**Preface to "Distributed Power Generation Scheduling, Modelling and Expansion Planning"**

Due to the decentralization of energy production, electrical distribution systems are in a transition process for the incorporation of distributed energy resources such as renewable-based distributed generators and energy storage units with the aim of achieving an efficient, sustainable, and environmentally friendly network. This new context, where distributed energy resources comes into play, calls for changes in the way distribution systems are operated and planned.

The deployment of renewable-based distributed generators in the network offers a wide variety of technological, economic, and environmental benefits. However, the uncertainty associated with the variability of renewable energy sources significantly hinders the operation and planning of such devices. Nevertheless, the effect of uncertainty may be partially compensated for by the installation of energy storage units, which increases the manageability of the grid. Moreover, demand response and dynamic pricing are also an efficient way to mitigate the uncertainty and improve the system efficiency. In addition, the increasing penetration of electric vehicles represents a new source of generation and demand, depending on whether the vehicles act in a V2G or in a G2V mode, which needs to be accounted for by the system operators and planners. In order to better manage such an amount of distributed energy resources, two different concepts have emerged, namely the aggregator, grouping the energy consumption or generation of several consumers, and the microgrid, which is a small-scale power system that can be operated either independently or grid-connected.

Within this new paradigm, new approaches for the operation and planning of distributed power generation are yet to be explored. This Special Issue aims to integrate them in a comprehensive manner to investigate the resulting effects.

> **Javier Contreras, Gregorio Mu ˜noz-Delgado** *Editors*
