The plant comprises: a DC-voltage electric power source (3), whose operating conditions vary as a function of at least one uncontrollable quantity, for each value of the uncontrollable quantity the source presenting a characteristic curve of the supplied power as a function of a controlled quantity, wherein each characteristic curve presents a maximum for an optimal value of said controlled quantity; a power conditioning circuit (5); a regulation loop (9) to adjust the controlled quantity maximizing the power supplied by the source when said uncontrollable quantity varies. The regulation loop is de-signed in such a way as to determine whether, for the actual value of said uncontrollable quantity, the actual value of the controlled quantity (V.in) is greater or lower than the optimal value and to generate a regulation signal (V.in-REF) to modify the actual value of the controlled quantity towards the optimal value.