This work treats about the development of fault diagnosis strategies applied Photovoltaic (PV) systems. The proposed methodology uses the comparison between the model and measurement divided in two parts: First part, a model of high detail is designed pf the PV system to allow to detect faults. A model to emulate electrical characteristics of PV system under faults conditions is developed. The second part of the work treats about the method of fault detection for power converters connected into the grid. Real-time emulation allows validating results of fault-detection algorithms also in Real Time.