This document discusses the interaction between the Load Frequency Control (LFC) loop and the Automatic Voltage Regulator (AVR) loop in a power plant. It presents a model that combines the LFC and AVR loops to regulate both frequency and voltage. The model is tested on a single-area power system in simulation. Results show the dynamic and steady-state responses of the combined LFC-AVR system with PID controllers minimize frequency overshoot and transient oscillations while maintaining zero steady-state error.