Development and optimization of three-DOF modulation for single-stage matrix ac-dc converters based on real-time calculation

Abstract

Driven by the rapid global energy transition and smart grid advancement, solid-state transformers (SSTs) have become essential in modern power systems. Among SST components, the single-stage matrix (SSM) ac–dc converter is particularly attractive due to its simple structure, minimal component count, and ease of control. However, maintaining high efficiency with the SSM converter is challenging, primarily because of its wide input voltage range and the significant influence of half-bridge capacitors on the inductor current. To address these issues, this article proposes a novel three-degree-of-freedom (DOF) asymmetric modulation method based on traditional extended phase-shift modulation, introducing an additional DOF into the dc-side full-bridge structure. Through mode classification, comprehensive modeling, and optimization, an optimized modulation trajectory (OMT) was developed. The proposed OMT ensures that all power switches achieve zero-voltage switching operation while minimizing the root mean square of the inductor current and enabling real-time calculation. Finally, experimental validation demonstrates that the proposed OMT achieves up to 4.14% efficiency improvement compared to recent work, thereby confirming the method’s effectiveness and accuracy.