This paper proposes a new coordinated voltage control scheme between STATCOM (Static Synchronous Compensator) and reactive power compensation devices, such as shunt elements(shunt capacitor and shunt reactor) and ULTC(Under-Load Tap Changer) transformer in a local substation. If STATCOM and reactive power compensators are cooperatively used with well designed control algorithm, the target of the voltage control can be achieved in a suddenly changed power system. Also, keeping reactive power reserve in a STATCOM during steady-state operation is always needed to provide reactive power requirements during emergencies. This paper describes the coordinative voltage control method to keep or control the voltage of power system in an allowable range of steady-state and securing method of momentary reactive power reserve using PSS/E with Python. In the proposed method of this paper, the voltage reference of STATCOM is adjusted to keep the voltage of the most sensitive bus to the change of loads and other reactive power compensators also are settled to supply the reactive power shortage in out range of STATCOM to cope with the change of loads. As the result of simulation, it is possible to keep the load bus voltage in limited range and secure the momentary reactive power reserve in spite of broad load range condition.