Out-of-Step Protection for a Synchronous Generator via Energy Function-Based Stability Assessment Using a Single Local Speed Measurement

This study proposes a scheme for determining the loss of synchronism in synchronous generators based on the direct method, utilizing a single local speed measurement within a generator system. By employing individual machine energy functions, this approach establishes a theoretical foundation for determining synchronization thresholds from the perspective of a single generator. Building on this foundation, clear criteria are suggested for determining whether a generator remains stable. The feasibility of the proposed method is verified through its application to synchronous generators, considering a comprehensive setup environment for implementing the proposed algorithm. Case studies are conducted using time-domain simulations in MATLAB/Simulink on the IEEE 39-bus system with varying system inertia and the IEEE 118-bus system. These case studies evaluate the robustness of the proposed criteria and algorithm in determining out-of-step conditions from an energy conversion perspective, analyzing variations in system inertia, control system parameters, power system scale, and fault scenarios across benchmark systems. Furthermore, the performance of the proposed protection scheme is compared with previous studies, highlighting its advantages. By interpreting the loss of synchronism phenomenon using only local measurements from existing systems, the proposed scheme demonstrates robustness against changes in the characteristics of the connected power system. It also simplifies the detailed settings required for effective operation of the protection scheme.