We present a systematic method to design ubiquitous continuous fast-acting distributed load control for frequency regulation in power networks where the control goals and operational constraints are formulated as a constrained optimal load control (OLC) problem, and the load control is derived as a distributed algorithm to solve OLC. We prove that the swing dynamics and the branch power flows, together with load-side frequency control, serve as a first-order distributed primal-dual algorithm for OLC. Our controller can rebalance supply and demand after disturbances, restore the frequency to its nominal value, preserve the scheduled inter-area power flows, and maintain line flows within thermal limits, in concert with generator-side controls. As for communication requirement, the primary frequency regulation can be achieved on the load side in a completely decentralized manner, as for generator-side control, because the local frequency deviations at each bus convey exactly the right information about the global power imbalance for the loads to make individual decisions that turn out to be globally optimal. For secondary frequency regulation, unlike generator-side control, the load-side control is distributed, requiring only message passing among neighbors. We prove that our load-side control is globally asymptotically stable, and illustrate via simulations that it also improves the transient performance.
(Joint work with Changhong Zhao and Enrique Mallada (Caltech), Lina Li (Harvard)),and Ufuk Topcu (UPenn))
Steven H. Low is a Professor of the Department of Computing & Mathematical Sciences and the Department of Electrical Engineering at Caltech. Before that, he was with AT&T Bell Laboratories, Murray Hill, NJ, and the University of Melbourne, Australia. He is a Senior Editor of the IEEE Transactions on Control of Network Systems and the IEEE Transactions on Network Science & Engineering, is on the editorial boards of NOW Foundations and Trends in Networking, and in Electric Energy Systems, as well as Journal on Sustainable Energy, Grids and Networks. He is an IEEE Fellow and received his B.S. from Cornell and PhD from Berkeley.