Inverter has power derating

Temperature derating prevents the sensitive semiconductors in the inverter from overheating. Once the permissible temperature on the monitored components is reached, the inverter shifts its operating point to a reduced power level. The power is reduced in steps. In extreme cases, the inverter will shut down completely.

In this case, the maximum DC voltage of the inverter acts more as a technical boundary than a normal operating curve. There is no PV array operating point that requires the inverter to feed in at full power at temperatures above 31°C (at 800 V). On principle, temperature derating has no negative effects on the inverter.

Derating is the controlled reduction of the inverter power. In normal operation, inverters operate at their maximum power point. At this operating point, the ratio between PV voltage and PV current results in the maximum power. The maximum power point changes constantly depending on solar irradiation levels and PV module temperature.

If the inverter remains in this state for more than a few minutes, it issues a “Derating” warning. The inverter continues to display this warning until it shuts down at sunset. Temperature derating can occur for many reasons, e.g. if the inverter cannot dissipate heat due to unfavorable installation conditions.

This behavior reduces the inverter output power ("derating"). In this document, the derating behavior of the inverters is shown in graphic form. The derating behavior is given for the minimum MPP voltage, the rated input voltage and the maximum MPP voltage.

Derating rarely occurs when the PV system is well matched. Derating is more common when the inverter is undersized relative to the PV array (see Section 2, page 2 for the causes of frequent temperature derating). You can determine the ideal design for your PV system with the "Sunny Design" software.