H6 inverters are one of the new technologies for solar inverters. The thermal stress of power semiconductor devices (PSDs) of the H6 inverter dictates their lifetime. At NCPRE, we have studied two existing modulation schemes for H6 inverters, and analysed their thermal stress distribution. It is found that unequal stress distribution exists among PSDs for both modulation strategies.

This results in the early failure of some PSDs, which forms a weak link in the design of the inverter. To address this issue, a hybrid modulation strategy and associated thermal controller for the lifetime enhancement of PSDs in the H6 solar inverter is proposed. The proposed thermal controller dictates the hybridization angle to equalize the thermal stress of the PSDs.

The simulation studies show that the thermal controller varies the hybridization angle between 7° and 56°. With the help of this variation, even distribution of thermal stresses among the PSDs is achieved. The proposed technique achieves 26.5% improvement in lifetime for the selected solar mission profile. This work was done by NCPRE students Abhishek Chanekar, Nachiketa Deshmukh, and Akash Gangwar, under the guidance of Prof. Sandeep Anand.