Managing load deferability to provide power regulation

Providing frequency regulation services in power networks has become an important part of network operation, traditionally carried out by fast responding generators. In this paper we consider regulation services from the demand side, through a new actor in the power market: a demand aggregator that manages a large number of consumer loads. The aggregator exploits the deferability of certain loads to control the consumption profile and thus reduce regulation needs, or even provide regulation services to others. We analyze this control through macroscopic ODE models inspired by queueing systems, where a fluid state represents load quantities. Two versions are considered: a one-state model that tracks the entire load population, and a two-state version that separately tracks quantities of currently deferrable and non-deferrable loads. The control input is the fraction of deferrable loads that are active, and is controlled using a combination of feedforward for tracking of a reference signal, and feedback to reduce the impact of random fluctuations. The performance of such controllers is evaluated by simulation using regulation signals from real networks.