Hybrid co-simulation and real-time validation techniques for power electronics-dominated grids

The rapid integration of inverter-based resources is transforming power systems into power electronics-dominated grids, where dynamic phenomena cannot be fully captured by conventional phasor-domain analysis. This paper reviews hybrid co-simulation and real-time validation techniques for high-IBR-penetration grids, covering electromagnetic transient modeling, multi-rate EMT-RMS coupling, network equivalencing, and hardware acceleration. GPU, FPGA, and heterogeneous real-time platforms are compared in terms of model fidelity, latency, scalability, and implementation burden. Standardized co-simulation interfaces including HELICS and FMI are discussed as mechanisms for integrating electrical, communication, and control domains. Hardware-in-the-loop methods are positioned as staged validation tools that complement software simulation by incorporating actual controllers, power hardware, interface delays, and measurement nonidealities. This review also addresses weak-grid stability, grid-forming converter validation, multi-vendor model interoperability, and requirements from IEEE 2800−2022, NERC EMT guidelines, IEC standards, and CIGRE technical guidance. By organizing these topics into a unified validation workflow, this paper identifies open challenges in scalable EMT simulation, model portability, cyber-physical validation, and digital-twin-based model refinement.