**Preface to "Integration of Renewable and Distributed Energy Resources in Power Systems "**

Decarbonization, digitalization, and decentralization are transforming our power systems towards a more sustainable energy system. The integration of large amounts of renewable generation is required to achieve an almost 100% decarbonized power system. Many of the new renewable generators, wind and solar, are connected to distribution grids. Digitalization allows changing the traditional paradigm of passive grid operation and planning to smart grids with higher levels of automation and self-control, maintaining the security of supply and economic efficiency. Communications and cybersecurity are required to interconnect millions of sensors and equipment connected not only on the network but also on the customer side. In this Special Issue, we have the opportunity to delve deeply into some of the advances that are required to achieve this transformation. Microgrids are a new concept to operate, in a clever manner, thousands of new control equipment located on customer premises, such as flexible demand, renewable generation sources, and storage installations. In addition, microgrids is an alternative to create more resilient systems against extreme weather conditions or massive cyberattacks. New planning techniques for urban districts and grid development tackling uncertainty regarding load growth and flexibility are also needed. Finally, new operational and planning criteria are explored to integrate a massive penetration of distributed generation, electric vehicles, and controllable loads.

> **Tom´as G ´omez San Rom´an, Jos´e Pablo Chaves-Avila ´** *Editors*
