The Automatic Voltage Regulator (AVR) plays a key role in maintaining system stability by controlling generator excitation. This study proposes a novel-reaching law and implements a double integral sliding mode controller (DISMC) to enhance AVR performance. A state-space model of the AVR system is developed and analyzed for controller design. Key performance metrics, including overshoot, settling time, and rise time, were evaluated and compared with traditional sliding mode control (SMC) and terminal sliding mode control (TSMC). Simulation results indicated that DISMC outperformed both SMC and TSMC, exhibiting superior transient response, faster error elimination, and a smoother control signal with low chattering. All designs, analyses and validations are conducted using MATLAB/MATLAB Simulink software.