Modeling and control of thermostatically controlled loads

TL;DR

This paper develops an analytical linear model for the aggregate power response of thermostatically controlled loads (TCLs) to control inputs, enabling improved power tracking and control design amidst increasing renewable energy integration.

Contribution

It introduces a linearized analytical model for homogeneous TCL populations and designs an LQR controller for effective power tracking, including methods for uncertain load dynamics.

Findings

LQR controller successfully tracks step, ramp, and sinusoidal signals.

The model provides a basis for controller design for TCLs in power systems.

Proposes a probing method for systems with uncertain load characteristics.

Abstract

As the penetration of intermittent energy sources grows substantially, loads will be required to play an increasingly important role in compensating the fast time-scale fluctuations in generated power. Recent numerical modeling of thermostatically controlled loads (TCLs) has demonstrated that such load following is feasible, but analytical models that satisfactorily quantify the aggregate power consumption of a group of TCLs are desired to enable controller design. We develop such a model for the aggregate power response of a homogeneous population of TCLs to uniform variation of all TCL setpoints. A linearized model of the response is derived, and a linear quadratic regulator (LQR) has been designed. Using the TCL setpoint as the control input, the LQR enables aggregate power to track reference signals that exhibit step, ramp and sinusoidal variations. Although much of the work assumes a homogeneous population of TCLs with deterministic dynamics, we also propose a method for probing the dynamics of systems where load characteristics are not well known.