Bottom-up design methodology for a hybrid AC/DC microgrid with energy storage and photovoltaic generating units

Utilization of renewable energy sources such as wind and solar photovoltaic has been increasing in the last decades due to high energy demand, elevated pollution and the continuous decrease in fuel reserves. Renewable sources are generally intermittent and variable, therefore energy storage systems have been developed to meet user needs. This scenario led to the concept of microgrid, which is related to the combination of loads, micro-sources and storage devices in a network element that is part of the complex electrical system. More recently, the idea of a hybrid AC/DC microgrid has been proposed and consists in separating AC and DC elements of the microgrid in order to reduce power losses and simplify the control strategy. In this paper, bottom-up methodology is used to design a hybrid AC/DC microgrid. It begins with a simple battery-converter-load system, and ends with a hybrid microgrid formed by two battery banks, a photovoltaic array, AC and DC loads, as well as five power converters. The converters are modeled and controlled by using well-known methods, and the design approach is validated through several simulations under changes in reference and load power.