Comparison of two schemes for closed-loop decentralized frequency control and overload alleviation

The paper compares two methodologies for distributed closed-loop feedback control that, based on local measurements of power flows and frequency, minimize the redispatch needed to restore the nominal frequency, relieve line overloads and restore inter-area flows following a disturbance. The first, called Disturbance-Based Unified Control (DBUC), derives control by estimating the disturbance from measurements. The second, called Unified Control (UC), exploits network dynamics to carry out primal-dual algorithm for solving the optimization problem. We analyze a modification of UC called Decoupled Unified Control (DUC) to show that DUC algorithm is very similar to DBUC, despite using very different approaches to derive them, leading to almost identical transients as shown by simulation studies undertaken on 39-bus New England system model and comparing DBUC/DUC with standard AGC.