Inverter, Reliability, Qualification and Testing, System Performance
Summary / Abstract:
To understand the impacts of humidity on photovoltaic (PV) inverters, mission profiles were developed to accurately describe the different processes and rates based on the environmental factors of temperature, relative humidity, and irradiance. The operating environment of the device introduces stress factors dependent on component temperature, relative humidity, and component voltage. The development of profiles started from looking at historical climate conditions at Cocoa, Florida, a hot and humid location. The profile developed from the field location was compared with existing humidity test profiles in industrial and military standards to determine acceleration factors. Prior to the evaluation of the mission profiles, critical components in the PV inverter were identified based on vendor discussions along with failure modes of interest. The profiles considered in this study were demonstrated using a 4- kVA string inverter. The measurements from the critical components including film capacitor were substituted in the device manufacturer-specified equation to determine the severity of each test. The severity of each test was compared against the severity of the 24-hour result to determine the acceleration factor of each test. The acceleration factors were determined to be within a range of 1.2-6 for the existing humidity tests from standards when compared against the mission profile developed from field data. This optimal humidity/thermal profile will be passed to the International Electrotechnical Commission (IEC) standards development group for inverter qualification testing.