Fault tolerant design for electronic power transformer

Electronic power transformer (EPT) is a promising electrical device in flexible AC transmission systems (FACTS). Despite its advantages, the large number of power electronic devices used in EPT increases the fault probability. In this paper, fault tolerant strategy for EPT is designed to improve its reliability. Four protection schemes to achieve redundancy in cascaded H-bridge (CHB) converter based EPT is proposed. Furthermore, a new topological circuit structure with multi-windings medium frequency transformer is introduced for better utilization of the H-bridge cell and control flexibility under fault conditions. A three phase 6-level CHB converter based EPT simulation platform is set up in MATLAB/SIMULINK, its operating principle and control method are discussed. The effectiveness of the proposed strategy is verified by the simulation results.