This book examines the role of model validation of power system planning and operation to optimize its performance in terms of frequency control. It presents the detailed model validation for the Iranian Power Grid system, where the frequency performance was analysed and improved using existing and new standard models to identify the influencing parameters. Although the model validation was employed for a specific, practical large-scale system, the framework (concepts, methods, and formulations) can be used for by any type of power system. As such, this book describing a generalized framework for model validation with a real case study is useful for both power industry experts and academia.