Development of an optimal operation approach considering demand side flexibility in microgrids

In recent years, the concept of microgrid has gained popularity due to providing more reliable, sustainable and economical power system, and this idea has also become interesting topic for system operators. Microgrids are capable of generating electricity from renewable energy sources and conventional production units such as micro turbines, combined heat and power units, fuel cells etc. and are able to provide their own supply-demand power balance with energy storage units internally and the other microgrids. They can be operated in grid-connected mode and providing bi-directional power flow with the main grid. Moreover, in case of a fault (malfunction), microgrids can be switched off and turned to operate in islanded mode to protect system from any negative effects. When considering dynamic nature of production and consumption profile especially in microgrids where renewable energy systems are widely used, providing of power balance becomes difficult and causes major problems in terms of system operation. In addition to energy storage unit, the demand side management, one of the most crucial ancillary services of smart grid concept, has become a remarkable application field. Besides the stationary batteries, electric vehicles (EVs) can also be preferred as an energy storage which provide grid-to-vehicle (G2V) and vehicle-to-grid (V2G) power flow. Additionally, the direct load control applications which allow the system operator to shape consumer's controllable load profile, can also be integrated into the system as a different type of demand response. There are many studies that have contributed to the literature related to the microgrids. It should be stated that, although main topics are in various field, studies are focused on ensuring voltage/frequency stability, improving the grid connection conditions, and energy quality. Energy management strategies and demand response programs are preferred to provide economic operation of microgrid which has become more prominent recently. In this study, a scenario-based stochastic algorithm is presented for the volatile renewable energy sources such as wind and photovoltaic farms considering the mentioned programs. Stationary batteries and EVs are used as an energy storage units in the system. Furthermore, the uncertainties caused by these structures are taken into account and a more realistic approach is developed. Thermostatically controlled equipments are also used as a demand response source and their effects on microgrid operation are investigated. The proposed structure is modeled by using mixed integer linear programming (MILP) and solved in general algebraic modeling system (GAMS) simulation program with commercial CPLEX solver.