (304,404,504) comprises a control part maintaining the input voltage to the power delivery device (304,404,504) at a predetermined value.