Impacts of Aggregator-Induced Communication Delays on the Stability of Bidirectional Chargers in V2G Systems

The integration of electric vehicles (EVs) via vehicle-to-grid (V2G) technology supports frequency regulation in electrical power systems. However, communication delays introduced by the V2G aggregator when coordinating bidirectional chargers can adversely affect primary control performance, potentially compromising overall system stability. This paper analyzes the influence of these communication-induced delays using an impedance-based small-signal modeling framework for bidirectional chargers, which incorporates time delays via Padé approximations. Stability boundaries are examined under varying delay conditions, current-loop bandwidths, and short-circuit ratios (SCRs). Case studies validate the theoretical findings, demonstrating that communication delays significantly reduce phase margins and can induce instability, especially in weak grid scenarios with low SCRs.