Ensuring system security and stability is an ever-present concern in power system engineering due to the crucial importance of reliable power supply in modern society. The growth of renewable energy increases the number of power electronic converters present in the power network since they are needed to interface non-conventional forms of generation to standard 50 or 60 Hz system. This changes the network's physical structure and causes new threats to security. Compared to conventional power equipment, power electronic converters are subject to rigid capacity constraints which make them prone to lose functionalities during large disturbances and trigger fault cascading. On the other hand, converters have higher flexibility and faster response which enable more versatile patterns of dynamic control. Therefore, a new methodology for both converter design and system operation is needed to take advantage of the strengths and mitigate the weaknesses of converters in supporting grid security. This problem is difficult because power electronic converters have sophisticated internal dynamics which further interact with a complex power network with a vast number of nodes and uncertain disturbance scenarios. What adds to the difficulty is that converters and networks are created by very different owners and supply chains that newly come together but still have different perspectives and technical languages. This fellowship aims to establish a common technology framework for converter manufacturers and network operators, and find a systematic methodology and practical tools for grid-supportive converter design and converter-based grid security management. The proposed research sets out to do three things. First, it will find analytical methods to quantify the support provided by and stress placed on converters regarding network security, from which converter design guidelines will be derived to optimize the security support functions in a cost-effective way. Second, it will build computational platforms for network operators to use a vast number of converters synergistically for real-time security management. Third, it will develop proof-of-concept prototypes, demonstrate their application potential in a complex power system, and promote commercialization and standardization.