On damping capabilities and sizing of dynamic range of FACTS devices for damping control

The effectiveness of FACTS devices for power swing damping is dependent on the controllability, disturbance size and the dynamic control range. This dependence arises because, device limits may often be hit during the transients following realistic disturbances. It is necessary to quantify and specify this aspect at the planning stage, so that the appropriate dynamic range of the devices can be determined. While the damping is also dependent on the controller design and feedback signals, these may not be known a priori at the planning stage. Therefore, we derive an approximate characterization of the achievable damping as related to the dynamic range and disturbance size. This will assist a system planner to determine the size of dynamic range of a device at a given location, and also to compare various alternative FACTS devices and locations. A case study of a four-machine system with a Thyristor Controlled Series Capacitor (TCSC) damping controller is presented to illustrate the concept.