In recent years worldwide grid-connected solar photovoltaic (PV) systems deployment, in residential, commercial, and utility scale markets, is experiencing significant growth. With the increasing share of distributed, independent power producer (IPP) and utility owned generation portfolios, these PV plants' components, especially the inverters, are commanding a greater level of attention to assure availability and performance. A recent study by one of the major PV fleet operators with 500 PV plants concluded that PV inverters are responsible for the 69% of the recorded downtime event. There have been several reported incidents in Europe where emissions from PV inverters have interfered with electronic revenue metering. With increased PV inverter deployment there is an increased need to share selection and qualification and documentation best practices that lead to improved plant reliability and uptime.
The work discussed here addresses key issues and describes utility current practices for selecting, qualifying and accepting PV inverters. Presently there are no complete performance criteria for grid-connected inverters. As penetration levels rise, utilities will increasingly need clear, complete specifications that can be easily referenced and broadly supported. Considering the interconnection resemblance and maturity, electricity metering industry specifications are closely studied to provide insight into the nature and extent of criteria needed for PV inverters. This report also provides a brief description of existing electric grid interconnection, communication, and safety standards and certifications applicable to PV inverters. Commercially available utility-scale (= 250kW) grid-connected inverters are studied and comparisons are made in terms of various parameters including DC, AC, environmental, and communication.