Method and apparatus for protection of several strings of photovoltaic generator from reverse currents

To protect several strings (2) of a photovoltaic generator (3) that are connected in groups via a respective DC / DC converter (8) to a common DC intermediate circuit parallel (4), before flowing back, the over each of the DC / DC converter (8) detects the current flowing and an occurring return flow (17) through one of the DC / DC converter (8) / DC converter (8) is terminated by driving the DC.