Increasing Efficiency and Lowering Costs for Solar Photovoltaic Systems
Prof. Katherine A. Kim co-authored the paper entitled “Converter Rating Analysis for Photovoltaic Differential Power Processing Systems,” published in the IEEE Transactions on Power Electronics. For photovoltaic (solar cell) power generation systems, high efficiency and low cost are important factors to achieve world-wide adoption. Differential power processing (DPP) is a recently-introduced architecture for photovoltaic systems that increases efficiency while decreasing the cost of the power converters. This paper uses analytical simulations to model photovoltaic systems as they degrade over their 25-year lifetime, and identifies appropriate power ratings for various types of DPP power converters that result in the most effective performance over the system’s full lifetime.
Title: Converter Rating Analysis for Photovoltaic Differential Power Processing Systems
Authors: Katherine A. Kim, Pradeep S. Shenoy and Philip T. Krein
Abstract: When photovoltaic (PV) cells are connected in series, they experience internal and external mismatch that reduces output power. Differential power processing (DPP) architectures achieve high system efficiency by processing a fraction of the total power while maintaining distributed local maximum power point operation. This paper details the computational methods and analysis used to determine the operation of PV-to-bus and PV-to-PV DPP architectures with rating-limited converters. Simulations for both DPP architectures are used to evaluate system performance over 25 years of operation. Based on data from field studies, a PV power coefficient of variation can be estimated as 0.086 after 25 years. An improvement figure of merit reflecting the ratio of energy produced to that delivered in a conventional system is introduced to evaluate comparative performance. Converter ratings of 15-17% for PV-to-bus and 23-33% for PV-to-PV architectures are identified as appropriate ratings for a 15-submodule system (five PV panels in series). Both DPP architectures with these ratings are shown to deliver up to 2.8% more power compared to a conventional series-string architecture based on the expected panel variation over 25 years of operation. DPP converters also outperform dc optimizers in terms of lifetime performance.
Journal: IEEE Transactions on Power Electronics (IF: 6.008)
Publication Date: April 2015