Double vector control for series connected voltage source converters

The voltage source converter, connected in series with the grid, as a static series compensator (SSC) is suited to protect sensitive loads against incoming supply disturbances such as voltage dips. Dynamic performance of the SSC is very important since it is essential to start compensation for voltage sags without a sensible delay. This paper proposes a double-vector control algorithm to be implemented to the SSC to improve its dynamic performance. The proposed algorithm incorporates both current and voltage controllers with an inner current control loop and outer voltage control loop. The validity of the proposed algorithm has been demonstrated through a PSCAD/EMTDC simulation, when the grid is subjected to a symmetrical three-phase voltage dip. Simulation results have proved that the proposed algorithm is able to improve the transient response of the SSC, compared to traditional control concepts, such as concepts related to phasors of the sequence components and RMS calculations.