This work concerns design of control systems for "Demand Dispatch" to obtain ancillary services to the power grid by harnessing inherent flexibility in many loads. With careful design, the grid operator can harness this flexibility to regulate supply-demand balance. The deviation in aggregate power consumption can be controlled just as generators provide ancillary service today. Distributed control techniques are called for, much like those used today to provide congestion control in communication networks. The main message is that intelligence should be concentrated as much as possible at the load. In this way it is possible to design local control loops so that the aggregate of loads appears as a passive input-output system, while strict QoS constraints are maintained for each load.
