This paper proposes a centralized voltage control system for distribution system to meet the impact of PV growth. The system consists of a server machine at control center and many field devices like voltage regulators, line switches with sensor to measure power flow and voltage, and Information and Communication Technologies (ICT) network under Smart Grid paradigm. The system gathers measurement values from switches through the ICT network and chooses the best voltage profile and voltage regulators condition to achieve the profile with use of our advanced Optimal Power Flow. The test results at our Smart Grid facilities with 4MW photovoltaic generators are also given to prove the effectiveness of the developed system.