Model Predictive Control Based Advanced Switching Strategy for H-Bridge Converter Used in SMES Applications to Obtain Even Loss Sharing

The power converters are mostly prone to frequent failures. One of the major causes for their failures is uneven distribution of power losses among the semiconductor devices. The conventional equal loading bus clamping pulse width modulation scheme guarantees equal loss sharing among the devices when the converter operates at unity power factor (pf). However, when the converter operates at non-unity pf, some of the devices are heavily stressed due to higher loss density, i.e., junction temperatures of some of the devices become higher than the others. This paper proposes four switching sequences based on model predictive control for a grid-connected single-phase H-bridge converter used in various applications including superconducting magnetic energy storage system. In each sector, two switching sequences having different zero vectors are selected alternately. The proposed strategy can achieve balanced loss sharing and almost uniform thermal stress among the devices of the converter under all pf. The novelty of the proposed technique is verified with a scaled-down laboratory test prototype.