New techniques and approaches are constantly being introduced to analyze and enhance the transient stability of renewable energy-source-dominated power systems. This review article extensively discusses recent papers that have proposed novel and innovative techniques for analyzing and enhancing the renewable source-dominated power system’s transient stability. The inherent low-inertia characteristics of renewable energy sources combined with fast-acting power electronic devices pose new challenges in power systems. Different stability concerns exist for grid-following and subsequent grid-forming converter/inverter connections to power grids; hence, distinct solutions for enhancing the transient stability have been devised for each. Moreover, the fundamental concepts and characteristics of converter/inverter topologies are briefly discussed in this study. Recent discussions and reviews of analysis and enhancement techniques in transient stability could lead to new ways to solve problems in power systems that rely primarily on renewable energy sources.

The integration of renewable energy sources ( RES ) into the grid predominantly utilizes voltage source converters ( VSC ) with a grid-following ( GFL ) connection strategy. This approach, however, often faces instability issues in low-inertia grid regions. To enhance grid resilience in renewable-dominated power systems, grid-forming ( GFM ) connection strategies have been introduced, with the virtual synchronous machine ( VSM ) technique based on GFM control being particularly prevalent. Consequently, transient stability investigations of power systems employing both GFL and GFM connection techniques have gained increasing relevance. This paper proposes an innovative fast direct transient stability analysis ( DTSA ) approach that leverages Lyapunov’s direct method to assess the transient stability of a GFM with VSM control technique, incorporating the influence of parallel-connected VSC with GFL control strategy. The proposed DTSA approach models the GFL as a current source with parallel internal reactance and the GFM as a voltage source with series internal reactance. Detailed analytical derivations of the DTSA approach using transient energy functions, along with the DTSA criterion for the interconnected system, are presented to determine the critical clearing time ( CCT ) of the GFM -employed VSC . Furthermore, Matlab/Simulink-based electromagnetic transient ( EMT ) time-domain ( t - d ) simulation responses are utilized to validate the accuracy and computational effectiveness of the proposed fast DTSA approach. In addition, the proposed DTSA approach offers considerable benefits for efficiently assessing and managing power systems that heavily rely on RES in terms of operational planning and contingency management.

Newly developed tools and techniques are continuously established to analyze and monitor power systems’ transient stability limits. In this paper, a model-based transient stability index for each generator is proposed from the synchronizing torque contributions of all other connected generators in a multi-machine interconnected power system. It is a new interpretation of the generator’s synchronizing torque coefficient (STC) in terms of electromechanical oscillation modes to consider the synchronizing torque interactions among generators. Thus, the system operator can continuously monitor the system’s available secured transient stability limit in terms of synchronizing torque more accurately, which is helpful for planning and operation studies due to the modal based index. Furthermore, the popular transient stability indicator critical clearing time (CCT), and the traditionally determined synchronizing torque values without other generator contributions, are calculated to verify and compare the performance of the proposed transient stability index. The simulations and test result discussions are performed over a western system coordinating council (WSCC) 9-bus and an extensive New England 68-bus large power test system cases. The open-source power system analysis toolbox (PSAT) on the MATLAB/Simulink environment is used to develop, simulate, validate and compare the proposed transient stability index.