Patent ID: 6847184

Claim:
An excitation controller comprising: a voltage detector for detecting output terminal voltage of a synchronous machine connected to a power transmission system through a transformer; a current detector for detecting output current of the synchronous machine; and a voltage setter for setting output terminal target voltage of the synchronous machine based on the output current of the synchronous machine detected by said current detector, reactance of the transformer, and high-side target voltage of the transformer, wherein said excitation controller controls an excitation system of the synchronous machine based on deviation of the output terminal voltage detected by said voltage detector from the output terminal target voltage set by said voltage setter, and active current and reactive current of the output current of the synchronous machine are calculated from the output current detected by said current detector and the output terminal voltage detected by said voltage detector, and said voltage setter calculates and sets the output terminal target voltage of the synchronous machine to compensate for a voltage drop in the transformer corresponding to a phase angle variation, which is a phase difference between high-voltage and low-voltage sides of the transformer.