Transformer-less back-to-back cascaded converters offer advantages such as high transmission efficiency

high power density

and low costs. However

the traditional single-side modulation algorithm can lead to DC-link capacitor short-circuit faults

limiting the widespread application of the converter. To address the issue

a bilateral unified two-dimensional space vector pulse width modulation strategy is proposed in this paper. Firstly

by analyzing the formation mechanism of capacitor short-circuit faults

a simplified fault criterion model is established

and the criteria of selecting switch states that can avoid capacitor short-circuit faults are summarized. Secondly

based on the distribution characteristics of port voltages on both input and output sides

a two-dimensional vector space coordinate system is constructed

with corresponding vector synthesis algorithms specially designed for different subsector types. Finally

the effectiveness and feasibility of the proposed modulation algorithm are verified through simulation analysis and experimental validation. The results indicate that the proposed strategy not only effectively mitigates the faults but also exhibits excellent operational performance in terms of power quality and transmission efficiency.