In-situ condition monitoring system to study the ageing of power semi-conductor devices in photovoltaic inverters

摘要

This paper presents a new method for in-situ condition monitoring of semi-conductor devices, in photovoltaic DC/AC inverters. It consists on measuring the voltage drop across the Collector-Emitter junction, the dynamic resistance and the thermal impedance of each device. Using this method, the monitoring can be done without disconnecting the drivers, neither the DC-link capacitors, nor the DC-link bus. Moreover, the condition monitoring is done under the actual DC-link voltage, hence there is no need for an independent current source. This method was tested in an accelerated ageing test bench, and validated by comparison with classical measurement tests. In addition, examples of condition monitoring implementation in DC/AC photovoltaic inverters are finally proposed.