Alternate method for evaluating power-temperature derating characteristics of grid tie solar photovoltaic inverter

The existing method for evaluating the derating characteristics is generally carried out with the use of a thermal cyclic chamber based on manufacturer requirements as there are no international standards pertaining to this characteristics test. This paper proposes an alternative test method which is developed for manufacturers and test laboratories across the world which can easily be adopted because of its advantages like low cost in terms of investment, practicality, accuracy and less time-consuming. The proposed alternate method for the temperature derating test is validated by carrying out the test on a three-phase 60 kW grid tie solar PV inverter with input DC MPPT voltage of 850 V. The experimental analysis and results show that during the power- temperature derating process, the variations in input DC voltage, output AC voltage, frequency, power factor, and voltage harmonics are constant. The variations were observed in the output AC current and input DC current showed a similar pattern by having maximum value during maximum continuous power delivery period i.e. 66 kW active power output and starts decreasing to 43 kW till the inverter tripped. It is concluded that the temperature difference (ΔT) between the external ambient air temperature and the internal ambient air temperature plays a major role in the power-temperature derating process of an inverter.