Active thermal control of IGBT power electronic converters

Thermal cycling is one of the main sources of aging and failures in power electronics. A possibility to reduce the stress to semiconductors is to control the amount of losses that occur in the device during operation. This work presents an active thermal controller that aims at reducing the junction temperature variations in the case of variable power profile. The switching frequency of the converter is the parameter that is affected by the active thermal control, while the operation of the converter remains unchanged. The novelty of the approach is that the switching frequency variation is exploited to prevent excessive cooling down of the semiconductor during a power reduction. A thermal model is used to estimate the losses, so the prior knowledge of the mission profile is not needed. The results of the proposed solution are validated with an experimental prototype and a wide-bandwidth temperature measurement system directly applied to the semiconductor chip. Finally, the impacts of the controller on the module's lifetime is estimated.