Transient energy transfer control of frequency-coupled energy storage devices in low inertia prosumer energy systems

Abstract

If the energy source of rotational inertia is expanded to include the stored static energy, the transient stability of prosumer energy systems is enhanced by the energy transfer between frequency-coupled hybrid energy storage device (HESD) and synchronous generator (SG). In this paper, first, the conversion relationships between the stored energy in the battery and capacitor, and the mechanical kinetic energy of SG are established. Subsequently, the virtual inertia hidden in HESD is obtained for the frequency-coupled capability. Second, the small disturbance model of a prosumer energy system with virtual inertia is derived, and the impact of frequency-coupled HESD on frequency stability and damping characteristics is analyzed. Third, based on the mechanism analysis of system transient stability, a novel energy transfer control strategy adapted to the HESD is proposed. By sharing transient energy between the SG and HESD, both the frequency variation and rotor angle oscillation can be prevented using a unified controller. Last, a typical test system with high penetration of photovoltaic (PV) arrays is implemented on a hardware-in-the-loop platform. The results demonstrate that under the proposed control strategy, the transient stability of prosumer energy systems with frequency-coupled HESD can be significantly improved.