Title:	Update on Rankings of Conversion Efficiencies and Energy Yield of Micro-Inverters, Including Inverters for Two PV Modules
Author(s):	S. Krauter, J. Bendfeld
Keywords:	Power Conditioning, Yield, Small Grid-Connected PV Systems, Inverter
Topic:	Performance, Reliability and Sustainability of Photovoltaic Modules and Balance of System Components
Subtopic:	Inverters and Balance of System Components
Event:	33rd European Photovoltaic Solar Energy Conference and Exhibition
Session:	5DO.5.1
Pages:	1477 - 1481
ISBN:	3-936338-47-7
Paper DOI:	10.4229/EUPVSEC20172017-5DO.5.1
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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To compare efficiency and yield of most micro-inverters available on the world market in 20142017, an in- and outdoor test laboratory at the University of Paderborn have been set up. The inverters have been fed by identical and calibrated crystalline silicon PV modules of 215 Wp. To monitor accurately AC power output and yield, each of the micro-inverters has been equipped with a calibrated precision electricity meter. For micro-inverters requiring control units for grid-feeding that has been acquired also. The comparison includes energy yield over one to two years and efficiency-load characteristics. Purchase costs vary considerably between the models in comparison, sometimes inverter costs are higher than module costs, particularly if an additional grid-connection or interface device is necessary for operation. The weighted conversion efficiency according to EU and CEC standards has been measured and compiled. While some inverters have been optimized for high irradiance levels, they ranked better at the CEC efficiency, others performed very well also for low irradiance levels, thus ranking higher at in the EU-efficiency tables. These results deviated from the actual energy yield measurements, which showed a slightly different ranking. One device showed an extreme deviation of the efficiency rating from the yield results. An accurate but very slow MPPT algorithm that hardly could follow quickly changing irradiance conditions has possibly caused this effect. Apparently, some inverters are been optimized to show excellent EU and CEC efficiency ratings. The new inverters featuring two inputs did not show an exceptional performance at the EU- and CEC-ratings (ranking 58 only), but they achieved rank 1 and 2 at the AC energy yield ranking. For the customer the AC yield is a major performance indicator of the microinverter and should be included in the datasheet. Further investigations are on the way, including degradation and temperature effects