Safe protocol for controlling power consumption by a heterogeneous population of loads

Abstract — Recent studies on control of aggregate power of an ensemble of thermostatically-controlled-loads (TCLs) have been concentrated on shifting the temperature set points of each TCL in the population. A sudden shift in the set point, however, is known to be associated with undesirable power oscillations which require closed-loop control strategies to regulate the aggregate power consumption of the population. In this article, we propose a new approach which we term as a “safe protocol” to implement the shift in temperature set point. It is shown analytically and verified numerically that by shifting the set point “safely ” the aggregate power consumption can be changed to a different value within a time frame of the order of a TCL’s cycle duration and avoid the undesired oscillations seen otherwise in a “sudden ” shift. We discuss how the excess aggregate energy transferred under a safe shift in the set point could potentially mitigate the burden due to abnormal energy generation within a short time span. Keywords- Load control, ancillary services, hysteresis-based control, renewable energy. I