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Evaluation of the DC Bus Link Capacitors and Power Transistor Modules in the Qualification Testing of PV Inverters
P. Hacke, D. Clemens, R. Thiagarajan, J. Flicker, H. Igarashi
Photovoltaic Modules and BoS Components
Subtopic: Inverters and Balance of System Components
Event: 37th European Photovoltaic Solar Energy Conference and Exhibition
Session: 4DO.7.5
ISBN: 3-936338-73-6
0,00 EUR
Document(s): presentation


To achieve useful, fair, and cost-effective design qualification and type approval testing for PV inverters, two procedures were developed and demonstrated to evaluate the bus link capacitors and power transistor—and where applicable, its module—for long term reliability. We evaluate the inverter under simulated use conditions with a heat run tests to find the highest operating temperatures reached by these components. The procedures are demonstrated in this study with a 4-kW class string inverter. The maximum temperature of the DC bus link capacitors was determined to be 76.4°C when the ambient temperature was at the inverter’s maximum rated temperature of 60 °C with derating occurring. On the other hand, the power transistor module’s maximum temperature using the heat sink temperature as the index, 86.0 °C, occurred in an ambient of 42.8°C when derating was not occurring. The conditions found for upper temperatures exhibited by these components are respectively implemented in the dry heat and thermal cycling tests in IEC 62093 “Power conversion equipment for photovoltaic systems – Design qualification testing” draft so that the levels applied in the tests are in proportion to those experienced in the field. As a result, fairer evaluation of inverter reliability is realized.