Simple topologies for AC-link flexible AC transmission systems

Vector switching converter VeSC has been recently introduced as an alternative for controlling power flow in power system's complex interconnections by direct AC-AC conversion, and novel FACTS devices have been recently introduced based on the VeSC, such as the Xi (Xi) and Gamma (Gamma) controllers. This paper introduces the simplified vector switching converter SVeSC and the topology of the Xi (Xi) and Gamma (Gamma) controllers based on this novel simplified scheme, which reduce the number of switches, increasing the reliability and reducing the cost of implementation, while holds the operating principle. The control system of AC-link FACTS devices is simpler than the control system of the DC-link approach, and free of PLL and trigonometric calculations. Simulation results of the active power flow control between two nodes by the proposed simplified Xi (Xi) controller are provided to prove the operating principle.