Voltage-regulating system for a power system, and voltage-regulating method

Disclosed are a voltage-regulating system for a power system and a voltage-regulating method. According to one embodiment of the present invention, a voltage-regulating system for regulating voltage in a power system comprises: a fast-adaptive voltage regulator for regulating output data of a fast-adaptive reactive power supply; a reactive power cooperative regulator for generating reserve comparison information using the output data and reactive power reserve supply reference information that is inputted, and generating an operation start signal using the reserve comparison information and retention range information that is inputted; and a static voltage regulator for receiving the operation start signal and power system drift data and selecting a static reactive power supply, and maintaining a power system voltage using the static reactive power supply.