The climate emergency necessitates faster and wide-scale decarbonization of power grids and daily economic activities. As a result, it has triggered large-scale deployments of inertia-less power electronics renewable power generators with intermittent output powers as replacements for existing fossil fuel-based power plants which can dispatch their output powers and possess massive inertia. Power grid decarbonization in this manner presents significant operational and security challenges and exacerbates the risks of instability due to several factors such as low inertia, lack of spinning reserve to quickly nullify active power mismatch between demand and supply, and insufficient fault current for the correct operation of protection systems. Also, the inability to source or sink large active powers in weak ac grids that may result from decommissioning of a large number of existing generators is among the major concerns. Additionally, the transition toward power electronics dominated power systems that consist of numerous grid-following and grid-forming converters and HVdc systems is another major technical challenge that grid operators may face as many of the fundamentals that will dictate steady-state and transient behaviors in the future grid may differ, including methods for assessing grid stability. Modern power converters are versatile and can address many potential challenges that may emerge, nonetheless, their complex dynamics spread over a range of frequencies and must be understood. The highlighted challenges call for new control, protection, technologies, and solutions to be developed to enable the following: safe and reliable operation of power grids during the decarbonization period, in which coexistence of grid-forming and grid-following converters and conventional power plants must be managed carefully, and after the transition to zero-carbon energy systems; increased integration of renewable power generations at all voltage levels; holistic strategies for ac and dc fault handling in both onshore and offshore ac or dc grids; and ways for improving stability and extending active power sourcing and sinking limits in weak ac grids. This Special Issue aimed to foster and document the latest research that addresses the abovementioned emerging challenges. In response to the call for papers, the total number of manuscripts received was 63, and 42 papers were accepted for publication. The submitted manuscripts came from 19 different countries, covering all ten IEEE regions, i.e., China, Brazil, Finland, India, Hong Kong, France, Denmark, Iran, the U.K., the USA, France, Australia, Germany, South Africa, Spain, Canada, Mexico, Belgium, and Taiwan. From the accepted papers, 25 papers address issues directly relevant to this special topic. Broadly, the papers can be categorized as follows: converter topologies, faults and protection, control and stability, and review.