Exclusion of PV Inverter Measurement Data Affected by Power Clipping and Detection of String Disconnection

High-quality operation and maintenance services are vital to the health of large photovoltaic (PV) power plants. Diagnosis methods using the electric energy data measured by PV inverters (PVIs) are widely applicable and cost-effective. It is usual that PVIs have connection of PV modules exceeding those rated power. In this work, it is reported that the power clippings by PVIs can occur even in the winter. Exclusion of the measured data affected by the power clipping causes the ratios of two PVI’s electric energies to be stabilized. It is demonstrated that the string disconnections can be detected using the ratios.