Evolution of Control Strategies for Frequency Regulation in Renewable-Integrated Interconnected Power Systems with Electric Vehicle Participation

High penetration of renewable energy sources and large-scale electrification of transport are fundamentally transforming frequency stability requirements in interconnected modern power systems. Reduced system inertia, stochastic renewable variability, and communication-dependent coordination introduce dynamic uncertainties that challenge conventional load frequency control (LFC) frameworks. Vehicle-to-grid (V2G) enabled electric vehicles offer fast and distributed frequency support; however, state of charge (SoC) constraints, stochastic availability and mobility patterns introduce additional uncertainty that complicates control design and coordinated inter-area regulation. This review synthesizes state-of-the-art LFC strategies for multi-area renewable and EV integrated power systems, examining how diverse control architectures respond to practical deployment constraints and system-level coordination demands. The analysis is organized across classical and fractional-order controllers, cascaded structures and intelligent data-driven frameworks, with attention to associated tuning paradigms including metaheuristic optimization and adaptive learning mechanisms. Enabling technologies, including hybrid energy storage systems, HVDC interconnections and FACTS devices are analysed in terms of their contribution to operational flexibility and resilient frequency regulation in renewable rich smart grids. Key limitations arise at both the control-design and system levels. Control-layer challenges include high-dimensional tuning complexity and dependence on offline reconfiguration, which constrain adaptability under dynamic operating conditions. At the system level, reduced inertia, uncertain EV availability, scalability under heterogeneous grid technologies, and communication resilience demands collectively challenge secure and reliable frequency regulation. The review concludes with emerging research directions emphasizing adaptive, communication-aware and cyber-resilient architectures to support reliable frequency regulation and sustainable transformation of renewable dominated power systems.