Energy Storage Systems in Solar-Wind Hybrid Renewable Systems

In island countries, microgrid systems have the ability to provide reliable and improved power quality especially in the vast country with low population density in remote regions. There are two major types of smart grid design in the absence of central grid, namely DC microgrid and AC microgrid. When microgrids are enabled with renewable energy sources, energy storage units increase the reliability in power supply for the load demand on consumer end. The optimized means of extracting power from renewable energy resources like wind, solar, and fuel cell is difficult in islanding mode of operation. Due to occurrence of power imbalance, energy storage units are required which support the energy requirement when power generation cannot meet the load demand. A microgrid is controlled by a supervisory controller that decides which energy storage units are connected to satisfy the load demand. Though the task is simple, appropriate control strategies are required by the microgrid to cope up with disturbances such as sudden changes in environmental and load conditions. An energy storage unit should be designed to fulfill the requirement of fast and dynamic transition of power consumed by loads connected with microgrid. In AC microgrid, the presence of local energy sources and the ability to regulate voltage and frequency can alleviate the burden for conventional generating unit. In DC microgrid, such a problem does not exist; however, the issue of voltage handling is needed to be dealt with. This chapter deals with the integration of energy storage system (ESS) with DC and/or AC microgrid and related energy management control algorithms. It also addresses the research challenges and solutions towards smooth operational behavior of ESS by integrating microgrid enabled with renewable energy sources. The detailed design specifications of ESS for 500 kW microgrid enabled with solar-wind hybrid renewable energy system (RES) is discussed. Validation through simulation studies is performed to understand the operation of effective and efficient integration of ESS with microgrid operating under islanded conditions.