FAULT ANALYSIS OF STRING BASED INVERTERS PV PLANT WITH THE REFERENCE TO HARMONICS RESONANCE EFFECT

The paper analyzes a photovoltaic (PV) power system plant based on string inverters operating in parallel and it specifically analyzes the faults experienced in the plant system. A fault classification and a root-cause analysis oriented to be used for reliability improvement are done based on field experience acquired through long-term operation and maintenance activities in a 536 kW PV power plant. The harmonic resonance effect, that can appear with significant negative consequences in multiple string inverters based PV systems, is carefully considered as being one of the most frequent reasons for operation faults. Practical reliability improvement suggestions are also given.