Transient energy transfer control of frequency-coupled hybrid energy storage devices

Purpose This study aims to enhance the transient stability of renewable-dominated power systems by proposing a novel energy transfer control scheme for frequency-coupled hybrid energy storage devices (HESDs), thereby mitigating the application risks associated with their insufficient frequency regulation capability. Design/methodology/approach A coordinated virtual inertia control framework is developed for the frequency-coupled HESD. First, the conversion relationships between the stored energy in battery and capacitor, and the mechanical kinetic energy of synchronous generator (SG) are established. Second, the small disturbance model of a power 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. Findings It can be concluded that the proposed energy transfer control strategy effectively enhances the transient stability of power systems with high renewable penetration by sharing transient energy between the SG and HESD, which simultaneously suppresses frequency deviations and rotor angle oscillations. Originality/value Existing studies have examined energy conversion between storage and generators, yet systematic quantitative modeling of battery/capacitor-to-kinetic energy conversion remains unestablished. Although virtual inertia is widely discussed, the explicit small-signal modeling of frequency-coupled HESD and its damping impact mechanisms are still inadequately explored. In addition, the design of an energy transfer control strategy that integrates transient stability mechanism analysis for hybrid energy storage systems and achieves simultaneous suppression of both frequency deviations and rotor angle oscillations represents a novel contribution to the field.