Compensation of unbalanced voltage dips using vector-controlled static series compensator with LC-filter

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 current-control loop. The validity of the proposed algorithm is demonstrated through PSCAD/EMTDC simulation, when the grid is subjected to unbalanced three-phase voltage dips.