Advanced series and parallel converters for power system stability improvement

FACTS devices, such as synchronous series compensator, static compensator, unified power flow controller, thyristor series capacitors, SMES devices etc. are gaining increasing attention for their capabilities to dynamically adjust the network configuration to enhance steady-state performance as well as system stability. Several converter topologies have been proposed in the recent literature, however those based on voltage source inverters (VSI) seem to be more promising due to their intrinsic capability to rapidly respond to network changes such as perturbations following a fault and their property of being immune to resonance problem. In the paper a new topology for inverter based FACTS is proposed. This configuration, based on a three-phase two-leg inverter is employed for both series and parallel connected compensators. A control strategy based on sliding-mode technique is employed for tracking of appropriate reference quantities. A great simplicity in design and control, as well as good tracking performances are demonstrated through numerical simulations.