Controlling aggregates of deferrable loads for power system regulation

This paper considers the role of a demand aggregator that manages a large number of consumer loads, with the objective of participating in the frequency regulation market. The key feature to be exploited is load deferrability in time, which enables the aggregator to adapt the consumption profile and thus reduce its own consumption of regulation, and even be a provider of regulation services to others. Rather than a microscopic model that considers individual loads and their scheduling, we consider here a macroscopic viewpoint drawn from fluid models of queueing systems. Here the state variable is the quantity of currently dispatchable loads, and the control input dictates the fraction of those which are currently active. The dynamics is a simple nonlinear ODE that allows us to design a controller with a feedforward term to track an external regulation reference, and a feedback term to reduce the impact of random load oscillations, in an agnostic way to the microscopic scheduling. The performance of this controller is evaluated by simulation using practical regulation signals.