Energy management for islanded microgrid with energy storage systems

Microgrid is a new form of electrical network interconnected with renewable energy resources mainly used for remote areas. A microgrid has two operational modes, grid-connected and isolated modes. In isolated mode operation, the microgrid needs to overcome the intermittent power generated by renewable energy resources (PV or wind turbines) as the amount of generation is largely affected by weather condition. In order to optimise the power dispatch and maintain power-quality for an islanded microgrid, an energy management system for a low-voltage islanded microgrid with an energy storage system (battery in this thesis) is presented. The main objective of this energy management system is to optimise power dispatch and to make effective use of power generated by renewable resources (solar power in this paper) for an islanded microgrid to achieve the purpose of installing an environmental friendly power grid. The proposed energy management system is divided into two parts. Firstly, the system determines the battery charging/discharging state and the backup DG operating time based on the power generated by PV, base DG and load demand in each time step. From the decision-making process, the battery power, battery state of charge and the backup DG operating time is available for the next stage of the energy management system. Secondly, the modified Gauss-Seidel load flow iteration process is run in MATLAB for computing the bus voltage and transmission line power losses in each time step. The Gauss-Seidel load flow analysis is a typical calculation strategy for evaluating the operation of power flow in an electrical network. In order to verify the effectiveness of the proposed energy management system, four case studies are provided in this report under different power profiles and load profiles. The energy management system is used not only for optimizing power dispatch for an isolated microgrid with renewable energy resources and an energy storage system, but also for sizing battery and diesel generators before the installation of the microgrid with reasonable prediction of load demand and renewable power generation