Dynamic Modelling and Control Design of Advanced Energy Storage for Power System Applications

MOLINA, MARCELO GUSTAVO

Dynamic Modelling

In-Tech Education and Publishing

Lugar: Viena; Año: 2010; p. 49 - 92

In recent years, it has been gradually seen that energy storage systems (ESS) advanced solutions have received significant interest for power utility applications. Such modern devices include super (or ultra) capacitors (SCES or UCES), superconducting magnetic energy storage (SMES), flywheels (FES) and innovative batteries (IBESS) among others. These ESSs can play a crucial, multi-functional role since storage facilities are designed to excel in a dynamic environment. Other factors driving the incorporation of these novel storage technologies include reduced environmental impact, rapid response, high power, high efficiency, and four-quadrant control, solving many of the challenges regarding the increased use of renewable energy sources, and enhancing the overall reliability, power quality, and dynamic security of power systems. By combining the technology of energy storage with a recent type of power electronic equipments, such as flexible alternating current transmission systems (FACTS), the power system can take advantage of the flexibility benefits provided by the advanced ESSs and the high controllability provided by power electronics aiming at controlling and optimizing the performance of the electric system. The application of FACTS controllers based on voltage source inverters (VSI) has been settled world-wide as the next generation of fast reactive power compensators for improving both transient and dynamic stabilities. In this sense, shunt compensation provided by a static synchronous compensator (STATCOM) has already proved its benefits on existing power systems. A STATCOM can only exchange reactive power with the electric grid. This feature limits its degrees of freedom and therefore its impact on the power system operation. As demonstrated by various previous studies, simultaneous active and reactive power compensation has more valuable effect on counteracting PS disturbances. In this way, a STATCOM integrated with energy storage through an appropriate interface leads to a more flexible integrated controller which provides additional benefits and improvements in the PS. This technology permits to rapidly and simultaneously control active and reactive power, still preserving FACTS benefits, but adding a degree of freedom for increasing the effectiveness of the overall control. This chapter will thoroughly describe the dynamic modelling and the control design of a STATCOM integrated with advanced ESSs for power utility applications. More specifically, of the various advanced storage systems nowadays existing, the three foremost ones will be considered, i.e. ultra capacitors, SMESs and flywheels. To this aim, major operating characteristics of these modern devices will firstly be analyzed and a detailed modelling approach will be presented for both transmission and distribution level applications. Moreover, a simplified state-space averaged mathematical model of the combined STATCOM-ESS controller will be provided. By using concepts of instantaneous power on the synchronous-rotating d-q reference frame, a novel three-level control scheme will then be proposed for improving the power quality and security of the PS. Eventually, the dynamic behaviour of the presented models and control algorithms will fully be evaluated through a computational implementation in the MATLAB/Simulink environment with fixed-step discretization method, and using the SimPowerSystems blockset. The results obtained will demonstrate the excellent dynamic performance of the STATCOM-ESS as well as the benefits of its use in the power system.