The transformation of the existing electric power systems into modern smart grids is gaining momentum as more countries seek to lower their energy consumption and greenhouse gas(GHG) emissions. The transformation requires the integration of significant renewable energy and other transmission and distribution assets, which raises tremendous technical challenges involving voltage and frequency stability, energy storage, system balancing, intermittency of renewable energy, and more. As an integral part of modern power systems, distributed energy resources(DER) have been rapidly deployed throughout the world, initially as an effective means of clean generation to displace fossil fuels and subsequently as resources to provide power system functions. DERs include distributed generation systems such as wind, solar and CHP systems, energy storage units including electric vehicles, controllable loads, and associated conversion and control systems in power distribution networks. The innovative solutions to facilitate the seamless integration of DERs into electrical grids have never been so important. These solutions are critical to enabling maximum penetration of renewable energy, while allowing utilities to maintain high standards of grid stability, reliability, and energy costs. The purpose of this Special Issue is to disseminate the recent technological advancement in distributed energy resources, pertinent to analysis, design, conversion, control, performance, and application.