A General Method to Calculate the Critical Fault Clearing Time of A Synchronous Generator

Fault ride-through (FRT) capability of a synchronous generator is required by most grid codes. The PCC voltage and critical fault clearing time (CFT) are two important parameters to assess the FRT capability. Current studies are mainly based on repetitive simulations, which are very time-consuming. Thus, a general method is proposed to calculate PCC voltage and CFT of a synchronous generator connected to an infinite bus through a linear network. First, equivalent Thevenin voltage and reactance before, during and after the fault are calculated respectively. Then, by applying the equal-area criteria, critical clearing angle can be obtained, and CFT can be calculated by improved Euler method. Finally, a four-bus network is used as a case study. The results are in consistent with the simulations and the theoretical analysis.