Connecting and Integrating Variable Renewable Electricity in Utility Grid

The utility grid challenge is to meet the current growing energy demand, taking into account the environmental issues. Nowadays many power electronic devices enable the connection of distributed and variable renewable energy sources to the utility grid, but too often these devices do not consider the integration of ancillary services. To enhance overall utility grid performance and to achieve a high level of renewable energy penetration into the grid, control strategies of power management through smart interfaces should be developed to build a more flexible and robust utility grid. From control to protection and energy management, combined with information and communication, the concept of a smart grid and microgrids were born in recent years. As a main element of the smart grid, a microgrid that combines distributed energy sources and loads is considered as an effective and promising approach to address the variable renewable energy source integration issues and traditional grid issues. With communication technology, a microgrid can interact with a smart grid to assist grid power balancing by advanced energy management and thus reduce the cost and improve power quality. For urban areas, a building-integrated DC microgrid combined with a DC bus distribution is proposed. The building-integrated microgrid can supply a tertiary building through a hierarchical supervision able to exchange messages with the smart grid and metadata. This chapter reviews issues in utility grids and aims to introduce the urban microgrid based on renewable electricity and connected to the future smart grid, thus putting this study in the current scientific and technological context.