Stability Analysis of Smart Solid-State Transformer

The emergence of renewable energy makes the traditional power system face great challenges, and the construction of energy Internet is the way to solve the problem. As the core component of the energy Internet, smart solid-state transformer (ST) is susceptible to power fluctuations from various load ports, which may cause imbalance of its own power supply and demand at all levels and lead to voltage instability. Therefore, it is crucial to determine the stability boundaries for stable operation. This paper proposes a method of stability determination based on power balance point. Based on the average model of a three-level ST and the Jacobian matrix is derived. The singularity of the Jacobian matrix is used to determine the stability of the ST. The study of the power balance point shows that the instability of the ST upper stage causes the output voltage to drop, resulting in the instability of the lower stage, while the instability of the lower stage does not necessarily lead to the instability of the upper stage. A three-stage type ST simulation model based on MATLAB/SIMULINK is developed to demonstrate the effectiveness of the proposed method .