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Multi-variable extremum seeking control for a multi-functional variable refrigerant flow system

A multi-variable extremum seeking control is proposed as a model-free strategy to maximize the energy efficiency in real time for a multi-functional variable refrigerant flow system. For the cooling-only, heating-only, cooling-dominated, heating-dominated, and heat-recovery modes, the manipulated inputs of extremum seeking control include compressor suction/discharge pressure set-point, outdoor unit fan speed, bypass flow valve opening, and superheat set-points for evaporating heat exchangers. The feedback of extremum seeking control is the total power of the compressor motor, outdoor, and indoor unit fans. The proposed control strategy is validated with a Modelica-based dynamic simulation model, in terms of both steady-state and transient performance.