Coordinated PWM-Based Active Thermal Control for Power Semiconductor Devices in Parallel Grid-Tied Inverters

This article proposes a new active thermal control method for power semiconductor devices in parallel grid-tied inverters using coordinated pulsewidth modulation (PWM), which breaks the limitation that the PWM-based active thermal control cannot reduce the switching frequency below rated value, and therefore provides more regulation freedom to improve the reliability of power semiconductor devices. In specific, both frequency and phase shift values of PWM sequences will be adjusted coordinately to relieve the junction temperature of parallel inverters while keeping the total high-frequency harmonics at point of common coupling (PCC) to meet the quality requirement. The presented method is applicable to parallel inverters with identical or different input power. Finally, experimental results verified the performance of the proposed method.