Coordinated state-estimation method for air-conditioning loads to provide primary frequency regulation service

The penetration of large-scale renewable generation leads to a shortage of primary frequency regulation resources as well as increasing regulation demand. By exploiting the thermal capacity of buildings, the authors achieve linear power-frequency characteristics comparable to turbine droop control via clustering a number of air-conditioning units (ACs) to participate in primary frequency regulation without affecting indoor comfort. Due to the bandwidth limitations and latency in communication, the real-time centralised control method face great challenges. This study proposes a two-level coordinated state-estimation method to reduce the coordination burden, in which a central coordinator and local controller for each AC are involved. The central coordinator periodically gathers the working state of every AC and estimated thermal parameters individually, then broadcasts this identified model parameters - the coordination information - to each local controller. Resorting to a state-estimation method considering the coordinated information and local measurements, local controller determines whether to toggle the state of local AC to realise a fast frequency response. Simulation results show that the approach can effectively manage a large number of ACs with heterogeneous parameters to provide a primary frequency regulation service without inducing a rebound effect.