Voltage dips due to faults are considered the most critical power quality problem to sensitive industrial loads. The voltage source converter, connected in series with the grid as a static series compensator (SSC), is suited to protect sensitive loads against such disturbances. This paper proposes a fast control algorithm to improve the dynamic performance of the SSC. Because most faults are single-or double-phase, this algorithm uses a fast technique for separating positive and negative sequence components of the supply voltage, which are then controlled separately. Thus, two controllers are implemented for the two sequences, each based on double vector control, i.e. constituted by a voltage-control loop and a currentcontrol loop. The validity of the proposed algorithm is demonstrated through PSCAD/EMTDC simulation, when the grid is subjected to unbalanced three-phase voltage dips. 904 0-7803-7420-7/02/$17.00 he also works part-time at ABB Sweden, where he is involved in the development of Light-concept devices. His interests are control of grid-connected converters, wind power and power quality.