Deciphering the Power Derating Due To Temperature In Commercial Photovoltaic Inverters
Abstract
Commercial photovoltaic inverters operating in harsh conditions activate self-protection that reduces power, undermining energy yield and service life. Manufacturers’ datasheets seldom disclose full derating curves, and there is no standard test protocol. This study proposes and validates a structured, reproducible method to quantify thermal power derating and verify adherence to manufacturer specifications. It also combines a controlled thermal chamber, PV emulator source, and utility grid emulator with temperature steps from 25 to 60 °C. Tests on two single-phase 8 kW inverters show that Inverter A is derated by 17.8% at nominal voltage and 9.2% at maximum voltage, with onset at 50–55 °C, despite catalog claims of no derating. Inverter B reached 33.6% at nominal voltage and 27.9% at minimum voltage, with thermal shutdown at the minimum voltage and onset at 50–60 °C. Performance differences align with cooling strategies: forced plus natural convection maintained continuous operation, whereas natural convection alone led to progressive heat buildup and instability. The findings support publishing complete derating curves at multiple MPP voltages and requiring independent tests in technical due diligence. The proposed protocol improves cross-lab comparability and narrows the gap between stated and delivered field performance.
Keywords
Photovoltaic, Inverters, Thermal, Power Derating, Standard, Laboratory Test