Real-time optimization of integrated subcooling transcritical CO₂ heat pump water heater via phasor extreme seeking control (ESC)

This article presents a novel approach to real-time optimization of integrated subcooling transcritical CO₂ heat pump water heater using the phasor ESC. Compared to the traditional dither-demodulation ESC, the phasor ESC shows improvements in optimization efficiency. A dynamic model of the heat pump system with high fidelity was developed in Dymola. Starting from a single phasor ESC for discharge pressure, we proposed practical guidelines for tuning the ESC parameters, such as the dither signal frequency, which significantly shortens the searching process by almost half. The effectiveness and adaptability of the multi-variable phasor ESC were demonstrated under various operating conditions, including time-varying disturbances such as ambient temperature. Simulation results showed that the phasor ESC outperforms both standard strategies and classic ESC in terms of performance.