This book offers a comprehensive assessment of the stability of modern power systems through advanced nonlinear analysis frameworks. It addresses the new challenges to power system stability posed by the anticipated integration of numerous power-electronic-interfaced devices needed to support renewable energy generation. Given the diverse operational timescales associated with controllers for power-electronic-interfaced devices, these devices can have an impact on a wide range of dynamic phenomena, thereby significantly influencing the system's dynamic performance and stability. The methodologies presented effectively manage the significant changes in system dynamics introduced by these devices. This research utilizes nonlinear methodologies, specifically bifurcation theory, to analyse various stability types in such power-electronic-rich systems. The book adopts a bifurcation-based methodology to evaluate power system stability through detailed examination of each type of instability mechanism. The methodology developed is extended to explore the interactions between multiple types of system stability considering the impacts of different voltage-source-converter controllers and grid strengths. Finally, to reduce the high computational burden imposed by the proposed methodology, a hybrid network model is developed to assess the system stability efficiently. Stability Assessment of Power Systems with Multiple Voltage Source Converters is of interest to students, researchers, and industry professionals in the field of electrical engineering.