Mitigation of Oscillations in Switching Frequency-Based Active Thermal Control

Power electronics modules are highly susceptible to thermal cycling stress during operation, which can significantly reduce their lifespan. Active thermal control (ATC) techniques are deployed to mitigate this stress and enhance module longevity. Among the various ATC strategies, switching frequency-based active thermal control (SF-ATC) is the simplest and most commonly used to suppress the junction temperature variation, reducing the accumulated damage. However, this method can lead to oscillations and instability in the switching frequency, which can negatively impact both the power converter operation and the ATC performance. While solutions to mitigate oscillations have been proposed, the issue of instability has not been adequately addressed in the literature. This study presents a comprehensive analytical and Simulink-based simulation and investigation of the switching frequency instability in SF-ATC. Furthermore, a modification of the classic SF-ATC is proposed to mitigate oscillations and instability. The proposed SF-ATC aims to enhance the overall ATC performance in terms of thermal swing reduction and limit the impact on the converter operation (e.g., power quality). The effectiveness of the proposed method is then experimentally validated.