Load frequency control by aggregations of thermally stratified electric water heaters

In this paper, we present a dynamic model of an electric water heater which describes the thermal stratification inside the water tank. The goal of this modeling is to accurately describe the power consumption behavior of a large water heater population and to assess customer comfort loss (lack of hot water) in the presence of external control actions. We present four rule-based control approaches for aggregate power setpoint tracking and compare them by means of time-domain simulations and numerical comparisons. As a control signal, we use a scaled load frequency control (LFC) time series added to a time-varying baseline of the aggregate water heater load.