A Thermal Stress Sharing Voltage Source Inverter and Sequential PWM Technique for Lifetime Enhancement of IGBTs

The failure of voltage source inverter (VSI) is primarily caused by thermal stress across its component switches. In the commonly used H-bridge VSI, the switches experience considerable thermal stress thereby reducing its reliability and lifetime. Hence, this paper presents a thermal stress sharing single phase VSI (TSSI) to decrease the thermal stress and prolong the lifetime of IGBTs. The proposed TSSI incorporates switches in parallel to the existing switches of H-bridge VSI in order to achieve thermal sharing. To ensure appropriate operation of parallel switches, a novel sequential pulse width modulation (Seq-PWM) technique is devised. The improvement in lifetime expectancy of proposed TSSI with Seq-PWM is evaluated by comparing power loss and thermal analysis with those of H-bridge VSI with conventional PWMs. The theoretical analysis is validated with simulations in PLECS software and experiments on a hardware prototype. The results suggests that the life-span of the TSSI with Seq-PWM is improved multi-fold. Therefore, due to its increased lifespan, the proposed TSSI with Seq-PWM is expected to save the expenses of frequent replacement of VSIs.