The present invention relates to an optimizer, for a solar string power generation system, comprising an Injection Circuit (IC), connected to at least one string, from an array of strings of solar panels, wherein the output of said IC is connected to the DC bus of the solar inverter. The IC comprises: (i) an MPPT mechanism, for finding the MPP of the connected string; (ii) a DC/DC converter, for converting part of the power of said connected string; wherein the DC/DC converter, converts only a part of the power of the string, that is connected to the IC, when the string is impaired, for compensating for the relative voltage difference between the voltage MPP, of the impaired string, and the MPP voltage of the DC bus of the solar inverter and the array of strings.