A Control Strategy for a V2G- Aggregator for Microgrid Regulation

Abstract

The power system is a very complex and sensitive to sudden change in load, line tripping, generator problem and islanding of grid. These conditions create voltage, current and frequency transients on the utility grid. The second issue is the overloading of the distribution system in which the distribution system is overstressed and increase the losses of the distribution lines and distribution transformer. In these situations, the protection system will operate and the continuity of the service will disturb the distribution system due to load shedding. According to these difficulties, the stability and service continuity of the distribution system is a challenging task. In this research, Electric Vehicles Batteries are used for overcoming the discontinuity of service, overloading and transient conditions of the distribution system due to their rapid response, efficient control and minimum cost. In this research, introduce a two-way power delivery in which the regulation of charging and discharging of Electric Vehicle Batteries has been introduced to overcome the overloading, line tripping and transient conditions of the distribution system. When power will deliver from utility grid to Electric Vehicles Batteries then the charging current of Electric Vehicles Batteries will be controlled according to the distribution load and protect the distribution transformer and distribution lines to overloading. When the secondary load of the distribution transformer will increase the charging current of the Electric Vehicles Batteries will be decreased by using the charging station controller and protect the distribution transformer to overloading. When the load connected to the secondary side of the distribution transformer will increase again then the charging current of the Electric Vehicles Batteries will be zero and the battery charging will be stopped. When the load connected to the secondary side of the distribution transformer will increase to a specific limit then Electric Vehicles Batteries will start to discharging and provide the power to distribution loads and protect the distribution transformer and distribution lines to overloading without load shedding. When the secondary load of the distribution transformer will decrease, then batteries charging current will increase again and Electric Vehicles Batteries charge to its full rating capacity.7 When the abnormal condition occurs in the utility grid, in this condition utility grid switch to islanding mode then Electric Vehicles Batteries behave as a distributed energy source and deliver power to the grid thus increasing the stability of the utility grid in islanding condition. In both overloading and islanding conditions, the charging and discharging of Electric Vehicles Batteries will be controlled and protect the distribution system to overloading and transients without any extra expense. For this purpose, PI controllers, Fuzzy Logic controllers, and Fuzzy Logic-based PI controllers are used to improve the stability of the grid network during overloading and transient response using Grid to Vehicle (G2V) and Vehicle to Grid (V2G) technologies. This proposed controllers have been simulated in MATLAB/SIMULINK and tested on reference distribution systems. Experimental outcomes illustrate that the proposed controllers successfully stabilize the grid during overloading and transients. Experimental outcomes also illustrate that the Fuzzy Logic controllers provide the better response as compare to PI controllers for stabilizing the grid during overloading and transient conditions.