Thermally Compensated Discontinuous Modulation Strategy for Cascaded H-Bridge Converters

A widely adopted multilevel converter topology is the cascaded H-bridge (CHB), as it can provide voltage and power scalability. However, since the CHB converter can be composed by cells with different remaining lifetime, it could be useful to delay a fault of higher aged cells in order to prolong the entire converter's lifetime. In this paper, a thermally compensated discontinuous pulse width modulation (DPWM) strategy is proposed in order to reduce the thermal stress for power semiconductors in power modules of higher aged cells. Considering the thermal cycles as the most influencing cause of wear out of power modules, the proposed method compensates the thermal cycles under a varying power profile by manipulating the clamping angle of the DPWM. Moreover, the proposed method obtains a comparable total harmonic distortion performance to the phase-shifted carrier modulation.