Coordinated power tracking and cooling capacity allocation for flexible and comfortable operation of photovoltaic driven variable refrigerant flow systems

Photovoltaic generation has become a major energy source for buildings, but its fluctuations pose significant challenges to supply-demand balance. Variable refrigerant flow air conditioning systems are among the primary energy consuming devices in buildings and possess considerable load flexibility, offering potential to directly respond to photovoltaic fluctuations. Therefore, developing photovoltaic driven variable refrigerant flow air conditioning systems is regarded as an effective approach to mitigating the impact of fluctuating photovoltaic generation on utility grids. However, previous control strategies on variable refrigerant flow air conditioning systems are primarily based on temperature setpoints, which are not capable of realizing accurate control of power, leading to mismatch between photovoltaic generation and electricity consumption. To address this issue, this study proposed a coordinated control strategy for photovoltaic driven variable refrigerant flow air conditioning systems, in which compressor frequency is regulated to track photovoltaic generation, while electronic expansion valve openings are adjusted through superheat control to achieve rational cooling capacity allocation among indoor units. This approach enables fast power control, achieving real-time utilization of photovoltaic generation while maintaining indoor thermal comfort. Under the proposed strategy, the system achieves a self-consumption ratio of 92.5%, and the peak grid power accounts for only 33.3% of the rated power of the variable refrigerant flow air conditioning system, representing a 34.3% increase in self-consumption ratio and a 64.7% reduction in peak grid power compared with the conventional strategy. This work provides a feasible solution for achieving the real-time supply-demand balance of photovoltaic driven variable refrigerant flow air conditioning systems.