Analysis of electrical and thermal characteristics of PV array under mismatching conditions caused by partial shading and short circuit failure of bypass diodes

Abstract

In this paper, the problems of PV arrays under partial shading and a short circuit failure of bypass diode were analyzed with modeling the mathematical equation by using simulation, and the electrical and thermal characteristics were analyzed in an outdoor with a module which fabricated assuming a real PV array. The simulation model shows the mismatch current due to a bypass diode failure is proportional to the number of fault diodes and parallel strings in PV arrays. From the results of a field experiment, a reverse current did not flow into the mismatching string under partial shading regardless of system operation status, but the temperature of bypass diode in the case of system operation was 15–23 °C higher than that of the other case. However, in case of the fault bypass diode with the system off, the reverse current of 17A flowed into a fault string. Besides, the surface temperature of fault bypass diode reached above 140 °C, and some solar cells within a fault string was 18 °C higher than normal strings. In this paper, we verified that the short circuit failure of bypass diode creates a mismatch loss in PV system, and the reverse current causes electric-thermal problems in PV array.