Field installation and evaluation of a 20kw rooftop PV system using 3.5kw string level MPPT DC/DC converters and a central inverter

Abstract

High energy yield has been and continues to be a major driver in PV installations. With the continuous improvement in PV modules' performance, there is a need to extract as much power as possible from the modules under various weather conditions. Over the past three years, we proposed, analyzed, built, installed, and monitored a PV system with string level MPPT dc/dc converters and a central inverter to understand and quantify the benefits of distributed MPPT. Our team performed detailed simulation studies on multiple architectures (module level to multi-string level MPPT), quantified the benefits of each architecture, selected an approach (string level), and designed a novel high efficiency partial power dc/dc converter, built it and tested it in the lab (with a PV emulator) and in the field with actual PV strings and a grid tied inverter. A rooftop installation was built with two systems side by side (a distributed and a central inverter) and has been monitored over the past 9 months.