Cascade control mode of indoor temperature PIλDµ and supply air temperature PDµ for multi-evaporator air-conditioning system

Aiming at regulating performance parameters of the multi evaporator air-conditioning system (MEACS), this project proposes a cascade control mode of indoor temperature PIλDµ and supplys air temperature PDµ and an improved multi-objective artificial fish swarm algorithm (IMOAFSA) is designed to tune parameters of fractional order PID controller for indoor temperature (IT-FOPIDC) and fractional order PD controller for supply air temperature (SAT-FOPDC), so as to stabilize the state point of supply air of MEACS and improve the regulation quality of indoor temperature. Firstly, according to the basic single objective artificial fish swarm algorithm (BSOAFSA), an adaptive factor is constructed to execute the nonlinear decreasing evolution to the visual field and step size in the fish swarm, so an improved single objective artificial fish swarm algorithm (ISOAFSA) is rebuilt. Secondly, on the basis of this ISOAFSA, Gaussian variation is introduced into external files (EF) to design an improved multi-objective artificial fish swarm algorithm (IMOAFSA) in order to continuously tune eight parameters of IT-FOPIDC and SAT-FOPDC. Finally, the control effects hosted by this cascade control system for indoor temperature and supply air temperature are numerically simulated. The results show that the designed IMOAFSA finds out Pareto optimal solutions (POS) of eight parameters of these two controllers and continuously updates them, which can obviously reduce fluctuation of supply air temperature and further improve the control quality of indoor temperature such as minor steady-state error, the smaller overshoot, the appropriate damping ratio and the shorter adjustment time, etc. © 2024 South China University of Technology. All rights reserved.