Simulation Analysis of Really Occurred Accident Caused by Short Circuit Failure of Blocking Diode and Bypass Circuit in the Photovoltaics System

Abstract

In Photovoltaic Systems (PVSs), Bypass Diode (BPD) and Blocking Diode (BLD) are used. However, if BPD and BLD are damaged by induced lightning, the diodes' impedance may become less than 10Ω. The currents generated by a normal string flow to a string which includes damaged BPD and BLD, and may generate heat and born out. In this paper, we investigate the cause of the accident due to BPD and BLD simultaneous breakdown actually occurred in Japan using computer simulation. The simulation results confirmed that the cause of the accident is damaged BPC and BLD. Moreover, we confirmed that the highest risk lies in the situation where PV panels are cut off from power conditioners while generating electricity.