基于载波重构的级联 H 桥变流器可靠性提升策略

To address the issue of uneven thermal stress distribution in power devices under in-phase disposition PWM (IPD-PWM), an improved carrier disposition PWM strategy is proposed. Aimed at enhancing the reliability of converter systems, this strategy leverages the concept of carrier reconstruction by optimizing the dynamic distribution ranges of modulation waves and carriers. With a focus on balancing the switching losses among submodules, the mechanism by which the modulation wave range influences switching losses at varying modulation ratios is analyzed in depth. The results of Matlab-PLECS co-simulation thermal modeling and experiments on a seven-level converter platform verify that the improved strategy achieves balanced thermal stress distribution in power devices while maintaining output harmonic characteristics identical to those under the traditional IPD-PWM. Consequently, the overall lifetime of the converter is significantly extended.