This paper proposes a modified model for active power/ frequency support of multi-area power system analysis that takes into account the effects of AC/DC systems under deregulated environment of the power market. The AC part of studied system is comprised of conventional generators and HVAC lines, while DC systems are related to the parts with converter station models and HVDC interconnection. Simulations performed by Matlab software demonstrate how renewable power plants can serve as conventional generators in AGC control loops under constraints determined by the market rules. This scenery is considered one of the most promising evolutions of the future electrical power systems.