Experimental Studies of Failure Detection Methods in PV Module Strings

The diagnosis and monitoring of PV systems are important to minimize the outage period and maximize the lifetime output. The objective of this research is to develop the failure detection technologies for PV systems which can be integrated into the power conditioners. There are some failure detection methods such as thermal methods, visual methods, and electrical methods. Between these methods, the electrical methods seem to be the most appropriate to integrate into the power conditioners. To determine the position of the failed module in PV array, the time domain reflectometry (TDR) is the most promising in electrical failure detection methods. In TDR method, the inputted signal into PV cell / module / string and the reflected signal from the circuit are compared. The signal delay and the change of waveform shape are translated into the failure position in the line and the type of failure. In our fundamental experiments under the dark conditions, the line length of several cells string and the line length of a module in which many cells are connected in series could be detected by TDR. These results show the possibility that TDR can find the electrical property changes of PV modules and can be used for failure detection method. Based on these fundamental experiments, the detailed diagnosis methods should be studied in more depth for their realization into power conditioners or test equipments.