Energy storage systems to provide ancillary services to the power system

Abstract

Abstract The power system has experienced a significant transformation in the last years, notably due to the large increase of power electronic-based technologies. These new technologies are mostly based on converter-interfaced generation (CIG), which have different dynamic response characteristics than classical synchronous generators. Power systems with high penetration of CIG are characterized by low grid inertia due to the lack of frequency containment provided by synchronous generators. This thesis discusses integrating energy storage systems into the power system to overcome the challenges caused by the increasing penetration of CIGs. Different types of energy storage technologies are studied, and recommendations on the size of energy storage systems are proposed based on the functionalities to be implemented. Moreover, modelling and control methods for Battery and Supercapacitor Energy Storage Systems integrated with grid-connected converters are presented. These grid-connected converters use grid-forming control strategies to provide functionalities of the synchronous generators, such as inertial response. Different grid-forming control strategies are presented and compared. Finally, a dc-link voltage based synchronization control is proposed. The dc-link voltage control utilized the dc-link dynamics to synchronize the grid-forming converter with the grid. Time domain simulations in Simulink and PSCAD are performed to analyze the different controllers and the system’s dynamic behaviour.