Characteristics and operational control strategies of grid‐forming long‐/short‐duration energy storage systems: A review

Energy storage systems (ESSs) are increasingly critical for maintaining the stability and flexibility in power systems with rising renewable penetration. Grid‐forming (GFM) ESSs have emerged as a pivotal technology, capable of providing essential voltage and frequency support by establishing grid references in converter‐dominated systems. This paper presents a comprehensive review of ESSs, categorizing them into ultra‐short‐, short‐ and long‐duration ESSs (USDESSs, SDESSs and LDESSs). Given the challenges associated with multi‐time‐scale support requirements and the stability of parallel‐connected GFM units, this review further synthesizes hierarchical coordination and cluster‐level cooperative control strategies for GFM ESSs. Furthermore, it places special emphasis on control strategies for GFM ESSs under extreme operating conditions. Meanwhile, it reviews the role of intelligent sensing and digital twin technology in enabling the acquisition of observable states for GFM ESSs. Finally, this paper discusses intelligent sensing and operation about digital twin for GFM ESSs.