UPFC controllers; DC-voltage regulator; unified power flow controller
A comprehensive approach to the design of UPFC controllers (power-flow controller, DC-voltage regulator and damping controller) is presented. Studies reveal that damping is adversely affected by the incorporation of a DC-voltage regulator. Investigations were carried out to understand the relative effectiveness of modulation of the UPFC control signals m/sub B/, /spl delta//sub B/, m/sub E/ and /spl delta//sub E/ on damping of the system oscillations, using a controllability index. A dual damping controller based on simultaneous modulation of UPFC control signals m/sub B/ and /spl delta//sub E/ is proposed. Investigations reveal that alternative damping controllers (damping controller m/sub B/, damping controller /spl delta//sub E/ and dual damping controller) provide robust dynamic performance under wide variations in loading condition and system parameters.