eeh power systemslaboratory

Residential thermostatically controlled loads (TCLs), such as refrigerators and air conditioners, can be used for fast time-scale demand response to manage energy imbalances in power systems. Many direct load control strategies rely on information exchange between a central controller and loads in realtime. This project investigates the effects of limited bandwidth, latencies, and lost measurement or input signals on the ability to centrally control load aggregations to follow requests for a desired demand level. It builds on past work within aggregate TCL modeling, estimation, and control by adapting estimation and control strategies from networked control theory that explicitly handle the previously mentioned communications issues. The results of this work show that in the absence of delays, a central controller requires infrequent information to track highly dynamic demand changes. Specifically, it is shown that requests on all frequency control time-scales are fulfilled when receiving TCL measurements every fifteen minutes. The introduction of delays degrades performance, as expected. However, the controller adequately fulfills requests comparable to secondary frequency control with average TCL transmission delays of 60 seconds and average input delays of 20 seconds. Faster reference changes can be tracked adequately, but delays become increasingly important with high frequency reference changes and may cause inadequate tracking in some cases. Methods are suggested for overcoming these shortcomings and allow the reliable fulfillment of high-frequency demand changes.