Transient Stability Analysis of Low-Inertia Shipboard Electrical Systems

Transient stability analysis (TSA) of synchronous generators (SGs) is essential for reliable operation of electrical systems. Conventionally, the equal area criterion (EAC) is used to assess the transient stability of SGs, assuming that they are connected to a bus with a fixed frequency. However, during disturbances in low-inertia systems, e.g., small microgrids and shipboard power systems, the frequency of the main ac bus may noticeably deviate. This paper proposes a new formulation within the EAC method for calculating the critical clearing time (CCT) of SGs in low-inertia electrical systems, considering the effect of variations in system frequency during TSA. To verify the effectiveness of the extended EAC, the CCTs of SGs in a multi-machine shipboard power system are obtained using the proposed formulation and compared with time-domain simulation results. The proposed EAC method estimates the CCTs more accurately when the main ac bus frequency varies following a disturbance.