Extremum Seeking Control for Energy Optimization of Vapor Compression Systems

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Figure 6: The overall power consumption (black line) is driven from about 700 W to 450 W while the heat load and room temperature remain constant, which results in an increase in COP from 2.9 to 4.4 for this operating point.

In this paper, an energy optimizing extremum seeking controller is developed for vapor compression systems (VCS) that automatically discovers sets of inputs that minimizes the energy consumption while the machine is in operation. This controller optimizes an input-output map (from VCS inputs to electrical energy consumed) in realtime, and without relying on a model of the dynamics of a vapor compression system. A detailed algorithm and rules for tuning the controller gains will be described. Experiments are performed on an inverter-driven room air conditioner that demonstrate convergence of inputs to their optimal values, resulting in an improvement in COP of 10-20% for some operating points.