Enhanced Reliability of 1500-V Photovoltaic Inverters with Junction Temperature Limit Control

This paper investigates the potential to enhance the reliability of 1500-V single-stage photovoltaic (PV) inverters with a junction temperature control strategy, where PV inverters can operate either in the maximum power point tracking mode or a junction temperature limit control mode depending on the thermal stress on the inverter power devices. With this, the junction temperature of the power devices in the PV inverter can be kept below a certain limit during operation. The effectiveness (i.e., reliability enhancement) of the proposed junction temperature control on the PV inverter reliability is demonstrated on a 60-kW three-level 1500-V PV inverter installed in Denmark. Case study results indicate that the proposed control has a high ability to enhance the inverter reliability, where the lifetime of the highest stressed power device can be extended to a large extent, while incurring a negligible reduction in energy yield.