Modified Transient Stability Evaluation Methodology of a Multi-Machine Power System Incorporating Renewable Energy Resources

This paper investigates the effect of integrating Renewable Energy Sources (RESs) into a system on the Critical Clearing Time (CCT) as a direct transient stability measure. The developed methodology quantifies the stability margin based on the fault clearing time. Moreover, the methodology considers the dynamic system performance under fault conditions as a worst-case scenario to determine the CCT. The proposed technique is a novel numerical methodology presented to study the transient stability of a multi-machine power system with the existence of a RES. Different from the typical solution of the swing equation of a two-machine power system, the proposed methodology numerically solves the swing equation of a multi-machine system. From this, accurate solutions are obtained to determine the optimal penetration level of the RES. Moreover, this work aims to derive an explicit relationship between the rotor angle deviation of the synchronous generator and the penetration level of the RES. Consequently, the CCT associated with the maximum power angle deviation can be determined. The proposed methodology is validated by comparing the results with dynamic simulations using the power-system-simulator (PSS®E) software package developed by Siemens. The IEEE 9-bus system is considered as a benchmark, with the results exhibiting great agreement with the PSS®E results, thus confirming the effectiveness of the proposed methodology.