In load frequency control (LFC), it is essential to transmit measurements of control signals from the control center to plant side and remote terminal units (RTU) to control center. Therefore, time delays become inevitable due to the use of conventional communication channels. The dynamic performance of LFC system would be degraded by these delays. This paper is dedicated to the delay-dependent stability of the LFC of hybrid power generation subsystem. The system studied includes wind turbine generator (WTG), photovoltaic system (PV), ultra-capacitor (UC) bank for energy storage, fuel cell (FC) system and diesel generator(DG). Delay margin is stated for the upper bound on the delay for stability of LFC system. An analytical method is used to compute delay margins. Delay margins are calculated for wide range of proportional-integral (PI) controller. Such results could be utilized to tune the PI controllers as to achieve a compromise between the dynamic performance and the delay margin. It has been determined in which intervals, the controller parameters of the proposed hybrid system can be selected while the system is in stable region. the results are presented in tables and graphs. Simulation study of the proposed system with Matlab / Simulink was performed. The results of the simulation studies and the theoretical studies showed compatibility. Simulation studies verify the effectiveness of the proposed method.