DC fault analysis of solid-state transformer using circuit equivalent

The use of power converters in modern power systems is making the system more active. To enhance the future power grid's reliability, efficiency, interactivity, and security, digital controllers and power electronic circuits are being employed. One critical component of the power system is the 50-Hz transformer, which is currently robust. However, there is growing interest in solid-state transformers (SSTs) or power electronic transformers (PETs) as potential alternatives to conventional transformers. These alternatives are particularly relevant for the future grid, which will have a high penetration of renewable energy sources, electric vehicles, and nonlinear loads. To analyze the impact of faults in the power network, it is necessary to establish an accurate circuit model for SSTs, which has not been adequately addressed in the existing literature. This research paper proposes an averaged representation of SSTs and compares the results of switched and averaged models under varying load conditions for the designed SST. Additionally, an equivalent circuit model is developed for DC fault analysis using transformation techniques and a transformer analogy to shift parameters to the DC fault location. The proposed circuit equivalent model is compared with the switched model, offering accurate and efficient results for a pole-to-pole and pole-to-ground DC fault.