A Novel High-Voltage Thyristor-Based Unipolar to Bipolar DC Power Grid Interface Converter

DC transformers (DCTs) with bipolar outputs typically serve as interfaces to interconnect grids with both unipolar and bipolar configurations. However, the voltage ratings of power switches limit the widespread adoption of fully controlled power electronic devices in conventional voltage balancers. Furthermore, the technique of series-connected power electronic switches also imposes constraints on the voltage rating of DCTs, impeding their practical application. This paper introduces an improved thyristor-based voltage balancer that has evolved from the conventional voltage balancer design. In this device, the adoption of thyristors enables the interconnection of medium/high voltage grids with differing voltage levels. The proposed topology is presented alongside an analysis of its operating principles. Additionally, the shutdown characteristics of the thyristors in this device are also investigated. Finally, the accuracy and feasibility of the proposed voltage balancer are verified through a MATLAB/Simulink model.