Controlling Air Conditioners for Frequency Regulation: A Real-World Example

Even though thermostatically controlled loads like air conditioners present a great potential for providing ancillary services to the electric power grid, the practical challenges associated with their real-time coordination have not received the necessary attention. In this work, we present a nondisruptive load control application, specifically, we demonstrate how real residential air conditioners can provide frequency regulation. Aggregate power adjustment is achieved by modifying the ON/OFF modes of the air conditioners. To account for both single and multi-zone houses, we extend the currently available techniques and develop an approach that can be used for controlling aggregations that include both types of houses. A discussion of the practical challenges encountered in our field experiments is provided, along with the hardware and software approaches we developed to circumvent them. We argue that limitations of current thermostat APIs introduce significant challenges and are an impediment to widespread adoption of fast load control applications.

I. Introduction

Demand response has been widely proposed as a means of helping mitigate renewable intermittency. It has the potential for providing fast balancing services, like frequency regulation, to the electric power grid. More specifically, residential air conditioners (ACs), which belong to the class of Thermostatically Controlled Loads (TCLs), are considered an excellent candidate for such approaches. Firstly, they are ubiquitous. Furthermore, their thermal inertia allows small adjustments to their operating profile, and hence to their power consumption, without impact on the end user. This means that a utility, system operator, or third-party aggregator can coordinate AC load to provide grid services in a nondisruptive manner [1].