Utilization of Inverter Operating Point Shifts as a Quality Assessment Tool for Photovoltaic Systems

Abstract

This paper presents a novel approach for the automated identification of electrically impaired strings in photovoltaic (PV) systems, which is solely based on monitored inverter data. By shifting the inverter operating points of two or more strings to a common voltage level on the direct current side, the effect of defects such as bypassed substrings is actively amplified so that defects can be detected reliably. The presented Common Voltage Test is illustrated using an electrical simulation based on the extended two-diode model. The effectiveness of the proposed approach is demonstrated using real monitoring data of an inverter in a PV power plant in Bavaria, Germany. For validation, electrically defective PV modules within the PV system are identified and located using aerial infrared thermography. Facilitating an automated reliable detection of faulty strings in PV systems, the approach is especially useful for large-scale PV power plants since only the faulty strings need to be examined in greater detail. Consequently, the maintenance becomes more efficient so that the maintenance costs may be reduced significantly.