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Currently, the production and installation quantity of photovoltaic modules has been increasing rapidly. Meanwhile, the failure cases are also increasing. Accordingly, many failures are results of the Hot-Spot phenomenon. This is a phenomenon in which the entire or part of the defective cell becomes hot when shadow occurs on the cell for a long period. In severe cases, the phenomenon causes breaking of the cell and a fire. While there are many Hot-Spot inspection methods, such as using infrared cameras, the inspection instruments of these methods are expensive, and these methods also require a lot of time and effort during the inspection. Previously, the authors proposed a Hot-Spot detection system included into PCS. In this paper, we proposed plug-in type Hot-Spot detection system, and report about effectiveness of the system.

Currently, the production and the number of installations of PV (photovoltaic) modules have been increasing rapidly because of a feed-in tariff in Japan. Accordingly, the number of failures has also increased. Many failures are a result of the Hot-Spot phenomenon in which defective cell becomes hot when shadow occurs on the cell. On the other hand, if shadow occurs on normal cell, there are cases that P&O method that is MPPT (maximum power point tracking) control method incorporated in conventional PV system cannot track maximum power point and generated power decreases. The correspondence is required rapidly if these trouble occur. However, conventional PV system monitors generated power, correspondence is impossible by monitoring generated power. Previously, the authors developed real time Hot-Spot detection system that incorporates into PCS (power conditioning system). Thus, the authors developed plug-in type Hot-Spot monitoring system that includes "PV peak shift method" and confirmed effectiveness of the system in this time. "PV peak shift method" loads "Scan method" that is MPPT control method and measures I-V (current-voltage) characteristic by changing voltage of module from open to short by "Scan method" on a regular basis. The developed Hot-Spot monitoring system uses slope of I-V characteristic of PV module. Inserting developed system into already installed PV system, Hot-Spot can be easily monitored in real time and PV system can be operated at maximum power point.