Grid-aware control of an ensemble of air-conditioning loads

An aggregation of flexible loads such as air conditioners (ACs) can be controlled to provide ancillary services in electricity grid. These services, however, may impact the power quality of the low-voltage (LV) side of the grid. This paper proposes a two-stage system-wide power tracking algorithm while satisfying user’s comfort level and voltage limits at all connection points. In the first stage, a centralized model predictive control (MPC) optimizes the temperature setpoint offset of ACs to balance the aggregated demand. In the second stage, we first run a Power Flow (PF) to find the voltages across the LV network. Then, an integral controller regulates the voltage by shaping the desired aggregated load profile. The integral gain is taken from the demand-voltage flexibility function that has been characterized when no coordination mechanism is in place. Simulation results demonstrate the efficiency of the proposed algorithm in a typical real-world LV network with 302 flexible loads.