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PV inverter performance and reliability: What is the role of the bus capacitor?

IEEE Journal of Photovoltaics

Kaplar, Robert K.; Marinella, Matthew J.; Granata, Jennifer E.

In order to elucidate how the degradation of individual components affects the state of the photovoltaic inverter as a whole, we have carried out SPICE simulations to investigate the voltage and current ripple on the DC bus. The bus capacitor is generally considered to be among the least reliable components of the system, so we have simulated how the degradation of bus capacitors affects the AC ripple at the terminals of the PV module. Degradation-induced ripple leads to an increased degradation rate in a positive feedback cycle. Additionally, laboratory experiments are being carried out to ascertain the reliability of metallized thin film capacitors. By understanding the degradation mechanisms and their effects on the inverter as a system, steps can be made to more effectively replace marginal components with more reliable ones, increasing the lifetime and efficiency of the inverter and decreasing its cost per watt towards the US Department of Energy goals.

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TYPE Journal Article YEAR 2012
OSTIDOI

Gap analysis towards a design qualification standard development for grid-connected photovoltaic inverters

Conference Record of the IEEE Photovoltaic Specialists Conference

Venkataramanan, Sai B.; Ayyanar, Raja; Maracas, George; Tamizhmani, Govindasamy; Marinella, Matthew J.; Granata, Jennifer E.

A dedicated design qualification standard for PV inverters does not exist. Development of a well-accepted design qualification standard, specifically for PV inverters will significantly improve the reliability and performance of inverters. The existing standards for PV inverters such as ANSI/UL 1741 and IEC 62109-1 primarily focus on safety of PV inverters. The IEC 62093 discusses inverter qualification but it includes all the BOS components. There are other general standards for distributed generators including the IEEE 1547 series of standards which cover major concerns like utility integration but they are not dedicated to PV inverters and are not written from a design qualification point of view. In this paper some of the potential requirements for a design qualification standard for PV inverters are addressed. The missing links in existing PV inverter related standards are identified and with the IEC 62093 as a guideline, the possible inclusions in the framework for a dedicated design qualification standard of PV inverter are discussed. Some of the key missing links are related to electric stress tests. Hence, a method to adapt the existing surge withstand test standards for use in design qualification standard of PV inverter is presented. © 2011 IEEE.

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TYPE Conference YEAR 2011
ScopusOSTI

Utility-scale grid-tied PV inverter reliability workshop summary report

Atcitty, Stanley A.; Granata, Jennifer E.; Quintana, Michael A.

A key to the long-term success of the photovoltaic (PV) industry is confidence in the reliability of PV systems. Inverters are the most commonly noted cause of PV system incidents triggered in the field. While not all of these incidents are reliability-related or even necessarily failures, they still result in a loss of generated power. With support from the U.S. Department of Energy's Solar Energy Technologies Program, Sandia National Laboratories organized a Utility-Scale Grid-Tied Inverter Reliability Workshop in Albuquerque, New Mexico, January 27-28, 2011. The workshop addressed the reliability of large (100-kilowatt+) grid-tied inverters and the implications when such inverters fail, evaluated inverter codes and standards, and provided discussion about opportunities to enhance inverter reliability. This report summarizes discussions and presentations from the workshop and identifies opportunities for future efforts.

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TYPE SAND Report YEAR 2011
OSTIDOI

A reliability and availability sensitivity study of a large photovoltaic system

Collins, Elmer W.; Mundt, Michael J.; Stein, Joshua S.; Sorensen, Neil R.; Granata, Jennifer E.; Quintana, Michael A.

A reliability and availability model has been developed for a portion of the 4.6 megawatt (MWdc) photovoltaic system operated by Tucson Electric Power (TEP) at Springerville, Arizona using a commercially available software tool, GoldSim{trademark}. This reliability model has been populated with life distributions and repair distributions derived from data accumulated during five years of operation of this system. This reliability and availability model was incorporated into another model that simulated daily and seasonal solar irradiance and photovoltaic module performance. The resulting combined model allows prediction of kilowatt hour (kWh) energy output of the system based on availability of components of the system, solar irradiance, and module and inverter performance. This model was then used to study the sensitivity of energy output as a function of photovoltaic (PV) module degradation at different rates and the effect of location (solar irradiance). Plots of cumulative energy output versus time for a 30 year period are provided for each of these cases.

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TYPE Conference YEAR 2010
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Impacts of humidity and temperature on the performance of transparent conducting zinc oxide

Yaklin, Melissa A.; Schneider, Duane A.; Granata, Jennifer E.

The impact of humidity and temperature on a zinc oxide based transparent conducting oxide (TCO) was assessed under accelerated aging conditions. An in situ electroanalytical method was used to monitor the electrical properties for a conducting zinc oxide under controlled atmospheric (humidity, temperature and irradiation) conditions. A review of thin film photovoltaic (PV) literature has shown one major failure mode of cells/modules is associated with the ingress of water into modules in the field. Water contamination has been shown to degrade the performance of the TCO in addition to corroding interconnects and other conductive metals/materials associated with the module. Water ingress is particularly problematic in flexible thin film PV modules since traditional encapsulates such as poly(ethyl vinyl acetate) (EVA) have high water vapor transmission rates. The accelerated aging studies of the zinc oxide based TCOs will allow acceleration factors and kinetic parameters to be determined for reliability purposes.

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TYPE Conference YEAR 2010
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Multiple junction cell characterization using the LBIC method : early results, issues, and pathways to improvement

Finn, Jason R.; Granata, Jennifer E.

A light beam induced current (LBIC) measurement is a non-destructive technique that produces a spatial graphical representation of current response in photovoltaic cells with respect to position when stimulated by a light beam. Generally, a laser beam is used for these measurements because the spot size can be made very small, on the order of microns, and very precise measurements can be made. Sandia National Laboratories Photovoltaic System Evaluation Laboratory (PSEL) uses its LBIC measurement technique to characterize single junction mono-crystalline and multi-crystalline solar cells ranging from miniature to conventional sizes. Sandia has modified the already valuable LBIC technique to enable multi-junction PV cells to be characterized.

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TYPE Conference YEAR 2010
OSTI

Improved test method to verify the power rating of a photovoltaic (PV) project

Conference Record of the IEEE Photovoltaic Specialists Conference

Kimber, A.; Dierauf, T.; Mitchell, L.; Whitaker, C.; Townsend, T.; NewMiller, J.; King, D.; Granata, Jennifer E.; Emery, K.; Osterwald, C.; Myers, D.; Marion, B.; Pligavko, A.; Panchula, A.; Levitsky, T.; Forbess, J.; Talmud, F.

This paper reviews the PVUSA power rating method [1-6] and presents two additional methods that seek to improve this method in terms of model precision and increased seasonal applicability. It presents the results of an evaluation of each method based upon regression analysis of over 12 MW of operating photovoltaic (PV) systems located in a wide variety of climates. These systems include a variety of PV technologies, mounting configurations, and array sizes to ensure the conclusions are applicable to a wide range of PV designs and technologies. The work presented in this paper will be submitted to ASTM for use in the development of a standard test method for certifying the power rating of PV projects. ©2009 IEEE.

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TYPE Conference YEAR 2009
ScopusOSTI

Multiple junction cell characterization using the LBIC method: Early results, issues, and pathways to improvement

Conference Record of the IEEE Photovoltaic Specialists Conference

Finn, Jason R.; Hansen, Barry R.; Granata, Jennifer E.

A Light Beam Induced Current (LBIC) measurement is a non-destructive technique that produces a spatial graphical representation of current response in photovoltaic cells with respect to position when stimulated by a light beam. Generally, a laser beam is used for these measurements because the spot size can be made very small, on the order of microns, and very precise measurements can be made. Sandia National Laboratories Photovoltaic System Evaluation Laboratory (PSEL) uses its LBIC measurement technique to characterize single junction mono-crystalline and multi-crystalline solar cells ranging from miniature to conventional sizes. Sandia has modified the already valuable LBIC technique to enable multi-junction PV cells to be characterized. ©2009 IEEE.

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TYPE Conference YEAR 2009
ScopusOSTI
60 Results
60 Results