Output feedback TCSC controllers to improve damping of meshed multi-machine power systems

Methods for the co-ordinated design of output feedback damping controllers, for thyristor-controlled series compensators (TCSCs) in a meshed power system, are developed in the paper. The locations for installing TCSCs and the co-ordination of TCSC controls are determined by analysing the mode controllability. The analysis of mode observability is used to select the effective output feedback signals local to the TCSC locations. The design of controller gains is divided into two steps. First, initial gains for each controller are calculated according to the coordination determined by the analysis of the mode controllability. These initial gains are then optimised by using linear programming to satisfy the given design criteria. It is shown that, by using this procedure, the desired damping of the critical modes can be achieved without significantly deteriorating the damping of the other modes and the stability of the power system. It is also shown that the prolonged saturation in the TCSC actuators and the adverse interaction among TCSC controllers can be avoided. The proposed controller design methods are validated by a case study