This paper presents a control system design for a large-scale photovoltaic (PV) solar farm to mitigate Fault-Induced Delayed Voltage Recovery (FIDVR) in power transmission systems. The proposed control system utilizes an adaptive droop control technique, which is capable of providing both voltage stabilization and reactive power compensation simultaneously. FIDVR is a phenomenon that causes voltage dips and prolonged voltage recovery times, leading to instability and equipment damage. The control system mitigates FIDVR, while also providing voltage stabilization and reactive power compensation simultaneously. To mitigate FIDVR, the proposed control system employs reactive power control using a STATCOM controller connected to a Voltage Source Converter. A MATLAB/SIMULINK simulation study was conducted to evaluate the effectiveness of the proposed control system in a realistic power transmission system. This was done with a large-scale PV plant and comprehensive induction motor loads. The simulation results revealed that the proposed control system can successfully reduce FIDVR in the power transmission system with minimal losses while maintaining network stability. The simulation results demonstrate that the proposed PV-STATCOM control system can effectively mitigate FIDVR, even if the solar farm is located more than 100 km away from the motor loads. The significance of this work lies in the potential of the proposed control system to improve the stability and reliability of power transmission systems. In addition, it increases the integration of renewable energy sources.