Photovoltaic Inverter Reliability Assessment
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
As the price of PV modules drops, the price of power electronics become more important. Power electronics now constitute 8%-12% of the total lifetime PV cost. As of 2010, the inverter and associated power conditioning components accounted for $$\$$0.25$/W, well above the DOE benchmark of $$\$$0.12$/W by 2020. As efforts to reduce PV module costs yield diminishing returns, the importance of understanding and reducing inverter costs becomes an increasingly critical and cost-effective investment toward achieving the DOE SunShot goals. With this in view, this report showcases and describes an approach to help assess and predict the reliability of photovoltaic (PV) inverters. To predict the reliability, thermal cycling is considered as a prominent stressor in the inverter system. To evaluate the impacts of thermal cycling, a detailed linearized model of the PV inverter is developed along with controllers. This research also develops models and methods to compute the losses of the power electronics switches and other components in a PV inverter. The losses are then used to estimate the junction and heat sink temperature. The model is verified by developing an in-house inverter. Additionally, to assess the scalability of the research, the hardware inverter is placed inside a thermal chamber to verify the losses for different ambient temperatures. After the verification of the model, a reduced-order model of the inverter is implemented to translate the profile of ambient temperature and solar irradiance into the profile of junction temperatures of the switches. The estimated junction temperature data are used to identify inverter reliability indices and predict the useful lifetime of the inverter system. After developing the models to predict the useful lifetime of the system, the impact of reactive power on the overall reliability of the system will be studied. The first chapter involves the motivation behind the research on assessing the reliability of PV inverters. The inverter power stage and controller design of the power converter used in this research is also explained in detail in this chapter. The second chapter presents the various losses of the power converter system and the translation of power loss into temperature increase with thermal modeling. The results of the loss modeling and the thermal modeling are also explained in detail in this chapter. The third chapter involves implementing the reduced-order model to translate the mission profile of ambient temperature and solar irradiance into profile of the junction temperatures of the switches. The final chapter involves identifying reliability indices, which are of interest for this system to predict the remaining useful life of the system, and concludes with the impact of reactive power on the overall reliability of the inverter system.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1573462
- Report Number(s):
- NREL/TP-5D00-74462
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effect of Reactive Power on Photovoltaic Inverter Reliability and Lifetime: Preprint
Effects of Reactive Power on Photovoltaic Inverter Reliability and Lifetime