  Considering the potential of thermostatically controlled loads (TCLs) to
provide flexibility in demand response or load control, a semi-Markov model
(SMM) for the ON/OFF controlled TCL is developed in this paper. This model
makes full use of the adjustment flexibility of TCLs when the control period is
long and maintains the diversity of switch state in the cluster. This model
also can satisfy user comfort and protect user privacy. Then, this paper adopts
the cyber-physical system (CPS) to realize the coupling of the discrete control
process and the continuous physical process. Finally, the proposed model is
applied to the coordination of large-scale heterogenous air-conditioners (ACs)
based on the equivalent thermal parameters (ETP) model. Simulation results
verify that under the proposed approach, the power of TCLs cluster can track
the control signal accurately, with both user comfort and diversity of TCL
cluster's operation states guaranteed.
