Turn-on control method and turn-on control circuit for an invertor coupling a solar generator to the electricity mains

摘要

Known turn-on control methods and turn-on control circuits provide the monitoring of the solar generator no-load voltage (open-circuit voltage), the invertor being activated when this voltage exceeds a predetermined threshold value. The turn-on accuracy is unsatisfactory because the no-load voltage is strongly dependent on the module temperature. In contrast, the novel method provides the measurement of the short-circuit current of the solar generator (1) and the stipulation of a corresponding short-circuit current threshold value, the invertor being turned on in the event of this threshold value being exceeded. A circuit relating to this contains a short circuit (Ki) with a short-circuit current measuring element (2) as well as an evaluation unit (10, 3, 4) for identifying when the threshold value is exceeded and the invertor is activated. On account of the comparatively low dependence of the short-circuit current on the temperature, very accurately timed turning-on of the invertor is produced for varying solar module temperatures. Use in photovoltaic installations which feed power to the electricity mains. IMAGE